阅读说明：本技术 气溶胶供应设备 (Aerosol supply device ) 是由 托马斯·保罗·布兰迪诺 爱德华·约瑟夫·哈利迪 威廉·斯蒂芬·哈特 亚当·罗奇 米切尔·托森 于 2020-03-09 设计创作，主要内容包括：一种用于气溶胶供应设备的加热器装置,包括：感受器,被布置成加热气溶胶生成材料,其中感受器可通过用变化的磁场穿过来加热；第一配线,在第一位置处连接到感受器；第二配线,在第二位置处连接到感受器,其中第二位置与第一位置间隔开；以及电子电路,被配置成基于在第一配线与第二配线之间测量的电势差来确定感受器在第一位置处的温度。(A heater apparatus for an aerosol provision device, comprising: a susceptor arranged to heat the aerosol-generating material, wherein the susceptor is heatable by passing through with a varying magnetic field; a first wiring connected to the susceptor at a first position; a second wire connected to the susceptor at a second location, wherein the second location is spaced apart from the first location; and electronic circuitry configured to determine a temperature of the susceptor at the first location based on a potential difference measured between the first wire and the second wire.)

1. A heater apparatus for an aerosol provision device, comprising:

a heater component arranged to heat an aerosol-generating material;

a first wire connected to the heater block at a first location;

a second wire connected to the heater block at a second location, wherein the second location is spaced apart from the first location; and

electronic circuitry configured to:

determining a temperature of the heater component at the first location based on a potential difference measured between the first wire and the second wire.

2. The heater apparatus according to claim 1, wherein the heater component and the second wire have substantially the same seebeck coefficient.

3. The heater apparatus of claim 1 or 2, wherein the heater component and the second wire comprise substantially the same metal or alloy.

4. The heater apparatus of claim 1 or 2, wherein the heater component and the second wire each comprise at least 95 wt% iron.

5. The heater apparatus of claim 4, wherein the heater component comprises steel containing 99.18 wt% to 99.62 wt% iron, and the second wire comprises at least 99 wt% iron.

6. The heater apparatus according to any one of claims 1 to 5, wherein the first wiring has a different composition from the heater block and the second wiring.

7. The heater apparatus of claim 6, wherein the first wire is made of a copper-nickel alloy.

8. The heater apparatus according to any one of claims 1 to 7, further comprising:

a third wire connected to the heater block at a third location, wherein the third location is spaced apart from the first location and the second location;

wherein the electronic circuitry is further configured to:

determining a second temperature of the heater block at the third location based on a second potential difference measured between the third wire and the second wire.

9. The heater apparatus according to claim 8, wherein the third wiring has a composition satisfying at least one of:

a composition different from that of the heater block and the second wiring; and

the composition is the same as that of the first wiring.

10. The heater apparatus of claim 9, wherein the first and third wires are made of a copper-nickel alloy.

11. The heater apparatus of any one of claims 8 to 10, wherein the first position is closer to a first end of the heater block than the second position, and the second position is closer to the first end of the heater block than the third position.

12. The heater apparatus of claim 11, wherein the second position is located on the heater block at a midpoint between the first position and the third position.

13. The heater apparatus according to any one of claims 1 to 12, wherein at least one of the following is satisfied:

at the first location where the first wire is connected to the heater block, the first wire is covered by a protective coating; and is

At the second position where the second wire is connected to the heater block, the second wire is covered by a protective coating.

14. A heater apparatus for an aerosol provision device, comprising:

a heater component arranged to heat an aerosol-generating material;

a first wire connected to the heater block at a first location;

wherein the first wire is covered with a protective coating at the first position where the first wire is connected to the heater block.

15. The heater apparatus of claim 13 or 14, wherein the protective coating comprises a metal or metal alloy.

16. The heater apparatus according to claim 15, wherein the protective coating comprises nickel.

17. The heater apparatus of claim 13 or 14, wherein the protective coating comprises a sealant.

18. An aerosol provision device comprising:

a heater device according to any one of claims 1 to 17; and

an induction coil for generating a varying magnetic field.

19. An aerosol provision system comprising:

the aerosol provision device of claim 18; and

an article comprising an aerosol generating material.

Technical Field

The present invention relates to a heater arrangement for an aerosol provision device and to an aerosol provision device.

Background

Smoking articles such as cigarettes, cigars and the like burn tobacco during use to produce tobacco smoke. Attempts have been made to provide alternatives to these tobacco-burning articles by producing products that release compounds without combustion. An example of such a product is a heating device that releases a compound by heating a material, rather than burning the material. The material may be, for example, tobacco or other non-tobacco products that may or may not contain nicotine.

Disclosure of Invention

According to a first aspect of the present disclosure there is provided a heater arrangement for an aerosol provision device, the heater arrangement comprising:

a heater component arranged to heat an aerosol-generating material;

a first wire connected to the heater block at a first location;

a second wire connected to the heater block at a second location, wherein the second location is spaced apart from the first location; and

electronic circuitry configured to:

the temperature of the heater block at the first location is determined based on a potential difference measured between the first wire and the second wire.

According to a second aspect of the present disclosure, there is provided an aerosol provision apparatus comprising:

a heater device according to the first aspect; and

an induction coil for generating a varying magnetic field.

According to another aspect of the present disclosure, there is provided a heater device for an aerosol provision apparatus, the heater device comprising:

a susceptor arranged to heat the aerosol-generating material, wherein the susceptor is heatable by passing through with a varying magnetic field;

a first wiring connected to the susceptor at a first position;

a second wire connected to the susceptor at a second location, wherein the second location is spaced apart from the first location; and

electronic circuitry configured to:

the temperature of the susceptor at the first location is determined based on a potential difference measured between the first wire and the second wire.

According to another aspect of the present disclosure, there is provided a heater device for an aerosol provision apparatus, the heater device comprising:

a heater component arranged to heat an aerosol-generating material; and

a first wire connected to the heater block at a first location;

wherein the first wire is covered with the protective coating at a first position where the first wire is connected to the heater block.

Further features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention, given by way of example only, which is made with reference to the accompanying drawings.

