It is known that low-voltage power circuit breakers are used in industrial electrical systems characterized by relatively high currents and power levels.

Their particular function is to ensure, for a required nominal current value, connection and disconnection of the load and protection against abnormal events (for example overloads or short-circuits).

The connection and disconnection of the load occurs by virtue of the action of an actuation device, which is operatively connected to the moving contacts that are present in each electric pole of the circuit breaker. The actuation device moves the moving contact of each electric pole, causing its separation/coupling with respect to the corresponding fixed contact, respectively during opening/closure of the circuit breaker.

Protection of the circuit breaker against abnormal events generally occurs by means of automatic opening of the circuit. This is ensured by specific protection devices which can send, if the current exceeds a preset value, an electric fault signal to a release device, which performs, by means of an appropriate kinematic system, the disconnection of the moving contact of each electric pole. This fact provokes the automatic opening of the circuit breaker, with proportionally inverse delay times as the fault current rises.

These protection devices are commonly known as protection relays.

It is known that a requirement that is strongly felt by low-voltage power circuit breaker manufacturers is to ensure interchangeability of the protection devices, with which the circuit breakers are provided. This, in fact, entails considerable

advantages. For example, the possibility to fit the same circuit breaker with protection devices preset for different nominal currents allows to simplify manufacturing processes, increase the possibility to respond to market requirements, and make simple any change of the nominal current of a given user/load even when the electrical system/panel is already installed.

Some constructive solutions that meet this requirement of the current art are known. These solutions generally relate to circuit breakers of relatively large sizes, which correspond for example to nominal current values of 250A or more (circuit breaker width of 105 mm or more). With reference to figures 1 and 2, some constructive solutions commonly adopted for this type of power circuit breaker can be seen. The automatic circuit breaker 1 comprises a main body 2, in which a set of three electric poles, the actuation device of the circuit breaker, and the release device, both described earlier and not shown in the figure, are accommodated. A second casing 3, which accommodates the circuit breaker protection device is also noticeable.

The known solution, which is shown in figure 1, accommodates the protection device 3 inside the main body 2. In this case, the operation for connecting the second casing 3 to the main body 2 entails disassembling the front part 5 of the body of the circuit breaker by using screws or other movable fixing elements 4.

In the known solution illustrated in figure 2, the casing 3 is connected externally to the lower part of the main body of the circuit breaker 2. The connection is again performed by using screws or other movable fixing elements.

Both solutions proposed in figures 1 and 2, while achieving the purposes for which they have been provided, are characterized by some drawbacks.

Screws or other movable fixing elements are generally used in order to connect the protection device to the main body of the circuit breaker. This entails a considerable waste of time during the installation or replacement of the

protection device. The need to provide suitable seats for the insertion of screws or other movable fixing elements entails a reduction in the room available for accommodating the protection device. This fact considerably limits the possibility of interchanging a protection device of a certain type (for example an electronic relay) with another protection device of a different type (for example a magnetothermal relay).

Accordingly, the possibilities to optimize the performance of the circuit breaker, according to the requirements of the electric system in which it is inserted, are therefore reduced considerably.

In smaller power circuit breakers, for example for a nominal current of 160 amperes or less (circuit breaker width of 90 mm or less), the possibility of ensuring interchangeability of the protection devices is further limited. In order to replace the protection device, it is, in fact, generally necessary to completely disassemble the circuit breaker body. This operation cannot be performed easily by the user or retailer but it requires the intervention of specialized personnel.

This entails a considerable increase in intervention costs to replace the protection device.

Furthermore, the retailer of the circuit breaker, in order to meet the various requirements of his customers, must keep in stock a large number of circuit breakers, each fitted with a different type of protection device.

The aim of the present invention is to provide a low-voltage power circuit breaker, which allows interchanging the protection device very simply without the need for the intervention of specialized personnel.

Within the scope of this aim, an object of the present invention is to provide a low-voltage power circuit breaker, which allows connecting the protection device to the circuit breaker in a modular manner and without using screws and other movable fixing elements.

Another object of the present invention is to provide a low-voltage power

circuit breaker, which allows interchanging the protection device even for relatively small circuit breakers (nominal current of 160 amperes or less or circuit breaker width of 90 mm or less).

Another object of the present invention is to provide a low-voltage power circuit breaker, which allows easily interchanging protection devices of different types, particularly of the electronic, electromagnetic, magnetothermal types and the like.

Thus, the present invention provides a low-voltage power circuit breaker, which comprises a first casing accommodating at least an electric pole comprising at least a fixed contact and a moving contact, which couples/uncouples with said fixed contact during the closure/opening operations of the low voltage power circuit breaker. The first casing further accomodates actuation means, operatively connected to the moving contact. The accomodation means provide the moving contact with the energy required for coupling/uncoupling with said fixed contact, during the closure/opening operations of the low voltage power circuit breaker.

The low voltage circuit breaker, according to the present invention, further comprises a second casing, which accomodates protection means for protecting the low-voltage power circuit breaker from abnormal events.

The low-voltage power circuit breaker, according to the present invention, is characterized in that the first casing and/or the second casing comprise direct coupling means that are suitable to connect the first casing and the second casing in a modular manner.

