DESCRIPTION

The present invention relates to a switching apparatus for medium voltage electric systems.

For the purpose of the present application, the term "medium voltage" (MV) relates to operating voltages at electric power distribution level, which are higher than 1 kV AC and 1.5 kV DC up to some tens of kV, e.g. up to 72 kV AC and 100 kV DC.

MV electric systems typically adopt two different kinds of switching apparatuses.

A first type of switching apparatuses, including for example circuit breakers or disconnectors, is basically designed for protection purposes, namely for carrying (for a specified time interval) and breaking currents under specified abnormal circuit conditions, e.g. under short circuit conditions.

A second type of switching apparatuses, including for example contactors, is basically designed for manoeuvring purposes, namely for carrying and breaking currents under normal circuit conditions including overload conditions.

As is known, in most traditional switching apparatuses, driving systems including spring operated mechanisms and/or electromagnetic actuators are typically adopted for moving the movable contacts.

These switching apparatuses suffer of some drawbacks.

Very often, it is quite difficult to ensure a stable and repeatable switching of the electric contacts during an opening manoeuvre or a closing manoeuvre of the switching apparatus. Friction phenomena, changes in environmental conditions, changes in operational conditions of the components, and the like, may in fact have a strong influence on the operation of the driving system moving the movable contacts.

The above mentioned problems often result in relevant wear phenomena of the electric contacts with a reduction of the operational life of these latter and a consequent need of frequent maintenance interventions.

Another drawback of these traditional switching apparatuses is represented by frequent over- travel or back-travel phenomena of the movable contacts, which may lead to the onset of relevant mechanical stresses on the kinematic chain driving the movable contacts and, in switching apparatuses of the vacuum operating type, on the bellows sealing the vacuum bulbs, with a consequent reduction of the operational life of these parts of the switching apparatus. In the attempt of solving or mitigating the above mentioned drawbacks, traditional switching apparatuses often employ mechanical dampers or other mechanical arrangements to provide an improved control of the motion of the movable contacts during an opening or closing manoeuvre of the switching apparatus.

However, these solutions generally entail a higher complexity of the kinematic chain operatively coupled with the movable contacts with consequent increase of the overall occupied volumes and of the industrial manufacturing time and costs of the switching apparatus.

More recent switching apparatuses employ driving systems for moving the movable contacts, which include electric motors with a closed control loop, e.g. servomotors.

In general, these apparatuses represent an important improvement with respect to spring operated or magnetically operated switching apparatuses since they can offer a much higher degree of control of the motion of the movable contacts.

However, currently available switching apparatuses of this type adopt complicated solutions to mechanically couple the electric motor with the movable contacts, which still offer poor performances in terms of structural compactness and in terms of reliability in transmitting motion to the movable contacts.

The main aim of the present invention is to provide a switching apparatus for MV electric systems that allows solving or mitigating the above mentioned problems.

More in particular, it is an object of the present invention to provide a switching apparatus having an improved driving system for the movable contacts, which provides an improved motion control, high precision and reliability in actuating the movable contacts during an opening manoeuvre or a closing manoeuvre.

Still another object of the present invention is to provide a switching apparatus that is provided with a driving system having high compactness and structural simplicity.

Still another object of the present invention is to provide a switching apparatus that can be easily manufactured at industrial level, at competitive costs with respect to the solutions of the state of the art.

In order to fulfill these aim and objects, the present invention provides a switching apparatus, according to the following claim 1 and the related dependent claims.

Characteristics and advantages of the invention will emerge from the description of preferred, but not exclusive embodiments of the switching apparatus, according to the invention, non- limiting examples of which are provided in the attached drawings, wherein:

- Figure 1-2, 2A, 3-8 are schematic views of the switching apparatus, according to the invention;

- Figure 9-13 are schematic views to illustrate operation of the switching apparatus, according to the invention. With reference to the figures, the present invention relates to a switching apparatus 1 for medium voltage (MV) electric systems.

The switching apparatus 1 may be a circuit breaker, a disconnector, a contactor, or another similar device.

The switching apparatus 1 may be of the vacuum operating type, as shown in the cited figures, or a gas insulated switching device.

The switching apparatus 1 comprises a pole section 11 and a basement 12, which respectively include the electric poles and the main actuation components of the switching apparatus. Taking as a reference a normal installation position of the switching apparatus 1, shown in figures 1-3, the pole section 11 is overlapped to the basement 12.

Conveniently, the switching apparatus 1 comprises an outer frame 10, which may at least be partially made of electrically insulating material of known type.

The outer frame 10 is adapted to be fixed to a support (not shown) during the installation of the switching apparatus 1.

The switching apparatus 1 comprises one or more electric poles 2.

