Electric device and fuse system

Abstract

The invention refers to a fuse system and an electric device (1) with assembling method, comprising an electric element (2) comprising a body (2A) and a terminal (3), an electrical conductor (5) being electrically connected to the terminal (3) by a fusible joint, an arc shield (6), at least one conductive spring (7) and a conductive connection element (8), wherein connection terminals of the at least one conductive spring (7) and the conductive connection element (8) are in electrical contact, wherein the at least one conductive spring (7) is pre-stressed and is configured to push the arc shield (6) between the terminal (3) and the electrical conductor (5), wherein by pushing the arc shield (6) the connection terminals of the at least one conductive spring (7) and the conductive connection element (8) are electrically disconnected.

Description

[0001] Description

[0002] ELECTRIC DEVICE AND FUSE SYSTEM

[0003] The present invention relates to an electric device , a fuse system comprising the device , the process of triggering the fuse system and an assembling method .

[0004] Standard thermally protected varistors often contain a metal oxide varistor (MOV) material , a thermal disconnection system and a connected indicator system .

[0005] The varistor is the voltage dependent component , which overheats in the case of signi ficant electrical surge events in a main circuit .

[0006] The thermal disconnection system is a mechanical moving and thermally triggered system which serves to ensure that the main circuit opens completely in case of overheating of the varistor due to surge events .

[0007] The indicator system is configured to provide an electrical signal of a disconnection status . It has to be isolated from the high voltage main circuit , what makes the design and assembly of a state-of-the-art thermal protective varistor highly complex and costly as disclosed, e . g . , in the published documents US 6636403 B2 , EP 2511915 Al , US 9496112 B2 , US 6430019 Bl , US 11482354 B2 and CN 106711983 A.

[0008] It is thus a task of the present invention to provide an improved or simpli fied device , fuse system and assembly solution . The present invention provides an electric device, which may be a thermally protected varistor, comprising at least an electric element comprising a body and a terminal.

[0009] The body may comprise or may be a varistor. The varistor may comprise or may consist of a metal oxide varistor (MOV) material such as, e.g., ZnO.

[0010] The body may have any suitable shape, e.g., a plate shape, a cylindrical or a cuboid shape.

[0011] The terminal may be an electrode or another kind of metallization on a surface of the body. The terminal comprises an electrically conducting material. The terminal may comprise a metal or a metal alloy. Preferably, a second terminal may be applied on another surface of the body. The two terminals may be applied on two opposing surfaces of the body in order to apply an electric voltage to the body.

[0012] The electric device does further comprise an electrical conductor being electrically connected to the terminal by a fusible joint, e.g., a solder joint. The electric conductor may be an electrically conducting metal wire, e.g., a copper wire, or something similar, e.g., a leaf spring.

[0013] The electric device does further comprise an arc shield and two conductive springs, wherein, at least in a normal operating state, the connection terminals of the two conductive springs are in electrical contact.

[0014] Alternatively, as described in the claims, the electric device may also comprise only one conductive spring, which can be pre-stressed, and another conductive connection element di f ferent than a spring instead of a second spring .

[0015] The alternative conductive connection element has to be inserted separately .

[0016] All further embodiments may also be configured with the other conductive connection element di f ferent than a spring .

[0017] Preferably, at least one of the springs or both springs are in direct mechanical contact with the arc shield . Preferably, electrical contact between the two springs is forced by the arc shield holding the springs in a pre-defined position .

[0018] The at least one or both of the springs may be mechanically pressed against the arc shield .

[0019] I f only one spring is pressed against the arc shield, the other spring may abut to a structural element of a housing of the electric device .

[0020] The cross section of the springs may have any shape , e . g . , rectangular, or circular . The outer shape of the spring may be any shape , e . g . , a U-shape or an S-shape .

