EP2325859B1 - Gas-isolated high voltage switch - Google Patents

Description

TECHNICAL AREA

The present invention relates to a gas-insulated high voltage switch according to the preamble of claim 1.

A switch of the aforementioned type is generally a circuit breaker, which dominated in the voltage range of about 70 kV breaking currents of more than 10 kA. Such a switch has a switch housing which is filled with an arc-containing insulating gas, such as based on sulfur hexafluoride and / or nitrogen and / or carbon dioxide, of generally up to a few bar pressure. In order to achieve a rapid dielectric solidification of a switching path formed between the opening switching pieces when switching off a current, the contact pieces are driven in opposite directions to each other. The required force is applied by a single drive of the switch. Therefore, a reversing gear is attached to a fixed to a first two switching pieces insulating the switch. This transmission transmits the force introduced by the drive into the first contact piece to the second contact piece or, conversely, the force introduced by the drive into the second contact piece onto the first contact piece. The force occurring here is considerable. The attachment of the nozzle to the first contact piece is relatively simple, since the contact piece has a centrally guided arcing contact and a coaxial surrounding hollow rated current contact, in which the nozzle can be secured with a first of its two ends in a dielectrically safe manner. Since the nozzle is arranged displaceably relative to the second switching piece, the coupling of the deflecting gear on the extinguishing gas serving second end of the nozzle is more expensive, especially in this case, the gas tightness and the control of the electric field in the coupling point are observed.

STATE OF THE ART

A switch of the type mentioned is described in EP 0 809 268 A2 and US 6,271,494 B1 , In this switch, the force of the switch drive is introduced into an insulating nozzle carrying a first contact piece and transmitted via a reversing gear on the opposite direction to the first contact piece driven second contact piece. As in EP 0 809 268 A2 shown, the insulating nozzle on a Ausblasende the nozzle arranged on the outer bead, behind which a first clamping ring is engaged. Before the bead, a second clamping ring is arranged, which supports the first clamping ring and / or the end of the nozzle so as to prevent unlocking of the first clamping ring. At least one of the two clamping rings, a drive element of the deflection gear can be coupled. In order to enable the engagement of the first clamping ring, he or the end of the nozzle must be elastically deformable. However, this generally requires along the switch axis guided, affecting the gas tightness and the dielectric strength slots in the nozzle end or in the first clamping ring. Therefore, additional means, such as a field electrode controlling the electric field in the region of the coupling, are required.

At an im EP 1 983 538 A1 described switch of the type mentioned, the force of the switch drive is introduced into the second contact piece and transmitted via a deflection gear and an insulating nozzle on the nozzle-carrying, counter-driven to the second contact piece first contact piece. At the discharge end of the insulating nozzle, an annular body 80 is arranged, which carries a drive element 51 of the deflection gear and is fastened by means of a screw connection to an outer bead of the nozzle.

PRESENTATION OF THE INVENTION

The invention, as indicated in the claims, the object is to provide a switch of the type mentioned, which can be made easily and inexpensively and is also characterized by good mechanical and electrical properties.

According to the invention defined in claim 1, a gas-insulated high-voltage switch is provided with two along an axis relatively movable switching pieces, attached to a first of the two switching pieces nozzle for blowing a switching arc with quenching gas and a fixedly mounted deflection gear, the one with the nozzle and is connected to the other with the second contact piece, wherein the nozzle has a hollow insulating body which forms a bottleneck and at least one adjoining the constriction portion of a diffuser, and includes a arranged at a Ausblasende the nozzle metal ring body, the form-fitting with the one External profile having insulating body is connected and carries a drive or driven element of the deflection gear, wherein the annular body in a concentric arrangement has a form fit to the insulator producing intermediate ring and a on the Intermediate ring deferred and attached to the intermediate ring ring for supporting the drive or driven element.

In the outer surface of the intermediate ring can be guided around the axis, an annular outer groove and in an on the outer surface of the intermediate ring almost free resting resting inner surface of the support ring may be formed around the axis, an annular inner groove, wherein the two grooves are arranged and formed that at a taking place during the manufacture of the switch relative displacement of the support ring and intermediate ring along the axis arranged in the outer or in the inner groove snap ring to form a secured against axial displacement connection of support and intermediate ring in the inner or in the outer groove spreads.

The inner surface of the support ring can run out at its end facing the first contact piece in a conically widening insertion, which reduces the diameter of the snap ring prior to its spreading in the relative displacement due to elastic deformation.

