Electric current conducting rod for vacuum bulb

Abstract

There is provided an electric current conducting rod (20) for a medium or high voltage vacuum bulb, comprising:- a first rod element (1) extending along an axis (D),- a second rod element (2), integral with the first rod element (1),- a reinforcing sleeve (3) arranged radially around the first rod element (1), in which the reinforcing sleeve (3) is axially compressed between the first rod element (1) and the second rod element (2). Abstract figure: Figure 4

Description

Title of the invention: Electric current conduction rod for vacuum bulb Technical field

[0001] The present invention relates to the field of medium voltage or high voltage vacuum interrupting devices, also called vacuum interrupters or vacuum interrupters. The vacuum interrupters are associated with actuators to cut off the current in a part of the circuit. Prior art

[0002] As is well known, a vacuum bulb comprises two cut-off contacts arranged opposite each other. Each contact comprises a rod for supplying the electric current, and a disc-shaped contact body, integral with the rod. The current supply rods are generally made of copper, due to the high electrical and thermal conductivity of this metal. The contacts are arranged in an envelope forming a sealed enclosure placed under vacuum. The contacts can be moved relative to each other. When the contacts are pressed against each other, current can pass from one contact to the other. When the contacts are separated from each other, the current is interrupted.

[0003] In order to facilitate the integration of vacuum interrupters in medium voltage or high voltage electrical distribution apparatus, it is desirable to reduce their size, in particular their diameter. To maintain at least the same dielectric strength performance, the diameter of the contacts must also be reduced, in order to limit the electric field between the contacts and the external enclosure to an acceptable value. Current supply rods of reduced diameter are thus used. The mechanical stresses resulting from impacts when the contacts close are thus higher, and the mechanical strength of the current supply rods can become problematic. Indeed, the current supply rods can become deformed and their length can decrease, which leads to a loss of contact force.

[0004] There is therefore a need to have reinforced electrical contacts, which can accept higher mechanical constraints than those of known solutions. Summary

[0005] To this end, the invention provides an electric current conduction rod for a medium or high voltage vacuum bulb, comprising: - a first rod element extending along an axis, - a second rod element, integral with the first rod element, - a reinforcing sleeve arranged radially around the first rod element, wherein the reinforcing sleeve is axially compressed between the first rod member and the second rod member.

[0006] During operation of a vacuum bulb, the main mechanical stresses experienced by the electric current conduction rod are compression stresses. The reinforcing sleeve, mounted in compression, reinforces the first element. During the service life of the rod, any fining of the first element or the second element tends to increase the compression of the reinforcing sleeve. The reinforcing sleeve thus provides lasting reinforcement of the rod. It is thus possible to produce electric current conduction rods having a small diameter and sufficient mechanical strength to ensure the desired product life.

[0007] The features listed in the following paragraphs can be implemented independently of each other or in any technically possible combination:

[0008] The reinforcing sleeve is compressed in an axial direction, i.e. the direction of the axis of the electric current conduction rod.

[0009] The electric current conducting rod is configured to be attached to a contact body extending transversely to the axis.

[0010] One of the first rod member and the second rod member is configured to be attached to the contact body.

[0011] According to one embodiment of the electric current conduction rod, the reinforcing sleeve is cylindrical.

[0012] The reinforcement sleeve has a hollow cylinder shape.

[0013] The first rod element and the second rod element are coaxial.

[0014] The reinforcing sleeve and the first rod element are coaxial.

[0015] According to one embodiment of the electric current conduction rod, the reinforcing sleeve, the first rod element and the second rod element are coaxial.

[0016] According to an exemplary embodiment of the electric current conduction rod, the first rod element is made of copper.

[0017] Similarly, the second rod element may be made of copper.

[0018] According to an exemplary embodiment of the electric current conduction rod, the reinforcing sleeve is made of stainless steel.

[0019] A stainless steel reinforcement sleeve improves the mechanical resistance of the copper elements.

[0020] According to one embodiment of the electric current conduction rod, an axial compression rate of the reinforcing sleeve is between 0.1% and 5.0%.

[0021] According to one embodiment of the electric current conduction rod, the first rod element comprises a shoulder forming a stop for a first axial end of the reinforcement sleeve.

