CN114788406A - Heater assembly - Google Patents

Abstract

The present invention relates to a heater assembly for an aerosol generating device. The heater assembly includes a flexible electrically insulating backing film, a flexible heating element supported on a surface of the electrically insulating backing film, and a cover film positioned on the surface of the electrically insulating backing film to at least partially seal the heating element is encapsulated between the cover film and the backing film. The backing film, heating element, and cover film together form a thin film heater assembly, and a graphite layer is disposed against the outer surface of the thin film heater assembly, the graphite layer at least partially overlapping the heating element. The heater assembly further includes a tubular heating chamber arranged to receive an aerosol-generating consumable; wherein the thin film heater assembly is wrapped around an outer surface of the tubular heating chamber, wherein the electrically insulating backing film faces the Heating the chamber. In this way, the graphite layer serves to distribute the heat generated by the heating element evenly within the plane of the thin film heater assembly during use. In particular, the high thermal conductivity of graphite means that heat spreads laterally within the thin film heater assembly quickly to prevent localized hot spots, such as in areas close to the heating element.

Description

heater assembly

technical field

The present invention relates to a method of making a heater assembly, and more particularly to a method of making a heater assembly for an aerosol-generating device.

Background technique

Thin-film heaters are used in a wide variety of applications that often require flexible low-profile heaters that can conform to the surface or object to be heated. One such application is in the field of aerosol-generating devices, such as reduced-risk nicotine delivery products, including electronic cigarettes and tobacco vapor products. Such devices heat the aerosol-generating substance within the heating chamber to generate vapor. One means of heating the consumable is to use a heater assembly that includes a thin film heater that conforms to the surface of the heating chamber to ensure efficient heating of the aerosol generating material within the chamber.

Thin film heaters typically include a resistive heating element encased in a hermetic envelope of flexible electrically insulating film, having contacts to the heating element for connection to a power source, these contacts typically being soldered to the heating element's on the exposed part.

Such thin film heaters are typically fabricated by depositing a layer of metal on an electrically insulating film support, etching the metal layer supported on the film into the desired heating element shape, applying a second layer of electrically insulating film to the on the etched heating element and hot pressing to seal the heating element with an electrically insulating film envelope. The electrically insulating film is then die cut to create openings for contacts that are soldered to the portions of the heating element exposed through the openings

These conventional thin film heaters, formed from planar heating elements sealed within an insulating film envelope, must then be attached to the surface to be heated. In the context of an aerosol-generating device, this involves attaching a thin-film heater to the outer surface of a heating chamber to form a heater assembly for transferring heat to an aerosol-generating consumable placed within the chamber.

Such conventional thin film heaters and heater assemblies suffer from a number of disadvantages. A known problem is that the heating is generally not uniform across the thin film heater. In particular, hot spots can often occur in the area of the heating track, resulting in non-uniform heater temperatures across the heating area of the thin film heater. The resistance of the heater track increases as the metal gets hotter, and this exacerbates this effect, causing existing hot spots to get hotter due to the greater resistance in these regions and the associated increase in localized resistive heating. In some cases, this can lead to burning of the electrically insulating sealing layer and reduced performance when thin film heaters are used in the device.

It is an object of the present invention to make progress in addressing these problems to provide an improved heater assembly and method of making a heater assembly

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provided a heater assembly for an aerosol generating device, the heater assembly comprising: a flexible electrically insulating backing film; a flexible heating element supported on the electrically insulating backing on the surface of the backing film; a cover film positioned on the surface of the electrically insulating backing film so as to at least partially enclose the heating element between the cover film and the backing film; wherein the a backing film, the heating element, and the cover film together form a thin film heater assembly; a graphite layer disposed against an outer surface of the thin film heater assembly, the graphite layer at least partially overlapping the heating element; and a tubular a heating chamber arranged to receive an aerosol-generating consumable; wherein the thin film heater assembly is wrapped around an outer surface of the tubular heating chamber, wherein the electrically insulating backing film faces the heating chamber room.

In this way, the graphite layer serves to distribute the heat generated by the heating element evenly within the plane of the thin film heater assembly during use. In particular, the high thermal conductivity of graphite means that heat spreads laterally within the thin film heater assembly quickly to prevent localized hot spots, such as in areas close to the heating element. By overlapping the graphite layer with the heating element, heat is rapidly conducted to the graphite layer and then spread over the area corresponding to the graphite layer. This prevents localized areas of the consumable from exceeding the optimum temperature for aerosolization and possible burns that release unwanted compounds into the vapor for inhalation by the user. The graphite layer also ensures that the consumable is heated uniformly in order to effectively aerosolize the entire volume of the consumable, thereby overcoming the known problems of waste associated with incomplete heating of the aerosol-generating consumable in prior art devices. When heating aerosol-generating consumables, uniform heating over a fine length scale is required to avoid the waste and hot spot problems discussed above, and the use of heating assemblies for these applications is therefore particularly preferred.

The thin film heater assembly includes a plurality of film layers that are stacked to provide a multi-layer planar assembly. The term "overlap" is intended to describe how the surface areas of the layers overlap in the plane of the thin film heater assembly, even though they are separated by one or more layers. "Partially overlapping" is intended to mean that the graphite layer and the heating element are positioned such that they overlap in the plane of the thin film heater assembly. In other words, the heating elements and graphite sheets (in their respective layers) cover corresponding portions of the surface area of the thin film heater assembly. Preferably, the graphite layer covers the heating area of the heating element, wherein the heating area is the surface area defined by the heating track of the heating element. These definitions apply whether the thin film heater assembly is in a planar configuration (ie, lying flat), or whether it wraps around a curved heating chamber.

The graphite layer may rest against the flexible electrically insulating backing film (ie against the first side of the thin film heater assembly) and/or against the cover film (ie against the side of the thin film heater assembly opposite the first side) on the second side) positioning. Preferably, the graphite layer is attached to the outer surface of the thin film heater assembly, ie the graphite layer is attached to an electrically insulating backing film or cover film, eg using an adhesive.

