The invention relates to a vaporizing assembly for an aerosol-generating system and a delivery system for evaporating a liquid aerosol-forming substrate. In particular, the invention relates to handheld aerosol-generating systems such as electrically operated aerosol-generating systems.

Known aerosol-generating systems comprise a liquid storing portion for storing liquid aerosol-forming substrate and an electrically operated vaporizer having a heating element for evaporating the aerosol-forming substrate. An aerosol to be inhaled (e.g. "puffed") by a user is generated when the evaporated aerosol-forming substrate condenses in an airflow passing the heating element. The liquid aerosol-forming substrate is supplied to the heating element by means of a wick having a set of fibers coupled to the liquid storing portion. Based on this technology it may be challenging to accurately control the amount of aerosol-forming substrate that is supplied to the heating element and is to be incorporated in the generated aerosol. Therefore, it is also challenging to control the amount of aerosol-forming substrate inhaled by the user per inhalation cycle.

It would be desirable to provide a vaporizing assembly for an aerosol-generating system and a delivery system that provide some control of the amount of vaporized aerosol- forming substrate contained in the generated aerosol. Moreover, it would be desirable to achieve repeatability of generating an aerosol with a predetermined amount of vaporized aerosol-forming substrate per inhalation cycle.

According to a first aspect of the present invention, a vaporizing assembly suitable for an aerosol-generating system is presented. The vaporizing assembly comprises a sheet heating element and a delivery device for delivering a liquid aerosol-forming substrate from a liquid storing portion to the sheet heating element, wherein the sheet heating element is spaced apart from the delivery device and is configured for heating the delivered liquid aerosol-forming substrate to a temperature sufficient to volatilize at least a part of the delivered liquid aerosol-forming substrate. The sheet heating element is fluid permeable and comprises a plurality of electrically conductive filaments.

As used herein, a sheet heating element comprises a thin, preferably substantially flat, electrically conductive material, such as a mesh of fibers, a conductive film, or an array of heating strips, suitable for receiving and heating an aerosol-forming substrate for use in an aerosol generating system.

As used herein, "thin" means between about 8 micrometers and 2 millimeters, preferably between 8 micrometers and 500 micrometers, and most preferably between 8 micrometers and 100 micrometers. In the case of a mesh made up of filaments, these would individually preferably be less than 40 micrometers in diameter.

As used herein, "substantially flat" preferably means having a planar profile, such that it can be disposed in the vaporizing assembly spaced apart from the delivery device and receive a jet or spray from the device substantially uniformly across the heating element. However, in some applications it may be desirable to apply curvature to the sheet heating element in order to optimize the delivery of the substrate, depending on the characteristics of the delivery distribution of the delivery device. Accordingly, the "substantially flat" characteristic of the sheet heating element pertains to the form of the element in its manufacture, but not necessarily to its arrangement in the vaporizing assembly. In a preferred embodiment the sheet heating element is also disposed in a substantially flat orientation in the vaporizing assembly, spaced and opposed from the delivery device.

As used herein, "electrically conductive" means formed from a material having a resistivity of 1 x 10 ^"4 ohm meters, or less.

The sheet heating element preferably comprises a plurality of openings. For example, the sheet heating element may comprise a mesh of fibers with interstices between them. The sheet heating element may comprise a thin film or plate, optionally perforated with small holes. The sheet heating element may comprise an array of narrow heating strips connected in series.

The sheet heating element has preferably a surface area of less than or equal to about 100 square millimeters, allowing the sheet heating element to be incorporated in to a handheld system. The sheet heating element may, have a surface area of less than or equal to about 50 square millimeters.

In a preferred embodiment, electrically conductive filaments are arranged in a mesh to form the sheet heating element, of size between 160 and 600 Mesh US (+/- 10%) (i.e. between 400 and 1500 filaments per centimeter (+/- 10%)). The width of the interstices is preferably between 200 micrometer and 10 micrometer, most preferably 75 micrometer and 25 micrometer. The percentage of open area of the mesh, which is the ratio of the area of the interstices to the total area of the mesh, is preferably between 25 and 56 percent. The mesh may be formed using different types of weave or lattice structures. Alternatively, the electrically conductive filaments consist of an array of filaments arranged parallel to one another.

In an embodiment, an electrically conductive film or plate may form the sheet heating element, made of metal, conductive plastic, or other appropriate conductive material. In a preferred embodiment, the plate of film is perforated with holes that have a size on the order of interstices as described in the mesh embodiment above.

