Patent Publication Number: US-2023157364-A1

Title: Method of manufacturing an aerosol provision apparatus and an aerosol provision apparatus

Description:
PRIORITY CLAIM 
     The present application is a Continuation of U.S. application Ser. No. 16/334,579, filed Mar. 19, 2019, which is a National Phase entry of PCT Application No. PCT/EP2017/073363, filed Sep. 15, 2017, which claims priority from U.S. Provisional Application No. 62/396,999, filed Sep. 20, 2016, which is hereby fully incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a method of manufacturing an aerosol provision apparatus and to an aerosol provision apparatus. 
     BACKGROUND 
     Articles such as cigarettes, cigars and the like burn tobacco during use to create tobacco smoke. Attempts have been made to provide alternatives to these articles, which burn tobacco, by creating products that release compounds without burning. Examples of such products are so-called heat-not-burn products, also known as tobacco heating products or tobacco heating devices, which release compounds by heating, but not burning, the material. The material may be for example tobacco or other non-tobacco products or a combination, such as a blended mix, which may or may not contain nicotine. 
     SUMMARY 
     According to a first aspect of the present disclosure, there is provided a method of manufacturing an aerosol provision apparatus for heating smokable material to volatilize at least one component of the smokable material, the method comprising: providing a heater arrangement for heating smokable material contained in use within the apparatus, the heater arrangement comprising at least a first heating zone and a second heating zone for heating different portions of the smokable material; providing a temperature sensor for each of the first and second heating zones, each temperature sensor for providing temperature measurements to be used as input temperature measurements for a temperature control loop, the control loop for controlling the heater arrangement to heat its associated respective heating zone to a target temperature based on the input temperature measurements acquired by the associated temperature sensor; and positioning each temperature sensor in its associated heating zone at a respective position selected so that if the heating arrangement were to heat the first and second heating zones so that the temperature sensors measure the same pre-selected target temperature, a temperature gradient across the length of the heating zones between the temperature sensors would be optimized as being substantially flat. 
     According to a second aspect of the present disclosure, there is provided an aerosol provision apparatus for heating smokable material to volatilize at least one component of the smokable material, the apparatus comprising: a heater arrangement for heating smokable material contained in use within the apparatus, the heater arrangement comprising at least a first heating zone and a second heating zone for heating different portions of the smokable material; and a temperature sensor for each of the first and second heating zones, each temperature sensor for providing temperature measurements to be used as input temperature measurements for a temperature control loop, the control loop for controlling the heater arrangement to heat its associated respective heating zone to a target temperature based on the input temperature measurements acquired by the associated temperature sensor; wherein each temperature sensor is positioned in its associated heating zone at a selected position so that, if the heating arrangement were to heat the first and second heating zones so that the temperature sensors measure the same pre-selected target temperature, a temperature gradient across the length of the heating zones between the temperature sensors would be optimized as being substantially flat. 
     According to a third aspect of the present disclosure, there is provided a method of manufacturing an aerosol provision apparatus for heating smokable material to volatilize at least one component of the smokable material, the method comprising: providing a heater arrangement for heating smokable material contained in use within the apparatus, the heater arrangement comprising at least a first heating zone and a second heating zone for heating different portions of the smokable material; providing a temperature sensor for each of the first and second heating zones, each temperature sensor for providing temperature measurements to be used as input temperature measurements for a temperature control loop, the control loop for controlling the heater arrangement to heat its associated respective heating zone to a target temperature based on the input temperature measurements acquired by the associated temperature sensor; and positioning each temperature sensor in its associated heating zone at a respective position selected so that the temperature sensor for the first heating zone is halfway between a first end of the heater arrangement and a centre of the heater arrangement or is closer to the first end of the heater arrangement than it is to the centre of the heating arrangement, and the temperature sensor for the second heating zone is halfway between a second end of the heater arrangement and a centre of the heater arrangement or is closer to the second end of the heater arrangement than it is to the centre of the heating arrangement. 
     According to a fourth aspect of the present disclosure, there is provided an aerosol provision apparatus for heating smokable material to volatilize at least one component of the smokable material, the apparatus comprising: a heater arrangement for heating smokable material contained in use within the apparatus, the heater arrangement comprising at least a first heating zone and a second heating zone for heating different portions of the smokable material; a temperature sensor for each of the first and second heating zones, each temperature sensor for providing temperature measurements to be used as input temperature measurements for a temperature control loop, the control loop for controlling the heater arrangement to heat its associated respective heating zone to a target temperature based on the input temperature measurements acquired by the associated temperature sensor, and wherein each temperature sensor is positioned in its associated heating zone at a respective position selected so that the temperature sensor for the first heating zone is halfway between a first end of the heater arrangement and a centre of the heater arrangement or is closer to the first end of the heater arrangement than it is to the centre of the heating arrangement, and the temperature sensor for the second heating zone is halfway between a second end of the heater arrangement and a centre of the heater arrangement or is closer to the second end of the heater arrangement than it is to the centre of the heating arrangement. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which: 
         FIG.  1    shows a perspective view of an example of an aerosol provision apparatus for heating a smokable material. 
         FIG.  2    shows a lateral cross-sectional view of the apparatus of  FIG.  1    with a consumable article inserted. 
         FIG.  3    shows a lateral cross-sectional view of the apparatus of  FIG.  1    without a consumable article inserted. 
