Normally closed power contactor

Abstract

The invention relates to a normally closed contactor (21) which comprises a fixed contact (22) and a movable contact (23) facing each other in a housing (25), the movable contact (23) being movable between a closed position and an open position. A contact pressure spring (26) pushes the movable contact towards the fixed contact. An actuator (27) comprises a movable portion (29) rigidly connected to the movable contact (23) which moves it from the closed position to the open position. A return spring (33) pushes the movable portion (29) into its closed position. The mechanical anti-rebound device (34) comprises a first locking part (35) rigidly connected to the housing and a second locking part (36) opposite the first and rigidly connected to the movable portion (29), these locking parts (35, 36) being engaged in mutual locking when the movable contact (23) is in its closed position.

Description

DESCRIPTION Normally closed power contactor TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of power contactors, in particular that of normally closed power contactors.

[0002] The present invention relates to a normally closed power contactor and in particular comprising a mechanical anti-bounce device. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] A power contactor is an electrical device designed to establish or interrupt the flow of electric current. It usually includes a fixed contact and a movable contact, which allow the flow of current when they are in mechanical contact, and which interrupt the flow of current when they are at a distance from each other.

[0004] A normally closed power contactor is a contactor for which, in the rest state, the fixed contact is in mechanical contact with the moving contact, which therefore allows the flow of electric current.

[0005] The field of the invention being that of normally closed power contactors, for reasons of simplification, such a normally closed power contactor will hereinafter simply be referred to as a “contactor”.

[0006] Figure 1 shows the usual geometry of such a contactor in its rest position.

[0007] As shown in Figure 1, a contactor 1 according to the prior art comprises a fixed contact 2 and a movable contact 3 facing each other housed at least partially in a contactor chamber 4 protected by a casing 5. The contactor 1 extends along an axis X-X'. A contact pressure spring 6 pushes the movable contact 3 towards the fixed contact 2 so that in the rest position of the contactor 1, the fixed contact 2 is in mechanical contact with the movable contact 3. The contactor 1 also comprises an actuator 7 extending along the axis X-X', for example with a linear motor, generally electromagnetic, but which can also be of the pneumatic, hydraulic, or other type. In Figure 1, it is an actuator 7 with an electromagnetic motor which is shown, comprising a winding 16, an external protection generally designated as a body 8, a fixed part 15 fixed to the body 8 and generally designated as a yoke, and a movable part 9 generally designated as a movable core. The movable part 9 longitudinally moves the movable contact 3 away from the fixed contact 2 along the axis X-X' when the actuator 7 is powered, compressing the contact pressure spring 6 elastically and preventing the flow of current. Referring to Figure 1, when the linear motor is actuated, the movable part 9 of the actuator 7 and the movable contact 3 move to the right.

[0008] According to an embodiment of the prior art shown in Figure 1, the fixed contact 2 comprises a contact pad 17, while the movable contact 3 also comprises a contact pad 18, these contact pads 17, 18 being provided to be in contact and allow the passage of electric current when the fixed 2 and movable 3 contacts are in mutual contact.

[0009] The movement of the movable contact 3 by the actuator 7 is guided by a guide subassembly comprising a movable axis 10, a first part of which is connected to the movable contact 3 and a second part of which is integral with the movable part 9 of the actuator 7 by means of a connecting rod 14. The movable axis 10 of the guide subassembly and the movable part 9 of the actuator 7 are guided in sliding along the axis X-X', that is to say along the linear movement axis of the actuator 7. For the movable axis 10, this guidance is carried out by a guide ring 11 mounted in the contactor chamber 4 and fixed to the casing 5, while the guidance of the movable part 9 of the actuator 7 is carried out by a guide part 12 mounted on or in a single piece with the body 8 of the actuator 7.

[0010] In the actuator 7, the end of the movable part 9 which is not connected to the movable contact 3 is in contact with a return spring 13, also referred to as a "core return spring", which is elastically compressed when the movable part 9 is moved away from the fixed contact 2. The return spring 13 is usually located between the fixed part 15 and the movable part 9 of the actuator 7.

