EP1818959A1 - Electrical switching device having reinforced electrical contacts - Google Patents

Abstract

The switch has a mobile contactor element (30) connected to contact zones of fixed contactor elements (10, 20), where the elements are made of copper. The fixed contactor elements are in the form of coils and create an electromagnetic field (B) to form an attraction force (F) on the mobile element during passage of current. The fixed contactor elements are disposed opposite to each other, and the mobile contactor element is disposed between the coils to separate the contact zones of large height equal to the height of the coils.

Description

The present invention relates to electrical switches which comprise stationary and mobile contact elements capable of generating, at the passage of the current, an electromagnetic field which creates a force of attraction of said contact elements between them.

The invention finds a particularly advantageous application in the realization of an intersection or a switch.

BACKGROUND

In general, in the electrical switches, the contact areas between the fixed and moving contact elements are of small surface area. The passage of the current is then concentrated on these surfaces of small dimensions, which causes a necking of the current creating electromagnetic fields at the origin of Laplace forces pushing said moving contact elements out of contact with said fixed contact elements.

These repulsive forces, proportional to the square of the value of the intensity of the current, are negligible as long as the current passing through the switch, operating normally, retains a so-called moderate value. They are independent of the direction of the current.

On the other hand, when the value of the intensity of the current increases suddenly, for example during a short-circuit, these repulsive forces can take important values and cause the opening of the contact between the fixed and moving contact elements.

An electric arc can then be created between the fixed and moving contact elements. Such an electric arc has adverse consequences on the operation of the electrical switch. For example, it can develop a thermal power that can superficially melt parts of said fixed and movable contactors which, if they come into contact with each other, can be welded together.

In order to avoid this phenomenon of magnetic repulsion between the fixed and mobile contact elements, switches have been developed in which said moving contactor elements are capable of generating, at the passage of the current, an electromagnetic field which creates a force of attraction said contacting elements fixed and movable with each other.

In particular, there is known such an electrical switch in which there are provided two moving contact elements which are in the form of thin lamellae arranged on either side of two fixed contact elements and adapted to come into contact with the free ends of these fixed contact elements. Thus, during the passage of the current, a first portion of the current passes through one of the moving contactor elements and a second portion of this current passes through the other mobile contactor elements. The passage of the current in each of the two movable contactor elements creates attractive forces of the movable contact elements towards each other which counteract said repulsive forces.

The main disadvantage of such an electrical switch is that it requires, in order to operate, two moving contactor elements, which increases its cost and its bulk.

On the other hand, in order for the attraction forces to be able to counteract said repulsive forces, the current in each of the moving contact elements must be split into exactly two equal parts. In fact, if it splits into two unequal parts, the value of the forces of attraction falls sharply. Thus, it is necessary that the moving contact elements have similar geometries. It is also necessary that the electrical resistances formed by the contact zones between the different fixed and moving contactor elements are identical. This implies that the electrical switch comprises on each movable contactor element additional support mechanical support, such as a spring, so that the pressures applied at the contact areas by the two movable contact elements are equal, which increases the cost and difficulty of implementation of the electrical switch.

Document is also known US 4,467,301 an electrical switch comprising two fixed contact elements in the form of elongated turns which each have a free end and which are arranged in the extension of one another. This electrical switch also comprises a movable contact element, formed by a plate which passes through the turns along an axis parallel to the axis passing through the centers of the two turns. When the plate is lowered, the ends of this plate are adapted to make electrical contact between the ends of the two turns. Each turn then generates, when traversed by an electric current, a field electromagnetic which plates the movable contact element against the ends of the two turns, which against the effects of repulsion.

However, the two turns have, for the passage of the plate through them, openings which reduce the intensity of the electromagnetic fields they generate. In addition, the position of the two turns relative to each other does not allow them to create around the moving contact element a uniform electromagnetic field and significant intensity. Therefore, in order to create a magnetic field sufficient to counter the repulsive effects, the turns must have significant dimensions, which makes them bulky. This size is further increased by the arrangement of the turns in the extension of one another.

