Heating Apparatus

Abstract

A heating apparatus for an aerosol generating device includes a heating element supported within a housing and extending along the length of the housing, an air flow path arranged to transport air over the heating element, and a liquid supply configured to supply liquid to the heating element, wherein the heating element includes a woven sheet of electrically conductive fibres, and wherein the fibres are arranged with a regular orientation to form a woven mesh that transports liquid by capillary action, in use. The woven sheet includes a first array of electrically conductive fibres extending in a first direction.

Claims

1. A heating apparatus for an aerosol generating device, comprising: a heating element supported within a housing and extending along a length of the housing; an air flow path arranged to transport air over the heating element; and a liquid supply configured to supply liquid to the heating element, wherein the heating element comprises a woven sheet of electrically conductive fibres, wherein the electrically conductive fibres are arranged with a regular orientation to form a woven mesh configured to transports liquid by capillary action, in use, and wherein the woven sheet comprises: a first array of electrically conductive fibres extending in a first direction.

2. The heating apparatus of claim 1, wherein the electrically conductive fibres are displaced at regular intervals.

3. The heating apparatus of claim 1, wherein the woven sheet further comprises: a second array of electrically conductive fibres extending in a second direction, wherein the first array of electrically conductive fibres and the second array of electrically conductive fibres intersect to form the woven mesh.

4. The heating apparatus of claim 3, wherein the mesh is woven such that each fibre in the first array alternately winds over opposite sides of subsequent fibres of the second array.

5. The heating apparatus of claim 4, wherein the mesh is woven such that each fibre in the second array alternately winds over opposite sides of subsequent fibres of the first array.

6. The heating apparatus of claim 3, wherein the first and second directions are substantially orthogonal.

7. The heating apparatus of claim 1, wherein the woven sheet of the heating element comprises one or more slots extending inwardly from at least one edge of the woven sheet.

8. The heating apparatus of claim 3, further comprising at least one additional fibre woven into the mesh, wherein the at least one additional fibre comprises a different material to the electrically conductive fibres of the first and second arrays.

9. The heating apparatus of claim 3, further comprising a third array of electrically conductive fibres extending in a third direction, wherein the third array of electrically conductive fibres is arranged to intersect with the first array of electrically conductive fibres and the second array of electrically conductive fibres.

10. The heating apparatus of claim 9, wherein the third direction is substantially orthogonal to the first direction and the second direction.

11. The heating apparatus of claim 9, wherein at least two of the first, second and third arrays of electrically conductive fibres comprise different materials and/or different fibre thicknesses.

12. The heating apparatus of claim 1, wherein at least one region of the mesh is stretched or compressed relative to a surrounding region of the mesh.

13. The heating apparatus of claim 1, wherein a thickness of the mesh in a central region is greater than a thickness of the mesh in a peripheral region.

14. The heating apparatus of claim 1, wherein the liquid supply at least partially surrounds the housing and is configured to directly interface with the heating element along the length of the housing.

15. An aerosol generating device comprising the heating apparatus of claim 1, wherein the heating element is secured within the aerosol generating device by stitching the woven mesh.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Embodiments of the invention are now described, by way of example, with reference to the drawings, in which:

[0024] FIG. 1 is a schematic view of a heating apparatus for an aerosol generating device in an embodiment of the invention;

[0025] FIG. 2 is a schematic top view of a heating element in an embodiment of the invention;

[0026] FIG. 3 is a schematic view of the internal structure of a woven heating element in an embodiment of the invention;

[0027] FIG. 4 is a schematic view of a heating element comprising fibres of different thicknesses in an embodiment of the invention;

[0028] FIG. 5 is a schematic view of the heating element depicted in FIG. 3 comprising an additional interwoven fibre in an embodiment of the invention; and

[0029] FIG. 6 is a schematic view of the heating element depicted in FIG. 3 further comprising locally stretched and locally compressed regions in an embodiment of the invention.

DETAILED DESCRIPTION

[0030] FIG. 1 shows a heating apparatus 2 in an embodiment of the invention that comprises a heating element 4, a liquid store 6 and a housing 8. The heating apparatus 2 is configured to be set in an aerosol generating device comprising a battery and a mouthpiece.