[0011] When the power supply to the actuator 7 is stopped, the pressure force exerted by the contact pressure spring 6 and the return spring 13 pushes the movable contact 3 into mechanical contact with the fixed contact 2. Referring to Figure 1, when the linear motor of actuator 7 is no longer powered, the moving part 9 of actuator 7 and the moving contact 3 move to the left.

[0012] When the movable part 9 of the actuator 7 reaches the end of its travel, the movable part 9 of the actuator 7 or a part integral with it strikes a stop, for example a fixed part of the casing 5 of the contactor 1 or a part integral with it. The movable part 9 of the actuator 7 is then a mass suspended from the return spring 13 which thereby undergoes an impact and then undergoes oscillations linked to the damping coefficient of the return spring 13. These oscillations caused by the return spring 13 generate mechanical rebounds of the movable contact 3 on the fixed contact 2.

[0013] Indeed, when a switch, commutator, relay, etc. is actuated, what a human perceives as a single instantaneous response to each change in state of the device may in fact involve hundreds of opening and closing actions that persist for several thousandths of a second before the contacts position. It is these multiple opening and closing actions that are referred to as bounces.

[0014] When the power supply is switched off, the moving contacts close on the fixed contacts but rebounds can occur via the core return spring.

[0015] These mechanical bounces can cause arcing, which can lead to serious problems, such as welding and contact erosion. These bounces can therefore reduce the performance of the contactor and can even lead to the contacts sticking together, rendering the contactor inoperative.

[0016] The characteristics of these bounces depend on several parameters, including the closing force, the nature of the contact material, the shape of the contacts, and the characteristics of the electrical circuit. In power contactors, the switching kinematics of the contact produce vibrations throughout the system. Normally, these bounces have little or no effect on the circuit, but if the system includes a digital circuit fast enough to detect and respond to multiple bounces, this can have serious consequences.

[0017] Anti-bounce solutions have been developed to prevent or reduce bounce within a contactor, or to neutralize its effects.

[0018] Among these solutions are software-based anti-bounce solutions, but these solutions, although they protect electrical circuits from the harmful effects of bounces, do not protect the contactor itself, particularly against damage resulting from electric arcs.

[0019] The common hardware solution to prevent bounce is to increase the stiffness of the springs, particularly the core return spring. This solution, while seemingly simple to implement, requires a more powerful actuator, which is therefore larger and heavier. These drawbacks are unacceptable for aeronautical applications where weight and volume are critical.

[0020] There is therefore a need for a hardware anti-bounce solution that is not based on modifying the properties of the existing springs. Advantageously, this solution must be simple to implement, reliable, robust, inexpensive and it must not modify the mechanical properties of the contactor.

[0021] The means for implementing it must be light and not increase the overall volume of the contactor equipped with it. SUMMARY OF THE INVENTION

[0022] The invention offers a solution to the problems mentioned above, by providing a mechanical anti-rebound device which, when the fixed contact and the movable contact are in the closed position, immobilizes the movable part of the actuator which is integral with the movable contact with an immobilization force whose force is greater than the rebound forces in order to prevent the latter from undergoing oscillations caused by the return spring.

[0023] One embodiment of the invention relates to a normally closed power contactor comprising: a housing, a fixed contact and a movable contact housed at least partially in the housing and located opposite each other, the movable contact being movable between a closed position where it is in mechanical contact with the fixed contact and an open position where it is at a distance from the fixed contact, a contact pressure spring exerting a thrust force on the movable contact towards the fixed contact, the normally closed power contactor being such that it comprises a mechanical anti-rebound device comprising: a first locking part secured to the housing, and a second locking part opposite the first locking part and secured to the movable contact; such that the first locking part and the second locking part are engaged in mutual locking by elastic deformation when the movable part is in the first position.

