EP1560663B1 - Ultrasonic standing wave spraying arrangement - Google Patents

Description

The invention relates to an ultrasonic standing wave atomizer for generating a paint spray for painting a workpiece with a sonotrode, with a sonotrode the oppositely arranged component, wherein in case of operation in the space between the sonotrode and component a standing ultrasonic field is formed, and with a paint supply device , by means of the paint in the vicinity of a maximum of the sound velocity of the ultrasonic field can be fed.

For painting workpieces, in particular in mass painting, as they frequently occur in the automotive industry, the generally known high-speed rotary atomizers are currently preferably used. During high-rotation atomization, the paint is passed through the interior of a metal bell and thus reaches its front side facing the workpiece. The metal bell is usually driven by a compressed air turbine and rotates at up to 80,000 revolutions per minute. By acting centrifugal forces, the paint then passes to the bell edge of the front page to tear down there in fine droplets. In this way, it is achieved that the droplet size of the paint spray required for a sufficient quality of a lacquer layer is in the range of 10 μm to 60 μm.

General considerations that have become generally known show that paint can also be produced by means of an ultrasonic standing wave sputtering, for example according to the document U.S. 4,981,425 in principle can be atomized. Following these general considerations, however, average droplet sizes were measured in the atomization between 100 .mu.m and 200 .mu.m, even larger droplets occurring in individual cases. However, such large drops affect the quality of the paint layer so negative that an application in painting technology is unattractive.

It has been proposed how an ultrasonic standing wave atomizer assembly for generating a paint spray for painting a workpiece may be configured to achieve smaller droplet sizes. Thus, for example, certain embodiments of the sonotrode and of the component, blocking elements or laminar rings have become known which improve the quality of the paint spray mist produced and thus comparatively small droplet sizes can be achieved. The disadvantage here is that only comparatively small flow rates of paint can be atomized by the known arrangement.

Based on this prior art, it is the object of the invention to provide an ultrasonic standing wave atomizer for generating a paint spray, with which it is possible to increase the atomized amount of paint, so the so-called paint rate and thereby a selected range of occurring droplet sizes observed.

This object is achieved by the ultrasonic standing wave atomizer arrangement according to the invention for producing a paint spray for painting a workpiece having the features mentioned in claim 1.

Accordingly, the ultrasonic standing wave atomizer arrangement according to the invention of the type mentioned has a paint supply device which has at least two pipe sections for the application of paint in the region of the stationary ultrasonic field. In addition, at least two of the pipe sections are arranged in the region of a selected maximum of the sound velocity of the stationary ultrasonic field. According to the invention, it is thus provided that a selected maximum of the sound velocity of a standing ultrasonic wave is used to atomize a comparatively large amount of paint into paint droplets. It has in fact been found that, in particular with simply constructed ultrasound standing-wave atomizer arrangements, a selected maximum of the sound velocity is particularly well-formed in the standing ultrasound field, for example in standing ultrasound fields with an odd number of sound breeches, the mean velocity bump. This means that this maximum is particularly stable, with a comparatively high speed of sound. This particularly good sputtering properties of the selected maximum is inventively to increase the amount of paint to be atomized or the Lackdurchflusses used by the paint supply device and provided that at least two pipe pieces are arranged for the application of paint in the range of the selected maximum. Thus, the amount of paint to be atomized can advantageously be increased. An advantageous embodiment of the ultrasonic standing wave atomizer arrangement according to the invention is achieved when the component is a further sonotrode. In this way, the sputtering ability of the standing ultrasonic field can be increased. In addition, such a more stable ultrasonic field can be formed.

A further advantageous embodiment of the subject invention provides that the distance of the pipe sections in the region of the selected maximum to each other is so large that separate paint fins are formed for each piece of pipe. A Lacklamelle forms from the paint exit point on the pipe sections from vibrational physical reasons in any case. If the distance between the pipe sections chosen so large that the paint fins can form separate from each other without mutual interference, at least one area is avoided in which meet droplets of different paint fins and can recombine in such a way to larger droplets. The quality of the paint spray mist is improved with the proposed arrangement.

