Patent Description:
Aerosol canisters are used to deliver an aerosolised product such as an insecticide, a paint, a household product (e.g. air freshener or cleaning product) or a personal product (e.g. deodorant, antiperspirant or hairspray).

The product is typically contained in a steel or aluminium canister which is fitted at its open end with a dispensing valve. The stem of the dispensing valve is fitted with an actuator which can be depressed towards the canister to operate the valve to release the aerosolised product. The dispensing valve also comprises a dip tube which extends to the base of the canister and through which the product is carried for dispensing.

In order to force the product up the dip tube and to propel the product from the canister in the form of an aerosol, a liquid or compressed gas propellant is contained within the canister along with the product.

Current liquefied gas propellants are mainly hydrocarbons such as n-butane, iso-butane, propane and mixtures thereof. The most common propellant is a butane-propane blend (also known as liquefied petroleum gas (Ipg)). These hydrocarbon propellants flash-vaporise on leaving the aerosol canister and are capable of producing very fine sprays. The hydrocarbon propellant forms a two-phase (liquid and saturated vapour) system within the canister and a dynamic equilibrium exists between the two phases giving a near constant vapour pressure irrespective of whether the canister is full or nearly empty. This means that the product can be delivered at a near constant flow rate. The main problem the current liquefied gas propellants is that they are flammable VOCs.

Less flammable compressed gas propellants such as air or nitrogen are also used but they provide little atomizing energy and thus less fine sprays. They also result in inconsistent product delivery flow rates because the pressure in the canister decreases as the product is dispensed.

Attempts have been made to improve the spray characteristics in canisters using compressed inert gases such as air and nitrogen by using a dispensing valve which introduces compressed gas into the flow through the valve stem of the dispensing valve (commonly known as a vapour tap). Such a dispensing valve is described in <CIT>. This dispensing valve includes a significant number of components.

<CIT> proposes a pressure package system for providing a working pressure on a fluid included in a pressure package, the system being provided with a pressure package in which a product chamber is included for holding the fluid and in which a working pressure chamber is included for keeping a propellant at the working pressure, the system being further provided with a pressure controller and a high-pressure chamber connected with the pressure controller for keeping the propellant in supply at a relatively high pressure, the pressure package system being further provided with a wall which is designed to be movable relative to the pressure controller, a first side of the wall bounding the working pressure chamber at least partly and a second side of the wall, facing away from the working pressure chamber, bounding the product chamber at least partly.

<CIT> proposes a pressurised container for a product in liquid or paste form, the container including an inner chamber designed to contain a gas under a relatively high pressure, and equipped with a valve which responds to the pressure outside the chamber. The chamber contains an absorbent in granule or powder form, designed to increase substantially the quantity of gas in the chamber.

There is the need to provide an improved aerosol canister that can maintain a steady flow rate even when compressed gas propellants are used. There is also a need for a simplified dispensing valve that can be used to deliver a metered dose of a product.

According to the present invention there is provided an aerosol canister according to claim <NUM>.

By providing a canister which is divided into a high pressure chamber and a low pressure chamber by a pressure regulating valve, it is no longer necessary to use a flammable liquefied propellant which maintains a dynamic equilibrium between a liquid and vapour phase. It is possible to use a compressed gas propellant such as carbon dioxide, nitrogen, nitrous oxide or air which has a reduced flammability, odour and environmental impact, and easier, safer handling/transport/storage. The two chambers and pressure regulating valve ensure that the pressure in the low pressure chamber remains constant throughout the life of the canister so that a consistent delivery of the product is maintained.

Optional features of the invention will now be set out.

The low pressure chamber is positioned between the partition wall and the pressure regulating valve. In this way, the low pressure chamber can receive propellant from the high pressure chamber, as is explained in more detail below.

The product reservoir may include an opening for receiving a dispensing valve. The openings of the partition wall and the product reservoir may be axially co-aligned, i.e. in order to receive the same dispensing valve.

In some embodiments, the aerosol canister comprises a housing for enclosing the high pressure chamber, low pressure chamber and product reservoir.

In some embodiments, the low pressure chamber may contain only propellant (i.e. substantially no product), preferably only vaporised propellant. The product reservoir may contain only product (i.e. substantially no propellant). The product reservoir may contain a solution, suspension or emulsion of the product e.g. an aqueous or alcohol solution/suspension/emulsion of the product. The solvent used to form the solution/suspension/emulsion may be (for example) acetone, ethanol, isopropanol, a chlorinated hydrocarbon or kerosene. The nature of the solvent can selected to control the desired particle size of the aerosolized product. Ethanol is preferred for some products.

The product may comprise a consumer product such as: an insecticide (e.g. a pyrethrin/pyrethroid insecticide), a household product e.g. paint, air-freshener, polish, or detergent; a personal product such as hairspray, perfume, deodorant or disinfectant.

Alternatively, the product may be a medicinal product, e.g. an inhalable drug. The inhalable drug may comprise a bronchodilator such as a beta-agonist (e.g. salbutamol, terbutaline, fenoterol), a long-acting beta-agonist (e.g. salmeterol, formoterol) or an anti-cholinergic (such as ipratropium bromide, tiotropium bromide). The inhalable drug may comprise an anti-inflammatory drug such as a steroid (e.g. beclomethasone, budesonide, ciclesonide, fluticasone, triamcinolone) or a cromoglycate drug (e.g. sodium cromoglycate, nedocromil sodium). The inhalable drug my comprise a vaccine, insulin, antibiotics, antifungals, antibacterials, anaesthetics, pulmonary surfactants or pain medications.

The high pressure chamber may be external to the low pressure chamber. For example, the low pressure chamber may be separate from the high pressure chamber. In some embodiments, the high pressure chamber and/or the low pressure chamber each comprises a respective connection element for connection to the pressure regulating valve which is interposed between the two chambers. This allows the low pressure to be manufactured separately from the high pressure chamber.

The connection element may be a screw-, snap-, push or interference-fit connection.

In other embodiments, the high and/or low pressure chamber may be integral with the pressure regulating valve.

In some embodiments, the pressure regulating valve is provided at an upper end of the high pressure chamber. In this case, the high pressure chamber connection element may be provided at the upper end of the high pressure chamber. The opening in the low pressure chamber for receiving the metering valve may thus be provided at an upper end of the low pressure chamber. The opening provides a path from the low pressure chamber to atmospheric pressure. In some such embodiments, the pressure regulating valve is provided at a lower end of the low pressure chamber. In this case, the low pressure chamber connection element may be provided at the lower end of the low pressure chamber. The pressure regulating valve may be interposed between (and optionally integral with) the upper end of the high pressure chamber and the lower end of the low pressure chamber. This provides a canister having an elongated profile similar to the profile of known aerosol canisters.

