Patent Publication Number: US-2017347711-A1

Title: Cartridge for use with apparatus for heating smokable material

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a National Phase entry of PCT Application No. PCT/EP2015/080587, filed Dec. 18, 2015, which claims priority from GB Patent Application No. 1423316.7, filed Dec. 29, 2014, each of which is hereby fully incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a cartridge for use with apparatus for heating smokable material, and to apparatus for heating smokable material. 
     BACKGROUND 
     Smoking articles such as cigarettes, cigars and the like burn tobacco during use to create tobacco smoke. Attempts have been made to provide alternatives to these articles by creating products that release compounds without combusting. Examples of such products are so-called “heat not burn” products or tobacco heating devices or products, which release compounds by heating, but not burning, material. The material may be, for example, tobacco or other non-tobacco products, which may or may not contain nicotine. 
     SUMMARY 
     According to a first aspect of the present disclosure, there is provided a cartridge for use with apparatus for heating smokable material to volatilize at least one component of the smokable material, the cartridge comprising: a housing defining a chamber; and a heating device located in the chamber, the heating device being arranged to heat smokable material to volatilize at least one component of the smokable material, the heating device comprising a heating element and smokable material arranged on the heating element. 
     In an exemplary embodiment, the heating element is heatable by passing an electric current through the heating element. 
     In an exemplary embodiment, the cartridge comprises two electrically-conductive terminals that are accessible from an exterior of the cartridge, wherein the heating element is electrically connected across the electrically-conductive terminals. 
     In an exemplary embodiment, the smokable material is bonded to the heating element. In an exemplary embodiment, the smokable material is bonded by an adhesive to the heating element. 
     In an exemplary embodiment, the housing has a volatilized material flow path extending therethrough for permitting volatilized material to pass from the chamber out of the housing. 
     In an exemplary embodiment, the housing has one or more apertures extending therethrough for permitting volatilized material to pass from the chamber out of the housing. 
     In an exemplary embodiment, all of the housing is made of non-porous material. 
     In an exemplary embodiment, all of the housing is made of porous material for permitting volatilized material to pass from the chamber out of the housing. 
     In an exemplary embodiment, a first portion of the housing is made of porous material for permitting volatilized material to pass from the chamber out of the housing, and a second portion of the housing is made of non-porous material. 
     In an exemplary embodiment, the first portion of the housing has one or more apertures extending therethrough for permitting volatilized material to pass from the chamber out of the housing. 
     In an exemplary embodiment, the second portion of the housing has one or more apertures extending therethrough for permitting volatilized material to pass from the chamber out of the housing. 
     In an exemplary embodiment, the porous material comprises polyethylene or nylon. 
     In an exemplary embodiment, the housing has an air flow path extending therethrough for admitting air into the chamber from an exterior of the housing. 
     In an exemplary embodiment, the housing has a hole extending therethrough for admitting air into the chamber from an exterior of the housing. In an exemplary embodiment, the housing comprises a first housing part attached to a second housing part that is non-unitary with the first housing part, and wherein the first and second housing parts define the hole between the first and second housing parts. In an exemplary embodiment, the first and second housing parts cooperate so as to define the chamber. 
     In an exemplary embodiment, all of the housing is made of non-porous material. 
     In an exemplary embodiment, all of the housing is made of porous material for admitting air into the chamber from an exterior of the housing. 
     In an exemplary embodiment, a first portion of the housing is made of porous material for admitting air into the chamber from an exterior of the housing, and a second portion of the housing is made of non-porous material. 
     In an exemplary embodiment, the first portion of the housing has a hole extending therethrough for admitting air into the chamber from an exterior of the housing. 
     In an exemplary embodiment, the second portion of the housing has a hole extending therethrough for admitting air into the chamber from an exterior of the housing. 
     In an exemplary embodiment, the porous material comprises polyethylene or nylon. 
     In an exemplary embodiment, part of the cartridge comprises, or is impregnated with, a flavorant. In an exemplary embodiment, the part of the cartridge is the housing. 
     In an exemplary embodiment, the smokable material comprises tobacco. 
     In an exemplary embodiment, the smokable material is in a solid state. 
     In an exemplary embodiment, the smokable material comprises particles of the smokable material. 
     In an exemplary embodiment, the cartridge has an asymmetric exterior cross-sectional shape. 
     According to a second aspect of the present disclosure, there is provided a cartridge for use with apparatus for heating smokable material to volatilize at least one component of the smokable material, the cartridge comprising: a housing defining a chamber; and smokable material located in the chamber; wherein the housing has a volatilized material flow path extending therethrough for permitting volatilized material to pass from the chamber out of the housing. 
     In an exemplary embodiment, the housing has one or more apertures extending therethrough for permitting volatilized material to pass from the chamber out of the housing. 
     In an exemplary embodiment, all of the housing is made of non-porous material. 
     In an exemplary embodiment, all of the housing is made of porous material for permitting volatilized material to pass from the chamber out of the housing. 
     In an exemplary embodiment, a first portion of the housing is made of porous material for permitting volatilized material to pass from the chamber out of the housing, and a second portion of the housing is made of non-porous material. 
     In an exemplary embodiment, the first portion of the housing has one or more apertures extending therethrough for permitting volatilized material to pass from the chamber out of the housing. 
     In an exemplary embodiment, the second portion of the housing has one or more apertures extending therethrough for permitting volatilized material to pass from the chamber out of the housing. 
     In an exemplary embodiment, the porous material comprises polyethylene or nylon. 
     In an exemplary embodiment, the housing has an air flow path extending therethrough for admitting air into the chamber from an exterior of the housing. 
     In an exemplary embodiment, the housing has a hole extending therethrough for admitting air into the chamber from an exterior of the housing. In an exemplary embodiment, the housing comprises a first housing part attached to a second housing part that is non-unitary with the first housing part, and wherein the first and second housing parts define the hole between the first and second housing parts. In an exemplary embodiment, the first and second housing parts cooperate so as to define the chamber. 
     In an exemplary embodiment, all of the housing is made of non-porous material. 
     In an exemplary embodiment, all of the housing is made of porous material for admitting air into the chamber from an exterior of the housing. 
     In an exemplary embodiment, a first portion of the housing is made of porous material for admitting air into the chamber from an exterior of the housing, and a second portion of the housing is made of non-porous material. 
     In an exemplary embodiment, the first portion of the housing has a hole extending therethrough for admitting air into the chamber from an exterior of the housing. 
     In an exemplary embodiment, the second portion of the housing has a hole extending therethrough for admitting air into the chamber from an exterior of the housing. 
     In an exemplary embodiment, the porous material comprises polyethylene or nylon. 
     In an exemplary embodiment, part of the cartridge comprises, or is impregnated with, a flavorant. In an exemplary embodiment, the part of the cartridge is the housing. 
     In an exemplary embodiment, the smokable material comprises tobacco. 
     In an exemplary embodiment, the smokable material is in a solid state. 
     In an exemplary embodiment, the smokable material comprises particles of the smokable material. 
     In an exemplary embodiment, the cartridge has an asymmetric exterior cross-sectional shape. 
     According to a third aspect of the present disclosure, there is provided a cartridge for use with apparatus for heating smokable material to volatilize at least one component of the smokable material, the cartridge comprising: a housing defining a chamber; and smokable material located in the chamber; wherein the housing has an air flow path extending therethrough for admitting air into the chamber from an exterior of the housing. 
     In an exemplary embodiment, the housing has a hole extending therethrough for admitting air into the chamber from an exterior of the housing. In an exemplary embodiment, the housing comprises a first housing part attached to a second housing part that is non-unitary with the first housing part, and wherein the first and second housing parts define the hole between the first and second housing parts. In an exemplary embodiment, the first and second housing parts cooperate so as to define the chamber. 
     In an exemplary embodiment, all of the housing is made of non-porous material. 
     In an exemplary embodiment, all of the housing is made of porous material for admitting air into the chamber from an exterior of the housing. 
     In an exemplary embodiment, a first portion of the housing is made of porous material for admitting air into the chamber from an exterior of the housing, and a second portion of the housing is made of non-porous material. 
     In an exemplary embodiment, the first portion of the housing has a hole extending therethrough for admitting air into the chamber from an exterior of the housing. 
     In an exemplary embodiment, the second portion of the housing has a hole extending therethrough for admitting air into the chamber from an exterior of the housing. 
     In an exemplary embodiment, the porous material comprises polyethylene or nylon. 
     In an exemplary embodiment, part of the cartridge comprises, or is impregnated with, a flavorant. In an exemplary embodiment, the part of the cartridge is the housing. 
     In an exemplary embodiment, the smokable material comprises tobacco. 
     In an exemplary embodiment, the smokable material is in a solid state. 
     In an exemplary embodiment, the smokable material comprises particles of the smokable material. 
     In an exemplary embodiment, the cartridge has an asymmetric exterior cross-sectional shape. 
     According to a fourth aspect of the present disclosure, there is provided apparatus for heating smokable material to volatilize at least one component of the smokable material, the apparatus comprising an assembly having an interface, and a cartridge according to any one of the first, second and third aspects of the present disclosure, wherein the cartridge is for co-operating with the interface of the assembly. 
     In an exemplary embodiment, the apparatus is arranged to heat the smokable material to volatilize the at least one component of the smokable material without combusting the smokable material when the cartridge is co-operating with the interface of the assembly. 
     In an exemplary embodiment, the apparatus comprises a heating element for heating the smokable material, wherein the assembly comprises a controller for controlling the supply of electrical power to the heating element from an electrical power source when the cartridge is co-operating with the interface of the assembly. 
     In an exemplary embodiment, the apparatus comprises a heating element for heating the smokable material, wherein the assembly comprises a controller arranged to control heating of the heating element so as to cause heating of the smokable material to volatilize the at least one component of the smokable material without combusting the smokable material when the cartridge is co-operating with the interface of the assembly. 
     In an exemplary embodiment, the cartridge is able to co-operate with the interface in only one orientation relative to the assembly. 
     In an exemplary embodiment, the interface comprises a recess for receiving at least a portion of the cartridge. In an exemplary embodiment, the recess has an interior cross-sectional shape corresponding to an exterior cross-sectional shape of the cartridge. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  shows a perspective view of an example of an apparatus for heating smokable material to volatilize at least one component of the smokable material. 
         FIG. 2  shows a schematic cross-sectional view of the apparatus of  FIG. 1 . 
         FIG. 3  shows a perspective view of a mouthpiece of the apparatus of  FIG. 1  when detached from the rest of the apparatus. 
         FIG. 4  shows a cross-sectional view of the mouthpiece of  FIG. 3 . 
