EP2284860A2 - Electric resistance and installation switching device with electric resistance - Google Patents

Abstract

The electrical resistance (1) has a resistance element (2) and two connecting pieces (3,4) assigned to the resistance element. The resistance element is formed from a stack of partial-metal sheet pieces (5,6,7,8,9,10, 11). The partial-sheet metal pieces are arranged with their broad sides parallel to each other and in a stacking direction behind one another and spaced from each other. Independent claims are also included for the following: (1) a method for manufacturing an electrical resistance; and (2) an electric installation switching device with a contact point.

Description

The invention relates to an electrical resistor, in particular a selective resistor for a selective main circuit breaker, with a resistance element and at least two connecting pieces associated with the resistance element, according to the preamble of claim 1.

The invention also relates to a method for producing an electrical resistance according to claim 11.

Finally, the invention also relates to an electrical switching device having a first contact point, which is moved in a short circuit of an electromagnetic actuator in the open position, and with a second contact point, which is permanently opened by a first thermal release via a switch lock, and with a parallel to arranged in the first contact point parallel current path, in which a current-limiting resistor is arranged, according to the preamble of claim 12th

Known generic resistors that can be designed as high load resistance due to their purpose, for example, designed as a wound wire wound resistors. Such wound wire wound resistors can be very voluminous in design on short-circuit load and thus require a relatively large installation space in a service switching device. claim. In addition, such large-scale wirewound resistors have a relatively high weight. In a space-saving small version of such Wirewound resistors, it may happen that occurs when a short-circuit current in the resistor in a short time such a high temperature at the resistance that the latter can be destroyed by overheating. Furthermore, insufficient heat dissipation takes place in the known wound wire resistors via the connecting wires, so that heat build-up can occur in the region of the resistance element itself, whereby overheating is accelerated in the event of a short-circuit load.

In the DE 28 54 711 an installation switching device is shown with a resistor, wherein the resistor is made there as a resistance wire, for example made of CrAl1255, Cu or other alloys, wherein the wire is wound into a coil, due to their design and the required resistance value, a relatively large amount of space claimed. In addition, such a coil-shaped resistor generates a large magnetic field, so that the coil must be wound consuming antiparallel. When using bare wires, the coil must be wound on a high-temperature-resistant support body, to prevent the windings attract when energized and thus cause a Windungsschluß. If the resistance wire is insulated, then come as insulating expensive and poorly manageable materials such. B. glass silk used.

In the DE 102 03 443 an installation switching device is shown with a resistor, wherein the resistor there has a resistor body made of ceramic there with a negative temperature coefficient. However, such a resistor is expensive and therefore unsuitable for use in service switching devices for cost reasons.

The present invention is therefore in the light of the prior art, the object of developing a generic electrical resistance to the effect that he has a high resistance to short-circuit load, a space-saving form with low weight and large heat dissipation to the electrical connections and cost while a simple structure can be produced, and to provide a method for producing such a resistor.

Furthermore, the invention has the object, an improved electrical service switching device with a first contact point, which is moved in the event of a short circuit of an electromagnetic actuator in the open position, and with a second contact point of a first thermal release via a switching mechanism is permanently opened, and with a parallel to the first contact point arranged parallel current path, in which a current-limiting resistor is arranged to create, which has a high resistance to short-circuit load in a small design and easy to assemble at large heat dissipation from the resistor and is inexpensive to produce.

The problem underlying the invention is achieved according to the invention in terms of resistance by a generic resistor having the characterizing features of claim 1.

According to the invention, the resistance element is formed from a stack of partial sheet metal pieces consisting of a resistance sheet material, wherein the partial sheet metal pieces are arranged with their broad sides parallel to each other and in the stacking direction one behind the other and spaced from each other, wherein adjacent part sheet metal pieces in the stacking direction alternately right and left a perpendicular to the broad side of the partial sheet metal pieces extending center plane are electrically connected to each other at their narrow sides, so that the current path from the first, edge sheet metal piece to the opposite stacking, second edge sheet metal piece meandering through the remaining part sheet metal pieces.

According to a very advantageous embodiment, the first and the second marginal sheet metal piece form the electrical connection pieces.

According to a further advantageous embodiment, the partial sheet metal pieces are held by means of at least one holding device made of insulating material at a distance from each other.