Preferably, the switching apparatus 1 is of the multi-phase (e.g. three-phase) type, thereby comprising a plurality (e.g. three) of electric poles 2.

Preferably, each electric pole 2 comprises a corresponding insulating housing 23, which are conveniently fixed to the basement 12 of the switching apparatus.

The insulating housings 23 of the electric poles 2 form corresponding portions of the outer frame 10 at the pole section 11 of the switching apparatus.

Preferably, each insulating housing 23 is formed by an elongated (e.g. cylindrical) hollow body of electrically insulating material of known type.

Preferably, each insulating housing 23 defines an internal volume, in which the components of the corresponding electric pole 2 are accommodated.

Advantageously, each electric pole 2 comprises a first pole terminal 21 and a second pole terminal 22, which may be mechanically fixed to the housing 23 by means of suitable flanges. The pole terminals 21, 22 are adapted to be electrically connected with a corresponding electric conductor (e.g. a phase conductor) of an electric line.

The insulating housing 23 and the pole terminals 21, 22 of the electric poles 2 of the switching apparatus 1 may be of known type and will not here described in more details for the sake of brevity. For each electric pole 2, the switching apparatus 1 comprises a fixed contact 3 and a movable contact 4, which are in electrical connection with the first and second pole terminals 21, 22 respectively.

Each movable contact 4 is reversibly movable along a corresponding displacement axis Al, which conveniently forms the main longitudinal axes of the corresponding electric pole 2 (figures 5, 6).

Preferably, the displacement axes Al of the movable contacts 4 are mutually parallel and lye on a common displacement plane.

In particular, each movable contacts 4 is reversibly movable (see the corresponding bidirectional displacement arrow figure 3) between a decoupled position (opening position) from the corresponding fixed contact 3 and a coupled position (closing position) with the corresponding fixed contact 3.

The passage of the movable contacts 4 from the coupled position with to the decoupled position from the corresponding fixed contacts 3 represents an opening manoeuver of the switching apparatus 1 whereas the passage of the movable contacts 4 from the decoupled position from to the coupled position with the corresponding fixed contacts 3 represents a closing manoeuver of the switching apparatus 1.

The electric contacts 3, 4 of the switching apparatus 1 may be of known type and will not here described in more details for the sake of brevity.

Preferably, the switching apparatus 1 is of the vacuum operating type as shown in the cited figures.

In this case, for each electric pole 2, the switching apparatus 1 comprises a vacuum chamber 25, in which a corresponding pair of movable and fixed contacts 3, 4 is placed and can be mutually coupled/decoupled.

The vacuum chambers 25 may be of known type and will not here described in more details for the sake of brevity.

The switching apparatus 1 comprises an actuation assembly 5 providing actuation forces to actuate the movable contacts 4 (figure 6).

In particular, the actuation assembly comprises, for each electric pole, an actuation shaft 52 capable of providing mechanical forces to actuate the movable contacts 4 during an opening manoeuvre or a closing manoeuv re o the switching apparatus.

Each rotation shaft 52 rotates about a rotation axis A2, which is preferably perpendicular to the displacement axis A l of the mov able contacts 4. Each rotation shaft 52 thus provides rotational mechanical forces to actuate the movable contact 4 of the corresponding electric pole 2 during an opening manoeuvre or a closing manoeuvre of the switching apparatus.

Preferably, as shown in the cited figures, the actuation assembly 5 comprises, for each electric pole, an electric motor 51 having an actuation shaft 52 as output shaft (as shown in the cited figures) or, alternatively, having its output shaft mechanically coupled to a corresponding actuation shaft 52 by means of a suitable gear mechanism.

In alternative embodiments of the invention (not shown), however, the actuation assembly 5 may comprise a single electric motor having its output shaft mechanically coupled to the actuation shaft 52 corresponding to each electric pole 2 by means of suitable gear mechanisms.

Preferably, as shown in the cited figures, the actuation assembly 5 comprises, for each electric motor 51, a power and control unit 53 (figure 2A).

Preferably, each power and control unit 53 comprises suitable electric circuits to feed the corresponding electric motor 51 and suitable electronic circuits (e.g. including on or more digital processing unit, such as microprocessors) to control operation of the corresponding electric motor 51.

In alternative embodiments of the invention (not shown), however, the actuation assembly 5 may comprise a single power and control unit 53 for all the electric motor 51.

For each electric pole, the switching apparatus 1 comprises a motion transmission assembly 150 including a corresponding eccentric mechanism 6 and a corresponding transmission mechanism 7.

Preferably, each motion transmission assembly 150 comprises a corresponding supporting frame 151, conveniently fixed to the outer frame 10 of the switching apparatus.

