EP4411768A1

EP4411768A1 - An actuation unit for a switching apparatus

Info

Publication number: EP4411768A1
Application number: EP23154957.7A
Authority: EP
Inventors: Corrado Rizzi; Alessandro Stucchi; Ettore Pellegrinelli; Dario Leidi
Original assignee: ABB Schweiz AG
Current assignee: ABB Schweiz AG
Priority date: 2023-02-03
Filing date: 2023-02-03
Publication date: 2024-08-07
Also published as: CN118448188A

Abstract

An actuation unit for a switching apparatus comprising a rotating contact shaft coupled to the movable contacts of said switching apparatus and first mechanical actuation means coupled to said contact shaft and configured to actuate said contact shaft during a closing manoeuvre of said switching apparatus.

Said first mechanical actuation means include a spring assembly, a first lever member coupled to said spring assembly and a plurality of second lever members coupling said first lever member to said contact shaft.

Said first mechanical actuation means include a rotating cam assembly including one or more cam members couplable to the first lever member of said first mechanical actuation means. The actuating unit comprises mechanically interacting brake members configured to reduce the rotational speed of said cam assembly, when said cam assembly is rotating towards a rest position, during a closing manoeuvre of said switching apparatus.

Description

Field of the invention

The present invention relates to the field of electrical systems operating at low or medium voltage levels. In particular, the present invention relates to an actuation unit for a switching apparatus operating at low or medium voltage levels.

Background

Switching apparatuses, such as circuit breakers, contactors, disconnectors and the like, are widely used in switchgears, electric power distribution lines, or other electrical systems.
As is known, a switching apparatus typically comprises a plurality of electric poles, each including a fixed contact and a movable contact. The movable contacts of the electric poles are mechanically and electrically coupled with and decoupled from the corresponding fixed contacts during closing and opening manoeuvres of the switching apparatus.
A switching apparatus generally comprises an actuation unit operatively coupled to the movable contacts in order to move reversibly these latter between the above-mentioned coupled and uncoupled positions relative to said fixed contacts.
In many switching apparatuses of the state of the art, such an actuation unit comprises a rotating contact shaft mechanically coupled to the movable contacts of the electric poles and mechanical actuation means mechanically coupled to said contact shaft for actuating this latter (and consequently the movable contacts of the electric poles) during a closing manoeuvre of the switching apparatus.
Typically, said mechanical actuation means are of the spring-operated type. They comprise one or more actuation springs mechanically coupled to the contact shaft through a suitable kinematic chain. During a closing manoeuvre of the switching apparatus, the actuation springs are triggered to pass from a loaded condition to a released condition. In this way, the stored mechanical energy can be transmitted through the above-mentioned kinematic chain and be employed to actuate the contact shaft.
In order to bring the above-mentioned actuation springs in a loaded condition (loading manoeuvre), the actuation unit comprises mechanical loading means coupled to the kinematic chain linking the actuation springs to the contact shaft.
In many cases, these mechanical loading means include an actuator operable by a user, for example a lever mechanism or an electric motor, and a rotating cam assembly mechanically coupled to said actuator and to a lever member of said kinematic chain. The cam assembly includes suitable cam elements to actuate the above-mentioned lever member.
When a loading operation of the spring assembly has to be carried out, a user activates the above-mentioned actuator. This latter actuates the cam assembly, which in turn actuates the lever member coupled thereto and, consequently, bring the actuation springs in a loaded condition. In this way, the actuation springs can store the mechanical energy necessary to carry out a closing manoeuvre of the switching apparatus.
During a closing manoeuvre of the switching apparatus, the above-mentioned cam assembly moves back to a rest position upon actuation by the above-mentioned lever member as the actuation springs release the stored mechanical energy.
The actuation unit of currently available switching apparatuses has some aspects to improve in relation to the above-mentioned mechanical loading means.
As a matter of fact, due to the relatively high amount of mechanical energy released by the actuation springs, the cam assembly comes back to the rest position with a high rotational speed as it is subject to high actuation forces imparted by the above-mentioned lever member. When reaching the above-mentioned rest position, the cam assembly typically hits with strength some surrounding components, for example parts of the above-mentioned lever member, which operates, in practice, as an end-of-run element for the cam assembly.
It has been seen that these repeated collisions may cause a deterioration of the structural integrity of the involved parts over time. This may lead to their structural failure with consequent need for time-consuming and expensive maintenance interventions.

