EP0693319A1 - Spraying device comprising a container for a coating material and method for cleaning and filling such a container - Google Patents

Abstract

The device comprises a projector (1) and a reservoir (5) with a piston (9) displaced by an operating rod (12). The rod may be mechanically disconnected from the piston and from the translational drive system (15,16), and from the device (17) measuring the displacement of the rod. The rod may simply apply pressure to the piston (9) or its drive mechanism, allowing its removal. During at least part of the cleaning and refilling phases of the reservoir the piston itself is moved by the product being pumped into the reservoir. <IMAGE>

Description

The invention relates to a device for spraying coating product of the type comprising a piston reservoir. It further relates to a method of filling the reservoir with such a device.

In many industrial applications, coating product projectors on board machines are used which move opposite the objects to be coated. It is sometimes useful to combine a coating product reservoir with one or more projectors. This allows for example to apply electrically conductive coating products, such as water-soluble paints, by the electrostatic way without resorting to expensive and complex electrical insulation systems or to electrostatic charging systems by Corona effect difficult to implement. artwork. Installations of this type are known from patent applications FR-A-2609252, FR-A-2695327 and FR 9303829 in the name of the applicant, the content of which is included, by reference, in the present application.

The precision sought for the flow rate of coating product leaving the headlight essentially depends on the precision of the movement control of the piston inside the tank. It appeared that the systems comprising a piston controlled by an actuating rod are more precise than the pneumatically or hydraulically controlled systems, that is to say driven with a gas. In addition, systems with pneumatic or hydraulic control necessarily include a pressure regulator located between the tank and the projector. This regulator is used to control the pressure or the flow of product supplied to the projector. It has its own volume which corresponds to a quantity of coating product which cannot be sprayed during the coating phases: this quantity must be poured into a drain when the color changes. The regulator must also be cleaned with solvent when changing colors. The systems with piston actuation rod being more precise, they make it possible to dispense with the pressure regulator and therefore to save product and solvent.

However, during the operation of an installation, it may prove necessary to carry out the standard exchange of a tank or a box containing a projector and a tank. This change must be rapid so as not to disrupt current production. It may also be necessary to inspect the inside of a tank for possible product leaks. This inspection should also be as quick as possible.

Known systems including a piston controlled by a rod cannot be dismantled easily. The operator's task is therefore long and delicate, which is incompatible with rapid maintenance. Finally, the cost of the drive and displacement measurement means and the calibration to which they are subject does not allow them to be changed at each maintenance operation.

In the systems of the prior art, at the end of the spraying phase, the piston of the coating product tank must not be completely pressed against the corresponding face of the tank in order to allow the swirling movement of the cleaning product on its front face , i.e. the face in contact with the coating product. In general, 1 or 2 mm studs are provided which serve as a stop and keep the piston away from the bottom of the tank. However, the corresponding volume of paint is lost at the end of each spraying phase since it is poured into a drain while being pushed by the cleaning product. This increases the operating cost of the installation. In addition, part of the cleaning product is only used to remove this remaining paint and not to effectively clean the front face of the piston, which corresponds to a second additional cost.

The invention solves all of these problems.

It relates to a device for spraying coating product, of the type comprising at least one sprayer and a piston reservoir displaced by an actuating rod, characterized in that the rod is capable of being mechanically detached from the piston or from its means drive in translation.

In particular, the piston and the actuating rod can be in simple support one against the other. The rod pushes the piston during the spraying phases, which allows precise dosing of the amount of sprayed paint. The rod is integral with its drive and displacement measurement means constituted, for example, by a stepping motor and by an encoder, which are mounted on the structural element which supports the assembly constituted by the projector and by the tank. As for the piston, it is trapped in the tank. Thus, it is possible to separate the reservoir and the piston which it contains from the structural element and from the rod which is integral with it.

It is also possible to provide that the rod is integral with the piston but that it can be easily disengaged from its drive and displacement measurement means by translation along its axis of symmetry: We can then easily move away from the structural element the assembly formed by the reservoir, the piston and the rod.

In both cases, the tank is secured to the structural element by a laying plane. By a judicious choice of the geometry of the tank and the installation plan, it is possible to access the interior of the tank quickly.

The invention also relates to a method for filling a reservoir of coating product in a device for spraying coating product, the reservoir being of the piston type, characterized in that, during the spraying phases, the piston is moved by an actuating rod and in that, during at least part of the tank cleaning or filling phases, the piston is moved by the product entering the tank.

