Fluid-permeable heating unit with lid

Abstract

A fluid-permeable heating unit (10) for an aerosol generating system, the heating unit (10) comprising: a lid (12) comprising a hollow body (14) with a first (16) and a second (18) lid opening, wherein the first lid opening (16) opposes the second lid opening (18), wherein the lid (12) further comprises a support (28) with a support opening (30), and wherein the support (28) covers the first lid opening (16), such that the support opening (30) coincides with at least a portion of the first lid opening (16); wherein the cover (12) and the support (28) are integrally formed; a substantially flat, electrically conductive, fluid-permeable heating element (20), wherein the heating element (20) is configured to vaporize the aerosol-forming liquid substrate, and wherein the heating element (20) is mounted on the support (28) such that the heating element (20) extends through the first opening of the lid (16); and a piece of host material (24) configured to retain the aerosol-forming liquid substrate, wherein at least a portion of the piece of host material (24) is disposed in the hollow body (14) between the first (16) and second (18) opening of the lid.

Description

Fluid-permeable heating unit with lid The present invention relates to aerosol generating systems, such as electrically operated portable smoking systems. In particular, the present invention relates to heating units for aerosol generating systems in which the aerosol-forming substrate is a liquid and is vaporized. Electrically operated portable aerosol generating systems are known, consisting of a device portion comprising a battery and electronic control circuitry, a cartridge portion comprising a supply of aerosol-forming substrate contained in a liquid storage portion, and an electrically operated heating unit acting as a vaporizer. A cartridge comprising both a supply of aerosol-forming substrate contained in a liquid storage portion and a vaporizer is sometimes referred to as a "cartomizer." The heating unit may comprise a fluid-permeable heating element in contact with a capillary medium such as an elongated wick soaked in the liquid aerosol-forming substrate contained in the liquid storage portion.The cartridge portion typically comprises not only the supply of the aerosol-forming substrate and an electrically operated heating unit, but also a nozzle through which the user sucks during use to draw the aerosol into their mouth. WO2016 / 096780 describes an aerosol generating system comprising a cartridge having a cartridge housing and a heater arranged to cover an open proximal end of the cartridge housing. The heater may comprise a mesh connected to electrical contacts. The electrical contacts are provided on a polyimide substrate. The housing may comprise a high-release material that serves as a liquid reservoir and directs the liquid toward the heater for evaporation. However, this document does not describe a system having a cap and support that are integrally formed. A heating unit with a fluid-permeable heating element can have a fragile structure. The components of the heating unit can easily shift during transport, packaging, and use. Manufacturing a cartridge with such a heating unit can be difficult. It would be convenient to provide an improved heating unit for an aerosol generating system that allows for easier manufacturing at lower costs and provides a more rigid structure to prevent displacement of the heating unit components. According to a first aspect of the present invention, a fluid-permeable heating unit is provided for an aerosol generating system, the heating unit comprising a lid, the lid comprising a hollow body with a first and a second lid opening, wherein the first lid opening opposes the second lid opening, the lid further comprising a support with a support opening, and wherein the support covers the first lid opening, such that the support opening coincides with at least a portion of the first lid opening; wherein the lid and the support are integrally formed;A substantially flat, electrically conductive, fluid-permeable heating element, wherein the heating element is configured to vaporize the aerosol-forming substrate, and wherein the heating element is mounted in the lid such that the heating element extends through the first opening of the lid; and a piece of host material configured to retain the liquid aerosol-forming substrate, wherein at least a portion of the piece of host material is disposed in the hollow body between the first and second openings of the lid. The solution presented here is to attach a cap with a hollow body to the heating element to improve the element's stability and to provide a guide for a capillary medium that can be placed within the cap's hollow body. Using a cap can simplify the manufacturing of the heating unit and improve its rigidity. An additional purpose of the heating unit according to the present invention may be to seal a filled cartridge. The idea is to pre-assemble all the parts of the heating unit and then manipulate this one-piece component to facilitate sealing the cartridge. As used herein, "substantially flat" means initially formed in a single plane and not wrapped around or otherwise adapted to fit a curved or other non-flat shape. As used herein, "electrically conductive" means formed from a material having a resistivity of 1 x 10⁻⁴ ohms or less. As used herein, "electrically insulating" means formed from a material having a resistivity of 1 x 10⁴ ohms or more. As used herein, "fluid-permeable" in relation to a heating unit means that the aerosol-forming substrate, in a gaseous phase and possibly a liquid phase, can readily pass through the heating element of the heating unit. The heating unit comprises a lid formed from a material with a high thermal decomposition temperature and capable of withstanding rapid temperature changes. The heating element is supported within the lid. Preferably, the lid is molded from plastic granules. The plastic granules may be polyether ether ketone (PEEK), liquid crystal polymers (LCP), or any other polymeric material. Preferably, the lid material is overmolded onto the underside of the