GB2466631A

GB2466631A - A spray device for atomising fluids having at least three nozzles with a restriction

Info

Publication number: GB2466631A
Application number: GB0819264A
Authority: GB
Inventors: Philip Alan Durrant; Phillippe Luginbuhl
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-10-21
Filing date: 2008-10-21
Publication date: 2010-07-07
Also published as: GB0819264D0

Abstract

A spray device suitable for spraying a fragrance, medical or personal care product, wherein the liquid is forced by the action of pressure from a vessel into a spray head having at least three nozzles, the nozzles each having a restriction 4 in the flow path which at it narrowest has cross-sectional area of between 40µm2 (i.e. square micrometres) and 2000 square micrometres. Within 200µm (micrometres / microns) from the nozzle constriction / throat 4, any channel 10 leading to or from the nozzles becomes larger than 80 square micrometres. The emitted jets may converge so as to collide, or may diverge. The nozzles may be created by laser on a plate 8 having thickness of between 10 and 2000 micrometres, thereby forming an atomising element / perforated membrane 8. The channel 10 leading to the restriction 4 may be dome shaped (convergent and tapering) terminating at the nozzle. The passage may alternatively assume an hourglass (Venturi) profile.

Description

METHOD AND APPARATUS FOR THE CREATION OF A

FINE SPRAY FOR APPLICATIONS RELATED TO AIR Evidently, cylindrical jets have a larger surface area to volume ratio than a sheet with the same thickness as CARE: AMBIENT SCENTING AND PERSONAL CARE: the diameter of the jet.

COSMETIC, SKIN AND EYE CARE.

The energy source of the waves can be: internal, relating to disturbances that perturb the liquid flow, such as imperfections in conduit and nozzle walls; or external, relating to interaction with the external

References Cited atmosphere.

Liquid Atomisation, L. Bayvel and Z. Orzechowski, Lord Rayleigh produced the first mathematical Taylor & Francis, 1993. description of the break-up mechanism in the 19th century and this was later extended by C. Weber to Internal Flow Characteristics of Simplex Swirl include external aerodynamic sources.

Atomisers N. K. Rizk and A. H. Lefebvre, Reference: Liquid Atomisation, L. Bayvel and Purdue University, West Lafayette, Indiana. Z.Orzechowski, Taylor & Francis, 1993.

USPTO Patent Application #: 20060275220 One aspect of the invention is atomisation by means of Rayleigh break-up through the use ofjets.

Patent US 5,261,601 The current method almost universally used for Patent WO 2004/089551 A2 generating personal care sprays incorporates a swirl chamber. The liquid is forced through tangential ports DESCRIPTION OF THE INVENTION into a swirl chamber to create a liquid vortex with an air-core emerging through an orifice into the ambient atmosphere in the form of a hollow conical sheet with FIELD OF THE INvENTIoN high angular and axial velocity. The sheet disintegrates This invention relates to a method and apparatus for with distance to form a conical spray.

generating a fine atomised spray suitable for use in air care and personal care applications. The liquid is delivered to the swirl chamber by means of a pump, comprising a piston which, is manually BACKGROUND OF THE INVENTION driven through a chamber containing the liquid dose to Dr. Allen Dc Vilbiss, invented the medical atomizer be atomised forcing it into the swirl chamber. A spring with a rubber bulb for manual pressurization and a is manually compressed during this procedure and the single nozzle in Ohio in 1887. This basic design evolved stored energy in the spring is then used to force the into elegant atomizers for perfume application, piston to its starting position drawing the next dose of Subsequent development has led to the integration of the liquid into the chamber via a unidirectional valve.

the pump into the container cap and a wide diversification of applications including air care and This method suffers from a number of disadvantages.

personal care applications.

A relatively high velocity is required for the liquid The majority of systems rely on Rayleigh break-up for delivered from the pump in order for atomisation to the formation of the spray. occur after passing through the swirl chamber.

The process of atomisation due to Rayleigh break-up Also, the atomised liquid spray exits the head at high occurs when waves of increasing amplitude develop on velocity resulting in potentially uncomfortable impact the surface of a liquid due to movement through the with the skin. In addition the swirl chamber delivers a ambient atmosphere. leading to instability, which causes relatively wide distribution of droplet sizes. Droplet disintegration of the liquid into airborne droplets. diameters of several hundred micrometers are commonly produced, especially when insufficient Rayleigh break-up occurs most readily in moving liquid pressure is applied to the spray actuator. This where the surface area is large compared to the volume, combined with the high impact velocity often results in as the energy in the surface is relatively high. This an unpleasant "shower effect" with liquid running on occurs when the liquid is in the form of sheets or jets or the skin requiring subsequent wiping to spread the spherical droplets. cosmetic. For perfumes, this is not advisable as the friction reportedly changes the characteristics of the It is another object of the invention to provide a spray perfume. with the majority of airborne droplet diameters below micrometers for improved tactile appreciation.

