WO2025126027A1

WO2025126027A1 - A method and set-up for manufacturing an embossed sheet of material and obtaining a controlled material thickness and a filtering element

Info

Publication number: WO2025126027A1
Application number: PCT/IB2024/062418
Authority: WO
Inventors: Charles Boegli; Gabriel Dumitru
Original assignee: Boegli Gravures SA
Current assignee: Boegli Gravures SA
Priority date: 2023-12-11
Filing date: 2024-12-10
Publication date: 2025-06-19
Anticipated expiration: 2026-06-11
Also published as: WO2025125854A1

Abstract

A method for manufacturing an embossed sheet of material and obtaining a controlled material thickness, the embossed sheet of material being configured to obtain a filtering element configured for an inhalable drug delivery device, and for filtering a mainstream gas flow passing through the filtering element. The method comprises embossing the sheet of material at least with embossing features by means of an embossing rollers system in which embossing features formed on a first base surface of a first embossing roller and corresponding embossing features formed on a second base surface of a second embossing roller are in a congruence with each other, the embossing features comprising profile embossing features configured for embossing at least an aerodynamic profile on the sheet of material, configured to modify in a determined manner flow properties for the mainstream gas flow passing through the filtering element by creating a gas flow turbulence occurrence in the filtering element; embossing the sheet of material with separating base surface zones located between embossing features, and corresponding to the first base surface and the second base surface. For each embossing feature the corresponding congruence is configured to be such that for a first subset of the embossing features, corresponding protrusion and recess embossing features located respectively on different embossing rollers have a value of height of the protrusion embossing feature greater than a value of depth of the recess embossing feature; thereby configuring a width of the nip between the first and the second embossing rollers, which has a first nip width value for the separating base surface zones, and different nip width values smaller than the first nip width value for embossing features of the first subset of the embossing features; thereby enabling to obtain the controlled material thickness of the embossed sheet of material with respectively a first value of the material thickness when the sheet of material is embossed with the separating base surface zones, and different values of the material thickness smaller than the first value of the material thickness when the sheet of material is embossed with embossing features of the first subset of the embossing features.

Description

A METHOD AND SET-UP FOR MANUFACTURING AN EMBOSSED SHEET OF MATERIAL AND OBTAINING A CONTROLLED MATERIAL THICKNESS AND A FILTERING ELEMENT

Technical field of invention

The invention is in the field of manufacturing for the inhalable drug delivery system industry, including smoking products in which medical drugs or nicotine may be dispensed in a gas to a user in various inhalable ways, comprising for example vapor, heated tobacco, and conventional burned tobacco as known from cigarettes and cigars, more specifically in a field of embossing, and relating to a component of a filtering element, and the filtering element as such.

Background of the invention

Numerous prior art references discuss the technical field of the invention specifically for the cigarette industry.

Prior art publication "Basic principle of cigarette design and Function" by Ken Podraza, Philip Morris, Presentation to LSRO 29-30 October 2001 contains a wealth of information about the parameters ruling the manufacturing and the consumption of cigarettes.

A further prior art publication "Effect of cigarette filter components on its efficiency and smoking characteristic of cigarettes", Sobhy Mohammed Mohsen, Abdalla S.M. Ammar, Ateya Fathy, Bioscience Research, January 2018, Pages 325-336, is a further source of information more focused on cigarette filters of cigarettes.

French publication FR 2 418628 discusses a method and a device for transforming a fibrous sheet of material in order to manufacture a cigarette filter or simple filter. The publication describes how to make a certain topographical profile on the sheet to obtain a filtering structure, whereby the height of the profile may be varied during the process, to vary at the same time a transversal stretching of the sheet, and hence its texture's characteristics, to obtain on one hand an embossed texture or on the other hand a longitudinal creped texture, or any intermediate texture, whereby the characteristics may be varied without any discontinuity. Hence the draft of the resulting filter may be adjusted as needed by suitably adapting the texture. Since the publications of above prior art documents, smoking and other inhalable drug delivery systems have undergone significant development with a recent multiplication of utilization domains. In addressing an enhanced user experience, much research and development has been centered around the filtering element of a such a device, which currently primarily serves the purpose of filtering the gas generated from the drug containing part of the inhalable drug delivery system. The user then receives a mainstream gas into his mouth by drawing through the filter on the opposite end of the cigarette. Certain cigarettes or other inhalable drug delivery systems incorporate filter elements or tows having absorbent materials dispersed therein, such as activated carbon or charcoal materials in particulate or granular form. For example, a filtering element can possess multiple segments, and at least one of those segments can comprise particles of high carbon-content materials.

Following facts may be retrieved from the reading of both above cited prior art documents "Basic principle of cigarette design and Function" and "Effect of cigarette filter components on its efficiency and smoking characteristic of cigarettes":

Paper cigarette filters offer a higher smoke-component removal efficiency as the conventional cellulose acetate cigarette filters, at a same filter characteristic pressure drop, but this increase comes with a poor visual appearance. A filter pressure drop is the amount of suction that must be used to pull smoke through the filter, at a standardized suction volume (35 ml puff in 2s).

The term "Retention", used at further points in the description of this invention, is alternative way of designating a filtering efficiency, i.e., a percentage of gas components (e.g., particulates) that are removed by the filtering element.

As the pressure drop increases for a given filtering configuration, filtration efficiency increases due to a reduction in a mainstream gas velocity. In the same time, particulate phase materials can be removed to some degree with a filtering element produced of fibrous materials, while gases (CO, NOx) are not removed.

Considering its dynamics, a gas flow velocity shall increase as the gas passes through a constriction section, whereas its static pressure shall decrease in accord with the principle of conservation of mechanical energy (Bernoulli's principle). Thus, any gain in kinetic energy a gas may attained by its increased velocity through a constriction section is balanced by a drop in pressure. As Bernoulli's principle is invertible, by passing through an expansion section the gas flow velocity shall decrease and its static pressure should rise. Furthermore, if a gas flow presents an alternance of a constriction section and an expansion section, turbulences will appear in the gas flow.

Sustainable substrates (e.g., paper- or cellulosed-based) used to produce sustainable cigarette filters, of filters for other various drug delivery devices may undergo a step of accelerated drying, e.g., using forced air drying, which has a direct impact on their thickness stability.

These sustainable substrates of variating thickness are leading - upon their folding and transforming into a filter rod - to filters with variating filling factors (i.e., impact on gas flow / filtering properties) and also on influences on their mechanical properties, e.g., stiffness.

A grammage of these sustainable substrates may vary for instance between 25 gsm and 100 gsm and their thicknesses vary - typically and according to their fabrication process - between 50 pm and 500 pm. Therefore, the mass density of such substrates may typically be found in the region between 0.1 g/cm3 and 1.0 g/cm3.

The sustainable substrate's grammage gives a much better idea as to the actual thickness of a paper. As a general rule, anything 10-35 gsm is of tissue consistency; 35-70 gsm is lighter textweight, 70- 100 gsm is medium textweight, 100-120 gsm is heavy textweight/light cardstock, 120-150 gsm is regular cardstock weight, 150-200 gsm is heavy cardstock, and greater than 200 gsm is super heavy cardstock.

Departing from prior art knowledge, the invention aims at providing a method and an embossing setup to manufacture a novel embossed sheet of material configured to be folded to obtain a filter element which constitutes an alternative to existing technology, and is applicable for an inhalable drug delivery system in general.

A further problem addressed by the invention is to provide a method and an embossing set-up to manufacture an embossed sheet of material that has a controlled material thickness. This may allow to compensate for a material that is uneven prior to embossing, i.e., has a variable thickness, and to confer an improved control of draft through a filtering element made using the embossed sheet of material. A further problem addressed by the invention is to provide a filtering element comprising an embossed sheet of material having the controlled material thickness, in order to have a way of controlling a draft of the filtering element and obtain a desired draft for mass production of such filtering elements.

Summary of the invention

In a first aspect, the invention provides a method for manufacturing an embossed sheet of material and obtaining a controlled material thickness, the embossed sheet of material being configured to obtain a filtering element configured for an inhalable drug delivery device, and for filtering a mainstream gas flow passing through the filtering element. The method comprises steps of: providing the sheet of material; embossing the sheet of material at least with embossing features by means of an embossing rollers system in which embossing features formed on a first base surface of a first embossing roller and corresponding embossing features formed on a second base surface of a second embossing roller are in a congruence with each other, and by feeding the sheet of material to a nip between the first embossing roller and the second embossing roller, the embossing features comprising profile embossing features configured for embossing at least an aerodynamic profile on the sheet of material, the embossed aerodynamic profiles being configured to modify in a determined manner flow properties for the mainstream gas flow passing through the filtering element by creating a gas flow turbulence occurrence in the filtering element; embossing the sheet of material with separating base surface zones located between embossing features, and corresponding to the first base surface and the second base surface. For each embossing feature the corresponding congruence is configured to be such that for a first subset of the embossing features, corresponding protrusion and recess embossing features located respectively on different embossing rollers have a value of height of the protrusion embossing feature greater than a value of depth of the recess embossing feature; thereby configuring a width of the nip between the first and the second embossing rollers, which has a first nip width value for the separating base surface zones, and different nip width values smaller than the first nip width value for embossing features of the first subset of the embossing features; thereby enabling to obtain the controlled material thickness of the embossed sheet of material with respectively a first value of the material thickness when the sheet of material is embossed with the separating base surface zones, and different values of the material thickness smaller than the first value of the material thickness when the sheet of material is embossed with embossing features of the first subset of the embossing features. In a preferred embodiment, the configuring for each embossing feature of the corresponding congruence is further such that for a second subset of the embossing features, corresponding protrusion and recess embossing features located respectively on different embossing rollers have a value of height of the protrusion embossing feature smaller than or equal to a value of depth of the recess embossing feature, thereby configuring a width of the nip between the first and second embossing rollers, which has further different nip values greater than or equal to the first nip width value for embossing features of the second subset of the embossing features; thereby enabling to obtain further different values of the material thickness greaterthan or equal to the first value of the material thickness when the sheet of material is embossed with embossing features of the second subset of the embossing features.

