Note: Descriptions are shown in the official language in which they were submitted.
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PRODUCT DISPENSING SXSTEMS
This invention relates to systems for dispensing substances from containers
and,
more particularly, to such systems employing a very simple but effective two
phase
solid/gas adsorption/desorption mode of operation.
A large number of products are on the general market packaged in canisters -
some
of which cause the product to be dispensed therefrom in the form of small or
atomised particles and are therefore commonly referred to as 'aerosols' - and
which
can be dispensed from the canister by means of a gas (or vapour) pressure
generated in situ in the canister, ie acting as a dispensing or propellant
gas. Such
products include ones for personal care including hair sprays, shaving creams,
deodorants and the like and ones for household use including cleaning
substances,
room fragrances, insect repellents and the like, and many more.
In some cases, such products are admixed with the pressurised gas in the
canister
and the operation of a (typically) push-down operating valve causes both the
product
and the gas to be dispensed from the pack by means of the gas pressure via a
'dip
tube' extending in to the product and linked to a nozzle which is commonly
associated with the release valve, all of which are commonly contained in a
dispense assembly or dispense block.
In other cases, the product and pressurised gas are separated from each other
within the canister. Typically, some form of divider or membrane is present in
the
canister, for example, one in the form of a bag containing the product which
is
sealingly attached to the canister internal wall in the vicinity of the
release valve; the
gas is present between the divider and the internal walls of the pack, ie
surrounding
the bag and the gas pressure in turn exerts pressure on the product in the
bag.
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Alternatively, the divider may be a piston which slides within the canister
with the
product on one side and a gas on the other side and which acts to drive the
product
from the canister by the action of gas pressure.
Whichever type of pressure pack is adopted wil! depend on the nature of the
product
and the use to which it is to be put and on the nature and properties of the
propellant
gas, in particular whether the propellant gas might react with the product or
whether,
for example, it might be flammable or odorise the product.
The use of chlorofluorocarbons (CFCs) previously became very popular as
propellant gases for such product dispense canisters in that they can be
readily
condensed and vaporised in a reversible manner responsive to the surrounding
pressure. This was followed by the use of hydrofluorocarbons (HFCs) and also
hydrochloroflurocarbons (HCFCs) which were regarded as being somewhat more
environmentally friendly.
However, more recently, such propellant gases have in general been phased out
owing to their acknowledged environmentally harmful properties, in particular
ozone
depletion of the upper atmosphere.
Alternative propellant gases which have been commonly used are certain
hydrocarbon gases including liquid petroleum gases (LPGs) such as propane and
butane. Such gases, however, are by their nature extremely flammable, are
environmentally harmful in some respects and in addition can introduce an
odour in
to the product being dispensed.
It is known that numerous attempts have been made to replace LPG propellant
gases with gases such as air, nitrogen, carbon dioxide and the like. These
attempts
have largely been effected simply by utilising a pressurised gas within the
canister;
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in practice, the canister valve is depressed to propel the product from the
canister in
the general manner described above.
However such attempts have been largely unsuccessful due to the large pressure
changes in the canister during use, commonly leading to reduced dispense
characteristics at low pressures and a loss of pressure before full product
dispense
which results in a slow dispense of the last product from the canister.
In addition, it is known that there has been considerable effort to develop
further
alternative propellant systems for such product dispense. For example, there
is
disclosed in European Patent Application No. 385 773 the use of two-phase
gas/solid or gas/liquid or three phase gas/liquid/solid propellant systems in
which the
solid is a polymer having molecular microvoids occupied by the gas or
gas/liquid
under pressure and the gas is released therefrom when the pressure of the
system
is reduced.
There is additionally disclosed in a further European Patent Application No.
502 678
the use of a three phase gas/liquid/solid propellant system in which the solid
is a
material such as a foam or a fibrous mass having open voids occupied by the
gas/liquid under pressure and the gas is released therefrom when the pressure
of
the system is reduced.
It is known that efforts to develop such prior systems were based primarily on
the
preferred embodiments described in these European applications, namely the use
of
a gas/liquid/solid system in which carbon dioxide as the gas was dissolved in
acetone as the liquid which itself occupied voids in a solid.