The high concentration of large droplets impacting at high velocity can also leave marks or stains on clothing. In manually activated swirl chamber systems, the delivery takes place over a short period, typically very It is another of the objects of the invention to provide a much less than one second and is accompanied by a low velocity spray with low impact with the skin and sharp audible hiss.

reduced "shower effect".

The control of the quantity and placement of the spray The spray produced by the conventional method just is thereby solely by means of repetition of the spray described is necessarily conical in form, and in order to cycle, whereas a spray of longer or continuous duration reduce impact with the human skin, current spray allows the user more time to redirect the spray during systems are designed, such that the spray is dispersed use and to select the quantity by the duration of over a wide angle, typically 45 to 60 degrees. (See Fig. activation.

8 of the accompanying drawing).

It is another object of the invention to provide a spray This wide angle reduces the freedom of the designer of with duration of more than one second to allow a the container, as the spray should not impinge upon the greater degree of control over the quantity and shoulder of the container, direction of the spray.

This in turn limits the minimum height of the spray head In a typical manual spray perfume atomiser system, the (h mm. See Fig. 8 of the accompanying drawing), as the force required to effectively drive the liquid through outlet is depressed towards the container by the length the swirl chamber is of the order of S Newtons.

of the delivery stroke (stroke, See Fig.8 of the attached drawing) during use. The piston in such a pump has a surface area of the order of 16 square millimetres, so the pressure required Such a limitation is significant as the main thrust of to operate the swirl chamber is of the order of: current cosmetic container design is towards rendering the pump mechanism as discrete as possible to allow SN/16 mm2 = 31.25N/lcm2/10 = 3.125 Bar more complex forms, in a business where product and brand image is of prime importance. In many systems, a further 10 Newtons, is required to compress the return spring. So the total manual force It is another object of the invention to allow control of used to operate a manual spray is approximately 15 the form and direction of the spray to provide additional Newtons.

freedom in container design.

The total acceptable force for manually operated Tests have shown that long duration sprays with atomisers should be significantly less than 20 Newtons.

constituent droplets of diameter less than 100 micrometers have significantly improved tactile It is another object of the invention that the generation appreciation. of the spray should not require a force of more than 20 Newtons when using a manually operated pump.

The sensation on the human skin is less abrupt, providing a better experience that can be used to Continuous sprays are currently achieved by using the differentiate higher quality products. combination of the liquid with volatile propellants such as chlorofluorocarbons (CFCs) maintained in liquid In addition, accidental or deliberate direction of the fine form under pressure in a sealed container.

slow moving spray onto clothing is much less likely to leave marks or stains as the concentration and A manually released valve releases the liquid through a penetration are reduced compared to a swirl chamber swirl chamber or other simple nozzle to form a spray.

system.

The propellant returns to its gaseous state at the lower Smaller slow moving droplets are also particularly ambient pressure, so the spray is mainly comprised of suitable for eye care applications, the target liquid, not the propellant in liquid form.

The Montreal protocol 1989 is an international than 10 micrometers since these droplets are small agreement designed to protect the ozone layer by enough to pass directly into human lung.

phasing out the use of a number of substances believed to be responsible for ozone depletion, particularly It is another object of the invention that the proportion chlorofluorocarbons (CFCs.) of droplets in the spray with an airborne diameter of less than 10 micrometers in the spray is insignificant.

Alternative propellants to CFCs have been introduced, which do not contain ozone-depleting chemicals. For medical applications, the technical specifications Recently, pressurised nitrogen has been used, are more stringent, and the cost restrictions are particularly for cosmetic applications, generally less restiictive than those for mass-produced cosmetic spray systems. As a result, the techniques These alternatives however, are generally more developed rely on relatively expensive technology.

expensive and contribute to the build up of greenhouse gases, which are increasingly considered to be a Recent advances in liquid aerosol generation for the deleterious human contribution to global warming. treatment of COPD can be broadly separated into two areas: In terms of environmental impact, a system that provides a spray of longer duration based on a i) The generation of aerosols using ultrasonic Il1echanical pump is considerably superior to a system transducers to create vibrations, which are used to using propellants. break down the liquid into a spray.

