INDUCTOR

The present invention relates to a method of manufacturing a cartridge for use with an aerosol-generating system, in particular for use with an e-cigarette. The cartridge is provided with an identification inductor having a particular inductance which is indicative of the employed cartridge or the aerosol-forming medium stored in the cartridge.

Frequently used e-cigarettes have a modular construction and usually comprise a replaceable cartridge with a storage component for holding an aerosol-forming substrate. The aerosol-forming substrate comprised in the cartridge may vary considerably in composition, flavour, strength or other characteristics. Consumers may wish to interchange cartridges at will. However, the optimum vaporization conditions may depend on the composition of the aerosol-forming substrate comprised in the cartridges. Thus, in order to perfectly adapt the vaporization unit to the specific aerosol-forming substrate chosen by the consumer, it would be desirable to include in the e-cigarettes automatic recognition means which can identify the replaceable cartridge or the aerosol-forming substrate stored therein, in order to automatically change the control settings of the vaporization equipment accordingly.

EP 2 399 636 A1 is directed to an aerosol generator comprising a replaceable cartridge as described above, wherein the cartridge comprises one or more electrical components for distinguishing the cartridge from other cartridges. The electrical components may be one or more electrical resistors, capacitances or inductances. The aerosol generator comprises means for determining the electrical characteristics of the one or more electrical components. The aerosol generator may further comprise a look-up table stored in a memory unit, in which the characteristics of the electrical components are associated with data identifying the respective cartridge. In order to allow for distinguishing between different cartridges a plurality of electrical components may be used.

In EP 2 399 636 A1 the additional electrical components for distinguishing the cartridge from other cartridges are provided in separate electrical circuits and therefore require the use of additional electric contacts, via which the additional electrical components are connected to the control circuitry. Additional contacts increase complexity of the structure of the aerosol- generating system. This makes production more expensive and represents an additional source for malfunction.

The present invention aims at overcoming the above mentioned problems and aims to provide a reliable method for making cartridges electronically distinguishable while only insignificantly increasing their structural complexity.

According to a first aspect of the invention there is provided a method of manufacturing a cartridge suitable for use with an aerosol-generating system. The method comprises the steps of providing a liquid storage portion, providing an electrical component having a predefined resistance, forming the electrical component into an electrical inductor having a particular inductance, and mounting the electrical inductor to the cartridge. The inductance of the electrical inductor is indicative of the particular cartridge. The inductance of the electrical inductor may also be indicative of an aerosol-forming substrate filled in or to be filled in the liquid storage portion of the cartridge.

The electrical component may be a suitably shaped, electrically conductive wire. For a given material, the total resistance of an electrically conductive wire is determined by its cross- section and its length. The wire may be made from a conductive material having low resistivity, such as copper, silver, aluminum or alloys thereof. The lower the resistance of the electrical component, the less electrical energy is dissipated in the electrical component and the lower is the influence of the electrical component to the remaining electrical circuit.

The electrically conductive wire may be formed into a solenoid, such as an inductive coil, having a particular inductance. The resulting inductance of a coil formed from an electrically conductive wire depends on the length, the radius and the number of turns of the inductive coil. In this way a plurality of identical wires, i.e. wires made from identical material, with identical cross-section and identical length, may be formed into a plurality of inductive coils with differing inductance. As the length of the wires remains unchanged, the total resistance of the inductive coils also remains substantially constant. In this context "substantially constant" means that the total resistance is identical, and basically only varies due to material inhomogeneity or production tolerances.

In order to manufacture the wires into coils with varying inductance, it is possible to change at least one of the number of turns, the diameter of the coil, and the overall length of the coil. If the full length of the wire is formed into coil shape, a change of one of the parameters also leads to a change of the other parameters. However, it is not necessary that the full length of the wire is formed into coil shape. It might as well be possible to keep one or two of the parameters coil diameter, coil length and number of turns constant. The excess wire portion that is not formed into coil shape could then be used for example to connect the cartridge circuit to the power source contacts.

The method may further comprise the steps of providing an electrical heating element, mounting the electrical heating element to the cartridge and connecting an electrical inductor in series to the electrical heating element. Throughout this specification, the combination of the heating element and the inductor is referred to as the "cartridge circuit". Typically the heating element is powered in aerosol-generating systems by a direct current power source. Such direct current electric circuits are only marginally influenced by the presence of an additional inductance. Moreover, if the inductive element is made from a low resistivity material, the total resistance also only has a negligible influence on the power consumption and basically does not affect the heater properties of the heating element.

