Nebulizer system for freshening the air

CA 02909796 2015-10-19 WO 2014/177805 PCT / FR2014 / 051025 1 NEBULIZATION SYSTEM FOR REFRESHING THE AIR Technical field of the invention The invention relates to nebulization systems capable of generating a mist of microdroplets of a liquid , for example water, for the purpose of cooling the atmosphere, and more particularly small-sized nebulization systems which can be mounted on a sales stall to humidify and cool fresh products displayed for sale, or in a vehicle to humidify and refresh the air and make it pleasant to breathe.

STATE OF THE ART Such systems are known as such.

Patent EP 0 691 162 describes a nebulization system with a concentration nozzle in which a piezoelectric element immersed in water generates a mist of water droplets at the outlet of a nozzle which concentrates the ultrasound generated by said piezo element. -electric at its exit point;

.. the fog is then carried away by a current of air generated by a fan.

This nozzle is generally arranged vertically, with the focusing outlet pointing upwards; the nozzle can also be tilted, for example at 450.

Such systems are commonly used on stalls selling fresh produce; this normally corresponds to a stationary and stable environment.

On the other hand, no use is known in vehicles, which represent a non-stationary and disturbed environment.

In addition, the systems used on stalls can be improved insofar as a stall, too, can be disturbed by shocks and other mechanical disturbances, insofar as it is surrounded by people who can come into mechanical contact. with him.

More particularly, mechanical disturbances can cause a fluctuation in the water supply to the concentration nozzle.

However, if the piezoelectric element is not constantly immersed during its operation, it can be damaged.

The applicant has noticed that the constructive measures which aim to reduce the size of the system, and in particular its height, tend to increase the risk that the piezoelectric element is temporarily incompletely submerged or even dry.

More particularly, it is observed that when one seeks to tilt the nozzle, which contributes to reducing the total height of the system, the operation of the system CA 02909796 2015-10-19 WO 2014/177805 PCT / FR2014 / 051025 2 is less resistant much to mechanical disturbances than in the case of a vertical nozzle.

Likewise, when one seeks to reduce the overall quantity of water in the system, which contributes to reducing the overall size of the system, the risk of a lack of water in the nozzle is increased.

OBJECT OF THE INVENTION The present invention constitutes an improvement of this system, in particular with a view to its use in environments disturbed by movement, acceleration, vibration or shock, and in particular in vehicles.

More precisely, the aim of the invention is to present a compact, robust, reliable and simple to use, light and inexpensive nebulization device which can be used to humidify, refresh and / or perfume and / or disinfect the air. of the passenger compartment of a vehicle.

Another object is to present a compact, robust, reliable and simple to use, light and inexpensive nebulizing device which can be used for humidifying or cooling goods, in particular fresh products, displayed for sale on a stall.

Yet another object is to present a compact, robust, reliable and simple to use, light and inexpensive nebulization device which can be used to humidify, refresh and / or perfume and / or disinfect the air of a stationary room. , such as a workshop, and in particular under mechanically disturbed conditions, for example by vibrations or shocks.

The requirement for compactness results from the need for a small general size of the device, and in particular for a limited height, which is particularly great when the device is to be integrated into a vehicle interior.

The robustness requirement arises from the need for resistance of the device against disturbed conditions, and from its reliable operation under disturbed conditions, such as slopes, sudden acceleration and braking, vibrations, shocks.

It also results from the desire to avoid frequent maintenance of the nebulizer.

The requirement for ease of use results in particular from the practical impossibility of asking the user to ensure the regular supply of water to the nebulizer.

The requirement for lightness results from the general need to limit the mass which is added to a vehicle (and in particular to an aircraft) by adding additional options and functions.

The price requirement militates in favor of a device of simple construction.

3 These objectives are achieved by a nebulization device capable of generating and spreading a mist of micro-droplets to cool and / or humidify the ambient atmosphere of a room and / or to cool and / or humidify products displayed on a sales display, and / or to refresh and / or perfume the atmosphere of a passenger compartment, said device comprising (a) a nebulization nozzle provided with at least one liquid inlet port and at least one liquid outlet port, and on the opposite side of said outlet port a piezoelectric element capable of emitting waves acoustic in said liquid, and the cross section of said nozzle exhibiting a progressive narrowing towards said first outlet, so that in said nozzle the acoustic waves are focused to create a mist of droplets of said liquid;

(b) a collection tank which supplies said nozzle with liquid, (c) a pump called a circulation pump connected on the one hand to the collection tank and on the other hand to said nozzle by the at least one inlet port provided in said nozzle, said circulation pump being able to generate in said nozzle a liquid pressure sufficient to maintain a jet of liquid leaving through said outlet orifice of the nozzle, (d) a pressurizing chamber which is traversed by the liquid leaving the circulation pump before entering said nozzle, said nebulization device according to which the volume of the upper part of the pressurizing chamber being situated at a fluid level greater than the higher of the following three points: the highest nozzle water inlet, the upper edge of the nozzle outlet, the highest point of the piezo element, is at least twice as large than the volume of the nozzle.

This nebulization device forms the first object of the invention.

It can be produced according to different embodiments and variants.

The inlet section of the nozzle (ie the sum of the surfaces of the inlet orifices) must be greater than the section of the outlet orifice, and preferably at least three times greater, in order to avoid the phenomenon of cavitation. in the nozzle.

Date Received / Date Received 2020-05-29 3a Thus, the device according to the invention has a V5 / V4 ratio and a dimensioning of the outlet orifice of the nozzle and of the liquid inlet orifices of the nozzle such as when the circulation pump stops supplying water, the piezoelectric element remains immersed in said liquid (and could thus continue to operate without risk Date Received / Date Received 2020-05-29 CA 02909796 2015-10-19 WO 2014/177805 PCT / FR2014 / 051025 4 ) for a duration ts which is advantageously at least one second and preferably between 1 and 10 seconds, and preferably between 2 and 5 seconds.

Thanks to its nozzle for focusing acoustic waves generated by a piezoelectric element, the nebulization device according to the invention is able to create and spread a mist formed of droplets with a typical average diameter of between 0.5 μm and 10 μm. , preferably between 1 µm and 5 µm.