[0031] In use, the heating element 4 is arranged to receive electrical energy from the battery in order to generate an aerosol by heating an aerosol generating liquid that is drawn onto the heating element 4 from the liquid store 6 via capillary action. One or more airflow channels 10 are provided in the housing 8, and configured to, on user inhalation, direct air from outside the heating apparatus 2 through the air flow channel 10 and toward the mouthpiece of the aerosol generation device. This means that aerosol that has been generated by heating aerosol generating liquid on the heating element 4 will be carried along the air flow channel 10 to exit the device.

[0032] The heating element 4 is substantially planar and is mounted in the housing 8. The housing 8 includes a first portion 12 placed above the top major side of the heating element 4 and a second portion 14 placed below the lower major side of the heating element 4 such that the heating element 4 is held between the two housing portions. The housing 8 acts as a vaporisation chamber which is configured to collect generated aerosol within the inner spaces of the two housing portions 12 and 14.

[0033] One or more edges of the heating element 4 are exposed to the liquid store 6 which surrounds the housing 8 and heating element 4. The edges of the heating element 4 may extend beyond the outer limits of the heater housing 8, or alternatively the first and second housing portions 12 and 14, when constructed, form a gap between the two housing portions 12 and 14 which allows aerosol generating liquid from the liquid store 6 to come into contact with the heating element edge, whereby the liquid is drawn further across the heating element 4 via capillary action.

[0034] The heating element 4 comprises a woven sheet of electrically conductive fibres. The term “sheet” refers to a planar shape with a thickness many times smaller than its length or breadth. However, the skilled person will appreciate a non-planar woven arrangement of electrically conductive fibres may also be used as a heating element. The woven fibres form a porous network of fibres, thereby providing the heating element 4 with wicking properties. Hence, the provision of an additional wicking element to transport vaporisable liquid from the liquid store 6 is not required within the heating apparatus 2.

[0035] The thickness of the sheet of heating element 4 may be varied along its length or across its breadth. In one example, the sheet of heating element 4 may be configured such that it is thicker in the centre of the sheet, and thinner at the sheet edge. This arrangement encourages the wicking of liquid from the liquid store at the sheet edge, as more liquid is able to be stored in the thicker central region of the sheet. For example, the thickness of the heating element 4 in the central region may be up to twice the thickness of the heating element 4 in the peripheral region.

[0036] In one example, the heating element 4 may be stitched to one or more of the components within the heating apparatus 2. In another example, the heating element 4 may be welded to one or more components.

[0037] FIG. 2 shows a schematic top view of the heating element 4 in an embodiment of the invention. The heating element 4 has two contact ends 5 which may be connected to a power source (not shown). In use, an electric current passes through the heating element 4 between the contact ends 5, thereby causing the heating element 4 to generate heat. The heating element 4 also includes a plurality of slots 7, which are arranged to cause an electric current to follow a serpentine path as it flows between the two contact ends 5. This results in different concentrations of current along the path, and the establishment of temperature gradients across the heating element. In alternative arrangements, the heating element 4 may comprise a simple shape, such as a rectangle, and different current concentrations may be established across the heating element 4 by alternative means.

[0038] FIG. 3 shows a schematic view of the internal structure of the heating element 4 in an embodiment of the invention. The heating element 4 comprises a first array 16 of electrically conductive fibres extending in a first direction, and a second array 18 of electrically conductive fibres extending in a second perpendicular direction. The fibres in the first array 16 and second array 18 are regularly spaced and woven in a plain weave pattern, such that each fibre of the first array 16 is passed over alternately on a first side and a second opposite side by the second array 18 of fibres, and vice versa, thereby forming a woven planar layer of fibres. Typical interval values for the fibre spacing in each array range from 25 to 500 microns, for example 250 microns.

