FR3055817A1 - NOZZLE FOR A DEVICE FOR APPLYING A COATING PRODUCT AND APPLICATION DEVICE COMPRISING SUCH A NOZZLE - Google Patents

Abstract

The invention relates to a nozzle (2) for a device for applying a coating product, this nozzle comprising a product passageway configured to be selectively closed by a needle (22). The conduit comprises an ejection section which is flared and rounded. The invention also relates to a device for applying a coating product, comprising such a nozzle (2).

Description

© Publication no .: 3,055,817 (only to be used for reproduction orders) (© National registration no .: 16 58548 ® FRENCH REPUBLIC

NATIONAL INSTITUTE OF INDUSTRIAL PROPERTY

COURBEVOIE © IntCI ⁸

B 05 B 1/02 (2017.01), B 05 B 9/01

A1 PATENT APPLICATION

©) Date of filing: 14.09.16. (30) Priority: © Applicant (s): EXEL INDUSTRIES Société anonyme - FR. @ Inventor (s): BENNANI TARIK. ©) Date of public availability of the request: 16.03.18 Bulletin 18/11. (© List of documents cited in the preliminary search report: See the end of this brochure (© References to other related national documents: ©) Holder (s): EXEL INDUSTRIES Société anonyme. ©) Extension request (s): (© Agent (s): LAVOIX.

OF A COATING PRODUCT AND DEVICE

FR 3 055 817 - A1 (64) NOZZLE FOR AN APPLICATION APPLICATION DEVICE COMPRISING SUCH A NOZZLE (© The invention relates to a nozzle (2) for a device for applying a coating product, this nozzle comprising a product passage duct configured to be selectively closed by a needle (22). The duct comprises an ejection section which is flared and of rounded shape. The invention also relates to a device for applying a product of coating, comprising such a nozzle (2).

NOZZLE FOR A DEVICE FOR APPLYING A COATING PRODUCT AND APPLICATION DEVICE COMPRISING SUCH A NOZZLE

The present invention relates to a nozzle for an application device, in particular for a spray gun for coating product and an application device comprising such a nozzle.

In known manner, a spray gun comprises a spray head with a head ring and a nozzle arranged coaxially inside the head. The nozzle comprises a product passage channel, which is configured to be selectively closed by a needle movable in translation inside the nozzle. The movement of the needle regulates the opening of the passage of the coating product. Depending on the position of the needle, the coating product will be expelled from the nozzle with more or less flow.

The spray head arranged around the nozzle comprises two diametrically opposite horns, which are each traversed by a compressed air ejection duct. Each duct is configured so that the air is expelled radially in the direction of the jet. The latter is then atomized into fine droplets. The smaller the droplet size, the greater the pressure and / or flow rate of the air jets. However, a too high compressed air pressure leads to the formation of a mist, sometimes called "overspray" in English, which decreases the transfer rate of the gun, that is to say the ratio between the amount of product sprayed by the gun and the amount of product actually deposited on the part to be coated.

The invention aims to propose a nozzle for a spray gun, which makes it possible to project a wider jet and with better finesse of spraying, without however increasing the pressure and / or the flow rate of the air jets.

To this end, the invention relates to a nozzle for a device for applying a coating product, such as a gun, this nozzle comprising a product passage channel, configured to be selectively closed by a needle. According to the invention, the duct comprises an ejection section which is flared and of rounded shape.

Thanks to the invention, in operating conditions of the gun, the flow of coating product circulating in the channel is attracted, by capillarity and / or because of the surface tension values, by the rounded wall of the flared section: c ' is the Coanda effect. Thus, the rounded wall of the flared section deflects the coating product from its initial path and the coating product "sticks" to the wall of the section to the point of detachment. When it detaches from the wall, the product retains a substantially tangent direction, so that the spray is enlarged. The nozzle according to the invention therefore makes it possible to obtain a wider product jet than a standard nozzle. The pistol's footprint is therefore also wider. The widening of the jet also leads to greater destabilization of the jet, so that the jet is easier to atomize and the spray is finer. Thus, by considering equivalent compressed air pressure settings, the nozzle according to the invention makes it possible to obtain a wider spray and finer drops than with a nozzle of the prior art.

