Electrically heated smoking system with improved heater

Abstract

To provide an electrically heated smoking system for receiving an aerosol-forming substrate.SOLUTION: The system comprises at least one heater for heating the aerosol-forming substrate to form aerosol, and a power supply for supplying power to the at least one heater. The at least one heater comprises one or more electrically conductive tracks (103, 203, 303, 403, 503) on an electrically insulating substrate (101, 201, 301, 401, 501). In one arrangement, the one or more electrically conductive tracks (103, 203, 303, 403, 503) have temperature-coefficient-of-resistance characteristics such that the one or more electrically conductive tracks can act as resistive heaters and as a temperature sensor. In another arrangement, the electrically heated smoking system further comprises a thermally insulating material (507) for insulating the at least one heater from the outside of the electrically heated smoking system.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an electrically heated smoking system including a heater for heating an aerosol-forming substrate. [Background technology]

[0002] US-A-5,353,813 discloses a braided tubular array for use as an external heating element in an electric smoking article. The heating element comprises several carbon braids arranged around a spirally wound paperboard reinforcing tube. One electrical connection is formed at the free end of the braid, while a common carbon ring connects to the other end of the carbon braid to form a common electrical connection. When power is applied to the braids, they heat up to produce a heating zone with a temperature ranging from 300°C to approximately 900°C. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US-A-5 353 813 Summary of the Invention [Problem to be solved by the invention]

[0004] The present inventors have recognized that it would be advantageous to provide an electrically heated smoking system that is easier to manufacture and requires fewer components in its construction. [Means for solving the problem]

[0005] According to a first aspect of the present invention, there is provided an electrically heated smoking system for receiving an aerosol-forming substrate, the system comprising at least one heater for heating the substrate to form an aerosol, and a power supply for supplying power to the at least one heater, the at least one heater comprising one or more conductive tracks on an electrically insulating substrate, the one or more conductive tracks having a temperature coefficient of resistance characteristic such that the one or more conductive tracks can act both as a resistive heater and as a temperature sensor.

[0006] There is also provided, according to a first aspect of the present invention, a heater for use in an electrically heated smoking system, the heater comprising one or more electrically conductive tracks on an electrically insulating substrate.

[0007] According to a first aspect of the present invention, there is also provided the use of a heater in an electrically heated smoking system, the heater comprising one or more conductive tracks on an electrically insulating substrate, the one or more conductive tracks having a temperature coefficient of resistance characteristic such that the one or more conductive tracks can act both as a resistive heater and as a temperature sensor.

[0008] The use of a heater including conductive tracks on an electrically insulating substrate that can function as both a heater and a temperature sensor can reduce the number and size of components required for an electrically heated smoking system, thereby reducing the size of the electrically heated smoking system. Furthermore, the electrically insulating substrate can be made very thin, further reducing its size. Furthermore, some or all of the necessary electronics, wiring, and connections can be incorporated onto the same electrically insulating substrate as the heater. Furthermore, the heater can be manufactured more directly and cost-effectively than some prior art heaters, which require each heating element to be individually formed. The heater allows for great flexibility in design, i.e., the conductive tracks can be arranged on the electrically insulating substrate as desired and to provide the desired heat distribution.

[0009] Preferably, the electrically heated smoking system further comprises electronic circuitry arranged to control the supply of electrical power from the power source to the at least one heater.

[0010] Preferably, the power supply supplies power to the at least one heater based on the temperature sensed by the one or more conductive tracks and a desired temperature. That is, feedback is provided that enables the power supply to maintain the temperature of the heater and the aerosol-forming substrate at a particular desired temperature. This is achieved without the need for separate temperature sensors. Preferably, the electrically heated smoking system includes electronic circuitry arranged for this purpose. Preferably, the desired temperature is a temperature at which the heater will heat, but not burn, the aerosol-forming substrate.

[0011] Preferably, the electrically heated smoking system further comprises a thermal insulating material for insulating the at least one heater. The thermal insulating material is capable of insulating the material from the exterior of the electrically heated smoking system. Preferably, the heater comprises a portion of an electrically insulating base having a thermally insulating and / or reflective structure thereon.

[0012] According to a second aspect of the present invention, there is provided an electrically heated smoking system for receiving an aerosol-forming substrate, the system comprising at least one heater including one or more conductive tracks on an electrically insulating substrate for heating the substrate to form an aerosol, a power supply for supplying power to the at least one heater, and thermal insulating material for insulating the at least one heater.

[0013] According to a second aspect of the present invention there is also provided a thermal insulating material for use in an electrically heated smoking system having a heater comprising one or more conductive tracks on an electrically insulating substrate.

[0014] According to a second aspect of the present invention there is also provided the use of a thermal insulating material in an electrically heated smoking system having a heater comprising one or more electrically conductive tracks on an electrically insulating substrate.

[0015] The thermal insulating material reduces heat loss from the heater and protects users of the electrically heated smoking system from burns. The thermal insulating material is preferably positioned around the aerosol-forming substrate to provide maximum thermal insulation. The thermal insulating material must be a material that will not deteriorate at the high temperatures reached in the electrically heated smoking system. Not all thermal insulating materials will be suitable. Preferably, the thermal insulating material comprises a metal or another non-combustible material. In one example, the metal is gold. In another example, the metal is silver. Metals are advantageous because they can reflect heat within the electrically heated smoking system.

