Method and apparatus for producing a sheet of aerosol-generating substrate for aerosol-generating articles

Abstract

An apparatus for producing a sheet of aerosol-generating substrate for aerosol-generating articles comprises a slot die (5) in fluid communication with a container (2) for a slurry mixture (3) and a surface (6) located under the slot die (5), moving with respect to the slot die (5) along a conveying direction (D) and configured to receive the slurry mixture (3) from the slot die (5) to form a cast sheet (S). The slot die (5) comprises a head (9) delimiting internally a manifold (10) and a narrow section (15) terminating in a slot outlet (14) facing the surface (6). The slot die (5) comprises deformable membranes (18) placed inside the head (9) and actuation devices (20) operatively connected to the deformable membranes (18) and configured to deform the deformable membranes (18) upon receiving command signals. A control unit (23) is operatively connected to the actuation devices (20) and is configured to issue the command signals to control the actuation device (20).

Description

[0001] METHOD AND APPARATUS FOR PRODUCING A SHEET OF AEROSOLGENERATING SUBSTRATE FOR AEROSOL-GENERATING ARTICLES

[0002] The present disclosure relates to a method and to an apparatus for producing a sheet of aerosol-generating substrate for aerosol-generating articles.

[0003] Aerosol-generating articles or heat-not-burn cigarettes, in which an aerosolgenerating substrate is heated rather than combusted, are known in the art. Typically, in such heated aerosol-generating articles, an aerosol is generated by the transfer of heat from a heat source to the physically separate aerosol-generating substrate or material, which may be located in contact with, within, around, or downstream of the heat source. During use of the aerosol-generating article, volatile compounds are released from the aerosol-generating substrate by heat transfer from the heat source and are entrained in air drawn through the aerosol-generating article. As the released compounds cool, they condense to form an aerosol.

[0004] An aerosol-generating article is an assembly of different kinds of components which are rod-shaped elements (small cylinders) enclosed in one or more wrapping materials. One of the rod-shaped elements is usually made of a substrate which generates aerosol when heated (Heat Not Burn consumable). The aerosol-generating substrate is usually made from a continuous sheet which is gathered, wrapped in a wrapper and cut in a plurality of rod-shaped elements.

[0005] Currently, a sheet of aerosol-generating substrate is prepared by casting a slurry on a moving belt through a casting box. For instance, a tobacco slurry is transformed into tobacco cast leaf by the following operations: the tobacco slurry (tobacco powder, water, glycerine, fibres and binders) is manufactured in a tank, the tobacco slurry is then poured into an open-air casting box having an exit at its bottom, an exit height is controlled by a knife which cast the exiting tobacco slurry at a determined thickness on a moving conveyor (e.g. a metal belt), the tobacco slurry is then progressively dried to become tobacco cast leaf. WO2016096963A1 , WO2016050471 and WO2017089589 disclose methods for the preparation of tobacco slurries and casting of the slurries through casting boxes to form the sheets.

[0006] In this technical field, it would be desirable to have a method and an apparatus for producing a sheet of aerosol-generating substrate for aerosol-generating articles able to improve the quality of the manufactured aerosol-generating substrates and thus of the resulting aerosol-generating articles. It would be desirable to have an apparatus and a method capable of manufacturing sheets of aerosol-generating substrate such as to guarantee an optimal and consistent experience to the final user.

[0007] It would be particularly desirable to have an apparatus and a method capable of providing an accurate and constant thickness of the sheets of aerosol-generating substrate.

[0008] It would be also desirable to have an apparatus and a method capable of manufacturing homogeneous sheets of aerosol-generating substrate.

[0009] Indeed, constant thickness and homogeneity of the sheet allow to provide an accurate and replicable amount of substance in each consumable and in each aerosol-generating article, thus assuring a consistency of smoking experiences to the user.

[0010] It would be further desirable to have an apparatus and a method capable of manufacturing homogeneous sheets of aerosol-generating substrate from slurries with high viscosity, i.e. , a viscosity higher than 4000 cP measured at 35 °C with a shear rate of 100 Hz (viscosity depends on temperature and shear rate during the measurement), and / or with viscosity that changes during casting.

[0011] Particularly, it would be further desirable to have an apparatus and a method allowing to control thickness and grammage of the cast sheet obtained from slurries with high viscosity and / or changing viscosity.

[0012] The present disclosure relates to an apparatus for producing a sheet of aerosolgenerating substrate for aerosol-generating articles. The apparatus may comprise a mixer configured for mixing ingredients of a recipe and water to form a slurry mixture. The apparatus comprises a slot die in fluid communication with the mixer or with a container for the slurry mixture, the container being operatively interposed between the mixer and the slot die. The apparatus may comprise a surface located under the slot die, moving with respect to the slot die along a conveying direction and configured to receive the slurry mixture from said slot die to form a cast sheet. The apparatus may also comprise an oven to dry the cast sheet. The slot die comprises a head delimiting internally: a manifold having at least one inlet in fluid communication with the mixer or with the container, a narrow section in fluid communication with the manifold and terminating in a slot outlet facing the surface. The slot die further comprises: at least one deformable membrane placed inside the head and delimiting at least in part the manifold and / or the narrow section; at least one actuation device operatively connected to the at least one deformable membrane and configured to deform said at least one deformable membrane upon receiving command signals; a control unit operatively connected to the at least one actuation device and configured to issue said command signals to control the actuation device. The present disclosure also relates to a method for producing a sheet of aerosolgenerating substrate for aerosol-generating articles. The method may start from a slurry mixture comprising water, vegetable and / or alkaloid particles, a binder and an aerosol forming agent. The method is carried out through an apparatus for producing a sheet of aerosol-generating substrate for aerosol-generating articles. The apparatus may comprise a mixer configured for mixing ingredients of a recipe and water to form a slurry mixture. The apparatus comprises a slot die in fluid communication with the mixer or with a container for the slurry mixture, the container being operatively interposed between the mixer and the slot die. The apparatus may comprise a surface located under the slot die, moving with respect to the slot die along a conveying direction and configured to receive the slurry mixture from said slot die to form a cast sheet. The slot die comprises a head delimiting internally: a manifold having at least one inlet in fluid communication with the mixer or with the container, a narrow section in fluid communication with the manifold and terminating in a slot outlet facing the surface. The slot die further comprises: at least one deformable membrane placed inside the head and delimiting at least in part the manifold and / or the narrow section; at least one actuation device operatively connected to the at least one deformable membrane and configured to deform said at least one deformable membrane upon receiving command signals; a control unit operatively connected to the at least one actuation device and configured to issue said command signals to control the actuation device.

[0013] The present disclosure also relates to a method for producing a sheet of aerosolgenerating substrate for aerosol-generating articles, wherein said method comprises: mixing a recipe with water to form a slurry mixture, the recipe comprising as ingredients vegetable and / or alkaloid particles, a binder and an aerosol forming agent; feeding the slurry mixture to a slot die and depositing the slurry mixture on a surface via said slot die to form a cast sheet, optionally drying the cast sheet. The slot die comprises a head delimiting internally: a manifold having an inlet, a narrow section in fluid communication with the manifold and terminating in a slot outlet facing the surface; wherein the slot die further comprises at least one deformable membrane placed inside the head and delimiting at least in part the manifold and / or the narrow section. The method further comprises: deforming said at least one deformable membrane while depositing the slurry mixture. Said method may be carried out through an apparatus for producing a sheet of aerosol-generating substrate for aerosol-generating articles. The apparatus may comprise a mixer configured for mixing ingredients of a recipe and water to form a slurry mixture. The apparatus comprises a slot die in fluid communication with the mixer or with a container for the slurry mixture, the container being operatively interposed between the mixer and the slot die. The apparatus may comprise a surface located under the slot die, moving with respect to the slot die along a conveying direction and configured to receive the slurry mixture from said slot die to form a cast sheet. The apparatus may also comprise an oven to dry the cast sheet. The slot die comprises a head delimiting internally: a manifold having at least one inlet in fluid communication with the mixer or with the container, a narrow section in fluid communication with the manifold and terminating in a slot outlet facing the surface. The slot die further comprises: at least one deformable membrane placed inside the head and delimiting at least in part the manifold and / or the narrow section; at least one actuation device operatively connected to the at least one deformable membrane and configured to deform said at least one deformable membrane upon receiving command signals; a control unit operatively connected to the at least one actuation device and configured to issue said command signals to control the actuation device.