Drawings

Figure 1 shows a front view of an example of an aerosol provision device;

figure 2 shows a front view of the aerosol provision device of figure 1 with the outer cover removed;

figure 3 shows a cross-sectional view of the aerosol provision device of figure 1;

figure 4 shows an exploded view of the aerosol provision device of figure 2;

figure 5A shows a cross-sectional view of a heating assembly within an aerosol provision device;

FIG. 5B shows a close-up view of a portion of the heating assembly of FIG. 5A;

FIG. 6 shows a first induction coil and a second induction coil wound around an insulating member;

FIG. 7 shows a schematic diagram of a standard thermocouple;

figure 8 shows a schematic view of a susceptor and two standard thermocouples according to an example;

figure 9 shows a schematic view of a susceptor and two thermocouples according to another example;

figure 10 shows another schematic view of the susceptor of figure 9; and

figure 11 shows another schematic view of the susceptor of figure 9.

Detailed Description

As used herein, the term "aerosol-generating material" includes materials which, when heated, provide a volatile component, typically in the form of an aerosol. The aerosol-generating material comprises any tobacco-containing material and may, for example, comprise one or more of tobacco, a tobacco derivative, expanded tobacco, reconstituted tobacco or a tobacco substitute. The aerosol-generating material may also comprise other non-tobacco products which may or may not contain nicotine depending on the product. The aerosol-generating material may be in the form of, for example, a solid, a liquid, a gel, a wax, or the like. The aerosol-generating material may also be a combination or mixture of materials, for example. The aerosol generating material may also be referred to as "smokable material".

Devices are known which heat an aerosol-generating material to volatilise at least one component of the aerosol-generating material, typically to form an aerosol which can be inhaled, without igniting or burning the aerosol-generating material. Such devices are sometimes described as "aerosol-generating apparatus", "aerosol provision apparatus", "heating but non-combustion apparatus", "tobacco heating product apparatus" or "tobacco heating apparatus" or the like. Similarly, there are also so-called e-vaping devices that typically vaporize an aerosol-generating material in the form of a liquid, which may or may not contain nicotine. The aerosol-generating material may be in the form of or provided as part of a rod, cartridge or cassette cartridge or the like that can be inserted into the device. A heater for heating and volatilising the aerosol-generating material may be provided as a "permanent" part of the device.

The aerosol provision device may receive an article comprising an aerosol generating material for heating. In the text, an "article" is a component that includes or contains the aerosol-generating material used (which is heated to volatilize the aerosol-generating material) and optionally other components used. The user may insert the article into the aerosol provision device before it is heated to generate an aerosol for subsequent inhalation by the user. The article may be, for example, of a predetermined or particular size, configured to be placed within a heating chamber of an apparatus sized to receive the article.

A first aspect of the present disclosure defines a heater component arranged to heat an aerosol-generating material. In some examples, the heater component is a susceptor. As will be discussed in more detail herein, a susceptor is an electrically conductive object that is heated via electromagnetic induction. Thus, the susceptor may be heated by passing through it with a varying magnetic field. An article comprising aerosol-generating material may be received within the susceptor. Once heated, the susceptor transfers heat to the aerosol generating material, thereby releasing the aerosol.

In this example, the aerosol provision device may monitor the temperature of the heater component at one or more locations while heating. This helps to ensure that the aerosol-generating material is heated to the correct temperature. For example, if the temperature of the heater component is too high, the aerosol generating material may overheat, which may affect the taste/flavour of the aerosol. If the temperature of the heater block is too low, the amount of aerosol generated may be too low. Accordingly, it may be useful to monitor and control the temperature of the heater components during heating.

To monitor the temperature of the heater block in one or more zones, one or more temperature sensors may be in contact with the heater block. For example, the temperature sensor may be a thermocouple. As is well known, a thermocouple is a device for sensing temperature, the thermocouple comprising two different electrical conductors/wires. Typically, two wires are joined together at one end to form a "measurement junction" and the second end of the wire may form a "reference junction". According to the seebeck effect, a voltage is generated between the wires, which voltage depends on the temperature difference between the measurement junction and the reference junction. If the temperature of the reference junction is known, the temperature at the measurement junction can be determined from the measured potential difference between the wires. Electronic circuitry, such as a controller and a voltmeter, can infer temperature based on the measured potential difference.

In the first aspect, the thermocouple is provided by using the first wire and the second wire. The first wire is connected to the heater block at a first location, and the second wire is connected to the heater block at a second location. The first wire and the second wire must be different in order to function as a thermocouple. The heater component may act as an extension of the second wire between the second location and the first location, rather than joining the two wires together at the first location to form a measurement junction. Thus, the temperature measured by the electronic circuitry of the device is the temperature at the first location. The temperature is determined based on a potential difference measured between the first wiring and the second wiring. Thus, the first wire and the heater block form a measurement junction at the first location, rather than the first wire and the second wire.

Since the heater component acts as an extension of the second wire, this means that the second wire does not need to be connected to the first wire at the first location. Allowing the second wiring to be connected anywhere along the heater block allows more freedom in the construction of the device. For example, rather than routing a longer wire through the device to connect the wire to the first wire, a shorter second wire may be used.

If the heater element is made of a material that is "similar" to the second wire, the heater element may form a true extension of the second wire. In this context, similar materials refer to materials that behave in a similar manner when there is the same temperature difference between two points along the material. In other words, when the same temperature difference exists between two points, the voltages generated along the two materials are the same or substantially the same. Since the temperature is estimated based on the measured potential difference, the degree of similarity between the materials will determine the accuracy of the temperature measurement. For example, if the second wire and the heater block are made of exactly the same material, they will behave in the same manner when a temperature gradient is applied to them. Thus, in theory, the device is indistinguishable from a standard thermocouple when the second wire is directly connected to the first wire. If the heater block and the second wire have different compositions, the temperature estimated by the electronic circuit may be different from the temperature measured by the standard thermocouple. Therefore, the degree of similarity between the heater block and the second wiring affects the accuracy of the measured temperature. The degree of similarity thus depends on the accuracy of the temperature measurement required. If the user requires a very accurate temperature measurement, the second wire and the heater block should be made of very similar materials, whereas if the user only requires a rough estimate of the temperature, the heater block and the second wire may be less similar. By changing the material of the heater block or the second wire, the user can determine the measurement error by comparing the estimated temperature with the temperature of a standard thermocouple.

Two materials that produce the same or similar voltages when the same temperature difference exists between the two points can be said to have substantially the same (intrinsic) seebeck coefficient. Therefore, the effective seebeck coefficient of the first wire and the effective seebeck coefficient of the combined second wire and heater component should be substantially the same as the effective seebeck coefficient of the first wire and the effective seebeck coefficient of the second wire. Thus, materials with similar seebeck coefficients will provide more accurate temperature estimates.

