Patent Publication Number: US-2023148662-A1

Title: Aerosol delivery system

Description:
PRIORITY CLAIM 
     The present application is a continuation application of application Ser. No. 16/497,264, filed Sep. 24, 2019, which in turn is a National Phase entry of PCT Application No. PCT/GB2018/050706, filed Mar. 19, 2018, which claims priority from GB Patent Application No. 1704999.0, filed Mar. 29, 2017, each of which is hereby fully incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates to aerosol delivery systems such as electronic nicotine delivery systems (e.g. electronic cigarettes and the like). 
     BACKGROUND 
     Aerosol delivery systems such as electronic cigarettes (e-cigarettes) generally contain an aerosol precursor material or aerosol source, such as a reservoir of a source liquid containing a formulation, typically including nicotine and often flavorants, or a solid material such as a tobacco-based product, from which an aerosol is generated for inhalation by a user, for example through atomization/heat vaporization. Thus, an aerosol delivery system will typically comprise an aerosol generation chamber containing an atomizer or vaporizer, e.g. a heating element, arranged to atomize (or vaporize) a portion of precursor material to generate an aerosol in the aerosol generation chamber. As a user inhales on the device through a mouthpiece and electrical power is supplied to the atomizer, air is drawn into the device through inlet holes and into the aerosol generation chamber where the air mixes with the atomized precursor material to form an aerosol. There is a flow path connecting between the aerosol generation chamber and an opening in the mouthpiece so the incoming air drawn through the aerosol generation chamber continues along the flow path to the mouthpiece opening, carrying some of the aerosol with it, and out through the mouthpiece opening for inhalation by the user. 
     Aerosol delivery systems may comprise a modular assembly including both reusable and replaceable cartridge parts. Typically a cartridge part will comprise the consumable aerosol precursor material and the atomizer, while a reusable device part will comprise longer-life items, such as a rechargeable battery, device control circuitry, activation sensors and user interface features. The reusable part may also be referred to as a control unit or battery section and replaceable cartridge parts may also be referred to as cartomizers. 
     Cartomizers are electrically and mechanically coupled to a control unit for use, for example using a screw thread or bayonet fixing with appropriately engaging electrical contacts. When the aerosol precursor material in a cartomizer is exhausted, or the user wishes to switch to a different cartomizer having a different aerosol precursor material, a cartomizer may be removed from the control unit and a replacement cartomizer attached in its place. 
     Switching between cartomizers can be inconvenient for a user, especially if a user is repeatedly switching between two or more flavors on a regular basis as this requires disassembly and reassembly of the electronic cigarette by splitting the aerosol delivery device into its modular components to switch flavor. Electronic cigarettes have been thus been proposed with different precursor/source material arranged in a single device to provide different aerosols (e.g., having different flavors) to a user inhaling on the mouthpiece, either automatically or in response to user selection. The sources of material to be vaporized are typically located within the electronic cigarette and so still requires disassembly and reassembly of the electronic cigarette if the user wishes to switch to using a further source material or to lend one of the sources of material to another user. 
     SUMMARY 
     Various approaches are described herein which seek to help address some of these issues. 
     According to a first aspect of certain embodiments there is provided an aerosol delivery system including a first aerosol delivery device comprising a first engagement mechanism, a first power supply, and a first vaporizer, wherein the first vaporizer is arranged to selectively receive power from the first power supply to generate a first aerosol from a first aerosol precursor material for user inhalation; and a second aerosol delivery device comprising a second engagement mechanism, a second power supply, and a second vaporizer, wherein the second vaporizer is arranged to selectively receive power from the second power supply to generate a second aerosol from a second aerosol precursor material for user inhalation; wherein the first engagement mechanism of the first aerosol delivery device and the second engagement mechanism of the second aerosol delivery device are arranged to releasably co-engage with one another to selectively couple the first aerosol delivery device to the second aerosol delivery device so the first aerosol delivery device and the second aerosol delivery device may be used together to deliver the first and second aerosols to a single user when they are coupled together and may be used independently to deliver the first and second aerosols to different users when they are not coupled together. 
     According to a second aspect of certain embodiments there is provided an aerosol delivery device comprising: a power supply; a vaporizer arranged to selectively receive power from the power supply to generate an aerosol from an aerosol precursor material for user inhalation; and an engagement mechanism for releasably co-engaging the aerosol delivery device with a further aerosol delivery device arranged to generate a further aerosol for user inhalation so the aerosol delivery device and the further aerosol delivery device may be used together to deliver aerosol to a single user when they are coupled together and the aerosol delivery device may be used independently of the other aerosol delivery device when the aerosol delivery device is not coupled to the other aerosol delivery device. 
     According to a third aspect of certain embodiments there is provided an aerosol delivery system including first aerosol delivery means comprising first engagement means, first power supply means, and first vaporizing means, wherein the first vaporizing means is arranged to selectively receive power from the first power supply means to generate a first aerosol from a first aerosol precursor material for user inhalation; and second aerosol delivery means comprising second engagement means, second power supply means, and second vaporizing means, wherein the second vaporizing means is arranged to selectively receive power from the second power supply means to generate a second aerosol from a second aerosol precursor material for user inhalation; wherein the first engagement means of the first aerosol delivery means and the second engagement means of the second aerosol delivery means are arranged to releasably co-engage with one another to selectively couple the first aerosol delivery means to the second aerosol delivery means so the first aerosol delivery means and the second aerosol delivery means may be used together to deliver the first and second aerosols to a single user when they are coupled together and may be used independently to deliver the first and second aerosols to different users when they are not coupled together. 
     It will be appreciated that features and aspects of the disclosure described above in relation to the first and other aspects of the disclosure are equally applicable to, and may be combined with, embodiments of the invention according to other aspects of the disclosure as appropriate, and not just in the specific combinations described above. 
    
    
     
       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    schematically represents an aerosol delivery device having an uncoupled cartomizer and control unit in cross-section along a longitudinal axis thereof for use in an aerosol delivery system in accordance with an embodiment of the disclosure. 
         FIG.  2    schematically represents the control unit of  FIG.  1    in cross-section along a longitudinal axis thereof. 
         FIG.  3    schematically represents the cartomizer of  FIG.  1    in cross-section along a longitudinal axis thereof. 
         FIG.  4    schematically represents the aerosol delivery device of  FIG.  1    in perspective view showing the outer surfaces thereof. 
         FIG.  5 A  schematically represents an aerosol delivery system comprising the aerosol delivery device of  FIG.  1    and a second aerosol delivery device, both shown in cross-section along respective longitudinal axes thereof in an uncoupled state. 
         FIG.  5 B  schematically represents the aerosol delivery system of Figure SA in a releasably magnetically coupled state. 
         FIG.  5 C  schematically shows the aerosol delivery system of  FIG.  5 B  as viewed along a longitudinal axis in a direction towards the mouthpieces/mouthpiece ends of the releasably magnetically coupled aerosol delivery devices. 
         FIG.  6 A  shows an aerosol delivery system comprising two aerosol delivery devices in an uncoupled state in accordance with a second embodiment of the disclosure, each aerosol delivery device having an interlocking section configured to mechanically engage with a respective interlocking section. 
         FIG.  6 B  shows the aerosol delivery system of  FIG.  6 A  in a releasably mechanically coupled state. 
     
    
    
     DETAILED DESCRIPTION 
     Aspects and features of certain examples and embodiments are discussed/described herein. Some aspects and features of certain examples and embodiments may be implemented conventionally and these are not discussed/described in detail in the interests of brevity. It will thus be appreciated that aspects and features of apparatus and methods discussed herein which are not described in detail may be implemented in accordance with any conventional techniques for implementing such aspects and features. 
     The present disclosure relates to aerosol delivery systems, which may also be referred to as aerosol provision systems, such as e-cigarettes. Throughout the following description the term “e-cigarette” or “electronic cigarette” may sometimes be used; however, it will be appreciated this term may be used interchangeably with aerosol delivery system and electronic aerosol delivery system. Furthermore, and as is common in the technical field, the terms “vapor” and “aerosol”, and related terms such as “vaporize” and “aerosolize”, may also be used interchangeably. 
