EP0556121B1 - Nozzle for liquid spraying - Google Patents

Description

The present invention relates to a liquid spray nozzle.

A liquid spray nozzle is, in general, a part comprising an internal vacuum, called a turbulence chamber, connected on one side to a power source, and the wall opposite to the inlet is generally of hemispherical shape. In the generally hemispherical end wall of the turbulence chamber, there opens an outlet orifice, which, at the point where it opens into the turbulence chamber, has a much smaller section, not more than half and preferably less than a fifth of the cross section of the turbulence chamber. In general, the outlet opening widens outward away from the turbulence chamber, but this is not mandatory.

Thanks to this particular shape, the liquid passing through the nozzle, subjected to an abrupt succession of compression and depression, bursts into multiple droplets. The outlet orifice can be of circular section, or of flattened section, depending on the shape of the jet of droplets which it is desired to obtain.

The projection nozzles, which are intended to give a higher speed to a jet of liquid, without however causing it to burst into droplets, have a markedly different shape, with a gradual narrowing, possibly followed by an equally gradual widening. The progressiveness of the section variations results in an increase in the speed of the jet without dispersing it.

The size of the droplets formed at the outlet of a spray nozzle of given dimensions and shape depends, among other things, on the pressure of the liquid in the turbulence chamber.

With conventional spray nozzles, for a given nozzle and a liquid, there is a correlation between the flow rate of the liquid and the pressure thereof, and therefore the size of the droplets. In many fields of technology, we would like to be able to vary these parameters independently of each other. For example, it may be desired to vary the flow rate while keeping the size of the droplets constant. This is the case, for example, in the agricultural technique, where the size of the droplets conditions the effectiveness of treatments with phytosanitary products, but where the quantity of products deposited per unit area must remain constant, which requires that the nozzle flow rate is adjusted to the speed of movement of the carrier. This is also the case in many other fields of the technique, for example the humidification of papers or fabrics according to their water content inside a processing machine. In other cases, one may wish to vary the size of the droplets, for example to modify their cooling effect, without being obliged to simultaneously modify the flow rate.

It would be desirable to be able to have a nozzle which makes it possible to act on the size of the droplets and the flow of liquid, independently of one another.

Of course, such a nozzle must be inexpensive, robust and easy to maintain.

We have proposed, see for example US-A-2,959,359, GB-A-951,589, DE-A-17,430, US-A-3,776,470, devices for modifying the shape of liquid jet projection nozzles , and therefore their performance, but it has not been written or suggested to apply similar techniques to spray nozzles. The reason is undoubtedly that it is more difficult to deform a part containing a turbulence chamber with a hemispherical wall, followed by a narrow passage orifice, than a conventional jet projection nozzle. Indeed, a conventional jet projection nozzle can be made of a thin-walled piece, easy to deform. On the contrary, a projection nozzle necessarily consists of a solid part, in which the projection chamber and the outlet orifice are hollowed out, and it undoubtedly seemed impossible at the time to deform such a part in a controlled manner .

In document DE-A-2,439,226, a nozzle has been proposed the end of which is made up of a block of elastic material, inside which the turbulence chamber and the outlet orifice are hollowed out. The object of this provision is not to modify at will the shape of the nozzle, but to allow, by deformation of the orifice, the escape of a foreign solid which would block the nozzle, the latter then resuming its usual form.

The object of the invention is to provide a liquid spray nozzle, the performance of which can be varied at will, within certain limits, that is to say the size of the droplets for a given flow rate, or vice versa. flow without changing the size of the droplets.

To obtain this result, the invention provides a liquid spray nozzle, comprising a body having an internal cavity and carrying a nozzle composed of a solid part made of elastically deformable material, this part having a turbulence chamber connected to the internal cavity. of the body, and an axial outlet orifice, opening into the turbulence chamber through an opening of section at most equal to half that of the turbulence chamber and with an abrupt variation in the section of passage of the liquid, characterized in that that a movable constraint piece is provided, the displacement of which acts to deform the end piece, and means for preventing the displacement of the constraint piece from substantially deforming the turbulence chamber.

According to a simple embodiment, to prevent deformation of the turbulence chamber, the constraint part moves substantially transversely by acting on the part of the endpiece which contains the outlet orifice.

This embodiment has the advantage of its simplicity, when applied to a spray nozzle whose outlet orifice has a flattened section: it nevertheless has, even in this case, the disadvantage of modifying the shape of the outlet.

According to a more complicated embodiment, but of more general scope, the constraint part is frustoconical and moves axially by acting on the outlet end of the end piece, and the latter has a peripheral groove in the vicinity of the level of the connecting passage the turbulence chamber at the outlet orifice, this groove being of calculated shape and dimension so that the deformation imposed by the constraint part is not transmitted substantially to the turbulence chamber.

