Patent Application
20240334971
The present disclosure relates to a heating chamber assembly in which an aerosol generating substrate is heated to form an aerosol. The disclosure is particularly applicable to a portable aerosol generation device, which may be self-contained and low temperature. Such devices may heat, rather than burn, tobacco or other suitable aerosol substrate materials by conduction, convection, and/or radiation, to generate an aerosol for inhalation.
The popularity and use of reduced-risk or modified-risk devices (also known as vaporisers) has grown rapidly in the past few years as an aid to assist habitual smokers wishing to quit smoking traditional tobacco products such as cigarettes, cigars, cigarillos, and rolling tobacco. Various devices and systems are available that heat or warm aerosolisable substances as opposed to burning tobacco in conventional tobacco products.
A commonly available reduced-risk or modified-risk device is the heated substrate aerosol generation device or heat-not-burn device. Devices of this type generate an aerosol or vapour by heating an aerosol substrate that typically comprises moist leaf tobacco or other suitable aerosolisable material to a temperature typically in the range 150° C. to 350° C. Heating an aerosol substrate, but not combusting or burning it, releases an aerosol that comprises the components sought by the user but not the toxic and carcinogenic by-products of combustion and burning. Furthermore, the aerosol produced by heating the tobacco or other aerosolisable material does not typically comprise the burnt or bitter taste resulting from combustion and burning that can be unpleasant for the user and so the substrate does not therefore require the sugars and other additives that are typically added to such materials to make the smoke and/or vapour more palatable for the user.
In order to heat the aerosol substrate, it is desirable to provide alternative heating means which may be used in different scenarios.
For example, when using an aerosol generation device, the user must wait for the aerosol substrate to reach a required temperature for aerosol generation. Thus, in order to improve user convenience, it is desirable to provide an alternative way of heating the aerosol substrate which reduces the waiting time.
According to a first aspect, the present disclosure provides a heating chamber for an aerosol generation device, the heating chamber comprising one or more walls adapted to receive an aerosol substrate, the heating chamber further comprising: a pair of arc electrodes arranged on the one or more walls to form a spark gap.
Arc electrodes provide an alternative way of supplying heat to the heating chamber. Additionally, the arc electrodes can provide a way of rapidly supplying localized heat to a specific area of the heating chamber.
Optionally, the spark gap has a breakdown voltage of at least 500V. By setting a high breakdown voltage (for example by changing the size of the spark gap between the electrodes), it is made more difficult to run the arc electrodes from an un-adapted generic power supply for other heater types, improving safety.
Optionally, the spark gap has a breakdown voltage of less than 10 kV. When the breakdown voltage is reached, the arc electrodes suddenly draw a power that increases with the breakdown voltage. By limiting the breakdown voltage (for example by changing the size of the spark gap between the electrodes) the sudden change in power draw can be limited, reducing stress on the power supply.
Optionally, the arc electrodes comprise nickel, iridium or platinum. Nickel, iridium and platinum have relatively high melting points compared to, for example, copper or gold circuitry, and may be used to increase the lifetime of the arc electrodes.
Optionally, the one or more walls of the heating chamber are thermally conductive, and the pair of arc electrodes is arranged on an outer surface of the one or more walls. This arrangement mean that the arc electrodes are separated from the aerosol substrate, and maintenance of the arc electrodes is simplified across multiple uses of the heating chamber to heat the aerosol substrate.
Optionally, the heating chamber comprises an inner volume defined by an inner surface of the one or more walls, the inner surface of the one or more walls comprises a protrusion extending into the inner volume, the outer surface of the one or more walls comprises a recess corresponding to the protrusion, and the spark gap extends across the recess. A protrusion as described here may, for example, be used to position the aerosol substrate within the heating chamber, to define an air flow channel around the aerosol substrate, and/or to compress the aerosol substrate. However, such an inward protrusion may be more difficult to heat. In the case that the protrusion of the inner surface has a corresponding recess of the outer surface (for example, where the protrusion is formed by folding, stamping, or extruding a material of the one or more walls), then the recess provides a suitable location for a heating element configured to supply heat locally to the protrusion. A pair of arc electrodes may advantageously be arranged such that the spark gap extends across the recess in order to provide a localized supply of heat to the protrusion.
Optionally, the heating chamber is a tubular heating chamber, and the protrusion is a rib extending along an axis of the tubular heating chamber. With this configuration, the rib can provide an extended guide to position the aerosol substrate, define an air flow channel around the aerosol substrate and/or compress the aerosol substrate along an extended section of the aerosol substrate.