In a further preferred embodiment, the method for manufacturing the embossed sheet of material further comprises arranging the embossing features in a plurality of stripes, each stripe comprising protrusion features and recess features corresponding to embossing features on each of the first embossing roller and the second embossing roller, and each embossed stripe being oriented longitudinally along a straight line on the sheet of material, the profile embossing features thereby being arranged according to an orientation of the stripe on the embossing rollers.

In a further preferred embodiment, the embossing features further comprise radial embossing features configured to delimitate each stripe on opposite lateral sides of the stripe, on the first and second embossing rollers, and further configured to form longitudinal-delimitation embossed features that delimitate the embossed stripe on the sheet of material, on the opposite lateral sides of the embossed stripe.

In a further preferred embodiment, the radial embossing features are further configured to emboss a folding line into the sheet of material.

In a further preferred embodiment, the radial embossing features are further configured to form a plurality of enclosing walls on the first embossing roller and on the second embossing roller, describing at least an enclosure around one or a plurality of the profile embossing features, and, for each enclosure, an enclosure opening in the enclosure connecting the enclosure to a successive enclosure in the orientation direction of the stripe, the enclosure having a corresponding maximum enclosure expansion section area in the orientation direction of the stripe and the enclosure opening having a corresponding enclosure opening constriction section area in the orientation direction of the stripe which is smaller than the corresponding maximum enclosure expansion section area. The radial embossing features are further configured to define at least one alternance of the enclosure opening constriction section area and the maximum enclosure expansion section area in the orientation direction of the stripe, formed by the enclosure opening and the enclosure respectively, with a crosssection area ratio between the maximum enclosure expansion section area and the enclosure opening constriction section area of the profile in a range from 15:1 to 2:1. In a further preferred embodiment, the embossed embossing features comprise at least one from a list comprising a recessed shape in the sheet of material and a protrusion in the sheet of material.

In a further preferred embodiment, the sheet of material may be either woven or not-woven and comprises any material from a list comprising paper, a cellulose-based material, wool, plant- or animal-based fibrous material.

In a further preferred embodiment, the profile embossing features are further configured to produce a height of the aerodynamic profile that is in a range of 1 to 15 times of a thickness of the sheet of material.

In a further preferred embodiment, the embossing of the sheet of material is configured to be a wallpaper-like embossing producing an uninterrupted and repeating pattern of embossed aerodynamic features.

In a further preferred embodiment, each one of the profile embossing features as a height in a range between 0,1 mm and 2,5 mm.

In a further preferred embodiment, the method for manufacturing the embossed sheet of material further comprises a step of adjusting the width of the nip to the first nip width value by providing a shoulder at each extremity of the first and second embossing rollers, the shoulders being configured to produce the first nip width value when at each extremity of the first and the second embossing rollers the shoulders from the first embossing roller are in contact with corresponding ones of the shoulder from the second embossing roller.

In a further preferred embodiment, the step of adjusting the width further comprises providing pressuring means configured to exert pressure between the first embossing roller and the second embossing roller, and enable a maintaining of the controlled material thickness.

In a further preferred embodiment, the first nip width value is chosen in function of a predetermined grammage of the sheet of material, and of a desired value for the first value of the material thickness. In a further preferred embodiment, the sheet of material has a grammage in a range between 10 gsm and 100 gsm and a thickness in a range between 0,02 mm and 1,5 mm.

In a further preferred embodiment, a ratio between the controlled material thickness of the embossed sheet and an initial thickness of the material sheet prior to embossing is in a range of 1:1 to 1:5.

In a further preferred embodiment, a ratio between a statistic standard deviation of the initial thickness of the sheet of material and a statistic standard deviation of the controlled material thickness of the embossed sheet is between 1:1 and 1:3.

In a further preferred embodiment, the method for manufacturing the embossed sheet of material further comprisies a step of heating the sheet of material prior to embossing.

In a further preferred embodiment, at least one of the first and the second embossing rollers is maintained at a constant temperature in a range of 20°C to 60°C.

In a second aspect, the invention provides an embossing set-up for manufacturing an embossed sheet of material and obtaining a controlled material thickness, configured to obtain a filtering element configured for an inhalable drug delivery device, and for filtering a mainstream gas flow passing through the filtering element. The set-up comprises features of: an embossing rollers system in which embossing features formed on a first base surface of a first embossing roller and corresponding embossing features formed on a second base surface of a second embossing roller are in a congruence with each other, the embossing system being configured to emboss the sheet of material in a nip between the first embossing roller and the second embossing roller, the embossing features comprising profile embossing features configured for embossing at least an aerodynamic profile on the sheet of material, the embossed aerodynamic profile being configured to modify in a determined manner flow properties for the mainstream gas flow passing through the filtering element by creating a gas flow turbulence occurrence in the filtering element. The embossing rollers system further comprises for embossing the sheet of material, separating base surface zones located between embossing features, and corresponding to the first base surface and the second base surface, the corresponding congruence of each of the embossing features is configured to enable that for a first subset of the embossing features, corresponding protrusion and recess embossing features located respectively on different embossing rollers have a value of height of the protrusion embossing feature greater than a value of depth of the recess embossing feature; thereby configuring a width of the nip between the first and the second embossing rollers, which has a first nip width value for the separating base surface zones, and different nip width values smaller than the first nip width value for embossing features of the first subset of the embossing features; thereby enabling to obtain the controlled material thickness of the embossed sheet of material with respectively a first value of the material thickness when the sheet of material is embossed with the separating base surface zones, and a different value of the material thickness smaller than the first value of the material thickness when the sheet of material is embossed with embossing features of the first subset of the embossing features.

In a further preferred embodiment, the corresponding congruence of each the embossing features is further configured to enable that for a second subset of the embossing features, corresponding protrusion and recess embossing features located respectively on different embossing rollers have a value of height of the protrusion embossing feature smaller than or equal to a value of depth of the recess embossing feature, thereby configuring a width of the nip between the first and second embossing rollers, which has further different nip values greater than or equal to the first nip width value for embossing features of the second subset of the embossing features; thereby enabling to obtain further different values of the material thickness greater than or equal to the first value of the material thickness when the sheet of material is embossed with embossing features of the second subset of the embossing features.

In a further preferred embodiment, the embossing rollers system is further configured to emboss the sheet of material with a plurality of stripes, each stripe comprising protrusion features and recess features corresponding to embossing features on each of the first embossing roller and the second embossing roller, and each embossed stripe being oriented longitudinally along a straight line on the sheet of material, the profile embossing features being arranged according to an orientation of the stripe on the embossing rollers.

In a further preferred embodiment, the embossing features further comprise radial embossing features configured to delimitate each stripe on opposite lateral sides of the stripe, on the first and second embossing rollers, and further configured to form longitudinal delimitation embossed features that delimitate the embossed stripe on the sheet of material, on opposite lateral sides of the embossed stripe.

In a further preferred embodiment, the radial embossing features are further configured to emboss a folding line into the sheet of material. In a further preferred embodiment, the radial embossing features are further configured to form a plurality of enclosing walls on the first embossing roller and on the second embossing rollers describing at least an enclosure around one or a plurality of the profile embossing features, and, for each enclosure, an enclosure opening in the enclosure connecting the enclosure to a successive enclosure in the orientation direction of the stripe, the enclosure having a corresponding maximum enclosure expansion section area in the orientation direction of the stripe and the enclosure opening having a corresponding enclosure opening constriction section area in the orientation direction of the stripe which is smaller than the corresponding maximum enclosure expansion section area. The radial embossing features are further configured to define at least one alternance of the enclosure opening constriction section area and the maximum enclosure expansion section area in the orientation direction of the stripe, formed by the enclosure opening and the enclosure respectively, with a cross-section area ratio between the maximum enclosure expansion section area and the enclosure opening constriction section area of the profile in a range from 15:1 to 2:1.

In a further preferred embodiment, the embossed embossing features comprise at least one from a list comprising a recessed shape in the sheet of material and a protrusion in the sheet of material.

In a further preferred embodiment, the sheet of material may be either woven or non-woven and comprises any material from a list comprising paper, a cellulose-based material, wool, plant- or animal-based fibrous material.

In a further preferred embodiment, the embossing rollers system and the embossing features are configured for embossing of the sheet of material to be a wallpaper-like embossing producing an uninterrupted and repeating pattern of embossed aerodynamic features.