[0022] The first rod element comprises a first cylindrical portion of a first diameter and a second cylindrical portion of a second diameter greater than the first diameter, the second cylindrical portion comprising a first abutment surface on which a first axial end of the reinforcing sleeve bears.

[0023] Preferably, an outer edge of the shoulder is flared in shape.

[0024] This shape makes it possible to limit dielectric constraints.

[0025] The outer edge of the shoulder is convex in shape.

[0026] According to one embodiment, the reinforcing sleeve surrounds the first cylindrical portion of the first rod element over the entire length of the reinforcing sleeve.

[0027] According to an exemplary embodiment of the electric current conduction rod, the second rod element forms a stop for a second axial end of the reinforcing sleeve.

[0028] The second rod element comprises a second abutment surface on which a second axial end of the reinforcing sleeve bears.

[0029] According to one embodiment of the electric current conduction rod, the second rod element comprises a flat portion forming a receiving surface for the second axial end of the reinforcing sleeve, the flat portion extending in a radial direction by a flared portion, the flared portion being distant from the reinforcing sleeve in an axial direction.

[0030] As for the first rod element, this shape makes it possible to limit dielectric constraints.

[0031] The flared portion of the second rod element is convex in shape.

[0032] According to one embodiment of the electric current conduction rod, the thickness of the reinforcing sleeve is between 0.1 millimeters and 5.0 millimeters.

[0033] According to an exemplary embodiment, a ratio of the thickness of the reinforcing sleeve and an outer diameter of the reinforcing sleeve is between 0.01 and 0.1.

[0034] According to an exemplary implementation of the electric current conduction rod, the reinforcing sleeve is in contact with a lateral surface of the first rod element.

[0035] According to one embodiment of the electric current conduction rod, the reinforcing sleeve is radially constrained.

[0036] According to one embodiment of the electric current conduction rod, the reinforcing sleeve is in contact with a lateral surface of the second rod element.

[0037] According to one embodiment, the reinforcing sleeve is arranged radially around the first rod element and around the second rod element.

[0038] According to a variant, a radial clearance is present between the reinforcement sleeve and a lateral surface of the first rod element.

[0039] According to this variant of the electric current conduction rod, the radial clearance can be between 0.5% and 2% of a diameter of the reinforcement sleeve.

[0040] According to one embodiment, an axial length of the reinforcing sleeve is between 50% and 80% of an axial length of the first rod element.

[0041] According to an exemplary embodiment of the electric current conduction rod, an axial length of the reinforcing sleeve is between 5% and 50% of a total axial length of the rod.

[0042] According to one embodiment, the first rod element and the second rod element are fixed by brazing.

[0043] According to an exemplary embodiment, an axial end of the first rod element terminates in a pin and an axial end of the second rod element comprises a housing configured to receive the pin of the first rod element.

[0044] Alternatively, an axial end of the second rod member terminates in a pin and an axial end of the first rod member includes a housing configured to receive the pin of the second rod member.

[0045] The pawn and the housing have complementary shapes.

[0046] The invention also relates to a method of assembling an electric current conduction rod as described above. The assembly method comprises the steps: - provide a first stem element, - provide a second rod element, - provide a reinforcement sleeve, - insert the first rod element inside the reinforcement sleeve, - axially compress the reinforcement sleeve between the first rod element and the second rod element, - fix together the first rod element and the second rod element.

[0047] The invention also relates to an electrical cut-off contact for a medium or high voltage vacuum bulb, comprising: - an electric current conduction rod as described previously, - a contact body fixed to the electric current conducting rod, the contact body extending transversely to the axis.

[0048] The invention also relates to a medium or high voltage vacuum bulb, comprising: - a first electrical cut-off contact as previously described, - a second electrical cut-off contact as previously described, at least one of the first contact and the second contact being configured to be moved along the axis between a so-called open position in which the contacts are spaced apart from each other and a so-called closed position in which the contacts rest on each other so as to allow the passage of electric current between the first contact and the second contact. Brief description of the drawings

[0049] Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the attached drawings, in which:

[0050] [Fig-1] is a schematic side view of a medium voltage vacuum bulb or high voltage,

[0051] [Fig.2] is a side view, in section, of a medium voltage or high voltage vacuum interrupter according to an embodiment of the invention,

[0052] [Fig.3] is a side view of an electric current conducting rod of the vacuum bulb of [Fig.2],