In the inner surface of the support ring, a radially inwardly extending annular step may be formed, which is seated with an annular surface forming the step height on an end face of the insulating body provided at the discharge end of the nozzle. The Annular step may form a portion of the diffuser and have an inner surface flaring towards the discharge end of the nozzle.

The intermediate ring may be formed slotted and have a predominantly axially aligned, in the manufacture of the switch spreading of the intermediate ring enabling longitudinal joint. The intermediate ring may be formed in several parts and have at least two by predominantly axially extending longitudinal joints separate ring parts. The outer profile of the insulating body may have at least one annular led around the axis increase or depression, in which a largely congruent recess or increase of the intermediate ring is fitted. The at least one annular led around the axis increase of the insulating body may extend along the axis over at least half of the axial extent of the intermediate ring.

Alternatively, the intermediate ring can also be formed free of joints and screwed to the insulating body, wherein the screw has a molded into the inner surface of the intermediate ring internal thread and an outer thread formed in the lateral surface of the insulating body. In an adjoining the external thread portion of the lateral surface of the insulating body may be formed an annular guided around the axis bead which is snapped into an inner groove formed in the inner surface of the intermediate ring.

A gap-free field electrode comprising the intermediate ring can be molded into the support ring or attached to the support ring.

On the outer surface of the support ring, a comprehensive seal the support ring may be attached to protect the rated current contacts of the two contact pieces before the action of arc gases.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig.1

eine Aufsicht auf einen längs einer Achse A geführten Schnitt durch eine Ausführungsform des geöffneten Hochspannungsschalters nach der Erfindung,

Fig.2

in Explosionsdarstellung eine erste Ausführungsform eines Kraftübertragungselements des Hochspannungsschalters nach Fig.1,

Fig.3

eine gegenüber der ersten Ausführungsform abgewandelte zweite Ausführungsform des Kraftübertragungselements,

Fig.4

eine gegenüber der ersten und zweiten Ausführungsform abgewandelte dritte Ausführungsform des Kraftübertragungselement, und

Fig.5

eine Ausführungsform eines im Kraftübertragungselement nach den Figuren 2 bis 4 einsetzbaren Tragrings.

With reference to drawings, the invention will be explained in more detail below. Hereby shows:

Fig.1

a plan view of a guided along an axis A section through an embodiment of the open high-voltage switch according to the invention,

Fig.2

in an exploded view of a first embodiment of a power transmission element of the high-voltage switch after Fig.1 .

Figure 3

a modified from the first embodiment, the second embodiment of the power transmission element,

Figure 4

a comparison with the first and second embodiment modified third embodiment of the power transmission element, and

Figure 5

an embodiment of a power transmission element according to the FIGS. 2 to 4 usable carrying rings.

WAYS FOR CARRYING OUT THE INVENTION

In all figures, like reference numerals designate like-acting parts. The in the Figures 1 and 2 shown high-voltage switch is designed as a circuit breaker and includes a filled with a compressed insulating gas, such as based on sulfur hexafluoride or a sulfur hexafluoride gas filled and largely tubular shaped housing 10 and a housing 10 received, largely axially symmetric shaped contact arrangement with two along an axis A relative mutually displaceable switching pieces 20 and 30th

The contactor 20 has in coaxial arrangement a hollow arcing contact 21 and a hollow arcing contact surrounding the hollow rated current contact 22, whereas the contact piece 30 in a coaxial arrangement includes a designed as a pencil arcing contact 31 and a surrounding the arcing contact 31 hollow rated current contact 32.

The contact piece 20 is guided in a gas-tight manner along the axis A in a fixed, metal hollow body 40 and is connected via a hollow contact carrier 23 of the arcing contact 21 with an insulator, not shown, located at ground potential drive D of the switch.

The hollow body 40 includes an axially aligned, the rated current contact 22 coaxially comprehensive, fixed hollow cylinder 41 which is bounded by a fixed cylinder base 42 along the axis A to the left. In the cylinder bottom an opening is provided, in which the hollow contact carrier 23 of the arcing contact 21 is mounted gas-tight while maintaining its axial displaceability.