In other embodiments (e.g. where the canister is used in an inverted configuration), the pressure regulating valve is provided at a lower end of the high pressure chamber. In this case, a high pressure chamber connection element may be provided at the lower end of the high pressure chamber. The pressure regulating valve may be provided at an upper end of the low pressure chamber. In this case, the low pressure chamber connection element may be provided at the upper end of the low pressure chamber. In some embodiments, the pressure regulating valve is interposed between (and optionally integral with) the lower end of the high pressure chamber and upper end of the low pressure chamber. This provides a canister having an elongated profile similar to the profile of known aerosol canisters.

In some embodiments, the pressure regulating valve is a mechanical valve i.e. it is operative in response to a change in force on its components as a result of a drop in pressure in the low pressure chamber rather than in response to any electrical signal.

In some embodiments, the pressure regulating valve is a demand valve such as that used in SCUBA dive apparatus. Such a valve can be sourced from Beswick Engineering (USA).

The pressure regulating valve may be forced towards a closed position, in which there is no fluid flow path between the high pressure chamber and the low pressure chamber, when the pressure in the low pressure chamber is at the predetermined pressure. In other words, the fluid flow-path between the high pressure chamber and the low-pressure chamber is closed when the low pressure chamber is at the predetermined pressure.

When the low pressure chamber drops below the predetermined pressure, e.g. due to propellant being dispensed from the low-pressure chamber, the pressure regulating valve may be forced into an open position (i.e. by the fluid pressure in the high pressure chamber), in which there is a fluid flow path from the high pressure chamber to the low pressure chamber. In other words, the fluid flow-path between the high pressure chamber and the low pressure chamber is opened.

In the open position, liquefied or compressed gas propellant from the high pressure chamber flows into the low pressure chamber until the pressure in the low pressure chamber matches the predetermined pressure and the pressure regulating valve is forced to close again.

Accordingly, by carefully controlling the forces exerted on the pressure regulating valve by the pressurised fluid in the high-pressure chamber and the pressurised fluid in the low-pressure chamber, the pressure regulating valve can open/close below/above the predetermined pressure.

In some embodiments, the pressure regulating valve comprises a tubular valve stem which is moveable within a valve body defined by a high pressure end wall (adjacent the high pressure chamber) and a low pressure end wall (adjacent the low pressure chamber). Each of the end walls has at least one opening for communication with the respective high pressure/low pressure chamber. The high pressure end wall of the valve body may define the upper end of the high pressure chamber. The low pressure end wall of the valve body may define the lower end of the low pressure chamber.

The tubular valve stem has a high pressure end and a low pressure end. The surface areas of the high pressure end and the low pressure end may be selected so that the pressure regulating valve closes/opens above/below the predetermined pressure. The high pressure end may have a smaller surface area than the low pressure end. Preferably, the surface area of the high pressure end and the surface area of the low pressure end are dimensioned so that the pressure regulating valve closes at the predetermined pressure.

In the closed position, the high pressure end is closed against a valve seat defined by the high pressure end wall by the pressure in the low pressure chamber such that flow from the high pressure chamber through the tubular valve stem is prevented. In the open position, a reduced pressure in the low pressure chamber forces the high pressure end away from the valve seat/high pressure end wall so that liquefied or compressed gas propellant can flow from the high pressure chamber through the tubular valve stem and into the low pressure chamber through the low pressure end wall of the valve body.

The low pressure end of the tubular valve stem may be provided with a stem flange e.g. an annular stem flange, the stem flange providing a surface upon which the pressure in the low pressure chamber can act against the fluid pressure in the high pressure chamber to force the pressure regulating valve into the closed position (with the high pressure end of the tubular valve stem held against the valve seat defined by the high pressure end wall of the valve body). In the open position, the stem flange is forced towards and may abut the low pressure end wall under the force of the resilient element.

In some embodiments, a resilient element (e.g. a coiled/helical spring) may be provided to bias the pressure regulating valve into the open position.

The spring constant of the resilient element may be selected to determine the pressure needed in the low pressure chamber to keep the pressure regulating valve in the closed position. Once the pressure in the low pressure chamber drops below this predetermined pressure (as a result of emitting the product from the canister), the resilient element forces the pressure regulating valve to open so that liquefied or compressed gas propellant from the high pressure chamber flows into the head space within the low pressure chamber until the pressure in the low pressure chamber matches the predetermined pressure and the pressure regulating valve is forced to close again.

The biasing force of the resilient element may supplement the force applied to the pressure regulating valve by the fluid in the high-pressure chamber and the fluid in the low-pressure chamber, e.g. to ensure that the pressure regulating valve closes at the predetermined pressure. For example, the resilient element may help to bias the pressure regulating valve into the open position when the low pressure chamber drops below the predetermined pressure.

In the open position, the resilient element may bias the high pressure end away from the valve seat/high pressure end wall so that liquefied or compressed gas propellant can flow from the high pressure chamber through the tubular valve stem and into the low pressure chamber through the low pressure end wall of the valve body. In the closed position, the predetermined pressure in the low pressure chamber may overcome the biasing force of the resilient element, to move the high pressure end towards the valve seat/high pressure end wall so that liquefied or compressed gas propellant cannot flow from the high pressure chamber to the low pressure chamber.

The resilient element may be affixed between the stem flange and a valve body flange (e.g. annular flange) depending from a wall of the valve body proximal the high pressure end wall. The resilient element will be compressed between the two flanges in the closed position. The resilient element (e.g. the coiled spring) may surround the tubular valve stem.

A gas permeable (liquid-impermeable) member e.g. a porous frit may be provided in the pressure regulating valve or in the low pressure chamber for at least partially blocking the opening in the low pressure end wall of the pressure regulating valve body. This helps to prevent any leakage of liquid from the low pressure chamber into the high pressure chamber, and/or vice versa.

A side wall of the valve body may comprise at least one vent (to atmosphere) between the valve body flange and the low pressure end wall to accommodate the changes in the volume defined between the hollow valve stem flange and the valve body flange. The at least one vent is positioned so that it is always on the high pressure side of the valve stem flange.

In preferred embodiments, the liquid propellant is carbon dioxide and the high pressure chamber contains liquefied carbon dioxide. The pressure within the high pressure chamber may be around 6000kPa or 7000kPa at <NUM>, or even higher such as around <NUM>,000kPa. The high pressure chamber will typically have a volume of around <NUM>-<NUM>.

In this case, the high pressure chamber may be a high pressure carbon dioxide canister such as those supplied by Leland Gases (USA).

Carbon dioxide is especially preferred not only because of its reduced environmental impact compared to VOCs but also because it is readily available (e.g. as a by-product from brewing processes). Furthermore, it is an insect-attractant (and therefore ideal when the product is an insecticide).

The propellant could comprise compressed gases such as compressed air, nitrogen, nitrous oxide, oxygen, helium, argon or xenon.

The pressure within the low pressure chamber will be above atmospheric pressure. It may be around <NUM> kPa. It may be at a maximum pressure of around 1000kPa. The pressure within the low pressure chamber can be selected (e.g. in combination with the solvent used to form the solution/suspension/emulsion) to provide the desired particle size of the aerolized product.

