CA2814977A1

CA2814977A1 - Aerosol generator

Info

Publication number: CA2814977A1
Application number: CA2814977A
Authority: CA
Inventors: Fredrik Andersson; Christian Tache; Amir Feriani
Original assignee: British American Tobacco Investments Ltd
Current assignee: British American Tobacco Investments Ltd
Priority date: 2010-11-08
Filing date: 2011-10-27
Publication date: 2012-05-18
Also published as: MX2013005173A; WO2012062600A1; AU2011328313A1; BR112013011400A2; CN103180053A; RU2013126199A; EP2637801A1; GB201018796D0; JP2013544141A; KR20130116887A

Abstract

A generally cylindrical aerosol generator which can be used as a substitute for a conventional cigarette has a longitudinal extending horn member (8) that carries a piezoelectric actuator (9) mounted within a main housing (4) and a mouthpiece housing (5). A cartridge (7) contains an aerosolizable liquid (28) in a chamber having an inner chamber wall (13) extending longitudinally between the proximal and distal ends (15, 16) of the cartridge, defining a receptacle to receive the horn member (8) from the distal end, a longitudinally extending outer chamber wall (17) surrounding the inner wall, a proximal inner end wall (18) bridging the inner chamber wall at the proximal end, and a proximal outer end wall (19) longitudinally spaced from the inner wall to define a discharge region (20). A nozzle (23) discharges liquid from the discharge region through the outer end wall as an aerosol (39). A capillary driver wall (24) is disposed between the inner and outer chamber walls, spaced from the inner wall to define a longitudinally extending capillary passageway (25) sufficiently narrow to drive liquid within the chamber by capillary action along the gap to the discharge region, where it is aerosolised by the vibratory action of the piezo device that is transmitted along the horn (8) to the discharge region (20).

Description

Aerosol generator Field This invention relates to an aerosol generator which uses a vibratory source such as a piezoelectric device to atomise liquid to produce an aerosol and a cartridge for use in such a generator, and has particular but not exclusive application to providing an aerosol of a liquid containing a nicotine based substance or a flavourant, which may be used as a substitute for a conventional cigarette.
Background Piezoelectric generators have been proposed hitherto for creating an atomised spray. For example WO 2002/241777 discloses the use of a piezo device both to create vibrations in a fluid flow and also to monitor the flow by using the device as a pressure transducer. FR
2929861 illustrates that it is known to use capillary action to feed liquid to a piezo electric actuator to create an aerosol. Also, JP 2004313871 discloses an atomiser using piezo device which feeds vibrations through a horn to focus them when creating the aerosol spray.
The present invention provides an improved aerosol generator that utilises a cartridge of liquid to be aerosolised, which may be used as a cigarette substitute device.
Summary The invention provides a cartridge for an aerosol generator, comprising a chamber to receive an aerosolisable liquid, the chamber having proximal and distal ends, a generally tubular inner chamber wall extending longitudinally between the proximal and distal ends, a longitudinally extending outer chamber wall surrounding the inner wall, a proximal inner end wall bridging the inner wall at the proximal end, a proximal outer end wall longitudinally spaced from the inner wall to define a discharge region between the proximal end walls, a nozzle to discharge liquid from the discharge region through the outer end wall as an aerosol, and a capillary driver wall between the inner and outer chamber walls, the capillary driver wall being spaced from the inner chamber wall to provide a longitudinally extending capillary passageway sufficiently narrow to drive liquid within the chamber by capillary action along the capillary passageway to the discharge region.

