EP3479906A1 - Spray nozzle with pre-atomisation narrowing, and spray head and spraying device comprising such a nozzle - Google Patents

Abstract

This spray nozzle (34) for spraying a product defines a passage (60) for the circulation of the product through the nozzle (34), said passage (60) opening out of the nozzle ( 34), at an upstream end (56) thereof, through a wide connection port (62), and at a downstream end (58) of the nozzle (34) through a narrow spray orifice (64) to spray the product. This passage (60) has, between the connection orifice (62) and the spray orifice (64), at least one pre-atomization shrink (66) capable of atomizing the product, followed by an enlargement (68). ) downstream of said pre-atomization narrowing (66).

Description

The present invention relates to a spray nozzle for spraying a product, of the type defining a passage for the circulation of the product through the nozzle, said passage emerging outside the nozzle, at an upstream end thereof by a wide connection orifice, and at a downstream end of the nozzle by a narrow spray orifice, suitable for spraying the product.

The invention also relates to a spray head for a product spraying device, of the type comprising an annular ring having a central orifice, and a spraying nozzle of the aforementioned type housed in said central orifice, substantially coaxially with the annular ring.

The invention also relates to a spraying installation of the type comprising a source of product to be sprayed and a spraying head of the aforementioned type, the source of the product to be sprayed being fluidly connected to the connection orifice of the spray nozzle.

• alimentation d'une buse de pulvérisation du type précité, par son orifice de raccordement, avec le produit de revêtement,
• première atomisation du produit de revêtement lors de la traversée, par ledit produit de revêtement, du rétrécissement de pré-atomisation, et
• deuxième atomisation du produit de revêtement lors de la traversée, par ledit produit de revêtement, de l'orifice de pulvérisation.

The invention finally relates to a method of spraying a coating product, of the type comprising the following steps:

• supplying a spray nozzle of the aforementioned type, through its connection orifice, with the coating product,
• first atomizing the coating product during the passage, by said coating product, the pre-atomization shrinkage, and
• second atomizing the coating product during the passage, by said coating product, the spray orifice.

Spraying facilities of the aforementioned type are known. They are intended to ensure the bursting of a coating product in fine droplets so as to coat a large area with a small amount of product. For this purpose, the coating product is supplied under pressure by a source and conducted under pressure to a spray nozzle.

Several competing solutions exist to perform this spraying.

We first mention pneumatic spraying. According to this solution, the coating product is supplied by the source with an overpressure with respect to the very low atmospheric pressure, typically between 0.5 and 1.5 bar. Compressed air is blown at the outlet of the nozzle and it is this compressed air that atomizes the liquid film ejected by the nozzle. This solution has the advantage of having a very high quality finish. It is also relatively cheap. However, it has the disadvantage of have a low transfer rate, a large amount of the coating product being dispersed in the environment without reaching the surface to be coated.

Another solution consists of airless spraying. According to this solution, the coating product is supplied by the source at very high pressure, typically at a pressure of between 160 and 300 bar. It is then the narrowness of the spray orifice that causes the product to burst. There is no air involved. This solution has the advantage of an excellent transfer rate. However, it has the disadvantage of requiring pumping equipment capable of providing the coating product at very high pressure, and involves a very large consumption of compressed air for the supply of these pumps. This makes it an expensive technology.

A final solution is the mixed spray. According to this technology, the coating product is supplied by the high pressure source, typically at a pressure of between 50 and 150 bar. As in the case of airless spraying, it is the narrowness of the spray orifice that causes the product to burst. This spraying is however not optimal, given the relatively low pressure at which the coating product is supplied by the source. To improve the atomization of the product, compressed air is blown at the outlet of the nozzle, as in the pneumatic spraying technology. This solution makes it possible to obtain substantially the same quality of finish as with airless spraying, with a good transfer rate, being more economical since the coating product is supplied at a lower pressure. However, it has the disadvantage of remaining relatively expensive compared to the pneumatic spray solution.

It is an object of the invention to reduce the pressure at which the coating product is to be provided when working in airless or mixed spray, while maintaining the transfer rates and finishing qualities usually obtained with these products. technologies.

