GB2545884A

GB2545884A - Sprays

Info

Publication number: GB2545884A
Application number: GB1519631.4A
Authority: GB
Inventors: Felten Bernhard; Greenwood Julia; James Smith Simon
Original assignee: Cambridge Consultants Ltd
Current assignee: Cambridge Consultants Ltd
Priority date: 2015-11-06
Filing date: 2015-11-06
Publication date: 2017-07-05
Also published as: GB201519631D0

Abstract

Spray device 2 comprising an outlet 12 with an adjustable cross section, a cyclone chamber 4 connected to the outlet and at least one inlet (6,8 Fig.1) for connection to a fluid source. The cyclone chamber further comprises a cross sectional area which decreases in a direction away from the outlet and a closed base 10. In use, at least one fluid entering the chamber forms a reverse flow cyclone in which the fluid travels in a first direction away from the inlet(s) to the base of the chamber and thereafter reverses direction and travels towards the outlet, forming a spray. The spray is emitted from the outlet wherein the size of the cross sectional area of the outlet varies depending on the pressure of the fluid(s) entering the chamber. The outlet may be completely or partially formed of a flexible resilient material portion 14, 20. The outlet may comprise an outer rigid wall (18, fig.6) and a flexible resilient inner portion 14. The outlet cross section may have an hourglass profile. The chamber may be provided with an extended outlet with a fixed or adaptable cross sectional area similar to that of the outlet.

Description

SPRAYS

This invention relates to methods and apparatus for spraying liquids, in particular to the atomization of a liquid to form a spray.

Traditionally sprays are formed by forcing liquid through a narrow nozzle which gives rise to high shear forces that breaks the liquid into small droplets. This can be driven by pressurising the liquid (e.g. in spray canisters) or by using pressure differences generated by gas flow (e.g. in airbrushes). However in both cases a wide range of droplets sizes are produced, giving an inconsistent spray quality.

Moreover in arrangements driven by pressurising the liquid, it is typically accepted that pressures of the order of 4 bar or more are necessary to produce acceptable results. This can cause difficulties and carries with it a certain level of costs. It would ideally therefore be preferable to be able to have a lower operating pressure.

As described in the Applicant’s earlier application WO2015/052493, a spray device utilising a reverse cyclone chamber may be used to improve the quality of the spray which is produced. When using a reverse cyclone chamber, the flow rate and spray size is determined by the pressure ratio of liquid in the cyclone chamber and the size of the outlet. It is known that in a reverse cyclone chamber with a fixed outlet size, the flow rate can be increased by increasing the pressure of the fluids entering the chamber. However, there is a limit to the flow rate which can be achieved, beyond which no further increase can be achieved irrespective of the increase in pressure of the fluids. As the pressure within the chamber is increased, the flow rate eventually reaches an asymptote and increases thereafter only by negligible amounts.

When viewed from a first aspect, the present invention provides a device for producing a spray comprising an outlet with an adjustable cross section, a cyclone chamber connected to the outlet and at least one inlet for connection to a fluid source, wherein the cyclone chamber comprises a cross section which decreases in a direction away from the outlet and a closed base such that in use at least one fluid entering the chamber forms a reverse flow cyclone in which the fluid travels in a first direction away from the inlet to the base of the chamber and thereafter reverses direction and travels towards the outlet, thereby forming a spray which is emitted from the outlet wherein the size of the cross section of the outlet varies depending on the pressure of the fluid(s) entering the chamber.

Thus it will be seen by those skilled in the art that in accordance with the invention a reverse cyclone chamber has an outlet, the cross section of which varies depending on the pressure of the fluid(s) entering the chamber. This may be advantageous in allowing a spray with a wide range of flow rates to be produced. Furthermore the use of a reverse cyclone chamber ensures that an improved spray quality is achieved since it is highly selective of droplet size. The ability for the cross section of the outlet to be varied ensures that it is possible that the cross section of the outlet is appropriate for the pressure of the fluid(s).

