Apparatus and method for producing microfoams

Abstract

An apparatus or method for producing microfoams, the apparatus comprising a flow channel having an inlet (107, 110) and an outlet, and a source of foamable liquid (101) and pressurized gas (102) arranged to flow into the inlets (107, 110), the flow channel comprising a spatially oscillating flow channel (106) to provide an oscillating flow direction, the spatially oscillating flow channel (106) oscillating about a bulk flow direction, the spatially oscillating flow channel (106) providing a series of planar cross sections perpendicular to the flow direction, the planar cross sections including a sub-series of planar cross sections perpendicular to the bulk flow direction within the plane (46), the sub-series including at least one surface (46) that does not overlap with at least one other surface (46) within the sub-series.

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for producing microfoams by utilizing a channel having an inlet and an outlet. [Background technology]

[0002] Foams are two-phase systems consisting of a continuous liquid or solid phase surrounding individual gaseous entities. The continuous phase of a foam typically contains surfactants or stabilizers that prevent the cells from coalescing and thus preventing them from reverting to the continuous gas phase and separating from the foam. Microfoams can be defined as a special case of foams in which the cells are typically smaller than 100 micrometers and have low polydispersity (e.g., a standard deviation of less than 40 micrometers).

[0003] Methods and apparatus for producing microfoams are known. Mechanical whipping relies on the use of mechanical moving parts to reduce bubble size using mechanical shear, for example in a high shear mixer. Such mixers rely on the rotation of a high speed impeller or beater head to mix the various phases and other ingredients. Head speeds in these devices are typically greater than 10,000 rpm.

[0004] Thus, known methods of producing microfoams are rather expensive and bulky to manufacture, making them unsuitable for use as disposable articles, for example as part of consumer packaging.

[0005] Microfoams can also be produced by aerosol cans containing dissolved or liquefied gas propellants, but these are increasingly recognized as problematic both environmentally and from a health and safety standpoint.

[0006] U.S. Patent Application Publication No. 2015 / 0360853 A1 discloses a method for producing microfoams by feeding a foamable liquid and pressurized gas through a packed column, but packed columns have the disadvantage of creating dead zones that can cause hygiene issues. Summary of the Invention [Means for solving the problem]

[0007] The present invention utilizes a novel geometry comprising a spatially oscillating channel that has been found to deliver microfoam by simply introducing a foamable liquid and pressurized gas into the inlet. Under appropriate conditions, microfoam is generated within the oscillating channel and exits through the outlet of the channel.

[0008] In a first aspect, the present invention relates to an apparatus for producing microfoams, comprising a flow channel having an inlet and an outlet, and a source of foamable liquid and pressurized gas arranged to flow into the inlet, the flow channel configured as a spatially oscillating flow channel to provide an oscillating flow direction, the spatially oscillating flow channel oscillating about a bulk flow direction, the spatially oscillating flow channel providing a series of planar cross sections perpendicular to the flow direction, the planar cross sections including a sub-series of planar cross sections perpendicular to the bulk flow direction within the plane, the sub-series including at least one surface that does not overlap with at least one other surface within the sub-series.

[0009] In a second aspect, the present invention relates to a method for producing microfoams employing an apparatus including a channel having an inlet and an outlet, the method comprising the steps of supplying a gas and a foamable liquid under pressure into an inlet of the channel, the channel comprising a spatially oscillating channel to provide an oscillating flow direction, the spatially oscillating channel oscillating about a bulk flow direction, the spatially oscillating channel providing a series of planar cross sections perpendicular to the flow direction and including a sub-series of planar cross sections perpendicular to the bulk flow direction within the plane, the sub-series including at least one surface that does not overlap with at least one other surface within the sub-series.

[0010] Thus, by employing a spatially oscillating geometry and under appropriate supply pressure, foamable liquids and gases form microfoams, likely because the spatially oscillating channel provides a special shear environment that generates microfoams due to the vibrations.

[0011] For a given microfoam, a specific range of gas to liquid ratios must be achieved, which can be readily obtained by varying the source pressures and / or flow path resistances of the gas and liquid, respectively, using methods well known to those skilled in the art.

[0012] Thus, the spatially oscillating flow channel is static but oscillates in space to provide a flow direction that changes direction continuously about the bulk flow direction.

[0013] Because the device and method do not contain any moving parts, they can be made relatively inexpensively and at almost any scale, allowing them to be used in small scale dispensing applications through to industrial applications.

[0014] In the context of the present invention, two surfaces "do not overlap" if there is no line perpendicular to one surface that passes through the other surface.

[0015] The flow path includes a bulk flow direction along which the spatially oscillating flow path oscillates. The bulk flow direction can be considered the general flow direction of the flow path in the absence of oscillation. Thus, the spatially oscillating flow path continuously changes direction (generally to either side of the bulk flow direction), which appears to be essential for microfoam formation. Geometric shapes such as arcs, helices, and spirals that involve curvature but do not oscillate spatially around the bulk flow direction do not naturally produce microfoam because the geometries do not involve a change of direction around the bulk flow direction.

