EP0107167A1 - High sensivity striker - Google Patents

Abstract

Striker characterized in that the flux of the magnet (8) which is used for the sticking of a movable core (9) associated to a striking rod (11) has a high magnitude owing to the selection of a flat cylindrically wound magnet (8), thereby providing a high sticking force. Application to the control of circuit breakers.

Description

The present invention relates to an electromechanical striker intended to release, under the action of an electrical signal, mechanical energy previously stored in a banded spring. Such a striker is used for tripping a circuit breaker when a fault occurs, the electrical signal being produced from the results of electrical measurements carried out on the electrical circuit to be protected.

Such strikers have already been designed and produced. French patent 1,592,767 describes in particular a striker comprising a large spring maintained bandaged by a movable part under the action of mechanical energy of low value, this energy being produced by a second movable member having mechanical potential energy released by the action of an electric current.

The second movable member is a metal part compressing a small spring, held by a magnet and released by the action of a current in a coil which creates a magnetic flux opposing that of the magnet.

Such a striker has a number of faults.

The large number of parts it contains makes it a high cost device: moreover, it is difficult to obtain repetitive characteristics from one device to another, in particular because of the dispersions of the characteristics of the springs and of the complexity of the mechanical member for holding the percussion rod. Corrosion of parts can lead to operational incidents.

To overcome these drawbacks, the Applicant has designed and described, in French patent No. 7,738,236 filed on 19.12.77 having as its title "Striker", a striker of the type comprising a sliding percussion rod capable of assuming a fixed position in which the rod maintains a spring banded, the fixed position of the rod being obtained by magnetic attraction by means of a magnetic circuit with permanent magnet, and an electric coil allowing to cancel said attraction to allow the relaxation of the spring which drives the rod , the magnetic circuit comprising, on the one hand, two pole pieces threaded on said rod, one fixed in contact with the magnet, the other mobile, said pole pieces each comprising a shoulder respectively coming into contact with one and the other end of a spring threaded on the rod, and on the other hand, a housing surrounding the pole pieces and having a bottom in contact with the magnet and a cover provided with an orifice through which the rod protrudes, the rod having a bulge allowing it to join in translation with the moving part, said coil surrounding the pole pieces.

Such a striker has many advantages.

There are few parts, they are easy to machine and not subject to wear. The absence of a mechanical stage allows safe operation and reproducible performance, from one device to another. The cost price is modest.

The assembly is not very sensitive to corrosion.

Despite this, the aforementioned striker does not meet the new operating requirements imposed by the network operators.

On the one hand, operators require a level of energy developed by the moving part higher than that which can be obtained from strikers of the aforementioned types. This level is of the order of 30 N.cm, while the strikers of the aforementioned types only reach 10 N.cm.

Furthermore, the specifications assign a very low value to the current which must feed the striker coil during the operation of the striker; however, one must not, always according to the specifications required, multiply the ampere-turns of the coil, under penalty of having to increase the dimension of the latter beyond certain imposed limit values.

An object of the present invention is to produce a striker of small volume, releasing a large energy under the action of a low electrical energy.

Another object of the invention is to produce a striker with a high degree of insensitivity to shocks, so as not to inadvertently release its energy in the absence of an electrical signal. In particular, it is desired that the striker remains insensitive to any acceleration up to a value of 100 g.

The subject of the present invention is a striker intended to releasing mechanical energy under the action of an electrical signal, characterized in that it comprises a cylindrical metal shell with a bottom, made of material permeable to magnetic flux, the shell comprising inside an axial cylindrical pillar extending from the bottom over a part of the length of the housing, an electrical coil arranged coaxially with said pillar and surrounding it, a fixed cylindrical magnetic core coaxial with the housing, placed in the extension of the coil, having an outside diameter less than the inside diameter of the housing and having at one end a shoulder by which it is in contact with the inner lateral surface of the case, a magnet in the form of a magnetic rubber band wound in a cylinder and placed between the inner surface of the case and the lateral surface of the fixed core, a spring having the same axis as the coil and the bearing and bearing by a first end on a fixed element (bottom or fixed core), and a core m obile capable of sliding in the fixed core and having a shoulder on which a second end of the spring is supported, the core having a planar end coming to rest on the planar end of the pillar with a magnetic attraction force due to the passage of the lines of magnetic forces created by the magnet, said force opposing the opposing force of the spring, the magnetic core pushing, in its displacement which occurs when the flux of the magnet is counterbalanced by the flux of the coil, the force of the spring then becoming greater than the magnetic force, a percussion rod passing through a cover of the case of non-magnetic material.