Summary of the invention

The main aim of the present invention is to provide an actuation unit for a switching apparatus operating at low or medium voltage levels, which allows solving or mitigating the above-mentioned problems.
More in particular, it is an object of the present invention to provide an actuation unit, which ensures higher levels of reliability in operation.
As a further object, the present invention is aimed at providing an actuation unit, which has a relatively simple and space-saving structure.
Still another object of the present invention is to provide an actuation unit, which 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 an actuation unit for a switching apparatus, according to the following claim 1 and the related dependent claims.
In a general definition, the actuation unit, according to the invention, is configured to actuate one or more movable contacts of the switching apparatus during a closing manoeuvre and an opening manoeuvre of said switching apparatus.
The actuation unit, according to the invention, comprises a contact shaft, which is coupled to the movable contacts of the switching apparatus and is reversibly movable about a corresponding first rotation axis, and first mechanical actuation means, which are coupled to said contact shaft and are configured to actuate said contact shaft during a closing manoeuvre of said switching apparatus.
The first mechanical actuation means comprise a spring assembly including one or more spring elements. The spring assembly is configured to take reversibly a loaded condition, at which said spring elements are loaded and consequently store mechanical energy, and a released condition, at which said spring elements have released the stored mechanical energy.
The first mechanical actuation means further comprise a kinematic chain coupling the spring assembly to the contact shaft. Such a kinematic chain includes a first lever member movable about a second rotation axis parallel to the first rotation axis of the contact shaft and coupled to the spring assembly. In particular, the first lever member is configured to move reversibly, by rotating according to opposite directions about said second rotation axis, between a first position, which corresponds to a loaded condition of said spring assembly, and a second position, which corresponds to a released condition of said spring assembly.
The actuation unit, according to the invention, further comprises mechanical loading means configured to actuate said first lever member in order to make said spring assembly pass from said released condition to said loaded condition.
Said mechanical loading means comprise a cam assembly movable about a third rotation axis parallel to the first rotation axis of the contact shaft and including one or more cam units, each having a cam surface couplable to said first lever member. Said cam assembly is configured to move reversibly, by rotating about said third rotation axis according to a predefined direction, between a third position, which corresponds to a first position of said first lever member, and a fourth position, which corresponds to a second position of said first lever member.
In operation, said cam assembly actuates said first lever member and makes said first lever member move from said second position to said first position, when said cam assembly moves from said fourth position to said third position upon actuation by an actuating device coupled to said cam assembly. Said cam assembly holds said first lever member when said cam assembly is in said third position and it leaves said first lever member free to move from said first position to said second position, when said cam assembly moves away from said third position.
In operation, said first lever member actuates said spring assembly and makes said spring assembly pass from said released condition to said loaded condition, when said first lever member moves from said second position to said first position upon actuation by said cam assembly. Said first lever member holds said spring assembly in said loaded condition when first said lever member is in said first position and it leaves said spring assembly free to pass from said loaded condition to said released condition, when said first lever member moves away from said first position.
According to the invention, the actuation unit comprises mechanically interacting brake members to brake said cam assembly, when this latter moves from said third position to said fourth position.
At least a cam unit comprises a first brake member configured to come into frictional contact with a corresponding second brake member in fixed position relative to said cam unit, during a rotation movement of said cam assembly from the third position to the fourth position.
The mechanical interaction between said first and second brake members causes a reduction of the rotational speed of said cam assembly while this latter is moving from said third position to said fourth position.
According to an aspect of the invention, said first and second brake members are positioned one relative to another, so that said first brake member comes into frictional contact with said second brake member at an initial stage of the rotation movement of said cam assembly from said third position to said fourth position.
According to an aspect of the invention, each first brake member is formed by a contoured head protruding from a first surface of a corresponding cam unit, said first surface facing a second surface of a corresponding support wall of said actuation unit, on which a second brake member is arranged.
According to an aspect of the invention, each second brake member is formed by an elastically deformable lamina fixed to a second surface of support wall of said actuation unit, which faces a first surface of a corresponding cam unit of said cam assembly, on which a first brake member is arranged.
Preferably, each elastically deformable lamina has first and second end regions fixed to said second surface and a bent central region oriented in such a way to protrude from said second surface towards the first surface of a corresponding cam unit, on which a first brake member is arranged.
Preferably, the bent central region of each elastically deformable lamina is subject to an elastic compression when the contoured head of a corresponding cam unit comes into frictional contact with said elastically deformable lamina.
Preferably, each elastically deformable lamina is made of a spring steel material.
According to an aspect of the invention, the above-mentioned spring assembly includes a first end portion fixed to a third support wall, a second end portion opposite to said first end portion and coupled to said first lever member and one or more compression springs arranged between said first and second end portions.
According to an aspect of the invention, the above-mentioned first lever member has a third end portion coupled to said spring assembly and a fourth end portion opposite to said first end portion relative to said second rotation axis and coupled to said contact shaft through one or more second lever members. Said first lever member further comprises one or more sliding elements arranged at said fourth end portion. Each sliding element has a sliding surface couplable to the cam surface of a corresponding cam unit.
According to an aspect of the invention, said cam assembly comprises a pair of cam units spaced apart one from another along third rotation axis. Each cam unit has a cam surface couplable to said first lever member and a first surface facing a second surface of a corresponding support wall of said actuation unit.
In a further aspect, the present invention relates to a switching apparatus, according to the following claim 14 and the related dependent claims.

