EP4597530A1

EP4597530A1 - Contact bridge assembly and electrical switching device

Info

Publication number: EP4597530A1
Application number: EP24398001.8A
Authority: EP
Inventors: Roman Dietrich; Tiago Teixeira
Original assignee: TE Connectivity Solutions GmbH; Tyco Electronics Componentes Electromecanicos Ltda
Current assignee: TE Connectivity Solutions GmbH; Tyco Electronics Componentes Electromecanicos Ltda
Priority date: 2024-02-02
Filing date: 2024-02-02
Publication date: 2025-08-06

Abstract

The present invention relates to a contact bridge assembly (1) for an electrical switching device (4), the contact bridge assembly (1) comprising a mounting section (38) configured to be attached to a drive element, such as an armature (32) of the switching device (4), at least two separate, movable contacts (12) configured to electrically contact stationary contacts (14) of the switching device (4), a support plate (40) arranged between the mounting section (38) and the movable contacts (12), a main elastic element (48), and at least two secondary elastic elements (52), wherein the main elastic element (48) is arranged between the mounting section (38) and the support plate (40), and wherein the secondary elastic elements (52) are each arranged between the support plate (40) and a different one of the movable contacts (12). The provision of the at least two separate movable contacts (12) allows a compensation of manufacturing tolerances (44) via the elastic elements (48, 52). Further, the present invention relates to an actuator (2) with such a contact bridge assembly (1) and an electrical switching device (2).

Description

Technical Field to which the Invention Relates

The present invention relates to a contact bridge assembly for an electrical switching device, such as a contactor or relay. Further, the present invention relates to an electrical switching device, in particular a contactor or relay for high-voltage, automotive applications. However, the applicability of the present invention also extends to other fields of electrical engineering.

Background Art

In general, electrical switching devices, such as contactors and relays, are used in the field of electrical engineering for closing or opening electric circuits. The aim is to switch comparatively strong load currents with comparatively weak control currents. In particular, the control currents are used to actuate a drive element, such as an armature which in turn holds together or moves apart separable contacts that conduct the load currents. Herein, the drive element is a movable part e.g., of a solenoid, a coil assembly, an electromagnetic motor, an actuator or the like built into the electrical switching device.
Since the closing and opening of the electric circuit takes place at the separable contacts, there is a need to safely and reliably hold together and move these separable contacts apart.

