ELECTROSTATIC ATOMIZER FOR ELECTROSTATICALLY COATED WORKPIECES

Abstract

An electrostatic atomizer for electrostatically coating a workpiece, in particular for coating vehicle bodies or parts thereof, with a coating material, having both an inner electrode and an outer electrode for electrostatically charging the coating material.

Claims

1. An electrostatic atomizer for the electrostatic coating of workpieces with a coating material, comprising: an internal electrode and an external electrode for electrostatic charging of a coating material.

2. The electrostatic atomizer according to claim 1, wherein the internal electrode and the external electrode can each be actuated separately via their own electrical supply line.

3. The electrostatic atomizer according to claim 1, further comprising a plurality of external electrodes which can each be actuated via their own electrical supply line.

4. The electrostatic atomizer according to claim 1, wherein the external electrode is configured to be brought into at least two different positions with respect to a front end of the electrostatic atomizer.

5. An electrostatic coating system comprising an electrostatic atomizer according to claim 1; at least one high voltage source connected to the internal electrode, to the external electrode or to both the internal electrode and the external electrode, of the electrostatic atomizer; and a control unit configured to control the at least one high voltage source.

6. The electrostatic coating system according to claim 5, wherein the at least one high voltage source comprises two high voltage sources, wherein one of the two high voltage sources is connected to the internal electrode of the electrostatic atomizer, and the other of the two high voltage sources is connected to the external electrode of the electrostatic atomizer.

7. The electrostatic coating system according to claim 5, wherein the control unit is configured to apply high voltage of a same or different magnitude to the internal electrode and the external electrode.

8. The electrostatic coating system according to claim 6, wherein the control unit is configured to change a respective high voltage of one or both high voltage sources quasi-continuously in opposite directions, from one end value to another end value.

9. The electrostatic coating system according to claim 5, wherein the electrostatic atomizer comprises a plurality of external electrodes, and the control unit is configured to separately control the plurality of external electrodes.

10. A method of painting vehicle bodies comprising the step of using an electrostatic atomizer as claimed in claim 1.

11. The electrostatic coating system according to claim 5, wherein the control unit is configured to change a high voltage of the at least one voltage source quasi-continuously.

12. A method of painting vehicle bodies comprising the step of using an electrostatic coating system as claimed in claim 5.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In the following, embodiments of the invention are explained in more detail based on the drawings.

[0031] FIG. 1 shows an electrostatic atomizer according to the invention with an internal electrode and a ring of external electrodes with two separate high voltage sources;

[0032] FIG. 2 shows an electrostatic atomizer according to the invention with an internal electrode and a ring of external electrodes which can be actuated separately;

[0033] FIG. 3 shows an electrostatic atomizer according to the invention with an internal electrode and a ring of external electrodes which can be actuated separately and can be folded to the atomizer head;

[0034] FIG. 4 shows an electrostatic atomizer according to the invention with an internal electrode and a ring of external electrodes with a common high voltage source.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0035] FIG. 1 shows an electrostatic coating systems, denoted overall by 10, with an electrostatic atomizer 11, here in the form of a rotary atomizer.

[0036] The electrostatic atomizer 11 has a paint line 12 via which a paint 16 can be fed as coating material to a rotary bell plate 14 at the front distal end of the electrostatic atomizer 11. The electrostatic atomizer 11 then generates an initially rotationally symmetrical spray cone 18 of atomized paint 16, which is directed onto a workpiece 20.

[0037] As symbolically indicated in the figures, the workpiece 20 for electrostatic coating is electrically connected to earth potential 22 via a support device not shown here, such as a skid for conveying vehicle bodies.

[0038] In contrast, the electrostatic atomizer 11 has an electrically conductive area as an internal electrode 24 in the paint line 12 for the internal charging of the paint 16 before atomizing the coating material.

[0039] This internal electrode 24 is connected via an electrical supply line 26 to a first high voltage source 28, which in turn is actuated by a control unit 30.

[0040] Furthermore, in addition to the internal electrode 24, the electrostatic atomizer 11 has at its front end a ring of a plurality of external electrodes 32a, 32b and 32c, only three of which are shown in the drawing. However, the exact number of external electrodes 32a, 32b and 32c generally depends on the configuration of the atomizer 11. The external electrodes 32a, 32b and 32c are each connected to a second high voltage source 36 via an electrical supply line 34. The second high voltage source 36 is also actuated by the control unit 30.

