Abstract:
There is provided a smoking article, comprising: an inner rod of aerosol generating material; an inner wrapper, circumscribing the inner rod; and a combustible outer rod circumscribing the inner wrapper, wherein combustion of the outer rod is arranged to heat the inner rod to generate an aerosol for delivery through the inner rod.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a smoking article, for example a Heat-Not-Burn (HNB) device. 
       BACKGROUND 
       [0002]    Heat-Not-Burn (HNB) devices which are sometimes also referred to as non-combustion type smoking articles are being developed as a possible alternative to conventional cigarettes. HNB technology generates an aerosol by heating rather than burning tobacco and/or other smoking materials. Examples of coaxial HNB cigarettes are known from US Publication No. US 2005/0066985 and U.S. Pat. No. 5,265,626. 
         [0003]    A disadvantage of known HNB products, for example Premier™ and Eclipse™ introduced by RJ Reynolds Tobacco Company is that they do not provide a similar user experience to conventional tobacco burning cigarettes. For example, the above HNB products look, feel and taste different to conventional cigarettes. 
       SUMMARY 
       [0004]    According to the invention there is provided a smoking article, comprising: an inner rod of aerosol generating material; a inner wrapper, circumscribing the inner rod; and a combustible outer rod circumscribing the inner wrapper, wherein combustion of the outer rod is arranged to heat the inner rod to generate an aerosol for delivery through the inner rod. 
         [0005]    Advantageously the aerosol is generated through heating but not burning the inner rod. In addition, combustion of the outer rod provides a visual indictor of consumption to the user. 
         [0006]    Conveniently, the inner wrapper is substantially non-flammable. This can help prevent combustion of the inner rod. 
         [0007]    The inner wrapper may be substantially non-permeable. 
         [0008]    Preferably, the smoking article comprises a central low impedance path which is surrounded by a high impedance path. 
         [0009]    Typically, the outer rod is of a higher density than the inner rod creating a pressure drop to control airflow through the inner rod. 
         [0010]    Preferably, the smoking article further comprises a filter arranged to create a pressure drop by having portions of varying density in the filter to control airflow through the inner rod. 
         [0011]    Optionally, airflow is restricted to flow through the inner rod only. 
         [0012]    The inner wrapper may comprise bands, spaced along the length of the inner wrapper, wherein the bands are arranged to enable the inner rod to break and be disposed of along with ash from the outer rod. 
         [0013]    The inner rod can have break portions, spaced along the length of the inner rod, the break portions becoming brittle when heated to enable the inner rod to break and be disposed of along with ash from the outer rod. 
         [0014]    Typically, the aerosol generating material and/or the combustible material of the outer rod is tobacco or a tobacco substitute. 
         [0015]    The aerosol generating material can include additives, including humectants, and may be substantially non-combustible. Advantageously, humectants may i) prevent or arrest combustion of the inner rod, ii) contribute to the flavour and sensory experience for the consumer, and iii) prevent the aerosol generating material from drying out. 
         [0016]    The invention also includes a method of manufacturing a smoking article described above. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    Embodiments of the present invention will now be described by way of illustrative example with reference to the accompanying drawings, in which: 
           [0018]      FIG. 1   a  is a perspective view of a coaxial smoking article showing internal features of a body of the smoking article, including an inner rod and inner wrapper, in dashed lines. 
           [0019]      FIG. 1   b  is transverse cross-sectional view of the body of coaxial smoking article of  FIG. 1 ; 
           [0020]      FIG. 2  is a longitudinal cross-sectional view of the coaxial smoking article of  FIG. 1 , showing an expanded view of a coaxial rod arrangement of the body; 
           [0021]      FIG. 3   a  is the longitudinal cross-sectional view of  FIG. 2 , showing an expanded view of a filter arrangement for the smoking article; 
           [0022]      FIG. 3   b  is the longitudinal cross-sectional view of  FIG. 2 , showing an expanded view of an alternative filter arrangement to that of  FIG. 3   a ; and 
           [0023]      FIG. 4  is a longitudinal cross-sectional view of the coaxial smoking article of  FIG. 1 , part way though consumption. 
       
    
    
       [0024]      FIGS. 1   a,    1   b  and  2  show a coaxial smoking article  1 , referred to hereinafter as a cigarette, that has a body  2  and a filter  4 . The body  2  of the cigarette is of coaxial construction and has an inner rod  6 , an inner wrapper  8 , an outer rod  10  and an outer wrapper  12 . 
       DETAILED DESCRIPTION 
       [0025]    The inner rod  6  of the coaxial arrangement contains tobacco or a tobacco substitute. The inner rod  6  is heated during use to cause volatilisation of low boiling point components within the product, while avoiding pyrolysis or combustion of the tobacco or volatiles. This volatilisation leads to the creation of a vapour which is drawn through the cigarette  1  and is then condensed into an aerosol and inhaled by the consumer. The volatilised components include water, nicotine, humectants and light volatiles. 
