AEROSOL-GENERATING DEVICE HAVING MULTI-LAYER INSULATION

Abstract

An aerosol-generating device is provided, including: an outer housing; a heater configured to heat an aerosol-forming substrate; and a plurality of layers of thermal insulation arranged around at least a part of the heater, the plurality of layers of thermal insulation including a first thermal insulation layer, a second thermal insulation layer, a radiation reflector layer being arranged between the first and the second thermal insulation layers, and a heat spreader layer including the outer housing of the aerosol-generating device. An aerosol-generating system is also provided, including the aerosol-generating device and an aerosol-generating article including an aerosol-generating substrate.

Claims

1.-23. (canceled)

24. An aerosol-generating device, comprising: an outer housing; a heater configured to heat an aerosol-forming substrate; and a plurality of layers of thermal insulation arranged around at least a part of the heater, wherein the plurality of layers of thermal insulation comprises: a first thermal insulation layer, a second thermal insulation layer, a radiation reflector layer being arranged between the first and the second thermal insulation layers, and a heat spreader layer comprising the outer housing of the aerosol-generating device.

25. The aerosol-generating device according to claim 24, wherein the heat spreader layer is formed from a material having a thermal conductivity of at least 200 W/m.Math.K.

26. The aerosol-generating device according to claim 24, wherein the heat spreader layer is anisotropic such that a thermal conductivity in directions substantially parallel to the heat spreader layer is higher compared to a thermal conductivity in a direction substantially perpendicular to the heat spreader layer.

27. The aerosol-generating device according to claim 24, wherein the heat spreader layer further comprises graphite.

28. The aerosol-generating device according to claim 24, wherein an overall thickness of the plurality of layers of thermal insulation within the aerosol-generating device is less than 2 mm.

29. The aerosol-generating device according to claim 24, further comprising a cavity configured to receive an aerosol-generating article.

30. The aerosol-generating device according to claim 29, wherein the cavity comprises the heater.

31. The aerosol-generating device according to claim 29, wherein the plurality of layers of thermal insulation are further arranged across a distal end of the cavity.

32. The aerosol-generating device according to claim 29, wherein the plurality of layers of thermal insulation surround substantially a whole of the cavity.

33. The aerosol-generating device according to claim 24, further comprising a power source and control circuitry configured to control a supply of power to the heater, wherein at least a portion of the plurality of layers of thermal insulation is arranged between the heater and the control circuitry.

34. The aerosol-generating device according to claim 24, wherein the heater is a tubular heater comprising an internal space arranged to receive an aerosol-generating article.

35. The aerosol-generating device according to claim 34, wherein the tubular heater further comprises a tubular substrate having a heating element disposed on or within the tubular substrate.

36. The aerosol-generating device according to claim 35, wherein the heating element is disposed on an external surface of the tubular substrate.

37. The aerosol-generating device according to claim 24, further comprising a barrier configured to separate one or more of the plurality of layers of thermal insulation from an airflow pathway for conveying aerosol to a user.

38. An aerosol-generating system, comprising: an aerosol-generating device according to claim 24; and an aerosol-generating article comprising an aerosol-forming substrate.

Description

[0099] Examples will now be further described with reference to the figures in which:

[0100] FIG. 1 is a schematic partial cross-section of part of an aerosol-generating device in accordance with one embodiment showing an electric heater and multi-layer insulation.

[0101] FIG. 2 is a schematic drawing of the interior of an aerosol-generating device in accordance with another embodiment showing an aerosol-generating article received within the device.

[0102] FIG. 3A is an enlarged cross-section of the area labelled A in FIG. 2 and shows a heater and multi-layer insulation arrangement in accordance with one embodiment.

[0103] FIG. 3B is an enlarged cross-section of the area labelled A in FIG. 2 and shows a heater and multi-layer insulation arrangement in accordance with another embodiment.