• - la figure 1 est une vue en coupe axiale d'un percuteur selon l'invention, en position armée,
• - la figure 2 est une vue en coupe axiale du même percuteur après fonctionnement.
• - la figure 3 est une vue en coupe axiale du percuteur montrant les lignes de force dues à l'aimant,
• - la figure 4 est une vue en coupe axiale du percuteur montrant les lignes de forces dues à la bobine,
• - la figure 5 est une vue partielle en coupe axiale et la figure 6 une vue partielle en coupe transversale d'un percuteur selon une variante de réalisation des moyens de réglage.
• - la figure 7 est une vue en coupe axiale d'un percuteur selon une variante de réalisation de l'invention.

The invention will be better understood from the description below of a preferred embodiment with reference to the appended drawing in which:

• FIG. 1 is a view in axial section of a striker according to the invention, in the armed position,
• - Figure 2 is an axial sectional view of the same striker after operation.
• FIG. 3 is a view in axial section of the striker showing the lines of force due to the magnet,
• - Figure 4 is an axial sectional view of the striker showing the lines of force due to the coil,
• - Figure 5 is a partial view in axial section and Figure 6 a partial view in cross section of a striker according to an alternative embodiment of the adjustment means.
• - Figure 7 is an axial sectional view of a striker according to an alternative embodiment of the invention.

Figure 1 is an axial sectional view of a striker according to a first embodiment. The striker is entirely of cylindrical revolution.

It comprises a cylindrical housing 1 provided with a bottom 2 and a central cylindrical pillar 3 starting from the bottom and extending over a length of between 1/3 and half the length of the housing.

The housing, its bottom and the pillar are preferably made from a single piece of metal; the metal chosen is preferably a soft iron. A part of the magnetic circuit of low reluctance is thus obtained. If, however, a housing with a crimped bottom is produced, it will be necessary to increase the number of turns of the winding to take account of the additional reluctance due to the air gap. Between the housing and the bottom around the pillar are arranged, coaxially, a spring 4, one end 4A of which rests on the bottom 2, and a coil 5, which occupies the entire volume between the spring and the side wall of the housing. The length 1 of the winding and the length lo of the pillar are chosen so that the difference d of these lengths is between 1/15 and 1/4 of the length lo so that the underside of the pillar is inside the coil. Supply wires 5A from the coil pass through a bottom bore.

The magnetic circuit is completed by a fixed core 7, of cylindrical shape having an axial bore. The outside diameter of the core is less than the inside diameter of the case, except at one end or a shoulder 7A comes into contact with the inside wall of the case. The fixed core 7 abuts against a shoulder 1A of the internal wall of the housing at the end of the coil.

The thickness of the side wall of the housing is therefore smaller, but constant from the shoulder 1A to its end opposite the bottom.

In the annular space between the fixed core 7 and the housing 1, a magnet 8 is arranged in the form of a magnetized rubber band wound in a cylinder. The magnetization of the strip being perpendicular to the surface of the strip, the fact of having it wound in a cylinder determines a radial magnetization.

A movable core 9 is placed in the fixed core; it has a shoulder 9A on which the end 4B of the spring 4 bears.

This mobile core, made of soft magnetic material, has a flat end surface 9B which comes into contact with the end of the pillar 3.

The flux created by the magnet passes through the fixed core 7, the moving part 9, the pillar 3, the bottom 2 and closes by the side wall 1 of the case.

The induction crossing the surface 9B produces a bonding force of the core 9 on the pillar; this force is opposed to that of the spring which is banded in the position of FIG. 1.

The lines of force of the magnet 8 are partially closed by the shoulder 7A of the core 7 without crossing the surface 9B.

