BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is an exploded view of a low-voltage circuit breaker according to the invention;
FIG. 2 is a partial cross-sectional view of a rotating element of a low-voltage device according to the invention;
FIG. 3 is a perspective view of a first embodiment of an element made of ferromagnetic material used in a low-voltage device according to the invention;
FIG. 4 is a perspective view of a second embodiment of an element made of ferromagnetic material used in a low-voltage device according to the invention;
FIG. 5 is a further view of the element of FIG. 4;
FIG. 6 is a perspective view of a third embodiment of an element made of ferromagnetic material used in a low-voltage device according to the invention;
FIG. 7 is a perspective view of a fourth embodiment of an element made of ferromagnetic material used in a low-voltage device according to the invention;
FIG. 8 is a view of a portion of rotating element and of a corresponding element made of ferromagnetic material according to the embodiment of FIG. 4;
FIG. 9 is a perspective view of a fifth embodiment of an element made of ferromagnetic material used in a low-voltage device according to the invention;
FIG. 10 is a view of a portion of rotating element and of a corresponding element made of ferromagnetic material according to the embodiment of FIG. 9;
FIG. 11 is a perspective view of a sixth embodiment of an element made of ferromagnetic material used in a low-voltage device according to the invention;
FIG. 12 is a view of a portion of rotating element and of a corresponding element made of ferromagnetic material according to the embodiment of FIG. 11.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference to the attached figures, the device for low-voltage systems according to the invention, in this case a circuit breaker 1, comprises an outer casing, which in the embodiment illustrated comprises two half-shells 2 and 2′. The half-shells house a plurality of poles, in this case three, each of said poles containing at least one fixed contact and at least one mobile contact 3 that can be coupled to/uncoupled from one another. The mobile contact 3 can be made of a single piece or else of a plurality of pieces adjacent to one another, as clearly illustrated in FIG. 2.
The circuit breaker moreover comprises a rotating element 4 that is defined by a shaped body 5 made with an insulating material. In a position corresponding to each pole of the circuit breaker, the shaped body 5 comprises at least one seat 6 that is designed to house at least the mobile contact 3 of the corresponding pole. Advantageously, the mobile contacts of each pole can be equipped with contact springs 14, configured, for example, as in any solution of the known art. In order to enable movement of the rotating element 4, the circuit breaker 1 also comprises a control mechanism 7 that is operatively connected to said rotating element 4. Furthermore, a closing mask 9 is generally present; said mask 9 is usually applied on one of the half-shells 2′ and can if necessary be easily removed by an operator in order to gain access to the internal parts of the circuit breaker 1.
For a detailed description of an example of switch, the reader is referred to the patent application No. BG2005A000026, the description of which is incorporated herein for reference.
The circuit breaker according to the invention moreover comprises elements made of ferromagnetic material that are positioned in the seat 6 of the mobile contact 3, made in the shaped body 5 of the rotating element 4. In the device according to the invention, the elements made of ferromagnetic material are in general shaped and positioned in such a way as to be kept fixed with respect to said shaped body 5 and coat at least one portion of the inner surface of the seat 6.
With reference to the attached figures, it may in fact be noted how the elements made of ferromagnetic material form a coating of at least part of the internal surfaces of the seats 6 of the mobile contact 3. In principle, the containment of the electrodynamic interference improves as the proportion of the coated, and hence shielded, area of the seats 6 of the mobile contacts increases. On the other hand, it is necessary to respect the physical limits dictated, for example, by the presence of other components or by the dielectric distances that determine galvanic separation between contiguous poles.
Preferably, said one or more elements made of ferromagnetic material coat at least 25% of the inner surface of said seat 6. It has in fact been noted from experiments that elements made of ferromagnetic material even of modest dimensions, such as, for example, the ones illustrated in FIG. 11, which provide a covering of approximately 25% of the internal surfaces of the seats 6, enable an increase in the electrodynamic strength of approximately 8% to be obtained (49 kA to 690 V all other conditions being equal). The size, shape and continuity of the elements of magnetic shielding hence do not represent a particularly critical factor.
