CN110914930B

CN110914930B - Encapsulated overvoltage protection in the form of a coaxial arrangement with a cup-shaped housing

Info

Publication number: CN110914930B
Application number: CN201880045372.2A
Authority: CN
Inventors: E·策纳; F·格克; C·朗格
Original assignee: Individual
Current assignee: Denza Europe Ag
Priority date: 2017-07-07
Filing date: 2018-06-20
Publication date: 2022-03-04
Anticipated expiration: 2038-06-20
Also published as: DK3459090T3; EP3459090B1; CN110914930A; EP3459090A1; DE102017118181A1; WO2019007686A1; DE102017118181B4

Abstract

The invention relates to an encapsulated overvoltage protection in the form of a coaxial arrangement, having: a cup-shaped housing; first and second electrodes; a disk-shaped surge arrester electrically connected to the electrode and located in the cup-shaped housing; and a fusible element for establishing a short circuit between the electrodes in the event of an overvoltage arrester overload, at least some parts of the cup-shaped housing forming one of the electrodes, accommodating or supporting this electrode, the second of the electrodes being connected in a manner like a punch to the disk-shaped overvoltage arrester. According to the invention, the second electrode has at least one radial recess or blind hole in its section facing the surge arrester, in which recess or blind hole a spring-force-preloaded, electrically conductive contact pin is inserted, the path of movement of which is blocked by the fusible element and is released in the event of an overload of the surge arrester, so that the contact pin establishes a stable short circuit between the second electrode and the cup-shaped housing.

Description

Encapsulated overvoltage protection in the form of a coaxial arrangement with a cup-shaped housing

Technical Field

The invention relates to an encapsulated overvoltage protection in the form of a coaxial arrangement.

Background

EP 2677524 a1 discloses an overvoltage protection device based on a disk-shaped varistor, wherein the varistor is inserted into a cup-shaped housing forming one electrode and is connected to the other electrode.

An electrically conductive material that melts at a defined temperature, for example a solder, is arranged in an annular free space formed as a chamber.

An insulating film is accommodated in an annular gap provided around the disk-shaped varistor at the peripheral side.

Both such solder and the insulating film can form a short circuit to achieve a fault-protected state when the varistor used is overloaded.

The solder has a melting point less than a temperature at which the dielectric insulating material contained in the gap breaks down.

In the overvoltage protection device according to EP 1798742B 1, the same is assumed by a cup-shaped housing with a disk-shaped varistor inserted therein, which is connected to both electrodes. An electrode can be formed here by the bottom of the cup-shaped housing. The other electrode is located on the upper side of the varistor and leads to an electrical external connection.

A second of the electrodes has a circumferential recess which is filled with an electrically conductive fusible material.

The conductive, fusible material is responsive to heat from the varistor. When the varistor is overloaded, the material melts and enters the chamber-like free space, so that a short circuit is formed between the first and second electrodes.

Depending on the thermal properties of the varistor when it is overloaded, the solder used in the cited prior art solutions melts intensively to some extent. The short circuit condition formed is only determined when a sufficiently large amount of solder melts and a correspondingly reliable electrical connection is formed. A stable and reproducible short-circuit path can therefore only be formed randomly under unforeseeable conditions.

Furthermore, due to the design principle chosen for the fusible conductor, a state indication, in particular a simple mechanical state indication, cannot be realized.

Disclosure of Invention

Starting from the above, it is therefore the object of the present invention to provide an improved encapsulated overvoltage protection device of coaxial design, having a cup-shaped housing and a first and a second pole as well as a disk-shaped overvoltage arrester, which is designed as a varistor and which, in the event of an overvoltage arrester overload, can achieve a stable short circuit in all cases in order, for example, to enable an external fuse to respond. In the event of a short circuit, the release of gas should be avoided, as should the formation of an arc in the event of an extreme overload. Finally, the novel device to be realized offers the possibility of integrating a status indicator in order to be able to identify in a simple manner whether an overload situation has occurred during operation of the overvoltage protection device and whether the device needs to be replaced if possible.

