Aerosol generation system providing preferential evaporation of nicotine

Abstract

SOLUTION: An aerosol-generating system includes: a heater assembly comprising at least one heating element; and an aerosol-forming substrate comprises a liquid mixture comprising nicotine and a first aerosol-former, the first aerosol-former having a higher boiling temperature than the nicotine. The system further includes a power source for supplying power to the heater assembly, a mouthpiece, and a control circuit for controlling power to the heater assembly, wherein the control circuit supplies power to at least one heating element of the heater assembly to maintain it at a first power or at a first temperature or within a first temperature range between smoking sessions. And a second power, higher than the first power, is supplied to raise the temperature above the first temperature or first temperature range in order to vaporize nicotine preferentially over the first aerosol-former during a smoking session.EFFECT: The aerosol-forming substrate is heated by the heating element both during and between smoking sessions, the heating of the aerosol-forming substrate between smoking sessions promoting preferential evaporation of nicotine.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to an aerosol generation system, and more particularly to an aerosol generation system that generates an aerosol containing nicotine by heating an aerosol-forming substrate.

Background Art

[0002] One type of heated aerosol generation system that generates an aerosol containing nicotine is an e-cigarette. An e-cigarette typically heats a liquid containing nicotine and an aerosol-forming body to generate an aerosol.

[0003] Nicotine-containing liquids for use by consumers in aerosol generation devices such as e-cigarettes typically contain relatively low concentrations of nicotine. High concentrations of nicotine can irritate the skin and can be harmful if ingested. The nicotine concentration of nicotine-containing liquids is regulated by some jurisdictions to be, for example, 20 mg / ml or less.

[0004] However, in order for an e-cigarette to satisfy users who have previously smoked traditional cigarettes, the e-cigarette needs to deliver an amount of nicotine comparable to that of the traditional cigarette used by the user for each smoking event. Without this level of nicotine delivery, the user may return to smoking traditional cigarettes.

Summary of the Invention

Problems to be Solved by the Invention

[0005] Using a nicotine-containing liquid having a relatively low concentration of nicotine, such as 20 mg / ml or less, as a substrate for generating an aerosol is difficult to deliver sufficient nicotine for each smoking by the user to satisfy habitual smokers. Previous attempts to solve this problem have included providing a solid form of a preliminary nicotine source within the aerosol generating device, from which nicotine is released by heating it, or through it, or by drawing vapor through it. However, this significantly increases the complexity and cost of the e-cigarette. Also, it is difficult to obtain consistent nicotine delivery with that type of system.

[0006] It would be desirable to provide an aerosol generating system that can deliver a higher amount of nicotine during each smoking by the user using a nicotine-containing liquid having a given nicotine concentration without the need for an additional nicotine source.

Means for Solving the Problem

[0007] In a first aspect of the present invention, a heater assembly including at least one heating element; an aerosol-forming substrate proximate to the heater assembly, the aerosol-forming substrate including a liquid mixture including nicotine and a first aerosol-forming agent, the first aerosol-forming agent having a boiling temperature higher than that of nicotine; a power source for supplying power to the heater assembly to generate an aerosol from the aerosol-forming substrate; a mouthpiece through which the user smokes to draw the aerosol out of the aerosol generating device; A control circuit configured to control the supply of power to a heater assembly, wherein during and between puffs by a user, the control circuit is configured to supply a first power to at least one heating element of the heater assembly, or to supply sufficient power to maintain at least one heating element of the heater assembly at a first temperature or within a first temperature range, and during a puff by a user, the control circuit is configured to supply a second power to at least one heating element of the heater assembly to preferentially vaporize nicotine over a first aerosol former, 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 above the first temperature or first temperature range, and an aerosol generating device comprising the control circuit is provided.

[0008] Advantageously, the aerosol forming substrate is heated by the heating element both during a puff and during and between puffs by a user. The aerosol forming substrate preferably remains in contact with or in proximity to the heating element throughout the operation of the device. The aerosol forming substrate may comprise a liquid held in a holding material or capillary in contact with or in proximity to the heating element. Preferential evaporation of nicotine is promoted by heating the aerosol forming substrate during and between puffs by a user.

