ROTARY atomizer

Description

[0001] The invention relates to a rotary atomizer for applying a spray jet of a coating agent (e.g. paint) to a component (e.g. motor vehicle body component).

[0002] Such rotary atomizers are well known from the prior art (e.g., EP 0 715 896 B1) and comprise a bell cup as the application element, which is mounted on a bell cup shaft of the rotary atomizer that rotates during operation. The bell cup shaft is typically driven by a compressed air turbine. A paint tube for supplying the paint to be applied runs within the hollow bell cup shaft of the rotary atomizer. A paint nozzle is inserted into the end of the paint tube and discharges the paint toward the bell cup. A distributor disc holder is arranged centrally in the bell cup, to which a distributor disc holder arranged on the front side is attached.

[0003] The paint initially emerging axially from the paint nozzle hits the distributor disc and is largely directed radially outwards onto the overflow surface of the bell cup, so that the paint then finally reaches the spray edge of the bell cup and is sprayed off there.

[0004] A portion of the paint initially emerging axially from the paint nozzle passes through a central hole in the distributor disc in order to permanently wet the frontal paint flow surface of the distributor disc with paint.

[0005] In addition, the well-known rotary atomizer also features an external flushing option for flushing the outer surface of the bell cup with a flushing agent. For this purpose, flushing agent can be introduced into the bell cup via the paint nozzle. This agent then flows through external flushing channels into an external flushing chamber at the rear of the bell cup, from where the flushing agent then flows over the outer surface of the bell cup.

[0006] The above description explains the correct operation of the rotary atomizer, in which the paint emerging from the paint nozzle flows exclusively forward, partly through the central bore in the distributor disc and partly radially outward onto the overflow surface of the bell cup. In practice, however, it has been shown that under certain operating conditions, some of the paint emerging from the paint nozzle can flow backward in the bell cup, for example, through the external flushing channels into the external flushing chamber of the bell cup or into the nozzle chamber surrounding the paint nozzle. This backflow of paint must, however, be prevented at all costs during operation, as it can lead to contamination of the bell cup and the rotary atomizer and thus to a faulty painting result.

[0007] Regarding the state of the art, reference should also be made to US 8 851 397 B1, DE 10 2009 037 604 A1, EP 0 715 896 B1 and DE 30 00 002 A1.

[0008] The invention is therefore based on the object of improving the known rotary atomizer described at the outset.

[0009] This object is achieved by a rotary atomizer according to the invention according to the main claim.

[0010] The invention is based on the fluidic knowledge that the disturbing backflow of the paint within the bell cup is caused by unsuitable pressure conditions within the bell cup system.

[0011] The invention therefore encompasses the general technical teaching of designing the rotary atomizer and the bell cup system such that the air pressure at the paint nozzle outlet during operation is always lower than the rearward air pressure in the nozzle chamber of the bell cup and in the external flushing channels. This pressure difference prevents a disruptive backflow of the coating agent from the paint nozzle outlet toward the nozzle chamber. An overpressure in the nozzle chamber of the bell cup and in the external flushing channels compared to the air pressure at the paint nozzle outlet prevents this disruptive backflow of the coating agent.

[0012] Within the scope of the invention, it was recognized that various design dimensions of the rotary atomizer influence the pressure ratio between the air pressure at the outlet of the paint nozzle on the one hand and the air pressure in the nozzle chamber of the bell cup or in the external flushing channels on the other. These include the following design dimensions: Cross section of the central bore in the distributor disc of the bell cup, diameter of a central bore of the distributor disc holder, gap width of the gap between the distributor disc and the overflow surface of the bell cup, gap width of the annular gap between the bell cup or the distributor disc holder and the paint nozzle, gap width of the annular gap between the paint nozzle and the inner wall of the nozzle chamber, gap width of the annular gap between the bell cup shaft and the inner paint pipe, gap width of the annular gap of the outer rinsing chamber on the outside of the bell cup shaft, and gap width of the gap between the front side of the shaping air ring and the rear side of the bell cup.