     The present disclosure provides an aerosol delivery system which includes at least two aerosol delivery devices. Each aerosol delivery device is provided with components required to generate aerosol from a respective aerosol precursor material that can be located within the aerosol delivery devices and to subsequently deliver aerosol generated from this precursor material to a user. The present disclosure provides a system whereby aerosol delivery devices comprise respective engagement mechanisms that can be co-engaged with one another to selectively couple together the aerosol delivery devices such that, during use, the first and second aerosol delivery devices can deliver the first and second aerosols to a single user. For instance, the user can inhale on mouthpiece openings of both aerosol delivery devices simultaneously to receive a mixture of the aerosols separately generated by the coupled aerosol delivery devices. The engagement mechanism may be mechanical or magnetic in nature and provides a sufficiently strong coupling to prevent separation of the aerosol delivery devices during normal use (i.e., when inhaling on the mouthpiece openings simultaneously) but enables the aerosol delivery devices to be separated under (deliberate) application of a separation force to the aerosol delivery devices. In an uncoupled state, each aerosol delivery device is configured to generate aerosol independently of the other aerosol delivery device—that is, each aerosol delivery device is capable of independent use. In this way, switching of the aerosol delivery devices, e.g., to provide a different flavor or aerosol precursor material combinations, can be performed intuitively and easily without disassembling individual aerosol delivery devices. 
       FIG.  1    is a schematic diagram of an aerosol delivery device  10  in accordance with some embodiments of the present disclosure. The aerosol delivery device  10  has a generally cuboidal shape (see also  FIG.  4   ), extending along a longitudinal axis indicated by dashed line LA, and comprises two main components, namely a control unit  20  and a cartomizer  30 . 
     The cartomizer  30  includes an internal chamber containing a reservoir of liquid formulation including nicotine (or more generally a precursor material), a heater (or more generally a vaporizer/atomizer), and a mouthpiece end  35 . The cartomizer  30  may further include a wick or similar facility to transport a small amount of the liquid formulation from the reservoir to the heater. The control unit  20  includes a re-chargeable battery as a power supply/source to provide power to the aerosol delivery device  10  and a circuit board for generally controlling the aerosol delivery device  10 . When the heater receives power from the battery, as controlled by the circuit board, the heater atomizes (heats) the nicotine and this aerosol (vapor) is then inhaled by a user through the mouthpiece end  35 , specifically through one or more openings  352  therein (see  FIGS.  3  and  4   ). 
     The control unit  20  and cartomizer  30  are detachable from one another by separating in a direction parallel to the longitudinal axis LA, as shown in  FIG.  1   , but are joined together when the device  10  is in use by a connection, indicated schematically in  FIG.  1    as  25 A and  25 B, to provide mechanical and electrical connectivity between the control unit  20  and the cartomizer  30 . The electrical connector on the control unit  20  that is used to connect to the cartomizer  30  may also serve as a socket for connecting a charging device (not shown) when the control unit  20  is detached from the cartomizer  30 , or alternatively, the control unit  20  may be provided with a dedicated charging port (such as a USB port) at one end thereof, e.g., the end opposite the end configured to couple to the cartomizer  30 . The cartomizer  30  may be detached from the control unit  20  and disposed of when the supply of nicotine is exhausted (and replaced with another cartomizer if so desired). 
       FIG.  1    schematically indicates various surfaces of the cartomizer  30  and control unit  20 . Specifically, the control unit  20  has an upper/top surface  222  and a lower/bottom surface  224 . The lower surface  224  is the surface of the control unit  20  directly opposite the upper surface  222 . Equally, the cartomizer  30  has an upper surface  322  and a lower surface  324 . The lower surface  324  is the surface of the cartomizer  30  directly opposite the upper surface  322 . It will be appreciated that this terminology, i.e., upper/lower or equivalent, is used purely for convenience of explanation and is not intended to suggest a particular orientation of the aerosol delivery device  10  should be adopted in normal use. In some cases, and as will become apparent later, the aerosol delivery device  10  may be rotated about the longitudinal axis LA such that the upper surfaces  222  and  322  face downwards, i.e., the orientation of the surfaces as seen in  FIG.  1    is reversed. 
       FIG.  1    (and also  FIG.  3    described later) represents the mouthpiece end  35  of the cartomizer  30  as a separate box. It should be understood that this representation is not meant to signify that the mouthpiece end  35  is a separate piece/component of the cartomizer  30 , but rather a region of the cartomizer  30  which engages with the user&#39;s lips when the user desires to inhale aerosol generated by the device  10  with the mouthpiece end  35  of the cartomizer  30  being modified in some way to allow aerosol to pass from inside the cartomizer  30  to outside, e.g., by one or more openings  352 . Equally, it should be understood that in alternative implementations the mouthpiece end  35  is provided as a separate component that is attachable to and detectable from the main body of the cartomizer  30 . In these alternative implementations, the main body of the cartomizer (which contains the reservoir for storing the aerosol precursor) can be replaced or switched with another main body, e.g., when the reservoir is empty or to change flavors of the aerosol generated. Retaining the mouthpiece end  35  may be advantageous when switching aerosol delivery devices between different users for reasons of hygiene. 
     As also seen in  FIG.  1   , the control unit  20  in this implementation comprises two magnetic portions  226  spaced from each other along the longitudinal axis LA. The magnetic portions  226  form a first engagement mechanism arranged to co-engage with a second engagement mechanism of a second aerosol delivery to selectively magnetically couple the aerosol delivery device  10  to the second aerosol delivery device. The magnetic portions  226  can have the magnetic poles aligned in any desired orientation. That is, the magnetic portions can be arranged to either have the magnetic poles in an upper/lower arrangement (e.g., south pole facing toward the upper surface  222  and north pole facing toward the lower surface  224 ) or in a left/right arrangement (e.g., south pole facing toward the connection  25 B and north pole facing toward the opposite end of the control unit  20 ). The magnetic coupling will be described in more detail below. 
     Between the magnetic portions  226  are provided two electrical contacts  228  which are configured to provide positive and negative electrical terminals respectively. The electrical contacts  228  are connected to a controller within the control unit  20  and the power source. In essence, the electrical contacts  228  enable power and/or control signals to be passed to/from the power source or controller respectively from/to a second aerosol delivery device magnetically coupled to the aerosol delivery device  10  by the magnetic portions  226 . That is, the power and/or control signals can be passed between coupled aerosol delivery devices using the electrical coupling. The electrical coupling will be described in more detail below. 
     It should be appreciated that the magnetic portions  226  and electrical contacts  228  are not shown to scale in  FIG.  1   . In  FIG.  1   , these portions  226  and contacts  228  are schematically represented as protruding into the body of the control unit  20  and being flush with the lower surface  224  thereof. However, the magnetic portions  226  and electrical contacts  228  in other embodiments can be constructed as strips applied to/provided on the surface  224  of the body of the control unit  20  and protrude by an amount equal to the thickness of the strip from the surface  224 . 
       FIGS.  2  and  3    provide schematic diagrams of the control unit  20  and cartomizer  30  respectively of the aerosol delivery device of  FIG.  1   . Note that various components and details, e.g. such as wiring and more complex shaping, have been omitted from  FIGS.  2  and  3    for reasons of clarity in addition to the magnetic portions  226  and electrical contacts  228 . 
     As shown in  FIG.  2   , the control unit  20  includes, as the power source, a re-chargeable battery or cell  210  for powering the aerosol delivery device  10 , as well as a chip, such as a (micro)controller for controlling the aerosol delivery device  10 . The controller is attached to a small printed circuit board (PCB)  215  that also includes a sensor unit. If a user inhales on the mouthpiece end  35 , air is drawn into the aerosol delivery device  10  through one or more air inlet holes (not shown in  FIGS.  1  and  2   ). The sensor unit detects this airflow, and in response to such a detection, the controller provides power from the battery  210  to the heater  155  in the cartomizer  30 . 