The use of a deformable nozzle brings adjustment possibilities which had not been exploited until now, and makes it possible to achieve the desired goal, for example by increasing the section of the orifice when the flow rate must be increased, or by decreasing it when it must be reduced, the pressure upstream of the nozzle remaining substantially constant, or alternatively by varying the supply pressure and the section of the orifice in order to vary the size of the droplets to constant flow, or by varying the flow, the pressure and the section of the orifice according to another pre-established law, according to the desired result.

In the simplest way, the constraint part is a hollow part, having an interior surface converging towards the outside, which can move axially to exert on the end piece a radial compressive force tending to reduce the section of the orifice, a displacement of the stress piece in the opposite direction, releasing the compressive force, which tends to widen the orifice to the dimension it has at rest.

It may however be advantageous to provide that the constraint part engages the end piece and is capable of exerting on the end piece, when it moves, a radial tensile force tending to increase the section of the orifice.

Advantageously, if the orifice is of circular section at rest, the internal surface of the constraint part has a shape of revolution. It can also have an oval section, so as to modify the shape of the orifice, and therefore of the jet of droplets which it produces. If the orifice is in the form of a slot, the part of the internal surface of the constraint part which cooperates with the end piece is flattened in cross section.

According to a modality which can be combined with the previous one, the constraint part can slide axially along the body while being immobilized in rotation, and a micrometric screw device ensures its sliding movement.

According to an advantageous embodiment, a pressure sensor disposed in the supply circuit of the device is connected to a control member able to control the movements of the stress piece in response to signals from the pressure sensor.

• Figure 1 est une coupe axiale d'une buse conforme à l'invention.
• Figure 2 est un schéma d'ensemble d'une installation de pulvérisation comprenant des buses conformes à l'invention.
• Figure 3 est un schéma d'une autre installation conforme à l'invention.
• Figure 4 est une vue, prise suivant l'axe, d'une variante de l'embout de la figure 1.
• Figure 5 est une coupe selon la ligne V-V de la figure 4.
• Figure 6 montre une autre forme de réalisation de l'embout de la figure 4.

The invention will be explained in more detail with the aid of practical examples illustrated with the aid of the figures, among which:

• Figure 1 is an axial section of a nozzle according to the invention.
• Figure 2 is an overall diagram of a spraying installation comprising nozzles according to the invention.
• Figure 3 is a diagram of another installation according to the invention.
• Figure 4 is a view, taken along the axis, of a variant of the nozzle of Figure 1.
• Figure 5 is a section along the line VV in Figure 4.
• Figure 6 shows another embodiment of the nozzle of Figure 4.

The nozzle comprises a body 1 which has an axial passage 2 for the liquid. At one of its ends, means are provided for connection with an intake manifold.

The axial passage 2 ends, at the opposite end, in a turbulence chamber 3, of hemispherical shape, provided in an end piece 4 secured to the body 1, and made of a different material, which allows a deformation of this end piece at the level of the output section.

It will be noted that, as a variant, the end piece 4 can also be in one piece with the body 1, the deformability then results only from the shape and the thickness of the end piece.

The end piece has at its end an orifice 5 in the form of a slot, and more specifically a dihedral opening towards the outside, the orifice 5 opens, at its end opposite to the outside, into the turbulence chamber 3. The elastomer from which the end piece 4 is made gives it flexibility in terms of deformation, making it possible to obtain a variation in the cross-section of the liquid passage, and ensures that it returns to its initial shape (position in which the end piece 4 practically does not undergo any deformation).

A constraint part 6 is driven in a translational movement relative to the body 1 and the end piece 4 without rotation possible thanks to two bosses and grooves 1A. This keeps the slot 5 and a slot 7 of the constraint part 6 aligned, and consequently the possible passage of the jet when the nozzle is under pressure.

A peripheral groove 8 is hollowed out in the outer surface of the endpiece 4 in the vicinity of a plane perpendicular to the axis which passes through the zone where the orifice 5 opens into the turbulence chamber. The shape and position of the groove 8 are such that the deformation of the end piece 4 resulting from a displacement of the stress piece occurs essentially in the part of the end piece which is located between the groove 8 and the end of the end piece, and that the turbulence chamber does not is not distorted.

The shape of the constraint part 6 can vary depending, in particular, on the shape of the end piece 4 and its orifice 5. the part of the part 6 which slides on the body 1 has a shape adapted to it, and therefore cylindrical in general. The part which cooperates with the end piece may have an inner surface with a more or less flattened elliptical section, or else a circular section. The nozzle 4, in each case, will have a shape adapted to preserve substantially the flattened shape of the jet of droplets which results from the elongated shape of the orifice 5. In the case where the orifice 5 is of circular section, it is clear that the constraint part will advantageously have a form of revolution.

