EP2015873B1 - Application element for a rotary sprayer and associated operating method - Google Patents

Abstract

The unit has an overflow surface (8), which rotates with an application element e.g. bell disk, in a coating operation and a surface layer (11), on which a thin coating medium (10) with a film thickness (dLACK) is formed in operation. A boundary surface friction acts between the film and the layer, where the layer reduces the friction between the film and the overflow surface. The medium contains a paint, which contains a flat, firm paint particle (12) with a specific particle length and forms a paint film on the layer (11), where the film thickness is smaller than the particle length. An independent claim is also included for an operating procedure for a rotary atomizer with a rotary application unit.

Description

The invention relates to an application element for a rotary atomizer, in particular in the form of a bell cup or a rotary disk, as well as an associated operating method according to the independent claims.

For the series painting of components, such as motor vehicle bodies, it is known to use high-rotation atomizers, which have as an application element a rapidly rotating bell cup. The paint to be applied is supplied to the rotating bell cup usually through a central paint tube and then flows on the bell cup via an overflow surface to an outer and annular peripheral spray-off edge, where the paint is thrown off due to the centrifugal force.

Out EP 0 951 942 A2 Such a bell cup is known, which is specially intended for the coating of effect coatings containing solid effect particles, which are also referred to as effect pigments or "flakes".

When using the conventional bell cup for the application of effect paints, however, occur undesirable differences in color and tone effect in comparison to the classic compressed air atomization, which are caused by the different material treatment in the sputtering process. In particular, during the film formation and the coating film flow in the region of the overcurrent surfaces, high frictional and shear forces occur, which are the light-reflecting Effect particles of the paint mixture can damage. During the surface manufacturing process (eg dirt inclusions, surface defects), shell construction (eg surface and substrate defects) and during further manufacturing steps such as final assembly, damage to the finished coated body may occur or may be detected during manufacture. These damages must be eliminated. These subsequent, local, manual repairs are usually carried out by means of a Luftzerstäubers. Thus, in the combination of an automatic painting by means of a high-rotation atomizer with a manual improvement by means of an air atomizer despite the different application techniques, the visual appearance for both application methods must be equivalent.

The reasons for this mixed operation are that existing paints (formulations) should not be changed. Furthermore, there are still manual paint scopes in the paint line (between the automated cells / zones) where e.g. Interior painting is carried out by means of air atomizer. In addition, the conversion or automation of existing paint lines is gradual, resulting in a mixed operation again.

For preventative prevention of the differences in color due to the different application techniques, the coating materials used are therefore preliminarily adjusted in their recipe so that after their different processing again equivalent results. The thus required preparatory pigment correction represents a considerable material and organizational additional effort. In particular, the color matching ability must be controlled in a batch change of paint supplies. In addition, the required refinishes for the manual Reworking small quantities with limited shelf life and hard-to-calculate demand quantity, so that the costs per liter are significantly higher than the material costs for the normal automatic coating application with the high-speed rotary atomizer. Furthermore, the need for manual rectification can not be removed from the usual production loop, so that must be kept ready for all production coatings corresponding refinishes and kept for mixing with agitators in motion.

A disadvantage of the aforementioned bell cup according to EP 0 951 942 A2 On the one hand, the desired color is achieved by a high speed, which has a negative effect on the efficiency. On the other hand this increased Lenkuftwerte be achieved.

Furthermore, it is off DE 101 12 854 A1 a conventional bell cup for a high-rotation atomizer, in which the overflow surface is coated with a surface layer in order to improve the abrasion behavior of the overflow surface and thus the service life of the bell cup. However, this known bell cup with a coated overflow surface has the above-mentioned disadvantages when applying effect coatings.

Furthermore, it is off JP 08155348 a bell cup is known whose overflow surface is coated with a surface layer of fluororesin, which is intended to improve the flushing behavior. However, this bell cup also has the above-mentioned disadvantages in an application of effect paints.