Brief description of the drawings

Further characteristics and advantages of the invention will emerge from the description of preferred, but not exclusive embodiments of the contactor, according to the invention, nonlimiting examples of which are provided in the attached drawings, wherein:

Figure 1 is a schematic view of the switching apparatus including an actuation unit, according to the invention;
Figures 2-8 are schematic views of some mechanical components of the actuation unit shown in figure 1;
Figures 9-14 are schematic views showing the operation of the mechanical components shown in figures 2-8.

Detailed description of the invention

With reference to the figures, the present invention relates to an actuation unit for a switching apparatus, such as a circuit breaker, a contactor, a disconnector or the like.
The actuation unit, according to the invention, is particularly suitable for use in medium voltage switching apparatuses, i.e., operating at voltage levels higher than 2.0 kV AC and 2.5 kV DC up to several tens of kV, for example 72 kV AC and 100 kV DC. In principle, however, it may be used also in low-voltage switching apparatuses, i.e., operating at voltage levels lower than 2.0 kV AC and 2.5 kV DC.
Figure 1 shows a schematic view of a switching apparatus 100 including an actuation unit 1 according to the invention.
The switching apparatus 100 comprises one or more electric poles 101.
Preferably, the switching apparatus 100 is of the multi-phase type, more particularly of the three-phase type, as shown in the cited figures.
For each electric pole 101, the switching apparatus 100 comprises a fixed contact 102 and a movable contact 103, which are electrically connected to corresponding first and second pole terminals 104, 105 electrically connectable to suitable conductors of an electric line.
The movable contact 103 of each electric pole 101 is reversibly movable between a decoupled position and a coupled position relative to the corresponding fixed contact 102. When it is in a decoupled position, the movable contact 103 is electrically and mechanically decoupled from the corresponding fixed contact while, when it is in a coupled position, the movable contact 103 is electrically and mechanically coupled with the corresponding fixed contact. Preferably, as in the switching apparatus shown in the cited figures, each movable contact 103 moves translationally along a main longitudinal axis of a corresponding electric pole. In principle, however, the movable contacts of the switching apparatus may move rotationally to couple with or decouple from the corresponding fixed contacts.
The transition of the movable contacts 103 from a coupled position with to a decoupled position from the corresponding fixed contacts 102 represents an opening manoeuvre of the switching apparatus whereas the transition of the movable contacts 103 from a decoupled position to a coupled position with the corresponding fixed contacts 102 represents a closing manoeuvre of the switching apparatus.
In general, the electric poles 101 of the switching apparatus may be realized at industrial level according to solutions of known type. Therefore, in the following, these components will be described in relation to the aspects of interest of the invention only, for the sake of brevity. The switching apparatus 100 comprises an actuation unit 1 configured to actuate the movable contacts 103 of the electric poles during a closing manoeuvre and an opening manoeuvre of the switching apparatus.
Preferably, the actuation unit 1 comprises an outer enclosure 3 and a number of internal support walls 10 partitioning the internal volume of the actuation unit and providing support to the internal components thereof.
According to the invention, the actuation unit 1 comprises a contact shaft 4 coupled to the movable contacts 103 of the electric poles through suitable motion transmission mechanisms (not shown), for example of the crank-lever type.
For the sake of clarity, it is specified that the terms "connect-" and "couple-" used in this disclosure generally relate to a mechanical connection or coupling between the involved parts or components. In other words, the terms "connect" or "couple" should be intended as "mechanically couple-" and "mechanically connect-" unless otherwise specified.
The contact shaft 4 is reversibly movable about a corresponding first rotation axis A₁ preferably oriented along a longer dimension of the actuation unit.
According to the invention, the actuation unit 1 comprises first mechanical actuation means 5, 6, 7 configured to actuate the contact shaft 4 during a closing manoeuvre of the switching apparatus.
The above-mentioned first mechanical actuation means comprises a spring assembly 5 including one or more spring elements 50.
The spring assembly 5 is configured to take reversibly a loaded condition A, at which the spring elements 50 are loaded and store mechanical energy, and a released condition B, at which the spring elements 50 have released the stored mechanical energy.
In the embodiment shown in the cited figures, the spring assembly 5 includes a first end portion 51 fixed to an internal support 16 of the actuation unit, a second end portion 52 opposite to said first end portion and one or more compression springs 50 arranged between said first and second end portions, conveniently in such a way to be mutually coaxial.
The above-mentioned first mechanical actuation means further comprises a kinematic chain 6, 7 coupling the spring assembly 5 to the contact shaft 4.
Such a kinematic chain includes a first lever member 6 configured to rotate about a second rotation axis A₂ parallel to the first rotation axis A₁ of the contact shaft 4.
The first lever member 6 is coupled to the spring assembly 5 and (indirectly) to the contact shaft 4.
The first lever member 6 is configured to move reversibly between a first position C, which corresponds to a loaded condition A of the spring assembly 5, and a second position D, which corresponds to a released condition B of the spring assembly 5. The first lever member 6 moves between the above-mentioned first and second positions C, D by rotating according to opposite directions Ri, R₂ about the second rotation axis A₂.