         FIG. 5  shows a perspective view of a first casing portion of the apparatus of  FIG. 1  when detached from the rest of the apparatus. 
         FIG. 6  shows a schematic cross-sectional view of the first casing portion of  FIG. 5 . 
         FIG. 7  shows a perspective view of a second casing portion of the apparatus of  FIG. 1  when detached from the rest of the apparatus. 
         FIG. 8  shows another schematic perspective view of the second casing portion of  FIG. 7  with a shell of the second casing portion that defines a compartment of the second casing portion removed. 
         FIG. 9  shows a schematic perspective cross-sectional view of a portion of the second casing portion of  FIG. 8 . 
         FIG. 10  shows a perspective view of, in isolation, a portion of a second electrical conductor of the second casing portion of  FIGS. 8 and 9  around a resilient member. 
         FIG. 11  shows a schematic perspective cross-sectional view of a portion of the apparatus of  FIGS. 1 and 2 . 
         FIG. 12  shows a schematic cross-sectional view of a portion of the apparatus of  FIGS. 1 and 2 . 
         FIG. 13  shows a schematic perspective view of a portion of the apparatus of  FIGS. 1 and 2  with portions thereof removed to expose second and third pins thereof. 
         FIG. 14  shows a perspective view of, in isolation, a cartridge of the apparatus of  FIG. 1 . 
         FIG. 15  shows a schematic cross-sectional view of the cartridge of  FIG. 14 . 
         FIG. 16  shows another schematic perspective cross-sectional view of a portion of the apparatus of  FIGS. 1 and 2  with an overall flow path therethrough indicated. 
         FIG. 17  shows a schematic close-up cross-sectional view of a portion of a heating device of the cartridge of  FIG. 15 . 
         FIG. 18  shows a schematic cross-sectional view of a cartridge. 
         FIG. 19  shows a schematic cross-sectional view of a cartridge. 
         FIG. 20  shows a schematic cross-sectional view of a cartridge. 
         FIG. 21  shows a schematic cross-sectional view of a cartridge. 
     
    
    
     DETAILED DESCRIPTION 
     As used herein, the term “smokable material” includes materials that provide volatilized components upon heating, typically in the form of an aerosol. “Smokable material” may be a non-tobacco-containing material or a tobacco-containing material. “Smokable material” may, for example, include one or more of tobacco per se, tobacco derivatives, expanded tobacco, reconstituted tobacco, tobacco extract, homogenized tobacco or tobacco substitutes. The smokable material can be in the form of ground tobacco, cut rag tobacco, extruded tobacco, gel or agglomerates. “Smokable material” also may include other, non-tobacco, products, which, depending on the product, may or may not contain nicotine. 
     As used herein, “polysaccharides” encompasses polymeric carbohydrate molecules composed of long chains of monosaccharide units bound together by glycosidic linkages, and salts and derivatives of such compounds. Suitably, derivatives of such compounds may have ester, ether, acid, amine, amide, urea, thiol, thioether, thioester, thiocarboxylic acid or thioamide side groups on the monosaccharide units. Example polysaccharides include cellulose and cellulose derivatives and alginic acid and salts thereof. In some embodiments, the polysaccharide may adhere the smokable material to the heating element. In other embodiments, the adhesive may comprise the polysaccharide as an adhesion promoter. 
     As used herein, “cellulose derivatives” are compounds in which the hydroxyl groups of cellulose are partially or fully substituted by various groups. Example cellulose derivatives are cellulose esters and ethers. In some embodiments, the cellulose derivative may comprise a cellulose ether, which may include alkyl, hydroxyalkyl and carboxyalkyl cellulose ethers. In some embodiments, the cellulose derivative may be a hydroxyalkyl cellulose ether, such as hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methylcellulose, hydroxypropyl methylcellulose and hydroxyethyl ethylcellulose. The cellulose derivative may be selected from hydroxyethyl methylcellulose, hydroxypropyl methylcellulose and hydroxyethyl ethylcellulose in some cases. The cellulose derivative may comprise or substantially consist of hydroxypropyl methylcellulose. 
     As used herein, “polyimide” refers to any polymer comprising or substantially formed of imide monomers and may be saturated or unsaturated. The polyimide may be hydrophobic. 
     As used herein, “polyester” refers to polymers which contain the ester functional group in their main chain. They may be formed by the esterification condensation of polyfunctional alcohols and acids. In some cases, the ester functional group is present about half or the repeating units, or in the majority of or substantially all of the repeating units. Polyesters may be saturated or unsaturated, aliphatic, semi-aromatic or aromatic, and may be copolymers or homopolymers. The polyester may be hydrophobic. 
     As used herein, the terms “flavor” and “flavorant” refer to materials which, where local regulations permit, may be used to create a desired taste or aroma in a product for adult consumers. They may include extracts (e.g., licorice, hydrangea, Japanese white bark magnolia leaf, chamomile, fenugreek, clove, menthol, Japanese mint, aniseed, cinnamon, herb, wintergreen, cherry, berry, peach, apple, Drambuie, bourbon, scotch, whiskey, spearmint, peppermint, lavender, cardamom, celery, cascarilla, nutmeg, sandalwood, bergamot, geranium, honey essence, rose oil, vanilla, lemon oil, orange oil, cassia, caraway, cognac, jasmine, ylang-ylang, sage, fennel, piment, ginger, anise, coriander, coffee, or a mint oil from any species of the genus  Mentha ), flavour enhancers, bitterness receptor site blockers, sensorial receptor site activators or stimulators, sugars and/or sugar substitutes (e.g., sucralose, acesulfame potassium, aspartame, saccharine, cyclamates, lactose, sucrose, glucose, fructose, sorbitol, or mannitol), and other additives such as charcoal, chlorophyll, minerals, botanicals, or breath freshening agents. They may be imitation, synthetic or natural ingredients or blends thereof. They may be in any suitable form, for example, oil, liquid, or powder. 
     Referring to  FIGS. 1 and 2 , there is shown a perspective view and a schematic cross-sectional view of an example of an apparatus  1  for heating smokable material to volatilize at least one component of the smokable material. The apparatus  1  is arranged to heat smokable material to volatilize at least one component of the smokable material, typically to form an aerosol which can be inhaled, without combusting, or burning, the smokable material. The apparatus  1  comprises a first casing portion  10 , a second casing portion  20 , a mouthpiece  30  and a cartridge  40 . The combination of the first and second casing portions  10 ,  20  constitutes a casing of the apparatus  1 . The combination of the first and second casing portions  10 ,  20  and the mouthpiece  30  constitutes an assembly having an interface (discussed below) with which the cartridge  40  is able to co-operate. Each of these components will be discussed in turn. 
     The first casing portion  10  is located between the second casing portion  20  and the mouthpiece  30 . Each of the first and second casing portions  10 ,  20  and the mouthpiece  30  defines a respective portion of the outer casing of the overall apparatus  1 . Accordingly, the outward appearance of the apparatus  1  is defined by the combination of the first and second casing portions  10 ,  20  and the mouthpiece  30 . 
     Referring to  FIGS. 1, 5 and 6 , the first casing portion  10  is generally tubular and elongate, has first and second opposite longitudinal ends  11 ,  12 , and defines the interface for co-operating with the cartridge  40 . In this embodiment, the interface comprises a recess  13  for receiving the cartridge  40 . In other embodiments, the interface can take a different form, such as a shelf, a surface, or a projection, and optionally requires mechanical mating with the cartridge  40  in order to co-operate with the cartridge  40 . The second longitudinal end  12  of the first casing portion  10  defines an opening  14  into the recess  13 . The opening  14  is shaped and sized so that the cartridge  40  is movable through the opening  14  to allow a user to insert the cartridge  40  into the recess  13  and/or to remove the cartridge  40  from the recess  13 , as will be described in more detail below. The first longitudinal end  11  of the first casing portion  10  comprises a first connector  15  that is releasably engageable with a second connector  25  of the second casing portion  20 , as is also described in more detail below. 
     Referring to  FIGS. 1, 2, 7 and 8 , the second casing portion  20  is generally tubular and elongate, has first and second opposite longitudinal ends  21 ,  22 , and defines a compartment  23 . A plurality of first electrical components is contained in the compartment  23 . The first electrical components in this embodiment comprise an electrical power source  24  in the form of a rechargeable battery, a printed circuit board (PCB)  26  and a universal serial bus (USB) charging interface  27 . In other embodiments, the electrical power source  24  may be other than a rechargeable battery, such as a non-rechargeable battery or a capacitor. The charging interface  27  is accessible at the exterior of the apparatus  1  at the first longitudinal end  21  of the second casing portion  20 . An electrical charging circuit and a voltage regulator  26   b  are provided on the PCB  26 . The combination of the electrical charging circuit and the charging interface  27  constitutes a charging arrangement of the apparatus  1 . The electrical charging circuit is electrically connected to positive and negative terminals  24   a ,  24   b  of the battery  24  and is electrically connected to the charging interface  27 . The battery  24  is chargeable by connecting the charging arrangement to an external supply (not shown) of electrical power using the charging interface  27 . The electrical charging circuit comprises an overcharge preventer for preventing overcharging of the battery  24 . In variations to the illustrated embodiment, the charging interface  27  may take a form other than that dictated by the USB standard and/or may be located elsewhere on the second casing portion  20  or elsewhere on the apparatus  1 . In some embodiments, the charging arrangement may be omitted. 
     Referring to  FIG. 7 , the second longitudinal end  22  of the second casing portion  20  comprises the second connector  25  that is engageable with the first connector  15  of the first casing portion  10 . In this embodiment, the first connector  15  is engageable with the second connector  25  so as to connect the second casing portion  20  to the first casing portion  10 . In other embodiments, the first and second casing portions  10 ,  20  may be permanently connected, such as through a hinge or flexible member, so that engagement of the first connector  15  with the second connector  25  would not connect the second casing portion  20  to the first casing portion  10 , as such but would serve to facilitate partial separation or opening of the first casing portion  10  and the second casing portion  20 . In this embodiment, the first connector  15  is releasably engageable with the second connector  25  so as to detachably connect the second casing portion  20  to the first casing portion  10 . Accordingly, if the rechargeable battery  24  contained in the second casing portion  20  becomes exhausted, a user is able to swap the second casing portion  20  for another second casing portion  20  containing a non-exhausted electrical power source  24 . The user is thus able to continue using the apparatus  1 , for example during recharging of the first, exhausted rechargeable battery  24 . In other embodiments, the first connector  15  may not be disengageable from the second connector  25  once the first and second connectors  15 ,  25  are connected to each other. In such other embodiments the second casing portion  20  becomes permanently connected to the first casing portion  10  on engagement of the first and second connectors  15 ,  25 . 
