EP3871792B1 - Spray nozzle with flat jet and low drift - Google Patents

Description

The invention relates to a spray nozzle.

A spray nozzle is externally presented as a case having an inlet orifice and an outlet orifice. Inside, the nozzle body is arranged to allow the dispersion of a liquid in the form of droplets, and to form at the outlet a jet of droplets, or spray, which has a determined distribution in space. More generally, a nozzle body is arranged to generate a dispersion of droplets at the outlet of an outlet orifice of the nozzle. Such nozzles are for example used in the agricultural field to spray phytosanitary products on crops.

There are different types of nozzles according to the particular shape of their jet: nozzles called straight jet, flat jet, cone jet, which can be a hollow cone, or even a full cone.

The present invention relates to spray nozzles of the flat jet type.

The essential characteristics of the flat jet are its angle of opening, and the law of distribution of the droplets inside this angle of opening, so that one obtains a uniform cumulative distribution of the drops when the nozzles are associated on a ramp and spaced between them.

In sprayers, a nozzle is most often placed every 50 cm. And the characteristics of the nozzles are chosen to ensure a substantially uniform distribution of the product to be sprayed over the surface of the agricultural land concerned.

We know how to do this with known nozzles, but there remains a problem. It works well without wind. However, the wind can cause the spray area to extend beyond the surface of the agricultural land concerned. First of all, it's a loss of efficiency. But it is also potentially harmful in the case of sprayed products which are aggressive and/or dangerous for living beings. It should therefore be avoided.

The applicant thought that a solution would be to increase the size of the sprayed droplets, to reduce their sensitivity to the wind. But getting nozzles that have the same opening angle, with uniformity of the cumulative distribution of droplets inside this angle, and this for larger droplets, is not a simple problem.

In general, a nozzle comprises a body forming a case and which encloses one or more organs and/or elements designed to disturb the jet, that is to say to act on the flow of liquid and to modify its characteristics before its release. ejection through the outlet orifice, depending on the desired spray and the shape of the desired outlet jet.

The US patent US5133502A , entitled "FLAT-JET NOZZLE TO ATOMIZE LIQUIDS INTO COMPARATIVELY COARSE DROPS" or "flat jet nozzle for atomizing liquids into comparatively large drops" constitutes a proposal in this direction. But he only gets modest drop sizes (his figure 6 ), which remain below 500 micrometers, even with low inlet pressure down to 1 bar.

The document FR2838069 discloses a spray nozzle consisting of a body defining an axial cavity comprising a calibration pad, a so-called “divergent” part and a so-called “convergent” part.

The document US5615836 discloses a nozzle capable of producing air-filled drops,

The document US4128206 discloses a low drift flat spray nozzle.

The Applicant produces a range of so-called AVI nozzles which also achieve median drop sizes of approximately 500 micrometers.

These are so-called air injection flat jet nozzles, that is to say using an autonomous suction of the nozzle making it possible to increase the size of the drops much more effectively than the US patent US5133502A , for higher pressures.

In a nozzle of the AVI type, from the inlet to the outlet, the nozzle body can first enclose a "core", which is a part of generally cylindrical shape, defining an internal passage of increasing internal cross-section. This passage is placed in communication with the outside air, substantially at the level of its weakest cross-section, hence a Venturi effect. The central exit orifice of this core leads to a working chamber, which will ensure the transition with the exit orifice of the nozzle. In order to be able to produce a flat jet, it is advisable to provide an insert provided with an outlet slot. This slot forms the exit orifice of the nozzle, of which it also defines the opening angle.

But this nozzle also provides drop sizes limited to 500 micrometers, without making it possible to reach super-large drop sizes, which would typically have an average size of 800 micrometers, over an interval extending from 400 micrometers to 1.2 mm.

In other words, the nozzle described with direct impaction has a limitation which depends on the contact surface of the liquid with the wall of the Venturi and therefore the final length of the nozzle. It produces drops in the range of 500 - 600 µm depending on the type of impaction injector. The goal is to overcome this limitation while maintaining the nozzle size.

