EP4687526A1

EP4687526A1 - Cartridge for an aerosol-generating system with improved sealing element

Info

Publication number: EP4687526A1
Application number: EP23720730.3A
Authority: EP
Inventors: Bo Jiang; Chiara FASCIANI; Samuel Raphaël BONNELY; Baoling LEI
Original assignee: Philip Morris Products SA
Current assignee: Philip Morris Products SA
Priority date: 2023-03-29
Filing date: 2023-03-29
Publication date: 2026-02-11
Also published as: CN121013658A; WO2024197664A1; KR20250158821A; JP2026511552A

Abstract

There is provided a cartridge (100, 10) for an aerosol-generating system, the cartridge (100, 10) comprising: a cartridge body (104) comprising a liquid storage portion (108) for holding a liquid aerosol-forming substrate; a heater assembly (10, 112) comprising a heating element (116) for vaporising the liquid aerosol-forming substrate and a porous ceramic body (118) for conveying liquid aerosol-forming substrate from the liquid storage portion (108) to the heating element (116); and a sealing element (300) configured to provide a sealing engagement between the porous ceramic body (118) and the cartridge body (104). The sealing element (300) comprises one of a) cotton or polyethylene (PE); b) a thermoplastic elastomer (TPE); and c) a silicone-free rubber.