In the embodiment shown in the cited figures, the first lever member 6 has a third end portion 61 coupled to the spring assembly 5 (namely to the second end portion 52 of this latter) and a fourth end portion 62, which is opposite to the third end portion 61 relative to the rotation axis A₂ and is coupled (indirectly) to the contact shaft 4. At the fourth end portion 62, the first lever member 6 comprises one or more sliding elements 65, each having a sliding surface 650. Figure 3 shows in more details a possible configuration for the first lever member 6 according to the embodiments shown in the cited figures. In this case, the first lever member 6 comprises first lever arms 63 extending in parallel according to a longer dimension of the first lever member and second lever arms 64 traversal to the first lever arms 63 and joining these latter at the opposite end portions 61, 62 of the first lever member.
In an intermediate position between the above-mentioned end portions, each lever arm 63 has a shaped protrusion 66 oriented outwardly (i.e., according to an opposite direction relative to the other lever arm). The shaped protrusions 66 are aligned along the second rotation axis A₂ of the first lever member 6 and are configured to be pivoted on a pair of opposite support walls 10 of the actuation unit (figures 4-5).
At the fourth end portion 62, the first lever member 6 further comprises a pair of rollers 65, each protruding outwards from a corresponding lever arm 63 (in parallel to a corresponding protrusion 66). The rollers 65 are aligned along an axis parallel to the second axis A₂. The rollers 65 form the above-mentioned sliding elements of the first lever arm 6 and their rolling surfaces 650 form the above-mentioned sliding surfaces.
As mentioned above, the first lever member 6 is coupled (indirectly) with the contact shaft 4. Conveniently, the above-mentioned kinematic chain further includes a plurality 7 of second lever members mutually hinged at a plurality of rotation axes parallel to the first rotation axis A₁ of the contact shaft 4 and coupling the first lever member 6 (namely the fourth end portion 62 thereof) to the contact shaft 4.
Conveniently, the actuation unit 1 comprises also second mechanical actuation means 2 configured to actuate the contact shaft 4 during an opening manoeuvre of said switching apparatus.
In general, the above-mentioned contact shaft 4, first mechanical actuation means 5, 6, 7 and second mechanical actuation means 2 may be realized at industrial level according to solutions of known type. Therefore, in the following, they will be described only in relation to the aspects of interest of the invention, for the sake of brevity.
According to the invention, the actuation unit 1 further comprises mechanical loading means 8, 9 configured to actuate the first lever member 6 of the first mechanical actuation means in order to load the spring assembly 5, i.e., bring this latter from the released condition B to the loaded condition A.
The above-mentioned mechanical loading means advantageously comprise one or more actuating devices 8 that can be activated by a user to load the spring assembly 5. In practice, the actuating device 8 are configured to provide the mechanical energy necessary to bring the spring assembly 5 from a released condition B to a loaded condition A.
As shown in figure 1, the actuating devices 8 may include, for example, a lever mechanism that can be manually operated by a user. Alternatively, or in addition to the above, the actuating devices 8 may include an electric motor activatable through a suitable user interface.
In general, the above-mentioned actuating devices 8 may be realized at industrial level according to solutions of known type. Therefore, in the following, they will be described only in relation to the aspects of interest of the invention, for the sake of brevity.
The above-mentioned mechanical loading means further comprise a cam assembly 9 configured to rotate about a third rotation axis A₃ parallel to the first rotation axis A₁ of the contact shaft. The cam assembly 9 includes a motion transmission shaft 91 and one or more cam units 92 coupled to said motion transmission shaft.
As shown in the cited figures, the motion transmission shaft 91 has opposite ends pivoted on opposite support walls 10 of the actuation unit to rotate about the third rotation axis A₃.
The motion transmission shaft 91 is coupled to the one or more actuating devices 8, preferably at one of its opposite ends. To this aim, suitable gear mechanisms (not shown) of known type can be employed.
Each cam unit 92 is coupled to the motion transmission shaft 91 in such a way to rotate together with said motion transmission shaft.
Each cam unit 92 includes a cam surface 920 couplable to the first lever member 6, more particularly to the sliding surface 650 of a corresponding sliding element 65 of the first lever member.
Each cam unit 92 further includes a first surface 92a facing a second surface 10a of a corresponding support wall 10.
Preferably, for each cam unit 92, the first surface 92a is a side surface facing a support wall 10 of the actuation unit on which the cam assembly 9 is pivoted.
Preferably, for each cam unit 92, the second surface 10a is the facing surface of a support wall 10 on which the cam assembly 9 is pivoted.
According to the embodiment shown in the cited figures, the cam assembly 9 comprises a pair of cam units 92 spaced apart one from another along the third rotation axis A₃ and arranged on the motion transmission shaft 91, preferably in proximity of the opposite support walls 10 of the actuation unit 1, on which said motion transmission shaft is pivoted. Each cam unit 92 has thus a side surface 92a (first surface) facing an opposite surface 10a (second surface) of a corresponding support wall 10.
According to other embodiments of the invention, however, the cam assembly 9 may comprise a single cam unit 92 in proximity of a corresponding support wall 10 of the actuation unit 1. Figures 6-8 schematically show a cam unit 92 of the cam assembly 9, according to an embodiment of the invention.
Each cam unit 92 preferably includes a cam element 921 arranged coaxially with the motion transmission shaft 91 and forming a single piece with this latter. The cam element 921 includes an edge surface forming the above-mentioned cam surface 920.
Each cam unit 92 preferably includes a spacer element 922 fixed to the cam element 921 and interposed between the cam element 921 and a corresponding support wall 10. The spacer element 922 includes the above-mentioned first surface 92a.
Preferably, the spacer element 922 has a cup-shaped portion, through which the motion transmission shaft 91 can pass. Said cup-shaped portion is fixed to the corresponding cam element 921 in such way to anchor the spacer element 922 to the motion transmission shaft 91. Preferably, in distal position from the corresponding cam element 921, the spacer element 922 has a flat a ring-shaped edge with the first surface 92a facing an opposite second surface 10a of the corresponding support wall 10.
