Patent Publication Number: US-10314339-B2

Title: Electronic vapor provision system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a National Phase entry of PCT Application No. PCT/GB2015/052100, filed on 21 Jul. 2015, which claims priority to GB Patent Application No. 1412954.8, filed on 22 Jul. 2014, which are hereby fully incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to electronic vapor provision systems such as electronic nicotine delivery systems, including e-cigarettes. 
     BACKGROUND 
     Electronic vapor provision systems such as e-cigarettes generally contain a reservoir of liquid which is to be vaporized, for example, nicotine. When a user inhales on the device, a heater is activated to vaporize a small amount of liquid, which is then inhaled by the user through a mouthpiece. More particularly, such devices are usually provided with one or more air inlet holes located away from the mouthpiece. When a user sucks on the mouthpiece, air is drawn in through the inlet holes and past the vapor source, such as the heater supplied with nicotine or other liquid from a cartridge. 
     In some known devices, the user can exercise a certain degree of control over the air inflow into the device. Such control may be utilized, for example, to alter the draw resistance of the device. An electronic vapor provision system should provide a user with an airflow control mechanism that helps to achieve ease-of-use and reliability. 
     SUMMARY 
     The invention is defined in the appended claims. 
     Some embodiments of the disclosure provide an electronic vapor provision system that comprises a housing, a vaporizer contained within the housing, and a mouthpiece at one end of said system. The mouthpiece provides an air outlet. One or more air inlet holes are provided in a portion of the housing. In response to a user inhalation at the mouthpiece, air flows into the system through the one or more air inlet holes, past the vaporizer, and out through the mouthpiece. The system further includes a collar located around the portion of the housing in which the one or more air inlet holes are provided. The collar is movable with respect to the housing. The system further includes a mechanism for positively engaging the collar and the housing at a plurality of predetermined positions as the collar is moved with respect to the housing. Different ones of said plurality of predetermined positions result in different degrees of alignment between the one or more air inlet holes of the housing and the collar, thereby providing different levels of ventilation into the system. 
     Other embodiments provide an electronic vapor provision system having one or more air inlet holes for drawing air into the system in response to a user inhalation and a variable ventilation mechanism having a plurality of predetermined settings, wherein each setting corresponds to a different degree of occlusion of the one or more air inlet holes, and the variable ventilation mechanism can be latched into any of said plurality of predetermined settings. 
     Other embodiments provide a body portion and/or a vaporizer portion for an electronic vapor provision system according to one of the above embodiments. 
     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 electronic vapor provision system may be provided in accordance with the approach 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: 
         FIG. 1  is a schematic (exploded) diagram of an electronic vapor provision system such as an e-cigarette in accordance with some embodiments of the disclosure. 
         FIG. 2  is a schematic diagram of the body of the e-cigarette of  FIG. 1  in accordance with some embodiments of the disclosure. 
         FIG. 3  is a schematic diagram of the vaporizer portion of the e-cigarette of  FIG. 1  in accordance with some embodiments of the disclosure. 
         FIG. 4  is a schematic diagram showing certain aspects of one end of the body portion of the e-cigarette of  FIG. 1  in accordance with some embodiments of the disclosure. 
         FIG. 5  is a schematic diagram showing a collar or sleeve fitted around a part of the body of the e-cigarette of  FIG. 1  in accordance with some embodiments of the disclosure. 
         FIGS. 6A, 6B, 6C  are schematic diagrams showing three different positions of the collar of  FIG. 5  for providing three respective amounts of ventilation into the e-cigarette of  FIG. 1  in accordance with some embodiments of the disclosure. 
         FIG. 7  is a schematic diagram showing a collar or sleeve fitted around a part of the body of the e-cigarette of  FIG. 1  in accordance with some embodiments of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a schematic diagram of an electronic vapor provision system such as an e-cigarette  10  in accordance with some embodiments of the disclosure (not to scale). The e-cigarette  10  has a generally cylindrical shape, extending along a longitudinal axis indicated by dashed line LA, and comprises two main components, namely a body  20  and a cartomizer  30 . The cartomizer includes an internal chamber containing a reservoir of nicotine, a vaporizer (such as a heater), and a mouthpiece  35 . The reservoir may be a foam matrix or any other structure for retaining the nicotine until such time that it is required to be delivered to the vaporizer. The cartomizer  30  also includes a heater for vaporizing the nicotine and may further include a wick or similar facility to transport a small amount of nicotine from the reservoir to a heating location on or adjacent the heater. 
     The body  20  includes a re-chargeable cell or battery to provide power to the e-cigarette  10  and a circuit board for generally controlling the e-cigarette  10 . When the heater receives power from the battery, as controlled by the circuit board, the heater vaporizes the nicotine and this vapor is then inhaled by a user through the mouthpiece. 
     The body  20  and cartomizer  30  are detachable from one another by separating in a direction parallel to the longitudinal axis LA, as shown in  FIG. 1 , but are joined together when the device  10  is in use by a connection, indicated schematically in  FIG. 1  as  25 A and  25 B, to provide mechanical and electrical connectivity between the body  20  and the cartomizer  30 . The electrical connector on the body  20  that is used to connect to the cartomizer  30  also serves as a socket for connecting a charging device (not shown) when the body  20  is detached from the cartomizer  30 . The other end of the charging device can be plugged into a USB socket to re-charge the cell in the body  20  of the e-cigarette  10 . In other implementations, a cable may be provided for direct connection between the electrical connector on the body  20  and a USB socket. 
