The invention relates to an electric switching device, such as a relay, comprising a first and a second terminal, a contact sub-assembly having at least two contact members and configured to be moved from a connecting position, in which the contact members contact each other, to an interrupting position, in which the contact members are spaced apart from each other, a current path extending, in the connecting position of the contact sub-assembly, from the first terminal to the second terminal via the contact sub-assembly and being interrupted in the interrupting position of the contact sub-assembly.

Such electric switching devices are generally known from the prior art. If the contact members are in the connecting position, the current path extends continuously through the electric switching device and a current is flowing through the electric switching device along the current path. If the contact members are moved apart, the current path and thus the current flowing through the electric switching device is disrupted.

Electric switching devices, in particular relays, are mass-produced articles which need to be of simple structure and inexpensive to manufacture. Moreover, the switching action should be reliable over many cycles.

The present invention strives to address these issues and aims to provide an electric switching device, such as relay, which is not costly to produce, has a simple structure and is reliable. Further the invention aims to provide a method for actuating an electric switching device. The electric switching device according to the invention further comprises a Lorentz force generator comprising at least two conductor members located in the current path and arranged to generate a Lorentz force acting on the conductor members and wherein the Lorentz force is mechanically translated into an opening force in the contact sub-assembly, the opening force biasing the contact sub-assembly into the interrupting position. The electric switching device according to the invention uses the current flowing through the current path in order to provide a Lorentz force which is mechanically translated into an opening force to move the contact members apart from each other. That enables to design an electric switching device with a simple structure which is inexpensive to manufacture. The electric switching device according to the invention is also reliable over many switching cycles because the generation of a Lorentz force does not lead to mechanic abrasion or other wear at the conductor members. In the prior art, it is known to use the Lorentz force for increasing the contact pressure between the contact members of the contact sub-assembly. The present invention, however, uses the Lorentz force in a different way: the Lorentz force is mechanically translated to interrupt or aid interruption of the current path, e.g. by moving the contact members apart, at a specific point of time (zero current crossing). The Lorentz force may, according to the invention, also be used to move the contact members together to establish contact. As can be seen from specific embodiments discussed below, this does not preclude that the Lorentz force is additionally used for applying contact pressure between the contact members and triggers the interrupting position at a later point in time. The following description of the invention may, independently from one another, lead to further improvements of the electric switching device. If not otherwise indicated, the various features may be combined as required for a specific application of the invention.

For example, the mechanical translation of the Lorentz force into an opening force may be direct in that the conductor member applies the Lorentz force immediately on at least one of the contact members, e.g. by prying them apart. The mechanical translation may also be indirect in that at least one mechanical element is interposed operatively between the Lorentz force generator and the contact sub-assembly. The path of action of the Lorentz force is then extending via the mechanical element to the contact sub-assembly.

The path of action of the Lorentz force, along which the Lorentz force is translated into the opening force, may define a force-flux path. The electric switching device may be a mono-stable or bi-stable relay. The currents in the current path may be in the range of milli-amperes up to several kilo-amperes, depending on the application.

The Lorentz force generator is preferably arranged in series to the contact sub-assembly, i.e. either in front of or behind the contact sub-assembly in the current path. According to another advantageous embodiment, at least one of the conductor members may be configured to be deflected, in a triggered state, by the Lorentz force relative to an initial currentless state. The deflection may be used as a driving motion which translates the opening force to a driven element of the switching device and finally to the contact sub-assembly. The deflection may also be used to load an energy storage, such as a spring member, which then generates the opening force at the contact sub-assembly. In this way, the Lorentz force is translated into the opening force via the spring member. The spring member is located in the path of action of the Lorentz force. The use of an energy storage which is fed by the Lorentz force has the advantage that the opening force may still be applied at the contact sub-assembly after the current path has been disrupted and the Lorentz force has ceased.

The deflectable conductor member may be provided with a fixed end and a moveable end opposite the fixed end. Such a lever-like configuration may be used to increase or decrease the Lorentz force, or to change a movement driven by the Lorentz force.

According to another embodiment, the moveable end of the preferably deflectable conductor member may be provided with at least one contact member, in particular at least one switching contact of the switching device. In such an embodiment, the switching contact may be directly driven by the Lorentz force. The deflectable conductor member may be a trigger spring, which is elastically deformed by the Lorentz force in the triggered, i.e. deflected, state relative to an initial, currentless state. The use of a trigger spring allows to adjust the way in which the Lorentz force is given off by the Lorentz generator. For example, the trigger spring may be configured to have a specific force/deflection characteristic so that the temporal development of the opening force generated at the contact sub-assembly does not need to be linearly proportional to the temporal development of the Lorentz force. If a trigger spring is used, the deflection of the conductor member may be caused, at least in parts, by its elastic deformation. In addition, a rigid body deflection, i.e. a rotation and/or translation, may be superimposed on the deformation.

