The invention concerns a switching contact system for a switching device operated by electric current. The invention is applicable to switching systems such as relays, switches, contactors, switching devices, circuit breakers. Reluctance force elements are used in this context for the generation of a high number of contact movements. This results in a reduction in friction coefficients under high current.

Relays, switches and switching devices must pass a variety high current test. In addition to ensuring the safety of persons and equipment, i.e. that the device does not exhibit or cause any external damage but need not function following the test, there is an increased demand in preserving the switching function following the test. This requires that the switch contacts within the device do not fuse after the test but rather may be opened under normal operating voltage. In addition, the insulation properties of the electrical paths must be retained.

Contact fusion occurs when high current, i.e. a current of several kilo-amperes in most cases, melts the contact alloy locally at one or more contact points in a contact pair and this melting fuses the contact pieces in contact pair when solidifying, especially after cessation of the current.

The circumstance that either repulsion forces from antiparallel current paths or attraction forces from parallel current paths are used in some relays in order to create contact pressure intended to prevent a contact gap during the short-circuit is known. However, this design does not generate enough force to avoid contact fusion which would be possible as a result of very large forces in order to avoid alloy melting or by moving the contacts relative to each other.

Different approaches may be applied in order to avoid the sustained fusion of contact points in switching contacts when carrying very high currents. An initial approach is to increase contact pressure in such a way that the points of contact for the contact pieces are enlarged by pressure. This results in a reduction of contact resistance which likewise reduces local heating. The amount of molten contact material would then be too small to create a bond between the contact pair when its solidifies again. A second possible approach is to generate a force external to the system which is large enough to break any fusion following the current flow. A third approach may avoid the sustained fusion of the switch contacts by using contact systems arranged in parallel to reduce the current through individual contacts. This results in a reduction in heating in each contact system and, consequently, melt quantities. Another approach is to select special contact alloys which become brittle at high currents and the respective fusion may then be easily disengaged. Silver carbide (AgC) contacts can be used for example. However, they are not suitable for high switching cycles whilst bum-up is too high in such cases.

The purpose of the invention is to provide a switching contact system which is capable of preventing or breaking contact fusions in an efficient and cost-effective manner, while still permitting a high number of switching cycles and a miniaturized design. The purpose of the invention is achieved by means of a switching contact system for a switching device operated by electric current having the features of claim 1. Additional embodiments are described in the dependent claims.

The switching contact system according to the invention comprises one or more contact pairs, each of which consists of a first contact piece which is attached to a first electrically conductive component which is stationary relative to the housing of the switching device, and a second contact piece which is movable relative to the first contact piece for the switching function. The contact pieces are positioned relative to each other in such a way, that the second, movable contact piece can be pressed onto the first contact piece by means of a contact force.

Furthermore, the switching contact system according to the invention comprises a flexible and electrically conductive contact piece support with one or more current paths, which is attached and electrically connected with a first end to a second electrically conductive component which is stationary relative to the housing of the switch and which carries the second movable contact piece at a position opposite the first contact piece. The first and second electrically conductive components are usually conductor. The contact force is based at least in part on suspension properties of the flexible contact piece support and/or suspension properties of additional spring elements exerting a spring force on the flexible contact piece support or may also be applied by external drive components, for example by solenoid units.

According to the invention, the switching contact system comprises at least one ferromagnetic element, which - either is stationary relative to the switching device housing and, with respect to a direction of the flexible malleability of the contact piece support, is adjacent to the latter and, at least in the non-deformed state of the contact piece support, is spaced apart from the latter in such a way that, in the activated state, there is an attractive force - between the activated current paths of the contact piece support and the ferromagnetic element or is applied to the contact piece support and with reference to a direction of flexible malleability, a second electrically conductive, flexible contact piece support is arranged adjacent to the contact piece support with the ferromagnetic element and, in the non-deformed state, is spaced apart at least in areas such that, in the activated state, there is an attractive force between the ferromagnetic element and the current paths of the second contact piece support which preferably results in the deformation of the current paths. In an operating state of the switching contact system, at a short-circuit, The contact piece support is bent such an attraction force is caused that moves the second movable contact piece relative to the first contact piece and causes a leverage force such that an initial electrical contact point between the second movable contact piece and the first contact piece is shifted and such that any existing sticking points between the second movable contact piece and the first contact piece are broken up.