[0014] The present disclosure also relates to a process for manufacturing aerosol-generating article components, comprising: manufacturing a sheet of aerosol-generating substrate for aerosol-generating articles in an apparatus for producing a sheet of aerosol-generating substrate for aerosol-generating articles or through a method for producing a sheet of aerosol-generating substrate for aerosol-generating articles; gathering the sheet of aerosolgenerating substrate and wrapping the gathered sheet of aerosol-generating substrate in a wrapper to form a continuous rod; cutting the continuous rod into a plurality of aerosolgenerating article components each having a rod shape, each aerosol-generating article component comprising a gathered sheet formed from a cut portion of the sheet of aerosolgenerating substrate. Said apparatus for producing a sheet of aerosol-generating substrate for aerosol-generating articles may comprise a mixer configured for mixing ingredients of a recipe and water to form a slurry mixture. The apparatus comprises a slot die in fluid communication with the mixer or with a container for the slurry mixture, the container being operatively interposed between the mixer and the slot die. The apparatus may comprise a surface located under the slot die, moving with respect to the slot die along a conveying direction and configured to receive the slurry mixture from said slot die to form a cast sheet. The apparatus may also comprise an oven to dry the cast sheet. The slot die comprises a head delimiting internally: a manifold having at least one inlet in fluid communication with the mixer or with the container, a narrow section in fluid communication with the manifold and terminating in a slot outlet facing the surface. The slot die further comprises: at least one deformable membrane placed inside the head and delimiting at least in part the manifold and / or the narrow section; at least one actuation device operatively connected to the at least one deformable membrane and configured to deform said at least one deformable membrane upon receiving command signals; a control unit operatively connected to the at least one actuation device and configured to issue said command signals to control the actuation device. Said method for mixing a recipe with water to form a slurry mixture comprises: mixing a recipe with water to form a slurry mixture, the recipe comprising as ingredients vegetable and / or alkaloid particles, a binder and an aerosol forming agent; feeding the slurry mixture to a slot die and depositing the slurry mixture on a surface via said slot die to form a cast sheet. The slot die comprises a head delimiting internally: a manifold having an inlet, a narrow section in fluid communication with the manifold and terminating in a slot outlet facing the surface; wherein the slot die further comprises at least one deformable membrane placed inside the head and delimiting at least in part the manifold and / or the narrow section. The method further comprises: deforming said at least one deformable membrane while depositing the slurry mixture. Before gathering, the process may comprises: weakening the sheet of aerosol-generating substrate by making weakened lines in said sheet of aerosol-generating substrate, optionally through a crimping step generating a plurality of substantially parallel ridges or corrugations.

[0015] The present disclosure also relates to an aerosol-generating article comprising at least one aerosol-generating article component made through said process for manufacturing aerosol-generating article components.

[0016] The inventor found that the disclosed apparatus and method for producing a sheet of aerosol-generating substrate for aerosol-generating articles allows to assure homogeneity and constant thickness of the cast slurry mixture and of the resulting sheet, also when a viscosity of the slurry mixture changes over time and / or depends on the position inside the head of the slot die. Indeed, the actions of the deformable membrane or membranes aim to reach an even deposition of the slurry mixture on the surface by keeping an even distribution of the slurry mixture in the manifold and / or by pushing or restraining the slurry mixture.

[0017] The inventor found that the controlled deformation of the least one deformable membrane allows to accurately adjust distribution on the surface of the slurry mixture exiting through the slot outlet.

[0018] The inventor also found that the deposition through the slot die allows to accurately control the pressure drop through the slot die and the flow rate of slurry mixture deposited by the slot die.

[0019] The inventor also found that the deformable membrane / s does not generate shear stress in the slurry mixture and so do not interfere with the slurry viscosity, but only adjust the slurry repartition or flow. The inventor also found that the deposition through the slot die prevents reaction of the slurry mixture with air and propension to dry, since the slurry mixture, unlike in the open- air casting box, is isolated from the external environment.

[0020] The inventor also found that the deposition through the slot die prevents formation of agglomerates that could jeopardize the homogeneity of the casted slurry along time.

[0021] In some embodiments, deforming comprises: deforming the at least one deformable membrane at least between a first configuration, in which said at least one deformable membrane lies recessed with respect to an internal surface of the manifold or of the narrow section, and a second configuration, in which said at least one deformable membrane protrudes inside the manifold or the narrow section.

[0022] In some embodiments, the command signal is configured to deform the at least one deformable membrane at least between a first configuration, in which said at least one deformable membrane lies recessed with respect to an internal surface of the manifold or of the narrow section, and a second configuration, in which said at least one deformable membrane protrudes inside the manifold or the narrow section.

[0023] In the first configuration, the at least one deformable membrane may be concave. In the second configuration, the at least one deformable membrane may be convex.

[0024] In some embodiments, the head has at least one chamber fashioned in an inner wall of the manifold and / or of the narrow section and closed by said at least one deformable membrane to allow deformation of the deformable membrane.

[0025] The inventor found that the recessed and protruded configurations allow to change the volume inside the head of the slot die.

[0026] In some embodiments, the at least one deformable membrane can take an undeformed configuration. In the undeformed configuration, the at least one deformable membrane may lie flush with an inner wall of the manifold and / or of the narrow section.

[0027] In some embodiments, a stiffness of the at least one membrane is such that the at least one membrane is in the undeformed configuration when subjected to a normal expected pressure of the slurry mixture in the slot die. This normal pressure is a “neutral” pressure from which the undeformed deformable membrane can be made into a concave or convex shape.

[0028] The inventor found that, in the undeformed configuration and if the stiffness of the membrane is sufficiently high, it is as if the membrane is not present.

[0029] In some embodiments, the command signals are configured to deform the at least one deformable membrane according to a deformation speed and to adjust said deformation speed. A first deformation speed towards the first configuration may be different from a second deformation speed towards the second configuration. The first deformation speed may be faster than the second deformation speed such that a suction force is created on the slurry mixture inside the head. The second deformation speed may be faster than the first deformation speed such that a pushing force is created on the slurry mixture inside the head.

[0030] In some embodiments, the command signals are configured to deform the at least one deformable membrane according to a magnitude of deformation and to adjust said magnitude of deformation.

[0031] The inventor found that adjusting the deformation speed or speeds and / or the magnitude of deformation provide a plurality of control parameters that affects properties and distribution of the slurry mixture on the surface.

[0032] In some embodiments, it is provided for detecting properties of the of the slurry mixture, wherein said at least one deformable membrane is deformed as a function of the detected properties. A type of deformation, concave or convex, a speed of deformation and a magnitude of a deformation of the at least one deformable membrane may be function of the detected properties. At least one sensor may be operatively connected to the control unit and may be positioned and configured to detect properties of the slurry mixture. The control unit may issue the command signals as a function of the detected properties.

[0033] The inventor found that the control unit may thus control the slurry mixture deposition in real time through a control loop.

[0034] The detected properties may comprise a viscosity of the slurry mixture. The at least one sensor may be a viscosity sensor. The at least one sensor may be an inline viscosimeter. The viscosity of the slurry mixture may be detected in the slot die or upstream of the slot die. The viscosity sensor may be positioned and configured to detect viscosity of the slurry mixture in the slot die or upstream of the slot die. The viscosity of the slurry mixture may be between 150000 and 500000 cP (centi-Poise).

[0035] The at least one sensor may be positioned and configured to detect a property of the slurry mixture deposited on the surface downstream of the slot outlet. Said properties may be detected at different points arranged transversally on the slurry mixture deposited on the surface. In some embodiments, the at least one sensor comprises a plurality of sensors positioned downstream of the slot outlet and at different points arranged transversally on the slurry mixture cast on the surface. The detected properties may comprise a thickness and / or a color and / or a texture of the slurry mixture deposited on the surface. For instance, the at least one sensor is configured to detect a thickness and / or a color and / or a texture of the slurry mixture deposited on the surface. For instance, the thickness of the cast sheet is between 400 pm and 650 pm. The inventor found that, this way, properties of the cast sheet may be controlled across its width.

