RU2842953C2 - Method of air leakage testing - Google Patents

Abstract

FIELD: ventilation.

SUBSTANCE: method of testing the quality of the air flow path defined in a product. Product comprises multiple component parts connected together to form product, each part determines section of air flow path. Method includes steps of increasing pressure in the air flow path to a predetermined pressure, measuring leakage from the air flow path under pressure for a predetermined period of time, determining the leakage rate over a predetermined period of time and determining whether the leakage rate exceeds the allowable threshold leakage rate. Method is carried out at high temperature compared to ambient temperature.

EFFECT: development of testing method of air flow path quality under conditions of temperature that is higher compared to ambient temperature.

15 cl, 6 dwg

Description

The present invention relates to a method for testing the quality of an air flow path determined in a product. The product may be a heater assembly for an aerosol generating device or an aerosol generating device. The present invention further relates to a heater assembly and an aerosol generating device comprising the heater assembly.

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 provided 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 air flow passage through the aerosol generating device. It is known to provide seals around the air flow passage and between the heating chamber and the housing to prevent aerosol from leaking out of the air flow passage and into other parts of the aerosol generating device, which may cause damage to the electronics of the device. The seals may be located in direct contact with the heating chamber and are therefore typically formed from a heat-resistant polymer such as silicone or polysiloxane. However, exposure of such polymer seals to the heating temperatures of the heating chamber may result in the formation of unwanted by-products that may contaminate the aerosol. In addition, such heating temperatures may degrade the seals over time.

Polymer seals located between the heating chamber and the housing of the device can provide a heat conduction path that transfers heat from the heating chamber to the materials surrounding the heating chamber. This lost heat reduces the heat available to heat the aerosol-forming substrate and reduces the efficiency of the aerosol-generating device.

An additional problem encountered when sealing air flow passages within aerosol generating devices is manufacturing tolerances. Variations in component dimensions due to manufacturing tolerances can result in poor engagement between components and possibly gaps through which aerosol can leak. Achieving good sealing engagement between components typically requires tight manufacturing tolerances, which can be difficult to achieve in high-speed manufacturing processes such as injection molding. Variations in product dimensions can also result in inconsistent product quality. That is, some products may have leakage issues while others do not. It would be desirable to provide the consumer with consistent product quality.

According to an example of the present invention, a method for testing the quality of an air flow path defined in a product is provided. The product comprises a plurality of components, each of which defines a section of the air flow path. The plurality of components are connected together to form the product. The method includes the steps of increasing the pressure in the air flow path to a specified pressure, measuring the leakage from the air flow path under pressure for a specified period of time, determining the leakage rate for a specified period of time and determining whether the leakage rate exceeds an acceptable threshold leakage rate.

A product, such as a heater assembly for an aerosol generating device, or an aerosol generating device containing such a heater assembly, is typically manufactured in high volume and from components that are themselves manufactured in high volume by processes such as injection molding. These products include an air flow path, and satisfactory use of the products may depend on the air flow path meeting the requirements. A reliable, compliant air flow path can typically be achieved by using polymer seals (e.g., silicone seals). However, as mentioned above, such seals may be undesirable in some circumstances. By testing the quality of the air flow path in the products, those products can be rejected that have air flow paths that do not meet the requirements, i.e., air flow paths that leak to such an extent that they prevent satisfactory use of the product. The quality test method may conveniently be provided as an automated quality test method. The quality test method may conveniently be included as part of the manufacturing process for the product.

The product may define an air flow inlet and an air flow outlet. If the product is an aerosol generating device, for example, the air flow inlet may allow air to be drawn into the aerosol generating device, and the air flow outlet may be connected to an opening for containing an aerosol generating article. The air flow and any generated aerosol may exit the opening through an aerosol generating article contained in the aerosol generating device.

The air flow path may have an air flow inlet defined through the first of the plurality of components and an air flow outlet defined through the second of the plurality of components. The air flow path may be defined by passages in more than one of the plurality of components. The passages in adjacent components may be located at joints and may be connected when assembling the plurality of components. The joints between the components may be the most likely places for leakage from the air flow path. The product may have multiple connections between the components and, therefore, many potential leaks from the air flow path.

At least two of a plurality of component parts may be joined together by mechanical press fit joints to form a product. Such joints may also be known as interacting joints or interacting connections. A press fit joint may be held together solely by the interaction between the two components or may depend on pressure exerted by a device such as a screw or clamp.

The pressure in the air flow path may be increased to a predetermined pressure of 0.2 kPa to 1 kPa. The pressure should be high enough to detect a leak, but not so high as to damage the product. The predetermined pressure may be, for example, 0.3 kPa to 0.9 kPa, for example, 0.35 kPa to 0.8 kPa, for example, 0.4 kPa to 0.7 kPa, for example, 0.45 kPa to 0.6 kPa. It may be preferable that the pressure in the air flow path is increased to a predetermined pressure of 0.45 kPa to 0.55 kPa, for example, approximately 0.5 kPa.