In a set of embodiments the outlet comprises a flexible resilient portion allowing the outlet cross section to be increased or decreased depending on the pressure of the fluid(s) entering the chamber. This is advantageous as the spray device can automatically dynamically adapt to the change in pressures of the fluid(s) in the cyclone chamber without requiring manual interaction of the user with the spray device. As the pressure in the cyclone chamber increases, the cross section of the outlet increases as the flexible resilient portion of the outlet flexes outwards to produce a larger opening in response. The increased pressure inside the chamber may result from increasing the pressure of the fluid(s) entering the chamber through the at least one inlet.

Similarly, as the pressure within the cyclone chamber decreases, the outlet reduces in size. This resilience of the outlet ensures that the size of the outlet is always appropriate for the pressure of the fluid(s) within the chamber. This dynamic adjustment may be particularly advantageous over a spray device with manual adjustment where a user may forget to change the size of the outlet when the fluid(s) are changed to different pressures, which may subsequently affect the quality of the spray being emitted from the spray device.

In a set of embodiments the outlet is formed from walls which are configured such that when the outlet expands, its shape remains constant. For example, it may be preferable that an outlet that initially has a circular shape, continues to have a circular shape as it is forced to expand. In some embodiments, for example, this may be achieved by forming the outlet from a wall with a uniform thickness. This may be advantageous as the size of the outlet may then increase uniformly in all directions as the pressure is increased. Keeping the shape of the outlet constant ensures that the spray device consistently produces a spray of the same shape irrespective of the pressure of the fluid(s). The use of an outlet formed from a wall with a uniform thickness may be appropriate for outlets which have a uniform cross section, for example those with a circular cross section. However, in cases where the shape of the outlet is not uniform, it may be necessary to provide an outlet which does not have walls with a uniform thickness. Designing the outlet in such a way may permit certain portions of the outlet to expand by different amounts thus ensuring that the cross section of the outlet increases/decreases in a uniform manner to maintain a constant shape.

In a further set of embodiments the flexible resilient outlet comprises multiple sections. Such an embodiment may be advantageous in permitting the cross section of the outlet to increase in all directions around the outlet. As discussed previously, an embodiment with this arrangement may be particularly useful where the outlet has a more complex shape such as an elongated slot where it is necessary for certain regions to expand further than others to ensure that the shape remains constant.

In a further set of embodiments the outlet extends substantially into the cyclone chamber and the resilient portion of the outlet is hinged or flexed at a point upstream of the outlet aperture where fluid first enters the outlet. This would allow the entrance to the outlet to remain fixed. This is advantageous as it ensures that the internal features of the cyclone chamber remain constant and thus do not detrimentally affect the reverse cyclone that is produced inside the cyclone chamber. This may help to ensure that a high quality spray is produced.

In a set of embodiments the entire outlet is formed of a resilient material. This may be advantageous in making production of the outlet relatively simple. However, producing the entire outlet from a flexible resilient material may cause certain parts of the outlet to flex undesirably. Therefore, in an alternative set of embodiments only part of the outlet is formed of a flexible resilient material. This resilient part may be attached by any suitable means to the non-resilient portion. Such an embodiment may be advantageous as it allows for parts of the outlet which extend into the cyclone chamber to remain fixed and thus be unaffected by the fluid(s) pressures.

In a set of embodiments the outlet comprises an outer rigid wall and a flexible resilient inner portion. During operation the inner portion is able to flex towards the outer wall which acts to prevent the inner portion from flexing any further. This prevents the inner resilient portion from flexing too far which may cause fatigue.

The Applicant also appreciates that beyond a certain point, when the cross section of the outlet is increased, it may have a detrimental effect on the quality of the spray which is produced. The limiting position provided by the outer rigid wall helps to prevent this.