The invention improves the performance of such a nozzle.

• un noyau, définissant intérieurement un passage, de section transversale croissante, en communication avec l'extérieur sensiblement au niveau de sa section transversale la plus faible, d'où un effet Venturi, ladite section transversale la plus faible commençant à proximité de la zone d'entrée de fluide,
• un insert, muni d'une fente de sortie formant l'orifice de sortie (16) de la buse et définissant l'angle d'ouverture de celle-ci,

le noyau et l'insert étant distants l'un de l'autre et formant entre eux une chambre de travail dans le corps.Generally, the proposed spray nozzle is of the type comprising a body, which has a fluid inlet zone and a fluid outlet orifice, the body housing

• a core, internally defining a passage, of increasing cross-section, in communication with the outside substantially at the level of its smallest cross-section, resulting in a Venturi effect, said smallest cross-section beginning near the zone of fluid inlet,
• an insert, provided with an outlet slot forming the outlet orifice (16) of the nozzle and defining the opening angle of the latter,

the core and the insert being spaced from each other and forming between them a working chamber in the body.

It is characterized in that the nozzle further comprises an additional part called a spark gap, housed in the working chamber, arranged to form an obstacle to the flow of the fluid, this spark gap comprising two through axial orifices, each forming a fluid passage, on either side of a radial plane, so that the two flows passing through the orifices of the spark gap combine and then impact the surface of the outlet slot of the insert, finally generating a flat jet.

From another point of view, the spray nozzle proposed is of the type comprising a body forming a casing, which has an inlet orifice and an outlet orifice, and which has, on the side of the inlet orifice, a fluid inlet area. From the inlet to the outlet, the nozzle body can first enclose a “Venturi core”, which is a part of generally cylindrical shape, defining an internal passage of increasing internal straight section. This passage is placed in communication with the outside air, substantially at the level of its weakest cross-section, hence the Venturi effect. The central exit orifice of this core leads to a working chamber, which will ensure the transition with the exit orifice of the nozzle. In order to be able to produce a flat jet, it is advisable to provide an insert fitted with a exit slot. This slot forms the exit orifice of the nozzle, of which it also defines the opening angle.

The proposed nozzle is characterized in that it comprises, in the working chamber, and upstream of the insert, an additional part here called spark gap. This piece forms an obstacle to the flow of the liquid flow. It comprises two through passages or longitudinal orifices, on either side of a central plane. At the outlet of the spark gap, the two flows which have passed through the orifices of the spark gap will regroup. And they will then impact the surface of the outlet slot of the insert, to finally generate a flat jet.

The invention provides a blade at the outlet of the spark gap, in the central plane. At the outlet of the spark gap, the two flows will circulate along this blade and follow its surface by the "teapot effect" (sometimes incorrectly called the Coanda effect), before regrouping to impact the surface of the outlet slot of the spark gap. insert.

The spark gap blade is adjusted or “indexed” to the insert slot. That is to say that the plane of the blade substantially merges with the plane of the outlet slot of the insert.