Finally, the elongated shape of the turns allows only a small clearance in height of the plate to open or close the electrical contact between the turns. Therefore, when the electrical switch is open, if the potential difference between the two turns is large, the small distance between the ends of the plate of the ends of turns may cause dangerous arcing.

OBJECT OF THE INVENTION

In order to overcome the aforementioned drawbacks of the state of the art, the present invention proposes an electrical switch provided with a limited number of parts, less expensive to produce and easier to assemble.

More particularly, there is provided according to the invention an electrical switch comprising two fixed contactor elements and a movable contactor element adapted to electrically connect two contact zones of the two fixed contactor elements located on one axis, the two fixed contactor elements having turns forms. disposed opposite one another, the movable contact member having a lamella shape which is arranged between the two fixed contactors and whose greatest length extends parallel to the turns, the two fixed contact elements being adapted during the passage of the current, to create, in the space in which is located said moving contactor element, an electromagnetic field oriented in a direction different from that of the axis passing through the two contact zones, to create on the movable contactor element a pulling force directed towards said contact areas.

Thus, thanks to the invention, the shapes and positions of the fixed contactor elements make it possible to create a relatively uniform electromagnetic field between the turns and of high intensity, which is oriented so that it generates a Laplace force to counteract the repulsive forces.

The Laplace forces being proportional to the angle formed between the direction of the electromagnetic field and that of the current in the moving contactor element (which corresponds here to the direction of the axis passing through the two contact zones), the position of the movable contact element generates maximum attraction forces. Furthermore, a single mobile contactor element is sufficient here to implement the electrical switch according to the invention, which reduces its cost of production.

On the other hand, thanks to the architecture of the switch, since the moving contactor element is located between the turns, it can deviate from the two contact zones by a large height, for example equal to the height of the turns. Thus, when the switch is open, and the two contact zones are at very different potentials, no electric arc is formed. This height therefore gives the switch a very important dielectric strength.

According to a first advantageous characteristic of the electrical switch according to the invention, each turn is formed by a thin lamella of significant height extending in a rectangle.

Thus, when the spiral-shaped fixed contactor element is traversed by an electric current, it produces an electromagnetic field in a direction normal to the plane of the turn. The movable contactor element which advantageously extends longitudinally in a direction parallel to the plane of the turn, is then subjected to a Laplace force of significant value oriented perpendicularly to its length in the direction of the contact zones of the fixed contactor elements. . Furthermore, the coil extending in a rectangle shape, its size is reduced, which reduces the overall size of the electrical switch.

Advantageously, the lamella constituting said fixed contact member comprises on at least a part of its length a return oriented towards the other fixed contactor element.

Thus, the presence of this return makes it possible to reduce the size of the turn formed by the fixed contacting element without diminishing the value of the electromagnetic field induced by the latter.

According to another advantageous characteristic of the electrical switch according to the invention, each contact zone of each fixed contacting element extends in a plane comprising the directions of the electromagnetic field and the axis passing through the two contact zones.

Advantageously, the movable contactor element comprises two rivets adapted to cooperate with two rivets arranged on each contact zone of each fixed contactor element.

Thus, the contact surfaces between the movable contact member and the contact areas comprise a calibrated area so that the repulsion forces to be countered have values that can be approximated.

Preferably, each fixed contactor element has a shape adapted, during the passage of the current, to create, in the space in which is located said movable contactor element, a uniform electromagnetic field.

Advantageously, the two turns formed by the fixed contacting elements are arranged coaxially and parallel to one another and are separated from each other by a distance equal to the width of the openings which they delimit internally. in a position called Helmholtz.

For the record, so-called Helmholtz coils form a device consisting of two circular turns of the same radius, parallel, and placed coaxially at a distance from each other equal to their radius. By circulating an electric current in these turns, a magnetic field is created in their vicinity which has the particularity of being relatively uniform. This device has the advantage of being efficient while being inexpensive.

Here, the turns are not circular, for reasons of space, but they are arranged in the position of Helmholtz, so that their performances are almost identical to those of circular turns.