According to a more specific embodiment, a contact spring, as widely used in relays, may double as the trigger spring.

In one configuration, at least one conductor member may be more rigid than the trigger spring. In particular, the more rigid contact member may be regarded as a rigid body over the operational range of currents of the Lorentz force generator. Alternatively, both or all conductor members of the Lorentz force generator may be configured as trigger springs. In a switching device which is configured for very large currents in the kilo-ampere range, the various components of the current path need to have a large cross-section to safely conduct the current. If a trigger spring is used, the high cross-sectional area needed for the large currents may be detrimental to the flexibility of the trigger spring. To achieve large deflections for a given current in the current path and thus a given Lorentz force, however, the trigger spring needs to have a certain flexibility. In order to obtain such a flexibility, it may be advantageous if the trigger spring comprises a mid-section and end sections where the end sections bordering the mid- section and where the deflectability of the trigger spring is higher in the mid-section than in the end sections. The increased deflectability in the mid-section will lead to an easier deformation of the trigger spring in this area, and thus to large stroke generated by the Lorentz force generator.

If a multi-layered trigger spring that comprises several layers of conductive sheet metal is used, the layers may, at least partly, be non-parallel to each other at the mid-section to increase deflectability there. For example, at least one of the layers may be bent at the mid-section.

According to another embodiment, a pivotable actuating lever may be provided, which is driven by the Lorentz force or the Lorentz force generator, respectively. As explained above, the lever may be used to translate and alter the Lorentz force before it acts on the contact sub-assembly as an opening force. Using a pivotable lever may e.g. be useful if the direction of the Lorentz force has to be reversed. Such a reversal may be accomplished by having a lever which is supported at a mid-section. The actuating lever may double as an over-stroke spring. If a contact spring is used as the trigger spring of the Lorentz force generator, the contact sub-assembly may be used as a bearing point for the actuating lever. The contact sub-assembly may form a bearing point about which the actuating lever is pivoted by the Lorentz force generator. In such an embodiment, the Lorentz force generator may be configured to press the contact members against each other and to trigger an opening force at the contact members, which may later open the contact assembly.

The contact sub-assembly may be used as a support of the deflectable conductor member of the Lorentz force generator in the triggered state.

According to another embodiment, the at least two conductor members may be fixed to one another, preferably at at least one of their ends. The affixation of the at least connector elements to one another is an easy way of connecting them electrically. Of course, the affixation should allow the Lorenz force to be tapped, e.g. by allowing a deflection of at least one of the conductor members.

The at least two conductor members of the Lorentz force generator may be connected in series to obtain a simple configuration of the switching device.

According to another embodiment, the switching device may further comprise an actuator subassembly that is adapted to be driven by the Lorentz force generator, in particular by the Lorentz force, from a closed position to an open position. The actuator sub-assembly may be operatively connected to the contact sub-assembly and be configured to drive the contact sub-assembly at least from the interrupting position to the open position Further, a spring member may be provided, which generates the opening force if the actuator sub-assembly is in the open position and the contact sub-assembly is in the connecting position. In this configuration, the actuator sub-assembly is triggered by the Lorentz force and loads the spring member, which serves as an energy storage. The spring member then effects the actual separation of the contacts, which may occur at a time when a current in the current path has decreased and an attracting Lorentz force which is effective at the contact members decreases below the force exerted by the loaded spring member.

The actuator sub-assembly may, in one embodiment, comprise actuation members such as an electromagnet and an armature which is moved dependent on the magnetic field generated by the electromagnet. In such an actuator sub-assembly, the Lorentz force may be used for driving the actuator in addition or as an alternative to the electromagnetic field generated by the electromagnet.

The spring member is preferably interconnected operatively between the actuator sub-assembly and the contact sub-assembly. The spring member, which is loaded by moving the actuator subassembly from the closed to the open position, may be one of the conductor members, such as the trigger spring. In this configuration, the trigger spring is first deflected due to the Lorentz force and then experiences another deflection due to the action of the actuator sub-assembly. The spring member may, in another configuration, also comprise an over-stroke spring which is used otherwise by the actuator sub-assembly in the closed position to generate a well-defined contact force that presses the contact member together.