     As shown in  FIG.  3   , the cartomizer  30  includes an air passage  161  extending along the central (longitudinal) axis of the cartomizer  30  from the mouthpiece end  35  to the connector  25 A for joining the cartomizer to the control unit  20 . A reservoir  160  of nicotine-containing liquid is provided around the air passage  161 . This reservoir  160  may be implemented, for example, by providing cotton or foam soaked in the liquid. The cartomizer also includes a heater  155  in the form of a coil of wire for heating liquid from reservoir  160  to generate aerosol to flow through air passage  161  and out through mouthpiece end  35 . The mouthpiece end  35  is provided with two openings  352  fluidly connected to the air passage  161  through which aerosol can be passed to the user&#39;s lungs. The heater is powered through lines  166  and  167 , which are in turn connected to opposing polarities (positive and negative, or vice versa) of the battery  210  via connector  25 A (the details of the wiring between the power lines  166  and  167  and connector  25 A are omitted from  FIG.  3   ). 
     One end of the control unit  20  provides a connector  25 B for joining the control unit  20  to the connector  25 A of the cartomizer  30 . The connectors  25 A and  25 B provide mechanical and electrical connectivity between the control unit  20  and the cartomizer  30 . The connector  25 B includes two electrical terminals, an outer electrode  240  and an inner electrode  250 , which are separated by insulator  260 . The connector  25 A likewise includes an inner electrode  175  and an outer electrode  171 , separated by insulator  172 . The insulator  172  is surrounded by the outer electrode  171 . The outer electrodes  171  and  240  and inner electrodes  175  and  250  are formed from an electrically conductive material, such as metal, or are coated/plated with a conductive material (e.g., silver-plated) while the insulators  171  and  260  are formed from a non-conductive material, such as plastic, rubber, silicone, or any other suitable material. When the cartomizer  30  is connected to the control unit  20 , the inner electrode  175  and the outer electrode  171  of the cartomizer  30  engage the inner electrode  250  and the outer electrode  240  respectively of the control unit  20 . The inner electrode  250  is mounted on a coil spring  255  so that the inner electrode  175  pushes against the inner electrode  250  to compress the coil spring  255 , thereby helping to ensure good electrical contact when the cartomizer  30  is connected to the control unit  20 . 
     The cartomizer connector  25 A is provided with two lugs or tabs  180 A,  180 B, which extend in opposite directions away from the longitudinal axis of the cartomizer  30 . These tabs  180 A,  180 B are used to provide a mechanical connection between the cartomizer  30  and the control unit  20 . The tabs  180 A,  180 B in this implementation flexibly engage with corresponding recesses (not shown) in the control unit  20  to provide a snap-fit type engagement to couple the cartomizer  30  to the control unit  20  when the cartomizer  30  is forced toward the control unit  20  along the longitudinal axis LA. In this regard, the tabs  180 A,  180 B are compressible in a direction towards the longitudinal axis LA to enable the cartomizer  30  to be inserted into the control unit  20  and are shaped so as to resist separation of the cartomizer  30  and control unit  20  when the tabs  180 A,  180 B are engaged with the corresponding recesses. The snap-fit engagement provides a secure and robust connection between the cartomizer  30  and the control unit  20  so that the cartomizer  30  and control unit  20  are held in a fixed position relative to one another, without wobble or flexing, and the likelihood of any accidental disconnection is very small. Other snap-fit engagement mechanisms may be provided that are constructed in an alternative manner to that described above. Moreover, it will be appreciated that other embodiments may use a different form of connection between the control unit  20  and the cartomizer  30 , such as a bayonet or a screw connection. 
     As mentioned above, the cartomizer  30  is generally disposed of once the liquid reservoir  160  has been depleted, and a new cartomizer is purchased and installed. Alternatively, the cartomizer  30  may be refilled with a new liquid and replaced. In either case the cartomizer  30  is generally removed from the control unit  20 . 
       FIG.  4    is a schematic perspective view of the aerosol delivery device  10  of  FIGS.  1  to  3    when the cartomizer  30  and control unit  20  are coupled together. In this implementation, the aerosol delivery device  10  is generally cuboidal and has a generally trapezoidal cross-section when viewed in a plane perpendicular to the longitudinal axis LA, wherein the longest side of the trapezium is curved between the two non-parallel sides of the trapezium. The separation distance between the two non-parallel sides is referred to herein as the width W of the aerosol delivery device  10  and increases in a direction from the lower surface  324  to the upper surface  322 . The terms longest side and shortest side refer to the relative length of the sides taken in the width direction.  FIG.  4    also shows the height H of the device which is the maximum separation distance between the longest, curved side and the shortest side, in addition to the length L, which is the total length of the aerosol delivery device  10  (i.e., cartomizer  30  and control unit  20  combined). The length direction is parallel to the longitudinal axis LA. 
     Accordingly, the upper surfaces  222  and  322  are curved in a width direction along the length of the aerosol delivery device  10 . The cartomizer  30  and control unit  20  have the same cross-section along the longitudinal axis LA so that the respective upper and lower surfaces  222 ,  322 ;  224 ,  324  are contiguous with one another when the cartomizer  30  and control unit  20  are coupled together. The curved upper surfaces  222  and  322  provide a device that some users may find easier to grip/hold. 
       FIG.  4    also shows the two mouthpiece openings  352  at the mouthpiece end of the cartomizer  30 . These openings  352  communicate with air flow channels provided throughout the aerosol delivery device  10  to allow air to be inhaled from outside the aerosol delivery device  10 , through the device  10  to mix with the vaporized aerosol precursor material, and out through the openings  352  of the mouthpiece end  35  into the user&#39;s lungs. The openings  352  are provided in a crescent-shape wherein the upper opening is longer in length than the lower opening. It should be appreciated that this is one exemplary way of arranging the openings  352  and other arrangements of openings may be provided, such as a number of circular holes disposed in a predefined pattern or a single opening. In some implementations, the openings are arranged to provide a certain directionality to the air exiting the device. For example, the openings may be configured to direct air along a direction inclined with respect to the longitudinal axis. 
       FIGS.  5 A and  5 B  schematically show an aerosol delivery system  100  in accordance with some embodiments of the present disclosure.  FIG.  5 A  schematically shows the aerosol delivery system  100  in an uncoupled/decoupled state while  FIG.  5 B  schematically shows the aerosol delivery system  100  in a coupled state. 
     Referring to  FIG.  5 A  first, the aerosol delivery system  100  of the present disclosure includes a plurality of aerosol delivery devices in an uncoupled state and shown having a separation distance between the delivery devices. The principles of this disclosure will be described herein with reference to two aerosol delivery devices but it should be appreciated the principles can equally be applied to an aerosol delivery system comprising more than two aerosol delivery devices. 
       FIG.  5 A  shows a first aerosol delivery device  10  which is the aerosol delivery device  10  of  FIGS.  1  to  4   . The cartomizer  30  and control unit  20  are coupled together by the connectors  25 A and  25 B and are provided in a state ready to generate and deliver aerosol to a user. In this state, a user can inhale on mouthpiece end  35  and receive aerosol generated by the aerosol delivery device  10  as described above. 
     In addition,  FIG.  5 A  shows a second aerosol delivery device  10 ′. The second aerosol delivery device  10 ′, in this implementation, includes similar components to the first aerosol delivery device  10 . Components of the second aerosol delivery device  10 ′ will be distinguished from those of the first aerosol delivery device  10  by use of a prime (′). Accordingly, for reasons of brevity, components having like reference signs but differing only by the presence of a prime have the same function and construction as the un-primed component previously described, unless described to the contrary. Therefore, the second aerosol delivery device  10 ′ comprises a second cartomizer  30 ′ including a second mouthpiece end  35 ′ and a second control unit  20 ′. The second cartomizer  30 ′ and second control unit  20 ′ are coupled together by connections  25 A′ and  25 B′ and are provided in a state ready to generate and deliver aerosol to a user. In this state, a user can inhale on the second mouthpiece end  35 ′ and receive aerosol generated by the second aerosol delivery device  10 ′ as described in a similar manner with respect to the first aerosol delivery device  10 . 