[0036] In some embodiments, at least one sensor is a laser sensor or a camera.

[0037] The inventor found that these sensors do not contact the cast sheet and thus do not alter homogeneity of the deposited slurry mixture.

[0038] In some embodiments, the command signals are configured to deform the at least one deformable membrane at least between the first configuration or the second configuration and / or adjust the deformation speed and / or to adjust the magnitude of deformation as a function of properties detected through the at least one sensor.

[0039] The inventor found that the control unit may thus control the deposited slurry mixture in real time through a control loop.

[0040] In some embodiments, the slot die comprises a plurality of deformable membranes. In some embodiments, the slot die comprises a plurality of actuation devices. One or more of the actuation devices may be controlled by the control unit independently of others or each actuation device may be controlled by the control unit independently of the others. Each deformable membrane may be deformed as a function of a position of said deformable membrane in the manifold and / or in the narrow section. Each membrane may have an area between 1 mm2and 100 mm2. Each membrane may have a circular or rectangular perimeter.

[0041] The inventor found that deformations of the plurality of deformable membranes allows a local control of the slurry mixture inside the head.

[0042] In some embodiments, the manifold has an elongated shape extending along a main direction parallel to the slot outlet. The main direction and the elongated shape may be straight, or the main direction and the elongated shape may be arched. A cross section of the manifold may be a circle or half a circle or a tear drop shape. The cross section is in a plane perpendicular to the main direction. The narrow section may be in fluid communication with the manifold all along a longitudinal extension of the manifold. The narrow section may taper from the manifold towards the slot outlet. The narrow section may be delimited by flat faces. The narrow section may comprise a land section connected to the manifold and a slot section terminating with the slot outlet. The land section may taper towards the slot section and the slot section may be delimited by two parallel flat faces. At least when the slot die is operative, the narrow section and the slot outlet may be positioned below the manifold.

[0043] In some embodiments, the deformable membranes are aligned with each other along the main direction of the manifold. The inventor found that the distribution of the deformable membranes along the main direction allows to control the deposition of the slurry mixture across the width of the cast sheet.

[0044] In some embodiments, the deformable membranes are located on an upper inner face of the manifold. The deformable membranes may be arranged symmetrically with respect to a centerline plane of the slot die transverse to the slot outlet.

[0045] In some embodiments, it is provided for deforming each deformable membrane as a function of the properties of the slurry mixture detected by the plurality of sensors in each point. In some embodiments, the actuation devices of the deformable membranes are controlled as a function of the positions of the deformable membranes and of the properties of the slurry mixture detected by the plurality of sensors in each point.

[0046] The inventor found that this kind of control allows to balance uneven situations created by localized changes of properties, for instance viscosity, of the slurry mixture.

[0047] In some embodiments, deforming said at least one deformable membrane comprises: changing a deformation of said at least one deformable membrane with high frequency in order to create waves in the slurry mixture. In some embodiments, the command signals from the control unit are configured to change the configuration of the at least one deformable membrane with high frequency or ultrasonic frequency, in order to create waves in the slurry mixture. The high frequency is higher than 8 kHz. The ultrasonic frequency is higher than 20 kHz.

[0048] The inventor found that this “dynamic” actuation of the membrane / s allows to create complementary flows in the slurry mixture. The membrane / s may have a pushing action and increase the speed of the slurry mixture toward the slot outlet or, conversely, may have a sucking action and decrease said speed. The inventor found that the dynamic actuation of the membrane / s allows also to re-direct part of the slurry in the manifold. The inventor found that such waves with small wavelengths will damper along the travel of the slurry mixture from the manifold to the slot outlet, and so will not jeopardize the homogeneous deposition of the slurry mixture.

[0049] In some embodiments, deforming said at least one deformable membrane comprises: bringing and keeping said at least one deformable membrane in a deformed configuration to change a volume of the manifold and / or the narrow section.

[0050] In some embodiments, the command signals from the control unit are configured to keep the at least one deformable membrane in a deformed configuration to adjust a volume of the manifold and / or the narrow section. Some deformable membranes may be brought in the first configuration, to increase a local volume close to said deformable membranes in the first configuration. Other deformable membranes may be brought in the second configuration, to decrease a local volume close to said deformable membranes in the second configuration.

[0051] The inventor found that this “static” actuation of the membrane / s allows to responsively adjust the internal volume of the manifold according, for instance, to unpredicted variations in the slurry mixture viscosity that are detected by viscosity sensor(s) and / or by the sensors capturing the transversal heights of the deposition, for the deposition on the surface to remain even.

[0052] The at least one actuation device may be piezoelectric. In some embodiments, the at least one deformable membrane may comprise a piezoelectric material and the at least one actuation device may comprise a voltage source electrically connected to the piezoelectric material of the at least one deformable membrane. In some embodiments, a piezoelectric element is coupled to the at least one membrane and the at least one actuation device may comprise a voltage source electrically connected to the piezo electric element. A magnitude of a deformation of the at least one membrane may be proportional to a voltage applied by the voltage source.

[0053] The inventor found that the piezoelectric actuation device is particularly suitable for the “dynamic” actuation of the membrane / s.

[0054] In some embodiments, the head has at least one chamber fashioned in an inner wall of the manifold and / or of the narrow section and closed by said at least one deformable membrane to allow deformation of the deformable membrane, wherein the piezoelectric material or the piezoelectric element is in the chamber.

[0055] The inventor found that the piezoelectric element is reliable since it is protected inside the chamber.

[0056] In some embodiments, the at least one actuation device is pneumatic. The at least one deformable membrane is gas-tight and a chamber may delimited on a side of the at least one deformable membrane opposite the manifold and / or the narrow section, the chamber allowing deformation of the deformable membrane.

[0057] In some embodiments, feeding the slurry mixture to the slot die comprises: pumping the slurry mixture to the slot die, optionally with a flow rate between 0.5 dm3 / s and 1 dm3 / s, optionally of 0.8 dm3 / s. The at least one actuation device may comprise a gas pump in fluid connection with the chamber. The gas pump may be configured to pump gas in the chamber or to withdraw gas from the chamber. The gas may be air. The command signals from the control unit may be configured to apply a pressure of the gas in the chamber to deform the at least one deformable membrane and / or to keep a deformation of said at least one deformable membrane. The inventor found that the pneumatic actuation device is particularly suitable for the “static” actuation of the membrane / s.

[0058] In some embodiments, at least one pipe is connected to the at least one inlet and to the mixer or to the container. The at least one pipe may have a diameter between 5 cm and 10 cm. In some embodiments, a plurality of pipes are connected to a plurality of inlets. Said pipes may be between three to six.

[0059] The inventor found that the plurality of pipes allows a distributed inflow of slurry mixture in the manifold.

[0060] In some embodiments, a pump is operating between the mixer or the container and the slot die. The pump may be a volumetric pump, optionally a cavity pump. The pump may be in fluid communication with the pipe or pipes.

[0061] The surface located under the slot die may be a belt of a conveyor, optionally a metal belt.

[0062] In some embodiments, the slot outlet has a transversal width between 2 m and 4 m and / or the slot outlet has a gap between 0.3 mm and 10 mm. In some embodiments, a distance between the slot outlet and the surface is between 0.5 mm and 1.2 mm. In some embodiments, the slot outlet is transversal to the conveying direction. The slot outlet may be a straight slit.

[0063] As used in the present description, the term “recipe” means a group of ingredients without any limitation concerning the order and the timing in which they are combined with each other and / or with water.

[0064] As used in the present description, the term “slurry” which means a watery mixture of insoluble matter with a water content so high (e.g., 70 percent - 80 percent) that cannot be kneaded or rolled out as opposed to a “dough” which means a mixture that is stiff enough to be kneaded or rolled out.

[0065] As used in the present description, the terms “upstream” and “downstream” are used to describe the relative positions of components, or portions of components, of the apparatus in relation to the direction in which a material or materials passes through the apparatus along a given path.

