EP0029205B1 - High-current switch - Google Patents

Description

The invention relates to a high-current switch with opposing planar contact disks, 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 and a sealing ring made of flexible electrically insulating plastic material, the edges of which are fastened by means of clamping devices to fastening surfaces of the support plate which run around the contact element. Such a high-current switch is already known from DE-A1-2807810.

The known switch has many advantages. It reliably protects the contacts against the corrosive ambient air of, for example, electrolysis systems, on which such high-current switches are preferably used. In addition, the known switch already has a device that prevents the switch from assuming a closed position in idle mode. However, the switching path that can be achieved with the known high-current switch is very limited and is only a few millimeters. The publication mentions a value of 2 mm, which is usually sufficient for low-voltage applications. In certain applications, however, the high-current switch must also be able to disconnect higher voltages, which requires a contact gap when the switch is open, which can be well over 2 mm. In this case, the arrangement according to the prior art no longer works satisfactorily. Nevertheless, if you pull the two support plates of the switch shown in the citation as far apart as required by the voltage load, the plastic material ring is stretched so much that it may tear or at least the adhesive between the edge of the plastic material ring and the annular fastening surface on the support plate comes loose . In general, this sealing surface does not seem to work particularly reliably, if in addition to this seal used by the plastic ring, another membrane seal is used, which is made of metal. The switch is thereby quite complex, so that the sub-task of the present invention, namely to make the switch cheaper, is not solved. But the second part of the task remains unsolved, as the switching-off arcs spray material to the outside, which is not reflected on the flexible plastic ring and may possibly fall off when it moves, but rather on the rigid, insulating ceramic ring, which is thereby caused in the course of Time will lose its insulation ability and thus the switch for switching operations with z. B. makes higher voltage unsuitable.

The same can be said of a switch known from US-A-3,950,628. Here too, the structure is relatively complicated, even if the bellows construction enables such a large distance to be removed from the contact disks that even higher voltages can be switched per se. However, here too, a rigid insulating ring is so far in the area of the contact disks that there is a risk that material sprayed off as a result of electric arc heating will deposit on it, thereby reducing the insulating ability over time. The Teflon coating for the metal bellows mentioned in the publication is only applied on the outside and is essentially intended to prevent corrosion of the metal bellows as a result of the outside atmosphere. The aspects of the invention are not addressed.

The object of the invention is to provide a switch of the type mentioned, which on the one hand can be manufactured much more cost-effectively than is the case with the switch known from DE-A1-2 807 810, without sacrificing operational reliability or service life would have to be made, and in addition, the contact resistance between the two open contact elements is not deteriorated by sprayed contact disk material in the course of many operating cycles, which would be disadvantageous especially if the switch is to serve as an empty switch. Because of the latter application, the switch should also allow a sufficiently large distance between the contact disks in the open position without the plastic material membrane being stressed too much.

This object is achieved in that the fastening ring surface comprises a cylinder outer ring surface and that the flexible sealing ring made of plastic material catches sprayed-off material due to arcing phenomena and causes material adhering during switching operations to fall off.

The first sub-feature ensures that even if the contact disks have to be placed at a greater distance in order to also allow higher voltages, the membrane does not separate undesirably from the fastening ring surfaces, as would be possible in the prior art, while the second sub-feature ensures that material sprayed off due to arcing does not adhere to the device forming the insulation between the two contacts and thereby deteriorates the contact resistance over time, as is also the case in the prior art must be feared.

The subclaims represent advantageous developments of the subject matter of the main claim.

The tightness between the flexible membrane and the fastening ring surfaces of the support plates is completely sufficient since there is no need to work with a vacuum. For additional security - also against unwanted sliding - however, an annular groove can be made in the fastening ring surface, into which a correspondingly shaped annular bead fits on the inner surface of the membrane edge (claim 2). The attachment can be made even more secure by additional clamping devices, such as conventional hose clamps or novel stainless steel strips (claim 4).

In order not to have to make the material of the membrane too flexible, it is advantageous according to a further development of the invention if the membrane has a bulge, the dimensions of which are adapted to the switching path of the contact elements (claim 3). 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 membrane with a larger bulge will be used.