The use of acetone as the liquid in such a system would generally mean that it
was
useful only in canisters employing a membrane, for example a bag containing
the
product, in order to separate the propellant system from the product to be
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dispensed. However, acetone is an aggressive chemical and it is also known
that it
was found that the use of acetone in such systems tended to cause problems
associated with chemical attack of the membrane material and leakage of the
acetone through and around the membrane and resulting failure of the membrane.
A further prior attempt to produce a product dispense system utilising gas
pressure
is disclosed in UK Patent Specification No. 1 542 322 in which a propellant
gas,
including propane/butane, certain CFCs and carbon dioxide, is adsorbed on to a
solid with dispense gas pressure being produced in situ during use of the
system by
means of bringing the solid in to contact with a propellant displacing agent -
preferably water - in order to release the adsorbed gas. As such, the system
as a
whole is necessarily very complex due in particular to the need to employ the
propellant displacing agent during use and provide means to bring it in to
contact
with the solid.
There is therefore a need for an improved aerosol propellant system that
overcomes
the problems associated with currently disclosed systems.
It has now been found that the use of a new system not involving polymeric
materials and not involving troublesome liquids or displacing agents and being
more
suitable for commercially viable assembly in to the aerosol canister can
provide an
efficient sorption/desorption propellant system for product dispense.
In accordance with the invention, there is provided a dispensing system for
dispensing a product from a canister, which comprises a solid/gas arrangement
in
which the gas is adsorbed on to the solid under pressure and desorbed
therefrom
when the pressure is released and in which the solid comprises activated
carbon
and the gas comprises one or more of nitrogen, oxygen (or mixtures thereof
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including air), carbon dioxide, nitrous oxide and argon, the container having
valve
means to allow the gas adsorbed on to the carbon to be desorbed and effect
product
dispense.
The gas is preferably carbon dioxide in view of its generally superior
adsorption
characteristics in relation to activated carbon as an adsorbent.
The term 'adsorbed gas' used herein refers to the gas used in the invention.
It has been surprisingly found that such a system, despite its simplicity, can
provide
the basis for an efficient, safe, reliable and reproducible system for product
dispense.
It has been found in particular that the new dispense system can provide - by
means
of careful selection of the type of activated carbon employed, the amount of
carbon,
the initial pressure and therefore the amount of gas adsorbed on the carbon -
a iow
pressure change during intermittent use between an initial product dispense
and full
product dispense from a canister.
The pressure change afforded by the invention between a 'full' and 'empty'
canister
is such that the canister in which it is positioned can maintain an effective
discharge
of product with an effective and acceptable controlled spray pattern in terms
in
particular of its being uniform and/or homogeneous with a predetermined
particle
size and distribution.
Systems of the invention have been shown to be particularly suited to the
dispensing
of products from small, hand-held 'aerosol' canisters, for example ones having
a 200
or 300m1 capacity. The term 'aerosol' when used herein includes any hand-held
dispensing devices for the delivery of product whether or not the product is
actually
atomised or whether or not it incurs any other form of product break-up.
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In the implementation of the invention, and in first embodiments thereof, the
dispensing system is preferably incorporated in to a canister in which a
product to be
dispensed is held under gas pressure. In such embodiments, carbon dioxide
desorbed from the carbon adsorbent pressurises the canister and maintains the
pressure therein generally and during actuation of the canister dispensing
valve in
particular.
Preferably, the product and the solid/gas arrangement are present in separate
compartments in the canister. This is primarily to keep the product and the
solid
apart from each other in order to hold the solid in a predetermined part of
the
canister and/or to ensure in particular that the product, which may for
example be in
aqueous or other type of solution, does not contaminate the solid and thereby
detract from its efficiency of adsorption.
In some instances, the compartments may be separated by means of a wholly or
substantially impermeable membrane. This membrane may take the form of a
flexible bag which is sealingly attached either to the interior wall of the
canister or to
the canister operating valve or dispense block and which in use holds the
product to
be dispensed. The solid/gas arrangement is generally positioned within the
canister
outside the bag such that pressure is exerted on the exterior of the bag when
pressure therein is released on actuation of the valve and product dispense
effected
via the valve through a nozzle. An elastic material may be employed to form
the bag.