[0053] [Fig.4] is a side view, in section, of the electric current conducting rod of [Fig.3],

[0054] [Fig.5] is a schematic side view detailing the electrical conduction rod of [Fig.4],

[0055] [Fig.6] is a schematic side view of an electrical conduction rod, according to an alternative embodiment,

[0056] [Fig.7] is a schematic side view of an electrical conduction rod, according to another alternative embodiment,

[0057] [Fig.8] is a perspective view diagrammatically showing different steps of a method of assembling the electric current conduction rod of Figures 2 to 4. Description of the embodiments

[0058] In order to facilitate the reading of the figures, the different elements are not necessarily represented to scale. In these figures, identical elements bear the same references. Certain elements or parameters may be indexed, that is to say designated for example by first element or second element, or even first parameter and second parameter, etc. This indexing is intended to differentiate similar, but not identical, elements or parameters. This indexing does not imply a priority of one element or parameter over another and the names may be interchanged. When it is specified that a subsystem comprises a given element, this does not exclude the presence of other elements in this subsystem. Similarly, when it is specified that a subsystem comprises a given element, it is understood that the subsystem comprises at least this element.

[0059] In the various figures, the X, Y, Z axes designate the three directions of space in order to identify the viewing angle of each figure.

[0060] [Fig.l] shows a medium or high voltage vacuum bulb 50. The 50 vacuum bulb includes: - a first 30a electrical cut-off contact, - a second 30b electrical cut-off contact. At least one of the first contact 30a and the second contact 30b is configured to be moved along the axis D between a so-called open position O in which the contacts 30a, 30b are spaced apart from each other, and a so-called closed position F in which the contacts 30a, 30b bear against each other so as to allow passage of electric current between the first contact 30a and the second contact 30b.

[0061] The vacuum interrupter 50 is part of a medium or high voltage cut-off device, such as a circuit breaker or a disconnector. When the electrical cut-off contacts 30a, 30b are in contact with each other, an electric current can flow. In part A of [Fig.l], the sign C schematizes the passage of the electric current. When the contacts 30a, 30b are separated from each other, the flow of electric current is interrupted, generally after a transient period during which an electric arc is present between the two contacts 30a, 30b. In part B of [Fig.l], the electrical contacts are separated by a distance represented by the sign g, and the flow of electric current from one contact to the other is interrupted.

[0062] The contacts 30a, 30b are arranged in an insulating envelope 40 forming a sealed enclosure placed under vacuum. A cylindrical protective screen 35, visible in [Fig. 2], is arranged inside the insulating casing 40. The contacts 30a, 30b are arranged inside the volume delimited by the protective screen 35. The protective screen 35 prevents metal particles detaching from the contacts when an electric arc is created from being deposited on the internal surface of the insulating casing 40.

[0063] Each contact 30a, 30b respectively comprises an electric current conduction rod 20a, 20b extending along an axis D and a contact body 10a, 10b fixed to the electric current conduction rod 20a, 20b. Each contact body 10a, 10b has a general disc shape and extends transversely to the axis D.

[0064] When the vacuum interrupter 50 is closed, an impact occurs between the two contacts 30a, 30b. This impact induces high mechanical stresses in the contacts, in particular in the electric current conduction rods 20a, 20b. The repetition of the impacts during successive uses of the vacuum interrupter tends to permanently deform the electric current conduction rods 20a, 20b. These deformations tend to reduce the length of these conduction rods, which reduces the pressure between the contact bodies 10a, 10b when they are in the current passage position. The risk of deformation is particularly present when the diameter of the rods is reduced, in order to reduce the size of the vacuum bulb, in particular the radial size.

[0065] It is therefore desirable to increase the mechanical resistance of the current conduction rods 20a, 20b, without increasing their diameter and without reducing their electrical conductivity.

[0066] [Fig. 3] represents an embodiment of an electric current conduction rod 20 for a medium or high voltage vacuum bulb 50. The electric current conduction rod 20 comprises: - a first rod element 1 extending along an axis D, - a second rod element 2, integral with the first rod element 1, - a reinforcing sleeve 3 arranged radially around the first rod element 1, in which the reinforcing sleeve 3 is axially compressed between the first rod element 1 and the second rod element 2.

