Heater element and method for manufacturing a heater element

Abstract

An elongated metal heater element (40) for use in an aerosol generating device (20) is disclosed. The heater element extends between a proximal end (44) and a distal end (45). The proximal end is configured to be attached to an aerosol generating device for electrical communication therewith. The heater element has either or both a plurality of surface notches (48) formed on a surface of the heater element and a plurality of subsurface cavities (480) defined below the surface of the heater element.

Description

Technical Field

[0001] The present disclosure relates to a heater element suitable for use in an aerosol generating device. The present disclosure also relates to a method of manufacturing such a heater element.

Background Art

[0002] Heater elements for use as part of an aerosol generating device are known in the art. More specifically, electric heater elements that generate heat by resistive heating under the action of an electric current are known. Such electric resistive heater elements can take the form of a ceramic substrate on which a metallic resistive heating track is disposed. In use, the electricity supplied to the resistive heating track can induce heating of the track. An aerosol generating device incorporating such a known resistive heater element can be used in a known aerosol generating article containing a plug of an aerosol forming substrate. In use, the resistive heater element is inserted into the aerosol generating article such that the heater element is in direct contact with the aerosol forming substrate. The heat transferred from the resistive heater element to the aerosol forming substrate vaporizes the components of the aerosol forming substrate. The vapors emitted from the substrate are cooled and condensed as they pass through the aerosol generating article to form an aerosol for inhalation by the user. However, by repeatedly using the aerosol generating device with different aerosol generating articles, residues can gradually accumulate on the heater element. This residue can prevent the heater element from transferring heat to the aerosol forming substrate and can also impart an undesirable flavor to the vapors emitted from the aerosol forming substrate. Thus, the presence of such residues on the heater element can be detrimental to the user experience with respect to the aerosol generating device. Cleaning may be performed to remove this residue from the surface of the heater element. However, cleaning can potentially apply one or a combination of tensile, compressive, and torsional forces to the heater element. Since the ceramic substrate is inherently brittle, applying force to such known ceramic-based heater elements during cleaning can cause the heater element to fracture.

[0003] Because metallic materials generally have greater ductility than ceramic materials, replacing a ceramic substrate with a substrate made of metallic material may help reduce the likelihood of the heater element fracturing. However, metallic materials generally have a higher thermal conductivity compared to ceramic materials. When a metallic material is used as the substrate for a heater element instead of a ceramic material, the relatively high thermal conductivity of the metallic substrate means that heat conducted from the resistance heating track into the substrate can be rapidly transferred throughout the metallic substrate. The rapid passage of heat through the metallic substrate can correspondingly cause the substrate temperature to rise rapidly. This rise in substrate temperature can thereby lead to overheating of sensitive components of the aerosol generator associated with the control and operation of the heater element. For example, the control circuit used to control the power supply to the heater element is often located close to where the heater element is positioned within the aerosol generator. Therefore, excessive heat from the metallic substrate can be conducted to the sensitive control circuit and damage it. Furthermore, damage to components of the aerosol generator can also result from heat radiating from excessively hot areas of the metallic substrate of the heater element. [Overview of the project] [Problems that the invention aims to solve]

[0004] Therefore, it is desirable to provide an improved resistance heater element that has enhanced heat flow control and can withstand forces that may be applied to the heater element during cleaning or operation (such as tensile, compressive, or torsional forces) without breaking. [Means for solving the problem]

[0005] According to a first aspect of the present disclosure, an elongated metal heater element is provided for use in an aerosol generator. The heater element extends between a proximal end and a distal end. The proximal end is configured to be attached to an aerosol generator for electrical communication with the aerosol generator. The heater element includes either or both of i) a plurality of surface notches formed on the surface of the heater element, and ii) a plurality of subsurface cavities defined below the surface of the heater element.

[0006] As used herein, the term “metal” is used to mean that a body or an entire body is made up of one or more metals. Therefore, the term “metal” encompasses specific metallic elements or alloys.

[0007] As used herein, the term "aerosol generator" is used to describe a device that generates an aerosol by interacting with an aerosol-forming substrate of an aerosol-generating article. Preferably, the aerosol generator is a smoking device that interacts with an aerosol-forming substrate of an aerosol-generating article to generate an aerosol that can be directly inhaled into the user's lungs through the user's mouth. The aerosol generator may be a holder for the smoking article. Preferably, the aerosol-generating article is a smoking article that generates an aerosol that can be directly inhaled into the user's lungs through the user's mouth. More preferably, the aerosol-generating article is a smoking article that generates a nicotine-containing aerosol that can be directly inhaled into the user's lungs through the user's mouth.

[0008] As used herein, the term "aerosol-forming substrate" refers to a substrate composed of, or containing, an aerosol-forming material that has the ability to generate aerosols by releasing volatile compounds upon heating.

[0009] By providing a metal heater element having multiple surface notches formed on its surface, the rate of heat transfer through the heater element at the locations of the surface notches is reduced compared to the same heater element without any such notches. The effect of forming notches on a metal heater element is that the thermally conductive metallic material that would otherwise be present to conduct heat is removed from the heater element. Therefore, the rate of heat transfer and the resulting temperature in one or more regions of the heater element can be controlled by the presence of such surface notches near one or more of those regions.

[0010] Providing a metal heater element having multiple subsurface cavities may offer the same advantages as those described above for surface notches. The use of subsurface cavities may be particularly beneficial for maintaining the bending stiffness of the heater element due to the inherent constraint effects of the metal substrate material that can enclose each subsurface cavity.

[0011] The use of surface notches or subsurface cavities can be compared to the use of through holes in metal heater elements. The use of surface notches or subsurface cavities of a given volume can maintain a higher level of bending stiffness in heater elements compared to through holes of the same volume. As used herein, the term “through hole” refers to a location where an opening extends between opposing surfaces of a heater element.

[0012] A surface notch is an open feature in that the notch is exposed on the surface of the heater element. In contrast, a subsurface cavity is a closed feature in that it is enclosed beneath the surface of the heater element and hidden from view.

[0013] In summary, the use of metal heater elements provided with either or both multiple surface notches and / or subsurface cavities offers improved thermal management for the heater element. These advantages coexist with the ductility derived from heater elements formed from metallic material. This inherent ductility reduces the likelihood of the heater element fracturing when subjected to tensile, compressive, or torsional forces during operation, use, or cleaning. Furthermore, surface notches and subsurface cavities reduce the mass of the heater element compared to the same heater element without such notches or cavities.