Furthermore, the membrane, whether of elastic or non-elastic material may be
used
and may be sealingly attached to any relevant part of the canister interior.
The substantially impermeable membrane may alternatively take the form of a
piston
slideably mounted in the canister interior with the gas/solid arrangement on
one side
of the piston and the product to be dispensed on the other side such that
actuation
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of a dispense valve causes pressure from gas desorbed from the solid to move
the
piston and urge product to be dispensed from the canister via the valve.
In other instances, the compartments may be separated by means of a fixed
partition. Such a fixed partition may usefully be positioned in the any useful
part of
the canister, and preferably including the base thereof, to form the solid/gas
arrangement compartment therein. It can, for example, be a concave-shaped disc
in
a 'flat' canister base or one of greater concavity than the (usually) concave-
shaped
canister base (as viewed from the exterior of the canister). It may
advantageously be
crimped to the canister between the canister walls) and its base to form an
annular
compartment between the disc and the base.
The solid compartment may also be in the form of a container or 'widget' that
may
be fixed to the canister (or part thereof) or allowed to be free within the
canister
interior.
In addition, the carbon container may be associated with the canister dip
tube, for
example by being mounted around the dip tube for ease of assembly of the
canister
generally and the positioning of the container therein and, separately to
allow for a
ready filling of the container with adsorbed gas via the dip tube and via a
one-way
valve therebetween.
Generally, the product and the solid/gas arrangement of the dispensing system
of
the invention are present in individual compartments in the canister, which
are
separated by a partition which may be fixed or displaceable. This keeps the
product
and the solid apart from each other in order to hold the solid in a
predetermined part
of the canister and/or to ensure in particular that the product, which may for
example
be in aqueous or other type of solution, does not contaminate the solid and
thereby
detract from its efficiency of adsorption.
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With a fixed partition, for example the substantially rigid wall of the carbon
container,
it is generally required that the gas from the solid/gas compartment can flow
in to the
product compartment, but not vice versa, and this can readily be effected by
having
a one-way valve in the partition.
Equally, there is a genera( need to provide means to allow the introduction of
carbon
dioxide in to the solid/gas compartment prior to use of and during use of the
system;
this can also be effected by a one-way valve to prevent back flow of the gas
from the
solid/gas compartment.
Each one-way valve should be designed such that is operates only under a
certain
applied pressure, for example a small fraction of 1 bar; otherwise the valve
does not
open.
With certain designs of valve, it is possible for a single valve to operate
separately
as a pressure thereof sensitive valve in either direction depending on the
requirements of the system.
In such embodiments, the container for the carbon should have one-way valve
means in order to allow the carbon dioxide to be desorbed from the solid and
pass in
to the product compartment when the pressure in the canister falls, ie on
operation
of the canister dispensing valve, and thereby maintain canister pressures at
predetermined levels for further use of the aerosol.
In all cases, the one-way valve means may be made from any material and be of
any suitable form including ones incorporated integrally in to the body of the
carbon
container. One form which is particularly useful may comprise an upstanding
valve
body terminating in a parallel, double plate arrangement - preferably formed
integrally with the wall of a product bag or fixed partition - such that the
plates act as
a closed valve in their usual position but which can move under their inherent
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resilience to an open position by virtue of gas pressure impinging thereon in
a
predetermined (single) direction, ie from the interior of the carbon
container; such a
valve is sometimes referred to as a 'sphincter' valve.
The one-way valve advantageously is formed integrally with the partition and
is
preferably made from a plastic material, for example PET or silicone rubber.
With a displaceable partition, this will generally be impermeable to the gas
and may
take the form, for example, of a bag for holding the product or a piston
slideable
within the canister with the desorbed gas from the carbon deforming the bag or
moving the piston within the canister under the increased gas pressure applied
thereon during actuation of the dispensing valve.
In separate embodiments of the invention, the dispensing system may be
implemented with a product not held before its dispense under gas pressure. In
such
embodiments, the desorbed gas is not used to effect product dispense until it
is
required in use. These embodiments may be put in to effect by restraining the
gas
pressure in the solid/gas container and effecting its release therefrom via
valve
means only when required during product dispense.