Leakage from the air flow path under pressure can be measured over a period of time from 1 second to 4 seconds, such as from 1.5 seconds to 3 seconds, such as for approximately 2 seconds.

The acceptable leakage threshold level may be 5 ml/min. Any leakage at a level that is lower than the acceptable leakage threshold level may be considered acceptable. That is, a product in which the leakage from the air flow path is less than the acceptable leakage threshold level may be considered to have a compliant air flow path. The acceptable leakage threshold level may vary depending on the nature of the product. It may be preferable that the acceptable leakage threshold level be 4.5 ml/min, or 4 ml/min, or 3 ml/min, or 2.5 ml/min, or 2 ml/min, or 1.5 ml/min, or 1 ml/min. For a heater assembly or an aerosol generating device containing a heater assembly, it may be preferable that the acceptable leakage threshold level not exceed 3 ml/min.

The pressure in the air flow path may be increased by means of a gas, such as air. The air may conveniently be supplied from a compressed air source, such as a pressurized air cylinder.

The product can be inserted into a fixture or a testing apparatus for the purpose of performing a quality test with respect to the air flow path of the product. The fixture or testing apparatus is preferably designed for specific dimensions of the product to be tested. The fixture or testing apparatus can comprise connections for connecting to the air flow path. One of the air flow inlet and the air flow outlet can be blocked, and the other of the air flow inlet and the air flow outlet can be connected to a source of pressurized gas, such as pressurized air, to increase the pressure in the air flow path.

The step of increasing the pressure in the air flow path to the specified pressure may include increasing the pressure in the air flow path to the specified pressure during a specified stabilization time. The specified stabilization time may be from 2 to 5 seconds, such as from 2.5 to 4 seconds, such as approximately 3 seconds.

The step of measuring leakage from the pressurized air flow path may include monitoring the pressure in the pressurized air flow path. For example, a pressure sensor or flow meter may be connected to the pressurized air flow path so that it can monitor the pressure or air flow in the pressurized air flow path. Just as an example, a commercially available pressure monitoring device such as the Furness FCO752 can be used. The Furness FCO752 provides an accuracy of +/- 0.02 ml and a maximum leak resolution of 0.001 ml/min.

The product can be connected to a test circuit. The test circuit can form part of a fixture or a test apparatus. The test circuit can comprise a source of gas increasing the pressure, for example an air cylinder. The test circuit can also comprise one or more of a pressure regulator, a coupling for enabling the test circuit to be connected to the air flow path, a first valve configured to operate in such a way as to enable the pressure in the air flow path to be increased, and a second valve configured to operate in such a way as to enable the pressure in the air flow path to be released. The method can include the steps of opening the first valve to increase the pressure in the air flow path to a specified pressure during a specified stabilization time, closing the first valve, measuring the leakage from the air flow path under pressure during a specified period of time after closing the first valve, and opening the second valve to enable the pressure in the air flow path to be released. The method may include the steps of opening the first valve to increase the pressure in the air flow path to a specified pressure for a specified stabilization time, closing the first valve, determining the leakage flow in the air flow path under pressure for a specified period of time after closing the first valve, and opening the second valve to allow the pressure in the air flow path to be released.

The product may be rejected if the leak rate is equal to or greater than the acceptable threshold leak rate. Alternatively, the product may be reprocessed, remanufactured or refurbished if the leak rate is equal to or greater than the acceptable threshold leak rate. The term "remanufactured" shall be used for all such processes where the product is not rejected outright but is reprocessed or remanufactured in a manner that eliminates any leakage problems identified by the quality test method. Remanufactured product may be retested. That is, remanufactured product may be resubmitted for airflow path quality testing to determine whether the leak rate has been sufficiently improved by remanufacturing.

The method may assign a different acceptable leakage threshold rate to determine whether the product is refurbished. For example, a product may be considered to have a compliant air flow path if the leakage rate is below the leakage threshold rate. A product may be considered suitable for refurbishment if the leakage rate is equal to or greater than the acceptable leakage threshold, but is lower than the leakage threshold after refurbishment. The leakage threshold after refurbishment for a product is higher than the acceptable leakage threshold for the same product. If the leakage rate is equal to or greater than the leakage threshold after refurbishment, the product may be rejected.

In preferred embodiments, the set pressure may be from 0.45 kPa to 0.55 kPa, such as approximately 0.5 kPa, and the allowable threshold leak rate may be 3 ml/min, or 2 ml/min, or 1 ml/min.

