EP2867912B1 - Electrical switch forming a fast actuation circuit breaker - Google Patents

Description

The present invention relates to an electrical switch forming in particular circuit breaker. More particularly, the invention relates to an electrical switch "with sliding assembly", and in particular an electrical switch of the type comprising a hollow body delimiting a cavity, a sliding assembly comprising at least one conductive portion and adapted to move in said cavity for a first position, said initial, to a second position, an actuator arranged to cooperate with said sliding assembly and move in said cavity, and at least two primary electrical conductive pads, respectively an upstream pad and a downstream pad, each comprising a ring opening in said cavity, said rings being coaxial and axially offset along the direction of movement of the sliding assembly, wherein the conductive portion of the sliding assembly is at least in tight electrical contact with the two primary electrical conductive pads when the sliding assembly is in its first re position and, when the sliding assembly is in its second position, the upstream electrical conductive pad is released from the conductive portion of said sliding assembly.

The electrical switch object of this disclosure forms mainly circuit breaker and can also be used as an electrical switch. It is particularly suitable for electrical circuits for high current.

Throughout the present description, the term "primary electrical conductive pads" refers to the electrical conductive pads which are connected to the conductive portion of the sliding assembly when it is in its first position, ie say when the electrical switch is in its initial state.

In contrast, the term "secondary electrical conductor pads" refers to the electrical conductive pads which are connected to the conductive portion of the sliding assembly only when the latter is in its second position (in the case where a component of the first electrical circuit has been isolated , for example because considered to be faulty, and where a second electrical circuit is closed).

In many applications, it is necessary to have fast and reliable electrical switches to open a faulty circuit to isolate one or more components including when they are faulty, and also allowing, if necessary, to simultaneously close a branch circuit.

The document FR 2,953,322 discloses an example of an electrical switch of the aforementioned type, according to the preamble of claim 1, wherein the electrical contact between the sliding assembly and the conductive pads is achieved by tightening the rings, or that these rings are split, which gives a certain elasticity to the electrical junction, that is to say that the sliding assembly is engaged by forced engagement between the rings. In the long term, the split rings however lose their shape, and have a tendency to ovalise under the effect of the relaxation of the stresses. In this case, the electrical contact between the rings and the sliding assembly may be uncertain or simply broken. The forced assembly of the sliding assembly between the annular rings of the conductive pads is difficult for him.

An object of the present invention is to provide an electrical switch without the disadvantages mentioned above.

In particular, an object of the present invention is to provide an electrical switch of the aforementioned type that can be assembled very simply, acting in a very short time and ensuring reliable electrical connections over time.

More specifically, the invention relates to an electrical switch comprising a hollow body delimiting a cavity, a sliding assembly comprising at least one conductive portion and adapted to move in said cavity from a first, so-called initial position to a second position, an actuator arranged to cooperate with said sliding assembly and move it in said cavity, and at least two primary electrical conductive pads, respectively an upstream pad and a downstream pad, each comprising a ring opening into said cavity, said rings being coaxial and axially offset along the direction of movement of the sliding assembly, wherein the conductive portion of the sliding assembly is connected by a clamping force with the two primary electrical conductive pads when the sliding assembly is in its first position and, when the sliding assembly is in its second position, the stud c onducteur Upstream electric is disengaged from the conductive portion of said sliding assembly, said switch being characterized in that the sliding assembly comprises at least one tube provided with a slot extending over its entire length, and in that the conductive portion of the sliding assembly is constituted by all or part of said split tube, the clamping force between the conductive portion and the primary electrical conductive pads being provided by the elasticity of the slotted tube.

In the above definition, the terms "upstream" and "downstream" are used to designate the position of one element relative to another by taking as a reference the direction of movement of the sliding assembly when it is actuated.

