Electric fuse with a melting member, a melting member suitable for being used in such fuse, and method for manufacturing thereof

Abstract

The present invention refers to an electric fuse with a melting member (4), in which, by means of a surprisingly simple and technologically feasible measures, mechanical damages of the melting member (4) are eliminated, namely damages, which might result from variable mechanical stresses, which even during the regular use of the fuse may occur due to temperature changes, which result from varying of the electric current through the melting member (4) and which may have a decisive impact in view of efficiency, durability and reliability of the fuse as such. The electric fuse consists of an electric insulating casing (1) with a central throughout passage (10), through which said melting member (4) extends and is surrounded by an arc extinguishing material (5). Said passage (10) within the casing (1) is on each one of the front sides (11, 12) of the casing (1) closed by means of an electric conductive cover (2, 3). Said melting member (4) is mechanically in a non-detachable manner and also electrically connected with each one of said covers (2, 3), wherein the invention proposes that the melting member (4) is conceived as strip (49'), which consisting of an electric conductive metallic plate having a pre-determined melting temperature and electric resistance, and which is easily deformable, namely extendable and / or shrinkable in its longitudinal direction. The invention also refers to the melting member (4) as such, and also to a method for manufacturing thereof.

Description

[0001] Electric fuse with a melting member, a melting member suitable for being used in such fuse, and method for manufacturing thereof

[0002] The invention refers to an electric fuse with knife-blade contacts. Such inventions belong to electricity, namely to basic electric components, namely to fuses, in which the current is flowing through a part of meltable material, which is by excessive current interrupted or relocated, and in particular to knife-blade fuses, wherein this particular invention also refers to construction concept of the melting member as such.

[0003] In this, the purpose of the invention is preventing damages on such fuse with a melting member, which may occur due to variations of mechanical stresses resulting from temperature changes, which may occur even during regular use of the fuse due to essential variations i.e. oscillations of the electric current through the melting member, and which may have crucial impact with regard to efficiency, durability and reliability of the fuse as such.

[0004] The present invention refers to an electric fuse, which comprises a tubular casing, consisting of an electric insulating material, as well as two covers, which consist of electric conductive material and are, each per se, tightly matching placed onto each open terminal portion of tubular said casing, and moreover also at least one melting member, which extends within the interior of said casing in the longitudinal direction thereof and is both mechanically and electrically connected to each one of said electric conductive covers. Said melting member consists of an electric conductive material in the form of a strip with pre-determined dimensions and in particular with exactly pre-determined cross-section. To this aim, said melting member is furnished with weakening areas, by which its cross-section is exactly defined, so that also the electric resistance of the melting member is well-defined in advance, which allows anticipation that, with a sufficiently high probability, by exceeding of a pre-defined electric current through the melting member, the melting member will due to its resistance start heating in the area adjacent to at least one of its weakened areas, upon which the material thereof stars melting, which leads to interruption of the melting member, which then becomes electric impermeable. Despite to that, there is often some risk that an electric arc starts burning between both interrupted parts of the melting member, which on the one hand still allows conducting of the electric current and on the other hand exposes the surrounding to the risk of fire, so that for such reason said melting member is usually embedded within a granulated silica or any other material, which is suitable for extinguishing of said electric arc and by which the throughout passage within said tubular casing is at least partially filled.

[0005] Such concept of the electric fuse is substantially applied in various embodiments of fuses, even in standardized fuses, namely in a fuse with cylindrical covers, which is disclosed in US 12,002,642 B2, or in a fuse with knife-blade contacts, which is disclosed in EP 3 210 231 Bl and WO 2022 / 025828 Al and in which said electric conductive covers are furnished with apart from each other protruding flat protrusions, by means of which the fuse is insertable into a fork-shaped contacting seat.