The conceptual design of the invention comprises primarily a combination of the first approach mentioned above, namely an increase in contact pressure, with a further approach, namely the generation of an intra-system force which moves the contact pieces of a contact pair towards each other during the current flow. On the one hand, this means that the contact points of one or more contact systems are permanently shifted to non-melted material, and on the other hand, this shifting generates mechanical forces or moments in the contact system that break up any previous fusions.

The effects discussed below are generated by introducing ferromagnetic elements, preferably steel elements. One of these effects is the formation of an attractive force between the activated current paths, also referred to below as layers, and the ferromagnetic elements, which are preferably made of steel. This attractive force is a magnetic reluctance force that occurs at ferromagnetic interfaces and on which the functioning of electromagnets is based. In addition, the attractive force results in a deformation of the flexibly formed current paths to which the movable contact piece, which moves when the contact opens, is attached. This mechanical deformation results in a relative movement of the contact pieces, so that the material melts at ever new locations and, consequently, that melting points remain small. Upon cessation of the current, the mechanical return movement, which occurs due to the potential energy previously stored by the flexible current paths, generates internal system leverage in the form of torque between the contact pieces which loosens any potential fusion. Since the ferromagnetic element, preferably made of steel, is inertially fixed to the device housing, the attractive force between the current path that includes a movable switching contact piece and the ferromagnetic element additionally increases the contact force or contact pressure.

The ferromagnetic elements can be arranged in various ways and must be scaled in conjunction with the number of contact pairs, the type of contact alloy, current path flexibility and high current intensity.

Current path systems with antiparallel current flow will be used according to a preferable embodiment of the invention.

This would permit the elastically deformable and electrically conductive contact piece carrier to be U-shaped or V-shaped in longitudinal section, whereby two opposite spring limbs, which are connected to each other by a connecting area, form the U- or V-limbs. A first spring limb is attached to the second electrically conductive component which is stationary relative to the switch housing, whereas the second, opposing spring limb bears the movable contact piece.

According to an alternative embodiment of the invention which uses a current path system with antiparallel current flow, the flexible and electrically conductive contact piece support is at least partially linear or I-shaped in longitudinal section and is attached at a first end to the second electrically conductive component, which is stationary relative to the switch housing in such a way that the contact piece support and the electrically conductive component form a V-shape in longitudinal section. The movable contact piece is mounted in the vicinity of the second, free end of the contact piece support.

Contact pressure can be further increased by reducing the distance of the antiparallel current paths and the resulting increase in repulsion forces between the current paths by using V-shaped and I-shaped current paths.

According to a preferred embodiment, an additional spring element in the form of an overtravel spring exerting a spring force on the contact piece support is attached to the second electrically conductive component which is stationary relative to the switching device housing and from there exerts a spring force on the contact piece support in the section on the opposite of which the moveable contact piece is located. Alternatively, an additional spring element in the form of an overtravel spring that is attached to a solenoid, itself exerting a spring force, may be used in order to create contact force. Similarly, an additional spring element in the form of an overtravel spring that is located in a connection system between the solenoid and the switching contact system, itself exerting a spring force on the contact piece support, may be used in order to create contact force.

Preferably, the contact piece support will comprise two or three current paths arranged one above the other. However, it may also include more than three current paths. The flexibility of the flexible current paths results from the number, length and cross-section of the current paths and is selected to be as high as possible under consideration of the following marginal conditions. The smallest possible size, high current, heating behaviour, force of the drive as well as the contact head shape, in particular the head radius, are decisive for the design. The ferromagnetic element may be fixed on the side of the contact piece support on which the movable contact piece is located, whereby it is offset from the contact piece support. When current flows through the flexibly formed current paths of the contact piece support, the attractive force causes a deformation of the current paths to which the movable contact piece, which moves when the contact is opened, is attached, in the direction of the ferromagnetic element.

When using a U-shaped contact piece support according to an alternative design, the ferromagnetic element is fixed on the side of the first spring limb of the U-shaped contact piece support which is attached to the second electrically conductive component fixed to the switch housing offset from such spring limb. In this case the current paths in the area of the first spring limb are curved in the direction of the ferromagnetic element.