heating element. More preferably, the lid is manufactured from VICTREX PEEK by overmolding it into a mesh-like strip. The underside of the heating element faces the first opening in the lid. Overmolding the lid onto the underside of the heating element is advantageous because no additional mounting material, such as terminals, is required to secure the heating element to the lid. Preferably, the lid is large enough to separate the liquid storage portion from the heating element by a distance of at least 1.5 millimeters, and preferably between 3 and 6 millimeters to provide a sufficient temperature drop across the lid. Advantageously, in this embodiment, the liquid storage portion can be made of a more cost-effective material with a lower thermal decomposition temperature, such as polyethylene or polypropylene. The heating unit further comprises a substantially flat heating element that allows for simple manufacturing. Geometrically, the term "substantially flat" and electrically conductive heating element refers to an arrangement of electrically conductive filaments that takes the form of an essentially two-dimensional topological manifold. Therefore, the substantially flat and electrically conductive heating element extends in two dimensions along a surface significantly more than in a third dimension. In particular, the dimensions of the substantially flat heating element in the two dimensions within the surface are at least five times larger than in the third dimension, normal to the surface.An example of a substantially flat heating element is a structure between two substantially parallel imaginary surfaces, where the distance between these two imaginary surfaces is substantially smaller than the extent within the surfaces. In some embodiments, the substantially flat heating element is flat. In other embodiments, the substantially flat heating element is curved along one or more dimensions, for example, forming a dome or bridge shape. The term "filament" is used throughout this description to refer to an electrical path between two electrical contacts. A filament can branch arbitrarily and diverge into several paths, or it can converge from several electrical paths into one path. A filament can have a round, square, flat, or any other cross-sectional shape. A filament can be straight or curved. The term "heating element" is used throughout the description to refer to an arrangement of one or, preferably, a plurality of filaments. The heating element may be an arrangement of filaments, for example, arranged parallel to each other. The heating element is permeable to fluids. The heating element may be cut to provide open areas when mounted through the first opening of the lid. Preferably, the open areas are created by cutting beveled window slots on each side of the heating element. Preferably, the filaments may form a mesh. The mesh may be woven or non-woven. The mesh may be formed using different types of grid or lattice structures. Alternatively, electrically conductive heating elements consist of an arrangement of filaments arranged parallel to each other.The mesh, arrangement or fabric of electrically conductive filaments can also be characterized by its ability to retain liquids. In a preferred embodiment, a substantially flat heating element can be constructed from a wire formed within a wire mesh. Preferably, the mesh has a plane wave design. Preferably, the heating element is a wire grid fabricated from a mesh-type strip. Electrically conductive filaments can define interstices between them, and these interstices can have a width of between 10 micrometers and 100 micrometers. Preferably, the filaments induce capillary action in the interstices, so that during use, the vaporized liquid is drawn into the interstices, increasing the area between the heating element and the aerosol-forming liquid substrate. The electrically conductive filaments can form a mesh with a size between 60 and 240 filaments per centimeter (+ / - 10 percent). Preferably, the mesh density is between 100 and 140 filaments per centimeter (+ / - 10 percent). More preferably, the mesh density is approximately 115 filaments per centimeter. The interstice width can be between 100 micrometers and 25 micrometers, preferably between 80 micrometers and 70 micrometers, more preferably approximately 74 micrometers. The percentage of open area of ​​the mesh, which is the ratio of the interstice area to the total mesh area, can be between 40 percent and 90 percent, preferably between 85 percent and 80 percent, more preferably approximately 82 percent. Throughout the description, the density of such a mesh is referred to as "first mesh density". In addition, the mesh may have one or more sections with increased mesh density, referred to as the "second mesh density," where the interstices between the filaments are less than 5 micrometers, preferably less than 2 micrometers, and more preferably approximately 1 micrometer. These one or more sections of the mesh with increased mesh density are referred to as "dense areas" throughout this description. Electrically conductive filaments can have a diameter between 8 micrometers and 100 micrometers, preferably between 10 micrometers and 50 micrometers, with the greatest preference being between 12 micrometers and 25 micrometers. The filaments can have a round cross-section or a flattened cross-section. The area of ​​the mesh, array, or fabric of the electrically conductive filaments can be small, for example, less than or equal to 50 square millimeters, preferably less than or equal to 25 square millimeters, and more preferably approximately 15 square millimeters. The size is chosen so as to incorporate the heating element within a portable system. Sizing the mesh, array, or fabric of electrically conductive filaments to less than or equal to 50 square millimeters reduces the total amount of energy required to heat the mesh, array, or fabric of electrically conductive filaments while ensuring sufficient contact between the mesh, array, or fabric of electrically conductive filaments and the liquid aerosol-forming substrate.The mesh, arrangement, or fabric of electrically conductive filaments may, for example, be rectangular and have a length of between 2 and 10 millimeters and a width of between 2 and 10 millimeters. Preferably, the mesh has dimensions of approximately 5 millimeters by 3 millimeters. The mesh or arrangement of electrically conductive filaments may cover an area of ​​between 30 percent and 90 percent of the open area of ​​the first opening in the lid through which the heating element extends. Preferably, the mesh or arrangement of electrically conductive filaments covers an area of ​​between 50 percent and 70 percent of the open area of ​​the first opening in the lid. More preferably, the mesh or arrangement of electrically conductive filaments covers an area of ​​between 55 percent and 65 percent of the open area of ​​the first opening in the lid. The heating element filaments can be made of any material with suitable electrical properties. 