The actuator sub-assembly should be stable at least in the open position. This means that no energy is needed to maintain the actuator sub-assembly in the open position. The actuator subassembly thus may snap into the open position once it has been triggered by the Lorentz force. The switching device should, according to another advantageous embodiment, provide an unobstructed deflector volume adjacent to the Lorentz force generator, particularly adjacent to the deflectable conductor member. The deflector volume is preferably configured to receive the at least one conductor member, which is deflected by the Lorentz force in the triggered state.

The invention may also be carried out by a method for actuating the electric switching device. According to the inventive method, a current is provided along a current path in order to generate a Lorentz force which is used to move the contact members apart and/or together. As laid out above, the Lorentz force may load a spring member and the spring member may then push the contact members apart. This latter aspect, which may be implemented by using the actuator sub-assembly, leads to a cascading action in that first, the Lorentz force is generated, which then loads the spring member. Finally, the spring member directs opening force onto the contact members. Thus, the Lorentz force may be translated into the opening force by the intermediate spring member. Instead of the spring member, another kind of force translator, or auxiliary device, may be used.

Such a design may be particularly useful for implementing a safety release mechanism, which interrupts the current path at the contact sub-assembly if a high current such as an over-current is present in the current path. By interrupting the current path, a circuitry or a machinery connected to the electric switching device may be protected from the over-current by maintaining a galvanic separation of the circuit or machinery. A deflection stroke of the conductor member by the Lorentz force may be used as a measure of the over-current.

The spring member may be loaded if a minimum deflection is exceeded and/or may be used as an energy storage to pry the contact members apart after the Lorentz force in the contact sub- assembly has fallen below the opening force. Such a sequence may ensure that the over-current has decreased to a predetermined value before the contact members are separated. Thus, generation of a switching arc between the contact members in the opening process may be reduced, or even avoided.

By adapting the opening force to the Lorentz force, the contact members can be moved apart from each other if a current close to zero, or even exactly zero, is flowing through the current path.

In the following, the invention is exemplarily described with reference to an embodiment using the accompanying drawings. In light of the above-described improvements, it is clear that the various features of the embodiment are shown in their combination only for explanation. For a specific application, individual features may be omitted if their associated advantage as laid out above is not needed.

In the drawings:

Fig. 1 shows a schematic side view of an electric switching device according to the invention in a connecting position; Fig. 2 shows a schematic side view of the electric switching device of Fig. 1 in an interrupting position; Fig, 3 shows a schematic side view of the electric switching device of Figs. 1 and 2 in a triggered state;

Fig. 4 shows the electric switching device of Figs. 1 to 3 in the triggered state;

Fig. 5 shows a schematic rendition of the temporal development of a current switched off by the electric switching device; and

Fig. 6 shows a schematic view of a trigger spring as used in the electric switching device according to the invention.

First, the configuration of the electric switching device according to the invention is explained with reference to Figs. 1 and 2. In Fig. 2, some of the reference signs of Fig. 1 have been omitted for clarity. The electric switching device 1 comprises a first terminal 2 and a second terminal 4, which may be electrically connected to machinery or circuitry (both not shown).

The electric switching device 1 further comprises a contact sub-assembly 6, which includes at least two contact members 8, 10. The contact sub-assembly 6 may be moved from a connecting position 12, in which in the contact members 8, 10 contact each other, to an interrupting position 14 shown in Fig. 2. In the interrupting position 14, the contact members 8, 10 are spaced apart from each other.

In the connecting position, a current path 16 extends in the connecting position 12 between the first and second terminals 2, 4. Thus, an electric current may flow between the first and second terminals 2, 4 along the current path 16. In the interrupting position, the current path is interrupted at the contact sub-assembly and no current may flow between the terminals 2, 4.

The electric switching device 1 further comprises a Lorentz force generator 18, which is explained further below with reference to Figs. 3 and 4. The Lorentz force generator 18 may be connected in series to the contact sub-assembly 6. It may be located in the current path 16 in front of or behind the contact sub-assembly 6. As shown in Figs. 1 and 2, the electric switching device 1 may further comprise an actuator subassembly 20, which may be configured to drive the contact sub-assembly 6 from the connecting position 12 to the interrupting position 14 and back.