[0066] The invention is defined in the claims. However, 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, embodiment, or aspect described herein.

[0067] EX1. An apparatus for producing a sheet of aerosol-generating substrate for aerosol-generating articles, the apparatus comprising: a mixer configured for mixing ingredients of a recipe and water to form a slurry mixture; a slot die in fluid communication with the mixer or with a container for the slurry mixture, the container being operatively interposed between the mixer and the slot die; a surface located under the slot die, moving with respect to the slot die along a conveying direction and configured to receive the slurry mixture from said slot die to form a cast sheet; an optional oven to dry the cast sheet; wherein the slot die comprises a head delimiting internally: a manifold having at least one inlet in fluid communication with the mixer or with the container, a narrow section in fluid communication with the manifold and terminating in a slot outlet facing the surface; wherein the slot die further comprises: at least one deformable membrane placed inside the head and delimiting at least in part the manifold and / or the narrow section; at least one actuation device operatively connected to the at least one deformable membrane and configured to deform said at least one deformable membrane upon receiving command signals; a control unit operatively connected to the at least one actuation device and configured to issue said command signals to control the actuation device.

[0068] EX2. The apparatus according to EX1 , wherein the command signal is configured to deform the at least one deformable membrane at least between a first configuration, in which said at least one deformable membrane lies recessed with respect to an internal surface of the manifold or of the narrow section, and a second configuration, in which said at least one deformable membrane protrudes inside the manifold or the narrow section.

[0069] EX3. The apparatus according to EX2, wherein in the first configuration the at least one deformable membrane is concave.

[0070] EX4. The apparatus according to EX2 or EX3, wherein in the second configuration the at least one deformable membrane is convex.

[0071] EX5. The apparatus according to any of EX2 to EX4, wherein the at least one deformable membrane can take an undeformed configuration; optionally, in the undeformed configuration, the at least one deformable membrane lies flush with an inner wall of the manifold and / or of the narrow section.

[0072] EX6. The apparatus according to EX5, wherein a stiffness of the at least one membrane is such that the at least one membrane is in the undeformed configuration when subjected to a pressure of the slurry mixture in the slot die. EX7. The apparatus according to any of EX1 to EX6, wherein the command signals are configured to deform the at least one deformable membrane according to a deformation speed and to adjust said deformation speed.

[0073] EX8. The apparatus according to EX7 when according to any of EX2 to EX6, wherein a first deformation speed towards the first configuration is different from a second deformation speed towards the second configuration.

[0074] EX9. The apparatus of EX8, wherein the first deformation speed is faster than the second deformation speed such that a suction force is created on the slurry inside the head.

[0075] EX10. The apparatus of EX8, wherein the second deformation speed is faster than the first deformation speed such that a pushing force is created on the slurry inside the head.

[0076] EX11. The apparatus according to any of EX1 to E10, wherein the command signals are configured to deform the at least one deformable membrane according to a magnitude of deformation and to adjust said magnitude of deformation.

[0077] EX12. The apparatus according to any of EX1 to EX11 , comprising at least one sensor operatively connected to the control unit and positioned and configured to detect properties of the slurry mixture; wherein the control unit issues the command signals as a function of the detected properties.

[0078] EX13. The apparatus according to EX12, wherein the at least one sensor is a viscosity sensor, optionally an inline viscosimeter.

[0079] EX14. The apparatus according to EX13, wherein the viscosity sensor is positioned and configured to detect viscosity of the slurry mixture in the slot die or upstream of the slot die; optionally the viscosity of the slurry mixture is between 150000 and 500000 cP (centiPoise).

[0080] EX15. The apparatus according to EX12, wherein the at least one sensor is positioned and configured to detect a property of the slurry mixture deposited on the surface downstream of the slot outlet.

[0081] EX16. The apparatus according to EX15, wherein the at least one sensor comprises a plurality of sensors positioned downstream of the slot outlet and at different points arranged transversally on the slurry mixture cast on the surface.

[0082] EX17. The apparatus according to EX15 or EX16, wherein the at least one sensor is configured to detect a thickness of the slurry mixture deposited on the surface; optionally the thickness of the cast sheet is between 400 pm and 650 pm.

[0083] EX18. The apparatus according to EX15 or EX16, wherein the at least one sensor is configured to detect a color and / or a texture of the slurry mixture deposited on the surface. EX19. The apparatus according to any of EX15 to EX18, wherein the at least one sensor is a laser sensor or a camera.

[0084] EX20. The apparatus according to any of EX12 to EX19 when EX12 is according to any of EX2 to EX6 or according to any of EX7 to EX10 or according to EX11 , wherein the command signals are configured to deform the at least one deformable membrane at least between the first configuration or the second configuration and / or adjust the deformation speed and / or to adjust the magnitude of deformation as a function of properties detected through the at least one sensor.

[0085] EX21. The apparatus according to any of EX1 to EX20, wherein the slot die comprises a plurality of deformable membranes and a plurality of actuation devices; optionally each membrane has an area between 1 mm2and 100 mm2; optionally Each membrane have a circular or rectangular perimeter.

[0086] EX22. The apparatus according to EX21 , wherein one or more of the actuation devices is / are controlled by the control unit independently of others or wherein each actuation device is controlled by the control unit independently of the others.

[0087] EX23. The apparatus according to any of EX1 to EX22, wherein the manifold has an elongated shape extending along a main direction parallel to the slot outlet.

[0088] EX24. The apparatus according to EX23, wherein the main direction and the elongated shape are straight or wherein the main direction and the elongated shape are arched.

[0089] EX25. The apparatus according to EX23 or EX24, wherein a cross section of the manifold is a circle or half a circle or a tear drop shape, the cross section being in a plane perpendicular to the main direction.

[0090] EX26. The apparatus according to any of EX23 to EX25, wherein, at least when the slot die is operative, the narrow section and the slot outlet are positioned below the manifold.

[0091] EX27. The apparatus according to any of EX23 to EX26, wherein the narrow section is in fluid communication with the manifold all along a longitudinal extension of the manifold.

[0092] EX28. The apparatus according to any of EX23 to EX27, wherein the narrow section tapers from the manifold towards the slot outlet.

[0093] EX29. The apparatus according to any of EX23 to EX28, wherein the narrow section is delimited by flat faces.

[0094] EX30. The apparatus according to any of EX23 to EX29, wherein the narrow section comprises a land section connected to the manifold and a slot section terminating with the slot outlet. EX31 . The apparatus according to EX30, wherein the land section tapers towards the slot section and the slot section is delimited by two parallel flat faces.

[0095] EX32. The apparatus according to any of EX23 to EX31 when EX23 is according to EX21 or EX22, wherein the deformable membranes are aligned with each other along the main direction of the manifold.

[0096] EX33. The apparatus according to EX32, wherein the deformable membranes are located on an upper inner face of the manifold.

[0097] EX34. The apparatus according to EX32 or EX33, wherein the deformable membranes are arranged symmetrically with respect to a centerline plane of the slot die transverse to the slot outlet.

[0098] EX35. The apparatus according to any of EX32 to EX34 when EX23 is according to any of EX16 to EX19, wherein the actuation devices of the deformable membranes are controlled as a function of the positions of the deformable membranes and of the properties of the slurry mixture detected by the plurality of sensors in each point.

[0099] EX36. The apparatus according to any of EX1 to EX35, wherein the command signals from the control unit are configured to change the configuration of the at least one deformable membrane with high frequency or ultrasonic frequency, in order to create waves in the slurry mixture.

[0100] EX37. The apparatus according to EX36, wherein the high frequency is higher than 8 kHz, wherein the ultrasonic frequency is higher than 20 kHz.

[0101] EX38. The apparatus according to any of EX1 to EX35, wherein the command signals from the control unit are configured to keep the at least one deformable membrane in a deformed configuration to adjust a volume of the manifold and / or the narrow section.

[0102] EX39. The apparatus according to any of EX1 to EX38, wherein the at least one actuation device is piezoelectric.

