EP1706335B1

EP1706335B1 - Product dispensing system and method of manufacturing it

Info

Publication number: EP1706335B1
Application number: EP05701912A
Authority: EP
Inventors: Michael Ernest Garrett
Original assignee: Kbig Ltd
Current assignee: Kbig Ltd
Priority date: 2004-01-23
Filing date: 2005-01-17
Publication date: 2011-03-16
Anticipated expiration: 2025-01-17
Also published as: WO2005070788A1; EP1706335A1; ATE501955T1; CA2553280A1; DE602005026905D1; US20140048566A1; US20060272537A1

Abstract

In a method of manufacturing a dispensing system for dispensing a product from a canister, comprising a solid/gas arrangement in which the gas is adsorbed onto the solid under pressure and desorbed therefrom when the pressure is released and in which the solid comprises activated carbon and the gas comprises at least one of nitrogen, oxygen or mixtures thereof including air, carbon dioxide, nitrous oxide and argon, the canister having valve means to allow the gas adsorbed onto the carbon to be desorbed for generating a pressure in the canister and effect product dispense, the activated carbon is held from the time of its production up to its installation in the canister under a blanketing gas atmosphere which does not prevent the gas to be adsorbed from occupying the adsorption sites of the activated carbon in the canister.

Description

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. 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 will 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; 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 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 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 US 4049158 , 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 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.
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 dispersing systems of the invention.
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 some instances, desorption of the initially held gas may be aided by high temperature or vacuum.
The present invention is concerned with means whereby such problems may be obviated.
In accordance with the invention, there is provided a method of manufacturing 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 including air), carbon dioxide, nitrous oxide and argon, the canister having valve means to allow the gas adsorbed on to the carbon to be desorbed and effect product dispense, characterised in that the-activated carbon is held under a blanketing atmosphere that does not prevent the adsorbed gas occupying the adsorption sites from the time of cooling (during its production) and maintained continuously up to the time of assembly of the canister.
The blanketing 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.
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 made in accordance with 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.
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.
The invention also provides for a dispensing system manufactured accordingly.
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 low 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 300ml 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.
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 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 wall(s) 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.
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 general 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 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
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 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 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 part 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 per 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 its molecules are much more closely packed together than in the usual gaseous form at the same temperature and pressure.
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.
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 (eg 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 (300ml) 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 60ml of carbon, more preferably 30 to 50ml of carbon, for example 40ml of carbon.
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 embodiment 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.
Additional preferred features of dispensing systems made in accordance with the invention are as defined in the claims of this Application.
In any event, the carbon granules or pellets or torroids may advantageously be presaturated 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.
In preferred embodiments and as stated above, the carbon granules/pellets/torroids 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	300ml
Carbon volume	50ml
'Free' canister volume	250ml
Liquid product volume	225ml
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.
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 made in accordance with 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 made in accordance with 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 made in accordance with 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 per se for aerosol canister in particular.
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 partition 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 lie 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 per 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 "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 made in accordance with the invention. The canister 31 comprises a cylindrical main body portion 32, an integrally formed circular base portion 33 of concave shape (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.
The canister is filled 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 45 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 46 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 tube 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.

Claims

A method of manufacturing a dispensing system for dispensing a product from a canister (1,31), which comprises a solid/gas arrangement in which the gas is adsorbed on to the solid (18) under pressure and desorbed therefrom when the pressure is released and in which the solid (18) comprises activated carbon and the gas comprises one or more of nitrogen, oxygen (or mixtures thereof including air), carbon dioxide, nitrous oxide and argon, the canister (1,31) having valve means (11, 38) to allow the gas adsorbed on to the carbon (18) to be desorbed and effect product dispense, characterised in that the activated carbon (18) is held under a blanketing atmosphere that does not prevent the adsorbed gas occupying the adsorption sites from the time of cooling (during its production) and maintained continuously up to the time of assembly of the canister (1,31).
A method of manufacturing a dispensing system according to Claim 1, characterised in that the blanketing atmosphere comprised carbon dioxide, helium or hydrogen.
A method of manufacturing a dispensing system according to Claim 1 or Claim 2, characterised in that the adsorbent gas comprises carbon dioxide and the blanketing atmosphere includes or comprises carbon dioxide itself.
A dispensing system manufactured according to any one of Claims 1 to 3, characterised in that the product and the solid/gas arrangement of the dispensing system of the invention are present in individual compartments in the canister (1,31).
A dispensing system according to Claim 4, characterised in that the individual compartments are separated by a fixed partition (5,36).
A dispensing system according to Claim 5, characterised in that gas from the solid/gas compartment flows in to the product compartment by having a one-way valve (7,46) in the partition.
A dispensing system according to any one of Claims 4 to 6, characterised in that means are provided to allow the introduction of carbon dioxide in to the solid/gas compartment and retain it therein prior to use of and during use of the system by having a one-way valve (7,47) in the carbon container to prevent back flow of the gas from the solid/gas compartment.
A dispensing system according to any one of Claims 4 to 6, characterised in that 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 displaceable partition impermeable to the gas.
A dispensing system according to Claim 8, characterised in that the displaceable partition is in the form of a bag for holding the product.
A dispensing system according to Claim 8, characterised in that the displaceable partition is in the form of a piston slideable within the canister (1,31).
A dispensing system according to any one of Claims 4 to 10, characterised in that the dispensing system is incorporated in to a canister (1,31) in which the product to be dispensed is held under gas pressure.
A dispensing system according to any one of Claims 4 to 10, characterised in that the product is not held before its dispense under gas pressure.
A dispensing system according to any one of Claims 4 to 12, characterised in that the carbon (18) is held in a container (8,44) which is proximate to the dispensing block (36).
A dispensing system according to Claim 13, characterised in that the dispensing block (36) and the carbon container (8,44) are joined by being made as an integrally formed unit.
A dispensing system according to any one of Claims 4 to 14, characterised in that the product is pre-treated with adsorbed gas prior to, or during, its introduction in to the canister (1,31).