Thanks to the preceding provisions, the closing of the electrical circuit connecting the primary electrical conductive pads is provided by reliable electrical contacts, as long as the electrical switch is in its initial position. As the connection between the primary electrical conductive pads and the conductive portion of the sliding assembly is a permanent electrical connection made by construction by the initial clamping of the split tube, the electrical contact between these elements is controlled and is not degraded during time even if the electrical switch is subject to vibration or shock. Unwanted phenomena such as false contacts, Joule losses, electric arcs, etc. are avoided. When, under the effect of the actuator, the sliding assembly passes from its first to its second position, at least one of the pads is no longer electrically connected to the conductive portion of the sliding assembly. The electrical connection between the two primary electrical conductive pads is broken, and the first electrical circuit is open.

Its slot gives the split tube an elasticity that facilitates the assembly of the electrical junction. The split tube can thus be engaged by forced engagement between the rings of the electrical conductive pads.

By forced engagement, it will be understood in particular the application of a substantially radial force on the free longitudinal ends of the tube so as to bring these ends together and reduce the radial size of the tube, and then, once the tube is introduced between the rings, the relaxation of these ends so that, under the effect of the elasticity of the tube, it comes to apply against the inner faces of the rings.

With such a split tube, any release of stress generating an increase in the diameter of the tube contributes to an improvement of the electrical contact and will be limited during assembly in the ring by the internal diameter of the ring.

The elasticity of the split tube provides a sufficiently high clamping force so that the electrical resistance is very low while limiting the forces required to move the slit tube during operation of the switch.

Practically, the clamping can be ensured by choosing a diameter of the split tube at rest about 4 to 5% higher than the internal diameter of the ring intended to receive said tube, and by assembling the split tube in the ring by acting on the elasticity of the tube material. Under such conditions, contact resistances of the order of 30 to 50 μOhm can be obtained.

• le jeu de serrage entre le diamètre des bagues des plots conducteurs et le diamètre externe du tube fendu au repos, et en particulier la contrainte initiale appliquée au tube fendu par le rapprochement des deux extrémités libres du tube délimitant la fente,
• l'épaisseur du tube fendu (la longueur du tube étant par ailleurs fonction du déplacement souhaité, pour des raisons liées à la tension maximale),
• la nature des matériaux.

More generally, the tightening force can be adjusted by playing on:

• the clamping clearance between the diameter of the rings of the conductive pads and the outside diameter of the slit tube at rest, and in particular the initial stress applied to the slit tube by the approximation of the two free ends of the tube delimiting the slit,
• the thickness of the split tube (the length of the tube being also a function of the desired displacement, for reasons related to the maximum tension),
• the nature of the materials.

The fact of having by construction of a clamping orthogonal to the axis of displacement reduces the effort required to move the slotted tube.

Moreover, the resistance to displacement of the split tube inside the cavity changes little with the level of clamping between the rings and the split tube.

Note that a split tube can be obtained very simply, from a standard tube which is then split by a simple milling or cutting operation.

In the present invention, continuous annular rings (i.e. not split radially) are preferably used. Such rings can be easily obtained by coining or stamping by industrial processes with satisfactory tolerances, without risk of loss of shape by release of stress (as is the case with split rings, which generally undergo ovalization at the level of slot).

According to an exemplary embodiment of the invention, the slot extends in the axial direction of the tube.

Advantageously, the width of the slot made in the tube may be chosen to compensate as much as possible for the difference in diameter between the conductive pads and the said split tube, the diameter of the latter being larger before forced assembly than that of the rings of the tubes. conductive pads.

According to an exemplary embodiment, the sliding assembly comprises a complementary clamping element introduced inside the split tube and configured to apply to the tube an external radial clamping force in the direction of the electrical conductive pads. Preferably, this complementary clamping element will be made of an insulating material.

According to an exemplary embodiment, the actuator is a pyrotechnic gas generator (for example a micro gas generator and its pyrotechnic initiator or a pyrotechnic initiator) and the sliding assembly comprises a piston movable inside said cavity, a gas expansion chamber being defined between said pyrotechnic gas generator and said piston. Preferably, the piston will be made of an insulating material.

According to an exemplary embodiment, the piston comprises at least one circumferential groove adapted to receive a seal.

