Medium or high voltage vacuum bulb

Abstract

A medium or high voltage vacuum interrupter (50) is proposed, comprising:- an insulator forming a receiving enclosure, the insulator being formed of two coaxial elements (1a, 1b),- two electrical contacts arranged in the insulator, configured to be moved relative to each other between a closed position and an open position,- a screen (4) radially surrounding the electrical contacts, configured to collect the metal particles emitted when an electric arc passes between the electrical contacts so as to protect the insulator from the emitted metal particles,the screen (4) comprising a fixing flange (5) clamped between the two elements (1a, 1b) of the screen (4),characterized in that the vacuum interrupter (50) comprises a seal (7) made of semiconducting material surrounding the insulator, the seal (7) being in electrical contact with the screen (4). Abstract figure: Figure 6

Description

Title of the invention: Medium or high voltage vacuum bulb Technical field

[0001] The present invention relates to the field of medium or high voltage vacuum interrupting devices, also called vacuum interrupters or vacuum bulbs. Vacuum interrupters are used in medium and high voltage electrical distribution devices, i.e. voltages greater than 1 kV. Vacuum interrupters are associated with actuators to cut off the current in a part of the circuit. Prior art

[0002] In a well-known manner, a vacuum bulb comprises two cut-off contacts arranged opposite each other. Each contact comprises a rod for supplying the electric current, and a body secured to the rod. The contacts are arranged in an insulating 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 flow from one contact to the other. When the contacts are separated from each other, the current is interrupted.

[0003] A protective screen is arranged inside the insulating casing and surrounds the electrical contacts. The screen prevents metal particles detaching from the contacts when an electric arc is created from being deposited on the internal surface of the insulating casing. In order to secure the screen to the insulating casing, it may be in two parts arranged side by side coaxially, and a portion of the screen serving as a retaining flange is clamped between the two parts of the insulating casing. This portion of screen serving as a retaining flange generates dielectric stresses.

[0004] It is desirable to have vacuum bulbs that can withstand higher voltages, without increasing their size and in particular without increasing their diameter. The dielectric stresses generated by the portion of screen serving as a retaining flange run counter to this objective.

[0005] There is therefore a need to have a vacuum bulb with improved dielectric strength. Summary

[0006] To this end, the invention provides a medium or high voltage vacuum bulb, comprising: - an insulator forming a receiving enclosure, the insulator being formed of two coaxial elements, - two electrical contacts arranged in the insulation, configured to be moved one relative to each other between a closed position in which the electrical contacts are supported on each other and an open position in which the electrical contacts are separated from each other, - a screen radially surrounding the electrical contacts, configured to collect metal particles emitted during the passage of an electric arc between the electrical contacts so as to protect the insulator from the emitted metal particles, the screen comprising a fixing flange clamped between the two elements of the screen, characterized in that the vacuum bulb comprises a seal made of semi-conductor material surrounding the insulator, the seal being in electrical contact with the screen.

[0007] The presence of the seal avoids the creation of a triple interface where the insulator, the screen and the gas surrounding the vacuum bulb meet. Thanks to the presence of the seal, two triple interfaces are created: a first interface between the insulator, a first portion of the seal and the gas surrounding the vacuum bulb, and a second interface between the screen, the insulator and a second portion of the seal. This separation of the interfaces makes it possible to increase the dielectric strength of the vacuum bulb. The semiconducting nature of the seal material makes it possible to ensure that the seal is at the electrical potential of the screen in its entirety, which allows the seal to have an electrical deflector effect reducing the electric field in this area. For the same performance, the size of the bulb can be reduced, or for the same size the performance of the vacuum bulb can be improved.

[0008] The features listed in the following paragraphs can be implemented independently of each other or in any technically possible combination:

[0009] The vacuum bulb is sealed.

[0010] The vacuum bulb is generally cylindrical in shape and extends along an axis.

[0011] The insulator, the screen and the electrical contacts are coaxial.

[0012] According to one aspect of the invention, the seal made of semi-conductor material is made of butadiene-acrylonitrile copolymers.

[0013] The seal is elastically deformable.

[0014] According to one embodiment of the vacuum bulb, the seal is in mechanical contact with the screen fixing flange.

[0015] The seal is in mechanical contact with the insulation.

[0016] According to another embodiment of the vacuum bulb, the seal is distant from the fixing flange of the screen, and an axial surface of at least one of the two coaxial elements of the insulator comprises an electrically conductive coating, the coating being in contact with the seal and with the fixing flange.

[0017] The electrically conductive coating present on the axial surface which is in contact on the one hand with the screen fixing flange and on the other hand with the seal ensures electrical contact between the two parts. The seal and the screen are thus placed at the same electrical potential.