     Referring to  FIGS. 5 to 8 , in this embodiment the first and second connectors  15 ,  25  are female and male connectors  15 ,  25 , respectively, and comprise co-operable female and male screw threads  15   a ,  25   a , respectively. In some other embodiments, the first and second connectors  15 ,  25  may be female and male connectors  15 ,  25 , respectively, and may comprise co-operable female and male screw threads, respectively. In still further embodiments, the first and second connectors  15 ,  25  may comprise co-operable structures other than screw threads, such as a pin and slot together defining a bayonet coupling, a protrusion and a hole together defining a snap-fit connection, a plug and a socket, or the like. 
     In this embodiment, the first and second connectors  15 ,  25  are electrically-conductive so that, when the first and second connectors  15 ,  25  are engaged, an electric current can be conducted from the second connector  25  to the first connector  15 , as discussed in more detail below. In this embodiment, each of the first and second connectors  15 ,  25  is made from a metal or a metal alloy, such as copper or stainless steel, etc. In other embodiments, one or both of the first and second connectors  15 ,  25  may be made from a different electrically-conductive material. 
     Referring to  FIG. 7 , it can be seen that in this embodiment the second screw thread  25   a  has four notches  25   n  therethrough, spaced circumferentially around the second screw thread  25   a . In other embodiments, there may be more or fewer notches  25   n  through the second screw thread  25   a . In this embodiment, each of the notches  25   n  extends linearly and radially through the second screw thread  25   a . In other embodiments, the notch(es)  25   n  may extend radially and non-linearly through the second screw thread  25   a , or linearly and non-radially through the second screw thread  25   a , or non-linearly and non-radially through the second screw thread  25   a . In this embodiment, the notches  25   n  are provided only through the second screw thread  25   a . In other embodiments, there may be one or more notches additionally or alternatively provided through the first screw thread  15   a . In some embodiments, the first and second connectors  15 ,  25  may be arranged so that the notch(es) provided through the first screw thread  15   a  align with the notch(es) provided through the second screw thread  25   a  when the first connector  15  is fully engaged with the second connector  25 . 
     When the first connector  15  is fully engaged with the second connector  25 , as shown most clearly in  FIG. 11 , the first and second connectors  15 ,  25  cooperate to define between the first and second connectors  15 ,  25  four inlets  60  for admitting air into the apparatus  1 , and more specifically into the recess  13  of the first casing portion  10 , from an exterior of the apparatus  1 . The inlets  60  fluidly communicate with the exterior of the apparatus  1  via an annular gap  62  that remains between the first and second connectors  15 ,  25  at an exterior surface of the apparatus  1  when the first connector  15  is fully engaged with the second connector  25 . The first connector  15  is fully engaged with the second connector  25  when no more of the first connector  15  can be made to engage with the second connector  25 . In this embodiment, this full engagement occurs when the first connector  15  cannot be moved further into the second connector  25 . This may, for example, be because the leading edge of the first screw thread  15   a  of the first connector  15  has reached the end of the second screw thread  25   a  of the second connector  25 , or because respective stops of the first and second connectors  15 ,  25  have been brought into contact with each other during the engagement of the first and second connectors  15 ,  25 . In other embodiments, there may be provided other mechanisms for defining the point at which the first and second connectors  15 ,  25  are fully engaged. In this embodiment, the first and second connectors  15 ,  25  are relatively movable to alter a cross-sectional area of each of the inlets  60 , while maintaining engagement of the first and second connectors  15 ,  25 , so as to control the flow of air through the inlets  60 . In this embodiment, the degree of engagement of the first and second connectors  15 ,  25  is changeable by rotating one of the first and second connectors  15 ,  25  relative to the other. This has the effect of correspondingly altering the axial dimension of the inlets  60  between the first and second connectors  15 ,  25 , so as to alter the cross-sectional area of each of the inlets  60 . In this embodiment, each of the inlets  60  is defined by a respective one of the notches  25   n  and a corresponding adjacent portion of the first connector  15 . In other embodiments in which more or fewer notches are provided, there would be correspondingly more or fewer inlets, respectively. 
     In this embodiment, the compartment  23  provided in the second casing portion  20 , and thus each of the first electrical components therein, is isolated from each of the inlets  60  by the material of the second connector  25 , a board comprising second and third electrical conductors  282 ,  283  (discussed below and shown in  FIGS. 9 and 10 ), and a plug  25   b  nested within the second connector  25  between the second connector  25  and the board. This helps prevent the first electrical components being brought into contact with dust or other foreign matter that might be drawn into the apparatus  1  through the inlet(s)  60  during operation of the apparatus  1 , which otherwise could negatively affect performance of the first electrical components. However, in other embodiments, the compartment  23  and/or the electrical power source  24  and/or the PCB  26  (if provided) and/or the charging interface  27  (if provided) may be fluidly connected to one or more or all of the inlets. 
     In this embodiment, the first and second casing portions  10 ,  20  comprise respective electrical connections for supplying electrical power from the electrical power source  24  to the first casing portion  10 , for powering the cartridge  40  as discussed below. More specifically, in this embodiment the second casing portion  20  comprises a first electrical conductor  281  (shown most clearly in  FIG. 8 ) that extends from the negative terminal  24   b  of the battery  24  to the second screw thread  25   a  of the second connector  25  and bypasses the voltage regulator  26   b , the second electrical conductor  282  (shown most clearly in  FIGS. 9 and 10 ) that extends from the positive terminal  24   a  of the battery  24  to the voltage regulator  26   b  on the PCB  26 , and a third electrical conductor  283  (also shown most clearly in  FIGS. 9 and 10 ) that extends from the voltage regulator  26   b  to a terminal  283   a . The third electrical conductor  283  is separated from the second electrical conductor  282  by an electrical insulator  284  so as to be electrically insulated from the second electrical conductor  282 . The terminal  283   a  is centrally located on the longitudinal axis of the second casing portion  20  at the second longitudinal end  22  of the second casing portion  20 . The terminal  283   a  is contactable via a hole  25   c  in the plug  25   b . In this embodiment, the terminal  283   a  is a positive terminal of the second casing portion  20 , and the second screw thread  25   a  of the second connector  25  is a negative terminal of the second casing portion  20 . 
     A portion of the second electrical conductor  282  is in contact with the positive terminal  24   a  of the battery  24 . A portion of the third electrical conductor  283  comprises the terminal  283   a . These portions of the second and third electrical conductors  282 ,  283  are wrapped around a resilient member  29 . The resilient member  29  biases the second electrical conductor  282  into contact with the positive terminal  24   a  of the battery  24  in a first direction. This helps to maintain good electrical contact between the second electrical conductor  282  and the positive terminal  24   a  of the battery  24 . The resilient member  29  also biases the portions of the second and third electrical conductor  282 ,  283  into contact with the plug  25   b  in a second direction. This helps to provide a seal between the second and third electrical conductors  282 ,  283  and the plug  25   b , thereby to aid isolation of the compartment  23  from the inlets  60 . The second electrical conductor  282  extends from the positive terminal  24   a  of the battery  24 , around the resilient member  29 , and along the majority of the longitudinal length of the second casing portion  20  to the PCB  26 , so as to electrically connect the positive terminal  24   a  of the battery  24  to the electrical charging circuit and the voltage regulator  26   b  on the PCB  26 , as previously mentioned. The third electrical conductor  283  extends from the voltage regulator  26   b  and along the majority of the longitudinal length of the second casing portion  20  to the terminal  283   a.    
     In this embodiment, each of the first, second and third electrical conductors  281 ,  282 ,  283  is made from a metal or a metal alloy, such as copper or stainless steel, etc., but in other embodiments one or more of the first, second and third electrical conductors  281 ,  282 ,  283  may be made from a different electrically-conductive material. 
     The respective electrical connections of the first and second casing portions  10 ,  20  for supplying electrical power from the electrical power source  24  to the first casing portion  10  in the present embodiment are further illustrated in  FIGS. 11 to 13 . The first screw thread  15   a  of the first connector  15  is in this embodiment a negative terminal of the first casing portion  10 , and is electrically connected to the negative terminal, i.e. the second screw thread  25   a  of the second connector  25 , of the second casing portion  20  when the first connector  15  is fully engaged with the second connector  25 . A plate  16  is mounted to the first connector  15 . The plate  15  is circular about a central axis that is coincident with the longitudinal axis of the first casing portion  10 . The plate  16  is within the first casing portion  10  between the first longitudinal end  11  of the first casing portion  10  and the recess  13  of the first casing portion  10 . Five holes  16   a - 16   e  are provided through the plate  16 . A first hole  16   a  of these holes is centrally located on the longitudinal axis of the first casing portion  10 . Within the first hole  16   a  is a first pin  17   a  that projects away from the plate  16  towards the first longitudinal end  11  of the first casing portion  10 . The first pin  17   a  is electrically-conductive and may be made from a metal or a metal alloy, such as copper or stainless steel or the like. The first pin  17   a  is a positive terminal of the first casing portion  10 . When the first connector  15  is fully engaged with the second connector  25 , as is most clearly illustrated in  FIG. 11 , the first pin  17   a  is located in the hole  25   c  in the plug  25   b  and is in surface contact with the positive terminal, i.e. the terminal  283   a , of the second casing portion  20 . 
     Referring to  FIG. 12 , within second and third holes  16   b ,  16   c  of the holes through the plate  16  are second and third pins  17   b ,  17   c  that project away from the plate  16  in an opposite direction to the pin  17   a , and into the recess  13 . Each of the second and third pins  17   b ,  17   c  is electrically-conductive and may be made from a metal or a metal alloy, such as copper or stainless steel or the like. Herein, the second pin  17   b  is referred to as a “first electrically-conductive terminal” and the third pin  17   c  is referred to as a “second electrically-conductive terminal”. Moreover, herein, the first pin  17   a  is referred to as a “third electrically-conductive terminal”, the terminal  283   a  of the second casing portion  20  is referred to as a “fourth electrically-conductive terminal”, the first screw thread  15   a  of the first connector  15  is referred to as a “fifth electrically-conductive terminal”, and the second screw thread  25   a  of the second connector  25  is referred to as a “sixth electrically-conductive terminal”. The first and second electrically-conductive terminals  17   b ,  17   c  are for supplying electrical power to the cartridge  40 , when the interface is co-operating with the cartridge  40  (i.e. when the cartridge  40  is fully located in the recess  13 ) and the first connector  15  is fully engaged with the second connector  25 . 