In the embodiments in which the switching apparatus 1 comprises an electric motor 5 for each electric pole 2, each electric motor 5 may be fixed to the supporting frame 151 of a corresponding motion transmission assembly 150, as shown in the cited figures.

As mentioned above, the switching apparatus 1 comprises, for each electric pole, an eccentric mechanism 6 operatively coupled with a corresponding actuation shaft 52 so as to be actuated by this latter.

Each eccentric mechanism 6 is arranged in such a way to be actuated by rotational mechanical forces provided by the corresponding actuation shaft 52 and provides, in turn, translational mechanical forces to actuate the movable contact 4 of the corresponding electric pole 2 during an opening manoeuvre or a closing manoeuvre of the switching apparatus. As mentioned above, the switching apparatus 1 comprises, for each electric pole, a transmission mechanism 7 operatively coupled with a corresponding eccentric mechanism 6 so as to be actuated by this latter.

Each transmission mechanism 7 is arranged in such a way to be actuated by translational mechanical forces provided by the corresponding eccentric mechanism 6 and transmit, in turn, translational mechanical forces to the movable contact 4 of the corresponding electric pole 2 during an opening manoeuvre or a closing manoeuvre of the switching apparatus.

During an opening manoeuvre or a closing manoeuvre of the switching apparatus, each eccentric mechanism 6 is mov able between a first end-of-run position P I (figure 9), at which the corresponding mov able contact 4 is decoupled from the respectiv e fixed contact 3, and a second end-of-run position P2 (figure 13 ), at which the corresponding movable contact 4 is coupled to the respective fixed contact 3.

Each eccentric mechanism 6 reaches its first end-of-run position P I at the end of an opening manoeuvre of the switching apparatus and stably maintains said first end-of-run position until a closing manoeuvre of the switching apparatus is carried out.

Each eccentric mechanism 6 reaches its second end-of-run position P2 at the end of a closing manoeuvre of the switching apparatus and stably maintains said second end-of-run position until an opening manoeuvre of the switching apparatus is carried out.

Preferably, during an opening manoeuvre or a closing manoeuvre of the switching apparatus, each eccentric mechanism 6 passes through a first deadlock position PD1 (figure 10), at which the corresponding movable contact 4 is decoupled from the respective fixed contact 3 and reaches a point of ma imum distance from, said fixed contact.

Preferably, during an opening manoeuvre or a closing manoeuvre of the switching apparatus, each eccentric mechanism 6 passes through a second deadlock position PD2 (figure 12), at which the corresponding movable contact 4 is coupled with the respective fixed contact 3 and a corresponding contact spring 71 of the transmission mechanism 7, operatively coupled with said movable contact, stores a maximum amount of elastic energy (figure 3).

Preferably, during a closing manoeuv re of the switching apparatus, each eccentric mechanism

6:

- leaves the first end-of-run position PI, at which the corresponding movable contact 4 is decoupled from the fixed contact 3 and is spaced from said fixed contact of a distance shorter than the maximum distance reached by the mov able contact 4 when the eccentric mechanism 6 is in the first deadlock position PD1;

- passes through the first deadlock position PD 1 ; - passes through a first intermediate position PI 1 at which the movable contact 4 couples with the fixed contact 3;

- passes through the second deadlock position PD2;

- reaches the second end-of-run position P2, at which the corresponding movable contact 4 is coupled (with a given coupling pressure) with the respective fixed contact 3 and the respective contact spring 71 , which is coupled with said movable contact, stores an amount of elastic energy lower than the maximum amount of elastic energy, which is stored when the eccentric mechanism 6 is in the second deadlock position PD2.

Preferably, during an opening manoeuvre of the switching apparatus, each eccentric mechanism 6:

- leaves the second end-of-run position P2, at which the corresponding movable contact 4 is coupled with the respective fixed contact 3 and the respective contact spring 71 , coupled with said movable contact, stores an amount of elastic energy lower than the maximum amount of elastic energy, which is stored when the eccentric mechanism 6 is in the second deadlock position PD2;

- passes through the second deadlock position PD2;

- passes through a second intermediate position PI2 at which the movable contact 4 decouples from the fixed contact 3 (figure 11);

- passes through the first deadlock position PD 1 ;

- reaches the first end-of-run position P I . at which the corresponding movable contact 4 is decoupled from the fixed contact 3 and is spaced from said fixed contact of a distance

(sufficient to avoid re-striking or arching phenomena) shorter than the maximum distance reached by the movable contact 4 when the eccentric mechanism 6 is in the first deadlock position PD1.

In the following, the eccentric mechanism 6, which is arranged at each electric pole of the switching apparatus, is described in more details with particular reference to the preferred embodiment shown in the cited figures.