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 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, constantan, alloys containing nickel, cobalt, chromium, aluminum-titanium-zirconium, hafnium, niobium, molybdenum, tantalum, tungsten, tin, gallium, manganese, and iron, and superalloys based on nickel, iron, cobalt, stainless steel, Timetal®, iron-aluminum alloys, and iron-manganese-aluminum alloys. Timetal® is a registered trademark of Titanium Metals Corporation. The filaments may be coated with one or more insulators. The preferred materials for electrically conductive filaments are stainless steel and graphite, with 300 series stainless steels such as AISI 304, 316, 304L, and 316L being the most preferred. Additionally, the electrically conductive heating element may comprise combinations of the above materials. A combination of materials can be used to improve resistance control of the substantially flat heating element.For example, materials with high intrinsic resistance can be combined with materials with low intrinsic resistance. This can be advantageous if one of the materials is more beneficial from other perspectives, such as price, machinability, and other physical and chemical parameters. Advantageously, a substantially flat filament arrangement with higher resistance reduces parasitic losses. Advantageously, high-resistivity heaters allow for more efficient use of battery energy. Preferably, the filaments are made of wire. More preferably, the wire is made of metal, and most preferably of stainless steel. The electrical resistance of the mesh, arrangement, or fabric of electrically conductive filaments of the heating element may be between 0.3 ohms and 4 ohms. Preferably, the electrical resistance is equal to or greater than 0.5 ohms. More preferably, the electrical resistance of the mesh, arrangement, or fabric of electrically conductive filaments is between 0.6 ohms and 0.8 ohms, and most preferably approximately 0.68 ohms. The electrical resistance of the mesh, arrangement, or fabric of electrically conductive filaments is preferably at least one order of magnitude, and more preferably at least two orders of magnitude, greater than the electrical resistance of the electrically conductive contact areas. This ensures that the heat generated by the passage of current through the heating element is localized in the mesh or arrangement of electrically conductive filaments.It is advantageous to have a low overall resistance for the heating element if the system is electrically powered by a battery. A high-current, low-resistance system allows for the delivery of high energy to the heating element. This enables the heating element to quickly heat the electrically conductive filaments to the desired temperature. The hollow body of the cap can be configured to contain a capillary medium. Preferably, the feeding unit comprises a host material piece made of the capillary medium to retain the aerosol-forming liquid substrate. Advantageously, the cap and the host material piece can be sized to have approximately the same cross-sectional area. As used herein, approximately the same size means that the cross-sectional area of ​​the cap comprising the first opening can be up to 30 percent smaller or larger than that of the capillary material. The shape of the interior space of the cap's hollow body can further be similar to the shape of the capillary material so that the unit and the material essentially overlap. Preferably, the host material piece is essentially the same size and shape as the interior space of the hollow body. Preferably, the interior space of the hollow body is essentially cylindrical.The volume of the interior space of the hollow body can be between 50 cubic millimeters and 500 cubic millimeters, preferably between 100 cubic millimeters and 250 cubic millimeters, with greater preference approximately 150 cubic millimeters. The host material piece can be provided at least partially in contact with the heating element. When the unit and the material are substantially similar in size and shape, manufacturing can be simplified and the robustness of the manufacturing process can be improved. Preferably, the heating unit comprises a carrier material made of a capillary medium for transporting the aerosol-forming liquid substrate from the host material to the heating element. The carrier material may be provided in contact with the heating element. Preferably, the carrier material is disposed between the heating element and the host material. In this case, the host material is not in direct contact with the heating element. The carrier material may be made of a material capable of ensuring that aerosol-forming liquid substrate is in contact with at least a portion of the heating element's surface extending through the first opening of the lid. The carrier material may be in contact with the electrically conductive filaments. The carrier material may extend into the spaces between the filaments. The heating element may draw aerosol-forming liquid substrate into the spaces by capillary action. Preferably, the carrier material is in contact with the electrically conductive filaments essentially over the entire extent of the open area of ​​the first opening of the lid. A capillary material is a material that actively transports liquid