EP0054499B1 - Circuit breaker with neutral-line disconnection - Google Patents

Description

The present invention relates generally to circuit breakers.

As is known, a circuit breaker generally comprises a fixed contact, a movable contact urged by elastic opening means in the direction of a tripped position for which it is away from said fixed contact, and a control mechanism intended to ensure, on the one hand, the passage and the maintenance in the latched position of said movable contact, under the control of an engagement and release lever mounted movably between an engaged position and a tripped position, and, secondly on the other hand, the release of this movable contact, in response to the movable element of a triggering member, which can for example be a magnetic triggering member or a thermal triggering member.

Such a circuit breaker is inserted by its fixed and mobile contacts on the conductor to be checked, and, in a polyphase installation, it is in practice a phase conductor.

When such a phase conductor is for example the seat of a short circuit, the movable contact, which is therefore a phase contact, is commanded to open on intervention of the magnetic trip member; it is the same in the case of an overload, the triggering member then intervening being the thermal triggering member.

During such an opening of the mobile phase contact, which therefore occurs under load, it does not fail to develop, between this mobile phase conductor and the fixed phase conductor from which it moves away, an arc, which, to spare these contacts, is advantageously absorbed by a deionization chamber provided for this purpose in the vicinity of these.

It is now desirable, at least for certain applications, to be able to ensure, in multi-phase installations, not only a phase cut, as succinctly described above, but also a neutral sectioning.

The circuit breakers meeting this requirement therefore comprise, in addition to a fixed phase contact and a mobile phase contact, with the corresponding control means, as recalled above, at least one fixed neutral contact and a piloted mobile neutral contact. in closing and opening by an engagement and release lever mounted movable between an engaged position and a triggered position.

In a first type of embodiment already proposed to date, two separate modules are in fact associated, one for the phase contacts, and the other for the neutral contacts, and these separate modules are each controlled by a lever d individual engagement and triggering, that of the phase module being provided with a lateral extension by which it can control that of the neutral module in engagement, but not in triggering, and the latter being able to be controlled in triggering only using a tool.

Besides that such an embodiment is particularly bulky, it does not make it possible to ensure an automatic neutral sectioning during a phase cut, such sectioning having to be controlled manually.

In a second type of embodiment already known to date, the phase contacts and the neutral contacts are arranged in the same module, and they are controlled by the same engagement and tripping lever.

However, the arrangements there are such that the neutral disconnection occurs simultaneously with a phase cut, so that the corresponding conductors are loaded.

However, if, by a deionization chamber, as mentioned above, the phase conductors can be protected from the effects of the arc which then develop between them, it is hardly the same for the neutral conductors, because the small volume available in the single module concerned.

However, it has been proposed, in particular in German patent No. 674,919, to implement a disengageable locking member which, under the control of the movable element of a trigger member, in practice a magnetic trigger member, is movable between a locking position, for which it leaves the movable neutral contact free, and a locking position, for which, when tripped, that is to say when the mobile phase contact is released, it maintains temporarily in the engaged position, said movable neutral contact.

In practice, in this German patent n ° 674 919, the disengageable locking member thus implemented intervenes directly on the movable neutral contact.

This arrangement, even assuming that it is actually feasible, can in reality only be suitable if the assembly is part of a determined architecture, according to which, in particular, the movable element of the triggering member moves in the vicinity of the contact. moving neutral, without moving away from it when triggered.

Without the use of bulky deflection levers that are detrimental to performance, it cannot, however, be suitable for cases where the assembly is of a different architecture, and in particular where it is of the architecture described in the French patent n ° 2 226 745, according to which, on tripping, the movable element of the tripping member deviates from the area available for the implantation of neutral contacts.

The present invention generally relates to a provision for overcoming this difficulty.

