WO2015170354A1

WO2015170354A1 - Moulded case circuit breaker and method for assembling the same

Info

Publication number: WO2015170354A1
Application number: PCT/IT2015/000108
Authority: WO
Inventors: Roberto Boffelli
Original assignee: Bticino S.P.A.
Priority date: 2014-05-07
Filing date: 2015-04-20
Publication date: 2015-11-12
Also published as: CN105097369A; EP3140846A1; CN105097369B; RU2016142719A3; RU2016142719A; TR201815193T4; CL2016002813A1; EP3140846B1; RU2660912C2

Abstract

A moulded case circuit breaker is described comprising at least a first contact branch (C1) comprising at least a first contact element (P1) and at least a first support element (S1) of the first contact element (P1), at least a first connection terminal (T1) electrically connected to, or integrated into, the first support element (S1); - an actuating mechanism (15) of the first support element (S1) adapted to move the latter so that the first contact element (P1) can be moved from a rest position to a working position and vice versa; - a first case (10) housing and supporting the first contact branch (C1) and the actuating mechanism (15); - a second contact branch (C2) comprising at least a second contact element (P2), adapted to be contacted by the first contact element (P1) when this is in the working position, at least a second support element (S2) of the second contact element (P2) and at least a second connection terminal (T2) electrically connected to, or integrated into, the second support element (S2); - a second case (20) coupled to the first case (10) housing and supporting the second contact branch (C2); - at least one fastening element (31, 32) adapted to couple and maintain the first (10) and the second (20) case integral to each other.

Description

"MOULDED CASE CIRCUIT BREAKER AND METHOD FOR ASSEMBLING THE SAME"

DESCRIPTION

The present disclosure refers to the technical field of electrical installations and, more particularly, regards a moulded case circuit breaker and a method for assembling the same.

A moulded case circuit breaker, as opposed to a circuit breaker of the so-called "open" type, has a housing made of insulating material that, in addition to providing protection against external agents, supports the internal circuits and mechanisms of the circuit breaker and terminals for connection to the external line and load circuits.

Currently, moulded case circuit breakers are generally used as protective devices in the fields of electrical distribution, industrial automation and advanced service fields to interrupt currents having, for example, a value up to 3200 A. Some manufacturers in the industry provide the market different types of moulded case circuit breakers with different functions, since, for example, the market requires various types of moulded case circuit breakers, each of which can be equipped or not with an internal residual current protection device. One possible type of moulded case circuit breaker is, for example, an automatic circuit breaker with magnetothermic type trip system, which, in practice, comprises only electromechanical devices. Another possible type of moulded case circuit breaker is, for example, an automatic circuit breaker with electronic type trip system, wherein the trip system is interlocked with an electronic control. Therefore, a single manufacturer must have different production lines, which results in relatively high product production and management costs.

Alternatively, the belong to the state of the prior art includes solutions that associate to a moulded case circuit breaker an external residual current protection module connectable to one of the two arrays of electric connection terminals of the moulded case circuit breaker, which makes the final assembly relatively bulky because, for example, there is a significant increase in the height of the final assembly compared to the height of only the moulded case circuit breaker. The solution described above is also relatively expensive as it requires the purchase of two separate units, each having their own case, which must be electrically interconnected.

The purpose of the this disclosure is to provide a moulded case circuit breaker such as to overcome the drawbacks mentioned above with reference to the moulded case circuit breakers of the prior art.

This purpose is achieved through a moulded case circuit breaker as generally defined in claim 1. Preferred and advantageous embodiments of said moulded case circuit breaker are defined in the appended dependent claims.