On the outer surface of the contact carrier 23, a sleeve 24 is fixed, which at its the switching piece 30 end facing an insulating material, such as PTFE, containing and the arc contact 21 surrounding auxiliary nozzle 52 carries. At its end facing the drive D is a radially outwardly guided wall 25, on the outer edge of the rated current contact 22 is fixed. The switch piece 30 facing the end of the rated current contact 22 carries on its inside a hollow, typically containing PTFE insulator 51, which has a constriction 53 and at least one adjoining the constriction portion of a diffuser 54 of a nozzle 50. The sleeve 24, the wall 25, the rated current contact 22 and held in the rated current contact 22 end of the insulating body 51 define a heating volume 60 for receiving hot, ionized gas, which is formed by a switching arc resulting from the opening of the switch. The heating volume 60 communicates via a limited by the insulating body 51 and the auxiliary nozzle 52 heating channel 61 with one of the bottleneck and the diffuser of the nozzle 50 radially and the two open arcing contacts 21 and 31 axially limited, the switching arc receiving arc zone 62. At one of the diffuser 54th formed Ausblasende the nozzle 50, a metal annular body 70 is arranged, which is positively connected to the outer profile 55 having an insulating body 51.

The hollow cylinder 41, the cylinder bottom 42, the contact carrier 23 and the wall 25 of the sleeve 24 define a compression space 43 of a piston-cylinder compression device with a formed by the parts 23, 41 and 42 fixed hollow cylinder and one of the wall 25 and formed by the Drive D moving piston. The compression space 43 communicates via a arranged in the wall 25 check valve 26 with the heating volume 60, if the pressure in the compression chamber 43 is less than in the heating volume 60. If the pressure in the compression chamber 43 when closing the switch is less than the filling pressure of the insulating gas in the switch housing 10, fresh insulating gas is conducted from the switch housing 10 into the compression space 43 via a non-illustrated, arranged in the cylinder bottom 42 check valve.

Gas stored in the heating volume 60 and in the compression space 43 is guided into the arc zone 62 when the switch is opened by the heating channel 61 and inflates the switching arc so that, as the current to be cut approaches a zero crossing, ionized arc gas passes through the discharge opening of the nozzle 50 and through the hollow space Contact carrier 23 is removed from the arc zone 62.

The reference numeral 80 denotes a stationary mounted deflection of the switch. This gear includes two fixedly mounted gears 81, which engage on the one hand in one of two racks 82. The racks 82 are each integrated on one of two oppositely arranged surfaces in a trained as a rod 83 and rigidly connected to the arcing contact 31 output member of the deflection gear 80. On the other hand, the gears 81 each but also in one of two racks 84, which are arranged axially displaceable opposite to the rod 83. The racks 84 are rigidly connected to the ring body 70. Since the annular body 70 is positively connected to the insulating body 51, and since the drive D of the switch via the contact piece 20, the insulating body 51 and the annular body 70 transmits power to the racks 84, they act as a drive element of the reversing gear 80th

The deflection gear can also be designed as a lever mechanism. The force deflection is then by a fixed, two-armed Reached lever on which one arm is typically articulated as a drive element and on the other arm typically acting as a driven element of the deflecting rod.

Instead of the switching piece 20 driving force can also be introduced via the reversing gear 80 in the contact arrangement of the switch. If the reversing gear 80, for example, designed as a rack and pinion, then the rod 83 of a in Fig.1 Accordingly, the racks 84 then act not as an on, but as an output element of the deflection gear 80 and transmit driving force through the nozzle 50 to the contact piece 20. When opening the switch, the drive D resp. D 'apply the force for accelerating the switching pieces 20, 30, the nozzles 50 and 52 and the deflection gear 80 and for compression of the insulating gas located in the compression space 43. Since considerable forces are transmitted via the nozzle 50, the positive connection of the insulating body 51 with the annular body 70 should be extremely stable.

