Patent Publication Number: US-2018035706-A1

Title: Smoking Article and Mouthpiece Therefor

Description:
TECHNICAL FIELD 
     The invention relates to a smoking article and a mouthpiece therefor, particularly but not exclusively to a smoking article, a mouthpiece for a smoking article and a method for forming a mouthpiece for a smoking article. 
     BACKGROUND 
     Cigarettes and other smoking articles produce an aerosol, smoke in the case of cigarettes, which is inhaled by a user. Filters for smoking articles are used to modify the aerosol before it reaches the user&#39;s mouth. Filters known in the art for this purpose may be formed from a plug of fibrous cellulose acetate or other materials with similar physical properties. 
     To enhance the removal of certain smoke constituents various additives may be added to smoking article filters. Examples include smoke adsorbents such as activated carbon which adsorbs certain smoke constituents thus removing them from the smoke stream passing through the filter. In addition to removing constituents from smoke, filter additives may impart characteristics to smoke or other aerosols passing through the filter. For example, fragrances and flavourants may be incorporated into the filter which alter the aroma and taste characteristics of the aerosol. 
     SUMMARY 
     In accordance with aspects of the invention, there is provided a smoking article comprising a smoking article rod portion having a recess and a mouthpiece attachable to the smoking article rod portion comprising an elongate cylindrical element arranged to be inserted into the recess by a user, wherein the cylindrical element comprises an outer surface having at least one raised area, and the at least one raised area is arranged to engage with an inner surface of the recess to provide a resistance to the movement of the cylindrical element within the recess, and wherein the at least one raised area is arranged to provide a lower resistance to movement of the cylindrical element into the recess than out of the recess. 
     The cylindrical element can comprise adjacent first and second portions each extending partially along the length of the cylindrical element, the first portion being arranged to be inserted into the recess by a user, and an annular element arranged around the second portion of the cylindrical element, the annular element having a larger external diameter than the internal diameter of the recess. 
     The annular element can comprise a wrapper forming at least part of the outer surface of the annular element. 
     The internal diameter and/or length of the recess and the external diameter and/or length of the cylindrical element can be arranged to substantially correspond such that at least a portion of the cylindrical element can be received within and substantially fill the recess. 
     The cylindrical element can comprise a smoke modifying additive. The smoke modifying additive can be distributed throughout the cylindrical element and/or annular element, the smoke modifying additive can be contained within at least one frangible capsule, the smoke modifying additive can comprise a botanical additive, the smoke modifying additive can comprise an adsorbent and/or the additive can be loaded on a thread extending through the cylindrical element and/or annular element. 
     The annular element can be attached to the cylindrical element using an adhesive. 
     The cylindrical element can comprise a wrapper forming at least part of the outer surface of the cylindrical element. 
     The at least one raised area can be formed by embossing an outer surface of the cylindrical element. 
     The at least one raised area can have a first section with a relatively steep incline as it rises away from the outer surface of the cylindrical element and a second section with a relatively shallow incline as it rises away from the outer surface of the cylindrical element, and wherein the second section can be arranged to be forward of the first section as the cylindrical element is inserted into the recess. 
     The at least one raised area can have a first section and a second section, and wherein the first section can have a wider circumferential extent than the second section, and wherein the second section can be arranged to be forward of the first section as the cylindrical element is inserted into the recess. 
     The body of the cylindrical element can comprise fibrous filtration material. 
     The at least one raised area can comprise at least one circumferentially extending raised area configured to engage with an inner surface of the corresponding recess to prevent or restrict air flow between the inner surface of the corresponding recess and the outer surface of the cylindrical element. 
     The cylindrical element can further comprise an outer surface having at least one circumferentially extending raised area configured to engage with an inner surface of the corresponding recess to prevent or restrict air flow between the inner surface of the corresponding recess and the outer surface of the cylindrical element. 
     The cylindrical element can comprise a wrapper forming at least part of the outer surface of the cylindrical element, and wherein the at least one circumferentially extending raised area can be formed by embossing the wrapper. 
     The circumferentially extending raised area can extend around substantially the whole circumference of the cylindrical element. 
     In accordance with further aspects of the invention, there is provided a mouthpiece for attachment to a smoking article by a user, the mouthpiece comprising an elongate cylindrical element arranged to be inserted into a corresponding recess by a user, wherein the cylindrical element comprises an outer surface having at least one raised area, and the at least one raised area is arranged to engage with an inner surface of the recess to provide a resistance to the movement of the cylindrical element within the recess, and wherein the at least one raised area is arranged to provide a lower resistance to movement of the cylindrical element into the recess than out of the recess. 
     In accordance with further aspects of the invention, there is provided a method for forming a mouthpiece as defined above, comprising forming a wrapping material having the at least one raised area arranged thereon, forming an elongate cylinder of filter material and wrapping the wrapping material around the elongate cylinder of filter material. 