[0006] Said melting member is usually, at least in high-performance fuses for protection of high-current electric circuit, a single straight strip, which consists of electric conductive metallic plate and is furnished with said weakening areas and is on each one of its terminal portions soldered to the belonging electric conductive cover on the fuse casing, so that the melting member is both mechanically and electrically connected with said covers. In general, the melting member may be either uniform, or may also be assembled of e.g. two, three or even up to twelve metallic strips of the previously explained art, which are in suitable manner arranged within the interior of said electric insulating tubular casing of the fuse, such that said strips are spaced apart from each other and are, each per se, also surrounded by said arc extinguishing material, wherein each of them is mechanically and electrically connected with said covers. Said pre-defined resistance of each one of said strips, namely either of an uniform or of an assembled melting member, can be achieved on the other hand by suitable selection of the material of said metallic strip with a pre-determined width and thickness, and on the other hand by proper arrangement said cross-section weakening areas, which are equidistantly spaced in the longitudinal direction of the strip, wherein each one of said weakening areas on the strip is formed as a transversally arranged sequence of preferably round throughout bores of a predetermined diameter, which are equally distanced apart from each other, so that a passage of a pre-determined width is available between each two neighboring bores, by which a precisely defined cross-section of each melting member is established, which allows conducting of the electric current throughout such melting member. Such concept of the melting member is explained in more detail in EP 3 210 231 Bl, although this document is merely dealing with efficient extinguishing of electric arc by means of additional silicone barriers applied in the areas between each neighboring weakening areas on the melting member.

[0007] Also in a solution according to US 12,002,642 B2, the melting member is arranged within the interior of the electric insulating tubular casing, and is conceived in accordance with the previously described concept, which means that it is on each one of its terminal portions electrically and mechanically, e.g. by means of soldering, connected with each one of electrically conductive covers, which are each per se arranged on each one of terminal portions of the said casing. In such case, each of said covers comprises, in its interior, an additional plastically deformable barrier, which is arranged transversely with regards to said tubular casing, and by which on the one hand the passage within the casing is covered, while on the other hand the melting member is mechanically and electrically connected there-with. The purpose of embedding of said barrier is establishing of larger mutual distance between both parts of the melting member upon melting and interruption thereof, which contributes to extinguishing of the electric arc. When the melting member starts melting, some gas is released, by which said barrier becomes deflected outwardly, and pulls the belonging part of the melting member attached thereto. Consequently, both parts of the interrupted melting member are then essentially more distanced apart from each other, as they would be without applying such a measure.

[0008] In known solutions, generally a quick and efficient interruption of the electric circuit throughout the fuse should be assured as soon as the electric loading would exceed a pre-determined value, which may, e.g., occur in a short-circuit situation, or an excessive current through the melting member. In such cases, the melting member starts overheating in the area of one of said weakened areas, and is then locally molten, upon which the melting member remains interrupted and unable to conduct the electric current.

[0009] In particular in AC-electric circuit, the melting member is pretty uniformly loaded during the regular operation of the fuse, so that, except in a short-circuit or in an excessive current situation, the melting member as such should normally not be exposed to stresses, which during said regular operation could lead to mechanical damages of the melting member and consequently to unreliable operation of the fuse as such. Also in DC-electric circuits, in which during its regular operation the electric current through the melting member is at least approximately uniform, the melting member as such should not be exposed to stresses, which could during a regular operation lead to damages of the melting member and consequently to reliable operation of the fuse as such.

[0010] However, in appliances for exploitation of natural energy sources, namely in electric circuits belonging to solar plants or wind turbine electric plants, or also in electric vehicles, the electric circuits are often characterized by quite variable operation regime and electric loadings. When protecting such an electric circuit by means of a fuse with a melting member, the last is also furnished with weakened areas and is aimed to interrupt the electric current, if the electric current would exceed a pre-determined value. Due to variations of the electric current through such melting member, the last may often essentially heat, although the value of the electric current is still below the maximal allowable value, upon which it is cooled due o decreasing of the electric current there-through. Consequently, due to such frequently and randomly repeated heating, together with expanding, and cooling, together with shrinking, such melting member is exposed to essential mechanical stresses, which may during the time lead to damages, or even to interruption, of the melting member, although the maximal allowable value of the electric current there-through has in fact never been reached at all. Namely, the melting member is mechanically connected with both covers, and the distance between said covers is fixed, so that by heating of the melting member, the last would need to extend, which leads to plastic deformation of its material in said weakened areas. Thus, the melting member should have the possibility to extend, when heated, but the distance between the covers is fixed, which in plasticized state of the material leads to compression of the material and increasing of the transversal cross-section of the material in said weakened areas, which per se leads to certain change of its electric resistance, which is however a crucial characteristics of the electric fuse. In addition to that, as soon as the electric current through the fuse is reduced, said plasticized material is solidified, and is moreover shrinking during the further cooling of the melting member, which is however difficult due to said fixed distance between both covers, to which it is attached. Consequently, upon cooling down the melting member, the material between bores in said weakened areas is exposed to essential tension stresses. Those skilled in the art will no doubt understand that such repeating exposure of the melting member to essential variations of the electric current and to related temperature changes may easily lead to mechanical damages thereof in the sense of either interruption or cracking in the area of at least a part of material in said weakened areas thereof, which however leads to essential change of its cross-section and consequently to interruption of conduction of the electric current through the fuse, although the nominal value of the current has not been reached or even exceeded at all.

