Patent Publication Number: US-11653701-B2

Title: Aerosol source for a vapor provision system

Description:
PRIORITY CLAIM 
     The present application is a National Phase entry of PCT Application No. PCT/GB2018/050726, filed Mar. 21, 2018, which claims priority from GB Patent Application No. 1704674.9, filed Mar. 24, 2017, each of which is hereby fully incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to an aerosol source for an electronic vapor provision system such as an e-cigarette. 
     BACKGROUND 
     Many electronic vapor provision systems, such as e-cigarettes and other electronic nicotine delivery systems, are formed from two main components or sections, namely a cartomizer and a control unit (battery section). The cartomizer generally includes a reservoir of liquid and an atomizer for vaporizing vaporizing the liquid. These parts may collectively be designated as an aerosol source. The atomizer may be implemented as an electrical (resistive) heater, such as a wire formed into a coil or other shape and a wicking element in proximity to the heater which transports liquid from the reservoir to the heater. The control unit generally includes a battery for supplying power to the atomizer. In operation, the control unit may be activated, for example by detecting when a user inhales on the device and/or when the user presses a button, to provide electrical power from the battery to the heater. This activation causes the heater to vaporize a small amount of liquid delivered by the wicking element from the reservoir, which is then inhaled by the user. 
     A consistent and efficient generation of vapor requires effective wicking of the liquid from the reservoir by the wicking element. Accordingly, the configuration of the wicking element is of interest. 
     SUMMARY 
     According to a first aspect of some embodiments described herein, there is provided an aerosol source for an electronic vapor provision system comprising: a heating element; an atomizing chamber; a reservoir for holding free-flowing source liquid; a porous wick extending from the atomizing chamber to the reservoir and comprising a heater portion in cooperation with the heating element within the atomizing chamber and at least one liquid collecting portion within the reservoir, the liquid collecting portion having a maximum cross-sectional parameter that is greater than an equivalent cross-sectional parameter of the heater portion. 
     According to a second aspect of some embodiments described herein, there is provided an atomizer for an electronic vapor provision system comprising: a heating element; and a porous wick comprising a heater portion in cooperation with the heating element and at least one liquid collecting portion contiguous with the heater portion for placement in a reservoir of source liquid, the liquid collecting portion having a maximum cross-sectional parameter that is greater than an equivalent cross-sectional parameter of the heater portion. 
     According to a third aspect of some embodiments described herein, there is provided a wick for an atomizer of an electronic vapor provision system, made from porous material and comprising: a heater portion for cooperation with a heating element; and at least one liquid collecting portion contiguous with the heater portion for placement in a reservoir of source liquid, the liquid collecting portion having a maximum cross sectional parameter that is greater than an equivalent cross-sectional parameter of the heater portion. According to a fourth aspect of some embodiments described herein, there is provided a cartomizer for an electronic vapor provision system comprising an aerosol source according to the first aspect, or an atomizer according to the second aspect, or a wick according to the third aspect. 
     These and further aspects of the certain embodiments are set out in the appended independent and dependent claims. It will be appreciated that features of the dependent claims may be combined with each other and features of the independent claims in combinations other than those explicitly set out in the claims. Furthermore, the approach described herein is not restricted to specific embodiments such as set out below, but includes and contemplates any appropriate combinations of features presented herein. For example, an aerosol source or a vapor provision system including an aerosol source may be provided in accordance with approaches described herein which includes any one or more of the various features described below as appropriate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments of the disclosure will now be described in detail by way of example only with reference to the following drawings in which: 
         FIG.  1    shows a cross-section through an example e-cigarette comprising a cartomizer and a control unit in which embodiments may be implemented. 
         FIG.  2    shows a perspective external view of the cartomizer of  FIG.  1   . 
         FIG.  3    shows an exploded view of the components of the example cartomizer of  FIG.  2   . 
         FIGS.  4 A and  4 B  show perspective views of an example wick and heater assembly being fitted into a cartomizer plug included in the cartomizer of  FIG.  2   . 
         FIGS.  5 A and  5 B  show perspective views of an inner frame and vent seal being fitted to the cartomizer plug of  FIGS.  4 A and  4 B . 
         FIG.  6 A  shows a perspective view of the  FIGS.  4 A to  5 B  components being fitted into a shell of the cartomizer of  FIG.  2    to form a reservoir. 
         FIG.  6 B  shows a perspective view of the reservoir formed in  FIG.  6 A  being filled with source liquid. 
         FIG.  7    shows an exploded view of components of a further example cartomizer in which embodiments may be implemented. 
         FIG.  8    shows a partial cross-sectional side view of an example aerosol source for a cartomizer. 
         FIG.  8 A  shows a schematic side view of an example wick. 
         FIGS.  9 ,  10  and  11    show schematic side views of further example wicks. 
         FIG.  12    shows a partial cross-sectional side view of a further example aerosol source. 
         FIG.  13    shows a partial transverse cross-sectional view of a yet further example aerosol source. 