The housing may contain an opening through which a dispensing valve will extend. The housing preferably forms a seal e.g. a hermetic seal around the dispensing valve. The housing may comprise a cylindrical housing and may be formed, for example, from aluminium or steel. The housing may comprise a valve to allow venting to atmosphere of any air expelled from the pressure regulating valve i.e. during changes in the volume between the hollow valve stem flange and the valve body flange.

In some embodiments (especially when the product is an insecticide or air freshener), the canister may comprise an automatic actuator for automatically dispensing the product. The automatic actuator may be of the known type e.g. configured to automatically dispense the product at a regular time interval and/or upon detection of motion in the vicinity of the canister.

The dispensing valve may be of the known type e.g. such as that manufactured by Bespak or Salvalco.

In other embodiments the canister may have a dispensing valve for dispensing a metered dose. This is increasingly desirable where the product is an insecticide since insecticides are becoming increasingly potent. The dispensing valve may be a metering valve.

Embodiments of the invention and reference examples useful in understanding the invention will now be described by way of example with reference to the accompanying drawings in which:.

<FIG> and <FIG> show a reference example of an aerosol canister <NUM> contained within an aluminium housing <NUM>.

The canister <NUM> comprises a high pressure chamber <NUM> which is a high pressure carbon dioxide canister containing around <NUM> (<NUM>-<NUM>) liquefied carbon dioxide. Such a high pressure carbon dioxide canister may be obtained from Leland Gases (USA). The pressure within the high pressure chamber <NUM> is around <NUM>-7000kPa.

The canister <NUM> further comprises a low pressure chamber <NUM> containing:.

The headspace <NUM> within the low pressure chamber <NUM> contains gaseous carbon dioxide. The target predetermined pressure within the low pressure chamber <NUM> is above atmospheric pressure and around 300kPa.

The low pressure chamber <NUM> has an opening <NUM> at its upper end for receiving a metering valve <NUM>. The metering valve is shown in more detail in <FIG> and <FIG>. The canister <NUM> sealed within the housing <NUM> by a lid portion <NUM> of the housing <NUM>.

The low pressure chamber <NUM> can be filled with the product before crimping of the metering valve <NUM> or it can be filled through the metering valve <NUM>. Both options are current practice. A porous frit <NUM> is provided to seal the product within the low pressure valve prior to connection to the high pressure chamber.

The canister <NUM> further comprises a pressure regulating valve <NUM> interposed between the high pressure chamber <NUM> and low pressure chamber <NUM>.

The low pressure chamber <NUM> is primed with carbon dioxide to fill the head space <NUM> after connection of the pressure regulating valve <NUM> and the high pressure chamber <NUM>.

The pressure regulating valve <NUM> is adapted to provide a flow path from the high pressure chamber <NUM> to the low pressure chamber <NUM> when the pressure in the low pressure chamber <NUM> drops below a predetermined pressure.

By providing a canister <NUM> which is divided into a high pressure chamber <NUM> and a low pressure chamber <NUM> by a pressure regulating valve <NUM>, it is possible to use a propellant such as carbon dioxide which has a reduced environmental impact compared to the currently used VOCs.

The two chambers <NUM>, <NUM> and pressure regulating valve <NUM> ensure that the pressure in the low pressure chamber <NUM> remains constant throughout the life of the canister <NUM> so that a consistent flow of product (e.g. insecticide, air freshener or deodorant) is maintained as discussed below.

The pressure regulating valve <NUM> is interposed between an upper end of the high pressure chamber <NUM> and a lower end of the low pressure chamber <NUM>. This provides a canister <NUM> having an elongated profile similar to the profile of known aerosol canisters.

The pressure regulating valve <NUM> is a mechanical valve i.e. it is operative in response to a change in force on its components as a result of a drop in pressure in the low pressure chamber rather than in response to any electrical signal.

The pressure regulating valve <NUM> is similar to a demand valve such as that used in SCUBA dive apparatus.

The pressure regulating valve <NUM> is forced towards an open position (shown in <FIG>) in which there is a flow path from the high pressure chamber <NUM> to the low pressure chamber <NUM>, when the pressure in the low-pressure chamber falls below a predetermined pressure value. The pressure regulating valve <NUM> is forced into a closed position when the pressure in the low pressure chamber <NUM> is at (or above) the predetermined pressure (shown in <FIG>). As discussed below, the dimensions of the pressure regulating valve are carefully selected to achieve movement of the valve at the predetermined pressure.

In some examlpes, a spring <NUM> may be provided to apply bias to the pressure regulating valve. The spring <NUM> is pictured in <FIG> and <FIG>. But as will become clear below, the spring is not necessary. The spring constant of the coiled spring <NUM> can be selected to control the predetermined pressure in the low-pressure chamber at which the pressure regulating valve <NUM> moves to the closed position.

Once the pressure in the low pressure chamber <NUM> drops below the predetermined pressure (as a result of emitting a dose of the insecticide from the canister <NUM>), the pressure regulating valve <NUM> is forced to open by the carbon dioxide pressure in the high-pressure chamber (and optionally also by a spring, as discussed above) so that liquefied carbon dioxide from the high pressure chamber <NUM> flows into and vaporises within the head space <NUM> within the low pressure chamber <NUM> until the pressure in the low pressure chamber <NUM> matches the predetermined pressure once more and the pressure regulating valve <NUM> is forced to close.

The pressure regulating valve <NUM> comprises a tubular valve stem <NUM> which is moveable within a valve body defined by a high pressure end wall <NUM> and a low pressure end wall <NUM>. Each of the end walls <NUM>, <NUM> has at least one opening <NUM>, <NUM> for communication with the respective high pressure/low pressure chamber <NUM>, <NUM>. The opening <NUM> in the low pressure end wall <NUM> is sealed by a porous frit <NUM> which is permeable to gas (carbon dioxide) but not to the product solution/suspension/emulsion.

The tubular valve stem <NUM> has a high pressure end and a low pressure end.

In the closed position shown in <FIG>, the high pressure end is sealed against a valve seat defined by the high pressure end wall <NUM> by the pressure in the low pressure chamber <NUM> such that flow from the high pressure chamber <NUM> through the tubular valve stem <NUM> is prevented.

In the open position shown in <FIG>, the drop in pressure in the low pressure chamber <NUM> arising from actuation of the canister, allows the high pressure end to move away from the valve seat/high pressure end wall <NUM> (due to the pressure in the high-pressure chamber) so that liquefied carbon dioxide can flow from the high pressure chamber <NUM> through the tubular valve stem <NUM> and into the low pressure chamber <NUM> through the opening <NUM> in the low pressure end wall <NUM> of the valve body.

This increases the pressure within the low pressure chamber <NUM> until the pressure regulating valve <NUM> is forced back to the closed position once the predetermined pressure is reached.