     In this embodiment, the second electrically-conductive terminal  17   c  is electrically connected to the fifth electrically-conductive terminal  15   a  via a controller  50  contained in the first casing portion  10 . Moreover, in this embodiment, the first electrically-conductive terminal  17   b  is electrically connected to the third electrically-conductive terminal  17   a  via the controller  50 . In this embodiment, the controller  50  comprises an integrated circuit (IC). In other embodiments, the controller  50  may take a different form. The controller  50  is for controlling the supply of electrical power to a heating element  410  in the cartridge  40 , when the cartridge  40  is fully located in the recess  13 , as will be described in more detail below. When the first connector  15  is fully engaged with the second connector  25 , the third electrically-conductive terminal  17   a  is in surface contact with the fourth electrically-conductive terminal  283   a , and the fifth electrically-conductive terminal  15   a  is in surface contact with the sixth electrically-conductive terminal  25   a . That is, the first casing portion  10  is connected to the second casing portion  20  with the third and fifth electrically-conductive terminals  17   a ,  15   a  in surface contact with the fourth and sixth electrically-conductive terminals  283   a ,  25   a , respectively. 
     Accordingly, when the first connector  15  is fully engaged with the second connector  25 , the positive terminal  24   a  of the electrical power source  24  is electrically connected to the controller  50  via the voltage regulator  26   b , and the negative terminal  24   b  of the electrical power source  24  is electrically connected to the controller  50  by an electrically-conductive path that is free of the voltage regulator  26   b . Since each of the first and second screw threads  15   a ,  25   a  is part of the casing of the apparatus  1 , the electrically-conductive path comprises a part of the casing. 
     In this embodiment, the controller  50  is located in the first casing portion  10 , and more specifically radially outwardly of the recess  13  and between the first and second longitudinal ends  11 ,  12  of the first casing portion  10 . The controller  50  is operated in this embodiment by user-actuation of an actuator  18 . The actuator  18  is located at the exterior of the first casing portion  10  radially outwardly of the controller  50  and the recess  13  and takes the form of a push-button. In other embodiments, a different form of actuator  18  may be provided, such as a toggle switch, a dial, or the like. In this embodiment, the controller  50  is isolated from each of the inlets  60  by the plate  16  and the section of the first casing portion  10  that defines the recess  13 . In other embodiments, additional or alternative electrical components located in the first casing portion  10  may be isolated from the inlets  60 . This helps prevent the electrical components in the first casing portion  10  being brought into contact with dust or other foreign matter that might be drawn into the apparatus  1  through the inlet(s)  60  during operation of the apparatus  1 , which otherwise could negatively affect performance of those electrical components. However, in other embodiments, the controller  50  and/or other electrical components in the first casing portion  10  may be fluidly connected to one or more of the inlets  60 . 
     In other embodiments, the controller  50  may be provided in the plate  16  of the first casing portion  10 , or in the second casing portion  20 . The controller  50  may be provided on a PCB or another structure. In embodiments in which the controller  50  is comprised in the second casing portion  20 , one of the positive and negative terminals  24   a ,  24   b  of the electrical power source  24  may be electrically connected to the controller  50  via the voltage regulator  26   b , and the other of the positive and negative terminals  24   a ,  24   b  of the electrical power source  24  may be electrically connected to the controller  50  by an electrically-conductive path that is free of the voltage regulator  26   b.    
     In this embodiment, the first, third and fourth electrically-conductive terminals  17   b ,  17   a ,  283   a  are electrically connected to the positive terminal  24   a  of the electrical power source  24 , and the second, fifth and sixth electrically-conductive terminals  17   c    15   a ,  25   a  are electrically connected to the negative terminal  24   b  of the electrical power source  24 , when the first connector  15  is engaged with the second connector  25 . In some other embodiments, the polarities of the terminals  24   a ,  24   b  of the battery  24  may be reversed. 
     Providing that one of the positive and negative terminals  24   a ,  24   b  of the electrical power source  24  is electrically connected to the controller  50  via the voltage regulator  26   b , while the other of the positive and negative terminals  24   a ,  24   b  of the electrical power source  24  is electrically connected to the controller  50  by an electrically-conductive path that is free of the voltage regulator  26   b , helps to simplify manufacture of the apparatus  1 . Fewer connections to the voltage regulator  26   b  may be required and the electrically-conductive path can be provided regardless of the location of the voltage regulator  26   b  in the apparatus  1 . This also gives a designer of the apparatus  1  greater design freedom when designing the apparatus  1 . 
     The mouthpiece  30  of this embodiment of the apparatus  1  will now be described in more detail, with particular reference to  FIGS. 3 and 4 . The mouthpiece  30  is generally tubular and elongate and has first and second opposite longitudinal ends  31 ,  32 . The first longitudinal end  31  of the mouthpiece  30  is a first longitudinal end of the apparatus  1 , whereas the first longitudinal end  21  of the second casing portion  20  is a second longitudinal end of the apparatus  1 . The second longitudinal end  32  of the mouthpiece  30  comprises a connector  33  that is engageable with a second connector  19  of the first casing portion  10  at the second longitudinal end  12  of the first casing portion  10 . 
     In this embodiment, the connector  33  of the mouthpiece  30  is engageable with the second connector  19  of the first casing portion  10  so as to connect the mouthpiece  30  to the first casing portion  10 . In other embodiments, the mouthpiece  30  and the first casing portion  10  may be permanently connected, such as through a hinge or flexible member, so that engagement of the connector  33  of the mouthpiece  30  with the second connector  19  of the first casing portion  10  would not be so as to connect the mouthpiece  30  to the first casing portion  10 , as such. In this embodiment, the connector  33  of the mouthpiece  30  is releasably engageable with the second connector  19  of the first casing portion  10  so as to detachably connect the mouthpiece  30  to the first casing portion  10 . In other embodiments, the connector  33  of the mouthpiece  30  may not be disengageable from the second connector  19  of the first casing portion  10  once connected thereto. In such other embodiments the mouthpiece  30  may become permanently connected to the first casing portion  10  on engagement of the connector  33  of the mouthpiece  30  with the second connector  19  of the first casing portion  10 . 
     In this embodiment, the connector  33  of the mouthpiece  30  and the second connector  19  of the first casing portion  10  respectively comprise two protrusions and two corresponding holes or recesses. The protrusions and recesses together define a snap-fit connection for connecting the mouthpiece  30  to the first casing portion  10 . In other embodiments the connector  33  of the mouthpiece  30  and the second connector  19  of the first casing portion  10  may comprise other forms of co-operable structures, such as co-operable screw threads, a bayonet coupling, a plug and a socket, or the like. 
     The mouthpiece  30  comprises an inlet  34  at the second longitudinal end  32  of the mouthpiece  30 , an outlet  35  at the first longitudinal end  31  of the mouthpiece  30 , and a channel  36  fluidly connecting the inlet  34  with the outlet  35 . In this embodiment, the channel  36  extends substantially linearly along the longitudinal axis of the mouthpiece  30 . In other embodiments, the channel  36  may be located elsewhere in the mouthpiece  30  or may take other than a substantially linear form. The mouthpiece  30  also comprises a seal  37  surrounding the inlet  34 . In this embodiment, the seal  37  defines the inlet  34 , but in other embodiments the inlet  34  may be defined by another member and the seal  37  may surround the other member. In this embodiment, the seal  37  is flexible and resilient, but in other embodiments the seal  37  may be hard, rigid or inflexible. Moreover, in this embodiment the seal  37  comprises an O-ring that is attached to the rest of the mouthpiece  30 , but in other embodiments the seal  37  could take a different form and may not even be circular. For example, in some embodiments, the seal  37  may be co-molded with the rest of the mouthpiece  30 . In some such embodiments, the seal  37  may be resilient while other portions of the mouthpiece  30  are less resilient or inflexible. 
     In some embodiments, the mouthpiece  30  may comprise, or be impregnated with, a flavorant. The flavorant may be arranged so as to be picked up by the hot aerosol as the aerosol passes through the channel  36  of the mouthpiece  30  in use. 
     The mouthpiece  30  is locatable relative to the first casing portion  10  so as to cover the opening  14  into the recess  13 . More specifically, in this embodiment, the mouthpiece  30  is locatable relative to the first casing portion  10  so as to cover the opening  14  with the outlet  35  at the exterior of the apparatus  1 , and with the seal  37  facing the recess  13 . When the mouthpiece  30  is so located relative to the first casing portion  10 , the seal  37  is for contacting the cartridge  40  when the cartridge  40  is in the recess  13  to seal the inlet  31  of the mouthpiece  30  to the cartridge  40  in use. In this embodiment, when the mouthpiece  30  is so located relative to the first casing portion  10 , and when the cartridge  40  is in the recess  13 , the seal  37  is compressed between the channel  36  and the cartridge  40 . This presses the cartridge  40  into the recess  13 , which in turn helps ensure that the seventh and eighth electrically-conductive terminals  47   a ,  47   b  (discussed below) of the cartridge  40  are in surface contact with the first and second electrically-conductive terminals  17   b ,  17   c , respectively. 
     The cartridge  40  of this embodiment of the apparatus  1  will now be described in more detail, with particular reference to  FIGS. 14, 15 and 17 . In this embodiment, the cartridge  40  comprises a housing  43  defining a chamber  44 . A heating device  400  is located within the chamber  44 . In other embodiments, the housing  43  may be omitted or take a different form to that illustrated. In some embodiments, the heating device may be comprised in an apparatus that does not comprise a cartridge. As will be described in more detail below, in this embodiment, the heating device  400  comprises a heating element  410  with smokable material  420  arranged on the heating element  410 . The heating element  410  is for heating the smokable material  420 , and is a support on which the smokable material  420  is arranged. The heating device  400  is arranged to heat the smokable material  420  to volatilize at least one component of the smokable material  420  to create volatilized material. Typically, this volatilization causes the formation of an aerosol. The aerosol is inhalable by a user of the apparatus  1  via the channel  36  of the mouthpiece  30 . Operation of the apparatus  1  will be described in more detail below. 
     In this embodiment, the housing  43  comprises first and second housing parts  43   a ,  43   b  that cooperate so as to define the chamber  44 . The heating device  400  extends from the first housing part  43   a  into the chamber  44  and towards and through the second housing part  43   b . The first and second housing parts  43   a ,  43   b  define first and second longitudinal ends  41 ,  42  of the cartridge  40 , respectively. In other embodiments, first and second longitudinal ends  41 ,  42  of the cartridge  40  may both be defined by one housing part, i.e. by one component. In this embodiment, the first housing part  43   a  is non-unitary with the second housing part  43   b  and is attached to the second housing part  43   b . In this embodiment, this attachment is effected through a snap-fit connection between the first and second housing parts  43   a ,  43   b , but in other embodiments the attachment may be effected through other mechanisms. In this embodiment, all of the housing  43  is made of non-porous material. Accordingly, air is unable to pass through the material of the housing  43  itself. However, with the first and second housing parts  43   a ,  43   b  so attached, the first and second housing parts  43   a ,  43   b  cooperate so as to define an air flow path  45  in the form of a hole  45  between the first and second housing parts  43   a ,  43   b . The air flow path  45  extends through the housing  43  and is for admitting air into the chamber  44  of the cartridge  40  from an exterior of the housing  43 . 