[0016] Preferably, the thermal insulating material comprises a plurality of air cavities. The air cavities are arranged in a regular pattern. In one preferred embodiment, the air cavities are hexagonal and arranged in a honeycomb structure. The thermal insulating material can be provided on the electrically insulating substrate in addition to the conductive tracks, thereby allowing for the manufacture of the conductive tracks and the thermal insulating material as a single element. In some manufacturing methods, the conductive tracks and the thermal insulating material can be made as part of the same process. Alternatively, the thermal insulating material can be provided in the electrically heated smoking system as a separate element.

[0017] As in the first aspect of the present invention, the electrically insulating substrate can be made very thin to reduce its size. Furthermore, some or all of the necessary electronics, wiring, and connections can be incorporated on the same electrically insulating substrate as the heater. Furthermore, the heater can be manufactured more directly and cost-effectively than some prior art heaters, which require each heating element to be formed separately. The heater allows for considerable design flexibility, i.e., conductive tracks can be simply positioned on the electrically insulating substrate as desired and to provide the desired heat distribution.

[0018] Preferably, the electrically heated smoking system further comprises electronic circuitry arranged to control the supply of electrical power from the power source to the at least one heater.

[0019] Preferably, the power source provides power to the at least one heater based on a desired temperature. Preferably, the electrically heated smoking system includes electronic circuitry arranged for this purpose. Preferably, the desired temperature is one at which the heater heats, but does not burn, the aerosol-forming substrate.

[0020] Preferably, the one or more conductive tracks have a temperature coefficient of resistance characteristic that enables the one or more conductive tracks to act as a resistive heater and a temperature sensor.

[0021] In one embodiment according to any aspect of the present invention, one or more conductive tracks include multiple portions, each portion being separately connectable to a power source. This provides several advantages. First, it allows different portions to be heated for different durations, thereby enhancing the smoking experience depending on the properties of the aerosol-forming substrate. Second, it allows different portions to be heated at different temperatures, thereby also enhancing the smoking experience depending on the properties of the aerosol-forming substrate. Third, it allows specific portions of the heater to be conductive at any one time, thereby ensuring that only a portion of the aerosol-forming substrate is heated at any one time. This is considered advantageous as it means that each portion of the aerosol-forming substrate is heated only once and is not reheated.

[0022] In one embodiment according to any aspect of the invention, the one or more conductive tracks comprise a single track of conductive material. A first end of the single track is connectable to a power source and a second end of the single track is also connectable to a power source. In that case, the power source is also connectable to one or more central sections of the single track to provide multiple sections, each section being individually connectable to a power source. In another embodiment according to any aspect of the invention, the one or more conductive tracks comprise multiple tracks of conductive material, each track being individually connectable to a power source.

[0023] In both aspects of the invention, the conductive tracks are arranged on the electrically insulating substrate in a configuration that is most suitable for heating the aerosol-forming substrate. Any number of configurations are possible.

[0024] In a first embodiment of any aspect of the present invention, the electrically insulating substrate is rigid and is arranged to be inserted into the aerosol-forming substrate. If the electrically insulating substrate is appropriately sized and rigid, it can be inserted directly into the aerosol-forming substrate. The electrically insulating substrate can be reinforced to provide sufficient rigidity. In that case, if a thermally insulating material is provided, it can be provided to surround the aerosol-forming substrate.

[0025] In a second embodiment of any aspect of the present invention, the electrically insulating substrate is tubular, and one or more conductive tracks are inside the tubular electrically insulating substrate. Such a configuration can be used as an external heater. The external heater can be used to surround or partially surround the aerosol-forming substrate. In one embodiment, the aerosol-forming substrate is solid and in the form of a cylindrical plug. In that case, the internal diameter of the external heater is preferably the same as or slightly larger than the external diameter of the aerosol-forming plug. In the second embodiment, if a thermally insulating material is provided, it is provided to surround the aerosol-forming substrate and the external heater. The thermally insulating material can be provided on the electrically insulating substrate, and the external heater can be formed by rolling the electrically insulating substrate so that the conductive tracks face the inside of the tube and the thermally insulating material faces the outside of the tube.

[0026] In a third embodiment of any aspect of the present invention, the electrically insulating substrate is tubular, and one or more conductive tracks are on the outside of the tubular electrically insulating substrate. Such a configuration can be used as an internal heater. The internal heater can be inserted into the aerosol-forming substrate. In one embodiment, the aerosol-forming substrate is solid and comprises a hollow tube of the aerosol-forming substrate. In that case, preferably, the outer diameter of the internal heater is the same as or slightly smaller than the inner diameter of the tube of the aerosol-forming substrate. In that case, if a thermally insulating material is provided, it is provided to surround the aerosol-forming substrate.

[0027] In both aspects of the invention, the at least one heater may comprise an edge heater for heating an edge of the aerosol-forming substrate, the edge heater comprising one or more conductive tracks on an electrically insulating substrate. In one embodiment, the edge heater comprises a spiral conductive track on a circular or substantially circular electrically insulating substrate.