It is another object of the invention that a fine spray This technique requires power to operate and involves with duration of more than 1 second can be generated batteries and expensive components, which are not using a manual pump to minimise environmental appropriate for low-cost applications.

impact.

ii) Techniques relying on Micro-Electro-Mechanical It is another object of the invention that a continuous Systems (MEMS) manufacturing technology, whereby fine spray can be generated using a pressurised the micro-mechanical components are fabricated using container, compatible micro-machining processes that selectively etch away parts of a silicon wafer or add new structural A recent innovation in spray systems for cosmetic layers to form mechanical devices.

applications, with the similar goal of generating a low cost fine spray is detailed in USPTO Patent Application Whilst capable of creating very fine sprays with having application number 20060275220. droplet diameters of much less than 10 micrometers, these manufacturing technologies involve expensive Presented therein is a method for reducing the size, equipment and clean room environment, which are not velocity and size distribution of droplets by introducing compatible with very low cost applications.

a 100 to 200 micrometers diameter nozzle after the swirl chamber. It is another object of the invention that the production of the atomising head should not require expensive The need for a relatively long duration is however, not manufacturing technologies.

addressed, so a spray of short duration is still expected.

Generally the materials are in the form of very thin The main drivers for the new generation of finer mist sheets of brittle silicon or like material, with associated sprays have been related to medical applications, handling problems.

particularly for inhalers used in the treat ment of Chronic Obstructive Pulmonary Disorder (COPD). It is another object of the invention that the atomising head should not be made of brittle or fragile materials.

For COPD treatment applications, the aim is to achieve a precisely controlled dose of slow moving spray with Recent advances in low-cost manufacturing the diameter of the majority of airborne droplets technologies enable the realisation of very small required to be less than 10 micrometers to ensure deep apertures that can be used to form very fine jets to lung penetration. form sprays instead of the coned sheet from swirl chamber systems.

For scenting purposes, it is important to avoid the generation of droplets with an airborne diameter of less These include microinjection moulding of plastics. -generate a fine spray wherein the proportion of electroforming of metals and photolithographic forming constituent droplets having an airborne diameter of less of epoxy resins, than 10 micrometers is insignificant; -provide a spray with a duration of substantially more Metals, plastics and ceramics, can also be laser drilled, than 1 second, when powered by reasonable manual effort of the order of 15 N to generate a pressure of 3 It is another object of the invention that the atomising Bar in a typical nmnually operated pump; head takes advantage of modern low-cost manufacturing -provide a practically continuous spray when the technology and materials, liquid is supplied from a pressurised container; -provide a relatively low spray velocity; Patent US 5,261,601 describes such a rigid metal -take advantage of low-cost manufacturing electroformed plate with nozzles in an ultrasonic system technology; for medical applications. The liquid is maintained in -allow control of the form of the spray; contact with the membrane and then broken up into -use colliding jets to reduce droplet size and allow the droplets by resonant modes set up in the plate by an use of larger nozzle geometries.

ultrasonic transducer.

DETAILED DESCRIPTION OF THE INVENTION

A well-known method for further reducing the size of the droplets, involves the direction of jets such that they According to the present invention there is provided a collide producing yet finer droplets. A good description method and apparatus for creating a spray by forcing of this method can be found in Liquid atomisation by L. liquid under pressure from a container via a conduit Bayvel and Z. Orzechowski, Taylor & Francis. 1993. through an array of nozzles to form jets, which break up into airborne droplets due to the phenomenon of This technique is commonly used in fuel injection, Rayleigh break-up to form a spray.

rocket motors and paint sprays.

Figure la of the accompanying drawing shows the A recent patent with publication number WO functional parts of the system used for the embodiment 2004/08955 1 A2, describes a technique for generating a of the invented method and apparatus when a very fine spray with droplet diameters of less than 10 mechanical pump [11] is used to draw the liquid [1] micrometers for medical applications, which takes of from the container [2] and to pressurise the liquid [5] two orthogonal colliding jets to form smaller droplets. and force it via a conduit through an atomising element [8] to form jets [6], which break up into droplets [7].

The manufacturing technology is very precise; using The pump [11] is shown symbolically as a blank relatively expensive MEMS micro machining rectangle since the details of the pump mechanism are technology and so is not wholly appropriate for lower not an object of this invention.

cost applications.

Figure lb of the accompanying drawing shows the The requirement for very small nozzle apertures is functional parts of the system used for the embodiment alleviated, of the invented method and apparatus when the liquid is pre-pressurised [5] in the container [2] and released It is another object of the invention to provide a method through a valve mechanism [12] via a conduit [3] and apparatus for spray generation that can take through an atomising element [8] to form jets [6], advantage of colliding jets to reduce the requirement for which break up into droplets [7]. The valve [12] is very small nozzle dimensions. shown symbolically as a blank rectangle since the details of the valve mechanism are not an object of this The invention overcomes the disadvantages of systems invention.

based on the swirl chamber, and those based on ultrasonic transducers or MEMS technology by Figure 2 of the accompanying drawing shows an providing a low-cost method and apparatus for expanded view of the liquid under pressure [5] passing generating aerosols that can: via a conduit [31 and channels [10] in an atomising element [8] through nozzles [4] to form jets [6] , which -generate a fine spray wherein the majority of break up into droplets [7].

constituent droplets have an airborne diameter of less than 100 micrometers; According to one aspect of the invention, each of the nozzles is comprised of restriction in the flow path of the liquid flow with the minimum cross sectional area of the restriction being between 40 square micrometers = i0 Ns rn at 20°C (for water) and 2000 square micrometers.