A spring 9, mounted between the body 1 and the conical part 6, exerts on the latter an axial force tending to repel it. This spring thus prevents the translation of the part 6 caused accidentally, and which would modify the pressure instantaneously at a nozzle.

On the other hand, the desired movement on this part will be obtained precisely by means of a nut 10. In fact, this nut is driven by a movement of rotation and translation, provided by a micrometric thread 1B between the nut and the body 1. This nut is integral with a pinion 11 by means of a screw 12.

The pinion 11 has the function of ensuring the rotation of the nut and of carrying out the adjustment making it possible to adjust the pressure.

The rotation of the pinion 11 is, for its part, ensured by another pinion 13 driven by a motor 14.

The motor 14 is advantageously, but not necessarily, a stepping electric motor, in the in the case of automated or remote control. In a simpler embodiment, it can be replaced by a manual control, with means for locating the angular position of the pinion 11.

FIG. 2 schematically shows an installation equipped with nozzles according to the invention and intended to supply droplets of constant size from a positive displacement pump whose flow rate can vary. Typically, such a problem arises in the treatment of vegetation using phytosanitary products, when the installation is carried by a vehicle which can have a variable speed, the flow rate of the pump varying with the speed of the vehicle for spray a constant amount of product per unit area. However, the diagram in FIG. 2 can be suitable for installations in many other technical fields, with adaptations which are within the reach of those skilled in the art.

A boom 20 carries a series of nozzles 21 in accordance with the invention, each equipped with a motor 14. The supply circuit of the boom 20 comprises a reservoir of product to be sprayed 22, a pump 23, the useful flow of which is regulated by a control system 24 itself controlled by the movement of the carrier vehicle. A pipe 25 connects the spray pump 23 to the boom 20. A pressure sensor 26, inserted in the pipe 25, measures the pressure in the circuit.

It will be noted that the reference 26 can designate, instead of a pressure sensor, a flow sensor, or even an assembly formed by a pressure sensor and a flow sensor.

The sensor 26 is connected to a control unit 27 in which the measured value is recorded, which is that of the pressure in the example described here. The face of the housing is equipped with a button 28 with which the desired working value is displayed. If the measured value is greater than the desired working value, the difference between these two values is compensated by electronics which, by means of pulses, act on the motor 14, which is a stepping motor. The motor, turning in steps, therefore acts on the conical tip with great precision, and thus allows the tip 4 to open, thereby obtaining an adjustment of the measured value relative to the desired value.

Likewise, if the measured value is lower than the desired working pressure, the difference will be compensated so as to act on the constraint part 6, which will close the end piece 4 a little more, hence a value automatically set to the value desired.

In the example described, an increase or decrease in pressure is the consequence of a variation in the speed of advance of the device. We are thus sure to have a volumetric system at constant pressure whatever this forward speed, or obeying any other law chosen, depending on this speed.

If the sensor 26 is a flow sensor, or a set of flow and pressure sensors, the description of the above operation remains valid provided that the pressure is replaced therein by the flow or by a function chosen at pressure-flow couple advance.

While we are trying, in the example described, to obtain droplets of constant size, it can be equipped, possibly by means of a remote control, to vary the size of the drops at will. It is known that, for example when it is desired to form a mist, it is advantageous to be able to vary, depending on the circumstances, the size of the droplets produced. In this case, the installation can also be represented by the diagram in FIG. 2, provided that the reference 23 designates a pumping system with stabilized outlet pressure, and the reference 26 a flow sensor.

Figure 3 shows another installation diagram, intended to supply a machine with a product whose the humidity must be continuously adjusted to a certain value.

The product to be treated 30 is poured from a hopper 31 onto a conveyor belt 32. An equalizing device 33 brings the layer of product on the belt 32 to a constant thickness.

A gamma ray probe 34 determines the humidity level of the incoming product. A temperature probe 35 likewise determines the temperature of the product. The signals from the probes 34 and 35 are sent to a computer 36. An adjustable nozzle 37, according to the invention, is connected to a water tank 38 by a pump 39. The computer 36 permanently controls the pump 39 and the nozzle 37 for continuously adjusting both the water flow and the droplet size as a function of the humidity and the temperature of the product, the droplets being larger if the product is hotter. The probes 34 and 35 can also be placed after the nozzle, in the direction of movement of the product.

