Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H71/00—Details of the protective switches or relays covered by groups H01H73/00 - H01H83/00
  • H01H71/10—Operating or release mechanisms
  • H01H71/12—Automatic release mechanisms with or without manual release
  • H01H71/24—Electromagnetic mechanisms
  • H01H71/32—Electromagnetic mechanisms having permanently magnetised part
  • H01H71/321—Electromagnetic mechanisms having permanently magnetised part characterised by the magnetic circuit or active magnetic elements
  • H01H71/322—Electromagnetic mechanisms having permanently magnetised part characterised by the magnetic circuit or active magnetic elements with plunger type armature

Definitions

• 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.
• 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 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.
• 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 protrudes the rod, 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 hardly 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.
• the subject of the present invention is a striker intended to release mechanical energy under the action of a.
• electrical signal characterized in that it comprises a cylindrical metal casing with a bottom, made of material permeable to magnetic flux, the casing comprising inside an axial cylindrical pillar extending from the bottom over a part of the length of the casing, an electric 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 interior lateral surface of the housing, a magnet in the form of a magnetic rubber band wound in a cylinder and placed between the interior surface of the housing and the lateral surface of the fixed core, a spring having the same axis as the coil and the bearing and supported by a first end on a fixed element (bottom or fixed core), and a movable core capable of sliding in the fixed core and having a shoulder on which a second end of the spring rests, the core having a planar end which comes to rest on the planar end of the pillar with
• FIG. 1 is a view in axial section of a striker according to the invention, in the armed position,
• FIG. 1 is an axial sectional view of the same striker after operation.
• - Figure 3 is an axial sectional view of the striker showing the lines of force due to the magnet
• - Figure 4 is an axial sectional view of the striker showing las lines of force due to the coil
• FIG. 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 adjusting means.
• - Figure 7 is an axial sectional view of a striker according to an alternative embodiment of the invention.
• FIG. 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 between 1/3 and half the length of the housing.
• the housing, its bottom and the pillar are preferably made of a single piece of metal; the metal chosen is preferably a soft iron. A part of the low reluctance magnetic circuit 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 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 of the coil pass through a bore in the bottom.
• 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.
• 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 housing.
• 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 large surface of the magnet with the magnetic circuit makes it possible to work at low levels of induction.
• the games and the surface conditions in this contact zone are therefore not critical. Particular attention is paid to the surface condition of the faces of the shoulder 7A in contact with the housing so as to reduce the value of the reluctance of the corresponding air gap.
• the end 9B of the movable core will be carefully ground and possibly nickel-plated, so that the air gap formed with the end surface of the pillar 3 has as little 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.
• 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.
• the mobile core is lightened at the maximum; it can also be separated from the rod 11 as shown in the aforementioned French patent 7,738,236.
• the adjustment of the device is done by various means of which several examples are given below. We can group two of these means, or all three, 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.
• 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 pushing 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 comprise a tube pushing the magnet and operated by a micrometric screw.
• a dynamometer exerts traction on 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 shape of a circular sector (see FIG. 6) serve as a magnetic shunt by reducing the induction created by the magnet in the movable core 9 and reducing the reluctance for 1s flux created by the coil.
• 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 reluctance required 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.
• the spring 8 is supported on the lower part of the fixed core 7. This arrangement has several advantages:

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• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Electromagnets (AREA)
• Breakers (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=9278453

Family Applications (1)

Country Status (5)

Cited By (1)

Families Citing this family (6)

Citations (4)

• 1982
  • 1982-10-21 FR FR8217607A patent/FR2535107A1/fr active Granted
• 1983
  • 1983-10-17 WO PCT/FR1983/000208 patent/WO1984001662A1/fr unknown
  • 1983-10-17 JP JP58503283A patent/JPS59501928A/ja active Granted
  • 1983-10-18 DE DE8383110368T patent/DE3369422D1/de not_active Expired
  • 1983-10-18 EP EP19830110368 patent/EP0107167B1/fr not_active Expired

Patent Citations (4)

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