The actuator sub-assembly 20 comprises an electromagnetic drive system 22 that acts upon an armature 24, which is moved depending on an electromagnetic field generated by the electromagnetic drive system 22. The actuator sub-assembly may be driven upon switching signals applied to at least one control terminal 26.

The actuator sub-assembly 20 is shown in Fig. 2 in an open position 28, which is associated with the interrupting position 14 of the contact sub-assembly 6 if the Lorentz force generator 18 is inactive. A closed position 30 of the actuator sub-assembly 20 is associated with the connecting position 12 of the contact sub-assembly 6, as shown in Fig. 1 .

The actuator sub-assembly 20 is at least mono-stable in the open position 28. Thus, the actuator sub-assembly 20 rests stably in the open position 28 if no external forces act on the actuator sub-assembly 20 or no external energy is supplied to the control terminal 26. In other variants, the actuator sub-assembly 20 may have more than one stable position, i.e. may be bi- or tri- stable, or may have even more stable states. In a bi-stable configuration, the closed position 30 may also be stable.

In the present example, the stability of the actuator sub-assembly 20 is achieved by positioning a magnet 32, e.g. permanent magnet, in the vicinity of the armature 24, such that the armature 24 stays attracted by the magnet 32 in the interrupting position 14. Other means than a magnet 32, such as a spring, may also lead to a stable open position 28. For attaining the closed position 30, it may be sufficient that the electromagnetic field of the electromagnetic drive system 22 collapses, so that the attractive force of the magnet 32 automatically moves the armature 24 to the open position 30 as shown in Fig. 2. To move the armature 24 from the open position 28 to the closed position 30, the electromagnetic drive system 22 has to build up an electromagnetic field which exerts a force counteracting the attractive force of the magnet 32 on the armature 24. If the force generated by the electromagnetic drive system 22 overcomes the attractive force of the magnet 32, the armature 24 will move into the closed position 30 and thereby drive the contact sub-assembly 6 from the interrupting position 14 to the connecting position 12. The moveability of the electric switching device 1 between the connecting position 12 and the interrupting position 14 is indicated by the double-ended arrow A.

In the following, the configuration of the Lorentz force generator 18 is explained with reference to Figs. 3 and 4. To keep the figures simple, some of the reference numerals of Figs. 1 and 2 have been omitted. Fig. 3 shows the contact sub-assembly 6 in the connecting position, and the actuator subassembly 20 in the close position 12. The Lorentz force generator 18 comprises at least two conductor members 34, 36. The conductor members 34, 36 are preferably located in the current path 16. If an electric current is applied along the current path 16, a Lorentz force 38 is generated which acts between the conductor members 34, 36. The direction of the Lorentz force depends on the direction of the current in the conductor members 34, 36. If the current is of the same direction in the conductor members 34, 36, the Lorentz force 38 will act to attract to the conductor members 34, 36 to each other. Thus, the Lorentz force 38 may directly act on the contact sub-assembly 6 as an opening force 40. In the embodiment shown, the direction of the current in the conductor member 34 is opposite to the direction of the current in the conductor member 36. Thus, the Lorenz force 38 will push the conductor members 34, 36 apart. Although the immediate effect of the Lorentz force 38 will thus result in a closing force 41 at the contact members 8, 10, it is also translated into the opening force 40 by being translated along a force-flux path 42. The mechanical translation may, for example, be effected by mechanically linking the Lorentz force generator 18 to the contact subassembly 6, so that the Lorentz force is translated along the mechanical linkage. In such a configuration, the Lorentz force acts along the force-flux path 42.

As explained below, the mechanical translation may involve the generation of an intermediate actuating force 43 which is used to operate the actuator sub-assembly 20. The actuator sub- assembly 20 may, in turn, generate the opening force 40 upon operation.

As shown in Fig. 3, at least one of the conductor members 34, 36 may be configured to be deflected by the Lorentz force 38 relative to an initial currentless state, which may be the open state 14 shown in Fig. 2. By way of example only, it is the conductor member 34 in the following which is deflected by the Lorentz force 38. The deflectable conductor member 34 is fixed at one end 44, while the other end 46 is moveable. The deflection of the conductor member 30 may in particular be an elastic deformation. If this is the case, the conductor member 30 is a trigger spring 48, of which the deflection will trigger the opening of the contact sub-assembly 6.

As the trigger spring 48, a contact spring may be used as it is usually present in the electric switching devices 1 . If the conductor member 30 is in the deflected state, the moveable end 46 may be supported by the contact sub-assembly 6 in the triggered state as shown in Fig. 3.