In the example which has been described, the opening and the closing of the orifice is made only by elasticity, a displacement of the movable part 6 until bringing it out of contact with the end piece 4 results in l maximum opening of the slot. It is however possible to provide that the moving part can widen, still in an elastic manner, the dimensions of the orifice.

According to the variant of FIGS. 4 and 5, the end piece 40, made of elastic material, has longitudinal grooves 41 with dovetail section, which converge towards the axis. A rigid constraint piece 42, which can slide axially around the end piece 41 has longitudinal dovetail ribs 43, projecting radially towards the axis, and which penetrate into the grooves 41. It can be seen that a displacement longitudinal of the part 42 increases the section of the orifice 44 of the endpiece relative to the section which it has at rest.

The words "dovetailed" must be understood here in a very broad sense, they apply to any groove whose bottom is wider than the entry, and to any rib of suitable shape.

Figure 6, similar to Figure 4, corresponds to an arrangement where the orifice 44 of the nozzle is in the form of a slot instead of being of circular section. There are provided only two dovetail grooves 41, diametrically opposite in the direction perpendicular to the elongation of the slot 44, and two corresponding ribs 43. The ribs 43 tend, by deviating, to widen the slot in it giving the form shown in phantom.

It can be observed that the grooves 41 could also be placed in the direction of the elongation of the slot 44. In this case, the spacing of the ribs tends to close the slot.

It will be understood that the ribs can be carried by the end piece and the grooves provided in the constraint part, without this changing the operation.

The solution of FIGS. 4 to 6 makes the material of the end piece 40 work by deformation on either side of a rest position, hence a lower fatigue than in the case of FIG. 1. On the other hand, machining is more expensive. The choice between solutions is therefore essentially a question of price.

Claims (11)

1. A liquid spraying nozzle, comprising a body (1) having an internal cavity (2) and carrying an endpiece (4) composed of a solid component made from an elastically deformable material, this component having a swirl chamber (3), connected to the internal cavity of the body, and an axial outlet orifice (5), opening out into the swirl chamber via a passage of cross-section which is at most equal to half that of the swirl chamber and with a sudden variation of the cross-section of the passage for the liquid,
      characterized in that:

   - a mobile restraining component (6) is provided, whose displacement acts in order to deform the endpiece,

   - and in that means are provided for preventing the displacement of the restraining component from substantially deforming the swirl chamber.
2. The nozzle of Claim 1, wherein, in order to prevent the deformation of the swirl chamber (3), the restraining component (6) can be displaced substantially transversely by acting on the part of the endpiece which contains the outlet orifice.
3. The nozzle of Claim 1, wherein the restraining component (6) is frustoconical and can move axially acting on the outlet end of the endpiece, characterized in that the endpiece has a peripheral groove (8) in the vicinity of the level of the passage connecting the swirl chamber to the outlet orifice, this groove being of calculated shape and dimensions so that the deformation imposed by the restraining component is not substantially transmitted to the swirl chamber (3).
4. The nozzle of Claim 3, wherein the orifice (5) is of circular cross-section at rest, characterized in that the internal surface of the restraining component has a shape of revolution.
5. The nozzle of Claim 3, wherein the orifice (5) has a circular cross-section at rest, characterized in that the internal surface of the restraining component has an oval cross-section.
6. The nozzle of Claim 3, wherein the orifice (5) is slit shaped, characterized in that the part of the internal surface of the restraining component which interacts with the endpiece (4) is flattened in transverse section.
7. The nozzle of Claim 2, characterized in that the restraining component (6) comes into engagement with the endpiece and is able to exert on the endpiece, when it moves, a radial traction force tending to increase the cross-section of the orifice.
8. The nozzle of Claim 1, wherein the restraining component (6) may slide axially along the body by being rotationally immobilised, and in that a micrometer screw device (11) provides its sliding displacement.
9. A spraying installation equipped with at least a nozzle (21) according to anyone of claims 1-8, characterized in that it comprises a pressure sensor (26) arranged in the feed circuit (20, 21-25) of the device, and connected to control electronics able to control the displacements of the restraining component (6) in response to the signals from the pressure sensor (26).
10. A spraying installation equipped with at least a nozzle (21), according to anyone of claims 1-8, characterized in that it comprises a flowrate sensor (26) arranged in the feed circuit (20, 21-25) of the device, and connected to control electronics able to control the displacements of the restraining component (6) in response to the signals from the flowrate sensor (26).
11. A spraying installation intended continuously to adjust the wetness of a product, and equipped with a nozzle according to anyone of claims 1-8, characterized in that it comprises a sensor (34) sensitive to the wetness of the product and connected to control electronics able to control the displacements of the restraining component (6) in response to the signals of the said sensor.

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