EP1095704A1 - Electrostatic liquid spraying device - Google Patents

Abstract

The electrostatic aerosol forming machine has a wick (4) to disperse micro-droplets and fed by capillary action. The wick is in contact with an electrode (7) under high voltage. The wick is made of a material with high electrical resistance to maintain a low current flow, and is placed in a chamber (1). The lower end of the wick is held in a bowl (5) extending through the wall of the chamber.

Description

The present invention relates to a spraying device electrostatic liquid, very conventionally comprising a wick emission of microdrops in contact with an electrode subjected to a high tension, said wick having an emission end in the form of tip for spraying precisely by the so-called effect of point.

This long-known peak effect is used in many many applications, including spraying micro amounts of ink on paper-type media in printing devices, the misting of particles in the atmosphere for therapeutic purposes (aromatherapy), olfactory (diffusion of perfumes), pesticides, etc.

Its principle, simple to understand, is however generally not easy to be implemented in a perfectly controlled and regulated manner. The problem is indeed to permanently bring and maintain a very small but substantially constant amount of liquid in the area of the tip. As soon as part of this liquid is withdrawn, during the spraying, it should be replaced continuously and regularly.

As the quantities involved are very small, the problem of management Continuous and regular flow of liquid is particularly very delicate. Of a in general, the existing devices use the capillary forces to supply the end of the wick with liquid. What is called very generally the wick is therefore a structure allowing progression liquid by capillary action.

To have, at the level of the point, a quantity of liquid in continuous whatever the operating conditions, it is necessary to study very carefully the environment of the wick, especially if we want to favor a simple design of the device, that is to say allowing the capillary forces to be exerted in the best conditions without resorting to sophisticated mechanical systems of the type micro-pump, if necessary controlled by the quantity of liquid on the tip, etc. The development of a simple system that meets the requirements aforementioned remains however a complicated problem, because it is necessary to master and at the same time balance various internal parameters such as the quantity of liquid on the emission surface, the very nature of said liquid, the level of tension applied to the end of the wick, while preserving user safety during operation and while controlling possibly parameters external to the device itself (room temperature) which favor or on the contrary inhibit the perception of the product emitted into the atmosphere.

The material and layout configuration chosen for the drill bit are particularly critical elements of the study because they determine the amount of liquid available at the tip, knowing that the spraying is not carried out correctly when the quantity of liquid is too large, or for that matter when it is too low.

The preferred field of application of the invention is that of diffusion of perfumes in the atmosphere. In the prior art, the document PCT W092 / 15339 describes an electrostatic generator of aerosols emitting in particular products intended to perfume the ambient air. The structure of the apparatus described comprises a capillary element provided with a plurality of filaments, annularly arranged around a structural electrode complex, and whose free ends form a slightly clump flared outwards. These filaments, for example made of glass fibers, can be braided, and / or assembled in groups distributed on the periphery annular, thus forming a kind of fiber sleeve surrounding the complex structure forming electrode. Said sleeve is itself surrounded a protective and / or stiffening envelope.

The assembly is then partially immersed in a tank or a cartridge filled with liquid to vaporize, the latter moistening gradually the fibers by capillary action. When high voltage is applied via the electrode, aerosol emission is theoretically possible symmetrically around the perimeter of the wick.

In this configuration, the liquid to be emitted is present in the form of a film placed on the walls of the filaments. The management of said film, with a view of its vaporization, poses the problems mentioned before, and is specific to the system parameters: nature of the filaments, length and beam structure, etc. Apart from the known general principle which is at the basis of the invention, the elements and results described are of course not generalizable to other devices if the structure, configuration, and the materials of these are different. This is the case for the device of the invention.

Thus, in this one, the material constituting the wick is for example absorbent, and the wick shape is not annular but compact, with a point at one of its ends. Especially for these reasons, obtaining a vaporization device emitting micro drops of a perfectly controlled and regulated manner results from a specific study resulting in a particular configuration.