[0067] During operation of a vacuum bulb, the main mechanical stresses experienced by the electric current conduction rods are compression stresses. The reinforcing sleeve 3, mounted axially compressed, reinforces the first rod element 1. During the service life of the rod 20, any fining of the first element 1 or of the second element 2 tends to increase the compression of the reinforcing sleeve 3. The reinforcing sleeve 3 thus allows lasting reinforcement of the rod 20. It is thus possible to produce electric current conduction rods having a small diameter and sufficient mechanical strength to ensure the desired duration for the product.

[0068] The reinforcing sleeve 3 is compressed in an axial direction, i.e. the direction of the axis D of the electric current conduction rod 20.

[0069] The reinforcing sleeve 3 surrounds the first rod element 1 over at least a portion of the length of the first rod element 1. The length of the first rod element 1 is understood to mean the dimension measured along the axis D of the first rod element 1. At least a portion of the first rod element 1 is inside the reinforcing sleeve 3. The reinforcing sleeve 3 is radially external to the first rod element 1. The reinforcing sleeve 3 is compressed, in the direction of the axis D, between the first rod element 1 and the second rod element 2.

[0070] The electric current conduction rod 20 is configured to be traversed by an electric current. The first rod element 1 and the second rod element 2 are both configured to be traversed by an electric current.

[0071] The electric current conducting rod 20 is configured to be attached to a contact body 10 extending transversely to the axis D. The contact body 10 has a general disc shape. Slots extending from the outer periphery of the disc towards a radially central zone of the disc may be formed. These slots ensure rotation of the electric arc during current breaking phases.

[0072] One of the first rod element 1 and the second rod element 2 is configured to be attached to the contact body 10.

[0073] The rod 20 has the general shape of a cylinder of revolution with axis D. Thus, the first rod element 1 and the second rod element 2 also have the general shape of a cylinder of revolution with axis D.

[0074] The reinforcing sleeve 3 is cylindrical. The reinforcement sleeve 3 has a hollow cylinder shape. The reinforcement sleeve 3 has a symmetry of revolution around its axis D.

[0075] The first rod element 1 and the second rod element 2 are coaxial. The reinforcement sleeve 3 and the first rod element 1 are coaxial. According to the illustrated embodiment of the electric current conduction rod 20, the reinforcing sleeve 3, the first rod element 1 and the second rod element 2 are coaxial.

[0076] The first rod element 1 is made of copper. Likewise, the second rod element 2 is made of copper. The use of copper to form the first element 1 and the second element 2 of the rod ensures high electrical and thermal conductivity.

[0077] The reinforcing sleeve 3 is here made of stainless steel. For example, the reinforcement sleeve is made of AISI 316L stainless steel. A stainless steel reinforcement sleeve improves the mechanical resistance of the copper elements.

[0078] According to one embodiment of the electric current conduction rod 20, an axial compression rate of the reinforcing sleeve 3 is between 0.1% and 5.0%. Due to the axial compression exerted on the reinforcing sleeve 3, the length of the reinforcing sleeve 3 is shorter when it is mounted on the conduction rod 20 than when it is in the free state. The free state is the unmounted state, i.e. when no stress is applied to the reinforcement sleeve 3. No external stress means any force other than the force of gravity and the reaction force of the support on which the reinforcement sleeve is placed. The axial compression ratio of the reinforcement sleeve 3 is defined by the difference between the length L0 of the reinforcement sleeve 3 in the free state and the length L3 of the reinforcement sleeve 3 once compressed, divided by the length L0 of the reinforcement sleeve 3. reinforcement 3 in the free state. The lengths L and LO are measured along the axial direction D of the reinforcement sleeve 3.

[0079] For example, the reinforcing sleeve 3 may have a length LO of 50 millimeters in the free, unassembled state. If the length L3 in the assembled and compressed state is equal to 49.5 millimeters, the compression ratio is equal to 1%.

[0080] As shown in [Fig.3] and [Fig.4], the first rod element 1 comprises a shoulder 4 forming a stop for a first axial end 5 of the reinforcing sleeve 3.

[0081] The first rod element 1 comprises a first cylindrical part 7 of a first diameter d1 and a second cylindrical part 8 of a second diameter d2 greater than the first diameter d1. The second cylindrical part 8 comprises a first stop surface 11 on which a first axial end 5 of the reinforcing sleeve 3 comes to bear.

