Abstract
A heating element for an aerosol-generating system is provided, the heating element including: a plurality of first filaments; and a plurality of second filaments, in which the plurality of first filaments are configured to heat a liquid aerosol-forming substrate, the plurality of second filaments are configured to convey the liquid aerosol-forming substrate to wet at least a portion of the heating element with the liquid aerosol-forming substrate, and the heating element is arranged to form a mesh, the plurality of first filaments being arranged in a first direction and the plurality of second filaments being arranged in a second direction, and the second direction being transverse to the first direction. A heater assembly, a cartridge, and a method of manufacturing a heating element, are also provided.
Claims
1.-15. (canceled)
16. A heating element for an aerosol-generating system, the heating element comprising: a plurality of first filaments; and a plurality of second filaments, wherein the plurality of first filaments are configured to heat a liquid aerosol-forming substrate, wherein the plurality of second filaments are configured to convey the liquid aerosol-forming substrate to wet at least a portion of the heating element with the liquid aerosol-forming substrate, and wherein the heating element is arranged to form a mesh, wherein the plurality of first filaments are arranged in a first direction and the plurality of second filaments are arranged in a second direction, and wherein the second direction is transverse to the first direction.
17. The heating element according to claim 16, wherein the plurality of first filaments are formed from an electrically conductive material.
18. The heating element according to claim 16, wherein the plurality of second filaments are hydrophilic.
19. The heating element according to claim 16, wherein the plurality of second filaments are formed from a non-metallic material.
20. The heating element according to claim 16, wherein the plurality of first filaments are formed from a magnetic metallic material and the plurality of second filaments are formed from a non-metallic hydrophilic material, and wherein the heating element further comprises a plurality of third filaments, which are formed from a non-magnetic metallic material.
21. The heating element according to claim 16, wherein the heating element further comprises an interwoven mesh.
22. A heater assembly for an aerosol-generating system, the heater assembly comprising a heating element according to claim 16 and a transport material configured to convey a liquid aerosol-forming substrate to the heating element.
23. The heater assembly according to claim 22, wherein portions of some of the plurality of second filaments are integrated into the transport material.
24. The heater assembly according to claim 22, further comprising at least two electrical contacts configured to supply electrical power to the heating element, wherein each of the electrical contacts is connected to at least one of the plurality of first filaments.
25. A cartridge for an aerosol-generating system, the cartridge comprising a heater assembly according to claim 22 and a liquid storage portion configured to hold a liquid aerosol-forming substrate.
26. An aerosol-generating system, comprising: a cartridge according to claim 25; and an aerosol-generating device comprising a power supply configured to supply electrical power to the heating element, wherein the cartridge is configured to be removably coupled to the aerosol-generating device.
27. A method of manufacturing a heating element for an aerosol-generating system, the method comprising: providing a plurality of first filaments configured to heat a liquid aerosol-forming substrate; providing a plurality of second filaments configured to convey the liquid aerosol-forming substrate along at least a portion of their length to distribute the liquid aerosol-forming substrate across at least a portion of the heating element; and arranging the heating element to form a mesh, wherein the plurality of first filaments are arranged in a first direction and the plurality of second filaments are arranged in a second direction, the second direction being transverse to the first direction.
Description
[0114] Examples will now be further described with reference to the figures in which:
[0115] FIG. 1 is a schematic plan view of a heating element in accordance with an example of the present disclosure.
[0116] FIG. 2 is a schematic plan view of a heating element in accordance with another example of the present disclosure.
[0117] FIG. 3A is a schematic illustration of one arrangement of the filaments of the heating element of FIG. 2.
[0118] FIG. 3B is a schematic illustration of another arrangement of the filaments of the heating element of FIG. 2.
[0119] FIG. 4 is a perspective view of a heater assembly in accordance with an example of the present disclosure.
[0120] FIG. 5 is a plan view of a heater assembly in accordance with another example of the present disclosure.
[0121] FIG. 6A is an enlarged cross-sectional view through part of a heater assembly in accordance with an example of the present disclosure.
[0122] FIG. 6B is an enlarged cross-sectional view through part of a heater assembly in accordance with another example of the present disclosure.
[0123] FIG. 7 is a schematic illustration of an example aerosol-generating system comprising a cartridge and an aerosol-generating device according to an example of the present disclosure.
[0124] FIG. 8A is a schematic illustration of an apparatus used for measuring the wicking performance of a heating element.
[0125] FIG. 8B is a graph showing the absorption of liquid aerosol-forming substrate versus time for three different heating element samples.
