Contact arrangement for a switching element and switching element

Abstract

The present invention relates to a contact arrangement (2) for a switching element (1), wherein the contact arrangement (2) has an electrically conductive contact bridge (26) which is movable along a switching direction (38) and two contact groups (18a, 18b) which are spaced apart from one another, wherein each of the two contact groups (18a, 18b) has an electrically conductive, stationary fixed contact (16) and an electrically conductive switching contact (20) which is arranged on the contact bridge (26) and can be contacted with the associated fixed contact (16), wherein the contact bridge (26) has a closed position (34), an open position (32) and a short-circuit position (36), and wherein in the closed position (34) the switching contacts (20) of the two contact groups (18a, 18b) electrically contact the respective associated fixed contacts (16), in the open position (32) the switching contacts (20) of the two contact groups (18a,18b) have a predefined contact distance (D) measured in the switching direction (38) from the respective associated fixed contacts (16), and in the short-circuit position (36), there is a contact overtravel clearance (d) measured in the switching direction (38) between the switching contacts (20) of the two contact groups (18a, 18b) and the respective associated fixed contacts (16), which is at most one-thirtieth of the predefined contact distance (D) from the open position (32). Due to the proximity of the switching and fixed contacts in the short-circuit position, arcs occurring in the contact groups can be kept short or small. Furthermore, the present invention relates to a switching element with such a contact arrangement.

Description

[0001] The present invention relates to a contact arrangement for a switching element, for example, an electrical DC switching element, such as a high-voltage contactor or relay. Furthermore, the present invention relates to a switching element with such a contact arrangement. Furthermore, the invention relates to a method for adjusting a contact overtravel in such a switching element.

[0002] In many areas of technology, electrical circuits are opened and closed for control purposes using switching elements. Usually, related contact elements are separated from each other or brought into contact with each other by a drive device. When closed, an electric current can flow through the circuit and operate electrical devices and modules arranged in the circuit. Opening the circuit, in turn, interrupts the current flow, allowing the circuit's operation to be stopped if necessary.

[0003] In many applications, for example, in electromobility, a short circuit in an electrical circuit can lead to an excessively high current flow, which inevitably also flows through the contact elements of the switching element. This so-called short-circuit current usually flows until an electrical fuse (e.g., a safety fuse) in the circuit is triggered. At least during this reaction time of the fuse, the short-circuit current endangers not only the switching element and all other components of the circuit, but also the surroundings of the circuit.

[0004] There is therefore a need for electrical switching elements that can withstand short-circuit currents for as long as possible without endangering people or the environment.

[0005] The object of the present invention is therefore to provide means which increase the safety in general and the resistance to short-circuit currents in particular in electrical switching elements.

[0006] This object is achieved by a contact arrangement of the type mentioned at the outset, wherein the contact arrangement has an electrically conductive contact bridge movable along a switching direction and two contact groups spaced apart from one another, wherein each of the two contact groups has an electrically conductive, stationary fixed contact and an electrically conductive switching contact arranged on the contact bridge and contactable with the associated fixed contact, wherein the contact bridge has a closed position, an open position and a short-circuit position, and wherein in the closed position the switching contacts of the two contact groups electrically contact the respective associated fixed contacts, in the open position the switching contacts of the two contact groups have a predefined contact distance measured in the switching direction from the respective associated fixed contacts,and in the short-circuit position between the switching contacts of the two contact groups and the respective associated fixed contacts there is a contact overtravel clearance measured in the switching direction which is at most one thirtieth of the predefined contact distance from the open position.

[0007] In other words, in the closed position, there is two-way contact, with both contact groups closed. And in the open position, the respective switching and fixed contacts of the two contact groups are at least thirty times as far apart as in the short-circuit position, which is limited or defined by the contact overtravel. The switching and fixed contacts of the two contact groups are correspondingly close in the short-circuit position.

[0008] The present invention is advantageous because, due to the short-circuit position of the contact bridge, the contact arrangement can be placed in a state in which the contact arrangement can survive a short circuit in the circuit for as long as possible without damage, or at least without dangerous damage. A switching element with the contact arrangement according to the invention also "survives" such a short circuit event correspondingly undamaged, at least until the circuit's fuse blows.

[0009] In particular, the proximity of the switching and fixed contacts of both contact groups in the short-circuit position serves to keep arcs occurring between the respective switching and fixed contacts as short or small as possible in the event of a short circuit. This limitation of the respective arc extension reduces or limits the arc voltage and, accordingly, the power dissipated by the arcs. Thus, the destructive power input from the arcs into the switching element is kept as low as possible.