     The mouthpiece as described above and elsewhere herein can be a filter unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1 a    is a side-on cross sectional view of a smoking article including a smoking article rod portion and a mouthpiece, in the present example a filter unit, separate from the smoking article rod portion; 
         FIG. 1 b    is a perspective view of the smoking article shown in  FIG. 1   a;    
         FIG. 2 a    is a side-on cross sectional view of the smoking article of  FIG. 1 a    with the filter unit attached to the smoking article rod portion; 
         FIG. 2 b    is a perspective view of the smoking article shown in  FIG. 2   a;    
         FIGS. 3( a ) to 3( d )  are side-on cross sectional views of respective mouthpieces, in these examples filter units, containing various smoke modifying additives for use with the smoking article illustrated in  FIGS. 1 a , 1 b , 2 a    and  2   b;    
         FIG. 4  is a perspective view of a smoking article including a smoking article rod portion and a mouthpiece, in the present example a filter unit, separate from the smoking article rod portion, and in which the filter unit comprises at least one raised area for holding the filter unit in engagement with the smoking article rod portion; 
         FIG. 5  is a perspective view of a smoking article including a smoking article rod portion and a mouthpiece, in the present example a filter unit, separate from the smoking article rod portion, and in which the filter unit comprises at least one circumferentially extending raised area; 
         FIG. 6  is a perspective view of a smoking article including a smoking article rod portion and a mouthpiece, in the present example a filter unit, separate from the smoking article rod portion, and in which the filter unit comprises both the at least one raised area illustrated in  FIG. 4  and the at least one circumferentially extending raised area illustrated in  FIG. 5 ; 
         FIG. 7  is a perspective view of a smoking article including a smoking article rod portion and a mouthpiece, in the present example a filter unit, separate from the smoking article rod portion, and in which the filter unit comprises at least one circumferentially extending raised area for holding the filter unit in engagement with the smoking article rod portion; 
         FIG. 8  is a side-on cross sectional view of a mouthpiece, in the present example a filter unit, having an offset cylindrical element, for use with the smoking article illustrated in  FIGS. 1 a , 1 b , 2 a    and  2   b;    
         FIG. 9  is a side-on cross sectional view of a smoking article including a smoking article rod portion and two of the filter units of  FIG. 8  connected to the smoking article rod portion; 
         FIG. 10  is a flow diagram illustrating a method for forming a mouthpiece, in the present example a filter unit, as described herein; 
         FIG. 11  is a flow diagram illustrating a method for forming the cylindrical element of the filter unit described with reference to  FIG. 4 ; and 
         FIG. 12  is a flow diagram illustrating a method for forming the cylindrical element of the filter unit described with reference to  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
     As used herein, the term “smoking article” includes smokable products such as cigarettes, cigars and cigarillos whether based on tobacco, tobacco derivatives, expanded tobacco, reconstituted tobacco or tobacco substitutes and also heat-not-burn (HnB) products, and other nicotine delivery products such as aerosol generation devices including e-cigarettes. The smoking article may be provided with a filter for the gaseous flow drawn by the smoker. 
     Smoking articles such as cigarettes and their formats are often named according to the cigarette length: “regular” (typically in the range 68-75 mm, e.g. from about 68 mm to about 72 mm), “short” or “mini” (68 mm or less), “king-size” (typically in the range 75-91 mm, e.g. from about 79 mm to about 88 mm), “long” or “super-king” (typically in the range 91-105 mm, e.g. from about 94 mm to about 101 mm) and “ultra-long” (typically in the range from about 110 mm to about 121 mm). 
     They are also named according to the cigarette circumference: “regular” (about 23-25 mm), “wide” (greater than 25 mm), “slim” (about 22-23 mm), “demi-slim” (about 19-22 mm), “super-slim” (about 16-19 mm), and “micro-slim” (less than about 16 mm). Accordingly, a cigarette in a king-size, super-slim format will, for example, have a length of about 83 mm and a circumference of about 17 mm. Cigarettes in the regular, king-size format are preferred by many customers, namely with a circumference of from 23 to 25 mm and an overall length of from 75 to 91 mm. 
     Each format may be produced with filters of different lengths, smaller filters being generally used in formats of smaller lengths and circumferences. Typically the filter length will be from about 15 mm, associated with short, regular formats, to 30 mm, associated with ultra-long super-slim formats. The tipping paper will have a greater length than the filter, for example from 3 to 10 mm longer, such that the tipping paper covers the filter and overlaps the tobacco rod to connect the filter to the tobacco rod. 
     Smoking articles described herein can be made in any of the above formats. 