[0021] The electric device may comprise the housing which is preferably electrically isolating and encapsulates all other parts of the electric device . The housing may be or comprise a casting or molding and may comprise or consist of a non- conductive material such as a plastic material . The casting may be casted around the other elements of the electric device , preferably at least around the electric element . The other structural elements beside the electric element may be covered by an additional cover which may be another part of the housing . According to the invention, the at least one of the two conductive springs is pre-stressed and is configured to push the arc shield between the terminal and the electrical conductor when the fusible j oint gets loose , and the electrical conductor and the terminal are electrically disconnected . The arc shield is then pushed to the former position of the fusible j oint which gets loose because of melting at high temperatures .

[0022] The arc shield is positioned accordingly and is under prestress since the pre-stressed spring applies on the arc shield .

[0023] According to the invention, by pushing the arc shield the connection terminals of the two conductive springs are electrically disconnected, preferably because the at least one of the springs is relaxed by pushing the arc shield between the terminal and the electrical conductor, whereas the other spring, e . g . , remains at a defined position or is relaxed to another position than the at least one spring .

[0024] By the disclosed configuration, the springs which are required to pre-stress the arc shield are also suitable to provide a closed electrical circuit which is opened when the fusible j oint gets loose and melts .

[0025] In particular, according to an embodiment , the two conductive springs may be terminal wires of an indicator circuit , so called indicator pins , wherein the indicator circuit is configured to indicate electrical contact between the electrical conductor and the terminal , wherein the indicator circuit is configured to be closed when the electrical conductor and the terminal are electrically connected .

[0026] On the other hand, the indicator circuit gets opened since the springs loose contact , when the fusible j oint gets loose , and the electrical conductor and the terminal get electrically disconnected .

[0027] By the disclosed configuration, the springs which are required to pre-stress the arc shield are also suitable to provide an indicator circuit which is configured to indicate electrical contact between the electrical conductor and the terminal , wherein the indication circuit is advantageously separated from a main circuit comprising the electric element , the terminal and the electrical conductor . Thus , no additional galvanic isolation between the two circuits is required .

[0028] Also , by using the springs , no other additional structural elements of the electronic device are required for the indicator circuit , which would be not required without the indicator circuit .

[0029] In other words , the springs have two functions . First , to provide a mechanic force to trigger the disconnection of the terminal and the electrical conductor . Second, to provide a signal for the indicator circuit , which is isolated from the main circuit , which has a higher voltage .

[0030] Thus , the instrumental ef fort can be minimi zed, and the assembly process can be simpli fied . In other words , the at least one spring is used to force the arc shield to move out when the fusible j oint opens in the event of overheating of the electric device , in particular of the electric element and its body . At the same time , the contact between the springs opens and can thus be used as an electrical indicator for an overheating event . Hereto , a signaling device , e . g . , a LED may be arranged in an electrical circuit with the springs .

[0031] It means that the springs have two functions : Providing mechanic force to trigger the thermal disconnect between the terminal and the electrical conductor and providing a signal for the indicator circuit which is isolated from the high voltage main circuit .

[0032] The arc shield provides protection against arcing events and guarantees the electrical disconnection between the terminal and the electrical conductor in case of overheating events when the fusible j oint gets loose .

[0033] According to an embodiment , after pushing the arc shield, the two conductive springs are configured to be electrically disconnected by a spatial gap .

[0034] This configuration is advantageous for guaranteeing an electric isolation between the springs , thus generating or terminating an indication signal .

[0035] According to an embodiment , both of the two conductive springs are pre-stressed and are configured to push the arc shield between the terminal . This configuration is advantageous since the pre-stress can be maximi zed . Since the two springs are configured to move to di f ferent positions when relaxing a spatial gap is provided .

[0036] According to an embodiment , the two conductive springs comprise an electrically conductive metal , preferably, at least one of copper and a copper alloy, which are high- conductive materials .

[0037] According to an embodiment , the body of the electric element is a varistor, preferably a metal oxide varistor . The varistor is advantageously protected against overheating events by the disclosed arrangement and mechanism .

[0038] The invention further relates to an electrical fuse system comprising the electric device according to anyone of the embodiments as described before .