In a set of embodiments the cross section of the outlet has an hour-glass shape. The hour-glass shape is a symmetrical elongate shape which is wider at its ends and thinner in the central portion. The particular shape at the ends of the outlet or the transition to the central portion is not critical. An hour-glass shaped outlet is advantageous for use with the spray device as it is possible to produce a spray which has a uniform intensity profile rather than a Gaussian intensity profile which is produced by a typical circular outlet. The hour-glass shape permits more liquid to flow through the outer portions than the inner central portion which ultimately results in a flatter intensity profile when the spray is projected from the outlet. Such embodiments may be advantageous as the outlet ensures that an even distribution of spray is achieved. This may be particularly advantageous in painting operations where it is preferable to apply an even coat of paint to an object. It is appreciated by the Applicant that in such embodiments the resilient portion of the outlet may be more complicated to account for the complicated cross section of the outlet. This may include part of the walls of the outlet being constructed from a thicker resilient material or a material with higher resiliency to ensure that when the outlet increases in size it does so approximately uniformly in all dimensions.

In another set of embodiments an extended outlet is provided on the cyclone chamber. The extended outlet focusses the spray as it leaves the cyclone chamber. Preferably the extended outlet comprises an elongate tube with a cross section which is similar to the outlet cross section. The benefit of providing an extended outlet is that it can provide a more intense spray with a smaller intensity distribution. A focussed spray may be more appropriate for use in intricate operations such as painting. It is appreciated that it may be desirable to adapt the size of the cross section at the end of the extended outlet as well in order to allow for increased pressures. However, it is also appreciated that this may not always be appropriate and in an alternative set of embodiments the extended outlet has a fixed cross section. In such embodiments it may be necessary for the size of the cross section of the extended outlet to be similar to that of the maximum size of the flexible outlet of the cyclone chamber.

In a set of embodiments the cyclone chamber is provided with a plurality of inlets for connection to fluid sources. Providing a plurality of inlets is advantageous as it allows multiple fluids to be mixed within the cyclone chamber. This may, for instance, involve mixing a liquid and a gas to produce a spray or alternatively involve mixing multiple liquids to produce a spray with different qualities, e.g., in the case of painting operations, colour. Such embodiments may also find use in various applications, for example those in which multiple fluids are mixed together to form a spray and wherein such fluids are perhaps unstable when stored together normally.

The spray device according to the present invention may find various applications some including but not limited to: deodorant, hairspray, sun cream, body lotion (wet/dry), fake tan, dermatological cream, hair removal cream, hair gel, thick viscous liquids, paint (different colours), industrial cooling, water, decontamination, agricultural chemicals, pesticides, surfactants and heavy metals.

Some of the embodiments of the present invention will now be described, by way of example only, and with reference to the accompanying drawings, in which:

Fig. 1 shows a view of a spray device in accordance with the present invention;

Fig. 2 shows a view from below the device of Fig. 1;

Fig. 3 shows an alternative view of the device of Fig. 1;

Fig. 4 shows a cross sectional view of the device of Fig. 1;

Fig. 5 illustrates the formation of a reverse flow cyclone in a cyclone chamber;

Fig. 6 shows a cross sectional view of the device of Fig. 1 highlighting the outlet portion;

Fig. 7 is a graph of the flow rate against internal pressure for three reverse cyclone chambers with different outlet sizes;

Fig. 8 shows a cross-sectional view of a second embodiment of the invention Fig. 9 shows a cross-sectional view of a third embodiment of the invention;

Fig. 10 shows a cross-sectional view of a fourth embodiment of the invention;

Fig. 11 shows a cross-sectional view of a fifth embodiment of the invention;

Fig. 12 shows a cross-sectional view of a sixth embodiment of the invention where the ratio of fluids entering the chamber is unequal;

Fig. 13 shows a cross-sectional view of a seventh embodiment of the invention;

Fig. 14 shows an end-on view of the outlet of the seventh embodiment of the invention;

Fig. 15 shows a cross-sectional view of an eighth embodiment of the invention;

Fig. 16 shows a cross-sectional view of a ninth embodiment of the invention;

Fig. 17 shows a cross-sectional view of a tenth embodiment of the invention; and

Fig. 18 shows a cross-sectional view of an eleventh embodiment of the invention.