In some embodiments, the method may be performed at an elevated temperature compared to the ambient temperature. The compliance of the seal formed between the components of the product may vary depending on the temperature. It may be desirable to evaluate the compliance of the air flow path at an elevated temperature in order to reproduce the operating conditions. Thus, the gas supplied to increase the pressure in the air flow path may be heated, for example, heated to a temperature of more than 100 degrees Celsius, for example, more than 150 degrees Celsius, for example, more than 200 degrees Celsius. If the product contains a heater, the heater may be activated during the quality test method to increase the temperature of the product being tested.

In some embodiments, the product may be a heater assembly for an aerosol generating device. The heater assembly may be an integral part of the aerosol generating device.

As an example, the heater assembly may comprise a first heater body comprising an air inlet, a second heater body comprising an aerosol outlet, and a heating chamber for heating an aerosol-forming substrate. The heating chamber may be in fluid communication with both the air inlet and the aerosol outlet to define an air flow path through the heater assembly.

The heating chamber may be located between the first and second heater bodies; and the first and second heater bodies may be attached to each other by means of a mechanical press fit.

The heating chamber may be located between the first and second heater housings; and the first and second heater housings may be attached to each other by means of a fastening element. The fastening element may be configured to apply an axial force to the first and second heater housings to bring the axially opposite inner surfaces of the first and second heater housings into sealing engagement with the corresponding axially opposite end surfaces of the heating chamber to seal the air flow passage. The fastening element may provide a threaded fastening element or a snap-on fastening element.

The heater assembly may comprise a plurality of fasteners. The plurality of fasteners may be symmetrically spaced around the outer perimeter of the first and second heater housings.

Each of the first heater body, the second heater body and the heating chamber may comprise an air flow channel, wherein the air flow channels are in communication so as to together define a passage for the air flow.

The heating chamber may comprise a tubular heating chamber. The tubular heating chamber may have a tubular wall thickness of 0.05 millimeters to 1.00 millimeters, preferably 0.05 millimeters to 0.50 millimeters, and more preferably approximately 0.10 millimeters.

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

The assembled heater may comprise at least one electric heating element for heating the aerosol-forming substrate. The assembled heater may comprise a plurality of electric heating elements. The electric heating element or elements may be arranged around the outer surface of the heating chamber or surround it. The electric heating element or elements may be arranged around the inner surface of the heating chamber or surround it. The electric heating element or elements may be part of the heating chamber or made 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, for example, 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, nickel, cobalt, chromium, aluminum, titanium, zirconium, hafnium, niobium, molybdenum, tantalum, tungsten, tin, gallium, manganese, gold, and iron-based superalloys, stainless steel, Timetal ^™ , Kanthal ^™ , and other iron-chromium-aluminum alloys, and iron-manganese-aluminum-based alloys. In composite materials, the electrically resistive material may optionally be embedded in, encapsulated in, 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 having a certain relationship between temperature and specific resistance. Heating elements formed in this manner may be used both for heating and for monitoring the temperature of the heating element during operation.

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

The heater assembly may comprise a flexible heating element arranged around the outer surface of the heating chamber or surrounding it. The flexible heating element may have a length substantially equal to the length of the aerosol-forming substrate provided in the aerosol-generating article. The heating chamber may be longer than the heating element. The heating chamber may comprise at least one end portion that is not covered or surrounded by the heating element. An end portion that is not covered or surrounded by the heating element may be provided at both ends of the heating chamber. The end portion or portions may serve as separating portions to prevent direct contact between the heating element and other components of the heater assembly. Each end portion or portions may have a length of less than 2 millimeters, preferably less than 1 millimeter and preferably approximately 0.5 millimeters. Advantageously, the separating portions will have a lower temperature during heating than the portion of the heating chamber covered or surrounded by the heating element. The separating portions may comprise funnel-shaped end portions or stepped end portions.

In some embodiments, the product may be an aerosol generating device. The heater assembly may be an integral part of the aerosol generating device. The aerosol generating device may comprise a housing in which the heater assembly and a power supply unit for supplying power to the heater assembly are located. The heater assembly may be the heater assembly described above. The aerosol generating device may define an air flow path between an inlet of the aerosol generating device and an outlet of the aerosol generating device. The air flow path may comprise an air flow path defined through the heater assembly.

The power supply may be any suitable power supply, such as a DC voltage source. In one embodiment, the power supply is a lithium-ion battery. Alternatively, the power supply 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 the user between the fingers of one hand.

The aerosol generating device may further comprise a control circuit configured to control the supply of electric power to the heater assembly. The control circuit may comprise a microprocessor. The microprocessor may be a programmable microprocessor, a microcontroller, or an application-specific integrated circuit (ASIC), or another 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, display elements. The power may be supplied to the heater assembly continuously after activation of the device or may be supplied intermittently, for example, from puff to puff. The power may be supplied to the heater assembly in the form of electric current pulses, for example, by means of pulse width modulation (PWM).