More specifically, it relates to a circuit breaker, of the type comprising a fixed phase contact, a mobile phase contact urged by elastic opening means in the direction of a tripping position for which it is moved away from said contact. fixed phase, a control mechanism intended to ensure, on the one hand, the passage and the maintenance in the latched position of said mobile phase contact, under the control of a latching and tripping lever mounted movably between a latched position and a tripped position, and, on the other hand, the release of this movable phase contact, in response to the movable element of a tripping member, at least one fixed neutral contact, one movable neutral contact controlled in closing and opening by said engagement and trigger handle and a disengageable locking member which, under the control of the movable element of the trigger member, is movable between an unlocking position, for the which it leaves free the moving neutral contact, and a locking position, for which it temporarily maintains the latter in the latched position, this circuit breaker being characterized in that said locking member intervenes by means of the latching lever and triggering, said locking member leaving free said engagement and trigger lever when it is in the unlocked position, and temporarily holding it in the engaged position when it is in the locked position.

Thus, according to the invention, as long as, during a phase cut, the corresponding tripping member is excited, and this is in practice so as long as the arcing then arises between the phase contacts n ' is not dissipated, the engagement and tripping lever is blocked in the engaged position, and it itself maintains said engaged neutral contact in the engaged position.

It is only after dissipation of the arc having arisen between the phase contacts, and therefore only after complete opening of these, that the interlocking and tripping lever is released, and that it controls then in the triggered position this one.

Thus, a systematic systematic opening sequence is established between the phase contacts and the neutral contacts, which means that the neutral contacts can only be commanded to open after the phase contacts.

As a result, the neutral sectioning is not carried out under load, and the neutral contacts are thus provided, no destructive arc being able to develop between them.

In practice, the same module can advantageously contain the phase contacts and the neutral contacts, and therefore, the same interlocking and tripping lever be common to these.

This advantageously balances the requirements of a minimum space requirement and effective protection of the neutral contacts.

In addition, the arrangement according to the invention makes it possible to provide these advantages with a circuit breaker of the type described in French patent No. 2,226,745 without disturbing the recognized performance thereof.

In a preferred embodiment, the interlocking and tripping lever is connected to the movable neutral contact via a connecting rod and an elastic means, one of the roles of which is to maintain the desirable contact pressure between this movable neutral contact and the fixed neutral contact with which it is associated.

In practice, this contact pressure is important.

This is not only due to the structure of the device, but also to the electrodynamic phenomenon of repulsion developing between the fixed and mobile neutral contacts, during the passage of a current.

Indeed, this repulsion, almost zero under normal conditions, increases very rapidly as soon as a fault current appears, even though the neutral contact must be kept closed as long as the phase contact arc has not not absorbed.

By reaction, the connecting rod is then the object of a thrust, which could result in a disturbance of the operation of the assembly.

According to a development of the invention capable of overcoming this risk, the movable neutral contact passes through the yoke of a magnetic circuit of which it carries the armature.

Thus, according to the invention, as long as, during a phase interruption, the arc established between the fixed phase contact and the mobile phase contact has not dissipated, the aforementioned magnetic circuit remains energized and the contact mobile neutral is attracted by the corresponding cylinder head, which tends to keep it in the engaged position.

The thrust on the connecting rod is then relieved accordingly.

There is therefore thus, in this case, a particularly advantageous combination between the disengageable locking member and the magnetic circuit both associated with the neutral contact.

• la figure 1 est, suivant la ligne I-I de la figure 2, une vue en élévation-coupe d'un disjoncteur suivant l'invention, représenté en position enclenchée ;
• la figure 2 en est une vue en coupe transversale, suivant la ligne brisée II-II de la figure 1 ;
• les figures 3, 4 et 5 sont des vues reprenant pour partie celle de la figure 1 et concernant chacune respectivement diverses phases de fonctionnement du disjoncteur suivant l'invention entre sa position enclenchée et sa position déclenchée ;
• les figures 6 à 10 sont des vues respectivement analogues à celles des figures 1 à 5 et se rapportent à une autre forme de réalisation du disjoncteur suivant l'invention.

