EP3078053A1

EP3078053A1 - Hermetically sealed-off low-voltage high-rupture-capacity fuse

Info

Publication number: EP3078053A1
Application number: EP14806586.5A
Authority: EP
Inventors: Ludger Sandhäger
Original assignee: EFEN GmbH
Current assignee: EFEN GmbH
Priority date: 2013-12-04
Filing date: 2014-11-27
Publication date: 2016-10-12
Also published as: CN105765688A; DE102013113496A1; WO2015082307A1

Abstract

The present invention relates to a low-voltage high-rupture-capacity fuse (1) having a hollow body (3) which delimits a switching space (2) and which has at least one opening (4A, 4B), wherein a fusible element (6) which is embedded in quartz sand (5) is arranged in the switching space (2), wherein the opening (4A, 4B) is closed by a covering element (7A, 7B), and wherein an associated contact element (8A, 8B), which is electrically conductively connected to the fusible element (6), is arranged on the covering element (7A, 7B). In order to provide a low-voltage high-rupture-capacity fuse for outdoor use, which fuse provides a high degree of safety even in the event of switching and also ensures a high level of current limiting and also a stable and reliably predictable switching characteristic, the invention proposes that the switching space (2) is hermetically sealed off.

Description

Hermetically sealed NH fuse

DESCRIPTION The present invention relates to an NH fuse having a hollow space delimiting a switching chamber, which has at least one opening, wherein a quartz sand-embedded fusible conductor is arranged in the switch chamber, wherein the opening is closed by a cover element and wherein an associated, is arranged electrically conductively connected to the fuse element connected contact element.

For NH fuses, i. Low-voltage high-performance fuses are fuses designed for low-voltage networks. Fuses are overcurrent protective devices which, when a current flowing therethrough exceeds a certain value over a certain period of time, break a circuit by melting a fused conductor. Known embodiments of NH fuses as high-performance fuses ensure a reliable shutdown of fault currents of up to 100 kA, the rated current can be up to 1, 6 kA. NH fuses are used in particular in public power grids, for example in transformer stations and main distributions.

Depending on national standards, NH fuses, for example in China, are also used outdoors in public power grids. Outdoor use means outside of buildings and results in the fuse being placed directly in the open air and exposed to weather conditions unprotected. Such known outdoor NH fuses consist essentially only of a free one, i. Directly exposed to the environment, fusible link.

The fusible conductor of such an outdoor NH fuse is usually made of copper or a zinc alloy. If a predetermined current flows through the fuse or the fusible conductor for a sufficient period of time, the latter melts as a result of the heat development resulting from the current flow and interrupts the circuit, ie the fuse switches. However, in the case of an NH fuse which is made of a free fusible link and which is arranged in the outer region, in particular the effects of the weather prove to be problematic. For example, corrosion effects on the fusible conductor can occur. However, a stable switching characteristic can not be ensured by such a corroded fusible conductor. In addition, such an NH fuse with free fusible conductor on an insufficient current limit. During melting of the fusible conductor, a portion of the fusible conductor evaporates depending on the size of the current to be cut off, whereby a plasma is formed, via which a current flow in the form of an arc can take place. As a result of such an arc, when the fuse is switched, there may be a temporary continuation of the current flow through the fuse. The generation of an arc is additionally influenced by the composition or the state of the medium surrounding the melt conductor. Thus, in the case of a fusible conductor arranged in the open air, the conductivity of the surrounding air is increased, for example, by high air humidity, thereby promoting the disadvantageous generation of an arc. Finally, when switching the fuse and melting the fusible conductor, molten conductor material may drip off the fuse. An NH fuse installed on a pole in public places, as is the case for example in the Chinese power grid, poses a significant health hazard for people who are close to these facilities. Against this background, it is therefore an object of the present invention to provide a NH fuse for outdoor use, which provides a high level of safety even in case of switching and also ensures a strong current limit and a stable and predictable switching characteristic. This object is achieved in that the switching room of the NH fuse is hermetically sealed.

Hermetically sealed in the sense of the present invention means that the switch room is completely sealed at least with respect to ambient humidity. For a fuse for outdoor use, this means that the tightness for temperatures from about -30 ° C to about + 50 ° C, with a relative humidity of about 10% to 100%, a wind pressure of up to 700 Pa and a height of up to 2000 m above sea level. NN is ensured.

