WO2025233056A1

WO2025233056A1 - Method and apparatus for manufacturing rod-shaped elements for aerosol-generating articles

Info

Publication number: WO2025233056A1
Application number: PCT/EP2025/058721
Authority: WO
Inventors: Valerio D'AMBROGI; Luca CALABRESE
Original assignee: Philip Morris Products SA
Current assignee: Philip Morris Products SA
Priority date: 2024-05-07
Filing date: 2025-03-31
Publication date: 2025-11-13
Anticipated expiration: 2026-11-07

Abstract

A method for manufacturing rod-shaped elements for aerosol-generating articles, comprises: making openings (20) in a strip of material (15) while the strip of material (15) is conveyed along a conveying path, wherein each opening (20) extends at least in part transversally on the strip of material (15); pulling the strip of material (15) along a conveying direction (F) to stretch the strip of material (15) and open the openings (20) thus forming a net-like structure; gathering the strip of material (15) in a rod-shaped configuration and wrapping the strip of material (15) in a wrapper (27) to form a continuous rod (28); cutting the continuous rod (28) in a plurality of rod-shaped elements. Before gathering or when gathering, the strip of material (15) is stabilized by mechanically deforming and/or entangling the strip of material (15) conveyed along the conveying path and pulled along the conveying direction (F) in order to keep the net-like structure in the rod-shaped elements.

Description

METHOD AND APPARATUS FOR MANUFACTURING ROD-SHAPED ELEMENTS FOR AEROSOL-GENERATING ARTICLES

The present disclosure relates to a method and apparatus for manufacturing rodshaped elements for aerosol-generating articles.

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.

An aerosol-generating article is an assembly of different kinds of rod-shaped elements (small cylinders) enclosed in one or more wrapping materials. For instance, one of the rodshaped elements is usually made of a gathered sheet of a substrate which generates aerosol when heated. Another rod-shaped element could be made of polylactic acid which helps to cool down the air heated in the substrate before it reaches the consumer. Another rod-shaped element could be made of cellulose acetate that has a filter function.

In order to manufacture the rod-shaped elements, a main material of the rod-shaped elements (e.g. aerosol-generating substrate with or without tobacco ingredient or polylactic acid or paper or cellulose acetate tow) provided in strip-like sheet format may be submitted to various pre-treatments, then goes through a “rod forming” stage where the strip of material is guided into a converging device and exits as a rod of material having a desired diameter. The rod of material is then wrapped in a continuous sheet of wrapping paper which is progressively closed on the rod of material. The resulting continuous wrapped rod is then cut by a rotating knife in rod-shaped elements which are input to an assembly line. The different kinds of rod-shaped elements are afterwards aligned, abutted and wrapped in a further sheet material to form a continuous rod. The continuous wrapped rod made of different rod-shaped elements is then cut in smaller rods which are the final consumables or are used to manufacture the final consumables.

Among the cited various pre-treatments, the sheet of material is submitted to a crimping process which is usually applied after the sheet of material has been unwound from a bobbin or pulled out from a bale and just before the sheet of material is pulled into the converging device, such as a funnel-shaped device, to get shaped into the continuous wrapped rod. According to known crimping processes, the sheet of material is continuously fed to a pair of interleaved rollers (crimping rollers) able to impress a plurality of longitudinally (or sometime transversally) extending crimp corrugations to the continuous sheets. The crimping process creates ridges and grooves in the band of material and weakens the band of material.

The crimping process is helpful for folding and gathering the sheet of material into the rod. Indeed, the corrugations define folding lines and facilitate folding and gathering of the sheet of material. The defined folding line by the corrugations ensure regular and homogeneous folding of the material when it gets shaped into a rod. The crimping process also influences, inter alia, the amount of air contact, the Resistance to Draw (RTD), and others properties and, hence, is directly experienced by the users of the aerosol-generating articles. It could best ensure the consistency and replicability of the product performance and characteristic of the aerosol-generating article.

Other kinds of pre-treatment are disclosed, for instance in documents US4168712A and US3188924A.

US4168712A discloses a process for manufacturing of rod-like articles of the tobacco industry comprising a filler with a surrounding wrapper. The process includes the steps of forming the filler by feeding continuously at least one web of filler material which has lines of spaced slits extending across the width of the web, the slits in each line being offset from those in adjacent lines; stretching the web so as to open up the slits while distorting out of their original plane the interconnected strip-like portions of the web left between the slits; compressing the web laterally to form a filler; enclosing the thus-formed filler in a wrapper to form a continuous rod; and cutting the continuous rod into individual portions.

US3188924A discloses a method for the production of reticulated webs starting from thin flexible sheet or strip material for the manufacture of smoke filters. The method consists in submitting sheet or strip material to a slitting operation to form an array of elongated slits arranged in substantially parallel rows with the slits in adjacent rows in staggered relationship and thereafter stretching the slit sheet or strip in the direction transverse to the rows of slits. By stretching the sheet or strip after slitting, the elongated slits are caused to open to form holes of an approximate hexagonal contour resulting in a web exhibiting a honeycomb pattern with parts of the boundaries of the hexagons twisted from the plane of the starting sheet or strip so that a reticulated web is produced of greater overall thickness than that of the starting sheet or strip and with non-planar faces on both sides of the median plane of the original sheet or strip. Steps are also taken to stabilize the material. The starting sheet or strip are provided with a coating of a thermoplastic resin material, the web after stretching being subjected to heat to flux the resin. Alternatively, a setting agent such as a solution of ethyl cellulose in alcohol is sprayed on to the slit and stretched web. The reticulated web material is then folded, gathered or bundled to form filter bodies for use as tobacco smoke filters.

Document CN113057370A discloses a filter tip rod with a micro-cavity structure which is formed by wrapping an opened tow and forming tiny cavities in the opened and expanded tow fiber unfolding surface by utilizing high-energy laser. The tow fiber is then rolled into a filter tip rod.

In this technical field, it would be desirable to have an apparatus and a method capable of manufacturing rod-shaped elements for aerosol-generating articles such as to improve the quality of the aerosol-generating articles and guarantee an optimal experience to the final user.

It would be desirable to have an apparatus and a method for manufacturing the rodshaped elements which is capable of improving control and stability of expected features of the rod-shaped elements, so that the material and the aerosol-generating articles could provide the best expected effect. Particularly, it would be desirable to improve control of a contact area of air drawn in aerosol-generating substrates to obtain an optimal exchange surface, an expected Resistance To Draw (RTD) and/or filtration level of the filter plugs.

It would be desirable to have an apparatus and a method for manufacturing the rodshaped elements of improved flexibility, to allow production of rod-shaped elements and aerosol-generating articles of different types and/or provided with different properties.

It would be desirable to have an apparatus and a method for manufacturing the rodshaped elements which is capable of pre-treating the strips of material while improving the known crimping methods and devices.

The present disclosure relates to a method for manufacturing rod-shaped elements for aerosol-generating articles. The method comprises: conveying continuously a strip of material along a conveying path and in a conveying direction parallel to a longitudinal direction of said strip of material; making openings in the strip of material while the strip of material is conveyed along the conveying path, wherein each opening extends at least in part transversally on the strip of material; pulling the strip of material along the conveying direction to stretch the strip of material and open the openings thus forming a net-like structure while the strip of material is conveyed along the conveying path. The method also comprises: gathering the strip of material having the net-like structure in a rod-shaped configuration and wrapping the strip of material in the rod-shaped configuration in a wrapper to form a continuous rod while the strip of material with the net-like structure and is conveyed along the conveying path. The method may also comprise: cutting the continuous rod in a plurality of rod-shaped elements. Before gathering or when gathering, the strip of material is stabilized by mechanically deforming and/or entangling said strip of material conveyed along the conveying path and pulled along the conveying direction in order to keep the net-like structure in the rod-shaped elements.