[0011] The present invention generally refers to an electric fuse with a melting member, wherein such fuse generally comprises a tubular casing, which as such consists of an electric insulating material and is furnished with a centrally arranged longitudinal passage, which is on each one of both front sides of said casing tightly closed by means of an electrically conductive contact cover. An electrically conductive melting member is available between said contact covers, which extends along said passage within the casing and is in the area of each one of its terminal portions mechanically, in a non-detachable manner, and also electrically connected with each one of said contact covers. In this, said melting member consists of a material having a pre-determined electric resistance and melting temperature and is formed of a metallic strip of a pre-determined thickness and width, which is, when extending in the longitudinal direction of said passage within the fuse casing, in a previously mentioned manner mountable between said covers and is furnished with at least three weakened areas, which are, when observed in the longitudinal direction of the melting member of the fuse, arranged equidistantly with regard to each other. Each of said weakened areas consists of a sequence of throughout bores, wherein each one of said sequences is oriented transversally with regard to said longitudinal direction of the melting member, and said bores are uniformly distanced apart from each other and are equal to each other with regard to a shape and a characteristic dimension thereof.

[0012] Correspondingly, an electric conductive bridge is arranged between each two neighboring bores and has a pre-determined cross-section, which is defined by its thickness, which corresponds to said thickness of the strip, and its width, which corresponds to the distance between each two neighboring bores within the sequence of each weakened area on the melting member. Thus, depending on the width of said metallic strip of the melting member and the number of said throughout bores and the bridges available among them, the complete cross-section of each weakened area is defined, on which the electric resistance of the melting member as such is depending. Moreover, said passage within the fuse casing is filled with a granulated electric insulating and arc extinguishing material, by which the melting member is at least partially surrounded.

[0013] The invention proposes that said melting member is conceived as a strip, which consists of an electrically conductive metallic material having pre-determined electric resistance and melting temperature, and which is easily deformable, namely extensible and / or shrinkable in its longitudinal direction, and which comprises straight terminal portions, which extend co-planar with each other in the longitudinal direction of said throughout passage within the fuse casing, between which there is a corrugated central portion, which is formed as a sequence of ridges and grooves of a pre-determined width and height, which are in view of dimensions thereof equal to each other and extend equidistantly and transversely with regard to the longitudinal axis of the melting member and in parallel with each other. Accordingly, a groove is available between each two neighboring ridges, or vice versa. All disposable weakened areas, which consist of mutually equal throughout bores having a characteristic dimension of each of them smaller than said width of said ridges or said grooves and being equidistantly arranged at the distance apart from each other, are arranged in just some of disposable ridges, or in just some of disposable grooves, namely exclusively on the one side of the melting member, when observed relatively to the central longitudinal direction of the passage within the fuse casing.

[0014] In a preferred embodiment the thickness (A) of the metallic plate or the metallic strip, of which the melting member consists, is selected within the range

[0015] 0,04 mm A 0,5 mm, the width (d) of each bridge between each two neighboring bores in each weakened area is selected within the range

[0016] 0,1 mm <1 d 0,5 mm, said width (B) of each ridge and also of each groove is determined on the basis of the thickness (A) of the metallic strip, of which the melting member consists, in such a way that the following condition is fulfilled

[0017] 10xA B 40xA while said width (C) of each ridge and also of each groove is determined depending on characteristic dimension (D) of each one of said throughout bores in the belonging weakened area in such a way, that the following condition is fulfilled

[0018] 1,0 x D <; C 2,0xD.

[0019] In one of the embodiments of invention, each one of both electric conductive covers, with which the melting member is electrically and mechanically connected, is furnished with a plane, smooth and continuous external front surface.

[0020] In another embodiment of the invention, each electric conductive covers, with which the melting member is electrically and mechanically connected, is in the area of its external front surface furnished with an electric conductive protrusion, which is arranged rectangular with respect to said front surface and protrudes in a direction away from the fuse casing and the melting member. In this, said apart from each other protruding protrusions on said electric conductive covers are coplanar i.e. arranged within the same plane and are formed as knife-blade contacts of the fuse.