The embedding of the fusible conductor in quartz sand causes melting of the fusible conductor and the quartz sand begins to melt, whereby energy is dissipated from the fusible conductor. In addition, the quartz sand also has an insulating effect. As a result, the generation of an arc is avoided and achieved a strong current limit. In particular, a plasma formation in the region of the circuit interruption is prevented, as they are approx Melt conductor can occur. The switching characteristic of a fuse is characterized by its pass-through value, ie the value of the integral of the squared current through the fuse over time. When multiplied by the ohmic resistance of the fuse, the I ² t value describes that energy value which is still permissible without switching the fuse. The heat output, ie the current heat at the fusible conductor, depends on the square of the current and leads within a certain time to a certain temperature. If the I ² t value is exceeded, the current flow leads to a temperature causing the fuse to switch. More specifically, the resulting temperature is so high that melting of the fusible conductor occurs and current flow through the fuse is interrupted. This limit heat output can be precisely adjusted by applying a solder to the fuse element. For example, a copper fusible conductor has a melting temperature of 1083 ° C. By applying a solder, the melting temperature can be lowered to about 170 ° C. In the case of a sufficient heat output, the solder first melts and diffuses into the molten copper conductor, forming a liquid alloy, which leads to an interruption of the fusible conductor by its melting at a temperature below the melting temperature of the pure fusible conductor.

An arrangement of the fusible conductor in the quartz sand is advantageously carried out within a hollow body, which limits a switching space and holds therein the sand with the embedded fusible conductor. However, there is the risk that due to the heat generated when switching the fuse pressure increase in the hollow body is caused, which can lead to damage of the fuse to an explosion. In particular, given the resulting at switching liquid melt products with very high temperatures, this entails a significant risk of injury to people in the area. This is all the more true if these fuses are arranged in public space. In addition, in the case of an explosion there is also the danger of further property damage to the power network as well as objects in the immediate vicinity. The hollow space bounding the switching space is expediently an elongated, elongated cuboid having four side surfaces, two longitudinal ends and rounded longitudinal edges. This cuboid is hollow inside and open at the two longitudinal ends. These two openings are each closed by a cover, wherein the cover are held by means of corresponding holding elements, such as screws. It is also conceivable, however, a hollow body with more or less than two openings.

A hermetically sealed switch chamber ensures that the pressure development in the hollow body is predictable, since the composition of matter inside the hollow body is constant and remains unaffected by the environment. An increase in pressure, which would entail a risk of explosion, can thus be avoided. In particular, the risk of evaporation of moisture in the hollow body can be dispelled. The exclusion of liquid from the switch room also leads to a more stable switching characteristic of the fuse. Especially in regions with high humidity, the ambient humidity can lead to a changed switching behavior. In particular, there may be less current limitation due to increased conductivity of the wet fuse environment. A hermetic seal can prevent these problems by ensuring a well-defined and constant material composition inside the hollow body.

For example, the fusible conductor disposed in the sealed hollow body has the shape of a band, i. an elongated, flat, flat designed ladder. This conductor strip has a plurality of recesses, so that it has, at least in sections, a grid structure consisting of a plurality of narrow bridge webs.

The contacting of the NH fuse is advantageously carried out via two contact elements, between which the fusible conductor is arranged. These contact elements are configured for example in the form of contact blades. The contact blades have a flat oblong elongated cuboid shape. Advantageously, the contact blades each have a recess in the form of a slot. In this case, both slots can be aligned in the longitudinal direction of the fuse. This has the advantage of a high flexibility in the use of the fuses. The contact blades are inserted into a circuit by receiving connection elements in the oblong holes. With longitudinal slots, uniformly configured NH fuses can be used for devices with different distances between the corresponding connection elements. Alternatively, a first slot in the longitudinal direction of the fuse and a second slot in the transverse direction to be aligned. This has the advantage of easy handling during assembly of the fuse. Thus, the longitudinally aligned slot can be pushed over a first connecting element and then the fuse can be connected by means of a rotary movement with a second connecting element by the transversely arranged slot is pivoted on this second connecting element. Here, the first aligned in the longitudinal direction slot also allows a limited extent, an adjustment of the fuse to different distances between the two connection elements. In addition, the corners of the contact blades and the slots are appropriately rounded to avoid sharp edges and thus a corresponding risk of injury. In one embodiment, the hollow body consists of a hermetically sealed, electrically insulating material, in particular of glazed ceramic, of ceramic with an epoxy resin coating or of a plastic, preferably of a duroplastic or thermoplastic. Furthermore, it may be advantageous if the hollow body is designed to be hydrophobic at least on its outer side. The hydrophobic formation can be effected either by the choice of the hollow body material or by a corresponding coating of the outside of the hollow body. In this case, a hydrophobic formation is understood to mean that a water droplet applied to the outside of the hollow body has a contact angle of more than 90 ° and preferably of more than 120 °. By this measure, the formation of a surface contamination is avoided and the Kriechwegbildung the current, for example after the triggering of the fusible conductor, excluded over the surface of the hollow body.