Technical Object to be Achieved

The object of the present invention is therefore to improve contactors and other electrical switching devices in terms of safety and reliability.
This object is achieved by a contact bridge assembly for an electrical switching device, the contact bridge assembly comprising a mounting section configured to be attached to a drive element, such as an armature of the switching device, at least two separate, movable contacts configured to electrically contact stationary contacts of the switching device, a support plate arranged between the mounting section and the movable contacts, a main elastic element and at least two secondary elastic elements, wherein the main elastic element is arranged between the mounting section and the support plate, and wherein the secondary elastic elements are arranged each between the support plate and a different one of the movable contacts.
Herein, one movable contact and one stationary contact jointly form a pair of the above-mentioned separable contacts. Due to manufacturing tolerances, the shape and dimension of the movable contacts and the stationary contacts is usually subject to a certain degree of variation. In addition, the stationary contacts often have a height tolerance, meaning that their position within the electrical switching device is also subject to variation.
The provision of the at least two separate movable contacts allows a compensation of these tolerances via the elastic elements. In particular, the at least two secondary elastic elements make it possible to compensate the tolerances individually for each pair of separable contacts.
This, in turn, contributes to safer and more reliable operation conditions of any electrical switching device employing the contact bridge assembly according to the present invention. Hence, the contact bridge assembly solves the above-defined object.
The invention can further be improved by the following embodiments which are advantageous in themselves and which can be arbitrarily combined with one another.
According to one possible embodiment, the movable contacts may be spaced apart from each other. Thereby, little mechanical interference will occur between the movable contacts, which gives the movable contacts a higher degree of freedom during the tolerance compensation.
According to another possible embodiment, the support plate may form or hold a separation rib extending at least partly between the movable contacts. Advantageously, the separation rib can serve as a linear guide for the movable contacts. If more than two movable contacts are provided, the support plate may form or hold one separation rib between each pair of adjacent movable contacts.
Preferably, each movable contact is a contact bar configured to contact two different stationary contacts of the switching device. For example, each contact bar may be embodied as an electrically conductive contact carrier with at least two electrically conductive contact pieces attached (e.g. welded, soldered, press-fit) on each end thereof. Herein, the contact pieces face toward the stationary contacts. Thus, when the contact bar is in contact with the two stationary contacts, a conductive path is established between the two stationary contacts. In particular, the conductive path may extend from one of the two stationary contacts, via one of the two contact pieces, through the contact carrier, via the other one of the two contact pieces and to the other one of the two stationary contacts.
Alternatively, each contact bar may be embodied as a single monolithic elongate part with contact surfaces on each end thereof. The contact surfaces fulfill the function of the contact pieces. In particular, the contact surfaces may be bare metal surfaces or coated surfaces.
Multiple conductive paths are created in a parallel orientation by providing the movable contacts each in the form of the above-described contact bar. This is especially advantageous in high-voltage applications as will be explained henceforth.
As was already mentioned at the outset, electrical switching devices are used for influencing strong current flows within electric circuits. These strong current flows can be part of the normal operation of the electric circuit (i.e. load currents) or can derive from electrical faults in the electric circuit (i.e. fault currents). In both cases, the electrical switching device is capable of closing and opening the electric circuit.
A short-circuit in the electric circuit can lead to excessive current flows (i.e. short-circuit currents) that surpass the load currents and the fault currents. For such a case, the electric circuit containing the switching device usually also contains a fuse, which is adapted to safely open the electric circuit and interrupt the flow of the short-circuit currents.
However, fuses normally have a certain reaction time which creates a delay between the emergence of the short-circuit currents and their interruption. During this reaction time of the fuse, the short-circuit currents flow through the electrical switching device. This is particularly challenging for high-voltage applications where the short-circuit currents often induce strong repulsion forces between the separable contacts. If the repulsion forces manage to move the separable contacts away from each other, an arc discharge ensues. This arc discharge leads to the generation of extremely high pressure and possibly even to a so-called arc flash where the electrical switching device might burst.
This is where the multiple conductive paths come into effect. By providing multiple parallel paths for the short-circuit current, the current flow is split up and only part of the short-circuit current flows through each contact bar. Since the repulsion forces are proportional to the square of the current, splitting up the current reduces the overall repulsion forces. That is, the sum of all repulsion forces induced individually by the partial currents of the split-up current is smaller than the repulsion force induced by the undivided current. In other words, having the multiple parallel conductive paths reduces the risk of the repulsion forces moving apart the separable contacts. Thus, the switching device is more likely to withstand the repulsion forces until the fuse "blows".
Consequently, each conductive path that is created by providing an additional contact bar in the contact bridge assembly further reduces the overall repulsion forces induced by the short-circuit current. That is, when designing the contact bridge assembly, the number of contact bars may be increased or decreased according to an expected amperage of the short-circuit current that the switching device needs to withstand.
Moreover, the contact bridge assembly is preferably configured to be scalable during manufacture and assembly. This scalability may be achieved by adding further contact bars and/or replacing existing contact bars. In particular, if the total installation space needs to remain unchanged, thinner contact bars may be installed in place of already existing contact bars. For this purpose, a set of multiple contact bars may be provided, wherein specific contact bars of the set are combinable into a subset to arrive at the desired total number of contact bars that is assembled in the contact bridge assembly. Any remaining contact bars of the set may be set aside and used for another contact bridge assembly.
In order to keep the conductive paths mutually separated, the movable contacts may be insulated from each other. In particular, any separation rib of the support plate may be made of insulative material.
According to another possible embodiment, the contact bridge assembly may comprise a cage structure, wherein the support plate is movably guided within the cage structure. In particular, the support plate may be linearly guided within the cage structure. Further, the movable contacts may also be guided within the cage structure. This adds to the stability of the contact bridge assembly.
Optionally, the mounting section of the contact bridge assembly may be located on the cage structure. This way, the cage structure can facilitate the handling of the contact bridge assembly during the manufacturing of the switching device.
The movable contacts, especially the above-mentioned contact pieces of the contact bar may protrude from the cage structure. In particular, one contact piece may protrude on each side of the cage structure. Thus, the cage structure does not interfere with the accessibility of the contact pieces for the stationary contacts.
According to another possible embodiment, the movable contacts may be in electrical connection with the support plate. In particular, the support plate may be made of a conductive material or may at least comprise an electrically conductive core. Thereby, the support plate can also serve as a conductive path.