The backing film may include polyimide, such as a polyimide film with a Si adhesive layer. Alternatively or additionally, the backing film may comprise a fluoropolymer, such as PTFE. When the backing film comprises a fluoropolymer, it may comprise an at least partially defluorinated surface layer formed, for example, by surface treatments such as plasma and/or chemical etching. This allows an adhesive to be applied to the treated surface that would not otherwise adhere with the very low friction surface provided by the fluoropolymer. Additionally or alternatively, the backing film may comprise PEEK. Preferably, the flexible electrically insulating backing film has a thickness of less than 80 μm, preferably less than 50 μm, and preferably greater than 20 μm.

The cover film preferably includes a heat shrinkable film. In this way, the heat shrink film not only serves to seal the heating element between the heat shrink film and the backing film, but also serves to provide an attachment mechanism so that the thin film heater assembly can be attached to the heating chamber by heat shrinking . The heat shrink film may include one or more of polyimide, fluoropolymers such as PTFE, and PEEK. The heat shrinkable film is preferably a preferential heat shrinkable film arranged to preferentially shrink in one direction. For example, the heat shrinkable film may be polyimide 208x tape manufactured by Dunstone Corporation. The heat shrink film can be in the form of an initially flat layer, i.e., a piece of tape that is arranged to wrap around the heating chamber, or the heat shrink film can be in the form of a tube that is arranged to pass around the heating chamber (i.e. , over the heating chamber) and is heated so that it shrinks to the surface of the heating chamber.

Preferably, the cover film is attached using an adhesive disposed on the surface of the flexible electrically insulating backing film that supports the heating element. The adhesive may be, for example, a silicone adhesive. The adhesive provides a simple means of securely securing both the heating element and the cover film to the backing film. The flexible electrically insulating backing film may include an adhesive layer, for example, the flexible electrically insulating backing film may be a polyimide film with a Si adhesive layer. The heating element can be attached by subsequently heating the flexible electrically insulating backing film, the adhesive layer and the positioned heating element to bond the heating element to the surface using the adhesive. Subsequent heating may be a heating step for shrinking the heat shrink film to attach the film heater to the heating chamber.

The heating element is preferably a flexible planar heating element. Preferably, the heating element is a planar heating element comprising: a heater track that follows a circuitous path over a heating area in the plane of the heating element; and two contact feet for Connected to a power source, the contact feet extend away from the heater track in the plane of the heating element. Preferably, the heater track is configured to provide substantially uniform heating over the heating area. The heater track path may be a serpentine or tortuous path over the heating area, and the heater track may be of substantially uniform width and thickness. Preferably, a cover film is attached so as to enclose the heater track between the backing film and the cover film, leaving the contact feet exposed. In this way, the heater track is electrically insulated between the electrically insulating backing film and the heat shrink film, while the contact pins are exposed so that they can be connected to a power source. The contact pins can be long enough to allow direct connection to a power source when thin film heaters are employed in the device. For example, the length of the contact feet may be substantially equal to or greater than one or both of the dimensions defining the heating area. The circuitous paths may be configured to leave empty areas within the heating zone.

The heater assembly includes a tubular heating chamber; wherein the thin film heater assembly wraps around an outer surface of the tubular heating chamber, wherein the electrically insulating backing film faces the heating chamber. In this way, a thin film heater assembly can be applied to heat the contents of a heating chamber, where the graphite layer is used to evenly distribute the heat from the heating element to provide improved heating of the heating chamber.

Preferably, the heating chamber includes one or more notches in the outer surface, and the thin film heater assembly is positioned relative to the heating chamber such that a temperature sensor attached to the flexible electrically insulating backing film is positioned within the notches. Preferably, the method further comprises wrapping an additional electrically insulating film around the attached thin film heater assembly. In some examples, the additional electrically insulating film may have a lower thermal conductivity than the backing film.

Preferably, the graphite layer is disposed between the electrically insulating backing film of the thin film heater assembly and the outer surface of the heating chamber. The graphite layer may be attached to the heating chamber or to the backing film of the thin film heater assembly prior to wrapping the thin film heater assembly around the heating chamber. This provides a simple way to accurately align the graphite layer so that it overlaps the heated area during assembly.

Alternatively, the graphite layer may be placed against the outer surface of the cover film of the thin film heater assembly. This step may be performed after heat shrinking to attach the thin film heater assembly to the heating chamber.

Preferably, the heater assembly includes a second graphite layer; wherein the first graphite layer is disposed between the electrically insulating backing film and the outer surface of the heating chamber; and the second graphite layer is disposed against the outer surface of the cover film. This provides a further optimized heat distribution, as the heating element is positioned between the two graphite layers, which together serve to spread the heat through the thin film heater assembly, and does not require extensive additional work during assembly.

Preferably, the heater assembly further comprises an electrically insulating sealing layer disposed around the outer surface of the wrapped thin film heater assembly and the one or more graphite layers. This provides enhanced thermal insulation, allowing heat to be directed to the heating chamber more efficiently. Additionally, the thin film heater may be sealed to prevent the release of one or more by-products during heating. In some examples, the layers of the thin film heater are configured to provide enhanced heat transfer from the heating element in one direction. For example, the thickness and/or material properties of one or more of the flexible electrically insulating backing film, the second flexible electrically insulating film, and the one or more sealing layers are selected to correspond to the direction of the heating chamber during use direction provides enhanced heat transfer. For example, the insulating backing film may have increased thermal conductivity relative to the cover film layer and/or the sealing layer. In this way, heat transfer to the heating chamber is facilitated and heat transfer out of the heating chamber is reduced to mitigate heat loss. Preferably, the side of the thin film heater that is arranged in contact with the heating chamber is configured to have a higher thermal conductivity than the opposite outer side. Preferably, the sealing layer has a lower thermal conductivity than the backing film.

Preferably, the heating element is a planar heating element comprising: a heater track that follows a circuitous path over a heating area in the plane of the heating element; wherein the graphite layer covers the surface of the thin film heater assembly area, which corresponds to the heating area of the heating element. This ensures that the heat is evenly distributed over the heated area of the thin film heater assembly.