[0082] In the example shown in [Fig.4], an outer edge of the shoulder 4 is flared in shape. This shape helps to limit dielectric constraints.

[0083] More precisely, the outer edge of the shoulder 4 is here convex in shape.

[0084] According to the embodiment illustrated in Figures 2 to 6, the reinforcing sleeve 3 surrounds the first cylindrical part 7 of the first rod element 1 over the entire length of the reinforcing sleeve 3.

[0085] The second rod element 2 forms a stop for a second axial end 6 of the reinforcing sleeve 3. The second rod element 2 comprises a second abutment surface 12 on which a second axial end 6 of the reinforcing sleeve 3 bears.

[0086] As shown in [Fig.4], the second rod element 2 comprises a flat portion 14 forming a receiving surface for the second axial end 6 of the reinforcing sleeve 3. The flat portion 14 is extended in a radial direction by a flared portion 15. The flared portion 15 is distant from the reinforcing sleeve 3 in an axial direction D. In other words, the flared portion 15 is offset along the axis D relative to the reinforcing sleeve 3.

[0087] As for the first rod element 1, this shape with a flared edge makes it possible to limit dielectric constraints.

[0088] The flared portion 15 of the second rod element 2 is here convex in shape.

[0089] The thickness e of the reinforcing sleeve 3 is between 0.1 millimeters and 5.0 millimeters.

[0090] According to an exemplary embodiment, a ratio of the thickness e of the reinforcement sleeve 3 and of an external diameter d3 of the reinforcement sleeve 3 is between 0.01 and 0.1. The ratio of thickness e to outer diameter d3 is understood to be the result of the quotient of thickness e and outer diameter d3. When this ratio is for example 0.05, the thickness e is equal to 0.05 times the external diameter d3. For an external diameter equal to 20 millimeters, the thickness e of the reinforcement sleeve is then equal to 1 millimeter.

[0091] According to the embodiments illustrated in Figures 3 to 5, the reinforcing sleeve 3 is in contact with a lateral surface 9 of the first rod element 1.

[0092] The reinforcing sleeve 3 can be radially constrained. In other words, the first rod element 1 can exert a radial thrust directed towards the outside of the reinforcement sleeve 3.

[0093] [Fig.5] details this aspect. The arrows Fal, Fa2 schematically indicate the axial stresses exerted on the reinforcement sleeve 3. The arrow Fal corresponds to the force applied by the first rod element 1 on the reinforcement sleeve 3, and the arrow Fa2 corresponds to the force applied by the second rod element 2. The arrows Fr diagram the radial stresses exerted by the first rod element 1 on the reinforcement sleeve 3.

[0094] During use of the vacuum bulb, the repetition of the mechanical compressive stresses on the current-conducting rods tends to deform them. Thus, a perfectly cylindrical rod element before use tends to gradually decrease in length and increase in diameter, at least over part of its length. In [Fig. 5], the zones designated by the sign 21 correspond to zones in which there remains a clearance between the internal lateral surface 13 of the reinforcement sleeve 3 and the external lateral surface 9 of the first rod element 1. The zone denoted 22 corresponds to a zone in which the external lateral surface 9 of the first rod element 1 is in contact with the internal surface 13 of the reinforcement sleeve 3. In this zone, the first rod element 1 exerts a radial stress on the reinforcement sleeve 3. In [Fig.5], the size of the zones 21 and the amplitude of the deformation of the first rod element 1 have been exaggerated to improve the readability of the figure.

[0095] The reinforcing sleeve 3 thus opposes the local increase in diameter of the first rod element 1, and limits its radial deformation, in addition to limiting its axial deformation.

[0096] [Fig.7] illustrates another embodiment of the electric current conduction rod 20. According to this embodiment, the reinforcing sleeve 3 is in contact with a lateral surface 19 of the second rod element 2.

[0097] The reinforcing sleeve 3 is arranged radially around the first rod element 1 and around the second rod element 2.

[0098] In other words, a portion of the first rod element 1 and a portion of the second rod element 2 extend inside the volume delimited by the internal surface 13 of the reinforcing sleeve 3. The junction 16 between the first rod element 1 and the second rod element 2 is, in this embodiment, arranged inside the reinforcing sleeve 3. The junction is understood to mean the contact area between the first element 1 and the second element 2.

