Patent Publication Number: US-2023147576-A1

Title: Multi-channel and reversed airflow mouthpiece for an aerosol-generating article comprising activatable element

Description:
The present invention relates to a mouthpiece for an aerosol-generating article, an aerosol-generating system comprising the mouthpiece and the aerosol-generating article, and to a method for assembling the mouthpiece. 
     Today a number of different aerosol-generating systems are known in which inhalable vapor is generated in different ways. In the so-called e-vaping devices a liquid aerosol-forming substrate is vaporized by electrically powered heating devices. In heat-not-burn devices, a solid aerosol-forming substrate that may contain tobacco material is heated but not burned. These heat-not-burn devices may be electrically powered. There are also heat-not-burn systems in which heat is generated by combustion or chemical reactions. 
     In all these systems the aerosol-forming substrate is vaporized by the heating element and then aerosol is formed. Aerosol formation, in particular droplet size, total particulate matter yield (TPM), aerosol temperature or homogeneity of the aerosol, depends upon multiple factors, such as cooling of the air downstream of the aerosol-forming substrate and air pressure. Aerosol formation also depends on environmental conditions, such as temperature, air pressure or humidity. Accordingly changes in average temperature and humidity levels may be relevant factors that affect aerosolization formation in aerosol-generating systems. 
     It would be desirable to provide a mouthpiece for an aerosol-generating system to improve aerosol generation. 
     It would be desirable to provide a mouthpiece for an aerosol-generating system which allows the aerosol-generating system to reach optimized aerosolization independent from the environmental or climate conditions. 
     It would be desirable to provide an adjustable mouthpiece that may be configured during use to influence aerosolization characteristics and to meet user preferences. In particular, it would be desirable to provide an adjustable mouthpiece in which cooling characteristics and flavoring characteristics may be tuned during use to meet user preferences. 
     According to an embodiment of the invention there is provided a mouthpiece for an aerosol-generating article. The mouthpiece is formed from at least two main parts that can be axially inserted into each other to define an aerosol flow path. The two main parts are axially moveable relative to each other between a first assembled position and a second assembled position. The mouthpiece further comprises an activatable element for modifying, upon activation, a characteristic of an aerosol. The activatable element is activated upon movement of the two main parts from the first assembled position into the second assembled position. 
     The mouthpiece of the present invention allows managing the air-flow along the aerosol flow path from the aerosolization point of an aerosol-generating device towards an outlet of the mouthpiece. In particular, the possibility of activating the activatable element may be used to personally adapt the inhalation conditions that modify aspects of the generated aerosol, such as flavor, droplet size, temperature, or total particulate matter yield. 
     The aerosol flow path of the mouthpiece may include a plurality of channels. The total length of the aerosol flow path is defined by the sum of the lengths of each individual channel. The channels may be arranged such that the total length of the aerosol flow path may be greater than the axial length of the mouthpiece. Thus, by the specific arrangement of the channels, an effective extension of the airflow path is achieved in respect of conventional mouthpieces with only one generally linear airflow channel. Extension of the airflow path enhances cooling and homogenization of the aerosol. 
     The channels may be tubular channels. The tubular channels may be co-axially arranged within the mouthpiece. The inlet end of the mouthpiece may be in direct fluid connection with a tubular channel that is arranged along the central longitudinal axis of the mouthpiece. The airflow path may then continue through the one or more further co-axially arranged channels. The outermost of the co-axially arranged tubular channels is in direct fluid connection with the outlet end of the mouthpiece. 
     With the co-axial arrangement of the tubular channels, a well-defined and symmetric airflow path through the mouthpiece is provided. Such symmetric design allows for optimal and repeatable inhalation conditions. 
     In embodiments of the mouthpiece, the aerosol flow direction through the plurality of channels may differ. The aerosol flow direction through the plurality of channels may be reversed between each consecutively arranged aerosol flow channels. In this way the aerosol is guided multiple times through the mouthpiece from the inlet end to the outlet end such that a significant extension of the airflow path is achieved. 
     Within the airflow path of the mouthpiece, a plurality of expansion chambers may be formed. These expansion chambers may be formed at the reversal points between two consecutively arranged tubular channels. The expansion chambers may affect the aerosol characteristics by temporarily expanding the airflow volume and by reversing the airflow direction. In this way a homogeneous aerosol with a desired particle size may be obtained. In addition, the temperature of the aerosol may be reduced by the expansion. 
     The outermost tubular channel may extend to the outlet end of the mouthpiece and may define an annular or ring-shaped outlet end of the mouthpiece. 
     The mouthpiece may have any desired outer shape. Advantageously, the mouthpiece has an outer shape that corresponds to the outer shape of the aerosol-generating devices to which the mouthpiece is to be attached. For example, the mouthpiece may have a tubular or cylindrical outer shape and may define a central, longitudinal axis. 