An embodiment of the present invention shown in Figure 1 comprises a spray device 2. The spray device 2 comprises a cyclone chamber 4, two inlets 6, 8, a closed base 10 and an outlet 12. The cyclone chamber 4 has a diameter that reduces in aperture towards the closed base 10. The outlet 12 is formed from a resilient, flexible conical section 14.

Figure 2 shows a view from the underside of the spray device 2. Here it can be seen that the inlets 6, 8 are positioned on the cyclone chamber 4 such that the fluid enters the cyclone chamber 4 tangentially. The outlet 12 is positioned in the centre of the cyclone chamber 4 such that fluid forming the central vortex of the reverse cyclone in the cyclone chamber 4 is able to pass directly out the outlet 12 as explained below with reference to Figure 5.

Figure 3 shows an alternative view of the spray device 2. In this Figure the conical section 14 can be seen more clearly. The flexible conical portion 14 is able to flex outwards to increase the size of the outlet 12. It can be seen that there is space provided around the flexible conical portion 14 to facilitate its flexing. This Figure also clearly illustrates how the diameter of the cyclone chamber 4 reduces towards the closed base 10. The inlets 6, 8 can be directly or indirectly connected to a fluid supply.

Figure 4 shows a cross sectional view of the spray device 2 through the line A-A in Figure 3. In this view it can be seen that the outlet 12 comprises a portion which extends into the cyclone chamber 4. This is comprised of an elongate portion defined by outer walls 20 and an internal tapered section 16. The flexible conical portion 14 allows the size of the outlet 12 to change in response to pressure in the chamber as will be explained below. As seen in this Figure, as the flexible conical portion 14 flexes outwards the degree of tapering on the tapered section 16 also changes. It is appreciated that this may also affect the quality and the flow rate of the spray produced.

Operation of the spray device will now be described with additional reference to Figure 5 which shows a typical reverse cyclone chamber (flexible outlet 12 not shown) The spray device 2 is capable of producing a plurality of liquid droplets which can be sprayed through the outlet 12. Fluid enters the spray device 2 via the fluid inlets 6, 8 and enters the cyclone chamber 4 tangentially setting up a reverse cyclonic flow. The fluids flow along the internal wall of the cyclone chamber 4 forming a spiralling path. The path advances along the length of the cyclone chamber 4, with the diameter of the path, decreasing as the cyclone chamber 4 tapers towards the closed base 10. When the fluids reach the closed base 10 of the cyclone chamber 4, the flow is reversed, setting up a smaller vortex 17 which travels up the centre of the cyclone chamber 4 as shown by the arrow 21. The combination of the large outer vortex 19 travelling in one direction and the smaller vortex 17 travelling within the outer vortex 19 in the opposite direction is known as a reverse flow cyclone. Shear forces act on the fluid as it travels towards the closed base 10 and as it travels towards the outlet 12. There is substantial variation in tangential velocity across the cyclone chamber 4, which creates a steep velocity gradient. This causes efficient atomisation, creating droplets with a small variation in size. The shear forces generated act on the fluids both as they travel down towards the base of the chamber 10, and as they travel back towards the tapered section 16. As the fluids travel along a relatively long path, the fluids have an increased residence time in the cyclone chamber 4, enhancing mixing and increasing the quality of the spray produced.

The flexible portion 14 is caused to flex outwards by an amount dependent on the pressure inside the cyclone chamber 4. The fluid inside the cyclone chamber 4 applies a force to the internal tapered section 16 and thus the flexible conical section 14. As the fluid pressure is increased the flexible conical section 14 experiences a larger force from the fluids causing it to flex outwards. The flexible conical section 14 is made from a resilient material, for example rubber, such that it provides a force to resist the internal forces which arise due to the pressure within the cyclone chamber 4.

The flexible portion 14 is able to flex outwards, increasing the size of the outlet 12, until it reaches a maximum position whereby the flexible portion 12 comes into contact with the internal walls 18 of the spray device 2. The inside walls 20 of the outlet 12 extend into the cyclone chamber substantially past the fluid inlet 6.