     The second cartomizer  30 ′ may, optionally, differ from the cartomizer  30  by comprising a different source liquid in its reservoir  160 ′ having, for example, a different flavor or a different strength/concentration of nicotine. Otherwise, in this implementation, the second cartomizer  30 ′ is identical to the cartomizer  30 . 
     The second control unit  20 ′ differs in construction from the control unit  20  by the second engagement mechanism; specifically, in the orientation/alignment of the magnetic portions  226 ′. In this implementation, the magnetic portions  226 ′ are arranged to have the polarity of each magnetic portion  226 ′ reversed compared to the polarity of magnetic portions  226  of the first aerosol delivery device  10  to allow for a magnetic coupling between magnetic portions  226  of the first aerosol delivery device  10  and magnetic portions  226 ′ of the second aerosol delivery device  10 ′.  FIG.  5 A  shows two double-headed arrows indicative of the magnetic forces acting between the magnetic portions  226  and  226 ′ of the respective aerosol delivery devices  10 ,  10 ′. As should readily be understood by one skilled in the art, when the magnetic poles of the magnetic portions  226 ′ of the second aerosol delivery device  10 ′ are reversed with respect to the corresponding magnetic portions  226  of the first aerosol delivery device  10 , an attractive magnetic force is generated causing the magnetic portions  226  and  226 ′ to be attracted to one another. 
     Accordingly, when the magnetic force is sufficiently strong, the aerosol delivery devices  10 ,  10 ′ are forced towards one another by the attractive magnetic force and couple together.  FIG.  5 B  shows the first and second aerosol delivery devices  10 ,  10 ′ in a magnetically coupled state. In this state, the mouthpiece ends  35  and  35 ′ of each aerosol delivery device  10 ,  10 ′ are provided adjacent one another. In this regard, the magnetic force of coupling should be strong enough to not cause sliding/twisting/slipping of one aerosol delivery device relative to another during normal use (i.e., when inhaling on the devices), but should be sufficiently weak to enable a user to separate the devices  10 ,  10 ′ by applying a force, or component thereof, in the direction in which the force of magnetic attraction acts. Hence, when coupled, a user can manipulate the two devices  10 ,  10 ′ as though they were handling a single device without the devices  10 ,  10 ′ becoming separated. 
     When coupled, the longitudinal axes LA, LA′ of the respective aerosol delivery devices  10 ,  10 ′ are substantially parallel as can be seen in  FIG.  5 B . Equally, because of the positioning of the magnetic portions  226  and  226 ′, the aerosol delivery devices  10 ,  10 ′ are provided such that the lengths thereof overlap/align. In other words, the overall length of the aerosol delivery system  100  from an edge of the first or second aerosol delivery device  10 ,  10 ′ furthest in one direction along the longitudinal axis to an opposite edge furthest in the opposite direction along the longitudinal axis is approximately the same as the length of an individual aerosol delivery device  10 ,  10 ′, barring any minor misalignments. 
       FIG.  5 C  schematically represents the aerosol delivery system  100  in a coupled state (i.e., of  FIG.  5 B ) when viewed along the longitudinal axis LA in a direction towards the mouthpiece ends  35 ,  35 ′ as shown by line  5 C in  FIG.  5 B . As can be seen, the lower surfaces  224 ,  324  and  224 ′,  324 ′ of each aerosol delivery device  10 ,  10 ′ abut in the coupled state (and hence, relatively speaking, the lower surfaces  224 ′ and  324 ′ are actually the uppermost surfaces of the second aerosol delivery device  10 ′). In a coupled state, a user places their lips on the upper surface  322  of the first aerosol delivery device  10  (specifically an upper lip) and on the upper surface  322 ′ of the second aerosol delivery device  10 ′ (specifically a lower lip) to engage with the adjacent mouthpiece ends  35  and  35 ′ simultaneously. In this way, when a user inhales on the aerosol delivery system  100  in a coupled state, a mixture of air is inhaled including air that passes through the first aerosol delivery device  10  (and which may include aerosol generated by the first aerosol delivery device) and air that passes through the second aerosol delivery device  10 ′ (and which may include aerosol generated by the second aerosol delivery device). Air (which may include the generated aerosol) exits the respective aerosol delivery devices via the openings  352  and  352 ′ as shown in  FIG.  5 C . Thus, a user can inhale a mixture of aerosol generated by both aerosol delivery devices  10 ,  10 ′. 
     The total height of the aerosol delivery system  100  is equal to twice the height H of the individual aerosol delivery devices  10 ,  10 ′ as indicated in  FIG.  5 C . Therefore, the height H for each individual device  10 ,  10 ′ should be chosen to provide a comfortable total height in the coupled state for a user to engage with both mouthpiece ends. By way of example only, the total height may be on the order of 15 mm meaning that each individual aerosol delivery device has a height H of 7.5 mm. This ensures the user is able to engage with both mouthpieces  35 ,  35 ′ in a coupled state and each mouthpiece end separately in an uncoupled state. 
     It should be understood that in the coupled state each of the aerosol delivery devices  10 ,  10 ′ can be operated to generate aerosol from the respective source liquids contained therein. The single user can thus inhale a mixture of both aerosols when the two devices are co-engaged/coupled. To change the respective aerosol combination (i.e., flavors/strengths) a user disconnects/decouples the first and second aerosol delivery devices  10 ,  10 ′ and exchanges the second aerosol delivery device  10 ′ for a third aerosol delivery device (not shown) having a different source liquid contained therein. Such changing of aerosol combinations does not require any significant disassembly of the individual aerosol delivery devices  10 ,  10 ′. Instead, the user can intuitively and easily swap aerosol sources by changing entire aerosol delivery devices without disconnecting individual cartomizers of the respective aerosol delivery devices. 
     Additionally, when the first and second aerosol delivery devices  10 ,  10 ′ are magnetically coupled, the electrical contacts  228  and  228 ′ of each aerosol delivery device  10 ,  10 ′ are brought into contact to electrically couple/connect the control unit  20  with the control unit  20 ′. In a similar way to the magnetic portions  226  and  226 ′, the control unit  20  may differ in construction from the control unit  20  in that the polarities of the electrical contacts  228 ′ of the second aerosol delivery device  10 ′ are reversed with respect to the polarities corresponding electrical contacts  228  on the first aerosol delivery device  10 . This enables an appropriate electrical connection when the first and second aerosol delivery devices  10 ,  10 ′ are magnetically coupled together. As described above, the electrical connection enables power and/or control signals to be passed between the first and second aerosol delivery devices  10 ,  10 ′. 
     The control signals are electrical signals that are received at either of the controllers located in the aerosol delivery devices and are used to determine how the respective aerosol delivery devices  10 ,  10 ′ should operate. 
     Control signals include, for example, an indication of the volume or amount of aerosol to be generated for each of the respective aerosol delivery devices  10 ,  10 ′ upon inhalation by a user. In this example, each of the controllers of the delivery devices  10 ,  10 ′ are provided with source identification information which identifies the source liquid (more generally, the aerosol precursor material) contained in the respective aerosol delivery devices  10 ,  10 ′. For example, the first aerosol delivery device  10  may have a source liquid having an apple flavoring while the second aerosol delivery device  10 ′ may have a source liquid having a strawberry flavoring. The source identification information can be programmed into the control unit  20 ,  20 ′ of the respective delivery devices  10 ,  10 ′ by a user prior to using the aerosol delivery devices  10 ,  10 ′ e.g., through connecting to a computer or the like via a USB cable or, alternatively, each cartomizer  30 ,  30 ′ is provided with an electronically readable chip or the like storing the source identification information and, when the cartomizers  30 ,  30 ′ are coupled to their respective control units  20 ,  20 ′, the chip is read by the controller to obtain the source identification information. 
