GB2510400A

GB2510400A - Foam Dispenser

Info

Publication number: GB2510400A
Application number: GB1301875.9A
Authority: GB
Inventors: Mark Nicmanis
Original assignee: Cambridge Consultants Ltd
Current assignee: Cambridge Consultants Ltd
Priority date: 2013-02-01
Filing date: 2013-02-01
Publication date: 2014-08-06
Also published as: MX2015009835A; BR112015018329A2; KR20150118172A; CN105102134A; PT2950935T; EP2950935A1; BR112015018329B1; RU2643045C2; ES2817543T3; DK2950935T3; AU2014210903A1; ZA201506154B; DK3222362T3; CA2898877A1; GB2525801A; CA2898877C; KR102218818B1; EP3222362B1; US20150360853A1; ES2633273T3

Abstract

The present invention relates to a dispenser for producing a foam without requiring the use of liquefied gas. The dispenser 20 comprises a receptacle 37 for holding a surfactant solution 21, a means for supplying a gas 23, and a means for conveying said surfactant solution in said receptacle and said gas along a flow path towards an outlet 29. The conveying means comprises a conduit 31 having a foaming section 25 for generating the foam from the surfactant solution 21 and the gas 23. The foaming section 25 has internal dimensions adapted to provide a foam having a quality characterised by predefined limits. Later embodiments relate to a foaming component, and a method of producing foam of said component.

Description

Foam Dispenser The present invention relates to dispensers, in particular loam dispensers capable of producing a foam using a compressed gas, but without requiring use of volatile organic compounds (VOCs).

Common foam and aerosol dispensers produce a loam or an aerosol using VOCs, where the VOCs are provided as a liquelied gas which acts as a propellant. For example, many aerosol dispensers use liquelied petroleum gas (LAG) or the like. However, environmental agencies in many different countries are currently attempting to phase out the use of such dispensers due to the health risks associated with them, such as sensory irritation and respiratory problems.

VOCs are also llammable and more expensive than compressed gas propellants.

To date it has not been possible to produce satislactorily high quality loams without the use olVOCs, while ensuring dispensing devices are suitably cost efficient to manufacture.

The present invention aims to address these issues, by providing a device which enables generation ol sufficiently high quality foams (e.g. having a relatively high gas phase volume and a relatively small and uniform bubble size) without the use ol VOCs.

The present invention provides a dispenser br producing a foam without requiring the use ol liquefied gas, from an outlet, said dispenser comprising: a receptacle for holding a surfactant solution; means br supplying a gas; means for conveying said surfactant solution in said receptacle and said gas along allow path towards said outlet; wherein said conveying means comprises a conduit having a loaming section for generating said loam Irom said surfactant solution and said gas; and wherein said loaming section has internal dimensions adapted to provide a foam having a quality characterised by predefined limits.

The boaming section may comprise at least one loam enhancing element disposed in said flow path and the internal dimensions of the foaming section may be provided, at least in part, by the at least one loam enhancing element.

The at least one foam enhancing element may comprise at least one ol: a generally spherical element; a generally cuboid element; a generally cylindrical element; a generally conical element; a porous element; and an element extending Irom an internal surface of the boaming section into said flow path.

The foaming section may further comprise at least one retaining element for retaining the at least one foam enhancing element within the foaming section.

The predefined limits may comprise an average bubble diameter of less than 70 microns.

The predefined limits may comprise an average bubble diameter of less than 60 microns.

The predefined limits may comprise an average bubble diameter of between 30 and 70 microns.

The predefined limits may comprise a uniformity characterised by a standard deviation of less than 35 microns.

The predefined limits may comprise a uniformity characterised by a standard deviation of less than 25 microns.

The predefined limits may comprise a uniformity characterised by a standard deviation of between 10 and 35 microns.

The internal dimensions may comprise a wetted surface area of greater than 1800 square millimetres.

The internal dimensions may comprise a wetted surface area of greater than 3000 square millimetres.

The internal dimensions may comprise a wetted surface area of between 4500 and 6000 square millimetres.

The internal dimensions may comprise a wetted surface area to void space volume ratio of greater than 4 square millimetres per cubic millimetre.

The internal dimensions may comprise a wetted surface area to void space volume ratio of greater than 16 square millimetres per cubic millimetre.

The internal dimensions may comprise a wetted surface area to void space volume ratio of between 20 and 25 square millimetres per cubic millimetre.

The internal dimensions may comprise a wetted surface area to two phase flow length ratio of greater than 3 square millimetres per millimetre.

The internal dimensions may comprise a wetted surface area to two phase flow length ratio of greater than it square millimetres per millimetre.

The internal dimensions may comprise a wetted surface area to two phase flow length ratio of greater than 8 square millimetres per millimetre.

The internal dimensions may comprise a two phase flow length of greater than 40 millimetres.

The internal dimensions may comprise a two phase flow length of greater than 60 millimetres.

The internal dimensions may comprise a two phase flow length of greater than 1200 millimetres.

The internal dimensions may comprise a foaming section diameter of less than 10 millimetres.

The internal dimensions may comprise a foaming section diameter of less than 4 millimetres.

The internal dimensions may comprise a foaming section diameter of between 0.1 and 10 millimetres.

The predefined limits may comprise a uniformity characterised by a standard deviation of less than 60% of the average bubble diameter.

The predefined limits may comprise a uniformity characterised by a standard deviation of less than 50% of the average bubble diameter.

The dispenser may further comprise: means for applying pressure to the surfactant solution in said receptacle to drive said surfactant solution along said conduit and towards said foaming section and for driving foam generated by said foaming section to said outlet.

The pressure applying means may be provided by said gas which is held under pressure within said receptacle.

The gas may be held at a pressure of between 2 bar and 25 bar.

The gas may be held at a pressure of between 2 bar and 8 bar.

The concentration of said gas in said surfactant solution may be less than 350 milligrams per kilogram of said surfactant solution.

The gas may comprise a non-liquefied gas. The non-liquefied gas may comprise at least one of: air, nitrogen, carbon dioxide, one or more noble gases.

The conveying means may comprise a bifurcated tube having a gas inlet and a surfactant solution inlet which meet at a point of bifurcation at which said gas and said surfactant solution mix, in operation, prior to entering the foaming section.

The gas inlet and said surfactant solution inlet may be vertically separated from one another.