In a further preferred embodiment, the embossing set-up further comprises a shoulder at each extremity of the first and the second embossing rollers enabling an adjusting of the width of the nip to the first nip width value, the shoulders being configured to produce the first nip width value when at each extremity of the first and the second embossing rollers the shoulders from the first embossing roller are in contact with corresponding ones of the shoulder from the second embossing roller.

In a further preferred embodiment, the embossing set-up further comprises pressuring means configured to exert pressure between the first embossing roller and the second embossing roller, and to enable a maintaining of controlled material thickness.

In a further preferred embodiment, the first nip width value is chosen in function of a predetermined grammage of the sheet of material, and of a desired value for the first value of the material thickness.

In a further preferred embodiment, the sheet of material has a grammage in a range between

10 gsm and 100 gsm and a thickness in a range between 0,02 mm and 1,5 mm.

In a further preferred embodiment, the embossing set-up further comprises a step of heating the sheet of material prior to embossing.

In a third aspect, the invention provides a filtering element configured for an inhalable drug delivery device, and for filtering a mainstream gas flow passing through the filtering element. The filtering element comprises an embossed sheet of material, with a controlled material thickness, wherein the sheet of material is embossed at least with embossing features by means of an embossing rollers system in which the embossing features formed on a first base surface of a first embossing roller and corresponding embossing features formed on a second base surface of a second embossing roller are in a congruence with each other, and by feeding the sheet of material to a nip between the first embossing roller and the second embossing roller, the embossing features comprising profile embossing features configured for embossing at least an aerodynamic profile on the sheet of material, the embossed aerodynamic profile being configured to modify in a determined manner flow properties for the mainstream gas flow passing through the filtering element by creating a gas flow turbulence occurrence in the filtering element. The sheet of material is further embossed with separating base surface zones located between embossing features, and corresponding to the first base surface and the second base surface. The corresponding congruence of each of the embossing features is configured to be such that for a first subset of the embossing features, corresponding protrusion and recess embossing features located respectively on different embossing rollers have a value of height of the protrusion embossing feature greater than a value of depth of the recess embossing feature; thereby configuring a width of the nip between the first and the second embossing rollers, which has a first nip width value for the separating base surface zones, and different nip width values smaller than the first nip width value for embossing features of the first subset of the embossing features; thereby enabling to obtain the controlled material thickness of the embossed sheet of material with respectively a first value of the material thickness when the sheet of material is embossed with the separating base surface zones, and a different value of the material thickness smaller than the first value of the material thickness when the sheet of material is embossed with embossing features of the first subset of the embossing features.

In a further preferred embodiment, the configuring for each embossing feature of the corresponding congruence is further such that for a second subset of the embossing features, corresponding protrusion and recess embossing features located respectively on different embossing rollers have a value of height of the protrusion embossing feature smaller than or equal to a value of depth of the recess embossing feature, thereby configuring a width of the nip between the first and second embossing rollers, which has further different nip values greater of equal to the first nip width value for embossing features of the second subset of the embossing features; thereby enabling to obtain further different values of the material thickness greater than or equal to the first value of the material thickness when the sheet of material is embossed with embossing features of the second subset of the embossing features.

In a further preferred embodiment, the embossed sheet of material is configured to comprise a plurality of stripes, each stripe comprising protrusion features and recess features corresponding to embossing features on each of the first embossing roller and the second embossing roller, and each embossed stripe being oriented longitudinally along a straight line on the sheet of material, the profile embossing features thereby being arranged according to an orientation of the stripe on the embossing rollers.

Brief description of the figures

The invention will be better understood through the detailed description of preferred embodiments and in reference to the figures, wherein

Figure 1 illustrates an embossing set-up for manufacturing an embossed sheet of material and obtaining a controlled material thickness, the sheet of material being configured to be folded and obtain a filtering element, according to an example embodiment of the invention;

Figure 2 illustrates an embossing set-up with a detail on the embossed sheet of material with a controlled material thickness, according to a further example embodiment of the invention;

Figure 3 schematically illustrates an obtaining of filtering elements using an embossed sheet of material issued from the method of manufacturing according to a further example embodiment of the invention;

Figures 4a and 4b schematically illustrates example embodiments for embossing rollers with and without a toothed wheel at an extremity, according to example embodiments of the invention;

Figure 5 schematically illustrates a set of embossing rollers with ring-shaped shoulders at extremities of the rollers, according to an example embodiment of the invention;

Figure 6 illustrates the set of embossing rollers from Figure 5 in a different perspective;

Figure 7 illustrates the set of embossing rollers from Figure 6 in a variant with radial recesses replacing ring-shaped shoulder, according to an example embodiment of the invention;

Figure 8 illustrates an example of a manufactured embossed sheet of material with embossed features and embossed separating base surface zones according to an example of the invention;

Figures 9a and 9b illustrate respectively a cross-section through a set of embossing rollers together with an example of the embossed sheet of material produced therewith, wherein the embossing rollers have shoulders in contact, according to example embodiments of the invention; Figures 10a and 10b illustrate respectively a cross-section through a set of embossing rollers together with an example of the embossed sheet of material produced therewith, wherein the embossing rollers have radial recesses at their extremities, according to example embodiments of the invention;

Figures 11 a and 11 b illustrate respectively a cross-section through a set of embossing rollers together with an example of the embossed sheet of material produced therewith, wherein the embossing rollers have radial recesses at their extremities, according to example embodiments of the invention;

Figures 12a and 12b illustrate further examples of embossings in which the material is controlled through embossing, according to the invention;

Figure 13 illustrates a further example of an embossed sheet of material manufactured according to the invention;

Figures 14a and 14b illustrate further examples of embossed sheets of material according to the invention;

Figure 15 illustrates a further example of an embossed sheet of material according to the invention;

Figure 16 schematically illustrates how a filtering element, in this case a cigarette filter, may be mounted to a tobacco containing section in order to obtain a cigarette according to prior art;

Figures 17 schematically illustrates a structure of an inhalable drug delivery device; and

Figure 18 contains a flowchart illustrating a preferred embodiment of the method for manufacturing the embossed sheet of material and obtaining a controlled material thickness according to the invention.

Same references are used to reference same or similar feature illustrated throughout the figures.

Detailed description of preferred embodiments

As previously mentioned, the invention is in the field of manufacturing forthe inhalable drug delivery system industry, including smoking products in which medical drugs or nicotine may be dispensed in a gas to a user in various inhalable ways, comprising for example vapor, heated tobacco, and conventional burned tobacco as known from cigarettes and cigars, more specifically in a field of embossing, relating to a component of a filtering element, and to the filtering element as such. Accordingly, the filtering element be configured to filterthe gas, i.e. , a mainstream gas flow. In one example, the filtering element may correspond to a cigarette filter used in a tobacco cigarette and the mainstream gas flow produced to be filtered is from smoke of burned tobacco. In a further example, the filter element may correspond to a non-burning cigarette filter used in a non-burning tobacco cigarette, in which case the mainstream gas flow produced to be filtered results from heating the tobacco. Various other embodiments, in which for example nicotine would be included in some other gas, for example vapour, the filter element would be configured to filter the corresponding mainstream gas flow and possibly retain particles that need not be included in the inhaled filtered gas administrated to a user.

The inventive device and method result from ecology-motivated research which for example aims to replace conventional cellulose acetate cigarette filters with other categories of suitable, sustainable sheet-materials, more preferably with filters made of paper-based materials, or any material from a list comprising paper, wool, plant- or animal-based fibrous material.

The invention provides a method and a device configured for manufacturing a sheet of material, and obtaining a controlled material thickness, that may be used as a component of a filtering element and that comprises embossed features for influencing a flow of the mainstream gas flow traversing the filtering element. The embossed features have a direct impact on slowing / speeding of the mainstream gas flow and, in that manner, reducing or enhancing the retention of particulates from the gas in fibers of the sheet of material, whereas a constancy of the controlled material thickness of the embossed sheet material has a direct positive impact on the reduction of the statistic variations of the filtering elements obtained through folding of the embossed sheet of material.

Preferably the sheet of material is a cellulose-based material, or any material from a list comprising paper, wool, plant- or animal-based fibrous material.

Furthermore, several classes may be distinguished regarding the sheet of material to be embossed, like the (i) woven sheets of materials including paper and paper-hybrid substrates, mainly containing interlaced fibers, as well as (ii) various non-woven sheets of material such as these described in the patent applications WO 2010112024 or US 10076135.

Referring to Figure 1 this illustrates an embossing set-up 100 according to an example embodiment of the invention. The embossing set-up 100 is configured for manufacturing an embossed sheet of material 200, and obtaining a controlled material thickness. The embossed sheet of material is configured to be folded and to obtain a filtering element configured for filtering a mainstream gas flow passing through the filtering element (filtering element and mainstream gas flow not illustrated in Figure 1). Without further tools attached to it, the embossing set-up 100 may also be denoted as an offline embossing system. The embossing set-up 100 comprises embossing rollers, i.e. , a first embossing roller 101 and a second embossing roller 102, and is configured to realize embossing of embossing features (embossing features not illustrated in Figure 1) on the sheet of material 103. The first embossing roller 101 and the second embossing roller 102 may optionally be mounted in a quick exchange device 104 and are configured to cooperate with each other to emboss in a nip 105 the sheet of material 103 fed between the first embossing roller 101 and the second embossing roller 102. A synchronization of the first embossing roller 101 and the second embossing roller 102 may be implemented in various manners, one of which is suggested in the illustration of Figure 1, and is not limitative for the embossing set-up 100, which comprises toothed wheels on the extremities of the rollers, which cooperate with each other. Other embodiments for synchronization may for example involve a servo-control mechanism (not illustrated) which controls angular positions of each roller relative to the other roller, or a combination of toothed wheels and the servo-control mechanism.

