EP0029205A1 - High-current switch - Google Patents

Abstract

A switch is described which has two opposing contact elements (12) which are supported by support plates (14) which are movable in the axial direction and are enclosed in a gastight manner by a housing which is supported by the support plates (14) and an annular membrane (16). is formed. The switch is particularly suitable for high currents at relatively low voltages, e.g. occur during electrolysis. The membrane (16) consists of a bellows part made of flexible electrically insulating plastic material, the edges of which are fastened by means of clamping devices to fastening surfaces (20) of the support plate (14) running around the contact element (12). The switch has a high contact resistance when it is switched off, because the internal flexibility of the membrane (16) caused by switching arcs on the contact material sprayed onto the membrane (16) cannot hold onto it, but falls off.

Description

The invention relates to a switch with opposing contact elements, which are supported by axially acting support plates, and with a gas-tight housing enclosing the contact elements, which is formed by the support plates and an annular membrane, which is gas-tightly connected to the two support plates .

Such a switch serving as a low-voltage switch is already known from DE-OS 27 02 103, the housing of the known switch being evacuated, so that it is a low-voltage vacuum switch. In such a vacuum switch, the air pressure creates a pressure force which acts on the support plates and which must be taken into account in the actuating device for the switch. This is disadvantageous because it affects the universal applicability of the switch. Another disadvantage is that the need to evacuate the switch housing makes the manufacturing process considerably more complicated because the final assembly of the known switch, including complicated soldering and plating processes, must be done under vacuum. Another disadvantage is that the annular membrane member that closes the vacuum space between the contact elements is in three parts. It consists of two corrugated metallic washers, which are soldered tightly on the one hand to the contact elements or support plates, on the other hand to a partially metallized ceramic ring forming the third part. The ceramic ring serves to isolate the two contact elements. It is also disadvantageous here that this ceramic ring is sensitive to shock and that, over time, spray-on contact material can form a conductive layer on this ceramic ring, which can considerably impair the insulation values.

A vacuum circuit breaker according to US Pat. No. 40.75 448 also has similar disadvantages.

In order to avoid the vacuum system, which is disadvantageous in various respects, the applicant's German patent application P 28 52 471.2 proposes a low-voltage switch which is also encapsulated but contains a protective gas in the housing instead of a vacuum. As an annular membrane, the switch contains a stainless steel bellows, which is soldered to one contact element on one edge and is screwed gas-tight at its other edge via a Teflon seal, which also provides the necessary insulation.

Although this switch works quite satisfactorily, the proposed system is still too expensive for many applications.

The object of the invention is to provide a switch of the type mentioned, which can be manufactured much more cost-effectively than is the case with the low-voltage switch known from DE-OS 27 02 103. The cost savings should be achieved without sacrificing operational reliability and service life, and in particular it should also be achieved that the contact resistance between the two open contact elements does not change during the course deteriorated by many operating cycles, which is particularly disadvantageous if the switch is to serve as an empty switch.

This problem is solved in that
the annular membrane is formed by a bellows part made of flexible electrically insulating plastic material, the edges of which are fastened by means of clamping band devices to fastening ring surfaces of the support plates running around the contact element.

Compared to the known ring-shaped membrane, which consists of three individual parts and must be soldered to the contact elements or support plates in a vacuum, the ceramic ring required for insulation purposes being sensitive to breakage on the one hand and collecting contact material that has been sprayed off over time, which leads to a deterioration in the contact resistance leads when the contact elements are open, the novel low-voltage switch does not have these disadvantages, because the bellows part formed from the flexible plastic material does not have to be soldered to the contact elements or support plates in a cumbersome manner, but is simply pushed onto the corresponding seat surface, with the clamping devices possibly integrated into the plastic material and no longer require any special measures to fix the annular membrane. Another advantage is that the plastic material is already electrically insulating and a special insulating ring is unnecessary, that the plastic material is completely unbreakable and, as tests have shown, compared to the heat and material influences occurring during switching during the expected is switch life fully grown and also on the inner membrane surface is precipitating sprayed off _K ontaktmaterialteilchen by the inner movement of the diaphragm during the switching operation do not adhere, but fall off and thus there is no fear of the contact resistance between the two contact elements deterioration.