[0103] EX40. The apparatus according to EX39, wherein the at least one deformable membrane comprises a piezoelectric material and wherein the at least one actuation device comprises a voltage source electrically connected to the piezoelectric material of the at least one deformable membrane.

[0104] EX41. The apparatus according to EX39, wherein a piezoelectric element is coupled to the at least one membrane and wherein the at least one actuation device comprises a voltage source electrically connected to the piezo electric element.

[0105] EX42. The apparatus according to EX40 or EX41 , wherein the head has at least one chamber fashioned in an inner wall of the manifold and / or of the narrow section and closed by said at least one deformable membrane to allow deformation of the deformable membrane, wherein the piezoelectric material or the piezoelectric element is in the chamber.

[0106] EX43. The apparatus according to any of EX40 to EX42, wherein a magnitude of a deformation of the at least one membrane is proportional to a voltage applied by the voltage source.

[0107] EX44. The apparatus according to any of EX1 to EX35, wherein the at least one actuation device is pneumatic.

[0108] EX45. The apparatus according to EX44, wherein the at least one deformable membrane is gas-tight and a chamber is delimited on a side of the at least one deformable membrane opposite the manifold and / or the narrow section, the chamber allowing deformation of the deformable membrane.

[0109] EX46. The apparatus according to EX45, wherein the at least one actuation device comprises a gas pump in fluid connection with the chamber, the gas pump being configured to pump gas in the chamber or to withdraw gas from the chamber; optionally the gas being air.

[0110] EX47. The apparatus according to EX46, wherein the command signals from the control unit are configured to apply a pressure of the gas in the chamber to deform the at least one deformable membrane and / or to keep a deformation of said at least one deformable membrane.

[0111] EX48. The apparatus according to any of EX1 to EX47, comprising at least one pipe connected to the at least one inlet and to the mixer or to the container; optionally the at least one pipe has an inner diameter between 5 cm and 10 cm.

[0112] EX49. The apparatus according to EX48, comprising a plurality of pipes connected to a plurality of inlets, optionally between three to six pipes.

[0113] EX50. The apparatus according to any of EX1 to EX49, comprising a pump operating between the mixer or the container and the slot die.

[0114] EX51. The apparatus according to EX50, wherein the pump is a volumetric pump, optionally a cavity pump.

[0115] EX52. The apparatus according to EX50 or EX51 when EX50 is according to EX48 or EX49, wherein the pump is in fluid communication with the pipe or pipes.

[0116] EX53. The apparatus according to any of EX1 to EX52, wherein the surface located under the slot die is a belt of a conveyor, optionally a metal belt.

[0117] EX54. The apparatus according to any of EX1 to EX53, wherein the slot outlet has a transversal width between 2 m and 4 m.

[0118] EX55. The apparatus according to any of EX1 to EX54, wherein the slot outlet has a gap between 0.3 mm and 10 mm. EX56. The apparatus according to any of EX1 to EX55, wherein a distance between the slot outlet and the surface is between 0.5 mm and 1.2 mm.

[0119] EX57. The apparatus according to any of EX1 to EX56, wherein the slot outlet is transversal to the conveying direction; optionally the slot outlet is a straight slit.

[0120] EX58. The apparatus according to any of EX1 to EX57, wherein the head has at least one chamber fashioned in an inner wall of the manifold and / or of the narrow section and closed by said at least one deformable membrane to allow deformation of the deformable membrane.

[0121] EX59. A method for producing a sheet of aerosol-generating substrate for aerosolgenerating articles starting from a slurry mixture comprising water, vegetable and / or alkaloid particles, a binder and an aerosol forming agent; the method being carried out through the apparatus of any of EX1 to EX58.

[0122] EX60. A method for producing a sheet of aerosol-generating substrate for aerosolgenerating articles, comprising: mixing a recipe with water to form a slurry mixture, the recipe comprising as ingredients vegetable and / or alkaloid particles, a binder and an aerosol forming agent; feeding the slurry mixture to a slot die and depositing the slurry mixture on a surface via said slot die to form a cast sheet; optionally drying the cast sheet; wherein the slot die comprises a head delimiting internally: a manifold having an inlet, a narrow section in fluid communication with the manifold and terminating in a slot outlet facing the surface; wherein the slot die further comprises at least one deformable membrane placed inside the head and delimiting at least in part the manifold and / or the narrow section; wherein the method further comprises: deforming said at least one deformable membrane while depositing the slurry mixture.

[0123] EX61 . The method according to EX60, wherein said method is carried out through the apparatus of any of EX1 to EX58.

[0124] EX62. The method according to EX60 or EX61 , further comprising: detecting properties of the of the slurry mixture; wherein said at least one deformable membrane is deformed as a function of the detected properties.

[0125] EX63. The method according to EX62, wherein a type of deformation, concave or convex, a speed of deformation and a magnitude of a deformation of the at least one deformable membrane are function of the detected properties.

[0126] EX64. The method according to EX62 or EX63, wherein the detected properties comprise a viscosity of the slurry mixture. EX65. The method according to EX64, wherein the viscosity of the slurry mixture is detected in the slot die or upstream of the slot die.

[0127] EX66. The method according to any of EX62 to EX65, wherein the detected properties comprise a thickness of the slurry mixture deposited on the surface.

[0128] EX67. The method according to any of EX62 to EX66, wherein the detected properties comprise a color and / or a texture of the slurry mixture deposited on the surface.

[0129] EX68. The method according to EX66 or EX67, wherein said properties are detected at different points arranged transversally on the slurry mixture deposited on the surface.

[0130] EX69. The method according to any of EX60 to EX68, wherein the slot die comprises a plurality of deformable membranes; wherein each deformable membrane is deformed as a function of a position of said deformable membrane in the manifold and / or in the narrow section.

[0131] EX70. The method according to EX69 when according to EX68, comprising: deforming each deformable membrane as a function of the properties of the slurry mixture detected by the plurality of sensors in each point.

[0132] EX71. The method according to any of EX60 to EX70, wherein deforming comprises: deforming the at least one deformable membrane at least between a first configuration, in which said at least one deformable membrane lies recessed with respect to an internal surface of the manifold or of the narrow section, and a second configuration, in which said at least one deformable membrane protrudes inside the manifold or the narrow section.

[0133] EX72. The method according to EX71 , wherein in the first configuration the at least one deformable membrane is concave and in the second configuration the at least one deformable membrane is convex.

[0134] EX73. The method according to any of EX60 to EX72, wherein deforming said at least one deformable membrane comprises: bringing and keeping said at least one deformable membrane in a deformed configuration to change a volume of the manifold and / or the narrow section.

[0135] EX74. The method according to EX73 when according to EX71 or EX72, wherein some deformable membranes are brought in the first configuration, to increase a local volume close to said deformable membranes in the first configuration, and other deformable membranes are brought in the second configuration, to decrease a local volume close to said deformable membranes in the second configuration. EX75. The method according to any of EX60 to EX72, wherein deforming said at least one deformable membrane comprises: changing a deformation of said at least one deformable membrane with high frequency in order to create waves in the slurry mixture.

[0136] EX76. The method according to EX75, wherein the high frequency is higher than 8 kHz, wherein the ultrasonic frequency is higher than 20 kHz.

[0137] EX77. The method according to any of EX60 to EX76, wherein feeding the slurry mixture to the slot die comprises: pumping the slurry mixture to the slot die, optionally with a flow rate between 0.5 dm3 / s and 1 dm3 / s, optionally of 0.8 dm3 / s.

[0138] EX78. A process for manufacturing aerosol-generating article components, comprising: manufacturing a sheet of aerosol-generating substrate for aerosol-generating articles in the apparatus according to any of EX1 to EX58 or through the method according to any of EX59 to EX77; gathering the sheet of aerosol-generating substrate and wrapping the gathered sheet of aerosol-generating substrate in a wrapper to form a continuous rod; cutting the continuous rod into a plurality of aerosol-generating article components each having a rod shape, each aerosol-generating article component comprising a gathered sheet formed from a cut portion of the sheet of aerosol-generating substrate.

[0139] EX79. The process according to EX78, wherein, before gathering, the process comprises: weakening the sheet of aerosol-generating substrate by making weakened lines in said sheet of aerosol-generating substrate, optionally through a crimping step generating a plurality of substantially parallel ridges or corrugations.