The characteristics and advantages of the invention will become apparent from the description which follows, by way of example, with reference to the appended schematic drawings in which:

• Figure 1 is, along line II of Figure 2, an elevational section of a circuit breaker according to the invention, shown in the engaged position;
• Figure 2 is a cross-sectional view along the broken line II-II of Figure 1;
• Figures 3, 4 and 5 are views partly taking that of Figure 1 and each respectively concerning various operating phases of the circuit breaker according to the invention between its engaged position and its tripped position;
• Figures 6 to 10 are views respectively similar to those of Figures 1 to 5 and refer to try another embodiment of the circuit breaker according to the invention.

The circuit breaker according to the invention will not be described here in all its details, only being more particularly made here the description of those of its elements, shown in accented lines in the figures, which are necessary for understanding the invention.

In practice, this is a circuit breaker, the mechanism of which is essentially essentially of the type described in particular in French patent No. 2,226,745 mentioned above.

Such a circuit breaker generally comprises a housing 10 formed, in the embodiment shown, of two shells 11, 11 'suitably facing one another and suitably connected to each other by screws or rivets.

This box 10 is equipped laterally, accessible from the outside, on the one hand, with two phase connection terminals 12A, 12B, shown in solid lines in FIG. 1, and on the other hand, with two connection terminals for neutral 13A, 13B, shown in broken lines in this figure 1.

Internally, it contains, in particular, a fixed phase contact 14, a mobile phase contact 15, a control mechanism 16, detailed below, a magnetic trip member 17, and a thermal trip member 18.

It also contains at least one fixed neutral contact, and in practice two fixed neutral contacts 19A, 19B, and one movable neutral contact 20.

The fixed phase contact 14 forms one of the external plates of a deionization chamber 22, the other plates of which have not been shown in the figures.

The mobile phase contact 15 has, in its central region, a slot 23, and, in line with the latter, it carries, by two lateral wings 24, 24 ', a pin 25 mounted movably in grooves 26, 26' shells 11, 11 'of the housing 10.

It is mounted movable between an engaged position, for which, in FIG. 1, it is in contact with the fixed phase contact 14, and a tripped position, for which, in FIG. 5, it is at a distance therefrom.

Elastic opening means permanently urge it towards this triggered position.

In the embodiment shown, it is a spring 21 which bears on the housing 10.

The magnetic trip member 17 comprises a coil 27 and a core 28 mounted to move in the axis thereof, while the thermal trip member 18 is formed by a bimetallic strip carried by a plate 29 adjustable in position under the control of a screw 30 accessible from the outside.

By a braid 32, the phase connection terminal 12A is connected to one end of this bimetal strip, while the other end of the latter is connected by a braid 33 to the mobile phase contact 15.

By a copper plant, which will not be detailed here, the fixed phase contact 14 is connected to one of the ends of the coil 27 of the magnetic trip member 17, while the other end of this coil 27 is, similarly, connected to the phase connection terminal 12B.

The control mechanism 16 is intended to ensure, on the one hand, the passage and the maintenance in the engaged position of the mobile phase contact 15, under the control of an engagement and trigger lever 35, and, on the other hand, the release of this mobile phase contact 15, in response either to the mobile core 28 of the magnetic trip member 17, or, via this mobile core 28, to the bimetallic strip 18 constituting the thermal trip member 18, this bimetal strip having for this purpose its end disposed opposite said movable core 28, for action thereon.

In the embodiment shown, the engagement and trigger lever 35, which, in general, is movably mounted between an engaged position, FIG. 1, and a triggered position, FIG. 5, and which, for its control , projecting finger 40 accessible from the outside, is, by pins 42, 42 'which it has laterally, pivotally mounted in the shells 11, 11' of the housing 10.

By a torsion spring which will not be detailed here, it is permanently biased towards its triggered position.

