Note: Descriptions are shown in the official language in which they were submitted.
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Device for Enabling Vapour Emanation
Field of the Invention
This invention relates to a device that enables the emanation of a chemical
formulation, such as an insecticide or a fragrance, into surrounding
atmosphere. The
invention also relates to a device that enables the emanation of a chemical
formulation
and is releasably insertable into an electrical heating apparatus used to
vapourize the
chemical formulation.
Back~ound to the Invention
A number of patent documents disclose portable devices that enable the
application of a herbicide or an insecticide, particularly for the purpose of
killing weeds
and the like. Such an example is disclosed in US Patent No 4,309,842 in which
a
portable hand-held herbicide and insecticide applicator comprises a tube 12
which acts
as a handle and connected at one end of the handle is a pair of hollow prong
sections.
The prong sections together with the handle 12 form a liquid reservoir conduit
for the
pesticide or herbicide and extending between the ends of the prong sections is
an
absorptive rope mop which is saturated with the liquid pesticide or herbicide.
The user
then drags the device over weeds and the like such that the saturated rope mop
comes
into contact with the weeds and thereby eventually kills the weeds.
Other devices include sprayer systems that have a reservoir and use an
electric
motor, such as is disclosed in US Patent No 6,109,548. This sprayer system
reduces
the need to manually create pressure within a portable spray unit. A valve
stem within
the reservoir may be utilised by a user to connect a conventional air tank
thereto for
inserting high amounts of air pressure directly into the reservoir without
requiring the
use of a manual or electric pump. Where a power switch is closed the electric
motor
operates the air compressor whenever the air pressure within the reservoir
drops below
a predetermined level. A manual pump may be utilised when the electric pump
fails or
a battery connected to the electric motor becomes discharged.
Other systems involve the atomisation of liquids, such as is disclosed in US
Patent No 4,356,528. This patent discloses an invention that utilises
electrostatic
spraying of liquid compositions, particularly over leaves of plants, by
supplying a
liquid to a spray orifice, which is preferably of capillary dimensions. The
spray orifice
preferably has a charged surface which is electrically conducting or semi-
conducting
and which is adjacent a field intensifying electrode, the arrangement being
such that the
liquid is drawn out primarily by electrostatic forces, atomised into
electrically charged
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particles and projected past the electrode. Thus the particles wrap around the
leaves of
the plants and coat both upper and lower surfaces of the leaves.
None of the above prior art systems provide a substantially low cost device
that
enables the discharge of a chemical formulation into surrounding atmosphere,
particularly for the purpose of a personal insect repellent or in situations
where a
portable small apparatus may be used in a room which periodically enables the
emanation or vapourization of the chemical formulation. The present invention
provides a device, such as in the form of a cartridge, that fits into a recess
of a portable
apparatus that enables such a periodic discharge of a chemical formulation. It
may be
refilled or replaced completely when all the chemical formulation has been
discharged.
There is a need for such an apparatus that is substantially low cost to run,
may be run
on batteries or mains power and last a substantial length of time without
having to
replace batteries or provide a new or refilled reservoir of the chemical
formulation.
The present invention has substantial advantages over the above mentioned
applicators and sprayers and conventional aerosol sprayers as there is no need
for the
user to physically operate the device as it may be left in an area, as a
portable unit or a
fixed unit depending on the power supply, to automatically enable discharge of
a
chemical vapour into a surrounding atmosphere.
Some patents disclose the use of a cartridge insertable into a heating unit
incorporating a wick in continuous contact with a chemical formulation.
Examples
include US patent numbers 5903710, 5976503 and 6123935. However in all these
patents the heater element is in direct contact with the wick which has the
disadvantage
of excessive wear on the wick requiring replacement of the wick, and therefore
the
whole unit, after a number of uses. Furthermore in US patent number 6123935
there is
no defined aperture through which vapourized chemical formulation is guided to
the
atmosphere. An end strip of the wick is exposed to the atmosphere from which
the
vapour escapes, leading to excessive formulation being used.