[0013] The invention therefore preferably provides that the above-mentioned design dimensions of the rotary atomizer are coordinated with one another in such a way that the desired pressure conditions are set, namely in such a way that the air pressure at the outlet opening of the paint nozzle during operation is always lower than the air pressure in the nozzle chamber of the bell cup and in the external rinsing channels in order to avoid the disturbing backflow of the coating agent from the outlet opening of the paint nozzles backwards in the direction of the nozzle chamber.

[0014] It should be noted that the air pressure at the outlet of the paint nozzle is influenced, among other things, by the following design dimensions of the rotary atomizer: Cross-section of the central bore in the distributor disc of the bell cup, gap width of the gap between the distributor disc and the overflow surface of the bell cup, gap width of the annular gap between the bell cup and the paint nozzle.

[0015] The air pressure in the rear area of ​​the bell cup system (for example in the nozzle chamber of the bell cup or in the external flushing channels), on the other hand, is influenced by the following design dimensions of the rotary atomizer, among others: Gap width of the annular gap between the bell cup or the distributor disc holder of the bell cup and the paint nozzle, diameter of the center bore of the distributor disc holder, gap width of the annular gap between the paint nozzle and the inner wall of the nozzle chamber, gap width of the annular gap between the bell cup shaft and the inner paint pipe, gap width of the annular gap of the outer rinsing chamber on the outside of the bell cup shaft, and gap width of the gap between the front side of the shaping air ring and the rear side of the bell cup.

[0016] The invention therefore preferably provides that the design dimensions from the two aforementioned groups are matched to one another in a suitable manner in order to achieve the desired pressure conditions.

[0017] In a preferred embodiment of the invention, the number of external flushing channels in the bell cup is less than 10, 9, 8, 7, 6 or even less than 5 in order to achieve the pressure ratio to prevent backflow. It should be noted that the external flushing channels are usually distributed over the circumference of the bell cup and counteract the disruptive backflow, so that reducing the number of external flushing channels increases the flow resistance and thus contributes to achieving the desired pressure ratios. Accordingly, the external flushing channels together can have a total cross-sectional area that is less than 4mm 2< , 6mm 2< , 10mm 2< , 15mm 2< , 20mm 2< , 25mm 2< , 30mm 2< or 35mm 2< in order to achieve the pressure ratio to prevent backflow.

[0018] It has proven advantageous for the outer flushing channels to each have an inner diameter of 1 mm - 2 mm, in particular essentially 1.5 mm, in order to achieve the pressure ratio required to prevent backflow. An excessively small inner diameter of the outer flushing channels is disruptive because it impairs external flushing processes. On the other hand, an excessively large diameter of the outer flushing channels is disruptive because it facilitates the disruptive backflow of paint within the bell cup system. The range of the inner diameter of the outer flushing channels according to the invention, from 1 mm - 2 mm, therefore represents a good compromise.

[0019] It should also be mentioned that the external flushing channels preferably have a total length of 5mm-15mm, 7mm-10mm or 8mm-8.7mm.

[0020] It has proven advantageous for the outer flushing channels to consist of several (e.g., two) straight tap holes that merge into one another and are angled to each other. This is advantageous from a manufacturing perspective, as the tap holes can be created by drilling. It is also advantageous from a flow perspective, as the kink in the outer flushing channels counteracts the undesirable backflow of the paint.

[0021] Preferably, the tap holes leading into the outer flushing chamber of the bell cup are shorter than the paint tap holes on the paint nozzle side.

[0022] The shorter tap holes leading into the outer flushing chamber of the bell cup are preferably each 0.5 mm - 2 mm or 1.0 mm - 1.4 mm long. The longer tap holes on the paint nozzle side, on the other hand, are preferably 5 mm - 10 mm or 6 mm - 8 mm long.