         FIG.  4    shows a perspective side view of the apparatus of  FIG.  1    with some external panels absent to show interior components of the apparatus. 
         FIG.  5   a    shows a side view of an internal component of the apparatus of  FIG.  1   . 
         FIG.  5   b    shows a first perspective view of the internal component of the apparatus of  FIG.  1   . 
         FIG.  5   c    shows a second perspective view of the internal component of the apparatus of  FIG.  1   . 
         FIG.  5   d    shows an end view of the internal component of the apparatus of  FIG.  1   . 
         FIG.  6    shows an end view of an alternative internal component of the apparatus of  FIG.  1   . 
         FIG.  7    shows a plan view of a front panel of the aerosol provision apparatus for heating a smokable material. 
         FIG.  8    shows a side view of a front panel of the apparatus of  FIG.  7   . 
         FIG.  9    shows a perspective view of a front panel of the apparatus of  FIG.  7   . 
         FIG.  10    shows a plan view of a front panel of the apparatus of  FIG.  7    with a consumable article inserted. 
         FIG.  11    shows a schematic plan view of a heater arrangement for use in the aerosol provision apparatus for heating a smokable material. 
         FIG.  12    shows a perspective view of an example arrangement of the heater arrangement of  FIG.  11    with a consumable article inserted. 
         FIG.  13    is a graph showing a first gradient of temperature within the aerosol provision apparatus for heating a smokable material as a function of a spatial dimension of the aerosol provision apparatus. 
         FIG.  14    shows a graph showing the time evolution of a pair of target and corresponding measured temperatures within the heating arrangement of  FIG.  12   . 
     
    
    
     DETAILED DESCRIPTION 
     As used herein, the term “smokable material” includes materials that provide volatilized components upon heating, typically in the form of an aerosol. “Smokable material” includes any tobacco-containing material and may, for example, include one or more of tobacco, tobacco derivatives, expanded tobacco, reconstituted tobacco or tobacco substitutes. “Smokable material” also may include other, non-tobacco, products, which, depending on the product, may or may not contain nicotine. “Smokable material” may for example be in the form of a solid, a liquid, a gel or a wax or the like. “Smokable material” may for example also be a combination or a blend of materials. 
     Apparatus is known that heats smokable material to volatilize at least one component of the smokable material, typically to form an aerosol which can be inhaled, without burning or combusting the smokable material. Such apparatus is sometimes described as a “heat-not-burn” apparatus or a “tobacco heating product” or “tobacco heating device” or similar. Similarly, there are also so-called e-cigarette devices, which typically vaporize a smokable material in the form of a liquid, which may or may not contain nicotine. The smokable material may be in the form of or provided as part of a rod, cartridge or cassette or the like which can be inserted into the apparatus. A heater for heating and volatilizing the smokable material may be provided as a “permanent” part of the apparatus or may be provided as part of the smoking article or consumable which is discarded and replaced after use. A “smoking article” in this context is a device or article or other component that includes or contains in use the smokable material, which in use is heated to volatilize the smokable material, and optionally other components. 
     Referring initially to  FIGS.  1  to  4   , there is shown an example of an apparatus  1  arranged to heat smokable material to volatilize at least one component of said smokable material, typically to form an aerosol which can be inhaled. The apparatus  1  is a heating apparatus  1  which releases compounds by heating, but not burning, the smokable material. The apparatus  1  is an aerosol provision device that is an inhalation device (i.e. a user uses it to inhale an aerosol provided by the device). The apparatus  1  is hand-held. 
     A first end  3  is sometimes referred to herein as the mouth or proximal end  3  of the device  1  and a second end  5  is sometimes referred to herein as the distal end  5  of the device  1 . The apparatus  1  has an on/off button  7  to allow the apparatus  1  as a whole to be switched on and off as desired by a user. 
     The apparatus  1  comprises a housing  9  for locating and protecting various internal components of the apparatus  1 . In the example shown, the housing  9  comprises a uni-body sleeve  11  that encompasses the perimeter of the apparatus  1 , capped with a top panel  17  which defines generally the ‘top’ of the apparatus  1  and a bottom panel  19  which defines generally the ‘bottom’ of the apparatus  1 . In another example the housing comprises a front panel, a rear panel and a pair of opposite side panels in addition to the top panel  17  and the bottom panel  19 . 
     The top panel  17  and/or the bottom panel  19  may be removably fixed to the uni-body sleeve  11 , to permit easy access to the interior of the apparatus  1 , or may be “permanently” fixed to the uni-body sleeve  11 , for example to deter a user from accessing the interior of the apparatus  1 . In an example, the panels  17  and  19  are made of a plastics material, including for example glass-filled nylon formed by injection molding, and the uni-body sleeve  11  is made of aluminum, though other materials and other manufacturing processes may be used. 
     The top panel  17  of the apparatus  1  has an opening  20  at the mouth end  3  of the apparatus  1  through which, in use, a consumable article  21  containing smokable material may be inserted into the apparatus  1  and removed from the apparatus  1  by a user. 
     The housing  9  has located or fixed therein a heater arrangement  23 , control circuitry  25  and a power source  27 . In this example, the heater arrangement  23 , the control circuitry  25  and the power source  27  are laterally adjacent (that is, adjacent when viewed from an end), with the control circuitry  25  being located generally between the heater arrangement  23  and the power source  27 , though other locations are possible. 
