RU2849514C2 - Heating unit with separate sealing elements - Google Patents

Abstract

FIELD: aerosol.

SUBSTANCE: heating assembly (410) for an aerosol generating device comprises: a first heater housing (412) comprising an air inlet (418); a second heater housing (414) containing an aerosol outlet (420); a tubular heater (416) for heating a substrate forming the aerosol; an air flow path (422) through the heating assembly from the air inlet to the aerosol outlet, wherein the air flow path passes through the first heater housing, the tubular heater, and the second heater housing; a first sealing member (426) configured to seal the first heater casing relative to the tubular heater; and a second sealing member (424) configured to seal the second heater casing relative to the tubular heater; wherein the first and second sealing elements are separated from the air flow path.

EFFECT: improvement in design.

21 cl, 9 dwg

Description

The present invention relates to a heating unit for an aerosol-generating device. The present invention also relates to an aerosol-generating device comprising the heating unit. In particular, but not exclusively, the present invention relates to a hand-held electric aerosol-generating device for heating an aerosol-forming substrate, generating the aerosol, and delivering the aerosol to the user's mouth. The present invention also relates to an aerosol-generating system comprising the aerosol-generating device and the aerosol-forming substrate.

Aerosol-generating devices that heat an aerosol-forming substrate to produce an aerosol without burning the aerosol-forming substrate are known in the art. The aerosol-forming substrate is typically housed within an aerosol-generating article, along with other components such as filters. The aerosol-generating article may be in the form of a rod for inserting the aerosol-generating article into a heating chamber of the aerosol-generating device. A heating element is typically located in or around the heating chamber to heat the aerosol-forming substrate after the aerosol-generating article is inserted into the heating chamber of the aerosol-generating device.

The heating chamber may be located within the housing of the aerosol-generating device and form part of the airflow path through the device. One method of attaching the heating chamber to the housing of the aerosol-generating device is a mechanical press fit. However, due to manufacturing tolerances, mechanical press fits make it difficult to achieve an airtight seal between the housing and the heating chamber. Gaps may remain between the housing and the heating chamber, allowing aerosol to escape from the heating chamber and the airflow path into the portion of the housing surrounding the heating chamber. Escaping aerosol may condense in the portion of the housing surrounding the heating chamber and form a slurry. When the consumer uses the aerosol-generating device, the slurry is repeatedly heated, which may lead to the formation of unwanted byproducts. These byproducts may enter the airflow path through the gaps between the housing and the heating chamber and negatively impact the user's experience of using the aerosol-generating device.

Furthermore, gaps between the housing and the heating chamber can lead to heat loss from the heating chamber, which can reduce the device's thermal efficiency and the heat available to heat the aerosol-forming substrate. This can also degrade the user experience.

It would be desirable to provide a heating unit for an aerosol-generating device with improved sealing of its airflow path. It would be desirable to provide a heating unit for an aerosol-generating device that is more energy-efficient and improves aerosol delivery to the user.

According to an example of the present invention, a heating unit for an aerosol generating device is proposed. The heating unit may comprise a first heater housing. The first heater housing may comprise an air inlet. The heating unit may comprise a second heater housing. The second heater housing may comprise an aerosol outlet. The heating unit may comprise a tubular heater for heating an aerosol-forming substrate to generate the aerosol. The heating unit may comprise an air flow path. The air flow path may pass through the heating unit from the air inlet to the aerosol outlet. The air flow path may pass through the first heater housing. The air flow path may pass through the tubular heater. The air flow path may pass through the second heater housing. The heating unit may comprise a first sealing element. The first sealing element may be configured to seal the first heater housing relative to the tubular heater. The heating unit may comprise a second sealing element. The second sealing element may be configured to seal the second heater housing relative to the tubular heater. The first sealing element may be separated from the airflow path. The second sealing element may be separated from the airflow path.

According to an example of the present invention, a heating unit for an aerosol generating device is proposed. The heating unit comprises: a first heater housing comprising an air inlet; a second heater housing comprising an aerosol outlet; a tubular heater for heating an aerosol-forming substrate for generating an aerosol; and an air flow path passing through the heating unit from the air inlet to the aerosol outlet, wherein the air flow path passes through the first heater housing, the tubular heater, and the second heater housing. The heating unit further comprises a first sealing element configured to seal the first heater housing relative to the tubular heater; and a second sealing element configured to seal the second heater housing relative to the tubular heater. The first and second sealing elements are separated from the air flow path.

The first and second sealing elements provide a seal around the tubular heater, which is advantageous. This helps prevent aerosol leakage from the tubular heater into the first and second heater housings, reducing the likelihood of slurry formation in the first and second heater housings and the formation of unwanted byproducts. Furthermore, the first and second sealing elements are separated from the airflow path, preventing contact between the heated aerosol, air, and the sealing element. This helps reduce the likelihood of aerosol damage to the sealing elements and the potential release of unwanted byproducts. Furthermore, the sealing elements limit the entry of unwanted byproducts into the aerosol or airflow in the airflow path. Furthermore, the first and second sealing elements are separated from the airflow path to prevent contact between the aerosol and the first and second sealing elements. This helps prevent aerosol damage to the sealing elements and reduces the likelihood of any substances released from the sealing elements entering the airflow path. Another advantage of the first and second sealing elements providing a seal around the tubular heater is that it helps reduce the leakage of heated aerosol and air from the tubular heater, which improves the energy efficiency of the heating unit.

In the context of this document, when determining the location of the first and second sealing elements relative to the airflow path, the term "separated" means that there is a physical partition between the sealing elements and the airflow path. For example, a tubular heater may act as a physical partition between the first and second sealing elements and the airflow path, i.e., a wall of the tubular heater may be located between the first and second sealing elements and the airflow path. Furthermore, the first and second heater housings or the interface between the first and second heater housings and the tubular heater may act as a physical partition between the first and second sealing elements and the airflow path.

The first sealing element may comprise an annular seal. The first sealing element may be located between the inner surface of the first heater housing and the outer surface of the tubular heater. In this arrangement, the first sealing element is located on the opposite side of the tubular heater from the airflow path, so that the tubular heater acts as a physical barrier between the first sealing element and the airflow path, which is advantageous.

The second sealing element may comprise an annular seal. The second sealing element may be positioned between the inner surface of the second heater housing and the outer surface of the tubular heater. In this arrangement, the second sealing element is positioned on the opposite side of the tubular heater from the airflow path, so that the tubular heater acts as a physical barrier between the second sealing element and the airflow path, which is advantageous.

At least one of the first and second sealing elements can be located in a groove or recess formed in the inner surface of the corresponding one of the first and second heater casings. The first sealing element can be located in a groove or recess formed in the inner surface of the first heater casing. The second sealing element can be located in a groove or recess formed in the inner surface of the second heater casing. The first end of the tubular heater can be located in a groove or recess formed in the inner surface of the first heater casing. The second end of the tubular heater can be located in a groove or recess formed in the inner surface of the second heater casing. The groove provides an effective way to hold the sealing element in place and also helps protect the sealing element, which is an advantage. The groove provides an effective way to hold the tubular heater in place, which is an advantage.

The first heater housing may include a tube holder for supporting the tubular heater. An airflow path may extend through the tube holder. The tube holder provides an effective means of supporting the tubular heater. The tube holder also facilitates separation of the tubular heater from the rest of the first heater housing for thermal insulation or isolation of the rest of the first heater housing from the relatively high temperatures reached by the tubular heater.

The first sealing element may be positioned between the tube holder and the outer surface of the tubular heater. This arrangement facilitates a seal between the tube holder component of the first heater housing and the tubular heater.

The first and second sealing elements may comprise opposing end sections of a tubular heater. The opposing end sections may be secured in a sealing manner to the inner surfaces of the first and second heater housings. In this arrangement, the interface between the first and second heater housings and the tubular heater acts as a physical barrier between the first and second sealing elements and the airflow path, which is advantageous. That is, the sealing fit of the opposing end sections of the tubular heater to the inner surfaces of the first and second heater housings helps seal the airflow path and protect the opposing end sections.