Likewise, the secondary elastic elements may be electrically conductive. Thus, each serves as a conductive path. For example, the secondary elastic elements may be made of spring steel. If the secondary elastic elements are non-conductive, the movable contacts may still be in electrical connection with the support plate via the separation ribs.
According to an embodiment with easy manufacturing, each secondary elastic element may be a leaf spring. The main elastic element is preferably a helical spring. This allows retrofitting the contact bridge assembly to contactors which conventionally use a helical spring therein. Of course, the main elastic element and the secondary elastic elements also may each be any kind of spring element. As such, "elastic element" may be synonymous to "spring element".
Optionally, each secondary elastic element may comprise two end sections and a middle section located between the two end sections. Moreover, the middle section may be convexly shaped, in particular curved or bent, towards the support plate. The two end sections may each be fixed to the corresponding movable contact. For example, the end sections may be welded, soldered, press-fit, form-fit or screwed to the corresponding movable contact.
According to another embodiment, each secondary elastic element may be chucked between a fixture fixing the two end sections to the corresponding movable contact. In particular, a distance from one end section to the other end section may be maintained constant by a fixture between the two end sections and the corresponding movable contact. Thus, the secondary elastic elements can be provided with increased stiffness, since the two end sections cannot move away from each other to give in to a deformation force acting e.g. on the middle section.
Further, each secondary elastic element may comprise two stemming sections, wherein each stemming section extends straightly between the middle section and a different one of the end sections. In other words, the respective stemming sections reach from the middle section to one of the end sections, wherein no curve or bend is present in the stemming section. As a result, the secondary elastic elements may each have a roof-top or coat-hanger shape, which has proved to be the optimal shape in terms of flexibility and rigidity.
The above-mentioned form-fit between the secondary elastic element and the corresponding movable contact may be achieved by providing the movable contact with form-fit elements. For example, the movable contact embodied as the contact bar may comprise a shoulder on each of its two ends. The shoulders may be arranged opposite the contact pieces with respect to the contact carrier and may project away from the contact pieces. A distance between the shoulders may be shorter than the length of the corresponding secondary elastic element. Thus, the two end sections of the secondary elastic element may each rest against one of the shoulders and the stemming sections may stem against the shoulders if the middle section of the secondary elastic element is pushed towards the movable contact.
If no cage structure is provided, the secondary elastic elements are preferably fixed to the support plate, e.g. by welding, soldering, press-fitting or screwing their middle section to the support plate. This prevents loss of the movable contacts.
Alternatively, a permanent fixation between the secondary elastic elements and the support plate may be omitted. For example, each secondary elastic element may removably abut against the support plate. That is, the secondary elastic elements merely abut against the support plate, but are otherwise removable from the support plate. In particular, each secondary elastic element may have a positioning hole, where a positioning pin or peg of the support plate can be inserted. In the course of the tolerance compensation, the removable abutment increases the degree of freedom of the movable contacts since no torsional moments are transferred between the secondary elastic elements and the support plate.
Preferably, the above-mentioned positioning hole is located in the middle section of the corresponding elastic element. Further, the curve or bend of the middle section may allow a rolling movement, while abutting against the support plate. This ensures a smooth movement of the movable contacts during the tolerance compensation.
A loss of the movable contacts may then be prevented by means of the cage structure. In particular, the movement range of the movable contacts may be defined by the cage structure. For example, the movable contacts may be pressed against a bottom of the cage structure, while the electric circuit is open.
According to another embodiment, a spring constant of the main elastic element is lower than the spring constants of the secondary elastic elements. In other words, the secondary elastic elements may be stiffer than the main elastic element. Hence, the main elastic element is responsible for a majority of the travel, while the secondary elastic elements only serve for minor travel during tolerance compensation.
The object defined in the outset can also be achieved by an actuator for the switching device, wherein the actuator comprises the contact bridge assembly according to any one of the above-described embodiments and a linearly movable drive assembly, wherein the mounting section of the contact bridge assembly is attached to a drive element, such as an armature of the drive assembly.
The actuator benefits from the technical effects and advantages of the contact bridge assembly as explained above. In particular, the actuator can be readily used in a switching device to increase its safety and reliability.
Optionally, the drive assembly may be or comprise a solenoid or coil for actuating the contact bridge assembly. The drive element, in particular the armature of the drive assembly may transfer an actuation force and a resulting actuation movement from the drive assembly to the contact bridge assembly. Alternatively, manual actuation may also be utilized, where the drive element may be a plunger to which the mounting section is attached.
A switching device comprising such an actuator and at least two stationary contacts also achieves the above-defined object when the actuator is configured to move the drive assembly and the contact bridge assembly such that the movable contacts and the stationary contacts can be brought together and separated in order to control a load current flowing through the switching device. Optionally, the switching device may comprise a housing and/or blow-out magnets. The operational safety and reliability of the switching device are improved due to the technical effects and advantages of the contact bridge assembly.
Advantageously, the switching device can be configured to allow force balancing. In particular, when the movable contacts and the stationary contacts are brought together, an actuating force of the actuator may be distributed uniformly by the support plate and the at least two secondary elastic elements to result in equal contact forces acting between the respective movable contacts and the stationary contacts. This is mainly achieved due to the degree of freedom that is provided by having the separately arranged movable contacts.
According to another possible embodiment, the switching device may comprise a magnetic circuit that is driven by the load current, wherein the magnetic circuit comprises a movable ferromagnetic core and a stationary ferromagnetic bracket, wherein the movable contacts are arranged between the ferromagnetic core and the ferromagnetic bracket, and wherein an attraction force between the ferromagnetic core and the ferromagnetic bracket is generated in the driven state of the magnetic circuit. Thereby, the magnetic circuit holds the movable contacts against the stationary contacts in the driven state, especially increasing the holding force during a short-circuit scenario.
Further, the switching device may optionally be configured to have a plurality of connection sections. A power cable can be provided for each connection section and be fastened to and contacted on the associated connection section. The switching device can comprise, in particular, a plurality of fastening elements, contacting elements, and/or current-carrying elements at the connection sections. The connection sections are interconnected via the contact bridge assembly.
The invention shall be explained in more detail hereafter by way of example with reference to the drawings. The feature combinations illustrated in the embodiments shown by way of example can be supplemented by further features in accordance with the above statements in correspondence with the properties of the invention required for a specific application. Individual features can also be omitted in accordance with the above statements from the embodiments described if the effect of these features is of no relevance for a specific application. The same reference numerals in the drawings are always used for elements having the same function and/or the same structure.