The tightness between the flexible membrane and the mounting ring surfaces of the support plates is completely sufficient since there is no need to work with a vacuum. For additional security, however, an annular groove can be made in the fastening ring surface, into which a correspondingly shaped annular projection fits on the inner surface of the bellows edge. The attachment can be made even more secure by additional clamping devices, such as conventional hose clamps or new stainless steel ring bands.

In order not to make the material of the bellows part too flexible. To have to, it is advantageous according to a development of the invention if the bellows part has a bulge, the dimensions of which are adapted to the switching path of the contact elements. If the switching path is only short, for example, it is only a few millimeters, a relatively small bulge is sufficient. However, the switching path is larger, for example when the switch as z. B. In addition to a circuit breaker to be used for higher voltage loads with an opening path of 16 mm, for example, a bellows with a larger bulge will be used.

The bellows part must be made of plastic, which on the one hand ensures sufficient electrical insulation, but on the other hand also withstands the environmental influences that arise both from the inside of the switch (hot gases and spraying contact material in the case of switching operations under residual load) and from the outside (acids and alkalis and corrosive gases occur when used in electrolysis systems). So-called fluoroelastomers have been found to be particularly suitable, for example a fluoroelastomer sold by 3M Deutschland GmbH under the trade names "Fluorel FC-2176" and "Fluorel FC-2177". The material has good chemical and heat resistance, high crosslinking speed and high elongation even at higher ambient temperatures.

Normally, the two support plates holding the contact elements are held rigidly by the actuating device, so that no special guidance of the two support plates to one another is required within the switch. However, if the switch is to be used in systems where this precise guidance of the support plates is not provided, according to a further development of the invention, at least one axial hole, in particular a blind hole, through the respective contact element, can be provided in the support plates, the holes being aligned with one another and have an insulating guide pin which is axially displaceable in at least the one hole. It is useful to give the guide pin a round cross-section and to keep it axially displaceable in the two holes with little play. With this arrangement, a sufficiently good guidance of the two contact elements or support plates is achieved in a very simple manner.

The guide pin can consist of glass-fiber reinforced polyamide, it usually being sufficient if only one guide pin arranged centrally with respect to the contact element is provided. If necessary and with larger contact surfaces, which may be necessary at very high currents, several guide pins can also be arranged.

A particularly cheap manufacture of the switch according to the invention can be achieved in particular in that the switch, apart from the bellows, consists of the same components for both contact sides. The fact that the housing does not need to be evacuated, but instead can be filled with an inert gas, for example the cheap nitrogen, also has a reducing effect, this filling process being necessary only at the very end in the manufacture of the switch, so that the previous steps do not require special protective gas or vacuum devices. If the requirements are not too high, it is even possible to dispense with filling with inert gas. Some circuits under current load cause material burns in the housing, the still existing ones remove interfering substances, such as moisture in particular, presumably by binding these substances to the resulting combustion products, be it by absorption or adsorption or by chemical reaction, so that a protective gas atmosphere is created automatically.

Another manufacturing reduction can be achieved in that, in contrast to the prior art, the support plate _- from z. B. chrome copper can be made in one piece by mold casting, then only a material processing on the contact surfaces for the bellows part and for the contact element is necessary. The contact element can most advantageously consist of a metal disk which is soldered into a corresponding depression on the support plate. Suitable materials for the contact elements include disks made of a silver-nickel alloy, the silver content preferably being 90%.

If the support plate is produced by die casting, blind holes for attachment to the actuating devices can be produced in a particularly simple manner on the outer sides of the support plates in that threaded inserts are cast in at the same time.

Instead of this, threaded through holes can of course also be used, should this be cheaper in terms of production.

The novel switch described above can also serve as a switch element of an empty switch, which then consists of several such empty switch elements, especially when the current to be transmitted in the switched-on state, for example, significantly exceeds 10,000 A, because otherwise the contact area becomes so large that accurate parallel guidance leads to mechanical difficulties.

Likewise, a combination of several empty switch elements is advantageous if the permissible voltage when switched off should be more than, for example, 1,000 to 2,000 V, because then the necessary air gap (at 1,000 V AC or 1,200 V DC according to VDE regulations 9 mm) and creepage distance (at the specified stresses 16 mm) would have to be increased to such an extent that mechanical complications again occur.

In order to combine several switch elements into one switch, according to a further development of the invention, the elements can be placed with their support plates on connecting lugs, which in turn are attached to a fixed mounting rail on one side of the switch and a mounting rail displaceable in the direction of the switch element axes of the switch can be kept insulated, the connecting lug on the fixed rail with the associated support plate advantageously being in one piece and the connecting lug on the movable rail advantageously consisting of a large number of parallel metal sheet strips such as copper sheet strips to simplify the construction on the one hand and the mobility on the other hand the moveable rail not to be affected by the rigidity of a connecting bracket.