[0009] This temperature control strategy promotes the preferential evaporation of nicotine over the first aerosol former. In other words, the generated vapor has a higher ratio of nicotine relative to the first aerosol former than it does relative to the liquid. This means that the generated aerosol formed from the vapor provides the user with a greater amount of nicotine per puff than simply heating the liquid does during puffing by the user. By continuously maintaining the liquid at a temperature close to the boiling point of nicotine, a thermodynamic equilibrium is maintained. This ensures a significant preferential evaporation of nicotine compared to the first aerosol former. The temperature of the heating element, or the power supplied to the heater assembly, is increased during puffing by the user to ensure that a sufficient aerosol density and a sufficient amount of nicotine are delivered to the user during each puff. In this way, a liquid having a relatively low concentration of nicotine can still be used to provide a satisfactory user experience.

[0010] Advantageously, the first temperature or the first temperature range is below the boiling point of the first aerosol former. More preferably, the first temperature or the first temperature range is below the boiling point of nicotine. This results in a greater disparity in the evaporation rates between nicotine and the first aerosol former.

[0011] As used herein, an aerosol former refers to any suitable well-known compound or mixture of compounds that, in use, facilitates the formation of a high-density stable aerosol and is substantially resistant to thermal decomposition at the operating temperature of the system. Suitable aerosol formers are well known in the art and include, but are not limited to, polyhydric alcohols (such as triethylene glycol, 1,3-butanediol, glycerin), esters of polyhydric alcohols (such as glycerol monoacetate, diacetate, or triacetate), and aliphatic esters of monocarboxylic, dicarboxylic, or polycarboxylic acids (such as dimethyl dodecanedioate, dimethyl tetradecanedioate).

[0012] The boiling point of a liquid is the temperature at which the vapor pressure of the liquid is equal to the external pressure surrounding the liquid. As used herein, the boiling point refers to the normal boiling point or atmospheric boiling point, which is the temperature at which the vapor pressure of the liquid is equal to the pressure at sea level (1 atmosphere).

[0013] The first aerosol former may be glycerol, also known as glycerin. Glycerol has a higher boiling point than nicotine. Glycerol is commonly used as an aerosol former for aerosols inhaled by humans.

[0014] The aerosol-forming substrate may include a second aerosol former, which has a lower boiling temperature than the first aerosol former. The second aerosol former is propylene glycol. Providing a second aerosol former with a lower boiling point allows for finer control over the ratio of nicotine contained in the generated aerosol. The second aerosol former 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 former.

[0015] The control circuit may be configurable by the user to select a first temperature or first temperature range or 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 throughout use, or may vary over the course of a use session.

[0016] The control circuit may be configured to calculate a second power depending on the first power or first temperature or 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 may be the power required to maintain a predetermined first temperature of the heating element or aerosol-forming substrate.

[0017] The heater assembly may include a plurality of heating elements. The control circuit may be configured to supply power only to a portion of the plurality of heating elements between puffs by the user. The control circuit may be configured to supply power to more or all of the heating elements during puffing by the user. In this way, the temperature of the liquid aerosol-forming substrate may be maintained between puffs by the user and may be increased as desired during puffing by the user.

[0018] The first power may be sufficient power to maintain the temperature of the heating element or the aerosol-forming substrate at approximately 200 degrees Celsius. In one embodiment, the heating element is a resistive heating element having an electrical resistance of 0.7 to 0.8 ohms and the first power is about 2 watts. The first power may be 1 to 3 watts, more preferably 1.4 to 2 watts.

[0019] The first temperature may be 150 to 200 degrees Celsius. This is lower than the boiling point of nicotine but high enough to cause significant evaporation of nicotine.

[0020] The first temperature range may be 150 to 200 degrees Celsius.

[0021] The second power may be selected to provide a desired total amount of nicotine delivered per puff and to provide a desired total amount of aerosol condensate (ACM) per puff. Also, the duration of application of the second power also affects the total amount of nicotine delivered per puff and the total amount of aerosol condensate delivered per puff.

[0022] The second power may be 2 to 6 watts, more preferably 2.4 to 3 watts. The second power may be 1 to 4 watts greater than the first power. In one embodiment, the second power is 3 watts and the first power is 2 watts.