[0023] In addition, the outer flushing chamber in the bell cup also influences the pressure conditions in the bell cup system. It has been shown that increasing the outer diameter of the outer flushing chamber has a positive effect on the pressure conditions. Therefore, the outer diameter of the flushing chamber in the bell cup is preferably larger than 30.5 mm, 31 mm, 31.5 mm, 32 mm, or 32.5 mm.

[0024] Another important design dimension is the gap width between the overflow surface of the bell cup on the one hand and the distributor disc on the other. Within the scope of the invention, this gap width should preferably be in the range of 0.1 mm to 0.25 mm, and in particular in the range of 0.15 mm to 0.2 mm.

[0025] However, the gap between the overflow surface of the bell cup on the one hand and the distributor disc on the other is important not only in terms of its width, but also in terms of its length in the direction of flow. The gap length between the overflow surfaces of the bell cup on the one hand and the distributor disc on the other hand is therefore preferably in the range of 3 mm to 10 mm, 3.5 mm to 7.5 mm, or 4.5 mm to 5.5 mm.

[0026] It was already mentioned above that the paint nozzle is arranged in the bell cup in a nozzle chamber formed by the bell cup. It has proven advantageous to enlarge the diameter of the nozzle chamber in order to increase the radial gap width between the paint nozzle on the one hand and the inner wall of the nozzle chamber on the other. This also contributes to optimizing the pressure ratio and preventing backflow of the paint. The nozzle chamber in the bell cup therefore preferably has a diameter of more than 11 mm, 11.5 mm, 12 mm, 12.5 mm, 13 mm, or even more than 13.3 mm. A nozzle chamber diameter of 13.4 mm has proven particularly advantageous in each case.

[0027] Another important design dimension of the rotary atomizer is the gap width of the axial gap between the shaping air ring of the rotary atomizer on the one hand and the rear of the bell cup on the other. It has proven advantageous to increase this axial gap width of the gap between the shaping air ring and the rear of the bell cup. The axial gap between the shaping air ring on the one hand and the rear of the bell cup on the other hand is therefore preferably greater than 3.0 mm, 4 mm, 4.5 mm, 5 mm or 5.2 mm, with a value of 5.3 mm proving particularly advantageous. It should be noted that the bell cup shaft is preferably exposed in the axial gap between the shaping air ring and the rear of the bell cup without an external cover in order to advantageously influence the pressure ratio and prevent backflow.

[0028] The pressure conditions in the bell cup system are also influenced by the outer diameter of the paint nozzle. Therefore, the paint nozzle preferably has an outer diameter of less than 4 mm, 3.5 mm, 3 mm, or even less than 2.8 mm at its free end, with an outer diameter of 2.6 mm or 3.2 mm having proven particularly advantageous.

[0029] In the preferred embodiment of the invention, a distributor disc holder is mounted centrally in the bell cup as a separate component, as is also known from the prior art. The distributor disc is then mounted on the distributor disc holder. The paint nozzle protrudes through a central bore in the distributor disc holder, wherein the central bore preferably has an inner diameter of substantially 3.2 mm or 3.8 mm. The annular gap between the paint nozzle on the one hand and the surrounding distributor disc holder on the other hand, in contrast, preferably has a radial gap width of 0.2 mm - 0.6 mm, with a value of 0.3 mm having proven particularly advantageous.

[0030] In addition to the annular gap between the paint nozzle on the one hand and the distributor disc holder on the other hand, the axial gap length should also be mentioned, which is preferably in the range of 4.5mm-8.5mm or 5.5mm-7.5mm, whereby a value of 6.5 has proven to be advantageous.

[0031] Furthermore, in addition to the annular gap between the paint nozzle and the surrounding distributor disc holder, the axial cross-section of the annular gap must also be mentioned, which preferably has a cross-sectional area of ​​2mm 2< -7mm 2< , 3mm 2< -6mm 2< or 4mm 2< -5mm 2<.

