EP1729317B1 - Helically wound fusible conductor for fuse element with plastic sealing - Google Patents

Description

The invention relates to a winding fuse for a fuse element with an electrically insulating or high-resistance core around which at least one fuse wire is wound. Furthermore, the invention relates to methods for producing such a winding winding conductor.

Wickelschmelzleiter the type mentioned are used for some time in fuse components. For example, a fusible conductor wire is wound around a core made of a plurality of glass fibers, wherein a predetermined winding density is to be maintained in order to achieve desired properties. Such a prefabricated winding fusible conductor is then cut to a predetermined length and introduced, for example, in a ceramic tube and thereby electrically connected to the electrically conductive end caps, which are placed on the tube and mechanically fastened at the same time. For electrical and mechanical attachment of the winding fusible conductor is soldered, for example, to the end caps.

By doing U.S. Patent No. 5,736,919 a fuse element with a winding fusible conductor is described, wherein the winding fusible conductor is wound around an electrically insulating core. In this case, the fusible conductor is inserted in a spiral-shaped depression formed in the core surface in order to improve the heat dissipation from the fusible conductor to the core. The helical groove can be made by pressing the fuse wire into a plastic elastic surface of the core as it winds up. For stabilization, the core may contain a harder carrier inside.

In the patent GB 227,928 a fuse component is described in which a fused by an insulating ceramic sheath fuse wire spirally around a insulating core is wrapped around. The insulating ceramic cladding surrounding the fuse wire limits the propagation of the metal vapor as the fuse wire is severed. In addition, the insulated fuse wire can be fixed on the insulating core by means of an enamel layer and additionally supported by a cladding material. It has been found that the fuse components using a winding fusible conductor have a lower switching capacity than fuse components using a conventional wire melting conductor. This is due in particular to an insufficient extinction of the arc generated during shutdown.

The object of the invention is therefore to provide a fuse component with a winding fuse, which shows an improved turn-off.

This object is achieved by a winding fusible conductor having the features of claim 1 and a method for producing such a winding fusible conductor having the features of claim 8 or claim 11.

The winding fusible conductor for a fuse element with an electrically insulating or high-resistance core, on which at least one fuse wire is wound, wherein the core has gaps, pores or other spaces, is characterized in that a temperature-resistant plastic is applied to the core such that at least the covered between the fusible wire exposed surface areas of the core of the plastic and the interstices formed between the wound fuse wire and the surface of the core (ie columns) and at least the outer interstices of the core with the plastic substantially (ie, at least so far that no capillary caused will be filled out).

The invention is based on the recognition that the breaking capacity is worsened by residues of the flux used in the soldering of the fusible wire, these remainders being due to the fact that the flux during soldering due to capillary action in gaps and interspaces of the Core or between the wound fuse wire and the surface of the core penetrate.

The introduction of a temperature-resistant plastic according to the invention constitutes a "seal" of the gaps and spaces which prevents penetration of the flux.

According to the invention, a winding fusible conductor is produced by first impregnating a core with a non-cured liquid plastic material, wherein the surface of the core is coated with a layer of the plastic material, then the impregnated core is wrapped with the fusible conductor wire prior to curing of the plastic material and finally the Plastic material is allowed to harden, so that a temperature-resistant plastic is formed. In this manufacturing process, the amount of uncured plastic liquid material in the core can be sized so that when wrapping the core, all gaps and gaps between the fuse wire core and inside the core are closed, but the outwardly facing surfaces of the fuse wire remain free , This has the advantage that the winding fusible conductor remains solderable without the need to first remove the plastic.

In an alternative manufacturing method, the fuse wire is first wound on the core. Subsequently, the winding conductor is coated with a not yet cured liquid plastic material so that the plastic material can penetrate into spaces between the fuse wire and the core and in the pores, gaps or other spaces of the core. Then the plastic material hardens, so that a temperature-resistant plastic is formed. This alternative method offers the advantage that a conventional winding fusible conductor can be used as the starting material.

In the case of the winding-type fusible conductor according to the invention, the flux can no longer penetrate into the spaces between the fusible conductor wire and core and into the core, as a result of which Switching capacity is improved. In addition, the fuse wire is fixed after curing of the plastic on the core, which allows higher winding densities of, for example, over 60%.

In a typical embodiment, the core is comprised of a plurality of glass and / or ceramic fibers, with the interstices between the individual fibers also being substantially filled by the plastic. The cores of a plurality of parallel glass or ceramic fibers are compressed during winding, so that - in the first manufacturing process alternative - after a prior impregnation of the fibers with the plastic material, a part of the plastic material is pressed out during winding from the core and remains between the wire windings. If a relatively large excess of the liquid plastic material remains, then the excess plastic material can be subsequently removed by mechanical stripping of the winding fusible conductor.