Although not shown, the fluid inlet 6 has an aperture in the cyclone chamber 4 which allows fluid to enter the cyclone chamber 4. The inside walls 20 of the outlet 12 prevent fluid travelling directly from the inlet 6 to the outlet 12 and force the fluid to travel towards the base 10 of the cyclone chamber 4 to establish a reverse cyclone. By forcing the fluid to the closed base 10 this increases the path length of the fluid which increases residence time in the cyclone chamber 4 thus enhancing the mixing and increasing the quality of the spray produced.

Figure 6 shows another cross sectional view of the spray device 2 highlighting the outlet 12 and the flexible portion 14. Here it can be seen that only the top flexible conical portion 14 is able to flex outwards and increase the outlet size as there is a space for it do so. The lower walls 20 are unable to flex. Also shown in the Figure is the spray 15 produced from the spray device 2. It can be seen that the spray 15 is emitted from the outlet 12.

Figure 7 shows a graph 22 of the pressure within the cyclone chamber 4 against flow rate of the fluid leaving the outlet 12. The pressure within the cyclone chamber 4 is ultimately determined by the pressure of the fluid entering the cyclone chamber 4 by the inlets 6, 8. A first line 24 shows the relationship between the pressure and flow rate when the spray device has an outlet with a fixed size. A second line 26 shows the relationship between the pressure and flow rate for a smaller fixed outlet size where the outlet is smaller than the outlet for the first line 24. It can be seen that both lines corresponding to fixed outlet apertures reach an asymptotic level where the flow rate increases minimally irrespective of significant increases in pressure. A third line 28 shows the relationship between pressure and flow rate for an embodiment of the present invention which utilises a flexible outlet. It can be seen that a wide range of flow rates can be achieved with the same range of pressures as those for the fixed apertures.

The features of the embodiments which will be described below are general features that can be applied to any spray device embodying the invention and in any combination. In these embodiments like features are denoted by like reference numerals

The quality of the spray produced by the spray device may be further improved in some circumstances by providing a protuberance 30 located opposite the entrance to the outlet 12 as seen in Figure 8. The protuberance 30 is preferably a pin shaped structure. The advantage of having a protuberance 30 located at the base 10 of the cyclone chamber 4 is that it forces fluid towards the edges 32 of the cyclone chamber 4. This causes an increase in the path length of the fluid and increases its tangential velocity. This causes the fluid to break up further and reduces the number of large droplets thus producing a better quality spray. The better quality spray typically has a narrow particle size distribution.

Figure 9 shows another example of a spray device which helps to minimise the amount of fluid which bypasses the cyclone chamber 4 and travels straight out of the outlet 12. It is appreciated that when fluid bypasses the cyclone chamber and passes directly out of the outlet 12, the particle size distribution in the resulting spray is undesirably significantly increased. As shown in this embodiment, a protuberance 34 is located on the wall of the cyclone chamber 4. Preferably this protuberance 34 is located approximately level with the opening 36 of the aperture. Fluid which enters the cyclone chamber 4, via the inlets 6, 8, travels towards the closed base 10 firstly along the internal walls 20 of the outlet 12 and the outer walls of the cyclone chamber 4. As the fluid passes the edge of the internal walls 20 it may have a tendency to pass directly out of the outlet 12. However, with the protuberance 34, this tendency is reduced. As the fluid passes over the protuberance 34 it is forced to move faster. This establishes a pressure gradient towards the edge 32 of the cyclone chamber 4, directing the fluid away from the opening 36. This reduces the amount of fluid that is able to bypass the cyclone chamber 4 and escape via the opening 36 to the outlet 12.

Figure 10 shows another embodiment of the spray device comprising a protuberance 38 located on the internal wall 20 which forms the outlet 12. This is preferably located at the inner part of the wall 20 proximal to the aperture 36 where the fluid first enters the outlet 12. The protuberance 38 located at this position helps to divert fluid entering the cyclone chamber 4 away from the outlet aperture 36, and instead directs it towards the closed base 10. This is already partially achieved by the walls 20 of the outlet however the protuberance 38 helps further to increase the effects of directing the fluid towards the closed base 10. This ensures that a consistent quality of spray is produced which is free of large droplets.