Preferably, the eccentric mechanism 6 comprises an eccentric body 61 mechanically coupled with a corresponding actuation shaft 52 so as to solidly rotate with this latter.

Preferably, the eccentric mechanism 6 comprises a clamping element 68 for the mechanical coupling between the corresponding eccentric body 61 and actuation shaft 52. In this way the eccentric body 61 and the corresponding actuation shaft 52 can rotate together as a single piece.

Conveniently, the eccentric body 61 comprises an eccentric axis A 5 parallel to the rotation axis A 2 and spaced from this latter (figure 6).

On a plane π perpendicular to the rotation a is A 2 of the actuation shaft 52 (e.g. including the displacement axis Al), the eccentric axis A5 of the eccentric body 52 defines an eccentric centre EC of the eccentric body 52 (figures 5, 8, 1 1).

Conveniently, the eccentric body 61 comprises a crank axis A3 passing through the eccentric centre EC and the rotation axis 52 on a plane π perpendicular to this latter (figures 5, 11). As will be better described in the fol lowing, the crank axis A3 is aligned with the displacement axis Al when the eccentric mechanism 6 is the deadlock positions PD1 , PD2. Preferably, the eccentric body 61 comprises a first shaped cavity 61 1 coaxial with the corresponding actuation shaft 52, in particular w ith the rotation axis A 2 of this latter (figure 6).

Preferably, the first shaped cav ity 61 1 is a blind cav ity having a cylindrical shape.

Preferably, the actuation shaft 52 is at least partial ly inserted w ithin the first cav ity 61 1 for mechanical coupling w ith the eccentric body 61 .

In the cited figures, a preferred embodiment for such an eccentric body 61 is shown ( figures 6, 8).

According to such an embodiment, the eccentric body 61 comprises a main portion 613 extending along the eccentric axis A5.

Preferably, the main portion 613 is made by a solid piece of material (e.g. steel) with a cylindrical symmetry along the eccentric axis A5.

On a first side of the main portion 61 3, w hich faces the actuation shaft 52. the eccentric body 61 preferably comprises the first shaped cav ity 61 1 .

On a second side of the main portion 613, which is opposite to said first side, the eccentric body 61 preferably comprises a shaped protrusion 612 coaxial with the first cav ity 61 1 and the corresponding actuation shaft 52 accommodated therein, along the rotation axis 52.

Preferably, the shaped protrusion 61 2 has a cylindrical shape and forms a single piece with said main portion 61 3 .

Preferably, the eccentric mechanism 6 comprises a bearing clement 69 in a fixed position (e.g. conv eniently fi ed to the supporting frame 1 5 1 ), to which the shaped protrusion 61 2 is mechanical ly coupled at a distal end from the main portion 61 3.

Conveniently, the shaped protrusion 612 is mechanically coupled with the bearing element 69 in such a way to be free to rotate together with the eccentric body 61 and the actuation shaft 52.

The above described embodiment for the eccentric body 61 allows remarkably reducing possible mechanical plays thereby ensuring a stable and correct positioning of the eccentric body 61 along the rotation a is A2.

Further, the assembly formed by the eccentric body 61 and the actuation shaft 52 is particularly robust and compact from a structural point of view.

Preferably, each eccentric mechanism 6 of the switching apparatus comprises a connecting rod body 620 mechanically coupled with the eccentric body 61 so as to be rotatably movable with respect to this latter.

Preferably, the connecting rod body 620 comprises a connecting rod axis A 4 on a plane π perpendicular to the rotation axis A 2 of the actuation shaft 52 (figure 11).

As will be better described in the following, the connecting rod a is A4 is aligned with the displacement axis Al when the eccentric mechanism 6 is the deadlock positions PDl, PD2. As it will be better illustrated in the following, the eccentric axis A3 and the connecting rod axis A 4 form, along a plane π perpendicular to the rotation axis A2, a first angle a or a second angle a' (preferably = ') having an absolute value of few degrees (e.g. lower or equal to 5 °) when the eccentric mechanism 6 reaches the first end-of-run position PI or the second end-of-run position P2, respectively.

As it will be better illustrated in the following, this feature, which is obtained respectively thanks to an over-rotation of eccentric mechanism 6 beyond the first deadlock position PDl or the second deadlock position PD2, contributes to ensure that the first end-of-run position P I or the second end-of-run position P2 are stably maintained by the eccentric mechanism 6 at the end of a closing or opening manoeuvre of the switching apparatus.

It is evidenced that, when the eccentric mechanism 6 is in the first end-of-run position PI, the over-rotation of a small angle a implies a small reduction of the distance between the movable contact 4 and the electric contact 3 with respect to the maximum stroke reached when the eccentric mechanism 6 is in the first deadlock position PDl .