The capillary passageway may narrow from the distal end towards the proximal end so that the force due to capillary action on the liquid increases towards the proximal end.
The invention also includes an aerosol generator configured to receive the cartridge, comprising a generally tubular housing, an elongate horn member configured longitudinally within the housing to extend into the distal end of the cartridge chamber to engage the interior surface the inner chamber wall, and a vibratory actuator on the horn member to create vibrations therein to be transmitted to the proximal inner end wall of the chamber to act on liquid in the discharge region to cause discharge thereof through the nozzle.
Brief description of the drawings In order that the invention may be more fully understood an embodiment will now be described by way of illustrative example with reference to the accompanying drawings in which:
Figure 1 is the schematic perspective view of an aerosol generator, Figure 2 is a longitudinal sectional view of the generator shown in Figure 1, Figure 3 is a perspective view of a cartridge for use in the aerosol generator, Figure 4 is an exploded view of the cartridge illustrated in Figure 3, Figure 5 is an enlarged sectional view of the cartridge when installed in the mouth piece of the aerosol generator, with the horn removed, Figure 6 is a sectional view of the cartridge installed in the mouthpiece of the generator, also illustrating the horn in section, Figure 7 is a schematic circuit diagram of a driver circuit board used in the device to actuate the piezoelectric generator, and Figure 8 is a schematic circuit diagram of a detection circuit to detect when the user sucks on the mouthpiece, to actuate the device and produce an aerosol with the circuitry shown in Figure 6.
Detailed description Referring to Figure 1, an aerosol generator 1 has a generally cylindrical outer surface extending from a generally circular proximal end 2 to circular distal end 3.
The device 1 has a main housing 4 and a mouthpiece housing 5 with a proximal end aperture 6 through which aerosol is delivered to a user.
The mouthpiece 5 is removably mounted on the housing 4, for example as a push-fit or bayonet mounting (not shown).
A cartridge 7 containing an aerosolisable liquid is received within the mouthpiece housing 5 and can be interchanged when empty by removal of the housing 5 from the main body housing 4. As illustrated in Figure 2, main housing 4 contains a horn 8 on which is mounted a piezoelectric transducer 9. The housing 4 also contains electrical circuitry 10 coupled to the piezoelectric transducer 9 both to cause it to oscillate and also to detect pressure variations when the user draws on the mouthpiece housing 5. The circuitry 10 is driven by batteries 11 in the housing 4. Also, a LED 12 is mounted at the distal end 3 of the device, to be driven by the circuitry 10 to indicate when the device is in use.
The cartridge 7 is illustrated in more detail in Figures 3 and 4. The cartridge 7 has generally toroidal configuration with a generally tubular inner chamber wall 13 having a distal end opening 14 (shown in Figure 5) and extending from proximal end 15 to distal end 16. A
tubular outer chamber wall 17 surrounds the inner chamber wall 13 and also extends between the proximal and distal ends 15, 16. A proximal inner end wall 18 closes the proximal end of the inner chamber wall so that the interior of the inner chamber wall 13 together with the proximal inner end wall 18 define a receptacle open at the distal end 16, that receives the horn 8 as will be described in more detail hereinafter.
Also, the outer chamber wall 17 is closed at its proximal end by an outer proximal end wall 19 that is longitudinally spaced from the proximal inner end wall 18 to define a discharge region 20 shown clearly in Figure 5. The proximal outer end wall 19 includes an opening 21 that receives a nozzle plate 22 formed with at least one aperture 23 for forming an aerosol from liquid in the cartridge, to be supplied into the mouthpiece housing 5. A
generally frustoconical capillary driver wall 24 is mounted on the interior surface of the proximal outer end wall 19 so as to provide a capillary passageway 25, illustrated in Figures 4 and 5, between the inner chamber wall 13 and the capillary driver wall 24. As illustrated in Figures 4 and 5, the passageway 25 narrows from the distal end 16 towards the proximal end 15.