[0014] The distribution and size of surface notches and subsurface cavities may be selected and arranged to provide thermal management and temperature control for one or more specific areas of a metal heater element, while maintaining sufficient bending stiffness in the heater element to allow it to withstand forces encountered during operation, use, and cleaning. For example, if a metal heater element is intended to be inserted into an aerosol-forming substrate of an aerosol-generating article, the heater element should have sufficient bending stiffness to withstand insertion without bending.

[0015] Individual notches and cavities may be defined by one or more curved surfaces. For example, the surface of a notch may correspond to a portion of the surface of a sphere or ellipsoid. As a further example, the surface enclosing a cavity may correspond to the surface of a sphere or ellipsoid. The use of notches and cavities consisting of curved surfaces also reduces the possibility that individual notches and cavities will act as mechanical stress-increasing mechanisms when the heater element is subjected to tensile, compressive, or torsional forces. However, other shapes may be used for notches and cavities. For example, surface notches may be circular in plane, each defining a cylindrical hole extending into the surface of the heater element. Alternatively, surface notches may be hexagonal in plane, defining hexagonal holes extending into the surface of the heater element.

[0016] The heater element comprises a metal substrate and one or more resistance heating tracks, one or more of which may be disposed on the metal substrate. Multiple surface notches and subsurface cavities of the heater element may then be formed on or within the metal substrate. During use, current can be supplied to one or more resistance heating tracks of the heater element via the proximal end of the heater element. The flow of current along one or more resistance tracks results in heating of the tracks by resistance heating (also known as Ohm heating or Joule heating).

[0017] The metallic material of the metal heater element may include titanium or stainless steel. Furthermore, Inconel® alloy 617 may also be suitable, possessing a combination of high-temperature strength and oxidation resistance. For Inconel® alloy 617, the nickel and chromium content provides oxidation resistance, while the aluminum and nickel content also imparts high-temperature oxidation resistance. As an example, the heater element may take the form of a metallic substrate formed from titanium, stainless steel, or Inconel® alloy 617, with one or more resistance heating tracks arranged on one or more surfaces of the substrate. Other metallic materials may be used for the metal heater element, and the material is selected according to factors that may include bending stiffness, thermal conductivity, oxidation resistance, and chemical reactivity.

[0018] Multiple surface notches and subsurface cavities in a heater element may occupy a cumulative volume of 15% to 30% of the volume of the corresponding heater element without such notches and cavities. As used herein, the term “cumulative volume” refers to the sum of the volumes occupied by all surface notches and subsurface cavities formed in the heater element. Generally, a larger cumulative volume of a heater element occupied by surface notches or subsurface cavities results in a greater corresponding reduction in conductive heat transfer through the metal heater element in use. However, a larger cumulative volume occupied by notches or cavities reduces the bending stiffness of the heater element. By limiting the cumulative volume to 15% to 30%, a balance is provided between two conflicting desires: i) reducing excessive heat flow and the resulting high temperatures in the metal heater element, and ii) maintaining sufficient bending stiffness in the heater element to allow the element to withstand axial compressive forces without simply bending. However, conveniently, multiple surface notches and subsurface cavities in a heater element can account for a cumulative volume of 17% to 26% of the volume of the corresponding heater element that does not include these notches and cavities.

[0019] A heater element may not contain any through-holes extending through its thickness. In contrast to surface notches and subsurface cavities, "through-holes" can extend entirely between opposing surfaces of a heater element.

[0020] However, alternatively, the heater element may further include multiple through-holes extending through the thickness of the heater element. In this way, the heater element may include a combination of different categories of features corresponding to the removal of metallic material from the metallic heater element, providing improved thermal management of the heater element in use. For example, the heater element may include multiple through-holes along either multiple surface notches or multiple subsurface cavities. Alternatively, the heater element may include multiple through-holes, multiple surface notches, and multiple subsurface cavities. The multiple through-holes may be distributed along the length of the heater element. Each through-hole may allow airflow across the heater element in use.

[0021] Multiple surface notches and subsurface cavities of a heater element may be formed to define one or more honeycomb arrangements. As used herein, the term “honeycomb arrangement” refers to a repeating pattern of notches or cavities. The honeycomb arrangement may be two-dimensional; for example, it may be defined by separate layers of surface notches or subsurface cavities extending along two mutually orthogonal axes. Alternatively, the honeycomb arrangement may be three-dimensional. The use of such a honeycomb arrangement ensures that the region of the heater element in which the honeycomb arrangement is located has substantially uniform thermal and structural properties.

[0022] The heater element may contain multiple surface notches and no subsurface cavities at all. Alternatively, the heater element may contain multiple subsurface cavities and no surface notches at all.

[0023] At least a portion of the multiple surface notches and subsurface cavities of the heater element may be provided in an internal region of the heater element, which extends between the proximal end and 33% of the heater element's length relative to the proximal end. Since the proximal end is configured to be attached to an aerosol generator, ensuring that the internal region of the heater element includes at least a portion of the surface notches and subsurface cavities can help avoid overheating of electronic components of the aerosol generator located adjacent to the proximal end. Since the control electronics of the aerosol generator are often located at or near the proximal end of the heater element, providing notches or cavities in the internal region of the heater element can prevent excessive temperatures from developing in this region of the heater element and in adjacent components of the aerosol generator. Conveniently, at least 40% of the total volume of the multiple surface notches and subsurface cavities of the heater element, or at least 50%, or at least 60%, or at least 70%, or at least 80%, of the volume is provided in the internal region. Providing such a high volume proportion of surface notches and / or surface cavities provides a barrier against conductive heat transfer through the metallic material of the heater element in the inner region, thereby enhancing thermal protection for components of the aerosol generator adjacent to the inner region of the heater element. In one embodiment, all of the multiple surface notches and subsurface cavities of the heater element may be provided within the inner region of the heater element.

[0024] If at least some of the multiple surface notches and subsurface cavities of a heater element are provided in the inner region of the heater element (as described in the previous paragraph), the surface notches and subsurface cavities in the inner region may extend transversely over at least 90% or at least 95% of the transverse width of the heater element. Such arrangement of notches or cavities helps to provide a barrier against conductive heat transfer through the metal substrate near the proximal end, and the barrier extends over substantially the entire transverse width of the heater element.