[0039] In the electrical fuse system, the fusible j oint between the electrical conductor and the terminal is configured to get loose when the electric element heats up, since the fusible j oint comprises or consist of a low temperature melting metal , e . g . , a solder material such as soldering tin .

[0040] The arc shield is configured to be pushed by the at least one of the two conductive springs between the electrical conductor and the terminal when the fusible j oint gets loose . Thereby, the arc shield may remove residuals of the fusible j oint .

[0041] The terminal and the electrical conductor are then electrically disconnected and a further electric current through the electric element and further heat production are prevented .

[0042] At the same time , the two conductive springs are then electrically disconnected by the relaxation of at least one spring when the arc shield is moved . The disconnect of the springs thus provides a signal for indicating triggering of the fuse .

[0043] The invention further relates to the process of triggering the fuse and indicating triggering of the fuse as disclosed before .

[0044] The invention further relates to the process of triggering the electrical fuse system and indicating the triggering of the electrical fuse system by electrical disconnection between the two conductive springs .

[0045] A signaling device may signal the electrical disconnection between the two conductive springs . The signaling device may be a LED . The device may signal the electrical disconnection by switching of f .

[0046] The invention further relates to an assembling method for an electric device , comprising the steps :

[0047] - providing an electric element comprising a body and a terminal ,

[0048] - connecting of the terminal and an electrical conductor by a fusible j oint material ,

[0049] - applying of an arc shied adj acent to the electrical conductor and of two conductive springs ,

[0050] - pre-stressing of at least one of the two conductive springs , wherein the arc shield is pressed against the electrical conductor by the at least one conductive spring, which is pre-stressed and wherein connection terminals of the two conductive springs are electrically connected .

[0051] According to an embodiment , in the step of applying the two conductive springs a spring twin element is applied, in which the two springs are configured in one single element , and wherein the spring twin element is singulated into the two single conductive springs after application, e . g . , by cutting them into two parts .

[0052] The further configurations may be according to anyone of the embodiments as speci fied above .

[0053] In the following, the invention is exemplarily described by figures . The invention is not limited by the examples . The details of the examples may be combined di f ferently than described below and in any suitable way . Detailed steps or embodiments of the examples below may be combined with steps or embodiments of the above-described electrical device or assembling method .

[0054] The figures show :

[0055] Figure 1 : Perspective view of a first embodiment of an electric device without an insulating cover . The insulating cover is neglected for means of better illustration . The figure shows the device in a manufacturing state before the springs are singulated .

[0056] Figure 2 : Perspective view of the first embodiment of the electric device without the insulating cover . The insulating cover is neglected for means of better illustration . The figure shows the device in an operating state after singulating the springs but before the fuse is triggered .

[0057] Figure 3 : Side view corresponding to figure 2 .

[0058] Figure 4 : Perspective view of the first embodiment of the electric device without the insulating cover . The insulating cover is neglected for means of better illustration . The figure shows the device in a state when the fuse is triggered .

[0059] Figure 5 : Side view corresponding to figure 4 .

[0060] Figure 6 : First step of a manufacturing method to manufacture a second embodiment of the electronic device . An electric element comprising body and terminals are assembled .

[0061] Figure 7 : Second step of a manufacturing method to manufacture a second embodiment of the electronic device . The electric element is encased .

[0062] Figure 8 : Third step of a manufacturing method to manufacture a second embodiment of the electronic device . The arc shield, the springs and the electric conductor are assembled .

[0063] Figure 9 : Forth step of a manufacturing method to manufacture a second embodiment of the electronic device . The electric conductor is contacted to the terminal by solder .

[0064] Figure 10 : Fi fth step of a manufacturing method to manufacture a second embodiment of the electronic device . The housing of the electronic device is closed by a cover . Figure 11 : Fi fth step of a manuf cturing method to manufacture a second embodiment of the electronic device . The spring twin element is singulated into two springs .