The aerosol generating device may comprise a device casing. The device casing may comprise a heater assembly, a power supply unit, and a control circuit. The casing may comprise an opening for accommodating an aerosol generating article. The opening may be connected to an aerosol outlet of the second heater housing related to the heater assembly to enable insertion of the aerosol generating article into the heating chamber. The casing may comprise an air inlet. The air inlet may be connected to an air inlet of the first heater housing related to the heater assembly.

The casing 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 applications in the food or pharmaceutical industries, such as polypropylene, polyetheretherketone (PEEK) and polyethylene. The material is preferably lightweight and non-brittle.

According to a further example of the present invention, a method for producing a heater assembly for an aerosol generating device is provided. The method includes the steps of providing a first heater body comprising an air inlet; providing a second heater body comprising an aerosol outlet; providing a heating chamber for heating an aerosol-forming substrate and arranging the heating chamber so that it is in fluid communication with both the air inlet and the aerosol outlet to determine an air flow path through the heater assembly; arranging the heating chamber between the first and second heater bodies; attaching the first and second heater bodies to each other; and testing the quality of the air flow path determined through the heater assembly by: increasing the pressure in the air flow path to a predetermined pressure; measuring leakage from the air flow path under pressure for a predetermined period of time; determining the leak rate for a predetermined period of time; and determining whether the leak rate is equal to or exceeds an acceptable threshold leak rate.

The method may further include the step of restoring or rejecting any heater assembly in which the leak rate is equal to or higher than the permissible threshold leak rate. The step of testing the quality of the air flow path determined through the heater assembly may be carried out according to the method disclosed above.

According to a further example of the present invention, there is provided a heater assembly formed by the method of manufacturing a heater assembly for an aerosol generating device as disclosed above.

According to a further example of the present invention, a method for producing an aerosol generating device is provided, wherein the method comprises the following steps: providing a casing; providing a heater assembly; providing a power supply unit for supplying electric power to the heater assembly; arranging a heating chamber and a power supply unit inside the casing so as to define an air flow path between an air flow inlet of the aerosol generating device and an air flow outlet of the aerosol generating device, wherein the air flow path comprises a passage for air flow through the heater assembly; and testing the quality of the air flow path defined through the aerosol generating device by: increasing the pressure in the air flow path to a predetermined pressure; measuring leakage from the air flow path under pressure for a predetermined period of time; determining the leak rate for a predetermined period of time; and determining whether the leak rate is equal to or exceeds an acceptable threshold leak rate.

The method may further comprise a step of recovering or rejecting any aerosol generating device in which the leak rate is equal to or higher than the permissible threshold leak rate. The step of testing the quality of the air flow path determined through the heater assembly may be carried out according to the method disclosed above.

According to a further example of the present invention, there is provided an aerosol generating device formed by the method for manufacturing an aerosol generating device as disclosed above.

According to a further example of the present invention, there is provided an aerosol generating device formed by the method of manufacturing an aerosol generating device as disclosed above, comprising a heater assembly formed by the method of manufacturing a heater assembly for an aerosol generating device as disclosed above.

Aerosol generating devices as disclosed herein may preferably be used in combination with disposable aerosol generating articles comprising an aerosol forming substrate. An aerosol generating system may comprise an aerosol generating device as disclosed herein and an aerosol generating article configured for use with the aerosol generating device.

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

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

According to an example of the present invention, there is provided an aerosol generating system comprising: an aerosol generating device according to any of the examples described above; and an aerosol generating article comprising an aerosol-forming substrate.

In the context of this document, 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 configured to be combined with it to heat the aerosol-generating article.

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

The aerosol-generating article may have a total length of about 30 mm to about 100 mm. The aerosol-generating article may have an outer diameter of about 5 mm to about 12 mm. The aerosol-generating substrate may have a length of about 10 mm to about 18 mm. In addition, the diameter of the aerosol-generating substrate may be from about 5 mm to about 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 an acetate cellulose filter plug. The filter plug has a length of about 7 mm in one embodiment, but may have a length of about 5 mm to about 12 mm.

In one embodiment, the aerosol-generating article may have a total length of about 45 mm. The aerosol-generating article may have an outer diameter of about 7.3 mm, but may have an outer diameter from about 7.0 mm to about 7.4 mm. In addition, the aerosol-generating substrate may have a length of about 12 mm. Alternatively, the aerosol-generating substrate may have a length of about 16 mm. The aerosol-generating article may comprise an outer paper wrapper. In addition, the aerosol-generating article may comprise a gap between the aerosol-generating substrate and the filter plug. The gap may be about 21 mm or about 26 mm, but may be in the range from about 5 mm to about 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 contain a tobacco-containing material containing volatile tobacco flavor compounds that are released from the substrate upon heating. Alternatively, the aerosol-forming substrate may contain a non-tobacco material. The aerosol-forming substrate may further contain an aerosol-forming agent. Examples of suitable aerosol-forming agents include glycerol and propylene glycol.

