Ceramic Wick and Targeted Heating

Abstract

A system includes: a cylindrical ceramic wick for an aerosol generating device and a susceptor surrounding at least part of the wick. The wick has an outer surface, a hollow core and a base. The base includes an indentation arranged such that, when, in use, the indentation engages with a cylindrical cup, defining an airflow path for allowing air to flow from the exterior of the wick into the hollow core. The outer surface includes a raised portion arranged such that, when, in use, a susceptor engages with the wick, the raised portion abuts the susceptor. The susceptor includes perforations, spaced axially on the susceptor, and arranged such that regions are formed between two axially adjacent perforations, the regions overlap with the raised portion and when, in use, an eddy current flow is induced in the susceptor, the flow of the eddy current is concentrated in the regions.

Description

TECHNICAL FIELD

The present invention relates to a cylindrical ceramic wick and a susceptor for an aerosol generating device. More specifically, it relates to an aerosol generating device such as an e-cigarette, heat-not-burn devices and the like which are capable of producing an aerosol. The wick has structured ends for allowing air to flow from an exterior of the wick into the interior of the wick, and a raised portion on the outer surface of the wick for abutting a susceptor in use. The susceptor has a plurality of perforations spaced axially.

BACKGROUND

Inhalers or aerosol generating devices such as e-cigarettes or vaping devices are becoming increasingly popular. They generally heat or warm an aerosolisable substance to generate an aerosol for inhalation, as opposed to burning tobacco as in conventional tobacco products.

Some aerosol generating devices include a wicking element or wick for transporting a liquid aerosolisable substance from a liquid reservoir to a heater to be vaporised, mixed with air, and subsequently inhaled.

One method of heating the aerosolisable substance is with induction heating. One way of achieving induction heating is by providing an inducting element around the wick, and providing a susceptor between the wick and the inducting element. The susceptor is made from a material such that when a current is passed through the inducting element, an eddy current is induced in the susceptor. Further, a susceptor is conventionally provided with a number of perforations randomly distributed through the susceptor. The perforations are provided to allow vapor to escape from the wick.

By placing the wick and susceptor close to each other, an eddy current generated in the susceptor can heat the susceptor material and subsequently heat the liquid aerosolisable substance in the wick.

However, existing inductor and susceptor arrangement are limited in that they require relatively large amount of energy and are slow to heat up. This results in a problem that the time to first puff is delayed.

Therefore a need exists to provide a new way to heat aerosolisable substances in a wick to address these issues.

SUMMARY OF THE INVENTION

An aspect of the invention provides cylindrical ceramic wick for an aerosol generating device. The wick comprises an outer surface, a hollow core and a base, wherein the base comprises at least one indentation arranged such that, when, in use, the indentation engages with a cylindrical cup, an airflow path for allowing air to flow from the exterior of the wick into the hollow core is defined; and the outer surface comprises a raised portion arranged such that, when, in use, a susceptor engages with the wick, the raised portion abuts the susceptor.

Advantageously, the wick comprises a raised portion for abutting a susceptor. This reduces the contact surface between the wick and the susceptor, thereby increasing the heat flux through the wick and decreasing heat up time to first puff.

The heat flux through the wick is inversely proportional to the contact area between the susceptor and the wick. By providing a raised portion on the wick, the contact area between the susceptor and the wick is reduced. Consequently, heat flux is increased

The at least one raised portion may extend along a longitudinal axis of the wick. By providing longitudinal raised portions, a channel in which air can flow is formed. This is advantageous for encouraging vapour to flow towards a user when, in use, the wick is provided in an aerosol generating device and the user attempts to inhale vapour.

Preferably, the at least one raised portion comprises between 2 and 20 raised portions. More preferably, the at least one raised portion preferably comprises between 5 and 15 raised portions. Even more preferably, the at least one raised portion preferably comprises between 8 and 12 raised portions.

By providing a number of raised portions, the amount of vapour which can be vaporised is increased. Specifically, the more raised portions, the more vapour that can be formed. At the same time, the contact surface area between the wick and the susceptor is kept lower than if no raised portions were provided.