The ferromagnetic element can be in the form of a straight, i.e. cuboid plate, but also in the form of a plate partially curved in the direction of the contact piece support. In general, the ferromagnetic element can be designed in any relevant form for positioning on or next to the contact piece supports. Preferably the ferromagnetic element is a plate of steel, iron, nickel or cobalt and ferromagnetic alloys thereof.

An alternative design of the current path systems according to the invention is characterised by a parallel current flow resulting in attracting effects of the current paths. Such systems are already being used to increase contact pressure, but this is intended to stiffen the current paths given that this ensures efficient power transmission. However, by introducing ferromagnetic elements in a suitable form on or between the current paths, the attractive forces can also increase the malleability of the current paths and thus the mutual displacement of the contacts. With regard to force generation, nearly the same relationships apply to arrangement and flexibility of the current paths than are applicable to anti-parallel current path systems with the difference that the ferromagnetic element may not only be arranged in a stationary position relative to the contact device but also may be arranged on the contact piece supports.

According to an embodiment of a switching contact system with parallel current flow, a ferromagnetic element is arranged separately between the parallel current paths of the opposing contact piece supports and is stationary in relation to the switching device housing. According to another embodiment of a switching contact system with parallel current flow, one or more ferromagnetic elements are arranged on one or both opposing contact piece supports, preferably on the side of the contact piece support facing outwards, i.e. on the side of the contact piece support which does not face the adjacent contact piece support.

Preferably, the second movable contact piece has a convex contact surface.

Further details, features and advantages of embodiments of the invention are given in the following description of sample embodiments with reference to the corresponding drawings.

The invention shall be explained in detail in one exemplary embodiment by reference to Figures 1 to 11.

Fig. 1: A switching contact system with a contact piece support attached to a long current path with U-shaped current paths and with a ferromagnetic element below the contact piece support,

Fig. 2: A switching contact system with a contact piece support attached to a short current path with U-shaped current paths and with a ferromagnetic element below the contact piece support, Fig. 3: A switching contact system with a contact piece support with U-shaped current paths and antiparallel current flow with ferromagnetic element below the contact piece support in the state of high current flow,

Fig. 4: A switching contact system with a contact piece support with U-shaped current paths and antiparallel current flow with ferromagnetic element above the contact piece support,

Fig. 5: A switching contact system with a contact piece support with U-shaped current paths and antiparallel current flow with a flat cuboid ferromagnetic element below the contact piece support,

Fig. 6: A switching contact system with a contact piece support with U-shaped current paths with a curved ferromagnetic element below the contact side of the contact piece support in a deactivated state,

Fig. 7: A switching contact system with a contact piece support with I-shaped current paths and antiparallel current flow with a curved ferromagnetic element below the contact piece support with an antiparallel current flow of several kilo-amperes,

Fig. 8: A switching contact system with two pairs of opposing contact piece supports for a parallel current flow and a separate ferromagnetic element between the parallel current paths,

Fig. 9: A switching contact system comprising two pairs of opposed contact piece supports for a parallel current flow and two attached ferromagnetic elements on the outward facing sides of the opposing contact piece supports, Fig. 10: An additional switching contact system comprising two pairs of opposed contact piece supports for a parallel current flow and two attached ferromagnetic elements on the outward facing sides of the opposing contact piece supports, and

Fig. 11: A switching contact system comprising two pairs of opposed contact piece supports for a parallel current flow each of which including an attached ferromagnetic element on the outward facing side of the moveable contact piece supports.