Typically, materials having the same or similar composition will have substantially the same seebeck coefficient. Thus, in some examples, the heater component and the second wire may comprise substantially the same metal or alloy (i.e., they both have substantially the same composition). The first wiring has a different composition from the heater block and the second wiring. For example, the first wiring has a different seebeck coefficient from the heater block and the second wiring.

For example, the heater element may comprise at least 95 wt% of a particular metal or alloy and the second wire may comprise at least 95 wt% of the same metal or alloy. Preferably, the heater element may comprise at least 97 wt% of a particular metal or alloy and the second wiring may comprise at least 97 wt% of the same metal or alloy. More preferably, the heater element may comprise at least 99 wt% of a particular metal or alloy and the second wiring may comprise at least 99 wt% of the same metal or alloy. It has been found that materials comprising substantially the same metal or alloy provide more accurate temperature measurements.

In a particular example, the heater block and the second wire each comprise at least 95 wt% iron. Preferably, the heater element and the second wiring each comprise at least 96 wt% iron, or the heater element and the second wiring each comprise at least 97 wt% iron, or the heater element and the second wiring each comprise at least 98 wt% iron. More preferably, the heater element and the second wiring each comprise at least 99 wt% iron. It has been found that materials containing substantially the same wt% iron provide more accurate temperature measurements.

In another example, the heater component comprises steel containing 99.18 wt% to 99.62 wt% iron, and the second wire comprises at least 99 wt% iron. Steels with iron contents of 99.18 wt% to 99.62 wt% may be referred to as AISI 1010 carbon steel (defined by the american iron and steel association). More preferably, the second wire may comprise at least 99.5 wt% iron, for example 99.6 wt% iron. It has been found that such materials provide accurate temperature measurements within about ± 5 ℃.

The first wiring may be made of a copper-nickel alloy. The copper-nickel alloy may be an alloy containing about 55 wt% copper and 45 wt% nickel, such as constantan, trade name^TMA commercial copper nickel alloy. Thus, the second wiring may contain iron, and the first wiring contains a copper-nickel alloy such as constantan. A thermocouple including an iron wire and a copper-nickel wire is generally called a J-type thermocouple. Thus, the first wiring, the second wiring, the heater member and the electronic circuit form a J-shapeAnd a thermocouple.

In some examples, it may be desirable to measure the temperature of the heater block in two or more zones/zones. For example, a first thermocouple device may measure the temperature of the heater block at a first location in a first zone/zone (as described above), and a second, additional thermocouple device may measure the temperature of the heater block at a third location in a second zone/zone. For example, a first section may be heated by a first induction coil and a second section may be heated by a second induction coil.

Accordingly, the heater device may further comprise a third wire connected to the heater block at a third location, wherein the third location is spaced apart from the first location and the second location. The electronic circuit may be further configured to determine a second temperature of the heater block at the third location based on a second potential difference measured between the third wire and the second wire.

Thus, the third wire and the combined second wire and heater means act as part of a second thermocouple, at which time the potential difference between the second wire and the third wire is measured to obtain the temperature at the third location. Thus, two thermocouples can be constructed by using only three wires, instead of four wires that are typically required for two thermocouples. Similarly, three thermocouples may be constructed by using four wires, and four thermocouples may be constructed by using five wires. Therefore, each thermocouple shares a common wiring (second wiring). Thus, the heater element also forms an extension of the second wire between the second location and the third location. Therefore, in order to measure the temperature at the first position, the potential difference between the first wiring and the second wiring may be measured, and in order to measure the temperature at the third position, the potential difference between the third wiring and the second wiring may be measured. This arrangement enables the second wire to be used as part of the first thermocouple and as part of the second thermocouple, which reduces the complexity of the apparatus. By using fewer wires, the weight and cost of the device may be reduced.

The third wiring has a composition satisfying at least one of: (i) a composition different from that of the heater block and the second wiring; and (ii) the same composition as the first wiring. For example, in (i), the third wire must be made of a different metal/alloy than the heater block and the second wire to function as a thermocouple. In (ii), the third wiring may be substantially the same as the first wiring, and thus may also be made of a copper-nickel alloy. This may simplify the process of estimating the temperature by the electronic circuit. For example, because the materials are the same, the same algorithm as used in the first thermocouple device can be used to estimate the temperature in the second thermocouple device.

The first location may be closer to the first end of the heater block than the second location, and the second location may be closer to the first end of the heater block than the third location. Thus, the second position may be located between the first position and the third position. This reduces the length of the heater member serving as an extension of the second wiring, which can make temperature estimation of the first position and the third position more accurate. The first end of the heater block may be the proximal/mouth end of the heater block.

In a particular arrangement, the heater block is surrounded by two induction coils. The first induction coil is wound around the heater member in a first region/zone and the second induction coil is wound around the heater member in a second region/zone. The first location may be located at a midpoint in the first region/partition and the third location may be located at a midpoint in the second region/partition. In some examples, the first induction coil and the partition are shorter than the second induction coil and the partition. For example, the first induction coil may have a length of between about 15mm and about 20mm, and the second induction coil may have a length of between about 25mm and about 30 mm. Thus, the heater block may have a length of between about 40mm and about 50 mm. In a specific example, the first induction coil is arranged towards the mouth/proximal end of the heater block (i.e. the end closer to the mouth of the user when the device is in use) and the second induction coil is arranged towards the distal end of the heater block. In a more specific example, the first location may be located about 32-36mm from the distal end of the heater block and the third location may be located about 12-16mm from the distal end of the heater block.

Preferably, the second location is located on the heater block at a midpoint between the first location and the third location. This means that the distance between the first position and the second position is substantially equal to the distance between the second position and the third position. This means that the distance over which the heater means acts as an extension of the second wire is minimized for both thermocouple devices. Reducing this distance may improve the accuracy of the temperature estimation. In examples where the first and second induction coils are controlled based on measured temperatures, more accurate temperature estimation may result in more accurate control of the induction coils. When the induction coil is operated more accurately, it can prevent the aerosol-generating material from overheating (by ensuring that the partition is not too hot) and can ensure that the aerosol-generating material is not under-heated (by ensuring that the partition is heated to the correct temperature). More precise control of the induction coil can make the device more energy efficient.

In another example, the second location and the third location are located at substantially the same distance along the heater block (they may be located at different points around the circumference of the heater block). The distance is measured from one end of the heater block. In another example, the third location (and the first location) is further along the heater block than the second location. Both arrangements allow the length of the second wiring to be reduced, which can reduce the mass and cost of the apparatus.

Preferably, the first, second and third wires are separate and are not joined together along their lengths.

