DE3302034A1 - Electrical melting fuse - Google Patents

Abstract

In electrical melting fuses having a melting conductor which has connecting ends on both sides of its strip-shaped, flat response region, which is constructed with constriction points, which connecting ends are electrically connected to the contact elements of the fuse, the power loss in operation can be significantly reduced without any detrimental effect on the response characteristic in that at least one of the connecting ends is constructed thickened, by enlarging the conductor cross-section, but without significantly enlarging the conductor surface and the melting conductor regions with respect to the strip-shaped response region. This thickened construction can be carried out by: folding together a blank which is enlarged in the region of the connecting end or electrically conductively applying an additional conductor strip onto the connecting end, or using a conductor strip which is pre-profiled in a thickened manner in the region of the connecting end, or providing connecting ends in the form of round wires or pins, the strip-shaped, flat response region being capable of being formed in a blank in the form of a wire or pin by pressing together between the connecting ends which remain in the original profile.

Description

The invention relates to electrical fuses

with a fusible link, which is narrowed on both sides has formed response area terminal ends, which with the contact elements the fuse are electrically connected.

The fuses of this type on the market there is a considerable problem, the power loss that inevitably occurs during operation reduce, because this is converted into heat in the fuse and ultimately leads to noticeable warming within security systems. It can therefore too only a limited number of such known or common fuses be arranged in a confined space within security systems. On the other hand is it is necessary with fuses, the response area equipped with bottlenecks to train the fusible conductor with a sufficiently high ohmic resistance so there in the event of an overcurrent load on a protected electrical system part in the response area The fuse element generates sufficient heat to ensure that the fuse complies with the regulations corresponding to a load with a specified excess with respect to the nominal current to be addressed within a specified time.

To meet these requirements, not only must there be enough heat in the Response range of the fusible conductor are generated, but it must also be the heat conduction be kept sufficiently small from the response range of the heat conductor.

It is therefore an object of the invention to provide an electrical fuse to improve on their fusible conductor in such a way that the electrical leakage conduction and thus the ohmic resistance causing the fuse to heat up noticeably reduced, but the response characteristics of the fuse essentially remains retained.

This object is achieved according to the invention in that at least one of the connection ends of the fusible conductor with an increase in the cross-section of the fusible conductor, but at most due to the enlargement of the conductor surface caused by the thickening and the width of the fusible conductor is thicker than the band-shaped response area is trained.

This ensures that the ohmic resistance in the connection ends of the fusible conductor is noticeably reduced. Although it is due to the Wiedemann-Franz-Lorenz'schen law existing relationship between electrical Conductivity and thermal conductivity are to be expected from the thickening at least one connection end of the fusible conductor besides the reduction of the ohmic Resistance also increases heat dissipation and thus an unwanted influence the response characteristics of the fuse would have to occur. But it has Surprisingly found that, if with the reduction of the ohmic resistance Greater heat dissipation at one or both connection ends of the fuse element should occur, this is so controlled by the invention that a disadvantageous Influencing the response characteristics, in particular also a disadvantageous influencing the time response characteristic of full-range fuses avoided can be.

The thickening of one or both connecting ends of the fuse element compared to the band-shaped flat response area formed with constrictions or both connection ends leave 1.5 to multiple conductor cross-sections of the connection ends to reach the response range without being critical or difficult manageable heat dissipation occurs from the response area.

The desired proportions in the conductor cross-section of one or both Connection ends and the response area can be achieved particularly advantageously, when the fusible conductor is formed from strip material over its entire length or width is formed with a substantially uniform thickness and that the Fusible conductor in the area of at least one of its connecting ends made of this strip material enlarged and folded over once or several times. The folded Layers of the fusible conductor strip can be at the transition to the response area, preferably be connected to one another in an electrically conductive manner by welding. In a The fusible conductor strip is a particularly advantageous embodiment of the invention cut in the area of at least one connection end with increased length and the excess length of the fusible tape is folded back onto the respective connection end. As a result, the blank for the fusible conductor can have the same width throughout be trained, which allows optimal economy of tape material.