S The dispenser may be configured to produce a foam without using volatile organic compounds, VOCs.

According to another aspect of the present invention there is provided a foaming component, for a foam dispenser, for producing a foam without requiring the use of liquefied gas, said foaming element comprising: means for conveying a surfactant solution from a receptacle and a gas along a flow path; wherein said conveying means comprises a conduit having a foaming section for generating said foam from said surfactant solution and said gas; and wherein said foaming section has internal dimensions adapted to provide a foam having a quality characterised by predefined limits.

According to another aspect of the present invention there is provided a dispenser for producing a foam without requiring the use of liquefied gas, from an outlet, said dispenser comprising: a receptacle for holding a surfactant solution; means for supplying a gas; means for conveying said surfactant solution in said receptacle and said gas along a flow path towards said outlet; wherein said conveying means comprises a conduit having a foaming section for generating said foam from said surfactant solution and said gas; and wherein said foaming section has internal dimensions conforming to at least one of the following parameters: a welled surface area of greater than 1800 square millimetres; a welled surface area to void space volume ratio of greater than 4 square millimetres per cubic millimetre; a foaming section diameter of less than 10 millimetres; and a two phase flow length of greater than 40 millimetres. The gas may be held at a pressure of between 2 bar and 8 bar.

According to another aspect of the present invention there is provided a method of producing a foam without requiring the use of liquefied gas, using a foam dispenser as described above, or using a foaming component as described above.

According to another aspect of the present invention there is provided a method of producing a foam without requiring the use of liquefied gas, said method comprising: holding, in a receptacle, a surfactant solution; conveying said surfactant solution in said receptacle and a gas from a gas supply along a flow path towards an outlet; wherein said conveying step comprises conveying said surfactant solution and said gas in a conduit having a foaming section for generating said foam from said surfactant solution and said gas; and wherein said foaming section has internal dimensions adapted to provide a foam having a quality characterised by predefined limits.

According to another aspect of the present invention there is provided a dispenser for producing a foam, from an outlet, said dispenser comprising: a receptacle for holding a surfactant solution; means for supplying a gas; means for conveying said surfactant solution in said receptacle and said gas along a flow path towards said outlet; wherein said conveying means comprises a conduit having a foaming section for generating said foam from said surfactant solution and said gas; and wherein said foaming section has internal dimensions adapted to provide a foam having a quality characterised by predefined limits.

Embodiments of the present invention will now be described, by way of example only, with reference to the following figures, in which: Figure 1 schematically illustrates, in simplified overview, a dispenser system for dispensing foam; Figure 2 illustrates, in simplified form, a specific embodiment of a dispensing device for dispensing a foam; Figure 3 illustrates, in simplified form, another embodiment of a dispensing device for dispensing a foam; Figure 4 illustrates, in simplified form, part of a foaming section of a dispensing device; Figure 5 illustrates, in a simplified manner, a sample of foam created using a known foam dispenser; Figure 6 illustrates, in a simplified manner, a sample of foam created using a dispensing device substantially corresponding to the dispensing device illustrated in Figure 2; Figure 7 is a graph showing a number density distribution for a range of bubble diameters, for the foam samples illustrated in Figures 5 and 6.

Figure 1 schematically illustrates, in simplified overview, a dispenser system 8 according to the present invention. The dispenser system comprises a supply of a surfactant solution 11 (or a solution comprising another appropriate foaming agent) and a gas supply 13. The surfactant solution 11 and gas supply 13 are in fluid communication with a foaming section 15 which is configured for mixing the surfactant solution with the gas provided by the gas supply 13 to form a loam having the desired properties. The foaming section 15 is in fluid communication with an outlet 19 via a valve 17, to allow the foamed mixture of surfactant solution and gas to be conveyed from the foaming section 15 to the outlet 17 where the foam can exit the dispenser system 8.

Pressure is applied to the surfactant solution 11, from a suitable source 10, in order to drive the surfactant solution 11 into the foaming section 15. Although not illustrated, it will be appreciated that the same source of pressure 10, or a separate source of pressure, may be applied to drive the gas 13 into the foaming section 15. The surfactant solution 11 comprises a liquid surfactant, while the gas held in the gas supply comprises, in this embodiment, a non-liquefied gas, providing a compressed gas propellant. The gas comprises any suitable gas which is not liquefied at the operating pressure of the gas, which is preferably between 2 bar gauge and 25 bar gauge and more preferably between 2 bar gauge and 8 bar gauge and further preferably between 4 bar gauge and 6 bar gauge. Advantageously, the gas does not need to contain volatile organic compounds (VOCs).

As the gas 13 is not provided in liquefied form, only comparably small amount of gas, or none, will be present in the surfactant solution 11 (generally in dissolved form), in contrast to foam dispensers which use liquefied gas propellants. Preferably, the concentration of gas 13 in the surfactant solution 11 is 350 milligrams per kilogram of surfactant solution plus or minus 50 milligrams per kilogram, or the concentration may be less than 350 milligrams per kilogram, or less than 100 milligrams per kilogram of the surfactant solution 11.

In use, therefore, both the surfactant solution and the gas enter the foaming section 15, causing the surfactant solution and the gas to combine to form a foam comprising bubbles of the gas within the liquid surfactant, having predefined desired characteristics (e.g. having a target gas phase volume, meeting a target average bubble size, meeting a target standard deviation, meeting a target bubble concentration per unit volume, and/or having a target bubble size distribution). For many applications, for example, the following characteristics are generally desirable: a target gas phase volume that is relatively high (typically, for example, in excess of 90% or more preferably in excess of 95%), a relatively small average bubble diameter (typically, for example, below 100 microns, more preferably below 70 and further more preferably around 60 microns or even lower, or between 30 and 70 microns), a low standard deviation in the bubble diameter (typically, for example, below 35 microns and more preferably in the region of 25 microns plus or minus 2 microns, or an even lower value, or between 10 and 35 microns). Furthermore, the standard deviation may represent less than 60% of the average bubble diameter, or more preferably less than 50% of the average bubble diameter.

The pressure exerted on the surfactant by the source of pressure 10, as well as driving the surfactant held to enter the foaming section 15, also drives the foam held within the foaming section 15 to pass into the valve 17 and to exit the dispensing system 8 at the outlet 19. If a source of pressure other than the source of pressure 10 is used to propel the gas 13 into the foaming section 15, then this separate source of pressure also helps to drive the foam held within the foaming section 15.

