AU2012203843B2 - Extraction of liquid in a container - Google Patents

Abstract

There is disclosed in a spray container for liquids, the use of a single hollow-fibre hydrophilic capillary membrane which is adapted to pass liquid in preference to gas under an applied pressure differential as a dip tube. n 50

Description

Australian Patents Act 1990 - Regulation 3.2A ORIGINAL COMPLETE SPECIFICATION STANDARD PATENT Invention Title "Extraction of liquid in a container" The following statement is a full description of this invention, including the best method of performing it known to us:- 1 EXTRACTION OF LIQUID IN A CONTAINER The content of the complete specification of Australian patent application no. 2007301797 as originally filed is incorporated herein by reference. 5 The present invention relates to fluid delivery devices that function in any one of many orientations. In the field of conventional liquid carriers, particularly spray dispensers, is that it is 10 typically necessary to hold the carrier in a particular orientation if liquid is to be dispensed. This can make the carriers awkward to use in various circumstances. According to a first aspect of the present invention, there is provided, in a spray container for liquids, the use of a single hollow-fibre hydrophilic capillary membrane 15 which is adapted to pass liquid in preference to gas under an applied pressure differential as a dip tube. According to a second aspect of the present invention, there is provided a method of extracting liquid from a container which incorporates a dip tube consisting of a 20 single hollow-fibre hydrophilic capillary membrane positioned within the container and coupled to an output of the container, the method comprising applying a pressure differential across a wall of the single hollow-fibre hydrophilic capillary membrane, and passing liquid within the container through the wall of the single hollow-fibre hydrophilic capillary membrane and thereby to the output, wherein 25 liquid can be extracted when the container is held in substantially any orientation. A preferred embodiment of the present invention provides a fluid delivery device comprising a fluid path defined by a liquid reservoir, said membrane adapted to pass liquid in preference to gas, and an output, the device being configured to 30 induce a flow of liquid along the fluid path through the membrane to the output under a pressure differential, wherein the membrane extends substantially across an entire length of the liquid reservoir such that the device is operable to dispense liquid in any orientation in which the liquid in the reservoir is in contact with the membrane. 35 Fluid can thus be dispensed from the delivery device in any one of many orientations. The application of the invention is not limited to the extraction of water; it extends to any liquid. Equally, the pressure need not be provided by C NRPonrDCC\AM\4A1654_l.DOC-296/2012 -2 air but may be provided by any gas. The membrane may have a pore size chosen according to the requirements of the particular device, on the basis of such variables as: the viscosity of the liquid, the surface area of the membrane and the applied pressure. The device need not be required for 5 filtration, so that the pore size need not be limited by the requirement to remove any particular matter from the device. The means for pressurising the liquid reservoir may involve mechanical means such as a pump. Alternatively, they may include pre-pressurising the 10 liquid reservoir before or during assembly of the device. Moreover, other means for pressurising the reservoir are envisaged, such as chemical means. The membrane need not act as a filter, but will pass liquids in preference to 15 gas. The device may be arranged such that the one or more membranes are always in contact with liquid in the liquid reservoir regardless of the orientation or the reservoir. In one possible arrangement, the sidewalls of the liquid reservoir are substantially covered by the one or more membranes. 20 One possible arrangement comprises a water bottle containing an ultra-fine filter. Water is passed through the filter under pressure. This allows the water to be passed through finer filters than would be possible if the container were not pressurised. Arrangements disclosed herein m ay make use of existing filter types that have not typically been used in portable devices. 25 A pore size of less than or equal to 25 nanometres is preferable, being sufficient to remove most microbiological matter from the liquid, including viruses, thereby providing safe drinking water and a far more effective portable water filtration system than has previously been available. However, 30 for additional security, some preferred embodiments of the invention may have a pore size of less than or equal to 20 nanometres, and more C :NRPonblDCC\AZM\.4416654_1 DOC.29A161212 -3 preferably have a pore size of less than or equal to 15 nanometres. As is known in the art, the pore size of a material is in fact an average of the individual sizes of the pores (or holes) in the material, since it is inevitable 5 that any material comprising a large number of pores will include some variation in these individual sizes. In preferred embodiments of the present invention have, there is a tightly defined distribution of pore sizes such that the difference between the maximum pore size and the average pores size is minimized. Preferably, the standard deviation of the pore size distribution 10 is less than 30% of the average pore size, and more preferably is less than 15% of the average pore size. In some preferred embodiments of the invention, the membrane has a maximum pore size of less than or equal to 30 nanometres, more preferably, less than or equal to 25 nanometres, and most preferably less than or equal to 20 nanometres. In other embodiments, 15 the maximum pore size may be even lower in order to perform nanofiltration or reverse osmosis, for example. Some preferred embodiments of the present invention may be suitable for ultrafiltration, that is to remove all particles of a size greater than 0.01 20 microns, whilst others may be suitable for nanofiltration or reverse osmosis. Reverse osmosis filters are capable of removing everything (including salts and oils) apart from pure water (H 2 0) from a liquid. Nanofiltration removes particles of a size greater than 0.001 microns (including aqueous salts). 25 In other arrangements, membranes of the type incorporated into preferred embodiments of the invention may together form a plurality of sub-filters. The sub-filters may be exact replicas of each other or may differ in any parameter. For example, the sub-filters may become progressively finer (have progressively smaller pore sizes) along a fluid path. Additional filters 30 may be placed in the fluid path as required.