[0099] According to the variant illustrated in [Fig.6], a radial clearance j is present between the reinforcing sleeve 3 and a lateral surface 9 of the first rod element 1.

[0100] According to this variant of the electric current conduction rod 20, the radial clearance j can be between 0.5% and 2% of a diameter d3 of the reinforcement sleeve 3.

[0101] The reinforcing sleeve 3 may surround the first rod element 1 only over a portion of the length of the first rod element 1. An axial length L3 of the reinforcement sleeve 3 is for example between 50% and 80% of an axial length L1 of the first rod element 1.

[0102] According to an exemplary embodiment of the electric current conduction rod 20, an axial length L3 of the reinforcing sleeve 3 is between 5% and 50% of a total axial length of the rod 20.

[0103] The first rod element 1 and the second rod element 2 are for example fixed by brazing.

[0104] An axial end of the first rod element 1 terminates in a pin 17 and an axial end of the second rod element 2 comprises a housing 18 configured to receive the pin 17 of the first rod element 1. This type of embodiment is illustrated in [Fig.4].

[0105] According to a variant not shown, an axial end of the second rod element 2 ends with a pin and an axial end of the first rod element 1 comprises a housing configured to receive the pin of the second rod element 2. Pawn 17 and slot 18 have complementary shapes.

[0106] The solder can at least partially fill the space between the pin 17 and the housing 18. Similarly, the solder forms a bonding layer between the facing surfaces of the first element 1 and the second element 2. In figures 5, 6, 7 the pin and the housing have not been shown.

[0107] [Fig.8] illustrates a method of assembling an electric current conduction rod 20 as described previously. The assembly process involves the following steps: - provide a first element 1 of rod, - provide a second rod element 2, - provide a reinforcement sleeve 3, - insert the first rod element 1 inside the reinforcement sleeve 3, - axially compress the reinforcing sleeve 3 between the first rod element 1 and the second rod element 2, - fixing together the first rod element 1 and the second rod element 2.

[0108] An electric current conduction rod 20 is thus obtained.

[0109] A contact body is then fixed to the electric current conduction rod 20 in order to form an electric cut-off contact 30a. The vacuum interrupter comprises two contacts 30a, 30b. Each 30a, 30b electrical cut-off contact for a 50 medium or high voltage vacuum bulb comprises: - a rod 20a, 20b for conducting electric current as described previously, - a contact body 10a, 10b fixed to the electric current conduction rod 20, the contact body 10a, 10b extending transversely to the axis D.

[0110] According to an alternative embodiment not shown, the internal diameter of the reinforcing sleeve 3 is, in the free state, less than the external diameter of the portion of rod element that it surrounds. In other words, the reinforcing sleeve 3 is in this case tightly mounted on the rod element(s) that it surrounds. The assembly is carried out for example by heating the reinforcement sleeve before inserting the rod element, the temperature increase making it possible to temporarily increase the internal diameter of the reinforcement sleeve 3. Alternatively, the rod member may be cooled so that its diameter decreases to allow its insertion.

[0111] In the example of [Fig.2], each of the two electrical contacts 30a, 30b of the vacuum bulb 50 comprises a conduction rod 20a, 20b respectively comprising a reinforcing sleeve 3a, 3b. The 50 medium or high voltage vacuum bulb thus comprises: - a first 30a electrical cut-off contact as previously described, - a second electrical cut-off contact 30b as previously described, at least one of the first contact 30a and the second contact 30b being configured to be moved along the axis D between a so-called open position O in which the contacts 30a, 30b are spaced apart from each other and a so-called closed position F in which the contacts 30a, 30b bear against each other so as to allow passage of electric current between the first contact 30a and the second contact 30b.

[0112] According to an alternative embodiment not shown, only one of the two electrical contacts comprises a conduction rod 20 comprising a reinforcing sleeve 3.

[0113] According to the example of [Fig.2], contact 2a is movable and contact 2b is fixed. According to a variant not shown, contact 2a and contact 2b are both movable.

Claims

Claims

1. Electric current conducting rod (20) for a medium or high voltage vacuum bulb (50), comprising: - a first rod element (1) extending along an axis (D), - a second rod element (2), integral with the first rod element (1), - a reinforcing sleeve (3) arranged radially around the first rod element (1), in which the reinforcing sleeve (3) is axially compressed between the first rod element (1) and the second rod element (2).