[0010] In addition, due to the comparatively close proximity of the switching and fixed contacts, the arcs require more time to escape from the respective contact group to the outside, causing damage to the rest of the contact arrangement or switching element due to the resulting voltage increase. This means that the destructive power input from the arcs is not only reduced but also delayed by the contact bridge in the short-circuit position (in the best case, until the fuse blows).

[0011] Finally, the proximity of the switching and fixed contacts in the short-circuit position also mitigates the influence of any blow-out magnets installed in the switching element next to the contact arrangement. This will be explained in more detail below with reference to the switching element according to the invention.

[0012] Overall, the damage caused by arcs is reduced and less dangerous. Damage to the switching element can be considered harmless as long as no bursting or flame or smoke emission is observed. However, after such a short circuit, replacement of the contact arrangement or the entire switching element may be necessary if further use is no longer possible due to damage.

[0013] The invention can be further improved by the following embodiments, each of which is advantageous in itself and can be combined with one another as desired.

[0014] According to a first possible embodiment, the contact arrangement can be designed such that, when a short-circuit current flows through the contact arrangement, the contact bridge moves independently from the closed position to the short-circuit position solely due to the repulsive forces occurring within the contact groups and without the aid of any drive devices of the switching element. In particular, these repulsive forces can separate the contact bridge, including the switching contacts, from the fixed contacts and move them into the short-circuit position, so that no sensors, controllers, actuators, or other devices causing dead time need to be involved. The repulsive forces are caused by current-induced forces, such as the Lorentz force, and act instantly on the contact bridge when the short circuit occurs.

[0015] The drive mechanism of the switching element mentioned above can be used to move the contact bridge from the closed position to the open position. This will be explained in more detail below with reference to the switching element according to the invention.

[0016] Preferably, the contact overtravel clearance in the short-circuit position is at most one-thirtieth of the clearance and creepage distance specified by the standard for the contact arrangement (e.g., according to DIN EN 60664-1 (VDE 0110-1)). The switching and fixed contacts can be separated from each other by an opening gap in the open position and by a levitation gap in the short-circuit position. The opening gap can correspond to the specified clearance and creepage distance and, for example, for certain applications, have a length of 3 mm + / - 10% measured in the switching direction. As long as the specified clearance and creepage distances are maintained, the opening gap can also be less than 3 mm + / - 10%, depending on the application.

[0017] The levitation gap, on the other hand, is at least thirty times smaller, so that the contact overtravel clearance in the short-circuit position for an opening gap of 3 mm + / - 10% is a maximum of 0.1 mm + / - 10%. This length of the levitation gap is also measured in the switching direction and ensures that the arcs that occur in the event of a short circuit remain particularly short or small.

[0018] Of course, the length of the levitation gap can also be chosen to be even shorter, for example, no more than 100 µm + / - 10%, in particular no more than 20 µm + / - 10%, and above all no more than 10 µm + / - 10%. In other words, the levitation gap can be 300 times, in particular 1500 times, and above all 3000 times smaller than the opening gap. It is also conceivable to limit the length of the levitation gap to 0 µm, subject to unavoidable manufacturing tolerances. This means that the switching contacts of the two contact groups then electrically contact the corresponding fixed contacts in the short-circuit position, so that the closed position and the short-circuit position coincide, and no detectable arcing occurs.

[0019] The contact bridge is preferably a rod-shaped or bar-shaped component that extends along a longitudinal direction of the contact bridge. The longitudinal direction of the contact bridge can be perpendicular to the switching direction. The two contact groups can be spaced apart from each other accordingly in the longitudinal direction of the contact bridge and perpendicular to the switching direction. This creates a sufficiently large distance between the contact groups, which, when the contact bridge is in the open position, prevents unwanted current flashover from the fixed contact of one contact group to the fixed contact of the other contact group.

[0020] According to another possible embodiment, the contact bridge can be movably held in a support structure. In particular, the contact bridge can be movably held in the support structure between a first stop point and a second stop point, wherein the first stop point is arranged closer to the fixed contacts than the second stop point. For the sake of simplicity, the first stop point will be referred to as the upper stop point and the second stop point as the lower stop point.

[0021] The support structure can stabilize the movement of the contact bridge, while the respective stop points define the open and short-circuit positions. For example, in the open position, the contact bridge rests against the upper stop point and in the short-circuit position, against the lower stop point, provided the repulsion forces in the event of a short circuit are sufficiently large. In the closed position, the contact bridge is located between the upper and lower stop points. The closed position is defined by the position of the contacting switching and fixed contacts of the two contact groups.

