FR3134524A1 - HEATED SPRAY GUN - Google Patents

Abstract

Spray gun for a powdery product to be applied hot to a surface to be treated, comprising: - a main body (1); - an ambient air inlet (4); - a powder product supply inlet (6) positioned between the aeraulic drive device (5) and the spray gun (3); - a spray channel (31) for the powdery product; - a thermal insulator (32) arranged around the spray channel (31); - at least one electric heating element (321) arranged in the thermal channel (320); characterized in that the gun further comprises: - a spacing (33) between the spray channel (31) and the thermal insulator (32), the spacing (33) having a substantially conical shape converging in the direction of the free end of the barrel (3); and - means for injecting into said space (33) an air flow in the form of a helical flow (70) around the spray channel (31) towards the free end of the barrel ( 3). Figure to be published for the abstract: Figure 1

Description

HEATED SPRAY GUN Technical field of the invention

The present invention relates to a heating spray gun intended for the application by hot spraying under pressure, of a powder product, in particular thermosetting, said powder product being applied to a surface which is itself preheated.

In the remainder of the description, the invention is described in relation to the application of thermosetting paint. However, any hot-applicable powder material is concerned.

It is known to spray paints that cure hot. This spraying is usually carried out by a device which includes a source of pressurized air, a control box, a powder paint reserve, a powder paint supply and a spray gun. Such a device is for example described in documents WO 2008/073110 A1 and US 4,065,057, the powdery product being sprayed in a flow of hot air onto a surface to be treated which is at room temperature.

To improve the application of the powder product on the surface to be painted, it is customary to preheat the surface by means of an additional heating device or by means of a flow of hot air generated by the spray gun as proposed in document FR3065655.

However, despite the significant practicality of the device proposed in document FR3065655, we sometimes notice an irregularity in the paint applied to the surface to be treated. Indeed, the painted surface has an “orange peel” effect in certain places, that is to say that the surface has bumpy roughness in the form of islands. These irregularities are explained in particular by the presence, in the projected flow, of packets consisting of a mixture of product in liquid form and in powder form, and which have therefore not been completely liquefied before reaching the surface.

The presence of these packets finds its origin in particular in the irregularity of the supply of powder in the barrel of the gun. Indeed, the entrainment of the powder by the air leaving the drive screw is, by nature, not continuous but discrete. Powder packets detach as the powder is fed following the rotation speed of the helical feed screw. These packages, if they are not broken up by the air pressure in the barrel, are thus projected as they are into the current of hot air. However, we easily understand that individual grains in a hot flow melt quickly, thanks to a rapid heat transfer between the carrier gas, here hot air, and the grain, while packages of agglomerated grains subjected to the same conditions put more of time, due to weak contact with the carrier gas and slow conduction internal to the aggregate. As a result, these packets made up of a mixture of liquid-solid agglomerated products arrive on the surface to be painted, and adhere to the surface without spreading as would be the case for a liquid, and thus take the form of irregularities of the type " orange peel” as mentioned.

The present invention is thus an improvement of the spraying device described in document FR 30 65 655, while remaining compact, reliable, light and easy to use.

The present invention therefore relates to a spray gun for a powdery product to be applied hot to a surface to be treated. The gun comprises a main body extended downwards by a handle and forwards by a substantially cylindrical spray barrel with a longitudinal central axis, an ambient air inlet associated with an air drive device, and an air inlet. supply of powdered product positioned between the aeraulic drive device and the spray gun. The gun further comprises a channel for spraying the powdery product, opening out at the free end of the spray barrel in a substantially central position. The spray channel is supplied with air by the aeraulic drive device, and the powder product is injected or driven into the spray channel by means of the air supply by the drive device. A thermal insulator arranged around the spray channel is pierced longitudinally right through at least one thermal channel supplied with air flow by the aeraulic drive device, and at least one electric heating element arranged in the thermal channel is configured to allow the circulation of the air flow in the thermal channel and to heat said air flow to at least a predefined temperature.

According to the invention, the gun further comprises:
- a spacing between the spray channel and the thermal insulator, this spacing having a substantially conical shape converging towards the free end of the barrel; And
- means for injecting into said space, a flow of air circulating in the space in the form of a helical flow around the spray channel in the direction of the free end of the barrel.

