FR2619322A1 - Installation for spraying a coating product such as, for example, a water-soluble paint - Google Patents

Abstract

Installation for spraying a coating product, especially a conducting water-soluble paint. The installation includes a colour-changing unit 11 connected via a distribution circuit 12 to a sprayer 13; an intermediate reservoir 41, capable of being disconnected from the colour-changing unit, is constituted by a pipe section of the circuit 12, which can be brought into communication with a reservoir 44 of rinsing product pressurised so as to be able to push the injected paint into the said intermediate reservoir. Application to the painting of bodywork elements in the automobile industry.

Description

"Installation for spraying coating product such as
for example a water-soluble paint "
The invention relates to an installation for spraying a coating product, in particular a conductive coating product, such as a water-soluble paint or a metallic paint, applied electrostatically; it relates more particularly to a new arrangement making it possible to rapidly ensure changes to such products. The invention finds its preferred field of application in the fields where the objects to be covered follow one another along the same projection location and where any two consecutive objects must generally be covered with coating products of different colors. operating constraints imposing extremely rapid color change cycles are encountered in particular in the automotive industry for painting body parts. The invention is more particularly intended to solve the additional problems posed, in this context, the electrostatic application of water-soluble paints or certain metallized paints, relatively conductive.

 A paint spraying installation, in a production unit as large as an automobile manufacturing plant, for example, generally comprises several very long closed-loop paint circulation circuits (these circuits can cross an entire part from the factory) which establish the link between large paint tanks and the different projection booths. It is therefore necessary to provide such a circuit by color and another circuit of the same kind for the solvent or the cleaning product. For obvious safety reasons, these circuits are connected to earth.

 Furthermore, in a paint spray booth thus supplied, the objects to be painted, in this case automobile bodies, in the example envisaged, are carried by conveyor means passing through the booth, in which are located electrostatic projection means liable to evolve in a certain "activity zone" inside the cabin.

 These projection means can be "bowls" rotating at high speed, or pneumatic or hydrostatic spraying. One of the usual problems to solve in this type of installation is that of the color change between two consecutive objects. Indeed, in the automobile industry, in particular, there is no question of painting the bodies in series, according to the color. The most frequent case, on the contrary, is that where the color must practically be changed after each bodywork. This implies being able to implement rinsing and drying cycles of the projection means, which are extremely rapid. For example, a color change can take place every minute or so and the time allowed for carrying out all the operations necessary for the color change is of the order of ten seconds.

 In known conventional installations, all the coating product circulation circuits are connected, as well as a compressed air circuit and a cleaning product circuit, through controlled isolation valves, to a manifold, one of which common output branch is connected to the projector. This known arrangement will hereinafter be referred to as "coating product changing unit" or, more simply, "color changing unit". Conventionally, to change color, the valve of the coating product circuit used must be closed. , a certain time (calculated) before the end of the current spraying phase, then open the compressed air valve to push the remaining product towards the projector. Then carry out a cleaning cycle comprising a succession of product injections cleaning and compressed air until the ducts are clean and dry. Finally, another valve from another coating product circuit is opened to fill the manifold and the conduits until a little coating product of the new color leaves the projector. A new phase of projection-painting can then begin.

 When the installation has only a small number of coating products of different colors, for example three or four, the collector can be placed fairly close to the projector. On the other hand, when there are too many different coating products (there can be up to twenty or more) this solution is no longer practicable and the color change unit must then be placed away from the spotlights. When the objects to be coated are bulky, and this is the case with automobile bodies, the projection means are subject to large displacements parallel to the largest dimension of these objects, in particular in the case of robots, for example five or six meters. In this case, the color changing unit is very far from the projector (s), which considerably increases the volumes of ducts to be cleaned, and therefore the time of the color changing sequences. Therefore, with each change of color, the amounts of coating product and cleaning product lost are significant, of the order of several hundred cubic centimeters.

 In the case of an electrostatic installation, all these problems relating to color change are further accentuated when it is desired to use coating products with low resistivity, such as for example water-based paints, while retaining the advantages of '' an electrostatic projection. In this case, the projector is often brought to a high voltage and it is advisable to avoid the short circuit between this projector and the circuits of circulation of coating product connected to the ground. To deal with the specific problem of color change with a low resistivity coating product, French patent N 2572662 proposes to fill an intermediate reservoir with the quantity of paint just necessary for each application. The arrangement is such that this intermediate reservoir sometimes carried to earth potential when it is filled, and sometimes to high voltage when it powers the projector (s). This intermediate tank is unique for all colors, from. so that each change of color requires cleaning of the tank but also of all the conduits which are connected to it.