According to a further advantageous embodiment, finger-like incisions are formed in the partial sheet metal pieces, which alternately extend in each case from a first edge side in the direction of the respective opposite edge side, so that the current path in a partial piece of sheet metal between the two narrow sides takes a meandering course ,

According to a further advantageous embodiment, the resistance element consists of a metal strip which is folded transversely to the strip direction.

According to a further advantageous embodiment, the folds extending laterally in the longitudinal direction of the band connect directly to each other with adjacent partial band pieces.

According to a further advantageous embodiment, the folds are formed substantially zig-zag-shaped, and the resistance element is compressed in a holding device arranged such that the zig-zag course of the folds in favor of substantially parallel to each other in the stacking direction successively arranged part-band pieces is overcome.

According to a further advantageous embodiment, the resistance element is folded meander-shaped.

According to a further advantageous embodiment, a gap is left between adjacent part-tape pieces in the stacking direction.

According to a further advantageous embodiment, the resistance element is a stamped and bent part, wherein the finger-like cuts of the partial sheet metal pieces are punched out in the metal strip.

• Ausstanzen von fingerartigen Einschnitten aus einem Metallband aus einem Widerstandsblechmaterial, wobei die fingerartigen Einschnitte abwechselnd jeweils von einer ersten Randseite aus in Richtung auf die jeweils gegenüberliegende Randseite sich erstrecken,
• im wesentlichen zick-zack-förmiges Falten des Metallbandes quer zur Bandrichtung;
• komprimiertes Anordnen des zick-zack-förmig gefalteten Metallbandes in einer Haltevorrichtung, so dass der zick-zack-förmige Verlauf der Faltungen zugunsten im wesentlichen parallel zueinander in Stapelrichtung hintereinander angeordneter Teil-Bandstücke überwunden ist.

The object underlying the invention is achieved according to the invention with respect to the method for producing the resistor in that the method comprises the steps:

• Punching finger-like incisions from a metal strip made of a resistance sheet material, the finger-like incisions alternately extending in each case from a first edge side in the direction of the respectively opposite edge side,
• essentially zigzag-shaped folding of the metal strip transversely to the strip direction;
• compressed arrangement of the zig-zag folded metal strip in a holding device, so that the zig-zag course of the folds in favor of substantially parallel to each other in the stacking direction successively arranged part-tape pieces is overcome.

The object underlying the invention is achieved with respect to the service switching device by a generic service switching device in which the current-limiting resistor comprises a resistor element and at least two connecting elements associated with the resistor element, and wherein the resistor element is formed from a stack of partial sheet metal pieces, which consists of a resistance sheet material exist, wherein the partial sheet metal pieces with their broad sides parallel to each other and in the stacking direction one behind the other and from each other are arranged, wherein adjacent part-sheet metal pieces in the stacking direction alternately right and left of a perpendicular to the broad side of the partial sheet metal pieces extending center plane are electrically connected to each other at their narrow sides, so that the current path from the first, marginal piece of sheet metal to the stacking direction, second marginal piece of sheet metal meandering through the remaining part sheet metal pieces.

An advantageous embodiment of a service switching device according to the invention is characterized in that the resistance element consists of a metal strip which is folded transversely to the belt direction, and that the folds extending laterally in the belt longitudinal direction connect directly adjacent partial belt pieces with each other.

A further advantageous embodiment of an installation switching device according to the invention is characterized in that the folds are formed substantially zigzag-shaped, and that the resistance element is arranged in such a compressed manner in a holding device, that the zigzag-shaped course of the folds in favor of substantially parallel is overcome in the stacking direction successively arranged part-tape pieces.

A further advantageous embodiment of a service switching device according to the invention is characterized in that at least one conductor section, with which the resistor is switched into the parallel current path, resiliently presses against the first or the second marginal piece of sheet metal.

Further advantageous embodiments and improvements of the invention and further advantages can be taken from the subclaims.

figure description

Figures and description serve to better understand the subject. Articles or parts of objects which are substantially the same or similar may be given the same reference numerals. The figures are merely a schematic representation of an embodiment of the invention.

Figur 1

ein Ausführungsbeispiel eines erfindungsgemäßen Widerstandes,

Figur 2

das Ausführungsbeispiel nach Fig. 1, betrachtet aus Richtung A, von der Rückseite,

Figur 3

ein gestanztes Metallband vor der Faltung zu einem erfindungsgemä- ßen Widerstandselement, sowie

Figur 4

schematisch die Einsicht in ein erfindungsgemäßes Installations- schaltgerät mit einem erfindungsgemäßen Widerstand.

