Induction heating assembly for steam generating equipment

Abstract

To provide an induction heating assembly for a vapor generating device.SOLUTION: An induction heating assembly 10 for a vapor generating device 1 includes: an outer body; an induction coil 16 arranged inward of the outer body; and a heating compartment defined inward of the induction coil and arranged to receive, in use, an object comprising a vaporizable substance 22 and an induction-heatable susceptor 24, where the separation between the outer body and the induction coil defines an air vent 14 arranged to allow air to flow around the induction coil and to the heating compartment.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an induction heating assembly for a steam generating device. [Background technology]

[0002] Devices that heat, rather than burn, a substance to produce a vapor for inhalation have become popular among consumers in recent years.

[0003] Such devices may use one of a number of different approaches to provide heat to the substance. One such approach is to simply provide a heating element where electrical power is provided to heat the heating element, which in turn heats the substance to generate steam.

[0004] One way to achieve such steam generation is to provide a steam-generating device that uses induction heating techniques. In such devices, an induction coil (hereinafter also referred to as the inductor and the induction heating device) comprises the device, and a susceptor comprises the steam-generating material. When a user activates the device, electrical energy is applied to the inductor, which in turn generates an electromagnetic (EM) field. The susceptor couples with the EM field to generate heat, which is transferred to the material, heating it and producing steam.

[0005] Using induction heating to generate steam may provide controlled heating and therefore controlled steam generation. However, in practice, such an approach can unwittingly create inappropriate temperatures within the steam generating device. This wastes power, makes its operation expensive, and risks damaging components or wasting the steam generating device, which can inconvenience users who expect a simple and reliable device.

[0006] This has previously been addressed by monitoring the temperature of the device, however, some monitored temperatures have proven unreliable, and providing temperature monitoring adds to the component count and uses additional power even when overall power usage is more efficient due to temperature monitoring. Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention seeks to alleviate at least some of the problems mentioned above. [Means for solving the problem]

[0008] According to a first aspect, there is provided an induction heating assembly for a steam generating apparatus, the heating assembly including: an outer body; an induction coil arranged inside the outer body; and a heating chamber defined inside the induction coil and arranged to accommodate, in use, an object comprising a vaporizable substance and an inductively heatable susceptor, wherein a separation between the outer body and the induction coil defines an air hole arranged to allow air to flow around the induction coil and into the heating chamber.

[0009] The susceptor may include, but is not limited to, one or more of aluminum, iron, nickel, stainless steel, and alloys thereof, such as nickel-chromium. By applying an electromagnetic field to its vicinity, the susceptor may generate heat due to eddy currents and magnetic hysteresis losses, resulting in the conversion of energy from electromagnetic energy to thermal energy.

[0010] The applicants have discovered that by allowing air to flow around the induction coil to the longitudinal ends of the heating chamber, heat can be transferred to the air before it enters the heating chamber. This cools the induction coil, allowing it to function more efficiently and stabilize its operation, and also reduces the amount of heat that needs to be applied directly to the vaporizable substance because the air passing into the heating chamber also heats the vaporizable substance (or at least reduces the cooling effect it has). This reduces the amount of energy required to heat the vaporizable substance. A further benefit is that heat transfer to the outer body is limited, thereby preventing the outer body, and therefore the outer surface, from becoming hot. These benefits are achieved without the need to increase the distance between the induction coil and the inductively heatable susceptor when an object is placed in the heating chamber. This means that energy transfer from the induction coil to the susceptor is not reduced, allowing energy transfer, and therefore heat generation, to be as efficient as possible.

[0011] The induction coil may be a cylindrical induction coil. In such a case, the induction coil may be disposed radially inside the outer body, the heating chamber may be defined radially inside the induction coil, and the separation between the outer body and the induction coil defining the air hole may be a radial separation. As an alternative to a cylindrical induction coil, the induction coil may be a spiral planar induction coil.

[0012] The air vents can be shaped to direct the air flow around the induction coil before directing it into the heating chamber. This not only insulates the outer body by separating the induction coil from the outer body with air in the air vents, but also heats the air before it passes into the heating chamber, reducing the amount of heat that needs to be added to the heating chamber. This not only reduces power usage, but also protects the user from heat exposure.