Depending on whether the switches are to be connected in parallel or in series, the connecting tabs of the adjacent switch elements will each be connected in parallel or in rows one behind the other.

In order not only to enable a switch-off, in particular an empty switch, but also a switch-over, it is also possible to connect two switches or switch elements to a mechanical switch drive in such a way that the other is switched off when one is switched on. If you connect two switches or switch elements with two other switches or switches elements mechanically via a cross connection in such a way that two contacts open and two others close during the switching process, results in a two-pole changeover switch, which can be used, for example, as a pole reverser in general switchgear construction, in electroplating or in electric furnace construction. In particular, the two-pole switch can be used to switch from one system to another system. When used as an empty switch, the switch described here essentially only has a larger opening path of, for example, 9 mm, which means that it can not only be used as an empty switch for (almost de-energized) switching on and off of currents, if between the open contact pieces of each pole only a relatively low voltage occurs at the moment of switching, while voltages of, for example, 1,000 V are then permitted in the switched-off state, but this large opening travel also results in special operational reliability.

The invention is explained in more detail below on the basis of exemplary embodiments which are illustrated in the drawings.

• Fig. 1 eine Seitenansicht einer Ausführungsform des erfindungsgemäßen Schalters bzw. Schalterelements;
• Fig. 2 einen Axialschnitt durch den in Fig. 1 dargestellten Schalter, der gemäß der dargestellten Ausführungsform einen Führungszapfen aufweist;
• Fig. 3 eine Schnittansicht durch den Schalter der Fig. 2 längs der Linien III-III;
• Fig. 4 eine Seitenansicht einer anderen Ausführungsform des erfindungsgemäßen Schalters;
• Fig. 5,6 einen Axialschnitt durch bzw. eine Draufsicht auf die in Fig. 4 dargestellte Ausführungsform;
• Fig. 7 eine perspektivische Darstellung einer als Klemmeinrichtung besonders geeigneten neuartigen Schlauchschelle;
• Fig. 8 eine Detailansicht des Verschlusses dieser in Fig. 7 dargestellten Schlauchschelle;
• Fig. 9 eine Seitenansicht eines aus fünf Schalterelementen bestehenden fünfphasigen Ein-/Ausschalters;
• Fig. 10 eine Querschnittansicht durch den Schalter der Fig. 9;
• Fig. 11 eine Draufsicht auf den Schalter der Fig. 9;
• Fig. 12 eine Seitenansicht eines sechs Schalterelemente umfassenden dreiphasigen Umschalters; und
• Fig. 13 eine Querschnittansicht durch den Umschalter der Fig. 12.

It shows

• Figure 1 is a side view of an embodiment of the switch or switch element according to the invention.
• FIG. 2 shows an axial section through the switch shown in FIG. 1, which according to the illustrated embodiment has a guide pin;
• Fig. 3 is a sectional view through the switch of Figure 2 along the lines III-III.
• Fig. 4 is a side view of another embodiment of the switch according to the invention;
• 5,6 shows an axial section through or a top view of the embodiment shown in FIG. 4;
• 7 shows a perspective illustration of a new type of hose clamp that is particularly suitable as a clamping device;
• FIG. 8 shows a detailed view of the closure of this hose clamp shown in FIG. 7;
• 9 is a side view of a five-phase on / off switch consisting of five switch elements;
• Fig. 10 is a cross sectional view through the switch of Fig. 9;
• Fig. 11 is a plan view of the switch of Fig. 9;
• 12 shows a side view of a three-phase changeover switch comprising six switch elements; and
• 13 is a cross-sectional view through the changeover switch of FIG. 12.

1 shows the side view of a switch 10 according to one embodiment, which is explained in more detail in FIG. 2 in a longitudinal sectional view and in FIG. 3 in a cross-sectional illustration. The switch consists of two opposite contact elements in the form of two circular contact disks 12, each of which is held by a support plate 14. Preferably, the contact disc 12, the z. B. consists of a silver alloy with a silver content of about 90%, placed in a corresponding depression in the end face of the support plate 14 and soldered to the entire surface. The depression results in a special protection of the edge of the plate 12 against lifting off under greater thermal stress.