[0018] According to an alternative embodiment of the vacuum bulb, or in a complementary manner, a space separating the screen fixing flange and the seal comprises an electrically conductive grease.

[0019] The grease is for example a silicone grease.

[0020] According to one aspect of the proposed vacuum bottle, the seal is removable.

[0021] According to an example of use, the seal can thus be put in place specifically for the conditioning procedure to remove surface defects from the contact bodies of the vacuum interrupter. The seal can then be removed for use of the interrupter in an electrical appliance. According to another example of use, the seal can be retained for the entire duration of use of the vacuum bulb.

[0022] The gasket can be added to the vacuum bulb.

[0023] Once mounted, the seal can be removed from the vacuum bulb.

[0024] The insulator has the shape of a cylinder of revolution.

[0025] The two elements of the insulator have the shape of a hollow cylinder.

[0026] The two elements of the insulator are arranged side by side in an axial direction and are separated from each other by the screen mounting flange.

[0027] The two elements of the insulator have an identical internal diameter.

[0028] The two elements of the insulator have an identical external diameter.

[0029] The insulator is ceramic.

[0030] The screen comprises a cylindrical portion surrounding the electrical contacts.

[0031] The screen is for example made of copper.

[0032] The shield mounting flange extends radially outwardly from an outer surface of the cylindrical portion of the shield.

[0033] The screen fixing flange extends in a plane transverse to the axis of the screen.

[0034] The screen fixing flange is annular in shape.

[0035] The screen mounting flange is made of copper.

[0036] The screen fixing flange is in contact with each of the two elements of the insulation.

[0037] The screen fixing flange is compressed in an axial direction between the two elements of the insulator.

[0038] The connection between the screen fixing flange and each of the two elements of the insulation is watertight.

[0039] An axial surface of the first element is in contact with a first face of the screen fixing flange.

[0040] An axial surface of the second element is in contact with a second face of the screen mounting flange.

[0041] An outer side surface of the fixing flange is radially recessed from an outer side surface of the first element of the insulator. Similarly, the outer side surface of the fixing flange is radially recessed from an outer side surface of the second element of the insulator.

[0042] An outer diameter of the fixing flange is greater than an average diameter of the first element and the second element.

[0043] The seal partially covers an outer side surface of the first element and an outer side surface of the second element.

[0044] The seal partially covers an axial surface of the first element and an axial surface of the second element.

[0045] According to one embodiment of the vacuum bulb, the seal is toroidal in shape when the seal is in the free state.

[0046] According to an exemplary embodiment, a diameter of a cross-section of the seal is between 5 millimeters and 40 millimeters.

[0047] According to an exemplary embodiment, an average diameter of the seal is between 50 millimeters and 200 millimeters.

[0048] Preferably, a ratio of the diameter of a cross-section of the seal to the average diameter of the seal is between 0.05 and 0.2.

[0049] This form factor allows the joint to closely match the shape of the ends of the insulation elements, while also allowing sufficient coverage of the axial end portions of the elements.

[0050] According to one embodiment of the vacuum bulb, the seal comprises in the free state: - a toroidal portion, - an annular portion extending radially inwards, the annular portion being in contact with the first element and with the second element in an axial direction.

[0051] The annular portion allows the seal to have a shape facilitating the establishment of mechanical contact with the screen fixing flange.

[0052] A first face of the annular portion is in contact with an axial surface of the first element of the insulator.

[0053] A second face of the annular portion, opposite the first face, is in contact with an axial surface of the second element of the insulator.

[0054] The annular portion extends toward the axis of the toroidal portion in an equatorial plane of the toroidal portion.

[0055] According to one embodiment of the vacuum bulb, the annular portion of the seal is distant from the fixing flange of the screen.

[0056] More precisely, the annular portion of the seal is distant from a lateral surface ex- outer side of the screen mounting flange.

[0057] A lateral surface of the annular portion of the seal is distant from the outer lateral surface of the screen fixing flange, in a radial direction.

[0058] An outer lateral surface of the fixing flange, a lateral surface of the annular portion of the seal, an axial surface of the first element and an axial surface of the second element define an annular-shaped volume.

[0059] A volume separating the annular portion of the seal and the screen fixing flange is at least partially filled with an electrically conductive grease.

[0060] The volume separating the annular portion of the seal and the screen fixing flange can be completely filled with an electrically conductive grease.

[0061] The cavity delimited by the outer lateral surface of the fixing flange, the lateral surface of the annular portion of the seal, an axial surface of the first element and an axial surface of the second element is filled, partially or totally, with an electrically conductive grease.