       FIG. 1 a    is a side-on cross sectional view of a smoking article  1  including a smoking article rod portion  2 , also referred to as an aerosol generating portion, and a mouthpiece, in the present example a filter unit  3  separate from the smoking article rod portion  2  and attachable to the smoking article rod portion  2  by a user.  FIG. 1 b    is a perspective view of the smoking article  1  shown in  FIG. 1 a   . In the present example, the smoking article rod portion  2  is in the regular, king size format, namely having a length in the range 75-91 mm and a circumference in the range 23 to 25 mm. In particular, the length of the smoking article rod portion  2  is 83 mm and it has a circumference of 24.6 mm in the present example. The smoking article  1  is a cigarette and the smoking article rod portion  2  includes a tobacco rod  4  wrapped in a wrapping material  5 , in this case cigarette paper. The smoking article rod portion  2  includes a filter  6  at its mouth end comprising a first section  7  located at the tobacco rod end of the filter  6 . The first filter section  7  is, in the present example, formed from cellulose acetate tow  8  wrapped in a first plug wrap  9 . The filter  6  also includes a second section  10  located downstream of the first section  7  and comprising a tubular element  11  wrapped in a second plug wrap  12 . The tubular element  11  is, in the present example, open at the mouth end of the smoking article rod portion  2  and defines a recess or cavity  13  at that end. A mouth end surface  16  of the tubular element  11  is exposed at the mouth end of the smoking article rod portion  2 . The tobacco rod  4  and first and second filter sections  7 ,  10  are connected by a tipping material  14  overlaying the first and second filter sections  7 ,  10  and partially overlaying the wrapping material  5 . In other embodiments, the first and second filter sections  7 ,  10 , and any other sections forming the filter  6 , can be connected together using a further plug wrap (not shown), prior to connection of the filter  6  to the tobacco rod  4  using the tipping material  14 . 
     The filter unit  3  includes a cylindrical element  20  and an annular element  21 . The cylindrical element  20  has adjacent first and second portions  20   a ,  20   b , each extending partially along the length of the cylindrical element  20 . In the present example, the first portion  20   a  extends from an insertion end of the cylindrical element  20  to an intermediate position  22  along the length of the cylindrical element  20 . In the present example, the cylindrical element  20  is 13 mm in length and the intermediate position  22  is 6 mm along the length of the cylindrical element  20  from the insertion end. The first portion  20   a  of the cylindrical element  20  is arranged to be inserted, by a user, into the recess  13  at the mouth end of the smoking article rod portion  2 . 
     The annular element  21  is arranged around the second portion  20   b  of the cylindrical element  20 . The annular element  21  has a larger external diameter than the internal diameter of the recess  13 . In the present example, the second portion  20   b  of the cylindrical element  20  extends from a mouth end of the cylindrical element  20  and ends at the intermediate position  22  along the length of the cylindrical element  20 . A surface  23  of the annular element  21  is exposed on the end of the annular element  21  arranged to face the smoking article rod portion  2  in use, and abuts the mouth end surface  16  of the tubular element  11  when the filter unit  3  is attached to the smoking article rod portion  2 , as described below. 
     The first portion  20   a  of the cylindrical element  20  is arranged to be inserted into a recess in a smoking article, in the present case into the recess  13  formed by the tube section  11 . The internal diameter and/or length of the recess  13  and the external diameter and/or length of the first portion  20   a  of the cylindrical element  20  are arranged to substantially correspond such that the first portion  20   a  of the cylindrical element  20  can be received within and substantially fill the recess  13 . For instance, the internal diameter and/or length of the recess  13  can be substantially the same as the external diameter and/or length of the first portion  20   a  of the cylindrical element  20 . In practice, the correspondence between the dimensions of the recess  13  and those of the first portion  20   a  of the cylindrical element  20  will depend on the materials used to form these components and the desired closeness of the fit between them. It is likely to be preferable that the recess dimensions are slightly larger than the dimensions of the first portion  20   a , to facilitate insertion of the cylindrical element  20  into the recess  13 . 
     In the example of  FIGS. 1 a  and 1 b   , the recess  13  has an internal diameter of 5.10 mm and the cylindrical element  20  has an external diameter of 5.03 mm. In alternative examples, the internal diameter of the recess  13  and external diameter of the cylindrical element  20  can have other values, for instance diameters in the range from 3 mm to 10 mm. In the example of  FIGS. 1 a  and 1 b   , the recess  13  has an internal length of 6 mm and the first portion  20   a  of the cylindrical element  20  has a length of 6 mm. In alternative examples, the internal length of the recess  13  and length of the first portion  20   a  of the cylindrical element  20  can have other values, for instance lengths in the range from 3 mm to 20 mm. 
     In the present example, the annular element  21  is attached to the cylindrical element  20  using an adhesive (not shown). The annular element  21  may be attached to the cylindrical element  20  by means other than an adhesive, for example by mechanical means such as a friction fit or other locking arrangement. 
     In use, the smoking article  1  is provided to users with the filter unit  3  and smoking article rod portion  2  as separate components. Prior to a user first using the smoking article rod portion  2 , the filter unit  3  can be attached to the smoking article rod portion  2  by inserting the first portion  20   a  of the cylindrical element  20  into the recess  13 . The first portion  20   a  of the cylindrical element  20  is inserted into the opening of the recess  13  and pushed into the recess  13  until the surface  23  of the annular element  21  abuts the mouth end surface  16  of the tubular element  11 , preventing further insertion. The user can select whether or not to attach the filter unit  3  to the smoking article rod portion  2  prior to smoking the smoking article  1 , and can in this way control the length of filter of the smoking article  1  and therefore the level of filtration of the aerosol generated by the smoking article  1 . 