But you can also put the fusible link in at least one of the Connecting the forming areas with a greater width than in the response area Cut the forming area and laterally to form the respective connection end fold up. This is of particular importance when one or both ends of the connection should receive multiple thickness than the response range of the fusible conductor.

One possibility for this type of thickened terminal end formation consists in that the fusible conductor is trapezoidal at at least one of its connecting ends from the fusible conductor width in the response area to double to multiple, for example triple width at the free end is cut and the side Widenings, if necessary, folded overlapping laterally onto the respective connection end will.

The proportions in the conductor cross-section provided according to the invention one or both terminal ends and the response area can also be advantageous achieve that the fusible conductor in at least one of its connecting ends is thickened by means of an additional conductor strip of selected thickness, which is in electrically conductive connection to the corresponding cut to the fuse element molded connection end is applied, preferably welded on. This kind the thickening of one or both connecting ends is preferred if the strip material from which the fusible link is to be made, the formation of a in the area of the connection ends the enlarged cut.

Another way to get the desired proportions in the conductor cross-section to reach one or both ends of the connection and the response range exists according to the invention in that the fusible conductor is formed from strip material that in at least one of its areas forming the connection ends of the fusible conductor with a greater band thickness than in its forming the response area of the fusible conductor Area is pre-profiled.

The use of such a pre-profiled strip material is required a particularly simple method of manufacturing the fusible conductor because it is folded up or any other additional treatment of the thickened connection end is not necessary. However the pre-profiled strip material is naturally more expensive than one in all areas strip material of the same thickness. Therefore, the use of pre-profiled Strip material are preferred when fusible conductors are thickened Connecting ends are to be produced in large numbers.

Finally, there is a possibility of formation according to the invention of fusible conductors with thickened connection ends in that the fusible conductor wire-like material with a minimized volume-to-surface ratio, preferably from round profile wire, in which the response area by flattening with smaller conductor cross-section than the terminal ends is molded. Can be preferred the response area can be molded into the respective piece of wire by pressing. It can easily be accepted that the response range is on larger width and smaller thickness than the terminal ends is formed. It will one generally defines the response area formed in the piece of wire by pressing Cut smoothly at the sides to create defined surface and shape relationships in the response area to ensure.

But you can also expand the response range with axial stretching form substantially the same width and smaller thickness than the terminal ends. In this way, too, precisely defined shape and conductor relationships can be achieved on the Establish response area.

Because the relationship between electrical conductivity and thermal conductivity fluctuates within certain limits with the various electrically conductive materials, one can provide in further development and improvement of the invention that at least one of the connection ends of the fusible conductor is thicker than the response area is formed and consists of such a material that is considerably less specific Thermal conductivity, but only slightly lower electrical conductivity than that Has material from which the actual response area of the fusible conductor is made.

One might assume that there would be a further improvement as a result could achieve that you even get the contact elements, especially contact blades through the front plates of a fuse link to the vicinity of the response area of the fusible conductor could lead to the ohmic resistance even further to belittle. In fact, it has surprisingly been found that the Inside a fuse link extending parts of contact elements, in particular Contact knives to such a large extent thermal bridges inside the fuse link to the outside that external conditions, especially the outside temperature, are considerable Influence the response of the fuse link to overload current. Such External influences are, however, due to the thickening according to the invention of one or both Terminal ends of the fusible conductor and their connection to the contact elements excluded, even if such an area has increased conductor thickness one or both connection ends attached directly to the respective contact element is.

Attaching the connection ends to the respective contact elements can be made much easier in the context of the invention if it is provided that the fusible conductor at the free end of its connection ends with the same tape thickness as is formed in the response area and with these end areas of simple tape thickness attached to the contact elements in an electrically conductive manner, preferably welded is. For this purpose, a thickened connection end equipped with a larger conductor cross-section can be used a reduction in thickness at its end region to be connected to the contact element to the simple tape thickness of the fusible conductor. In this way you can conventional and novel ways of connecting the fusible conductor to the contact elements much easier and safer to perform.