         FIG.  14    shows a schematic side view of an example wick and heater assembly. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    shows a cross-sectional view through an e-cigarette  100  in accordance with some embodiments of the disclosure. The e-cigarette comprises two main components or sections, namely a cartomizer  200  and a control unit  300 . As discussed in more detail below, the cartomizer  200  includes a chamber  270  defining a reservoir of source liquid, a heater (not shown in  FIG.  1   ) to generate vapor from the source liquid, and a mouthpiece. The liquid in the reservoir  270  (sometimes referred to as source liquid or e-liquid) typically includes nicotine in an appropriate solvent, and may include further constituents, for example, to aid aerosol formation, and/or for additional flavoring. The cartomizer  200  further includes a wicking element (wick)  500 , which provides a wicking, capillary or similar facility to transport a small amount of liquid from the reservoir  270  to a heating location on or adjacent the heater. The heater and the wick  500  may be collectively designated as an atomizer or vaporizer. The atomizer or vaporizer and the reservoir  270  may collectively be designated as an aerosol source. Therefore, the cartomizer  200  is the section of the e-cigarette  100  which, in this example, houses the atomizer and the aerosol source. 
     The control unit  300  includes a re-chargeable cell or battery  350  to provide power to the e-cigarette  100 , a printed circuit board (PCB) for generally controlling the e-cigarette (not shown in  FIG.  1   ), and a pressure sensor or airflow sensor  345  for detecting a user inhalation (via a pressure drop). When the heater receives power from the battery  350 , as controlled by the PCB in response to the sensor  345  detecting a user puff on the e-cigarette  100 , the heater vaporizes the liquid from the wick  500  and this vapor is then inhaled by a user through the mouthpiece. 
     For ease of reference, the x and y axes are marked in  FIG.  1   . The x axis will be referred to herein as the width of the device (from side to side), while the y axis will be referred to herein as the height axis, where the cartomizer  200  represents the upper portion of the e-cigarette  100  and the control unit  300  represents the lower portion of the e-cigarette  100 . Note that this orientation reflects how a user holds the e-cigarette  100  during normal operation of the device, given that the wick  500  is located in the lower part of the reservoir  270  in the cartomizer  200 . Therefore holding the e-cigarette  100  in this orientation brings the wick  500  into contact with liquid at the bottom of the reservoir  270 . Other devices may have a wick oriented or positioned differently. 
     A z axis (not shown in  FIG.  1   ) is also assumed, which is perpendicular to the x and y axes shown in  FIG.  1   . The z axis will be referred to herein as the depth axis. In this example the depth of e-cigarette  100  is significantly less than the width of the e-cigarette  100 , thereby resulting in a generally flat or planar configuration (in the x-y plane). Accordingly, the z axis can be considered as extending from face to face of the e-cigarette  100 , where one face may be regarded (arbitrarily) as the front face of the e-cigarette and the opposing face as the back face of the e-cigarette  100 . 
     The cartomizer  200  and the control unit  300  are detachable from one another by separating in a direction parallel to the y-axis, but are joined together when the device  100  is in use so as to provide mechanical and electrical connectivity between the cartomizer  200  and the control unit  300 . When the e-liquid in the reservoir  270  has been depleted, the cartomizer  200  can be removed and a new cartomizer attached to the control unit  300 . Accordingly, the cartomizer  200  may sometimes be referred to as a disposable portion of the e-cigarette  100 , while the control unit  300  represents a re-usable portion. In other examples, the cartomizer  200  may be configured such that the reservoir  270 , when empty, can be refilled with liquid, so that the cartomizer can also be re-usable. 
       FIG.  2    is a perspective external view of the cartomizer  200  of the e-cigarette of  FIG.  1    in accordance with some embodiments of the disclosure. This external view confirms that the depth of the cartomizer  200  (and the e-cigarette  100  as a whole), as measured parallel to the z axis, is significantly less than the width of the cartomizer  200  (and the e-cigarette  100  as a whole), as measured parallel to the x axis. 
     The cartomizer  200  comprises two main portions (at least from an external viewpoint). In particular, there is a lower or base portion  210  and an upper portion  220 . The upper portion  220  provides a mouthpiece  250  for the e-cigarette. When the cartomizer  200  is assembled with the control unit  300 , the base portion  210  of the cartomizer sits within the control unit  300 , and hence is not externally visible, whereas the upper portion  220  of the cartomizer protrudes above the control unit  300 , and hence is externally visible. Accordingly, the depth and width of the base portion  210  are smaller than the depth and width of the upper portion  220 , to allow the base portion  210  to fit within the control unit  300 . The increase in depth and width of the upper portion  220  compared with the base portion  210  is provided by a lip or rim  240 . When the cartomizer  200  is inserted into the control unit  300 , this lip or rim  240  abuts against the top of the control unit  300 . 
     As shown in  FIG.  2   , the side wall of base portion  210  includes a notch or indentation  260  for receiving a corresponding latching member from the control unit  300 . The opposite side wall of the base portion  210  is provided with a similar notch or indentation to likewise receive a corresponding latching member from the control unit  300 . It will be appreciated that this pair of notches  260  on the base portion  200  (and the corresponding latching members of the control unit) provide a latch or snap fit connection for securely retaining the cartomizer  200  within the control unit  300  during operation of the device. 
     As also shown in  FIG.  2   , the bottom wall  211  of the base portion  210  includes two larger holes  212 A,  212 B on either side of a smaller hole  214  for air inlet into the cartomizer during user inhalation. The larger holes  212 A and  212 B are used to provide positive and negative electrical connections from the control unit  300  to the cartomizer  200 , in particular to the heater and the PCB. When a user inhales through the mouthpiece  250  and the device  100  is activated, air flows into the cartomizer  200  through the air inlet hole  214 . This incoming air flows past the heater (not visible in  FIG.  2   ), which receives electrical power from the battery in the control unit  300  so as to vaporize liquid delivered to the heater from the reservoir by the wick. This vaporized liquid is then incorporated or entrained into the airflow through the cartomizer, and hence is drawn out of the cartomizer  200  through mouthpiece  250  for inhalation by the user. 