[0022] According to another possible embodiment, the support structure can have an overtravel spring, which preloads the contact bridge toward the upper stop point. The upper stop point serves to prevent the contact bridge from falling out of the support structure. The overtravel spring, in turn, makes it possible to compensate for positional tolerances, manufacturing tolerances, and operational wear that occur between the two contact groups. Furthermore, the overtravel spring can be used in the inventive method for adjusting a contact overtravel of the contact arrangement described above, as explained below.

[0023] The method comprises the steps of fixing the holding structure to a shaft of the drive device of the switching element, positioning the contact bridge located at the upper stop point in the open position, moving the shaft along the switching direction until the contact bridge still located at the upper stop point reaches the closed position, further pushing the shaft along the switching direction against the spring force of the overtravel spring until the contact bridge in the closed position reaches the lower stop point, retracting the shaft by a length which is at most one thirtieth of the distance traveled during the moving and further pushing, and fixing the shaft to an armature of the drive device.The armature, in turn, is fixed in a position where it rests on a core of the drive mechanism, and where the overtravel spring is compressed or pressed together by the desired contact overtravel when the contact groups are closed. In particular, by retracting the shaft, the desired contact overtravel is set so that the contact bridge has a short-circuit position in addition to the open and closed positions.

[0024] According to an easily manufactured embodiment, the contact arrangement can have at least one blocking element against which the contact bridge abuts in the short-circuit position. Advantageously, the position of the at least one blocking element allows the contact overtravel clearance in the short-circuit position or the length of the levitation gap to be easily adjusted. In this case, the at least one blocking element preferably points toward the fixed contacts of the two contact groups along the switching direction. In particular, the lower stop point can be defined by the at least one blocking element.

[0025] To ensure that the desired contact overtravel clearance in the short-circuit position or the length of the levitation gap is not exceeded in the event of a short circuit, a travel gap can be provided between the contact bridge in the closed position and the at least one blocking element. The length of the travel gap, measured in the switching direction, corresponds to the desired contact overtravel clearance in the short-circuit position. Consequently, the repulsion forces acting in the event of a short circuit can only move the contact bridge out of the closed position by the length of the travel gap, at least as long as the repulsion force remains smaller than the holding force of the drive device.

[0026] A compact, space-saving design is achieved when at least one blocking element is rod-shaped and the overtravel spring is designed as a helical spring, spiral spring, or compression spring that extends coaxially with the rod-shaped blocking element. The rod-shaped blocking element can thus at least partially occupy the interior of the overtravel spring and does not require any additional installation space. With the contact bridge resting against the upper stop point, a length difference measured in the switching direction between the overtravel spring and the rod-shaped blocking element corresponds to the desired contact overtravel clearance in the short-circuit position.

[0027] Optionally, the support structure can include a cage in which the contact bridge is movably held (and, if present, also the overtravel spring and the rod-shaped blocking element). However, instead of the rod-shaped blocking element, the cage can also form the at least one blocking element and thus define the lower stop point. Furthermore, the cage can enclose the contact bridge and also define the upper stop point. This means that the cage fulfills a multiple function.

[0028] The contact bridge and the cage can have complementary guide elements, with the guide element of the cage adjacent to the at least one blocking element of the cage in the switching direction, and the guide element of the contact bridge aligned with the at least one blocking element of the cage in the switching direction. For example, the guide element of the cage can be implemented by a guide gap extending through the cage on one side relative to the contact bridge in the switching direction. Optionally, the cage can also be provided with guide gaps on both sides relative to the contact bridge.

[0029] For each guide gap of the cage, the contact bridge can have a projection as a guide element, wherein the projection is movably held in the associated guide gap. In particular, each projection can be linearly movable in the associated guide gap between an upper end and a lower end of the guide gap. In this case, the upper end is closer to the fixed contacts than the lower end, viewed in the switching direction.

[0030] The upper end of the guide gap preferably defines the upper stop point. The lower end of the guide gap can, in turn, form the cage's blocking element, which defines the lower stop point.

[0031] In order to utilize the contact force applied by the drive device of the switching element as fully as possible in the closed position, all contact surfaces of the fixed and switching contacts of both contact groups can run perpendicular to the switching direction and parallel to each other.

[0032] The fixed contacts and switching contacts can each be plate-shaped, lens-shaped, or dome-shaped contact elements. Within a contact group, the number of switching contacts and the number of fixed contacts can be the same or different. The switching contacts are attached to the contact bridge, in particular by welding, soldering, pressing, or screwing. To adequately maintain the aforementioned distance between the contact groups, the switching contacts can each be arranged at one end of the contact bridge.

