Heater assembly having a heater element separated from a liquid supply

Abstract

To provide good heating efficiency to a vaporiser assembly.SOLUTION: A vaporiser assembly for an electrically operated aerosol-generating device is provided, the assembly including: a substantially planar, fluid-permeable heating element (135) having a first side and a second side opposing the first side; and a liquid transport medium (136). The liquid transport medium has a first side in contact with the second side of the heating element and has a second side opposing the first side. The heating element extends over a first area of the first side of the liquid transport medium. A liquid supply conduit (138) having a first end is in contact with the second side of the liquid transport medium and extends over only a second area of the second side of the liquid transport medium, the second area being smaller than the first area. The liquid transport medium is disposed so as to transport liquid from the liquid supply conduit to the first area of the second side of the heating element.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to aerosol generating devices that heat a liquid substrate to form an aerosol, and in particular to handheld aerosol generating devices that produce an aerosol for inhalation by a user. [Background technology]

[0002] Handheld aerosol generation systems that produce aerosols for inhalation from liquid substrates are becoming more widely used both in the field of medical inhalers for drug delivery and in the field of smoking products that are alternatives to cigarettes, such as e-cigarettes.

[0003] In electronic cigarettes, the aerosol is typically formed by heating a liquid aerosol-forming substrate. The liquid is held in a liquid storage reservoir and delivered to the heating element by a capillary material or wick extending between the reservoir and the heating element. A high retention material (HRM) may be placed in contact with the heating element to hold the liquid in proximity to the heating element.

[0004] In one configuration, a mesh heater is simply placed on top of the HRM containing the liquid aerosol-forming substrate. The mesh heater forms part of the airflow passageway through which the user can draw vapor. The heating element is activated in response to the user's puff on the device. When the heating element is activated, liquid in the HRM near the heating element is vaporized and drawn away from the heating element by the user's puff. Additional liquid is then drawn from the liquid storage reservoir into the HRM. The function of the HRM or capillary wick is to ensure that an adequate amount of liquid is near the heating element, regardless of the system's orientation relative to gravity. Thus, with each puff by the user, a sufficient amount of liquid is vaporized to subsequently form an aerosol. The heating element and liquid storage reservoir are typically provided together as a disposable cartridge. This arrangement has the advantage of being simple to manufacture and robust. An example of this type of arrangement is described in WO2015117700A1.

[0005] One issue with this type of system is heating efficiency. Heat is transferred to a significant extent not only to the liquid desired to be vaporized, but also to the remaining liquid in the liquid storage reservoir that is not required to be vaporized during the user's puff. The thermal mass of the remaining e-liquid, which is heated by conduction and convection from the e-liquid being vaporized, creates heat losses at the heater area and therefore creates the need for additional power. In handheld devices, which are typically battery-powered, it is particularly important to improve heating efficiency, thereby reducing the need to frequently recharge or replace batteries and enabling the use of small form factor batteries.

[0006] It would be desirable to eliminate or reduce the severity of this problem. Summary of the Invention

[0007] In a first aspect, there is provided a vaporizer assembly for an electrically operated aerosol generating device, comprising: a generally planar fluid-permeable heating element having a first side and a second side opposite the first side; a liquid transport medium having a first side in contact with the second side of the heating element and a second side opposite the first side, the heating element extending over a first region of the first side of the liquid transport medium; a liquid supply conduit having a first end in contact with the second side of the liquid transport medium and extending only over a second area of ​​the second side of the liquid transport medium, the second area being smaller than the first area; A liquid transport medium is disposed to transport liquid from the liquid supply conduit to a first region on the second side of the heating element.

[0008] Having the liquid supply conduit extend over a relatively small area of ​​the liquid carrier medium compared to the heating element has the advantage that only a small percentage of the heat generated by the heater is transferred to the liquid in the liquid supply conduit. This provides better heating efficiency for the vaporizer assembly in that less heat is transferred away from the liquid carrier medium compared to the prior art arrangements described above. The second area may be less than 50% of the first area, and preferably less than 30% of the first area.

[0009] The liquid carrier medium advantageously covers the entire heating element, which maximizes aerosol generation for a given input power and also avoids hot spots at the edges of the carrier material, which can lead to the generation of undesirable compounds.

[0010] The liquid transport medium may have a capillary structure arranged to transport the liquid parallel to the second side of the heating element. This allows the liquid to be transported effectively throughout the heating element. In prior art systems, air bubbles can form in the HRM or capillary wick, which affects proper liquid transport from the liquid storage reservoir to the heating element. The arrangement of the present invention reduces the likelihood of air bubble formation in the liquid supply conduit. The liquid transport medium may be relatively thin so that any bubbles formed during liquid transport can easily escape and are unlikely to return to the liquid supply conduit.

[0011] The thickness of the liquid transport medium between the first side and the second side of the liquid transport medium may be between 1 mm and 5 mm. 2 ~500mm 2 may have an area of

[0012] The vaporizer assembly may be used, for example, in an electrical smoking system, to generate a paper or aerosol for inhalation by a user. The structure and operation of the vaporizer assembly may be such that all of the liquid held in the liquid transfer medium can be vaporized in a single puff by the user. Liquid that is subsequently drawn into the liquid transfer medium to replace the vaporized liquid is vaporized in subsequent puffs. By appropriately selecting the dimensions of the liquid transfer medium, a desirably consistent amount of paper can be produced in each puff by the user.