In an embodiment, narrow heating strips may be combined in an array to form the sheet heating element. The smaller the width of the heating strips in an array, the more heating strips may be connected in series in the sheet heating element of the present invention. An advantage of using smaller width heating strips that are connected in series is that the electric resistance of their combination into the sheet heating element is increased.

The delivery device comprises an inlet and an outlet. The delivery device is configured to receive a liquid aerosol-forming substrate at its inlet and to output, at its outlet, an amount of the liquid aerosol-forming substrate to be delivered to the sheet heating element.

The sheet heating element is configured for heating the delivered liquid aerosol- forming substrate to a temperature sufficient to volatilize at least a part of the delivered liquid aerosol-forming substrate.

The sheet heating element is spaced apart from the delivery device. As used herein, "spaced apart" means that the vaporizing assembly is configured for delivering the liquid aerosol-forming substrate from the delivery device via an air gap to the sheet heating element. Spaced apart also means that the delivery device and the sheet heating element are not coupled by a tubing segment for leading flow of the liquid aerosol-forming substrate from the delivery device to the heating element. Spaced apart may also mean that the delivery device and the sheet heating element are provided as individual members separated from each other by an air gap. The term spaced apart includes an integral combination of the delivery device and the sheet heating element into a combined component as long as the liquid aerosol-forming substrate has to pass through an air gap within this combined component immediately before being heated by the sheet heating element.

By providing the sheet heating element spaced apart from the delivery device, the amount of liquid aerosol-forming substrate delivered to the heating element may be better controlled compared to a vaporizer having a tubing segment for leading flow of the liquid aerosol-forming substrate from the delivery device to the heating element. Undesired capillary actions due to such tubing segment may be avoided which might otherwise for example give rise to undesirable movement of liquid between the heating element and the delivery device. When passing the air gap the delivered amount of the liquid aerosol-forming substrate may be transformed into a jet of droplets before hitting the surface of the sheet heating element. Thus, a uniform distribution of the delivered amount of the liquid aerosol- forming substrate on the sheet heating element may be enhanced, leading to better controllability and repeatability of generating an aerosol with a predetermined amount of vaporized aerosol-forming substrate per inhalation cycle.

The operating temperature of the sheet heating element may vary between 120 to

210 degrees Celsius, preferably from 150 to 180 degrees Celsius.

The sheet heating element comprises a plurality of electrically conductive filaments. Preferably, the sheet heating element is a mesh heating element, comprising the plurality of electrically conductive filaments. The plurality of electrically conductive filaments configures a mesh of the mesh heating element. The mesh is heated by applying electric power to the plurality of electrically conductive filaments. The sheet heating element may comprise a plurality of filaments which can be made of a single type of fibers, such as resistive fibers, as well as a plurality of types of fibers, including capillary fibers and conductive fibers.

The electrically conductive filaments may comprise 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, Timetal®, iron-aluminium based alloys and iron- manganese-aluminium based alloys. Timetal® is a registered trade mark of Titanium Metals Corporation. The filaments may be coated with one or more insulators. Preferred materials for the electrically conductive filaments are 304, 316, 304L, and 316L stainless steel, and graphite.

The electrical resistance of the plurality of electrically conductive filaments of the mesh heating element is preferably between 0.3 and 4 Ohms. More preferably, the electrical resistance of the plurality of electrically conductive filaments is between 0.5 and 3 Ohms, and more preferably about 1 Ohm. The electrical resistance of the plurality of electrically conductive filaments is preferably at least an order of magnitude, and more preferably at least two orders of magnitude, greater than the electrical resistance of electrical contact portions of the mesh heating element. This ensures that the heat generated by passing current through the mesh heating element is localized to the plurality of electrically conductive filaments.

The electrically conductive filaments may define interstices between the filaments and the interstices may have a width of between 10 micrometer and 100 micrometer. Preferably the filaments give rise to capillary action in the interstices, so that in use, liquid to be vaporized is drawn into the interstices, increasing the contact area between the heater assembly and the liquid.

The mesh of electrically conductive filaments may also be characterized by its ability to retain liquid, as is well understood in the art. Preferably, the mesh heating element comprises at least one filament made from a first material and at least one filament made from a second material different from the first material. This may be beneficial for electrical or mechanical reasons. For example, one or more of the filaments may be formed from a material having a resistance that varies significantly with temperature, such as an iron aluminium alloy. This allows a measure of resistance of the filaments to be used to determine temperature or changes in temperature. This can be used in a puff detection system and for controlling temperature of the heating element to keep it within a desired temperature range.