Fig. 1 and Fig. 2 each show a switching contact system 1.1; 1.2 with an essentially U-shaped contact piece support 2.1; 2.2. In one embodiment, the switching contact system L I; 1.2 can be used in relays. This contact piece support 2.1; 2.2 is flexible and electrically conductive and is formed by superimposed U-shaped current paths 3.1; 3.2. The U-shaped design of the contact piece support 2.1; 2.2 or the conductors 3.1; 3.2 results in an antiparallel current flow. The U-shaped contact piece support 2.1; 2.2 comprises two vertically arranged, interconnected spring limbs 4.1, 5.1; 4.2, 5.2, a first, upper spring limb 4.1; 4.2 and a second, lower spring limb 5.1; 5.2 as well as a rounded connecting area 6.1; 6.2, the U-base connecting the two spring limbs 4.1, 5.1; 4.2, 5.2 with each other. The switching contact system 1.1; 1.2 switches a contact between a first, stationary fixed contact piece 7 and a second, movable contact piece 8. The movable contact piece 8 is located in the vicinity of an available spring limb end below the second, lower spring limb 5.1; 5.2. Its respective counterpart, the fixed contact piece 7, is conductively connected to a first electrically conductive component 9.1; 9.2 which is stationary relative to the switching device housing. The flexible and electrically conductive contact piece support 2.1; 2.2 is affixed to a second electrically conductive component 10.1; 10.2 that is affixed and electrically connected to the switch housing at a first end. The movable contact piece 8 interacts with the fixed contact piece 7 in such a way that the switching contact system 1.1; 1.2 can be used to switch a circuit. As a result, the two contact pieces 7, 8 can be used to interrupt or close the circuit between the two components 9.1, 10.1; 9.2, 10.2, also referred to as the lower conductor 9.1; 9.2 and the upper conductor 10.1, 10.2, which are stationary in relation to the switching device housing. The two conductors 9.1, 10.1; 9.2; 10.2 are installed in a fixed position in relation to the switching device housing. The U-shaped contact piece support 2.1; 2.2 is firmly affixed to the upper conductor to which it is conductively connected via one spring limb end 4.1; 4.2 of the upper conductor 10.1; 10.2 on the top side of the upper conductor 10.1; 10.2. The stationary contact piece 7 is located directly on the upper side of the lower conductor 9.1; 9.2 to which it is conductively connected. In addition, a switching contact system 1.1; 1.2 according to Fig. 1 and Fig. 2 comprises a ferromagnetic element 11 which is stationary relative to the switching device housing and which, adjacent to it and in the respectively represented non-deformed state of the flexible contact piece support 2.1; 2.2 is offset there from in such a way that an attractive force is formed between the activated current paths 3.1; 3.2 or the flexible contact piece support 2.1; 2.2 and the ferromagnetic element 11 in the activated state. In both of the embodiment shown, the ferromagnetic element 11 is a flat cuboid steel plate located below the spring limb 5.1; 5.2 of the contact piece support carrying the movable contact piece 8, whereby the flat sides of the spring limb 5.1; 5.2 and the ferromagnetic element 11 are arranged opposite each other in the vicinity of the lower spring limb 5.1; 5.2 which is located between the rounded connecting area 6.1; 6.2 and the movable contact piece 8.

The switching contact systems 1.1, 1.2 shown in Fig. 1 and Fig. 2 differ, on the one hand, in the different lengths of the upper spring limb 4.1; 4.2 in relation to the length of a connection limb 12.1; 12.2 of the essentially L-shaped upper connector 10.1; 10.2 depicted in the example shown and, on the other, by the number of U-shaped current paths 3.1; 3.2 of the respective contact piece support 2.1; 2.2. The upper conductor 10.1; 10.2 can also have other shapes, for example it can be straight instead of L-shaped in longitudinal section. According to Fig. 1, the upper spring limb 4.1 of the contact piece support 2.1, comprising only two current paths 3.1, is attached to a relatively long L-connection limb 12.1 of the upper conductor 10.1. To some extent, the connection limb 12.1 is an extension of the U-limb formed by the upper spring limb 4.1 up to the area opposite the attachment location on the movable contact piece 8 on the lower spring limb 5.1. The upper spring limb 4.1 is relatively short compared to the lower spring limb 5.1. At the same time, the spring limb 5.1 is only made up of two current paths 3.1 which are lying on top of each other. This reduces both the length and the cross-section of the flexible contact piece support 2.1, thus lowering costs. Good degrees of mobility or malleability of the contact piece support 2.1 are ensured by distributing the required cross-section over only two current paths.

According to the design in Fig. 2, the upper spring limb 4.2 is comparatively longer and the connecting limb 12.2 of the upper conductor 10.2 is considerably shorter. The end of the upper spring limb 4.2 attached to the connection limb 12.2 extends to the aforementioned part of the connection limb 12.2, which is opposite the area where the movable contact piece 8 is attached to the lower spring limb 5.2. The cross-section of the contact piece support 2.2 is distributed over three current paths 3.2. The greater length of the contact piece support 2.2 results in sufficient mobility or malleability due to the antiparallel current flow and due to the attractive force of the ferromagnetic element 11, including in cases of three current paths 3.2 which are lying on top of each other.