It when the paint outlet openings of the at least two pipe sections in the range of the selected maximum of the sound velocity of a standing ultrasonic wave are arranged on a straight line, and when the straight line is perpendicular to an imaginary center line through the surface centers of the opposing sound surfaces is particularly advantageous the sonotrode and the component goes. In such an arrangement, the distance between the paint exit points on the pipe sections and the sonotrode or the component will be approximately equal in each case. A particularly advantageous position seen in the X direction in the range of the maximum speed of sound is reached.

The aforementioned advantage can also be achieved if three pipe sections are arranged in the region of a selected maximum of the sound velocity of a standing ultrasonic wave, and if these pipe sections or their paint outlet openings are arranged in a triangle. Particularly favorable is a Arrangement in an equilateral triangle. A further improvement is when the surface defined by the triangle is perpendicular to an imaginary center line passing through the centroids of the opposing sound surfaces of the sonotrode and the device. Also in this case, in turn, it is achieved that the paint outlet openings in the X direction are located in the region of the maximum of the sound velocity.

It has also been found that the sputtering rate can be improved by selecting the particular maximum to be closer to the sonotrode than to the device. Then there is the possibility that the so-called Kapilarwellenstäubungseffekt, that is the one effect that keeps the paint droplets away from it by the vibrations of the sonotrode and thus supports the sputtering process.

Further advantageous embodiments of the subject invention can be found in the dependent claims.

Reference to the exemplary embodiments indicated in the drawings, the invention, its advantages and further improvements of the invention will be explained and described in detail.

Fig. 1

Eine erste Ultraschall-Stehwellen-Zerstäuberanordnung,

Fig. 2

eine zweite Ultraschall-Stehwellen-Zerstäuberanordnung,

Fig. 3

eine dritte Ultraschall-Stehwellen-Zerstäuberanordnung,

Fig. 4

eine vierte Ultraschall-Stehwellen-Zerstäuberanordnung,

Fig. 5

eine fünfte Ultraschall-Stehwellen-Zerstäuberanordnung und

Fig. 6

eine sechste Ultraschall-Stehwellen-Zerstäuberanordnung.

Show it:

Fig. 1

A first ultrasonic standing wave atomizer arrangement,

Fig. 2

a second ultrasonic standing wave atomizer assembly,

Fig. 3

a third ultrasonic standing wave atomizer arrangement,

Fig. 4

a fourth ultrasonic standing wave atomizer arrangement,

Fig. 5

a fifth ultrasonic standing wave atomizer assembly and

Fig. 6

a sixth ultrasonic standing wave atomizer assembly.

1 shows a first ultrasonic standing wave atomizer arrangement 10 according to the invention in an isometric view. The coordinates are indicated by the directional arrows for the X, Y and Z directions in a Cartesian coordinate system.

In addition, the representation should have only sketchy character, so that the actual size ratios of this figure can not be removed.

A first sonotrode 12 is arranged opposite a first reflection body 14. In this figure, the sonotrode 12 is sketchily represented by a cylindrical base body 16 and a sound body 18, which protrudes from the first reflection body 14 facing end face of the cylindrical base body 16. The sound body 18 and the base body 16 have an approximately cylindrical shape. The opposite end surfaces of the sound body 18 and the first reflection body 14 are to be referred to as the first sound surface 20 for the end face on the sound body 18 and as a second sound surface 22 for the end face on the first reflection body 14. The first 20 and the second sound surface 22 are configured konkarv, that is, that their shape corresponds approximately to a portion of the surface of an imaginary hollow sphere. In order to illustrate this shape, a first dotted line 24 and a second dotted line 26 were drawn on the first sound surface 20. The point of intersection between the first 24 and the second line 26 lies exactly in the middle of the first sound surface 20. The first 24 and the second line 26 corresponding lines are also shown on the second sound surface 22, but without being provided with reference numerals closer. By the intersections of the first 24 with the second line 26 and the corresponding lines of the second sound surface 22, a central axis 28 is shown, which runs exactly in the X coordinate direction.