For this purpose, the subject of the invention is a spray nozzle of the aforementioned type, in which the passageway has, between the connection orifice and the spray orifice, at least one pre-atomization shrinkage capable of atomizing the product. followed by broadening downstream of said pre-atomization shrinkage.

• la buse de pulvérisation comprend un corps tubulaire orienté suivant une direction axiale et définissant intérieurement un conduit traversant débouchant dans une première extrémité axiale du corps par une première ouverture constituant l'orifice de raccordement, la buse de pulvérisation comprenant en outre un insert de pré-atomisation, logé dans ledit conduit traversant, définissant le rétrécissement de pré-atomisation ;
• le rétrécissement de pré-atomisation est formé par une cavité hémisphérique fendue par une fente ;
• la buse de pulvérisation comprend un organe de pulvérisation définissant l'orifice de pulvérisation, ledit organe de pulvérisation comprenant, de l'amont vers l'aval, une cavité de section transversale décroissante vers l'aval, suivie d'un canal de section transversale sensiblement constante raccordant fluidiquement la cavité à l'orifice de pulvérisation, le rétrécissement de pré-atomisation débouchant dans ladite cavité ;
• l'insert de pré-atomisation comprend un socle et, faisant saillie axialement depuis le socle, un doigt présentant une extrémité libre opposée au socle, ladite extrémité libre définissant le rétrécissement de pré-atomisation, le doigt étant logé sensiblement intégralement dans la cavité de l'organe de pulvérisation ;
• le socle présente une section transversale complémentaire à une section transversale du conduit ;
• l'organe de pulvérisation présente une face amont dans laquelle débouche la cavité, ladite face amont définissant un épaulement annulaire autour de la cavité, le socle étant en appui contre ledit épaulement annulaire ;
• le rétrécissement de pré-atomisation débouche à une distance du canal inférieure à la moitié de la longueur axiale de la cavité ;
• l'organe de pulvérisation est constitué par un insert de pulvérisation logé au moins en partie dans le conduit ; et
• le rapport du diamètre de l'orifice de pulvérisation sur le diamètre du rétrécissement de pré-atomisation est compris entre 0,5 et 0,8.

According to particular embodiments of the invention, the spray nozzle also has one or more of the following characteristics, taken separately or in any combination (s) technically possible (s):

• the spray nozzle comprises a tubular body oriented in an axial direction and defining internally a through duct opening into a first axial end of the body through a first opening constituting the orifice of connection, the spray nozzle further comprising a pre-atomization insert, housed in said through conduit, defining the pre-atomization narrowing;
• the pre-atomization shrinkage is formed by a hemispherical cavity slit by a slit;
• the spray nozzle comprises a spray member defining the spray orifice, said spray member comprising, from upstream to downstream, a cavity of decreasing cross-section downstream, followed by a cross-sectional channel substantially constant fluidically connecting the cavity to the spray orifice, the pre-atomization narrowing opening into said cavity;
• the pre-atomization insert comprises a base and, projecting axially from the base, a finger having a free end opposite the base, said free end defining the pre-atomization narrowing, the finger being housed substantially integrally in the cavity of the spraying member;
• the base has a cross section complementary to a cross section of the conduit;
• the sputtering member has an upstream face into which the cavity opens, said upstream face defining an annular shoulder around the cavity, the base being in abutment against said annular shoulder;
• the pre-atomization shrinkage opens at a distance from the channel less than half the axial length of the cavity;
• the spray member is constituted by a spray insert housed at least partly in the conduit; and
• the ratio of the diameter of the spray orifice to the diameter of the pre-atomization shrinkage is between 0.5 and 0.8.

The invention also relates to a spray head of the aforementioned type, wherein the spray nozzle is constituted by a nozzle as defined above.

According to a particular embodiment of the invention, the spray head also has the following characteristic:
the ring has an upstream end connected to a body of the spraying device and a downstream face facing away from said upstream end, and defines at least one rectilinear air channel intended to receive a compressed gas and opening into the downstream face, said air channel being oriented in a convergent direction.