Focusing of the acoustic waves will be more effective in creating a mist of droplets of said liquid if the gradual narrowing of the cross section of said nozzle towards said first outlet port is such that the acoustic waves are focused at said outlet port.

The focusing will advantageously take place in the longitudinal axis of the nozzle which passes through the center of the outlet orifice, and even more advantageously in the horizontal plane of said orifice or slightly outside this plane.

Said liquid to be nebulized is preferably water, which may include additives, such as perfumes and / or disinfectants (for example: H202, peracetic acid, citric acid).

The device according to the invention advantageously comprises ventilation means for creating an air flow which carries said mist of droplets to the outside of said device.

In general, said circulation pump can be of any suitable type; a propeller pump is fine.

It is advantageously located below the collection tank.

In one embodiment of the device according to the invention, said collection tank comprises at least one plate for stabilizing the level of liquid, arranged horizontally, vertically or at an angle, each comprising at least one opening.

This secures the supply of liquid to the circulation pump, stabilizes the liquid jet and makes the operation of the device more reliable.

Advantageously, said stabilization plates are at least two in number and are arranged so that the openings are offset from one another.

This enhances their effect of stabilizing the liquid level in the collection tank.

Alternatively or in addition, at least part of said openings can be closed by a valve which opens at least partially under water pressure coming from one side and closes under water pressure coming from the opposite side, or opens CA 02909796 2015-10-19 WO 2014/177805 PCT / FR2014 / 051025 less widely under a water pressure coming from one side than under an equivalent water pressure coming from the opposite side.

In another embodiment, at least one of said stabilization plates is made at least partially in the form of a grid or sieve.

5 Another means of rendering the operation of the device insensitive to mechanical disturbances consists of a specific construction of the bottom of said collection tank, which is inclined towards a discharge port through which the liquid enters said circulation pump.

In a variant, the collection reservoir has the shape of a funnel.

In one embodiment which can be combined with all the others, the longitudinal axis of said nozzle forms an angle of inclination a with respect to the horizontal which is between 00 and 45, preferably between 0 and 30 and again. more preferably between 5 and 20.

This allows a particularly compact construction of the device.

The device may include a collection tube suitable and arranged to collect the jet of liquid leaving the outlet orifice and to empty into said collection tank.

It can be tilted from the vertical.

Said air flow can pass through this collection tube, which carries said mist of droplets towards its outlet.

This decreases the height of the device and simplifies its construction.

In an embodiment which can be combined with the previous ones, the collection tank and said nozzle form a single block.

In another embodiment which can be combined with the previous ones, the device comprises a secondary liquid reservoir connected to the primary reservoir, said secondary reservoir preferably being a flexible or semi-rigid reservoir.

It supplies, permanently or intermittently, said collection tank, preferably by means of a pump.

In one embodiment which can be combined with the previous one or with all the others, the nebulization system according to the invention is supplied with water by a water recovery system from outside said nebulization system.

This recovered water can be condensation water that forms on the surfaces of materials in contact with ice melt water used for the direct refrigeration of fresh produce displayed on a stall.

The device may include a heating means capable of evaporating the residual liquid in said device after it has been stopped.

The same heating means can be used for CA 02909796 2015-10-19 WO 2014/177805 PCT / FR2014 / 051025 6 to heat the water contained in the device to a temperature sufficient to reduce its content of pathogenic germs.

The device according to the invention may also include at least one means for detecting a lack of liquid associated with a feedback loop for cutting or reducing the intensity of the acoustic waves emitted by the piezoelectric element in the event of a lack of liquid. 'water.

This detection means can be a sensor (for example a water level sensor in the primary tank, and / or a pressure sensor in the pressurization chamber), or a plurality of sensors, and / or can comprise a measurement of an electrical parameter of the circulation pump.

Another object of the invention is a method of starting up a device according to the invention, in which (a) liquid is made to enter the primary reservoir through the inlet orifice;

(b) when the level of said liquid rises in said primary tank to a preset point which is detected by a water level detector in the primary tank, the circulation pump is activated;

(c) the circulation pump creates sufficient liquid pressure so that the liquid can invade the nozzle, possibly after having invaded the pressurizing chamber, and to form a stable jet of liquid which comes out of the outlet orifice, knowing that during at least part of this time, liquid is made to enter the primary reservoir through the inlet orifice;

(d) when the level of said liquid in said primary reservoir has reached a preset point which is detected by a level detector, the power supply to the piezoelectric element is activated to create droplets of liquid.

More particularly, said starting process can be applied to a nebulization device capable of generating and spreading a mist of micro-droplets to cool and / or humidify the ambient atmosphere of a room and / or to cool and / or humidify products displayed on a sales display, and / or to refresh and / or perfume the atmosphere of a passenger compartment, said device comprising - a nebulization nozzle provided with at least one liquid inlet orifice and at least one liquid outlet orifice, and on the opposite side of said outlet orifice a piezoelectric element capable of emitting waves acoustic in said liquid, and the cross section of said nozzle exhibiting a progressive narrowing towards said first outlet, so that in said nozzle the acoustic waves are focused to create a mist of droplets of said CA 02909796 2015-10-19 WO 2014/177805 PCT / FR2014 / 051025 7 liquid (knowing that in said nozzle the acoustic waves can be focused for example at said outlet orifice);

- a collection tank which supplies said nozzle with liquid, - a pump called a circulation pump connected on the one hand to the collection tank and on the other hand to said nozzle by the at least one inlet orifice made in said nozzle, said circulation pump being able to generate in said nozzle a liquid pressure sufficient to maintain a jet of liquid leaving through said outlet orifice of the nozzle, - a pressurizing chamber which passes through the liquid leaving the circulation pump before entering said nozzle, said nebulization device being characterized in that the volume of the upper part of the pressurizing chamber is located at a liquid level greater than the higher of the following three points: the highest nozzle water inlet, the top edge of the nozzle outlet, the highest point of the ceramic, is at least two times (preferably at least six times and even more preferably at least twelve times) greater than the volume of the nozzle.

This device to which said start-up method is applied may have all of the variants described in relation to this device, or only some of them.

In step (d) of said start-up method, said preset point and / or said level detector may be the same (s) as in step (b)).