     The control circuitry  25  may include a controller, such as a microprocessor arrangement, configured and arranged to control the heating of the smokable material in the consumable article  21  as discussed further below. 
     The power source  27  may be for example a battery, which may be a rechargeable battery or a non-rechargeable battery. Examples of suitable batteries include for example a lithium-ion battery, a nickel battery (such as a nickel-cadmium battery), an alkaline battery and/or the like. The battery  27  is electrically coupled to the heater arrangement  23  to supply electrical power when required and under control of the control circuitry  25  to heat the smokable material in the consumable (as discussed, to volatilize the smokable material without causing the smokable material to burn). 
     An advantage of locating the power source  27  laterally adjacent to the heater arrangement  23  is that a physically large power source  27  may be used without causing the apparatus  1  as a whole to be unduly lengthy. As will be understood, in general a physically large power source  27  has a higher capacity (that is, the total electrical energy that can be supplied, often measured in Amp-hours or the like) and thus the battery life for the apparatus  1  can be longer. 
     In one example, the heater arrangement  23  is generally in the form of a hollow cylindrical tube, having a hollow interior heating chamber  29  into which the consumable article  21  comprising the smokable material is inserted for heating in use. Different arrangements for the heater arrangement  23  are possible. For example, the heater arrangement  23  may comprise a single heating element or may be formed of plural heating elements aligned along the longitudinal axis of the heater arrangement  23 . The or each heating element may be annular or tubular, or at least part-annular or part-tubular around its circumference. In an example, the or each heating element may be a thin film heater. In another example, the or each heating element may be made of a ceramics material. Examples of suitable ceramics materials include alumina and aluminum nitride and silicon nitride ceramics, which may be laminated and sintered. Other heating arrangements are possible, including for example inductive heating, infrared heater elements, which heat by emitting infrared radiation, or resistive heating elements formed by for example a resistive electrical winding. 
     In one particular example, the heater arrangement  23  is formed of a polyimide substrate on which is formed one or more heating elements and which is supported by a stainless steel support tube. The heater arrangement  23  is dimensioned so that substantially the whole of the smokable material, when the consumable article  21  is inserted in the apparatus  1 , is located within the heating element(s) of the heater arrangement  23  so that substantially the whole of the smokable material is heated in use. 
     The or each heating element may be arranged so that selected zones of the smokable material can be independently heated, for example in turn (over time) or together (simultaneously) as desired. 
     The heater arrangement  23  in this example is surrounded along at least part of its length by a thermal insulator  31 . The insulator  31  helps to reduce heat passing from the heater arrangement  23  to the exterior of the apparatus  1 . This helps to keep down the power requirements for the heater arrangement  23  as it reduces heat losses generally. The insulator  31  also helps to keep the exterior of the apparatus  1  cool during operation of the heater arrangement  23 . In one example, the insulator  31  may be a double-walled sleeve which provides a low pressure region between the two walls of the sleeve. That is, the insulator  31  may be for example a “vacuum” tube, i.e. a tube that has been at least partially evacuated so as to minimize heat transfer by conduction and/or convection. Other arrangements for the insulator  31  are possible, including using heat insulating materials, including for example a suitable foam-type material, in addition to or instead of a double-walled sleeve. 
     The housing  9  may further comprises various internal support structures  37  (best seen in  FIG.  4   ) for supporting all internal components, as well as the heating arrangement  23 . 
     The apparatus  1  further comprises a collar  33  which extends around and projects from the opening  20  into the interior of the housing  9  and a generally tubular chamber  35  which is located between the collar  33  and one end of the vacuum sleeve  31 . 
     One end of the chamber  35  connects to and is supported by the collar  33  and the other end of the chamber  35  connects to the one end of the vacuum sleeve  31  and hence supports the vacuum sleeve  31 . Accordingly, as best seen in  FIG.  3   , the collar  33 , the chamber  35  and the vacuum tube  31 /heater arrangement  23  are arranged co-axially, so that, as best seen in  FIG.  2   , when the consumable  21  is inserted in the apparatus  1 , it extends through the collar  33  and the chamber  35  into the heater chamber  29 . 
     As mentioned above, in this example, the heater arrangement  23  is generally in the form of a hollow cylindrical tube and this tube is in fluid communication with the opening  20  at the mouth end  3  of the device  1  via the chamber  35  and the collar  33 . 
     Referring now to  FIGS.  5   a  to  5   d   , in this example, the chamber  35  comprises a tubular body  35   a  that has a first open end  35   b  and a second open end  35   c . The tubular body  35   a  comprises a first section  35   d  that extends from the first open end  35   b  to approximately half away along the tubular body  35   a  and a second section  35   e  that extends from approximately half away along the tubular body  35   a  to the second open end  35   c . The first section  35   d  has a substantially constant internal diameter and the second section  35   e  has an internal diameter that tapers towards the second open end  35   c.    
     The chamber  35  further comprises a cooling structure  35   f , which in this example, comprises a plurality of cooling fins  35   f  spaced apart along the body  35   a , each of which is arranged circumferentially around the body  35   a.    