Fig. 3 shows a switching contact system 1.2 with the same structure as in Fig. 2, i.e. with an essentially U-shaped contact piece support 2.2 comprising three U-shaped current paths 3.2 which are lying on top of each other, forming two spring limbs 4.2, 5.2 which are connected to each other via a connection area 6.2. The switching contact system 1.2 switches a contact between a first, stationary fixed contact piece 7 and a second, movable contact piece 8. The movable contact piece 8 is located in the vicinity of an available spring limb end below the second, lower spring limb 5.2. The movable contact piece 8 interacts with the fixed contact piece 7 in such a way that the switching contact system 1.2 can be used to switch a circuit. As a result, the two contact pieces 7, 8 can be used to interrupt or close the circuit between the two components 9.1; 10.2, the lower conductor 9.2 and the upper conductor 10.2, which are stationary in relation to the switching device housing. In addition, the switching contact system 1.2 has a fixed ferromagnetic element 11 in the form of a flat cuboid steel plate which is located below the spring limb 5.2 of the contact piece support 2.2 on which the moveable contact piece 8 is arranged. The flat sides of the spring limb 5.2 and the ferromagnetic element 11 are thus opposite each other in the area of the lower spring limb 5.2 which is located between the rounded connection area 6.2 and the movable contact piece 8. Fig. 3 schematically represents the state of the switching contact system 1.2 with ferromagnetic element 11 during antiparallel current flow. On the one hand, repulsion forces are created between the opposing spring limbs 4.2, 5.2 as a result of the antiparallel current flow resulting from the U-shape of the current paths 3.2. This increases contact pressure between the contact pieces 7, 8 which is intended to prevent contact opening during a short circuit. In addition, in the activated state, an attractive force is created between the activated paths 3.2 of the contact piece support 2.2 and the ferromagnetic element 11 that is depicted by the arrows. The contact piece support 2.2 curves in the vicinity of the lower spring limb 5.2 as a result of this attractive force such that it moves closer to the ferromagnetic element 11. This mechanical bending when current flows through the contact pieces 7, 8 results in relative movement on the part of the contact pieces 7, 8 such that material consistently melts at different locations. Upon cessation of the current, the mechanical return movement, which occurs due to the potential energy previously stored by the flexible current paths 3.2 generates internal system leverage in the form of torque between the contact pieces 7, 8 which loosens any potential fusion. Since the ferromagnetic element 11, preferably made of steel, is inertially fixed to the switching device housing, the attractive force between current flow path 3.2, that includes a movable switching contact piece 8, and the ferromagnetic element 11 additionally increases the contact force or contact pressure.

Fig. 4 shows a switching contact system 1.3 with a contact piece support 2.3 comprising three U-shaped current paths 3.3 for the movable contact piece 8 forming a contact pair with the fixed contact piece 7. The fixed contact piece is conductively connected to a first electrically conductive component 9.3 which is stationary relative to the switching device housing. The U-shaped design of the contact piece support 3.3 results in an antiparallel current flow. In contrast to the designs described above, the ferromagnetic element 11, which is in the form of a cuboid ferromagnetic plate, is arranged above the upper spring limb 4.3 and not below the lower spring limb 5.3 of the contact piece support 2.3. The flat sides of the upper spring limb and the ferromagnetic element 11 are opposite each other in the area of the upper spring limb 4.3 located on an upper conductor 10.3 between the rounded connection area 6.3 and the attachment point of the contact piece support 2.3 comprising the second stationary electrically conductive component 10.3 arranged on the switching device housing.