In some examples, the first wire is covered by the protective coating at a first location where the first wire is connected to the heater block. Additionally or alternatively, the second wire is covered by the protective coating at a second location where the second wire is connected to the heater block. Additionally or alternatively, the third wire is covered by the protective coating at a third location where the third wire is connected to the heater block.

The protective coating can help reduce or prevent corrosion of the wiring or the material joining the wiring to the heater block at the location where the wiring is connected to the heater block. If the aerosol or condensed aerosol comes into contact with the exposed portion of the wiring, corrosion, such as acidic corrosion or galvanic corrosion, may occur. Wires with high iron content may be particularly susceptible to corrosion. Thus, the protective coating may act as a barrier by preventing the aerosol from contacting the wiring.

In some examples, the protective coating covers only a portion of the wire(s). For example, the coating may cover only the exposed conductive portions of the wires. The coating may only be present near the boundary/connection point of the wiring to the heater block.

In examples where the wiring includes an electrically insulating "jacket," the protective coating is different from the jacket.

In one particular arrangement, the protective coating comprises a metal or metal alloy. For example, during manufacture, the wiring may first be connected to the heater block and then coated with a metal or metal alloy. Thus, the coating is applied after the wiring has been connected to the heater block. The coating may for example cover/coat the entire heater element, or at least a portion of the outer surface near the connection point between the wiring of the heater element and the heater element.

The protective coating may comprise nickel. For example, nickel has good corrosion resistance properties. Furthermore, nickel is also ferromagnetic and therefore generates additional heat through magnetic hysteresis, which is particularly useful in aerosol provision devices.

In one example, the metal or metal alloy coating has a thickness of up to 15 microns, such as between about 1 micron and about 15 microns. In a particular example, the metal or metal alloy coating has a thickness between about 1.5 microns and about 2.5 microns.

In another arrangement, the protective coating includes a sealant. The sealant may be applied after the wiring is connected to the heater block. The sealant again acts as a barrier and prevents the aerosol from coming into contact with the wiring. The sealant can be moisture and water resistant.

Preferably, the sealant is a high temperature sealant. That is, the sealant is heat resistant. A heat resistant sealant may mean that the sealant has a high melting point. In aerosol provision devices where the heater element is heated to between about 200 ℃ and about 300 ℃, the sealant should be able to withstand temperatures of, for example, up to about 300 ℃ or up to about 350 ℃.

In some examples, the sealant is a silicone-based sealant. In some examples, the sealant is an alumina-based adhesive.

For example, the sealant may be Cramolin Isotemp^TM、Korthals、Aremco Ceramabond^TM、Glassbond^TM/Saureisen^TMProduct No. 3, Masterbond^TMHigh temperature bonding, sealing and coating compounds or Pi-Kem^TMA high temperature ceramic binder.

In some examples, the encapsulant is electrically insulating.

In one example, there is provided a thermocouple for an aerosol provision device, the thermocouple comprising a first wire and a second wire, wherein a first end of the first wire and a first end of the second wire form a measurement junction, and wherein the first end of the first wire is not connected (or joined) to the first end of the second wire. Thus, the first end of the first wire and the first end of the second wire may be connected to a conductive object (e.g., a susceptor) having a composition similar to one of the first wire and the second wire. Therefore, the thermocouple can function without connecting one ends of the two wires. The second end of the first wire and the second end of the second wire form a reference junction. The thermocouple may include any of the features described above.

In another aspect, a heater apparatus for an aerosol provision device is provided. The heater arrangement comprises a heater component arranged to heat the aerosol-generating material, a first wire connected to the heater component at a first location, wherein at the first location where the first wire is connected to the heater component, the first wire is covered by a protective coating. The protective coating may include any or all of the features described above.

In some examples, the heater device further comprises a second wire connected to the heater block at the first location. Accordingly, the first wiring and the second wiring may be connected to each other at the first position.

In other examples, the second wire is connected to the heater block at a second location, wherein the second location is spaced apart from the first location. Thus, in these examples, the heater component may form an extension of the first wire.

In examples including multiple wires connected to the heater block, the protective coating may be the same or may be different at each wire connection point. In some examples, only some of the wires are coated with a protective coating.

As briefly mentioned above, in some examples, the coil(s) is configured to cause, in use, at least one electrically conductive heating component/element (also referred to as heater component/element) to be heated such that thermal energy may be conducted from the at least one electrically conductive heating component to the aerosol-generating material, thereby causing the aerosol-generating material to be heated.

In some examples, the coil(s) is configured to generate, in use, a varying magnetic field for passing through the at least one heating component/element, thereby causing the at least one heating component to inductively heat and/or hysteresis heat. In such an arrangement, the or each heating element may be referred to as a "susceptor". A coil configured to generate, in use, a varying magnetic field for passing through at least one electrically conductive heating member such that the at least one electrically conductive heating member inductively heats may be referred to as an "induction coil" or "induction coil".

The device may comprise heating component(s), for example electrically conductive heating component(s), and the heating component(s) may be appropriately positioned relative to the coil(s) or may be appropriately positioned relative to the coil(s) to effect such heating of the heating component(s). The heating component(s) may be in a fixed position relative to the coil(s). Alternatively, both the apparatus and such article may comprise at least one respective heating component, for example at least one electrically conductive heating component, and the coil(s) may cause the heating component(s) of each of the apparatus and article to heat when the article is in the heating zone.

In some examples, the coil(s) is helical. In some examples, the coil(s) surround at least a portion of a heating zone of the device configured to receive aerosol-generating material. In some examples, the coil(s) is helical coil(s) that encircles at least a portion of the heating zone. The heating zone may be a receptacle shaped to receive the aerosol-generating material.

In some examples, the apparatus includes an electrically conductive heating member at least partially surrounding the heating zone, and the coil(s) is a helical coil(s) surrounding at least a portion of the electrically conductive heating member. In some examples, the electrically conductive heating member is tubular. In some examples, the coil is an induction coil.

Fig. 1 shows an example of an aerosol provision device 100 for generating an aerosol from an aerosol-generating medium/material. In general, the apparatus 100 may be used to heat a replaceable article 110 comprising an aerosol-generating medium to generate an aerosol or other inhalable medium for inhalation by a user of the apparatus 100.

The device 100 includes a housing 102 (in the form of an enclosure) that surrounds and contains the various components of the device 100. The apparatus 100 has an opening 104 in one end through which an article 110 may be inserted for heating by the heating assembly. In use, the article 110 may be fully or partially inserted into a heating assembly where it may be heated by one or more components of the heater assembly.