[0013] The heating chamber may be adjacent to the induction coil. The induction coil may be embedded in a wall of the heating chamber, but since there are no other elements between the wall in which the induction coil is embedded and the chamber of the heating chamber, and since the wall defines, in part, the heating chamber, applicants consider this to be included within the meaning of the term "adjacent."

[0014] As described above, the object includes a vaporizable substance and an inductively heatable susceptor. The vaporizable substance and the inductively heatable susceptor can be contained by the object. In this configuration, heat generated by induction occurs only within the object. As such, heat generated within the heating chamber is not generated outside the object when the object is placed within the heating chamber. In other words, the heating chamber can be configured to only cause heating within the object when the object is present within the heating chamber. This is because heat generated by the inductively heatable susceptor when current is passed through the induction coil occurs only within the object in such a configuration.

[0015] Heat may be generated outside the heating chamber. Typically, heat generated outside the heating chamber is generated by an induction coil. This heat may additionally heat any vaporizable material within the heating chamber.

[0016] The air holes can be positioned to allow air to flow around the induction coil and to any part of the heating chamber, but typically the air holes are positioned to allow air to flow around the induction coil and to the axial end of the heating chamber, which prevents the air holes from interfering in any way with the induction coil and allows the maximum amount of heat to be transferred to the air within the air holes, since its path to the axial end of the heating chamber is longer than if the air holes passed through to any other part of the heating chamber.

[0017] In the first embodiment, when the object is positioned in the heating chamber, the object may abut against the side of the heating chamber, and preferably, the heating chamber only has an airflow path that passes through the object when the object is positioned in the heating chamber. In this case, there may be no airflow path between the induction coil and the object, from the inlet to the heating chamber to the outlet of the heating chamber. This limits the airflow around the object between the object and the side of the heating chamber. This allows the susceptor to be placed as close as possible to the induction coil and increases the airflow through the object instead of around it.

[0018] The air vents may be formed in any suitable manner. Typically, the induction heating assembly further includes one or more separators disposed between the outer body and the induction coil to define two or more layers of air vents, thereby allowing for more efficient heat transfer from the induction coil to the air and therefore limiting the transfer of heat to the outer body because the multiple layers provide a greater surface area for the volume of air for heat transfer.

[0019] Alternatively or additionally, the induction heating assembly may further include ribs that mechanically support the outer body, induction coil, and optionally the separator, and divide the air holes into multiple segments. By this, applicants mean that there may be ribs that provide a mechanical connection between the outer body, induction coil, and, if present, separator, and that support these components and divide the air holes into multiple segments. This provides suitable structural support for the various components while allowing air to pass over a large surface area, thereby increasing heat transfer effectiveness. When the induction coil is a cylindrical induction coil, the segments may be annular segments.

[0020] Having multiple layers of air holes provides several options for how air passes through the air holes from the air hole inlet to the heating chamber. Generally, the multiple layers of air holes are arranged to provide an air flow path through the multiple air hole layers, passing from one air hole layer to another. This allows the air flow path to be longer by passing through multiple layers, increasing the length over which heat can be transferred to the air passing through the air holes. This also allows for more efficient heat transfer, as the air in one layer is warmed by the air in the inner layer. In this arrangement, the air path can preferably pass along the length of the heating chamber in one layer and in the opposite direction along the length of the heating chamber in the next layer.

[0021] In an alternative arrangement of air holes, the layers of air holes may be arranged to provide an air flow path through at least two air hole layers by separating each air hole layer. This is also a means of providing more efficient heat transfer by allowing the air in multiple layers to be heated simultaneously. Of course, the multiple layers, i.e., layers with separated air flow paths between them, may be radially adjacent (i.e., concentric) layers.

[0022] Generally, the induction heating assembly may further include structure within the air vent arranged to define one or more air flow passages, which increases the surface area through which the air must pass to transfer heat.