In its central zone, it is largely hollowed out by a slot 43, and it is integral with two flanges 44, 44 ′ jointly forming a buttonhole 45.

At one of its ends, this buttonhole 45 has a development forming a locking notch 46.

In addition to the engagement and trigger lever 35 thus formed, the control mechanism 16 also comprises, on the one hand, a latching and locking lug 48, and on the other hand, a trigger lever 49.

The latching and locking lug 48 is engaged transversely in the buttonhole 45 of the engagement and release lever 35, and, at its ends, it is slidably mounted in grooves 50, 50 'of the shells 11, 11 'of the housing 10.

The trigger lever 49 is generally bent.

In the region of its elbow, it is pivotally mounted on the axis 25 carried by the mobile phase contact 15, passing through it through its slot 23.

On either side of this bend zone, the trigger lever 49 has two arms 52, 53.

The arm 52 is engaged with the movable core 28 of the magnetic trip member 17, its end, which for this purpose has a circular contour, being engaged in a slot 54 of this movable core 28.

The arm 53 presents, for cooperation with the latching and locking lug 48, a latching notch 55; moreover, in the embodiment shown, it includes an extension 56 which, for its guidance, is engaged in the slot 43 of the engagement and release lever 35.

In the embodiment shown, the fixed neutral contacts 19A, 19B, which are each respectively connected by a suitable copperware to the corresponding neutral connection terminals 13A, 13B, are opposite, and the movable neutral contact 20 associated with them has, overall, the shape of a jumper.

In the embodiment shown, this movable neutral contact 20 passes right through a movable spacer in the form of a cage 58, which is made of insulating material, and it is subjected to elastic means, a simple spring 59 in this form of realization, which are supported on this mobile spacer 58.

In the embodiment shown, the same interlocking and tripping lever is common to the mobile phase contact 15 and to the movable neutral contact 20, so that the interlocking and tripping lever driving the latter is constituted by the engagement and release lever 35 described above.

With this engagement and trigger lever 35 there is associated a disengageable locking member 60 which, under the control of the movable core 28 of the magnetic trigger member 17, is movable between an unlocking position, FIG. 1, for which it leaves free the moving neutral contact, and a locking position, Figure 3, for which it temporarily maintains it in the engaged position.

According to the invention, the disengageable locking member 60 intervenes by means of the engagement and trigger lever 35, said locking member 60 leaving said engagement and trigger handle 35 free when it is in position. unlocking, and temporarily holding it in the released position when it is in the locked position.

In practice, in the embodiment shown, this disengageable locking member 60 forms a pawl pivotally mounted in the housing 10, by a pin 61, and comprises two spouts 63, 64, one for the action of the movable core 28 of the magnetic trigger member 17, the other for action on the engagement and trigger lever 35.

The spout 63 therefore extends opposite the movable core 28 of the magnetic trip member 17, and this movable core 28 includes an extension 65 allowing it to act on this spout 63.

At the same time, for action of the spout 64, the engagement and trigger lever 35 has a shoulder 66, formed by means of a notch 67.

By a connecting rod 70, the spacer 58 carrying the movable neutral contact 20 is subjected to the interlocking and tripping lever 35.

In practice, in the embodiment shown, this connecting rod 70 is articulated, on the one hand, to the spacer 58, at one of its ends, by a lug 71 mounted pivotally in a bore 72 thereof, and, on the other hand, to the interlocking and tripping lever 35, by a lug 73 also pivotally mounted in a bore 74 thereof.

For the engaged position shown in FIG. 1, the hooking catch 55 of the release lever 49 is engaged with the hooking and locking catch 48, and the latter is engaged with the locking catch 46 of the engagement and tripping lever 35, so that, the control mechanism 16 being thus locked, the mobile phase contact 15 is kept in abutment against the fixed phase contact with which it is associated.

At the same time, the mobile spacer 58 carrying the mobile neutral contact 20 is in the low position, so that the spring 59 associated with this mobile neutral contact 20 applies this against the fixed neutral contacts 19A, 19B with which it is associated. .