This method is implemented with a device according to the invention. During the cleaning or filling phases, it is possible either to move the rod away from the piston, or to disengage the drive means for translating the rod, or to move the drive means away from the rod. During the cleaning phases, it is the cleaning product which moves the piston whereas, during the filling phases, it is the coating product which moves the piston. Thanks to this process, no air volume is created in the tank before the product arrives. There is no risk of forming air bubbles in the product present in the tank. This method also makes it possible to push back the piston without the pressure which displaces it being transmitted to the means for actuating and / or measuring the displacement of the rod. This avoids excessive resistance to movement of the piston, which makes it possible to fill the reservoir all the more quickly and there is no risk of damaging the drive and displacement measurement means in the event of too rapid movement of the piston. , for example due to an overpressure in the coating product supply duct.

• la figure 1 est une vue schématique en coupe d'un dispositif selon l'invention,
• la figure 2 est une vue schématique en coupe d'une variante de l'invention et
• la figure 3 est une vue schématique en coupe d'une seconde variante de l'invention.

The invention will be better understood and other advantages thereof will appear more clearly in the light of the following description of three embodiments of a coating product spraying device conforming to its principle given solely by way of example and made with reference to the accompanying drawings in which

• FIG. 1 is a schematic sectional view of a device according to the invention,
• FIG. 2 is a schematic sectional view of a variant of the invention and
• Figure 3 is a schematic sectional view of a second variant of the invention.

The device of FIG. 1 comprises a rotary sprayer of coating product 1 provided with a spray bowl 2 driven in rotation by the rotor 3 of an air turbine not shown. The projector 1 is supplied with coating product through a conduit 4 having as its source a reservoir 5 mechanically secured to the projector 1. A valve 6 for cleaning / filling the reservoir is mounted at the periphery of a housing 7 containing the projector 1 and the reservoir 5. The valve 6 is designed to cooperate with a cleaning / filling station (not shown) to which the housing 7 can be moved at the end of the spraying phases. The valve 6 is connected to the reservoir 5 by a conduit 8 through which a cleaning product and a coating product circulate according to a predefined sequence. A piston 9, movable in translation inside the reservoir 5 is used to push the coating product into the conduit 4 during the spraying phases.

The housing 7 is mounted on a structural element 10 by means of a quick connector such that, by example, a ring 11 screwed onto an external thread 19 of the structural element 10 and resting on a recess in the housing 7. The quick connector could also be a hook system or any other equivalent system. The structural element 10 can be the wrist of a multi-axis robot, the arm of a lateral machine or the beam of a roof machine and, in general, any element, mobile or fixed, capable of carrying a projector. coating product.

An actuating rod 12 is simply supported on the rear face of the stud 9, that is to say the face which is not in contact with the coating product. The rod 12 is translated along its axis of symmetry XX ′ thanks to a screw-nut assembly. The nut or slide 13, on which the rod 12 is fixed by a key 13a, is immobilized in rotation by a groove and key system not shown. It is moved by the rotation of a screw 14, itself driven by a stepping motor 15 to which it is connected by a set of toothed belts 16. An encoder 17, associated with the motor 15, makes it possible to know at all times the position of the motor 15, therefore of the rod 12 and of the piston 9.

A laying plane 18 traversed in its central part by the actuating rod 12 is mounted at the end of the structural element 10 by means of screws not shown. It comprises orifices 19a, partially shown, into which open air supply conduits for the elements included in the housing 7 and, optionally, electrical connectors not shown, for example intended to allow projection by electrostatic means.

A centering pin 20 provided on the central part of the rear face of the piston 9 cooperates with a blind hole 21 located at the end of the rod actuation 12 to center the rod on the piston. Thus the forces transmitted to the piston 9 by the rod 12 are parallel to the axis XX 'which is also the axis of symmetry of the piston 9. The piston does not tend to move perpendicular to this axis, which would risk block, or even damage or damage the cylindrical part of the tank 5. A cylindrical jacket 22 made of stainless steel, ceramic or insulating material covers the internal cylindrical wall of the tank 5. This jacket 22 limits the friction of the segments 23 and 23 'and the O-ring 24 carried by the piston 9. On the side of the structural element 10, the jacket 22 is extended by a baffle made of insulating plastic material 25 which penetrates into the recesses 26 formed on the rear face of the piston 9 when the latter is in its position corresponding to the maximum filling of the reservoir 5 shown in FIG. 1. This baffle is, inter alia, used during the projection by electrostatic means of coating product; it serves to avoid the ramping of the high voltage of the mass of coating product contained in the tank 5 and brought to high voltage towards the structural element 10 which is grounded.