Preferably, the graphite layer is provided by a binder graphite sheet comprising a graphite layer and at least one binder layer. For example, the graphite layer may comprise a binder graphite tape. This provides a simple means of securing the graphite layer in place by using a layer of adhesive.

Preferably, the binder graphite sheet comprises a graphite layer having a thickness between 5 μm and 30 μm and a binder layer having a thickness between 0 μm and 35 μm, wherein preferably the graphite layer has between 10 μm and 12 μm and the adhesive layer has a thickness between 5 μm and 10 μm. In other examples, graphite tapes with a graphite layer thickness of 10 μm, 17 μm or 25 μm and a corresponding adhesive layer thickness of 6 μm, 10 μm or 30 μm can be used. This minimizes the thermal mass of the thin film heater assembly, thereby maximizing heat transfer to the heating chamber.

The thermal conductivity of the graphite layer is preferably between 700 W/m.K and 2000 W/m.K. This helps distribute the heat generated by the heater track efficiently over the entire heating area. The graphite layer preferably comprises a graphite polymer film.

The heater assembly preferably further includes a temperature sensor including a sensing portion (also referred to as a sensor head in the following description), and wherein the sensing portion is positioned in the area of the thin film heater assembly covered by the graphite layer. In other words, the graphite layer covers the sensor portion of the temperature sensor in the plane of the thin film heater. In this way, a temperature sensor can be used to monitor the heating temperature in order to accurately control the heater. In particular, this means that the graphite film overlaps both the heating element and the sensing portion of the temperature sensor so that the heat from the heating element is efficiently distributed to the sensing portion so that the temperature sensor provides an accurate measurement of the temperature of the heating element. This prevents overheating of the heating element as the exact temperature of the heating element can be monitored.

In another aspect of the invention, there is provided a method of making a heater assembly, the method comprising: providing a heating element supported on a surface of a flexible dielectric backing film; and attaching a cover film to attached to the surface of the dielectric backing film so as to at least partially encapsulate the heating element between the cover film and the dielectric backing film, wherein the backing film, the heating element and the The cover films together form a thin film heater assembly; a graphite layer is positioned, the graphite layer disposed against the outer surface of the thin film heater assembly, the graphite layer at least partially overlapping the heating element. This provides a simple method of assembly of a heater assembly with improved thermal characteristics and reduced risk of hot spots due to preferential heating at areas near the heating track of the heating element. The method also allows graphite heaters to be added at different stages of the assembly process to improve assembly efficiency, for example, graphite heaters can be added to the outer surface of the heating chamber during fabrication of the heating chamber, can be added during the assembly of the thin film heater assembly The graphite heater is added to the surface of the thin film heater assembly, or the graphite heater can be added as a final step after the thin film heater has been attached to the heating chamber.

Preferably, the graphite layer is provided by a binder graphite sheet comprising a graphite layer and at least one binder layer, and the step of positioning the graphite layer comprises: adhering the binder graphite sheet to the dielectric backing film; and/or affix the adhesive graphite sheet to the cover film. In an alternative step, the adhesive graphite sheet can be directly attached to the outer surface of the heating chamber.

Preferably, the method further comprises: wrapping the thin film heater assembly around an outer surface of a tubular heating chamber, with the dielectric backing film facing the outer surface of the heating chamber; and providing a layer consisting of a heat shrinkable layer cover the film and heat the thin film heater assembly to shrink the heat shrinkable layer, thereby securing the thin film heater assembly against the tubular heating chamber.

Preferably, the method further comprises: affixing an adhesive graphite sheet to the outer surface of the tubular heating chamber prior to wrapping the thin film heater assembly around the outer surface of the tubular heating chamber.

In another aspect of the present invention, there is provided an aerosol generating device, such as a heater assembly as set forth in the claims. In this way, the aerosol-generating device can provide improved heating by providing a more uniform heating temperature across the heating chamber.

Description of drawings

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

Figures 1A and 1B schematically illustrate a heater assembly according to the present invention from two reverse views;

Figure 2A illustrates a heater assembly including a thin film heater assembly wrapped around a heating chamber;

2B illustrates a cross-sectional view of a heater assembly including a thin film heater assembly wrapped around a heating chamber;

Figure 3A illustrates a heater assembly including a thin film heater assembly wrapped around a heating chamber;

3B and 3B respectively illustrate cross-sectional views of two examples of heater assemblies according to the present invention;

Figure 4 schematically illustrates a graphite layer for use in a heater assembly according to the present invention;

5A-5E illustrate a method of assembling a heater assembly according to the present invention;

Figure 6 illustrates an alternative assembly step in a method of assembling a heater assembly in accordance with the present invention.

Detailed ways

Figures 1A and 1B schematically illustrate a heater assembly 10 for an aerosol-generating device according to the present invention. The heater assembly 10 includes a flexible electrically insulating backing film 30 and a flexible heating element 20 supported on the surface of the electrically insulating backing film 30 . The heater assembly 10 further includes a cover film 50 positioned on the surface of the electrically insulating backing film 30 to at least partially enclose the heating element 20 between the cover film 50 and the backing film 30 . The assembled backing film 30 , heating element 20 and cover film 50 are collectively referred to as thin film heater assembly 100 . The heater assembly 10 further includes a graphite layer 40 disposed against the outer surface of the thin film heater assembly 100 , the graphite layer 40 at least partially overlapping the heating element 20 . In other words, the graphite layer 40 is applied to one of the two sides of the thin film heater assembly 100 where the thin film heater assembly 100 includes the flexible heating element 20 enclosed between the opposing backing film 30 and heat shrink film 50 .

The graphite layer 40 serves to quickly spread the heat generated around the heating area so that the heat is dispersed from any potential hot spots, resulting in a more uniform heating temperature across the heating area. Because graphite has a high thermal conductivity, typically between about 700 W/m.K and 2000 W/m.K, heat disperses laterally quickly in the plane of the thin film heater assembly 100 so that no hot spots are formed, and when aerosols are generated, such as The heater assembly 10 provides better performance when employed in a device-by-device. This can be achieved even if the graphite layer 40 is separated from the heating element 20 by one or more thin film layers.