In the intermediate space between the first sound surface 20 and the second sound surface 22, a first 30, a second 31 and a third pipe section 32 are shown, the free ends of which are arranged exactly in the middle between the sound surfaces 20, 22. That is, the tube pieces 30, 31, 32 are arranged side by side, with the free ends all lying in a plane defined by the central axis 28 and the second line 26. In addition, all free ends are connected to an imaginary straight line. The longitudinal axes of the pipe sections 30, 31, 32 are arranged parallel to the Y direction and connected with their ends opposite the ends with a Lackzuführeinrichtung 29 not shown in detail in this figure, the paint to be atomized by the first ultrasonic standing wave atomizer 10 in provides the required amount. But it is also within the Erfindungsgedankenens, when each of the pipe sections 30, 31, 32 is connected to a separate Lackzuführeinrichtung 29. In any case, this should also be meant with the paint supply device 29 described here.

The other end of the pipe sections 30, 31, 32 thus ends, so to speak, in "free space" without the connection with the paint supply device 29 being shown.

In order to be able to better show the processes in the stationary ultrasonic field between the first sound surface 20 and the second sound surface 22, the progressions of five sound rapids of the standing ultrasonic wave were shown in the interspace, the progressions being around the central axis 28, in the direction indicated by the X axis. and Y-plane spanned plane, are shown. In the example chosen, a first distance 34 between the first sound surface 20 and the pipe sections 30, 31, 32 and a second distance 36 between the pipe sections 30, 31, 32 and the second sound surface 22 is the same size. Thus, it is clear that the respective free ends of the pipe sections 30, 31, 32 are all situated in only one maximum of the sound velocity, namely in the middle of the five sound velocity bellies. In the configuration of the first ultrasonic standing-wave atomizer arrangement 10 selected for this arrangement, a first 34 or a second distance 36 of 17 mm results for an ultrasonic frequency of 24 kH and five sound-speed bellies. This means that sufficient space is available for cleaning or shaping air, which may be used to assist the atomization process or to guide the paint particles. With such an arrangement of three pipe sections 30, 31, 32 in only one Schallschnellebauch, ie in the range of maximum speed of sound is thus advantageously achieved that particularly high paint rates, in particular paint rates of more than 200 ml / min are readily achievable. In addition, it is ensured that the distribution of the diameter of the paint drops of the atomized paint remain within an acceptable range. The sputtering process is shown in this figure only symbolically at the respective free ends of the pipe sections 30, 31, 32, in which many small paint particles are shown around an atomized bubble shown exaggerated.

FIG. 2 shows a second ultrasonic standing wave atomizer assembly 40 which is substantially the same as the first ultrasonic standing wave atomizer assembly 10, which is why the reference numerals for similar components have been chosen the same. A significant difference between the first 10 and the second ultrasonic standing wave atomizer assembly 40 is that the arrangement of the pipe sections 30, 31, 32 no longer centrally between the acoustic bodies 18 and the first reflection body, in contrast to the arrangement shown in Fig. 1 takes place, but closer to the sound body 18. The arrangement of the pipe sections 30, 31, 32 is selected so that its paint outlet openings in turn come to rest in a selected maximum of sound velocity of the stationary ultrasonic wave, in the second maximum shown, viewed from the sound body 18 , This means that a third distance 38 between the sound body 18 and the pipe sections 30, 31, 32 is smaller than a fourth distance 39, determined as the distance between the pipe sections 30, 31, 32 and the first reflection body 14. In the arrangement shown here, it proves to be an advantage that the pipe sections 30, 31, 32 are closer to the first sonotrode 12. Namely, it has been found that the vibrations of the sound body 18 of the first sonotrode 12 by the vibration of the sound body 18 even relatively well prevent the atomized paint droplets from adhering to the sonotrode. In other words, the vibrations of the sound body 18 keep the paint droplets away from it.