When it is necessary to dismantle the housing 7 for a maintenance operation, it suffices to rotate the ring 11 to disengage it from the thread 19 and the entire housing 7 is detached from the structural element by a translational movement in the XX 'direction. The centering pin 20 is extracted from the blind hole 21 and the piston 9 and the actuating rod 12 are spaced from one another. Even if the assembly between the centering pin 20 and the blind hole 21 was blocked, the extraction of the centering pin would take place since the baffle 25 of the jacket 22 retains the piston inside the tank 5. Another box 7 can be immediately mounted in place of the previous one and production is interrupted for a minimum period. In practice, an operation of this type lasts less than a minute.

Disassembly of the casing 7 also allows the operator to visually check the interior of the reservoir 5 by pushing the piston back into the "empty reservoir" position (on the left in FIG. 1) and checking, for example, that the segments 23 and 23 ′ and the seal 24 are still effective. Indeed, the location of the actuating rod makes it possible to send a light beam into the tank and to inspect it.

According to a variant of the invention, the shirt 22 is not extended by a baffle. It is then possible to extract the piston 9 from the tank 5 by simple pulling to inspect the bottom of the tank.

Furthermore, when the housing 7 is mounted, the operation is as follows. During the projection phases, the motor 16 works in accordance with a set point, which turns the screw 14 and moves the slider 13 to the left of FIG. 1. The actuating rod 12 fixed on the slider 13 is also moved towards the left and pushes the piston 9 in the same direction, which has the effect of emptying the tank 5 in the direction of the projector 1 in accordance with the instruction. The encoder 17 detects the position of the motor 15, which makes it possible to know that of the piston 9. This precise system can be coupled with a digital control.

At the end of the projection phase, the piston 9 rests against the internal face of the reservoir 5 in which the inlet of the duct 4 is formed. As will appear in the description which follows, it is not necessary to hold the piston moved away from the bottom of the tank or to provide spacers on the front face of the piston.

The actuating rod 12 is moved back a short distance, of the order of 1 mm, which has the effect of moving it away from the piston 9. A determined quantity of cleaning product is injected into the conduit 8 through the valve 6. This cleaning product opens tangentially on the front face of the piston 9 which it repels since the rod 12 does not hold it in position. In this way, the volume necessary for the swirling movement of the cleaning product is created by the product itself. There is therefore practically no more paint volume lost at the end of each spraying phase, which consequently increases the economic performance of the device and reduces the pollution it induces. In addition, the friction forces of the product on the front face of the piston are higher the smaller the volume into which the product penetrates, which contributes to the cleaning efficiency.

After the cleaning phase, the rod 12 is brought by the motor 15 to a position close to that which it will have at the end of filling. The coating product is then injected into the reservoir 5 and moves the piston until it comes into abutment against the rod 12. During all this displacement, the only force which must be overcome by the coating product opening into the tank is that of the friction of the piston 5 on the jacket 22. As before, the motor 16 and the encoder 17 are not likely to be damaged. At the end of the filling period, the product which enters the reservoir must push the rod 12 and this movement is detected by the encoder 17 since it is transmitted by the belts 16 to the motor 15. The quantity of product present in the tank 5 can then be adjusted finely by controlling the last millimeters of the piston stroke with the drive system constituted by the motor 15, the toothed belts 16 and the encoder 17.

FIG. 2 represents a variant of the invention in which elements similar to those of FIG. 1 bear the same references increased by 100. This embodiment differs from the previous one in that the actuating rod 112 is fixed on the face rear of the piston 109, for example screwed into a thread 150. In its part furthest from the piston 109, the rod 112 is provided with a groove 151 and rests on two bearings 152 and 153 of a frame 154. The frame 154 carries a toothed wheel 155 driven by a disengageable motor 115. A sensor 117 for displacement of the rod 112 is also mounted on the frame 154. The rod 112 is housed in a sleeve 156 fixed relative to the structural element 110 and integral of the frame 154 thanks to a ring 157. Thanks to the groove, the rotational movements of the toothed wheel in one direction or the other correspond to translation of the rod 112 and of the piston 109 in both directions.