[0023] The second power may be sufficient power to maintain the heating element of the aerosol-forming substrate within a second temperature or a second range of temperatures. The second temperature or the second range of temperatures may be 200 to 250 degrees. In one embodiment, the second temperature is 220 degrees Celsius.

[0024] The apparatus may further comprise a liquid reservoir for holding the 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 a passive mechanism such as a capillary material which will be described in more detail below.

[0025] The heater assembly may comprise 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 current being provided by a power source. As another method, or additionally, the heating element may be a susceptor that is inductively heated by a time-varying magnetic field.

[0026] The heater assembly may also have a number of different forms. In some embodiments, the heater assembly comprises a mesh or perforated heating plate of the heating element. The heater assembly may comprise a substantially flat heating element to enable simple manufacture. The heating element may comprise, for example, a flat heating track in a meandering shape.

[0027] The heating element may comprise, for example, an array of filaments arranged parallel to each other. It is preferred that the filaments may form a mesh. The mesh may be woven or non-woven. The mesh may be formed using different types of woven or lattice structures. As another method, the conductive heating element consists of an array of filaments or a fabric of filaments.

[0028] In a preferred embodiment, the substantially flat heating element may be constructed of wires formed into a wire mesh. The mesh preferably has a plain weave design. The heating element may be a wire grill made from mesh strips.

[0029] The filaments may define gaps between the filaments, and the gaps may have a width of 10 micrometers to 100 micrometers. It is preferable that the filaments cause capillary action within the gaps so that a liquid that will be vaporized during use is drawn into the gaps, increasing the contact area between the heating element and the liquid aerosol forming substrate.

[0030] The area of the mesh, array, or fabric of conductive filaments may be small, for example, 50 square millimeters or less, preferably 25 square millimeters or less, and more preferably approximately 15 square millimeters. The size is chosen to fit the heating element into a handheld system. Setting the size of the mesh, array, or fabric of conductive filaments to 50 square millimeters or less reduces the total amount of electrical power required to heat the mesh, array, or fabric of conductive filaments while still ensuring that the mesh, array, or fabric of conductive filaments is in sufficient contact with the liquid aerosol forming substrate. The mesh, array, or fabric of conductive filaments may be, for example, rectangular and may have a length of 2 millimeters to 10 millimeters and a width of 2 millimeters to 10 millimeters. The mesh preferably has dimensions of approximately 5 millimeters × 3 millimeters.

[0031] The filament 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, "conductive" ceramics (e.g., molybdenum disilicide, etc.), carbon, graphite, metals, alloys, and composite materials made of ceramic materials and metal materials. Such composite materials may include doped ceramics or undoped ceramics. An example of a suitable doped ceramic is doped silicon carbide. Examples of suitable metals include titanium, zirconium, tantalum, and platinum group metals.

[0032] Examples of suitable alloys include stainless steel, constantan, nickel-containing, cobalt-containing, chromium-containing, aluminum-containing, titanium-containing, zirconium-containing, hafnium-containing, niobium-containing, molybdenum-containing, tantalum-containing, tungsten-containing, tin-containing, gallium-containing, manganese-containing, and iron-containing alloys, as well as nickel, iron, cobalt, stainless steel-based superalloys, Timetal® (registered trademark), iron-aluminum-based alloys, and iron-manganese-aluminum-based alloys. Timetal® is a registered trademark of Titanium Metals Corporation. The filament may be coated with one or more insulators. Preferred materials for the conductive filament are stainless steel and graphite, and more preferably 300 series stainless steels such as AISI 304, 316, 304L, 316L. Additionally, 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 a substantially flat heating element. For example, a material with a high resistivity may be combined with a material with a low resistivity. This may be advantageous when one of the materials is more beneficial from other viewpoints, such as price, machinability, or other physical and chemical parameters. Advantageously, a substantially flat filament arrangement having an increased resistance reduces parasitic losses. Advantageously, a heater with a high resistance enables more efficient use of battery energy.

[0033] The filament is preferably made of wire. The wire is more preferably made of metal, and most preferably made of stainless steel.

[0034] The electric resistance of the heating element may be from 0.3 ohms to 4 ohms. It is preferable that the electric resistance is 0.5 ohms or more. More preferably, the electric resistance of the heating element is from 0.6 to 2 ohms, and most preferably about 0.7 ohms.