       FIG.  3    is an exploded view of the cartomizer  200  of the e-cigarette of  FIG.  1    in accordance with some embodiments. The cartomizer includes a shell  410 , a vent seal  420 , an inner frame  430 , a heating coil  450  located on a wick  500 , a primary seal  460  (also referred to as the cartomizer plug), a printed circuit board (PCB)  470  and an end cap  480 . The view of  FIG.  3    shows the above components exploded along the longitudinal (height or y) axis of the cartomizer  200 . 
     The cap  480  is formed from substantially rigid plastic such as polypropylene and provides the base portion  210  of the cartomizer. The cap  480  is provided with two holes  260 ,  261  on each side. The lower hole  260  is for latching the cartomizer  200  to the control unit  300 . The upper hole  261  is for latching the end cap  480  to the shell  410  to complete assembly of the cartomizer  410  and retain the various components shown in  FIG.  3    in the correct position in the assembled cartomizer  410 . 
     Above the end cap is located the PCB  470 , which includes a central air hole  471  to allow air to flow through the PCB into the atomizer (the end cap  480  is likewise provided with a central air hole, shown in  FIG.  2    as feature  214 ). In accordance with some embodiments, the PCB does not contain any active electrical components, but rather provides a circuit or conductive path between the control unit  300  and the heater  450 . 
     Above the PCB  470  is located the primary seal  460 , which has two main portions, an upper portion which defines (in part) an atomizer chamber  465 , and a lower portion  462  which acts as an end seal for the reservoir  270 . Note that in the assembled cartomizer  200 , the reservoir of e-liquid is located around the outside of the atomizer chamber, and the e-liquid is prevented from leaving the cartomizer (at least in part) by the lower portion  462  of the cartomizer plug  460 . The cartomizer plug  460  is made from a material that is slightly deformable, to allow the lower portion  462  to be compressed a little when inserted into the shell  410 , and hence provide a good seal to retain the e-liquid in reservoir  270 . 
     Two opposing side walls of the atomizer chamber  465  are provided with respective slots  569  into which the wick  500  is inserted. This configuration locates the heater  450 , which is positioned on the wick  500 , near the bottom of the atomizer chamber to vaporize liquid introduced into the atomizer chamber  465  by the wick  500 . In some embodiments, the wick  500  is made of glass fiber rope (i.e. filaments or strands of glass fiber twisted together), and the heater coil  450  is made of nichrome (an alloy of nickel and chromium). However, various other formats of wick and heater are known and could be used in the cartomizer  200 ; these are discussed further below. The heater coil  450  has a wire lead dropping down from the wick at each end, by which the heater  450  is able to be electrically connected to the battery. The wick  500  has a flared shape, in that its end portions which reach into the reservoir  270  have an enlarged cross-section compared to its central portion around which the heater coil  450  is wrapped. The shape of the wick  500  is discussed further below. 
     The cartomizer plug  460  and the wick/heater assembly are surmounted by the inner frame  430 , which has three main sections. The inner frame  430  is substantially rigid, and may be made of a material such as polybutylene terephthalate. The lowermost section  436  of the inner frame  430  engages with the lower portion  462  of the cartomizer plug  460 , while the middle section  434  completes the atomizer chamber  465  of the cartomizer plug  460 . In particular, the inner frame  430  provides a top wall of the atomizer chamber, and also two side walls that overlap with the two side walls of the atomizing chamber  465  provided by the cartomizer plug  460 . The final section of the inner frame  430  is an airflow tube  432  that extends upwardly from the top wall of the atomizing chamber (part of the middle section  434 ) to connect with an outlet hole in the mouthpiece  250 . The tube  432  provides a passage for vapor produced in the atomizing chamber  465  to be drawn out of the e-cigarette  100  by inhalation through the mouthpiece  250 . 
     The vent seal  420  is inserted around the top of the airflow tube  432  to provide a seal between the inner frame and the outlet hole in the mouthpiece  250 . The vent seal  420  is made of a suitably deformable and resilient material such as silicone. Lastly, the shell  410  provides the external surface of the upper portion  220  of the cartomizer  200 , including the mouthpiece  250 , and also the lip or flange  240 , and also an outer wall for the reservoir  270  surrounding the atomizer chamber  465 . The shell  410  is formed of a substantially rigid material, such as polypropylene. The lower section  412  of the shell  410 , below the lip  240 , sits inside the end cap  480  when the cartomizer  200  has been assembled. The shell  410  is provided with a latch tab  413  on each side to engage with the hole  261  on each side of the end cap  480 , thereby retaining the cartomizer  200  in its assembled condition. 
     The airflow passage through the assembled cartomizer enters a central hole in the cap  480  (not visible in  FIG.  3   ) and then passes through the hole  471  in the PCB. The airflow next passes up into the atomizer chamber  465 , which is formed as part of the cartomizer plug  460 , flows around, over and past the assembly of the wick  500  and the heater  450 , and through the tube  432  of the inner frame  430  (and through vent seal  420 ), and finally exits through the hole (not shown) in the mouthpiece  250 . 