     In other embodiments, the air flow path  45  may be defined differently, such as by a hole formed through a component of the housing  43 . In some embodiments, the housing  43  may consist of more or fewer housing parts defining the chamber  44  and/or defining the air flow path  45 . In embodiments other than those shown in the Figures, a portion, or all, of the housing  43  may be made of porous material for admitting air into the chamber  44  of the cartridge  40  from an exterior of the housing  43 . That is, the air may be able to pass through the material of the housing  43  itself without there necessarily being a hole through the material or a gap between the first and second housing parts  43   a ,  43   b . Accordingly, the porous material itself provides one or more air flow paths extending through the housing  43  for admitting air into the chamber  44  of the cartridge  40  from an exterior of the housing  43 . In some embodiments, a first portion of the housing  43  may be made of porous material for admitting air into the chamber  44  from an exterior of the housing  43 , and a second portion of the housing  43  may be made of non-porous material. In some such embodiments, the first portion and/or the second portion of the housing  43  may have one or more holes extending therethrough for further admitting air into the chamber  44  from an exterior of the housing  43 . 
     In this embodiment, since all of the housing  43  is made of non-porous material, aerosol or volatilized material generated within the housing  43  is unable to pass through the material of the housing  43  itself. However, the housing  43  has a plurality of volatilized material flow paths extending therethrough for permitting the volatilized material to pass from the chamber  44  out of the housing  43 . In this embodiment, the volatilized material flow paths comprise a plurality of apertures  46  extending through the housing. In this embodiment, the apertures  46  extend through the second housing part  43   b . As shown in  FIGS. 2 and 16 , in this embodiment, when the mouthpiece  30  is located relative to the first casing portion  10  so as to cover the opening  14 , the seal  37  surrounds the apertures  46  at the exterior of the housing  43 , with the apertures  46  fluidly connected to the channel  36  via the inlet  34  of the mouthpiece  30 . In this embodiment, the apertures  46  are at the second longitudinal end  42  of the cartridge  40 . The second longitudinal end  42  is closer to the mouthpiece  30  in the assembled apparatus  1  than is the first longitudinal end  41  of the cartridge  40 . In some embodiments, the housing  43  may have only one volatilized material flow path extending therethrough for permitting the volatilized material to pass from the chamber  44  out of the housing  43 . For example, in some embodiments, there may be provided only a single aperture in place of the plurality of apertures  46 . 
     In embodiments other than those shown in the Figures, a portion, or all, of the housing  43  may be made of porous material for permitting aerosol or volatilized material to pass from the chamber  44  out of the housing  43 . That is, aerosol or volatilized material may be able to pass through the material of the housing  43  itself without there necessarily being one or more apertures through the material. Accordingly, the porous material itself provides one or more volatilized material flow paths extending through the housing  43  for permitting the volatilized material to pass from the chamber  44  out of the housing  43 . In some embodiments, a first portion of the housing  43  is made of non-porous material, and a second portion of the housing  43  is made of porous material for permitting volatilized material to pass from the chamber  44  out of the housing  43 . The second portion of the housing  43  may comprise a plate co-co-molded with the first portion of the housing  43 , for example. In some such embodiments, the first portion and/or the second portion of the housing  43  may have one or more apertures  46  extending therethrough for further permitting volatilized material to pass from the chamber  44  out of the housing  43 . In some embodiments, an inlet portion of the housing  43  may be made of porous material for admitting air into the chamber  44  of the cartridge  40  from an exterior of the housing  43 , and an outlet portion of the housing  43  may be made of porous material for permitting volatilized material to pass from the chamber  44  to the exterior of the housing  43 . The inlet and outlet portions may have the same, or different, porosities or void fractions. 
     Where used, the porous material of the housing  43  may comprise for example polyethylene or nylon. Different grades of polyethylene offer different levels of porosity. The use of polyethylene to provide a suitable housing, or portion of a housing, for permitting aerosol or volatilized material to pass from the chamber  44  to the exterior of the housing  43  will be apparent to the skilled person on consideration of this disclosure. In some embodiments, part of the cartridge, such as the housing, may comprise, or be impregnated with, a flavorant. The flavorant may be arranged so as to be picked up by the hot aerosol generated within the chamber  44  in use. 
     In this embodiment, and as shown in  FIG. 17 , the heating element  410  comprises a sandwich or laminate structure comprising three layers. The three layers are a first layer  411  of material, a layer  412  of electrically-conductive material, and a second layer  413  of material. The layer  412  of electrically-conductive material is located between, and in contact with, the first and second layers  411 ,  413  of material. The first layer  411  of material is a first support layer  411 , and the second layer  413  of material is a second support layer  413 . However, in other embodiments, the sandwich or laminate structure may comprise more or fewer layers. In some embodiments, such as this embodiment, the heating element  410  comprises a first support layer  411  and a layer  412  of electrically-conductive material on a surface of the first support layer  411  and defining one or more electrically-conductive tracks. In some embodiments, the heating element  410  may not comprise a sandwich or laminate structure. For example, in some embodiments one or both of the first and second support layers  411 ,  413  may be omitted. In some embodiments, one or more additional layers may be provided between the layer  412  of electrically-conductive material and the first support layer  411  and/or between the layer  412  of electrically-conductive material and the second support layer  413 . 
     The layer  412  of electrically-conductive material is retained relative to each of the first and second support layers  411 ,  413 . This can be achieved in a number of different ways. For example, as in this embodiment, the material of the first and second support layers  411 ,  413  may envelop or surround the layer  412  of electrically-conductive material, so as to retain the layer  412  of electrically-conductive material relative to each of the first and second support layers  411 ,  413 . Alternatively or additionally, some portion(s) of the material of the first and second support layers  411 ,  413  may be located in holes formed through the layer  412  of electrically-conductive material, so as to lock the first and second support layers  411 ,  413  to the layer  412  of electrically-conductive material. Alternatively or additionally, depending on the materials used, the material of the first and second support layers  411 ,  413  may bond naturally to the material of the layer  412  of electrically-conductive material, so as to lock the first and second support layers  411 ,  413  to the layer  412  of electrically-conductive material. Alternatively or additionally, the first and second support layers  411 ,  413  may be bonded to the layer  412  of electrically-conductive material by an adhesive. When provided, such adhesive may form additional identifiable adhesive layers between the layer  412  of electrically-conductive material and the first and second support layers  411 ,  413 , respectively. 
     In this embodiment, the material of the first support layer  411  is the same material as the material of the second support layer  413 . This can facilitate manufacture of the sandwich or laminate structure. During manufacture, the layer  412  of electrically-conductive material may be dipped in the material of the first and second support layers  411 ,  413  in fluid form, so as to coat some or all of the layer  412  of electrically-conductive material. Then, the material of the first and second support layers  411 ,  413  may be allowed to cure or set so as to harden, thereby retaining the resultant first and second support layers  411 ,  413  relative to the layer  412  of electrically-conductive material. 
     In this embodiment, the layer  412  of electrically-conductive material is a layer  412  of stainless steel. However, in other embodiments, the electrically-conductive material may be a different metal alloy, or a metal, or the like. For example, in some embodiments, the electrically-conductive material is, or comprises, one or more of: steel, stainless steel, copper and nichrome. In this embodiment, the electrically-conductive material is in the form of a foil, so that the layer  412  of electrically-conductive material is a foil layer  412 . In embodiments in which the electrically-conductive material is other than stainless steel, the layer  412  of electrically-conductive material nevertheless may be a foil layer  412 . 
     In this embodiment, the electrically-conductive material is etched in such a manner as to be patterned to provide the electrically-conductive tracks and to increase the surface area of the electrically-conductive material. For example, the patterning may cause the surface of the electrically-conductive material to be roughened or ridged or rippled or stippled, etc. In other embodiments, the electrically-conductive material may be printed in such a manner as to be patterned, or may be patterned by some other process. In still further embodiments, the electrically-conductive material may be non-patterned. For example, in some such embodiments, the layer  412  of electrically-conductive material may be a simple rectangular strip of the electrically-conductive material. 
     The electrically-conductive material of the heating element  410  is heatable by passing an electric current through the electrically-conductive material. By suitably patterning the electrically-conductive material, the surface area of the electrically-conductive material is increased so as to provide more area for heat conduction to the smokable material  420  arranged on the heating element  410 . The first and second support layers  411 ,  413  may be so thin as not to fill completely the resultant roughened or patterned surface of the electrically-conductive material. The smokable material  420  may, for example, fill the resultant roughened or patterned surface of the heating element  410 , so that the smokable material  420  has a higher surface area to volume ratio. In some embodiments, patterning of the electrically-conductive material can also act to set a cross sectional area and length of an electric current flow-path in the electrically-conductive material, so that heating of the heating element  410  can be achieved by passing a predetermined electric current through the electrically-conductive material. Moreover, by suitably patterning the electrically-conductive material, the electrically-conductive material can be shaped so that the electrically-conductive material is maintained at areas of the heating element  410  that are to be the focus of the heating. Accordingly, depending on the patterning provided, uniformity of heating of the smokable material  420  may be achieved in use. 
     In this embodiment, each of the first and second support layers  411 ,  413  is made of a material that is resistant to heat. In this embodiment, each of the first and second support layers  411 ,  413  is an electrical insulator. More particularly, each of these layers is resistant to heat at least over the expected range of temperatures of the heating element  410  that will arise in operation, such as for example 180 to 220 degrees Celsius. Polyimide is an example of material that is resistant to heat at least over this range of temperatures. In this embodiment, each of the first and second support layers  411 ,  413  is a layer of polyimide. As discussed elsewhere herein, the controller  50  is in some embodiments arranged to ensure that the heating element  410  is heated to a temperature within this range. Accordingly, the polyimide is able to withstand the heating of the electrically-conductive material during use of the device. In other embodiments, the material of the first support layer  411  may be other than polyimide, and/or the material of the second support layer  413  may be other than polyimide. In some embodiments, the first and second support layers  411 ,  413  are layers of respective different materials. However, whichever material or materials is/are used for the first and second support layers  411 ,  413 , preferably the material(s) are resistant to heat at least over the above-discussed temperature range. In this embodiment, each of the first and second support layers  411 ,  413  is a layer that is impervious to moisture, to prevent any moisture present in the smokable material  420  from contacting the layer  412  of electrically-conductive material. 