To avoid contamination of the contact surface and - especially when used in electrolysis baths - penetration To prevent harmful gases, the contact elements 12 are enclosed gas-tight by an annular membrane 16 which tightly connects the two support plates 14 together. In this way, the two support plates 14 together with the annular membrane 16 form a closed chamber 18 in which the contact disks 12 can move in the axial direction in a protected manner. The two support plates 14 can be moved towards one another by means not shown here until the two contact disks 12 lie against one another in their entire area and form a current transition which has a transmission power of several thousand amperes with a very low voltage drop. If, in contrast, the two supporting plates 14 and so that the contact discs 12 pulled apart by the actuating means, for example to 16 to 20 mm, _'an interruption of the circuit.

In order to keep the tensile or compressive load on the material of the membrane 16 as small as possible, it is provided with an outward bulge according to FIG. 2, so that the annular membrane forms a kind of bellows part. The inner part of the bellows part, which is made of flexible, electrically insulating plastic material, rests on fastening ring surfaces 20 which run around the contact element 12 and are formed by the support plates 14. It is advantageous to countersink this annular surface 20 with respect to the foot part 22 of the support plate 14, which itself does not need to be round, but can also be square, for example, as shown in FIG. 3, so that a support surface 24 extends over the entire circumference for the annular membrane 16 results.

The tight fit and the gas tightness of the connection between the membrane 16 and the support plate 14 can be further improved and increased by milling a groove 26 into the fastening ring surface 20, into which a correspondingly shaped annular projection or bead 28 of the inner surface of the edge of the bellows part 16 fits. As a further measure, a clamping device 30 is provided in the illustrated embodiment see that a standard hose clamp 30 may, as in _F ig. 1, or a more easily mountable and also a more uniform pressure clamping device, as shown in FIG. 7 in a perspective view.

7 consists of a stainless steel band 32 which ends at one end in an outwardly pointing hook 34, see the partially longitudinal section of FIG. 8, the hook 34 having a width which is less than the width of the band 32 is. The other end of the band 32 ends in a window-like opening 36 which, for the purpose of covering the membrane 16 with the band 32, extends over the hook 34. is laid. Compared to the usual hose clamps, this band does not give rise to bulging of the covered material in the area of the band ends during the fastening process, and this band can also be installed much more quickly.

In order to be able to easily grasp and tension the ends of the steel band 32, two round openings 38 are provided near the band ends, into which a corresponding pliers-like tool can be used to pull the two ends of the steel band 32 together and thereby the window 36 over the hook 34 to guide and thus lock the steel band 32 around the membrane 16.

Behind the fastening ring surface or shoulder 20, the support plate 14 is set down again, so that there is a further step 40 from which the actual carrier for the contact disk 12 extends in a cylindrical shape. In this way, all the surface areas of the membrane 16 delimiting the interior of the switch housing are approximately the same distance from the contact disk gap 42, so that u. U. splashing material distributed relatively uniformly on this surface 44, which contributes to the longer life of the membrane material.

The membrane 16 preferably consists of a fluoroelastomer which is sufficiently resistant to chemical attacks from the outside, which can occur when using the switch for electrolysis baths, and to chemical and thermal attacks from the inside. This material has the advantage that it can be processed as a raw elastomer using very simple injection molds and therefore there is the possibility of creating a series of switches with stepwise different nominal current values without great tool costs, so that the switch can be precisely adapted to the respectively required nominal current and so that optimal use of space is achieved. For example, a module row could be created in steps of 1000 A, which would range from 1000 to 10000 A. The. tool costs required for each current value, namely the costs for the injection mold for the membrane 16 and also the mold for producing the support plate 14, for example by means of mold casting, are thereby limited. In addition, as can be clearly seen in FIG. 2, both support plates 14 are constructed completely identically and can therefore be manufactured inexpensively with only one shape.

Another advantage of the production by means of gravity die casting would lie in the fact that threaded blind holes can be arranged in the foot part 22 of the support plate 14 in a very simple manner (not shown) by casting corresponding inserts during the mold casting. Alternatively, blind holes 54 can of course also be arranged subsequently (FIG. 4) or, instead, through holes 44, for. B. at the four corners of a rectangular support plate 14, as shown in Fig. 3.