Furthermore, for example DE 93 15 890 U1 Rotationszerstäuber known in which the coating powder to be applied triboelectrically by friction on a plastic surface is charged. For this purpose, the overflow surface of the bell cup on a surface layer of polytetrafluoroethylene (PTFE), which provides on the other hand, for a good triboelectric charging of the coating powder due to the friction between the flowing over the overflow coating powder on the one hand and the surface layer. However, this known bell cup is only limited for the application of effect paints, since in this case the disadvantages mentioned above occur.

Out DE 44 39 924 A1 It is known to coat Lackierglocken with an abrasion-resistant and low-friction carbon-containing coating, which also improves the Lackierbild, since the wettability of the surface of the Lackierglocke is improved. However, such coated Lackierglocken show the application of effect paint the problems described above.

Finally it is too EP 0 087 836 A1 known to reduce the surface friction on solid surfaces by friction-reducing coatings, for example, have a scale-like crystal structure or contain nitrides.

Furthermore, it should be noted on the prior art JP 61 035 868 A , which discloses an application element according to the preamble of claim 1 or an operating method according to the preamble of claim 13, GB 2 294 214 A . WO 99/49983 A . JP 2006 181556 A . GB 726 559 A and WO 2006/049341 A , However, none of these publications disclose the idea of reducing interfacial friction on an overflow surface by a friction reducing surface layer such that the paint film on the surface layer of the overflow surface has a film thickness smaller than the particle length of the paint particles.

The invention is therefore an object of the invention to provide a bell cup, which is as well suited for a low-damage effect particles for application of effect coatings.

This object is achieved by an application element according to claim 1, or an operating method according to claim 13.

The invention is based on the newly obtained technical knowledge that the above-mentioned problems in the application of effect paint caused by the interfacial friction between the paint film on the overflow surface of the bell cup on the one hand and the overflow surface on the other.

On the one hand, the inventors have recognized for the first time that the interfacial friction between the paint film and the overflow surface leads to high frictional and shear forces in the paint film, which deform the thin, flat effect particles of the effect paint and damage their surface, which leads to the disturbing color tone deviations described above ,

On the other hand, the boundary surface friction between the paint film and the overflow surface leads to relatively thick paint films, so that the thin, flat effect particles ("flakes") set up within the paint film. Furthermore, the interfacial friction can also cause the effect articles to move, especially at a length of e.g. 100 microns and a thickness of about 1 micron. The effect particles can be damaged by O-surface abrasion and breakage, which affects the desired hue (optical effect of the applied paint). The inventive reduction of the boundary friction between the paint film on the overflow surface, however, allows prevention of friction and shear damage to the effect particles.

In contrast to the coated bell cups from the prior art described at the outset, the surface coating in the invention thus deliberately causes a reduction in the interfacial friction, whereas the surface coating in the known bell plates only has the abrasion resistance increase or is required for a triboelectric charging.

In a variant of the invention, the interfacial friction between the paint film and the overflow surface is reduced by reducing the surface roughness of the surface layer on the overflow surface. Preferably, the surface roughness of the surface layer of the overflow surface is less than the film thickness of the coating agent film. For example, the surface roughness of the surface layer of the overflow surface may be smaller than 200 μm, 100 μm, 50 μm, 10 μm or even 5 μm.

In another variant of the invention, the interface friction between the paint film on the one hand and the surface layer of the overflow surface on the other hand reduced by the overflow surface has a friction-reducing texture, which may be, for example, a so-called riblet structure or a so-called artificial shark skin on is known and therefore need not be described in detail. Such a friction-reducing sharkskin film is available, for example, from the company 3M under the name "Scotchcal Marine Drag Reduction Tape".

It has already been mentioned above that the coating agent (material to be sputtered) is an effect varnish containing flat, solid particles having a certain particle length and forming a varnish film on the surface layer of the overflow surface, the interfacial friction thus far is lowered, that the paint film has a film thickness that is smaller than the particle length of the effect particles. This offers the advantage that the individual effect particles of the effect varnish within the paint film can not set up and therefore flow with an orderly spatial orientation over the overflow surface. The paint film on the overflow surface therefore has a film thickness during operation which is preferably less than 200 μm, 100 μm, 50 μm, 10 μm or even 5 μm.