[0033] In contrast to the contact bridge and the switching contacts, the stationary fixed contacts are fixed in place and cannot be moved without damaging them. For example, the fixed contacts can be mounted in a housing in which the contact bridge and the contact groups are located. For reasons of electrical safety, the housing is preferably made of an electrically non-conductive material.

[0034] The object underlying the above is also achieved by a switching element if it has a contact arrangement according to one of the above embodiments and further comprises a drive device which is designed to move the contact bridge of the contact arrangement between the closed position and the open position, wherein the drive device has a deactivated state in which the contact bridge is in the open position and an activated state in which the contact bridge can be in the closed position or in the short-circuit position.

[0035] The switching element represents a unit that can be directly inserted into an electrical circuit and, thanks to the functionality and advantages of the contact arrangement already explained, can safely withstand a short circuit. Consequently, the switching element is characterized by increased safety and resistance to short-circuit currents.

[0036] Furthermore, in the activated state of the drive device, the switching element can have both normal operation and short-circuit operation. In normal operation, an operating current flows through the two contact groups and the contact bridge in the closed position. In short-circuit operation, a short-circuit current that is higher than the operating current flows through the two contact groups and the contact bridge in the short-circuit position. Consequently, the switching element can withstand short-circuit currents that exceed the operating current. The short-circuit current also flows through the arcs that form in both contact groups in the event of a short circuit.

[0037] The switching element can have one or more blow-out magnets, each assigned to one of the two contact groups. When the contact bridge is moved from the closed position to the open position during normal operation, the blow-out magnets serve to expand and sever any arcs generated by the operating current and any plasma that may occur as a result of them, using magnetic force. Specifically, the arc root points are shifted along the respective contact surfaces of the fixed and switching contacts towards one surface edge. At the same time, the plasma is forced out of the associated opening gap and extends further outside the opening gap until it breaks and the current flow stops. This means that the blow-out magnets are each designed to blow out any arc that may occur in the opening gap of the associated contact group.

[0038] In particular, the expanding effect of the blow-out magnets would be counterproductive in the event of a short circuit, as the arcs are intended to be kept short or small. Advantageously, the aforementioned proximity of the switching and fixed contacts of both contact groups in the short-circuit position mitigates this expanding effect. Due to the intense heat generated, the aforementioned arc bases are surrounded by boiling contact material emitting metal vapor. Furthermore, opposing arc bases are so close to each other that the emitted metal vapor completely permeates and / or envelops the plasma of the respective arc. Accordingly, the metal vapor content of the plasma is high during short-circuit operation compared to normal operation. This high metal vapor content causes the plasma to remain in the short-circuit gap despite the magnetic force exerted by the blow-out magnets.

[0039] In the following, the invention is explained in more detail with reference to the drawings using several embodiments, the different features of which can be combined with one another as desired in accordance with the above remarks.

[0040] They show: Fig. 1 a schematic perspective sectional view of an electrical switching element according to the invention according to an exemplary embodiment; Fig. 2 a schematic side view of a contact arrangement according to an exemplary embodiment; Fig. 3 a schematic detailed view of the contact arrangement from Fig. 2; Fig. 4 a further schematic detailed view of the contact arrangement from Fig. 2; Fig. 5 a schematic perspective view of a contact arrangement according to another exemplary embodiment; Fig. 6 a schematic perspective view of a contact arrangement according to another exemplary embodiment; Fig. 7 a further schematic perspective view of the contact arrangement from Fig. 6; and Fig. 8 a further schematic perspective view of the contact arrangement from Fig. 6.

[0041] The schematic structure of an electrical switching element 1 according to the invention and of a contact arrangement 2 according to the invention is described with reference to the Fig. 1 to 8. The switching element 1 can be, for example, an electrical DC switching element 4, such as a high-voltage contactor or relay. However, the present invention is not limited to DC and / or high-voltage applications and can also be used in other electrical switching devices.

[0042] The contact arrangement 2 can, as in Fig. 1, be part of the switching element 1. In particular, the contact arrangement 2 can be installed in a housing 6 of the switching element 1 and / or have its own housing, preferably made of electrically non-conductive material.

[0043] Furthermore, a drive device 8 is installed in the housing 6 and is at least partially connected to the contact arrangement 2 in a force-transmitting manner.