Description

CARTRIDGE FOR AN AEROSOL-GENERATING SYSTEM WITH IMPROVED SEALING ELEMENT

The present invention relates to a cartridge for an aerosol-generating system. The invention also relates to an aerosol-generating system comprising the cartridge.
Aerosol-generating systems that heat a liquid aerosol-forming substrate in order to generate an aerosol for delivery to a user are generally known in the prior art. These systems typically comprise an aerosol-generating device and a replaceable cartridge. The cartridge includes a liquid aerosol-forming substrate that is capable of releasing volatile compounds when heated.
The cartridge typically also includes a heater for heating the liquid aerosol-forming substrate. In known aerosol-generating systems, the heater comprises a resistive heating element wound around a wick that supplies liquid aerosol-forming substrate to the heating element. The aerosol-generating device or cartridge also comprises a mouthpiece. When a negative pressure is applied at the mouthpiece, an electric current is passed through the heating element causing it to be heated by resistive or Joule heating, which, in turn, heats the liquid aerosol-forming substrate supplied by the wick. This causes volatile compounds to be released from the liquid aerosol-forming substrate that cool to form an aerosol. The aerosol is then drawn into a user’s mouth via the mouthpiece.
Such aerosol-generating cartridges have been found to have a number of drawbacks. One of them is “dry heating” or “dry puff” , which arises when the heating element is heated with insufficient liquid aerosol-forming substrate being supplied to the heating element. This can occur, for example, when a user has consumed all of the liquid aerosol-forming substrate in the cartridge such that the cartridge is depleted of liquid aerosol-forming substrate and needs replacing. During operation, it is preferable to maintain a supply of liquid aerosol-forming substrate to the heating element such that the heating element is maintained in a wet state because this helps to ensure that a satisfactory aerosol is produced when a user takes a puff. Dry heating can result in overheating of the heating element and, potentially, thermal decomposition of the liquid aerosol-forming substrate, which can produce undesirable by-products and an unsatisfactory aerosol. Allowing the aerosol-generating system to continue to operate when liquid aerosol-forming substrate is not being supplied to the heating element can result in a poor user experience.
In an attempt to address such issue, alternative cartridges have been proposed which comprise a heater assembly having a resistive heating element located on a heating surface of a porous body. In particular, heater assemblies have been proposed wherein the porous body is a ceramic body. Liquid aerosol-forming substrate is supplied from a liquid storage portion to the heating element via the pores of the porous body by capillary action. Heat generated by the heating element may be conducted through the porous body away from the heating surface.
However, it has been observed that, for sufficient liquid to be supplied to the heating element to prevent dry heating, the ceramic pores must be relatively large. Undesirably, this may accidentally lead to too much liquid being supplied to the heating surface, which may result into liquid leakage.
Additionally, the ceramic material of which the porous body is made is generally very rigid, and this may make assembling the porous body into the cartridge complicated, particularly in view of the rather tight tolerances. In known cartridges, an attempt has been made to address this by providing a silicone cap on the porous body.
It would be desirable to provide a cartridge for an aerosol-generating system that is adapted to substantially prevent leakages of liquid aerosol-forming substrate whilst at the same time countering the so-called dry heating. It would be desirable to provide a cartridge for an aerosol-generating system that is easy to assemble, so as to reduce the risk of damaging the heater assembly during manufacturing of the cartridge.
The present disclosure relates to a cartridge for an aerosol-generating system.
The cartridge may comprise a cartridge body. The cartridge body may comprise a liquid storage portion for holding a liquid aerosol-forming substrate. The cartridge may comprise a heater assembly. The heater assembly may comprise a heating element for vaporising the liquid aerosol-forming substrate. The heater assembly may further comprise a porous ceramic body for conveying liquid aerosol-forming substrate from the liquid storage portion to the heating element. The cartridge may comprise a sealing element configured to provide a sealing engagement between the porous ceramic body and the cartridge body.
The sealing element may comprise cotton or polyethylene (PE) . The sealing element may comprise 50 percent by weight or more of cotton or polyethylene (PE) . The sealing element may be made of cotton or polyethylene (PE) .
The sealing element may comprise a thermoplastic elastomer (TPE) . The sealing element may comprise 50 percent by weight or more of a thermoplastic elastomer (TPE) . The sealing element may be made of a thermoplastic elastomer (TPE) .
The sealing element may comprise a silicone-free rubber. The sealing element may comprise 50 percent by weight or more of a silicone-free rubber. The sealing element may be made of a silicone-free rubber.
According to a first aspect of the invention, there is provided a cartridge for an aerosol-generating system, the cartridge comprising: a cartridge body comprising a liquid storage portion for holding a liquid aerosol-forming substrate; a heater assembly comprising a heating element for vaporising the liquid aerosol-forming substrate and a porous ceramic body for conveying liquid aerosol-forming substrate from the liquid storage portion to the heating element; and a sealing element configured to provide a sealing engagement between the porous ceramic body and the cartridge body. The sealing element comprises one of: a) cotton or polyethylene (PE) ; a thermoplastic elastomer (TPE) ; a silicone-free rubber.
The present disclosure also relates to an aerosol-generating system. The aerosol-generating system may comprise a cartridge as described above. The aerosol-generating system may comprise an aerosol-generating device. The aerosol-generating device may comprise a power supply for supplying power to the heater assembly of the cartridge. The aerosol-generating device may comprise control circuitry for controlling the supply of power from the power supply to the heater assembly.
According to a second aspect of the invention, there is provided an aerosol-generating system comprising: a cartridge according to the first aspect of the invention; an aerosol-generating device comprising: a power supply for supplying power to the heater assembly of the cartridge, and control circuitry for controlling the supply of power form the power supply to the heater assembly of the cartridge.
In a cartridge for an aerosol-generating system in accordance with the present invention, the sealing element is advantageously adapted to be wrapped around the porous ceramic body of the heater assembly and interposed between the porous ceramic body and a cartridge body. On top of preventing leakages of liquid aerosol-forming substrate, such arrangement facilitates assembly of the porous ceramic body into the cartridge. This is because the inherent flexibility of cotton, polyethylene (PE) , thermoplastic elastomers (TPE) and silicone-free rubbers advantageously at least partly compensates for tight tolerances in the geometry and dimensions of the heater assembly and the cartridge body.
At the same time, the sealing element comprising one of cotton or polyethylene (PE) , thermoplastic elastomers (TPE) and silicone-free rubbers is advantageously adapted to protect the outer surface of the porous ceramic body of the heater assembly against wear and tear which might be caused by friction between the porous ceramic body and the cartridge body.
In contrast to certain existing cartridges for aerosol-generating systems, wherein a silicone-based sealing element is provided between the heater assembly and the cartridge body, cartridges for aerosol-generating systems in accordance with the present invention have the additional benefit that no siloxanes –the functional groups that form the backbone of silicones –can be released from the sealing element during use when the liquid aerosol-forming substrate is heated and get into the aerosol that is delivered to the user. This is desirable because certain siloxanes, such as D4 (octamethylcyclotetrasiloxane) and D5 (decamethylcyclopentasiloxane) , have been identified as hazardous substances, due to their being persistent and bioaccumulative, and may cause health issues if inhaled.
As used herein, the term “aerosol-generating device” relates to a device that interacts with a liquid aerosol-forming substrate to generate an aerosol.
As used herein, the terms “cartridge” and “aerosol-generating cartridge” relate to a component that interacts with a liquid aerosol-forming device to generate an aerosol. An aerosol-generating cartridge contains, or is configured to contain, a liquid aerosol-forming substrate.