= 73 i0 N ni' (for water) Each nozzle is comprised of a restriction in the path along which the liquid flows and can take a number of rnozzie = 3.51116 m forms.

Puq = 1000 kg ni (for water) Figure 4a of the accompanying drawing shows the simplest case of a nozzle [4] in an atomising element With these values we obtain �= 10.26 micrometers, [8], where the cross sectional area of the nozzle remains which means that 100 % of the droplets [7] must have constant through the thickness of the atomising element a diameter higher than 10.26 micrometers.

[8] and there are no channels leading to or from the nozzle. This is in very good agreement with experimental results obtained with nozzle diameter of 7 Figure 4b of the accompanying drawing shows the cross micrometers: the proportion of the volume of the spray section of six different forms of combinations of nozzles with a droplet diameter lower than 10 micrometers was [4] and channels [10] in an atomising element [8]. negligible.

For cosmetic, skin care, eye care and ambient scenting Figure 9a of the accompanying drawing shows the applications a high level of precision is not required so distribution of droplet diameters from parallel jets [6] the exact shape of the nozzle is not critical. Typically from an array of 80 nozzles [4] with a cross sectional the cross section of the nozzle is circular, but other area of 40 square micrometers in a metal atomising shapes give the same advantages, including, but not element [8] driven by a mechanical pump.

restricted to oval, square rectangular and polygonal cross sections. This results in a practical minimum cross sectional area of the nozzles of 40 square micrometers for cosmetic, Figure 4c of the accompanying drawing shows the plan skin care, eye care and ambient scenting applications.

view of twelve examples of possible forms of nozzles.

The maximum cross sectional area of the nozzle to achieve a spray wherein a substantial proportion of the The droplet [7] size is related to the cross sectional area airborne droplets [7] have a diameter of less than 100 of the restriction. micrometers depends upon the form of the nozzle and other local condition that are not readily calculated.

The Rayleigh-Weber theory gives: Trials have shown that a maximum of 2000 square 6 micrometers is a practical maximum for cosmetic, skin Dg �= 2rnozzle 1.436 1+3 05 care, eye care and ambient scenting applications.

(Psqiq,) ) It is a clear advantage of the invention that a very fine for a circular nozzle [4] spray with excellent tactile properties is generated with the diameter of the droplets being substantially where: between 10 micrometers and 100 micrometers.

According to another aspect of the invention the Dg = droplet [7] diameter. . nozzles are housed in one or more thin atomising elements [8], each with a thickness between 10 rnozzie = radius of the nozzle [4] micrometers and 2000 micrometers.

= liquid viscosity.

Figures 3a and 3b of the accompanying drawing show a typical atomising element [8] with an array of 21 Puq = liquid density nozzles [4] and channels [10].

= liquid surface tension. . . 0 The atomising element [8], which incorporates the nozzle [4], is a key element of the invented method and Assuming that the liquid to be delivered has the same apparatus.

viscosity as water: The atomising element provides a rigid robust support According to another aspect of the invention, the cross and protection for the nozzle, which can be fragile due sectional area of any channel in the atomising element to the small dimensions involved, or conduit leading to. or from any of the nozzles becomes larger than 80 square micrometers within a This is in contrast with a membrane, which is essentially distance of 200 micrometers of the nozzles.

flexible and subject to distortion under pressure, which can result in modification of the form and direction of Figure 3b of the accompanying drawing shows the spray. channels [10] leading too and from the nozzles [4] with cross sectional areas much larger than those of the In practice, the thickness of the atomising element is nozzles.

limited by the environment of use, and by the nozzle Il1anufacturing technology. Where there are no obvious channels in the atomising element leading to or from the nozzles, the conduit Below 10 micrometers, the plate becomes too fragile or through which the liquid is delivered to the nozzles flexible to be practical, even with a small surface area. under pressure also has a very much larger cross sectional area than that of the nozzles.