It is further evidenced that, when the eccentric mechanism 6 is in the second end-of-run position P2, the over-rotation of a small angle a' implies a small reduction of the elastic energy stored by the contact spring 71 with respect to the maximum elastic energy stored when the eccentric mechanism 6 is in the second deadlock position PD2.

Preferably, the connecting rod body 620 comprises a second shaped cav ity 62 1 coaxial with the eccentric body 61 , in particular with the eccentric axis A 5 of this latter (figure 6).

Preferably, the second shaped cav ity 621 is a pass-through cavity hav ing a cylindrical shape. Preferably, the eccentric body 61 (in particular its main portion 613) is at least partially inserted within the second cavity 621 for mechanical coupl ing with the rod body 62.

Preferably, the connecting rod body 620 comprises a bearing coupling arrangement (e.g. of the ball bearing, needle bearing or roller bearing type) in the second cavity 621 for mechanical coupling with the eccentric body 61 , in particular with the main portion 613 of this latter.

In this way, when the eccentric body 61 rotates together with the actuation shaft 52, the connecting rod body 620 can swing with respect to the eccentric body 61 (in a same relative direction) about the eccentric axis A5 of this latter.

Preferably, the connecting rod body 620 is rotatably coupled with the transmission mechanism 7 at a hinging point 65.

Preferably, the eccentric mechanism 6 comprises an end-of-run element 66 in a fixed position, e.g. conveniently fixed to the supporting frame 1 5 1 .

As it will be better illustrated in the follow ing, the connecting rod body 62 abuts against the end-of-run element 66 when the eccentric mechanism 6 reaches the first end-of-run position P I (figure 9) or the second end-of-run position P2 (figure 13).

The arrangement of the end-of-run element 66 contributes to ensure that the first end-of-run position P 1 or the second end-of-run position P2 are stably maintained by the eccentric mechanism 6 at the end of a closing or opening manoeuvre of the switching apparatus.

Preferably, in the eccentric mechanism 6, the distance between the hinging point 65 of mechanical connection with the transmission mechanism 7 and the eccentric centre EC of the eccentric body 61 , along a plane π perpendicular to the rotation axis A 2 of the actuation shaft 52, is much longer than the maximum distance (ma imum stroke) that the movable contact 4 can reach with respect to the fi ed contact 3 during a closing or opening manoeuvre of the switching apparatus.

As an example, such a distance may be at least ten time longer that the maximum stroke available for the movable contact 4.

It has been verified by the inventors that such a solution allows remarkably reducing mechanical stresses on the eccentric mechanism 6 (in particular the presence of lateral forces acting on the connecting rod body 620).

Further, the provision of a lengthened connecting rod body 620 allows reducing the mechanical energy that the actuation assembly 5 has to provide to move the movable contacts 4.

In the cited figures, a preferred embodiment for the connecting rod body 620 is shown (figures 6, 8, 1 1). According to such an embodiment, the connecting rod body 620 comprises a main portion 62 made by a solid piece of material (e.g. steel) and extending, preferably with a tetrahedral symmetry, along the connecting rod axis A4.

The main portion 62 comprises the second shaped cavity 621 passing through the thickness of said main portion.

On a distal end with respect to the second cavity 621, the connecting rod body 620 comprises an elongated portion 63 extending along the connecting rod axis A4.

Preferably, the elongated portion 63 of the connecting rod body 620 is formed by a shaped rod extending longitudinally along the connecting rod axis A4, as shown in the cited figures. At one end. the shaped rod 63 is solidly coupled with the main portion 62 of the connecting rod body 620.

At an opposite end 632, distal ly from the main portion 62, the shaped rod 63 is rotatabiy coupled with the transmission mechanism 7 at the hinging point 65.

As an alternative, the elongated portion 63 may be formed by a protrusion made in one piece with the main portion 62 of the connecting rod body 620.

In the following, the transmission mechanism 7, which is arranged at each electric pole of the switching apparatus, is described in more details with particular reference to the preferred embodiment shown in the cited figures (figures 3, 6).

Preferably, the transmission mechanism 7 comprises a plunger member 72 and a contact spring 71 .

The plunger member 72 extends longitudinally along the displacement axis A 1 and has opposite first and second ends 721, 722 respectively at a distal position from and a proximal position with the movable contact 4.

The first end 72 1 of the plunger member is mechanically coupled with the eccentric mechanism 6. more particularly with the connecting rod body 620 of this latter, at the hinging point 65.

The second end 722 of the plunger member 72 abuts against the contact spring 72 of the transmission mechanism 7 and the movable contact 4.

The contact spring 71 is arranged along the displacement axis A 1 coaxially with the plunger member 72.