The apparatus 100 of this example includes a first end member 106 that includes a cover 108 that is movable relative to the first end member 106 to close the opening 104 when no article 110 is in place. In fig. 1, the cover 108 is shown in an open configuration, however the cover 108 may be moved to a closed configuration. For example, the user may slide the cover 108 in the direction of arrow "a".

The device 100 may also include a user-operable control element 112, such as a button or switch, which when pressed operates the device 100. For example, a user may turn on the device 100 by operating the switch 112.

Device 100 may also include electrical components, such as a jack/port 114 that may receive a cable to charge a battery of device 100. For example, receptacle 114 may be a charging port, such as a USB charging port.

Fig. 2 depicts the device 100 of fig. 1 with the housing 102 removed and the article 110 absent. The apparatus 100 defines a longitudinal axis 134.

As shown in fig. 2, the first end member 106 is disposed at one end of the apparatus 100, and the second end member 116 is disposed at an opposite end of the apparatus 100. Together, the first end member 106 and the second end member 116 at least partially define an end face of the apparatus 100. For example, a bottom surface of the second end member 116 at least partially defines a bottom surface of the device 100. The edges of the housing 102 may also define a portion of the end face. In this example, the cover 108 also defines a portion of the top surface of the device 100.

The end of the device closest to the opening 104 may be referred to as the proximal end (or mouth end) of the device 100, since in use it is closest to the user's mouth. In use, a user inserts the article 110 into the opening 104, operates the user control 112 to begin heating the aerosol-generating material, and draws in aerosol generated in the apparatus. This causes the aerosol to flow through the device 100 along a flow path towards the proximal end of the device 100.

The other end of the device furthest from the mouth 104 may be referred to as the distal end of the device 100, since in use it is the end furthest from the mouth of the user. When a user draws on the aerosol generated in the device, the aerosol flows out of the distal end of the device 100.

The device 100 also includes a power supply 118. The power source 118 may be, for example, a battery, such as a rechargeable battery or a non-rechargeable battery. Examples of suitable batteries include, for example, lithium batteries (such as lithium ion batteries), nickel batteries (such as nickel cadmium batteries), and alkaline batteries. The battery is electrically coupled to the heating assembly to provide power when required and under the control of a controller (not shown) to heat the aerosol generating material. In this example, the batteries are connected to a central support 120 that holds the batteries 118 in place.

The device also includes at least one electronics module 122. The electronic module 122 may include, for example, a Printed Circuit Board (PCB). PCB 122 may support at least one controller (e.g., a processor) and memory. PCB 122 may also include one or more electrical traces to electrically connect the various electronic components of device 100 together. For example, the battery terminals may be electrically connected to the PCB 122 so that power may be distributed throughout the device 100. The receptacle 114 may also be electrically coupled to a battery through an electrical track.

In the exemplary apparatus 100, the heating assembly is an induction heating assembly and includes a plurality of components to heat the aerosol generating material of the article 110 by an induction heating process. Induction heating is the process of heating an electrically conductive object, such as a susceptor, by electromagnetic induction. The induction heating assembly may comprise an induction element, such as one or more induction coils, and comprises means for passing a varying electrical current (e.g. an alternating current) through the induction element. The varying current in the inductive element generates a varying magnetic field. The changing magnetic field passes through a susceptor appropriately positioned relative to the inductive element and generates eddy currents within the susceptor. The susceptor has an electrical resistance to eddy currents, and thus the flow of eddy currents against this electrical resistance causes the susceptor to be heated by joule heating. In the case of susceptors comprising ferromagnetic materials such as iron, nickel or cobalt, heat may also be generated by hysteresis losses in the susceptor (i.e. the direction of the magnetic dipole in the magnetic material changes due to the magnetic dipole being aligned with a changing magnetic field). In induction heating, heat is generated within the susceptor, allowing for rapid heating, as compared to heating, for example, by conduction. Furthermore, no physical contact between the induction heater and the susceptor is required, allowing for increased freedom of construction and application.

The induction heating assembly of the example apparatus 100 includes a susceptor device 132 (referred to herein as a "susceptor"), a first induction coil 124, and a second induction coil 126. The first induction coil 124 and the second induction coil 126 are made of an electrically conductive material. In this example, the first and second induction coils 124, 126 are made of litz wire/cable wound in a spiral manner to provide spiral induction coils 124, 126. Litz wire comprises a plurality of individual wires that are individually insulated and twisted together to form a single wire. Litz wire is intended to reduce skin effect losses in conductors. In the exemplary apparatus 100, the first induction coil 124 and the second induction coil 126 are made of copper litz wire having a rectangular cross section. In other examples, the litz wire may have a cross-section of other shapes, such as circular.

The first induction coil 124 is configured to generate a first varying magnetic field for heating a first section of the susceptor 132, and the second induction coil 126 is configured to generate a second varying magnetic field for heating a second section of the susceptor 132. In this example, the first induction coil 124 is adjacent to the second induction coil 126 in a direction along the longitudinal axis 134 of the device 100 (i.e., the first induction coil 124 and the second induction coil 126 do not overlap). The susceptor arrangement 132 may comprise a single susceptor, or two or more separate susceptors. One end 130 of the first induction coil 124 and one end of the second induction coil 126 may be connected to the PCB 122.

It should be understood that in some examples, the first induction coil 124 and the second induction coil 126 may have at least one characteristic that is different from one another. For example, the first inductive coil 124 may have at least one different characteristic than the second inductive coil 126. More specifically, in one example, the first induction coil 124 may have a different inductance value than the second induction coil 126. In fig. 2, the first induction coil 124 and the second induction coil 126 have different lengths such that the first induction coil 124 is wound on a smaller section of the susceptor 132 than the second induction coil 126. Thus, the first inductive coil 124 may include a different number of turns than the second inductive coil 126 (assuming substantially the same spacing between the individual turns). In yet another example, the first inductive coil 124 may be made of a different material than the second inductive coil 126. In some examples, the first induction coil 124 and the second induction coil 126 may be substantially identical.

In this example, the first induction coil 124 and the second induction coil 126 are wound in opposite directions. This may be useful when the induction coils are activated at different times. For example, initially, the first induction coil 124 may operate to heat a first section of the article 110, and at a later time, the second induction coil 126 may operate to heat a second section of the article 110. Winding the coils in opposite directions helps to reduce the current induced in the coils that are not active when used in conjunction with a particular type of control circuit. In fig. 2, the first inductive coil 124 is right-handed and the second inductive coil 126 is left-handed. However, in another embodiment, the induction coils 124, 126 may be wound in the same direction, or the first induction coil 124 may be left-handed and the second induction coil 126 may be right-handed.