[0140] EX80. An aerosol-generating article comprising at least one aerosol-generating article component made according to the process of EX78 or EX79.

[0141] Examples will now be further described with reference to the figures in which:

[0142] Figure 1 shows schematically an apparatus for producing a sheet of aerosolgenerating substrate for aerosol-generating articles according to the invention;

[0143] Figures 2 and 3 show respective cross sections of a slot die of the apparatus of figure 1 ;

[0144] Figure 4 is an enlarged portion of the cross section of figure 3;

[0145] Figures 5, 6 and 7 show a detail of the slot die of figures 2, 3 and 4 in respective configurations;

[0146] Figures 8A and 8B show the slot die of figure 2 in a dynamic application;

[0147] Figures 9A and 9B show the slot die of figure 2 in a static application; Figure 10 shows schematically an apparatus for manufacturing an aerosol-generating article components;

[0148] Figures 11 and 12 show respectively a longitudinal section and a cross section of aerosol-generating article component manufactured through the apparatus of Figure 10;

[0149] Figure 13 is an exploded view of an aerosol-generating article comprising the aerosolgenerating article component of Figures 11 and 12;

[0150] Figure 14 is a flowchart of a method for producing a sheet of aerosol-generating substrate for aerosol-generating articles according to the invention.

[0151] Figure 10 shows an apparatus 100 for manufacturing aerosol-generating article components for aerosol-generating articles and may be part of a plant, not shown, for manufacturing aerosol-generating articles. An overview of the components and general operation of apparatus 100 is provided below, demonstrating the use of a cast sheet of aerosol-generating substrate “S” for making aerosol-generating article components 114. Subsequently, a detailed description of an apparatus 1 (shown in Figure 1) and a method for producing the sheet of aerosol-generating substrate “S” used by the apparatus 100 to create the aerosol-generating article component 114 will be provided.

[0152] Referring to Figure 10, the apparatus 100 includes a reel holder 101 where the sheet of aerosol-generating substrate “S” is coiled in a reel 103. The sheet of aerosol-generating substrate “S” may be composed of vegetable and / or alkaloid particles (e.g. tobacco or tobacco free), a binder and an aerosol forming agent (e.g. glycerine).

[0153] An extraction device (not shown) is configured to uncoil the sheet of aerosolgenerating substrate “S” from the reel 103, and a conveyor guides the sheet “S” along a conveying direction “C,” parallel to its longitudinal direction. For instance, the conveyor comprises a plurality of motorized rollers and / or one or more motorized belt conveyors located along the conveying direction "C".

[0154] Downstream of the reel holder 101 , in the conveying direction “C,” the apparatus 100 includes a weakening device 104 comprising counterrotating rollers 102 and 105 for weakening the sheet of aerosol-generating substrate “S”. Each counterrotating crimping roller 102, 105 is operatively connected to a motor (not shown) for rotation to generate a plurality of substantially parallel ridges or corrugations on the sheet of aerosol-generating substrate “S”.

[0155] Further downstream, the apparatus 100 includes a gathering device 106, a wrapping device 111 , and a cutter 113. The gathering device 106 includes a converging tool shaped like a tapered funnel 110, which transitions the sheet of aerosol-generating substrate “S” from a flat configuration (upstream of the gathering device) to a gathered rod-shaped configuration (downstream of the gathering device) as it is conveyed and pulled through the tool. In another example (not shown), the sheet of aerosol-generating substrate “S” is pulled through devices and / or conveyors from downstream of the converging tool.

[0156] The wrapping device 111 is designed to wrap the rod-shaped sheet of aerosolgenerating substrate “S” in a wrapper 109 to form a continuous rod 112. The wrapping device 111 comprises a guide cooperating with a feeder of the wrapper 109. The guide, not shown in figure, may comprise a U-shaped channel with additional folding elements configured to close the wrapper 109 around the gathered sheet of aerosol-generating substrate “S”. The feeder of the wrapper 109 is represented as an auxiliary reel holder 107 on which the wrapper 109 is wound in an auxiliary reel 108.

[0157] The cutter 113, such as a rotating blade, is positioned downstream of the wrapping device 111 and is designed to cut the continuous rod 112 into multiple aerosol-generating article components 114.

[0158] The apparatus 100 may also include a controller (not shown in the figures) configured to synchronize the operations of the reel holder 101 , the weakening device 104, the auxiliary reel holder 107, the conveyor, and the cutter 113.

[0159] One aerosol-generating article component 114 comprising the gathered sheet of aerosol-generating substrate “S” in the wrapper 109 is shown in figures 11 and 12.

[0160] An aerosol-generating article 200 comprising one aerosol-generating article component 114 is shown in in the exploded view of figure 13. The aerosol-generating article 200 comprises (from left to right in figure 13): a front plug 203 (solid plug), the aerosolgenerating article component 114, a tubular plug 205 (hollow plug, for instance of cellulose acetate), a fine tubular plug 206 (similar to the tubular plug 205 but with a thinner wall) and a filter plug 207 (mouthpiece filter, usually made of tow). Each plug has a wrapping of its own helping to contain properly their content. A tipping paper 208 connects the filter plug 207 to the rest of the plugs, and the front plug 203, aerosol-generating article component 114, tubular plug 205 and fine tubular plug 206 are wrapped together into a wrapping paper 209. The tubular plug 205 and fine tubular plug 206 are cooling plugs configured to cool down the aerosol formed by heating the aerosol-generating article component 114.

[0161] The apparatus 1 for producing the sheet of aerosol-generating substrate “S” is further described with reference to figures 1-7. As previously mentioned, the apparatus 1 is responsible for producing the sheet of aerosol-generating substrate “S”, which is subsequently reeled and used by apparatus 100 for making the aerosol-generating article component 114.

[0162] Referring to figure 1 , the apparatus 1 comprises a container 2 for a slurry mixture. The container is equipped with a mixer 2a for blending ingredients of a recipe and water to form a slurry mixture 3. For example, the slurry mixture 3 may be created from a blend of tobacco powder, water, glycerine, fibres, binders, or a combination of HPMC, botanical, and graphite products.

[0163] The apparatus 1 comprises a pump 4, such as a volumetric pump or a cavity pump, located downstream of the container 1. This pump 4 channels the slurry mixture 3 from the container 2 towards a slot die 5 for deposition onto a surface 6. Additionally, the apparatus 1 may include a pulsation dampener 7 connected to the container 2 to minimize flow pulsations or fluctuations caused by the pump 4. Particularly, the pulsation dampener 7, positioned downstream of the container 2 and the pump 4, absorbs the pulsations generated by the pump 4, ensuring a steady and continuous flow of the slurry mixture towards the slot die 5 for a more uniform deposition on the surface 6.

[0164] Furthermore, the apparatus 1 also includes a degasification tank 8 for removing dissolved gases and air bubbles from the slurry mixture 3. In the example of figure 1 , the degasification tank 8 is located downstream the container 2 and downstream the pulsation dampener 7 and allows the slurry mixture 3 to settle and release trapped air or gas. Consequently, the degasification tank 8 ensures that the slurry mixture 3 entering the slot die 5 is bubble-free, improving the quality of the cast slurry mixture on the surface 6.

[0165] The surface 6 is, for instance, a metal belt defining an upper branch of a belt conveyor. The upper branch is moved along a conveying direction “D” by motors, not shown. The surface 6, while moving along said conveying direction “D”, is configured to receive the slurry mixture from said slot die 5 to form the cast sheet of aerosol-generating substrate “S”.

[0166] The slot die 5 comprises a head 9 made of two pieces, shown in figure 3. The head 9 delimits internally a manifold 10 having two inlets 11 (only one visible in figure 3) in fluid communication with the container 1 through the degasification tank 8, the pulsation dampener 7 and the pump 4.

[0167] Particularly, two channels 12 are fashioned in the head 9 and open into the manifold 10 through one respective inlet 11. Each channel 12 is connected to a pipe 13 protruding from the head 9 and in fluid communication with the degasification tank 8. Each channel 12 and the respective pipe 13 delimit a duct. The duct may have an inner diameter between 5 cm and 10 cm.