[0024] According to one embodiment of the invention, the normally closed power contactor comprises: an actuator comprising a fixed part and a movable part connected to the movable contact, the movable part being movable between a first position and a second position, the movement of the movable part from the first position to the second position causing the movable contact to move from the closed position to the open position with a displacement force provided by the actuator when energized, and the displacement force provided by the actuator when energized is greater than the sum of the elastic deformation force of the mutual locking of the locking parts and the pushing force of the contact pressure spring.

[0025] According to another embodiment of the invention, the normally closed power contactor is such that: the first locking part or the second locking part comprises a flexible and elastic blade having an elastic portion and a portion raised relative to the elastic portion, and respectively the second locking part or the first locking part comprises a recessed receiving portion in which the raised portion is received when the first locking part and the second locking part are engaged in mutual locking.

[0026] According to a further embodiment of the invention, the hollow receiving portion is an annular groove.

[0027] According to one embodiment of the invention, the first locking part or the second locking part is a male part having a projecting part, while respectively the second locking part or the first locking part is a female part having a housing, the projecting part being inserted into the housing of the female part when the first locking part and the second locking part are engaged in mutual locking.

[0028] According to another embodiment of the invention, the female part has a flexible and elastic blade in the form of an annular crown.

[0029] According to an additional embodiment of the invention, the female part comprises several flexible and elastic blades arranged in a crown.

[0030] According to one embodiment of the invention, the immobilizing force exerted by the mechanical anti-rebound device is greater than 5 Newtons.

[0031] According to another embodiment of the invention, the normally closed power contactor is such that: the actuator comprises a fixed part, the power contactor comprises a return spring located between the fixed part and the movable part of the actuator, said return spring pushing the movable part into its first position with a pushing force, and the displacement force provided by the actuator when powered is greater than the sum of the elastic deformation force of the mutual locking of the locking parts, the pushing force of the contact pressure spring and the pushing force of the return spring.

[0032] According to an additional embodiment of the invention, the normally closed power contactor is such that: it comprises a movable shaft and a guide ring fixed to the casing, the movable contact is secured to the movable part by means of the movable shaft which is guided in sliding by the guide ring, and the first locking part is fixed to the guide ring or is formed in one piece with it.

[0033] In addition to the characteristics which have just been mentioned in the preceding paragraph, the normally closed power contactor according to embodiments of the invention may have one or more additional characteristics among the following, considered individually or according to all technically possible combinations: The first locking piece and the second locking piece are each a revolution piece. The return spring is located between the fixed part and the moving part of the actuator. On its face comprising the hollow receiving part, the male part has a tapered part located before the hollow receiving part, on the actuator side. The second locking part has a collar fixed on one face of the moving part of the actuator which is directed towards the fixed and moving contacts.

[0034] By means of the invention, a hardware anti-bounce solution is provided, which is not based on a modification of the properties of the spring(s) in place. This hardware anti-bounce solution provides a kind of harpoon which tends to lock the two contacts so as to prevent or limit the rebound phenomenon.

[0035] The mechanical anti-rebound device supplements the lack of force of the return spring in order to prevent the moving part of the actuator from recoiling after the shock caused by its contact with a stop.

[0036] The mechanical anti-bounce device according to the invention is advantageously reliable, robust and inexpensive, it is simple to implement without requiring major modification of existing contactors, nor modifying the mechanical properties of the contactor significantly. It is lightweight and can be easily housed in the body of the contactor without increasing its overall volume.

[0037] The mechanical anti-rebound device according to the invention generates an additional force to be provided by the actuator when moving the movable contact from the closed position to the open position, but this force is advantageously absorbed by the motorization of the actuator because said force must be provided in an operating range of the actuator which is not located in its critical zone of use.

[0038] Finally, the mechanical anti-bounce device according to the invention advantageously provides improved breaking performance, with tests having demonstrated a doubling of the breaking capacity under short-circuit current.

[0039] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0040] The figures are presented for information purposes only and in no way limit the invention.