So that the fuse can effectively limit the current flow in the case of a switching, the hollow body is advantageously designed to be electrically insulating. Otherwise there would be a danger of a power line over the hollow body despite melted melt conductor. For a electrical insulation, a hollow body made of ceramic is appropriate. However, when using an untreated ceramic due to their porosity no hermetic sealing of the switch room can be achieved. For this purpose, offers a preparation of the hollow body of a glazed ceramic. Through a glaze of the outer surface of the hollow body, the ceramic is hermetically sealed in the sense of the present invention. Likewise, however, a production of the hollow body of other electrically insulating and dense materials is conceivable. In order to achieve a sealing of the switching space according to the invention, besides a glazed ceramic, a ceramic with an epoxy resin coating is also suitable. Also conceivable is a hollow body of plastic, in particular thermoset or thermoplastic, which are also hermetically sealed in the context of the present invention. In one embodiment, the hollow body has two openings, wherein the two openings are each closed by a cover element and wherein on the cover elements in each case an associated, electrically conductively connected to the fuse element contact element is arranged. Conveniently, the hollow body comprises two openings, which are advantageously arranged at opposite ends of the hollow body and each closed with a cover. In this case, a current supply to the fusible conductor takes place via a first opening by means of a first contact element which is connected to a first associated cover element. ordered and electrically connected to a first end of the fuse conductor is connected. The current is dissipated from the fusible conductor again via a second opening by means of a second contact element, which is arranged on a second associated cover element and is connected in an electrically conductive manner to a second end of the fusible conductor.

In one embodiment, the cover elements each close an opening of the hollow body by means of a sealing element, in particular by means of a rubber seal, preferably a silicone seal, hermetically sealed. The openings of the hollow body are closed with cover elements. To ensure complete hermetic sealing of the switch room, i. the interior of the hollow body, ensure that these closure areas are hermetically sealed accordingly. This silicone seals offer. A sealing member made of silicone can be made very thin, which favors a compact design of the fuse. In addition, it provides a reliable and durable sealing effect. In particular, due to its elasticity, silicone is able to adapt to material expansion as a result of temperature fluctuations. Especially when using the fuse in the outdoor area such resistance to temperature fluctuations is a prerequisite for ensuring a sufficient sealing effect.

In addition to a silicone gasket but also a rubber seal is generally conceivable as an effective and durable sealing possibility for the openings of the hollow body, which is also resistant to temperature fluctuations. In one embodiment, the cover elements and / or contact elements each consist of a hermetically sealed and preferably electrically conductive material, in particular of copper.

Due to its good conductivity, copper is suitable for the design of electrically conductive elements of the fuse. Moreover, it offers the advantage of being hermetically sealed in the sense of the present invention. The cover elements could in principle also be designed non-conductive. However, for a simple and effective sealing a one-piece design of the cover and contact element is appropriate. In such a one-piece design cover and contact element consist of the same material. In order to allow a contacting of the fuse via electrically conductive contact elements, in this case, therefore, the cover is electrically conductive. Likewise, however, it is also conceivable to produce the contact element and / or cover elements from other electrically conductive materials known from the prior art for fuses. In one embodiment, the cover elements are each formed integrally with the associated contact element. By such a one-piece design of cover and contact elements, the tightness of the control room can be improved in an advantageous manner. So that current flows through the fuse, the contact elements with the fusible conductor are electrically connected. In the prior art, corresponding contact elements designed as contact blades are arranged in openings of the cover elements. However, such additional openings or mechanical contact points complicate the sealing of the switching room of the NH fuse. This can be effectively counteracted by means of a one-piece design. Conveniently, the contact and cover are made of the same electrically conductive and hermetically sealed material, such as copper. In one embodiment, outside the hollow body, a melting-conductor-free signaling device is arranged, which is set up so that it indicates during operation of the fuse whether the fuse has switched.

