EP3871792A1 - Spray nozzle with flat jet and low drift - Google Patents

Abstract

The spray nozzle is of the type comprising a body (1), which has a fluid inlet zone and a fluid outlet orifice, and which houses: - a core (2), internally defining a passage, of cross section increasing, in communication with the outside substantially at the level of its smallest cross section, hence a Venturi effect, - an insert (3), provided with an exit slot defining the opening angle of the nozzle , the core (2) and the insert (3) being distant from each other and forming between them a working chamber in the body (1). The nozzle further comprises an additional part (7) 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, and, at the outlet , a blade, in the central plane so that the two flows passed through the orifices of the spark gap circulate along this the blade and follow its surface before regrouping and then impacting the surface of the exit slot of the insert, finally generating a flat jet.

Description

The invention relates to a spray nozzle.

A spray nozzle appears externally as a case having an inlet port and an outlet port. 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, at the outlet of an outlet orifice of the nozzle, a dispersion of droplets. Such nozzles are for example used in the agricultural field to spray plant protection products on crops.

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

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

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

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

We know how to achieve this with known nozzles, but there remains a problem. It works well without wind. However, the wind can cause the spray area to overflow the surface of the agricultural land concerned. It is first of all 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 has thought that one solution would be to increase the size of the sprayed droplets, in order to reduce their sensitivity to the wind. But to obtain nozzles which have the same opening angle, with Uniformity of the cumulative droplet distribution within this angle, and 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 ejection through the outlet opening, depending on the desired spray pattern and the desired outlet jet shape.

US patent US5133502A , titled "FLAT-JET NOZZLE TO ATOMIZE LIQUIDS INTO COMPARATIVELY COARSE DROPS" or "flat jet nozzle for atomizing liquids into comparatively large drops" is 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 Applicant produces a range of so-called AVI nozzles which also arrive at median droplet sizes of around 500 micrometers.

These are so-called air injection flat jet nozzles, that is to say using an independent 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 may 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 outlet orifice of this core leads to a working chamber, which will ensure the transition with the outlet orifice of the nozzle. In order to be able to produce a flat jet, it is necessary to provide an insert provided with an exit slit. This slit forms the outlet 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 achieve super-large drop sizes, which would typically have an average size of 800 micrometers, over a range 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 objective is to overcome this limitation while maintaining the size of the nozzle.

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.In general, the proposed spray nozzle is of the type comprising a body, which has a fluid inlet region and a fluid outlet port, the body accommodating

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

the core and the insert being distant 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 axial through orifices, each forming a fluid passage, on either side of a radial plane, so that the two flows passed through the orifices of the spark gap come together and then impact the surface of the outlet slot of the insert, ultimately generating a flat jet.

From another point of view, the proposed spray nozzle is of the type comprising a case-forming body, which has an inlet port and an outlet port, and which has, on the side of the inlet port, a fluid inlet area. From the inlet to the outlet, the nozzle body may first enclose a "Venturi core", which is a generally cylindrical part, 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 the Venturi effect. The central outlet orifice of this core leads to a working chamber, which will ensure the transition with the outlet orifice of the nozzle. In order to be able to produce a flat jet, it is necessary to provide an insert fitted with a exit slot. This slit forms the outlet 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 part forms an obstacle to the flow of the liquid stream. It has 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 come together. And they will then impact the surface of the outlet slot of the insert, to finally generate a flat jet.

Preferably, a blade is provided at the outlet of the spark gap, in the central plane. On leaving the spark gap, the two flows will circulate along this blade and follow its surface by the "teapot effect" (sometimes wrongly called the Coanda effect), before regrouping to impact the surface of the outlet slit. the insert.

The spark gap blade is adjusted or "indexed" to the slot in the insert. That is to say that the plane of the blade merges substantially with the plane of the exit 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 become apparent 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 on a plane which passes through the exit slit.
• [ Fig 3 ] is an assembled view of the nozzle of the figure 1 , in section along a plane perpendicular to the plane of the exit slit.
• [ Fig 4 ] is an exploded front perspective view of the flat fan spray nozzle proposed here.
• [ Fig 5 ] is an assembled view of the nozzle of the figure 4 , in section on a plane which passes through the exit slit.
• [ Fig 6 ] is an assembled view of the nozzle of the figure 4 , in section along a plane perpendicular to the plane of the exit slit.
• [ 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 showing the performance of the nozzle with the spark gap of the figure 10 .
• [ Fig 12 ] is a graph showing the performance of the nozzle with the spark gap of the figure 9 .
• [ Fig 13 ] is a graph showing 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 it is difficult to convey other than by the drawing. Consequently, the drawings form an integral part of the description and can therefore not only serve to better understand the present invention, but also contribute to its definition, if necessary.

The figures 1 to 3 show a known flat fan spray nozzle, such as 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.

A noter que le mot alésage vise ici un élément femelle d'un ajustement circulaire, quel que soit son procédé d'usinage. En effet, les pièces n'étant pas métalliques, mais plutôt en matière synthétique ou en céramique, elle ne sont pas usinées par l'alésage classique pour les métaux.The nozzle comprises a body 1 which internally defines a hollow case, of generally cylindrical shape, with:

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

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

At the level of the bores 11 and 12 is inserted a Venturi core 2, which begins with a cover 20, resting on the flange 10. The Venturi core 2 internally comprises a first cylindrical volume right 21, followed by a conical volume 22. This defines an internal passage of increasing internal cross section.

