Heating apparatus for an aerosol generating device

Abstract

A heating apparatus (100) for an aerosol generating device is disclosed, the heating apparatus (100) including a vacuum insulator (102) having a major longitudinal axis and including an inner wall (104) and an outer wall (106) between which a vacuum (108) is trapped, a cavity (110) capable of receiving an aerosol forming substance, the cavity (110) being positioned radially inward of the inner wall, a heater (112) disposed within the vacuum insulator in thermal contact with the inner wall of the vacuum insulator, the heater (112) configured to heat the aerosol forming substance received within the cavity by thermal conduction to generate an aerosol, and one or more wires (132) configured to connect the heater to a power source, the one or more wires extending through at least one hole in the outer wall of the vacuum insulator, the one or more wires being circumferentially surrounded by the insulator (130). The insulator includes glass, and the one or more wires are made from a material having thermal expansion characteristics that substantially match the thermal expansion characteristics of the insulator.

Description

[Technical field]

[0001] The present invention relates to a heating apparatus for an aerosol generating device, in particular to a heating apparatus having a vacuum insulator. [Background technology]

[0002] One type of heating apparatus for an aerosol generating device uses a vacuum insulator and a heater disposed in thermal contact with an inner wall of the vacuum insulator. The vacuum insulator typically includes a central cavity positioned adjacent the inner wall that can receive an aerosol-generating material. The heater can heat the aerosol-generating substrate to generate an aerosol that is inhalable. The vacuum insulator can thermally insulate the outer surface of the aerosol generating device from the heater so that the aerosol generating device can be held comfortably by a user.

[0003] One of the challenges to overcome in manufacturing this type of heating device is how to power the heater from a power source outside the vacuum insulator while still maintaining an effective vacuum. It is an object of the present invention to address these challenges. Summary of the Invention [Means for solving the problem]

[0004] According to one aspect of the present invention, there is provided a heating apparatus for an aerosol generating device, the heating apparatus comprising: a vacuum insulator having a main longitudinal axis and including inner and outer walls between which a vacuum is trapped; a cavity capable of receiving an aerosol-forming substance, the cavity positioned radially inward of the inner wall; a heater disposed within the vacuum insulator in thermal contact with the inner wall of the vacuum insulator, the heater configured to heat the aerosol-forming substance received in the cavity by thermal conduction to generate an aerosol; and one or more wires configured to connect the heater to a power source, the one or more wires extending through at least one hole in the outer wall of the vacuum insulator, the one or more wires being circumferentially surrounded by the insulator, the insulator comprising glass, and the one or more wires being made from a material having thermal expansion characteristics substantially matching those of the insulator.

[0005] In this manner, an effective vacuum can be maintained while still allowing electrical connection between the heater and a power source. This can be accomplished by threading one or more wires through one or more holes in the exterior wall and providing insulation between the wires and the vacuum insulation. The present invention provides a method by which wires can be positioned through holes in the exterior wall without compromising the vacuum.

[0006] Preferably, the insulator is a thermal insulator and an electrical insulator. Thermal insulation is advantageous because it prevents heat from being conducted along the wires and thereby heating the walls of the vacuum insulator. Electrical insulation is advantageous because it allows the vacuum insulator to be made of a material that conducts electricity, such as a metal, without causing a short circuit between the two terminals of the power supply.

[0007] The heater is preferably a track heater printed or coated onto a vacuum insulator. The heater is preferably provided on the outer surface of the inner wall.

[0008] The outer wall may have a circumferential portion and a bottom portion. A surface normal vector at the outer wall may extend radially at the circumferential portion and axially at the bottom portion. At least one hole may extend through the circumferential portion or through the bottom portion. In some embodiments, a first hole may extend through the circumferential portion and a second hole may extend through the bottom portion.

[0009] Preferably, the heating device includes a first wire extending through a first hole in the outer wall and a second wire extending through a second hole in the outer wall. In this way, separate holes can be provided for the first wire and the second wire. This has been found to provide effective electrical insulation between the wires. This can also allow the wires to be spaced apart from one another for connection to different points on the heater.

[0010] Alternatively, the outer wall may include a hole through which both the first and second wires are positioned. In this case, the first and second wires may be embedded in a shared sheet or piece of insulation that circumferentially surrounds each wire. In this case, the first and second wires may be spaced apart to avoid shorting between the terminals of the power source.