[0013] The vaporizer assembly may include a housing, a heating element, and a liquid carrier medium held within the housing, the housing engaging or integral with the liquid supply conduit, such that the heating element and the liquid carrier medium may be held together and aligned with one another.

[0014] The heating element is fluid-permeable to allow paper to escape from the vaporizer assembly. Fluid-permeable in this context means that paper can escape from the liquid carrier medium through the plane of the heating element. To allow this, the heating element may have openings or pores through which paper can pass. For example, the heating element may comprise a mesh or fabric of electrically resistive filaments. Alternatively, or additionally, the heating element may comprise a sheet with holes or slots.

[0015] The heating element may be a resistive heating element that is directly supplied with electrical current in use.

[0016] The resistive heating element may include a plurality of gaps or openings extending from the second side to the first side through which a fluid may pass.

[0017] A resistive heating element may comprise multiple conductive filaments. The term "filament" is used throughout this specification to refer to an electrical path disposed between two electrical contacts. The filament may arbitrarily branch and diverge into several paths or filaments, respectively, or several electrical paths may merge into one path. The filaments may have a cross section that is round, square, flat, or of any other shape. The filaments may be arranged in a straight or curved manner.

[0018] The resistive heating element may be, for example, an array of filaments arranged parallel to one another. Preferably, the filaments may form a mesh. The mesh may be woven or non-woven. The mesh may be formed using different types of weave or lattice structures. Alternatively, the resistive heating element may consist of an array of filaments or fibers of filaments.

[0019] The filaments may define gaps between them, and the gaps may have a width of 10 micrometers to 100 micrometers. The filaments preferably create capillary action within the gaps so that liquid to be vaporized in use is drawn into the gaps, increasing the contact area between the heating element and the liquid aerosol-forming substrate.

[0020] The filaments may form a mesh having a size of 60 to 240 filaments per centimeter (±10 percent). The mesh density is preferably 100 to 140 filaments per centimeter (±10 percent). The mesh density is more preferably approximately 115 filaments per centimeter. The gap width may be 100 micrometers to 25 micrometers, preferably 80 micrometers to 70 micrometers, and more preferably approximately 74 micrometers. The open area of ​​the mesh, which is the ratio of the gap area to the total area of ​​the mesh, may be 40 percent to 90 percent, preferably 85 percent to 80 percent, and more preferably approximately 82 percent.

[0021] The filaments may have a diameter of 8 micrometers to 100 micrometers, preferably 10 micrometers to 50 micrometers, more preferably 12 micrometers to 25 micrometers, and most preferably approximately 16 micrometers. The filaments may have a round or flattened cross section.

[0022] The area of ​​the filament may be small, for example, 50 square millimeters or less, 25 square millimeters or less, and more preferably approximately 15 square millimeters. The size is selected to allow the heating element to be incorporated into a handheld system. The heating element may be, for example, rectangular and may have a length of 2 to 10 millimeters and a width of 2 to 10 millimeters.

[0023] 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, "conductive" ceramics (e.g., molybdenum disilicide), carbon, graphite, metals, alloys, and composites made of ceramic and metallic materials. Such composites may include doped 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.

[0024] Examples of suitable alloys include stainless steel, constantan, nickel-, cobalt-, chromium-, aluminum-, titanium-, zirconium-, hafnium-, niobium-, molybdenum-, tantalum-, tungsten-, tin-, gallium-, manganese-, and iron-containing alloys, as well as nickel-, iron-, cobalt-, and stainless steel-based superalloys, 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, with 300 series stainless steels, such as AISI 304, 316, 304L, and 316L, being more preferred. Additionally, the conductive heating element may include a combination of the above materials. Combinations of materials may be used to improve control of the resistance of the 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 if one of the materials is more advantageous from other perspectives, such as price, machinability, or other physical and chemical parameters. Advantageously, a substantially flat filament arrangement with increased resistance reduces parasitic losses. Advantageously, a heater with high resistance allows for more efficient use of battery energy.

[0025] Preferably, the filament is made of wire, more preferably the wire is made of metal, most preferably stainless steel.

[0026] The electrical resistance of the filament of the heating element may be between 0.3 ohms and 4 ohms. Preferably, the electrical resistance is 0.5 ohms or greater. More preferably, the electrical resistance of the heating element is between 0.6 and 0.8 ohms, and most preferably about 0.68 ohms.

[0027] Alternatively, the heating element may comprise a heating plate having an array of openings formed therein. The openings may be formed, for example, by etching or machining. The plate may be formed of any material having suitable electrical properties, such as those materials described above for the heating element filaments.

[0028] The heating element may be a susceptor element. As used herein, "susceptor element" means an electrically conductive element that heats when subjected to a varying magnetic field. This may be the result of eddy currents and / or hysteresis losses induced in the susceptor element. Advantageously, the susceptor element is a ferrite element. The material and geometry for the susceptor element can be selected to provide the desired electrical resistance and heat generation.