Another object of the invention is the use of the nebulization device according to the invention to generate and spread a mist of micro-droplets to cool and / or humidify the ambient atmosphere of a room and / or to cool and / or moisten products displayed on a sales display, and / or to refresh and / or perfume the atmosphere of a vehicle interior, in particular of a land, sea or air vehicle.

Figures The device according to the invention is illustrated schematically by Figures 1 to 5 which show different embodiments.

Figure 1 shows a device according to the invention, in side view (Figure la) and seen from above (Figure lb).

FIGS. 2a to 2d schematically and successively show four phases of the start-up and operation of the device of FIG. 1.

CA 02909796 2015-10-19 WO 2014/177805 PCT / FR2014 / 051025 8 Figure 3 shows another device according to the invention, in side view (Figure 3a) and seen from above (Figure 3b).

Figures 4a to 4d show schematically and successively four phases of the start-up and operation of the device of Figure 3.

FIG. 5 shows another embodiment of the device according to the invention: FIGS. 5a and 5b show the same device and are distinguished only by the number marks and geometric marks which could not all be placed on the same figure for a reason for congestion.

List of references used in the figures:

1 Piezoelectric ceramic 18 Micro-water droplets 2 Seal 19 Mist 3 Ceramic support 20 Opening in stabilization plate 4 Concentration nozzle 21 Nozzle wall 5 Pressure chamber 22 Pressure chamber wall pressure 6 Collecting tank (primary) 23 Base of the nozzle 7 Diffusion guide tube 24 Water presence sensor 8 Chamber filling pipe 5 25 Reservoir drain port 6 9 Water presence sensor 26 Background of the collection tank 6 Circulation pump 40 Nebulization device 11 Air inlet 12 Nebulization outlet V1 Water volume in the tank 6 13 Water filling inlet V2 Water volume in the pump 10 14 Inlet port d '' water from nozzle V3 Volume of water in chamber 5 (inf) Nozzle outlet opening V4 Volume of water in nozzle 4 16 Stabilization plates V5 Volume of water in chamber 5 (sup) 17 Jet of water Q Water flow generated by the ceramic 1 10 Description DETAILED The nebulization system or device 40 according to the invention comprises a concentration nozzle 4, of known type, capable of containing a liquid to be sprayed (typically water) and having an outlet orifice 15, the cross section of the 'interior of said concentration nozzle 4 exhibiting a progressive narrowing towards said outlet 15 orifice 15.

Said nozzle 4 also has, on the side opposite to its outlet orifice 15, a piezoelectric element (ceramic) 1 capable of emitting acoustic waves CA 02909796 2015-10-19 WO 2014/177805 PCT / FR2014 / 051025 9 in the liquid.

The internal wall of said nozzle 4 is made of a hard material capable of reflecting the acoustic waves generated by said piezoelectric element 1.

The converging shape of the internal walls of the nozzle 4 is determined so as to focus the ultrasonic acoustic waves at a place close to the central part of the outlet orifice 15; thus, a mist of micro-droplets of the liquid to be sprayed is generated when the nozzle 4 is filled with liquid and the ceramic 1 emits acoustic waves of suitable frequency and intensity.

Said converging shape of the internal walls of the nozzle 4 is preferably parabolic, which improves the efficiency of the concentration nozzle 4.

Said shape of the internal walls of tank 4 very advantageously shows radial symmetry.

According to the invention, and as illustrated in FIG. 1, the longitudinal axis of the nozzle 4 is inclined relative to the vertical.

This inclination, expressed by the angle a with respect to the horizontal (see FIG. 5b), aims to reduce the total height of the device 40. The angle a can be less than 65, preferably less than 450, more preferably. less than 300 and even more preferably less than 15.

It can be 5 or 0 (longitudinal axis of the nozzle oriented in the horizontal plane), and can even be negative, because during the operation of the piezoelectric element 1, the interior of the nozzle 4 is filled with the liquid to spraying by a pump 10 which maintains a liquid pressure in said nozzle 4; this requires a pump 10 of sufficient capacity. The inclination can be -90, that is to say that the outlet orifice 15 is at the bottom of the nozzle 4;

this gives a good fog yield but the nebulization system 40 then has a greater height than when the inclination a is 0; this greater height can make it more difficult to integrate it into a vehicle interior.

The inventors have found that an angle a comprised between 0 and 45 (preferably between 0 and 30, and even more preferably between 5 and 20) provides an excellent compromise between the nebulization efficiency, the size of the pump 10 and the bulk of the system 40 (to which the size of the pump 10 contributes).

In the context of the present invention, an angle α of between 0 and 30, and preferably between 5 and 20, is preferred.

In known manner, the nozzle 4 comprises at least one liquid inlet port 14 making it possible to fill said nozzle 4 with liquid to be sprayed.

This filling has two functions. On the one hand, knowing that in operation, part of the liquid contained in the nozzle 4 leaves in the form of mist, it is necessary to replenish the nozzle 4 with liquid. On the other hand, a continuous filling of the nozzle 4 associated with the recirculation of the liquid makes it possible to stabilize the operating conditions of the system 40 even in the presence of strong accelerations of the system, as can be found in a land, sea or air vehicle. for example.

CA 02909796 2015-10-19 WO 2014/177805 PCT / FR2014 / 051025 To this end, said nozzle 4 is supplied with liquid by at least one liquid reservoir 6, called primary reservoir or collection reservoir.

A pump 10 called a circulation pump connected on the one hand to said primary liquid reservoir 6 and on the other hand to the nozzle 4 (via a conduit 8) allows the liquid to circulate continuously in the nozzle. 4 and generate a jet of liquid 17 at the outlet of the outlet orifice 15 of the nozzle 4.

Said circulation pump 10 is advantageously located directly above the collection tank 6, as can be seen in the figures, in order to avoid as much as possible its deactivation by lack of water.

The admission of the liquid from the primary liquid reservoir 6 into the nozzle 4 takes place through at least one inlet port 14.

Preferably, a plurality of inlet orifices 14 are arranged around the longitudinal axis of the nozzle 4 in a zone close to the piezoelectric ceramic element 1.

The nebulization system 40 according to the invention comprises a pressurizing chamber 5 which communicates with the nozzle 4 via at least one orifice 14 for admitting water into the nozzle.