Above 2000 micrometers, the practical advantages of the plate are outweighed by the bulk, weight and One limiting factor in determining the minimum size eventually the additional cost of the material, of nozzles used for generating cosmetic sprays to date has been the pressure required to force sufficient liquid The atomising element can be realised as an integral through long narrow nozzles.

part of a larger structure, such as the conduit or pump housing. Assuming that the nozzles are a cylindrical channel having a length Lllq and a radius rnozzle, the liquid head More than one atomising element can be used in a loss (pressure difference) through one nozzle of the single system. For example, a number of elements atomising element is given by: could be used to generate sprays in two or more opposing directions to increase dispersion. llq

It is a clear advantage of the invention that the Tr4 lOZ2khq atomising element provides a robust vehicle to support and protect small fragile nozzles [4] lIiq = Liquid viscosity According to another aspect of the invention, the number of nozzles [4] is more than three. Luq = Length of the nozzle in the atomising element through which the liquid flows If only one or two nozzles are used, the risk of blockage °/iq N = Liquid flow rate through one nozzle [4] is greatly increased. There is no redundancy in the system and even a slight blockage in one of the nozzles would result in catastrophic failure to produce droplets rnozzie hq = Radius of the nozzle [4] of the required small size.

It can be readily seen that the pressure loss in each nozzle is directly proportional to the length of the Increasing the number of nozzle from 3 upwards nozzle and inversely proportional to the surface area of reduces the risk and increases design flexibility, the nozzle.

There is no fixed upper limit to the number of nozzles As a result, it is desirable to keep the length of the that can be used for this method and apparatus of nozzle to a minimum and minimise the pressure loss in generating spray.

any channel leading to the nozzle.

It is a clear advantage of the invention that the effects of This is achieved by ensuring that the cross sectional accidental blockage are reduced through redundancy. area of the channel leading to the nozzle becomes larger than 80 square micrometers within 200 It is a further advantage of the invention that the micrometers of the nozzle.

quantity of liquid delivered with time can be controlled in part by the number of nozzles.

By so doing. the pressure loss in any channel leading to the nozzle is kept to an insignificant level compared to It is evident that there are many possible forms of that in the nozzle itself. nozzles and channels through atomisation plates that take advantage of this invention.

For example: we suppose that we have 100 nozzles and that we atomise 0.1 ml of liquid during lets sayS According to another aspect of the invention, the seconds. Thus °fiq N = 0.0002 ml Is through each single atomising element or plates is a composite, being made nozzle [4]. up of thinner plates or layers.

With The atomising element can be made up of one or more thinner plates or layers.

qiiq = 1O Ns m2 at 20°C (for water) It is simpler to realise a nozzle aperture of small Liiq = 5. 10 m dimensions in very thin materials. In addition the length of the nozzles is kept to a minimum by realising QIIqN 2 10b0 m3/s (0.0002 nil/s i.e. 0.2 microliter/s them in a very thin plate or membrane.

= 0.2 mm3/s for each single nozzle) By bonding the thin plate or membrane housing the rnozz,e fig = 35 10 m nozzles to one or more thicker plates, a robust, rigid composite atomising element can be formed.

N = 100 (number of nozzles) Figure 5 of the accompanying drawing shows an We find: APuq = 17000 Pa = 0.17 bar for one nozzle. example of a composite atomisation element [8] consisting of a thin plate [9] housing the nozzles [4], So for 100 nozzles we get APliq = 17 bars, which is two support plates [13] , which house channels [10], readily achieved using a small mechanically operated and two bonding layers [14] that bond and seal the pump with a piston having a small diameter, other plates [9,13] together. This composite atomising element is an example only and other forms can be In order to use conventional valve and pump devised that take advantage of the invented method or mechanisms, the geometry of the channels and the apparatus.

nozzles in the atomising element can be varied for reducing the liquid head loss whilst maintaining the The bonding can be achieved by several methods, quantity of atomized liquid during the pump actuation. including anodic bonding, which requires the deposition of metal layers on the surfaces to be This can be done by reducing the number and the length bonded. Various adhesives can also be used as the of the nozzles in the atomising element, andlor by bonding layer.

increasing the diameter of the nozzles.

For example; the nozzles can be realised in a thin plate It is a clear advantage of the invention that the liquid or membrane and the advantages of the rigidity of the head loss for generating a fine continuous spray can be atomising element can be achieved by bonding two adapted in such a way that the spray should not require thicker plates with both the nozzles and the larger a force of more than 20 Newtons when using a manually holes corresponding to the positions of the nozzles that operated pump. form input and output channels for the liquid.

It is also essential that any channel leading from the It is a clear advantage of the invention that small nozzle is very much larger than the nozzle to avoid nozzles can be realised in an appropriate fragile or interfering with the jets or subsequent spray. flexible material, and the robustness of the atomising element can be achieved using thicker plates and For nozzles with a surface area of less than 80 square stronger materials.

micrometers, this implies that the cross sectional area of the channels or conduit must be become larger than that According to another aspect of the invention, the of the nozzle within a short distance of the nozzle. nozzles are directed such that the liquid jets converge.