[0035] The liquid storage part may include a liquid holding material for holding the liquid aerosol forming substrate. The liquid holding material may be a foam, and a spongy mass of a collection of fibers. The liquid holding material may be formed of a polymer or a copolymer. In one embodiment, the liquid holding material is a spun polymer. The holding material may be, for example, a porous ceramic or glass fiber.

[0036] The apparatus preferably includes a capillary material for transporting the liquid aerosol forming substrate to the heating element. The capillary material may be provided in contact with the heating element. The capillary material is preferably disposed between the heating element and the holding material.

[0037] The capillary material can be made of a material capable of ensuring that there is a liquid aerosol forming substrate in contact with at least a part of the surface of the heating element. The capillary material may extend into the gaps of the heating element. The heating element may draw the liquid aerosol forming substrate into the gaps by capillary action.

[0038] A capillary material is a material that actively transports liquid from one end of the material to another. The capillary material may have a fibrous or sponge-like structure. The capillary material preferably comprises a bundle of capillaries. For example, the capillary material may comprise a plurality of fibers or threads, or other fine tubes. The fibers or threads may generally be aligned to transport the liquid aerosol forming substrate towards the heating element. Alternatively, the capillary material may comprise a sponge-like or foam-like material. The structure of the capillary material forms a plurality of small holes or tubes through which the liquid aerosol forming substrate can be transported by capillary action. The capillary material may comprise 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 metal or plastic materials, fibrous materials, such as fibrous materials made of spun fibers or extruded fibers (cellulose acetate, polyester, or combined polyolefins, polyethylene, terylene or polypropylene fibers, nylon fibers or ceramics, etc.). The capillary material may have any suitable capillary phenomenon 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 vapor pressure that enable the liquid aerosol forming substrate to be transported through the capillary medium by capillary action.

[0039] The liquid holding material and the capillary material may have heat resistance up to 250 degrees Celsius. The liquid holding material and the capillary material preferably have a relatively weak interaction with nicotine.

[0040] The aerosol forming substrate comprises a liquid mixture comprising nicotine and a first aerosol forming agent. The liquid mixture preferably comprises 4% by mass or less of nicotine, more preferably 2% by mass or less of nicotine. The liquid mixture is preferably 20 mg / ml or less.

[0041] The liquid mixture may contain up to approximately 98% by mass of a first aerosol former. Preferably, the liquid mixture contains 75% by mass or less of the first aerosol former. The first aerosol former may be glycerol.

[0042] The liquid mixture preferably contains 25% by mass or less of a second aerosol former. The liquid mixture preferably contains approximately three times by mass of the first aerosol former than the second aerosol former.

[0043] The liquid mixture may contain water. The liquid mixture may contain flavor compounds.

[0044] Advantageously, the power source is 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 require recharging. For example, the power source may have a capacity sufficient to enable continuous generation of aerosol for about six minutes, or a multiple of six minutes.

[0045] The control circuit may comprise a microcontroller. The microcontroller is preferably a programmable microcontroller. The electrical circuit may comprise further electronic components. The electrical circuit may be configured to regulate the supply of power to the heater assembly. The power may be supplied to the heater assembly in the form of current pulses.

[0046] The control circuit may comprise an airflow sensor positioned to detect smoking by a user in the system. The airflow sensor may comprise a microphone or a capacitance sensor. Alternatively or additionally, smoking by the user may be indicated to the control circuit by the user pressing a button on the system immediately before or during each smoking by the user.

[0047] The aerosol generating device is preferably a handheld device. The aerosol generating device is preferably portable. The aerosol generating device may have a size comparable to that of a conventional cigarette or roll-up tobacco cigarette. The aerosol generating device may have an overall length of approximately 30 millimeters to approximately 150 millimeters. The aerosol generating device may have an outer diameter of approximately 5 millimeters to approximately 30 millimeters.

[0048] The device may be an electric smoking device such as an e-cigarette. The device may comprise a reusable part including a power source and a control circuit, and a consumable part including an aerosol forming substrate. The heater assembly may be within the reusable part, or within the consumable part, or partly within both. Alternatively, the heater assembly may be provided within a separate component. The liquid aerosol forming substrate may be held within a reservoir. The reservoir may be refillable.