The arrangements which have just been described make it possible, under a relatively small footprint, to have a contact surface between the magnet 8 and the magnetic circuit much larger than in the strikers previously described. This results in a large magnetic flux, and therefore a great bonding force.

This deliberately overabundant bonding flux is shunted at the level of the shoulder 7A.

This reduces the. reluctance of the magnetic circuit for the lines of force generated by the coil (Figure 4), therefore the ampere-turns for controlling the opposing flux. This flux no longer has to pass through the magnet, the reluctance of which is high and close to that of air.

The large surface of the magnet with the magnetic circuit makes it possible to work at low levels of induction. The clearances and the surface states in this contact zone are therefore not critical.

Particular care is taken over the surface state of the shoulder 7A in contact with the housing so as to reduce the value of the reluctance of the corresponding air gap. Likewise, the end 9B of the movable core will be carefully adjusted and possibly nickel-plated, so that the air gap formed with the end surface of the pillar 3 has as low a reluctance as possible.

The striker is completed by a percussion rod 11, passing through a cover 13 of the housing made of non-magnetic material.

• en l'absence de courant dans la bobine, le noyau mobile 9 et le pilier 3 sont au contact, attirés magnétiquement dans le circuit magnétique comprenant l'aimant 8, le noyau fixe 7 et le noyau mobile 9 et se refermant par le fond 2 et la surface latérale du boîtier avec un très faible entrefer 9B. La force magnétique de contact est suffisante pour maintenir bandé le ressort 4.

The operation of the device is as follows:

• in the absence of current in the coil, the movable core 9 and the pillar 3 are in contact, attracted magnetically in the magnetic circuit comprising the magnet 8, the fixed core 7 and the movable core 9 and closing by the bottom 2 and the lateral surface of the housing with a very small air gap 9B. The magnetic contact force is sufficient to keep the spring 4 bandaged.

A pulse, of suitable direction, in the coil, creates a magnetic flux which, (figure 4) in the air gap 9B, is opposite to that created by the magnet (figure 3). The bonding force becomes lower than that of the spring which relaxes (FIG. 2) and drives by its shoulder 9A, the movable core 9 which itself drives the percussion rod 11.

The percussion rod controls the closing devices of the circuit breaker.

It will be noted that to make the device insensitive to shocks or vibrations and to prevent untimely operations, the mobile core is lightened as much as possible; it can also be separated from the rod 11 as shown in the aforementioned French patent 7,738,236.

The adjustment of the device (adjustments of the magnetic bonding and mechanical forces of the spring) is done by various means of which several examples are given below.

We. may group two or all of these means, or use only one.

The first means consists in adjusting the mechanical force of the spring 4 by placing at one of its ends one or more washers of calibrated thickness such as 30. The bonding force of the spring is measured by means of a dynamometer fixed to the movable core. The knowledge of the characteristics of the spring makes it possible to establish an abacus or a table giving the total thickness of washers to be put in place.

• Le flux généré par l'aimant 8 dans le circuit magnétique dépend entre autre de sa surface de contact avec le noyau fixé 7.

A second means of adjustment is based on the following considerations:

• The flux generated by the magnet 8 in the magnetic circuit depends among other things on its contact surface with the fixed core 7.

A means of adjusting the adhesive strength of the movable core 9 consists in gradually driving in the annular magnet 8 before the non-magnetic cover 13 is put in place.

The magnet is therefore gradually inserted around the core 7.

The tool may include a tube pushing the magnet and operated by a micrometric screw. A dynamometer pulls the core 9.

The position of the magnet is thus precisely determined, which gives the desired bonding force. This ring is then immobilized by means of one or more screws 21 passing through the wall 1 through a bore 20 and wedging the magnet on the core.

The non-magnetic cover 13, then placed, does not disturb the adjustment.

A third way is to adjust the bonding strength by means of additional shunt (see Figures 5 and 6).

One or more metallic pieces such as 40 are applied to the lower end of the fixed core. These pieces, made of soft iron, preferably in the form of a circular sector (see FIG. 6) serve as magnetic shunt by reducing the induction created by the magnet in the movable core 9 and reducing the reluctance for the flux created by the coil.

