CH625087A5

CH625087A5 - Busbar coupling

Info

Publication number: CH625087A5
Application number: CH1495377A
Authority: CH
Inventors: Erich Silbermann
Original assignee: Siemens Ag
Priority date: 1977-02-03
Filing date: 1977-12-07
Publication date: 1981-08-31
Also published as: IT1092144B; DE2704541B2; DE2704541C3; NO780139L; NO142019C; SE7800728L; JPS5398081A; ES466630A1; NO142019B; DE2704541A1; IT7819653A0

Description

Die Erfindung wird im folgenden anhand eines Ausführungsbeispiels in den Figuren 1 bis 4 näher erläutert. Dabei zeigt: The invention is explained below with reference to an embodiment in Figures 1 to 4. It shows:

Figur 1 ein bewegliches Kontaktbrückenteil für ein Drehstromsystem mit drei Kontaktbrücken im Grundriss, 1 shows a movable contact bridge part for a three-phase system with three contact bridges in the plan,

Figur 2 das Kontaktbrückenteil im Aufriss, FIG. 2 shows the contact bridge part in elevation,

Figur 3 die ortsfesten Kontaktstücke im Grundriss, wobei das Kontaktbrückenteil herausgezogen ist, und schliesslich Figure 3 shows the fixed contact pieces in the floor plan, with the contact bridge part pulled out, and finally

Figur 4 die ortsfesten Kontaktstücke mit eingeschobenen Kontaktbrücken von unten. Figure 4 shows the fixed contact pieces with inserted contact bridges from below.

In Figur 1 ist mit dem Bezugszeichen 1 das bewegliche Kontaktbrückenteil einer erfindungsgemässen Stromschienenkupplung für ein Drehstromsystem bezeichnet. Dieses Kontaktbrückenteil 1 weist drei gleich gestaltete einzelne Kontaktbrücken 2 auf, die auf einer Tragplatte 3 aus Isolierstoff, beispielsweise Pertinax, befestigt sind. Jede der Kortaktbrücken 2 umfasst eine metallische Führungsplatte 4, in die als Federelement jeweils eine Schraubenfeder 5 eingeführt ist. Jede der Führungsplatten 4 ist mit endseitig rechtwinklig abgebogenen Befestigungslappen 6 an der Tragplatte 3 so festgeschraubt, dass die drei Führungsplatten 4 auf gleicher Höhe und mit der Plattenebene senkrecht zur Tragplatte 3 angeordnet sind. Darüber hinaus schliesst jede der Führungsplatten 4 mit den Kanten der rechteckigen Tragplatte 3 einem Winkel von 45° ein. Wie ferner aus Figur 1 erkennbar ist, weisen die Windungsflächen der Schraubenfedern 5 bereits vor dem Einführen zwischen die Kontaktstücke eine zusätzliche seitliche Verkippung zur Schraubenfederachse auf, wobei die Kippachse senkrecht zur Tragplatte 3 verläuft. Die Windungen der Schraubenfedern 5 weisen somit eine erhöhte Schrägstellung auf, so dass die Schraubenfeder 5 im Ausführungsbeispiel etwas in Richtung auf die Ebene der Führungsplatte 4 hin verkippt erscheint. Diese Verkippung wird der Schraubenfeder 5 beim Fertigungsvorgang mitgegeben. In Figure 1, the reference numeral 1 denotes the movable contact bridge part of a busbar coupling according to the invention for a three-phase system. This contact bridge part 1 has three identically designed individual contact bridges 2, which are fastened on a support plate 3 made of insulating material, for example Pertinax. Each of the contact bridges 2 comprises a metallic guide plate 4, into each of which a helical spring 5 is inserted as a spring element. Each of the guide plates 4 is screwed to the support plate 3 with fastening tabs 6 bent at right angles so that the three guide plates 4 are arranged at the same height and with the plate plane perpendicular to the support plate 3. In addition, each of the guide plates 4 encloses an angle of 45 ° with the edges of the rectangular support plate 3. As can also be seen from FIG. 1, the winding surfaces of the coil springs 5 already have an additional lateral tilt to the coil spring axis before insertion between the contact pieces, the tilt axis running perpendicular to the support plate 3. The windings of the coil springs 5 thus have an increased inclination, so that the coil spring 5 in the exemplary embodiment appears to be tilted somewhat in the direction of the plane of the guide plate 4. This tilt is given to the coil spring 5 during the manufacturing process.