The invention will be better understood from the following detailed description of a particular embodiment, provided by way of example and, therefore, in no way limiting, in relation to the accompanying drawings, wherein:

- Figure 1 is a tridimensional view of a general embodiment of a moulded case circuit breaker;

- Figure 2 is a side plan view of the moulded case circuit breaker of Figure 1 showing a first and second case coupled together;

Figure 3 is a three dimensional view of the moulded case circuit breaker of Figure 1, in which is predominantly visible the upper face of the circuit breaker;

- Figure 4 is a side sectional view of a first particular embodiment of the moulded case circuit breaker of Figure 1;

- Figure 5 is a side sectional view of the moulded case circuit breaker of Figure 4, in which the two cases ά

are shown uncoupled from each other;

- Figure 6 is a tridimensional view of the first case of the general embodiment of the moulded case circuit breaker of Figure 1 and the first particular embodiment of Figure 4;

- Figure 7 is a tridimensional view of the second case of the particular embodiment of the moulded case circuit breaker of Figure 4;

- Figure 8 is a tridimensional view of a variant embodiment of the second case of Figure 7 ;

Figure 9 is a tridimensional view showing, respectively, a first contact branch and a second contact branch of the moulded case circuit breaker of Figure 1 in an opening operating configuration;

- Figure 10 is a tridimensional view showing the first and second contact branch of Figure 9 in a closing operating configuration;

- Figure 11 is a side sectional view of a second particular embodiment of the moulded case circuit breaker of Figure 1;

- Figure 12 is a side sectional view of the moulded case circuit breaker of Figure 11, in which the two cases are shown uncoupled from each other;

- Figure 13 is a tridimensional view of the second case of the moulded case circuit breaker of Figure 11; and

- Figure 14 is a tridimensional view of a variant embodiment of the second case of Figure 13.

In the figures, equal or similar elements will be indicated by the same reference numbers.

With reference to the accompanying figures, a non- limiting embodiment of a moulded case circuit breaker is shown, globally indicated with 1. In the particular example shown in the figures and which will be described below, the moulded case circuit breaker 1 is a multipolar circuit breaker and, in particular, a tripolar circuit breaker. According to a variant embodiment, the moulded case circuit breaker 1 is a four-pole circuit breaker. However, the teachings of this description also extend to a moulded case circuit breaker 1 having a different number of poles, for example unipolar or bipolar.

From now on we will refer, without thereby introducing any limitation, to the case where in the circuit breaker 1 is, as in the example shown in the figures, a multipolar moulded case circuit breaker.

With reference to Figures 1 and 2, the moulded case circuit breaker 1 comprises a first case 10, made of an electrically insulating material such as, for example, a resin, and a second case 20 coupled to the first case 10, also made of an electrically insulating material such as a resin. The above cases 10 and 20 are formed, for example, by injection moulding, in two pieces separate from each other.

With reference to Figures 5 and 12, the moulded case circuit breaker 1 comprises at least one fastening element 31,32 adapted to couple and maintain the first 10 and the second 20 cases stably fixed to each other. It is preferable to provide a plurality of fastening elements 31,32. According to an embodiment, the at least one fastening element 31,32 is adapted to removably couple the two cases 10,20, and, for example, is embodied by one or more screws 31,32 or in one or more pairs of screws 31,32. In an alternative embodiment, the at least one fixing element 31,32 is an irreversible fixing element and, for example, is embodied by at least one rivet. In the particular example shown in the figures, a plurality of fastening elements are provided in the form of screws or pairs of screws 31 that, passing through the first case 10, are inserted in suitable seats 42 of the second case 20 and in the form of screws or pairs screws 32 that, passing through first the second housing 20, are inserted in suitable seats 41 provided in the first housing 10.

According to a possible embodiment, the first case 10 comprises a first case portion 11 and a second case portion 12 made in two separate pieces, for example by injection moulding, and coupled together. The second case portion 12 is operatively interposed between the first case portion 11 and the second case 20. Preferably, the first case 10 comprises a lid 13 removably coupled to the first case portion 11. The lid 13 is, for example, coupled to the first case portion 11 by means of screws that, passing through the lid 13, are inserted in respective screwing seats provided in the first case portion 11.