• [Fig 1] est une vue éclatée en perspective avant d'une buse de pulvérisation à jet plat connue.
• [Fig 2] est une vue assemblée de la buse de la figure 1, en coupe selon un plan qui passe par la fente de sortie.
• [Fig 3] est une vue assemblée de la buse de la figure 1, en coupe selon un plan perpendiculaire au plan de la fente de sortie.
• [Fig 4] est une vue éclatée en perspective avant de la buse de pulvérisation à jet plat ici proposée.
• [Fig 5] est une vue assemblée de la buse de la figure 4, en coupe selon un plan qui passe par la fente de sortie.
• [Fig 6] est une vue assemblée de la buse de la figure 4, en coupe selon un plan perpendiculaire au plan de la fente de sortie.
• [Fig 7] illustre en perspective un premier mode de réalisation de la pièce ajoutée dite éclateur.
• [Fig 8] illustre en perspective un second mode de réalisation de la pièce ajoutée dite éclateur.
• [Fig 9] illustre en perspective un troisième mode de réalisation de la pièce ajoutée dite éclateur.
• [Fig 10] illustre en perspective un quatrième mode de réalisation de la pièce ajoutée dite éclateur.
• [Fig 11] est un graphique illustrant les performances de la buse avec l'éclateur de la figure 10.
• [Fig 12] est un graphique illustrant les performances de la buse avec l'éclateur de la figure 9.
• [Fig 13] est un graphique illustrant les performances de la buse avec l'éclateur de la figure 8.
• [Fig 14] est une vue agrandie de la fente de sortie de la buse.

Other characteristics and advantages of the invention will appear on examination of the detailed description below, and of the appended drawings, in which:

• [ Fig 1 ] is an exploded front perspective view of a known flat fan spray nozzle.
• [ Fig 2 ] is an assembled view of the nozzle of the figure 1 , in section along a plane which passes through the outlet slot.
• [ Fig.3 ] is an assembled view of the nozzle of the figure 1 , in section along a plane perpendicular to the plane of the outlet slot.
• [ Fig 4 ] is a front perspective exploded view of the flat fan spray nozzle provided herein.
• [ Fig.5 ] is an assembled view of the nozzle of the figure 4 , in section along a plane which passes through the outlet slot.
• [ Fig 6 ] is an assembled view of the nozzle of the figure 4 , in section along a plane perpendicular to the plane of the outlet slot.
• [ Fig 7 ] illustrates in perspective a first embodiment of the added part called spark gap.
• [ Fig.8 ] illustrates in perspective a second embodiment of the added part called spark gap.
• [ Fig.9 ] illustrates in perspective a third embodiment of the added part called spark gap.
• [ Fig. 10 ] illustrates in perspective a fourth embodiment of the added part called spark gap.
• [ Fig.11 ] is a graph illustrating the performance of the nozzle with the spark gap of the figure 10 .
• [ Fig. 12 ] is a graph illustrating the performance of the nozzle with the spark gap of the figure 9 .
• [ Fig. 13 ] is a graph illustrating the performance of the nozzle with the spark gap of the figure 8 .
• [ Fig. 14 ] is an enlarged view of the nozzle exit slot.

The drawings and the description below contain, for the most part, elements of a certain nature, which are difficult to convey other than by drawing. Consequently, the drawings form an integral part of the description and may therefore not only serve to better understand the present invention, but also contribute to its definition, where appropriate.

THE figures 1 to 3 show a known flat jet spray nozzle, such as the Applicant's AVI-110-04 nozzle.

• Un premier alésage 11, muni d'une collerette 10, côté entrée, et un suivi d'un second alésage 12 un peu plus étroit,
• Un troisième alésage 13, suivi d'un quatrième alésage 14 un peu plus étroit,
• Enfin, un alésage de sortie 15.

The nozzle comprises a body 1 which internally defines a hollow case, of generally cylindrical shape, with:

• A first bore 11, provided with a collar 10, on the inlet side, and followed by a second bore 12 which is a little narrower,
• A third bore 13, followed by a slightly narrower fourth bore 14,
• Finally, an output bore 15.

Note that the word bore refers here to a female element of a circular fit, whatever its machining process. Indeed, the parts not being metallic, but rather made of synthetic material or ceramic, they are not machined by the conventional boring for metals.

At the bores 11 and 12 is inserted a Venturi core 2, which begins with a cover 20, resting on the collar 10. The Venturi core 2 has a first cylindrical volume inside straight 21, followed by a conical volume 22. This defines an internal passage of increasing internal straight section.

The volume 21 is traversed by radial passages 25A and 25B, which communicate via an annular recess 26 with outside air inlets 18 arranged through the wall of the body 1.