[0028] In both aspects of the invention, the conductive tracks preferably comprise an electrically resistive material. More preferably, the conductive tracks are metallic. Most preferably, the conductive tracks comprise one or more of silver, platinum, copper, nickel, and palladium. Other materials are also available, such as electrically "conductive" ceramics (such as molybdenum disilicide), carbon, graphite, metal alloys, and composites made of ceramic and metallic materials. Such composites can include doped or undoped ceramics. Examples of suitable doped ceramics include doped silicon carbide. Examples of suitable metals include those listed above, as well as titanium, zirconium, and tantalum. Examples of suitable metal alloys include stainless steel, nickel, cobalt, chromium, aluminum, titanium, zirconium, hafnium, niobium, molybdenum, tantalum, tungsten, tin, gallium, manganese, and iron-containing alloys, as well as nickel, iron, cobalt, and stainless steel-based superalloys, Timetal®, and iron-manganese-aluminum-based alloys. Timetal® is a registered trademark of Titanium Metals Corporation, 1999 Broadway, Suite 4300, Denver, Colorado. In composite materials, depending on the kinetics of energy transfer and the required external physicochemical properties, the electrically resistive material can optionally be embedded or encapsulated in or coated with an insulating material, or vice versa.

[0029] In both aspects of the invention, the conductive tracks can be plated with a protective layer. The conductive tracks can be plated with one or more of gold, nickel, and glass. Plating the conductive tracks can be advantageous if the conductive tracks comprise a material that easily oxidizes or corrodes in some way.

[0030] In both aspects of the invention, the electrically insulating substrate preferably comprises one or more of paper, glass, ceramic, anodized metal, coated metal, and polyimide. Ceramics may include alumina (Al2O3) or zirconia (ZrO2). Other suitable materials may also be used.

[0031] In a first embodiment of any aspect of the invention, the at least one heater is formed by providing an electrically insulating substrate, depositing a conductive paste onto the electrically insulating substrate using a template to form a pattern of the conductive paste, and drying the conductive paste to form conductive tracks.

[0032] In the first embodiment, the electrically insulating substrate can be any suitable electrically insulating material, but is preferably a ceramic or anodized metal. In the first embodiment, the conductive paste can be any suitable paste, but preferably contains metal particles. The metal can be silver. The conductive paste can also contain a binder and a plasticizer.

[0033] In a second embodiment of any aspect of the invention, at least one heater is formed by providing an electrically insulating substrate, covering substantially the entire surface of the electrically insulating substrate with a conductive material, protecting portions of the conductive material with a mask that forms a pattern of the conductive material, and removing the unprotected portions of the conductive material.

[0034] In the second embodiment, the electrically insulating substrate can be any suitable electrically insulating material, but polyimide is preferred. In the second embodiment, the conductive material can be any suitable material, but preferably comprises a metal alloy. The metal can be copper. The conductive tracks can be plated with one or more protective layers. In one embodiment, the copper conductive tracks are plated with a first layer of nickel and a second layer of gold.

[0035] In a third embodiment of any aspect of the invention, at least one heater is formed by providing an electrically insulating substrate, coating the electrically insulating substrate with a metal film, coating the metal film with a layer of photoresist material, protecting portions of the photoresist material with a mask that forms a pattern of conductive paste, removing the unprotected portions of the photoresist material using a light source and chemicals (the exposed photoresist material is soluble in certain solvents), removing portions of the metal film that are not protected by the photoresist material, and removing remaining portions of the photoresist material to expose the metal film in the form of conductive tracks.

[0036] In the third embodiment, the electrically insulating substrate can be any suitable electrically insulating material, but is preferably ceramic. Most preferably, the substrate is alumina (Al2O3) or zirconia (ZrO2). In the third embodiment, the metal film can be any suitable metal film, but is preferably a platinum film. The conductive tracks can be plated with one or more protective layers. In one embodiment, the conductive tracks can be plated with a layer of glass.

[0037] In both aspects of the invention, the aerosol-forming substrate preferably comprises a tobacco-containing material containing volatile tobacco flavour compounds that are released from the aerosol-forming substrate upon heating. Alternatively, the aerosol-forming substrate may comprise a non-tobacco material.

[0038] In both aspects of the invention, preferably the aerosol-forming substrate further comprises an aerosol-forming agent. Examples of suitable aerosol-forming agents are glycerin and propylene glycol.

[0039] In both aspects of the present invention, the aerosol-forming substrate is preferably a solid substrate. In a preferred embodiment, the aerosol-forming substrate comprises a tubular substrate having a cavity for accommodating at least one heater. The solid substrate may comprise, for example, one or more of powders, granules, pellets, flakes, spaghetti, strips, or sheets containing one or more of herb leaves, tobacco leaves, tobacco vein fragments, reconstituted tobacco, homogenized tobacco, extruded tobacco, and effervescent tobacco. The solid substrate may be in loose form or may be provided in a suitable container or cartridge. Optionally, the solid aerosol-forming substrate may contain additional tobacco or non-tobacco volatile flavor compounds that are released upon heating of the substrate.

[0040] In both aspects of the invention, the solid aerosol-forming substrate may optionally be provided on or embedded in a heat-stable carrier. In a preferred embodiment, the carrier is a tubular carrier having a thin layer of solid substrate deposited on its interior surface, its exterior surface, or both its interior and exterior surfaces. Such a tubular carrier may be formed, for example, of paper or paper-like material, non-woven carbon fiber mat, low-mass open-mesh metal screen, or perforated metal foil, or any other heat-stable polymer matrix. Alternatively, the carrier may take the form of a powder, granules, pellets, flakes, spaghetti, strips, or sheets.