[0041] [Fig. 1] Figure 1 is a longitudinal sectional view of a normally closed power contactor according to the prior art shown in the closed state.

[0042] [Fig. 2] Figure 2 is a longitudinal sectional view of a normally closed power contactor according to the invention shown in the closed state.

[0043] [Fig. 3] Figure 3 is a longitudinal sectional view of a normally closed power contactor according to the invention shown in the open state.

[0044] [Fig. 4] Figure 4 is a detail view of Figure 2.

[0045] [Fig. 5] Figure 5 is a detail view of Figure 3. DETAILED DESCRIPTION

[0046] Unless otherwise specified, the same element appearing in different figures has a single reference.

[0047] In this description, the term "solid" means a mechanical part which is mechanically joined, directly or indirectly, to another, but without play, so that any movement made by one part causes an identical movement, without possible play, for another part which is solid with it.

[0048] Similarly, by the term "connected" we mean a mechanical part which is mechanically connected, directly or indirectly, to another, with possible play, so that any movement made by one part can cause, but not necessarily, a movement, with possible play, for another part which is connected to this one.

[0049] Finally, by "part of revolution" is meant a three-dimensional part whose general body shape can be formed by rotating a flat surface around an axis. Known examples of part of revolution are cones and cylinders, hollow or solid. Indeed, certain parts of the normally closed power contactor according to the invention may have a general cylindrical shape, with conical parts, grooves and / or ribs. In order to designate parts which can have this complex shape, we then speak of part of revolution.

[0050] As a reminder, a normally closed power contactor will hereinafter simply be referred to as a “contactor”.

[0051] Generally, the contactor 21 of the invention comprises a fixed contact 22 and a movable contact 23 provided opposite each other in a contactor chamber 24 protected by a casing 25. The movable contact 23 is movable between a closed position where it is in mechanical contact with the fixed contact 22 and an open position where it is at a distance from the fixed contact 22. A contact pressure spring 26, preferably housed in the contactor chamber 24, pushes the movable contact 23 towards the fixed contact 22.

[0052] The contactor 21 of the invention extends along an axis X-X' and also comprises an actuator 27, with a linear motor of the electromagnetic, pneumatic, hydraulic or other type. The actuator 27 comprises a fixed part 47 and a movable part 29, the movable part 29 being connected to the movable contact 23 and preferably moved by a linear motor. The movable part 29 of the actuator 27 is movable along the axis X-X' between a first position and a second position, corresponding to the closed position and the open position of the fixed 22 and movable 23 contacts. Indeed, the movable part 29 is connected to the movable contact 23 so that the movement of the movable part 29 from the first position to the second position causes a movement along the axis X-X' of the movable contact 23 from the closed position to the open position.

[0053] The actuator 27 comprises a return spring 33 which pushes the movable part 29 into its first position. This return spring 33 is preferably located between the fixed part 47 and the movable part 29 of the actuator 27.

[0054] In Figures 2 to 5, the actuator 27 is shown by way of example in the form of an electromagnetic actuator 27, comprising a winding 48 and an external protection designated as body 28 in which the fixed part 47, the movable part 29, the winding 48 and the return spring 33 are housed.

[0055] According to an embodiment of the invention shown in Figures 2 to 5, the movable part 29 of the actuator 27 is secured by means of a connecting rod 46 to a movable axis 30 which separates the movable contact 23 from the fixed contact 22 when the movable part 29 is moved from the first position to the second position, corresponding to the opening position of the fixed 22 and movable 23 contacts.

[0056] According to a preferred embodiment of the invention shown in Figures 2 to 5, the fixed contact 22 comprises a contact pad 50, while the movable contact 23 also comprises a contact pad 51, these contact pads 50, 51 being designed to be in contact and allow the passage of electric current when the fixed 22 and movable 23 contacts are in mutual contact. The fixed 22 and movable 23 contacts are for example made of copper, while the contact pads 50, 51 are for example made of silver oxide and brazed onto their respective contact.