     In this embodiment, the heating element  410  is planar, or at least substantially planar. A planar heating element  410  tends to be simpler to manufacture. However, in other embodiments, the heating element  410  may be non-planar. For example, in some embodiments, the heating element  410  may be folded, or crimped, or corrugated, or cruciform in cross section, or the like. A substantially cylindrical heater format is also envisaged. A non-planar heating element  410  can have an outer surface that is better suited to retaining the smokable material  420  thereon. For example, when a corrugated or similar heating element  410  is used, the smokable material  420  may adhere or bond more readily to troughs in the outer surface of the heating element  410  formed by the corrugations. Additionally, a non-planar heating element  410  provides more surface area for conduction of heat to the smokable material  420 . It can then support more smokable material  420  in a layer of a given thickness. Smokable materials such as tobacco are often poor heat conductors and so it may be desirable to provide the smokable material  420  in relatively thin layers to reduce electrical power consumption or to increase the rate of heating the smokable material  420 . 
     In this embodiment, the smokable material  420  comprises tobacco and is arranged on the heating element  410  in two portions  421 ,  422 , as shown in for example  FIGS. 15 and 17 . In this embodiment, the smokable material  420  is in a solid state and comprises particles of the smokable material. The first and second portions  421 ,  422  of the smokable material  420  are bonded by an adhesive to the heating element  410 , as described in more detail herein. More specifically, the first portion  421  of the smokable material  420  is bonded to the first support layer  411  so that the first support layer  411  lies between the layer  412  of electrically-conductive material and the first portion  421  of the smokable material  420 . The second portion  422  of the smokable material  420  is bonded to the second support layer  413  so that the second support layer  413  lies between the layer  412  of electrically-conductive material and the second portion  422  of the smokable material  420 . Accordingly, the first and second portions  421 ,  422  of the smokable material  420  are arranged on first and second portions of the heating element  410 , namely on respective surfaces of the first and second support layers  411 ,  413 . In this embodiment, the respective surfaces are respective first and second sides of the heating element  410 . Moreover, in this embodiment, the first and second sides are respective opposite sides of the heating element  410 . In other embodiments, the first and second sides may be non-opposite sides of the heating element  410 , such as adjacent sides of the heating element  410 . 
     As shown in  FIG. 17 , in this embodiment the adhesive forms additional identifiable adhesive layers  310 ,  320  between the heating element  410  and the first and second portions  421 ,  422  of the smokable material  420 , respectively. However, in some embodiments, the smokable material  420  may be interspersed within the adhesive so that the first and second portions  421 ,  422  of the smokable material  420  comprise the adhesive and no further identifiable adhesive layers are present. In some embodiments, the adhesive may be omitted and the smokable material  420  may be bonded to the heating element  410 , or arranged on the heating element  410 , by some other mechanism. 
     In some embodiments, the first portion  421  of the smokable material  420  has a form so as to be heatable by the heating element  410  more quickly than the second portion  422  of the smokable material  420 . More specifically, in this embodiment for example, the first portion  421  of the smokable material  420  is arranged on the heating element  410  with a first thickness and the second portion  422  of the smokable material  420  is arranged on the heating element  410  with a second thickness. Thus, the first portion  421  of the smokable material  420  has the first thickness and the second portion  422  of the smokable material  420  has the second thickness. The second thickness is greater than the first thickness. Herein, in this context, “thickness” means a depth of the relevant portion  421 ,  422  of the smokable material  420  as measured from the surface of the heating element  410  on which the smokable material  420  is arranged in a direction normal to that surface. 
     In some embodiments, first and second portions  421 ,  422  of the smokable material  420  may be arranged on first and second portions of the heating element  410  that are first and second portions of one side of the heating element  410 . That is, the first and second portions  421 ,  422  of the smokable material  420  may be on the same side of the heating element  410 . 
     For example, as shown in the embodiment of  FIG. 18 , the smokable material  420  is arranged so that a first portion  421  of the smokable material  420  on a first side  410   a  of the heating element  410  has a first thickness and a second portion  422  of the smokable material  420  on the first side  410   a  of the heating element  410  has a second thickness. The second thickness is greater than the first thickness. A similar arrangement of the smokable material  420  is provided on a second side  410   b  of the heating element  410  opposite from the first side  410   a.    
     As shown in  FIG. 18 , the thickness of the smokable material  420  on the first side  410   a  of the heating element  410  tapers from the first portion  421  of the smokable material  420  to the second portion  422  of the smokable material  420 . In this embodiment, the taper is linear or substantially linear. In other embodiments, the taper may be non-linear; for example, the outer surface of the smokable material  420  may be concave or convex. In still other embodiments, the smokable material  420  may be arranged on the first side  410   a  of the heating element  410  to a thickness that increases in a stepwise manner from the first portion  421  of the smokable material  420  to the second portion  422  of the smokable material  420 . In one such embodiment, as shown in  FIG. 19 , there is only a single step in the thickness of the smokable material  420  arranged on the first side  410   a  of the heating element  410 . The single step is at the point where the first portion  421  of the smokable material  420  meets the second portion  422  of the smokable material  420 . In another such embodiment, as shown in  FIG. 20 , there are plural steps in the thickness of the smokable material  420  between the first and second portions  421 ,  422  of the smokable material  420  arranged on the first side  410   a  of the heating element  410 . In the embodiment shown in  FIG. 20 , the first and second portions  421 ,  422  of the smokable material  420  are at respective opposite ends of the smokable material  420 . However, in other embodiments, this may not be the case. 
     In some embodiments, the smokable material  420  may be arranged only on one side of the heating element  410 . For example, in respective alternative embodiments to those shown in  FIGS. 18 to 20 , the smokable material  420  on the first side  410   a  or the second side  410   b  of the heating element  410  may be omitted. 
     By arranging different portions of the smokable material  420  on the heating element  410  with different thicknesses, progressive heating of the smokable material  420 , and thereby progressive generation of aerosol, is achievable. More specifically, in use, only a relatively small degree of heating of the heating element  410  is required to cause the first, thinner portion  421  of the smokable material  420  to become heated, thereby to initiate volatilization of at least one component of the smokable material  420  in the first portion  421  of the smokable material  420  and formation of an aerosol in the first portion  421  of the smokable material  420 . As the heating element  410  further heats up, the second, thicker portion  422  of the smokable material  420  becomes sufficiently heated to initiate volatilization of at least one component of the smokable material  420  in the second portion  422  of the smokable material  420  and formation of an aerosol in the second portion  422  of the smokable material  420 . The aerosol is output from respective outer surfaces of the first and second portions  421 ,  422  of the smokable material  420 . Accordingly, an aerosol is able to be formed relatively rapidly for inhalation by a user, and the heating device  400  is arranged to continue forming an aerosol thereafter for subsequent inhalation by the user even after the first, thinner portion  421  of the smokable material  420  may have ceased generating aerosol. The first portion  421  of the smokable material  420  may cease generating the aerosol when it becomes exhausted of volatilizable components of the smokable material  420 . 
     In other embodiments, additionally or alternatively to the variation in thickness of the smokable material  420  in any of the above-described embodiments, the first and second portions  421 ,  422  of the smokable material  420  may have different mean particle sizes. That is, the first portion  421  of the smokable material  420  may comprise particles of the smokable material  420  having a first mean particle size, and the second portion  422  of the smokable material  420  may comprise particles of the smokable material  420  having a second mean particle size. The second mean particle size is greater than the first mean particle size. Typically, particles of the smokable material  420  having a smaller mean particle size are heatable more quickly by a given heat source than are particles of the smokable material  420  having a greater mean particle size. By providing different portions of the smokable material  420  with different mean particle sizes, progressive heating of the smokable material  420 , and thereby progressive generation of aerosol, is achievable substantially as discussed above. 
     In some embodiments, the smokable material  420  may be provided having a mean particle size of 0.6 to 0.9 mm or 0.7 to 0.8 mm. Mean particle size can, however, vary across the smokable material. In some embodiments, the smokable material is prepared using mesh separation (or sieves) such that the majority or substantially all of the smokable material has a particle size in the above mentioned ranges. In some embodiments, a heater area of 6 cm 2  coated with such particulate smokable material  420  may provide an acceptable consumer experience lasting nominally three minutes. This size may, of course, be adjusted for a longer or shorter experience, as required. In some embodiments, the smokable material  420  may be in the form of a gel. The gel may or may not comprise particles of smokable material. 
     While in each of the above-described embodiments the smokable material  420  comprises a first portion  421  having a form so as to be heatable by the heating element  410  more quickly than a second portion  422  of the smokable material  420 , in other embodiments this feature may be omitted. 
     The adhesive used to bond the smokable material  420  to the heating element  410  comprises a polysaccharide such as cellulose, a cellulose derivative, alginic acid or an alginate salt, suitably sodium, potassium or calcium alginate. In one embodiment, the adhesive comprises a cellulose derivative, suitably hydroxypropyl methyl cellulose (HPMC). In other embodiments, the adhesive used to bond the smokable material  420  to the heating element  410  comprises alginic acid or an alginate salt, suitably sodium, potassium or calcium alginate. Polysaccharides such as these demonstrate good wettability properties, which aid in bonding the smokable material  420  to the heating element  410 . This is particularly the case when the adhesive is bonding smokable material  420  to a hydrophobic surface, such as a polyimide hydrophobic surface. It is also desirable that the adhesive be food acceptable and optionally, a food grade material. 
     In one embodiment, the identifiable adhesive layers  310 ,  320  between the heating element  410  and the smokable material  420  comprises a polysaccharide. The adhesive layers  310 ,  320  are disposed on, and substantially completely cover the support layers  411 ,  413 . The adhesive may cover the heating element  410  at least partially. In other embodiments, the adhesive may be disposed directly on the electrically conductive material  12 . In each case, the adhesive and smokable material  420  are coated onto the outermost layer of the heating element  410 . 
     In this embodiment, identifiable layers of adhesive  310 ,  320  are arranged on the support layers  411 ,  413 , which themselves surround the electrically conductive material  412 . Portions  421 ,  422  of the smokable material are layers disposed on top of the adhesive layers  310 ,  320 . In other embodiments, separate layers of adhesive and smokable material  420  cannot be identified. A layer comprising the adhesive and smokable material may be disposed on the support layers  411 ,  413 . The smokable material  420  may be at least partially or completely dispersed within the adhesive. 
     In some embodiments, the cartridge  40  contains a mass of thermal insulation material between the heating device  400  and the housing  43 . By “mass of thermal insulation material”, it is meant that the thermal insulation material is not a gas or not merely a gas. 