The sheet heating element is fluid permeable. As used herein, fluid permeable in relation to a sheet heating element means that the aerosol-forming substrate, in a gaseous phase and possibly in a liquid phase, can readily pass through the sheet heating element. General advantageous of a fluid permeable heater may be enhanced surface area and improved vaporization. In addition, the provision of a fluid permeable heater may also allow improved mixing of vaporized liquid aerosol-forming substrate with an air flow.

Preferably, the sheet heating element is substantially flat. As used herein, substantially flat means formed in a single plane and not wrapped around or other conformed to fit a curved or other non-planar shape. A flat heating element can be easily handled during manufacture and provides for a robust construction.

In embodiments where the sheet heating element is a mesh heating element, the mesh heating element may comprise a plurality of mesh layers stacked in an intended direction of airflow through the mesh heating element. Each mesh layer can be easily handled during manufacture and provides for a robust construction. Moreover, the stacked mesh layers improve vaporization of the liquid aerosol-forming substrate.

Preferably, the sheet heating element has a square geometry. The sheet heating element may have a heating area with a square geometry with dimensions of each side within a range of 3 millimeters to 7 millimeters, preferably from 4 millimeters to 5 millimeters.

The sheet heating element may comprise a plurality of narrow heating strips arranged spaced apart from each other on a plane. The heating strips are preferably in a rectangular shape and spatially arranged substantially parallel to each other. The heating strips may be electrically connected in series. By appropriate spacing of the heating strips, a more even heating may be obtained compared with for example where a sheet heating element having the same area is used.

Preferably, the delivery device is configured to deliver a predetermined amount of the liquid aerosol-forming substrate to the sheet heating element upon performing one activation cycle. The predetermined amount of the liquid aerosol-forming substrate is delivered via the air gap from the delivery device to the sheet heating element. By depositing the liquid aerosol-forming substrate onto the sheet heating element directly, the liquid aerosol-forming substrate may remain substantially in its liquid state until it reaches the sheet heating element, although small droplets near the element may aerosolize before contacting it. The predetermined amount of the liquid aerosol-forming substrate may be a dose equivalent to produce a desired volume of aerosol in the sheet heating element.

Preferably, the delivery device is configured for spraying the liquid aerosol-forming substrate onto the sheet heating element as a spraying jet with a size and shape appropriate to the geometry of the sheet heating element. The delivery device may be adapted to spray the liquid aerosol-forming substrate onto the sheet heating element to cover at least 90 percent, preferably at least 95 percent, of an upstream surface of the sheet heating element facing the delivery device.

The delivery device may comprise a classic type atomizer spray nozzle, in which case a flow of air is supplied through the nozzle by the action of puffing from the user, creating a pressurized air flow that will mix and act with the liquid creating an atomized spray in the outlet of the nozzle. Several systems are available on the market including nozzles that work with small volumes of liquid, in sizes that meet the requirements to fit in small portable devices. Another class of nozzle that may be used is an airless spray nozzle, sometimes referred to as a micro-spray nozzle. Such nozzles create micro spray cones in very small sizes. With this class of nozzles, the airflow management inside the device, namely inside the mouth piece, surrounds the nozzle and the heating element, flushing the heating element surface towards the outlet of the mouth piece, preferably including a turbulent air flow pattern of the aerosol exiting the mouth piece.

For either class of nozzle, the distance of the air gap between the delivery device and the sheet heating element facing the nozzle, is preferably within a range from 2 to 10 millimeters, more preferably from 3 to 7 millimeters. Any type of available spraying nozzles may be used. Airless nozzle 062 Minstac from manufacturer "The Lee Company" is an example of a suitable spray nozzle.

Preferably, the delivery device comprises a micropump for pumping the liquid aerosol-forming substrate from a liquid storage portion. By using the micropump instead of a capillary wick or any other passive medium to draw liquid, only the actually required amount of liquid aerosol-forming substrate may be transported to the sheet heating element. Liquid aerosol-forming substrate may only be pumped upon demand, for example in response to a puff by a user.

The micropump may allow on-demand delivery of liquid aerosol-forming substrate at a flow rate of for example approximately 0.7 to 4.0 microliters per second for intervals of variable or constant duration. A pumped volume of one activation cycle may be around 0.5 microliters in micropumps working within a pumping frequency from 8 to 15 hertz. Preferably, the pump volume in each activation cycle, as a dose of liquid aerosol-forming substrate per puff, may be of around 0.4 to 0.5 microliters.