[0044] The switching element 1 can be installed in an electrical circuit (not shown) to be controlled. For this purpose, the switching element 1 has two connection sections 10a, 10b, each spaced apart from one another and arranged on an outer side 12 accessible from outside the housing 6. Furthermore, the connection sections 10a, 10b are configured on their respective outer side 12 to receive an electrical conductor (not shown) or a fixing element (not shown) of the electrical conductor.

[0045] As in Fig. 2, an electrically conductive, stationary fixed contact 16 of the contact arrangement 2 can be attached to an inner side 14 of the connection sections 10a, 10b opposite the outer side 12 and held stationary with respect to the housing 6. Each fixed contact 16 belongs to one of two contact groups 18a, 18b of the contact arrangement 2.

[0046] The two contact groups 18a, 18b are spaced apart from one another similarly to the connection sections 10a, 10b and each have an electrically conductive switching contact 20 that can be contacted with the associated fixed contact 16. The fixed contacts 16 and switching contacts 20 can each be plate-shaped contact elements 22, although lens-shaped, dome-shaped, or other shaped contact elements are also conceivable. Each fixed contact 16 and the associated switching contact 20 create a contact point 24 or a contact location when contacted (see Fig. 3).

[0047] A movable, electrically conductive contact bridge 26 extends between the two contact groups 18a, 18b. Preferably, the contact bridge 26 is a rod-shaped or bar-shaped component 28 that extends along a contact bridge longitudinal direction 30. The two contact groups 18a, 18b and the connecting sections 10a, 10b are spaced apart from one another in the contact bridge longitudinal direction 30.

[0048] The switching contacts 20 of both contact groups 18a, 18b are arranged on the contact bridge 26. In particular, the switching contacts 20 can be welded, soldered, pressed, riveted, or screwed to the contact bridge 26. Likewise, the fixed contacts 16 can be welded, soldered, pressed, or screwed to the connection sections 10a, 10b.

[0049] Alternatively, the switching contacts 20 can be an integral part of the contact bridge 26 or applied thereto as a coating. Likewise, the fixed contacts 16 can also be an integral part of the respective connection section 10a, 10b or applied thereto as a coating.

[0050] The contact bridge 26 has an open position 32, a closed position 34, and a short-circuit position 36. Between the open position 32 and the closed position 34, the contact bridge 26 is preferably linearly movable along a switching direction 38. The drive device 8 can be used for this movement.

[0051] In other words, the drive device 8 can be configured to move the contact bridge 26 between the closed position 34 and the open position 32. In particular, the drive device 8 can have a deactivated state 40, in which the contact bridge 26 is in the open position 32, and an activated state 42, in which the contact bridge 26 can be in the closed position 34 or in the short-circuit position 36.

[0052] As in Fig. 1 and Fig. 2, the switching contacts 20 of the two contact groups 18a, 18b are spaced apart from the respective associated fixed contacts 16 in the open position 32. In particular, the switching contacts 20 in the open position 32 have a predefined contact distance D measured in the switching direction 38 from the respective associated fixed contacts 16. In this case, the switching contacts 20 and fixed contacts 16 in the open position can be spaced apart by an opening gap 44. The opening gap 44 can correspond to a standardized air and creepage distance and, for example, for certain applications, have a length of 3 mm + / - 10% measured in the switching direction 38. This means that no electrical current can flow between the connection sections 10a, 10b via the contact bridge 26 or any current flowing up to that point is interrupted. The circuit is accordingly open.

[0053] Depending on the application, the opening gap 44 can also be less than 3 mm + / - 10%, as long as the specified clearance and creepage distances are maintained. Contact arrangement 2 can then be dimensioned accordingly to be more compact and space-saving.

[0054] In the closed position 34, the switching contacts 20 of the two contact groups 18a, 18b electrically contact the respective fixed contacts 16 (see Fig. 5 to 7). This closes the circuit, allowing the electrical current to flow between the terminal sections 10a, 10b via the contact bridge 26. The closed position 34 represents the normal operation of the switching element 1, in which an operating current flows through the terminal sections 10a, 10b, the contact groups 18a, 18b, and the contact bridge 26.

[0055] In order to utilize the contact force originating from the drive device 8 as completely as possible in the closed position 34, all contact surfaces of the fixed contacts 16 and switching contacts 20 can run perpendicular to the switching direction 38 and parallel to each other (see Fig. 2).

[0056] The short-circuit position 36 is intended for the case that a short circuit occurs in the circuit and causes a short-circuit current that is higher than the operating current. In the short-circuit position 36, a contact overtravel clearance d measured in the switching direction 38 lies between the switching contacts 20 of the two contact groups 18a, 18b and the respective associated fixed contacts 16, which is at most one-thirtieth of the predefined contact distance D from the open position 32 (see Fig. 4 and Fig. 8). Switching element 1 is then in short-circuit operation.