If the actuating device for the two support plates 14 of the switch 10 has no or insufficient axial guidance, such an axial guidance can also be provided within the switch, as can be seen in FIG. 2. The axial guide here consists in a simple manner of a guide pin 48 which is arranged in an axial blind hole 50 arranged in each support plate 14 with a ge know game 52 is run. The guide pin 48 can for example consist of glass fiber reinforced polyamide.

The guide pin 48 need not necessarily be present, for example FIGS. 4 to 6 show an embodiment. of the switch according to the invention, which does not have such an additional guide. Otherwise, the illustrated embodiment is quite analogous to the embodiment shown in FIGS. 1 to 3, but instead of the through holes 44, blind holes 54 are provided for fastening the support plates to the switch actuation devices (not shown).

As can be seen in FIG. 5, the membrane 16 can be provided on its outer edges with a depression 56 which is arranged above the bead 28 (which engages in a groove 26 in the fastening ring surface 20) and into which, for example a fastening spiral 58, a fastening ring 60 or a band 62 can engage.

The somewhat more complicated installation of blind holes has the advantage over through holes that the entire outer surface of the support plate is available for the replacement of older switches by the new switches, so that any drilling patterns can be realized.

The switch described above in several embodiments, which, as already mentioned, can be designed to switch currents in the range from 1,000 to 12,000 A, for example. can also be used to construct a switch comprising a plurality of switch elements of the type described.

9 shows a switch 70 constructed from five switch elements 10, FIG. 10 showing a sectional view through one of the switch elements 10. As can be seen from the figures, the lower support plate 14, which is integrally connected to the outside in a connecting plate 15 goes, carried by an insulating piece 72 which in turn is fastened on a fastening rail 74 which is U-shaped in cross section.

The upper support plate 14 clamps with a further support plate 80 a connection tab 76 consisting of individual copper sheet strips with the interposition of a further insulating piece 78. This part, consisting of the components 14, 76, 78 and 80, is connected via a cushion-shaped connecting member 82 to an upper fastening rail 84 which is displaceable in the direction of the axis of the switch 10 and which in turn is U-shaped in cross section.

The lower connection plate 15 and the upper connection plate 76 are each connected to the connection contact strips 86 and 88, which are only shown in broken lines in FIG. 10, for example, each with four screw bolts, which each pass through four corresponding bores 90 and 92 in the lower and upper connection plate 15 and 76, see FIG. 11.

The fastening rails 74 and 84 are held by a suitable frame construction, which are held, for example, by side plates 94, 96, the upper fastening rail being connected at both ends to an eccentric drive and thereby being able to be moved up and down, the drive being, for example, by means of connecting rods 98 arranged on both sides takes place, which are connected to a drive shaft 100. The drive shaft 100 in turn can be actuated either by a manual drive, for example by a lateral hand lever, or by a rotating front drive, or else by a motor drive, for which a corresponding space 102 is provided on the left side in FIG. 9, for example.

The distances between the individual connecting lugs 76 and 15, as well as the distances between the contact elements within the individual switch elements 10, depend on the respective required dielectric strength of the switch in the switched-off state. If the individual connection tabs 76 and 15 are connected in parallel to each other in order to achieve higher rated currents, the distances with regard to the dielectric strength do not play a role, but if, for example, the connection tab 15 of one switch element 10 is connected to the connection tab 76 of the next one in order to achieve higher dielectric strength Switch element 10 is connected by a bridge connection, the connecting tab 15 is in turn connected to the connecting tab 76 of the next switch element, etc.

In most cases, however, it will be cheaper to provide correspondingly larger distances between the contact elements for higher voltages and to combine several switch elements only for the purpose of a higher nominal current carrying capacity.

If the switching operations take place with almost currentless operation, so that neither a particularly high current flows through the switch during the switch-off process and only a low voltage is applied to the contact elements (open circuit breaker operation), arcing phenomena do not occur or only to a limited extent. The switch according to the invention is then suitable for higher nominal powers and also higher switching frequencies.

Compared to previously known empty switches, which all work with non-encapsulated knife contact constructions, there is much greater operational reliability as well as lower manufacturing costs with the same nominal current. Another advantage is the more compact design and greater insensitivity to external influences.

Switches of the type shown in Fig. 9, in particular when used as an empty switch or even consisting of only one element switches can also be combined in such a way that there is the possibility of switching, see Figs. 12 and 13, the one Side view (similar to FIG. 9) or a cross section (similar to FIG. 10) of such Selector switch 170, which mechanically combines two switch elements 10 for each phase in such a way that the other switch element is closed while one switch element is being closed. There are then a flexible connecting lug 76 and two fixed connecting lugs 77, 79 provided centrally between the support plates 14 of two cooperating switch elements 10.