According to an advantageous embodiment, the first case 10 comprises a front face 4 and a rear face 5 opposite to the front face and the second case 20 is coupled to the first case 10 from the side the said rear face 5. For the purposes of this description "front face" means the face of the first case 10 that, during normal use of the circuit breaker, is facing the operator and is opposite to an installation wall, for example the wall of an electrical switchboard. Preferably and not limited to, the rear face 5 of the first case 10 has a protruding portion 6 and a recessed portion 7 that define a step, and the second case 20 is arranged above said protruding portion 6 at the recessed portion 7 for levelling said step and imparting a general outer shape of rectangular parallelepiped to the assembly formed by the first case 10 and the second case 20. In the particular embodiment shown in the figures, the first case 10 has a section that, in a plane perpendicular to the rear face 5, is essentially L-shaped; in this regard, note L-shape of the first case 10 visible in Figures 5 and 12. Furthermore, the second case 20 is preferably shaped like a half-shell with a quadrangular plan or generally quadrangular.

The moulded case circuit breaker 1 also comprises a manual control device 3, such as a rotary control lever 3. The manual control device 3 can be alternately moved between two positions corresponding, respectively, to an operational state of opening and an operational state of closing of the moulded case circuit breaker 1. The manual control device 3, for example, passes through an opening provided in the first case 10. In the particular example shown, the manual control device 3 passes through an opening defined in the first portion 11 of the first case 10 and an opening defined in the lid 13. Preferably, the manual control device 3 projects from the front face 4 of the first case 10. The manual control device 3 can also be actuated by a motorized device coupled to the moulded case circuit breaker, for example as shown in Figure 5 of European patent EP 2001036 Bl.

The manual control device 3 is operatively connected to an actuating mechanism housed and supported by the first case 10 and adapted to determine the switching of the moulded case circuit breaker 1 between the two operating states of opening and closing. Different types of actuating mechanisms are known to an expert in the field that can be used in a moulded case circuit breaker 1 and, for this reason, it is considered superfluous to dwell on this mechanism in more detail in this description. Generally, an actuating mechanism may include levers, elastic elements, connecting rods, a rotary actuating mechanism 15 (visible in Figures 9 and 10) as well as, for example, described in European patent EP 2259278 Bl, etc. From now on, the actuating mechanism will be indicated with the reference 15 to indicate the whole through one of its parts.

With reference to Figures 9 and 10, the moulded case circuit breaker 1 comprises at least a first contact branch CI comprising at least a first contact element PI and at least a first support element SI of the first contact element PI, at least a first connection terminal Tl electrically connected to, or integrated into, the first support element SI. The actuating mechanism 15 of the first support element SI adapted to move the latter so that the first contact element PI can be moved from a rest position (shown in Figure 9) to a working position (shown in Figure 10) and vice versa. 1 r\

The first case 10 houses and supports the first contact branch CI and the actuating mechanism 15. In other words, the first case 10 houses and supports the first contact branch CI and the actuating mechanism 15.

Furthermore, the moulded case circuit breaker 1 comprises a second contact branch C2 comprising at least a second contact element P2 , adapted to be contacted by the first contact element PI when this is in the working position, at least a second support element S2 of the second contact element P2 and at least a second connection terminal T2 electrically connected to, or integrated into, the second support element S2. As can be clearly seen in Figures 7 and 8, the second case 20 houses and supports the second contact branch C2. In other words, the second case 20 performs a supporting function for the second contact branch C2.

In the case where, as in the example shown, the moulded case circuit breaker 1 is multipolar, the at least one first contact branch CI and the at least one second contact branch C2 each comprise a plurality of contact branches, each associated with a respective phase of the moulded case circuit breaker 1. However, in the case of a multipolar moulded case circuit breaker 1, it is convenient that the actuating mechanism 15 be common to the different contact branches and that it be controlled by a common actuating element 3.

According to a preferred embodiment, the first contact element PI and the second contact element P2 are pads made of a highly conductive material, such as sintered silver alloy.