[0126] Referring to FIG. 1, there is shown a schematic plan view of a heating element 1. The heating element 1 is a hybrid heating element comprising a plurality of first filaments 2, which are configured to heat a liquid aerosol-forming substrate (not shown), and a plurality of second filaments 4, which are configured to convey a liquid aerosol-forming substrate to wet at least a portion of the heating element 1 with liquid aerosol-forming substrate. The plurality of first filaments 2 and plurality of second filaments 4 extend in the same direction and are interlaced. In other words, each second filament 4 is arranged between neighbouring ones of the plurality of first filaments 2. The plurality of first filaments 2 and plurality of second filaments 4 are held in place by attaching them to an underlying substrate or transport material (not shown).
[0127] The plurality of first filaments 2 are electrically conductive and are made from stainless steel wire. The plurality of second filaments 4 are made from glass fibre threads which are hydrophilic. Liquid aerosol-forming substrate is conveyed or drawn along the length of the plurality of second filaments 4 by capillary action between the fibres of the glass fibre threads. This, in turn, helps to draw or convey liquid aerosol-forming substrate along the plurality of first filaments 2. In addition, the spaces 6 between the first 2 and second 4 filaments act as capillary channels which help to convey and draw liquid aerosol-forming substrate along the plurality of first filaments 2. Therefore, the plurality of second filaments 4 help to consistently wet the heating element 1 by distributing liquid aerosol-forming substrate within or over the heating element 1.
[0128] In use, the plurality of first filaments 2 of the heating element 1 may be inductively or resistively heated. Heat generated by the plurality of first filaments 2 vaporises the liquid aerosol-forming substrate, which is released from the heating element 1 in the spaces 6 between the first 2 and second 4 filaments. The glass fibre threads of the plurality of second filaments 4 are able to withstand the temperatures of the plurality of first filaments 2 during heating.
[0129] FIG. 2 shows a schematic plan view of another example heating element 10. The heating element 10 comprises an interwoven mesh 12 comprising a plurality of first filaments and a plurality of second filaments having interstices or apertures 14 therein. FIGS. 3A and 3B shows different arrangements of the pluralities of first and second filaments of the heating element 10. Each of FIGS. 3A and 3B show only part of the heating element 10 which has been enlarged for clarity. Similar to the heating element 1 of FIG. 1, the plurality of first filaments are made from electrically conductive stainless steel wire and are configured to heat a liquid aerosol-forming substrate (not shown). The plurality of second filaments 14b are made from hydrophilic glass fibre threads and are configured to convey a liquid aerosol-forming substrate to wet at least a portion of the heating element 1 with liquid aerosol-forming substrate.
[0130] In the arrangement of FIG. 3A, the plurality of first filaments 16a, 16b, that is, the heating filaments, are arranged in a mesh configuration. Half of the plurality of first filaments 16a are arranged in a first direction of the interwoven mesh and the other half of the plurality of first filaments 16b are arranged in a second direction of the interwoven mesh which is substantially orthogonal to the first direction. The apertures 14 are arranged between, and are bounded by, the plurality of first filaments 16a, 16b.
[0131] In the arrangement of FIG. 3A, the plurality of second filaments 18a, 18b, that is, the wicking filaments, are arranged between the plurality of first filaments 16a, 16b in both the first and second directions such that each space between neighbouring ones of the plurality of first filaments 16a, 16b contains a second filament 18a, 18b. In other words, the interwoven mesh heating element of FIG. 3A contains alternating first 16a and second 18a filaments in the first direction and alternating first 16b and second 18b filaments in the second direction. The first and second directions are substantially orthogonal to one another. The plurality of second filaments 18a, 18b intersect in the apertures 14 between the plurality of first filaments 16a, 16b and occupy at least a portion of the area of each of the apertures 14. In this arrangement, the plurality of second filaments 18a, 18b help to convey or draw liquid aerosol-forming substrate into the interstices or apertures 14 between the plurality of first filaments 16a, 16b and along the plurality of first filaments 16a, 16b, which in turn helps to wet the heating element 10.
[0132] In the arrangement of FIG. 3B, the heating element 10 is arranged in a mesh configuration. The plurality of first filaments 16, that is, the heating filaments, are arranged in a first direction and the plurality of second filaments 18, that is, the wicking filaments, are arranged in a second direction. The second direction is substantially orthogonal to the first direction. In this arrangement, the plurality of second filaments 18 help to convey or draw liquid aerosol-forming substrate into the spaces 14 between the plurality of first filaments 16 which helps to wet the heating element 10.
[0133] It should be noted that FIGS. 1, 2, 3A and 3B are schematic and are not to scale. For clarity, the figures have been simplified and the size of their features altered. For example, the filaments have been enlarged and their aspect ratio changed. In addition, fewer filaments are shown than would be present in an actual heating element.