Die Schraubenfeder 5 ist aus einer federharten Kupfer-Beryllium-Legierung, die eine gute Leitfähigkeit und geeignete The coil spring 5 is made of a spring-hard copper-beryllium alloy, which is good conductivity and suitable

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Federeigenschaften aufweist. Zur Verbesserung der Kontakteigenschaften ist jede Schraubenfeder 5 mit einem Silberüberzug versehen. Has spring properties. To improve the contact properties, each coil spring 5 is provided with a silver coating.

Figur 2 zeigt den Kontaktbrückenteil 1 im Aufriss. In dieser Darstellung sind die beiden rechten Führungsplatten ohne eingelegte Schraubenfeder 5 dargestellt, um die Details der Gestaltung der Führungsplatten besser erkennbar zu machen. Jede Führungsplatte 4 weist einen im wesentlichen rechteck-förmigen Ausschnitt 7 auf, in den die Schraubenfeder 5 eingeführt wird. Von zwei einander gegenüberliegenden Rechteckseiten stehen aufeinander zu gerichtete Führungszungen 8 ins Innere des Rechtecks ab, die dazu bestimmt sind, in den zylindrischen Hohlraum der Schraubenfeder 5 einzugreifen und die Schraubenfeder auf diese Weise am vorgesehenen Ort zu halten. Diese Gestaltung der Führungsplatte 4 verursacht nur geringen Fertigungsaufwand, sichert aber eine zuverlässige Festhaltung der als Federelement dienenden Schraubenfeder 5. Ein Austausch einer Schraubenfeder 5 ist mühelos möglich, indem diese in axialer Richtung zusammengepresst und aus dem zwischen den Führungszungen bestehenden Zwischenraum entnommen wird. Ebenso einfach ist es, eine Schraubenfeder 5 in die metallische Führungsplatte 4 einzusetzen. Die vier Ecken des rechteckförmigen Ausschnitts 7 jeder Führungsplatte 4 weisen beidseitige Ansenkungen 9 auf. Damit wird die Verkippung der endseitigen Windungen der Schraubenfeder 5 ohne mechanische Behinderung oder starke Behinderung oder starke Belastung der anliegenden Windungsstellen ermöglicht. Figure 2 shows the contact bridge part 1 in elevation. In this illustration, the two right guide plates are shown without inserted coil spring 5, in order to make the details of the design of the guide plates more recognizable. Each guide plate 4 has an essentially rectangular cutout 7 into which the coil spring 5 is inserted. From two opposing sides of the rectangle project toward each other guide tongues 8 in the interior of the rectangle, which are intended to engage in the cylindrical cavity of the coil spring 5 and in this way to hold the coil spring at the intended location. This design of the guide plate 4 causes only little manufacturing effort, but ensures reliable retention of the helical spring 5 serving as a spring element. A helical spring 5 can be easily replaced by compressing it in the axial direction and removing it from the space between the guide tongues. It is just as easy to insert a helical spring 5 into the metallic guide plate 4. The four corners of the rectangular section 7 of each guide plate 4 have countersinks 9 on both sides. This enables the end windings of the helical spring 5 to be tilted without mechanical hindrance or severe hindrance or heavy loading of the adjacent winding locations.