The invention further relates to a spray gun comprising a spray head as defined above.

The invention further relates to a spraying installation of the aforementioned type, wherein the spray head is constituted by a head as defined above.

• la source de produit à pulvériser est apte à fournir le produit à pulvériser avec une pression supérieure 20 bars, avantageusement supérieure à 100 bars, et
• la source de produit à pulvériser est apte à fournir le produit à pulvériser avec une pression comprise entre 20 et 300 bars, avantageusement comprise entre 20 et 150 bars.

According to particular embodiments of the invention, the spraying installation also has one or more of the following characteristics, taken in isolation or according to any combination (s) technically possible (s):

• the source of the product to be sprayed is capable of supplying the product to be sprayed with a pressure greater than 20 bars, advantageously greater than 100 bars, and
• the source of the product to be sprayed is capable of supplying the product to be sprayed with a pressure of between 20 and 300 bars, advantageously between 20 and 150 bars.

The invention further relates to a spraying method of the aforementioned type, wherein the spray nozzle is constituted by a nozzle as defined above.

• le produit de revêtement est fourni à la buse à une pression supérieure à 20 bars, avantageusement supérieure 100 bars, et
• le produit de revêtement est fourni à la buse à une pression comprise entre 20 et 300 bars, avantageusement comprise entre 20 et 150 bars.

According to particular embodiments of the invention, the sputtering method also has one or more of the following characteristics, taken alone or according to any combination (s) technically possible (s):

• the coating product is supplied to the nozzle at a pressure greater than 20 bar, preferably greater than 100 bar, and
• the coating product is supplied to the nozzle at a pressure of between 20 and 300 bar, advantageously between 20 and 150 bar.

• la Figure 1 est une vue schématique d'une installation de pulvérisation selon l'invention,
• la Figure 2 est une vue éclatée et en perspective, de trois-quarts avant, d'un applicateur de l'installation de pulvérisation de la Figure 1,
• la Figure 3 est une vue en perspective, de trois-quarts avant, d'une tête de pulvérisation de l'applicateur de la Figure 2,
• la Figure 4 est une vue en coupe longitudinale de la tête de pulvérisation de la Figure 3, le plan de coupe étant matérialisé par le plan IV-IV sur la Figure 3,
• la Figure 5 est une vue en coupe longitudinale d'une buse de pulvérisation de la tête de pulvérisation de la Figure 3,
• la Figure 6 est une vue en perspective d'un insert de pré-atomisation de la buse de pulvérisation de la Figure 5,
• la Figure 7 est une vue en perspective d'une variante de l'insert de pré-atomisation de la Figure 6, et
• la Figure 8 est une vue en coupe longitudinale de l'insert de pré-atomisation de la Figure 7.

Other features and advantages of the invention will appear on reading the description which follows, given solely by way of example and with reference to the drawings, in which:

• the Figure 1 is a schematic view of a spraying installation according to the invention,
• the Figure 2 is an exploded and perspective view, three-quarters front, of an applicator of the spray installation of the Figure 1 ,
• the Figure 3 is a perspective view, three-quarters front, of a spray head of the applicator of the Figure 2 ,
• the Figure 4 is a longitudinal sectional view of the spray head of the Figure 3 , the cutting plane being materialized by the plane IV-IV on the Figure 3 ,
• the Figure 5 is a longitudinal sectional view of a spray nozzle of the spray head of the Figure 3 ,
• the Figure 6 is a perspective view of a pre-atomization insert of the spray nozzle of the Figure 5 ,
• the Figure 7 is a perspective view of a variant of the pre-atomization insert of the Figure 6 , and
• the Figure 8 is a longitudinal sectional view of the pre-atomization insert of the Figure 7 .

The spraying installation 10 shown on the Figure 1 comprises, in known manner, a source 12 of coating material, a supply 13 of compressed gas, an applicator 14 for applying the coating product to a surface to be coated, a first fluidic connection 15 fluidly connecting the source 12 to the applicator 14, and a second fluidic connection 16 fluidly connecting the supply 13 to the applicator 14. The coating product is advantageously constituted by a fluid, for example by a paint, a dye, a glue, or a putty having typically a viscosity of between 20mPa.s and 500mPa.s

In the following, the terms "upstream" and "downstream" orientation refer to the direction of flow of the coating product in the installation 10, said coating product flowing from upstream to downstream. .