In the exemplary embodiment shown in the figures, the cover film includes a heat shrinkable film layer 50 . This provides several advantages. In particular, the heat shrink film not only seals (at least a portion of) the heating element 20 between the backing film 30 and the opposing heat shrink film, but also serves as a means of attaching the thin film heater assembly 100 to the surface of the heating chamber means of attachment. It thus provides an efficient way of attaching heating elements while minimizing the amount of additional material and associated thermal mass in the layers of the thin film heater assembly. Further details of this attachment mechanism are provided below.

In the example of FIG. 1 , a graphite layer 40 is applied to the surface of the flexible electrically insulating backing film 30 . That is, the thin film heater assembly 100 is first formed by positioning a planar heating element between the backing film and the heat shrink 50 . This thin film heater assembly can be attached using an adhesive positioned between the layers, in particular, the backing film can include an adhesive layer for attaching both the heating element 20 and the cover film 50 . The graphite layer 30 is then positioned on the opposite surface of the heating element 20 against the backing film 30 such that the graphite layer at least partially overlaps the heating element 20 . In other examples of the invention, the graphite layer 40 may be applied on the opposite side of the thin film heater assembly 100, ie against the heat shrink film layer 50, as will be described in more detail below.

Preferably, as shown in Figure 1, the size and shape of the graphite layer 40 substantially corresponds to the size and shape of the heating region 22 defined by the heating track 21 of the heating element 20, as best seen in Figure IB. In particular, the graphite layer 40 preferably covers an area on the outer surface of the thin film heater assembly 100 that substantially corresponds to the heating area 22 of the heating element. In this way, the heat is evenly distributed over the entire intended heating area.

In the example of FIGS. 1A and 1B , the thin film heater assembly additionally includes a temperature sensor 70 in the form of a thermistor 70 having a temperature sensing portion 71 (“sensor head”) and a sensor connection 72 . Importantly, the sensor head 71 is positioned in the area of the thin film heater assembly 100 covered by the graphite layer 40 . In particular, the thermistor may be positioned such that the sensing portion is positioned between the backing film 30 and the cover film 50 adjacent to the heater track 21 of the heating element 20 . The graphite layer 40 is then positioned such that it covers both the heating area 22 and the sensor head 71 . In this way, heat is efficiently distributed to the temperature sensor head 71 so that the temperature sensor provides an accurate measurement of the actual heating temperature of the heating element 20 . When employed in a device, this allows accurate control of the heater using the measured temperature of the heating element to provide accurate heating temperatures and to ensure that the heating element 20 does not overheat, where the temperature sensor is not positioned to provide accurate heating of the heating element 20 itself. Examples of readings that may occur.

As shown in FIG. 2A , the thin film heater assembly 100 is wrapped around the outer surface of the tubular heating chamber 60 to provide uniform heating of the heating chamber 60 over the heating region 22 . Figure 2A shows the assembled heater assembly 10 comprising a flexible electrically insulating backing film 30, a flexible heating element 20, a heat shrinkable film layer 50 and a graphite layer 40, all wrapped around a tubular heating chamber around the outer surface of the heating element 20 so that when a power source is connected to the contacts 24 on the extended contact feet 23 of the heating element 20, heat can be transferred to the chamber 60. The example of FIG. 2 uses the heater assembly 10 of FIG. 1 with the graphite layer 40 applied against the surface of the backing film.

The thin film heater assembly 100 is then wrapped around the heating chamber 60 such that the graphite layer 40 and the flexible electrically insulating backing film 30 are adjacent to the outer surface of the heating chamber 60 . This is shown in the cross-section shown in Figure 2B. In particular, heater assembly 10 is arranged such that graphite layer 40 is positioned against the outer surface of heating chamber 60, flexible electrically insulating backing film 30 is positioned around graphite layer 40, heating element 20 is positioned against backing film 30, and Finally a heat shrinkable film layer 50 is wrapped around the outer surfaces of the layers to secure the thin film heater assembly to the heating chamber 60 . The assembly 10 shown in FIG. 2 may then be initially heated to shrink the heat shrink film 50 to seal the thin film heater assembly 100 against the outer surface of the heating chamber 60 .

Although in the example of FIGS. 1 and 2 the graphite layer 40 is applied to the surface of the backing film 30 of the thin film heater assembly prior to wrapping the thin film heater assembly 100 around the heating chamber 60, in the present invention In other examples, the graphite layer 40 may be applied directly to the outer surface of the heating chamber, followed by wrapping the thin film heater assembly 100 (including the backing film 30, heating element 20 and heat shrink film 50) over the graphite layer 20 and heating around the chamber 60 such that the graphite layer 20 at least partially overlaps the heating element 20 .

FIGS. 3A-3C illustrate an alternative example of the present invention in which the graphite layer 40 is disposed against the outer surface of the heat shrink film 50 of the thin film heater assembly 100 instead of the backing film 30 . Specifically, rather than applying the graphite layer 40 against the backing film 30 as shown in FIGS. 1A and 1B , the graphite layer 40 is applied to the opposite side of the thin film heater assembly 100 such that the graphite layer abuts the cover film 50 (at In this case on the heat shrink 50), but still overlapping the heating zone 22 in the same manner as shown in Figure 1 . The thin film heater assembly 100 is then wrapped around the tubular heating chamber 60 with the graphite layer 40 attached to the heat shrink film 50, as shown in Figure 3A. In particular, the thin film heater assembly 100 is still wrapped around the heating chamber 60 such that the electrically insulating backing film 30 faces the outer surface of the heating chamber 60 , but the graphite layer 40 is disposed around the outer surface of the heat shrink 50 .