[0011] The insulator comprises glass. In one example, the insulator comprises borosilicate glass. In other embodiments, the insulator can comprise other suitable insulating glass materials.

[0012] The one or more wires are made from a material having thermal expansion characteristics that substantially match those of the insulator, which provides an airtight and stable seal of the vacuum chamber because the mechanical bond integrity is maintained over a wide temperature range. Each wire can be bonded with a glass insulator in an oven to provide a very strong connection that is maintained even when the wire is heated by conduction due to its connection to the heater.

[0013] Preferably, the one or more wires include Kovar, a family of iron alloys. In one example, nickel-cobalt iron alloys can be used. These materials provide substantially the same thermal expansion properties as glass over a wide range of temperatures, from room temperature to at least the normal operating temperature of the heater.

[0014] Preferably, the insulator comprises borosilicate glass and the one or more wires comprise Kovar. This combination provides a particularly effective seal for vacuum throughout the operating temperatures of the heating device.

[0015] Preferably, the heating device includes a sensor positioned within the vacuum insulator and a sensor wire connected to the sensor and extending through a further hole in the vacuum insulator, the sensor wire being circumferentially surrounded by the insulator. This may allow a sensor to be provided within the vacuum chamber, primarily to monitor the operation and function of the heater, without compromising the integrity of the vacuum. This is preferably achieved with a Kovar sensor wire encased in a glass insulator. Any type of sensor may be used, such as a temperature sensor or a pressure sensor. In some embodiments, multiple sensors may be provided.

[0016] Preferably, the further holes extend through the outer wall of the vacuum insulator. The further holes may be provided in a circumferential portion or in a bottom portion of the outer wall.

[0017] Alternatively, the further hole extends between the inner and outer walls of the vacuum insulator.

[0018] In some embodiments, the sensor wire may be provided in a different area of ​​the vacuum insulation or on a different surface of the exterior wall compared to the wire or wires for the heater.

[0019] Preferably, the heater is a resistive heater. The heater may comprise an electrical resistive track printed or coated on the inner wall. The resistive track may be provided on a specific section of the inner wall or may be coated or printed on the inner wall to cover substantially all of the inner wall. The resistive track may follow a serpentine or wave-like path on the inner wall from a first end of the track to a second end. In another example, the heater may comprise one or more resistive heating plates or elements provided on the inner wall. The heating plates or elements may also be provided as a wave-like or serpentine resistive track.

[0020] Preferably, the heater includes an exposed exterior surface having a material that is susceptible to oxidation reactions in the presence of oxygen. Many heaters include materials that oxidize in the presence of oxygen that may adversely affect the performance of the heater if an oxidation resistant coating is not applied. In this manner, allowing the heater to have an exposed exterior surface without an oxidation resistant coating can make the heater cheaper, less massive, and / or easier to produce, taking advantage of the heater being placed in a vacuum.

[0021] Preferably, the inner wall has a thickness of about 0.1 mm or less. Thus, the inner wall has a thickness corresponding to the significantly improved thermal efficiency threshold of the vacuum insulator. The outer wall may have a thickness of about 0.25 mm.

[0022] Preferably, one or more wires each extend through a different hole in the outer wall, each hole containing a corresponding insulation surrounding the corresponding wire. More preferably, each respective hole is sized primarily to accommodate the corresponding wire to minimize the amount of insulation contacting the outer wall. In this manner, each hole can be sized to minimize the circumference or perimeter of the outer wall that contacts the insulation, which better retains the vacuum within the vacuum insulation. Those skilled in the art will appreciate that "sized primarily to accommodate a single wire" means that each hole is made as small as possible to hold a single insulated wire while still allowing for practical assembly of the insulation around each wire. Thus, in some instances, each hole may have a diameter of about 1.5, 2, or 3 times the diameter of its corresponding wire. The insulation within each hole may surround the corresponding wire with a thickness approximately equal to the thickness of the corresponding wire, i.e., about 0.5 to 2 times the thickness of the wire.

[0023] According to a further aspect of the present invention there is provided an aerosol generating device configured to generate an aerosol for inhalation by a user, the aerosol generating device including a heating apparatus as described above.