     The reservoir  270  of e-liquid is contained in the space between this airflow passage and the outer surface of the cartomizer  200 . Thus the shell  410  provides the outer walls (and top) of the reservoir  270 , while the lower section  436  of the inner frame in conjunction with the base portion  462  of the primary seal  460  and end cap  480  provide the bottom or floor of the reservoir  270 . The inner walls of the reservoir are provided by the atomizing chamber  465  of the primary seal  460 , in cooperation with the middle section  434  of the inner frame, and also the airflow tube  432  of the inner frame  430  and the vent seal  420 . In other words, the e-liquid is stored in the reservoir space between the outer walls and the inner walls. The wick  500  passes through apertures in the inner walls so that liquid from the reservoir  270  can penetrate inside the inner walls by way of absorption and wicking within the wick  500  to the heater  450 . Other liquid penetration into the air flow passage should be minimized to inhibit liquid from leaking out of the hole in the mouthpiece  250 . 
     The capacity of the space forming the reservoir  270  is typically of the order of 2 ml in accordance with some embodiments, although it will be appreciated that this capacity will vary according to the particular features of any given design. Note that unlike for some e-cigarettes, the e-liquid reservoir  270  is not provided with any absorbent material (such as cotton, sponge, foam, etc.) for holding the e-liquid. Rather, the reservoir chamber contains the liquid alone so that the liquid can move freely within the reservoir  270 . Such a configuration may be referred to as a “free liquid” reservoir, and has advantages including generally supporting a larger capacity, and also making the filling procedure less complex. 
       FIGS.  4 A and  4 B  illustrate the wick/heater assembly being fitted into the cartomizer plug in accordance with some embodiments of the disclosure. The wick/heater assembly is formed from the heater wire  450  and the wick  500 . In this example, the wick  500  comprises glass fibers formed into a generally elongate shape. The heater  450  comprises a coil of wire  551  wound around a central portion of the wick  500 . At each end of the coil  551  there is a contact wire  552 A,  552 B, which together act as the positive and negative terminals to allow the coil  551  to receive electrical power. 
     As visible in  FIG.  4 A , the primary seal  460  includes the base portion  462  and the atomizing chamber  465 . The atomizing chamber  465  comprises four walls in a rectangular arrangement, a pair of opposing side walls  568 , and a pair of opposing front and back walls  567 . Each of the opposing side walls  568  includes a slot  569  which has an open end at the top (and in the centre) of the side wall, and a closed end  564  relatively near the bottom of the atomizing chamber  465 . The two slots  569  extend more than halfway down their respective side walls  568 . 
     Referring now to  FIG.  4 B , this shows the wick/heater assembly fitted into the atomizing chamber  465  of the cartomizer plug. In particular, the wick/heater assembly is positioned so that the wick  500  extends between, and protrudes out of, the two opposing slots  569 A,  569 B, with the heater coil (not shown in  FIG.  4 B ) located between the slots  569 A,  569 B so that it is inside the atomizer chamber  465 . The wick  500  is lowered until it reaches the closed end  564  of each slot. In this position, the coil  551  is then located entirely in the atomizing chamber  465  and only the wick  500  that extends out of the slots reaches into the reservoir area  270 . It will be appreciated that this arrangement allows the wick  500  to draw liquid from the reservoir  270  into the atomizing chamber  465  for vaporization by the wire heater coil  551 . Having the wick  500  located near the bottom of the atomizing chamber  465 , and more particularly also near the bottom of the reservoir  270 , helps to ensure that the wick retains access to liquid in the reservoir even when the level of liquid drops as the liquid is consumed.  FIG.  4 B  also shows how the heater contact wires  552 A,  552 B extend below the primary seal  460 . 
       FIGS.  5 A and  5 B  illustrate the inner frame and the vent seal being fitted into the cartomizer plug in accordance with some embodiments of the disclosure. Thus, as previously described, the inner frame  430  comprises a base section  436 , a middle section  434  and an air tube  432  located at the top of the inner frame. The base section contains two slots  671 A,  671 B extending in a horizontal sideways direction (parallel to the x axis). As the base section  436  of the inner frame is lowered down past the atomizing chamber  465 , the portions of the wick  500  that extend out from each side of the atomizing chamber  465  pass through these slots  671 A,  671 B, thereby allowing the base section of the inner frame to be lowered further until it is received in the lower portion  462  of the cartomizer plug. 
     As noted above, the middle section  434  of the inner frame complements and completes the atomizing chamber  465  of the cartomizer plug  460 . In particular, the middle section provides two opposing side walls  668  and a top wall or roof  660 . The latter closes the top of the atomizing chamber  465 , except in respect of the air tube  432  which extends up from the atomizing chamber  465  to the outlet hole of the mouthpiece  250 . 
     Each of the opposing side walls  668  includes a slot  669 A,  669 B which extends upwards (parallel to the y axis) from the bottom of the side wall to the closed end of the respective slot. Accordingly, as the base section  436  of the inner frame is lowered down past the atomizing chamber  465 , the portions of the wick  500  that extend out from each side of the atomizing chamber  465  pass through these slots  669 A,  669 B (in addition to slots  671 A,  671 B). This therefore allows the side walls  668  of the inner frame  430  to overlap the side walls  568  of the cartomizer plug. Further downward movement of the inner frame  430  is prevented once the closed end of slots  669 A,  669 B contacts the wick  500 , which coincides with the base section  436  of the inner frame being received into the lower portion  462  of the cartomizer plug. At this stage, the combination of cartomizer plug  460 , heater/wick assembly, and inner frame  430 , has been formed as shown in  FIG.  5 B , and the vent seal  420  can now be fitted onto the air tube (pipe)  432  of the inner frame  430 . 