Specifically, the main electrostatic spray device of the invention comprises a wick for emitting micro-drops supplied in liquid by absorption, since a part is immersed in said liquid, said cylindrical wick having an emission end tip-shaped external powered by capillary action, and also being contact with an electrode subjected to a high voltage allowing said peak effect spraying. According to the invention, the wick is arranged vertically in a receiving chamber made of insulating material which is continuously supplied with liquid to be emitted. The wick, made in one absorbent capillary material having an electrical resistance provided for maintain the current at a safety level allowing contact without risk, soaking over substantially the lower half of its length in the liquid and is contained on substantially its upper half in a nozzle passing through a wall of the receiving chamber, outside of which said nozzle flares around the pointed end of the wick, the total length of the wick being such that the capillary forces are kept substantially constant. An electrode immersed in the liquid filling the receiving chamber is in contact with said wick near its lower end.

The structure obtained was notably designed to guarantee safety maximum of users. Despite the high operating voltage, necessary to apply the principle that is the basis of the device it is indeed theoretically possible to touch any part of the device without risk of electric shock, because the current is maintained at a extremely low value, due to the technical choices made for the device design.

The invention is in fact the fruit of a systematic desire for optimization elements and groups of elements that constitute it, as well as functional and structural interdependencies that link them. All the In particular, the following parameter values have been determined after extensive and repeated testing.

The simplicity of the structure, the ease of use and manufacturing have were also major goals at the time of design, especially for economic reasons both in the production phase only for maintenance during operation.

Preferably, the continuous supply of the receiving chamber is produced by gravitational flow from a reservoir adjoining said reception room.

The whole works thus without the need to add to it motor means, allowing for example to ensure a filling constant of the reception room, even to establish a component mechanical pressure in addition to the capillary forces (compressor). Such engine components, which at first glance make the control of a more exact processes, actually complicate the system, and make it less reliable. In certain applications, it is however interesting to use it.

According to a preferential arrangement, the reception room is horizontal in appearance, the electrode being disposed axially there and covered over almost its entire length in said chamber by a sleeve insulation allowing the end to protrude into contact with the wick. The electrode is therefore perfectly isolated from the liquid over almost its entire length.

In the configuration of the invention, it is moreover integral with a blanking plug of the receiving chamber, located at one of its axial ends, in which it is connected to the conductor connecting it to the high voltage producing circuit.

This circuit is classic, for example based on a Greinacher assembly allowing the production of high voltage by multiplication of a voltage initial thanks to a succession of Schenkel doublers.

To ensure good electrical continuity, the connection of the electrode and conductor connecting to the high production circuit tension is carried out via an anti-Corona sphere. The latter is preferably made of aluminum, as well as the electrode.

The voltage delivered to the electrode is between 20 kV and 25 kV, and from preferably between 23 kV and 24 kV.

For example, a negative DC voltage of the order of 23 kV is used, the current being kept at a very low value, of the order of 10 ^-9 A. The short distance traveled by the liquid under tension in the wick, the use of an absorbent non-conductive material for said wick, the resistivity of the liquid, greater than 10 ⁶ Ω m and the very low value of the current favor the spraying while preventing the maintenance of a current at its free end. in tip shape. The risks of arcing or electrocution are minimal, even non-existent. As will be described in more detail below, the choice of highly insulating materials at all levels contributes to this result.

Thus, the wick, practically insulating, is of length between 10 and 20 mm, preferably between 13 mm and 17 mm for a diameter of one value from 1.4 mm to 2 mm.

According to one possibility, this wick and acetate. It's the case in particular for the applications of the device of the invention such as fragrance diffuser used individually.

When the main device of the invention is coupled to a system more general air circulation, even air conditioning, which can require an emission of micro drops in a different form (jet more concentrated), the wick can be provided in polyamide. The section of the wick can then have a pattern depending on the type of emission desired.

The short length of the wick allows to maintain the forces of substantially constant capillarity, which avoids as mentioned previously the use of external drive means to ensure optimal liquid availability at the tip.

