DESCRIPTION

Technical field

The present invention is developed in the field of fuses for the protection of electrical circuits. The invention is particularly directed to high voltage automotive fuses.

Background art

In the automotive sector, particularly for electric or hybrid traction mobility, direct current fuses are known which are suitable for low voltage use, with nominal voltages of 12, 24 or 48 V, and at high voltage, with nominal voltages of 500, 1000 or 1500 V.

They comprise a metallic fuse element, with two electrical terminals that allow the connection thereof in series to an electrical circuit. The two terminals are connected to each other through a fuse portion of the fuse element. The fuse portion is configured to conduct electric currents into the circuit into which the fuse is inserted, until a maximum current is reached. Beyond the maximum current, localized resistors of the fuse portion, formed for example as section narrowings of the fuse portion, cause an overheating of the fuse element until it melts, interrupting the electrical connection between the terminals and keeping them isolated as long as the electrical voltage remains at the expected levels.

The melting event, depending on the intensity of the current that causes it, can occur in a substantially explosive way, with the risk of damaging components close to the fuse. An enclosure then encloses the fuse portion, with the dual purpose of containing the burst and of housing extinguishing material, for example particular types of sand. In this description, the noun “fuse” or the term “fuse device” is used to denote the assembly of fuse element, enclosure, and if provided extinguishing material or any other component stably mounted thereto.

The prior art document US 7659804 shows some examples of fusible devices in which the enclosure has a tank-shaped base element, with an upper opening for inserting extinguishing material, and a cover element that closes the base element above. The cover element can be fixed to the base element for example by elastic clips.

Summary of the invention

An object of the present invention is to provide a fuse device of simple construction and assembly, and with good properties of containment of the burst that is caused during melting.

This and other objects are reached by a fuse device according to any one of the appended claims.

The fuse device of the invention has an enclosure with a base element and a cover element. The base element has a recess for extinguishing material surrounded by perimeter walls. Along one or more of these perimeter walls, the base element also includes reinforcement walls, external to the recess. The cover element also has reinforcement walls that mechanically couple with the reinforcement walls of the base element.

Thanks to the concomitant presence of the perimeter walls and of the reinforcement walls, the bursts inside the recess are contained more effectively.

However, both the base element and the cover element can be made by simple injection moulding. Furthermore, the fuse device can be assembled by simply mounting the fuse element to the base element, filling the recess with extinguishing material, and subsequently coupling the cover element to the base element.

Further features and advantages of the invention will be recognisable by a person skilled in the art from the following detailed description of exemplary embodiments of the invention.

Brief Description of the Figures

For a better understanding of the following detailed description, some embodiments of the invention are illustrated in the accompanying drawings, wherein:

- figure 1 shows a perspective view of a fuse device according to an embodiment of the invention, in which a component of the enclosure has been removed to better visualise its interior,

- figure 2 shows a perspective view of the fuse device of figure 1, when the enclosure is assembled,

- figure 3 shows a sectional view of the fuse device of figures 1 and 2, and

- figure 4 shows an enlarged detail of the section of figure 3.

DETAILED DESCRIPTION

A fuse device 1 comprises an electrically conductive, e.g. metallic, fuse element 2 and an electrically insulating, e.g. polymeric, preferably thermoplastic or thermosetting, enclosure 3.

The fuse element 2 has two end portions 21, spaced apart from each other in a longitudinal direction X-X, and a fuse portion 22, which is arranged between the end portions 21 and electrically connects the end portions 21 to each other. The end portions 21 are configured in a known manner for the connection to electrical terminals of electrical devices (not illustrated). For this purpose, each end portion 21 may have a recess or a hole 211 shaped to receive an electrical terminal.

The fuse portion 22 is configured to melt when when am electric current equal to or greater than a predetermined electric current flows therethrough. For this purpose, the fuse portion 22 may comprise in known manner one or more narrowings.

In the illustrated embodiments the fuse element 2 is formed starting from a metal foil, but for the purposes of the present invention the fuse element may also have different shapes, for example with a thread-like fuse portion 22.