Therefore, the off Fig. 2 apparent ring body 70 formed in several parts and has - with respect to the axis A - in concentric arrangement a positive connection to the insulator 51 producing intermediate ring 90 and a pushed onto the intermediate ring 90 and the form-fitting locking support ring 100 for attaching the attached as or output element of the Deflection gear 80 acting racks 84. The intermediate ring 90 is made of a hard and elastically well deformable material, typically a steel, such as a spring steel. The positive connection to the insulating body 51 is achieved by a molded into the inside of the intermediate ring 90 inner profile 91, which engages in the outer profile 55 and so by positive locking a secured against axial displacement connection of insulating body 51 and intermediate ring 90 allows. In order to ensure the positive connection, the rigid ring, preferably made of steel, support ring 100 is pushed onto the intermediate ring 90. The support ring 100 can be connected much easier with the intermediate ring 90 as the intermediate ring with the insulating body 51 and can, while maintaining a good power transmission in the axial direction and about the axis A pivotally mounted on the intermediate ring 90th be stored. By this pivotal mounting switch parts can be easily adjusted in the manufacture of the switch and easier to interconnect. In addition, the side facing away from the racks 84 surface of the support ring 100 can be designed as a joint-free field electrode which shields the triple formed by insulator 51, ring body 70 and insulating triple point electrically particularly effective and prevents unwanted elevations of the electric field on the surface of the insulator 51. At the same time, the support ring 100 supports the intermediate ring 90 radially outward and thus prevents widening of the intermediate ring 90 and thus also a reduction or cancellation of the positive connection.

Out Fig.2 It can be seen that in the outer surface of the intermediate ring 90 guided around the axis A, annular outer groove 92 is formed. This groove is used to receive a snap ring 110. The snap ring spreads after insertion into the groove 92 and is then fixed in the axial direction in the groove 92. In a resting on the outer surface of the intermediate ring 90 inner surface of the support ring 100 is guided around the axis A, annular inner groove 101 is formed.

When manufacturing the switch, the support ring 100 is pushed with its end remote from the discharge end of the nozzle 50 on the already arranged on the insulating body 51 intermediate ring 90. The inner surface of the support ring 100 extends at the end to be pushed into a conically expanding insertion profile 102. The diameter of the snap ring 110 is therefore reduced when pushed by elastic deformation. As soon as the snap ring lies over the inner groove 101, it snaps into its groove while enlarging its diameter, thereby securing the support ring 100 against axial displacement. Alternatively, the snap ring 110 can first be spread in the inner groove 101 and then the support ring 100 are pushed with the spread in the groove 101 snap ring 110 on the already arranged on the insulating body 51 intermediate ring 90, wherein the axially fixed in the inner groove 101 snap ring 110 in the Outer groove 92 snaps and thereby secures the tag ring against axial displacement.

In the inner surface of the support ring 100, a radially inwardly extending annular step 103 is formed, which has a height of this stage defining annular surface 104. This stage is arranged so that an end face 56 of the insulating body 51 provided at the discharge end of the nozzle 50 is seated on the annular surface 104 of the annular step 103 when the snap ring 110 snaps into the internal groove 101. By this Aufsitzen the positive connection of the insulating body 51 is relieved with the annular body 70 during switching operations, in which the insulating body 51 is claimed by the force introduced by the drive to pressure. In a switch in which the drive D acts directly on the contact carrier 23, this relief occurs when closing, in a switch in which the force of the drive D 'directly into the drive element of the deflection (rod 83) is initiated, however To open. Since the drive when opening must transmit the force necessary for compressing the insulating gas located in the compression space 43, the relief of the positive connection of the insulating body 51 with the annular body 70 at a drive D 'having switch is particularly advantageous.

Out Fig.1 It can be seen that the annular step 103 advantageously forms at the same time a section of the diffuser 54 and has an inner surface 105 flared toward the discharge end of the nozzle 50.

In order to facilitate the arrangement of the intermediate ring 90 on the insulating body 51, the intermediate ring 90 is formed slotted and has a predominantly axially aligned, from Fig.2 apparent longitudinal joint 93. In the manufacture of the switch, the intermediate ring is spread open transversely to the longitudinal joint 93 and subsequently spread in the outer profile 55. The spreading process can be omitted if the intermediate ring 90 is formed in two or more parts and has one of the number of ring parts corresponding to the number of longitudinal joints, which allow a direct insertion of the ring parts in the outer profile 55.

In order to realize a good power transmission, the outer profile 55 of the insulating body 51 at least one annularly guided around the axis A increase 57 or recess 58, in which a largely congruently formed recess 94 or increase 95 of the intermediate ring 90 is fitted. As Fig. 2 can be seen, the outer profile 55 by a plurality of elevations 57th and recesses 58 caused comb-like structure. Because of this structure, the force to be transmitted is uniformly introduced via the outer profile 55 into the insulating body 51.

From the embodiment according to Figure 3 It can be seen that it is sufficient if the insulating body 51 only has an annular led about the axis A increase 57 which engages in the only one recess 94 having intermediate ring 90. Extends, as in Figure 3 shown, the increase 57 along the axis A over at least half of the axial extent of the intermediate ring 90, a large effective shear surface of the insulating body 51 and thus a high strength of the positive connection between the insulating body 51 and annular body 70 is achieved.