[0062] A ratio between the diameter of a cross-section of the toroidal part and the outer diameter of the insulator is between 0.05 and 0.2.

[0063] A ratio between the inner diameter of the toroidal part and the outer diameter of the insulator is between 0.8 and 0.95.

[0064] A portion of the first element in contact with the seal comprises a chamfer.

[0065] Similarly, a portion of the second element in contact with the seal comprises a chamfer.

[0066] The invention also relates to a method of packaging a vacuum ampoule. The process involves the following steps: (i) provide a vacuum flask comprising: - an insulator forming a receiving enclosure, the insulator being formed of two coaxial elements, - a pair of electrical contacts arranged in the insulator, comprising a movable contact and a fixed contact, - a screen radially surrounding the electrical contacts, configured to collect the metal particles emitted when an electric arc passes between the electrical contacts so as to protect the insulation from the emitted metal particles, the screen comprising a fixing flange tightened between the two elements of the screen, (ii) provide a seal, (iii) equipping the vacuum bulb with a seal surrounding the insulator, the seal being in electrical contact with the screen, (iv) moving the contacts of the vacuum bulb apart and increasing an electrical voltage between the electrical contacts until an electric arc is created between the contacts, (v) iterate the step of creating an electric arc so as to condition the surfaces of the electrical contacts, (vi) remove the vacuum bulb seal.

[0067] The addition of the seal for the vacuum bulb conditioning phase makes it possible to increase the voltage between the electrical contacts without creating a discharge between the vacuum bulb insulation and the external environment. Electric arcs can be created in a preferential manner between the electrical contacts, which allows the conditioning of the vacuum bulb to be accelerated.

[0068] Step (vi) is optional. According to a variant of the proposed packaging method, the seal can remain mounted on the vacuum bulb for the entire duration of use of the vacuum bulb. In this case, the bulb is mounted in an electrical device equipped with its seal. The presence of the seal improves the dielectric strength of the vacuum bulb in service.

[0069] Step (vi) of dismantling the seal is thus replaced by a step: (vi') maintain the seal on the vacuum interrupter until the vacuum interrupter is fitted into an electrical appliance. Brief description of the drawings

[0070] Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the attached drawings, in which:

[0071] [Fig-1] is a schematic side view of a vacuum bulb,

[0072] [Fig.2] is a side view, in section, of a vacuum bulb,

[0073] [Fig.3] is a side view of a vacuum bulb according to one embodiment of the invention,

[0074] [Fig.4] is a partial side and sectional view of the vacuum bulb of [Fig.3], not equipped with its seal,

[0075] [Fig.5] is a partial side and sectional view of the vacuum bulb of [Fig.3],

[0076] [Fig.6] is a partial side and sectional view of an alternative embodiment of the vacuum bulb of [Fig.3],

[0077] [Fig.7] represents a seal equipping a vacuum bulb according to one embodiment,

[0078] [Fig.8] represents a seal equipping a vacuum bulb according to another method of rea lization,

[0079] [Fig.9] is a block diagram of a method for conditioning a vacuum ampoule according to the invention. Description of the embodiments

[0080] 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. Some elements or parameters may be indexed, i.e. designated for example by first element or second element, or 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 includes a given element, this does not exclude the presence of other elements in this subsystem. Similarly, when it is specified that a subsystem includes a given element, it is understood that the subsystem includes at least this element.

[0081] In the various figures, the axes X, Y, Z designate the three directions of space in order to identify the viewing angle of each figure.

[0082] [Fig.l] and [Fig.2] show a medium or high voltage vacuum bulb 50. The 50 vacuum bulb includes: - a first electrical cut-off contact 2, - a second electrical cut-off contact 3. At least one of the first contact 2 and the second contact 3 is configured to be moved along an axis D between a so-called open position O in which the electrical contacts 2, 3 are spaced apart from each other, and a so-called closed position F in which the electrical contacts 2, 3 are supported on each other so as to allow a passage of electric current between the first contact 2 and the second contact 3.

[0083] The vacuum interrupter 50 is part of a medium voltage cut-off device, such as a circuit breaker or a disconnector. In part A of [Fig.l], the electrical cut-off contacts 2, 3 are in contact with each other, and an electric current can flow. In part A of [Fig.l], the sign C schematizes the passage of the electric current. When the contacts 2, 3 are moved apart 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 electrical contacts 2, 3. 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.