If the aerosol-forming substrate is a solid aerosol-forming substrate, the solid aerosol-forming substrate may comprise, for example, one or more of the following: powder, granules, pellets, grains, thin tubes, strips or sheets containing one or more of the following: grass leaf, tobacco leaf, 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 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, "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% by weight of aerosol forming agent on a dry weight basis. Alternatively, the homogenized tobacco material may contain from 5% to 30% by weight of aerosol forming agent on a dry weight basis. The sheets of homogenized tobacco material may be formed by agglomerating loose tobacco obtained by grinding or otherwise comminuting one or both of the lamina of the tobacco leaf and the 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 by-products of the loose tobacco generated, for example, during the processing, handling, and shipping of the tobacco. The sheets of homogenized tobacco material may comprise one or more intrinsic binders, i.e., tobacco endogenous binders, one or more extrinsic binders, i.e., tobacco exogenous binders, or a combination thereof, to promote agglomeration of the bulk tobacco; alternatively or additionally, the sheets of homogenized tobacco material may comprise other additives, including, but not limited to, 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. In the context of the present document, the term "corrugated sheet" means a sheet having a plurality of substantially parallel ridges or corrugations. Preferably, when the aerosol-generating article is assembled, the substantially parallel ridges or corrugations extend along or parallel to the longitudinal axis of the aerosol-generating article. This advantageously simplifies the assembly of the corrugated sheet of homogenized tobacco material to form the aerosol-forming substrate. However, it will be understood 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 certain embodiments, the aerosol-forming substrate may comprise an assembled sheet of homogenized tobacco material that is substantially uniformly textured over substantially the 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 substrate forming the aerosol can be provided on or embedded in a thermally stable carrier. The carrier can be in the form of a powder, granules, beads, grains, thin tubes, strips or sheets. Alternatively, the carrier can be a tubular carrier having a thin layer of the solid substrate applied to its inner surface, or to its outer surface, or to both its inner and outer surfaces. Such a tubular carrier can be formed, for example, from paper or a paper-like material, a non-woven mat of carbon fibers, a lightweight metal mesh with open cells, or a perforated metal foil, or any other thermally stable polymer matrix.

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

Although solid aerosol-forming substrates are mentioned above, it will be understood by one skilled in the art that other forms of aerosol-forming substrate may be used with other embodiments. For example, the aerosol-forming substrate may be a liquid aerosol-forming substrate. If a liquid aerosol-forming substrate is provided, the aerosol-generating device preferably comprises means for retaining the liquid. For example, the liquid aerosol-forming substrate may be retained in a container or a liquid-storing portion. Alternatively or additionally, the liquid aerosol-forming substrate may be absorbed by a porous carrier material. The porous carrier material may be made of any suitable absorbent plug or piece, such as a foamed metal or plastic material, polypropylene, terylene, nylon fibers, or ceramics. The liquid aerosol-forming substrate may be retained in the 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 non-woven web or a bundle of fibers in which tobacco components have been incorporated. The non-woven web or bundle of fibers may contain, for example, carbon fibers, natural cellulose fibers, or fibers 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 examples will now 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 an exploded perspective view of an assembled heater for use as a component of the aerosol generating device of Fig. 1;

Fig. 3 is a schematic diagram showing the elements of the quality testing apparatus connected to the product (e.g. heater assembly or aerosol generating device) for testing;

Fig. 4 is a flow chart illustrating a step-by-step process for testing the air flow path quality of a product using the apparatus of Fig. 3;

Fig. 5 is a block diagram illustrating a step-by-step process for manufacturing an assembled heater for an aerosol generating device; and

Fig. 6 is a block diagram illustrating a step-by-step process for manufacturing an aerosol generating device.

Fig. 1 is a schematic cross-sectional view showing the interior of an aerosol generating device 100 and an aerosol generating article 200 housed within the aerosol generating device 100. Together, the aerosol generating device 100 and the aerosol generating article 200 form an aerosol generating system. Fig. 1 shows the aerosol generating device 100 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 comprising a heater assembly 1, a power supply unit 103 and a control circuit 105. In Fig. 1 it can be seen that the heater assembly 1 comprises a first heater housing 2, a heating chamber 6, a heater mount 8 and a second heater housing 4. The heating chamber 6 has a flexible heating element (not shown) arranged around it for heating the heating chamber 6. The power supply unit 103 is a battery and in this example is a rechargeable lithium-ion battery. The control circuit 105 is connected to both the power supply unit 103 and the heating element and controls the supply of electrical energy from the power supply unit 103 to the heating element for regulating the temperature of the heating element.