Figure 4b of the accompanying drawing shows a variety A further important innovation is the creation of of nozzles [4] and channels [10] in an atomising smaller droplets by directing the nozzles such that the element [8] that satisfy this requirement.

jets or subsequently formed droplets converge and A third means of achieving colliding jets or droplets, is collide at a short distance from the atomising element, to form the plates with an indentation that is comprised of flat or curved facets. For example in the form of a The collision causes the jets or droplets to break up into square section open based pyramid.

yet smaller droplets.

According to another aspect of the invention, the Figure 6 of the accompanying drawing shows an nozzles can be directed such that the jets or droplets atomising element [8] with the region housing the are divergent.

nozzles [4] and channels [10] being in the form of a concave dome such that the jets [6] converge and It is a clear advantage of the invention that it provides collide [15] to form droplets [7] with a small diameter. a further degree of spray design freedom for wider aerosol distribution.

Fig 9b of the accompanying drawing shows the distribution of droplet diameters from colliding jets [15] One practical means of achieving divergent jets is to from an array of 80 nozzles [4] with a cross sectional form atomising element into a convex dome.

area of 40 square micrometers in a metal atomising element [8] driven by a mechanical pump. Figure 7a of the accompanying drawing shows an atomising element [8] with the region housing the The resulting average droplet diameter is reduced from nozzles [4] and channels [10] being in the form of a approximately 40 micrometers by a factor of two or convex dome such that the jets [6] diverge to form a more to less than 20 micrometers with colliding jets. diverging spray.

Trials have shown that a maximum cross sectional area A second means is to angle the nozzles in a flat for the nozzle of 2000 square micrometers is a practical atomising element such that the jets are divergent.

maximum to achieve a spray with a significant proportion of droplets with a diameter of less than 100 Another means of achieving divergent jets is to form micrometers, with colliding jets. the atomising element with an indentation that is comprised of flat or curved facets. For example in the It is a clear advantage of the invention that the form of a square section open based pyramid.

requirement for small restrictions in the nozzles to form a fine mist spray is reduced, alleviating the requirement It is evident that there are many possible ways of for manufacturing precision, thus reducing cost. achieving diverging jets using nozzles through an atomising element that take advantage of this It is a further advantage of the invention that the larger invention.

nozzle dimensions thus enabled: reduce the risk of blockage, as larger particulate contaminants can pass It is a clear advantage of the invention that the through. distribution and direction of the nozzles can be readily selected to direct the spray away from the container to In an embodiment of the invention the nozzles are avoid unwanted collision.

formed to focus the jets at a larger distance from the atomising element such that the initial spray dispersion Figure 7b of the accompanying drawing shows an angle is reduced without necessarily creating smaller atomising element [8] with the region housing the droplets through collision, nozzles [4] and channels [10] being in the form of a convex dome such that the jets [6] diverge to form a It is a clear advantage of the invention that it allows diverging spray. Only nozzles in the upper half of the greater freedom of design for the container, dome have been implemented such that the spray is directed at an upward angle away from the lower One practical means of achieving converging jets or quadrant where the container is usually situated.

droplets is to form the atomising element into a concave dome. It is evident that there are many possible ways of achieving directing the jets away from the container A second means of achieving convergent jets is to angle using nozzles through an atomising element that take the nozzles in the atomising element or plates such that advantage of this invention.

the jets are convergent.

It is a clear advantage of the invention that the According to another aspect of the invention a atomising head can be manufactured using low cost disturbance is introduced in the channel or conduit, materials and processes. leading to the nozzle to introduce rotational or transversal motion in the liquid flow to promote A number of materials can be used to realise the Raleigh break-up.

atomising element.

As the liquid is under pressure, and the output is For lowest cost and maximum integration, plastic restricted, the liquid velocity is also low. It is not materials are optimum. The nozzles and atomising practical to realise air-cored vortex that is achieved in a element can be fonned in a single micro-moulding swirl chamber.

process and domed and indented forms are readily achieved. It is however possible to create local disturbances in the liquid flow to encourage Rayleigh break-up. This Metal plates are also feasible, apertures of less than ten reduces the droplet size and the pressure required for microns can be realised at low cost in relatively thick atomisation.

plates using an electroforming process. Galvanic growth of metals, especially Nickel on a resist pre-form The disturbances are created in the channel or conduit allows production of 250um thick films with 5-before the nozzles to create rotational and transversal micrometer holes. movement iii the liquid flow and through imperfections in the nozzle aperture.

Metal pre-forms can be stamped and the nozzles can be realised using other means such as laser drilling or This could be achieved for example by incorporating a etching. swirl chamber immediately before the atomising element or in the atomising element before the nozzles.

