Air pressure measurement to detect obstructions in the airflow path

Abstract

A method for detecting the presence of an obstruction in an airflow path of an aerosol generating system, the system (100) comprising a heater assembly (202) for heating an aerosol-forming substrate (210), a power source (302), an airflow path defined between an air inlet (218) and an air outlet (306) and passing through the heater assembly (202), and at least one sensor (216) for sensing an airflow characteristic of air in the airflow path. The method includes a) measuring a value associated with the airflow characteristic during the course of a user puff based on a signal from the at least one sensor, b) comparing the measured value to a predetermined value, c) detecting an obstruction in the airflow path based on the comparison, limiting power supplied to the heater assembly, and providing an indication if an obstruction is detected.

Description

[Technical field]

[0001] The present disclosure relates to a method for detecting the presence of an obstruction in an airflow path of an aerosol generation system. In particular, the present disclosure relates to a method for detecting the presence of an obstruction caused by agglomeration of residues of an aerosol-forming substrate in a heater assembly of the aerosol generation system. The present disclosure also relates to an aerosol generation system comprising an electrical circuit configured to detect the presence of an obstruction in the airflow path. [Background technology]

[0002] Aerosol generating devices configured to generate an aerosol from an aerosol-forming substrate, such as a tobacco-containing substrate, are known in the art. Many known aerosol generating devices generate an aerosol by application of heat to the substrate by a heater assembly. The heater assembly is heated when power is provided by a power source of the aerosol generating device. The generated aerosol can then be inhaled by a user of the device. Summary of the Invention [Problem to be solved by the invention]

[0003] Over time, use of the aerosol generating device can cause residues of the aerosol-forming substrate to agglomerate within the heater assembly. This is undesirable because if a clogged heater assembly is not replaced or cleaned, the agglomerated residues can heat up and burn during continued use of the device. The burnt agglomerated residues can impart a burnt flavor to the aerosol generated by the device, which negatively impacts the user experience of the device.

[0004] An aerosol generating device typically defines an airflow path between an air inlet and an air outlet. The airflow path is configured such that, in use, the generated aerosol passes into the airflow path. A user may inhale the generated aerosol by sucking on the air outlet.

[0005] Often, the airflow path is configured to pass through a heater assembly. In such cases, clogging of the heater assembly by agglomerated residue of the aerosol-forming substrate increases the resistance to drawing air through the airflow path when a user draws on the aerosol generating device during use. This is because the agglomerated residue creates an obstruction in the airflow path. Increased resistance to drawing can be associated with a poor user experience.

[0006] It would be desirable to provide a method for detecting when a heater assembly of an aerosol generating device becomes clogged. It would be desirable to provide such a method that does not impact the user experience of the device and is simple and low cost. It would also be desirable to provide a method that can accurately detect clogged heater assembly regardless of the user of the device. It would be desirable to provide an aerosol generating system for carrying out the method. [Brief description of the drawings]

[0007] [Figure 1] 1 is a schematic cross-sectional view of a first embodiment of an aerosol generating system according to the present invention. [Diagram 2] 2A and 2B are schematic diagrams of cross-sections of the ceramic wick of the aerosol generation system of FIG. 1, where FIG. 2A shows an unobstructed wick and FIG. 2B shows the same wick with an obstruction. [Diagram 3] 1 is a graph showing the pressure profile of a puff measured downstream of a wick when the wick is unobstructed and when the wick is obstructed. [Figure 4] 1 is a flow diagram of a method for detecting an obstacle. [Diagram 5] 5 is a flow diagram of a method for determining a predetermined value for the method of FIG. 4. [Figure 6] 2 is a schematic cross-sectional view of a second embodiment of an aerosol generation system according to the present invention; FIG. [Figure 7] 1 is a graph showing a representation of a puff differential pressure profile measured by a first sensor downstream of the heater assembly and a second sensor upstream of the heater assembly. [Figure 8]1 is a schematic diagram showing a cross-section of a third embodiment of an aerosol generation system according to the present invention. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] According to a first aspect of the present disclosure, there is provided a method for detecting the presence of an obstruction in an airflow path of an aerosol generating system. The system may comprise a heater assembly for heating an aerosol-forming substrate. The system may further comprise a power source. The system may further include an airflow path defined between an air inlet and an air outlet. The airflow path may pass through the heater assembly. The system may comprise at least one sensor for sensing an airflow characteristic of air in the airflow path.

[0009] The method may include measuring a value associated with the airflow characteristic based on a signal from the at least one sensor. The value may be measured during the course of a user puff. The method may include comparing the measurement to a predetermined value. The method may include detecting an obstruction in the airflow path based on the comparison. The method may include limiting power supplied to the heater assembly if an obstruction is detected. Alternatively, the method may include providing an indication if an obstruction is detected.

[0010] By detecting an obstruction and limiting the power supplied to the heater assembly or providing an indication, the user is advantageously made aware of the obstruction. By detecting an obstruction and informing the user of its presence, the user can advantageously cease use of the aerosol generation system and take appropriate steps to remove the obstruction.

[0011] Limiting the power may include preventing power from being supplied to the heater assembly.

[0012] The indication may preferably be in the form of powering an LED of the aerosol generating system. However, other means for providing the indication are possible, including, for example, haptic feedback. Alternatively, the aerosol generating system may be configured to communicate with a smartphone or other electronic device and configured to provide an indication on the smartphone or electronic device.

[0013] As used herein, an obstruction means a total or partial blockage of the airflow path.

[0014] As mentioned above, an obstruction may be detected based on measurements of airflow characteristics. For example, the airflow characteristic may be pressure. The obstruction causes a pressure drop in the airflow path. Assuming that the user draws air from the air outlet through the airflow path, such that the airflow is driven by the user's inhalation, the pressure may be lower downstream of the obstruction than it would be if the obstruction were not present. The pressure may be lowest in the area immediately downstream of the obstruction. Another example of an airflow characteristic that may be used is flow rate. The flow rate may be higher downstream of the obstruction than it would be if the obstruction was not present. The flow rate may be highest in the area immediately downstream of the obstruction.

[0015] The method has the advantage that it is simple and low cost to implement within an aerosol generating system, as it only requires the presence of one or more sensors to measure airflow characteristics, and further, the method can be performed during a puff, advantageously without impacting the user of the aerosol generating system.

[0016] The obstruction may be in a portion of the airflow path through the heater assembly. The obstruction may be caused by agglomeration of residue of the aerosol-forming substrate within the heater assembly. The residue may effectively cause a restriction in a portion of the airflow path through the heater assembly.

[0017] By notifying the user of the obstruction, the user can advantageously stop using the aerosol generating system to avoid heating or burning of residues that would otherwise adversely affect the taste of the aerosol generated by the aerosol generating system.

[0018] A heater assembly that is blocked by agglomerations of aerosol-forming substrate residue may be referred to as being "clogged."

[0019] The predetermined value may be the value of the airflow characteristics in normal use, where there are no obstructions in the airflow path. The predetermined value may represent the value of the airflow characteristics during initial use of the aerosol generating system. This may be particularly advantageous when the obstruction is caused by agglomeration of residues on the aerosol-forming substrate, as the value represents the airflow characteristics where residue build-up is minimized.

[0020] Where the predetermined value is the value of the airflow characteristic in normal use with no obstructions in the airflow path, the comparison with the predetermined value may include calculating a difference between the predetermined value and the measured value, As will be appreciated, whether the difference is positive or negative depends on the airflow characteristic, the set-up of the at least one sensor, and the order of calculation.

[0021] An obstruction may be detected when the magnitude of the difference between the predetermined value and the measured value exceeds a predetermined limit. The predetermined limit may correspond to a pressure difference of 60 to 160 Pa. Preferably, the predetermined limit may correspond to a pressure difference of 80 to 150 Pa.

[0022] The predetermined value may be a predetermined threshold. The predetermined threshold may represent a value of the airflow characteristic that is indicative of an obstructed airflow path. The comparison of the measured value to the predetermined threshold may include a direct comparison. If the measured value is the same as the predetermined threshold, an obstruction may be detected. For an airflow characteristic that decreases in response to an obstruction, an obstruction may be detected if the measured value is less than the predetermined threshold. For an airflow characteristic that increases in response to an obstruction, an obstruction may be detected if the measured value is greater than the predetermined threshold.

[0023] The measurement used in the comparison with the predetermined value or threshold may be a value measured over the course of a single puff, or the measurement may be an average of several measurements taken at different times during the course of a single puff.

[0024] The measurement may be an average of values ​​of the airflow characteristics measured during multiple puffs. The average may be measured over the course of successive puffs, for example 2, 3, 4, or 5 successive puffs. The average may advantageously avoid false detection of an obstruction as a result of aberrant user behavior during a single puff.