     The chamber  35  also comprises a flange portion  35   g  around the second open end  35   c  and a plurality of projections or clips  35   h  also arranged around the second open end  35   c . Each clip  35   h  is generally I′ shaped and comprises a first portion  35   h   1  that is joined to the flange portion  35   g  and a second portion  35   h   2  that is generally perpendicular to first portion  35   h   1  and which extends in a direction generally parallel to the longitudinal axis of the tubular body  35   a . Each second portion  35   h   2  comprises a stepped surface  35   i  that faces towards an axis that extends along the longitudinal axis of the tubular body  35   a  and which stepped surface  35   i  is slightly curved. 
     As best seen in  FIG.  3   , in this example, the chamber  35  is located in the housing  9  between the collar  33  and the vacuum tube  31 /heater  23 . More specifically, (i) at the second end  35   c , the flange  35   g  butts an end portion of a polyimide tube of the heater arrangement  23  with the clips  35   h  resiliently engaging with the polyimide tube via their stepped surfaces  35   i  and the outer surfaces of the clips mating with an inside of the vacuum sleeve  31  ( ii ) at the first open end  35   b , the chamber  35  connects to the collar  33  by means of ridges  60 , which form part of the collar  33  and project into the chamber  35 . The ridges  60  are angled from a first end  62  of the collar  33  to a second end  63  of the collar towards an axis that extends along the longitudinal axis of the collar  33  and chamber  35 . The ridges lie flush with the internal surface of the chamber  35  to form a snug fit. 
     As is best appreciated from  FIG.  2   , the inner diameter of the first section  35   d  of the hollow chamber  35  is larger than the external diameter of the consumable article  2 . There is therefore an air gap  36  between the hollow chamber  35  and the consumable article  21  when it is inserted in the apparatus over at least part of the length of the hollow chamber  35 . The air gap  36  is around all of the circumference of the consumable article  21  in that region. 
     As best seen in  FIG.  5   c    and  FIG.  5   d   , at the second open end  35   c , the chamber  35  comprises a plurality (in this example 3) of small lobes or ridges  35   j  arranged circumferentially around an inner surface of the chamber  35  at the periphery of second open end  35   c . Each of the lobes  35   j  extends a small distance in a direction parallel to the longitudinal axis of the chamber  35  and also extends a small amount radially at the second open end  35   c . Together, the lobes  35   j  provide a gripping section that grips the consumable article  21  in order to correctly position and retain the portion of the consumable article  21  that is within the chamber  35  when the consumable article  21  is within the apparatus  1 . Between them, the lobes  35   j  gently compress or pinch the consumable article  21  in the region or regions of the consumable article that are contacted by the lobes  35   j . The lobes  35   j  may be comprised of a resilient material (or be resilient is some other way) so that they deform slightly (for example compress) to better grip the consumable article  21  when it is inserted in the apparatus  1  but then regain their original shape when the consumable article  21  is removed from the apparatus  1 . The lobes  35   j  may be formed integrally with the chamber  35  or may be separate components that are attached within the chamber  35 . The inner diameter around the lobes, may be, for example, 5.377 mm. 
     In an alternative example shown in  FIG.  6   , a resilient gripping section  35   k  within the hollow chamber  35  defines a substantially oval aperture  351  which, may extend along the longitudinal axis of the hollow chamber  35 , and which when the consumable article  21  is inserted in the apparatus  1 , gently compresses or pinches the section of the consumable article  21  that is in the oval aperture  351  so that this section of the consumable article  21  is deformed from being circular to being oval in cross section. In one example, the gripping section  35   k  is located towards the first open end  35   b . In one example, the width of the oval section could be increased or decreased to increase or decrease the insertion/retention force. In a further example, small grooves (not shown) could be added in the surface of the oval aperture  351  that would interfere with the consumable article  21  rather than the entire surface area of the oval aperture  351 . This would minimize insertion/removal sensitivity to the transitions of the various consumable article components (tobacco, tipping paper, paper tube) passing through the gripping section  35   k.    
     In a further example a combination of the lobes  35   j  and the oval gripping section  35   k  could be used to retain the consumable article  21  in the hollow chamber  35 . For example, an oval gripping section  35   k  and the arrangement of lobes  35   j  could be spaced apart longitudinally in the hollow chamber  35  and act separately to retain an inserted consumable article  21  in place, or, the lobes  35   j  could be arranged around the surface of the oval gripping section  35   k.    
     The chamber  35  may be formed of for example a plastics material, including for example polyether ether ketone (PEEK). 
     Referring again to  FIGS.  2  to  4   , in an example, the heating chamber  29  has a region  38  of reduced internal diameter towards the distal end  5 . This region  38  provides an end stop for the consumable article  21  passed through the opening at the mouth end  3 . This region  38  of reduced internal diameter, may for example be provided by a hollow tube of the type described in detail in our co-pending U.S. Provisional Patent Application No. 62/185,227, filed on Jun. 26, 2015, the entire content of which is incorporated herein by reference. 
     The apparatus  1  may further comprise a door  39  at the distal end  5  that opens and closes an opening in the rear panel to provide access to the heating chamber  29  so that the heating chamber can be cleaned. Examples of suitable doors are also discussed in more detail in our co-pending U.S. Provisional Patent Application No. 62/185,227. 
     Referring now to  FIGS.  7  to  10    in particular, there is shown an example of the top panel  17  of the apparatus  1 . The top panel  17  generally forms the front end  3  of the housing  9  of the apparatus. The top panel  17  supports the collar  33  which defines an insertion point in the form of the opening  20  through which the consumable article  21  is removably inserted into the apparatus  1  in use. 