According to an exemplary embodiment, the piston is made of an insulating material, and comprises a first part adapted to slide along the cavity and a second part, located in the extension of the first, adapted to be introduced, at least partially, inside the split tube to form a guide element of said tube.

According to an exemplary embodiment, the second part is forcibly mounted inside the split tube. The guiding element thus has as an additional function of forcing the radial opening of the split tube, thus reinforcing the electrical connection with the rings of the conductive pads.

According to an exemplary embodiment, the piston has a cavity opening axially, upstream, the space defined by this cavity constituting at least a portion of the gas expansion chamber.

According to an exemplary embodiment, the switch comprises at least one secondary electrical conductive pad disposed downstream of said first and second primary electrical conductive pads and wherein the stroke of the sliding assembly is such that, when in said second position, said second primary electrical conductive pad is electrically connected to said secondary electrical conductive pad by said conductive portion of the sliding assembly.

The structure defined above is favorable to the extension of the number of circuit breakers and / or switches. In this spirit, according to a possible variant, the switch is characterized in that it comprises at least two groups of two primary conductive pads arranged in the extension of each other from upstream to downstream and in that said sliding assembly comprises a corresponding number of conductive portions electrically insulated from each other, each of said conductive portions exclusively connecting the conductive pads of each group when said sliding assembly is in its initial position.

It should be noted that in the variant described above, the upstream primary conductive pad of a group of two primary conductive pads located downstream of another may play the function of secondary conductive pad with respect to this group.

In this same type of embodiment comprising several groups of primary conductive pads, it can also be ensured that the arrangement of said sliding assembly and conductive pads of the two groups is such that, for an intermediate position of said sliding assembly, the pads both groups are electrically connected via said conductive portions.

For example, to obtain this result, said two conductive portions are separated by an insulator of less thickness than that of a conductive pad so that at a given moment of the race, the two conductive portions of the sliding assembly are electrically connected by the thickness of a ring of one of the conductive pads. This transient position allows, for example the momentary closure of a bypass circuit for ensuring the continuity of an electrical circuit during the path of the sliding assembly.

According to an exemplary embodiment, the cavity of the hollow body is terminated in its downstream portion by a guide portion for guiding the sliding assembly when the latter passes from its first to its second position. This guiding portion allows appropriate positioning of the slotted conductive sliding tube when it is in its second position. In cases where, in this second position, the electrical switch is intended to close one or more branch circuits, the guide portion makes it possible to ensure reliable and good quality electrical contacts between certain electrical conductive pads and the one or more conductive portions of the sliding assembly.

• les figures 1A, 1B sont des vues schématiques en coupe longitudinale illustrant la structure et le fonctionnement d'un interrupteur électrique, formant coupe-circuit ;
• la figure 2 est une vue en perspective éclatée d'une réalisation technologique possible d'un interrupteur électrique conforme aux figures 1A et 1B ;
• les figures 3A à 3C sont des vues schématiques illustrant la structure et le fonctionnement d'un autre mode de réalisation ;
• les figures 4A à 4C sont des vues semblables aux figures 3A à 3C illustrant encore une autre variante ; et
• la figure 5 illustre encore une variante de piston pouvant être utilisé avec la présente invention.

The invention will be better understood and other advantages thereof will appear more clearly in the light of the following description of several embodiments of an electrical switch according to its principle, given solely as examples and with reference to the accompanying drawings, in which:

• the Figures 1A, 1B are schematic views in longitudinal section illustrating the structure and operation of an electrical switch, forming a circuit breaker;
• the figure 2 is an exploded perspective view of a possible technological achievement of an electrical switch in accordance with Figures 1A and 1B ;
• the FIGS. 3A to 3C are schematic views illustrating the structure and operation of another embodiment;
• the Figures 4A to 4C are views similar to FIGS. 3A to 3C illustrating yet another variant; and
• the figure 5 further illustrates a piston variant that can be used with the present invention.

With particular reference to figures 1 and 2 , there is shown a first embodiment of an electric switch 11 according to the invention and forming here more particularly a circuit breaker for any electrical circuit connected to two primary electrical conductor pads 13, 14 in the sense defined above.