In an advantageous embodiment, the plastic material used is a silicone which is applied in the liquid state and cured later. The cured silicone is temperature resistant. In an advantageous development of the silicone one or more arc-quenching materials are mixed, preferably a melamine powder. This additionally supports the arc-quenching effect of the silicone coating.

Advantageous and / or preferred developments of the invention are characterized in the subclaims.

• Figur 1 eine schematische Darstellung eines Ausführungsbeispiels des erfindungsgemäßen Wickelschmelzleiters;
• Figur 2 eine schematische Schnittdarstellung eines Schmelzsicherungsbauelements mit dem erfindungsgemäßen Wickelschmelzleiter; und
• Figur 3 eine schematische Schnittdarstellung einer alternativen Ausführungsform eines Schmelzsicherungsbauelements mit dem erfindungsgemäßen Wickelschmelzleiter.

In the following the invention will be explained in more detail with reference to preferred embodiments shown in the drawings. In the drawings show:

• Figure 1 is a schematic representation of an embodiment of the winding fuse according to the invention;
• Figure 2 is a schematic sectional view of a fuse element with the inventive winding fuse; and
• Figure 3 is a schematic sectional view of an alternative embodiment of a fuse element with the inventive winding fuse.

FIG. 1 is a schematic representation of a section of a winding fusible conductor 1 according to the invention. A fusible conductor wire 2 is wound on an insulating or high-resistance core 3. The fuse wire 2 is, for example, a wire made of a tin-plated silver-copper alloy core having a circular cross section and a diameter in the range of 0.05 mm to 0.5 mm. Of course, a variety of other alloys and metals are conceivable. The cross section need not be circular, but it can be wound, for example, a metal strip. Thinner or thicker wires are also conceivable depending on the desired properties. The core 3 could for example consist of a more or less flexible rod of an insulating material (eg glass, glass ceramic, plastic or ceramic) or high-resistance material (eg semiconductor or high-resistance metal conductor). However, in preferred embodiments, the core is a bundle of glass and / or ceramic fibers. Preferably, the core is glass fiber, i. H. a bundle of twisted or spun glass fibers. In the raw state, the glass fibers of the glass silk lie relatively loosely together, so that many spaces are formed. When wrapping the glass core 3 with the fuse wire 2, the glass fiber is compressed, d. H. The individual glass fibers are pressed together.

In the manufacture of the inventive winding fusible conductor 1, in which a core of glass fiber is used, the core 3 is soaked before wrapping with a (still) liquid silicone plastic, so that fill the spaces between the glass fibers with the plastic material. Of course, not all gaps need to be filled; It is basically sufficient if the outer layers of the glass silk fill with the plastic, so that the glass silk is sealed so that no more liquids in the possibly still existing inner spaces can get. When wrapping the impregnated core 3 with the fuse wire 2, a part of the plastic material is pushed out of the glass fiber and remains on the core 3 and fills the gaps (gaps) between the fuse wire 2 and the core 3. Remains too much excess plastic material, it can be stripped in still liquid state of the winding fusible conductor 1. But it is also conceivable and preferred that the inclusion of the liquid plastic material in the raw core 3 is dimensioned so that after wrapping stripping is no longer required. FIG. 1 shows the remaining plastic material 4 between the individual turns of the fusible conductor wire 2. Subsequently, the plastic hardens, wherein hardening in the sense of setting is to be understood. The plastic material does not need to be hard. On the contrary, when using silicone, the cured temperature-resistant plastic preferably remains soft or elastic, so that the winding fusible conductor 1 remains flexible.

As the plastic material, a silicone is preferably used, wherein the silicone material for example consists of two components, which are mixed before application. Preferably, arc-quenching materials, in particular melamine powder, are added to the silicone. For example, ten parts of silicone resin are mixed with four parts of melamine powder.

Figure 2 shows a schematic representation of a fuse element 5, in which the winding fuse 1 according to the invention is used. The winding fusible conductor 1 comprises a core 3 onto which the fuse wire 2 is wound and in which the spaces between the turns of the fuse wire 2 are filled with the plastic material 4. In the schematic representation in Figure 2, the applied plastic material 4 is shown for clarity only on the left half of the winding fusible conductor 1. The fuse 5 comprises an insulating tube 6 made of glass, plastic or ceramic, in the interior 7 of the Wikkelschmelzleiter 1 is included. The tube 6 may have a round or rectangular cross-section. The interior 7 may be filled with air, gas filled, empty or filled with another material. Two end caps 8 are placed on the ends of the tube 6 (eg, soldered or glued on). The fusible conductor 1 is soldered onto the bottoms of the end caps 8, the solder being shown schematically in FIG. 2 by the solder regions 9. But the solder joint can also be much smaller than it is shown in Figure 2 with the hatched areas 9. The hatched area 9 may in this case also be a sealing material which is introduced into the end caps.