 In addition, in this type of installation, it is relatively difficult to adjust the quantity of coating product to be introduced into the intermediate tank. The quantity must, in fact, be sufficient for the object to be painted in full. However, any excess is lost on rinsing, which leads to a reduction in the overall deposition yield and can cause all or part of the gains provided by the electrostatic application to be lost. The invention solves these problems.

 In this spirit, the invention therefore essentially relates to a coating product spraying installation of the type comprising a coating product changing unit, means for supplying rinsing product, at least one distribution circuit, downstream of said unit and supplying at least one projector ensuring the spraying of said product, as well as an intermediate tank, forming part of this distribution circuit, characterized in that said intermediate tank consists of a section of conduit of said distribution circuit and in that that controlled connection means are arranged to push said coating product, in the spraying phase, from said rinsing product.

 The fact of having transformed the intermediate tank into a conduit has many advantages.

 - The intermediate tank, thanks to its new shape, is much easier to clean, which requires less rinse aid and therefore saves time.

 - By "pushing" the coating product with the solvent or rinsing product, over the entire length of the intermediate tank, one already begins to clean all the conduits located upstream and the intermediate tank itself, during the projection phase of said coating product.

 - Thanks to one or more flow sensors judiciously placed in the installation, it is possible to very precisely control the quantity of product injected in each cycle as well as the spraying of this product.

 On the other hand, the coating product changing unit is earthed, for the reasons stated above. If the installation is suitable for an application of said coating product by electrostatic means, said distribution circuit is then sequentially connected to a high voltage applied to the electrostatic projector. In this case, the installation is further characterized in that said controlled connection means are arranged between, on the one hand, said section of conduit and on the other hand, said unit and means for supplying rinse aid. isolated from the earth, so as to be able to push said coating product, in the electrostatic projection phase, from rinsing product coming from these isolated supply means.

The invention will be better understood and other advantages thereof will appear more clearly in the light of the description which follows, of several installations in accordance with its principle, given solely by way of example and made with reference to the accompanying drawings wherein:
- Figure 1 is a block diagram of a first embodiment of a paint spraying installation according to the invention;
- Figure 2 is a diagram of a variant of the embodiment of Figure 1; and
- Figure 3 is a block diagram of another embodiment of a paint spraying installation according to the invention and allowing to obtain even shorter color change cycles.

 Referring more particularly to FIG. 1, the painting projection installation shown comprises a color changing unit 11 and a distribution circuit 12 extending between said color changing unit 11 and at least one electrostatic projector 13 fitted with a needle valve 14 controlling the passage of the paint. This projector is placed in a projection booth, not shown, in which transit objects to be painted in different colors. The distribution circuit 12 is therefore supplied by the color change unit 11 which selects the desired shade. The distribution circuit 12 provides, in turn, a certain amount of paint of the selected shade, predetermined as a function of the importance of the object to be painted, to the projector 13. During the paint projection phase, the projector is brought to high voltage; the conventional high voltage source is not shown. As mentioned previously, the paint used is conductive (water-soluble paint or metallic paint) and the distribution circuit 12 is brought to high voltage at the same time as the projector. In known manner, the color changing unit 11 comprises an assembly selection solenoid valves 11A, making it possible to put its outlet collector 15 in communication with one of the following circuits: - either one of the paint circulation circuits 16A, 16B, 16C, each circuit 16 corresponding to a given color - or a circuit for circulating rinse aid 17; for a water-soluble paint, it is water possibly added with alcohol, - or a compressed air supply circuit 18.

 The outlet of the collector 15 is connected to the distribution circuit 12 by isolation means comprising a first isolation conduit 20, a controlled valve 21 and purge means 22. The downstream end of the isolation conduit 20 is connected to the distribution circuit 12 via the valve 21 and to the purge means 22 via a controlled valve 25, via a portion of insulating conduit 24. The installation also includes purge means 26 connected by via a valve 27, to the distribution circuit 12 at the downstream end thereof, that is to say in the vicinity of the projector 13. A pressure regulator 29, rinsable, of a known type , is connected to the downstream end of circuit 12, that is to say as close as possible to the projector 13.A flow sensor 30, which will be described in detail below, is also inserted in circuit 12 in the vicinity from its upstream end. A cleaning unit 35 is connected by a valve 36 to the purge means 26, the connection being made in the vicinity of the valve 27 so as to be able to clean and dry the portion of conduit 28 connecting this valve 27 to the purge means 26.