       FIG.  6 A  illustrates the combination of the inner frame  430 , wick/heater assembly, and primary seal  460  being fitted into the shell  410 . The various walls that define the reservoir  270  are thereby brought into conjunction to create the reservoir, so the cartomizer  200  is now ready for filling with source liquid. 
       FIG.  6 B  shows the cartomizer  200  assembled up to this point. Filling with liquid is performed, as indicated by arrows  701 A,  701 B, through holes  582 A and  582 B in the primary seal  460  and through slots  671 A,  671 B in the inner frame  430 . To complete the cartomizer  200  as it is depicted in  FIG.  2   , the PCB  470  is installed in a rectangular indentation  584  in the underside of the primary seal  460 , and the end cap  480  is fitted over the end of the cartomizer plug  460  and the lower section  412  of the shell  410 . In this fully assembled state (see  FIG.  2   ), the end cap  480  covers and therefore closes the holes  582 A,  582 B in the cartomizer plug that were used for filling the liquid reservoir  270 . Accordingly, the reservoir  270  is now fully sealed, apart from the opening on each side of the atomizing chamber  465  through which the wick  500  passes into the atomizing chamber  465 . 
     An electronic cigarette may be configured otherwise than in the example described thus far while including a flared wick.  FIG.  7    shows an exploded view of components of a cartomizer according to a further example. Many of the components are similar to those of the  FIGS.  1 - 6    example, but differently shaped so that the cartomizer has a more elongate and less flat shape. The cartomizer is composed of a base part  1  that forms the lower face of the cartomizer. A bottom plug  2  closes the lower end of a reservoir, which is otherwise comprised by a wall portion  3  in the form of an annular outer wall that engages into the plug  2  and a top plug or seal  4  which engages into the top end of the wall portion  3 . A flared wick  500  has a heater coil  450  wrapped around it, and is located within the volume defined by the wall portion  3 . A tubular air channel  5  sits inside the wall portion  3  so that it surrounds the wick  500  and heater  450 , partitioning these parts from the reservoir and forming an atomizing chamber. The tubular channel  5  comprises an oppositely disposed pair of slots  5 A extending upwardly from its lower edge, and the end portions of the wick  500  are receiving in these slots so as to reach into the reservoir for the purpose of collecting liquid from the reservoir. A vent seal  6  is pushed into an opening  4 A in the top plug  4 ; this is aligned with the tubular channel  5 A. A hollow shell  7  forms the exterior of the cartomizer  200 , and receives the other components within itself to align the air channel formed by the tubular channel  5  and the vent seal  6  with an air outlet  7 A in a mouthpiece  7 B of the shell  7 . The base part closes the lower end of the shell  7 . A lower portion  7 C of the shell  7  is recessed compared to the mouthpiece  7 B, to be received inside an upper part of a control unit, similar to the connected arrangement of the  FIGS.  1 - 6    example. 
     Embodiments of the disclosure are not limited to these example devices, and may be implemented in vapor provision systems configured in other ways. 
     It will be appreciated from these examples that the reservoir of an electronic cigarette can comprise a relatively small volume, formed by closely spaced walls. The wick necessarily protrudes into this volume to be able to absorb the liquid contained in the reservoir, but there may be very little space available to accommodate it. Accordingly, when the reservoir is filled, air bubbles may be trapped around the wick, such as between the ends of the wick and the outer wall of the reservoir. Surface tension of the liquid may also inhibit flow of the liquid around the wick, both during filling and during subsequent use. Proper filling of the reservoir may thus be prevented, giving a reduced effective reservoir capacity. Also, absorption of liquid by the wick may be inhibited if liquid does not fully surround the wick ends owing to air bubbles and surface tension effects. 
     To address this, it is proposed to provide a shaped wick which flares out at the portion or portions that extend into the reservoir. This increased width or cross-section improves absorption of liquid by the wick so that liquid transfer from the reservoir to the heater is enhanced, and consistent vapor production can be maintained. 
     The wick or wicking element can comprise any suitable porous material, having a pore structure that provides a wicking capability to transport liquid absorbed by one part of the material (a part inside a reservoir of liquid) to another part (adjacent a heating element) by a capillary action. Example materials include fiber-based structures such as bundles, strands, threads, ribbons or ropes formed from woven, non-woven, spun, plaited or twisted fibers of cotton, wool, glass or artificial fibers, or solid/rigid non-fiber-based materials with integral interstitial pores, such as porous ceramics. The manner in which the flared shape is provided will be appropriate to the material used for the wick. 
     A porous ceramic or other solid material may be fabricated directly into the required flared shape, for example by molding or machining. A density of the wick material may be substantially the same at the flared end parts as in the part adjacent the heating element. Alternatively, the size and/or distribution of the pores may differ at the end part compared to the heating portion, for example with a larger pore size and/or a higher density of pores at the end part or parts, and smaller pore size and/or lower density of pores in the part adjacent the heating element. In other words, the porosity varies across the wick, with a higher porosity in the flared part or parts intended to be immersed in the reservoir and a lower porosity in the vicinity of the heating element. The larger volume of porous material, and optionally the larger pore size/ higher pore quantity/higher porosity, of the flared portion(s) will all aid in improving the ability of the wick material to absorb liquid from the reservoir. 