[0021] The fuse according to the invention may comprise a single melting member, which is centrally arranged within said passage in the fuse casing and which is mechanically and electrically connected with said electric conductive fuse cover and is surrounded with arc extinguishing material. However, a further embodiment is also possible according to the invention, in which at least two melting members are foreseen, which are arranged in parallel with each other within said passage in the fuse casing, and which are spaced apart from each other and are each per se mechanically and electrically connected with said electric conductive fuse covers and also surrounded with arc extinguishing material. One of the further embodiments of the invention provides that each one of said throughout bores in each weakened area of the melting member is formed as a round bore with a characteristic dimension, which corresponds to the diameter of circumferential circle of the bore.

[0022] An alternative embodiment of the invention provides that each one of said throughout bores in each weakened area of the melting member is formed as an elliptic bore with a characteristic dimension, which corresponds to the longer geometric axis of the ellipse, which forms the circumference of the bore.

[0023] A further alternative embodiment of the invention provides that each one of said throughout bores in each weakened area of the melting member is formed as a rectangular bore with a characteristic dimension, which corresponds to the longer side of the rectangle, which forms the circumference of the bore.

[0024] A still further alternative embodiment of the invention provides that each one of said throughout bores in each weakened area of the melting member is formed as a square bore with a characteristic dimension, which corresponds to the side of the square, which forms the circumference of the bore.

[0025] The invention also refer to the melting member as such, wherein said melting member comprises all previously mentioned features, by which the initially exposed technical problem is solved, and which is as such mountable into one of electric fuses, which are characterized by previously mentioned features.

[0026] The invention furthermore refers to a method for manufacturing of a melting member by processing of an electric conductive metal plate having a predetermined thickness and consisting of a material with a pre-determined melting temperature and electric resistance, which is cut to strips of a pre-determined length and width and furnished with a pre-determined number of weakened areas, which are in the longitudinal direction of said strip spaced apart from each other, such that each of said weakened areas consists of a perforated, transversally with regard to said longitudinal direction of the strip extending sequence of equally distanced throughout bores of a pre-determined shape and characteristic dimension, so that an electric conductive bridge is established between each two neighboring bores, the thickness of which corresponds to the distance between each two neighboring throughout bores) of said pre-determined shape and characteristic dimension.

[0027] When performing such method according to the invention

[0028] - in the first step ( ) a suitable band-shaped raw material is formed of an electric conductive metallic plate having a pre-defined electric resistance, a pre-defined melting temperature and a pre-defined thickness (A), wherein the width of said raw-material band is selected in such manner that it is equal or longer than the total length of the melting member with claimed features and processed according to the subsequent steps in its straight i.e. flat state, wherein said thickness (A) of the metallic plate is selected within the range

[0029] 0,04 mm A 0,5 mm,

[0030] - upon which, in the second step («"), said raw-material band, namely said metallic plate, is by means of cold deformation transformed to a semi-product, consisting of unprocessed flat terminal areas as well as of an orthotropic, namely bent and corrugated central area, which consists of a sequence of substantially rectangular in their profile shaped ridges and grooves of a pre-determined width (C) and height (B), which extend equidistantly and in parallel with each other and are mutually equal with regard to dimensions thereof, so that between each two neighboring ridges on said semi-product a groove is formed, or vice versa, so that, depending on said thickness (A) of said plate as well as on each selected shape and characteristic dimension (D) of said throughout bores in said weakened areas of the melting member the height (B) of each one of said ridges, and also of each one of said grooves, fulfills the condition

[0031] 10xA B 40xA, and the width (C) of each one of said ridges, as well as of each one of said grooves, fulfills the condition

[0032] 1,0xD C 2,0xD;

[0033] - upon which, in the third step (Hi), in the area of at least three of said ridges, or in the area of at least three of said grooves, said metallic plate is exposed to perforating with the aim of providing said weakened areas by forming of an along each selected ridge, or of an along each selected groove extending and centrally arranged sequence of equidistantly, namely at a distance (d), which is selected within the range

[0034] 0,1 0,5 mm, apart from each other spaced through bores of a pre-determined shape and characteristic dimension (D), so that between each two neighboring throughout bores an electric conductive bridge is established, the thickness of which corresponds to thickness (A) of the metallic plate, and the width thereof corresponds to the distance (d) between each two neighboring throughout bores) of a pre-determined shape and characteristic dimension (D), - upon which, in the fourth step (iv), said semi-product, upon being cold formed in said second step (z7) and then perforated in said third step (Hi), is exposed to cutting in the transversal direction with regard to orientation of the metallic band as used in the first step ( / ), due to establishing of separate strips with corrugated central area and a pre-determined width (T), which corresponds to the width of the produced melting member, which is then, if needed, followed by final cutting due to adjusting of the length of the final product, which is performed in the longitudinal direction, when taking into consideration the orientation of the belt used in the first step ( / *), namely adjusting of the length thereof, which corresponds to the length (L) of a finalized melting member suitable for being integrated into an electric fuse, which is determined by the distance between both electric conductive covers on the casing of the electric fuse, into which said melting member is mountable.