[0057] Preferably, the contact overtravel clearance d in the short-circuit position 36 is at most one-thirtieth of the normal opening width for the contact arrangement 2. The switching contacts 20 and fixed contacts 16 can be spaced from each other in the short-circuit position 36 by a levitation gap 46. The levitation gap 46, or its length measured in the switching direction 38, is at least thirty times smaller than the opening gap 44. With the aforementioned contact spacing D in the open position 32 of 3 mm + / - 10%, the contact overtravel clearance d in the short-circuit position 36 is correspondingly at most 0.1 mm + / - 10%.

[0058] The proximity of the switching contacts 20 and the fixed contacts 16 in the short-circuit position 36, as just described, ensures that arcs occurring between them are kept as short or small as possible. Thus, the destructive power input from the arcs is comparatively low, so that the switching element 1 can withstand a short circuit in the circuit for as long as possible without damage, or at least without dangerous damage.

[0059] The contact arrangement 2 can be designed such that, when a short-circuit current flows through the contact arrangement 2, the contact bridge 26 moves independently and without the assistance of the drive device 8 from the closed position 34 to the short-circuit position 36 solely due to the repulsive forces occurring within the contact groups 18a, 18b. While the drive device 8 can certainly be in its activated state 42, it does not itself perform any additional movement. Rather, the repulsive forces can separate the contact bridge 26, including the switching contacts 20, from the fixed contacts 16 and move them into the short-circuit position 36.

[0060] The movement of the contact bridge 26 can be stabilized by a holding structure 48 of the contact arrangement 2, wherein the contact bridge 26 is held movably in the holding structure 48.

[0061] In particular, the contact bridge 26 can be movably held in the holding structure 48 between an upper stop point 54a and a lower stop point 54b, wherein the upper stop point 54a is arranged closer to the fixed contacts 16 than the lower stop point 54b.

[0062] In the exemplary embodiments shown, the contact bridge 26 is in the open position 32 at the upper stop point 54a (see Fig. 2) and in the short-circuit position 36 at the lower stop point 54b (see Fig. 4 and Fig. 8). In the closed position 34, the contact bridge 26 is located between the upper stop point 54a and the lower stop point 54b. The closed position 34 is defined by the position of the contacting switching contacts 20 and fixed contacts 16.

[0063] The holding structure 48 of the exemplary embodiments shown has an overtravel spring 52, with which the contact bridge 26 is pretensioned toward the upper stop point 54a. The compression of the overtravel spring 52 generates the contact force and, in turn, makes it possible to compensate for positional differences, manufacturing tolerances, and operational wear between the two contact groups 18a, 18b. For example, a closing force generated by the drive device 8 can be 120 N + / -10%. Of this, the contact bridge 26 is subjected to 50 N + / -10% as contact force. The remaining 70 N + / -10% can be used to absorb the aforementioned repulsion forces in the event of a short circuit. In particular, the lower stop point 54b serves to absorb the repulsion forces and transmit them to the holding structure 48 toward an armature (not shown) of the drive device 8.Until the lower stop point 54b is reached, the contact bridge 26 is moved only minimally (e.g., by 0.1 mm + / - 10%) from the closed position 34 in the event of a short circuit. Without the presence of the lower stop point 54b, the repulsion forces in the event of a short circuit would compress the overtravel spring 52 and create an undesirably large contact gap D (e.g., 1.5 mm + / - 10%), which in turn would result in correspondingly long or large arcs.

[0064] In conjunction with the overtravel spring, the upper stop point 54a serves to prevent the contact bridge 26 from being pushed out of the holding structure 48 by the spring force and falling out. For example, the holding structure 48 can have a cage 50 that holds the contact bridge 26. The contact bridge 26 can be shackle-locked in the cage 50 (see Fig. 5 to 8). The cage 50 can in turn define the upper stop point 54a, for example, by a portion of the cage 50 projecting at least partially beyond the contact bridge 26 along the switching direction 38 and by this projecting portion being at least partially aligned with the contact bridge 26 in the switching direction 38. Furthermore, the cage 50 can enclose the contact bridge 26 and also define the lower stop point 54b.

[0065] In particular, the contact bridge 26 and the cage 50 can have guide elements 64a, 64b that are designed to be complementary to one another. The guide element 64a of the cage 50 can be a guide gap 58 that extends through the cage 50 on one side in the switching direction 38 with respect to the contact bridge 26. Preferably, the cage 50 is provided with guide gaps 58 on both sides with respect to the contact bridge 26 (see Fig. 5).