The source 12 is adapted to supply the coating product at an outlet pressure of between 20 and 300 bar, in particular between 20 and 150 bar and advantageously between 20 and 80 bar. For this purpose, the source 12 typically comprises a coating product reservoir (not shown), and a pump (not shown) for pumping the coating material into the reservoir and discharging it to the fluidic connection 16 at the outlet pressure.

The feed 13 is adapted to supply a gas, typically air, compressed, preferably at a pressure between 0.2 bar and 6 bar, preferably between 0.2 bar and 2 bar. For this purpose, the supply 13 is for example constituted by an air compressor.

The first fluidic connection 15 fluidly connects an outlet 17 of the source 12 to a first inlet 18 of the applicator 14. It is typically constituted by a flexible pipe.

The second fluidic connection 16 fluidly connects an outlet 19 of the supply 13 to a second inlet 20 of the applicator 14. It is typically constituted by a flexible pipe.

With reference to the Figure 2 the applicator 14 comprises a body 21 and a spray head 22 mounted on the body 20.

The body 21 carries the first inlet 18 of the applicator 14 and comprises a tube 23 internally defining a duct (not shown) fluidly connecting said inlet 18 to an outlet 24 of the coating product out of the body 21, said orifice 24 defining the end of the tube 23.

The body 21 also carries the second inlet 20 and defines internally a cavity (not shown) fluidly connecting said inlet 20 to an outlet port 26 of compressed gas out of the body 21. The orifice 26 is, in the example shown, arranged concentrically around the orifice 24.

In the example shown, the applicator 14 is constituted by a spray gun. The body 21 is shaped like a stick and carries a trigger 28 adapted to actuate a valve (not shown) and to be moved relative to the body 21 between a position at rest, in which the valve closes the fluid connections between the inputs 18 , And the outlet ports 24, 26, and an actuated position, in which the valve releases said fluidic connections.

The spray gun 14 is typically a manual spray gun. Alternatively, the spray gun 14 is an automatic spray gun.

With reference to the Figure 3 , the spray head 22 comprises an annular ring 30 having a central orifice 32, and a spray nozzle 34 housed in said central orifice 32.

The annular ring 30 is centered on an axis A-A '. It comprises an annular body defining the central orifice and a skirt mounted rotatably about the axis A-A 'relative to the body.

As visible on the Figure 4 , the body 36 has a downstream face 40, facing away from the body 21, and an upstream face 42 facing the body 21. The body 36 further defines a plurality of air channels 44 ( Figure 3 ), 46, rectilinear, opening into the upstream faces 42 and downstream 40, each air channel 44, 46 being oriented in a convergent direction, that is to say cutting the axis A-A '.

The spray head 22 is mounted on the body 21 so that the air channels 44, 46 are fluidly connected to the outlet port 26. Thus, the air channels 44, 46 are fluidly connected to the source 13 of compressed gas.

The air channels 44, 46 comprise in particular first air channels 44, which converge on the nozzle 34, and second air channels 46, which converge downstream of the nozzle 34.

The skirt 38 protrudes upstream relative to the body 36. It has an internal thread 50 adapted to cooperate with external thread 52 complementary formed on the body 21 so as to be screwed on the body 21. It defines an upstream end 54 of connection of the ring 30 to the body 21. The downstream face 40 is oriented opposite this upstream end 54.

With reference to the Figure 5 , the spray nozzle 34 has an upstream end 56, facing the body 21, and a downstream end 58, facing away from the body 21. The nozzle 34 also defines a passage 60 for the circulation of the coating product. through the nozzle 34, said passage 60 opening out from the nozzle 34, at the upstream end 56, by a wide connection port 62, and at the downstream end 58 by a narrow spray orifice 64, able to spray the product coating product. For this purpose, the spray orifice 64 typically has a diameter substantially between 0.3 mm and 1.15 mm.