     For example, in the embodiment shown in  FIG. 21 , the cartridge  40  is the same as the cartridge  40  shown in  FIG. 15  except that the cartridge of  FIG. 21  includes a mass of thermal insulation material  430  between the heating device  400  and the housing  43 . In this embodiment, the thermal insulation material  430  surrounds the heating device  400 , fills a space between the heating device  400  and the housing  43 , and is in contact with the housing  43  and the smokable material  420  of the heating device  400 . In other embodiments, the thermal insulation material  430  may encircle the heating device  400  without fully surrounding the heating device  400 . In some embodiments, the thermal insulation material  430  may be in contact with only one of the housing  43  and the heating device  400 , and may not fill the space therebetween. 
     In the embodiment of  FIG. 21 , the thermal insulation material  430  comprises wadding. However, in other embodiments, the thermal insulation material  430  may comprise one or more materials selected from the group consisting of: wadding, fleece, non-woven material, non-woven fleece, woven material, knitted material, nylon, foam, closed cell foam, polystyrene, closed cell polystyrene foam, polyester, polyester filament, polypropylene, a blend of polyester and polypropylene. Other types of thermal insulation material may also be suitable. 
     In the cartridge  40  shown in  FIG. 21 , the thermal insulation material  430  has a density of about 100 grams per square meter (gsm) and a thickness of about 1.2 millimeters. In other embodiments, one or both of the thickness and the density of the thermal insulation material  430  may be different. However, if the density is too high, the thermal insulation material  430  may act as a filter and attenuate the aerosol output from the heating device  400 . Alternatively, if the density is too low, the thermal insulation material  430  may not provide effective thermal insulation. An appropriate density, particularly when the thermal insulation material  430  comprises wadding or fleece, may be between about 60 and about 140 gsm, or between about 80 and about 120 gsm. When the thermal insulation material  430  comprises a material other than wadding or fleece, a density of the thermal insulation material  430  may be chosen to effect similar thermal properties to those achieved when the thermal insulation material  430  comprises wadding or fleece of the above density. In some embodiments, the mass of thermal insulation material  430  is heat resistant at least over the expected range of temperatures of the heating element  410  that will arise in operation, such as for example 180 to 220 degrees Celsius as discussed above, and will not degrade when subjected to such operation temperatures. 
     In some embodiments, the cartridge  40  comprises thermal insulation material in the form of a laminate or sandwich structure having a plurality of layers of material. In some such embodiments, an outer layer of the layers of material forms the housing  43 , or a portion of the housing  43 , of the cartridge  40 , and one or more other layers of the sandwich structure forms the mass of thermal insulation material  430 . Accordingly, in some embodiments, the housing  43 , or a portion of the housing  43 , may be integrally formed with the mass of thermal insulation material  430 . 
     In some embodiments, the thermal insulation material helps to retard heat loss from the heating device  400  in use. In some embodiments, the thermal insulation material helps to ensure that volatilized material generated in the chamber  44  in use does not condense on the inner surface of the housing  43 . In some embodiments, the provision of the mass of thermal insulation material helps to increase the surface area on which aerosol generated in the cartridge  40  in use may form. In some embodiments, a head space remains between the mass of thermal insulation material and the housing  43 , which further helps to increase the surface area on which aerosol generated in the cartridge  40  may form in use. In some embodiments, such a mass of thermal insulation material helps to increase the amount of aerosol generated in the cartridge  40  in use, and thus may enhance the consumer experience. 
     While the cartridge  40  shown in  FIG. 21  is a variation of the cartridge  40  shown in  FIG. 15 , similarly, in respective variations to the embodiments shown in  FIGS. 18 to 20 , the cartridge  40  may comprise a mass of thermal insulation material between the heating device  400  and the housing  43 . Indeed, in respective variations to each of the embodiments of a cartridge  40  discussed herein, the cartridge  40  may comprise a mass of thermal insulation material between the heating device  400 , or heating element  410 , and the housing  43 . 
     In some embodiments, in which the heating element  410  or the smokable material  420  is omitted from the cartridge  40 , the mass of thermal insulation material may be provided in the cartridge  40  between the housing  43  and the smokable material  420  or the heating element  410 , respectively. In some such embodiments, the mass of thermal insulation material encircles and/or contacts the smokable material  420  or the heating element  410 , respectively. In some such embodiments, the mass of thermal insulation material contacts the housing  43  and/or fills a space between the housing  43  and the smokable material  420  or the heating element  410 , respectively. 
     Generally speaking, the heating device  400  may be manufactured by locating the layer  412  of electrically-conductive material between the first layer  411  of material and the second layer  413  of material to form the heating element  410 , and arranging the smokable material  420  on the heating element  410 . In this embodiment of the method, the smokable material  420  is arranged on the heating element  410  after the layer  412  of electrically-conductive material has been located between, and in contact with, the first and second support layers,  411 ,  413 . 
     In this embodiment of the method, the method comprises patterning the electrically-conductive material, such as by etching or printing the electrically-conductive material for example, to form the layer  412  of electrically-conductive material. In some embodiments, the electrically-conductive material is located on one of the first and second support layers  411 ,  413 , then patterned, and then the other of the first and second support layers  411 ,  413  is applied to locate the layer  412  of electrically-conductive material between the first and second support layers  411 ,  413 . In other embodiments, the electrically-conductive material is patterned and then located between the first and second support layers  411 ,  413 . In some embodiments, the electrically-conductive material may be located between the first and second support layers  411 ,  413  and then patterned. In still further embodiments, the method does not comprise patterning the electrically-conductive material. 
     When manufacturing the heating device, the electrically-conductive material of the layer  412  of electrically-conductive material is stainless steel. However, in other embodiments, the electrically-conductive material may be a different metal alloy, or a metal, as discussed above. 
     In this embodiment of the manufacturing method, each of the first and second layers  411 ,  413  of material is a layer of polyimide. However, as discussed above, in other embodiments the material of the first support layer  411  may be other than polyimide, and/or the material of the second support layer  413  may be other than polyimide. In some embodiments, the first and second support layers  411 ,  413  are layers of respective different materials. 
     In this embodiment of the manufacturing method, the smokable material  420  comprises tobacco and the method comprises bonding the smokable material  420  to the heating element  410 . More specifically, and as discussed above, the first portion  421  of the smokable material  420  is bonded to the first support layer  411  and the second portion  422  of the smokable material  420  is bonded to the second support layer  413 . As discussed above, in other embodiments, the smokable material  420  may be arranged on the heating element  410  in a number of different ways, such as only on one side of the heating element  410 . However, for conciseness, detailed discussion of the various possible arrangements will not be provided again. In this embodiment, the bonding comprises bonding the smokable material  420  by an adhesive to the heating element  410  as described in more detail herein. In some other embodiments, the adhesive may be omitted and the method may comprise bonding the smokable material  420  to the heating element  410  by some other mechanism, or otherwise arranging the smokable material on the heating element  410 . 
     In this embodiment, after the electrically conductive material is located between the support layers  411 ,  413 , the heating element  410  is annealed at 200° C. and surface treated using an oxygen plasma, suitably by corona treatment. The treated heating element is then dipped into an aqueous solution of a polysaccharide (such as hydroxypropyl methyl cellulose or an aqueous solution comprising alginic acid or salt thereof) so as to coat some or all of the support layers  411 ,  413 . The heating element  410  is then removed from the aqueous solution and subsequently dipped into a smokable material so as to coat some or all of the adhesive. The heating element  410  is then removed from the smokable material, and the adhesive hardens or is hardened by curing, drying and/or setting. In other embodiments, the separate adhesive and smokable material layers may be added by sequential spraying steps, or by other methods known to a person skilled in the art; for example, the adhesive may be applied using spray coating, transfer coating, slot die extruding and the smokable material may be added using spray coating, fluidized bed, electrostatic coating. In these embodiments, layers of the adhesive  310 ,  320  are disposed on the support layers  411 ,  413 . Portions  421 ,  422  of smokable material  420  are adhered to the support layers  411 ,  413  by the adhesive layers. The portions  421 ,  422  of smokable material  420  are arranged substantially separate from the adhesive layers  310 ,  320 . 
     The solution concentration of the aqueous solution is selected to have a suitable viscosity, having a low enough viscosity that it can easily be applied to the heating element, and a high enough viscosity such that it can be retained on the surface of the heating element before it is hardened. The polysaccharide concentration in an aqueous solution may be from about a 2% w/w, 4% w/w or 5% w/w solution to about a 7% w/w, 8% w/w or 10% w/w solution (suitably a 2-10% w/w solution, or a 5-7% w/w solution). 
     In other embodiments, the smokable material  420  and adhesive may not be in identifiably separate layers. By way of an example, the smokable material may be initially dispersed in a polysaccharide solution. The heating element  410  may then dipped into this dispersion, or the dispersion may be sprayed onto the heating element  410  to from a single layer on the surface of the support layers  411 ,  413 , the single layer comprising both the adhesive and the smokable material  420 . 
     In this embodiment, and as indicated in  FIG. 12 , the cartridge  40  comprises two electrically-conductive terminals  47   a ,  47   b , which herein are referred to as a “seventh electrically-conductive terminal”  47   a  and an “eighth electrically-conductive terminal”  47   b , respectively. The heating element  410  is electrically connected across the seventh and eighth electrically-conductive terminals  47   a ,  47   b  and is heatable by passing an electric current through the heating element  410  via the seventh and eighth electrically-conductive terminals  47   a ,  47   b . The seventh and eighth electrically-conductive terminals  47   a ,  47   b  are located in respective recesses, but are accessible from the exterior of the cartridge  40 . In this embodiment, when the cartridge  40  is fully received in the recess  13 , the seventh and eighth electrically-conductive terminals  47   a ,  47   b  are in surface contact with the first and second electrically-conductive terminals  17   b ,  17   c , respectively. Accordingly, the heating element  410  can be caused to heat by applying electrical power to the first and second electrically-conductive terminals  17   b ,  17   c.    