[0016] The spatially oscillating flow path may include a regularly repeating pattern, provided that it oscillates about the bulk flow direction, or the spatially oscillating flow path may include random elements or irregular dimensions.

[0017] The cross section of the vibrating channel can be any geometric shape, but is typically a regular shape such as a rectangle, circle, oval, diamond, or the like.

[0018] The spatially oscillating channel comprises a single flow path between the inlet and outlet, meaning that the gas and liquid enter the inlet channel together along a single flow path until they reach the outlet.

[0019] This means that the spatial oscillating channel is a single channel without any branches or recombinations. A single oscillating channel with an inlet and an outlet offers advantages over devices that actually contain junctions. For example, a single oscillating channel minimizes or prevents the appearance of dead zones.

[0020] However, this single flow path may include additional inlets that introduce liquid and / or gas into the single flow path. In addition, the single flow path may include additional outlets so that a portion of the flow branches off before leaving the device through one of the outlets. However, if the flow branches off in this manner, the branched fluids do not recombine downstream and simply leave the device through the outlet. In this way, the benefits of a unidirectional flow path are maintained in the device despite the potential presence of two or more inlets and outlets.

[0021] However, multiple single spatially oscillating channels can be grouped in parallel to increase throughput if desired.

[0022] The average cross-sectional area of the spatial oscillation channel is 0.5 to 5 mm 2 It has been found that making it so that:

[0023] Preferably, a sub-series includes at least one facet that does not overlap with either of the two faces in the sub-series adjacent to it.

[0024] In a preferred embodiment, at least 10, preferably at least 20, and more preferably at least 40, faces in a subseries do not overlap with either of the two faces in the subseries adjacent to them. However, it has been found that beyond a certain number, there are diminishing returns in the quality of the foam produced. Therefore, it is preferred that there are fewer than 1000, preferably fewer than 200, and more preferably fewer than 100 faces in a subseries that do not overlap with either of the two faces in the subseries adjacent to them.

[0025] Preferably, substantially all of the faces in a subseries do not overlap with either of the two faces in the subseries adjacent to them.

[0026] A method or device according to any one of the preceding claims, wherein the average distance between the faces in the sub-series is between 0.5 and 20 mm.

[0027] The gas may include air, nitrogen, hydrocarbons, carbon dioxide, nitrous oxide, or indeed any compound or mixture of compounds in their gaseous state that a user may wish to entrap in the cells of the microfoam.

[0028] Microfoams have many characteristics that make them suitable for a wide range of industrial, commercial, domestic, and medical applications, including, but not limited to, soap-based foams, shaving creams, skin creams, sunscreens, coffee and milk foams, hair cosmetics, surface cleaning formulations, whipped cream, dairy foams (including ice cream), cooking foams, bakery and confectionery products, thermal and acoustic insulation, building materials, lightweight packaging, and void fillers. Preferred microfoams are based on dairy products (e.g., milk and / or cream or synthetic equivalents).

[0029] Microfoams are also useful in processes where a large gas / liquid interfacial area can be beneficial (e.g., in gas / liquid separation processes such as gas scrubbing or in gas / liquid reaction processes such as those occurring in fuel cells).

[0030] The device can be formed from a wide range of materials including plastics (e.g., polypropylene, PET, polyethylene, ABS, nylon, PLA, PVC, Teflon, acrylic, polystyrene, PEEK, etc.), metals, glass, engineered fiber matrices, or any other material that can be molded, milled, printed, cast, machined, sintered, etched, carved, forged, blown, punched, stamped, e-beam machined, laser cut, laminated, and formed into the appropriate shape.

[0031] If a very low-cost disposable (or perhaps single-use) device is needed, many of the plastics may be more preferable due to their low cost, may be reusable, and may be suitable for mass production methods such as injection molding. Reusable devices may be needed in other applications, such as milk foam modules in retail coffee vending machines or processing lines that make foamy food products. In such cases, metal, ceramic, or glass (possibly supported by surrounding structures) may be more suitable because they are more resistant to chemical and mechanical cleaning, heat treatment, steam cleaning, autoclaving, and consolidation.

[0032] The present invention can be used as a single geometric flow path for the production of low to medium volumetric flow rates of microfoam, or multiple foamer units can be run in parallel to achieve higher volumetric flow rates more suitable for industrial and manufacturing applications.

[0033] In one preferred embodiment, the device comprises a pressurized container including a closable outlet, the pressurized container containing foamable liquid and gas under pressure, the outlet of the device being arranged to deliver the foamable liquid and gas to an inlet of a spatially oscillating flow path coupled to the closable outlet of the device, such that when the closable outlet is opened, the pressure difference between the pressure within the container and the pressure at the outlet is sufficient to drive the foamable liquid and gas towards the inlet, thereby creating microfoam which exits through the outlet and then through the closable outlet of the device.