The outside diameter of the nozzle 34 is, for its part, preferably less than 15 mm.

The connection orifice 62 is fluidly connected to the outlet orifice 24 of the body 21. For this purpose, the tube 23 is engaged in the passage 60 through the connection orifice 62.

Thus, the connection port 62 is fluidly connected to the coating material source 12.

According to the invention, the passage 60 has, between the connection orifice 62 and the spray orifice 64, at least one pre-atomization shrink 66, able to atomize the product, the or each shrink 66 being followed by an enlargement 68 downstream of said constriction 66.

This pre-atomization shrinkage 66 makes it possible to obtain a finer spray at the outlet of the nozzle 34, and to lower the supply pressure of the nozzle 34 to a coating product without impairing the homogeneity of the jet of product. outlet of the nozzle 34.

In the example shown, the nozzle 34 comprises in particular a tubular body 70, a spray member 72, and a pre-atomization insert 74.

The body 70 is oriented in an axial direction B-B ', that is to say that the axial direction BB' forms the axis of the body 70. The body 70 is in particular cylindrical of revolution about said axis B-B .

The nozzle 34 is in particular arranged coaxially with the ring 30. Thus, the axis B-B 'coincides with the axis A-A'.

The body 70 has a first axial end 76 defining the upstream end 56 of the nozzle 34, and a second axial end 78 opposite the first axial end 76. The first axial end 76 is in particular flat and oriented transversely to the axial direction B-B '. The second axial end 78 is in particular frustoconical centered on the axis B-B '.

The body 70 internally defines a through conduit 79 opening into the first axial end 76 through a first opening 80 and into the second axial end 78 through a second opening 82, the first opening 80 forming, in the example shown, the connection 62.

The second opening 82 is in particular narrower than the first opening 80.

The through conduit 79 has a first section 84 of large diameter and a second section 86 of small diameter. The first section 84 opens out of the body 70 through the first opening 80, and the second section 86 opens out of the body 70 through the second opening 82.

The first section 84 has substantially the same diameter as the first opening 80. The second section 86 has substantially the same diameter as the second opening 82.

The first and second sections 84, 86 are joined to one another and the body 70 defines, at the interface between the first and second sections 84, 86, a radial shoulder 88 oriented towards the first opening 80. This shoulder 88 is in particular substantially plane and oriented transversely to the axis B-B '.

The spraying member 72 has an upstream face 90, housed in the conduit 79, and a downstream face 92, opposite to the upstream face 90 and disposed outside the body 70.

The upstream face 90 is substantially flat and is disposed substantially transversely to the axis B-B '. It has a diameter substantially equal to the diameter of the first section 84 of the duct 79.

The downstream face 92 is dome-shaped centered on the axis B-B 'and split with a slot 93 perpendicular to the axis B-B'. It is flush with its periphery the second axial end 78 of the body 70.

The slot 93 has lips that form between them an angle typically between 5 ° and 150 °, preferably between 20 ° and 110 °.

The spray member 72 defines the spray orifice 64.

The spraying member 72 further comprises, from upstream to downstream, a cavity 94 of decreasing cross-section downstream, followed by a channel 96 of substantially constant cross-section fluidly connecting the cavity 94 to the spray port 64.

The cavity 94 opens into the upstream face 90, said upstream face 90 defining, around the cavity 94, an annular shoulder 97 facing upstream.

The pre-atomization narrowing 66 opens into the cavity 94, said cavity 94 defining the enlargement 68 downstream of said narrowing 66.

The cavity 94 has, in the example shown, a bell shape.

The spray port 64 is formed by a narrowing terminating the channel 96 and split by the slot 93. This narrowing is particularly dome-shaped. The The diameter of the spray orifice 64 is defined as the major axis of the ellipse formed by the intersection of the slot 93 with said narrowing.

The spraying member 72 is in particular constituted by a spray insert attached to the body 70 and housed partly in the duct 79.

This insert 72 comprises a base 100 and, protruding axially from the base 100, along the axis B-B ', a finger 102 having a free end 104 opposite the base 100, said free end 104 defining the spray orifice 64 .