According to an advantageous embodiment, the first connection terminal Tl and the second connection terminal T2 comprise two portions of bar conductor axially aligned with each other along an axis of alignment Z-Z. Preferably, said bar conductors bar are conductors with quadrangular and, preferably, rectangular section. For the purposes of this description "bar conductor" means a conductor with a cross-section such as to ensure a certain rigidity to the conductor as opposed to relatively flexible conductors such as wires, cables, or wire threads.

Preferably, as shown in Figures 9 and 10, the first support element SI is an electrically conductive arm rotatably hinged, directly or indirectly, to the first case 10 to be rotated about an axis of rotation between two angularly spaced positions corresponding respectively to the rest position and the working position of the first contact element PI. Clearly, these positions correspond respectively to the operating state of opening and to the operating state of closing of the moulded case 1?

circuit breaker 1. For example, the first support element SI is a conductive arm bound to the rotary actuating element 15 and the latter is rotatably hinged to the first case 10, is supported by it and is made of electrically insulating material. It is possible to provide that this bond between the conductive arm and the rotary actuating element 15 provides, in any case, and in a manner known per se, a possibility of residual movement of the rotary arm and, therefore, of the first support element SI with respect to the rotary actuating element 15, for example to recover the wear of the contact elements PI, P2, or to compensate for any misalignment.

In the case in which a plurality of first contact branches CI is provided, each of these is equipped with a first support element SI and all the first support elements SI are preferably bound to the same rotary actuating element 15 and to the same actuating mechanism.

Again with reference to Figures 9 and 10, according to an embodiment, the first contact branch CI comprises a bar conductor 18 having an end portion, for example, provided with a through hole, which is the first connection terminal Tl. For example, the terminal Tl is a part of, or is electrically ^■ connected to, a connecting terminal not shown in the figures. Preferably the bar conductor 18 is electrically connected to the first support element SI via a flexible conductive thread 16, directly or by interposition of a conductive fastening plate 17 to which one end of said flexible braid 16 is welded. In this latter case, the conductive fastening plate 17 is, for example, riveted to the bar conductor 18.

With reference to Figures 9 and 10, according to a possible embodiment, the second contact element P2 is a fixed contact element and comprises a pad and the second support element S2 comprises a bar conductor 28 fastened to said second case 20 and having a first end portion to which said pad P2 is welded and a second opposite end portion which represents said second connection terminal T2. In the embodiment shown in the figures, said bar conductor 28 is essentially hook-shaped. For example, the terminal T2 is a part of, or is electrically connected to, a connecting terminal not shown in the figures.

According to a possible embodiment, the second case 20 also comprises at least one block made of insulating material 22, for example removably coupled to the second case 20, placed below the second contact element P2 and below the end portion of the second support element which carries the second contact element P2 and having the function of stiffening said end portion and which is preferably adapted to clamp the second support element S2 against a wall of the second case 20, for example through a fastening element 23 in the form of a screw.

Furthermore, with reference to Figure 7, in a possible embodiment in which the moulded case circuit breaker 1 comprises at least one guidance element of the electric arc 24 made of C-shaped or U-shaped ferromagnetic material, for example of the type generally described in European patent EP 1998349 Bl, the block made of insulating material 22 allows maintaining such guidance element of the electric arc 24 in place. It is clear that, in such an embodiment, the second case 20 also serves as the support and fastening base for the guidance element of the electric arc 24. It should be noted that the difference between the embodiment of the second case 20 shown in Figure 7 differs from that of Figure 8 for the fact that, in the first, three guidance elements of the electric arc 24 are provided (the example shown being non-limiting relative to a three-pole moulded case circuit breaker) , not provided in the embodiment of Figure 8. The same applies to the embodiments of Figures 13 and 14, which will be described later.