In other words, the present invention proposes to modify the device of the prior art by integrating the following elements:
- an empty space between the spray channel and the thermal insulator, so as to create an additional thermal insulator via the circulation of ambient air in this space;
- means for injecting ambient air into the space and for circulating this air in the space not longitudinally but following a helical trajectory around the spray channel; And
- means for increasing the speed of air flow, and in particular of the air circulating in the space, in particular via a progressive reduction of the diameter offered to the flow of air, inducing an increase in speed of air flow via the venturi effect which adds to the natural increase in speed linked to the expansion of the air.

The helical flow of air, exacerbated by an increase in speed, has the effect of adding a radial component to the speed of ejection of the air carrying the powder product at the outlet of the barrel. Thus, unlike the device of the prior art in which the trajectory of the product packets ejected at the outlet of the barrel follows an exclusively longitudinal direction, in the solution of the invention, due to the radial component of the speed, all or part packets of product ejected at the outlet of the barrel deviate or deviate significantly from this longitudinal direction, then hitting the hot air escaping from the thermal channel. The packets of powdered product therefore undergo sudden shearing which causes their deagglomeration followed by the immediate fusion of the fine powder particles released. Furthermore, still due to the radial ejection of the particles, the residence time of the powder particles in the hot zone between the end of the gun and the surface to be treated is increased, which in fact improves the time necessary to the complete fusion of deagglomerated particles.

Preferably, the spray channel has a substantially constant diameter. Thus, the conical shape of the spacing or spacing channel can be obtained by a progressive increase in the direction of the free end of the barrel, of the thickness (in the radial direction) of the thermal insulator. In other words, the spacing delimited by the spray channel and the thermal insulator has a constant internal diameter (that of the spray channel) and an external diameter which gradually reduces towards the free end of the barrel. .

According to one embodiment, the injection means comprise two vents supplied with air at one of their ends by the aeraulic drive device, the other of their ends opening into the space in a diametrically opposite manner in the direction radial. Each vent is conical in shape and converges in the direction of the spacing, the axis of revolution of each vent forming a predefined angle relative to the longitudinal central axis of the barrel.

In other words, the two conical vents positioned diametrically opposite are configured to allow the injection of ambient air into the spacing with a non-zero angle of incidence relative to the longitudinal central axis, in order to induce the helical flow of air in the space and therefore of the powder product leaving the spray channel. Preferably, the vents are at least symmetrical with respect to a longitudinal plane, this longitudinal plane extending in the longitudinal direction of the barrel and containing the longitudinal central axis of the spray channel. Furthermore, for each conical vent, the angle of incidence defined by the angle formed between the longitudinal central axis of the injection channel (or the central axis of the spacing) and the axis of revolution of the The conical vent is preferably between 20 and 80 degrees, and is usually substantially equal to 45 degrees.

In order to optimize on the one hand the preheating of the surface to be treated and on the other hand the melting of the powder product leaving the barrel, the thermal insulator can comprise a set of thermal channels distinct from each other, positioned parallel to the axis of the cylinder formed by the thermal insulator and uniformly distributed along the radii of said cylinder. Each thermal channel opens at the free end of the barrel and is supplied with pulsed air by the air drive device. Furthermore, at least one electric heating element is arranged in each of these thermal channels.

According to a variant, the thermal insulator can be formed of a single insulating layer, made of material chosen for its thermal insulation properties, and advantageously also for its electrical insulation properties. In this variant, the thermal channels are positioned in the thermal insulator while ensuring a sufficient thickness of thermal and/or electrical insulation between the thermal channels and the spray channel. In practice, the thermal insulation is made of a material resistant to high temperatures, for example refractory ceramic.

