WO2023104876A1

WO2023104876A1 - Method for manufacturing a ventilation zone in an aerosol- generating article

Info

Publication number: WO2023104876A1
Application number: PCT/EP2022/084773
Authority: WO
Inventors: Didier Bernard GRAF; Alexis Julien LOUVET; Luca BOSI; Marco SCAGNELLI; Federico Battista; Maria Sole ZINNA; Hans-Reiner Hoffmann; Ayoub LHAOU
Original assignee: Philip Morris Products S.A.
Priority date: 2021-12-08
Filing date: 2022-12-07
Publication date: 2023-06-15

Abstract

The invention relates to a method for manufacturing a first ventilation zone in a first aerosol-generating article and a second ventilation zone in a second aerosol-generating article, comprising the method steps: A) providing a first aerosol-generating article, B) forming first perforations in the first aerosol-generating article, thereby creating a first ventilation zone, C) determining the first air infusion value for the first aerosol-generating article, the air infusion value being determined by the equation (Pin-Pout).100%/Pin, wherein Pin is the air pressure applied at the first end face of the article and Pout is the air pressure detected at the second end face of the article, D) comparing said first air infusion value to a reference value, E) providing the second aerosol-generating article and forming second perforations in the second aerosol-generating article, thereby creating the second ventilation zone, wherein a size of the second perforations is adjusted based on the comparison between the determined first air infusion value and the reference value.

Description

METHOD FOR MANUFACTURING A VENTILATION ZONE IN AN AEROSOLGENERATING ARTICLE

The present invention relates to a method for manufacturing a ventilation zone in an aerosol-generating article. The aerosol-generating article may comprise an aerosol-forming substrate and may be adapted to produce an inhalable aerosol upon heating.

Aerosol-generating articles in which an aerosol-forming substrate, such as a tobaccocontaining substrate, is heated rather than combusted, are known in the art. Typically, in such heated smoking articles an aerosol is generated by the transfer of heat from a heat source to a physically separate aerosol-forming substrate or material, which may be located in contact with, within, around, or downstream of the heat source. During use of the aerosol-generating article, volatile compounds are released from the aerosol-forming substrate by heat transfer from the heat source and are entrained in air drawn through the aerosol-generating article. As the released compounds cool, they condense to form an aerosol.

Aerosol-generating articles with a ventilation zone including perforations are known. These ventilation zones allow ambient air to enter the aerosol-generating article during a user’s puff. This enables a better mixing of the air flow coming from the aerosol-forming substrate with the ambient air for facilitating the formation of an aerosol. The amount of air which may enter the aerosol-generating article during the user’s puff depends on the number, positions and the shape of the perforations. These perforations may be hard to form with low variability during a high-speed manufacturing process for the aerosol-generating articles.

A large quantity of aerosol-generating articles including the ventilation zones may be difficult to manufacture without great variations with regard to important characteristics of the aerosol-generating articles, such as to the amount of air, which can enter the aerosolgenerating articles through the ventilation zone. Differences in the characteristics of the aerosol-forming substrate of the large quantity of aerosol-generating articles to be manufactured may also cause differences in the characteristics of the aerosol-generating articles.

It would be desirable to provide a method for manufacturing a ventilation zone in an aerosol-generating article in order to manufacture an aerosol-generating article that can be operated efficiently and at high speed. It furthermore would be desirable to provide a method for manufacturing a ventilation zone in an aerosol-generating article, providing aerosolgenerating articles with a low variability of the air infusion value from one article to another.

It also would be desirable to provide a method for manufacturing a ventilation zone in different aerosol-generating articles, wherein these different aerosol-generating articles exhibit comparable characteristics. According to an aspect of the present invention there is provided a method for manufacturing a first ventilation zone in a first aerosol-generating article and a second ventilation zone in a second aerosol-generating article. The method may comprise a method step A), providing the first aerosol-generating article. The method may comprise a method step B), forming first perforations in the first aerosol-generating article, thereby creating a first ventilation zone. The method may comprise a method step C), determining a first air infusion value for the aerosol-generating article, the first air infusion value being determined by the equation (Pin-Pout)^,100%/Pin, wherein P_in is the pressure applied to the article to the first end face and P_out is the air pressure detected at the second end face of the article. The method may comprise a method step E) providing the second aerosol-generating article and forming second perforations in the second aerosol-generating article, thereby creating the second ventilation zone, wherein a size of the second perforations is adjusted based on the comparison between the determined first air infusion value and the reference value.

According to a further aspect of the present invention, there is provided a method for manufacturing a first ventilation zone in a first aerosol-generating article and a second ventilation zone in a second aerosol-generating article, comprising the method steps A) providing a first aerosol-generating article. The method also comprises the method step B) forming first perforations in the first aerosol-generating article, thereby creating a first ventilation zone. The method furthermore comprises the method step C) determining a first air infusion value for the first aerosol-generating article, the first air infusion value being determined by the equation (Pin-Pou ’IOC /o/Pin, wherein P_in is the pressure applied to the article to the first end face and P_out is the air pressure detected at the second end face of the article. The method also comprises the method step D) comparing said first air infusion value to a reference value. A method step E) providing the second aerosol-generating article and forming second perforations in the second aerosol-generating article, thereby creating the second ventilation zone is also included. The size of the second perforation is adjusted based on the comparison between the determined first air infusion value and the reference value in method step E).

This method for manufacturing a ventilation zone may enable the manufacturing of aerosol-generating articles having more uniform first and second perforations in the first and second ventilation zone. This may provide aerosol-generating articles having a low air infusion value variability between the first aerosol-generating article and the second aerosol-generating article. This may provide a plurality of aerosol-generating articles wherein individual aerosolgenerating articles within that plurality have a low variability of the air infusion value. This method may provide a means to control the change of the air infusion value during the production of large quantity of aerosol-generating articles and to provide aerosol-generating articles having more uniform air infusion value around a reference value. The second ventilation zone in the second aerosol-generating article may be produced immediately after the formation of the first ventilation zone in the first aerosol-generating article. This may provide direct feedback about the air infusion value produced in the first aerosolgenerating article for the formation of the second perforations creating the second ventilation zone in the second aerosol-generating article. This may provide an air infusion value which is more uniform between the first ventilation zone in the first aerosol-generating article and the second ventilation zone in the second aerosol-generating article.

Air infusion normally refers to the amount of air which can be drawn into an aerosolgenerating article via its ventilation zone when a user pulls on the article during a puff. The amount of air entering the aerosol-generating article during a user’s puff is however difficult to determine during a high-speed manufacturing process for aerosol-generating articles. Therefore, the method for manufacturing the ventilation zone of the present invention employs a different approach, wherein a certain air pressure is applied to a first end face and the air pressure at the second end face of the article is determined, as indicated by the above equation for the air infusion value. This allows an analogous assessment of the air infusion value which more compatible with a high-speed manufacturing process.

During method step C) an air blast may be applied to the first end face of the first aerosol-generating article. A pressure difference between the first end face and the second opposing end face of the first aerosol-generating article may be measured. In particular, the pressure being applied to the first end face may be compared to the pressure of air leaving the first aerosol-generating article through the second opposing end face as indicated by the equation described above.