[0025] The step of detecting an obstruction may be performed only after a predefined number of puffs of the device after the first puff. The step of detecting an obstruction may be performed only after a predefined period of time after the first puff. The step of detecting an obstruction may be performed only after a predefined duration of use of the device. In each of the above cases, the device may be configured to monitor use. The predefined number of puffs, the predefined period, or the predefined period of use may be selected as corresponding to an amount of use of the device after which an obstruction is expected. This may be particularly advantageous where the obstruction detected is an agglomeration of residues of the aerosol-forming substrate caused by extended use of the device. In this way, the method may advantageously not be performed where the likelihood of an obstruction being present is very low.

[0026] The method may further include limiting power supplied to the heater assembly after an obstruction is detected until the obstruction is removed, which advantageously prevents a user from using the aerosol generation system until the obstruction is removed.

[0027] The method may further include the step of removing the obstruction. The step of removing the obstruction may include replacing the heater assembly.

[0028] The step of replacing the heater assembly may include removing the heater assembly and replacing it with a new heater assembly. As mentioned above, the obstruction may be in a portion of the airflow path passing through the heater assembly. The obstruction may be caused by a build-up of aerosol-forming substrate residues in the heater assembly itself. The new heater assembly may be free of the obstruction. In particular, the new heater assembly may be completely free of aerosol-forming substrate residues. Hence, replacing the heater assembly with a new heater assembly may advantageously remove the obstruction in the airflow path.

[0029] Alternatively, replacing the heater assembly may include removing, cleaning, and then replacing the heater assembly. Cleaning the heater assembly may include removing any obstructions.

[0030] The aerosol generation system may comprise a cartridge and an aerosol generation device. The cartridge may be configured for use with the device. For example, the device may comprise a device housing defining a cavity configured to receive at least a portion of the cartridge during use. In such an arrangement, the cartridge may advantageously be disposable and the device may be reusable.

[0031] The cartridge may include a heater assembly, in which case removing the heater assembly may include removing the cartridge from the cavity of the device, as described above, and replacing the heater assembly with a new heater assembly may include replacing the entire cartridge with a new cartridge, as described above.

[0032] The heater assembly of the cartridge may be positioned such that it is inaccessible when the cartridge is received in the cavity. The heater assembly may be positioned such that it is accessible by removing the cartridge from the cavity. Thus, after removing the cartridge from the cavity, the heater assembly may be advantageously cleaned to remove any obstructions. The cartridge with the cleaned heater assembly may then be reinserted into the cavity.

[0033] Instead of replacing the heater assembly, the step of removing the obstruction may include cleaning the heater assembly while it remains connected to the aerosol generating device. The step of cleaning the heater assembly may include supplying power to the heater assembly between user puffs. This results in heating of the heater assembly. This heating of the heater assembly may advantageously remove the obstruction. In particular, when the obstruction is caused by residue of the aerosol-forming substrate, the residue may be heated by the heater assembly. This may advantageously result in thermal decomposition of the residue. Since this heating is performed between puffs, such heating of the residue may produce a burnt tasting aerosol, but this is not a problem, since the user does not inhale the aerosol. The power supplied to the heater assembly between user puffs may be greater than the power supplied to the heater assembly during the course of a user puff.

[0034] The aerosol-forming substrate may be a liquid aerosol-forming substrate.

[0035] As used herein, the term "aerosol-forming substrate" means a substrate made of or including an aerosol-forming material capable of releasing volatile compounds upon heating to generate an aerosol.

[0036] The term "aerosol-forming material" as used herein refers to a material that has the ability to release a volatile compound when heated to generate an aerosol. The aerosol-forming substrate may comprise or be composed of an aerosol-forming material.

[0037] The aerosol-forming substrate may include an aerosol former. As used herein, the term "aerosol former" refers to any suitable compound or mixture of compounds that, when used, facilitates the formation of an aerosol, for example, a stable aerosol that is substantially resistant to thermal degradation at the operating temperature of the system. Suitable aerosol formers are well known in the art and include, but are not limited to, polyhydric alcohols (such as triethylene glycol, 1,3-butanediol, glycerin, etc.), esters of polyhydric alcohols (such as glycerol monoacetate, diacetate, or triacetate, etc.), and aliphatic esters of mono-, di-, or polycarboxylic acids (such as dimethyl dodecanedioate, dimethyl tetradecanedioate, etc.).

[0038] The aerosol-forming substrate may comprise nicotine. The aerosol-forming substrate may comprise water. The aerosol-forming substrate may comprise glycerol, also called glycerin, which has a higher boiling point than nicotine. The aerosol-forming substrate may comprise propylene glycol. The aerosol-forming substrate may comprise plant-derived material. The aerosol-forming substrate may comprise homogenized plant-derived material. The aerosol-forming substrate may comprise tobacco. The aerosol-forming substrate may comprise tobacco-containing material. The tobacco-containing material may contain volatile tobacco flavour compounds. These compounds may be released from the aerosol-forming substrate upon heating. The aerosol-forming substrate may comprise homogenized tobacco material. The aerosol-forming substrate may comprise other additives and ingredients such as flavourants.

[0039] As used herein, the term "liquid aerosol-forming substrate" is used to refer to an aerosol-forming substrate in a condensed form. Thus, a "liquid aerosol-forming substrate" may be or include one or more of a liquid, a gel, or a paste. If the liquid aerosol-forming substrate is or includes a gel or paste, the gel or paste may liquefy upon heating. For example, the gel or paste may liquefy when heated to a temperature below 50, 75, 100, 150, or 200 degrees Celsius.

[0040] The liquid aerosol-forming substrate may be contained within a liquid storage portion. The liquid storage portion may be defined by a housing of the aerosol generation system. The liquid storage portion may be defined between an inner wall and an outer wall of the housing. The aerosol-forming substrate may preferably be contained within an annular space defined between the inner wall and the outer wall. The inner wall may define an internal passage through the liquid storage portion. An airflow path may pass through the internal passage of the liquid storage portion.

[0041] The heater assembly may include a wick. The wick may be configured to draw the liquid aerosol-forming substrate towards a heater element of the heater assembly. The wick may be in fluid communication with the liquid aerosol-forming substrate stored within the liquid storage portion.

[0042] The airflow path may pass through the wick. The wick may extend across the interior passage. The wick may extend across an entrance to the interior passage.

[0043] The obstruction may be in a portion of the airflow path that passes through the wick. The obstruction may be within the wick itself. The obstruction may be caused by agglomeration of residue of the liquid aerosol-forming substrate within the wick.

[0044] The wick may be a ceramic wick. The wick may be an air permeable ceramic wick. Airflow through a portion of the airflow path through the wick may pass through pores in the air permeable ceramic wick.

[0045] The obstruction may be within the pores of the breathable ceramic wick. The obstruction may be caused by the agglomeration of residue from the aerosol-forming substrate within the heater assembly. The residue may agglomerate within the pores of the wick.

[0046] The method may advantageously be particularly sensitive when the aerosol generating device comprises a breathable ceramic wick. As mentioned above, air may pass through the pores of the wick. Because the pores may be relatively small, the accumulation of residue in each of the pores will have a relatively large effect in restricting airflow. Thus, the change in airflow characteristics may be particularly noticeable when comparing airflow through an unobstructed wick with an obstructed wick that contains residue accumulation.

[0047] The heater assembly may comprise a heating element configured to be heated when power is supplied to the heater assembly. The airflow path may pass through the heating element. The obstruction may be in a portion of the airflow path that passes through the heating element. The obstruction may be caused by agglomeration of the aerosol-forming substrate on the heating element itself. Such residue may be particularly likely to overheat or burn during heating. As such, the method of the first aspect may be particularly advantageous when the airflow path passes through a heater assembly.

[0048] The heating element may be in the form of a mesh heater. The mesh heater may comprise a plurality of conductive filaments. The conductive filaments may form a mesh with a size of 160-600 mesh US (±10%) (i.e. 160-600 filaments per inch (±10%)). It may be preferred that the gap width is 75 μm to 25 μm. The obstruction may be an obstruction within the mesh heater. The filaments of the mesh heater may provide a relatively high surface area on which residues of the aerosol-forming substrate may form. Hence, agglomeration of residues of the aerosol-forming substrate may be a particular problem for mesh heaters. Therefore, the method of the first aspect may be particularly advantageous when the airflow path passes through a mesh heater of the heater assembly.

[0049] The method may advantageously be particularly sensitive when the aerosol generating device includes a mesh heater. Air passing through the mesh heater may pass through gaps between the filaments. Because the gaps may be relatively small, the buildup of residue on each of the filaments will have a relatively large effect in restricting the airflow. Therefore, the change in airflow characteristics may be particularly noticeable when comparing airflow through an unobstructed mesh heater to an obstructed mesh heater that includes residue buildup.