from one end to the other. The capillary material can be oriented, directly or indirectly by means of another capillary medium, in contact with a liquid storage portion to transport the aerosol-forming liquid substrate toward the heating element. The capillary material may include even more than two capillary materials, including one or more layers of the capillary material in direct contact with the mesh, arrangement, or weave of electrically conductive filaments of the heating element to promote aerosol generation. The capillary material may have a fibrous or spongy structure. Preferably, the capillary material comprises an array of capillaries. For example, the capillary material may comprise a plurality of fibers, threads, or other fine-gauge tubes. The fibers or threads may generally be aligned to transport the aerosol-forming liquid substrate toward the heating element. Alternatively, the capillary material may comprise a sponge-like or foam-like material. The structure of the capillary material forms a plurality of small holes or tubes through which the aerosol-forming liquid substrate can be transported by capillary action. The capillary material may comprise any suitable material or combination of materials.Examples of suitable materials include sponge or foam materials, ceramic or graphite-based materials in the form of sintered fibers or powders, foamed metal or plastic materials, fibrous materials such as spun or extruded fibers like cellulose acetate, polyester, or bonded polyolefin, polyethylene, terylene or polypropylene fibers, nylon fibers, or ceramics. The capillary material can have any capillarity and porosity suitable for use with different liquid physical properties. The aerosol-forming liquid substrate has physical properties, including but not limited to viscosity, surface tension, density, thermal conductivity, boiling point, and vapor pressure, that enable it to be transported through the capillary medium by capillary action. At least one of the capillary materials must be of sufficient volume to ensure that a minimum amount of aerosol-forming liquid substrate is present within it to prevent "dry heating," which occurs if insufficient aerosol-forming liquid substrate is supplied to the capillary material in contact with the mesh, array, or weave of electrically conductive filaments. A minimum volume of such capillary material may be provided to allow for 20 to 40 puffs by the user. An average volume of aerosol-forming liquid substrate volatilized during a puff lasting 1 to 4 seconds is typically 1 to 4 milligrams. Therefore, providing at least one capillary material with a volume to retain 20 to 160 milligrams of aerosol-forming liquid substrate can prevent dry heating. The lid may contain two or more different capillary materials, where the carrier material, in contact with the heating element, may have a higher thermal decomposition temperature, and the host material, in contact with the carrier material but not with the heating element, may have a lower thermal decomposition temperature. The carrier material effectively acts as a separator, keeping the heating element separate from the host material so that the host material is not exposed to temperatures above its thermal decomposition temperature. As used herein, "thermal decomposition temperature" means the temperature at which a material begins to decompose and lose mass by generating gaseous products.The host material component can advantageously occupy a larger volume than the carrier material component and can contain more aerosol-forming substrate than the carrier material component. The host material component can have superior wicking performance compared to the carrier material component. The host material component can be less expensive than the carrier material component. The host material component can be made of polypropylene. The carrier material piece can separate the heating element from the host material piece by a distance of at least 0.5 millimeters, preferably between 0.5 millimeters and 2 millimeters, and more preferably about 0.75 millimeters to provide a sufficient temperature drop across the carrier material piece. The support can be a flat disc covering at least the first opening of the lid and having a thickness between 0.25 mm and 5 mm, preferably between 0.5 mm and 2.5 mm, and more preferably about 0.8 mm. The opening of the support can be between 10 mm and 50 mm, preferably between 20 mm and 30 mm, and more preferably about 25 mm. The heating element can be mounted on the support. A surface of the support is in contact with the heating element and represents a contact area that increases the contact area compared to a lid without a support. The support reduces the size of the first opening of the lid to the size of the opening of the support.Increasing the contact area between the bracket and the heating element can improve the rigidity of the heating unit and facilitate its assembly. Ideally, the cover that includes the bracket is overmolded onto the underside of the heating element. Preferably, the transport material is positioned in the opening of the support. Preferably, the transport material is essentially the same size and shape as the opening of the support. Preferably, the cover comprises at least one wall forming the hollow body extending from the support. Preferably, the wall extends perpendicular to the support. Preferably, the wall extends perpendicular to a plane of the heating element. The heating element may have at least two electrically conductive contact areas. These conductive contact areas may be positioned on an edge area of ​​the heating element. Preferably, at least two electrically conductive contact areas are each positioned in a dense area of ​​the heating element. The electrically conductive contact areas may be positioned at the ends of the heating element. A conductive contact area may be attached to the electrically conductive filaments. A conductive contact area may comprise a patch of tin. Alternatively, a conductive contact area may be integral with the electrically conductive filaments. Pursuant to a second aspect of the present invention, a cartridge for an aerosol