The valve 17 can occupy an open or closed position. When the valve 17 is in the open position the foam is allowed to flow from the foaming section 15 to the outlet 19, and when the valve 17 is in the closed position the flow of foam from the foaming section 15 to the outlet 19 is prevented or restricted. In this way, the valve 17 controls the dispensing of foam from the dispensing system 8.

By way of example only, in one exemplary foam, produced by experimentation, the foam formed has a mean bubble diameter of approximately 60 microns, and a standard deviation in bubble diameter of approximately 25 microns at a time approximately 3 seconds after the foam has been dispensed from the dispensing system 8.

Figure 2 illustrates an embodiment of a dispensing device 20. The dispensing device 20 comprises a container in the form of an enclosed receptacle 37 for holding a surfactant solution 21 and a compressed gas propellant 23 under pressure, which are mixed, in operation, by the dispensing device to form a foam 41. The receptacle 37 has an opening 39 which is sealed by a valve 27. The valve 27 forms an airtight seal with the receptacle 37 in order that, when the valve is closed, neither the compressed gas propellant 23 nor the surfactant solution 21 can exit the receptacle 37. This is particularly important as in this embodiment the use of a compressed gas propellant means that the pressure within the receptacle 37 will be higher than the atmospheric pressure surrounding the receptacle.

As illustrated, in this embodiment the receptacle 37 acts as both a gas supply and a surfactant solution supply (e.g. performing the functions of both the supply of surfactant solution 11 and the gas supply 13 of Figure 1).

The valve 27 comprises a valve inlet 45 and a valve stem 47 which is moveably connected to the valve 27 in a slidable manner. The valve stem 47 comprises a valve stem inlet 49 disposed near a lower end of the valve stem 47 and a valve outlet 57 disposed near an upper end of the valve stem 47, the valve stem inlet 49 and the valve outlet 57 being in fluid communication via a channel 51. The valve stem 47 can be moved between an open position and a closed position. In the open position, fluid communication is permitted between the valve inlet 45 and the valve outlet 57, via the valve stem inlet 49 and the channel 51. When S the valve stem 47 is in its closed position, such fluid communication is prevented due to the sealing of the valve stem inlet 49 caused by the engagement of the valve stem inlet 49 with a surface of the valve 27. The valve stem 47 is biased into the closed position by a spring 43.

The dispensing device further comprises an actuator 55 mounted to the valve stem 47 for actuating the valve under pressure from a user. The actuator 55 comprises a nozzle 29 for directing foam which exits the valve outlet 57 to discharge the foam from the dispensing device 20.

As shown in Figure 2, a fluid conduit 60 is provided, in the receptacle 37, for communicating the surfactant solution 21 and the gas 23 to a foaming section 25 of the conduit 60 and for communicating foam from the foaming section 25 to the valve 27. The fluid conduit 60, in this embodiment, comprises a bifurcated tube having a gas inlet section 35 arranged for receiving the gas and a liquid inlet section 33 arranged for receiving the surfactant solution. The gas and liquid inlet sections 33, 35 converge at a manifold 31 at the junction of the bifurcated tube to conduct the gas 23 and surfactant solution 21 respectively into a common section of the fluid conduit 60, in which common section the foaming section 25 is provided. Hence, in this example, the foaming section 25 is downstream from the liquid and gas inlet sections 33, 35.

In this embodiment, the foaming section 25 of the fluid conduit 60 extends from the bifurcation of the fluid conduit 60 to an end of the fluid conduit distal from the bifurcation, said end at which the fluid conduit 60 connects to the valve 27.

Preferably, the length of the foaming section 25 is greater than 10 mm and more preferably is in the range of 50 to 70 mm.

As illustrated, the liquid inlet section 33 extends proximate to the base of the receptacle 37, while the gas inlet section 35 extends proximate to the top of the receptacle 37. This arrangement ensures that, when the dispensing device 20 is oriented in its upright position (as illustrated in Figure 2), the surfactant solution 21, which has a higher density than the compressed gas propellant 23, will occupy a lower part of the receptacle 37, while the compressed gas propellant 23 will occupy the remaining part at the top of the receptacle 37 not occupied by the surfactant solution, referred to as the headspace. However, it is noted that when the dispensing device 20 is held in a different orientation, in particular an upside down" orientation, gas inlet section 35 may serve as a liquid inlet section and the liquid inlet section 33 may seive as a gas inlet section.

As mentioned previously, the compressed gas propellant 23, due to its conipressed nature, creates a pressure inside the receptacle 37 which is higher than the atmospheric pressure which exists outside the i-eceptacle. The compressed gas propellant 23 therefore exeits a force on the surfactant solution 21. Preferably, the pressure of the gas propellant in the headspace is above 1 bar, and more preferably is above 2 bar, and preferably below 25 bar.

As the liquid inlet 33 is located below the liquid level of the surfactant solution (as illustrated in Figure 2), the force exerted on the surfactant solution 21 by the compiessed gas propellant 23 drives the surfactant solution 21 to enter the foaming section 25 via the liquid inlet section 33.

As the gas inlet section 35 is located above the liquid level of the surfactant solution, the compressed gas propellant is able to enter the foaming section 25 via the gas inlet 35.

When the valve 27 is closed, i.e. when the valve stem 47 occupies its closed position, the dispensing device 20 is sealed and no surfactant solution nor gas propellant is perniitted to exit the dispensing device 20. However, when the valve 27 is opened, i.e. when the valve stem 47 occupies its open position, the surfactant solution 21 and the gas propellant 23 are able to exit the dispensing device 20 via the valve outlet 57 and nozzle 29. In this situation, due to the force exerted on the surfactant solution 21 by the compressed gas propellant 23, the surfactant solution 21 is drawn into the foaming section 25 via the liquid inlet 33 and the manifold 31. The action of the surfactant solution 21 passing the gas inlet of the manifold 31 causes the gas propellant 23 to be diawn into the flow stieam of surfactant solution and thus into the manifold 31 and the foaming section 25.