[0084] The first electrical contact 2 comprises a cylindrical rod 22 and a disc-shaped contact body 21. The contact body 21 is integral with the rod 22 and extends transversely to the cylindrical rod 22. Likewise, the second electrical contact 3 comprises a cylindrical rod 32 and a disc-shaped contact body 31, integral with the cylindrical rod 32 and extending transversely to the cylindrical rod 32. Each contact body 21, 31 is fixed respectively to the cylindrical rod 22, 32, for example by soldering. When the electrical contacts 2, 3 are in contact, the contact body 21 and the contact body 31 are supported on each other. In the closed position, a spring, not shown, maintains a preload between the contact bodies 21, 31. In other words, a contact pressure is applied in the closed position between the contact bodies 21, 31, this contact pressure being determined by the force applied by the spring. The preload spring is part of the control mechanism of the vacuum interrupter 50. The electrical contacts 2, 3 are arranged in an insulating envelope, also called insulator 1. A protective screen 4 is arranged inside the insulator 1, radially arranged between the electrical contacts 2, 3 and the inner wall of the insulator 1. The protective screen 4 prevents metal particles detaching from the contacts 2, 3 when electric arcs are created from being deposited on the inner surface of the insulator 1.

[0085] [Fig.3] is an exterior view of the proposed vacuum bottle 50.

[0086] The medium or high voltage vacuum bulb 50 comprises: - an insulator 1 forming a receiving enclosure, the insulator 1 being formed of two coaxial elements 1a, 1b, - two electrical contacts 2, 3 arranged in the insulator 1, configured to be moved relative to each other between a closed position F in which the electrical contacts 2, 3 are supported on each other and an open position O in which the electrical contacts 2, 3 are spaced apart from each other, - a screen 4 radially surrounding the electrical contacts 2, 3, configured to collect metal particles emitted during the passage of an electric arc between the electrical contacts 2, 3 so as to protect the insulator 1 from the emitted metal particles. The screen 4 comprises a fixing flange 5 clamped between the two elements 1a, 1b of the screen 4. The vacuum bulb 50 comprises a seal 7 made of semiconducting material surrounding the insulator 1, the seal 7 being in electrical contact with the screen 4.

[0087] The presence of the seal 7 avoids the creation of a triple interface where the insulator 1, the screen 4 and the gas surrounding the vacuum bottle 50 would meet. Thanks to the presence of the seal 7, two distinct triple interfaces are created: a first triple interface between the insulator 1, a first portion of the seal 7 and the gas surrounding the vacuum bottle 50, and a second triple interface between the screen 4, the insulator 1 and a second portion of the seal 7. This separation of the triple interfaces makes it possible to increase the dielectric strength of the vacuum bulb 50. The semiconducting nature of the material of the seal 7 makes it possible to ensure that the seal 7 is at the electrical potential of the screen 4 in its entirety, which allows the seal 7 to have an electrical deflector effect reducing the electric field in this area. For the same performance, the size of the bulb can be reduced, or for the same size the performance of the vacuum bulb can be improved.

[0088] The vacuum bulb 50 is generally cylindrical in shape and extends along an axis D. The insulator 1 has the shape of a cylinder of revolution.

[0089] The two elements 1a, 1b of the insulator 1 have the shape of a hollow cylinder. The two elements 1a, 1b of the insulator 1 are arranged side by side in an axial direction and are separated from each other by the fixing flange 5 of the screen 4. The insulator 1, the screen 4 and the electrical contacts 2, 3 are coaxial. The axis D is the common axis of the first element 1a of the insulator 1, of the second element 1b of the second element 1b of the insulator 1, of the screen 4, of the first electrical contact 2 and of the second electrical contact 3.

[0090] [Fig.4] represents a vacuum bulb 50 in which the seal 7 is not mounted. The two elements 1a, 1b of the insulator 1 have an identical internal diameter. This internal diameter is designated by the sign Di-1 in [Fig.4]. The two elements 1a, 1b of the insulator 1 have an identical external diameter. This external diameter is designated by the sign De-1 in [Fig.4].

[0091] The insulator 1 is made of ceramic. Insulator 1 is for example made of alumina, (chemical formula A12O3) More precisely, each element 1a, 1b is made of ceramic, for example alumina.

[0092] The screen 4 comprises a cylindrical portion 6 surrounding the electrical contacts 2, 3. The cylindrical portion 6 extends along the rods 22, 32 and is opposite the contact bodies 21, 31. Screen 4 is for example made of copper. The fixing flange 5 of the screen 4 extends radially outwards from an outer surface 6e of the cylindrical portion 6 of the screen 4.