[0065] Figure 12 : Perspective view of the second embodiment of the electric device without the insulating cover . The insulating cover is neglected for means of better illustration . The figure shows the device in an operating state after singulating the springs but before the fuse is triggered .

[0066] Figure 13 : Perspective view of the second embodiment of the electric device without the insulating cover . The insulating cover is neglected for means of better illustration . The figure shows the device in a state when the fuse is triggered .

[0067] In particular, figure 1 is directed to a first embodiment of an electric device 1 .

[0068] The electric device comprises the electric element 2 with a first terminal 3 and a second terminal 4 . The terminals are configured as metal terminals .

[0069] Only the terminals are freely exposed . The other parts of the electric element 2 , in particular a varistor body, are cased in a casing 9 comprising an insulating casting, e . g . , a plastic or polymer casting .

[0070] The other elements may be covered by an additional cover (not shown) in order to cover and protect all elements of the electric device 1 . The casing 9 and the cover form the housing of the device 1 . The first terminal 3 is in electrical contact to an electrical conductor 5 . The contacting is preferably configured as a fusible solder j oint . At temperatures below the melting temperature of the fusible solder j oint , the solder j oint is solid and the first terminal 3 and the conductor 5 are mechanically fixed together by the solder j oint .

[0071] The electrical conductor 5 in the example is configured as a spring conductor in the shape of a leaf spring .

[0072] Adj acent to the elastic part of the spring conductor 5 , an arc shield 6 abuts to the spring conductor . The arc shield 6 is pressed against the spring conductor 5 by a spring 7 . The spring 7 is electrically conductive .

[0073] During manufacturing, the spring 7 is inserted as a twin spring element , which is singulated into the spring 7 and an additional spring 8 afterwards . This method simpli fies the assembly process .

[0074] In alternative embodiments , another conductive connection element 8 di f ferent than a spring may be used instead of the second spring 8 . The alternative conductive connection element 8 has to be inserted separately .

[0075] Figure 2 shows the springs 7 and 8 after singulation . The springs are configured as leaf springs . After singulation, the two springs 7 and 8 can be used as terminals of an electric circuit for indicating the state of the fuse system . As can be seen in Figures 1 or 2 , the springs 7 and 8 are inserted in speci fically configured retention hooks of the housing, in particular of the casing 9 .

[0076] Wherein the spring 8 is pre-stressed and retained by the retention hooks , the spring 7 is pre-stressed by the arc shield 6 . The sprig 7 relaxes , when the arc shield 6 moves towards the fusible j oint .

[0077] In an operating state shown in figure 2 , the both springs 7 and 8 are pre-stressed an abuts each other . Thus , a closed electrical circuit may be formed by connecting the two springs to external conductors . An electric current can flow from the spring 7 to the spring 8 and an electrical signal can be generated .

[0078] In a case of an overheating event of the electrical element , in particular of a varistor body, the fusible j oint melts and the arc shield 6 is pressed by the spring 7 between the first terminal 3 and the electrical conductor 5 as illustrated in figure 4 .

[0079] Thus , the electrical contact between the terminal 3 and the electrical conductor 5 and an electric current is inhibited and further heat generation in the varistor body can be prevented . The fuse has been triggered .

[0080] Since the spring 8 is retained at the original position by the retaining hooks of the casing, also the contact between the two springs 7 and 8 is interrupted by a spatial distance between the relaxed spring 7 , which has been moved towards the arc shield 6 , and the spring 8 . Thus , an electric current in the indicator circuit is stopped whereby the overheating event in the main circuit can be indicated .

[0081] Figure 3 shows a side view corresponding to the perspective view of figure 2 .

[0082] In figure 3 the cover 10 is shown . Through a window 11 in the cover the electrical conductor 5 is visible ( operating state ) .

[0083] After the fuse was triggered and the arc shield 6 has moved, the arc shield 6 is visible through the window 11 , thus indicating the changed state . A side view of the device in the triggered state showing the window 11 is also shown in figure 5 .

