Note: Descriptions are shown in the official language in which they were submitted.
CA 02602880 2007-09-14
AEROSOL DISPENSER ASSEMBLY HAVING VOC-FREE
PROPELLANI' AND DISPENSING MECHANISM THEREFOR
Cross-Reference to Related Application
[0001] This application is a non-provisional claiming priority under 35 USC
119(e) to
provisional patent application no. 60/825,601, filed on September 14, 2006.
Field of the Disclosure
[0002] Improved aerosol dispenser systems are disclosed. More specifically,
aerosol
dispenser systems using a compressed gas propellant to expel a liquid product
from a
container are disclosed wherein the compressed gas propellant is innocuous,
VOC-free,
soluble in the liquid product at low temperatures and less soluble in the
liquid product at
higher temperatures. Still more specifically, the nozzle is equipped with a
heating element to
decrease the solubility of compressed gas propellant in the liquid product as
it leaves the
swirl chamber and passes through the exit orifice thereby causing cavitation
in the exit stream
leading to the formation of unstable product ligaments that form tiny
droplets. As a result, an
effective aerosol system is provided without depending upon conventional
hydrocarbon-
based propellants.
Background of the Disclosure
[0003] Aerosol dispensers have been commonly used to dispense personal,
household,
industrial, and medical products, and provide a low cost, easy to use method
of dispensing
products that are best used as an airborne mist or as a thin coating on
surfaces. Typically,
aerosol dispensers include a container, which holds a liquid product to be
dispensed, such as
soap, insecticide, paint, deodorant, disinfectant, air freshener, or the like.
A propellant is
us--d to discharge the liquid product from the container. The propellant is
pressurized and
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provides a force to expel the liquid product from the container when a user
actuates the
aerosol dispenser by pressing an actuator button or trigger.
[0004] The two main types of propellants used in aerosol dispensers today
include (1)
liquefied gas propellants, such as hydrocarbon and hydrofluorocarbon (HFC)
propellants, and
(2) compressed gas propellants, such as compressed carbon dioxide or nitrogen.
To a lesser
extent, chlorofluorocarbon propellants (CFCs) have been used. The use of CFCs,
however,
has essentially been phased out due to the potentially harmful effects of CFCs
on the
environment.
[0005] In an aerosol dispenser using a liquefied gas-type propellant, the
container is loaded
with the liquid product and propellant to a pressure approximately equal to or
slightly greater
than the vapor pressure of the propellant. After being filled, the container
still has a certain
amount of space that is not occupied by liquid. This space is referred to as
the "head space."
Since the container is pressurized to approximately the vapor pressure of the
propellant, some
of the propellant is dissolved or emulsified in the liquid product. The
remainder of the
propellant remains in the vapor phase and fills the head space. As the product
is dispensed,
the pressure in the container remains approximately constant as liquid
propellant moves from
the liquid phase to the vapor phase thereby replenishing discharged propellant
vapor.
[0006] In contrast, compressed gas propellants largely remain in the vapor
phase. As a
result, the pressure within a compressed gas aerosol dispenser assembly
decreases as the
vapor is dispensed.
[0007] While this aspect of using compressed gas propellants is
disadvantageous, the use
of compressed gas propellants may gain favor in the future as they typically
do not contain
volatile organic compounds (VOCs). In contrast, most liquefied gas-type
propellants are
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hydrocarbon-based and contain volatile organic compounds (VOCs) thereby making
their use
subject to various regulations and therefore disadvantageous.