The membrane should consist of a 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 when used in electrolysis systems) occur. So-called fluoroelastomers have been found to be particularly suitable, for example a fluoroelastomer sold by 3M Deutschlang 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, at least one axial, preferably centrally arranged hole, in particular a blind hole with a round cross section, can be provided in the support plates according to a development of the invention be, the holes being aligned with one another and receiving an insulating guide pin which is axially displaceable at least in one hole (claim 5). Expediently, the guide pin will be axially displaceable in the two holes with only a small amount of play, as a result of which the two contact disks or support plates are sufficiently well guided in a very simple manner, the guide pin preferably being made of glass fiber-reinforced polyamide (claim 6).

A particularly cheap manufacture of the switch according to the invention can be achieved in particular in that the switch, apart from the membrane, consists of the same components for both contact sides. The fact that the housing does not need to be evacuated also has a reducing effect, but instead can be filled with dried air or an inert gas, in particular nitrogen, during assembly (claim 7), this filling process only at the very end during manufacture of the switch is necessary so that the previous steps do not require any special protective gas or vacuum devices. Some circuits under current load cause material burns in the housing, which remove any interfering substances that are still present, such as residual moisture, presumably by the fact that these substances are bound to the resulting combustion products, be it by absorption or adsorption or by chemical reaction, so that a protective gas atmosphere is created automatically.

A further reduction in manufacturing cost can be achieved in that the contact disk consists of a silver or silver alloy circular contact disk soldered into a suitable recess in the support plate consisting of a hard copper alloy, in particular chrome copper (claim 8).

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 be used as an empty, off, on or switch (claim 9). Several empty switches of this type can also be combined, in particular if the current to be transmitted in the switched-on state substantially exceeds 10,000 A, for example, because otherwise the contact area becomes so large that precise parallel guidance leads to mechanical difficulties. Likewise, a combination of several circuit breakers is advantageous if the permissible voltage when switched off is more than, for example wise should be 1000 to 2000 V, because then the necessary air gap (at 1000 V AC or 1200 V DC according to the German VDE regulations 9 mm) and creepage distance (at the specified voltages 16 mm) would have to be increased so much that mechanical complications occur.

The novel switch can also be used as a low-voltage switch (off, on or changeover switch) (claim 10). In order to combine several switches, these can be placed with their support plates on connecting lugs, which in turn are kept isolated on a fixed mounting rail on one side of the switch and a mounting rail that can be moved in the direction of the switch axes on the other side of the switch, the ones on the fixed rail located connecting tab with the associated support plate advantageously in one piece and the connecting tab on the movable rail can advantageously consist of a large number of parallel metal sheet strips such as copper sheet strips, on the one hand to simplify the construction, on the other hand, the mobility of the movable rail is not due to the stiffness of a connecting tab to affect.

Depending on whether the switches are to be connected in parallel or in series, the connecting tabs of the switches located next to one another will be connected in parallel or in rows one behind the other.

In order to enable not only 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 switch elements mechanically via a cross connection in such a way that two contacts open and two others close during the switching process, a two-pole changeover switch results, which is used, for example, as a pole reverser in general switchgear construction, in electroplating technology or can be used in electric furnace construction. In particular, the two-pole switch can be used to switch from one system to another system.

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;
• Fig. einen Axialschnitt durch den in Fig. 1 dargestellten Schalter, der gemäß der dargestellten Ausführungsform einen Führungszapfen aufweist;
• Fig. eine Schnittansicht durch den Schalter der Fig. 2 längs der Linien 111-111;
• 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. eine perspektivische Darstellung einer als Klemmeinrichtung besonders geeigneten neuartigen Schlauchschelle;
• Fig. eine Detailansicht des Verschlusses dieser in Fig. 7 dargestellten Schlauchschelle;
• Fig. 9 eine Seitenansicht einer aus fünf Schaltern bestehenden fünfphasigen Ein-/Ausschaltereinrichtung;
• Fig.10 eine Querschnittsansicht durch die Einrichtung der Fig. 9;
• Fig. 11 eine Draufsicht auf die Einrichtung der Fig. 9;
• Fig. 12 eine Seitenansicht einer sechs Schalter umfassenden dreiphasigen Umschaltereinrichtung und
• Fig. 13 eine Querschnittsansicht durch die Umschaltereinrichtung der Fig. 12.