generating system is provided. The cartridge comprises the heating unit according to the first aspect of the present invention, a liquid storage portion for storing aerosol-forming liquid substrate, and a retainer for retaining the heating unit components and for keeping the heating unit in contact with the liquid storage portion. Preferably, the cartridge comprises a nozzle for containing the liquid storage portion. Preferably, a piece of host material is disposed in the interior space of the hollow body of the heating unit lid. A piece of carrier material may be disposed in the opening of a support bracket that covers the first opening of the lid. The lid acts as a rigid housing for the carrier material and the piece of host material. The retainer keeps the heating unit in contact with the liquid storage portion by means of the carrier material and the piece of host material. Preferably, a proximal end of the lid wall abuts the support bracket, and a distal end of the lid wall engages with the liquid storage portion. The cartridge may be a disposable item to be replaced with a new cartridge once the liquid storage portion of the cartridge is empty or falls below a minimum volume threshold. Preferably, the cartridge is pre-filled with liquid aerosol-forming substrate. The cartridge may be refillable. The cartridge and its components can be made of thermoplastic polymers, such as polyether ether ketone (PEEK). In accordance with a third aspect of the present invention, an aerosol generating system is provided, comprising a main unit and the cartridge in accordance with the second aspect of the present invention, wherein the cartridge is detachably coupled to the main unit. The aerosol generating system can be an electrically powered smoking system. As used herein, the cartridge that is "detachably mounted" on the main unit means that the cartridge and main unit can be attached to and detached from each other without significantly damaging either the main unit or the cartridge. An aerosol generating system may further comprise electrical circuits connected to the heating unit and to a source of electrical power; the electrical circuits are configured to monitor the electrical resistance of the heating unit or of one or more filaments of the heating unit, and to control the supply of power to the heating unit depending on the electrical resistance of the heating unit or of one or more filaments. The electrical circuit may include a microprocessor, which may be a programmable microprocessor. The electrical circuit may also include other electronic components. The electrical circuits may be configured to regulate a power supply to the heating unit. Power may be supplied to the heating unit continuously after system activation or intermittently, such as on a puff-by-puff basis. Power may be supplied to the heating unit in the form of electrical current pulses. The aerosol generating system advantageously comprises a power supply, typically a battery within the main housing. Alternatively, the power supply may be another form of charge storage device, such as a capacitor. The power supply may require recharging and may have a capacity sufficient to store enough energy for one or more smoking experiences; for example, the power supply may have sufficient capacity to allow continuous aerosol generation for a period of approximately six minutes or for a period that is a multiple of six minutes. In another example, the power supply may have sufficient capacity to allow a predetermined number of puffs or discrete activations of the heating unit. Preferably, the aerosol generating system comprises a housing. Preferably, the housing is elongated. 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 these materials, or thermoplastics suitable for food or pharmaceutical applications, for example, polypropylene, polyetheretherketone (PEEK), and polyethylene. Preferably, the material is lightweight and non-brittle. Preferably, the aerosol generating system is portable. The aerosol generating system can be comparable in size to a conventional tobacco or cigarette. The smoking system can have a total length between approximately 30 millimeters and approximately 150 millimeters. The smoking system can have an external diameter between approximately 5 millimeters and approximately 30 millimeters. An aerosol-forming substrate is a substrate capable of releasing volatile compounds that can form an aerosol. These volatile compounds can be released by heating the aerosol-forming substrate. The aerosol-forming substrate may comprise material of plant origin. The aerosol-forming substrate may comprise tobacco. The aerosol-forming substrate may comprise a tobacco-containing material containing volatile tobacco-flavored compounds that are released from the aerosol-forming substrate upon heating. Alternatively, the aerosol-forming substrate may comprise a material that does not contain tobacco. The aerosol-forming substrate may comprise homogenized plant-based material. The aerosol-forming substrate may comprise homogenized tobacco material. The aerosol-forming substrate may comprise at least one aerosol former. The aerosol-forming substrate may comprise other additives and ingredients, such as flavorings. A method for manufacturing a fluid-permeable heating unit according to the first aspect may comprise a step of providing a substantially flat, electrically conductive heating element, and a step of overmolding a cap onto the edge areas of one side of the heating element. The cap comprises a hollow body with a first and a second cap opening. The first cap opening is opposite the second cap opening. The heating element is mounted in the cap such that the heating element extends through the first cap opening. The step of providing a heating element may include providing a mesh strip. The mesh strip may comprise an alternating sequence of mesh sections with a first mesh density and a second mesh density. Having sections of a higher density may increase the stability of the mesh during handling. The step of providing the heating element may further comprise punching beveled window slots on each side of a mesh section with the first mesh density, and