In addition, the representation of the pipe sections 30, 31, 32 and the atomizing bubbles shown with the atomized paint particles show that the distance between the pipe sections 30, 31, 32 to each other is selected so that at the free ends of the pipe sections 30, 31, 32nd each form independently working sputtering areas, so that for each pipe section 30, 31, 32 separate paint fins are formed. This has the advantage that the areas in which the discharged paint is atomized to particles, do not interfere with each other. Thus, the sputtering process is improved and a comparatively high sputtering rate is achieved.

Fig. 3 shows a further advantageous embodiment of the subject invention with a third ultrasonic standing wave atomizer assembly 50, which is constructed substantially similar to the first ultrasonic standing wave atomizer assembly 10. To facilitate the comparability between the used components, therefore, the same reference numerals were again used for comparable components.

A significant difference between the arrangement in this figure and that in Fig. 1 is that in this figure, a fourth 42, a fifth 43 and a sixth pipe section 44 are located exactly midway between the sound body 18 and the first reflection body 14. The corresponding paint outlet openings of the pipe sections 42, 43, 44 are accordingly again arranged in the range of the mean maximum speed of sound, but the paint outlet openings are no longer in the plane spanned by the X, Z direction, but the middle fifth pipe section 43 is located in positive Y direction, above the plane spanned by the X, Z direction, while the fourth 42 and the sixth pipe section 44 are below the plane spanned by the X, Z direction. However, all three paint outlet openings continue to lie together in a plane parallel to the plane defined by the Y, Z direction. Thus, the three paint outlet openings form, as it were, an imaginary triangle, which is located in a plane parallel to the plane spanned by the Y, Z direction. This embodiment has the advantage that the distance between the paint outlet openings can be further increased without leaving the selected maximum speed of the sound. In this way, the atomization can be further improved and at the same time the paint rate can be increased.

4 shows a fourth ultrasonic standing wave atomizer arrangement 60 with a second reflection body 46, which is arranged opposite a second sonotrode 48. Three first paint tubes 52 are in turn arranged centrally between the second reflection body 46 and the second sonotrode 48. As already shown in FIG. 1, the paint outlet openings of the first paint tubes 52 are aligned along an imaginary line in the Z direction. A special feature of the arrangement shown is that a second sound body 54 on the second sonotrode 48 and the second reflection body 46 have approximately a cuboid shape, wherein the opposing sound surfaces of the second sound body 54 and the second reflection body 46, namely the third sound surface 56th on the second sounding body 54 and the fourth sounding surface 48 on the second reflecting body 46, have a shape corresponding to a skirt portion of a cylindrical body.

It proves to be an advantage if the imaginary central axis of the cylindrical body is parallel to that line 62 which passes through the paint outlet openings of the first paint tube 52. The projections 64 of the central axis of the imaginary cylinder on the third 56 and on the fourth sound surface 58 are shown as dotted lines. With such an arrangement, it is achieved that the maximum of the sound velocity in the stationary ultrasonic field is as wide as possible, that is to say it has the largest possible extent in the direction of the line 62, which here coincides with the Z direction.

A fifth ultrasonic standing wave atomizer assembly 70 is shown in FIG. In this case, the arrangement shown is similar to that of FIG. 4, so that the second paint tubes 52 are in turn arranged centrally between a fifth sound surface 66 and a sixth sound surface 68. In contrast to the sound surfaces shown in FIG. 4, the fifth 66 and the sixth sound surface 68 are composed of planar partial surfaces, whose shape, however, is modeled on that of a jacket portion of a cylindrical body. In this way, a widening of the range of the maximum sound velocity in the stationary ultrasonic field is also achieved.