[0039] The fibres of the first array 16 and second array 18 may be made of a metal, such as stainless steel, non-stainless steel, iron, copper, tungsten, aluminium, brass, Nichrome, Kanthal, Cupronickel and other alloys, or any other metal (element, compound or alloy). Alternatively, the fibres may be made of a non-metal material such as molybdenum disilicide, silicon carbide and other ceramics or semiconductors, or any other non-metal. The fibres of the first and second arrays 16 and 18 may be made of the same material or may differ between within each array 16 and 18.

[0040] The regular arrangement of fibres reduces the local variation in properties across the heating element 4. Capillary forces act uniformly across the heating element 4 and the variance in current density across the heating element 4 is reduced. In addition, the woven arrangement ensures that each fibre is securely held within the heating element 4, such that the likelihood of fibres becoming loose or falling out of the heating element 4 is low. The mechanical strength of the heating element 4 is also increased.

[0041] As will be readily appreciated by the skilled person, the first and second arrays 16 and 18 may be woven into a variety of other patterns. Examples include twill, basketweave, satin or leno arrangement, or any other woven pattern.

[0042] In order to ensure liquid is transported to the centre of the heating element 4, the heating element 4 may comprise multiple planar layers of fibres, stacked in a direction perpendicular to the plane of each layer. The multiple layers of woven fibres may be sintered together to improve the homogeneity of the heating element 4. The number of layers may be varied in different regions of the heating element 4, for example to increase the thickness of a central region of the heating element 4.

[0043] The skilled person will also appreciate that the heating element 4 may comprise a third array of woven fibres extending in a third direction. In one example, the third direction may be orthogonal to the first and second directions.

[0044] FIG. 4 shows a schematic view of an alternative heating element 20 in an embodiment of the invention, for use in heating apparatus 2.

[0045] The heating element 20 comprises a first array 22 of electrically conductive fibres extending in a first direction, and a second array 24 of electrically conductive fibres extending in a second perpendicular direction. The fibres in the first array 22 are thicker than the fibres in the second array 24. Hence, the resistance of fibres in the first array 22 is greater than the resistance of fibres in the second array 24 (when the fibres are made out of the same material), and the degree of resistive heating is varied in the first and second directions. As such, a temperature gradient may be established across the heating element 20. Typically, the fibres range in thickness from 25 microns to 250 microns, for example 100 microns.

[0046] It will be understood by the skilled person that the fibre thickness may also be varied within the same array, depending on the desired temperature profile across the heating element 20 and other operational requirements.

[0047] In an alternative embodiment, the material of each fibre may be varied between arrays 16 and 18, or may differ within each array 16 and 18. This provides an alternative method of varying the fibre resistance in different directions, enabling the establishment of temperature gradients across the heating element 4, or preferential paths for the current to flow.

[0048] FIG. 5 shows a schematic view of heating element 4 in embodiment of the invention, for use in heating apparatus 2. The heating element 4 comprises an additional material 26 woven into the mesh fibres. In this way, the heating element 4 may be provided with different properties in different regions.

[0049] In one example, the additional woven material may be chosen such that it has a higher conductivity than the fibres of the mesh. Hence, when electrical energy is supplied to the heating element 4, a preferential current path is provided. For example, a central region of higher conductivity may be provided across the sheet such that current preferentially flows through the central region, thus preferentially heating the area, creating temperature gradients which can be utilised to optimise the wicking properties of the heating element. In one arrangement, the mesh may comprise aluminium fibres and the additional woven material 26 may comprise Nichrome.

[0050] FIG. 6 shows a schematic view of heating element 4 in an embodiment of the invention, for use in heating apparatus 2.

[0051] The heating element 4 has been manipulated to provide locally compressed regions 4 having a reduced spacing between fibres, and locally stretched regions 30 having an increased spacing between fibres. The locally stretched region 30 will produce an area of high current density, and the locally compressed region 28 will produce an area of low current density. Areas of high current density will become hotter than areas of low current density, such that a temperature gradient is established across the mesh.

[0052] In addition, the change in spacing between fibres will alter the size of interstices within the mesh, leading to a variation in capillarity properties or possibly the provision of a preferential current path. The size and frequency of compressed and stretched regions 28 and 30 may be tailored according to the operational requirements of the heating element 4.