The micropump may be configured to pump liquid aerosol-forming substrates that are characterized by a relatively high viscosity as compared to water. The viscosity of a liquid aerosol-forming substrate may be in the range from about 15 to 500 millipascal seconds, preferably in the range from about 18 to 81 millipascal seconds.

In some embodiments the delivery device may comprise a manually operated pump for pumping the liquid aerosol-forming substrate from a liquid storage portion. A manually operated pump reduces the number of electric and electronic components and thus, may simplify the design of the vaporizing assembly.

According to a further aspect of the present invention, there is provided a vaporizing assembly suitable for an aerosol-generating system is presented. The vaporizing assembly comprises a sheet heating element and a delivery device for delivering a liquid aerosol- forming substrate from a liquid storing portion to the sheet heating element, wherein the sheet heating element is spaced apart from the delivery device and is configured for heating the delivered liquid aerosol-forming substrate to a temperature sufficient to volatilize at least a part of the delivered liquid aerosol-forming substrate.

According to a second aspect of the present invention, there is provided an aerosol- generating system comprising the vaporizing assembly according to the first aspect described above and further comprising a user operation detection unit for detecting an operation of a user to initiate aerosol generation. The user operation detection unit may be configured by a puff detection system, e.g. a puff sensor. Alternately or optionally, the user operation detection unit may be configured by an on-off button, e.g. an electrical switch. The on-off button may be configured for triggering activation of at least one of the micropump and the heating element when being pressed down by a user. A duration of the on-off button being pressed down may determine the duration of activation of at least one of the micropump and the heating element, e.g. by the user constantly pressing down the on-off button during performing a puff.

Preferably, the aerosol-generating system further comprises a control unit which is adapted for activating the delivery device with a predetermined time delay after activating the heating element in response to a detected user operation. Upon activation by the user, such as using the on-off button or the puff sensor, the control unit may activate the sheet heating element first, and then, after delay of around 0.3 to 1 seconds, preferably from 0.5 to 0.8 seconds, may activate the delivery device. The duration of activation may be fixed or may correspond to a user action like pressing the on-off button or puffing as e.g. detected by the user operation detection unit. Alternatively, the control unit may be adapted to activate the sheet heating element and the delivery device simultaneously.

Preferably, the aerosol-generating system may comprise a device portion and a replaceable liquid storage portion. The device portion may comprise a power supply and the control unit. The power supply may be any type of electric power supply, typically a battery. The power supply for the delivery device may be different from the power supply of the sheet heating element or may be the same.

The aerosol-generating system may further comprise electric circuitry connected to the vaporizing assembly and to the power supply which is an electrical power source. The electric circuitry may be configured to monitor the electrical resistance of the sheet heating element, and preferably to control the supply of power to the sheet heating element dependent on the electrical resistance of the sheet heating element.

The electric circuitry may comprise a controller with a microprocessor, which may be a programmable microprocessor. The electric circuitry may comprise further electronic components. The electric circuitry may be configured to regulate a supply of power to the vaporizing assembly. Power may be supplied to the vaporizing assembly continuously following activation of the system or may be supplied intermittently, such as on a puff-by-puff basis. The power may be supplied to the vaporizing assembly in the form of pulses of electrical current.

The power supply may be a form of charge storage device such as a capacitor, a super-capacitor or hyper-capacitor. The power supply may require recharging and may have a capacity that allows for the storage of enough energy for one or more user experiences; for example, the power supply may have sufficient capacity to allow for the continuous generation of aerosol for a period of around 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 for a predetermined number of puffs or discrete activations of the vaporizing assembly.

For allowing air to enter the aerosol-generating system, a wall of the housing of the aerosol-generating system, preferably a wall opposite the vaporizing assembly, preferably a bottom wall, is provided with at least one semi-open inlet. The semi-open inlet preferably allows air to enter the aerosol-generating system, but no air or liquid to leave the aerosol- generating system through the semi-open inlet. A semi-open inlet may for example be a semi-permeable membrane, permeable in one direction only for air, but is air- and liquid-tight in the opposite direction. A semi-open inlet may for example also be a one-way valve. Preferably, the semi-open inlets allow air to pass through the inlet only if specific conditions are met, for example a minimum depression in the aerosol-generating system or a volume of air passing through the valve or membrane.

The liquid aerosol-forming substrate is a substrate capable of releasing volatile compounds that can form an aerosol. The volatile compounds may be released by heating the liquid aerosol-forming substrate. 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 flavor compounds, which are released from the liquid aerosol-forming substrate upon heating. The liquid aerosol-forming substrate may alternatively comprise a non- tobacco-containing material. The liquid aerosol-forming substrate may comprise homogenized plant-based material. The liquid aerosol-forming substrate may comprise homogenized tobacco material. The liquid aerosol-forming substrate may comprise at least one aerosol-former. The liquid aerosol-forming substrate may comprise other additives and ingredients, such as flavourants.