Thus, the electromagnetic field created by the turns has a maximum value.

• la direction du champ électromagnétique est orthogonale à la direction de l'axe passant par les deux zones de contact ; et
• l'élément contacteur mobile est réalisé dans un matériau conducteur non magnétique.

Other advantageous and non-limiting characteristics of the electrical switch according to the invention are the following:

• the direction of the electromagnetic field is orthogonal to the direction of the axis passing through the two contact zones; and
• the movable contactor element is made of a non-magnetic conductive material.

Advantageously, each of the fixed and mobile contactor elements is made of copper.

Advantageously finally, the fixed contact elements are identical.

Thus, the manufacturing cost of the electrical switch is decreased.

DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT

The following description with reference to the accompanying drawings given as non-limiting examples, will make it clear what the invention is and how it can be achieved.

• la figure 1 est une vue schématique en coupe longitudinale d'un commutateur électrique selon l'invention ;
• la figure 2 est une vue éclatée en perspectives des éléments contacteurs fixes et mobile du commutateur électrique de la figure 1 ;
• la figure 3 est une vue schématique assemblée des éléments contacteurs fixes et mobile de la figure 2 ;
• la figure 4 une vue schématique des éléments contacteurs fixes et mobile de la figure 3 illustrant des lignes de champ électromagnétique ; et
• la figure 5 est une vue schématique assemblée d'une variante de réalisation des éléments contacteurs fixes et mobile de la figure 3.

In the accompanying drawings:

• Figure 1 is a schematic longitudinal sectional view of an electrical switch according to the invention;
• Figure 2 is an exploded perspective view of the fixed and movable contact elements of the electrical switch of Figure 1;
• Figure 3 is an assembled schematic view of the fixed and movable contactor elements of Figure 2;
• Figure 4 is a schematic view of the fixed and movable contactor elements of Figure 3 illustrating electromagnetic field lines; and
• FIG. 5 is an assembled diagrammatic view of an alternative embodiment of the fixed and movable contactor elements of FIG. 3.

Figure 1 schematically shows an electrical switch 1 to be connected to two branches of an electrical circuit to open or close.

This electrical switch 1, here a modular apparatus, comprises a housing 2 in the form of a rectangular wafer, in which are arranged two fixed contactor elements 10, 20 and a movable contactor element 30 which is controlled in position by means control unit 40 for electrically connecting the two fixed contact elements 10, 20.

The housing 2 has a bottom wall 2A and a front face accessible to a user, and four side walls, two main.

Advantageously, as shown more particularly in FIG. 2, the two fixed contactor elements 10, 20 have an identical shape adapted, during the passage of an electric current in the electrical switch 1, to create an electromagnetic field B. More precisely, each fixed contact element 10, 20 has a first portion 10A, 20A intended to be connected to a branch of said electric circuit, and a second portion in the form of a turn 10B, 20B.

The first parts 10A, 20A of the fixed contact elements each consist of a thin strip extending in a plane parallel to the bottom wall 2A of the housing 2, along the same axis V but in opposite directions.

The turns 10B, 20B are each constituted by a thin slat having a large section height. Each lamella extends in a plane parallel to the main lateral faces of the casing 2, and forms a square loop defining a square central opening. The planes in which the two turns 10B, 20B extend are therefore parallel to each other and are separated from each other by a distance equal to the width of the central openings that the turns delimit internally.

Each turn 10B, 20B thus has four straight branches including a first lower leg 13A, 23A which is fixed to the bottom wall of the housing 2 and which is connected to the first portion 10A, 20A of the corresponding fixed contactor element 10, 20 .

For this purpose, the free end of this first branch has an elbow oriented towards the other fixed contacting element 10, the upper edge of which is connected to the first part 10A, 20A of the corresponding fixed contact element 10, 20.

The fourth branch 13B, 23B of each turn extends to near the first branch 13A, 23A so that each turn is almost closed. The end of this fourth branch 13B, 23B is also bent and extends in a plane parallel to the bottom wall 2A of the housing 2, in the direction of the other fixed contact element 10, 20. This bent end then forms a contact zone 11, 21 facing towards the front of the housing 2.