The susceptor 132 of this example is hollow, thus defining a receptacle for receiving aerosol-generating material. For example, the article 110 may be inserted into the susceptor 132. In this example, the susceptor 120 is tubular and has a circular cross-section.

The apparatus 100 of fig. 2 further includes an insulating member 128, which may be generally tubular and at least partially surrounds the susceptor 132. The insulating member 128 may be constructed of any insulating material (e.g., plastic). In this particular example, the insulating member is composed of Polyetheretherketone (PEEK). The insulating member 128 may help insulate various components of the apparatus 100 from heat generated in the susceptor 132.

The insulating member 128 may also fully or partially support the first and second induction coils 124, 126. For example, as shown in fig. 2, the first and second induction coils 124, 126 are positioned around the insulating member 128 and in contact with the radially outward surface of the insulating member 128. In some examples, the insulating member 128 does not abut the first and second induction coils 124, 126. For example, there may be a small gap between the outer surface of the insulating member 128 and the inner surfaces of the first and second induction coils 124, 126.

In a particular example, the susceptor 132, the insulating member 128, and the first and second induction coils 124, 126 are coaxial about a central longitudinal axis of the susceptor 132.

Fig. 3 shows a side view of the apparatus 100 in partial cross-section. In this example there is a housing 102. The rectangular cross-sectional shape of the first induction coil 124 and the second induction coil 126 is more clearly visible.

The apparatus 100 also includes a support 136 that engages an end of the susceptor 132 to hold the susceptor 132 in place. The support 136 is connected to the second end member 116.

The apparatus may also include a second printed circuit board 138 associated within the control element 112.

The device 100 further comprises a spring 142 and a second cap 140 arranged towards the distal end of the device 100. The spring 142 allows the second cover 140 to open to provide access to the susceptor 132. The user may open the second cover 140 to clean the susceptor 132 and/or the support 136.

The device 100 also includes an expansion chamber 144 that extends away from the proximal end of the susceptor 132 toward the opening 104 of the device. The retaining clip 146 is at least partially positioned within the expansion chamber 144 to abut and retain the article 110 when received within the apparatus 100. Expansion chamber 144 is connected to end member 106.

Fig. 4 is an exploded view of the device 100 of fig. 1, with the housing 102 omitted.

Fig. 5A depicts a cross-section of a portion of the apparatus 100 of fig. 1. Fig. 5B depicts a close-up of an area of fig. 5A. Fig. 5A and 5B illustrate the article 110 received within the susceptor 132, wherein the article 110 is sized such that an outer surface of the article 110 abuts an inner surface of the susceptor 132. This ensures that heating is most efficient. The article 110 of this example comprises an aerosol-generating material 110 a. The aerosol-generating material 110a is located within the susceptor 132. The article 110 may also include other components, such as filters, packaging materials, and/or cooling structures.

Figure 5B shows the susceptor 132 with its outer surface spaced from the inner surfaces of the induction coils 124, 126 by a distance 150, measured in a direction perpendicular to the longitudinal axis 158 of the susceptor 132. In one particular example, the distance 150 is about 3mm to 4mm, about 3mm to 3.5mm, or about 3.25 mm.

Figure 5B further illustrates the outer surface of the insulating member 128 spaced from the inner surfaces of the induction coils 124, 126 by a distance 152 measured in a direction perpendicular to the longitudinal axis 158 of the susceptor 132. In one particular example, the distance 152 is about 0.05 mm. In another example, the distance 152 is substantially 0mm such that the induction coils 124, 126 abut and contact the insulating member 128.

In one example, the wall thickness 154 of the susceptor 132 is about 0.025mm to 1mm, or about 0.05 mm.

In one example, the susceptor 132 is about 40mm to 60mm, about 40mm to 45mm, or about 44.5mm in length.

In one example, the wall thickness 156 of the insulating member 128 is about 0.25mm to 2mm, 0.25mm to 1mm, or about 0.5 mm.

Fig. 6 depicts the heating assembly of the apparatus 100. As briefly mentioned above, the heating assembly includes the first induction coil 124 and the second induction coil 126 arranged adjacent to each other in a direction along the axis 158 (also parallel to the longitudinal axis 134 of the apparatus 100). In use, the first induction coil 124 is operated first. This causes a first region/section of the susceptor 132 (i.e. the section of the susceptor 132 surrounded by the first induction coil 124) to heat up, which in turn heats up a first portion of the aerosol-generating material. At a later time, the first induction coil 124 may be turned off and the second induction coil 126 may be operated. This causes a second region/section of the susceptor 132 (i.e. the section of the susceptor 132 surrounded by the second induction coil 126) to heat up, which in turn heats a second portion of the aerosol-generating material. The second induction coil 126 may be turned on while the first induction coil 124 is operated, and the first induction coil 124 may be turned off while the second induction coil 126 continues to operate. Alternatively, the first induction coil 124 may be turned off before the second induction coil 126 is turned on. Electronic circuitry, including a controller, may control when each induction coil operates/energizes. The induction coil may be operated based on the temperature of the susceptor 132 to ensure that each zone is heated to the correct temperature at the correct time.

In some examples, a length 202 of the first induction coil 124 is shorter than a length 204 of the second induction coil 126. The length of each induction coil is measured in a direction parallel to the axis 158 of the susceptor (and also parallel to the axis 134 of the apparatus). The shorter first induction coil 124 is disposed closer to the mouth end (proximal end) of the device 100 than the second induction coil 126. When the aerosol generating material is heated, the aerosol is released. When the user inhales, the aerosol is drawn in the direction of arrow 206 towards the mouth end of the device 100. The aerosol exits the device 100 through the opening/mouthpiece 104 and is inhaled by the user. The first induction coil 124 is disposed closer to the opening 104 than the second induction coil 126.

In this example, the first induction coil 124 has a length 202 of about 20mm and the second induction coil 126 has a length 204 of about 30 mm. The first wire forming the first induction coil 124 is spirally wound on the insulating member 128. Similarly, a second wire is helically wound to form a second induction coil 126. Although the first and second wires are depicted as having a rectangular cross-section, they may have different shaped cross-sections, such as a circular cross-section.