The inventor found that the mechanical stabilization of the net-like structure allows to keep the net-like structure down to the rod-shaped elements and then to the final aerosol smoking articles.

The inventor found that the mechanical stabilization of the net-like structure allows to improve consistency of the properties of the rod-shaped elements and of the final aerosol smoking articles during manufacturing.

The inventor found that the stabilized net-like structure inside the aerosol-generating articles allows to improve control and stability of expected features and thus quality of the aerosol-generating articles.

The inventor found that the stabilized net-like structure provides an even air and aerosol distribution through the aerosol-generating article.

The inventor found that the stabilized net-like structure inside the aerosol-generating substrate plugs provides improved and adjustable contact area of the air drawn in and allows to obtain an optimal exchange surface.

The inventor found that the stabilized net-like structure inside the filter plugs provides stable and adjustable Resistance To Draw (RTD) and/or filtration level.

The inventor found that the disclosed method can be implemented in existing manufacturing processes and plants at somehow low cost and with low impact on the rest of the production line.

The inventor found that the disclosed method allows to change the properties of the manufactured rod-shaped elements through a fine-tuning but without radically changing parts of the plant.

The inventor found that the properties rod-shaped elements may be changed by designing the shape, size and distribution of the openings and/or by adjusting a pulling longitudinal force exerted on the strip of material, which are parameters which can be easily and accurately determined and controlled.

Gathering the strip of material in a rod-shaped configuration may comprise: pulling the strip of material through a converging tool. The converging tool may be shaped like a tapered funnel.

In some embodiments, when the strip of material is stretched and the openings are opened, the strip of material buckles outside a respective lying surface and the formed net- like structure is three-dimensional. In some embodiments, stabilizing the strip of material comprises: compressing the strip of material before gathering to flatten the net-like structure. Compressing the strip of material may comprise: running the strip of material provided with the net-like structure between two compressing rollers. Optionally, the two compressing rollers also pull the strip of material upstream along the conveying direction to open the openings and forming the net-like structure. Optionally, the two compressing rollers operate after making openings and before gathering.

If the net-like structure is three-dimensional, compressing the strip of material before gathering comprises: flattening the three-dimensional net-like structure into a bi- dimensional net-like structure.

The inventor found the compressing rollers allow to combine in a single device the pulling action and the freezing of the net-like structure.

In some embodiments, stabilizing the strip of material comprises: pulling through the converging tool an amount of material per unit length of the strip of material provided with the net-like structure equal to an amount of material per unit length of a same strip of material without openings, to entangle the strip of material into the rod-shaped configuration.

The inventor found that entangling the strip of material into the rod-shaped configuration allows to maintain into the rod-shaped elements the three-dimensional structure of the net-like structure.

In some embodiments, pulling through the converging tool the amount of material per unit length of the strip of material provided with the net-like structure equal to the amount of material per unit length of a strip of material without openings comprises: pulling simultaneously through the converging tool a plurality of strips of material with the net-like structure. Each strip of material of the plurality of strips of material is conveyed, provided with openings and pulled.

In some embodiments, if the stretched strip of material provided with the net-like structure is N-times longer than the same strip of material without openings, then the strips of material of the plurality of strips of material are N in number.

The plurality of strips of material may have all a same width (B). The strips of material of the plurality of strips of material may be between two and six in number.

In some embodiments, pulling through the converging tool the amount of material per unit length of the strip of material provided with the net-like structure equal to the amount of material per unit length of a same strip of material without openings comprises: pulling through the converging tool a strip of material with the net-like structure having a corrected width (Be) greater than a reference width (Bref) calculated for the same strip of material without openings.

In some embodiments, if the stretched strip of material provided with the net-like structure is N-times longer than the same strip of material without openings, then the corrected width (Be) is N-times the reference (Bref) width.

Pulling through the converging tool may be carried out by pulling the strip of material from downstream of the converging tool.

The inventor found that both options (“compressing rollers” or “entangling”) generate a random shaping and preservation of the net-like structure into the rod-shaped elements, assuring an even and homogeneous diffusion of the air through the length of the rod-shaped elements.

Each opening has two opposite end points and, before pulling the strip of material, a transversal width (W) of the opening between the two opposite end points may be greater than a longitudinal length (L) of the opening between the same two opposite end points. In some embodiments, the transversal width (W) is from 1 mm to 50 mm, optionally from 5 mm to 20 mm. In some embodiments, a ratio (W/L) of the transversal width (W) to the longitudinal length (L) is between 1.5 to 5.

The openings may be arranged in rows, each crossing the strip of material. A plurality of openings being aligned on each row. A plurality of said rows may follow each other along the longitudinal direction of the strip of material. A stretch of strip corresponding to a length of one rod-shaped element comprising a plurality of rows. The rows may be perpendicular to the longitudinal direction of the strip of material or the rows may delimit with the longitudinal direction of the strip of material an angle between 60° and 90°.

In some embodiments, the openings in each row are spaced from each other of a transversal distance (D). The transversal distance (D) may be from 1 to 50 mm, optionally from 2 to 10 mm. In some embodiments, the openings of one row are shifted of an offset transversal distance (A) with respect to the openings of another adjacent row. The offset transversal distance (A) may be greater than the transversal distance (D). In some embodiments, the offset transversal distance (A) is smaller than the transversal width (W).

In some embodiments, adjacent rows are spaced of a longitudinal distance (H). The longitudinal distance (H) may be smaller than the transversal width (W).

The inventor found that the geometry and distribution of the openings as disclosed above allow to create weakened lines along the strip of material that may be also not straight, so that, when the strip is gathered in the rod-shaped configuration, said strip may have folds other than longitudinal folds and may prevent formation of undesired air obstruction and/or wide air passages. In some embodiments, the openings are slits. Each slit may be straight or wavy or zig-zag.

In some embodiments, a shape of the openings is such that, when the strip of material is pulled along the conveying direction, a width (B) of said strip of material increases, i.e. the strip of material has an auxetic behaviour.

In some embodiments, before pulling the strip of material (strip of material not stretched), a width (B) of said strip of material is from 50 mm to 300 mm, optionally from 100 mm to 200 mm. In some embodiments, before pulling the strip of material (strip of material not stretched), a thickness of said strip of material is from 50 pm to 300 pm. In some embodiments, before pulling the strip of material (strip of material not stretched), a grammage of said strip of material is from 50 grams per square meter to 100 grams per square meter.

The rod-shaped element made through the method for manufacturing rod-shaped elements may be a filter plug or an aerosol generating plug or a cooling plug or a front plug. The strip of material may be an aerosol generating substrate, optionally tobacco cast leaf. The strip of material may be made of polylactic acid or of cellulose acetate or paper material, optionally a non-woven paper material.

In some embodiments, making openings in the strip of material comprises: directing at least one laser beam on the strip of material. The at least one laser beam may be moved transversely to the conveying direction while the strip of material moves in the conveying direction. Directing the at least one laser beam may comprise: dividing the at least one laser beam in a plurality of output laser beams and making said plurality of output laser beams impinge on the strip of material. Directing the at least one laser beam may comprise: focusing the at least one laser beam on the strip of material. A power range of the laser beam may be from 50 W to 500 W.

The inventor found that the use of laser makes it possible to generate apertures having complex shapes with high precision and/or to generate very small apertures.

The inventor also found that the use of laser allows to easily and quickly change shape, size and pattern of the apertures.

In some embodiments, making openings in the strip of material comprises: cutting the strip of material with blades. Making openings in the strip of material may comprise: running the strip between two cutting rollers, wherein at least one of the cutting rollers is provided with the blades.

The inventor found that the cutting rollers are suitable for high-speed production.