In US patent number 5945094, although a wick in contact with a chemical
formulation is not in direct contact with a heater, it has the disadvantage of
a separate
wick and cartridge, the wick requiring the removal of an impermeable membrane
to
expose the wet wick area to the atmosphere prior to use. Furthermore it is not
designed
to fit a range of existing heater devices in a releasably insertable manner.
Further problems that the present invention seeks to overcome include
providing an emanation device that is able to fit existing heater apparatus
and can
survive for lengthy periods at heater temperatures in excess of 130 degrees
Celsius,
survive prolonged contact with organic solvents and not stretch, warp or
creep.
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The present invention in a fiuther embodiment provides such a device that is
made from materials allowing a rigid laminated but flexible structure to
releasably fit a
wide range of existing heater devices. It also provides the advantages of
thermal
conduction via a part of the laminate structure for heat transfer to the wick.
By fitting
to existing heater devices, the present invention provides a cheaper option to
users
rather than having to buy a completely new device incorporating a heater unit.
Summary of the Invention
According to a first aspect of the invention there is provided a device for
enabling a chemical formulation to be vapourized into an atmosphere
comprising:
means for storing the chemical formulation;
wick means in continuous contact with the chemical formulation;
wick support means for supporting the wick means and having an aperture;
the wick means located within the wick support means;
means to locate the wick support means such that the aperture of the wick
support means is co-located with a heater means;
wherein the wick means is wet by the chemical formulation and upon contact
with the heater means vapourizes the chemical formulation through the aperture
of the
wick support means.
Preferably the wick support means is formed by a first portion and a second
portion affixable to the first portion. The wick means may be located between
the first
portion and the second portion of the wick support means. The aperture may be
located
in the first portion of the wick support means. The location means preferably
locates
each of the first portion and the second portion of the wick support means
such that the
aperture of the first portion of the wick support means is co-located with the
heater
means.Preferably the storage means is located on the second portion or the
first portion
of the wick support means.
Preferably the wick means is substantially elongate having a first portion in
continuous contact with the chemical formulation and a second portion in
contact with
the heater means. Preferably the heater means vapourizes the chemical
formulation in
the vicinity of the second portion of the wick means through the aperture of
the first
portion of the wick support means. Preferably the heater means is a
microheater
element and particularly an impedance means such as a resistor.
Preferably the second portion of the wick support means has an aperture co-
located with the heater means to enable the chemical formulation to vapourize
into the
atmosphere through the aperture of the second portion of the wick support
means.
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Preferably the heater means has one or more pulses applied thereto in repeated
fashion to provide heat in order to vapourize the chemical formulation.
Preferably the wick means has a resistance to flow of chemical formulation
from
the chemical formulation storage means sufficient to enable the second portion
of the
wick means to become wet after it has been dried by vapourization of the
chemical
formulation within a cycle of an applied pulse or pulses to the heater means.
Preferably the device is adapted to be received by portable apparatus having
the
heater means, where the heater means being supplied with power from a portable
power supply, such as batteries. Alternatively, the device may be adapted to
be
received by apparatus having heater means being supplied with power from a
fixed
power supply, such as from a mains supply.
Preferably the location means is a pair of indentations, one on each side of
the
wick support means, that act in an interference fit with corresponding
projections on
the apparatus, which when engaged provide an indication to a user that the
device is
correctly located with respect to the apparatus. Preferably a tactile
indication is
provided to the user that the device is correctly located. Alternatively, the
location
means may be a pair of projections, one on each side of the wick support
means, that
act in an interference fit with corresponding indentations on the apparatus,
which when
engaged provide an indication to a user that the device is correctly located
with respect
to the apparatus.
According to a second aspect of the invention there is provided a device for
enabling a chemical formulation to be vapourized into an atmosphere
comprising:
means for storing the chemical formulation;
wick means in continuous contact with the chemical formulation;
wick support means for supporting the wick means and in contact with the wick
means, the wick support means having an aperture;
wherein the wick means is wet by the chemical formulation and, upon
application of heat from a heater means to the wick support means indirectly
heats the
wet wick means and thereby vapourizes the chemical formulation into the
atmosphere
through an exposed portion of the wick means and the aperture of the wick
support
means;
wherein further the device is releasably insertable into a heater unit having
the
heater means.