According to a particularly advantageous embodiment, the first case 10 includes an arc extinguishing chamber 19 housing a deionization cell 8 and having an opening 9 facing towards the second case 20 and the second case 20 includes at least one compartment communicating with said extinguishing chamber 19 through said opening 9 adapted to receive the expansion of the gases developed upon the occurrence of an electric arc. In this way, the spaces available in the second case 20 are advantageously exploited for the expansion of the gases that develop upon the occurrence of an electric arc between the contact elements PI, P2, which implies an increase in the performance of the moulded case circuit breaker 1 in terms of breaking capacity and/or in terms of robustness over time to the wear phenomena related to electric arcs.

According to an embodiment, the first case comprises an automatic protection system with a trip system adapted to bring said first contact element Pi in the rest position upon detecting a condition of short-circuit or overcurrent. The body of knowledge of an expert in the field includes the various types of trip systems, both of the fully electromechanical type (automatic magnetothermic circuit breakers) and interlocked with an electronic control (automatic electronic circuit breakers). In this case, if the moulded case circuit breaker 1 includes a second housing 20 as shown in Figures 4, 5, 7 and 8, the moulded case circuit breaker 1 is an automatic, magnetic or electronic circuit breaker without a residual current protection system. If, 1 f.

instead, one wants to produce an automatic, magnetic or electronic moulded case circuit breaker with a residual current protection system, it is sufficient to couple a second case 20 to the first case 10 that, as in the examples shown in Figures 11 to 14, houses and supports a measuring toroid 50 adapted to detect a current imbalance between the plurality of contact branches C2. It is clear, therefore, that if said measuring toroid 50 is operatively connected to said trip mechanism, protection system of the moulded case circuit breaker 1 is either of the magnetic or residual current type. In other words, the first case 10 is a single module that can be fitted with accessories in different ways and that, coupled to a second module that can be of different types and that is represented by second housing 20 and by what this supports, allows producing a wide range of types of moulded case circuit breakers.

Advantageously, the measuring toroid 50 may be connected to the trip device, directly or by interposition of an electronic control module housed in the first case, by passing at least two conductors, each connected to a respective terminal of the measuring toroid 50, from the second case 20 to the first case 10. For example, it is possible to provide one or more passage channels 51 (visible in Figure 6) that, passing through a wall of the first case 10, open onto the rear face 5 of the first case 10, preferably on the projecting portion 6 of this. To facilitate wiring, one can advantageously provide a removable lid 52 coupled to the rear face 5 of the first case 10.

Referring again to Figures 11-14, according to a possible embodiment wherein in the second case 20 a measuring toroid 50 is provided, it is possible to provide that each of the contact branches C2 housed in the second case 20 and supported by this, comprises a first bar conductor 28', a second bar conductor 28' ' and an electric connection element 28' ^{1 1} between the first 28' and second 28' ' bar conductor that crosses the measuring toroid 50. For example, as shown in Figures 13 and 14, the first 28' and second 28' ' bar conductor are fixed to the second case 20 by means of screws, and the third bar conductor 28' " ' is a rigid conductor bar having an end portion riveted, or otherwise attached and electrically connected, to the first conductor bar 28' and an opposite end portion, riveted, or otherwise attached and electrically connected, to the second conductor bar 28' ' . Also in this example one can provide insulating blocks 22 that are preferably interposed between the first 28' and second 28' ¹ bar conductor. Also in this case, such insulating blocks 22 stiffen the second support element S2 and, possibly, keep in place the guidance elements of the electric arc 24, if these are provided, as in Figure 13. In the examples of Figures 13 and 14, such insulating blocks 22 do not perform the function of fixing the second support S2 to the second case 20, contrary to what has been described for the examples of Figures 7 and 8.