Finally, the top of the core is equipped with a flow rate calibration element 29, which here is a pellet with a calibration orifice.

In the core 2 a Venturi effect occurs, due to the nozzle formed by the calibration disc 29, and the volumes 21 and 22. The intensity of the Venturi effect depends on the pressure of the liquid at the inlet. And the Venturi effect itself results in the production of a liquid+air mixture in the cavity 23 located downstream of the Venturi core.

In an outer peripheral rib of the core 2, there is provided an O-ring 4, which provides sealing between the annular recess 26 and the downstream of the core 2.

Further down, the body 1 contains a spray insert 3, which has a cylindrical cavity 30 leading to a slot 31, which is in the plane of the figure 2 , and perpendicular to the plane of the picture 3 . This slot 31 constitutes the outlet orifice of the nozzle.

The insert 3 is put in place and held by screwing and has for this purpose a peripheral threaded portion located close to its end 16 and designed to cooperate with a corresponding thread (not visible) of the bore 15 of the body 1. In another embodiment, the insert 3 is assembled to the body 1 by crimping. For that. The insert 3 is positioned in the body 1 then pushed in using a press.

The Venturi effect makes it possible in particular to obtain slightly larger drops, due to the creation of the air/liquid mixture, but without doing much better than 500 micrometers.

The proposed nozzle will now be described, with reference to the figures 4 to 6 .

This nozzle has the same general structure as that of the figures 1 to 3 .

We will therefore not describe again the common points of the figures 1 to 3 on the one hand, and 4 to 6, on the other hand.

On the figures 4 to 6 , the internal space 23 located upstream of the insert is occupied by an additional part 7 called here spark gap.

On the upstream side, the spark gap comprises a cylindrical peripheral cupola 70, which engages in a recess 28 made in the downstream outer periphery of the core 2, and abuts on a shoulder 29 of this core 2. In its radial part, the cupola 70 comprises two through passages or longitudinal orifices 71 and 72, provided symmetrically on either side of a central radial plane 73.

The spark gap continues with a blade 75, also placed symmetrically with respect to the central radial plane 73.

At the outlet of the spark gap, the two flows which have passed through the orifices 71 and 72 will circulate along the blade 75 and follow its surface by “teapot effect” to regroup. The two streams thus grouped together will come to impact the outlet surface of the insert 3 and generate a flat jet of the “flat fan” type (flat fan).

The circulation of the fluid through the nozzle 1 is as follows.

A supply of liquid to be sprayed is connected to the nozzle 1. The flow enters through the orifice of the ceramic calibration disc 29 of circular section then, directed by the pressure, it moves into the duct of the core 2, of restricted section then widening. The presence of air intakes (25A, 25B, 26, 18) at the level of the most restricted section of the core, combined with the low pressure of the flow at this place (consequence of its acceleration), allows the suction of the outdoor air by Venturi effect and its mixing with the flow.

On entering the spark gap, the mixture thus obtained comes into contact with the surface between the two orifices of the spark gap. The impact will generate a sharp drop in the energy of the flux, which will be directed by pressure towards the two outlet orifices 71 and 72 of the spark gap. At the outlet of the spark gap, the two flows will circulate along the blade 75 and follow its surface by “teapot effect” to regroup. The two streams thus grouped together will impact the outlet surface 31 of the insert 3 and generate a flat jet of the “flat fan” type with controlled angle and dispersion.

THE figures 7 to 10 show four embodiments of the spark gap 7, tested by the Applicant.

On the figure 7 , the spark gap has no blade.

On the figure 8 , the spark gap has a substantially flat blade 75B, as shown in the figures 4 to 6 .

On the figure 9 , the spark gap also has a flat blade 75C, but provided with cylindrically-shaped channels based on an arc of a circle, which come as an extension of the orifices 71 and 72.

On the figure 10 , the spark gap still has a 75D flat blade, but this time provided with transverse striations.