[0049] In a second aspect of the present invention, there is provided a method of generating a nicotine-containing aerosol from an aerosol forming substrate within an aerosol generating system for a user to smoke during use, the aerosol forming substrate comprising a liquid mixture comprising nicotine and a first aerosol forming agent, the first aerosol forming agent having a boiling temperature higher than that of nicotine, the method comprising maintaining the aerosol forming substrate within a first temperature range between puffs by the user, heating the aerosol forming substrate to a second temperature above the first temperature range during a puff by the user, thereby vaporizing nicotine preferentially over the first aerosol forming agent.

[0050] The second temperature is preferably below the boiling temperature of the first aerosol forming agent. The aerosol forming substrate may comprise a second aerosol forming agent, the second aerosol forming agent having a boiling temperature lower than that of the first aerosol forming agent.

[0051] The first temperature range may be below the boiling temperatures of nicotine and the second aerosol forming agent.

[0052] It will be apparent that the features described in connection with the first aspect of the present invention are applicable to the second aspect of the present invention.

[0053] The present invention provides for the preferential evaporation of nicotine, leading to a nicotine concentration in the generated aerosol that is higher than the nicotine concentration in the liquid aerosol-forming substrate. This enables a satisfactory user experience even when using a liquid containing a low concentration of nicotine. This helps people to quit conventional cigarettes. It also enables the use of liquids containing low concentrations of nicotine, which are particularly easier to handle during transport and use in the case of refillable systems.

[0054] Here, by way of example only, embodiments of the present invention will be described with reference to the following accompanying drawings.

Brief Description of the Drawings

[0055]

Figure 1

Figure 2

Figure 3

Figure 4

[0056] In an aerosol generating system that generates an aerosol for user inhalation by heating an aerosol-forming substrate, there are typically two different types of heating control. The most common type of heating control for a liquid aerosol-forming substrate is so-called "flash" heating, where an amount of liquid is rapidly heated over a short period of time to generate vapor. Flash heating may coincide with the timing of user smoking or inhalation such that the aerosol is generated only during user smoking. Flash heating is also used to vaporize a thin film or coating of the aerosol-forming substrate. The other type of heating control is so-called "continuous" heating, where the aerosol-forming substrate is heated over a sustained period, independent of user smoking or inhalation. This type of heating control is more common when heating a solid aerosol-forming substrate of larger mass, such as a tobacco rod.

[0057] 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 condensate (ACM) during user smoking. Preferential evaporation of nicotine means that nicotine vaporizes at a significantly higher rate than at least one other component of the liquid mixture such that the nicotine concentration in the generated vapor is higher than the nicotine concentration in the liquid mixture. By using a liquid mixture containing an aerosol-forming agent having a boiling temperature higher than that of nicotine (or a lower vapor pressure than nicotine) and a hybrid of continuous heating and flash heating, a significant increase in the nicotine concentration in the vapor and thus in the generated aerosol can be achieved. Maintaining the liquid mixture at a temperature closer to the boiling point of nicotine than to the boiling point of the aerosol-forming agent between puffs promotes preferential evaporation of nicotine. Raising the temperature of the heating element or enhancing the power supplied to the heating element during user puffing enables the delivery of a desired total amount of ACM and nicotine in each user puff.

[0058] Preferentially evaporating nicotine enables the use of liquid mixtures having a lower nicotine concentration. This is advantageous because the lower nicotine concentration in the liquid simplifies the handling of the liquid during manufacturing, transportation, and use, and is particularly beneficial when the end user needs to refill an aerosol generating system with this liquid. It also enables the use of liquids that clearly comply with national or international regulations while still providing a satisfactory experience to the user.

[0059] Figure 1 is a simplified cross-sectional view of an aerosol generating system 10 according to an embodiment of the present invention. The system of Figure 1 comprises a cartridge 20 and an apparatus portion 40 that are connected together.

[0060] The cartridge comprises a supply of a liquid aerosol-forming substrate and a heater assembly. The apparatus portion comprises a power source and a control circuit. The apparatus portion functions to supply power to the heater assembly in the cartridge to vaporize the liquid aerosol-forming substrate. The vaporized aerosol-forming substrate is entrained in an air stream through the system, the air stream being provided by the user sucking on the mouthpiece of the cartridge. The vaporized aerosol-forming substrate cools in the air stream to form an aerosol before being drawn into the user's mouth.