[0057] Due to the manufacturing tolerances of the actuator 27 and the erosion of the contacts 23 and 22 or the contact pads 50, 51 of said contacts 23, 22, the movement of the movable part 29 from the first position to the second position causes a movement of the movable contact 23 from the closed position to the open position with a certain delay, after a very short stroke, for example of the order of 1 millimeter, due to a clearance between the movable axis 30 and the movable contact 23. This delay of the order of 1 millimeter corresponds to an assertion stroke of the contact pressure spring 26.

[0058] In the case where the contacts 23 and 22 are each equipped with a contact pad 50, 51, this value of the order of 1 millimeter corresponds to the erosion that the contact pads 50, 51 will undergo during their life. Thus, at the start of the life of the contact pads 50, 51, the assertion stroke of the contact pressure spring 26 is of the order of 1 millimeter, while at the end of the life of the contact pads 50, 51, this assertion stroke tends towards 0 millimeter. Between these two values ​​the contact pressure decreases slightly, but minimally, the contact pressure spring 26 being chosen accordingly.

[0059] For this purpose, according to an embodiment given by way of example and shown in Figures 2 to 5, the movable contact 23 is driven away from the fixed contact 22 by an intermediate part 49 mounted integrally on the movable axis 30 when said intermediate part 49 is driven to bear on the movable contact 23 by connecting rod 46, by means of the movable axis 30 and the connecting rod 46. When the movable part 29 of the actuator 27 is moved from the first position to the second position, the connecting rod 46, the movable axis 30 and the intermediate part 49 are moved in an identical manner.At the end of a very short stroke, for example less than 1 millimeter, and during which the movable contact 23 is not moved, a stop 52 located on the intermediate part 49 opposite the movable contact 23 comes into contact with said movable contact 23 and drives it away from the fixed contact 22, and continues to move it away from it as long as the movable part 29 of the actuator 27 is moved from the first position to the second position. This movement stops when the movable part 29 of the actuator 27 is in the second position, the movable contact 23 then being in the open position, at a distance from the fixed contact 22.

[0060] According to an embodiment of the invention shown in Figures 2 to 5, the movement along the axis X-X' of the movable part 29 of the actuator 27 is guided by a guide part 32, for example mounted on or in a single piece with the body 28 of the actuator 27, while the movement along the axis X-X' of the movable axis 30 is guided by a guide ring 31, for example fixed to the casing 25.

[0061] When the movable part 29 is moved from its second position to its first position, this movable part 29 or a part integral with it, for example the movable axis 30, strikes an end-of-travel stop, which tends to make it move back and therefore to move the movable part 29 away from its second position. The return spring 33 then tends to push the movable part 29 back into its second end-of-travel position, which again strikes an end-of-travel stop, and so on in an oscillating manner, which results in multiple opening and closing actions between the movable contact 23 and the fixed contact 22 which are designated as rebounds.

[0062] In order to prevent rebounds caused by the return spring 33 when the moving part 29 is moved from its second position to its first position, the contactor 21 of the invention comprises a mechanical anti-rebound device 34 provided to fix the moving masses in the closed position before these masses rebound due to the end-of-travel stop and oscillate due to the return spring 33.

[0063] The mechanical anti-rebound device 34 of the invention comprises a first locking part 35 secured to the casing 25, and a second locking part 36 located opposite the first locking part 35 and secured to the movable part 29 of the actuator 27. When the movable part 29 is moved from the second position to the first position, the first locking part 35 and the second locking part 36 are engaged in mutual locking. This locking engagement exerts an immobilizing force on the second locking part 36 greater than the tension forces exerted by the return spring 33 so that the second locking part 36 can no longer rebound due to the return spring 33 when it is locked with the first locking part 35.