The low pressure end of the tubular valve stem <NUM> is provided with an annular stem flange <NUM> with a seal or gasket <NUM> around its outer peripheral edge. The stem flange <NUM> provides a surface upon which the pressure in the low pressure chamber <NUM> can act to force the pressure regulating valve <NUM> into the closed position shown in <FIG> (with the high pressure end of the tubular valve stem <NUM> held against the valve seat defined by the high pressure end wall <NUM> of the valve body).

The stem flange <NUM> gives the low pressure end of the stem <NUM> a larger surface area than the high-pressure end of the stem <NUM>. This is crucial for operation of the pressure regulating valve. By carefully selecting the surface area of the low pressure end of the stem (i.e. the area of the stem flange), the force F=PA (where F=force, P=pressure, and A=area) applied to the low-pressure end by the carbon dioxide propellant in the low-pressure chamber will cause the valve to close only when the predetermined pressure is reached in the low-pressure chamber (i.e. by the low pressure chamber filling with propellant from the high-pressure chamber).

For example, if the high-pressure chamber has a pressure of 6000kPa, and the predetermined/target pressure in the low pressure chamber is <NUM> kPa, then the area of the stem flange <NUM> at the low-pressure end of the stem should be 20x larger than the surface area of the high-pressure end of the stem <NUM>. Accordingly, as soon as the pressure in the low-pressure chamber rises above 300kPa, the carbon dioxide in the low-pressure chamber will exert a force on the stem flange <NUM> that is larger than the force exerted on the high-pressure end of the stem <NUM> by the carbon dioxide in the high-pressure chamber. The pressure regulating valve is thereby forced into the closed position.

Once the pressure in the low-pressure chamber drops back below 300kPa, e.g. by dispensing insecticide product from the canister, then the annular stem flange <NUM> is forced towards and abuts the low pressure end wall <NUM> as shown in <FIG>. The pressure regulating valve is thus forced back into the open position.

Where a coiled spring <NUM> is provided to supplement the forces exerted by the carbon dioxide in the high and low pressure chambers, it is affixed between the stem flange <NUM> and an annular valve body flange <NUM> depending from a side wall of the valve body proximal the high pressure end wall <NUM>. The coiled spring <NUM> is compressed between the two flanges <NUM>, <NUM> in the closed position shown in <FIG>. The coiled spring <NUM> surrounds the tubular valve stem <NUM>.

The side walls of the valve body comprise vents <NUM>, <NUM>' (to atmosphere) between the valve body flange <NUM> and the low pressure end wall <NUM> to accommodate the changes in the volume defined between the hollow valve stem flange <NUM> and the valve body flange <NUM> during actuation of the valve.

The vents <NUM>, <NUM>' are positioned so that they are always on the high pressure side of the valve stem flange <NUM>. As the tubular valve stem <NUM> moves to the open position, air will be drawn through the vents <NUM>, <NUM>'. As the tubular valve stem <NUM> moves to the closed position, air will be pushed out through the vents <NUM>, <NUM>'. These vents may not be needed in many examples where the movement between the open and closed positions is minimal.

As discussed above, the arrangement of the high pressure chamber <NUM>, low pressure chamber <NUM> and the pressure regulating valve <NUM>, ensures a constant pressure is maintained within the low pressure chamber <NUM> by flow and vaporisation of liquid carbon dioxide from the high pressure chamber <NUM> when the pressure in the low pressure chamber <NUM> drops below a predetermined pressure. This constant pressure in the low pressure chamber ensures a consistent dose of insecticide/air freshener/deodorant is delivered each time.

<FIG> and <FIG> show a cross-section through a reference example metering valve <NUM>.

The metering valve <NUM> is provided in the opening <NUM> of the low pressure chamber <NUM> of a canister <NUM>. The low pressure chamber <NUM> contains an ethanolic suspension/solution/emulsion of product <NUM> and gaseous carbon dioxide in the headspace <NUM>.

The metering valve <NUM> comprises a metering valve body <NUM> which is divided into a propellant metering chamber <NUM> and a product metering chamber <NUM> by an intermediate wall <NUM>. The product metering chamber <NUM> is defined by the intermediate wall <NUM> and a first axial end wall <NUM> of the valve body. The propellant metering chamber <NUM> is defined by the intermediate wall <NUM> and a second axial end wall <NUM> of the valve body.

The metering valve <NUM> further comprises a cylindrical metering valve stem <NUM> housed within the metering valve body <NUM> and having a dispensing nozzle <NUM> at its first axial end. The dispensing nozzle <NUM> extends from the product metering chamber <NUM>. The metering valve stem <NUM> has an opposing second axial end portion <NUM> extending from the propellant metering chamber <NUM>.

The first axial end wall <NUM> of the valve body <NUM> comprises a first metering valve stem hole <NUM> for receiving the dispensing nozzle <NUM> of the metering valve stem <NUM>, the dispensing nozzle <NUM> extending from the valve body <NUM> through the first axial end wall <NUM> of the valve body <NUM>.

The intermediate wall <NUM> comprises an intermediate metering valve stem hole <NUM>' for receiving the metering valve stem.

The second axial end wall <NUM> of the valve body <NUM> comprises a second metering valve stem hole <NUM>" for receiving the second axial end portion <NUM> of the metering valve stem <NUM>, the second axial end portion <NUM> of the metering valve stem <NUM> extending from the valve body <NUM> through the second axial end wall <NUM> of the valve body <NUM>.

The metering valve stem holes <NUM>, <NUM>', <NUM>" are dimensioned to form a seal around the metering valve stem <NUM> to prevent leakage of propellant/product through the metering valve stem holes <NUM>, <NUM>', <NUM>". The metering valve stem holes <NUM>, <NUM>', <NUM>" may each comprise a respective gasket or o-ring (not shown) for assisting sealing around the metering valve stem <NUM>.

The propellant metering chamber <NUM> is tubular and cylindrical. The propellant metering chamber <NUM> is sized to hold a predetermined quantity of propellant suitable to deliver a single dose of product. The propellant metering chamber <NUM> may have a volume of between <NUM> and <NUM> microlitres e.g. around <NUM> microlitres.

The product metering chamber <NUM> is tubular and cylindrical. It is sized to hold a predetermined quantity of insecticide. The product metering chamber <NUM> may have a volume of between <NUM> and <NUM> microlitres.

Preferably the relative volume ratio of the product metering chamber <NUM> to the propellant metering chamber <NUM> is about <NUM>:<NUM>.

The metering valve stem <NUM> extends within the propellant metering chamber <NUM> and product metering chamber <NUM> from the dispensing nozzle <NUM> at its first axial end which extends from the product metering chamber <NUM> to the second axial end portion <NUM> which extends from the propellant metering chamber <NUM> i.e. the second axial end portion <NUM> of the metering valve stem <NUM> is external to the metering valve body <NUM>.