     The outlet end of the mouthpiece may have any other desired form and may be formed by the outer wall of the mouthpiece. The mouthpiece may comprise a cavity recessed from the outlet end of the mouthpiece. This cavity may also be denoted as a volumetric recess. Such volumetric recess may be regarded as a final expansion chamber of the airflow path. Accordingly, the volumetric recess may contribute to homogenization of the aerosol and in particular may facilitate cooling of the aerosol. A recessed outlet may enable to reach further enhanced aerosolization at the outlet end of the mouthpiece, and therefore different perception and satisfaction of the consumer. 
     The mouthpiece may comprise a central channel that extends from the inlet end and that radially diverges along the direction of the aerosol flow. The mouthpiece may further comprise at least two tubular channels that are co-axially arranged in respect of the central channel and that are in fluid communication with the central channel. The aerosol flow direction through these three channels may be reversed between each consecutively arranged aerosol flow channels. Accordingly, in the central channel, the direction of the airflow runs from the inlet end towards the outlet end. In the adjacent second tubular channel, the airflow direction is reversed and runs from the outlet and towards the inlet end. At the end of the second tubular channel, airflow direction is again inverted such that in the third tubular channel, the airflow direction is again directed towards the outlet end. At the end of the third tubular channel, the aerosol is discharged from the mouthpiece. 
     In this way the aerosol is guided multiple times through the mouthpiece from the inlet end to the outlet end such that a significant extension of the airflow path is achieved. 
     In order to further alter the characteristic of the aerosol, the mouthpiece comprises an activatable element. The activatable element may comprise a substance for modifying a property of the aerosol that is guided through the mouthpiece. Before activation of the activatable element, the substance is prevented from interaction with the aerosol. Upon activation of the activatable element, the substance is released and is allowed to modify a property of the aerosol. This property may be one or more of a sensorial property of the aerosol, a dimensional property of the aerosol and a flavor of the aerosol. 
     The activatable element may comprise a breakable capsule in which the substance for modifying said property of the aerosol is contained. Upon activation of the activatable element, the capsule of the encapsulated liquid may be ruptured and the previously encapsulated liquid may be freed into the vicinity of the activatable element. 
     The activatable element may comprise a substrate. The substrate may be used as a support for the capsule holding the encapsulated liquid. The capsule holding the encapsulated liquid may be attached to the substrate. 
     The substrate may be configured to be porous and to take up the previously encapsulated liquid after activation. The porous material may take up at least a part of the previously encapsulated liquid. The porous material may be configured to take up all of the previously encapsulated liquid. By configuring the substrate to be able to take up all of the freed, previously encapsulated liquid, the liquid will at any time be safely retained within the mouthpiece. In particular, it can be avoided that the liquid leaves the mouthpiece through its outlet end. 
     The substrate may be a low-density material that has a low resistance to draw (RTD). Due to its low resistance to draw, the substrate does not significantly affect the overall resistance to draw of the mouthpiece. 
     The substrate may be provided such as to extend at least partly over the cross section of the aerosol flow path within the mouthpiece when the main parts are in the second assembled position. The substrate may extend over at least 50 percent of the cross section of the aerosol-flow path. The substrate may extend over at least 70 percent of the cross section of the aerosol-flow path. The substrate may extend over at least 90 percent of the cross section of the aerosol-flow path. The substrate may extend over substantially the complete cross section of the aerosol-flow path. By providing the substrate at least partly within the aerosol flow path, the aerosol is at least partly guided through the substrate such that interaction between the previously encapsulated substance and the aerosol is facilitated. 
     The activation means that are used for activation of the activatable element may depend on the type of encapsulation used. Gel capsules, such as hard-shelled or soft-shelled gelatin capsules, may be activated by rupturing the shell. The shell may be ruptured by pressing or piercing. 
     In embodiments one of the main parts may comprise a piercing element for activating the activatable element. The piercing element may pierce a capsule holding the encapsulated liquid upon activation. 
     The piercing element may be an elongated element. The piercing element may extend in parallel to the longitudinal axis of the mouthpiece. The piercing element may have a conical shape or may be needle-shaped. 
     The piercing element may be configured such that when the two main parts are in the first assembled position, the apex of the piercing element is located at a distance from the activatable element. Upon relative axial movement of the two main parts into the second assembled position, the piercing element may be guided towards the activatable element and may be configured to activate the activatable element. The piercing element may be configured to rupture the capsule of the activatable element when the two main parts are moved into the second assembled position. 