As used herein, the term “liquid aerosol-forming substrate” relates to a liquid substrate capable of releasing volatile compounds that can form an aerosol. Such volatile compounds can be released by heating the aerosol-forming substrate.
As used herein, the term “heating element” refers to a component which transfers heat energy to the liquid aerosol-forming substrate.
As used herein, the term “porous body” refers to a component which has a plurality of pores, at least some of which are interconnected. The porous body has a liquid absorption surface, namely a surface which is exposed to and may be in direct contact with the liquid aerosol-forming substrate. The porous body has a heating surface, namely a surface on which the heating element may be located.
As described briefly above, a cartridge for an aerosol-generating system in accordance with the present invention comprises a heater assembly. The heater assembly comprises a heating element for vaporising a liquid aerosol-forming substrate, and a porous ceramic body for conveying the liquid aerosol-forming substrate to the heating element.
The porous body may have a liquid adsorption surface. The porous body may have a heating surface. The heating element may be located on the heating surface of the porous body.
The porous ceramic body comprises a plurality of pores. The plurality of pores are interconnected to provide a fluid pathway for liquid aerosol-forming substrate through the porous body, from the liquid absorption surface to the heating surface.
The porous ceramic body may comprise at least one of an oxide ceramic material, a non-oxide ceramic material, a glass-ceramic material. Preferably, the porous ceramic body comprises at least one of alumina, aluminosilicate, zirconia, silicon carbide, silicon nitride, a lithium-aluminosilicate glass-ceramic, a silicide material, and a boride material.
The porous ceramic body may comprise a capillary material that conveys a liquid aerosol-forming substrate through the material by capillary action. The porous ceramic body may have a fibrous or porous structure. The porous ceramic body may comprise a bundle of capillaries. For example, the porous ceramic body may comprise a plurality of fibres or threads or other fine bore tubes. The porous ceramic body may comprise, for example, ceramic-based fibrous materials.
The pores of the porous body may have any shape. The pores of the porous body may be interconnected pores. The porous body may comprise a plurality of longitudinal pores extending from the liquid adsorption surface of the porous body to the heating surface of the porous body.
The provision of longitudinally extending pores may advantageously facilitate efficient transfer of liquid aerosol-forming substrate from the liquid adsorption surface of the porous body to the heating surface of the porous body.
The average pore size of the porous body may vary between the liquid adsorption surface and the heating surface.
The provision of a porous body which includes a variation of pore size between the liquid adsorption surface and the heating surface may advantageously help to control the transport of liquid aerosol-forming substrate from a reservoir of liquid aerosol-forming substrate to the heating element. Specifically, the variation of pore size between the liquid adsorption surface and the heating surface may allow the porous body to provide a consistent supply of aerosol-forming substrate to the heating surface. This may advantageously contribute to avoiding the undesirable “dry heating” .
The average pore size of the porous body may vary in any way between the liquid adsorption surface and the heating surface. The average pore size may vary from relatively larger pores at the liquid adsorption surface to relatively smaller pores at the heating surface.
The porous body may have a heating end and a liquid adsorption end, the heating surface being disposed at the heating end, and the liquid adsorption surface being disposed at the liquid adsorption end. The porous body may have a first average pore size of the liquid adsorption end, and a second average pore size at the heating end, first average pore size being greater than the second average pore size.
The provision of a porous body having a larger average pore size at the liquid adsorption end, and a smaller average pore size at a heating end may particularly facilitate efficient transfer of liquid aerosol-forming substrate from the liquid adsorption end of the porous body to the heating end of the porous body without allowing leakage. In particular, the inventors of the present invention have identified that liquid aerosol-forming substrate is transferred from the liquid adsorption end of the porous body to the heating end of the porous body by capillary action. How rapidly the liquid aerosol-forming substrate moves through the porous body depends on a number of factors including, but not limited to, the geometry of the pores, the surface tension between the liquid aerosol-forming substrate and the porous body, the viscosity of the liquid aerosol-forming substrate, the surface tension of the liquid aerosol-forming substrate. The inventors of the present invention have identified the need to balance these factors to provide efficient transfer of liquid aerosol-forming substrate to the heating surface of the porous body while preventing leakage of the liquid aerosol-forming substrate.
Firstly, in order to provide an efficient capillary flow of liquid through the porous body, the capillary pressure must overcome the viscous drag pressure. Secondly, to prevent leakage, inertial forces must not overcome the capillary pressure. These two requirements are realised by providing a porous body with larger pores at the liquid adsorption end and smaller pores at the heating end.
The porous ceramic body may comprise a longitudinal surface extending between the liquid adsorption surface and the heating surface. The longitudinal surface may be liquid impermeable. The heating element and the porous ceramic body may be integrally formed.
The porous ceramic body may comprise a longitudinal groove extending along the longitudinal surface of the porous ceramic body between the liquid absorption surface and the heating surface.
The longitudinal groove may extend all the way from the liquid absorption surface of the porous ceramic body to the heating surface of the porous ceramic body. The provision of a longitudinal groove may allow air to pass from the liquid absorption surface of the porous ceramic body to the heating surface of the porous ceramic body. During use, the longitudinal grooves may advantageously direct and channel air towards the heating surface of the porous ceramic body when a user draws on the aerosol-generating system. When the air passes the heating surface, it may become entrained with aerosol generated by the heating element before being delivered to a user.
The porous ceramic body may comprise more than one longitudinal groove. For example, the porous ceramic body may comprise at least 2, at least 3, at least 4, or at least 5 longitudinal grooves. Where the porous ceramic body comprises more than one longitudinal groove, the longitudinal grooves may be evenly distributed around the periphery of the porous ceramic body.
The porous ceramic body may have a substantially constant cross section. For example, the cross sectional area of the liquid absorption surface of the porous ceramic body may be substantially the same as the cross sectional area of the heating surface.
The porous ceramic body may have any shape. For example the porous ceramic body may be generally cylindrical. Where this is the case, both the liquid absorption surface and the heating surface may be circular. The porous ceramic body may have the shape of a regular cuboid. Where this is the case, both the liquid absorption surface and the heating surface may be square.
The liquid absorption surface of the porous ceramic body may have an area that is different to an area of the heating surface of the porous body. The surface area of the heating surface may be larger than the surface area of the liquid absorption surface.
The surface area of the liquid absorption surface may be larger than the surface area of the liquid absorption surface.
The porous ceramic body may have any cross sectional shape. The porous ceramic body may have a rectangular or a circular cross sectional shape.
The heating element may be any heating element. The heating element may be fluid permeable.
As used herein with reference to the present invention, the term “fluid permeable” in the context of the heating element means that liquid aerosol-forming substrate is able to pass from one side of the heating element to the other side of the heating element without needing to go around the heating element.
It will be understood that for the heating element to be fluid permeable, the material from which the heating element is made may be fluid permeable. Alternatively, the material from which the heating element is made may be fluid impermeable, but the structure or arrangement of the heating element may nevertheless allow liquid aerosol-forming substrate to pass from one side of the heating element to the other side of the heating element.
The heating element may be an electrical heating element. For example, the heating element may be a resistive heating element. The heating element may have any suitable shape or form. Examples of suitable shapes and forms include but are not limited to a band, a strip, a filament, a wire, a mesh, a flat spiral coil, fibres or a fabric.