In embodiments in which the heating elements are powered by direct current power sources, such as batteries, the voltage drop across and the current flow through the heating element are substantially constant during use. However, in order to determine the inductance of the inductor, the response of the inductor upon a change of the current flow has to be determined. Typically the inductance is therefore determined upon activation or deactivation of the electric circuit or by applying alternating current. Thus, determination of the inductance and identification of the cartridge is therefore preferably carried out, at times when the heating element is not activated.

In use the cartridge circuit is connected to a power source and is controlled by the electric circuitry of the aerosol-generating system. The electrical contacts for contacting the cartridge circuit to the control circuitry may be provided as point contacts, rectangular contacts, circular contacts, or as concentric ring contacts. Small contact areas allow for a compact construction, but might require that the cartridge resumes a specific orientation in order to close the contact. In contrast thereto, larger contact areas, in particular ring contacts, do not require a specific orientation of the cartridge and therefore simplifies handling of the system for the consumers.

One advantage of the present invention is that the inductive element can be connected in series with the heating element and therefore two electric contacts may be sufficient in order to power the heating device and to determine the inductance of the electric inductor. This reduces complexity and increases reliability and performance of the system.

If the various inductive components are formed from an identical piece of wire, the manufacturing method and the involved logistics during manufacture is significantly simplified. Instead of providing a plurality of differing inductive components for the manufacturing process, the method of the present invention requires only one electrical component, such as an electrically conductive wire. This wire is then formed by means, which are readily available to the skilled person, during manufacturing of the cartridge into inductive components with differing particular inductances.

During manufacturing, each cartridge is equipped with a specific inductive component, whose inductance is indicative of the aerosol-forming substrate that is already comprised or that is to be filled in the liquid storage portion of the cartridge.

The electrical inductor may be mounted to the cartridge at any suitable position. The electrical inductor may be mounted on the inside of the cartridge, such that the inductor is not accessible by the consumer during normal replacement handling of the cartridge. The electrical inductor may also be mounted on the outside of the cartridge. In order to further protect the inductor in this case from unwanted or inadvertent manipulation, the cartridge may further be provided with a cap which is adapted to cover the electrical inductor.

In embodiments in which the heating element is provided in the form of a heating coil, the inductance of the heating circuit can also be varied by modification of the heating coil itself. The variation of the inductance of the heating coil follows the same principles as the modification of the inductance of the additional electrical inductor as described above. By varying the inductance of the heating coil, a separate inductor is not required anymore. However, the design of the heating coil needs also to comply with certain requirements of the atomizing process, such as the diameter and the length of the wick portion to be heated. Accordingly less degree of freedom is available for the variation of the dimensions of the coil.

In a second aspect the invention is directed to a cartridge suitable for use with an aerosol-generating system, wherein the cartridge comprises a liquid storage portion and an electrical inductor having a pre-defined resistance and a particular inductance, wherein the particular inductance of the electrical inductor is indicative of the employed cartridge or the aerosol-forming substrate comprised in or to be filled in the liquid storage portion of the cartridge.

The cartridge may further comprise a heating element, which is connected in series to the electrical inductor; wherein the heating element and the electrical inductor form a cartridge circuit.

In a third aspect, the invention is directed to an aerosol-generating system, in particular an e-cigarette, comprising the above mentioned cartridge, and a device portion, comprising a power supply and an electronic circuitry. The electronic circuitry is adapted to determine the electrical inductance of the electric inductor, and to associate the electrical inductance with data identifying the cartridge.

Preferably, the cartridge and the device portion are separate or individual bodies or units. In other words, the cartridge may be manufactured, packaged and sold separately of the device portion. The cartridge may be mountable to the device portion or receivable by the device portion in use. As such, the device portion may durable and may be configured for multiple uses, and the cartridge may be consumable and replaceable after one or two uses. In some embodiments, the device portion may be configured to be used with different cartridges.

The cartridge may be releasably mountable to a device portion of an aerosol- generating system. The cartridge may be releasably mounted to the device portion of the aerosol-generating system.