[0104] FIGS. 4A and 4B show two different test arrangements for testing the thermal insulation performance of an aerosol-generating device.

[0105] FIG. 1 shows part of an aerosol-generating device 10 having an electric heater 12 and a plurality of layers of thermal insulation 14 arranged between the electric heater 12 and a housing 16. The electric heater is tubular and has an internal space having a diameter D for receiving an aerosol-generating article (not shown) of similar diameter. The electric heater is therefore positioned externally to an aerosol-forming substrate within the aerosol-generating article. The tubular structure of the electric heater 12 is made from aluminium oxide ceramic and a heating element 18 made from Kanthal circumscribes its outer cylindrical surface in a serpentine or undulating fashion. The heating element 18 has two ends 18a and 18b arranged at one end of the electric heater 12 and connected to electrical leads (not shown) for connecting the electric heater 12 to a power source (not shown) via control circuitry (not shown). The electric heater 12 is configured to be heated to a temperature of approximately 210 degrees centigrade to heat an aerosol-forming substrate to generate an aerosol.

[0106] FIG. 1 shows a general structure for a plurality of layers of thermal insulation 14 in accordance with the present disclosure, which comprises a first thermal insulation layer 20, a radiation reflector 22, a second thermal insulation layer 24 and a heat spreader layer 26. At least one of the layers, for example, the radiation reflector 22, is optional and may be omitted in certain embodiments, as discussed below. Furthermore, the heat spreader layer 26 may be replaced by another component of the aerosol-generating device 10, for example, the outer housing 16, which is the case in one of the embodiments discussed below.

[0107] The first thermal insulation layer 20 has a high operating temperature (that is, around 250 degrees centigrade or more) so that it is capable of withstanding the operating temperature of the heater 12. In addition to being a thermal insulator, the first thermal insulation layer 20 is also an electrical insulator to avoid short circuiting the connections of any electrical components it may come into contact with. A thin film insulator such as Kapton tape may be used. Alternatively, thicker foam or aerogel insulators may be used.

[0108] The radiation reflector 22 is arranged adjacent to, and outward of, the first thermal insulation layer 20, although it may be located differently. The radiation reflector 22 is generally formed from a thin metallic foil or a metallised material having a reflective surface facing the heater 12. It is important that the radiation reflector 22 is spaced apart from the heater 12, for example, by air or a layer of thermal insulation, so that there is space into which thermal radiation can be reflected. Furthermore, if the radiation reflector 22 were located in contact with the heater, heat would be transfer by conduction through the radiation reflector 22 reducing its effectiveness and risking the reflective surface of the radiation reflector 22 becoming tarnished or otherwise degraded by the heater 12.

[0109] The second thermal insulation layer 24 is arranged adjacent to, and outward of, the radiation reflector 22, although it may be located differently. The second thermal insulation layer 20 has a high operating temperature (that is, around 200 degrees centigrade or more). The operating temperature of the second thermal insulation layer 24 does not need to be as high as the first thermal insulation layer 20 because it is located further away from the heater 12 and is at least partially protected by the first thermal insulation layer 20. A thin film insulator such as an aerogel film may be used or, alternatively, thicker foam or aerogel insulators may be used.

[0110] The heat spreader layer 26 is arranged adjacent to, and outward of, the second thermal insulation layer 24, although it may be located differently. The heat spreader layer 26 is typically made from a sheet of material or foil having high thermal conductivity (that is, at least 200 W/m.Math.K). However, in preferred embodiments, an anisotropic heat spreader layer 26 is used such as a pyrolytic graphite sheet. This has relatively high thermal conductivity (that is, greater than 700 W/m.Math.K) in directions parallel to the plane of the sheet (that is, in the x-y directions) and relatively low thermal conductivity (that is, less than 30 W/m.Math.K) in directions perpendicular to the sheet (that is, the z direction). Consequently, the heat spreader layer 26 spreads or distributes heat effectively within the layer, that is, in directions parallel to the heat spreader layer 26, but reduces heat transfer through the thickness of the layer, that is, in directions perpendicular to the heat spreader layer 26. By spreading out the heat, the heat spreader layer 26 helps to reduce the risk of hotspots forming on the outer surface of the housing 16. By reducing heat transfer through the thickness of the layer, the heat spreader layer 26 effectively helps to insulate the housing from the heat generated by the heater 12.