Preferably the exposed portion of the wick means is one end or one edge of the
wick means.
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According to a third aspect of the invention of the invention there is
provided a
device for enabling a chemical formulation to be vapourised into the
atmosphere and
releasably insertable into a heating unit, the device comprising:
means for storing the chemical formulation;
wick means for contacting the chemical formulation;
a housing enclosing a portion of the wick means adapted to engage and retain
the device in the heater unit, the heater unit having a heater means; and
wick support means in contact with the wick means and proximal to the heater
means when the device is inserted into the heater unit;
wherein the wick means is wet by the chemical formulation and is heated
indirectly by the wick support means to vapourize the chemical formulation
through an
aperture of the housing into the atmosphere.
According to a fourth aspect of the invention there is provided a device for
enabling a chemical formulation to be vapourized into the atmosphere
comprising:
a substrate;
means for storing the chemical formulation;
wick means for contacting the chemical formulation;
a housing enclosing a portion of the wick means;
the wick means, housing and storage means in contact with the substrate and
the
wick means extending between the housing and the storage means;
wherein the device is releasably insertable into a heater unit having a heater
means whereby the substrate is heated by the heater means and thereafter the
wick
means, wet by the chemical formulation, is heated to vapourize the chemical
formulation through an aperture in the housing into the atmosphere.
According to a fifth aspect of the invention there is provided a method of
constructing a device for enabling a chemical formulation to be vapourized
into the
atmosphere, the method comprising the steps of
forming a substrate comprising a first layer made of a first material;
forming a storage means for the chemical formulation and made from a second
material;
forming a housing made from the second material;
placing a wick means on the substrate; and
bonding the storage means and the housing to the substrate such that the wick
means is partially enclosed by the housing and extends into the storage means
to enable
contact with the chemical formulation.
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According to a sixth aspect of the invention there is provided a device for
enabling a chemical formulation to be vapourized into the atmosphere
comprising:
means for storing the chemical formulation;
wick means for contacting the chemical formulation;
wick support means in contact with the wick means and proximal to a heater
means;
such that when the chemical formulation is not in direct contact with the wick
.
means, due to the orientation of the heater means, the chemical formulation
moves
along a side of the storage means by capillary action until the chemical
formulation
reaches the wick means in contact with the storage means, thereby wetting the
wick
means;
whereupon the wick means is heated indirectly by the wick support means to
vapourize the chemical formulation into the atmosphere.
According to a seventh aspect of the invention there is provided a device for
enabling a chemical formulation to be vapourized into the atmosphere
comprising:
means for storing the chemical formulation;
wick means for contacting the chemical formulation;
wick support means in contact with the wick means and proximal to a heater
means;
such that the wick means extends along an edge joining the storage means and
the wick support means whereby the chemical formulation moves along the wick
means by capillary action until the chemical formulation reaches an area of
the wick
means that is heated indirectly by the wick support means to vapourize the
chemical
formulation into the atmosphere regardless of the orientation of the device.
Brief Description of the Drawings
Preferred embodiments of the invention will hereinafter be described, by way
of
example only, with reference to the accompanying drawings wherein:
Figure 1 illustrates a schematic view of separated components of a device
according to a first embodiment of the present invention;
Figure 2 is a top view of the device of Figure 1 shown fitted in an engaged
position;
Figure 3 is a side sectional view taken through the device of Figure l;
Figure 4 is a schematic view of a second embodiment of the device;
Figure 5 is a schematic view of a third embodiment of the device;
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Figure 6 is a side view of a fourth embodiment of the device adapted to fit a
heater unit;
Figure 7 is a perspective view from above of the embodiment of Figure 6 shown
separated from a heater unit which the device is adapted to engage;
Figure 8 is a perspective view from above of the device of Figure 6 shown
fitted
to the heater unit;
Figure 9 is a side view of the device fitted to the heater unit in Figure 8
with a
portion of the heater unit removed for clarity; and
Figure 10 is an enlarged view of the joining of a shell of the chemical
formulation storage means to a substrate.