     For a fibrous wick, the cross-section at the reservoir ends may be enlarged compared to the heating part by fraying or unraveling fibers which are woven, spun, twisted and/or bundled together, and spreading or splaying the resulting separated fibers or strands of fibers away from each other. Individual fibers may be separated from each other, or individual plies comprising two or more fibers may be separated from each other, or a combination of the two, depending on the configuration of the fibers. Any such arrangement which increases the fiber-to-fiber spacing of at least some of the adjacent fibers in the enlarged part of the wick might be employed. This has the effect of reducing the density of the wick material in the flared sections, since the fibers have a larger separation and are less tightly packed together compared to the heater portion. A similar effect may be achieved by using a relatively loosely spun, woven or twisted length of fibers, or a loosely packed bundle of fibers, and compressing or squashing one part to form a heater section. The remaining uncompressed part or parts will be splayed out compared to the compressed part and hence have a larger cross-section. The compression or confinement of the heater portion of the wick may be maintained by tying or wrapping further fibers around the wick fiber or fiber bundle; these securing fibers may be the same as or different from the wick material. Alternatively, the heating element may be used to compress the fibers if it has the form of a wire coil; the wire may be tightly wrapped around a fiber or fiber bundle to squeeze the fibers together at the same time as forming a coil. 
       FIG.  8    shows a schematic side view of a simple example flared wick generally in accordance with embodiments of the disclosure, shown inside a partial cross-sectional view of a section of a cartomizer. The wick  500  has a central portion H disposed inside an atomizing chamber  465 , extending across the chamber perpendicularly to the direction of airflow through the chamber (indicated by the arrow A). A heater  450  in the form of a wire coil is wrapped around the central portion H. Accordingly this part of the wick  500  may be considered as a heater portion, a heated portion or a heating element portion, or alternatively an atomizing portion. The atomizing chamber  465  is bounded by an annular wall  270   b  (shown in cross-section), on the far side (outside) of which lies a reservoir  270  of source liquid. An outer annular wall  270   a  forms the outside of the reservoir  270 , and possibly also the exterior wall of the cartomizer. The reservoir is hence also annular and surrounds the atomizing chamber  465 . The reservoir  270  contains only source liquid, so that the liquid is free-flowing within the reservoir. 
     The inner annular wall  270   b  has two oppositely arranged apertures  270   c  in it, aligned perpendicularly to the airflow A, and the wick  250  has end portions E 1 , E 2  which are continuous with the heater portion H, but extend through the apertures  270   c  to reach into the interior of the reservoir  270  for the purpose of absorbing liquid held in the reservoir  270 . The end portions E 1 , E 2  may therefore be considered as liquid-collecting portions, liquid absorbing portions, or reservoir portions. The wick has an axis L indicated by a dotted line which is designated as a longitudinal axis, although this does not imply that the extent of the wick along the direction of the axis L is necessarily its largest dimension. In this example, the longitudinal axis is arranged orthogonally to the direction of airflow A. Also, the longitudinal axis is straight, and the heater portion H and the end portions E 1 , E 2  are arranged contiguously along the axis L so that the wick has an overall straight linear configuration, and might be considered as elongate. The longitudinal axis may be curved or bent in other configurations, however. 
     Each of the end portions E 1 , E 2  has a flared (or, conversely, tapered) shape, in that a cross-section through the wick in a plane perpendicular to the longitudinal axis L is larger along at least one dimension at an end portion E 1 , E 2  than at the heater portion H. This may be thought of as the wick having a length (along the L direction), and a width at its end portions which is larger than a width at its heater portion, where the width is orthogonal to the length. Similarly or alternatively, a perimeter (which may be a circumference if the wick has a generally circular cross-section or rod-like format) of the end portions is larger than a perimeter of the heater portion. The heater portion, being the part inside the atomizing chamber, on a first side of the wall separating the atomizing chamber from the reservoir, may have a constant or average width, diameter, perimeter, circumference or cross-sectional area over its length, and each end portion, being the part in the reservoir, on a second side of the separating wall, may have a greatest width, diameter, perimeter, circumference or cross-sectional area which is larger than the corresponding constant or average parameter for the heater portion. The flared shaped may also be described as the wick having a width, perimeter or cross-sectional area which increases from a first value at a heater portion of the wick, or at a position where the wick aligns with the aperture in the separating wall, to a second value at an end, liquid-collecting, portion of the wick, where the second value is larger than the first value. The increase may be in a single dimension only orthogonal to the axis L (such as thickness only or height only), or may be in two dimensions orthogonal to the axis L and to each other (thickness and height). Both the thickness and the height may conveniently be designated as a width, being a dimension orthogonal (transverse) to the longitudinal axis of the relevant portion of the wick, namely a local longitudinal axis. In wicks with a circular cross section, the width is a diameter. An increase over two dimensions may or may not be such as to maintain the same cross-sectional shape (but not size) from the heater portion to the end portions. Note that the greatest (widest) part of the end portion(s) of the wick may or may not be at its physical extremity, depending on the external shape adopted for the end part. 
     The various measures of width, diameter, thickness, height, perimeter, circumference and cross-sectional area are all of interest, and a constant (linear) or varying (non-linear) increase in any of these measures over at least part of the longitudinal extent of a wick end portion can be implemented to provide a flared shape. The measures are all features of the cross-section of the wick at the location of interest, so may collectively be designated as cross-sectional parameters, cross-sectional measures, cross-sectional values, or cross-sectional numerical values. Within this set of parameters, the width measures (thickness, height, diameter) are linear measures, so may be considered as cross-sectional dimensions, since “dimension” typically denotes a linear extent. 
