ACTUATION UNIT FOR A SWITCHING APPARATUS

Abstract

An actuation unit for a switching apparatus is provided. The actuation unit includes a rotating contact shaft coupled to the movable contacts of the switching apparatus and first mechanical actuation means coupled to the contact shaft and configured to actuate the contact shaft during a closing maneuver of the switching apparatus. The first mechanical actuation means include a spring assembly, a first lever member coupled to the spring assembly and a plurality of second lever members coupling the first lever member to the contact shaft. The first mechanical actuation means include a rotating cam assembly including one or more cam members couplable to the first lever member of the first mechanical actuation means. The actuating unit includes a brake member for reducing the rotational speed of the cam assembly, when the cam assembly is rotating towards a rest position, during a closing maneuver of the switching apparatus.

Claims

1. An actuation unit for a switching apparatus wherein said actuation unit is configured to actuate one or more movable contacts of said switching apparatus during a closing maneuver and an opening maneuver of said switching apparatus, wherein said actuation unit comprises: a contact shaft coupled to the one or more movable contacts of said switching apparatus and reversibly movable about a corresponding first rotation axis; and first mechanical actuation means coupled to said contact shaft and configured to actuate said contact shaft during a closing maneuver of said switching apparatus, wherein said first mechanical actuation means comprise: a spring assembly including one or more spring elements, wherein said spring assembly is configured to take reversibly a loaded condition, at which said spring elements are loaded and store mechanical energy, and a released condition, at which said spring elements have released the stored mechanical energy; and a kinematic chain coupling said spring assembly to said contact shaft, said kinematic chain including a first lever member movable about a second rotation axis parallel to said first rotation axis and coupled to said spring assembly, wherein said first lever member is configured to move reversibly 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, wherein said actuation unit further comprises mechanical loading means configured to actuate said first lever member and said spring assembly in order to make said spring assembly pass from said released condition to said loaded condition, wherein said mechanical loading means comprise a cam assembly movable about a third rotation axis parallel to said first rotation axis and including one or more cam members, each cam member having a cam surface couplable to said first lever member, wherein said cam assembly is configured to move reversibly 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, wherein said actuation unit comprises, for at least a cam member of said cam assembly, a brake member configured to brake said cam assembly, and wherein each brake member is in a fixed position relative to a corresponding cam member and has a sliding surface configured to come into frictional contact with the cam surface of a corresponding cam member, during a rotation movement of said cam assembly from said third position to said fourth position, a mechanical interaction between the sliding surface of each brake member and the cam surface of the corresponding cam member causing a reduction of a rotational speed of said cam assembly.

2. The actuation unit according to claim 1, wherein each brake member is positioned relative to a corresponding cam member, so that the sliding surface of said brake member comes into frictional contact with the cam surface of said cam member at an initial stage of the rotation movement of said cam assembly from said third position to said fourth position.

3. The actuation unit according to claim 1, wherein each brake member is fixed to a corresponding support wall of said actuation unit in proximal position to a corresponding cam member of said cam assembly.

4. The actuation unit according to claim 1, wherein each brake member has a portion of elastic material including said sliding surface.

5. The actuation unit according to claim 1, wherein each brake member is formed by a roller fixed to a support wall of said actuation unit.

6. The actuation unit according to claim 5, wherein each roller has an outer layer of elastic material including said sliding surface.

7. The actuation unit according to claim 1, wherein said 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.

8. The actuation unit according to claim 1, wherein said first lever member has a third end portion coupled to said spring assembly and a fourth end portion opposite to said third end portion and coupled to said contact shaft through one or more second lever members, said first lever member comprising one or more sliding elements arranged at said fourth end portion, each sliding element having a sliding surface couplable to the cam surface of a corresponding cam member of said cam assembly.

9. The actuation unit according to claim 1, wherein said cam assembly comprises a pair of cam members spaced apart one from another along said third rotation axis.

10. The actuation unit according to claim 9, wherein the actuation unit comprises a brake member for each cam member.

11. The actuation unit, according to claim 1, wherein said cam assembly is configured to actuate said first lever member and make 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, wherein said cam assembly is configured to hold said first lever member when said cam assembly is in said third position, and wherein said cam assembly is configured to leave 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.