[0066] For each guide gap 58 of the cage 50, the contact bridge 26 can have a projection 66 as a guide element 64b, wherein the projection 66 is movably held in the associated guide gap 58. In particular, each projection 66 can be linearly movable in the associated guide gap 58 between an upper end 60a and a lower end 60b of the guide gap 58. In this case, the upper end 60a, viewed in the switching direction 38, is closer to the fixed contacts 16 than the lower end 60b. The upper end 60a of the guide gap 58 accordingly defines the upper stop point 54a. The lower end 60b of the guide gap 58 can, in turn, define the lower stop point 54b.

[0067] According to the Fig. 1 to 5, the contact arrangement 2 can have a separate blocking element 62 against which the contact bridge 26 strikes in the short-circuit position 36. In this case, the blocking element 62 points along the switching direction 38 towards the fixed contacts 16 and defines the lower stop point 54b. In particular, the blocking element 62 can be designed in a rod-shaped manner. A helical spring 68 can be used as the overtravel spring 52, which extends coaxially to the rod-shaped blocking element 62. The rod-shaped blocking element 62 can thus at least partially occupy the interior space 70 of the overtravel spring 52. With the contact bridge 26 in the closed position 34, a length difference L measured in the switching direction 38 between the overtravel spring 52 and the rod-shaped blocking element 62 corresponds to the desired contact overtravel free travel d in the short-circuit position 36 (see Fig. 3).

[0068] In other words, a travel gap 72 can be provided between the contact bridge 26 in the closed position 34 and the blocking element 62, the length of which, measured in the switching direction 38, corresponds to the desired contact overtravel free travel d in the short-circuit position 36. Consequently, the repulsion forces acting in the event of a short circuit can only move the contact bridge 26 by the length of the travel gap 72 from the closed position 34, and it is structurally ensured that the desired contact overtravel free travel d cannot be exceeded in the short-circuit position 36, at least as long as the repulsion forces do not overcome the existing holding force of the drive device 8.

[0069] The aforementioned force-transmitting connection between the drive device 8 and the contact arrangement 2 can be realized, for example, by a shaft 74 of the drive device 8, wherein the shaft 74 is connected to a connecting portion 56 of the support structure 48 in a form-fitting, force-fitting, and / or material-fitting manner. The shaft 74, in turn, sits on an armature (not shown) of the drive device 8, which can be manipulated by means of a coil arrangement 76 of the drive device 8.

[0070] As in Fig.2 to 4, the switching element 1 can also have two blow-out magnets 78, each assigned to one of the two contact groups 18a, 18b. When the contact bridge is moved from the closed position 34 to the open position 32 during normal operation, the blow-out magnets 78 serve to expand and sever any arcs generated by the operating current through the action of magnetic force. This means that the two blow-out magnets 78 are each designed to blow out an arc occurring in the associated opening gap 44. Furthermore, the interaction of the blow-out magnets 78 with the arc occurring in the levitation gap 46 of the associated contact group 18a, 18b is reduced. Reference symbol 1 switching element 2 Contact arrangement 4 DC switching element 6 housings 8 Drive device 10a, 10b connecting section 12 Outside 14 Inside 16 fixed contact 18a, 18b Contact Group 20 switching contact 22 Contact element 24 contact points 26 Contact bridge 28 rod-shaped / beam-shaped component 30 Contact bridge longitudinal direction 32 Opening position 34 Closed position 36 Short-circuit position 38 Switching direction 40 deactivated state 42 activated state 44 Opening gap 46 Levitation gap 48 Support structure 50 cage 52 Overtravel spring 54a, 54b anchor point 56 connecting section 58 Guide gap 60a, 60b end 62 Blocking element 64a, 64b guide element 66 lead 68 coil spring 70 interior 72 lifting gap 74 shaft 76 coil arrangement 78 Blow-out magnet d Contact overtravel free travel D Contact distance L Length difference QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited non-patent literature

[0000] DIN EN 60664-1

[0016]