       FIG.  8 A  shows a schematic side view of an example wick to illustrate the flared configuration. A central heater portion H has a longitudinal extent L 1  along the axis L, a width W 1  perpendicular to the axis L and a perimeter P 1  in a plane perpendicular to the axis L. On each side of the central portion, the width (and hence also the perimeter) increases to form end portions E 1  and E 2  which terminate to a maximum width W 2  greater than W 1  and a maximum perimeter P 1  greater than P 2 . A first end portion E 1  has a length L 2  along the axis L, and the second end portion E 2  has a length L 2  along the axis L. The boundary or junction between the central portion H and each end portion E 1 , E 2  is indicated as “a”, and marks the point where the wick is intended to pass through an aperture in a wall of a reservoir (correspondingly, a wall of the atomizing chamber housing the heater). This junction or boundary may be considered as a “neck” of the end portion, beyond which the wick flares outwards. The junctions “a” will align with the reservoir wall, and indicate the location where the heater portion of the wick transitions into an end portion. The two widths W 1  and W 2  are separated in the longitudinal dimension L along the length of the generally elongate wick, where L is orthogonal to the width dimension. The increase in dimension to form the flare may be linear so that the sides of the wick in the end portions are straight, and angled outwards with respect to the central portion, as in the  FIG.  8    example. In the  FIG.  8 A  example, the increasing width is nonlinear so that the width increases more rapidly towards the ends of the wick, giving curved sides to the wick  500  so that each end has a “trumpet” shape. A combination of linear and nonlinear increases may be used to give a desired profile for the wick  500 . The increase in width/perimeter/cross-section of the end portion compared to the central portion may commence at the location of the boundary “a”, or at any location after the point “a”, towards the physical end of the wick, remote from the heater portion and within the end portion, or before the point “a”, away from the physical end of the wick and within the heater portion. 
     Note that in the  FIGS.  8  and  8 A  examples, the largest width/perimeter (W 2  or P 2 ) for the end portions is at their extremity, but this need not be the case. 
     Regular shapes such as in  FIGS.  8  and  8 A  may be obtained for a solid wick material such a porous ceramic. Wicks formed from fibers or fiber bundles may have a less regular, more ragged shape, within a flared outline, but the overall impression will be the same, with a clearly increased width and perimeter for the end portions compared to the heater portion. 
     The greater dimension for the end portions may be larger or smaller compared to the central portion as required. Any flaring of the end sections can have a positive effect on wicking, with greater flaring producing a more noticeable effect. So, width (or depth or thickness) W 2  is greater than W 1  such that W 2 /W 1  has any value greater than 1. For example, W 2 /W 1  may be at least 1.25, or at least 1.5, or least 2, or at least 3, or at least 4 or at least 5. In terms of circumference or perimeter (in other words, the measurement around the wick at the position of the width of interest), P 2  is greater than P 1  such that P 2 /P 1  has any value greater than 1. For example, P 2 /P 1  may be at least 1.25, or at least 1.5, or at least 2, or at least 3, or at least 4, or at least 5. In terms of cross-sectional area orthogonal to the longitudinal axis, the maximum area A 2  of the end portion is greater than the area Al of the heater portion such that A 2 /A 1  has any value greater than 1. For example, A 2 /A 1  may be at least 1.25, or at least 1.5, or least 2, or at least 3, or at least 4 or at least 5. 
     In many examples, the heater portion will be of a generally constant thickness or width, so that the width W 1 , the perimeter P 1  and the cross-sectional area A 1  are the same in the middle of the wick (and at other intermediate locations) as at the neck location where the end portion begins. However, this need not be the case, and the heater portion may have a variable cross-section. In this case, a value for W 1  or P 1  or A 1  for comparison with the equivalent parameter W 2  or P 2  or A 2  for the end portion can be taken from the width or the perimeter or the cross-sectional area at the neck. 
       FIG.  9    shows a perspective view of an example wick with a generally circular cross-section, and in which the increased parameter or parameters to form the flared ends E 1 , E 2  is in two dimensions, so that the circular cross-section is preserved from the central portion H to the end portions E 1 , E 2 . The increase is non-linear so that the wick as a curved profile. The overall shape of the wick may be considered as a “dumb-bell” shape 
       FIG.  10    shows a perspective view of an example wick in which the increase to form the flared shape is in one dimension only. The central portion H has a square cross-section. In the end portions E 1 , E 2 , the width in the thickness direction (as illustrated, into the plane of the page) stays the same as for the central portion H, but the width in the height direction (as illustrated, vertically in the plane of the page) increases linearly over the longitudinal extent of the end portions. The overall shape of the wick may be considered as a “bow-tie” shape. 
     As a further example, a wick with a central square portion as in  FIG.  10    may have a two-dimension increased width as in  FIG.  9   , to preserve the square cross-section within the end portions. Also, a flat-sided heater portion may expand into curved or rounded end portions, or a curved or rounded heater portion may expand into flat end portions. There is no requirement to preserve any shape or geometrical features from the heater portion to the end portions, merely that there is at least one transverse dimensional increase to achieve the flared shape. 