[0029] The susceptor element may be a ferrite mesh susceptor element. Alternatively, the susceptor element may be an iron-based susceptor element.

[0030] The susceptor element may comprise a mesh. As used herein, the term "mesh" encompasses grids and arrays of filaments having spaces therebetween, and may include fibers and non-woven fibers.

[0031] The mesh may comprise a plurality of ferrite or iron-based filaments. The filaments may define gaps between them, and the gaps may have a width of 10 μm to 100 μm. The filaments preferably create capillary action within the gaps so that in use, liquid to be vaporized is drawn into the gaps, increasing the contact area between the susceptor element and the liquid.

[0032] The filaments may form a mesh with a size of 160 to 600 mesh US (+ / - 10%) (i.e., 160 to 600 filaments per inch (+ / - 10%)). The gap width is preferably 75 μm to 25 μm. The open area ratio of the mesh, which is the ratio of the gap area to the total area of ​​the mesh, is preferably 25 to 56%. The mesh may be formed using different types of weave or lattice structures. Alternatively, the filaments may consist of a series of filaments aligned parallel to one another.

[0033] The filaments may have a diameter of 8 μm to 100 μm, preferably 8 μm to 50 μm, and more preferably 8 μm to 40 μm.

[0034] The area of ​​the mesh may be small, preferably less than 500mm², to allow it to be incorporated into a handheld system. The mesh may for example be rectangular and have dimensions of 15mm x 20mm.

[0035] Advantageously, the susceptor elements have a relative permeability of 1 to 40,000. Lower permeability materials may be used when it is desired to rely on eddy currents for the majority of the heating, and higher permeability materials may be used when hysteresis effects are desired. Preferably, the material has a relative permeability of 500 to 40,000. This provides efficient heating.

[0036] The housing may also be vapor permeable to allow the paper to escape. The housing may also be vapor permeable adjacent the second side of the liquid transport medium. This allows the paper to escape from the other side of the fluid transport material, further reducing the possibility of trapped air bubbles that would interfere with liquid transport.

[0037] The vaporizer assembly may include a liquid retention material in the liquid supply conduit, which may ensure liquid supply to the liquid transport medium regardless of the orientation of the vaporizer assembly relative to gravity. The liquid retention material is preferably different from the liquid transport medium. The liquid supply conduit may include one or more capillaries.

[0038] The liquid supply conduit may extend generally perpendicular to the first side of the heating element, which maximizes the distance between the heating element and the second end of the liquid supply conduit. In use, the second end of the liquid supply conduit may be adjacent to the main liquid reservoir.

[0039] When viewed perpendicular to the first side of the heating element, the first region may not completely cover the second region. This reduces heat transfer from the heating element to the liquid supply conduit. When viewed perpendicular to the first side of the heating element, the heating element may not overlap the second region. This further increases the distance between the heating element and the first end of the liquid supply conduit, thereby reducing heat transfer from the heating element to the liquid supply conduit. The liquid supply conduit may have a cross-sectional area that is approximately 25% of the area of ​​the liquid transport medium. The liquid supply conduit may have a diameter of 2 mm to 5 mm.

[0040] In a second aspect, there is provided a cartridge for an aerosol generation system, the cartridge including a vaporizer assembly according to the first aspect and a liquid reservoir, the liquid supply conduit having a second end opposite a first end in communication with the liquid supply reservoir.

[0041] The heating element and liquid carrier medium may be separable from the liquid supply reservoir. The liquid supply conduit may be fixed to the heating element, or to the liquid supply reservoir, or to both. The liquid supply conduit may take the form of a bottleneck in the liquid supply reservoir. The liquid supply reservoir may comprise a reservoir housing. The reservoir housing may be integral with the liquid supply conduit.

[0042] In a third aspect, there is provided an aerosol generation system comprising a vaporizer assembly according to the first aspect, a liquid supply conduit having a second end opposite a first end communicating with a liquid supply reservoir, a power source, and control circuitry configured to control the supply of power from the power source to the vaporizer assembly.

[0043] The aerosol generation system may be a handheld system. The aerosol generation system may include a mouthpiece that allows a user to inhale the aerosol generated by the aerosol generation system. The aerosol generation system may include a main unit and a cartridge that engages with the main unit during use. The main unit may include a housing. The housing may hold a power source and control circuitry. The vaporizer assembly and liquid reservoir may be provided in the cartridge. The vaporizer assembly may be part of the main unit and the liquid reservoir provided in the cartridge. The housing may receive at least a portion of the cartridge. The mouthpiece may be part of the main unit or the cartridge.

[0044] The aerosol generation system may include an airflow passageway extending from the air inlet, through the vaporizer assembly, to an outlet, which may be in the mouthpiece.

[0045] The aerosol-generating system may have a size comparable to that of a conventional cigar or cigarette. The aerosol-generating system may have a total length of about 30 mm to about 150 mm. The aerosol-generating system may have an outer diameter of about 5 mm to about 30 mm.

