EP0061382B1 - Electromagnetic relay with indifferent working position - Google Patents

Description

The present invention relates to an electromagnetic relay comprising a relay box consisting of a relay base and a relay cover, in which is placed at least one switch provided with two electrical contacts disposed respectively on a support and a movable blade connected to a third electrical contact, each switch being disposed in a switch box consisting of a switch base and a switch cover made of non-magnetic material, said blade being able to tilt from the first to the second contact or vice versa under the action of an external magnetic field created by a permanent magnet and a control coil, arranged above the switch cover, each switch housing being associated with a magnet, said coil being provided of a magnetic circuit having a first part passing through the coil.

Such relays are known and are used in many applications. Generally, these relays are designed to operate in a particular position when it comes to relays with wet mercury contacts.

As described in the article by Messrs JA Legrand and M. Frances entitled "New construction for a mercury wetted switch for operation in any position" - Proceeding of the 10th international conference on Electronic contact phenomena - 25/29 August 1980, volume 2 page 625 to 634, it is often desirable to have relays wetted with mercury whose operating position is indifferent. In this article, it is described in particular how a relay provided with a switch with wet mercury contacts can be controlled using a permanent magnet associated with a coil provided with a magnetic circuit. The permanent magnet is arranged above the housing containing the first and the second contact against which the movable blade comes to bear. The permanent magnet gives each of these fixed contacts an opposite magnetic polarity. By sending an electric pulse having a determined direction in the coil, a magnetic pulse is created which polarizes the moving blade in a direction identical to the polarization of the fixed blade on which it rests. There is therefore an effect of repulsion of this fixed blade and attraction by the other fixed blade of opposite polarization which causes the movable blade to switch from one contact to the other. Conversely, by sending a pulse of opposite sign in said coil, the movable blade switches again against the first contact.

The presence of this permanent magnet notably makes it possible to considerably improve the shock immunity of such a relay, avoiding untimely tilting from one position to the other during an impact. However, it can be seen that the control power generated in the coil is relatively large when the latter is provided with a usual magnetic circuit. However, in many uses, it is desirable to have as low a control power as possible. This problem has been resolved in document FR-A-2029737, in which it is proposed to close the magnetic circuit around the switch so as to reduce the dimensions of the control coil. However, the assembly described in this patent does not allow satisfactory mechanical fixing in a housing. In addition, it is necessary to provide isolation means between the magnetic circuit and the switch connections.

The relay according to the invention is characterized in that said magnetic circuit comprises a second U-shaped part comprising three branches, a first branch, a second branch extending the first and a third branch extending the second and which is fixed under said switch base which is made of material conducting the magnetic field to ensure the closing of the external magnetic field, this second U-shaped part making on the one hand each switch housing, the permanent magnet associated with it and the coil and ensuring on the other hand the closing of the external magnetic field so as to reduce the control power of the switch, the second U-shaped part of the magnetic circuit coming to rest by its second branch on the relay base , while its first branch comes into contact with a flange made by the relay base in the vicinity of an output contact passing through said relay base.

With such a structure of the magnetic circuit, it has been found that the simple fact of adding this second U-shaped part to the magnetic circuit made it possible to increase the gain in control power by a factor of approximately 2 compared to the same circuit. magnetic not closed. Furthermore, the shape of this circuit makes it possible to make the coil, the magnet and the housing substantially integral, which thus form a compact assembly. Furthermore, this second part of the magnetic circuit will preferably rest on the base of the relay providing good positioning of the assembly in the relay housing.

It is understood that such a structure applies to any type of movable blade relay disposed in a housing, as well as to any type of monostable or bistable operation of said relay. The monostable or bistable operation of the relay according to the invention depends on the relative position of the switch contacts and of the poles of the permanent magnet. When these are arranged symmetrically with respect to the fixed contacts of the switch, we then obtain a bistable operation, while if we shift on one side or the other said permanent magnet, we will get a return blade automatically in one position or the other. The reliability of the contacts is further improved by using switches with wet contacts containing mercury or any equivalent liquid. However, it has been found that to obtain good repetitive operation of the switch under the action of the magnetic field outside tick, it was necessary to provide the fixed contacts of the switch with small non-magnetic plates arranged projecting from said contact. Indeed, there is a phenomenon of attraction of two magnetic poles of the same nature when they are in intimate contact with each other. It is therefore necessary to leave a certain distance between the flexible blade and the movable contacts to avoid this phenomenon of attraction.

Finally, the invention obviously applies to the case where several switches are arranged in the same assembly to form a relay: in this case, the magnetic circuit according to the invention will be based on the switch housings. Also, several coils and a plurality of switches may be arranged in the same assembly and form a single relay, seen from the outside, while remaining within the scope of the invention.