The base 100 is integrally housed in the first section 84 of the duct 79. It has a cross section substantially complementary to that of said first section 84 and defines the upstream face 90. It also defines a radial shoulder 106, opposite to the upstream face 90, resting against the shoulder 88 of the body 70.

The base 100 preferably has an axial thickness of less than 4 mm. In particular, it is formed by a substantially flat plate orthogonal to the finger 102.

The finger 102 comprises a first portion 108, cylindrical, and a second section 110 in the form of a dome.

The first section 108 is attached to the base 100. It is entirely housed in the second section 86 of the duct 79. It has a cross section substantially equal to that of said second section 86.

The second section 110 is disposed outside the duct 79. It defines the free end 104 and the downstream face 92.

The pre-atomization insert 74 is attached to the body 70 while being housed in the conduit 79, and defines the pre-atomization shrinkage 66.

The pre-atomization insert 74 comprises a base 112 and, protruding axially from the base 112, along the axis B-B ', a finger 114 having a free end 116 opposite the base 112, said free end 116 defining the pre-atomization shrinkage 66.

The base 112 is integrally housed in the first section 84 of the duct 79. It has a cross section substantially complementary to that of said first section 84. It bears against the annular shoulder 97.

The base 112 also defines a downstream face 117 of the pre-atomization insert 74, oriented downstream and opposite to the annular shoulder 97.

In addition, as visible on Figures 6 and 7 , the base 112 has at least one, in particular two, flat (s) 119, which prevents the rotation of the insert 74 relative to the body 70.

The finger 114 is housed substantially completely in the cavity 94.

The finger 114 comprises a first section 118 connecting to the base 112, and a second section 120 constituted by the free end 116. In a first variant of the insert 74, shown in FIGS. Figures 5 and 6 it also comprises an intermediate section 122 between the first and second sections 118, 120.

The first section 118 is cylindrical. In the first variant, it extends from the base 112 to the intermediate section 122. In a second variant, shown in FIGS. Figures 7 and 8 it extends from the base 112 to the free end 116.

The free end 116 is dome-shaped slotted with a slot 123 perpendicular to the axis B-B '. It is housed in the cavity 94 and is arranged so that the pre-atomization shrinkage 66 opens at a distance from the channel 96 less than half the axial length of the cavity 94.

The slot 123 has lips which form between them an angle typically between 5 ° and 150 °, preferably between 20 ° and 110 °.

The intermediate section 122, when it exists, has a frustoconical shape and extends from the first section 118 to the second section 120. In addition, the slot 123 extends into said intermediate section 122.

The pre-atomization insert 74 internally defines, from upstream to downstream, a cavity 124 of decreasing cross section downstream, followed by a channel 126 of substantially constant cross-section fluidly connecting the cavity 124 to the constriction pre-atomization 66.

The cavity 124 opens into the downstream face 117. It has, in the example shown, a downstream section 130, cylindrical, opening into the downstream face 117, and a frustoconical upstream section 132.

The pre-atomization shrinkage 66 is, in the example shown, formed by a hemispherical cavity 134 having a base 136 opening into the channel 126 and a top 138, opposite the base 136, split by the slot 123. It has a diameter smaller than the cavity 94 of the spray member 72, this diameter being defined as being the major axis of the ellipse formed by the intersection of the slot 123 with the hemispherical cavity 134.

This specific form of the pre-atomization shrinkage 66 makes it possible to obtain a finer spray and to further lower the feed pressure of the nozzle 34 to a coating product without impairing the homogeneity of the jet of product leaving the the nozzle 34.

The diameter of the pre-atomization shrinkage 66 is preferably between 0.3 mm and 1.15 mm and greater than or equal to the diameter of the spray orifice 64. In particular, the diameter of the pre-atomization shrinkage 66 is as the report the diameter of the spray orifice 64 on the diameter of the pre-atomization shrinkage 66 is between 0.5 and 1.0.