     In some embodiments, the cartridge  40  is able to be received fully in the recess  13  in only one orientation relative to the first casing portion  10 . In this embodiment, this is due to the cartridge  40 , and more specifically the housing  43 , having an asymmetric exterior cross-sectional shape that corresponds to an asymmetric interior cross-sectional shape of the recess  13 . In other embodiments, the cartridge  40  may be able to be received in the recess  13 , or able to co-operate with the interface, in only one orientation relative to the first casing portion  10  due to the provision of one or more other mechanisms. For example, in some embodiments, the housing  43  of the cartridge  40  may have rotational symmetry and thus have a symmetric exterior cross-sectional shape, and the cartridge  40  may have a key projecting from the housing  43  that gives the overall cartridge  40  an asymmetric exterior cross-sectional shape that corresponds to an asymmetric interior cross-sectional shape of the recess  13 . Providing that the cartridge  40  is able to co-operate with the interface in only one orientation relative to the first casing portion  10  helps to ensure that the cartridge  40  is correctly assembled with the rest of the apparatus  1  with the seventh and eighth electrically-conductive terminals  47   a ,  47   b  in surface contact with the first and second electrically-conductive terminals  17   b ,  17   c , respectively. However, in some embodiments, the cartridge may be receivable fully in the recess  13  in more than one orientation relative to the first casing portion  10 . 
     As discussed above, in this embodiment the controller  50  is for controlling the supply of electrical power to the heating element  410  from the electrical power source  24 , when the interface  13  is co-operating with the cartridge  40 . When the apparatus  1  is fully assembled with the first connector  15  fully engaged with the second connector  25 , and with the cartridge  40  fully and correctly received in the recess  13 , actuation of the actuator  18  by a user causes the controller  50  to cause an electric current to be applied across the seventh and eighth electrically-conductive terminals  47   a ,  47   b , and thus across the heating element  410 . Such actuation of the actuator  18  may cause completion of an electrical circuit in the controller  50 . As the electric current is so applied across the heating element  410 , the heating element  410  heats up so as to heat the smokable material  420 . In this embodiment, the electrical resistance of the heating element  410  changes as the temperature of the heating element  410  increases. The controller  50  monitors the electrical resistance of the heated heating element  410  and then adjusts the magnitude of the electrical current applied across the heating element  410  on the basis of the monitored electrical resistance as necessary, in order to ensure that the temperature of the heating element  410  remains within the above-discussed temperature range of about 180 degrees Celsius to about 220 degrees Celsius. Within this temperature range, the smokable material  420  is heated sufficiently to volatilize at least one component of the smokable material  420  without combusting the smokable material  420 . Accordingly, the controller  50 , and the apparatus  1  as a whole, is arranged to heat the smokable material  420  to volatilize the at least one component of the smokable material  420  without combusting the smokable material  420 . In other embodiments, the temperature range may be other than this range. 
     As discussed above, the plate  16  has five holes  16   a - 16   e  therethrough, and the first to third pins  17   a ,  17   b ,  17   c  are provided in the first to third  16   a ,  16   b ,  16   c  of these holes. The fourth and fifth holes  16   d ,  16   e  of the five holes  16   a - 16   e  remain open and fluidly connect the recess  13  with the inlets  60  defined by the cooperation of the first and second connectors  15 ,  25 . Moreover, when the cartridge  40  is fully received in the recess  13 , the air flow path  45  defined by the cooperation of the first and second housing parts  43   a ,  43   b  of the cartridge  40  is fluidly connected with the recess  13 . Accordingly, and as shown in  FIG. 16 , in the fully-assembled apparatus  1 , there is defined an overall flow path that extends from the exterior of the apparatus  1 , then through any one of the inlets  60  defined by the cooperation of the first and second connectors  15 ,  25 , then through either one of the fourth and fifth holes  16   d ,  16   e  in the plate  16 , then through the recess  13 , then through the air flow path  45  defined by the cooperation of the first and second housing parts  43   a ,  43   b  of the cartridge  40 , then through the chamber  44  of the cartridge  40 , then through any one of the apertures  46  extending through the housing  43  of the cartridge  40 , and then through the channel  36  of the mouthpiece  30  to the exterior of the apparatus  1 . The seal  37  of the mouthpiece  30  prevents air from bypassing the chamber  44  of the cartridge  40  when travelling from the recess  13  to the channel  36  of the mouthpiece  30 . 
     An exemplary operation of the apparatus  1  of this embodiment will now be described. A user ensures that the mouthpiece  30  is at a location relative to the first casing portion  10  at which the cartridge  40  is movable through the opening  14 . The user then passes the cartridge  40  through the opening  14  and into the recess  13  so as to bring the seventh and eighth electrically-conductive terminals  47   a ,  47   b  of the cartridge  40  into surface contact with the first and second electrically-conductive terminals  17   b ,  17   c , respectively. The user then moves the mouthpiece  30  relative to the first casing portion  10  to a location at which the mouthpiece  30  covers the opening  14 , with the outlet  35  of the mouthpiece  30  at the exterior of the apparatus  1 , and with the seal  37  contacting and compressing against the cartridge  40  and surrounding the apertures  46 . The mouthpiece  30  is retained at this location through engagement of the connector  33  of the mouthpiece  30  with the second connector  19  of the first casing portion  10 . 
     Before, during or after such movements of the cartridge  40  and mouthpiece  30  relative to the first casing portion  10 , the user also ensures that the first connector  15  of the first casing portion  10  is fully engaged with a second connector  25  of the second casing portion  20 . As discussed above, when the first and second connectors  15 ,  25  are fully engaged, the third electrically-conductive terminal  17   a  is in surface contact with the fourth electrically-conductive terminal  283   a , and the fifth electrically-conductive terminal  15   a  is in surface contact with the sixth electrically-conductive terminal  25   a.    
     When the actuator  18  is subsequently actuated by actuated by the user, the controller  50  is operated to cause an electric current to be applied across the seventh and eighth electrically-conductive terminals  47   a ,  47   b  and thus across the heating element  410 . This application of the electric current causes the heating element  410  to heat up so as to heat the smokable material  420  to volatilize at least one component of the smokable material  420  without combusting the smokable material  420 , as discussed above. Typically, this volatilization causes the formation of an aerosol in the chamber  44  of the cartridge  40 . The user inhales the aerosol by drawing on the outlet  35  of the mouthpiece  30 . This causes the aerosol to be drawn from the chamber  44  of the cartridge  40  and into the user&#39;s mouth via the apertures  46  of the cartridge  40  and via the channel  36  of the mouthpiece  30 . This drawing of the aerosol from the chamber  44  of the cartridge  40  causes a reduction in pressure in the chamber  44 . This reduction in pressure causes air to be drawn into the chamber  44  via the annular gap  62 , the inlets  60  defined between the first and second connectors  15 ,  25 , the fourth and/or fifth holes  16   d ,  16   e  in the plate  16 , the recess  13 , and the air flow path  45  defined by the cooperation of the first and second housing parts  43   a ,  43   b  of the cartridge  40 , in turn. The user is able to carry out subsequent such inhalations to inhale subsequent volumes of the aerosol. 
     When the smokable material  420  has been spent, or substantially all of the smokable material  420  has been spent, the user may move the mouthpiece  30  relative to the first casing portion  10  to a location at which the cartridge  40  is movable through the opening  14 . The user may then remove the cartridge  40  from the recess  13  via the opening  14 . The user can subsequently insert another, unspent cartridge  40  into the recess  13  and repeat the above process. The heating element  410  may become dirtied with the volatilized material or the spent smokable material  420  in use. By locating the heating element  410  in the cartridge  40 , rather than in the first casing portion  10 , each time a new, unspent cartridge  40  is used, the user is provided with a fresh heating element  410 . Accordingly, the user does not need to be concerned with cleaning the heating element  410 . 
     In some embodiments, the apparatus  1  is provided fully assembled. In the fully assembled state, the first connector  15  of the first casing portion  10  is engaged with the second connector  25  of the second casing portion  20 , and the connector  33  of the mouthpiece is engaged with the second connector  19  of the first casing portion  10 . In some such embodiments, the cartridge  40  is located in the recess  13 . In other such embodiments, no cartridge  40  is in the recess  13 . In other embodiments, the apparatus  1  may be in kit form, with the first connector  15  of the first casing portion  10  disengaged from, but engageable with, the second connector  25  of the second casing portion  20  and/or with the connector  33  of the mouthpiece disengaged from, but engageable with, the second connector  19  of the first casing portion  10 . In some such kit-form apparatuses, the cartridge  40  may be located in the recess  13 . In other such kit-form apparatuses, one or more examples of the cartridge  40  may be provided as part of the apparatus but outside of the recess  13 . 
     In this embodiment, the apparatus  1  has only one heating element. In other embodiments, the apparatus  1  may have more than one heating element. In this embodiment, the cartridge  40  is intended to be used and then replaced by an alternative cartridge  40 , as discussed above. However, in other embodiments, the cartridge  40  may not be replaceable and the apparatus  1  may be for only single use. In some embodiments, the apparatus  1  may not include a cartridge  40 . In some embodiments, the heating element  410 , or the heating device  400 , may be integral with the first casing portion  10  and may be irremovable from the first casing portion  10 . In some embodiments, the electrical power source  24  may be integral with the second casing portion  20  and may be irremovable from the second casing portion  20 . In some embodiments, the first casing portion  10  may be integral or unitary with the second casing portion  20 , or may be permanently fixed to the second casing portion  20 . Therefore, in some embodiments, the casing of the apparatus  1  may be a one-piece casing, and may not have the first and second connectors  15 ,  25  discussed above. In some embodiments, the positive and negative terminals  24   a ,  24   b  of the electrical power source  24  may be permanently electrically connected to the controller  50 . In some embodiments, the mouthpiece  30  may be immovable relative to the first casing portion  10 . In some embodiments, the mouthpiece  30  may be integral or unitary with the first casing portion  10 . 
     In each of the embodiments discussed above, the smokable material  420  is arranged on a support that is a heating element  410 . However, in some embodiments, the support may be other than a heating element  410 . In some embodiments in which the support is other than a heating element  410 , the support may have any of the features of the heating element  410  discussed herein. In some embodiments in which the support is other than a heating element  410 , the smokable material  420  may have any of the features of the smokable material  420  discussed herein, and so may be arranged on the support in any of the manners discussed herein for the arrangement of the smokable material  420  on the heating element  410 . In some embodiments in which the support is other than a heating element  410 , the smokable material  420  and the support may be comprised in a device, rather than a heating device as such. 
     In order to address various issues and advance the art, the entirety of this disclosure shows by way of illustration and example various embodiments in which the claimed invention may be practiced and which provide for a superior apparatus for heating smokable material to volatilize at least one component of the smokable material. The advantages and features of the disclosure are of a representative sample of embodiments only, and are not exhaustive and/or exclusive. They are presented only to assist in understanding and teach the claimed and otherwise disclosed features. It is to be understood that advantages, embodiments, 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 embodiments may be utilized and modifications may be made without departing from the scope and/or spirit of the disclosure. Various embodiments may suitably comprise, consist of, or consist in essence of, various combinations of the disclosed elements, components, features, parts, steps, means, etc. The disclosure may include other inventions not presently claimed, but which may be claimed in future.