[0024] Embodiments of the invention will now be described, by way of example, with reference to the drawings, in which: [Brief description of the drawings]

[0025] [Figure 1] 1 shows a perspective view of a heating device according to one embodiment of the present invention; [Diagram 2] 1 shows a schematic cross-sectional view of a portion of a heating device according to an embodiment of the present invention. [Figure 3A] 1 shows a perspective view of a portion of a heating device according to one embodiment of the present invention; [Figure 3B] 1 shows a perspective view of a portion of a heating device according to one embodiment of the present invention; [Figure 3C] 1 shows a perspective view of a portion of a heating device according to one embodiment of the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Fig. 1 shows a schematic perspective view of a heating apparatus for an aerosol generating device according to one embodiment of the present invention, and Fig. 2 shows a schematic cross-sectional view of a part of the heating apparatus shown in Fig. 1.

[0027] 1 and 2, a heating device 100 is provided that includes a vacuum insulator 102 including an inner wall 104 and an outer wall 106 radially spaced apart from one another such that a vacuum 108 is trapped between the inner wall 104 and the outer wall 106. The heating device 100 includes a cavity 110 disposed adjacent the inner wall 104 that is configured to receive a consumable including a tobacco rod and a filter held together by a tip wrapper. The consumable can be inserted into the cavity 110 by a user through an opening 111 to the cavity 110 such that the consumable is held in place by friction with the inner wall 104.

[0028] A heater 112 is provided within the vacuum 108 and on an outer surface of the inner wall 104. The heater 112 is configured to heat when an electric current is passed through the heater 112 and to transfer this heat to the inner wall 104 by conduction. The heat is then transferred through the inner wall 104 by conduction such that the inner surface of the inner wall 104 heats the consumables and air in the cavity 110. The heater 112 may be powered by a battery or any other power source provided on the aerosol generating device.

[0029] The outer wall 106 includes a circumferential portion 106a having a surface normal vector extending radially into the cavity 110 and a bottom portion 106b having a surface normal vector parallel to a major longitudinal axis of the vacuum insulator 102. A first heater wire 114 and a second heater wire 116 are each threaded through a respective hole in the bottom portion 106b and configured to electrically connect the heater 112 to a power supply and control electronics provided on the aerosol generating device. A first connection lead 118 is provided for electrically connecting a first end 120 of the heater 112 to the first heater wire 114. A second connection lead 122 is provided for electrically connecting the second heater wire 116 to a second end 124 of the heater 112. The first and second connection leads 118, 122 may be fused to the heater 112 or to the inner wall 104.

[0030] A temperature sensor (not shown) is provided within the vacuum insulator 102. A first sensor wire 126 and a second sensor wire 128 are also provided through respective holes in the bottom portion 106b. The first sensor wire 126 and the second sensor wire 128 are configured to electrically connect the temperature sensor to power and control electronics provided on the aerosol generating device. The first sensor wire 126 and the second sensor wire 128 may also be attached to additional respective connection leads (not shown) configured to electrically connect each sensor wire to the temperature sensor.

[0031] The first and second heater wires 114, 116 and the first and second sensor wires 126, 128 may be collectively referred to as "wires" 132. As shown in Figures 1 and 2, each of the wires 132 is disposed through a respective hole in the bottom portion 106b. Each of the wires 132 is joined to the bottom portion 106b by one of a number of airtight seals 130 that prevent ingress of air into the interior of the vacuum insulator 102. Each of the seals 130 includes an insulator that circumferentially surrounds one of the wires 132.

[0032] The vacuum insulator 102 is hollow and confines a vacuum 108 between its curved inner wall 104 and its curved outer wall 106. The vacuum insulator 102 has a generally cylindrical shape that allows the vacuum insulator 102 to completely surround the consumable. The vacuum insulator 102 provides thermal insulation so that the heater 112 can effectively heat the aerosol generating substrate while not heating other parts of the aerosol generating device, particularly the parts of the aerosol generating device that are held by the user. The vacuum insulator 102 is elongated along its main longitudinal axis, as shown in FIG. 1. This allows the vacuum insulator 102 to receive a consumable in the form of an elongated rod, including tobacco. The vacuum insulator 102 has a generally elliptical or generally circular cross-sectional shape when viewed along one of the ends of the vacuum insulator 102 parallel to its longitudinal axis. However, in other embodiments, the vacuum insulator 102 may have other types of cross-sectional shapes, such as a generally square or generally polygonal shape.