The seat 6 preferably has a first side wall 91 and a second side wall 92, opposed to one another. In this case, conveniently, the elements made of ferromagnetic material are set in a position corresponding to said first side wall 91 of the seat 6, and, more preferably, said elements are set in a position corresponding to at least said first side wall 91 and second side wall 92 of said seat 6.
With reference to FIGS. 2 and 8, according to a particular embodiment, the elements made of ferromagnetic material are kept in position by the pin of the mobile contacts 8. In this case, in practice, the elements of magnetic shielding interact operatively with said pin of the mobile contacts 8 and with the shaped body 5, and concur to distribute the action of thrust or of tugging on an extensive and not concentrated portion of the rotating element 4. By the expression “interact operatively with said pin of the mobile contacts 8 and with the shaped body 5” it is meant that, thanks to this particular conformation of the elements of magnetic shielding, the stresses, instead of being concentrated in the proximity of the hole 80 for passage of the pin of the mobile contacts 8, are distributed over a relatively extensive region of the shaped body 5. In this case, then, the elements made of ferromagnetic material, in addition to exerting an action of shielding, also exert an action of mechanical reinforcement of the shaped body 5 of the rotating element 4.
The shape, dimensions and location of the elements made of ferromagnetic material can be different according to the needs. For example, with reference to FIG. 3, in a first embodiment, the elements made of ferromagnetic material can substantially comprise a first shaped body 10, which has a hollow portion with substantially rectangular cross section 11. The outer surface of the portion 11 is shaped so as to substantially mate with the inner surface of the seat 6 made in the shaped body 5 of the rotating element. In other words, the walls 111, 112, 113, 114 of the portion 11 are designed to couple with the internal walls of the seat 6, coating them either totally or in part.
With reference to FIGS. 4, 5 and 8, in a first embodiment, the elements made of ferromagnetic material can substantially comprise a second shaped body 20, which has a hollow portion with a substantially rectangular cross section 21. The outer surface of the portion 21 is shaped so as to substantially mate with the inner surface of the seat 6 made in the shaped body 5 of the rotating element (see FIG. 8). The shaped body 21 of the element made of ferromagnetic material moreover comprises a first tab 12 and a second tab 13, which extend from the hollow portion 21 of the shaped body 20. With reference to FIG. 8, the tabs 12 and 13 preferably project from the width of the rectangular hollow portion 21 so as to engage, for example, by snap action, in corresponding housings 22 and 23, defined in the side walls 92 and 91 of the seat 6.
Preferably, defined on said first tab 12 and second tab 13 are a first hole 32 and second hole 33 for passage of said pin of the mobile contacts 8. In this way, the stresses generated in a position corresponding to the pin of the mobile contacts 8, instead of being concentrated on a limited area adjacent to the hole 80, can be distributed over a far more extensive surface.
According to a particular embodiment, with reference to FIG. 6, at least one part of the outer perimeter of the hollow portion 31 of the element made of ferromagnetic material 30, has a bent-over edge 35, designed to co-operate with a corresponding coupling surface, defined on the shaped body 5. The term “outer perimeter” is intended to indicate the area of hollow portion 31 of the element 30 closest to the mouth of the seat 6 once the element made of ferromagnetic material 30 has been inserted in said seat 6 according to the modalities illustrated in FIG. 8.
The element made of ferromagnetic material 10, 20, 30 illustrated in FIGS. 3 to 6 can advantageously be made of a single piece, appropriately shaped and bent. Once inserted in the seat 6, the element made of ferromagnetic material remains easily in position thanks to the interaction between the outer surface of the hollow portion 11, 21, 31 and the inner surface of the seat 6, as well as, in the cases illustrated in FIG. 4, 5, 6, thanks to the interaction between the tabs 12, 13 and the corresponding seats 22, 23.