[0008] One way to reduce the VOC content in liquefied gas-type aerosols is to
reduce the
amount of the propellant used to dispense the liquid product without adversely
affecting the
product performance. Specifically, before the techniques of commonly assigned
U.S. Patent
No. 7,014,127 to Valpey et al. (incorporated herein.by reference), reducing
the propellant
content in the aerosol air freshener resulted in excessive product remaining
in the container
after the propellant is depleted (product retention), an increase in the size
of particles of the
dispensed product (increased'particle size), and a reduction in spray rate,
particularly as the
container nears depletion. Techniques of the '127 patent provide a way to
minimize the
particle size of a dispensed product in order to maximize the dispersion of
the particles in the
air and to prevent the particles from "raining" or "falling out" of the air,
while reducing the
amount of liquefied gas-type propellant to 25% by weight or less. By reducing
the amount of
liquefied gas-type propellant inthe container, the VOC is reduced.
[0009] The techniques of the '127 patent involve maintaining a Clark/Valpey
(CV) value
for the system at 25 or less, where CV=2.5(D-32)+l0JQ-1.1 J+2.6R, where D is
the average
diameter in micrometers of particles dispensed during the first forty seconds
of spray of the
assembly, Q is the average spray rate in grams/second during the first forty
seconds of spray
of the assembly, and R is the amount of the product remaining in the container
at the end of
ihe life of the assembly expressed as a percentage of the initial fill weight.
[0010] One method of reducing the particle size of a dispensed liquid product
in liquefied
gas propellant systems is disclosed in U.S. Patent No. 3,583,642 to Crowell et
al. which is
incorporated herein by reference. The '642 patent discloses various spray
heads that
incorporate a "breakup bar" for inducing turbulence in a product/propellant
mixture prior to
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the mixture being discharged from the nozzle outlet. Such turbulence
contributes to reducing
the size of the mixture particles discharged from the spray head. While the
'642 patent
discloses one-piece spray heads with breakup bars, breakup bars have been
incorporated into
nozzle inserts for spray heads.
[0011] To provide an alternative to liquefied gas-type propellants and to
eliminate any
VOCs attributable to the propellant of an aerosol product, improved aerosol
dispensing
systems incorporating VOC-free compressed gas propellants are needed. However,
to satisfy
consumers, the employment of VOC-free compressed gas propellants should result
in aerosol
droplets with physical properties that are equivalent to or better than
droplets produced by
liquefied gas-type propellants.
[0012] Specifically, a Sauter mean diameter is defined as the diameter of a
droplet having
the same volume/surface ratio as the entire spray. Conventional liquefied gas~-
type aerosol
systems provide Sauter mean diameters at or below 35 m. The same performance
or better
is needed for some compressed gas propellant systems.
[0013] The small droplet size of conventional aerosol systems is obtained by
exploiting the
phenomena of cavitation within the area leading to the exit nozzle. Cavitation
involves the
formation of bubbles in the exit stream that form thin ligaments of liquids
which grow into
primary droplets. A Weber number for a droplet is a ratio of inertia forces to
surface tension
force. If the Weber number exceeds a critical value, the droplet can overcome
the effects of
surface tension and break up into smaller droplets, which is preferred. Thus,
to effectively
compete with liquefied gas-type systems, a compressed gas system is needed
that provides
good cavitation and that produces droplets with high Weber numbers.
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Summary of the Disclosure
[0014] An aerosol dispenser assembly is provided that comprises a container
holding a
liquid product and a compressed gas propellant for propelling the liquid
product from the
container. The compressed gas propellant comprises a gas that is soluble in
the liquid
product at room temperature and that has a reduced solubility in the liquid
product at
temperatures exceeding room temperature. The assembly further comprises a
valve attached
to the container for selectively dispensing the liquid product from the
container as a mist.
The valve comprises an actuator cap with an insert which comprises an exit
orifice and a
heater that at least partially surrounds the exit orifice.
[0015] The heater may be disposed in the insert. In contrast, the heater may
be embedded
in the actuator cap and surround or substantially surround the insert. As yet
another
alternative, the insert may be metallic and may be heated by resistance or
induction heating.
Still another option would be to fabricate a unitary actuator cap without a
separate insert with
the heater being built_into the actuator cap and surrounding the exit orifice.