[0032] Finally, it should be noted that the invention not only claims protection for the rotary atomizer according to the invention described above. Rather, the invention also claims protection for a corresponding operating method, which, in addition to the design dimensions described above, also provides for certain operating parameters, such as the rotational speed of the bell-cup shaft, the mass flow of the coating agent, and the mass flow of the shaping air. The aforementioned design dimensions and the aforementioned operating parameters are preferably coordinated with one another in such a way that the desired pressure conditions are established in the bell-cup system in order to avoid undesirable backflow of the coating agent in the bell-cup system.For this purpose, the air pressure at the outlet opening of the paint nozzle must be lower than the air pressure in the nozzle chamber of the bell cup and in the external rinsing channels so that no backflow of the coating agent occurs.

[0033] Other advantageous developments of the invention are characterized in the subclaims or are explained in more detail below together with the description of the preferred embodiment of the invention with reference to the figures. They show: Figure 1 is a cross-sectional view of a rotary atomizer according to the invention with a bell plate according to the invention, Figure 2 is an enlargement of Figure 1 in the area of ​​the distributor disc holder, Figure 3 an enlargement of Figure 2 in the area of ​​the gap between the distributor disc and the overflow surface of the bell cup, Figure 4 an enlargement of Figure 1 in the area of ​​the paint nozzle, Figure 5 an enlargement of Figure 4in the area of ​​the paint nozzle outlet.

[0034] The drawings show a preferred embodiment of a rotary atomizer 1 according to the invention, which can be used for paint application in a painting system for painting motor vehicle body components.

[0035] The rotary atomizer 1 has a bell-cup shaft 2 which rotates during operation and is hollow and is usually driven by a compressed air turbine, the compressed air turbine not being shown for the sake of simplicity.

[0036] A bell plate 3 is screwed onto the free end of the bell plate shaft 2, which is known from the prior art.

[0037] The paint to be applied is fed from the rotary atomizer 1 via a paint tube 4 which runs coaxially in the hollow bell-cup shaft 2 of the rotary atomizer.

[0038] A paint nozzle 5 is inserted into the free end of the paint tube 4, which is inserted into the Figures 4 and 5 shown in detail and described in a similar form, for example, in DE 10 2009 037 604 A1. The paint nozzle 5 firstly has an axially continuous paint channel 6 which guides the paint to be applied from the paint tube 4 to an outlet opening 7 of the paint nozzle 5. The paint nozzle 5 also contains a rinsing agent channel 8 which branches off in the direction of flow into two rinsing agent channels 9, 10. During a rinsing process, a portion of the rinsing agent supplied via the rinsing agent channel 8 is released axially forward through the rinsing agent channel 9 in order to rinse the bell cup 3. Another portion of the rinsing agent, on the other hand, is branched off above the rinsing agent channel 10 in order to rinse a nozzle chamber 11 which surrounds the paint nozzle 5.

[0039] In the bell cup 3, a distributor disc holder 12 is mounted centrally, which carries a distributor disc 13, wherein the distributor disc 13 is fastened to the distributor disc holder 12 by several bolts 14 arranged distributed over the circumference.

[0040] In the center of the distributor disc 13 there is a central bore 15 so that a part of the paint emerging from the paint nozzle 5 can flow through the central bore 15 in the distributor disc 13 in order to wet the front surface of the distributor disc 13 with paint during operation.

[0041] The majority of the paint emerging from the paint nozzle 5, however, is diverted radially outwards by the distributor disc 13 and passes through a gap 16 between the distributor disc 13 and an overflow surface 17 outwards to a spray edge 18 of the bell cup 3, where the paint is finally sprayed off.