In these separate embodiments of the invention, the desorbed gas may be used
to
effect product dispense by:
i) causing the desorbed gas pressure to act directly on a product to effect
product
dispense, for example by urging the product through a dip tube inserted in to
the
product in the canister, or
ii) causing the desorbed gas pressure to act indirectly on the product to
effect
product dispense, for example by its impingement on to a piston slideably
mounted
in a canister body or part thereof, or
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iii) causing the desorbed gas to effect product dispense by fluid dynamic
(fluidic)
action through the formation of a vacuum in to which a product is drawn,
sucked or
otherwise urged, for example by causing desorbed gas to flow through a venturi
in
which the gas flow is increased and the pressure is decreased in the 'throat'
thereof,
ie a partial vacuum is formed, and to which the product container can be
linked to
effect product dispense.
In these separate embodiments of the invention, it may be advantageous -
especially in regard to paragraphs i) and ii) above - to provide valve means
to
release the pressure applied directly or indirectly to the product to effect
its dispense
when the canister is not being used.
Use of the separate embodiments with an unpressurised canister is particularly
useful in the case of a product in which the propellant gas can dissolve.
In all embodiments, the carbon is advantageously held in a container which is
preferably proximate to the dispensing block, for example by being attached
thereto
or may be less firmly linked, for example via a tube through which the carbon
dioxide
can be introduced in to the container.
In such preferred embodiments, the dispensing block itself advantageously
incorporates a canister dispensing valve and' passageways linking the interior
of the
canister with the exterior thereof via the valve. As such, the dispensing
block,
together with the carbon container, can readily and effectively be sealingly
inserted
in to an aperture in the canister during canister assembly.
In particular, the linkage of the container to the dispensing block generally
allows
firstly for a ready operation of the pressure pack and secondly allows for a
simple
mode of manufacture and assembly of the aerosol canister by allowing for the
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dispensing block - incorporating the canister dispensing valve, necessary
passageways linking the interior of the canister with the exterior thereof,
and also the
carbon container linked thereto - to be inserted in to an aperture in the
canister,
ideally the top of the canister, advantageously in a single assembly step.
The invention therefore allows standard designs of canister to be employed
without
modification to the body thereof in order to suit implementation of the
invention
generally and to include canisters made of either steel or aluminium or other
material.
In preferred embodiments, the dispensing block and the carbon container are
advantageously joined, for example by being made as an integrally formed unit,
for
example with the carbon container being situated beneath the dispensing block
in a
normal upright orientation of the canister. It is also advantageous for a dip
tube to
depend from the dispensing block, preferably being positioned centrally
(axially) in
the carbon container and, in use of the propellant system, extending in to the
body
of the canister within the product to be dispensed.
The container for the carbon can be, for example, made of a flexible
plastic/polymer
material in the form of a bag or alternatively be cylindrical in shape and
advantageously made from a more rigid material, again preferably from a
plastic/polymer material. The container is preferably cylindrical in shape.
In general, it is preferred for the carbon to be placed in the container prior
to the final
assembly of the canister, ie prior to insertion of the dispensing block and in
to the
product itself to which the container is linked in to the canister aperture as
described
above.
The product to be dispensed by the system of the invention is commonly
inserted in
to the canister via a dip tube depending from the dispensing block and through
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which, in use of the aerosol, the product is dispensed via the dispensing
valve in the
reverse direction. The solid/gas container is advantageously linked to the
dispensing
block, for example by being positioned co-axially about the dip tube and as
such can
be regarded as an integral parfi of the dispensing block. In such cases, the
block as
a whole can therefore readily be placed in a canister aperture simultaneously
during
canister assembly.
Means must also be provided for the introduction of the gas under pressure in
to the
carbon container in order to cause it to be adsorbed on to the carbon and
subsequently desorbed therefrom on operation of the dispensing valve. This can
be
effected, for example, by providing a suitable route via the dispensing block
in to the
container interior and including (as described above) a one-way valve to
prevent
back flow of the gas.
Overall, therefore, and in all embodiments of the invention, the product
dispensing
system provides a simple and effective way of utilising gas desorbed from the
adsorbent ,her se in order to provide a sufficient gas volume to produce an
initial gas
pressure and thereafter to maintain gas volumes, and necessary gas pressures,
to
enable a complete product dispense to be effected.