Auf der den Kontaktbrücken 2 abgewandten Fläche der Tragplatte 3 ist ein u-förmiges Halteglied 10 angebracht, das so gestaltet ist, dass ein in jeder Schaltanlage zum Herausziehen oder Einsetzen von Sicherungen vorhandener Sicherungszuggriff 11 als Handhabe an den Kontaktbrückenteil 1 ansetzbar ist. On the surface of the support plate 3 facing away from the contact bridges 2, a U-shaped holding member 10 is attached, which is designed in such a way that a fuse pull handle 11 present in each switchgear for pulling out or inserting fuses can be attached to the contact bridge part 1 as a handle.

Figur 3 zeigt den ortsfesten Teil 12 der Stromschienenkupplung von der Betätigungsseite her. Die drei Stromschienen 13 eines Drehstromsystems weisen eine rechteckige Querschnittsfläche auf und sind parallel zueinander angeordnet. Jede der Stromschienen 13 weist eine Trennstrecke 14 auf, deren Form kommt dadurch zustande, dass jede Stromschiene 13 in einem Winkel von 45° zu den Seitenkanten, aber senkrecht zur Zeichenebene durchtrennt wird und die so entstandenen Stromschienenteile im Trennabstand befestigt werden. Das so entstandene Stirnflächenpaar 15 stellt zwei ortsfeste, gegeneinander isolierte Kontaktstücke dar, die durch die Kontaktbrücke 2 überbrückt werden können, wenn diese in die Trennstrecke 14 eingeschoben wird. Die Stirnflächen 15 der Stromschienen 13 können geriefelt sein, so dass definierte Linien- oder Punktkontakte zwischen den Stromschienenenden und den anliegenden Windungsteilen der Schraubenfeder 5 Zustandekommen. Figure 3 shows the fixed part 12 of the busbar coupling from the actuation side. The three busbars 13 of a three-phase system have a rectangular cross-sectional area and are arranged parallel to one another. Each of the busbars 13 has a separating section 14, the shape of which comes about because each busbar 13 is cut at an angle of 45 ° to the side edges, but perpendicular to the plane of the drawing, and the busbar parts thus formed are fastened at a separation distance. The end face pair 15 thus created represents two fixed, mutually insulated contact pieces which can be bridged by the contact bridge 2 when it is inserted into the isolating section 14. The end faces 15 of the busbars 13 can be corrugated, so that defined line or point contacts between the busbar ends and the adjacent winding parts of the coil spring 5 occur.

Die Stromschienen 13 sind zur Bedienungsseite hin durch eine isolierende Abdeckplatte 16 verdeckt und mit dieser durch Verschraubungen 17 verbunden. Die isolierende Abdeckplatte 16 kann Bestandteil einer Wandung einer Zelle sein, in der beispielsweise ein durch vor- und nachgeordnete Trennstrecken freischaltbarer Leistungsschalter untergebracht sein kann. Die Abdeckplatte 16 weist drei Führungsdurchbrüche 18 auf, die an die Trennstrecken 14 der Stromschienen 13 angepasst sind. Jeder Führungsdurchbruch 18 weist eine Verjüngung 19 in Richtung auf die Stromschienen 13 hin auf und geht endseitig in ihre Stirnflächen 15 über. Ferner weist jeder Durchbruch 18 der Abdeckplatte 16 zwei schräg gegenüberliegende, durchgehende Führungsnuten 20 auf, in die die Führungsplatten 4 des Kontaktbrückenteils eingesetzt werden können und die die exakte Führung der zur Überbrückung dienenden Schraubenfedern 5 sicherstellen. Ferner weist die Abdeckplatte 16 jeweils am Ort zweier einander gegenüberliegender Ecken der Führungsdurchbrüche 18 Führungsflächen 21 auf, die Teil einer Schraubenfläche sind. Diese Führungsfläche kommt dadurch zustande, dass die in der Frontfläche der Abdeckplatte 16 einer Kante entsprechende Strecke 22 in Richtung zu den Stromschienen 13 hin gedreht wird, bis sie die Endlage 22a an der stromschienenseitigen Endfläche der Abdeckplatte 16 erreicht hat. The busbars 13 are covered on the operating side by an insulating cover plate 16 and connected to it by screw connections 17. The insulating cover plate 16 can be part of a wall of a cell, in which, for example, a circuit breaker that can be isolated by upstream and downstream separation sections can be accommodated. The cover plate 16 has three guide openings 18 which are adapted to the separating sections 14 of the busbars 13. Each guide opening 18 has a taper 19 in the direction of the busbars 13 and merges into its end faces 15 at the end. Furthermore, each opening 18 of the cover plate 16 has two diagonally opposite, continuous guide grooves 20, into which the guide plates 4 of the contact bridge part can be inserted and which ensure the exact guidance of the helical springs 5 used for bridging. Furthermore, the cover plate 16 has guide surfaces 21 at the location of two opposite corners of the guide openings 18, which are part of a screw surface. This guide surface is brought about by the fact that the distance 22 corresponding to an edge in the front surface of the cover plate 16 is turned in the direction of the busbars 13 until it has reached the end position 22a on the end surface of the cover plate 16 on the busbar side.