According to another variant, the thermal insulator can be formed of two insulating layers, namely a first insulating layer to form the spacing with the spray channel, and a second insulating layer surrounding the first insulating layer and in which the thermal channels. The thicknesses and materials of the insulating layers are chosen to resist high temperatures and to ensure electrical insulation and also thermal insulation in order to prevent the air circulating in the spray channel from being heated to the point that the powder hardens at inside the barrel. Advantageously, for the first insulating layer, we will favor a material having thermal insulation properties adapted to the high temperatures generated in the gun, and for the second layer, we will favor a material having electrical insulation properties adapted to the voltages and currents circulating in the gun. For example, the first material may be refractory ceramic, for example silicon silicate, and the second insulating layer may be mica.

The gun advantageously comprises modules configured to implement a process for spraying a powdery product comprising a preheating phase prior to an application phase.

In practice, the heating elements present in the thermal channels are usually coupled to a regulated electrical supply and controlled in relation to a surface temperature measured by a temperature measuring module, such as a pyrometer. The assembly is advantageously sized and configured to generate a flow of hot air following an adjustable and predefined set temperature, and this in a repeatable manner from one test to another. Thus designed, the device can authorize a selection of air temperature between 500 and 1000 °C, for measured temperatures, for example for dynamic spot temperatures measured by the pyrometer, between 50 and 500 °C, depending on the nature of the substrate materials concerned by the application.

The gun can also integrate a user interface, a module for actuating the powder supply into the barrel by the operator, such as a trigger, and a control module configured to control all of the gun modules in depending on the nominal preheating and application conditions which are predefined.

The preheating phase, during which any injection of powder into the barrel is blocked, may in particular include:
- a measurement, continuously or per cycle, of the temperature of a zone of the surface to be treated;
- regulation of the electrical supply as a function of said measured temperature to reach a predefined set temperature corresponding to a nominal temperature required for the application of the powder product;
- when the set temperature is reached, an indication to the operator that the gun can move into the application phase.

The application phase, which can only begin if the nominal preheating condition is obtained and during which the gun enters a semi-automatic mode controlled by the measured substrate temperature, includes:
- a measurement, continuously or by cycle, of the temperature of a zone of the surface to be treated;
- regulation of the electrical supply as a function of said measured temperature and predefined application conditions;
- a check according to the following scenario:
i) when the application speed is assessed as insufficient, which can result in a measured temperature which remains higher than an application setpoint temperature for a predefined time, for example a few seconds, an indication is given to the operator to accelerate the advance of the gun, and if after a predefined time following this indication, for example a few more seconds, no reaction is detected on the part of the operator, the thermal power is reduced;
ii). when the application speed is assessed as too high, which can result in a substrate temperature lower than the application setpoint temperature, an indication is given to the operator that he must reduce the application speed , and if after a predefined time, for example a few seconds, the application conditions are not respected, the powder supply is interrupted, and the operator must carry out an operation, for example releasing the trigger to restart the application. Automatic reestablishment of application is not preferable to avoid untimely application to an uncontrolled area.

According to a variant, the spray gun integrates a database, for example in the form of a concordance table, indicating to the system the value of the heating temperatures depending on the type of powdery product to be sprayed and the type of surface to be sprayed. to treat. Thus, the adjustment module can automatically define the set temperatures for the preheating and heating phases after collecting the material data.

Other characteristics and advantages of the present invention will appear more clearly on reading the description which follows, made with reference to the appended drawings, given by way of non-limiting examples, in which:

There is a cutaway perspective view of a schematic representation of the powder gun according to one embodiment of the invention, showing the arrangement of the different parts;

There is a perspective view of a simplified schematic representation of the injection block coupled to the barrel of the powder gun, according to one embodiment;

There is a schematic representation of the injection block, according to one embodiment;

There is a view of the front face of the injection block of the and some in which the conical vents are made, according to one embodiment;

There is a sectional view along the CC axis of the injection block of the ;

There is an enlarged view of the powder gun portion of the , integrating the vents according to one embodiment.

A powder gun according to one embodiment is illustrated in the and comprises a main body 1 extended downwards by a handle 2 and forwards by a substantially cylindrical spray barrel 3 with a longitudinal central axis 30, an ambient air inlet 4 associated with an aeraulic drive device 5 , and a supply inlet 6 for powdery product, for example in the form of a powder, positioned or opening between the aeraulic drive device 5 and the spray gun 3.