[0033] The vacuum insulator 102 includes an opening 111 at one longitudinal end for receiving consumables and is closed at the opposite end. Thus, as shown in Figures 1 and 2, the vacuum insulator 102 has a cup-shaped cross section when viewed perpendicular to its longitudinal axis. In other embodiments, the vacuum insulator 102 may be open at both longitudinal ends so as to have a tubular cross section when viewed perpendicular to its longitudinal axis. In such a case, the outer wall 106 may include only or mainly the circumferential portion 106a, and each of the wires 132 may be provided through a respective hole in the circumferential portion 106a while being surrounded by a respective seal 130. In the embodiment of Figures 1 and 2, the inner wall 104 and the outer wall 106 are joined or welded to each other at the same end of the vacuum insulator 102 where the opening 111 is found. The bottom portion 106b and the circumferential portion 106a are also joined or welded at the joint 134 shown in Figure 2.

[0034] The opening 111 and the inner wall 104 have the same cross-section along the entire longitudinal extent of the inner wall 104. In other embodiments, the opening 111 may flare outward to allow a user to more easily insert the consumable into the cavity 110.

[0035] The outer wall 106 comprises stainless steel. In other embodiments, the outer wall 106 can comprise other suitable materials, such as other metals, alloys, or plastics. The circumferential portion 106a of the outer wall 106 comprises a single curved surface that is substantially or generally cylindrical. The outer wall 106 can have other shapes depending on the alternative shape of the vacuum insulator.

[0036] The inner wall 104 may have a thickness of about 0.1 millimeters (mm) or less. Having a relatively small thickness reduces the thermal mass of the vacuum insulator 102 and increases the thermal conductivity through the inner wall 104 to the cavity 110 and the consumables. In particular, less heat is conducted away from the cavity 110 by the outer surface of the inner wall 104. The 0.1 mm or less threshold has been found to be important in improving the energy efficiency of the heating apparatus 100 through these mechanisms. In particular, an inner wall thickness of 0.1 mm has been found to provide significantly improved thermal efficiency as compared to an inner wall thickness of 0.25 mm.

[0037] The outer wall 106 may have a thickness of approximately 0.25 mm, which may be preferred over a thickness of 0.1 mm to provide improved mechanical robustness and thermal insulation to the vacuum insulator 102 .

[0038] The cavity 110 is substantially cylindrical and positioned immediately adjacent to the inner wall 104. Preferably, the side of the inner wall 104 facing the cavity 110, i.e., the "inner surface" of the inner wall 104, is substantially or completely free of additional components such that the consumable can directly contact the inner surface when received within the cavity 110. This maximizes the efficiency of heat transfer from the inner wall 104 to the consumable. Furthermore, the lack of additional components keeps the thermal mass of the heating device low, which can improve the time required to heat the tobacco to an aerosol-generating temperature.

[0039] In the embodiment of Figures 1 and 2, the heater 112 is a resistive heater configured to generate heat when an electric current is applied. The heater 112 includes a winding resistive heating track extending from a first end 120 to a second end 124 of the heater 112. The track follows an undulating path along the length of the inner wall 104, as shown in Figure 1. The first end 120 and the second end 124 of the heater 112 are connected to a first connecting lead 118 and a second connecting lead 122, respectively. The first heater wire 114 is configured to electrically connect with a first terminal of a battery in the aerosol generating device, and the second heater wire 116 is configured to connect with the opposite terminal of the battery. Thus, a battery can be used to supply an electric current through the heating track during operation of the heating apparatus 100. The electrical resistance of the heater 112 then causes the heater 112 to generate heat in response to a current passing through the heater 112 through the first heater wire 114 and the second heater wire 116 .

[0040] The heater 112 is printed or coated on the exterior surface of the inner wall 104. In other embodiments, the heater 112 may include a heating element or plate disposed and attached to the inner wall 104. Thus, the heater 112 may provide "trace heating" to the cavity 110. The heater 112 may have a corrugated shape on the surface of the inner wall 104 such that substantially the entire length of the inner wall 104 is heated, as shown in FIG. 1. In other embodiments, the heater 112 may cover substantially the entire circumference and / or area of ​​the inner wall 104.

[0041] The heater 112 may comprise a material that is susceptible to oxidation reactions in the presence of oxygen and may be provided without an oxidation-resistant coating, thus exposing the heater 112 to the vacuum 108 and taking advantage of the lack of oxygen within the vacuum insulator 102 to make the heater 112 cheaper and / or easier to manufacture.