In this embodiment, the foaming section 25 comprises a number of foam enhancing elements 53 disposed within the foaming section 25 and along the flow path of the surfactant solution and the gas propellant. The foam enhancing elements 53 produce a high quality foam with the desciibed desirable characteristics by providing a means foi increasing the wetted surface area of the foaming section 25, the wetted surface area to void space volunie ratio of the foaming section 25 and the wetted surface area to two phase flow length ratio (see comments on parameters in Table 1, below). Preferably, the foaming section 25 confoinis to at least one of key parameters 1 to 4 listed in Table 1, and more preferably conforms to all of parameters 1 to 4. It will be appreciated that, in other embodiments, a similar high quality foam can be produced without the use of foam enhancing elements 53. It will also be appreciated that for any of the parameters listed in Table 1 a value can be chosen (preferably within the given preferred range) in order to produce a foam having a desired quality.

The presence of the foam enhancing elements 53 within the foaming section 25 enables the foarriing section 25 to conform to at least key parameters 1 and 2 of Table 1, while using a foaming section of appropriate dimensions (e.g. a length of less than 70 mm) so that it may fit easily within say a typically sized aerosol can (e.g. 100-200mm in height).

Preferably, the wetted surface area to two phase flow length ratio is greater than 3 square millimetres per millimetre, or more preferably greater than ii square millimetres per millimetre.

A higher wetted surface area to two phase flow length ratio may be preferable for producing a desired foam, for example greater than 8 square millimetres per millimetre.

In this example, foam enhancing elements 53 comprise a plurality of generally spherical beads of glass (or other suitable material such as a plastic material).

The foaming section 25 also includes retainers 65 and 67 which are disposed at opposing ends of the foaming section 25. The retainers 65, 67 are located within the flow path of the foaming section 25, and are formed from a mesh-like material, in order to allow surfactant solution 21 and gas 23 (along with a foam comprising the surfactant solution and the gas) to pass through and thus travel along the fluid conduit 60. However, the retainers 65, 67 inhibit movement of the foam enhancing elements 53 along the fluid conduit 60, thus maintaining the position of the foam enhancing elements 53 and preventing their discharge from the dispensing device 20.

The presence of these foam enhancing elements 53 causes improved mixing of the gas propellant 23 with the surfactant solution 21 and enhances the formation of the foam 41 (for a given foaming section tube shape and/or dimensions) by, effectively, increasing the wetted surface area to void space volume ratio within the foaming section 25.

It has been found that the wetted surface area of the foaming section 25 (and any fluid conduit on either side), and in particular the wetted' area that comes into contact with the surfactant solution, has a material effect on foam properties. Accordingly, the wetted surface area may be tailored to provide a foam having particular required characteristics. In particular, it has been found that the ratio of the welled surface area of the foaming section 25 (and any fluid conduit on either side) to the volume of the void space of the foaming section 25 (and any fluid conduit on either side), through which the surfactant solution and gas passes, affects the quality of the foam produced. Accordingly, this ratio may be tailored to provide a foam having particular required characteristics. Other parameters found to have a potential effect on foam quality include: the internal diameter of the foaming section 25; surface area to two phase flow length ratio; the internal diameter of the liquid inlet; the internal diameter of the gas inlet; the surface tension of the surfactant; the viscosity of the surfactant; the pressure (e.g. headspace S pressure) applied to the gas and/or surfactant (or the ratio of such pressures); and the length of the fluid conduit from the manifold to the outlet (provided that the wetted surface area to void space volume ratio in the conduit remains above an appropriate threshold for the type of foam being produced).

It has been found that having an internal foaming section 25 surface area of at least 1,800 square millimetres provides a foam of sufficiently high quality for many applications. A higher wetted surface area may be preferable for producing a desired foam, for example greater than 3000 square millimetres or greater than 3700 square millimetres. Nevertheless, particularly high quality foams can be produced using a much higher surface area, for example between 4500 and 6000 square millimetres. A wetted surface area to void space volume ratio of at least 4 square millimetres per cubic millimetre has been found to provide a foam of sufficiently high quality for many applications. A higher welled surface area to void space volume ratio may be preferable for producing a desired foam, for example greater than 16 square millimetres per cubic millimetre. Nevertheless, particularly high quality foams can be produced using a much higher ratio, for example between 20 and 25 square millimetres per cubic millimetre.

While the valve 27 remains open, the foam 41 formed from the surfactant solution 21 and gas propellant 23 is conveyed through the foaming section 25 and into the valve 27 via the valve inlet 45. The open configuration of the value 27 allows the foam to pass through the valve, and the foam 41 is then discharged from the dispensing device 20 at the actuator outlet 29.

Figure 3 is a simplified illustration of a section through a dispensing device 120 according to a further embodiment. A container comprising a receptacle 137 is provided which is adapted to hold a supply of surfactant solution 121 and a supply of gas 123. In this embodiment, the gas 123 is not a compressed gas propellant and instead is provided at a pressure similar to that of the ambient air surrounding the dispensing device 120. The dispensing device 120 includes a liquid inlet 133 located proximate to the bottom of the receptacle 137, and further includes a gas inlet 135 located proximate to the top of the receptacle 137. This arrangement ensures that when the dispensing device 120 is oriented in its upright position, as illustrated in Figure 3, the liquid inlet 133 will be located below the liquid level of the surfactant solution, while the gas inlet will be located above the liquid level of the surfactant solution thereby allowing gas to enter the gas inlet 135. Preferably, the liquid inlet 133 is located at the lowest point of the receptacle 137 in order to ensure that all of the surfactant solution 121 held within the receptacle 137 is able to enter the liquid inlet 133.

The dispensing device 120 includes a one-way valve 170 which is configured to allow ambient air to enter into the receptacle 137 and to restrict or prevent gas 123 and surfactant solution 121 from exiting the receptacle 137. In this embodiment, the one-way valve 170 is disposed near or at the top of the receptacle 137 in order that air which enters into the receptacle 137 via the one-way valve 170 does so above the level of the surfactant solution, thus inhibiting the creation of bubbles of air within the surfactant solution 121.

The dispensing device 120 further comprises a foaming section 125 which is in fluid communication with the liquid inlet 133 and connected to the gas inlet 135 via a tube 160 which allows fluid communication between the foaming section 125 and the gas inlet 135.