[0025] When some of the plurality of surface notches and subsurface cavities of the heater element are provided in the inner region of the heater element (as described in the preceding paragraph), some of the plurality of surface notches and subsurface cavities of the heater element may also be provided in the intermediate region of the heater element, and the intermediate region extends from 33% to 90% of the length of the heater element that is elongated with respect to the proximal end. By including surface notches or subsurface cavities in the intermediate region of the heater element in addition to the surface notches or subsurface cavities in the inner region, a more gradual change in the heat transfer rate through the heater element can be provided when progressing from one region of the heater element to another region. Ensuring such a gradual change in the heat transfer rate through the heater element can be beneficial in avoiding excessive thermal stress generated in the metallic material of the heater element.

[0026] The heater element defines a blade that extends transversely outwardly from the longitudinal axis along the longitudinal axis and has opposing first and second elongated surfaces. By providing the heater element in the form of a blade, the element is particularly suitable for passing through and being inserted into the aerosol-forming substrate of an aerosol-generating article. The heater element may further include a resistive heating track disposed on the first elongated surface, and the heater element includes a plurality of surface notches on the second elongated surface, and the surface notches on the second elongated surface form at least 80% of the total volume of the plurality of surface notches of the heater element. The second elongated surface may not include the resistive heating track. As discussed in the preceding paragraph, passage of an electric current along the resistive heating track can result in resistive heating of the track. The first elongated surface may substantially not include surface notches. As an example, alternatively, any surface notches of the heater element may be provided on the second elongated surface.

[0027] The plurality of surface notches and subsurface cavities of the heater element may be arranged in one or more groups that are symmetrical in one or more transverse directions. The one or more groups that are symmetrical in one or more transverse directions may include a first group, a second group, and a third group. The first group may be symmetrically arranged about the longitudinal axis and may extend transversely over at least 90%, or at least 95%, of the transverse width of the heater element in the inner region of the heater element. The inner region may extend between the proximal end and 33% of the length of the heater element relative to the proximal end. The second and third groups may be symmetrically arranged relative to each other on both sides of the longitudinal axis in the middle region of the heater element, and the middle region extends from 33% to 90% of the length of the heater element relative to the proximal end. The second and third groups may be axially spaced from the first group. The second and third groups may be joined to each other on the longitudinal axis.

[0028] Preferably, the heater element is configured to be removably attached to the aerosol generating device. In this way, the heater element can be removed for cleaning and then reinstalled. Further, the heater element may be removed and replaced with a replacement heater element.

[0029] In a second aspect of the present disclosure, an aerosol generating device configured to receive an aerosol forming substrate is provided. The aerosol generating device includes the elongated metal heater element described in relation to the first aspect of the present disclosure. The aerosol generating device also includes a power source. The proximal end of the heater element is attached to the attachment position of the aerosol generating device. The power source is in electrical communication with the heater element so as to resistively heat the heater element during use.

[0030] The power source is preferably in the form of a battery, which thereby provides power to the aerosol generating device and helps to make the device portable. Conveniently, the battery is rechargeable, and by way of example, a lithium-ion battery may be used as the power source.

[0031] The aerosol generator may be configured such that, when the aerosol-forming substrate is received into the device during use, a heater element extends into the aerosol-forming substrate to heat it and generate an inhalable aerosol from which it can be inhaled. As an example, the heater element may be formed as a blade, as described in the preceding paragraph. The distal end of the blade may terminate at a single point, thereby assisting the blade's entry into the aerosol-forming substrate. One or more longitudinal edges of the blade may be sharp.

[0032] The aerosol-forming substrate is preferably a solid aerosol-forming substrate. However, the aerosol-forming substrate may contain both solid and liquid components. Alternatively, the aerosol-forming substrate may be a liquid aerosol-forming substrate.

[0033] The aerosol-forming substrate preferably contains nicotine. More preferably, the aerosol-forming substrate contains tobacco. Alternatively, or additionally, the aerosol-forming substrate may contain a non-tobacco-containing aerosol-forming material.

[0034] When the aerosol-forming substrate is a solid aerosol-forming substrate, the solid aerosol-forming substrate may contain one or more of the following: medicinal herb leaves, tobacco leaves, tobacco stems, puffed tobacco, and homogenized tobacco, and may also contain one or more of the following: powder, granules, pellets, fragments, yarn, slivers, or sheets.

[0035] Optionally, the solid aerosol-forming substrate may contain tobacco or non-tobacco volatile flavor compounds, which are released upon heating of the solid aerosol-forming substrate. The solid aerosol-forming substrate may also contain, for example, one or more capsules containing additional tobacco volatile flavor compounds or non-tobacco volatile flavor compounds, which may melt during heating of the solid aerosol-forming substrate.

[0036] Optionally, the solid aerosol-forming substrate may be provided on or embedded within a thermally stable carrier. The carrier may take the form of a powder, granules, pellets, fragments, yarns, strips, or sheets. The solid aerosol-forming substrate may be deposited on the surface of the carrier, for example, in the form of a sheet, foam, gel, or slurry. The solid aerosol-forming substrate may be deposited over the entire surface of the carrier, or, alternatively, in a pattern to provide non-uniform flavor delivery during use.

[0037] In one preferred embodiment, the aerosol-forming substrate comprises homogenized tobacco material. As used herein, the term “homogenized tobacco material” refers to material formed by agglomerating particulate tobacco.

[0038] The aerosol-forming substrate preferably comprises an aggregate of homogenized tobacco material sheets. As used herein, the term “sheet” refers to a layered element having a width and length substantially greater than its thickness. As used herein, the term “aggregated” is used to describe a sheet that is wrapped, folded, or otherwise compressed or compressed substantially transversely to the longitudinal axis of the aerosol-generating article.

[0039] The aerosol-forming substrate preferably contains an aerosol-forming compound. As used herein, the term "aerosol-forming compound" is used to describe any suitable well-known compound or mixture of compounds that facilitates aerosol formation during use and is substantially resistant to thermal decomposition at the operating temperature of the aerosol-generating article.

[0040] Suitable aerosol-forming materials, as known in the art, include, but are not limited to, polyhydric alcohols (such as propylene glycol, triethylene glycol, 1,3-butanediol, and glycerin), esters of polyhydric alcohols (such as glycerol monoacetate, diacetate, and triacetate), and aliphatic esters of monocarboxylic acids, dicarboxylic acids, or polycarboxylic acids (such as dimethyl dodecanediate and dimethyl tetradecanediate). Preferred aerosol-forming materials are polyhydric alcohols (e.g., propylene glycol, triethylene glycol, 1,3-butanediol, and most preferably glycerin) or mixtures thereof.

