EP1331037A2 - Method and spraying apparatus for coating workpieces in series - Google Patents

Abstract

The method involves controlling the spray jet shape of the atomizer with a controllable annular gas flow concentric to the atomizer's spray cone axis and coating different regions of the workpiece using different jet shapes At least two mutually independently controllable gas flows are produced that emanate at different radial distances from the spray cone axis and are adjusted depending on the workpiece region to be coated. AN Independent claim is also included for the following: an atomizer for serial coating of workpieces.

Description

The invention relates to a method for coating a Workpiece and an atomizer for the series coating of Workpieces with outlet openings for an area that limits the spray cone Gas flow according to the preamble of the independent Claims. In particular, it is the control the steering air of electrostatic rotary atomizers, such as for the series coating of workpieces such as vehicle bodies are common. But it can also be other types about atomizers. The invention is suitable for any Coating material including wet paint and powder paint.

In conventional rotary atomizers (DE 4306800), which are the coating material by the action of one with usually atomizing more than 40,000 rpm rotating bell is known from the atomizer onto the conical bell outer surface Directional air directed not only that at the bell plate tear-off edge additionally radially sprayed paint particles a pulse towards the electrostatic forces to the workpiece, but for spray jet forming and partially also serves to support atomization. The steering air emerges from a ring of holes in the end face of a front end of the atomizer housing arranged steering air ring out. Number, diameter, shape and direction of the holes can to optimize air speed, air volume and Spray jet width may be different. The one you want Amount of steering air, which also gives the spray jet width, is specified as a parameter of the coating process and in closed loop.

Instead of bores, annular-gap-shaped outlet opening arrangements can also be used be provided for the steering air. With one from the EP 0092043 known rotary atomizer is in addition to a radially inner annular gap for the actual steering air outer annular gap provided by the same compressed air source is fed like the inner ring gap. The gap width of one or both ring gaps are adjustable. The one from the additional The outer air jacket supplied in the annular gap has the task that of the color cloud in interaction with the inner air jacket compensate for emerging turbulence and erupting Color particles traced back to the cloud.

Rotary atomizers are also known, in which additional to radially inner air openings, radially outer auxiliary outlet openings are intended for air that has a backward movement the paint particles in the atomizer should prevent.

Generally there is the problem with atomizers that for different Workpiece areas of different width spray cones required are. Known high speed rotary atomization systems for example for painting vehicle bodies are preferably designed so that for areas the surface painting bell plate with larger diameter used and spray jet widths (defined as "SB 50%", i.e. as width at 50% of the maximum layer thickness of the individual profile) 300 to 550 mm. For the detail and interior painting as well as for attachments and small parts like mirrors, strips and bumpers, however, are smaller bell plates and beam settings of 180 - 300 mm more appropriate. For smaller or narrower spray patterns, the is as Relationship between sprayed material and precipitating Material defined coating application efficiency higher than with wider spray patterns, which means considerable paint and Cost savings can be achieved.

EP 1114677 describes atomizers with interchangeable bells known, which is in terms of diameter, spray direction and Differentiate the amount of steering air and depending on the shape of the coating Item and the color used, etc. can be selected should, for example with a large diameter for external surfaces and with a small diameter for the interior surfaces of vehicle bodies.

In practice, the inside surfaces of vehicle bodies are like e.g. Door entry areas, door rebates, trunk, engine compartment and However, the inside of the lid or hood etc. has not been included so far Rotary atomizers coated, but usually with Spray guns that rotate the paint, not with it Atomize compressed air. These spray guns create an elongated, relatively sharply concentrated spray pattern, which for the Coating of the narrow surfaces better indoors than the usual large-area round spray patterns the rotary atomizer. Especially with the interior painting Powder can spray guns but coating defects caused by powder sintering (so-called spitters) that need to be reworked. Except for the paint quality is also the application efficiency of the spray guns worse than with rotary atomizers.