The present disclosure relates to an apparatus for manufacturing rod-shaped elements for aerosol-generating articles, wherein the apparatus is configured to carry out a method for manufacturing rod-shaped elements for aerosol-generating articles. The method comprises: conveying continuously a strip of material along a conveying path and in a conveying direction parallel to a longitudinal direction of said strip of material; making openings in the strip of material while the strip of material is conveyed along the conveying path, wherein each opening extends at least in part transversally on the strip of material; pulling the strip of material along the conveying direction to stretch the strip of material and open the openings thus forming a net-like structure while the strip of material is conveyed along the conveying path. The method also comprises: gathering the strip of material having the net-like structure in a rod-shaped configuration and wrapping the strip of material in the rod-shaped configuration in a wrapper to form a continuous rod while the strip of material with the net-like structure and is conveyed along the conveying path. The method may also comprise: cutting the continuous rod in a plurality of rod-shaped elements.

The present disclosure also relates to an apparatus for manufacturing rod-shaped elements for aerosol-generating articles, wherein the apparatus comprises: at least one conveyor defining a conveying path and a conveying direction; a perforator or cutout device placed along the conveying path; a dragging device placed downstream of perforator or cutout device along the conveying path; a gathering device placed downstream of the perforator or cutout device. The apparatus may also comprise a wrapping device placed downstream of the gathering device. The apparatus may also comprise a cutter placed downstream of the wrapping device. The apparatus further comprises a control unit configured to control the apparatus to perform the following procedure: conveying continuously a strip of material along the conveying path and in the conveying direction parallel to a longitudinal direction of said strip of material through the at least one conveyor; making openings in the strip of material while the strip of material is conveyed along the conveying path through the perforator or cutout device such that each opening extends at least in part transversally on the strip of material; pulling the strip of material along the conveying direction through the dragging device to stretch the strip of material and open the openings thus forming a net-like structure while the strip of material is conveyed along the conveying path. The procedure may also comprise: gathering the strip of material having the net-like structure in a rod-shaped configuration in the gathering device while the strip of material with the net-like structure and is conveyed along the conveying path. The procedure may also comprise: cutting the continuous rod in a plurality of rod-shaped elements through the cutter. Before gathering or when gathering, said procedure further comprises: stabilizing the strip of material by mechanically deforming and/or entangling said strip of material conveyed along the conveying path and pulled along the conveying direction in order to keep the net-like structure in the rod-shaped elements. Said apparatus is configured to carry out a method for manufacturing rod-shaped elements for aerosol-generating articles. The method comprises: conveying continuously a strip of material along a conveying path and in a conveying direction parallel to a longitudinal direction of said strip of material; making openings in the strip of material while the strip of material is conveyed along the conveying path, wherein each opening extends at least in part transversally on the strip of material; pulling the strip of material along the conveying direction to stretch the strip of material and open the openings thus forming a net-like structure while the strip of material is conveyed along the conveying path. The method also comprises: gathering the strip of material having the net-like structure in a rod-shaped configuration and wrapping the strip of material in the rod-shaped configuration in a wrapper to form a continuous rod while the strip of material with the net-like structure and is conveyed along the conveying path. The method may also comprise: cutting the continuous rod in a plurality of rod-shaped elements.

In some embodiments, when the strip of material is pulled and the openings are opened, the strip of material buckles outside the respective lying surface and the formed net-like structure is three-dimensional.

In some embodiments, the apparatus comprises two compressing rollers placed along the conveying path between the perforator or cutout device and the gathering device, the two compressing rollers being configured to flatten the net-like structure to stabilize the strip of material.

The two compressing rollers may comprise rubber lateral surfaces.

In some embodiments, the two compressing rollers also define the dragging device or are part of the dragging device configured to pull the strip of material along the conveying direction to open the openings and forming the net-like structure while the strip of material is conveyed along the conveying path.

In some embodiments, the gathering device comprises a converging tool. The converging tool may be shaped like a tapered funnel. The gathering device is configured to gather the strip of material having the net-like structure in a rod-shaped configuration while the strip of material with the net-like structure is conveyed along the conveying path.

In some embodiments, the conveyor comprises a plurality of sub-conveyors each configured to convey a respective strip of material towards the gathering device along a respective conveying sub-path.

In some embodiments, the apparatus comprises a plurality of perforators or cutout devices each placed along a respective conveying sub-path to make openings in the respective strip of material. In some embodiments, the perforator or cutout device comprises a laser device arranged and configured to emit a laser beam making the openings in the strip of material while the strip of material is conveyed along the conveying path. The laser device is controlled by a control unit of the apparatus to emit intermittently the laser beam to make the plurality of openings. The laser device may comprise a laser source and a beam splitter, the beam splitter being arranged and configured to divide the laser beam from the laser source in a plurality of laser sub-beams impinging on the strip of material. The laser device may comprise a focusing lens arranged and configured to focus the laser beam or the laser sub-beams on the strip of material. The laser device may be arranged and configured to move the laser beam or the laser sub-beams transversely to the conveying direction of the strip of material. The laser device may be a carbon dioxide laser.

The inventor found that the carbon dioxide lasers, having a wavelength from 9 to 11 pm (infrared), allow to engrave in efficient manner, since many natural and synthetic materials have strong absorption in the infrared range and the laser is not reflected.

The inventor found that the laser beam splitter, for instance a diffractive optical element (DOE), provides a uniform intensity distribution of the laser sub-beams and the geometry and number of the set of sub-beams is very accurately determined.

The inventor found that the focusing lens allows to decrease the Heat Affected Zone (HAZ), e.g., the burned area around the laser cut.

In some embodiments, the apparatus further comprises a blower and/or a vacuum system arranged and configured to remove smoke and/or to dissipate heat generated by operation of the laser device.

In some embodiments, the perforator or cutout device comprises two cutting rollers, wherein at least one of the cutting rollers is provided with blades.

The present disclosure also relates to a rod-shaped element for aerosol-generating articles, comprising: a strip of material having a net-like structure and gathered in a rodshaped configuration; a wrapper wrapping said gathered strip of material; wherein the net- like structure of the strip of material is stabilized in the rod-shaped element by mechanically deformation and/or entanglement.

The present disclosure also relates to an aerosol-generating article, comprising at least one rod-shaped element as disclosed above.

The aerosol generating article comprises a filter plug, an aerosol generating plug and optionally a cooling plug, wherein said rod-shaped element is the filter plug and/or the aerosol generating plug and/or the optional cooling plug and/or a front plug.

Said rod-shaped element for aerosol-generating articles may be made according to a method for manufacturing rod-shaped elements for aerosol-generating articles, wherein the method comprises: conveying continuously a strip of material along a conveying path and in a conveying direction parallel to a longitudinal direction of said strip of material; making openings in the strip of material while the strip of material is conveyed along the conveying path, wherein each opening extends at least in part transversally on the strip of material; pulling the strip of material along the conveying direction to stretch the strip of material and open the openings thus forming a net-like structure while the strip of material is conveyed along the conveying path. The method also comprises: gathering the strip of material having the net-like structure in a rod-shaped configuration and wrapping the strip of material in the rod-shaped configuration in a wrapper to form a continuous rod while the strip of material with the net-like structure and is conveyed along the conveying path. The method also comprises: cutting the continuous rod in a plurality of rod-shaped elements.

