WO2009037224A1

WO2009037224A1 - Spray head for a fluid substance

Info

Publication number: WO2009037224A1
Application number: PCT/EP2008/062238
Authority: WO
Inventors: Michel BAUFUMÉ
Original assignee: Baufume Michel
Priority date: 2007-09-21
Filing date: 2008-09-15
Publication date: 2009-03-26
Also published as: FR2921279B1; FR2921279A1

Abstract

The present invention relates to a spray head for a fluid substance containing an active material and a carrier liquid that can evaporate, which head comprises a body (4) for receiving said substance that communicates with a canula (40) for conveying said substance to a spray nozzle (401), the internal surface of which defines a channel for conveying said liquid to said nozzle (401). Said canula (40) includes at least one capillary retention zone (51), i.e. at least one zone in which, in the absence of intentional flow of liquid in the channel (6), the liquid present is held in place, without migrating towards said nozzle (401), in particular by capillary effect.

Description

HEAD FOR SPRAYING A FLUID PRODUCT

The present invention relates to a spray head of a fluid product containing an active material and a vector liquid capable of evaporating.

It relates more particularly to a spray head which comprises a body for receiving said liquid which communicates with a cannula for conveying it to a spray nozzle.

One of the most commonly used systems for spraying a liquid is to pass it through a nozzle, the outlet of which the jet resolves into fine droplets. The nozzle consists of an orifice of small diameter relative to that of the cannula which brings the liquid.

FR-A-2 833 930 describes a fluid dispensing bottle whose evacuation is caused by deformation of the wall of the container.

The actuation of the bottle creates a biphasic spray, by mixing a liquid and a gas present together in the container. The bottle has a spray head which is an axial extension of the body of the bottle.

The inner part of this head is occupied by a piece of porous material, itself connected to a dip tube. A groove abuts the base of this piece, at the end of the dip tube. Thus, even if the bottle is used upside down, the piece of porous material can be supplied with liquid.

For many common applications, the liquid to be sprayed is contained in a container pressurized by a gas, the assembly being commonly called "bomb". In a number of cases, it is desirable not to mix the liquid to be sprayed with the propellant.

One of the solutions employed for this purpose is to have an impervious and flexible pouch inside the container. The liquid is introduced inside the bag during manufacturing operations. The bag is sealingly connected to the tubing which conducts the liquid towards the spray nozzle. The pressurized gas fills the space between the inside of the container and the outside of the flexible and impervious bag containing the liquid to be sprayed. It compresses the liquid in the pocket. A valve placed in Out of the pocket allows to release the liquid which will thus be expelled through the nozzle via the junction tubing.

In other embodiments, the liquid expulsion pressure is provided by a user operated pump. In all cases, the principle of spraying is to expel a liquid through a nozzle called orifice, whose diameter is small in front of the other dimensions of the circuit used by the fluid, thanks to the pressure difference that prevails on both sides. other of this orifice. The jet is then resolved into droplets that are distributed in the environment.

The same principle can be used to dispense viscous liquids, creams, gels or foams. But in this type of application, there is often no spray proper.

One of the difficulties that can be faced by the users of these bombs comes from the clogging of the nozzle.

Such situations occur in particular after a certain period of non-use. The first use does not usually pose this kind of difficulty, if the product has remained confined in the bomb during the storage time and has not yet passed through the nozzle. One of the causes of clogging encountered is the drying of the product contained in the bomb. This is particularly the case when said product consists of a diluted active ingredient, dissolved or suspended in a vector liquid.

The role of this vector liquid consists inter alia in adapting the viscosity of the product to obtain a fine spray, which will distribute the active ingredient homogeneously in a large volume.

After actuating the valve, the downstream fluid circuit, and in particular the nozzle forming the distal end, is filled with product. The product is then in contact with the atmosphere, which will cause its drying, and then clogging.

Depending on the modes of use, the product can be brought into contact with the atmosphere at its distal end and this is naturally the most frequent case. It can also be performed by its proximal end, in cases where the tip carrying the nozzle is disassembled, for example to be stored in the package of the bomb between two uses. In some cases, the air-product contact may be minimized by the use of a watertight cap and removable end placed at the distal end, the proximal end remaining as for it fitted on the bottle.

One of these situations is encountered in the case of bombs filled with saline liquids, such as seawater used for therapeutic purposes.