According to advantageous but not compulsory aspects of the invention, such a nozzle may include one or more of the following characteristics, taken in any technically admissible combination:

The ejection section is arranged in the extension of a channel with a constant passage section.

The ejection section is tangent to the channel.

The channel has a length at least equal to 0.4 mm.

The channel has a diameter of less than 4.5 mm, preferably less than 0.9 mm.

The ejection section has a constant radius of curvature.

- Alternatively, the ejection section has a variable radius of curvature.

The ejection section comprises a succession of portions of variable radius, which are each tangent to the previous portion and / or to the following portion.

The radius of curvature of each portion of the ejection section is less than that of all the downstream portions.

The invention also relates to a device for applying a coating product, such as a gun, comprising a nozzle as described above.

Advantageously, the application device further comprises a device for rotating the product, arranged upstream of the ejection section of the nozzle.

The invention and other advantages thereof will appear more clearly in the light of the following description of an embodiment of a nozzle in accordance with its principle, given only by way of example and made with reference to the drawings in which:

FIG. 1 is a perspective view of a spray gun for coating product, comprising a nozzle according to the invention,

FIG. 2 is a partial section in plane II of FIG. 1,

FIG. 3 is a section through the nozzle shown alone, and

- Figure 4 is an enlarged view of Box IV in Figure 3.

In Figure 1 is shown a device for applying a coating product. In the example, this device is a manual spray gun 1. The coating product can be a liquid comprising one or more components or a pulverulent material. It can be paint, primer, varnish, etc.

The gun 1 comprises a body 10, a grip stock 11 and an actuating trigger 12 articulated on the body 11. It also comprises a spray head 14 and a head ring 16 arranged around the head 14. The head 14 and the head ring 16 are centered on a spraying axis XX ′.

As shown in Figure 2, the head 14 is hollow. It includes two protrusions 14a and 14b, more commonly called ears or horns, arranged diametrically opposite one with respect to the other. The horns 14a and 14b protrude parallel to the axis X-X ’with respect to the rest of the head 14. They each delimit two orifices 140 for ejecting compressed air. The orifices 140 are shaped to guide air jets in the direction of the spray axis X-X ’. More specifically, the air jets from the orifices 140 have a substantially radial and centripetal direction relative to the spray axis X-X ’of the gun. By the adjective "substantially" is meant that there is a deviation of a few degrees between a direction strictly radial to the axis X-X "and the direction of the air jets. The gun shown in Figure 1 is therefore a pneumatic type gun, using air jets for the formation of the spray.

A nozzle 2 is arranged coaxially inside the head 14. The nozzle 2 is a part with a geometry of revolution around the axis X-X ’. In the example, the nozzle 2 comprises two coaxial parts 2a and 2b, the part 2a being arranged inside the part 2b. The nozzle 2 defines a passage 6 for the product. The conduit 6 is located inside the part 2a. The nozzle 2 is a nozzle of the "flat jet" type, that is to say a nozzle whose imprint takes the form of a stretched ellipse. However, as a variant, the nozzle 2 can be a “round jet” type nozzle, that is to say a nozzle the imprint of which takes the form of a disc or a ring.

In operation, the air jets from the horns 14a and 14b of the head 14 strike the jet of product ejected through the nozzle 2. Advantageously, push buttons 18 and 20 are provided to respectively interrupt the spraying of product and / or the use of compressed air.

The conduit 6 is configured to be selectively closed by a needle 22 movable axially in translation inside the nozzle 2. The movement of the needle 22 is controlled by the trigger 12. A spring (not shown) makes it possible to recall the needle 22 in the closed position when the trigger 12 is released.

An upstream direction is defined as a direction oriented in the direction opposite to the liquid flow and a downstream direction as a direction oriented in the direction of the flow. In the configuration of Figure 3, the upstream is directed downward, while the downstream is directed upward.