Proximal ly to the movable contact 4, the contact spring 71 has a first end 71 1 mechanically coupled (e.g. solidly fixed) with said movable contact whereas, distally from the movable contact 4, the contact spring 71 has a second end 712 abutting against the plunger member 72, in particular with the second end 722 of this latter. During a closing or opening manoeuvre of the switching apparatus, the plunger member 72 can move relatively with respect the movable contact 4, when this latter is coupled with the fixed contact 3. Such a relative movement is made possible by the presence of the contact spring 71 , which, in fact, is subject to compression or release thereby storing or releasing elastic energy.

Preferably, the contact spring 71 is mounted on the movable contact 4 in such a way to be in a biasing state (i.e. slightly compressed) even when the movable contact 4 is decoupled from the fixed contact 3.

Preferably, the plunger member 72 is formed by a shaped rod at least partial ly made of electrically insulating material .

As shown in the cited figures, the mov able plunger 72 may comprise multiple portions (ev en made of different materials) joined together and aligned along the displacement axis Al . Preferably, the plunger member 72 comprises a first portion 72 A (e.g. made of steel ) distal I y positioned from the movable contact 4 and including the first end 721.

Conveniently, the portion 72 A of the plunger member is accommodated in a volume defined by the supporting frame 1 5 1 of the motion transmission assembly 1 50.

Preferably, the plunger member 72 comprises a second portion 72 B (e.g. made of electrically insulating material ) proximally positioned to the movable contact 4 and including the second end 722.

Conveniently, the portion 72 B of the plunger member protrudes from the supporting frame 151 of the motion transmission assembly 150 and is accommodated in the housing member 23 of electric pole 2.

Preferably, the second end 722 of the plunger member (at the second portion 72B thereof) is cup-shaped and defines a v olume for accommodating at least partially the contact spring 71 . Preferably, the second end 722 of the plunger member comprises a first coupling surface 723, which mechanical ly couples with the movable contact 4, in particular with a second coupling surface 4 1 of this latter during an opening manoeuvre of the switching apparatus.

Conveniently, said first and second coupling surfaces are formed respectively by a shaped edge 723 of the second end 722 of the plunger member and a shaped edge 41 of the movable contact, which are arranged in such a way to mutually abut during an opening manoeuv re of the switching apparatus.

Preferably, the second end 722 of the plunger member comprises a thi d coupling surface 724. which mechanical ly couples w ith the contact spring 71 . in particular w ith the second end 712 of this latter, during a closing manoeuv re of the sw itching apparatus. Conveniently, the mentioned coupling surfaces 724 is formed by a bottom portion of the cup- shaped end 722 of the plunger member.

Preferably, the transmission mechanism 7 comprises one or more guide or axial bearing elements 74 slidingly coupled with the plunger member to ensure the correct alignment of this latter with the displacement axis Al .

The operation of the switching apparatus 1 for an electric pole 2 is now described in more details.

Opening state of the switching apparatus

When the switching apparatus 1 is in an opening state, the movable contact 4 is decoupled from the fixed contact 3 and is spaced from this latter of a distance slightly shorter (few hundredths of mm) than the maximum distance (maximum stroke) that can be reached by said movable contact (figures 2, 9).

The contact spring 71 is not compressed (with respect to its biasing state).

The eccentric mechanism 6 is in the first end-of-run position PI .

The connecting rod body 620 of the eccentric mechanism 6 abuts against the guide element 66.

The connecting rod a is A4 of the connecting rod body 620 is not aligned with the displacement axis Al of the movable contact

The eccentric axis A3 of the eccentric body 61 and the connecting rod axis A 4 of the connecting rod body 620 form a first angle a of few degrees (e.g. lower or equal to 5°).

The electric motor 5 can be switched off as the eccentric mechanism 6 is capable of stably maintaining the first end-of-run position P 1 until a closing manoeuvre of the switching apparatus is carried out.

The abutment of the connecting rod body 620 against the end-of-run element 66 prevents any movement of the eccentric mechanism 6 in the rotation direction D l .

On the other hand, as the eccentric axis A3 and the connecting rod axis A4 are not mutually aligned, any force directed to move the movable contact 4 towards the fixed contact 3 (e.g. the vacuum force caused by the pressure difference between the inside and the outside of the vacuum chamber) has a lateral component opposing to a movement of the eccentric mechanism in the rotation direction D2.

Such a lateral component stably maintains the connecting rod body 620 in the abutment position against the guide element 66 until the electric motor 51 is activated in order to carry out a closing manoeuvre. Closing manoeuyre

In order to carry out a closing manoeuvre, the electric motor 51 is activated and the actuation shaft is rotated according to the rotation direction D2 (figure 9).