[0041] In both aspects of the invention, the solid aerosol-forming substrate may be deposited on the surface of a carrier in the form of, for example, 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 deliver a non-uniform flavor during use.

[0042] In both aspects of the invention, the carrier may alternatively be a nonwoven fiber or fiber bundle having the tobacco compound incorporated therein. The nonwoven fiber or fiber bundle may comprise, for example, carbon fiber, natural cellulose fiber, or cellulosic fiber.

[0043] In both aspects of the present invention, the aerosol-forming substrate can alternatively be a liquid substrate. When a liquid aerosol-forming substrate is provided, the electrically heated smoking system preferably includes a means for holding the liquid. For example, the liquid aerosol-forming substrate can be held in a container. Alternatively or additionally, the liquid aerosol-forming substrate can be absorbed into a porous carrier material. The porous carrier material can be made of any suitable absorbent plug or absorber, such as, for example, foamed metal or plastic material, polypropylene, terylene, nylon fiber, or ceramic. The liquid aerosol-forming substrate can be held in the porous carrier material before use of the electrically heated smoking system, or alternatively, the liquid aerosol-forming substrate material can be released into the porous carrier material at or immediately before use. For example, the liquid aerosol-forming substrate can be provided in the form of a capsule. The capsule shell preferably dissolves upon heating to release the liquid aerosol-forming substrate into the porous carrier material. The capsule can optionally contain a solid in combination with the liquid.

[0044] If the aerosol-forming substrate is a liquid aerosol-forming substrate, the electrically heated smoking system may further include means for heating a small amount of liquid at a time. The means for heating a small amount of liquid at a time may, for example, include a liquid passageway in communication with the liquid substrate. The liquid aerosol-forming substrate is typically forced into the liquid passageway by capillary force. The at least one heater is preferably positioned so that, during use, only the small amount of liquid aerosol-forming substrate in the liquid passageway is heated and vaporized, rather than the liquid in the container.

[0045] Alternatively or additionally, when the aerosol-forming substrate is a liquid aerosol-forming substrate, the electrically heated smoking system may further include an atomizer including at least one heater in contact with the liquid aerosol-forming substrate source. In addition to the heater, the atomizer may include one or more electromechanical elements, such as piezoelectric elements. Additionally or alternatively, the atomizer may also include elements that use electrostatic, electromagnetic, or pneumatic effects. The electrically heated smoking system may further include a condensation chamber.

[0046] In both aspects of the invention, the aerosol-forming substrate may alternatively be any other type of aerosol-forming substrate, such as, for example, a gaseous aerosol-forming substrate, or any combination of various types of aerosol-forming substrates.

[0047] In both aspects of the invention, during operation the aerosol-forming substrate may be completely contained within the electrically heated smoking system, in which case a user can puff on the mouthpiece of the electrically heated smoking system. Alternatively, during operation the aerosol-forming substrate may be partially contained within the electrically heated smoking system, in which case the aerosol-forming substrate forms part of an individual article, and a user can puff on the individual article directly.

[0048] In both aspects of the invention, the electrically heated smoking system may further include a sensor for detecting airflow indicative of a user taking a puff. In that embodiment, preferably the sensor is connected to a power source, and the system is arranged to energize the at least one heater when the sensor detects that the user is taking a puff. Alternatively, the system may further include a switch that is manually operable by the user to initiate a puff.

[0049] In both aspects of the invention, the electrically heated smoking system preferably further comprises a housing designed to be held by a user to receive the aerosol-forming substrate. The housing preferably houses at least one heater, a power source, and any other components required for the system, such as electronic circuitry. In one embodiment, the housing comprises a shell and a replaceable mouthpiece.

[0050] In both aspects of the invention, in one preferred embodiment, the power source is a DC voltage supply. In one embodiment, the power source is a lithium ion battery. Alternatively, the power source can be a nickel-metal hydride battery, a nickel cadmium battery, or a lithium phosphate battery.

[0051] Features described with respect to one aspect of the invention may be equally applicable to other aspects of the invention. In particular, the features and advantages of the one or more conductive tracks acting as both a resistive heater and a temperature sensor described with respect to the first aspect of the invention may be equally applicable to the second aspect of the invention. The features and advantages of the thermal insulating material described with respect to the second aspect of the invention may also be equally applicable to the first aspect of the invention.