     An optimal mixture of the flavors in the example given may be in the ratio of 2:1, for instance, as determined by the manufacturer of the cartomizers  30 ,  30 ′ or as set by a user based upon their preferences. When the first and second aerosol delivery devices  10 ,  10 ′ are first coupled, the source identification information is exchanged between the two devices using the electrical connection. Therefore, the first aerosol delivery device  10  receives an indication that it is to be mixed with a strawberry flavoring and, as a result, the controller controls the amount of power supplied to the heater  155  to generate a quantity of apple-flavored aerosol that is suitably mixed with the strawberry-flavored aerosol. This can be implemented based upon a look-up table referencing all produced flavors from the manufacturer and combinations thereof. Equally, the second aerosol delivery device  10 ′ receives source identification information from the first aerosol delivery device  10 ′ and correspondingly controls the heater  155 ′ to generate a suitable quantity of strawberry-flavored aerosol in a similar manner It should be appreciated that, in some implementations, the quantity of aerosol generated in respective aerosol delivery devices is also a function of the air flow flowing through the aerosol delivery device as detected, for example, using a suitable sensor. In these implementations, aerosol is generated in each device as a function of both the flavor ratio and the detected air flow such that, regardless of the strength of the air flow, the flavor ratio is maintained. 
     It should be appreciated that the above describes a situation whereby the volume of aerosol (and hence the ratio of flavors) is set automatically based upon the detected flavors to be combined and inhaled. In alternative implementations, a user may have direct control over the quantity of aerosol produced. As described above, a suitable sensor, such as a puff sensor is used to activate the heater  155 ,  155 ′ when a puff is detected. To adjust the flavor ratio, the user may, for example, press on one or more buttons located on the upper surfaces  222  and  222 ′ of the respective control units  20 ,  20 ′ (not shown in the figures). Such buttons may allow dynamic changing of the ratio of flavors prior to or during inhalation (e.g., by increasing or decreasing the quantity produced by each individual aerosol delivery device  10 ,  10 ′). In some implementations, pressing a button on the first aerosol delivery device  10  may impact upon the aerosol generated by the second aerosol delivery device  10 ′. In this case, the control signals may include indications of button presses made on one of the aerosol delivery devices. 
     In other implementations, the user may perform some action that affects the air flow through one of the aerosol delivery devices when the devices are coupled. For example, the user may puff on only one of the mouthpiece ends (or more strongly on one end) or may block the openings of one mouthpiece end of the aerosol delivery device. The output from both puff sensors in these cases would be different and the difference can be attributed to certain control functions of the aerosol delivery device. For example, the aerosol delivery device having the larger airflow value as detected by the puff sensors may be controlled to increase the proportion of aerosol it generates in the mixture by increasing the relative power supplied to the heater, for example while decreasing the relative power supplied to the heater of the other aerosol delivery device. That is, if one aerosol delivery device is instructed to increase the volume of aerosol output (thus making the mixture more apple-based), the output of the other aerosol delivery device is decreased. A user can set the desired ratio based upon interacting with one or the other of the devices. The total volume of aerosol inhaled will depend upon the strength of the puff but the volume of each flavor inhaled is set relative to the total volume based upon the flavor ratio. 
     In other implementations, the control signals include communications between the controllers of the first and second aerosol delivery devices  10 ,  10 ′, where said communications are used to establish a master controller responsible for controlling the functions of both the first and second aerosol delivery devices  10 ,  10 ′. Using a master controller may help reduce energy/power consumption because other controllers can be placed in a stand-by/lower-power mode. In addition, other components, e.g., flow/puff sensors, may also be placed in a low-power mode. 
     In this regard, when first coupled, the controllers are arranged to send device information (which may include the source identification information in addition to other parameters such as current battery charge, software/hardware version, usage statistics, etc.) to the other controller of the other aerosol delivery device. The controllers are programmed to determine, from the available controllers, a single controller (master controller) by comparing the received device information to their own device information. Each controller then determines whether or not it should be a master controller. If it is decided that a first controller should not be a master (e.g., because the battery charge is low compared to other devices, or the controller is not compatible with the other controller(s), or for some other reason) then no further action is taken. 
     Conversely, if the first controller determines that it should be a master controller, it transmits a signal (via the electrical connection) indicating its eligibility to the remaining controllers. If the remaining controllers do not consider themselves master controller candidates then the remaining controllers send an acknowledgement (ACK) signal back to the controller. If the total number of ACK signals is equal to the total number of sets of device information received, the controller then appoints itself master controller and assumes responsibility for each of the controllers (and hence the functions of each of the aerosol delivery devices  10 ,  10 ′). Conversely, if one of the remaining controllers determines that it is a candidate master controller, it transmits a negative acknowledgement (NACK) signal back to the first controller. On receiving the NACK signal the first controller does not become a master controller, and the controller sending the NACK signal remains a master controller candidate. The process can be cycled through until a master controller is selected or until the process is timed-out in which case a master controller may be selected at random from the candidate set. 
     It should be appreciated that the above is merely an example of how the master controller can be selected from a number of controllers. The exact process of how a master controller is selected is not particularly significant for the principles of the present disclosure, but rather that communications can occur between controllers of different aerosol delivery devices  10 ,  10 ′ using the electrical connection. However, one skilled in the art will be aware of other processes which may be used in conjunction with or in place of the above described selection process for selecting the master controller. 
     In addition to control signals, the electrical contacts  228  and  228 ′ also allow for power to be exchanged/transferred between aerosol delivery devices  10 ,  10 ′. In other words, electrical power from the battery or cell  210  of the first aerosol delivery device  10  can be transferred to the battery or cell  210 ′ of the second aerosol delivery device  10 ′ or directly to the heater  155 ′ of the cartomizer  30 ′ of the second aerosol delivery device  10 ′. 
     For example, electrical power can be shared between the first and second aerosol delivery devices  10 ,  10 ′ to provide the respective batteries  210 ,  210 ′ with the same level of charge. In other words, power can be supplied from the battery having the greatest charge to the battery having the lowest charge in order to charge the battery having the lowest charge. Power can be transferred from one battery to another until each of the batteries has equal or approximately equal charge so that, if decoupled, both aerosol delivery devices may be individually used to generate aerosol. In other implementations, the charge is distributed in proportion to the output ratio of aerosol; for instance, using the example above, power is distributed in a 2:1 ratio between first and second aerosol delivery devices  10 ,  10 ′. 
     In one implementation, the control units  20  and  20 ′ are provided with appropriate circuitry configured to distribute power between the batteries in a passive manner—that is, as soon as the electrical connection is made using the contacts  228  and  228 ′, power is transferred until the batteries reach an appropriate level of charge. Alternatively, the control units  20  and  20 ′ are provided with circuitry configured to transfer power in response to certain actions. These certain actions may include, for example, a user pressing on a button provided on the upper surface  222  and/or  222 ′ of the control unit  20  and/or  20 ′ or in response to a detected puff/inhalation as detected by a suitable sensor. 
     In yet another alternative implementation, power is not supplied to the batteries  210  and  210 ′ but is instead supplied directly to the heater  155  and/or  155 ′ in response to a detected puff. For example, the controllers may determine which of the batteries has the greatest charge (based upon transmitting device information between the aerosol delivery devices  10 ,  10 ′) and use the determined battery to supply power to both the heater  155  and heater  155 ′ via the electrical connection. In this way, the battery having the greatest charge at any one time can preferentially be used to generate aerosol in both of the aerosol delivery devices  10 ,  10 ′. When the difference in charge reaches zero, or reverses (i.e., the battery supplying the power to both heater  155  and heater  155 ′ becomes the battery with the lowest charge), then the battery responsible for supplying the power to both devices is switched and the other battery is used in its place. In this way, when the difference in charge between the batteries is small, the batteries are alternated between, meaning that at any one time the batteries have approximately the same level of charge. This provides similar benefits as described above. 