-4 A device according to one example may filter water with a pressure differential of any size. For example, the operating pressure differential of a is then preferably greater than 10 kPa, more preferably in the range of 50 kPa-1500 kPa, more preferably in the range of 100 kPa-1000 kPa, more 5 preferably 150 kPa-300 kPa. The membrane is attractive to water and therefore water is passed through it in preference to other liquids and to gases. In this way, there can be provided not only improved filtration but also a filter operable even when it is 10 not completely immersed in the liquid. The surface area of the of the membrane is preferably greater than 0.05 m 2 more preferably greater than 0.1 M 2 , more preferably greater than 0.2 M 2 more preferably greater than 0.25 M 2 . A preferred surface area is about 15 0.3 m2. Preferably, the surface area is less than 1 M 2 . The membrane is preferably semi-premeable and acts to filter water as only particles smaller than their pore size may pass through them. The membrane may incorporate carbon or other chemical elements, or comprise 20 a reverse osmosis membrane. The membrane may comprise ultrafiltration, nanofiltration or reverse-osmosis membrane. In preferred embodiments of the invention, once water enters the membrane, it is transferred along a tube-like structure thereof to an output. 25 As a result, water may enter at any point along the membrane and reach the output while also being filtered. When a pressure differential exists between the container and the outside atmosphere, and the output is open, liquid in the container will pass through 30 the membrane to the output regardless of the orientation of the device. Liquids can thus be dispensed from the container in any one of many C \NRPortbKDCC\AZM"43654_1 DOC-29/6/2.12 -5 orientations. The membrane may be substantially along an entire length of the liquid reservoir, whereby any liquid in the reservoir may be in contact therewith. 5 Preferably it lies along over 70% of the length of the reservoir, more preferably over 80% of that length and more preferably still, over 90% of that length. 10 In particular embodiments, the output includes a flow restrictor, preferably comprising a nozzle having an open position and a closed position, where liquid may be extracted when the nozzle is in an open position. In particular embodiments, the means for effecting a pressure differentials 15 comprises a pump. The pump may be a manually operated pump. Alternatively, pressurising means such as compressed gas, or chemical reactants may be used. The pump could be a piston pump comprising a non-return valve through 20 which air may be passed into the container, and a piston shaft through which a piston head may be moved such that air is passed through the non-return valve. In one preferred embodiment, the pump is removable from the device to 25 allow the liquid reservoir to be refilled. In one arrangement, the piston shaft runs through the filter. Preferably, the liquid reservoir, the filter, and the piston shaft in that arrangement are substantially cylindrical and have substantially the same central axis, 30 whereby there is provided a compact device, improving portability. Preferably, the filter comprises an annular housing having an outer wall C NRPonb1\DCC\AZN44665_ I DOC-296/2012 -6 having a plurality of holes therethrough. The filter may be substantially cylindrical. Preferably, the holes are distributed across substantially the whole length of the filter. 5 Devices according to particular examples comprise removable filters, allowing for filter replacement and cleaning. Preferred embodiments of the present invention may comprise a visual indicator allowing inspection of the contents of the device. For example, a 10 transparent window may be provided in the liquid reservoir. A device according to a one example may comprise pressure regulation means. For example, the pressure regulation means may include a release valve adapted to release liquid and/or air if the pressure in the container 15 exceeds a predetermined level. The membrane outer perimeter in the plane normal to the entire length of the membrane may define an area greater than or equal to 50% of the area of the liquid reservoir in this plane. 20 In one arrangement, the membrane may surround the liquid reservoir, or, if placed within the reservoir, extend substantially across the reservoir. This helps to ensure that liquid is in contact with the membrane at all times. 25 The invention has application to dispensers used for spray paints, deodorants and perfumes, amongst others, which conventionally require the dispenser to be held in a given orientation, particularly when the level of liquid within the container is low. 30 Principles of the present invention have been found to be advantageous in filters, both generally and in the context of spray container dip tubes.

