Technical field

The invention relates to a fuse for protection of electrical devices, in particular transformers, voltage transformers, electric motors, capacitor banks and electronic devices.

Background

Electric fuses which use an arc-extinguishing material after the fuse element has melted are known in the art. Currently known solutions allow such devices to be constructed, but they are not without disadvantages. The inconveniences include mainly the risk of spilling out the arc-extinguishing material and the excess of free space inside the fuse. In addition, the fuses contain intermediate elements between the core and outer end caps, which complicate the structure and assembly of the fuse. Further, binders in the form of an adhesive or mortar are often used, thus generating additional costs due to material consumption and complexity of the technological process.

US8937524B2 discloses a fuse which has no intermediate parts. The disclosed fuse includes a housing, inner and outer end caps located at the ends of the housing, with the outer end caps being press-fitted onto the inner end caps. The inner end caps have an opening that allows a fuse element to pass, which fuse element consists of a core and a wound conductor. Each of the two ends of the conductor is placed between the inner and the outer end cap, for both ends of the housing, respectively. The conductor is held in place by a clamp, and the contact between the components is provided by electrical conductivity. No soldering is used for additional fixation of the conductor. The disclosed solution does not solve all the problems presented above, therefore it was necessary to develop a solution that would be free from the disadvantages mentioned above.

Summary of the invention

The present invention relates to a fuse comprising a cylindrical housing, a core with a fuse element wound thereon, two inner end caps and two outer end caps. The inner end caps and the outer end caps are cylindrical in shape with one base, wherein the inner end caps are located on both ends of the housing, and the outer end caps are located on the inner end caps. The inner end caps have openings in the axis of the housing. The housing and the core are made of an electrically non-conductive material, while the inner end caps, the outer end caps and the fuse element are made of an electrically conductive material. The space between the core and the housing is filled with an arc-extinguishing material. The fuse is characterized in that it has electrically non-conductive inserts and two end caps of the core made of an electrical conductor. The end caps of the core are basically cylindrical in shape with a single base, wherein the base includes an opening in the axis of the housing. The end caps of the core include an arm. The core is located between the bases of the inner end caps inside the housing. The end caps of the core are put on the both ends of the core. The fuse element is connected to the end caps of the core, and each of the end caps of the core is affixed through an arm to the corresponding inner end cap. An insert is provided between each inner end cap and the outer end cap.

Preferably, the cross section of the core is star-shaped, preferably with three or five points. Preferably, the housing is made of porcelain.

Preferably, the core is made of porcelain.

Preferably, the insert is made of cardboard, preferably pressboard.

Preferably, the end cap of the core is welded or soldered to the inner end cap.

Preferably, a rating plate is provided on the housing.

Preferably, the housing has a smaller diameter at the end portions than at the central portion. Preferably, the arc-extinguishing material is sand.

Brief description of the Figures

The invention is illustrated in the embodiment in the drawing, wherein:

Fig. 1 - shows a longitudinal section of the fuse.

Fig. 2a and 2b - show a cross section of the fuse.

Detailed description of preferred embodiment of the invention The fuse of the present solution will now be described in more detail with reference to Fig. 1, which shows a longitudinal section of a preferred embodiment of the fuse. The fuse includes a cylindrical housing 3 which comprises inside a core 1 with a fuse element wound thereon (not shown). To facilitate assembly, the housing 3 may have a smaller diameter at the end portions than at the central portion. The core 1 and the housing 3 are made of an electrically non-conductive material, preferably of porcelain. The fuse element is made of an easily fusible electrically conductive material, wherein the specific material or diameter is selected each time the fuse is designed for required voltages and currents.

The end caps 2 of the core 1, made of an electrically conductive material, are placed on both ends of the core 1, wherein the fuse element is connected to the end caps 2 of the core 1. The end caps 2 of the core 1 are press-fitted and are held on the core 1 due to the frictional forces. The end caps 2 of the core 1 are basically cylindrical in shape with a single base which has an opening in the axis of the housing 3. The end caps 2 of the core 1 further comprise an arm 2a.

Two inner end caps 4 are placed on the housing 3, one on each of the two ends of the housing 3. The inner end caps 4 are press-fitted onto the housing 3. The inner end caps 4 further include openings, which in an assembled fuse are located in the axis of the casing 3. These openings are used for pouring in an arc-extinguishing material, which fills the space between the corel and the housing 3. These openings also allow the fuse element to be electrically connected to the electrically conductive outer components of the fuse.

The arm 2a of the end cap 2 of the core 1 is affixed to the inner end cap 4, preferably by soldering or welding. This connection ensures low resistance and a secure connection.

After the arc-extinguishing material, preferably being sand, is put in place, the inserts 6 are placed on the inner end caps 4. The inserts 6 are made of an electrically non-conductive material such as cardboard or pressboard.

Then, an outer end cap 5 is placed on each inner end cap 4, to press the insert 6. The outer end cap 5 is press-fitted and held in place by the frictional forces. The inner end caps 4 and the outer end caps 5 are cylindrical in shape with a single base. The inner end caps 4, the outer end caps 5 and the fuse element are made of an electrically conductive material.

In an assembled fuse, the core 1 is located between the bases of the inner end caps 4. Preferably, a rating plate 7 is placed on the housing 3. Fig. 2 shows a cross section of the fuse. The cross-section of the core 1 may be star-shaped, preferably with three points, as in Fig. 2B, or with five points, as in Fig. 2A.

Parts list:

1 - core

2 - end cap of the core

3 - housing

4 - inner end cap

5 - outer end cap

6 - insert

7 - rating plate