In common with the foaming section 25 described above in relation to Figure 2, the foaming section 125 comprises a number of foam enhancing elements 135 which allow generation of a high quality foam formed from the surfactant solution 121 and the gas 123, beneficial within a relatively short length of foaming section. In this embodiment, the gas 123 is preferably air. It will be appreciated that, in other embodiments, a similar high quality foam, having the described desired characteristics, can be produced without the use of foam enhancing elements 153.

The foaming section 125 is connected to and in fluid communication with an outlet 129 from which the foam generated in the foaming section can be dispensed. A valve 127 controls the flow of foam from the foaming section 125 to the outlet 129 and is preferably configured to only allow foam to flow from the foaming section 125 to the outlet 129 when the foam exerts a pressure above a threshold pressure on the valve 127.

In order to drive both the gas 123 and the surfactant solution 121 to enter the foaming section 125, a pressure must be applied to the gas 123 and the surfactant solution 121. In this exemplary embodiment, the receptacle 137 is flexible and preferably to some extent collapsible, as indicated by the curved sides of the receptacle 137. The pressure can therefore be applied to the gas 123 and to the surfactant 121 by compressing the receptacle 137 and thus decreasing the volume of the receptacle 137. This action may be perfornied by hand or alternatively apparatus may be provided for compressing the receptacle 137; such an apparatus is not illustrated in Figure 3, but such apparatus could comprise a hand operated pump configured to engage with the outlet 129 and use suction to draw out the contents of the receptacle 137.

Figure 4 illustrates, in simplified form, part of a foaming section 425 which can, tor example, be provided as part of the dispensing device illustrated in any of the Figures, or supplied separately. The foaming section 425 is only shown in part, as indicated by the cutaway lines at the top and bottom of the foaming section. As shown, the foaming section 425 comprises a number of foam enhancing elements 453 which are held within the fluid conduit 460 and in the flow path of the surfactant and the gas which are carried through the foaming section. In this embodiment, the foam enhancing elements 453 comprise a plurality of generally spherical glass beads The foaming section 425 also includes retainers 465, 467 which are equivalent to retainers 65, 67 shown in Figure 2.

As shown, each of the foam enhancing elements 453 have a diameter, denoted d, where d is preferably in the range of 0.5 to 2 mm and more preferably in the range of 1 to 1.3 mm.

Preferably, the average value of d for the plurality of foam enhancing elements 453 is in the range of 1 to 1.5mm and more preferably in the vicinity of 1.23 mm, plus or minus 0.10 mm.

The diameter of each of the foam enhancing elements 453 is advantageously less than 1/3 of the inner diameter of the tube which forms the foaming section of the fluid conduit.

Beneficially, this helps to prevent undesirably large voids being left around the inner circumferential surface of the tube which would prevent the wetted surface area to void space volume ratio from obtaining a sufficiently high value.

As illustrated in Figure 4, the foaming section 425 has an internal diameter, denoted D. Preferably, D in a diameter of the foaming section 425 is between 0.1 mm and 10 mm, and more preferably is less than 4 mm, for example between 2 mm and 4 mm.

Figure 5 illustrates, in a simplified manner, a sample of foam 500 created using known techniques, (see steps 9 to 12 of the experimental method, below) in order to determine typical characteristics of known foams for comparison purposes. As shown in Figure 5, the foam 500 comprises a plurality of air bubbles 501 held within a surfactant solution 502. Each air bubble 501 has a diameter, denoted by label A in Figure 5. In the sample of foam 500 illustration Figure 5, the mean bubble diameter is 80 microns, and the standard deviation of the bubble diameters is 60 microns. The largest bubble in the illustrated sample has a diameter of 278 microns.

Figure 6 illustrates, in a simplified manner, a sample of foam 600 created using a dispensing device substantially corresponding to the dispensing device illustrated in Figure 2. The foam, 600, was created according to a method described in steps 1-8 of the experimental method, below. The foam 600 comprises a plurality of bubbles 601 of nitrogen held within a surfactant solution 602. Each bubble 601 has a diameter, denoted B' in Figure 6. The mean bubble diameter in the illustrated sample of foam 600 is 60 microns and the standard deviation in bubble diameter is 25 microns. The largest bubble in the foam sample 600 illustrated in Figure 6 has a diameter of 130 microns.

Figure 7 is a graph showing a number density distribution for a range of bubble diameters for the foam sample 500 illustrated in Figure 5 and for the foam sample 600 illustrated in Figure 6.

On the graph illustrated in Figure 7, the x axis represents the diameter of bubbles in the foams 500, 600 measured in microns and they axis represents the number density of bubbles with a particular diameter. The data points relating to the foam 500 illustrated in Figure 5, generated by the prior art foam mechanism are denoted by diamond shape data points, while the data points corresponding to the foam 600, illustrated in Figure 6, are denoted by square shaped data points. A curve fit has been added to each of the two sets of samples. As can be seen from the graph, when compared to the foam 500, the foam 600 has a greater number density of bubbles in the range of 40 microns to 100 microns, peaking around 53 microns.

Furthermore, it can be seen that the majority of bubbles in the foam sample 600 lie in the range of 40 to 100 microns. Having a large number of bubbles in this range produces a high quality foam having a "richer" texture. Furthermore, it can be seen from the graph of Figure 7 that the standard deviation of the foam 600 is less than that of the foam 500 generated by the prior art dispensing mechanism. Having a smaller standard deviation in bubble sizes increases the horriogeneity and thus quality of the foam.

Advantageously, the dispensing devices, system and foaming section described enable the creation of rich, creamy foams (high gas phase volumes of >95%, air bubbles with a preferable mean diameter of 60 microns and a narrow size distribution, preferable standard deviation: <25 microns), without the use of volatile organic compounds (VOC).

The described system, devices and sections provide better quality foams than those produced using other possible mechanisms and gases dissolved in surfactant solutions. This is because maximum gas phase volume of the foams formed using gases dissolved in surfactant solutions is typically only 4 times the volume of the liquid as this is the upper limit to the amount of gas that can be dissolved in the surfactant solution.

The described system, devices and foaming sections are also advantageous over alternative foaming devices which, for example, might involve the sucking or blowing of bubbles through small apertures. The small apertures are expensive to machine and block easily, and bubbles are formed by Rayleigh-Taylor instabilities and hence are typically the same size as the orifice. The present invention does not require machining of small features and the bubbles produced are typically an order of magnitude smaller than the smallest orifice.