Said rod-shaped element for aerosol-generating articles may be made through an apparatus for manufacturing rod-shaped elements for aerosol-generating articles, wherein the apparatus comprises: at least one conveyor defining a conveying path and a conveying direction; a perforator or cutout device placed along the conveying path; a dragging device placed downstream of perforator or cutout device along the conveying path; a gathering device placed downstream of the perforator or cutout device. The apparatus also comprises a wrapping device placed downstream of the gathering device. The apparatus also comprises a cutter placed downstream of the wrapping device. The apparatus further comprises a control unit configured to control the apparatus to perform the following procedure: conveying continuously a strip of material along the conveying path and in the conveying direction parallel to a longitudinal direction of said strip of material through the at least one conveyor; making openings in the strip of material while the strip of material is conveyed along the conveying path through the perforator or cutout device such that each opening extends at least in part transversally on the strip of material; pulling the strip of material along the conveying direction through the dragging device to stretch the strip of material and open the openings thus forming a net-like structure while the strip of material is conveyed along the conveying path. The procedure also comprises: gathering the strip of material having the net-like structure in a rod-shaped configuration in the gathering device while the strip of material with the net-like structure and is conveyed along the conveying path. The procedure also comprises: cutting the continuous rod in a plurality of rod-shaped elements through the cutter. Before gathering or when gathering, said procedure further comprises: stabilizing the strip of material by mechanically deforming and/or entangling said strip of material conveyed along the conveying path and pulled along the conveying direction in order to keep the net-like structure in the rod-shaped elements. As used in the present description, the term “strip” means a sheet of material having a main longitudinal dimension hundreds or thousands of times higher than a width (B) of the sheet of material and the width that is hundreds of times or thousands of times higher than a thickness (t) of the sheet of material.

As used in the present description, the term “longitudinal” means a direction aligned with the longitudinal dimension of the strip of material and thus with the conveying direction of the strip of material.

As used in the present description, the “transversal” refers to a direction perpendicular to the longitudinal direction and lying in the lying plane of the strip of material.

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.

EX1. A method for manufacturing rod-shaped elements for aerosol-generating articles, comprises: conveying continuously a strip of material along a conveying path and in a conveying direction parallel to a longitudinal direction of said strip of material; making openings in the strip of material while the strip of material is conveyed along the conveying path, wherein each opening extends at least in part transversally on the strip of material; pulling the strip of material along the conveying direction to stretch the strip of material and open the openings thus forming a net-like structure while the strip of material is conveyed along the conveying path; gathering the strip of material having the net-like structure in a rod-shaped configuration and wrapping the strip of material in the rod-shaped configuration in a wrapper to form a continuous rod while the strip of material with the net-like structure and is conveyed along the conveying path; cutting the continuous rod in a plurality of rod-shaped elements; wherein, before gathering or when gathering, the strip of material is stabilized by mechanically deforming and/or entangling said strip of material conveyed along the conveying path and pulled along the conveying direction in order to keep the net-like structure in the rod-shaped elements.

EX2. The method according to EX1 , wherein stabilizing the strip of material comprises: compressing the strip of material before gathering to flatten the net-like structure. EX3. The method according to EX2, wherein compressing the strip of material comprises: running the strip of material provided with the net-like structure between two compressing rollers.

EX4. The method according to EX3, wherein the two compressing rollers also pull the strip of material upstream along the conveying direction to open the openings and forming the net-like structure.

EX5. The method according to EX3 or EX4, wherein the two compressing rollers operate after making openings and before gathering.

EX6. The method according to any of EX1 or EX5, wherein, when the strip of material is stretched and the openings are opened, the strip of material buckles outside a respective lying surface and the formed net-like structure is three-dimensional.

EX7. The method according to EX6 when according to any of EX2 to EX5, wherein compressing the strip of material before gathering comprises: flattening the three- dimensional net-like structure into a bi-dimensional net-like structure.

EX8. The method according to any of EX1 to EX7, wherein gathering the strip of material in a rod-shaped configuration comprises: pulling the strip of material through a converging tool.

EX9. The method according to EX8, wherein the converging tool is shaped like a tapered funnel.

EX10. The method according to EX8 or EX9, wherein stabilizing the strip of material comprises: pulling through the converging tool an amount of material per unit length of the strip of material provided with the net-like structure equal to an amount of material per unit length of a same strip of material without openings (without net-like structure), to entangle the strip of material into the rod-shaped configuration.

EX11 . The method according to EX10, wherein pulling through the converging tool the amount of material per unit length of the strip of material provided with the net-like structure equal to the amount of material per unit length of a strip of material without openings comprises: pulling simultaneously through the converging tool a plurality of strips of material with the net-like structure.

EX12. The method according to EX11 , wherein each strip of material of the plurality of strips of material is conveyed, provided with openings and pulled.

EX13. The method according to EX11 or EX12, wherein, if the stretched strip of material provided with the net-like structure is N-times longer than the same strip of material without openings, then the strips of material of the plurality of strips of material are N in number. EX14. The method according to any of EX11 to EX13, wherein the plurality of strips of material have all a same width (B).

EX15. The method according to any of EX11 to EX14, wherein the strips of material of the plurality of strips of material are between two and six in number.

EX16. The method according to EX10, wherein pulling through the converging tool the amount of material per unit length of the strip of material provided with the net-like structure equal to the amount of material per unit length of a same strip of material without openings comprises: pulling through the converging tool a strip of material with the net-like structure having a corrected width (Be) greater than a reference width (Bref) calculated for the same strip of material without openings.

EX17. The method according to EX16, wherein, if the stretched strip of material provided with the net-like structure is N-times longer than the same strip of material without openings, then the corrected width (Be) is N-times the reference width (Bref).

EX18. The method according to any of EX8 to EX17, wherein pulling through the converging tool is carried out by pulling the strip of material from downstream of the converging tool.

EX19. The method according to any of EX1 to EX18, wherein each opening has two opposite end points and, before pulling the strip of material, a transversal width (W) of the opening between the two opposite end points is greater than a longitudinal length (L) of the opening between the same two opposite end points.

EX20. The method according to EX19, wherein the transversal width (W) is from 1 mm to 50 mm, optionally from 5 mm to 20 mm.

EX21. The method according to EX19 or EX20, wherein a ratio (W/L) of the transversal width (W) to the longitudinal length (L) is between 1.5 to 5.

EX22. The method according to any of EX1 to EX21 , wherein the openings are arranged in rows, each crossing the strip of material; a plurality of openings being aligned on each row; a plurality of said rows following each other along the longitudinal direction of the strip of material; a stretch of strip corresponding to a length of one rod-shaped element comprising a plurality of rows.

EX23. The method according to EX22, wherein the rows are perpendicular to the longitudinal direction of the strip of material or the rows delimit with the longitudinal direction of the strip of material an angle between 60° and 90°.

EX24. The method according to EX22 or EX23, wherein the openings in each row are spaced from each other of a transversal distance (D).

EX25. The method according to EX24, wherein the transversal distance (D) is from 1 to 50 mm, optionally from 2 to 10 mm EX26. The method according to any of EX22 to EX25, wherein the openings of one row are shifted of an offset transversal distance (A) with respect to the openings of another adjacent row.

EX27. The method according to EX24 and EX26, wherein the offset transversal distance (A) is greater than the transversal distance (D).

EX28. The method according to EX26 or EX27 when EX22 is according to any of EX19 to EX21 , wherein the offset transversal distance (A) is smaller than the transversal width (W).

EX29. The method according to any of EX22 to EX28, wherein adjacent rows are spaced of a longitudinal distance (H).

EX30. The method according to EX29 when EX22 is according to any of EX19 to EX21 , wherein the longitudinal distance (H) is smaller than the transversal width (W).

EX31 . The method according to any of EX1 to EX30, wherein the openings are slits.

EX32. The method according to EX31 , wherein each slit is straight or wavy or zigzag.

EX33. The method according to any of EX1 to EX32, wherein a shape of the openings is such that, when the strip of material is pulled along the conveying direction, a width (B) of said strip of material increases, i.e. the strip of material has an auxetic behaviour.

EX34. The method according to any of EX1 to EX33, wherein, before pulling the strip of material (strip of material not stretched), a width (B) of said strip of material is from 50 mm to 300 mm, optionally from 100 mm to 200 mm.

EX35. The method according to any of EX1 to EX34, wherein, before pulling the strip of material (strip of material not stretched), a thickness of said strip of material is from 50 pm to 300 pm.