Unlike the ones from the Figures 2 and 3 apparent embodiments of the annular body 70, the intermediate ring 90 may also be formed without joints. As Figure 4 can be removed, the intermediate ring is then bolted to the insulating body 51. The screwing in this case has a the inner profile 91 corresponding and also molded into the inner surface of the intermediate ring 90 internal thread 91 'on. In this internal thread an external thread 55 'is screwed, which is formed according to the outer profile 55 in the lateral surface of the insulating body 51. An otherwise according to the embodiments of the Figures 2 and 3 trained support ring 100 can then be axially fixed as described above with the aid of the snap ring 110 which is inserted into the grooves 92 and 101. In a subsequent to the external thread 55 'portion of the lateral surface of the insulating body 51 is an annular guided around the axis A bead 59 is formed, which has over a guided when screwing the intermediate ring 90 to the bead end 96 of the intermediate ring 90 excess. Upon further screwing the end 96 is guided over the bead 59 and thereby deforms the bead elastic. Towards the end of the Aufschraubvorgangs the bead 59 relaxes again and snaps into an inner groove 97, which adjoins the end 96 and is formed in the inside of the intermediate ring 90. At the same time suggests the end 96 of the intermediate ring on a molded into the lateral surface of the insulator 51 and the Aufschraubvorgang finishing stop 59 '. By the expansion of the bead 59 in the inner groove 97 is a loosening by screwing on Insulator 51 fixed intermediate ring 90 prevents. By contrast, the support ring 100 is pivotally mounted about the axis A on the intermediate ring 90.

In all embodiments, the support ring 100 comprises the intermediate ring 90, the support ring is formed without joints and is also provided with a surface electrode acting as a smooth surface. The support ring 100 therefore prevents expansion of the slotted formed intermediate ring and therefore holds the multi-part intermediate ring firmly together. At the same time it covers all longitudinal joints of the intermediate ring, whereby an influence of the intermediate ring 90 is suppressed on the control of the electric field acting in the switch. The field control is - as in the FIGS. 2 to 4 shown - achieved by a molded directly into the support ring field electrode 106, but can also by a Figure 5 apparent, attached to the support ring 100 hollow field electrode 106 'can be achieved. The use of such a field electrode reduces the moving mass in a switching operation and accordingly reduces the size of the drive D respectively. D '.

In order to prevent that during a switching operation in the arc zone 62 formed by the switching arc hot gas to the rated current contacts 22, 32, is on the outer surface of the support ring 100 a comprehensive from the support ring Fig.1 apparent seal 107 applied. This gasket slides during a switching operation on a arranged in rated current contact 32 and rigidly connected thereto hollow cylindrical screen 33. From the arc zone 62 exiting hot gas is then through the hollow contact carrier 23 and through the nozzle 50 and the gas-tight to the nozzle 50 subsequent screen 33rd only in areas of the switch housing 10 out of the rated current contacts 22, 32 are far away.

LIST OF REFERENCE NUMBERS

10

switch housing

20

switching piece

21

Arcing contact

22

Current Rating Contact

23

Contact carrier of the arcing contact 21

24

shell

25

wall

26

check valve

30

switching piece

31

Arcing contact

32

Current Rating Contact

33

umbrella

40

hollow body

41

hollow cylinder

42

cylinder base

43

compression chamber

50

jet

51

insulator

52

auxiliary nozzle

53

Bottleneck of the nozzle 50

54

Diffuser of the nozzle 50

55

outer profile

55 '

external thread

56

face

57

increase

58

deepening

59

bead

59 '

attack

60

heating volume

61

heating duct

62

Arc zone

70

ring body

80

deflecting

81

gears

82, 84

racks

83

pole

90

intermediate ring

91

internal profile

91 '

inner thread

92

external groove

93

longitudinal joint

94

deepening

95

increase

96

End of the intermediate ring 90th

97

inner groove

100

support ring

101

inner groove

102

profiled entry

103

annular step

104

ring surface

105

palm

106, 106 '

field electrode

107

poetry

110

snap ring

A

axis

D, D '

switch drives

Claims (13)