In some examples, the at least one raised portions cover between 30% to 80% of the outer surface. Preferably, the at least one raised portions cover between 50% to 60% of the outer surface. Accordingly, the contact area between the susceptor and the wick is reduced by between 30% and 80%, which gives rise to a corresponding increase in heat flux through the wick.

It is to be understood that the ranges specified above are merely examples, and the skilled person would be well aware of another number of raised portions that could be provided, or another percentage of the outer surface covered by the raised portions than those specified above.

A second aspect of the invention provides a susceptor for a cylindrical wick. The susceptor comprises at least one plurality of perforations, wherein the perforations are spaced axially on the susceptor, and arranged such that regions are formed between two axially adjacent perforations and when, in use, an eddy current flow is induced in the susceptor, the flow of the eddy current is concentrated in the regions.

By aligning the perforations axially, regions are formed which, in use, result in generated eddy currents being concentrated in the regions. In other words, the susceptor provides localised heating. Further, by virtue of the eddy currents being concentrated, the heat generated in the regions is greater than could be achieved by an eddy current dispersed over a greater area.

In some advantageous examples, the at least one plurality of perforations comprises between 2 and 20 pluralities spaced circumferentially on the susceptor. Preferably, the at least one plurality of perforations comprises between 5 and 15 pluralities spaced circumferentially on the susceptor. Even more preferably, the susceptor, comprises between 8 and 12 pluralities spaced circumferentially on the susceptor.

By providing a number of pluralities of perforations, the number of areas of concentrated eddy currents is increased. Accordingly, the number of areas of localised heating is also increased.

Advantageously, an area of the perforations varies along an axial direction of the susceptor. In some examples, an area of the perforations varies along a circumferential direction of the susceptor.

Varying the area of the perforations in the axial or circumferential direction facilitates different amounts of concentration of eddy currents in different parts of the susceptor. In this way, localised heating is provided at a wider range of temperatures.

Further, the perforations may be circular, with a diameter of between 0.5 mm and 3 mm. Circular perforations with diameter is the stated range provide localised heating which effectively heats aerosolisable substance without burning it.

A third aspect provides a system. The system comprises: a cylindrical ceramic wick for an aerosol generating device comprising an outer surface, a hollow core and a base, wherein the base comprises at least one indentation arranged such that, when, in use, the indentation engages with a cylindrical cup, an airflow path for allowing air to flow from the exterior of the wick into the hollow core is defined; and the outer surface comprises a raised portion arranged such that, when, in use, a susceptor engages with the wick, the raised portion abuts the susceptor; and a susceptor surrounding at least part of the cylindrical wick, comprising at least one plurality of perforations, wherein the perforations are spaced axially on the susceptor, and arranged such that regions are formed between two axially adjacent perforations, the regions overlap with the at least one raised portion and when, in use, an eddy current flow is induced in the susceptor, the flow of the eddy current is concentrated in the regions.

In this way, a system for heating aerosolisable vapour quickly and efficient is provided. The benefits of the wick and the susceptor have been discussed above. By combining them, and requiring that the regions overlap the raised regions, and even greater heat flux is achieved through the wick, which drastically reduces time to first puff.

Further, while the eddy current is concentrated in regions between axially adjacent perforations, the eddy current density in regions between circumferentially adjacent perforations is reduced. In use, circumferentially adjacent regions will not contact the wick, therefore the amount of wasted heat is reduced.

A fourth aspect provides an aerosol generating device comprising the wick of the first aspect.

A fifth aspect provides an aerosol generating device comprising the susceptor of the second aspect.

A sixth aspect provides an aerosol generating device comprising the system of the third aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary wick and susceptor will now be described by way of example with reference to the accompanying drawings, in which:

FIG. 1 shows an example ceramic wick, including raised portions;

FIG. 2A shows an example susceptor, including axially aligned perforations;

FIG. 2B shows a zoomed in view of a plurality of perforations from FIG. 2A, including areas of relatively high and low eddy current density;

FIG. 3 shows an example system comprising the wick and the susceptor;

FIG. 4 shows another example susceptor, with elliptical perforations;

FIG. 5 shows another example susceptor with perforations of variable area; and

FIG. 6 shows another example susceptor with regions of variable area.