       FIG. 2 a    is a side-on cross sectional view of the smoking article  1  of  FIGS. 1 a  and 1 b    with the filter unit  3  attached to the smoking article rod portion  2 .  FIG. 2 b    is a perspective view of the same smoking article  1  with the filter unit  3  attached to the smoking article rod portion  2 . 
     In the present example, the cylindrical element  20  comprises fibrous filtration material  25  and is circumferentially wrapped in a wrapper  26 , in the present case plug wrap material, leaving its longitudinal ends unwrapped. In alternative embodiments, the cylindrical element  20  may be formed in other ways. The cylindrical element  20  may alternatively be formed from other fibrous materials and can be arranged to have a different construction. The cylindrical element  20  may, for instance, be formed from stiff paper, plastic, card or other materials as an open or closed ended hollow tube. The cylindrical element  20  also need not be wrapped in a wrapper, but could, for instance, be formed without a wrapper such as a non-wrapped acetate (NWA) plug formed from cellulose acetate fibres. The fibrous filtration material  25  may comprise cellulose acetate fibres and/or other materials used to form fibres, such as polyvinyl alcohol (PVOH), polylactic acid (PLA), polycaprolactone (PCL), poly(1-4 butanediol succinate) (PBS), poly(butylene adipate-co-terephthalate)(PBAT), starch based materials, paper, cotton, aliphatic polyester materials and polysaccharide polymers. 
     In the present example, the annular element  21  comprises fibrous filtration material  27 , formed into a tube and circumferentially wrapped in a wrapper  28 , in the present case plug wrap material, leaving its longitudinal ends unwrapped. In alternative embodiments the annular element  21  may be formed in other ways. For instance, the annular element  21  may alternatively be formed from other fibrous materials. The annular element  21  also need not be wrapped in a wrapper, but could, for instance, be formed without a wrapper such as a non-wrapped acetate (NWA) tube formed from cellulose acetate fibres. The fibrous filtration material  27  may comprise cellulose acetate fibres and/or other materials used to form fibres, such as polyvinyl alcohol (PVOH), polylactic acid (PLA), polycaprolactone (PCL), poly(1-4 butanediol succinate) (PBS), poly(butylene adipate-co-terephthalate)(PBAT), starch based materials, paper, cotton, aliphatic polyester materials and polysaccharide polymers. The annular element  21  may alternatively be formed from a sheet material, such as tipping paper, wrapped around the cylindrical element  20  to form a single or multiple layers of the sheet material around the cylindrical element  20 . The annular element  21  may alternatively be formed from plastic or another moulded material. 
     The cylindrical element  20  and/or annular element  21  may contain a filter plasticiser. Filter plasticisers operate by softening the fibrous filter material from which a filter element is constructed such that the individual fibres can bond to each other to form a more rigid structure. A filter plasticiser such as glycerin triacetate, also referred to as triacetin, can, for instance, be used in the cylindrical element  20  and/or annular element  21  when these elements are formed from a fibrous filtration material such as cellulose acetate. A higher level of plasticiser than is usually used in a filter element can be used to provide additional firmness to either component. For instance, greater than 7%, greater than 10%, greater than 12% or greater than 15% plasticiser can be used in either component, by weight of the fibrous filtration material used. 
     In the present example, the longitudinal extent of the first portion  20   a  of the cylindrical element  20  is substantially equal to the longitudinal extent of the recess  13 . The longitudinal extent of the first portion  20   a  of the cylindrical element  20  may, in alternative examples, be shorter or longer than the longitudinal extent of the recess  13 . The cylindrical element  20  and/or annular element  21  may comprise an aerosol modifying additive. 
       FIGS. 3 a  to 3 d    are side-on cross sectional views of respective mouthpieces, in the present example filter units  30 ,  40 ,  50 ,  60 , which can be used as alternative mouthpieces to the filter unit  3  described with reference to  FIGS. 1 a , 1 b , 2 a , and 2 b   . The filter units  30 ,  40 ,  50 ,  60  of  FIGS. 3 a  to 3 d    are generally similar in construction to the filter unit  3  of  FIG. 1 a   , and the same reference numerals are used to denote equivalent features. 
     In the filter unit  30  of  FIG. 3 a   , the fibrous filtration material  25  of the cylindrical element comprises particles of an aerosol modifying additive  31  disposed therein. The aerosol modifying additive  31  is, in the present example, activated carbon. However, other additives can be used, such as adsorbents other than carbon, or flavour imparting additives. For instance, the additive may be a botanical additive. The botanical additive may, where local regulations permit, comprise at least one plant based material selected from liquorice,  hydrangea , Japanese white bark  magnolia  leaf, chamomile, fenugreek, clove, Japanese mint, aniseed, cinnamon, herb, wintergreen, spearmint, peppermint, lavender, cardamom, celery, cascarilla, geranium, vanilla,  cassia , caraway, jasmine, ylang-ylang, sage, fennel, ginger, anise and coriander. 
     In the present embodiment, the aerosol modifying additive  31  is distributed throughout the fibrous filtration material  25  of the cylindrical element  20 . The aerosol modifying additive  31  may alternatively or additionally be distributed throughout the fibrous filtration material  27  of the annular element  21 . 