EX36. The method according to any of EX1 to EX35, wherein, before pulling the strip of material (strip of material not stretched), a grammage of said strip of material is from 50 grams per square meter to 100 grams per square meter.

EX37. The method according to any of EX1 to EX36, wherein the rod-shaped element is a filter plug or an aerosol generating plug or a cooling plug or a front plug.

EX38. The method according to any of EX1 to EX37, wherein the strip of material is an aerosol generating substrate, optionally tobacco cast leaf; or wherein the strip of material is made of polylactic acid or cellulose acetate or paper material, optionally a nonwoven paper material.

EX39. The method according to any of EX1 to EX38, wherein making openings in the strip of material comprises: directing at least one laser beam on the strip of material. EX40. The method according to EX39, comprising: moving the at least one laser beam transversely to the conveying direction while the strip of material moves in the conveying direction.

EX41 . The method according to EX38 or EX39, wherein directing the at least one laser beam comprises: dividing the at least one laser beam in a plurality of output laser beams and making said plurality of output laser beams impinge on the strip of material.

EX42. The method according to any of EX39 to EX41 , wherein directing the at least one laser beam comprises: focusing the at least one laser beam on the strip of material.

EX43. The method according to any of EX39 to EX42, wherein a power range of the laser beam is from 50 W to 500 W.

EX44. The method according to any of EX1 to EX38, wherein making openings in the strip of material comprises: cutting the strip of material with blades.

EX45. The method according to EX44, wherein making openings in the strip of material comprises: running the strip between two cutting rollers, wherein at least one of the cutting rollers is provided with the blades.

EX46. An apparatus for manufacturing rod-shaped elements for aerosol-generating articles, the apparatus being configured to carry out the method according to any of EX1 to EX45.

EX47. An apparatus for manufacturing rod-shaped elements for aerosol-generating articles, comprising: at least one conveyor defining a conveying path and a conveying direction; a perforator or cutout device placed along the conveying path; a dragging device placed downstream of perforator or cutout device along the conveying path; a gathering device placed downstream of the perforator or cutout device; a wrapping device placed downstream of the gathering device; a cutter placed downstream of the wrapping device; a control unit configured to control the apparatus to perform the following procedure: o conveying continuously a strip of material along the conveying path and in the conveying direction parallel to a longitudinal direction of said strip of material through the at least one conveyor; o making openings in the strip of material while the strip of material is conveyed along the conveying path through the perforator or cutout device such that each opening extends at least in part transversally on the strip of material; o pulling the strip of material along the conveying direction through the dragging device to stretch the strip of material and open the openings thus forming a net-like structure while the strip of material is conveyed along the conveying path; o gathering the strip of material having the net-like structure in a rod-shaped configuration in the gathering device while the strip of material with the net- like structure and is conveyed along the conveying path; o wrapping the strip of material in the rod-shaped configuration in a wrapper through the wrapping device to form a continuous rod; o cutting the continuous rod in a plurality of rod-shaped elements through the cutter; wherein, before gathering or when gathering, said procedure further comprises: stabilizing the strip of material by mechanically deforming and/or entangling said strip of material conveyed along the conveying path and pulled along the conveying direction in order to keep the net-like structure in the rod-shaped elements.

EX48. The apparatus of EX47, wherein said apparatus is configured to carry out the method according to any of EX1 to EX45.

EX49. The apparatus of EX47 or EX48, comprising two compressing rollers placed along the conveying path between the perforator or cutout device and the gathering device, the two compressing rollers being configured to flatten the net-like structure to stabilize the strip of material.

EX50. The apparatus of EX49, wherein the two compressing rollers comprise rubber lateral surfaces.

EX51 . The apparatus of EX49 or EX50, wherein the two compressing rollers also define the dragging device or are part of the dragging device configured to pull the strip of material along the conveying direction to open the openings and forming the net-like structure while the strip of material is conveyed along the conveying path.

EX52. The apparatus of any of EX47 to EX51 , wherein, when the strip of material is pulled and the openings are opened, the strip of material buckles outside the respective lying surface and the formed net-like structure is three-dimensional.

EX53. The apparatus of any of EX47 to EX52, wherein the gathering device comprises a converging tool, optionally shaped like a tapered funnel; the gathering device being configured to gather the strip of material having the net-like structure in a rod-shaped configuration while the strip of material with the net-like structure is conveyed along the conveying path.

EX54. The apparatus of any of EX47 to EX53, wherein the conveyor comprises a plurality of sub-conveyors each configured to convey a respective strip of material towards the gathering device along a respective conveying sub-path; wherein the apparatus comprises a plurality of perforators or cutout devices each placed along a respective conveying sub-path to make openings in the respective strip of material.

EX55. The apparatus of any of aspects EX47 to EX54, wherein the perforator or cutout device comprises a laser device arranged and configured to emit a laser beam making the openings in the strip of material while the strip of material is conveyed along the conveying path; optionally the laser device is controlled by a control unit of the apparatus to emit intermittently the laser beam to make the plurality of openings.

EX56. The apparatus of EX55, wherein the laser device comprises a laser source and a beam splitter, the beam splitter being arranged and configured to divide the laser beam from the laser source in a plurality of laser sub-beams impinging on the strip of material.

EX57. The apparatus of EX55 or EX56, wherein the laser device comprises a focusing lens arranged and configured to focus the laser beam or the laser sub-beams on the strip of material.

EX58. The apparatus of any of EX55 to EX57, wherein the laser device is arranged and configured to move the laser beam and/or the laser sub-beams transversely to the conveying direction of the strip of material.

EX59. The apparatus of any of EX55 to EX58, wherein the laser device is a carbon dioxide laser.

EX60. The apparatus of any of EX55 to EX59, wherein the apparatus further comprises a blower and/or a vacuum system arranged and configured to remove smoke and/or to dissipate heat generated by operation of the laser device.

EX61 . The apparatus of any of aspects EX47 to EX54, wherein the perforator or cutout device comprises two cutting rollers, wherein at least one of the cutting rollers is provided with blades.

EX62. A rod-shaped element for aerosol-generating articles, comprising: a strip of material having a net-like structure and gathered in a rod-shaped configuration; a wrapper wrapping said gathered strip of material; wherein the net-like structure of the strip of material is stabilized in the rod-shaped element by mechanically deformation and/or entanglement.

EX63. The rod-shaped element for aerosol-generating articles according to EX62, wherein said rod-shaped element is made according to the method of any of EX1 to EX45 and/or through the apparatus of any of EX46 to EX61 .

EX64. An aerosol-generating article, comprising at least one rod-shaped element according to EX62 or EX63.

EX65. The aerosol generating article according to EX64, comprising a filter plug, an aerosol generating plug and optionally a cooling plug and optionally a front plug; wherein said rod-shaped element is the filter plug and/or the aerosol generating plug and/or the optional cooling plug and/or the front plug.

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

Figure 1 shows an apparatus for manufacturing rod-shaped elements for aerosolgenerating articles according to the invention;

Figure 2 is a 3D view of a portion of the apparatus of figure 1 ;

Figure 3 is a 3D view of another portion of the apparatus of figure 1 ;

Figure 4 is a 3D view of further portion of the apparatus of figure 1 ;

Figure 5 is a 3D view of another portion of the apparatus of figure 1 ;

Figure 6 shows part of a variant embodiment of the apparatus of figure 1 ;

Figure 7 shows a strip of material, processed in the apparatus of figure 1 and according to a method of the invention, in a first configuration;

Figure 8 is an enlarged view of a portion of the strip of material of figure 7;

Figure 9 shows the strip of material of figures 7 and 8 in a second configuration;

Figure 10 is a 3D view of a part of the strip of material in the second configuration;

Figures 11 to 15 show respective variants of the strip of material in the first configuration;

Figure 16 shows another variant of the strip of material in the first configuration;

Figure 17 shows the strip of material of figure 16 in the second configuration;

Figures 18 and 19 show respectively a longitudinal section and a cross section of a rod-shaped element manufactured through the apparatus of figures 1 to 5;

Figure 20 is an exploded view of an aerosol-generating article comprising the rodshaped element of figures 18 and 19;

Figure 21 is a flowchart of a method for manufacturing rod-shaped elements for aerosol-generating articles according to the invention.