Preferably, the surface layer on the overflow surface is at least partially made of a nitride including, for example, titanium nitride, chromium nitride, titanium carbon nitride, zirconium nitride, tungsten carbon nitride, and aluminum titanium nitride as materials for the surface layer the overflow area are suitable. However, within the scope of the invention it is also possible that the surface layer on the overflow surface consists at least partially of glass, ceramic, metal or so-called nanoparticles. In principle, however, all chemically neutral, mechanically stable and adhering materials are suitable as the material for the friction-reducing surface layer.

It should also be mentioned that the friction-reducing surface layer is preferably provided locally limited to the entire overflow surface and / or other Lackflussflächen. However, there is the alternative possibility that the friction-reducing surface layer is limited to those areas of the overflow surface, which are exposed to high centrifugal forces during operation. Furthermore, there is the possibility that the entire rotating application element is coated with a friction-reducing surface layer.

Furthermore, the surface layer of the overflow surface is preferably more resistant to abrasion and / or harder than the uncoated overflow surface in order to improve the abrasion behavior of the overflow surface and thus the service life of the application element. Therefore, the surface layer of the overflow surface has preferably a Vickers hardness of more than 500 HV, 1000 HV, 1500 HV, 2000 HV or even more than 3000 HV.

It should also be mentioned that the surface layer of the overflow surface preferably consists of a different material than the overflow surface underneath.

However, there is also the alternative possibility that the surface layer of the overflow surface consists of the same material as the overflow surface underneath. In this variant, the boundary friction can be reduced for example by a suitable surface texture of the surface layer.

For example, the surface layer of the overflow surface may consist of a film applied to the overflow surface, which may, for example, be a so-called shark skin film used in aircraft construction for reducing the frictional resistance and has already been mentioned above.

It can already be seen from the above description that the application element according to the invention is preferably a bell cup for a high-rotation atomizer. However, the invention is not limited to bell plates in terms of the type of application element, but also includes, for example, so-called rotary discs for disc atomizers. Pavel Svejda, for example: "Modern painting technology, processes and application methods", Vincentz-Verlag 2003, page 75 f., Describes such rotary disks and the associated disk atomizers. known.

In addition, the invention comprises not only the above-described inventive application element as a single component, but also a rotary atomizer with such an application element and a coating machine, in particular a multi-axis painting robot, with such a rotary atomizer.

Finally, the invention also encompasses a corresponding operating method for such a rotary atomizer, in which the boundary surface friction between the coating agent film on the overflow surface and the overflow surface itself is purposefully reduced by a friction-reducing surface layer.

In the operating method according to the invention, the boundary surface friction is preferably reduced to such an extent that the thickness of the paint film on the overflow surface decreases so much that the film thickness is smaller than the particle length of the effect particles (so-called "flakes", to be distinguished from pigments), so that the Effektpartikel inside the lacquer layer nicht.aufstellen can.

Thus, the invention offers the advantage that an effect varnish can be applied automatically by a rotary atomizer without the need for specific varnishes without impairing the efficiency without the air consumption rising due to increased steering pressure values, so that the color tone result without correction is the same varnish material the paint formulation of the quality of a compressed air atomization can be adjusted.

Figur 1

eine Querschnittsansicht eines erfindungsgemäßen Glockentellers für die Applikation eines Effektla- ckes sowie

Figur 2

eine stark vergrößerte Querschnittsansicht der Über- strömfläche des Glockentellers aus Figur 1.

Other advantageous developments of the invention are characterized in the subclaims or will become apparent from the following Description of the preferred embodiment of the invention with reference to the figures explained in more detail. Show it:

FIG. 1

a cross-sectional view of a bell cup according to the invention for the application of Effektla- ckes and

FIG. 2

a greatly enlarged cross-sectional view of the overflow surface of the bell cup FIG. 1 ,

The drawing in FIG. 1 shows a bell cup 1 for a high-rotation atomizer for the application of an effect varnish. The structure and operation of the bell cup 1 is largely conventional and in EP 0 951 942 A2 described.