It is generally diluted so that one is in the vicinity of the isotonicity. It is used in particular for nasal or ear sprays, by adapting to the bomb a cannula or a nozzle whose end comprises a spray nozzle. For this type of application, very variable durations can extend between two uses, and it is found that one can actually arrive at clogging.

A microscopic study reveals that corking comes from the crystallization of salt from seawater, which occurs especially at the nozzle and in the adjacent area.

The chronological monitoring of the evaporation of seawater shows that the removal of the liquid is not uniform throughout the cannula or tip. The water preferentially withdraws smooth zones and / or whose geometry comprises the largest radii of curvature. Conversely, it will appear to adhere to the wall and gather in areas of small radius of curvature or rough (it should be noted that in fact a rough area corresponds to a multitude of micro-zones with small radii of curvature).

Such a phenomenon is found in many other circumstances and originates in surface tension. The appended FIG. 1 is an illustration of such a phenomenon.

There is shown a cylindrical tube 1 with a diameter of the order of 1 to 2 mm, one of the two ends is constituted by a nozzle 10 of even smaller diameter (for example 0.2 to 0, 4 mm).

It is filled with seawater and then placed on a flat surface in the open air to follow the phenomenon of evaporation.

It is found that the liquid remains "hooked" at the nozzle 10 of small diameter. On the other hand, the front F of the initial liquid moves back from the other end of the tube, of greater diameter, until it comes near the nozzle, in a position marked F 'in the figure. Seawater is gradually concentrated in salt until the crystallization of salt. If you start from seawater without changing its concentration dilution, saturation occurs after evaporation of about 90% of the initial volume, and crystallization then begins. When all the water is evaporated, the salt crystals represent a volume fraction equal to 1.4% of the volume of initial seawater

(the apparent volume may be higher if there are gaps between the crystals) The crystals formed clog the nozzle 10 and possibly the adjacent inner portion of the tube 1, depending on the dimensions of this tube and the volume of initial seawater .

If we transpose the phenomenon analyzed here to what happens in the nozzle or cannula spray a bomb, it appears that the nozzle will be blocked by the salt crystals from the entire volume of water initially present in the tip or cannula, downstream of the valve.

Everything happens as if the nozzle, by its capillary properties, pumped during the evaporation all the salt available in the seawater initially filling the nozzle or the cannula. Of course, the same analysis applies in cases where it is not pure sea water, but whose concentration has been adjusted, for example to approach isotonicity.

The same goes for any aqueous saline solution and more generally for any material in solution or in suspension in a liquid other than water and likely to evaporate.

The present invention aims to solve these problems by proposing a spray head of a fluid product containing an active material and a liquid vector that can evaporate which, even after several uses, does not become clogged at its spray nozzle that is to say within which there is no "capillary pumping", namely phenomenon of transfer and accumulation of active substance causing clogging.

Thus, the present invention relates to a spray head of a fluid product containing an active material and an evaporable liquid vector, which comprises a receiving body of said product which communicates with a cannula for the delivery of this product. ci until a spray nozzle, its inner surface defining a channel for conveying said fluid product to said nozzle. It is essentially characterized by the fact that said cannula contains at least one capillary retention zone, that is to say at least one zone in which, in the absence of a deliberate flow of liquid in the channel, the liquid present is retained on place, without migration to said nozzle in particular by capillarity. We do not seek, as one would expect, to periodically open the channel of passage of the liquid through the nozzle.

On the contrary, the aim here is to control the distribution of the deposition of active material which takes place during the evaporation of the vector liquid, so that said deposition takes place over a large part, or even over the entire length. of the cannula, instead of concentrating at the level of the nozzle and its immediate vicinity.

The volume of this active material is less than that of the mixture that it initially formed with the carrier liquid (and even often very low), the deposit will be in the form of a thin layer. There can therefore be more than a small reduction in the passage section of the nozzle or any part of the cannula previously prone to clogging.

In addition, the active material distributed in a thin layer on the walls is likely to be reincorporated, during a subsequent spraying, into the "new" liquid that will circulate, thus avoiding any progressive accumulation of the deposit. The "new" liquid is in fact at nominal concentration, in principle well below the saturation limit, which gives it a potential for redissolving the active ingredient.

To obtain such a result, several means can be implemented, alone or in combination. They have the common feature of distributing the deposit of active material on a multitude of small areas or continuously over the entire surface.