[0023] The air flow may follow any suitable path. Generally, one or more air passages are arranged in one or more of the following patterns: a spiral around the induction coil; a zigzag along the length of the coil; and a zigzag across the coil. This maximizes the length of each air passage, allowing for more efficient heat transfer from the induction coil because the air spends a longer time passing along each air passage, allowing more heat to be absorbed. When the induction coil is a cylindrical induction coil, the spiral may be a spiral that rotates around the induction coil, the zigzag along the length of the coil may be axial, and the zigzag across the coil may be circumferential.

[0024] The air passage(s) may cover any amount of the induction coil to allow heat transfer from the induction coil. Generally, the air passage(s) may cover more than 50%, preferably 50-90%, and more preferably 50-80% of the outer surface of the induction coil. Applicants have found that this provides a suitable amount of surface area that allows heat transfer to occur while maintaining structural rigidity and not overly complicating manufacture.

[0025] The induction heating assembly may further include an electromagnetic shield, the shield being positioned: between the coil and the innermost air hole; between the concentric air holes; substantially surrounding the periphery of the outermost air hole; or as part of the wall of the air hole. The EM shield limits the amount of EM radiation emitted from the assembly. By providing the EM shield adjacent to the air hole, as in this case (whether still surrounded or not), heat can also be transferred from the EM shield to the air, warming the EM shield to a temperature above that of the air within the air hole.

[0026] The induction coil can be placed in any suitable location, and typically is located within the wall that houses the heating chamber, thereby protecting the induction coil from environmental factors in the air and from components within the object.

[0027] The assembly may be configured to operate in a varying electromagnetic field, during use, having a magnetic flux density of about 0.5 Tesla (T) to about 2.0 T at the highest concentration point.

[0028] The power supply and circuitry may be configured to operate at high frequencies, preferably between about 80 kHz and 500 kHz, preferably between about 150 kHz and 250 kHz, and more preferably about 200 kHz.

[0029] The induction coil may comprise any suitable material, but typically the induction coil may comprise Litz wire or Litz cable.

[0030] The susceptor can be shaped to provide holes that allow air to pass through during use. This can be achieved by providing a susceptor in the shape of a tube, i.e., by providing a tubular susceptor. This is beneficial because the susceptor generates heat and allows for efficient preheating of the air entering the object / cartridge as the air passes through the tube. Tubular susceptors have also been found to generate heat better than susceptors of other shapes, and as such, have a closed-circuit electrical path. The susceptor also provides an electromagnetic shield for the user due to its shape and the way it interacts with electromagnetic influences. Accordingly, although the susceptor can be used solely to generate heat, there are generally induction-heatable susceptors that have a tubular shape that forms at least a portion of the air holes. Of course, this susceptor can be a separate susceptor in addition to the susceptor that constitutes the object.

[0031] According to a second aspect, there is provided a steam generation system comprising an induction heating assembly according to the first aspect; an object comprising a vaporizable substance and an inductively heatable susceptor; wherein, in use, the object is located within the heating chamber of the assembly.

[0032] The vaporizable material may be any suitable material capable of producing vapor. The material may include plant-derived materials, and in particular, the material may include tobacco. Typically, the vaporizable material is a solid or semi-solid tobacco material, which allows repeated and consistent application of heat to hold the susceptor in place within the object. Exemplary types of vapor-generating solid materials include powders, granules, pellets, tobacco shreds, strands, porous materials, or sheets.

[0033] Preferably, the vaporizable substance may comprise an aerosol former. Examples of aerosol formers include polyhydric alcohols and mixtures thereof, such as glycerin or propylene glycol. Generally, the vaporizable substance may comprise an aerosol former content of about 5% to about 50% on a dry weight basis. Preferably, the vaporizable substance may comprise an aerosol former content of about 15% on a dry weight basis.

[0034] The vaporizable substance may also be the aerosol former itself. In this case, the vaporizable substance may be a liquid. In this case, the object may have a liquid retaining substance (e.g., fiber bundle, porous material such as ceramic, etc.) that retains the liquid to be vaporized by a vaporizer such as a heater, and vapor is produced from the liquid retaining substance and released / radiated toward the air outlet so that it can be inhaled by the user.