The purge means 22 and 26 are connected to the earth.

 The cleaning unit 35 includes controlled connection means able to put successively in communication with the valve 36, either the rinsing product circulation circuit 17, or a compressed air distribution circuit 18. The conduit 37 connecting the the cleaning unit 35 at the valve 36 is made of insulating material, the cleaning unit 35 being earthed.

 It should be noted, at this stage of the description, that all the conduits, which connect the various constituent elements of the installation, are advantageously made of insulating material. Some of them, such as for example the conduit 20 mentioned above, whose specific function is to allow electrical insulation between two important parts of the installation when one of them is brought to high voltage, are more specifically called "insulation conduits". The length of such an insulation pipe is calculated so that it has sufficient resistance to high voltage, once it has been cleaned with rinse aid and dried internally with water. 'pressurized air.

 An intermediate tank 41, which can be rinsed off, is part of the distribution circuit 12 and, according to an important characteristic of the invention, this intermediate tank consists of a section of conduit of length AB of this distribution circuit 12. Of course, this section of duct is insulating, and its length is determined according to the volume of paint necessary to completely cover an object. The circuit 12 is also connected, by means of controlled connection means, on the one hand to the color changing unit 11 and on the other hand, to means for supplying rinse aid 40, isolated of the earth. In the example of FIG. 1, said controlled connection means comprise the valve 21 already mentioned, and a valve 45, controlled, inserted between the upstream end of the circuit 12 and an outlet conduit 42 of a reservoir 44 containing said rinse aid. This tank 44 is electrically isolated from the ground. It is waterproof and pressurized, so that one can (thanks to the pressure prevailing in the tank) "push" paint in circuit 12, during the spraying phase, from rinse aid coming from the insulated tank 44 and discharged into the conduit 42 under the action of the pressure prevailing in the reservoir 44. To do this, the reservoir 44 is connected to a supply and pressurization unit 46 capable of delivering rinse aid coming from a circuit 47 (to complete the level in the reservoir 44) and compressed air from a circuit 48. The compressed air serves both to establish the pressure in the reservoir 44 and to dry the insulating conduit 49 connecting the unit 46 to the tank, after a refreshing phase thereof. These upgrades are made when the tank 44 is not brought to high voltage; it is then temporarily depressurized to allow the air to flow and the duct 49 to dry out. In the example shown, the rinse aid reservoir is kept pressurized at a high pressure (of the order of 15 bars) to be able to push the paint despite the length of the section of conduit 41 forming the intermediate reservoir.

 Under these conditions, the regularity of the spraying, as the "length" of paint decreases, is ensured by the pressure regulator 29. The sequencing of all the valves and units which have just been described, as well as piloting the pressure regulator 29, are operated under the control of a computer, not shown. Many commercially available computers can provide this function. Its programming is within the reach of the skilled person. This computer essentially receives information representative of the liquid flow rate (paint or rinsing product), which flows in the circuit 12. This information is produced from the signal delivered by the flow sensor 30.

 The operation of the installation of Figure 1 is as follows.

 When filling, the high voltage is set to zero and the color change unit 11 is controlled to select one of the paints. This flows towards the projector, the valves 21 and 27 being open.

When the quantity necessary to paint an object is engaged between the collector 15 of the color changing unit and the circuit 12, the valve corresponding to the paint selected in the unit 11 is closed and that of the circuit 17 is opened simultaneously. From this moment, the paint is pushed by rinse aid coming from circuit 17. The lengths of conduits are calculated so that, when the paint reaches the projector (point B) the "limit" between the rinse aid and the paint, is located at A, that is to say at a point located downstream of the valve 21 and (preferably) downstream of the flow sensor 30.

 The valve 27 is closed and the valves 25 and 45 are opened.

This ensures continuity of the pushing fluid (that is to say the rinsing product) between the pressurized reservoir 44 and the distribution circuit 12. The rinsing product, which then comes from the reservoir 44, is directed a short instant, towards the purge means 22 through the valve 25.

 Once this continuity has been ensured, all the valves are closed and the valve 25 is opened again. The insulation pipe 20 and the pipe 24 are then cleaned and dried using rinse aid and air. tablet from the color changing unit. At the same time, cleaning and drying are carried out.

conduits 28 and 37 from the cleaning unit 35 and conduit 49 from the unit 46.

 The high voltage is then established and painting begins by opening the valve 45. The flow is constantly monitored and regulated from the flow sensor 30 and the pressure regulator 29, via the computer.