Opposite end sections of the tubular heater can be sealingly secured within grooves or recesses formed in the inner surfaces of the first and second heater housings. In this arrangement, the portions of the first and second heater housings around the grooves or recesses act as a physical barrier between the opposite end sections of the tubular heater and the airflow path, preventing aerosol from coming into contact with the sealing elements, which is advantageous.

Opposite end sections of the tubular heater can be embedded into the inner surfaces of the first and second heater housings. In this arrangement, the portions of the first and second heater housings surrounding the embedded opposite end section of the tubular heater act as a physical barrier between the opposite end sections of the tubular heater and the airflow path, preventing aerosol from coming into contact with the sealing elements, which is advantageous.

The first and second heater shells may be sealed or joined to opposite end sections of the tubular heater by one or more of the following processes: insert casting, overmolding, melt deposition, high frequency welding, and ultrasonic welding.

The opposite end sections of the tubular heater have a machined surface quality with an ISO roughness value in the range of N9 to N12. The surface roughness can be determined in accordance with the surface roughness specifications set out in ISO 1302 and, in particular, ISO 1302:1992. The surface roughness of the opposite end sections can be achieved by any suitable manufacturing or machining process, including, but not limited to, abrasive abrasion, casting, coating, cutting, etching, plastic deformation, sintering, wear, and erosion.

In arrangements in which the first and second sealing elements comprise opposite end sections of a tubular heater, the heating assembly may further comprise a third sealing element configured to further seal the first heater housing relative to the tubular heater. The heating assembly may further comprise a fourth sealing element configured to further seal the second heater housing relative to the tubular heater. This arrangement helps provide an additional degree of sealing of the airflow path, which is advantageous.

The third sealing element may comprise an annular seal. The third sealing element may be located between the inner surface of the first heater housing and the outer surface of the tubular heater. In this arrangement, the third sealing element is located on the opposite side of the tubular heater from the airflow path, so that the tubular heater acts as a physical barrier between the third sealing element and the airflow path, which is advantageous.

The fourth sealing element may comprise an annular seal. The fourth sealing element may be located between the inner surface of the second heater housing and the outer surface of the tubular heater. In this arrangement, the fourth sealing element is located on the opposite side of the tubular heater from the airflow path, so that the tubular heater acts as a physical barrier between the fourth sealing element and the airflow path, which is advantageous.

In one example, the tubular heater may be enclosed by first and second heater housings. This arrangement may help prevent aerosol leakage from the airflow path into the aerosol-generating device, which is advantageous.

In another example, the heating unit may further comprise a heater sleeve surrounding at least a portion of the tubular heater, wherein the heater sleeve is positioned between the first and second heater housings. The heater sleeve may help prevent aerosol leakage from the airflow path into the aerosol-generating device.

The first sealing element may be positioned against the inner surface of the first heater housing, the outer surface of the tubular heater, and the inner or end surface of the heater sleeve. This arrangement may help ensure a sealing fit between the first heater housing, the tubular heater, and the heater sleeve to seal the airflow path.

The second sealing element may be positioned against the inner surface of the second heater housing, the outer surface of the tubular heater, and the inner or end surface of the heater sleeve. This arrangement may help ensure a sealing fit between the second heater housing, the tubular heater, and the heater sleeve to seal the airflow path.

The first and second heater shells can be radially spaced from the tubular heater, creating a hollow air space around the tubular heater. The hollow air space helps provide thermal insulation for the tubular heater, which reduces heat loss from the tubular heater and also helps reduce heat transfer to the outside of the heating unit, which is an advantage.

The first and second heater housings may be made of any suitable material. Preferably, the first and second heater housings are made of a heat-resistant plastic capable of withstanding temperatures of at least 250 degrees Celsius, preferably at least 300 degrees Celsius, and more preferably at least 350 degrees Celsius. In one example, the first and second heater housings may be made of polyetheretherketone (PEEK). This material is a good thermal insulator and helps reduce heat transfer from the heating element.

The diameter of the tubular heater at the first end of the tubular heater may be larger than the diameter along the length of the tubular heater. The diameter of the tubular heater at the second end of the tubular heater may be larger than the diameter along the length of the tubular heater. The diameter of the tubular heater at each end of the tubular heater may be larger than the diameter of the tubular heater in the region between the two ends of the tubular heater. The advantage of having the diameter of one or both ends of the tubular heater larger than the diameter of the tubular heater along the length of the tubular heater, for example, in the region between the two ends of the tubular heater, is that this allows for greater manufacturing tolerances for the tubular heater and other components of the heating assembly. This may facilitate assembly of the heating assembly and reduce the number of machining or finishing steps required during the manufacture of the tubular heater.

Another advantage of having a larger end diameter for the tubular heater than other parts of the tubular heater is that the internal diameter at one or both ends of the tubular heater will be larger than the internal diameter of the airflow path in other components of the heating assembly with which the tubular heater interacts, such as the first and second heater housings. This helps prevent the end surface of the tubular heater from protruding or being compressed into the internal airflow path, which could potentially damage the aerosol-generating article when it is inserted into the tubular heater.

The outside diameter of one or both ends of the tubular heater may be up to 40 percent larger, preferably up to 35 percent larger, more preferably up to 30 percent larger, and even more preferably up to 27 percent larger than the outside diameter of the portion of the tubular heater between the two ends of the tubular heater. The outside diameter of one or both ends of the tubular heater may be larger by a value of 10 percent to 40 percent, 15 percent to 35 percent, 20 percent to 30 percent, or 25 percent to 30 percent than the outside diameter of the portion of the tubular heater between the two ends of the tubular heater.

One or both ends of the tubular heater may have an outside diameter of about 7.6 millimeters to about 10.7 millimeters, preferably about 9.0 millimeters to about 10.0 millimeters, and more preferably about 9.7 millimeters. The portion of the tubular heater between the two ends may have an outside diameter of about 6.5 millimeters to about 8.0 millimeters, preferably about 7.0 millimeters to about 8.0 millimeters, and more preferably about 7.6 millimeters.

The inner diameter of the tubular heater between the two ends of the tubular heater may substantially correspond to or be substantially equal to the outer diameter of the aerosol-generating article. In some embodiments, the inner diameter of the tubular heater may be slightly smaller than the outer diameter of the aerosol-generating article, such that the aerosol-generating article is compressed within the tubular heater. For example, the outer diameter of the aerosol-generating article may be approximately 7.4 millimeters, and the inner diameter of the tubular heater may be approximately 7.3 millimeters. The length of the tubular heater may substantially correspond to or be substantially equal to the length of the aerosol-generating substrate located in the aerosol-generating article.

A portion of the first end of the tubular heater may be flared or funnel-shaped. A portion of the second end of the tubular heater may be flared or funnel-shaped. A portion of each end of the tubular heater may be flared or funnel-shaped. The axial length of each portion of each end of the tubular heater that is flared or funnel-shaped may be from 3.5 percent to 15 percent of the total length of the tubular heater, preferably from 5 percent to 10 percent of the total length of the tubular heater, and more preferably about 8 percent of the total length of the tubular heater. The flared or funnel-shaped end portion or end portions of the tubular heater may be located at an angle of 30 to 60 degrees, 40 to 50 degrees, or at an angle of about 45 degrees relative to the longitudinal axis of the tubular heater or heating assembly.

A flared or funnel-shaped section of a tubular heater offers a convenient way to provide a tubular heater with a diameter at one or both ends that is larger than the diameter of the heater in the area between the two ends, which is advantageous. Furthermore, a flared or funnel-shaped section of a tubular heater provides a smooth transition between the larger and smaller diameters, facilitating the insertion of the aerosol-generating product into the tubular heater. Furthermore, a flared or funnel-shaped section of a tubular heater provides an improved seal for the airflow path.