The wick plunges into the liquid contained in the reception, the internal volume of which is preferably cylindrical and connected by a channel opening in its lower part to a pace tank vertical, giving the receiving chamber an overall shape in L to the device.

The intervals of the optimal values, obtained by tests, are as follows: the internal volume of the receiving chamber is between 1.5 and 2.5 cm ³ , and the diameter of the connection channel with the reservoir is between 1, 8 and 2.2 mm.

To facilitate the manufacture of the system and reduce costs, the receiving chamber and the tank are made in one piece of a insulating material closed at both ends along the axis of the chamber reception by a blanking plug for the latter and a plate closure for the tank.

The upper wall of the vertical tank has an opening threaded, which can alternatively be blocked by a threaded plug or by a drilled screw, then acting respectively as a filling orifice or vent.

Filling the reservoir, as soon as the liquid level becomes insufficient, is ensured by this upper orifice easily accessible by final operating configuration, as will be seen below.

The insulating materials used have a dielectric constant of preferably between 25 and 50 kV / mm. For example, high density polyethylene.

All envelopes are also provided in a material highly insulating, to guarantee maximum safety. Polyethylene high density has, in addition to its insulating characteristics, the advantage of work very easily, hence its choice allowing in particular to reduce manufacturing costs.

The high voltage generator is itself insulated, and designed not to generate no parasite. The voltage value required to obtain the peak effect is notably determined by the resistivity of the liquid.

As an indication, with the components mentioned above, the flow of liquid is approximately 0.05 ml per hour in continuous operation. A tank with a capacity of 40 ml is therefore sufficient for one month.

For optimal operation, ensure perfect control of the device is not enough, however.

The environment of said device of the invention also influences the results obtained. Vaporization is for example much more delicate to check if the ambient temperature drops below a threshold set at around 20 ° C.

The olfactory yield, which depends on the evaporation of the micro drops sprayed, is no longer as high if the temperature drops, due to lower evaporation.

The device of the invention is therefore, if necessary, arranged in a special environment which favors spraying and evaporation.

An additional system is provided for pulsing, at the outlet of the nozzle, air at a temperature at least equal to 20 ° C., said system having furthermore been designed to create a depression in the outlet zone nozzle.

The surface tension which is exerted on spheres, and in particular on the micro drops emitted, increases in parallel with the temperature, and promotes product vaporization. However, avoid breaking the olfactory molecules by too high a temperature (> 45 ° C). depression created by the system also promotes the rise of the liquid in the wick for feeding the tip.

According to the invention, this additional system includes a venturi at one ends of which are successively arranged a resistor heater and a fan, and in the central part of reduced section from which is made an orifice receiving the flared part of the nozzle containing the tip of the wick.

The heated air is forced into one of the two divergent cones of the venturi, which has the effect of increasing its speed at the emitting tip.

According to one possibility, the heating resistor is coupled to a sensor of temperature which activates said resistance when the air temperature is measured at a value below 20 ° C.

Concretely, a possible configuration of said system is as follows: the external volume of the venturi consists of two end portions parallelepiped-shaped and also of a central portion parallelepiped of lower section, leaving free on two sides a prismatic volume in L in which the device is adjusted and fixed spraying, the nesting of the two elements giving the whole a external volume of general parallelepipedal appearance.

In addition, the assembly formed by the two nested elements is fixed axially to a box also of parallelepipedal shape containing electrical circuits for generating a high voltage, for managing timing of spraying, fan management and resistance heater, as well as these last two elements, as described in more detail below.

It is indeed necessary to add a management of the operating time, in particular to avoid saturating the air in a room with a given volume olfactory product. A conventional electronic circuit therefore allows intermittent spraying, with a stop time for example equal to the duration of active operation.

According to a possible configuration, the part of the venturi / spraying device protruding from said housing is covered with a sliding cover of external section substantially equal to that of said housing, and completing it.