Claims

[1] Contact arrangement (2) for a switching element (1), wherein the contact arrangement (2): - an electrically conductive contact bridge (26) movable along a switching direction (38) and - has two contact groups (18a, 18b) spaced apart from each other, where each of the two contact groups (18a, 18b): - an electrically conductive, stationary fixed contact (16) and - an electrically conductive switching contact (20) arranged on the contact bridge (26) and contactable with the associated fixed contact (16), wherein the contact bridge (26) has a closed position (34), an open position (32) and a short-circuit position (36), and wherein ◯ in the closed position (34) the switching contacts (20) of the two contact groups (18a, 18b) electrically contact the respective associated fixed contacts (16), ◯ in the open position (32), the switching contacts (20) of the two contact groups (18a, 18b) have a predefined contact distance (D) measured in the switching direction (38) from the respective associated fixed contacts (16), and ◯ in the short-circuit position (36) between the switching contacts (20) of the two contact groups (18a, 18b) and the respective associated fixed contacts (16) there is a contact overtravel free travel (d) measured in the switching direction (38), which is at most one thirtieth of the predefined contact distance (D) from the open position (32). [2] Contact arrangement (2) according to claim 1, wherein the contact overtravel free travel (d) in the short-circuit position (36) is at most 0.1 mm. [3] Contact arrangement (2) according to claim 1 or 2, wherein the switching contacts (20) of the two contact groups (18a, 18b) electrically contact the respective associated fixed contacts (16) in the short-circuit position (36). [4] Contact arrangement (2) according to one of claims 1 to 3, wherein the contact bridge (26) is movably held in a holding structure (48) between an upper stop point (54a) and a lower stop point (54b), wherein the upper stop point (54a) is arranged closer to the fixed contacts (16) than the lower stop point (54b). [5] Contact arrangement (2) according to claim 4, wherein the contact bridge (26): - in the open position (32) at the upper stop point (54a), - in the closed position (34) between the upper stop point (54a) and the lower stop point (54b) and - in the short-circuit position (36) is at the lower stop point (54b). [6] Contact arrangement (2) according to claim 4 or 5, wherein the holding structure (48) has an overtravel spring (52) with which the contact bridge (26) is prestressed towards the upper stop point (54a). [7] Contact arrangement (2) according to one of claims 1 to 6, wherein the contact arrangement (2) has at least one blocking element (62) against which the contact bridge (26) strikes in the short-circuit position (36). [8] Contact arrangement (2) according to claim 7, wherein the lower stop point (54b) is defined by the at least one blocking element (62). [9] Contact arrangement (2) according to claim 7 or 8, wherein a stroke gap (72) is provided between the contact bridge (26) located in the closed position (34) and the at least one blocking element (62), the length of which, measured in the switching direction (38), corresponds to the contact overstroke free travel (d) in the short-circuit position (36). [10] Contact arrangement (2) according to one of claims 7 to 9, wherein the at least one blocking element (62) is designed in the shape of a rod, and wherein the overtravel spring (52) is designed as a helical spring (68) which extends coaxially to the rod-shaped blocking element (62). [11] Contact arrangement (2) according to one of claims 7 to 9, wherein the holding structure (48) has a cage (50) in which the contact bridge (26) is movably held, wherein the cage (50) forms the at least one blocking element (62). [12] Contact arrangement (2) according to claim 11, wherein the contact bridge (26) and the cage (50) have guide elements (64a, 64b) which are designed to be complementary to one another, wherein the guide element (64a) of the cage (50) adjoins the at least one blocking element (62) in the switching direction (38) and the guide element (64b) of the contact bridge (26) is aligned with the at least one blocking element (62) in the switching direction (38). [13] Switching element (1) with a contact arrangement (2) according to one of claims 1 to 12 and a drive device (8) which is designed to move the contact bridge (26) of the contact arrangement (2) between the closed position (34) and the open position (32), wherein the drive device (8) has a deactivated state (40) in which the contact bridge (26) is in the open position (32) and an activated state (42) in which the contact bridge (26) can be in the closed position (34) or in the short-circuit position (36). [14] Switching element (1) according to claim 13, wherein the switching element (1) in the activated state (42) of the drive device (8) has a normal operation and a short-circuit operation, wherein in normal operation an operating current flows through the two contact groups (18a, 18b) and the contact bridge (26) in the closed position (34) and wherein in short-circuit operation a short-circuit current which is higher than the operating current flows through the two contact groups (18a, 18b) and the contact bridge (26) in the short-circuit position (36). [15] Switching element (1) according to claim 13 or 14, wherein the switching contacts (20) of the two contact groups (18a, 18b) and the respectively associated fixed contacts (16) are spaced apart in the open position (32) by an opening gap (44) and in the short-circuit position (36) by a levitation gap (46), wherein an arc occurring in the levitation gap (46) of the respective contact group (18a, 18b) has a higher metal vapor content than an arc occurring in the opening gap (44) of the corresponding contact group (18a, 18b).

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