     The piercing element may be configured such as to assist in defining the aerosol flow path within the mouthpiece. The piercing element may be formed such as to guide the aerosol towards the substrate. For example, in the second assembled position, the apex of a conical piercing element may penetrate completely through the substrate of the activatable element and may even extend into an area upstream from the activatable element. The apex of the piercing element may then be used to guide the aerosol into soaked areas of the substrate. In this way the piercing element may be used to enhance interaction between the aerosol and the previously encapsulated liquid. 
     The mouthpiece may be formed from any suitable material such as polymeric materials. Suitable materials include food and/or medical grade polymeric compounds, in particular thermoplastic polyester elastomers (TPC-ETs), Polyoxymethylene Compounds (POM), High Density Polyethylene (HDPE), Low Density Polyethylene (LDPE), Polybutylene terephthalate (PBT), acrylic multipolymer, biodegradable polylactic acid (PLA) or cyclic olefin copolymer (COC). 
     The mouthpiece may be constructed from at least two main parts that can be axially inserted into each other. These two main parts may be formed such that when axially inserted into each other, the airflow path is defined by these two main parts. 
     The mouthpiece may be formed from an outer part and an inner part. The outer part may form a central inner channel and may comprise a tubular outer wall that at the same time forms the outer wall of the mouthpiece. 
     The inner part may have a hollow cylindrical shape with a side wall, one open end and one closed end. The inner part may be axially inserted into the outer part in such a way that the side wall of the inner part is located between the central channel and the outer wall of the outer part. In this way a second channel is formed between the sidewall of the inner part and the central channel. A third channel is performed between the sidewall of the inner part and the outer wall of the outer part. Thus, when the two parts are assembled, an airflow channel is formed from the inlet end through the central channel and further on through the second and third channel towards the outlet end of the mouthpiece. This two-part construction facilitates manufacture of a mouthpiece with a mazelike course of the airflow path. 
     This two-part construction allows manufacturing of the individual parts by conventional and well-known blow molding processes. Such processes may be more convenient to handle than other potential manufacturing techniques required for manufacturing a mouthpiece according to the present invention as an integral part. 
     The two main parts of the mouthpiece can be assembled in a first position. The two main parts are further configured to be axially moveable into a second assembled position. In order to achieve this functionality, the two main parts of the mouthpiece may have corresponding interlocking structures. The interlocking structures engage with each other upon assembly such that a mouthpiece with predetermined dimensions may be obtained. In addition, the interlocking structures assist in maintaining the mouthpiece in the assembled configuration. In particular, the interlocking structures are formed such as to prevent inadvertent disassembly of the mouthpiece during use. 
     The interlocking structures may comprise one or more protrusions and one or more locking cavities that are provided at opposing surfaces of the main parts of the mouthpiece. The interlocking structures may comprise three protrusions and three corresponding locking cavities that are provided at opposing surfaces of the main parts of the mouthpiece. Upon assembly, each of the one or more protrusions provided on a surface of the one part engage with a corresponding locking cavity provided on a surface of the other part of the mouthpiece. The protrusions may be provided at the outer surface of the side wall of the inner part, while the locking cavities may be provided at the inner surface of the outer wall of the outer part. 
     The protrusions and locking cavities may be evenly distributed over the circumference of the two parts, such that after assembly the two parts are firmly held in a co-axially aligned position. The interlocking structures may be provided as two or more sets of interlocking structures that are provided at different axial positions along the side walls of the two main parts of the mouth piece. Each set may consist of three or more protrusions and locking cavities. By providing two or more sets of interlocking structures, the two main parts can be reliably held in a predetermined orientation with respect to each other. 
     By configuring the interlocking structures in the form of corresponding protrusions and locking cavities, a simple but reliable manufacture of a two-part mouthpiece is enabled. The connection between the interlocking structures can be configured such that an inadvertent disassembly of the mouthpiece is prevented, while an intended disassembly may be facilitated by controlled pulling apart of the two parts. 
     In order to allow the two main parts of the mouthpiece to be assembled in two different axial positions along the longitudinal axis of the mouthpiece, additional interlocking structures may be provided. For example, the outer part may comprise three sets of locking cavities that are to cooperate with two sets of protrusions provided at the inner part. The inner part may be inserted in the outer part in such a way that the two sets of protrusions of the inner part engage with the first and the second set of locking cavities of the outer part such that a mouthpiece with a first configuration is obtained. Alternatively, the inner part may be inserted such that the two sets of protrusions of the inner part engage with the second and third set of locking cavities of the outer part such that a mouthpiece with a second configuration is obtained. The dimensions of the airflow channels formed within the mouthpiece in the first and in the second configuration differ from each other. Accordingly, a mouthpiece with adjustable characteristics in terms of airflow management and overall aerosolization performance is obtained. 