The volume 21 is crossed by radial passages 25A and 25 B, which communicate by means of an annular recess 26 with external air inlets 18 provided through the wall of the body 1.

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

In core 2, a Venturi effect occurs, due to the nozzle formed by the calibration pellet 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 seals between the annular recess 26 and the downstream side of the core 2.

Lower 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 figure 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 near 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 and 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 figures 4 to 6 .

This nozzle has the same general structure as that of 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 here called a spark gap.

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

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

On leaving 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 a “teapot effect” in order to regroup. The two flows thus grouped together will impact the outlet surface of the insert 3 and generate a flat jet of the “flat fan” type.

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 pellet 29 of circular section then, directed by the pressure, it moves in 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 point (consequence of its acceleration), allows the suction of the outside air by the Venturi effect and its mixture 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 strong drop in the energy of the flow, which will be by pressure directed towards the two outlet openings 71 and 72 of the spark gap. At the outlet of the spark gap, the two flows will circulate along the 75 blade and follow its surface by “teapot effect” to regroup. The two flows thus grouped together will impact the outlet surface 31 of the insert 3 and generate a flat jet of the “flat fan” type at the 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 does not have a 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 cylindrical-shaped channels based on an arc of a circle, which are 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 ridges.

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 fitted with nozzles 50 cm apart, suspended approximately 50 cm (in practice, 40 to 60 cm) above the ground, or more particularly approximately 50 cm above the ground. cultures. 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 pushed 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 desired to have nozzles classified as 90% anti-drift, with comparable flow rate and spray angle.

On the figures 11 to 13 is shown a theoretical curve, 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.

The figure 14 illustrates, in enlarged view, the outlet slit of the nozzle, which is of width L.

The Applicant has 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 slit width L. This slit width has been increased from L = 0.9 mm to L = 1.3 mm in the case of the AVI-110-04 nozzle, in order to enlarge the average diameter of the drops. More generally, the slot size is increased from 40 to 50%.

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

The Applicant then decided to position an intermediate part, called a “spark gap”, between the core and the insert (assembled on the core).

The nozzles thus obtained have proved to be functional: their priming takes place as soon as the nozzle is started up and the flow bursts and the formation of a flat fan-type jet is obtained.

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

All advanced nozzle models have average droplet diameters of around 800 µm, a gain of around 50%. This result is considered to be 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 required level of drift reduction.

It thus seems that the geometry of the spark gap has a preponderant impact on the reforming of the jet at its outlet and therefore on the operation of the nozzle and on its conformity 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 burst solutions and the geometries specific to each of these solutions. The nozzles were then characterized in terms of angle, flow rate, visual observations and distribution on the ground of the fluid applied.

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.

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

However, the other distributions ( figures 11 and 12 ) are also promising, and could be useful in certain cases, in particular if we deviate from the typical construction of the 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,
• The insert 3 can be ceramic, or else plastic,
• The spark gap 7 is made of plastic, but can also be made of ceramic,
• The Venturi 2 core can be made of plastic or ceramic,
• The pellet 1 is made of plastic, or even of 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 shaping 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 spark gap 7, in relation to that induced by insert 3, which involves controlling the overall surface area 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, by 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 flow spacing and sizing of the blade. The fact that the outside diameter of the orifices is close to or tangent to the diameter of the insert can also play a role. The flow spacing, the width of the blade and its length are adapted for each model in order to maximize the impaction energy of the two flows, and to allow an optimal bursting (produced by the discharge insert) at low pressure.

The mastery of these elements makes it possible to produce a spray angle sufficient to optimize the spray 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 problem known from the state of the art, which is the condition of having to make the two walls of the exit slot parallel, is avoided in particular. Parallel walls have the effect of reducing the visible area of rupture of the ligaments forming the drops.

Claims (5)

A spray nozzle of the type comprising a body (1), which has a fluid inlet region and a fluid outlet port, the body (1) accommodating - a core (2), internally defining a passage, of increasing cross section, in communication with the outside substantially at the level of its smallest cross section, hence a Venturi effect, said smallest cross section starting nearby of the fluid inlet area, - an insert (3), provided with an outlet slit (31) forming the outlet orifice (16) of the nozzle and defining the opening angle of the latter, the core (2) and the insert (3) being distant from each other and forming between them a working chamber (23) in the body (1),
characterized in that the nozzle further comprises an additional part (7) called a spark gap, housed in the working chamber (23), arranged to form an obstacle to the flow of the fluid, this spark gap comprising two axial through orifices (71, 72), each forming a fluid passage, on either side of a radial plane (73), and, at the outlet, a blade (75), in the central plane so that the two flows passing through the orifices ( 71, 72) of the spark gap circulate along this blade and follow its surface before regrouping and then impacting the surface of the outlet slot (31) of the insert, ultimately generating a flat jet. Spray nozzle according to claim 1, characterized in that the blade (75B) is substantially flat. Spray nozzle according to Claim 2, characterized in that the flat blade (75C) is provided with channels (750) in cylindrical shape based on an arc of a circle, which extend from the orifices (71, 72). Spray nozzle according to one of claims 2 and 3, characterized in that the flat blade (75D) is provided with transverse ridges (755). Spray nozzle according to one of claims 2 to 4, characterized in that the blade (75) is indexed parallel to the slot (31) of the insert (3).

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