[0042] In this embodiment, each of the wires 132 includes Kovar, a group of iron alloys configured to exhibit specific thermal expansion properties that match those of glass, such as borosilicate glass. In one example, Kovar has a thermal expansion coefficient of approximately 5×10 at 30-200° C. -6 / K, approx. 10×10 at 800℃ -6 / K. Borosilicate glass has a thermal expansion characteristic of 3×10 -6 / K. Borosilicate glass is particularly preferred because Kovar can be configured to have thermal expansion properties that match those of borosilicate glass, allowing the borosilicate glass to form a hermetic seal around the Kovar wire over a wide temperature range.

[0043] Each of the seals 130 includes an insulator that circumferentially surrounds one of the respective wires 132. Each seal 130 is embedded in a respective hole in the bottom portion 106b, with each of the wires 132 positioned through the respective hole. In this embodiment, the seal 130 includes Kovar wires 132 and glass, which allows the seal 130 to form an airtight joint over a wide range of temperatures. It is important to have substantially matching thermal expansion characteristics because heat from the heater 112, which typically operates at temperatures in excess of 100° C., can reach the bottom portion 106b by conduction through the inner wall 104 and the circumferential portion 106a. This particular material selection for the wires 132 and seal 130 therefore provides a particularly effective mechanical joint over a wide range of operating temperatures, thereby helping to maintain the integrity of the vacuum. Additionally, the glass electrically insulates the bottom portion 106b from the wires 132, thereby eliminating the need for a separate insulating layer to prevent electrical conduction from the wires 132 to the outer wall 106.

[0044] During manufacturing of the heating device 100, the seal 130 is preformed into a ring shape inside the hole in the bottom portion 106b before threading the wire 132 through the seal 130. The seal 130 and wire 132 can then be bonded or welded together using an oven to form a strong permanent bond after cooling. This can provide a convenient method of manufacturing the heating device 100.

[0045] In other embodiments, the wire 132 and the seal 130 may comprise other conductive and insulating materials, respectively. In particular, the wire 132 and the seal 130 may comprise materials selected to have substantially matching thermal expansion characteristics over the typical operating temperatures of the heating device 100.

[0046] 1 and 2, the wire 132 is provided through a hole in the bottom portion 106b of the outer wall 106. However, in other embodiments, the wire 132 and seal 130 may be provided elsewhere on the outer wall 106, such as through a hole in the circumferential portion 106a or at a different location on the bottom portion 106b.

[0047] A temperature sensor (not shown) may be provided on the inner surface of the outer wall 106 or the outer surface of the inner wall 104 within the vacuum insulator 102. The temperature sensor may be configured to detect the temperature of the heater 112 or the cavity 110 and transmit the detected temperature to a controller provided on the aerosol generating device incorporating the heating apparatus 100. The temperature sensor may transmit the detected temperature via one or more additional connection leads (not shown) attached to one or both of the first sensor wire 126 or the second sensor wire 128. In one example, the temperature sensor may include a thermistor. In other embodiments, the temperature sensor may be co-located with or replaced by other types of sensors, such as a pressure sensor.

[0048] As mentioned above, the heating device 100 can be used with or provided within an aerosol generating device. The aerosol generating device typically includes a battery or other power source for powering the heater 112, a button or other input mechanism for allowing a user to activate the heater 112, and a controller for controlling the electronic components of the device, such as the heater 112. The heating device 100 can be provided within a housing of the aerosol generating device, the housing including an opening aligned with the opening 111 of the heating device 100. The aerosol generating device can be configured as an electronic smoking device.

[0049] The heating device 100 is configured for use with a consumable that includes tobacco and a filter, which may be held together by a tip wrapper. The consumable may be a cylindrical rod, although other shapes of consumables designed to be received within the cavity 110 may also be used. Other forms of aerosol-forming material may also be used in place of or in addition to tobacco.

[0050] 1 and 2, an exemplary use of a heating apparatus 100 for use in an aerosol generating device will now be described.

[0051] During use, a user may insert a consumable into cavity 110 through opening 111. When the user is ready to begin vaporization, the user may press a button on the aerosol generating device, after which the controller may allow electrical current to flow from the battery to heater 112 via first heater wire 114 and second heater wire 116. Heater 112 generates heat through the electrical resistance of heater 112 that is transferred to interior wall 104 by conduction and radiation.