This ratio of diameters reinforces the fineness of the spraying and makes it possible to lower the supply pressure of the nozzle 34 more and more with the coating product without impairing the homogeneity of the jet of product at the outlet of the nozzle 34.

The passage 60 is thus formed successively, from upstream to downstream, by the cavity 124, followed by the channel 126, then the pre-atomization shrinkage 66, before a downstream portion of the cavity 94, followed by the channel 96 and finally, the spray orifice 64.

A method of spraying coating product by means of the installation 10 will now be described.

First, the sources 12, 13 of coating product and compressed gas are activated. Inputs 18, 20 of the body 21 are then supplied with coating material and pressurized gas.

Then, a user actuates the trigger 28. This has the effect of putting in fluidic communication the inputs 18, 20 respectively with the outlets 24, 26. The spray nozzle 34 is then fed, through its connection port 62, product coating material, said coating product being at a pressure of between 20 and 300 bar, in particular between 20 and 150 bar and advantageously between 20 and 80 bar. Simultaneously, the air channels 44, 46 are fed with gas under pressure.

The coating product, coming under pressure, is atomized a first time as it passes through the pre-atomization shrink 66. It then disperses in the form of droplets in the downstream part of the cavity 94, before entering the channel 96. and to be atomized a second time as it passes through the spray orifice 64. The coating product then disperses in the form of droplets in the space at the outlet of the nozzle 34. This dispersion is increased thanks to the compressed gas blown by the channels 44, 46 which strikes these droplets and burst them.

In this way, despite the relatively low coating material feed pressure, an excellent dispersion of the coating product is obtained, similar to that which can usually be observed in mixed spraying with conventional feed pressures.

Thanks to the invention described above, one thus obtains a quality of finish and a transfer rate similar to those usually encountered in mixed spraying, with however a feed pressure of reduced coating product.

In addition, the compactness of the pre-atomization insert 74 makes it possible to use for the body 70 of the nozzle 34, the spray insert 72 and the ring 30 the same as those usually used for mixed spraying. It is thus possible to equip very easily and inexpensively existing spray facilities.

Moreover, the compactness of the pre-atomization insert 74 makes it possible to minimize the dead volumes and, thus, avoids unwanted flows at the release of the trigger 28, in particular when using very fluid products such as hues or top-coat paints for example.

According to a variant (not shown) of the invention, the installation 10 does not include a source of compressed gas fluidly connected to the applicator 14. The spraying of the coating product is then done without air. In this case, the source 12 of the coating product is capable of supplying the coating product at a pressure greater than 20 bar, preferably greater than 100 bar, and the coating product is supplied at such a pressure during the spraying process. .

As with the case of the mixed spray, the invention makes it possible here, in an airless spray, to obtain a quality of finish and a transfer rate similar to those usually encountered, with, however, a reduced feed pressure of the coating product. .

In addition, the compactness of the pre-atomization insert 74 makes it possible to use for the body 70 of the nozzle 34, the spray insert 72 and the ring 30 the same as those usually used for airless spraying. It is thus possible to equip very easily and inexpensively existing spray facilities.

Finally, the compactness of the pre-atomization insert 74 makes it possible to minimize the dead volumes and, thus, avoids unwanted flows at the release of the trigger 28, in particular when using very fluid products such as shades. or top-coat paints for example.

Claims (17)