If the winding fusible conductor 1 is soldered onto the inner bottoms of the end caps 8, a flux is of course used in addition to the solder. The inventive sealing of the fusible conductor 1 by means of the plastic material 4 prevents melted or liquid parts of the flux from migrating along the winding fusible conductor due to the capillary action. Such no longer removable flux residues would form a source of carbon and, in the event of shutdown (severing) of the fusible conductor, form conductive bridges which assist in reigniting the arc in the succeeding halfwaves.

FIG. 3 shows an alternative embodiment of a fuse component 10. Two contact pins 12 are led through a base 11. On the base 11, a protective cap 13 is placed. In the interior space between the base 11 and protective cap 13, the ends of the connecting pins 12 open into terminal lugs 14, to each of which one end of a winding semiconductor conductor 1 is attached. The winding fusible conductor 1 is attached to the terminal lugs 14, each with a solder joint 15.

Numerous alternative embodiments are conceivable within the scope of the inventive concept. For example, a wiper fusible conductor 1 may be used in which one or more insulating fibers are wound around the core 3 in parallel with the fuse wire 2, the adjacent turns of the Melt wire 2 thus hold at a predetermined distance from each other. The combination of such a development with the seal according to the invention improves the breaking capacity and the reproducibility of the properties of the winding conductor.

Claims (13)

1. A helically wound fusible conductor for a fuse component (5), including:

   an electrically insulating or high resistance core (3), onto which at least one fusible conductive wire (2) is wound, the core (3) including gaps, pores or other voids,

   wherein a temperature-resistant plastic material (4) is applied to the core (3) such that at least the surface regions of the core disposed between the fusible conductive wire are covered by the plastic material and the gaps defined between the wound fusible conductive wire (2) and the surface of the core (3) and at least the outer voids in the core (3) are substantially filled with the plastic material.
2. A helical wound fusible conductor as claimed in Claim 1, characterised in that the core (3) consists of a plurality of glass and/or ceramic fibres and the gaps between the glass and/or ceramic fibres are also substantially filled by the plastic material (4).
3. A helically wound fusible conductor as claimed in Claim 1 or 2, characterised in that the plastic material (4) envelopes the helically wound fusible conductor (1) such that the outer surfaces of the fusible conductive wire (2) are also covered with the plastic material.
4. A helically wound fusible conductor as claimed in one of Claims 1 to 3, characterised in that one or more insulating fibres are wound around the core parallel to the fusible conductive wire, which maintain the adjacent windings of the fusible conductive wire at a predetermined spacing from one another.
5. A helically wound fusible conductor as claimed in one of Claims 1 to 4, characterised in that the plastic material is a silicone.
6. A helically wound fusible conductor as claimed in Claim 5, characterised in that one or more arc-extinguishing materials are mixed into the silicone.
7. A helically wound fusible conductor as claimed in Claim 6, characterised in that melamine powder is mixed into the silicone.
8. A method of manufacturing a helically wound fusible conductor in which a fusible conductive wire is wound around an insulating or high resistance core, wherein:

   a) the core is impregnated with an unset, liquid plastic material, whereby the surface of the core is also coated with a layer of the plastic material,

   b) the fusible conductive wire is wound around the impregnated core before the setting of the plastic material, and

   c) the plastic material is permitted to set so that a temperature-resistant plastic material is formed.
9. A method as claimed in Claim 8, characterised in that the core is impregnated with an amount of the liquid plastic material, which, with a compression of the core accompanying the winding around of the fusible conductive wire, results in excess plastic material being squeezed out.
10. A method as claimed in Claim 9, characterised in that after the winding of the fusible conductive wire, excess plastic material is removed by wiping.
11. A method of manufacturing a helically wound fusible conductor, in which a fusible conductive wire is wound around an insulating or high-resistance coil, wherein the core includes gaps, pores or other voids, wherein

    a) the fusible conductive wire is wound onto the core

    b) the helically wound fusible conductor is then coated with an as yet unset liquid plastic material such that the plastic material can penetrate into gaps between the fusible conductive wire and the core and into the pores, gaps or other voids in the core, and

    c) the plastic material is permitted to set so that a temperature-resistant plastic material is formed.
12. A method as claimed in Claim 11, characterised in that after the coating process, excess plastic material is wiped off from the helically wound fusible conductor.
13. A method as claimed in one of Claims 8 to 12, characterised in that a settable silicone resin is used as the liquid plastic material.

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