Figur 4 schliesslich zeigt die Stromschienenkupplung mit eingeschobenem Kontaktbrückenteil 1 von der Rückseite her, also mit Blick auf die Stromschienen 13. Die Stirnflächen 15 der Stromschiene 13 weisen in Figur 4 eine Riefelung 23 zur Verbesserung der Kontaktgüte auf. Jede der Trennstrecken zwischen den Stirnflächen 15 ist durch eine eingeschobene Kontaktbrücke 2 überbrückt. Der Überbrückung dienen die Windungen der Schraubenfeder 5, die jeweils an zwei einander gegenüberliegenden Stellen mit den Stirnflächen 15 in engem Kontakt stehen. Wie aus Figur 4 erkennbar ist, ist die bereits im entspannten Zustand der Schraubenfeder 5 vorhandene seitliche Verkippung im eingeführten Zustand der Schraubenfeder 5 noch beträchtlich verstärkt, so dass die einzelnen Windungen der Schraubenfeder nahezu in Längsrichtung der Stromschienen orientiert sind. Diese Verkippung bis zur in Figur 4 dargestellten Endlage erfolgt kontinuierlich, beginnend beim Einführen der Kontaktbrücken 2 in die Führungsdurchbrüche 18 (Fig. 3). Da die eingesetzten Schraubenfedern 5 bereits im entspannten Zustand eine seitliche Verkippung aufweisen, weichen die einzelnen Windungen der Schraubenfeder 5 beim Durchlaufen der Verjüngung 19 der Führungsdurchbrüche durch verstärkte seitliche Verkippung einer Deformation der Windungsfläche aus. Damit komme ein beachtlicher Federweg mit einer Vorteilhaft «weichen» Federkennlinie zustande. Eine zusätzliche Sicherheit zur Herbeiführung der seitlichen Verkippung der Windungsflächen der Schraubenfedern 5 bieten die Führungsflächen 21, deren Gestalt im Zusammenhang mit Figur 3 näher erläutert ist. Die Ganghöhe der Schraubenfedern 5 ist darüber hinaus so dimensioniert, dass vor dem Einschieben der Schraubenfedern 5 in die Führungsdurchbrüche 18 die einzelnen Windungen einen Abstand aufweisen, dass aber im eingeschobenen Zustand die einzelnen Windungen jeder Schraubenfeder dicht, das heisst sich seitlich berührend, aneinanderlie-gen. Damit wird eine gute Materialfüllung der Trennstrecke erreicht, so dass Nennströme bis in den kA-Bereich erreichbar sind. Da der Strom über die Trennstrecke über jeweils zwei Halbwindungen einer jeden Windung der Schraubenfeder 5 verläuft und somit diese Leiterstücke von einem gleichgerichteten Strom durchflössen werden, kommt eine anziehende Kraftwirkung zwischen beiden Windungshälften zustande, die eine Erhöhung des Kontaktdruckes an den Stirnflächen 15 der Stromschienen 13 bewirkt. Eine verstärkte Festhaltung der Kontaktbrücken 2 in der Trennstrecke im Kurzschlussfall kann dadurch sichergestellt werden, dass die beiden Berührungsstellen jeder Windungsfläche mit den Stirnflächen 15 in der dem Führungsdurchbruch abliegenden Hälfte der Stirnflächen 15 zu liegen kommen. Die Halbierungsebene verläuft dabei parallel zur Zeichenebene der Figur 4 durch die Mitte der Stromschienen 13. Finally, FIG. 4 shows the busbar coupling with the inserted contact bridge part 1 from the rear, ie with a view of the busbars 13. The end faces 15 of the busbar 13 have ribbing 23 in FIG. 4 to improve the contact quality. Each of the separation paths between the end faces 15 is bridged by an inserted contact bridge 2. The bridges are used for the turns of the helical spring 5, each of which is in close contact with the end faces 15 at two opposite points. As can be seen from FIG. 4, the lateral tilt already present in the relaxed state of the coil spring 5 is considerably reinforced in the inserted state of the coil spring 5, so that the individual turns of the coil spring are oriented almost in the longitudinal direction of the busbars. This tilting up to the end position shown in FIG. 4 takes place continuously, starting with the insertion of the contact bridges 2 into the guide openings 18 (FIG. 3). Since the coil springs 5 already have a lateral tilt in the relaxed state, the individual windings of the coil spring 5 evade deformation of the winding surface when the taper 19 passes through the guide openings by increased lateral tilting. This results in a considerable spring travel with an advantageously "soft" spring characteristic. The guide surfaces 21, the shape of which is explained in more detail in connection with FIG. 3, provide additional security for causing the lateral tilting of the winding surfaces of the helical springs 5. The pitch of the coil springs 5 is also dimensioned such that the individual windings are at a distance from each other before the coil springs 5 are inserted into the guide openings 18, but that the individual windings of each coil spring lie tightly against one another in the inserted state, that is to say they touch each other laterally . This ensures good material filling of the isolating section so that nominal currents down to the kA range can be achieved. Since the current over the isolating path runs over two half-turns of each turn of the coil spring 5 and thus these conductor pieces are flowed through by a rectified current, there is an attractive force effect between the two turn halves, which causes an increase in the contact pressure on the end faces 15 of the busbars 13 . An increased retention of the contact bridges 2 in the isolating section in the event of a short circuit can be ensured in that the two points of contact of each winding surface come to rest with the end faces 15 in the half of the end faces 15 remote from the guide opening. The bisecting plane runs parallel to the drawing plane of FIG. 4 through the middle of the busbars 13.