C \NRPonblDCC\AZM\4436654_ I DOC-29/6/2012 -7 In a device according to a preferred embodiment of the invention, a fluid path is arranged such that when an output is in an open position, a pressure differential induces a flow of liquid along the fluid path through the 5 membrane to the output. A device according to one arrangement comprises a pump for pressurising a liquid reservoir such that, when an output is in an open position, a pressure differential induces a flow of water along a fluid path through the membrane 10 to the output. The pump may comprise a non-return valve through which air may be pumped into the liquid reservoir, and a piston shaft, through which a piston head may be moved such that air is pumped through the non-return valve. The piston shaft may be substantially surrounded by a said membrane. The membrane may provide filtering. 15 One arrangement may offer a portable water bottle incorporating a filter, the bottle having a compact and ergonomic design, wherein the piston shaft passes through the centre of a filter comprising a said membrane allowing an efficient use of space within the device as well as providing a stable 20 arrangement for actuation of the pump. It also allows the surface area of the filter to be optimised without interfering with the action or location of the piston. The invention will now be described, by way of non-limiting example only, with 25 reference to the accompanying drawings, in which: Figure 1 shows a device according to one example; Figure 2 shows a cut away sectional view of the device of Figure 1; Figure 3 shows a cut away sectional drawing of a replaceable filter cartridge; 30 Figure 4 shows a detailed cut away sectional drawing of a pump; and, Figure 5 shows a cut away sectional drawing of a spray can.

C \NRPonblDCOAZM\443654_ IDOC-29A//2112 -8 Figure 1 shows a water bottle. The bottle comprises a container 10 acting as a liquid reservoir attached to a cap 50 and lid 60 at one end and a removable base 30 at the other. A handle 40 is integrally formed with the 5 base 30 but has a degree of freedom along the axis of the container 10. When constructed the bottle is sealed and is both water- and air-tight. Also shown in Figure 1 is a strap 70 attached to the bottle to aid portability. Figure 2 shows a cross-section of the bottle shown in Figure 1. As can be 10 seen from Figure 2, a filter cartridge 20 is disposed within the container 10. The filter cartridge 20 abuts the base 30 and is removably attached to the cap 50 by a screw thread 54. Various food grade seals 12 are provided so that the seal between the filter cartridge 20 and the cap 50 and base 30 is both water and air tight. 15 The handle 40 is connected to a pump, which comprises a piston shaft 42 and a piston head 44, which runs through the piston shaft 42. When the base 30 is attached to the container (as shown in Figure 2) the piston shaft 42 runs through the hollow centre of the filter 20. In this example, the base 20 30 is removably attached to the container 10 by means of a screw thread 14, with a food grade seal provided to ensure that the connection is both water and air-tight. The handle 40 and piston head 44 are fixed relative to each other such that 25 movement of the handle 40 is effective to move the piston head 44 within the piston shaft 42. A non-return valve 46 is included at the distal end of the piston shaft 42, which allows movement of the piston head 44 into the piston shaft 42 to force air into the container 10, thereby increasing the pressure in the container 10, while movement of the head away from the distal end of 30 the piston shaft does not remove the applied pressure.