Of course for this the length of the magnet must be such that its lower end does not exceed or better, or slightly behind the inner end of the fixed core.

The apparatus may include a second coil, coaxial with the coil 5, for the electrical reset of the striker (not shown in the drawing).

Figure 7 shows, in section a striker according to a variant of achievement.

The fixed core 7 and the housing 1 form a single block obtained by any known means.

This arrangement makes it possible to overcome the reluctance dispersions between the core 7 and the housing 1. The required reluctance is no longer obtained by the hardly reproducible length of an air gap, but by the choice of the height L which is easy. adjust once and for all for a well-defined induction.

• - elle permet d'augmenter le diamètre de la bobine, donc le volume de cuivre et donc pour un même nombre d'ampère-tours, de diminuer le courant et l'énergie de commande,
• - elle permet d'utiliser un ressort à caractéristique plus plate, c'est-à-dire ayant une force de répulsion en position enclenchée plus faible pour une même force en position déclenchée.

The spring 8 is supported on the part. bottom of the fixed core 7. This arrangement has several advantages:

• - it makes it possible to increase the diameter of the coil, therefore the volume of copper and therefore for the same number of ampere-turns, to decrease the current and the control energy,
• - It allows the use of a spring with a flatter characteristic, that is to say having a repelling force in the engaged position, lower for the same force in the released position.

This reduction in spring repulsion force also results in a drop in operating amp-turns for the same resistance to mechanical shock.

The partial shunting caused by the magnetized turns of the spring is avoided, the lines of force passing through them in the vicinity of the junction of parts 3 and 9.

Claims (7)

1 / Striker intended to release mechanical energy under the action of an electrical signal, characterized in that it comprises a cylindrical metallic shoemaker (1) with a bottom (2), made of material permeable to magnetic flux, the shoemaker comprising inside, an axial cylindrical pillar (3) extending from the bottom over part of the length of the shoemaker, an electric coil (5) arranged coaxially with said pillar and surrounding it, a cylindrical fixed magnetic core (7) coaxial case, placed in the extension of the coil, having an outside diameter smaller than the inside diameter of the case and having at one end a shoulder (7A) by which it is in contact with the inner side surface of the case, a magnet (8) under shape of a magnetic rubber band wound in a cylinder and placed between the inner surface of the case (1) and the lateral surface of the fixed core (7), a spring (4) having the same axis as the coil and the bearing and supported by a first ex end (4A) on a fixed element (bottom or fixed core), and a movable core (9) which can slide in the fixed core and having a shoulder (9A) on which rests a second end of the spring, the core having a flat end (9B) coming to rest on the flat end of the pillar (3) with a magnetic attraction force due to the passage of the lines of magnetic forces created by the magnet, said force opposing the antagonistic force of the spring, the magnetic core pushing, in its displacement which occurs when the flux of the magnet is counterbalanced by the flux of the coil, the force of the spring then becoming greater than the magnetic force, a percussion rod (11) passing through a cover of the non-magnetic material housing. 2 / striker according to claim 1, characterized in that the spring (4) is disposed between the pillar (3) and the coil (5), and bears on the bottom (2) by its first end (4A). 3 / striker according to claim 2, characterized in that the housing 1 has a narrowing of the thickness of its side wall defining a shoulder (1A) against which the fixed core (7) abuts by its shoulder (7A). 4 / striker according to claim 1, characterized in that the fixed core (7) and the housing (1) form a single piece, the spring bearing by its first end (4A) on the core (7). 5 / striker according to one of claims 1 to 4, characterized in that the lateral surface of the housing comprises at least one threaded hole (20) in which is placed a screw (21) for locking the magnet (8). 6 / striker according to one of claims 1 to 5, characterized in that it comprises washers (30) for adjusting the force of the spring (4) disposed at one of its ends. 7 / striker according to one of claims 1 to 6, characterized in that metal parts (40) are placed in contact with the lower end of the fixed core (7) to form magnetic shunts. 8 / striker according to one of claims 1 to 7, characterized in that it comprises arranged coaxially with the coil (5), a second coil for the electrical resetting of the striker.

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