     In yet further implementations, each of the control units  20 ,  20 ′ comprises a dedicated USB (or similar) charging port as described above. When coupled, a user may connect a USB power cable (i.e., a USB cable configured to supply power from a power source such as mains electricity) to either one of the USB charging ports. When a USB power cable is connected to a USB port, the electrical power supplied is distributed to the respective batteries  210 ,  210 ′ using the electrical contacts  228 ,  228 ′ so that both batteries may be charged using a single power cable and single port. For example, if a user connects the USB power cable to the control unit  20 , the control unit  20  (or master controller) is configured to distribute some or all of the received power to the battery  210 ′ of the control unit  20 ′ via the electrical contacts  228  and  228 ′. The power may be transferred in accordance with any pre-set conditions. For example, the power may be distributed so that each battery receives half of the input power (i.e., 50% of the power is directed to battery  210  and 50% to battery  210 ′). Alternatively, the ratio of power distribution may be selected based upon the current level of charge of the batteries  210 ,  210 ′ with the battery having the lower charge being distributed a larger proportion of the incoming power. In other implementations, the power is first distributed to the battery of the control unit coupled to the power cable, e.g., battery  210 , to charge that battery to a certain level (e.g., fully charged) before being distributed to the battery of the control unit not coupled to the power cable, e.g., battery  210 ′. In this way, a user can sufficiently charge both (or multiple) aerosol delivery devices with only a single power cable and a single connection of the cable to the aerosol delivery system. This provides the user with a much simpler charging mechanism as the user only has to be concerned with connecting the cable to any of the charging ports. 
     An aerosol delivery system  100  in which two aerosol delivery devices  10 ,  10 ′ are magnetically and electrically coupled together via respective engagement mechanisms co-engaging has been described above. In the described implementation, magnetic portions  226 ,  226 ′ and electrical contacts  228 ,  228 ′ are provided on one surface of the respective aerosol delivery devices. However, in other implementations, secondary (or further) magnetic portions and electrical contacts are disposed on other surfaces of the aerosol delivery devices. For example, the engagement mechanism of each aerosol delivery device is provided with two groups of magnetic portions and electrical contacts (disposed on the upper surfaces  222 ,  222 ′ and the lower surfaces  224 ,  224 ′). In this implementation, each of the magnetic portions on the upper surfaces  222 ,  222 ′ have their poles aligned in the same first direction, while each of the magnetic portions on the lower surfaces  224 ,  224 ′ have their magnetic poles aligned in a second, opposite direction. Accordingly, such an arrangement facilitates the magnetic coupling of the upper and lower surfaces of respective aerosol delivery devices. Thus, unlike the described implementation above, if magnetic coupling is not permitted between two surfaces (because the magnetic portions  226 ,  226 ′ repel each other), then in this implementation a user can rotate one aerosol delivery device by  180 ° about the longitudinal axis LA to provide a magnetic attraction between the secondary magnetic portions. Equally, the same can be said for the electrical contacts. 
     Moreover, in a further implementation, the engagement mechanisms (i.e., the magnetic portions) and the electrical contacts are disposed on the surfaces corresponding to the non-parallel sides of the generally trapezoidal cross-section of the aerosol delivery device in  FIG.  4    (i.e., the sides connecting the upper and lower surfaces  222 ,  222 ′ and  224 ,  224 ′). This arrangement can facilitate the magnetic coupling of many aerosol delivery devices in a ring-type arrangement by disposing aerosol delivery devices such that their non-parallel surfaces abut. 
     Although the magnetic portions  226 ,  226 ′ of the engagement mechanisms and electrical contacts  228 ,  228 ′ have been described as being provided on/in on/in surfaces of the control unit  20 ,  20 ′, it should be understood that the engagement mechanisms (magnetic portions  226 ,  226 ′) and/or electrical contacts  228 ,  228 ′ may additionally or alternatively be provided on surfaces of the cartomizers  30 ,  30 ′. 
     Furthermore, in alternative implementations, the engagement mechanism of the second aerosol delivery device  10 ′ comprises the housing of the control unit  20 ′ or cartomizer  30 ′. In this implementation, the second aerosol delivery device is made of a magnetic material — that is, the housing of the control unit  20 ′ is formed from a material that is magnetically attracted to the engagement mechanism of the first aerosol delivery device  10  (e.g., magnetic portions  226 ). Precise aligning of the magnetic portions  226  and  226 ′ is therefore not required in this implementation and it is irrelevant whether or not magnetic portions on opposing devices are aligned in a manner to provide attractive magnetic coupling therebetween as in  FIG.  5 A . Instead, magnetic coupling occurs between the magnetic portions  226  and an area of the control unit  20 ′. Although in this implementation it is not required that both aerosol delivery devices  10 ,  10 ′ are provided with the magnetic portions  226 ,  226 ′, in other implementations both aerosol delivery devices  10 ,  10 ′ are provided with their engagement mechanisms comprising both the magnetic portions  226  or  226 ′ and the housing of the respective cartomizer  30 ,  30 ′ and/or and/or control unit  20 ,  20 ′. This can enable a stacked arrangement of aerosol delivery devices for example where coupling between two delivery devices of the stack is achieved by the magnetic portions of one aerosol delivery device coupling to the housing of the other delivery device as described above. 
     It should be noted that the reservoirs  160 ,  160 ′ may be constructed to contain any amount of aerosol precursor depending upon the application at hand. However, in one implementation, the total volume of liquid aerosol precursor material contained in each reservoir is set to, e.g., 2 ml divided by the number of aerosol delivery devices intended to be coupled together. Thus, for an aerosol delivery system consisting of two aerosol delivery devices, each reservoir is constructed to contain a maximum of 1 ml of liquid aerosol precursor. In this way, the total volume of liquid aerosol precursor material does not exceed 2 ml in normal use when the individual aerosol delivery devices are coupled. 
     Described above is an aerosol delivery system  100  comprising two aerosol delivery devices  10  and  10 ′ that are magnetically coupled together. However, the principles of the present disclosure can be applied to aerosol delivery devices that comprise mechanical engagement mechanisms providing co-engagement of the aerosol delivery devices. That is, the aerosol delivery devices are selectively coupled together mechanically through the engagement mechanisms rather than magnetically. 
       FIGS.  6 A and  6 B  schematically show two aerosol delivery devices  610  and  610 ′ as viewed along a direction offset from the longitudinal axes thereof according to a second implementation of the present disclosure that, when coupled together, form a mechanically interlocked/coupled aerosol delivery system  600 . 
     Specifically,  FIG.  6 A  shows a first aerosol delivery device  610  and a second aerosol delivery device  610 ′ in a decoupled state. The first and second aerosol delivery devices  610 ,  610 ′ comprise respective cartomizers  630  and  630 ′ and control units  620  and  620 ′. In  FIG.  6 A , the second control unit  620 ′ is shown decoupled from the second cartomizer  630 ′ and, as such, connectors  625 A′ and  625 B′ are exposed, while the first control unit  610  is shown coupled to the first cartomizer  630  via connectors (not shown). 
     The internal construction of the control units  620 ,  620 ′ and the cartomizers  630 ,  630 ′ is not shown in  FIGS.  6 A and  6 B ; rather, only the outer surfaces of the aerosol delivery devices  610 ,  610 ′ are shown. However, the first and second aerosol delivery devices  610  and  610 ′ comprise the necessary internal components required to function as an aerosol delivery device, e.g., components similar to those shown in  FIGS.  2  and  3    with respect to the cartomizer  30  and control unit  20 . The skilled person would readily employ the necessary components as required in view of the implementation described above and in accordance with conventional approaches. 
     The aerosol delivery devices  610 ,  610 ′ in the second implementation generally have a hemi-cylindrical shape; that is, the cross-section at either end of the aerosol delivery devices  10 ,  10 ′ is semi-circular. However, instead of the control units  620 ,  620 ′ having magnetic portions to provide magnetic coupling as in the first implementation of  FIGS.  1  and  5 A to  5 C , the aerosol delivery devices  610 ,  610 ′ (specifically a section of the cartomizers  630 ,  630 ′ thereof) are provided with interlocking sections  631 ,  631 ′. The interlocking sections constitute the respective engagement mechanisms of this implementation. 