FIG. 3B shows a cross-section through the arrangement of FIG. 3A illustrating the order of layers in heater assembly 10 . In particular, the backing film 30 abuts the outer surface of the heating chamber 60; the heating element 20 is supported on the outer surface of the backing film 30; and the heat shrink film 50 is wrapped around the outer surface of the heating element 20 to The thin film heating element 20 is sealed against the outer surface of the chamber 60; and a graphite layer 40 is applied to the outer surface of the wrapped heater assembly 10, as shown in Figure 3B. In this arrangement, the graphite 40 still provides the same effect of spreading the heat generated in the heating element 20 laterally through the planar layer to spread the heat and prevent any hot spots from forming.

An alternate example of heater assembly 10 is shown in cross section in FIG. 3C. This example combines a first graphite layer 41 (shown in FIG. 1 ) arranged against the flexible electrically insulating backing film 30 and a second graphite layer 42 (shown in FIGS. 3A and 3B ) arranged against the surface of the heat shrink 50 shown). Preferably, the two graphite layers 41 , 42 are arranged to overlap the heating area 22 of the heating element 20 in order to disperse heat throughout the layers of the heater assembly 10 , in particular laterally, to prevent the formation of any hot spots. In particular, the alternative example of FIG. 3C includes the first graphite layer 41 applied directly to the outer surface of the heating chamber 60 or applied directly to the backing film 30, such that when the thin film heater assembly 100 wraps When wrapped around the heating chamber 60 , the first graphite layer is located between the heating chamber 60 and the backing film 30 . As with all examples, flexible heating element 20 is supported on backing film 30 and heat shrink 50 is wrapped around the outer surface of heating element 20 to seal heating element 20 between backing film 30 and heat shrink 50 . The second graphite layer 42 is arranged on the outer surface of the heat shrink 50 . In this way, the heating element 20 is located between the first graphite layer 41 and the second graphite layer 42, which further optimizes the dispersion of the heat generated at the heating element 20 throughout the layers to prevent the formation of hot spots.

Each of the illustrated examples may additionally include an electrically insulating sealing layer (not shown) that may wrap around the outermost surfaces of the arrangements shown in Figures 2B, 3B, and 3C. An electrically insulating sealing layer such as a polyimide film may be applied to the thin film heater assembly prior to wrapping the thin film heater assembly 100 around the heating chamber 60 , ie, to the planar assembly shown in FIGS. 1A and 1B . Alternatively, the electrically insulating sealing layer may be applied after attaching the layers of the heater assembly 10 such that it wraps around the assembled heater assembly 10 (such as the arrangement shown in Figures 2B, 3B and 3C) around the outermost surface.

Figure 4 shows a graphite film layer 40 that may be applied as the graphite layer 40 in the described example of the invention. In particular, the graphite layer 40 may be provided by a binder graphite sheet comprising a graphite layer 43 and at least one binder layer 44 . The example of FIG. 4 shows a graphite sheet or tape with a graphite layer 43 and a single adhesive layer 44 , but in other examples, the graphite tape 40 may include multiple adhesive layers, particularly in the graphite layer 43 An adhesive layer 44 is included on each opposite side of the . The adhesive layer 44 may comprise an acrylic or silicon adhesive, wherein the thickness 43t of the graphite layer may be between 5 and 30 microns, preferably between 10 and 12 microns, and the adhesive layer has The thickness 44t of can be between 0 and 35 microns, preferably between 5 and 10 microns. Examples of commercially available graphite ribbons that can be used for this application include EYGA121801F sold by Panasonic ^™ and DSN5012-05DC sold by DSN Thermal Solutions ^™ . Such graphite ribbons have a graphite layer of about 10 microns and an adhesive layer of about 6 microns. A graphite ribbon 40 having a graphite layer of about 10 to 12 microns and an adhesive layer having a thickness 44t of between 5 and 10 microns is optically preferred, in particular, the graphite ribbon is positioned in the heating chamber 60 and heated between elements 20. The thermal conductivity of the graphite ribbon 40 may be in the range of 700 W/mK to 2000 W/mK. The graphite ribbon may have a specific gravity between about 0.85 g/cm ³ and 0.213 g/cm ³ . The graphite layer 43 of the tape may be a pyrolytic graphite sheet, which is formed in particular from a highly oriented graphite polymer film. Such graphite layers can withstand temperatures up to 400°C, making them well suited for use in heating chambers 60 where elevated temperatures are required. Such graphite tapes can be protected by a PTE release liner that protects the adhesive film 44 and can be removed prior to attaching the graphite sheet 40 to the thin film heater assembly 100 or heating chamber 60 .

Further details of a heater assembly 10 according to the present invention and a method of making such a heater assembly 10 will now be described with reference to FIGS. 5 and 6 .

As shown in FIG. 5A , the first step involves providing a heating element 20 supported on the surface of a flexible electrically insulating backing film 30 . This can be achieved in several different ways. In particular, the heating element 20 can be etched from a thin metal sheet of about 50 μm (eg, stainless steel sheet such as 18SR or SUS304), although other materials and heater thicknesses can be selected depending on the application. The specific metal and thickness of the metal sheet is selected such that the resulting heating element 20 is flexible so that it can deform together with the supporting flexible membrane 30 to conform to the shape of the surface to be heated. A metal sheet may first be deposited on the surface of the flexible electrically insulating backing film 30 and then etched to form the heater track 21 pattern while being supported on the film. Alternatively and preferably, the heating element 20 may be etched from the metal sheet independently of the flexible electrically insulating backing film. For example, separate metal foils can be chemically etched from both sides to provide one or more connected heating elements 20 that are then separated and positioned on the surface of the electrically insulating backing film 30 .

The exemplary heating element 20 shown in the figures is a planar heating element 20 that includes a heater track 21 that follows a circuitous path over a heating region 22 in the plane of the heating element 20 . The heating element has two contact feet 23 allowing connection to a power supply, these contact feet 23 extending away from the heater track 21 in the plane of the heating element 20 . The contact legs may also extend in a plane inclined with respect to the heating element. The heater track 21 is preferably shaped to provide substantially uniform heating over the heating zone 22 . In particular, the heater track is shaped such that it does not contain sharp corners, and is of uniform thickness and width, with a substantially constant gap between adjacent portions of the heater track 22 , such that at specific points within the heating zone 22 Increased heating is minimized. In the example of FIG. 5A , the heater track 21 follows a serpentine path over the heater area 22 and is divided into two parallel track paths 21 a and 21 b , each connected to two contact pins 23 . The heater layer 23 may be soldered at connection points 24 on each contact pin 23 to allow connection of the heater to the PCB and power supply.