     The e-cigarette  10  is provided with one or more holes (not shown in  FIG. 1 ) for air inlet. These holes connect to an air passage through the e-cigarette  10  to the mouthpiece  35 . When a user inhales through the mouthpiece  35 , air is drawn into this air passage through the one or more air inlet holes, which are suitably located on the outside of the e-cigarette  10 . This airflow (or the resulting change in pressure) is detected by a pressure sensor that in turn activates the heater to vaporize the nicotine from the cartridge. The airflow passes through, and combines with, the nicotine vapor, and this combination of airflow and nicotine vapor then passes out of the mouthpiece  35  to be inhaled by a user. The cartomizer  30  may be detached from the body  20  and disposed of when the supply of nicotine is exhausted (and replaced with another cartomizer if so desired). 
     It will be appreciated that the e-cigarette  10  shown in  FIG. 1  is presented by way of example, and various other implementations can be adopted. For example, in some embodiments, the cartomizer  30  is provided as two separable components, namely a cartridge comprising the nicotine reservoir and mouthpiece (which can be replaced when the nicotine from the reservoir is exhausted), and a vaporizer comprising a heater (which is generally retained). As another example, the charging facility may connect to an additional or alternative power source, such as a car cigarette lighter. 
       FIG. 2  is a schematic (simplified) diagram of the body  20  of the e-cigarette  10  of  FIG. 1  in accordance with some embodiments of the disclosure.  FIG. 2  can generally be regarded as a cross-section in a plane through the longitudinal axis LA of the e-cigarette  10 . Note that various components and details of the body  20 , e.g. such as wiring and more complex shaping, have been omitted from  FIG. 2  for reasons of clarity. 
     As shown in  FIG. 2 , the body  20  includes a battery or cell  210  for powering the e-cigarette  10 , as well as a chip, such as an application specific integrated circuit (ASIC) for controlling the e-cigarette  10 . The ASIC may be positioned alongside or at one end of the battery  210 . The ASIC is attached to a sensor  215  to detect an inhalation on mouthpiece  35  (or alternatively the sensor  215  may be provided on the ASIC itself). The sensor  215  is located at an appropriate position within the e-cigarette  10 , most commonly within the body portion  20 , to experience a passing airflow caused by the inhalation. Such positioning is usually determined, at least in part, by the location of the air inlet(s) for the e-cigarette  10 . In response to a detection of inhalation by the sensor  215 , the ASIC provides power from the battery  210  to a heater in the cartomizer  30  to vaporize nicotine into the airflow which is inhaled by a user. 
     The body  20  further includes a cap  225  to seal and protect the far (distal) end of the e-cigarette  10 . In some embodiments, there is an air inlet hole provided in or adjacent to the cap  225  to allow air to enter the body and flow past the sensor  215  when a user inhales on the mouthpiece  35 . This airflow therefore allows the sensor  215  to detect the user inhalation. 
     At the opposite end of the body  20  from the cap  225  is the connector  25 B for joining the body  20  to the cartomizer  30 . The connector  25 B provides mechanical and electrical connectivity between the body  20  and the cartomizer  30 . The connector  25 B includes a body connector  240 , which is metallic (silver-plated in some embodiments) to serve as one terminal for electrical connection (positive or negative) to the cartomizer  30 . The connector  25 B further includes an electrical contact  250  to provide a second terminal for electrical connection to the cartomizer  30  of opposite polarity to the first terminal, namely body connector  240 . The electrical contact  250  is mounted on a coil spring  255 . When the body  20  is attached to the cartomizer  30 , the connector  25 A on the cartomizer  30  pushes against the electrical contact  250  in such a manner as to compress the coil spring in an axial direction, i.e. in a direction parallel to (co-aligned with) the longitudinal axis LA. In view of the resilient nature of the spring  255 , this compression biases the spring  255  to expand, which has the effect of pushing the electrical contact  250  firmly against connector  25 A, thereby helping to ensure good electrical connectivity between the body  20  and the cartomizer  30 . The body connector  240  and the electrical contact  250  are separated by a trestle  260 , which is made of a non-conductor (such as plastic) to provide good insulation between the two electrical terminals. The trestle  260  is shaped to assist with the mutual mechanical engagement of connectors  25 A and  25 B. 
       FIG. 3  is a schematic diagram of the cartomizer  30  of the e-cigarette  10  of  FIG. 1  in accordance with some embodiments of the disclosure.  FIG. 3  can generally be regarded as a cross-section in a plane through the longitudinal axis LA of the e-cigarette  10 . Note that various components and details of the body  20 , e.g. such as wiring and more complex shaping, have been omitted from  FIG. 3  for reasons of clarity. 
     The cartomizer  30  includes an air passage  355  extending along the central (longitudinal) axis of the cartomizer  30  from the mouthpiece  35  to the connector  25 A for joining the cartomizer to the body  20 . A reservoir of nicotine  360  is provided around the air passage  335 . This reservoir  360  may be implemented, for example, by providing cotton or foam soaked in nicotine. The cartomizer  30  also includes a heater  365  for heating nicotine from reservoir  360  to generate nicotine vapor to flow through air passage  355  and out through mouthpiece  35  in response to a user inhaling on the e-cigarette  10 . The heater  365  is powered through lines  366  and  367 , which are in turn connected to opposing polarities (positive and negative, or vice versa) of the battery  210  via connector  25 A (the details of the wiring between the power lines  366  and  367  and connector  25 A are omitted from  FIG. 3 ). 