[0035] Upon heating, the vaporizable material may release volatile compounds, which may include nicotine or flavor compounds, such as tobacco flavorings.

[0036] The object may be a capsule containing a vaporizable substance within a breathable shell during use. The breathable material may be a material that is electrically insulating and non-magnetic. The material has high breathability, allowing air to flow through the material that is resistant to high temperatures. Examples of suitable breathable materials include cellulose fibers, paper, cotton, and silk. The breathable material may also function as a filter. Alternatively, the object may be a vaporizable substance wrapped in paper. Alternatively, the object may be a vaporizable substance held within a material that is not breathable but includes suitable perforations or openings to allow air flow. Alternatively, the object may be the vaporizable substance itself. The object may be formed into a substantially stick shape.

[0037] The susceptor may be located in any suitable location and in any suitable manner within the body. Generally, the susceptor(s) are held within and surrounded by a vaporizable material such that the vaporizable material forms a heat-absorbing layer between the susceptor(s) and the outer surface of the assembly during use. This not only effectively heats the vaporizable material, but also limits the amount of heat transferred to other components of the steam generation system.

[0038] Examples of induction heating assemblies are described in detail below with reference to the accompanying drawings. [Brief explanation of the drawings]

[0039] [Figure 1] 1 shows a schematic diagram of an exemplary steam generation device. [Figure 2] 1 illustrates an exploded view of an exemplary steam generating device. [Figure 3] 3 shows a cross section of the steam generating device shown in FIG. 2 taken along plane AA of FIG. 2. [Figure 4] 4 illustrates a cross section of an alternative exemplary steam generating device taken along the same plane as that shown in FIG. 3. [Figure 5] 4 shows a cross section of a further exemplary steam generating device taken along the same plane as shown in FIG. 3; [Figure 6] 4 illustrates a cross section of another exemplary steam generating device taken along the same plane as shown in FIG. 3. [Figure 7] 7 shows a partial schematic diagram of an example corresponding to the example of FIG. 6. [Figure 8] 7 shows a partial schematic diagram of an alternative example corresponding to the example of FIG. 6. [Figure 9] 1 shows a schematic diagram of a portion of an exemplary steam generating device including an exemplary air flow path. [Figure 10] 1 shows a schematic diagram of a portion of an exemplary steam generating apparatus with an alternative exemplary air flow path. DETAILED DESCRIPTION OF THE INVENTION

[0040] Applicants now describe an example steam generating device, including a description of an example induction heating assembly and an example inductively heatable cartridge. An example method for monitoring the temperature within the steam generating device is also described.

[0041] 1 and 2, an exemplary steam generating apparatus is shown generally at 1 in an assembled configuration in FIG. 1 and in an unassembled configuration in FIG.

[0042] The exemplary vapor generating device 1 is a handheld device (by which applicants mean a device that a user can hold and support in one hand unaided) that includes an induction heating assembly 10, an inductively heatable cartridge 20, and a mouthpiece 30. Vapor is emitted by the cartridge when the cartridge is heated. In response, vapor is generated by using the induction heating assembly to heat the inductively heatable cartridge. Vapor can then be inhaled by the user through the mouthpiece.

[0043] In this example, the user inhales vapor by drawing air into the device 1, through or around the inductively heatable cartridge 20, and out the mouthpiece 30 as the cartridge heats up. This is achieved by the cartridge being located within a heating chamber 12 defined by a portion of the induction heating assembly 10, the heating chamber being in gas communication with an air inlet 14 formed within the assembly and an air outlet 32 formed in the mouthpiece when the device is assembled. This allows air to be drawn through the device by the application of negative pressure, typically created by a user inhaling air through the air outlet.

[0044] Cartridge 20 is an object that includes a vaporizable substance 22 and an inductively heatable susceptor 24. In this example, the vaporizable substance includes one or more of tobacco, humectant, glycerin, and propylene glycol. The susceptor is a plurality of electrically conductive plates. In this example, the cartridge also includes a layer or membrane 26 that contains the vaporizable substance and the susceptor, and the layer or membrane is breathable. In other examples, the membrane is not present.

