Plastic and nonmetallic article shaping or treating: processes – Forming articles by uniting randomly associated particles – Liquid binder applied subsequent to particle assembly
Reexamination Certificate
2000-02-11
2001-02-20
Le, H. Thi (Department: 1773)
Plastic and nonmetallic article shaping or treating: processes
Forming articles by uniting randomly associated particles
Liquid binder applied subsequent to particle assembly
C264S319000, C264S320000, C264S322000, C264S331110, C427S487000, C427S493000, C427S547000, C427S598000, C427S127000, C427S221000
Reexamination Certificate
active
06190589
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to molded magnetic materials. More specifically, the invention is a molded magnetic article such as a transformer core and a fabrication method therefor.
2. Description of the Related Art
Power transformers typically make use of magnetic cores made from soft magnetic materials, i.e., materials having a magnetization direction that can be easily changed. Geometric shapes for such cores generally include complex geometric shapes that define a closed path, e.g., a hollow square or rectangular “picture frame” shape, a donut shape, etc. The magnetic cores are generally fabricated from magnetic ingots that mold-set into a desired shape using heat and pressure. Current magnetic core fabrication methods require extremely high pressures (e.g., on the order of 250 kilograms per square inch (ksi) in order to achieve acceptable levels of magnetic induction saturation or B
MAX
of approximately 13 kilogauss (kG). Such results are best achieved as reported by Speed et al, in “Magnetic Properties of Compressed Powdered Iron”, Transaction of American Institute of Electrical Engineers, Volume XL, p. 1321-1359, 1921. However, the application of such high pressures reduces the life of the mold sets thereby raising the production cost of magnetic cores.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a molded magnetic article and fabrication method therefor.
Another object of the present invention is to provide a molded magnetic article and fabrication method that uses relatively low molding pressures.
Still another object of the present invention is to provide a molded magnetic article having improved mechanical properties.
Yet another object of the present invention is to provide a fabrication method to produce magnetically soft and mechanically strong magnetic cores for use in transformers.
Other objects and advantages of the present invention will become more obvious hereinafter in the specification and drawings.
In accordance with the present invention, a molded magnetic article comprises a plurality of particles of ferromagnetic material embedded in a polymer binder. The particles and polymer binder are molded under pressure into a geometric shape. Each particle is an oblate spheroid having a radius-to-thickness aspect ratio approximately in the range of 15-30. Each oblate spheroid has flattened poles that are substantially in perpendicular alignment to a direction of the molding pressure throughout the geometric shape. In the method of fabrication, a mold defines the geometric shape of the article. The mold is filled with the particles and polymer binder which are heated to a temperature that causes the polymer binder to flow. Pressure is applied to the mixture in the mold in a direction that is perpendicular to a desired axis of magnetization of the article.
REFERENCES:
patent: 4197146 (1980-04-01), Frischmann
patent: 4592889 (1986-06-01), Leupold et al.
patent: 5589010 (1996-12-01), Gay
patent: 5742223 (1998-04-01), Simendinger, III et al.
patent: 6054210 (2000-04-01), Bryant et al.
Bryant Robert G.
Fox Robert L.
Namkung Min
Wincheski Russell A.
Edwards Robin W.
Le H. Thi
The United States of America as represented by the Administrator
LandOfFree
Fabrication of molded magnetic article does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fabrication of molded magnetic article, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fabrication of molded magnetic article will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2605981