     The connector  25 A includes an inner electrode  375 , which may be silver-plated or made of some other suitable metal. When the cartomizer  30  is connected to the body  20 , the inner electrode  375  contacts the electrical contact  250  of the body  20  to provide a first electrical path between the cartomizer and the body. In particular, as the connectors  25 A and  25 B are engaged, the inner electrode  375  pushes against the electrical contact  250  so as to compress the coil spring  255 , thereby helping to ensure good electrical contact between the inner electrode  375  and the electrical contact  250 . 
     The inner electrode  375  is surrounded by an insulating ring  372 , which may be made of plastic, rubber, silicone, or any other suitable material. The insulating ring  372  is surrounded by the cartomizer connector  370 , which may be silver-plated or made of some other suitable metal or conducting material. When the cartomizer  30  is connected to the body  20 , the cartomizer connector  370  contacts the body connector  240  of the body  20  to provide a second electrical path between the cartomizer  30  and the body  20 . In other words, the inner electrode  375  and the cartomizer connector  370  serve as positive and negative terminals (or vice versa) for supplying power from the battery  210  in the body to the heater  365  in the cartomizer  30  via supply lines  366  and  367  as appropriate. 
     The cartomizer connector  370  is provided with two lugs or tabs  380 A,  380 B, which extend in opposite directions away from the longitudinal axis of the e-cigarette  10 . These tabs are used to provide a bayonet fitting in conjunction with the body connector  240  for connecting the cartomizer  30  to the body  20 . This bayonet fitting provides a secure and robust connection between the cartomizer  30  and the body  20 , so that the cartomizer  30  and body  20  are held in a fixed position relative to one another, without wobble or flexing, and the likelihood of any accidental disconnection is very small. At the same time, the bayonet fitting provides simple and rapid connection and disconnection by an insertion followed by a rotation for connection, and a rotation (in the reverse direction) followed by withdrawal for disconnection. It will be appreciated that other embodiments may use a different form of connection between the body  20  and the cartomizer  30 , such as a snap fit or a screw connection. 
       FIG. 4  is a schematic diagram of certain details of the connector  25 B at the end of the body  20  in accordance with some embodiments of the disclosure (but omitting for clarity most of the internal structure of the connector as shown in  FIG. 2 , such as trestle  260 ). In particular,  FIG. 4  shows the external housing  201  of the body  20 , which generally has the form of a cylindrical tube. This external housing  201  may comprise, for example, an inner tube of metal with an outer covering of paper or similar. 
     The body connector  240  extends from this external housing  201  of the body  20 . The body connector  240  as shown in  FIG. 4  comprises two main portions, a shaft portion  241  in the shape of a hollow cylindrical tube, which is sized to fit just inside the external housing  201  of the body  20 , and a lip portion  242  which is directed in a radially outward direction, away from the main longitudinal axis (LA) of the e-cigarette  10 . Surrounding the shaft portion  241  of the body connector  240 , where the shaft portion  241  does not overlap with the external housing  201 , is a collar or sleeve  290 , which is again in a shape of a cylindrical tube. The collar  290  is retained between the lip portion  242  of the body connector  240  and the external housing  201  of the body  20 , which together prevent movement of the collar  290  in an axial direction (i.e. parallel to axis LA). However, collar  290  is free to rotate around the shaft portion  241  (and hence also axis LA). 
     As mentioned above, the cap  225  is provided with an air inlet hole to allow air to flow past sensor  215  when a user inhales on the mouthpiece  35 . However, the majority of air that enters the device  10  when a user inhales flows through collar  290  and body connector  240  as indicated by the two arrows in  FIG. 4 . In some embodiments, the cap  225  may not be provided with an air inlet hole. In this case all of the air that enters the device  10  when a user inhales may flow through the collar  290  and the body connector  240  as indicated by the two arrows in  FIG. 4 . Alternatively, there may be other routes for air into the e-cigarette  10 , for example, generally at the join between the body  20  and the cartomizer  30 , and/or using one or more air inlet holes located elsewhere in the e-cigarette  10 . 
       FIG. 5  illustrates how the collar  290  and body connector  240  permit air to flow into the e-cigarette  10  in accordance with some embodiments. (Note that  FIG. 5  is sectioned where the body connector  240  enters the external housing  201 , hence the portion of the shaft  241  of the body connector  240  that is located inside the external housing  201  is omitted from  FIG. 5 .) 
     As shown in  FIG. 5 , the collar  290  is provided with three notches or openings  295 A,  295 B and  295 C, which are azimuthally spaced around the circumference of the collar  290 . Each notch or opening  295 A,  295 B and  295 C allows air to flow through the collar  290  in a radial direction, i.e. from outside the collar  290  to inside the collar  290 . The shaft  241  of the body connector  240  also includes openings, in particular apertures  245 A and  245 B, which are likewise azimuthally spaced around the circumference of the shaft  241 . Note that the portion of the shaft  241  that extends into the external housing  201  (not shown in  FIG. 5 ) may provide the fourth side or edge of these openings, or alternatively the openings may extend into the region of the shaft  241  that overlaps the external housing  201 . 
     As mentioned above, and as indicated by arrow  299  in  FIG. 5 , the collar  290  may be rotated around the longitudinal axis LA of the shaft  241  and e-cigarette  10 . Such rotation alters the relative azimuthal positioning of the collar  290  and the shaft  241 , including the relative azimuthal positioning of the holes therein. In particular, such rotation changes the relative alignment between the notches  295 A,  295 B and  295 C in the collar  290  and the openings  245 A and  245 B in the shaft  241 . 