DETAILED DESCRIPTION

Next, various aspects of the invention will be described. Note that the same or similar portions are denoted with the same or similar reference signs in the descriptions of the drawings below. Note that the drawings are schematic, and a ratio of each size in the drawings may be different from a real one. Therefore, specific sizes and dimensions should be judged in consideration of the following description.

Examples of the present disclosure relate to a ceramic wick having structured ends, or indentations, which engage with a cup or other surface in use. The wick is cylindrical, and typically made of porous ceramic. The wick therefore provides wicking action for an aerosolisable substance, such as a vaping liquid, also known as an e-liquid. In addition, because, in use, the indentations engage a cup, an airflow path is defined from the exterior of the wick to the interior. When the wick engages a cup, the indentation forms part of an airflow path that facilitates airflow from the exterior of the wick into the hollow core.

Further, the wick comprises a raised portion on the outer surface. In use, the raised portion engages or abuts a susceptor. The heat flux between the susceptor and the raised portion is increased compared to an arrangement where no raised portion is included on the wick. This means that in use, when an aerosol generating device comprising the wick is turned on, the time required to heat an aerosolisable substance is reduced. This is commonly referred to as the time to first puff.

Referring to FIG. 1, an example of a cylindrical ceramic wick 100 is shown. The wick 100 includes a hollow core 110 and base 120. The base 120 further comprises one or more indentations, such as indentation 122. At least one indentation is arranged on the base 120. At least one raised portion 130 is provided on the outer surface of the wick 100, but optionally, between 2 and 20 raised portions are provided. Preferably, between 5 and 15 raised portions are provided, and even more preferably, between 8 and 12 raised portions re provided.

The base 120, indentations 122 and raised portions 130 may be formed by cutting away sections of the wick 100. For example, sections of the wick 100 may be cut away by milling and machining the surface. Alternatively, the wick 100 may be formed with the base 120, indentations 122 and raised portions 130, by sintering.

Further, the raised portion or portions may cover between 30% to 80% of the other surface. Preferably, the raised portion or portions cover between 50% and 60% of the outer surface.

The benefit of reducing time to first puff is achieved with one raised portion, however, by providing additional raised portions, the time to first puff may be further reduced. The percentage of the outer surface covered by the raised portions affects the size of the total contact area between the susceptor and the wick 100 in use. Overall, by reducing the amount of contact between the wick 100 and the susceptor, the heat flux into the wick 100 is increased compared to a conventional wick without a raised portion.

At the same time, the specified range of percentages ensures that enough of the wick 100 is in contact with the susceptor that sufficient vapor can be produced in use. That is, the total contact area between the raised portions 130 and a susceptor is not so low that vapor cannot be sufficiently produced.

It is to be understood that the ranges specified above are merely examples, and the skilled person would be well aware of another number of raised portions that could be provided, or another percentage of the outer surface covered by the raised portions than those specified above.

The raised portion 130 may extend along a longitudinal axis of the wick. In use, the raised portion engages a susceptor and creates an airflow path between the wick and the susceptor. In this way, providing longitudinal raised portions increases airflow through the wick 100.

Referring to FIG. 2A, a susceptor 200 is illustrated. The susceptor 200 is cylindrical and made from a suitable magnetic material such that an eddy current may be induced in the susceptor 200. For an example, induction coils may be arranged to surround the susceptor.

Advantageously, the susceptor 200 is provided with at least one plurality of perforations, such as perforations 210 and 220. The perforations are spaced axially on the susceptor, and arranged such that regions 230 are formed between two axially adjacent perforations. To be clear, as shown in FIG. 2, a plurality of axially spaced perforations are two or more circular perforations extending along a longitudinal axis of the susceptor. The diameter of the perforations may be between 0.5 mm and 3 mm.

The advantages of the plurality of axially spaced perforations is realised with at least one plurality of perforations. However, between 2 and 20 pluralities of perforations may be provided with circumferential spacing. The circumferential spacing may be the same between each of the pluralities of perforations, or the spacing may vary. Preferably, between 5 and 15 pluralities of perforations are provided on the susceptor, and more preferably, between 8 and 12 pluralities are provided.