[0111] The housing 16 is arranged adjacent to, and outward of, the heat spreader layer 26. The plurality of layers of thermal insulation 14 helps to reduce the transfer of heat from the heater 12 to the outer housing 16, thereby reducing the likelihood of the outer housing, or a portion of it, becoming too hot (that is, exceeding a temperature of 50 degrees centigrade) and maintaining the housing 16 a temperature which is not uncomfortable for a user to hold. In this example, the housing 16 is made from a polyether ether ketone (PEEK), which itself is a reasonable thermal insulator. However, the housing 16 could be made from a material having a higher thermal conductivity so that the outer housing 16 also acts as a heat spreader.

[0112] FIG. 2 shows the interior of an aerosol-generating device 100 and an aerosol-generating article 200 received within the aerosol-generating device 100. Together, the aerosol-generating device 100 and aerosol-generating article 200 form an aerosol-generating system. In FIG. 2, the aerosol-generating device 100 is shown in a simplified manner. In particular, the elements of the aerosol-generating device 100 are not drawn to scale. Furthermore, elements that are not relevant for the understanding of this embodiment have been omitted.

[0113] The aerosol-generating device 100 comprises a housing 102 containing a power source 103, an electric heater 106, control circuitry 105 and a plurality of layers of thermal insulation 108. The power source 103 is a battery and, in this example, it is a rechargeable lithium ion battery. The control circuitry 105 is connected to both the power source 103 and the heater 106 and controls the supply of electrical energy from the power source 103 to the electric heater 106 to regulate the temperature of the electric heater 106.

[0114] The housing has an opening 104 at a proximal or mouth end of the aerosol-generating device 100 through which an aerosol-generating article 200 is received. The aerosol-generating device 100 and plurality of layers of thermal insulation 108, are shown in cross-section in FIG. 2. The plurality of layers of thermal insulation 108 surrounds the heater 106 and a cavity 110 within the housing 102 in which the aerosol-generating article 200 is received. In particular, the plurality of layers of thermal insulation 108 both circumscribe the heater 106 and cavity 110 to reduce heat transfer to the housing 102 and are arranged across a distal end of the cavity 110 to reduce heat transfer to the control circuitry 105. The plurality of layers of thermal insulation 108 can have various different arrangements of thermal insulation layers, two of which are described below with reference to FIGS. 3A and 3B.

[0115] The heater 106 is tubular and has the same design as the heater in FIG. 1. The aerosol-generating article 200 passes through the internal space in the tubular heater 106 when the aerosol-generating article 200 is received within the aerosol-generating device 100.

[0116] The aerosol-generating article 200 comprises an end plug 202, an aerosol-forming substrate 204, a hollow tube 206, a mouthpiece filter 208 and a paper wrapper 210. The aerosol-forming substrate 204 comprises a plug of tobacco or tobacco-based material. When the aerosol-generating article 200 is fully received within the aerosol-generating device 100, the aerosol-forming substrate 204 is located within the heater 106 such that the heater 106 can heat the aerosol-forming substrate 204 to form an aerosol. The end plug 202 and mouthpiece filter 208 are formed from cellulose acetate fibres.

[0117] The aerosol-generating device 100 may further comprise: a sensor (not shown) for detecting the presence of the aerosol-generating article 200; a user interface (not shown) such as a button for activating the heater 106; and a display or indicator (not shown) for presenting information to a user, for example, remaining battery power, heating status and error messages.