     Each interlocking section  631 ,  631 ′ is defined, in this implementation, from the end of the mouthpiece end  635 ,  635 ′ joined to the interlocking section  631 ,  631 ′ to the opposite end of the cartomizer  630 ,  630 ′. The interlocking section  631 ,  631 ′ is formed from a transparent material to enable a user to see inside the cartomizer  630 ,  630 ′. The interlocking section  631 ,  631 ′ is a hollow structure and includes a reservoir for each aerosol delivery device in this implementation in which the aerosol precursor material/liquid formulation is stored. Owing to the transparent construction, a user can visually detect when the aerosol precursor is running low or requires replacement. However, the aerosol delivery devices  610 ,  610 ′ may generally be formed from any suitable materials, e.g., opaque plastic, metal, etc. 
     As can be seen in  FIG.  6 A , the interlocking sections  631 ,  631 ′ are constructed in a manner such that the hemi-cylindrical shape progressively rotates about the longitudinal axis LA when moving along the respective longitudinal axes LA, LA′ by a constant amount. That is, for the first aerosol delivery device  610 , as one passes from the mouthpiece end  635  towards the opposite end of the cartomizer  630 , the hemi-cylindrical shape rotates, e.g., clockwise, about the longitudinal axis LA by a total of approximately 270°. By way of example only, the hemi-cylindrical shape may be rotated clockwise by a constant amount of 54° per cm, thus meaning the interlocking section is approximately  5  cm in length (along the longitudinal axis). Similarly, the cartomizer  630 ′ of the second aerosol delivery device  610 ′ has a hemi-cylindrical shape that rotates at the same pitch as cartomizer  630  along the longitudinal axis LA′ in the interlocking section  631 ′. In both interlocking sections  631 ,  631 ′ shown in  FIG.  6 A , it should be appreciated that the semi-circular cross-section at the start of the interlocking section (i.e., the ends directly after the mouthpiece ends  635 ,  635 ′) is offset relative to the semi-circular cross-section at the opposite end by 270° or 90° depending upon the definition of the direction of rotation about the longitudinal axis. 
     It should be appreciated, however, that in other implementations the extent to which the hemi-cylindrical cross-sectional shape is rotated along the longitudinal axis of the cartomizer  630 ,  630 ′ may be more or less than that described above. For example, in one implementation, the hemi-cylindrical shape is rotated by a total of 90° about the longitudinal axis LA, LA′ when moving from one end of the interlocking section along the longitudinal axis to the other end. That is, in this example, the hemi-cylindrical shape is rotated at a constant amount of 18° per cm over a length of 5 cm. In addition, in other implementations, the degree of rotation is not constant along the length of the interlocking section—for example, the rotation amount may vary along the length of the longitudinal axis LA, LA′. However, in the case of a varying rotation amount, the interlocking sections  631 ,  631 ′ should be provided with the same or a similar degree/magnitude of variation at each position along the longitudinal axis. 
     This construction of the interlocking sections  631 ,  631 ′ enables a user to couple together the aerosol delivery devices  610 ,  610 ′ using a mechanical coupling.  FIG.  6 B  schematically shows the aerosol delivery system  600  in a (releasably) coupled state whereby the user has performed a certain action to enable the aerosol delivery devices  610 ,  610 ′ to mechanically couple. 
     In this implementation, the specific action involves aligning the interlocking sections  631 ,  631 ′ of the respective aerosol delivery devices  610 ,  610 ′ and twisting/pressing the interlocking sections  631 ,  631 ′ together such that the flat surfaces of the hemi-cylindrical shapes of both aerosol delivery devices  610 ,  610 ′ abut.  FIG.  6 B  schematically shows the aerosol delivery system  600  in a (mechanically) coupled state, whereby the first and second aerosol delivery devices  610 ,  610 ′ of  FIG.  6 A  have been manipulated such that the interlocking portions  631 ,  631 ′ interlock. As can be seen in  FIG.  6 B , when the separate aerosol delivery devices  610 ,  610 ′ are interlocked, they define a cylindrical shape (composed of the respective hemi-cylindrical shapes) and share a common longitudinal axis. When coupled, the hemi-cylindrical shapes of the interlocking sections  631 ,  631 ′ of this implementation are rotated in the same direction along the common longitudinal axis (e.g., clockwise) but the starting positions are offset from one another by 180°. Moreover, the interlocking sections  631 ,  631 ′ enable the mouthpiece ends  635 ,  635 ′ of the respective aerosol delivery devices  610 ,  610 ′ to be provided adjacent one another when the devices  610 ,  610 ′ are coupled. 
     The construction of the interlocking sections  631 ,  631 ′ enables the interlocking sections (and thus the cartomizers  630 ,  630 ′ and attached control units  620 ,  620 ′) to be mechanically coupled together and held in a way such that only a specific set of actions will separate/uncouple the interlocking sections  630 ,  631 ′. Therefore, the interlocking sections  631 ,  631 ′ prevent or substantially prevent sliding/twisting/slipping of one aerosol delivery device relative to another during normal use (i.e., when inhaling on the devices), but enable quick and intuitive separation of the aerosol delivery devices  610 ,  610 ′ under application of the appropriate force/movement. 
     Although not shown, the interlocking sections  631 ,  631 ′ are formed with a dividing wall running along the length of the respective interlocking sections to define two compartments within the hollow interior of the interlocking sections. In cross-section, the dividing wall divides the cross-section of the interlocking portions. The two compartments are fluidly isolated within the interlocking section. One of the compartments forms the reservoir and contains the aerosol precursor (e.g., the fluid to be vaporized). The other compartment forms an air passage, e.g., similar to air passage  161 , to allow air to be passed from the control unit  620 ,  620 ′ to the mouthpiece end  635 ,  635 ′. 
     In some implementations, the dividing wall is semi-circular in shape and, when viewed in cross-section, splits the semi-circular shape of the interlocking section into a first compartment having a semi-circular shape with a smaller radius than the overall semi-circular shape of the interlocking section, and a second compartment having an annular cross-section with a radius greater than the first compartment. In other words, the second compartment is formed to surround the outer curved edge of the first compartment, although it should be appreciated that the compartments can be formed to have other cross-sectional shapes. In this implementation, the dividing wall is twisted in accordance with the rotation of the respective interlocking section. 
     In the releasably coupled state, as with the aerosol delivery system  100 , the mouthpiece ends  635 ,  635 ′ of the respective aerosol delivery devices  610 ,  610 ′ are adjacent one another. Equally, the respective longitudinal axes LA, LA′ of the first and second aerosol delivery devices  610 ,  610 ′ are provided parallel to one another. In much the same way as described for system  100 , a user can place their lips around the respective mouthpiece ends  635 ,  635 ′ to engage both mouthpiece ends simultaneously. When a user inhales on the mouthpiece ends  635 ,  635 ′, air passes along the air passage (second compartment) of the respective interlocking sections (either prior to or after being mixed with the generated aerosol for the respective aerosol delivery devices  610 ,  610 ′ depending upon the location of the heater) and into the mouthpiece end  635 ,  635 ′. As a result, a user inhaling on the mouthpiece ends  635 ,  635 ′ can be provided with a mixture of aerosols generated by both the first and second aerosol delivery devices  610 ,  610 ′. It should be readily understood that, as with the aerosol system  100  described above, the aerosol system  600  permits users to intuitively and easily switch liquid formulations (e.g., flavors) without disassembling and reassembling the aerosol delivery devices  610 ,  610 ′. Additionally, each of the aerosol delivery devices  610 ,  610 ′ is able to function independently in the decoupled state; that is, a user may inhale aerosol generated by device  610  when not coupled to device  610 ′. 