Embodiments of the invention are described below with reference to Drawing explained in more detail. The figures show: FIG. 1, one designed according to the invention NH fuse-link when the ceramic body is cut open and has been emptied of the extinguishing agent; Figure 2 shows a blank for the production of a fuse link according to Fig. 1 provided fusible conductor and the fusible conductor itself in side view; FIG. 3a shows a fusible conductor similar to that of FIG. 2 in an enlarged part cut along line 3-3; FIG. 3b shows partial sections corresponding to FIG. 3a a similar fusible conductor made of profiled fusible conductor strip: Figure 4a further possibilities for increasing the conductor thickness in a fusible conductor according to FIG. 2 in a representation corresponding to FIG. 3a; Figure 4b of Figure 4a corresponding possibilities for increasing the conductor thickness by means of pre-profiled Fusible conductor strip in a representation corresponding to FIG. 4a; Figure 5a another Possibility to increase the conductor thickness in a fusible conductor as shown in the figure 2 in a representation corresponding to FIG. 3a; Figure 5b one of the fusible link thickness according to FIG. 5a corresponding training with pre-profiled fusible strip in a corresponding Representation as in FIG. 5a; FIG. 6a shows another possibility for enlargement the conductor thickness in a fusible strip according to Figure 2 in a corresponding depiction like Figure 3a; FIG. 6b shows a configuration corresponding to the thickness of the fusible conductor according to FIG. 6a with pre-profiled fusible tape in a representation corresponding to FIG. 6a; FIG. 7 shows the cut of a modified fusible conductor with widened cut Connection ends in plan view and by folding the connection ends from the Cut finished fuse element in plan view; FIG. 8 a modified one Embodiment of the blank with widened cut connection ends in Top view and the one completed by folding the connection ends from this blank Fusible conductor in plan view; FIG. 9 shows a fusible conductor with connection ends in the form of round profile wire in plan view; FIG. 10 shows the fusible conductor according to FIG. 9 in Side view; FIG. 11 shows a fusible conductor with connection ends in wire form with an elliptical shape Cross section in plan view and FIG. 12 the fusible conductor according to FIG. 11 in side view.

In the example of Figure 1 is a NH fuse link 11 with a Fusible conductor 12 provided inside a socket-shaped ceramic body 13 is arranged. The ceramic body 13 is on both end faces with one face plate each 14 closed and in its interior with the fusible conductor 12 (not shown) powdery or granular extinguishing agent, e.g. extinguishing sand, filled. On the outside, each end plate 14 has a contact element, shown in FIG Example a Contact blade 15.

The fusible conductor 12 has two connection ends 16 and 17 and between them a response area 18. The connection ends are mechanically strong and electrical conductively connected to the inner surface of the end plates 14, in particular welded there. The connection end 16 is formed somewhat longer than the connection end 17. When assembling the NH fuse link, you can first use the fusible link 12 with its shorter connection end 17 on one end plate 14 opposite one another attach to the contact blade 15, for example by welding. Then this faceplate becomes attached to the ceramic body while inserting the fusible conductor in its interior. The longer connection end 16 of the fusible conductor 12 is then so far from the ceramic body 13 before that it is conveniently attached or welded to the second face plate 14 can be and then screwed this faceplate to the face of the ceramic body 13 can be.

In the example in FIG. 1, the fusible link 12 is in its response range 18 three bottlenecks, namely two shorter bottlenecks 19, the short-circuit current respond and a central, i.e. arranged between the two shorter constrictions 19, longer bottlenecks 20, which responds to overcurrent loading. The on overcurrent load appealing bottleneck 20 is in a conventional manner with a running across the Width of the fusible conductor 12 extending bead 21 and adjoining it provided with a eutectic solder 22. The fusible link 12 consists in the illustrated Example made of copper tape.

