ES2584238T3 - Procedure and sprayer for serial coating of parts - Google Patents

Abstract

The method involves controlling the spray jet of the sprayer of the spray cones of the sprayed coating material by limiting adjustable gas flow that is encircled circularly. Two independently adjustable gas flows are generated that emerge in different radial distances from the spraying cone axis and are set as a function of the workpiece areas that are to be coated. An independent claim is also included for sprayer for serial coating.

Description

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DESCRIPTION

Procedure and sprayer for serial coating of parts.

The present invention relates to a method for coating a piece and a sprayer for series coating of parts with outlet openings for a gas stream that delimits the spray cone, according to the preamble of the independent claims. In particular, it is the control of the guidance air of electrostatic rotary sprayers, as they are customary for the serial coating of parts such as automobile vehicle bodies. However, it can also be other types of sprayers. The invention is suitable for discretionary coating material including wet paint and powder paint.

In usual rotary sprayers (DE 4306800), which spray the coating material by means of the action of a bell that usually rotates with more than 40,000 r / min, it is directed as known as guiding air

from the sprayer to the outer surface of the conical hood which, not only gives the paint particles

sprayed radially on the separating edge of the bell plate additionally to the forces

electrostatics an impulse in the direction of the piece, but also serves to form the jet of

spraying and, in part, also for support during spraying. The guide air exits a crown of holes in the front surface of a guide air ring disposed at the front end of the spray housing. The number, the diameter, the shape and the direction of the drills can be different for the optimization of the air velocity, the volume of air and the width of the spray jet. The volume of guidance air desired in each case, which also results in the width of the spray jet, is predetermined as a parameter of the coating process and is regulated in a closed regulation circuit.

Instead of drills, arrangements of outlet openings in the form of an annular slit for the guiding air can also be provided. In a rotary sprayer, known thanks to EP 0092043, it is provided, in addition to a radially inner annular slit for the guidance air itself, an external annular slit, which is fed by the same source of pressurized air that the inner annular slit. The slit width of one or both annular slits is adjustable. The external air lining supplied by the additional annular slit has the task of compensating the edge turbulence, formed by the color cloud in interaction with the interior air lining, and bringing back the color particles that are detached from the cloud .

Rotary sprayers are also known in which, in addition to radial internal air openings, radial external auxiliary outlet openings for air are provided, which should prevent a backward movement of color particles to the sprayer.

In the sprayers there is, in general, the problem that spray cones of different width are required for different part areas. The known high-speed rotation spray systems, for example for painting car bodies of vehicles, are preferably designed such that bell plates with a larger diameter are used for surface painting areas and jet widths are adjusted spray (defined as "SB 50%", that is, as a width for 50% of the maximum layer thickness of the individual profile) of approximately 300 to 550 mm. For the painting of detail and of the interior space as well as for annexed and small pieces, such as mirrors, slats and bumpers, on the contrary smaller bell plates and jet adjustments of 180-300 mm are more suitable. In the case of smaller or narrower spray patterns, the paint application performance, defined as the ratio between the sprayed material and the material that precipitates, is greater than for wider spray patterns, with which significant savings can be achieved of paint and costs.

EP 1114677 discloses sprayers with interchangeable hoods, which differ with respect to the diameter, the direction of spraying and the volume of guiding air and which must be chosen depending on the shape of the object to be coated and the color used. for this, for example with a large diameter for external surfaces and with a small diameter for internal surfaces of car bodywork.

In practice, the internal surfaces of car body bodies, such as the access areas of the doors, the recesses, the trunk, the engine compartment and the inner sides of the cover or bonnet, etc. so far they have not been coated with rotary sprayers but, usually, with spray guns, which do not spray paint by rotation except by pressurized air. These spray guns generate an elongated spray pattern, relatively relatively concentrated, which is better for coating the narrower surfaces in the inner zone than the large-area round spray patterns, usual so far, of the sprayers rotating Especially during the interior painting with dust, these spray guns can give coating faults by sintering dust (the so-called sizzling), which must be retouched in an expensive way. In addition to the quality of painting, the application performance of spray guns is also worse than for rotary sprayers.