[0050] The airflow characteristic measured by the at least one sensor may be any airflow characteristic that changes in response to the presence of a restriction in the airflow path. Preferably, the airflow characteristic may be a fluid mechanical characteristic. More preferably, the airflow characteristic may be a pressure, a flow velocity, or a volumetric flow rate. The airflow characteristic may also be a differential airflow characteristic. Preferably, the airflow characteristic may be a differential pressure. Other suitable airflow characteristics include environmental characteristics. For example, the temperature or humidity of the air flowing through the airflow path may also be affected by the obstruction.

[0051] The at least one sensor may comprise a sensor for measuring a fluid mechanical property. Preferably, the at least one sensor may comprise a pressure sensor, a flow rate sensor, or a volume sensor. The one or more sensors may include a temperature sensor or a humidity sensor. The sensor may be a MEMS sensor.

[0052] The aerosol generating system may comprise at least a first sensor. The first sensor may be downstream of the heater assembly. It may be advantageous to locate the first sensor downstream of the heater assembly, since the effect of an obstacle on the airflow characteristics may be greater downstream of the obstacle than upstream of the obstacle. This may advantageously mean that the obstacle can be detected more accurately. While the first sensor is downstream of the heater assembly, the closer it is to the heater assembly, the more the airflow characteristics may be affected by an obstacle in the heater assembly. Again, this may advantageously mean that the obstacle can be detected more accurately. The first sensor may be less than 5 centimeters from the heater assembly, preferably less than 4 centimeters from the heater assembly, preferably less than 3 centimeters from the heater assembly, preferably less than 2 centimeters from the heater assembly.

[0053] As used herein, the terms "upstream" and "downstream" are used to describe the relative position of an element or portion of an element of an aerosol generation system or cartridge with respect to the direction in which a user draws on the aerosol generation system or cartridge during use of the aerosol generation system or cartridge.

[0054] The first sensor may be the only sensor.

[0055] The aerosol generating system may preferably comprise at least a first sensor downstream of the heater assembly and a second sensor upstream of the heater assembly. In this case, the value measured during the user puff may advantageously be a differential value. For example, if the first and second sensors are pressure sensors, the value measured during the user puff may be a differential pressure measurement. A differential pressure measurement may advantageously be more reliable than a single pressure measurement. A differential pressure measurement may more accurately identify an obstruction, since it may eliminate factors that affect the measurements of both the first and second sensors. For example, factors such as puff intensity fluctuations and noise may be detected by both the first and second sensors, but may be eliminated when the difference between the measurements of these sensors is determined.

[0056] The magnitude of the pressure difference may be increased when the airflow path includes an obstruction within the heater assembly compared to when the airflow path does not include the obstruction because the obstruction may cause a pressure drop in the portion of the airflow path that passes through the heater assembly, which may be detected by first and second sensors located on opposite sides of the heater assembly.

[0057] The step of measuring a value associated with the airflow characteristic may include calculating a difference between a signal from the first sensor and a signal from the second sensor, whereby a differential value may be calculated.

[0058] The method may further comprise determining the predetermined value during a threshold determination step involving one or more user puffs. Determining the predetermined value during the threshold determination step may advantageously mean that the predetermined value may be user specific, rather than a value set during manufacture. Different users may have different puff characteristics when using the aerosol generating system. For example, a first user may typically have a stronger puff strength than a second user. This means that the same predetermined value for a first user may not be suitable for a second user. Using an inappropriate predetermined value for the airflow characteristics may result in an inaccurate detection of an obstacle when one is not actually present, or a failure to detect an obstacle when one is actually present. By determining the predetermined value during the threshold determination step, the predetermined value may advantageously be selected to complement the user, which may advantageously improve the accuracy of the method.

[0059] Determining the predetermined value may include measuring a value associated with a characteristic of the air during the course of each user puff during the threshold determination stage. The predetermined value may be determined based on one or more measurements.

[0060] The threshold determination step may involve more than one puff, and the predetermined value may be determined based on an average of the measurements from each puff of the threshold determination step.

[0061] The threshold determination step may involve two, three or four puffs. Preferably, the threshold determination step involves five puffs.

[0062] The first puff of the threshold determination step may be triggered when a user puffs on the aerosol generating system for the first time. In other words, the first puff of the threshold determination step may represent the first use of the heater assembly. This may be advantageous when the obstruction is caused by agglomeration of aerosol-forming substrate residue, since it means that the measurements during each puff of the threshold determination step represent the value of the airflow characteristics when the airflow path is unobstructed and contains minimal aerosol-forming substrate residue.

[0063] Alternatively or additionally, the user may trigger the threshold determination step at a later time. The aerosol generation system may preferably be provided with a user interface that the user may use to trigger the threshold determination step. This may advantageously allow the predetermined value to be modified during use of the aerosol generation system. This may be advantageous, for example, when the aerosol generation is being used by a different user whose typical puff profile differs from that of a previous user. The threshold determination step may include one or more subsequent puffs.

[0064] Alternatively, the threshold determination step may include the last one or more puffs, in which case the aerosol generating system may maintain a record of measurements of the airflow characteristics during each puff stored in a memory of the electrical circuitry of the aerosol generating system, and the predetermined value may be determined based on the stored values.

[0065] Method steps relating to detecting obstructions in the airflow path may not be performed during the threshold determination stage.

[0066] As mentioned above, the predetermined value may be the value of the airflow characteristics in normal use, with no obstructions in the airflow path. In that case, the predetermined value may be determined directly from measurements of the airflow characteristics during the threshold determination step. For example, if the predetermined value is based on an average of measurements from each puff in the threshold determination step, the predetermined value may be equal to the average.

[0067] Alternatively, as discussed above, the predetermined value may be a predetermined threshold, in which case the step of determining the predetermined value as the predetermined threshold may further include converting a measurement or an average measurement calculated over two or more puffs to the predetermined threshold.

[0068] The conversion may include increasing or decreasing the measurement or average measurement by a predetermined amount. The predetermined amount may correspond to a pressure of 60-160 Pa. Preferably, the predetermined amount may correspond to a pressure of 80-150 Pa. The conversion may include decreasing the average of the measurement if the measurement represents a pressure. The conversion may include increasing the average of the measurement if the measurement represents a differential pressure or flow rate.

[0069] The conversion may include increasing or decreasing the average value by a scale factor. The scale factor may be predetermined. The scale factor may be a factor by which the intermediate value is multiplied to arrive at a pre-defined threshold. The scale factor may advantageously be selected to represent the amount by which the airflow characteristic typically increases or decreases as a result of an obstruction compared to an airflow characteristic without the obstruction.

[0070] In a second aspect, an aerosol generation system is provided. The aerosol generation system may comprise a heater assembly for heating an aerosol-forming substrate. The aerosol generation system may comprise a power source. The aerosol generation system may comprise an airflow path. The airflow path may be defined between an air inlet and an air outlet. The airflow path may pass through the heater assembly. The aerosol generation system may comprise at least one sensor for sensing airflow characteristics of air in the airflow path.

[0071] The aerosol generation system may comprise an electrical circuit. The electrical circuit may comprise a memory. The electrical circuit may be connected to the heater assembly and to a power source. The electrical circuit may be configured to measure a value associated with the airflow characteristics during the course of a user puff. The electrical circuit may be configured to base the measurement on a signal from the at least one sensor. The electrical circuit may be configured to compare the measurement to a predetermined value.

[0072] The electrical circuitry may be configured to detect an obstruction in the airflow path based on the comparison. The electrical circuitry may be configured to limit power supplied to the heater assembly if an obstruction is detected until the obstruction is removed.

[0073] The advantages of detecting an obstruction based on comparing measurements associated with airflow characteristics to predetermined values ​​have already been discussed in relation to the first aspect, and the same advantages apply to the second aspect.

[0074] Furthermore, other features discussed in relation to the first aspect in relation to the method also apply to the second aspect in relation to the system.

[0075] The electrical circuit may be configured to carry out the method of the first aspect.

[0076] The power source may be a battery. The battery may be a rechargeable battery. The power source may be configured to provide power to the heater assembly.

[0077] The aerosol-forming system may comprise an aerosol-forming substrate. The aerosol-forming substrate may be a liquid aerosol-forming substrate. The liquid aerosol-forming substrate may be contained within a liquid storage portion. The liquid storage portion may be defined by a housing of the aerosol generation system. The liquid storage portion may be defined between an inner wall and an outer wall of the housing. The aerosol-forming substrate may preferably be contained within an annular space defined between the inner wall and the outer wall. The inner wall may define an internal passage through the liquid storage portion. An airflow path may pass through the internal passage of the liquid storage portion.