In an example, the apparatus 100 includes one or more temperature sensors for sensing the temperature of the susceptor 132. For example, one temperature sensor may be provided for each section of the susceptor 132. As described above, the susceptor 132 includes a first section and a second section, and the electronic circuitry (which may include a controller) operates the induction coils 124, 126 as desired. In the present apparatus, the temperature sensor for measuring the temperature of the susceptor 132 is a thermocouple. For example, the temperature sensor may be located at or near the midpoint of the zone.

Figure 7 depicts a diagram of an exemplary thermocouple that may be used to measure the temperature of the susceptor 132 at one or more locations. The thermocouple comprises two conductors 210, 212 connected at one end to form a temperature T₁The other end of the conductors 210, 212 is maintained at a second known temperature T₂. The two conductors 210, 212 are made of different materials. For example, the first conductor 210 is made of iron and the second conductor 212 is made of a copper-nickel alloy, such as constantan. Thus, the thermocouple is a type J thermocouple. In other examples, different types of thermocouples comprising different pairs of different conductors may be used, such as E-type, K-type, M-type thermocouples.

When T is₁And T₂At different times, each conductor 210, 212 generates a voltage due to the seebeck effect. The voltage generated by the first conductor 210 is V₁＝S₁Δ T, the voltage generated by the second conductor 212 is V₂＝S₂Δ T, wherein S₁And S₂The seebeck coefficient of the first conductor 212 and the seebeck coefficient of the second conductor 212, respectively, Δ T ═ T₂-T₁. Thus, the voltmeter V will measure the potential difference between the two conductors 210, 212, which is defined by V ═ V₁-V₂＝S₁△T-S₂△T＝S_1，2And delta T is obtained. S_1，2＝S₁-S₂Is the effective seebeck coefficient of the conductor pair. Albeit S₁And S₂Is an inherent material property of the conductor itself, but S_1，2Is the effective seebeck coefficient describing the thermoelectric performance of the thermocouple. The thermocouple may be calibrated based on a known temperature, which may determine the effective seebeck coefficient when measuring V. Therefore, if T₂And S_1，2It is known that T can then be determined by measuring the voltage V₁. E.g. T₂It may be kept at room temperature.

Figure 8 is a schematic view of a susceptor 132 comprising two "standard" thermocouples that may be used to measure the temperature of the susceptor at two locations. The reference junction of each thermocouple is not shown in fig. 8. For example, the reference junction may be a thermistor located on the PCB 122.

The first conductor 218 and the second conductor 220 are connected to the susceptor 132 at a first location 222. The first conductor 218 and the second conductor 220 form part of a first thermocouple that measures the temperature of the susceptor 132 in the first zone at a first location 222. Third and fourth conductors 224 and 226 are connected to susceptor 132 at second location 228. The third and fourth conductors 224, 226 form part of a second thermocouple that measures the temperature of the susceptor 132 in the second zone at a second location 228. The temperature at the first location 222 may be determined based on the measured voltage between the first conductor 218 and the second conductor 220. Similarly, a second temperature at second location 228 may be determined based on the measured voltage between third conductor 224 and fourth conductor 226.

In the exemplary heater arrangement of fig. 8, each thermocouple includes two wires/two conductors connected together at a measurement junction. It has been found, however, that for each thermocouple, the two conductors need not be connected together if the susceptor 132 is made of a material that is "similar" to one of the conductors. The two wires of the thermocouple may alternatively be connected to the susceptor at different locations. Thus, the susceptor 132 forms an extension of one of the wires/conductors. A conductor different from the susceptor is connected at the location where the temperature is to be measured. The conductor similar to the susceptor may be connected anywhere on the susceptor. Allowing one of the conductors/wires to be connected anywhere along the susceptor allows more freedom in the construction of the device.

Thus, fig. 9 depicts an alternative arrangement to the heater arrangement depicted in fig. 8. In such an arrangement, a first conductor/wire 232 is connected to the susceptor 132 at a first location 230. A second conductor/wire 234 is connected to the susceptor 132 at a second location 240. Thus, the first location 230 and the second location 240 are spaced apart along the susceptor. In this example, the second wire 234 is made of a similar material as the susceptor 132, such that the susceptor 132 forms an extension of the second wire 234. The first wire 232 is different from the susceptor 132 and the second wire 234. The measurement junction is a boundary between different materials, and thus the measurement junction is located at a first location 230. Thus, the first wire 232, the second wire 234, and the susceptor 132 form part of a first thermocouple that measures the temperature of the susceptor 132 in the first zone at the first location 230. The temperature may be determined based on a potential difference measured between the first wire 232 and the second wire 234.

If the susceptor 132 and the second wire 234 are similar materials (i.e., they have similar intrinsic seebeck coefficients), the effective seebeck coefficient of the thermocouple is similar to that of the thermocouple in the case where the first wire 232 and the second wire 234 are arranged as shown in fig. 8. For example, if the susceptor 132 is made of substantially the same metal or alloy as the second wire 234, the susceptor 132 and the second wire 234 may have similar intrinsic seebeck coefficients and therefore will produce the same voltage when a temperature gradient is present. In this example, the first wire 232 is made of a copper-nickel alloy, such as constantan, the susceptor 132 is made of carbon steel containing about 99.18 wt% to 99.62 wt% iron, and the second wire 234 contains about 99.6 wt% iron. Thus, the susceptor 132 and the second wire 234 have a similar composition such that the susceptor 132 forms an extension of the second wire 234 between the first location 230 and the second location 240. Figure 10 depicts a path 242 along the susceptor 132 between the first position 230 and the second position 240. Thus, the algorithm described with respect to fig. 7 is also well suited for the devices of fig. 9 and 10, since the path 242 along the susceptor appears in substantially the same manner as a length of the second wire 234.

If it is desired to measure the temperature of the susceptor 132 at another location (e.g., at the third location 236), a third conductor/wire 238 may be connected to the susceptor 132 at the third location 236. The third wire 238 may have the same or different composition as the first wire 232. As with the first thermocouple, the different conductor/wire need not be directly connected to the third wire 238 at the third location 236. Conversely, the second wire 234 may also form part of the second thermocouple even though the second wire is connected to the susceptor 132 at the second location 240. Again, this is because the susceptor 132 is made of a material that is "similar" to the second wire 234. Thus, the susceptor 132 forms an extension of the second wire 234 between the second location 240 and the third location 236. In this example, the third wire 238 is different from the susceptor 132, which means that the measurement junction is located at the third location 236. Thus, the third wire 238, the second wire 234, and the susceptor 132 form part of a second thermocouple that measures the temperature of the susceptor 132 in the second zone at a third location 236. The temperature is determined based on the potential difference measured between the third wire 238 and the second wire 234.