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When, for the complete painting of a piece, for a high application performance and a uniform complete paint layer, both wide and also narrow spray jet adjustments are necessary and the coating operation must not be interrupted by a change of head of Spraying, due to the lack of the possibility of adjusting the spray jet sufficiently, compromises between the size of the bell plate with the corresponding supply of guiding air and the width of the jet with respect to performance, must be adopted. Paint consumption and color tone. By reducing the speed of rotation, although a better spray stream strictness can be achieved, a lower spray fineness and a worsening of the coating quality must be accepted. Since it has not yet been possible to adjust the spray jet with the guidance air of a sprayer both in one and also in the other areas of width mentioned above for optimum operation, noticeable disadvantages such as painting result in practice. insufficient or impossible interior or detail, a greater “Overspray” (the portion of paint that is sprayed passing in front of the object), lower application performance, higher paint consumption and insufficient paint quality.

JP-A 07024367 and US-A 5 954 275 disclose electrostatic rotary sprayers with two circular annular air nozzle arrangements, which surround the axis of rotation concentrically at different radial distances, serving the air flow of the nozzles Radial internal air like mold air for the spray cone and which can be charged by radially external air flow, to reduce the spray cone to avoid "Overspray" during coating small and narrow part areas. Air currents can be controlled by pressure regulating components.

JP 08099052 A describes a rotary sprayer, whose guide air ring has a concentric nozzle arrangement for a first stream of air oriented towards the edge of the bell plate and a second stream of air oriented towards the perfometer of the bell plate , which are generated simultaneously by air sources with adjustable amounts of air for this purpose. The objective of the first air stream oriented towards the edge of the bell plate is to help spray paint, called micropulverization, while the second air stream oriented towards the bell plate perfometer should widen.

JP 0909448 A describes different rotary sprayers, whose guide air rings contain two or more concentric nozzle arrangements for the air currents that cross each other in suitable directions, which should deal with uniform micropulverization in a spray cone. , in particular, of metallic paint and of obtaining a good application performance. In some examples of embodiments, all nozzles are fed from a common air channel. In other examples of embodiments, different separate air currents are generated for the spray function or for the formation of a spray jet, whose supply channels are connected to some individually adjustable light sources. To improve the spraying effect, the air nozzles can be configured as supersonic nozzles.

EP 0 695 582 A1 discloses a high speed rotation sprayer intended in particular for the application of effects paint, which has an annular nozzle for the generation of parallel air currents with respect to the spray cone, and in the which radially outside the bell plate are provided, on only one side, for example, additional air nozzles in the form of a slit or of a semicircle, to convert the spray cone to an asymmetric shape.

EP-A 0 878 238 also discloses a rotary sprayer with radially external guided air holes and radially internal auxiliary air holes. Auxiliary air from radially inner holes is used during washing of the outer surface of the bell plate during coating breaks.

US-A 4792094 discloses a rotary sprayer with a radial internal annular arrangement of guiding air nozzles and two pairs of additional guiding air nozzles, which are diametrically opposed to each other radially out of the annular nozzle arrangement. By means of the external air stream oriented towards the internal air stream, the spray jet of the sprayer can be passed from a circular shape to an oval cross-sectional shape or similar to a weight. A similar nozzle arrangement is also described in JP H0291656.

The invention poses the problem of avoiding the inconvenience existing so far and proposing a method or control system for a sprayer which makes it possible to adjust the width of the spray jet, also without mechanical control of the opening arrangement of exit, in a margin of width essentially greater than until now and that in spite of this guarantees an optimal coating operation with a good application performance and a good quality of painting.

This problem is solved by the features of the claims.

In a first example of embodiment of the invention this is also possible without changing the spray head and without mechanical variation of the arrangement of outlet openings. In a second example of how to

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embodiment may be suitable, on the contrary, depending on the areas to be coated, change the spray hood and / or the arrangement of outlet openings for the guiding air currents.

Said at least two guiding air currents (or other gas currents that serve the same purpose), regulated in a closed regulation circuit, are not generated simultaneously in the first embodiment in the normal case, but optionally depending on the pieces or part areas to be coated. However, simultaneous combined use of both air currents, regulated in each case separately from each other, is also possible.

The invention makes it possible to paint complex part geometries and, in particular, complete bodies, including interior, exterior and detail painting, with the same rotary sprayer, with maximum paint application performance attainable, by means of selectively adjusted spray jet widths. the whole area that is needed. By means of two steering airs that can be adjusted separately from each other, the spray jet widths can be optimally adapted in each case to the object to be coated.