The housing 102 comprises an opening 104 at the near, or mouthpiece, end of the aerosol-generating device 100, through which the aerosol-generating article 200 is received. The opening 104 is connected to an opening in the heater assembly 1, through which the aerosol exits from the heater assembly 1. The opening can be considered an air outlet of the aerosol-generating device. However, it will be understood that the aerosol mainly exits from the heater assembly 1 and the aerosol-generating device 100 through the aerosol-generating article 200. The housing 102 further comprises an air inlet 106 at the far end of the aerosol-generating device 100. The air inlet 106 is connected to the air inlet located at the far end of the first tubular section 2b of the first heater body 2. The first tubular section 2b delivers air from the air inlet 106 to the heating chamber 6.

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 above-mentioned 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 rod containing 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 substance. The end plug 202 and the filter 208 of the mouthpiece are formed from acetyl cellulose fibers.

In use, the distal end of the aerosol generating article 200 is inserted into the aerosol generating device 100 through the opening 104 in the casing 102 and is pushed into the aerosol generating device 100 until it engages with a stop (not shown in Fig. 1) located on the heater mount 8, after which it is fully inserted. The stop helps to correctly position the aerosol forming substrate 204 inside the heating chamber 6, so that the heating chamber 6 can heat the aerosol forming substrate 204 to form an aerosol.

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

In use, the user inserts the aerosol-generating article 200 into the aerosol-generating device 100, as shown in Fig. 1. The user then starts a heating cycle by activating the aerosol-generating device 100, for example, by pressing a switch to turn on the device. In response to this, the control circuit 105 controls the supply of electric power from the power supply unit 103 to the heating element (not shown) to heat the heating element, which in turn heats the heating chamber 6. During the heating cycle, the heating element heats the heating chamber 6 to a predetermined temperature or to a range of predetermined temperatures according to a temperature profile. The heating cycle can last approximately 6 minutes. The heat from the heating chamber 6 is transferred to the aerosol-forming substrate 204, which releases volatile compounds from the aerosol-forming substrate 204. The 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 puffs or inhales through the filter 208 of the mouthpiece. The generated aerosol is then drawn through the filter 102 of the mouthpiece into the user's mouth.

Fig. 2 shows an exploded perspective view of the heater assembly 1 of Fig. 1 before assembly. The components of the heater assembly 1, i.e. the first heater housing 2, the heater mount 8, the heating chamber 6 and the second heater housing 4, are shown spaced apart in the axial direction in Fig. 2. To assemble the heater assembly 1, the heater mount 8 is mounted inside the first hollow section 2a of the shell of the first heater housing 2. A hollow plug 8c, which extends to the far side from the first side 8a of the heater mount 8, is pressed into an internal recess (not shown) formed in the near end of the first tubular section 2b.

The heating chamber 6 is then pressed into an internal recess (not shown in Fig. 2) formed in the near end wall of the second hollow section 4a of the shell of the second heater body 4. A guide (not shown) is inserted inside through the second tubular section 4b of the second heater body 4 and through the internal space inside the heating chamber 6 to maintain the components in axial alignment. The subassembly of the second heater body 4 and the heating chamber 6 is then mounted on the subassembly comprising the first heater body 2 and the heater mount 8. The far end of the guide is inserted into an internal channel (not shown) for the air flow of the heater mount 8 to maintain the components in axial alignment. The first and second heater bodies 2, 4 are then secured to each other using two bolts 34 and washers 36. The guide is then removed. When fastening the first and second heater housings 2, 4, an axial force is applied to hold the components of the heater assembly 1 in axial sealing engagement and to seal the air flow passage through the heater assembly. The air flow passage is therefore sealed between the air inlet 38 located at the far end of the first tubular section 2b of the first heater housing 2 and the aerosol outlet 10 located at the near end of the second heater housing 4.

After assembly, the integrity or compliance of the air flow path within the heater assembly is tested. A quality testing apparatus designed to test the compliance of the air flow path comprises: a clamping fixture for receiving the heater assembly; a seal for blocking the air flow outlet of the heater assembly; a coupling for forming a sealed connection with the air flow inlet of the heater assembly; a compressed air source and associated regulators, pipes and valves adapted to increase the pressure in the air flow path of the heater assembly; and a pressure sensor or flow sensor adapted to detect changes in pressure or flow rates in the pressurized air flow path. In a particular embodiment, pressure measurements are obtained using a Furness FCO752 production line flow meter.