In an embodiment of the invention, the cartridge is a replaceable tank, which comprises an electrical inductor for identifying the tank and the aerosol-forming substrate contained therein, while the heating element may form part of the device portion. The liquid from the tank is conveyed to the heating element by suitable passive or active conveying means. Passive conveying means may include a capillary tube or wick, which extends into the replaceable tank and which forward the aerosol-forming substrate to the heating element by capillary action. Active conveying means may include pumps or syringe systems which may be actively controlled by a control circuit. Typically such active conveying means can be activated upon a corresponding signal from a puff sensor.

In embodiments in which the heating element forms part of the device portion, the heating element is not replaced upon replacement of the tank. However, it may be possible that the heating element is replaceably mounted to the device portion, such that the user can insert a new heating element when necessary.

The device portion may comprise a memory device for storing a look-up table, the lookup table comprising data representing the electrical inductance of the inductors, each electrical inductance value being associated with data identifying a cartridge.

Preferably, the look-up table may further comprise data representing one or more inductance values, each inductance value further associated with parameters representing a different energy profile to be applied to the heating element. Each inductance value is associated with a different cartridge identifier. This means that the aerosol-generating system can be configured to deliver a constant amount, for example volume or mass of aerosol to the user even when cartridges containing different aerosol-forming substrates are inserted into the aerosol-generating system.

For example, a particular aerosol-forming substrate contained within one cartridge may require more energy to be vaporized, than a different aerosol-forming substrate contained within another cartridge. By associating an inductance value or a particular cartridge identifier with a heating profile stored in a look-up table, a constant amount of aerosol can be delivered to the user independent of the type of aerosol-forming substrate stored in the cartridge.

The invention will be further described, by way of example only, with reference to the accompanying drawings in which:

Fig. 1 shows an embodiment of the invention with an inductor mounted to a cartridge; Fig. 2 shows an electronic circuit diagram for a cartridge circuit comprising a heating element and an inductor for identifying the cartridge of the present invention; and

Fig. 3 shows a plurality of inductors having identical resistance and differing inductance.

In Fig. 1 an example of a typically used aerosol-generating system 10 is depicted. The aerosol-generating system 10 of Fig. 1 is an electrically heated aerosol-generating system 10 and comprises a two-part housing 12 having a device portion 14 and a cartridge 16. In the device portion 14, there is provided an electric power supply in the form of a battery 18 and an electric control circuitry 20. The cartridge 16 comprises a liquid storage portion 22 containing aerosol-forming substrate 24, a capillary wick 26 and a heating element in the form of a heating coil 28. In this embodiment the liquid storage portion 22 is a cylindrical structure defining a central air flow channel 30. The ends of the capillary wick 26 extend into the liquid storage portion 22. A central portion of the capillary wick 26 extends through the air flow channel 30 and is at least partially surrounded by the heating coil 28. The heating coil 28 is connected to the electric circuitry 20 via appropriate electrical connections (not shown). The housing 10 also includes an air inlet 32, and an air outlet 34 at the mouthpiece end. In the device depicted in Fig. 1 b, the cartridge 16 is removable from the device portion 14, and comprises the liquid storage portion 22 and the atomizer 26, 28. Such devices are therefore also referred to as "cartomizers".

In use, operation is as follows. Liquid aerosol-forming substrate 24 is transferred by capillary action from the liquid storage portion 22 from the ends of the wick 26 which extend into the liquid storage portion 22 to the central portion of the wick 26 which is surrounded by the heating coil 28. When a user draws on the device at the air outlet 34, ambient air is drawn through air inlet 32. A puff detection system (not shown) senses a puff and activates the heating coil 28. The battery 18 supplies electrical energy to the heating coil 28 to heat the central portion of the wick 26 surrounded by the heating coil 28. The aerosol-forming substrate 24 in the central portion of the wick 26 is vaporized by the heating coil 28 to create a supersaturated vapour. The supersaturated vapour is mixed with and carried in the air flow from the air inlet 32. In the air flow channel 30 the vapour condenses to form an inhalable aerosol, which is carried towards the outlet 34 and into the mouth of the user.

In addition to the above described elements an inductor 40 is provided to the cartridge 16. The inductor 40 is connected to the control circuitry 20 and allows the control circuitry 20 to identify the liquid storage portion 22 and in particular the type of aerosol-forming substrate 24 comprised in the liquid storage portion 22. As indicated in Figures 1 a, 1 b the inductor 40 may be placed in the liquid storage portion 22. In this embodiment the resistor 40 is not visible to the user and is protected from damage during normal handling of the aerosol-generating system 10.

