EP0044757A1 - Method for reducing the radio static interference generated by the operation of an electric switch - Google Patents

Abstract

1. Method of reducing the radioelectric interferences generated upon operation of an electrical interrupter with non-abrupt opening and closing of the contacts, characterized in that an interrupter is selected which is such that the surface of at least one of the contacts (3, 5) is provided with a rought zone formed of a multiplicity of craters (9).

Description

The present invention relates to an electrical switch with contact break at negligible level of radio interference.

A large number of electrical devices are controlled by contact break switches. Known contact breakers usually include contacts with a smooth smooth surface. During the closing of these contacts, the movable contact approaches the fixed contact and when the ignition distance is reached, an arc occurs and generates parasites as long as the contacts are not completely closed. When these contacts open, an arc appears as soon as a small spacing of the contacts has occurred. This arc gives rise to parasites and only extinguishes when the movable contact is distant from the fixed contact by a length greater than the ignition distance. Thus the switching operations performed by these known switches usually produce annoying radio interference. In some known switches, the contacts are provided with a divided surface in the form of heterogeneous striations or asperities in points. This embodiment makes it possible to avoid to a certain extent a bonding or a welding of these contacts but cannot prevent an annoying creation of radioelectric disturbance.

For these reasons, in order to eliminate these disturbances as much as possible, expensive anti-parasite devices are usually associated with these known switches to make them acceptable in their use.

The aim of the present invention is to avoid these drawbacks and makes it possible to produce an economical electrical switch with contact breakage having a negligible level of radio interference.

According to the invention, an electrical switch with contact breakage having a negligible level of radioelectric disturbances comprises at least one of the contacts provided in its surface with a rough area, constituted by a multitude of craters.

• - la figure 1, représente une vue partielle et schématique d'un interrupteur électrique à ouverture et à fermeture de contacts non brusques, réalisé selon l'invention, montrant les deux contacts dans leur position de fermeture ;
• - la figure 2, représente une autre vue partielle et schématique de l'interrupteur de la figure 1, montrant les deux contacts dans leur position d'ouverture ;
• - la figure 3, représente à une autre échelle une vue partielle et schématique du contact fixe de l'interrupteur de la figure 1 ;
• - la figure 4 représente à une autre échelle une vue partielle et schématique du contact mobile de l'interrupteur de la figure 1 ;
• - la figure 5, représente un diagramme des parasites engendrés par l'ouverture des contacts d'un interrupteur de même type que celui de la figure 1, équipé de contacts classiques à surface unie et lisse ou surface divisée ;
• - la figure 6, représente un diagramme des parasites engendrés par la fermeture des contacts de l'interrupteur dont le diagramme de parasites d'ouverture est illustré dans la figure 5 ;
• - la figure 7, représente un diagramme des parasites d'ouverture des contacts de l'interrupteur de la figure 1, et
• - la figure 8, représente un diagramme des parasites de fermeture des contacts de l'interrupteur de la figure 1.

To better understand the invention, there are described below, a number of embodiments illustrated by the accompanying drawings,

• - Figure 1 shows a partial and schematic view of an electrical switch for opening and closing non-abrupt contacts, produced according to the invention, showing the two contacts in their closed position;
• - Figure 2 shows another partial and schematic view of the switch of Figure 1, showing the two contacts in their open position;
• - Figure 3 shows on another scale a partial and schematic view of the fixed contact of the switch of Figure 1;
• - Figure 4 shows on another scale a partial and schematic view of the movable contact of the switch of Figure 1;
• - Figure 5 shows a diagram of the parasites generated by the opening of the contacts of a switch of the same type as that of Figure 1, equipped with conventional contacts with smooth and smooth surface or divided surface;
• - Figure 6 shows a diagram of the parasites generated by the closing of the switch contacts whose opening parasite diagram is illustrated in Figure 5;
• FIG. 7 represents a diagram of the parasites for opening the contacts of the switch in FIG. 1, and
• FIG. 8 represents a diagram of the parasites for closing the contacts of the switch in FIG. 1.

In the example illustrated in Figures 1 and 2, the switch 1 comprises a base 2 in which are mounted a fixed contact 3 on a fixed support 4 and a movable contact 5 on an elastic blade 6 for example that of the known type, provided a central tab. The opening and closing of these two contacts 3 and 5 are performed by an insulating finger 7 which controls the position of the elastic blade 6 carrying the movable contact 5. A screw 8 mounted in the base 2, acts as a stop and ensures the adjustment of the spacing of the movable contact 5 by relative to the fixed contact 3, in their opening.

According to an important characteristic of the invention, at least one of the fixed 3 and movable 5 contacts has a surface comprising at least one rough area. This rough surface area has a multitude of small craters 9. These craters 9 have a dimension of the order of several microns to a few hundred microns. Thanks to this particular surface condition of these contacts 3 and 5, their opening or closing generates radiographic disturbances only to a negligible level. A comparative test illustrated in FIGS. 5 to 7 makes it possible to highlight the advantages provided by the switches produced according to the invention compared with known switches, provided with contacts of the conventional type with a smooth and smooth surface and divided surface. FIGS. 5 and 6 show the parasites due to the separation or rupture of the contacts of the type with a smooth smooth surface and a surface divided in the form of heterogeneous ridges or asperities in points while FIGS. 7 and 8 illustrate the parasites generated by the separation of contacts with a rough surface consisting of craters according to the invention.

In the example illustrated, the craters on the surface of these two contacts 3 and 5 are obtained by stamping. When forming these contacts by stamping, an anvil with imprint produced by electro-erosion is used.

The contacts thus formed can be either welded to their support as shown in FIG. 3 or crimped onto the latter as shown in FIG. 4.

The insulating finger 7 which actuates the contacts 3 and 5 can be controlled manually or automatically. In the case of a thermostatic switch, the finger 7 is controlled by means of a capsule filled with a thermodilatable fluid.

Claims (4)

1. Electric switch with contact break at negligible level of radio interference, having contacts (3, 5) having a rough surface characterized in that it comprises at least one of the contacts (3, 5) provided in its surface with a rough area formed by a multitude of craters (9). 2. Switch according to claim 1, characterized in that it comprises contacts (3, 5) having in their surface craters of the order of several microns to a few hundred microns. 3. Switch according to claim 1, characterized in that it comprises contacts (3, 5) provided in their surface with craters (9) obtained by stamping. 4. Switch according to claim 3, characterized in that it comprises contacts (3, 4) having in their surface craters obtained by means of a matrix anvil provided with an imprint made by electro-erosion.

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