[0093] The fixing flange 5 of the screen 4 extends in a plane P transverse to the axis D of the screen 4. The fixing flange 5 of the screen 4 is annular in shape. The fixing flange 5 of the screen 4 is made of copper. The fixing flange 5 of the screen 4 is fixed to the cylindrical portion 6 surrounding the electrical contacts 2, 3 by soldering. The fixing flange 5 and the cylindrical part 6 of the screen 4 are thus at the same electrical potential.

[0094] The fixing flange 5 of the screen 4 is in contact with each of the two elements 1a, 1b of insulation 1. The fixing flange 5 of the screen 4 is compressed in an axial direction between the two elements 1a, 1b of the insulator 1. The connection between the fixing flange 5 of the screen 4 and each of the two elements 1a, 1b of the insulation is watertight.

[0095] An axial surface 10a of the first element 1a is in contact with a first face 15 of the fixing flange 5 of the screen 4. An axial surface 10b of the second element 1b is in contact with a second face 16 of the fixing flange 5 of the screen 4.

[0096] The vacuum bulb 50 is sealed. The pressure inside the vacuum bulb 50 is for example less than 104 millibar. The gaseous medium in which the vacuum bottle 50 is arranged is for example ambient air. The ambient air in which the vacuum bottle is placed is represented diagrammatically by the signs A in FIGS. 4, 5, 6.

[0097] An outer lateral surface 17 of the fixing flange 5 is radially set back from an outer lateral surface 11a of the first element 1a of the insulator 1. Similarly, the outer lateral surface 17 of the fixing flange 5 is radially set back from an outer lateral surface 11b of the second element 1b of the insulator 1. An outer diameter De-5 of the fixing flange 5 is greater than an average diameter Dm-1 of the first element 1a and of the second element 1b. The average diameter Dm-1 of the first element la is the average between the internal diameter Di-1 and the external diameter De-1.

[0098] [Fig.5] and [Fig.6] are views of the area designated by the sign F in [Fig.4]. In these figures, the vacuum bulb 50 is equipped with a seal 7.

[0099] The seal 7 made of semi-conductor material is made of butadiene-acrylonitrile copolymers. This material is also called nitrile rubber, and is commonly referred to by the English acronym NBR for “nitrile butadiene rubber”. The seal 7 is elastically deformable.

[0100] The seal 7 is in the example illustrated a single-piece part. The seal 7 is for example obtained by molding.

[0101] According to an embodiment of the vacuum bulb 50 illustrated in [Fig.5], the seal 7 is in mechanical contact with the fixing flange 5 of the screen 4. The electrical contact between the seal 7 and the fixing flange 5 of the screen 4 is then obtained by establishing direct mechanical contact between the two parts.

[0102] The seal 7 is in mechanical contact with the insulator 1. More precisely, the seal 7 is in mechanical contact with the first element 1a of the insulator 1. The seal 7 is also in mechanical contact with the second element 1b of the insulator 1. The seal 7 surrounds the insulator 1 and partly covers the outer surface 11a of the first element 1a of the insulator 1, as well as the outer surface 11b of the second element 1b.

[0103] The seal 7 partly covers an outer lateral surface 11a of the first element 1a and an outer lateral surface 11b of the second element 1b. The seal 7 partially covers an axial surface 10a of the first element 1a and an axial surface 10b of the second element 1b.

[0104] [Fig.6] illustrates an embodiment of the vacuum bulb 50 in which the seal 7 is distant from the fixing flange 5 of the screen 4. A space designated by the sign V radially separates the fixing flange 5 and the screen 4. The seal 7 is not in mechanical contact with the fixing flange 5 of the screen 4.

[0105] An axial surface 10a, 10b of at least one of the two coaxial elements 1a, 1b of the insulator 1 comprises an electrically conductive coating 14, the coating 14 being in contact with the seal 7 and with the fixing flange 5.

[0106] The electrically conductive coating 14 is present on an axial surface of at least one element 1a, 1b, this axial surface being in contact on the one hand with the fixing flange 5 of the screen 4 and on the other hand with the seal 7. The coating 14 makes it possible to ensure electrical continuity between the seal 7 and the fixing flange 5. The seal 7 and the screen 4 are thus placed at the same electrical potential.

[0107] The coating 14 is for example a metallic layer deposited on the axial end of an element of the insulator 1. According to the example of [Fig.6], only the first element 1a of the insulator 1 comprises the electrically conductive coating 14. According to an example not shown, the first element 1a and the second element 1b each comprise an electrically conductive coating deposited on their respective axial end.

[0108] A space V separating the fixing flange 5 from the screen 4 and the seal 7 comprises an electrically conductive grease. The electrical contact between the seal 7 and the fixing flange 5 of the screen 4 can be obtained, or completed, thanks to the electrical conduction of the grease interposed between the seal 7 and the fixing flange 5 of the screen 4.