       FIGS. 6A, 6B and 6C  are schematic diagrams showing the collar  290  in three different azimuthal (rotational) positions with respect to the shaft  241 . In the position of  FIG. 6A , the two holes or openings  245 A and  245 B of the body connector  240  are both aligned with corresponding openings or notches in the collar  290 , namely openings  295 A and  295 B respectively. In this configuration, air can therefore enter the e-cigarette  10  through both openings  245 A and  245 B (via openings  295 A and  295 B respectively). In contrast, notch  295 C in the collar  290  is not aligned with any corresponding opening in the shaft  241 , and hence no air is able to enter within the e-cigarette  10  through notch  295 C. 
     In the position of  FIG. 6B , the collar  290  has been rotated in a clockwise direction with respect to the shaft  241 , so that the two holes or openings  245 A and  245 B are no longer aligned with openings  295 A and  295 B respectively. However, notch  295 C has now been rotated to align with opening  295 A. Accordingly, in this configuration, air can enter the e-cigarette  10  through opening  245 A (via opening  295 C), but not through opening  245 B, and no air is able to enter the inside of the e-cigarette  10  through notches  295 A and  295 B. 
     Lastly, in the position of  FIG. 6C , the collar  290  has been further rotated in a clockwise direction with respect to the shaft  241 , so that none of the openings  245 A and  245 B in the shaft  241  is aligned with an opening  295 A,  295 B,  295 C in the collar  290 . Accordingly, in this position or orientation, air is prevented from entering the e-cigarette  10  through collar  290  and shaft  241 . 
     In some implementations, a user may still be able to inhale through the e-cigarette  10  even when in the configuration of  FIG. 6C —for example, the e-cigarette  10  may be provided elsewhere with one or more additional air inlet holes (apart from openings  295 A, B and C); alternatively (or additionally) there may be air ingress for example at the join between the body  20  and the cartomizer  30 . However, if such alternative air inlet options are not provided in the e-cigarette  10 , then the configuration of  FIG. 6C  can be considered, in effect, as a form of “off” position, in that the user will no longer be able to inhale through the e-cigarette  10  in this position. The e-cigarette  10  may be provided with external markings to indicate this “off” position to a user. In addition, the collar  290  may be resiliently biased to return to this “off” position, for example, as some form of safety mechanism. 
     In other implementations, the user may still be able to inhale through the e-cigarette  10  in the configuration of  FIG. 6C , but such inhalation might not be detectable by sensor  215 —for example, because the amount of airflow is too weak (i.e. below some threshold setting for sensor  215 ) and/or because the airflow from points of air ingress into the e-cigarette  10  is arranged to have a different routing (not past the sensor  215 ). In such a situation, although a user can inhale, the heater  365  is not activated, and therefore no nicotine vapor is produced. In these circumstances, the configuration of  FIG. 6C  would again represent, in effect, an “off” position. 
       FIG. 7  is a schematic illustration that further indicates how the collar  290  and body connector  240  permit air to flow into the e-cigarette  10  in accordance with various embodiments of the disclosure. There are some differences between the implementation shown in  FIG. 7  compared with the implementation shown in  FIG. 5 . Thus in  FIG. 7  the shaft portion of  241  of the body connector  240  does not extend past the outwardly directed lip portion  242  (in an axial direction towards the mouthpiece). In addition, the notches  295 A,  295 B and  295 C in  FIG. 5  are located at the boundary between the collar  290  and the external housing  201 , whereas the notches  295 A,  295 B and  295 C in  FIG. 7  are located at the boundary between the collar  290  and the lip portion  242  of the body connector  240 . Consequently, the notches  295 A,  295 B and  295 C in  FIG. 5  can be considered as extending into the collar  290  in an axial direction towards the mouthpiece  35 , whereas the notches  295 A,  295 B and  295 C in  FIG. 7  can be considered as extending into the collar  290  in an axial direction towards the cap  225 . It will be appreciated by the skilled person that both such arrangements (and indeed any intermediate positionings) are able to provide variable ventilation to the vaporizer as described herein. 
     Furthermore, while  FIG. 7  is sectioned, like  FIG. 5 , in a plane transverse to the longitudinal axis LA of the e-cigarette  10 , the positioning of this sectioning is slightly different from  FIG. 5 . In particular, this sectioning goes through the collar  290  as well, so there is a portion of the collar  290  (extending axially towards the cap  225 ) that is omitted from  FIG. 7  (the corresponding portion of the shaft  241  that passes inside this collar  290 , and also the portion of the shaft  241  that passes inside the external housing  201 , are likewise omitted by this sectioning of  FIG. 7 ). At least some of this omitted portion of the collar  290  may be azimuthally (circumferentially) complete, i.e. notches  295 A,  295 B and  295 C do not extend the full length of the collar  290  in an axial direction LA. This then allows the collar  290  to comprise a single unit, which can assist with easier fabrication. 
     Nevertheless, the implementation shown in  FIG. 7  shares the same general configuration of  FIGS. 5 and 6 , in that the collar  290  is provided with three holes or notches  295 A,  295 B and  295 C, two of which ( 295 A and  295 B) are diametrically opposite one another, while the third notch ( 295 C) is circumferentially offset from the other two. Similarly, the shaft  241  of the body connector  240  has two openings ( 245 A,  245 B) which are again diametrically opposite one another. The collar can be rotated around the shaft  241  as indicated by the arrow  299  into the three angular positions shown in  FIGS. 6A, 6B and 6C . These three positions correspond to two air holes ( 245 A,  245 B) in the body connector  240  being open (as per the position of  FIG. 6A , and also as shown in  FIG. 5 ); one of the two air holes ( 245 A) in the body connector  240  being open (as per the position of  FIG. 6B , and also as shown in  FIG. 7 ); and none of the two air holes in the body connector  240  being open (as per the position of  FIG. 6C ). 