[0078] The aerosol-forming substrate may be adsorbed, coated, impregnated or otherwise loaded onto a carrier or support. In one embodiment, the aerosol-forming substrate is a liquid substrate held within a capillary material. The capillary material may have a fibrous or spongy 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 be generally aligned to carry the liquid to the heater. 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 can move 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, expanded metal or plastic materials, fibrous materials, such as fibrous materials made of spun or extruded fibers (such as cellulose acetate, polyester, or bonded polyolefin, polyethylene, terylene or polypropylene fibers, nylon fibers or ceramics). The capillary material may have any suitable capillary action and porosity to be used with different liquid physical properties. The liquid has physical properties including, but not limited to, viscosity, surface tension, density, thermal conductivity, boiling point, and vapor pressure that allow the liquid to be moved through the capillary material by capillary action. The capillary material may be configured to carry the aerosol-forming substrate to the heater assembly.

[0079] The capillary material may be contained in the liquid storage portion. The capillary material may fill the liquid storage portion.

[0080] The heater assembly may include a wick. The wick may be configured to draw the liquid aerosol-forming substrate towards a heater element of the heater assembly. The wick may be in fluid communication with the liquid aerosol-forming substrate stored within the liquid storage portion.

[0081] The airflow path may pass through the wick. The wick may extend across the interior passage. The wick may extend across an entrance to the interior passage.

[0082] The obstruction may be in a portion of the airflow path that passes through the wick. The obstruction may be within the wick itself. The obstruction may be caused by agglomeration of residue of the liquid aerosol-forming substrate within the wick.

[0083] The core may be an air permeable ceramic core. Airflow through a portion of the airflow path through the core may pass through pores in the air permeable ceramic core.

[0084] The obstruction may be within the pores of the breathable ceramic wick. The obstruction may be caused by the agglomeration of residue from the aerosol-forming substrate within the heater assembly. The residue may agglomerate within the pores of the wick.

[0085] The heater assembly may include a heating element configured to be heated when electrical power is supplied to the heater assembly.

[0086] The airflow path may pass through the heating element. The obstruction may be in a portion of the airflow path that passes through the heating element. The obstruction may be caused by agglomeration of the aerosol-forming substrate on the heating element itself.

[0087] The heating element may be configured to heat the ceramic wick in use. This may result in heating and vaporization of the aerosol-forming substrate contained within the ceramic wick. The heating element may be in contact with the ceramic wick. Heat may be conducted from the heating element to the ceramic wick. Alternatively, or additionally, the heating element may be configured to draw the aerosol-forming substrate from the wick. The heating element may then be configured to directly heat the aerosol-forming substrate. The heating element may be in the form of a conductive track on the wick. The heating element track may be printed on the wick.

[0088] The heating element may preferably be in the form of a mesh, which may be configured such that the aerosol-forming substrate is drawn into the gaps between the filaments of the mesh, which may advantageously provide more efficient heating of the aerosol-forming substrate by the heating element.

[0089] The heater element of the heater assembly may be a resistively heatable heating element. The power source may be configured to supply power to the heating element to resistively heat it. The heating element may include or be formed from any material having suitable electrical and mechanical 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 composites made of ceramic and metallic materials. Such composites may include doped or undoped ceramics. Examples of suitable doped ceramics include doped silicon carbide. Examples of suitable metals include titanium, zirconium, tantalum, and platinum group metals. 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, and nickel, iron, cobalt, 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 wire may be coated with one or more electrical insulators. Preferred materials may be 304, 316, 304L, 316L stainless steel, and graphite.

[0090] The heater element may be a susceptor element. As used herein, "susceptor element" means an electrically conductive element that heats up when subjected to a fluctuating magnetic field. This may be the result of eddy currents and / or hysteresis losses induced in the susceptor element. Possible materials for the susceptor element include graphite, molybdenum, silicon carbide, stainless steel, niobium, aluminum, and virtually any other electrically conductive 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.

[0091] The heater assembly comprising a susceptor element as a heating element may further comprise an inductor coil. The susceptor element may be positioned relative to the inductor coil such that the susceptor element is heated when a high frequency oscillating current is passed through the inductor coil. The power supply of the aerosol generation system may be configured to provide an alternating current to the inductor coil.

[0092] The aerosol generation system may include at least a first sensor for sensing airflow characteristics of the air in the airflow path. The first sensor may be downstream of the heater assembly.

[0093] The first sensor may be the only sensor.

[0094] The aerosol generation system may preferably include at least a first sensor downstream of the heater assembly and a second sensor upstream of the heater assembly, in which case the electrical circuit may be configured to calculate a difference between the signals from the first and second sensors as part of measuring the value associated with the airflow characteristic, whereby a differential value may be calculated.

[0095] The obstruction may be in a portion of the airflow path through the heater assembly. The obstruction may be caused by agglomeration of residue of the aerosol-forming substrate within the heater assembly.

[0096] The predetermined value may be the value of the airflow characteristic in normal use, where there are no obstructions in the airflow path. The predetermined value may represent the value of the airflow characteristic in initial use of the aerosol generation system. The comparison with the predetermined value may include an electrical circuit configured to calculate the difference between the predetermined value and the measured value. As will be appreciated, whether the difference is positive or negative depends on the airflow characteristic, the set-up of the at least one sensor, and the order of calculation.

[0097] The electrical circuit may be configured to detect an obstruction when the magnitude of the difference exceeds a predetermined limit. An obstruction may be detected when the magnitude of the difference between the predetermined value and the measured value exceeds a predetermined limit. The predetermined limit may correspond to a pressure of 60-160 Pa. Preferably, the predetermined limit may correspond to a pressure of 80-150 Pa.

[0098] Alternatively, the predetermined value may be a predetermined threshold. The predetermined threshold may represent a value of the airflow characteristic that is indicative of an obstructed airflow path. The electrical circuitry may be configured to directly compare the measurement to the predetermined threshold.

[0099] The electrical circuitry may be further configured to determine a predetermined value during a threshold determination stage involving one or more user puffs. The electrical circuitry may be configured to measure a value associated with a characteristic of the air during the course of each user puff during the threshold determination stage. The predetermined value may be determined based on the one or more measurements.

[0100] The threshold determination step may involve more than one puff, and the predetermined value may be determined based on an average of the measurements from each puff of the threshold determination step.

[0101] The threshold determination step may involve two, three or four puffs. Preferably, the threshold determination step involves five puffs.

[0102] The electrical circuitry may be configured such that the threshold determination phase begins the first time a user takes a puff on the aerosol generating system, in other words, the first puff of the threshold determination phase may represent the first use of the heater assembly.

[0103] Alternatively or additionally, the electrical circuitry may be configured to allow a user to initiate the threshold determination step at a later time.Preferably, the aerosol generating system may comprise a user interface that a user may use to trigger the threshold determination step.

[0104] The threshold determination step may include the next puff or puffs. Alternatively, the threshold determination step may include the last puff or puffs. In this case, the electrical circuitry may be configured to maintain a record of measurements of the airflow characteristics during each puff stored in a memory of the electrical circuitry of the aerosol generation system. The predetermined value may be determined based on the stored values.

[0105] As mentioned above, the predetermined value may be the value of the airflow characteristic in normal use, with no obstructions in the airflow path. In that case, the electrical circuitry may be configured to determine the predetermined value directly from measurements of the airflow characteristic during the threshold determination step. For example, if the predetermined value is based on an average of measurements from each puff during the threshold determination step, the predetermined value may be equal to the average.

[0106] Alternatively, as discussed above, the predetermined value may be a predetermined threshold, in which case the circuitry may be configured to convert an average of the measurements from each of the threshold determination steps into a threshold value.

[0107] The conversion may include increasing or decreasing the average of the measurements by a predetermined amount. The predetermined amount may correspond to a pressure of 60-160 Pa. Preferably, the predetermined amount may correspond to a pressure of 80-150 Pa. The conversion may include decreasing the average of the measurements if the measurements represent pressure. The conversion may include increasing the average of the measurements if the measurements represent differential pressure or flow rate.

[0108] The conversion may include increasing or decreasing the average value by a scale factor. The scale factor may be predetermined. The scale factor may be a factor by which the intermediate value is multiplied to arrive at a pre-defined threshold. The scale factor may advantageously be selected to represent the amount by which the airflow characteristic typically increases or decreases as a result of an obstruction compared to an airflow characteristic without the obstruction.

[0109] The obstruction may be removed by replacing the heater assembly. Replacing the heater assembly may include removing the heater assembly and replacing it with a new heater assembly. Alternatively, replacing the heater assembly may include removing, cleaning, and then replacing the heater assembly.

[0110] Alternatively, the step of removing the obstruction may include cleaning the heater assembly while it remains connected to the aerosol generating device. In such a case, the electrical circuit may be configured to provide power to the heater assembly between user puffs. The power provided to the heater assembly between user puffs may be greater than the power provided to the heater assembly during the course of a user puff. The obstruction may be caused by residue of the aerosol-forming substrate. The power provided may be sufficient to heat the heater assembly high enough to cause thermal decomposition of the residue.