[0041] The aerosol-forming substrate may contain a single aerosol-forming body. Alternatively, the aerosol-forming substrate may contain a combination of two or more aerosol-forming bodies.

[0042] A third aspect of the present disclosure provides a method for manufacturing a heater element. The method comprises providing a metal substrate and forming either or both of the following: i) a plurality of surface notches on the surface of the metal substrate, and ii) a plurality of subsurface cavities defined below the surface of the metal substrate.

[0043] First, multiple metal blanks may be cut from a sheet of metal material, with each blank forming a "metal substrate" for a given heater element. Conveniently, surface notches and subsurface cavities can be formed in the sheet of metal material before cutting the sheet into individual blanks. Alternatively, surface notches and subsurface cavities may be formed in each blank after cutting from the sheet of metal material.

[0044] Advantageously, the forming process may include etching the metal substrate to form multiple surface notches. For example, chemical or mechanical etching processes may be used to form notches on the substrate surface. Chlorine etching is an example of a suitable chemical etching process. Mechanical etching may take the form of machined notches on the substrate surface.

[0045] Preferably, the heater element produced as a result of this method is the same as the metal heater element described in the preceding paragraph with respect to the first aspect of this disclosure.

[0046] A fourth aspect of the present disclosure provides a method for manufacturing a heater element. The method comprises providing a supply of a metallic material and additively manufacturing a heater element from the supply of the metallic material to stepwise form the heater element such that it includes either or both of i) a plurality of surface notches on the surface of the heater element and ii) a plurality of subsurface cavities defined below the surface of the heater element.

[0047] Forming heater elements using additive manufacturing is particularly beneficial for enabling the creation of hidden structural features, such as subsurface cavities. As an example, the metallic material may be supplied in powder form, or alternatively, as a powder and liquid slurry. Conveniently, the additive manufacturing process may include three-dimensional screen printing.

[0048] Preferably, the heater element produced as a result of this method is the same as the metal heater element described in the preceding paragraph with respect to the first aspect of this disclosure.

[0049] The present invention is defined in the claims. However, a non-exclusive list of non-limiting embodiments is provided below. One or more features of these embodiments may be combined with one or more features of other embodiments, forms, or aspects described herein.

[0050] Here, we will further describe the examples with reference to the following figures. [Brief explanation of the drawing]

[0051] [Figure 1] Figure 1 is a schematic diagram of the components of an aerosol delivery system. [Figure 2a]Figure 2a is a top-down perspective view of a heater element used in the aerosol generator of the aerosol delivery system shown in Figure 1, in which multiple surface notches are defined on the surface of the heater element. [Figure 2b] Figure 2b is a perspective view from the bottom of the heater element shown in Figure 2a. [Figure 3a] Figure 3a is a detailed plan view of a portion of the upper surface of an exemplary heater element according to this disclosure, in which the heater element is provided with a surface notch that is circular in plan and extends into the upper surface of the heater element, forming a notch with a partially spherical shape. [Figure 3b] Figure 3b is a cross-sectional view along section BB of a portion of the heater element in Figure 3a. [Figure 4a] Figure 4a is a detailed plan view of the upper surface of another exemplary heater element according to this disclosure, in which the heater element is provided with a surface notch having a cylindrical hole that is circular in plan and extends into the upper surface of the heater element. [Figure 4b] Figure 4b is a cross-sectional view along section CC of a portion of the heater element in Figure 4a, showing how the cylindrical holes of each surface notch extend into the upper surface of the heater element. [Figure 5a] Figure 5a is a detailed plan view of the upper surface of another exemplary heater element according to this disclosure, in which the heater element is provided with a surface notch having a hexagonal hole that is hexagonal in plan and extends into the upper surface of the heater element. [Figure 5b] Figure 5b is a cross-sectional view along section DD of a portion of the heater element in Figure 5a, showing how the hexagonal holes of each surface notch extend into the upper surface of the heater element. [Figure 6a] Figure 6a is a detailed plan view of the upper surface of another exemplary heater element according to this disclosure, in which the heater element is provided with a surface notch having a hexagonal hole that is hexagonal in plan and extends into the upper surface of the heater element. [Figure 6b]Figure 6b is a detailed plan view of the lower surface of a portion of the heater element in Figure 6a, where both the resistance heating track and the arrangement of hexagonal surface notches in the plan are provided on the lower surface of the heater element. [Figure 6c] Figure 6c is a cross-sectional view along section EE of a portion of the heater element shown in Figures 6a and 6b, illustrating how the hexagonal holes of the surface notches extend into both the upper and lower surfaces of the heater element. [Figure 7a] Figure 7a is a detailed plan view of the upper surface of a portion of another exemplary heater element according to this disclosure, in which the heater element is provided with a spherical subsurface cavity. [Figure 7b] Figure 7b is a cross-sectional view along section FF of a portion of the heater element in Figure 7a, showing how the cavity is arranged within a single subsurface layer embedded within the heater element. [Figure 8] Figure 8 is a cross-sectional view of the modified heater element (along section FF) of Figures 7a and 7b, in which the heater element is provided with the arrangement of three layers of subsurface cavities embedded within the heater element. [Figure 9] Figure 9 is a cross-sectional view of another heater element, combined with the embodiments of Figures 5a, 5b and 7a, 7b, in which the arrangement of hexagonal surface notches in a planar view is provided on the upper surface of the heater element, and the arrangement of spherical subsurface cavities is provided as a single layer embedded within the heater element. [Figure 10] Figure 10 is a perspective view of five different heater elements, each having a different arrangement of surface notches. [Figure 11] Figure 11 is a schematic diagram of a machining assembly for manufacturing multiple heater elements from a sheet of metal substrate. [Modes for carrying out the invention]