In some preferred examples, the heating element is planar. The planar heating element may extend substantially in a plane.
In some preferred examples, the heating element comprises a mesh. The heating element may comprise an array of filaments forming a mesh. As used herein the term "mesh"
encompasses grids and arrays of filaments having spaces therebetween. The term mesh also includes woven and non-woven fabrics.
The filaments may be formed by etching a sheet material, such as a foil. This may be particularly advantageous when the heater assembly comprises an array of parallel filaments.
If the heating element comprises a mesh or fabric of filaments, the filaments may be individually formed and knitted together.
The heating element may comprise an electrically resistive heating element. The heating element may be made from any suitable electrically conductive material. Suitable 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 of 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 metals from the platinum group. Examples of suitable metal alloys include stainless steel, constantan, nickel-, cobalt-, chromium-, aluminium-, titanium-, zirconium-, hafnium-, niobium-, molybdenum-, tantalum-, tungsten-, tin-, gallium-, manganese-and iron-containing alloys, and super-alloys based on nickel, iron, cobalt, stainless steel, iron-aluminum based alloys and iron-manganese-aluminum based alloys. is a registered trade mark of Titanium Metals Corporation. The heating element may be made from stainless steel, for example, a 300 series stainless steel such as AISI 304, 316, 304L, 316L. In a preferred example, the electrical heating element may comprise one of more of NiCr and TiZr.
Additionally, the heating element may comprise combinations of the above materials. A combination of materials may be used to improve the control of the resistance of the heating element. For example, materials with a high intrinsic resistance may be combined with materials with a low intrinsic resistance. This may be advantageous if one of the materials is more beneficial from other perspectives, for example price, machinability or other physical and chemical parameters. Advantageously, high resistivity heating allow more efficient use of battery energy.
The electrical heating element may be formed from an electrically conductive material deposited on to the porous element. As used herein, the term “electrically conductive material” denotes a material having a resistivity of 1x10-2 Ωm, or less. As used herein, the term “deposited” means applied as a layer or coating by a physical or chemical process, for example in the form of a liquid, plasma or vapour which subsequently condenses or aggregates to form the electrical heating element, rather than simply being laid on or fixed to the porous body as a solid, pre-formed component.
The electrical heating element may be deposited directly on to the porous outer surface. In other words, the electrically conductive material that forms the electrical heating element is deposited onto the porous body such that the electrical heating element is in direct contact with the porous body.
In some examples, the electrically conductive material of the electrical heating element may be at least partially diffused into the porous body. As used herein, the term “diffused into the porous body” means that the electrically conductive material is interspersed with the material of the porous body at the interface between the electrically conductive material and the porous body, for example, by extending into the pores of the porous body. This arrangement may help to secure the electrical heating element to the porous body and increase contact between the electrical heating element and the porous body to improve heating of the liquid aerosol-forming substrate and aerosol delivery.
The electrically conductive material from which the electrical heating element is formed may be deposited onto the porous body in any suitable manner. For example, the electrically conductive material may be deposited onto the porous body as a liquid using a dispensing pipette or syringe, or using a fine-tipped transferring device such as a needle.
In some examples, the at least one heating element comprises a printable electrically conductive material printed on the porous body. In such embodiments, any suitable known printing technique may be used. For example, one or more of screen-printing, gravure printing, flex-printing, inkjet printing. Such printing processes may be particularly applicable for high speed production processes.
Alternatively, the electrically conductive material, from which the electrical heating element is formed, may be deposited onto the porous body by one or more vacuum deposition processes, such as evaporation deposition and sputtering.
The at least one heating element may be formed from any suitable electrically conductive material. In certain preferred embodiments, the electrically conductive material comprises one or more of a metal, an electrically conductive polymer and an electrically conductive ceramic.
Suitable electrically conductive metals include, but are not limited to, aluminium, silver, nickel, gold, platinum, copper, tungsten, and alloys thereof. In some embodiments, the electrically conductive material comprises a metal powder suspended in a glue, such as an epoxy resin. In one embodiment, the electrically conductive material comprises silver-loaded epoxy.
Suitable electrically conductive polymers include PEDOT (poly (3, 4-ethylenedioxythiophene) ) , PSS (poly (p-phenylene sulfide) ) , PEDOT: PSS (mixture of both PEDOT and PSS) , PANI (polyanilines) , PPY (poly (pyrrole) s) , PPV (Poly (p-phenylene vinylene) ) , or any combination thereof.
Suitable electrically conductive ceramics include ITO (Indium Tin Oxide) , SLT (lanthanum-doped strontium titanate) , SYT (yttrium-doped strontium titanate) , or any combination thereof.
The electrically conductive material may further comprise one or more additives selected from a group consisting of: solvents; curing agents; adhesion promoters; surfactants; viscosity reduction agents; and aggregation inhibitors. Such additives may be used, for example, to aid deposition of the electrically conductive material on the porous outer surface of the porous body, to increase the amount by which the electrically conductive material diffuses into the porous outer surface of the porous body, to reduce the time required for the electrically conductive material to set, to increase the level of adhesion between the electrically conductive material and the porous body, or to reduce the amount of aggregation of suspended particles, such as metal particles or powder, in the electrically conductive material prior to application onto the porous outer surface of the porous body.
The heater assembly may further comprise a thermally insulating layer having a lower thermal conductivity than the porous ceramic body, wherein the thermally insulating layer is disposed between and is in contact with each of the porous ceramic body and the heating element, and the thermally insulating layer is configured to reduce heat transfer from the heating element to the porous ceramic body.
As described briefly above, a cartridge for an aerosol-generating system in accordance with the present invention comprises a cartridge body comprising a liquid storage portion for holding a liquid aerosol-forming substrate.
The cartridge body may be formed from a durable material. The cartridge body may be formed from a liquid impermeable material. The cartridge body may be formed form a mouldable plastics material, such as polypropylene (PP) or polyethylene terephthalate (PET) . The cartridge body of the cartridge may define a portion of the liquid storage portion or reservoir. The cartridge housing may define the liquid storage portion. The cartridge body and the liquid storage portion may be integrally formed. Alternatively, the liquid storage portion may be formed separately from the cartridge body and arranged in the cartridge body.
The liquid aerosol-forming substrate may be liquid at room temperature. The liquid aerosol-forming substrate may comprise both liquid and solid components. The liquid aerosol-forming substrate may comprise nicotine. The nicotine containing liquid aerosol-forming substrate may be a nicotine salt matrix. The liquid aerosol-forming substrate may comprise plant-based material. The liquid aerosol-forming substrate may comprise tobacco. The liquid aerosol-forming substrate may comprise a tobacco-containing material containing volatile tobacco flavour compounds, which are released from the aerosol-forming substrate upon heating. The liquid aerosol-forming substrate may comprise homogenised tobacco material. The liquid aerosol-forming substrate may comprise a non-tobacco-containing material. The liquid aerosol-forming substrate may comprise homogenised plant-based material.
The liquid aerosol-forming substrate may comprise one or more aerosol-formers. An aerosol-former is any suitable known compound or mixture of compounds that, in use, facilitates formation of a dense and stable aerosol and that is substantially resistant to thermal degradation at the temperature of operation of the system. Examples of suitable aerosol formers include glycerine and propylene glycol. Suitable aerosol-formers are well known in the art and include, but are not limited to: polyhydric alcohols, such as triethylene glycol, 1, 3-butanediol and glycerine; esters of polyhydric alcohols, such as glycerol mono-, di-or triacetate; and aliphatic esters of mono-, di-or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate. The liquid aerosol-forming substrate may comprise water, solvents, ethanol, plant extracts and natural or artificial flavours.