The number of pluralities in the above range ensures that sufficiently many regions of concentrated eddy current are formed in use, while also ensuring that the structural integrity of the susceptor is not compromised.

The axial arrangement of the perforations is beneficial for concentrating eddy currents induced in the susceptor. Specifically, when an eddy current is induced in susceptor 200, then eddy current density in the regions 230, and all such regions, is increased. This achieved since the flow of the eddy current is deflected away from the perforations, into the regions 230. In other words, the eddy current flow is concentrated in regions where the cross-sectional area of the material it is flowing through is reduced. Since the perforations are axially aligned, this leads to areas of higher eddy current density (i.e. in the regions 230). Correspondingly, areas of low eddy current density are also formed between circumferentially adjacent perforations. For example, still referring to FIG. 2A, eddy current density is relatively low in areas 240.

The positions of regions 230 and areas 240 may be better understood with reference to FIG. 2B, which shows a zoomed in view of the boxed portion of FIG. 2A. The regions of relatively concentrated eddy current 230 are indicated by dashed-line ellipses, while the areas of relatively low eddy current density 240 are indicated by the dotted-line ellipses.

As such, the susceptor is heated to higher temperatures in the regions 230. The susceptor 200 not only provides targeted heating, in that the heat produced is concentrated in the regions 230, but also higher temperatures in regions 230 owing to the concentrated eddy current.

The wick 100 shown in FIG. 1 and the susceptor 200 shown in FIG. 2A each provide advantages in terms of decreasing time to first puff. As shown in FIG. 3, the wick 100 and the susceptor 200 may be combined to form a system 300.

In the system 300 the regions 230 are aligned with the raised portions 130. It has been discussed that providing a raised portion 130 provides a higher heat flux through the raised portion 130. Combining this with the increased temperatures arising from the concentrated eddy currents drastically increases the heat flux into the raised portion. As a result, the time to first puff is significantly reduced.

Further, it has been discussed that the eddy current induced in circumferentially adjacent areas 240 is relatively low. In the system 300, the areas 240 are not in contact with a raised portion 130. Accordingly, the system is also efficient, since heat is not excessively wasted where the susceptor 200 does not abut the raised portion 130.

The size of the regions 230 as well as the size and shape of the perforations can be varied. This allows for different concentrations of eddy current to be realized.

Referring to FIG. 4, an exemplary susceptor 400 having a plurality of elliptical perforations 410 and 420 is shown, as well as the regions 430 between axially adjacent perforations. The elliptical perforations 410 and 420 are oriented with their minor axis aligned with the axial direction. Conversely, the major axes of the elliptical perforations 410 and 420 are aligned with the circumferential direction. This orientation provides larger regions 430 in which an eddy current in relatively concentrated.

Referring to FIG. 5, in some examples the size of the perforations is increased in an axial direction. In this example, we will refer to the axial direction as extending from a first edge 502 of the susceptor 500 to a second edge 504 of the susceptor 500. However, it is emphasised that the direction of the axial axis could be reversed to achieve the same effect. The increasing size of the perforations is shown in terms of the pluralities of perforations 510 and 520 in the susceptor 500. Correspondingly, it can be seen that the size of the region 530 decreases in the axial direction. As a result, in use, the regions 530 of the susceptor have varying temperature in the axial direction. This provides another level of targeted heating. For example, the arrangement of FIG. 5 may be particularly useful in situations where one end of a wick frequently contains more aerosolisable substance than another end.

Referring now to FIG. 6, instead of, or as well as varying the area of the perforations, the area of the regions can also be varied in an axial direction of the susceptor 600. For example, as shown, the area of region 630 is relatively large compared to the area of region 640, while the size of the perforations is uniform throughout the susceptor 600. This is another way of providing a variable heating profile with targeted heating.

While the figures show different examples of how the perforations and the regions van be varied, it is to be understood that the different variation types may be included on the same susceptor. That is, the different example variations are not mutually exclusive and may be combined.