[0052] The invention will now be further described, by way of example only, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0053] [Figure 1a] 1A-1C illustrate a first embodiment of a method for forming a heater for an electric smoking system. [Figure 1b] 1A-1C illustrate a first embodiment of a method for forming a heater for an electric smoking system. [Figure 1c] 1A-1C illustrate a first embodiment of a method for forming a heater for an electric smoking system. [Figure 1d] 1A-1C illustrate a first embodiment of a method for forming a heater for an electric smoking system. [Figure 2a] 10A-10C illustrate a second embodiment of a method for forming a heater for an electric smoking system. [Figure 2b] 10A-10C illustrate a second embodiment of a method for forming a heater for an electric smoking system. [Figure 2c] 10A-10C illustrate a second embodiment of a method for forming a heater for an electric smoking system. [Figure 2d] 10A-10C illustrate a second embodiment of a method for forming a heater for an electric smoking system. [Figure 2e] 10A-10C illustrate a second embodiment of a method for forming a heater for an electric smoking system. [Figure 3a] 10A-10C illustrate a third embodiment of a method for forming a heater for an electric smoking system. [Figure 3b] 10A-10C illustrate a third embodiment of a method for forming a heater for an electric smoking system. [Figure 3c] 10A-10C illustrate a third embodiment of a method for forming a heater for an electric smoking system. [Figure 3d] 10A-10C illustrate a third embodiment of a method for forming a heater for an electric smoking system. [Figure 3e] 10A-10C illustrate a third embodiment of a method for forming a heater for an electric smoking system. [Figure 3f] 10A-10C illustrate a third embodiment of a method for forming a heater for an electric smoking system. [Figure 4] FIG. 1 shows a first embodiment of a heater for use in an electrically heated smoking system. [Figure 5a] FIG. 1 shows a second embodiment of a heater for use in an electrically heated smoking system. [Figure 5b] FIG. 1 shows a second embodiment of a heater for use in an electrically heated smoking system. DETAILED DESCRIPTION OF THE INVENTION

[0054] As mentioned above, the present invention provides an electrically heated smoking system including a heater. The heater includes one or more conductive tracks on an electrically insulating substrate. The heater can be formed by several different manufacturing processes. Figures 1a to 1d illustrate a first manufacturing process; Figures 2a to 2d illustrate a second manufacturing process; and Figures 3a to 3d illustrate a third manufacturing process.

[0055] FIGS. 1a through 1d illustrate a manufacturing process using a technique similar to that used in screen printing. This manufacturing process can be used with either the first or second embodiment of the present invention. Referring to FIG. 1a, first, an electrically insulating substrate 101 is provided. The electrically insulating substrate can include any suitable electrically insulating material, such as, but not limited to, a ceramic such as MICA, glass, or paper. Alternatively, the electrically insulating substrate can include an electrical conductor insulated from the conductive tracks by, for example, oxidizing or anodizing its surface, or both (as depicted in FIG. 1b and described below). One example is anodized aluminum. Alternatively, the electrically insulating substrate can include an electrical conductor to which an intermediate coating called a glaze is added. In this case, the glaze serves the dual function of electrically insulating the substrate from the conductive tracks and reducing bending of the substrate. Creases in the electrically insulating substrate can lead to cracks in the conductive paste (as depicted in FIG. 1b and described below) that can damage the resistor.

[0056] Referring to FIG. 1b, while the electrically insulating substrate is held securely in place, for example, by vacuum, a metal paste 105 is coated onto the electrically insulating substrate using a notch 107. While any suitable metal paste can be used, by way of example, the metal paste is silver paste. In a particularly advantageous example, the paste contains 20% to 30% binder and plasticizer, and 70% to 80% metal particles, typically silver particles. The notch 107 provides a template for the desired conductive tracks. After the metal paste 105 is coated onto the electrically insulating substrate 101, the electrically insulating substrate and paste are fired, for example, in a sintering furnace. In a first firing phase between 200°C and 400°C, the organic binder and solvent are burned off. In a second firing phase between 350°C and 500°C, the metal particles are sintered.

[0057] Referring to Figure 1c, an electrically insulating substrate 101 results having thereon one or more conductive tracks 103. The conductive track or tracks include a heating resistor and the necessary connection pads.

[0058] Finally, the electrically insulating substrate 101 and the conductive tracks 103 are formed into a suitable configuration for use as a heater in an electrically heated smoking system. Referring to FIG. 1d, the electrically insulating substrate 101 can be wound into a tubular configuration so that the conductive tracks are located inside the electrically insulating substrate (FIG. 1d(i)). In that case, the tube can function as an external heater for a solid plug of aerosol-forming material. The inner diameter of the tube can be the same as or slightly larger than the diameter of the aerosol-forming plug. Alternatively, the electrically insulating substrate 101 can be wound into a tubular configuration so that the conductive tracks are located outside the electrically insulating substrate (FIG. 1d(ii)). In that case, the tube functions as an internal heater and can be inserted directly into the aerosol-forming substrate. This works well when the aerosol-forming substrate takes the form of a tube of tobacco material, such as a tobacco mat. In that case, the outer diameter of the tube can be the same as or slightly smaller than the inner diameter of the aerosol-forming substrate. Alternatively, if the electrically insulating substrate is sufficiently rigid or reinforced in some way, some or all of the electrically insulating substrate and conductive tracks can be used directly as an internal heater by simply inserting the electrically insulating substrate and conductive tracks directly into the aerosol-forming substrate (Figure 1d(iii)).

[0059] 2a to 2e show a second manufacturing process for a heater for an electrically heated smoking system. This manufacturing process can be used with either the first or second aspect of the present invention. This manufacturing process is based on PCB manufacturing technology. Referring to FIG. 2a, first, an electrically insulating substrate 201 is provided. Again, the electrically insulating substrate can comprise any suitable electrically insulating material. In this example, the electrically insulating substrate 201 comprises polyimide.

[0060] Referring to FIG. 2b, second, a metal foil 205 is applied substantially over the entire electrically insulating substrate 201. This can be achieved by lamination or by a physical vapor deposition (PVD) process, followed by chemical reaction electrical reinforcement. While any suitable metal can be used, in one example, the metal foil is copper. Copper has the advantage of having a high temperature coefficient of resistance, which may mean that it is relatively simple to use the conductive tracks as temperature sensors as well as heaters. This is explained more fully below. Other metals can also be used, such as, but not limited to, nickel or platinum.