[0111] The aerosol generation system may comprise a cartridge and an aerosol generation device. The cartridge may be configured for use with the device. For example, the device may comprise a device housing defining a cavity configured to receive at least a portion of the cartridge during use. In such an arrangement, the cartridge may advantageously be disposable and the device may be reusable. The power source may be configured to provide power to the heater assembly only when the cartridge is engaged with the aerosol generation device.

[0112] The cartridge may comprise at least a portion of the heater assembly. Preferably, the cartridge may include a heater element of the heater assembly. When the heater assembly comprises both a susceptor element and an inductor coil, the cartridge may comprise at least the susceptor element. The cartridge may further comprise an inductor coil.

[0113] Alternatively, the aerosol generating device may include an inductor coil. The cartridge and the aerosol generating device may be configured such that when the cartridge is received by the device, the susceptor is positioned such that it is heated by the inductor coil to generate the aerosol.

[0114] The cartridge may comprise an aerosol-forming substrate. When the aerosol-forming substrate is a liquid aerosol-forming substrate contained in a liquid storage portion, the cartridge may include a liquid storage portion. The housing defined in the liquid storage portion may be a cartridge housing.

[0115] The aerosol generating device may include a power source.

[0116] The air outlet of the airflow path may be defined in a mouthpiece portion of the aerosol generation system. The cartridge may comprise the mouthpiece. In use, when the cartridge is engaged with the aerosol generation device, a user may inhale at the mouthpiece of the cartridge. This may cause air to flow through the air inlet and then across, over, through or through the heater assembly or heating element before passing through the air outlet.

[0117] Below is provided a non-exhaustive list of non-limiting examples, any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