In arrangements in which the tubular heater has flared or funnel-shaped end portions and in which the first and second sealing elements comprise opposite end sections of the tubular heater, the first and second sealing elements may comprise elongated sections at each end of the tubular heater that extend in a direction parallel to the longitudinal axis of the tubular heater. Each elongated section of the tubular heater may have a length of 1 to 2 millimeters and preferably about 1.5 mm. The length of each elongated section may be from 3.5 percent to 15 percent of the total length of the tubular heater, preferably from 7 percent to 12 percent of the total length of the tubular heater, and more preferably about 9 percent of the total length of the tubular heater.

The tubular heater may be made of any suitable material, including, but not limited to, ceramic, metal, or metal alloy. An example of a suitable material is stainless steel.

The heating unit may comprise at least one electric heating element for heating the aerosol-forming substrate. The heating unit may comprise multiple electric heating elements. The electric heating element or elements may be located around or encircle the outer surface of the tubular heater. The electric heating element or elements may be located around or encircle the inner surface of the tubular heater. The electric heating element or elements may be part of the tubular heater or integral with it.

The electric heating element or elements may comprise an electrically resistive material. Suitable electrically resistive materials include, but are not limited to, semiconductors such as doped ceramics, electrically conductive ceramics (such as molybdenum disilicide), carbon, graphite, metals, metal alloys, and composite materials made from a ceramic material and a metallic material. Such composite materials may comprise doped or undoped ceramics. Examples of suitable doped ceramics include doped silicon carbides. Examples of suitable metals include titanium, zirconium, tantalum, and platinum group metals. Examples of suitable metal alloys include stainless steel, alloys containing nickel, cobalt, chromium, aluminum, titanium, zirconium, hafnium, niobium, molybdenum, tantalum, tungsten, tin, gallium, manganese, gold, and iron, and superalloys based on nickel, iron, and cobalt; stainless steel; Timetal™, Kanthal™, and other iron-chromium-aluminum alloys; and iron-manganese-aluminum alloys. In composite materials, the electrically resistive material may optionally be embedded in, encapsulated within, or coated with the insulating material, or vice versa, depending on the energy transfer kinetics and the desired external physicochemical properties.

One or more heating elements may be formed using a metal or metal alloy characterized by a specific relationship between temperature and resistivity. Heating elements formed in this manner can be used both to heat and to monitor the heating element's temperature during operation.

The heating element may be deposited within or onto a rigid carrier material or substrate. The heating element may be deposited within or onto a flexible carrier material or substrate. The heating element may be formed as a track on a suitable insulating material, such as ceramic, glass, or polyimide film. The heating element may be sandwiched between two insulating materials.

The heating unit may comprise a flexible heating element located around or surrounding the outer surface of the tubular heater. The flexible heating element may have a length substantially equal to the length of the aerosol-forming substrate located in the aerosol-generating article.

The tubular heater may be configured to accommodate at least a portion of an aerosol generating article (as defined below).

According to an example of the present invention, an aerosol-generating device is provided. The aerosol-generating device may comprise a heating unit according to any of the heating units described above. The aerosol-generating device may comprise a power source for supplying electrical power to the heating unit.

According to an example of the present invention, an aerosol-generating device is provided. The aerosol-generating device comprises a heating unit according to any of the heating units described above. The aerosol-generating device comprises a power source for supplying electrical power to the heating unit.

The power source may be any suitable power source, such as a DC power source. In one embodiment, the power source is a lithium-ion battery. Alternatively, the power source may be a nickel-metal hydride battery, a nickel-cadmium battery, or a lithium-based battery, such as a lithium-cobalt, lithium-iron phosphate, or lithium-polymer battery.

Preferably, the aerosol generating device is a hand-held aerosol generating device that is comfortably held by a user between the fingers of one hand.

The aerosol-generating device may further comprise a control circuit configured to control the supply of electrical power to the heating unit. The control circuit may comprise a microprocessor. The microprocessor may be a programmable microprocessor, a microcontroller, or an application-specific integrated circuit (ASIC), or other electronic circuit capable of providing control. The control circuit may comprise additional electronic components. For example, in some embodiments, the control circuit may comprise any of sensors, switches, and display elements. Power may be supplied to the heating unit continuously upon activation of the device, or may be supplied intermittently, such as from puff to puff. Power may be supplied to the heating unit in the form of pulses of electrical current, such as by pulse-width modulation (PWM).

An aerosol-generating device may comprise a device housing. The device housing may contain a heating element, a power source, and a control circuit. The housing may comprise an opening for accommodating an aerosol-generating article. The opening may be connected to an aerosol outlet of a second heater housing of the heating element to allow insertion of the aerosol-generating article into the tubular heater. The housing may comprise an air inlet. The air inlet may be connected to the air inlet of the first heater housing of the heating element.

The housing may comprise any suitable material or combination of materials. Examples of suitable materials include metals, alloys, plastics, or composites containing one or more of these materials, or thermoplastics suitable for food or pharmaceutical applications, such as polypropylene, polyetheretherketone (PEEK), and polyethylene. The material is preferably lightweight and non-brittle.

According to one example of the present invention, an aerosol-generating system is provided. The aerosol-generating system may comprise an aerosol-generating device according to any of the aerosol-generating devices described above. The aerosol-generating system may comprise an aerosol-generating article comprising an aerosol-forming substrate.

According to one example of the present invention, an aerosol-generating system is provided. The aerosol-generating system comprises an aerosol-generating device according to any of the aerosol-generating devices described above. The aerosol-generating system comprises an aerosol-generating article comprising an aerosol-forming substrate.

As used herein, the term "aerosol-generating article" refers to an article containing an aerosol-forming substrate that, when heated in an aerosol-generating device, releases volatile compounds that can form an aerosol. The aerosol-generating article is separate from the aerosol-generating device and is designed to be combined with it to heat the aerosol-generating article.

The aerosol-generating article may be substantially cylindrical in shape. The aerosol-generating article may be substantially elongated. The aerosol-generating substrate may be substantially cylindrical in shape. The aerosol-generating substrate may be substantially elongated.

The aerosol-generating article may have an overall length of approximately 30 mm to approximately 100 mm. The aerosol-generating article may have an outer diameter of approximately 5 mm to approximately 12 mm. The aerosol-generating substrate may have a length of approximately 10 mm to approximately 18 mm. Furthermore, the diameter of the aerosol-generating substrate may be from approximately 5 mm to approximately 12 mm. The aerosol-generating article may comprise a filter plug. The filter plug may be located at the downstream end of the aerosol-generating article. The filter plug may be a cellulose acetate filter plug. In one embodiment, the filter plug has a length of approximately 7 mm, but may have a length of from approximately 5 mm to approximately 12 mm.

The terms "upstream," "downstream," "proximal," and "distal" are used to describe the relative positions of components or component parts of an aerosol-generating device and an aerosol-generating article. The aerosol-generating articles and devices of the present invention have a proximal end through which, during use, the aerosol exits the article or device for delivery to the user, and an opposite distal end. The proximal end of an aerosol-generating article or device may also be referred to as a mouthpiece end. During use, the user draws on the proximal end of the aerosol-generating article to inhale the aerosol generated by the article or device. The terms "upstream" and "downstream" refer to the direction of aerosol movement through an aerosol-generating article or aerosol-generating device when a user draws on the near end of the aerosol-generating article. The near end of the aerosol-generating article is located downstream relative to the distal end of the aerosol-generating article. The near end of the aerosol-generating article may also be referred to as the downstream end of the aerosol-generating article, and the distal end of the aerosol-generating article may also be referred to as the upstream end of the aerosol-generating article.

In one embodiment, the aerosol-generating article may have an overall length of approximately 45 mm. The aerosol-generating article may have an outer diameter of approximately 7.3 mm, but may have an outer diameter from approximately 7.0 mm to approximately 7.4 mm. In addition, the aerosol-generating substrate may have a length of approximately 12 mm. Alternatively, the aerosol-generating substrate may have a length of approximately 16 mm. The aerosol-generating article may comprise an outer paper wrapper. Furthermore, the aerosol-generating article may comprise a gap between the aerosol-generating substrate and the filter plug. The gap may be approximately 21 mm or approximately 26 mm, but may range from approximately 5 mm to approximately 28 mm. The gap may be provided by a hollow tube. The hollow tube may be made of cardboard or cellulose acetate.