When it is necessary to dismantle the housing 107, the motor 115 is disengaged and the ring 111 is unscrewed. The housing 107 can then be removed. It drives the rod 112 which is integral with the piston, which is possible since the groove can drive the toothed wheel freely due to the disengagement of the motor 115. The disassembly of the housing 107 is thus easy and rapid and has advantages similar to those envisaged with the embodiment of Figure 1.

At the end of a spraying phase, the piston 109 is pushed by the rod 112 against the corresponding face of the reservoir 105. As before, it is not necessary to allow a dead volume of coating product to remain in the reservoir. In Indeed, at the start of the cleaning phase, the motor 115 is disengaged and the cleaning product opening tangentially in the bottom of the tank 105 pushes the piston 109 to a position detected by the sensor 117. At the signal given by the sensor 117 , the motor 115 is re-engaged and blocks the piston in the cleaning position. Likewise, during the filling phase, the motor 115 is disengaged until the piston reaches the position corresponding to the desired quantity of coating product according to the characteristics of the object to be coated. It is then re-engaged to lock the piston in position until the start of the projection phase. The dosage of the quantity of coating product entering the reservoir is thus quick and precise.

FIG. 3 represents a second variant of the invention in which elements similar to those of FIG. 1 have the same references increased by 200. This embodiment differs from that of FIG. 1 in that the rod 212 is integral with the piston 209, for example integrally formed therewith. At its end furthest from the piston, it is in simple support in a housing 250 located at the end of another rod 251 actuated by a drive system constituted by a stepping motor 215 and by the associated belts 216 A displacement sensor 217 allows the translations of the rod 251 to be controlled. The operation is similar to that of the embodiment of FIG. 1, the separation between the two rods 212 and 251 taking place in place of that of the piston 9 with the rod 12. The assembly and disassembly are also rapid and the method of the invention can be implemented by causing the rod 251 to be transalted in the X'X direction at the start of the cleaning phase and / or from filling phase of the reservoir 205 to move it away from the rod 212.

The invention has been presented with a rotary type projector but of course applies to a pneumatic sprayer, electrostatic or not. A combination of the three embodiments shown is further possible.

Claims (10)

1 ° - Device for spraying coating product, of the type comprising at least one projector (1,101,201) and a reservoir (5,105,205) with piston (9,109,209), said reservoir being periodically filled with coating product and / or cleaned with a product of cleaning, characterized in that said piston is moved by an actuating rod (12,112,212) during the projection phases, and in that said rod is capable of being mechanically detached from said piston or from its translation drive means ( 15,16,115,155,215,216, 251) when filling or cleaning said tank. 2 ° - Device according to claim 1 characterized in that said piston (9) and said rod (12) are in simple support one against the other. 3 ° - Device according to claim 2 characterized in that said piston (9) and said actuating rod (12) carry centering means relative to one with respect to the other (20,21). 4 ° - Device according to claim 1 characterized in that it comprises means for retaining (25) said piston (9) inside said tank (5). 5 ° - Device according to claim 1 characterized in that said rod (112) is integral with said piston (109) and in that the drive means (115,155,215,216,251) of said rod allow the extraction of said rod. 6 ° - Device according to claim 5 characterized in that said drive means (115,155) of said rod are disengageable. 7 ° - Device according to claim 5 characterized in that said drive means (215,251) comprise an element (251) in simple support against the end of said rod (212) which is not integral with said piston (209) . 8 ° - Method for cleaning or filling a reservoir (5,105,205) of coating product in a device for spraying coating product, said reservoir being of the piston type (9,109,209), characterized in that, during the phases of projection, the piston is moved by an actuating rod (12,112,212) and in that, during at least part of the cleaning or filling phases of said tank, said piston (9,109,209) is moved by the product entering said tank, a space being provided between said piston (9) and said rod (12) or between said rod (212) and the means for translational drive (215,216,251) of said rod. 9 ° - A method of cleaning or filling a reservoir (5,105,205) of coating product in a device for spraying coating product, said reservoir being of the piston type (9,109,209), characterized in that, during the phases of projection, the piston is moved by an actuating rod (12,112,212) and in that, during at least part of the cleaning or filling phases of said tank, said piston (9,109,209) is moved by the product entering said tank, the drive means (115,155) in translation of said rod being disengaged. 10 ° - Method according to one of claims 8 or 9 characterized in that, before the start of the next cleaning phase, said rod (12) is distant from said piston (9), said drive means (215,216,251) are moved away from said rod (212) or said drive means (115) are disengaged.

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