12. The actuation unit according to claim 1, wherein said first lever member is configured to actuate said spring assembly and make said spring assembly pass from said released condition to said loaded condition, when a first motion transmission assembly moves from said second position to said first position upon actuation by said cam assembly, wherein said first lever member is configured to hold said spring assembly in said loaded condition when first said lever member is in said first position, and wherein said first lever member is configured to leave 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.

13. A switching apparatus comprising the actuation unit according to claim 1.

14. The switching apparatus according to claim 13, wherein the switching apparatus is configured to operate at medium voltage levels.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Further characteristics and advantages of the disclosure will emerge from the description of example, but not exclusive embodiments of the contactor, according to the disclosure, non-limiting examples of which are provided in the attached drawings, wherein:

[0039] FIG. 1 is a schematic view of the switching apparatus including an actuation unit, according to the disclosure;

[0040] FIGS. 2-5 are schematic views of some mechanical components of the actuation unit shown in FIG. 1;

[0041] FIGS. 6-9 are schematic views showing the operation of the mechanical components shown in FIGS. 2-5.

DETAILED DESCRIPTION

[0042] With reference to the figures, the present disclosure relates to an actuation unit for a switching apparatus, such as a circuit breaker, a contactor, a disconnector or the like.

[0043] The actuation unit, according to the disclosure, 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.

[0044] FIG. 1 shows a schematic view of a switching apparatus 100 including an actuation unit 1 according to the disclosure.

[0045] The switching apparatus 100 includes one or more electric poles 101.

[0046] The switching apparatus 100 may be of the multi-phase type, more particularly of the three-phase type, as shown in the cited figures.

[0047] For each electric pole 101, the switching apparatus 100 includes 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.

[0048] 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.

[0049] As in the switching apparatus shown in the cited figures, each movable contact 103 may move 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.

[0050] 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 maneuver 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 maneuver of the switching apparatus.

[0051] 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 disclosure only, for the sake of brevity.

[0052] The switching apparatus 100 includes an actuation unit 1 configured to actuate the movable contacts 103 of the electric poles during a closing maneuver and an opening maneuver of the switching apparatus.

[0053] The actuation unit 1 may include 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.

[0054] According to the disclosure, the actuation unit 1 includes 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.

[0055] 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.

[0056] The contact shaft 4 is reversibly movable about a corresponding first rotation axis A.sub.1 may be oriented along a longer dimension of the actuation unit.

[0057] According to the disclosure, the actuation unit 1 includes first mechanical actuation means 5, 6, 7 configured to actuate the contact shaft 4 during a closing maneuver of the switching apparatus.

[0058] The above-mentioned first mechanical actuation means includes a spring assembly 5 including one or more spring elements 50.

[0059] 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.

[0060] 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.

[0061] The above-mentioned first mechanical actuation means further includes a kinematic chain 6, 7 coupling the spring assembly 5 to the contact shaft 4.

[0062] Such a kinematic chain includes a first lever member 6 configured to rotate about a second rotation axis A.sub.2 parallel to the first rotation axis A.sub.1 of the contact shaft 4.

[0063] The first lever member 6 is coupled to the spring assembly 5 and (indirectly) to the contact shaft 4.

[0064] 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 R.sub.1, R.sub.2 about the second rotation axis A.sub.2.

[0065] 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 A.sub.2 and is coupled (indirectly) to the contact shaft 4. At the fourth end portion 62, the first lever member 6 includes one or more sliding elements 65, each having a sliding surface 650.

[0066] FIG. 5 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 includes 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.

[0067] 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 A.sub.2 of the first lever member 6 and are configured to be pivoted on a pair of opposite support walls 10 of the actuation unit (as shown in FIG. 3).

[0068] At the fourth end portion 62, the first lever member 6 further includes 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 A.sub.2. 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.

[0069] 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 A.sub.1 of the contact shaft 4 and coupling the first lever member 6 (namely the fourth end portion 62 thereof) to the contact shaft 4.

[0070] Conveniently, the actuation unit 1 includes also second mechanical actuation means 2 configured to actuate the contact shaft 4 during an opening maneuver of said switching apparatus.

[0071] 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 disclosure, for the sake of brevity.

[0072] According to the disclosure, the actuation unit 1 further includes 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.

[0073] The above-mentioned mechanical loading means advantageously include 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.

[0074] As shown in FIG. 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.

[0075] 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 disclosure, for the sake of brevity.