[0034] The present invention will now be described with reference to the following figures. [Brief explanation of the drawings]

[0035] [Figure 1] FIG. 1 is a schematic diagram of the apparatus used to produce the microfoams in the examples. [Figure 2] 1 is an image of a microfoam produced by an apparatus according to the present invention. [Figure 3] FIG. 1 is a plan view of a zigzag device including an oscillating channel that does not fall within the scope of the present invention. [Figure 4] FIG. 1 is a plan view of a notched device including a vibrating channel that is not within the scope of the present invention. [Figure 5] FIG. 1 is a plan view of a serpentine device including an oscillating channel according to the present invention. [Figure 6] FIG. 1 is a plan view of a notched device including a vibrating channel according to the present invention. [Figure 7] 1 is a perspective view of an apparatus including a vibrating channel according to the present invention; [Figure 8] 1 is a cross-sectional side view of an apparatus according to the present invention for delivering microfoam. [Figure 9] FIG. 9 is a cross-sectional side view of a variation of the device shown in FIG. 8, showing only the lid assembly. [Figure 10] FIG. 10 is a side cross-sectional view of a second inventive device for delivering microfoam. DETAILED DESCRIPTION OF THE INVENTION

[0036] Example Turning to the accompanying drawings, Figure 1 shows a diagram of the experimental rig. A compressor 12 was used to supply pressurized air via 2.5 mm ID tubing 13 to a T-connector 14. The T-connector 14 supplied pressurized air to a container 15 containing surfactant-loaded liquid (liquid container) and a container 16 containing only gas (gas container). Tubing (2.5 mm ID) connected the outlets of both containers to a second T-connector 17, which was then connected (via 2.5 mm ID tubing) to a microfoam generator 18. The liquid containers were oriented so that the tubing connected to the compressor fed into the headspace of the liquid container, and the tubing leading to the microfoam generator was connected to the liquid container below the liquid line. In Figure 1, connector 17 is a T-connector, but it could also be a Y-connector or other connector geometry that provides the correct gas / liquid ratio (preferably as intermittent packets over the gas / liquid conduits leading to the microfoam generator).

[0037] Each of the three classes of geometric shapes exemplified herein (zigzag, notched, and serpentine) was printed from PLA on a 3D printer and contained within a plastic casing to contain the pressure. Tubing was connected to the casing via a quick-fit leading to the inlet port of the microfoam generator. A needle valve 19 was installed in the line between the outlet of the pressure vessel and the inlet of a T-connector leading to the microfoam generator so that the flow rates of liquid and gas could be adjusted.

[0038] When the compressor was turned on, the headspaces of the gas and liquid containers were pressurized, forcing gas to flow from the gas container through the needle valve into a second T-connector and liquid to flow from the liquid container through the needle valve into a second T-connector. At the second T-connector, the gas and liquid combined into a gas / liquid mixture that was forced through the microfoam generator. The needle valve was adjusted to provide a range of different flow rates of gas and liquid to the microfoam generator. When microfoam was achieved, the air-to-gas ratio could be varied to produce microfoams with a range of liquid-to-gas ratios, resulting in products with textures ranging from fluid wet foams to very firm dry foams. Maximum air content values are reported in the examples below.

[0039] It has been found that to produce foamable fluid microfoams with a viscosity of 1 cp, the apparent liquid velocity is preferably in the range of 500-750 mm / s (most of the data falls within this range), and next most preferably in the range of 250-1500 mm / s (all of the data falls within this range).

[0040] To produce microfoams with higher viscosities (5-50 cP), the apparent liquid velocity was preferably in the range of 500-2000 mm / s (most of the data was within this range), and most preferably in the range of 500-2500 mm / s (all of the data was within this range). Apparent liquid velocity = (volumetric flow rate of foamable fluid) / (minimum cross-sectional area within the flow channel).

[0041] The viscosities of the liquids tested were as follows: Fairy® liquid (diluted 1 part in 10 parts water): 1 cp, skim milk (<0.3% fat): 5 cp, whipped cream (39.8% fat): 50 cp. Each foam was tested at 25°C with diluted Fairy® Liquid (1 part Fairy® Liquid: 10 parts water), a dishwashing detergent available in the UK that is primarily sodium lauryl sulfate. The compressor pressure was set at 5 bar. In all cases, the air phase volume contained within the final microfoam was >95%. The test conditions and examples under which the microfoams were produced are recorded in Table 1.

[0042] [Table 1-1]

[0043] [Table 1-2]

[0044] For a select number of geometries, the experiment was repeated with chilled (5°C) skim milk (approximately 1% fat content). Initially, the compressor pressure was set at 5 bar, but this was repeated at 8 bar if no microfoam was produced. The results are shown in Table 2.

[0045] [Table 2]

[0046] For a select number of geometries, the example was repeated with cooled (4°C) whipped cream (38% fat content). Initially, the compressor pressure was set at 5 bar, but this was repeated at 8 bar if no microfoam was produced. The results are shown in Table 3.

[0047] [Table 3]

[0048] For dairy products (skim milk, cream), there was a dependency of the microfoam on the deteriorating performance related to product temperature. Around 7°C, foaming properties and microfoam stability for milk and cream appeared to deteriorate, consistent with observations elsewhere in the dairy literature.