From upstream to downstream, the conduit 6 comprises a first section 60, cylindrical, a second section 62, frustoconical, the passage section of which decreases from upstream to downstream, a third section 64, also frustoconical and whose section decreases from upstream to downstream, a fourth section 66 and an ejection section 68, which forms a downstream end section of the duct 6. The section 64 at a convergence angle A64 of between 10 ° and 90 °, in the example equal to 20 °

Advantageously, the section 66 is a channel of constant passage section, in particular a cylindrical channel. The diameter d66 of channel 66 defines the caliber of the nozzle

2. In practice, the caliber of a nozzle varies between 0.4 mm (4 gauge nozzle) and 2.7 mm (27 gauge nozzle).

Advantageously, the diameter d66 of the channel 66 is less than or equal to 4.5 mm, which makes it possible to obtain, compared to a standard nozzle, a greater number of small drops (of diameter less than 45 microns) and a smaller number of large drops (with a diameter greater than 60 microns).

Even more advantageously, the diameter d66 of the channel 66 is less than or equal to 0.6 mm. In the example, it is equal to 0.6 mm, which corresponds to a 6-gauge nozzle. Indeed, the widening effect of the spray is more pronounced for the small-caliber nozzles, that is to say for nozzles whose size is between 4 to 6.

Preferably the channel 66 has a length I66 measured along the axis X-X ’which is at least equal to 0.4 mm. This minimum length makes it possible, on the one hand, to guarantee that the flow rate at the nozzle outlet corresponds to the desired flow rate and, on the other hand, to facilitate the manufacture of the nozzle.

The nozzle 2 according to the invention is obtained by machining an existing nozzle, in particular by machining a standard nozzle of the same caliber. This machining operation consists in machining the downstream end of the section 6 to obtain an ejection section 68 having a flared and rounded shape. Thanks to this shape, the product runs along the wall of the section 68 and is ejected with a diverging direction relative to the spray axis X-X ’. As a result, the spray is enlarged compared to a standard nozzle. In addition, the spray is more unstable, and therefore easier to atomize.

A plane P is defined as the sealing plane of the needle 22 inside the nozzle 2. The plane P is perpendicular to the spray axis XX 'and is arranged in the example at the interface between the section 64 and the channel 66. The nozzle 2 according to the invention has the advantage that the position of the sealing plane P along the axis XX ′ is standard, that is to say that the nozzle 2 is compatible with an existing needle in trade, such as needle 22. This makes it possible to guarantee the flow rate of the nozzle 2 and to limit the presence of dead volumes, liable to retain product and to cause the formation of drops after the closure of nozzle 2.

In practice, the stroke of the needle 22 varies between 4 mm and 4.6 mm, so that the sealing plane P is positioned, relative to a reference point, at a dimension preferably between 20 mm and 20, 6 mm. In the example, the sealing plane P is located at a dimension of 20 mm. This rib range guarantees that the passage freed by the retraction of the needle 22 is sufficient so as not to shear too much the fluid circulating inside the nozzle 2.

The ejection section 68 is contiguous with an edge 8, that is to say that the section 68 and the edge 8 have an edge in common. The edge 8 is an annular edge centered on the spray axis X-X ’. In the example, the edge 8 and the ejection section 68 are tangent. However, this is not necessary as it has no influence on the width of the spray. In fact, the product stalls in practice from the wall before the end of the ejection section 68. Thus, as a variant, the edge 8 and the section 68 may not be tangent.