Showing:

FIG. 1

an embodiment of a resistor according to the invention,

FIG. 2

the embodiment according to Fig. 1 , viewed from direction A, from the back,

FIG. 3

a stamped metal strip before folding to a resistance element according to the invention, and

FIG. 4

schematically the insight into an inventive installation switching device with a resistor according to the invention.

It will be the first FIG. 3 considered. This shows a metal strip 20 made of a resistance metal, for example, from CrAl1255, Cu or other alloys. The metal strip 20 is elongated and has two edge sides 16, 17 running parallel in the direction of longitudinal extension. Several finger-like incisions 19, 18 are formed in the metal strip 20, which are arranged one behind the other in the longitudinal direction of the metal strip 20 so as to form an interdigital structure. The cuts 18, 19 can be punched particularly favorable from the metal strip 20.

If you like the metal band as in the FIG. 3 viewed from left to right, you can see the following. First comes a wide first connector 4 without incision. This is followed by a broad finger-like incision, which extends from the lower edge side 17 in the direction of the upper edge side 16 back, without reaching them. Between the lower edge 17 opposite end of the broad finger-like incision and the upper edge side 16 thus remains in the metal strip 20 is a narrow web 21, also referred to as a folding web 21.

The folding web 21 is adjoined by a narrow finger-like incision which, starting from the upper edge side 16, extends in the direction of the lower edge side 17, again without reaching it.

The finger-like incisions run parallel to each other and perpendicular to the longitudinal direction of the edge sides 16, 17. At the outgoing of the upper edge 16 incision joins outgoing from the lower edge 17 side incision, then again emanating from the upper edge 16 side and back on from the lower edge side 17 outgoing, and then a broad finger-like incision, which extends from the upper edge side 16 in the direction of the lower edge side 17. By the latter wide incision thus created at the lower edge 17 a folding web 22, similar to the folding web 21 as described above. The two folding webs 21 and 22 define between them a partial tape piece 29 in which an interdigital structure is stamped.

The described sequence of narrow and wide cuts continues to the right in the longitudinal direction of the metal strip 20. The partial band piece 29 is adjoined by a partial band piece 30 which lies between the folding web 22 and a further folding web 23 which is again located on the upper edge side 16. Further partial band pieces 31, 32, 33, 34, 35 are each bounded by folding webs 24, 25, 26, 27, 28 lying alternately on the upper and lower edge sides 16, 17. In each of the partial band pieces there is an interdigital structure such as described above. The last folding web 28 is adjoined by a second connecting piece 3 in which there are two narrow cuts and thus form an interdigital structure in the connecting piece 3 only on its first half. The right part of the second connecting piece 3 is without incision and forms a smooth connection surface.

A current path extending from the first connection piece 4 to the second connection piece 3 is forced into a looped or meandering path because of the interdigital structure formed by the cuts 18, 19, so that the flow path lengthens with reduced cross-sectional area and thus the flow path electrical resistance of the metal strip increases. By dimensioning the interdigital structure, for example the number and depth of the narrow incisions, the resistance value of the electrical resistance of the metal strip 20 can thus be adjusted to a desired value.

When the metal band 20 after FIG. 3 is folded transversely to the tape direction at the folding webs 21, 22, 23, 24, 25, 26, 27, 28, so that the folds are formed substantially zig-zag-shaped and are compressed so that the zig-zag course the folds in favor of a substantially parallel to each other in a stacking direction A successively arranged part-tape pieces 4, 29, 30, 31, 32, 33, 34, 35, 3 is overcome, arises in the Figures 1 and 2 shown structure of the resistance element. 2 FIG. 1 shows a resistor 1 with the resistance element 2 in isometric view on the side of the second connector 3, whereas FIG. 2 shows the resistance in isometric view on the side of the first connector 4.