[0046] The power source may be a DC power source. The power source may be a battery. The battery may be a lithium-based battery, such as a lithium cobalt battery, a lithium iron phosphate battery, a lithium titanate battery, or a lithium polymer battery. The battery may be a nickel-metal hydride battery or a nickel-cadmium battery. The power source may be another form of charge storage device, such as a capacitor. The power source may require recharging and may be configured for numerous charge-discharge cycles. The power source may have a capacity that allows for storage of sufficient energy for one or more user experiences; for example, the power source may have a capacity sufficient to allow continuous generation of aerosol for a period of approximately six minutes, corresponding to the typical time it takes to smoke a conventional cigarette, or a multiple of six minutes. In another embodiment, the power source may have a capacity sufficient to allow for a predetermined number of puffs or for discontinuous activation of the atomizer assembly.

[0047] The control circuit may comprise a microcontroller. Preferably, the microcontroller is a programmable microcontroller. The control circuit may comprise further electronic components. The control circuit may be configured to regulate power supply to the heating element. Power may be supplied to the heating element continuously after system activation, or may be supplied intermittently, such as with each puff. Power may be supplied to the aerosol-generating element in the form of current pulses. The control circuit may include an airflow sensor, and the control circuit may supply power to the heating element when a puff by the user is detected by the airflow sensor.

[0048] In operation, a user may activate the system by puffing on the mouthpiece or by providing some other user input, such as by pressing a button on the system. The control circuit then supplies power to the heating element, which may be supplied for a predetermined time or for the duration of the user's puff. The heating element then heats the liquid in the liquid carrier medium to form paper, which escapes from the vaporizer assembly, passes through the system, and enters the airflow passage. The paper cools and condenses to form an aerosol, which is then drawn into the user's mouth.

[0049] In all aspects of the present invention, the liquid may be a liquid aerosol-forming substrate. As used herein with respect to the present invention, an "aerosol-forming substrate" is a substrate capable of releasing a volatile compound capable of forming an aerosol. The volatile compound may be released by heating the aerosol-forming substrate.

[0050] The liquid aerosol-forming substrate may be liquid at room temperature. The liquid aerosol-forming substrate may comprise nicotine. The liquid aerosol-forming substrate containing nicotine may be a nicotine salt matrix. The liquid aerosol-forming substrate may comprise a plant-derived material. The liquid aerosol-forming substrate may comprise tobacco. The liquid aerosol-forming substrate may comprise a tobacco-containing material containing volatile tobacco flavour compounds that are released from the aerosol-forming substrate on heating. The liquid aerosol-forming substrate may comprise a homogenised tobacco material. The liquid aerosol-forming substrate may comprise a non-tobacco-containing material. The liquid aerosol-forming substrate may comprise a homogenised plant-derived material.

[0051] The liquid aerosol-forming substrate may include one or more aerosol formers. The aerosol former is any suitable, well-known compound or mixture of compounds that facilitates the formation of a dense, stable aerosol during use and is substantially resistant to thermal decomposition at the operating temperature of the system. Examples of suitable aerosol formers include glycerin and propylene glycol. Suitable aerosol formers are well-known in the art and include, but are not limited to, polyhydric alcohols (e.g., triethylene glycol, 1,3-butanediol, glycerin), esters of polyhydric alcohols (e.g., glycerol monoacetate, diacetate, or triacetate), and aliphatic esters of monocarboxylic, dicarboxylic, or polycarboxylic acids (e.g., dimethyl dodecanedioate, dimethyl tetradecanedioate). The liquid aerosol-forming substrate may include water, solvents, ethanol, plant extracts, and natural or artificial flavors.

[0052] The liquid aerosol-forming substrate may comprise nicotine and at least one aerosol former. The aerosol former may be glycerin or propylene glycol. The aerosol former may comprise both glycerin and propylene glycol. The liquid aerosol-forming substrate may have a nicotine concentration of about 0.5% to about 10% (e.g., about 2%).

[0053] In all aspects, the liquid transport medium is a material that transports a liquid from one end of the material to the other. The liquid transport medium may be a capillary material. The capillary material may have a fibrous or spongy structure. Preferably, the capillary material 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 be generally aligned to transport the liquid aerosol-forming substrate toward the heating element. Alternatively, the capillary material may comprise a spongy 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 move by capillary action. Because the liquid transport medium is exposed to the high temperatures of the heating element, it must be stable at those temperatures.

[0054] The liquid transport medium may comprise any suitable material or combination of materials. Examples of suitable materials include sponge or foam materials, ceramic or graphite-based materials in the form of fibers or sintered powders, expanded metal or plastic materials, and fibrous materials, such as spun or extruded fibers (such as glass fibers, cellulose acetate, polyester, or bonded polyolefin, polyethylene, terylene, or polypropylene fibers, nylon fibers, or ceramics). The fibers may be woven or form an amorphous structure. The liquid transport medium may have any suitable capillary and porosity for use 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 allow the liquid aerosol-forming substrate to be transported through the liquid transport medium by capillary action.

[0055] In all embodiments, the liquid-retaining material in the liquid supply conduit may also be a capillary material. However, it need not withstand temperatures as high as the liquid transport medium. The liquid-retaining material may be a foam, a sponge, or a collection of fibers. The liquid-retaining material may be formed of a polymer or copolymer. In one example, the liquid-retaining material is woven polypropylene and polyethylene terephthalate.