C \JRPonblDCAZM\441454_I DOC-29/WV,2w2 -9 It is envisaged that the handle 40 may include cavities for the storage of personal items. The handle 40 may also lock into the base 30 when not in use (for example, through appropriately designed protrusions from the handle into the base). 5 Though the illustrated arrangement uses a hand actuated pump mechanism to pressurise the container, one skilled in the art will recognise that other means for pressurising the container may be used in accordance with the present invention. For example, compressed gas or means to deform the 10 container may be used. For example, the container itself may be flexible so as to allow a user to introduce pressure by squeezing the container. The pump illustrated is a simple 1:1 pump, in that the pressure that the user must overcome to actuate the pump is equal to the pressure in the 15 container. Nevertheless, it is possible to use ratcheting, or gearing, systems. These mechanisms allows easier hand actuation of the pump (and consequently enable to pressure inside the container to be increased to a greater level than would otherwise be possible). 20 As shown in Figure 2, the filter is sealed to the cap 50 via the screw thread 52. The cap 50 effectively acts as a nozzle and includes a non-chewable spout 52, which is engaged to a liquid seal when in a closed position such that liquid cannot pass through the nozzle 50. When the spout 52 is in an open position, liquid may pass through the nozzle 50. In this preferred 25 arrangement, the spout 52 may be locked into the closed position (shown in Figure 2) by twisting relative to its axis. When the nozzle 50 and filter 20 are sealed into place as shown in Figure 2, liquid may only enter the nozzle 50 via the filter 20. 30 The cap 50 also incorporates an additional carbon filter 56, which attached to the structure of the cap 50 by a screw 58 embedded in the carbon filter C\NRPonbl\DCC\AZMW436654_I DOC-29A16/2012 - 10 56. The device is arranged to ensure that liquid passes through the carbon filter 56 before leaving the bottle through the cap 50. Carbon filters are known to be effective in the removal of chemicals from water. Alternatively, or indeed additionally, different filters could be incorporated into the cap 50. 5 For example, resin filters are known as effective desalinization filters. Filters of this or other types may also be incorporated into the filter cartridge 20. The carbon filter is an active carbon filter, although other types of carbon based filters (such as charcoal filters) may be adopted. 10 Carbon filtration, which utilizes a process known as adsorption, is a particularly effective technique for chlorine removal. Pesticides, herbicides, and other organic contaminants (especially volatile organics) may also removed by this material. 15 Carbon also removes trihalomethanes from the water. Trihalomethanes are a class of chemicals which result from the interaction of chlorine and decaying organic matter in the public water supply. These chemicals are known carcinogens, and the high levels found in local water supplies have 20 been a cause for concern in recent years. Activated carbon fibers (referred to as ACF) or other forms of carbon such as powders are manufactured by activating carbonized material at an elevated temperature in an activating gas atmosphere, typically steam and/or carbon 25 dioxide and/or ammonia. Carbonized fibers are made by carbonizing polyacrylonitrile, phenol resin, pitch or cellulose fibers in an inert atmosphere. Such methods are well known in the art. Activated carbons and, especially, known activated carbon fibers, have good 30 adsorption capacity toward organic substances and an excellent ability to remove chlorine from water. A standard activated carbon fiber filter, well C WNRPonbrDCC\AZM\4436654_ DOC-29112012 - 11 known in the art, or a modified activated carbon fiber filter may be used. Examples of modified activated carbon materials are disclosed in US 4,831,011, US 4,366,085 and US 5,705,269. 5 The activated carbon matrix may provide, for example, bactericidal, cation exchange, anion-exchange, heavy metal complex formation or other additional desired properties. 10 Though the spout 52 is actuated by direct movement away from the filter 20, other means for extracting the liquid are envisaged. For example, a variable valve mechanism, the valve being open and closed through movement on a screw thread, could be used. 15 A pre-filter (not shown in Figure 2) may also be included. In one arrangement, this pre-filter takes the form of a mesh that covers the lower end of the container 10 when the base 30, handle 40 and pump are removed. The mesh may include linear cut lines at appropriate positions such that when the base 30, handle 40 and pump are attached to the filter, 20 the pump may pass through the mesh without difficulty. Alternatively, the mesh may be removable from the device prior to attaching the base 30, handle 40 and pump. The pre-filter is designed to remove macroscopic and large microscopic impurities from the water before the filter cartridge 20 is used to remove smaller particles, bacteria and viruses. 25 In order to remove impurities from a liquid, the base 30 (along with the handle 20 and pump) is removed from the container and the untreated liquid is poured into the container (through the pre-filter). The base 30, handle 40 and pump are then reattached to the container and the pump handle 42 is 30 repeatedly moved from a withdrawn position to the closed position shown in Figures 1 and 2, thereby moving the piston head 44 up and down through C NRPonbl\DCCAZM\44 (654_1 DOC-29/6/I2012 - 12 the piston shaft 42. This has the effect of forcing air through the non-return valve 46, thereby increasing the pressure within the container. After pressurising the container 10, the user opens the cap 50 by moving the 5 spout 52 away from the body of the container 10. The pressure forces the water through the filter 20 into the cap 50 (via aperture 55) and ultimately out of the bottle for the user to collect. Having passed through the filter 20 the liquid may be considered safe to use (for example, as drinking water). The flow rate may be approximately 2.5 litres/minute at an induced pressure 10 differential of 0.25 bar. Figure 3 shows the filter cartridge 20. As shown, the filter cartridge 20 comprises a substantially annular housing 22 in which the fibre membranes 24 are disposed. The outer wall of the housing 22 contains a number of 15 holes, allowing water from the container to enter the fibre membranes 24. These fibres are substantially in the form of flexible tubes, with the sidewalls of the tubes being semi-permeable. Water enters via the outer wall into the porous sidewalls of the fibre membranes 24, and as it does so is filtered. The water then passes through the fibre membranes into a receiving cavity 20 28. After the filtered water reaches the receiving cavity 28 it subsequently passes to the user via the cap shown in Figure 2. As shown in Figure 2, the fibre membranes are supported within a resin layer 26 at the upper end of the filter cartridge, this acts both to ensure the correct location and orientation of the fibre membranes and to provide a seal to prevent water 25 that has not passed through the fibre membranes reaching the receiving cavity. Clearly, with smaller openings in the semi-permeable membranes, smaller particles will be filtered from the liquid. The openings may be sufficiently 30 small to perform ultra-filtration, that is sufficiently small to remove viruses from the flow. Liquids such as water will not pass through such a fine filter C NRPortb\DCC\AZM\446654_I DOC-29AW2012 - 13 without sufficient pressure, and preferred arrangements provide means for introducing that pressure. Other envisaged types of filtration are nano filtration and reverse osmosis. 