     In the above example the inner part may be arranged in two pre-defined axial positions with respect to the outer part of the mouthpiece. By providing additional sets of interlocking structures, additional pre-defined axial positions of the inner part with respect to the outer part may be established. In this way versatility of the corresponding mouthpiece can be further increased. 
     The activatable element is provided within the mouthpiece. When the two main parts are assembled in the first position, the activatable element may be located between corresponding structures of the two main parts. The activatable element may be held in place by being clamped within the mouthpiece. The activatable element may be held in place by being clamped within one of the main parts or by being clamped between corresponding structures of the two main parts. 
     In an embodiment the activatable element may be located within one of the expansion chambers that are formed at the reversal points between the consecutive longitudinal channels. For example, in the first assembled position of the two main parts of the mouthpiece, the activatable element may be located in the first expansion chamber in flow direction of the aerosol through the mouthpiece. The activatable element may have a size that corresponds to the inner diameter of the inner main part, and may be frictionally held within the inner main part. 
     The piercing element may be provided at a closed end of the inner main part of the mouthpiece. The piercing element may extend in parallel to the longitudinal axis of the mouthpiece with the pointed end extending into the inner volume of mouthpiece. Upon axial movement of the two main parts into the second assembled position, the piercing element formed at the closed end of the inner main part may be moved towards the activatable element until the activatable element is clamped between the piercing element of the inner part and the side walls of the central channel of the outer main part of the mouthpiece. Upon finalization of the axial movement into the second assembled position, the piercing element is further moved towards the activatable element thereby rupturing the capsule wall and freeing the encapsulated liquid. 
     The freed liquid is dispersed into the substrate of the activatable element and may then interact with any aerosol guided through the mouthpiece after this activation procedure. The freed liquid may be dispersed throughout the substrate. The freed liquid may be dispersed partly throughout the substrate. The freed liquid may be dispersed substantially throughout the complete substrate. By dispersing the freed liquid throughout the substrate, the available contact area for interaction of the liquid with the aerosol is increased. 
     The mouthpiece of the present invention may be used with any kind of aerosol-generating device or aerosol-generating article. In this regard, the inlet end of the mouthpiece may comprise a connection portion configured to attach the mouthpiece to such aerosol-generating device or aerosol-generating article. 
     The connection portion may employ any suitable mechanism that allows a user to removably attach the mouthpiece to an aerosol-generating device or an aerosol-generating article. For example, the connection portion can be a male/female coupling. The male/female coupling may be correspondingly shaped coupling elements which are configured to provide a friction-fit or form-fit connection. 
     A friction-fit connection may be established by the coupling elements having corresponding shape that can be inserted into each other and that are maintained in the connected position by friction between the coupling elements. 
     A form-fit connection may be obtained by providing the coupling elements with threaded portions forming a screwed joint. Such coupling elements may include 90° male/female fittings that are quickly and reliable attached to each other by 90° rotation of the coupling elements. Of course, also coupling elements including higher rotation angles may be employed. Male/female screw couplings enable reliable and leak free connections and allow for hermetic fastening of the mouthpiece to an aerosol-generating device or an aerosol-generating article. 
     The connection portion may be configured as a pharma or medical device type coupling. Pharma or medical device type couplings additionally may increase integrity of the generated aerosol. 
     The invention also relates to an aerosol-generating system comprising a mouthpiece as described above and an aerosol generating device and/or an aerosol-generating article. The mouthpiece and the aerosol-generating device or the aerosol-generating article have corresponding connection portions to removably attach the mouthpiece to the aerosol-generating device or the aerosol-generating article. The aerosol generating device or the aerosol-generating article can be any of the currently available aerosol generating devices or aerosol-generating articles including but not limited to heat not burn products (HNB) or vaping systems, in which liquid substrate is aerosolized. 
     The invention also relates to a method for assembling a mouthpiece. The method includes providing an outer part, wherein the outer part forms a central inner channel and a tubular outer wall of the mouthpiece. The method further includes providing an inner part, wherein the inner part has a hollow cylindrical shape with a side wall, one open end and one closed end. The method further includes providing an activatable element. 
     The activatable element is inserted into the inner part of the mouthpiece. The inner part is the inserted in an axial direction into the outer part such that the side wall of the inner part is located between the central channel and the outer wall of the outer part. The activatable element may be located in the first expansion chamber formed in the mouthpiece in flow direction of the aerosol. 