[0056] Embodiments of the invention will now be described in detail, by way of example only, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0057] [Figure 1] FIG. 1 is a schematic diagram of an aerosol generating system according to a first embodiment of the present invention. [Figure 2a] FIG. 2a shows in detail the vaporizer assembly of the embodiment shown in FIG. [Figure 2b] FIG. 2b is an underside view of the vaporizer assembly of FIG. 2a. [Figure 3a] FIG. 3a is a schematic cross-sectional view of a vaporizer assembly according to a second embodiment of the present invention. [Figure 3b] FIG. 3b is a view of the back side of the vaporizer assembly of FIG. 3a. [Figure 4] FIG. 4 is a schematic diagram of an aerosol generating system according to a third embodiment of the present invention.

[0058] 1 is a schematic diagram of an aerosol generation system according to a first embodiment of the present invention. The system comprises two main components: a cartridge 100 and a main body 200. A connecting end 115 of the cartridge 100 is removably connected to a corresponding connecting end 205 of the main body 200. The main body contains a battery 210 (in this example, a rechargeable lithium-ion battery) and a control circuit 220. The aerosol generation device 10 is portable and has a size comparable to that of a conventional cigar or cigarette.

[0059] The cartridge 100 includes a housing 105 containing an atomization assembly 120 and a liquid storage compartment 130 that defines a liquid supply reservoir. A liquid aerosol-forming substrate is held within the liquid storage compartment. The atomization assembly is connected to the bottleneck of the liquid storage compartment. The atomization assembly includes a heating element 135 in the form of a fluid-permeable mesh on a liquid transport medium 136. The liquid transport medium 136 covers the entire heating element. A liquid supply conduit 138 extends between the bottleneck of the liquid storage compartment and the liquid transport medium 136. A high-retention material (HRM) or capillary material is disposed within the liquid supply conduit 138. Liquid from the liquid storage compartment is drawn into the liquid supply conduit and spreads throughout the liquid transport medium. This means that a certain volume of liquid within the liquid transport medium is adjacent to the heating element, where it can be easily vaporized by the heating element.

[0060] Airflow passages 140 , 145 extend through the system from the air inlet 150 through the heater element 135 and from the heating element to an opening 110 in the housing 105 at the mouth end.

[0061] Heating element 135 is a susceptor that is inductively heated when exposed to a high frequency oscillating magnetic field. An inductor coil 225, in this example a pancake coil, is positioned within the main body adjacent to heating element 135. A control circuit supplies a high frequency oscillating current to coil 225, which in turn generates a time-varying magnetic flux across the heating element.

[0062] The system is configured to allow a user to draw or inhale the aerosol into their mouth by inhaling or sucking on the opening at the mouth-end of the cartridge. In operation, when a user inhales on the opening at the mouth-end, air is drawn from the air inlet through the airflow passage, past the heating element, and out the opening at the mouth-end. A control circuit is configured to control the supply of power from the battery 210 to the coil 225. This in turn controls the temperature of the heating element and, therefore, the amount and characteristics of the paper produced by the atomization assembly. The control circuit may include an airflow sensor, and the control circuit may supply power to the coil when the airflow sensor detects that the user is drawing on the cartridge. This type of control arrangement is well established in aerosol generating systems such as inhalers and e-cigarettes. Thus, when a user inhales on the opening at the mouth-end of the cartridge, the atomization assembly is activated, generating paper that is entrained in the airflow passing through the airflow passage 140. The paper cools in the airflow within passageway 145 to form an aerosol, which is then drawn through opening 110 in the oral end into the user's mouth.

[0063] The embodiments shown in Figures 1-3 all rely on induction heating. Induction heating works by placing a conductive article to be heated in a time-varying magnetic field. Eddy currents are induced in the conductive article. If the conductive article is electrically isolated, the eddy currents are dissipated by Joule heating of the conductive article. In aerosol-generating systems that operate by heating an aerosol-forming substrate, the aerosol-forming substrate itself typically does not have sufficient conductivity to be inductively heated in this manner. Therefore, in the embodiments shown in Figures 1-3, a susceptor element is used as the conductive article being heated. The aerosol-forming substrate is then heated by the susceptor element via thermal conduction, convection, and / or thermal radiation. Because a ferromagnetic susceptor element is used, heat is also generated by hysteresis losses as magnetic domains switch within the susceptor element.

[0064] The embodiment described in Figures 1-3 uses an inductor coil to generate a time-varying magnetic field. The inductor coil is designed not to experience significant Joule heating. In contrast, the susceptor element is designed to experience significant Joule heating of the susceptor.

[0065] The oscillating magnetic field passes through the susceptor element, inducing eddy currents in the susceptor element. The susceptor element heats as a result of Joule heating and hysteresis losses, reaching a temperature sufficient to vaporize the aerosol-forming substrate proximate to the susceptor element. As described in more detail below, the vaporized aerosol-forming substrate is entrained in air flowing from the air inlet to the air outlet, where it cools before entering the user's mouth and forming an aerosol within the mouthpiece. When a puff is detected, the control electronics supplies an oscillating current to the coil for a predetermined duration (5 seconds in this example), and then turns off the current until a new puff is detected.