If in the overall painting of a workpiece for high application efficiency and uniform overall paint layer both wide and narrow spray settings are necessary and the coating company not by changing the spray head to be interrupted, you have to, because of the Setting the spray jet small enough, compromises between Bell plate size with corresponding steering air supply and Beam width in terms of efficiency, paint consumption and color received. By reducing the speed, a better one Constrict the spray jet, but it does less atomization fineness and deterioration of the coating quality. Since it hasn't been was possible with the direct air of a given atomizer Spray jet both in one and in the other adjust the above-mentioned width ranges for optimal operation, In practice there are considerable disadvantages such as insufficient ones or impossible interior or detail painting, increased Overspray (the amount of paint sprayed past the object), lower Application efficiency, increased paint consumption and insufficient Painting quality.

The invention is based, so far the task To avoid disadvantages and a process or an atomizer specify the setting of the spray jet width without mechanical control of the exhaust port arrangement in one essential wider width range than before and yet possible optimal coating operation with good order efficiency and ensure good painting quality.

This object is solved by the features of the claims.

In a first embodiment of the invention, this is done even without changing the spray head and without mechanical changes of the outlet opening arrangement. In a second embodiment it may be appropriate, depending on the areas to be coated, the atomizer bell and / or the Exchanging the outlet opening arrangement for the steering air flows.

The at least two regulated in the closed control loop Steering air flows (or other serving the same purpose Gas flows) are in the first embodiment in Normally not generated at the same time, but optionally depending of the workpieces or workpiece areas to be coated used. But it is also the simultaneous one Combined use of both regulated separately from the other Air currents possible.

The invention enables the painting of complex workpiece geometries and especially of complete bodies including interior, Exterior and detail painting with the same rotary atomizer at maximum achievable paint application efficiency specifically set spray jet widths in the total required Area. With two separately adjustable steering vents the spray jet widths can optimally match the one to be coated Object can be adjusted.

The optimally adapted spray jet creates a total less overspray than before, resulting in higher application efficiency and lower paint consumption. Through this Optimization also improves the painting quality.

Fig. 1

einen Rotationszerstäuber mit einem erfindungsgemäßen Lenkluftring;

Fig. 2a

einen Schnitt durch den Lenkluftring des Zerstäubers nach Fig. 1;

Fig. 2b

eine Draufsicht auf den in Fig. 2a von links gesehenen Lenkluftring;

Fig. 3

einen Rotationszerstäuber für Pulverlack; und

Fig. 4

eine schematische Frontansicht des Zerstäubers nach Fig. 3.

The invention is explained in more detail in the exemplary embodiment shown in the drawing. Show it:

Fig. 1

a rotary atomizer with a steering air ring according to the invention;

Fig. 2a

a section through the steering air ring of the atomizer of FIG. 1;

Fig. 2b

a plan view of the steering air ring seen from the left in Fig. 2a;

Fig. 3

a rotary atomizer for powder coating; and

Fig. 4

3 shows a schematic front view of the atomizer according to FIG. 3.

Apart from the steering air control described here Spray steel can the electrostatic shown in Fig. 1 High-speed rotary atomizers correspond to the prior art, for example according to the already mentioned DE 4306800. In the on known way sits on the bell plate 1 facing Front end of the atomizer housing 2 coaxial to the atomizer axis 3 a steering air ring 4. In the radial one End face 5 of the steering air ring 4, the bell cup 1 and thus the one formed by the sprayed coating material Spray cone facing, lead to those described below Bores 12, 13 for setting the spray jet width escaping steering air. Which are conical as shown circumferential surface 7 of the ring body 4 that widens towards the rear is continuously aligned with the adjacent peripheral surface 8 of the housing 2. Due to the uninterrupted, continuous outer shape of the air swirls around the entire atomizer circumference Atomizers and undesirable influence on the spraying process on the bell plate 1 and dirt on the atomizer housing avoided.