       FIG.  11    shows a perspective view of an example wick formed from a bundle of fibers. In the central portion H, the fibers are spun or twisted together. In the end portions E 1 , E 2 , the fibers are separated from each other and spaced apart. Hence the width of the end portions is larger than the width of the central portion. Such a configuration can be achieved by taking a length of bundled fibers previously twisted, spun, intertwined, woven or plaited together, and unraveling the fibers at each end of the length to splay them into a flared shaped. Alternatively, individual fibers may be taken, and twisted, spun, intertwined, woven or plaited together in a central region to form a narrower bundle for the heater portion of the wick. Alternatively, as mentioned above, the central narrower bundle might be formed by binding, tying or wrapping a central region of the bundle to compress and confine the fibers in that region, using additional fibers of a same or a different type, or by using the coils of a heating element. 
     The examples thus far have comprised wicks with a central heater portion and two end portions, in a linear alignment with the heater portion in the centre between the end portions. Such an arrangement is convenient for an annular reservoir surrounding an atomizing chamber, where it is desired for the wick to reach across the chamber and into the reservoir on two opposite sides. However, the present embodiments are not limited in this regard, and the wick may comprise any number of flared end portions intended for immersion in a reservoir and contiguous with a heater portion intended for location in an atomizing chamber. 
       FIG.  12    shows a simplified partial cross-section of an example wick with one flared end. The wick comprises a heater portion H linearly arranged continuously with a single end portion E 1 . The heater portion H is provided with a heating element  450  in the form of a wire coil wrapped around the wick; these parts are disposed in an atomizing chamber  465 . A wall  270   b  divides the atomizing chamber  465  from a reservoir  270 , and the wick is arranged to extend through an aperture  270   c  in the wall so that the flared end portion E is situated inside the reservoir. 
       FIG.  13    shows a simplified view of an example wick with four flared ends, shown in transverse cross-section through an aerosol source (i.e. perpendicular to the airflow direction, which will be into the plane of the page). It is known to configure an atomizer to comprise a pair of wicks, each with a heating element, and arrange them in a cross shape with respect to air flow through an atomizing chamber surrounded by an annular reservoir, so that both ends of each wick reach into the reservoir. The present disclosure invention may be applied to such an arrangement, either by flaring the ends of two separate two-ended wicks, or by providing a single cross-shaped wick in which each of the four arms terminate in a flared end portion.  FIG.  13    shows an example of this configuration. The wick  500  has a central portion H in the form of a cross, which is surrounded by a heating element  450  which may comprise one, two or more wire coils, for example. This portion is located in an atomizing chamber which is divided from an annular reservoir  270  by an inner annular wall  270   b.  An outer annular wall  270   a  forms the exterior of the reservoir  270 . The inner wall  270   b  has four apertures  270   c,  aligned with the four arms of the wick  500  so that the arms extend through the apertures  270   c  into the reservoir, wherein one or more transverse dimensions of the arms are increased to form flared end portions E 1 -E 4  for liquid absorption. The wick might be considered to have a “Maltese cross” shape. 
     For wick configurations having more than one flared end portion, each end portion may or may not be the same size and shape. End portions of the same size and shape provide a symmetric wick, whereas differing end portions (by size and/or shape and/or amount of flare) provide an asymmetric wick which may be preferred in some cases, depending on the configuration and arrangement of the atomizing chamber and the reservoir. For end portions or arms with differing amounts of flare, each arm will have a width or perimeter or cross sectional area which is greater than that of the heater portion, but may differ from that of the other arm or arms. 
     The examples already presented have each assumed an atomizer configuration (the combination of a wick and a heater) in which a heating element is provided externally to a wick, for example the heater is a coil wrapped around a (central) heater portion of the wick. The disclosure is not limited in this regard, however. As an alternative, the heating element may be embedded within the porous material of the wick, at the location of the heater portion intended to be arranged within an atomizing chamber. 
       FIG.  14    shows a simplified side view of an example wick with an embedded heater. The wick  500  has a central heater portion H and two flared ends E 1 , E 2 . Note that the ends terminate in a rounded shape, and are hence an example in which the maximum width/area/perimeter of the flared ends is located inwardly from the physical extremity of the wick. A heater  450  in the form of a wire is disposed within the wick material of the heater portion H, and has follows a serpentine path in this region, with two external leads  552 A and  552 B extending from the serpentine section to the exterior of the wick  500  for electrical connection of the heater  450 . The heater may have any shape within the wick material, and may be formed from wire or from a conductive layer, for example. Similarly, external heating elements may take any shape and are not limited to coils. 
     Note that while the Figures depict various examples of flared wicks in simple outline which may suggest a solid wick material such as porous ceramic, any of the various shapes and configurations, plus others within the scope of the disclosure which will be apparent to the skilled person, can be configured in a fiber-based format or a sold material format. 
     Further, while the end portion(s) of the wick and the heater portions are adjacent to one another, they need not be arranged along a straight line. In other words, the longitudinal axis (L in  FIGS.  8  and  8 A ) need not be a straight line. There may be one more bends in the axis, for example, a two-ended wick may have a U-shape, in which the end portions form an angle of around 90 degrees to the heater portion. Nevertheless, the end portions will still have a width greater than a width of the heater portion, measured orthogonally with respect to the local longitudinal axis regardless of any bends, turns or angles in the axis as a whole. Also, one may define the flared, increased width of the end portion or portions of the wick as the end portion having a maximum width, perimeter or cross-sectional area that is larger than a width, perimeter or cross-sectional area of the wick at the point (the neck of the end portion) where it is intended to pass through an aperture in the wall of the atomizing chamber to reach into the reservoir. 
     In conclusion, 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. The disclosure may include other inventions not presently claimed, but which may be claimed in future.