The liquid aerosol-forming substrate may comprise nicotine and at least one aerosol-former. The aerosol-former may be glycerine or propylene glycol. The aerosol former may comprise both glycerine and propylene glycol. The liquid aerosol-forming substrate may have a nicotine concentration of between about 0.5 percent by weight and about 10 percent by weight, for example about 2 by weight.
Additionally, a cartridge for an aerosol-generating system in accordance with the present invention comprises a sealing element configured to provide a sealing engagement between the porous ceramic body of the heater assembly and the cartridge body.
In some embodiments, the sealing element comprises a cup-shaped body configured to be arranged onto the porous ceramic body of the heater assembly. Preferably, the cup-shaped body has an opening at one end and defines an internal cavity for receiving at least part of the porous ceramic body. More preferably, an overall shape and volume of the internal cavity substantially match an overall shape and volume of the porous ceramic body. Thus, the cup-shaped body of the sealing element can be tightly wrapped around the periphery of the porous ceramic body to hold the porous ceramic body in a particularly secure fashion. This advantageously ensures the provision of a particularly tight and stable sealing engagement between the porous ceramic body and the cartridge body.
In certain embodiments, the sealing element comprises cotton or polyethylene (PE) . Preferably, the sealing element comprises at least 50 percent by weight of cotton or polyethylene (PE) . More preferably, the sealing element comprises at least 60 percent by weight or at least 70 percent by weight or at least 80 percent by weight or at least 90 percent by weight of cotton or polyethylene (PE) .
In certain preferred embodiments, the sealing element comprise 95 percent by weight or more of cotton or polyethylene (PE) .
In particularly preferred embodiments, the sealing element is substantially entirely made of cotton or polyethylene (PE) .
Use of cotton or polyethylene (PE) is beneficial in that the sealing element displays good flexibility and may display a certain degree of liquid retention capability. At the same time, sealing elements made from cotton or polyethylene (PE) have been found to be particularly effective at protecting the porous ceramic body of the heater assembly against damages that may be caused during manufacturing and assembly, as well as during an accidental drop of the aerosol-generating system.
In contrast to known cartridges for aerosol-generating system wherein the heater assembly is wrapped in a silicone sealing elements, cartridges in accordance with the present invention that include a cotton or PE sealing element display extremely low or no emissions (less than 100 nanograms/100 puffs) of siloxanes.
Preferably, a density of the polyethylene (PE) is at least 0.91 grams/cubic centimetre. Preferably, a density of the polyethylene (PE) is less than or equal to 0.96 grams/cubic centimetre. In certain embodiments, a density of the polyethylene (PE) is from 0.91 grams/cubic centimetre to 0.96 grams/cubic centimetre.
In certain embodiments, the sealing element comprises a thermoplastic elastomer (TPE) . Preferably, the sealing element comprises at least 50 percent by weight of a thermoplastic elastomer (TPE) . More preferably, the sealing element comprises at least 60 percent by weight or at least 70 percent by weight or at least 80 percent by weight or at least 90 percent by weight of a thermoplastic elastomer (TPE) .
In certain preferred embodiments, the sealing element comprise 95 percent by weight or more of a thermoplastic elastomer (TPE) .
In particularly preferred embodiments, the sealing element is substantially entirely made of a thermoplastic elastomer (TPE) .
Thermoplastic elastomers (TPEs) have been found to be particularly suitable for compensating for tight tolerances and facilitating assembly of the heater assembly into the cartridge body. Additionally, they form an impermeable, protective surface that is adapted to ensure a particularly tight sealing of the heater assembly within the cartridge. A sealing element made from a thermoplastic elastomer (TPE) has a smooth and soft finish, which is especially suitable for wrapping the porous ceramic body of the heater assembly and can minimise the risk of damaging the porous ceramic body during manufacturing of the cartridge.
In contrast to known cartridges for aerosol-generating system wherein the heater assembly is wrapped in a silicone sealing elements, cartridges in accordance with the present invention that include a TPE sealing element display extremely low or no emissions (less than 100 nanograms/100 puffs) of siloxanes.
Preferably, the thermoplastic elastomer has a Shore A hardness from 60 to 80.
As used herein, the term “Shore A hardness” is used to describe the durometer hardness of a rubber-like material, and is assessed in accordance with ASTM D2240 (2015) . The test effectively measures the penetration of a specified indentor into a specimen of the material under specified conditions of force and time. To this purpose, the specimen is placed on a hard flat surface. The indentor for the instrument is then pressed into the specimen making sure that it is parallel to the surface. The hardness is read within one second of firm contact with the specimen. The test specimens are generally 6.4 millimetres thick. It is possible to pile several specimens to achieve a thickness of 6.4 millimetres, but use of one specimen is preferred.
More preferably, the thermoplastic elastomer has a Shore A hardness from 65 to 75. In particularly preferred embodiments, the thermoplastic elastomer has a Shore A hardness of 70.
The inventors have found that a TPE having a Shore A hardness within the ranges described above is flexible enough to wrap the ceramic porous heater and at the same time provides desirable protection against wear and tear.
An example of a suitable thermoplastic elastomer for use in a sealing element of a cartridge in accordance with the present invention iswhich is commercially available from KRAIBURG TPE GmbH & Co. KG.
In certain embodiments, the sealing element comprises a silicone-free rubber. Preferably, the sealing element comprises at least 50 percent by weight of a silicone-free rubber. More preferably, the sealing element comprises at least 60 percent by weight or at least 70 percent by weight or at least 80 percent by weight or at least 90 percent by weight of a silicone-free rubber.
In certain preferred embodiments, the sealing element comprise 95 percent by weight or more of a silicone-free rubber.
In particularly preferred embodiments, the sealing element is substantially entirely made of a silicone-free rubber.
In some embodiment, the silicone-free rubber is an unsaturated rubber that can be cured by sulphur vulcanisation. For example, the silicone-free rubber may be selected from the group consisting of: natural polyisoprene (cis-1, 4-polyisoprene natural rubber (NR) and trans-1, 4-polyisoprene gutta-percha) , synthetic polyisoprene, polybutadiene (BR) , chloroprene rubber (CR) , polychloroprene, neoprene, baypren, butyl rubber (IIR) , halogenated butyl rubber (BIIR) , styrene-butadiene rubber (SBR) , nitrile rubber (NBR) , and hydrogenated nitrile rubber (HNBR) .
In other embodiments, the silicone-free rubber is a saturated rubber that cannot be cured by sulphur vulcanisation. For example, the silicone-free rubber may be selected from the group consisting of: EPM (ethylene propylene rubber, a copolymer of ethene and propene) and EPDM rubber (ethylene propylene diene rubber, a terpolymer of ethylene, propylene and a diene-component) , epichlorohydrin rubber (ECO) , polyacrylic rubber (ACM, ABR) , fluoroelastomers (FKM, and FEPM) Viton, Tecnoflon, Fluorel, Aflas and Dai-El, perfluoroelastomers (FFKM) Tecnoflon PFR, Kalrez, Chemraz, Perlast, polyether block amides (PEBA) , chlorosulphonated polyethylene (CSM) , (Hypalon) , ethylene-vinyl acetate (EVA) .
In further embodiments, the silicone-free rubber is a 4S elastomer. For example, the silicone-free rubber may be selected from the group consisting of: resilin, elastin, polysulphide rubber, elastolefin, poly (dichlorophosphazene) .
Silicone-free rubbers of the types described above have been found to provide an impermeable, protective surface around the heater assembly, that is adapted to ensure a particularly tight sealing of the heater assembly within the cartridge. A sealing element made from a silicone-free rubber of the types described above can be provided that presents a smooth and soft finish. This makes such a sealine element especially suitable for wrapping the porous ceramic body of the heater assembly and minimising the risk of damaging the porous ceramic body during manufacturing of the cartridge.