[0035] The invention will be disclosed in more detail on the basis of embodiment and in relationship with the enclosed drawings, wherein

[0036] Fig. 1 presents a known electric fuse with a melding member in longitudinal cross-section in its diametric plane;

[0037] Fig. 2 presents the fuse according to Fig. 1, also in longitudinal cross-section, but in another diametric plane perpendicular with regard to the plane of Fig. 1;

[0038] Fig. 3 presents the fuse according to the invention in longitudinal cross-section in its diametric plane analogous to Fig. 1;

[0039] Fig. 4 presents the fuse according to the invention in longitudinal cross-section in its diametric plane analogous to Fig. 2;

[0040] Fig. 5 presents a further embodiment of the fuse, also in longitudinal crosssection in its diametric plane analogous to Fig. 3;

[0041] Fig. 6 presents a detail P according to Fig. 3 in isometric view; Fig. 7 presents a raw material used in manufacturing of the melting member according to Figs. 3 - 6, in isometric view;

[0042] Fig. 8 presents a semi-product upon performing of the second step of a method for manufacturing of the melting member according to Figs. 3 - 6, in isometric view;

[0043] Fig. 9 presents a semi-product upon performing of the third step of a method for manufacturing of the melting member according to Figs. 3 - 6, in isometric view;

[0044] Fig. 10 schematically presents performing of the fourth step of a method for manufacturing of the melting member according to Figs. 3 - 6, in isometric view.

[0045] A classic electric fuse with a melting member 4, which is known in the prior art, is shown in Figs 1 and 2. Such fuse generally comprises tubular casing 1, which consists of an electric insulating material, in particular of ceramics, but when desired, it may also consist of any other insulating material with sufficient electric insulating capability and resistance against mechanical damages or weather impacts, like e.g. of a properly reinforced composite material on the basis of artificial resins. Said casing 1 is furnished with a centrally arranged longitudinal passage 10, which is on each one of both front sides 11, 12 of said casing 1 tightly closed by means of an electrically conductive contact cover 2, 3. An electrically conductive melting member 4 is available between said contact covers 2, 3, and extends along said passage 10 within the casing (1) and is in the area of each one of its terminal portions 44’, 44” mechanically in a non-detachable manner, and also electrically, connected with each one of said contact covers 2, 3. In practice, the melting member 4 is usually soldered to both contact covers 2, 3. Besides, the melting member 4 is conceived in such a way that it consists of a material, which has a pre-determined electric resistance and melting temperature, and is formed of a metallic strip 49’ of a pre-determined thickness A and width T, which is, when extending in the longitudinal direction 100 of said passage 10 within the fuse casing 1, in a previously mentioned manner mountable between said covers 2, 3 and is furnished with at least three weakened areas 40, 40’, 40” (Fig. 1), which are, when observed in the longitudinal direction of the melting member 4 of the fuse, arranged at least approximately equidistantly with regard to each other.

[0046] Each of said weakened areas 40, 40’, 40” consists of a sequence of throughout bores 41, 41 ’, 41 ”, wherein each one of said sequences is oriented transversally with regard to said longitudinal direction of the melting member 4, and said bores 41, 41’, 41” are distanced apart from each other at uniform distance d. Said bores 41, 41’, 41” are equal to each other with regard to shape and also a characteristic dimension D thereof, which should in a round bore mean a diameter thereof, in an elliptic bore the longer axis of the ellipse, in a rectangular bore its longer side, and in a square bore one of the sides thereof.