[0061] Figure 2 is a perspective view of the system shown in Figure 1. A system with the same hardware components is described in International Patent Publication No. WO 2018 / 019485.

[0062] The apparatus portion 40 comprises a housing 46 that holds a lithium-ion battery 42 and a control circuit 44. The apparatus portion also comprises a spring-loaded electrical contact element (not shown) configured to contact electrical contact pads on the heater assembly in the cartridge. A button 41 is provided to activate the device by operating a switch within the control circuit. When the device is activated, the control circuit supplies power from the battery to the heater in the cartridge.

[0063] Cartridge 20 has a mouthpiece end with a mouthpiece 23 through which the user can smoke. The mouthpiece end is remote from the device portion. The device end of the cartridge is in the vicinity of the device portion.

[0064] Cartridge 20 comprises a housing 22. Within the housing 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 with a flat mesh heating element is held on a heater cap 30. The heater cap is fitted over the open end of the storage container. A liquid retaining 32 material is positioned within the cap. Capillary material 31 is positioned between the heater assembly 28 and the retaining material 32. A protective cover 33 is fitted to the housing and keeps the heater assembly and heater cap in the storage container. The protective cover also covers the heating element and protects it from damage.

[0065] Heater cap 30 has an opening formed in the front face and the heater assembly extends across the opening. The heater assembly comprises a pair of electrical contact pads secured to the heater cap and the heating element, which comprises a mesh of conductive heater filaments secured to electrical contacts across and opposite the opening. This type of heater assembly is described in International Patent Publication WO 2015 / 117702.

[0066] As can be seen from FIG. 1, when the protective cover 33 is in place within the cartridge, it is pressed against the periphery of the heater assembly but does not contact the heating element. As will be described in more detail with reference to FIG. 3, an air flow path to and from the heating element is provided between the protective cover 33, the heater assembly 28, and the storage container 24.

[0067] The protective cover is shaped to provide a barrier between the airflow path passing over the heating element and the electrical contact pads. The protective cover contacts the heater assembly between the exposed portion of the contact pads and the central portion of the heating element to provide this barrier and to secure the heater assembly to the storage container. This arrangement reduces the possibility that leaked or condensed liquid aerosol-forming substrate will contaminate the contact surfaces of the electrical contact pads and the electrical contact elements. Additionally, a layer of liquid retention material (not shown in any figure) may be provided on the interior of the protective cover or on the exterior of the storage container to further reduce the possibility that leaked or condensed liquid from within the airflow path will leak out and contaminate other components of the system, and to absorb liquid condensed within the airflow path.

[0068] Cartridge 20 is connected to the device portion 40 by a press fit. The cartridge housing is shaped to allow the cartridge 20 to be connected to the device portion 40 in only two orientations, which ensures that the spring-loaded electrical contact elements are received within the openings and contact the contact pads of the heater assembly. The connection ribs 48 of the device portion engage recesses 25 on the cartridge housing to hold the cartridge and the device portion together.

[0069] The cartridge housing 22 and the storage container 24 are integrally molded and formed of polypropylene. The liquid retention material 32 is formed of a polypropylene PET copolymer. The capillary material 31 is formed of glass fiber. 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).

[0070] To assemble the cartridge, the storage container is first filled with the aerosol-forming substrate. Next, the liquid holding material 32 is positioned into the open end of the storage container and the capillary material 31 is positioned on top of the liquid holding material. The heater cap, to which the heater assembly is already fixed, is then positioned into the open end of the storage container. The storage container and the heater cap may comprise a keying mechanism to ensure that the heater cap is positioned on the storage container in the correct orientation. The protective cover 33 is then fitted onto the housing 22 to hold all of the cartridge components in place.

[0071] The system is a handheld system sized to comfortably fit in the user's hand. In operation, after the cartridge and the device portion are connected together, the user presses the button 41 to activate the device. The user then draws air through the system by puffing on the mouthpiece 23. As will be described later, after activation of the device, the control circuit continuously supplies power to the heater assembly based on the detected puffing by the user. The vaporized aerosol-forming substrate passes through the heating element and into the airflow passing through the system.