Spray nozzle (34) for spraying a product, defining a passage (60) for the circulation of the product through the nozzle (34), said passage (60) opening out of the nozzle (34), at an upstream end (56) thereof, through a wide connection port (62), and at a downstream end (58) of the nozzle (34) through a narrow spray orifice (64) suitable for spraying the product, characterized in that the passage (60) has, between the connection orifice (62) and the spray orifice (64), at least one pre-atomization shrink (66) capable of atomizing the product, followed an enlargement (68) downstream of said pre-atomization narrowing (66). The spray nozzle (34) of claim 1, wherein the pre-atomization shrink (66) is formed by a hemispherical cavity (134) slit by a slot (123). Spray nozzle (34) according to claim 1 or 2, comprising a tubular body (70) oriented in an axial direction (B-B ') and defining internally a through conduit (79) opening into a first axial end (76) of the body (70) through a first opening (80) constituting the connection port (62), the spray nozzle (34) further comprising a pre-atomization insert (74) housed in said through conduit (79), defining the pre-atomization narrowing (66). A spray nozzle (34) according to any one of the preceding claims comprising a spray member (72) defining the spray orifice (64), said spray member (72) comprising, from upstream to downstream a cavity (94) of decreasing cross section downstream, followed by a substantially constant cross sectional channel (96) fluidically connecting the cavity (94) to the spray orifice (64), the pre-shrinkage atomization (66) opening into said cavity (94). A spray nozzle (34) according to claim 4 taken in combination with claim 3, wherein the pre-atomization insert (74) comprises a base (112) and, projecting axially from the base (112), a finger (114) having a free end (116) opposite the base (112), said free end (116) defining the pre-atomization narrowing (66), the finger (114) being housed substantially integrally in the cavity (94) of the spray member (72). The spray nozzle (34) of claim 5, wherein the pedestal (112) has a cross section complementary to a cross section of the conduit (79). Spray nozzle (34) according to claim 5 or 6, wherein the spraying member (72) has an upstream face (90) into which the cavity (94) opens, said upstream face (90) defining an annular shoulder ( 97) around the cavity (94), the base (112) bearing against said annular shoulder (97). A spray nozzle (34) according to any one of claims 4 to 7, wherein the pre-atomization shrink (66) opens at a distance from the channel (96) less than half the axial length of the cavity (94). ). Spray nozzle (34) according to any one of claims 4 to 8, taken in combination with claim 2, wherein the spray member (72) is constituted by a spray insert housed at least partly in the conduit (79). A spray nozzle (34) according to any one of the preceding claims, wherein the ratio of the diameter of the spray orifice (64) to the diameter of the pre-atomization shrink (66) is between 0.5 and 0 8. A spraying head (22) for a product spraying device (14), said spraying head (22) comprising an annular ring (30) having a central orifice (32), and a spraying nozzle (34) according to the any of the preceding claims housed in said central hole (32), substantially coaxially with the ring (30). The spray head (22) according to claim 11, wherein the ring (30) has an upstream end (54) for connection to a body (21) of the spray device (14) and a downstream face (40) facing the opposite said upstream end (54), and defines at least one rectilinear air channel (44, 46) for receiving a compressed gas and opening into the downstream face (40), said air channel (44, 46); ) being oriented in a convergent direction. A spray gun (14) comprising a spray head (22) according to claim 11 or 12. Spray plant (10) comprising a source of spray material (12) and a spray head (22) according to claim 11, wherein the source of spray material (12) is capable of supplying the product to be sprayed with a higher pressure at 20 bar, preferably greater than 100 bar, and being fluidly connected to the connection port (62) of the spray nozzle (34). Spray plant (10) comprising a source of spraying material (12), a source of compressed gas (13), and a spraying head (22) according to claim 12, the source of spraying material (12) being suitable supplying the product to be sprayed with a pressure of between 20 and 300 bar, preferably between 20 and 150 bar, and being fluidly connected to the connection port (62) of the spray nozzle (34), and the source of compressed gas (13) being fluidly connected to the or each air channel (44, 46) of the ring (30). Process for spraying a coating product, characterized in that it comprises the following steps: - supplying a spray nozzle (34) according to any one of claims 1 to 10, through its connection port (62), with the coating product, the coating product being at a pressure greater than 20 bar, preferably greater than 100 bar, first atomization of the coating product during the crossing, by said coating product, of the pre-atomization shrinkage (66), and - Second atomization of the coating product during the crossing, by said coating product, the spray orifice (64). Process for spraying a coating product, characterized in that it comprises the following steps: - supplying a spray nozzle (34) according to any one of claims 1 to 10, through its connection port (62), with the coating product, the coating product being at a pressure of between 20 and 300 bars, preferably between 20 and 150 bars, first atomization of the coating product during the crossing, by said coating product, of the pre-atomization shrinkage (66), and - Second atomization of the coating product during the crossing, by said coating product, the spray orifice (64).

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