[0061] After the metal foil 205 is applied to the electrically insulating substrate, subtractive methods are used to remove unwanted areas of copper. Referring to Figure 2c, a mask 207 is used, typically in combination with chemical etching, which dissolves the copper in all areas not protected by the mask. This results in the device shown in Figure 2c, which includes an electrically insulating substrate 201 with conductive areas 209.

[0062] Referring to FIG. 2d, the conductive areas 209 can then be plated. FIG. 2d shows one conductive area 209 for simplicity. Plating is advantageous when using copper because copper oxidizes quickly. If an oxide layer has already formed, it can be difficult to solder the copper to form the necessary connections. In this example, the conductive areas 209 are plated with a bilayer including a first layer 211 of nickel followed by a second layer 213 of gold. The result is an electrically insulating substrate 201 having one or more conductive tracks 203 thereon. The one or more conductive tracks include a heating resistor and the necessary connection pads.

[0063] Finally, the electrically insulating substrate 201 and the conductive tracks 203 are formed into a suitable configuration for use as a heater in an electrically heated smoking system. Referring to FIG. 2e, the electrically insulating substrate 201 can be wound into a tubular configuration so that the conductive tracks 203 are located inside the electrically insulating substrate (FIG. 2e(i)). In that case, the tube can function as an external heater for the aerosol-forming substrate. Alternatively, the electrically insulating substrate 201 can be wound into a tubular configuration so that the conductive tracks are located outside the electrically insulating substrate (FIG. 2e(ii)). In that case, the tube functions as an internal heater and can be inserted directly into the aerosol-forming substrate. Alternatively, if the electrically insulating substrate is sufficiently rigid or reinforced in some way, some or all of the electrically insulating substrate and conductive tracks can be used as an internal heater by simply inserting the electrically insulating substrate and conductive tracks directly into the aerosol-forming substrate (FIG. 2e(iii)).

[0064] It should be noted that the method described with respect to Figures 2a to 2e can also be used to form an additional thermally insulating reflective layer, as will be described in more detail below.

[0065] 3a to 3e show a third manufacturing process for a heater for an electrically heated smoking system. This manufacturing process can be used with either the first or second aspects of the present invention. This manufacturing process is based on photolithography techniques. Referring to FIG. 3a, first, an electrically insulating substrate 301 is provided. Again, the electrically insulating substrate can comprise any suitable electrically insulating material. In this example, the electrically insulating substrate 301 comprises a thick ceramic, such as, but not limited to, alumina (Al2O3) or zirconia (ZrO2).

[0066] Referring to Figure 3b, a structured metal film 305 is formed on an electrically insulating substrate 301. In this example, the metal film is platinum, although any suitable metal can be used.

[0067] 3c, a photoresist layer 307 is then applied over the metal film 305. The photoresist layer may be applied by any suitable technique, such as, for example, but not limited to, spin coating.

[0068] Referring to Figure 3d, unwanted areas of the photoresist are removed. This is accomplished by using mask 309 to expose the photoresist to a high intensity beam of light from light source 311. A chemical change occurs in the exposed areas of the photoresist so that these layers can then be removed by a chemical agent called a developer.

[0069] With the photoresist removed in the unprotected areas, the metal film 305 is etched using a wet or dry etch. This dissolves the metal film in all areas not protected by photoresist. With the metal etched, the remaining photoresist is removed with a solvent, resulting in the device shown in FIG. 3e, which includes an electrically insulating substrate 301 with conductive areas 313.

[0070] Finally, referring to Figure 3f, the electrically insulating substrate 301 and the conductive areas 313 can be optionally coated with a protective layer 315 to prevent corrosion or oxidation of the conductive areas. In this example, the protective layer is a glass layer. The result is an electrically insulating substrate 301 having one or more conductive tracks thereon. The one or more conductive tracks include a heating resistor and the necessary connection pads.

[0071] The heater may be mounted within the electrically heated smoking system using a special frame, such as a metal clamp, or the heater may be an integral part of a monolithic ceramic base located within the electrically heated smoking system.

[0072] Figures 4 and 5a and 5b show two alternative embodiments of the heater of the present invention.

[0073] FIG. 4 shows a first embodiment of a heater for use with an aerosol-forming substrate. In FIG. 4, the heater 400 comprises a flat, rigid, electrically insulating substrate 401 having conductive tracks 403 thereon (the heater can be in the form shown in FIG. 1d(iii) or FIG. 2e(iii)). The conductive tracks are connectable to a power source (not shown) through connector 405. The heater 400 can be inserted directly into a plug in the aerosol-forming substrate, shown generally at 407. The heater shown in FIG. 4 can be used in either the first or second aspects of the present invention. If the conductive tracks have suitable temperature coefficient of resistance characteristics, they can act as both a resistive heater and a temperature sensor. The heater can be combined with a thermal insulating material to thermally insulate at least one heater from the exterior of the electrically heated smoking system with which it is used.