Fig. 1: shows a schematic illustration of a contact bridge assembly according to an exemplary embodiment;
Fig. 2: shows another schematic illustration of the contact bridge assembly from Fig. 1;
Fig. 3: shows a schematic perspective illustration of the contact bridge assembly according to a further exemplary embodiment in an exploded view;
Fig. 4: shows a schematic perspective illustration of an actuator according to an exemplary embodiment;
Fig. 5: shows a schematic sectional side view of the actuator from Fig. 4;
Fig. 6: shows a schematic perspective illustration of the actuator according to a further exemplary embodiment;
Fig. 7: shows a schematic sectional side view of a switching device with the actuator from Fig. 6;
Fig. 8: shows a schematic perspective illustration of the contact bridge assembly according to a further exemplary embodiment in an exploded view;
Fig. 9: shows a schematic illustration of a contact bridge assembly according to another exemplary embodiment; and
Fig. 10: shows another schematic illustration of the contact bridge assembly from Fig. 9.

In the following, the schematic structure of a contact bridge assembly 1, an actuator 2 and an electrical switching device 4 according to the invention will be explained with reference to Figs. 1 to 10. The electrical switching device 4 may be a contactor 6 or a relay used for controlling a load current in an electric circuit 8. The actuator 2 and in particular the contact bridge assembly 1 may be part of the switching device 4. Further, the switching device 4 may further comprise a housing 10 and/or blow-out magnets (not shown).
As can be seen in the schematic views of Figs. 1 and 2, the contact bridge assembly 1 comprises at least two separate, movable contacts 12 configured to electrically contact stationary contacts 14 of the switching device 4. Herein, one movable contact 12 and one stationary contact 14 jointly form a pair 16 of separable contacts 18. In other words, each movable contact 12 only contacts one of the stationary contacts 14.
As shown in the embodiment of Fig. 3, each movable contact 12 may also be configured to contact two different stationary contacts 14 of the switching device 4. For example, each movable contact 12 may be a contact bar 20 embodied as an electrically conductive contact carrier 22 with at least two electrically conductive contact pieces 24 on each end 26 thereof. Herein, the contact pieces 24 face towards the stationary contacts 14. Thus, when the contact bar 20 is in contact with the two stationary contacts 14, a conductive path 28 is established between the two stationary contacts 14. In particular, the conductive path 28 may extend from one of the two stationary contacts 14, via one of the two contact pieces 24, through the contact carrier 22, via the other one of the two contact pieces 24 and to the other one of the two stationary contacts 14. In this case, one contact piece 24 and one stationary contact 14 may jointly form the pair 16 of separable contacts 18.
By moving apart (see Fig. 1) or bringing together (see Fig. 2) the separable contacts 18, the electric circuit 8 can be opened or closed, respectively, by means of the electrical switching device 4. The movement of the movable contacts 12 is generated by the actuator 2. In particular, the actuator 2 comprises a drive assembly 30 with an armature 32. For example, the drive assembly 30 may be a solenoid, a coil assembly, an electromagnetic motor or any other type of linearly movably actuation device. The armature 32 of the drive assembly 30 transfers an actuation force 34 and a resulting actuation movement 36 from the drive assembly 30 to the contact bridge assembly 1. For this purpose, the contact bridge assembly 1 comprises a mounting section 38 configured to be attached to the armature 32. In Fig. 4, the mounting section 38 is attached to the armature 32.
In order to distribute the actuation force 34 and the resulting actuation movement 36 to all movable contacts 12, the contact bridge assembly 1 further comprises a support plate 40 arranged between the mounting section 38 and the movable contacts 12. Optionally, the support plate 40 may form a separation rib 42 (see Fig. 3). In particular, the support plate 40 and the separation rib 42 may be formed out of plastic as one single piece (e.g. by means of injection-molding or 3D-printing).
In the assembled state of the contact bridge assembly 1, the separation rib 42 may extend at least partly between the movable contacts 12 (see Fig. 4). Advantageously, the separation rib 42 can act as an element to maintain the movable contacts 12, in particular the contact bars 20 in place when currents are flowing into the same direction there through. Due to their flowing direction, said currents each generate a strong attractive force that acts to join all contact bars 20. As a consequence, this separation function is needed to withstand the attractive forces between the contact bars 20. Further, the separation rib 42 can serve as a linear guide for the movable contacts 12, in particular the contact bars 20. If more than two movable contacts 12 are provided, the support plate 40 may form one separation rib 42 between each pair of adjacent movable contacts 12.