According to the invention, this pressurizing chamber 5 has a certain internal volume relative to the volume of the nozzle 4, which ensures better stability of the water pressure in the nozzle 4 under disturbed conditions as described above;

this will be explained in detail below in relation to figure 5.

According to the invention, this pressurizing chamber 5 can have different shapes.

In a variant shown in Figure 1, the nozzle 4 is made with a double wall, the internal wall 21 being the actual wall of the nozzle 4, capable of reflecting the acoustic waves, as described above, and the external wall 22 enclosing with the wall 21 of the nozzle 4 a volume which forms said pressurizing chamber 5.

The pressurizing chamber 5 enclosed between its outer wall 22 and the wall 21 of the nozzle 4 is connected, on the one hand, to the interior of the nozzle 4 by at least one liquid inlet 14 (and preferably, as indicated above, by a plurality of inlet openings 14 arranged radially, for example four orifices), and on the other hand to the collection tank 6 via the conduit 8.

In the embodiment of the invention illustrated in FIG. 1, the collection tank 6 .. and the nozzle 4 form a single unit.

This makes it possible to simplify its construction; such a one-piece element is more robust and better withstands the disturbed environment of a vehicle.

The outlet 15 of the nozzle 4 preferably has a circular shape.

In one embodiment, its diameter is between 3 and 8 mm, and advantageously between 4 and 6 mm; the internal length of the nozzle is between 25 mm and 42 mm, knowing that CA 02909796 2015-10-19 WO 2014/177805 PCT / FR2014 / 051025 11 this distance corresponds to the near field of the ultrasound generated by the piezoelectric ceramic 1 By way of example, it is possible to use a nozzle of height 38 mm, with an outlet orifice with a diameter of 6 mm.

The inlet section of the nozzle 4 (ie the sum of the surfaces of the inlet orifices 14) must be greater than the section of the outlet orifice 15 (preferably at least three times greater) in order to avoid the phenomenon. cavitation in nozzle 4 (as well as a lack of water).

This condition is fulfilled, for example, with four inlet orifices 14 with a diameter of 5 mm for an outlet orifice 15 with a diameter of 6 mm.

In particular for the use of the nebulization system 40 in a vehicle, provision is made advantageously for the liquid jet 17 generated at the outlet 15 of the nozzle 4 to empty into a collection tube 7, the longitudinal axis of which is preferably inclined. relative to the vertical.

The collection tube 7 can be crossed by an air flow generated by a ventilation means (not shown in the figures), which is preferably adjustable in flow rate and which is located upstream, downstream or inside the collection tube 7.

Said air flow enters the nebulization system 40 through an air inlet 11 and carries the water microdroplets 18 generated by the nozzle 4 around the water jet 17.

Thus a mist 19 of micro-droplets forms which leaves the collection tube 7 through its outlet 12 and enters its destination environment, for example the passenger compartment of a vehicle.

The water jet 17 projects against the internal wall of the collection tube 7, and the liquid thus collected is thrown into the water tank 6.

Thus, the collection tube 7 also serves as a guide tube for the diffusion of the mist.

This embodiment may also be suitable for a stationary nebulization system 40, in particular a system mounted on a stand.

In one embodiment of the invention, the device comprises, in addition to the primary collection tank 6, a so-called secondary liquid tank (not shown in the figures), which can be deported and connected to the liquid circuit represented by the primary collection tank 6 and the nozzle 4 via a conduit.

This makes it possible to reduce the size and the bulk of the primary tank 6.

Said secondary liquid reservoir can be made of any suitable material, which can be flexible, rigid or semi-rigid.

It can in particular be made of metal (in particular aluminum, stainless steel) or plastic (in particular PE and PP).

As will be explained in greater detail below, the secondary tank may include or contain a heating resistance or more generally a heating means, in order to ensure the hygiene, in particular bacteriological, of this volume of water by heating the water. water and / or the walls at a temperature sufficient to at least partially destroy pathogenic germs, and more generally to disinfect and / or dry the entire device 40.

CA 02909796 2015-10-19 WO 2014/177805 PCT / FR2014 / 051025 12 In general, the piezoelectric ceramic element 1 is preferably of cylindrical shape, typically a wafer of circular shape. For example, it can have a diameter of 20 mm or 25 mm.

The ultrasound frequency is advantageously between 1.3 kHz and 2.3 kHz.

It can be, for example, 1.68 MHz.

In one embodiment, the piezoelectric ceramic element 1 is fixed on the outer wall 22 of the pressurizing chamber 5 at the base 23 of the nozzle 4 by a support 3; a seal 2 ensures the seal between said pressurizing chamber 5 and the support 3.

Said piezoelectric element 1 can absorb significant electrical power, for example 40 W for a diameter of 20 mm.

About 40% of this power is returned in the form of acoustic energy transmitted to the liquid, the rest is dissipated in thermal form.

For this reason, during its operation, the piezoelectric element 1 must be constantly cooled by the liquid in order to avoid its deterioration by overheating.

The inventors have realized that when the piezoelectric element 1 runs dry even for a very short time, it risks being damaged or even destroyed.

To avoid this, the inventors have provided that the nebulization system 40 comprises appropriate means making it possible to prevent said piezoelectric element 1 from operating (ie from not emitting acoustic waves or only acoustic waves of very low power) when the piezoelectric element 1 is not immersed in the liquid to be sprayed.

These means can take different forms, and generally comprise at least one means for detecting the lack of liquid and / or a means for detecting the heating of the piezoelectric element 1, and a means of feedback on the power supply. electrical of said piezoelectric element 1.

Said means for detecting the lack of liquid may be a level sensor 9 or a presence sensor which cuts or regulates the operation of the piezoelectric element I.

This sensor 9 can be an optical sensor or a capacitive sensor or else an inductive sensor, but among these three, an optical sensor which has better reliability is preferred.

This sensor 9 can be located at different places, in particular in the collection container, or inside the nozzle 4, or else in the pressurizing chamber 5 of the nozzle 4.

In one embodiment, a sensor located in the primary reservoir 6 is used.

It is also possible to use an ultrasonic sensor, acting as an analog sensor making it possible to measure the instantaneous flow rate of the system.

Said means for detecting the lack of liquid may be a sensor which detects the presence of the jet of liquid 17 at the outlet of the outlet orifice 15 of the nozzle 4.

