EP1708221B1 - Protection device comprising a fuse and an insulation element for switching off, and use of said device in a lightning arrestor - Google Patents

Abstract

The device has an insulator (3) exerting an elastic force on a fuse, where the fuse secures an electrical connection between connection studs (11, 12) in its operational configuration and breaks the connection in its final breaking configuration under the effect of a temperature rise and the force. The insulator has two wings respectively adjacent to the studs and with front edges supported on the fuse in the operational configuration, where the ends of the fuse are mechanically maintained by the respective studs against a traction force along a direction in which the studs are aligned. An independent claim is also included for a lightning arrestor using this protection device.

Description

The invention relates, in general, the protection of electrical equipment.

More specifically, the invention relates, according to a first of its aspects, an electrical protection device comprising at least first and second connection pads aligned in a first direction and separated by a predetermined distance, a fuse conductive part having first and second ends respectively in electrical and mechanical contact with the first and second pads, and an electrically insulating piece exerting on the fuse piece an elastic force applied between the two pads in a second direction perpendicular to the first, the fuse piece initially adopting an operational configuration in which it provides an electrical connection between the first and second pads, and adopting, under the effect of a rise in temperature and the elastic force, a final configuration of rupture in which the electrical connection is broken, the insulating part being solicited by means ns resilient to adopt, in the operational configuration of the fuse piece, an armed position in which it exerts said elastic force on the fuse piece, and to adopt, in the rupture configuration of the fuse piece, a triggered position in which it s interposed between the first and second pads.

Such a device is for example described in the Japanese patent document JP 8031299 or in the document " US 5,113,169 A "

This document describes a protection system well known to those skilled in the art, especially under the name of "surge arrester cell", and of which various other examples are given in the patents. US 3,889,222 , US 4,015,228 or US 4,288,833 .

Systems of this type conventionally include a clipping component, such as a varistor, which is connected in series with a temperature sensitive switch.

Indeed, as indicated in the three US patents mentioned above, the varistors are, towards the end of their life, the seat of a significant heating, the thermosensitive switch having precisely the function of disconnecting the varistor before that this heating does not reach a value such that it generates risks of explosion or fire.

According to the Japanese patent document JP 8031299 , the temperature sensitive switch is formed of a fuse wire stretched between the first and second pads and subjected to an elastic bias in the direction of rupture.

In case of excessive heating, the wire loses its mechanical strength by partial or total melting, and undergoes a break insulating from each other the first and second pads.

In such an arrangement, the mode of rupture of the fuse piece is critical and poses serious problems of reproducibility.

In particular, the structure disclosed by the Japanese patent document JP 8031299 does not exclude the risk that the fuse is broken by leaving a weak electrical path resistant against an electric arc likely to form in this type of device.

In this context, the purpose of the invention is to propose a protection device free of such a risk.

To this end, the device of the invention, moreover in accordance with the generic definition given in the preamble above, is essentially characterized in that the insulating part has first and second sails respectively adjacent to the first and second pads. , extending in respective planes perpendicular to the first direction, and having front edges resting on the fuse piece in the operational configuration thereof.

Thanks to this arrangement, the fuse piece undergoes, during its rupture, a shear avoiding the uncontrolled appearance of metal residues likely to provide a preferred path for an electric arc. In the preferred embodiment of the invention, the fuse piece is constituted by a block of predefined shape and its first and second ends are mechanically held by the respective first and second pads against the effect of traction in the first direction. .

To facilitate the rupture of the fuse piece, the insulating part may have a cavity defined between the first and second webs and extending in the second direction, the front edges of these first and second webs of the insulating part may also be bevelled to be sharp.

The cavity is for example delimited, in a third direction perpendicular to the first and second directions, by a third sail.

To complete the insulation of the pads after rupture, the insulating part advantageously has, in the third direction, a dimension, or height, greater than the corresponding dimension, or height, of the fuse piece.

In addition, the triggered position of the insulating piece is preferably separated from the armed position of this piece by a stroke at least equal to the distance between the two pads.

To facilitate its positioning, the insulating part may comprise a rest face extending parallel to the first and second directions and resting on the fuse piece in the operational configuration thereof.