As shown in Figures 5 and 6, the space between the inner and the outer chamber walls 13, 17, contains liquid from which aerosol is formed. The capillary driver wall 24 cooperates with the inner chamber wall 13 to drive the liquid by capillary action into the discharge region 20. Apertures 26 in the proximal outer wall 19 allow air to enter into the cartridge 7 in order to prevent an air lock, as illustrated by arrows 27. The liquid is illustrated by reference 28 in Figures 5 and 6. The passage of the liquid 28 towards the discharge region 20 is illustrated by arrows 29. As illustrated in Figure 6, the horn 8 has a frustoconical or cylindrical tongue 30 that fits through the opening 14 closely within the interior of recess 31 formed by the inner chamber wall 13. The tongue 30 has a proximal end 32 that is spaced from the interior surface of the proximal inner end wall 18. The inner surface of the inner chamber wall 13 and the outer surface of the tongue 30 may include cooperating grooves and recesses 33, 34 to releasably hold the tongue within the chamber wall when the cartridge is inserted into the generator. The horn 8 also includes a generally cylindrical base member 35 from which the tongue 30 extends, the base number being mounted in a resilient mounting that comprises an 0 ring 36, within the main housing 4. The piezoelectric device 9 is mounted on the distal end 38 of the horn 8, on the base number 35 so that on actuation the horn can vibrate back and forth longitudinally within interior cylindrical region 37 of the main housing 4.
In use, the piezoelectric device 9 is actuated and produces ultrasonic vibrations in the base member 35, which are transmitted along and are focussed by the tongue 30 onto the inner chamber wall 13. The spacing between the end 32 of the tongue and the proximal inner chamber wall 18, ensures that the wall 18 is free to vibrate in the manner of a drum which causes liquid in the discharge region 20 to be urged through the aperture 23 to form an aerosol 39 that is illustrated in Figure 5, which is directed through the outlet 6 of the mouthpiece housing 5.
When the user draws on the mouthpiece housing 5, air is drawn into the aerosol 39 as illustrated in Figure 6 by arrows 40. Referring to Figure 1, main housing 4 includes an air inlet aperture 41 which, referring to Figure 6, allows air to enter in the direction of arrows 42 and pass through longitudinal passageways defined by diametrically opposed exterior grooves 43 in the outer chamber wall 17, illustrated in Figures 3 and 4.
Referring to Figures 5 and 6, the mouthpiece housing 5 defines a plenum 44 between the outlet 6 and the proximal outer end wall 19 of the cartridge 7. In use, the air flow 40 shown in Figure 6 mixes with the aerosol 39 shown in Figure 5 and passes to the user through outlet 6.
When the user draws on the mouthpiece housing 5, the resulting pressure reduction in plenum 44 is detected by the piezoelectric device 9 which is coupled to electrical circuitry that switches an electrical drive to the device 9 in order to cause it to produce the aerosol 39.
The electrical circuitry is shown in Figures 7 and 8 and includes a breath detector circuit 45 together with a driver circuit 46. The driver circuit 46 is shown in detail in Figure 7 and includes a micro controller 47 responsive to an output from the breath detector circuit 45 indicative that the user is drawing on the mouthpiece housing 5. As explained later, the breath detector circuit 45 provides a step voltage change in response to the user drawing on the mouthpiece housing 5, and in response, the micro controller 47 generates a pulsed rectangular waveform as illustrated in graph G1, which is applied to a driver circuit 48, that acts as a modulator to modulate the output of an oscillator 49 typically operating a frequency in a range of 420 -450 KHz illustrated in graph G2, although other suitable frequencies could be used. The resulting modulated output is shown in graph G3 and supplied to a voltage converter circuit 50 and then to a switching circuit 51 that supplies the modulated waveform to the piezoelectric device 9 at a frequency to cause it to produce ultrasonic vibrations which, as previously explained are transmitted through the horn 8 to the discharge region 20 to cause ejection of liquid 28 through nozzle 23 as the aerosol 39 shown in Figure 5. The components of the driver circuit 46 receive a regulated drive voltage from regulator 52 that is powered by batteries 53 which, as previously explained, are mounted in the battery compartment 11 shown in Figure 2. The batteries may also illuminate the LED 12 shown in Figure 2 either continuously or when the driver circuit 46 is actuated. The batteries 53 may be rechargeable batteries in which case an external battery charger 54 may be provided, for example as a cradle or some other convenient configuration to allow the batteries 53 to be recharged by the user.
Referring to Figure 8, the breath detector circuit 45 comprises a preamplifier 55 which amplifies a signal received via the switching circuit 51 from the piezoelectric element 9, and the amplified signal is illustrated schematically in graph G4. A signal processor 56 detects the envelope of the signal shown in graph G4 and a threshold detector 57 detects step changes in the signal from the processor 56. As illustrated in graphs G5, G6 and G7, when the user draws on the mouthpiece housing 5, when the flow rate of draw increases above a threshold, in this case around 1.6 litres/minutes as shown in graph G6, a step change occurs in the output of the signal processor 56, due to the air turbulence in the mouthpiece, which can be detected by threshold detector 57 to switch on the driver circuit 46. The voltage output from the threshold detector 57 is illustrated schematically in graph G8. Thus, the piezoelectric element 9 switches from being a pressure sensor to a ultrasonic driver so as to produce the aerosol 39 in response to the user drawing on the mouthpiece housing 5. It will be noted that the piezo detects the air turbulence resulting from drawing on the mouthpiece without actually being directly exposed directly to the airflow itself.
The components of the breath detector circuit 45 are driven by the batteries 53.
Thus, the aerosol generator device can produce an aerosol from the liquid 28 in the cartridge 7. The liquid may contain a suitable active ingredient such as nicotine, which case the device may be used as a substitute for a conventional cigarette. The liquid may contain a flavourant in addition to or instead of nicotine or may contain other active ingredients.
Once the contents of the cartridge have been consumed, the mouthpiece housing 5 may be removed and the cartridge 7 pulled away from the horn 8 and replaced with another.
It has been found that the piezoelectric arrangement provides an efficient aerosol generation technique. In particular, the shape of the tongue 30 of horn 8 amplifies the ultrasonic vibrations from the piezoelectric element 9 onto the inner proximal end wall 18 which because of its spacing from the proximal end 32 of the tongue, is free to vibrate like a drum and hence pressurise liquid in the discharge region 20 to drive the liquid through the aperture 23 to form the aerosol.
Furthermore, the progressively tapering of the capillary passageway 25 assists in transporting liquid from the interior of the cassette to the discharge region, producing a progressively increasing capillary force along the cartridge towards the proximal end 15 for driving the liquid 28 into the discharge region 20. Also, when the generator is held in a vertical configuration, gravity assists with driving the liquid 28 from the space between the outer chamber wall 17 and the capillary driver wall 24, into the capillary passageway 25, to assist in delivery of the liquid to the discharge region 20.
It will be understood that because the cartridge is replaced periodically, quality of the successively used cartridges 7 should have generally similar spray characteristics. The cartridge 7 can be checked in situ in terms of its spray characteristics, which has been found to be highly dependent on the frictional force between the tongue 30 of the horn 8 and the inner chamber wall 13, which in turn results in a different electrical load on the piezo device 9. Referring to Figure 7, the driver 48 or the voltage converter 50 may be configured to adaptively adjust its voltage to compensate the load variations of the piezo device from cartridge to cartridge so as to maintain a uniformity of the aerosol spray 39 produced when cartridges are changed in the device.
It will be understood that many modifications and variations may be made to the described example of aerosol generator and cartridge, within the scope of the claims hereinafter. For example the nozzle(s) 23 my be formed directly in the cartridge outer wall rather than in a separate nozzle plate. Also, breath detection may be performed by other means than the piezo device to allow simultaneous aerosol generation and breath detection.