     Note that being able to control the airflow adjustment by moving collar  290 , which is located circumferentially around, but separate from (in effect, external to) the main housing of the e-cigarette  10 , such as shaft  241 , has certain benefits. Thus the collar  290  only extends a relatively short distance in the axis direction (LA) compared to other components of the e-cigarette  10 , such as the body  20  or cartomizer  30 . This allows the collar  290  to be relatively lightweight and easy for a user to rotate. In addition, rotating the collar  290  rather than an underlying component, such as the body  20  or cartomizer  30 , does not impact the connection  25 A,  25 B between the body  20  and the cartomizer  30 , which can therefore remain intact. 
     It will also be appreciated that the configuration of  FIG. 6A  allows multiple holes on the collar  290  to be aligned respectively with multiple holes on the shaft  241 , i.e. as shown in  FIG. 6A , hole  295 B is aligned with hole  245 B, and hole  295 A is aligned with hole  245 A. Having multiple such through-holes (i.e. going through both the collar  290  and shaft  241 ) reduces the risk of a user accidentally blocking the airflow when holding the e-cigarette  10  with their fingers. Although  FIG. 6A  shows two such through-holes, other embodiments may provide additional through-holes (according to the particular setting of the collar  290 ) to further reduce the risk of occlusion by a user&#39;s finger(s). 
     Compared with the implementation shown in  FIG. 5 , the implementation of  FIG. 7  has some additional features to provide greater control over the rotation of the collar  290  about the shaft  241 . One of these features provides a small ridge, bump or other protrusion  248  formed on the radially outer surface of the shaft  241 , i.e. on the surface of the shaft  241  that abuts against the inner radial surface of the collar  290 . This inner radial surface of the collar  290  is provided with three, azimuthally (circumferentially) spaced incisions or indentations  294 A,  294 B and  294 C. As the collar is rotated about the shaft  241 , as indicated by arrow  299 , the outward protrusion  248  on the shaft  241  may be received into any one of the indentations  294 A,  294 B and  294 C. For example,  FIG. 7  shows the protrusion  248  received into the middle indentation  294 B. 
     The three indentations  294 A,  294 B and  294 C therefore define, in effect, three predetermined relative angular positions between the collar  290  and the shaft  241 . When the protrusion  248  is received into one of these indentations  294 A,  294 B or  294 C, the collar  290  and shaft  241  are thereby held or latched (positively engaged) into the corresponding or respective predetermined relative angular position. In particular, when held in any of these predetermined positions, the engagement of the protrusion with corresponding indentation prevents the collar  290  from being able to rotate freely or easily around the shaft  241 . The collar  290  therefore remains in that predetermined angular position relative to the shaft  241  unless the user takes a particular action, e.g. applies sufficient torque, to disengage the protrusion  248  from the indentation  294 A,  294 B or  294 C (as described in more detail below). 
     The predetermined positions of the three indentations  294 A,  294 B and  294 C are arranged to correspond to the three configurations shown in  FIGS. 6A  through to  6 C. Thus  FIG. 6A  corresponds to protrusion  248  located in indentation  294 A, whereby both of air holes  245 A and  245 B are open for ventilation through the collar  290 ;  FIG. 6B  corresponds to protrusion  248  located in indentation  294 B, whereby only one of the air holes  245 A is open for ventilation through the collar  290  (as shown in  FIG. 7 ); and  FIG. 6C  corresponds to protrusion  248  located in indentation  294 C, whereby neither of air holes  245 A and  245 B is open for ventilation through the collar  290 . Accordingly, the user is provided with tactile feedback (a positive engagement or latching click, which may also provide audible feedback) as the collar  290  is rotated around the sleeve to each of the three ventilation levels as represented by the positioning of indentations  294 A,  294 B and  294 C, and moreover the collar  290  will remain in that engaged position as selected by the user unless or until the user makes a positive decision to rotate the collar to a different predetermined engagement position. Note that in some embodiments, the exterior surface of the e-cigarette  10 , in particular the collar  290  plus the lip  242  and/or external housing  201 , may be provided with some visual marking or indication of the engagement positions, or at least an indication of which rotational direction for the collar  290  increases or decreases the level of ventilation. 
     It can be seen from  FIG. 7  that there is a hollow portion  246  in the wall of the shaft  241  immediately below (radially inside) the notch  248 . This hollow portion  246  extends a short distance in an azimuthal direction around the shaft  241 , and defines in effect a bridge or span  249  in the outer portion of the shaft  241 . The outward protrusion  248  is located off this bridge  249  in approximately the middle portion of the bridge  249  (as determined in a circumferential direction). The hollow portion  246  introduces some flexibility or resilience into the position of the protrusion  248 . In particular, the default position for the bridge  249  may be as shown in  FIG. 7 , with the protrusion  248  located within one of the indentations  294 A,  294 B or  294 C. However, if the user wishes to rotate the collar  290  to a different predetermined engagement position, then if they apply a sufficient rotational force (torque), the bridge  249  is able to deform resiliently by bending slightly into the hollow portion  246 . This allows the protrusion  248  to disengage from the indentation by moving slightly radially inwards, and then to rotate along the inside of the collar  290  to the new desired engagement position. When this position is reached, the resilient nature of the bridge  249  pushes the protrusion  248  radially outwards again into the corresponding indentation  294 , thereby allowing the bridge  249  to resume its default position as shown in  FIG. 7  and thereby latching the collar  290  into the new predetermined engagement position. In other implementations, the material of the collar  290  and/or the shaft  241  may have sufficient elasticity to allow the hollow portion  246  to be omitted (or some other design may be adopted to provide the desired resilience). 