The continuity of the phase and neutral conductors concerned is thus ensured.

If, for example, the phase conductor is the subject of a short circuit, the magnetic trip member 17 comes into action, so that its movable core 28 is controlled in movement, according to arrow F1 in the figure 1.

This results in a double effect, Figure 3: on the one hand the trigger lever 49 is escaping from the latching and locking lug 48, which unlocks the entire control mechanism 16, and, on the other hand, the pawl 60 is engaged, by its spout 64, with the shoulder 66 of the engagement and trigger lever 35, which temporarily maintains the latter in the engaged position.

The control mechanism 16 being unlocked, the mobile phase contact 15 passes into the triggered position, under the stress of the opening spring 21 which is associated with it, FIG. 4, and it drives with it the trigger lever 49.

During the transition to the tripped position of the mobile phase contact 15, a large electric arc arises between the latter and the fixed phase contact 14 from which it moves away.

However, jointly, until this arc is extinguished, the magnetic tripping member 17 remains excited, its coil 27 being traversed by a strong current due to this arc, which keeps the movable core 28 of this arc in the locked position. magnetic triggering member 17, and, by the latter, of the disengageable locking member 60, and which therefore keeps the engaging and triggering lever 35 in the engaged position.

The movable neutral contact 20 is therefore, throughout the duration of the arc in question, maintained in the closed position.

After extinction of said arc, the movable core 28 of the magnetic trip member 17 is no longer the object of any request, so that the engagement and trigger lever 35 is released.

Under the stress of its return spring, it switches to the triggered position, along arrow F2 in FIG. 5.

Driven by it the rod 70 in turn drives the movable spacer 58, and, by the lower part of the cage constituting the latter, the movable neutral contact 20, so that the latter moves away from the neutral contacts fixed 19A, 19B and goes into the open position, Figure 5, for which the continuity of the neutral conductor is in turn interrupted.

But, as will have been noted, the interruption of this continuity occurs after the interruption of phase conductor continuity, so that said conductors are no longer then in charge.

At the same time, for the triggered position of the engagement and trigger lever 35, the trigger lever 49 is again engaged with the latching and locking lug 48, by its latching notch 55, so that the control mechanism 16 is reset.

It is therefore sufficient, in order to bring the assembly into the engaged position, to bring the engagement and trigger lever 35 back into the engaged position, by tilting the latter in the opposite direction to that marked by the arrow F2 in FIG. 5.

When the phase conductor is subject to an overload, it is the thermal trigger member 18 which comes into action: the bimetallic strip which constitutes it acts on the movable core 28 of the magnetic trigger member 17, and a triggering process similar to that described above develops.

In the embodiment shown in FIGS. 6 to 10, the mobile neutral contact 20 is pivotally mounted around a fixed axis 87.

According to the invention, and as is better visible in FIGS. 6 and 7, it crosses the yoke 81 of a magnetic circuit of which it carries the armature 82.

More precisely, over a part of its length, this cylinder head 81 has a U-shaped profile, and it therefore comprises two wings 83, 83 'and a sole 84, and, jointly, the movable contact 20 extends at least partly between said wings 83, 83 'of the cylinder head 81, and the frame 82 which it carries projects laterally to cooperate with them.

In the embodiment shown, the armature 82 is fixed to the movable contact 20 by spot welding, and, at its ends 85, 85 ', the sole 84 of the cylinder head 81 is made integral with the housing 10, by engagement in two grooves 86, 86 'thereof.

As before, for the control of the movable neutral contact 20 by the interlocking and tripping lever 35, a connecting rod 70 is articulated at one of its ends to said interlocking and tripping lever 35.