[0042] Furthermore, the rotary atomizer 1 with the bell cup 3 also enables external rinsing of an outer surface 19 of the bell cup 3 in order to clean the outer surface 19 of the bell cup 3. For this purpose, external rinsing channels 20 are provided in the bell cup 3, distributed around the circumference, each consisting of two straight and mutually angled tap holes. The external rinsing channels 20 originate from the nozzle chamber 11 and open outward into an external rinsing chamber 21, wherein the rinsing agent can then flow outward from the external rinsing chamber 21 onto the outer surface 19 of the bell cup 3 during a rinsing process, which is known per se from the prior art.

[0043] Furthermore, it should be noted that the rotary atomizer 1 has a shaping air ring 22 to shape the paint spray jet emitted by the bell cup 3, which is known per se from the prior art. For this purpose, the shaping air ring 22 can direct shaping air from the rear onto the outer surface 19 of the bell cup 3 via an annular ring of shaping air nozzles 23. It should be noted that a gap 24 with a specific axial width exists between the rear side of the bell cup 3 and the shaping air ring 22.

[0044] Within the scope of the invention, various design dimensions of the rotary atomizer 1 and the bell cup 3 are relevant for achieving the inventive objective of changing the backflow of paint in the bell cup 3. The following design dimensions are to be mentioned here: Diameter A of the central bore in the distributor disc holder 12 of the bell cup 3, gap width B of the gap 16 between the distributor disc 13 and the overflow surface 17 of the bell cup 3, gap width C of an annular gap 25 between the distributor disc holder 12 of the bell cup 3 and the paint nozzle 5, gap width D of an annular gap between the paint nozzle 5 and the inner wall of the nozzle chamber 11, gap width E of an annular gap 27 between the paint pipe 4 and the bell cup shaft 2, gap width F of an annular gap 28 formed by the outer rinsing chamber 21 of the bell cup 3, and gap width G of the gap between the bell cup 3 and the shaping air ring 22.

[0045] The above-mentioned design dimensions of the bell cup 3 and the rotary atomizer are coordinated in this embodiment such that the air pressure at the outlet opening of the paint nozzle 5 during operation is always lower than the air pressure in the nozzle chamber 11 and in the external rinsing channels 20 of the bell cup 3. This prevents a disturbing backflow of the paint to the rear.

[0046] The following values ​​for the individual construction dimensions have therefore proven to be advantageous: A = 3.2mm or A = 3.8mm, B = 0.15mm-0.2mm, C = 0.3mm, D = 1.7mm, E = 0.75mm, F = 3.25mm, G = 5.3mm.

[0047] Within the scope of the invention, deviations of ±30%, ±20%, ±10%, ±5% or ±2% are possible for the above-mentioned values.

[0048] Furthermore, it should be mentioned that the number of external flushing channels 20 has been reduced to six external flushing channels 6 compared to the state of the art, which also has a positive effect on the pressure conditions. List of reference symbols:

[0049] 1 Rotary atomizer 2 Bell cup shaft of the rotary atomizer 3 Bell cup 4 Paint tube of the rotary atomizer 5 Paint nozzle of the rotary atomizer 6 Paint channel in the paint nozzle 7 Paint nozzle outlet 8-10 Flushing agent channels in the paint nozzle 11 Nozzle chamber on the rear side of the bell cup 12 Distributor disc holder of the bell cup 13 Distributor disc of the bell cup 14 Bolt for connecting the distributor disc to the distributor disc holder 15 Center hole in the distributor disc of the bell cup 16 Gap between distributor disc and overflow surface of the bell cup 17 Overflow surface of the bell cup 18 Spray edge of the bell cup 19 Outer surface of the bell cup 20 External flushing channels of the bell cup 21 External flushing chamber of the bell cup 22 Deflecting air ring of the rotary atomizer 23Shaping air nozzles 24Gap between bell cup and shaping air ring 25Annular gap between distributor disc holder in the bell cup and paint nozzle 26Annular gap between paint nozzle andNozzle chamber 27 Annular gap between paint tube and bell cup shaft 28 Annular gap formed by the external flushing chamber ADiameter of the central bore in the distributor disc holder BGap width of the gap between distributor disc and overflow surface of the bell cup CGap width of the annular gap between distributor disc holder in the bell cup and paint nozzle DRadial gap width of the annular gap between paint nozzle and nozzle chamber ESPan width of the annular gap between paint tube and bell cup shaft FRadial gap width of the annular gap formed by the external flushing chamber GAxial gap width of the gap between bell cup and shaping air ring