The metering valve stem <NUM> comprises a product channel <NUM> extending axially within the metering valve stem <NUM> between a product outlet <NUM> at a first axial end of the product channel <NUM> and a product inlet <NUM> at a second axial end of the product channel <NUM> in the second axial end portion <NUM> of the metering valve stem <NUM>.

The product outlet <NUM> is a radial opening in a side wall of the metering valve stem <NUM>.

The product inlet <NUM> is provided (outside of the metering valve body <NUM>) in the second axial end portion <NUM> of the metering stem valve <NUM>. The product inlet <NUM> is an axial opening provided in the axial end face <NUM> of the second axial end portion <NUM> of the metering valve stem <NUM>. The axial product inlet <NUM> is off-set from the centre of the axial end face <NUM> of the second axial end portion <NUM> of the metering valve stem <NUM>.

The product channel <NUM> extends axially through the metering valve stem <NUM> (within the propellant metering chamber <NUM>) from the axial product inlet <NUM> to the radial product outlet <NUM>. The axial extension of the product channel <NUM> is greater than the axial extension of the propellant metering chamber <NUM>.

The metering valve stem <NUM> may further comprise a tubular extension <NUM> (e.g. a flexible tubular extension) fitted to the second axial end portion <NUM> by connection at the axial end face <NUM> of the second axial end portion <NUM>. This is shown in <FIG> and <FIG>. The tubular extension <NUM> is in fluid communication with the product channel <NUM>.

The metering valve has a propellant channel <NUM> which comprises a conduit extending axially within the metering valve stem <NUM> between a propellant outlet opening <NUM> at a first axial end of the propellant channel (conduit) <NUM> and a propellant inlet opening <NUM> at a second axial end of the propellant channel (conduit) <NUM> in the second axial end portion <NUM> of the metering valve stem <NUM>.

The propellant outlet opening <NUM> is a radial opening in the side wall of the metering valve stem.

The propellant inlet opening <NUM> is provided (outside of the metering valve body <NUM>) in the second axial end portion <NUM> of the metering stem valve <NUM>. The propellant outlet opening <NUM> is a radial opening provided in a side wall of the second axial end portion <NUM> of the metering valve stem <NUM>. The propellant inlet opening <NUM> is closer to the axial end face <NUM> of the second axial end portion <NUM> of the metering valve stem <NUM> than the propellant outlet opening <NUM> (i.e. the spacing between the propellant inlet opening <NUM> and the axial end face <NUM> of the second axial end portion <NUM> is less than the spacing between the propellant outlet opening <NUM> and the axial end face <NUM>). The propellant inlet opening <NUM> will be provided further from the axial end face <NUM> of the second axial end portion <NUM> of the metering valve stem <NUM> than the product inlet <NUM> (i.e. the spacing between the propellant inlet opening <NUM> and the axial end face <NUM> of the second axial end portion <NUM> is more than the spacing between the product inlet <NUM> and the axial end face <NUM> - in this specific example, the product inlet is, in fact, provided in the axial end face <NUM>).

The propellant channel (conduit) <NUM> extends axially through the metering valve stem <NUM> from the radial propellant inlet opening <NUM> to the radial propellant outlet opening <NUM>. The axial extension of the propellant channel (conduit) <NUM> is less than the axial extension of the propellant metering chamber <NUM> and less than the axial extension of the propellant channel <NUM>.

The propellant channel (conduit) <NUM> extends axially within the metering valve stem <NUM> parallel and adjacent to a portion of the product channel <NUM>.

The metering valve stem <NUM> further includes a connecting channel <NUM> which comprises an axially extending conduit having a radial inlet opening <NUM> and a radial outlet opening <NUM> (both provided in the side wall of the metering valve stem <NUM>).

A portion of the connecting channel (conduit) <NUM> extends parallel to and adjacent the product channel <NUM>. The product outlet <NUM> is radially aligned with a central axial end portion of the connecting channel (conduit) <NUM> i.e. the product outlet <NUM> is radially interposed between the inlet opening <NUM> and outlet opening <NUM> of the connecting channel (conduit) <NUM>.

The dispensing nozzle <NUM> is a hollow tube having a side port <NUM> and an axial end port <NUM>.

The metering valve stem <NUM> further comprises an annular propellant metering chamber flange <NUM> extending within the propellant metering chamber <NUM>. A coiled spring <NUM> is retained within the propellant metering chamber <NUM> between the propellant metering chamber flange <NUM> and the second axial end wall <NUM> of the valve body <NUM>. It surrounds the metering valve stem <NUM> in the propellant metering chamber <NUM>.

The metering valve stem <NUM> further comprises an annular product metering chamber flange <NUM> extending within the product metering chamber <NUM>.

The metering valve stem <NUM> is movable within the metering valve body <NUM> to a dispensing position (shown in <FIG>) in which there is no fluid communication between the product channel <NUM> and the product metering chamber <NUM>. The fluid communication between the product channel <NUM> and the product metering chamber <NUM> is prevented by occlusion of the product channel <NUM> which is achieved by occlusion of the product outlet <NUM>. The radial product outlet <NUM> is aligned with (and occluded by) the intermediate wall <NUM> of valve body i.e. the product outlet <NUM> is positioned within the intermediate metering valve stem hole <NUM>'.

In the dispensing position shown in <FIG>, fluid communication between the propellant channel (conduit) <NUM> and the propellant metering chamber <NUM> is prevented. The fluid communication between the propellant channel (conduit) <NUM> and the propellant metering chamber <NUM> is prevented by isolation of the propellant channel (conduit) <NUM> from the propellant metering chamber <NUM> which is achieved by isolation of the propellant outlet opening <NUM> from the propellant metering chamber <NUM>. In the dispensing position, the propellant outlet opening <NUM> is positioned outside of the propellant metering chamber <NUM> (and the metering valve body <NUM>).

In the dispensing position shown in <FIG>, the propellant metering chamber <NUM> and product metering chamber <NUM> are in fluid communication with atmosphere via the dispensing nozzle <NUM> of the metering valve stem <NUM> such that a metered dose of product and propellant can be dispensed from the metering valve body <NUM>. In the dispensing position, the side port <NUM> of the dispensing nozzle <NUM> is located within the product metering chamber <NUM> such that there is fluid communication between the product metering chamber <NUM> and the axial end port <NUM> of the dispense nozzle <NUM> (which vents to atmosphere).

The connecting channel (conduit) <NUM> fluidly connects the propellant metering chamber <NUM> to the product metering chamber <NUM> when the metering valve stem <NUM> is in the dispensing position. The radial inlet opening <NUM> of the connecting channel (conduit) <NUM> is positioned within propellant metering chamber <NUM> and the radial outlet opening <NUM> of the connecting channel (conduit) <NUM> is positioned within the product metering chamber <NUM>. In this way, the propellant metering chamber <NUM> is in fluid communication with the dispensing nozzle <NUM> via the product metering chamber <NUM> and the propellant and product can be dispensed simultaneously.