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Claims

625 087 2 PATENT CLAIMS

1. Busbar coupling with two fixed, mutually insulated contact pieces, which are opposite to each other and a movable contact bridge to bridge the The invention relates to a busbar coupling

Contact pieces and at least one spring element for 5 two fixed, mutually insulated contact pieces

Ensuring the contact pressure, characterized, opposite each other, and a movable contact

that the spring element serves as the contact bridge, which is designed as a screw bridge for bridging the contact pieces and at least ben spring (5) and that the design is such a spring element for ensuring the contact pressure that the helical spring (5) between the contact pieces (13) In electrical switchgear, a large number can be inserted, so that each turn of the helical spring (5) requires separation paths at 10 points. These are used for

the contact pieces (13) on two diametrically opposed sections of the system in order to ensure safe working under pressure. on elements of the switchgear, for example a cable

(2) coordinated parallelogram-like guideway not to have considerable fluctuations in the contact quality (18) which can be closed towards the contact pieces.

tapers (19), at two diagonally opposite corners there is the task of specifying a busbar coupling of the type mentioned at the beginning of the guide surfaces oblique towards the contact pieces, the manufacturing friendliness, which ver when inserting the contact bridge (2) ver - Speed, space economy and uniform contact pressure due to the strong tilting of the winding surfaces of the coil spring due to an improved tolerance compensation. (5) initiate. According to the invention, the object is achieved in that