It shows

• Fig. 1 is a side view of an embodiment of the switch according to the invention;
• FIG. 1 shows an axial section through the switch shown in FIG. 1, which according to the illustrated embodiment has a guide pin;
• Fig. A sectional view through the switch of Figure 2 along lines 111-111.
• Fig. 4 is a side view of another embodiment of the switch according to the invention;
• 5, 6 an axial section through or a top view of the embodiment shown in FIG. 4;
• A perspective view of a new type of hose clip particularly suitable as a clamping device;
• Fig. 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 device consisting of five switches;
• 10 shows a cross-sectional view through the device of FIG. 9;
• Fig. 11 is a top view of the device of Fig. 9;
• 12 is a side view of a three-phase changeover device comprising six switches and
• 13 is a cross-sectional view through the changeover device of FIG. 12.

1 shows the side view of a switch 10 according to an 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 bar 14 and soldered to the entire surface. The depression results in a special protection of the edge of the contact disk 12 against lifting off when there is a greater thermal load.

In order to avoid contamination of the contact surface and - in particular when used in electrolysis baths - to prevent the ingress of harmful gases, the contact disks 12 are enclosed in a gas-tight manner by an annular membrane 16 which tightly connects the two support plates 14 to one another. 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 relative to one another 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, on the other hand, the two support plates 14 and thus the contact disks 12 are pulled apart by the actuating device, for example by 16 to 20 mm, the circuit is interrupted.

To the tensile or compressive load of the To keep 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. The inner edges of the membrane 16, which is made of flexible, electrically insulating plastic material, rests on fastening ring surfaces 20 which run around the contact disk 12 and are formed by the support plates 14. It is advantageous to countersink this fastening ring surface 20 with respect to the base 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 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 the membrane 16 fits. As a further measure, a clamping device 30 is also provided in the illustrated embodiment, which can be a conventional hose clamp, as shown in FIG. 1, or a simple, mountable and also more uniform pressure-exerting stainless steel band 32, as is shown in FIG. 7 is shown in perspective view, and which ends at one end in an outwardly facing hook 34, see the partially longitudinal section of Fig. 8, wcbs; the hook 34 has a width that is less than the width of the stainless steel band 32. The other end of the stainless steel band 32 ends in a window-like opening 36 which is placed over the hook 34 for the purpose of covering the membrane 16 with the stainless steel band 32. Compared to conventional hose clamps, this band does not bulge 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 stainless steel band 32, two round openings 38 are provided near the ends of the band, into which a corresponding plier-like tool can be used to pull the two ends of the stainless steel band 32 together and thereby open the opening 36 over the hook 34 to guide and thus to lock the stainless steel band 32 around the membrane 16.

Behind the mounting ring surface 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 given approximately the same distance from the contact disk gap 42, so that u. U. splashing material distributed relatively uniformly on the 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 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 10,000 A. The tool costs required for each current value, namely the costs for the injection mold for the membrane 16 and the mold for producing the support plate 14, for example by means of mold casting, are thus 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 45, 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 guided with a certain clearance 52 in an axial blind hole 50 arranged in each support plate 14. 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 very analogous to the embodiment shown in FIGS. 1 to 3, but instead of the through holes 45, blind holes 54 for fastening the support plates to the switch be actuating devices (not shown) are provided.

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 mounting 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 1000 to, for example, 12,000 A, can also be used to construct a switch device comprising several switches of the type described.