As a result of the embossing, the embossed sheet of material 200 is obtained with a plurality of embossed features (not individually shown in Figure 1, and represented as dots on the surface of the embossed sheet of material 200 for a better reading). For further explanations, a zone 106, which will subsequently be examined in the description, e.g., in relation to examples illustrated in Figure 8, is identified on the embossed sheet of material 200.

An optional bobbin dispensing device (not illustrated) may be configured to carry a bobbin with a web of sheet of material 103 and unwind it out towards the embossing set-up 100. A product bobbin device (not illustrated) may also optionally be provided to rewind the web of embossed sheet of material 200 for later use in a filtering element manufacturing.

The sheet of material 103 may for example be provided in the form of a web of sheet material, either woven or non-woven, which may for example comprise cellulose-based material, or any material from a list comprising paper, wool, plant- or animal-based fibrous material.

Further concerning the sheet of material 103, this preferably comprises fibers with a cut length in a first range of 0,5 mm to 6,0 mm, and with a diameter in a second range of 10 pm to 500 pm, the fibers being randomly distributed to deliver an air permeability. A sheet of material's air permeability is configured with filtration capabilities of substances present in a gas, e.g., cigarette or any other gas as mentioned for example in the previously presented gases.

A further preferred embodiment of the embossing set-up 100 according to the invention may be part of an online production process as illustrated in Figure 2, the embossing set-up 100 then being part of an online production line for manufacturing a filter element of length L (filter element and length not represented in Figure 2). The online production line further comprises for example a compacting device 201 comprising a funnel 202 into which the embossed sheet of material 200 is fed, folded and formed into a filter rod 203 output by the compacting device 201 . Hence the embossed sheet of material 200 is compacted with the funnel 202. The filter rod 203 may be pulled by means of a pulling jig 204 to a further process step 206 of cutting illustrated under reference 300 in Figure 3. The further process step involves cutting the filter rod 203 into individual pieces comprising, as an example, two filter elements 301 each, having the length L, by means of a cutting device 302. As previously described in Figure 1 as being an option, the production line may comprise the bobbin dispensing device 205 configured to carry the bobbin with the web of sheet of material 103 and unwind it out towards the embossing set-up 100. A magnified view 207 on initial sheet of material 103 before embossing, schematically shows inhomogeneities 208 of the material thickness, while a further magnified view 209 schematically shows an example embossing 210 on the embossed sheet of material 200 with the controlled material thickness.

Referring again to Figure 3, this further illustrates a magnified view of a section 303 at an extremity of one of the filter elements 301 in which the embossed sheet of material 200 is folded and compacted to fit in a cylindrical wrapper 304, also represented as a section of the cylindrical wrapper 304. Foldings of the embossed sheet of material 200 appear to be in a plurality of angles. A detailed view 305 of a part of the section 303, in which the view is slightly from an angle, schematically illustrates how the embossed sheet of material 200 is folded and packed in a manner of an accordion. In the view 305 a material thickness 306 is represented to be the same all over, and while this may be desired to be in this manner, there may also be embossed features (not shown in the Figure 3) in which the material thickness may be different.

As will be explained hereinbelow throughout the description, the invention provides a solution to obtain a controlled material thickness, while at the same time embossing features of different kinds in the sheet of material.

Referring now to Figure 4a, this illustrates an example embodiment for any one of embossing rollers 101 and 102, which comprises a rotation axis 400, a roller surface 401 and a toothed wheel 402 at one extremity of the embossing roller 101, 102, enabling the embossing roller 101 , 102 to be driven by a motor assembly having a corresponding toothed wheel (not represented in Figure 4a). The roller surface 401 may carry embossing features (not represented) which protrude from or recess in a base surface (not explicitly represented) of the embossing roller 101, 102. Examples of embossing features will be given hereinbelow.

Referring now to Figure 4b, this shows a further example embodiment for any one of embossing rollers 101 and 102, which is similar to that of Figure 4b, except that it doesn't comprise any toothed wheel. In this example the embossing roller 101 , 102, is typically driven by a servo motor mechanism (not represented) that directly rotates the rotation axis 400.

Figure 5 represents a set of embossing rollers 501 , 502, bearing protrusion and recess embossing features (not illustrated in Figure 5), each comprising at a corresponding extremity a toothed wheel 503, 504, the teeth of which intertwine to synchronously drive the embossing rollers 501, 502, to rotate about respective rotation axes 505, 506. The embossing rollers 501 , 502, further each comprise two ring-shaped shoulders 507, 508, one towards each extremity of the respective embossing roller 501, 502, and configured such that a ring-shaped shoulder on one embossing roller faces a corresponding ring-shaped shoulder of the opposite embossing roller. The ring-shaped shoulders 507, 508, are generally designed to form a ring which centered on the rotation axis of the embossing roller, whose circumference protrudes from a base surface of the embossing roller where it is located. This level of detail is not illustrated in Figure 5 to maintain a better readability.

Figure 6 represents the set of embossing rollers 501 , 502, of Figure 5 but in a different perspective, togetherwith two magnified views 509, 510, of areas where the ring-shaped shoulders 507 and 508 are resting on each other as may be the case during embossing. This is substantiated by distance 511 between the ring-shaped shoulders 507 and 508 being 0, while a nip 512 is maintained between the embossing rollers 501 and 502 with a determined nip width value n separating a base surface 514 of the embossing roller 501 from an opposite base surface 513 of the embossing roller 502. The base surfaces are schematically represented and in the views 509 and 510 do not comprise any embossing features in the example of Figure 6. The determined nip width value n of the nip 512 enables to insert a sheet of material in it (sheet of material not represented) for embossing.

In a further example represented in Figure 7 the ring-shaped shoulders of Figure 6 may be replaced by radial recesses 701 and 702, which each form recesses in the embossing rollers 501 and 502 respectively as compared to the base surfaces 513 and 514. Hence, when the embossing rollers 501 and 502 are pressured one towards the other, as is depicted by arrows 705 in the radial recesses 701 and 702, their base surfaces 513 and 514 may be coming into contact such that a distance 703 tends to become similar to that of a sheet of material inserted therein for embossing (not illustrated in Figure 7), and a distance 704 between radial recesses 701 and 702 facing each other from one embossing roller to the other is greater than 0. The pressure depicted by the arrows 705 may be exerted by pressuring means comprised in the embossing set-up (not illustrated in Figure 7 as is well known in the prior art, for example by hydraulic pressuring means.

Figure 8 depicts an upper view of an example of a manufactured embossed sheet of material 800 with embossed features in reference to surface 106 in Figures 1 and 2 , in which a controlled material thickness is obtained. The embossed features comprise embossed profile embossing features 801, a magnified view 803 of which shows various shapes and sizes. The embossed profile embossing features 801 are configured to obtain at least an aerodynamic profile on the sheet of material 800, which may be obtained for example by a determined number of the embossed profile embossing features 801, in various shapes (segment(s), arc of circle) and/or sizes, the embossed aerodynamic profiles being configured for an end product, namely a filtering element (not illustrated in Figure 8), to modify in a determined manner flow properties for the mainstream gas flow passing through the filtering element by creating a gas flow turbulence occurrence in the filtering element. The sheet of material further comprises embossed separating base surface zones 802 located between embossed profile embossing features 801. The embossed separating base surface zones 802 result from embossing with separating base surface zones located between profile embossing features of the embossing rollers (not illustrated in Figure 8, and corresponding to the first base surface and the second base surface of the embossing rollers (not illustrated either). The embossed profile embossing features 801 result from embossing features formed on a first base surface of a first embossing roller and corresponding embossing features formed on a second base surface of a second embossing roller, which are in a congruence with each other (not illustrated in Figure 8) and for which the congruence is configured by adjusting heights of protrusion and depths of recesses of the embossing features as will be explained in further examples herein below. The example of Figure 8 is intended to show a possible layout of embossed profile embossing features 801 and embossed separating base surface zones 802 on an embossed sheet of material 800.

Figure 9a illustrates a cross-section view 909 through a set of embossing rollers together with an example of the embossed sheet of material 907 produced therewith according to an example embodiment of the invention. In the cross-section view 909, the first embossing roller 501 and the second embossing roller 502 are seen in cross-section. A magnified view 911 of one extremity of the set of embossing rollers from view 909 details that the shoulders of the rollers are in contact in a similar manner as in Figure 6. The cross-section view 909 shows a nip corresponding to separating base surface zones 906 located between embossing features 901 , 902, 903, and corresponding to a first base surface and a second base surface of the first embossing roller 501 and the second embossing roller 502. The cross-section view 909 further shows nips corresponding to a first subset of embossing features 901 , 902, 903. The embossing features 901, 902, 903 are formed on the first base surface of the first embossing roller 501 and corresponding embossing features 901 , 902, 903 are formed on the second base surface of the second embossing roller 502, and are in a congruence with each other.