To the electrical resistance of the fusible conductor 12 and thus its Reducing power loss during operation is at least one of the two connection ends 16 or 17, but preferably both connection ends 16 and 17 with a greater thickness than the areas of the Response range 18 trained. Figures 2 to 10 show different possibilities for this: In the example shown in Figure 2 and Figure 3a, which is also essentially the illustration of the fusible conductor in FIG. 1 corresponds to a blank 23 of fusible conductor strip provided, the total length 24 is chosen so that on both sides of the response area Terminal ends are arranged, which is about twice the length of the finished fusible conductor 12 provided connection ends 16 and 17 have.

These double-long connection ends are then connected to the dashed Lines 25 folded inward and electrical in the vicinity of the response area 18 conductively combined, for example welded together. Figure 2 shows this the possibility of spot welds 26, while in Figure 1 linear welds 27 are shown.

In this way, the terminal ends 16 get from their outer ends up to the welded connections 26 and 27, respectively, essentially double the thickness and thus double the effective conductor cross-section compared to the areas free from bottlenecks of the response range 18.

As Figure 3b shows, you can achieve the same effect if of Sections 23 'of profiled fusible tape is assumed in the area the connection ends 16 'and 17 or increased in the area of one of these connection ends, for example twice as thick as in the response area 18. The production of fusible conductors 12 from blanks 23 'made of such profiled fusible conductor strip recommended for large-scale production of fuses, while in production in smaller series the possibility of folding over the end areas of the blank 23 seems cheaper.

In the example in FIG. 4a, modifications are provided to the effect that that the thickness of the terminal ends 16 and 17 is increased even more. In the right Part of Figure 4a is based on a blank 23 according to Figure 2 made of fusible tape between the folded parts of the connection ends 16 an additional strip-shaped one electrical conductor 28 made of the same material, for example copper, as that Fusible tape inserted and by means of an additional welding point 29 into secure electrical contact with the folded-over parts of the terminal end 16 brought. Another modification option can be found in the left part of the Figure 4a. There only a relatively short end of the connecting end 17 is folded over. About this folded over part of the connection end 17 is an additional strip-shaped one electrical conductor 30 folded and with the additional welds 31 and 32 brought into secure electrical contact with the connecting end 17.

According to Figure 4b, it is also conceivable with these design options, Sections 23 ″ of appropriately pre-profiled fusible tape to be used.

Naturally, those in the right-hand part and left-hand part of FIGS. 4a and 4b can be used separately from one another, with one easily can provide only one of the connecting ends 16 or 17 thickened and the other connecting end to be carried out in the same thickness as the response area 18.

The possible embodiments according to FIG. 4a and FIG. 4b can be largely adapt to those requirements that you can adjust the thermal conductivity of the fusible conductor in the vicinity of the response area 18 should be kept as small as possible, in order not to excessively large amounts of heat from the response area 18, in particular from the overcurrent discharge appealing bottleneck 20.

In the example in FIG. 5a, further modification options are shown. The fusible conductor 12a corresponds essentially to a fusible conductor 12 according to FIG 2. In the example shown in the left part of FIG. 5a, a blank is used 23a assumed from fusible strip 23a, which is longer than on both sides is that according to FIG. Instead of the one in Figure 2 by the dashed line 25, the blank 23a is made of fusible tape two folds and two welds 27 such that the connection end thus formed 17e obtained three times the material thickness over a substantial part of its length. At the The free end is the blank 23a over the outer fold around an end region 17f let protrude, which then has only the simple tape thickness, same thickness as the fusible conductor in the response area 18. With this design of the connection end 17e it is possible to weld with the contact elements 15 or the end plates 14 easier to execute. It can even be designed with a single thickness The weld-on end 16f or 17f on the end face of the ceramic body 13 leads to the outside, i.e. press into the sealing ring inserted there or through one in the face plate 14 attached slot to the outside and on the outside of the contact element weld on.