• la fig. 1, un interrupteur muni d'une bobine de commande selon l'art connu,
• la fig. 2, un relais muni de l'interupteur commandé selon la fig. 1,
• la fig. 3, un interrupteur muni d'un circuit magnétique de commande selon l'invention,
• la fig. 4, un relais muni d'un dispositif selon la fig. 3,
• la fig.5, un schéma de contacts électriques munis de plaquettes amagnétique,
• la fig. 6, un exemple de réalisation de l'invention avec plusieurs interrupteurs composant le même relais.

The invention will be better understood with the aid of the following embodiments given without limitation, together with the figures which represent:

• fig. 1, a switch provided with a control coil according to the known art,
• fig. 2, a relay provided with the switch controlled according to FIG. 1,
• fig. 3, a switch provided with a magnetic control circuit according to the invention,
• fig. 4, a relay provided with a device according to FIG. 3,
• fig.5, a diagram of electrical contacts fitted with non-magnetic plates,
• fig. 6, an embodiment of the invention with several switches making up the same relay.

In fig. 1, there is shown a switch provided with a magnet and a control coil according to the prior art. Such a device is described for example in the article mentioned above. It comprises a switch 1 consisting of a base 2 and a cover 3 arranged thereon. Inside the base where generally prevails or a controlled atmosphere 8, are arranged two fixed contact supports 4 and 5 extended by the contacts 24 and 25 and respectively crossing the base 2 through glass beads 12 and 13 then ending with the posts 10 and 9. A movable blade 6 in contact with mercury 7 can switch from contact 24 to contact 25 and vice versa. The base 2 is connected to a contact electrode 11. On the cover 3 of the switch 1 is disposed a permanent magnet 14 on which is placed a coil 15 supplied with current by 17 and 18 and in which is placed a magnetic circuit 16 of linear shape well known to those skilled in the art.

• L'aimant permanent 14 positionné ici de façon sensiblement symétrique par rapport aux contacts 4 et 5, place la lame mobile sur l'un ou l'autre des contacts 4 ou 5 (sur le contact 4 sur la fig. 1). Sous l'action d'un champ magnétique créé par la bobine alimentée par une impulsion via 17 et 18, on crée un champ magnétique qui polarise la lame mobile 6 dans un sens identique à celui du contact sur lequel elle repose et opposé à celui de l'autre contact. Sous l'action de ce champ extérieur, la lame mobile 6 vient alors s'appuyer sur le contact fixe 25. Compte tenu de la disposition symétrique de l'aimant permanent 14, ladite lame 6 reste au contact de 25. Ainsi que cela a été expliqué ci-dessus, une disposition asymétrique de l'aimant 14 par rapport aux contacts 24 et 25 provoquerait un fonctionnement monostable de ce relais (et donc un retour de la lame 6 sur le contact 24 lors de la suppression du champ de la bobine).

The operation of this device is easy to understand:

• The permanent magnet 14 positioned here in a substantially symmetrical manner with respect to the contacts 4 and 5, places the movable blade on one or the other of the contacts 4 or 5 (on the contact 4 in FIG. 1). Under the action of a magnetic field created by the coil supplied by a pulse via 17 and 18, a magnetic field is created which polarizes the moving blade 6 in a direction identical to that of the contact on which it rests and opposite to that of the other contact. Under the action of this external field, the movable blade 6 then comes to bear on the fixed contact 25. In view of the symmetrical arrangement of the permanent magnet 14, said blade 6 remains in contact with 25. As has explained above, an asymmetrical arrangement of the magnet 14 with respect to the contacts 24 and 25 would cause a monostable operation of this relay (and therefore a return of the blade 6 on the contact 24 during the suppression of the field of the coil ).

In fig. 2 is shown a relay using the device described in FIG. 1. In this figure, the same elements as those of the previous figure have the same references. The relay 100 includes a base 102 and a cover 101 as well as contact tabs, only some of which have been shown, such as 103 and 104, the device of FIG. 1 is placed horizontally as shown in this figure. The operation of this relay is identical to what has been explained with the aid of fig. 1.

In fig. a device similar to FIG. 1, but provided with a magnetic circuit according to the invention. In this figure, the same elements as those of the previous figures have the same references. The magnetic circuit 16 is extended by a magnetic circuit 106 having the shape of a U, the branch 107 of which is connected to 16 and is extended by the vertical branch 108 then the horizontal branch 109 which is fixed under the base 2 of the switch 1. The operation of this device is strictly identical to that of the device of FIG. 1. However, it can be seen that such a structure allows a power gain of a factor of 2.