According to an alternative embodiment, illustrated in FIG. 7, the element made of ferromagnetic material 40 can advantageously comprise crimping means 400, designed to favour coupling between the ferromagnetic element itself and the shaped body 5. This is particularly advantageous in the case where the positioning of the element made of ferromagnetic material within the seat 6 is obtained by co-moulding, via insertion of the element 40 in the mould of the shaped body 5 of the rotating element 4.
An alternative embodiment, illustrated in FIG. 9 and 10, envisages that the elements made of ferromagnetic material 50 comprise a second shaped body 52 and a third shaped body 53. Each of said second and third shaped bodies 52, 53 has a first hollow portion 54 with substantially U-shaped cross section, defined by a first wall 55, a second wall 56 and a third wall 57 substantially perpendicular to one another. The outer surface of the hollow portion 54 is made so as to mate substantially with at least one portion of the inner surface of said seat 6. A third tab 58 extends from said second wall 56 and engages, for example by snap action, in corresponding housings 580, defined in the seat 6 of the shaped body 5. As illustrated in FIG. 10, the second and third shaped bodies 52, 53 are inserted in the seat 6 so that the respective hollow portions 54 face one another. Preferably, defined on said third tab 58 is a third hole 59 for passage of said pin of the mobile contacts 8.
In order to improve the ease of positioning in the seat 6, the second and third shaped bodies 52, 53 can advantageously have engagement means 501 designed to engage in corresponding housings 500, defined on said shaped body 5 of said rotating element.
A further alternative embodiment, illustrated in FIGS. 11 and 12, envisages that the elements made of ferromagnetic material 60 comprise a fourth plate-shaped body 61 that has a surface 62 substantially mating with at least one portion of the inner surface of said seat 6. As illustrated in said figures, it is preferable for the elements made of ferromagnetic material to comprise two plate-shaped bodies 61, positioned on the opposed side walls 91, 92 of the seat 6. In order to improve the ease of positioning in the seat 6, the plate-shaped bodies 61 moreover comprise engagement means 621 designed to engage in corresponding housings 620, defined on the shaped body 5 of said rotating element.
Preferably, defined on said fourth plate-shaped body 61 is a fourth hole 63 for passage of said pin of the mobile contacts 8. Furthermore, in order to improve the distribution of the mechanical stresses over the rotating element, the fourth shaped body 61 has at least one portion of bent-over edge 65 designed to co-operate with a corresponding coupling surface 650, defined on said shaped body 5.
Preferably said elements made of ferromagnetic material 10, 20, 30, 40, 50, 50 are made of steel.
As mentioned previously, the elements made of ferromagnetic material enable increase of the electrodynamic strength of the circuit breaker and consequently improve the performance thereof, all other conditions being equal. It may in fact be noted that, also with a covering of just approximately 25% of the inner surface of the seat 6 of the mobile contacts, which may be obtained, for example, with the elements of FIG. 11 and 12, it is possible to obtain an increase in the electrodynamic strength of approximately 8% (from 45 kA to 49 kA, with a voltage of 690 V, all other conditions being equal). Using, instead, the elements of the solution illustrated in FIG. 4, which forms a covering of approximately 45% of the internal surfaces of the seats 6, it is possible to increase the electrodynamic strength by approximately 13% (from 45 kA to 51 kA with a voltage of 690 V, all other conditions being equal). The data indicated above refer to the particular cases that form the subject of the experimentation, but may vary considerably in an absolute sense, by applying the inventive idea to switches with different basic characteristics. These results are in any case of considerable importance in so far as they highlight that it is possible to obtain switches with substantially improved performance, without intervening markedly on the structure and on the essential components of the switch itself.
On the basis of what has been described above, it may be seen that the single-pole or multi-pole device for low-voltage systems, in particular a circuit breaker or a disconnector, according to the invention, enables the problems typically present in the switches of the known art to be solved and improves the electrodynamic strength considerably.
On the basis of the description provided, other characteristics, modifications or improvements are possible and evident to the average person skilled in the branch. Said characteristics, modifications and improvements are hence to be considered as forming part of the present invention. In practice, the materials used, as well as the contingent dimensions and shapes, may be any whatsoever according to the needs and the state of the art.
Patent Application
20080087532