[0052] While the heater 112 is operating, the vacuum 108 within the vacuum insulator 102 inhibits heat leakage from the cavity 110. Thus, the cavity 110, heater 112, and vacuum insulator 102 form a highly efficient heating oven that can heat the tobacco in the consumable to a desired aerosol-generating temperature. The controller can be configured to direct the heater 112 to heat the tobacco to a temperature below the combustion temperature of the tobacco. It may take several seconds for the cavity 110 to reach the aerosol-generating temperature.

[0053] As the tobacco heats, an aerosol is produced within the cavity 110. A user can then inhale the aerosol by drawing air from the cavity 110 through a filter. This may draw air into the cavity 110 from the periphery of the opening 111 such that the user can continuously inhale the aerosol from the cavity 110.

[0054] At the same time, while the heater 112 is operating, heat reaches the seal 130 and wire 132 by radiation and conduction through the walls of the vacuum insulator 102. The wire 132 and seal 130 comprise Kovar and glass, respectively, which allow them to thermally expand at substantially the same rate as the temperature rise of the wire 132 and seal 130. This provides a secure and airtight mechanical bond even while the heater 112 is turned on and the heating device 100 is reaching its peak operating temperature.

[0055] In the embodiment of Figures 1 and 2, heat from the heater 112 that is transferred by conduction through the vacuum insulator 102 to the wire 132 and seal 130 must travel upwards towards the junction between the inner wall 104 and the outer wall 106 at the opening 111. The heat must then travel down the circumferential portion 106a before reaching the bottom portion 106b to heat the wire 132 and seal 130. Thus, in this embodiment, the bottom portion 106b substantially corresponds to the maximum "conduction path length" of heat from the heater 112 traveling through the vacuum insulator 102. While heat is traveling by conduction, some heat is transferred back to the inner wall 104 by radiation or is lost from the vacuum insulator 102. Thus, in terms of minimum conduction path length, less heat reaches areas further away from the heater 112. These additional areas generally correspond to the coldest areas of the vacuum insulator 102 during use. The coldest areas are generally determined by the particular shape of the vacuum insulator and the location of the heater.

[0056] Therefore, by positioning the wire 132 and seal 130 in the bottom portion 106b, the efficiency of the heating device 100 can be increased by minimizing the amount of heat lost from the cavity 110 by conduction through the walls of the vacuum insulator 102.

[0057] 3A-3C show perspective views of a portion of a heating device according to various embodiments of the present invention: FIG 3A shows a perspective view of the bottom portion 106b of the vacuum insulator 102 of FIGS.

[0058] 3B illustrates an alternative bottom portion 206b that may be used in place of bottom portion 106b in the heating device 100 as described above. Bottom portion 206b includes a plurality of wires 232, including two heater wires and two or more sensor wires. Each of wires 232 is disposed through a respective hole in bottom portion 206b and sealed by one of a plurality of seals 230. Bottom portion 206b may allow an additional number of sensors or other electronic components to be disposed within vacuum insulator 102.

[0059] Wire 232 and seal 230 may be configured similarly to any of the embodiments of wire 132 and seal 130 described above. In particular, wire 232 and seal 230 may comprise Kovar and glass, respectively, or may alternatively comprise other suitable conductors and insulators, as described above.

[0060] 3C shows an alternative bottom portion 306b that may be used in place of bottom portion 106b in the heating device 100 as described above. Bottom portion 306b includes a plurality of wires 332, including a central pair of heating wires with two individual heater wires for connection to either end of heater 112. Wires 332 also include four thinner wires provided for connection to two sensors provided within vacuum insulator 102. Bottom portion 306b includes a ring of stainless steel (or other suitable material) and an insulating sheet 330 including glass provided inside the ring to form a generally circular end of outer wall 106. Each of wires 332 is provided through a respective hole in insulating sheet 330 and is hermetically bonded to insulating sheet 330. Insulating sheet 330 thus circumferentially surrounds each of wires 332. Wires 332 are spaced apart to prevent shorting between any of wires 332. The insulating properties of the seal 330 prevent unwanted electrical connections between each of the wires 332 .

[0061] Otherwise, wire 332 and insulating sheet 330 may be configured similarly to the embodiments of wire 132 and seal 130 described above. In particular, wire 332 and insulating sheet 330 may comprise Kovar and glass, respectively, or may alternatively comprise other suitable conductors and insulators.