The spray barrel 3 of the gun comprises a powder spray channel 31 , this spray channel 31 opening out at the free end of the barrel 3 in a substantially central position. The spray channel 31 is substantially cylindrical and is supplied with air and powder via the aeraulic drive device 5 . In particular, the powder supplied via the supply inlet 6 is injected or driven into this spray channel 31 via the injection of ambient air by the aeraulic drive device 5 . Thus, the spray channel 31 is only configured to allow the entrainment and spraying of the powder via an air flow which must remain as close as possible to the ambient temperature so in particular that the powder, for example paint in powder, does not polymerize in the spray channel 31 .

The spray barrel 3 of the gun further comprises a thermal insulator 32 arranged around the spray channel 31 . The thermal insulator 32 integrates thermal channels 320 distinct from each other and positioned longitudinally and radially in the spray gun 31 . Each thermal channel 320 opens at the free end of the barrel 3 and is supplied with a flow of ambient air by the aeraulic drive device 5 . Each thermal channel 320 integrates one or more electric heating elements 321 . The heating elements 321 are configured to allow the circulation of air flows in the thermal channels 320 while heating this air flow to a predefined temperature, so that the hot air 322 ejected at the free end of the barrel 3 forms a hot zone between the outlet of the barrel 3 and the surface to be treated. In practice, the thermal insulator 32 can integrate for example fourteen thermal channels each advantageously having a constant diameter, for example 7 mm. Each heating element 321 can be in the form of an electrical resistance configured to provide, for example, an electrical power of 1450 W, or 3000W in total.

Thus, the air circulating in the thermal channels 320 is heated and the powder circulating in the spray channel 31 remains at room temperature. Once the powder is sprayed out of the spray gun, the powder is then entrained into the hot air stream 322 . The thermal insulator 32 is preferably silicon silicate, or any other thermal insulator with high thermal insulating power.

To reinforce the thermal insulation of the powder circulating in the channel, the gun further integrates an empty spacing 33 between the spray channel 31 and the thermal insulator 32 . This spacing 33 thus forms a sort of air layer which provides additional thermal insulation to the spray channel 31 . As illustrated in , the spacing 33 has a substantially conical shape and converges towards the free end of the barrel 3. In other words, the spacing 33 between the spray channel 31 and the thermal insulator 32 is gradually reduced in the direction of the free end of the barrel 3. In practice, the conical shape of the spacing 33 can be obtained by using a spray channel 31 of substantially constant diameter, combined with a progressive increase in the direction of the free end of the barrel, of the thickness (in the radial direction) of the thermal insulator 32. In practice, the ratio between the thickness of the spacing located upstream (that is to say the spacing portion by which ambient air is injected into the space) and the thickness of the space located downstream (i.e. the space portion at the free end of the barrel) is between 6 mm and 15 mm, nominally 9 mm.

In practice, the gun can comprise a block 8 disposed in the body 1 and configured to be coupled to the aeraulic drive device 5 , to the powder supply inlet 6 and to the spray gun 3 . Such a block 8 is represented schematically in . In particular, as can be seen in the and the , the block 8 integrates a central channel 80, one of the ends of which is coupled to the aeraulic drive device 5, and the other end is coupled to the spraying channel 31. The powder supply inlet 6 opens into this central channel 80 so as to allow the flow of ambient air injected into this central channel 80 by the aeraulic drive device 5 to drive the powder into the spray channel 31. This body 8 further comprises vents, for example two vents 7a, 7b, opening into the spacing 33, as well as one or more through orifices opening into the thermal channels 320 and configured(s) to allow air to enter these thermal channels 320. This block 8 thus makes it possible to inject air in an isolated manner into the different channels of the gun, namely the spray channel 31, the thermal channels 320, and the spacing channel 33.