       FIG. 7  also illustrates that the inner radial surface of the collar  290  is provided with a circumferentially extending opening or slot  297 . The azimuthal limits of this opening  297  are defined by radially directed walls  298 A,  298 B formed in the collar  290 —i.e. these walls  298 A,  298 B are perpendicular to their local circumferential or tangential direction about the longitudinal axis LA. The shaft  241  has a tab, tooth or lug  243  (etc) directed in a radially outwards direction which is located within the opening  297 . As the collar  290  is rotated with respect to the shaft  241 , the tab  243  moves within (circumferentially along) the slot  297 . This rotational movement of the tab  243  is limited by the two walls  298 A,  298 B in the collar  290 . In particular, further rotation of the collar  290  in one direction (clockwise in the implementation of  FIG. 7 ) is prevented when the tab  243  abuts against wall  298 A, while further rotation of the collar  290  in the opposite direction (anti-clockwise in the implementation of  FIG. 7 ) is prevented when the tab  243  abuts against wall  298 B. 
     In the implementation of  FIG. 7 , the position of the tab  243  abutting against wall  298 A corresponds to an angular orientation of the collar  290  with respect to the shaft  241  such that the protrusion  248  is located within indentation  294 A. It will appreciated that further rotation of the collar  290  in the clockwise direction (in the configuration of  FIG. 7 ) is not needed, since the other predetermined engagement positions, as determined by the positions of indentations  294 B and  294 C, lie in an anti-clockwise direction with respect to indentation  294 A. Similarly, the position of the tab  243  abutting against wall  298 C corresponds to an angular orientation of the collar  290  with respect to the shaft  241  such that the protrusion  248  is located within indentation  294 C. Further rotation from this position of the collar  290  in the counter-clockwise direction is not needed, since the other predetermined engagement positions, as determined by the positions of indentations  294 B and  294 A, lie in a clockwise direction with respect to indentation  294 C. 
     Accordingly, the interaction of lug  243  with slot  297 , and in particular with end walls  298 A and  298 B, serves to limit the rotation of the collar  290  with respect to the shaft  241  to a predetermined range (corresponding to the angular separation of the end walls  298 A and  298 B less the angular width of the tab  243 ). This predetermined range is set, in the implementation of  FIG. 7 , to encompass the set of predetermined engagement positions (offering the corresponding particular levels of ventilation), such that rotation of the collar  290  around the shaft  241  is permitted within the circumferential range of the predetermined engagement positions, but is not permitted outside this circumferential range. One effect of this restriction is to prevent a 360 degree rotation of the collar  290  with respect to the shaft  241 . This makes it generally easier to operate the device  10 , since the user always encounters the predetermined engagement positions in a consistent ordering and spacing (one direction to increase ventilation, the other to decrease ventilation), which would not be the case if full circular rotation of the collar  290  about the body connector  240  was permitted. However, other implementations may omit the lug  243  and associated slot  297  to permit 360 degree rotation of the collar  290  with respect to the shaft  241  (for example, to simplify the construction of the electronic vapor provision system). 
     Thus various embodiments as described herein provide an electronic vapor provision system, for example, an e-cigarette  10  or other type of such device, for providing nicotine or other vapors to a user. Such an electronic vapor provision system has a housing and a vaporizer (such as a heater) contained within the housing. A mouthpiece is located at one end of the system to provide an air outlet. A user can inhale or draw on the mouthpiece to receive vapor from the electronic vapor provision system. 
     The air inlet (which may comprise multiple openings) into the housing is provided with a facility to control ventilation as described herein. This air inlet is located upstream of the vaporizer, so that the ventilation control described herein alters the flow of air past the vaporizer, e.g. heater  365 . In general, allowing more ventilation increases the amount of vapor produced (and hence inhaled), since increased airflow past the heater removes the existing vapor and helps further liquid to vaporize from the heater. In other words, increasing the ventilation to allow more air to flow into the e-cigarette tends to increase the amount of nicotine content (or other vapor content) inhaled by a user out through mouthpiece  35 . 
     The variable ventilation can also be used to adjust the draw resistance of the e-cigarette  10 . Thus as a user inhales, the lungs in effect work against the draw resistance, i.e. the work required to pull air into and then through the e-cigarette  10  into the lungs. For most users, there is a range of draw resistance that helps them to perform a steady inhalation. However, if the draw resistance is too low, the inhalation may become too rapid and unsteady, while if the draw resistance is too high, the inhalation may become unduly burdensome. The most suitable level of draw resistance varies from one user to another user, based e.g. on physiological factors. Accordingly, providing variable ventilation as described herein can help a user to configure the draw resistance of e-cigarette  10  to an appropriate value for their own personal preferences and characteristics. 