The aerosol-forming substrate may be a solid aerosol-forming substrate. Alternatively, the aerosol-forming substrate may contain both solid and liquid components. The aerosol-forming substrate may comprise a tobacco-containing material containing volatile tobacco flavor compounds that are released from the substrate upon heating. Alternatively, the aerosol-forming substrate may comprise a non-tobacco material. The aerosol-forming substrate may further comprise an aerosol-forming agent. Examples of suitable aerosol-forming agents include glycerin and propylene glycol.

If the aerosol-forming substrate is a solid aerosol-forming substrate, the solid aerosol-forming substrate may contain, for example, one or more of the following: powder, granules, beads, pellets, thin tubes, strips, or sheets containing one or more of the following: grass leaves, tobacco leaves, tobacco rib fragments, reconstituted tobacco, homogenized tobacco, extruded tobacco, and expanded tobacco. The solid aerosol-forming substrate may be in bulk form or may be provided in a suitable container or cartridge. Optionally, the solid aerosol-forming substrate may contain additional tobacco or non-tobacco volatile flavor compounds intended to be released upon heating of the substrate. The solid aerosol-forming substrate may also contain capsules that, for example, contain additional tobacco or non-tobacco volatile flavor compounds, and such capsules may melt during heating of the solid aerosol-forming substrate.

As used herein, the term "homogenized tobacco" refers to a material formed by agglomerating loose tobacco. The homogenized tobacco may be in the form of a sheet. The homogenized tobacco material may contain more than 5% of the aerosol-forming substance on a dry weight basis. Alternatively, the homogenized tobacco material may contain from 5% to 30% by weight of the aerosol-forming substance on a dry weight basis. Sheets of homogenized tobacco material may be formed by agglomerating loose tobacco obtained by grinding or otherwise comminuting one or both of the lamina and stems of the tobacco leaf. Alternatively or additionally, the sheets of homogenized tobacco material may contain one or more of tobacco dust, tobacco fines, and other loose tobacco by-products generated, for example, during the processing, handling, and shipping of tobacco. The sheets of homogenized tobacco material may contain one or more internal binders, i.e., tobacco endogenous binders, one or more external binders, i.e., tobacco exogenous binders, or a combination thereof, to promote agglomeration of the bulk tobacco; and alternatively or additionally, the sheets of homogenized tobacco material may contain other additives, including, without limitation, tobacco and non-tobacco fibers, aerosol forming agents, humectants, plasticizers, flavoring agents, fillers, aqueous and non-aqueous solvents, and combinations thereof.

In a particularly preferred embodiment, the aerosol-forming substrate comprises an assembled corrugated sheet of homogenized tobacco material. As used herein, the term "corrugated sheet" refers to a sheet having a plurality of substantially parallel folds or corrugations. Preferably, when the aerosol-generating article is assembled, the substantially parallel folds or corrugations extend along or parallel to the longitudinal axis of the aerosol-generating article. This simplifies the assembly of the corrugated sheet of homogenized tobacco material to form the aerosol-forming substrate, which is advantageous. However, it should be noted that corrugated sheets of homogenized tobacco material for inclusion in an aerosol-generating article may alternatively or additionally have a plurality of substantially parallel folds or corrugations that are located at an acute or obtuse angle to the longitudinal axis of the aerosol-generating article when the aerosol-generating article is assembled. In some embodiments, the aerosol-forming substrate may comprise an assembled sheet of homogenized tobacco material that is substantially uniformly textured across substantially its entire surface. For example, the aerosol-forming substrate may comprise an assembled corrugated sheet of homogenized tobacco material that comprises a plurality of substantially parallel folds or corrugations that are substantially uniformly spaced across the width of the sheet.

Optionally, the solid aerosol-forming substrate may be provided on or embedded in a thermally stable carrier. The carrier may be in the form of a powder, granules, beads, chips, thin tubes, strips, or sheets. Alternatively, the carrier may be a tubular carrier having a thin layer of the solid substrate deposited on its inner surface, its outer surface, or both its inner and outer surfaces. Such a tubular carrier may be made, for example, of paper or a paper-like material, a nonwoven carbon fiber mat, a lightweight open-cell metal mesh, or perforated metal foil, or any other thermally stable polymer matrix.

The solid aerosol-forming substrate can be applied to the carrier surface in the form of, for example, a sheet, foam, gel, or suspension. The solid aerosol-forming substrate can be applied to the entire surface of the carrier or, alternatively, can be applied in a pattern to ensure non-uniform delivery of the flavor additive during use.

Although solid aerosol-forming substrates are mentioned above, one skilled in the art will appreciate that other embodiments may utilize other forms of aerosol-forming substrate. For example, the aerosol-forming substrate may be a liquid aerosol-forming substrate. In the case of a liquid aerosol-forming substrate, the aerosol-generating device preferably includes means for retaining the liquid. For example, the liquid aerosol-forming substrate may be retained in a container or liquid storage portion. Alternatively, or additionally, the liquid aerosol-forming substrate may be absorbed in a porous carrier material. The porous carrier material may be made of any suitable absorbent plug or component, such as foamed metal or plastic material, polypropylene, terylene, nylon fibers, or ceramic. The liquid aerosol-forming substrate may be retained in a porous carrier material prior to use of the aerosol-generating device, or, alternatively, the liquid aerosol-forming substrate material may be released into the porous carrier material during or immediately prior to use. For example, the liquid aerosol-forming substrate may be provided in a capsule. The capsule shell preferably melts upon heating and releases the liquid aerosol-forming substrate into the porous carrier material. The capsule may optionally contain a solid in combination with a liquid.

Alternatively, the carrier may be a nonwoven fabric or fiber bundle incorporating tobacco components. The nonwoven fabric or fiber bundle may contain, for example, carbon fibers, natural cellulose fibers, or fibers made from cellulose derivatives.

The features described in relation to one of the above examples may be equally applied to other examples of the present invention.

The present invention is defined in the claims. However, a non-exhaustive list of non-limiting examples is provided below. Any one or more features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

Example 1. A heating unit for an aerosol generating device comprising: a heating chamber for heating an aerosol-forming substrate; an air inlet and an aerosol outlet; wherein an air flow path passes through the heating unit from the air inlet to the aerosol outlet, wherein the air flow path passes through the heating chamber.

Example 2. The heating unit according to example 1, further comprising a first heater housing, wherein the first heater housing comprises an air inlet.

Example 3. A heating unit according to any of examples 1 or 2, further comprising a second heater housing, wherein the second heater housing comprises an outlet for an aerosol.

Example 4. A heating unit according to any of examples 1-3, further comprising a first sealing element configured to seal the first heater casing relative to the heating chamber.

Example 5. A heating unit according to any of examples 1-4, further comprising a second sealing element configured to seal the second heater casing relative to the heating chamber.

Example 6. The heating unit according to example 5, wherein the first and second sealing elements are separated from the air flow path.

Example 7. A heating unit according to any one of examples 3-6, wherein the air flow path passes through the first heater housing, the heating chamber and the second heater housing.

Example 8. A heating unit according to any of examples 4-7, wherein the first sealing element comprises an annular seal and is located between the inner surface of the first heater casing and the outer surface of the heating chamber.

Example 9. A heating unit according to any of examples 5-8, wherein the second sealing element comprises an annular seal and is located between the inner surface of the second heater casing and the outer surface of the heating chamber.

Example 10. A heating unit according to any one of examples 5-9, in which at least one of the first and second sealing elements is located in a groove or recess formed in the inner surface of a corresponding one of the first and second heater housings.