According to other advantageous and nonlimiting features:

said capillary retention zone is constituted by at least a part of the internal surface of said channel;

a stem closed at its ends is fitted into said cannula, the outer and respectively inner surfaces of said rod and cannula delimiting said delivery channel, and at least a part of the external surface of said rod and / or of the internal surface of said cannula located opposite the stem, forms at least one capillary retention zone.

said capillary retention zone is a porous and / or hydrophilic and / or rough zone and / or formed of concave surfaces with a small radius of curvature and / or parallel surfaces forming projections separated in pairs by a small air gap; only a portion of the outer surface of said rod and / or of the inner surface of said cannula forms at least one capillary retaining zone, and at least one other part of said surface forms a capillary migration zone, ie an area in which, in the absence of a deliberate flow of liquid in the channel, the liquid initially present on said surface portion moves up to to the adjoining retention zone, as evaporation of the vector liquid; between two capillary retention zones extends a capillary migration zone;

said retention and capillary migration zones have an annular shape with a longitudinal axis (X-X ');

it comprises at least one capillary migration zone which has the shape of a longitudinal groove;

it comprises at least one additional capillary migration zone which has the shape of a longitudinal groove and which passes through said annular zones;

said capillary migration zone is an area of low wettability, in particular a non-porous and / or hydrophobic and / or smooth zone and / or formed of convex surfaces of large radius of curvature;

said body comprises a mobile and / or deformable member, able to be actuated during a spraying command, this member being resiliently returned to its rest position at the end of the spraying command, so as to generate a flow of suction of the liquid remaining in said cannula.

Other features and advantages of the present invention will appear on reading the following description of a preferred embodiment. This description will be given with reference to the accompanying drawings in which: - Figure 2 is a general view, from the side, of a container provided with a spray head according to the present invention;

- Figure 3 is a side view, in section along a longitudinal median plane, of a first embodiment of this head;

- Figure 4 is a top view, also in section along a longitudinal median plane, of the distal end of the cannula of said head;

- Figure 5 is a partial view, in longitudinal section, of said cannula, more particularly for showing an embodiment of the rod that it contains;

- Figure 6 is a view similar to the previous, to show another embodiment of the rod; - Figure 7 is an end view of yet another embodiment of this rod;

Figure 8 is a cross-sectional view of an additional embodiment of the rod; FIG. 9 is a longitudinal sectional view of the rod of FIG.

8;

- Figure 10 is a view similar to Figure 3 of an alternative embodiment of the head.

In Figure 2 attached is shown very schematically a spray kit 2 formed of a pressure vessel 3 of trade at the top of which is connected a spray head 4 according to the invention. This head is provided with a cannula 40 forming a projection. Figure 3 provides a better understanding of the structure of the head 4. This is preferably made of plastic. It extends along a generally vertical Y-Y 'axis in the use position.

In a known manner, this head is open downwards. It comprises a first peripheral cylindrical wall 41 intended to facilitate its centering when it is put in place on a container such as that of FIG. 2. It also comprises a second "internal" cylindrical wall.

42 and coaxial with the previous one, which is intended to be connected to a dispensing nozzle of the liquid contained in the container.

The duct delimited by this wall 42 opens on the internal space

43 of the head 4. The cannula 40 is in one piece with the head 4 and extends along an axis

X-X 'perpendicular to the Y-axis'. It communicates with the space 43. In a different embodiment and not shown, the head and the cannula could consist of separate parts, connectable to one another.

The distal end of the cannula is shaped into a small diameter nozzle 401. In this cannula is housed a rod 5 with closed ends. It has dimensions such that its outer surface 50 defines with the inner surface 400 of the cannula 40 a liquid flow channel 6 to be sprayed.

Referring now to Figure 4 which more particularly illustrates the distal end of the cannula and stem. The rod 5 is provided with pins 51 which extend radially and which are intended to keep it centered on the axis X-X ', while keeping a spacing unchanged between it and the longitudinal wall 402 of the cannula 40.

These spikes are advantageously distributed in several groups along the longitudinal extent of the rod and regularly separated angularly.

The rod abuts against an annular wall 407 projecting inwardly of the cannula and which is in one piece with the distal end wall 403 in which is formed an axial channel forming the nozzle 401.

In the upper part of this wall are formed channels 405 which open at a tangential incidence in a cylindrical turbulence chamber 406 delimited by the wall 407, the rod 5 and the wall 403.

This room communicates with the nozzle 401.

Such a structure is known from the state of the art.