In addition to
resistance or induction heating, additional heating techniques may be employed
such as radio
frequency (RF).
[0016] The container may comprise an interior surface coated with a polymeric
coating to
prevent or retard migration of compressed gas propellant through the container
wall. The
compressed gas propellant may comprise carbon dioxide, nitrogen or a
combination of
carbon dioxide and nitrogen. In any event, the compressed gas propellant is
soluble in the
liquid product at low temperatures and less soluble or relatively insoluble at
higher
temperatures.
[0017] The actuator cap may comprise a post disposed downstream of a primary
passage in
the actuator cap and upstr;::am of the outlet. The post mateably receives the
insert which
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comprises a bore that serves as an exit orifice. For compressed gas aerosol
systems,
performances may be enhanced by increasing turbulence. One way of providing
turbulence
is with a swirl chamber. The swirl chamber may be formed by the insert and
post. The swirl
chamber may be disposed between the primary passage and the exit orifice.
[0018] In a refinement, the heater at least partially surrounds the swirl
chamber.
[0019] Turbulence may also be increased by providing a break-up bar. The
insert may
include the break-up bar. Inserts without break-up bars are also suitable and
within the scope
of this disclosure.
[0020] In another refinement, the compressed gas propellant comprises carbon
dioxide
which is soluble in the liquid product at room temperature and wherein the
heater heats the
liquid product and dissolved carbon dioxide in the swirl chamber to produce
bubbles of
carbon dioxide as the solubility of carbon dioxide in the liquid product is
reduced by the
heating. The production of carbon dioxide bubbles (i.e., cavitation) in the
exit stream results
in the formation of unstable ligaments of liquid product in the exit stream.
These unstable
ligaments are then converted into droplets in the exit stream. Preferably, the
pressure and
exit stream is sufficient to result in further atomization of_the primary
droplets into smaller
droplets.
[0021] In a refinement, the dispensed mist has a particle size of less than 35
m over at
least 75% of the life of the dispenser assembly.
[0022] In a refinement, the dispenser assembly is capable of dispensing over
90% by
weight of the liquid product from the container.
[0023] In a refinement, the heater is a positive temperature coefficient (PTC)
heater.
[0024] In a refinement, the assembly further comprises a battery for powering
the heater.
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[0025] In a refinement, a method is disclosed for providing an aerosol mist
using a
compressed gas propellant. The method comprises providing a pressurized
container holding
a liquid product and a compressed gas propellant within a container body. The
compressed
gas propellant comprises a gas that is soluble in the liquid product at room
temperature and
that has a reduced solubility in the liquid product at temperatures exceeding
room
temperature. The container further comprises a valve attached to the container
for selectively
dispensing an exit stream of liquid product and compressed gas propellant
through an exit
orifice and a heater near the exit orifice. The method further comprises
activating the valve
to dispense liquid product and propellant through the exit orifice and heating
the exit orifice
to reduce the solubility of the compressed gas propellant in the liquid
product in the exit
stream. The method further comprises generating cavitation in the exit stream
by forming
btibbles of gas propellant and ligaments of liquid product in the exit stream,
and converting
the ligaments into droplets of liquid product in the exit stream.
[0026] In a refinement, the droplets produced by the above method have a
Sauter mean
diameter of less than 35 m.
[0027] In a refinement, the method further comprises converting the droplets
to smaller
droplets through secondary atomization in the exit stream.
[0028] In a refinement, the valve used in the above method comprises an
actuator cap
comprising a primary passage and exit orifice with a post disposed in the exit
orifice and
downstream of a primary passage. The post mateably receives an insert which
comprises a
bore providing communication between the primary passage and the exit orifice.
The insert
and post further defining a swirl chamber between the post and the bore.
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[0029] In a refinement, a Weber number for the droplets is sufficiently high
thereby
resulting in secondary atomization in the exit stream. For example, the
inventors have
identified a Weber number of 8 or above is sufficiently high for such a
purpose.