To summarise, in the dispensing position shown in <FIG>:.

The metering valve stem <NUM> is movable within the metering valve body <NUM> between the dispensing position and a filling position (shown in <FIG>) in which fluid communication is provided between the product channel <NUM> and the product metering chamber <NUM> so that product can enter the product metering chamber <NUM> through the metering valve stem <NUM> via the product channel <NUM>. The product channel <NUM> is un-occluded and the product outlet <NUM> is positioned within the product metering chamber <NUM>.

In the filling position, fluid communication is also provided between the propellant channel (conduit) <NUM> and the propellant metering chamber <NUM> so that propellant can enter the propellant metering chamber <NUM> through the metering valve stem <NUM> via the propellant channel (conduit) <NUM>. The propellant outlet opening <NUM> is positioned within the propellant metering chamber <NUM> whilst the propellant inlet opening <NUM> remains external to the propellant metering chamber <NUM>/metering valve body <NUM>.

In the filling position, the propellant and product metering chambers <NUM>, <NUM> fill with the propellant and product respectively through the metering valve stem <NUM> in preparation for dispensing to atmosphere from both chambers <NUM>, <NUM> in the dispensing position via the dispensing nozzle <NUM>.

In the filling position shown in <FIG>, there is no fluid communication between the propellant metering chamber <NUM> and the product metering chamber <NUM>. The radial inlet opening <NUM> of the connecting channel (conduit) <NUM> is aligned with (and occluded by) the intermediate wall <NUM> of the valve body <NUM> i.e. the inlet opening <NUM> of the connecting channel (conduit) <NUM> is positioned within the intermediate metering valve stem hole <NUM>'.

In the filling position shown in <FIG>, there is no fluid communication between the metering valve body <NUM> and atmosphere. Both the side port <NUM> and axial end port <NUM> of the dispensing nozzle <NUM> are located externally of the product metering chamber <NUM>/metering valve body <NUM>.

The propellant metering chamber flange <NUM> acts to limit axial movement of the metering valve stem <NUM> by abutment against the intermediate wall <NUM> on the propellant metering chamber <NUM> side in the filling position. It also helps to seal the intermediate metering valve stem hole <NUM>' at the intermediate wall <NUM> of the valve body <NUM> thus helping to prevent fluid communication between the propellant metering chamber <NUM> and the product metering chamber <NUM>.

The product metering chamber flange <NUM> acts to limit axial movement of the metering valve stem <NUM> by abutment against the first axial end wall <NUM> of the valve body <NUM> in the filling position. It also helps to seal the first metering valve stem hole <NUM> at the first axial end wall <NUM> of the valve body <NUM> thus helping to prevent fluid communication between the product metering chamber <NUM> and the dispensing nozzle <NUM>/atmosphere.

To summarise, in the filling position shown in <FIG>:.

<FIG> and <FIG> show a cross-section through a second reference example of a metering valve <NUM>.

Many features of the second reference example of the metering valve are as described for the first reference example shown in <FIG> and <FIG> and therefore common reference numerals are used. Features common to both examples will not be described again below.

The metering valve <NUM> comprises a metering valve body <NUM> which is divided into a propellant metering chamber <NUM> and a product metering chamber <NUM> by an intermediate wall <NUM>. The intermediate wall <NUM> comprises an axially extending tubular occluding wall <NUM> which encircles the dispensing nozzle <NUM> of the metering valve stem <NUM> in the vicinity of the side port <NUM>. The tubular occluding wall <NUM> comprises a first radial aperture <NUM> and a diametrically opposed second radial aperture <NUM>'.

The metering valve has a propellant channel <NUM>' which comprises a recess extending axially along the surface of the metering valve stem <NUM> between a propellant outlet end <NUM>' at a first axial end of the propellant channel (recess) <NUM>' and a propellant inlet end <NUM> at a second axial end of the propellant channel (recess) <NUM> in the second axial end portion <NUM> of the metering valve stem <NUM>.

The propellant inlet end <NUM>' is provided (outside of the metering valve body <NUM>) in the second axial end portion <NUM> of the metering stem valve <NUM>. The propellant inlet end <NUM>' is closer to the axial end face <NUM> of the second axial end portion <NUM> of the metering valve stem <NUM> than the propellant outlet end <NUM>' (i.e. the spacing between the propellant inlet end <NUM>' and the axial end face <NUM> of the second axial end portion <NUM> is less than the spacing between the propellant outlet end <NUM>' and the axial end face <NUM>). The propellant inlet end <NUM>' will be provided further from the axial end face <NUM> of the second axial end portion <NUM> of the metering valve stem <NUM> than the product inlet <NUM> (i.e. the spacing between the propellant inlet end <NUM> and the axial end face <NUM> of the second axial end portion <NUM> is more than the spacing between the product inlet <NUM> and the axial end face <NUM> - in this specific example, the product inlet is, in fact, provided in the axial end face <NUM>).

The propellant channel (recess) <NUM>' extends axially along the surface of the metering valve stem <NUM> from the radial propellant inlet end <NUM>' to the radial propellant outlet end <NUM>'. The axial extension of the propellant channel (recess) <NUM>' is less than the axial extension of the propellant metering chamber <NUM> and less than the axial extension of the propellant channel <NUM>.

The propellant channel (recess) <NUM>' extends axially along the metering valve stem <NUM> parallel and adjacent to a portion of the product channel <NUM>.

The metering valve stem <NUM> further includes an axially extending connecting channel (recess) <NUM>' which comprises a recess extending axially along the surface of the metering valve stem <NUM> between an inlet end <NUM>' and an outlet end <NUM>'.

The product outlet <NUM> is radially aligned with the connecting channel (recess) <NUM>' and diametrically opposed to the inlet end <NUM>' of the connecting channel (recess) <NUM>'.

The metering valve stem <NUM> is movable within the metering valve body <NUM> to a dispensing position (shown in <FIG>) in which there is no fluid communication between the product channel <NUM> and the product metering chamber <NUM>. The fluid communication between the product channel <NUM> and the product metering chamber <NUM> is prevented by isolation of the product channel <NUM> from the product metering chamber <NUM> which is achieved by positioning of the product outlet <NUM> within the propellant metering chamber <NUM>.

In the dispensing position shown in <FIG>, fluid communication between the propellant channel (recess) <NUM>' and the propellant metering chamber <NUM> is prevented. The fluid communication between the propellant channel (recess) <NUM>' and the propellant metering chamber <NUM> is prevented by isolation of the propellant channel (recess) <NUM>' from the propellant metering chamber <NUM> which is achieved by isolation of the propellant outlet end <NUM>' from the propellant metering chamber <NUM>. In the dispensing position, the propellant outlet end <NUM>' is positioned outside of the propellant metering chamber <NUM> (and the metering valve body <NUM>).