 The invention therefore makes it possible to clean the distribution circuit 12, the flow sensor 30 and the various valves immediately after the passage of the paint, since the latter is pushed by rinsing product. To this saving of time, there is added that which results from the fact that the shape of the intermediate reservoir 41, that is to say the section of conduit of length AB, is that which is most easily and quickly cleaned.

 The flow sensor 30 is brought to high voltage during the projection phase; it must therefore be able to develop a signal that can be used despite the presence of this high voltage. Several solutions are possible. Preferably, a sensor with a mechanical structure similar to that of a gear pump will be used. The sensor is traversed by the liquid which drives rotating gear wheels. These can therefore easily be used to develop a variable frequency signal depending on the flow rate, thanks to an appropriate transducer placed opposite a toothed wheel. This transducer can for example be of variable reluctance. Isolation can be ensured by a transformation into light pulses and a transfer by optical fiber.

 The embodiment of FIG. 2 is very similar to that of FIG. 1. The analogous elements bear the same reference numbers and will not be described again. The sequencing is the same. On the other hand, the pressure regulator 29 is eliminated, while a volumetric pump 50, rinsable, is inserted in the distribution circuit 12, preferably in the vicinity of the flow sensor 30, that is to say near the upstream end of the distribution circuit 12. Preferably, the flushable pump 50 is a gear pump. Under these conditions, the pressure of the compressed air in the circuit 48 and therefore in the reservoir 44 can be much lower (from the order of a few bars) since it is only used for feeding the pump 50. The filling, therefore the color change, is nevertheless faster and the product is not subjected to strong pressure variations. It only "rises" in pressure when it is going to be sprayed.

 The embodiment of Figure 3 further reduces the time of color change operations. In general, the distribution circuit, described with reference to FIG. 1, is replaced by two distribution circuits 12a, 12k so as to be able to clean and fill a distribution circuit during the spraying of the paint previously engaged in the other distribution channel.

 On the other hand, in the example of FIG. 3, the color changing unit 11 remains unique, as are the means for supplying rinse aid 40, isolated from the ground. Each distribution circuit 12a, 12b therefore comprises a section of conduit forming an intermediate reservoir 41a, 41b, rinsable and controlled connection means are arranged to alternately connect each of these sections of conduit to the color change unit 11 and to the means rinse aid supply 40, respectively.

 In the diagram of Figure 3, elements similar to those of Figure 1 have the same reference numerals. In addition, similar elements belonging to or specifically connected to a 12â or 12k distribution circuit bear an index a or k respectively.

 Thus, the insulated reservoir 44, connected as previously to a supply and pressurization unit 46, communicates with the two circuits 12a and 12b via (in particular) two valves 45a, 45 ~ controlled, respectively.

A first flow sensor 60 is inserted between the outlet of the reservoir 44 and the two common inlets of the two valves 45a, 45b. The color changing unit 11 also communicates with the two circuits 12a and 12b via (in particular) two controlled valves 64a, 64b, while a second flow sensor 61 is inserted between the output of the unit 11 and the two common entrances of the two valves 64e, 64k. The pressure regulator 29 is here inserted immediately upstream of the projector 13 or of a group of such projectors.

This projector is here common to the two distribution circuits 12a, 12é. The purge means 26 are connected immediately upstream of this regulator via a controlled valve 62.

With regard to the distribution circuit 12â, between the valve 45a and the flow sensor 61 on the one hand, and the pressure regulator 29 on the other hand, the following elements are encountered successively:
The output of the flow sensor 61, associated with the color changing unit is connected by the valve 64a to a first isolation conduit 20a extending between the valve 64a and an inlet of a three-way valve 66a ( type with two inputs and one output). Said first insulation conduit 20 therefore plays the same role as conduit 20 which is described with reference to FIG. 1. A three-way valve 65q, with two inputs and one output, has one of its inputs connected to the outlet of valve 45 and its other inlet connected to a cleaning unit 68a similar to unit 35 of the installation of FIG. 1.

 The outlet of the valve 65a is connected to the other inlet of the valve 66â via a second isolation conduit 70ê.

 The outlet of valve 66a is connected to purge means 22q via a controlled valve 25a and to the section of conduit 41â forming the intermediate reservoir of circuit 12a, via a valve 74a.

 The intermediate tank 41a of length AB, therefore extends here between the valve 74a and a valve 27a.