The circuit breaker switch 11 comprises a hollow body 16 of electrically insulating material delimiting a cavity 19, an actuator 23 and the two primary electrical conductive pads 13, 14 opening into the cavity 19.

The electric switch 11 also comprises a sliding assembly 20 that can be moved in the cavity. In the example, the cavity 19 is cylindrical and the sliding assembly 20 is itself essentially cylindrical.

The sliding assembly 20 comprises a split tube 21 which comprises at least one conductive portion. In the example shown on the figures 1 and 2 the split tube 21 is fully conductive.

The sliding assembly 20 further comprises a sliding drawer 22 of insulating material forming a kind of piston, adapted to move inside the cavity, so as to carry with it the split tube 21.

According to the example, the actuator 23 is a pyrotechnic gas generator, known per se, installed in the hollow body so as to communicate with the cavity 19.

A gas expansion chamber 25 is defined between the pyrotechnic gas generator 23 and one of the axial end faces of the piston 22. In the example, more particularly, the piston 22 has a cavity 26 in its upstream face. directed towards the gas generator 23, and this cavity 26 constitutes a part of the gas expansion chamber 25.

In the initial position where the sliding spool 22 is substantially in contact with the actuator 23, that is to say with the expansion chamber 25 reduced to its minimum volume, the two electrical conductive pads 13, 14 are electrically connected between them, via the split tube 21 in a first position, called initial. The electrical contact is established via the conductive portion (here all) of the split tube 21.

As shown, the split tube 21 moves to a second position in the cavity ( Figure 1B ), under the effect of the actuator 23, that is to say during the ignition of the pyrotechnic gas generator and in this case the electrical connection between the two conductive pads 13, 14 is broken, so that the primary upstream electrical conductive pad 13 is separated from the split tube 21.

According to a remarkable feature of the invention, the two conductive pads comprise two coaxial rings 13a, 14a axially offset along the direction of movement of the sliding assembly 20 and these rings 13a, 14a are at least in close contact with the portion conductive of the sliding assembly (here the split tube 21) when it is in said first position. In the example, the inner faces of the rings 13a, 14a are flush with the wall of the cavity 19. When the sliding assembly is in its second position, the ring 13a is disengaged from the conductive portion of the sliding assembly (ie from the tube split 21).

Advantageously, in said first position, the split tube 21 is engaged by forced engagement between the rings 13a, 14a of said primary conductive pads 13, 14, which ensures an excellent electrical connection between said primary conductive pads during the entire period preceding the actuation of the electric switch 11.

The figure 2 shows how one can achieve a simple and economical way an electrical switch according to the circuit breaker just described.

The hollow body 16 is defined by the assembly of two housing elements 30, 31, respectively left 30 and right 31.

The housing member 30 has two threaded blind holes 32 surmounted by a laterally open recess 33 and whose shape is defined to accommodate a portion of each electrical conductive pad 13, 14 and a portion of a gas generator holder 12 .

Each electrical conductive pad has a ring 13a and 14a extended laterally by a connection bar 13b and 14b protruding outside the insulating hollow body so as to be connected to the external electrical circuit to the circuit breaker.

The second housing member 31 has two through holes 36 for inserting fixing screws 37. In the same manner as the first housing member 30, it further comprises a laterally open recess 34 whose shape is defined to accept a portion of each electrical conductor pad 13, 14 and a portion of the gas generator support 12.

The gas generator support 12 is mounted between the two housing elements 30, 31 and comprises a bore 38 which receives at its end the gas generator 23. The gas generator 23 is mounted inside said support 12 so that defining the gas expansion chamber 25 within said bore 38.

As mentioned above, the split tube 21 is forcibly engaged in each of the two rings 13a, 14a.

In this way, in said first initial position, the two axially offset and coaxial rings 13a, 14a are electrically connected via the split metal tube 21.

In the example shown, the insulating drawer 22 is inserted inside the slotted slotted tube 21. Thus, the insulating drawer 22 performs the following functions:

A first portion or upstream portion 41, cylindrical in shape, of diameter substantially equal to the diameter of the cavity 19, slides along the inner faces of said cavity.