This means is CA 02909796 2015-10-19 WO 2014/177805 PCT / FR2014 / 051025 13 less preferred because it causes a delay in the detection of an immersion fault of said piezoelectric element 1.

Said means for detecting the lack of liquid may be a pressure sensor in the nozzle 4 and / or in the pressurizing chamber 5 and / or at the outlet of the circulation pump 10 and / or in the duct 8.

Another means for detecting the lack of liquid in the nozzle 4 is a sensor of the temperature at the surface and / or inside said piezoelectric element 1, which makes it possible to detect the rapid heating of said piezoelectric element. 1 before he took damage.

This detection can be done for example using a thermocouple.

In the context of the present invention, thermal detection at the level of the piezoelectric element 1 is however not a preferred embodiment: the means which more directly detect the lack of liquid, and at an earlier stage, are preferred. to which the lack of liquid has not yet disturbed the operation of said piezoelectric element 1.

It is possible to combine two or more detection means, selected from those which have just been presented and / or from those which will be described below.

Different types of pumps can be used for the circulation pump 10.

It must have an adjustable flow rate; a pump adjustable between 0.1 and 2.8 liters / min is suitable for a nozzle 4 which has the dimensions indicated above.

In an advantageous embodiment, which is well suited to a miniaturized system which can be used for the passenger compartment of a vehicle, the circulation pump 10 can be a propeller pump.

Advantageously, this pump absorbs a direct current and the voltage is adjusted to vary the speed of rotation and therefore the delivery pressure at the outlet of the nozzle 4, which makes it possible to modify the length of the jet 17.

Generally speaking, a system as described above presents the risk that the circulation pump 10 temporarily sucks air rather than liquid when the water level in the collection tank 6 changes sharply, for example. following acceleration, braking or sudden tilting of the vehicle.

There is also a risk of air bubbles forming in the collection tank 6 if the environment is very disturbed; these air bubbles can be swallowed by the pump 10.

The suction of air can even lead to the temporary or permanent deactivation of the pump.

This risks leading to a drop in the water pressure in the nozzle 4 and to a lack of liquid such that the piezoelectric element 1 is no longer submerged.

CA 02909796 2015-10-19 WO 2014/177805 PCT / FR2014 / 051025 14 To avoid a lack of liquid in the nozzle 4, three means are proposed which can be combined (and to which can be added, if necessary, the detection means lack of liquid presented above): The collection tank 6 may have a shape characterized by an at least partially inclined bottom 26, the low point of which is close to its discharge orifice 25; this shape can be a funnel shape as in Figure 1 or another shape as in Figures 3a and 5.

Furthermore, as illustrated in Figures 1, 2 and 5, the collection tank 6 can be compartmentalized by at least one plate 16 called the stabilization plate which has the effect of stabilizing the liquid level, and preferably of a plurality of such stabilization plates, which can be arranged in the vertical, horizontal or inclined direction.

Said stabilization plate 16 is a plate comprising at least one opening 20 through which the liquid can flow.

The third means announced above is linked to the volume of the pressurizing chamber 5; it will be presented below in relation to figure 5.

As indicated above, the collection tank 6 may include at least one liquid level stabilization plate 16 which is substantially horizontal which extends over all or part of the width of the tank, and it may also or in addition , comprise at least one plate which is not horizontal, for example a vertical plate, which extends over all or part of the height of said tank.

The reservoir may have plates which are substantially parallel.

Preferably, the openings 20 of two adjacent parallel plates 16 are not located at the same location, that is to say do not overlap, but are offset in the plane of the plate.

Figure 1 shows an example of a funnel-shaped collection tank 6 provided with three horizontal and parallel liquid level stabilizing plates 16; their openings 20 do not overlap.

The collection tank 6 may include a liquid discharge (not shown in the figures) in its lower part which advantageously constitutes the lowest point of the nebulization system; thus the dead volume is minimized in the event of shutdown of the system 40, after it has been emptied through this lowest point.

To further improve the effect of the stabilizing plates 16, at least part of said openings 20 can be closed at least in part by a valve which opens at least partially under a pressure of water coming from one side and closes. under water pressure from the opposite side, or opens less widely under water pressure from one side than under equivalent water pressure from the opposite side.

In a variant which can be combined with the valves, said stabilizing plates 16 can be made all in part in the form of grids or sieves.

CA 02909796 2015-10-19 WO 2014/177805 PCT / FR2014 / 051025 It is also possible to position at least one stabilization plate 16 in the guide tube 7 as shown schematically in FIG. 4d.

This solves a problem which is specific to nebulization systems whose nozzle 4 has a longitudinal axis inclined relative to the vertical and whose jet of liquid 17 is collected in a guide tube 7: there is a risk of formation of air bubbles when collecting liquid from the jet; these bubbles can be found in the collection tank 6 and be sucked by the circulation pump 10, of which they are liable to disturb the correct operation.

The inventors have found that a stabilization plate 16 disposed in the guide tube 7 can decrease the formation and transport of air bubbles.

10 FIGS. 2a to 2d schematically and successively show the start-up and operation of the device 40 according to the invention shown in FIG. 1.

As shown in Figure 2a, system 40 is filled by allowing liquid to enter through inlet 13.

The filling can be carried out through a solenoid valve or by a peristaltic pump or other types of pump (piston, membrane, etc.) (not shown in the figure) located upstream of the inlet 13; this filling causes the liquid level in the reservoir 6 and the conduit 8 to rise to a point detected by a water presence sensor 9 from which the circulation pump 10 is started.

As shown in Figure 2b, the gradual filling of the reservoir 6 through the inlet 13 and the pressure generated by the circulation pump 10 cause the liquid to invade the pressurization chamber 5 then the nozzle 4, and a short water jet 17 comes out of the outlet 15.

When the liquid level in the tank 6 is sufficient again (as detected for example by the water presence sensor 9) and the piezoelectric element completely submerged, see figure 2c, the power supply of the piezoelectric element 1 is activated.

The ceramic 1 is excited at its resonant frequency, which has the consequence of generating an acoustic wave which is channeled by the nozzle 4 acting, thanks to the specific shape of its internal wall, as a concentrator of acoustic waves.