We will now turn to one of the preferred applications of the invention, which is the spreading of products to be sprayed on the surface of agricultural land, for example the phytosanitary products concerned.

These applications use spreading booms, typically equipped with nozzles spaced 50 cm apart, suspended approximately 50 cm (in practice, 40 to 60 cm) above the ground, or more particularly approximately 50 cm above the crops. Known AVI nozzles, for example AVI-110-04, can be used for these applications. But they produce droplets which, at the edge of the area to be sprayed, can be blown by the wind, possibly disintegrate, and reach, for example, inhabited surfaces, which is harmful to their occupants, at least in the case of phytosanitary products. harmful to health. It is now desirable to have nozzles classified as 90% anti-drift, with a comparable flow rate and spray angle.

On the figures 11 to 13 a theoretical curve is represented, of Gaussian appearance, which represents the desired distribution in volume of spraying by the nozzle, as a function of the horizontal distance from the axis of the latter. The spacing of the dispersion on the ground is +/- 50 cm. With the theoretical curve, two nozzles 50 cm apart will produce a substantially uniform spray on the ground.

There figure 14 illustrates, in enlarged view, the exit slot of the nozzle, which is of width L.

The Applicant sought to improve the existing nozzle AVI-110-04 to have droplets less sensitive to the wind. It considered that the size of the drops produced by an AVI-type nozzle is directly dependent on the geometric parameters of the insert, in particular its slot width L. This slot width has been increased, from L = 0.9 mm at L = 1.3 mm in the case of the AVI-110-04 nozzle, in order to increase the average diameter of the drops. More generally, the slot size is increased by 40 to 50%.

It was then observed that the nozzles thus obtained presented significant priming difficulties, due to a flow of liquid of too low pressure at the outlet of the core.

The Applicant then decided to position an intermediate piece, called a "gap", between the core and the insert (assembled on the core).

The nozzles thus obtained have proven to be functional: they are primed as soon as the nozzle is started up and the flow bursts and the formation of a jet of the flat fan type is obtained.

Several models of nozzles have been assembled with spark gaps (those of the figure 7 And 10 ) and subject to droplet size measurements.

All advanced nozzle designs feature average drop diameters of around 800 µm, a gain of around 50%. This result is considered fully satisfactory.

The proposed solution is not only to reconcile distribution and size of very large drops, but to ensure that it can work at pressures of 2 bar and more while obtaining the level of drift reduction required.

It thus seems that the geometry of the spark gap has a major impact on the reformation of the jet at its exit and therefore on the operation of the nozzle and its compliance with the standard (flow rate, angle, distribution of the fluid spread).

A multitude of spark gaps, examples of which are presented in Figures 7 to 10 , was tested by varying the bursting solutions and the geometries specific to each of these solutions. The nozzles were then characterized in terms of angle, flow rate, visual observations and ground distribution of the fluid spread.

Results are given in figures 11 to 13 for three types of spark gap (those of figures 8 to 10 ), the rest of the nozzle being the same.

There figure 13 indicates the best match between the theoretical curve and the nozzle flow distribution.

However, the other distributions ( figure 11 And 12 ) are also promising, and could be used in certain cases, in particular if one deviates from the typical construction of spreading booms, in particular the inter-nozzle spacing of 50 cm.

• Le corps de buse 1 est en matière plastique,
• L'insert 3 peut être en céramique, ou bien en matière plastique,
• L'éclateur 7 est en matière plastique, mais peut aussi être en céramique,
• Le noyau Venturi 2 peut être en matière plastique ou en céramique,
• La pastille 1 est en matière plastique, ou encore en céramique.

In a particular embodiment:

• The nozzle body 1 is made of plastic material,
• The insert 3 can be made of ceramic, or else of plastic material,
• The spark gap 7 is made of plastic material, but can also be made of ceramic,
• The Venturi 2 core can be plastic or ceramic,
• The pad 1 is made of plastic material, or even ceramic.