[0052] Example 1 An elongated metal heater element for use in an aerosol generator, wherein the heater element extends between a proximal end and a distal end, the proximal end being configured to be attached to the aerosol generator for electrical communication with the aerosol generator, and the heater element includes either or both of i) a plurality of surface notches formed on the surface of the heater element, and ii) a plurality of subsurface cavities defined below the surface of the heater element. Example 2 An elongated metal heater element according to Example 1, wherein the heater element comprises a metal substrate and one or more resistance heating tracks, the one or more resistance heating tracks being disposed on the metal substrate, and a plurality of surface notches and subsurface cavities of the heater element are formed on or within the metal substrate, respectively. Example 3 An elongated metal heater element according to either Example 1 or 2, wherein multiple surface notches and subsurface cavities of the heater element represent a cumulative volume of 15% to 30% of that of a corresponding heater element that does not contain any such notches and cavities. Example 4 An elongated metal heater element according to Example 3, wherein multiple surface notches and subsurface cavities of the heater element occupy a cumulative volume of 17% to 26% of the volume of a corresponding heater element that does not contain any such notches and cavities. Example 5 An elongated metal heater element according to any one of Examples 1 to 4, wherein the heater element does not include a through hole extending through the thickness of the heater element. Example 6 An elongated metal heater element according to any one of Examples 1 to 4, wherein the heater element further includes a plurality of through holes extending through the thickness of the heater element. Example 7 An elongated metal heater element according to Example 6, in which multiple through holes are distributed along the length of the heater element. Example 8 An elongated metal heater element according to any one of Examples 1 to 6, wherein multiple surface notches and subsurface cavities of the heater element are formed to define one or more honeycomb arrangements. Example 9 An elongated metal heater element according to any one of Examples 1 to 8, wherein the heater element includes multiple surface notches and does not include subsurface cavities. Example 10 An elongated metal heater element according to any one of Examples 1 to 8, wherein the heater element includes multiple subsurface cavities and does not have surface notches. Example 11 An elongated metal heater element according to any one of Examples 1 to 10, wherein at least a portion of the multiple surface notches and subsurface cavities of the heater element are provided in an inner region of the heater element, the inner region extending between the proximal end and 33% of the length of the heater element relative to the proximal end. Example 12 An elongated metal heater element according to Example 11, wherein at least 40% of the total volume of the multiple surface notches and subsurface cavities of the heater element, or at least 50% of the volume, or at least 60% of the volume, or at least 70% of the volume, or at least 80% of the volume is provided to the inner region. Example 13 An elongated metal heater element according to either Example 11 or 12, wherein the surface notches and subsurface cavities in the inner region extend transversely over at least 90% or at least 95% of the transverse width of the heater element. Example 14 An elongated metal heater element according to any one of Examples 11-13, wherein all of the multiple surface notches and subsurface cavities of the heater element are provided in the inner region of the heater element. Example 15 An elongated metal heater element according to any one of Examples 11 to 14, wherein some of the multiple surface notches and subsurface cavities of the heater element are provided in an intermediate region of the heater element, and the intermediate region extends to 33% to 90% of the length of the elongated heater element relative to the proximal end. Example 16 An elongated metal heater element according to any one of Examples 1 to 15, wherein the heater element defines a blade having opposing first and second elongated surfaces, extending transversely outward from the longitudinal axis along the longitudinal axis. Example 17 An elongated metal heater element according to Example 16, further comprising a resistance heating track disposed on a first elongated surface, wherein the heater element comprises a plurality of surface notches on a second elongated surface, and the surface notches on the second elongated surface form at least 80% of the total volume of the plurality of surface notches of the heater element. Example 18 An elongated metal heater element according to Example 17, wherein the first elongated surface substantially does not contain surface notches. Example 19 An elongated metal heater element according to any one of Examples 16 to 18, wherein multiple surface notches and subsurface cavities of the heater element are arranged in one or more transversely symmetrical groups. Example 20 An elongated metal heater element according to Example 19, comprising: a first group having one or more transversely symmetrical groups arranged symmetrically about the longitudinal axis and extending transversely over at least 90% or at least 95% of the transverse width of the heater element in the inner region of the heater element, with the inner region extending between the proximal end and 33% of the length of the heater element relative to the proximal end; and second and third groups having two or three transversely symmetrically arranged on both sides of the longitudinal axis in the intermediate region of the heater element, with the intermediate region extending from 33% to 90% of the length of the heater element relative to the proximal end. Example 21 An elongated metal heater element according to Example 20, in which the second and third groups are coupled to each other along the longitudinal axis. Example 22 An elongated metal heater element according to any one of Examples 1 to 21, wherein the heater element is configured to be detachably attached to an aerosol generator. Example 23 An aerosol generator configured to receive an aerosol-forming substrate, wherein the aerosol generator comprises an elongated metal heater element and a power supply according to any one of Examples 1 to 22, the proximal end of the heater element being attached to the mounting position of the aerosol generator, and the power supply being electrically connected to the heater element to resistively heat the heater element during use. Example 24 An aerosol generator according to Example 23, wherein the aerosol generator is configured such that when an aerosol-forming substrate is received into the device during use, a heater element extends into the aerosol-forming substrate to heat the substrate and generate an inhalable aerosol from it. Example 25 A method for manufacturing a heater element, the method comprising providing a metal substrate and forming either or both of the following: i) a plurality of surface notches on the surface of the metal substrate, and ii) a plurality of subsurface cavities defined below the surface of the metal substrate. Example 26 A method for manufacturing a heater element according to Example 25, wherein the forming step includes etching a metal substrate to form a plurality of surface notches. Example 27 A method for manufacturing a heater element, the method comprising: providing a supply of a metallic material; and adding a heater element from the supply of metallic material to stepwise form the heater element such that it includes either or both of i) a plurality of surface notches on the surface of the heater element, and ii) a plurality of subsurface cavities defined below the surface of the heater element. Example 28 A method for manufacturing a heater element according to Example 27, wherein the additive manufacturing process includes three-dimensional screen printing. Example 29 A method for manufacturing a heater element, wherein the manufactured heater element resulting from the method is one of Examples 1 to 22 or one of Examples 25 to 28.

[0053] Figure 1 is a schematic diagram of the aerosol delivery system 10. The aerosol generation system 10 is a smoking system for generating inhalable aerosols. The system 10 is formed by a combination of an aerosol generator 20 and an aerosol generating article 30.