     In the filter unit  40  of  FIG. 3 b   , the fibrous filtration material  25  of the cylindrical element  20  comprises a frangible capsule  41  inserted therein containing a liquid payload comprising a flavourant, such as menthol. The frangible capsule  41  is positioned at the intermediate position  22  between the first and second portions  20   a ,  20   b  of the cylindrical element, and therefore lies beneath the end of the annular element  21  at that location. The user can squeeze the end of the annular element  21  to cause a pressure to be exerted on the capsule such that it breaks to release the flavourant contained therein to thus modify aerosol drawn through the filter unit  40 . In the filter unit  50  of  FIG. 3 c   , the fibrous filtration material  25  of the cylindrical element  20  comprises an elongate aerosol modifying element  51  inserted therein. In the present example, the elongate aerosol modifying element  51  comprises a thread loaded with a flavourant such as menthol. The flavourant loaded onto the thread  51  is released as aerosol is drawn through the filter unit  50 . 
     In the filter unit  60  of  FIG. 3 d   , the cylindrical element  20  comprises a first plug  61  and a second plug  62 , longitudinally aligned, separated and wrapped in the plug wrap  26  such that a cavity is formed between the first and second plugs  61 ,  62 . The cavity contains an aerosol modifying additive  63  disposed therein, such as those described with reference to  FIG. 3   a.    
     In any of the mouthpieces or filter units described herein, an additional mouth-end filter section can be provided. In filter units containing additives such as activated carbon or botanical additives, the additional mouth-end filter section can prevent particles of such additives from reaching the user&#39;s mouth. 
     In addition or as an alternative to the feature of the filter units described herein, the wrapper wrapping the cylindrical element  20  and/or annular element  21  of the filter units described herein may comprise an additive such as menthol or chili flavour, to provide additional flavour, aroma and/or other sensate characteristics to the filter units. 
       FIG. 4  is a perspective view of a smoking article  70  including a smoking article rod portion  2  and a mouthpiece, in the present example a filter unit  71 , separate from the smoking article rod portion  2 , and in which the filter unit  71  comprises at least one raised area  73  for holding the filter unit  71  in engagement with the smoking article rod portion  2 . The smoking article  70  of  FIG. 4  is generally similar in construction to the smoking article  1  of  FIG. 1 a   , and the same reference numerals are used to denote equivalent features. The filter unit  71  comprises a cylindrical element  20  and an annular element  21  corresponding to those previously described. However, the outer surface of the first portion  20   a  of the cylindrical element  20  has at least one raised area  73  arranged to engage with an inner surface of the recess  13 . In the present example four such raised areas  73  are disposed circumferentially around the first portion  20   a  of the cylindrical element  20 . Each raised portion  73  protrudes approximately 1 mm at its highest point or region from the outer surface, although can be arranged to protrude more or less than this. 
     In the present example, the raised portions  73  are generally triangular shaped in both plan view and longitudinal cross sectional view, although other shapes can be used. 
     The raised areas  73  are provided approximately half-way along the length of the first portion  20   a  of the cylindrical element, which in the present case is in a region about 3 mm from the annular element  21 . However, the raised areas  73  can alternatively be provided in other locations around the first portion  20   a  of the cylindrical element  20 . 
     The raised areas  73  are arranged to provide a resistance to the movement of the first portion  20   a  of the cylindrical element  20  within the recess  13 . The raised areas  73  can also have the effect of centring the first portion  20   a  in the recess and providing a buffer between the cylindrical element and the recess to absorb any inaccuracies in the dimensions of either component caused by tolerances in the manufacture of either component. The raised areas  73  are arranged to provide a lower resistance to movement of the first portion  20   a  of the cylindrical element  20  into the recess  13  than out of the recess  13 . This is achieved, in the present example, by the raised area  73  having a first section  73   a  with a relatively sharp incline as it rises away from the outer surface of the cylindrical element  20  to the highest point or region of the raised area  73 , and a second section  73   b  with a relatively shallow incline as it rises away from the outer surface of the cylindrical element  20  to the highest point or region of the raised area  73 . The second section  73   b  is arranged to face in the direction of movement of the cylindrical element  20  into the recess  13 . The second section  73   b  is arranged to be forward of the first section  73   a  as the cylindrical element  20  is inserted into the recess  13 . In particular, the second section  73   b  is closer to the end of the first portion  20   a  opposite to the annular element  21  than the first section  70   a . The raised area  73  therefore provides a relatively low level of frictional engagement with the inner surface of the recess  13  on insertion of the first portion  20   a  into the recess  13 . The first section  73   a  is arranged to face in the direction of movement of the cylindrical element  20  out of the recess  13 . In particular, the first section  73   a  is closer to the end of the first portion  20   a  adjacent the annular element  21 . The raised area  73  therefore provides a relatively high level of frictional engagement with the inner surface of the recess  13  on retraction of the first portion  20   a  out of the recess  13 . 