[0109] In addition, the grease placed in the annular space V between the seal 7 and the fixing flange 5 of the screen 4 makes it possible to avoid the presence of air bubbles in this space separating the two parts. The grease is for example a silicone grease.

[0110] The seal 7 is removable.

[0111] According to an example of use, the seal 7 can thus be put in place specifically for the conditioning procedure carried out during the manufacture of the vacuum ampoule 50. This conditioning procedure aims to remove surface defects from the contact bodies 21, 31 of the vacuum bottle 50. To do this, electric arcs are created between the contacts, and these electric arcs allow the surface defects forming angular singularities on the surface of the new contact bodies to melt and disappear. The seal 7 can then be removed once the procedure for conditioning the vacuum bottle 50 is complete. The seal 7 is thus absent from the vacuum bottle 50 when using the vacuum bottle 50 in an electrical appliance.

[0112] According to another example of use, the seal 7 can be kept for the entire duration of use of the vacuum bulb 50. For example, seal 7 is installed before the packaging procedure and is then left in place.

[0113] The gasket 7 can be added to the vacuum bulb 50. Once fitted, the seal 7 can be removed from the vacuum bulb 50.

[0114] Multiple successive assemblies and disassemblies can be carried out without damaging the seal 7. The seal 7 can for example be dismantled to facilitate the installation of the vacuum bulb 50 in an electrical device.

[0115] According to one embodiment of the vacuum bulb 50, the seal 7 is toroidal in shape when the seal 7 is in the free state. In other words, the seal has the shape of a torus in the absence of mechanical stress likely to deform the seal. [Fig.7] represents the seal 7 in the free state, that is to say not mounted on the vacuum bulb 50.

[0116] According to an exemplary embodiment, a diameter Dt-7 of a cross-section of the seal 7 is between 5 millimeters and 40 millimeters. The diameter Dt-7 of a cross-section of the seal 7 is the diameter in the free state, i.e. without deformation. It is therefore the dimension when the seal 7 is not mounted on the vacuum bulb 50. The diameter Dt-7 is also called the torus diameter.

[0117] According to an exemplary embodiment, an average diameter Dm-7 of the seal 7 is between 50 millimeters and 200 millimeters. The average diameter of the torus is understood to be the average between the internal diameter Di-7 of the torus and the external diameter De-7 of the torus. As before, the average diameter Dm-7 of joint 7 is the diameter in the free state, i.e. without deformation. The inner diameter Di-7 and the outer diameter De-7 are measured parallel to the equatorial plane P7 of joint 7.

[0118] Preferably, a ratio of the diameter Dt-7 of a cross-section of the seal 7 and the average diameter Dm-7 of the seal 7 is between 0.05 and 0.2. This form factor allows the seal 7 to closely match the shape of the ends of the lateral surface of the elements 1a, 1b of the insulator 1, while also allowing sufficient coverage of the axial end portions 10a, 10b of the elements 1a, 1b.

[0119] According to the embodiments illustrated in Figures 5 and 6, the seal 7 comprises in the free state: - a toroidal portion 8, - an annular portion 9 extending radially inwards, the annular portion 9 being in contact with the first element 1a and with the second element 1b in an axial direction.

[0120] The annular part 9 allows the seal 7 to have a shape facilitating the establishment of mechanical contact with the fixing flange 5 of the screen 4.

[0121] A first face 19 of the annular portion 9 is in contact with an axial surface 10a of the first element 1a of the insulator 1. A second face 20 of the annular portion 9, opposite the first face 19, is in contact with an axial surface of the second element 1b of the insulator 1.

[0122] The annular portion 9 extends towards the axis D of the toroidal portion 8 in an equatorial plane P8 of the toroidal part 8. The thickness of the annular part 9 is smaller than the diameter of the toroidal part 8. The annular part 9 can therefore be easily inserted into the space separating the axial surface 10a of the first element 1a from the axial surface 10b of the second element 1b.

[0123] In [Fig.5] and in [Fig.6], the toroidal part 8 is shown taking into account, in a schematic manner, the deformation undergone in contact with the external surface 11a, 11b of the insulator 1.

[0124] According to the embodiment of [Fig.6], the annular portion 9 of the seal 7 is distant from the fixing flange 5 of the screen 4.

[0125] More precisely, the annular portion 9 of the seal 7 is distant from an external lateral surface 17 of the fixing flange 5 of the screen 4. A lateral surface 18 of the annular portion 9 of the seal 7 is thus distant from the external lateral surface 17 of the fixing flange 5 of the screen 4, in a radial direction.