In Figure 6a is shown at a connection end 16e, like the corresponding one Thickening of one or both ends of the connection is achieved simply by having a additional conductor strips 23b in an electrically conductive connection by means of two Welding points 27 is attached to the connection end. This ladder strip has a thickness corresponding to the desired reduction in ohmic resistance, for example twice as thick as the connecting end formed on the blank 23a. In the case of a connecting end 16e according to FIG. 6a, provision can also be made one such applied conductor strip 23b, the end region 16f of the connection end in the thickness of the connecting end formed on the blank 23a remain unchanged.

As FIGS. 5b and 6b show, the embodiments according to Figure 5a and Figure 6a with sections 23 'made of pre-profiled fusible strip produce, the pre-profiling of the desired thickness formation on the connection elements 16'e and 17'e correspond.

It is also the case with fusible conductors according to FIGS. 5a, 6a, 5b and 6b possible that only one terminal end 16 or 17 is thickened while the other end of the connection only in the same thickness as the fusible tape in the response area 18 is executed.

In the example in FIG. 7, the fuse element 12 is made from a fuse element blank 12a is formed, which is prepared with widened connection ends 16a and 17a. These cut connection ends 16a and 17a have about a part of their length twice as wide as the blank 12a in the response area 18. As in FIG. 7 in the lower part Part shows, the connection ends 16 and 17 of the fuse element 12 are folded in laterally. The fusible conductor 12 is then given a shape that corresponds to that of the fusible conductor according to Figure 2 is practically the same. The end regions 16f and 17f have how in the examples of FIGS. 5a and 6a only single thickness. To the folded To fix parts of the connection ends 16 and 17, and the flow of current over the connection ends To improve, weld points 26 can be provided, which are shown in FIG are indicated as spot welds, but can easily also be weld lines can, as shown in Figure 1 at 27. In many cases, however, it is enough to fix it of the folded ends from providing only one or two spot welds 33, which in contrast to the representation in FIG. 7 possibly also directly can be arranged at the border of the response area 18.

In the example of Figure 8, one possibility is shown in which of a blank 12b made of fusible tape of constant thickness is assumed, its cutting at the end areas provided for the formation of the connection ends 16b and 1Tb widened trapezoidally towards the outer ends from the response area 18 is formed, namely to three times the width of the response area 18. Die lateral widening triangles are - as the lower part of Figure 8 shows - folded over the central rectangular part of the connection ends 16 and 17. The fusible link 12 then has essentially the same shape as that of Figure 2. Um To fix the folded parts in their position, additional welding points can be used 33 can be provided. As shown in dashed lines, the trapezoidal extensions at a distance from the blank end edges end in a manner analogous to the example of FIG. 7 to form end regions 16f and 17f of single thickness on the finished fusible conductor 12.

In the embodiment of the fusible conductor shown in FIGS. 9 and 10 12c, the connection ends 16c and 17c are designed in the form of round profile wire. In this example, the fusible conductor 12c is made in one piece from a corresponding round profile material produced, in which the band-shaped flat response area 18 in the wire-shaped or pin-shaped cut made of round profile material with considerable reduction in thickness is pressed in. This press-fit creates an axial extension with a lateral squeeze. In this way the response area is 18 formed in a considerably larger width than the terminal ends 16c and 17c. To the Achieving defined form relationships and conductor relationships is the response area 18 produced by pressing at its side edges in the FIG 9 cut smooth and axially parallel to the manner shown.

In the example of Figures 11 and 12, there is a fusible link 12d with terminal ends 16d and 17d, which have elliptical to oval flattened round profiles, wherein the flat area lies in the plane of the response area 18. In the preparation of such a fusible conductor 12d is based on a pin-shaped profile piece, which is compressed in the response area 18 to be produced under an axial tensile effect will. The material displacement in the response area 18 essentially takes place in the axial direction.

If material is inevitably squeezed out laterally, this will removed by cutting so that the response area 18 is substantially the same Width as the connection ends 16d and 17d, but considerably smaller than this having. The cross section of the fusible conductor 12d is thus in the response area 18 Bandy thin and elliptical in the connection ends 16d and 17d, as shown laterally is indicated in FIG.