In contrast to known cartridges for aerosol-generating system wherein the heater assembly is wrapped in a silicone sealing elements, cartridges in accordance with the present invention that include a silicone-free rubber sealing element display extremely low or no emissions (less than 100 nanograms/100 puffs) of siloxanes.
The cartridge may have a mouthpiece arranged at a mouth end of the cartridge. The mouthpiece may have an aerosol outlet through which generated aerosol may be drawn by a user. The cartridge may have a connection end configured to couple the cartridge to an aerosol-generating device.
The cartridge may comprise an air inlet. The cartridge may comprise an enclosed airflow passage from the air inlet to the aerosol outlet. The enclosed airflow passage may extend from the air inlet, past the heater assembly, to the aerosol outlet. The enclosed airflow passage may pass around an external surface of the liquid storage portion. Alternatively, the enclosed airflow passage may pass through the liquid storage portion. For example, the liquid storage portion may have an annular cross-section defining an internal passage, and the airflow passage may extend through the internal passage of the liquid storage portion.
The cartridge may comprise a first airflow pathway that extends from the air inlet towards the heater assembly in a first direction. The cartridge may comprise a second airflow pathway that extends past the electrical heating element and is configured to entrain the aerosol. The cartridge may comprise a third airflow pathway that extends from the heater assembly to an aerosol outlet in a second direction. The second direction may be opposite to the first direction. The second airflow pathway may provide a fluid connection between the first airflow pathway and the third airflow pathway.
As mentioned before, a cartridge in line with the foregoing description finds use in an aerosol-generating system comprising the cartridge and an aerosol-generating device comprising: a power supply for supplying power to the heater assembly of the cartridge, and control circuitry for controlling the supply of power form the power supply to the heater assembly of the cartridge.
The cartridge may comprise the liquid aerosol-forming substrate in the liquid storage portion. The liquid aerosol-forming substrate may be as described above.
The aerosol-generating system may be portable. The aerosol-generating system may have a size comparable to a conventional cigar or cigarette.
The aerosol-generating device may comprise a housing. The housing may be elongate. The housing may comprise any suitable material or combination of materials. Examples of suitable materials include metals, alloys, plastics or composite materials containing one or more of those materials, or thermoplastics that are suitable for food or pharmaceutical applications, for example polypropylene, polyetheretherketone (PEEK) and polyethylene. The material is preferably light and non-brittle.
The aerosol-generating device housing may define a cavity or recess for receiving a portion of a cartridge. The aerosol-generating device may have a connection end configured to removably connect the aerosol-generating device to a cartridge. The connection end may comprise the cavity or recess for receiving the cartridge.
The aerosol-generating device may have a distal end, opposite the connection end. The distal end may comprise an electrical connector configured to connect the aerosol-generating device to an electrical connector of an external power supply, for charging the power supply of the aerosol-generating device.
The aerosol-generating device may contain control circuitry. The control circuitry may comprise any suitable controller or electrical components. The controller may comprise a memory. Information for performing the above-described method may be stored in the memory. The control circuitry may comprise a microprocessor. The microprocessor may be a programmable microprocessor, a microcontroller, or an application specific integrated chip (ASIC) or other electronic circuitry capable of providing control. The control circuitry may be configured to supply power to the heating element continuously following activation of the device, or may be configured to supply power intermittently, such as on a puff-by-puff basis. The power may be supplied to the heating element in the form of pulses of electrical current, for example, by means of pulse width modulation (PWM) . The control circuitry may comprise further electronic components. For example, in some embodiments, the control circuitry may comprise any of: sensors, switches, display elements.
The aerosol-generating device may contain a power supply in the form of a battery. The battery may be rechargeable. The battery may be a Lithium based battery, for example a Lithium-Cobalt, a Lithium-Iron-Phosphate, a Lithium Titanate or a Lithium-Polymer battery. The battery may be a Nickel-metal hydride battery or a Nickel cadmium battery. The power supply may be another form of charge storage device such as a capacitor. The power supply may be rechargeable and be configured for many cycles of charge and discharge. The power supply may have a capacity that allows for the storage of enough energy for one or more user experiences of the aerosol-generating system; for example, the power supply may have sufficient capacity to allow for the continuous generation of aerosol for a period of around six minutes, corresponding to the typical time taken to smoke a conventional cigarette, or for a period that is a multiple of six minutes. In another example, the power supply may have sufficient capacity to allow for a predetermined number of puffs or discrete activations of the aerosol-generating system.
Below, there is provided a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, or embodiment, or aspect described herein.
Example EX 1: A cartridge for an aerosol-generating system, the cartridge comprising: a cartridge body comprising a liquid storage portion for holding a liquid aerosol-forming substrate; a heater assembly comprising a heating element for vaporising the liquid aerosol-forming substrate and a porous ceramic body for conveying liquid aerosol-forming substrate from the liquid storage portion to the heating element; and a sealing element configured to provide a sealing engagement between the porous ceramic body and the cartridge body.
Example EX 2: A cartridge according to Example EX1, wherein the sealing element comprises cotton or polyethylene (PE) .
Example EX 3: A cartridge according to Example EX2, wherein the sealing element comprises at least 50 percent by weight of cotton or polyethylene (PE) .
Example EX 4: A cartridge according to Example EX2, wherein the sealing element comprises at least 60 percent by weight of cotton or polyethylene (PE) .
Example EX 5: A cartridge according to Example EX2, wherein the sealing element comprises at least 70 percent by weight of cotton or polyethylene (PE) .
Example EX 6: A cartridge according to Example EX2, wherein the sealing element comprises at least 80 percent by weight of cotton or polyethylene (PE) .
Example EX 7: A cartridge according to Example EX2, wherein the sealing element comprises at least 90 percent by weight of cotton or polyethylene (PE) .
Example EX 8: A cartridge according to Example EX2, wherein the sealing element comprises at least 95 percent by weight of cotton or polyethylene (PE) .
Example EX 9: A cartridge according to Example EX2, wherein the sealing element is substantially entirely made of cotton or polyethylene (PE) .
Example EX 10: A cartridge according to Example EX1, wherein the sealing element comprises a thermoplastic elastomer (TPE) .
Example EX 11: A cartridge according to Example EX10, wherein the sealing element comprises at least 50 percent by weight of a thermoplastic elastomer (TPE) .
Example EX 12: A cartridge according to Example EX10, wherein the sealing element comprises at least 60 percent by weight of a thermoplastic elastomer (TPE) .
Example EX 13: A cartridge according to Example EX10, wherein the sealing element comprises at least 70 percent by weight of a thermoplastic elastomer (TPE) .
Example EX 14: A cartridge according to Example EX10, wherein the sealing element comprises at least 80 percent by weight of a thermoplastic elastomer (TPE) .
Example EX 15: A cartridge according to Example EX10, wherein the sealing element comprises at least 90 percent by weight of a thermoplastic elastomer (TPE) .
Example EX 16: A cartridge according to Example EX10, wherein the sealing element comprises at least 95 percent by weight of a thermoplastic elastomer (TPE) .
Example EX 17: A cartridge according to Example EX10, wherein the sealing element is substantially entirely made of a thermoplastic elastomer (TPE) .
Example EX 18: A cartridge according to Example EX1, wherein the sealing element comprises a silicone-free rubber.
Example EX 19: A cartridge according to Example EX18, wherein the sealing element comprises at least 50 percent by weight of a silicone-free rubber.
Example EX 20: A cartridge according to Example EX18, wherein the sealing element comprises at least 60 percent by weight of a silicone-free rubber.
Example EX 21: A cartridge according to Example EX18, wherein the sealing element comprises at least 70 percent by weight of a silicone-free rubber.
Example EX 22: A cartridge according to Example EX18, wherein the sealing element comprises at least 80 percent by weight of a silicone-free rubber.