The plastic material is typically a polyoxymethylene or POM, which is a polymer of the polyacetal family, for its ease of shaping and the associated mechanical properties, or any other equivalent plastic material, chemically compatible with the fluid to be spread.

The ceramic may be alumina, also for its ease of forming and the associated mechanical properties, or an equivalent material.

• La présence de la lame 75 qui, de par l'adhésion du fluide contre celle-ci va limiter les turbulences des jets en sortie d'éclateur d'une part, et d'autre part limiter les turbulences en sortie de buse (orifice de sortie); et
• Un écartement des flux et le dimensionnement de la lame. Le fait que le diamètre extérieur des orifices soit proche ou tangent au diamètre de l'insert peut également jouer un rôle. L'écartement de flux, la largeur de la lame et sa longueur sont adaptés pour chaque modèle de manière à maximiser l'énergie d'impaction des deux flux, et de permettre un éclatement (produit par l'insert de décharge) optimal à faible pression.

The dimensioning of the spark gap 7 is chosen with respect to two main constraints. The first constraint is control of the discharge coefficient induced by the spark gap 7, in relation to that induced by the insert 3, which involves controlling the overall surface of the two orifices of the spark gap. The second constraint is an optimal impaction of the two flows leaving the spark gap 7 in the insert 3. This optimal impaction is obtained by:

• The presence of the blade 75 which, due to the adhesion of the fluid against it, will limit the turbulence of the jets at the outlet of the spark gap on the one hand, and on the other hand limit the turbulence at the outlet of the nozzle (orifice of exit); And
• A spacing of the flows and the dimensioning of the blade. The fact that the outer diameter of the holes is close to or tangent to the diameter of the insert can also play a role. The flux gap, the width of the blade and its length are adapted for each model so as to maximize the impaction energy of the two fluxes, and to allow an optimal burst (produced by the discharge insert) at low pressure.

Control of these elements makes it possible to produce a sufficient spray angle to optimize jet overlaps at lower pressure below 3 bar, and this without the need to size the height of the outlet slot 31 of the insert 3 of noticeable way. In this way, a known problem of the state of the art is avoided in particular, which is the condition of having to make the two walls of the outlet slot parallel. Parallel walls have the effect of reducing the visible area of rupture of the ligaments forming the drops.

Claims (5)

1. Spray nozzle of the type comprising a body (1), which has a fluid inlet region and a fluid outlet orifice, the body (1) housing

   - a core (2), internally defining a passage, of increasing cross-section, in communication with the outside substantially at the point of its smallest cross-section, resulting in a Venturi effect, said smallest cross-section starting close to the fluid inlet region,

   - an insert (3), provided with an outlet slot (31) forming the outlet orifice (16) of the nozzle and defining the opening angle thereof,

   the core (2) and the insert (3) being at a distance from one another and forming between them a working chamber (23) in the body (1).

   the nozzle further comprising an additional part (7) called a splitter, housed in the working chamber (23), arranged to form an obstacle to the flow of the fluid, this splitter comprising two axial through-orifices (71, 72), each forming a fluid passage, on either side of a radial plane (73),

   characterised in that the splitter comprises, at the outlet, a blade (75), in the central plane such that the two streams passing through the orifices (71, 72) of the splitter, flow along this blade and follow its surface before combining and then impinging the surface of the outlet slot (31) of the insert, ultimately generating a flat jet.
2. Spray nozzle according to claim 1, characterised in that the blade (75B) is substantially flat.
3. Spray nozzle according to claim 2, characterised in that the flat blade (75C), is provided with channels (750) with cylindrical shape based on an arc of a circle, which extend the orifices (71, 72).
4. Spray nozzle according to one of claims 2 and 3, characterised in that the flat blade (75D) is provided with transverse ridges (755).
5. Spray nozzle according to one of claims 2 to 4, characterised in that the blade (75) is indexed parallel to the slot (31) of the insert (3).

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