As an alternative to the above-described single-piece embodiment, the separation ribs 42 may also be provided as oblong, continuous blades or fins (not shown) made out of ferromagnetic material. These blades or fins may then be attached to, mounted to or overmolded by the support plate 40. Thereby, the separation ribs 42 are capable of catching and concentrating the field lines of each contact bar 20. This, in turn, reduces the attractive forces generated by the load currents between the different contact bars 20. Lastly, it also helps to maintain a capability to overcome misalignment e.g. in case of differences in contact heights as will be described next.
Due to manufacturing tolerances 44, the stationary contacts 14 often have a height tolerance, meaning that their position within the electrical switching device 4 is subject to variation. This is shown in Fig. 1. The shape and dimension of the movable contacts 12 as well as of the stationary contacts 14 can also vary within a certain range. As a means to compensate the manufacturing tolerances 44, the contact bridge assembly 1 comprises multiple elastic elements. The achieved tolerance compensation 46 is visible in Fig. 2.
First, the contact bridge assembly 1 comprises a main elastic element 48 arranged between the mounting section 38 and the support plate 40. Preferably, the main elastic element 48 is a helical spring 50 as shown in Fig. 3.
Second, the contact bridge assembly 1 comprises at least two secondary elastic elements 52 in which each are arranged between the support plate 40 and a different one of the movable contacts 12. In particular, one secondary elastic element 52 is provided for each movable contact 12.
Thereby, the secondary elastic elements 52 make it possible to compensate the manufacturing tolerances 44 individually for each pair 16 of separable contacts 18.
The secondary elastic elements 52 may be leaf springs 54. In particular, each secondary elastic element 52 may comprise two end sections 56 and a middle section 58 located between the two end sections 56. Moreover, the middle section 58 may be convexly shaped, in particular curved or bent, towards the support plate 40. The two end sections 56 may each be fixed to the corresponding movable contact 12 (see Fig. 4). For example, the end sections 56 may be welded, soldered, press-fit, form-fit 60 or screwed to the corresponding movable contact 12.
Further, each secondary elastic element 52 may comprise two stemming sections 62, wherein each stemming section 62 extends straightly between the middle section 58 and a different one of the end sections 56. As can be seen in Fig. 3, the respective stemming sections 62 reach from the middle section 58 to one of the end sections 56, wherein no curve or bend is present in the stemming section 62. As a result, the secondary elastic elements 52 may each have a roof-top or coat-hanger shape.
The above-mentioned form-fit 60 between the secondary elastic element 52 and the corresponding movable contact 12 may be achieved by providing the movable contact 12 with form-fit elements 64. For example, the movable contact 12 embodied as the contact bar 20 may comprise a shoulder 66 on each of its two ends 26. The shoulders 66 may be arranged opposite the contact pieces 24 with respect to the contact carrier 22 and may project away from the contact pieces 24. A distance 68 between the shoulders 66 may be shorter than the length 70 of the corresponding secondary elastic element 52. Thus, the two end sections 56 of the secondary elastic element 52 may each rest against one of the shoulders 66 and the stemming sections 62 may stem against the shoulders 66 if the middle section 58 receives the actuation force 34 from the armature 32.
As can be seen in Fig. 5, each secondary elastic element 52 may be chucked between a fixture fixing the two end sections 56 to the corresponding movable contact 12. In particular, a distance from one end section 56 to the other end section 56 may be kept constant by this fixture resulting from the form-fit 60. Thus, the secondary elastic elements 52 can be provided with increased stiffness, since the two end sections 56 cannot move away from each other to give in to the actuation force 34 acting on the middle section 58.
Optionally, the contact bridge assembly 1 may comprise a cage structure 72 (see Fig. 3). In the assembled state of the contact bridge assembly 1, the support plate 40 may be movably guided within the cage structure 72 (see Fig. 4). In particular, the support plate 40 may be linearly guided within the cage structure 72. For this purpose, the cage structure 72 may comprise internal guiding walls 74 which offer a sliding surface 76 for the support plate 40. Further, the movable contacts 12 may also be guided within the cage structure 72.
As can further be seen in Fig. 4, the movable contacts 12, especially the contact pieces 24 of the contact bar 20 may protrude from the cage structure 72. In particular, one contact piece 24 may protrude on each side of the cage structure 72.
Preferably, the drive assembly 30 and the contact bridge assembly 1 are electrically isolated from each other. For this purpose, the cage structure 72 may comprise an insulation wall 78 connecting the guiding walls 74. As is shown in Fig. 3, the mounting section 38 of the contact bridge assembly 1 may be located on the cage structure 72, in particular on the insulation wall 78.