[0054] The aerosol generator 20 has an elongated housing 21 made of a polymer material. The elongated housing 21 houses a power supply 22, a controller 23, and a mounting position 24. A metal heater element 40 is detachably mounted to the mounting position 24 by using a press-fit connection. The heater element 40 is formed of a metal substrate 41 and has a resistance heating track 42 overlaid on the surface of the substrate (see, for example, Figure 2b). The structure of the heater element 40 will be described in more detail in the following paragraphs. The heater element 40 is mounted to the mounting position 24 such that the resistance heating track 42 is electrically connected to the mounting position. An access opening 25 is provided at one end of the elongated housing 21. A blind cavity 26 extends from the access opening 25 into the interior of the elongated housing 21. The heater element 40 extends from the closed end 27 of the blind cavity 26 toward the access opening 25.

[0055] The aerosol generating article 30 is cylindrical in shape and extends between a distal end 31 and an oral end 32. The aerosol generating article 30 has a wrapper 33, which is in the form of cigarette paper. The plug of the aerosol forming substrate 34, the hollow acetate tube 35, the tubular spacer element 36, and the mouthpiece filter 37 are arranged coaxially and continuously within the wrapper 33. The aerosol generating article 30 is received in a blind cavity 26 such that the heater element 40 is inserted into the plug of the aerosol forming substrate 34.

[0056] In the aerosol generator 20, a power supply 22 is connected to a controller 23 and provides power to the controller 23. In the illustrated embodiment, the power supply 22 is a rechargeable lithium-ion battery. The controller 23 is connected to a mounting position 24 and provides current to the mounting position 24 and thereby to the resistive heating track 42 of the heater element 40. The controller 23 is in the form of control electronic equipment and incorporates a memory module 23a. The memory module 23a contains instructions accessible by the controller 23's processor (not shown) that control the supply of current to the resistive heating track 42 of the heater element 40. The current supplied from the controller 23 to the mounting position 24 causes resistive heating of the resistive heating track 42. Some of the heat generated by the resistive heating track 42 is conducted into the metal substrate 41 beneath the heater element 40.

[0057] During use, the heat generated by the heater element 40 is transferred to the plug of the aerosol-forming substrate 34. As a result of the heating of the aerosol-forming substrate 34, vapor is emitted from the aerosol-forming substrate. In response to the user inhaling the mouth end 32 of the article 30, ambient airflow (indicated by arrows in Figure 1) is drawn into the air passage 28, which is circumferentially arranged between the elongated housing 21 and the blind cavity 26. The airflow then enters the distal end 31 of the aerosol-generating article 30, passes through the plug of the aerosol-forming substrate 34, and mixes with the vapor emitted from the aerosol-forming substrate. The vapor mixture then passes downstream through the interior of the aerosol-generating article 30 towards the mouth end 32, during which time the vapor condenses to form an aerosol. The aerosol passes through the mouthpiece filter 37 and is inhaled into the user's lungs.

[0058] Figures 2a and 2b show perspective views of the upper and lower surfaces, respectively, of the heater element 40 used in the aerosol delivery system 10 of Figure 1. The terms “upper” and “lower” are used only in relative orientation. As described above, the heater element 40 is formed from a metal substrate 41. The metal substrate 41 is titanium or stainless steel. However, in alternative embodiments, the metal substrate 41 may be formed from other metals or alloys. The resistance heating track 42 is overlaid on the surface of the metal substrate 41 (see Figure 2b). In the embodiments shown in Figures 2a and 2b, the resistance heating track 42 is in the form of fine metal wires deformed into a coil shape. However, in alternative embodiments (not shown), the resistance heating track 41 may take other forms, such as a metal sheet that is stamped or otherwise formed into a coil-shaped pattern. The metal substrate 41 of the heater element 40 extends longitudinally along the axis 43 and transversely outward from the axis between the proximal end 44 and the distal end 45, defining the blade-shaped profile for the heater element 40. The heater element 40 is detachably mounted at the mounting position 24 at the proximal end 44. The first plane 46 and the second plane 47 define the lower and upper surfaces of the metal substrate 41, respectively. The resistance heating track 42 is arranged on the lower surface 46 (see Figure 2b). Multiple surface notches 48 are formed on the upper surface 47. The surface notches 48 extend partially through the thickness t of the metal substrate 41. The multiple surface notches 48 are arranged in three groups 49a, 49b, and 49c. Group 49a of the surface notches 48 is provided in the inner region 50 of the heater element 40, which extends between the proximal end 44 and approximately 33% of the length L of the heater element relative to the proximal end. In the embodiment shown in Figure 2a, approximately 40% of the surface notches 48 formed on the heater element 40 are located in group 49a in this inner region 50. Groups 49b and 49c accommodate the remaining 60% of the surface notches 47 formed on the heater element 40, and both groups are transversely symmetrical with respect to the axis 43 in the intermediate region 51 of the heater element. The intermediate region 51 extends from 33% to 90% of the length L of the heater element 40 relative to the proximal end 44.These two transversely symmetrical groups 49b and 49c of the surface notches 48 are joined along axis 43 to define an arrowhead shape when viewed in a plane, i.e., in the direction of arrow A. The surface notches 48 of group 49a extend over more than 95% of the transverse width W of the heater element 40. For the heater elements 40 in Figures 2a and 2b, no surface notches 48 are defined on the lower surface 46 of the metal substrate 41. However, in alternative embodiments (such as the exemplary heater elements in Figures 6a-6c, which will be discussed in a later paragraph), multiple surface notches 48 are also provided on the lower surface 46 of the metal substrate 41.

[0059] For the heater elements in Figures 2a and 2b, the surface notches 48 defined on the heater element 40 occupy approximately 18% of the cumulative volume of the corresponding heater element without such notches. This results in a mass reduction of approximately 18% compared to the corresponding heater element without such notches. In alternative embodiments, the surface notches 48 occupy a larger or smaller cumulative volume depending on the desired degree of heat flow control. Furthermore, in alternative embodiments (not shown), the distribution of the surface notches 48 along the length L and width W of the heater element 40, and the proportion of the surface notches 48 in the inner region 50 and the intermediate region 51, may differ from those shown and discussed for the heater elements in Figures 2a and 2b.

[0060] Figures 3–9 show portions of various exemplary heater elements 40 having different surface notch or subsurface cavity arrangements compared to the heater elements illustrated in Figures 2a and 2b. For convenience, features common to the various exemplary heater elements 40 are referred to using similar reference numerals.