     The inner part and the outer part used in the method for forming a mouthpiece may correspond to the inner part and the other part as described above. In particular, these parts may be provided with interlocking structures such that upon assembly thereof a mouthpiece with predefined dimensions and predefined airflow path is obtained. 
     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: A mouthpiece for an aerosol-generating article, the mouthpiece being formed from at least two main parts that can be axially inserted into each other to define an aerosol flow path, 
     wherein the two main parts are axially moveable relative to each other between a first assembled position and a second assembled position, 
     the mouthpiece further comprising an activatable element for modifying upon activation a characteristic of an aerosol, and 
     wherein upon movement of the two main parts from the first assembled position into the second assembled position, the activatable element is activated. 
     Example B: A mouthpiece according to Example A, wherein the activatable element comprises a substrate and an encapsulated liquid. 
     Example C: A mouthpiece according to one of the preceding examples, wherein upon activation of the activatable element the encapsulated liquid is at least partly released to the substrate. 
     Example D: A mouthpiece according to one of the preceding examples, wherein one of the main parts comprises a piercing element that pierces the activatable element to activate the activatable element. 
     Example E: A mouthpiece according to one of the preceding examples, wherein the piercing element is an elongated element that extends in parallel to the longitudinal axis of the mouthpiece. 
     Example F: A mouthpiece according to one of the preceding examples, wherein the substrate is a low-density material and wherein the activatable element is provided such as to extend at least partly over the cross section of the aerosol flow path when the main parts are in the second assembled position. 
     Example G: A mouthpiece according to one of the preceding examples, wherein the mouthpiece comprises 
     an inlet end, configured to allow an aerosol to flow into the mouthpiece, 
     an outlet end, configured to allow the aerosol to flow out of the mouthpiece, 
     wherein the aerosol flow path extends between the inlet and the outlet end, and 
     wherein the mouthpiece is formed such that the flow direction of the aerosol is reversed at least once between the inlet and the outlet end, and 
     wherein the substrate is held in position by being clamped within the mouthpiece. 
     Example H: A mouthpiece according to one of the preceding examples, wherein the mouthpiece is formed from an outer part and an inner part, wherein the outer part forms a central inner channel and a tubular outer wall of the mouthpiece, and wherein the inner part has a hollow cylindrical shape with a side wall, one open end and one closed end, wherein the inner part is axially inserted into the outer part in such a way that the side wall of the inner part is located between the central channel and the outer wall of the outer part. 
     Example I: A mouthpiece according to Example H, wherein the piercing element is provided at the closed end of the inner part and wherein the apex of the piercing element extends into an area upstream from the activatable element, when the inner part and the outer of the mouthpiece are assembled in the second position. 
     Example J: A mouthpiece according to one of the preceding examples, wherein the two main parts of the mouthpiece have corresponding interlocking structures that engage with each other such that a mouthpiece with predetermined dimensions is obtained. 
     Example K: A mouthpiece according to one of the preceding examples, wherein the interlocking structures comprise one or more protrusions and one or more one or more locking cavities that are provided at opposing surfaces of the main parts of the mouthpiece. 
     Example L: A mouthpiece according to one of the preceding examples, wherein the interlocking structures comprise one or more sets of interlocking structure such that the two main parts may be assembled in two or more different axial positions with respect to each other. 
     Example M: Aerosol-generating system comprising an aerosol-generating device and a mouthpiece according to one of the preceding examples. 
     Example N: Aerosol-generating system according to Example M, wherein the aerosol-generating device and the mouthpiece comprise corresponding connection portions, such that the mouthpiece is removably attachable to the aerosol-generating device. 
     Example O: A method for assembling a mouthpiece, comprising the steps of: 
     (a) providing an outer part, wherein the outer part forms a central inner channel and a tubular outer wall of the mouthpiece, 
     (b) providing an inner part, wherein the inner part has a hollow cylindrical shape with a side wall, one open end and one closed end, 
     (c) providing an activatable element, 
     (d) assembling the outer part, the inner part and the activatable element, by inserting the activatable element into the inner part and inserting the inner part in an axial direction into the outer part such that the side wall of the inner part is located between the central channel and the outer wall of the outer part. 
     Features described in relation to one aspect may equally be applied to other aspects 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 mouthpiece according to the invention; 
         FIG.  2    shows a mouthpiece according to the invention with a two-part housing; 
         FIG.  3    shows a 3D view and a plan view of the outlet end of the mouthpiece of  FIG.  1   ; 
         FIG.  4    shows two embodiments of an activatable element; 
         FIG.  5    shows the activation of the activatable element; 
         FIG.  6    shows dimensions of the mouthpiece of  FIG.  5   ; 
         FIG.  7    shows an aerosol-generating device with a mouthpiece of  FIG.  5   . 
     