[0066] Figure 2a illustrates the vaporizer assembly of Figure 1 in more detail. In the example shown in Figure 2, the vaporizer assembly has a housing 137. The housing 137 is integrally formed with a liquid storage container. The housing 137 holds a mesh susceptor 135, a liquid carrier medium 136, and a capillary material 139 within a liquid supply conduit 138.

[0067] The heating element 135 comprises a stainless steel mesh. It is generally planar. Figure 2b is an underside view of the vaporizer assembly. The mesh is generally rectangular, but has a central opening 131 cut out. The central opening is such that, when viewed perpendicular to the plane of the mesh, the opening covers the liquid supply conduit. The outline of the liquid supply conduit 138 is shown in dotted lines in Figure 2b. In this way, the heating element is detached from the liquid supply conduit, so there is no significant heat transfer from the heating element to the liquid in the liquid supply conduit. The opening can be any shape. For example, it may be circular to match the circular liquid supply conduit. In this example, the opening is square.

[0068] In this example, the liquid transport medium 136 is formed from a glass fiber material. Glass fiber typically has suitable heat resistance. The glass fiber is woven to provide capillary action to transport liquid in a direction parallel to the surface of the mesh susceptor element. In particular, the liquid transport medium is arranged to transport liquid from the area in contact with the liquid supply conduit to the periphery of the liquid transport medium.

[0069] The capillary material 139 of the liquid supply conduit 138 is oriented to carry the liquid to the liquid transport medium 136, in this example perpendicular to the surface of the mesh susceptor element. The capillary material 139 may be made of woven polypropylene or poly(ethylene terephthalate) (PET).

[0070] It can be seen from Figure 2b that the area of ​​the liquid supply conduit in contact with the liquid transfer medium is only a fraction of the total area of ​​the liquid transfer medium. The smaller the area of ​​the liquid supply conduit in contact with the liquid transfer medium, the lower the heat transfer from the heater to the liquid in the liquid supply conduit. However, the contact area must be large enough to allow for replenishment of the liquid throughout the liquid transfer medium in a short period of time. This allows the user to take successive puffs in a short period of time and still receive sufficient and consistent aerosol with each puff. In this example, the liquid supply conduit has a diameter of approximately 5 mm and the liquid transfer medium is approximately 300 mm. 2 The capillary material in the liquid supply conduit may have a volume similar to the liquid transport medium.

[0071] In use, when the induction coil 225 is activated as a result of a sensed user puff, the heating element heats the liquid held in the liquid transfer medium 136 to a temperature sufficient to vaporize it. Heating is maintained for a duration sufficient to vaporize substantially all of the liquid in the liquid transfer medium, which may be a fixed period of time, such as two seconds. The current through the coil is then stopped, allowing the heating element to cool until the next activation of the coil. Following vaporization of the liquid in the liquid transfer medium, additional liquid flows from the capillary material in the liquid supply conduit into the liquid transfer medium. Simultaneously, liquid from the liquid storage compartment replaces the liquid in the liquid supply conduit. In this way, another similar volume of liquid is delivered to the heating element ready for the user's next puff. This provides a consistent aerosol volume. Additionally, the separation of the heating element from the main body of the liquid storage compartment improves heating efficiency.

[0072] 2a and 2b, the vaporizer housing 137 is not fluid permeable and covers the backside of the liquid carrier medium, meaning that any paper generated in the liquid carrier medium must escape through the susceptor 136 to be entrained in the airflow.

[0073] 3a and 3b illustrate another embodiment of a vaporizer that can be used in the system shown in FIG. 1, in which paper generated in the liquid carrier medium 336 can escape through both a first side of the liquid carrier medium adjacent to the heating element (again, a mesh susceptor in the example of FIGS. 3a and 3b), and a second side opposite the first side.

[0074] Figure 3a is a schematic diagram of a portion of a vaporizer assembly and liquid storage compartment 330. The basic shape of the vaporizer assembly is the same as the embodiment of Figure 2. A housing 337 is integrally formed with the liquid storage compartment. A heating element 335 is separated from the main body of the liquid storage compartment by a bottleneck formed by a liquid supply conduit 338. The housing 337 holds a mesh susceptor 335, a liquid carrier medium 336, and a capillary material 339 within the liquid supply conduit 338.

[0075] The heating element 335 comprises a stainless steel mesh and is generally planar. The liquid transport medium 336 is formed from a glass fiber material. The glass fibers are woven to provide capillary action to transport liquid in a direction parallel to the surface of the mesh susceptor element. In particular, the liquid transport medium is arranged to transport liquid from the area in contact with the liquid supply conduit to the periphery of the liquid transport medium.

[0076] The capillary material 339 of the liquid supply conduit 338 is oriented to carry the liquid to the liquid transport medium 336, in this example perpendicular to the surface of the mesh susceptor element. The capillary material 339 may be made of woven polypropylene or poly(ethylene terephthalate) (PET).