     It should be understood that interlocking section  631  is able to be mechanically interlocked with interlocking section  631 ′ because the rotation of the hemi-cylindrical shapes are in the same directions about the longitudinal axes. Interlocking section  631  would not be able to interlock with another interlocking section having the same shape but rotated in the opposite direction about its longitudinal axis (e.g., anticlockwise by a constant amount of 54° per cm) in this implementation. Therefore, in much the same way as with the magnetic portions  226  and  226 ′, certain interlocking sections (and thus cartomizers/control units) cannot be combined. This may also be the case where the rotation about the longitudinal axis is in the same direction but the variation in rotation degree along the longitudinal axes of the respective interlocking sections is different. This may be useful in preventing certain flavors or nicotine strengths, for example, from being combined as these liquid formulations can be stored in mutually exclusive interlocking sections. 
     Although not shown in  FIGS.  6 A and  6 B , the aerosol delivery devices  610 ,  610 ′ may also be provided with electrical contacts, similar to electrical contacts  228 ,  228 ′ to permit control signals or power to be transferred between coupled aerosol delivery devices  610 ,  610 ′. For example, the electrical contacts may be disposed on the flat (i.e., non-curved) surface of the hemi-cylindrical control units  620 ,  620 ′. Hence, when performing the interlocking motion, the electrical contacts are bought into contact to electrically couple the two aerosol delivery devices  610 ,  610 ′. The transfer of power and/or control signals may be carried out as described above. 
     The interlocking sections  631 ,  631 ′ described above are merely given as an example and it will be appreciated by the skilled person that the interlocking sections  631  and  631 ′ can take other shapes to provide a mutually interlocking function. For instance, the degree of rotation of the hemi-cylindrical shape may be more or less than described, or the general cross-section may be square or, more generally, polygonal in the interlocking sections as opposed to hemi-cylindrical. Equally, although the interlocking portions  631 ,  631 ′ are shown as being formed in the cartomizers  630 ,  630 ′, it should be understood that the control units  620 ,  620 ′ may alternatively or additionally comprise the interlocking sections. 
     The above described second implementation makes use of the shape of the interlocking sections/cartomizers to provide a mechanical coupling. The engagement mechanisms by which the mechanical coupling occurs are therefore integrally formed with the aerosol delivery devices. In other implementations, the mechanical coupling of two or more aerosol delivery devices is achieved in other ways using an integrally formed mechanical coupling. 
     For example, although not shown, the aerosol delivery devices may integrally comprise one or more clips positioned on an outer surface thereof and configured to receive a portion of the other aerosol delivery device. The engagement mechanism of the first aerosol delivery device in this implementation is the one or more clips integrally formed with the outer surface thereof, while the engagement mechanism of the second aerosol delivery device is a section or part of the outer surface of the second aerosol delivery device that can be received by the one or more clips. For example, for a second aerosol delivery device having a circular or approximately circular cross-section, the clip is provided in a C-shape whereby the body of the second aerosol delivery device can be pressed into the inner part of the C-shape clip through the separation between the ends of the C. In this implementation, the C-shape clip is resiliently deformable and has an internal diameter/dimension slightly less (e.g. less than 10%, or less than 5%) than the diameter/dimension of the opposing aerosol delivery device. Accordingly, the resiliently deformable C-shape clip applies a radially compressive force on the opposing aerosol delivery device when located in the internal region of the C-shaped clip. Here, radially compressive force means a force acting towards the central point of the internal region of the C-shaped clip along a diameter thereof. Therefore, in this implementation, the two aerosol delivery devices can be mechanically coupled to provide a non-slipping/sliding arrangement during normal use. It should be apparent that the aerosol delivery devices can be coupled such that the mouthpiece ends thereof generally align as described above. 
     In alternative implementations, one aerosol delivery device may be provided with an integrally formed protrusion as the first engagement mechanism on an outer surface thereof which is shaped in a manner to be mechanically received (and held) in a correspondingly shaped recess provided on an outer surface of the other aerosol delivery device as the second engagement mechanism. Accordingly, by inserting the protrusion into the recess, and optionally sliding/rotating/pressing the protrusion into the recess (which may define a track along which the protrusion is guided during coupling), the two aerosol delivery devices can be mechanically coupled and held together during normal use. The protrusion and recess may take any corresponding shape that enables the two devices to be releasably locked together, e.g., corresponding T-shapes when viewed in cross-section. Such mechanical coupling mechanisms are generally known in the art and any suitable mechanism may be used in accordance with the principles of the present disclosure. 
     Additionally, the principles of the present disclosure do not require a specific mechanical coupling mechanism to be used. Any available mechanism that would be suitable may be used. 
     It has been described above that system  100  comprises aerosol delivery devices having a generally cuboidal shape, while system  600  comprises aerosol delivery devices have a generally hemi-cylindrical shape  600 . However, the principles of the present disclosure are not limited to aerosol delivery devices having the described shapes and aerosol delivery devices having any shape can be used, provided that coupling between surfaces thereof is permitted. Additionally, the aerosol delivery devices  10 ,  10 ′  610 ,  610 ′ have been described generally as being a two-piece construction comprising separate but connectable cartomizers  30 ,  30 ′,  630 ,  630 ′ and control units  20 ,  20 ′,  620 ,  620 ′. However, the principles of the present disclosure apply to aerosol delivery devices being formed of more or less than two main constituent components. For example, the disclosure applies to aerosol delivery devices having a single-piece (i.e., integrated) construction. 
     It has also generally been disclosed above that aerosols generated by each of the aerosol delivery devices are mixed and inhaled. That is, the air that the user inhales comprises a mixture of the different aerosols that is mixed upon exiting the mouthpiece end. However, in other implementations, the two aerosols may be substantially kept separate during inhalation by the user. In these implementations, the different generated aerosols are directed to different areas of the mouth using mouthpiece ends  35 ,  35 ′ that impart directionality to the individual aerosols as described above. When the aerosol delivery devices are coupled, the different aerosols are directed along different directions. For example, the aerosol generated by a first device may be generally directed along a first direction angled with respect to the longitudinal axis LA, LA′ while aerosol generated by a second device may be generally directed along a second direction angled with respect to the longitudinal axis but different from the first direction. Although the areas of the mouth that the aerosol is directed to will depend upon the orientation of the coupled aerosol delivery devices, one could imagine the different aerosols being separately directed to the left and right sides of the mouth cavity. 
     Thus, there has been described an aerosol delivery system including: a first engagement mechanism, a first power supply, and a first vaporizer, wherein the first vaporizer is arranged to selectively receive power from the first power supply to generate a first aerosol from a first aerosol precursor material for user inhalation; and a second aerosol delivery device comprising a second engagement mechanism, a second power supply, and a second vaporizer, wherein the second vaporizer is arranged to selectively receive power from the second power supply to generate a second aerosol from a second aerosol precursor material for user inhalation; wherein the first engagement mechanism of the first aerosol delivery device and the second engagement mechanism of the second aerosol delivery device are arranged to releasably co-engage with one another to selectively couple the first aerosol delivery device to the second aerosol delivery device so the first aerosol delivery device and the second aerosol delivery device may be used together to deliver the first and second aerosols to a single user when they are coupled together and may be used independently to deliver the first and second aerosols to different users when they are not coupled together. 
     While the above described embodiments have in some respects focused on some specific example aerosol delivery systems, it will be appreciated the same principles can be applied for aerosol delivery systems using other technologies. That is to say, the specific manner in which various aspects of the aerosol delivery system function are not directly relevant to the principles underlying the examples described herein. 
     In order to address various issues and advance the art, this disclosure shows by way of illustration various embodiments in which the claimed invention(s) may be practiced. 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 to teach the claimed invention(s). 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 of the claims. Various embodiments may suitably comprise, consist of, or consist essentially of, various combinations of the disclosed elements, components, features, parts, steps, means, etc. other than those specifically described herein, and it will thus be appreciated that features of the dependent claims may be combined with features of the independent claims in combinations other than those explicitly set out in the claims. The disclosure may include other inventions not presently claimed, but which may be claimed in future.