In this example, the third wire 238 is made of a copper-nickel alloy such as constantan and is substantially the same as the first wire 232. Because the susceptor 132 and the second wire 234 have similar compositions, the susceptor 132 forms an extension of the second wire 234 between the second location 240 and the third location 236. Figure 11 depicts a path 244 along the susceptor 132 between the third position 236 and the second position 240. Thus, the algorithm described with respect to fig. 7 is also well suited for the arrangement of fig. 9 and 11, since the path 244 along the susceptor exhibits substantially the same manner as a length of the second wire 234.

Returning to fig. 9, the first location 230 is located in a first zone on the susceptor 132, wherein the first zone is defined as the area located below the first inductive coil 124 surrounding the susceptor 132. Preferably, the first location 230 is located towards the midpoint of the first partition. Similarly, the third location 236 is located in a second zone on the susceptor 132, wherein the second zone is defined as the area located below the second induction coil 126 surrounding the susceptor 132. Preferably, the third location 236 is disposed toward a midpoint of the second partition.

In an example, the susceptor 132 has a length 250 of about 44mm measured between its distal end 252 and its proximal end 252. The first location 230 may be located about 35mm from the distal end 252 of the susceptor 132 and the third location 236 may be located about 14mm from the distal end 252. The distance between distal end 252 and first location 230 is represented by distance 256, and the distance between distal end 252 and third location 236 is represented by distance 258. The distances 256, 258 are measured parallel to the longitudinal axis 158 of the susceptor 132.

In a particular example, the first induction coil 124 has a length between about 15mm and about 20mm, such as about 19mm, and the second induction coil 126 has a length between about 25mm and about 30mm, such as about 28 mm. Thus, the first induction coil 124 and the second induction coil 126 may extend beyond the two ends 252, 254 of the susceptor 132.

In the example of fig. 9-11, the second wire 234 is connected to the susceptor 132 at a second location 240 located between the first location 230 and a third location 236. Preferably, the second location 240 is disposed at a midpoint between the first location 230 and the third location 236 such that the lengths of the paths 242, 244 are substantially equal. This is desirable to ensure that the temperatures estimated at the first and third locations 230 and 236 have the same uncertainty. The temperature estimate may have an uncertainty factor because the susceptor 132 is assumed to behave the same as the second wire 234, depending on the compositional difference (and thus the inherent seebeck coefficient difference) between the susceptor and the second wire 234.

If the second wire 234 were instead connected to the susceptor 132 at a fourth location 248 (see fig. 9), the path length between the fourth location 248 and the first location 230 would be much shorter than the path length between the fourth location 248 and the third location 236. This may mean that the temperature estimated at the first location 230 is more reliable than the temperature estimated at the third location 236. Similarly, if second wire 234 were instead connected to susceptor 132 at fifth location 246 (see fig. 9), the path length between fifth location 246 and first location 230 would be much longer than the path length between fifth location 246 and third location 236. This may mean that the temperature estimated at the first location 230 is less reliable than the temperature estimated at the third location 236.

In some example devices, positioning the second wire at a midpoint between the first location and the third location may allow for more accurate temperature estimation, such that the first and second induction coils may be more efficiently operated/controlled. In certain tests, it was found that the device was able to reduce energy by up to 3% when located at position 240 compared to positions 248, 246.

However, it should be understood that depending on the material and composition of the susceptor 132 and the second wire 232, uncertainty in the temperature estimate may be negligible, such that the second wire 232 may be connected anywhere on the susceptor 132.

In the above examples, the conductors/wires may be connected to the susceptor by various methods, such as by spot welding. The conductors/wires may surround the periphery of the susceptor at the same or different locations. Preferably, the first, second and third conductors/wires surround the periphery at the same location to minimize path lengths between the first and second locations and the first and third locations.

As mentioned, in some examples of the apparatus of fig. 8, the first thermocouple and the second thermocouple are type J thermocouples. For example, first conductor 218 and third conductor 224 are made of iron, and second conductor 220 and fourth conductor 226 are made of a copper-nickel alloy, such as constantan. Although the arrangement of fig. 8 requires the use of four wires, it may provide a useful alternative to the arrangement of fig. 9 in that it provides redundancy if either the first conductor 218 or the third conductor 224 is disconnected from the susceptor 132 (e.g. due to corrosion). For example, if the first conductor 218 is disconnected from the susceptor 132, the temperature of the susceptor may still be measured at the first location 222 using the second conductor 220 and the third conductor 224, since the section of the susceptor 132 between the first location 222 and the second location 228 forms an extension of the third conductor 224. Similarly, if the third conductor 224 is disconnected from the susceptor 132, the temperature of the susceptor may still be measured at the second location 228 using the first conductor 218 and the fourth conductor 226, since the section of the susceptor 132 between the first location 222 and the second location 228 forms an extension of the first conductor 218.

Thus, the device of fig. 8 may function in a manner similar to that described in fig. 9-11 when one of the conductors is disconnected. Thus, in some examples, electronic circuitry (e.g., a controller) in the device is configured to: (i) determine that first conductor 218 has been disconnected from the heater component, and (ii) responsively determine a temperature of heater component 132 at first location 222 based on a potential difference measured between third conductor 224 and second conductor 220. Similarly, electronic circuitry (e.g., a controller) in the device is configured to: (i) determine that third conductor 224 has been disconnected from the heater component, and (ii) responsively determine a temperature of heater component 132 at second location 228 based on a potential difference measured between first conductor 218 and fourth conductor 226. For example, if the potential difference measured between the first conductor 218 and the second conductor 220 is not within an expected range, the electronic circuit may determine that the first conductor 218 has been disconnected. Similarly, for example, if the potential difference measured between third conductor 224 and fourth conductor 226 is not within an expected range, the electronic circuit may determine that third conductor 224 has been disconnected.

In any of the above examples, such as the examples described in fig. 8-11, any or all of the connection points (i.e., where the wiring connects to the susceptor 132) may include a protective coating. The protective coating covers the conductor at the point where it connects to the susceptor 132 and may protect the wiring from corrosion. The protective coating may include a metal layer or metal alloy layer, such as nickel. In other examples, the coating may include a sealant. This may reduce the likelihood of the conductor breaking away from the susceptor 132.

The above-described embodiments are to be understood as illustrative examples of the invention. Other embodiments of the invention are also contemplated. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.