[0030] Another disclosed aerosol dispenser assembly comprises a container
holding a
liquid product and a compressed gas propellant comprising carbon dioxide for
propelling the
liquid product from t-he container. The carbon dioxide is soluble in the
liquid product at room
temperature with a reduced solubility in the liquid product at temperatures
exceeding room
temperature. The assembly further comprises a valve attached to the container
for selectively
dispensing the liquid product from the container as a mist. The valve
comprises an actuator
cap having an exit orifice and a heater that at least partially surrounds the
exit orifice. The
heater heats the liquid product and dissolved carbon dioxide in the exit
orifice to produce
bubbles of carbon dioxide and ligaments of liquid product inthe exit stream as
the solubility
of carbon dioxide in the liquid product is reduced by the heating and the
ligaments of liquid
product that are converted in the exit orifice into droplets having a mean
diameter of less than
35 pm.
[0031] In one aspect, the solubility of carbon dioxide in many liquid products
is exploited.
Specifically, carbon dioxide is soluble in numerous polar liquid products at
relatively low
temperatures, including room temperature. However, a heating of the liquid
product and
dissolved carbon dioxide results in the formation of bubbles of carbon
dioxide, resulting in
cavitation or the formation of unstable liquid product ligaments in the exit
stream. These
unstable ligaments are then converted into droplets having relatively small
Sauter mean
diameters of less than 35 m.
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[0032] Preferably, the droplets formed in the exit stream have a sufficiently
high Weber
number thereby enabling the droplets to be converted into smaller droplets in
the exit stream
through secondary atomization.
[0033] In accordance with one aspect of the disclosure, an aerosol dispenser
assembly is
provided comprising a container at least partially filled with a propellant; a
valve assembly
coupled to the container; and an actuator cap coupled to the valve assembly,
the actuator cap
comprising an exit orifice and a heater.
[0034] In accordance with another aspect of the disclosure, an aerosol
dispenser assembly
is provided comprising a non-corrosive container at least partially filled
with a propellant,
wherein the propellant is a highly soluble gas having a solubility that
decreases rapidly with
increase in temperature; a valve assembly coupled to the container; and an
actuator cap
coupled to the valve assembly for selectively dispensing droplets of a liquid
product, the
actuator cap comprising an exit orifice and a heater.
[0035] In accordance with another aspect of the disclosure, an aerosol
dispenser assembly
is provided comprising a non-corrosive container at least partially filled
with a propellant,
wherein the propellant is a highly soluble gas having a solubility that
decreases rapidly with
increase in temperature; a coating within an interior of the container,
wherein the coating is
non-permeable to the propellant; a valve assembly coupled to the container;
and an actuator
cap coupled to the valve assembly, the actuator cap comprising an exit orifice
and a PTC
heater.
[0036] In accordance with another aspect of the -disclosure, a method for
dispensing fine
droplets from a compressed gas aerosol system is provided comprising the steps
of providing
an aerosol system comprising a pressurized container at least partially filled
with a liquid
product and a propellant, wherein the propellant is a highly soluble gas
having a solubility
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that decreases rapidly with increase in temperature, the aerosol system
further comprising a
valve assembly, an actuator cap, an exit orifice and a heater; activating the
actuator cap and
the valve assembly and passing the liquid product and the propellant toward
the exit orifice;
instantaneously heating the liquid product and the propellant at the exit
orifice; and
dispensing the liquid product in the form of thin ligaments with sufficient
velocity.
[0037] Other advantages and features will be apparent from the following
detailed
description when read in conjunction with the attached drawings.
Brief Description of the Drawings
[0038] For a more complete understanding of the disclosed method-s and
apparatuses,
reference should be made to the embodiment illustrated in greater detail on
the accompanying
drawings, wherein:
[0039] FIG. I is a partial cross-sectional perspective view of an aerosol
dispenser assembly
made in accordance with this disclosure.