5 The filter is effective to remove bacteria, viruses, cysts, parasites, fungi and all other water-born pathogens. In fact, filter removes all microbiological matter from the water. Safe drinking water is therefore delivered to the user. Suitable fibre membranes are available commercially, for example X-flow 10 (TM) capillary members from Norit (www.norit.com) may be used. This hollow fibre ultrafiltration membrane is effective to screen all turbidity, bacteria as well as viruses. Material suspended in the water causes cloudiness called turbidity. This is 15 caused by clay, silt, microorganisms, and organic and inorganic materials. Turbidity is reported in "turbidity units." A reading greater than 5 units can be seen easily. Treated drinking water should have turbidity levels between 0.05 and 0.3 turbidity units. 20 Pathogens removed may include bacteria, protozoa, spores, viruses, cysts, and worms. The drinking water limit for fecal coliform bacteria is one organism for every 100 milliliters (mL) of sample water. The membrane openings may be smaller than 20 nanometres, smaller than 25 15 nanometres or even smaller than 10 nanometres. This ensures that viruses as well as bacteria are filtered from the water. Advantage of hydrophilic membranes is that water (or other liquid) passes therethrough in preference to air (or any other gas). Alternatively or additionally, a device designed to pass an oil-based liquid substance may comprise filter 30 membranes which are oleophilic (oil-attracting). Therefore, when a mixture of liquid and gas are in contact with the filter and the pressure in the container C \NRPorblDCC\AZM\4436654_1.DOC.29/06/21112 -14 is increased the liquid (which is attracted to the surface of the filter membranes) is pushed through the filter before any gas. The hydrophilic and hydrophobic properties of a membrane material are 5 related to the surface tension of the material. The fundamental importance of surface tension comparison is that liquids having lower surface tension values will generally spread on materials of higher surface tension values. The higher the surface tension value of the material, the more hydrophilic 10 the material is. Hydrophilic membranes tend to exhibit greater fouling resistance than hydrophobic membranes. Particles that foul in aqueous media tend to be hydrophobic. For example, membranes disclosed herein preferably have a surface tension 15 of greater than 25 dynes/cm, more preferably greater than 30 dynes/cm, more preferably greater than 35 dynes/cm. The membrane preferably comprises materials selected from the group consisting of polytetrafluoroethylene, polyamide, polyimide, polysulfone, 20 polyethersulfone, polyvinylidene fluoride, polypropylene, polyvinyl chloride, polyvinyl pyrrolidone, polycarbonate, polyacrylonitrile, cellulose, cellulose acetate, mixtures, blends and copolymers thereof. Preferred membrane filter may be selected from the group consisting of 25 polysulfone, polyethersulfone, polyvinylidene fluoride, polyvinyl pyrrolidone, polyacrylonitrile, cellulose, cellulose acetate, mixtures, blends and copolymers thereof. A particularly preferred membrane filter material comprises a blend of 30 polyethersulfone and polyvinylpyrrolidone. Polyethersulfone (PES) polyvinylpyrrolidone (PVP) blends are highly oxidant tolerant (>250,000 ppm C \NRPortblDCC\AZM\4436654 DOC-29/Wr2012 - 15 hours for chlorine, tolerant to permanganate and ozone), are tolerant to wide pH range (2-12 continuous operation, <1 for cleaning), exhibit resistance to oils and grease, and are highly hydrophilic. 5 A filter may in some applications be oleophilic, in other circumstances it is desirable to filter oil from the initial water. For example, this would be advantageous if drinking water is required from an initial source of water that has been contaminated by oils. A hydrophilic and non-oleophilic filter improves the filtration of oil from the initial source since water is attracted to 10 the filter over oil and is therefore extracted preferentially. Membranes used in preferred embodiments of the present invention may have a retention of greater than log 6 (99.9999%) of bacteria, cysts, parasites and fungi, and greater than log 4 (99.99%) of viruses from the 15 water. The membranes may also remove sediments and other deposits from the water. In some applications, a filter cartridge 20 comprises a plurality of layers of fibre membranes, each filtering particles of differing sizes from the liquid. 20 The membranes may also be formed from non-fibrous materials, such as ceramics. In one possible arrangement, the outer wall of the annular housing 22 of the filter cartridge contains a plurality of holes. These lie along the entire length 25 of the filter cartridge 20. This allows water to be extracted from the device regardless of the device's orientation (as water will always be in contact with the fibre membranes 24). As water is passed though the filter membranes in preference to air, opening the cap 50 will always filter water and provide it to the user in preference to releasing air and thereby reducing the pressure in 30 the storage area. For this reason the device may be used as long as any liquid is in contact with the filter (that is, it does not require the filter to be C \NRPonrbl\DCCAAZM\441W>54 I DOC-29)6/21I12 - 16 submerged entirely in the liquid). As a result, since the filter preferably extends across substantially the entire length of the container, the device may be operated in any orientation as liquid will always be in contact with the filter at some region regardless of orientation. 5 The preference for releasing liquid over air is also used to provide a spray that works with the device in any orientation. Such a device operates analogously to what is shown in the Figures but uses an adapted cap to ensure that the liquid was released from the device in the form of a spray. 10 The housing 22 shown in Figure 3 extends around the circumferential sidewalls (both internal and external) of the filter cartridge 20, and also covers the end walls, particularly the bottom end (that is, the opposite end to the location of the receiving cavity 26). It should also be understood that the 15 cartridge may comprise a further protective layer on its inner wall. This protects against damage to the fragile fibre membranes when the device is assembled (for example, when the piston shaft 42 is placed in position through the centre of the filter cartridge 20). 20 The holes in the housing 22 may comprise a mesh, such that large particles in the liquid are removed before they reach the filter membranes. This provides a pre-filtration process before the liquid enters the filter membrane itself (in addition, or alternatively, to the pre-filtration provided by the above described pre-filter). 25 The filter cartridge is removably attached to the reset of the device as shown in Figure 2. An advantage of this architecture is that, although fully sealed when in place, the filter cartridge may be removed for cleaning or replacement at any time. In this way, the entire device need not be replaced 30 if the filter cartridge becomes damaged in some way.