[0062] Returning to the embodiment of FIG. 3A, one further advantage of this arrangement relates to the full circumference of the joint between the bottom portion 106b and the seal 130. In this embodiment, each wire 132 and corresponding seal 130 is provided through a dedicated hole in the bottom portion 106b. The use of a dedicated hole for each wire 132 means that the holes can have a smaller diameter, thereby minimizing the full circumference of contact between the seal 130 and the bottom portion 106b. This contributes to a more reliable retention of the sealed vacuum 108, as the bottom portion 106b may not have thermal expansion characteristics that match those of the seal 130.

[0063] In contrast, for example, the embodiment of Figure 3C uses a single insulating sheet 330 and a bottom portion 306b that includes a ring with an inner hole sized to accommodate several wires 332. Thus, in Figure 3C, the circumference of the joint or interface between the insulating sheet 330 and the bottom portion 306b is equal to the inner circumference of the ring that makes up the bottom portion 306b. This arrangement may have a larger circumference of contact between the insulating sheet 330 and the bottom portion 306b compared to the arrangement of Figure 3A, and may be less effective at retaining the vacuum 108 compared to an embodiment similar to Figure 3A.

[0064] In the example of FIG. 3A having four wires 132, by using a dedicated hole for each wire 132, the circumference of the interface between the seal 130 and the bottom portion 106b can be significantly reduced by adjusting the size of each dedicated hole compared to a similar arrangement of four wires with an insulating sheet.

[0065] The size of each hole may be made as small as possible without interfering with the structure of the vacuum insulator 102, i.e., without making it unduly difficult to assemble the seal 130 and wire 132 while maintaining the vacuum 108. Thus, each hole is primarily sized to minimize, in other words, as much as practically possible, the perimeter of contact between the seal 130 and the bottom portion 106b.

[0066] These advantages apply equally to the arrangement of Figure 3B, which similarly uses a dedicated hole for each wire 232. Dedicated holes used in this manner may be positioned at other locations on the outer wall 106 as well.

Claims

1. 1. A heating apparatus for an aerosol generating device, comprising: a vacuum insulator having a major longitudinal axis and including an inner wall and an outer wall between which a vacuum is trapped; a cavity capable of receiving an aerosol forming substance, the cavity being positioned radially inward of the inner wall; a heater disposed within the vacuum insulator in thermal contact with the inner wall of the vacuum insulator, the heater configured to heat an aerosol-forming material received within the cavity by thermal conduction to generate an aerosol; one or more wires configured to connect the heater to a power source, the one or more wires extending through at least one hole in the outer wall of the vacuum insulator, the one or more wires being circumferentially surrounded by an insulator; Including, the insulation comprises glass, and the one or more wires are made from a material having thermal expansion characteristics that substantially match the thermal expansion characteristics of the insulation; heating device.

2. The heating device of claim 1 including a first wire extending through a first hole in the outer wall and a second wire extending through a second hole in the outer wall.

3. The heating device of claim 1 or 2, wherein the one or more wires comprise Kovar.

4. 4. The heating device of claim 1, further comprising a sensor positioned within the vacuum insulator and a sensor wire connected to the sensor and extending through a further hole in the vacuum insulator, the sensor wire being circumferentially surrounded by an insulator.

5. The heating device of claim 4 , wherein the additional holes extend through the outer wall of the vacuum insulator.

6. The heating device of claim 4 , wherein the further hole extends between the inner wall and the outer wall of the vacuum insulator.

7. The heating device according to claim 1 , wherein the heater is a resistive heater.

8. 8. The heating apparatus of claim 1, wherein the heater includes an exposed outer surface having a material susceptible to oxidation reactions in the presence of oxygen.

9. 9. The heating device of claim 1, wherein the inner wall has a thickness of about 0.1 mm or less.

10. The heating device of claim 1 , wherein the insulator comprises borosilicate glass.

11. 11. The heating device of claim 1, wherein the one or more wires each extend through a different respective hole in the outer wall, each hole including a corresponding insulation surrounding a corresponding wire.

12. 12. The heating device of claim 11, wherein each respective hole is sized primarily to accommodate the corresponding wire so as to minimize the amount of insulation contacting the exterior wall.

13. 13. An aerosol generating device configured to generate an aerosol for inhalation by a user, comprising a heating apparatus according to any one of claims 1 to 12.

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