Alarm devices for NH fuses are known from the prior art in the form of identifiers that serve as switching state indicators. Here we differentiate between top detectors, center detectors and combi detectors. These identifiers each consist of a colored metal element. In the case of a top indicator this is a top or front side of the fuse arranged resiliently biased indicator. This indicator is held by an auxiliary fusible conductor in a resiliently biased position. After melting of the fusible conductor, the current is passed through the serving as a holding wire auxiliary fusible conductor. As a result, the auxiliary fusible conductor of the indicator melts, whereupon the indicator leaps upward or frontally. If the indicator is thus visible, this means that the fuse has switched. In the case of a center indicator, a further opening is arranged centrally in a side wall of the hollow body. In this opening, a colored Kennmelderplättchen is arranged, which is held by a serving as a holding wire auxiliary fusible conductor. If this auxiliary melting conductor melts, the indicator is no longer held and falls out of the opening. Thus, if the indicator is no longer visible, or no longer arranged at its original position in the opening of the hollow body, this means that the fuse has switched. In the case of a combination indicator, the indicator is elongated stretched and has two ends. A first end is arranged at the top or front side of the fuse and is resiliently biased by an auxiliary fusible conductor in the form of a holding wire. The second end is positioned behind an opening in a laterally arranged side space of the hollow body. This adjoining room is separated by a partition wall Switch room of the fuse disconnected. If the auxiliary melting conductor then melts when the fuse is switched, the first end of the indicator leaks upwards or frontally, while the second end of the indicator is pulled away from its position behind the lateral opening. Thus, if the first end of the indicator is visible at the top or the front, while the second end of the indicator is no longer recognizable by the lateral opening, this means that the fuse has switched.

Top and combination detectors have the disadvantage that the auxiliary fusible conductor is guided through an opening out of the control room out to the resiliently biased characteristic element. In this case, the auxiliary fusible conductor must remain movable in the opening so that it can yield during melting and the spring can relax. However, such an opening of the hollow body can hardly be hermetically sealed if at the same time a movable mounting of the auxiliary melting conductor is to be retained in this opening. In addition, an additional opening increases the susceptibility of the seal. A center detector requires an additional opening, behind which the colored identification plate is visible from the outside. In the presence of a code indicator with auxiliary fusible conductor, the switch room of the fuse therefore generally has at least one further opening in comparison with the switch room of a non-contact NH fuse. Additional openings but make it difficult to seal the control room. In particular, this increases the risk that decreases over time due to strong weather conditions, the tightness of the control room.

In a reporting device with auxiliary fusible conductor, this auxiliary fusible conductor is also expediently likewise to be arranged in Ouarzsand in order to ensure a strong current limitation of the fuse. Thus, such an auxiliary fusible conductor is to be arranged in a switch room. Independently of this, an arrangement of the auxiliary melting conductor in a delimited switching space ensures a stable and reliably predictable switching characteristic of the signaling device. In addition, as in the case of the main molten conductor, a release or dripping of molten conductor material is thereby avoided. When outdoor use of such a detector, however, in turn, the problem of a risk of explosion in the course of a corresponding pressure development in the control room of the indicator. In the case of an indicator, however, a hermetic seal of the corresponding switching space for the auxiliary fusible conductor designed more problematic and prone to failure than in the case of a switch room for a normal fusible conductor, as the indicator, as explained above, must be visible to the outside. In a fusible conductor signaling device a comparable problematic heat generation is avoided. Therefore, it is expedient to provide a melting-conductor-free signaling device, for example in the form of an electrically operated visual signal generator. In this case, the current flow through the signaling device when switching the fuse and Meldens the signaling device is not completely interrupted as in an indicator with auxiliary fusible link. Instead, a current flow is provided in the case of a melting-conductor-free signaling device in the form of an electrically operated visual signaling device, although the fuse after switching has a very high internal resistance of approximately 100 kΩ in order to ensure sufficiently strong insulation.

