KR820002146B1 - Fuse employing oriented plastic and a conductive layer - Google Patents

Abstract

Fuse (II) has a substrate with thickness proportional to nominal current rating, and an adhering conductive layer 0.5-2mils thick. The layer (13,14) opens at low and melts at high overcurrent conditions. There may be a number of conductive patterns on a single substrate which is pref. of polypropylene or polystyrene and is permanently encapsulated by an electrical Pulg with at least one conductor connected to the layer. The layer is e.g. of silk-screened conductive ink, and the two overcurrent conditions are e.g. 200% and 800%.

Description

Improved fuse

1 is an explanatory diagram of a fuse embodiment according to the present invention;

2 is an explanatory view of a plug embodiment utilizing a fuse according to FIG.

The present invention relates to fuses and more particularly to fuses used in electrical plugs connected to low power devices.

Since Edison first used thin wires in lamps to create sealed fuses, fuses have intentionally used weak links, conductors with low melting points, to prevent overcurrent. As is known to those skilled in the art, the current ratio of a fuse is a nominal ratio and the opening of the link is in fact dependent on a number of factors, such as the actual current, time, circulation and thermal inertia of the conductive link, and also the thermal inertia of the link. Depends on the size of the link. For the use of electrical devices of 3 amps or more, the size of the protective link is also a reasonable fuse for manufacturing. If it is less than 3 amps, the link will naturally become smaller. Thus, when expressed in percentage, the standard tolerance remains the same, but the actual value is very small, making the fuse more difficult and expensive to manufacture. For low power devices that emit sturdy stringsets or clocks or similar 0.5 amp or less currents, the problem arises when the device itself needs to be fused, and the fuse will significantly increase the cost of the device. The fuse is preferably installed inside or near the plug for best safety. However, replaceable fuses are expensive to manufacture and add to the cost of the device. Assuming that an overcurrent condition breaks the device and the device needs to be replaced, the cost may be reduced by installing a non-renewable fuse plug. However, most small mechanical or electrical devices do not have polarized plugs. Since both ends of the lead are heated, both sides of the plug must be fused. Therefore, the problem that the fuse is doubled and the price is doubled.

In summary, in the present invention, two printed circuit fuse conductors are connected in series to each line or conductor in the plug. In a printed circuit, a conductive layer is coated on a directional plastic thin film. For a 200% low overcurrent condition, the thermal characteristics of the substrate open the circuit partially by pulling the conductor. For 800% high excess current, part of the conductor melts and evaporates from the substrate. The present invention will be more fully understood with reference to the accompanying drawings and the following detailed description.

1 shows a suitable embodiment of a printed circuit fuse for fuses both sides of a lead according to the present invention. In particular, fuse 11 comprises a plastic substrate with shielded conductors l3 and 14. Here, the conductor is shown in a U-shape, but this fusible link can be configured in any form with an extension for implementing fuse characteristics. The particular type of fuse shown in FIG. 1 is for use with the plug shown in FIG. The plastic substrate 12 may be composed of any suitable plastic having the following characteristics. That is, in order to withstand the flame in the form of a thin film, the substrate 12 must have a property that the plastic shrinks away from heating to burn a portion of the substrate. It was a directional plastic that this method was carried out. However, this directional plastic is a revival to the public, although it is known in the plastics industry. As used herein, "aromatic plastic" refers to plastics that are stressed along at least one axis in the most intermediate stage of forming a plastic sheet. Thus, for example, so-called ground plastics are unsuitable for use in the present invention. The stress can occur along one axis or along two axes, in the latter case this plastic is sometimes called biaxial oriented plastic. In addition to the above fire test, the suitability of the plastic thin film material can be further measured with a polarizing scope device when the plastic is transparent. Here, polarization is transmitted through the plastic and observed through the polarization filter. As is known in the art, the polarization plane is rotated by the stress of the plastic to generate image image accents.