[0134] FIG. 4 is a perspective view of a heater assembly 100 comprising the mesh heating element 10 of FIG. 2 and a transport material 102. The mesh heating element 10 may have the filament arrangement of either FIG. 3A or 3B described above. The transport material is made from porous ceramic. Any suitable ceramic may be used for the transport material. The heating element 10 is fixedly attached to an upper surface of the transport material 102. Any suitable method of fixation can be used to attach the heating element 10 to the transport material.
[0135] The transport material 102 is arranged to convey a liquid aerosol-forming substrate (not shown) to the mesh heating element 10. As described above in respect of FIG. 2, a plurality of interstices or apertures are defined between the filaments of the mesh heating element 10. During heating, vaporised aerosol-forming substrate can be released from the heater assembly 100 via the apertures to generate an aerosol.
[0136] The heater assembly 100 further comprises a pair of electrical contacts 104 for supplying electrical power to the mesh heating element 10. The electrical contacts 104 comprise a pair of tin pads which are bonded directly to the mesh heating element 10 and are arranged on opposing sides of the mesh. Whilst the electrical contacts cover a portion of the mesh heating element 10, a sufficient area of the mesh heating element 10 remains and this does not affect aerosol generation.
[0137] FIG. 5 is a plan view of another example heater assembly 200 comprising a heater mount 202 and an interwoven mesh heating element 204. A rectangular opening 206 is formed in an upper end 202a of the heater mount 202 and passes through the upper end 202a of the heater mount 202 into an internal compartment (not shown) which comprises a liquid aerosol-forming substrate (not shown). Liquid aerosol-forming substrate is able to pass through the rectangular opening 206 to the mesh heating element 204. A transport material (not shown) may be arranged in the rectangular opening 206 in contact with the mesh heating element 204 to convey liquid aerosol-forming substrate to the mesh heating element 204. The mesh heating element 204 extends across the rectangular opening 206 and is fixedly attached to the upper surface 202a of the heater mount 202 on opposing sides of the heater mount 202. Any suitable method of fixation can be used to attach the heating element 204 to the heater mount 202. The heater mount 202 is made from PEEK.
[0138] The heater mount 202 is configured to be received with an induction coil (not shown) of an aerosol-generating device (not shown) so that the mesh heating element 204 can be inductively heated. The mesh heating element 204 comprises a plurality of first filaments 204a which are made from magnetic stainless steel wire such as AISI 430. The plurality of first filaments 204a are configured to be inductively heated to heat a liquid aerosol-forming substrate. The plurality of first filaments 204a are arranged in a first direction of the interwoven mesh heating element 204, which first direction is aligned with the direction of the applied varying magnetic field provided by the induction coil. The mesh heating element 204 also comprises a plurality of second filaments 204b which are made from glass fibre threads. The plurality of second filaments 204b are configured to convey a liquid aerosol-forming substrate to wet at least a portion of the mesh heating element 204 with liquid aerosol-forming substrate. The plurality of second filaments 204b are arranged in a second direction of the interwoven mesh heating element 204. The second direction is substantially orthogonal to the first direction. The mesh heating element 204 further comprises two pluralities of third filaments 204c which are made from non-magnetic stainless steel wire such as AISI 304. The pluralities of third filaments 204c are configured not to be inductively heated. The pluralities of third filaments 204c are also arranged in a first direction of the interwoven mesh heating element 204 and are located on either side of the region of the mesh heating element 204 formed by the plurality of first filaments 204a.
[0139] The mesh heating element 204 is fixedly attached to the heater mount in the regions of the mesh heating element 204 formed by the pluralities of third filaments 204c. The pluralities of third filaments 204c made from non-magnetic stainless steel wire are not heated by the induction coil of the aerosol-generating device and therefore significant heating of the regions of the mesh heating element 204 formed by the pluralities of third filaments 204c is avoided. This helps to reduce heating and thermal stress in the areas where the mesh heating element 204 is fixedly attached to the heater mount 202, which in turn helps to reduce damage to the heater mount 202 caused by heating of the mesh heating element 204.
[0140] FIG. 6A shows an enlarged cross-sectional view through part of an example heater assembly 300a comprising the mesh heating element 10 of FIG. 2 and a transport material 302. The mesh heating element 10 has the filament arrangement of FIG. 3B described above. That is, the mesh heating element 10 comprises a plurality of first or heating filaments 16 arranged in a first (warp) direction and a plurality of second or wicking filaments 18 arranged in a second (weft) direction, which is substantially orthogonal to the first direction. However, the filament arrangement of FIG. 3B or any other suitable filament arrangement could be used. The transport material is made from a porous ceramic. Any suitable ceramic may be used for the transport material. The heating element 10 is fixedly attached to an upper surface 302a of the transport material 302. Any suitable method of fixation can be used to attach the heating element 10 to the transport material 302.