[0168] The head 9 has a slot outlet 14 which faces the surface 6. The slot outlet 14 is a straight slit transversal to the conveying direction “D” and fashioned on a bottom face of the head 9. For instance, the slot outlet 14 has a transversal width between 2 m and 4 m and a gap, measured parallel to the conveying direction, between 0.3 mm and 10 mm. Furthermore, a distance between the slot outlet 14 and the surface 6, measured along a vertical direction, is between 0.5 mm and 1.2 mm. When the slot die 5 is operative, the slot outlet 14 is positioned below the manifold 10. The manifold 10 has an elongated shape extending along a main direction “M” which is arched and substantially parallel to the slot outlet 14. In other words, the arched main direction “M” of the manifold 10 lies in a plane containing also the straight slit or a mid-line of the straight slit. A cross section of the manifold 10, carried out along a plane perpendicular to the main direction, is shaped like a half a circle (figures 1 and 3). In other embodiments, not shown, the cross section is a circle or a tear drop.

[0169] The manifold 10 is in fluid communication with the slot outlet 14 through a narrow section 15 comprising a land section 16 connected to the manifold 10 followed by a slot section 17 terminating with the slot outlet 14. The land section 16 tapers from the manifold 10 towards the slot section 17 and is delimited by two converging flat faces. The slot section

[0170] 17 is delimited by two parallel flat faces.

[0171] The slot die 5 further comprises a plurality of deformable membranes 18 located on an upper inner face of the manifold 10 and aligned with each other along the main direction of the manifold 10 (figure 2). Each deformable membrane 18 closes a respective chamber 19 fashioned in an inner wall of the manifold 10. Therefore, a face of each membrane 18 opposite the chamber 19 delimits part of the manifold 10. For instance, each membrane has an area between 1 mm2and 100 mm2and a circular or rectangular perimeter.

[0172] In other embodiments, not shown in the attached figures, the deformable membranes

[0173] 18 are located in the narrow section 15 or both in the manifold 10 and in the narrow section 15.

[0174] In the example embodiment of figure 2, the deformable membranes 18 are arranged symmetrically with respect to a centerline plane “P” of the slot die 5 transverse to the slot outlet 14.

[0175] An actuation device 20 is operatively connected to each deformable membrane 18 and is configured to deform the deformable membranes 18 upon receiving command signals. In the embodiment of figures 5, 6 and 7 (showing only one membrane 18 of the plurality), the actuation device 20 comprises a piezoelectric element 21 coupled to each membrane 18 and a voltage source 22 electrically connected to the piezo electric element 21 . The piezoelectric element 21 is in the chamber 19.

[0176] In other embodiments, not shown in the appended figures, a piezoelectric material is part of the deformable membranes 18 and the voltage sources 22 are electrically connected to the piezoelectric material of the deformable membranes 18.

[0177] A control unit 23 is operatively connected to each actuation device 21 and is configured to issue command signals to control the actuation device 21. The control unit 23 controls a voltage “V” applied by each voltage source 22 to the respective piezoelectric element 21. Upon applying the voltage “V” to the piezoelectric element 21 , said piezoelectric element 21 deforms and also the deformable membrane 18 is deformed. A magnitude and / or a sign of the voltage “V” causes the deformable membrane 18 to deform between a first configuration and a second configuration.

[0178] In the first configuration (figure 6), the deformable membrane 18 lies recessed with respect to an internal surface of the manifold 10 and the face of the membrane 18 opposite the chamber 19 is concave. In the second configuration (figure 7), the deformable membrane 18 protrudes inside the manifold 10 and the face of the membrane 18 opposite the chamber 19 is convex. A magnitude of a deformation of the membrane 18, i.e. the maximum deflection of the deformable membrane 18, is proportional to an entity of the voltage “V” applied and commanded by the control unit 23.

[0179] Furthermore, the command signals from the control unit 23 are configured to drive the voltage sources 22 such as to deform the deformable membranes according to a deformation speed and to adjust said deformation speed. For instance, a first deformation speed towards the first configuration is different from a second deformation speed towards the second configuration. If the first deformation speed is faster than the second deformation speed then a suction force is created on the slurry 3 inside the head 9. If the second deformation speed is faster than the first deformation speed then a pushing force is created on the slurry 3 inside the head 9.

[0180] The chamber 19 permits the deformable membrane 18 to take the recessed first configuration in which said deformable membrane 18 enters the chamber 19.

[0181] In the example embodiment shown in the attached figures, if no voltage is applied, the deformable membrane 18 remains undeformed and lies flush with the inner wall of the manifold, as represented in figure 5. Furthermore, the deformable membrane 18 may be designed to have a stiffness such that it keeps the undeformed configuration (of figure 5) when subjected to a normal expected pressure of the slurry mixture 3 in the slot die 5.

[0182] The apparatus 1 comprise a viscosity sensor 24 configured for detecting viscosity of the slurry mixture 3. The viscosity sensor 24 may be for instance located in the slot die 5 (figure 5) or in the container 2 or may be an inline viscosimeter located in the pipeline connecting to the container 2 to the slot die 5. The viscosity of the slurry mixture 3 is between 150000 and 500000 cP (centi-Poise).

[0183] In the illustrated embodiment, the apparatus 1 further comprise a plurality of sensors 25 positioned downstream of the slot outlet 14 and at different points arranged transversally on the sheet of aerosol-generating substrate “S” cast on the surface 6. The sensors 25 may be laser sensors or a cameras and are configured to detect thickness, color, texture of the slurry mixture deposited on the surface 6 at these different points. The thickness of the cast sheet is usually between 400 pm and 650 pm.

[0184] The viscosity sensor 24 and the sensors 25 are operatively connected to the control unit 23 and the control unit 23 is configured to elaborate signals from the viscosity sensor 24 correlated to the viscosity and from the sensors 25 correlated, thickness, color, texture of the slurry mixture and to issue the command signals to the voltage sources 22 as a function of these detected properties.

[0185] The command signals are configured to deform the deformable membranes 18 through the respective voltage sources 22 between the first configuration and the second configuration and to adjust the deformation speed and / or the magnitude of deformation as a function of detected properties. Each actuation device 20 is controlled by the control unit 23 independently of the others, such that the actuation devices 20 of the deformable membranes 18 are controlled as a function of the positions of the deformable membranes 18 and of the properties of the slurry mixture 3.

[0186] The adoption of piezoelectric elements 21 and voltage sources 22 of the detailed embodiment allows to change dynamically the configuration of deformable membranes 18 with a high frequency (higher than 8 kHz) or an ultrasonic frequency (higher than 20 kHz), in order to create waves in the slurry mixture and to re-direct part of the slurry in the manifold, i.e. to control flows of the slurry in the head 9.

[0187] However, the command signals from the control unit 23 may also configured to keep the deformable membranes 18 in respective deformed configurations (constant voltage applied to the piezo) in order to statically adjust a volume of the manifold 10. Some deformable membranes 18 may be brought and kept in the first configuration, to increase a local volume close to said deformable membranes 18, and other deformable membranes 18 may be brought in the second configuration, to decrease a local volume close to said deformable membranes 18.

[0188] Figures 8A and 8B show an example of dynamic application. The arrows indicate the direction of the flows of slurry mixture and the sizes of the arrows indicate the importance of the slurry mixture flows. In figure 8A, the deformable membranes 18 are not activated and the slurry 3 running in the manifold 10 does not produce an even deposition on the cast sheet on the surface 6. The sensors 25 indicate that the slurry mixture 3 arriving at position “A” is not sufficient (i.e., it provides a too small thickness of the cast sheet), while the slurry mixture 3 arriving at position “B” is too important. In figure 8B, the control unit 23 has activated the deformable membranes 18’ and 18” with an intensity (frequency and magnitude) such that more slurry mixture 3 is pushed to position “A” and less to position “B”, balancing the flows of slurry mixture 3 passing through the slot die outlet 14 and obtaining again an even deposition of the slurry mixture 3 on the surface 6.