[0118] [Example] Example 1. 1. A method for detecting the presence of an obstruction in an airflow path of an aerosol generating system, the system comprising: a heater assembly for heating an aerosol-forming substrate; a power source; an airflow path defined between an air inlet and an air outlet and passing through the heater assembly; and at least one sensor for sensing an airflow characteristic of air in the airflow path, the method comprising: determining a value associated with the airflow characteristic during the course of a user puff based on signals from the at least one sensor; comparing the measured value with a predetermined value; detecting an obstruction in the airflow path based on the comparison; and limiting power supplied to the heater assembly or providing an indication if an obstruction is detected. Example 2. The method of example 1, wherein the obstruction is within a portion of the airflow path through the heater assembly. Example 3. The method of any one of the preceding claims, wherein the obstruction is caused by agglomeration of residue of the aerosol-forming substrate within the heater assembly. Example 4. The method according to any one of the preceding claims, wherein the predetermined value is a value of the airflow characteristic in normal use, without any obstructions in the airflow path. Example 5. The method according to any one of the preceding claims, wherein the predetermined value represents a value of the airflow characteristic at the first use of the aerosol generating system. Example 6. 6. The method according to any one of claims 1 to 5, wherein the comparison with the predetermined value comprises calculating the difference between the predetermined value and the measured value. Example 7. 7. The method of example 6, wherein an obstruction is detected when the magnitude of the difference between the predetermined value and the measured value exceeds a predetermined limit. Example 8. 8. The method according to embodiment 7, wherein the predetermined limit corresponds to a pressure of 60 to 160 Pa. Example 9. A method according to any one of the preceding claims, wherein the predetermined value is a predetermined threshold value representing a value of the airflow characteristic when the airflow path is obstructed. Example 10. The method of example 9, wherein the comparison of the measured value with the predefined threshold is a direct comparison. Example 11. The method of example 19, wherein an obstacle is detected if the measured value is the same as a predetermined threshold, or an airflow characteristic that decreases in response to an obstacle is detected if the measured value is less than the predetermined threshold, or an airflow characteristic that increases in response to an obstacle is detected if the measured value is greater than the predetermined threshold. Example 12. 12. The method of any one of claims 1-11, further comprising limiting the power supplied to the heater assembly after an obstruction is detected until the obstruction is removed. Example 13. The method according to any one of Examples 1 to 12, further comprising removing the obstruction. Example 14. 14. The method of example 13, wherein removing the obstruction comprises replacing the heater assembly. Example 15. 15. The method of example 14, wherein the step of replacing the heater assembly includes removing the heater assembly and replacing it with a new heater assembly. Example 16. The method of example 14, wherein the step of replacing the heater assembly includes removing, cleaning, and then replacing the heater assembly. Example 17. 17. The method of example 16, wherein cleaning the heater assembly comprises removing obstructions. Example 18. The method of any one of Examples 13 to 17, wherein the aerosol generation system comprises a cartridge and an aerosol generation device, the cartridge being configured for use with the device and comprising a heater assembly, and the step of removing the heater assembly comprises removing the cartridge from the cavity of the device. Example 19. 14. The method of example 12 or 13, wherein removing the obstruction comprises cleaning the heater assembly while the heater assembly remains connected to the aerosol generating device. Example 20. 20. The method of example 19, wherein the heater assembly is powered between user puffs. Example 21. 21. The method of example 20, wherein the power supplied to the heater assembly between user puffs is greater than the power supplied to the heater assembly during the course of a user puff. Example 22. The method according to any one of Examples 1 to 21, wherein the aerosol-forming substrate is a liquid aerosol-forming substrate. Example 23. The method of example 22, wherein the liquid aerosol-forming substrate is contained within a liquid reservoir defined by a housing of the aerosol generating system. Example 24. 24. The method of example 23, wherein the liquid reservoir is defined between an inner wall and an outer wall of the housing. Example 25. 25. The method of example 24, wherein the interior wall defines an interior passageway through the liquid storage portion, and the airflow path passes through the interior passageway. Example 26. The method of any one of examples 1-25, wherein the heater assembly comprises a wick configured to draw the liquid aerosol-forming substrate towards a heater element of the heater assembly. Example 27. The method of example 26, wherein the airflow path passes through the wick. Example 28. The method of example 27, wherein the liquid aerosol-forming substrate is contained within a liquid storage portion defined between inner and outer walls of a housing of the aerosol generating system, the inner wall defining an internal passage through the liquid storage portion through which the airflow path passes, and the wick extending across the internal passage. Example 29. The method of example 28, wherein the wick extends across an entrance to the internal passageway. Example 30. 30. The method of any one of Examples 1-29, wherein the heater assembly comprises a heating element configured to heat when power is supplied to the heater assembly, and the airflow path may pass through the heating element. Example 31. The method of example 30, wherein the heating element is in the form of a mesh heater. Example 32. The method according to any one of the preceding embodiments, wherein the airflow property is a fluid-mechanical property such as pressure, flow rate, or volume. Example 33. The method of any one of Examples 1-32, wherein the at least one sensor comprises a sensor for measuring a fluid mechanical property, such as a pressure sensor, a flow rate sensor, or a volume sensor. Example 34. The method of any one of Examples 1 to 33, wherein the aerosol generation system comprises at least a first sensor downstream of the heater assembly. Example 35. The method of example 34, wherein the first sensor is less than 5 centimeters from the heater assembly, preferably less than 4 centimeters from the heater assembly, preferably less than 3 centimeters from the heater assembly, preferably less than 2 centimeters from the heater assembly. Example 36. The method of example 34 or 35, wherein the first sensor is the only sensor. Example 37. The method of any one of Examples 1-35, wherein the aerosol generation system comprises at least a first sensor downstream of the heater assembly and a second sensor upstream of the heater assembly. Example 38. 38. The method of example 37, wherein the step of measuring a value associated with the airflow characteristic comprises calculating a difference between the signal from the first sensor and the signal from the second sensor. Example 39. The method according to any one of Examples 1 to 38, wherein the method further comprises determining a predetermined value during a threshold determination stage comprising one or more user puffs. Example 40. The method of Example 39, wherein the step of determining the predetermined value includes measuring a value associated with a characteristic of the air during the course of each user puff during the threshold determination stage. Example 41. The method of example 39 or 40, wherein the threshold determination step comprises two or more puffs. Example 42. The method of Example 41, wherein the predetermined value is determined based on an average of measurements from each puff during the threshold determination step. Example 43. A method according to any one of Examples 39 to 42, wherein the first puff of the threshold determination step is triggered when a user puffs on the aerosol generation system for the first time. Example 44. A method according to any one of Examples 39 to 43, wherein the first puff of the threshold determination step is triggered by a user at any time. Example 45. The method of example 44, wherein the aerosol generating system comprises a user interface that a user can use to trigger the threshold determination step. Example 46. The method of example 44 or 45, wherein the threshold determination step comprises one or more of the following puffs: Example 47. The method of example 44 or 45, wherein the threshold determination step includes the last one or more puffs. Example 48. The method according to any one of Examples 39 to 47, wherein the predetermined value is determined directly from measurements of the airflow characteristics during the threshold determination step. Example 49. The method of any one of Examples 39 to 47, wherein the predetermined value is a predetermined threshold, and the step of determining the predetermined value as the predetermined threshold further comprises converting a measurement value or an average measurement value calculated over two or more puffs to the predetermined threshold value. Example 50. 50. The method of example 49, wherein the transformation comprises increasing or decreasing the measurement or average measurement by a predetermined amount. Example 51. 51. The method of claim 50, wherein the predetermined amount corresponds to a pressure of 60 to 160 Pa. Example 52. 52. The method of claim 51, wherein the predetermined amount corresponds to a pressure of 80 to 150 Pa. Example 53. 1. An aerosol generation system comprising: a heater assembly for heating the aerosol-forming substrate; Power supply, an airflow path defined between the air inlet and the air outlet, the airflow path passing through the heater assembly; at least one sensor for sensing an airflow characteristic of the air in the airflow path; an electrical circuit comprising a memory, connected to the heater assembly and to a power source, the electrical circuit being configured to measure a value associated with the airflow characteristic during the course of a user puff based on signals from the at least one sensor, and to compare the measurement to a predetermined value; An aerosol generation system, wherein the electrical circuit is configured to detect an obstruction in the airflow path based on the comparison, and configured to limit the power supplied to the heater assembly if an obstruction is detected until the obstruction is removed. Example 54. The aerosol generation system of Example 53, wherein the electrical circuit is configured to carry out the method of any one of Examples 1 to 52. Example 55. 55. The aerosol-generating system of Example 53 or 54, further comprising an aerosol-forming substrate. Example 56. 56. The aerosol-generating system of Example 55, wherein the aerosol-forming substrate is a liquid aerosol-forming substrate. Example 57. 57. The aerosol generating system of Example 56, wherein the liquid aerosol-forming substrate contains a liquid storage portion. Example 58. An aerosol generation system as described in Example 57, wherein the liquid storage portion is defined between an inner wall and an outer wall of the housing of the aerosol generation system. Example 59. 59. The aerosol-generating system of Example 58, wherein the aerosol-forming substrate is contained within an annular space defined between the inner wall and the outer wall. Example 60. 60. An aerosol generation system as described in Example 58 or 59, wherein the inner wall defines an internal passage through the liquid storage portion. Example 61. An aerosol generation system described in any one of Examples 57 to 60, further comprising a capillary material filling the liquid storage portion. Example 62. An aerosol generating system described in any one of Examples 53 to 61, wherein the heater assembly includes a wick configured to draw the liquid aerosol-forming substrate towards a heater element of the heater assembly. Example 63. 63. The aerosol generation system of Example 62, wherein the airflow path passes through the wick. Example 64. An aerosol generation system as described in Example 63, wherein the obstacle is within a portion of the airflow path through the wick. Example 65. An aerosol generating system according to any one of Examples 62 to 64, wherein the wick is a breathable ceramic wick. Example 66. An aerosol generation system described in any one of Examples 53 to 65, wherein the heater assembly comprises a heating element configured to heat when power is supplied to the heater assembly. Example 67. An aerosol generation system as described in Example 66, wherein the heater element of the heater assembly may be a resistively heatable heating element. Example 68. 67. The aerosol generating system of Example 66, wherein the heater element is a susceptor element. Example 69. 69. The aerosol generation system of example 68, further comprising an inductor coil. Example 70. An aerosol generation system described in any one of Examples 53 to 69, comprising a first sensor downstream of the heater assembly. Example 71. An aerosol generation system described in any one of Examples 53 to 70, comprising a first sensor downstream of the heater assembly and a second sensor upstream of the heater assembly. Example 72. An aerosol generation system as described in Example 71, wherein the electrical circuit is configured to calculate the difference between the signals from the first sensor and the second sensor as part of measuring a value associated with the airflow characteristic. Example 73. An aerosol generation system described in any one of Examples 53 to 72, wherein the predetermined value is a value of the airflow characteristic during normal use when there are no obstacles in the airflow path. Example 74. An aerosol generation system described in any one of Examples 53 to 73, wherein the comparison with the predetermined value includes an electrical circuit configured to calculate the difference between the predetermined value and the measured value. Example 75. An aerosol generation system as described in Example 74, wherein the electrical circuit is configured to detect an obstruction when the magnitude of the difference exceeds a predetermined limit. Example 76. 76. The aerosol generating system of Example 75, wherein the predetermined limit corresponds to a pressure of 60 to 160 Pa. Example 77. 77. The aerosol generating system of Example 76, wherein the predetermined limit corresponds to a pressure of 80 to 150 Pa. Example 78. An aerosol generation system described in any one of Examples 53 to 72, wherein the predetermined value is a predetermined threshold value representing the value of the airflow characteristic when the airflow path is obstructed. Example 79. An aerosol generation system as described in Example 78, wherein the electrical circuit is configured to directly compare the measurement value with a predetermined threshold value. Example 80. An aerosol generation system described in any one of Examples 53 to 79, wherein the electrical circuit is configured to determine a predetermined value during a threshold determination stage including one or more user puffs. Example 81. An aerosol generation system as described in the embodiment described in Example 80, wherein the electrical circuit is configured to measure a value associated with a characteristic of the air during the course of each user puff during the threshold determination stage. Example 82. An aerosol generation system as described in Example 81, wherein the threshold determination step includes two or more puffs, and the predetermined value is determined based on an average of the measurements from each puff during the threshold determination step. Example 83. An aerosol generating system as described in Example 82, wherein the threshold determination step includes two, three, or four puffs. Example 84. The aerosol generating system of Example 82, wherein the threshold determination step comprises five puffs. Example 85. An aerosol generation system described in any one of Examples 80 to 84, wherein the electrical circuit is configured such that the threshold determination step begins when a user first inhales the aerosol generation system. Example 86. An aerosol generation system described in any one of Examples 80 to 85, wherein the electrical circuit is configured to allow a user to later initiate the threshold determination step. Example 87. An aerosol generation system described in any one of Examples 80 to 86, wherein the electrical circuit is configured to determine the predetermined value directly from the measurement of the airflow characteristics during the threshold determination step. Example 88. An aerosol generation system described in any one of Examples 80 to 86, wherein the predetermined value is a predetermined threshold value and the electrical circuit is configured to convert the measurement value from a single puff of the smoke or each puff of the threshold determination step to a threshold value. Example 89. An aerosol generating system as described in Example 88, wherein the conversion includes increasing or decreasing the average of the measurement value by a predetermined amount. Example 90. The aerosol generating system of Example 89, wherein the predetermined amount corresponds to a pressure of 60 to 160 Pa. Example 91. 91. The aerosol generating system of Example 90, wherein the predetermined volume corresponds to a pressure of 80 to 150 Pa. Example 92. An aerosol generation system according to any one of Examples 53 to 91, comprising a cartridge and an aerosol generation device, the cartridge being configured for use with the device. Example 93. 93. The aerosol generation system of Example 92, wherein the cartridge comprises at least a portion of the heater assembly. Example 94. An aerosol generation system as described in Example 93, wherein the cartridge comprises a heater element of the heater assembly. Example 95. An aerosol generation system as described in Example 93 or 94, wherein the heater assembly comprises a susceptor element and an inductor coil as a heater element, and the cartridge comprises the susceptor element. Example 96. An aerosol generation system as described in Example 95, wherein the cartridge further comprises an inductor coil. Example 97. 96. The aerosol generation system of Example 95, wherein the aerosol generation device comprises an inductor coil. Example 98. 98. The aerosol generating system according to any one of Examples 92 to 97, wherein the aerosol generating device is equipped with a power source.

[0119] Features described with respect to one example or embodiment may also be applicable to other examples and embodiments.

[0120] The embodiments will now be further described with reference to the figures.

[0121] Fig. 1 shows a schematic cross-sectional view of an aerosol generation system 100 according to a first embodiment of the present disclosure. The system comprises a cartridge 200 and an aerosol generation device 300. As shown in Fig. 1, a portion of the cartridge 200 is received in a cavity of the device 300. The cartridge 200 is removable from the cavity of the device 300.

[0122] The cartridge 200 includes a heater assembly 202 that includes a resistive heater element 204 and a ceramic wick 206. The resistive heater element 204 is in the form of a conductive track printed on the ceramic wick 206. The resistive heater element 204 is formed of a conductive material that is configured to heat when an electrical current is passed through it. The ceramic wick 206 is breathable.

[0123] The cartridge 200 further comprises a liquid storage portion 208 containing a liquid aerosol-forming substrate 210. The liquid storage portion 208 is defined by a cartridge housing. The cartridge housing comprises an inner wall 211 and an outer wall 212, with the liquid storage portion 208 being defined between the inner wall 211 and the outer wall 212. The liquid storage portion 208 is annular. The inner wall 211 further defines an interior passageway 214 on an opposite side of the inner wall 211 to the liquid aerosol-forming substrate 210.

[0124] The heater assembly 202 is positioned at an end of the cartridge 200 such that a ceramic wick 206 of the heater assembly 202 extends across the interior passageway 214. The ceramic wick 206 also extends into an end portion of the liquid storage portion 208.