         [0026]    The inner rod  6  preferably contains a blend of tobacco or tobacco substitute which has been specifically formulated for the coaxial HNB cigarette although existing tobacco blends or tobacco substitutes may be used for the inner rod  6 . 
         [0027]    The tobacco blend of one embodiment may include additives which are included to enhance the sensorial attributes of the aerosol. For example, additives such as propylene glycol, glycerol or triacetin may be added to the tobacco blend. 
         [0028]    The inner rod  6  may also contain tobacco substitutes such as Baltec, Fibex or recon sheet or paper. 
         [0029]    The blend of tobacco or tobacco substitutes used in the inner rod  6  is chosen to prevent or impede combustion of the inner rod  6 . In one embodiment, the blend is high in humectants to fulfil this function of preventing or impeding combustion. Humectants have an additional benefit of enhancing the aerosol produced by the inner rod  6  when heated which in turn may improve the sensory experience of the HNB cigarette of the present embodiment. High levels of humectants in the inner rod  6  may completely prevent combustion of the inner rod  6 . 
         [0030]    Humectants, when added to the tobacco or tobacco substitute have a further benefit of preventing the tobacco from becoming too dry. 
         [0031]    The inner rod  6  is circumscribed by the inner wrapper  8 , as shown in  FIGS. 1   a,    1   b  and  2 . The inner wrapper  8  is a non-permeable or semi-permeable material, which prevents or impedes gas or vapours from being drawn into the inner rod  6  along the length of the cigarette. 
         [0032]    In addition, the inner wrapper  8  of one embodiment is non-flammable, or is of sufficiently low flammability to prevent or arrest combustion of the inner rod  6 . 
         [0033]    The inner wrapper of one embodiment is a cigarette paper having the one or more of the above properties. 
         [0034]    The inner rod  6  and inner wrapper  8  are circumscribed by the outer rod  10 , as shown in  FIGS. 1   a  and  1   b.  The outer rod  10  comprises a combustible material, such as tobacco or a tobacco substitute, which is combusted during use. 
         [0035]    Combustion of the outer rod  10  leads to heating of the inner rod  6  which in turn generates the aerosol for delivery to the consumer. The quality of the material of the outer rod  10  need not be as high as the quality of the inner rod, since the primary function of the outer rod  10  is not to provide the aerosol to the consumer, but rather is to heat the inner rod  6  for that purpose. 
         [0036]    The outer rod  10  is circumscribed by the outer wrapper  12 . In one embodiment, the outer wrapper  12  is a conventional cigarette paper. 
         [0037]    The construction of the inner rod  6 , inner wrapper  8 , outer rod  10  and outer wrapper  12 , in one embodiment, may be achieved through conventional coaxial cigarette manufacturing technology and is not discussed herein in any further detail. 
         [0038]    As shown in the figures, the filter  4  is situated at the mouth end of the cigarette. During use, air from the body  2  of the cigarette  1  is drawn into the consumer&#39;s mouth through the filter  4 . In one embodiment, the filter  4  is made of cellulose acetate. 
         [0039]    The filter  4  can be designed to control the airflow through the cigarette  1  as the consumer inhales through the cigarette  1 . In one embodiment, as shown in  FIG. 3   a , airflow, depicted by arrow  14 , through the body  2  of the cigarette  1  is through the inner rod  6  only, such that no airflow or aerosol is derived from the combustible outer rod  10 . 
         [0040]    In an alternative embodiment, shown in  FIG. 3   b , a major airflow, depicted by arrow  16 , is through the inner rod  6 , while a minimal airflow, depicted by arrows  18 , is drawn from the combustible outer rod  10 . 
         [0041]    In both embodiments, the majority of the aerosol drawn into the consumer&#39;s mouth is derived from the inner rod  6 . This is because the smoking article has a low-impedance path which is surrounded by a high-impedance path. 
         [0042]    In one embodiment, control of the airflow  14 ,  16 ,  18  is achieved by developing a pressure drop between the inner rod  6  and outer rod  10 , such that the airflow through the cigarette  1  flows through the inner rod  6  by following the path of least resistance. 
         [0043]    The pressure drop can be manipulated as a result of different densities of the materials used in the inner rod  6  and the outer rod  10 . For example, when the inner rod  6  has a lower density than an outer rod  10 , airflow through the inner rod  6  is at a higher rate than through the outer rod  10 . 
         [0044]    In addition to, or independently of, the variations in the density of the inner and outer rods  6 ,  10 , the filter  4  is also arranged to provide the desired pressure drop. As shown in  FIGS. 3   a  and  3   b , the filter  4  has a central portion  20  and an outer portion  22  of different densities. As such, airflow through the central portion  20  is greater than through the outer portion  22  because the central portion  20  has a lower density than the outer portion  22 . 