So far, with reference to Figures 4 to 14, examples have been described in which the second support element S2, and therefore the second contact element P2, are rigidly fixed to the second case 20. Nevertheless, as regards the second case 20 and what is supported by it, it is also possible to provide embodiment variants wherein the second support element S2 comprises a movable arm adapted to allow a rotation of second contact element P2. In this way, it is possible to produce moulded case circuit breakers 1 with the desired performance in terms of selectivity, wherein targeted techniques are provided to limit the repulsive effect between the first contact element PI and the second contact element P2. See, in this regard, what is described in European patent application EP 2377134 Al . For example, it is possible to provide that :

the second support element S2 comprises a bar conductor rigidly fixed to the second case 20; 1 Ω

- said movable arm is rotatably hinged to said fixed bar conductor;

the second case 20 also includes at least one elastic element acting, by compression or traction, on said movable arm and configured to maintain, in a condition of regular operation of the circuit breaker 1, the second contact element P2 as close as possible to the first case 10.

In this way it is possible to further extend the range of moulded case circuit breakers that can be produces by coupling the second case 20 to the first case 10.

From the description just made, it is possible to understand how a moulded case circuit breaker 1 of the type described above fully achieves the intended purposes .

It should also be noted that the detailed description made above for the moulded case circuit breaker 1 also corresponds to the description of a method for assembling a moulded case circuit breaker 1 comprising the steps of:

- assembling together said first case 10, said first contact branch CI and said actuating mechanism 15;

- assembling together said second case 20 and said second contact branch C2; -7Π

- coupling said second case 20 to said first case 10 through said fastening elements 31, 32, which makes the two cases 10,20, stably connected to each other.

The aforementioned assembly method greatly reduces the production costs of a wide range of moulded case circuit breakers, with great benefit to both manufacturers and purchasers .

According to an embodiment, the aforementioned assembly method also includes a step of connecting at least one electrical signal cable between the first case and the second case by passing it inside said cases. In this way, it is possible, for example, to wire an element contained in the second case, such as, for example, the measuring toroid, to a trip or control device housed in the first case.

Obviously, a person skilled in the art, in order to satisfy contingent and specific needs, may make numerous modifications and variations to the moulded case circuit breaker 1, all however contained within the scope of the invention as defined by the following claims.

Claims

1. Moulded case circuit breaker (1) comprising:

- at least a first contact branch (CI) comprising at least a first contact element (PI) and at least a first support element (SI) of the first contact element (PI) , at least a first connection terminal (Tl) electrically connected to, or integrated into, the first support element (SI) ;

- an actuating mechanism (15) of the first support element (SI) adapted to move the latter so that the first contact element (PI) can be moved from a rest position to a working position and vice versa;

- a first case (10) housing and supporting the first contact branch (CI) and the actuating mechanism (15) ;

- a second contact branch (C2) comprising at least a second contact element (P2), adapted to be contacted by the first contact element (PI) when this is in the working position, at least a second support element (S2) of the second contact element (P2) and at least a second connection terminal (T2) electrically connected to, or integrated into, the second support element (S2);

- a second case (20) coupled to the first case (10) housing and supporting the second contact branch (C2);

- at least one fastening element (31, 32) adapted to couple and maintain the first (10) and the second (20) case stably fixed to each other.

2. Moulded case circuit breaker (1) according to claim 1, wherein the moulded case circuit breaker (1) is multipolar and wherein said at least first (CI) and second (C2) contact branch each include a plurality of contact branches, each associated to a respective electrical phase, and wherein said actuating mechanism (15) is common to the different branches.

3. Moulded case circuit breaker (1) according to any one of the previous claims, wherein said at least one first support element (SI) is rotatably hinged, directly or indirectly, to the first case (10) for being rotated about an axis of rotation between two angularly spaced positions corresponding respectively to the working position and the rest position of the first contact element ( PI ) .

4. Moulded case circuit breaker (1) according to any one of the previous claims, wherein the first connection terminal (Tl) and the second connection terminal (T2) comprise two portions of bar conductor axially aligned with each other.

5. Moulded case circuit breaker (1) according to any one of the previous claims, wherein the first case (10) comprises a front face (4) and a rear face (5) opposite to the front face and wherein the second case (20) is v..