[0064] The immobilizing force exerted by the mechanical anti-rebound device 34 is preferably greater than 5 Newtons, which makes it possible to avoid the rebound phenomenon, while nevertheless allowing an actuator 27 usually used in a contactor 21 to have sufficient power to move the movable part 29 from the first position to the second position and thus separate the first locking part 35 and the second locking part 36 which are engaged in mutual locking.

[0065] According to a preferred embodiment of the invention, the first locking part 35 and the second locking part 36 are each a part of revolution.

[0066] According to a preferred embodiment of the invention, the first locking part 35 or the second locking part 36 comprises a flexible and elastic blade 37 having a raised portion 38 relative to the rest of the body of the flexible and elastic blade 37 and which is received in a hollow receiving portion 39 provided in the other locking part - that is to say respectively the second locking part 36 or the first locking part 35 - when the first locking part locking piece 35 and the second locking piece 36 are engaged in mutual locking, the other locking piece 36 being respectively the second locking piece 36 or the first locking piece 35.

[0067] According to this embodiment, it is the engagement of the raised portion 38 in the recessed receiving portion 39 which locks the first locking part 35 with the second locking part 36 in the manner of a clip. The force to deform the flexible and elastic blade 37 is not significant compared to the closing forces caused by the contact pressure spring 26 and by the return spring 33. Similarly, the elastic deformation force of the flexible and elastic blade 37 is less than the force of the actuator 27 when it is powered, so the locking force of the first locking part 35 with the second locking part 36 is largely exceeded by the force developed by the actuator 27.

[0068] In Figures 2 to 5, illustrating a preferred embodiment of the invention, it is the second locking part 36 which comprises a flexible and elastic blade 37, while it is the first locking part 35 which has a hollow receiving part 39.

[0069] The hollow receiving part 39 is preferably an annular groove 40. This annular groove 40 is preferably provided to receive a raised part 38 of a flexible and elastic blade 37 in the form of an annular crown or the raised part 38 of several flexible and elastic blades 37 arranged in a crown.

[0070] According to a preferred embodiment of the invention, the first locking part 35 or the second locking part 36 is a male part having a projecting part 41, while the other locking part - respectively the second locking part 36 or the first locking part 35 - is a female part having a housing 42, the projecting part 41 being inserted into the housing 42 of the female part when the first locking part 35 and the second locking part 36 are engaged in mutual locking.

[0071] The female part preferably comprises a flexible and elastic blade 37 in the form of an annular crown or several flexible and elastic blades 37 arranged in a crown.

[0072] In Figures 2 to 5, illustrating a preferred embodiment, the first locking part 35 is a male part, while the second locking part 36 is a female part.

[0073] According to a preferred embodiment of the invention, the male part has a tapered part 43 provided on its face comprising the hollow receiving part 39, this tapered part 43 being located before the hollow receiving part 39, on the side of the actuator 27, so as to form a guide and sliding ramp for the raised part 38 of each flexible and elastic blade 37.

[0074] The second locking part 36 preferably has a collar 44, for example substantially orthogonal to the flexible and elastic blade 37, which is fixed on the face 45 of the movable part 29 of the actuator 27 which is directed towards the fixed 22 and movable 23 contacts.

[0075] According to one embodiment of the invention, the movable contact 23 is connected to the movable part 29 via the movable axis 30 which is guided in sliding by a guide ring 31 fixed to the casing 25. According to this embodiment, the first locking part 35 is preferably fixed to the guide ring 31 or in a single piece with it.

[0076] Of course, the first locking part 35 can be fixed to another element of the contactor 21, even in the case where the latter comprises a guide ring 31.

[0077] It will also be noted that the mechanical anti-bounce device 34 may comprise several first locking parts 35 and second locking parts 36. Similarly, the contactor 21 according to the invention may comprise several mechanical anti-bounce devices 34.

[0078] Finally, although the figures illustrate a single-pole contactor 21, it is obvious that the mechanical anti-bounce device 34 can be fitted to a multi-pole contactor, for example two-pole or three-pole. In these configurations, a single mechanical anti-bounce device 34 can be used, which retains the moving masses of all the poles, or else a mechanical anti-bounce device 34 can be provided individually for each pole, the principle always being to counter the forward-backward oscillation forces caused by the rebounds of the moving masses.