In its upstream face, directed upwards on the figures 1 and 2 , the first part 41 comprises a cavity 26, here also substantially cylindrical, which partially delimits the initial volume of the expansion chamber 25.

As is apparent from the figure 2 the first portion 41 has two circumferential grooves 61, 62 spaced axially from each other and each receiving an O-ring 63, 64. Thus, the piston 22 closes the gas expansion chamber 25 and allows the rapid increase of pressure in the enclosed environment of this chamber. The gases generated in the gas expansion chamber 25 are prevented from infiltrating to the conductive rings 13a, 14a.

A groove 65 is advantageously formed in at least one of said grooves and configured to form a calibrated passage for exhausting air from the gas expansion chamber when mounting the piston 22 into the generator support. gas 12.

The piston 22, located at least partly upstream of the split tube, has the function of transmitting to said tube 21 the pressure force generated by the gases in the gas expansion chamber 25 and allowing the circuit to be broken by moving said tube 21.

This first portion 41 is extended by a second downstream portion 42, of slightly smaller diameter chosen to allow its insertion, possibly by force, inside the split tube once it inserted between the rings 13a, 14a.

This second part can act as a guide element for the split tube, during its displacement inside the cavity 19.

It may also, in an advantageous embodiment, form a complementary clamping member of the split tube against the rings 13a, 14a.

After triggering of the pyrotechnic gas generator 23, the situation is illustrated in FIG. Figure 1B . The electrical connection between the two pads 13, 14 is interrupted.

Note that the piston 22 has here, on a portion directly upstream of the split tube, a diameter at most equal to the outer diameter of the tube once inserted between the rings. In the illustrated example, the diameter of the upstream portion of the piston is even slightly less than that of the split tube, so that the piston, driving the split tube, can slide easily between the rings, without being blocked. This is made possible here by a slight difference in diameter between the most upstream part of the cavity along which the piston (here formed by the bore of the generator support) slides and its downstream part (formed by the elements of housings), wider, into which the rings open.

As seen in the drawings, the cavity 19 extends downstream by a guide portion 45 which guides the split tube 21 when it passes from the first to the second position and to ensure that it here is a rectilinear trajectory.

A damping pad 9 is inserted into the bottom of the cavity 19. If necessary, this damping pad 9 has the function of reducing the energy of the impact of the split conductive tube 21 and the insulating piston 22 when the two pieces come into contact. on the bottom of the switch body 16.

Referring now more specifically to Figures 3A-3C , we note that the electric switch 11A which forms both a circuit breaker and a switch is obtained in a simple manner from the same modules as those described above.

More particularly, when the sliding assembly 20 is in the first so-called initial position, the situation from the electrical point of view is in accordance with the figure 3A , that is to say that the two primary electrical conductive pads 13, 14 are, as in the previous example, interconnected by the split tube 21.

The electric switch 11A, however, comprises, in addition to the two primary conductive pads 13, 14, a secondary electrical pad 50 situated downstream of the primary downstream conductive pad 14, also comprising a ring 50a extended laterally by a conduction bar 50b projecting out of the body of the switch.

When the sliding assembly is in its first position, the secondary conductive pad is disengaged from the split tube 21.

On the other hand, when, after triggering of the pyrotechnic gas generator 23, the sliding assembly 20 is in its second position ( figure 3C ), the downstream primary electrical conductive pad 14 is electrically connected to said secondary electrical conductive pad 50 through the split tube 21 while the upstream primary electrical conductive pad 13 is disengaged from the conductive split tube 21. The length of the split tube 21 is such that, for a brief moment, during the travel of the sliding assembly 20, the three studs 13, 14, 50 are electrically connected by the split tube 21. This is the situation illustrated on FIG. figure 3B . Thus, a bypass circuit can be closed before opening the circuit breaker.

