Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1998-08-21
2001-04-03
Michl, Paul R. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
active
06211283
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to (i) methods for coating, with electrically insulating films, metallic surfaces with interior corners, (ii) articles of manufacture so produced, and particularly (iii) electric motors containing them. More particularly, this invention relates to methods that can form an insulating film with excellent electrical insulating properties on the surface of a sheet-steel-laminated motor core by bringing the surface of such a motor core into contact with an autodepositing waterborne coating composition.
DESCRIPTION OF RELATED ART
Many motor cores used, for example, in small motors, require electrical insulation between electrically conductive core elements and distinct electrically conductive windings in close proximity to the core elements. The insulation has generally been provided by an insulating treatment of the core elements.
This insulating treatment has heretofore consisted of forming an insulating layer on the motor core surface using electrodeposition coatings, solvent-based sprays, powder paints, and the like. However, insulating layers applied using the aforesaid paints have a pronounced tendency to debond at the corners of the motor core, and the occurrence of this debonding causes these insulating layers to suffer from a diminished insulating performance. This has required that the insulating layer be thick.
Recent requirements on motors have been for smaller size, thinner configurations, higher performance (higher withstand voltages), and thinner insulation.
Japanese Patent Application Laid Open [Kokai or Unexamined] Number Hei 5-300681 [300,681/1993] discloses a technology for reducing the thickness of the insulation. This reference teaches the formation of insulation with excellent insulating properties and an excellent corner-coating capacity. The insulation described therein comprises two layers with a total thickness of 50 to 80 micrometres and is formed by coating the motor core surface with an epoxy resin functioning as primer and then with a ceramic paint functioning as top coat. This reference states simply that the insulating layer should consist of multiple layers; it is not limited to two layers and may consist of a larger number, such as three or four layers. This technology requires at least two coating operations to form the insulating layer and thus suffers from the drawback of poor productivity.
PROBLEMS TO BE SOLVED BY THE INVENTION
A major object of the present invention is to provide a method for coating the surface of laminated motor cores, or other surfaces with interior corners, with an electrical insulating film wherein said method can shorten the insulating treatment operation, can provide a thinner electrical insulating layer than heretofore available, and/or can provide a surface that has a coating with excellent electrical insulating properties, in particular, a high-quality electrical insulating layer in the corners of the surface.
SUMMARY OF THE INVENTION
It has been found that the desired thinner, high-quality insulating film can be generated in a shorter insulating treatment operation by contacting a surface, especially that of a laminated motor core, with an autodepositing waterborne coating composition comprising a coating-forming resin emulsion, acid, oxidizing agent, metal ion, and water, and by thereafter drying by heating.
In specific terms, the present invention provides a method for coating a surface with at least one interior corner, preferably a corner formed by an intersection between a substantially planar surface and a convex arcuate surface, so that the corner includes a deeper recess than would be formed by intersection between two mutually perpendicular substantially planar surfaces, with an electrical insulating film, characterized by forming an electrical insulating film on the surface by steps of:
(I) depositing an uncured resin film on said surface by bringing the surface into contact with an autodepositing waterborne coating composition comprising, or more preferably consisting essentially of, a coating-forming resin emulsion, acid, oxidizing agent, metal ions, and water; and then
(II) drying the said uncured resin film, while it remains in place on the surface, by heating.
The present invention also provides an alternative method for coating such a surface with an electrical insulating film, characterized by forming an electrical insulating film on the surface by steps of
(I) depositing an uncured resin film on said surface by bringing the surface into contact with an autodepositing waterborne coating composition comprising, or more preferably consisting essentially of, a coating-forming resin emulsion, acid, oxidizing agent, metal ions, and water;
(II) contacting said uncured resin film with an aqueous chromium-containing solution; and then
(III) drying said uncured resin film, while it remains in place on the surface, by heating.
Other embodiments of the invention include liquid autodeposition coating compositions especially adapted for use in a process according to the invention and articles of manufacture including a surface coated by a process according to the invention.
REFERENCES:
patent: 3709743 (1973-01-01), Dalton
patent: 4357372 (1982-11-01), Leister
patent: 4389328 (1983-06-01), Bellettiere
patent: 4527992 (1985-07-01), Friese
patent: 5252363 (1993-10-01), Anderson
patent: 5352726 (1994-10-01), Hall
patent: 5663601 (1997-09-01), Wakabayashi et al.
patent: 5688560 (1997-11-01), Honda
patent: 5760112 (1998-06-01), Hirota
Honda Takumi
Takahashi Kenji
Henkel Corporation
Michl Paul R.
Roylance Abrams Berdo & Goodman L.L.P.
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