Optionally, a plurality of pairs of arc electrodes are arranged on the one or more walls, each pair forming a respective spark gap across the recess, and the pairs of electrodes being spaced axially along the tubular heating chamber. This configuration of pairs of arc electrodes may advantageously be used with a rib-shaped protrusion extending along the axis of the tubular heating chamber, to provide localized heating along the length of the rib.
Optionally, the inner surface of the one or more walls comprises a plurality of ribs arranged around the axis of the tubular heating chamber, the outer surface of the one or more walls comprises a recess corresponding to each protrusion, and a respective pair of arc electrodes is arranged on the one or more walls to form a spark gap across each recess. A plurality of heated ribs may be used to further position the aerosol substrate, define an air flow channel around the aerosol substrate, and/or compress the aerosol substrate, while supplying heat more evenly.
Optionally, the heating chamber further comprises a planar heater extending around the one or more walls. A planar heater may be provided to supply a uniform heat from around the heating chamber. This may be used in cooperation with the pair of arc electrodes, which provide localized heat at one specific required position.
According to a second aspect, the present disclosure provides an aerosol generation device comprising: a heating chamber comprising one or more walls adapted to receive an aerosol substrate, and a pair of arc electrodes arranged on the one or more walls to form a spark gap; and a power source connected to the pair of arc electrodes and configured to apply a voltage between the pair of arc electrodes that is greater than a predetermined breakdown voltage of the spark gap, in order supply heat to the heating chamber.
Optionally, the predetermined breakdown voltage is at least 500V.
Referring to
The consumable 1 comprises a rod-shaped portion 11 and a filter 12.
The rod-shaped portion 11 contains aerosol generating substrate. The aerosol generating substrate is a material which, when heated, generates an aerosol.
The aerosol may be passively allowed to dissipate from the aerosol generating system, but is preferably drawn out of the consumable 1 by air flow through the filter 12.
The aerosol generating substrate may, for example, comprise tobacco or nicotine. The substrate may be a solid block, or may be loose material packed in a wrapper 13. Preferably the substrate comprises randomly oriented tobacco strands containing tobacco powder and an aerosol former. Suitable aerosol formers include: a polyol such as sorbitol, glycerol, and glycols like propylene glycol or triethylene glycol; a non-polyol such as monohydric alcohols, acids such as lactic acid, glycerol derivatives, esters such as triacetin, triethylene glycol diacetate, triethyl citrate, glycerin or vegetable glycerin. In some embodiments, the aerosol generating agent may be glycerol, propylene glycol, or a mixture of glycerol and propylene glycol.
Tobacco strands may be obtained by, for example, mixing the tobacco powder and the aerosol former, drying the mixture in sheets, and shredding the sheets. A substrate density is preferably between 0.3 mg/mm3 and 0.6 mg/mm3.
The substrate density represents the mass of the substrate per volume unit in the rod-shaped portion. For randomly oriented tobacco strands, the substrate density can be controlled by adjusting the density of the tobacco sheet during production and by adjusting the filling rate of the strands in the rod-shaped portion. For example, the tobacco sheets have a density of 0.45 mg/mm3 and a filing rate of strands is 75% provides a substrate density of 0.337 mg/mm3.
The tobacco sheet may be paper reconstituted tobacco sheet, extruded tobacco sheet or cast tobacco sheet.
The wrapper 13 may, for example, comprise paper, a combination of paper aluminium foil, cardboard, or any material suitable for storing an aerosol generating substrate and allowing the substrate to be heated in the heating chamber. For example, the wrapper can be paper with air permeability 0-50 CU, basis weight of 25-80 g/m2 and thickness 30-80 μm with or without aluminium foil of 20-30 μm thickness. The wrapper 13 may be omitted in embodiments where the substrate is self-supporting, for example where the substrate is a compressed tobacco substrate having soft granular texture such as described in applications EP 19209350.8 entitled “crumbed tobacco substrate” or EP 19209346.6 entitled “hot pressed tobacco substrate”.
The aerosol generating device 2 comprises a heating chamber 21 and a heater 22.
The heating chamber 21 is a tubular structure with an internal hollow in which the consumable 1, or the rod-shaped portion 11 of the consumable 1, may be received. Specifically, the heating chamber comprises a side wall extending between a first end 212 and a second end 213. The first end 212 is open, or openable in use, in order to allow the rod-shaped portion 11 to be inserted. The second end 213 may be open as shown in
The heater 22 may be any heater suitable to deliver heat into the internal hollow of the heating chamber 21 through its side wall. For example, the heater 22 may be a planar heater attached to a flexible support and wrapped around the side wall of the heating chamber 21. Such a planar heater may be in the form of a resistive track driven by electricity, and the support may be one or more plastic or polymer sheets, for example a polyimide, a fluoropolymer such as PTFE, or a polyetheretherketone (PEEK). Alternatively, other types of heater may be used such as ones in which heat is provided by a chemical reaction such as fuel combustion. The heating chamber may further be surrounded by a heat insulator such as a vacuum tube, heat insulation fibre (e.g. Superwool) and/or aerogel.