Figure 11 shows an embodiment of the spray device which addresses a different issue associated with some reverse cyclone chambers. Using a typical tangential inlet may cause vapour cavities to form in the liquid, a process known as cavitation. If this liquid then propagates through the cyclone chamber 4 it can prevent laminar flow within the chamber and thus waste energy. Cavitation effects are particularly noticeable in larger cyclone chambers and ultimately result in undesirable spluttering of the spray from the outlet 12. Figure 11 shows an example of a spray device which addresses this problem through the provision of anti-cavitation vanes 40 in the cyclone chamber 4 proximal to the fluid inlets 6, 8. The vane 40 has a triangular in shape and leads towards the wall 20 of the outlet 12. The vane 40 forces the fluids to pass through the small gap 42 formed between the vane 40 and the wall 20 helping to encourage laminar flow thus preventing cavitation.

Figure 12 shows an example of a spray device wherein the flow of fluid into the cyclone chamber 4 from the inlets is not equal. This may be achieved by providing different sized inlets 206, 208 to the cyclone chamber 204. Alternatively the pressurised fluids entering the inlets 206, 208 could be pressurised to different amounts such that more fluid is able to enter through the inlet where the fluid is at a higher pressure. Arrows 244 and 246 illustrate the amount of fluid that is able to enter through the inlets 206, 208 respectively. By changing the volume of the fluid which is able to enter via each inlet 206, 208 it is possible to adjust the mixing ratio of the fluids. This has various applications for example in painting operations where different amounts of fluids may be introduced to produce different types or colours of paints.

Figures 13 and 14 show an embodiment of the spray device where the outlet 212 has a ‘hour-glass’ shape. This shape is wider at the edges and narrower in the centre. The advantage of using such an outlet is that it produces a spray 248 that has a uniform intensity distribution i.e. with a ‘top hat’ profile. A spray 248 that has such a profile would be particularly advantageous in various applications, for example, painting where it is desirable to produce a spray that has a uniform thickness, this would prevent a the user from repeatedly having to go over certain regions to ensure coverage which may result in certain regions receiving more paint than others.

Figure 14 shows an end-on view of the hour-glass shaped outlet 212.The outlet 212 is symmetrical, with a thinner central portion 249 and wider end portions 251. It is appreciated that whilst the outlet 212 is shown to have a smooth transition between the thinner central portion 249 and wider outer portions 251, this may not always be necessary and the thinner central portion 249 may suddenly increase in size to the wider outer portions 251.

Figure 15 shows an embodiment of the spray device which comprises an air curtain 50 provided around the spray cone 52 which is emitted from the outlet 12. The air curtain 50 forms a column of air which reduces the “footprint” of the spray, and also helps to reduce stray droplets from the spray 52. This is particularly advantageous where control of the spray is required, for example in delicate paint operations where it may not be desirable for droplets to reach parts other than the target area. The air curtain 52 could be provided by a plurality of outlets connected to a gas source. Alternatively it may be provided in a ring shaped structure for use with circular exit apertures. The supply of air for the air curtain 52 may be provided by a separate source external to the spray device, alternatively it may be provided from one of the fluid sources for the cyclone chamber. Preferably the air curtain 50 is relatively focussed so that it does not cause the spray 52 to break up further. An air curtain 50 as described above could be retrofitted to an existing spray device.

Figure 16 shows an alternative embodiment of the spray device whereby the outlet 12 is provided with an extended portion 54. The extended portion 54 aims to narrow the cone angle of the spray 56 and thus produces a focussed spray 56 as it leaves the extended portion 54. It may be possible to vary the length of the extended portion 54 in order to vary the focus of the spray 56. A spray device with a focussed spray 56 may be particularly useful when a highly directional spray is required for example in delicate spray applications.