As can be seen on the and the , the two vents 7a , 7b are conical in shape and converge in the direction of the spacing 33. On the is a view of the front face of the block 8, that is to say of the portion configured to be coupled to the barrel 3, the profile of the vents 7a, 7b is presented in dotted lines with the exception of the ends opening into the spacing 33 which are shown in solid lines. The two vents 7a, 7b are supplied with ambient air at one of their ends by the aeraulic drive device 5, and the other of their ends opens diametrically opposite into the spacing 33. The axis of revolution 71 of each vent 7a, 7b forms a non-zero angle of incidence α with respect to the longitudinal central axis 30. This angle of incidence α corresponds to the angle of injection of the ambient air into the spacing 33 , and is for example 45 degrees. Furthermore, the angle β formed between the axis of revolution 71 of the conical vent 7a and its lateral surface (or its generatrix) can be of the order of 4 degrees.

Thus, each vent 7a , 7b injects ambient air into the spacing 33 with a non-zero angle of incidence α relative to the longitudinal central axis 30 of the spray channel 31 , so as to induce the circulating air in the spacing 33 a helical trajectory 70 around the spray channel 31 . This helical trajectory 70 of the air leaving the barrel coupled with the acceleration induced by the narrowing of the spacing 33 makes it possible to disagglomerate the packets of powder 9 leaving the barrel while bringing the powder into the hot zone located between the barrel and the surface to be treated, and while increasing the residence time of the powder in this hot zone. In practice, the paint powder is projected out of the gun barrel at room temperature, before being carried away by the flow of hot air. This avoids the polymerization of the paint in the barrel, while allowing the projected powder to be heated to a temperature suitable for being applied to the surface to be treated.

Preferably, the vents 7a, 7b can be symmetrical with respect to a longitudinal plane extending in the longitudinal direction of the barrel 3 and containing the longitudinal central axis 30 of the spray channel 31 . The two vents 7a, 7b can also extend radially and can be symmetrical with respect to the center of the spray channel 31 . Any other positioning of the conical vents making it possible to inject ambient air into the spacing 33 with a non-zero air injection angle relative to the longitudinal central axis 30 and to induce a helical flow, can also be considered.

The ambient air inlet 4 can be equipped with an air filtration device, and the aeraulic drive device 5 is preferably an electric turbine configured to provide an air flow with a flow rate of between 50 and 200 L/min, preferably between 80 and 150 L/min, for example substantially equal to 100 L/min.

The powder supply inlet 6 can be coupled to a supply device containing the powder to be injected into the barrel 3 and which can be in the form of a reservoir, for example removably mounted on the spray gun. spray or integrated into it. It may also be a cartridge having an opening in its lower part, this opening being bordered by a mounting means adapted for the removable mounting of the cartridge on the gun. The feed device may include powder feed regulating means configured to release the powder in a controlled manner. This regulation device can in particular be configured to regulate the quantity and flow rate of powder to be released into the channel, without requiring an external regulation device. For example, the power supply regulation device may include an Archimedes screw extending downwards through a bearing secured to a motor. The admission of the powder into the channel can also be done by means of a solenoid valve, or by means of an electric rotary valve.

A manual actuation device, for example in the form of a trigger, can be provided on the handle 2 and connected to the device for regulating the supply of powdery product to control its flow rate. For example, manually operating the trigger by the user makes it possible to regulate the quantity and flow rate of powder that is sprayed.

In practice, it is advantageous to preheat the surface to be treated before applying the powder product. The surface to be treated can be preheated using the flow of hot air leaving the thermal channels. To do this, the heating elements present in the thermal channels are coupled to a regulated electrical supply and controlled in relation to a surface temperature measured by a temperature measuring module, such as a pyrometer. The assembly is advantageously sized and configured to generate a flow of hot air following an adjustable and predefined set temperature, and this in a repeatable manner from one test to another. Thus designed, the device can authorize a selection of air temperature between 500 and 1000 °C, for measured temperatures, for example for dynamic spot temperatures measured by the pyrometer, between 50 and 500 °C, depending on the nature of the substrate materials concerned by the application.

Thus, according to another embodiment, the spray gun can comprise:
- a module for adjusting a preheating or application setpoint temperature;
- a module for measuring and detecting the temperature of the surface to be treated and/or the air flow leaving the barrel, for example in the form of a pyrometer;
- a heating element control module to generate a first flow of hot air to heat the surface to be treated during a preheating phase and to generate a second flow of hot air during an application phase.