In all embodiments of the invention, a pressure regulator may be used to
regulate
the gas pressure released from the adsorbent of the dispense system of the
invention to a predetermined pressure level or within a predetermined range of
pressure. For example, a 10 bar(a) pressure provided by desorbed gas may be
regulated to produce propellant gas at 3 bar(a).
With regard to the gas, it should be introduced in to the dispensing system
under
pressure and which will be adsorbed on to the carbon such that ifs molecules
are
much more closely packed together than in the usual gaseous form at the same
temperature and pressure.
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This means that, when the gas is introduced under pressure in to a "gas space"
surrounding the carbon, considerably more gas will be adsorbed on to the
carbon.
Consequently, as the system is activated, typically by actuating the pressure
release
valve, there will in practice be only a relative and surprisingly small
pressure
reduction within the system which, in use of the system, therefore allows for
the
effective dispensing of all of the product.
In preferred embodiments utilising carbon dioxide gas, it is injected
initially under
pressure in liquid form, for example down a dip tube depending from or
integrally
formed with the valve block.
Adding the carbon dioxide in this way will generally produce a mixture of
carbon
dioxide snow and cold carbon dioxide gas.
Using carbon dioxide in the form of a liquid or snow can in practice at least
partially
thermally balance the heat of adsorption of the carbon dioxide on to the
carbon and
maintain temperatures close to ambient.
A double valve arrangement may be employed for measuring exact quantities of
liquid carbon dioxide present between two valves positioned in a delivery tube
of
constant cross-section so as to define the required volume of gas needed for
each
canister as they pass along a conveyor assembly line. This is preferably
effected by
closing the upstream valve once the required volume of carbon dioxide is
present
between the valves and allowing the volume to 'vaporise', and to urge the
stream of
snow/gas in to the canister.
The gas may also be charged in to the container in the form of solid carbon
dioxide
which is easy to handle and affords the benefits described above for liquid
carbon
dioxide.
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In general, it is beneficial to charge the gas in to the container by means
other than
a 'bung hole' in the base of the canister as the presence of a bung hole may
lead to
gas leakage during storage/use of the canister.
Activated carbons are well known per se and have the advantage that they are
relatively inexpensive; they are non-polymeric substances. In general,
activated
carbons are manufactured from a variety of carbonaceous materials including
(1)
animal material (blood, flesh, bones, etc), (2) plant materials such as wood,
coconut
shell, corn cobs, kelp, coffee beans, rice hulls and the like and (3) peat,
coal, tars,
petroleum residues and carbon black.
Activation of the raw carbonaceous materials can be effected in a variety of
known
ways including calcining at high temperature leg 500°C-700°C) in
the absence of
air/oxygen followed by activation with steam, carbon dioxide, potassium
chloride or
flue gas at, say, 850°C to 900°C, followed by cooling and
packaging.
Selected activated carbons are suitable for use in the systems of the
invention, for
example ones having a density of from 0.2g/cm3 to 0.55g/cm3, preferably
0.35g/cm3
to 0.55g/cm3.
The quantity of carbon required in implementing the invention will vary
depending on
parameters including the gas employed, the initial and final pressures during
the
dispense of product, the nature of the product and its physical
characteristics and
the desired properties of the dispensed product. As such, the carbon may
advantageously occupy from 5 to 95% of the canister interior volume.
In the case of a standard size (300m1) canister, it is preferred for many
product types
to have a carbon content of from 5 to 30% of carbon (by volume) which
generally
equates, for selected carbons, to the presence of 10 to 60m1 of carbon, more
preferably 30 to 50m1 of carbon, for example 40m1 of carbon.
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With other product types, especially those of relatively high concentration of
active
ingredient(s), the carbon content may usefully be from 30 to 95%, preferably
from 60
to 90%.
In the case of the higher concentration products in particular, but also
generally, the
product dispensed from the nozzle of a canister incorporating a system of the
invention may advantageously be improved by causing a separate bleed of gas to
be directed in to the dispensing valve or block and therein to mix with
product being
expelled therefrom in order to effect a greater dispersion of the dispensed
product.