[0049] When microfoam was produced, measurements consisted of the liquid flow rate and the volume of gas within the microfoam. A sample of diluted Fairy® liquid microfoam produced by the notched foamer was collected in a Petri dish. The Petri dish was inverted and a microscopic image was taken from above (through the glass). The image was taken within 3 seconds of the sample being collected. This microscopic image is shown in Figure 2. The microscopic image was converted to a bubble size distribution, which was found to have a mean of 39.2 micrometers and a standard deviation of 25.21 micrometers.

[0050] In Table 1, it can be seen that the notched, zigzag, and serpentine foamers are also capable of producing microfoam from dilute Fairy® liquid.

[0051] The notched foamer also proved capable of producing a very fine and uniform foam structure (mean bubble size of 39.2 micrometers with a standard deviation of 25.21 micrometers). A total of 354 bubble sizes were evaluated to generate these statistics.

[0052] Tables 2 and 3 show that the notched, zigzag, and serpentine foamers were able to produce microfoams from cooled skim milk and whipped cream. For the notched foamer, the maximum air content of the whipped cream was 58%, which is close to the maximum air content achievable by mechanical whipping.

[0053] Nomenclature for foamer test geometries The majority of the tests were performed on variations of three foamer geometries (zigzag, notched, and serpentine). The foamer geometries described in the table were introduced so that the foamers could be referenced concisely and clearly.

[0054] 1) Zigzag foamer: consists of a rectangular channel with width "wz" (measured perpendicular to the page) and depth "dz". The zigzag shaped channel is created by extending a triangular prism (with an isosceles triangular base) into the channel as shown in Figure 3. The prism extends a distance "ez" into the channel, and the distance between adjacent vertices is represented by "sz". The angle between identical faces of the triangle is represented in degrees "at", and the total number of triangles contained within the foamer is represented by "nt". The nomenclature Z(wz, dz, ez, az, sz, nz) will indicate that the foamer has a zigzag geometric shape with the parameters as defined above.

[0055] 2) Notched foamer: consists of a rectangular channel of width "wn" and depth "dn" (measured perpendicular to the plane of the paper). Regularly spaced notches (rectangular prisms) extend into the channel a distance "en" from either side in an alternating arrangement as shown below in Figure 4. The width of the notches is "bn", the spacing between the notches is "sn", and the total number of notches in the geometry is "nn". These parameters are shown in Figure 4. The nomenclature N(wn, dn, en, bn, sn, nn) will indicate that the foamer has a notched geometry with the parameters as defined above.

[0056] 3) Serpentine foamer: A curved channel was defined as the area swept out by an arc of "as" degrees between two concentric cylinders of radii "ri" and "ro" and height "ds". A serpentine foamer was created by connecting together a total of "ns" number of channels as shown in Figure 5. The nomenclature S(ro, ri, ds, as, ns) will denote that the foamer has a serpentine geometry with parameters as defined above.

[0057] An example of a zigzag geometry that does not fall within the scope of the present invention is shown in FIG. 3, which shows a plan view of an oscillating channel 20 having a generally variable rectangular cross-section and spatially oscillating about the bulk flow direction indicated by arrow 22. Note that there are many planar cross-sections 24, 26, 28 of subseries that are perpendicular to the bulk flow direction. However, it should also be noted that surface 26 within a subseries overlaps with surfaces 24 and 28 and therefore does not fall within the scope of the present invention. Nevertheless, if parameter ez is increased, a geometry may fall within the scope of the present invention when surface 26 no longer overlaps with surfaces 24 or 28.

[0058] An example of a notch geometry outside the scope of the present invention is shown in FIG. 4, which shows a plan view of an oscillating channel 30 having a generally constant rectangular cross-section overall and spatially oscillating about the bulk flow direction indicated by arrow 32. Note that there are many planar cross-sections 34, 36, 38 of subseries that are perpendicular to the bulk flow direction. However, it should also be noted that surface 36 within a subseries overlaps with surfaces 34 and 38 and therefore does not fall within the scope of the present invention. Nevertheless, if parameter en is increased to be greater than wn / 2, the geometry would fall within the scope of the present invention if surface 36 no longer overlaps with surfaces 34 or 38.

[0059] An example of a serpentine geometry within the scope of the present invention is shown in Figure 5, which shows a plan view of an oscillating channel 40 having a generally constant rectangular cross-section overall and oscillating spatially about the bulk flow direction indicated by arrow 42. Note that there are many planar cross-sections 44, 46, 48 of sub-series that are perpendicular to the bulk flow direction. Note also that surface 46 within a sub-series does not overlap with surfaces 44 and 48 and is therefore within the scope of the present invention.

[0060] An example of a cutout geometry within the scope of the present invention is shown in Figure 6, which shows a plan view of an oscillating channel 50 having a generally rectangular cross-section and oscillating spatially about the bulk flow direction indicated by arrow 52. Note that there are many planar cross-sections 54, 56, 58 of sub-series that are perpendicular to the bulk flow direction. Note also that surface 56 within a sub-series does not overlap with surfaces 54 and 58 and is therefore within the scope of the present invention.