Example EX 23: A cartridge according to Example EX18, wherein the sealing element comprises at least 90 percent by weight of a silicone-free rubber.
Example EX 24: A cartridge according to Example EX18, wherein the sealing element comprises at least 95 percent by weight of a silicone-free rubber.
Example EX 25: A cartridge according to EX18, wherein the sealing element is substantially entirely made of a silicone-free rubber.
Example EX26: A cartridge according to any one of Examples EX2 to EX9, wherein the polyethylene has a density from 0.91 g/cm3 to 0.96 g/cm3.
Example EX27: A cartridge according to any one of Examples EX10 to EX17, wherein Examples will now be further described with reference to the accompanying Figures, wherein:
Figure 1 is a schematic cross-sectional view of an aerosol-generating system according to an example of the present disclosure;
Figure 2A is a schematic perspective view of the porous ceramic body of the heater assembly of the aerosol-generating system of Figure 1;
Figure 2B is another schematic perspective view of the porous ceramic body of Figure 2A; and
Figure 2C is a schematic perspective view of a sealing element configured to provide a sealing engagement between the porous ceramic body of Figures 2A and 2B and the cartridge body in the aerosol-generating system of Figure 1.
It will be appreciated that the figures in the present application are schematic and have been simplified for the purposes of clarity. Consequently, some features may have been omitted and the features are not necessarily drawn to scale.
References to orientations such as vertical, horizontal, above, below, upper and lower, etc. when describing the features of the present disclosure are not intended to imply any limitation on the orientation of those features but are merely intended to show the relative spatial arrangement of features, particularly with reference to the figures or in normal use. It will be appreciated that the features of the present disclosure may have different orientations in use.
Referring to Figure 1, there is shown schematically an aerosol-generating system 10 according to an example of the present disclosure. The aerosol-generating system 10 comprises two main components, a cartridge 100 and a main body part or aerosol-generating device 200. The aerosol-generating device 200 comprises a housing 202 and is adapted to receive at one end a respective connection end 102 of the cartridge 100. In more detail, the cartridge 100 is removably connectable to the aerosol-generating device 200 by inserting the connection end 102 of the cartridge 100 into a recess defined within the aerosol-generating device 200. The connection end 102 of the cartridge 100 and the recess of the aerosol-generating device 200 each have electrical contacts or connections (not shown) which are arranged to cooperate to provide an electrical connection between the cartridge 100 and the aerosol-generating device 200. The aerosol-generating device 200 contains a power source in the form of a battery 204, which in this example is a rechargeable lithium ion battery, and control circuitry 206. The aerosol-generating system 50 is portable and has a size comparable to a conventional cigar or cigarette.
The cartridge 100 comprises a cartridge body 104. The cartridge body 104 defines a mouthpiece 106 at an end opposite the connection end 102. Further, the cartridge body 104 internally defines a reservoir or liquid storage portion 108 for holding liquid aerosol-forming substrate 110. The liquid storage portion 108 has an opening in its lower end or base and a heater assembly 112 is arranged in the opening.
The heater assembly 112 includes a heating element 116 and a porous ceramic body 118.
The heating element 116 is configured to vaporise an aerosol-forming substrate, such as a liquid aerosol-forming substrate, to form an aerosol. The heating element 116 is configured to convert electrical energy into heat energy by material resistance of the heating element 116 to an electrical current.
The porous ceramic body 118 is configured to convey the liquid aerosol-forming substrate to the heating element 116. In other words, the porous ceramic body 118 supplies the liquid aerosol-forming substrate to the heating element 116.
Figures 2A and 2B show two perspective views of the porous ceramic body 118 of the cartridge 100 of Figure 1.
The porous ceramic body 118 has a first end face and an opposing second end face. The first end face is a liquid absorption surface 130 and the second end face is a heating surface 140. In the example of Figures 2A and 2B , the liquid absorption surface 130 and the heating surface 140 are both substantially flat surfaces. The porous ceramic body 118 also has a plurality of lateral faces extending between the liquid absorption surface 130 and the heating surface 140. In this example, the porous ceramic body 118 has a first lateral face 150 opposing a second lateral face 160, and a third lateral face 170 opposing a fourth lateral face 180.
The porous ceramic body 118 comprises a plurality of pores. The plurality of pores are interconnected to provide a fluid pathway for liquid aerosol-forming substrate through the porous body 118, from the liquid absorption surface 130 to the heating surface 140. The porous body 118 is formed from a ceramic material that does not chemically interact with the liquid aerosol-forming substrate, such as for example Ca₂SiO₃ or SiO₂ (or Ca₂SiO₃ and SiO₂) .
The cartridge 100 further comprises a sealing element 300 configured to provide a sealing engagement between the porous ceramic body 118 and the cartridge body 104. A schematic perspective view of the sealing element 300 is shown in the drawing of Figure 2C.
The sealing element 300 comprises a substantially parallelepiped, cup-shaped body 302 configured to be arranged onto the porous ceramic body 118. The cup-shaped body 302 has an opening 304 at one end and defines an internal cavity 306 to receive the porous ceramic body 118. The overall shape and the volume of the internal cavity 306 substantially match the overall shape and volume of the porous ceramic body 118, so that the cup-shaped body 302 of the sealing element 300 can be tightly wrapped around the periphery of the porous ceramic body 118.
In the example of Figure 1, the sealing element is made of polyethylene PE having a density of from 0.91 g/cm3 to 0.96 g/cm3. However, it will be appreciated that, in accordance with the present disclosure, the sealing element 300 may be replaced with one made of a thermoplastic elastomer (TPE) or with one made of a silicone-free rubber.
An air flow passage 400 extends through the cartridge 10 from an air inlet 402 formed in a side of the housing 202, past the heating element 116 of the heater assembly 112, and from the heater assembly 112 to a mouthpiece opening 404 formed in the cartridge body 104 at the end of the mouthpiece 106.
In the drawing of Figure 1, thick arrows are used to represent schematically a direction of airflow into, through and out of the air flow passage 400 during use of the aerosol-generating system. While the drawing of Figure 1 schematically shows two discrete accesses for air inlet into the air flow passage 400, it will be appreciated that an air inlet may extend continuously around the perimeter of the housing 202 at the interface between the cartridge body 104 and the housing 202 of the aerosol-generating device 200.
The aerosol-generating system 10 is configured so that a user can puff or draw on the mouthpiece 106 of the cartridge 100 to draw aerosol into their mouth through the mouthpiece opening 404.
In operation, when a user puffs on the mouthpiece 106, air is drawn through the air flow passage 400 from the air inlet 402, past the heater assembly 112 and to the aerosol outlet defined by the mouthpiece opening 404. The control circuitry 206 controls the supply of electrical power from the battery 204 to the cartridge 100 when the system is activated. The electrical power supplied to the cartridge 100 controls the amount and properties of the vapour produced by the heater assembly 10. The control circuitry 206 may include an airflow sensor (not shown) and the control circuitry 206 may supply electrical power to the heater assembly 10 when user puffs are detected by the airflow sensor. Alternatively, a user may activate the aerosol-generating system 10 by pressing a button (not shown) . When a user puffs on the mouthpiece 106 of the cartridge 100, the heater assembly 112 is activated and generates a vapour that is entrained in the air flow passing across the heater assembly 112. The vapour cools within the cartridge to form an aerosol prior to reaching the user’s mouth via the mouthpiece opening 404.
For the purpose of the present description and of the appended claims, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term "about" . Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein. In this context, therefore, a number A is understood as A ± 10 percent (10%) of A. Within this context, a number A may be considered to include numerical values that are within general standard error for the measurement of the property that the number A modifies. The number A, in some instances as used in the appended claims, may deviate by the percentages enumerated above provided that the amount by which A deviates does not materially affect the basic and novel characteristic (s) of the claimed invention. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.