The spray gun may further comprise an information device connected to the temperature measuring module, which displays the measured temperature or which indicates to the user by a light, sound, tactile and/or visual signal that the measured temperature has reaches the chosen temperature. The information device can for example be a simple diode, a display screen, a sound diffuser, a vibrator or a combination of these devices.

According to a variant, the spray gun may include a database, for example in the form of a concordance table indicating the value of the heating temperatures depending on the type of powdery product to be sprayed and the type of surface to be treated. Thus, the adjustment module can automatically define the preheating and heating setpoint temperatures. The database can also include a chart giving the electrical voltage to be applied to the electrical resistances as a function of the target temperature to be reached.

In practice, the heating elements are first controlled to heat the air circulating in the thermal channels so as to project a flow of hot air at a first temperature in order to preheat the surface to be treated. When the gun detects that the temperature of the surface to be treated reaches the set temperature, the heating elements are controlled to project a flow of hot air at a second temperature, and the supply of paint powder to the spray channel is triggered, automatically or manually by the user. The powder is thus propelled into the spray channel at room temperature thanks to the thermal insulator and the swirling flow of air generated by the vents in the gap. Furthermore, the conicity of the spacing makes it possible to reduce the loss of kinetic energy due to the friction of the fresh air on the surface of the insulation and thus makes it possible to maintain the rotation speed of the vortex generated by the vents. The swirling flow of air leaving the barrel causes a swirling flow of powder leaving the barrel allowing the packets of powder present to deagglomerate before reaching the surface to be painted. The paint particles are thus transported by the flow of hot air whose temperature allows, in combination with the temperature of the surface to be painted, the polymerization of the paint powder on the surface.

During the application of the paint, the temperature of the surface to be painted may vary and in particular decrease. Under these conditions, the gun can be configured to detect this temperature variation and generate a report to the user. The gun can, automatically or manually, temporarily cut off the paint powder supply and trigger surface preheating.

In practice, the following scenario can be considered.

In the preheating phase of the surface to be treated during which the injection of pulverulent powder into the barrel is not authorized, the operator is warned in real time by feedback from the pyrometer that the surface to be treated is being heated. heating but not yet at the desired set temperature for the application. This phase ends when the measured temperature has reached the nominal value required for the application, and the operator is warned by the setpoint feedback from the pyrometer that he can now move on to the application phase.

During the application phase, after triggering the trigger by the operator, the gun enters a semi-automatic mode controlled by the temperature of the substrate measured by the pyrometer. During this application phase,
- if the advance of the gun during application, due to the operator's gesture, is insufficient compared to the gun's capabilities, the temperature of the substrate is reported as excessive and the user is informed that he can accelerate the application. After a few seconds if the operator does not react, the thermal power is reduced because the operator may have chosen to reduce the speed on an area of the surface to be treated, for example due to a connection interface with another material temperature sensitive, a limit of the area to be painted, a negotiation of a contour, etc. ;
- conversely if the application speed is too high, due to the operator's gesture, the temperature of the substrate is returned as insufficient and the user is informed that he must reduce the application speed because he then applies at a speed higher than the maximum speed allowed by the power of the device. After a few seconds, the powder supply is interrupted if the application conditions are still not respected. In this case, the operator must release the trigger to restart the application. The automatic restoration of operations is in fact disabled to avoid untimely application to an uncontrolled area.

Claims (10)