For the first subset of the embossing features, the congruence for each embossing feature is configured to be such that corresponding protrusion and recess embossing features located respectively on different embossing rollers have a value of height of the protrusion embossing feature greater than a value of depth of the recess embossing feature. Thereby a width of the nip between the first and the second embossing rollers is configured, which has a first nip width value for the separating base surface zones 906, and different nip width values smaller than the first nip width value for embossing features 901 , 902, 903 of the first subset of the embossing features. Further thereby, this enables to obtain the controlled material thickness of the embossed sheet of material with respectively a first value of the material thickness when the sheet of material is embossed with the separating base surface zones 906, and different values of the material thickness smaller than the first value of the material thickness when the sheet of material is embossed with embossing features 901, 902, 903 of the first subset of the embossing features.

View 907 shows a detail from a sheet of material embossed according to the invention, in which, using same reference numbers as for the embossing features and for the separating base surface features from the embossing rollers, embossed separated base surface zones 906 and embossings from the embossing features 901 , 902, 903 are shown; the embossings from embossing features 901 and 902 may be called protrusion features, whereas the embossings from embossed features 903 are in the opposite direction and may be called recess features. Furthermore, a dashed line 912 suggests the location of the cross-section view depicted in 909.

The embossing features 902 and 903 are profile embossing features, which are configured for embossing at least an aerodynamic profile (referenced 902 and 903 in view 907) on the sheet of material, the embossed aerodynamic profiles being configured to modify in a determined manner flow properties for the mainstream gas flow passing through the filtering element by creating a gas flow turbulence occurrence in the filtering element (filtering element and gas flow not illustrated in the Figure).

The embossing features 901 are radial embossing features configured to delimitate stripes on opposite lateral sides of the stripe, on the first and second embossing rollers, and further configured to form longitudinal-delimitation embossed features that delimitate the embossed stripe on the sheet of material, on the opposite lateral sides of the embossed stripe. Each stripe comprises protrusion features and recess features corresponding to embossing features 902 and 903 on each of the first embossing roller and the second embossing roller, and each embossed stripe being oriented longitudinally along a straight line on the sheet of material, the profile embossing features thereby being arranged according to an orientation of the stripe on the embossing rollers.

Referring now to Figure 9b, this illustrates a cross-section view 910 through a set of embossing rollers together with an example of the embossed sheet of material 908 produced therewith according to an example embodiment of the invention. In the cross-section view 910, the first embossing roller 501 and the second embossing roller 502 are again seen in cross-section. A magnified view 911 of one extremity of the set of embossing rollers from view 910 details that the shoulders are in contact in a similar manner as in Figure 6. Cross section view 910 shows a nip corresponding to separating base surface zones 906 located between embossing features 907, 902, 903, and corresponding to a first base surface and a second base surface of the first embossing roller 501 and the second embossing roller 502. Cross-section view 910 further shows nips corresponding to the first subset of embossing features 902, 903 and nips corresponding to a second subset of embossing features 907. The embossing features 907, 902, 903 are formed on the first base surface of the first embossing roller 501 and corresponding embossing features 907, 902, 903 are formed on the second base surface of the second embossing roller 502, and are in a congruence with each other.

The nature of the first subset of embossing features has already been described in relation for Figure 9a.

For the second subset of the embossing features, the congruence for each embossing feature is configured to be such that corresponding protrusion and recess embossing features located respectively on different embossing rollers have a value of height of the protrusion embossing feature smaller than or equal a value of depth of the recess embossing feature. Thereby a width of the nip between the first and the second embossing rollers is configured, which, as previously explained in relation to Figure 9a, has the first nip width value for the separating base surface zones 906, and further different nip width values greater than or equal to the first nip width value for embossing features 907 of the second subset of the embossing features. Further thereby, this enables to obtain the controlled material thickness of the embossed sheet of material with respectively the first value of the material thickness when the sheet of material is embossed with the separating base surface zones 906, and further different values of the material thickness greaterthan or equal to the first value of the material thickness when the sheet of material is embossed with embossing features 907 of the second subset of the embossing features.

View 908 shows a detail from a sheet of material embossed according to the invention, in which, using same reference numbers as for the embossing features and for the separating base surface features from the embossing rollers, embossed separated base surface zones 906 and embossings from the embossing features 907, 902, 903 are shown; the embossings from embossing features 907 and 902 may be called protrusion features, whereas the embossings from embossed features 903 are in the opposite direction and may be called recess features. Furthermore, a dashed line 913 suggests the location of the cross-section view depicted in 910.

The embossing features 902 and 903 are profile embossing features, which are configured for embossing at least an aerodynamic profile (referenced 902 and 903 in view 908) on the sheet of material, the embossed aerodynamic profiles being configured to modify in a determined manner flow properties for the mainstream gas flow passing through the filtering element by creating a gas flow turbulence occurrence in the filtering element (filtering element and gas flow not illustrated in the Figure).

The embossing features 907 are radial embossing features configured to delimitate stripes on opposite lateral sides of the stripe, on the first and second embossing rollers, and further configured to form longitudinal-delimitation embossed features that delimitate the embossed stripe on the sheet of material, on the opposite lateral sides of the embossed stripe. Each stripe comprises protrusion features and recess features corresponding to embossing features 902 and 903 on each of the first embossing roller and the second embossing roller, and each embossed stripe being oriented longitudinally along a straight line on the sheet of material, the profile embossing features thereby being arranged according to an orientation of the stripe on the embossing rollers.

Figure 10a illustrates a cross-section view 1009 through a set of embossing rollers together with an example of the embossed sheet of material 1007 produced therewith according to an example embodiment of the invention. In the cross-section view 1009, the first embossing roller 501 and the second embossing roller 502 are seen in cross-section. A magnified view 1011 of one extremity of the set of embossing rollers from view 1009 details that radial recesses are at extremities of the rollers, and the rollers are pressured toward each other in a similar manner as in Figure 7. The cross-section view 1009 shows a nip corresponding to separating base surface zones 1006 located between embossing features 1001, 1002, 1003, and corresponding to a first base surface and a second base surface of the first embossing roller 501 and the second embossing roller 502. The cross-section view 1009 further shows nips corresponding to a first subset of embossing features 1001 , 1002, 1003. The embossing features 1001, 1002, 1003 are formed on the first base surface of the first embossing roller 501 and corresponding embossing features 1001 , 1002, 1003 are formed on the second base surface of the second embossing roller 502, and are in a congruence with each other.

For the first subset of the embossing features, the congruence for each embossing feature is configured to be such that corresponding protrusion and recess embossing features located respectively on different embossing rollers have a value of height of the protrusion embossing feature greater than a value of depth of the recess embossing feature. Thereby a width of the nip between the first and the second embossing rollers is configured, which has a first nip width value for the separating base surface zones 1006, and different nip width values smaller than the first nip width value for embossing features 1001 , 1002, 1003 of the first subset of the embossing features. Further thereby, this enables to obtain the controlled material thickness of the embossed sheet of material with respectively a first value of the material thickness when the sheet of material is embossed with the separating base surface zones 1006, and different values of the material thickness smaller than the first value of the material thickness when the sheet of material is embossed with embossing features 1001 , 1002, 1003 of the first subset of the embossing features.

View 1007 shows a detail from a sheet of material embossed according to the invention, in which, using same reference numbers as for the embossing features and for the separating base surface features from the embossing rollers, embossed separated base surface zones 1006 and embossings from the embossing features 1001 , 1002, 1003 are shown; the embossings from embossing features 1001 and 1002 may be called protrusion features, whereas the embossings from embossed features 1003 are in the opposite direction and may be called recess features. Furthermore, a dashed line 1012 suggests the location of the cross-section view depicted in 1009.

Referring now to Figure 10b this illustrates a cross-section view 1010 through a set of embossing rollers together with an example of the embossed sheet of material 1008 produced therewith according to an example embodiment of the invention. In the cross-section view 1010, the first embossing roller 501 and the second embossing roller 502 are again seen in cross-section. A magnified view 1011 of one extremity of the set of embossing rollers from view 1010 details that radial recesses are at extremities of the rollers, and the rollers are pressured toward each other in a similar manner as in Figure 7. The cross-section view 1010 shows a nip corresponding to separating base surface zones 1006 located between embossing features 1007, 1002, 1003, and corresponding to a first base surface and a second base surface of the first embossing roller 501 and the second embossing roller 502. The cross-section view 1010 further shows nips corresponding to the first subset of embossing features 1002, 1003 and nips corresponding to a second subset of embossing features 1007. The embossing features 1007, 1002, 1003 are formed on the first base surface of the first embossing roller 501 and corresponding embossing features 1007, 1002, 1003 are formed on the second base surface of the second embossing roller 502, and are in a congruence with each other.

The nature of the first subset of embossing features has already been described in relation for Figure 10a.