[0041] The electrostatic coating system 10 according to FIG. 1 functions as follows:

[0042] Depending on the desired charging mechanism for an upcoming painting procedure of a total coating process, the control unit 30 controls either the first high voltage source 28 or the second high voltage source 36 or both in order to apply high voltage to the internal electrode 24 or the external electrodes 32a, 32b, 32c with respect to the workpiece 20 and to thereby achieve an electrostatic charge of the paint 16.

[0043] For example, to paint the inside of a vehicle body, the control unit 30 can only activate the interior charging via the first high voltage source 28 and for the painting procedure on the outside of the vehicle body can only activate the external charging via the second high voltage source 36.

[0044] In addition, however, the control unit 30 is also configured, for example, to activate a basic charge via the first high voltage source 28 by specifying a high voltage value there. The external charging can then be activated additionally via the second high voltage source 36.

[0045] The control unit 30 can also be configured to switch continuously from internal charging via the first high voltage source 28 to external charging via the second high voltage source 36 by gradually reducing the charge via the internal electrode 24 while gradually increasing the charge via the external electrodes 32a, 32b and 32c. The control unit 30 can also generate a corresponding transition in the reverse direction. In this way, various transitions between internal charging and external charging of the coating material are conceivable and possible with the electrostatic atomizer 11.

[0046] FIG. 2 shows an electrostatic coating system 10 which differs from the embodiment according to FIG. 1 in that the individual external electrodes 32a, 32b and 32c of the atomizer 11 are provided in each case with their own electrical supply lines 34a, 34b and 34c which are connected to the second high voltage source 36. The second high voltage source 36 and the control unit 30 are thereby configured such that high voltage can be applied to the individual external electrodes 32a, 32b and 32c separate from one another.

[0047] In this way, the control unit 30 can actuate certain of the external electrodes 32a, 32b or 32c by correspondingly actuating the second high voltage source 36 in order to generate an external charge that produces an asymmetric shape for the spray cone 18.

[0048] FIG. 3 shows an electrostatic coating system 10, which differs from the embodiment according to FIG. 2 in that the individual external electrodes 32a, 32b and 32c of the atomizer 11 are each connected to the front end of the atomizer 11 via a locking joint 33.

[0049] As indicated by the arc-shaped arrows, this allows the external electrodes 32a, 32b and 32c to be brought into different positions. For example, the external electrodes 32a, 32b and 32c can be folded towards the front end of the atomizer 11 or spread away from the front end of the atomizer 11 by means of actuators not shown or by external actuation. This makes it possible, for example, to switch off the high voltage at the external electrodes 32a, 32b and 32c for painting the interior of a vehicle body and to reduce the external dimensions of the atomizer 11 by folding the external electrodes 32a, 32b and 32c.

[0050] Independent of the foldable external electrodes 32a, 32b and 32c, the embodiment shown in FIG. 3 also differs in the configuration of the high voltage source 36 for the external electrodes 32a, 32b and 32c and their actuation via the control unit 30.

[0051] Regarding FIG. 2, it is conceivable that the high voltage source 36 there has a type of multiplex switch at the output which switches the respective outputs for the electrical supply lines 34a, 34b and 34c on or off in order to activate different external electrodes 32a, 32b and 32c. This multiplex switch can then be actuated via the control line between the control unit 30 and the high voltage source 36.

[0052] In contrast, FIG. 3 shows a variation with a plurality of high voltage sources 36 for the respective supply lines 34a, 34b and 34c. This makes it possible to apply high voltages of different magnitudes to the individual external electrodes 34a, 34b and 34c.

[0053] Of course, the two concepts can also be combined. In addition, individual external electrodes 34a, 34b and 34c can also be combined in groups, each supplied via a common supply line 34a, 34b and 34c.

[0054] FIG. 4 shows an electrostatic coating system 10 which differs from the previous embodiments in that for the internal electrode 24 and for the ring of external electrodes 32a, 32b and 32c only a common first high voltage source 28 is provided by the two electrical supply lines 26 and 34, preferably inside the atomizer head, being connected to each other. This means that the internal charging and the external charging can only be switched on and off together.

[0055] A further variation of the invention, not shown here, comprises an atomizer which, in addition to the paint line 12 described above, also comprises a further paint line which is optionally equipped with or without an internal electrode. In this way, different types of paint can be used even more easily with both internal and external charging.