A first continuous rod may be provided as a first aerosol-generating article. A second continuous rod may be provided as a second aerosol-generating article. The first and the second continuous rod may include at least two aerosol-generating articles. Preferably, the two aerosol-generating articles may be connected to each other. This may form a “double stick’ or a “double aerosol-generating article". Preferably, the first continuous rod and the second continuous rod each consists of two aerosol-generating articles. Two single first and two single second aerosol-generating articles can be produced from these continuous rods by cutting the rod in the middle, thereby producing the two single aerosol-generating articles. Producing larger continuous rods of the aerosol-generating articles may ease the manufacturing process.

Two first ventilation zones may be manufactured in a first continuous rod including two first aerosol-generating articles. Likewise, two second ventilation zones may be manufactured in the second continuous rod including two second aerosol-generating articles. This ensures that a ventilation zone is manufactured in every aerosol-generating article in the continuous rod. In a further embodiment, the method is for manufacturing a first ventilation zone in a predetermined first number of first aerosol-generating articles. During the method steps A) and B) a predetermined first number of first aerosol-generating articles may be provided and first perforations may be formed in each of the first aerosol-generating articles of the predetermined first number of first aerosol-generating articles. During method step C) the individual first air infusion values of the first aerosol-generating articles may be determined and an average first air infusion value thereof may be calculated.

This may allow the production of a large quantity of a predetermined number of first aerosol-generating articles.

Furthermore, the method may be for manufacturing a second ventilation zone in a predetermined second number of second aerosol-generating articles. During method step E) the predetermined second number of second aerosol-generating articles may be provided. Second perforations may be formed in each of the second aerosol-generating articles of the predetermined second number of first aerosol-generating articles, thereby producing second ventilation zones in the predetermined second number of second aerosol-generating articles. The second perforations may be formed based on the comparison between the determined average first air infusion value and the reference value.

This method may allow the production of a large number, a predetermined number of second ventilation zones based on the average first air infusion value determined from the production of the first ventilation zones.

The predetermined first number of first aerosol-generating articles may be at least 50, preferably at least 100, more preferably at least 1000 first aerosol-generating articles. The predetermined first number of first aerosol-generating articles may be the same as the predetermined second number of second aerosol-generating articles. This may allow the manufacturing of a large number of first and second ventilation zones, wherein the respective large first and second number of aerosol-generating articles has first and second air infusion values which are adjusted to the target air infusion value.

The reference value may be a target air infusion value for the first and second aerosolgenerating article. This may allow the production of the first and second ventilation zone in the first and second aerosol-generating articles wherein the respective first and second air infusion values are adjusted to the target air infusion value. The target air infusion value may be a target air infusion value for a first and second continuous rod.

The air infusion value may be different for a single first aerosol-generating article and for a first continuous rod, containing two aerosol-generating articles. The air infusion value for a single first aerosol-generating article or a continuous rod may be expressed as a percentage value and may be between 30 percent and 80 percent, preferably between 40 percent and 60 percent between 45 percent and 55 percent. These percent ranges for the air infusion value may be acceptable in order to manufacture aerosol-generating articles having an acceptable air infusion value. Preferably, the target air infusion value may be set between 40 percent to 60 percent, more preferably 50 percent for a single aerosol-generating article.

The air pressure applied to the first aerosol-generating article at the first end face during method step C) for determining the first air infusion value may be applied at constant air pressure. The air pressure applied to the first aerosol-generating article at the first end face may be between 5 millibars and 50 millibars, preferably between 10 millibars and 30 millibars, more preferably between 15 millibars to 18 millibars. This may provide a quick and easy method of determining the air infusion value of the aerosol-generating articles during manufacturing of the ventilation zones.

An air blast may be applied through a nozzle having a diameter of between 1 .6 to 2.0 millimeters, preferably 1.8 millimeters.

In particular, an air blast of 17 millibars may be applied at constant pressure to the first end face of the first aerosol-generating article for determining the first air infusion value. The first air infusion value may be determined at a temperature of 22 degrees Celsius, a pressure of about 101 kilopascal and a relative humidity of about 50 percent to 60 percent, preferably 60 percent. The time for applying the air blast may be between 25 milliseconds to 60 milliseconds.

The method for manufacturing first and second ventilation zones in the first and second aerosol-generating article may be controlled externally to the manufacturing process of the ventilation zone, for example in a laboratory. In the external controlling process, the air infusion value may be determined at constant air flow. This may be different to the determination of the air infusion value during the manufacturing process, which may be done at constant air pressure. Owing to the different measurement methods, an air infusion value determined during the manufacturing of the ventilation zones at constant air pressure may be different to the air infusion value for an aerosol-generating article determined in the laboratory at constant air flow. This may necessitate converting the air infusion values determined “in-line” at constant air pressure during the manufacturing process into the respective air infusion values determined in the laboratory at constant air flow.

The conversion between the air infusion values determined during the manufacturing of the ventilation zones at constant air pressure and the air infusion values determined in the laboratory at constant air flow may be done by applying a conversion factor. The conversion factor may be dependent on the resistance-to-draw (RTD) of the aerosol-generating articles.

Unless otherwise specified, the resistance to draw (RTD) of a component or the aerosol-generating article is measured in accordance with ISO 6565-2015. The RTD refers the pressure required to force air through the full length of a component. The terms “pressure drop" or “draw resistance" of a component or article may also refer to the “resistance to draw”. Such terms generally refer to the measurements in accordance with ISO 6565-2015 are normally carried out at under test at a volumetric flow rate of about 17.5 millilitres per second at the output or downstream end of the measured component at a temperature of about 22 degrees Celsius, a pressure of about 101 kPa (about 760 Torr) and a relative humidity of about 60%.

The RTD value may differ during the manufacturing process for the ventilation zones in the aerosol-generating article due to some variability in the tobacco used for the aerosolforming substrate between different aerosol-generating articles produced. These different RTD values also may influence the respective air infusion values of the aerosol-generating articles.

In a method step A2) before method step B) a first resistance-to-draw RTD value of the first aerosol-generating article may be measured. The resistance to draw value may be measured by applying a constant air flow to the first end face of the first aerosol-generating article and measuring the increase in air pressure at said first end face of the first aerosolgenerating article due to the air resistance of the article. The air flow may have a pressure of up to 2500 millibar, preferably 2100 millibar directed through a nozzle having a diameter of 0.2 millimeter.

Furthermore, individual first resistance to draw values may be determined for each of the first aerosol-generating articles of the predetermined first number of first aerosolgenerating articles.

Preferably, the individual first resistance to draw values are determined for a predetermined first number of first continuous rods. Each first continuous rod may contain two first aerosol-generating articles connected to each other.

The resistance to draw values of such a first continuous rod may be between 30 millimetres H2O to 160 millimetres H2O.

Individual first air infusion values of the first aerosol-generating articles determined in step C) at constant air pressure may be corrected on the basis of the first individual RTD values. This may provide corrected individual first air infusion values. These RTD corrected individual first air infusion values may correspond to the respective air infusion values measured in the laboratory at constant air flow. This may allow comparison between the first air infusion values determined in method step C) during the manufacturing of the first ventilation zones with the air infusion values determined in the laboratory at constant air flow.