[0126] In other words, a radial clearance is present between the annular portion 9 of the seal 7 and the fixing flange 5 of the screen 4.

[0127] An outer lateral surface 17 of the fixing flange 5, a lateral surface 18 of the annular portion 9 of the seal 7, an axial surface 10a of the first element 1a and an axial surface 10b of the second element 1b define a volume V of annular shape.

[0128] The volume V separating the annular portion 9 of the seal 7 and the fixing flange 5 of the screen 4 is filled at least partially with an electrically conductive grease. The volume V separating the annular portion 9 of the seal 7 and the fixing flange 5 of the screen 4 can be completely filled with an electrically conductive grease.

[0129] The cavity delimited by the outer lateral surface 17 of the fixing flange 5, the lateral surface 18 of the annular portion 9 of the seal 7, an axial surface 10a of the first element 1a and an axial surface 10b of the second element 1b is filled, partially or totally, with an electrically conductive grease.

[0130] A ratio between the diameter of a cross-section of the toroidal part 8 and the outer diameter De-1 of the insulator 1 is between 0.05 and 0.2. A ratio between the inner diameter of the toroidal part 8 and the outer diameter De-1 of the insulator 1 is between 0.8 and 0.95.

[0131] A portion of the first element 1a in contact with the seal 7 comprises a chamfer 14a. Likewise, a portion of the second element 1b in contact with the seal 7 comprises a chamfer 14b. The chamfer 14a of the first element 1a connects a portion of the axial surface 10a of the first element 1a and a portion of the outer lateral surface 11a of the first element 1a. The same applies to chamfer 14b of the second element 1b.

[0132] The chamfers 14a, 14b facilitate the insertion of the seal 7 between the axial surfaces 10a, 10b of the first element 1a and the second element 1b.

[0133] A conditioning process can be applied to a vacuum bulb. This conditioning is applied when the bulb is new, before it is mounted on an electrical appliance.

[0134] The invention also relates to a method of packaging a vacuum ampoule 50. The process for packaging a vacuum ampoule 50 comprises the steps: (i) provide a vacuum ampoule 50 comprising: — an insulator 1 forming a receiving enclosure, the insulator 1 being formed of two coaxial elements 1a, 1b, — a pair of electrical contacts 2, 3 arranged in the insulator 1, comprising a movable contact 2 and a fixed contact 3, — a screen 4 radially surrounding the electrical contacts 1, 2, configured to collect the metal particles emitted when an electric arc passes between the electrical contacts 2, 3 so as to protect the insulator 1 from the emitted metal particles, the screen 4 comprising a fixing flange 5 clamped between the two elements 1a, 1b of the screen 4, (ii) provide a seal 7, (iii) equipping the vacuum bulb 50 with a seal 7 surrounding the insulator 1, the seal 7 being in electrical contact with the screen 4, (iv) moving the contacts of the vacuum bulb 50 apart and increasing an electrical voltage between the electrical contacts 2, 3 until an electric arc is created between the contacts 2, 3, (v) iterating step (iv) of creating an electric arc so as to condition the surfaces of the electrical contacts 2, 3, (vi) remove the seal 7 from the vacuum bulb 50.

[0135] The addition of the seal 7 for the conditioning phase of the vacuum bottle 50 makes it possible to increase the voltage between the electrical contacts 2, 3 without creating a discharge between the insulation of the vacuum bottle 50 and the external environment. Electric arcs can be created in a preferential manner between the electrical contacts 2, 3, which makes it possible to increase the voltage at which the conditioning is carried out. The duration of the conditioning phase of the vacuum interrupter 50 can thus be shortened.

[0136] Step (vi) is optional. According to a variant of the proposed packaging method, the seal 7 can remain mounted on the vacuum bulb 50 for the entire duration of use of the vacuum bulb 7. The bulb is thus mounted in an electrical device equipped with its seal 7. The presence of the seal 7 makes it possible to improve the dielectric strength in service of the vacuum interrupter 50, and also to accelerate the conditioning phase.

[0137] Step (vi) of dismantling the seal 7 is thus replaced by a step: (vi') hold the seal 7 on the vacuum bulb 50 until the vacuum bulb 50 is mounted in an electrical device. The electrical device can be, for example, a circuit breaker.