     In the present example, the raised areas  73  also have a wider circumferential extent in the first section  73   a  as compared to the second section  73   b , again providing greater frictional engagement with the inner surface of the recess  13  on extraction of the cylindrical element  20  as compared to insertion of the cylindrical element  20 . In the present example, the circumferential extent of the raised areas  73  in the first section  73   a  is approximately 3 mm and in the second section  73   b  is approximately 0.5 mm, although other dimensions can be used. 
     In the present example, the at least one raised area  73  is formed by embossing the wrapper  72  which forms the outer surface of the cylindrical element  20 . However, alternative arrangements are possible. For instance, the raised area  73  can be formed using an add-on material such as varnish, lacquer, adhesive or equivalent, or by a plastic, paper or other material protrusion which is adhered to the outer surface of the cylindrical element  20 . In addition, any shape of raised portion  73  can be used which provides greater frictional engagement with the inner surface of the recess  13  on extraction of the cylindrical element  20  as compared to insertion of the cylindrical element  20 . 
       FIG. 5  is a perspective view of a smoking article  80  including a smoking article rod portion  2  and a mouthpiece, in the present example a filter unit  81 , separate from the smoking article rod portion  2 . The filter unit  81  comprises at least one circumferentially extending raised area  83 . The smoking article  80  of  FIG. 5  is generally similar in construction to the smoking article  1  of  FIG. 1 a   , and the same reference numerals are used to denote equivalent features. The filter unit  81  comprises a cylindrical element  20  and an annular element  21  corresponding to those previously described. However, the outer surface of the first portion  20   a  of the cylindrical element  20  has at least one circumferentially extending raised area  83  arranged to engage with an inner surface of the recess  13 . In the present example, first and second circumferentially extending raised areas  83   a ,  83   b  are provided, longitudinally spaced apart. However, in alternative embodiments, a single circumferentially extending raised area  83  can be provided, or more than two can be provided. 
     The first and second circumferentially extending raised areas  83   a ,  83   b  each extend continuously around the outer surface of the first portion  20   a  of the cylindrical element  20 . In particular, the circumferentially extending raised areas  83   a ,  83   b  extend around substantially the whole of the circumference of the cylindrical element  20 , in the present example forming bands or rings around the cylindrical element  20 . However, other arrangements are possible, such as circumferentially extending raised areas which extend around some, but not the whole of the outer surface of the cylindrical element  20 , or areas having other patterns such as a spiral configuration. 
     The first and second circumferentially extending raised areas  83   a ,  83   b  each prevent or restrict air flow between the inner surface of the recess  13  and the outer surface of the cylindrical element  20 . This is achieved by the circumferentially extending raised areas  83   a ,  83   b  forming a seal between the outer surface of the cylindrical element and the inner surface of the recess  13 , by pressing against the inner surface of the recess  13 . Preventing or restricting air flow between the inner surface of the recess  13  and the outer surface of the cylindrical element  20  can help to prevent or restrict external air from entering the smoking article  80  between the filter  6  of the smoking article rod portion  2  and the filter unit  83 . In addition, Preventing or restricting air flow between the inner surface of the recess  13  and the outer surface of the cylindrical element  20  can help to prevent or restrict aerosol formed by the smoking article rod portion  2  bypassing the cylindrical element  20  and/or annular element  21  by passing between the two. 
     The circumferentially extending raised areas  83   a ,  83   b  can be formed by embossing the wrapper  82  forming the outer surface of the cylindrical element  20 . In the present example, the circumferentially extending raised areas  83   a ,  83   b  are 1 mm in height above the surface of the cylindrical element  20  and have a width of 1 mm. However, other dimensions can be used, such as between 0.5 mm and 10 mm in width and between 0.5 mm and 5 mm in height. Also, in the present example the first and second circumferentially extending raised areas  83   a ,  83   b  are separated by a 2 mm spacing between them, although other spacing can be used, such as between 1 mm and 20 mm depending on the size and configuration of the cylindrical element  20 . The circumferentially extending raised areas  83  are provided approximately half-way along the length of the first portion  20   a  of the cylindrical element, which in the present case is in a region about 3 mm from the annular element  21 . However, the circumferentially extending raised portions  83  can alternatively be provided in other locations around the first portion  20   a  of the cylindrical element  20 . 
       FIG. 6  is a perspective view of a smoking article  90  including a smoking article rod portion  2  and a mouthpiece, in the present example a filter unit  91 , separate from the smoking article rod portion  2 , and in which the filter unit  91  comprises both the at least one raised area  73  as described with reference to  FIG. 4 , and the at least one circumferentially extending raised area  83  as described with reference to  FIG. 5 . The smoking article  90  of  FIG. 6  is generally similar in construction to the smoking article  1  of  FIG. 1 a   , and the same reference numerals are used to denote equivalent features. The at least one raised area  73  is provided on the outer surface of the first portion  20   a  of the cylindrical element  20  further from the annular element  21  than the at least one circumferentially extending raised area  83 . In particular, in the present example, four raised areas  73  are provided spaced around the circumference of the cylindrical element  20  and spaced approximately 4 mm from the annular element  21 . First and second circumferentially extending raised areas  83  are provided, spaced approximately 2 mm from the annular element  21 . The raised areas  73  and circumferentially extending raised areas  83  can be formed by embossing the wrapper  92  forming the outer surface of the cylindrical element  20 . 