[0141] The plurality of second filaments 18 convey or wick liquid aerosol-forming substrate from the transport material 302 into the spaces 14 between the plurality of first filaments 16 of the mesh heating element 10 as denoted by arrows A in FIG. 6A. This assists in wetting the mesh heating element 10 and improves the contact between the plurality of first filaments 16 and the transport material 302, which improves the transfer of liquid aerosol-forming substrate from the transport material 302 to the plurality of first filaments 16. The plurality of first filaments 16 heat and vaporise the liquid aerosol-forming substrate and vaporised aerosol-forming substrate escapes from the heater assembly 300a via the spaces 14 in the mesh heating element 10. The mesh heating element 10 is consistently wetted between uses, which assists in the production of an improved and more consistent aerosol.
[0142] FIG. 6B shows an enlarged cross-sectional view through part of another example heater assembly 300b. The arrangement of FIG. 6B is the same as that of FIG. 6A with the exception that the mesh heating element 10 has been integrated or embedded into the ceramic transport material 302 such that the upper surface 302a of the transport material 302 now contacts the plurality of first filaments 16, that is, the heating filaments. The portions of the plurality of second filaments 18, that is, the wicking filaments, which are below the plurality of first filaments 16 are embedded within the ceramic. The undulating shape of the plurality of second filaments 18 helps to achieve integration of the mesh heating element 10 with the transport material because it provides portions which can be embedded in the ceramic. The portions of the plurality of second filaments 18 below the plurality of first filaments 16 may be embedded in the pores of the porous ceramic transport material or the transport material may be formed with grooves or depressions for receiving portions of the plurality of second filaments 16. Alternatively, the transport material may be directly deposited on the underside of the mesh heating element 10 by some form of physical, vapour or electro deposition process.
[0143] FIG. 7 is a schematic illustration of an example aerosol-generating system. The aerosol-generating system comprises two main components, a cartridge 400 and a main body part or aerosol-generating device 500. A connection end 415 of the cartridge 400 is removably connected to a corresponding connection end 505 of the aerosol-generating device 500. The connection end 415 of the cartridge 400 and connection end 505 of the aerosol-generating device 500 each have electrical contacts or connections (not shown) which are arranged to cooperate to provide an electrical connection between the cartridge 400 and the aerosol-generating device 500. The aerosol-generating device 500 contains a power source in the form of a battery 510, which in this example is a rechargeable lithium ion battery, and control circuitry 520. The aerosol-generating system is portable and has a size comparable to a conventional cigar or cigarette. A mouthpiece 425 is arranged at the end of the cartridge 400 opposite the connection end 415.
[0144] The cartridge 400 comprises a housing 405 containing the heater assembly 100 of FIG. 4 and a liquid storage compartment or portion having a first storage portion 430 and a second storage portion 435. A liquid aerosol-forming substrate is held in the liquid storage compartment. Although not illustrated in FIG. 7, the first storage portion 430 of the liquid storage compartment is connected to the second storage portion 435 of the liquid storage compartment so that liquid in the first storage portion 430 can pass to the second storage portion 435. The heater assembly 100 receives liquid from the second storage portion 435 of the liquid storage compartment. At least a portion of the ceramic transport material of heater assembly 100 extends into the second storage portion 435 of the liquid storage compartment to contact the liquid aerosol-forming substrate therein.
[0145] An air flow passage 440, 445 extends through the cartridge 400 from an air inlet 450 formed in a side of the housing 405 past the mesh heating element of the heater assembly 100 and from the heater assembly 100 to a mouthpiece opening 410 formed in the housing 405 at an end of the cartridge 400 opposite to the connection end 415.
[0146] The components of the cartridge 400 are arranged so that the first storage portion 430 of the liquid storage compartment is between the heater assembly 100 and the mouthpiece opening 410, and the second storage portion 435 of the liquid storage compartment is positioned on an opposite side of the heater assembly 100 to the mouthpiece opening 410. In other words, the heater assembly 100 lies between the two portions 430, 435 of the liquid storage compartment and receives liquid from the second storage portion 435. The first storage portion 430 of the liquid storage compartment is closer to the mouthpiece opening 410 than the second storage portion 435 of the liquid storage compartment. The air flow passage 440, 445 extends past the mesh heating element of the heater assembly 100 and between the first 430 and second 435 portions of the liquid storage compartment.
