Baths – closets – sinks – and spittoons – Tubs
Reexamination Certificate
2000-11-29
2001-10-30
Eloshway, Charles R. (Department: 3751)
Baths, closets, sinks, and spittoons
Tubs
C004S584000
Reexamination Certificate
active
06308349
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a sanitary tub with an outer shell made of a steel sheet, an inner shell made of plastic, and an intermediate layer connecting the two shells. A protective coating is applied to the outer shell for protection against corrosion.
2. The Prior Art
Sanitary tubs are known from DE-C 44 31 716, in which the outer shell is pickled and basically enameled on the back side. Since the adhesion of the intermediate layer consisting of a polyurethane or a methacrylic compound is inadequate on an enameled surface, no enameling is provided on the inner surface of the steel sheet shell. This makes manufacturing of the tub more difficult because a commonly used immersion process cannot be applied for the enamel coating. The coating of enamel applied to the inner side has to be mechanically removed, for example by sandblasting, or at least have the surface roughened. According to another design described in DE-C 44 31 716, the outer shell, which is deep-drawn from steel sheet, is pickled and passivated before the acrylic shell is molded on the inner side and glued to the steel blank. In a last process step, the rust-preventing coating is applied to the outer shell of the composite tub. In this step, the ledge and the inner side of the composite tub, which is already manufactured, have to be covered by a costly process. Furthermore, there is the risk that the protection against corrosion may be incomplete along the ledge of the tub because of the required coverings.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a sanitary tub having the structure described above, without damaging the corrosion protection on the outer shell and the connection between the outer and inner shells during production.
This object is accomplished by providing the outer shell with a coating both on the inner and outer sides that consists of a conversion layer produced by phosphatizing, and a lacquer. This coating forms an abrasive surface and an impact-resistant protective layer on the outer side. On the inner side of the shell. The coating provides an adhesive agent between the steel sheet and the intermediate layer that is effective without mechanical roughening. According to the invention, before the steel blank is joined with the plastic inner shell, it is provided both on the inner and outer sides with a coating that can be applied by economical application methods. The coating consists of a conversion layer that can be produced by iron or zinc phosphatizing, and a lacquer applied to the conversion layer. Since the entire steel blank is lacquered and no covering is required, it is possible to employ economical lacquering methods that are suitable for mass production. The lacquer can be applied by air atomizing, airless spraying, electrostatic spraying, by immersion methods, or by electro-immersion painting. The present invention uses an anti-corrosion coating agent protecting the steel sheet shell against corrosion as well as providing a good adhesion between the outer shell and the adjoining intermediate layer producing the connection between the plastic inner shell and the metallic outer shell. Therefore, the coating agent satisfies the different functions of the outer side of the steel blank and the inner surface of the steel blank.
The intermediate layer preferably consists of a polyurethane or a methacrylic compound. The conversion coating substantially contains iron phosphates with components of iron oxide, or zinc phosphates depending on the selected phosphatizing method.
In addition, the invention discloses the method of manufacturing the sanitary tub having an inner and outer shell. An intermediate layer is applied between the inner shell and the outer shell. A protective coating is then applied to an inner and outer side of the outer shell. The protective coating comprises a conversion layer produced by phosphatizing, and a lacquer forming an abrasion and impact resistant layer on the outer side, and an adhesive agent on the inner side between the outer shell and the intermediate layer without roughening.
REFERENCES:
patent: 3816234 (1974-06-01), Winfield
patent: 3826629 (1974-07-01), Pryor et al.
patent: 5494718 (1996-02-01), Adams et al.
patent: 5580621 (1996-12-01), Kuszaj et al.
patent: 24 18 118 (1975-10-01), None
patent: 44 31 716 (1996-02-01), None
patent: 0 015 020 (1980-09-01), None
Collard & Roe P.C.
Eloshway Charles R.
Franz Kaldewei GmbH & Co. KG
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