The Figures 4A-4C illustrate another embodiment of a switch 11B that can be made from components generally similar to those shown in FIG. figure 2 and in which several groups of two primary conductive pads arranged in the extension of one another, upstream to downstream can be associated with the same sliding assembly. In the example, only two groups of such pairs of primary conductive pads have been shown, but it is clear that the device can be "expanded" in a modular fashion to include a larger number of groups of such pads.

There is a hollow body 16 of electrically insulating material delimiting a cavity 19, axially longer than in the previous embodiments, a pyrotechnic actuator 23 mounted at one end of this hollow body to define a gas expansion chamber 25 with the adjacent end of the piston 22A.

The piston 22A, illustrated in more detail on the figure 5 , here has a different form from that of the embodiments described above, in that it is not extended by a complementary guide portion intended to be introduced into the split tube. In other words, the split tube 21A is here dissociated from a movable piston 22A inside the cavity 19. The piston 22A is then inserted between the split tube 21A and the pyrotechnic gas generator, the chamber of expansion 25 being defined between this piston 22A and the actuator 23.

The piston 22A, which comprises only one portion 41 of diameter adapted to slide along the cavity 19, thus solicits the slit tube 21A only axially, to move it from the first to the second position.

In the example, there is a first group of two primary conductive pads 113, 114 and a second group of two primary conductive pads 213, 214 while the split tube comprises a corresponding number, that is to say here two, conductive portions 58, 59 electrically isolated from each other. According to the example, the split tube 21A comprises two metal parts separated by an insulating portion 60 extending, in the initial position, between the two groups of pairs of primary conductive pads. In this way, each of said conductive portions 58, 59 connects exclusively the conductive pads of each group when the sliding assembly is in its initial position, illustrated on the Figure 4A . After actuation of the pyrotechnic gas generator, the situation is that of the figure 4C that the slit tube 21 is completely clear of the upstream primary conductive pad 113 of the first group (the upstream group), that the downstream primary conductive pad 114 of the first group is in contact with the upstream primary conductive pad 213 of the second group by through the upstream split tube 58 while the downstream primary conductive pad 214 of the second group (downstream) is in electrical contact with the downstream portion of the split tube 59 but is electrically isolated from all other conductive pads because the portion insulator 60 is located between the two primary conductive pads of the second group (downstream). Thus, in this arrangement, a function of switch is made between the two groups of primary conductive pads, that is to say that the upstream primary conductive pad 213 of the second group plays the role of secondary conductive pads relative to the first group.

As noted in the drawings, said two conductive portions of the split tube 21A are separated by an insulator 60 of less thickness than that of a conductive pad and in particular the upstream conductive pad 213 of the second group. So, as illustrated on the Figure 4B during the trajectory of the sliding assembly, and because the contact between the upstream portion of the split tube 21A and the upstream conductive pad of the first group has not yet been broken, all the conductive pads of the two groups are interconnected during a short time interval via the split tube.

In all the embodiments, it is advantageous to provide a passage of small section between the cavity 19 and the outside through the body 16, to facilitate the displacement of the sliding assembly 20.

In addition, the combustion products of the gas generator may be conductive or contain metal particles. If the circuit to be cut is under high voltage, an electric arc or a metallization can occur in the chamber 25 after displacement of the piston 22. The piston 22 is thus advantageously made of an insulating material, so that after actuation, both rings 13a, 14a are separated by an insulating part.

Claims (13)

1. An electric switch (11, 11A, 11B) comprising:

   · a hollow body (16) defining a cavity (19);

   · a sliding assembly (20) comprising at least one conductive portion (21, 21A, 58, 59) and adapted to move in said cavity (19) from an "initial" first position to a second position;

   · an actuator (23) arranged to co-operate with said sliding assembly (20) and to move it in said cavity (19); and