2. busbar coupling according to claim 1, thereby switching switch. In addition, separation marks serve that the winding surfaces of the helical spring stretch to divide or couple larger switchgear (5) sections before the insertion between the contact pieces 15.

have a lateral tilt to the coil spring axis. In switchgear in the low-voltage range (up to 1 kV), the tilt axis perpendicular to the coil spring axis is usual in it for the production of such isolating paths, isolating switches

The direction of insertion of the coil spring is. use or special separating tabs, the operating

(3) are attached. 55 contact bridge is capable of extremely high tolerances between

3. Busbar coupling according to claim 1 or 2, voltage with an insulating tool requires special care, characterized in that for holding the screw-2 "The use of disconnectors is expensive and little space-eco-der (5) a metallic guide plate (4) is provided who are nomic. A disadvantage of the separating tabs is that, in addition to an inner, essentially rectangular cut-out (7), it also has inadequate operating safety due to its low level of operating safety, two of the rectangles lying opposite one another requiring a lot of installation space.

Sides running in the direction of the coil spring axis. A rail coupling of the type mentioned at the outset emerges from tongues (8). 25 AEG Auxiliary Book 2, ELITERA Verlag, 10th edition, page 212,

4. busbar coupling according to claim 3, characterized picture 5/101, known. There are two fixed, mutually characterized, that the guide plate (4) is countersunk (9) on both sides at the corners of the insulated contact pieces, each consisting of a pair of contact tongues of rectangular cutout (7). opposite each other and are each with a busbar

5. busbar coupling according to claim 3 or 4, section connected. Each Kon serving as a contact piece is characterized in that the guide plate (4) is fastened vertically by a pair of clock tongues (Lyra contact) through the ends of a ring-shaped support plate (3) made of insulating material. segment-shaped spring compressed. The

6. busbar coupling according to claims 1 to 5, coupling of the busbar sections is carried out by insertion-characterized in that the contact pieces are busbars a movable contact bridge in the form of a langge-nen (13), the end faces (15) are used to make contact. stretched metallic conductor in both pairs of contacts.

7. Busbar coupling according to one of claims 1 to 33 This arrangement requires a not inconsiderable effort 6, characterized in that the contact pieces are covered laterally in the manufacture and attachment of the contact tongue pairs by an insulating cover plate (16), and the spring element to ensure the Contact pressure is mainly due to the projection of the contact bridge, due to tolerances and material fatigue

8. busbar coupling according to claims 3,6 and 7, serves as a contact bridge, the spring element, which is characterized as a screw-characterized in that the separation distance between the spring and that the design is such that busbars (13) in the form of an oblique parallelo - Coil spring can be inserted between the contact pieces, so gramms (14) and that through guide grooves (20) in that each turn of the coil spring on the contact pieces cover plate (16), the guide plate (4) parallel to the front? O on two diametrically opposite points under pressure surfaces (15) of the busbars (13) can be inserted. is present.

9. Busbar coupling according to one of claims 5 to Thus, the contact bridge not only serves the Stromfü-8 for a three-phase system, characterized in that three tion, but at the same time ensuring an adequately parallel helical springs (5) on a support plate contact pressure. The designed as a coil spring

10. busbar coupling according to claim 9, thereby see the stationary contact pieces to compensate, so that the opposite of the coil springs - the contact bridge not only easily and inexpensively manufacturing surface of the support plate (3) with a holding member (10) is available , but also the requirements for the assembly, with which a safety handle (11) can be connected. the contact pieces can be reduced. Because everyone

11. Busbar coupling according to one of claims 1 «> winding of the coil spring on both contact pieces to 10, characterized in that the coil spring (5) is applied, a rectified current flow through each is made of a spring-hard copper alloy and that half turn. This causes - due to the magnetic surface of which is provided with a silver coating. Attraction between the current-carrying half turns

12. Busbar coupling according to claims 6 to 11, ten - an increase in the contact pressure on the contact - characterized in that the end faces (15) of the current- «parts of the winding parts under current flow.