[0072] Puffing by the user is detected by a flow sensor (not shown) within the device portion and is in fluid communication with the airflow through the device. However, in another embodiment, the flow sensor may be omitted and the user will need to press the button 41 immediately prior to each puff.

[0073] Figure 3 illustrates the airflow through the cartridge when the user smokes on the mouthpiece 23. Air is drawn into the system through the suction port 60 formed between the housing of the device body and the housing of the cartridge 22. The air then passes through an opening formed in the connection portion of the device portion and enters a cavity formed between the device portion and the protective cover 33. The air is then drawn into the cartridge through both the air suction holes 37 on the front wall of the protective cover and the dilution air suction port 50. The air drawn through the air suction holes 37 impinges on the heating element and entrains the vaporized aerosol-forming substrate. The mixture of air and vapor 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 suction port 50 is mixed with the vapor / air mixture from the heater assembly. As the mixture travels through the airflow path 54, the vapor cools and an aerosol is formed. This aerosol is drawn into the user's mouth through the mouthpiece 23.

[0074] The airflow path includes a 90-degree bend and follows the outside of the storage container. Any large droplets or debris in the airflow do not pass around the bend and strike the protective cover 33. This helps to ensure that the desired aerosol reaches the user.

[0075] Figure 4 illustrates the delivery of power to the heating element during operation of a system of the type shown in Figure 1 for preferentially evaporating nicotine over glycerin in a liquid mixture. The system is activated at time t = 0 when the user presses button 41. The control circuit 44 supplies approximately 2 watts to the heating element. This raises the temperature of the liquid in proximity to the heating element to between 180 and 200 degrees Celsius. When smoking by the user is detected by the flow sensor, the control circuit supplies a short burst of higher power. In this example, the control circuit supplies 3 watts of power for 3 seconds. Due to the airflow passing over the heating element during smoking by the user, there is cooling of the heating element and also a reduction in pressure in proximity to the heating element. This means that there is only a limited increase in the heating element temperature during the period when higher power is supplied, but there is a significant increase in liquid vaporization. In this embodiment, the heating element reaches a temperature of 220 degrees Celsius or less during each smoking by the user.

[0076] The liquid aerosol-forming substrate 26 in the first embodiment contains 74 wt% glycerin, 24 wt% propylene glycol, and 2 wt% nicotine. This mixture can be heated such that nicotine evaporates preferentially over glycerin. Nicotine has a normal boiling point of 247 degrees Celsius, glycerin has a normal boiling point of 290 degrees Celsius, and propylene glycol has a normal boiling point of 188 degrees Celsius.

[0077] This heating control strategy has been found to result in, on average, over the first 8 puffs of a usage session, nicotine close to 4 mass% in the delivered aerosol and less than about 74 mass% glycerin in the delivered aerosol.

[0078] The additional power applied during smoking increases the aerosol condensate (ACM) and the total nicotine delivered compared to simply applying 2 watts throughout the session. In particular, the ACM increases from 1.4 mg / puff to 2 mg / puff and the nicotine increases from approximately 20 μg / puff to 50 μg / puff.

[0079] In another embodiment, the liquid aerosol forming substrate 26 comprises 98% by weight of vegetable glycerin, 24% by weight and 2% by weight of nicotine. As shown in FIG. 4, the same power control strategy is used. The resulting aerosol contains on average 2.8% by weight of nicotine over the first 8 puffs, which is also greater than the nicotine concentration in the liquid.

[0080] The additional power applied during puffing increases the aerosol condensate (ACM) and the total nicotine delivered compared to simply applying 2 watts throughout the session. In particular, the ACM increases from 1.4 mg / puff to 2.25 mg / puff, and the nicotine increases from approximately 32 μg / puff to 40 μg / puff.

[0081] Applying power higher than 3 W during puffing by the user was found to further increase the delivered ACM and total nicotine, but the percentage of nicotine by weight in the delivered aerosol was not significantly improved.