The quality testing apparatus may include automation. For example, the heater assembly (or any other product being tested) may be automatically transferred to the quality testing apparatus and inserted into a fixture. The air flow outlet may then be sealed and the sealed connection applied to the air flow inlet so that the test procedure can be applied. After the test is complete, the heater assembly is removed from the fixture and may be classified depending on whether the air flow path was found to be compliant or not.

Fig. 3 is a schematic diagram showing the components of a quality testing apparatus connected to a product (e.g., a heater assembly or an aerosol generating device) for testing. An air source 3000 is connected to a product 3010 via air lines or pipes 3020. The pressure from the air source 3000 is controlled by a pressure regulator 3030. A first test valve 3040 is located between the air source 3000 and the product 3010. By opening the first test valve 3040, the pressure in the air flow path inside the product 3010 increases. Then, the first test valve 3040 can be closed. The leak rate in the pressurized air flow path can be determined by a pressure sensor 3070 (e.g., Furness FCO752) located in the pressurized section of the apparatus. After completion of the test, the release valve 3050 may be opened to release pressure in the system and allow the product 3010 to be removed from the apparatus.

The step-by-step process of testing the quality of the air flow path of a product using the apparatus of Fig. 3 can be illustrated by the flow chart of Fig. 4.

Step T1: - the product 3010 is inserted into the fixture of the testing apparatus and the air flow path of the product is connected to the test circuit of the apparatus. This may involve blocking or sealing one of the air flow inlet or air flow outlet and connecting the other of the air flow inlet or air flow outlet to a source of compressed air.

Step T2: - The pressure regulator 3030 is adjusted to deliver an air pressure of 0.5 kPa. The first test valve 3040 is opened and air is passed through the air lines 3020 to increase the pressure in the product air flow path.

Stage T3: - a pressure of 0.5 kPa is applied to the product air flow path for a stabilization period of 3 seconds.

Step T4: - the first test valve 3040 is closed.

Step T5: - Pressure sensor 3070 monitors the pressure in the product air flow path for a 2 second test period.

Step T6: - Calculate the leakage rate from the air flow path. If the leakage rate is less than 3 ml/min, the air flow path is considered to be compliant and the product is passed as fit for use.

Step T7: - release valve 3050 is opened to release the remaining pressure.

Stage T8: - the product is removed from the apparatus.

The quality testing method described in this document may conveniently be incorporated into a method for manufacturing a product. For example, the quality testing method for an air flow path may form a late stage in a production line that produces the product.

A step-by-step process for manufacturing an assembled heater for an aerosol generating device may be illustrated by the block diagram of Fig. 5.

Step A1: - providing a first heater housing comprising an air inlet.

Step A2: - providing a second heater housing comprising an air outlet, which may be referred to as an aerosol outlet.

Step A3: - Provide a heating chamber to heat the aerosol-forming substrate.

Step A4: - a heating chamber is positioned between the first heater body and the second heater body. The heating chamber is positioned in fluid communication with both the air inlet and the air outlet to define an air flow path through the heater assembly.

Step A5: - the first heater body and the second heater body are attached to each other, thereby forming a heater assembly.

Step A6: - the heater assembly air flow path compliance is tested using the method set out in the flow chart of Fig. 4.

Step A7: - If the air flow path is found to comply with the requirements, the heater assembly may be shipped for use as a component part of an aerosol generating device.

Step A8: - If the air flow path is not deemed to meet requirements, the heater assembly may be sent for refurbishment or may be rejected.

The step-by-step process of manufacturing the aerosol generating device can be illustrated by the block diagram of Fig. 6.

Step B1: - Provide a housing for the aerosol generating device. The housing defines an air flow inlet and an air flow outlet. The air flow outlet may also be referred to as the aerosol outlet.

Step B2: - a heater assembly is provided for the aerosol generating device. The heater assembly defines an air flow path passing through it. The heater assembly may be a heater assembly formed using the method illustrated in Fig. 5.

Step B3: - Provide a power supply to supply power to the heater.

Step B4: - Provide electronics to control power supply and operation of the device.

Step B5: - The heater assembly, power supply, and electronics are positioned within the housing and connected to each other. An air flow path is determined that extends from the housing air flow inlet, through the heater assembly, and to the housing air flow outlet.

Step B6: - testing the compliance of the air flow path of the aerosol generating device with the requirements using the method set out in the flow chart of Fig. 4.

Step B7: - If the air flow path is considered to comply with the requirements, the aerosol generating device may be packaged for sale to consumers.

Step B8: - If the air flow path is not considered to be in compliance, the aerosol generating device may be sent for refurbishment or may be rejected.