The dispensing devices, system and foaming section described can be used to generate, for example, shaving foams, cleaning foams, hair mousse, dairy foams and other food foams, industrial and pharmaceutical foams. The dispensing device 20 illustrated in Figure 2 uses a compressed gas as a propellant and therefore the dispensing device 20 can produce a substantially continuous flow of foam when the valve is opened. This makes the dispensing device 20 particularly well suited for producing the shaving foams, hair mousse and dairy foams, where a relatively large amount of foam is often desired for use. The dispensing device 120 illustrated in Figure 3, on the other hand, does not use a compressed gas as a propellant and therefore requires the receptacle 137 to be compressed in order to propel the surfactant solution and gas into the foaming section of the dispensing device 120. The dispensing device 120 illustrated in Figure 3 is particularly well suited to producing cleaning foams, for example, hand soap foams, where generally a relatively smaller amount of foam is required for each use.

If this technology is used in conjunction with freezing technology (for example a refrigeration cycle, a cold temperature sink, or a low temperature phase change material) then an ice cream dispensing appliance could be made.

Key Parameters: Preferable Values Parameter Value Comments Wetted surface area > 1800 mm2 This is the total surface area within the foaming section, from the bifurcation of the fluid conduit to the end of the fluid conduit (e.g. the end where the fluid conduit connects to the valve). It includes the surface area of the internal surface of the foaming section plus the surface area of any foam enhancing elements contained within the foaming section.

2 Wetted surface area to > 4 mm2/mm This is the surface area within the void space volume foaming section divided by the volume ratio of free space within the foaming section.

3 Foaming section 0.1 mm < to < 10 diameter mm (preferably less than 4 mm) 4 Two phase flow length > 40 mm This is the smaller of: (preferably greater a) the distance the gas/surfactant than 60 mm) mixture travels from the point where the gas and surfactant solution are first brought into contact with each other to the point where the wetted surface area to void space volume reduces to (and remains) below 4 mm2/mm3 b) the distance the gas! surfactant mixture travels from the point where the gas and surfactant solution are first brought into contact with each other to the point of dispense (e.g. the actuator nozzle) Minimum constriction 0.1 mm2 size in the valve 6 Gas inlet diameter 0.1 mm2 to 4 mm2 7 Liquid inlet diameter 0.1 mm2 to 4 mm2 8 Surface tension of the > 50 dyne/cm surfactant 9 Viscosity of the <200 centiPoise surfactant Headspace pressure 2 bar gauge to 25 bar gauge 11 Mean diameter of <60 microns bubbles in the foam 12 Standard deviation of <25 microns bubbles in the foam 13 Maximum bubble size < 130 microns

Table 1.

Method used to obtain the bubble size data 1. A sample formulation was prepared consisting of 1 part Original Fairy liquid ® and 4 parts water.

2. 100 mL of this sample was placed in a 210 mL bottle which was sealed with an aerosol valve with 3 minimum constriction size of 1 mm diameter.

3. A 60 mm tube with an internal diameter of 3.175 mm was used as the foaming section.

The tube was filled with glass ballotini spheres in the size range 1-1.3mm with a mean particle size of 1.23 mm. The total internal/wetted surface area of the system was 5294 mm2 and the wetted surface area to void space volume ratio for this mixer was 22.5 mm2/mm3. The mixer had 2.5 mm diameter circular liquid and air intakes.

4. The mixer was incorporated into the diptube of an aerosol valve with 3 x 1 mm constrictions.

5. The aerosol valve crimp sealed the bottle and nitrogen was used to pressurize the headspace to 5 bar gauge.

6. A sample of the foam was dispensed onto a glass microscope slide and an image was taken 3 seconds after dispense.

7. The image is shown in Figure 6 below 8. The bubble size distribution was determined from the image. The number density distribution is shown in Figure 7 and was found to have a mean bubble diameter of 60 microns and a standard deviation of 25 microns (representing a standard deviation of 42% of the mean bubble diameter). The largest bubble in this image had a diameter of 130 microns. The bubble diameters were determined as the maximum length of a line that can be drawn within the enclosed curves on the image.

9. 100 mL of the sample was placed in a bottle fitted with a prior art mechanism.

10. A sample of the foam was dispensed onto a glass microscope slide and an image was taken 3 seconds after dispense.

11. The image is shown in Figure 5 below 12. The bubble size distribution was determined from the image. The number density distribution was found to have a mean bubble diameter of 80 microns and a standard deviation of 60 microns (representing a standard deviation of 75% of the mean bubble diameter). The largest bubble in this image had a diameter of 278 microns. The bubble diameters were determined as the maximum length of a line that can be drawn within the enclosed curves on the image.

Modifications and Alternatives Although the foam enhancing elements 53, 153, 453 have been described as generally spherical beads of glass, the foam enhancing elements may be generally spherical beads of any other suitable materials such as a plastic material, and may be beads of a different shape, for example generally cuboid, generally cylindrical or generally conical. The foam enhancing elements may alternatively comprise any other features, for example bristles or projections extending from the internal surface of the fluid conduit into the flow path of the surfactant solution and gas. It will be appreciated that in an alternative embodiment the foam enhancing elements may be formed as part of the fluid conduit itself, for example projections extending from the inner surface of the fluid conduit into the flow path of the surfactant solution and gas.

Furthermore, the foam enhancing elements may alternatively comprise a single foam enhancing element, for example a porous material.

Furthermore, any combination of different types of foam enhancing elements may be used.

The foaming section 25, 125, 425 may not comprise any foam enhancing elements 52, 153, 453. The foaming section may be adapted to enhance the generation of foam within the foaming section. In particular, the foaming section may comprise a long, thin tube, which is configured to produce a foam with the described desired properties without requiring foam enhancing elements. In this case, in order to produce such a foam the tube of the foaming section should conform to at least one of the parameters 1 to 4 listed in table 1, and additionally (or alternatively) be less than or equal to 1 mm in diameter and greater than 1200 mm in length.

The foaming section may follow a serpentine, helical or other non-linear path in order to increase the length of the foaming section and to increase mixing and possibly induce turbulence in the flow of surfactant solution and gas through the fluid conduit, without greatly increasing the space the fluid conduit occupies. This is especially beneficial in embodiments where the foaming section is provided as a long thin tube without containing any foam enhancing elements.