[0040] FIG. 2 is a partial front sectional view of an aerosol assembly made in
accordance
with this disclosure.
[0041] FIG. 3 is a front elevational view of an actuator cap made in
accordance with this
disclosure.
[0042] FIG. 4 is an enlarged partly sectional view of the actuator cap shown
in FIG. 3.
[0043] FIG. 5 is an exploded cross-sectional view of the actuator cap, stem
and insert
shown in FIGS. 3 and 4.
[0044] FIG. 6 is a front view of the insert shown in FIGS. 4 and 5.
[0045] FIG. 7 is a rear view of the insert shown in FIGS. 4-6.
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[0046] FIG. 8 is a cross-sectional view taken substantially along line 8-8 of
FIG. 7.
[0047] FIG. 9 is a partial cross-sectional view of yet another aerosol
dispenser assembly
made in accordance with this disclosure.
[0048] FIG. 10 is a cross-sectional view of the insert used in the aerosol
dispenser valve
shown in FIG. 9.
[0049] FIG. '11 is a rear view of the insert shown in FIG. 10.
[0050] FIG. 12A is a partial sectional view of the actuator cap shown in FIG.
1,
particularly illustrating the placement of a heater adjacent in the insert at
least partially
surrounding the swirl charnber.
[0051] FIG. 12B is a side sectional view of the insert shown in FIG. 12A.
[0052.] FIG. 13 is a side sectional view of an insert equipped with a break-up
bar.
[0053] FIG. 14 is another side sectional view of the insert shown in FIG. 13.
[0054] FIG. 15 is another side sectional v.iew of the insert shown in FIGS. 13-
14.
[0055] FIG. 16 is a front plan view of the insert shown in FIGS.13-15.
[0056] FIG. 17 is a rear plan view of the insert shown in FIGS. 13-16.
[0057] FIG. 18 is a front perspective view of the insert shown in FIGS. 13-17.
[0058] FIG. 19 is a rear perspective view of the insert shown in FIGS. 13-18.
[0059] It should be understood that the drawings are not to scale and that the
disclosed
embodiments are sometimes illustrated diagrammatically and in partial views.
In certain
instances, details which are not necessary for an understanding of the
disclosed methods and
apparatuses or which render other details difficult to perceive may have been
omitted. It
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CA 02602880 2007-09-14
should be understood, of course, that this disclosure is not limited to the
particular
embodiments illustrated herein.
Detailed Description of the Disclosure
[0060] As shown in FIGS. 1 and 2, an aerosol dispenser assembly 10 includes a
container
11 covered by a mounting cup 12. A mounting gasket 13 is disposed between an
upper rim
(not shown) of the container 11 and the underside of the mounting cup 12. A
valve assembly
14 is used to selectively release the contents from the container 1 I to the
atmosphere. The
valve assembly comprises a valve body 15 and a valve stem 16. The valve stem
16 includes
a lower end 16a that is mounted through a return spring 17. An actuator cap 8
is mounted on
top of the valve stem 16 and defines a primary passageway 19. The actuator cap
18 also
defines an exit orifice shown generally at 22 and which will be discussed in
greater detail
below.
[0061] The valve body 14 is affixed to the underside of the mounting cup 12 by
a friction
fit and the valve stem 16 extends through the friction cup 12. The actuator
cap 18 is
frictionally fitted onto the upwardly extending portion of the valve stem 16.
The lowerend
of the valve body 15 is connected to a dip tube 23. Gaskets may or may not be
required
between the valve body I5 and the mounting cup 12 and between the valve stem
16 and the
mounting cup 12, depending upon the materials used for each component.
Suitable materials
will be apparent to those skilled in the art that will permit a gasket-less
construction.
Similarly, gaskets or seals are typically not required between the actuator
cap 18 and the
upper portion of the valve stem 16.