     The collar  33  extends around and projects from the opening  20  into the interior of the housing  9 . In one example, the collar  33  is integral with the top panel  17  of the housing so the collar  33  and the top panel  17  form a single piece. In an alternative example, the collar  33  is a distinct element from the top panel  17 , but can be attached to the top panel  17  through an attachment, such as a locking mechanism, adhesive, or screws. Other attachments that are suitable for attaching the collar  33  to the top panel  17  may be used. 
     In this example, the collar  33  comprises a plurality of ridges  60  arranged circumferentially around the periphery of the opening  20  and which project into the opening  20 . The ridges  60  take up space within the opening  20  such that the open span of the opening  20  at the locations of the ridges  60  is less than the open span of the opening  20  at the locations without the ridges  60 . The ridges  60  are configured to engage with a consumable article  21  inserted into the apparatus to assist in securing it within the apparatus  1 . 
     In one example, the ridges  60  are circumferentially equally spaced around the periphery of the opening  20 . In one example, there are four ridges  60 , in other examples there may be more or fewer than four ridges  60 . 
       FIG.  9    shows a plan view of the top panel  17  of the apparatus with a consumable article  21  inserted into the opening  20 . The ridges  60  project into the opening  20  to engage with the consumable article  21 . The open spaces  61  defined by adjacent pairs of ridges  60  and the consumable article  21  form ventilation paths  61  around the exterior of the consumable article  21 . These ventilation paths  61 , as will be explained in more detail below, allow hot vapors that have escaped from the consumable article  21  to exit the apparatus  1  and allow cooling air to flow into the apparatus  1  around the consumable  21 . The example in  FIG.  10    shows four ventilation paths  61  located around the periphery of the consumable article  21 , which provide ventilation for the apparatus  1  although there may be more or less such ventilation paths  61 . 
     As mentioned above, the ridges  60  project radially into the opening  20  but, as best appreciated from  FIG.  8   , they also extend from the top panel  17  into the housing  9 . The projection of the ridges  60  are angled towards each other, such that as the ridges  60  extend into the housing, the distance between the ridges  60  decreases. As best seen in  FIG.  3   , the projection of the ridges  60  into the housing enables the collar  33  to connect to the chamber  35  by means of the ridges  60  extending through the first open end  35   b  of the chamber  35  and engaging an inner wall of the chamber  35 . 
     Referring again particularly to  FIG.  2   , in one example, the consumable article  21  is in the form of a cylindrical rod which has or contains smokable material  21   a  at a rear end in a section of the consumable article  21  that is within the heating arrangement  23  when the consumable article  21  is inserted in the apparatus  1 . A front end of the consumable article  21  extends from the apparatus  1  and acts as a mouthpiece assembly  21   b  which includes one or more of a filter for filtering aerosol and/or a cooling element  21   c  for cooling aerosol. The filter/cooling element  21   c  is spaced from the smokable material  21   a  by a space  21   d  and is also spaced from the tip of mouthpiece assembly  21   b  by a further space  21   e . The consumable article  21  is circumferentially wrapped in an outer layer (not shown). In one example, the outer layer of the consumable article  21  is permeable to allow some heated volatilized components from the smokable material to escape the consumable article  21 . 
     In operation, the heater arrangement  23  will heat the consumable article  21  to volatilize at least one component of the smokable material  21   a.    
     The primary flow path for the heated volatilized components from the smokable material  21   a  is axially through the consumable article  21 , through the space  21   d , the filter/cooling element  21   c  and the further space  21   e  before entering a user&#39;s mouth through the open end of the mouthpiece assembly  21   b . However, some of the volatilized components may escape from the consumable article  21  through its permeable outer wrapper and into the space  36  surrounding the consumable article  21  in the chamber  35 . 
     It would be undesirable for the volatilized components that flow from the consumable article  21  into the chamber  35  to be inhaled by the user, because these components would not pass through the filter/cooling element  21   c  and thus be unfiltered and not cooled. 
     Advantageously, the volume of air surrounding the consumable article  21  in the chamber  35  and the fin-cooled interior wall of the chamber  35  causes at least some of the volatilized components that escape the consumable article  21  through its outer layer to cool and condense on the interior wall of the chamber  35  preventing those volatilized components from being possibly inhaled by a user. 
     This cooling effect may be assisted by cool air that is able to enter from outside the apparatus  1  into the space  36  surrounding the consumable article  21  in the chamber  35  via the ventilation paths  61 , which allows fluid to flow into and out of the apparatus. A ventilation path  61  will be defined between a pair of the plurality of neighboring ridges  60  to provide ventilation around the outside of the consumable article  21  at the insertion point. 
     In one example, a second ventilation path  61  is provided between a second pair of neighboring ridges for at least one heated volatilized components to flow from the consumable article  21  at a second location. Therefore ventilation is provided around the outside of the consumable article  21  at the insertion point by the first and second ventilation paths  61 . 
     Furthermore, heated volatilized components that escape the consumable article  21  through its outer wrapper do not condense on the internal wall of the chamber  35  and are able to flow safely out of the apparatus  1  via the ventilation paths  61  without being inhaled by a user. 