The power circuit breaker, according to the present invention, has the advantage that it is provide with a modular structure (constituted by the assembly of the first casing and the second casing), which does not require, for assembly, the use of screws or other movable fixing elements except those required to provide the electrical connections. The low-voltage power circuit breaker, according to

the present invention, therefore allows installing and, most of all, interchanging the protection device in a simple way, without requiring the intervention of specialized personnel.

Further characteristics and advantages of the low-voltage power circuit breaker, according to the present invention, will become apparent from the description of a preferred but not exclusive embodiments, illustrated only by way of non- limitative example, in the accompanying drawings, wherein: figure 1 is a schematic view of a known low-voltage power circuit breaker of relatively large size; figure 2 is a schematic view of another known low-voltage power circuit breaker of relatively large size; figure 3 is a schematic view of a preferred embodiment of the low-voltage power circuit breaker, according to the present invention; and figure 4 is a view of a detail of the preferred embodiment of the low-voltage power circuit breaker, according to the present invention, illustrated in figure 3.

A preferred embodiment of the low-voltage power circuit breaker according to the present invention is described with reference to figure 3.

The low-voltage power circuit breaker, designated by the reference numeral 12, comprises a first casing 11, advantageously made of insulating material, which accommodates one or more electric poles (preferably three, not shown). Each electric pole comprises at least a fixed contact and a moving contact (not shown), which can be mutually coupled. The casing 11 furthermore comprises actuation means (not shown), which are operatively connected to the moving contact of each one of the electric poles. The actuation means preferably comprise an actuation device (not shown), which is suitable to provide, by means of a kinematic chain, the energy required to move the moving contact during the circuit breaker opening/closure operations. The first casing 11 furthermore comprises release actuation means (not shown), which are suitable

to cause the separation of the moving contacts of from the corresponding fixed contacts, in response to an electric fault signal. The release actuation means can be physically separated from the actuation means described above: in this case, they are advantageously constituted by one or more release devices (advantageously of the electromagnetic type), which are capable of producing, in response to an electric fault signal, for example by virtue of the action of a preloaded spring, the separation of the electric contacts in a preset time.

Alternatively, the release actuation means can be physically integrated with the actuation means. When the electric fault signal is received, they produce the intervention of the actuation means, which move the kinematic chain operatively connected to the moving contacts.

The low-voltage power circuit breaker, according to the present invention, furthermore comprises a second casing 13, advantageously made of insulating material, which accommodates protection means for protecting the circuit breaker from abnormal events. The protection means are electrically connected, for example by means of a screw 16, to the above described release actuation means and are suitable to send them an electric fault signal. In practice, the protection means, as soon as the current exceeds a preset value, send an electric fault signal to the release actuation means, which automatically separate the electric contacts (moving contact and fixed contact). The particularity of the low-voltage power circuit breaker, according to the present invention, resides in the fact that the casings 11 and 13 comprise direct coupling means 14, which are suitable to connect the casings 11 and 13 in a modular manner. The expression"to connect in a modular manner"is used to designate the coupling of two separate elements (in this case the casings 11 and 13) without having to perform any structural modification of these elements, such as for example the disassembly/reassembly of parts.

The direct coupling means comprise mechanical coupling means, which do not

entail the use of screws or other movable fixing elements, in order to provide the connection between the casings 11 and 13.

Preferably, the direct coupling means comprise one or more interlocking and sliding arrangements, which have, according to another preferred embodiment, a plurality of insertion guides that can be mutually coupled. This can be easily noticed for example with reference to figure 4. This figure shows that the direct coupling means comprise one or more interlocking and sliding arrangements of the dovetail type.

As an alternative, the direct coupling means can comprise for example one or more snap-acting interlocking arrangements.

By virtue of the presence of the direct coupling means it is possible to easily and rapidly provide the power circuit breaker, according to the present invention, with the most suitable protection device. The lack of screws or movable fixing elements to assemble the casings 11 and 13 entails a significant increase in the space available inside the casing 13. This allows to use the same type of casing to easily accommodate different types of protection device, such as for example protection relays of the electromagnetic, magnetothermal, electronic type and the like.

In this manner, the power circuit breaker, according to the present invention, can be provided with the protection devices that are most suitable for its operation.

Furthermore, replacement of the protection means of a certain type with others of a different type also becomes straightforward. It is, in fact, enough to extract the casing 13 and replace it (arrow 160) with another one, which comprises the selected protection means.

This allows the user to considerably reduce the intervention costs for installing and/or re-adapting the circuit breaker. Further, the retailer can meet the requirements of his customers while significantly reducing the quantity and

value of the goods in stock.

Finally, it has been found that the low-voltage power circuit breaker, according to the present invention, allows to interchange the protection means even for relatively low nominal current values, particularly for values of 160 amperes or less (circuit breaker width of 90 mm or less). This is essentially due to the use of the space available to accommodate the protection means. This is a considerable advantage in terms of flexibility and response to market requirements.

The low-voltage power circuit breaker, according to the present invention, thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept.

All the details may furthermore be replaced with other technically equivalent elements. In practice, the materials used, so long as they are compatible with the specific use, as well as the dimensions, may be any according to requirements and to the state of the art.