By means of the optimally adapted spray jet, less “Overspray” is generated globally than until now with the consequence of a higher application efficiency and lower paint consumption. Optimization improves paint quality at the same time.

The invention is explained in greater detail from the exemplary embodiment shown in the drawing. In the drawing:

Fig. 1 shows a rotary sprayer with a guide air ring according to the invention; Fig. 2a shows a section through the guide air ring of the sprayer according to Fig. Fig. 2b shows a top view on the guide air ring, seen from the left in Fig. 3 shows a rotary sprayer for powder paint; and Fig. 4 shows a schematic front view of the sprayer according to Fig. 3.

Except for the guidance air control of the spray jet described herein, the high speed electrostatic rotation sprayer shown in Fig. 1 can correspond to the state of the art, for example according to the aforementioned DE 4306800 document. In the manner known per se, a guide air ring 4 sits on the front end, facing the bell plate 1, of the spray housing 2, coaxially with respect to the spray shaft 3, on the surface 5 which it extends radially from the guide air ring 4, which is oriented towards the bell plate 1 and consequently to the spray cone formed by the sprayed coating material, the holes 12, 13, which are described below, for the guiding air that comes out to adjust the spray jet width. The perimeter surface 7 of the annular body 4, which extends conically backwards according to the representation, is aligned without steps with the adjacent perimeter surface 8 of the housing 2. Thanks to the continuous external shape without interruptions of the entire perimeter of the sprayer, they avoid swirling air around the sprayer and an undesired influence on the spray process on the bell plate 1 as well as fouling of the spray housing.

The front surface 5 of the guide air ring 4 can be found, as in the exemplary embodiment shown, axially behind the bell plate 1, being able to extend according to the representation radially inwards until close to the hollow shaft of the turbine of air that drives the bell plate. The guide air ring could also be fully inserted into the open front end of the spray housing. In other embodiments, the guide air ring can, however, extend, with its arrangement of outlet openings, also axially forward, up to the bell plate.

Fig. 2a and Fig. 2b show the guiding air ring 4 itself. On its front surface 5, in two graduated circles 10 or 11, there are concentric with respect to the spray axis 3 (Fig. 1) and therefore with respect to the axis of the spray cone which coincides with it, with different diameters, in each case crowns of guiding air drills 12 or 13, distributed with uniform angular distances.

In the example shown, the holes 12, 13 can in each case lead to parallel shafts on the front surface, although other arrangements are also possible. The radially inner holes 13 are fed by an annular channel 14 within the guide air ring 4, which is connected to a pressurized air duct (not shown) of the sprayer, while the outer holes 12 of the air ring of guided 4 run, starting from the front surface 5, first axially and then, as shown, with a rear part 16 approximately axially with respect to the perimeter surface 7, radially outwardly to an annular channel 17 which, with the air ring mounted guide, is formed between its rear side and the adjacent parts of the sprayer and is fed by another air duct under pressure from the sprayer.

Instead of the two drill crowns 12 or 13, arrangements of annular slit-type outlet openings can also be provided in a guide air ring or possibly also in separate components of the sprayer.

one;

Fig. 2a,

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The two mentioned pressurized air ducts can be connected, for example, in each case with a pressurized air connection of the sprayer for external ducts, which can lead in each case to a proper air regulation system. For example, when complexity is not desired for two separate air regulators, the pressurized air ducts can also be connected through a switching valve, controlled depending on the work piece area to be coated in each case. , to an air regulation system common to holes 12 and 13. The switching valve does not have to be outside the sprayer, but can be mounted on the sprayer, for example in the valve unit 18, so that then a single external guide air connection is necessary. The guiding air could also be regulated inside the sprayer.