Detailed Description of the Preferred Embodiments
With reference to Figure 1 there is shown a device divided into its respective
components, that enables a chemical formulation, such as an insecticide or a
fragrance,
to be delivered to a particular site via a wicking arrangement. Although the
device
shown in Figure 1 includes a first portion and second portion affixable to one
another,
it is to be noted that an alternative singular construction (one piece) for a
wick support
means may be used, such as a container made by an injection moulding process.
Specifically there is shown a first portion 1, which is substantially planar
and formed of
a suitable material, such as PET (polyethylene terephthalate). The first
portion 1 has. a
pair of indentations or notches 12 for the purposes of correctly locating the
device and
more particularly to locate an aperture 13 and aperture 7 over a heater means
in the
form of a microheater element 10 (see Figure 3). Each of the notches 12 are
designed
to interact with a corresponding pair of projections (or lugs) 15 formed in a
housing
into which this device fits in such a manner that the interaction between the
lugs and
the notches are an interference fit. This provides an indication to the user,
in a tactile
manner, that the devices are correctly engaged in the corresponding housing.
A second portion or top portion S is similarly made from PET and preferably
has formed therein a blister or indentation 6 which forms a reservoir for
housing the
chemical formulation. The portion 5 similarly has an aperture 7 and
indentations or
notches 16 designed to interact with corresponding projections or lugs 17, in
a similar
interference fit to the notches and lugs associated with the base portion or
first portion
1. Both.the portions 1 and 5 are designed to be joined or sealed together by
suitable
bonding means such as at portions 8 shown in Figures 2 and 3. Also shown in
Figure 1
is a wick 4 that has a portion therein located within the body of the
reservoir 6 housing
the chemical formulation and a portion co-located between the apertures 13 and
7 of
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the first portion 1 and second portion 5 respectively. Thus the wick 4 has one
end
portion 18, with reference to Figures 2 and 3, which is immersed,
particularly, in a
formulation such that the solid-liquid-vapour contact angle for the
formulation, wick
and air is 0°, and such that the wick 4 is completely wet out by the
formulation, and a
second end portion 19 that is in communication with the apertures 13 and 7 and
a
heater means 10. Preferably, the heater means 10 is a microheater element,
such as a
surface mount resistor. Preferably the wick is a thin flat absorbent material
that is
capable of wicking the active ingredient solution from the reservoir 6 to the
microheater element 10. It provides a sufficiently low lateral resistance to
fluid flow
such that the dried area of the wick 4 in the vicinity of the portion 19 over
the
microheater element 10 is re-wet by the formulation in a time that is shorter
than the
pulse repetition cycle which delivers pulses to the microheater element 10.
Such a
pulse delivery arrangement is disclosed in a co-pending British patent
application
number 0316381.3 to the same applicant. The wick 4 preferably has a
sufficiently low
transverse resistance to fluid flow such that the active ingredient held in
the wick 4 can
emanate as vapour from the top surface of the wick 4 through aperture 7 by
migration
through the wick in accordance with the timing of the applied pulses to the
microheater
element 10. Thus the portion 19 of the wick must be able to be wet easily to
enable
sufficient vapour to be dispersed into the atmosphere by the application of a
pulse or
series of pulses to the microheater element 10 and be thereby replaced within
the time
of the arnval of the next pulse that supplies current to the microheater
element 10.