In the embodiment shown in FIGS. 6 to 10, the mobile spacer to which the connecting rod 70 is articulated at its other end by a lug 71, is a lever 89 which is pivotally mounted in a bore 72 of this connecting rod 70, and which is itself articulated on the housing 10, by a pin 90 pivotally mounted in bores 91, 91 'of the shells 11, 11' thereof.

In addition, in this embodiment, the connecting rod 79 has, at its lower end, a notch 106, delimited by a stop 107, and the frame 82 secured to the contact 20, which for this purpose has an extension 82A, is engaged by the latter in said notch 106 of the connecting rod 70.

In the embodiment shown in FIGS. 6 to 10, the spring 59 is a torsion spring comprising two torsion branches 92, 92 ′ of opposite pitch, and, by these, it is mounted on the axis 90, in a recess 93 of the lever 89.

By a U-shaped middle portion 94, connecting its branches 92, 92 ', this spring 59 bears on the armature 82 of the magnetic circuit associated with the movable neutral contact 20, and by the end of these branches of twist 92, 92 ', it is supported on a shoulder 96 of the lever 89.

Thus, the spring 59 exerts pressure on the shoulder 96 of the lever 89, in the direction of the arrow C1 in FIG. 6, and on the frame 82, in the direction of the arrow C2 in this FIG. 6.

In the embodiment shown in Figures 6 to 10, a U-shaped rod 100 is further pivotally mounted on the engagement and trigger lever 35 by a bending 101, which engages in a bore 102 of the flange 44. Its opposite end 103, which forms the base of the U, and which extends in the vicinity of the mobile phase contact 15, is left free, but it can act on said mobile phase contact 15, being guided laterally by a lug 104 of the shells 11, 11 'and the arm 53 of the trigger lever 49.

For the rest, the embodiment shown in Figures 6 to 10 is identical to that shown in Figures 1 to 5.

Its operation is also similar to that previously described.

But, in addition, during the transition to the triggered position of the mobile phase contact due for example to a short circuit, the magnetic circuit consisting of the yoke 81 and the armature 82 is all the more excited that, due to the electric arc having then arisen between the phase contacts 14, 15, the current passing through it has increased and is then very high. The force of attraction which results therefrom between this cylinder head 81 and this armature 82 increases in proportion, and, applied to the movable neutral contact 20, it contributes at least partially to the maintenance in the engaged position thereof, thereby relieving as much the force which must also be applied to this movable neutral contact 20, via the lever 89 and the spring 59, the connecting rod 70.

After extinction of said arc, the armature 82 linked to the movable neutral contact 20 is released from any magnetic attraction, and, the engagement and tripping lever 35 being itself released by the disengageable locking member 60, the connecting rod 70 comes, by its stop 107, to tear off and drive this movable neutral contact 20, as did previously, in the embodiment shown in FIGS. 1 to 5, the lower part of the cage then constituting the movable spacer 58 associated, for passage into the tripped position of this neutral contact mobile 20. Such an arrangement is favorable to safety insofar as the assured neutral sectioning is “fully visible”: when the engagement and tripping lever 35 is in the tripped position, the movable neutral contact 20 is then also with certainty in the triggered position.

During resetting, the end 103 of the rod 100 abuts on the mobile phase contact 15 and delays the closing of the latter, so that, by the action of the spring 59, the mobile neutral contact 20 finds it engaged before him.

During a manual tripping maneuver, the end 103 of the rod 100 very quickly pushes the phase contact 15, so that, again, the opening of the latter, thus accelerated, takes place before that of the movable neutral contact 20.

Instead of being pivotally mounted, the engagement and trigger lever 35 could be slidingly mounted.

In this case, the disengageable locking member associated with it can be very simply formed directly by an extension of the movable core 28 of the magnetic trigger member 17.

At the same time, instead of being hinged to such an interlocking and tripping lever, the connecting rod 70 to which the movable neutral contact 20 is subjected can cooperate with a cam integral with this interlocking and tripping lever 35.