Arrows show the path of a liquid through the cannula. This liquid is distributed uniformly in the channel 6 and rushes into the grooves 405. It arrives, in the form of swirling flows, in the chamber

406 and is distributed externally by the nozzle 401 in a generally conical shaped jet.

When the spraying has ceased, there is of course still liquid inside the cannula 40.

In such a structure and in accordance with the state of the art, the orifice of the nozzle 401, the grooves 405 and the turbulence chamber 406 spontaneously constitute a capillary retention zone which "pumps", during the evaporation of the vector liquid, the salt contained in the duct 6 and can become clogged, especially at the orifice 401.

According to the invention, at least a portion of the outer surface 50 of said rod 5 and / or of the inner surface 400 of the cannula 40 situated opposite the rod, forms at least one capillary retaining zone; to say at least one zone in which, in the absence of a deliberate flow of liquid in the channel 6, the liquid present on said surface is retained on the spot, without migration towards said nozzle 401, during the evaporation phase.

Preferably, one will deal with one or more capillary retention zones, separated by zones called capillary migration zones.

The capillary retention zones will make it possible to retain the liquid product during the evaporation of the vector liquid. Migration areas capillary have the opposite properties, namely that the liquid product is difficult to hang on.

As a result, the product initially contained in the cannula and whose volume will be reduced due to the evaporation of the carrier liquid, will gradually be confined to the capillary retention zones.

The product initially present with regard to the capillary migration zones will migrate, thanks to the capillary pumping phenomenon, into the capillary retention zones.

This phenomenon will progress thus until the capillary migration zones "empty" completely in favor of the capillary retention zones. The product will then be "fragmented" and distributed among all the capillary retention zones.

From this moment, no transfer of liquid product will be possible between the retaining zones, since migration zones will no longer contain product and capillary pumping assumes fluid continuity. The holding areas will therefore be isolated from each other.

At the end of the drying, the active material will be distributed among all the retention zones, without accumulating in the nozzle and the butcher.

Various means make it possible to produce the capillary retention zones. By way of nonlimiting example, it is possible to use materials whose surface is hydrophilic, either spontaneously, by coating or by modification of the surface, for example by cold plasma of a carefully chosen gas.

It is also possible to make inserts of hydrophilic material. Another way is to organize the geometry of the area so as to place areas promoting capillarity, in application of the law of Jurin. By way of nonlimiting example, it is possible, for example, to use zones with a concave surface with a small radius of curvature, or an association of parallel surfaces separated by a small gap. It is also possible to use porous or microstructured materials. Conversely, the capillary migration zones will be of low wettability and preferably consist of hydrophobic materials, by nature, coating or treatment. The surfaces will preferably be convex or with a small radius of curvature.

Thus, according to the invention, one can replace the rod 6 inserted into the cannula 40, originally made of polyethylene difficult to wettable, by a porous ceramic rod of the same dimensions. During drying after spraying and assuming that salt water is present, the porous ceramic rod, because of its good capillary properties, retains the saline water initially contained in line 6 and prevents it from going to supply salt to the capillary retention zone constituted by the nozzle 401, the grooves 405 and the turbulence chamber 406. It can even pump, at least partially, the water initially contained in these regions. It follows that the salt will be distributed on the outer surface 50 of the porous rod 5 and in its volume, practically not impinging on the coaxial cylindrical volume 6 existing between the cannula 40 and the rod 5. The flow of Fluid circulating in this cylindrical volume is therefore not substantially modified.

In one embodiment not shown, one can realize one or longitudinal grooves along the generatrices of the rod 5, sizing them so that they play the role of capillary migration zone. Under these conditions, during the drying process, the liquid contained in the grooves will disappear first, in favor of the rest of the rod, and well before the liquid reaches the saturation threshold.

As a result, the groove or grooves will constitute channels completely free of any crystallization, which will guarantee, during a subsequent spraying, the free passage to the incoming liquid. An equivalent arrangement may be formed by producing the longitudinal grooves, not in the rod 5 but in the inner wall 400 of the cannula 40.

Alternatively, the ceramic constituting the rod 5 may be replaced by a bundle of agglomerated fibers, which has good capillary properties. Such products are commonly used in writing instruments such as felts or ball markers.

In the embodiment of FIG. 5, use is made of a polymer rod 5 made by injection, part of the surface of which is roughened, and more precisely microstructured according to the so-called "diamond point" profile.