The whole is therefore finally presented as a homogeneous housing of parallelepipedal appearance.

• la figure 1 représente une coupe axiale du dispositif de pulvérisation de l'invention ;
• la figure 2 est une coupe axiale simplifiée du bouchon obturateur de la chambre de réception ;
• la figure 3 montre une vue en perspective de la buse évasée ;
• la figure 4 montre une vue en perspective du système pulsant de l'air réchauffé ;
• la figure 5 représente une vue en perspective du boítier principal contenant les circuits électriques ; et
• la figure 6 est une représentation schématique des éléments contenus dans le boítier de la figure 5.

The invention will now be described in more detail, with reference to the appended figures, for which:

• Figure 1 shows an axial section of the spray device of the invention;
• Figure 2 is a simplified axial section of the shutter plug of the receiving chamber;
• Figure 3 shows a perspective view of the flared nozzle;
• Figure 4 shows a perspective view of the pulsating system of the heated air;
• Figure 5 shows a perspective view of the main housing containing the electrical circuits; and
• Figure 6 is a schematic representation of the elements contained in the housing of Figure 5.

The distinctive elements of the heart of the invention appear in FIG. 1. The L-shaped prismatic volume includes a receiving chamber (1) horizontal in appearance adjoining a tank (2) vertical in appearance. A canal (3) small diameter connects the two containers, allowing the liquid stored in said tank (2) to flow by gravity to the chamber (1), in which the lower part of the wick (4) dips. The level in the receiving chamber (1) must remain substantially constant, so that the submerged length of the wick is also constant, and that the capillary forces can always be exerted under the same conditions.

The wick (4) is centered in a funnel-shaped nozzle (5), the flared part opens towards the outside of the upper wall of the reception room (1). The tip (6) of this wick (4) is entirely contained in the flared volume of the nozzle (5).

In its lower part, the wick (4) is in contact with an electrode metallic (7), preferably aluminum, which is surrounded on almost its entire length by an insulating sleeve (8).

The top of the tank (2) comprises for example a drilled screw (9) of which the orifice serves as a vent in normal operation. The threaded hole in which is inserted the screw serves as a more filling hole (via a syringe or equivalent) when the liquid level is insufficient.

The receiving chamber (1) and the tank are made in one part, except for a closure plate (10) for the tank (2) and a closure plug (11) for the receiving chamber (1), preferably high density polyethylene. This plug (11), very shown schematically in Figure 1, appears more explicitly in Figure 2.

As mentioned above, the tank (2) has a capacity of around 40 ml, while the receiving chamber (1) has a volume of approximately 2 ml, connected to the reservoir by a conduit having a diameter of approximately 1.5 mm.

The wick (4), made of acetate, has a length not exceeding 15 mm, and it is in contact with an electrode (7) having a diameter of approximately 2 mm. This electrode (7) is connected to a high voltage wire (12) via a anti-Corona sphere (13). The walls of the receiving chamber (1) have a thickness of approximately 6 mm which guarantees perfect electrical insulation, insulation which is supplemented by the other dielectric components of the system: liquid, wick, nozzle, etc ... which have resistivities and / or high dielectric constants.

The choice of materials, dimensions, relative positioning of components and the value of the high voltage leads, in the configuration of Figure 1, excellent functioning of the device sprayer, and therefore at high spraying performance.

The blanking plug (11), also made of high density polyethylene dielectric constant between 25 and 50 kV / mm, has a internal bore (14) housing the anti-Corona sphere (13) and the sleeve (8) surrounding the electrode (7). An external thread (15) allows its fixing by screwing at the axial end of the receiving chamber (1). The wire (12) allows the connection with the electronic circuit producing the high voltage, in the occurrence a negative DC voltage of approximately 23 kV.

Figure 3 specifies the exact shape of the nozzle (5), substantially in funnel with a lower cylindrical part intended to be inserted in an orifice of corresponding dimension made in the wall upper of the reception room (1). The acetate wick (4) has the additional advantage of retaining the liquid, which does not drip when tilting the system.