It is possible to provide that the protection device of the invention comprises a varistor, whether the first pad is connected to a first supply terminal of the varistor or constitutes it, that the second pad is connected to a first connection terminal the device to an electrical network or constitutes it, and that the varistor comprises a second power supply terminal which is connected to a second terminal of the device connection to an electrical network or which constitutes it.

According to a second aspect, the invention also relates to the application of the device as described above to the production of a lightning arrester cell.

• la figure 1 est une vue en perspective d'un dispositif de protection conforme à l'invention vu sous un premier angle d'observation, la pièce fusible y étant illustrée en configuration opérationnelle et la pièce isolante en position armée;
• la figure 2 est une vue agrandie du détail repéré par la référence II sur la figure 1;
• la figure 3 est une vue en perspective d'un dispositif de protection conforme à l'invention vu sous un deuxième angle d'observation, la pièce fusible y étant toujours illustrée en configuration opérationnelle et la pièce isolante en position armée;
• la figure 4 est une vue en perspective agrandie de la pièce fusible utilisée dans le dispositif illustré aux figures 1 à 3;
• la figure 5 est une vue de dessus du dispositif illustré aux figures 1 à 3;
• la figure 6 est une vue en perspective légèrement agrandie du dispositif de protection représenté à la figure 3 et sous le même angle d'observation, la pièce fusible y étant illustrée en configuration de rupture et la pièce isolante en position déclenchée;
• la figure 7 est une vue agrandie et écorchée du détail repéré par la référence VII sur la figure 6;
• la figure 8 est une vue de dessus du dispositif illustré à la figure 6, la pièce fusible étant représentée en configuration de rupture et la pièce isolante en position déclenchée;

• la figure 9 est une vue en coupe partielle du dispositif illustré à la figure 8 et observé suivant l'incidence définie par les flèches IX-IX de la figure 8;
• Les figures 10a à 10c sont des vues en perspective agrandies illustrant l'assemblage d'une pièce fusible et de deux plots conformes à une forme d'exécution possible de ces éléments dans le cadre de l'invention; et
• Les figures 11a à 11c sont des vues en perspective agrandies illustrant l'assemblage d'une pièce fusible et de deux plots conformes à une autre forme d'exécution possible de ces éléments dans le cadre de l'invention.

Other characteristics and advantages of the invention will emerge clearly from the description which is given hereinafter, by way of indication and in no way limitative, with reference to the appended drawings, in which:

• the figure 1 is a perspective view of a protection device according to the invention seen at a first viewing angle, the fuse piece being illustrated in operational configuration and the insulating part in the armed position;
• the figure 2 is an enlarged view of the detail identified by reference II on the figure 1 ;
• the figure 3 is a perspective view of a protection device according to the invention seen at a second angle of observation, the fuse piece being always illustrated in operational configuration and the insulating part in the armed position;
• the figure 4 is an enlarged perspective view of the fuse piece used in the device illustrated in FIGS. Figures 1 to 3 ;
• the figure 5 is a top view of the device shown in Figures 1 to 3 ;
• the figure 6 is a slightly enlarged perspective view of the protective device shown in FIG. figure 3 and at the same angle of observation, the fuse piece being shown in rupture configuration and the insulating part in the tripped position;
• the figure 7 is an enlarged and scratched view of the detail identified by reference VII on the figure 6 ;
• the figure 8 is a top view of the device shown in FIG. figure 6 , the fuse piece being shown in rupture configuration and the insulating part in the tripped position;

• the figure 9 is a partial sectional view of the device illustrated in FIG. figure 8 and observed according to the incidence defined by arrows IX-IX of the figure 8 ;
• The Figures 10a to 10c are enlarged perspective views illustrating the assembly of a fuse piece and two pads according to a possible embodiment of these elements within the scope of the invention; and
• The Figures 11a to 11c are enlarged perspective views illustrating the assembly of a fuse piece and two pads in accordance with another possible embodiment of these elements within the scope of the invention.

As previously announced, the invention relates to an electrical protection device comprising in particular two connection pads 11 and 12, a fusible conductive part 2, and biasing means typically constituted by an insulating part 3 and a spring 4 acting on this part. insulating 3.

The connection pads 11 and 12 are aligned in a direction D1 ( figures 7 and 10a ), are separated by a determined distance d ( figure 4 ), and are respectively in electrical and mechanical contact with the ends 21 and 22 of the fuse piece 2.