[0147] The aerosol-generating system is configured so that a user can puff or draw on the mouthpiece 425 of the cartridge to draw aerosol into their mouth through the mouthpiece opening 410. In operation, when a user puffs on the mouthpiece 425, air is drawn through the airflow passage 440, 445 from the air inlet 450, past the heater assembly 100, to the mouthpiece opening 410. The control circuitry 520 controls the supply of electrical power from the battery 510 to the cartridge 400 when the system is activated. This in turn controls the amount and properties of the vapour produced by the heater assembly 100. The control circuitry 520 may include an airflow sensor (not shown) and the control circuitry 520 may supply electrical power to the heater assembly 100 when user puffs are detected by the airflow sensor. This type of control arrangement is well established in aerosol-generating systems such as inhalers and e-cigarettes. When a user puffs on the mouthpiece opening 410 of the cartridge 400, the heater assembly 100 is activated and generates a vapour that is entrained in the air flow passing through the air flow passage 440. The vapour cools within the airflow in passage 445 to form an aerosol, which is then drawn into the user's mouth through the mouthpiece opening 410.
[0148] In operation, the mouthpiece opening 410 is typically the highest point of the system. The construction of the cartridge 400, and, in particular, the arrangement of the heater assembly 100 between first and second storage portions 430, 435 of the liquid storage compartment, is advantageous because it exploits gravity to ensure that the liquid substrate is delivered to the heater assembly 100 even as the liquid storage compartment is becoming empty, but prevents an oversupply of liquid to the heater assembly 100 which might lead to leakage of liquid into the air flow passage 440.
[0149] FIG. 8A shows a schematic illustration of an apparatus 600 used for measuring the wicking performance of a mesh heating element 602. A 10 mm×5 mm rectangular sample of a mesh heating element 602 is prepared. The sample mesh heating element 602 is suspended vertically by one of its narrower edges from a weighing scale 604 that is capable of accurately measuring the weight of objects weighing as little as 0.0001 grams. The weighing scale may be connected to a computer (not shown) which logs measured weights over time. A container 606 containing an amount of liquid aerosol-forming substrate 608 underlies the sample mesh heating element 602. The mesh heating element 602 is lowered until the bottom horizontal narrow edge 602a of the sample mesh heating element 602 is in contact with the liquid aerosol-forming substrate 608 in the container 606. The amount of liquid absorbed by the mesh heating element 602 is then recorded against elapsed time from when wicking begins, that is, the time at which the sample mesh heating element 602 is brought into contact with the liquid aerosol-forming substrate. Liquid absorption by the sample mesh heating element 602 is due to vertical wetting of the heating element 602 with liquid aerosol-forming substrate.
[0150] FIG. 8B shows a graph of liquid aerosol-forming substrate absorption in grams versus elapsed time in milliseconds for three different mesh heating element samples. The samples have the materials and dimensions shown in Table 1 below.
TABLE-US-00001 TABLE 1 Sample Materials and dimensions Sample 1 AISI 430 stainless steel wire, wire diameter 63 micron, mesh aperture size 80 micron Sample 2 AISI 312 stainless steel wire, wire diameter 25 micron, mesh aperture size 100 micron Sample 3 AISI 312 stainless steel wire, wire diameter 25 micron, mesh aperture size 100 micron, glass-fibre threads added in one direction of mesh (in FIG. 8A they are in the vertical direction), thread width is approximately equal to aperture size, that is, around 100 micron, thread thickness is approximately equal to wire diameter, that is, around 25 micron
[0151] As can be seen from Table 1, Samples 1 and 2 are made from a single material. However, Sample 3 is a hybrid mesh and comprises both stainless steel wire as first filaments and glass-fibre threads as second filaments.
[0152] The graph of FIG. 8B shows the relative performance of Samples 1 to 3. As can be seen from the graph, the hybrid mesh of Sample 3 exhibits significantly improved performance compared to Samples 1 and 2 in terms of the rate of liquid absorption and the amount of liquid absorbed. Sample 3 has a higher rate of absorption of liquid aerosol-forming substrate compared to Samples 1 and 2. This means that the mesh heating element of Sample 3 will rewet more quickly following a previous puff than the other two samples. In addition, after 500 milliseconds, the amount of liquid absorbed by the hybrid mesh of Sample 3 is approximately two times higher than Sample 2, the nearest contender, suggesting that wicking and wetting performance is better in Sample 3 and that fast wicking and wetting is achieved. Therefore, it can be concluded from FIG. 8B that the provision of a hybrid mesh improves wicking and wetting performance. This will help to achieve more consistent aerosol generation between successive puffs and between aerosol-generating devices of the same type.