     The chamber  35  and the ventilation both aid in reducing the temperature and the content of water vapor composition released in heated volatilized components from the smokable material. 
     Referring now to  FIG.  11   , there is shown a first schematic plan view of an example of a heater arrangement  23  for use in an apparatus for heating smokable material.  FIG.  11    illustrates schematically different heating zones and sub-heating zones of this example of the heater arrangement  23 . The heater arrangement  23  shown in  FIG.  11    may be used in, for example, a device  1  of the type described above. 
     The heater arrangement  23  has a plurality of heating zones for heating different portions of the smokable material to volatilize at least one component of the smokable material inserted into the device  1 . In the specific example shown, the heater arrangement  23  has a first heating zone  220  and a second heating zone  230 . In other examples the heater arrangement  23  may have only one heater zone or more than two heating zones. At least one of the heating zones may be formed so as to provide plural sub-heating zones within the zone for heating different portions of the smokable material. In other words, at least one of the first and second heating zones  220  and  230  may comprise at least a first sub-heating zone and a second sub-heating zone. 
     In the example of  FIG.  11   , the heater arrangement  23  is arranged so that the first and second heating zones  220  and  230  are arranged either side of a center of the heater arrangement (T). Furthermore, in this example, the first heating zone  220  of the heater arrangement  23  has a first sub-heating zone  222 , a second sub-heating zone  224  and a third sub-heating zone  226  and the second heating zone  230  has a first sub-heating zone  232 , a second sub-heating zone  234  and a third sub-heating zone  236 . 
     The first sub-heating zone  222  of the first heating zone  220  is located towards a first end of the heater arrangement  23 , which first end is located towards the mouthpiece end of the device  1 . The first sub-heating zone  232  of the second heating zone  230  is located towards a second end of the heater arrangement  23 , which second end is located towards the distal end of the device  1 . On the other hand, the second sub-heating zones  224  and  234  of the first and second heating zones  220  and  230  respectively are located towards the centre of the heater arrangement with respect to the first sub-heating zones  222  and  232 . In this example, the third sub-heating zones  226  and  236  of the first and second heating zones  220  and  230  respectively are located closest to the centre of the heater arrangement  23 . 
     In this example, the first sub-heating zone  222 , the second sub-heating zone  224  and the third sub-heating zone  226  of the first heating zone  220  all provide different heating watt densities, with the first sub-heating zone  222  providing a higher watt density than does the second sub-heating zone  224  which provides a higher watt density than does the third sub-heating zone  226 . Similarly, in this example, the first sub-heating zone  232 , the second sub-heating zone  234  and the third sub-heating zone  236  of the second heating zone  230  all provide different heating watt densities, with the first sub-heating zone  232  providing a higher watt density than does the second sub-heating zone  234  which provides a higher watt density than does the third sub-heating zone  236 . This arrangement provides for a higher heat flux at the ends of the heater arrangement  23  where heat can most easily escape, in order that a more even temperature, in other words a flatter temperature gradient, may be maintained within the zones  220  and  230 . 
     In other examples, there may be some sub-heating zones that have the same watt density and other sub-heating zones that have different watt densities. 
     In use, the different watt densities of the sub-heating zones of the heater arrangement  23  provide a simple way of ensuring that different heat fluxes act on different portions of the smokable material. The heater arrangement  23  can therefore, in some examples, heat different portions of the smokable material in the device  1  to different temperatures. In a specific example, a mouth end portion of the smokable material is heated with a lower heat flux than other portions of the smokable material. The lower heat flux can result in more water vapor condensing from the aerosol prior to inhalation by the user. This can reduce the temperature of the aerosol and also reduce the likelihood of the phenomenon known as “hot puff”. 
     The different watt densities of the various sub-heating zones  222 ,  224 ,  226 ,  232 ,  234 ,  236  of the heater arrangement  23  may be achieved in different ways. For example, the various sub-heating zones  222 ,  224 ,  226 ,  232 ,  234 ,  236  may have heating elements having different properties, such as being formed of different materials and/or having different electrical resistances and/or different dimensions (including for example different thicknesses or, more generally, different cross-sectional areas). As another example, the various sub-heating zones  222 ,  224 ,  226 ,  232 ,  234 ,  236  may have different heat capacities. 
     The heating zones  220 ,  230  of the heater arrangement  23  may have different dimensions (lengths, widths, depths) from one another. In the specific example of FIG.  11 , the six sub-heating zones  222 ,  224 ,  226 ,  232 ,  234 ,  236  of the heater arrangement  23  are of the same width A. However the lengths of the sub-heating zones  222 ,  224 ,  226 ,  232 ,  234 ,  236  are not all the same. In this example, the length U, Z of the first sub-heating zone  222  of the first heating zone  220  and the first sub-heating zone  232  of the second heating zone  230  may be the same or substantially similar. However, in this example, the lengths U, Z of the first sub-heating zone  222  of the first heating zone  220  and the first sub-heating zone  232  of the second heating zone  230  are different from the lengths V, W, X, Y of the other sub-heating zones  224 ,  226 ,  234 ,  236 . 
     In some specific examples, the length U may have a range of 5 mm to 6 mm, the length V may have a range of 9 mm to 10 mm, the length W may have a range of 6 mm to 7 mm, the length X may have a range of 6 mm to 7 mm, the length Y may have a range of 9 mm to 10 mm, and the length Z may have a range of 5 mm to 6 mm. The total length of the first heating zone  220  is equal to the sum of the lengths U, V and W, and the total length of the second heating zone  230  is equal to the sum of the lengths X, Y and Z. 