[0061] Figure 3a is a plan view (in the direction of arrow A in Figure 2a) of the upper surface 47 of a portion of an exemplary heater element 40. Multiple surface notches 48 are formed on the upper surface 47 of the metal substrate 41. The surface notches 48 are circular in plan and have a radius of r. The surface notches 48 are formed in a repeating honeycomb-type pattern in which adjacent rows of notches are offset from one another. As shown in the cross-sectional view of Figure 3b, each of the surface notches 48 extends into the upper surface 47 of the metal substrate 41 and provides a notch surface profile that is partially spherical. Each notch 48 extends partially through the thickness t of the substrate 41, to a depth d (see Figure 3b). Because the notch surface profile is partially spherical, the depth d is equal to the radius r. In an alternative embodiment (not shown), the surface profile of the notches 48 is elliptical. In a further alternative embodiment (not shown), the dimensions of the notches 48 vary in different regions of the heater element 40. Furthermore, the spacing between adjacent notches 48 can vary in different regions of the heater element 40. For example, referring to Figure 2a, the notches 48 in the inner region 50 may be larger than those in the intermediate region 51, or they may be spaced closer together. Such variations in notch dimensions and spacing between adjacent notches 48 in different regions of the heater element 40 can be used to provide different levels of thermal conductivity in those different regions.

[0062] Figure 4a is a plan view of the upper surface of a portion of another exemplary heater element 40 (in the direction of arrow A in Figure 2a). Multiple surface notches 48 are formed on the upper surface 47 of the metal substrate 41. In common to the embodiments in Figures 3a and 3b, the surface notches 48 are formed in a repeating honeycomb-type pattern, circular in plan, with radius r, and adjacent rows of notches offset from one another. However, as shown in the cross-sectional view in Figure 4b, each of the surface notches 48 has a cylindrical hole that extends into the upper surface 47 of the metal substrate 41 and provides a cylindrical notch surface profile. Each notch 48 extends partially through the thickness t of the substrate 41, to a depth d (see Figure 4b). In alternative embodiments (not shown), the dimensions of the notches 48 vary in different regions of the heater element 40. Furthermore, the spacing between adjacent notches 48 may vary in different regions of the heater element 40. As an example, referring to Figure 2a, the notches 48 in the inner region 50 may be larger than the notches 48 in the intermediate region 51, or they may be spaced closer together. Such variations in notch dimensions and spacing between adjacent notches 48 in different regions of the heater element 40 can be used to provide different levels of thermal conductivity in those different regions.

[0063] Figure 5a is a plan view (in the direction of arrow A in Figure 2a) of the upper surface 47 of a portion of an exemplary heater element 40. Multiple surface notches 48 are formed on the upper surface 47 of the metal substrate 41. The surface notches 48 are hexagonal in plan. The surface notches 48 are formed in a repeating honeycomb-type pattern in which adjacent rows of notches are offset from one another. As shown in the cross-sectional view of Figure 5b, each of the surface notches 48 has a hexagonal hole extending into the upper surface 47 of the metal substrate 41. Each notch 48 extends partially through the thickness t of the substrate 41, to a depth d (see Figure 5b). In alternative embodiments (not shown), the dimensions of the notches 48 vary in different regions of the heater element 40. Furthermore, the spacing between adjacent notches 48 may vary in different regions of the heater element 40. As an example, referring to Figure 2a, the notches 48 in the inner region 50 may be larger than the notches 48 in the intermediate region 51, or they may be spaced closer together. Such variations in notch dimensions and spacing between adjacent notches 48 in different regions of the heater element 40 can be used to provide different levels of thermal conductivity in those different regions.

[0064] Figure 6a is a plan view (in the direction of arrow A in Figure 2a) of the upper surface 47 of a portion of an exemplary heater element 40. The notch arrangement on the upper surface 47 is identical to that of the heater element 40 in Figure 5a, with multiple surface notches 48 formed on the upper surface of the metal substrate 41. The surface notches 48 are hexagonal in plan and are formed in a repeating honeycomb-type pattern where adjacent rows of notches are offset from each other. However, this embodiment of the heater element differs from the heater elements in Figures 5a and 5b in that the surface notches 48 are also provided on the lower surface 46 of the metal substrate 41. The notches on the lower surface 46 are hexagonal in plan, as are the notches on the upper surface 47. However, there are fewer notches 48 on the lower surface 46 than on the upper surface 47. As can be seen in Figure 6b, the notches 48 on the lower surface 46 are located on both sides of the resistance heating track 42. As shown in the cross-sectional view of Figure 6c, each notch 48 extends partially through the thickness t of the base 41, to a depth d. In an alternative embodiment (not shown), the dimensions of the notch 48 vary in different regions of the heater element 40. Furthermore, the spacing between adjacent notches 48 may vary in different regions of the heater element 40. As an example, referring to Figure 2a, the notches 48 in the inner region 50 may be larger than the notches 48 in the intermediate region 51, or they may be spaced closer together. Such variations in notch dimensions and spacing between adjacent notches 48 in different regions of the heater element 40 can be used to provide different levels of thermal conductivity in those different regions.

[0065] Figure 7a is a plan view of the upper surface 47 of a portion of an exemplary heater element 40 (in the direction of arrow A in Figure 2a). In contrast to the exemplary heater elements 40 in Figures 3-6, no surface notches 48 are provided on the metal substrate. Rather, a layer of spherical subsurface cavities 480 is embedded within the metal substrate 41, with each cavity having a diameter Φ (see the cross-sectional view in Figure 7b). The contours of these subsurface cavities 480 are shown by dashed lines in the plan view in Figure 7a. The subsurface cavities 480 are formed in a repeating honeycomb-type pattern where adjacent rows of embedded cavities 480 are offset from one another (see Figure 7a). In alternative embodiments (not shown), the subsurface cavities 480 have an elliptical morphology. In further alternative embodiments (not shown), the dimensions of the subsurface cavities 480 vary in different regions of the heater element 40. Furthermore, the spacing between adjacent cavities 480 may vary in different regions of the heater element 40. As an example, referring to Figure 2a, the subsurface cavities 480 of the inner region 50 may be larger than the subsurface cavities 480 of the intermediate region 51, or they may be spaced close together. Such variations in cavity dimensions and spacing between adjacent subsurface cavities 480 in different regions of the heater element 40 can be used to provide different levels of thermal conductivity to those different regions.