A loss of the movable contacts 12 may be prevented by means of the cage structure 72. In particular, the movement range of the movable contacts 12 may be limited by the cage structure 72. For example, the movable contacts 12 may be pressed against a bottom 80 of the cage structure 72, while the electric circuit 8 is open. For this purpose, the cage structure 72 may comprise a bottom wall 82 connecting the guiding walls 74 and being arranged opposite of the insulation wall 78 with respect to the support plate 40. The movable contacts 12 abut against the bottom wall 82, until they are brought into contact with the stationary contacts 14. Upon closing the electric circuit 8, the movable contacts 12 are lifted from the bottom wall 82.
Due to the cage structure 72 limiting the movement range of the movable contacts 12, a permanent fixation between the secondary elastic elements 52 and the support plate 40 may be omitted. For example, each secondary elastic element 52 may removably abut against the support plate 40. That is, the secondary elastic elements 52 merely abut against the support plate 40, but are otherwise removable from the support plate 40. In particular, each secondary elastic element 52 may have a positioning hole 84, where a positioning pin 86 or peg 88 of the support plate 40 can be inserted. In the course of the tolerance compensation 46, the removable abutment increases the degree of freedom of the movable contacts 12 since no torsional moments are transferred between the secondary elastic elements 52 and the support plate 40.
As can be seen in Fig. 3, the positioning holes 84 are each located in the middle section 58 of the corresponding elastic element 52. Further, the curve or bend of the middle section 58 may allow a rolling movement, while abutting against the support plate 40.
If no cage structure 72 is provided, the secondary elastic elements 52 may be fixed to the support plate 40, e.g. by welding, soldering, press-fitting or screwing their middle section 58 or one of their end sections 56 to the support plate 40 (see Fig. 1).
In the embodiment of Figs. 1 and 2, the movable contacts 12 are in electrical connection with the support plate 40. In particular, the support plate 40 may be made of a conductive material 90 or may at least comprise an electrically conductive core 92. Likewise, the secondary elastic elements 52 may also be electrically conductive. For example, the secondary elastic elements 52 may be made of spring steel. Thereby, the support plate 40 and the secondary elastic elements 52 serve as part of the conductive path 28, which runs from one of the stationary contacts 14, via one of the movable contacts 12 and one of the secondary elastic elements 52, through the support plate 40, via the other one of the secondary elastic elements 52 and the other one of the movable contacts 12 until it reaches the other one of the two stationary contacts 14.
Consequently, the contact bridge assembly of Figs. 1 and 2 only has a single conductive path 28. If a short-circuit 94 occurred in the electric circuit 8, an excessively high current (i.e. short-circuit current 96) would flow through the contact bridge assembly 1 until a fuse 98 contained in the electric circuit 8 interrupts the short-circuit current 96. During this reaction time of the fuse 98, strong repulsion forces between the separable contacts 18 could be induced by the short-circuit current 96. If these repulsion forces manage to move the separable contacts 18 apart, an arc discharge ensues. This arc discharge leads to the generation of extremely high pressure and possibly even to a so-called arc flash where the electrical switching device 4 might burst. In order to reduce the risk of the repulsion forces moving the separable contacts 18 apart, the embodiments shown in Figs. 3 to 7 employ several features allowing the repulsion forces to be withstood until the fuse "blows". These features will be described in the following:
For one, the embodiments shown in Figs. 3 to 10 comprise multiple parallel conductive paths 28 which are created by providing the movable contacts 12 each in the form of the contact bar 20. At the multiple parallel conductive paths 28, the current flow of the short-circuit current 96 is split up and only a part of the short-circuit current 96 flows through each contact bar 20. Since the repulsion forces are proportional to the square of the current, splitting up the current reduces the overall repulsion forces. That is, the sum of all repulsion forces induced individually by the partial currents of the split-up current is smaller than the repulsion force induced by the undivided current.
Consequently, each conductive path 28, created by providing an additional contact bar 20 in the contact bridge assembly 1 further reduces the overall repulsion forces induced by the short-circuit current 96. In other words, when designing the contact bridge assembly 1, the number of contact bars 20 may be increased or decreased according to an expected amperage of the short-circuit current 96 that the switching device 4 needs to withstand. For example, the contact bridge assembly 1 may be designed for three, four, five or more contact bars 20 depending on the short-circuit current 96.