The deflection due to the Lorentz force 38 may lead to a curved shape of the conductor member 30 due to the two support points at the fixed end 44 and at the contact sub-assembly 6. The at least two conductor members 34, 36 of the Lorentz generator 18 preferably extend parallel and adjacent to each other, as shown in the figures. This ensures that the Lorentz force 38 is generated with maximum efficiency.

If the conductor members 34, 36 are fixed to each other at the fixed end 44 of the conductor member 30, the conductor members 34, 36 may be connected in series within the current path 16.

According to the embodiment shown in Figs. 1 to 4, the Lorentz force generator 18 is used as part of a safety release mechanism, which automatically transfers the contact sub-assembly 6 from the connecting position 12 to the interrupting position 14 if an over-current is or has been present in the current path 16. As the amount of deflection of the at least one deflectable conductor member 34 depends on the strength of the current running through the current path 16, the disruption of the current path 16 at the contact sub-assembly 6 is initiated only if a predefined maximum deflection is exceeded.

In the present example, however, the Lorentz force 38 acts indirectly on the contact subassembly 6. This is explained in the following. The Lorentz force generator 18 is mechanically linked to the actuator sub-assembly 20, so that the Lorentz force 38 acts on the actuator sub-assembly 20. The linkage may be realized by mechanically coupling the deflectable conductor member 34 directly to the actuator subassembly 20. In the present example, however, the Lorentz force generator 18 is only indirectly coupled to the actuator sub-assembly 20 in that an over-stroke spring 50 is arranged in between. The over-stroke spring 50 forms an actuating lever 52 together with the conductor member 30. While the contact sub-assembly 6 acts as a pivot support for the actuating lever 52. Thus, the deflection of the deflectable conductor member 34 due to the Lorentz force 38 leads to a pivoting motion of the actuating lever 52 about the contact sub-assembly 6. The Lorentz force 38 effects both a pressing together of the contact members 8, 10 by the closing force 43, which thus also act as a bearing point for the actuating lever 52, and a pivoting motion at the side of the actuating lever 52 opposite the Lorentz force generator 18 with respect to the contact subassembly 6. Consequently, the over-stroke spring 50 is moved in the opposite direction as indicated by the arrow 48. Thus, due to the lever-like structure, the Lorentz force 38 is translated at the end of the over-stroke spring 50 into the actuating force 43 of different strength and opposite direction. Via the over-stroke spring 50 and the actuating force 43, the actuator subassembly 20 is biased into the open position 28 and thus triggered.

If the switching device 1 is mono-stable, a very small force acting on the actuator sub-assembly 20 may be sufficient to move it into the open position 28. In case of a bi-stable actuator subassembly 20, which rests stably also in the closed position, the Lorentz force 38, or, more specifically, the actuating force 43 derived therefrom, will need to exceed a threshold for moving the actuator sub-assembly 20 out of the stable closed position.

In Fig. 4, the actuator sub-assembly 20 has been moved into the open position 28 by the Lorentz force 38. In the present embodiment, a spring member 56, such as the over-stroke spring 50, or the trigger spring 48, is arranged between the actuator sub-assembly 20 and the contact sub- assembly 6. Thus, the actuator sub-assembly 20 may assume the open position 28, while the contact sub-assembly 6 still rests in the connecting position 14. This is only possible if the intermediate spring member 56 is loaded.

In the present case, where the trigger spring 48 doubles as an intermediate spring member 56, the deformation of the trigger spring 48 is increased if the actuator sub-assembly 20 is in the open position 28 and the contact sub-assembly 6 is the connecting position 12. As the actuator sub-assembly 20 is stable in the open position 28, it will keep the intermediate spring member loaded until the contact sub-assembly 6 is moved into the interrupting position 14. The load of the spring member 56, is now independent of the Lorentz force and thus from the electric current in the current path 16. The transition from the closed position 12 to the open position 14 as initiated by the Lorentz force generator 18 will occur if the current in the current path 16 has decreased:

The Lorentz force acts in the contact sub-assembly 6 and over compensates the opening force 40 generated by the Lorentz force 38 in the Lorentz force generator 18 if the current in the current path 16 is large enough. If the electric current decreases, the Lorentz force acting in the contact sub-assembly 6 will also decrease until the opening force 40 generated by the spring member 56 is stronger. If this is the case, the contact members 8, 10 will be separated and the trigger spring 14 will relax. The switching device will assume the state shown in Fig. 2, as indicated by arrow D.