Figure 4 shows the part of the system intended to pulsate air at the level of the nozzle (5), secondarily creating a depression favoring the rise of the liquid in the wick (4). It is actually a kind of venturi with two portions of cones (20, 21) connected by a cylindrical portion (22) into which an orifice (23) which also leads into a recess (24) of the envelope (B) containing the venturi, recess (24) which has a substantially parallelepipedal appearance.

This recess (24) is extended on the rear face of the envelope (B) of the venturi by a second recess (25) perpendicular to the first, giving the whole a hollow L-shape. It is in this L-shaped housing that fits the tank (2) / receiving chamber (1) assembly shown in Figure 1, the nozzle (5) then being housed in the orifice (23). The upper end of said nozzle (5) containing the tip (6) of the wick (4) thus opens into the cylindrical section (22) of the venturi.

The housings (26, 27) formed in the sole of the envelope (B) of the venturi allow the fixing of a tab C (not shown) fixing itself the spraying device, by any known means, to the envelope (B).

Two lateral recesses (28, 29) are used to fix the enclosure (B) of the venturi in a housing (30) shown in Figure 5. One piece front (31) consisting of two symmetrical parts comes for this purpose enclose the envelope (B) of the venturi, at the level of the recesses (28, 29) arranged on either side of the cone (21). The assembly is then slipped in rails (35) of the lower cover (32) fitting in slides side (33, 34) of the front piece (31), the same rails existing in the upper cover (36) for closing the housing (30). Hoods (32, 36) can then if necessary be screwed into said grooves (33, 34), and in similar grooves made in the opposite wall (37) of the housing (30). The latter has an additional intermediate wall (38) which use will be seen below. A passage (39) has been provided for the wiring in the front piece (31).

FIG. 6 schematically represents the content of the housing (30): the power supply is shown to the left of the intermediate wall (38), and comprises a transformer (40) and a card comprising the multiplier tension (41). To the right of this wall, there are successively the fan (42) in the axis of the inlet cone (21) and the resistance (43) heating, allowing air to be forced into the venturi heated, if the temperature sensor (not shown) indicates that the temperature fell below the critical threshold of 20 ° C.

Figure 5 shows that the intermediate wall (34) has a cutout (44) surmounting the bottom of the housing (30) allowing passage the whole management electronic card, located nearby and parallel to said bottom. The device of the invention can of course operate with the energy of the sector.

The covers (32, 36) and partitions (37, 38) are for example made of Expanded PVC. The heating resistor has a power of the order of 100 W, in the configuration used. An additional hood sliding (not shown), having the same external dimensions that the housing (30) is intended to slide around the part of the envelope (B) external to the housing (30) and can come, in the closed position, to the contact with the latter, or free access to the spraying device by open position, for example for filling the tank.

The configuration described above is of course only an example illustrative of the invention, which cannot be held to be exhaustive of this last. The invention, on the contrary, covers all variants of shape, configuration and materials entering human knowledge art.

Claims (21)