Fig. 5 shows a switching contact system 1.4 with an essentially I-shaped contact piece support 2.4. This contact piece support 2.4 is flexible and electrically conductive and is formed by one or more, in this case three U-shaped current paths 3.4 which are lying on top of each other. The switching contact system 1.4 switches a contact between a first, stationary fixed contact piece 7 and a second, movable contact piece 8. The fixed contact piece 7 is conductively connected to a first electrically conductive component 9.4 which is stationary relative to the switching device housing. The I-shaped contact piece support 2.4 is attached to a second electrically conductive component 10.4 which is stationary relative to the switching device housing and which is arranged in the form of an elongated fixed or non-flexible conductor preferably by means of a rivet or welded connection. The I-shaped contact piece support 2.4 forms a V-shape in longitudinal section with a pointed apex area together with the stationary electrically conductive component 10.4. The movable contact piece 8 is mounted in the vicinity a free end of the contact piece support 2.4. Compared to the U-shaped versions of the contact piece support, this reduces the distance between the antiparallel current-carrying parts, in this case the I-shaped current paths 3.4 and the stationary electrically conductive component 10.4. This more compact arrangement substantially increases the repulsive forces. In addition, the switching contact system 1.4 has a fixed ferromagnetic element 11 in the form of a flat cuboid steel plate which is located below the I-shaped contact piece support 2.4. This ferromagnetic element 11 is adjacent to the I-shaped contact piece support 2.4 and, is offset from it in the non-deformed state of the flexible contact piece support 2.4 shown here. It is offset from the latter in such a way that, in the activated state, an attractive force is created between the activated current paths 3.4 or the flexible contact piece support 2.4 and the ferromagnetic element 11. In the embodiment shown, the ferromagnetic element 11 is a flat cuboid steel plate located below the I-shaped contact piece support 2.4, whereby the flat underside of the I-shaped contact piece carrier 2.4 and the flat upper side of the ferromagnetic element 1 G oppose each other in parallel in one location of the I-shaped contact piece support 2.4 located between the attachment point of the I-shaped contact piece support 2.5, i.e. the V apex, and the movable contact piece 8. The movable contact piece 8 is fastened in the area of the free end of the contact piece support 2.4 opposite the apex, whereby the I-shaped contact piece support 2.4 is curved at this end 13 in relation to the remaining area of the contact piece support 2.4 in such a way that it is aligned in parallel to the stationary electrically conductive component 10.4 rather than obliquely. An inclined alignment could also be preferred with regard to the curve depending on additional requirements for the switching contact system 1.4.

Fig. 6 shows an additional version of the invention in the form of a switching contact system 1.5, which switches a contact between a first, stationary fixed contact piece 7 and a second, movable contact piece 8. In this embodiment as well, the contact piece support 2.5 is primarily in I-shaped form, however it comprises only two current paths 3.5a, 3.5b from which an internal current path 3.5b is arranged in a straight line in longitudinal section along its longitudinal axis. The other, outer current path 3.5a is predominantly straight in longitudinal section along its longitudinal axis, but in an area adjacent to the apex of the V-shape it has a curve section 14 projecting outwards from its plane extending transversely to the longitudinal axis over the entire width of the I-shaped contact piece support. This curved section 14 is also called a bead. The fixed contact piece 7 is conductively connected to a first electrically conductive component 9.5 which is stationary relative to the switching device housing. The I-shaped contact piece support 2.5 is attached to a second electrically conductive component 10.5 which is stationary relative to the switching device housing and which is arranged in the form of an elongated fixed or non-flexible conductor preferably by means of a rivet and welded connection. The I-shaped contact piece support 2.5 forms a V-shape in longitudinal section with a pointed apex area together with the stationary electrically conductive component 10.5. The curve section 14 of the outer current path 3.5a described above is adjacent to this apex area. In contrast to the embodiment shown in Fig. 5, the first electrically conductive component 9.5, which is stationary relative to the switching device housing, and the second electrically conductive component 10.5, which is stationary relative to the switching device housing, do not run parallel to each other.