In particular, a first compensation factor may be calculated taking into consideration the first RTD values determined. This first compensation factor may be determined, taking into consideration a first RTD value measured for a first continuous rod containing two first aerosolgenerating articles connected together, also denoted as “double stick”. The compensation factor may be experimentally determined for different aerosol-generating articles depending on the RTD values of the articles. An example for the determination of the compensation factor is shown in Figure 5. The compensation factor may be a percentage factor and may depend on the RTD values determined for the first continuous rods. The compensation factor may be between -20 percent and +20 percent, preferably between -8 percent and +4 percent. The compensation factor may be applied to the respective first air infusion values determined in method step C) during the production of the first ventilation zones. This may result in either subtracting or adding a certain percentage to the first air infusion values determined during the production at constant air pressure in order to obtain the respective air infusion values obtained in the laboratory at constant air flow.

In method step E) of one embodiment of the method of the present invention the average corrected first air infusion value may be compared to the reference value. Furthermore, in step E) the size of the second perforations may be adjusted based on the comparison between the average corrected first air infusion value and the reference value. This may allow adjusting the size of the second perforations based on the air infusion values obtained in the laboratory at constant air flow.

During method step D) a delta value may be calculated. The delta value may be the difference between the average corrected first air infusion value and the reference value. In method step E), the size of the second perforations may be adjusted based on the delta value.

The delta value may be 0 if the average corrected first air infusion value is the same as the reference value. According to one embodiment of the method for manufacturing a ventilation zone of the invention, the size of the second perforations may be adjusted in method step E) if the delta value is other than 0. In another embodiment of the method for manufacturing a ventilation zone of the invention, the size of the second perforations may only be adjusted in method step E) if the delta value is above a certain threshold. For example, the size of the second perforations may only be adjusted, if the delta value is below or above a value of -0.5 percent to 0.5 percent, preferably, the delta value preferably may be between - 0.3 percent and 0.3 percent, preferably between -0.2 percent and 0.2 percent. A delta value within the described ranges may not result in an adjustment of the size of the second perforations. A negative delta value may indicate, that the average corrected first air infusion value of the first predetermined number of first aerosol-generating articles is below the reference value. A positive delta value may indicate that the average corrected first air infusion value of the first predetermined number of first aerosol-generating articles is above the reference value.

In method step E) the size of the second perforations may be one of decreased or increased in comparison to the size of the first perforations.

In particular, the size of the second perforations may be increased in comparison to the size of the first perforations, if the corrected first air infusion value is smaller than the reference value. The size of the second perforations may be decreased in comparison to the size of the first perforations, if the corrected first air infusion value is larger than the reference value.

During method step B) slits or ovals may be formed as first perforations. These first perforations may in the first aerosol-generating article have a width and a length. During method step E) the length of the second perforations in the second aerosol-generating article may be adjusted. In particular during method step E) only the length of the second perforations may be adjusted, maintaining the same width as the first perforations. Adjustment may be done by one of increasing or decreasing the length of the second perforations in comparison to the length of the first perforations depending on the delta value.

First and second aerosol-generating articles with first and second air infusion values being too high or too low also might be rejected out of the production stream. In particular, first and second aerosol-generating articles with air infusion values being outside the range of between 30 percent and 80 percent may be rejected.

One or more of the first and second perforations may have a non-circular cross-section. One or more of the first and second perforations may be slit-shaped or may have an oval crosssection. Preferably, the one or more of the first and second perforations may have an ovality, the ovality being the ratio of a large diameter of a perforation divided by a small diameter of the perforation, of at least 1.5, preferably at least 2, preferably at least 3, more preferably at least 4, most preferably at least 5.

During one or both of method step B) and method step E) a laser device may be employed for forming the first and second perforations in the first and second aerosolgenerating articles or for adjusting the size of the second perforations in comparison to the first perforations.

In method step E) the laser device may be employed for adjusting the size of the perforations by changing the “set point of duty cycle” for the laser. The “duty cycle” of the laser device is the ratio between the time period, the laser is active, forming the perforations of the ventilation zone and the total time of cycle for forming the perforations. The higher the “duty cycle” the longer the time the laser is active and the larger the length of the perforations.

In method step E) a second air infusion value for the second aerosol-generating article may be determined. Furthermore, individual second air infusion values of the second aerosolgenerating articles of the predetermined second number of second aerosol-generating articles can be determined and an average of these individual second air infusion values can be calculated.

In a method step E) a second resistance-to-draw RTD value of the second aerosolgenerating article may be measured. If second perforations are formed in second aerosolgenerating articles of a predetermined second number of first aerosol-generating articles, individual second RTD values may be determined for each of the second aerosol-generating articles.

An average first RTD value may be calculated from the individual first RTD values of the first aerosol-generating articles. Similarly, an average second RTD value may be calculated from the individual second RTD values of the second aerosol-generating articles. The average first RTD value may in particular be determined for a predetermined first number of first continuous rods. The average second RTD value may be determined for a predetermined second number of second continuous rods.

The first continuous rods may be cut, in order to provide single first aerosol-generating articles. The first single air infusion values of the single first aerosol-generating articles may be determined. Similarly, the second continuous rods may be cut in order to provide single second aerosol-generating articles. The second single air infusion values of the single second aerosolgenerating articles may be determined. The first and second single air infusion values may be determined in a similar way to the air infusion value for the first aerosol-generating article described above.

The first air infusion values of the first continuous rods containing two single first aerosol-generating articles may be different to a first single air infusion value of one single first aerosol-generating article. Furthermore, the difference between the air infusion values of continuous rods containing two single aerosol-generating articles and the respective single air infusion values of the individual aerosol-generating articles created from the rods by cutting may also depend on the RTD values of the respective continuous rods. For example, a continuous rod with a filter section having a low resistance to draw value range of around 44 millimetres H2O to 59 millimetres H2O and having an air infusion value of 70 percent would result in an air infusion value of the respective single aerosol-generating article of 35 percent. A continuous rod with a filter section having a resistance to draw value range of 59 millimetres H2O to 71 millimetres H2O and having an air infusion value of 80 percent, will yield a single aerosol-generating article with an air infusion value of 50 percent after cutting. A continuous rod with a filter section having a resistance to draw of value range of around 71 millimetres H2O to 86 millimetres H2O with an air infusion value of 85 percent will result in a single aerosolgenerating article having an air infusion value of 59 percent after cutting.

There may be correlation between air infusion values of continuous rods and the respective single air infusion values of the single aerosol-generating articles produced by cutting the continuous rods. The correlation between the air infusion values of the continuous rods and the respective single rods may be dependent on the respective RTD values measured for the continuous rods. Therefore, measuring the RTD of the continuous rods before the manufacturing of the ventilation zones in the rod may allow to determine which air infusion value for the continuous rods is required in order to result in a desired air infusion value in single aerosol-generating articles after cutting. This will allow to adjust and set the reference value depending on the measured RTD of the continuous rods. This will allow the reference value for the air infusion values of the continuous rod to be set in such a way that single aerosol-generating articles can finally be produced having a desired air infusion value. This desired air infusion value for the single aerosol-generating articles after cutting the continuous rod may be 50 percent. If first and second continuous rods are produced as first and second aerosol-generating articles, the reference value may a target air infusion value for a continuous rod. This target air infusion value for the continuous rod may be set in such a way in order for the individual aerosol-generating article having a desired air infusion value after cutting of the continuous rod. This desired air infusion value for the individual aerosol-generating article may be 50 percent.

The method of manufacturing the ventilation zones in the aerosol-generating articles also may comprise setting the reference value in method step D) depending on the RTD value measured for the first aerosol-generating article in method step A2). Depending on whether a high, medium or low resistance to draw value has been measured, the reference value, in particular the reference air infusion value, more particular, the reference air infusion value for the continuous rod containing two aerosol-generating articles may be set. Since the air infusion value for the continuous rods can be assigned to air infusion values of the single aerosolgenerating articles after cutting the rods, desired single air infusion values can be obtained by setting the reference air infusion value of the continuous rod dependent on the RTD value measured for the rods.