In one embodiment, the signaling device is electrically conductively connected to the contact elements. In a melting-conductor-free signaling device, which is electrically operated, a power supply through an electrically conductive connection with the contact elements is expedient. The power supply of the signaling device thus takes place via the circuit in which the fuse is installed, with a correspondingly high resistance ensures a sufficiently strong current limit. In addition, such a conductive connection takes place with the contact elements outside of the control room, wherein the seal of the control room, in contrast to reporting devices with an auxiliary fusible conductor remains unaffected.

In one embodiment, a gripping tab is arranged on each of the cover elements, and the signaling device is in each case electrically conductively connected to the contact elements via the gripping tabs.

Such grip bottles are used to handle the NH fuse when inserting and removing. They are arranged at the two longitudinal ends of the hollow body and protrude laterally beyond it in the transverse direction. Contacting the signaling device via the grip tabs offers the advantage that the signaling device can be kept at a distance from the hollow body by means of the protruding grip tabs. As a result, a disadvantageous influence on the signaling device as a consequence of the heat development of the fuse during switching is avoided. In addition, such a conductive connection takes place between the contact elements and the signaling device via the grip tabs outside the hollow body and thus independently of the sealing of the switching space. Conveniently, the grip tabs are each formed integrally with the associated contact elements and cover elements. On the one hand, this ensures an electrical connection between contact element and gripping tab, on the other hand, thus negative influences on the switching chamber seal, for example in the form of additional screw connections in the cover elements, are avoided.

In one embodiment, the signaling device has a visual signal transmitter, in particular an LED. In the outdoor area, NH fuses used, for example in China, are generally arranged pivoted to power pylons at a height of approximately 3 to 5 m at an angle of approximately 10-15 ° relative to the direction of the solder. It is useful, both day and night, to be able to recognize if a fuse or which has switched. For this purpose, the alarm signal of the reporting device should be well visible regardless of the external light conditions at a distance of up to 10-15 m with a visibility angle of up to 60 ° and the signal source clearly identifiable. For this purpose, a visual signal transmitter, in particular an LED, is recommended. A correspondingly powerful conventional LED is clearly visible even at low or no ambient light at a distance of 10-15 meters and can be easily integrated into an electrically operated, melting-wire-free signaling device. In combination with a sufficiently high resistance, a sufficient insulation is also ensured.

In one embodiment, the signaling device is arranged at a distance from the hollow body. The spacing of the signaling device from the hollow body minimizes any influence on the signaling device due to the generation of heat during switching of the fuse. For the purpose of such a spacing, an electrically conductive contacting of the signaling device via the grip tabs is particularly suitable. Here, the grip bottles serve as spacers between the signaling device and the hollow body. In particular, in an electrically operated, melter-free signaling device whose electronics are protected from the heat radiation of the fuse conductor.

In one embodiment, an insulating element is arranged between the signaling device and the hollow body for thermally isolating the signaling device from the hollow body.

In order to prevent heat transfer from the switching space of the hollow body to the signaling device particularly effective, a thermal insulating element arranged between the hollow body and the signaling device is expedient. By this, the insulating effect is further increased in comparison to a simple spacing of the signaling device without insulating, in which the insulation consists only of the air between the reporting device and the hollow body. In particular, the isolation in this case is largely independent of the environmental influences.

In one embodiment, the electrically conductive connection between the signaling device and the contact elements has the lowest possible thermal conductivity, so that the signaling device is largely thermally decoupled. As a result of the electrically conductive contacting of the signaling device with contact elements of the NH fuse, a thermally conductive connection between the fuse of the fuse and the signaling device is inevitably produced. In order to minimize heat transfer via this electrical contact, it is expedient to realize the contacting by the thinnest possible connecting elements with a low thermal conductivity. Thus, as far as possible thermal decoupling of the signaling device can be achieved. A thermal decoupling within the meaning of the present invention means that the signaling device is thermally decoupled from the NH fuse so far that their function is unaffected by the temperature of the fuse conductor in the usual working range of the fuse. When switching the fuse may reach temperatures of about 200-250 ° C and more. The signaling device is considered to be largely thermally decoupled within the meaning of the present invention, if it is so well insulated from the heat development of the fusible conductor that heats their electronics to at most about 85 ° C. When using an LED, the insulation should limit the maximum heating of the LED to about 70 ° C to ensure full functionality of the LED.