The partial band pieces 4, 29, 30, 31, 32, 33, 34, 35, 3 are in the manner of a sheet stack in parallel and spaced from one another in the stacking direction A. Therefore, the partial band pieces are also generally referred to as partial sheet metal pieces 5, 6, 7, 8, 9, 10, 11. On their narrow sides, they are alternately connected electrically by the folds or folding webs 21, 22, 23, 24, 25, 26, 27, 28. The current path from the first terminal 4 to the second terminal 3 now runs to a certain extent in a double meander, once in the meander on the metal strip 20, as described above, and second in the meandering fold, the stack according to FIGS. 1 and 2 forms.

On their narrow sides, the partial sheet metal pieces 4, 5, 6, 7, 8, 9, 10, 11, 3 held by a holding device 14, 15 of insulating material at a distance. This is here a holding plate from the rib-like retaining walls protrude vertically. The retaining walls fix the partial sheet metal pieces and prevent them from being compressed so far that they could touch each other and thus create a short circuit between adjacent partial sheet metal pieces. Therefore, a separate insulation, such as an insulating layer on the metal strip 20, can be dispensed with. This has the advantage that a higher thermal load capacity of the resistor 1 is given. In fact, an insulating layer would have a lower temperature resistance than the metal strip 20. Also, the holding device can be made of an insulating material with high heat resistance, such as ceramic or a heavy-duty plastic. However, a coating of the metal strip 20 with such a heavy-duty plastic would be too expensive. Another advantage is the small footprint, which thus arises for a heavy-duty resistance element.

The metal strip 20 can be inexpensively manufactured as a stamped and bent part.

The marginal part band pieces 3, 4 are well suited as large-scale fittings. The resistor 1 can be particularly advantageous clamped with contact clamping springs on the two part-tape pieces 3, 4 and thus electrically and mechanically installed at its destination. A good heat dissipation can be achieved via the large-area connection pieces 3, 4, which is advantageous for highly loaded resistors.

• platzsparende Bauform,
• Stanzbiegeteil aus Widerstandsmaterial gut und wirtschaftlich herstellbar,
• Keine Isolation durch Lacke oder andere Isolierschichten erforderlich, dadurch keine Beschränkung der Temperaturbeständigkeit durch Isoliermaterial und thermisch und elektrisch hoch belastbar,
• Gute Wärmeabfuhr durch die großflächigen Kontaktstücke 3, 4,
• Einfache Kontaktierungsmöglichkeit beim Einbau durch Federdruckkontakte.

In the following, advantages of an electrical resistance according to the invention are again summarized:

• space-saving design,
• Stamped bent part made of resistance material good and economically producible,
• No insulation required by paints or other insulating layers, thereby no limitation of the temperature resistance by insulating material and high thermal and electrical loads,
• Good heat dissipation through the large contact pieces 3, 4,
• Easy contacting option when installed by spring pressure contacts.

A resistor according to the invention could also be obtained in a different way than described above by folding a metal strip. It would be possible, for example, to bring partial sheet metal pieces 3, 5, 6, 7, 8, 9, 10, 11, 4 in stacking direction A one behind the other into a holding device 14, 15 and then connect them electrically alternately on their narrow sides on the right and left, for example by one soldered or welded corresponding connectors, or by attaching wire bridges or sheet metal bridges. However, the above-described manner of producing a resistance according to the invention by folding a sheet-metal strip is a very elegant and economical procedure, but the invention should not be limited thereto.

A selective main circuit breaker 40, as shown in the Fig. 4 is shown schematically, has a housing 42 which may be formed either of a cup-shaped housing lower part and a lid or two approximately the same shell halves. Within this housing 42 is a first contact point 41 with a fixed contact piece 44 and a movable contact piece 43. The movable contact piece 43, which is arranged on a pivotable contact lever 45, is pivoted by an electromagnet when a short-circuit current occurs, so that the contact point 41st is opened. This contact point 41 is associated with a parallel current path 46, in which a resistor 1 is located. When the contact point 41 is opened, there arises an arc which migrates into an arc splitter stack 47. In addition, the current is commutated in the parallel current path 46 and limited by the electrical resistance 1. The main circuit breaker 40 can also be switched by hand. For this purpose, he has a handle 53 which cooperates with a rear derailleur 52. The rear derailleur 52 also provides for a permanent open position of the contact point 41. Details of the structure of the rear derailleur and the rest of the internal structure of a main line circuit breaker are known and, for example in the DE 102008016035 A1 to which reference is made in this regard.