In addition, a switching contact system 1.5 according to Fig. 6 comprises a ferromagnetic element I F which is stationary relative to the switching device housing and which, adjacent to it and in the respectively represented non-deformed state of the flexible contact piece support 2.5 is offset there from in such a way that an attractive force is formed between the flexible contact piece support 2.5 and the ferromagnetic element 1 F in the activated state. In the embodiment shown, the ferromagnetic element 1 F is a curved steel plate located below the I-shaped contact piece support 2.5, whereby the flat underside of the I-shaped contact piece carrier 2.5 and the slightly upwardly curved upper side of the ferromagnetic element 1 F oppose each other in one location of the I-shaped contact piece support 2.5 located between the attachment point of the I-shaped contact piece support 2.5, i.e. the V apex, and the movable contact piece 8. As shown in Fig. 6, an additional spring element in the form of an overtravel spring 15 exerting a spring force on the contact piece support 2.5 is attached to the second electrically conductive component 10.5 affixed to the switching device housing. From there, the overtravel spring 15 exerts a spring force on the contact piece support 2.5 in the vicinity on the rear of which the movable contact piece 8 is located. Alternatively or in addition, an overtravel spring 15 can also be arranged in the linear solenoid or the connection system between the linear solenoid and the switching contact system 1.5.

Fig. 7 schematically represents the state of the switching contact system 1.5 with ferromagnetic element I F during antiparallel current flow. On the one hand, the antiparallel current resulting from the V-shaped arrangement of the contact piece support 2.5 exerts repulsion forces on the conductor 10.5. This increases contact pressure between the contact pieces 7, 8 which is intended to prevent contact opening during a short circuit. In addition, in the activated state, an attractive force is created between the activated paths of the contact piece support 2.5 and the curved ferromagnetic element I F. The contact piece support 2.5 curves as a result of this attractive force such that it moves closer to the ferromagnetic element I F. This mechanical bending when current flows through the contact pieces 7, 8 results in strong relative movement on the part of the contact pieces 7, 8 such that material consistently melts at different locations. Upon cessation of the current, the mechanical return movement, which occurs due to the potential energy previously stored by the flexible current paths of the contact piece supports 2.5, generates internal system leverage in the form of torque between the contact pieces 7, 8 which loosens any potential fusion. Since the ferromagnetic element I F, preferably made of steel, is inertially fixed to the switching device housing, the attractive force between contact piece support 2.5, that includes a movable switching contact piece 8, and the ferromagnetic element I F additionally increases the contact force or contact pressure. An alternative design of the current path systems according to the invention is characterised by a parallel current flow resulting in attracting effects of the current paths. Such systems are already being used to increase contact pressure, but this is intended to stiffen the current paths given that this ensures efficient power transmission. However, by introducing ferromagnetic elements in a suitable form on or between the current paths, the attractive forces can also increase the malleability of the current paths and thus reduce contact fusion. Fig. 8 shows a switching contact system 1.6 with several contact piece supports 2.6, more precisely a switching contact system 1.6 with two pairs of opposing contact piece supports 2.6a, 2.6b; 2.6c, 2.6d arranged on both sides of an electromagnet 16 for a parallel current flow. In each case, a ferromagnetic element 11 is arranged separately between the parallel current paths of the opposing contact piece supports 2.6a, 2.6b or 2.6c, 2.6d. With regard to force generation, nearly the same relationships apply to arrangement and flexibility of the current paths than are applicable to anti-parallel current path systems with the difference that the ferromagnetic element 11 may, as shown in Fig. 8, not only be arranged in a stationary position on the switching device housing relative to the contact device but also may be arranged on the contact piece supports 2.6. For example, Fig. 9 and Fig. 10 each show a switching contact system 1.6 with two pairs of opposing contact piece supports 2.6a, 2.6b; 2.6c, 2.6d for a parallel current flow in the current paths of the respective opposing contact piece supports 2.6a, 2.6b; 2.6c, 2.6d, whereby the ferromagnetic elements 11 are arranged on the outward-facing sides of the opposing contact piece supports 2.6. According to the embodiment shown in Fig. 9, the ferromagnetic element 11 forms an additional path or a layer on the contact piece support 2.6 which is designed as a leaf spring, whereby the ferromagnetic element 11 is, in all cases, designed to be somewhat shorter than copper current paths, but extends over the entire free end 17 of the contact piece support 2.6. In this case a ferromagnetic element 11a; l id is located as a further path on each outer side of a so-called primary contact piece support 2.6a; 2.6d which is in turn positioned on the side of the pair of contact piece supports facing outwards in relation to the electromagnet 16. Another ferromagnetic element l ib; l ie is located on the side of the so-called secondary contact piece support 2.6b; 2.6c facing in the direction of electromagnet 16 on the side opposing the primary contact piece support 2.6a; 2.6d. The contact that closes first and opens last is described as the primary contact, whereas the contact that opens first and opens last is described as the secondary contact. The embodiment of the switching contact system with a parallel current path shown in Fig. 10 differs from the embodiments shown in Fig. 9 only in that the ferromagnetic elements 11a, l ib, l ie, l id each extend over the middle section 18, but not the free end 17, of the contact piece support 2.6.