Such improvements are especially useful with more concentrated and/or more
viscous products which might otherwise be difficult to disperse adequately for
effective spray pattern or whatever.
In preferred embodiments of the invention, the activated carbon is present in
the
form of one or more pellets or torroids, ie in a much larger size than the
granules in
which it is normally supplied, for example of a size of at least 0.5 cm in
length or
greater. Such pellets or torroids may be fabricated by sintering or other
binding
processes and preferably will allow for a much larger surface area for the
carbon
dioxide and therefore a commensurately larger and more effective gas release
on
reduced pressure.
The pellets or torroids can advantageously be manufactured as sticks or tubes
and/or with surface ribs or grooves or with apertures therethrough; all such
forms
can be capable of aiding adsorption/desorption of the gas.
In general, specific ways of treating and/or handling the carbon are important
aspects of the invention and may be essential for the implementation of
dispensing
systems of the invention.
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In particular, it has been found that there may be a propensity for the
required
properties of the carbon to degrade after the carbon activation process. Such
degradation may include adsorption sites on the carbon being blocked by a gas
or
gases present in the atmosphere present around the carbon and which cannot
subsequently be displaced by the gas that is to be adsorbed as the working gas
in
the dispensing systems of the invention. Although the blocking process may be
reversible in certain cases, displacement by the preferred gas may not be
effected
completely and therefore would detract from the subsequent adsorption of the
gas.
In some instances, desorption of the initially held gas may be aided by high
temperature and/or vacuum.
In accordance with preferred aspects of the invention, therefore, the
activated
carbon is held, advantageously from the time of its production, under a
blanketing
atmosphere; this atmosphere may comprise the adsorbed gas itself, or a gas or
gases (including mixtures with the adsorbed gas) that do not prevent the
adsorbed
gas subsequently occupying the carbon adsorption sites, in particular by
virtue of
being held at the adsorption sites on the carbon less strongly than the
adsorbed gas.
Certain gases, including water vapour, are more strongly held at the carbon
adsorption sites than the adsorbed gas and carbon dioxide in particular and
therefore should be rigorously excluded from the atmosphere around the carbon;
subsequent attempts to dislodge the strongly held gases will not be
successful.
Although some gases are less strongly held at the adsorption sites than carbon
dioxide and other adsorbed gases, they may still interfere with the subsequent
adsorption efficiency characteristics of the adsorbed gas and should be
avoided as
blanketing gases.
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In the case of carbon dioxide as the adsorbed gas, the blanketing atmosphere
preferably includes or comprises carbon dioxide itself. This can be especially
advantageous in the implementation of the invention in dispensing systems when
the carbon dioxide is preferably adsorbed on to the carbon at elevated
temperatures. Other suitable gases include helium and hydrogen which are
generally capable of being displaced from the adsorption sites by carbon
dioxide.
The potential use of other blanketing gases can be established by a skilled
adsorption scientist on a theoretical or practical basis.
Adsorption is an exothermic process in which considerable amounts of heat may
be
generated. The adoption of these preferred embodiments with a blanketing
atmosphere that includes carbon dioxide itself is beneficial in that it allows
an initial
level of adsorption of carbon dioxide to occur - together with a dissipation
of the
generated heat - prior to the use of the carbon in dispensing systems of the
invention. This can lead to significant advantages from the resultant lower
amounts
of heat generated when the remaining carbon dioxide is adsorbed under pressure
in
subsequent high speed production of canisters incorporating the dispensing
systems
of the invention.
With all adsorbed gases, the blanketing of the carbon is preferably effected
from the
time of cooling and is preferably maintained continuously up to the time of
(final)
assembly of the canisters in which the dispensing systems are employed. To
achieve this, the use of containers for holding the blanketed carbon is
required in
order to isolate the carbon from undesirable gases.
In any event, the carbon granules or pellets or torroids may advantageously be
pre-
saturated with carbon dioxide (or other adsorbed gas) prior to use in order to
improve the adsorption parameters. The granules/pellets/torroids may be
advantageously cooled in such pre-saturisation processes by use of cooled
carbon
dioxide, for example carbon dioxide solid or snow being in contact with the
carbon.