According to other embodiments of the invention, each cam unit may be configured differently from the solution shown in the cited figures. As an example, each cam unit may include only the cam element. In this case, a side surface of the cam element forms the first surface facing a second surface of a corresponding support wall.
The cam assembly 9 is configured to move reversibly, by rotating about the third rotation axis A₃ according to a same predefined direction R₃, between a third position E, which corresponds to a first position C of the first lever member 6, and a fourth position F, which corresponds to a second position D of the first lever member 6.
The cam surface 920 of each cam unit 92 is oriented in such a way that it couples with the sliding surface 650 of a corresponding sliding element 65 of the first lever member 6, when the cam assembly 9 moves from the fourth position F to the third position E.
According to the embodiment shown in the cited figures, the actuation unit 1 comprises mechanical triggering means 13 couplable to the cam assembly 9, more particularly to a cam unit 92 of said cam assembly.
The triggering means 13 include a trigger lever 130 configured to engage and hold the cam assembly 9 in the third position E once this latter has reached the third position E and to leave the cam assembly 9 free to move from the third position E to the fourth position F, when a closing manoeuvre of said switching apparatus is carried out.
In general, the above-mentioned triggering means 13 may be realized at industrial level according to solutions of known type. Therefore, in the following, they will be described only in relation to the aspects of interest of the invention, for the sake of brevity.
The operation of the above-mentioned first mechanical actuation means 5, 6, 7 and mechanical loading means 8, 9 is briefly described in the following with reference to figures 9-11.
The spring assembly 5 is supposed to be in a released condition B (figure 11).
In this situation, it is necessary to bring it in loaded condition A in order to make the actuation unit 1 ready to drive a closing manoeuvre of the switching apparatus.
When the spring assembly 5 is in a released condition B, the first lever member 6 is in the second position D and the cam assembly 9 is in the fourth position F.
In order to load the spring assembly 5, the user activates an actuating device 8.
Upon actuation by the actuating device 8, the cam assembly 9 rotates according to the predefined third direction R₃ and moves from the fourth position F (figure 11) towards the third position E (figure 9). During this movement of the cam assembly, the cam surface 920 of each cam unit 92 couples with the sliding surface 650 of a corresponding sliding element 65 of the first lever member 6. The cam assembly 9 thus actuates the first lever member 6, which is moved, according to a first direction Ri, from the second position D (figure 11) towards the first position C (figure 9). In doing so, the first lever member 6 actuates the spring assembly 5 in such a way to compress the spring elements 50 (reference T₁). The spring assembly 5 is thus brought from the released condition B (figure 11) to a loaded condition A (figure 9).
When it reaches the third position E, a cam unit 92 of the cam assembly 9 is engaged by the triggering means 13. The triggering lever 130 engages a corresponding can unit 92 and holds the whole cam assembly 9 in the third position E. In turn, the cam assembly 9 holds the first lever member 6 in the first position C and the first lever member 6 holds the spring assembly 5 in the loaded condition A.
The actuation unit 1 is now ready to drive a closing manoeuvre of the switching apparatus.
In order to carry out a closing manoeuvre of the switching apparatus, the user activates the triggering means 13. The trigger lever 130 moves in such a way to disengage from the cam assembly 9.
The cam assembly 9 is now free to move from the third position E (figures 9-10) to the fourth position F (figure 11) by rotating always according to the predefined third direction R₃. The cam assembly 9 thus leaves the first lever member 6 free to move from the first position C (figures 9-10) to the second position D (figure 11) by rotating according to a second direction R₂ opposite to the first direction R₁. In turn, the first lever member 6 leaves the spring assembly 5 free to pass (reference T₂) from the loaded condition A (figure 9) to a released condition B (figure 11). In doing so, the spring assembly 5 releases the stored mechanical energy, which is thus transmitted through the first lever member 6 and the second lever members 7 to the contact shaft 4. In this way, the contact shaft 4 can actuate the movable contacts 103 of the switching apparatus. As a consequence of the release of the spring assembly 5, the first lever 6 actuates the cam assembly 9 while moving away from the first position C. This latter is thus pushed away from the third position E and can freely rotate towards the fourth position F (rest position). An essential aspect of the invention consists in that the actuation unit 1 comprises mechanically interacting brake members 11, 12 configured to brake the cam assembly 9 during the rotation movement from the third position E to the fourth position F (such a rotation movement occurs during a closing manoeuvre of the switching apparatus as explained above).
At least a cam unit 92 comprises a first brake member 11 configured to come into frictional contact with a corresponding second brake member 12 in fixed position relative to said cam unit, during a rotation movement of said cam assembly 9 from the third position E to the fourth position F.
The mechanical interaction between the first and second brake members 11, 12 causes a reduction of the rotational speed of the cam assembly 9.
According to the embodiment shown in the cited figures, the actuation unit 1 comprises a pair of mechanically interacting first and second brake elements 11, 12 for each cam unit 92 of the cam assembly 9.
According to other embodiments (not shown), however, even if the cam assembly 9 comprises a pair of cam units 92, the actuation unit 1 may include mechanically interacting brake members 11,12 only for one of the cam units 92 of the cam assembly 9.