    
    
     In  FIG.  1    a mouthpiece  10  according to the present invention is depicted. The mouthpiece is of tubular shape and defines an airflow path  20  between the inlet end  12  and the outlet end  14 . In  FIG.  1    the inlet end  12  is provided at the left-hand side of the mouth piece  10  and is provided with a connection portion  16  for connecting the mouthpiece  10  to an aerosol-generating device. The outlet end  14  is provided at the opposite end of the mouthpiece  10  and is configured to be taken into the mouth by a user for inhalation. 
     The airflow path  20  between the inlet end  12  and the outlet end  14  comprises a plurality of tubular channels  22 ,  23 ,  24 , which are concentrically and coaxially arranged. The tubular channels  22 ,  23 ,  24  are arranged such that the airflow direction is reversed twice before the aerosol is exiting the mouthpiece  10  at the outlet end  14 . 
     The mouthpiece  10  comprises a central channel that extends from the inlet end  12  and that extends towards the outlet end  14  of the mouthpiece. The central channel  22  radially diverges along the direction of the aerosol flow. In other words, the diameter of the central channel  22  increases along the direction of the aerosol flow. At the end of the central channel  22  the flow direction of the aerosol is inverted and the aerosol is further guided through co-axially arranged intermediate tubular channel  23  towards the inlet end  12  of the mouthpiece  10 . At the end of intermediate channel  23  the flow direction of the aerosol is again inverted and the aerosol is guided through co-axially arranged outer tubular channel  23  towards the outlet end  14  of the mouthpiece  10 . The aerosol is finally discharged through the outlet end  14  for inhalation by the consumer. 
     With the design of the present invention, the length of the airflow path  20  through the mouthpiece  10  is effectively elongated such that additional time for dissipating thermal energy is available. In addition, expansion chambers  25 ,  26  are formed at the reversal points between consecutive channels  22 ,  23 ,  24 . These expansion chambers  25 ,  26  assist in cooling and homogenization of the aerosol. 
     In addition thereto, there is provided an activatable element  28  that is located within expansion chamber  25 . The activatable element  28  is provided in the airflow path  20  and is used for further modifying a characteristic of the aerosol. 
     The mazelike airflow path  20  of the mouthpiece  10  is suitably obtained by manufacturing the housing of the mouthpiece  10  from two parts as indicated in  FIG.  2 A . The first or outer part  30  of the mouthpiece  10  is depicted on the left-hand side of  FIG.  2   a    and defines the inlet  32 , the connection portion  34 , the central channel  22  and a tubular outer wall  36  of the mouthpiece  10 . The inner part  40  of the mouthpiece  10  is generally U-shaped. It has a hollow cylindrical shape with a side wall  42 , one open end  44  and one closed end  46 . At the inner side of the closed end  46  a piercing element  84  is provided. The piercing element  84  has a conical shape with a pointed end. The pointed end is directed towards the central channel  22  of the outer part  30 . Inner part  40  is formed such that it can be axially inserted with its open end  44  into the outer part  30  of the mouthpiece  10 . 
     In addition to the outer part  30  and inner part  40 , the activatable element  28  is provided. Upon assembly of the mouthpiece  10 , the activatable element  28  is inserted between the inner part  30  and the outer part  40  of the mouthpiece  10 . This can be achieved by inserting at first the activatable element  28  into the inner volume of the inner part  40 . Subsequently, the inner part  40  comprising the activatable element  28  may be inserted into the outer part  30  of the mouthpiece  10 . When fully assembled, the side wall  42  of the inner part  40  is located between the central channel  22  and the outer wall  36  of the outer part  30 . Further, the activatable element is located within the first expansion chamber  25  of the mouthpiece  10  as depicted in  FIG.  2     b.    
     The two main parts  30 ,  40  of the mouthpiece  10  have corresponding interlocking structures  50  that engage with each other when the mouthpiece  10  is fully assembled. The interlocking structures  50  are formed such that they maintain the mouthpiece  10  in the fully assembled configuration during the user experience. The interlocking structures  50  further ensure that a mouthpiece  10  with predetermined dimensions is obtained. 
     In the embodiment depicted in  FIG.  2   , the inner part  40  of the mouthpiece  10  comprises protrusions  52  provided at the outer circumference of the side wall  42  of the inner part  40 . The outer part  30  comprises corresponding locking cavities  54 , which are provided to the inner surface  38  of the outer wall  36  of the outer part  30 . In the fully assembled state, the protrusions  52  of the inner part  40  engage with the locking cavities  54  of the other part  30 , as depicted in  FIG.  2 B . The inner part  40  of the mouthpiece  10  comprises two sets of protrusions  52 A,  52 B that are axially spaced from each other. The outer part  30  of the mouthpiece  10  comprises three sets of locking cavities  54 A,  54 B,  54 C that are also axially spaced from each other. 