Claims

1. An aerosol generator including:
a cartridge (7) for containing a liquid to be aerosolised, comprising a chamber to receive an aerosolizable liquid, the chamber having proximal and distal ends, a generally tubular inner chamber wall (13) extending longitudinally between the proximal and distal ends (15,16), a longitudinally extending outer chamber wall (17) surrounding the inner wall, a proximal inner end wall (18) bridging the inner wall at the proximal end, a proximal outer end wall (19) longitudinally spaced from the inner wail to define a discharge region between the proximal end walls, a nozzle (23) to discharge liquid from the discharge region through the outer end wall as an aerosol, and a capillary driver wall (24) between the inner and outer chamber walls, the capillary driver wall being spaced from the inner chamber wall to provide a longitudinally extending capillary passageway sufficiently narrow to drive liquid within the chamber by capillary action along the capillary passageway to the discharge region, a generally tubular housing (5), an elongate horn member configured (8) longitudinally within the housing so as to extend into the distal end of the cartridge chamber and engage the interior surface of the inner chamber wail such that the container is removably mounted thereon for interchange, and a vibratory actuator (9) on the horn member to create vibrations therein to be transmitted to the proximal inner end wall of chamber to act on liquid in the discharge region to cause discharge thereof through the nozzle.

2. A cartridge according to claim 1 wherein the capillary passageway narrows from the distal end towards the proximal end so that the force due to capillary action on the liquid increases towards the proximal end.

3. A cartridge according to claim 1 or 2 wherein the nozzle comprises at least one hole in a nozzle plate received in an aperture in the proximal outer end wall.

4. A cartridge according to any preceding claim including an air inlet aperture in the proximal outer end wall to allow ingress of air into the chamber.

5. A cartridge according to any preceding claim wherein the chamber comprises a first cartridge element including the inner and outer chamber walls the inner proximal end wall and a distal end wall extending between the inner and outer chamber walls at the distal end, and a second cartridge element comprising the capillary driver wall and the outer proximal end wall.

6. A generator according to claim 1 including a mouthpiece at one end of the housing and a detector to detect air turbulence in the mouthpiece to actuate the vibratory actuator and generate the aerosol.

7. A generator according to claim 6 wherein the mouthpiece is removable from the housing to allow insertion and removal of the cartridge.

8. A generator as claimed in claim 6 or 7 wherein the vibratory actuator comprises a piezoelectric element and the detector includes said piezoelectric element to detect the air turbulence.

9. A generator according to claim 8 including electrical circuitry in the housing to drive the piezoelectric element to produce ultrasonic vibrations and also to be responsive to electrical signals from the actuator to detect pressure changes detected by the piezoelectric element.

10. A generator according to claim 9 wherein the housing includes a battery compartment to receive a battery to power the circuitry.

11. A generator according to any one of claims 7 to 10 wherein the horn comprises an elongate tongue having a proximal end to be inserted into the tubular inner chamber wall from the distal end thereof, and a base member at the distal end of the tongue, resiliently mounted in the housing, the piezoelectric element being mounted on the base member.

12. A generator according to claim 11 wherein the base member is generally cylindrical and mounted in a resilient O-ring in the housing.

13. A generator according to claim 1 wherein the outer chamber wall includes a longitudinal groove to provide a passageway for air to enter the mouthpiece to be mixed with liquid discharged from the nozzle.

14. A generator according to claim 1 or wherein the inner chamber wall of the cartridge is frustoconical and the horn is tapered to engage the interior surface of the inner chamber wall.

15. A generator according to claim 13, or 14 wherein horn and the interior surface of the inner chamber wall are formed with cooperating rings and grooves to releasably engage them together.

16. A generator according to any one of the preceding claims wherein the proximal end of the horn when fitted in the inner wall of the chamber is spaced from the inner proximal end wall permitting vibration thereof to discharge liquid from the discharge region through the nozzle.