During method step A) a first aerosol-generating article may be provided, wherein the first aerosol-generating article comprises a first hollow tube section and a first substrate section. Preferably, the first aerosol-generating article further may comprise a first filter section. The first hollow tube section may be located downstream of the first substrate section in the first aerosol-generating article.

Second aerosol-generating article may also comprise a second hollow tube section, and a second substrate section. Preferably, the second aerosol-generating article further may comprise a second filter section. The second hollow tube section may be located downstream of the second substrate section in the second aerosol-generating article.

In particular, the second aerosol-generating article may be structured in the same way as the first aerosol-generating article. The second aerosol-generating article may contain the same elements as the first aerosol-generating article.

A continuous first rod may contain two identical first aerosol-generating articles connected to each other. Similarly, a continuous second rod may contain two identical second aerosol-generating articles connected to each other. In the following the design of the first and second aerosol-generating articles will be described in greater detail. Any referral to an “aerosol-generating article” in general will therefore relate to both the first and second aerosolgenerating article. Continuous first rods and continuous second rods can be formed from the respective first and second aerosol-generating articles by connecting for example two first aerosol-generating articles.

As used herein, the terms “upstream", and “downstream", are used to describe the relative positions of sections of the aerosol-generating article or an aerosol-generating device used together with the aerosol-generating article in relation to the direction in which the aerosol is transported through the aerosol-generating article during use. The aerosol-generating article according to the invention comprises a proximal end through which, in use, an aerosol exits the aerosol-generating article. The proximal end of the aerosol generating device may also be referred to as the mouth end or the downstream end. In use, a user draws on the downstream or mouth end of the aerosol-generating article in order to inhale an aerosol generated by the aerosol-generating system. The aerosol-generating system comprises an upstream end opposed to the downstream or mouth end. The mouth end is downstream of the distal end. The distal end of the aerosol-generating device or aerosol-generating article may also be referred to as the upstream end. Components, or portions of components, of the aerosolgenerating article or the aerosol-generating device may be described as being upstream or downstream of one another based on their relative positions to the direction in which the aerosol is transported through the aerosol-generating article or the aerosol-generating device during use of the article or the aerosol generating device.

The filter section may be a cellulose acetate filter plug. The filter section may be approximately 7 mm in length in one embodiment, but may have a length of between approximately 5 mm to approximately 10 mm.

The hollow tube section may comprise one or both of a support section and an aerosolcooling section.

The substrate section may comprise aerosol-forming substrate.

The aerosol-forming substrate may have a length of approximately 10 mm. Alternatively, the aerosol-forming substrate may have a length of approximately 12 mm. Further, the diameter of the aerosol-forming substrate may be between approximately 5 mm and approximately 12 mm.

By way of example, the hollow tube section may further comprise a support element positioned immediately downstream of the aerosol-forming substrate, and an aerosol-cooling element may be located between the support element and the downstream end (or mouth end) of the aerosol-generating article. In more detail, the aerosol-cooling element may be positioned immediately downstream of the support element. In some preferred embodiments, the aerosolcooling element may abut the support element. The hollow tube section of aerosol-generating articles in accordance with the present invention preferably comprises an intermediate hollow section comprising a support element arranged in alignment with, and downstream of the rod of aerosol-forming substrate. In particular, the support element may be located immediately downstream of the rod of aerosolforming substrate and may abut the rod of aerosol-forming substrate.

The support element may be formed from any suitable material or combination of materials. For example, the support element may be formed from one or more materials selected from the group consisting of: cellulose acetate; cardboard; crimped paper, such as crimped heat resistant paper or crimped parchment paper; and polymeric materials, such as low density polyethylene (LDPE). In a preferred embodiment, the support element is formed from cellulose acetate. Other suitable materials include polyhydroxyalkanoate (PHA) fibres.

The support element may comprise a hollow tubular element. In a preferred embodiment, the support element comprises a hollow cellulose acetate tube.

The support element is arranged substantially in alignment with the rod. This means that the length dimension of the support element is arranged to be approximately parallel to the longitudinal direction of the rod and of the article, for example within plus or minus 10 degrees of parallel to the longitudinal direction of the rod. In preferred embodiments, the support element extends along the longitudinal axis of the rod.

The support element preferably has an outer diameter that is approximately equal to the outer diameter of the rod of aerosol-forming substrate and to the outer diameter of the aerosol-generating article.

The support element may have an outer diameter of between 5 millimetres and 12 millimetres, for example of between 5 millimetres and 10 millimetres or of between 6 millimetres and 8 millimetres. In a preferred embodiment, the support element has an external diameter of 7.2 millimetres plus or minus 10 percent. The support element may have a length of between 5 millimetres and 15 millimetres. In a preferred embodiment, the support element has a length of 8 millimetres.

A peripheral wall of the support element may have a thickness of at least 1 millimetre, preferably at least about 1 .5 millimetres, more preferably at least about 2 millimetres.

The support element may have a length of between about 5 millimetres and about 15 millimetres.

Preferably, the support element has a length of at least about 6 millimetres, more preferably at least about 7 millimetres.

In preferred embodiments, the support element has a length of less than about 12 millimetres, more preferably less than about 10 millimetres.

In some embodiments, the support element has a length from about 5 millimetres to about 15 millimetres, preferably from about 6 millimetres to about 15 millimetres, more preferably from about 7 millimetres to about 15 millimetres. In other embodiments, the support element has a length from about 5 millimetres to about 12 millimetres, preferably from about 6 millimetres to about 12 millimetres, more preferably from about 7 millimetres to about 12 millimetres. In further embodiments, the support element has a length from about 5 millimetres to about 10 millimetres, preferably from about 6 millimetres to about 10 millimetres, more preferably from about 7 millimetres to about 10 millimetres.

In a preferred embodiment, the support element has a length of about 8 millimetres.

A ratio between the length of the support element and the length of the rod of aerosolforming substrate may be from about 0.25 to about 1 .

Preferably, a ratio between the length of the support element and the length of the rod of aerosol-forming substrate is at least about 0.3, more preferably at least about 0.4, even more preferably at least about 0.5. In preferred embodiments, a ratio between the length of the support element and the length of the rod of aerosol-forming substrate is less than about 0.9, more preferably less than about 0.8, even more preferably less than about 0.7.

In some embodiments, a ratio between the length of the support element and the length of the rod of aerosol-forming substrate is from about 0.3 to about 0.9, preferably from about 0.4 to about 0.9, more preferably from about 0.5 to about 0.9. In other embodiments, a ratio between the length of the support element and the length of the rod of aerosol-forming substrate is from about 0.3 to about 0.8, preferably from about 0.4 to about 0.8, more preferably from about 0.5 to about 0.8. In further embodiments, a ratio between the length of the support element and the length of the rod of aerosol-forming substrate is from about 0.3 to about 0.7, preferably from about 0.4 to about 0.7, more preferably from about 0.5 to about 0.7.

In a particularly preferred embodiments, a ratio between the length of the support element and the length of the rod of aerosol-forming substrate is about 0.66.

A ratio between the length of the support element and the overall length of the aerosolgenerating article substrate may be from about 0.125 to about 0.375.