The fuse piece 2 initially adopts an operational configuration illustrated in particular in figures 4 , 10c and 11c , in which it provides an electrical connection between the pads 11 and 12.
In this operational configuration of the fuse piece 2, the insulating part 3 adopts, under the load of the spring 4, an armed position ( Figures 1 to 3 and 5 ) in which it exerts an elastic force F ( figure 2 ) on the fuse piece 2, this force being applied between the pads 11 and 12 in the direction D2 transverse to the direction D1.

However, the fuse piece 2 can also adopt, under the effect of a rise in temperature and the elastic force F, a rupture configuration in which the electrical connection between the pads 11 and 12 is broken.

In this rupture configuration of the fuse piece 2, the insulating part 3 adopts, under the bias of the spring 4, a triggered position ( Figures 6 to 9 ) in which it interposes between the studs 11 and 12.

According to the invention, the insulating part 3 has two webs 31 and 32, respectively adjacent to the pads 11 and 12.

These webs 31 and 32 extend in respective planes perpendicular to the direction D1 of alignment of the pads, and their respective front edges, 310 and 320, bear against the fuse piece 2 in the operational configuration thereof.
The fuse piece 2 is advantageously constituted by a block of predefined shape, for example made of bismuth or a bismuth alloy.

The expression "predefined block of shape" must be understood here as applicable to any block of material that can be handled at room temperature, without any particular precaution, or to be stored in bulk, at ambient temperature, with other blocks. of the same type without undergoing visible deformation.

Each of the connection pads 11 and 12 and the corresponding end 21 or 22 of the fuse piece 2 are provided with respective mechanical retaining means 51 and 52 ( Figures 10a to 11c ) typically taking, although not limitingly, the shape of complementary reliefs, and to withstand a tension exerted between each pad and the fuse piece in the direction D1 of alignment of the pads 11 and 12.

According to the invention, and as shown in particular figure 7 , the insulating part 3 has two webs 31 and 32, respectively adjacent to the pads 11 and 12, and extending in respective planes perpendicular to the direction D1.

The respective front edges 310 and 320 of these webs 31 and 32 bear on the fuse piece 2 in the operational configuration thereof to exert on the fuse piece a shearing force, and are preferably beveled to be relatively sharp.

The insulating part 3 advantageously has ( figure 7 ) a cavity 30 extending in the direction D2 for applying the force F and suitable for recovering the central fragment of the fuse piece when it breaks.

This cavity is defined between the webs 31 and 32 and preferably delimited by a third web 33 forming a floor.

The insulating part 3 advantageously has, in the third direction D3, a height H3 greater than the corresponding height H2 of the fuse piece 2.

To facilitate its positioning, the insulating part 3 also has a rest face 34 perpendicular to the direction D3 and resting on the fuse piece 2 in the operational configuration thereof.

It is also advisable to ensure that the triggered position of the insulating part 3 ( figure 8 ) is separated from the armed position of that piece 3 ( figure 5 ) by a stroke at least equal to the distance d ( figure 4 ) separating the two studs 11 and 12.

As shown by Figures 10a to 11c , the retaining means 51 and 52 which are provided with the studs 11 and 12 and the fuse piece 2 are shaped to allow force entrenchment of the fuse piece in these pads by a relative movement in a direction D3 perpendicular to both the direction D1 of mutual alignment of the pads 11 and 12 and the direction D2 of application of the elastic force F.

Under these conditions, the electrical contact of the fuse piece 2 with the pads 11 and 12 results at least in part from this encasement, and is preferably provided only by the latter.

The retaining means 51 and 52, which are respectively provided with the pads 11, 12 and the fuse piece 2, have respective bearing surfaces S1 and S2 opposite one another and inclined with respect to the direction D1 ( Figures 10a to 11c ).

In fact, these respective bearing surfaces S1 and S2 are arranged to exert on each other increasing bearing forces in response to increasing traction exerted between each of the pads 11 and 12 and the fuse piece 2.

More precisely, if the studs 11 and 12 equipping the functional subassemblies illustrated in FIGS. Figures 10c and 11c are biased by an elastic tensile force tending to separate them from each other, and thus tending to separate each of the fuse piece 2, this traction force will be neutralized by the opposing force represented by the mutual support surfaces S1 and S2.