The solution according to the invention is achieved with an encapsulated overvoltage protection in the form of a coaxial arrangement according to the invention, which overvoltage protection has: a cup-shaped housing; first and second electrodes; a disk-shaped surge arrester, which is in particular designed as a varistor, is electrically connected to the electrodes and is located in the cup-shaped housing; and a fusible element for establishing a short circuit between the electrodes in the event of an overload of the surge arrester, at least some parts of the cup-shaped housing forming, accommodating or supporting one of the electrodes, the second electrode of which is in contact with the disk-shaped surge arrester in a punch-like manner, wherein the second electrode has at least one radial recess or blind hole in its section facing the surge arrester, in which recess or blind hole a spring-force-preloaded, electrically conductive contact pin is inserted, the path of movement of which is blocked by the fusible element and is released in the event of an overload of the surge arrester, so that the contact pin establishes a stable short circuit between the second electrode and the cup-shaped housing.

The overvoltage protection device is based on a coaxial design. The overvoltage protection device starts from a cup-shaped housing. Here, the housing, in particular the housing bottom, may constitute one of the necessary electrodes. On the outside of the cup-shaped housing, known connection and fastening means can be present, for example in the form of screws.

The varistor, which is preferably used as a surge arrester, has a disk-like shape which is adapted in size to the cavity defined by the cup-shaped housing.

A disk-shaped varistor, which is preferably inserted parallel to the bottom of the cup-shaped housing, is in contact with the second electrode, preferably under mechanical pretension.

The second electrode may have a punch-like configuration and lead to a respective external terminal.

The external terminals may likewise be realized as pins, but alternatively also as blind holes or the like.

The cup-shaped housing is closed in a manner known per se by a sealing insert and a lid.

In the event of an overload of the surge arrester, a temperature rise occurs inside the cup-shaped housing. This thermal energy is used to trigger a short circuit between the two electrodes and, unlike the prior art, is not triggered directly by a fusible element bridging the two electrodes, but indirectly by releasing an electrically conductive spring-loaded contact pin.

In this connection, the second electrode has a radial recess or blind hole in its section pointing towards the surge arrester. The recess or blind hole is filled with the electrically conductive, spring-force-preloaded contact pin, the path of movement of which is blocked by the fusible element and is released in the event of an overload of the surge arrester, so that the contact pin establishes a stable short circuit between the second electrode and the cup-shaped housing.

In the manner according to the invention, the fusible element blocks the contact pin and releases it when the surge arrester is overloaded to a sufficient extent to provide sufficient thermal energy.

At this time, the short-circuit current is directed directly from the second electrode to the first electrode via the contact pin.

The contact pins which have to carry the short-circuit current can be designed accordingly, irrespective of the properties and material composition of the fusible element, since no current-carrying capacity of the fusible element is required.

By this functional separation, it is also possible to use non-conductive fusible elements which have completely different response characteristics than conventional soldering materials.

By selecting the mechanical pretensioning force of the contact pins, in particular by designing the spring constant for generating the mechanical pretensioning force, a rapid movement of the or each contact pin in the direction of the associated electrode is ensured, so that arcing can be effectively prevented and no harmful gas emissions occur.

The fusible element is preferably designed as a rod-shaped barrier in one or more bores extending transversely to the recess or blind bore.

The rod-shaped blocking element is in close, thermally conductive contact with one end thereof with the surface of the surge arrester.

The respective opening preferably extends as far as the surface of the disk-shaped surge arrester, so that the blocking element can be brought into thermal contact without an interfering heat dissipation structure in between.

In a development of the invention, the second electrode has a projection with an axially extending cavity.

This cavity can accommodate a spring-force preloaded signal rod whose lower end pointing towards the contact pin is blocked by the contact pin in its locked position and is released in the event of a short circuit.