The enclosure 3 comprises a base element 31, preferably made of one piece, and a cover element 32, preferably made of one piece.

The base element 31 has a bottom wall 311. In the illustrated embodiments, the bottom wall 311 is substantially planar, and may constitute a base for supporting the base element 31 when it is desired to place extinguishing material in the fuse device. More in detail, the bottom wall 311 preferably develops in a plane parallel to the longitudinal direction X-X and to a transverse direction Y-Y with respect to the longitudinal direction X-X. When the base element 31 is in an extinguishing material filling position, the longitudinal direction X-X and the transverse direction Y-Y are substantially horizontal.

However, embodiments in which the bottom wall 311 has other shapes are not excluded, for example a shape with arcuate cross-section and centre of curvature at a longitudinal axis of the enclosure 3.

The base element 31 also has perimeter walls 312, 313 connected to the bottom wall 311. Each perimeter wall 312, 313 extends between a respective lower edge, at the bottom wall 311, and a respective upper edge, or free edge 314, spaced from the bottom wall 311 in a height direction Z-Z. The height direction Z-Z is transverse to the longitudinal direction X-X and the transverse direction Y-Y. In the filling position, the height direction Z-Z is substantially vertical. It should however be noted that, following assembly of the fuse device 1, this can be used with any spatial orientation.

The perimeter walls 312, 313 surround an extinguishing material recess 315.

In particular, the perimeter walls 312, 313 are free of openings through them or between them, so as to retain the extinguishing material in the recess and prevent it from escaping. The recess 315, in the filling position, is opened upwards at the free edges 314 of the perimeter walls 312, 313, to receive the extinguishing material.

In the preferred embodiment, the perimeter walls 312, 313 comprise two end walls 312 and two side walls 313. The end walls 312 are spaced apart from each other in the longitudinal direction X-X and are arranged transverse to the longitudinal direction X-X.

Preferably, the end walls 312 of the base element 31 have respective slots 316 open at the free edges 314 of the end walls 312. In the filling position the slots 316 are then open upwards, where the cover element 32 will be positioned as described below.

The fuse element 2 extends through the slots 316 of the end walls 312 of the base element 31. The fuse portion 22 is at least partially located in the recess 315, while the end portions 21 protrude outside the enclosure 3.

The side walls 313 of the base element 31 connect the end walls 312 together.

The side walls 313 are spaced from each other in the transverse direction Y-Y.

According to one aspect of the invention, the base element 31 has one or more reinforcement walls 317. Each reinforcement wall 317 of the base element 31 extends along a respective perimeter wall 312, 313 of the base element 31. Preferably, the base element 31 has reinforcement walls 317 extending along both side walls 313 of the base element 31. These are represented with an arcuate section, centred at the longitudinal axis of the enclosure 3.

More preferably, the base element 31 has reinforcement walls 317 extending along all perimeter walls 312, 313 of the base element 31, i.e. both side walls 313 and both end walls 312 of the base element 31.

The reinforcement walls 317 of the base element 31 are external to the recess 316. Each reinforcement wall 317 of the base element 31 has an upper edge, or free edge 318, external to the recess and spaced from the respective perimeter wall 312, 313. Furthermore, each reinforcement wall 317 of the base element 31 has a lower edge that connects to the respective perimeter wall 312, 313 and/or to the bottom wall 311 of the base element 31, for example to the lower edge of the respective perimeter wall 312, 313.

It should be noted that the base element 31 can be shaped in such a way that it can be obtained in a single piece by injection molding. As is known, injection molding involves the use of two half-molds. Between the two coupled half-molds there is a cavity, into which molten material, generally polymeric, is inserted. Following the solidification of the material, the two half-molds are separated, and the solid material is removed from the half-molds.