[0045] As mentioned above, induction heating assembly 10 is used to heat cartridge 20. The assembly includes an induction heater in the form of induction coil 16 and a power supply 18. The power supply and induction coil are electrically connected so that power can be selectively transferred between the two components.

[0046] In this example, the induction coil 16 is substantially cylindrical, so that the induction heating assembly 10 is also substantially cylindrical in shape. The heating chamber 12 is defined radially inward of the induction coil and has a base at the axial end of the induction coil and a sidewall around the radially inner periphery of the induction coil. The heating chamber is open at the axial end of the induction coil opposite the base. When the steam generator 1 is assembled, the opening is covered by the mouthpiece 30, and the opening to the air outlet 32 is located at the opening of the heating chamber. In the example shown in the drawings, the air inlet 14 is provided at the base of the heating chamber, opening into the heating chamber.

[0047] As mentioned above, the cartridge 20 is heated to produce vapor. This is accomplished by supplying AC current, converted from DC current, to the induction coil 16 by the power supply 18. This AC current flows through the induction coil and generates a controlled EM field in the area near the coil. The generated EM field provides power to an external susceptor (in this case, the cartridge's susceptor plate), which absorbs the EM energy and converts it to heat, thereby achieving induction heating.

[0048] More specifically, power provided to the induction coil 16 causes a current to flow through the induction coil, generating an EM field. As noted above, the current provided to the induction coil is an alternating current (AC) current. This generates heat within the cartridge because, when the cartridge is positioned within the heating chamber 12, the susceptor plates are intentionally positioned (substantially) parallel to the radius of the induction coil 16, or at least have a certain length parallel to the radius of the induction coil, as shown in the drawings. Accordingly, when AC current is provided to the induction coil while the cartridge is positioned within the heating chamber, the susceptor plates are positioned such that the EM field generated by the induction coil couples to each susceptor plate, thereby inducing eddy currents within each plate. This generates heat in each plate by induction.

[0049] The plates of cartridge 20 are in thermal communication with vaporizable material 22, in this example by direct or indirect contact between each susceptor plate and the vaporizable material. This means that when susceptor 24 is inductively heated by induction coil 16 of induction heating assembly 10, heat is transferred from susceptor 24 to vaporizable material 22, heating vaporizable material 22 and producing a vapor.

[0050] The induction coil 16 is embedded in the wall 28, which limits contact between the induction coil and the environment surrounding the induction coil. During use, heat passes from the heating chamber 12 to the wall in which the induction coil is embedded and which provides the sidewall of the heating chamber. The induction coil also generates a small amount of heat due to the resistance of the coil.

[0051] To utilize this heat and to transfer heat away from the induction coil to cool it, as described above, the air inlet 14, connected to the base of the heating chamber, passes from an opening at one end of the induction coil adjacent where the mouthpiece 30 and induction heating assembly 10 contact, over the wall in which the induction coil is embedded, to the opposite end of the induction coil, across this end, and to an opening in the base of the heating chamber. When a user inhales air through the air outlet 32 in the mouthpiece, air is drawn through the air inlet into the heating chamber (as shown by arrow 48 in FIG. 1), through the cartridge (if there should be one), and through the air outlet (as shown by arrow 50 in FIG. 1).

[0052] When the air in the air inlet 14 is cooler than the wall 28 in which the induction coil 16 is embedded, heat is transferred from the wall (and therefore from the induction coil) to the air, warming the air and cooling the wall and induction coil. Therefore, the air passing through the cartridge is warmer than the air outside the steam generator 1.

[0053] 1 and 2, the air inlet 14 is surrounded by an outer wall 34. The outer wall provides a barrier between the air inlet and the exterior of the steam generating apparatus 1. If the outer wall is warmer than the air in the air inlet, heat will also be transferred from the outer wall to the air in the air inlet.