Example 11. A heating unit according to any one of examples 2-10, wherein the first heater housing comprises a holder for holding the heating chamber, and the air flow path passes through the holder.

Example 12. The heating unit according to example 11, in which the first sealing element is located between the holder and the outer surface of the heating chamber.

Example 13. The heating unit according to example 5, in which the first and second sealing elements comprise opposite end sections of the heating chamber, wherein the opposite end sections are secured with a sealing fit to the inner surfaces of the first and second heater casings.

Example 14. The heating unit of example 13, wherein the opposite end sections of the heating chamber are secured in a sealing fit within grooves or recesses formed in the inner surfaces of the first and second heater housings.

Example 15. The heating unit according to example 13, in which the opposite end sections of the heating chamber are built into the inner surfaces of the first and second heater housings.

Example 16. A heating unit according to any of examples 13-15, wherein the opposite end sections extend in a direction parallel to the longitudinal axis of the heating chamber for a length of from 5 percent to 15 percent of the total length of the heating chamber.

Example 17. A heating unit according to example 13, wherein the opposite end sections of the heating chamber have a machined surface quality with an ISO roughness value in the range from N9 to N12.

Example 18. A heating unit according to any of examples 13-17, further comprising a third sealing element configured to further seal the first heater casing relative to the heating chamber.

Example 19. A heating unit according to any of examples 13-18, further comprising a fourth sealing element configured to further seal the second heater casing relative to the heating chamber.

Example 20. A heating unit according to any of examples 18 or 19, wherein the third sealing element comprises an annular seal and is located between the inner surface of the first heater casing and the outer surface of the heating chamber.

Example 21. A heating unit according to any of examples 18-20, wherein the fourth sealing element comprises an annular seal and is located between the inner surface of the second heater casing and the outer surface of the heating chamber.

Example 22. A heating unit according to any of examples 3-21, wherein the heating chamber is enclosed by first and second heater housings.

Example 23. A heating unit according to any one of examples 3-21, further comprising a heater sleeve surrounding at least a portion of the heating chamber, wherein the heater sleeve is located between the first and second heater housings.

Example 24. The heating unit according to example 23, in which the first sealing element is adjacent to the inner surface of the first heater casing, the outer surface of the heating chamber and the inner or end surface of the heater sleeve.

Example 25. A heating unit according to example 23 or 24, wherein the first sealing element is adjacent to the inner surface of the second heater casing, the outer surface of the heating chamber and the inner or end surface of the heater sleeve.

Example 26. A heating unit according to any one of examples 1-25, wherein the diameter of the heating chamber at each end of the heating chamber is greater than the diameter of the heating chamber in the region between the two ends of the heating chamber.

Example 27. A heating unit according to example 26, wherein a portion of each end of the heating chamber is flared or funnel-shaped.

Example 28. The heating unit of example 27, wherein the axial length of the flared or funnel-shaped end of the heating chamber is from 5 percent to 15 percent of the total length of the heating chamber.

Example 29. A heating unit according to any of examples 1-28, wherein the heating chamber comprises a tubular heater.

Example 30. An aerosol generating device comprising: a heating unit according to any one of examples 1-29; and a power source for supplying electrical power to the heating unit.

Example 31. An aerosol generating system comprising: an aerosol generating device according to example 30; and an aerosol generating article containing an aerosol forming substrate.

Below, the examples will be further described with reference to the drawings, in which:

Fig. 1 is a schematic sectional view showing the inside of an aerosol generating device according to an example of the present invention and an aerosol generating article housed inside the aerosol generating device;

Fig. 2 is a sectional view of a portion of an aerosol generating device having a heating unit according to an example of the present invention;

Fig. 3 is an enlarged schematic sectional view of the sealing device designated A in Fig. 2;

Fig. 4 is a sectional view of a heating unit according to another example of the present invention;

Fig. 5 is an enlarged schematic sectional view of the sealing device designated E in Fig. 4;

Fig. 6 is a side view of an illustrative tubular heater for use in a heating assembly according to the present invention;

Fig. 7 is a sectional view of a heating unit according to another example of the present invention;

Fig. 8 is a side view of another illustrative tubular heater for use in a heating assembly according to the present invention; and

Fig. 9 is a sectional view of a heating unit according to another example of the present invention.

Fig. 1 shows a schematic cross-sectional view of the interior of an aerosol-generating device 100 and an aerosol-generating article 200 located inside the aerosol-generating device 100. Together, the aerosol-generating device 100 and the aerosol-generating article 200 form an aerosol-generating system. In Fig. 1, the aerosol-generating device 100 is shown in a simplified form. In particular, the elements of the aerosol-generating device 100 are not shown to scale. In addition, elements that are not essential for understanding the aerosol-generating device 100 have been omitted.

The aerosol generating device 100 comprises a housing 102 containing a heating unit 10, a power source 103, and a control circuit 105. The heating unit 10 comprises a first heater housing 12, a second heater housing 14, and a tubular heater 16 for heating an aerosol-forming substrate. The tubular heater 16 forms at least partially a cavity for accommodating a portion of an aerosol-generating article 200 and has a flexible heating element (not shown) located around its outer surface for heating the tubular heater 16 and, in turn, the aerosol-generating article 200. The power source 103 comprises a battery, and in this example, is a rechargeable lithium-ion battery. The control circuit 105 is connected to both the power source 103 and the heating element (not shown) and controls the supply of electrical energy from the power source 103 to the heating element to regulate the temperature of the heating element.

The first heater housing 12 is attached to the second heater housing 14, and together they surround or enclose the tubular heater 16 to prevent leakage of the aerosol generated inside the tubular heater 16 into the aerosol generating device 100. The heating unit 10 further comprises a first sealing element (not shown in Fig. 1) configured to seal the first heater housing 12 relative to the tubular heater 16, and a second sealing element (not shown in Fig. 1) configured to seal the second heater housing 14 relative to the tubular heater 16. The first and second sealing elements help to further prevent leakage of the aerosol from the tubular heater 16 into the aerosol generating device 100, and various sealing arrangements are discussed in more detail below.

The first heater housing 12 comprises an air duct section 12a and a support section 12b. The air duct section 12a extends parallel to the longitudinal axis of the aerosol generating device 100 from the distal end of the aerosol generating device 100 to the support section 12b. The support section 12b is configured to support the tubular heater 16 and to be attached to the second heater housing 14. The air inlet 18 is located at the distal end of the air duct section 12a of the first heater housing 12. The air inlet 18 is connected to the opening 106 formed at the distal end of the housing 102. Air can enter the aerosol generating device 10 through the opening 106 and the air inlet 18 and flow through the air duct section 12a to the tubular heater 16.

The outlet opening 20 for the aerosol is located at the near end of the second casing 14 of the heater. The outlet opening 20 for the aerosol is connected to the opening 104 formed at the near end of the housing 102. The opening 104 is also connected to the inside of the tubular heater 16, and the article 200 generating the aerosol can be placed in the tubular heater 16 through the opening 104. The article 200 generating the aerosol is longer than the cavity formed partially by the tubular heater 16 inside the device 100 generating the aerosol, and, therefore, the near or mouthpiece end of the article 200 generating the aerosol protrudes from the device 100 generating the aerosol when the article 200 generating the aerosol is completely inserted.

The air flow path (indicated by a plurality of arrows 22 in Fig. 1) passes through the heating unit 10 from the air inlet 18 to the aerosol outlet 20 and passes through the first heater housing 12, the tubular heater 16 and the second heater housing 14. The aerosol exits the heating unit 10 through the aerosol outlet 20 connected to the opening 104 in the housing 102. However, it will be understood that during use, the aerosol mainly exits from the heating unit 10 and the aerosol generating device 100 through the aerosol generating article 200, when the aerosol generating article is placed in the aerosol generating device 100.