Wet and dry etching can be used to etch away metal through a resist film prepared using a photolithographic process. These holes can be as small as 1 micrometer in diameter in a relatively thick metal atornising element.

Formed and stamped ceramic atomisation plates are also feasible by stamping and forming green state clay prior to vitrification.

Lasers can also be used to open channels and small apertures to form nozzles in plastic, metal and ceramic atomising elements [8]. Current technology allows the high speed drilling of apertures down to 20 square micrometers in stainless steel and other metal films up to 200 micrometers in thickness.

For plastic, the current state of the art is 700 square micrometer apertures in polymers, but it is likely that the lack of precision requirements for this application will allow yet smaller holes to be practical.

As a result of MEMS technology advances, there are now photosensitive epoxy resins that can be processed to create chemically and mechanically stable three-dimensional microstructures, which can be used to realise the atomising elements.

It is a clear advantage of the invention that the Il1anufacturing technology and materials of the atomising element is compatible with low cost applications.

DRAWING

DESCRIPTION OF FIGURES

The figures are included for illustration of the invented method and apparatus and are not to scale. The figures are intended to represent examples of aspects of the invented method and do not exhaustively depict all possible embodiments thereof.

Figure Ia shows the functional parts of the system used for the embodiment of the invented method when a mechanical pump [11] is used to draw the liquid [1] from the container [2] and to pressurise the liquid [5] and force it via a conduit through an atomising element [8] to form jets [6], which break up into droplets [7]. The pump [11] is shown symbolically as a blank rectangle since the details of the pump [11] mechanism are not an object of this invention.

Figure lb shows the functional parts of the system used for the embodiment of the invented method when the liquid is pre-pressurised [5] in the container [2] and released through a valve mechanism [12] via a conduit [3] through an atomising element [8] to form jets [6], which break up into droplets [7]. The valve [12] is shown symbolically as a blank rectangle since the details of the valve [12] mechanism are not an object of this invention-Figure 2 shows an expanded view of the liquid under pressure [5] passing via a conduit [3] and channels [10] in an atomising element [8] through nozzles [4] to form jets [6] , which break up into droplets [7].

Figure 3a shows a typical atomising element [8] in plan view with an array of 21 nozzles [4] and channels [10].

Figure 3b shows the cross section of a typical atomising element [8] showing the nozzles [4] with channels [10].

Figure 4a shows the cross section of a simple nozzle [4] in a simple atomising element [8].

Figure 4b shows the cross section of six different forms of combinations of nozzles [4] and channels [10] in an atomising element [8] showing the size of the channels [10] becoming larger than the nozzle [4] size within a short distance. These forms are examples only and other forms can be devised that take advantage of this invented method. It should be noted that in all of the six examples, the method will generate jets [6] and droplets [7] in either direction, whether the pressurised liquid is introduced from the left or the right of the atomising element [8] as shown in the figure.

Figure 4c shows the plan view of twelve different forms of nozzles. These forms are examples only, many other forms can be devised that take advantage of this invented method.

Figure 5 shows an example of a composite atomisation element [8] consisting of a thin plate [9] housing the nozzles [4], two support plates [13] , which house channels [10], and two bonding layers [14] that bond and seal the other plates [9,13] together. This composite atomising element [8] is an example only and other forms can be devised that take advantage of the invented method.

Figure 6 shows an atomising element [8] with the region housing the nozzles [4] and channels [10] being in the form of a concave dome such that the jets [6] converge and collide [15] to form droplets [7] with a small diameter.

Figure 7a shows an atomising element [8] with the region housing the nozzles [4] and channels [10] being in the form of a convex dome such that the jets [6] diverge to form a diverging spray.

Figure 7b shows an atomising element [8] with the region housing the nozzles [4] and channels [10] being in the form of a convex dome such that the jets [6] diverge to form a diverging spray. Only nozzles in the upper half of the dome have been implemented such that the spray is directed at an upward angle away from the lower quadrant where the container is usually situated.

Figure 8 is an illustration of the limitation of the minimum height of the pump actuation button [16] above the container shoulder, by the length of the actuation stroke and the dispersion angle of the spray.

Figure 9a shows the distribution of droplets when the invented method is used with an array of 80 nozzles [4], each with a cross sectional area of 40 square micrometers driven by a mechanical pump.

Figure 9b shows the distribution of droplets when the invented method is used with colliding jets [15] from an array of 80 nozzles [4], each with a cross sectional area of 40 square micrometers driven by a mechanical pump.