The wick 4 must also be sufficiently thin so that the top surface of the wick
4
can be heated sufficiently by the microheater element 10 in contact with the
opposite or
bottom surface of the wick 4. It generally is made of material that can
withstand high
temperatures generated by the microheater element 10 without disintegrating or
decomposing. Furthermore the wick 4 is made of a material having sufficient
thermal
insulation such that thermal energy transferred from the microheater element
10 heats a
small part of the wick 4 to a high temperature in order to sufficiently
vapourize the
chemical formulation. Suitable materials that the wick may be made from
include fine
papers such as butcher's paper (80 microns thick), cigarette paper (30 microns
thick),
or fine silk or cotton cloth (less than or equal to 100 microns in thickness)
in order to
achieve a sufficiently high efficiency (mg/J) for long battery life. The
arrangement that
supplies pulses to the microheater element 10 has power provided by a series
of
batteries.
The apertures 13 and 7 are primarily designed, as is clearly shown in Figure
3,
to be co-located over the microheater element 10 whereby the wick 4 which is
in
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contact with the microheater element 10 is able to disperse the active
ingredient of the
chemical formulation through the apertures 13 and 7 into the surrounding
atmosphere.
As is shown in this figure, the sealing regions 8 in the top and bottom
portions l and 5
are joined to each other directly to form an impermeable seal. Alternatively
the top and
bottom surfaces of the wick 4 may be joined to the respective surfaces of the
first
portion 1 and second portion 5.
The container forming the reservoir 6 for the chemical formulation preferably
holds a volume of active ingredient of chemical formulation that allows
suitable
duration of performance, preferably one to two millilitres that will last for
a few weeks
to a month. It is to be understood that other volume magnitudes of active
ingredients of
the chemical formulation are possible depending on the particular
circumstances. For
example, a lower limit of volume may be as low as 20 microlitres as a
consequence of
the potency or concentration of the active ingredient used. The end portion of
the wick
18 and a substantial portion of the wick 4 is in fact in contact with the
chemical
formulation in the reservoir 6 at all times and in all orientations. At the
other end 19 of
the wick 4 it is exposed to the atmosphere through the respective apertures 13
and 7
and is in contact with the microheater element 10 that allows the emanation of
the
chemical formulation into the surrounding atmosphere from either or both the
surfaces
of the wick 4. It is noted at a portion 20 of the reservoir 6 the first and
second portions
1 and 5 are bonded but still allow protrusion of the wick 4 to the atmosphere.
The
overall device, including the first portion 1 and second portion 5 holds the
wick 4 with
sufficient rigidity so that the exposed wick portions can be located with
precision onto
the microheater element 10. The form factor of the device must engage with the
mounting points, that is through the interference fit between the lugs and
notches, such
that the wick 4 is correctly located in relation to the microheater element
10. Tactile
feedback is provided to the user when the device is correctly engaged within a
respective housing that may be a bump, as an example, to indicate that it is
correctly
fitted. The reservoir 6 is preferably transparent or translucent so that the
user can see
how much chemical formulation is remaining and replace the reservoir 6 when
empty.
The particular reservoir 6 may be refilled or optionally the whole device with
a new
reservoir may be used and fitted into the apparatus housing the microheater
element 10
and a power management circuit in accordance with co-pending British patent
application number 0316381.3 to the same applicant.
Shown in Figure 4 is another embodiment of the invention, wherein as with the
embodiments shown in Figures 1 to 3, the wick 4 is located between portions l
and 5.
The device in Figure 4 has no indentations adapted to interference fit with
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corresponding projections but may be inserted into a receptacle which is
heated by a
heating device. Only the aperture 7 existing in the second or top portion 5
exists which
lies above end 19 of the wick 4. However, the aperture 7 may exist in only the
first
portion 1 in contact with end 19 of the wick 4. The other end 18 of wick 4 is
in
continuous contact with the chemical formulation in reservoir 6. The wick 4 is
thereby
wet by the chemical formulation such that the chemical formulation travels
along the
wick 4 through the sealed region 21 between the reservoir 6 and the top
portion 5
towards the end 19 whereby the region of the device enclosed by the dotted
line 22 is
heated such that the chemical formulation vapourizes and emanates through
aperture 7
into the surrounding atmosphere. Thus the reservoir 6 containing the chemical
formulation is not heated by the particular heating device.