[0076] The above-mentioned mechanical loading means further include a cam assembly 9 configured to rotate about a third rotation axis A.sub.3 parallel to the rotation axis A.sub.1 of the contact shaft 4.

[0077] The cam assembly 9 includes a motion transmission shaft 91 and one or more cam members 92 coupled to said motion transmission shaft.

[0078] 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 A.sub.3.

[0079] The motion transmission shaft 91 is coupled to the one or more actuating devices 8, may be at one of its opposite ends. To this aim, suitable gear mechanisms (not shown) of known type can be employed.

[0080] Each cam member 92 is coupled to the motion transmission shaft 91 in such a way to rotate together with said motion transmission shaft.

[0081] Each cam member 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.

[0082] According to the embodiment shown in the cited figures, the cam assembly 9 includes a pair of cam members 92 spaced apart one from another along the third rotation axis A.sub.3 and arranged on the motion transmission shaft 91, and may be in proximity of the opposite support walls 10 of the actuation unit 1, on which said motion transmission shaft is pivoted.

[0083] According to other embodiments of the disclosure, however, the cam assembly 9 may include a single cam member 92 in proximity of a corresponding support wall 10 of the actuation unit.

[0084] The cam assembly 9 is configured to move reversibly, by rotating about the third rotation axis A.sub.3 according to a same predefined direction R.sub.3, 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.

[0085] The cam surface 920 of each cam member 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.

[0086] According to the embodiment shown in the cited figures, the actuation unit 1 includes mechanical triggering means 13 couplable to the cam assembly 9, more particularly to a cam member 92 of said cam assembly.

[0087] The triggering means 13 include a triggering 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 in such a way to leave the cam assembly 9 free to move from the third position E to the fourth position F, when a closing maneuver of said switching apparatus is carried out.

[0088] 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 disclosure, for the sake of brevity.

[0089] 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 FIGS. 6-9.

[0090] The spring assembly 5 is supposed to be in a released condition B (FIG. 9).

[0091] 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 maneuver of the switching apparatus.

[0092] 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.

[0093] In order to load the spring assembly 5, the user activates an actuating device 8.

[0094] Upon actuation by the actuating device 8, the cam assembly 9 rotates according to the predefined third direction R.sub.3 and moves from the fourth position F (FIG. 9) towards the third position E (FIG. 6). During this movement of the cam assembly, the cam surface 920 of each cam member 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 R.sub.1, from the second position D (FIG. 9) towards the first position C (FIG. 6). In doing so, the first lever member 6 actuates the spring assembly 5 in such a way to compress the spring elements 50 (reference T.sub.1). The spring assembly 5 is thus brought from the released condition B (FIG. 9) to a loaded condition A (FIG. 6).

[0095] 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.

[0096] The actuation unit 1 is now ready to drive a closing maneuver of the switching apparatus.

[0097] In order to carry out a closing maneuver 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.

[0098] The cam assembly 9 is now free to move from the third position E (FIGS. 6-8) to the fourth position F (FIG. 9) by rotating always according to the predefined third direction R.sub.3. The cam assembly 9 thus leaves the first lever member 6 free to move from the first position C (FIGS. 9-10) to the second position D (FIG. 9) by rotating according to a second direction R.sub.2 opposite to the first direction R.sub.1. In turn, the first lever member 6 leaves the spring assembly 5 free to pass (reference T.sub.2) from the loaded condition A (FIG. 6) to a released condition B (FIG. 9).

[0099] 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).

[0100] An essential aspect of the disclosure consists in that the actuation unit 1 includes, for at least a cam member 92 of the cam assembly 9, a brake member 12 configured to brake said cam assembly during the rotation movement from the third position E to the fourth position F (such a rotation movement occurs during a closing maneuver of the switching apparatus as explained above).

[0101] Each brake member 12 is arranged in fixed position relative to a corresponding cam member 92 and has a sliding surface 120 configured to come into frictional contact with the cam surface 920 of the corresponding cam member 92, during a rotation movement of the cam assembly 9 from the third position E to the fourth position F (rest position). The mechanical interaction between the sliding surface 120 of each brake member 12 and the cam surface 920 of the corresponding cam member 92 causes a reduction of the rotational speed of the cam assembly.

[0102] According to the embodiment shown in the cited figures, the actuation unit 1 includes a brake member 12 for each cam member 92 of the cam assembly 9.