To attach the bell cup 1 to a bell-plate shaft of a high-rotation atomizer, the bell cup 1 has a mounting hub 2, which is provided with an external thread which is screwed into a correspondingly adapted internal thread of the bell-plate shaft.

The feeding of the effect varnish to the bell cup 1 takes place here by the attachment hub 2 and a central opening 3 in the bell cup 1.

At the end face-side outlet opening of the central opening 3 there is a deflection part 4 which has a centrally arranged and radially extending rear surface 5 and an outer, conically extending rear surface 6. The two rear surfaces 5, 6 of the deflection part 4 form a boundary surface of a gap, which is on the opposite side of a range 7 an otherwise conical overflow surface 8 is formed. The overflow surface 8 closes with the end face of the bell cup 1 at a nearly constant angle α and leads to an annular peripheral spray-off edge 9.

The effect paint is thus fed axially to the bell cup 1 via the attachment hub 2 and then passes through the center opening 3 in the bell cup 1. The deflecting part 4 then deflects the effect varnish in the radial direction, so that the effect varnish flows over the overflow surface 8 and is finally thrown off at the spray-off edge 9.

The particular feature of the bell cup 1 according to the invention is evident from the cross-sectional view in FIG FIG. 2 which shows the overflow surface 8 with a paint film 10 thereon and a friction-reducing surface layer 11 therebetween. Furthermore, it can be seen from the cross-sectional illustration that the paint film 10 has numerous long, flat effect particles 12 with a certain particle _length L _PARTICLE .

The friction-reducing surface layer 11 on the overflow surface 8 reduces the interfacial friction between the paint film 10 and the surface layer 11 or overflow surface 8 to such an extent that damage to the effect particles due to abrasion and cracking phenomena is prevented in order to prevent color tone deviations caused thereby compared with other sputtering methods and to avoid necessary adjustment expenses

Furthermore, it can be seen from the cross-sectional view that the friction-reducing surface layer 11 has a layer thickness d _layer, which is substantially less than the film thickness d _varnish of the varnish layer 10th

For example, the particle size L _{PARTICLES may be} in the range of L _PARTIKFL = 10 ... 40pm, while the film thickness d _LACK may be in the range of d _LACK = 5 ... 20μm, for example. The layer thickness D _{LAYER of} the friction-reducing surface layer 11 may be in the range of d _LAYER = 1..4μm. However, the invention is not limited to the above values but can be realized with other values of the particle size L _PARTICLE , the film thickness d _LACK and the layer thickness d _LAYER .

It should also be mentioned that the friction-reducing surface layer 11 in this embodiment consists of titanium nitride and reduces the interfacial friction between the lacquer layer 10 and the overflow surface 8 by a factor of 4.

LIST OF REFERENCE NUMBERS

1

A bell plate

2

mounting hub

3

center opening

4

deflecting

5

Radial rear surface of the deflector

6

Conical rear surface of the deflection part

7

Range of overcurrent area

8th

overflow

9

spray edge

10

paint layer

11

surface layer

12

effect particles

Claims (16)

1. An application element (1) for a rotary atomizer, in particular in the form of a bell-shaped plate or a rotary disk, comprising

   a) an overflow surface (8) which, in coating operation, rotates with the application element (1) and over which a coating agent that is to be applied flows, and

   b) a surface layer (11) situated on the overflow surface (8), on which, in operation, a thin coating agent film (10) with a defined film thickness (D_PAINT) forms, wherein a boundary surface friction acts between the coating agent film (10) and the surface layer (11) and the surface layer (11) reduces the boundary surface friction between the coating agent film (10) and the overflow surface (8),

   c) wherein the coating agent is a paint, in particular an effect paint, which includes flat, solid paint particles (12) with a defined particle length (L_PARTICLE) and forms a paint film (10) on the surface layer (11), characterised in