As shown in FIG. 2d, the water jet 17 is extended under the effect of the acoustic waves until it flows into the guide tube 7, and microdroplets 18 of water are torn off by the acoustic wave.

Under the effect of the air flow (represented by the arrows), a mist 19 forms; it leaves the guide tube 7 through its nebulization outlet 12.

The water jet 17 is collected by the guide tube 7 and the water is collected in the collection container 6 to be recycled in the system 40.

When the water level as detected by the water presence sensor 9 is insufficient to ensure that the piezoelectric element 1 is completely submerged, a loop of CA 02909796 2015-10-19 WO 2014/177805 PCT / FR2014 / 051025 16 feedback interrupts or decreases the operation of the piezoelectric element 1.

If this drop in level continues beyond a certain duration, water is added through the filling inlet 13, if possible, for example from said secondary tank.

The addition of water can also be done permanently, continuously or discontinuously, for example using a peristaltic pump (not shown in the figures), in order to compensate for the loss of water due to the nebulization.

Figure 3 shows another embodiment of the invention which differs from that of Figure 1 by the shape of the primary collection tank 6 and by the shape of the pressurizing chamber 5 (which will be explained in greater detail detail in relation to figure. 5).

The nebulization device 40 according to FIG. 3 is equipped with a second sensor 24 for the presence of water which is located in the pressurizing chamber 5, preferably in the upper part thereof; this second sensor 24 is optional.

More precisely, the primary collection tank has a shape characterized by an at least partially inclined bottom, the low point of which is close to its discharge orifice 25, but this shape is not that of a funnel as in FIG. 1. .

The device according to figure 3 does not show stabilization plates 16, but these can be added (for example in a manner analogous to what is shown in figure 5b).

FIGS. 4a to 4d schematically and successively show the start-up and operation of the device 40 according to the invention shown in FIG. 3;

this process is similar to that explained above in relation to FIGS. 2a to 2d.

As shown in Figure 4a, the system 40 is filled by allowing liquid to enter through the inlet 13.

As in the case of figure 2a, filling can be carried out through a solenoid valve or by a peristaltic pump or other types of pump (piston, membrane, etc.) (not shown in the figure) located upstream of the pump. entry 13;

this filling causes the liquid level in the reservoir 6 and the conduit 8 to rise to a point detected by a water presence sensor 9 from which the circulation pump 10 is started.

As shown in Figure 4b, the gradual filling of the reservoir 6 through the inlet 13 and the pressure generated by the circulation pump 10 cause the liquid to invade the pressurizing chamber 5 then the nozzle 4, and a short water jet 17 comes out of the outlet 15.

When the liquid level in the tank 6 is again sufficient (as detected for example by the water presence sensor 9) and the piezoelectric element completely submerged, see figure 4c, the power supply of the piezo element CA 02909796 2015-10-19 WO 2014/177805 PCT / FR2014 / 051025 17 electric 1 is activated.

The ceramic 1 is excited at its resonant frequency, which has the consequence of generating an acoustic wave which is channeled by the nozzle 4 acting, thanks to the specific shape of its internal wall, as a concentrator of acoustic waves.

As shown in FIG. 4d, the water jet 17 is extended under the effect of the acoustic waves until it flows into the guide tube 7, and micro-droplets 18 of water are torn off by the wave acoustic.

Under the effect of the air flow (represented by the arrows), a mist 19 forms; it leaves the guide tube 7 through its nebulization outlet 12.

The water jet 17 is collected by the guide tube 7 and the water is collected in the collection container 6 to be recycled in the system 40.

When the water level as detected by the water presence sensor 9 is insufficient to ensure that the piezoelectric element 1 is fully submerged, a feedback loop interrupts or decreases the operation of the piezoelectric element 1.

If this drop in level continues beyond a certain duration, water is added through the filling inlet 13, if possible, for example from said secondary tank.

The addition of water can also be done permanently, continuously or discontinuously, for example using a peristaltic pump (not shown in the figures), in order to compensate for the loss of water due to the nebulization.

In all the embodiments, a second water presence sensor 24 can be provided at the top of the pressurizing chamber 5: if this sensor indicates an insufficient level of liquid, a feedback loop can cut or reduce the pressure. powering the piezoelectric element 1 and / or increasing the flow rate of the circulation pump 10.

Thus, the volume of the chamber makes it possible to ensure protection of the piezoelectric element 1, the time that its power supply is cut off and the piezoelectric element 1 ceases to resonate.

Figure 5 shows another embodiment of the invention.

The guide tube 7 here at least partly forms the collection tank 6, so that its inclined bottom forms at least part of the inclined bottom of said collection tank 6.

It comprises at least one stabilization plate 16, and preferably (as in FIG. 5) a plurality of stabilization plates 16, arranged for example horizontally and / or vertically.

This embodiment allows a particularly compact construction of the nebulization system 40 and whose tolerance to mechanical disturbances is excellent.

It is not a problem if, in the event of a very large mechanical disturbance (shock), the liquid level of the collection tank 6 occasionally and temporarily overflows above the level of the outlet orifice 14 of the nozzle 4, so as to flood the water jet 17: this temporarily interrupts the production of mist 19, but does not jeopardize the ceramic element, and will not lead to a perceptible effect for the user of the system.

Figure 5 illustrates an essential aspect of the invention which is explained here in detail.

It is linked to the relationships between different volumes.

We denote by V1 the volume of liquid in the collection tank 6, by V2 the volume of liquid in the circulation pump 10, by V3 the volume of liquid in the pressurizing chamber 5 in the lower part of the nozzle 4 ( ie less than the height which defines the lower plane of the volume V5, see below) and by V4 the volume of liquid in the nozzle 4.

The volume V3 can be very low or even zero.

V5 denotes the volume of liquid in the upper part of the pressurizing chamber 5 located at a liquid level greater than the highest of the following three points: the orifice 14 for the water inlet of the nozzle located the highest, or the upper edge of the outlet 15 of the nozzle 4, the highest point of the piezoelectric ceramic 1.

Thus, whatever the inclination a of the nozzle 4, any point of the piezoelectric ceramic 1 is at a level lower than the volume V5.

In normal operation of the system 40 (see for example Figures 2d and 4d), the volumes V1, V2, V3, V4 and V5 are filled with liquid, the circulation pump 10 and the piezoelectric element 1 operate and generate a water jet 17 of approximately constant length, which illustrates the stationary state of the system.