The wick 100 and susceptor 200 described above are suitable for being arranged in an aerosol generating device. An aerosol generating device may be provided with only the wick 100, only the susceptor 200, or both. In any case, the benefit of reducing the time to first puff is realised. When in the device, the wick 100 is in fluidic contact with a liquid reservoir. The aerosol generating device may be provided with a power source connected to an induction element, as well as a number of other components typically provided with an aerosol generating device. The induction element is operable to induce an eddy current in the susceptor 200.

In conclusion, the wick 100 described above provides the advantage of decreasing the time to first puff by providing a raised portion that in use, reduces the contact area between the wick 100 and the susceptor, thereby increasing heat flux through the raised portion. The susceptor 200 also decreases the time to first puff by providing targeted heating. Targeted heating is achieved by providing a plurality of axially aligned perforations, which create regions where, in use, eddy currents are concentrated.

The wick 100 and susceptor 200 may also be combined, such that the regions are in contact with the raised portions to further decrease the time to first puff.

It is to be understood that the above described wick 100 and susceptor 200 may be modified according to design choices and manufacturer's preferences. For example, the radius and length of the wick 100, and the diameter of the susceptor 200 may be adjusted according to a design specification.

The foregoing description of illustrative embodiments have been presented for purposes of illustration and of description. It is not intended to be exhaustive or limiting with respect to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the disclosed embodiments.

Claims

1. A cylindrical ceramic wick for an aerosol generating device comprising an outer surface, a hollow core and a base, wherein the base comprises at least one indentation arranged such that, when, in use, the indentation engages with a cylindrical cup, an airflow path for allowing air to flow from the exterior of the wick into the hollow core is defined; andthe outer surface comprises a raised portion arranged such that, when, in use, a susceptor engages with the wick, the raised portion abuts the susceptor.

2. The wick of claim 1, wherein the at least one raised portion extends along a longitudinal axis of the wick.

3. The wick of claim 1, wherein the at least one raised portion comprises between 2 and 20 raised portions.

4. The wick of claim 3, wherein the at least one raised portion comprises between 5 and 15 raised portions.

5. The wick of claim 4, wherein the at least one raised portion comprises between 8 and 12 raised portions.

6. The wick of claim 1, wherein the at least one raised portions cover between 30% to 80% of the outer surface.

7. The wick of claim 6, wherein the at least one raised portions covers between 50% to 60% of the outer surface.

8. A susceptor for a cylindrical wick, comprising at least one plurality of perforations, wherein the perforations are spaced axially on the susceptor, and arranged such that regions are formed between two axially adjacent perforations and when, in use, an eddy current flow is induced in the susceptor, the flow of the eddy current is concentrated in the regions.

9. The susceptor of claim 8, wherein the at least one plurality of perforations comprises between 2 and 20 pluralities spaced circumferentially on the susceptor.

10. The susceptor of claim 9, wherein the at least one plurality of perforations comprises between 5 and 15 pluralities spaced circumferentially on the susceptor.

11. The susceptor of claim 10, wherein the at least one plurality of perforations comprises between 8 and 12 pluralities spaced circumferentially on the susceptor.

12. The susceptor of claim 8, wherein an area of the perforations varies along an axial direction of the susceptor.

13. The susceptor of claim 8, wherein an area of the regions varies along an axial direction of the susceptor.

14. The susceptor of claim 8, wherein the perforations are circular, with a diameter of between 0.5 mm and 3 mm.

15. A system, comprising: a cylindrical ceramic wick for an aerosol generating device comprising an outer surface, a hollow core and a base, whereinthe base comprises at least one indentation arranged such that, when, in use, the indentation engages with a cylindrical cup, an airflow path for allowing air to flow from the exterior of the wick into the hollow core is defined; andthe outer surface comprises a raised portion arranged such that, when, in use, a susceptor engages with the wick, the raised portion abuts the susceptor; anda susceptor surrounding at least part of the cylindrical wick, comprising at least one plurality of perforations, wherein the perforations are spaced axially on the susceptor, and arranged such that regions are formed between two axially adjacent perforations, the regions overlap with the at least one raised portion and when, in use, an eddy current flow is induced in the susceptor, the flow of the eddy current is concentrated in the regions.

16. An aerosol generating device comprising the wick of claim 1.

17. An aerosol generating device comprising the susceptor of claim 8.

18. An aerosol generating device comprising the system of claim 15.