For the purpose of the present specification 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". Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therebetween that may or may not be specifically recited herein. Accordingly, in this context, the number A is to be understood as A±5 percent (5%) 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 vary by the percentages listed above, provided that the amount by which A varies does not materially affect the essential and novel characteristic(s) of the claimed invention. Also, all ranges include the disclosed maximum and minimum points and include any intermediate ranges therebetween that may or may not be specifically listed herein.

Claims (36)

1. A method for testing the quality of an air flow path defined in a product, wherein the product comprises a plurality of component parts, each defining a section of the air flow path, joined together to form the product, wherein the method comprises the steps of: increasing the pressure in the air flow path to a given pressure; measuring leakage from a pressurized air flow path over a specified period of time; determining the leak rate over a given period of time; and determining whether a leak rate exceeds an acceptable threshold leak rate, wherein the product is an aerosol generating device or a heater assembly for an aerosol generating device, In this case, the method is carried out at an elevated temperature compared to the ambient temperature. 2. The method of claim 1, wherein the air flow path has an air flow inlet defined through the first of the plurality of component parts and an air flow outlet defined through the second of the plurality of component parts. 3. The method of claim 1 or 2, wherein at least two of the plurality of component parts are joined together by means of mechanical press fit joints to form a product. 4. A method according to any of the preceding claims, wherein the pressure in the air flow path is increased to a predetermined pressure of from 0.2 kPa to 1 kPa, such as from 0.3 kPa to 0.9 kPa, such as from 0.35 kPa to 0.8 kPa, such as from 0.4 kPa to 0.7 kPa, such as from 0.45 kPa to 0.6 kPa. 5. A method according to any of the preceding claims, wherein the leakage from the pressurized air flow path is measured over a period of time from 1 second to 4 seconds, such as from 1.5 seconds to 3 seconds, such as for about 2 seconds. 6. The method of any of the preceding paragraphs, wherein the permissible threshold leakage level is 5 ml/min, or 4.5 ml/min, or 4 ml/min, or 3 ml/min, or 2.5 ml/min, or 2 ml/min, or 1.5 ml/min, or 1 ml/min. 7. A method according to any one of the preceding claims, wherein the step of increasing the pressure in the air flow path to a predetermined pressure comprises increasing the pressure in the air flow path to the predetermined pressure for a predetermined stabilization time. 8. The method of any one of the preceding claims, wherein the step of measuring leakage from the pressurized air flow path comprises monitoring the pressure in the pressurized air flow path. 9. A method according to any one of the preceding claims, wherein the product is connected to a test circuit, wherein the test circuit comprises a source of pressure increasing gas, such as an air cylinder, a pressure regulator, a coupling for allowing the test circuit to be connected to the air flow path, a first valve adapted to be operated in such a way as to allow the pressure in the air flow path to be increased, and a second valve adapted to be operated in such a way as to allow the pressure in the air flow path to be released. 10. The method of any of the preceding claims, wherein the product is a heater assembly, and the heater assembly comprises: a first heater body comprising an air inlet; a second heater body comprising an aerosol outlet; and a heating chamber for heating an aerosol-forming substrate, the heating chamber being in fluid communication with both the air inlet and the aerosol outlet to define a flow path for air through the heater assembly. 11. The method according to claim 10, wherein the heating chamber comprises a tubular heating chamber. 12. The method according to any one of paragraphs 1-9, wherein the product is an aerosol generating device, and the aerosol generating device comprises a housing in which are located: heater assembly; and power supply for supplying electrical power to the heater assembly. 13. The method according to any one of claims 1-9 or 12, wherein the product is an aerosol generating device, wherein the aerosol generating device defines an air flow path between an inlet of the aerosol generating device and an outlet of the aerosol generating device, wherein the air flow path comprises a passage for air flow through the heater assembly. 14. A method according to any of the preceding claims, wherein the gas supplied to increase the pressure in the air flow path is heated to a temperature of more than 100 degrees Celsius, such as more than 150 degrees Celsius, such as more than 200 degrees Celsius. 15. A method for manufacturing an assembled heater for an aerosol generating device, the method comprising the steps of: providing a first heater housing comprising an air inlet; providing a second heater housing containing an outlet for the aerosol; providing a heating chamber for heating an aerosol-forming substrate and arranging the heating chamber so as to be in fluid communication with both the air inlet and the air outlet to define an air flow path through the heater assembly; the location of the heating chamber between the first and second heater bodies; attaching the first and second heater bodies to each other; and testing the quality of the air flow path determined through the heater assembly by: increasing the pressure in the air flow path to a given pressure; measuring leakage from a pressurized air flow path over a specified period of time; determining the leak rate over a given period of time; and determining whether the leak rate is equal to or exceeds the permissible threshold leak rate, In this case, the air flow path quality test is performed at an elevated temperature compared to the ambient temperature.