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In preferred embodiments and as stated above, the carbon
granules/pelletsltorroids
are usefully kept in contact with a source of carbon dioxide or other adsorbed
gas,
especially cold gas, liquid or snow, prior to placement in a canister and this
may
provide sufficient adsorbed gas for use in the system without the need to add
further
amounts of gas.
In the case of certain products, it has been found that it may be useful for
optimum
dispense characteristics to pre-treat the product with adsorbed gas prior to,
or
during, its introduction in to the canister. This can be especially useful in
the case of
highly soluble gases such as carbon dioxide, ie 'pre-carbonation'. Such a
process is
more useful in the case of product to be admixed with the adsorbed gas in the
canister; it may, however, also apply to product present in the canister
separated
from the adsorbed gas by a moveable partition including a bag whether or not
the
partition allows for a certain leakage of gas therethrough.
Working canisters incorporating the product dispense systems of the invention
have
been made to good effect in terms in particular of initial and final gas
pressures
during full product dispense as exemplified below with carbon dioxide adsorbed
gas
in particular:
Canister volume 300m1
Carbon volume 50m1
'Free' canister volume250m1
Liquid product volume225m1
Initial gas pressure 6 bara
Final gas pressure 4 bara (following full product
dispense)
Tests on a canister containing a larger carbon to product volume ratio
resulted in a
proportionately lower change between initial and final pressures.
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All tests were conducted using activated carbon samples treated and handled
with a
carbon dioxide blanketing atmosphere from the time of cooling during
production of
the carbon.
Tests with other adsorbed gases produced similar results depending on the
adsorption characteristics of the individual gases.
For a better understanding of the invention, reference will now be made, by
way of
exemplification only, to the accompanying drawings of which:
Figure 1 shows a schematic vertical section through a canister incorporating a
dispensing system of the invention;
Figure 2 shows a sectional view through the canister of Figure 1 along the
line II-II;
Figure 3 shows a schematic vertical section through a canister of different
design to
that of Figure 1 incorporating a dispensing system of the invention.
With reference to the drawings and to Figure 1 in particular, there is shown a
canister 1 incorporating a pressure pack dispensing system of the invention.
The
canister 1 comprises a cylindrical main body portion 2, a circular base
portion 3 of
concave shape (external view) and a circular top portion 4 of convex shape
(external
view), all made of aluminium alloy material.
The base portion 3 is sealingly crimped around its periphery to the lower edge
of the
main body portion 2 in a manner known a,~er se for aerosol canister in
particular.
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Sandwiched and sealingly held within the crimped structure between the main
body
portion 2 and the base portion 3 is a circular partition 5 made of plastic and
having a
greater concavity shape than the base portion 3.
The base portion 3 has a small circular "bung" 6 at its centre made of rubber
(or
other elastomer) and the partifiion 5 has an upstanding one-way valve 7
allowing for
the flow of fluid from a compartment 8 formed between the base portion 3 and
the
partition 5 and in to the upper compartment containing the substance to be
dispensed but not vice-versa.
The one-way valve 7 comprise two upstanding plates 9, 10 (see Figure 2) which
are
formed integrally with the partition 5 and which, by virtue of the relative
positioning of
the plates 9, 10 and the nature of the plastic material from which they are
made, are
biased to tie adjacent each other in the vicinity of their ends furthest from
the
partition 5.
As such, the one-way valve 7 will open by parting the plates 9, 10 when there
is, in
use, an excess pressure in the compartment 8 over that in the interior of the
remainder of the canister 1.
The plates 9, 10 will not part and the valve 7 will therefore not operate in
the
opposite direction as any excess pressure in the canister 1 will not cause
such
parting by virtue of the shape of the adjacent ends of the plates.
The top portion 4 is sealingly crimped around its periphery to the upper edge
of the
main body portion 2 again in a manner known her se for aerosol canisters in
particular.
Positioned centrally of the top portion 4 in an aperture thereof is an
operating valve
system 11 comprising a valve seat 12 against which a ball valve member 13 is
in its
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"closed" position held but which can be unseated in its "open " position by
depression of an operating button 14 against the action of a spring 15.
Release of
the button 14 causes re-seating of the valve member 13 by means of the spring
15.
