Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
2000-03-20
2001-06-26
Lam, Cathy (Department: 1775)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C428S901000, C361S275300, C361S275400, C361S303000, C361S306100, C361S311000
Reexamination Certificate
active
06251503
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to film condensers and metalized films for manufacturing the film condensers.
2. Description of Related Art
Film condensers are generally manufactured by preparing first and second plastic films on which a thin metal layer is deposited, placing the second film on the first film, rolling up the stacked films so as to form a cylindrical body, and forming a pair of terminal electrodes at both ends of the cylindrical body by thermal spraying.
Recently, for the purpose of improving safety, film condensers having a fuse function have been put to practical use. In such a film condenser with a fuse function, a plurality of uncoated portions are formed in a metal coating layer of at least one of the two metalized films so that the metal coating layer is divided into a plurality of rectangular electrode regions and narrow fuse portions electrically connecting each electrode region to one of the terminal electrodes. According to the film condensers of this type, should a short circuit occur between the electrode regions of the first and second metalized films, the fuse portion will instantly evaporate due to the heavy current passing therethrough, the supplement of the current to the area including the short circuit point can thereby be stopped.
In this type of film condenser, because at least one electrode region becomes incapacitated whenever a short circuit occurs in the condenser, the capacitance of the condenser will be gradually decreased. Furthermore, the breaking down of the fuse portions is likely to be occurred for other reasons, for example, by a corona discharge generated between the metal layers of the first and second metalized films. Therefore, the decrease ratio of the capacitance in the film condenser having a fuse function is relatively large, and it is desired to reduce the capacitance decrement generated by each brake down of the fuse portion.
In order to achieve this object, Japanese Patent Application, First Publication, No. Hei 4-225508 discloses a film condenser in which the area of the electrode regions is reduced by arranging a plurality of rectangular electrode regions in a lattice pattern. Each of the four corners of each electrode regions is connected by a fuse portion to the adjacent three corners of other electrode regions. That is, each fuse portion simultaneously connects four electrode regions.
However, in a film condenser of this type, when one of the fuse portions breaks down due to a short circuit, the fuse portions locating adjacent to the cut fuse portion are likely to break down, as if it is a chain reaction, due to the electrical shock. Therefore, in spite of small area of the electrode regions, the decrease of the capacitance which occurs at every break downs of the fuse portion cannot be improved in comparison with the conventional one.
SUMMARY OF THE INVENTION
The objective of the present invention is to provide film condensers and metalized films having fuse functions in which the decrease of the capacitance can be reduced while obtaining appropriate fuse functions.
In order to achieve this objective, the metalized film according to the first aspect of the present invention comprises a base film formed from an insulating material, and a metal coating layer formed on the base film. A plurality of uncoated portions are formed as area partition margins in the metal coating layer so as to respectively form, in the metal coating layer, a plurality of electrode regions, a plurality of fuse connecting regions surrounded by two or more of the electrode regions, and a plurality of fuse portions electrically connecting each one of the fuse connecting regions with the electrode regions surrounding the one of the fuse connecting regions.
The film condenser according to the first aspect of the present invention comprises first and second metalized films which are stacked up to each other, and at least the first metalized film is the above-described metalized film. The first and second metalized films may be rolled together to form a rolled capacitor or may be alternately piled up to form a stacked capacitor. The metal coating layer of the first metalized film is connected to a first electrode terminal, and the metal coating layer of the second metalized film is connected to a second electrode terminal.
According to the first aspect of the present invention, because a plurality of the fuse portions connected to the electrode regions adjoining each other are connected to each other via the fuse connecting region having a predetermined area, it is possible to thermally isolate the neighboring fuse portions from each other. Therefore, when one of the fuse portions is cut due to the short circuit, it is possible to prevent the neighboring other fuse portions from breaking down due to the heat generating at the evaporated fuse portion, the decrease of capacitance of a film condenser can thereby be reduced while obtaining a proper fuse function.
In the metalized film and the film condenser according to the second aspect of the present invention, a plurality of uncoated portions are formed as area partition margins in the metal coating layer so as to respectively form, in the metal coating layer, a plurality of electrode regions and a plurality of fuse portions electrically connecting neighboring ones of the electrode regions. Selected ones of the fuse portions have a different width from that of the other of the fuse portions, that is, the selected ones of the fuse portions have a different fusing current from that of the other of the fuse portions.
According to the second aspect of the present; invention, because selected ones of the fuse portions have a different fusing current from that of the other of the fuse portions, when a corona discharge occurs in one of the electrode regions, only the neighboring fuse portion(s) having a lower fusing current will be break down while the neighboring fuse portions having a higher fusing current remains uncut. Therefore, it is possible to reduce the unnecessary incapacitation of the electrode regions which may occur when a corona discharge occurs, it is thereby possible to restrain the decrease of the capacitance of the film condenser.
In the metalized film and the film condenser according to the third aspect of the present invention, a plurality of first uncoated portions are formed as electrode partition margins in said metal coating layer so as to respectively form, in said metal coating layer, a plurality of electrode regions and a plurality of first fuse portions electrically connecting neighboring ones of said electrode regions. Furthermore, a plurality of second uncoated portions are formed as terminal partition margins in said metal coating layer so as to respectively form, in said metal coating layer, terminal regions extending along an edge of said base film, and second fuse portions electrically connecting said terminal regions and said electrode regions.
According to the third aspect of the present invention, because the second fuse portions are formed to electrically connect said terminal regions and said electrode regions, it is possible to treat with short circuits which may occur near the terminal regions, the safety of the condenser can thereby be improved.
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Lam Cathy
Mitsubishi Shindoh Co. Ltd.
Pearne & Gordon LLP
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