[0062] While the dispenser assembly 10 of FIGS. 1-2 employs a vertical action-
type cap
18, it will be understood that other actuator cap designs may be used such as
an actuator
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button with an integral over cap, a trigger actuated assembly, a tilt action-
type actuator cap or
other designs.
[0063] In operation, when the actuator cap 18 is depressed, it forces the
valve stem 16 to
move downward thereby allowing liquid product to be dispensed. The propellant
forces the
liquid product up the dip tube 23 and into the valve body 15 via the orifice
or passageway 24.
From the valve body 15, the liquid product is propelled through the stem
orifices 26, out the
passageway 27 through the valve stem 16 and through the primary passageway 19
of the
actuator cap to the exit orifice 22. Preferably, two valve stem orifices 26
are employed
although a single valve stem orifice or up to four valve stem orifices may be
used. Multiple
valve stem orifices 26 provide greater flow and superior mixing of the
product.
[0064] The use of an insert and a post within the actuator cap 18 is not
specifically shown
in FIG. 1 but is illustrated in FIGS. 3-14 below. However, a heater 43 is
shown
schematically in FIG. 1. Typically, aerosol dispensers include a post-like
structure built into
the actuator cap and an insert that covers the post in the exit orifice. A
heater can be
employed in the insert or in the actuator cap around the insert to provide
heat to the swirl
chamber as described below. Also, the insert itself may be metallic for
induction or resistive
heating. One example of such construction is illustrated in FIGS. 3-8.
[0065] Specifically, referring to FIG. 3, an actuator cap 118 is disclosed
with a primary
passageway 119. Disposed within the passageway 119 is a post 131 that is
connected to or
formed integrally from the actuator cap 118. The post 131 mateably receives an
insert 132 as
illustrated in FIGS. 4-5. In the embodiment illustrated in FIGS. 3-5, the
actuator cap 118 fits
directly onto the valve stem 116 without the inclusion of a break-up bar (see
reference
numeral 21 in FIG. 1). Disposed between the insert 132 and the post 131 is a
small swirl
chamber shown at 133 in FIG. 4. Communication is provided to the swirl chamber
133
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through the connecting passage 134. Details regarding the construction of the
insert or
suitable inserts that may be used in accordance with this disclosure are
provided in FIGS. 6-8,
and 13.
[0066] A heater 143 is disposed within the insert 132 and surrounds the swirl
chamber 133
to heat the prospect/propellant mixture passing through the swirl chamber 133.
As discussed
below in connection with FIGS. 12-14, the heating generates bubbles of
propellant in the exit
stream, causing cavitation, the formation of unstable liquid product ligaments
and eventually,
small droplets of product having diameters of less than 35 m. Further, the
insert 132 may be
fabricated from metal so that the entire insert 132 serves as a-resistance
heater connected to
the electrical leads 144, 145.
[0067] Turning to FIGS. 6-8, the insert 132 is shown in greater detail. The
recess 133a
provides the space necessary for the swirl chamber 133 shown in FIG. 4. The
cylindrical
sidewall 135 includes a raised portion that results in a step 136 that engages
a catch 137 built
into the actuator cap 118 thereby enabling the insert 132 to be press-ft into
the actuator
button 118. The insert 132 has a front wall 138 and a discharge orifice 139.
Additional
details regarding the construction of the insert 132 and post 131 as shown in
FIGS. 3-8 can be
found in U.S. Patent No. 4,071,196.
[0068] The heating element 143 and electrical leads 144, 145 are shown in FIG.
8.
However, as noted above, the entire insert 132 may be fabricated from a high
resistance
metallic material and therefore the entire insert 132 may serve as a
resistance heater. The
entire insert 132 may also serve as an induction heating element.
[0069] Turning to FIGS. 9-12, a similar construction is shown whereby the
valve body 215
is mounted onto a dip tube 223 and beneath a valve stem 216. The actuator cap
218 also
includes a post 231 which mateably receives an insert 232 to provide a swirl
chamber 233
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therebetween as shown in FIG. 9. A stem orifice is shown at 226 and a return
spring at 217.