The end face 5 of the steering air ring 4 can be like that illustrated embodiment axially behind the bell cup 1 are located, as shown radially after inside up to close to the hollow shaft of the bell cup Air turbine can extend. The steering air ring could also fully inserted into the open front end of the atomizer housing his. In other embodiments, the steering air ring but also axially with its outlet opening arrangement extend further to the bell plate.

2a and 2b show the steering air ring 4 for itself. In its End face 5 open onto two of the atomizer axis 3 (Fig. 1) and thus to the spray cone axis coinciding with it concentric circles 10 and 11 with different Diameters of wreaths with uniform angular distances distributed steering air holes 12 or 13.

In the example shown, the bores 12 and 13 each open axially parallel in the end face, but are also other arrangements possible. The radially inner bores 13 are fed by an annular channel 14 within the steering air ring 4, the to a (not shown) compressed air line of the Atomizer is connected while the outer bores 12th the steering air ring 4 from the end face 5 initially axially and then as shown with a rear part 16 approximately parallel to the peripheral surface 7 radially outwards up to an annular channel 17 run, the between when the steering air ring is installed its back and the neighboring parts of the atomizer is formed and from another compressed air line of the atomizer is fed.

Instead of the two rings of holes 12 and 13 respectively also annular gap-like outlet opening arrangements in a steering air ring or possibly also in separate components of the atomizer.

The two compressed air lines mentioned can, for example with one compressed air connection of the atomizer for external Lines are connected, each to its own air control system being able to lead. For example, if the effort for two separate Air regulator is undesirable, the compressed air lines also depending on the one to be coated Workpiece area controlled changeover valve on one of the holes 12 and 13 common air control system can be connected. The switching valve does not have to be outside the atomizer but can also be built into the atomizer, for example in the valve unit 18, so that then only one only external steering air connection is required. The steering air could also be regulated within the atomizer.

When coating workpieces such as vehicle bodies is preferably the first regulated steering air from the radial inner bores 13 for setting wider spray jets (for example for SB 50% from 250 to 300 mm) for the exterior painting used while with the separate from the first Steering air regulated second steering air from the holes 12 the larger pitch circle 10 narrower spray jets (for example SB 50% from 50 to approx. 300 mm) for detail and interior painting be set, it may be appropriate if the two areas (as in the example considered) overlap. So with one and the same atomizer can without interrupting the coating operation and without accepting major disadvantages are the spray jet width as a whole area required for exterior, interior and detail painting (50 to 550 mm in the example under consideration) become. The two steering vents can be used separately and regulated, i.e. during the atomizer with the one steering air works, the other steering air can be switched off his. The first to emerge behind the bell plate 1 Steering air from the inner bores 13 hits relatively far behind on the peripheral surface that tapers conically backwards of the bell plate 1, with an air cushion around the bell plate generated and thereby advantageous during atomization uniform air distribution is effected. The second steering air from the outer holes 12, however, can be directed be a small radial distance (e.g. on the order of 1 mm) outside the spray edge of the bell plate on the thing to be atomized or already through the Rotation hits partially atomized paint material, causing the spray jet is constricted more than through the steering air from the inner holes, so that maximum Order efficiency is achieved and also difficult to achieve or small workpiece areas can be coated well.

