Note: Descriptions are shown in the official language in which they were submitted.
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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.
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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
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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.
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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
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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
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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
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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.