Preferably, a ratio between the length of the support element and the overall length of the aerosol-generating article substrate is at least about 0.13, more preferably at least about 0.14, even more preferably at least about 0.15. A ratio between the length of the support element and the overall length of the aerosol-generating article substrate is preferably less than about 0.3, more preferably less than about 0.25, even more preferably less than about 0.20.

In some embodiments, a ratio between the length of the support element and the overall length of the aerosol-generating article substrate is preferably from about 0.13 to about 0.3, more preferably from about 0.14 to about 0.3, even more preferably from about 0.15 to about 0.3. In other embodiments, a ratio between the length of the support element and the overall length of the aerosol-generating article substrate is preferably from about 0.13 to about 0.25, more preferably from about 0.14 to about 0.25, even more preferably from about 0.15 to about 0.25. In further embodiments, a ratio between the length of the support element and the overall length of the aerosol-generating article substrate is preferably from about 0.13 to about 0.2, more preferably from about 0.14 to about 0.2, even more preferably from about 0.15 to about 0.2.

In a particularly preferred embodiment, a ratio between the length of the support element and the overall length of the aerosol-generating article substrate is about 0.18.

Preferably, in aerosol-generating articles in accordance with the present invention the support element has an average radial hardness of at least about 80 percent, more preferably at least about 85 percent, even more preferably at least about 90 percent. The support element is therefore able to provide a desirable level of hardness to the aerosol-generating article.

If desired, the radial hardness of the support element of aerosol-generating articles in accordance with the invention may be further increased by circumscribing the support element by a stiff plug wrap, for example, a plug wrap having a basis weight of at least about 80 grams per square metre (gsm), or at least about 100 gsm, or at least about 110 gsm.

During insertion of an aerosol-generating article in accordance with the invention into an aerosol-generating device for heating the aerosol-forming substrate, a user may be required to apply some force in order to overcome the resistance of the aerosol-forming substrate of the aerosol-generating article to insertion. This may damage one or both of the aerosolgenerating article and the aerosol-generating device. In addition, the application of force during insertion of the aerosol-generating article into the aerosol-generating device may displace the aerosol-forming substrate within the aerosol-generating article. This may result in the heating element of the aerosol-generating device not being properly aligned with the susceptor provided within the aerosol-forming substrate, which may lead to uneven and inefficient heating of the aerosol-forming substrate of the aerosol-generating article. The support element is advantageously configured to resist downstream movement of the aerosol-forming substrate during insertion of the article into the aerosol-generating device.

In aerosol-generating articles in accordance with the present invention the overall RTD of the article depends essentially on the RTD of the substrate section and optionally on the RTD of filter section. This is because the hollow tubular section of the aerosol-cooling element and the hollow tubular section of the support element are substantially empty and, as such, substantially only marginally contribute to the overall RTD of the aerosol-generating article.

The overall RTD value of the single aerosol-generating article with the ventilation zone produced according to the method of the present invention and after cutting of the continuous rod may be between approximately 30 millimetres H₂O to approximately 70 millimetres H₂O, preferably between approximately 40 millimetres H₂O to approximately 60 millimetres H₂O.. The aerosol-forming substrate may comprise an aerosol-former. An aerosol-former is any suitable known compound or mixture of compounds that, in use, facilitates formation of a dense and stable aerosol and that is substantially resistant to thermal degradation at the temperature of operation of the aerosol-generating system. Suitable aerosol-formers may include, but are not limited to: polyhydric alcohols, such as triethylene glycol, 1 ,3-butanediol and glycerine; esters of polyhydric alcohols, such as glycerol mono-, di- or triacetate; and aliphatic esters of mono-, di- or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate. Aerosol formers may be polyhydric alcohols or mixtures thereof, such as triethylene glycol, 1 ,3-butanediol and glycerine. The aerosol-former may be propylene glycol. The aerosol former may include both glycerine and propylene glycol. The aerosol former may only include glycerine.

The aerosol-former may be present in an amount of 20 weight percent to 58 percent, preferably 25 weight percent to 45 weight percent, more preferred 30 weight percent to 38 weight percent on a dry weight basis based on the total amount of the aerosol-forming substrate. The term “dry weight basis” throughout the application refers to the weight of the aerosol-forming substrate calculated with the water removed via Karl-Fischer titration, for example after being heated to a temperature of 1 10 degrees Celsius at standard conditions for temperature and pressure and using potentiometry to determine the endpoint. The end point is detected by a bipotentiometric titration method. A second pair of Pt electrodes is immersed in the anode solution. The detector circuit maintains a constant current between the two detector electrodes during titration. Prior to the equivalence point, the solution contains I-, but little I2. At the equivalence point, excess I2 appears and an abrupt voltage drop marks the endpoint. The amount of charge needed to generate I2 and reach the endpoint can then be used to calculate the amount of water in the original sample. The aerosol-former content can be measured by gas chromatography in combination with a flame ionization detector.

In certain preferred embodiments, the aerosol-forming substrate may comprise homogenised plant material, preferably a homogenised tobacco material.

As used herein, the term “homogenised plant material’ encompasses any plant material formed by the agglomeration of particles of plant. For example, sheets or webs of homogenised tobacco material for the aerosol-forming substrates of the present invention may be formed by agglomerating particles of tobacco material obtained by pulverising, grinding or comminuting plant material and optionally one or more of tobacco leaf lamina and tobacco leaf stems. The homogenised plant material may be produced by casting, extrusion, paper making processes or other any other suitable processes known in the art.

The homogenised plant material can be provided in any suitable form. For example, the homogenised plant material may be in the form of one or more sheets. As used herein with reference to the invention, the term “sheet” describes a laminar element having a width and length substantially greater than the thickness thereof.

The homogenised plant material may be in the form of a plurality of pellets or granules.

The homogenised plant material may be in the form of a plurality of strands, strips or shreds. As used herein, the term “strand” describes an elongate element of material having a length that is substantially greater than the width and thickness thereof. The term “strand” should be considered to encompass strips, shreds and any other homogenised plant material having a similar form. The strands of homogenised plant material may be formed from a sheet of homogenised plant material, for example by cutting or shredding, or by other methods, for example, by an extrusion method.

The tobacco particles may have a nicotine content of at least about 2.5 percent by weight, based on dry weight. More preferably, the tobacco particles may have a nicotine content of at least about 3 percent, even more preferably at least about 3.2 percent, even more preferably at least about 3.5 percent, most preferably at least about 4 percent by weight, based on dry weight.

At least one susceptor element may be located in the substrate section. In general, the susceptor may comprise or maybe made of a material that is capable of generating heat, when penetrated by an alternating magnetic field. If the susceptor is conductive, then typically eddy currents are induced by the alternating magnetic field. If the susceptor is magnetic, then typically another effect that contributes to the heating is commonly referred to hysteresis losses. Hysteresis losses occur mainly due to the movement of the magnetic domain blocks within the susceptor, because the magnetic orientation of these will align with the magnetic induction field, which alternates. Another effect contributing to the hysteresis loss is when the magnetic domains will grow or shrink within the susceptor. Commonly all these changes in the susceptor that happen on a nano-scale or below are referred to as “hysteresis losses", because they produce heat in the susceptor. Hence, if the susceptor is both magnetic and electrically conductive, both hysteresis losses and the generation of eddy currents will contribute to the heating of the susceptor particles. If the susceptor is magnetic, but not conductive, then hysteresis losses will be the only means by which the susceptor will heat, when penetrated by an alternating magnetic field. An alternating magnetic field generated by one or several induction coils heat the susceptor, which then transfers the heat to the other components of the aerosol-forming substrate. This may facilitate the formation of an aerosol. The heat transfer may be mainly by conduction of heat.