According to the invention, the pressurizing chamber 5 is dimensioned so that it has a buffer volume (safety volume) V5 sufficient relative to the volume V4 of the nozzle 4, so that in the case of where the circulation pump 10 no longer pumps liquid (for example when the liquid level in the collection tank 6 is insufficient, or when the circulation pump 10 is deactivated), the volume V5 ensures during a certain period of time ts the water supply to the volume V4 of the nozzle 4, so that the piezoelectric element 1 is still flooded during this period of time ts.

This period of time ts can be used, in whole or in part, to cut off the power supply to the piezoelectric element 1, and / or to wait if the liquid level is restored on its own (in particular in the event of a disturbance. mechanical or when the circulation pump 10 has simply swallowed an air bubble).

The time ts must be long enough to allow the power supply to the piezoelectric element 1 to be completely cut off and its operation to be stopped; the Applicant has in fact observed that the stopping of the operation of the piezoelectric element 1 is not instantaneous when its power supply is cut: the piezoelectric element 1 continues to vibrate while the sound circuits power supply go empty.

CA 02909796 2015-10-19 WO 2014/177805 PCT / FR2014 / 051025 19 In general, it is preferred in the context of the present invention that the ratio of the volumes V5 / V4 is at least 2 and preferably d 'at least 6, and even more preferably at least 12.

More specifically, consideration is given to the desirable reaction time of the system to cut off the power supply to the piezoelectric element 1 in the event of a lack of water.

It is not necessarily desirable to cut off the power supply at the slightest drop in level in the pressurizing chamber 5, which risks leading to too intermittent generation of mist.

However, it must be ensured that when this drop continues or worsens beyond a certain duration, the power supply to the piezoelectric element 1 is cut off or at least greatly reduced.

Thus, the inventors consider that in a mechanically unstable environment (vehicle, stall surrounded by a crowd of people) the nebulization system 40 according to the invention must allow operation of the piezoelectric element 1 for a duration ts of between 1 and 10 seconds without liquid supply by the circulation pump 10, and preferably between 2 and 5 seconds.

In this context, an important parameter is the flow rate of liquid generated by the piezoelectric element 1 at the outlet of the orifice 14 of the nozzle 4 in the absence of pumping by the circulation pump 10; this flow rate (which is often manifested by the presence of a small jet of water called an acoustic fountain) depends (for an angle G (of positioning of the nozzle 4 and a given liquid) essentially on the power of the piezoelectric element 1 .

Even more precisely, the flow of the acoustic fountain can be expressed by Qpiezo = K x Pmax OR Pmax is the maximum electric power consumed by the piezoelectric element and Qpiezo is the flow of the acoustic fountain at this power Qpiezo, and K is a factor of proportionality.

A safety operating time of ts seconds is desired, that is to say that when the circulation pump 10 stops operating (in particular by deactivation), the system has a period of approximately ts seconds to shut off the system. power supply to the piezoelectric element 1.

Advantageously, the time ts is between 1 and 10 seconds, and a value between 2 and 5 seconds is preferred.

According to the invention, this objective can be achieved by providing a sufficient safety buffer volume V5, which corresponds to the volume of the pressurizing chamber 5 located at a liquid level higher than the upper edge of the outlet orifice 15. nozzle 4.

This volume must be greater than the volume V4 of nozzle 4.

CA 02909796 2015-10-19 WO 2014/177805 PCT / FR2014 / 051025 We therefore want V5 V4 Q xt pezo -s = This relation can be expressed by V5 k V4 + K x Pmax X ts.

In a typical example a nozzle 4 is used with a volume V4 of 0.0054 liters, and Qpiezo is 50 W for a supply voltage of 22 V with an acoustic efficiency 5 of about 40%; the angle is between 0 and 30.

Under these conditions P. is about 1.5 liters / min, and therefore K = 0.0005 I / VVs.

If we aim for a value t, = 5 seconds, V5 must be at least equal to 0.13 liters.

The V5 / V4 ratio is therefore 24.

As indicated above, the value ts can be less than 5 seconds, which tends to decrease the V5 / V4 ratio.

10 The ratio V5N4 can be estimated even more precisely, which takes into account in particular the value of the angle α and the sections of the orifices 14,15.

However, it is noted that except in an extreme situation (in particular: angle α less than -30, ratio of the sections of the outlet orifice 15 and of the inlet orifices 14 too low), the order of magnitude of the result does not change.

In order not to overburden the present description, we present a more precise estimate in greater detail in the appendix below.

Another problem with a nebulizer system 40 is its liquid supply.

If it is installed in a vehicle, it is not possible to have the water supply to the system ensured by a human operator (vehicle user, technician, etc.), like the windshield washer system. a vehicle.

In the event that the nebulization system 40 is installed on a retail stall, an external water supply is not always available, or cannot be monopolized by a permanent connection to the nebulization system 40; in this case, a secondary liquid reservoir of sufficient capacity can be provided which can be filled by an operator (for example every morning or once a week).

Advantageously, the nebulization system 40 according to the invention is supplied with water by a water recovery system from outside said nebulization system.

This recovery water can enter the nebulization system 40 through said secondary liquid reservoir.

This can be, for example, the condensation water that forms on the surfaces of materials in contact with the ice melt water used for the direct refrigeration of fresh products (e.g. fish, seafood) exposed on lethal.

It can also come from an air conditioning system, and more especially from the condensation water coming from said air conditioning system.

It can be admitted continuously or discontinuously in the nebulization system 40.

Whatever the origin of the recovery water, it must be purified before entering nozzle 4.

The purification can be carried out by heating to a sufficient temperature CA 02909796 2015-10-19 WO 2014/177805 PCT / FR2014 / 051025 21 for a sufficient duration (this heating can be carried out permanently or intermittently, for example by a heating resistance ), and / or by a filter element (for example a ceramic filter capable of removing particles of size greater than 1 μm and preferably greater than 0.5 μm).

To supply the filter element with water to be purified, a pump (for example a peristaltic pump) can be provided which generates sufficient pressure to overcome the pressure drop caused by the filter element.