[0066] Figure 8 is a cross-sectional view of a heater element 40 similar to that shown in Figure 7b, but differs in that three layers of subsurface cavities 480 are embedded within the metal substrate 41. In an alternative embodiment (not shown) in which multiple layers of subsurface cavities 480 are embedded within the metal substrate 41, the layers may differ from one another in terms of the size or spacing of the cavities 480 in each layer.

[0067] Figure 9 is a cross-sectional view of the heater element 40 corresponding to the combination of embodiments of Figures 5a, 5b and 7a, 7b. As can be seen, the surface notch 48 is formed on the upper surface 47 of the metal substrate 41, and the notch is hexagonal in plane (as in Figure 5a). However, in addition, a layer of subsurface cavity 480 is embedded in the metal substrate 41 (as in Figure 7a).

[0068] Figure 10 shows perspective views of five different heater elements 40, each having a different arrangement of surface notches 48.

[0069] Figure 11 is a schematic diagram of a machining assembly 60 for manufacturing heater elements from a sheet 400 of metal substrate material 41. The machining assembly 60 has a tool holder 61 for holding a machining tool 62. The sheet 400 of the metal substrate is provided and fixed in place to the machining assembly 60. The sheet 400 has a thickness corresponding to the desired thickness t of the heater element 40 as described in the preceding paragraph, but has sufficient width and length for multiple heater elements 40 to be formed from a single sheet 400. The machining assembly 60 operates the machining tool 62 to machine individual surface notches 48 on the upper surface of the metal sheet 400, and then moves the tool holder 61 and the machining tool 62 on the surface of the metal sheet 400 (see arrows in Figure 11) to repeat the machining operation at multiple desired positions. After the machining operation is complete, the resistance heater tracks 62 are arranged at predetermined intervals on the lower surface of the sheet 400. Next, the individual heater elements 40 are cut from the sheet 400, and the dashed lines in Figure 11 show the contours of two such heater elements 40. In another embodiment (not shown), the surface notches 48 are chemically etched onto the surface of the metal sheet 400 rather than being mechanically formed.

[0070] For the purposes of this specification and the appended claims, unless otherwise indicated, all numbers representing amounts, quantities, percentages, etc., should be understood in all cases as being modified by the term “approximately.” Furthermore, all ranges include the disclosed maximum and minimum points and any intermediate ranges therewith, which may or may not be specifically listed herein. Thus, in this context, the number “A” is understood as “A” ± 10%. In this context, the number “A” may be considered to include a number that falls within the general standard error to the measurement of the characteristic that the number “A” modifies. In some cases as used in the appended claims, the number “A” may deviate by the percentages listed above, provided that the amount of deviation does not substantially affect the basic and novel characteristics(s) of the claimed invention. Furthermore, all ranges include the disclosed maximum and minimum points and any intermediate ranges therewith, which may or may not be specifically listed herein.

Claims

1. An elongated metal heater element for use in an aerosol generator, wherein the heater element extends between a proximal end and a distal end, and the proximal end is configured to be attached to the aerosol generator for electrical communication with the aerosol generator. The heater element is i) A plurality of surface notches formed on the surface of the heater element, and ii) comprising any or both of a plurality of subsurface cavities defined beneath the surface of the heater element, An elongated metal heater element, wherein at least a portion of the plurality of surface notches and subsurface cavities of the heater element are provided to an inner region of the heater element, the inner region extending between the proximal end and 33% of the length of the heater element relative to the proximal end, and at least 40%, or at least 50%, or at least 60%, or at least 70%, or at least 80% of the total volume of the plurality of surface notches and subsurface cavities of the heater element is provided to the inner region.

2. The elongated metal heater element according to claim 1, wherein the plurality of surface notches and subsurface cavities of the heater element occupy a cumulative volume of 15% to 30% of the volume of the corresponding heater element that does not include such notches and cavities.

3. The elongated metal heater element according to claim 2, wherein the plurality of surface notches and subsurface cavities of the heater element occupy a cumulative volume of 17% to 26% of the volume of a corresponding heater element that does not contain any of these notches and cavities.

4. The elongated metal heater element according to any one of claims 1 to 3, wherein the heater element further comprises a plurality of through holes extending through the thickness of the heater element.

5. The elongated metal heater element according to any one of claims 1 to 4, wherein the plurality of surface notches and subsurface cavities of the heater element are formed to define one or more honeycomb arrangements.

6. The elongated metal heater element according to any one of claims 1 to 5, wherein the heater element includes the plurality of surface notches and does not include a subsurface cavity.

7. The elongated metal heater element according to any one of claims 1 to 5, wherein the heater element includes the plurality of subsurface cavities and does not include surface notches.

8. The elongated metal heater element according to any one of claims 1 to 7, wherein the surface notch and subsurface cavity of the inner region extend transversely over at least 90% or at least 95% of the transverse width of the heater element.

9. An elongated metal heater element according to any one of claims 1 to 8, wherein all of the plurality of surface notches and subsurface cavities of the heater element are provided in the inner region of the heater element.

10. An elongated metal heater element according to any one of claims 1 to 8, wherein a portion of the plurality of surface notches and subsurface cavities of the heater element is provided in an intermediate region of the heater element, and the intermediate region extends to 33% to 90% of the length of the elongated heater element with respect to the proximal end.

11. The elongated metal heater element according to any one of claims 1 to 10, wherein the heater element defines a blade having opposing first and second elongated surfaces, extending transversely outward from the longitudinal axis along the longitudinal axis.

12. The elongated metal heater element according to claim 11, wherein the heater element further includes a resistance heating track disposed on the first elongated surface, the heater element includes a plurality of surface notches on the second elongated surface, and the surface notches on the second elongated surface form at least 80% of the total volume of the plurality of surface notches of the heater element.

13. The elongated metal heater element according to claim 11 or claim 12, wherein the plurality of surface notches and subsurface cavities of the heater element are arranged in one or more transversely symmetrical groups.

14. An aerosol generator configured to receive an aerosol-forming substrate, wherein the aerosol generator comprises an elongated metal heater element according to any one of claims 1 to 13 and a power supply, the proximal end of the heater element being attached to the mounting position of the aerosol generator, and the power supply being electrically connected to the heater element to resistively heat the heater element when in use.

15. The aerosol generator according to claim 14, wherein the aerosol generator is configured such that when an aerosol-forming substrate is received into the device during use, the heater element extends into the aerosol-forming substrate to heat the aerosol-forming substrate and generate an inhalable aerosol therefrom.

Images