Figure 17 shows an alternative embodiment of the spray device wherein a valve 258 is incorporated in one of the inlets 206’. The arrows 260, 262 indicate the flow of fluid into the cyclone chamber 4. By including a valve on the inlet 206’ it is possible to switch the fluid supply 260 from that particular inlet 206’ on or off. This is advantageous when there are multiple inlets 206’, 208’ as different inlets 206’, 208’ can be turned on or off depending on the application of the spray. For example if a different colour is desired in paint applications, one of the fluid inlets that supplies a particular colour can be closed. Although in the embodiment shown a single valve 258 is provided it is appreciated that any number of valves could be provided on each of the inlets in order to achieve a higher degree of control of the fluid entering the cyclone chamber 4.

The Applicant has appreciated that in certain applications it is preferable to cut off the spray as soon as possible. When there is only one outlet 12, when the pressure is removed from the inlet 206”, 208”, for a short period of time spray continues to be emitted from the outlet 12. It is also possible to provide a bypass valve 264 to allow the flow of fluid out of the cyclone chamber 4 from an alternative outlet to the spray outlet 12. This can be seen in Figure 18. The bypass valve may be included on one of the inlets 206”, 208” and further means may be provided to permit outflow of fluid back through the inlets. Alternatively a dedicated outlet may be provided for fluid to escape the cyclone chamber 4 when the bypass valve 264 is opened. In this example a secondary outlet is provided on the wall of the cyclone chamber 4. When the user has finished using the spray device it may be switched off. This would open the bypass valve 264 which would allow the fluid in the cyclone chamber 4 to flow out of the bypass valve 264 rather than the outlet 12. This rapidly depressurises the cyclone chamber 4. This creates an almost instant switch off as it removes residue fluid from the cyclone chamber 4. This also helps to minimise the continuation of spray from the outlet 12 when the device is switched off.

Although the features shown in Figures 8 to 18 are of benefit when used in embodiments of the invention they may also be useful in other spray devices.

Claims

1. A device for producing a spray comprising an outlet with an adjustable cross section, a cyclone chamber connected to the outlet and at least one inlet for connection to a fluid source, wherein the cyclone chamber comprises a cross section which decreases in a direction away from the outlet and a closed base such that in use at least one fluid entering the chamber forms a reverse flow cyclone in which the fluid travels in a first direction away from the inlet to the base of the chamber and thereafter reverses direction and travels towards the outlet, thereby forming a spray which is emitted from the outlet wherein the size of the cross section of the outlet varies depending on the pressure of the fluid(s) entering the chamber.

2. A device according to claim 1, wherein the outlet comprises a flexible resilient portion allowing the outlet cross section to be increased or decreased depending on the pressure of the fluid(s) entering the chamber.

3. A device according to any preceding claim, wherein the outlet is formed from walls which are configured such that when the outlet expands, its shape remains constant.

4. A device according to any preceding claim, wherein the flexible resilient outlet comprises multiple sections.

5. A device according to any preceding claim, wherein the outlet extends substantially into the cyclone chamber and the resilient portion of the outlet is hinged or flexed at a point upstream of the outlet aperture where fluid first enters the outlet.

6. A device according to any preceding claim, wherein the entire outlet is formed of a resilient material.

7. A device according to any one of claims 1 to 5, wherein only part of the outlet is formed of a flexible resilient material.

8. A device according to claim 7, wherein the outlet comprises an outer rigid wall and a flexible resilient inner portion.

9. A device according to any preceding claim, wherein the cross section of the outlet has an hour-glass shape.

10. A device according to any preceding claim, wherein an extended outlet is provided on the cyclone chamber.

11. A device according to claim 10, wherein the extended outlet comprises an elongate tube with a cross section which is similar to the outlet cross section.

12. A device according to claim 10 or 11, wherein it is possible to adapt the size of the cross section at the end of the extended outlet.

13. A device according to claim 10 or 11, wherein the extended outlet has a fixed cross section.

14. A device according to any preceding claim, wherein the cyclone chamber is provided with a plurality of inlets for connection to fluid sources.