[0118] FIGS. 3A and 3B are enlarged schematic views of the area labelled A in FIG. 2 and shows a cross-section through a part of the aerosol-generating device 100 comprising the heater 106, the plurality of layers of thermal insulation 108 and the housing 102. FIGS. 3A and 3B have been simplified and elements of the aerosol-generating device 100 are not drawn to scale.

[0119] Furthermore, a number of the thermal insulation layers in the plurality of layers of thermal insulation 108 are compressible because they are formed from foams or aerogels or another compressible structure. This is beneficial because it allows the plurality of layers of thermal insulation 108 to conform to changes in profile within the aerosol-generating device 100. As can be seen in FIG. 2, the internal profile along the aerosol-generating device changes, for example, at the points where the aerosol-generating article 200 passes into and out of the electric heater 106 and where the house tapers towards its mouth end. At points where the profile narrows, any compressible materials in the plurality of layers of thermal insulation 108 will be compressed. However, the inventors have found that the amount of compression involved does not adversely affect the thermal performance of the insulation layers to any appreciable extent. In the following discussion, any reference to a thickness of a material is to its uncompressed thickness.

[0120] FIG. 3A shows a first arrangement 108a of the plurality of layers of thermal insulation for use in the aerosol-generating device 100 of FIG. 2. The first arrangement 108a of the plurality of layers of thermal insulation comprises a first thermal insulation layer 120, a heat spreader layer 122 and a second thermal insulation layer 124.

[0121] The first thermal insulation layer 120 comprises a polyimide aerogel sleeve having a thickness of 2.5 mm. A suitable polyimde aerogel sleeve includes, but is not limited to, a sleeve made from Airloy X116 polyimide aerogel manufactured by Aerogel Technologies of Boston, MA, USA.

[0122] The heat spreader layer 122 comprises a pyrolytic graphite sheet having a thickness of 25 microns. A suitable pyrolytic graphite sheet includes, but is not limited to, part number EYGA121803KV supplied by Panasonic of Newark, NJ, USA.

[0123] The second thermal insulation layer 124 comprises a polymer aerogel having a thickness of 1 mm. A suitable polymer aerogel includes, but is not limited to, Aerozero polymer film or block supplied by Blueshift Materials of Spencer, MA, USA.

[0124] FIG. 3B shows a second arrangement 108b of the plurality of layers of thermal insulation for use in the aerosol-generating device 100 of FIG. 2. The second arrangement 108b of the plurality of layers of thermal insulation comprises a first thermal insulation layer 130, a radiation reflector 132, a second thermal insulation layer 134 and the housing 102 forms a heat spreader layer.

[0125] The first thermal insulation layer 130 comprises a polyimide film having a thickness of 25 microns. A suitable polyimide film includes, but is not limited to, Kapton tape supplied by DuPont of Wilmington, DE, USA.

[0126] The radiation reflector 132 comprises an aluminium foil having a thickness of 0.016 mm. Any suitable aluminium foil of the required thickness may be used.

[0127] The second thermal insulation layer 134 comprises a polyimide foam having a thickness of 2.5 mm. A suitable polyimide foam includes, but is not limited to, Intek PFI-1120 polyimide foam supplied by Trelleborg of Trelleborg, Sweden.

[0128] To form a heat spreader layer, the polymer-based housing 102 of the aerosol-generating device of FIG. 2 is replaced with a tubular aluminium housing having an inside diameter of 17 mm and an outside diameter 18.5 mm. Aluminium has a higher thermal conductivity than plastic and helps to spread heat across the area of the housing. Any suitable aluminium housing may be used.

TESTING

[0129] To determine the thermal performance of using a plurality of layers of thermal insulation compared to just using a single layer, test examples of each of the arrangements of FIGS. 3A and 3B were prepared and were tested in the aerosol-generating device 100 of FIG. 2. As a control, further test examples comprising just a single layer of insulation were prepared and also tested in the aerosol-generating device 100 of FIG. 2.