Through this technical possibility, signaling of the state of the overvoltage protection device and also the actuation of a telecommunications device (fernmeldeneiderichtung) or an indicator (Kennmelder) can be achieved in a simple manner.

Thus, a release of the locking between the contact pin and the signal rod is achieved if the spring-force-preloaded contact pin moves in the direction of the short-circuit state when the surge arrester is thermally overloaded. The signal rod can thus be moved axially in the cavity and, for example, contact the telecommunications device with its upper end.

In addition, it is also possible to form one or more observation windows in order to be able to evaluate the position of the signal rod and thus the state of the overvoltage protection device.

The segments of the signaling wand can therefore be provided with differently coloured markings, wherein the colour change which occurs with the movement of the signaling wand can be seen in the region of the viewing window.

The signal rod is made of an electrically insulating material, whereby electrical safety in the operation of the device is ensured in this respect.

In a further development of the invention, the at least one disk-shaped surge arrester located in the cup-shaped housing is held and centered on the peripheral side by a cover-like insulating part, in which insulating part there is an opening on its periphery for smooth passage of the at least one contact pin.

In a preferred development of the invention, the second electrode of the punch has radial recesses in its section pointing toward the surge arrester, which recesses are oriented at or toward the center of the electrode section or intersect the center of the electrode section, each recess accommodating a spring-force-preloaded electrically conductive contact pin, the respective path of movement of which is blocked by the fusible element to be protected and is released in the event of an overload of the surge arrester.

By means of this embodiment with a plurality of spring-loaded contact pins that can be released in the event of an overload, the current-carrying capacity and thus the short-circuit reliability in the event of a short circuit are increased.

According to the embodiment described above, the invention therefore comprises a coaxial overvoltage protection based on a varistor, in particular an MOV (metal oxide varistor) based package, which activates a thermal short circuit in the event of an overload or overheating, which forms a defined short-circuit path of high current-carrying capacity within the package structure.

Due to the selected design of the separating device inside the coaxial arrangement, a simple mechanical status indicator can be realized, which can be integrated centrally into a connecting element or connecting bolt known per se. The status indicators in the respective connecting bolts can be combined with a remote communication device for remote signal indication if desired.

Drawings

The invention is explained in more detail below with reference to an embodiment and with the aid of the figures.

Wherein:

fig. 1a shows a longitudinal and a transverse cross-sectional view of an encapsulated overvoltage protection device according to the invention in the unactuated state, said overvoltage protection device having a spring-force preloaded electrically conductive contact pin inside a punch-type second electrode;

fig. 1b shows a longitudinal section and a transverse section of the overvoltage protection device according to fig. 1a, but in the triggered state, i.e. in the short-circuit state;

fig. 2a shows two different longitudinal sectional views for showing the spring-force-preloaded signaling rod as an indicator in the unactuated, i.e. engaged state, and the transverse sectional view associated therewith, which relates to the interaction of the latching end of the spring-force-preloaded signaling rod with the associated release section in the contact pin, likewise in the unactuated, i.e. operating state;

fig. 2b shows a longitudinal section similar to fig. 2a and a transverse section similar to fig. 2a, but in the trigger state, i.e. short-circuit state, in which the spring-force preloaded signal rod is moved upwards in the illustration and operates the microswitch as a telecommunication device;

fig. 3a shows a longitudinal section and a transverse section of the overvoltage protection, wherein a plurality of radial recesses are provided in the lower region of the punch-type second electrode and the overvoltage protection is in an unactuated, i.e. operating, state;

fig. 3b shows a longitudinal section and a transverse section similar to fig. 3a, but in the triggered state, i.e. short-circuited state; and

fig. 4 shows an exploded view of the components of an overvoltage protection device according to the invention, similar to the illustration of fig. 2a and 2b, with a simple electrically conductive contact pin and a spring-force preloaded signal rod.

Detailed Description

The encapsulated overvoltage protection according to the invention, which is described in more detail below, is based on a coaxial design with a cup-shaped housing 1.