[0061] An example of a two-dimensional spatially oscillating geometry is shown in Figure 7, which has an oscillating channel 60 having an overall generally constant rectangular cross section and which spatially oscillates about the bulk flow direction indicated by arrow 62. Note that there are many planar cross sections 64, 66, 68 of the subseries that are perpendicular to the bulk flow direction. Note also that plane 66 within the subseries does not overlap with planes 64 and 68 and is therefore within the scope of the present invention.

[0062] 8 and 10 show two different embodiments of a microfoam generating device that includes a pressurized container, which is disposable and may contain any gas, as described herein, but is refillable and refillable aerosol.

[0063] The first embodiment of the refillable and refillable aerosol of Figure 8 includes a holding container 104 for holding a foamable fluid 101, a compressed gas headspace 102, and a microfoam portion 105 having a gas conduit 108. Additionally, there is a pressurized gas fill port 115 having a one-way valve 116, and screw-on lid assemblies 112, 113 having a seal 111 incorporating manual valve spring assemblies 117, 118 and a nozzle 119 for control and dispensing of the microfoam.

[0064] The aerosol device is initially filled with foamable fluid at atmospheric pressure 103. The lid assembly 112 is then attached to the holding vessel 104, sealing the vessel contents from the atmosphere via connecting threads 113, compressible seal 111, and closed valves 116, 118 in the lid's channels 115, 121. The device's headspace 102 is pressurized to the desired level via connecting the high-pressure gas connector 114 to an external fill source of the desired gas. The fill source of gas can be provided by an air pump, gas compressor, pressurized gas header tank, pressurized gas cylinder, or small-volume pressurized gas valve. The fill gas passes through a one-way valve that allows gas into the device 116 but not out of the device 116. The gas flow then enters the holding vessel 104 via the fill gas / microfoam channel junction 156 and then through the channel 106 in the microfoam device 105. Using the microfoam flow path 121 and the spatial oscillation flow path of the foaming section 106 as a common conduit for the fill gas has the advantage that the pressurized gas flow back-flushes any blocked flow paths from drying out or coalescing material from the foamable fluid, or blocked flow paths from contamination. Once the desired gas pressure is achieved within the holding vessel 104, the external gas source can be disconnected from the high-pressure gas connector 114. Microfoam of the foamable liquid 101 is then generated by opening the manual valve 117. The valve 117 and its return spring 118 can be actuated by many means known in the art, such as a lever, trigger, and button (not shown). The position of the return spring 118 relative to the valve 117 can also be varied depending on the manual design choice. Opening the valve 117 allows pressure relief of the pressurized system within the holding vessel 104. The pressure release causes foamable fluid 101 to flow into foaming device fluid inlet 107 and pressurized gas to flow into inlet 110 of gas conduit 108, which is located in a gas headspace free of the foamable liquid level. The pressurized gas flow in gas conduit 108 and the foamable liquid flow from inlet 107 meet at gas / liquid junction 109, where the gas is entrained in the liquid flow. Microfoam is then produced as the two-phase fluid flow passes through oscillating channel 106 within microfoaming device 105.The microfoam then flows out of the microfoam device 105 through the microfoam channel 122 and the release valve 117. The microfoam finally exits the device 120 through the nozzle 119. Microfoam production stops when the manual override (lever, trigger, or button) is released and the valve return spring 118 closes the valve 117, equalizing the system pressure within the device.

[0065] The aerosol device can be refilled with gas at any time during use by connecting the closure to an external fill gas source via high pressure gas connector 114. To refill the aerosol with effervescent fluid, the residual gas pressure is released manually by closing valve 117. Once the aerosol is equalized to atmospheric pressure 103, the manual is released by closing valve 117 and the lid can be safely removed to refill the device with effervescent fluid.

[0066] A variation of the refillable and refillable aerosol embodiment shown in FIG. 8 is seen in FIG. 9. FIG. 9 shows only the threaded lid assembly 124, 125 of the entire device. In this variation, the filler gas flow from the pressurized gas fill port 127 passes through the one-way valve 128 and then through the filler gas outlet 133 and directly into the compressed gas headspace 102 through another opening in the seal 123, without connection to the microfoam flow path 134 via the filler gas-microfoam flow path junction 156. All other aspects of the lid assembly 125; namely, the quick-release high-pressure gas connector 126, the manual valves and return springs 130, 129, the nozzle 131, the microfoam section 122 with its gas conduit (not shown), and the microfoam outlet flow path 132, are as described with respect to FIG. 8. This variation may be advantageous in systems where it is undesirable for the foamable fluid to undergo pre-shear and gasification prior to microfoaming.