The susceptor may be ferromagnetic. The ferromagnetic susceptor may comprise or consist of a metal or metal oxide. The ferromagnetic susceptor may comprise one or more of iron, cobalt and nickel or the oxides thereof. Preferably, the susceptor may comprise or consist of Fe2C>3. The aerosol-generating article may further comprise a filter plug in the filter section downstream of the ventilation zone. The resistance to draw (RTD) of the filter plug may be between 5 millimetres H2O and 80 millimetres H2O, preferably between 10 millimetres H2O and 65 millimetres H2O, more preferably between 15 millimetres H2O and 50 millimetres H2O, more preferably between 20 millimetres H2O and 40 millimetres H2O, most preferably 30 millimetres H₂O.

During method step B) the perforations may be formed in the hollow tube section. A ventilation zone in the hollow tube section may allow ambient air to easily enter the aerosolgenerating article during a user’s puff. The ventilation zone in the hollow tube section may be arranged downstream of the substrate section. This may allow an airflow or an aerosol resulting from the aerosol-forming substrate of the substrate section to be mixed with the ambient air entering the aerosol-generating article through the perforations and to be cooled down. This may improve aerosol generation.

The ventilation zone formed during method step B) may comprise between 5 and 15 perforations, preferably between 7 and 14 perforations, more preferably between 9 and 13 perforations, more preferably between 10 and 12 perforations, most preferably 11 perforations.

The ventilation zone may comprise between 10 and 12 perforations.

Having a ventilation zone with perforations may enable that ambient air is drawn into the ventilation zone. This ambient air may mix with air drawn through the substrate section. Substrate section may be heated by an aerosol-generating device so that the aerosol-forming substrate is volatilized. The volatilized aerosol-forming substrate may be entrained in the air flowing through the rod of aerosol-forming substrate. This airflow mixes with the ambient air downstream of the substrate section in the ventilation zone. The mix of ambient air with the air drawn through the substrate section cools down to form an aerosol. Having a relatively low number of perforations, particularly 10 to 12 perforations, improves the mixing of ambient air drawn through the perforations into the ventilation zone with the air drawn into the ventilation zone through the substrate section. This improved mixing may result in an improved aerosol generation. Without being bound to any theory, a number of 10 to 12 perforations have been found to lead to the best mixture of ambient air and air carrying volatilized aerosol-forming substrate. The reason may be that this relatively small number of perforations necessitate relatively large perforations to enable a sufficient amount of ambient air being drawn into the ventilation zone. Relatively large perforation may lead to relatively strong turbulences between the two airflows and thus to an improved mixing of the two airflows. The airflow coming from the perforations may be strong enough to break the main airflow coming from the aerosolforming substrate thereby improving mixing of the airflows.

The ventilation zone may comprise 11 perforations. This number of perforations has shown to lead to the best mixing of ambient air with air carrying volatilized aerosol-forming substrate.

The perforations may be arranged surrounding the ventilation zone. The perforations may be arranged at least partly surrounding the ventilation zone.

During method step A) a continuous rod may be provided as the aerosol-generating article. The continuous rod may include up to 10 individual aerosol-generating articles, preferably up to five individual aerosol-generating articles, more preferably up to two individual aerosol-generating articles. Most preferably, the continuous rod may include two individual aerosol-generating articles. The individual aerosol-generating articles may be produced by cutting the continuous rod into individual aerosol-generating articles. The continuous rod may include two individual aerosol-generating articles connected to each other, wherein the downstream filter sections of both single aerosol-generating articles are located adjacent to each other in the continuous rod.

An individual aerosol-generating article may comprise an upstream substrate section, at least one hollow tube section which is located downstream of the substrate section, preferably, wherein the hollow tube section is adjacent to the substrate section. Further downstream of the at least one hollow tube section, a filter section may be located, for example a filter plug, such as a cellulose acetate filter plug.

The aerosol-generating article produced by the method of the present invention may be used in an aerosol-generating system. The aerosol-generating system may comprise an aerosol-generating article as described herein and an aerosol-generating device comprising a cavity for receiving the aerosol-generating article.

Such an aerosol-generating system may be configured to provide an aerosol from the aerosol-forming substrate of the substrate section of the aerosol-generating article as described herein.

The cavity of the aerosol-generating device may comprise inner walls with sections protruding inwards into the cavity. These protruding sections may contact the aerosolgenerating article received in the cavity. These protruding sections may allow the formation of an air flow path between the inner walls of the cavity and the aerosol-generating article. This may also allow the formation of an airflow path leading to the above-described ventilation zone of the aerosol-generating article.

The aerosol-generating device may include a heating element, in particular an inductive heating element, such as an inductive coil. Upon inductive heating of the aerosol-forming substrate of the aerosol-generating article received in the aerosol-generating device, the susceptor may be heated by the alternating magnetic field of the inductive heating element. This may also heat the aerosol-forming substrate. For induction heating, the heating element preferably comprises an induction coil. An alternating current may be supplied to the induction coil for generating an alternating magnetic field. The alternating current may have a high frequency. As used herein, the term "high frequency oscillating current means an oscillating current having a frequency of between 500 kilohertz and 30 megahertz. The high frequency oscillating current may have a frequency of from about 1 megahertz to about 30 megahertz, preferably from about 1 megahertz to about 10 megahertz and more preferably from about 5 megahertz to about 8 megahertz.

The heating element may be configured to heat the aerosol-generating article to a temperature ranging from 220 degrees Celsius to 400 degrees Celsius, preferably from 250 degrees Celsius to 290 degrees Celsius. The heating element may be configured to heat the aerosol-generating article, in particular the aerosol-forming substrate to a temperature below the combustion temperature of the aerosol-forming substrate. This may allow the use of an aerosol generated from a “heat not burn" aerosol-generating article.

The heating element may be configured as a resistive heating element. The heating element may be configured as a resistive heating coil, at least partly surrounding the cavity, for receiving the aerosol-generating article.

The heating element may be located adjacent to the cavity for receiving the aerosolgenerating article. The heating element may be located at least partly around the cavity for heating an aerosol-generating article received in the cavity. The heating element may surround a perimeter of the cavity for receiving the aerosol-generating article. This may allow a reliable and uniform heating of the substrate section of the aerosol-generating article.

Below, there is provided a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

Example A: Method for manufacturing a first ventilation zone in a first aerosolgenerating article and a second ventilation zone in a second aerosol-generating article, comprising the method steps:

A) providing a first aerosol-generating article,

B) forming first perforations in the first aerosol-generating article, thereby creating a first ventilation zone,

C) determining the first air infusion value for the first aerosol-generating article, the air infusion value being determined by the equation (Pin-Pou ’IOC /o/Pin, wherein P_in is the air pressure applied at the first end face of the article and P_out is the air pressure detected at the second end face of the article,

D) comparing said first air infusion value to a reference value,

E) providing the second aerosol-generating article and forming second perforations in the second aerosol-generating article, thereby creating the second ventilation zone, wherein a size of the second perforations is adjusted based on the comparison between the determined first air infusion value and the reference value.