Claims

A cartridge for an aerosol-generating system, the cartridge comprising:

a cartridge body comprising a liquid storage portion for holding a liquid aerosol-forming substrate;

a heater assembly comprising a heating element for vaporising the liquid aerosol-forming substrate and a porous ceramic body for conveying liquid aerosol-forming substrate from the liquid storage portion to the heating element; and

a sealing element configured to provide a sealing engagement between the porous ceramic body and the cartridge body, the sealing element comprising at least 50 percent by weight of one of:

a) cotton or polyethylene (PE) ;

b) a thermoplastic elastomer (TPE) ;

c) a silicone-free rubber.
A cartridge according to claim 1, wherein the sealing element comprises 95 percent by weight or more of the one of cotton or polyethylene (PE) ; a thermoplastic elastomer (TPE) ; and a silicone-free rubber
A cartridge according to claim 1, wherein the polyethylene has a density from 0.91 g/cm³ to 0.96 g/cm³.
A cartridge according to claim 1, wherein the thermoplastic elastomer has a density from 0.9 g/cm³ to 1.5 g/cm³.
A cartridge according to claim 1, wherein the silicone-free rubber is selected from the list consisting of natural polyisoprene (cis-1, 4-polyisoprene natural rubber and trans-1, 4-polyisoprene gutta-percha) , synthetic polyisoprene, polybutadiene rubber, chloroprene rubber, polychloroprene, neoprene, butyl rubber, halogenated butyl rubber, styrene-butadiene rubber, nitrile rubber, hydrogenated nitrile rubbers.
A cartridge according to claim 1, wherein the silicone-free rubber is selected from the list consisting of ethylene propylene rubber, ethylene propylene diene rubber, epichlorohydrin rubber, polyacrylic rubber, fluoroelastomers, perfluoroelastomers, polyether block amides, chloro-sulphonated polyethylene, ethylene-vinyl acetate.
A cartridge according to claim 1, wherein the silicone-free rubber is selected from the list consisting of resilin, elastin, polysulfide rubber, elastolefin, poly (dichlorophosphazene) .
A cartridge according to claim 1, wherein the porous ceramic body extends from a liquid absorption surface of the porous ceramic body to a liquid heating surface of the porous ceramic body and the heating element is provided on the liquid heating surface.
A cartridge according to claim 1, wherein the porous ceramic body extends from a liquid absorption surface of the porous ceramic body to a liquid heating surface of the porous ceramic body and the heating element is at least partly embedded within the porous ceramic body.
A cartridge according to any one of the preceding claims, wherein the sealing element comprises a cup-shaped body configured to be arranged onto the porous ceramic body.
A cartridge according to claim 10, wherein the cup-shaped body has an opening at one end and defines an internal cavity for receiving at least part of the porous ceramic body.
A cartridge according to claim 11, wherein an overall shape and volume of the internal cavity substantially match an overall shape and volume of the porous ceramic body.