     As described above, heater arrangement  23  is generally in the form of a hollow cylindrical tube, having a hollow interior heating chamber  29  into which the consumable article  21  comprising the smokable material is inserted for heating in use.  FIG.  12    illustrates the heater arrangement  23  in the form of a hollow cylindrical tube comprising heating zones  220  and  230 , and sub-heating zones  222 ,  224 ,  226 ,  232 ,  234  and  236  (not shown in  FIG.  12   ). 
     In the example of  FIG.  12   , there is provided a first temperature sensor  320 , and a second temperature sensor  330  for each of the first  220  and second  330  heating zones respectively. In some example, the temperature sensors  320  and  330  may be resistance temperature detectors (RTD). However, in other examples, the temperature sensors  320  and  330  may be other types of temperature sensors, for example, the sensors  320  and  330  may be thermocouples. 
     Each of the temperature sensors  320 ,  330 , in this example, provides temperature measurements to be used as input temperature measurements for a temperature control loop. In this example, there is a control loop associated with each of the heating zones  220  and  230 . Therefore, in this example, there is a first control loop associated with the first heating zone  220  and is provided input temperature measurements by the first temperature sensor  320 , and a second control loop associated with the second heating zone  230  and is provided input temperature measurements by the second temperature sensor  330 . Each control loop is for controlling the heater arrangement  23  to heat its associated respective heating zone  220 ,  230  to a target temperature based on the input temperature measurements acquired by the associated temperature sensor  320 ,  330 . In other words, the first control loop controls the heater arrangement  23  to heat the first heating zone  220  to a first target temperature based on input temperature measurements provided by the first sensor  320 , and the second control loop controls the heater arrangement  230  to heat the second heating zone  230  to a second target temperature based on input temperature measurements provided by the second sensor  330 . In this example, the first and second control loops are implemented by the controller included in the control circuitry  25 . 
     The first and second control loops, in some examples, may be proportional integral derivative (PID) control loops. However, in other examples, any control loop suitable for the smokable material heating device  1  may be used. For example, a control loop based on the rate of change of temperature with time when its respective heating zone is generating heat may be used. In some examples, the first and second control loops may control the heater arrangement  23  to heat the first and second heating zones  220  and  230  by turning the respective first and second heating zones  220  and  230  on or off. The heating zones  220  and  230  may therefore be individually controlled. 
     It will be understood that the temperatures measured by the first and second temperatures sensors  320  and  330  provide an indication of the temperature within the associated first and second heating zones  220  and  230  respectively. When a sensor measures a given temperature, it can be assumed that at least a part of the heating zone with which that sensor is associated is at the temperature measured by that sensor. However, the temperature sensors  320  and  330  do not necessarily indicate the precise temperature at all points of the heating zones  220  and  230 . Since the first and second control loops control the heating zones  220  and  230  using input temperature measurements acquired by the sensors  320  and  330  respectively, the first and second control loops effectively control the temperature in the immediate surroundings of the sensors  320  and  330  respectively. Therefore, it will be understood that the precise position of the temperature sensors  320  and  330 , which provide input temperature measurements to their respective control loops to control the temperature of the heating zones  220  and  230 , affects the temperature gradient along the length of both the heating zones  220  and  230 . The precise position of the sensors  320  and  330  relative to their respective heating zones  220  and  230 , as well as their position relative to each other determines the overall temperature gradient over all the zones  220  and  230 . Factors such as the length of the zones  220  and  230 , the widths of the sub-heating zones  222 ,  224 ,  226 ,  232 ,  234  and  236 , and the properties and dimensions of the thermal insulator  31 , among other factors, may also contribute to the temperature gradient along the length of the zones  220  and  230 . 
     In this example, each temperature sensor  320 ,  330  is positioned in its associated respective heating zone at a selected position so that, if the heating arrangement  23  were to heat the first and second heating zones  220  and  230  so that the temperature sensors  320  and  330  measure the same pre-selected target temperature, a temperature gradient across the length of the heating zones between the temperature sensors, and therefore across the length of the chamber  29 , would be optimized as being substantially flat. In other words, the temperature sensors  320  and  330  are positioned such that if the first and second control loops were to control the heater arrangement  23  to heat the heating zones  220  and  230  to first and second target temperatures set equal to each other, the temperature between the sensors  320  and  330  would be substantially constant as a function of the length of the heating zones. 
     It will be understood that when the temperature sensors  320  and  330  measure the same pre-selected target temperature, it can be assumed that the heating zones  220  and  320  are also at that same pre-selected target temperature. 
     The positions of the temperature sensors  320  and  330  for obtaining a substantially flat temperature gradient are selected having regard to the other factors affecting the temperature gradient along the length of the heating zones  220  and  230  mentioned above. 
     In one example, each temperature sensor  320 ,  330  is positioned in its associated respective heating zone at a respective position selected so that the first temperature sensor  320  for the first heating zone  220  is halfway between the first end of the heater arrangement  23  or is closer to the first end of the heater arrangement  23  than it is to the centre of the heater arrangement  23 , and the second temperature sensor  330  for the second heating zone  230  is halfway between the second end of the heater arrangement  23  and a centre of the heater arrangement  23  or is closer to the second end of the heater arrangement  23  than it is to the centre of the heating arrangement  23 . 