The flexible electrically insulating backing film 30 must have suitable properties to provide a flexible matrix to support and electrically insulate the heating element 20. Suitable materials include polyimide, PEEK, and fluoropolymers such as PTFE. In this case the heating element comprises a heater track pattern 21 etched from a 50 μm stainless steel 18SR layer supported on a single sided polyimide/Si adhesive film The agent film included a 25 μm polyimide film with a 37 μm silicon adhesive layer. The heating element 20 is supported on adhesive to allow the heating element to be attached to the backing film. The thin film heater assembly 100 of FIG. 5A can be pre-prepared and stored with a release layer attached to the adhesive surface supporting the heating element 20 to preserve the adhesive layer until it is ready for use. The release layer may be provided, for example, of polyester or similar material. The release layer can then be peeled off to reveal the tacky adhesive layer supporting the heating element for the next assembly step shown in Figure 5B.

In the exemplary method of making heater assembly 100 , the next step is to apply heat shrink film layer 50 directly to the surface of electrically insulating backing film 30 to at least partially encapsulate heating element 20 within heat shrink film 50 and the backing film 30. Heat shrink film 50 may be attached directly to the surface of heater element 20 with an adhesive to encapsulate heating region 20 between backing film 30 and heat shrink 50 . In particular, heater track 21 is insulated within the sealed envelope formed by flexible backing film 30 and heat shrink 50, while contact pins 23 remain exposed to allow connection to a power source.

The heat shrink 50 is larger than the backing film 30 and the heating element 20 such that the heat shrink extends beyond the heating element 20 by a predetermined distance in two orthogonal directions 51 , 52 . This alignment of heat shrink 50 relative to heating element 20 allows for later alignment of heating region 22 relative to heating chamber 60 . Therefore, careful control of the dimensions of these extensions 51, 52 of the heat shrink at this stage allows the heater assembly 100 to be attached to the heating chamber 60 in a simple manner to provide precise alignment. The relative alignment of the heat shrink and film heater 10 can be accomplished in several different ways. The heat shrink 50 can be pre-cut to the correct size and then aligned with the edges of the flexible electrically insulating backing film 30 to provide the correct predetermined distances 51, 52 for these extensions. Alternatively, an alignment device can be used to achieve such precise alignment.

In particular, a series of corresponding alignment holes (not shown) may be provided in both backing film 30 and heat shrink 50 that may be used for opposing alignment of backing film 30 and heat shrink 50 allow. The alignment holes are arranged so that when the holes of the backing film 30 are aligned with the alignment holes of the heat shrink 50, the heat shrink 50 is precisely positioned at the correct position relative to the film heater 10 so that the heat shrink 50 extends beyond the correct length 51 , 52 of the heating zone 22 to allow precise alignment of the heating element 20 relative to the heating chamber 60 when attached. The heat shrink 50 is then aligned relative to the film heater 10 using a positioning jig that includes a support surface with upstanding alignment pins whose relative displacement corresponds to the backing film 30 and heat shrink 50 position of the alignment holes on the . The heating element 20 and heat shrink 50 on the backing film 30 can then be positioned on the surface of the alignment fixture such that the alignment pins extend through the backing film alignment holes to secure the heat shrink relative to the heating element 20 and the backing film 30 are precisely aligned.

The heat shrink 50 extends beyond the heating area 20 in the opposite direction from the contact feet 23 to provide an alignment area 52 of the heat shrink 50 . The alignment region 52 may be aligned with the top edge of the heating chamber 60 such that the heating region 20 is positioned along the length of the heating chamber from the top edge of the heater track 21 at a distance corresponding to the predetermined length 52 of the alignment region. location. In this way, the heater element 20 can be positioned at the correct location along the heating chamber 60 . The heat shrink 50 also has an attachment area 51 that extends beyond the heater track 21 and the backing film 30 in a direction perpendicular to the direction in which the contact feet 23 extend to provide the attachment area 51 . The direction of attachment region 51 extending from heating element 20 toward heat shrink 50 may be referred to as the "wrap direction" since this portion of heat shrink 50 allows it to wrap around tubular heating chamber 60 and subsequently heat shrink. Shrink to provide the desired tight connection. Similarly, the direction opposite the heater feet 23 in the direction in which the alignment region 52 extends from the heating element 20 may be referred to as the upward or alignment direction, which corresponds to the long axis of the heating chamber 60 , pointing toward the top opening end. These extension distances 51 , 52 can be configured by cutting the heat shrink 50 to the correct size before or after attachment to the surface of the electrically insulating backing film 30 .

As shown in FIG. 5B , a temperature sensor 70 is attached to the thin film heater assembly 100 between the flexible backing film 30 and the heat shrink 50 . In this case, the temperature sensor 70 is a thermistor having a sensor head 71 configured to detect local temperature and temperature sensor connections 72 configured to sense the sense from the sensor head 71 . The test signal is carried to the PCB. As shown most clearly in FIG. 5A , the heater track 22 is preferably shaped to leave a void 22v within the heating zone 22 . The sensor head 71 is positioned in the void 22v between the backing film 30 and the heat shrink 50 so that the sensor head is in close proximity to the heater track 21 . By positioning the sensor head 71 in close proximity to the heating element 20 between the heat shrink 50 and the backing film 30 , the temperature sensor 70 is sealed in close proximity to the heating element to provide an accurate temperature reading of the heated area 22 . This is further improved by providing a graphite sheet 40 covering both the heating element 20 and the sensor head 71 .

As shown in FIG. 5B , the heat shrink 50 is preferably positioned such that the free edge region 32 of the backing film 30 is exposed. This free edge region 32 is folded onto the heat shrink film 50 to seal the edges of the backing film 30 and heat shrink 50, and the temperature sensor head 71 is folded to secure it within the fold.