The foaming section may be provided as a distinct section, and may be connectable to the -valve and the manifold, or to the fluid conduit parts located either side of the foaming section.

The foaming section may have a narrower, or wider, diameter than the rest of the fluid conduit.

Although the retainers 65, 67, 465, 467 are described as being formed from a mesh-like material, the skilled person will appreciate that the retainers can take any suitable fonm provided they allow surfactant solution and gas (along with a foam comprising the surfactant solution and the gas) to pass through and also inhibit movement of the foam enhancing elements. For example, each retainer may coniprise at least one aperture sized such that the foam enhancing elenients cannot pass through the aperture.

In an alternative embodiment, no retainers are provided, and instead the foam enhancing elements are held in position in the foaming section by virtue of the friction which exists between the foani enhancing elenients and the inner surface of the foaming section, and the friction between the foam enhancing elements themselves. In this alternative embodiment, the foam enhancing elements aie disposed within the foaming section such that the foaming section undergoes some deformation around the foam enhancing elements, helping to hold the foam enhancing elements in place. Also, the foaming section may be resilient, and as a result exerts a compressive force on the foam enhancing elements, increasing the friction between the foaming section and the foam enhancing elements, as well as between the foam enhancing elements themselves.

In Figures 2, 3 and 4 it is shown that the foam enhancing elements 53, 153, 453 are disposed along part of the length of the foaming section. However, it will be appreciated by those skilled in the alt that it may be advantageous to piovide foam enhancing elements along substantially the full length of the foaming section.

It is described above that the foaming section 25, 125, 425 extends from the bifurcation of the fluid conduit to the end of the fluid conduit distal from the bifurcation, e.g. the point of connection between the fluid conduit and the valve. Alternatively, the foaming section may extend over substantially the entirety of the two phase flow length of the dispensing device, the two phase flow length being the distance the gas! surfactant mixture travels from the bifurcation point to the point of dispense (e.g. the actuator nozzle), as long as the wetted surface aiea to void space volume iatio remains above 4 mrn2lrnm3.

The valves referred to in the description above may comprise any type of suitable valve not limited to the types of valves illustrated in the figures.

Although in the above embodiments the gas used as a propellant has been described as compressed gas, a liquefied gas may be used instead of or in addition to a compressed gas as a propellant.

The compressed gas propellant may comprise any suitable gas, for example air, nitrogen, or noble gas. Furthermore, dissolved gas (e.g. carbon dioxide or nitrous oxide) may be used instead of or in addition to compressed gas, advantageously further enhancing the quality of the foam produced by the dispensing device.

Although Figure 3 illustrates that the gas inlet and gas 123 are provided in the container 137, in an alternative embodiment the gas inlet may be provided externally from the container 137 as illustrated in Figure 8. Figure 8 is a simplified illustration of a section through a dispensing device 220 according this alternative embodiment. In this embodiment, the container 137 does not hold any substantial gas supply. Instead, the gas used to create a foam is taken from the ambient air surrounding the dispensing device 220, using the external gas inlet 135.

The gas inlet 135 may include a one-way value in order to prevent air or surfactant solution from escaping from the gas inlet. This embodiment of dispensing device could be used in conjunction with a hand operated pumping mechanism in order to provide a hand operated trigger-head foamer.

The dispensing devices, system and foaming section described can be used as part of a module in a larger appliance to create foam, for example a wall mounted foam soap dispenser or a milk frother.

The dispensing devices, system and foaming section described can also be used in an air or steam driven appliance or incorporated into a disposable pod to generate foams. This would enable to generation of foams (e.g. dairy foams) without the requirement for disposable sparklets. For example, the foaming section could form part of a pod containing milk or flavouring. The pod could be inserted into an appliance, for creating a foamy milkshake or foamed milk to top a coffee.

The dispensing system, devices and the foaming section may be used to generate emulsions, comprising a suspension of globules of a first liquid within a second liquid, in which the first liquid is not miscible. The gas and liquid inlets could be used as inlets for the first and second liquids respectively. If necessary, the receptacle 37, 137 could be modified to hold the first and second liquids in separate sections. Passing the first and second liquids through a foaming section 25, 125, 425 advantageously enhances the mixing of the first and second liquids, producing a well-mixed and homogenous emulsion, with the first liquid forming small globules. In this way, it would be possible to generate emulsions on demand. This would enable generation of emulsions at the point of use and hence relax the stability requirements on many emulsion products.

Specifically, emulsions could be created on demand within an aerosol, re-usable pod or appliance, to create, for example salad dressings, skin creams, anti-microbial micro-emulsions, pharmaceutical emulsions, shampoos, conditioners and paints.

The present dispensing system, and devices may be used to produce an aerosol, comprising a suspension of liquid droplets in a gas. The surfactant solution could be replaced with a liquid for expelling as an aerosol, and a liquefied gas propellant could be used in place of or in addition to a compressed gas. Passing the liquid and gas through the foaming section would advantageously enhance mixing of the liquid gas to produce a fine aerosol of very small liquid droplets.