     In the example of  FIG.  13   , the temperature sensors  320  and  330  are positioned such that the temperature gradient between the sensors  320  and  330  is substantially flat. In this example, the end of the heater arrangement  23  towards the mouthpiece end of the device  1  is indicated by the dashed line  133 . The length of the heater arrangement  23  in this example is 42 mm. Dashed lines  131  and  132  indicate the positions of the temperature sensors  320  and  330  respectively. In this example, the sensor  320  is placed 10.4 mm from the mouth piece end of the heater arrangement  23 , and the sensor  330  is placed 31.6 mm from the mouthpiece end of the heater arrangement  23 . If in this example, the lengths U, V, W, X, Y and Z are within the specific ranges described above in relation to a specific example, the first temperature sensor  320  (associated with/for the first heating zone  220 ) is positioned in the second sub-heating zone  224  of the first heating zone  220 , and the second temperature sensor  234  (associated with/for the second heating zone  230 ) is positioned in the second sub-heating zone  234  of the second heating zone  230 . The dashed line  134  indicates the centre of a dead zone at 21 mm from the mouthpiece end of the heater arrangement  23 , the dead zone being a zone of the heating chamber  29  associated with gap between the sub-heating zone  226  if the first heating zone  220  and the sub-heating zone  236  of the second heating zone  230  indicated by the length T in  FIG.  11   . 
     In the example of  FIG.  13   , the temperature, at which the centre of the heater arrangement  23  (and the heating chamber  29 ) is desired to be, is 250° C. The first target temperature for zone  220  and the second target temperature for zone  230  are therefore both 250° C. The line  138   a  indicates the maximum acceptable temperature of 255° C., and the line  138   b  indicates the minimum acceptable temperature of 245° C. when the desired temperature is 250° C. Part  135  of the temperature gradient indicates the temperature decreasing towards the distal end of the heater arrangement  23 , and part  137  of the length temperature gradient indicates the temperature decreasing towards the mouthpiece end of the heater arrangement  23 . However, the temperature gradient, in this example, between the position  131  of the sensor  320  and the position  132  of the sensor  330  is substantially flat. 
     In examples of the device  1 , the controller may be configured to vary the first and second target temperatures for the zones  220  and  230  respectively, independently during a session of use of the device  1 . In one example, the controller is configured to control the first and second target temperatures for the zones  220  and  230  such that they are not set to the same temperature or they do not reach the same temperature at substantially any point during a session of use of the device  1 . However, it should be appreciated that selecting the positions of the first and second temperature sensors  320  and  330  such that if both the first and second target temperature are the same temperature the temperature gradient between the first sensor  320  and the second sensor  330  is substantially flat, provides the benefit of optimizing the heating of the tobacco within the heating chamber  29 . 
     More specifically, if the location of the first and second sensors  320  and  330  is selected as described above, excessive or inadequate heating of certain regions of the tobacco in the heating chamber  29  may be avoided during a session of use in which the controller does not set the first and second target temperatures to be the same temperature or they do not reach the same temperature. For example, if the first and second sensors  320  and  330  are placed too close together, irrespective of the first and second target temperatures set by the controller, when both the first and second target temperatures are non-zero, the temperature between the two sensors may become excessively high and the tobacco in the region of the heating chamber  29  between the two temperature sensors may be excessively heated. Conversely, if the first and second temperature sensors  320  and  330  are placed too far apart, the tobacco in the region of the heating chamber  29  in between the two temperature sensors may not be adequately heated and the tobacco in this region may be wasted. 
       FIG.  14    is an example of the variation of the first and second target temperatures, and the corresponding variation of the temperatures measured by the sensors  320  and  330  during some examples of a session of use of the device  1 . In  FIG.  14   , the first target temperature (the target temperature of zone  220 ) is indicated by Ta target , and the temperature measured by the sensor  320  associated with zone  220  is indicated by Ta m . On the other hand, the second target temperature (the target temperature of zone  230 ) is indicated by Tb target , and the temperature measured by the sensor  330  associated with zone  230  is indicated by Tb m .  FIG.  14    illustrates that the first control loop controls the heater arrangement  23  such that the measured temperatures Ta m  of the zone  220  increases towards Ta target , and once the first target temperature Ta target  is reached, the measured temperature Ta m  is maintained at the first target temperature Ta target . The second control loop similarly controls the heater arrangement  23  such that the measured temperatures Tb m  of the zone  230  increases towards Tb target , and once the second target temperature Tb target  is reached, the measured temperature Tb m  is maintained at the second target temperature Tb target . 
     The various embodiments described herein are presented only to assist in understanding and teaching the claimed features. These embodiments are provided as a representative sample of embodiments only, and are not exhaustive and/or exclusive. It is to be understood that advantages, embodiments, examples, functions, features, structures, and/or other aspects described herein are not to be considered limitations on the scope of the invention 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 claimed invention. Various embodiments of the invention may suitably comprise, consist of, or consist essentially of, appropriate combinations of the disclosed elements, components, features, parts, steps, means, etc., other than those specifically described herein. In addition, this disclosure may include other inventions not presently claimed, but which may be claimed in future.