The connecting rod body 620 leaves its in abutment position against the guide element 66 and rotates according to the same rotation direction D2 as any force opposing the movement of the eccentric mechanism 6 in the rotation direction D2 is overcome by the forces exerted by the actuation shaft 52.

The eccentric mechanism 6 thus moves towards the first deadlock position PD1 (figures 9, 10).

During the mov ement of the eccentric mechanism 6 between the first end-of-run position P 1 and the first deadlock position PD1, the movable plunger 72 slightly moves (some hundredths of mm) according to the translation direction D3 (along the displacement axis Al) thereby further distancing the movable contact 4 from the fixed contact 3 (figure 10).

When the first deadlock position PD 1 is reached by the eccentric mechanism 6, the eccentric axis A3, the connecting rod axis A 4 and the displacement axis A 1 are mutually aligned and the movable contact 4 reaches its maximum distance from the fixed contact 3.

As it is moved by the actuation shaft 52, the eccentric mechanism 6 passes over the first deadlock position PD1 and moves towards the second deadlock position PD2.

The movable plunger 72 moves according to the translation direction D4 (along the displacement axis Al) thereby moving the movable contact 4 towards the fixed contact 3

(figure 11).

During its movement between the first deadlock PD l and the second deadlock position PD2, the eccentric mechanism 6 reaches a first intermediate position PI1, at which the movable contact 4 couples with the fixed contact 3.

During the movement of the eccentric mechanism 6 between the first end-of-run position P 1 and the intermediate position PI, as the movable contact 4 is not coupled with the fixed contact 3, the contact spring 71 is not compressed (with respect to its biasing state) and it moves solidly with the movable plunger 72 and the movable contact 4.

As it is still moved by the actuation shaft 52, the eccentric mechanism 6 passes over the first intermediate position PI1 and continues to move towards the second deadlock position PD2. During the movement of the eccentric mechanism 6 between the first intermediate position PI 1 and the second deadlock position PD2, the plunger member 72 moves (according to the direction D4) relatively with respect the movable contact 4 and the contact spring 71 is subject to compression. When the second deadlock position PD2 is reached by the eccentric mechanism 6, the eccentric axis A3, the connecting rod axis A4 and the displacement axis A 1 are mutually aligned and the contact spring 71 reaches its maximum compression (figure 12).

As it is moved by the actuation shaft 52, the eccentric mechanism. 6 passes over the second deadlock position PD2 and moves towards the second end-of-run position P2 (over-rotation with respect to the second deadlock position PD2).

During the movement of the eccentric mechanism 6 between the second deadlock position PD2 and the second end-of-run position P2 , the movable plunger 72 slightly moves (some hundredths of mm), according to the di ection D3, relatively with respect the mov able contact 4.

The contact spring 71 releases some elastic energy with respect to the maximum compression state reached with the eccentric mechanism 6 at the second deadlock position PD2.

The closing manoeuvre ends when the eccentric mechanism 6 reaches the second end-of-run position P2 (figure 12).

Closing state of the switching apparatus

When the switching apparatus 1 is in a closing state, the movable contact 4 is coupled from the fixed contact 3 (figure 13).

The contact spring 71 is compressed but it stores an amount of elastic energy lower than the maximum amount of elastic energy stored with the eccentric mechanism 6 at the second deadlock position PD2.

The connecting rod body 620 of the eccentric mechanism 6 abuts against the guide element 66.

The connecting rod axis A 4 of the connecting rod body 620 is not aligned with the displacement axis Al of the movable contact.

The eccentric axis A3 of the eccentric body 61 and the connecting rod axis A4 of the connecting rod body 620 form a second angle a' of few degrees (e.g. lower or equal, to 5°). The electric motor 5 can be switched off as the eccentric mechanism 6 is capable of stably maintaining the second end-of-run position P2 until an opening manoeuvre of the switching apparatus is carried out.

The abutment of the connecting rod body 620 against the end-of-run element 66 prevents this latter from moving (eccentrically with respect to the actuation shaft 52) in the rotation direction D2.

On the other hand, as the eccentric axis A3 and the connecting rod axis A4 are not mutually aligned, any force directed to mov e the movable contact 4 away from the fixed contact (e.g. the weight force of the movable plunger 72) has a lateral component directed in such a way to oppose a movement of the eccentric mechanism 6 in the rotation direction D l .

Such a lateral component stably maintains the connecting rod body 620 in the abutment position against the guide element 66 until the electric motor 51 is activated in order to carry out an opening manoeuvre.

Opening manoeuyre

In order to carry out an opening manoeuvre, the electric motor 51 is activated and the actuation shaft is rotated according to the rotation direction Dl (figure 13).