During the coating of parts such as for example car bodywork, the first regulated guide air, of the radially inner holes 13, is preferably used for the adjustment of wider spray jets (for example for SB 50% from 250 to 300 mm) for the external painting, while with the second guide air, regulated separately from the first guide air, the holes 12 fit in the graduated circle 10 larger narrower spray jets (for example SB 50% of 50 at approximately 300 mm) for interior and detail painting, it may be appropriate that the two zones (as in the example considered) overlap. With one and the same sprayer it is possible, therefore, without interruption of the coating operation and without having to accept essential disadvantages of the width of the spray jet, in total for exterior, interior and detail painting, adjust the necessary area ( in the example considered from 50 to 550 mm). The two steering airs can be used and regulated separately from each other, that is, while the sprayer works with a guiding air, in each case another guiding air may be disconnected. The first guiding air that exits behind the bell plate 1, of the inner holes 13, impacts relatively far back on the perimeter surface, which narrows backwards, of the bell plate 1, generating around the bell plate a cushion of air and, as a result, it gives rise to a uniform air distribution during spraying. The second guiding air, of the outer holes 12, may instead be oriented such that it impacts a small radial distance (for example in the order of magnitude of 1 mm) outside the spray edge of the bell plate on the paint material to be sprayed or already partially pulverized by rotation, thereby favoring a stronger stricture of the spray jet than by means of air in the direction of the inner holes, so that maximum application performance is achieved and hard-to-reach or small part areas can also be well coated.

As another exemplary embodiment of the invention, the front part of an electrostatic rotary sprayer is shown in longitudinal section in Fig. 3, for example mounted on the wrist of a robot, for powder painting or other shaped coating material. of dust Like the electrostatic wet paint sprayer according to Fig. 1, the sprayer contains a drive turbine 30, driven for example by pressurized air, for the rotary spray hood 33 attached to the leading end of the hollow shaft 31. Through a cylindrical tube 32 extends coaxially from the hollow shaft 31, which serves as a powder channel of the sprayer, to the interior of the hub piece 35 of the bell 33, where, according to the representation, it axially flows out of the housing of the sprayer 36. The powder tube 32 is connected in the sprayer to a powder hose (not shown) from an external supply of air and dust. Sprayer bell 33 consists of a known shape (EP 1238710; US 5353995) essentially of an outer piece 38, arranged in a hub piece 35, which has an inner conical surface 40 of the shape shown, and an inner piece 42 seated in the space in front of the surface 40, which has an inner surface 46 opposite the surface 40 with the formation of a slit channel 44 and which is rigidly connected to the outer part 38. The slit channel 44 is therefore limited by the two conical surfaces 40 and 46. The radially external perimeter surface 49 of the outer and axially rear bell piece 38, that is to say that oriented to the main part of the sprayer, runs according to the representation (and unlike the mentioned known dust bells) widening only smoothly conically forward, so that with the axis of rotation it forms an acute angle of preferably less than 20 °, in the example shown approximately 5 °. In its path through the tube 32 and through the slit channel 44, the coating powder can be charged in the usual manner with high tension.

As in the exemplary embodiment according to Fig. 1, an adjustable guiding air stream 50 (or other gas stream) protruding radially out of the perimeter surface 49 of the hood 33, which surrounds or annularly charges the cone of spraying, which can be oriented approximately with parallel axis. Radially out of the current 50 another air or gas stream 51 comes out, whose output direction is also inclined axially, but according to the representation against the direction of the axis, an acute angle inward, in a manner that cuts the direction of the current 50 inside. The directions indicated by the arrows shown may run in such a way that they do not cut the outer surface of the bell 33, but pass in the vicinity of the bell. Suitably, the radially external gas stream 51 may be oriented approximately toward the dust outlet point of the spray hood 33.

The radially external current 51 does not here have a circular ring shape as the current 50, but instead consists of parts separated from one another, for example upper and lower planes, which, upon impacting on the internal current 50 and on the spray cone, must press it flattening it to adopt an oval cross-sectional shape (ovalize). Exit openings provided for this purpose can be recognized in the

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schematic representation of Fig. 4. While the guiding air stream 50 in a circular annular manner leaves the crown, which concentrically surrounds the axis of rotation, of a large number of openings 52, may be provided for the two flat parts of the current 51 two straight slits 53 or 53 ', which oppose, parallel tangentially to each other with respect to the circular ring formed by the openings 52, on opposite sides of the axis of rotation. The slits 53, 53 'are located in such a way symmetrically with respect to the axis of rotation, that the line that joins, perpendicularly with respect to the longitudinal direction of its opening of opening, its central points cuts the axis of rotation. The slits 53, 53 'are fed, on their inner side of the spray side, by pressurized air ducts 54. Instead of the two slits, parallel rows of in each case a sufficient number of openings can also lead to the target.