The contacting of the resistor 1 by means of ribbon conductors 48 and 49. The conductor 48 may be formed as a straight component, and the conductor 49 may have in the region of the contacting surface 3, 4 of the resistor 1 has a convex portion to the contacting surface. Instead of a rectilinear conductor 48, it is also possible to use one which has a section convex toward the contacting surface 3, 4 of the resistor 1. At least one of the two conductor pieces 48, 49 is resilient. Both conductor pieces 48, 49 can also be resilient. The conductor 49 may be formed so that it with an angled portion 50 and a bend or angle 51, the resistor. 1 holds.

Of course, other known holding and contacting mechanisms can be used. For example, the resistor 1 by a contact spring (not shown here) resiliently contacted and held it. The internal structure of the service switching device 40 is in Fig. 4 only very schematically and exemplified, with many details that are not related to the design or storage of the resistor 1, are not shown. Other known installation switching devices, with different circuit diagram and other spatial arrangement of the inner assemblies are therefore covered by the present invention, as long as they include only one resistor 1 as described in the present invention.

LIST OF REFERENCE NUMBERS

1

electrical resistance

2

resistive element

3

Connecting piece, partial piece of sheet metal, part strip piece

4

Connecting piece, partial piece of sheet metal, part strip piece

5

Part-sheet piece

6

Part-sheet piece

7

Part-sheet piece

8th

Part-sheet piece

9

Part-sheet piece

10

Part-sheet piece

11

Part-sheet piece

14

holder

15

holder

16

edge side

17

edge side

18

finger-like incision

19

finger-like incision

20

metal band

21

Folding bridge, folding

22

Folding bridge, folding

23

Folding bridge, folding

24

Folding bridge, folding

25

Folding bridge, folding

26

Folding bridge, folding

27

Folding bridge, folding

28

Folding bridge, folding

29

Part-piece band

30

Part-piece band

31

Part-piece band

32

Part-piece band

33

Part-piece band

34

Part-piece band

35

Part-piece band

40

electrical installation switchgear

41

first contact point

42

casing

43

movable contact piece

44

fixed contact piece

45

swiveling contact lever

46

Parallel current path

47

Arc splitter stack

48

Ribbon cable conductors

49

Ribbon cable conductors

50

bend

51

fold

52

derailleur

53

shifter

A

stacking direction

Claims (15)