Finally, instead of being constituted by an axially movable core, the movable element of the magnetic trip member may as well be, for example, a pallet mounted pivotally or movable parallel to itself, provided that this element, in deployed position, when the magnetic trip member is energized, either able to act on the disengageable locking member according to the invention, either directly or indirectly.

Claims (12)

1. A circuit breaker of the type comprising a fixed phase contact (14), a movable phase contact (15) which is urged by resilient opening means (21) in the direction of a tripped position in which it is spaced from said fixed phase contact (14), an actuating mechanism (16) which is intended on the one hand to cause said movable phase contact (15) to move into and be maintained in the closed position under the control of a closing and tripping hand lever (35) which is mounted movably between a closed position and a tripped position, and, on the other hand, to cause liberation of said movable phase contact (15), in response to the movable element (28) of a tripping member (17), at least one fixed neutral contact (19), a movable neutral contact (20) which is pilot-controlled in respect of closing and opening by said closing and tripping lever (35) and a disengageable locking member (60) which, under the control of the movable element (28) of the tripping member (17), is movable between an unlocking position in which it leaves free the movable neutral contact (20) and a locking position in which it temporarily holds same in a closed position, characterised in that said locking member (60) comes into action by way of the closing and tripping lever (35), said locking member (60) leaving free said closing and tripping lever (35) when said locking member is in the unlocking position and holding same temporarily in a closed position when said locking member is in a locking position.

2. A circuit breaker according to claim 1 wherein said disengageable locking member (60) is mounted pivotally characterised in that said disengageable locking member (60) comprises two catch portions (63, 64), one for action of the movable element (28) of the tripping member (17) and the other for action on the closing and tripping lever (35).

3. A circuit breaker according to either one of claims 1 and 2 characterised in that, for action of the disengageable locking member (60), the closing and tripping lever (35) comprises a shoulder (66).

4. A circuit breaker according to any one of claims 1 to 3 wherein the movable neutral contact (20) is subjected to the force of resilient means (59) which bear against a movable support member (58, 89), characterised in that said movable support member (58, 89) is coupled to a link rod (70) which is subjected to the action of the closing and tripping lever (35).

5. A circuit breaker according to claim 4 wherein the closing and tripping lever (35) is mounted pivotally characterised in that the link rod (70) is pivotally connected on the one hand to said closing and tripping lever (35), at one of the ends thereof, and on the other hand, to the movable support member (58, 89), at the other of the ends thereof.

6. A circuit breaker according to either one of claims 4 and 5 characterised in that the movable support member (58) is in the form of a cage and the movable neutral contact (20) passes therethrough whereby, upon tripping, the link rod (70), by said movable support member (58), can entrain said movable neutral contact (20).

7. A circuit breaker according to either one of claims 4 and 5 characterised in that the link rod (70) has an abutment (107) for entraining the movable neutral contact (20) upon tripping.

8. A circuit breaker according to any one of claims 1 to 5 and 7 characterised in that the movable neutral contact (20) passes through the yoke (81) of a magnetic circuit of which it carries the armature (82).

9. A circuit breaker according to claim8 characterised in that, over at least a part of its length, the yoke (81), is of U-shaped configuration and therefore comprises two limbs (83, 83') and a base (84), the movable neutral contact (20) extending at least partially between said limbs of said yoke (81) and said armature (82) projecting laterally to co-operate with said limbs.

10. A circuit breaker according to claims 7 and 9 in combination characterised in that the abutment (107) on the link rod (70) defines a recess (106) in said link rod (70), in which is engaged the armature (82) carried by the movable neutral contact (20).

11. A circuit breaker according to any one of claims 4, 5 and 7 characterised in that the movable support member (89) is a lever which is pivotally connected to the link rod (50) and to the housing (10).

12. A circuit breaker according to any one of claims to 11 characterised in that pivotally mounted on the closing and tripping lever (35) is a link member (100), the end (103) of which is free and extends in the vicinity of the movable phase contact (15) for acting thereon.

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