For the second subset of the embossing features, the congruence for each embossing feature is configured to be such that corresponding protrusion and recess embossing features located respectively on different embossing rollers have a value of height of the protrusion embossing feature smaller than or equal a value of depth of the recess embossing feature. Thereby a width of the nip between the first and the second embossing rollers is configured, which, as previously explained in relation to Figure 10a, has the first nip width value forthe separating base surface zones 1006, and further different nip width values greater than or equal to the first nip width value for embossing features 1007 of the second subset of the embossing features. Further thereby, this enables to obtain the controlled material thickness of the embossed sheet of material with respectively the first value of the material thickness when the sheet of material is embossed with the separating base surface zones 1006, and further different values of the material thickness greater than or equal to the first value of the material thickness when the sheet of material is embossed with embossing features 1007 of the second subset of the embossing features.

View 1008 shows a detail from a sheet of material embossed according to the invention, in which, using same reference numbers as forthe embossing features and forthe separating base surface features from the embossing rollers, embossed separated base surface zones 1006 and embossings from the embossing features 1007, 1002, 1003 are shown; the embossings from embossing features 1007 and 1002 may be called protrusion features, whereas the embossings from embossed features 1003 are in the opposite direction and may be called recess features. Furthermore, a dashed line 1013 suggests the location of the cross-section view depicted in 1010.

Figure 11a and Figure 11 b illustrate further examples of the invention, in which embossing rollers with radial recesses as shown in magnified views 1100 and 1106 are used. Figure 11a depicts an isometric view 1101 from the surface of the first embossing roller 501 , and a cross-section view of embossing features 1103 in which respectively corresponding protrusion and recess embossing features 1104, 1105 present on the embossing rollers 501 and 502 are shown, and the magnified view 1100, in which the recessed radii of the embossing rollers 501 and 502 are evidenced. Figure 11b depicts an isometric view 1107 from the surface of a further first embossing roller 501, a cross-section view of embossing features 1109 in which respectively corresponding protrusion and recess embossing features 1110, 1111 present on the embossing rollers 501 and 502 are shown, and the magnified view 1106, in which the recessed radii ofthe embossing rollers 501 and 502 are evidenced. In both examples, the first embossing roller 501 and the second embossing roller 502 are pressured towards each other, which enables a maintaining of the controlled thickness ofthe embossed sheet of material. The embossing features 1104 and 1110 belong to the second subset of the embossing features as discussed for Figures 9b and 10b, because the congruence for each embossing feature is configured to be such that corresponding protrusion and recess embossing features located respectively on different embossing rollers have a value of height of the protrusion embossing feature smaller than or equal a value of depth of the recess embossing feature, in this particular example the value of height appear to be equal to the value of depth. Thereby a width of the nip between the first and the second embossing rollers is configured, in which further different nip width values equal to the first nip width value for embossing features 1104, 1100 of the second subset of the embossing features. Furtherthereby, this enables to obtain the controlled material thickness of the embossed sheet of material with respectively the first value of the material thickness when the sheet of material is embossed with the separating base surface zones, and further different values of the material thickness equal to the first value ofthe material thickness when the sheet of material is embossed with embossing features 1104, 1100 of the second subset of the embossing features.

Examples of controlling a material thickness through embossing different sheets of materials and with different distributions of protrusion and recessed embossed features are illustrated by means of Figure 12a and Figure 12b, which illustrate respectively an upper view a zone of the sheet of material embossed according to the invention. Figure 12a shows a zone 1200 of sheet of material embossed according to invention, which contains an embossed base surface zone 1201, embossed protrusion embossing features 1202 and 1203, and embossed recessed embossing features 1204. Thickness measurements were carried out in 20 different points of the embossed base surface 1201 of the embossed sheet of material and a mean value and the corresponding standard deviation were calculated. Figure 12b shows a zone 1205 of a sheet of material embossed according to invention, which contains an embossed base surface zone 1207 and embossed protrusion embossing features 1202 and 1206. Thickness measurements were carried out in 20 different points of the base surface 1201 of the embossed sheet of material and a mean value and the corresponding standard deviation were calculated.

In one example, a sheet of material to produce a cigarette filter, having a grammage of 35 gsm and a mean thickness value of 320 pm, exhibited a standard deviation of its mean material thickness of 15 pm prior to its embossing according to the invention. After the embossing with an embossing linear force of 7,3 kN/m applied between the embossing rollers 501 and 502 (not shown in Figure 12a), the base surface 1201 exhibited a mean material thickness of 125 pm and a standard deviation of its mean material thickness of 7 pm. In a further example, a sheet of material to produce a cigarette filter, having a grammage of 62 gsm and a mean thickness value of 395 pm, which exhibited a standard deviation of its mean material thickness of 36 pm priorto its embossing, was embossed with a linear force of 11 ,6 kN/m applied between the embossing rollers 501 and 502 (not shown in Figure 12a and Figure 12b), according to the invention, to obtain embossed sheets 1200, 1205 of material of controlled thickness, as in Figure 12a and Figure 12b, respectively. After the embossing, the base surface 1201 exhibited a mean material thickness of 104 pm and a standard deviation of its mean material thickness of 14 pm, whereas the base surface 1207 exhibited a mean material thickness of 113 pm and a standard deviation of its mean material thickness of 18 pm.

Further different examples of embossing according of the invention, to obtain an embossed sheet of material with a controlled thickness, showed that the ratio between the material thickness of the embossed sheet of material and the material thickness of the non-embossed sheet of material varies with a ratio in a range from of 1 :1 to 1 :5, whereas the ratio between the standard deviation of the material thickness of the embossed sheet of material and the standard deviation ofthe material thickness of the non-embossed sheet of material varies in range of 1 :1 to 1 :3

Figure 13 illustrates an example of realization of the invention, and contains a detailed view from a sheet of material 1300 embossed according to the invention, which shows embossed base surface zones 1302 and embossed protrusion embossing features 1301 , arranged in an array-like manner described by the dimensional parameters p and /. Figure 13 further illustrates in a cross-section view 1304 along a line 1303 of the embossed sheet of material 1300, an embossed height hi and material thicknesses 1305 and 1306 of the embossed sheet of material in zones corresponding respectively to the base surface zones 1302 and to the protrusion features 1301. In this example the material thickness 1306 obtained after embossing with protrusion features 1301 is smaller than the material thickness 1305 obtained after embossing with base surface feature zones 1302.

Figure 14a illustrates a further example of realization of the invention, and contains a detailed view from a sheet of material 1400 embossed according to the invention, which shows an embossed base surface zone 1401 and both embossed protrusion and recess embossed radial features 1403 and 1402, separated by a distance /, whereas each embossed radial feature defines a plurality of enclosures 1411 , which are longitudinally distributed along the embossed radial feature and separated from each other by a distance p. Figure 14a further includes a cross-section view 1410 along a line 1408 of the embossed sheet of material 1400, in which a height hi of the protrusions 1403 and a depth h₂ of the recesses 1402 are illustrated. Furthermore, a material thickness 1405 and 1404 of the embossed sheet of material in zones respectively corresponding to the embossed base surface zone 1401 , and to the embossed protrusion features 1403 or embossed recess features 1402 is depicted.

As an option, Figure 14b illustrates a further example of realization of the invention, and contains a detailed view from a sheet of material 1406 embossed according to the invention, which shows a base surface 1401 and embossed protrusion radial features 1403, separated by a distance /, whereas each embossed radial feature 1403 defines a plurality of enclosures 1413, which are longitudinally distributed along the corresponding embossed radial feature and separated by a distance p. Figure 14b further includes a cross-section view 1412 of the embossed sheet of material along a line 1409, in which a height hi of an embossed protrusion feature is illustrated. Furthermore, material thicknesses 1407 and 1408 of the embossed sheet of material 1406 in zones corresponding to the embossed base surface zones 1407 and to the embossed protrusion features 1403.

Figure 15 illustrates a further example of realization of the invention, and contains a detailed view from a sheet of material 1500 embossed according to the invention, which shows a base surface zone 1501 and embossed segments 1502, arranged in an array-like manner described by the dimensional parameters p and /. Figure 15 further illustrates in a cross-section view 1504 taken along a line 1503 of the embossed sheet of material 1500, the embossed height hi and material thicknesses 1506 and 1505 of the embossed sheet of material in zones corresponding both to the embossed base surface zones and to the embossed segments 1502.

Figure 16 schematically illustrates how a cigarette filter 1601 -type filtering element from a double filter 301 may be mounted to a tobacco containing section 1603 in order to obtain a cigarette 1605 according to prior art. Part (A) shows the double filter 301 . Part (B) shows the double filter 301 positioned between tobacco containing sections 1603, and a filter paper 1602 being wound and glued around the double filter 301 and partly over a part of each tobacco containing section 1603, resulting in a double cigarette 1604 shown in part (C). Part (D) shows one of cigarettes 1605 obtained after cutting a double cigarette 1604 in a middle 1606 thereof.

Figure 17 schematically illustrates the structure of an inhalable drug delivery system 1700A and 1700B, according to the prior art. Part (A) depicts a delivery system comprising a drug containing component 1701 and a filtering element 1702 fabricated using a sheet of material embossed according to the invention. Part (B) depicts an inhalable drug delivery system comprising the drug containing component 1701 , a cooling component 1703, and of the filtering element 1702 fabricated using a sheet of material embossed according to the invention.