The radius of curvature of the ejection section 68 is chosen according to the dimension of the sealing plane P in the range from 20 mm to 20.6 mm and according to the caliber of the nozzle. The radius of curvature of the ejection section 68 is chosen as large as possible in order to obtain the widest possible jet at the outlet of the nozzle. However, for the sake of alignment with the head 14 and in order not to disturb the air flows, which are predominant in the formation of the jet, the ejection diameter d2 of the nozzle 2 is kept, that is to say that the diameter d2 is identical to that of a standard nozzle of the same caliber. This diameter requires that the edge 8 has a minimum width I8, in the example equal to 0.15 mm. In the example, the radius of curvature of the section 68 is 1.73 mm. However, in a variant not shown and when the sealing plane P is located at a dimension of 20.6 mm, the radius can be equal to 1 mm. Consequently, for a 6-gauge nozzle, the radius of curvature of the flared section 68 is between 1 mm and 1.73 mm.

Advantageously, the ejection section 68 is tangent to the channel 66. This tangency between the start of the ejection section 68 and the channel 66 improves the flow of the fluid in the nozzle 2. In addition, the fluid detaches from the constituent wall of the section 68 at a point disposed more downstream than if there were not this tangency. In other words, this tangency makes it possible to accentuate the Coanda effect.

In the example, the radius of curvature of the ejection section 68 is constant. However, as a variant not shown, it is possible to provide a flared ejection section 68 with a variable radius of curvature. In this case, the ejection section comprises a succession of portions of variable radius, which are each tangent to the previous portion and / or to the next portion. Preferably, the radius of curvature of each portion of the section 68 is less than that of all the portions arranged downstream.

Alternatively, the radius of the ejection section 68 can be an arc following a spline of predefined mathematical equation. It can be a parabolic curve of the type y = ax ² + bx + c, a hyperbolic curve of the type y = a / bx + c, a logarithmic curve of the type y = a.ln (bx ) + c or again exponential of the type y = a. exp (bx) + c.

In a variant not shown, the gun 1 is used to spray any other type of liquid, such as for example a lubricant.

According to another variant not shown, the nozzle is mounted in another type of application device, such as for example an automatic gun, which is remotely controlled and which therefore does not require manual action on the part of an operator .

According to another variant not shown, the application device comprises a device for rotating, which is mounted inside the nozzle 2. This device drives the fluid in rotation upstream of the ejection section 68. Advantageously, this device comprises a body, the shape and dimensions of which are complementary to those of the conduit 6. This body defines at least one helical groove and / or a helical hole for the passage of the fluid. The rotation of the fluid makes it possible to further widen the spray and is capable of providing a synergistic effect with the Coanda effect, in particular when the caliber of the nozzle is between 0.7 mm and 1.2 mm.

The characteristics of the variants and of the embodiment envisaged above can be combined with one another to generate new embodiments of the invention.

Claims (11)

1. Nozzle (2) for a device for applying (1) a coating product, this nozzle comprising a conduit (6) for passage of the product configured to be selectively closed by a needle (22), characterized in that the conduit (6) comprises an ejection section (68) which is flared and of rounded shape. 2. Nozzle according to claim 1, characterized in that the ejection section (68) is arranged in the extension of a channel (66) of constant passage section. 3. Nozzle according to claim 2, characterized in that the ejection section (68) is tangent to the channel (66). 4. Nozzle according to claim 2 or 3, characterized in that the channel (66) has a length (I66) at least equal to 0.4 mm. 5. Nozzle according to one of the preceding claims, characterized in that the channel (66) has a diameter (d66) less than 4.5 mm, preferably less than 0.9 mm. 6. Nozzle according to one of the preceding claims, characterized in that the ejection section (68) has a constant radius of curvature. 7. Nozzle according to one of claims 1 to 5, characterized in that the ejection section (68) has a variable radius of curvature. 8. Nozzle according to the preceding claim, characterized in that the ejection section comprises a succession of portions of variable radius, which are each tangent with the previous portion and / or with the following portion. 9. Nozzle according to the preceding claim, characterized in that the radius of curvature of each portion of the ejection section is less than that of all the downstream portions. 10. Device (1) for applying a coating product, such as a gun, comprising a nozzle (2) according to one of the preceding claims. 11. Device according to claim 10, characterized in that it further comprises a device for rotating the product, disposed upstream of the ejection section (68) of the nozzle (2). η 2/3