     Each set of protrusions  52 A,  52 B consists of three or more protrusions  52  that are equidistantly distributed over the circumference of the side wall  36  of the inner part  30 . Correspondingly, each set of locking cavities  54 A,  54 B,  54 C consists of three or more locking cavities  54  that are also equidistantly distributed over the inner surface  38  of the outer wall  36  of the outer part  30 . In the first assembled position of the two main parts, as depicted in FIG.  2   b,  the protrusions  52 A,  52 B are engaged with the locking cavities  54 A,  54 B. In this axial position of the two main parts the activatable element is not activated. By moving the inner part  40  in an axially direction towards the second assembled position in which the protrusions  52 A,  52 B are engaged with the locking cavities  54 B,  54 C, the activatable element may be activated as will be discussed further below in connection with  FIG.  5   . 
       FIG.  3    shows a perspective view and a side view of a mouthpiece  10  according to the present invention. In the perspective view of  FIG.  3 A  the tubular overall shape of the mouthpiece  10  and the spherical shape of the closed end  46  of the inner part  40  can be seen. The side view of  FIG.  3 B  shows the circumferential distribution of a set of interlocking structures  50  consisting of three elements which are equidistantly distributed over the circumference of the inner part  40  and the outer part  30 , respectively. 
       FIG.  4    shows embodiments of an activatable element  28 . The activatable element  28  comprises a substrate  80  and a capsule  82 ,  83  that is adhered to the substrate. The substrate  80  is provided in the form of a disc of low-density cellulose acetate tow. Due to its low density, the substrate material has a low resistance to draw and may not cause a perceivable increase in the overall resistance to draw of the mouthpiece  10  and or the aerosol-forming system  100  in which the mouthpiece  10  is to be used. 
     As depicted in  FIG.  4     a,  the capsule  82  provided on the activatable element  28  may be provided as a substantially spherical gel capsule. The capsule  82  may be filled with water, flavorant or any other active liquid. The capsule  82  may be provided centrally within the substrate  80  and may be affixed to the substrate  80  by conventional adhesives that are useful for this purpose. The diameter S of the substrate and the diameter T of the spherical capsule  82  may have dimensions as indicated below in table 1. 
     The capsule may alternatively be provided as a flat capsule  83  as depicted in the embodiment of  FIG.  4     b.  The flat capsule  83  may also be adhered to the substrate  80  by means of conventional adhesives known to the skilled person. The flat capsule  83  of  FIG.  4   b    may contain the same liquid as the spherical capsule  82  of the embodiment of  FIG.  4     a.  The diameter S of the substrate  80  and the diameter U of the flat capsule  83  may have dimensions as indicated below in table 1. 
     In order to activate the activatable element  28  so that the encapsulated liquid is released, a piercing element  84  is provided. The piercing element  84  and the piercing process will now be explained in connection with  FIG.  5   .  FIG.  5    depicts the mouthpiece of  FIG.  2   , wherein the outer part  30  of the mouthpiece  10  comprises three sets of locking cavities  54 . As depicted in  FIG.  5     a,  the mouthpiece  10  may be assembled in a first assembled position, in which the two sets of protrusions  52 A,  52 B engage with the first and the second set of locking cavities  54 A,  54 B. In this first assembled position, the activatable element  28  is provided in the expansion chamber  25  and is not yet activated. 
     In order to activate the activatable element  28 , the mouthpiece  10  may be brought into a second assembled position, as depicted in  FIG.  5     b.  In this second assembled position, the inner part  40  is moved in axial direction further into the outer part  30  until the two sets of protrusions  52 A,  52 B engage with the second and the third set of locking cavities  54 B,  54 C. In this second assembled position, the piercing element  84 , which is provided at the closed end  46  of the inner part  40  of the mouthpiece  10 , is moved towards the activatable element  28 . As depicted in  FIG.  5   b    the piercing element  84  is fully penetrating the capsule  82  and the substrate  80 , and the piercing element  84  even extends slightly into the central channel  22  formed in the center of the outer part  30  of the mouthpiece  10 . Thus, the piercing element  84  extends into an area upstream form the activatable element  28 . The piercing element  84  has ruptured the outer shell of the capsule  82 . The previously encapsulated liquid is freed thereby and is dispersed into the surrounding substrate  80 . Since the activatable element  28  extends over the full cross section of the airflow path  20  in this second assembled position, the complete aerosol is guided through the liquid-entrained substrate  80 . Thus, after activation of the activatable element  28 , the previously encapsulated liquid may be used to modify the aerosol and may cause the desired effect during the user experience. 
     Both parts  30 ,  40  of the mouthpiece  10  depicted in the figures are formed from thermoplastic polyester elastomers with food grade polymeric compounds to be used under Good Manufacturing Practice.  FIG.  6    again shows the inner and the outer part of a mouthpiece  10  and preferential ranges for the dimensions indicated in  FIGS.  4  and  6    are listed in table 1 below. 
     