As shown in
In order to position the consumable within the chamber 21, a plurality of inward protrusions 211 are configured to extend from the side wall of the heating chamber 21.
When the rod-shaped portion 11 is in the chamber 21, the protrusions 211 engage with and apply pressure to the consumable 1 in order to position the consumable securely within the chamber 21 at a position where it can be heated with greater efficiency. Additionally, the consumable 1 may be configured with a diameter greater than the space provided between the protrusions 211 such that the consumable 1 is compressed as it is positioned by the protrusions 211. This compression may further improve generation of aerosol from the consumable 1.
For example, when the heater 22 is configured to supply heat symmetrically through the side wall of the chamber 21 (e.g. the heater extends around the whole of the chamber 21 or comprises symmetrically arranged heater portions), the protrusions 211 may similarly be configured symmetrically relative to the length axis (i.e. around the length axis on an inner perimeter of the heating chamber 21) in order to assist positioning the consumable at a center of the chamber. In this context, “at a center” means substantially near the center in terms of the width of the chamber 21.
As shown in
However, the protrusions 211 also have the disadvantage of increasing a distance between the heater 22 and the consumable 1, and decreasing the thermal contact between the consumable 1 and the side wall of the chamber 21.
This increased distance between the heater 22 and the consumable 1 can mean that the temperature of the protrusions 211 is lower than desired. For example, in some designs, the protrusions 211 may be intended to provide the hottest points of the chamber 21, in order to deliver heat more efficiently to the rod-shaped portion 11. However, in practice, the distance between the heater 22 and the protrusions 211 can mean that the ends of the protrusions 211 are cooler than the rest of the chamber 21.
As a result, there is a need to provide a way to supply localized heat to a specific area of the heating chamber (where the specific area may, for example, be a protrusion 211).
Embodiments of the invention provide such localized heat, for example as shown in
The heating chamber 21 may have a similar shape as described for
In this example, the side wall of the tubular heating chamber 21 comprises one or more rib protrusions 211 (four protrusions in this example). The rib protrusions extend into the heating chamber 21 on an inner surface. The rib protrusions may have a corresponding recess on an outer surface. The rib protrusions also extend along the tubular heating chamber 21, for example in a similar shape to the rib protrusions 211 of
Preferably, the internal surface of the rib protrusions 211 (the surface facing into the heating chamber) follows a smooth curve. This means that, when the rib protrusion 211 compresses a consumable 1, it is less likely to break the consumable. In a transversal plane of the protrusion, the smooth curve is preferably the arc of a circle or a parabola, such that the consumable can deform along the surface, and increase contact area between the protrusion 211 and the consumable 1 for improved thermal contact. Even more preferably, the smooth curve has a radius of curvature of at least 0.2 mm, or more preferably at least 0.5 mm, these being relatively “blunt” curves which are less likely to break the consumable 1.
The heating chamber 21 may be formed from ceramic or metal. For example, the protrusions and recesses of the heating chamber 21 may be formed by bending or stamping sheet metal. In a preferred method, the heating chamber 21 is formed by deep drawing comprising: forming a metal disk blank it into an initial metal cup, annealing under vacuum or inert gas; and deep drawing the initial metal cup into an elongated tubular cup with a reduced tubular wall thickness as described in patent application EP 19196023.6 entitled “heating chamber”.
The first heating chamber differs from the previous configuration of
Each pair of arc electrodes 23 comprises a first electrode 231 and a second electrode 232 separated by a spark gap. The pair of arc electrodes are configured to be connected to a power supply and, when a breakdown voltage is applied by the power supply between the first electrode and second electrode, to dissipate heat in an electrical arc between the first electrode and second electrode.
Spark gaps have been used in other technical fields to provide localized heat. For example, spark gaps are used in some internal combustion engines.