The apparatus 1 shown in Figures 1 to 5 is configured for manufacturing rod-shaped elements for aerosol-generating articles 2 and may be part of a plant for manufacturing aerosol-generating articles 2. The apparatus 1 shown in Figures 1 to 5 is configured to carry out a method for manufacturing rod-shaped elements for aerosol-generating articles 2 as shown in figure 21 and as will be apparent from the following detailed disclosure.

One example embodiment of aerosol-generating article 2 is depicted in the exploded view of Figure 20 and comprises (from left to right in Figure 20): a front plug 3 (solid plug), an aerosol-generating plug 4, a tubular plug 5 (hollow plug, for instance of cellulose acetate), a fine tubular plug 6 (similar to the tubular plug 5 but with a thinner wall) and a filter plug 7 (mouthpiece filter, usually made of tow). Each plug has a wrapping of its own helping to contain properly their content. A tipping paper 8 connects the filter plug 7 to the rest of the plugs, and the front plug 3, aerosol-generating plug 4, tubular plug 5 and fine tubular plug 6 are wrapped together into a wrapping paper 9. The tubular plug 5 and fine tubular plug 6 are cooling plugs configured to cool down the aerosol formed by heating the aerosol-generating plug 4.

The aerosol-generating plug 4 comprises an aerosol-generating substrate 10 made of a sheet of material gathered in a continuous rod shape and wrapped in a wrapper 11. The material of the aerosol-generating substrate 10 may comprise reconstituted tobacco or tobacco-free herbaceous or plant-based material or a biodegradable fiber-based material. The filter plug 7 may be made of another sheet of material 12 of polylactic acid or cellulose or acetate tow or cotton gathered in a continuous rod shape and wrapped in a wrapper 13.

The rod-shaped elements made by the apparatus 1 shown in Figures 1 to 5 may be, for instance, the aerosol-generating plugs 4 or the filter plugs 7.

Figures 18 and 19 show respectively a longitudinal section and a cross section of the filter plug 7 manufactured through the apparatus 1 .

Referring to figure 1 , the apparatus 1 comprises a reel holder 14 and a strip of material 15 is coiled in a bobbin 15A on said reel holder 14. The strip of material 15 is for instance tobacco cast leaf or paper material, for instance a non-woven paper material. In other embodiments, not shown in the figures, a storage of the strip of material is a bale, for instance of cellulose acetate or polylactic acid.

An extraction device, not shown, is configured to uncoil the strip of material 15 from the bobbin 15A and a conveyor is configured to guide the strip of material 15 along a conveying path and in a conveying direction “F” parallel to a longitudinal direction of said strip of material 15. For instance, the conveyor comprises a plurality of motorized rollers and/or one or more motorized belt conveyors located along the conveying path.

Downstream of the reel holder 14, with respect to the conveying direction “F”, the apparatus 1 comprises a perforator or cutout device 16 placed along the conveying path. In the embodiment of figures 1 to 5, the perforator or cutout device 16 is a laser device. The laser device comprises a carbon dioxide laser source 17 configured to emit a laser beam “B”, a beam splitter 18 arranged and configured to divide the laser beam “B” from the laser source 17 in a plurality of laser sub-beams “B1” and a focusing lens 19 arranged between the laser source 17 and the beam splitter 18 and configured to focus the laser beam “B” on the beam splitter 18 and thus on the strip of material 15. The laser sub-beams “B1” impinge on an upper face of the strip of material 15 and remove material to make through openings 20 in said strip of material 15.

The laser device is arranged to make the through openings 20 in the strip of material 15 while the strip of material 15 is conveyed along the conveying path. The laser device comprises an actuator or motor, not shown in the figures, configured to move the laser subbeams “B1” transversely to the conveying direction “F” of the strip of material 15. The actuator or motor may be connected to the laser source 17 to make the laser source 17 swing about a swinging axis (see figure 2).

The laser device is also controlled by a control unit of the apparatus 1 to emit intermittently the laser beam “B” to make a plurality of discrete openings 20 in the strip of material 15, as depicted in figure 2. The exemplary openings 20 in figures 2, 3, 4, 5, 7, 8 and 9 are straight slits oriented perpendicular to the longitudinal direction of the strip of material 15. The control unit controls the laser source 17 and/or the laser source 17 is properly designed such that a power of the laser beam “B” cuts the through openings 20. For instance, a power range of the laser beam “B” is from 50 W to 500 W.

The apparatus 1 may also comprise a blower and/or a vacuum system, not shown in the figures, which is/are arranged and configured to remove smoke produced by the vaporization of material and/or to dissipate heat generated by operation of the laser device.

In an alternative embodiment, not shown in the figures, the openings 20 are made mechanically through blades. In this alternative embodiment, instead of the laser device shown in figure 1 , the perforator or cutout device 16 comprises a couple of cutting rollers having lateral surfaces facing each other and rotating in opposite directions about respective parallel axes. One or both the cutting rollers comprise/s blades defined by relieves and recesses fashioned on the respective lateral surface/s and the strip of material 15 runs between said two cutting rollers and the openings 20 are made by said blades.

The apparatus 1 further comprises a dragging device 21 placed downstream of the perforator or cutout device 16. The dragging device 21 comprises a first couple of rollers 22 followed by a second couple of compressing rollers 23, all comprising rubber lateral surfaces.

The rollers 22 of the first couple have lateral surfaces facing each other and rotate in opposite directions about respective parallel axes according to a first peripheral speed “V1”. The strip of material runs between the two rollers 22 of the first couple and is dragged by said rollers 22 an advanced with the first speed “V1”. The first speed “V1” is substantially the same speed of the strip of material 15 upstream of the rollers 22 of the first couple, i.e. the peripheral speed of the bobbin 15A.

The compressing rollers 23 of the second couple have lateral surfaces facing each other and rotate in opposite directions about respective parallel axes according to a second peripheral speed “V2”. The strip of material 15 runs between the two rollers 23 of the second couple and is dragged by said rollers 23 an advanced with the second speed “V2”. The second speed “V2” is greater than the first speed V1 such that the strip of material 15 which moves downstream of the rollers 22 of the first couple is pulled along the conveying direction “F”, i.e. longitudinally.

Thus, downstream of the rollers 22 of the first couple, the strip of material 15 is pulled and stretched, the openings 20 (which are straight slits upstream of the rollers 22 of the first couple, like in figure 7) are opened and take a rhombus shape (see figure 9). The stretched strip of material 15 presents therefore a net-like structure.

When the strip of material 15 is stretched and the openings 20 are opened, the strip of material 15 buckles outside a respective lying surface and the formed net-like structure of the strip of material 15, between the first couple of rollers 22 and the second couple of rollers 23, is three-dimensional as shown in detail in figure 10.

The two compressing rollers 23 of the second couple mechanical deform and flatten the three-dimensional net-like structure into a bi-dimensional net-like structure and stabilize said bi-dimensional net-like structure of the strip of material 15. Thus, the strip of material 15 keeps the flat bi-dimensional net-like structure also in the following parts of the conveying path and during the following method steps.

A gathering device 24 is placed along the conveying path and downstream of the two compressing rollers 23 of the second couple and a wrapping device 25 is placed downstream of the gathering device 24.