Once the thin film heater assembly 100 has been assembled, as shown in Figure 5B, a graphite film layer 40 in the form of an adhesive graphite tape is attached to the outer surface of the thin film heater assembly 100 such that the graphite film layer is in contact with the heated The heating area 22 defined by the heater track 21 at least partially overlaps. In this example, graphite ribbon 40 is attached to the exposed surface of backing film 30, as shown in Figure 5C (and Figure 1A). The size and shape of the graphite ribbon closely corresponds to the size and shape of the heating area 22 such that the graphite ribbon covers the area on the backing film 30 that corresponds to the heating area 22 . The graphite ribbon 40 also extends over the temperature sensing portion 71 of the temperature sensor so that the heat generated by the heating element 20 is efficiently distributed to the temperature sensor 70 and the temperature sensor provides an accurate reading of the heating element 20 temperature.

The graphite tape 10 is attached by applying the tape 40 with the adhesive layer against the backing film 30 . As mentioned above, although the graphite tape is applied to the surface of the backing film in this example, the graphite tape can also be applied to the heating chamber by using the adhesive layer 44 against the surface of the heating chamber to attach the graphite layer 43 The outer surface of the chamber 60 such that the graphite ribbon will overlap the heating element 20 when the thin film heater assembly 100 is wrapped around the heating chamber 60. Similarly, alternatively or additionally, a graphite layer 40 may be applied to the surface of the heat shrink layer 50 (the opposite surface to the surface that abuts the heating element 20) such that when the thin film heater assembly 100 is wrapped around the heating chamber When surrounding, the graphite layer is on the outside of the heating element (ie, radially away from the heating chamber 60).

Once the graphite layer 40 is attached to the thin film heater assembly 100 (or alternatively to the outer surface of the heating chamber 60) so as to overlap the heating region 22 of the heating element 20, the thin film heater assembly is then attached to the Heater chamber 60 . This can be accomplished by attaching two sheets of adhesive tape 55a, 55b to the thin film heater assembly 100 to allow the thin film heater assembly to be initially heated to shrink the heat shrink 60 The assembly is attached to the heating chamber 60 at the correct location.

The adhesive tapes 55a, 55b may be provided by multiple pieces of polyimide adhesive tape, such as a commercially available 0.5 inch polyimide tape with 12.7 micron polyimide and 12.7 micron silicone adhesive. As shown in Figure 5D, adhesive attachment strips 55a, 55b are positioned along each edge of the heat shrink 50 at the ends in the wrap direction. The thin film heater assembly 100 may then be attached to the heating chamber 60 by aligning the top edge 53 of the heat shrink 50 with the top edge 62 of the heating chamber 60, as shown in Figure 5E. This alignment step allows the heating region 22 and corresponding graphite layer 40 to be placed at the correct location along the heating chamber 60, given that the distance 52 of the alignment region is carefully chosen. Certain consumables will contain a certain amount of aerosol-generating material at certain locations, so it is important to heat the correct portion of the heater chamber 60 to effectively release vapors from the consumable.

The thin film heater assembly 100 is first attached to the heating chamber using adhesive tape 55a. The heating chamber 60 is a tubular heating chamber 60 arranged to contain a consumable to be heated in order to generate a vapor for inhalation by a user. The heating chamber 60 preferably has one or more notches 61 on the outer surface that provide internal protrusions that aid in the positioning and heat transfer of consumables received within the chamber 60 transfer. The perimeter of the heating chamber 60 preferably closely matches the width (length in a direction perpendicular to the extension of the contact feet) of the heating element 20 so that the heating element provides a complete circumferential ring around the chamber 60 . In other examples, the heater element 20 may be sized to encircle the circumference of the heating chamber more than once, ie the heating element may be sized to provide an integral number of circumferential rings around the heating chamber so that the No change in heating temperature occurs around the circumference. The thin film heater assembly 100 is positioned and attached such that the temperature sensor head 71 is located within the notch 61 on the outer surface of the heating chamber 60 to provide a more accurate reading of the interior temperature of the heating chamber 60 . In an alternative to the embodiment of FIG. 3C , a temperature sensor may also be positioned between the graphite layer 50 and the heat shrink 50 .

As mentioned above, in an alternative approach, the graphite layer 40 is attached directly to the heater chamber 60 as shown in FIG. 6 . In particular, the graphite layer 40 is positioned over a portion of the length of the heating chamber 60 that corresponds to the heating region 22 of the thin film heater assembly 100 when the assembly is wrapped around the heating chamber 60 such that the portion is the same as the heating region Overlap and serve to spread the generated heat evenly over the heating area 22 .

Once attached with the first adhesive tape portion 55a, the thin film heater assembly 100 is then wrapped around the heating chamber 60 such that the extended attachment portion 51 of the heat shrink 50 wraps circumferentially around the chamber 60 so as to cover the heating element 20 with the heat shrink 50, and then attach by a second piece of attachment tape 55b to provide the heater assembly 10 (including the heater element 20, backing film 30) shown in FIG. 2A , graphite layer 40, heat shrink film 50, thermistor 70 and heater chamber 60). Since the length of the attachment area 51 is approximately the same as the length of the heating area 22 (and thus the perimeter of the heating chamber 60 ), the attachment portion 51 is wrapped once to cover the heating area 22 , so that the In the attached heater assembly 10, the heater element is insulated by two layers of heat shrinkable film. The attachment area 51 may be sized to provide additional coverage of the heating element 20 more than once. For example, the attachment area 51 may extend beyond the heating element by a distance corresponding to an integer multiple of the outer perimeter of the heating chamber 60 .

As can be seen in Figure 2A, once assembled, the temperature sensor connections 72 and heater feet 23 are positioned so that they are aligned after this quick step for connection to the PCB. The attached heater assembly 10 is then heated to shrink the heat shrink 50 against the heating chamber 60, as shown in Figure 2A. For example, the assembly 10 can be heated in an oven at about 210°C for ten minutes to shrink the film, although the time and temperature can be adjusted for other types of thermal shrinkage. This process allows a large number of units to be heat treated simultaneously in a small oven. This is the only heating step that can simultaneously seal the film heater to the heating chamber and bond the backing film to the heat shrink.