An on / off switching device 70 constructed from five switches 10 is shown in FIG. 10, FIG. 10 showing a sectional view through one of the switches 10. As can be seen from the figures, the lower support plate 14, which merges in one piece towards the outside into a connecting lug 15, is carried by an insulating piece 72, which in turn is fastened on a fastening rail 74 with a U-shaped 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 with four screw bolts each, which are provided through four corresponding bores 90 and 92 in the lower and upper connection plate 15 and 76, respectively. 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 disks within the individual switches 10, depend on the respective required dielectric strength of the switch device in the switched-off state. If the individual connection tabs 76 and 15 are connected in parallel with each other in order to achieve higher nominal currents, the distances with regard to the dielectric strength do not play a role, but if, for example, to achieve higher dielectric strength, the connection tab 15 of a switch 10 with the connection tab 76 des next switch 10 is connected by a bridge connection, the connecting plate 15 is in turn connected to the connecting plate 76 of the next switch, etc.

In most cases, however, it will be cheaper to provide larger distances between the contact disks for higher voltages and to combine several switches only for the purpose of a higher rated 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 present at the contact disks (open circuit breaker operation), arcing phenomena do not occur between the contact disks 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.

Switch devices of the type shown in Fig. 9, in particular when used as an empty switch, or switches consisting of only one element 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 a switch 170, which mechanically combines two switches 10 for each phase in such a way that the other switch is opened during the closing of one switch. 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 switches 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 or off or switching currents if only a low voltage occurs at the moment of switching between the open contacts of each pole. 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 there is no switching under load. Due to their large opening path, special operational safety is given. 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 field of application of these empty switches is general switchgear construction, electroplating (e.g. also as a pole changer), electric furnace construction as well as 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 arises during the opening process, which, however, goes out immediately at the low voltages of only a few volts present here. 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, is thrown radially outward against the membrane 16 from the gap formed between the contact disks 12. However, since the membrane is bent and deflected within itself during the axial movement of the two support plates 14, hosed 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 disks 12 when the switch 10 is open.

Claims (10)

1. High-current switch with flat contact discs (12) located opposite one another and mounted on base plates (14) that are operated by force exerted axially, the contact discs (12) being enclosed by a gastight housing that comprises the base plates (14) and a circular membrane (16) that is fixed to the two base plates (14) by a gastight connection and consists of a sealing ring made of flexible, electrically insulating plastics material, the edges of which are fastened by clamps (30) to circular clamping faces (20) on the base plate (14) that encircle the contact element, characterised in that the circular clamping face (20) has a cylindrical outer surface and that the flexible plastics sealing ring collects material spattered due to arcing, and causes material that adheres to it to fall off by internal movement during switching operations.

2. Switch as in claim 1, characterised in that the circular clamping face (20) has a circular groove (26) into which fits a correspondingly shaped circular bead (28) on the inner surface of the edge of the membrane.

3. Switch as in one of claims 1 or 2, characterised in that the membrane (16) has a convexity of a size that accommodates the travel of the contact elements (12).

4. Switch as in one of claims 1 to 3, characterised in that the clamp (30) consists of a high-grade steel strip bent into a ring (32), terminating at one end in a hook (34) which points outwards and which is narrower than the high-grade steel strip (32), while the other end of the high-grade steel strip (32) has a window-like aperture (36) to receive the hook (34).

5. Switch as in one of claims 1 to 4, characterised in that the base plates (14) each have at least one axial, preferably centrally located, hole (50) that penetrates the associated contact disc (12), in particular a blind hole of circular cross section, the holes being aligned with each other and containing a non-conducting guide peg (48) which can move axially in at least one of the holes (50).

6. Switch as in claim 5, characterised in that the guide peg (48) can be moved axially in both holes (50), has only a small amount of clearance (52), and preferably consists of glass fibre reinforced polyamide.

7. Switch as in one of claims 1 to 6, characterised in that during assembly the housing is filled with dried air or an inert gas, particularly nitrogen.

8. Switch as in one of claims 1 to 7, characterised in that the contact disc (12) is a circular contact disc (12) made of silver or silver alloy and soldered into a suitable cavity in the base plate (14) which is made from a hard copper-base alloy, in particular chrome copper.

9. Switch as in one of claims 1 to 8, characterised by its use as a no-load switch (make, break or changeover switch).

10. Switch as in one of claims 1 to 9, characterised by its use as a low voltage switch (make, break or changeover switch).

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