The need to separate the half-molds from the solidified material imposes constraints on the shape of the piece to be molded. In the present case, the perimeter walls 312, 313 cannot be inclined with respect to the height direction Z-Z towards the inside of the recess 315, so as to allow the extraction of a half-mold part that is located during the injection inside the recess 315. Furthermore, where there is a reinforcement wall 317 of the base element 31 extending along a perimeter wall 312, 313, that perimeter wall 312, 313 cannot be inclined with respect to the height direction Z-Z towards the outside of the recess 315, to allow extraction of a half-mold part which is between the perimeter wall 312, 313 and the respective reinforcement wall 317 during injection.

Therefore, it is preferable that at least one perimeter wall 312, 313, in particular each perimeter wall 312, 313 where there is a reinforcement wall 317 for each perimeter wall 312, 313, extends substantially vertically, i.e. along the height direction Z-Z, when the base element 31 is placed in the filling position.

In the illustrated embodiment, the perimeter walls 312, 313 are substantially planar, but they are admissible, and can be considered substantially vertical, even perimeter walls 312, 313 that have a linear but not straight plan development.

The cover element 32 has a closing wall 321 shaped to close the recess 315 of the base element 31, by engaging the free edges 314 of the perimeter walls 312, 313. Preferably, the closing wall 321 sealingly engages the free edges 314 of the perimeter walls 312, 313, so as to prevent the escape of extinguishing material.

Preferably, the closing wall 321 has a central portion 322 and a groove 323 extending around the central portion 322. The central portion 322 is preferably substantially planar, and is represented parallel to the bottom wall 311.

The groove 323 is shaped to receive the free edges 314 of the perimeter walls 312, 313 of the base element 31. The central portion 322 thus protrudes towards the bottom wall 311, with respect to the free edges 314. Therefore, the central portion 322 of the closing wall 321 may compress the extinguishing material in the recess 315.

According to one aspect of the invention, the cover element 32 has one or more reinforcement walls, connected to the closing wall 321, for example arranged around the groove 323. More in detail, the cover element 32 has a reinforcement wall 324 for each reinforcement wall 317 of the base element 31. Reinforcement walls 324 of the cover element 32 extending along both side walls 313 of the base element 31, and preferably also along both end walls 312 of the base element 31 may then be provided. The reinforcement walls 324 along the side walls 313 may be with arcuate section shape, centred at the longitudinal axis of the enclosure 3.

In assembled condition, the reinforcement walls 324 of the cover element 32 are located outside the recess 315. More in detail, each reinforcement wall 324 of the cover element 32 has a free edge 325 shaped to removably couple to the free edge 318 of a respective reinforcement wall 317 of the base element 31.

Still in assembled condition, the reinforcement walls 317, 324 of the base element 31 and the cover element 32, which are coupled together along the free edges 318, 325, delimit one or more gaps around the recess 315 of the base element 31. In the illustrated embodiment, a single gap surrounding the perimeter walls 312, 313 of the base element 31 is recognizable. Two gap portions extend along the side walls 313, and two gap portions extend along the front walls 312. Note that the perimeter walls 312, 313 are shaped so as to prevent fluid communication between the recess and each gap so that each gap is free of extinguishing material.

It should be noted that also the cover element 32, like the base element 31, is obtainable by injection moulding, with fewer shape constraints due to its geometry.

For the purpose of a stable positioning of the fuse element 2 with respect to the enclosure, it can be provided that the fuse element 2 has one or more abutment panels 23, arranged transverse to the longitudinal direction X-X. The abutment panels 23 are positioned and configured to abut the perimeter walls 312, 313 of the base element 31, or the reinforcement walls 317 of the base element 31, or the reinforcement walls 324 of the cover element 32. In the illustrated embodiment, the abutment panels 23 are positioned in respective gaps between the end walls 312 and the reinforcement walls 317 of the base element 31.

In addition to the stable positioning of the fuse element 2, the abutment panels 23 are advantageous in that they cover the slots 316, preventing glowing material from coming out therefrom during a burst.

Obviously, a person skilled in the art will be able to make numerous equivalent modifications to the variants set forth above, without thereby abandoning the scope of protection defined by the appended claims.