A tube 16 depends downwardly from the valve system 11 and a discharge line for
the substance to be dispensed is formed from the lower end of the tube 16,
through
the tube 16 itself and via the valve mechanism to a discharge port 17 in the
operating button 14.
In the manufacture of the canister 1, activated carbon 18 is included in the
compartment 8 between the base portion 3 and the partition 5 and the substance
to
be dispensed is charged in to the canister 1 above the partition 5 via the
aperture in
the top portion prior to installation of the valve system 11.
With the valve system 11 in place, carbon dioxide gas or liquid is loaded in
to the
compartment 8 by means of a needle injection through the rubber bung 6,
causing
its adsorption in to the activated carbon 18 in the compartment 8.
The carbon dioxide gas pressure in the compartment 8 equalises the pressure in
the
canister 1 surrounding the substance to be dispensed via the one-way valve 7.
In use of the canister 1, the carbon dioxide pressure generated by the
pressure pack
system of the invention will, when the operating button 14 is depressed, urge
the
substance being dispensed from the canister 1 via the tube 16 and the valve
system
11 and the discharge port 17.
With reference to Figure 3, there is shown a canister 31 incorporating a
pressure
pack dispensing system of the invention. The canister 31 comprises a
cylindrical
main body portion 32, an integrally formed circular base portion 33 of concave
shape
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(external view) and a circular top portion 34 of convex shape (external view),
all
made of an aluminium alloy material.
Positioned centrally of the top portion 34 is an aperture 35 and sealingly
held therein
is a dispensing block 36 having a main passageway 37 therethrough and an
associated valve 38 for allowing, in use, product to be dispensed from the
interior of
the canister. Biassing means, for example a spring (not shown), urges the
valve
towards a closed position.
The passageway 37 is linked at one end to a reciprocatable valve actuating
hollow
tube 39 and at the other end to a 'dip' tube 40 extending in to the main body
portion
32.
An operating cap 41 is positioned over the dispensing block 36 and movement
(depression) thereof towards the body portion 32 actuates the hollow tube 39
and
causes opening of the valve 38.
A further passageway 42 in the dispensing block 36 has an opening adjacent the
operating cap 41 and extends in to the interior of a canister 44 attached to
the
dispensing block 36 and forming an integral unit therewith.
A one-way valve 45 is present in the passageway 42 to allow flow of fluid in
to the
container 44 but not vice versa. A further one-way valve 46 is present in the
base of
the container 44 to allow flow of carbon dioxide from the container 44 and in
to the
canister 31 when the pressure in the canister falls below that of the
container 44.
In assembling the canister including the pressure pack of the invention, the
dispensing block 36 (to include the dip tube 40 and the linked container 44)
is
sealingly inserted in to the aperture 35 in the canister top portion in a
single
assembly step.
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The canister is fiilled with liquid product to be dispensed via a needle
inserted in to
the hollow tube 39 and operates to open the valve 38 against the action of the
biasing means in order to allow the liquid to go through the passageway 37 and
dip
tube 40 and fill the canister up to the product level 47.
The container 44 is pre-packed with activated carbon held under an atmosphere
of
carbon dioxide since its production and additionally pre-flushed with carbon
dioxide.
After insertion of the dispensing block, etc in to the aperture 35 and product
in to the
canister interior, a source of carbon dioxide gas under pressure is attached
to the
passageway 42 for pressurisation of the container 44 via the one-way valve 46
and
to cause the adsorption of the carbon dioxide on to the activated carbon in
the
container. The presence of the further one-way valve 16 allows the carbon
dioxide to
pressurise the head space above the product in the canister 31 until the
respective
pressures are substantially equalised.
The operating cap 41 is then fitted over the dispensing block and the aerosol
canister is ready for use. Depression of the operating cap 41 moves the fiube
39 and
actuates the valve 38 to allow product to pass up the dip tube 40 and be
dispensed
from the canister via the passageway 37, the tube 39 and a passageway (not
shown) in the operating cap 41 to a nozzle 48 in the cap 41, all under the
carbon
dioxide gas pressure present in the head space.
Resulting loss of carbon dioxide pressure in the head space is replenished by
an
automatic flow of gas from the container 44 via the one-way valve 46. Pressure
in
the container 44 itself is maintained by desorption of further gas from the
activated
carbon.
