Patent Application
20070262170
The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein:
a and 2b are schematic views illustrating exemplary variations in the shroud air when painting vertical and horizontal components; and
The rotary atomizer 1 has numerous internal shaping air nozzles 6 which are disposed concentrically around the bell cup axis 3 and dispense an internal shaping air stream 7 onto the outer lateral surface of the bell cup 2 where the internal shaping air stream 7 forms the spray of coating medium 5.
In addition, the rotary atomizer 1 has several external shaping air nozzles 8 through which an external shaping air stream 9 is dispensed which additionally forms the spray of coating medium 5. It is understood less or more streams of shaping air, from alternately configured internal and external shaping nozzles, may be used without deviating from the present invention.
The rotary atomizer 1 of the present invention, in addition to an application element (e.g. a bell cup 2) for applying a spray of coating medium 5 to a part to be coated, has at least one shroud air nozzle 10 through which conditioned shroud air 11 is dispensed which at least partially surrounds the spray of coating medium 5 and thereby generates a specific microclimate in the environment of the spray of coating medium 5 which provides specific flash-off conditions. Preferably, the conditioned shroud air 11 surrounds the spray of coating material 5 like a sheath over its entire periphery and/or over its entire length between the application element 2 and the part to be coated.
In a preferred aspect, the rotary atomizer 1 has numerous shroud air nozzles 10 which are separate from the exterior shaping air nozzles 8 and also located concentrically about the bell cup axis 3 and dispense conditioned shroud air 11 which encloses the spray of coating medium 5 in the manner of a sheath and thereby provides controlled and defined flash-off conditions. In an alternate aspect, it is understood that the external shaping nozzles 8, or other shaping air nozzles, may serve as the shroud air nozzles 10.
When the shroud air 11 leaves the shroud air nozzles 10, it entrains a subsidiary stream 12 of ambient air where the entrained subsidiary stream 12 constitutes 0-50% of the shroud air 11 exiting the shroud air nozzles 10.
The supply of shroud air 11, the coating medium 5 and the shaping air is managed through a connecting flange 13 to which two separate shaping air lines 14, 15 can be attached. Moreover, shroud air lines 16, 17, 18 and an optional shroud air line 19 can be attached to the connecting flange 13 to supply the conditioned shroud air 11 to the rotary atomizer 1. The shroud air lines 16-19 are preferably connected to an air heater 20 and a mass air volumetric flow regulator 21.
As part of the conditioning or manipulating of the shroud air 11, shroud air 11 may be, as compared with the ambient air in the immediate environment of atomizer 1, heated, cooled, dried, humidified and/or otherwise altered from ambient. Heating of the shroud air 11 is achieved preferably by the heater 20 which is preferably structurally separated from the atomizer. Alternately, heating of the shroud air 11 may be accomplished through heating hoses or electric heating elements (not shown) where the heating elements can be located close to the outlet in the area of the shroud air nozzle 10, which results in low thermal losses. In the case of an electrostatic atomizer, the heating of the shroud air, however, for reasons of explosion protection, is preferably not undertaken by electric heating elements in the atomizer but by the aforementioned separate air heater 20.
Preferably, the shroud air 11 has an outlet temperature immediately at the shroud air nozzle 10 of more than +30° C. and less than +200° C., where any intermediate values within this range of values are possible. Other temperatures known by those skilled in the art may be used. The outlet temperature of the shroud air 11 can be varied as a function of the coating medium 5 employed. For example, water as a solvent evaporates less than organic solvents so that the outlet temperature of the shroud air can be raised during application of water-borne paint compared with the application of solvent-based paint.
Preferably, the shroud air 11 has a volumetric flow of more than 250 liters per minute (l/min) and less than 2500 l/min, where any intermediate values within this interval are possible. Other values known by those skilled in the art may be used.
The shroud air 11 preferably consists of air which is available in any case in painting installations in the form of compressed air. It is understood that a different gas other than air for the shroud air 11 may be used. For example, special gases are available which have a greater heat capacity, a greater electrical insulating capability and/or a higher saturation limit than air. The greater heat capacity offers the advantage that, after leaving the shroud air nozzle 10, the shroud air 11 looses only a little temperature, which provides defined flash-off conditions. A greater electrical insulation capability is, on the other hand, advantageous in the case of an electrostatic atomizer since the insulating capability of the shroud air 11 prevents a discharge of the electrostatically charged coating medium particles and thereby provides high transfer efficiency. A high saturation limit of the gas employed for the shroud air 11 is advantageous if the shroud air 11 is to absorb much solvent from the spray of coating medium. The shroud air 11 can also consist of, for example, sulfur hexafluoride (SF6) or inert gases (for example carbon dioxide (CO2) and nitrogen). Other altered air or other gases known by those skilled in the art may be used.
In a preferred aspect, the supply of shroud air 11 from the connecting flange 13 to the shroud air nozzles 10 is made by a shroud air passage between an inner housing 22 and an outer housing 23 of the rotary atomizer 1. This offers the advantage that the shroud air 11 is cooled only relatively little when conducted or passed through through the atomizer and therefore, still retains sufficient temperature at the shroud air nozzle 10.
In an alternate aspect, the shroud air II may be provided by the shaping air supply so that the connecting flange 13 of the atomizer with the flanged connections provided there does not have to be modified.