Yet another problem is the emptying of the nebulization system 40: it is not desirable that in the event of prolonged non-operation, the water stagnates in parts of the system, as this is liable to promote the proliferation of pathogenic germs.

For this, different variants are offered here.

In an advantageous embodiment, the liquid is drained through an orifice in the lower part of the collection tank 6.

This orifice may be the same as that through which the water arrives to fill said collection tank 6 (in this variant it is therefore the orifice bearing the reference 13).

A solenoid valve may be provided, and / or a suction and / or filling pump.

In a variant, the primary liquid reservoir 6 is filled by a reversible pump from the secondary liquid reservoir.

In this case, it is possible to empty the primary tank 6 into the secondary tank by this same pump; the secondary tank can then be emptied into the air conditioning system with which it communicates by a duct.

In another embodiment, which is particularly suitable for use of the nebulizer system 40 on a stall in a point of sale, the system has an external supply of pressurized water.

Given the fact that it is generally easier to install a pressurized water inlet than a water outlet, it would be desirable not to necessarily need a water outlet for such a nebulization system.

According to the invention, the nebulization system 40 comprises heating means allowing it to be emptied by complete evaporation of the liquid.

The water vapor generated in this way can also be used for at least partial decontamination of the system (in particular of the mist circulation ducts and pipes and of the guide tube of the diffusion 7, of the volume V1 as well as of the volumes V2, V3, V4 and V5).

Preferably, this heating means is a heating resistor which is not afraid of overheating if it is used dry; a known type of silicone coated heating resistor may be suitable.

This heating resistor can be installed inside the collection tank 6.

It can be used in different ways.

In particular, it can intermittently heat the water to a temperature sufficient to kill CA 02909796 2015-10-19 WO 2014/177805 PCT / FR2014 / 051025 22 certain types of pathogenic germs, such as the germs causing legionellosis contained in the fluid in the system and on its walls.

It can also be used to evaporate all the stagnant liquid in the system during a prolonged shutdown.

This avoids the use of bactericidal products. To this end, the temperature must be able to reach at least 70 ° C., as described in the patent application WO 2011/039487 of the applicant.

The device 40 according to the invention, thanks to its nozzle 4 for focusing acoustic waves generated by a piezoelectric element 1, is capable of creating and spreading a mist formed of droplets with a typical average diameter of between 0.5 pm and 10 pm, preferably between 1 pm and 5 pm.

This particle size depends in particular on the frequency of the acoustic waves produced by said piezoelectric element 1.

It can be used on board any type of vehicle, especially land, air or sea.

It can be used there in particular to refresh and / or humidify and / or perfume and / or disinfect the air of a passenger compartment (for example of a cabin of a railway car, of a ship or of an aircraft) or of a product transport volume.

It can also be used in stationary applications, for example in commercial, craft, industrial or residential premises, to cool and / or humidify and / or disinfect and / or perfume the ambient air.

It can be used in particular to refresh and / or humidify products (in particular fresh products) displayed for sale on a stall.

This device 40 has the advantages of being particularly compact (thanks to its design with an inclined nozzle 4 which empties its water jet into the guide tube 7 of the mist diffusion), particularly reliable (thanks to its resistance to mechanical disturbances). and thanks to its design which resists an interruption of the operation of the circulation pump 10 of a few seconds) and to require little maintenance (thanks to the water recovery system).

Annex to the description:

This appendix shows in greater detail the calculation of the V5 / V4 ratio for a device according to the invention which was produced by the inventors; it also serves as an example.

In this appendix the parameter ts is designated by t .security = and the angle a is designated by 8.

The known and measurable physical parameters are as follows:

- Ss Outlet section 15 of the concentration nozzle 4 - Se Inlet section 14 of the concentration nozzle 4 - H Height of the concentration nozzle 4, from the base to the Ss section - Electrical Electrical power CA 02909796 2015-10-19 WO 2014/177805 PCT / FR2014 / 051025 23 In order to limit the phenomenon of cavitation and a lack of water in the nozzle 4, the following conditions are set:

Se >> Ss ideally it is necessary that Se 3.5 Ss We know that the output speed of the viet jet 17 is linked to the acoustic power of the piezoelectric element 1 as well as to the geometric parameters of the nozzle 4:

life = f (Acoustic; H; Ss; 0) If we fix the geometric parameters H, Ss, O we obtain Vjet = f (Acoustic; 1 <1) with index K1 constant.

In addition we know that P acoustics = f (Pelectric; K2) with constant index K2.

We obtain Vjet = f (Pelectric; K1; K2) or Vjet = f (Pelectric; K3) with index K3 constant.

A description is given here of the operation in the event of deactivation of the circulation pump 10, in particular to evaluate the ratio of the volumes of water V5 / V4:

The initial conditions are as follows (steady state):

- System filled with water.

- Circulation pump 10 and acoustic (generation of the fog, excitation of the ceramic 1) in operation.

- The volumes V1, V2, V3, V4 and V5 are almost constant.

If the pump 10 is deactivated due to a disturbance in the suction of water in the collection tank 6, that is to say when the circulation pump 10 can no longer suck the volume V1 and V2 in water, the volume V5 (higher volume of water in the pressurizing chamber 5) must ensure the water supply for the volume V4 of the nozzle 4 for a safe time.

We therefore deduce the following relation: V5 get t .security V5 _k Vjet.

Ss = tsafety V5 K3 = P Électrique = Ss tsafety like Se 3 Ss CA 02909796 2015-10-19 WO 2014/177805 PCT / FR2014 / 051025 24 We can also say that: V5 [K3 = P Électrique = Se = tsafety] / 3 Un device produced by the inventors is characterized by the following parameters:

Se ¨ = __ mm2 with d = 6 mm for the diameter of the outlet opening 15 of the nozzle 4.

-2 We check that Se >> S and 100 >> 36.s, 4 We know that K3 = 0.02 for a nozzle diameter between 4 and 8 mm and O = 100 with H = 38 mm (H denotes the inner height of the nozzle 4).

In addition, in the Electrical example = 50 W (constant).

If we set tsecurity = 3 sec as an objective, we obtain:

V5? K3 = Electrical = Ss = tsafety and V5 k 85 ml.

The volume V5 must therefore be at least 85 ml to ensure a water supply in the volume of the nozzle V4 for 3 seconds.