The connecting rod body 620 leaves its in abutment position against the guide element 66 and rotates in the same rotation direction D 1 as any force opposing the movement of the connecting rod body 620 is overcome by the forces exerted by the actuation shaft 52.

The eccentric mechanism 6 moves towards the second deadlock position PD2 (figures 12, 13).

During the movement of the eccentric mechanism 6 between the second end-of-run position

P2 and the second deadlock position PD2, the movable plunger 72 slightly moves relatively

(some hundredths of mm ) with respect the movable contact 4 according to the translation direction D4.

The contact spring 71 is slightly compressed with respect to the compression state reached with the eccentric mechanism 6 at the second end-of-run position P2.

When the second deadlock position PD2 is reached by the eccentric mechanism 6. the eccentric axis A3, the connecting rod axis A 4 and the displacement axis A 1 are mutually al igned and the contact spring 71 reaches its maximum compression state.

As it is moved by the actuation shaft 52, the eccentric mechanism 6 passes over the second deadlock position PD2 and moves towards the second deadlock position PDl .

Du ing the mov ement of the eccentric mechanism 6 between the second deadlock position

PD2 and the first deadlock position PDl , the movable plunger 72 moves relatively with respect the mov able contact 4 according to the translation direction D3.

The contact spring 71 releases elastic energy with respect to the maximum compression state reached with the eccentric mechanism 6 at the second deadlock position PD2.

Du ing its movement from the second deadlock position PD2 to the first deadlock position PDl , the eccentric mechanism 6 reaches a second intermediate position PI2 (which preferably coincides with the first intermediate position PI 1 ), at which the movable contact 4 decouples from the fixed contact 3.

When the eccentric mechanism 6 reaches second intermediate position PI2, the second end 722 of the plunger member 73 couples with the mov able contact 4 and the mov able contact 4 is dragged away from the fixed contact 3 by the plunger member 72, along the translation direction D3, thereby decoupling from the fixed contact 3.

As it is still moved by the actuation shaft 52, the eccentric mechanism 6 passes over the second intermediate position PI2 and continues to move towards the second deadlock position PD2.

The connecting rod body 620 continues to be rotated in the rotation direction D l .

During the movement of the eccentric mechanism 6 from the second intermediate position PI2 and the first end-of-run position PI, as the movable contact 4 is no more coupled with the fixed contact 3, the contact spring 71 is not compressed (with respect to its biasing state) and it moves solidly with the plunger member 72 and the movable contact 4.

During the movement of the eccentric mechanism 6 from the second intermediate position PI2 and the first deadlock position PD1, the plunger member 72 moves away (according to the direction D3) with respect the fixed contact 3, as it is dragged by the plunger member 72.

When the first deadlock position PD 1 is reached by the eccentric mechanism 6, the eccentric axis A3, the connecting rod axis A4 and the displacement axis A 1 are mutually aligned and the movable contact 4 reaches its maximum distance from the fixed contact 3.

As it is moved by the actuation shaft 52, the eccentric mechanism 6 passes over the first deadlock position PD1 and moves towards the first end-of-run position PI (over-rotation with respect to the first deadlock position PD1).

During the movement of the eccentric mechanism 6 between the first deadlock position PD l and the first end-of-run position PI, the movable plunger 72 slightly moves (some hundredths of mm) according to the translation direction D4 along the displacement axis Al .

The movable contact 4 is thus slightly moved (some hundredths of mm) towards the fixed contact 4.

The opening manoeuvre ends when the eccentric mechanism 6 reaches the first end-of-run position PI .

The switching apparatus 1, according to the invention, provides remarkable advantages with respect to the known apparatuses of the state of the art.

The switching apparatus 1 is provided with a motion transmission assembly 150 that ensures top levels performances in actuating the movable contacts during an opening manoeuvre or a closing manoeuvre.

In particular, the eccentric mechanism 6 ensures high levels of motion control of the movable contacts and high precision and reliability. The eccentric mechanism 6, arranged as illustrated above, allows decreasing the axial length of the motion transmission assembly with respect to the traditional solutions of the state of the art, with relevant benefits in terms of reduction of vibration and mechanical stresses.

The eccentric mechanism 6 allows obtaining a very compact, simple and robust motion transmission assembly to move the movable contacts with relevant benefits in terms of size optimization for the overall structure of the switching apparatus.

Thanks to the to the eccentric mechanism 6, the switching apparatus can maintain a closing or an opening state without energizing the actuation assembly 5 with consequent relevant reduction of the electric power consumption.

The switching apparatus 1 , according to the invention, is thus characterised by high levels of reliability for the intended applications.

The switching apparatus 1, according to the invention, is of relatively easy and cheap industrial production and installation on the field.