The cup-shaped housing has a side wall 2 and a bottom 3.

On the outside of the base 3, there are connecting bolts 4 as electrical and mechanical fastening elements.

A disk-shaped surge arrester 5, which is in particular designed as a disk-shaped varistor, is arranged inside the cup-shaped housing 1.

One of the two surface sides of the surge arrester 5 is in contact with the bottom 3 of the cup-shaped housing.

Thus, the cup-shaped housing 1 forms a first electrode.

The second electrode 6, which may have a punch-like shape, has at least one radial recess or blind hole 8 at its end or section 7 pointing towards the surge arrester 5.

In the recess or blind hole 8, a spring-force preloaded contact pin 9 made of an electrically conductive material is inserted.

The movement path of the contact pin 9 is blocked by the fusible element 10.

When the surge arrester 5 is overloaded, the fusible element 10 reaches its melting point and the contact pins 9 preloaded by the spring force are displaced. The movement path of the electrically conductive contact pin 9 is thus released, so that the contact pin 9 establishes a stable short circuit between the second electrode 6 and the cup-shaped housing 1 or the wall section 2.

In the embodiment according to fig. 1a and 1b and 3a and 3b, the second electrode 6 has a threaded hole 11, which forms an electrical terminal.

The disk-shaped surge arrester 5 located on the cup-shaped housing 11 is centered on the peripheral side by a cover-like insulating element 12, the insulating element 12 having an opening 13 for the at least one contact pin 9 to pass through.

The open side of the cup-shaped housing 1 can be closed by a cover 14, wherein an additional sealing element 15 can be used.

The necessary contact pressure for the disk-shaped surge arrester 5 is achieved by means of a spring 16, which is able to compensate for thermally induced expansions of the entire arrangement or of components present inside the cup-shaped housing.

As can be seen from a comparative examination of the illustrations according to fig. 1a and 1b or fig. 3a and 3b, the contact pin 9 can be moved towards the inner wall of the cup-shaped housing 1 as the rod-shaped barrier as the fusible element 10 melts, in order to achieve the desired short circuit in a reproducible and reliable manner.

The extruded part of the fusible element can be accommodated by the gap-like free space as shown in the figure and thus no longer blocks the movement path of the contact pin 9.

With reference to fig. 2a and 2b, it should now be explained how the principle of the solution according to the invention can be advantageously extended with a status indicator, if necessary in combination with a remote communication device.

In this connection, the second electrode 6 has a projection with an axially extending cavity 17, in which cavity 17 a spring-force preloaded signal rod 18 is movably inserted.

The lower end of the signal rod 18, which is directed toward the contact pin 9, is blocked in its movement by said contact pin 9 and is released in the event of a short circuit. Fig. 2a here shows the working state in which the signal bar 18 is blocked, while fig. 2b shows the short-circuit state in which the signal bar 18 is released.

The upper end 19 of the signal rod 18 can thus directly or indirectly operate an electrical indicator 20 or a microswitch 21 located therein, as can be clearly seen from a comparison of fig. 2a and 2 b.

Further, the state of the signal rod 18 can be visually observed through the observation window 22.

In the embodiment according to fig. 2a and 2b, the signal rod 18 is guided by a hollow-cylindrical extension, namely a hollow cylinder 23, which is connected to the cavity 17 of the second electrode on the one hand and holds the indicator unit 20 on the other hand.

As shown in fig. 3a and 3b in longitudinal and transverse sectional views, respectively, in a development of the invention, the second electrode can have, in its section 7 pointing toward the surge arrester 5, a plurality of lateral recesses or blind holes 8 which are oriented toward or intersect at the center M or center of the electrode section 7, each recess or blind hole 8 accommodating a spring-loaded, electrically conductive contact pin 9, the respective path of movement of which is blocked by a corresponding fusible element 10 or blocking element in the operating state and is released in the event of an overload of the surge arrester.