[0130] To measure temperature, thermocouples were used and attached to relevant test points on the aerosol-generating device 100 as described below with respect to each test. The heater 106 was powered by an external laboratory power supply. The aerosol-generating device was held horizontal and stationary and was tested at an ambient temperature of approximately 23 to 25 degrees centigrade.

[0131] As can be seen in FIGS. 4A and 4B, an empty paper tube 300 without an aerosol-forming substrate or filters or plugs was used in the test in place of the aerosol-generating article 200 of FIG. 2. This is because some heat is dissipated in the aerosol generated by the aerosol-forming substrate 204 and to simulate a worst case scenario an empty paper tube 300 was used so that all heat was dissipated to the device 100.

[0132] The aerosol-generating device 100 and aerosol-generating article 200 had the dimensions shown in Table 1.

TABLE-US-00001 TABLE 1 Housing internal diameter 12.1 mm External diameter of heater 8.6 mm External diameter of aerosol- 7.0 mm generating article Available space between heater 1.75 mm and internal surface of housing Axial distance between distal 5.0 mm end of aerosol-generating article and control circuitry

[0133] The following test method was used: [0134] Heat the heater as quickly as possible to 210 degrees centigrade without exceeding a power limit of 12 Watts. [0135] Control the temperature of the heater to maintain it at 210 degrees centigrade for 6 minutes. [0136] Record the power and temperature at 6 minutes.

Test Example 1

[0137] Test Example 1 had the structure of the first arrangement 108a of the plurality of layers of thermal insulation shown in FIG. 3A. The plurality of layers of thermal insulation 108a circumferentially surrounded the heater 106 and the cavity 110 containing the paper tube 300. At a distal end of the cavity 110 in the gap between the paper tube and control circuitry 105, a single layer of polyimide aerogel identical to the first thermal insulation layer 120 in FIG. 3A was arranged.

[0138] As a control, a further test example was prepared having a single layer of thermal insulation equivalent to the first thermal insulation layer 120 in FIG. 3A, that is, a sleeve made from Airloy X116 polyimide aerogel manufactured by Aerogel Technologies of Boston, MA, USA and having a thickness of 2.5 mm.

[0139] As can be seen in FIG. 4A, thermocouples were attached at the following points: [0140] Point X1, on the outside of the paper tube at the point where it is located inside the heater 106. [0141] Point X2, on the outside of the housing 102 at the point overlying the mid-point of the heater 106. [0142] Point X3, on the outside of the housing 102 at a point to the left (towards a proximal end of the device) of point X2. [0143] Point X4, on the outside of the housing 102 at a point to the right (towards a distal end of the device) of point X2. [0144] Point X5, at the point where the electrical leads from the heater 106 are connected to the control circuitry 105.

[0145] Measurements X3 and X4 were made to assess the performance of the pyrolytic graphite sheet heat spreader and its ability to spread heat to reduce hotspots.

[0146] The results of the test on Test Example 1 are shown in Table 2 below.

TABLE-US-00002 TABLE 2 Test Measurement Units Control Example 1 Power @ 210 C., 6 mins. W 1.56 1.33 Temp. X1 (paper tube) C. 210.8 210.0 Temp. X3 (housing left) C. 88.4 47.9 Temp. X2 (housing middle) C. 89.1 47.4 Temp. X4 (housing right) C. 77.3 46.9 Temp. X5 (control circuitry) C. 49.8 44.0 Ambient temperature C. 23.0 23.0

[0147] The results show that the multi-layer insulation of Test Example 1 has improved thermal insulation performance compared to the single layer insulation of the control. As can be seen from temperature measurements X2, X3 and X4 the temperature on the outside of the housing is considerably lower for Test Example 1 than it is for the control. Each of these temperatures for Test Example 1 is below 50 degrees centigrade, the comfortable threshold temperature. There is also less deviation between temperature measurements X2, X3 and X4 for Test Example 1 compared to the control showing that the heat spreader layer is effective at spreading out the heat over its area to reduce the formation of hotspots.