Figure 18 contains a flowchart illustrating a preferred embodiment of the method for manufacturing the embossed sheet of material and obtaining a controlled material thickness according to the invention. A sheet of material 1800 is provided 1801 for embossing, and in embossed step 1802 embossed with at least embossing features by means of an embossing rollers system in which embossing features formed on a first base surface of a first embossing roller and corresponding embossing features formed on a second base surface of a second embossing roller are in a congruence with each other, and fed to a nip between the first embossing roller and the second embossing roller. The embossing features comprise profile embossing features configured for embossing at least an aerodynamic profile on the sheet of material, the embossed aerodynamic profiles being configured to modify in a determined manner flow properties for the mainstream gas flow passing through the filtering element by creating a gas flow turbulence occurrence in the filtering element. In a further embossing step 1805 the sheet of material is embossed with separating base surface zones located between profile embossing features, and corresponding to the first base surface and the second base surface. For each embossing feature the corresponding congruence is configured to be such that for a first subset 1803 of the embossing features, corresponding protrusion and recess embossing features located respectively on different embossing rollers have a value of height of the protrusion embossing feature greaterthan a value of depth of the recess embossing feature, thereby configuring a width of the nip between the first and the second embossing rollers, which has a first nip width value for the separating base surface zones, and different nip width values smaller than the first nip width value for embossing features of the first subset of the embossing features, thereby enabling to obtain the controlled material thickness of the embossed sheet of material with respectively a first value of the material thickness when the sheet of material is embossed with the separating base surface zones, and different values of the material thickness smaller than the first value of the material thickness when the sheet of material is embossed with embossing features of the first subset of the embossing features. For a second subset 1804 of the embossing features, corresponding protrusion and recess embossing features located respectively on different embossing rollers have a value of height of the protrusion embossing feature smallerthan or equal to a value of depth of the recess embossing feature, thereby configuring a width of the nip between the first and second embossing rollers, which has further different nip values greaterthan or equal to the first nip width value for embossing features of the second subset of the embossing features, thereby enabling to obtain further different values of the material thickness greater than or equal to the first value of the material thickness when the sheet of material is embossed with embossing features of the second subset of the embossing features. As a result of these steps, an embossed sheet of material 1806 is obtained with a controlled material thickness.

Claims

1 . A method for manufacturing an embossed sheet of material and obtaining a controlled material thickness, the embossed sheet of material being configured to obtain a filtering element configured for an inhalable drug delivery device, and for filtering a mainstream gas flow passing through the filtering element, the method comprising steps of: providing the sheet of material; embossing the sheet of material at least with embossing features by means of an embossing rollers system in which embossing features formed on a first base surface of a first embossing roller and corresponding embossing features formed on a second base surface of a second embossing roller are in a congruence with each other, and by feeding the sheet of material to a nip between the first embossing roller and the second embossing roller, the embossing features comprising profile embossing features configured for embossing at least an aerodynamic profile on the sheet of material, the embossed aerodynamic profiles being configured to modify in a determined manner flow properties for the mainstream gas flow passing through the filtering element by creating a gas flow turbulence occurrence in the filtering element; embossing the sheet of material with separating base surface zones located between embossing features, and corresponding to the first base surface and the second base surface; configuring for each embossing feature the corresponding congruence to be such that for a first subset of the embossing features, corresponding protrusion and recess embossing features located respectively on different embossing rollers have a value of height of the protrusion embossing feature greater than a value of depth of the recess embossing feature; thereby configuring a width of the nip between the first and the second embossing rollers, which has a first nip width value for the separating base surface zones, and different nip width values smaller than the first nip width value for embossing features of the first subset of the embossing features; thereby enabling to obtain the controlled material thickness of the embossed sheet of material with respectively a first value of the material thickness when the sheet of material is embossed with the separating base surface zones, and different values of the material thickness smaller than the first value of the material thickness when the sheet of material is embossed with embossing features of the first subset of the embossing features.

2. The method for manufacturing the embossed sheet of material, according to claim 1 , wherein the configuring for each embossing feature of the corresponding congruence is further such that for a second subset of the embossing features, corresponding protrusion and recess embossing features located respectively on different embossing rollers have a value of height of the protrusion embossing feature smallerthan or equal to a value of depth of the recess embossing feature, thereby configuring a width of the nip between the first and second embossing rollers, which has further different nip values greater than or equal to the first nip width value for embossing features ofthe second subset of the embossing features; thereby enabling to obtain further different values of the material thickness greater than or equal to the first value of the material thickness when the sheet of material is embossed with embossing features of the second subset of the embossing features.

3. The method for manufacturing the embossed sheet of material according to any one of claims 1 and 2, further comprising arranging the embossing features in a plurality of stripes, each stripe comprising protrusion features and recess features corresponding to embossing features on each of the first embossing roller and the second embossing roller, and each embossed stripe being oriented longitudinally along a straight line on the sheet of material, the profile embossing features thereby being arranged according to an orientation of the stripe on the embossing rollers.

4. The method for manufacturing the embossed sheet of material according to any one of claims 1 to 3, wherein the embossing features further comprise radial embossing features configured to delimitate each stripe on opposite lateral sides of the stripe, on the first and second embossing rollers, and further configured to form longitudinal-delimitation embossed features that delimitate the embossed stripe on the sheet of material, on the opposite lateral sides of the embossed stripe.

5. The method for manufacturing the embossed sheet of material according to claim 4, wherein the radial embossing features are further configured to emboss a folding line into the sheet of material.

6. The method for manufacturing of any one of claims 4 to 5, further wherein the radial embossing features are further configured to form a plurality of enclosing walls on the first embossing roller and on the second embossing roller, describing at least an enclosure around one or a plurality of the profile embossing features, and, for each enclosure, an enclosure opening in the enclosure connecting the enclosure to a successive enclosure in the orientation direction ofthe stripe, the enclosure having a corresponding maximum enclosure expansion section area in the orientation direction of the stripe and the enclosure opening having a corresponding enclosure opening constriction section area in the orientation direction of the stripe which is smaller than the corresponding maximum enclosure expansion section area, and to define at least one alternance of the enclosure opening constriction section area and the maximum enclosure expansion section area in the orientation direction of the stripe, formed by the enclosure opening and the enclosure respectively, with a cross-section area ratio between the maximum enclosure expansion section area and the enclosure opening constriction section area of the profile in a range from 15:1 to 2:1 .

7. The method for manufacturing of any one of claims 1 to 6, wherein the embossed embossing features comprise at least one from a list comprising a recessed shape in the sheet of material and a protrusion in the sheet of material.

8. The method for manufacturing of any one of claims 1 to 7, wherein the sheet of material may be either woven or not-woven and comprises any material from a list comprising paper, a cellulose-based material, wool, plant- or animal-based fibrous material.

9. The method for manufacturing of any one of the claims 1 to 8, whereby the profile embossing features are further configured to produce a height of the aerodynamic profile that is in a range of 1 to 15 times of a thickness of the sheet of material.

10. The method for manufacturing according to any one of the claims 1 to 9, further wherein the embossing of the sheet of material is configured to be a wallpaper-like embossing producing an uninterrupted and repeating pattern of embossed aerodynamic features.

11 . The method for manufacturing of any one of claims 1 to 10, whereby each one of the profile embossing features as a height in a range between 0,1 mm and 2,5 mm.

12. The method for manufacturing the embossed sheet of material according to any one of claims 1 to 11 , further comprising a step of adjusting the width of the nip to the first nip width value by providing a shoulder at each extremity of the first and second embossing rollers, the shoulders being configured to produce the first nip width value when at each extremity of the first and the second embossing rollers the shoulders from the first embossing roller are in contact with corresponding ones of the shoulder from the second embossing roller.

13. The method for manufacturing the embossed sheet of material according to any one of claims

1 to 12, wherein the step of adjusting the width further comprises providing pressuring means configured to exert pressure between the first embossing roller and the second embossing roller, and enable a maintaining of the controlled material thickness.

14. The method for manufacturing the embossed sheet of material according to any one of claims 1 to 13, wherein the first nip width value is chosen in function of a predetermined grammage of the sheet of material, and of a desired value for the first value of the material thickness.

15. The method for manufacturing the embossed sheet of material according to any one of the preceding claims, wherein the sheet of material has a grammage in a range between 10 gsm and 100 gsm and a thickness in a range between 0,02 mm and 1 ,5 mm.

16. The method for manufacturing the embossed sheet of material according to any one of claims 1 to 15, wherein a ratio between the controlled material thickness of the embossed sheet and an initial thickness of the material sheet priorto embossing is in a range of 1 :1 to 1 :5.

17. The method for manufacturing the embossed sheet of material according to any one of claims 1 to 15, wherein a ratio between a statistic standard deviation of the initial thickness of the sheet of material and a statistic standard deviation of the controlled material thickness ofthe embossed sheet is between 1 :1 and 1:3.

18. The method for manufacturing the embossed sheet of material according to any one of claims 1 to 17, further comprising a step of heating the sheet of material priorto embossing.

19. The method for manufacturing the embossed sheet of material according to any one of claims 1 to 18, wherein at least one of the first and the second embossing rollers is maintained at a constant temperature in a range of 20°C to 60°C.