The aerosol-generating system 10 depicted in Fig. 1 is only one exemplary aerosol- generating system in which the cartridge of the present invention may advantageously be used. The skilled person will readily appreciate that the identification system of the present invention may also be used with other known designs of aerosol-generating systems 10 employing replaceable cartridges 16.

In Fig. 2 an electrical circuit diagram of an embodiment of the invention is depicted. In this embodiment, the heating device, e.g. heating coil 28, is connected to two electric contacts Ti, T2 which in turn are connected to the two contacts of the power source (not shown) provided in the aerosol-generating system. In addition thereto, the circuit diagram of Fig. 2 also comprises an inductor 40, which is connected in series with the heating coil 28. The combination of heating device and inductor is also referred to as "cartridge circuit" in this specification. The control circuitry 20 of the aerosol-generating system 10 is adapted to determine the total inductance of the cartridge circuit, as discussed in the following.

As will be known to those skilled in the art, the relationship between the inductance L of an electrical circuit, the voltage V, and the current I through the circuit is:

The voltage induced across an inductor is equal to the product of the inductor's inductance and the rate of the change of current flowing through the inductor.

By measuring the potential difference across the inductor upon a change of the current I flowing through the inductor, the controller circuitry is able to determine the value of the inductor L according to the above relationship.

Having determined the value of inductor L associated with the cartridge, the control circuitry determines the cartridge type from the determined inductance value by searching a look-up table using the determined inductance value.

The look-up table may comprise one or more different inductance values, each inductance value associated with an identifier of a cartridge which can be used with the aerosol-generating system. The identifier may be indicative of the type of liquid contained within the cartridge.

The controller may determine the type of cartridge as the cartridge identifier stored in the look-up table which is associated with the inductance value stored in the look-up table which is closest in value to the cartridge inductance value determined by the controller. The look-up table may be stored in a read only memory (ROM) incorporated into the control circuitry or may be stored in a separate memory store.

In Fig. 3 one possible embodiment of the present invention is illustrated. In this embodiment a copper wire with a fixed length is used in order to form a plurality of solenoids or inductive coils 40 having differing inductance. All coils 40 are made from an identical piece of copper wire, such that the electrical resistance R of these inductive coils remains constant.

The copper wire used in the embodiments of Fig. 3 has a length of 150 millimetres and a diameter of 0.5 millimetres. Assuming a resistivity of copper of 1.7 ^* 10 ^"8 Ohm ^* meter, this results in a total resistance of the copper wire of approximately 0.01 Ohm. This resistance is sufficiently small, so that it does not affect the heater properties of the heating coil. The copper wire is wound into a coil having varying coil number of turns N and coil radius r. For a wire having a predefined length I and a predefined number of turns N, the radius r of the resulting coil is determined according to the relationship I = 2 π r N to : r = (2)

2 -π-JV

The inductance of the resulting solenoid, i.e. a short cylindrical coil with air core, can be determined from its geometrical dimensions according to the following formula: μ ₀ Ν ² Α 0A -n ² -N ² -r ²

L =— = (3)

I + 0.9r I + 0.9r

In this calculation the length I of the coil is considered to be approximately equal to the diameter of the wire multiplied by the number of turns of the coil.

The resulting dimensions and inductances for a copper wire having a total length of 150 millimetres and a diameter of 0.5 millimetres, are indicated in the following table:

Table 1 : Inductance values for coils with varying number of turns and radius It is important that the individual coils reproduced as exactly as possible, such that the electronic circuit is able to distinguish in a reliable way between these inductance values. The accuracy of the method for forming the inductive coils having a particular inductance is preferably equal to or better than +/- 5%.

The electronic control circuit 20 determines the inductance value of the cartridge circuit in order to verify the type of cartridge 16 and, thus, the type of the aerosol-forming substrate 24 provided in the currently inserted cartridge 16. Having determined the type of the aerosol- forming substrate 24, the electronic control circuitry 20 can adjust the settings for activation of the heating element 28 to the specific type of aerosol-forming substrate 24. In this way optimum vaporization conditions can be guaranteed for a wide variety of aerosol-forming substrates 24 usable with the aerosol-generation system 10.

The exemplary embodiments described above illustrate, but are not limiting. In view of the above discussed exemplary embodiments, other embodiments consistent with the above exemplary embodiment will now be apparent to one of ordinary skill in the art.