LIST OF ITEMS REFERENCED IN THE FIGURES

liquid [1] conlainer [2] condtiil [3] nozzle [4] liquid tinder pressure [5] jel [6] droplets [7] alomising plate [8] thin plate [9] channel [10] mechanical pump [11] valve mechanism [12] support plate [13] bonding layer [14] collision point[15] pump actuation button [16]

Claims

element having a thickness of between 10CLAIMSmicrometers and 2000 micrometers.A method for creating a fine spray for 5 A method as claimed in any of claims 1 to 4 ambient perfume or fragrance scenting and whereby the nozzles are incorporated into one cosmetic, skin care and eye care applications or more atomising elements, at least one of whereby: which is composite, being comprised of more Liquid is forced by the action of pressure from a than one thinner element, with the overall vessel into a spray head via a sealed thickness of the composite atomising element connection which connects the vessel to the being between 10 micrometers and 2000 spray head, the spray head comprising a micrometers.plurality of nozzles, and whereby the liquid is passed through the nozzles in the spray 6 A method as claimed in any of claims 4 to 5 head and into the atmosphere such that the wherein the part of the element incorporating liquid flows substantially through the the nozzles is domed.nozzles to form jets of liquid, Characterized in that: 7 A method as claimed in any of claims 1 to 6 wherein the conduit or channels leading to the (a) there are at least three nozzles: nozzles is formed to generate disturbances in (b) the nozzles are substantially comprised of the liquid flow that promote Rayleigh break-up.nozzles of a first type; and 8 An apparatus for creating a fine spray for ambient perfume or fragrance scenting and (c) the nozzles of the first type are arranged cosmetic, skin care and eye care applications such that: wherein: liquid is forced by the action of pressure i) each nozzle is comprised of a from a vessel into a spray head via a sealed restriction in the flow path of the connection which connects the vessel to the liquid.spray head, the spray head comprising a plurality of nozzles, and wherein the liquid ii) the cross sectional area of the is passed through the nozzles in the spray narrowest part of the restriction is head and into the atmosphere such that the between 40 square micrometers liquid flows substantially through the and 2000 square micrometers. nozzles to form jets of liquid, iii) the cross sectional area of any characterized in that: channel or conduit leading to or (a) there are at least three nozzles; from the nozzles becomes larger than 80 square micrometers (b) the nozzles are substantially comprised of within a distance of 200 nozzles of a first type; micrometers of the nozzle. and
2. A method as claimed in claim 1 wherein the nozzles are ananged so that the jets are (c) the nozzles of the first type are ananged substantially outwardly convergent so that the such that: jots or droplets substantially collide.i) each nozzle is comprised of a 3 A method as claimed in claim 1 wherein the restriction in the flow path of the nozzles are ananged so that the jets are liquid.substantially outwardly divergent.ii) the cross sectional area of the 4 A method as claimed in any of claims 1 to 3 narrowest part of the restriction whereby the nozzles are incorporated into one is between 40 square or more atomising elements, each atomising micrometers and 2000 square 17 An apparatus as claimed in any of claims 8 to micrometers. 16 wherein the part of the element in the apparatus incorporating the nozzles is domed.iii) the cross sectional area of any channel or conduit leading to or 18 An apparatus as claimed in any of claims 8 or from the nozzles becomes larger 15 wherein the part of the element in the than 80 square micrometers apparatus incorporating the nozzles is within a distance of 200 indented such that the indentation is micrometers of the nozzle. comprised of one or more facets.9 An apparatus as claimed in claim 8 wherein the 19 An apparatus as claimed in any of claims 8 to nozzles are arranged so that the jets are 18 wherein the conduit or channels leading to substantially outwardly convergent so that the the nozzles is formed to generate disturbances jets or droplets substantially collide, in the liquid flow that promote Rayleigh break-up.An apparatus as claimed in claim 8 wherein the nozzles are arranged so that the jets are substantially outwardly divergent.11 An apparatus as claimed in any of claims 8 to wherein the nozzles are incorporated into one or more atomising elements, each atomising element having a thickness of between 10 micrometers and 2000 micrometers.12 An apparatus as claimed in any of claims 8 to 11 wherein the nozzles are incorporated into one or more atomising elements, at least one of which is composite, being comprised of more than one thinner atomising element, with the overall thickness of the composite atomising element being between 10 micrometers and 2000 micrometers.13 An apparatus as claimed in claims 8 or 12 wherein any of the atomising elements incorporating the nozzles is made of plastic and is realised using micro moulding technology.14 An apparatus as claimed in claims 8 to 12 wherein any of the atomising elements incorporating the nozzles is made of metal and is realised using a stamping or electroforming process.An apparatus as claimed in claims 8 to 12 wherein any of the atomising elements incorporating the nozzles is comprised of photosensitive resin formed by means of a micro-fabrication technique 16 An apparatus as claimed in any of claims 8 to wherein any part of any of the nozzles is realised using a laser beam.