[0074] 5a and 5b show a second embodiment of a heater. In FIGS. 5a and 5b, the heater comprises an electrically insulating substrate 501. On a first portion 509 of the electrically insulating substrate are conductive tracks 503. The conductive tracks 503 are connectable to a power source (not shown) through connections 505. On a second portion 511 of the electrically insulating substrate 501, a thermally insulating, reflective honeycomb structure 507 is formed on the electrically insulating substrate. The heater of FIG. 5a is designed to be wound into a tube from left to right, with the portion 509 of the electrically insulating substrate with the conductive tracks on the inside and the portion 511 of the electrically insulating substrate with the thermally insulating honeycomb structure 507 on the outside. Preferably, the thermally insulating material is also highly reflective. The resulting heater is shown schematically in FIG. 5b. The honeycomb structure is then used to thermally insulate the heater, and can preferably be metallic. The heater shown in Figure 5b can be used as an external heater with a thermally insulating reflective honeycomb structure 507 on the outside to insulate the heater from the exterior of the electrically heated smoking system it is used with, thereby reducing heat loss and protecting the user's hands from burns.

[0075] In Figures 5a and 5b, the thermally insulating, reflective honeycomb structure is shown as an integral part of the heater. However, alternatively, the honeycomb structure can be formed separately and used as a stand-alone element in the electrically heated smoking system. In the case of an external heater, the honeycomb structure can be wrapped around an electrically insulating substrate and conductive tracks. In the case of an internal heater, the honeycomb structure can be disposed around an aerosol-forming substrate. Additionally, alternative structural arrangements for the thermally insulating material are possible.

[0076] The heaters shown in Figures 5a and 5b can also be used in the first aspect of the invention, i.e. if the conductive tracks have suitable temperature coefficient of resistance characteristics, they can act as resistive heaters as well as temperature sensors.

[0077] As already mentioned above, the manufacturing process shown in Figures 2a through 2e can also be used to create a honeycomb structure 507. Individual areas of an electrically insulating substrate can be plated in a manner similar to that shown in Figure 2d. When the underlying areas are then dissolved or otherwise removed, the plating will form air cavities that provide thermal insulation. In a preferred configuration, the air cavities are provided within the honeycomb structure, although other configurations are contemplated. Furthermore, multiple layers of the thermally insulating structure can be used, for example, by wrapping or stacking several layers, to provide maximum thermal insulation. Advantageously, the plating can include only one layer of gold. Gold is particularly useful because it will reflect heat toward the interior of the electrically heated smoking system, further reducing heat loss. Alternatively, the plating can include one layer of another metal, such as silver. Alternatively, the plating can include two layers similar to that shown in Figure 2d.

[0078] The use of a heater including conductive tracks formed on an electrically insulating substrate provides several advantages. The size of the components required for an electrically heated smoking system can be reduced, thereby reducing the size of the electrically heated smoking system. Furthermore, the electrically insulating substrate can be made very thin, allowing for further size reduction. Furthermore, some or all of the necessary electronics, wiring, and connections can be incorporated onto the same electrically insulating substrate as the heater.

[0079] Additionally, the heater can be manufactured more directly and cost-effectively than some prior art heaters, which require each heating element to be formed separately. The heater has a fairly flexible design, i.e., the conductive tracks can be placed directly on the electrically insulating substrate as desired and to provide the desired heat distribution.

[0080] Additionally, assuming the material used for the conductive tracks has suitable temperature coefficient of resistance characteristics, the conductive tracks can act as both a resistive heater and a temperature sensor, thereby eliminating the need for a separate temperature sensor and further reducing the size of the electrically heated smoking system, as will now be described in more detail below.

[0081] The temperature coefficient of resistance is a measure of the change in resistance with a given change in temperature. The general formula is given by: R = R0(1 + αT) where R is the resistance, R0 is the resistance at a given temperature (typically 0°C), T is the temperature, and α is the temperature coefficient of resistance. The temperature dependence of the conductor is substantially linear.

[0082] In one method, the voltage across and current through the conductive track are measured to determine the resistance. Then, assuming that R and α (both of which will be known for a given material) are known, the temperature can be determined. That is, the conductive track can act as a temperature sensor as well as a resistive heater.

[0083] The temperature coefficient of resistance α of the material should be reasonably reliable, i.e., it does not vary significantly over time or under certain conditions. Furthermore, using a material with a high value of the temperature coefficient of resistance α can be advantageous, as it means that a relatively small change in temperature results in a large change in resistance. Materials with high values ​​of α include platinum, nickel, and copper.