The aerosol-generating system may be an electrically operated system. Preferably, the aerosol-generating system is portable. The aerosol-generating system may have a size comparable to a conventional cigar or cigarette. The system may have a total length between approximately 45 millimeters and approximately 160 millimeters. The system may have an external diameter between approximately 7 millimeters and approximately 25 millimeters.

According to a third aspect of the present invention, there is provided a method for generating an aerosol, comprising the steps of: heating a sheet heating element; and delivering, by a delivery device provided spaced apart from the sheet heating element, a liquid aerosol-forming substrate to the sheet heating element, wherein the delivered liquid aerosol-forming substrate is heated by the sheet heating element to a temperature sufficient to volatilize at least a part of the delivered liquid aerosol-forming substrate.

Features described in relation to one aspect may equally be applied to other aspects of the invention.

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

Fig. 1 is a schematic view of a vaporizing assembly in accordance with an embodiment of the present invention;

Fig. 2 is a schematic illustration of a spraying jet generated by a vaporizing assembly in accordance with an embodiment of the present invention; and

Fig. 3 is a schematic view of an aerosol-generating system in accordance with an embodiment of the present invention.

Throughout the figures, the same reference signs will be assigned to the same or similar components and features.

Fig. 1 is a schematic view of a vaporizing assembly in accordance with an embodiment of the present invention. The vaporizing assembly 1 comprises a sheet heating element 2 and a delivery device 3 incorporated into a common housing 10. The delivery device 3 is configured by a micropump 6 and a spray nozzle 5 connected by a tubing segment 12. The micropump 6 is adapted to receive via a tubing segment 1 1 liquid aerosol- forming substrate from a replaceable liquid storing portion 8. The delivery device 3 is provided spaced apart from the mesh heater element 2. In detail, delivery device 3 and the mesh heater element 2 are separated by an air gap of distance D between an outlet 5A of the spray nozzle 5 and the upstream surface 2A of the sheet heating element 2 facing the spray nozzle 5. The spray nozzle 5 is adapted to receive an amount of liquid aerosol-forming substrate pumped from the micropump 6 via tubing segment 12 and to spray this amount of liquid aerosol-forming substrate as a spraying jet 4S onto the upstream surface 2A of the sheet heating element 2. The spray nozzle 5 is configured to generate the spraying jet 4S such that the amount of liquid aerosol-forming substrate is completely received by the sheet heating element 2 and covers the entire upstream surface 2A of the sheet heating element 2. The housing 10 comprises an air inlet 4 allowing air 15 to pass from outside the housing 10 into the vaporizing assembly 1 towards the upstream surface 2A of the sheet heating element 2. The sheet heating element 2 is adapted to allow passing through of the air 15 having entered from air inlet 4 towards a downstream surface 2B of the sheet heating element 2 opposite from the spray nozzle 5. Having passed through the sheet heating element 2, the air 15 combines with the aerosol-forming substrate vaporized by the sheet heating element 2 to form an aerosol 16.

Fig. 2 illustrates a spraying jet generated by a vaporizing assembly in accordance with an embodiment of the present invention. The spraying jet 4S output from the outlet 5A of the spray nozzle 5 of the vaporizing assembly illustrated in Fig. 1 has a size and shape fitted to the geometry of the upstream surface 2A of the sheet heating element 2. The upstream surface 2A has a square shape. The spraying jet 4S exhibits the same square shape. The size of the spraying jet 4S arriving at the upstream surface 2A is the same as the size of the upstream surface 2A.

Fig. 3 is a schematic view of an aerosol-generating system in accordance with an embodiment of the present invention. The aerosol-generating system 20 comprises the vaporizing assembly 1 illustrated in Fig. 1 adapted to generate a spraying yet as illustrated in Fig. 2. Moreover, the aerosol-generating system 20 comprises a liquid storing portion embodied by a replaceable container 8, an electronic control unit 9, a battery unit 13, wiring components 14 for electrically connecting the battery unit 13, the electronic control unit 9 and the electrically driven components of the vaporizing assembly 1 , i.e. the sheet heating element 2 and the micropump 6. Coupled to the housing 10 is a replaceable mouth piece 17 having an air flow outlet 18 provided for a user (not shown) in order to inhale the generated aerosol 16.