The overall outer diameter of this rod provides a small clearance but sufficient to engage the rod in the cannula 40 without difficulty during assembly of the device. The structure thus produced will create a plurality of micro-retention zones in the spaces between each point and the wall 402 of the cannula 40. An improvement in the "performance" of this rod is when two capillary retention zones 51 are separated by a capillary migration zone 52, which, like zones 51, has an annular extent.

As shown in FIG. 5, the zones 52 are recessed with respect to the zones 51, which further improves their capillary migration properties. The geometry of these grooves will give them capillary cutting properties.

During the evaporation of the vector liquid, the capillary migration zones will isolate from one another the capillary retention zones 51, themselves constituted by micro-retaining zones with diamond points. Within a first zone 51 and isolated from the rest of the rod, the deposition of active material will be concentrated around the diamond tips.

This process will thus progress from zone 51 to zone 51, without there being any transfer of active ingredient from one zone to another by capillary pumping. This arrangement can be advantageously combined with the longitudinal grooves previously described.

Other embodiments also implement this principle of segmentation in domains that isolate from each other during evaporation. This is the case of a polymer rod whose outer surface consists of a succession of annular zones successively hydrophilic and hydrophobic. This is also the case of a ceramic rod consisting of a succession of porous segments with hydrophilic behavior separated by non-porous segments so impermeable, achieving the capillary cut. Another variant consists in alternating along the rod two types of porous segments whose porosity is strongly different. The segments of high porosity will present, all things being equal, capillary properties much less intense and thus play the role of capillary migration.

Another embodiment is shown in FIG.

It consists in using a rod 5, for example made of polymer and made by injection, of different shape.

This rod here comprises an axial shaft 53 of small diameter from which radially extend disks 510 separated from each other by air gaps 511 of low value.

These disks are divided into several groups, each group constituting a zone 51 of capillary retention. They are separated two by two by a zone devoid of disks, which constitutes a capillary migration zone 52. The diameter of the disks 510 is smaller than the internal diameter of the cannula 40, and spikes or other equivalent devices can keep them centered in this cannula.

Within each group, the discs 510 are sufficiently close together to develop an important capillarity effect: they constitute capillary retention zones.

During spraying, the flow of liquid flows in the area between the cannula 40 and the outside of the disks 510, because of the game that has been reserved. This game also allows the easy implementation of the rod in the cannula. Said rod can be made in one piece, or reconstituted during assembly by stacking blocks of disks to reach the desired length.

In a similar manner to that described above, the principle of using longitudinal grooves can be implemented here.

Thus and as shown in Fig. 7, each elementary disc 510 has a notch or cutout 54 extending from the shaft 53 to its peripheral rim. Here it has the shape of an angular sector.

The notches 54 of all the disks are preferably aligned. They constitute secondary capillary migration means.

The alignment of these notches parallel to the generatrix of the rod 5 and defines a "pseudo" longitudinal channel capillary migration, which ensures a flow of liquid during subsequent spraying.

In such an embodiment, the radial clearance between the disks and the cannula can be made as small as desirable (taking into account the constraints associated with mounting), since the flow is effected by said longitudinal channel. In the embodiment of FIGS. 8 and 9, the head 4, shown very schematically, is devoid of rod 5. For the sake of simplification, the turbulence chamber and other means that normally equip the nozzle 401, have not been represented here.

We are dealing here with a longitudinal succession of capillary retaining zones 404 and capillary migration 403, the latter being slightly overhanging with respect to the former. They are formed in the inner wall of the cannula 40.

As is clear from Figure 8, these areas have, seen from the front, a shape in an arc. In yet another embodiment not shown in which the head 4 houses a rod 5, the latter is configured to present this alternating zones 403 and 404.

The advantages of the head according to the invention are further improved if, after spraying, the liquid is in the distal zone of the cannula 40, defined as going from the orifice of the nozzle to the first capillary migration zone that precedes it, is sucked.

Indeed, in the absence of liquid, there is no longer any risk of deposition of active ingredient in this part of the cannula, during the subsequent evaporation phase. The first zone of adjacent capillary migration also prohibits any return in this distal region of residual liquid from the proximal portion of the cannula.

Figures 3 and 10 illustrate embodiments of the spray head that incorporate such means. This is a movable member which is formed in the upper part of the body 4 and on which it comes to support when performing a spray.

To do this, the wall of the body is made in whole or in part of a material and / or a geometry that makes the mobile member deformable when pressed to trigger the spray, and which creates a springback when released support.