For this purpose, the example below clearly shows this gain in power: We take a relay as shown in fig. 1 with a coil, capable of switching the switch under 140 A x turns, 12 mm in height and comprising a magnetic core 16 of 1.5 mm in diameter. All other things being equal, using a U-shaped magnetic circuit comprising a branch 106 of 25 mm long and two branches 107 and 109 of 5 mm long and of the same section as the preceding magnetic core 16, the command is performs under the same conditions under 100 A x turns, i.e. a power gain of the order of 2.

In fig. 4, the device of FIG. 3 mounted in a relay box identical to that described in fig.2. In this fig. 4, the same elements as those of the preceding figures therefore bear the same references. It should be noted simply that the U-shaped magnetic circuit 106 is supported by its arm 108 on the base 102 of the relay, while its vertical arm 107 comes into contact with the flange 111 made by the base in the vicinity of the output contact 104. This allows better mechanical fixing of the device of FIG. 3 in the relay box.

In fig. 5, there is shown schematically the contacts of the switch 1 provided with non-magnetic plates allowing repetitive operation of the relay according to the invention. The electrical contacts 24 and 25 are respectively coated with an electrically conductive non-magnetic plate 113 and 112, having a slight overflow relative to said contacts. In the figure, the plates 112 and 113 have an identical overflow equal to e. In practice, it has been found that this distance e is preferably between and 0.05 mm and 1 mm and preferably 0.1 mm to 0.5 mm. The operation of the switch provided with its plates is as follows: the movable blade 6 has its end which is for example a north pole, the contact 25 also being a north pole. If the two contacts 25 and 6 were in intimate contact with each other, we know that there would be an attraction of these two blades despite the presence of the external magnetic field H. In order to improve the functioning of the relay, there are therefore non-magnetic blades 112 and 113 which maintain a certain distance between the contacts 24 and 25 respectively and the blade 6.

Fig. 6 shows a relay according to the invention with two switches and a U-shaped magnetic circuit. The same elements as those in the previous figures have the same references. The two housings 1 and 121 are arranged head to tail facing the magnetic core 16. The housing 121 is electrically isolated from the core 16 (generally conductive) by the insulation 123 which also separates the magnet 120 from said core 16. Each housing is well understood, as in the previous examples, an electrically conductive box of the type used for encapsulating transistors, in particular TO 5 type boxes, the dimensions of which make it possible to implement the invention. The magnetic circuit 106 is supported by its branches 107 and 109 respectively on the base of the housings 1 and 129. An electrical insulator 122 is placed between the branch 109 and the base of 121 to avoid short-circuits. The covers of the housings 1 and 121 are made of non-magnetic material, the bases being of magnetic material. As before, a power gain of the order of 2 is obtained.

Claims (4)

1. An electromagnetic relay comprising aτelay housing (100) constituted by a relay basis (102) and a relay cap (101), in which is placed at least one switch (1) supplied with two electrical contacts (24, 25) each disposed on a respective support (4, 5), and a movable reed (6) connected to a third contact (7), each switch (1) being disposed in a switch housing constituted by a switch basis (2) and a switch cap (3) made of non-magnetic material, said reed (6) being able to pivot from the first to the second contact or vice-versa under the action of an outside magnetic field created by a permanent magnet and a control coil (15) placed above the switch cap (3), each switch housing being associated to a magnet (4), said coil (15) being supplied with a magnetic circuit having a first portion (16) passing through the coil, characterized in that said magnetic circuit comprises a second portion of U-shape with three branches, a first branch (107) connected to one end of the first portion (16), a second branch prolonging the first branch (107) and a third branch (109) prolonging the second branch (108) and being fixed below said switch basis (2), the latter being of a material which conducts the magnetic field for ensuring the closing of the outer magnetic field, said second U-shaped portion making on the one hand integral each switch housing (19), the permanent magnet (14) associated to it and the coil (15), and ensuring on the other hand the closing of the outer magnetic field so as to reduce the control power of the switch (1), the second U-shaped portion of the magnetic circuit bearing by its second branch (108) on the relay basis (102), whereas the first branch (107) comes into contact with a rim (111) made by the basis of the relay (102) in the vicinity of an output contact (104) passing through said relay basis (102).

2. An electromagnetic relay according to claim 1, characterized in that each electrical contact (24, 25) of the switch (1) made of magnetic material is covered with a contact piece (112, 113) made of non-magnetic material.

3. An electromagnetic relay according to claim 2, characterized in that the contact piece (112, 113) of non-magnetic material ensures a distance between the fixed contacts and the mobile reed of at least 0,05 mm.

4. An electromagnetic relay according to one of the preceding claims, characterized in that it comprises two switches (1, 121) controlled by the same coil (15), the seocnd U-shaped portion of the magnetic circuit (106) bearing by its two lateral branches (107, 109) on the housing of each switch (1, 121), whereby electrically insulating pieces (122, 123) are disposed between the magnetic circuit (16, 106) and the housings for preventing electric short-circuits.

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