Electrical fuse Priority: German patent application P 32 02 384.7 of 01/26/1982 (internal priority) List of reference symbols 11 - NH fuse link 12, 12b, c, d - fusible link 13 - ceramic body 14 - face plate 15 - contact blade 16, 17 - connection ends 16b - end regions 16c, 17 '- connection ends 16c, d, e - connection end 16f - welding end 17b - end area 17c, d, e - connecting ends 17f - end area 18 - response area 19 - shorter bottleneck 20 - longer bottleneck 21 - bead 22 - Eutectic solder 23 - blank 23 ', 23 "- sections 23a - blank 23b - conductor strips 24 - total length 25 - dashed lines 26 - spot welds 27 - linear Welds 28 - electrical conductor 29 - welding point 30 - electrical conductor 31, 32 - welds 33 - spot weld

Claims (12)

Electronic fuse Priority: German patent application P 32 02 384.7 of 01/26/1982 (inner priority) patent claims electrical fuse with a fusible link, which is formed with narrow points on both sides of it Has response range terminal ends that are connected to the contact elements of the fuse are electrically connected, characterized in that at least one of the connection ends of the fusible conductor (12) with an increase in the conductor cross-section, but no more than enlargement of the conductor surface and the fusible conductor width caused by the thickening is thickened compared to the band-shaped response area (18). 2) fuse according to claim 1, characterized in that the fusible conductor (12) is formed from strip material that extends over its entire length or width is formed with a substantially uniform thickness, and that the Fusible conductor (12) made of this strip material in the region of at least one of its connection ends enlarged and folded over once or several times. 3) fuse according to claim 2, characterized in that the folded layers of fusible tape at the transition to the response area (18) are connected to one another in an electrically conductive manner, preferably by being welded together are. 4) fuse according to claim 2 or 3, characterized in that that the fusible tape in the area of at least one connection end with enlarged Cut the length and the excess length of the fusible tape to the respective Connector end is folded back .. 5) fuse according to claim 2 or 3, characterized in that that the fusible conductor strip in at least one of the areas forming the connection ends cut with sometimes greater width than in the area forming the response area and is folded up laterally to form the respective connection end. 6) fuse according to claim 5, characterized in that the Fusible conductor (12) trapezoidal from the at least one of its connecting ends Fusible conductor width in the connection area (18) to double to multiple, for example triple width at the free end is cut and the lateral Widenings, if necessary, folded overlapping laterally onto the respective connection end are. 7) fuse according to claim 1, characterized in that the Fusible conductor (12) in at least one of its connecting ends by means of an additional Conductor strip (23b) selected thickness is thickened, which is electrically conductive Connection to the corresponding molded fuse element blank (23) Connection end applied, preferably welded on. 8.) Fuse according to claim 1, characterized in that the fusible conductor (12) is formed from strip material (23 ', 23 ") which is in at least one of its connecting ends of the fusible conductor (12) forming areas with a larger Band thickness than in its forming the response area (18) of the fusible conductor (12) Area is pre-profiled. 9.) Fuse according to claim 1, characterized in that the fuse element made of wire-shaped material with a minimized volume-to-surface ratio, is preferably formed from round profile wire, in which the response area (18) formed by flattening with a smaller conductor cross-section than the connection ends is. 10.) Fuse according to claim 9, characterized in that the response area (18) to a greater width and smaller thickness than the terminal ends is shaped. 11.) Fuse according to claim 9, characterized in that the response area (18) with axial stretching to the same width and smaller Thickness is shaped as the terminal ends. 12.) Fuse according to one of claims 1 to 11, characterized in that that at least one of the connection ends of the fusible conductor (12) opposite the response area (18) is thickened and consists of such a material that considerably lower specific thermal conductivity, but only slightly lower electrical conductivity as the material from which the actual response area (18) of the Fusible conductor (12) consists.