[0067] A second embodiment of a refillable and replenishable aerosol for generating and dispensing microfoam is shown in FIG. 10. This embodiment includes a holding vessel 137 for holding foamable fluid 134, a compressed gas headspace 135, and a dip tube 154 having a gas conduit 141. In addition, there is a pressurized gas fill port 148 with a one-way valve 149, manual valve spring assemblies 150, 151, and screw-on lid assemblies 145, 146 with a seal 144 that captures a nozzle 152 containing a microfoam portion 138. The microfoam portion 138 may be integrated into the nozzle or may be removable to allow for cleaning, replacement, or exchange with a microfoam portion of a different design. The aerosol device is initially filled with foamable fluid at atmospheric pressure 136. The lid assembly 145 is then attached to the holding vessel 137, sealing the vessel contents from the atmosphere via connecting threads 146, compressible seal 144, and closed valves 149, 150 in the lid's channels 148, 145. The device's headspace 135 is pressurized to the desired level via connecting the high-pressure gas connector 147 to an external charge source of the desired gas. For the first aerosol embodiment, the charge source of gas may be provided by an air pump, gas compressor, pressurized gas header tank, pressurized gas cylinder, or small-volume pressurized gas valve. The charge gas passes through the one-way valve 149, enters the holding vessel 137 via the charge gas dip tube connection 155, then passes through the dip tube 154 and gas conduit 141, and exits through the dip tube inlet 140 and gas conduit inlet 143. Once the desired gas pressure is achieved within the holding vessel 137, the external gas source can be disconnected from the high-pressure gas connector 147. Microfoam of the foamable liquid 134 is then generated by opening manual valve 150. Valve 150 and its return spring 151 can be actuated by many means known in the art, such as levers, triggers, and buttons (not shown). Also, the position of return spring 151 relative to valve 150 can vary depending on the manual design choice. Opening valve 150 allows pressure relief of the pressurized system within holding vessel 137. Pressure relief results in foamable fluid 134 flowing into dip tube inlet 140 and pressurized gas flowing into inlet 143 of gas conduit 141, which is located in a gas headspace unrelated to the foamable liquid level.The pressurized gas flow in gas conduit 141 and the pressurized gas flow in dip tube inlet 140 meet at gas / liquid junction 142, where the gas is entrained in the liquid flow. The two-phase fluid flow passes through dip tube 154 and release valve 150, then into oscillating channel 139 of microfoam section 138 located in nozzle 152 of lid assembly 145. The generated microfoam finally flows out end microfoam section 153 and is dispensed for use. Microfoam generation stops when the manual lever (lever, trigger, or button) is released, causing valve return spring 151 to close valve 150 and equalize system pressure within the device.

[0068] The refillable and refillable aerosol device of Figure 10 can be refilled with gas at any time during use by connecting the closure to an external supply of fill gas via high pressure gas connector 147. To refill the aerosol with effervescent fluid, the residual gas pressure is released manually by closing valve 150. Once the aerosol pressure equalizes to atmospheric pressure 136, the manual is released by closing valve 150 and the lid can be safely removed to refill the device with effervescent fluid.

[0069] Variations of the aerosol device of Figure 10 can be consistent with the filler gas flow path modifications described in Figure 9. In this second embodiment (Figure 10), the filler gas flow from the quick release high pressure gas connector 147 enters the pressurized headspace 135 directly through a dedicated filler gas outlet, but does not enter through the dip tube 154 via the filler gas / dip tube junction 155. Again, this design is advantageous for systems where it is undesirable for the foamable fluid to undergo pre-shear and gasification prior to micro-foaming.

[0070] Alternatively, the aerosol embodiment shown in Figures 8 and 10 can be filled with foamable fluid through a nozzle with the manual valve in the open position, eliminating the need to remove and replace the lid assembly.

[0071] Although not shown in Figures 8, 9 and 10, a pressure relief valve may be incorporated into the holding vessel (104 in Figure 8, 137 in Figure 10) or lid assembly (112 in Figure 8, 125 in Figure 9, and 145 in Figure 10) to prevent over-pressurization and may additionally be used to depressurize the system prior to refilling with foamable fluid.

[0072] Another embodiment of the present invention is a non-refillable, non-fillable aerosol. Here, foam portion 105 depicted in FIG. 8 and foam portion 138 depicted in FIG. 10 would assume similar respective positions in a crimp-sealed aerosol with a single manual valve assembly. Such an aerosol may be filled with foamable fluid prior to application of the crimp-sealed lid assembly, or may be filled with foamable fluid through the manual valve after application of the crimp-sealed lid assembly. The aerosol may be pressurized by filling with a pressurized fill gas through the manual valve assembly.

[0073] 10 could include a dip tube 154, a gas conduit 141, and a bag containing foamable liquid 134. The foamer would still be incorporated into the nozzle as shown in FIG.