According to an aspect of the invention, for each involved cam unit 92, the first and second brake members 11, 12 are positioned one relative to another, so that the first brake member 11 comes into frictional contact with said second brake member 12 at an initial stage of the rotation movement of said cam assembly 9 from the third position E to the fourth position F. This solution is particularly advantageous as it allows reducing the rotational speed of the cam assembly, as soon as this latter starts moving. The cam assembly 9 is thus prevented from reaching excessively high values of rotational speed.
According to an aspect of the invention, each second brake member 12 is fixed to a support wall 10 of the actuation unit in proximal position to a corresponding cam member 92, namely at a second surface 10a of a corresponding support wall 10, which faces a first surface 92a of a corresponding cam unit 92 of the cam assembly 9.
Preferably, as mentioned above, the first surface 92a is the side surface of the cam unit 92, on which a first brake member 11 is arranged, while the second surface 10a is the surface of a support wall 10, on which the cam assembly is pivoted.
Each second brake member 12 is positioned so that it does not interact with the first brake member 11 of the corresponding cam unit 92, when the cam assembly 9 moves from the fourth position F to the third position E (i.e., during the loading of the spring assembly 5), and it comes into frictional contact with the first brake member 11 of the corresponding cam unit 92 only when the cam assembly 9 moves from the third position E to the fourth position F (i.e., during a closing manoeuvre of the witching apparatus).
According to an aspect of the invention, each first brake member is formed by a contoured head 11 protruding from the first surface 92a of a corresponding cam unit 92, which faces a second surface 10a of a corresponding support wall 10 on which the cam assembly 9 is pivoted. A second brake member 12 is arranged on the second surface 10a.
In the embodiment shown in the cited figures, each cam unit 92 includes a pin 11a arranged in parallel to the rotation axis A₃ of the cam assembly 92 and passing through the cam element 921 and the spacer element 922 of the cam unit. The pin 1 1a has a contoured head 11 protruding from the side surface 92a of the spacer element 922 towards the surface 10a of a corresponding support wall 10. Such a contoured head forms the above-mentioned first brake member 11. According to other embodiments of the invention (not shown), the contoured head 11 can be realized in one piece with the spacer element 922 (e.g., through a moulding process) or can be the protruding head of a pin fixed to the spacer element 922 only.
In the embodiments (not shown) in which each cam unit comprises only a cam element, the above-mentioned contoured head is formed on the side surface of said cam element, which faces the surface of a corresponding support wall on which the cam assembly is pivoted.
According to an aspect of the invention, each second brake member is formed by an elastically deformable lamina 12 fixed to the second surface 10a of a corresponding support wall 10, which faces a first surface 92a of a corresponding cam unit 92 of the cam assembly 9.
Preferably, each elastically deformable lamina is made of a spring steel material.
In the embodiment shown in the cited figures, each deformable lamina 12 is fixed to the surface 10a of a corresponding support wall 10, which faces the first surface 92a of a corresponding cam unit 92. A first brake member 12 is arranged on the first surface 92a.
In the embodiments (not shown) in which each cam unit 92 comprises only a cam element, each deformable lamina is fixed to the surface of a corresponding support wall, which faces the side surface of the cam element of a corresponding cam unit.
Preferably, each deformable lamina 12 has first and second end regions 12a, 12b fixed to the surface 10a of the corresponding support wall 10 and a bent central region 12c oriented in such a way to protrude from the second surface 10a towards a corresponding cam unit 92. Advantageously, the bent central region 12c of each deformable lamina 12 is subject to an elastic compression when a first brake member 11 of a corresponding cam unit 92 comes in frictional contact of with the deformable lamina.
The operation of the first and second brake members 11, 12 of the actuation unit 1 is described in more details with reference to figures 12-14.
When the cam assembly 9 moves from the third position E to the fourth position F by rotating according to the predefined third direction R₃, the contoured head 11 of each cam unit 92 comes into frictional contact with a corresponding deformable lamina 12 fixed to a support wall 10 (figure 12).
At this initial braking phase, the friction between each pin 11 and the corresponding deformable lamina 12 causes a certain dissipation of the kinetic energy of the cam assembly 9, which starts reducing its rotational speed.
As the rotation of the cam assembly 9 continues, the contoured head 11 reaches the bent portion 12c of the corresponding deformable lamina 12, which is thus subject to an elastic deformation. The elastic deformation of the bent portion 12c increases remarkably the dissipation of kinetic energy of the cam assembly 9. At this braking phase, the cam assembly 9 is subject to a maximum decrease of rotational speed.
As the rotation of the cam assembly 9 continues, the contoured head 11 reaches the bent portion 12c of the corresponding deformable lamina 12, which thus returns to its original shape. At this final baking phase, the friction between each pin 11 and the corresponding deformable lamina 12 causes a further reduction of the rotational speed of the cam, assembly 9.
As it is evident from the above, the mutual interaction between the protruding contoured head 11 of each cam unit 92 and the corresponding deformable lamina fixed to a support wall 10 effectively reduces the rotational speed of the cam assembly 9. This latter therefore reaches the rest position F with a lower level of kinetic energy. In this way, the effects of possible collisions (at the end of run of the cam assembly) of the cam units 92 (namely the cam elements 921) with the surrounding components (e.g., the sliding elements 65 of the first lever member 6) can be effectively mitigated.
As mentioned above, the mechanical interaction between each contoured head 11 and the corresponding deformable lamina 12 occurs at an initial stage of the rotational movement of the cam assembly 9, i.e., before this latter rotates at its maximum speed levels. It has been seen that this solution allows preventing even more effectively possible structural damages of components hit by the cam assembly 9, when this latter reaches its rest position F.