The first and second electrodes 231, 232 are preferably constructed from materials suitable for the temperatures associated with electrical arcs. As mentioned in the background, a typical temperature range for conventional aerosol generation devices is 150° C. to 350° C. However, the electron temperature associated with spark discharge can be in the range of 10,000° C., in a localised sense. This does not translate into such high average temperatures in a bulk gas filling the spark gap, which are typically in the more conventional range of hundreds of degrees Celsius. For example, the first and second electrodes 231, 232 may be driven based on a power supply with a small duty cycle (such as 5% or less, or 1% or less). Nevertheless, the electron temperature is significant where the path of a spark discharge approaches the first and second arc electrodes, where even a short-lived and local high temperature can damage the surface of the first and second arc electrodes. As a result, a high-melting-temperature material is preferable for the surface of the arc electrodes, such as nickel, iridium or platinum, in order to slow degradation due to arcing, and increase the useful lifetime of the first and second electrodes.
The breakdown voltage of the spark gap depends upon the width of the gap, the composition of gas in the gap, and the pressure of gas in the gap, according to Paschen's Law. In a typical construction, the first and second electrodes are separated by an unpressurized air gap, and the breakdown voltage is primarily controlled by varying the width of the gap. Nevertheless, it should be noted that the gas temperature and potentially gas pressure will increase during operation of the aerosol generation device, and thus the power supply must be able to apply the highest breakdown voltage across the range of operating temperatures at which the pair of arc electrodes may be used (for example, in the temperature range of 0° C. to 350° C.). Preferably, the spark gap has a breakdown voltage of at least 500V and less than 10 KV across the range of operating temperatures.
The first and second electrodes 231, 232 are also preferably point electrodes, such as protruding pins, to reduce the gap capacitance and the breakdown voltage.
In the example of
Preferably there are a plurality of pairs of arc electrodes 23 distributed around an axis of the heating chamber 21 in order to supply heat more evenly into the heating chamber 21. Even more preferably, the pairs of arc electrodes 23 are distributed symmetrically around a center of the tubular heating chamber 21. For example, as shown in
In some cases, a pair of arc electrodes 23 may be arranged in the recess of every rib protrusion, although this is not essential.
In the second heating chamber, a sleeve or wrap 22 that is arranged around an outer surface of the side wall of the heating chamber 21.
The sleeve or wrap 22 preferably comprises a further heating element configured to supply additional heat similarly to the configuration in of heating unit 22 in
Additionally or alternatively, the sleeve or wrap 22 may comprise an insulator, or may be surrounded by an insulator. In this case, the insulator is configured to retain heat within the heating chamber assembly, improve heating efficiency in the heating chamber assembly, and reduce heat leakage towards other components of an aerosol generation device.
For example, in one case, the sleeve or wrap 22 may comprise a planar heater (such as a thin-film heater) wrapped around the heating chamber 21. The planar heater may be secured in place by an insulating shell arranged around the heating chamber assembly. The insulating shell may, for example, be a plastic shell comprising, for example, PEEK.
As an addition to, or alternative to, the sleeve or wrap 22, a surface heating element may be attached to a part of the outer surface of the side wall of the heating chamber 21. For example, a planar heating element may be attached to a portion of the outer surface that is located between the recesses associated with two rib protrusions on the inner surface. The surface heating element may, for example, be a resistive electrical track printed or adhered onto the outer surface. In one example, pairs of arc electrodes 23 may be arranged in each recess on the outer surface corresponding to a rib protrusion, and a surface heating element may be arranged on the outer surface between each pair of adjacent recesses.
Comparing
In
On the other hand, in
The aerosol generation device 2 of this example is a self-contained portable device having an electrical power supply 25 and a controller 24 for controlling at least the one or more pairs of arc electrodes 23A, 23B.
The electrical power supply 25 is configured to supply power for dissipating heat using arcing between the one or more pairs of arc electrodes 23A, 23B. The electrical power supply 25 may be a specialised high voltage power supply suitable for directly applying the breakdown voltage across the one or more pairs of arc electrodes. Alternatively, the electrical power supply 25 or the controller 24 may comprise a step-up transformer to apply the breakdown voltage across the one or more pairs of arc electrodes 23A, 23B.
The device 2 may additionally comprise one or more thermistors for determining a temperature of a rib 221 or of the heating chamber 21.
The controller 24 may be configured to control the one or more pairs of arc electrodes 23A, 23B in order to heat the interior of the heating chamber according to a predetermined temperature profile.
Preferably, where the aerosol generating substrate comprises tobacco, the one or more pairs of arc electrodes 23A, 23B are controlled to heat the interior of the heating chamber 21 to at least 190° C., and more preferably between 230° C. and 300° C., for aerosol generation.