20. An embossing set-up for manufacturing an embossed sheet of material and obtaining a controlled material thickness, configured to obtain a filtering element configured for an inhalable drug delivery device, and for filtering a mainstream gas flow passing through the filtering element, comprising features of: an embossing rollers system in which embossing features formed on a first base surface of a first embossing roller and corresponding embossing features formed on a second base surface of a second embossing roller are in a congruence with each other, the embossing system being configured to emboss the sheet of material in a nip between the first embossing roller and the second embossing roller, the embossing features comprising profile embossing features configured for embossing at least an aerodynamic profile on the sheet of material, the embossed aerodynamic profile being configured to modify in a determined manner flow properties for the mainstream gas flow passing through the filtering element by creating a gas flow turbulence occurrence in the filtering element; the embossing rollers system further comprising for embossing the sheet of material, separating base surface zones located between embossing features, and corresponding to the first base surface and the second base surface; the corresponding congruence of each of the embossing features being configured to enable that for a first subset of the embossing features, corresponding protrusion and recess embossing features located respectively on different embossing rollers have a value of height of the protrusion embossing feature greater than a value of depth of the recess embossing feature; thereby configuring a width of the nip between the first and the second embossing rollers, which has a first nip width value for the separating base surface zones, and different nip width values smaller than the first nip width value for embossing features of the first subset of the embossing features; thereby enabling to obtain the controlled material thickness of the embossed sheet of material with respectively a first value of the material thickness when the sheet of material is embossed with the separating base surface zones, and a different value of the material thickness smaller than the first value of the material thickness when the sheet of material is embossed with embossing features ofthe first subset of the embossing features.

21 . The embossing set-up for manufacturing the embossed sheet of material, according to claim 20, wherein the corresponding congruence of each the embossing features is further configured to enable that for a second subset ofthe embossing features, corresponding protrusion and recess embossing features located respectively on different embossing rollers have a value of height of the protrusion embossing feature smallerthan or equal to a value of depth of the recess embossing feature, thereby configuring a width of the nip between the first and second embossing rollers, which has further different nip values greater than or equal to the first nip width value for embossing features ofthe second subset of the embossing features; thereby enabling to obtain further different values of the material thickness greater than or equal to the first value of the material thickness when the sheet of material is embossed with embossing features of the second subset of the embossing features.

22. The embossing set-up for manufacturing the embossed sheet of material, according to any one of claims 20 and 21 , the embossing rollers system being further configured to emboss the sheet of material with a plurality of stripes, each stripe comprising protrusion features and recess features corresponding to embossing features on each of the first embossing roller and the second embossing roller, and each embossed stripe being oriented longitudinally along a straight line on the sheet of material, the profile embossing features being arranged according to an orientation of the stripe on the embossing rollers.

23. The embossing set-up for manufacturing an embossed sheet of material of any one of claims 20 to 22, in which the embossing features further comprise radial embossing features configured to delimitate each stripe on opposite lateral sides of the stripe, on the first and second embossing rollers, and further configured to form longitudinal delimitation embossed features that delimitate the embossed stripe on the sheet of material, on opposite lateral sides of the embossed stripe.

24. The embossing set-up of claim 23, wherein the radial embossing features are further configured to emboss a folding line into the sheet of material.

25. The embossing set-up according to any one of claims 23 to 24, further wherein: the radial embossing features are further configured to form a plurality of enclosing walls on the first embossing roller and on the second embossing rollers describing at least an enclosure around one or a plurality of the profile embossing features, and, for each enclosure, an enclosure opening in the enclosure connecting the enclosure to a successive enclosure in the orientation direction ofthe stripe, the enclosure having a corresponding maximum enclosure expansion section area in the orientation direction of the stripe and the enclosure opening having a corresponding enclosure opening constriction section area in the orientation direction of the stripe which is smaller than the corresponding maximum enclosure expansion section area, and to define at least one alternance of the enclosure opening constriction section area and the maximum enclosure expansion section area in the orientation direction of the stripe, formed by the enclosure opening and the enclosure respectively, with a cross-section area ratio between the maximum enclosure expansion section area and the enclosure opening constriction section area of the profile in a range from 15:1 to 2:1 .

26. The embossing set-up of any one of claims 20 to 25, wherein the embossed embossing features comprise at least one from a list comprising a recessed shape in the sheet of material and a protrusion in the sheet of material.

27. The embossing set-up of any one of claims 20 to 26, wherein the sheet of material may be either woven or non-woven and comprises any material from a list comprising paper, a cellulose-based material, wool, plant- or animal-based fibrous material.

28. The embossing set-up of any one of the claims 20 to 27, whereby the profile embossing features are further configured to produce a height of the aerodynamic profile that is in a range of 1 to 15 times of a thickness of the sheet of material.

29. The embossing set-up of any one of the claims 20 to 28, further wherein the embossing rollers system and the embossing features are configured for embossing of the sheet of material to be a wallpaper-like embossing producing an uninterrupted and repeating pattern of embossed aerodynamic features.

30. The embossing set-up of any one of the claims 20 to 29, whereby each one of the profile embossing features as a height in a range between 0,1 mm and 2,5 mm.

31 . The embossing set-up according to any one of claims 20 to 30, further comprising a shoulder at each extremity of the first and the second embossing rollers enabling an adjusting of the width of the nip to the first nip width value, the shoulders being configured to produce the first nip width value when at each extremity of the first and the second embossing rollers the shoulders from the first embossing roller are in contact with corresponding ones of the shoulder from the second embossing roller.

32. The embossing set-up according to any one of claims 20 to 31 , further comprising pressuring means configured to exert pressure between the first embossing roller and the second embossing roller, and to enable a maintaining of controlled material thickness.

32. The embossing set-up according to any one of claims 20 to 31 , wherein the first nip width value is chosen in function of a predetermined grammage of the sheet of material, and of a desired value for the first value of the material thickness.

33. The embossing set-up according to any one of claims 20 to 32, wherein the sheet of material has a grammage in a range between 10 gsm and 100 gsm and a thickness in a range between 0,02 mm and 1 ,5 mm.

34. The embossing set-up according to any one of claims 20 to 33, wherein a ratio between the controlled material thickness ofthe embossed sheet and an initial thickness of the material sheet prior to embossing is in a range of 1 :1 to 1 :5.

35. The embossing set-up according to any one of claims 20 to 33, wherein a ratio between a statistic standard deviation of the initial thickness of the sheet of material and a statistic standard deviation of the controlled material thickness of the embossed sheet is between 1 :1 and 1 :3.

36. The embossing set-up according to any one of claims 20 to 35, further comprising a step of heating the sheet of material prior to embossing.

37. The embossing set-up according to any one of claims 20 to 36, wherein at least one ofthe first and the second embossing rollers is maintained at a constant temperature in a range of 20°C to 60°C.

38. A filtering element configured for an inhalable drug delivery device, and for filtering a mainstream gas flow passing through the filtering element, comprising an embossed sheet of material, with a controlled material thickness, wherein the sheet of material is embossed at least with embossing features by means of an embossing rollers system in which the embossing features formed on a first base surface of a first embossing roller and corresponding embossing features formed on a second base surface of a second embossing roller are in a congruence with each other, and by feeding the sheet of material to a nip between the first embossing roller and the second embossing roller, the embossing features comprising profile embossing features configured for embossing at least an aerodynamic profile on the sheet of material, the embossed aerodynamic profile being configured to modify in a determined manner flow properties for the mainstream gas flow passing through the filtering element by creating a gas flow turbulence occurrence in the filtering element; the sheet of material is further embossed with separating base surface zones located between embossing features, and corresponding to the first base surface and the second base surface; the corresponding congruence of each ofthe embossing features is configured to be such that for a first subset of the embossing features, corresponding protrusion and recess embossing features located respectively on different embossing rollers have a value of height of the protrusion embossing feature greater than a value of depth of the recess embossing feature; thereby configuring a width of the nip between the first and the second embossing rollers, which has a first nip width value for the separating base surface zones, and different nip width values smaller than the first nip width value for embossing features of the first subset of the embossing features; thereby enabling to obtain the controlled material thickness of the embossed sheet of material with respectively a first value of the material thickness when the sheet of material is embossed with the separating base surface zones, and a different value of the material thickness smaller than the first value of the material thickness when the sheet of material is embossed with embossing features ofthe first subset of the embossing features.

39. The filtering element according to claim 38, wherein the configuring for each embossing feature ofthe corresponding congruence is further such that for a second subset ofthe embossing features, corresponding protrusion and recess embossing features located respectively on different embossing rollers have a value of height of the protrusion embossing feature smallerthan or equal to a value of depth of the recess embossing feature, thereby configuring a width of the nip between the first and second embossing rollers, which has further different nip values greater of equal to the first nip width value for embossing features ofthe second subset of the embossing features; thereby enabling to obtain further different values of the material thickness greater than or equal to the first value of the material thickness when the sheet of material is embossed with embossing features of the second subset of the embossing features.

40. The filtering element according to any one of claims 38 and 39, further wherein the embossed sheet of material is configured to comprise a plurality of stripes, each stripe comprising protrusion features and recess features corresponding to embossing features on each of the first embossing roller and the second embossing roller, and each embossed stripe being oriented longitudinally along a straight line on the sheet of material, the profile embossing features thereby being arranged according to an orientation of the stripe on the embossing rollers.