[0074] Another embodiment of the present invention is a functional package for a foamable fluid for use with a durable or semi-durable foam dispensing device. This functional package is disposable, or more preferably, reusable. An example of such a functional package is shown in FIG. 11. The package includes a sealed foamer assembly 156 having a dip tube 157 with a single continuous flow path formed by a liquid inlet 158, a vibrating flow path 159, and a microfoam outlet 160. The sealed foamer assembly has an attached gas conduit 161 with a gas inlet 162 that intersects with a liquid inlet flow path 163 to form a gas / liquid mixing junction 164. The gas conduit 161 may be attached to the dip tube 157 as shown, or may be integrated into the dip tube 157 to form a single, compact structure (not shown). The sealed foamer assembly 156 also has a sealing flange 165 capable of forming a high-pressure seal with a durable or semi-durable foam dispensing device (FIG. 12). Attached to the sealed foamer assembly 156 is a liquid-holding vessel 166. The liquid-holding vessel 166 is attached to the sealing foamer assembly 156 in a manner that forms a complete seal and serves as a leak-proof liquid container. The liquid-holding vessel 166 is rigid and may be made of any suitable material, but may also be a flexible pouch (preferably formed from a barrier plastic or plastic / metal laminate). The liquid-holding vessel 166 contains a foamable fluid 167 and surrounds the dip tube 157 and gas conduit 161 of the sealing foamer assembly 156. The foamable fluid 167 may be introduced into the liquid-holding vessel 166 via a microfoam outlet 160 through an opening, such as a seam, in the liquid-holding vessel. The liquid-holding vessel 166 is sealed after filling, i.e., via a port or valve (not shown) incorporated into the wall of the liquid-holding vessel. The foamable fluid 167 will be filled into the liquid-holding vessel 166 in such a way that there is either no gas in the headspace 162 or there is a headspace 162 of the desired gas or mixture of gases at sub-atmospheric pressure. The package may also have a removable or frangible seal (not shown) applied to the microfoam outlet 160 to prevent leakage, protect the foamable fluid from contamination, and maintain the desired headspace conditions.If formed from a flexible pouch, the liquid-holding container 166 may be rolled or folded in a manner to reduce storage space and facilitate insertion into a durable foam dispensing device (FIG. 12). The folded or rolled fluid-holding device may additionally be sleeved with a removable or frangible cover made of plastic, foil, paper, card, or other suitable material for stability and to aid insertion into the foam dispensing device.

[0075] The exemplary functional package embodiment shown in FIG. 11 is designed for use with the durable foam dispensing device shown in FIG. 12. Prior to use, any removable seals or secondary packaging may be removed from functional package 168, which is then inserted into holding vessel 169 of the foam generating device. The holding vessel may have an O-ring or gasket 170 at its interface with sealing flange 171 of the functional package to provide a pressure seal. Alternatively, sealing flange 171 of functional package 168 may incorporate its own O-ring or gasket or may be formed from a suitable compliant material to form a pressure seal under compression. Lid assembly 172 secures to holding vessel 169 via threads 173 or other suitable mechanism, sealing the device flow path from the outside atmosphere. The lid assembly incorporates pressurized gas fill port 174 with one-way valve 175, manual valve spring assemblies 176, 177, and dispensing nozzle 178. The device is filled to the desired pressure with the required gas or gas mixture through pressurized gas fill port 174. The pressurized gas source can be provided by an air pump, gas compressor, pressurized gas cylinder, or small-volume pressurized gas valve. When filling the foam dispensing device, the fill gas passes through the oscillating flow path 179 of the functional package dip tube 180 and exits into the liquid holding vessel 181 through the liquid inlet 182 and the gas inlet 183 of the gas conduit. The liquid holding vessel 181 (if a flexible pouch) has an expanded volume equal to or greater than the volume of the holding vessel 169 of the device. If the liquid holding vessel 181 is rigid, it can have a volume that allows the maximum volume that fits into the holding vessel, or it can hold a higher pressure if the holding vessel has a smaller volume. Once the desired gas pressure is reached within the headspace 189 of the functional package 168, the external gas source can be disconnected from the high-pressure gas fill port 174.

[0076] Next, a microfoam of foamable fluid 184 is generated by opening manual valve 176. Valve 176 and its return spring 177 can be actuated by many means known in the art, such as a lever, trigger, or button (not shown). The position of return spring 177 relative to valve 176 can also vary depending on the manual design. Opening valve 176 allows pressure relief from pressurized liquid holding vessel 181 within holding vessel 169. Pressure relief results in foamable fluid 184 flowing into dip tube 180 via fluid inlet 182 and pressurized gas flowing into inlet 183 of gas conduit 185 (located in the gas headspace above the foamable liquid level). The pressurized gas flow in gas conduit 185 and the pressurized gas flow in dip tube inlet 182 meet at gas / liquid junction 186, where the gas is entrained in the liquid flow. The two-phase fluid flow passes through oscillating channel 178 within dip tube 179, where it is converted to microfoam. The microfoam then flows out of the functional package 168 through the lid microfoam channel 187 and the release valve 176. The microfoam finally exits the device 188 through the nozzle 178. Microfoam production stops when the manual mechanism (lever, trigger, or button) is released and the valve return spring 177 closes the valve 176, equalizing the system pressure within the device.