[0084] In the figures 6 to 13 a second embodiment is described in detail . Figures 6 to 11 show the manufacturing process and figures 12 and 13 show again the operating and the triggered state of the device , similar to figures 2 and 4 with regard to the first embodiment .

[0085] Figure 6 shows a first step of the manufacturing process . An electric element 2 comprising a body 2A and terminals 3 and 4 is assembled . The terminals 3 and 4 comprise or consist of an electrically conductible metal , such as copper, nickel , silver, gold, etc . , or metal alloy .

[0086] The first terminal is configured to be contacted by an electrical conductor 5 . The second terminal is already provided with a conductor part 4A for external contacting .

[0087] In a second step of the manufacturing process of the electronic device , the electric element is encased in a polymer or plastic casting or casing 9 . The polymer or plastic is electrically insulating .

[0088] The conductor part 4A of the second terminal and a contacting portion 3A of the first terminal are exposed for electrical contacting .

[0089] Speci fic retaining hooks 12 are configured in the outer shape of the casing 9 for accommodating the further elements such as the springs 7 and 8 , the arc shield 6 and the electrical conductor 5 .

[0090] In figure 8 , a third step of the manufacturing process of the electronic device is shown . The arc shield 6 , the springs 7 and 8 and the electric conductor 5 are assembled with the encased electric element 2 to build the electronic device 1 .

[0091] The arc shield 6 , the springs 7 and 8 and the electric conductor 5 may be arranged and fixed by the retaining hooks 12 .

[0092] The arc shield 6 of the shown embodiment is pivoted by fixation on an axis of the casing 9 .

[0093] The two springs 7 and 8 abut to the arc shield 6 as shown in figure 8 or 9 . At least the spring 7 pushes the arc shield 6 in a position, in which the arc shield covers the contacting portion 3A. For operation of the device 1 , the electric conductor 5 is contacted to the contacting portion 3A of the terminal 3 by solder which forms a fusible solder j oint , as shown in figure 9 .

[0094] Again, the electrical conductor 5 is formed as a leaf spring . The arc shield 6 is pivoted into a pre-stressed state , in which the springs 7 and 8 push the arc shield 6 against the electrical conductor 5 and towards the contacting portion 3A.

[0095] Afterwards , the housing of the electronic device 1 is closed by a cover 10 which is put on the casing 9 covering all elements of the device 1 . Only the electrical conductor 5 and the conductor part 4A for external electrical contacting of the electrical element in an electrical main circuit ( operating circuit ) are exposed; and the springs 7 and 8 for external electrical contacting and connection of , e . g . , a signaling device to build a separated indicator circuit .

[0096] In particular, the springs 7 and 8 may again be inserted as one single spring twin element which is singulated into two single springs afterwards in a following step as shown in figure 11 .

[0097] Figure 12 shows again a perspective view of the second embodiment of the electric device without the insulating cover . The insulating cover is only neglected for means of better illustration . The figure shows the device in the operating state after singulating the springs but before the fuse is triggered . When the body 2A of the electrical element 2, e.g., a varistor body and the adjacent terminals 3, 4 overheats, the solder material melts, and the fusible solder joint gets loose. In this stadium, the springs 7 and 8 push the arc shield 6 in between the electrical conductor 5 and the first terminal 3. The arc shield 6 moves by pivoting.

[0098] After pivoting of the arc shield 6, the springs 7 and 8, which were in electrical contact before pivoting, are not in electrical contact anymore, since the connection terminals were differently pre-stressed and the movement of the springs, in particular the connection terminals during relaxation is different.

[0099] Figure 13 shows the device in a state when the fuse is triggered. The indicator circuit, formed by the springs and external conductors is also interrupted. Thus, the interruption of the indicator circuit indicates the interruption of the main circuit.