This can be obtained by adjusting the thinning and / or the geometry of said wall (movable member 44 with a locally thinned and curved wall as shown in FIG 3, movable member 44 'with an accordion wall, as shown in FIG. Figure 10). The movable member may also be constituted by a insert or insert having functionally equivalent properties. The same applies if the head is made by bimaterial injection, a rigid material being used for the body 4, a thermoplastic elastomer being used for the spring return member 44/44 '. When pressing the aforementioned member, the wall thereof begins to deform before the applied force reaches the threshold required to trigger the spray.

Conversely, at the end of the spraying, when the user releases his support, the valve closes first and interrupts the feed of the fluid head from the container. Then, the springback creates an increase in the internal volume of the body 4, which causes an aspiration to transmitting to the nozzle 401. The device must be dimensioned such that the volume variation created by the springback is at least equal to the volume of the distal zone between the orifice of the nozzle 401 and the first migration zone. capillary that precedes it. Under these conditions, at the end of the spraying, the liquid is sucked upstream of the distal portion of the cannula where the nozzle is located. This distal part remains isolated and can no longer be supplied with liquid by capillarity before the next spraying. She can not get stuck. In all cases, it is therefore necessary to have provided at least one capillary migration zone in the cannula portion located upstream of the nozzle, in order to isolate the latter after the end of the suction phase.

The invention described here thus makes it possible to avoid clogging of the head by avoiding the concentration of active material during the evaporation of the vector liquid in a critical zone such as the orifice of small diameter of the nozzle and, moreover, by limiting or reducing the volume of liquid initially present in this critical zone, by re-aspiration at the end of the spraying.

Claims

1. Spray head of a fluid containing product containing an active material and a vector liquid capable of evaporating, which comprises a body (4) for receiving said product which communicates with a cannula (40) for routing it. ci until a spray nozzle (401), its inner surface (400) delimiting a channel (6) for conveying said fluid product to said nozzle, characterized in that said cannula (40) contains at least one capillary retention zone (51), ie at least one zone in which, in the absence of a deliberate flow of liquid in the channel (6), the liquid present is retained on the spot, without migration towards said nozzle ( 401), in particular by capillarity.

2. Spray head according to claim 1, characterized in that said zone is constituted by at least a portion of the inner surface (400) of said channel.

3. Spray head according to claim 1, wherein a rod (5) closed at its ends is fitted into said cannula (40), the external surfaces (50), respectively internal (400) of said rod (5) and cannula ( 40) delimiting said routing channel, characterized in that at least a portion of the outer surface (50) of said rod (5), forms at least one capillary retaining zone.

4. Spray head according to one of claims 1 to 3, characterized in that said capillary retention zone (51) is a porous and / or hydrophilic zone and / or rough and / or formed of concave surfaces of small radius bending and / or parallel surfaces (510) forming projections separated in pairs by a small air gap (511).

A spray head according to one of the preceding claims wherein only a portion of the outer surface (50) of said shaft (5) and / or the inner surface (400) of said cannula (40) forms at least one capillary retention zone (51), characterized in that at least one other part of said surface forms a capillary migration zone (52, 54), ie an area in which, in the absence of flow in the channel (6), the liquid initially present on said surface portion moves to the adjoining retaining zone (52) as the vector liquid evaporates.

6. spray head according to claim 5 comprising at least two areas (51) of capillary retention, characterized in that between two areas (51) of capillary retention extends a zone (52, 54) of capillary migration.

7. Spray head according to claim 6, characterized in that said retention zones (51) and migration (52) capillary have an annular shape of longitudinal axis (X-X ').

8. spray head according to claim 5, characterized in that it comprises at least one capillary migration zone which has the shape of a longitudinal groove (54).

9. Spray head according to claim 7, characterized in that it comprises at least one additional capillary migration zone which has the shape of a longitudinal groove (54) and which passes through said zones (51, 52) of shape. annular.

10. Head according to one of claims 5 to 9, characterized in that said capillary migration zone (52, 54) is a zone of low wettability, especially a non-porous and / or hydrophobic and / or smooth and / or formed of convex surfaces of large radius of curvature.

11. Head according to one of the preceding claims, characterized in that said body (4) comprises a movable and / or deformable member (44, 44 ') adapted to be actuated during a spray control, this member being resiliently returned to its rest position at the end of the spray control, so as to generate a suction flow of the liquid remaining in said cannula (40).