   · at least two primary electrically conductive tabs, respectively an upstream tab (13, 113, 213) and a downstream tab (14, 114, 214), each comprising a ring (13a, 14a) penetrating into said cavity (19), said rings (13a, 14a) being on the same axis and being offset axially in the travel direction of the sliding assembly (20) ;

   wherein the conductive portion (21, 21A, 58, 59) of the sliding assembly (20) is connected by a clamping force to the two primary electrically conductive tabs (13, 113, 213; 14, 114, 214) when the sliding assembly (20) is in its first position, and when the sliding assembly (20) is in its second position, the upstream electrically conductive tab (13, 113, 213) is separated from the conductive portion (21, 21A, 58, 59) of said sliding assembly (20);
   said switch (11, 11A, 11B) being characterized in that the sliding assembly (20) comprises at least one tube (21, 21A) split by a slot (29) extending along its entire length, and in that the conductive portion (21, 21A, 58, 59) of the sliding assembly (20) is constituted by all or part of said split tube (21, 21A), the clamping force between the conductive portion (21, 21A, 58, 59) and the primary electrically conductive tabs (13, 113, 213; 14, 114, 214) being provided by the resilience of the split tube.
2. An electric switch (11, 11A, 11B) according to claim 1, wherein the slot (29) extends in the axial direction of the tube (21, 21A).
3. An electric switch (11, 11A) according to claim 1 or claim 2, wherein the sliding assembly (20) includes an additional clamping element (42) inserted inside the split tube (21) and configured to apply an outwardly directed radial clamping force on said tube (21) towards the electrically conductive tabs (13, 14).
4. An electric switch (11, 11A, 11B) according to any one of claims 1 to 3, wherein the actuator (23) is a pyrotechnic gas generator and the sliding assembly (20) further includes a piston (22, 22A) movable inside said cavity (19), a gas expansion chamber (25) being defined between said pyrotechnic gas generator (23) and said piston (22, 22A).
5. An electric switch (11, 11A, 11B) according to claim 4, wherein the piston (22, 22A) includes at least one circumferential groove (61, 62) adapted to receive a sealing ring (63, 64).
6. An electric switch (11, 11A) according to claim 4 or claim 5, wherein the piston (22) is made of insulating material and comprises a first portion (41) adapted to slide along the cavity (19), and a second portion (42) that is situated in line with the first portion (41) and that is suitable for being inserted, at least in part, inside the split tube (21) in order to constitute a guide element for said tube (21).
7. An electric switch (11, 11A) according to claim 6, wherein the second portion (42) is mounted by force inside the split tube (21).
8. An electric switch (11, 11A, 11B) according to any one of claims 4 to 7, wherein the piston (22, 22A) presents a cavity (26) that is axially open upstream, the space defined by said cavity (26) constituting at least a portion of the gas expansion chamber (25).
9. An electric switch (11A) according to any one of claims 1 to 8, including at least one secondary electrically conductive tab (50) arranged downstream from said first and second primary electrically conductive tabs (13, 14), and wherein the stroke of the sliding assembly (20) is such that when it is in said second position, said second primary electrically conductive tab (14) is electrically connected to said secondary electrically conductive tab (50) by said conductive portion of the sliding assembly (20).
10. An electric switch (11A) according to claim 9, wherein the arrangement of the sliding assembly (20) and of the primary and secondary electrical conductive tabs (13, 14, 50) is such that in an intermediate position of said sliding assembly, said primary and secondary electrically conductive tabs (13, 14; 50) are electrically interconnected by said conductive portion (21) of said sliding assembly (20).
11. An electric switch (11B) according to any one of claims 1 to 10, including at least two groups of two primary conductive tabs (113, 114; 213, 214) arranged in line one with another from upstream to downstream and wherein said sliding assembly (20) includes a corresponding number of conductive portions (58, 59) that are mutually electrically insulated, each of said conductive portions (58, 59) interconnecting only the conductive tabs (113, 114; 213, 214) of each group when said sliding assembly (20) is in its initial position.
12. An electric switch (11B) according to claim 11, wherein the arrangement of said sliding assembly (20) and of the conductive tabs (113, 114; 213, 214) of the two groups is such that for an intermediate position of said sliding assembly (20), the electrically conductive tabs of the two groups are electrically interconnected via said conductive portions (58, 59).
13. An electric switch (11B) according to claim 12, wherein said conductive portions (58, 59) are separated by insulation (60) of thickness smaller than the thickness of a conductive tab.

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