With reference to Figure 5 there is shown a further embodiment in which the
wick 4 is mounted transversely across the longitudinal axis of the reservoir
6, top
portion 5 and bottom portion 1. The edges 23 and 24 of the wick 4 are
respectively
mounted flush with corresponding edges 25 and 26 of the top portion 5 (and
bottom
portion 1). However, the edges 23 and 24 remain exposed to the atmosphere
whereas
the remainder of the edges 25 and 26 of the top portion S remain sealed to the
corresponding lower portion 1 of the device. The portions of the wick 4
exterior to the
reservoir 6 apart from the edges 23 and 24 are also sealed so that no chemical
formulation emanates from these areas but only through edges 23 and 24. Thus
when
heat is applied to the region enclosed by the dotted line 27, the chemical
formulation in
reservoir 6 having wet the wick 4 and subsequently moved to the edges 23 and
24,
vapourizes to the surrounding atmosphere through edges 23 and 24 of the wick
4.
In a further embodiment, the wick 4 may be wholly enclosed or surrounded by
the chemical formulation in the reservoir but defining a boundary or partition
between
the reservoir and the wick 4. The wick 4 may be supported by a wick support
having
such a boundary or partition preferably to keep the wick substantially rigid.
Such a
support and partition may be made from suitable materials such as plastic or
PET. At
one or more locations along the partition or boundary, the wick 4 is not
sealed from the
reservoir 6. Thus at those particular locations the wick 4 is wet by the
chemical
formulation. An aperture may be located on one or both sides of the device in
communication with the wick 4 such that on heating the whole device (in the
region of
the wick 4 and the reservoir 6) the chemical formulation emanates through the
aperture
and is vapourized to the surrounding atmosphere. One particular arrangement of
this
embodiment is a wick in the shape of a star where the points of the star are
in contact
with the chemical formulation and define a substantially circular boundary
between the
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star-shaped wick and the reservoir of the chemical formulation. At the centre
of the
star is an aperture through which the chemical formulation is vapourized upon
application of heat.
Thus in use the device in accordance with the embodiment described with
reference to Figures 1 to 3, having a reservoir full of chemical formulation
such as
insecticide or a fragrance, is inserted into an opening of a corresponding
apparatus,
which may be portable or fixed depending on the power supply to the heater
means,
such that the user has tactile feedback via the interference fit between the
notches 12
and 16 and the lugs 15 and 17 respectively. This indicates to the user that
the apertures
7 and 13 are correctly located in substantially the same plane above the
microheater
element 10. The apparatus is then free for use by the user in any particular
application
whether as a personal device, or to be left in a room for example into which
the
chemical formulation is vapourized.
Using the device in accordance with the embodiments of Figures 4 and 5 or in
relation to the embodiment using the star-shaped wick, the device may be
inserted into
a receptacle having a heating means and be heated at various intervals until
the
chemical formulation in the reservoir 6 is fully depleted.
With reference to Figures 6 to 9 there is shown a further embodiment of the
invention. Specifically device 30 includes a reservoir 32 housing a chemical
formulation to be vapourized, housing 34 and a support means or substrate 36.
The
device 30 is adapted to be releasably detachable from a heater unit such as
that shown
at 38 in Figure 7. A wick 40 is in contact with an upper layer 42 of the
support 36 and
extends within the housing 34 and protrudes into the reservoir 32. A pair of
depressions 44 and 46 formed as part of the moulding of the housing 34 are
adapted to
keep pressure on the wick 40 so that it remains in contact with the layer 42
of the
support 36. An aperture 48 protrudes through the top portion of the housing 34
to
enable vapour resulting from the heating of the chemical formulation in the
wet wick
40 into the surrounding atmosphere. The support 36 also comprises a lower
layer 50.