[0077] The device can be refilled with gas at any time during use by connecting the closure to an external fill gas source via high-pressure gas connector 174. Once the foamable fluid 184 within functional package 168 is expended, the residual gas pressure is manually released by closing valve 176. Once the device has equalized to atmospheric pressure, the manual release is made by closing valve 176, and the lid can then be safely removed. Functional package 168 is then removed from holding vessel 169 and discarded or recycled. A new functional package 168 is inserted into the holding vessel, and the process is repeated.

Claims

1. 1. An apparatus for producing microfoams, said apparatus comprising: a spatially oscillating channel having an inlet and an outlet; and a source of foamable liquid and pressurized gas arranged to flow into said inlet under a supply pressure; the spatially oscillating flow channel is configured to provide an oscillating flow direction; The spatially oscillating flow channel oscillates around the bulk flow direction, the spatially oscillating flow channel provides a subseries of planar cross sections perpendicular to the oscillating flow direction, the subseries including a plurality of planar cross sections perpendicular to the bulk flow direction; the sub-series includes at least one planar cross-section that does not overlap with at least one other planar cross-section in the sub-series; The spatially oscillating flow path is a single flow path without any branching or recombination of flow paths; the supply pressure is suitable for providing a special shear environment in which the spatially oscillating channel generates microfoams due to vibration; the microfoam having an average cell diameter of less than 100 micrometers; An apparatus wherein at least ten planar cross sections in said sub-series do not overlap with any two planar cross sections in said sub-series adjacent to each of them.

2. The average cross-sectional area of the spatial oscillation flow path is 0.5 to 5 mm ２ 2. The device of claim 1, wherein:

3. 3. The device according to claim 1, wherein the average distance between the planar cross sections in the sub-series is between 0.5 and 20 mm.

4. A device according to any one of claims 1 to 3, wherein the foamable liquid is a dairy product or a synthetic equivalent.

5. 5. The apparatus of any one of claims 1 to 4, wherein the pressurized gas comprises air, nitrogen, a hydrocarbon, carbon dioxide, nitrous oxide, or mixtures thereof.

6. The device according to any one of claims 1 to 5, wherein the spatially oscillating channel is made of plastic.

7. the apparatus includes a pressurized vessel including a reclosable outlet; the container contains the foamable liquid and gas under pressure; the device is arranged to deliver the foamable liquid and gas to the inlet of the spatially oscillating channel, the outlet of which is coupled to the openable outlet of the device; 7. The device of any one of claims 1 to 6, wherein when the reclosable outlet is opened, the pressure differential between the pressure inside the container and the pressure at the outlet is sufficient to drive the foamable liquid and gas into the inlet, thereby creating a microfoam which then exits the outlet and then the reclosable outlet of the device.

8. 1. A method for producing a microfoam, the method employing an apparatus including a spatially oscillating channel having an inlet and an outlet; The method includes supplying a gas and a foamable liquid under a supply pressure into the inlet of the spatially oscillating channel; the spatially oscillating flow channel is configured to provide an oscillating flow direction; The spatially oscillating flow channel oscillates around the bulk flow direction, the spatially oscillating flow channel provides a subseries of planar cross sections perpendicular to the oscillating flow direction, the subseries including a plurality of planar cross sections perpendicular to the bulk flow direction; the sub-series includes at least one planar cross-section that does not overlap with at least one other planar cross-section in the sub-series; The spatially oscillating flow path is a single flow path without any branching or recombination of flow paths; the supply pressure is suitable for providing a special shear environment in which the spatially oscillating channel generates microfoams due to vibration; the microfoam has an average cell diameter of less than 100 micrometers; A method wherein at least ten planar cross sections in said sub-series do not overlap with any of the two other planar cross sections in said sub-series that are adjacent to each of them.

9. The average cross-sectional area of the spatial oscillation flow path is 0.5 to 5 mm ２ The method of claim 8, wherein

10. 10. The method according to any one of claims 8 to 9, wherein the average distance between the planar cross sections in the sub-series is between 0.5 and 20 mm.

11. A method according to any one of claims 8 to 10, wherein the foamable liquid is a dairy product or a synthetic equivalent.

12. The method of any one of claims 8 to 11, wherein the gas comprises air, nitrogen, a hydrocarbon, carbon dioxide, nitrous oxide or mixtures thereof.

13. The method according to any one of claims 8 to 12, wherein the spatially oscillating channel is made of plastic.

14. The method according to any one of claims 8 to 13, wherein the spatially oscillating channel is made by a 3D printer.

15. the apparatus includes a pressurized vessel including a reclosable outlet; the container contains the foamable liquid and gas under pressure; the device is arranged to deliver the foamable liquid and gas to the inlet of the spatially oscillating channel, the outlet of which is coupled to the openable outlet of the device; 15. A method according to any one of claims 8 to 14, wherein when the reclosable outlet is opened, the pressure differential between the pressure inside the container and the pressure at the outlet is sufficient to drive the foamable liquid and gas into the inlet, thereby creating a microfoam which then exits the outlet and then the reclosable outlet of the device.

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