Technical advantages of the invention

The actuation unit 1, according to the invention, provides remarkable advantages with respect to the known apparatuses of the state of the art.
The arrangement of the first and second brake members 11, 12 allows prolonging remarkably the operating life of the components of the actuation unit, which are configured to interact with the cam units 92 during the rotational movements of the cam assembly 9.
In particular, the arrangement of the first and second brake members 11, 12 in the actuation unit allows preventing or reducing possible structural damages to the sliding elements 65 of the first lever member 6, which are normally hit by the cam units 92, when the cam assembly 9 returns to its rest position F.
The actuation unit 1, according to the invention, can therefore ensure improved levels of reliability in operation, which allows reducing maintenance interventions and costs.
As it is evident from the above, the first and second brake members 11, 12 can be easily integrated with the structure of the cam units 92 and the adjacent support walls 10. The actuation unit 1 can thus be realized with a very simple and compact structure.
On the other hand, the first and second brake members 11, 12 are quite simple and cheap to realize at industrial level. The arrangement of these brake members thus does not entail relevant cost increases for the actuation unit 1, which can thus be industrially manufactured at competitive costs with respect to the solutions of the state of the art.

Claims

An actuation unit (1) for a switching apparatus (100),
wherein said actuation unit is configured to actuate one or more movable contacts (103) of said switching apparatus during a closing manoeuvre and an opening manoeuvre of said switching apparatus,

wherein said actuation unit (1) comprises:
- a contact shaft (4) coupled to the movable contacts (103) of said switching apparatus and reversibly movable about a corresponding first rotation axis (A₁);

- first mechanical actuation means (5, 6, 7) coupled to said contact shaft (4) and configured to actuate said contact shaft during a closing manoeuvre of said switching apparatus;

wherein said first mechanical actuation means (5, 6, 7) comprise:
- a spring assembly (5) including one or more spring elements (50), wherein said spring assembly is configured to take reversibly a loaded condition (A), at which said spring elements are loaded and store mechanical energy, and a released condition (B), at which said spring elements have released the stored mechanical energy;