[0125] The ceramic wick 206 is configured to draw the liquid aerosol-forming substrate 210 from the liquid reservoir 208. This has the effect of drawing the liquid aerosol-forming substrate 210 towards the heater element 204.

[0126] The aerosol generating device 300 comprises a power source in the form of a rechargeable battery 302 and an electrical circuit 304 that comprises a microcontroller, not shown.

[0127] Both the cartridge 200 and the aerosol generating device 300 include electrical contacts, not shown. The electrical contacts of the aerosol generating device 300 are electrically connectable to the battery 302. The electrical contacts of the cartridge 200 are electrically connected to the heater element 204. The electrical contacts of the cartridge 200 are configured to contact the electrical contacts of the aerosol generating device 300 when the cartridge 200 is received in a cavity of the device 300, as shown in FIG. 1. In this manner, power from the battery 302 can be supplied to the heater element 304 such that the heater element 304 is heated. The supply of power from the battery 302 to the heater element 304 is controlled by the electrical circuit 304. In particular, the electrical circuit 304 is configured to normally supply power to the heater element 304 during a puff, but prevents power supply if an obstruction is detected, as described below.

[0128] When the cartridge 200 is received in the cavity of the aerosol generating device 300, an airflow path is defined through the aerosol generating system from the air inlet 218 to the air outlet 306. The air inlet 218 is defined in the housing of the aerosol generating device. The air outlet 306 is defined in the housing of the cartridge 200. The airflow path passes from the air inlet 218 into a channel defined in the aerosol generating device 300 and then into the cavity. From there, the airflow path passes through the heater assembly 202. In particular, the airflow path passes between the tracks of the heater element 204 and then through the breathable ceramic wick 206. After the heater assembly 202, the airflow path passes through the internal passageway 214 of the cartridge 200 before terminating at the air outlet 306. The portion of the cartridge that includes the air outlet 306 may be referred to as the mouthpiece.

[0129] The path of air through the airflow pathway is indicated by the arrows shown in Figure 1. This is the path that air flows through the aerosol generation system 100 when a user of the system draws on the mouthpiece of the cartridge 200.

[0130] The cartridge 200 further comprises a first sensor 216, a portion of which is positioned in the airflow path downstream of the heater assembly 202. The first sensor 216 is a pressure sensor and is adapted to measure the pressure of the air in that portion of the airflow path. The distance between the first sensor 216 and the heater assembly is less than 2 centimeters. The first sensor 216 is a low voltage barometric pressure sensor (MS5637-02BA03) available from Digi-key electronics (https: / / www.digikey.com / ).

[0131] When a user puffs on the aerosol generating system, the electrical circuitry 304 is configured to provide power to the heater element 204 such that the heater element 204 is heated. The heater element 204 is in contact with the ceramic wick 206 such that heat from the heater element 204 is conducted to the ceramic wick 206 and then to the aerosol-forming substrate contained in the ceramic wick 206. This aerosol-forming substrate is then vaporized and drawn into the air passing through the ceramic wick 206 as the user draws on the mouthpiece. The vaporized substrate cools and condenses to form an aerosol within the interior passageway 214, which may then be inhaled by the user. The ceramic wick 206 continuously draws fresh aerosol-forming substrate from a liquid reservoir providing a continuous supply of substrate to be vaporized by the heater assembly.

[0132] The aerosol-forming substrate within the ceramic wick 206 is not necessarily completely vaporized. After a puff, a small amount of aerosol-forming substrate residue may remain within the heater assembly 202. Over time, this residue may agglomerate and create an obstruction in the airflow path. In particular, the residue may agglomerate within the ceramic wick 206 and within the heater element 204, creating an obstruction in a portion of the airflow path through the heater assembly 202.

[0133] Figure 2 is a schematic cross-sectional view of the ceramic wick 206 of the aerosol generating system 100, shown alone, separate from the rest of the system. Figure 2a shows the ceramic wick 206 without any agglomerated residue. The ceramic wick 206 includes a number of voids 207. Air can pass through the voids 207, so that the ceramic wick 206 is breathable. Additionally, the aerosol-forming substrate can be transported through the voids. The size of the voids is exaggerated in Figure 2.

[0134] Figure 2b shows the ceramic wick 206 with agglomerated residue within the pores 207. As shown in Figure 2b, this agglomeration essentially causes a restriction in each of the pores 207, reducing the ability of air to pass through the ceramic wick 206. In other words, the agglomeration of the aerosol-forming substrate residue within the ceramic wick 206 creates an obstruction in the airflow path through the aerosol-forming substrate.

[0135] Such obstructions in the airflow path of the aerosol generation system 100 are problematic. Overheating or burning of the residue can impart a burnt flavor to the aerosol generated by the aerosol generation system 100. Furthermore, an obstructed ceramic wick 206 increases the draw resistance of the aerosol generation system 100, which is undesirable. Thus, the electrical circuitry of the aerosol generation system 100 is configured to detect obstructions caused by residues of the agglomerated aerosol-forming substrate based on pressure measurements made by the first pressure sensor 216. This is possible because the presence or absence of obstructions in the airflow path will affect the pressure in the airflow path during use. This difference is depicted in FIG. 3.

[0136] 3 shows a graph 400 representing pressure downstream of the heater assembly 202 as measured by the first pressure sensor 216 both with and without an obstruction. The x-axis 405 of the graph 400 represents time and the y-axis 406 represents pressure. The graph shows a first puff 402 and a second puff 404. The first puff 402 represents an early puff of the aerosol generation system 100 before any substantial aerosol-forming substrate residue has coalesced. The second puff 404 represents a puff at a later time after there is substantial coalesced aerosol-forming substrate residue within the heater assembly 202. The x-axis has been cropped to show that these time-separated puffs are contiguous.

[0137] At the beginning of the first puff 402, the pressure increases almost instantaneously to a constant pressure that is maintained throughout the duration of the puff. At the end of the puff, the pressure drops almost instantaneously to zero.

[0138] The second puff 404 follows a similar pattern as the first puff 402. However, the constant pressure during the second puff 404 is lower than the pressure in the first puff 402. This is because during the second puff 404, an obstruction caused by the agglomeration of aerosol-forming substrate residue within the ceramic wick 206 creates a restriction in the airflow path. The restriction causes the flow rate to increase and the pressure to decrease. The first sensor 216 is close enough to the heater assembly 202 that this pressure decrease is noticeable.

[0139] 4 illustrates a method for detecting an obstruction in an airflow path. Method step 502 includes measuring pressure using the first sensor 216. This includes electrical circuitry 304 receiving signals from the first sensor 216 and those signals determining the pressure.

[0140] In step 504, the measured pressure value is compared to a predetermined value stored in the memory of the electrical circuit 304. In this case, the predetermined value represents the pressure value when there is no obstruction in the airflow path. If the difference between the predetermined value and the measured value is 100 Pa or more, an obstruction is detected because an obstruction causes a pressure drop downstream of the obstruction.

[0141] If an obstruction is detected, the method proceeds to step 506. At step 506, the electrical circuit 304 limits the power supply from the power source to the heater assembly 202. This prevents use of the aerosol generation system 100. Power is limited until the obstruction is removed. This may be accomplished by the user replacing the cartridge 200 with an unused cartridge or by cleaning the cartridge 200. Cleaning the cartridge may include either removing the cartridge 200 and physically cleaning the heater assembly 202 to remove any aggregated residue, or cleaning the cartridge while received within the aerosol generation device, and a heating procedure is initiated that causes thermal decomposition of the residue.

[0142] The predetermined value is determined during a threshold determination stage, the steps of which are illustrated in FIG.

[0143] At step 602, pressure is measured during the first user puff of aerosol generation. This involves electrical circuitry 304 receiving signals from first sensor 316 and those signals determining pressure. The measured pressure is stored in memory of electrical circuitry 304.

[0144] At step 604, step 602 is repeated four times for successive puffs, thus resulting in five pressure measurements stored in the memory of electrical circuitry 304.

[0145] At step 606, the electrical circuitry is configured to determine an average of the five pressure measurements, the average pressure value representing the pressure value when no obstruction is present in the airflow path, and the predetermined value is equal to the average.

[0146] The threshold determination phase described above begins with the first use of the aerosol generation system 100. The aerosol generation system 100 further comprises a user interface (not shown) connected to the electrical circuitry 304. A user of the device can initiate the threshold determination phase at a time later than the first use by entering into the user interface, for example by pressing a button on the user interface, which causes the method of Figure 5 to be repeated and a new threshold to be determined. This is useful, for example, when there is a new user of the aerosol generation system 100 with a different puff behavior.

[0147] The method of Figure 5 is performed, but not the method of Figure 4. In other words, the aerosol generation system 100 does not determine the presence of an obstruction during the threshold determination stage.