[0054] As mentioned above, air travels from air inlet 14 into heating chamber 12, as indicated by arrow 48. Cartridge 20 is flush with the heating chamber. As such, air must pass through the cartridge as it passes through the heating chamber containing the cartridge. Therefore, air flow around the cartridge is restricted, and there is no intentional airflow path around the cartridge between the cartridge and wall 28 in which induction coil 16 is embedded. The air traveling into the heating chamber is warmed before entering the heating chamber and cartridge, limiting the amount of heat lost from the cartridge to the air, thereby keeping the cartridge warmer.

[0055] 2 shows an EM shield 36 embedded in the wall 28 in which the induction coil 16 is embedded. The EM shield is located radially outward of the induction coil. When the steam generator 1 is in use, the EM shield may warm due to heat generated in the heating chamber 12 by the induction coil and due to currents generated in the shield due to the shielding process.

[0056] Figure 3 shows a cross section taken along plane AA of Figure 2. This shows a circular body, indicating that the steam generator is generally cylindrical. The heating chamber 12 is centrally located, surrounded by a wall 28 in which the induction coil 16 is embedded, along with an EM shield 36. As in Figure 2, it can be seen that the EM shield is located along the induction coil, radially outward of the coil.

[0057] The air holes 14 are located around the wall 28 in which the induction coil 16 and EM shield 36 are embedded. The air holes are divided into a plurality of arc-shaped holes 38, each of which provides an air flow path. The air holes are divided by ribs 40. The ribs connect the wall in which the induction coil and EM shield are embedded to the outer wall 34 that surrounds the air holes radially outward.

[0058] FIG. 4 shows the same cross section as shown in FIG. 3 for an alternative exemplary steam generator. Here, the device is still circular, with the heating chamber 12 located at its center. The heating chamber is again surrounded by a wall 28 in which the induction coil 16 and EM shield 36 are embedded, in the same configuration as the steam generator shown in FIGS. 2 and 3. Instead of arc-shaped holes forming airflow paths for the air holes, in this example, the air holes 14 are provided by a plurality of circular bores 39 evenly distributed around the radially outer annulus of the EM shield, as in FIG. 4. Each of the bores is separated from adjacent bores by a rib 40 that provides the airflow path and connects the wall in which the coil and EM shield are embedded to the outer wall 34 that forms the outer wall of the steam generator.

[0059] FIG. 5 shows the same cross section of a further alternative exemplary steam-generating apparatus. The apparatus is again circular, with the heating chamber 12 located at its center. A wall 28 surrounds the heating chamber. The induction coil 16 is embedded in this wall. However, instead of the EM shield also being embedded in this wall, as in the example shown in FIG. 3, an EM shield 36 is embedded in the outer wall 34. The outer wall is separated from the wall in which the coil is embedded by air holes 14. As in the example shown in FIG. 3, the air holes are divided into arc-shaped holes 38, which are separated by ribs 40. In this configuration, the arc-shaped holes 38 may be provided by a metal tube. In this case, the metal tube can act as a susceptor and provide preheating of the air entering the heating chamber 12. The metal tube may also be capable of acting as an EM shield.

[0060] FIG. 6 shows a cross section of another alternative exemplary steam generating device along the same plane as FIGS. 3-5. In this example, the device has the same structure as the example of FIG. 5, but instead of being an outer wall, the wall in which the EM shield is embedded is an intermediate wall 42. Radially outward from this intermediate wall is the outer wall 34. Between the outer wall and the intermediate wall are air holes 14, as well as between the intermediate wall and the wall 28 in which the induction coil 16 is embedded and which surrounds the heating chamber 12. Each air hole is divided into a plurality of arc-shaped holes 38 by ribs 40 extending between the respective walls for each air hole. Each arc-shaped hole again provides an air flow path.

[0061] In the example shown in Figure 6, the air vents 14 can have one of several configurations, with Figures 7 and 8 showing two such configurations.