- a kinematic chain coupling said spring assembly (5) to said contact shaft (4), said kinematic chain including a first lever member (6) movable about a second rotation axis (A₂) parallel to said first rotation axis (A₁) and coupled to said spring assembly (5), wherein said first lever member is configured to move reversibly between a first position (C), which corresponds to a loaded condition (A) of said spring assembly (5), and a second position (D), which corresponds to a released condition (B) of said spring assembly;

wherein said actuation unit (1) further comprises mechanical loading means (8, 9) configured to actuate said first lever member (6) and said spring assembly in order to make said spring assembly (5) pass from said released condition (B) to said loaded condition (A),

wherein said mechanical loading means (8, 9) comprise a cam assembly (9) movable about a third rotation axis (A₃) parallel to said first rotation axis (A₁) and including one or more cam units (92), each cam unit having a cam surface (920) couplable to said first lever member (6),

wherein said cam assembly (9) is configured to move reversibly between a third position (E), which corresponds to a first position (C) of said first lever member (6), and a fourth position (F), which corresponds to a second position (D) of said first lever member;

characterised in that said actuation unit (1) comprises mechanically interacting brake members (11, 12) to brake said cam assembly (9),

wherein at least a cam unit (92) comprises a first brake member (11) configured to come into frictional contact with a corresponding second brake member (12) in fixed position relative to said cam unit (92), during a rotation movement of said cam assembly (9) from said third position (E) to said fourth position (F), the mechanical interaction between said first and second brake members (11, 12) causing a reduction of the rotational speed of said cam assembly (9).
Actuation unit, according to one of the previous claims, characterised in that said first and second brake members (11, 12) are positioned one relative to another, so that said first brake member (11) comes into frictional contact with said second brake member (12) at an initial stage of the rotation movement of said cam assembly (9) from said third position (E) to said fourth position (F).
Actuation unit, according to one of the previous claims, characterised in that each first brake member is formed by a contoured head (11) protruding from a first surface (92a) of a corresponding cam unit (92), said first surface (92a) facing a second surface (10a) of a corresponding support wall (10) of said actuation unit (3), a second brake member (12) being arranged on said second (10a).
Actuation unit, according to one of the previous claims, characterised in that each second brake member is formed by an elastically deformable lamina (12) fixed to a second surface (10a) of a support wall (10) of said actuation unit (3), said second surface facing a first surface (92a) of a corresponding cam unit (92) of said cam assembly (9), a first brake member (11) being arranged on said first surface (92a).
Actuation unit, according to claim 5, characterized in that each elastically deformable lamina (12) has first and second end regions (12a, 12b) fixed to said second surface (10a) and a bent central region (12c) oriented in such a way to protrude from said second surface (10a) towards said first surface (92a).
Actuation unit, according to claims 4 and 5, characterized in that the bent central region (12c) of each elastically deformable lamina (12) is subject to an elastic compression when the contoured head (11) of a corresponding cam unit (92) comes into frictional contact with said elastically deformable lamina (12).
Actuation unit, according to one of the claims from 4 to 6, characterised in that each elastically deformable lamina (12) is made of a spring steel material.
Actuation unit, according to one of the previous claims, characterised in that said spring assembly (5) includes a first end portion (51) fixed to a third support wall (10c), a second end portion (52) opposite to said first end portion and coupled to said first lever member (6) and one or more compression springs (50) arranged between said first and second end portions (51, 52).
Actuation unit, according to one of the previous claims, characterised in that said first lever member (6) has a third end portion (61) coupled to said spring assembly (5) and a fourth end portion (62) opposite to said third end portion and coupled to said contact shaft (4) through one or more second lever members (7), said first lever member comprising one or more sliding elements (65) arranged at said fourth end portion (62), each sliding element (65) having a sliding surface (650) couplable to the cam surface (920) of a corresponding cam unit (92) of said cam assembly (9).
Actuation unit, according to one of the previous claims, characterised in that said cam assembly (9) comprises a pair of cam units (92) spaced apart one from another along said third rotation axis (A₃).
Actuation unit, according to one of the previous claims, characterised in that it comprises a pair of mechanically interacting first and second members (11, 12) for each cam unit (92).
Actuation unit, according to one of the previous claims, characterised in that said cam assembly (9) is configured to actuate said first lever member (6) and make said first lever member move from said second position (D) to said first position (C), when said cam assembly (9) moves from said fourth position (F) to said third position (E) upon actuation by an actuating device (8) coupled to said cam assembly, wherein said cam assembly (9) is configured to hold said first lever member (6) when said cam assembly is in said third position (E), wherein said cam assembly (9) is configured to leave said first lever member (6) free to move from said first position (C) to said second position (D), when said cam assembly moves away from said third position (E).
Actuation unit, according to one of the previous claims, characterised in that said first lever member (6) is configured to actuate said spring assembly (5) and make said spring assembly pass from said released condition (B) to said loaded condition (A), when said first lever member moves from said second position (D) to said first position (C) upon actuation by said cam assembly (9), wherein said first lever member (6) is configured to hold said spring assembly (5) in said loaded condition (A) when first said lever member is in said first position (C), wherein said first lever member (6) is configured to leave said spring assembly (5) free to pass from said loaded condition (A) to said released condition (B), when said first lever member moves away from said first position (C).
Switching apparatus, according to one or more of the previous claims, characterised in that it comprises an actuation unit (3), according to one or more of the previous claims.
Switching apparatus, according to claim 14, characterised in that it is configured to operate at medium voltage levels.