[0148] The predetermined value discussed in relation to Figures 4 and 5 is a value that represents a pressure value when no obstruction is present in the airflow path. In another embodiment, the predetermined value is a predetermined threshold. That is, the predetermined value is a value that represents a pressure when an obstruction is present. In this case, the comparison in step 504 involves comparing the predetermined threshold to the measurement to see if the measurement is at or below the predetermined threshold. If the measurement is at or below the predetermined threshold, an obstruction is detected.

[0149] The predetermined threshold value, which represents the pressure value when an obstacle is present, is determined according to a method similar to that shown in Figure 6. However, the average pressure determined in method step 606 represents the pressure in the absence of an obstacle, rather than in the presence of an obstacle. Therefore, the method includes the additional step of converting the average pressure to a threshold pressure value. This involves subtracting a predetermined amount from the average pressure. In this example, the predetermined amount is 100 Pa.

[0150] The aerosol generation system 100 has been described with respect to a system including a single sensor 216. Figure 6 shows a second embodiment of an aerosol generation system 700 further including a second pressure sensor 702 upstream of the heater assembly 202. Otherwise, the second embodiment of Figure 6 has the same features as the first embodiment of Figure 1, and like features are numbered accordingly.

[0151] The aerosol generation system 700, including both the first pressure sensor 216 and the second pressure sensor 702, is configured to determine a differential pressure measurement in both the obstruction detection method and the threshold determination stage. The second sensor 702 is a low voltage barometric pressure sensor (MS5637-02BA03) available from Digi-key electronics (http: / / www.digikey.com / ).

[0152] The electrical circuit 304 is configured to calculate a differential pressure measurement by subtracting the pressure measured by the first pressure sensor 216 from the pressure measured by the second pressure sensor 702. As discussed above, the pressure downstream of the heater assembly 202 measured by the first pressure sensor 216 will be lower than the pressure upstream of the heater assembly 202 measured by the second pressure sensor 702. Subtracting the measured pressures leaves a value that represents the pressure drop caused by the heater assembly 202, and importantly, any obstructions within the heater assembly 202.

[0153] FIG. 7 shows a graph 800 representing differential pressure both with and without an obstruction in the heater assembly 202. As in FIG. 3, the x-axis 805 of the graph 800 represents time. However, the y-axis 806 represents differential pressure rather than simply pressure. The graph shows a first puff 802 and a second puff 804. The first puff 802 represents an early puff of the aerosol-generating system 700 before any substantial aerosol-forming substrate residue has coalesced. The second puff 804 represents a much later puff after there is substantial coalesced aerosol-forming substrate residue in the heater assembly 202. The x-axis has been cropped to show that these time-separated puffs are continuous.

[0154] At the beginning of the first puff 802, the pressure increases almost instantaneously to a constant differential pressure and is maintained throughout the duration of the puff. At the end of the puff, the pressure drops almost instantaneously to zero. The constant differential pressure during the main part of the puff is not zero. This is because, despite the absence of residue within the heater assembly in the first puff, the heater assembly 202 itself still represents a restriction in the airflow path. Therefore, the constant differential pressure during the main part of the puff represents the pressure drop caused by the presence of a clean heater assembly 202.

[0155] The second puff 804 follows a similar pattern as the first puff 802. However, the constant differential pressure during the main portion of the second puff 804 is greater than the differential pressure of the first puff 802. This is because during the second puff 404, an obstruction caused by the agglomeration of the aerosol-forming substrate residue within the ceramic wick 206 creates a restriction in the airflow path. This increases the pressure drop across the heater assembly 202 and therefore increases the differential pressure measured during the main portion of the second puff 804.

[0156] The second embodiment aerosol generation system 700 operates similarly to the first embodiment aerosol generation system 100. However, any step of the method of the first embodiment aerosol generation system 100 that instead includes measuring pressure includes measuring a differential pressure in the second embodiment aerosol generation system 700. In the aerosol generation system 700, the predetermined value of step 504 represents a threshold differential pressure. A differential pressure measurement above this threshold indicates that the airflow path is blocked by residue of aerosol-forming substrate that has condensed within the heater assembly 202. Furthermore, the threshold differential pressure value is calculated by determining an average of five differential pressure measurements in steps 602-606.

[0157] 8 shows a third embodiment of an aerosol generation system 900. The aerosol generation system 900 has a different heater assembly than the second embodiment aerosol generation system 700. Otherwise, the aerosol generation systems 700 and 900 are identical and like features are numbered accordingly.

[0158] The third assembly aerosol generation system 900 includes an inductive heater assembly 902. Instead of a resistive heater element, the inductive heater assembly 902 includes a susceptor element 904. The susceptor element 904 is again provided as a track printed on the ceramic core 206.

[0159] The heater assembly 902 further comprises a flat spiral inductor coil 906. Flat spiral inductor coil 906 component of the aerosol generating device in the third embodiment. Therefore, in this embodiment, only a portion of the heater assembly 902 is contained within the cartridge.

[0160] The inductor coil 906 is positioned near the base of the cavity such that when the cartridge 200 is received within the cavity, the susceptor element 904 is in close proximity to the inductor coil 906 to facilitate efficient heating. The electrical circuitry 304 and the battery 302 are configured to supply high frequency alternating current to the inductor coil during use of the aerosol generation system 900, which causes heating of the susceptor element 904 and therefore the aerosol-forming substrate.

[0161] The aerosol generation systems 700 and 900 can be used to detect an obstacle in the airflow path and determine a predetermined value for the obstacle detection method in the same manner as described in connection with the aerosol generation system 100 of the first embodiment.

Claims

1. A method for detecting the presence of an obstacle in an airflow path of an aerosol generation system, the system comprising a heater assembly for heating an aerosol-forming substrate, a power source, an airflow path defined between an air inlet and an air outlet and passing through the heater assembly, and at least one sensor for sensing the airflow characteristics of the air in the airflow path, the method comprising: measuring a value associated with the airflow characteristics during user smoking based on a signal from the at least one sensor; comparing this measured value with a predetermined value; detecting an obstacle in the airflow path based on the comparison; limiting the power supplied to the heater assembly or providing an indication if an obstacle is detected; and wherein the measured value is an average of values of the airflow characteristics measured during a plurality of smokings, the method.

2. The method according to claim 1, wherein the obstacle is an obstacle in a portion of the airflow path passing through the heater assembly.

3. The method according to claim 1 or 2, further comprising the step of limiting the power supplied to the heater assembly until the obstacle is removed after the obstacle is detected.

4. The method according to claim 1 or 2, wherein the airflow characteristic is pressure and the at least one sensor is a pressure sensor.

5. The method according to claim 1 or 2, wherein the system comprises at least a first sensor downstream of the heater assembly and a second sensor upstream of the heater assembly.

6. The method according to claim 5, wherein the step of measuring the value associated with the airflow characteristics comprises calculating a difference between a signal from the first sensor and a signal from the second sensor.

7. The method according to claim 1 or 2, further comprising the step of determining the predetermined value during a threshold determination stage including one or more user smokings.

8. The method according to claim 7, wherein the first smoking of the threshold determination stage is triggered when the user first smokes the aerosol generation system.

9. The step of determining the predetermined value comprises: measuring a value associated with the characteristics of the air during each user smoking during the threshold determination stage; and determining the predetermined value based on the one or more measured values, the method according to claim 7.

10. The method according to claim 9, wherein the threshold determination stage includes smoking two or more times, and the predetermined value is determined based on the average of the measured values from each smoking in the threshold determination stage.

11. The method according to claim 1 or 2, further comprising the step of removing the obstacle.

12. The method according to claim 11, wherein the step of removing the obstacle includes replacing the heater assembly or cleaning the heater assembly while the heater assembly remains connected to the aerosol generating device.

13. An aerosol generating system, a heater assembly for heating an aerosol-forming substrate, a power source, an air flow path defined between an air inlet and an air outlet, the air flow path passing through the heater assembly, at least one sensor for sensing the air flow characteristics of the air in the air flow path, an electric circuit having a memory and connected to the heater assembly and the power source, configured to measure a value associated with the air flow characteristics during user smoking based on a signal from the at least one sensor and compare the measured value with a predetermined value, wherein the electric circuit is configured to detect an obstacle in the air flow path based on the comparison and limit the power supplied to the heater assembly when the obstacle is detected until the obstacle is removed, The aerosol generating system, wherein the measured value is the average of the values of the air flow characteristics measured during a plurality of smokings.

14. The aerosol generating system according to claim 13, wherein the heater assembly comprises a breathable ceramic core and the air flow path passes through the core.

15. The aerosol generating system according to claim 13 or 14, wherein the system comprises a cartridge and an aerosol generating device, the cartridge being configured to be used in the device, the cartridge comprising at least a part of the heater assembly, and the device comprising a power source and the electric circuit.

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