Claims

1. Rotary atomizer (1) for applying a spray jet of a coating agent, in particular a paint, to a component, in particular to a motor vehicle body component, having a) a shaping air ring (22) to discharge shaping air to form the spray jet of the coating agent, b) a hollow bell cup shaft (2) rotating during operation, c) a paint tube (4) arranged substantially coaxially in the hollow bell cup shaft (2), wherein the bell cup shaft (2) and the internal paint tube (4) enclose an annular gap (27) with a certain gap width (E) in radial direction, d) a paint nozzle (5) which is arranged substantially coaxially in the paint tube (4) and discharges the coating agent to be applied substantially in the axial direction through an outlet opening (7), e) a bell cup (3) mounted on the bell cup shaft (2) and rotating during operation with e1) a gap (24) between the front side of the shaping air ring (22) and the rear side of the bell cup (3) with a certain gap width (G) in axial direction, e2) a central bore for axial feed-through of the paint nozzle (5) with an annular gap (25) between the bell cup (3) and the paint nozzle (5) with a certain gap width (C) in radial direction, e3) an annular spray edge (18) for spraying the coating agent, e4) an outer circumferential surface (19), e5) an exterior rinsing chamber (21) on the rear side of the bell cup (3) for rinsing the outer circumferential surface (19) with a rinsing agent, the exterior rinsing chamber (21) forming an annular gap (28) on the outside of the bell cup shaft (2) with a specific gap width (F) in the radial direction, e6) several exterior rinsing channels (20) in the bell cup (3) between the paint nozzle (5) and the exterior rinsing chamber (21) for feeding rinsing agent from the paint nozzle (5) onto the outer circumferential surface (19) of the bell cup (3) for exterior rinsing of the bell cup (3), e7) a nozzle chamber (11) on the rear side of the bell cup (3) for receiving the paint nozzle (5) with an annular gap (26) between the paint nozzle (5) and the inner wall of the nozzle chamber (11) with a certain gap width (D) in radial direction, e8) an overflow surface (17) at the front face, wherein the coating agent to be applied, coming from the outlet opening (7) of the paint nozzle (5), flows in operation outwards over the overflow surface (17) to the spray edge (18) of the bell cup (3), and e9) a distributor disc (13) for distributing the coating agent emerging from the outlet opening (7) of the paint nozzle (5), wherein the distributor disc (13) - is arranged in the bell cup (3) at the front side, - directs the coating agent coming from the paint nozzle (5) partly radially outwards onto the overflow surface (17) of the bell cup (3) and partly axially through a central bore (15) in the distributor disc (13) onto the end face of the distributor disc (13), - wherein the distributor disc (13) encloses with the overflow surface (17) of the bell cup (3) a gap (16) with a certain gap width (B), e10) a distributor disc holder (12) which is arranged in the bell cup (3) and has a central bore (15) with a specific diameter (A), the distributor disc (13) being mounted on the distributor disc holder (12), characterized in f) that the rotary atomizer (1) is designed in such a way that the air pressure at the outlet opening (7) of the paint nozzle (5) during operation is lower than the air pressure in the nozzle chamber (11) of the bell cup (3) and in the outer rinsing channels (20), in order to prevent a backflow of the coating agent from the outlet opening (7) of the paint nozzle (5) backwards in the direction of the nozzle chamber (11) as a result of this pressure difference.