[0084] 1. An electrically heated smoking system for receiving an aerosol-forming substrate, comprising: at least one heater for heating the substrate to form an aerosol; a power source for supplying power to the at least one heater; Including, the at least one heater comprises one or more conductive tracks on an electrically insulating substrate, the one or more conductive tracks having a temperature coefficient of resistance characteristic such that the one or more conductive tracks can act both as a resistive heater and as a temperature sensor; A system characterized by: 2. The electrically heated smoking system described in 1, characterized in that the power source supplies power to the at least one heater based on the temperature sensed by the one or more conductive tracks and the desired temperature. 3. An electrically heated smoking system as described in 2, characterized in that the desired temperature is a temperature at which the heater heats but does not burn the aerosol-forming substrate. 4. An electrically heated smoking system as described in any one of 1 to 3, further comprising a thermal insulating material for insulating the at least one heater. 5. An electrically heated smoking system for receiving an aerosol-forming substrate, comprising: at least one heater comprising one or more conductive tracks on an electrically insulating substrate for heating the substrate to form an aerosol; a power source for supplying power to the at least one heater; a thermal insulating material for insulating the at least one heater; A system comprising: 6. An electrically heated smoking system as described in 5, characterized in that the one or more conductive tracks have a temperature coefficient of resistance characteristic such that the one or more conductive tracks can act as both a resistive heater and a temperature sensor. 7. An electrically heated smoking system as described in any one of 1 to 6, characterized in that the one or more conductive tracks include multiple portions, each portion being separately connectable to the power source. 8. An electrically heated smoking system as described in any one of 1 to 7, characterized in that the electrically insulating substrate is rigid and is arranged to be inserted into the aerosol-forming substrate. 9. An electrically heated smoking system as described in any one of 1 to 7, characterized in that the electrically insulating substrate is tubular and the one or more conductive tracks are inside the tubular electrically insulating substrate. 10. An electrically heated smoking system as described in any one of 1 to 7, characterized in that the electrically insulating substrate is tubular and the one or more conductive tracks are located outside the tubular electrically insulating substrate. 11. An electrically heated smoking system as described in any one of 1 to 10, characterized in that the at least one heater includes an end heater comprising one or more conductive tracks on an electrically insulating substrate for heating the end of the aerosol-forming substrate. 12. The conductive tracks comprise one or more of silver, platinum, copper, nickel, and palladium; the conductive tracks are plated with one or more of gold, nickel, and glass; the electrically insulating substrate comprises one or more of paper, glass, ceramic, anodized metal, coated metal, and polyimide; 12. An electrically heated smoking system according to any one of 1 to 11, characterized in that it has at least one of the following features. 13. A heater for use in an electrically heated smoking system, comprising: one or more conductive tracks on an electrically insulating substrate; Including, the one or more conductive tracks have a temperature coefficient of resistance characteristic such that the one or more conductive tracks can act as both a resistive heater and a temperature sensor; A heater characterized by: 14. Use of a heater in an electrically heated smoking system, comprising: the heater comprises one or more conductive tracks on an electrically insulating substrate, the one or more conductive tracks having a temperature coefficient of resistance characteristic such that the one or more conductive tracks can act as both a resistive heater and a temperature sensor; 10. Use of a heater characterized by: 15. A thermal insulating material for use in an electrically heated smoking system having a heater comprising one or more conductive tracks on an electrically insulating substrate. [Explanation of symbols]

[0085] 401 Electrical insulating substrate 403 Conductive Track 405 Conductive track connections 407 Aerosol-forming substrate plug

Claims

1. 1. An electrically heated smoking system configured to receive a solid aerosol-forming substrate, the solid aerosol-forming substrate being in the form of a cylindrical plug and comprising a tobacco-containing material containing volatile tobacco flavour compounds that are released from the solid aerosol-forming substrate upon heating, the electrically heated smoking system comprising: a housing for receiving said solid aerosol-forming substrate; at least one heater for heating the solid aerosol-forming substrate to form an aerosol, the at least one heater comprising one or more conductive tracks on an electrically insulating substrate, the heater being an external heater surrounding or partially surrounding the solid aerosol-forming substrate; a power source for supplying power to the at least one heater; a thermal insulating material including a plurality of air cavities provided as a separate element and positioned around the heater to insulate the heater, the thermal insulating material comprising a housing designed to be held by a user and containing the at least one heater, the power source, and the thermal insulating material; An electrically heated smoking system comprising:

2. 10. An electrically heated smoking system configured to receive a solid aerosol-forming substrate as described in claim 1, characterized in that the thermal insulating material comprises a material that will not deteriorate at the high temperatures reached in the electrically heated smoking system.

3. 10. An electrically heated smoking system configured to receive a solid aerosol-forming substrate as defined in claim 1, wherein the thermal insulating material forms a thermal insulating structure comprised of multiple layers.

4. 10. An electrically heated smoking system configured to receive a solid aerosol-forming substrate according to claim 1, wherein the thermally insulating material is cylindrical in shape.

5. 2. An electrically heated smoking system configured to receive a solid aerosol-forming substrate as described in claim 1, characterized in that the electrically insulating substrate having the one or more conductive tracks is configured to be wound into a tubular form.

6. 10. An electrically heated smoking system configured to receive a solid aerosol-forming substrate according to claim 1, wherein the air cavities are arranged in a regular pattern.

7. 10. An electrically heated smoking system configured to receive a solid aerosol-forming substrate according to claim 1, wherein the electrically insulating substrate is formed of polyimide.

8. 10. An electrically heated smoking system configured to receive a solid aerosol-forming substrate according to claim 1, wherein the conductive track comprises stainless steel.

9. An electrically heated smoking system configured to receive a solid aerosol-forming substrate according to any one of claims 1 to 8, characterized in that the one or more conductive tracks comprise a plurality of portions, each portion being separately connectable to the power source.

10. 10. An electrically heated smoking system configured to receive a solid aerosol-forming substrate according to claim 1, wherein, during operation, the solid aerosol-forming substrate is partially contained within the electrically heated smoking system.

11. 10. An electrically heated smoking system configured to receive a solid aerosol-forming substrate as described in claim 1, wherein the solid aerosol-forming substrate forms part of a separate article, and during operation, a user draws directly on the separate article.

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