Moreover, the contact bridge assembly 1 is preferably configured to be scalable during manufacture and assembly. For example, the scalability may be achieved by adding further contact bars 20 and/or replacing existing contact bars 20 with thinner contact bars 20' (see Fig. 8). In particular, a set 118 of multiple contact bars 20, 20' may be provided, wherein specific contact bars 20, 20' of the set 118 are combinable to arrive at the desired total number of contact bars 20, 20' that is assembled in the contact bridge assembly 1. For example, the set 118 may comprise three contact bars 20 of a certain width and four slightly thinner contact bars 20'. If a large short-circuit current 96 is expected during use, the contact bridge assembly 1 can be equipped with the four contact bars 20', while requiring the same installation space as the three (unequipped) contact bars 20. Herein lies another advantage of the present invention. Optionally, the set 118 may also comprise multiple support plates 40, 40' that are selectable based on which contact bars 20, 20' are to be equipped. In order to keep the conductive paths 28 mutually separated, the movable contacts 12 may be insulated from each other. In particular, any separation rib 42 of the support plate 40 may be made of insulative material. The use of an insulative material for the separation ribs 42 also improves the above-explained function of maintaining the movable contacts 12, in particular the contact bars 20 in place when attractive forces are generated by currents flowing through the contact bars 20. Due to their choice of material, the separation ribs 42 themselves are not affected by these currents. In particular, no attractive force that acts to join all contact bars 20 can be generated within the insulative separation ribs 42 themselves.
Alternatively or additionally, the movable contacts 12 may be spaced apart from each other. Thereby, less mechanical interference will occur between the movable contacts 12, which gives the movable contacts 12 a higher degree of freedom during the above-described tolerance compensation 46. Said higher degree of freedom will, in turn, allow force balancing to occur. That is, an actuating force 34 of the actuator 2 may be uniformly distributed by the support plate 40 and the at least two secondary elastic elements 52, when the movable contacts 12 and the stationary contacts 14 are brought together. Hence, equal contact forces act between the respective movable contacts 12 and the stationary contacts 14. In turn, the electric resistance at the movable contacts 12 and the stationary contacts 14 is equalized.
Another feature aimed at withstanding the repulsion forces may be a magnetic circuit 100 that is driven by the load current. The magnetic circuit 100 may comprise a movable ferromagnetic core 102 and a stationary ferromagnetic bracket 104. The movable contacts 12, in particular their contact carriers 22 are arranged between the ferromagnetic core 102 and the ferromagnetic bracket 104. For example, the ferromagnetic core 102 may extend through the cage structure 72 between the contact carriers 22 and the support plate 40, while the ferromagnetic bracket 104 is positioned outside of the cage structure 72 (see Fig. 6).
The ferromagnetic core 102 may be a U-shaped part 106 made of soft iron or any other kind of ferromagnetic material. The ferromagnetic bracket 104 may be a flat part likewise made of soft iron or any other kind of ferromagnetic material. The position of the ferromagnetic core 102 and the ferromagnetic bracket 104 may also be switched within the magnetic circuit 100.
In the driven state of the magnetic circuit 100, that is, when the load current flows through the contact bridge assembly 1, an attraction force between the ferromagnetic core 102 and the ferromagnetic bracket 104 is generated. Thereby, the magnetic circuit 100 holds the movable contacts 12 against the stationary contacts 14. In a short-circuit scenario in particular, the attraction force is comparatively high and holds the separable contacts 18 together. During normal operation, the attraction force generated by the load current is comparatively low and thus does not particularly hinder the actuation of the movable contacts 12.
Preferably, the ferromagnetic core 102 and the ferromagnetic bracket 104 are distanced from each other such that they are mutually spaced apart even when the movable contacts 12 are in contact with the stationary contacts 14. In other words, a gap between the ferromagnetic core 102 and the ferromagnetic bracket 104 is always larger than any gap between the movable contacts 12 and the stationary contacts 14.
Further, the switching device 4 may optionally be configured to have a plurality of connection sections 114. A power cable (not shown) can be provided for each connection section 114 and be fastened to and contacted on the associated connection section 114. The switching device 4 can comprise, in particular, a plurality of current-carrying elements 116, fastening elements (not shown) and/or contacting elements (not shown) at the connection sections 114. The connection sections 114 are interconnected via the contact bridge assembly 1.