[0148] Furthermore, the power required to hold the heater at 210 degrees centigrade in Test Example 1 is lower compared to the control showing that multi-layer helps to improve the efficiency of the system. In addition, the temperature X5 in Test Example 1 is lower showing that the arrangement helps to protect the control circuitry from heat generated by the heater 106.

Test Example 2

[0149] Test Example 2 had the structure of the first arrangement 108b of the plurality of layers of thermal insulation shown in FIG. 3B. The plurality of layers of thermal insulation 108b circumferentially surrounded the heater 106 and the cavity 110 containing the paper tube 300. As discussed above with respect to FIG. 3B, the polymer-based housing 102 of the aerosol-generating device of FIG. 2 is replaced with an aluminium housing to provide a heat spreader layer.

[0150] As a control, a further test example was prepared having a single layer of thermal insulation equivalent to the second thermal insulation layer 134 in FIG. 3B, that is, a sleeve made from Intek PFI-1120 polyimide foam supplied by Trelleborg of Trelleborg, Sweden and having a thickness of 2.5 mm. The control was used with the standard polymer-based housing 102 of the aerosol-generating device of FIG. 2.

[0151] As can be seen in FIG. 4B, thermocouples were attached at the following points: [0152] Point Y1, on the outside of the paper tube at the point where it is located inside the heater 106. [0153] Point Y2, on the outside of the housing 102 at the point overlying the mid-point of the heater 106. [0154] Point Y3, at the point where the electrical leads from the heater 106 are connected to the control circuitry 105.

[0155] The results of the test on Test Example 2 are shown in Table 3 below.

TABLE-US-00003 TABLE 3 Test Measurement Units Control Example 2 Power @ 210 C., 6 mins. W 1.45 1.80 Temp. Y1 (paper tube) C. 211 210 Temp. Y2 (housing) C. 89 39 Temp. Y3 (control circuitry) C. 48 53 Ambient temperature C. 23 25

[0156] The results show that the multi-layer insulation of Test Example 2 has improved thermal insulation performance compared to the single layer insulation of the control. As can be seen from temperature measurement Y2, the temperature on the outside of the housing is considerably lower for Test Example 2 than it is for the control. Temperature measurement Y2 for Test Example 2 is well below 50 degrees centigrade, the comfortable threshold temperature. Temperature measurement Y2 also shows that the use of a housing material with high thermal conductivity (that is, greater than 200 W/m.Math.K) can provide effective heat spreading.

Test Example 3

[0157] A third test example was also prepared. Test Example 3 had the same structure for the plurality of layers of thermal insulation as Test Example 1, that is, the first arrangement 108a of the plurality of layers of thermal insulation of FIG. 3A. However, in Test Example 3, the polymer-based housing 102 of the aerosol-generating device of FIG. 2 is replaced with a copper tubular housing having a diameter of 15 mm to provide an additional heat spreader layer to the pyrolytic graphite sheet heat spreader layer 122 of FIG. 3A. The thermocouple arrangement of FIG. 4B was used to measure temperature.

[0158] The results of the test on Test Example 3 are shown in Table 4 below.

TABLE-US-00004 TABLE 4 Measurement Units Test Example 3 Power @ 210 C., 6 mins. W 1.40 Temp. Y1 (paper tube) C. 210 Temp. Y2 (housing) C. 40 Temp. Y3 (control circuitry) C. 47 Ambient temperature C. 23

[0159] As can be seen from Table 4, the temperature on the outside of the housing (temperature measurement Y2) in Test Example 3 is 7 degrees centigrade lower than the equivalent temperature (temperature measurement X2) in Test Example 1. This therefore shows that the use of a housing material with high thermal conductivity (that is, greater than 200 W/m.Math.K) can further improve the heat spreading performance of the aerosol-generating device.