Finally, although not required, a final sealing layer of electrically insulating film can be added around the outside of the heating element to complete the heating assembly. The final insulating layer can be, for example, an additional adhesive polyimide layer such as a 1 inch polyimide tape with 25 micron polyimide and 37 micron silicon adhesive. This outer electrically insulating film layer provides an additional insulating layer and further ensures the attachment of the thin film heater 100 to the heating chamber 60 .

The thicknesses and/or materials of the backing film 30, heat shrink 50, and final insulating layer may be selected to enhance heat transfer to the heating chamber, such as by incorporating a lower thermal conductivity layer (in this example, the heat shrink 50 and insulating layer) are provided on the outside of the heating element and the layer with higher thermal conductivity is provided as the backing film.

Once the outer insulating electrically insulating film layer has been applied, the assembly 10 can be heated again. This second heating step allows further degassing of the outer electrically insulating film layer as well as other layers. For example, in the second heating stage, the heating temperature may be raised to a higher temperature than the heat shrinking stage, closer to the operating temperature of the device. This allows, for example, further degassing of the adhesive layer, which may not have occurred at the lower temperatures during the heat shrinking step. It is also beneficial to expose the heat shrink to a temperature closer to the operating temperature prior to heating during the first use of the device.

Once assembled, the graphite layer 40 is positioned such that it is aligned with the heating region 22 of the heating element and between the heating element 20 and the heating chamber 60, positioned around the heating element 20 such that the heating element 20 is positioned on the graphite Between layer 40 and heating chamber 60, or both. Due to the thermal conductivity of graphite, the graphite layer quickly spreads the heat generated by the heating element 20 in the planar direction to provide a uniform heating temperature over the area covered by the graphite layer 40, thereby reducing hot spots and reducing damage to the film due to localized overheating , and provide more uniform heat transfer to consumables received in the heating chamber 60 .

Claims (15)

1. A heater assembly for an aerosol-generating device, the heater assembly comprising:

a flexible electrically insulating backing film;

a flexible heating element supported on a surface of the electrically insulating backing film;

a cover film positioned over the surface of the electrically insulating backing film so as to at least partially encapsulate the heating element between the cover film and the backing film; wherein the backing film, the heating element and the cover film together form a film heater assembly;

a graphite layer disposed against an outer surface of the thin film heater assembly, the graphite layer at least partially overlapping the heating element; and

a tubular heating chamber arranged to receive an aerosol-generating consumable; wherein the thin film heater assembly wraps around an outer surface of the tubular heating chamber with the electrically insulating backing film facing the heating chamber.

2. The heater assembly of claim 1, wherein the graphite layer is disposed between the electrically insulating backing film of the thin film heater assembly and the outer surface of the heating chamber.

3. The heater assembly of claim 1, wherein the graphite layer is disposed against an outer surface of the cover film of the thin film heater assembly.

4. The heater assembly of claim 1, further comprising a second graphite layer; wherein,

a first graphite layer disposed between the electrically insulating backing film and the outer surface of the heating chamber; and is

The second graphite layer is disposed against the outer surface of the cover film.

5. The heater assembly of any one of claims 1 to 4, further comprising an electrically insulating seal layer disposed around the outer surface of the wrapped thin film heater assembly and the one or more graphite layers.

6. The heater assembly as claimed in any preceding claim, wherein the heating element is a planar heating element comprising: a heater track following a circuitous path over a heating zone in the plane of the heating element; wherein,

the graphite layer covers a region of the surface of the thin film heater assembly corresponding to the heating region of the heating element.

7. The heater assembly as claimed in any preceding claim, wherein the graphite layer is provided by an adhesive graphite sheet comprising a graphite layer and at least one adhesive layer.

8. The heater assembly of claim 7, wherein the adhesive graphite sheet comprises a graphite layer having a thickness of between 5 and 30 microns and an adhesive layer having a thickness of between 0 and 35 microns, wherein preferably the graphite layer has a thickness of between 10 and 12 microns and the adhesive layer has a thickness of between 5 and 10 microns.

9. A heater assembly as claimed in any preceding claim, wherein the thermal conductivity of the graphite layer is between 700W/m.k and 2000W/m.k.

10. The heater assembly as claimed in any preceding claim, wherein the graphite layer comprises a graphite polymer film.

11. The heater assembly as claimed in any preceding claim, further comprising a temperature sensor comprising a sensing portion; wherein the sensing portion is positioned in a region of the thin film heater assembly covered by the graphite layer.

12. A method of manufacturing a heater assembly comprising:

providing a heating element supported on a surface of a flexible dielectric backing film; and

attaching a layer of cover film over the surface of the dielectric backing film to at least partially enclose the heating element between the cover film and the dielectric backing film, wherein the attached backing film, the heating element and the cover film together form a thin film heater assembly;

positioning a graphite layer disposed against an outer surface of the thin film heater assembly, the graphite layer at least partially overlapping the heating element; and

wrapping the thin film heater assembly around an outer surface of a tubular heating chamber arranged to receive an aerosol generating consumable, wherein the dielectric backing film is directed towards the outer surface of the heating chamber.

13. The method of claim 12, wherein the graphite layer is provided by an adhesive graphite sheet comprising a graphite layer and at least one adhesive layer, and the step of positioning the graphite layer comprises:

affixing the adhesive graphite sheet to the dielectric backing film; and/or

The adhesive graphite sheet is adhered to the cover film.

14. The method of claim 12 or 13, further comprising:

providing a cover film comprising a heat shrinkable layer and heating the film heater assembly to shrink the heat shrinkable layer to secure the film heater assembly against the tubular heating chamber.

15. The method of claim 14, further comprising affixing an adhesive graphite sheet to an outer surface of a tubular heating chamber prior to wrapping the thin film heater assembly around the outer surface of the tubular heating chamber.

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