A third test to determine the suitability of a given plastic is to make sure that fuses are made for both low and high current states. For example, it has been found that suitable for use in the present invention using flame and overcurrent inspection are 0.5 to 2 mils thick polyflofilene. Different materials may have different specifications.

Other materials, such as Mylar and Polyethersulfane, have been found to be unsuitable for a nominal ratio of 1.5 amps because the substrate is too thin for certain uses. However, these materials are believed to be suitable at higher current ratios. In other words, the particular problem solved by the present invention is low cost and low nominal current fuse. However, high current fuses can also be made by the teachings of the present invention.

The conductive ink is applied to the substrate 12 by a method such as quenching, brushing, or silk screening. It's a good idea to use the silkscreen method here because you can easily create a variety of patterns. The conductive ink may use any suitable ink, such as those sold by E. I. Dupont De Nemours & Co., where Dupont 4929 air dry ink is silk screened onto substrate 12 and dried to a thickness of approximately 0.5 to 2 mils. As the ink thickness changes, the transition between the high transient breakage type and the low transient breakage type changes. However, if the conductors are too thin, problems may arise that are limited to the specific use of inrush currents that open the circuit at high overcurrent breakage.

By virtue of the present invention, the plastic thin film interacts with the conductive layer such that the circuit is mechanically opened by the expansion or breakage of the conductor during low excess current conditions. This provides similar time / temperature characteristics as fuses known in the art. The low overcurrent nominal fuse ratio thus depends on the thickness of the plastic substrate 12. Breakage of the circuit has the property of hair-breaking in the conductive layer, which limits the voltage at which a fuse of 500V or less, for example, can be applied.

In the high overcurrent type, the fuse according to the present invention acts like a conventional fuse and the time / temperature characteristic of the conductor is to rapidly open a circuit by evaporating a part of the conductor from the substrate. For example, this occurs at 800% overcurrent.

The fuse plug according to the present invention can be easily constructed using the printed circuit fuse of FIG. 1 installed in the suitable plug shown in FIG. In particular, the fuse plug 20 is suitably formed into two parts for convenience, and the other half is shown as the cell 21 in FIG. The appropriately formed metal foils 22 and 23 are suitably made of, for example, brass, and are stacked on and in contact with the respective conductors 13 and 14 of the fuse 11 and in contact with the tab 24. ) And (26) are placed in the cell (21). If desired, the inner portions of the lamellas 22 and 23 are preferably provided with bends 26 and 27 suitable for holding in place in the rooms 28 and 29, respectively, when assembled.

Next, the other half of the cell is superimposed on the cell 21. In the plugs fixed to each other by suitable adhesive or ultrasonic welding or heat welding, the conductors 35 and 36 and the conductors of the fuse 11 come into contact with each other.

As shown in FIG. 2, instead of stripping the insulating coated ends of the leads 33 and 34, a small conductive tab or tack is used to insulate each conductor and each conductor of the fuse 11 It is good to make contact.

As will be apparent from FIG. 2, the lamellas 22 and 23 of the plug 20 are inserted into a suitable socket or outlet. Subsequently, an excess current condition that requires protection in the device occurs, and if either of the conductors 33 or 34 is shorted to earth, the corresponding conductor is open circuited to protect the user.

The present invention can be modified within each of the ranges, for example, the conductors can be arranged on any suitable pattern as described above, and any number of fuse elements can be arranged on a single substrate. Do. When the fuse of the present invention is to be used as a separate element, that is, without being enclosed in a fused plug, for example, a conductive piece may be attached, and the fuse may be sealed with a gap capsule to adequately seal the fuse.

In general, sealing a fuse in a plastic cell is performed by bonding a piece to the end of the conductor and sealing the enclosure by ultrasonic waves.

Claims (1)

A directional plastic substrate having a thickness proportional to the nominal rated current of the fuse, and a conductive layer on the substrate with a thickness of 0.5 to 2 mils, the conductor being mechanically open at a low excess current and a high excess current In which the conductor is melted and opened.

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