   d) that the surface roughness of the surface layer (11) of the overflow surface (8) is less than the film thickness (D_PAINT) of the coating agent film (10) or that the surface layer (11) of the overflow surface (8) has a friction-reducing texture, in particular a riblet structure, so that the paint film (10) on the surface layer (11) of the overflow surface (8) has a film thickness (d_PAINT), which is less than the particle length (Lp_ARTICLE) of the paint particles (12).
2. The application element (1) according to claim 1, characterised in that the surface roughness of the surface layer (11) of the overflow surface (8) is less than 200 µm, 50 µm, 10 µm or 5 µm.
3. The application element (1) according to one of the preceding claims, characterised in that the surface layer (11) at least partially consists of a nitride.
4. The application element (1) according to claim 3, characterised in that the surface layer (11) at least partially consists of the following materials:

   a) titanium nitride,

   b) chromium nitride,

   c) titanium carbon nitride,

   d) zirconium nitride,

   e) tungsten carbon nitride,

   f) aluminium titanium nitride.
5. The application element (1) according to one of the preceding claims, characterised in that the surface layer (11) at least partially consists of the following materials:

   a) glass,

   b) ceramic material,

   c) metal,

   d) nanoparticles.
6. The application element (1) according to one of the preceding claims, characterised in that the surface layer (11) of the overflow surface (8) is more abrasion-resistant and/or harder than the uncoated overflow surface (8).
7. The application element (1) according to one of the preceding claims, characterised in that the surface layer (11) has a Vickers hardness of more than 1000 HV, 1500 HV or 2000 HV.
8. The application element (1) according to one of the preceding claims, characterised in that the surface layer (11) of the overflow surface (8) comprises a different material than the overflow surface (8) situated thereunder (8).
9. The application element (1) according to one of the claims 1 to 7, characterised in that the surface layer (11) of the overflow surface (8) is made from the same material as the overflow surface (8) situated thereunder.
10. The application element (1) according to one of the preceding claims, characterised in that the surface layer (11) of the overflow surface (8) is a film applied to the overflow surface (8).
11. A rotary atomizer, in particular bell atomizer or disk atomizer, with an application element (1) according to one of the preceding claims.
12. A painting machine, in particular a paint robot, comprising a rotary atomizer according to claim 11.
13. A method of operation for a rotary atomizer having a rotary application element (1), in particular a bell-shaped plate or a rotary disk, wherein a coating agent flows over an overflow surface (8) on the rotating application element (1) and forms a coating agent film (10) on the overflow surface (8) with a defined film thickness (d_PAINT), wherein the boundary surface friction between the coating agent film (10) and the overflow surface (8) is reduced by means of a friction-reducing surface layer (11) on the overflow surface (8), the coating agent being a paint which includes solid, flat paint particles (12) which have a defined particle length (Lp_ARTICLE) and forming a paint film (10) with a defined film thickness (d_PAINT) on the surface layer (11) of the overflow surface (8), characterised in that the boundary surface friction between the surface layer (11) of the overflow surface (8) and the paint film (10) is sufficiently small so that the film thickness (d_PAINT) of the paint film (10) is smaller than the particle length (L_PARTICLE) of the paint particles (12).
14. The method of operation according to claim 13, characterised in that

    a) an effect paint which includes solid, flat paint particles (12) is applied with the rotary atomizer, and

    b) following application of the effect paint by the rotary atomizer, no manual or automated correction of the effect paint applied is carried out.
15. The method of operation according to claim 13 or 14, characterised in that

    a) an effect paint which includes solid, flat paint particles (12) is applied with the rotary atomizer, and

    b) the application of the effect paint by means of a rotary atomizer can be combined with other spraying methods such that, with regard to colour tone and colour tone effect, equivalent results can be obtained without adjusting the paint material.
16. Use of an application element (1) according to one of the claims 1 to 10 for applying an effect paint which includes solid, flat paint particles (12).

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