In this example, the aerosol-generating article 200 comprises an end plug 202, an aerosol-forming substrate 204, a hollow tube 206, and a mouthpiece filter 208. Each of the aforementioned components of the aerosol-generating article 100 is a substantially cylindrical element, each of which has a substantially identical diameter. The components are arranged sequentially in adjacent coaxial alignment and are surrounded by an outer paper wrapper 210 to form a cylindrical rod. The aerosol-forming substrate 204 is a tobacco rod or plug comprising an assembled sheet of corrugated homogenized tobacco material surrounded by a wrapper (not shown). The corrugated sheet of homogenized tobacco material contains glycerin as an aerosol-forming agent. The end plug 202 and the mouthpiece filter 208 are formed from cellulose acetate fibers. The aerosol-forming substrate 204 is located in the aerosol-generating article 200, so that when the aerosol-generating article 200 is fully inserted into the aerosol-generating device 100, the aerosol-forming substrate 204 is located within the tubular heater 16 for heating the aerosol-forming substrate 204. It should be understood that another aerosol-generating article with different components or a different arrangement of components can also be used.

The aerosol generating device 100 may further comprise: a sensor (not shown) for detecting the presence of the aerosol generating article 200; a user interface (not shown), such as a button for activating a heating element; and a display or indicator (not shown) for providing information to the user, such as the remaining battery charge, heating status, and error messages.

During use, the user inserts the aerosol-generating article 200 into the aerosol-generating device 100, as shown in Fig. 1. The user then initiates a heating cycle by activating the aerosol-generating device 100, for example, by pressing a switch to turn on the device. In response, the control circuit 105 controls the supply of electric power from the power source 103 to the heating element (not shown) to heat the heating element, which, in turn, heats the tubular heater 16. During the heating cycle, the heating element heats the tubular heater 16 to a predetermined temperature or to a range of predetermined temperatures according to a temperature profile. The heating cycle can last about 6 minutes. The heat from the tubular heater 16 is transferred to the aerosol-generating substrate 204, which releases volatile compounds from the aerosol-generating substrate 204. Volatile compounds form an aerosol inside the aerosol generation chamber formed by the hollow tube 206. During the heating cycle, the user places the filter 208 of the mouthpiece of the aerosol-generating article 200 between the lips of his mouth and takes a puff or inhales through the filter 208 of the mouthpiece. This causes a pressure drop inside the aerosol-generating article 200, which is in fluid communication with the air inlet 18 and the opening 106 of the aerosol-generating device 100 through the air channel section 12a of the first heater housing 12. The pressure drop ensures that air is drawn into the aerosol-generating device 100 through the air inlet 18 and flows through the air channel section 12a into the aerosol-generating article 200. Air passes through the aerosol generating article 200, capturing the aerosol generated from the aerosol forming substrate 204, which is then drawn through the mouthpiece filter 208 into the user's mouth.

Fig. 2 is a sectional view of a portion of an aerosol generating device 300 having a heating unit 310 according to an example of the present invention. The aerosol generating device 300 of Fig. 2 has a general configuration similar to the aerosol generating device 100 of Fig. 1. The heating unit 310 comprises a first heater housing 312, a second heater housing 314, and a tubular heater 316 for heating an aerosol-forming substrate located inside the tubular heater 316. The tubular heater 316 has a flexible heating element 317 located around its outer surface for heating the tubular heater 316.

In the exemplary heating unit 310 of Fig. 2, the first heater housing comprises a tube holder 319 for holding a tubular heater 316. The tube holder 319 facilitates the positioning of the tubular heater 316 within the heating unit 310. An air channel 321 of the holder passes axially through the tube holder 319 to allow air to flow through the tube holder 319. The first heater housing 312 is attached to the second heater housing 314, and together the first 312 and second 314 heater housings enclose the tubular heater 316 and the tube holder 319 to prevent the aerosol generated within the tubular heater 316 from leaking into the aerosol generating device 300. The walls of the second heater housing 314 are radially spaced from the tubular heater 316 to form an air space 323 around the tubular heater 316. The air space 323 helps to insulate the tubular heater 316, which helps to reduce heat loss from the tubular heater 316, and also helps to reduce heat transfer to the outside of the heating unit 310 and the aerosol generating device 300.

The first heater housing 312 comprises an air duct section 312a and a support section 312b. The support section 312b is configured to be attached to the second heater housing 314. An air inlet (not shown) is located at the distal end of the air duct section 12a. An aerosol outlet 320 is located at the near end of the second heater housing 314 and is connected to an opening 304 formed at the near end of the housing 302 of the aerosol generating device 300. An aerosol generating article (not shown) may be placed in the tubular heater 316 through the opening 304. An air flow path (indicated by a plurality of arrows 322 in Fig. 2) passes through the heater assembly 310 from the air inlet (not shown) to the aerosol outlet 320 and passes through the first heater housing 312, including the tube holder 319, the tubular heater 316 and the second heater housing 314.

The heating unit 310 further comprises a first sealing element 326 that seals the tubular heater 316 relative to the tube holder 319 of the first heater housing 312. The first sealing element 326 comprises a sealing ring that surrounds the tubular heater 316 near the distal end of the tubular heater 316. The sealing ring contacts the outer surface of the tubular heater 316 and the tube holder 319 of the first heater housing 312 to provide a seal between these two components that prevents aerosol from leaking from the tubular heater 316 into the air space 323 surrounding the tubular heater 316 or other parts of the aerosol generating device 300. The areas sealed by the first sealing element are indicated by circles C and D in Fig. 2.

The heating unit 310 further comprises a second sealing element 324 that seals the tubular heater 316 relative to the second heater housing 314. The second sealing element 324 comprises a sealing ring that surrounds the tubular heater 316 near the near end of the tubular heater 316. The sealing ring contacts the outer surface of the tubular heater 316 and the inner surface of the second heater housing 314 to provide a seal between these two components that prevents aerosol from leaking from the tubular heater 316 into the air space 323 surrounding the tubular heater 316 or other parts of the aerosol generating device 300. The areas sealed by the second sealing element are indicated by circles A and B in Fig. 2.

The sealing rings of the first 326 and second 324 sealing elements are preferably formed from a perfluoroelastomer, such as FFKM, due to its elastic deformation properties, heat resistance, and low toxicity. Suitable sealing rings are Kalrez™ sealing rings from DuPont. However, other suitable sealing rings and materials may be used.

Fig. 3 is an enlarged schematic sectional view of the circled area designated A in Fig. 2, which is sealed by the second sealing element 324. The tubular heater 316 has a flared near end 316a, as described in more detail below with respect to Fig. 6. The inner surface of the second heater housing 314 contains a recess or groove 328 for receiving the flared near end 316a of the tubular heater 316. The second sealing element 324 is also located in the groove 328 and fits against the inner surface of the groove 328 and the outer surface of the tubular heater 316 to prevent aerosol leakage from the tubular heater 316 into the air space 323 between the tubular heater 316 and the second heater housing 314. The second sealing element 324 is located on the side of the tubular heater 316 opposite to where the air flow path 322 passes through the tubular heater 316, so that the walls of the tubular heater 316 act as a physical partition between the second sealing element 324 and the air flow path, which holds the second sealing element separate from the air flow path 322.

As described above with respect to Fig. 2, the second sealing element comprises a sealing ring and surrounds the outer surface of the tubular heater 316 in the region of the flared near end 316a, and therefore the mirror image of Fig. 3 will be visible in the circled area designated B in Fig. 2. A groove arrangement similar to that shown in Fig. 3 is also provided in the tube holder 319 of the first heater casing 312 at the far end of the tubular heater 316, that is, in the circled areas designated C and D in Fig. 2.

Fig. 4 shows a sectional view of a heating unit 410 according to another example of the present invention. The heating unit 410 of Fig. 4 has a general configuration similar to the heating units 10 and 310 of Fig. 1 and 2, respectively. The heating unit 410 comprises a first heater housing 412, a second heater housing 414, and a tubular heater 416 for heating an aerosol-forming substrate located inside the tubular heater 416. However, in the example of Fig. 4, the first heater housing 412 is not directly connected to the second heater housing 414, but instead, a heater sleeve 430 is located between the first 412 and second 414 heater housings. The heater sleeve 430 circumferentially surrounds substantially the entire length of the tubular heater 416, except for the two ends of the tubular heater 416, which are located inside the first 412 and second 414 heater housings.