C \NRPortbKDCC\AZM\4436654 I DOC-29/6/2012 - 17 Though not shown in the Figures, a visual indicator may be included to allow the user to identify the contents of the container. For example, this could take the form of a transparent window in the side of the container. Indeed, in a preferred embodiment of the invention, the entire side-walls of the 5 container are substantially translucent. A device according to an example may also include a pressure regulator within the container. For example, a valve may be provided in the container wall that opens at a predetermined pressure to allow either gas or liquid to 10 expelled without passing through the filter. If liquid is expelled it may be either siphoned into an additional compartment incorporated into the device, or may leave the device altogether. Other pressure regulation systems may include a device that indicates to the user that the pressure within the container has reached a certain level, or may disable the pump (or other 15 pressurisation means) once the pressure reaches this level. A possible pressure regulation device is shown in Figure 4, which also shows the non-return valve in more detail. As can be seen in this Figure, the non-return valve 46 has a mushroom-like shape. When the pump head 44 is 20 introduced to the pump shaft 42 the pressure in the pump shaft 42 causes the lateral extremities of the non-return valve 46 to rise slightly, allowing air to enter the container 10 via holes 48 in the pump shaft 42. When the pump head 44 is removed the lateral extremities of the non-return valve 46 are retracted over these holes 48 to prevent gas leaving the container 10. 25 The pressure is regulated by a ball bearing 441 disposed within a passageway at the tip of the pump head 44. The ball bearing 441 is biased towards the tip of the pump head 44 by a spring 442. When pressure is applied to the container 10 the ball bearing 441 retracts down the 30 passageway by a distance depending on the applied pressure. If the applied pressure reaches a pre-determined maximum level then the ball bearing 441 C .RPortb\DCC\AZM\4436654_1 DOC-29/06/2012 -18 is retracted to such an extent that air may pass through an escape passageway 443 and down the pump shaft 42, thereby preventing additional pressure from being applied to the container 10. The pressure required to retract the spring 442 will depend upon the length of the spring 442 and the 5. spring constant (according to Hooke's law). In this way the maximum pressure that can be applied to the container is regulated. A sealing ring 444 is used to ensure that air is forced into the device when the head 44 is moved upwards through the shaft 42. Channels or grooves 10 are provided in an upper ridge 445 holding the sealing ring 444 in place to ensure that on retraction of the pump head 44 from the pump shaft 42 air may pass into the region of the pump shaft 42 above the pump head 44 to avoid a vacuum in this region preventing extraction of the pump head 44. 15 As an example of the utility of pressure regulation, consider reverse osmosis. Reverse osmosis filters are capable of removing salt from water. However, as water from the storage area is filtered, that which remains in the storage area becomes more concentrated. This increases the likelihood that salt will get clogged in the filter, thereby reducing the filter's useful lifetime. It 20 is therefore advantageous to provide a mechanism to prevent this eventuality arising. It is also advantageous to regulate the pressure applied to the device to account for any failure in the filter membranes. For example, should the filter 25 become clogged it would be unsafe to force water through it at high pressure due to the possibility that contaminants may also be forced through the filter. In some circumstances it may be beneficial to create a flow of liquid in the container and around the filter. This has been found to reduce the rate at 30 which filter membranes become clogged, and thus ineffective. In one example, the expulsion of liquid at a given pressure (for example, by the C VSRPortbl\DCC\AZM\4436654_1 DOC.29/06/2012 - 19 pressure regulation mechanism) may be adapted to create an appropriate flow. Cross flow filtration processes, unlike conventional dead end filtration, have 5 a filtration surface that is continuously swept by flowing liquid. A portion of the feed fluid passes through the filter to become filtrate, or permeate, fluid. The other portion of the feed fluid continues past the filter media and exits the filter unit as concentrate, or retentate, fluid. The shear of the flowing liquid along the tube wall minimizes the buildup of the solids on the filtration 10 surface. Thus, cross-flow filtration affords the possibility of nearly steady state operation. With conventional dead-end filtration, the filtrate rate decays as the solids layer builds up. In cross-flow filtration, the direction of the feed flow is parallel to the filter surface so that accumulated solids are continuously swept away by the force of the flow. 15 Possible arrangements utilize hollow-fiber filter membranes for such purposes as the treatment of large volumes of water containing suspended matter. Hollow-fiber filter membranes have excellent filtering performance and, moreover, enable a large area of filter membrane to be contained in a 20 unit volume. Cross-flow filtration is a pressure-driven filtration process in which the process liquid flows parallel to the membrane surface. Under a pressure of 10 pounds per square inch (psi) to 100 psi, the filtrate passes through the 25 membrane and exits as clear permeate. The rejected species are retained and collected for disposal or recycling. The membrane's performance is measured by the permeate flux and the rejection of the constituent metals. In addition to the pore size, pore construction is critical to the performance of 30 a membrane. Conventional filters have irregularly shaped pores that permit aggregation of particles at bottlenecks and crevices within the cross section C \NRPonbl\DCC\AZM\441W654 I DOC-29/f./2cl 12 - 20 of the filter. The filtration membrane pores are asymmetrical and shaped like inverted cones, with smaller diameters on the feed side and larger diameters on the permeate side (Figure 3). Since any particle that passes through a pore continues unimpeded without accumulating within the membrane, UF 5 membrane pores do not plug. Cleaning of these filters is thus easy and inexpensive and routine cleaning allows for repeated use over long periods of time. With proper operation and maintenance, UF membranes will operate for several years without replacement. 