[0082] In the above embodiments, the power is supplied based on a predetermined power level. Alternatively, it is possible to control based on a desired temperature. The temperature of the heating element may be determined by monitoring its resistance 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 puffs by the user, and the power may be increased by 1 watt during each puff by the user, or the temperature may be increased by 20 degrees Celsius. Different combinations of controls may be used based on power or temperature. The temperature control may be based on a temperature range rather than a single target temperature. The power control may be based on controlling the load cycle of the supply current to the heating element(s).

[0083] Also, it is possible to use different types of heaters and use the same control strategy. The level of power required will depend on the characteristics of the heating element, and particularly on its electrical resistance if the heating element is a resistive heater.

[0084] Different users may prefer different aerosol characteristics. Therefore, it is also possible to allow the user to set the first power or the first temperature within the first temperature range, or the second power or the second temperature, or any combination of these parameters. The control circuit may be programmable by the user using a suitable user interface, either on the system or on a connected computer, tablet, or smartphone.

[0085] It is also possible to automatically set the first power or the first temperature within the first temperature range, or the second power or the second temperature, or any combination of these parameters, based on the identity of the liquid mixture used as the aerosol-forming substrate. The identity of the liquid mixture may be determined by detecting a barcode or other indicia on the cartridge, or may be input by the user using a suitable user interface, either on the system or on a connected computer, tablet, or smartphone. Different liquid mixtures may benefit from being heated to different temperatures.

[0086] The above exemplary embodiments are illustrative but not limiting. In light of the exemplary embodiments discussed above, other embodiments consistent with the above exemplary embodiments will be apparent to those skilled in the art.

Claims

1. An aerosol generating device, comprising: a heater assembly having at least one heating element; a storage part (24) for holding a liquid aerosol forming substrate adjacent to the heater assembly; a liquid delivery mechanism configured to deliver the liquid aerosol forming substrate from the storage part to at least one heating element; a power source for supplying power to the heater assembly to generate aerosol from the aerosol forming substrate; a mouthpiece for a user to smoke to draw out aerosol from the aerosol generating device; a control circuit configured to control the supply of power to the heater assembly, so as to supply first power to at least one heating element of the heater assembly during and between smoking by the user, or to supply power sufficient to maintain at least one heating element of the heater assembly at a first temperature of 150 to 200 degrees Celsius, and during smoking by the user, to supply second power to at least one heating element of the heater assembly to preferentially vaporize nicotine over an aerosol forming body having a boiling temperature higher than nicotine in the liquid aerosol forming substrate held in the storage part, wherein the second power is higher than the first power or is sufficient to raise the temperature of at least one heating element of the heater assembly above the first temperature.

2. The aerosol generating device according to claim 1, wherein the storage part contains the liquid aerosol forming substrate (26), and the liquid aerosol forming substrate (26) contains nicotine and a first aerosol forming body.

3. The aerosol generating device according to claim 2, wherein the first aerosol forming body is glycerol.

4. The aerosol generating device according to claim 2, wherein the first aerosol forming body has a boiling temperature higher than that of nicotine.

5. The aerosol generating device according to any one of claims 2 to 4, wherein the first temperature is lower than the boiling point of the first aerosol forming body.

6. The aerosol generating device according to any one of claims 2 to 5, wherein the first aerosol forming body is glycerol.

7. The aerosol-forming substrate according to any one of claims 2 to 6, wherein the aerosol-forming substrate includes a second aerosol-forming agent and the second aerosol-forming agent has a boiling temperature lower than that of the first aerosol-forming agent.

8. The aerosol generating device according to claim 7, wherein the second aerosol-forming agent is propylene glycol.

9. The aerosol generating device according to any one of claims 1 to 8, wherein the control circuit is configurable by the user to select the first temperature or the first power.

10. The aerosol generating device according to claim 9, wherein the control circuit is configured to calculate the second power depending on the first power or the first temperature.

11. The aerosol generating device according to any one of claims 1 to 10, wherein the heater assembly includes a plurality of heating elements, and the control circuit is configured to supply power only to a part of the plurality of heating elements between puffs by the user.

12. The aerosol generating device according to any one of claims 1 to 11, wherein the heater assembly includes a mesh of heating elements or a perforated heating plate.

13. The aerosol generating device according to any one of claims 1 to 12, wherein the second power is sufficient to raise the temperature of at least one heating element of the heater assembly to a temperature of 200 to 250 degrees Celsius.

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