Furthermore, in the example of Fig. 4, the tubular heater 416 is supported directly on top of the first heater housing 412, although a tube holder may be used if necessary, as in the example of Fig. 2. An air flow path (indicated by a plurality of arrows 422 in Fig. 4) passes through the heater assembly 410 from the air inlet 418 at the far end of the first heater housing 312 to the aerosol outlet 420 at the near end of the second heater housing 414 and passes through the first heater housing 412, the tubular heater 416 and the second heater housing 414.

The heating unit 410 further comprises a first sealing element 426 that seals the tubular heater 416 relative to the first heater casing 412 and the heater sleeve 430. The first sealing element 326 comprises a sealing ring that surrounds the tubular heater 416 near the distal end of the tubular heater 416. The sealing ring contacts the outer surface of the tubular heater 416, the inner surface of the first heater casing 412 and the surface of the distal end of the heater sleeve 430 to provide a seal between these components that prevents aerosol leakage from the heating unit 410 into the surrounding parts of the aerosol generating device 300.

The heating unit 410 further comprises a second sealing element 424 that seals the tubular heater 416 relative to the second heater casing 414 and the heater sleeve 430. The second sealing element 324 comprises a sealing ring that surrounds the tubular heater 416 near the near end of the tubular heater 416. The sealing ring contacts the outer surface of the tubular heater 416, the inner surface of the second heater casing 414 and the surface of the near end of the heater sleeve 430 to provide a seal between these components that prevents aerosol leakage from the heating unit 410 into the surrounding parts of the aerosol generating device 300.

The same materials that are used for the sealing rings of the first 326 and second 324 sealing elements of Fig. 2 can be used for the sealing rings of the first 426 and second 424 sealing elements of Fig. 4.

In Fig. 5 there is shown an enlarged schematic sectional view of the circled area designated E in Fig. 4, which is sealed by the second sealing element 424. As in the example of Fig. 3, the tubular heater 416 of Fig. 5 has a flared near end 416a. The inner surface of the second heater housing 414 and the surface of the near end of the heater sleeve 430 form a recess or groove 428 for receiving the flared near end 416a of the tubular heater 416. The second sealing element 424 is also located in the groove 428 and fits against the inner surface of the groove 428 and the outer surface of the tubular heater 416 to prevent aerosol from leaking from the tubular heater 416 into the air space 423 between the tubular heater 416 and the heater sleeve 430. The second sealing element 424 is located on the side of the tubular heater 416 opposite to where the air flow path 422 passes through the tubular heater 416, so that the walls of the tubular heater 416 act as a physical partition between the second sealing element 424 and the air flow path 422, which keeps the second sealing element 424 separate from the air flow path 422. A groove arrangement similar to that shown in Fig. 5 is also provided in the first heater housing 412 at the far end of the tubular heater 416.

Fig. 6 shows a side view of an illustrative tubular heater 16 for use in a heating unit according to the present invention. The tubular heater 16 comprises a stainless steel tube having a circular cross-section. A hollow internal space inside the tubular heater 16 has an internal diameter substantially corresponding to the external diameter of an aerosol-generating article, so that the tubular heater 16 can receive an aerosol-generating article (not shown) inside the internal space. A portion 16a of the tubular heater 16 at each end of the tubular heater 16 is flared outward to form a funnel-shaped form at each end of the tubular heater 16. Each of the flared portions 16a has a length l ₁ , and the percentage of the total length l of the tubular heater 16 that each length l ₁ of the flared portions constitutes can be in the range of 5 to 15 percent. Each of the flared end portions 16a of the tubular heater 16 forms an angle θ with the longitudinal axis of the tubular heater 16. In this example, θ is approximately 45 degrees, but other suitable angles can be used. Due to the flared end portions 16a, the outer diameter D at the two ends of the tubular heater 16 is larger than the outer diameter d of the tubular heater 16 between the two flared end portions 16a.

The portion 16b of the tubular heater 16 between the two flared end portions 16a has straight sides that are parallel to the longitudinal axis of the tubular heater 16. The straight portion 16b of the tubular heater 16 has a length that substantially corresponds to the length of the aerosol-forming substrate located in the aerosol-generating article configured to be placed inside the tubular heater 16.

Fig. 7 shows a sectional view of a heating unit 510 according to another example of the present invention. The heating unit 510 includes a first heater housing 512, a second heater housing 514, and a tubular heater 516 for heating an aerosol-forming substrate located inside the tubular heater 516. The tubular heater 516 is located between the first 512 and second 514 heater housings. An air flow path (indicated by a plurality of arrows 522 in Fig. 7) passes through the heating unit 510 from an air inlet 518 at the far end of the first heater housing 512 to an aerosol outlet 520 at the near end of the second heater housing 514 and passes through the first heater housing 512, the tubular heater 516, and the second heater housing 514.

Unlike the examples of Fig. 2 and 4, the heating assembly 510 of Fig. 7 does not use sealing rings as sealing elements for sealing the first 512 and second 514 heater housings relative to the tubular heater 516. Instead, in the example of Fig. 7, the first 526 and second 524 sealing elements comprise opposite end sections 516c of the tubular heater 516, wherein the end sections 516c are secured with a sealing fit to the inner surface 512a of the first heater housing 512 and the inner surface 514a of the second heater housing 514, respectively.

The first 526 and second 524 sealing elements may be formed by securing the end sections 516c of the tubular heater 516 with a sealing fit within the grooves or slots 512b and 514b that extend circumferentially around the inner surface 512a of the first heater casing 512 and the inner surface 514a of the second heater casing 514, respectively. In an alternative embodiment, the first 524 and second sealing elements 524 can be provided by forming the first 512 and second 514 heater casings around the end sections 516c of the tubular heater 516 or by pressing the end sections 516c of the tubular heater 516 into the first 512 and second 514 heater casings in such a way that the end sections 516c are built into the inner surface 512a of the first heater casing 512 and the inner surface 514a of the second heater casing 514, respectively. The sealing fit of the first 526 and second 524 sealing elements can be achieved using one or more of the following processes: insert casting, multi-layer casting, melt application, high-frequency welding and ultrasonic welding. It should be understood that any other suitable processes can also be used.

The end sections 516c of the tubular heater 516 are elongated so that they can pass into the grooves or slots 512b and 514b or into the inner surfaces 512a and 514a of the first 512 and second 514 heater casings, respectively, while maintaining the same length of the tubular heater 516 between the first 512 and second 514 heater casings. The surfaces of the end sections 516c of the tubular heater 516 are roughened in order to have a quality of the processed surface with an ISO roughness value in the range from N9 to N12, in order to facilitate the retention of the end portions 516c in the grooves or slots 512b and 514b or to facilitate the adhesion of the material of the first 512 and second 514 heater casings to the end portions 516c.

In the exemplary heating assembly 510 of Fig. 7, the opposite end sections 516c are sealed inside the first 512 and second 514 heater housings. The sealing fit of the opposite end sections 516c of the tubular heater 516 to the grooves or slots 512b and 514b or the inner surfaces of the first 512 and second 514 heater housings helps to seal the air flow path 522 and protect the opposite end sections 516c. In addition, the material of the first 512 and second 514 heater housings surrounding the end sections 516c acts as a physical partition between the end sections 516c and the air flow path.