The gathering device 24 comprises a converging tool shaped like a tapered funnel 26 which is configured to move the strip of material 15, having the stabilized net-like structure, from a flat configuration (upstream of the gathering device 24) to a gathered rod-shaped configuration (downstream of the gathering device 24, figures 1 , 4, 5) while the strip of material 15 with the net-like structure is conveyed along the conveying path and pulled through the converging tool. For instance, the strip of material 15 is pulled from downstream of the converging tool through devices and/or conveyors not shown in figures.

The wrapping device 25 is configured to wrap the strip of material 15 in the rod-shaped configuration in a wrapper 27 to form a continuous rod 28. The wrapping device 25 comprises a guide 29 cooperating with a feeder of the wrapper 27. The guide 29, not shown in details, may be known per se and may comprise a U-shaped channel with additional folding elements configured to close the wrapper 27 around the gathered strip of material 15. The feeder of the wrapper 27 is represented as an auxiliary reel holder 30 on which the wrapper 27 is wound in an auxiliary bobbin 31.

A cutter 32, for instance a rotating blade (see figure 5), is placed downstream of the wrapping device 25 and is configured for cutting the continuous rod 28 in a plurality of rodshaped elements, such as the aerosol-generating plugs 4. The net-like structure of the gathered strip of material 15 is therefore kept also in the final rod-shaped elements and in each aerosol generating article 2.

The above mentioned control unit, not shown, is operatively connected to the devices described above and is configured to control the apparatus 1 to perform the procedure above described and represented in the flowchart of figure 21 .

The apparatus 1 of the variant embodiment of figure 6 differs from the apparatus of figures 1 to 5 in that two strips of material 15 from respective bobbins 15A are employed, in each strip of material 15 openings 20 are formed through respective laser devices 16 and each strip of material 15 is stretched to open the openings 20 before gathering.

Therefore, a plurality of sub-conveyors each configured to convey a respective strip of material 15 towards the gathering device 24 along a respective conveying sub-path are provided. The apparatus 1 comprises a plurality of perforators or cutout devices 16 each placed along a respective conveying sub-path to make the openings 20 in the respective strip of material 15.

Differently from the apparatus of figures 1 to 5, the variant embodiment of figure 6 does not comprise the compressing rollers 23 of the second couple.

As in the apparatus of figures 1 to 5, each strip of material 15 runs between the two rollers 22 of the first couple and is dragged by said rollers 22 an advanced with the first speed “V1”. The first speed “V1” is substantially the same speed of the strip of material 15 upstream of the rollers 22 of the first couple, i.e. the peripheral speed of the bobbins 15A. The second speed “V2” is greater than the first speed “V1” such that each strip of material 15 which moves downstream of the rollers 22 of the first couple is pulled along the conveying direction “F”, i.e. longitudinally.

Differently from the apparatus of figures 1 to 5, the second speed “V2”, which is the linear speed of each strip of material 15 downstream of the two rollers 22 of the first couple, is provided to each strip of materials 15 through other conveyors not shown in figures.

The two strips of material 15 may be the same or different; the openings 20 in the two strips of material may be the same or different in shape and/or size.

Differently from the apparatus of figures 1 to 5 and from the method carried out by the apparatus of figures 1 to 5, the net-like structures of the two strips of material 15 are stabilized by mechanically entangling said strip of materials 15 one with the other in the tapered funnel 26. This entangling stabilizes the net-like structure of the strips of material 15. Thus, the strips of material 15 keeps the net-like structure also in the following parts of the conveying path and during the following method steps.

In order to entangle the two strips of material 15 of figure 6, said two strips of material 15 are pulled in the tapered funnel 26 such that the sum of the amounts of material per unit length of the two strips of material 15, each provided with the net-like structure, is equal to the amount of material per unit length of one similar strip of material without openings (i.e. without net-like structure).

Indeed, for a same pulling force and for a same speed of the strip of material 15, the openings 20 created by pulling and stretching the strip of material 15 decrease the quantity of material that is pulled into the tapered funnel 26 reported to a similar strip of material without openings. For instance, if the sum of the surfaces of the openings 20 per surface unit of a strip of material 15 is about 50%, it means that only half of the material enters the tapered funnel 26 reported to the same strip of material without openings. By pulling in the tapered funnel 26 the same amount of material of a strip of material 15 with openings (and the three-dimensional net-like structure) than what is expected with a strip of material without openings, the generated continuous rod 28 would be filled with a three-dimensional net-like structure of material that will be folded and compressed into the rod, so that the amount of material is the one that could be contained into the rod while the three- dimensional net-like structure expects a larger volume.

When pulling the two strips of material 15 in the tapered funnel 26 as disclosed above, the solid parts of the three-dimensional net-like structure fills as much as possible the empty volumes created by the openings 20 and creates an entanglement that fix into the plugs the compressed three-dimensional net-like structure, blocking this structure into itself. This solution, instead of a 2D net-like structure obtained with the compressing rollers 23, allows to keep a three-dimensional net-like structure into the rod-shaped elements.

The example above employs two strips of material 15. However, a plurality of strips of material 15 may be used, for instance, between two and six in number. If the stretched single strip of material 15 provided with the net-like structure is N-times longer than the same strip of material without openings, then N strips of material 15 having a same width (B) are employed.

According to another variant embodiment of the method, the entanglement in the tapered funnel 26 of the strip of material 15 provided with the three-dimensional net-like structure is achieved by feeding a single strip of material 15 but said strip of material 15 has a corrected width (Be) greater than a reference width (Bref) calculated for the same strip of material without openings. If the stretched strip of material 15 provided with the three- dimensional net-like structure is N-times longer than the same strip of material without openings, then the corrected width (Be) is N-times the reference width (Bref). Also in this way, the amount of material per unit length of the strip of material 15 provided with the three- dimensional net-like structure is equal to the amount of material per unit length of a same strip of material without openings. All the embodiments above disclosed (compressing rollers, entanglement with N strips of material, entanglement with corrected width) generate a random shaping and preservation of the net-like structure (bidimensional or three-dimensional) into the rodshaped elements and then into the plugs 3, 4, 5, 6, 7 of the aerosol-generating article 2, assuring an even homogeneous diffusion of the air through the plugs’ lengths.

In figures 7, 8 and 9, the openings 20 are straight slits arranged in rows. Each row crosses the strip of material 15. The rows and the slits in each row are perpendicular to the longitudinal direction of the strip of material 15. A plurality of said rows follow each other along the longitudinal direction of the strip of material 15. The sizes and pattern of the slits is such that a stretch of the strip of material 15 corresponding to a length of one rod-shaped element comprises a plurality of rows.

Each slit has two opposite end points and, before pulling the strip of material 15 (figures 7 and 8), (W) is a transversal width of the slit between the two opposite end points. A longitudinal length (L) of the slit between the same two opposite end points before pulling the strip of material 15 is zero. The slits in each row are spaced from each other of a transversal distance (D). (H) is a longitudinal distance between slits of two rows following each other. The slits of one row are shifted of an offset transversal distance (A) with respect to the openings of another adjacent row. When the slits are opened and take the rhombus shape (figure 9), (W) is the transversal width and (L’) the longitudinal length.

The following Table 1 contains example dimensions of the strip of material 15 and of the openings/slits 20 of figures 7, 8 and 9.

Table 1

Figure 11 shows a variant of the openings 20 in which said openings 20, when the strip of material 15 is not stretched, are slits aligned along rows and each row delimits with the longitudinal direction of the strip of material 15 an angle (a) of about 60°. Therefore, the transversal width (W) is greater than the longitudinal length (L): W = 1.732 * L. In other embodiments, said angle (a) may be between 60° and 90°. In figure 12, the slits are wavy and the rows are perpendicular to the longitudinal direction of the strip of material 15.

In figure 13, the slits are zig-zag and the rows are perpendicular to the longitudinal direction of the strip of material 15.