The downstream end of the length of conduit section AB is also connected to purging means 78a via a controlled valve 79a. The outlet of the valve 27a is connected to the pressure regulator 29 via a third isolation conduit 82ê and a controlled valve 83a, located in the vicinity of said regulator. The cleaning unit 35g is connected to the outlet of the valve 27a via a controlled valve 36ai. All these circuits and valves are easily rinsable.

 It is understood, at this stage of the description, that all the connection means (the valves) and said insulation conduits 20a, 70a and 82a are arranged to selectively isolate, from the electrical point of view, the corresponding distribution circuit 12a ( and consequently the rinsable tank 41a) of the color changing unit, the cleaning unit and the other distribution circuit 12b, respectively.

 It also appears that the arrangement is such that each isolation duct, defined above, is connected, by means of controlled valves, upstream to cleaning means and downstream to purging means. A distinction is thus made between the cleaning means of the color change unit 11 and the purge means 22a for treating the insulation conduit 20a, the cleaning unit 68a and the purge means 22q for treating the insulation conduit 70a and the cleaning unit 35a and the purging means 26 for treating the insulation conduit 82a. Of course, these cleaning units and purging means are automatically electrically isolated at each cleaning phase by the rinsing and cleaning operations. drying of the insulating conduits which terminate therein, as explained with reference to the embodiment of FIG. 1. the same is true of the means 46 relative to the rinse aid reservoir 44.

 The distribution circuit 12b is strictly identical to the circuit 12a and the corresponding elements have the same numerical references with the index b instead of a. A distinction is thus made between controlled valves 45k, 64k, 25b, 74b, 79b, 27k, 36b and 83b, three-way controlled valves 65k and 66k, cleaning means 68b and 35k. the. purge means 22k and 78b, the insulation conduits 20b, 70k and 82b and, of course, the insulating conduit forming intermediate reservoir 41 ~. All these elements are interconnected in the same way so that the 12k circuit does not need to be described again.

 As in the case of the installation in FIG. 1, the computer controls all of the valves as well as the pressure regulator 29; it receives signals developed from the two flow sensors 60 and 61. It should be noted that the isolation conduits 82a and 82k, which only have the function of "holding" the high voltage once rinsed and dried, have smaller cross sections than other conduits. The quantity of product contained in these conduits is therefore small compared to that which is contained in the section 41 or 41 k forming the rinsable tank. Furthermore, the conduits 82a, 82b and the valves and cleaning means which relate thereto can be eliminated if two independent projectors 13 and two groups of such projectors are provided.

 The operation is as follows.

 If it is assumed that one of the circuits, for example the circuit 12b, has just been filled with paint and that said first insulation conduit 20k has been cleaned and dried via the valves 66k, 25k and the purging means 22b , analogously to what has been described with reference to FIG. 1, the circuit 12X is therefore ready to paint, the paint being located between the closed valves 74k and 27k. This situation is reached during the projection phase implementing the distribution circuit i2a, therefore without loss of time. The circuit 12b is then isolated from the high voltage by the conduits 70é, 20a and 82k which have been previously cleaned and dried. Before restoring the high voltage in circuit 12k and starting to paint from this circuit, it is necessary to wait for the end of the projection phase in progress, implementing the distribution circuit 12a, in order to be able to isolate it electrically. To do this, it suffices to clean and dry the insulation pipe 70a and the insulation pipe 82a. From this moment, the continuity of the rinsing product between the reservoir 44 and the distribution circuit 12k can be established via the valves 45k, 65k, 66b and 25b, up to.

purge means 22b. The paint spraying phase can then start by closing the valve 25b and opening the valves 74k, 27k and 83k. During this time, a paint of another color is injected into the circuit 12a and the cycle is ended by cleaning and drying the conduit 20a.

 Of course, a variant similar to that of FIG. 2 can perfectly well be envisaged. It suffices, for example, to remove the pressure regulator 29 and to insert a positive displacement pump 90, rinsable, preferably a gear pump between the reservoir 44 and the flow sensor 60. The reservoir 44 then no longer needs to be pressurized to a high pressure.

 Finally, it should be noted that with an installation of the type described above, the fact of using a paint and a conductive solvent or rinsing product can become advantageous by making it possible to simplify the structure of the electrostatic projector 13, this is that is to say to lighten it, which can be very appreciable when such a projector is carried by a multi-axis robot. Indeed, it then becomes perfectly possible to apply the high voltage to another element than the projector and in particular to the reservoir 44.