[0189] In other embodiments, not shown in the appended drawings, the structure and features of the head 5 are the same as disclosed above but the actuation devices 20 are pneumatic. No piezoelectric elements 21 or piezoelectric material are provided. The deformable membranes 18 are gas-tight and the actuation devices 20 comprise one gas pump or more gas pumps in fluid connection with the chambers 19 through pipes.

[0190] The gas pump / s is / are configured to pump a gas in the chambers 19, for instance air, or to withdraw the gas from the chambers 19 such as to deform the membranes 18. The command signals from the control unit 23 are configured to apply a pressure of the gas in the chambers 19 to deform the deformable membranes 18 and / or to keep a deformation of the deformable membranes 18.

[0191] This variant embodiment is more suitable for a static control of the deformable membranes 18.

[0192] Figures 9A and 9B show an example of static application. In figure 9A, a slurry mixture flow 3 is represented through arrows. The arrows indicate the direction of the flows of slurry mixture 3 which entered the manifold 10. The sizes of the arrows indicate the importance of the slurry mixture flows. An increase of viscosity creates a situation in the central region “A” where the travel time of the slurry mixture 3 increases and the quantity of slurry mixture 3 decreases with respect to regions “B” at the ends of the manifold 10, creating a heterogeneous deposition of slurry mixture 3 on the surface 6. Figure 9B shows that through the deformable membranes 18 balancing is obtained.

[0193] The deformable membranes 18’ have been made concave at the end of the manifold 10 and deformable membranes 18” have been made convex close to the central region. This configuration of the deformable membranes 18 allow to recover an even deposition of slurry mixture on the surface 6.

[0194] The apparatus 1 disclosed above is configured to carry out a method for producing a sheet of aerosol-generating substrate for aerosol-generating articles, as schematically represented in figure 14.

[0195] The method provides for mixing the recipe with water to form the slurry mixture 3 in the container 2. The slurry mixture 3 is fed to the slot die 5, through the pump 4, the pulsation dampener 7 and the degasification tank 8. For instance, the slurry mixture 3 is pumped to the slot die 5 with a flow rate between 0.5 dm3 / s and 1 dm3 / s, optionally of 0.8 dm3 / s.

[0196] The slot die 5 deposits the slurry mixture 3 on the surface 6 while said surface 6 moves along the conveying direction “D” to form the cast sheet of aerosol-generating substrate “S”. During deposition, the viscosity of the slurry mixture 3, the thickness, color and texture of the the cast sheet of aerosol-generating substrate “S” deposited on the surface 6 are monitored and the deformable membranes 18 are deformed dynamically or statically (type of deformation, concave or convex, speed of deformation and magnitude of deformation) as a function of these detected properties.

[0197] After deposition, the cast sheet of aerosol-generating substrate “S” is progressively dried, for instance in an oven through which the cast sheet of aerosol-generating substrate “S” continuously moves while traveling along the conveying direction “D”.

Claims

CLAIMS1. Apparatus for producing a sheet of aerosol-generating substrate for aerosolgenerating articles, the apparatus comprising: a mixer (2a) configured for mixing ingredients of a recipe and water to form a slurry mixture (3); a slot die (5) in fluid communication with the mixer (20) or with a container (2) for the slurry mixture (3), the container (2) being operatively interposed between the mixer (2a) and the slot die (5); a surface (6) located under the slot die (5), moving with respect to the slot die (5) along a conveying direction (D) and configured to receive the slurry mixture (3) from said slot die (5) to form a cast sheet (S); wherein the slot die (5) comprises a head (9) delimiting internally: a manifold (10) having at least one inlet (11) in fluid communication with the mixer (2a) or with the container (2), a narrow section (15) in fluid communication with the manifold (10) and terminating in a slot outlet (14) facing the surface (6); wherein the slot die (5) further comprises: at least one deformable membrane (18) placed inside the head (9) and delimiting at least in part the manifold and / or the narrow section (15); at least one actuation device (20) operatively connected to the at least one deformable membrane (18) and configured to deform said at least one deformable membrane (18) upon receiving command signals; a control unit (23) operatively connected to the at least one actuation device (20) and configured to issue said command signals to control the actuation device (20).

2. Apparatus according to claim 1 , wherein the command signal is configured to deform the at least one deformable membrane (18) at least between a first configuration, optionally concave, in which said at least one deformable membrane (18) lies recessed with respect to an internal surface of the manifold (10) or of the narrow section (15), and a second configuration, optionally convex, in which said at least one deformable membrane (18) protrudes inside the manifold (10) or the narrow section (15).

3. Apparatus according to claim 1 or 2, comprising at least one sensor (24, 25) operatively connected to the control unit (23) and positioned and configured to detect properties of the slurry mixture (3); wherein the control unit (23) issues the command signals as a function of the detected properties.

4. Apparatus according to any of claims 1 to 3, wherein the slot die (5) comprises a plurality of deformable membranes (18) and a plurality of actuation devices (20), wherein one or more of the actuation devices (20) is / are controlled by the control unit (23) independently of others.

5. Apparatus according to claim 4, wherein the manifold (10) has an elongated shape extending along a main direction (M) parallel to the slot outlet (14) and, at least when the slot die is operative, the narrow section (15) and the slot outlet (14) are positioned below the manifold (10); wherein the deformable membranes (18) are aligned with each other along the main direction (M) of the manifold (10).

6. Apparatus according to claim 5 when claim 4 is according to claim 3, wherein the at least one sensor (24, 25) comprises a plurality of sensors (25) positioned downstream of the slot outlet (14) and at different points arranged transversally on the slurry mixture cast on the surface (6).

7. Apparatus according to claim 6, wherein the plurality of actuation devices (20) are controlled as a function of the positions of the deformable membranes (18) and of the properties of the slurry mixture (3) detected by the plurality of sensors (25) in each point.

8. Apparatus according to any of claims 1 to 7, wherein the command signals from the control unit (23) are configured to change the configuration of the at least one deformable membrane (18) with high frequency or ultrasonic frequency, in order to create waves in the slurry mixture (3).

9. Apparatus according to any of claims 1 to 7, wherein the command signals from the control unit (23) are configured to keep the at least one deformable membrane (18) in a deformed configuration to adjust a volume of the manifold (10) and / or the narrow section (15).

10. Apparatus according to any of claims 1 to 9, wherein the at least one actuation device (20) is piezoelectric or pneumatic.

11. Method for producing a sheet of aerosol-generating substrate for aerosol-generating articles, the method comprising:mixing a recipe with water to form a slurry mixture (3), the recipe comprising as ingredients vegetable and / or alkaloid particles, a binder and an aerosol forming agent; feeding the slurry mixture (3) to a slot die (5) and depositing the slurry mixture (3) on a surface (6) via said slot die (5) to form a cast sheet (S); wherein the slot die (5) comprises a head (9) delimiting internally: a manifold (10) having an inlet (11), a narrow section (15) in fluid communication with the manifold (10) and terminating in a slot outlet (14) facing the surface (6); wherein the slot die (5) further comprises at least one deformable membrane (18) placed inside the head (9) and delimiting at least in part the manifold (10) and / or the narrow section (15); wherein the method further comprises: deforming said at least one deformable membrane (18) while depositing the slurry mixture (3).

12. The method according to claim 11 , further comprising: detecting properties of the slurry mixture (3); wherein said at least one deformable membrane (18) is deformed as a function of the detected properties.

13. The method according to claim 12, wherein a type of deformation, concave or convex, a speed of deformation and a magnitude of a deformation of the at least one deformable membrane (18) are function of the detected properties.

14. The method according to any of claims 11 to 13, wherein the detected properties comprise a viscosity of the slurry mixture (3) and / or a thickness of the slurry mixture (3) deposited on the surface (6).

15. The method according to any of claims 11 to 14, wherein deforming said at least one deformable membrane (18) comprises: bringing and keeping said at least one deformable membrane (18) in a deformed configuration to change a volume of the manifold (10) and / or the narrow section (15) or wherein deforming said at least one deformable membrane (18) comprises: changing a deformation of said at least one deformable membrane (18) with high frequency in order to create waves in the slurry mixture (3).

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