     Note that the housing may comprise multiple different components. Unless otherwise indicated, a component may generally be considered as part of the housing if it contributes to preventing the ingress of air from outside the electronic vapor provision system (other than in respect of any inlet holes). For example, in the embodiment of  FIG. 4 , the external housing  201  and the body connector  201  both form part of the housing. In addition, the housing may contain both a body portion  20 , which includes at least a power source for the vaporizer, and a vaporizer portion  30  including the vaporizer. In some implementations, for example as shown in  FIG. 1 , the electronic vapor provision system has a first state in which the body portion is detached from the vaporizer portion, and a second state in which the body portion has a rigid connection to the vaporizer portion. This rigid connection, which may be achieved by any suitable mechanism, for example, a screw fit, a snap fit, a bayonet fitting, etc, prevents movement, in the second state, of the body portion relative to the vaporizer portion (other than to detach the vaporizer portion from the body portion into the first state). Note that in other embodiments the housing may, for example, contain three detachable portions, namely a body portion (containing a power cell), a vaporizer portion (containing a vaporizer) and a cartridge (containing a fluid reservoir). In other embodiments, these components (power cell, vaporizer and fluid reservoir) may be integrated into a single unit within an overall housing, and are not intended to be detached or separated by a user. 
     One or more air inlet holes are provided in a portion of the housing. In response to a user inhalation at the mouthpiece, air flows into the system through the one or more air inlet hole, passing the vaporizer, which introduces vapor into the airflow, and out through the mouthpiece. An air inlet hole may have any appropriate shape, for example, it may be circular, or elongate (such as a slot), etc. If multiple air inlet holes are provided in the portion of housing, they may all be the same as one another, or they may vary in shape, size and/or orientation. 
     In the example of  FIG. 4 , the portion of the housing having the one or more air inlet holes is located on the body portion  20  of the electronic vapor provision system, adjacent to the connection to the vaporizer portion (cartomizer)  30 . However, in other embodiments this portion of the housing may be located elsewhere, for example on the cartomizer itself, and/or away from the connection  25 . In addition, the electronic vapor provision system may be provided with one or more additional air inlet holes not in said housing portion, but rather in a different location, such as at or near cap  225 , as described above in relation to the embodiment of  FIG. 2 . 
     The electronic vapor provision system further includes a collar located around the portion of the housing that contains the one or more air inlet holes—for example, collar  290  as shown in  FIG. 4 . The collar is movable with respect to the housing. Moving the collar relative to the housing results in different degrees of alignment between the collar and the one or more air inlet holes of the housing, thereby changing the properties of the airflow into the electronic vapor provision system. Moreover, the system further includes a mechanism for positively engaging the collar and the housing at a plurality of predetermined positions as the collar is moved with respect to the housing. Different ones of said plurality of predetermined positions therefore correspond to providing different levels of ventilation into the system. 
     A user is therefore able to control the degree of ventilation into the system by moving the collar as appropriate to one of the predetermined positions. This control over ventilation can be used to impact various significant operating parameters of the system, such as draw resistance and volume of airflow past the vaporizer (which in turn can impact properties such as the droplet size and density of the vapor introduced into the airflow). Furthermore, the positive engagement mechanism ensures that the collar remains in the selected position (and hence the desired operating parameters are maintained) unless or until the user decides to change the position of the collar—for example, because the device is being shared between multiple users, because the cartomizer portion has been replaced, or because the mood or condition of the user has changed. 
     The collar is generally located on the outside of the housing, such as shown in  FIG. 4 , since it is then readily accessible for a user to move the collar. The outer surface of the collar may be textured or raised above the surrounding level of the housing in order to further facilitate user movement of the collar. In addition, the collar and/or housing may be provided with some visual indication of which direction to move the collar in order to increase (or decrease) the ventilation into the electronic vapor provision system. 
     In some implementations, such as shown in  FIG. 4 , the collar may have a fixed location with respect to the longitudinal axis LA of the electronic vapor provision system, and the movement of the collar comprises rotation about this axis. Hence the predetermined positions in this configuration are predetermined angular positions of the collar relative to the housing portion. In this case, the axial extent of the collar may be generally commensurate with that of the housing portion containing the one or more air inlet holes. 
     In other embodiments, the movement of the collar may comprise sliding along the housing in a direction parallel to the longitudinal axis LA of the electronic vapor provision system. Another possibility is to provide a screw thread on the housing portion and/or the collar itself so that the collar has a screw (helical) movement along the housing, with the axis of the helix parallel to the longitudinal axis LA of the electronic vapor provision system. In these latter two cases, the axial extent of the collar may be generally somewhat shorter than that of the housing portion containing the one or more air inlet holes. Accordingly, in such embodiments, axial movement of the collar may be used to decrease or increase the occlusion of the one or more air inlet holes in the housing, and the predetermined positions reflect differing amounts of such axial movement. 
     In some embodiments, there are three or more predetermined positions for positive engagement between the collar and the housing. Increasing the number of such predetermined positions helps to provide increased granularity of control. One of the predetermined positions may have the collar aligned so as to prevent air from entering the electronic vapor provision system via any of the one or more air inlet holes of the housing portion. This predetermined position might be selected, for example, when the system is not in use, in order to prevent or to help reduce evaporation loss of nicotine (or other fluid) through the one or more air holes in the housing portion. 
     Note that the device may still be operational even when the collar is aligned so as to prevent air from entering the electronic vapor provision system via any of the one or more air inlet holes of the housing portion. For example, a user inhalation may draw airflow into the system through one or more additional air holes (not located in this housing portion), such as near cap  225 , and/or through some leakage, for example, at the connection between the body portion and the vaporizer portion. 