[0077] In use, when the induction coil 225 is activated as a result of a detected user puff, the heating element heats the liquid held in the liquid transfer medium 3136 to a temperature sufficient to vaporize it. Heating is maintained for a duration sufficient to vaporize substantially all of the liquid in the liquid transfer medium, which may be a fixed period of time, such as two seconds. The current through the coil is then stopped, allowing the heating element to cool until the next activation of the coil. Following vaporization of the liquid in the liquid transfer medium, additional liquid flows from the capillary material in the liquid supply conduit into the liquid transfer medium. Simultaneously, liquid from the liquid storage compartment replaces the liquid in the liquid supply conduit. In this way, another similar volume of liquid is delivered to the heating element, ready for the user's next puff. This provides a consistent aerosol volume. Additionally, the separation of the heating element from the main body of the liquid storage compartment improves heating efficiency.

[0078] It can be seen from Figure 3b that the housing 337 allows the paper to escape both through the heating element 335 and through the rear surface of the liquid transport medium 336. The path of the paper is illustrated by the arrows in Figure 3a.

[0079] The primary airflow through the vaporizer is indicated by dotted arrows 340. Paper escaping through the rear surface of the liquid carrier medium 336 can join the primary airflow by passing through openings 342 formed in the vaporizer housing 337. FIG. 3b is a rear view of the liquid carrier medium 336 illustrating the housing structure. The rear surface of the housing 337, which holds the liquid carrier medium and heating element 335, is formed with a central portion 343 that couples or is integral with a liquid supply conduit 338 and a peripheral frame 344 that is joined to the central portion by a plurality of ribs 345. Between the ribs are spaces that allow paper to escape from the liquid carrier medium.

[0080] In this example, frame 344 has a size and shape that matches the cavity in the cartridge in which it is positioned. This is to confine the airflow to the desired airflow passage or passages through the cartridge. To that end, a slot or opening 342 is formed through the vaporizer housing to allow paper that escapes into space 341 behind liquid carrier medium 336 to join the main airflow 340. Alternatively, the vaporizer assembly may simply be made smaller than the cavity in which it is received, allowing paper to move around the periphery of housing 137 and join the main airflow.

[0081] The arrangement of Figures 3a and 3b has the advantage that bubbles generated in the liquid transport medium have multiple exit paths, reducing the possibility of bubbles becoming trapped in the liquid transport medium or migrating into the liquid supply conduit and interfering with efficient liquid transport to the heating element.

[0082] The embodiments described so far include heating elements that are heated by induction, although resistive heaters could alternatively be used. Figure 4 is a schematic diagram of an aerosol generation system according to a third embodiment of the invention. The system is similar to the system shown in Figure 1, but uses resistive heating rather than induction heating.

[0083] The device comprises two main components, a cartridge 400 and a main body 500. A connecting end 415 of the cartridge 400 is removably connected to a corresponding connecting end 505 of the main body 500. The main body contains a battery 510 (in this example a rechargeable lithium ion battery) and control circuitry 520.

[0084] The cartridge 400 includes a housing 405 containing an atomization assembly 420 and a liquid storage compartment 430 that defines a liquid supply reservoir. A liquid aerosol-forming substrate is held within the liquid storage compartment. The atomization assembly is connected to the bottleneck of the liquid storage compartment. The atomization assembly includes a heating element 435 in the form of a fluid-permeable mesh on a liquid transport medium 436. A liquid supply conduit 438 extends between the bottleneck of the liquid storage compartment and the liquid transport medium 436. A high-retention material (HRM) or capillary material 439 is disposed within the liquid supply conduit 438. Liquid from the liquid storage compartment is drawn into the liquid supply conduit and spreads throughout the liquid transport medium from there. This means that a certain volume of liquid within the liquid transport medium is adjacent to the heating element, where it can be easily vaporized by the heating element.

[0085] Airflow passages 440 , 445 extend through the system from the air inlet 450 through the heater element 435 and from the heating element to an opening 410 in the housing 405 at the mouth end.

[0086] As in the previous embodiment, the heating element 435 comprises a stainless steel mesh and is generally planar. However, the vaporizer assembly also includes a pair of electrical contact pads 460 positioned on opposite sides of the heating element. The contact pads are formed of a conductive material, such as copper, and are electrically connected to each other through the heating element 435.

[0087] The contact pads 460 face the main body and are contacted by electrical contact pins 560 on the main body. The electrical contact pins are spring loaded to ensure good contact with the contact pads 460 when the cartridge is connected to the main body. The electrical contact pins 560 on the main body are connected to the control circuit 520. Power is supplied to the heating element from the battery 510 via the electrical contact pads and electrical contact pins.

[0088] The liquid transport medium 436 is formed from a glass fiber material. The glass fibers are woven to provide capillary action to transport liquid in a direction parallel to the surface of the mesh susceptor element. Specifically, the liquid transport medium is arranged to transport liquid from the area in contact with the liquid supply conduit to the periphery of the liquid transport medium.

[0089] The capillary material 439 of the liquid supply conduit 438 is oriented to carry the liquid to the liquid transport medium 436. In this example, it is perpendicular to the surface of the heating element. The capillary material 439 may be made of woven polypropylene or poly(ethylene terephthalate) (PET).