Thus, the embodiment shown in Figs. 1 to 4 uses a cascading system where the Lorentz force is not directly acting on the closed contact sub-assembly 6 but is used first to deflect the trigger spring 48 (Arrow B) and then to transfer the actuator sub-assembly 20 into a stable open position 28, while the contact sub-assembly 6 is still in the connecting position 12 (Arrow C). This will load the spring member 56 which is operatively arranged between the actuator subassembly 20 and the contact sub-assembly 6 and generate the opening force 40.

In order to accommodate the deflection of the conductor member 34, an unobstructed deflector volume 57 may be provided adjacent to the Lorentz force generator 18. In the deflected state, the conductor member 34 extends into the deflector volume 57.

As the actuator sub-assembly 20 rests stably in the open position 28 independent of the current in the current path 16, the opening force 40 will still be applied if the current in the current path 16 has decreased. The decrease of the current in the current path 16 will also decrease the local Lorentz force which acts within the contact sub-assembly 6 and presses the contact members 8, 10 together. If the opening force 40 exceeds the local Lorentz force, the contact sub-assembly 6 will be transferred into the interrupting position 14 (Arrow D). Double-ended Arrow A indicates in contrast the normal switching operation.

The advantage of this cascading system is that the opening of the contact members 8, 10 is effected when no or a low current is in the current path 16. Thus, there is no danger of a switching arc being generated if the contact members 8, 10 start to separate.

Therefore, the embodiment shown in Figs. 1 to 4 is especially suited for high-current applications where several thousand amperes are running along the current path 16. But, with accordingly defined relationships of the parts, the function may also be possible with lower currents. Fig. 5 exemplarily shows the behaviour of current I over time t. At a time ti , an over-current l ₀ occurs. While the over-current is present l ₀ , the switching device 1 is transferred into the triggered state, as shown in Figs. 3 and 4. If the current further decreases, the opening force 40 will pry the contacts apart at a time t ₂ and interrupt the current path 16. Thus, starting from time t ₂ , the current I in the current path 16 will be zero. By carefully adjusting the properties of the spring member 56, the interruption of the current path 17 can be set close to a zero current, i.e. 1=0. As the Lorentz force 38 is generated by the Lorentz force generator 18 independent of whether alternating (AC) or direct current (DC) is used, the switching device 1 may be used both for AC and DC applications.

If the currents in the current path 16 are expected to be low such that no switching arc will occur upon separation of the contact members 8, 10, it may not be necessary to use the cascading system as discussed above. Instead, the Lorentz force 38 may be used to directly open the contact members 8, 10.

Further, the actuator sub-assembly 20 does not need to be an actuator sub-assembly 20 that is used to drive the contact sub-assembly 6 upon external signals. It may be configured to be solely driven by the Lorentz force generator 18.

The flexibility of the trigger spring 48 has to be adjusted depending on the over-current l ₀ which leads to the triggered state. As large currents need a large cross-section in the current path 16, the trigger spring 38 may be provided with a mid-section of increased deflectability. This is explained with reference to Fig. 6. In Fig. 6, the trigger spring 38 is shown without the remaining elements of the switching device 1 .

For large currents, the trigger spring 48 may be divided in two or more parallel sections. The trigger spring 38, doubling as a contact spring, may be provided with two contact members 8 and the over-stroke spring 50 opposite the fixed end. At a mid-section 58, which is located between two neighbouring end sections 60 of the trigger spring 38, deflectability may be increased, as indicated by the shaded areas.

If the trigger spring 48 comprises two or more layers 62, 64, the layers may be separated at the mid-section 58, e.g. by bending the layer 56 while keeping the layer 62, 64 straight. This will ensure high flexibility of the trigger spring 30 in spite of large cross-sections needed for high current. Reference Signs

1 electric switching device

2 first terminal

4 second terminal

6 contact sub-assembly

8 contact member

10 contact member

12 connecting position

14 interrupting position

16 current path

18 Lorentz force generator

20 actuator sub-assembly

22 electromagnetic drive system

24 armature

26 control terminal

28 open position

30 closed position

32 magnet

34 (deflectable) conductor member

36 conductor member

38 Lorentz force

40 opening force

41 closing force

42 force-flux path

43 actuating force

44 fixed end

46 moveable end

48 trigger spring

50 over-stroke spring

52 lever

54 arrow

56 spring member

57 deflector volume

58 mid-section of trigger spring

60 end sections of trigger spring

62, 64 layers of trigger spring