[0103] According to other embodiments (not shown), however, even if the cam assembly 9 includes a pair of cam members 92, the actuation unit 1 may include a brake member 12 only for one of the cam members 92 of the cam assembly 9.

[0104] According to an aspect of the disclosure, each brake member 12 is positioned relative to a corresponding cam member 92 of the cam assembly, so that the sliding surface 120 of the brake member comes into frictional contact with the cam surface 920 of the cam member 92 at an initial stage of the rotation movement of the 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.

[0105] According to an aspect of the disclosure, each brake member 12 has a portion of elastic material (for example rubber) including the sliding surface 120. This solution improves remarkably the dissipation of the kinetic energy of the cam assembly 9, when each cam member 12 comes into frictional contact with the corresponding cam member 92 of the cam assembly. The rotational speed of the cam assembly 9 may thus be reduced more efficiently.

[0106] According to an aspect of the disclosure, each brake member 12 is fixed to a support wall 10 of the actuation unit in proximal position to a corresponding cam member 92 of the cam assembly. Each brake member 12 is positioned so that it does not interact with the corresponding cam member 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 corresponding cam member 92 only when the cam assembly 9 moves from the third position E to the fourth position F (i.e., during a closing maneuver of the witching apparatus).

[0107] According to an aspect of the disclosure, each brake member 12 is formed by a roller fixed to a support wall 10 of the actuation unit as explained above. The roller 12 includes a sliding surface 120 couplable to the cam surface 920 of a corresponding cam member 92 when the cam assembly 9 moves from the third position E to the fourth position F.

[0108] Each roller 12 may have an outer layer 120a of elastic material (e.g., rubber), which includes the sliding surface 120. In practice, the rotating outer surface of the roller 12 forms the above-mentioned sliding surface 120 intended to come into frictional contact with the cam surface 920 of a corresponding cam member 92. As mentioned above, this solution makes more effective the braking action of the brake members 12. In fact, when a roller 12 comes into frictional contact with a corresponding cam member 92, the outer layer 120a is subject to an elastic deformation, which effectively dissipates the kinetic energy of the cam assembly 9.

[0109] The operation of brake member 12 of the actuation unit 1 is described in more details with reference to FIGS. 12-14.

[0110] When the cam assembly 9 moves from the third position E to the fourth position F by rotating according to the predefined third rotation direction R.sub.3, the sliding surface 120 of the roller 12 comes into frictional contact with the cam surface 920 of a corresponding cam member 92 (FIGS. 6-7).

[0111] At this initial braking phase, the outer layer 120a starts deforming elastically and the cam assembly 9 starts reducing its rotational speed.

[0112] As the rotation of the cam assembly 9 continues (FIG. 8), the cam member 92 causes a progressively increasing deformation of the outer layer 120a of the roller 12. The dissipation of kinetic energy of the cam assembly 9 increases accordingly. The cam assembly 9 is thus subject to a progressive decrease of rotational speed until it reaches the fourth position F (rest position).

[0113] As it is evident from the above, the mutual interaction between each brake member 12 and the cam surface 920 of the corresponding cam member 92 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 members 92 with the surrounding components (e.g., the sliding elements 65 of the first lever member 6) can be effectively mitigated.

[0114] As mentioned above, the mechanical interaction between each roller 12 and the cam surface 920 of the corresponding cam member 92 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 DISCLOSURE

[0115] The actuation unit 1, according to the disclosure, provides remarkable advantages with respect to the known apparatuses of the state of the art.

[0116] The arrangement of one or more brake members 12 allows prolonging remarkably the operating life of the components of the actuation unit, which are configured to interact with the cam members 92 during the rotational movements of the cam assembly 9.

[0117] In particular, the arrangement of the brake members 12 in the actuation unit allows preventing or reducing possible structural damages to the sliding elements 65 of the first lever 6, which are normally hit by the cam members 92, when the cam assembly 9 returns in its rest position F.

[0118] The actuation unit 1, according to the disclosure, can therefore ensure improved levels of reliability in operation, which allows reducing maintenance interventions and costs.

[0119] As it is evident from the above, the one or more brake members 12 can be easily integrated with the structure of the cam members 92 and the adjacent support walls 10. The actuation unit 1 can thus be realized with a very simple and compact structure.

[0120] On the other hand, the one or more brake members 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.