removing loose wires from the mesh sections cut with the first mesh density. Preferably, the first mesh density is less than the second mesh density. Preferably, the overmolding step of a cap in the edge areas of one side of the heating element comprises preheating the plastic granules, injecting the plastic granules into a mold to manufacture the cap, and overmolding the cap on the bottom of a mesh section with the second mesh density. Preferably, the overmolding stage of a lid in the edge areas of one side of the heating element further comprises cutting the heating unit from the mesh-type strip, and removing the waste from the heating unit. Preferably, the step of cutting the heating unit from the mesh-type strip comprises die-cutting a mesh from the mesh-type strip, wherein the heating element comprises the mesh, and wherein the mesh is cut into a mesh section with the second mesh density such that the mesh comprises a mesh section with the first mesh density that is bounded by the mesh sections with the second mesh density at each of the two ends of the cut mesh. Preferably, the method for manufacturing a fluid-permeable heating unit in accordance with the first aspect of the present invention further comprises joining at least two electrically conductive contact areas over each edge area on the other side of the heating element. The step of joining at least two electrically conductive contact areas on each edge area on the other side of the heating element may comprise providing a tin foil strip, cutting tin foil patches from the tin foil strip to a size corresponding to the shape and size of the mesh section with the second mesh density, and compressing a tin foil patch onto the mesh section with the second mesh density. It would be advantageous for the foil strip to be made of a softer material than the heating element material. Preferably, the method for manufacturing a fluid-permeable heating unit in accordance with the first aspect of the present invention further comprises inspecting the heating unit. Preferably, the heating unit inspection stage comprises transporting the heating unit to inspection stations, measuring the electrical resistance of the heating element of the manufactured heating unit, visually inspecting the heating element for a correct wire count, cleaning mesh cuts, correcting mesh integrity, debris and tin foil bonding, and rejecting the heating unit if the heating unit fails in at least one of the expected electrical resistance of the heating element and the expected result of the visual inspection. In accordance with an example not part of the present invention, an apparatus is provided for manufacturing a fluid-permeable heating unit in accordance with the method for manufacturing a fluid-permeable heating unit described. To manufacture a heating unit comprising a cover and a substantially flat, electrically conductive heating element with a mesh, the apparatus for manufacturing a fluid-permeable heating unit may comprise at least one of the following equipment units: - a mesh-type strip feed reel unit to provide a mesh-type strip, the mesh-type strip comprising an alternating sequence of mesh sections with a first mesh density and a second mesh density, - a tin foil type strip feed coil unit to provide a tin foil type strip, - a tin foil cutting station for indexing a length of tin foil that is positioned over the mesh section with the second mesh density and for cutting the tin patches from the provided tin foil strip, - a tin foil pressing station to compress and bond the tin patches onto the upper surface of the mesh section with the second mesh density, - a mesh window cutting station for die-cutting beveled window slots on each side of a mesh section with the first mesh density, - a first cleaning station to remove loose wires from the cut mesh sections with the first mesh density, small particles, dust, or debris by cleaning the surfaces of the cut mesh sections with air pressure and vacuum to remove debris, - an injection molding machine to preheat the plastic granules and inject them into a mold to manufacture the lid, - an injection overmolding tool for the mesh (possibly having a single cavity or multiple cavities) for overmolding the lid onto the underside of the mesh section with the second mesh density, - a heating unit cutting station for cutting the heating unit from the mesh-type strip by punching a mesh from the mesh-type strip, the heating element comprising the mesh, and the mesh being cut into a mesh section with the second mesh density such that the mesh comprises a mesh section with the first mesh density that is bounded by the mesh sections with the second mesh density at each of the two ends of the cut mesh, - a second cleaning station to remove loose wires from the mesh by cleaning the heating unit surfaces with air pressure and vacuum to remove debris, - a transfer unit for transporting the heating unit to a heating unit inspection station, the heating unit inspection station may comprise a heating unit resistance measuring station, a heating unit visual inspection station and a heating unit rejection station, - a mesh status test station, - a heating unit resistance measuring station for measuring the electrical resistance of the mesh and tin foil strip of the manufactured heating unit, - a visual inspection of the heating unit to visually inspect the heating unit, and - a heating unit rejection station to reject a heating unit that does not meet specifications. In a preferred manufacturing process, the equipment automatically manufactures a heating unit from a mesh-type strip, a tin foil-type strip, or from plastic granules. The heating unit comprises a cover and a substantially flat, electrically conductive heating element. A preferred manufacturing process may comprise manual loading of at least one mesh-type strip coil, one tin foil-type strip coil, and plastic granules. The preferred manufacturing process may further comprise at least one step of the method that is performed automatically by the manufacturing equipment. - provide a mesh-type strip, the mesh-type strip comprising an alternating sequence of mesh sections with a first mesh density