As another embodiment of the invention in FIG front part of a robot's wrist, for example mounted electrostatic rotary atomizer for powder coating or other powdery coating material in the Longitudinal section shown. Like the electrostatic wet paint sprayer 1 contains the atomizer, for example with compressed air powered drive turbine 30 for the front End of the hollow shaft 31 attached rotating atomizer bell 33. Coaxial extends through the hollow shaft 31 as a powder channel of the atomizer serving cylindrical tube 32 to in the hub portion 35 of the bell 33 into where it is shown opens axially outside the atomizer housing 36. The powder tube 32 is in the atomizer to one of an external air and Powder supply coming powder hose (not shown) connected. The atomizer bell 33 is known Way (EP 1238710; US 5353995) essentially from one on the hub part 35 attached outer part 38, the one has inner conical surface 40 of the shape shown, and one in the space in front of the surface 40 seated inner part 42, the one opposite surface 40 to form a gap channel 44 Has inner surface 46 and with the outer part 38 is rigidly connected. The gap channel 44 is therefore of the two conical surfaces 40 and 46 limited. The radially outer peripheral surface 49 of the outer and axially rear, i.e. the main part of the atomizer-facing bell part 38 runs as shown (and in contrast to the known ones mentioned Powder bells) are only slightly conical, so that it makes an acute angle with the axis of rotation preferably forms less than 20 ° in the example shown about 5 °. On its way through the pipe 32 and through the Split channel 44 can be the coating powder in the usual way be charged to high voltage.

As in the embodiment of FIG. 1 occurs radially outside the peripheral surface 49 of the bell 33 a the spray cone adjustable steering air flow surrounding or acting in a ring 50 (or other gas flow), which is approximately axially parallel can be directed. Radially outside the flow 50 occurs another air or gas flow 51, the direction of its exit also axially, but as shown against Axial direction is inclined inwards by an acute angle, so that it intersects the direction of the internal flow 50. The directions indicated by the arrows shown so that they do not cut the outer surface of the bell 33, but walk past the bell. Appropriately can the radially outer gas flow 51 approximately to the powder exit point the atomizer bell 33 be directed.

The radially outer flow 51 is not circular here like the flow 50, but consists of separate, e.g. flat top and bottom parts when hitting on the inner flow 50 and on the spray cone this into one Flatten oval cross-sectional shape (ovalize). The outlet openings provided for this purpose are in the schematic representation of Fig. 4 recognizable. While the annular steering air flow 50 from which the axis of rotation concentrically surrounding ring of a plurality of openings 52 emerges, can for the two flat parts of the flow 51st two straight slots 53 and 53 'may be provided facing each other tangential to the circular ring formed by the openings 52 on opposite sides of the axis of rotation in parallel. The slots 53, 53 'are symmetrical in this way the axis of rotation that is perpendicular to the longitudinal direction of their Mouth opening whose center connecting the line Axis of rotation intersects. The slots 53, 53 'are at their atomizer-side fed by compressed air lines 54. Instead of the two slots, parallel rows could also be used be purposeful from a sufficient number of openings.

The steering air openings 52 and / or the ovalization slots 53, 53 'can be located in an annular body 55 which is detachable and quickly and easily against another steering air ring with one other exhaust port arrangement interchangeable on the atomizer is attached. The atomizer bell can also be used with the steering air ring 33 for adaptation to the workpiece area to be coated be exchanged for another bell. The remaining part of the rotary atomizer can remain unchanged stay. The bells and steering air rings can e.g. through control of the robot are changed automatically.

A major advantage of the rotary atomizer described here is that the same basic atomizer for example with program-controlled body painting both for the exterior surfaces as well as for the automatic interior painting can be used. For the interior painting expediently a round steel bar with a smaller diameter than the Exterior paint created by the at the powder exit point the atomizing bell 33 air flow acting flat is ovalized from the slots 53, 53 '.

By using a rotary atomizer for all outside and Not only can the interior of the workpiece automatically controlled coating process simplified, but also the paint quality compared to the usual spray guns improved and the coating efficiency can be increased. Moreover it’s easier than before if one fails Robot to work with another robot.

In other cases, however, also in the embodiment 3 and 4 of the rotary atomizer all or at least different workpiece surfaces with the same bell and the same Coating the outlet opening assembly, being used for adjustment only the gas flows to the respective workpiece areas 50, 51 can be changed by means of the control loops.