Claims

CLAIMS

1. A normally closed power contactor (21) comprising: - a casing (25), - a fixed contact (22) and a movable contact (23) housed at least partially in the casing (25) and located opposite each other, the movable contact (23) being movable between a first closed position where it is in mechanical contact with the fixed contact (22) and a second open position where it is at a distance from the fixed contact (22), - a contact pressure spring (26) exerting a pushing force on the movable contact (23) in the direction of the fixed contact (22), - an actuator (27) comprising a fixed part (47) and a movable part (29) connected to the movable contact (23), the movable part (29) being movable between a first position and a second position, the movement of the movable part (29) from the first position to the second position causing a movement of the movable contact (23) from the first closed position to the second open position with a displacement force provided by the actuator (27) when it is powered, - a return spring (33) pushing the movable part (29) into its first position with a pushing force, - the normally closed power contactor (21) being characterized in that it comprises a mechanical anti-bounce device (34) comprising: - a first locking part (35) secured to the casing (25), and - a second locking part (36) opposite the first locking part (35) and secured to the movable contact (23); in that - the first locking part (35) and the second locking part (36) are engaged in mutual locking by elastic deformation when the movable part (29) is in the first position, this engagement in mutual locking exerting an immobilizing force on the second locking part (36) greater than the tension forces exerted by the return spring (33), the immobilizing force being the locking engagement force; and in that - the actuator (27) has sufficient power to move the movable part (29) from the first position to the second position and thus separate the first locking part (35) and the second locking part (36) and disengage their mutual locking.

2. A normally closed power contactor (21) according to claim 1, characterized in that the displacement force provided by the actuator (27) when energized is greater than the sum of the elastic deformation force of the mutual locking of the locking parts (35, 36), the pushing force of the contact pressure spring (26) and the pushing force of the return spring (33). [Claim s] Normally closed power contactor (21) according to claim 1 or claim 2, characterized in that: - the first locking part (35) or the second locking part (36) comprises a flexible and elastic blade (37) having an elastic part and a raised part (38) relative to the elastic part, and in that - respectively the second locking part (36) or the first locking part (35) comprises a hollow receiving part (39) in which the raised part (38) is received when the first locking part (35) and the second locking part (36) are engaged in mutual locking.

4. Normally closed power contactor (21) according to the preceding claim, characterized in that the hollow receiving part (39) is an annular groove (40). [Claim s] Normally closed power contactor (21) according to any one of the preceding claims, characterized in that the first locking piece (35) or the second locking piece (36) is a male piece having a projecting portion (41), while respectively the second locking piece (36) or the first locking piece (35) is a female piece having a housing (42), the projecting portion (41) being inserted into the housing (42) of the female piece when the first locking piece (35) and the second locking piece (36) are engaged in mutual locking.

6. Normally closed power contactor (21) according to the preceding claim, characterized in that the female part has a flexible and elastic blade (37) in the form of an annular crown.

7. Normally closed power contactor (21) according to claim 5, characterized in that the female part comprises several flexible and elastic blades (37) arranged in a crown. [Claim s] Normally closed power contactor (21) according to any one of the preceding claims, characterized in that the immobilizing force exerted by the mechanical anti-bounce device (34) is greater than 5 Newton.

9. Normally closed power contactor (21) according to any one of the preceding claims, characterized in that the return spring (33) is located between the fixed part (47) and the movable part (29) of the actuator (27).

10. Normally closed power contactor (21) according to any one of the preceding claims, characterized in that: - it comprises a movable axis (30) and a guide ring (31) fixed to the casing (25), in that - the movable contact (23) is secured to the movable part (29) by means of the movable axis (30) which is guided in sliding by the guide ring (31), and in that - the first locking part (35) is fixed to the guide ring (31) or is formed in one piece with it.

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