Example B: Method for manufacturing according to the preceding example, wherein during method step C) an air blast is applied to the first aerosol-generating article and a pressure difference is measured between both opposing first and second end faces of the first aerosol-generating article.

Example C: Method according to any of the preceding examples, wherein a first continuous rod is provided as a first aerosol-generating article and wherein a second continuous rod is provided as a second aerosol-generating article, wherein the first continuous rod and the second continuous rod includes at least two aerosol-generating articles, preferably wherein the first continuous rod and the second continuous rod consists of two aerosolgenerating articles.

Example D: Method according to any of the preceding examples for manufacturing a first ventilation zone in a predetermined first number of first aerosol-generating articles, wherein during the method steps A) and B) the predetermined first number of first aerosolgenerating articles is provided and wherein first perforations are formed in each of the first aerosol-generating articles of the predetermined first number of first aerosol-generating articles and wherein during method step C) the individual first air infusion values of the first aerosolgenerating articles are determined and wherein an average first air infusion value thereof is calculated.

Example E: Method according to the preceding example further for manufacturing a second ventilation zone in a predetermined second number of second aerosol-generating articles, wherein during method step E) the predetermined second number of second aerosolgenerating articles is provided and wherein second perforations are formed in each of the second aerosol-generating articles of the predetermined second number of first aerosolgenerating articles based on the comparison between the determined average first air infusion value and the reference value.

Example F: Method for manufacturing according to any of the preceding examples, wherein the reference value is a target air infusion value for the first and second aerosolgenerating article.

Example G: Method for manufacturing of any of the preceding examples, wherein in a method step A2) before method step B) a first resistance-to-draw RTD value of the first aerosol-generating article is measured, more preferably wherein the RTD value is measured by applying a constant air flow to the first end face of the first aerosol-generating article and measuring the increase in air pressure at said first end face of the first aerosol-generating article due to the air resistance of the article. Example H: Method according to the preceding example further dependent on example D, wherein individual first RTD values are determined for each of the first aerosolgenerating articles of the predetermined first number of first aerosol-generating articles.

Example I: Method for manufacturing according to the preceding example, wherein the individual first air infusion values of the first aerosol-generating articles determined in step C) are corrected on the basis of the first individual resistance-to-draw (RTD) values, thereby providing corrected individual first air infusion values and wherein an average corrected first air infusion value is calculated based on the corrected individual first air infusion values.

Example J: Method of manufacturing according to the preceding example, wherein in step E) the average corrected first air infusion value is compared to the reference value and wherein in step E) the size of the second perforations is adjusted based on the comparison between the average corrected first air infusion value and the reference value.

Example K: Method of manufacturing according to any of the preceding examples, wherein in method step E) a second air infusion value for the second aerosol-generating article is determined, preferably according to claim 5, wherein individual second air infusion values of the second aerosol-generating articles are determined and wherein an average second air infusion value thereof is calculated.

Example L: Method of manufacturing according to any of the preceding examples, wherein a second resistance-to-draw RTD value of the second aerosol-generating article is measured, more preferably according to claim 5, wherein individual second RTD values are determined for each of the second aerosol-generating articles of the predetermined second number of first aerosol-generating articles.

Example M: Method according to the preceding example further according to example H, wherein an average first RTD value is calculated from the individual first RTD values of the first aerosol-generating articles and wherein an average second RTD value is calculated from the individual second RTD values of the second aerosol-generating articles of the predetermined second number of first aerosol-generating articles.

Example N: Method according to the preceding example wherein the reference value is set in method step D) depending on the RTD value measured for the first aerosolgenerating article in method step A2).

Example O: Method for manufacturing an aerosol-generating article of the preceding examples D, E and H to O, wherein the predetermined first number of aerosol-generating articles is the same as the predetermined second number of aerosol-generating articles, preferably wherein the predetermined first and second number of aerosol-generating articles is at least 50, preferably at least 100, more preferably at least 1000 aerosol-generating articles.

Example P: Method for manufacturing an aerosol-generating article of the preceding example I, wherein during method step D) a delta value being the difference between the average corrected first air infusion value and the reference value is calculated and wherein in method step E), the size of the second perforations is adjusted based on the delta value.

Example Q: Method of manufacturing according to the preceding example, wherein in step E) the size of the second perforations is one of decreased or increased in comparison to the size of the first perforations.

Example R: Method for manufacturing of any of the preceding examples, wherein during method step C) the air infusion value in the aerosol-generating article is determined at constant air pressure at the first end face.

Example S: Method for manufacturing of any of the preceding examples, wherein during method step B) slits or ovals are formed as first perforations, the first perforations having a width and a length, and wherein during method step E) the length of the second perforations is adjusted.

Example T: Method for manufacturing of any of the preceding examples, wherein during method steps B) and method step E) a laser device is employed for forming the first and second perforations and increasing the size of the first and second perforations.

Example II: Method for manufacturing of any of the preceding examples, wherein during method step A) a first aerosol-generating article is provided, wherein the first aerosolgenerating article comprises a first hollow tube section and a first substrate section, preferably wherein the first aerosol-generating article further comprises a first filter section.

Example V: Method for manufacturing of the preceding example, wherein during method step B) the first perforations are formed in the first hollow tube section.

Features described in relation to one embodiment may equally be applied to other embodiments of the invention.

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

Fig. 1 shows a flow chart of one embodiment of a method of the present invention;

Fig. 2 depicts a flow chart of another embodiment of a method of the present invention also involving the calculation of the RTD value;

Fig. 3 depicts a schematic cross-sectional view of a continuous rod including two individual aerosol-generating articles with ventilation zones produced according to the present invention;

Fig. 4 depicts a schematic view of one single perforation of a ventilation zone produced according to the present invention.

Fig. 5 depicts a graph showing the compensation factor for the conversion of an air infusion value of an aerosol-generating article measured during the method of manufacturing the ventilation zone and the respective air infusion value determined in the laboratory. Fig. 6 shows a graph depicting the correlation between the RTD value of a double stick and the target air infusion value of the ventilation zones to be manufactured in the double stick in order to obtain a desired air infusion value of 50 percent for the individual articles after cutting of the double stick.

In the following the same elements are marked with the same reference numerals throughout all the figures.

Fig. 1 depicts a flow chart of one embodiment of the present invention. In a method step A) a first continuous rod, in particular including two individual first aerosol-generating articles without any ventilation zone is provided as indicated by the box titled “assembled stick’. In the second method step B) first perforations are generated in the aerosol-generating article, in particular in its first hollow tube section as indicated by the box titled “perforations". This can be done for example by employing a laser. In the third step C) the first air infusion value for the continuous first rod, including two individual first aerosol-generating articles is determined as shown in the box titled “air infusion measure (on double stick)". In the next step D) the air first infusion value is compared to a reference value (box titled “air infusion within targets"). If the measured first air infusion value is below or above the reference value, then the perforation parameters of the laser are adapted. The size of the second perforations within the second ventilation zone of the subsequently processed second aerosol-generating article in particular their length are increased or decreased in the subsequent method step E) in order to obtain a second aerosol-generating article with a new second air infusion value which is closer to the reference value, as indicated by the box titled “perforation parameters are adapted (length of the slits)".