An embodiment of a NH fuse according to the invention with a signaling device, which comprises an electrically operated visual signal generator, is operated according to a method comprising at least the following steps: passing a current through the fusible conductor between two contact elements, interrupting the power line between the two contact elements Melting the fusible conductor when a predetermined current is exceeded for a predetermined period of time, the method further comprising the steps of: diverting the current to the signaling device and indicating switching of the fuse by means of a visual signal resulting from a steady flow of the redirected current the visual signal generator is generated.

In particular, this method is expediently in a NH fuse with a switching space limiting hollow body used, which has two openings, wherein in the switch room an embedded in quartz sand melt conductor is arranged, wherein the openings are each closed with a cover, wherein on the cover in each case an associated, electrically conductively connected to the fuse element contact element is arranged, wherein the switching space is hermetically sealed and wherein on the cover each a gripping tab is arranged and an annunciator with a visual signal transmitter for indicating a switching of the fuse via the grip tabs electrically conductive is connected to the contact elements. Of course, the signaling device can also be connected via fastening screws which connect, for example, the cover elements with the hollow body. In this case can be dispensed with the grip tabs.

Conveniently, a signaling device is conductively connected via grip tabs with the contact elements, wherein the current is redirected when switching the fuse via the grip tabs to the annunciator. In the normal operating state of the fuse, however, the current flows through the contact elements through the fuse element. Switches the fuse, the current flow is interrupted by the fusible conductor and the power is at least partially diverted via the reporting device. This leads to a stable, by the internal resistance of the reporting device highly limited flow of current through which the visual signal generator is operated. This method is in contrast to the operation of a signaling device with auxiliary fusion conductor. In the case of the latter, after the current has been diverted, the auxiliary melting conductor melts away, as a result of which the current flow through the signaling device is also interrupted. In addition, the other, already explained above disadvantages of a reporting device with auxiliary fusible conductor are avoided when operating with a melter-free message device.

Further advantages, features and applications of the present invention will become apparent from the following description of three embodiments and the associated figures. Show it:

FIG. 1 shows a schematic longitudinal cross-section through a first NH fuse according to the invention,

FIG. 2 shows a first perspective view of a second NH fuse according to the invention,

Figure 3 is a second perspective view of a second NH fuse according to the invention obliquely from above and

Figure 4 is a side view of the second embodiment.

FIG. 1 shows a schematic cross section in the longitudinal direction through a first embodiment of a fuse 1 according to the invention. The NH fuse 1 has a hollow body 3 with a rectangular, elongated, elongate cross section, on the front and rear sides or upper and lower sides 20B and 20A, a cover element 7A, 7B is arranged in each case. The existing example of copper cover 7A, 7B are each in one piece with the contact elements 8A, 8B and the handle tabs 1 1A, 1 1 B configured. The contact elements 8B, 8A are arranged in the front-side and rear-side plane 20B and 20A, respectively, of the elongated cuboidal hollow body 3. The hollow body 3 is made of ceramic with a glazed surface 19 and has front and back respectively an opening 4A, 4B. The interior of the hollow body 3 forms the switching space 2, in which a fusible conductor 6 is embedded embedded in quartz sand 5. The fuse element 6 has a band-shaped, grid-like structure and consists for example of copper. Conveniently, a solder for reducing the melting temperature of the conductor 6 is applied to the fusible conductor 6. The two openings 4A, 4B of the hollow body 3, between which the fusible conductor 6 extends, are sealed off by means of silicone sealing rings 9A, 9B.

On one side of the hollow body 3, a LED 12, which is arranged in a plastic housing 18 and is spaced apart therefrom, is provided as an electrically operated signaling device 10. In the plastic housing 18, the electronics 16 of the annunciator 10 is included in addition to the LED 12. This signaling device 10 is connected by means of electrically conductive connecting elements 17A, 17B in the form of handle tabs 1 1A, 1 1 B with the integrally formed contact and cover elements 8A, 8B and 7A, 7B. If a predetermined current is exceeded for a predetermined period of time, the fusible conductor 6 melts, i. the fuse 1 switches, and the current flow between the two contact elements 8A, 8B is interrupted. The current now flows through the signaling device 10, whereby the LED 12 starts to light and thus indicates a switching of the fuse 1 to the outside. In this case, a sufficiently high resistance of the signaling device 10 ensures a strong current limitation by the switched fuse 1. By the spacing of the signaling device 10 from the hollow body 3, the heat transfer between the melting fuse element 6 and the electronics 16 is minimized.