In other words, the two turns have forms of rectangular loops, coaxial and separated from each other by a distance equal to the width of the central openings which they delimit internally. This distance corresponds here to the distance separating the first branch of the fourth branch of each turn.

The movable contactor element 30 forms a rectangular lamella whose greatest length extends in a direction of axis V parallel to the bottom wall 2A of the housing 2 and the plane of the turns 10B, 20B. It is arranged between the two turns 10B, 20B. More precisely, the two turns being arranged facing one another, they delimit between them a space in which is disposed the movable contactor element 30.

The two ends of the movable contactor element 30 and the contact areas 11, 21 of the fixed contact elements 10, 20 are each pierced with an opening accommodating a rivet 12, 22, 32 fixed by welding.

These rivets are adapted to bear against each other when, as shown in Figure 3, the movable contact member 30 comes into contact with the fixed contact elements 10, 20.

Advantageously, each of the fixed contactor elements 10, 20 and mobile 30 is made of a non-magnetic conductive material such as copper.

The rivets are in turn made of silver to limit the resistive losses at the contact points between the rivets 12, 22, 32 of the fixed switching elements 10, 20 and mobile 30.

As shown more particularly in FIG. 1, the control means 40 of the electrical switch 1 comprise a base 43 fixed to the movable contactor element 30 and extending longitudinally from this movable contactor element towards the front face of the housing 2.

The control means 40 further comprise an axis 41 which is pivotally mounted between the two main side walls of the housing 2, close to its front face, and which has two stable angular positions.

This axis 41 has on its cylindrical wall two tabs 41A, 41B spaced angularly from one another, including a first tab 41A protruding from the front face of the housing 2 to be manually manipulated by a user. The other tab 41B is connected by a rod 42 to the base 43 so as to transform a rotational movement of the axis 41 into a translation movement of the base 43 towards the bottom wall 2A of the housing 2.

In a stable position of the axis 41, the movable contactor element 30 is in contact with the two fixed contactor elements 10, 20, and in the other, it is out of contact.

Finally, the control means 40 comprise a return spring 44 placed in compression between the bottom wall 2A of the housing 2 and the movable contactor element 30.

According to an alternative embodiment of the invention, as shown in FIG. 5, the slats which form each turn 10B ', 20B' comprise over at least a part of their length a return 15, 25 directed towards the other fixed contactor element 10 ', 20'.

More specifically, here, the first lower leg of each turn 10B ', 20B' is folded over its entire length in a plane parallel to the bottom wall 2A of the housing 2 to form a flange which is fixed to the same bottom wall.

Each fixed contactor element 10, 20 then has a lower height and therefore a smaller footprint without its electromagnetic characteristics are substantially modified.

Anyway, to close the electrical contact between the two fixed contact elements 10, 20, the user rotates the axis 41 so that the base 43 exerts a normal support on the movable contact member 30 so that its two rivets 32 come into contact with each of the rivets 12, 22 of the fixed contact elements 10, 20.

The description of the operation of the electrical switch will be described with reference to FIGS. 3 and 4.

In normal operation, when a so-called moderate current passes through the electrical switch 1, this current flows in one of the two turns 10B, 20B, travels the moving contactor element 30 from one of its ends to the other, then passes in the other of the two turns 10B, 20B.

The passage of the current in the rivets 12, 22, 32 is concentrated in a small section, which causes a necking of the current and then generates secondary electromagnetic fields at these rivets. These secondary electromagnetic fields create repulsive forces Fr tending to push the movable contactor element 30 out of contact with the stationary contact elements 10, 20.

Moreover, still in normal operation, the passage of the current in each fixed contactor element 10, 20 generates, as shown more particularly in FIG. 4, a uniform electromagnetic field B between the two turns 10B, 20B, whose field lines are directed in the space defined between the two turns, in a direction W orthogonal to the plane of the turns.