Claims

Claims: 1. A dispenser for producing a foam without requiring the use of liquefied gas, from an outlet, said dispenser comprising: a receptacle for holding a surfactant solution; means for supplying a gas; means for conveying said surfactant solution in said receptacle and said gas along a flow path towards said outlet; wherein said conveying means comprises a conduit having a foaming section for generating said foam from said surfactant solution and said gas; and wherein said foaming section has internal dimensions adapted to provide a foam having a quality characterised by predefined limits.
2. The dispenser according to claim 1, wherein said foaming section comprises at least one foam enhancing element disposed in said flow path; and wherein said internal dimensions of the foaming section are provided, at least in part, by the at least one foam enhancing element.
3. The dispenser according to claim 2, wherein said at least one foam enhancing element comprises at least one of: a generally spherical element; a generally cuboid element; a generally cylindrical element; a generally conical element; a porous element; and an element extending from an internal surface of the foaming section into said flow path.
4. The dispenser according to claim 2 or 3, wherein said foaming section further comprises at least one retaining element for retaining the at least one foam enhancing element within the foaming section.
5. The dispenser according to any of claims I to 4, wherein said predefined limits comprise an average bubble diameter of less than 70 microns.
6. The dispenser according to any of claims 1 to 5, wherein said predefined limits comprise an average bubble diameter of less than 60 microns.
7. The dispenser according to any of claims 1 to 5, wherein said predefined limits comprise an average bubble diameter of between 30 and 70 microns.
8. The dispenser according to any of claims 1 to 7, wherein said predefined limits comprise a uniformity characterised by a standard deviation of less than 35 microns.
9. The dispenser according to any of claims 1 to 8, wherein said predefined limits comprise a uniformity chalactelised by a standard deviation of less than 25 micions.
10. The dispenser according to any of claims ito 7, wherein said predefined limits comprise a uniformity charactelised by a standard deviation of between 10 and 35 microns.
11. The dispensel according to any of claims 1 to 10, wherein said internal dimensions comprise a welled surface area of greater than 1800 square millimetres.
12. The dispenser according to any of claims 1 to 11, wherein said internal dimensions comprise a welled surface area of greater than 3000 square millimetres.
13. The dispensel according to any of claims 1 to 12, wherein said internal dimensions comprise a welled surface area of between 4500 and 6000 square millimetres.
14. The dispensel according to any of claims 1 to 13, wherein said internal dimensions comprise a wetted surface area to void space volume ratio of greatel than 4 squaie millimetres per cubic millimetre.
15. The dispensel according to any of claims 1 to 14, wherein said internal dimensions comprise a wefted surface area to void space volume ratio of greater than 16 square millimeties per cubic millimetie.
16. The dispenser according to any of claims 1 to 15, wherein said internal dimensions comprise a welled surface area to void space volume ratio of between 20 and 25 square millimeties per cubic millimetie.
17. The dispenser according to any of claims 1 to 16, wherein said internal dimensions comprise a wetted surface area to two phase flow length ratio of greater than 3 square millimetres per millimetre.
18. The dispenser according to any of claims 1 to 17, wherein said internal dimensions comprise a wetted surface area to two phase flow length ratio of greater than ii square millimetres per millimetre.
19. The dispenser according to any of claims 1 to 18, wherein said internal dimensions comprise a wetted surface area to two phase flow length ratio of greater than 8 square millimetres per millimetre.
20. The dispenser according to any of claims 1 to 19, wherein said internal dimensions comprise a two phase flow length of greater than 40 millimetres.
21. The dispenser according to any of claims 1 to 20, wherein said internal dimensions comprise a two phase flow length of greater than 60 millimetres.
22. The dispenser according to any of claims 1 to 21, wherein said internal dimensions comprise a two phase flow length of greater than 1200 millimetres.
23. The dispenser according to any of claims 1 to 21, wherein said internal dimensions comprise a foaming section diameter of less than 10 millimetres.
24. The dispenser according to any of claims 1 to 23, wherein said internal dimensions comprise a foaming section diameter of less than 4 millimetres.
25. The dispenser according to any of claims 1 to 23, wherein said internal dimensions comprise a foaming section diameter of between 0.1 and 10 millimetres.
26. The dispenser according to any of claims 1 to 25, wherein said predefined limits comprise a uniformity characterised by a standard deviation of less than 60% of the average bubble diameter.
27. The dispenser according to any of claims 1 to 26, wherein said predefined limits comprise a uniformity characterised by a standard deviation of less than 50% of the average bubble diameter.
28. The dispenser according to any preceding claim further comprising: means for applying pressure to the surfactant solution in said receptacle to drive said surfactant solution along said conduit and towards said foaming section and for driving foam generated by said foaming section to said outlet.
29. The dispenser according to claim 28, wherein said pressure applying means is provided by said gas which is held under pressure within said receptacle.
30. The dispenser according to claim 29, wherein said gas is held at a pressure of between 2 bar and 25 bar.
31. The dispenser according to claim 29, wherein said gas is held at a pressure of between 2 bar and 8 bar.
32. The dispenser according to claim 29 or 30, wherein the concentration of said gas in said surfactant solution is less than 350 milligrams per kilogram of said surfactant solution.
33. The dispenser according to any preceding claim wherein said gas comprises a non-liquefied gas.
34. The dispenser according to clairri 33, wherein said non-liquefied gas comprises at least one of: air, nitrogen, carbon dioxide, one or more noble gases.
35. The dispenser according to any preceding claim, wherein said conveying means comprises a bifurcated tube having a gas inlet and a surfactant solution inlet which meet at a point of bifurcation at which said gas and said surfactant solution mix, in operation, prior to entering the foaming section.
36. The dispenser according to claim 28, wherein said gas inlet and said surfactant solution inlet are vertically separated from one another.
37. The dispenser according to any preceding claim, wherein the dispenser is configured to produce a foam without using volatile organic compounds, VOCs.
38. A foaming component, for a foam dispenser, for producing a foam without requiring the use of liquefied gas, said foaming element comprising: means for conveying a surfactant solution from a receptacle and a gas along a flow path; wherein said conveying means comprises a conduit having a foaming section for generating said foam from said surfactant solution and said gas; and wherein said foaming section has internal dimensions adapted to provide a foam having a quality characterised by predefined limits.
39. A dispenser for producing a foam without requiring the use of liquefied gas, from an outlet, said dispenser comprising: a receptacle for holding a surfactant solution; means for supplying a gas; means for conveying said surfactant solution in said receptacle and said gas along a flow path towards said outlet; wherein said conveying means comprises a conduit having a foaming section for generating said foam from said surfactant solution and said gas; and wherein said foaming section has internal dimensions conforming to at least one of the following parameters: a wetted surface area of greater than 1800 square millimetres; a wetted surface area to void space volume ratio of greater than 4 square millimetres per cubic millimetre; a foaming section diameter of less than 10 millimetres; and a two phase flow length of greater than 40 millimetres.
40. The dispenser according to claim 39, wherein said gas is held at a pressure of between 2 bar and 8 bar.
41. A method of producing a foam without requiring the use of liquefied gas, using a foam dispenser according to claim 1 or 39, or using a foaming component according to claim 38.
42. A method of producing a foam without requiring the use of liquefied gas, said method comprising: holding, in a receptacle, a surfactant solution; conveying said surfactant solution in said receptacle and a gas from a gas supply along a flow path towards an outlet; wherein said conveying step comprises conveying said surfactant solution and said gas in a conduit having a foaming section for generating said foam from said surfactant solution and said gas; and wherein said foaming section has internal dimensions adapted to provide a foam having a quality characterised by predefined limits.