       FIG. 7  is a perspective view of a smoking article  100  including a smoking article rod portion  2  and a mouthpiece, in the present example a filter unit  101  separate from the smoking article rod portion  2 , and in which the filter unit  101  comprises at least one circumferentially extending raised area  103  for holding the filter unit  101  in engagement with the smoking article rod portion  2 . The smoking article  100  of  FIG. 7  is generally similar in construction to the smoking article  1  of  FIG. 1 a   , and the same reference numerals are used to denote equivalent features. The at least one circumferentially extending raised area  103  has the combined functions of the at least one raised area  73  described with reference to  FIG. 4  and the at least one circumferentially extending raised area described with reference to  FIG. 5 . In particular, the circumferentially extending raised area  103  is formed so as to have a forward section  103   b  with a relatively shallow incline as it rises away from the outer surface of the cylindrical element  20  to the highest point or region of the raised area  103 , and a rearward section  103   a  with a relatively steep incline as it rises away from the outer surface of the cylindrical element  20  to the highest point or region of the raised area  103 . The circumferentially extending raised area  103  therefore provides a relatively low level of frictional engagement with the inner surface of the recess  13  on insertion of the cylindrical element  20  into the recess  13  and a relatively high level of frictional engagement with the inner surface of the recess  13  on retraction of the cylindrical element  20  out of the recess  13 . In addition, the circumferentially extending raised area  103  also acts to prevent or restrict air flow between the inner surface of the recess  13  and the outer surface of the cylindrical element  20 . 
       FIG. 8  is a side-on cross sectional view of a mouthpiece, in the present example a filter unit  110 , having an offset cylindrical element  20 , for use with the smoking articles described herein. The filter unit  110  includes a cylindrical element  20  and an annular element  111 . The cylindrical element  20  is substantially the same as the cylindrical elements  20  described previously. However, in the present example, the annular element  111  is arranged around the second portion  20   b  of the cylindrical element  20  and also extends beyond the mouth end of the cylindrical element  20 . The annular element  111 , in the present example, has the same longitudinal length as the cylindrical element  20 . In particular, in the present example, both the cylindrical element  20  and the annular element  21  have a length of 13 mm. The intermediate position  22  is 6 mm along the length of the cylindrical element  20  from the insertion end, as previously described, and therefore the annular element  21  extends 6 mm beyond the mouth end of the cylindrical element  20 . The annular element  111  is wrapper in a wrapper  112 , such as tipping paper. The filter unit  110  of  FIG. 8  therefore has a recess  113  at its mouth end, which can receive the first portion  20   a  of a cylindrical element  20  of a filter unit as described herein. 
     The filter unit  110  of  FIG. 8  can be adapted to include any of the features of the filter units of  FIGS. 3 a  to 3 d   . A user can therefore select a first filter unit  110  as illustrated in  FIG. 8 , but including an aerosol modifying additive, and attach it to a smoking article rod portion  2  as described herein. The user can then select a further second filter unit, selected from any of the filter units described herein, and attach that filter unit to the first filter unit  110 . This enables a user to achieve the properties, such as filtration and aerosol modifying properties, of multiple filter units which can be connected to the same smoking article rod portion  2 . 
       FIG. 9  is a side-on cross sectional view of a smoking article  120  including a smoking article rod portion  2  and first  110   a  and second  110   b  of the filter units  110  of  FIG. 8 , connected to the smoking article rod portion  2 . The smoking article  120  of  FIG. 9  is generally similar in construction to the smoking article  1  of  FIG. 1 a   , and the same reference numerals are used to denote equivalent features. 
       FIG. 10  is a flow diagram illustrating a method for forming a mouthpiece, in the present example a filter unit, as described herein. In a first step (S 101 ) an elongate cylinder of filter material is formed having adjacent first and second portions, the first portion arranged to be inserted into a corresponding recess in a smoking article. The cylinder can, for instance, be formed using a filter rod maker in which filter tow is fed from a supply thereof into a garniture section of the maker in which it is compressed into a rod shape and wrapped in a wrapper such as a plug wrap. The plug wrap can be provided with embossed raised areas forming the raised areas  73  and the circumferentially extending raised areas  83  as described herein. The cylinder can be cut to its final length on the filter rod maker or into lengths which are multiples of its desired final length, which can be cut to size when combined with the annular element  21 . In a second step (S 102 ) an annular element  21  is applied around the second portion  20   b  of the elongate cylinder formed in step S 101 . For instance, the annular element  21  may be formed by wrapping a sheet material around the cylinder, or by sliding a tubular filter section over the cylinder. In each case, the annular element  21  can be adhered to the outer surface of the cylindrical element using an adhesive. 