The mounting cup and gasket are shown at 212, 213, respectively.
[0070] Details of the insert 232 are provided in FIGS. 10-12. The insert 232
includes a
cylindrical wall 235 with a barb or catch shown at 236 for engaging a recess
disposed in the
actuator cap body 218. The discharge orifice as shown at 239 in the front wall
at 238. The
recess 233a provides ample space for a swirl chamber 233 (see FIG. 9). Like
the insert 132
as shown in FIG. 7, the insel-.t 232 includes channels 241 directed toward the
recess 233a and
therefore the swirl chamber 233. The insert 232 also includes a heating
element 243.
[0071] Turning to FIGS. 12A-12B, the insert 332 is shown equipped with a PTC
resistive
heating element 243 that essentially surr.ounds the swirl chamber 333. As
liquid product
passes the cross-bar 321 in the passageway 319, and proceeds past the post
331, into the swirl
chamber 333, the heating element 243 heats the product flow stream thereby
reducing the
solubility of any compressed gas propellant in the exit stream 350. As a
result, cavitation
occurs, or bubbles of compressed gas propellant appear in the product flow
stream thereby
creating unstable thin ligaments of liquid product in the exit stream 350. The
unstable thin
ligaments of liquid product are then converted into small droplets having
diameters of less
than 351im. If a suitable pressure is provided within the container, and a
suitable velocity is
imparted to the primary droplets, the droplets will then further divide into
smaller droplets by
way of an atomization process.
[0072] It is believed that the cavitation process starts within the swirl
chamber 333 and
continues as the product flows through the discharge orifice 339 and into the
exit orifice 322.
A variety of different heaters can be employed, and while a simple resistance
heating element
may be used, a PTC heating element is preferred as it can easily maintain a
constant
temperature in the swirl chamber 333. Electrical leads for the heater 343 are
shown at 344,
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345. Examples of PTC heaters can be found in U.S. Patent Nos. 3,927,300,
3,338,476,
4,088,269, 4,212,425, 6,220,524 and 6,501,907. See also U.S. Patent No.
3,476,293.
[0073] Turning to FIGS. 13-19, an insert 432 is disclosed that includes a
breakup bar 451.
Essentially, as best seen in FIG. 19, two opposing channels 441 are disposed
in the insert 432.
As product travels towards the exit orifice 439, the product is directed
through the oppositely
directed channels 441 so the product engages the breakup bar and other product
to provide
highly turbulent flow before it reaches the exit orifice 439. FIG. 17
illustrates the placement
of the oppositely directed channels 441 between four circumferentially spaced
posts 452
which further promote turbulent swirling flow as product moves toward the exit
orifice 439.
[0074j In summary, an improved aerosol dispensing system is disclosed which
enables a
compressed gas propellant, such as carbon dioxide, to be used to deliver
liquid product.
Preferably, compressed gas propellant should be soluble in the liquid product
at room
temperature and less soluble or relatively insoluble in elevated temperatures.
Thereby, the
heating of the exit stream will result in cavitation or propellant bubbles
emerging in the exit
stream to form unstable thin ligaments. These unstable thin ligaments will
then be converted
into droplets which preferably will have a Weber number sufficiently high so
as to result in
secondary atomization and even smaller droplets. In any event, the proposed -
designs provide
an aerosol mist with a mean Sauter diameter of less than 35 m.
[0075] While only certain embodiments have been set forth, alternatives and
modifications
will be apparent from the above description to those skilled in the art. These
and other
alternatives are considered equivalents and within the spirit and scope of
this disclosure and
the appended claims.
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Industrial Applicability
[0076] An improved aerosol dispenser is provided using a compressed gas
propellant free
of volatile organic compounds and that includes an actuator cap equipped with
a heater for
reducing the particle size of the resulting mist.
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