and a second mesh density, - provide a tin foil strip, - index a length of tin foil that is positioned over the mesh section with the second mesh density, - Cut the tin patches from the provided tin foil strip, - compress to join the tin patches on the upper surface of the mesh section with the second mesh density, - punch the beveled window slots on each side of a mesh section with the first mesh density, - Remove loose wires from the cut mesh sections using the first mesh density, small particles, dust, or debris by cleaning the surfaces of the cut mesh sections with air pressure and vacuum to remove debris, - preheat the plastic granules, - inject the plastic granules into a mold to manufacture the lid, - overmolding the lid onto the underside of a mesh section with the second mesh density, - cutting the heating unit from the mesh strip by die-cutting a mesh from the mesh strip, the heating element comprising the mesh, and the mesh being cut into a mesh section with the second mesh density such that the mesh comprises a mesh section with the first mesh density bounded by the mesh sections with the second mesh density at each of the two ends of the cut mesh, - removing loose wires from the mesh, small particles, dust, or debris by cleaning the mesh surfaces with air pressure and vacuum to remove the debris, - transport the heating unit to an inspection station, - measure the electrical resistance of the mesh of the manufactured heating unit, - visually inspect the heating unit for correct wire count, clean mesh cuts, correct mesh integrity, debris and tin foil bonding, and - reject the heating unit if it does not meet the specifications. The characteristics described in relation to one aspect can be applied equally to other aspects of the invention. The embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1A is a side and top perspective view of a heating unit according to an embodiment of the present invention; Figure 1B is a side and bottom perspective view of a heating unit according to an embodiment of the present invention; Figure 1C is an exploded perspective view of a heating unit according to an embodiment of the present invention; Figure 2 is a cross-sectional, top, side and perspective view of a lid and a support according to an embodiment of the present invention; Figure 3 is a top side view of a support, a heating element, and contact areas according to an embodiment of the present invention; Figure 4 is a top side view of a mesh having two different mesh densities according to an embodiment of the present invention; Figure 5 is a top side view of a mesh-type strip for manufacturing a mesh according to an embodiment of the present invention; and Figure 6 is an exploded perspective view of a cartridge for an aerosol generating system according to an embodiment of the present invention. Figure 1A shows a heating unit 10 comprising a lid 12 with a first lid opening 16 on the upper side of the lid and a second lid opening 18 on the lower side of the lid 12. The first lid opening 16 is covered with a support 28 having a support opening 30. The heating unit 10 further comprises a heating element 20 extending through the support opening 30. Figure 1B shows the heating unit 10 from a bottom view. The interior space of the hollow body 14 of the lid 12 is visible. Figure 1C shows the components of the heating element 20 comprising a mesh 32. The mesh 32 has a first mesh section 44 with a first mesh density and, at each of its two ends, a second mesh section 46 with a second mesh density, wherein the second mesh density is greater than the first density. A tin foil patch 50 is bonded to each of the two mesh sections 46 of the second mesh density. The heating element 20, with its respective mesh 32, is disposed through the opening of support 30 of support 28 on top of lid 12. The entire mesh section 44 with the first mesh density is disposed over the opening of support 30. Figure 2 shows the lid 12 and its support 28. The support 28 is an integral part of the lid 12. The inner body of the hollow body 14 of the lid 12 is cylindrical. Sections AA and BB of Figure 2 show the lid 12 and its support 28 as an integral part, whereas the perspective view of Figure 2 shows the support 28 as a separate part. Sections AA and BB of Figure 2 show the first opening of the lid 16, which is partially closed by the support 28, such that only a smaller portion, referred to as the support opening 30, of the first opening of the lid 16 remains open, through which a heating element can be extended. Figure 3 shows the support 28 formed as a separate part of the cover 12, wherein the heating element 20 is mounted so that the mesh section 44 with the first mesh density extends through the opening of the support 30. Figure 4 shows a mesh 32 of the heating element 20. Mesh 32 comprises a mesh section 44 with a first mesh density and, at each of its two ends, a second mesh section 46 with a second mesh density. Figure 5 shows a mesh-type strip 42 from which a quantity of meshes 32 can be cut. Figure 6 shows a cartridge 40 according to one embodiment of the invention. The cartridge 40 comprises the heating unit 10 with a lid 12 and a heating element 20 disposed on a support 28 of the lid 12. A carrier material piece 26 is disposed in an opening 30 of the support 28. A host material piece 24 is disposed in the interior space of the hollow body 14 of the lid 12. The lid 12 acts as a rigid housing for the carrier material piece 26 and for the host material piece 24. The cartridge 40 further comprises a liquid storage portion for storing a liquid aerosol-forming substrate. A retainer 42 is used to retain the components of the heating unit 10 and to maintain the heating unit 10 in contact with the liquid storage portion 36 by means of the carrier material piece 26 and the host material piece 24.In addition, the cartridge 40 comprises a nozzle 38 in which the liquid storage portion 36 is disposed. The illustrative methods described above are for illustrative purposes but are not exhaustive. Based on the illustrative methods described above, other methods consistent with the above will now be evident to someone skilled in the technique.