Electrostatic liquid spraying device comprising a wick for the emission of micro cylindrical droplets, one of which part is immersed in said liquid, and has an emission end tip-shaped external, liquid supplied by capillary action, said wick being in contact with an electrode subjected to a high voltage allowing said peak effect spraying, characterized in that the wick, arranged vertically in a reception room made of insulating material, is continuously supplied with liquid at emitting, said wick, made of an absorbent capillary material having an electrical resistance provided to maintain the current at a level safety allowing safe contact, soaking on substantially the bottom half of its length in the liquid and being contained on substantially its upper half in a nozzle passing through the wall of the receiving chamber, outside of which said nozzle flares around the pointed end of the wick, the total length of the wick being such that the capillary forces are kept constant, a electrode immersed in the liquid filling the receiving chamber being in contact with said wick near its end lower. Electrostatic liquid spraying device according to the previous claim, characterized in that the feed continues of the receiving chamber is produced by gravitational flow in coming from a reservoir adjoining said receiving chamber. Electrostatic liquid spraying device according to one of the previous claims, characterized in that the reception is horizontal, the electrode being disposed axially therein and covered over almost its entire length in said chamber by an insulating sleeve leaving the end protruding into contact with the wick. Electrostatic liquid spraying device according to one of the previous claims, characterized in that the electrode is integral with a shutter plug of the receiving chamber, located at one of its axial ends, in which it is connected to the conductor connecting it to the high voltage producing circuit. Electrostatic liquid spraying device according to the previous claim, characterized in that the connection of the electrode and conductor connecting to the high production circuit tension is carried out via an anti-Corona sphere. Electrostatic liquid spraying device according to the previous claim, characterized in that said anti-Corona sphere and the electrode are made of aluminum. Electrostatic liquid spraying device according to one any of the preceding claims, characterized in that the voltage delivered to the electrode is between 15 kV and 30 kV, and preferably between 23 kV and 24 kV. Electrostatic liquid spraying device according to one any of the preceding claims, characterized in that the wick is between 10 and 20 mm in length, preferably between 13 mm and 17 mm for a diameter of 1.4 mm to 2 mm. Electrostatic liquid spraying device according to one any of the preceding claims, characterized in that the wick is made of acetate. Electrostatic liquid spraying device according to one any of the preceding claims, characterized in that the wick is made of polyamide. Electrostatic liquid spraying device according to one any of the preceding claims, characterized in that the internal volume of the receiving chamber is cylindrical, connected by a channel opening in its lower part to a pace tank vertical, giving the device an L shape. Electrostatic liquid spraying device according to the preceding claim, characterized in that the internal volume of the receiving chamber is between 1.5 and 2.5 cm ³ , and in that the diameter of the connection channel with the reservoir is between 1.8 and 2.2 mm. Electrostatic liquid spraying device according to the previous claim, characterized in that the receiving chamber and the tank are made in one piece of insulating material closed at both ends along the axis of the receiving chamber by a blanking plug for the latter and a closure plate for the tank. Electrostatic liquid spraying device according to one of the claims 11 to 13, characterized in that the upper wall of the vertical tank is pierced with a threaded opening that can alternatively be blocked by a threaded plug or by a screw pierced, then acting respectively as a filling orifice Wind. Electrostatic liquid spraying device according to one any of the preceding claims, characterized in that the insulating material has a dielectric constant of between 25 and 50 kV / mm, and is preferably high density polyethylene. Electrostatic liquid spraying device according to one any one of the preceding claims, characterized in that it has a system designed to pulsate, at the exit of the nozzle, air at a temperature at least equal to 20 ° C, said system further creating a vacuum in the nozzle outlet area. Electrostatic liquid spraying device according to the previous claim, characterized in that said system comprises a venturi at one end of which are successively arranged a heating resistor and a fan, in the central part of reduced section of which is formed an orifice receiving the flared part of the nozzle containing the tip of the wick. Electrostatic liquid spraying device according to the previous claim, characterized in that the heating resistance is coupled to a temperature sensor which activates said resistance when the air temperature has a value below 20 ° C. Electrostatic liquid spraying device according to one of the claims 16 to 18, characterized in that the external volume of the venturi consists of two end portions parallelepiped and also a central portion parallelepiped of lower section, leaving free on two sides a prismatic volume in L in which the device is adjusted and fixed spraying, the nesting of the two elements giving the whole an exterior volume with a generally parallelepipedal appearance. Electrostatic liquid spraying device according to the previous claim, characterized in that the assembly formed by the two nested elements are fixed axially to a gearbox parallelepiped containing the electrical circuits for generating a high voltage, time management of spraying, management of fan and heater, as well as the latter two elements. Electrostatic liquid spraying device according to the previous claim, characterized in that the part of the assembly venturi / spraying device protruding from said housing is covered a sliding cover of external section substantially equal to that of said housing, and supplementing it.

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