Fig. 11 likewise shows a switching contact system 1.6 with two pairs of opposing contact piece supports 2.6a, 2.6b; 2.6c, 2.6d for a parallel current flow in the current paths of the respective opposing contact piece supports 2.6a, 2.6b; 2.6c, 2.6d, whereby, in contrast to the sample embodiments in Fig. 10, only one ferromagnetic element 11a; 1 Id is affixed per pair of contact piece supports, namely only on the middle section 18 of the outwardly facing side of the respective primary contact piece support 2.6a, 2.6d.

Fig. 9 to Fig. 11 show sample embodiments for switching contact systems 1.6 with a parallel current flow, in which one or more ferromagnetic elements 11 are arranged on the contact piece support 2.6 and, with reference to one direction of flexible malleability, a second electrically conductive, flexible contact piece support 2.6a; 2.6b; 2.6c; 2.6d is arranged adjacently and, in the non-deformed state, is offset, at least in part, in such a way that, in the activated state, there is an attractive force that curves the current path in place between the ferromagnetic element 11 and the flexible current paths of the respectively opposing second contact piece supports 2.6a; 2.6b; 2.6c; 2.6d that results in relative movement on the part of the contact pieces and reduces fusion. List of reference symbols

1.1 Switch contact system

1.2 Switch contact system

1.3 Switch contact system

1.4 Switch contact system

1.5 Switch contact system

1.6 Switch contact system (with parallel current flow)

2.1 Contact piece support, U-shaped

2.2 Contact piece support, U-shaped

2.3 Contact piece support, U-shaped

2.4 Contact piece support, I-shaped

2.5 Contact piece support, I-shaped

2.6 Contact piece support (for parallel current flow)

2.6a Contact piece support (primary contact)

2.6b Contact piece support (ancillary contact)

2.6c Contact piece support (ancillary contact)

2.6d Contact piece support (primary contact)

3.1 Current path for a U-shaped contact piece support

3.2 Current path for a U-shaped contact piece support

3.3 Current path for a U-shaped contact piece support

3.4 Current path for an I-shaped contact piece support

3.5 Current path for an I-shaped contact piece support

3.5a External current path for an I-shaped contact piece support 3.5b Internal current path for an I-shaped contact piece support

4.1 Upper spring limb for a U-shaped contact piece support

4.2 Upper spring limb for a U-shaped contact piece support

4.3 Upper spring limb for a U-shaped contact piece support

5.1 Lower spring limb for a U-shaped contact piece support

5.2 Lower spring limb for a U-shaped contact piece support .3 Lower spring limb for a U-shaped contact piece support .1 Connection area of a U-shaped contact piece support

.2 Connection area of a U-shaped contact piece support

.3 Connection area of a U-shaped contact piece support

Stationary contact piece, fixed contact piece

8 Moveable contact piece

.1 First stationary electrically conductive component, lower conductor .2 First stationary electrically conductive component, lower conductor .3 First stationary electrically conductive component, lower conductor .4 First stationary electrically conductive component, lower conductor .5 First stationary electrically conductive component, lower conductor

10.1 Second stationary electrically conductive component, upper conductor

10.2 Second stationary electrically conductive component, upper conductor

10.3 Second stationary electrically conductive component, upper conductor

10.4 Second stationary electrically conductive component, upper conductor

10.5 Second stationary electrically conductive component, upper conductor 11 Ferromagnetic element

1 G Curved ferromagnetic element

11a Ferromagnetic element (on primary contact piece support)

1 lb Ferromagnetic element (on ancillary contact piece support)

11c Ferromagnetic element (on ancillary contact piece support)

l id Ferromagnetic element (on primary contact piece support)

12.1 Connection limb

12.2 Connection limb

13 End section of the I-shaped contact piece support

14 Protruding curve section

15 Overtravel spring

16 Electromagnet

17 End section of a contact piece support 18 Mid-section of a contact piece support