       
         
           
               
               
               
            
               
                   
                   
               
               
                   
                 Ranges (mm) 
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Dimensions 
                 Range 
                 Preferred Range 
               
               
                   
                   
               
               
                   
                 A 
                 3.5 to 9 
                 4 to 7 
               
               
                   
                 B 
                 3 to 7 
                 4 to 5 
               
               
                   
                 C 
                 0.5 to 5 
                 2 to 4 
               
               
                   
                 D 
                 3 to 14 
                 4 to 7 
               
               
                   
                 E 
                 3 to 11 
                 3 to 7 
               
               
                   
                 F 
                 8 to 23 
                 11 to 21 
               
               
                   
                 G 
                 9 to 25 
                 13 to 21 
               
               
                   
                 H 
                 0.05 to 0.4 
                 0.15 to 0.35 
               
               
                   
                 I 
                 21 to 45 
                 25 to 35 
               
               
                   
                 J 
                 3 to 8 
                 4 to 7 
               
               
                   
                 K 
                 4 to 9 
                 5 to 8 
               
               
                   
                 L 
                 1 to 7 
                 2 to 5 
               
               
                   
                 M 
                 4 to 11 
                 4.5 to 8.5 
               
               
                   
                 N 
                 5 to 12 
                 5 to 9 
               
               
                   
                 O 
                 4 to 13 
                 5 to 9 
               
               
                   
                 Q 
                 1 to 4 
                 1 to 3 
               
               
                   
                 R 
                 6 to 21 
                 13 to 18 
               
               
                   
                 S 
                 4 to 11 
                 4.5 to 8.5 
               
               
                   
                 T 
                 3 to 6 
                 2.5 to 5 
               
               
                   
                 U 
                 3.5 to 9 
                 4 to 6 
               
               
                   
                   
               
            
           
         
       
     
       FIG.  7    shows an aerosol-generating system  100  comprising an aerosol-generating device  60  and a mouthpiece  10  as described above. The aerosol-generating device  60  comprises a housing  62  with a power source  64 , control electronics  66 , an aerosol-forming substrate  68  and an aerosol-generation unit  70 . The aerosol-generation unit  70  includes an aerosol-forming chamber  72  which is provided at one end of the aerosol-generating device  60 . This end of the aerosol-generating device  60  further comprises a connection portion  74  to which a mouthpiece  10  as described above can be connected. When the mouthpiece  10  is connected to aerosol-generating device  60 , an airflow path  20  from the aerosol-forming chamber  72  through the mouthpiece  10  is established. This allows a user to inhale the aerosol created in the aerosol-forming chamber  72  through the mouthpiece  10 .