[0062] Figure 7 shows an exemplary steam-generating apparatus arrangement in a cross section similar to that shown in Figure 6. In the arrangement shown in Figure 7, the steam-generating apparatus has an outer wall 34 that provides a peripheral wall of the apparatus. Radially inward of the outer wall is an intermediate wall 42 that is radially spaced apart from the outer wall and from a wall 28 in which the induction coil 16 is embedded. The wall in which the induction coil is embedded is located radially inward of the intermediate wall and provides a sidewall of the heating chamber 12 defined radially inward of this wall.

[0063] There is an air hole 14 that passes from the exterior of the device into the heating chamber. There is a single air passageway extending through the air hole, designated 48 in FIG. 7 . The passageway enters the steam generator through the outer wall 34 at a point coinciding with the axial end of the heating chamber 12. The passageway then passes between the outer wall and an intermediate wall 42 to a point coinciding with the opposite axial end of the heating chamber. At this point, there is a passageway between the gap provided by the radial separation between the outer wall and the intermediate wall and the gap provided by the radial separation between the intermediate wall and the wall 28 in which the induction coil 16 is embedded. The air passageway passes through this passageway and returns between the intermediate wall and the wall in which the induction coil is embedded to a point again coinciding with the initial axial end of the heating chamber but at a shorter radial separation from the heating chamber than when the passageway entered the steam generator. Thus, at that axial end of the heating chamber, the passageway follows a further path into the heating chamber.

[0064] Figure 8 shows an alternative arrangement of an exemplary steam generating apparatus to that shown in cross section in Figure 7, similar to that shown in Figure 6. Like the arrangement shown in Figure 7, in the arrangement shown in Figure 8, the steam generating apparatus has an outer wall 34 that provides a peripheral wall of the apparatus. Radially inward of the outer wall is an intermediate wall 42 that is radially spaced apart from the outer wall and from a wall 28 in which the induction coil 16 is embedded. The wall in which the induction coil is embedded is located radially inward of the intermediate wall and provides a sidewall of the heating chamber 12 that is defined radially inward of this wall.

[0065] As in FIG. 7, in FIG. 8 there is an air hole 14 passing from the exterior of the device into the heating chamber. However, instead of the single air passage 48 of FIG. 7, the arrangement shown in FIG. 8 has an air passage, designated 50 in FIG. 8, which has a common beginning and a common end, but has two generally parallel sections between them. The passages enter the steam generator through the outer wall 34 at a point coinciding with the axial end of the heating chamber 12. The passages then branch. One section of the passage passes between the outer wall and the intermediate wall 42 in the gap provided by the radial separation of these walls. The other section of the passage passes through a passage into the gap provided by the radial separation between the intermediate wall and the wall 28 in which the induction coil 16 is embedded. This section of the passage then passes through this gap. The two sections rejoin at points coinciding with the opposite ends of the heating chamber 12. This is achieved by sections of the flow path passing between the outer wall and the intermediate wall, then through a passage in the intermediate wall, and then between the intermediate wall and the wall in which the induction coil is embedded, joining the sections to equivalent points at opposite axial ends of the heating chamber, after which the flow path continues along a common final section into the heating chamber at that axial end of the heating chamber.

[0066] Like the example shown in FIG. 6, the arrangement shown in FIGS. 7 and 8 has ribs (not shown in FIGS. 7 and 8) connecting and supporting the various walls that form the arc sections in the air vent 14.

[0067] 9 and 10 each show an exemplary air flow path that may be used in a steam generator. Each of these figures shows a cylinder representing a wall 28 in which an induction coil is embedded.

[0068] Figure 9 shows air flow passages 44 provided by air holes (not shown in Figures 9 and 10). The air flow passages pass in a zigzag pattern around the wall 28. By this, applicants mean that the flow passages have parallel sections that are aligned with the longitudinal axis of the cylindrical wall and that, at the end of the parallel sections, are joined to adjacent sections by curved sections of the air flow passage. In this configuration, one or more air flow passages are disposed around the entire wall.

[0069] 10 shows air flow passage 46, which is also provided by air holes (not shown). The air flow passage spirals around wall 28, passing from one axial end of the wall to the opposite axial end of the wall.