In the dispensing position shown in <FIG>, the propellant metering chamber <NUM> and product metering chamber <NUM> are in fluid communication with atmosphere via the dispensing nozzle <NUM> of the metering valve stem <NUM> such that a metered dose of product and propellant can be dispensed from the metering valve body <NUM>. In the dispensing position, the side port <NUM> of the dispensing nozzle <NUM> is aligned with the first radial aperture <NUM> through the tubular occluding wall <NUM> such that there is fluid communication between the product metering chamber <NUM> and the axial end port <NUM> of the dispense nozzle <NUM> (which vents to atmosphere).

The connecting channel (recess) <NUM>' fluidly connects the propellant metering chamber <NUM> to the product metering chamber <NUM> when the metering valve stem <NUM> is in the dispensing position. The inlet end <NUM>' of the connecting channel (recess) <NUM>' is positioned within propellant metering chamber <NUM> and the outlet end <NUM>' of the connecting channel (recess) <NUM>' is positioned within the product metering chamber <NUM> aligned with the second radial aperture <NUM>' through the tubular occluding wall <NUM>. In this way, the propellant metering chamber <NUM> is in fluid communication with the dispensing nozzle <NUM> via the product metering chamber <NUM> and the propellant and product can be dispensed simultaneously.

The metering valve stem <NUM> is movable within the metering valve body <NUM> between the dispensing position and a filling position (shown in <FIG>) in which fluid communication is provided between the product channel <NUM> and the product metering chamber <NUM> so that product can enter the product metering chamber <NUM> through the metering valve stem <NUM> via the product channel <NUM>. The product outlet <NUM> positioned within the product metering chamber <NUM>.

In the filling position, fluid communication is also provided between the propellant channel (recess) <NUM>' and the propellant metering chamber <NUM> so that propellant can enter the propellant metering chamber <NUM> via the propellant channel (recess) <NUM>'. The propellant outlet end <NUM>' is positioned within the propellant metering chamber <NUM> whilst the propellant inlet end <NUM>' remains external to the propellant metering chamber <NUM>/metering valve body <NUM>.

In the filling position, the propellant and product metering chambers <NUM>, <NUM> fill with the propellant and product respectively via the metering valve stem <NUM> in preparation for dispensing to atmosphere from both chambers <NUM>, <NUM> in the dispensing position via the dispensing nozzle <NUM>.

In the filling position shown in <FIG>, there is no fluid communication between the propellant metering chamber <NUM> and the product metering chamber <NUM>. The inlet end <NUM>' of the connecting channel (recess) <NUM>' is isolated from the propellant metering chamber <NUM> by positioning within the product metering chamber <NUM> (within the occluding wall <NUM>).

<FIG> and <FIG> show an embodiment of a canister <NUM>' according to the present invention, with the pressure regulating valve <NUM> in the closed and open positions respectively. Where the features of the canister of <FIG> and <FIG> are the same as shown in the canister of <FIG> and <FIG>, the same reference numerals are used. In other words, the pressure regulating valve <NUM> is identical, and operates in exactly the same way, as the pressure regulating valve <NUM> of <FIG> and <FIG>.

However, the configuration of the low pressure side <NUM> of the pressure regulating valve is different, and explained below.

As shown, the low pressure side <NUM> of the canister <NUM>' is split into two chambers - a low pressure chamber <NUM> for containing a gaseous propellant; and a product reservoir <NUM> for containing product, which is also at a low pressure relative to the high pressure chamber <NUM>. In fact, the product reservoir <NUM> is maintained at a base pressure that is below the predetermined pressure of the low pressure chamber <NUM>. Typically, the product in the product reservoir may be maintained at approximately atmospheric pressures.

The low pressure chamber <NUM> interacts with the high pressure chamber <NUM> in exactly the same way as the low pressure chamber <NUM> in <FIG> and <FIG>.

A partition wall <NUM> separates the low pressure chamber <NUM> from the product reservoir <NUM>. In use, the canister is assembled with a dispensing valve <NUM>. As shown, the dispensing valve <NUM> is received in openings <NUM>, <NUM> in the partition wall <NUM> and upper wall <NUM>, respectively.

The openings <NUM>, <NUM> in the partition wall <NUM> and upper wall <NUM> are dimensioned to seal against an outer surface of the dispensing valve <NUM>. Thus, the dispensing valve prevents product in the product reservoir <NUM> from mixing with propellant in the propellant chamber <NUM> of the canister <NUM>'. This is particularly advantageous where the propellant and product are immiscible, and/or where the product and propellant are relatively unstable in combination.

The propellant and product may only come into contact with each other after they enter the dispensing valve <NUM> from their respective chambers <NUM>, <NUM>. The dispensing valve used may be a metering valve as shown in <FIG> and <FIG>.

<FIG> and <FIG> show a third reference example metering valve , in a filling position and dispensing position respectively.

The metering valve stem <NUM> is urged into the filling position of <FIG> by a coiled spring (not shown). The metering valve stem <NUM> is movable into the dispensing position by application of a force sufficient to overcome the force of the spring, e.g. by a user depressing the dispensing nozzle <NUM> into the canister.

The metering valve <NUM> essentially comprises a cylindrical metering valve body <NUM>, within which is fitted cylindrical metering valve stem <NUM>.

The metering valve body <NUM> includes a propellant inlet <NUM> positioned at an axial end of the metering valve body <NUM>, for allowing propellant to flow into propellant metering chamber <NUM>; and a product inlet <NUM> for allowing product to flow into product metering chamber <NUM>, the product inlet including a side channel <NUM>. A separating wall <NUM> separates the product metering chamber <NUM> from a propellant metering chamber <NUM>. Metering valve stem <NUM> seals against an inner surface of the separating wall <NUM> through provision of a gasket (not shown), such that there is substantially no space between the separating wall <NUM> and metering valve stem <NUM> through which fluid can pass.

Product inlet <NUM> is in fluid communication with the product reservoir <NUM> of <FIG> and <FIG>. Propellant inlet <NUM> is in fluid communication with the propellant chamber <NUM> of <FIG> and <FIG>. Moreover, the opening <NUM> of partition wall <NUM> seals against the metering valve body <NUM>, and the opening <NUM> of the upper wall <NUM> also seals against the metering valve body <NUM>.

In practice, the canister <NUM>' and metering valve <NUM> are supplied to an assembly factory as separate parts. The product reservoir <NUM> is then filled with product simultaneously with the metering valve <NUM> being fitted to the canister. The metering valve <NUM> is cold welded to the openings <NUM>, <NUM> to ensure an effective seal.

A second canister partition wall <NUM> of the canister, with corresponding opening <NUM>, is shown in <FIG>. Partition walls <NUM>, <NUM> define between them an empty space <NUM>. Second partition wall <NUM> is provided for reasons that will become clear below.

Metering valve stem <NUM> includes a dispensing nozzle/hose <NUM>, with a side port <NUM> and an axial end port <NUM>; and a connecting channel <NUM> with a radial inlet opening <NUM> and a radial outlet opening <NUM>.