     In some embodiments, different predetermined positions for engagement may have the collar positioned so as to allow air to enter through a different number of the one or more air inlet holes in the housing portion. In such a configuration each air inlet hole in the housing portion may be either fully open or fully shut in a given predetermined position. For example, in a system having three air inlet holes in the housing portion, a first predetermined position may have none of the air inlet holes in the housing portion open, a second predetermined position may have one of the air inlet holes in the housing portion open (and the other shut), and a third predetermined position may have all of the air inlet holes in the housing portion open. In other embodiments, the predetermined positions may involve partial opening of one or more air inlet holes. For example, in a system having one air inlet hole in the housing portion, a first predetermined position may have none of the air hole in the housing portion open, a second predetermined position may have the air inlet hole in the housing portion one-third open, a third predetermined position may have the air inlet hole in the housing portion two-thirds open, and a fourth predetermined position may have the air inlet hole in the housing portion fully open. 
     In some embodiments, the mechanism for positively engaging the collar and the housing at a plurality of predetermined positions comprises a male part on one of the collar or the housing and a plurality of female parts on the other of the collar or the housing. Each female part can receive the male part and corresponds to a respective one of the plurality of predetermined positions. For example, in the embodiment of  FIG. 7 , the male part comprises the protrusion  248  on the housing (body connector  240 ) having an outward direction, and the female parts comprise the set of corresponding indentations  294 A,  294 B and  294 C on an inner surface of the collar. It will be appreciated that in other embodiments, the male part may be located on the inside of the collar, and the female parts on the outside of the housing. In addition, the nature of the male and female parts may vary according to the particular implementation. For example, if the collar is arranged to slide in an axial direction with respect to the housing, the male part may comprise a ridge extending part or all of the way around the circumference of the housing (i.e. in a plane perpendicular to the longitudinal axis LA), and the female parts may comprise corresponding circumferential grooves in the collar. 
     In some embodiments, the mechanism is configured to resiliently bias the collar and the housing into positive engagement at the plurality of predetermined positions as the collar is moved with respect to the housing. Such bias may be achieved using a suitable structure or configuration, such as the bridge or span  249  shown in  FIG. 7 . In other embodiments, such bias may rely primarily on the natural resilience of the material of the collar and/or the housing—e.g. a plastic collar may have sufficient natural resilience so as to be able to snap into and out of the different predetermined positions—and hence the bridge  249  (and associated hollow portion  246 ) may be omitted. 
     In some embodiments, the plurality of predetermined positions defines a range of movement of the collar with respect to the housing. The electronic vapor provision system may be configured to prevent movement of the collar with respect to the housing beyond said range. For example, in the embodiment of  FIG. 7 , movement of the collar with respect to the housing beyond the range of the predetermined positions is prevented by having the protrusion or lug  243  on the housing that abuts, at each end of the range, against a respective wall  298 A,  298 B on the collar. In other embodiments, in which the collar is movable in an axial direction relative to the housing, movement beyond the range of the predetermined positions may be prevented, for example, by providing outwardly directed ridges on the housing which the collar is unable to slide past. In other embodiments, there may be no restriction on the rotational movement of the collar with respect to the housing, so that 360 degree movement of the collar can be achieved around the longitudinal axis of the electronic vapor provision system. 
     In some embodiments, the collar itself is provided with one or more air inlet holes (these may be fully defined apertures, or indentations into the side of collar). In such an arrangement, movement of the collar relative to the air inlet holes of the housing portion may result in different degrees of overlap between the one or more air inlet holes of the housing portion and the one or more air inlet holes of the collar, which in turn produces different amounts of ventilation for the electronic vapor provision system. In other embodiments, the collar may not have any such air inlet holes. Instead, motion of the collar (such as along a longitudinal axis of the electronic vapor provision system) may cover or expose individual air inlet holes in the housing portion to adjust the ventilation. 
     In some embodiments, one of the plurality of predetermined positions provides an off setting for the electronic vapor provision system. This can help safety, in that it is more difficult to unintentionally activate the system in this setting, especially if the mechanism is resiliently biased to return to this predetermined position 
     The off setting can be implemented in various ways. For example, if the mechanism provides no ventilation in the predetermined position of the off setting, and there are no other ventilation paths into and through the electronic vapor provision system, a user is unable to inhale through the device. In other implementations, at least some inhalation may be feasible through the device, but such inhalation may not provide sufficient airflow past the sensor to activate the vaporizer. In some cases this may be because the overall airflow through the e-cigarette is very small (or zero), because the ventilation is likewise reduced (or zero). Alternatively, some or all of the airflow may be routed away from the airflow sensor, and hence again there is not sufficient airflow past the sensor to activate the vaporizer. Such a situation may arise for example because the predetermined position of the off setting directs any airflow through the mechanism so that it does not pass the sensor. Alternatively, the predetermined position of the off setting may prevent air ingress through the mechanism itself, and other airflow routes (if any) through the e-cigarette substantially avoid the sensor. 
     Note that although the body portion and the vaporizer may be sold together as a complete electronic vapor provision system as described herein, in some cases the different components may be sold individually, for example, as replacement unit if the nicotine in a cartridge is exhausted. Accordingly, some embodiments provide a body portion or vaporizer for use in an electronic vapor provision system, where the body portion or vaporizer is provided with a collar such as described herein. 
     Some embodiments provide an electronic vapor provision system having one or more air inlet holes for drawing air into the system in response to a user inhalation and a variable ventilation mechanism having a plurality of predetermined settings, wherein each setting corresponds to a different degree of occlusion of the one or more air inlet holes, and the variable ventilation mechanism can be latched into any of said plurality of predetermined settings. 
     Although the embodiments described above have just one collar for controlling ventilation into the electronic vapor provision system, other embodiments may have multiple such collars, each being used to control the ventilation through one or more air inlet holes in a corresponding portion of the housing. 
     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.