The construction described can be used particularly well as an empty switch and as a low-voltage switch. Empty switches are switches for almost currentless switching on, off or switching, low-voltage switches switches for switching on and off or switching currents when between the open switch pieces. ken each pole only a low voltage occurs at the moment of switching. A special form of the circuit breaker is the isolating switch, a circuit breaker for nominal currents of 1000 - 100,000 A, which are always to be used when not switched under load. Due to their large opening path, special operational safety is ensured. With a clearance of 9 mm and a creepage distance of 16 mm, the insulation capacity is 1000 V AC or 1200 V DC.

Empty switches as changeover switches are similar in their properties to the empty switch, but the changeover switch can be used to switch from one system to another. The area of application of these empty switches is general switchgear construction, electroplating (e.g. also as a pole changer), electric furnace construction and other areas with high currents but low voltages.

As already mentioned, the switch according to the invention can be used not only as an empty switch, but also as a low-voltage switch or switch, even for very high currents. The arrangement of the guide pins results in a guide which is sufficient to absorb even the forces which occur on the switch at such high currents (a few 100 to a few 1000 A) due to their magnetic action.

During switching operations under current load, in particular when a circuit carrying a high current is interrupted, the two support plates 14 and thus the contact disks 12 are pulled apart by the actuating device, for example by 3 to 4 mm, as a result of which the current is interrupted. An arc occurs during the opening process, which, however, goes out immediately when the low voltages of only a few volts are present. After all, a small part of the contact material is liquefied and evaporated by the arc and, by means of the magnetic forces and the resulting gases, flung radially outwards out of the gap formed between the contact disks 12 against the membrane 16. However, since the membrane is bent and deflected during the axial movement of the two support plates 14, sprayed-off contact disk materials cannot hold onto the inner wall of the membrane 16, but rather fall off from it again and collect over time at the lower end of the housing space 18 where they don't bother. The internal flexibility of the annular membrane 16 thus effectively prevents a reduction in the creep resistance between the two contact elements 12 when the switch 10 is open.

Claims (10)

1. Switch with opposing contact elements, which are supported by axially acting support plates, and with a gas-tight enclosing housing, which is formed by the support plates and an annular membrane, which is gas-tightly connected to the two support plates, characterized that the annular membrane (16) is formed by a bellows part made of flexible, electrically insulating plastic material, the edges of which are fastened by means of clamping devices (30) to fastening ring surfaces (20) of the support plate (14) running around the contact element (12). 2. Switch according to claim 1, characterized in that the fastening surface (20) has an annular groove (26) into which a correspondingly shaped annular bead (28) fits on the inner surface of the bellows edge. 3. Switch according to one of claims 1 or 2, characterized in that the bellows part (16) is made of an insulating, elastic plastic such as fluoroelastomer and has a bulge, the dimensions of which are adapted to the switching path of the contact elements (12). 4. Switch according to one of claims 1 to 3, characterized in that the clamping device consists of a stainless steel band (32) bent into a ring, which at one end in an outwardly pointing hook (34) with a width which is less than that of the band (32) ends, while the other end of the band (32) has a window-like opening (36) for receiving the hook (34). 5. Switch according to one of claims 1 to 4, characterized in that the support plates (14) each have at least one axial, preferably centrally arranged, the respective contact element (12) through hole (50), in particular blind hole with a round cross section, the holes aligned with each other and receiving an insulating guide pin (48) which is axially displaceable in at least one hole (50). 6. Switch according to claim 5, characterized in that the guide pin (48) is held axially displaceably in both holes (50) with only slight play (52) and preferably consists of glass fiber reinforced polyamide. 7. Switch according to one of claims 1-6, characterized in that the housing is filled with dried air or an inert gas, in particular nitrogen, during assembly. 8. Switch according to one of claims 1 to 7, characterized in that the contact element from a in a matching recess of a hard copper alloy, in particular chrome copper existing support plate (14) soldered circular disc (12) made of silver or silver alloy. 9. Switch according to one of claims 1 to 9, characterized by the use as an empty switch (off, on or switch). 10. Switch according to one of claims 1 to 9, characterized by the use as a low-voltage switch (off, on or changeover switch).

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