In the filling position as shown in <FIG>, radial inlet opening <NUM> of the connecting channel <NUM> is sealed/occluded from propellant metering chamber by O-ring <NUM>. Thus, while in the dispensing position, fluid is unable to flow between the propellant metering chamber <NUM> and the product metering chamber <NUM>. Moreover, side port <NUM> of dispensing nozzle <NUM> is sealed/occluded from product reservoir <NUM> and product metering chamber <NUM> by O-ring <NUM>. Thus, neither product, nor propellant, are able to exit the metering valve <NUM> in the filling position, and propellant is unable to enter the product reservoir.

In this filling position, propellant flows into the propellant metering chamber <NUM> from the low pressure chamber <NUM> via the open propellant inlet <NUM>; and product flows into the product metering chamber <NUM> from the product reservoir <NUM>, via the product inlet <NUM>. Accordingly, the two metering chambers fill with product and propellant, to a quantity prescribed by the respective sizes of the product and propellant metering chambers.

As propellant flows into the propellant metering chamber <NUM>, the pressure in the propellant chamber <NUM> will fall below the predetermined pressure. The pressure regulating valve of canister <NUM>' will therefore open, to allow propellant to flow into the low pressure chamber <NUM> from the high pressure chamber <NUM>, until the predetermined pressure is re-established in the low-pressure chamber (at which point the pressure regulating valve will close again).

In effect, a metered quantity of product and propellant is measured out by the metering valve in the filling position. In practice, the process of filling the metering chambers <NUM>, <NUM> with product and propellant takes a fraction of a second.

As shown in <FIG>, the side channel <NUM> of the product inlet <NUM> is positioned just above partition wall <NUM> (i.e. adjacent to the partition wall, on the same side of the partition wall as the axial outlet <NUM> of the dispensing nozzle <NUM>), and the product metering chamber <NUM> in turn is positioned just below the side channel <NUM>. Accordingly, even when the level of product in the product reservoir <NUM> runs low, product will still flow into the product metering chamber <NUM> under gravity when the metering valve stem <NUM> is in the filling position. Hence, the third reference example of <FIG> and <FIG> is configured to be used in the upright configuration shown, and the product in the product reservoir therefore doesn't have to be maintained under pressure.

Once the product metering chamber <NUM> and propellant metering chamber <NUM> are filled with product and propellant (respectively), the metering valve can then be moved into a dispensing configuration as shown in <FIG>, by translation of the metering valve stem <NUM> within the metering valve body <NUM>.

<FIG> shows the metering valve in the dispensing configuration.

In the dispensing configuration, the metering valve stem <NUM> is pressed into the metering valve body <NUM> relative to the filling position, e.g. by applying a force to the dispensing nozzle <NUM>.

In the dispensing position, a propellant inlet plug (O-ring) <NUM> seals/occludes the propellant inlet <NUM>, so that propellant cannot flow between the propellant chamber <NUM> and the propellant metering chamber <NUM>. Similarly, a product inlet plug (O-ring) <NUM> seals/occludes product inlet <NUM>, so that product cannot flow between the product reservoir <NUM> and the product metering chamber <NUM>.

Simultaneously, radial inlet <NUM> of connecting channel <NUM> is open to the propellant metering chamber <NUM>, radial outlet <NUM> of the connecting channel <NUM> is open to the product metering chamber <NUM>, and side port <NUM> of dispensing nozzle <NUM> is open to the product reservoir <NUM>.

Accordingly, the propellant (which is initially at the predetermined pressure) travels into the product reservoir <NUM> via the connecting channel <NUM>, continues through the product metering chamber <NUM> into the dispensing nozzle <NUM>, and finally out of the axial end port <NUM> to atmosphere. As the propellant passes through the product metering chamber <NUM>, it flushes the product out with it, thus causing the product to be dispensed from the dispensing nozzle under pressure.

Advantageously, the product and propellant only meet each other at the very last minute, i.e. milliseconds before they exit the dispensing nozzle. This is particularly advantageous where the propellant and product are immiscible, and/or where the product and propellant are relatively unstable in combination.

Once the product and propellant have been dispensed, the metering valve stem <NUM> will move back into the filling position, under the force of the coiled spring (now shown), where the product metering chamber <NUM> and propellant metering chamber <NUM> can fill once again.

While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the scope of the invention.

For example, the conduit propellant channel and/or the conduit connecting channel of the metering valve shown in <FIG> and <FIG> can be replaced with the recess channels shown in <FIG> and <FIG> (and vice versa). The dispense nozzle structure and occluding wall of the metering valve shown in <FIG> and <FIG> can be used in the <FIG>/<FIG> valve (and vice versa).

<FIG> and <FIG> show an embodiment of a canister <NUM>' according to the first aspect of the present invention, with the pressure regulating valve <NUM> in the closed and open positions respectively. Where the features of the canister of <FIG> and <FIG> are the same as shown in the canister of <FIG> and <FIG>, the same reference numerals are used. In other words, the pressure regulating valve <NUM> is identical, and operates in exactly the same way, as the pressure regulating valve <NUM> of <FIG> and <FIG>.

<FIG> and <FIG> show an embodiment of a metering valve according to the second aspect of the present invention, in a filling position and dispensing position respectively.

As shown in <FIG>, the side channel <NUM> of the product inlet <NUM> is positioned just above partition wall <NUM> (i.e. adjacent to the partition wall, on the same side of the partition wall as the axial outlet <NUM> of the dispensing nozzle <NUM>), and the product metering chamber <NUM> in turn is positioned just below the side channel <NUM>. Accordingly, even when the level of product in the product reservoir <NUM> runs low, product will still flow into the product metering chamber <NUM> under gravity when the metering valve stem <NUM> is in the filling position. Hence, the embodiment of <FIG> and <FIG> are configured to be used in the upright configuration shown, and the product in the product reservoir therefore doesn't have to be maintained under pressure.

Claim 1:
An aerosol canister (<NUM>') for dispensing a product, said canister (<NUM>') comprising:
a high pressure chamber (<NUM>) for containing a liquefied or compressed gas propellant;
a low pressure chamber (<NUM>) for containing a gas propellant;
a product reservoir (<NUM>) for containing a product to be dispensed; and
a pressure regulating valve (<NUM>) interposed between the high pressure chamber (<NUM>) and the low pressure chamber (<NUM>), the pressure regulating valve (<NUM>) adapted to provide a fluid flow path from the high pressure chamber (<NUM>) to the low pressure chamber (<NUM>) when the pressure in the low pressure chamber (<NUM>) drops below a predetermined pressure; wherein
the canister (<NUM>') further comprises a partition wall (<NUM>) interposed between the low pressure chamber (<NUM>) and the product reservoir (<NUM>);
characterised in that the partition wall (<NUM>) comprises an opening (<NUM>) for receiving a dispensing valve (<NUM>).