[0090] The system is configured to allow a user to draw or inhale the aerosol into their mouth by inhaling or sucking on the opening at the mouth-end of the cartridge. In operation, when a user inhales on the opening at the mouth-end, air is drawn from the air inlet through the airflow passage, past the heating element, and out the opening at the mouth-end. A control circuit controls the supply of power from the battery 410 to the heating element 435. This in turn controls the temperature of the heating element and, therefore, the amount and characteristics of the paper produced by the atomization assembly. The control circuit may include an airflow sensor, and the control circuit may supply power to the coil when the airflow sensor detects that the user is drawing on the cartridge. This type of control arrangement is well established in aerosol generating systems such as inhalers and e-cigarettes. Thus, when a user inhales on the opening at the mouth-end of the cartridge, the atomization assembly is activated, generating paper that is entrained in the airflow passing through the airflow passage 440. The paper cools in the airflow in passageway 445 to form an aerosol, which is then drawn into the user's mouth through opening 410 in the mouth end.

[0091] All of the described embodiments have the advantage that only the volume of liquid desired to be heated with each puff by the user is separated from the remaining liquid in the liquid storage compartment, so that that volume of liquid is vaporized quickly and efficiently with relatively little heat transfer to the remaining liquid.

Claims

1. 1. A vaporizer assembly for an electrically operated aerosol generating device, comprising: a generally planar heating element having a first side and a second side opposite the first side; a liquid transport medium having a first side in contact with the second side of the heating element and a second side opposite the first side, a thickness of the liquid transport medium between the first and second sides of the liquid transport medium being between 1 mm and 5 mm, and the heating element extending over a first region of the first side of the liquid transport medium; a liquid supply conduit having a first end in contact with the second side of the liquid transport medium and extending only over a second area of ​​the second side of the liquid transport medium, the second area being smaller than the first area; wherein the liquid transport medium is arranged to transport liquid from the liquid supply conduit to the first region on the second side of the heating element.

2. 2. The carburetor assembly of claim 1, wherein the second area is less than 50% of the first area.

3. 3. The vaporizer assembly of claim 1, wherein the liquid transport medium has a capillary structure arranged to transport liquid parallel to the second side of the heating element.

4. 10. The vaporizer assembly of claim 1, comprising a housing, the heating element, and the liquid carrier medium held within the housing, the housing engaging or being integral with the liquid supply conduit.

5. The vaporizer assembly of claim 4 , wherein the housing is vapor permeable adjacent the second side of the liquid carrier medium.

6. The vaporizer assembly of claim 5 , wherein the housing is perforated adjacent the second side of the liquid carrier medium.

7. 7. The vaporizer assembly of claim 6, wherein the housing includes a slot or opening adjacent the second side of the liquid transfer medium, the slot or opening defining a channel through the housing to the first side of the liquid transfer medium.

8. 7. The vaporizer assembly of claim 6, wherein the housing includes a slot or opening adjacent the second side of the liquid carrier medium, the slot or opening defining a channel through the housing to the first side of the heating element.

9. 5. The vaporizer assembly of claim 4, wherein the portion of the housing that holds the liquid transport medium and the heating element is formed by a central portion, the central portion being joined to the liquid supply conduit and a peripheral frame that is joined to the central portion by a plurality of ribs, or is integral with the liquid supply conduit and the peripheral frame, and wherein paper can escape from the liquid transport medium through the plurality of ribs.

10. The vaporizer assembly of claim 1 , further comprising a liquid-retaining material within the liquid supply conduit.

11. The vaporizer assembly of any preceding claim, comprising a capillary material within the liquid supply conduit.

12. The vaporizer assembly of any preceding claim, wherein the liquid supply conduit extends generally perpendicular to the first side of the heating element.

13. The vaporizer assembly of any one of claims 1 to 12, wherein the heating element comprises a mesh or fiber of electrically resistive filaments.

14. 14. The vaporizer assembly of claim 1, wherein the first region does not completely cover the second region when viewed in a direction perpendicular to the first side of the heating element.

15. 15. The vaporizer assembly of claim 14, wherein the heating element does not overlap the second region when viewed in a direction perpendicular to the first side of the heating element.

16. The vaporizer assembly of claim 1 , wherein the heating element comprises a susceptor element configured to be inductively heated.

17. A cartridge for an aerosol generation system, the cartridge defining a cavity containing the vaporizer assembly of claim 9 and a liquid reservoir, the liquid supply conduit having a second end opposite the first end communicating with the liquid reservoir.

18. 18. The cartridge of claim 17, wherein the heating element and the liquid transport medium are separable from the liquid reservoir.

19. 19. A cartridge according to claim 17 or 18, comprising the vaporizer assembly of claim 10, wherein the peripheral frame has a size and shape that matches the recess in the cartridge.

20. An aerosol generation system comprising: a vaporizer assembly according to any one of claims 1 to 19; a liquid reservoir; a liquid supply conduit having a second end opposite the first end communicating with the liquid reservoir; a power source; and a control circuit configured to control the supply of power from the power source to the vaporizer assembly.

21. 21. The aerosol generation system of claim 20, wherein the aerosol generation system is a handheld system having a mouthpiece that allows a user to inhale the aerosol generated by the aerosol generation system.

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