2. Rotary atomizer (1) according to claim 1, characterized in that the following design dimensions of the rotary atomizer (1) are matched to one another in such a way that the air pressure at the outlet opening (7) of the paint nozzle (5) during operation is lower than the air pressure in the nozzle chamber (11) of the bell cup (3) and in the outer rinsing channels (20): a) the diameter (A) of the central bore in the distributor disc holder (12) of the bell cup (3), b) the gap width (B) of the gap (16) between the distributor disc (13) and the overflow surface (17) of the bell cup (3), c) the gap width (C) of the annular gap (25) between the bell cup (3) and the paint nozzle (5), d) the gap width (D) of the annular gap (26) between the paint nozzle (5) and the inner wall of the nozzle chamber (11), e) the gap width (E) of the annular gap (27) between the bell cup shaft (2) and the internal paint tube (4), f) the gap width (F) of the annular gap (28) of the exterior rinsing chamber (21) on the outside of the bell cup shaft (2), and g) the gap width (G) of the gap (24) between the front side of the shaping air ring (22) and the rear side of the bell cup (3).

3. Rotary atomizer (1) according to one of the preceding claims, characterized in a) that the number of external rinsing channels (20) in the bell cup (3) is less than 10, 9, 8, 7, 6 or 5 to achieve the pressure ratio to prevent the backflow, and / or b) that the external rinsing channels together have a total cross-sectional area smaller than 4 mm2, 6 mm2, 10 mm2, 15 mm2, 20 mm2, 25 mm2, 30 mm2 or 35 mm2 to achieve the pressure ratio to prevent the backflow.

4. Rotary atomizer (1) according to any of the preceding claims, characterized in a) that the external rinsing channels (20) each have an internal diameter of 1 mm - 2 mm, in particular essentially 1.5 mm, in order to achieve the pressure ratio to prevent the backflow, and / or b) that the external rinsing channels (20) each have a total length of 5 mm - 15 mm, 7 mm - 10 mm or 8 mm - 8.7 mm.

5. Rotary atomizer (1) according to one of the preceding claims, characterized in a) that the external rinsing channels (20) each consist of several, in particular exactly two, straight tap bores which merge into one another and are angled towards one another, and / or b) that the tap holes opening into the exterior rinsing chamber (21) of the bell cup (3) are shorter than the tap holes on the paint nozzle side, and / or c) that the shorter tap holes opening into the exterior rinsing chamber (21) of the bell cup (3) each have a length of 0.5 mm - 2 mm or 1.0 mm-1.4 mm, and / or d) that the longer tap bores on the paint nozzle side each have a length of 5 mm - 10 mm or 6 mm - 8 mm.

6. Rotary atomizer (1) according to one of the preceding claims, characterized in that the exterior rinsing chamber (21) in the bell cup (3) has an external diameter of more than 30.5 mm, 31 mm, 31.5 mm, 32 mm or 32.5 mm in order to achieve the pressure ratio to avoid the backflow.

7. Rotary atomizer (1) according to any of the preceding claims, characterized in a) that the gap width (B) of the gap (16) between the overflow surface (17) of the bell cup (3) and the distributor disc (13) is in the range of 0.1 mm - 0.25 mm, in particular in the range of 0.15 mm - 0.2 mm, and / or b) that the gap (16) between the overflow surface (17) of the bell cup (3) and the distributor disc (13) has a gap length in the flow direction which is in the range of 3 mm - 10 mm, 3.5 mm - 7.5 mm or 4.5 mm - 5.5 mm.

8. Rotary atomizer (1) according to one of the preceding claims, characterized in that the nozzle chamber (11) in the bell cup (3) has an external diameter of more than 11 mm, 11.5 mm, 12 mm, 12.5 mm, 13 mm or more than 13.3 mm, in particular substantially 13.4 mm, in order to increase the radial gap width (D) between the paint nozzle (5) and the inner wall of the nozzle chamber (11) and thereby to achieve the pressure ratio to reduce the backflow.