Claims

1. A fluid-permeable heating unit (10) for an aerosol generating system, the heating unit (10) comprising: a lid (12) comprising a hollow body (14) with a first (16) and a second (18) lid opening, wherein the first lid opening (16) opposes the second lid opening (18), wherein the lid (12) further comprises a support (28) with a support opening (30), and wherein the support (28) covers the first lid opening (16), such that the support opening (30) coincides with at least a portion of the first lid opening (16); wherein the lid (12) and the support (28) are integrally formed; a substantially flat, electrically conductive, fluid-permeable heating element (20), wherein the heating element (20) is configured to vaporize the aerosol-forming liquid substrate, and wherein the heating element (20) is mounted on the support (28),such that the heating element (20) extends through the first opening of the lid (16); and a guest material piece (24) configured to retain the aerosol-forming liquid substrate, wherein at least a portion of the guest material piece (24) is disposed in the hollow body (14) between the first (16) and the second (18) opening of the lid.

2. The heating unit (10) according to claim 1, wherein the guest material piece (24) has essentially the same size and shape as the interior space of the hollow body (14).

3. The heating unit (10) according to claim 1, wherein the interior space of the hollow body (14) is essentially cylindrical.

4. The heating unit (10) according to any one of claims 1 to 3,wherein the host material piece (24) is provided at least partially in contact with the heating element (20).

5. The heating unit (10) according to any one of claims 1 to 3, further comprising a carrier material piece (26) configured to transport the aerosol-forming liquid substrate from the host material piece (24) to the heating element (20), and wherein the carrier material piece (26) is provided in contact with the heating element (20) and disposed between the heating element (20) and the host material piece (24).

6. The heating unit (10) according to any preceding claim, wherein the carrier material piece (26) is disposed in the opening of the holder (30).

7. The heating unit (10) according to any preceding claim,wherein the conveying material piece (26) has essentially the same size and shape as the opening of the support (30).

8. The heating unit (10) according to any preceding claim, wherein the heating element (20) comprises a mesh (32) with at least two electrically conductive contact areas, each positioned on an edge area of ​​the heating element (20), and wherein the mesh (32) extends through at least a portion of the first opening of the lid (16).

9. The heating unit (10) according to claim 8, wherein the at least two electrically conductive contact areas (34) are each positioned on a dense area of ​​the heating element (20).

10. A cartridge (40) for an aerosol generating system,The cartridge (40) comprises: the heating unit (10) according to any one of claims 1 to 9; a liquid storage portion (36) for storing the aerosol-forming liquid substrate; and a retainer (42) for retaining the components of the heating unit (10) and for maintaining the heating unit (10) in contact with the liquid storage portion (36).

11. The cartridge (40) according to claim 10 further comprises: a nozzle (38) for containing the liquid storage portion (36).

12. An aerosol generating system, comprising a main unit and the cartridge (40) according to claim 10 or claim 11, wherein the cartridge (40) is detachably coupled to the main unit.

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