In figure 14, the openings 20 are straight slits, each slit delimits with the longitudinal direction of the strip of material 15 an angle (a) of about 10°. Anyway, the rows are perpendicular to the longitudinal direction of the strip of material 15.

In figure 15, the openings 20 are wavy slits aligned in rows each perpendicular to the longitudinal direction of the strip of material 15. Each wavy slit comprises a first rounded portion with concavity facing downwards followed by a second rounded portion with concavity facing upwards.

Figure 16 shows openings 20 having, before stretching the strip of material 15, a diamond shape. The openings 20 comprises a first group of diamond openings 20 with the longest diagonal of the diamond perpendicular to the to the longitudinal direction of the strip of material 15 and a second group of diamond openings 20 with the longest diagonal of the diamond parallel to the to the longitudinal direction of the strip of material 15 such that the material between the openings is square shaped. This way, the strip of material 15 has an auxetic behaviour: i.e. when the strip of material 15 is pulled along the conveying direction, the width (B) of said strip of material 15 increases (see figures 16 and 17). As shown in figure 17, when the strip of material 15 is pulled and stretched, the angles of the diamond shapes change such that the width (B) increases to (B’).

Regardless of the specific shape of the openings 20, all the openings 20 shown in the figures have the transversal width (W) greater than the longitudinal length (L). For instance, a ratio (W/L) of the transversal width (W) to the longitudinal length (L) is between 1.5 to 5.

Furthermore, in all the openings 20 shown in the figures, the offset transversal distance (A) is greater than the transversal distance (D), the offset transversal distance (A) is smaller than the transversal width (W), the longitudinal distance (H) is smaller than the transversal width (W).

The following Table 2 contains further dimension ranges of the strip of material 15 and of the openings 20 according to the invention.

Table 2

Claims

1. A method for manufacturing rod-shaped elements for aerosol-generating articles, comprising: conveying continuously a strip of material (15) along a conveying path and in a conveying direction (F) parallel to a longitudinal direction of said strip of material (15); making openings (20) in the strip of material (15) while the strip of material (15) is conveyed along the conveying path, wherein each opening (20) extends at least in part transversally on the strip of material (15); pulling the strip of material (15) along the conveying direction (F) to stretch the strip of material (15) and open the openings (20) thus forming a net-like structure while the strip of material (15) is conveyed along the conveying path; gathering the strip of material (15) having the net-like structure in a rod-shaped configuration and wrapping the strip of material (15) in the rod-shaped configuration in a wrapper (27) to form a continuous rod (28) while the strip of material (15) with the net-like structure and is conveyed along the conveying path; cutting the continuous rod (28) in a plurality of rod-shaped elements; wherein the strip of material (15) is stabilized by mechanically deforming said strip of material (15) conveyed along the conveying path and pulled along the conveying direction (F) in order to keep the net-like structure in the rod-shaped elements; wherein stabilizing the strip of material (15) comprises: compressing the strip of material (15) before gathering to flatten the net-like structure.

2. The method according to claim 1 , wherein compressing the strip of material (15) comprises: running the strip of material (15) provided with the net-like structure between two compressing rollers (23).

3. The method according to claim 1 or 2, wherein, when the strip of material (15) is stretched and the openings (20) are opened, the strip of material (15) buckles outside a respective lying surface and the formed net-like structure is three-dimensional; wherein compressing the strip of material (15) before gathering comprises flattening the three- dimensional net-like structure into a bi-dimensional net-like structure.

4. The method according to any of claims 1 to 3, wherein each opening (20) has two opposite end points and wherein, before pulling the strip of material (15), a transversal width (W) of the opening (20) between the two opposite end points is greater than a longitudinal length (L) of the opening (20) between the same two opposite end points.

5. The method according to any of claims 1 to 4, wherein the openings (20) are arranged in rows, each crossing the strip of material (15); a plurality of openings (20) being aligned on each row; a plurality of said rows following each other along the longitudinal direction of the strip of material (15); a stretch of strip corresponding to a length of one rodshaped element comprising a plurality of rows; wherein the openings (20) of one row are shifted of an offset transversal distance (A) with respect to the openings (20) of another adjacent row.

6. The method according to claim 5, wherein the openings (20) in each row are spaced from each other of a transversal distance (D); wherein the offset transversal distance (A) is smaller than the transversal width (W) and the offset transversal distance (A) is greater than the transversal distance (D).

7. The method according to claim 5 or 6, wherein the rows delimit with the longitudinal direction of the strip of material an angle between 60° and 90°.

8. The method according to any of claims 1 to 7, wherein the openings (20) are slits, each slit being straight or wavy or zig-zag.

9. The method according to any of claims 1 to 8, wherein a shape of the openings (20) is such that, when the strip of material (15) is pulled along the conveying direction (F), a width (B) of said strip of material (15) increases.

10. The method according to any of claims 1 to 9, wherein making openings (20) in the strip of material (15) comprises: directing at least one laser beam (B, B1) on the strip of material (15).

11. The method according to claim 10, comprising: moving the at least one laser beam (B, B1) transversely to the conveying direction (F) while the strip of material (15) moves in the conveying direction (F).

12. An aerosol generating article, comprising at least one rod-shaped element made according to the method of any of claims 1 to 11 , wherein the at least one rod-shaped element comprises: a strip of material having a net-like structure and gathered in a rodshaped configuration; a wrapper wrapping said gathered strip of material; wherein the net- like structure of the strip of material is stabilized in the rod-shaped element by mechanically deformation.

13. An apparatus for manufacturing rod-shaped elements for aerosol-generating articles, comprising: at least one conveyor defining a conveying path and a conveying direction (F); a perforator or cutout device (16) placed along the conveying path; a dragging device (21) placed downstream of perforator or cutout device (16) along the conveying path; a gathering device (24) placed downstream of the perforator or cutout device (16); a wrapping device (25) placed downstream of the gathering device (24); a cutter (32) placed downstream of the wrapping device (25); a control unit configured to control the apparatus (1) to perform the following procedure: o conveying continuously a strip of material (15) along the conveying path and in the conveying direction (F) parallel to a longitudinal direction of said strip of material (15) through the at least one conveyor; o making openings (20) in the strip of material (15) while the strip of material (15) is conveyed along the conveying path through the perforator or cutout device (16) such that each opening (20) extends at least in part transversally on the strip of material (15); o pulling the strip of material (15) along the conveying direction (F) through the dragging device (21) to stretch the strip of material (15) and open the openings (20) thus forming a net-like structure while the strip of material (15) is conveyed along the conveying path; o gathering the strip of material (15) having the net-like structure in a rodshaped configuration in the gathering device (24) while the strip of material (15) with the net-like structure and is conveyed along the conveying path; o wrapping the strip of material (15) in the rod-shaped configuration in a wrapper (27) through the wrapping device (25) to form a continuous rod (28); o cutting the continuous rod (28) in a plurality of rod-shaped elements (4) through the cutter (32); wherein, before gathering, said procedure further comprises: stabilizing the strip of material by mechanically deforming said strip of material conveyed along the conveying path and pulled along the conveying direction in order to keep the net-like structure in the rod-shaped elements; wherein the apparatus (1) further comprises two compressing rollers (23) placed along the conveying path between the perforator or cutout device (16) and the gathering device (25), the two compressing rollers (23) being configured to stabilize the strip of material (15) by flattening the net-like structure.

14. The apparatus according to claim 13, wherein the two compressing rollers (23) comprise rubber lateral surfaces.

15. The apparatus according to claim 13 or 14, wherein the perforator or cutout device (16) comprises a laser device arranged and configured to emit a laser beam (B) making the openings (20) in the strip of material (15) while the strip of material (15) is conveyed along the conveying path; wherein the laser device is arranged and configured to move the laser beam (B) transversely to the conveying direction of the strip of material (15).