9. Rotary atomizer (1) according to one of the preceding claims, characterized in a) that the axial gap (24) between the shaping air ring (22) and the rear side of the bell cup (3) has an axial gap width (G) which is greater than 3.0 mm, 4 mm, 4.5 mm, 5 mm or 5.2 mm, in particular essentially 5.3 mm, in order to achieve the pressure ratio to prevent the backflow, and / or b) that the bell cup shaft (2) is exposed in the axial gap (24) between the shaping air ring (22) and the rear side of the bell cup (3) without an external cover in order to achieve the pressure ratio to prevent the backflow.

10. Rotary atomizer (1) according to one of the preceding claims, characterized in that the paint nozzle (5) has an outer diameter of less than 4 mm, 3.5 mm, 3 mm or 2.8 mm at its free end, in particular substantially 2.6 mm or 3.2 mm.

11. Rotary atomizer (1) according to one of claims 1 to 9, characterized in a) that the central bore in the distributor disc holder (12) has a diameter (A) of substantially 3. 2mm or 3.8 mm, and / or b) that the annular gap (25) between the inner paint nozzle (5) and the outer distributor disc holder (12) has a radial gap width of 0.2 mm-0.6 mm, in particular substantially 0.3 mm, and / or c) that the annular gap (25) between the inner paint nozzle (5) and the outer distributor disc holder (12) has an axial gap length of 4.5 mm - 8.5 mm or 5.5 mm - 7.5 mm, in particular substantially 6.5 mm, and / or d) that the annular gap (25) between the inner paint nozzle (5) and the outer distributor disc holder (12) has a cross-sectional area of 2 mm2 - 7 mm2, 3 mm2 - 6 mm2 or 4 mm2 - 5 mm2 in an axial cross section.

12. Operating method for a rotary atomizer (1) in accordance with one of the preceding claims, characterized in that the air pressure at the outlet opening (7) of the paint nozzle (5) is lower than the air pressure in the nozzle chamber (11) of the bell cup (3) and in the outer rinsing channels (20) in order to prevent a backflow of the coating agent from the outlet opening (7) of the paint nozzle (5) backwards in the direction of the nozzle chamber (11) due to this pressure difference.

13. Operating method according to claim 12, characterized in a) that the bell cup shaft (2) rotates at a certain speed, b) that the paint nozzle (5) discharges the coating agent with a certain flow rate, c) that the shaping air ring (22) discharges the shaping air with a certain flow rate, and d) that the following design dimensions and operating parameters are matched to one another in such a way that the air pressure at the outlet opening (7) of the paint nozzle (5) is lower than the air pressure in the nozzle chamber (11) of the bell cup (3) and in the outer rinsing channels (20), in order to prevent a backflow of the coating agent from the outlet opening (7) of the paint nozzle (5) backwards in the direction of the nozzle chamber (11) as a result of the pressure difference: d1) the diameter (A) of the central bore in the distributor disc holder (12) of the bell cup (3), d2) the gap width (B) of the gap (16) between the distributor disc (13) and the overflow surface (17) of the bell cup (3), d3) the gap width (C) of the annular gap (25) between the bell cup (3) and the paint nozzle (5), d4) the gap width (D) of the annular gap (26) between the paint nozzle (5) and the inner wall of the nozzle chamber (11), d5) the gap width (E) of the annular gap (27) between the bell cup shaft (2) and the internal paint tube (4), d6) the gap width (F) of the annular gap (28) of the exterior rinsing chamber (21) on the outside of the bell cup shaft (2), and d7) the gap width (G) of the gap (24) between the front side of the shaping air ring (22) and the rear side of the bell cup (3), d8) the speed of the bell cup shaft (2), d9) the flow rate of the coating agent, and d10) the flow rate of the shaping air.

14. Coating robot, in particular painting robot with a serial or parallel robot kinematics with several, in particular five, six or seven, movable axes and a rotary atomizer (1) according to one of claims 1 to 11.