The heater unit 38 is installed in a suitable electrical socket via the
terminals 52
and 54. Either after the heater unit 38 is inserted into the electrical socket
or prior to its
insertion, the device or cartridge 30 is fitted to the heater unit 38 such
that it appears as
in Figure 8 whereby layer 50 of the support 36 is either in direct contact
with an
existing heater 56 in the heater unit 38 or separated from the heater plate 56
by a small
air gap so that when the heater unit 38 is switched on, the support 36 is
heated by
convection or by direct contact with the heater plate 56. The wick 40 which is
wet by
the chemical formulation in reservoir 32 by capillary action is in turn heated
by its
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contact with support 36 whereby firstly layer 50 is heated and then layer 42
is heated
prior to the wick being heated. Once a nominal temperature, such as
130°C to 140°C is
reached, the chemical formulation is vapourized and dispersed into the
atmosphere
through aperture 48 and through the various apertures 58, 60 and 62 of the
heater unit
38. Projecting downwardly from elements interspersing the apertures 60 is a
flange 64
seen more clearly in Figure 9 that is designed to provide extra pressure on
any portion
of the housing 34 in order to keep the wick 40 in contact with the support 36.
Specifically the flange 64 may contact any part of the upper surface of the
housing 34
or be situated in one of the depressions 44 or 46. This is so that it can be
adaptable to
provide pressure to any inserted cartridge 30 that has a variation in the
number and
position of depressions or apertures. It also assists in providing additional
inertia
against the cartridge from coming out of the heater unit 38.
The construction of the device 30 has been chosen from materials designed to
withstand temperatures in excess of 130°C, be robust enough to
withstand contact with
organic solvents and be resistant to stretching, warping and creeping. In
addition it
must be resilient and flexible enough to provide easy insertion into and
removal from a
heater unit. A particular material chosen to make the bottom layer 50 of
support 36 is
crystalline PET (CPET) which is not usually selected for its efficient heat
transfer
properties. The thin layer 42 which is sealed or adhered to layer 50 is made
from
amorphous PET (APET). Both the reservoir 32 and the housing 34 are premoulded,
including the depressions 44 and 46 and the aperture 48 and are placed on top
of the
wick 40 which is akeady in position abutting layer 42. The reservoir 32 is
then filled
with the chemical formulation and both the housing 34 and reservoir 32, which
are
preferably made from APET, are thermally welded to the layer 42 made also from
APET. The fact that the layer 42, reservoir 32 and housing 34 are all made
from the
same material assists in the welding and bonding process. An additional strip
of APET
material 66 may be thermally welded between the reservoir 32 and housing 34 as
shown transversely across the device 30 in Figure 7. The seal around the
housing 34
and reservoir 30 such that it is bonded to the support 36 adds rigidity to the
overall
device 30 to enable it to properly engage the heating unit 38 and together
with the
support 36 provides the physical support for the wick 40. A particular
advantage with
the structure is that it provides a consistent release rate of the active
chemical
formulation in reservoir 32 through aperture 48.
A number of materials have been tested for the base support 36 to withstand
temperatures in excess of 130°C, be robust enough to withstand contact
with organic
solvents and be resistant to stretching, warping and creeping. Further
requirements
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CA 02534594 2006-O1-17
WO 2005/011373 PCT/GB2004/003186
were that the materials be capable of welding to other plastic parts, are
cheap and
available in commercial volumes. Most conventional thermoplastics, such as
polyethylene, polypropylene and polymethylmethacrylate, become very soft at
the
heater temperatures and are completely unsuitable. The thermoplastics deform,
melt
and/or adhere to the heater. Polycarbonate was tested and although it is a
high
temperature thermoformable material, it was found that thermoforming made the
polycarbonate vulnerable to solvent attack. The thermoformed portions
exhibited
severe stress crazing in contact with a solvent.
Other known materials include KAPTON~' (a registered trade mark in the name
E I Du Pont De Nemours and Company) which is a polyamide material and ULTEM~'
(a registered trade mark in the name General Electric Company), a
polyetherimide
material. However these materials are too expensive to produce.
