Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1999-09-27
2001-05-01
Hall, Carl E. (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C264S272130, C264S272190, C336S096000
Reexamination Certificate
active
06223421
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method of manufacturing transformer windings embedded in casting resin and more particularly to a method of manufacturing a transformer coil encapsulated in casting resin utilizing a disposable casting mold wherein the disposable mold acts both as a winding mandrel and as an inner mold shell for resin encapsulation. The invention is particularly suited to the manufacture of non-standard oval shaped or circular shaped epoxy encapsulated coils for dry type distribution transformers.
2. Description of the Prior Art
Currently the state of the art is precision made standard sized re-usable round shaped mandrels and molds in fixed size increments with costly tap inserts. Examples of prior art methods of encapsulating transformer coils are disclosed in U.S. Pat. Nos. 4,337,219, 4,540,536, 5,036,580 and 5,633,019.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a method of manufacturing a transformer coil encapsulated in casting resin utilizing a disposable casting mold wherein the disposable mold acts both as a winding mandrel and as an inner mold shell for resin encapsulation. It is a further object of the invention to provide a method of manufacturing a wide variety of oval or circular shaped resin encapsulated transformer coils by making the disposable inner and outer molds from low cost sheet metal. The invention process provides the advantages of flexible oval or circular dimensional sizes, flexible and incremental oval or circular shapes providing substantially reduced mandrel and molding costs, elimination of costly standard mold storage, elimination of the need for standard winding mandrels, and facilitates the opportunity to manufacture transformer coils in a round to oval configuration.
In accordance with the foregoing objects and advantages the present invention provides a method of manufacturing a transformer coil encapsulated in casting resin utilizing a disposable casting mold wherein the disposable mold acts both as a winding mandrel and as an inner mold shell for resin encapsulation. The method comprises the steps of forming an annular inner mold of predetermined shape around a winding mandrel of a coil winding machine to produce an integrated winding form/mandrel/inner mold for use in the winding process, placing the integrated winding/mandrel/inner mold in a winding machine, winding a coil around the inner mold while in the winding machine, removing the inner mold and coil wound thereon from the winding machine, forming an annular outer mold of predetermined shape over the finished coil to provide a manufactured coil and mold assembly, providing a seal for the manufactured coil and mold assembly to prevent casting resin leaks during the encapsulation process, filling the mold assembly with casting resin to encapsulate the coil, permitting the casting resin to harden on the coil, and removing the encapsulated coil from the casting mold assembly.
In accordance with another aspect of the invention the annular outer mold is provided with a mold dome. The method of the invention includes placing gasket material at the ends of the inner and outer molds and placing end plates against the material on the ends of the inner and outer molds to form a casting mold. The method further includes placing coil support plates at the top and each end of the mold dome of the outer mold to support the weight of the coil during encapsulation and curing processes, applying a predetermined compression force to the end plates ofthe casting mold and placing the casting mold containing the wound coil in a horizontal position in an evacuated chamber and pouring casting resin into an opening in the mold dome in the outer mold of the casting mold to encapsulate the coil.
In accordance with another aspect of the invention, the inner and outer molds are formed of sheet metal.
In accordance with another aspect of the invention, the predetermined shape of the inner and outer molds is oval shaped for the production of an oval coil.
In accordance with another aspect of the invention the predetermined shape of the inner and outer molds is circular shaped for the production of a round coil.
In accordance with another aspect of the invention at least one of the inner and outer molds is of one-piece construction.
In accordance with another aspect of the invention the inner mold includes inturned flanges at the radial ends of the sheet metal and removably secured together mechanically for ease of mold disassembly and the method includes the step of placing a gasket between the inturned flanges of the innermold before removably securing together the flanges and applying a liquid sealant to the outside of the mold gasket area.
In accordance with a further aspect of the invention, the method includes the step of applying a resin release agent to all exposed surfaces of the inner mold, applying a glass net to the exposed surfaces of the inner mold after the application of the resin release agent and prior to winding the coil onto the inner mold.
In accordance with a further aspect of the invention, the method includes the step of applying a glass net over the finished coil winding and applying a resin release agent to the inside of the outer mold prior to placing the outer mold over the coil.
In accordance with another aspect of the invention, the method includes the step of installing a plurality of compression rods to interconnect the end plates, and applying a torque to the compression rods to apply the predetermined compression force to the end plates of the casting mold.
In accordance with another aspect of the invention at least one of the inner and outer molds is of two-piece construction.
REFERENCES:
patent: 3041562 (1962-06-01), Gammel, Sr.
patent: 3248468 (1966-04-01), Anderson
patent: 3577506 (1971-05-01), Brown
patent: 4337219 (1982-06-01), Falkowski et al.
patent: 4540536 (1985-09-01), Altmann et al.
patent: 5036580 (1991-08-01), Fox et al.
patent: 5056214 (1991-10-01), Holt
patent: 5197180 (1993-03-01), Mihalko
patent: 5317300 (1994-05-01), Boesel
patent: 5331730 (1994-07-01), Brinn, Jr.
patent: 5481191 (1996-01-01), Rzedzian
patent: 5633019 (1997-05-01), Clark et al.
Lambert Wayne
Lanoue Thomas J.
Sarver Charles
ABB Power T&D Company Inc.
Hall Carl E.
Woodcock Washburn Kurtz Mackiewicz & Norris
LandOfFree
Method of manufacturing a transformer coil with a disposable... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of manufacturing a transformer coil with a disposable..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of manufacturing a transformer coil with a disposable... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2538790