2. An electric current conducting rod (20) according to claim 1, wherein the reinforcing sleeve (3) is cylindrical.

3. An electric current conducting rod (20) according to claim 1 or 2, wherein the reinforcing sleeve (3), the first rod member (1) and the second rod member (2) are coaxial.

4. Electric current conduction rod (20) according to one of the preceding claims, in which: - the first rod element (1) is made of copper, - the second rod element (2) is made of copper, - the reinforcing sleeve (3) is made of stainless steel.

5. Electric current conduction rod (20) according to one of the preceding claims, in which an axial compression rate of the reinforcing sleeve (3) is between 0.1% and 5%.

6. Electric current conduction rod (20) according to one of the preceding claims, in which the first rod element (1) comprises a shoulder (4) forming a stop for a first axial end (5) of the reinforcing sleeve (3).

7. An electric current conducting rod (20) according to the preceding claim, wherein an outer edge of the shoulder (4) is flared in shape.

8. An electric current conducting rod (20) according to one of the preceding claims, wherein the second rod element (2) forms a stop for a second axial end (6) of the reinforcing sleeve (3).

9. Rod (20) for conducting electric current according to the preceding claim, in which the second rod element (2) comprises a flat portion (14) forming a surface for receiving the second axial end (6) of the reinforcing sleeve (3), the flat portion (14) extending in a radial direction by a flared portion (15), the flared portion (15) being distant from the reinforcing sleeve (3) in an axial direction.

10. An electric current conducting rod (20) according to one of the preceding claims, wherein the thickness (e) of the reinforcing sleeve (3) is between 0.1 millimeters and 5.0 millimeters, and wherein a ratio of the thickness (e) of the reinforcing sleeve (3) and an outer diameter (d3) of the reinforcing sleeve (3) is between 0.01 and 0.

1.

11. An electric current conducting rod (20) according to one of the preceding claims, wherein the reinforcing sleeve (3) is in contact with a lateral surface (9) of the first rod element (1).

12. Electric current conduction rod (20) according to one of the preceding claims, in which the reinforcing sleeve (3) is radially constrained.

13. An electric current conducting rod (20) according to one of the preceding claims, wherein the reinforcing sleeve (3) is in contact with a lateral surface (19) of the second rod element (2).

14. Electric current conduction rod (20) according to one of claims 1 to 10, in which a radial clearance (j) is present between the reinforcing sleeve (3) and a lateral surface (9) of the first rod element (1), and in which the radial clearance (j) is between 0.5% and 2% of a diameter (d3) of the reinforcing sleeve (3).

15. Electric current conduction rod (20) according to one of the preceding claims, in which: - an axial length (L3) of the reinforcing sleeve (3) is between 50% and 80% of an axial length (L1) of the first rod element (1), and - an axial length (L3) of the reinforcing sleeve (3) is between 5% and 50% of a total axial length (L20) of the rod (20).

16. Method for assembling an electric current conduction rod (20) according to one of the preceding claims, comprising the steps of: - providing a first rod element (1), - providing a second rod element (2), - providing a reinforcing sleeve (3), - insert the first rod element (1) inside the reinforcement sleeve (3), - axially compress the reinforcing sleeve (3) between the first rod element (1) and the second rod element (2), - fixing together the first rod element (1) and the second rod element (2).

17. Electrical cut-off contact (30a, 30b), for vacuum bulb (50) of medium or high voltage, including: - an electric current conduction rod (20a, 20b) according to one of claims 1 to 15, - a contact body (10a, 10b) fixed to the electric current conduction rod (20), the contact body (10a, 10b) extending transversely to the axis (D).

18. Medium or high voltage vacuum bulb (50), comprising: - a first electrical cut-off contact (30a) according to the preceding claim, - a second electrical cut-off contact (30b) according to the preceding claim, at least one of the first contact (30a) and the second contact (30b) being configured to be moved along the axis (D) between a so-called open position (O) in which the contacts (30a, 30b) are spaced apart from each other and a so-called closed position (F) in which the contacts (30a, 30b) are supported on each other so as to allow a passage of electric current between the first contact (30a) and the second contact (30b).

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