Fig. 2 depicts a flow chart of another embodiment of the method of the invention. This embodiment of the method of the present invention includes the same method steps A), B), C), D) and E) as the method described above in Fig. 1. Additionally, this embodiment of the invention comprises a method step A2) before method step B) wherein individual first RTD values of a predetermined first plurality of first aerosol-generating articles are measured and wherein the average thereof is determined (box titled “RTD calculation"). Method step D) then both includes the application of an RTD correction factor based on the average of the RTD values determined in method step A2) to the air infusion values determined in method step C) and the comparison of this RTD corrected value with the reference value (boxes denoted “RTD correction factor applied to measure" and box titled “air infusion within targets").

Fig. 3 depicts a schematic cross-sectional view of a first continuous rod 11 including two separate individual first aerosol-generating articles 10, thereby forming a double stick. Such a double stick may be typically employed by the method of the present invention in order to produce two first ventilation zones in the double stick. A second continuous rod may include the same components and the same aerosol-generating articles as the first continuous rod. These individual first aerosol-generating articles 10 can be generated from the first continuous rod 1 1 by cutting the continuous rod along the dashed line 10A. The two individual aerosolgenerating articles 10 are connected to each other via their respective mouth end filter elements 20. These mouth end filter elements 20 are adjacent to the hollow tube section 14, which consists of the hollow support element 16 and the aerosol-cooling element 18. This hollow tube section 14 is adjacent to the substrate section 22 in the individual aerosolgenerating articles 10, wherein each substrate section 22 contains of susceptor 24. This substrate section 22 is flanked in each aerosol-generating article by the filter element 26. In the continuous rod two first ventilation zones 12 have been formed during the method step B) of the present invention in the hollow tube sections 14 of each individual first aerosolgenerating article. The air infusion value of such a first continuous rod 11 can be measured by applying a certain pressure to the first end face 11 A of the rod and determining the air pressure having passed through the rod at the second end face 11 B of the rod. The air pressure measured at the second end face 1 1 B of the rod will be lower than the air pressure applied the first end face 1 1 A, because air has passed through the perforations of the ventilation zones 12 reducing the air pressure.

The length of such a double stick may be 90 millimeters. Consequently, the length of the individual aerosol-generating articles after cutting of the double stick may be 45 millimeters. The diameter of the double stick may be 7.25 mm.

Fig. 4 shows a schematic view of one individual perforation 12A of the larger ventilation zones 12 depicted in Fig. 3. The perforation 12A has an oval shape with a width 13 and a length 15. Preferably, during method step E) of the method of the present invention only the length 15 is increased in order to better adapt the measured air infusion value to the reference value.

Fig. 5 shows a graph indicating the compensation factor for correcting the air infusion value determined during the method for manufacturing the ventilation zone based on the RTD value in order to obtain the respective air infusion value under laboratory conditions at constant airflow. The graph was obtained by fitting a curve into the respective individual values indicated by the black dots. The graph shows that for an RTD value of the double stick of around 60 mm Wg the compensation factor is around -5 percent. For an RTD value of the double stick of around 100 mmWg the correction factor would be 0. For high RTD values of the double stick of around 140 mmWg the correction factor would be around 2 percent.

Fig. 6 shows a graph depicting the correlation between the RTD value of a double stick and the respective air infusion value of the double stick which should be set as a reference value in order to obtain individual aerosol-generating articles with a desired air infusion value of 50 percent after cutting the double stick. The graph shows that the correlation between the air infusion of the double stick and the resulting air infusion of the individual aerosol-generating article after cutting off the double stick depends on the resistance to draw value of the double stick.

Claims

-26- CLAIMS

1 . Method for manufacturing a first ventilation zone in a first aerosol-generating article and a second ventilation zone in a second aerosol-generating article, comprising the method steps:

A) providing a first aerosol-generating article,

C) determining the first air infusion value for the first aerosol-generating article, the air infusion value being determined by the equation (Pin-Pout)^,100%/Pin, wherein P_in is the air pressure applied at the first end face of the article and P_out is the air pressure detected at the second end face of the article,

D) comparing said first air infusion value to a reference value,

2. Method for manufacturing according to the preceding claim, wherein during method step C) an air blast is applied to the first aerosol-generating article and a pressure difference is measured between both opposing first and second end faces of the first aerosolgenerating article.

3. Method according to any of the preceding claims, wherein a first continuous rod is provided as a first aerosol-generating article and wherein a second continuous rod is provided as a second aerosol-generating article, wherein the first continuous rod and the second continuous rod includes at least two aerosol-generating articles, preferably wherein the first continuous rod and the second continuous rod consists of two aerosol-generating articles.

4. Method according to any of the preceding claims for manufacturing a first ventilation zone in a predetermined first number of first aerosol-generating articles, wherein during the method steps A) and B) the predetermined first number of first aerosol-generating articles is provided and wherein first perforations are formed in each of the first aerosolgenerating articles of the predetermined first number of first aerosol-generating articles and wherein during method step C) the individual first air infusion values of the first aerosol- generating articles are determined and wherein an average first air infusion value thereof is calculated.

5. Method for manufacturing according to any of the preceding claims, wherein the reference value is a target air infusion value for the first and second aerosol-generating article.

6. Method for manufacturing of any of the preceding claims, wherein in a method step A2) before method step B) a first resistance-to-draw RTD value of the first aerosolgenerating article is measured, more preferably wherein the RTD value is measured by applying a constant air flow to the first end face of the first aerosol-generating article and measuring the increase in air pressure at said first end face of the first aerosol-generating article due to the air resistance of the article.

7. Method according to the preceding claim further dependent on claim 4, wherein individual first RTD values are determined for each of the first aerosol-generating articles of the predetermined first number of first aerosol-generating articles.

8. Method for manufacturing according to the preceding claim, wherein the individual first air infusion values of the first aerosol-generating articles determined in step C) are corrected on the basis of the first individual resistance-to-draw (RTD) values, thereby providing corrected individual first air infusion values and wherein an average corrected first air infusion value is calculated based on the corrected individual first air infusion values.

9. Method of manufacturing according to the preceding claim, wherein in step E) the average corrected first air infusion value is compared to the reference value and wherein in step E) the size of the second perforations is adjusted based on the comparison between the average corrected first air infusion value and the reference value.

10. Method according to the preceding claim further according to claim 7, wherein an average first RTD value is calculated from the individual first RTD values of the first aerosolgenerating articles and wherein an average second RTD value is calculated from individual second RTD values of the second aerosol-generating articles of the predetermined second number of first aerosol-generating articles.

11 . Method according to the preceding claim wherein the reference value is set in method step D) depending on the RTD value measured for the first aerosol-generating article in method step A2).

12. Method for manufacturing an aerosol-generating article of the preceding claims 4, 7 and 8, wherein the predetermined first number of aerosol-generating articles is the same as the predetermined second number of aerosol-generating articles, preferably wherein the predetermined first and second number of aerosol-generating articles is at least 50, preferably at least 100, more preferably at least 1000 aerosol-generating articles.

13. Method of manufacturing according to the preceding claims, wherein in step E) the size of the second perforations is one of decreased or increased in comparison to the size of the first perforations.

14. Method for manufacturing of any of the preceding claims, wherein during method step B) slits or ovals are formed as first perforations, the first perforations having a width and a length, and wherein during method step E) the length of the second perforations is adjusted.

15. Method for manufacturing of any of the preceding claims, wherein during method step A) a first aerosol-generating article is provided, wherein the first aerosolgenerating article comprises a first hollow tube section and a first substrate section, preferably wherein the first aerosol-generating article further comprises a first filter section.