According to a particularly advantageous embodiment at the industrial level, each of the pads 11 and 12 is formed of a metal blank, flexural elastic, cut and folded.

Furthermore, each of these pads 11 and 12, and the fuse piece 2 are dimensioned so that the embedding of this fuse piece 2 in each pad causes an elastic deformation of the blank constituting this pad, the electrical contact between the fuse piece 2 and this pad is thus optimized.

The device thus constituted can be applied to the production of a lightning arrester cell comprising a varistor 6.

In such a cell, the stud 11 may be connected to a first power supply terminal of the varistor 6 or directly constitute this first power supply terminal.

The stud 12 may in turn be connected to a first connection terminal of the cell to an electrical network or constitute directly this first branch terminal.

The second power supply terminal 62 of the varistor 6 can then be connected to a second connection terminal of the cell to an electrical network, or directly constitute this second branch terminal.

Claims (9)

1. Electrical protection device comprising at least first and second connection pads (11, 12) aligned along a first direction (D1) and separated by a determined distance (d), a fusible conducting piece (2) exhibiting first and second ends (21, 22) respectively in electrical and mechanical contact with the first and second pads (11, 12), and an electrically insulating piece (3) exerting on the fusible piece (2) an elastic force (F) applied between the two pads (11, 12) along a second direction (D2) perpendicular to the first (D1), the fusible piece (2) originally adopting an operational configuration in which it ensures an electrical link between the first and second pads (11, 12), and adopting, under the effect of a rise in temperature and the elastic force (F), a final breakage configuration in which the electrical link is ruptured, the insulating piece (3) being loaded by elastic means (4) so as to adopt, in the operational configuration of the fusible piece (2), an armed position in which it exerts the said elastic force (F) on the fusible piece (2), and to adopt, in the breakage configuration of the fusible piece (2), a tripped position in which it is interposed between the first and second pads (11, 12), characterized in that the insulating piece (3) exhibits first and second leaves (31, 32) respectively adjacent to the first and second pads (11, 12), extending in respective planes perpendicular to the first direction (D1), and exhibiting frontal edges (310, 320) bearing on the fusible piece (2) in the operational configuration of the latter, in that the fusible piece (2) consists of a block of predefined shape, and in that its first and second ends (21, 22) are held mechanically by the first and second respective pads (11, 12) against the effect of a tension along the first direction (D1).
2. Protection device in accordance with Claim 1, characterized in that the insulating piece (3) exhibits a cavity (30) defined between the first and second leaves (31, 32) and extending along the second direction (D2).
3. Protection device in accordance with Claim 2, characterized in that the cavity (30) is delimited, along a third direction (D3) perpendicular to the first and second directions (D1, D2), by a third leaf (33).
4. Protection device in accordance with any one of the preceding claims, characterized in that the insulating piece (3) exhibits, along a third direction (D3) perpendicular to the first and second directions (D1, D2), a dimension (H3), or height, that is greater than the corresponding dimension (H2), or height, of the fusible piece (2).
5. Protection device in accordance with any one of the preceding claims, characterized in that the said frontal edges (310, 320) of the insulating piece (3) are bevelled to a sharp edge.
6. Protection device in accordance with any one of the preceding claims, characterized in that the insulating piece (3) comprises a rest face (34) extending parallel to the first and second directions (D1, D2) and resting on the fusible piece (2) in the operational configuration of the latter.
7. Protection device in accordance with any one of the preceding claims, characterized in that the tripped position of the insulating piece (3) is separated from the armed position of this piece (3) by a travel at least equal to the distance (d) separating the two pads (11, 12).
8. Protection device in accordance with any one of the preceding claims, characterized in that it comprises a varistor (6), in that the first pad (11) is linked to a first power supply terminal of the varistor (6) or constitutes it, in that the second pad (12) is linked to a first terminal for wiring the device to an electrical network or constitutes it, and in that the varistor (6) comprises a second power supply terminal (62) which is linked to a second terminal for wiring the device to an electrical network or which constitutes it.
9. Application of a device in accordance with any one of the preceding claims to the realization of a lightning arrester cell.

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