Additionally, the one or more pairs of arc electrodes 23A, 23B are preferably controlled to maintain the interior of the heating chamber at at least 190° C., preferably above 200° C., for a predetermined puff sequencing time in which enough aerosol can be generated for a user to inhale a puff of aerosol. The puff sequencing time depends upon the particular aerosol generating substrate, and can be configured by testing the aerosol composition produced with different puff sequencing times, but has been found to be suitably at least four minutes in some cases. In other embodiments, rather than setting a predetermined puff sequencing time, the length of time for which the temperature is maintained may additionally or alternatively be based on a predetermined number of puffs of aerosol to be inhaled by a user. Puffs can be detected by, for example, detecting a temperature drop when ambient air is drawn into the heating chamber to replace heated, aerosol-rich air.
Preferably, the controller 24 is independently connected to each of at least two of the pairs of arc electrodes 23A, 23B. This means that the controller can individually activate pairs of arc electrodes 23A, 23B in order vary an amount of heat supplied to the heating chamber 21.
As shown in
In this specific embodiment, the second end 213 of the heating chamber 21 is closed, and air flow for drawing aerosol from the consumable is illustrated using arrows F1, F2 and F3. Air enters the heating chamber 21 at the first end 212 where the consumable 1 is spaced away from the side wall of the heating chamber 21. This space is defined by the protrusions 211, which position the consumable 1 within the chamber 21. Thus, an additional benefit of the protrusions 211 is that they support an air flow channel for air to be drawn through the consumable 1. After passing along the air flow channel supported by the protrusions 211, the air flows into the consumable 1 at an end adjacent to the second end 213 of the heating chamber 21. The air then flows through the rod-shaped portion 11 comprising the aerosol generating substrate and picks up the generated aerosol, flowing out of the consumable at arrow F3. The consumable 1 may comprise a space 14 for air to cool, and may comprise a filter 13. The space may advantageously be formed by a hollow paper tube. The filter 13 may advantageously be formed of two segments; one of which may be a hollow filter segment and the other may be a plain filter segment. The segments may be individually wrapped by plug wraps and combined by a common plug wrap to form the filter. The paper tube, filter and rod-shaped portion can be combined by a single or double layer of tipping paper. Ventilation holes may be formed, e.g. by lasering, through the wrapper, preferably through the paper tube and tipping paper in the close vicinity of the filter, for example at 1-2 mm distance.
As further shown in
Alternatively, where the consumable 1 is not configured for a user to directly inhale the aerosol from the consumable, the consumable 1 may comprise only the rod-shaped portion 11, and the aerosol-carrying air at arrow F3 may be further drawn through a structure of the aerosol generating device 2 to a reusable or semi-disposable mouthpiece of the aerosol generating device 2, separate from the consumable 1.
Preferably, the heating chamber 21 also comprises a platform 215 extending into the internal volume of the heating chamber 21 at the second end 213. The width of the platform is preferably smaller than the width of the consumable. The platform 215 promotes air flow by supporting the consumable 1 at least partly separated from the second end 213, as shown in
As shown in
A length L1 of the rod-shaped portion 11 can be compared with a length L2 of the ribs 211 (i.e. a length of the protrusions 211 parallel to a length axis of the rod-shaped portion 11), or an equivalent length L2 of the heating units 22 in the case that the heating units 22 extend directly into the heating chamber. For visual convenience, one end of the ribs 211 is aligned with an end of the rod-shaped portion 11 (as represented in transverse dotted line 19), but this need not generally be the case. The length L2 is preferably as least 50%, more preferably between 60% and 70%, of L1 (or of the length of a predetermined section that contains aerosol generating substrate, if this is not the whole length L1 of the rod-shaped portion 11), in order to substantially improve aerosol generation by compressing the aerosol generating substrate.
The alternative of
Firstly, the embodiment of
Secondly, the embodiment of
The embodiment of
For example, a pair of arc electrodes 23 may be arranged in an air flow channel defined by protrusions 211 such that, when a consumable 1 is inserted, the pair of arc electrodes 23 is not in direct contact with the consumable.
More generally, one or more pairs of arc electrodes may be arranged on any combination of inner and outer surfaces of the walls of the heating chamber 21.
In any of the above described embodiments, the first and second arc electrodes 231, 232 may have a straight shape as shown in
In the above described examples, rib protrusions 211 are fixed in position within a heating chamber. However, the rib protrusions 211 may be configured to move when a consumable 1 is positioned within the heating chamber 21. This may be used to achieve greater compression of the consumable 1 than can be achieved by manual insertion of a consumable 1 between the rib protrusions which are provided as extensions 211 of the heating chamber 21. For example, movement of the rib protrusions 211 may be controlled using a mechanism as described in EP 20200899.1.
| Number | Date | Country | Kind |
|---|---|---|---|
| 21185481.5 | Jul 2021 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/069764 | 7/14/2022 | WO |