         [0045]    The low-impedance and high impedance paths may be generated as a result of the different densities of the inner and outer rods and/or as a result of the above filter arrangement. 
         [0046]    A person skilled in the art will be able to envisage a number of potential filter arrangements which will enable development of a pressure drop. One such arrangement, shown in  FIGS. 3   a  and  3   b , comprises a substantially cylindrical filter portion, as the central portion  20 , having a tapered end closest to the body of the cigarette. The tapered end of the central portion is arranged to fit against a recess in a filter ring, being the outer portion  22 , which abuts the body  2  of the coaxial cigarette  1 . Alternatively, the outer portion/ring  22  may be integrally formed in the filter and arranged to have a higher density than the central portion  20  during manufacturing of the filter web. 
         [0047]    The pressure drop of the inner rod  6 , outer rod  10  and filter  8  arrangement is manipulated to maximise the flow down the inner rod  6 . However, it may not be necessary for the airflow  14  to be wholly along the inner rod  6  and some of the vaporous products produced by combustion of the outer rod  10  may be utilised to contribute to the flavour and the sensory experience for the consumer. 
         [0048]    Ventilation in the filter  4  or in the body  2  of the cigarette  1  may increase the rate of airflow though the inner rod  6  to ensure a suitable aerosol is delivered to the consumer. Such ventilation may be facilitated by providing perforations in tipping paper and plug wrap circumscribing the filter, in the outer wrapper, and/or in the inner wrapper. 
         [0049]    Use of the cigarette  1  will now be explained in more detail with reference to  FIG. 4 . Initially, a consumer lights a tip end  30  of the cigarette using conventional lighting means such as a match or a cigarette lighter. The lighting means applied to the tip end  30  causes the outer rod  10  at the tip end and the surrounding outer wrapper  12  to start to combust. During this lighting action the inner rod  6  will either fail to combust, or if combustion does commence, the inner rod  6  will not continue to combust. The blend of tobacco or tobacco substitute in the inner rod  6  is designed to arrest or prevent combustion of the inner rod  6 . 
         [0050]    Combustion of the outer rod  10  provides heat to the inner rod  6  which in turn volatises nicotine and flavour components from the inner rod tobacco or tobacco substitute without combustion of the inner rod  6 . The volatiles are transported through the inner rod  6 , from the tip end and are inhaled by the consumer through the filter  4 . 
         [0051]    Combustion of the outer rod  10  happens gradually from the tip end  30  toward the filter  4 . Combustion happens at a particular burn rate to ensure that the aerosol, including nicotine and flavour components, is delivered to the consumer throughout consumption. 
         [0052]      FIG. 4  shows the cigarette  1  part way through consumption. As shown, an ash portion  34  of the outer rod has already combusted and has turned to ash, and a combusting portion  36  of the outer rod  10  is in the process of combusting. Heat from this combusting portion  36  is transferred through the inner wrapper  8  to heat a corresponding portion  38  of the inner rod  6 . When this corresponding portion  38  of the inner rod  6  reaches a volatising temperature, the corresponding portion  38  of the inner rod generates the aerosol, as described above, which is inhaled through the inner rod  6  into the consumer&#39;s mouth. The heat transfer is through conduction as shown by the arrows  40  in  FIG. 4 . 
         [0053]    A distal end  42  of the combusting portion  36  turns to ash, while heat from the combusting portion  36  causes the outer rod  10  to continue to combust. In other words, heat from the portion  36  of the outer rod which is in the process of combusting travels along the length of the cigarette from the tip end  30  toward the filter  4 . As such, heat from the corresponding portion  38  of the inner rod also travels toward the filter as the outer rod  10  is combusted, ensuring that the inner rod  6  delivers the aerosol throughout the smoking process. 
         [0054]    Ash from the ash portion  34  of the outer rod  10  may naturally fall from the cigarette  1 . Advantageously, this provides a visual indicator of consumption to the consumer. 
         [0055]    In one embodiment, the inner rod  6  is banded with break portions, along the length of the cigarette. The break portions become brittle when heated, and are arranged to cause the inner rod  6  to break so that used portions of the inner rod (i.e. portions which have been heated and volatised) may be disposed of along with the ash from the outer rod. 
         [0056]    In addition, or alternatively, the inner wrapper  8  is banded with inflammable bands which are spaced along the length of the cigarette  1 . These bands help to cause breakage of the inner rod  6  so that used portions of the inner rod may be disposed of along with the ash from the outer rod. 
         [0057]    A person skilled in the art will appreciate that features of conventional cigarettes may also be included in the cigarette  1 , such features including conventional outer cigarette paper, plugwrap, tipping paper and suitable ventilation. 
         [0058]    A person skilled in the art will also appreciate that additives other than humectants may be used on the tobacco to enhance the aerosol and/or to prevent or impede combustion of the inner rod.