A relatively cheap material is biaxially oriented APET (bioPET) which is an
APET film that has been stretched firstly in one direction (eg. x axis) and
then in
another direction perpendicular to the first direction (eg. y axis). This
induces a high
degree of polymer chain alignment and produces a very robust high temperature
material. It is suitable for making oven bags. However it is only available in
very thin
films and these grades have no structural strength. Lamination of bioPET to a
stiff card
was attempted, however the resulting material was essentially a plastic coated
cardboard that, although provided the required temperature and solvent
resistance and
weldability, the base of the material was not rigid enough. The heated area
was twisted
and deformed and the thermoformed upper portion was stressed.
The most suitable material tested for layer 50 was CPET, which essentially is
APET into which is dispersed a finely powdered nucleating agent, such as
crystalline
polypropylene, together with a pigment depending on the grade. The layer 42 of
APET
is then laminated or bonded to one surface of the layer 50. The reason for
this
particular construction is that while the bulk of the plastic is amorphous, it
is readily
thermoformed but during thermoforming crystallization occurs rapidly due to
the
nature of the nucleating agent. The thermoformed portion is thus CPET with
superior
mechanical properties. The APET layer 42 remains untransformed and can be
bonded
or heat sealed to a further APET layer such as one incorporating the housing
34 and
reservoir 32. Grades of CPET material tested include 750 micron.
The initial layer of APET that is thermoformed to produce the reservoir 32 and
housing 34 has less stringent requirements. The temperature used for
thermoforming is
much lower than that used for support 36 as the upper portion containing the
reservoir
32 and housing 34 is not in direct contact with heater plate 56.
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WO 2005/011373 PCT/GB2004/003186
When the amount of chemical formulation remaining in the reservoir 32 is very
low and the device 30 is oriented as a result of the orientation of the
electrical socket or
heater unit 38, the welding of the upper shell 70 of the reservoir 32 to the
layer 42 is
such that the residual amount of chemical formulation 68 rises by virtue of
capillary
action. Thus near the join or edge 72 of the shell 70 to layer 42 the gap 74
created by
such a join allows the residual chemical formulation 68 to travel up the sides
of the
reservoir 32, effectively normal to the page of Figure 10. This provides a
substantial
advantage in that the wick 40 need not protrude fully into the reservoir 32.
By being in
contact with an upper surface 76 of the reservoir 32 adjacent where it joins
the layer 42
means that the advancing residual chemical formulation 68 may reach the end of
the
wick 40 and thereby provide additional chemical formulation to be vapourized.
Alternatively, the wick 40 may extend into the reservoir 32 specifically in
contact with the edge or join 72 or otherwise positioned in the gap 74,
preferably along
the entire periphery of the join 72. This enables a capillary action through
the wick 40
to take place when the amount of formulation in the reservoir 32 is low and
regardless
of the orientation of the device 30 or heating unit 38 receiving the device
30.
With reference to Figure 9 it is seen that the support 36 is flexible enough
to
bend at a location 80 in order to fit within the heater unit 38 and therefore
make contact
or be in close vicinity of the heating mat 56. Alternatively a step may be
provided in
the support 36 between the reservoir 32 and the housing 34 to facilitate easy
insertion
and removal of the device 30 to the heater unit 38. Alternatively there may be
a step
down or step up provided inside the heater unit 38 cooperating with the step
in the
support 36.
The housing 34 of the device 30 is specifically shaped and moulded to fit and
be
retained by the heater unit 38. The flange 64 also additionally assists in
retaining the
housing 34 and pressing the wick 40 against the layer 42. The step down
arrangement
from the reservoir 32 in the layer 36 provides a flexible strip that can be
fitted to an
increased range of existing heating units. . .
The wick may be made from a suitable material as previously mentioned in
relation to the first embodiment and generally the refill or chemical
formulation in
reservoir 32 will last between seven and fourteen nights in a single room.
Once a
cartridge or device 30 has been expelled of its chemical formulation it would
be a
simple matter of inserting a refill or new cartridge into the heater unit 38
to set off a
new seven to fourteen night period of use. It is noted that the reservoir 32
protrudes
from the heater unit 38 so that the user can. easily identify how much
chemical
formulation is left.
14