FIG. 2 shows a second embodiment according to the invention of a hermetically sealed NH fuse 1. The fuse 1 comprises an oblong elongated, cuboid hollow body 3 made of ceramic with a glazed surface 19. The contact elements arranged on the front side and on the back side, formed integrally with the cover elements 7A, 7B 8A, 8B each have a slot 14A, 14B. The cover elements 7A, 7B and the contact elements 8A, 8B consist for example of copper. A first of the two slots 14A is arranged in the longitudinal direction of the hollow body 3 or the fuse 1, a second slot 14B in the transverse direction. The cover elements 7A, 7B are held by means of holding elements 15 on the hollow body 3. In the illustrated embodiment, these are in each case four screws arranged in the corners of the cover elements 7A, 7B of the hollow body 3. The hollow body 3 limits the switching space 2 of the fuse 1, not visible in the illustration, to the fusible conductor 6 embedded in quartz sand 5 and has rounded longitudinal edges. .

- 14 -

The contact elements 8A, 8B are arranged in the plane of an outer side surface of the hollow body 3. In this case, the contact elements 8A, 8B have a flat longitudinally elongated cuboid shape, while the cover elements 7A, 7B have a square shape with rounded corners. Between the cover elements 7A, 7B and the hollow body 3, narrow disc-shaped sealing elements 9A, 9B made of silicone can be seen. On the cover elements 7A, 7B, a signaling device 10 is arranged by means of holding elements 15, exemplified by screws. This electrically operated signaling device 10 comprises a plastic housing 18 with the electronics 16 (not visible) and a visual signal generator 12, exemplified by an LED. The housing 18 of the signaling device 10 is held by means of connecting elements 17A, 17B spaced from the hollow body 3. In addition, electrical contact between the signaling device 10 and the contact elements 8A, 8B is produced via the cover elements 7A, 7B by means of the electrically conductive connecting elements 17A, 17B.

The one cover element 7A has an opening which can be closed by means of the screw 21. Sand can be introduced into the hollow body 3 through this opening. In order to hermetically seal the hollow body 3 after filling with sand, there is a seal between the screw 21 and the hollow body 3, e.g. a plastic gasket or a soft copper flat gasket arranged. Furthermore, the cover 7A has a recess 22. Since the cover member is made of sheet metal, the recess 22 on the inner side of the cover member forms a projection to which one end of the fusible conductor is secured, e.g. welded, is.

FIG. 3 essentially corresponds to FIG. 2, but here the NH fuse 1 is rotated by 180 °, so that the cover element 7B faces forwards and the cover element 7A is aligned to the rear. The cover member 7A has two fuse screws 23. While one end of the fusible conductor 6 disposed in the hollow body 3 is fixed to the cover member 7B, the other end is fixed to a fixing block. The fusible conductor screws 23 engage through the cover member 7A in the mounting block to secure the mounting block and thus the other end of the fusible conductor 6 on the cover 7A.

FIG. 4 shows a side view of the second embodiment. It can be clearly seen that the connecting elements 21 A, 21 B, which provide a connection of the signaling device 10 with the cover elements 7 A, 7 B, are bent inwards. The connecting elements are each connected at one end to the signaling device 10 and formed hook-shaped. This hook shape is formed by a spacing section extending substantially perpendicularly from the signaling device in the direction of the hollow body and a contact section extending perpendicularly thereto and substantially parallel to the covering elements. Of the Contact section has a bore whose inner diameter substantially corresponds to the outer diameter of the head of the fastening screw 15.

At least the spacer portion is designed to be resilient so that it presses the contact portion to the outside of the cover. By this measure, the signaling device can be easily clipped on demand on the NH fuse, where the distance sections are manually bent slightly outwards and then the reporting device is attached to the hollow body, so that the heads of the screws 15 within the holes in the contact section to come to rest. In addition, one or more tip-shaped projections can be arranged on the side of the spacer sections facing the cover element, which can punctiformly penetrate a corrosion layer possibly located on the cover element. Therefore, even if, due to corrosion, the contact resistances between the cover elements on the one hand and the spacer sections each increased to, for example, 1 kΩ, the functionality of the signaling device would not be jeopardized in the case of a typical internal resistance of an LED of 1 Ω.