10 Membranes may be used in hollow fiber configurations. Hollow fiber membranes are made by extruding polymers into the shape of a tube. Hollow fibers are resistant to channel plugging. Hollow fiber may be back pulsed or subjected to reverse flow conditions to achieve optimum removal of foulants. 15 Principles disclosed herein may be used in other applications. In particular, by providing one or more membranes adapted to pass liquid in preference to gases (for example, hydrophilic or oleophilic membranes) extending across substantially the entire length of a container, liquid stored within the 20 container may be transferred to an outlet via the membranes by the application of pressure regardless of the orientation of the container. Moreover, it is possible to select one liquid over another in this way (for example a non-oleophilic, hydrophilic membrane will separate water from oil). The pressure may be manually applied as described above. 25 Alternatively, the container may be pre-pressurised. Unlike the filtration task described above, a dispenser designed to function in any orientation need not be limited to any given pore size, since it does not need to remove particles of a given size from the liquid. The pore size may 30 be chosen instead on the basis of the preferred flow rate given the viscosity of the liquid, the surface area of the filter and the pressure within the C:\NRPonbrDCC\AZM\4436654_I.DOC-29/06/21 12 -21 container. Although the membranes in the above example are shown to be encompassed by the container, the reverse arrangement may also be 5 effective. That is the container may be surrounded by the membranes. As such, the liquid would be held in a region surrounded by the membranes. Figure 5 shows an example of a spray dispenser 100 which functions in any orientation. A membrane 120 is deployed within the outer wall of the 10 dispenser, defining a liquid reservoir 140 within the membrane 120. A mixture of gas and liquid is disposed in the liquid reservoir and is placed a higher pressure than the outside atmosphere. The area between the membrane 120 and the outer walls of the dispenser 15 defines a transfer region 130 and a cap 110 seals the top of the transfer region from the outside atmosphere. When the cap is opened a pressure differential exists between the liquid reservoir and the outside atmosphere, causing liquid to be forced through the membrane into the transfer region and ultimately through the cap to be expelled from the device. 20 The membrane shown in Figure 5 passes liquid in preference to gas and entirely surrounds the liquid reservoir. As a result, the device will expel water when the cap is opened regardless of its orientation. 25 Alternative arrangements may ensure that one or more membranes are in contact with liquid when the device is in any orientation. For example, a device having a rectilinear profile may have separate membranes running along substantially the entire length of each corner. 30 In alternative arrangements, there may be multiple layers in the sidewalls, consisting, for example, of membranes having differing granularities. Unlike C :\RPotbl\DCC\AZM\4436654_ IDOC-29fAt2U12 -22 the membranes described in the context of the water filter above, the membranes shown in Figure 5 are not in the form of hollow tubes. However, it is also envisaged that hollow tubes may be used in this context (and that alternative arrangements may be made in the case of the water filter above). 5 Similarly, the membranes need not be integrated with the walls but may be independent of them. In the preferred embodiments of the invention, the membranes are in the form of hollow tubes and simply replace the conventional extraction straws 10 found in prior art devices. In this way, the cost of manufacturing a dispenser that functions in any orientation is reduced. Once the hollow membrane has been placed in the dispenser, its flexibility allows it to be located as desired. For example, it many be pushed against the sidewalls. 15 It has been found that if the pores in the membrane walls are sufficiently small to ionize the water passing therethrough an advantageous capillary like effect aids the transfer of the liquid through the transfer region. Though the dispenser shown in Figure 5 is pre-pressurised, a number of 20 other techniques may be used to introduce a pressure differential between the container and the outside atmosphere. For example, a pump of the kind described in relation to the water filter above may be used. Alternatively, chemical means may be employed, or the sidewalls of the device may be flexible such that a user can apply pressure by squeezing the device. 25 Applications that benefit from the orientation-independent effects of the present invention include, but are not limited to, spray paints, spray deodorants, kitchen products and perfumes. These devices conventionally become ineffective in most orientations when the amount of liquid remaining 30 is low as they require liquid to enter an extraction tube at a specific point. In this regard, although semi-permeable membranes as described above can C ANRPonbl\DCC\AZM\44M1654- DOC-29/W/2112 -23 be used for the purposes of filtration the principles of the present invention apply to tasks that do not necessarily rely on filtration. While embodiments of the present invention have been described above, it 5 should be understood that they have been presented by way of example only, and not by way of limitation. It will be apparent to a person skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the present invention should not be limited by any of the above described 10 exemplary embodiments. Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer 15 or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be 20 taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Claims (8)