Claims (16)

 1- Installation for spraying coating product of the type comprising a coating product changing unit (11), means for supplying flushing product, at least one distribution circuit (12) downstream of said unit and supplying at least one projector ensuring the spraying of said product, as well as an intermediate tank (41) forming part of this distribution circuit, characterized in that said intermediate tank (41) consists of a section of conduit of said distribution circuit and in that controlled connection means are arranged to push said coating product, in the spraying phase, from said rinsing product.  2- Installation according to claim 1, for the application of said coating product electrostatically, in which said coating product changing unit is connected to the ground and in which said distribution circuit (12) is sequentially connected to a high voltage applied to at least one electrostatic headlight (13), characterized in that said controlled connection means are arranged between, on the one hand, said section of conduit and, on the other hand, said unit (11) and means supply of rinse aid (40), isolated from the ground, so as to be able to push said coating product, in the electrostatic spraying phase, from rinse aid coming from these isolated supply means (40) .  3- Installation according to claim 2, characterized in that said means for supplying rinsing product comprises a reservoir (44) electrically isolated from the ground, containing said rinsing product.  4- Installation according to claim 3, characterized in that said tank (44) is sealed and pressurized by being connected to a source of compressed air (48).  5- Installation according to one of claims 2 to 4, wherein said coating product changing unit comprises a circuit for rinsing product circulation (17) and a compressed air supply circuit (18), characterized in that this unit is connected to said section of conduit forming an intermediate reservoir (41) by isolation means comprising a first rinsable isolation conduit (20).  6- Installation according to one of the preceding claims, characterized in that a flow sensor (30) is inserted in said conduit of said distribution circuit, upstream of the section forming said intermediate tank (41).  7- Installation according to one of claims 4 to 6, characterized in that said rinse product reservoir (44) is kept pressurized at a high pressure and that a pressure regulator (29), rinsable, known per se, is inserted into said distribution circuit (12) in the vicinity of said electrostatic projector (13).  8- Installation according to one of claims 4 to 6, characterized in that said rinse aid reservoir (44) is kept pressurized at a low pressure and that a pump (50), preferably a gear pump, is inserted into said distribution circuit, upstream of said section of conduit forming said intermediate reservoir (41).  9- Installation according to one of claims 1 to 5, characterized in that it comprises two distribution circuits (12a, 12k) each comprising a section of conduit forming an intermediate tank (41a, 41X) above and in that means of controlled connection are arranged to alternately connect each of the sections of conduit forming intermediate reservoirs to a unit for changing the coating product (11) above and to means for supplying the above-mentioned rinsing product, respectively.  10- Installation according to claim 7, characterized in that each distribution circuit comprises a three-way valve (66a, 66k) or the like, with two inputs, one of the inputs being connected to said means for supplying rinse aid (40), the other inlet being connected to said color changing unit (11) and its outlet being connected to said section of conduit forming a rinsable reservoir (41a, 41k).  11- Installation according to claim 10, characterized in that each distribution circuit comprises isolation means comprising a first insulation conduit (20a, 20b) above, inserted between an inlet of said three-way valve (66ss, 66B ) and said unit (11) and a second isolation conduit (70a, 70b), inserted between the other inlet of said three-way valve and said means for supplying rinse aid (40) isolated from the ground.  12- Installation according to claim 11, wherein the projector (s) (13) are alternately supplied by the two distribution circuits, characterized in that the isolation means of each distribution circuit comprises ,. each, a third isolating conduit (82a, 82k), rinsable, inserted downstream of said section of conduit forming a rinsable reservoir.  13- Installation according to one of claims 9 to 12, characterized in that a first flow sensor (60) is inserted between said means for supplying rinse aid and the distribution circuits and in that a second flow sensor (61) is inserted between said unit (11) and the distribution circuits.  14- Installation according to one of claims 9 to 13, wherein said rinsing product supply means comprise an insulated, sealed and pressurized tank (44), characterized in that said rinsing tank is kept pressurized to a high pressure and that a pressure regulator (29), rinsable, known per se, is inserted in the vicinity of the electrostatic projector (s).  15- Installation according to one of claims 9 to 13, wherein said rinsing product supply means comprise an insulated tank (44) sealed and pressurized, characterized in that said rinsing tank is kept pressurized at a low pressure and that a pump (90), preferably a gear pump, is inserted between said insulated tank and the two distribution circuits (12a, 12k).  16- Installation according to one of claims 5, 11 or 12, characterized in that a said isolation conduit (20, 70, 82) is connected, by means of controlled valves, upstream to means of cleaning and downstream to purging means.