For purposes of the original disclosure, it is to be understood that all such features as will become apparent to those skilled in the art from the present description, drawings, and dependent claims, even though they have been specifically described only in connection with certain further features, both individually as well as in any combinations with other of the features or feature groups disclosed herein are combinable, unless this has been expressly excluded or technical conditions make such combinations impossible or pointless. On the comprehensive, explicit representation of all conceivable combinations of features and the emphasis on the independence of the individual characteristics of each other is omitted here only for the sake of brevity and readability of the description.

LIST OF REFERENCE NUMBERS

1 NH fuse

2 control room

3 hollow body

4A, 4B openings

5 quartz sand

6 fusible link

7A, 7B cover elements

8A, 8B contact elements

9A, 9B sealing elements

10 signaling device

1 1A, 1 1 B Handle tab

12 auto switches

14A, 14B slot

15 holding element

16 electronics

17A, 17B fasteners

18 housing

19 glazed surface

20A back or bottom

20B front or top

21 screw

22 deepening

23 Melting screw

IG current

Claims

P a n t a n s p r e c h e

NH fuse (1) having a switching space (2) limiting hollow body (3) having at least one opening (4A, 4B),

wherein in the switch room (2) in quartz sand (5) embedded fusible conductor (6) is arranged,

wherein the opening (4A, 4B) is closed with a cover element (7A, 7B) and wherein on the cover element (7A, 7B) an associated contact element (8A, 8B), which is electrically conductively connected to the fusible conductor (6), is arranged,

characterized in that

the switch room (2) is hermetically sealed.

NH fuse (1) according to claim 1, characterized in that the hollow body (3) consists of a hermetically sealed, electrically insulating material, in particular of glazed ceramic, of ceramic with an epoxy resin coating or of a plastic, preferably of a thermoset or thermoplastic, consists.

NH fuse (1) according to one of the preceding claims, characterized in that the hollow body (3) has two openings (4A, 4B), wherein the openings (4A, 4B) each with a cover (7A, 7B) are closed and wherein on the cover elements (7A, 7B) in each case an associated, electrically conductively connected to the fusible conductor (6) contact element (8A, 8B) is arranged

NH fuse (1) according to one of the preceding claims, characterized in that the cover elements (7A, 7B) each have an opening (4A, 4B) of the hollow body (3) by means of a sealing element (9A, 9B), in particular by means of a rubber seal, preferably a silicone seal, hermetically seal.

NH fuse (1) according to one of the preceding claims, characterized in that the cover elements (7A, 7B) and / or contact elements (8A, 8B) each consist of a hermetically sealed and preferably electrically conductive material, in particular of copper.

NH fuse (1) according to one of the preceding claims, characterized in that the cover elements (7A, 7B) are each formed integrally with the associated contact element (8A, 8B). NH fuse (1) according to any one of the preceding claims, characterized in that outside the hollow body (3) is arranged a non-melting message device (10) which is arranged so that it indicates during operation of the fuse (1), if the fuse (1), wherein preferably the signaling device (10) is electrically conductively connected to the contact elements (8A, 8B).

NH fuse (1) according to claim 7, characterized in that on the cover elements (7A, 7B) each a gripping tab (1 1A, 1 1 B) is arranged and that the signaling device (10) in each case via the grip tabs (1 1A, 1 1 B) is electrically conductively connected to the contact elements (8A, 8B).

NH fuse (1) according to any one of claims 7 to 8, characterized in that the signaling device (10) has a visual signal generator (12), in particular an LED.

NH fuse (1) according to any one of claims 7 to 9, characterized in that the signaling device (10) from the hollow body (3) is arranged spaced, wherein preferably between the signaling device (10) and the hollow body (3) an insulating element is arranged for thermally isolating the signaling device (10) from the hollow body (3).

NH fuse (1) according to any one of claims 1 to 10, characterized in that the hollow body consists at least on its outer side of a material or coated with a material which is selected such that an applied to the outside of the hollow body drops of water has a contact angle of more than 90 ° and preferably more than 120 °.

NH fuse (1) according to one of claims 7 to 1 1, characterized in that the signaling device can be clipped onto the hollow body or the cover elements, wherein preferably the signaling device is clipped onto the hollow body or the cover elements without tools.