rails (13) are corrugated (23). It is advantageous if the winding surfaces of the screw

Benfeder already have a lateral tilt to the coil spring axis before insertion between the contact pieces, the tilt axis running perpendicular to the coil spring axis in the direction of insertion of the coil spring. In the case of an ordinary coil spring, which does not have this peculiar winding, the winding surface is deformed when it is inserted between the contact pieces, so that it corresponds more to an ellipse than a circle. In the case of a helical spring, which has an additional lateral tilt from the outset, there is no deformation of the winding surface when it is inserted between the contact pieces, but rather a reinforcement of the lateral tilt. This tilting means a rotation of each individual turn of the coil spring about an axis which runs through the axis of the coil spring and is parallel to the direction of insertion. In this way, an increased spring travel and a softer spring characteristic is achieved compared to conventional coil springs. The result is improved tolerance acceptance and less mechanical stress on the coil spring.

A metal guide plate can be provided to hold the coil spring, which has an inner, substantially rectangular cutout, with guide tongues extending from two opposite rectangular sides in the direction of the coil spring axis. This ensures that the coil spring is held in a manner that is easy to install and functionally. The guide plate is easy to manufacture as a stamped part. The helical spring can be inserted into the guide plate without any effort - only after prior axial compression - where, when the helical spring is released, it slides over the two guide tongues and thus finds a reliable mounting. This makes it easy to replace "used" coil springs without spending a lot of time.

The guide plate can be countersunk on both sides at the corners of the rectangular cutout. This facilitates the increased lateral tilting of the individual turns of the coil spring when it is inserted between the contact pieces and prevents large mechanical loads at the contact points of the coil spring and guide plate when inserted.

It is advantageous if the guide plate is attached vertically to a support plate made of insulating material. This measure serves to protect the operator by largely eliminating the risk of unintentional contact with the live contact bridge.

It is advantageous if the contact pieces are busbars, the end faces of which are used for making contact. This makes it possible to completely dispense with additional contact pieces, so that considerable savings can be achieved in manufacture and assembly. The end faces of the busbars can be corrugated, so that a defined multiple line contact occurs between them and the adjacent points of the coil spring. This increases the current carrying capacity and resilience of the busbar coupling.

It is favorable if the contact pieces are covered laterally by an insulating cover plate which has a parallelogram-like guide opening which is essentially matched to the projection of the contact bridge and which tapers towards the contact pieces, the diagonal opposite corners of the contact bridge extending into oblique guide surfaces , which initiate an increased tilting of the winding surfaces of the coil spring when the contact bridge is inserted. The cover plate ensures that no live parts are accidentally touched by an operator. The design of the parallel aperture-like guide opening in the cover plate serves to ensure that a

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the lateral tilting of the individual winding surfaces of the coil spring is continuously reinforced.

In a preferred embodiment, the separation distance between the busbars is in the form of an oblique-angled parallelogram and the guide plate can be inserted parallel to the end faces of the busbars by guide grooves in the cover plate. For a three-phase system, three coil springs arranged in parallel can be attached to a support plate. Due to the parallel to each other, but obliquely to the longitudinal extension of the busbar end faces and the arrangement of the guide plates of the coil springs on the support plate made parallel to this end faces, a very space-efficient solution is achieved for a three-phase system, with a comparatively high conductor cross-section in the form of the coil spring in each separation section is introduced. With a single handle, a three-phase rail coupling can be made in a three-phase system or a three-phase isolating section can be produced.

The surface of the support plate opposite the coil springs can be provided with a holding member, with which a securing pull handle can be connected. Since such a safety pull handle is already present in every switchgear and can therefore be locked by the holding member to the support plate, no special handle is required for inserting or removing the contact bridge.

The coil spring can be made of a spring-hard copper alloy and its surface can be provided with a silver coating. The silver coating increases the current carrying capacity and the contact quality of the contact bridge, the copper alloy combines good conductivity with favorable spring properties and is highly thermally stable.