Claims

1. 1. An induction heating assembly for a steam generating apparatus, the induction heating assembly comprising: an outer body; a first wall disposed inside the outer body; an induction coil disposed inside the outer body and supported by the first wall; a second wall radially spaced from the first wall and radially spaced from the outer body; a heating chamber defined inside the induction coil and arranged, in use, to contain an object including a vaporizable substance and an inductively heatable susceptor; the outer body and the induction coil are separated from each other by the second wall; air holes are defined to allow airflow such that, in use, the air is heated before entering the object; The induction heating assembly includes a plurality of ribs that define a plurality of air flow passages in the air hole.

2. 2. The induction heating assembly of claim 1, wherein the air holes are shaped to direct the air flow along the induction coil.

3. 2. The induction heating assembly of claim 1, wherein the air holes are positioned to allow air flow such that, during use, air passes through in a direction along the length of the induction coil and is heated before entering the object.

4. The plurality of air flow paths include: a spiral around the induction coil; zigzag in the longitudinal direction of the induction coil, and zigzag in the transverse direction of the induction coil 10. The induction heating assembly of claim 1, wherein the induction heating assembly is arranged to be one or more of:

5. 10. The induction heating assembly of claim 1, wherein the plurality of air passages covers more than 50% of an outer surface of the induction coil.

6. The induction heating assembly of claim 1 , further comprising an electromagnetic shield, said electromagnetic shield substantially surrounding said air holes.

7. The induction heating assembly of claim 1 , wherein the induction coil is disposed substantially within the first wall.

8. The induction heating assembly of claim 1 , wherein the induction coil is embedded in the first wall.

9. The induction heating assembly of claim 1 , wherein the heating chamber is adjacent to the induction coil.

10. 1. A steam generation system comprising: The induction heating assembly of claim 1; an object including a vaporizable substance and an inductively heatable susceptor; The object is placed in the heating chamber of the induction heating assembly during use.

11. The steam generation system of claim 10 , wherein the vaporizable material and the inductively heatable susceptor are encapsulated by the body.

12. The steam generation system of claim 10 , wherein there is an inductively heatable susceptor forming at least a portion of the air hole.

13. the vaporizable material is a solid or semi-solid tobacco material; 11. The steam generation system of claim 10, wherein the susceptor is held within and surrounded by the vaporizable material such that the vaporizable material forms a heat absorbing layer between the susceptor and an outer surface of the induction heating assembly during use.

14. 2. The induction heating assembly of claim 1, wherein said induction coil is separated from said air hole by said first wall.

15. 1. An induction heating assembly for a steam generating apparatus, the induction heating assembly comprising: an outer body; a first wall disposed inside the outer body; an induction coil disposed inside the outer body and supported by the first wall; a heating chamber defined inside the induction coil and arranged, in use, to contain an object including a vaporizable substance and an inductively heatable susceptor; a second wall radially spaced from the first wall and radially spaced from the outer body; Including, the outer body and the induction coil are separated from each other by the second wall; air holes are defined to allow airflow such that, in use, the air is heated before entering the object; The induction heating assembly includes structure within the air hole that defines a plurality of air flow paths.

16. 16. The induction heating assembly of claim 15, wherein the air holes are positioned to allow air flow such that, in use, air passes through in a direction along the length of the induction coil and is heated before entering the object.

17. 1. An induction heating assembly for a steam generating apparatus, the induction heating assembly comprising: an outer body; a first wall disposed inside the outer body; an induction coil disposed inside the outer body and supported by the first wall; a second wall radially spaced from the first wall and radially spaced from the outer body; and a heating chamber defined inside the induction coil and arranged to contain, in use, an object including a vaporizable substance and an inductively heatable susceptor, the outer body and the induction coil are separated from each other by the second wall; The induction heating assembly defines an air hole including a plurality of ribs defining a plurality of air passages, the air hole permitting air flow along the induction coil.

18. 18. The induction heating assembly of claim 17, wherein the plurality of air passages extend along a length of the induction coil, and the air holes are positioned to allow air to flow along the induction coil and away from a mouthpiece of the steam generating device during use.

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