REFERENCE NUMERALS

1: contact bridge assembly
2: actuator
4: switching device
6: contactor
8: electric circuit
10: housing
12: movable contact
14: stationary contact
16: pair
18: separable contact
20, 20': contact bar
22: contact carrier
24: contact piece
26: end
28: conductive path
30: drive assembly
32: armature
34: actuation force
36: actuation movement
38: mounting section
40, 40': support plate
42: separation rib
44: manufacturing tolerances
46: tolerance compensation
48: main elastic element
50: helical spring
52: secondary elastic element
54: leaf spring
56: end sections
58: middle section
60: form-fit
62: stemming sections
64: form-fit elements
66: shoulder
68: distance
70: length
72: cage structure
74: internal guiding wall
76: sliding surface
78: insulation wall
80: bottom
82: bottom wall
84: positioning hole
86: positioning pin
88: positioning peg
90: conductive material
92: core
94: short-circuit
96: short-circuit current
98: fuse
100: magnetic circuit
102: core
104: bracket
106: U-shaped part
108: flat part
110: gap
112: gap
114: connection section
116: current-carrying element
118: set

Claims

Contact bridge assembly (1) for an electrical switching device (4), the contact bridge assembly (1) comprising:
- a mounting section (38) configured to be attached to a drive element, such as an armature (32) of the switching device (4),

- at least two separate, movable contacts (12) configured to electrically contact stationary contacts (14) of the switching device (4),

- a support plate (40) arranged between the mounting section (38) and the movable contacts (12),

- a main elastic element (48), and

- at least two secondary elastic elements (52),
wherein the main elastic element (48) is arranged between the mounting section (38) and the support plate (40), and wherein the secondary elastic elements (52) are arranged each between the support plate (40) and a different one of the movable contacts (12).
Contact bridge assembly (1) according to claim 1, wherein the at least two movable contacts (12) are spaced apart from each other.
Contact bridge assembly (1) according to claim 1 or 2, wherein the support plate (40) forms or holds a separation rib (42) extending at least partly between the movable contacts (12).
Contact bridge assembly (1) according to any one of claims 1 to 3, wherein each movable contact (12) is a contact bar (20) configured to contact two different stationary contacts (14) of the switching device (4).
Contact bridge assembly (1) according to any one of claims 1 to 4, wherein the contact bridge assembly (1) comprises a cage structure (72), and wherein the support plate (40) is movably guided within the cage structure (72).
Contact bridge assembly (1) according to any one of claims 1 to 5, wherein each secondary elastic element (52) is a leaf spring (54).
Contact bridge assembly (1) according to any one of claims 1 to 6, wherein each secondary elastic element (52) removably abuts against the support plate (40).
Contact bridge assembly (1) according to any one of claims 1 to 7, wherein each secondary elastic element (52) comprises two end sections (56) and a middle section (58) located between the two end sections (56), wherein the middle section (58) is convexly shaped towards the support plate (40) and wherein the two end sections (56) are each fixed to the corresponding movable contact (12).
Contact bridge assembly (1) according to claim 8, wherein each secondary elastic element (52) is chucked between a fixture fixing the two end sections (56) to the corresponding movable contact (12).
Contact bridge assembly (1) according to claim 9, wherein each secondary elastic element (52) comprises two stemming sections (62), wherein each stemming section (62) extends straightly between the middle section (58) and a different one of the end sections (56).
Contact bridge assembly (1) according to any one of claims 1 to 10, wherein a spring constant of the main elastic element (48) is lower than the spring constants of the secondary elastic elements (52).
Actuator (2) for a switching device (4), the actuator (2) comprising a contact bridge assembly (1) according to any one of claims 1 to 11 and a linearly moveable drive assembly (30), wherein the mounting section (38) of the contact bridge assembly (1) is attached to the drive element, in particular the armature (32) of the drive assembly (30).
Switching device (4) comprising an actuator (2) according to claim 12 and at least two stationary contacts (14), wherein the actuator (2) is configured to move the drive assembly (30) and the contact bridge assembly (1) such that the movable contacts (12) and the stationary contacts (14) can be brought together and separated in order to control a load current flowing through the switching device (4).
Switching device (4) according to claim 13, wherein, when the movable contacts (12) and the stationary contacts (14) are brought together, an actuating force of the actuator (2) is distributed uniformly by the support plate (40) and the at least two secondary elastic elements to result in equal contact forces acting between the respective movable contacts (12) and the stationary contacts (14).
Switching device (4) according to claim 13 or 14, wherein the switching device (4) comprises a magnetic circuit (100) that is driven by the load current, wherein the magnetic circuit (100) comprises a movable ferromagnetic core (102) and a stationary ferromagnetic bracket (104), wherein the movable contacts (12) are arranged between the ferromagnetic core (102) and the ferromagnetic bracket (104), and wherein an attraction force between the ferromagnetic core (102) and the ferromagnetic bracket (104) is generated in the driven state of the magnetic circuit (100).