Fig. 8 is a side view of the tubular heater 516 from the heating assembly 510 of Fig. 7, which shows the tubular heater 516 in more detail. The shape and size of the tubular heater 516 of Fig. 8 are essentially the same as those of the tubular heater 16 of Fig. 6, except that the tubular heater 516 of Fig. 8 has elongated end sections 516c. The tubular heater 516 comprises a stainless steel tube having a circular cross-section. The portion 516a of the tubular heater 516 near each end of the tubular heater 516 is flared outward to form a funnel shape at each end of the tubular heater 516. Each of the flared end portions 516a of the tubular heater 516 forms an angle ß with the longitudinal axis of the tubular heater 516. In this example, ß is approximately 45 degrees, but other suitable angles can be used. Due to the presence of the flared end portions 516a, the outer diameter D at the two ends of the tubular heater 516 is larger than the outer diameter d of the tubular heater 16 between the two flared end portions 516a. The two end sections 516c of the tubular heater 516 are elongated and extend for a distance l ₂ in a direction parallel to the longitudinal axis of the tubular heater 516. The percentage of the total length l of the tubular heater 516 that each length l ₂ of the end sections constitutes may be in the range of 5 to 15 percent. As described above, the surfaces of the end sections 516c of the tubular heater 516 are roughened to have a processed surface quality with an ISO roughness value in the range of N9 to N12.

Fig. 9 shows a sectional view of a heating unit 610 according to another example of the present invention. The heating unit 610 of Fig. 9 is a combination of the sealing arrangements provided in the heating units 410 and 510 of Fig. 4 and Fig. 7, respectively. The heating unit 610 comprises a first heater housing 612, a second heater housing 614 and a tubular heater 616 for heating an aerosol-forming substrate located inside the tubular heater 616. The tubular heater 616 is located between the inner surfaces of the first 612 and second 614 heater housings. A heater sleeve 630 is located between the opposite end surfaces of the first 612 and second 614 heater housings. The heater sleeve 630 circumferentially surrounds substantially the entire length of the tubular heater 616, except for the two ends of the tubular heater 616, which are located inside the first 612 and second 614 heater housings. The air flow path (indicated by a plurality of arrows 622 in Fig. 9) passes through the heater assembly 610 from the air inlet 618 at the far end of the first heater housing 612 to the aerosol outlet 620 at the near end of the second heater housing 614 and passes through the first heater housing 612, the tubular heater 616 and the second heater housing 614.

Similar to the heating unit 510 of Fig. 7, the heating unit 610 of Fig. 9 has first 626 and second 624 sealing elements comprising opposite end sections 616c of the tubular heater 616, wherein the end sections 616c are secured with a sealing fit to the inner surface 612a of the first heater casing 612 and the inner surface 614a of the second heater casing 614, respectively.

The heating unit 610 according to Fig. 9 further comprises a third sealing element 632 and a fourth sealing element 634 for sealing the tubular heater 616 relative to the first heater casing 612 and the heater sleeve 630 and for sealing the tubular heater 616 relative to the second heater casing 614 and the heater sleeve 630, respectively. The third 632 and fourth 634 sealing elements are the same as the first 426 and second 424 sealing elements of the heating unit 410 according to Fig. 4.

The third sealing element 632 comprises a sealing ring that surrounds the tubular heater 616 near the distal end of the tubular heater 616. The sealing ring contacts the outer surface of the tubular heater 616, the inner surface of the first heater housing 612 and the surface of the distal end of the heater sleeve 630 to provide a seal between these components that prevents aerosol from leaking from the heating unit 610 into the surrounding parts of the aerosol generating device (not shown).

The fourth sealing element 634 comprises a sealing ring that surrounds the tubular heater 616 near the near end of the tubular heater 616. The sealing ring contacts the outer surface of the tubular heater 616, the inner surface of the second heater housing 614 and the surface of the near end of the heater sleeve 630 to provide a seal between these components that prevents aerosol from leaking from the heating unit 610 into the surrounding parts of the aerosol generating device (not shown).

For the purposes of this description and the appended claims, except where otherwise indicated, all numbers expressing quantities, amounts, percentages, etc., are to be understood as modified in all instances by the term "about" or "approximately." Also, all ranges include the disclosed maximum and minimum points and include any intermediate ranges therebetween, which may or may not be specifically listed herein. Therefore, in this context, the number A is to be understood as A ± 5 percent of A. In this context, the number A may be considered to include numerical values that are within the normal standard error for the measurement of the property that the number A modifies. The number A, in some instances, when used in the appended claims, may deviate by the percentages listed above, provided that the amount by which A deviates does not materially affect the essential and novel characteristic(s) of the claimed invention. All ranges also include the disclosed high and low points and include any intermediate ranges therebetween that may or may not be specifically listed herein.

Claims (34)

1. A heating unit for an aerosol generating device comprising: a first heater housing comprising an air inlet; a second heater housing containing an aerosol outlet; tubular heater for heating the aerosol-forming substrate; an air flow path passing through the heating assembly from the air inlet to the aerosol outlet, the air flow path passing through the first heater housing, the tubular heater, and the second heater housing; a first sealing element configured to seal the first heater casing relative to the tubular heater; and a second sealing element configured to seal the second heater casing relative to the tubular heater; wherein the first and second sealing elements are separated from the air flow path. 2. The heating unit according to claim 1, wherein the first sealing element comprises an annular seal and is located between the inner surface of the first heater casing and the outer surface of the tubular heater. 3. The heating unit according to claim 1 or 2, wherein the second sealing element comprises an annular seal and is located between the inner surface of the second heater casing and the outer surface of the tubular heater. 4. A heating unit according to any one of the preceding claims, wherein at least one of the first and second sealing elements is located in a groove or recess formed in the inner surface of a corresponding one of the first and second heater housings. 5. A heating assembly according to any one of the preceding claims, wherein the first heater housing comprises a tube holder for holding the tubular heater, and wherein the air flow path passes through the tube holder. 6. The heating unit according to claim 5, wherein the first sealing element is located between the tube holder and the outer surface of the tubular heater. 7. The heating unit of claim 1, wherein the first and second sealing elements comprise opposite end sections of a tubular heater, wherein the opposite end sections are secured in sealing contact with the inner surfaces of the first and second heater housings. 8. The heating unit of claim 7, wherein the opposite end sections of the tubular heater are secured with a sealing fit within grooves or recesses formed in the inner surfaces of the first and second heater housings. 9. The heating unit of claim 7, wherein the opposite end sections of the tubular heater are embedded in the inner surfaces of the first and second heater housings. 10. The heating unit of claim 7, wherein the opposite end sections of the tubular heater have a machined surface quality with an ISO roughness value in the range of N9 to N12. 11. A heating unit according to any one of paragraphs 7-10, further comprising: a third sealing element configured to further seal the first heater casing relative to the tubular heater; and a fourth sealing element configured to further seal the second heater casing relative to the tubular heater. 12. The heating unit of claim 11, wherein the third sealing element comprises an annular seal and is located between the inner surface of the first heater casing and the outer surface of the tubular heater. 13. The heating unit according to claim 11 or 12, wherein the fourth sealing element comprises an annular seal and is located between the inner surface of the second heater casing and the outer surface of the tubular heater. 14. A heating assembly according to any one of the preceding claims, wherein the tubular heater is enclosed by first and second heater housings. 15. The heating assembly of any one of claims 1-13, further comprising a heater sleeve surrounding at least a portion of the tubular heater, wherein the heater sleeve is located between the first and second heater housings. 16. The heating unit of claim 15, wherein the first sealing element is adjacent to the inner surface of the first heater casing, the outer surface of the tubular heater and the inner or end surface of the heater sleeve. 17. The heating unit according to claim 15 or 16, wherein the second sealing element is adjacent to the inner surface of the second heater casing, the outer surface of the tubular heater and the inner or end surface of the heater sleeve. 18. A heating assembly according to any one of the preceding claims, wherein the diameter of the tubular heater at each end of the tubular heater is greater than the diameter of the tubular heater in the region between the two ends of the tubular heater. 19. The heating unit of claim 18, wherein a portion of each end of the tubular heater is flared or funnel-shaped. 20. An aerosol generating device comprising: a heating unit according to any of the preceding paragraphs; and power source for supplying electrical power to the heating unit. 21. An aerosol generating system comprising: an aerosol generating device according to claim 20; and an aerosol-generating article containing an aerosol-forming substrate.