Spray gun for a powdery product to be applied hot to a surface to be treated, the gun comprising:
- a main body (1) extended downwards by a handle (2) and forwards by a substantially cylindrical spray barrel (3) with a longitudinal central axis (30);
- an ambient air inlet (4) associated with an air drive device (5);
- a powder product supply inlet (6) positioned between the aeraulic drive device (5) and the spray gun (3);
- a spray channel (31) for the powdery product, opening out at the free end of the barrel (3) in a substantially central position, the spray channel (31) being supplied with air by the aeraulic drive device (5 ) and the powdery product being driven into the spray channel by means of the air supply by the aeraulic drive device (5);
- a thermal insulator (32) arranged around the spray channel (31) and pierced longitudinally right through with at least one thermal channel (320) supplied with air flow by the aeraulic drive device (5);
- at least one electric heating element (321) arranged in the thermal channel (320) and configured to allow the circulation of the air flow in the thermal channel (320) and to heat said air flow to at least one predefined temperature ;
characterized in that the gun further comprises:
- a spacing (33) between the spray channel (31) and the thermal insulator (32), the spacing (33) having a substantially conical shape converging towards the free end of the barrel (3); And
- means for injecting into said space (33) a flow of air circulating in the space (33) in the form of a helical flow (70) around the spray channel (31) in the direction of the free end of the barrel (3). Spray gun according to claim 1, characterized in that the spray channel (31) has a substantially constant diameter, and the thickness of the thermal insulator (32) gradually increases in the direction of the free end of the barrel. Spray gun according to claim 1 or 2, characterized in that the injection means comprise two vents (7a, 7b) supplied with air at one of their ends by the aeraulic drive device (5), the other of their ends opening into the space (33) in a diametrically opposite manner in the radial direction, each vent being of conical shape and converging in the direction of the spacing (33), the axis of revolution (70) of each vent (7a, 7b) forming a predefined angle of incidence (α) relative to the longitudinal central axis (30). Spray gun according to claim 3, characterized in that the vents (7a, 7b) are at least symmetrical with respect to a longitudinal plane extending in the longitudinal direction of the barrel and containing the longitudinal central axis (30). Spray gun according to claim 3 or 4, characterized in that for each conical vent (7a, 7b), the angle of incidence (α) defined by the angle formed between the longitudinal central axis (30) and the The axis of revolution (71) of the vent (7a, 7b) is between 20 and 80 degrees. Spray gun according to claim 5, characterized in that the angle of incidence (α) is 45 degrees. Spray gun according to one of claims 1 to 6, characterized in that the thermal insulator (32) comprises a plurality of thermal channels (320) distinct from each other and positioned parallel to the axis of the cylinder formed by the thermal insulator and uniformly distributed along the radii of said cylinder, each thermal channel opening at the free end of the barrel and being supplied with an air flow by the aeraulic drive device (5), at least one electric heating element being arranged in each thermal channel (320). Spray gun according to one of claims 1 to 7, characterized in that the thermal insulator (32) is formed of a first insulating layer forming said spacing (33) with the spray channel (31) and a second layer insulating layer surrounding the first insulating layer and in which the thermal channels (320) are positioned, the first insulating layer having at least thermal insulation properties adapted to the high temperatures generated in the gun, and the second insulating layer having at least thermal insulation properties electrical insulation adapted to the voltages and currents circulating in the gun. Spray gun according to one of claims 1 to 8, characterized in that it further comprises:
- a module for measuring the temperature of the surface to be treated;
- a regulated electrical supply coupled to the heating elements and controlled in relation to a surface temperature measured by a temperature measuring module;
- a trigger actuated by the operator to trigger the supply of powder into the barrel;
- a user interface;
- a control module configured to control all the gun components according to the predefined nominal preheating and application conditions. Process for spraying a powdery product comprising a preheating phase prior to an application phase,
- the preheating phase, during which any injection of powder into the barrel is blocked, comprising:
. a continuous or cycle measurement of the temperature of a zone of the surface to be treated;
. regulation of the electrical supply as a function of said measured temperature to reach a predefined set temperature corresponding to a nominal temperature required for the application of the powder product;
. when the set temperature is reached, an indication to the operator that the gun can move into the application phase.
- the application phase, which can only begin if the nominal preheating condition is obtained and during which the gun enters a semi-automatic mode controlled by the measured substrate temperature, including:
. a continuous or cycle measurement of the temperature of a zone of the surface to be treated;
. regulation of the electrical supply as a function of said measured temperature and predefined application conditions;
. a check according to the following scenario:
i) when the application speed is assessed as insufficient, an indication is given to the operator to accelerate the advance of the gun, and if after a predefined time following this indication, no reaction is detected on the part of the operator, the thermal power is reduced;
ii) when the application speed is assessed as too high, an indication is given to the operator that he must reduce the application speed, and if after a predefined time, the application conditions are not respected, the powder supply is interrupted, and the operator must carry out an operation to restart the application.