1. Gas-insulated high-voltage switch having two contact members (20, 30), which can be moved relative to one another along an axis (A), having a nozzle (50), which is attached to a first (20) of the two contact members, for blowing out a switching arc with quenching gas, and having a direction-changing transmission (80), which is mounted such that it is fixed, and is connected on the one hand to the nozzle (50) and on the other hand to the second contact member (30), with the nozzle (50) having a hollow insulating body (51) which forms a constriction (53) and at least one section, which is adjacent to the constriction, of a diffuser (54), and containing a metallic annular body (70) which is arranged at a blowing-out end of the nozzle (50), is connected in an interlocking manner to the insulating body (51), which has an external profile (55), and is fitted with an input-drive or output-drive element (84) of the direction-changing transmission (80), characterized in that the annular body (70) has a concentrically arranged intermediate ring (90), which produces the interlock with the insulating body (51), and a ring (100), which is pushed onto the intermediate ring (90) and is attached to the intermediate ring (90), for supporting the input-drive or output-drive element (84).
2. Switch according to Claim 1, characterized in that an annular outer groove (92), which is positioned around the axis (A), is formed in the outer surface of the intermediate ring (90), and an annular inner groove (101), which is positioned around the axis (A), is formed in an inner surface of the supporting ring (100), which rests on the outer surface of the intermediate ring (90) with virtually no play, and in that the two grooves (92, 101) are arranged and designed such that, in the event of any relative movement of the supporting ring (100) and intermediate ring (90) along the axis (A) during the manufacture of the switch, a circlip (110), which is arranged in the outer groove (92) or in the inner groove (101), spreads into the inner groove (101) or into the outer groove (92), forming a connection between the supporting ring (100) and the intermediate ring (90) which is secured against axial movements.
3. Switch according to Claim 2, characterized in that the inner surface of the supporting ring (100) ends in a conically widening insertion profile (102) at its end facing the first contact member (30), which insertion profile (102) reduces the diameter of the circlip (110), as a consequence of elastic deformation during the relative movement (100), before the circlip (110) spreads in.
4. Switch according to one of Claims 1 to 3, characterized in that an annular step (103) which extends radially inward is formed in the inner surface of the supporting ring (100) and has an annular surface (104), which forms the step height, which is seated on an end surface (56) of the isolating body (51), which end surface (56) is provided at the blowing-out end of the nozzle (50).
5. Switch according to Claim 4, characterized in that the annular step (103) forms a section of the diffuser (54) and has an inner surface (105) which widens conically toward the blowing-out end of the nozzle (50).
6. Switch according to one of Claims 1 to 5, characterized in that the intermediate ring (90) is slotted and has a longitudinal joint (93), which is aligned predominantly axially and allows the intermediate ring (90) to spread out during manufacture of the switch.
7. Switch according to one of Claims 1 to 5, characterized in that the intermediate ring (90) is formed from a plurality of parts and has at least two annular parts which are separated from one another by longitudinal joints which extend predominantly axially.
8. Switch according to one of Claims 6 or 7, characterized in that the external profile (55) of the insulating body (51) has at least one raised area (57) or depression (58), which is positioned in an annular shape around the axis (A) and into which a depression (94) or raised area (95), which is designed to be largely congruent, on the intermediate ring (90) is fitted.
9. Switch according to Claim 8, characterized in that the at least one raised area (57), which is positioned in an annular shape around the axis (A), on the insulating body (51) extends along the axis (A), over at least half of the axial extent of the intermediate ring (90).
10. Switch according to one of Claims 1 to 5, characterized in that the intermediate ring (90) has no joints and is screwed to the insulating body (51), wherein the screw connection has an internal thread, which is formed in the inner surface of the intermediate ring (90), and an external thread, which is formed in the envelope surface of the insulating body (51)
11. Switch according to one of Claims 1 to 10, characterized in that a bead (59) is formed in a section of the envelope surface of the insulating body (51) adjacent to the external thread (55'), is positioned in an annular shape around the axis (A) and is snapped into an inner groove (97), which is formed in the inner surface of the intermediate ring (90).
12. Switch according to one of Claims 1 to 11, characterized in that a field electrode (106, 106'), which has no joints and surrounds the intermediate ring (90), is formed in the supporting ring (100), or is fitted to the supporting ring (100).
13. Switch according to one of Claims 1 to 12, characterized in that a seal (107) which surrounds the supporting ring is fitted on the outer surface of the supporting ring (100), in order to protect rated current contacts (22, 32) of the two contact members (20, 30) against the influence of arc gases.

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