Finally, FIG. 6 shows a sixth ultrasonic standing wave atomizer arrangement, which starts from the arrangement of the first sonotrode 12 with the first reflection body 14, as shown in FIG. The reference numerals have been adopted accordingly from FIG. In this case, three second paint tubes 72 corresponding to the pipe sections 30, 31, 32, as shown in FIG. 1, are arranged, ie have an equal distance from the sonotrode 12 and the first reflection body 14, which here by the drawing of the second distance 36 is shown. In addition, in this figure, three third paint tubes 74 are shown, which are shown in the position corresponding to the position of the pipe sections 30, 31, 32 in FIG. This means that their distance between the third paint tube 74 and the sound body 18 corresponds to the third distance 38 according to FIG. 2. This is shown in this figure accordingly. In this embodiment of the subject invention is thus provided that a total of six paint tubes 72, 74 are disposed between the first sonotrode 12 and the first reflection body 14, in each case in two groups of three paint tubes 72, 74, so that in each case three Lackröhrchen 74 are arranged starting from the sound body 18 in the second maximum of the sound velocity and three paint tubes 72 in the third maximum and thus above the maximum of sound-fast. With such an arrangement, the rate of paint sputtering can be further increased.

In none of the above-mentioned example arrangements has been shown in detail, which further measures can have a favorable effect on the atomization or on the painting process as such. Thus, for example cleaning air can be used in the well-known manner that adhesion of atomized paint on the sonotrode or on the reflection body is substantially avoided. In addition, shaping air can be used so that the atomized paint particles preferably fly in the desired direction of the painting. The process of directional painting can also be supported by electrostatically charging the paint particles. This charging can be achieved in a generally known manner internally, that is with supplied at high voltage potential supplied paint, or by the so-called external charging, which usually charge the sputtered paint by high-voltage needles, which are located in the vicinity of the sputtering. The workpiece to be painted is then usually placed at ground potential, so that the electrically charged paint particles preferably fly to the workpiece. A combination of internal and external charging is readily possible.

Moreover, it is readily conceivable that the reflection body is another sonotrode, with the particular advantage that the standing ultrasonic field can be particularly strong. In addition, the controllability of the ultrasonic field is improved with such a measure.

LIST OF REFERENCE NUMBERS

10

first ultrasonic standing wave atomizer arrangement

12

first sonotrode

14

first reflection body

16

body

18

first soundbody

20

first sound surface

22

second sound surface

24

first line

26

second line

28

central axis

30

first piece of pipe

31

second piece of pipe

32

third piece of pipe

34

first distance

36

second distance

38

third distance

39

fourth distance

40

second ultrasonic standing wave atomizer assembly

42

fourth piece of pipe

43

fifth piece of pipe

44

sixth pipe section

46

second reflection body

48

second sonotrode

50

third ultrasonic standing wave atomizer arrangement

52

first paint tube

54

second sound body

56

third sound surface

58

fourth sound surface

60

fourth ultrasonic standing wave atomizer assembly

62

line

64

projections

66

fifth sound surface

68

sixth sound surface

70

fifth ultrasonic standing wave atomizer arrangement

72

second paint tube

74

third paint tubes

80

sixth ultrasonic standing wave atomizer arrangement

Claims (12)