Electrical resistor (1), in particular selective resistor for a selective main circuit breaker, comprising a resistance element (2) and at least two connecting pieces (3, 4) associated with the resistance element (2),
characterized in that the resistance element (2) is formed from a stack of partial sheet metal pieces (3, 5, 6, 7, 8, 9, 10, 11, 4) which consist of a resistance sheet material, the partial sheet pieces ( 3, 5,6,7,8,9,10, 11, 4) are arranged with their broad sides parallel to each other and in the stacking direction one behind the other and spaced from each other, wherein adjacent part sheet metal pieces (3, 5,6,7,8,9 , 10, 11, 4) in the stacking direction alternately on the right and left of a perpendicular to the broad side of the partial sheet metal pieces (3,5,6,7,8,9,10,11, 4) extending imaginary center plane electrically connected to each other at their narrow sides are, so that the current path from the first edge sheet metal piece (3) to the opposite stacking direction, second edge sheet metal piece (4) meandering through the remaining part sheet metal pieces (5,6,7,8,9,10, 11) , Electrical resistor (1) according to claim 1,
characterized in that the first and the second marginal sheet metal piece (3, 4) form the electrical connection pieces. Electrical resistor (1) according to claim 1,
characterized in that the partial sheet metal pieces (3, 5,6,7,8,9,10, 11, 4) are held by means of at least one holding device (14,15) made of insulating material at a distance from each other. Electrical resistor (1) according to claim 1,
characterized in that in the partial sheet metal pieces (3, 5,6,7,8,9,10,11,4) finger-like incisions (18, 19) are formed, which in each case alternately from a first edge side (17, 16) from in the direction of the respective opposite edge side (16, 17) extend, so that the current path in a partial sheet metal piece (3, 5,6,7,8,9,10, 11, 4) between the two narrow sides of a meandering Course takes. Electrical resistor (1) according to claim 1,
characterized in that the resistance element (2) consists of a metal strip (20) which is folded transversely to the strip direction. Electrical resistor (1) according to Claim 5,
characterized in that the folds (21, 22, 23, 24, 25, 26, 27, 28) extending laterally in the strip longitudinal direction are directly adjoining part strip pieces (3, 29, 30, 31, 32, 33, 34, 35, 4) connect with each other. Electrical resistor (1) according to Claim 6,
characterized in that the folds (21, 22, 23, 24, 25, 26, 27, 28) are formed substantially zig-zag-shaped, and that the resistance element (2) is compressed in such a manner in a holding device (14, 15) arranged that the zig-zag-shaped course of the folds (21, 22, 23, 24, 25, 26, 27, 28) in favor of substantially parallel to each other in the stacking direction (A) successively arranged part-band pieces (3, 29, 30, 31, 32, 33, 34, 35, 4) is overcome. Electrical resistor (1) according to claim 7,
characterized in that the resistance element (2) is folded meander-shaped. Electrical resistor (1) according to Claim 8,
characterized in that between adjacent part-tape pieces (3, 29, 30, 31, 32, 33, 34, 35, 4) in the stacking direction (A) is left a gap. Electrical resistor (1) according to Claim 5,
characterized in that the resistance element (2) is a stamped-bent part, wherein the finger-like notches (18, 19) of the partial sheet metal pieces (3, 29, 30, 31, 32, 33, 34, 35, 4) in the metal strip (20) are punched out. Method for producing an electrical resistance (1), characterized by the method steps Punching of finger-like incisions (18, 19) from a metal strip (20) of a resistance sheet material, wherein the finger-like incisions (18, 19) alternately from a first edge side (17, 16) in the direction of the respective opposite edge side (16 , 17) extend, - Substantially zigzag-shaped folding of the metal strip (20) transversely to the tape direction; - Compressed arranged the zigzag-shaped folded metal strip (20) in a holding device (14, 15), so that the zigzag-shaped course of the folds (21, 22, 23, 24, 25, 26, 27, 28 ) in favor of substantially parallel to each other in the stacking direction (A) successively arranged part-tape pieces (3, 29, 30, 31, 32, 33, 34, 35, 4) is overcome. Electrical service switching device (40) having a first contact point (41) which is moved in the open position by a short-circuit of an electromagnetic actuator, and a parallel current path (46) arranged parallel to the first contact point (41), in which a current-limiting resistor (1) is arranged
characterized in that the current-limiting resistor (1) comprises a resistance element (2) and at least two connection pieces (3, 4) associated with the resistance element (2), and in that the resistance element (2) consists of a stack of partial sheet pieces (3, 5 , 6,7,8,9,10, 11, 4), which consist of a resistance sheet material, wherein the partial sheet metal pieces (3, 5,6,7,8,9,10, 11, 4) with their Broad sides parallel to each other and in the stacking direction (A) are arranged one behind the other and spaced from each other, wherein adjacent part-sheet pieces (3, 5,6,7,8,9,10, 11, 4) in the stacking direction (A) alternately right and left one perpendicular to the broad side of the partial sheet metal pieces (3,5,6,7,8,9,10,11, 4) extending imaginary center plane are electrically connected to each other at their narrow sides, so that the current path of the first edge sheet metal piece (4th ) to the stacking direction (A) opposite, second edge sheet metal piece (3) meandering through the remaining part sheet pieces (5,6,7,8,9,10, 11) runs. Electrical service switching device (40) according to claim 12,
characterized in that the resistance element (2) consists of a metal strip (20) which is folded transversely to the belt direction, and that the side in the tape longitudinal direction extending folds (21, 22, 23, 24, 25, 26, 27, 28) directly adjoining part-band pieces (3, 29, 30, 31, 32, 33, 34, 35, 4) interconnect. Electrical service switching device (40) according to claim 13,
characterized in that the folds (21, 22, 23, 24, 25, 26, 27, 28) are formed substantially zig-zag-shaped, and that the resistance element (2) is compressed in such a manner in a holding device (14, 15) is arranged so that the zigzag-shaped course of the folds (21, 22, 23, 24, 25, 26, 27, 28) in favor of substantially parallel to each other in the stacking direction successively arranged part-band pieces (3, 29, 30, 31 , 32, 33, 34, 35, 4) is overcome. Electrical service switching device (40) according to claim 12,
characterized in that at least one conductor section (48, 49), with which the resistor (1) in the parallel current path (46) is turned on, resiliently against the first or the second edge sheet metal piece (3, 4) presses.

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