The movable contactor element 30, which is disposed in this space, is exposed to this electromagnetic field B. However, since it is traversed from one of its ends to the other by an electric current, it is subjected to a force Laplace called attraction force F, directed towards the bottom wall 2A of the housing 2. This attraction force F has the effect of attracting the movable contact element 30 in contact with the fixed contact elements 10, 20.

These attraction forces F and repulsion Fr retain in normal operation moderate values compared to the values of the mechanical forces generated by the control means 40 and the values of the forces of gravity.

On the other hand, when the value of the current flowing through the electric switch 1 increases abruptly, for example during a short-circuit, the repulsion forces Fr take very large values. They are advantageously countered by the attraction force F which also increases proportionally to the square of the value of the current flowing through the moving contactor element 30.

The different rivets 12, 22, 32 therefore remain in contact with each other so that no electric arc damaging to the electric switch 1 is created.

To open the contact, the user can act on the axis 41 in order to put the moving contact element 30 out of contact with the fixed contact elements 10, 20.

The present invention is not limited to the embodiments described and shown, but the skilled person will be able to make any variant within his mind.

Claims (11)

Electric switch (1) comprising two fixed contact elements (10, 20; 10 ', 20') and a movable contact element (30) adapted to electrically connect two contact regions (11, 21) of the two fixed contact elements (10, 20; 10 ', 20') located on an axis (V), the two fixed contact elements (10, 20; 10 ', 20') having turns shapes (10B, 20B; 10B ', 20B') arranged in the movable contact element (30) having a lamella-like shape which is arranged between the two stationary contact elements (10, 20, 10 ', 20') and whose greatest length is extends parallel to the turns (10B, 20B; 10B ', 20B'), the two fixed contact elements (10, 20; 10 ', 20') being adapted, when the current flows, to create, in the space in which is located said moving contactor element (30), an electromagnetic field (B) oriented in a direction (W) different from that of the axis (V) passing through the two zones of co ntact (11, 21), to create on the movable contact element (30) an attraction force (F) directed towards said contact areas (11, 21). Electrical switch (1) according to the preceding claim, characterized in that each turn (10B, 20B; 10B ', 20B') is formed by a thin strip of high height extending in a rectangle. Electrical switch (1) according to the preceding claim, characterized in that the lamella constituting said fixed contacting element (10 ', 20') comprises on at least a part of its length a return (15, 25) directed towards the other element fixed contactor (10 ', 20'). Electrical switch (1) according to one of the preceding claims, characterized in that each contact region (11, 21) of each fixed contact element (10, 20, 10 ', 20') extends in a plane comprising the directions (W) of the electromagnetic field (B) and the axis (V) passing through the two contact zones (11, 21). Electrical switch (1) according to one of the preceding claims, characterized in that the movable contactor element (30) comprises two rivets (32) adapted to cooperate with two rivets (12, 22) arranged on each contact zone (11). 21) of each fixed contact element (10, 20; 10 ', 20'). Electrical switch (1) according to one of the preceding claims, characterized in that each fixed contact element (10, 20, 10 ', 20 ') has a shape adapted, during the passage of the current, to create, in the space in which is located said movable contactor element (30), a uniform electromagnetic field (B). Electrical switch (1) according to the preceding claim, characterized in that the two turns (10B, 20B; 10B ', 20B') formed by the fixed contact elements (10, 20; 10 ', 20') are arranged coaxially and in parallel relative to each other and are separated from each other by a distance equal to the width of the openings they delimit internally, in a position called Helmholtz. Electrical switch (1) according to one of the preceding claims, characterized in that the direction (W) of the electromagnetic field (B) is orthogonal to the direction of the axis (V) passing through the two contact zones (11, 21). Electrical switch (1) according to one of the preceding claims, characterized in that the movable contact element (30) is made of a non-magnetic conductive material. Electrical switch (1) according to one of the preceding claims, characterized in that each of the fixed (10, 20; 10 ', 20') and movable (30) contact elements is made of copper. Electrical switch (1) according to one of the preceding claims, characterized in that the fixed contact elements (10, 20; 10 ', 20') are identical.

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