Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
1995-06-07
2001-03-06
Dye, Rena L. (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S036910, C428S035800, C428S035900, C138S143000, C138S146000, C029S460000, C427S475000, C427S482000, C427S485000, C427S409000
Reexamination Certificate
active
06197394
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to in-line coating of a continuously moving substrate, such as a tube or conduit, of the type used for applications such as metal fencing or electrical conduit. More specifically, this invention relates to galvanizing and overcoating of such substrates.
The art of forming and coating tubes and conduits for fencing and electrical conduit is an old art. Many manufacturing operations exist which use techniques decades old. As an example, modern galvanizing procedures have been described as the outdated inheritance of original hot dip galvanizing in which cold articles were dipped in heated zinc pots. See U.S. Pat. No. 4,352,838 at column 1, lines 13-19.
While the art is old, significant advances have been made by industry leaders. These advances include the advance of PCT Publication No. WO 93/0045 published Jan. 7, 1993, the advance of U.S. Pat. No. 5,364,661 issued Nov. 15, 1994, and the advance of U.S. Pat. No. 5,506,002, issued Apr. 19, 1996. As reflected in these patents and publication, galvanizing of continuous tubes and conduits has progressed to the point of rapid speeds of the tubes and conduits to be galvanized, on the order of six hundred feet per minute. Galvanizing has also progressed through the elimination of secondary or elevated zinc containers in favor of zinc pumped through cross-tees, spray nozzles and drip nozzles. Zinc application dwell times have been reduced to tenths of seconds, and contact zones to inches.
Industry leaders have also advanced the application of non-metal coatings, as well, as shown in U.S. Pat. No. 5,453,302, issued Sep. 26, 1995. As in this patent, protective coatings are applied by vacuum coating apparatus.
Applications of coatings through alternate coating technologies have also been disclosed. As shown in U.S. Pat. Nos. 3,559,280 issued Feb. 2, 1971, U.S. Pat. No. 3,616,983 issued Nov. 2, 1971, U.S. Pat. No. 4,344,381 issued Aug. 17, 1982 and U.S. Pat. No. 5,279,863, issued Jan. 18, 1994, electrostatic coating has been considered one possibility. As disclosed in U.S. Pat. No. 3,559,280, electrostatic spray coating is accomplished after water spray, sizing, straightening, and drying, and in the multiple steps and locations of a spraying or coating section, a separate following baking or hardening chamber, a separate following air blower and a separate following water spray. As disclosed in U.S. Pat. No. 3,616,983, electrostatic powder coating is accomplished as an alternative to other coating methods after earlier application of liquid coatings, and after heating applied by an external heater. As disclosed in U.S. Pat. No. 4,344,381, electrostatic spray coating is accomplished in an inert atmosphere by organic solvent-based, liquid coating materials.
U.S. Pat. Nos. 3,122,114; 3,226,817; 3,230,615; 3,256,592; 3,259,148; 3,559,280; 3,561,096; 4,344,381; 4,582,718; 4,749,125; 5,035,364; 5,086,973; 5,165,601; 5,279,863; and 5,364,661, and PCT Publication No. WO 93/00453 are incorporated by reference.
SUMMARY OF THE INVENTION
Despite the advances of the art, opportunity has remained for invention in the application of coatings to zinc coated and uncoated tubing. The times and distances for coatings to be applied and cured have created at least in part barriers to increases in speeds in the continuous in-line production of tubing. Overspray, drippage and the like have caused substantially incomplete usage of coating materials, and wastage. Coatings have been inconsistent in thickness and coverage, and thicker than needed.
In summary, therefore, the invention is both tube products and improvements in the methods of continuous production of coated tubing. As most preferred, the tubing and improved production include hot dip galvanize zinc coating of tubing, and before solidification of the zinc coating, in-line, clear coating of the tubing with organic polymer coating. The remaining latent heat of the galvanzing cures or thermosets the clear coating, and the clear coating preserves a consistency and shine, or reflectivity, of the zinc previously unseen in the finished products of continuous zinc coating of tubing, in the range of chrome. In additional embodiments, organic polymer coatings are applied to zinc coated and uncoated tubing, and the organic polymer coatings are applied by electrostatic application of powder. The powder is uncharged as it leaves its nozzles, and charged in fields created by an array of charged wire grids. The powder thermosets to coat the tubing in approximately five seconds, and coating is completed without liquid coating materials, applied heat, or any baking or hardening chamber.
The full scope the invention, and its objects, aspects, and advantages will be fully understood by a complete reading of this specification in all its parts, without restriction of one part from another.
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Polymers, Paint and Coulor Journal, Powder Coating—today's technology, A. Van de Werff, Scando B.V., Jan. 9, 1980.
Mild Edward E.
Seilheimer Stephen E.
Allied Tube & Conduit Corporation
Banner & Witcoff , Ltd.
Dye Rena L.
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