1. In a spray container for liquids, the use of a single hollow-fibre hydrophilic capillary membrane which is adapted to pass liquid in preference to gas under an applied pressure differential as a dip tube.

2. The use of a hollow-fibre hydrophilic capillary membrane of claim 1, wherein the membrane is flexible.

3. The use of a hollow-fibre hydrophilic capillary membrane of claim 1 or 2, wherein the membrane is sized to extend across substantially the length of the container.

4. The use of a hollow-fibre hydrophilic capillary membrane of any preceding claim, wherein the membrane is also oleophilic.

5. The use of a hollow-fibre hydrophilic capillary membrane according to any preceding claim, wherein the container is for spray paints, spray deodorants, kitchen products or perfumes.

6. A method of extracting liquid from a container which incorporates a dip tube consisting of a single hollow-fibre hydrophilic capillary membrane positioned within the container and coupled to an output of the container, the method comprising applying a pressure differential across a wall of the single hollow-fibre hydrophilic capillary membrane, and passing liquid within the container through the wall of the single hollow-fibre hydrophilic capillary membrane and thereby to the output, wherein liquid can be extracted when the container is held in substantially any orientation.

7. In a spray container for liquids, the use of a single hollow-fibre hydrophilic capillary membrane which is adapted to pass liquid in preference to gas under an applied pressure differential as a dip tube, substantially as 25 hereinbefore described with reference to the accompanying drawings.

8. A method of extracting liquid from a container which incorporates a dip tube consisting of a single hollow-fibre hydrophilic capillary membrane positioned within the container and coupled to an output of the container, substantially as hereinbefore described with reference to the accompanying drawings.