Claims (20)

Process for coating a workpiece with an atomizer,
in order to control the spray jet shape of the atomizer, the spray cone of the sprayed-off coating material is delimited by a controllable gas flow surrounding it, which emerges from the atomizer concentrically to the spray cone axis (3),
and different areas of the workpiece are coated with different spray jet shapes,
in particular for the serial painting of vehicle bodies with a painting robot,
characterized in that at least two gas flows which can be regulated independently of one another are generated and emerge at different radial distances from the spray cone axis (3) and are used as a function of the workpiece areas to be coated. A method according to claim 1, characterized in that with the one spray jet outer areas of a vehicle body or the workpiece and using the same atomizer or essential parts of the same atomizer with the other spray jet interior areas of this body or the workpiece are coated. A method according to claim 1 or 2, characterized in that a high-speed rotary atomizer is used. A method according to claim 3, characterized in that a rotary atomizer is used, the radially outer gas flow (51) directed towards the annular gas flow (50) brings the spray cone into an oval or flattened shape when the inner regions are coated. Method according to one of the preceding claims, characterized in that each gas flow is regulated in its own closed control loop. Method according to one of the preceding claims, characterized in that a regulated gas flow is supplied to the radially outer or the radially inner outlet openings (12, 13) via a changeover valve which is controlled as a function of the workpiece regions to be coated. Method according to one of the preceding claims, characterized in that only one gas flow is used for coating with a wider spray cone and only the other gas flow is used for coating with a narrower spray cone. A method according to claim 7, characterized in that the two areas in which the spray cone width is adjustable overlap each other. Method according to one of the preceding claims, characterized in that the workpiece is coated with powdered lacquer. Atomizer for the series coating of workpieces with at least one first annular arrangement concentrically surrounding its spray cone axis (3) from the spray cone, with outlet openings (13, 52) for a gas flow delimiting the spray cone,
with at least one further arrangement of outlet openings (12, 53) facing the spray cone, which have a different, in particular greater radial distance from the spray cone axis than the first arrangement,
and with a gas line arrangement leading to the outlet openings (12, 13, 52, 53), which is connected or can be connected to at least one control circuit for the gas flow, characterized in that the radially inner and the radially outer gas flow can be regulated separately from one another. Atomizer according to claim 10, characterized in that the radially inner outlet opening arrangement (13) and the radially outer outlet opening arrangement (12) are each connected or connectable to their own closed control loop. Atomizer according to claim 10, characterized in that the line arrangement leading to the outlet opening arrangements (12, 13) is connected or connectable to a common control circuit via a changeover valve. Atomizer according to claim 12, characterized in that the changeover valve is located in the atomizer. Atomizer according to one of claims 10 to 13, characterized in that each of the outlet opening arrangements (12, 13) is connected to a gas connection of the atomizer for one external gas supply line each. Atomizer according to one of claims 10 to 14, characterized in that the two outlet opening arrangements (12, 13) are located in the end face (5) of an annular body (4) facing the spray cone on the front end of the spray head (1) of the atomizer facing the spray cone holding housing (2). Atomizer according to claim 15, characterized in that the peripheral surface (7) of the ring body (4) is flush with the adjacent peripheral surface (8) of the housing (2). Atomizer according to one of claims 10 to 16 or according to the preamble of claim 10, characterized in that two radially outer outlet opening arrangements (53, 53 ') are provided which are at least approximately parallel to one another on opposite sides of the spray cone axis and are at least approximately tangential to one another of the annular outlet opening assembly (52). Atomizer according to claim 17, characterized in that the radially outer outlet opening arrangements consist of elongated slots (53, 53 '). Atomizer according to one of claims 10 to 18, characterized in that the outlet openings (52, 53) are located in a body (55) which is detachably and interchangeably mounted on the atomizer, and that for the atomizer at least two interchangeable bodies (55) with different Outlet opening arrangements are provided. Atomizer according to one of claims 10 to 19, characterized in that the exit direction of the radially outer gas flow (51) runs close to the spraying edge (47) of the atomizer bell (33) without cutting the outer surface of the atomizer bell (33).

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