Coating processes – Direct application of electrical – magnetic – wave – or... – Electrostatic charge – field – or force utilized
Reexamination Certificate
1999-03-03
2001-06-19
Meeks, Timothy (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Electrostatic charge, field, or force utilized
C427S485000, C427S580000, C427S250000, C427S385500, C427S386000, C204S192380
Reexamination Certificate
active
06248408
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention related generally to cathodic arc plasma physical vapor deposition processes, and more particularly to multiple layer formation processes.
2. Description of the Prior Art
The present invention basically comprises a combination of electrostatic powder coating techniques with cathodic arc plasma physical vapor deposition techniques, and has particular application to the coating of cast articles of manufacture composed of metal, plastic or other materials. Cast articles of manufacture typically have many voids and pits in the outer surface of the cast article, and it is desirable to remove or eliminate these voids and pits. Utilizing the prior art electrostatic powder coating process, an electrically charged powder coating is applied to an electrically grounded, cleaned cast article of manufacture. In this process, an electrostatic spray gun is utilized to spray a diffused cloud of electrically charged powder particles onto the grounded article. Following the powder layer application, the article is mounted into an oven to cure the powder layer. A typical curing process involves heating the powder coated article to a temperature of approximately 350° Fahrenheit for approximately 15-20 minutes. During the curing process the powder material melts and hopefully flows into the surface voids and pits to fill them. The melted outer surface of the powder layer thus becomes smooth. Following cooling and removal of the article from the oven, the article now has a smooth outer surface instead of the cast surface with its voids and pits. The cured powder layer also acts as a corrosion resisting layer on the outer surface of the article.
Typically, the prior art cured powder coating layer is relatively soft and lacking in aesthetic appeal. Therefore, an outer layer has been applied to the powder coated article, and the utilization of a cathodic arc plasma physical layer deposition process is known. In this outer layer deposition process, the article having a cured underlayer is mounted within the chamber of a PVD device and a vacuum atmosphere is created. Thereafter, the cathodic arc is struck and an outer layer is deposited upon the article. Typical outer layers consist of metal or metal compounds such as chromium, ZrN and TiN. Following deposition of the outer layer, the article is cooled and then removed from the PVD chamber. A high gloss, scratch resistant outer surface is provided to the article of manufacture, whereby a two layer overall coating process is completed.
A first problem with this two layer prior art process is that air bubbles sometimes become trapped in the voids and pits during the powder layer curing step. Following completion of the curing step the outer surface of the cured powder layer is smooth, however, the trapped air bubbles remain. Thereafter, when the article is placed within the PVD chamber and the vacuum is created, the air bubbles expand and often explode through the surface of the cured undercoat layer, thus creating pits and craters in the outer surface. The subsequent deposition of the PVD layer does not fully fill these pits and craters, whereupon a marred outer surface is obtained. A second problem with the prior art process, as compared to the present invention which is described herebelow, is that the prior art process unnecessarily utilizes energy and time in the oven mounting and curing process steps. As is next described, the present invention eliminates the oven mounting and curing process.
SUMMARY OF THE INVENTION
In the generalized method of the present invention a heat curable coating is first applied to an article of manufacture. Thereafter, an outer coating is applied to the article in a physical vapor deposition process, and the heat from the PVD process cures the first layer while the PVD coating is being deposited upon the article. In the preferred embodiments, the heat or ultraviolet curable coating is a powder coating and the cathodic arc of the PVD process provides the heat or ultraviolet that cures the powder coating. An infrared heat source within the PVD chamber may be utilized to preheat the powder coating which is typically composed of an epoxy-polymer compound. Articles of manufacture having the coating of the present invention formed thereon are manufactured with less energy and labor costs.
It is an advantage of the present invention that a coating process is developed which saves labor and energy over the prior art process.
It is another advantage of the present invention that a more rapid deposition process is provided.
It is a further advantage of the present invention that a deposition process is provided which develops a surface coating having fewer voids and pits.
It is still another advantage of the present invention that a deposition process is provided which combines the prior art two coating processes into a single coating process.
It is still a further advantage of the present invention that an article of manufacture is provided having an improved outer coating.
It is yet another advantage of the present invention that an article of manufacture is provided having a single layer which fills voids and pits in the surface of the article of manufacture is corrosion resistant and has a hard outer surface.
These and other features and advantages of the present invention will become understood by those skilled in the art upon reading the following detailed description which makes reference to the several figures of the drawings.
REFERENCES:
patent: 5219493 (1993-06-01), Seshadri
patent: 5221349 (1993-06-01), Tamagaki
patent: 5229233 (1993-07-01), Riddle et al.
patent: 5683756 (1997-11-01), Tanner et al.
Guillot Robert O.
Meeks Timothy
Oppenheimer Wolff & Donnelly LLP
Vacuum Plating Technology Corporation
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