In a preferred embodiment, the number of shroud air nozzles 10 can be in the range of 5 to 100, and the individual shroud air nozzles 10 have nozzle openings with a width of 1-15 mm in diameter. It is preferred that the opening width of the shroud nozzles 10 are greater than the opening widths of the shaping nozzles.
The application element is preferably a rotatable bell cup 2 which has a defined bell cup edge. Preferably, an axial distance of more than 2 millimeters (mm) and less than 150 mm is between the shroud air nozzle 10 and the edge of the bell cup. It is understood that other numbers of shroud air nozzles 10, widths of shroud air nozzle openings and axial distances between the bell cup and shroud nozzles 10 known by those skilled in the art may be used.
Furthermore, the shroud air nozzles 10 can be angled in the circumferential direction of the bell cup 2 and thus have a specified swirl angle where the shroud air nozzles 10 can be angled either in the rotational direction of the bell or against the rotational direction of the bell. The swirl angle of the shroud air nozzles 10 can be in the range of 0-45° where any intermediate values are possible.
a schematically shows the exemplary painting of a vertical component surface 24 by the rotary atomizer 1. Because of the vertical orientation of the component surface 24, the danger of coating or paint runs exists because of gravity (shown in the direction g) acting on the paint particles applied. To prevent such runs, the percentage of solids in the spray of coating medium 5 hitting the vertical component surface 24 is selectively increased in which the temperature T1 of the shroud air 11 is increased selectively by the air heater 20 (refer to
b, in contrast, shows the exemplary painting of a horizontal component surface 25 by the rotary atomizer 1. Because of the horizontal orientation of the component surface 25, the danger of coating or paint runs in the coating medium 5 on the component surface 25 is less, so that smaller amounts of liquid solvent have to evaporate into the shroud air 11. The shroud air 11 therefore, may have a lower temperature T2<T1 when the horizontal component surface 25 is being painted than when the vertical component surface 24 is being painted.
Referring to
The positioning control data is relayed by the robot control system 26 to an arithmetic logical unit 28 which determines therefrom the angle α of the component surface to be coated, for example whether the component surface is substantially horizontal or vertical. The angle α of the component surface is then relayed to a shroud air control 29 which influences, conditions and/or manipulates the shroud air 1, for example, as a function of the angle α of the component surface. The shroud air control 29 than selectively activates a shroud air drier 30, a shroud air heater 31 and/or a shroud air valve 32. In this example, the shroud air 11 is this influenced or conditioned as a function of the angle α of the component surface to be coated such that a run in the coating medium 5 on the component surface is prevented. To do thus, the shroud air is, for example, heated and dried more when coating vertically oriented component surfaces than when coating horizontally oriented component surfaces. Other methods of conditioning shroud air 11, determining the orientation of the component surface to be coated and controlling robot 27 known by those skilled in the art may be used.
It is further contemplated the robot control 26, the arithmetic logical unit 28 and the shroud air controls 29 can be integrated into a common electronic control unit 33. The possibility also exists that the robot controls 26, the arithmetic logical unit 28 and/or the shroud air controls 29 are implemented as software modules. Other combinations of control units or logic functions known by those skilled in the art may be used.
The inventive atomizer further, for example, includes an operating method wherein air 11 is dispensed which at least partially surrounds the spray of coating medium 5. Through manipulating of the shroud air 11 as a function of the spatial location or orientation of the surface of the part to be coated, the paint or coating applied when painting the surfaces of vertical parts can flow out more easily than during the painting of the surfaces of horizontal part so that the percentage of solids should be increased when painting vertical surfaces compared with the painting of horizontal surfaces.
The spatial location of the component surface to be coated is preferably determined and the shroud air 11 is manipulated as a function of the spatial location determined. Instead of the spatial location of the component surface to be coated, the spatial location of the atomizer can be determined since the atomizer is usually guided in accordance with the spatial location of the component surface to be coated. When using a multi-axis painting robot 27, the spatial location of the atomizer 1 can be determined in turn from the position-control signals from the robot controls.
Depending on the spatial location of the component surface to be coated and/or of the atomizer, the temperature, the humidity content and/or the volumetric flow of the shroud air 11 can be manipulated to achieve the desired characteristics of coating materials sprays.
Preferably, when coating a substantially vertical component surface, for example in
It is further understood that a process parameter of interest which may affect the shroud air 11 is the type of part to be coated. For example, when painting high-quality vehicle bodies or components, a different shroud air 11 can be dispensed than when painting lesser quality vehicle bodies.
In addition, the relevant process parameter which may affect the shroud air 11, is the coating medium used, for example, the percentage of solids or the percentage of solvents present in the coating medium or paint 5. The shroud air 11 can be adjusted in such a way that the percentage of solid bodies in the spray of coating medium 5 from a time between being dispensed at the application element and at impact on the component surface to be coated, increases by more than 5%, 10%, 25% or even 50%.
The invention is not limited to such painting installations in which conventional conditioning of the air is dispensed with, but also includes painting installations in which, in addition to the creation of a defined microclimate in the environment of the spray of coating medium, conditioning of the air in the entire spray booth is undertaken. The atomizer in accordance with the invention can optionally be a powder atomizer or a liquid paint atomizer.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited t the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2006 019 890.5 | Apr 2006 | DE | national |