The coaxial structure of the overvoltage protection device according to the invention can be seen in particular with reference to the exploded view of fig. 4. This illustration shows a cup-shaped housing 1 with a connecting screw 4, a disk-shaped varistor as a surge arrester 5, an exemplary rod-shaped blocking element as a fusible element 10, a contact pin 9 with a circumferential retraction 90 for releasing a signal rod 18, a spring 91 for generating a pretensioning force for moving the contact pin 9, a pretensioning spring 16, a spring 180 for preloading the signal rod 18, an insulator 12, which accommodates and centers the second ram-type electrode 6 and the surge arrester 5 in its interior. Furthermore, the sealing element 15 and the closure cap 14 can be seen.

The hollow cylinder 23 engages with its lower end pointing in the direction of the surge arrester 5 in a cylindrical recess of the second electrode 6, as is shown in detail in accordance with fig. 2a and 2 b.

The free end of the upper part of the signal rod 18 has a coloured symbol 182 which can be seen from the hollow cylinder 23 in response to the short-circuit mechanism or, in combination with the indicator unit 20, through the viewing window 22.

The upper end 182 of the signal rod 18 can interact with the microswitch 21 and trigger or lock the microswitch 21 on the contact ram. These elements of the indicator are realized by an indicator unit 20.

Claims

1. An encapsulated overvoltage protection device in the form of a coaxial structure, said overvoltage protection device having: a cup-shaped housing (1); a first electrode and a second electrode (6); a disk-shaped surge arrester (5), wherein the surge arrester (5) is electrically connected to the electrode and is located in the cup-shaped housing (1); and having a fusible element (10) for establishing a short circuit between the electrodes in the event of an overload of the surge arrester (5), at least some parts of the cup-shaped housing (1) forming, accommodating or supporting one of the electrodes, the second electrode (6) of which is in contact with the disk-shaped surge arrester in a punch-like manner, characterized in that the second electrode (6) has at least one radial recess or blind hole (8) in its section (7) facing the surge arrester (5), in which recess or blind hole (8) a spring-force-preloaded, electrically conductive contact pin (9) is inserted, the path of movement of the contact pin (9) being blocked by the fusible element (10) and being released in the event of an overload of the surge arrester (5) in such a way that the contact pin (9) establishes a stable short circuit between the second electrode (6) and the cup-shaped housing (1), the fusible element (10) is designed as a rod-shaped barrier which is located in a bore extending transversely to the recess or blind bore (8) and is in close, thermally conductive contact with the surface of the surge arrester (5) at one end thereof.

2. The encapsulated overvoltage protection device as claimed in claim 1, characterized in that the second electrode (6) has a projection with an axially extending cavity (17), in which cavity (17) a spring-force preloaded signal rod (18) is inserted, which is blocked by the contact pin (9) towards the lower end of the contact pin (9) and is released in the event of a short circuit.

3. Encapsulated overvoltage protection according to claim 2, characterized in that the upper end (19) of the signal rod (18) is adapted to directly or indirectly operate an electrical indicator (20).

4. Encapsulated overvoltage protection according to claim 2, characterized in that the status or position of the signal rod (18) is visible.

5. Encapsulated overvoltage protection device according to claim 1, characterized in that the disk-shaped overvoltage arrester (5) located in the cup-shaped housing (1) is centered on the peripheral side by a cap-shaped insulator (12), in which insulator (12) an opening (13) is provided for the passage of the at least one contact pin (9).

6. Encapsulated overvoltage protection device according to claim 1, characterized in that the second electrode (6) has, on its section (7) pointing towards the overvoltage arrester (5), a plurality of radial recesses (8) which intersect at the midpoint (M) or the center of this electrode section, each recess (8) accommodating a spring-force-preloaded, electrically conductive contact pin (9), the respective path of movement of which contact pins (9) is blocked by a fusible element (10) and is released in the event of an overload of the overvoltage arrester (5).

7. Encapsulated overvoltage protection device according to claim 1, characterized in that the overvoltage arrester (5) is constructed as a varistor.