Claims

Claims

1. Medium or high voltage vacuum bulb (50), comprising: - an insulator (1) forming a receiving enclosure, the insulator (1) being formed of two coaxial elements (1a, 1b), - two electrical contacts (2, 3) arranged in the insulator (1), configured to be moved relative to each other between a closed position (F) in which the electrical contacts (2, 3) are supported on each other and an open position (0) in which the electrical contacts (2, 3) are spaced apart from each other, - a screen (4) radially surrounding the electrical contacts (2, 3), configured to collect metal particles emitted during the passage of an electric arc between the electrical contacts (2, 3) so as to protect the insulator (1) from the emitted metal particles, the screen (4) comprising a fixing flange (5) clamped between the two elements (1a, 1b) of the screen (4),characterized in that the vacuum bulb (50) comprises a seal (7) of semiconducting material surrounding the insulator (1), the seal (7) being in electrical contact with the screen (4).,

2. Vacuum bulb (50) according to claim 1, wherein the seal (7) made of semiconducting material is made of butadiene-acrylonitrile copolymers.

3. Vacuum bulb (50) according to claim 1 or 2, wherein the seal (7) is in mechanical contact with the fixing flange (5) of the screen (4).

4. Vacuum bulb (50) according to claim 1 or 2, wherein the seal (7) is distant from the fixing flange (5) of the screen (4), and wherein an axial surface (10a, 10b) of at least one of the two coaxial elements (1a, 1b) of the insulator (1) comprises an electrically conductive coating (14), the coating (14) being in contact with the seal (7) and with the fixing flange (5).

5. Vacuum bulb (50) according to one of the preceding claims, wherein a space (V) separating the fixing flange (5) from the screen (4) and the seal (7) comprises an electrically conductive grease.

6. Vacuum ampoule (50) according to one of the preceding claims, in which the seal (7) is removable.

7. Vacuum bulb (50) according to one of the preceding claims, in which: - the seal (7) partly covers an outer lateral surface (11a) of the first element (1a) and an outer lateral surface (11b) of the second element (1b), and - the seal (7) partly covers an axial surface (10a) of the first element (1a) and an axial surface (10b) of the second element (1b).

8. A vacuum ampoule (50) according to one of claims 1 to 7, wherein the seal (7) is toroidal in shape when the seal (7) is in the free state.

9. A vacuum ampoule (50) according to one of the preceding claims, wherein a ratio of a diameter (Dt-7) of a cross-section of the seal (7) and an average diameter (Dm-7) of the seal (7) is between 0.05 and 0.

2.

10. Vacuum bulb (50) according to one of claims 1 to 7, in which the seal (7) comprises in the free state: - a toroidal portion (8), - an annular portion (9) extending radially inwards, the annular portion (9) being in contact with the first element (1a) and with the second element (1b) in an axial direction.

11. Vacuum bulb (50) according to the preceding claim, wherein the annular portion (9) extends towards the axis of the toroidal portion (8) in an equatorial plane (P8) of the toroidal portion (8).

12. A vacuum bulb (50) according to claim 10 or 11, wherein a ratio of a diameter (Dt-8) of a cross-section of the toroidal portion (8) to an outer diameter (De-1) of the insulator (1) is between 0.05 and 0.

2.

13. A vacuum bulb (50) according to one of claims 10 to 12, wherein a ratio between an inner diameter (Di-8) of the toroidal portion (8) and an outer diameter (De-1) of the insulator (1) is between 0.8 and 0.

95.

14. Vacuum cartridge (50) according to one of the preceding claims, wherein: - a portion of the first element (1a) in contact with the seal (7) comprises a chamfer (14a), and - a portion of the second element (1b) in contact with the seal (7) comprises a chamfer (14b).

15. A method of packaging a vacuum bulb, comprising the steps of: (i) providing a vacuum bulb (50) comprising: - an insulator (1) forming a receiving enclosure, the insulator (1) being formed of two coaxial elements (1a, 1b), - a pair of electrical contacts (2, 3) arranged in the insulator (1), comprising a movable contact (2) and a fixed contact (3), - a screen (4) radially surrounding the electrical contacts (1, 2), configured to collect the metal particles emitted during the passage of an electric arc between the electrical contacts (2, 3) so as to protect the insulator (1) from the emitted metal particles, the screen (4) comprising a fixing flange (5) clamped between the two elements (1a, 1b) of the screen (4), (ii) provide a seal (7), (iii) equipping the vacuum bulb (50) with a seal (7) surrounding the insulator (1), the seal (7) being in electrical contact with the screen (4), (iv) separating the contacts of the vacuum bulb (50) and increasing an electrical voltage between the electrical contacts (2, 3) until an electric arc is created between the contacts (2, 3), (v) iterate the step of creating an electric arc so as to condition the surfaces of the electrical contacts, (vi) remove the seal (7) from the vacuum bulb (50).

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