[0100] Reference signs

[0101] 1 electrical device

[0102] 2 electrical element

[0103] 2A body of the electrical element

[0104] 3 first terminal

[0105] 3A contacting portion

[0106] 4 second terminal

[0107] 4A conductor part

[0108] 5 electrical conductor

[0109] 6 arc shield

[0110] 7 spring

[0111] 8 conductive connection element , e . g . , second spring

[0112] 9 casing

[0113] 10 cover

[0114] 11 window

[0115] 12 retaining hooks

Claims

Patent claims (we claim)1. An electric device (1) comprising: an electric element (2) comprising a body (2A) and a terminal (3) , an electrical conductor (5) being electrically connected to the terminal (3) by a fusible joint, an arc shield (6) , at least one conductive spring (7) and a conductive connection element (8) , wherein connection terminals of the at least one conductive spring (7) and the conductive connection element (8) are in electrical contact, wherein the at least one conductive spring (7) is prestressed and is configured to push the arc shield (6) between the terminal (3) and the electrical conductor (5) when the fusible joint gets loose and the electrical conductor (5) and the terminal (3) are electrically disconnected, wherein by pushing the arc shield (6) the connection terminals of the at least one conductive spring (7) and the conductive connection element (8) are electrically disconnected .

2. The electric device (1) according to claim 1, wherein the at least one conductive spring (7) and the conductive connection element (8) are terminal (3) wires of an indicator circuit which is configured to indicate electrical contact between the electrical conductor (5) and the terminal (3) , wherein the indicator circuit is configured to be closed when the electrical conductor (5) and the terminal (3) are electrically connected.

3. The electric device (1) according to claim 1 or 2, whereinafter pushing the arc shield (6) , the at least one conductive spring (7) and the conductive connection element (8) are configured to be electrically disconnected by a spatial gap.

4. The electric device (1) according to one of the claims 1 to 3, wherein the conductive connection element (8) is configured as a second conductive spring, and both conductive springs (7, 8) are pre-stressed and are configured to push the arc shield (6) between the terminal (3) .

5. The electric device (1) according to one of the claims 1 to 4, wherein the at least one conductive spring (7) and / or the conductive connection element (8) comprise at least one of copper and a copper alloy.

6. The electric device (1) according to one of the claims 1 to 5, wherein the body (2A) of the electric element (2) is a varistor, preferably a metal oxide varistor.

7. Electrical fuse system comprising the electric device (1) according to one of the claims 1 to 6.

8. Electrical fuse system according to claim 7, wherein the fusible joint between the electrical conductor(5) and the terminal (3) is configured to get loose when the electric element (2) heats up, wherein the arc shield (6) is configured to be pushed by the at least one conductive spring (7) between the electrical conductor (5) and the terminal (3) when the fusible joint gets loose, and wherein the at least one conductive spring (7) and the conductive connection element (8) are electricallydisconnected when the arc shield (6) is pushed between the electrical conductor (5) and the terminal (3) .

9. Process of triggering the electrical fuse system according to claim 7 or 8 and indicating the triggering of the electrical fuse system by electrical disconnection between the at least one conductive spring (8) and the conductive connection element (8) .

10. Process of triggering the electrical fuse system according to claim 9, wherein a signaling device (1) signals the electrical disconnection between the at least one conductive spring (7) and the conductive connection element (8) .

11. Assembling method for an electric device (1) , comprising the steps:- providing an electric element (2) comprising a body (2A) and a terminal (3) ,- connecting of the terminal (3) and an electrical conductor (5) by a fusible joint material,- applying of an arc shied adjacent to the electrical conductor (5) and of at least one conductive spring (7) and of a conductive connection element (8) ,- pre-stressing of the at least one conductive spring (7) , wherein the arc shield is pressed against the electrical conductor (5) by the at least one conductive spring (7) , which is pre-stressed and wherein connection terminals of the at least one conductive spring (7) and the conductive connection element (8) are electrically connected.

12. Assembling method according to claim 11, wherein the conductive connection element (8) is configured as a secondconductive spring and wherein in the step of applying the two conductive springs (7, 8) a spring twin element is applied, in which the two springs (7, 8) are configured in one single element, and wherein the spring twin element is singulated into the two single conductive springs (7, 8) after application .

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