The guiding air openings 52 and / or the ovalization slits 53, 53 'can be found in an annular body 55, which is held in the sprayer so that it can be released and so that it can be changed quickly and quickly. simple by another guiding air ring with another arrangement of outlet openings. With the guiding air ring, the sprayer bell 33 can also be changed, for another bell, for adaptation to the part area to be coated in each case. The remaining part of the rotary sprayer can be unchanged at the same time. The guiding bells and air rings can be changed automatically, for example by robot control.

An essential advantage of the rotary sprayer described here is that the same basic sprayer can be used, for example, during program-controlled body painting for both external surfaces and also for automatic interior painting. For the interior painting, a round jet with a smaller diameter than the external one is suitably generated, which is ovalized, by means of the air current acting with a flat surface at the dust outlet point of the hood of the sprayer 33 of slits 53, 53 '.

By using a rotary sprayer for all external and internal parts of the part, not only can the development of the automatically controlled coating be simplified, but also the quality of paint can be improved compared to the usual spray guns so far and it is possible increase the degree of coating performance. It is also possible, more easily than until now, in case of a robot failure, to carry out its work with another robot.

In other cases, however, in the exemplary embodiment according to Figs. 3 and 4, coating the rotary sprayer all or at least different work surfaces with the same hood and the same arrangement of outlet openings, being modified for adaptation to the corresponding work areas only the gas streams 50, 51 by The regulation circuits.

Claims (10)

5 10 fifteen twenty 25 30 35 40 Four. Five fifty 55 60 65 1. Procedure for controlling the air for guiding rotary sprayers for the serial coating of parts, in particular of carriages of automobile vehicles, in which, to control the shape of the spray jet of the sprayer, the spray cone of the sprayed coating material is limited by an adjustable air flow, which surrounds it annularly, which leaves the sprayer concentrically with respect to the axis of the spray cone (3), in which different parts of the piece are coated, in each case, with another form of spray jet, and in which at least two independently adjustable air currents are generated between each other, leaving the axis of the spray cone (3) at different radial distances and depending on the areas of the parts to be coated, and of which the first regulated air stream is used to adjust the widest spray jets for the external coating of the part, characterized in that, with the second air stream regulated separately from the first air stream, the narrowest spray jets are adjusted for the detail and internal coating of the piece. 2. Method according to claim 1, characterized in that with a spray jet form external areas of a car body or part are coated and, with the use of the same sprayer or essential parts of the same sprayer, with the other form of spray jet, internal areas of this body or the part are coated. 3. Method according to claim 1 or 2, characterized in that a high speed rotation sprayer is used. Method according to claim 1, 2 or 3, characterized in that a rotary sprayer is used, whose radially external air stream (51), oriented towards the annular air stream (50), causes the spray cone to adopt a oval or flattened shape during coating of internal areas. 5. Method according to one of the preceding claims, characterized in that each air stream is regulated in its own closed regulation circuit. Method according to one of the preceding claims, characterized in that a regulated air flow is supplied, through a controlled switching valve depending on the part areas to be coated, to the outlet openings (12, 13) radially external or radially internal. Method according to one of the preceding claims, characterized in that, for coating with a wider spray cone, only one air stream is used and, for coating with a narrower spray cone, only the other is used. air stream. 8. Method according to claim 7, characterized in that the two zones, in which the width of the spray cone can be adjusted, in each case, overlap each other 9. Method according to one of the preceding claims, characterized in that the piece is coated with powder paint. 10. Control system capable of controlling at least two guiding air currents, independently adjustable between sf, of rotary sprayers during serial coating of parts, in particular of car body carts, with an air regulation system connected to a pressurized air connection of the sprayer, in which, to control the spray jet form of the sprayer, the spray cone of the sprayed coating material is limited by an adjustable air flow, which surrounds it annularly, which leaves the sprayer concentrically with respect to the axis of the spray cone (3), in which different parts of the piece are coated, in each case, with another form of spray jet, wherein said at least two independently adjustable air currents from each other leave the axis of the spray cone (3) at different radial distances and can be used depending on the areas of parts to be coated, and in which the control system controls the first regulated air flow to adjust the widest spray jets during the external coating of the part, characterized in that the control system is capable of controlling the second regulated air stream separately from the first air stream to adjust narrower spray jets during the detail and internal coating.