1. Ultrasonic standing-wave atomizer arrangement (10, 40, 50, 60, 70, 80) for producing a paint spray mist for painting a workpiece, with a sonotrode (12, 48), with a component (14) arranged lying opposite the sonotrode (12, 48), a standing ultrasonic field being formed in the intermediate space between the sonotrode (12, 48) and the component (14) in the case of operation, and with a paint-feeding device (29), by means of which paint can be fed into the vicinity of a maximum of the sound particle velocity of the ultrasonic field, characterized in that the paint-feeding device (29) has in the region of the standing ultrasonic field at least two pieces of pipe (30, 31, 32; 42, 43, 44) for discharging paint, and in that at least two of the pieces of pipe (30, 31, 32; 42, 43, 44) are arranged in the region of a selected maximum of the sound particle velocity of the standing ultrasonic field.
2. Ultrasonic standing-wave atomizer arrangement (10, 40, 50, 60, 70, 80) according to Claim 1, characterized in that the component (14) is a further sonotrode.
3. Ultrasonic standing-wave atomizer arrangement (10, 40, 50, 60, 70, 80) according to Claim 1 or 2, characterized in that the distance between the pieces of pipe (30, 31, 32; 42, 43, 44) in the region of the selected maximum is so great that sheets of paint that are separate from one another are formed for each piece of pipe (30, 31, 32; 42, 43, 44).
4. Ultrasonic standing-wave atomizer arrangement (10, 40, 50, 60, 70, 80) according to one of the preceding claims, characterized in that the paint outlet openings of the at least two pieces of pipe (30, 31, 32; 42, 43, 44) in the region of the selected maximum of the sound particle velocity of a standing ultrasonic wave are arranged on an imaginary straight line, and in that the straight line is perpendicular to an imaginary centre line which passes through the centroids of the opposing sound faces (20, 22, 56, 58) of the sonotrode (12, 48) and of the component (14, 46).
5. Ultrasonic standing-wave atomizer arrangement (10, 40, 50, 60, 70, 80) according to Claim 4, characterized in that the shape of the sound faces (66, 68) corresponds approximately to a segment of the generated surface of a cylinder reproduced with polyhedral surfaces, or the segment is cylindrical, and in that the longitudinal axis of the cylinder concerned is situated parallel to the straight line (24, 26, 62).
6. Ultrasonic standing-wave atomizer arrangement (10, 40, 50, 60, 70, 80) according to one of the preceding Claims 1 to 3, characterized in that three of the pieces of pipe (30, 31, 32; 42, 43, 44) are arranged in the region of a selected maximum of the sound particle velocity of a standing ultrasonic wave, and in that these pieces of pipe (30, 31, 32; 42, 43, 44) or their paint outlet openings are arranged in a triangle, in particular an equilateral triangle.
7. Ultrasonic standing-wave atomizer arrangement (10, 40, 50, 60, 70, 80) according to Claim 6, characterized in that the surface which is determined by the triangle is perpendicular to an imaginary centre line which passes through the centroids of the opposing sound faces (20, 22, 56, 58, 66, 68) of the sonotrode (12, 48) and of the component (14, 46).
8. Ultrasonic standing-wave atomizer arrangement (10, 40, 50, 60, 70, 80) according to one of the preceding claims, characterized in that the distance between the at least two pieces of pipe (30, 31, 32; 42, 43, 44) arranged in the region of a selected maximum of the sound particle velocity of a standing ultrasonic wave and the sonotrode (12, 48) is at most equal to the distance between these pieces of pipe (30, 31, 32; 42, 43, 44) and the component (14, 46).
9. Ultrasonic standing-wave atomizer arrangement (10, 40, 50, 60, 70, 80) according to one of the preceding claims, characterized in that the at least two pieces of pipe (30, 31, 32; 42, 43, 44) are provided with a hydrophobic surface, in particular a tetrafluoroethylene coating.
10. Ultrasonic standing-wave atomizer arrangement (10, 40, 50, 60, 70, 80) according to one of the preceding claims, characterized in that there is a flow of cleaning air, by which wetting of the sonotrode (12, 48) and/or of the component (14, 46) is avoided or reduced.
11. Ultrasonic standing-wave atomizer arrangement (10, 40, 50, 60, 70, 80) according to one of the preceding claims, characterized in that there is a flow of directing air, by which the direction of flight of the paint spray mist can be influenced.
12. Ultrasonic standing-wave atomizer arrangement (10, 40, 50, 60, 70, 80) according to one of the preceding claims, characterized in that there is at least one charging device for internal and/or external charging, by which the paint or the atomized paint particles can be electrostatically charged.

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