Coating processes – Measuring – testing – or indicating – Thickness or uniformity of thickness determined
Reexamination Certificate
2002-10-01
2004-11-02
Pianalto, Bernard (Department: 1762)
Coating processes
Measuring, testing, or indicating
Thickness or uniformity of thickness determined
C427S385500, C427S407100, C427S421100
Reexamination Certificate
active
06811807
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to a process and a device for producing a peel-off protective layer for surfaces, especially the painted surfaces of motor vehicle bodies, in which a curable liquid coating material is sprayed from a spray nozzle onto the surface to be protected and forms there a two-dimensional protective layer when cured.
Peel-off protective layers are placed on the painted surfaces of motor vehicles to protect them from environmental influences such as dirt and intense sunlight, especially during transport from the motor vehicle manufacturer and until the time of delivery to the customer. The protective layer is produced at the manufacturer's plant by the application of a liquid to the painted surface of a motor vehicle, and then this liquid is cured or solidified. The liquid can be an aqueous dispersion from which the water evaporates during curing, so that a kind of peel-off film is formed on the surface. The film thus produced can then be peeled off by hand before the vehicle is delivered to the buyer.
A significant disadvantage of conventional processes is that, because the liquid coating material is sprayed on, it is impossible to obtain a sharp contour at the edges of the sprayed-on areas of coating material; instead, individual particles or droplets are formed in the edge areas, which are separate and detached from the continuous protective layer (“overspray”). A protective layer in the form of individual particles does not offer sufficient protection to the paint after curing and also makes it almost impossible for the cured protective layer to be gripped by hand so that it can be peeled off. The individual particles, furthermore, must be removed manually or by some other labor-intensive means.
For these and other reasons, it would be desirable to provide a process and a device for producing a sharply contoured protective layer on a surface, such as the painted surfaces of motor vehicle bodies.
BRIEF SUMMARY OF THE INVENTION
The invention is directed to a process in which coating material emerges essentially as a continuous strand or strip of material from an applicator nozzle and is applied to the surface to be coated at the edges of the areas which have been sprayed with the coating material.
The invention is further directed to a device having at least one applicator nozzle for the application of coating material as an essentially continuous strand or strip of material to the surface to be coated.
The process according to the invention and the device according to the invention make it possible to produce a protective layer for surfaces having sharply defined lateral edges and thus a defined size. Because a continuous or nearly continuous strand or strip of material is applied to the edge areas of the sprayed-on coating material, a clean, sharply contoured edge is formed, without the occurrence of individual particles or droplets (overspray), which then cure on the surface. The sharply contoured, overspray-free edge can, after it has cured, be gripped easily by hand and lifted, and the protective layer thus produced can then be easily peeled off. According to the invention, a relatively large area is coated by spraying on the coating material, whereas, during or after the spraying step, an applicator nozzle which produces an essentially continuous strand or strip of material is used to produce a sharp-edged, overspray-free coating in the area of the outer edges of the sprayed-on coating, where individual sprayed-on liquid particles can be scattered.
According to an especially preferred embodiment of the process according to the invention, it Is provided that the protective layer sprayed on by the spray nozzle and the protective layer applied by the applicator nozzle consist of the same coating material and coalesce to form a single protective layer on the surface before they have cured. The viscosity of the coating material, which is essentially a function of temperature, is selected so that the coating material sprayed on by the spray nozzle and the coating material applied by the applicator nozzle flow into each other and form a single layer. The sprayed particles in the edge area coalesce completely with the coating material which has been applied as an essentially continuous strand or strip of material.
According to an elaboration of the process according to the invention, it is proposed that the protective layer sprayed on by the spray nozzle and the protective layer applied by the applicator nozzle have a thickness such that a protective layer is formed which, in the completely cured state, forms a completely closed protective layer which is essentially impermeable to water, gas, and dust and which can be peeled off by hand. A protective layer of this type is liquid-repellent, but does not usually dissolve upon contact with water and provides reliable protection during transport.
An especially preferred alternative embodiment of the process according to the invention is characterized in that the coating material emerges from the applicator nozzle as a flat strip of material which expands as its distance from the applicator nozzle increases. A flat strip of material of this type can be laid onto the surface in a defined manner at the edges of the previously or simultaneously sprayed-on coating. In the cured state, the protective layer can then be gripped by hand at this edge and peeled off without causing the protective layer to tear. For example, a slit nozzle or a specially designed nozzle with an essentially rectangular discharge opening could be used.
According to an alternative embodiment, it is provided that several strands or strips of material are applied from several applicator nozzles to the edge areas of the coating material sprayed onto the surface. In this way, a relatively wide overspray area can be covered with coating material.
To obtain a protective layer with a large surface area, it is provided that the coating material is sprayed on in an overlapping manner by means of several adjacent spray nozzles. The degree of overlap can be varied; it depends on the pressure of the coating material in the feed line and on the distance between the individual spray nozzles.
Another elaboration of the invention is characterized in that the spray nozzle and the applicator nozzle are fed from a common coating material source but by two coating material streams which are at least partially separate from each other. Because of the use of two separate coating material streams, it is possible for the pressure in one of the feed lines to be different from that in the other. The pressure of the coating material in the feed line to the spray nozzle will usually be much higher than the pressure in the coating material feed line to the applicator nozzle. In addition, the coating material can be supplied to the spray nozzle and to the applicator nozzle in alternation; in most cases, according to a preferred embodiment described in greater detail further below, the material will first be sprayed on over a wide area, and then a sharply contoured edge will be produced at the edge areas by means of the applicator nozzle.
According to a further elaboration of the process, it is provided that the pressures in the separate coating material streams leading to the applicator nozzle and to the spray nozzle are adjustable or controllable. The flow rates, measured either by weight or volume, of the separate coating material streams being supplied to the applicator nozzle and to the spray nozzle can preferably be adjusted or controlled also, so that precisely predetermined amounts of coating material can be applied to a specific surface and thus also so that the thickness of the protective layer can be predetermined.
By adjusting the temperature of the coating material automatically to a desired nominal value, it is possible effectively to control the flow properties or viscosity of the coating material, to control its spray or application behavior, and ultimately to control certain properties of the protective layer. The process accord
Reinke Klaus Peter
Zimmermann Konrad
Nordson Corporation
Wood Herron & Evans L.L.P.
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