       FIG. 11  is a flow diagram illustrating a method for forming the cylindrical element of the filter unit  71  as described herein with reference to  FIG. 4 . In a first step (S 201 ), a wrapping material having the at least one raised area arranged thereon is formed. For instance, a sheet wrapping material such as a plug wrap can be embossed or otherwise provided with the at least one raised area arranged thereon. In a second step (S 202 ), an elongate cylinder of filter material is formed, for instance using a filter rod maker. The cylinder can, for instance, be formed using a filter rod maker in which filter tow is fed from a supply thereof into a garniture section of the maker in which it is compressed into a rod shape. In a third step (S 203 ), the wrapping material is wrapped around the elongate cylinder of filter material. The cylinder of filter material can be cut to its final length on the filter rod maker or into lengths which are multiples of its desired final length, which can be cut to size at a later stage. 
       FIG. 12  is a flow diagram illustrating a method for forming the cylindrical element of the filter unit  81  as described herein with reference to  FIG. 5 . In a first step (S 301 ), a wrapping material having the at least one circumferentially extending raised area arranged thereon is formed. For instance, a sheet wrapping material such as a plug wrap can be embossed or otherwise provided with the at least one circumferentially extending raised area arranged thereon. In a second step (S 302 ), an elongate cylinder of filter material is formed, for instance using a filter rod maker. The cylinder can, for instance, be formed using a filter rod maker in which filter tow is fed from a supply thereof into a garniture section of the maker in which it is compressed into a rod shape. In a third step (S 303 ), the wrapping material is wrapped around the elongate cylinder of filter material. The cylinder of filter material can be cut to its final length on the filter rod maker or into lengths which are multiples of its desired final length, which can be cut to size at a later stage. 
     The smoking articles described herein provide users with the ability to modify the characteristics of the smoking article prior to or during use of the smoking article. Any of the filter units  3 ,  30 ,  40 ,  50 ,  60 ,  71 ,  81 ,  91 ,  101 ,  110  described herein can be attached to any of the smoking article rod portions  2 . For instance, a user can be supplied with one or more smoking article rod portions  2  and a selection of the filter units  3 ,  30 ,  40 ,  50 ,  60 ,  71 ,  81 ,  91 ,  101 ,  110  which can be selectively attached to the rod portions  2  by the user as desired. 
     Although certain arrangements for the filter units  3 ,  30 ,  40 ,  50 ,  60 ,  71 ,  81 ,  91 ,  101 ,  110  and smoking article rod portions  2  have been described herein, alternative designs are possible. For instance, in some embodiments, the annular element  21  of the respective filter unit  3 ,  30 ,  40 ,  50 ,  60 ,  71 ,  81 ,  91 ,  101 ,  110  can be omitted, and a filter unit provided comprising just the cylindrical element  20 . In this case, the cylindrical element  20  may comprise both first and second portions  20   a ,  20   b , or just the first portion  20   a  arranged to be received within the recess  13 . Mouthpieces other than filter units as described herein can be used, for instance a tubular mouthpiece with an axial flowpath therethrough, formed from a material such as plastic (polyvinyl chloride or other similar polymer material), paper or card. Mouthpieces which do not perform a filtration function, or provide a limited filtration function, can be provided for use in non-combustible smoking articles such as heat-not-burn (HnB) products and other nicotine delivery products such as aerosol generation devices including e-cigarettes. Such mouthpieces could, for instance, comprise the same structure and materials as the filter units described herein. In addition, although the smoking article rod portions  2  have been described as having first and second filter sections  7 ,  10 , they can alternatively include just the first filter section  7 , or additional filter sections in addition to the first and second filter sections  7 ,  10 . For instance, the smoking article rod portions  2  described herein may comprise an additional third filter section at the tobacco rod end of the filter  6 , this third section comprising an adsorbent such as activated carbon dispersed therein. Furthermore, the smoking article rod portions  2  need not include the second filter section  10  and can have instead a recess  13  at the mouth end of the smoking article rod portion  2  formed by a stiff plug wrap or tipping material. In this case, the corresponding filter units would be adapted to fit this alternative recess arrangement. 
     Embossing has been described herein for forming the raised areas  73 ,  83 ,  103  on their respective wrappers. Such wrappers can be embossed between a pair of suitably-shaped cooperating rollers to form the raised areas  73 ,  83 ,  103 . Multiple wrappers may be embossed simultaneously and in parallel between the rollers. 
     In order to address various issues and advance the art, the entirety of this disclosure shows by way of illustration various examples in which the claimed invention(s) may be practiced and provide for superior smoking articles and filter units. The advantages and features of the disclosure are of a representative sample of examples only, and are not exhaustive and/or exclusive. They are presented only to assist in understanding and teach the claimed features. It is to be understood that advantages, examples, examples, functions, features, structures, and/or other aspects of the disclosure are not to be considered limitations on the disclosure as defined by the claims or limitations on equivalents to the claims, and that other examples may be utilised and modifications may be made without departing from the scope and/or spirit of the disclosure. Various examples may suitably comprise, consist of, or consist essentially of, various combinations of the disclosed elements, components, features, parts, steps, means, etc. In addition, the disclosure includes other inventions not presently claimed, but which may be claimed in future.