O 2015/170354 PCT/IT2015/000108

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coupled to the first case (10) from the side of said rear face ( 5 ) .

6. Moulded case circuit breaker (1) according to claim

5, wherein the rear face (5) has a protruding portion (6) and a recessed portion (7) which define a step, and wherein the second case (20) is arranged above said protruding portion (6) at the recessed portion (7) for levelling said step and imparting a general outer shape of rectangular parallelepiped to the assembly formed by the first case (10) and the second case (20) .

7. Moulded case circuit breaker (1) according to claim

6, wherein said first case (10) has a section which in a plane perpendicular to said rear face (5) is essentially L-shaped .

8. Moulded case circuit breaker (1) according to claim

1, wherein the first case (10) comprises an automatic protection system with a trip system adapted to bring said first contact element (PI) in the rest position upon detecting a condition of short-circuit or overcurrent.

9. Moulded case circuit breaker (1) according to any one of the previous claims, wherein the second contact element is a fixed contact element and includes a pad (P2), wherein said second support element (S2) is a bar conductor (28) fixed to said second case (20) and having a first end portion to which said pad (P2) is welded and a second opposite end portion which represents said second connection terminal (T2) .

10. Moulded case circuit breaker (1) according to claim 9, wherein said bar conductor (28) is essentially hook-shaped.

11. Moulded case circuit breaker (1) according to claim 2, wherein the second case (20) comprises a measuring toroid (50) adapted to detect an imbalance of currents between said plurality of contact branches of the second contact branch (C2).

12. Moulded case circuit breaker (1) according to claims 8 and 11, wherein the measuring toroid (50) is operatively connected to said trip mechanism so that said protection system is both automatic and residual current.

13. Moulded case circuit breaker (1) according to claims 11 or 12, wherein each of said contact branches of the second contact branch (C2) comprises a first bar conductor (28' ), a second bar conductor (28* ') and an electric connection element (28''¹) between the first and the second bar conductor which passes through said measuring toroid (50).

14. Moulded case circuit breaker (1) according to any one of claims 1 to 8, wherein the second support element (S2) comprises a movable arm adapted to allow a rotation of said second contact element (P2).

15. Moulded case circuit breaker (1) according to claim 14, wherein the second support element (S2) comprises a bar conductor fixed to the second case (20) and wherein said movable arm is rotatably hinged to said bar conductor and wherein said second case (20) further comprises at least one elastic element acting on said movable arm and configured to maintain, in a condition of regular operation of the circuit breaker (1), the second contact element (P2) as close as possible to the first case (10) .

16. Moulded case circuit breaker (1) according to any one of the previous claims, wherein the first case (10) includes an arc extinguishing chamber (19) housing a deionization cell (8) and having an opening (9) facing towards the second case (20) and wherein the second case (10) includes at least one compartment communicating with said extinguishing chamber (19) through said opening (9) adapted to receive the expansion of gases that develop upon the occurrence of an electric arc.

17. Moulded case circuit breaker (1) according to any one of the previous claims, wherein the first case (10) comprises a first case portion (11) and a second case portion (12) made in two separate pieces and coupled together and wherein the second case portion (12) is operatively interposed between the first case portion (11) and the second case (20).

18. Moulded case circuit breaker (1) according to claim 17, wherein said first case (11) further comprises a lid (13) removably coupled to said first case portion (11).

19. A method of assembling a moulded case circuit breaker (1) according to any one of the previous claims, comprising the steps of:

- assembling together said first case (10), said first contact branch (CI) and said actuating mechanism (15);

- assembling together said second case (20) and said second contact branch (C2);

- coupling said second case (20) to said first case (10) through said fastening elements (31, 32).

20. An assembling method according to claim 19, further comprising a step of connecting at least one electrical signal cable between said first case (10) and said second case (20) by passing it inside said cases (10, 20) .