[0047] An electric conductive bridge 42’, 42” is arranged between each two neighboring bores 41, 41 ’, 41 ”, having a pre-determined cross-section, which is defined by its thickness, which corresponds to said thickness A of the strip 49’, and its width, which corresponds to the distance d between each two neighboring bores 41, 41’, 41” within the sequence of each weakened area 40, 40’, 40” on the melting member 4. Accordingly, on the basis of said width T of said metallic strip 49’ of the melting member 4 and the number of said throughout bores 41, 41', 41" and the bridges 42’, 42” available among them, the complete cross-section of each weakened area 40, 40’, 40” is well-defined, wherein the electric resistance of the melting member 4 depends on said cross-section. In addition to that, said passage 10 within the fuse casing 1 is normally filled with a granulated electric insulating and arc extinguishing material 5, by which the melting member 4 is at least partially surrounded, and which is e.g. a suitably granulated silica. The first embodiment of the invention is presented in Figs. 3 and 4. As visible in particular in Fig. 4, each melting member is prima facie conceived as a strip 49’, which is easily deformable in its longitudinal direction, namely easily extendable and / or shrinkable by applying just a small force, and which consists of an electrically conductive metallic material having pre-determined electric resistance and melting temperature. Such melting member 4 comprises straight and mutually co-planar terminal portions 44’, 44”, which extend in the longitudinal direction of said throughout passage 10 within the fuse casing 1, and between said terminal portions there is a corrugated central portion 48, which is formed as a sequence of ridges 45, 45’, 45” and grooves 46, 46’, 46” of a pre-determined width C and height B, which are in view of dimensions thereof equal to each other and extend equidistantly and transversely with regard to the longitudinal axis of the melting member 4 and in parallel with each other, so that a groove 46, 46’, 46” is available between each two neighboring ridges 45, 45’, 45”, or vice versa. Each disposable weakened areas 40, 40’, 40”, each one of which consist of a plurality of mutually equal throughout bores 41’, 41’, 41” having a characteristic dimension D, which is smaller than said width C of ridges 45, 45’, 45” or grooves (46, 46’, 46”), wherein said bores 41’, 41 ’, 41” are equidistantly arranged at the distance d apart from each other, wherein said weakened areas 40, 40’, 40” are arranged in just some of disposable ridges 45, 45’, 45”, or in just some of disposable grooves 46, 46’, 46”. This means that all disposable weakened areas 40, 40’, 40” are, either exclusively on ridges 45, 45’, 45” or exclusively on grooves 46, 46’, 46”, arranged exclusively on the one side of the melting member 4, when observed relatively to the central longitudinal direction 100 of the passage 10 within the fuse casing 1.

[0048] In this, the thickness A of the metallic plate 49 or the metallic strip 49’, of which the melting member 4 consists, is selected within the range 0,04 mm < A 0,5 mm, the width d of each bridge 42’, 42” between each two neighboring bores 41, 41 ’, 41” in each weakened area 40, 40’, 40” is selected within the range

[0049] 0,1 mm d 0,5 mm, said width B of each ridge 45, 45’, 45” and also of each groove 46, 46’, 46” is determined on the basis of the thickness A of the metallic strip 49’, of which the melting member 4 consists, in such a way that the following condition is fulfilled

[0050] 10xA <> B 40xA, while said width C of each ridge 45, 45’, 45” and also of each groove 46, 46’, 46”s determined depending on characteristic dimension D of each one of said throughout bores 41, 41’, 41 ” in the belonging weakened area 40, 40’, 40” in such a way, that the following condition is fulfilled

[0051] 1,0 x D C 2,0xD.

[0052] In one of the embodiment of the invention, each one of both electric conductive covers 2, 3, to which the melting member 4 is electrically and mechanically connected, is furnished with a plane, smooth and continuous external front surface 20, 30. The shape and dimensions of such a fuse can be arranged in accordance with a standardized fuse pursuant to standard IEC 60947-1 :2004, or 60947-1 :2020, or in accordance with one of variations, as disclosed in WO 2021 / 101453 Al. In a further embodiment of the invention, each one of the electric conductive covers 2, 3, to which the melting member 4 is electrically and mechanically connected, is in the area of its external front surface 20, 30 furnished with an electric conductive protrusion 21, 31, which is arranged rectangular with respect to said front surface and protrudes in a direction away from the fuse casing 1 and the melting member 4, wherein such a protrusion may, when desired, also be furnished with a throughout bore suitable for establishing of a detachable interconnection with an electric conductor, which is integrated in an electric circuit together with the melting member 4 of the electric fuse according to the invention. In a further possible embodiment of the invention, said apart from each other protruding protrusions 21, 31 on said electric conductive covers 2, 3 are arranged co-planar with each other, namely arranged within the same plane, and are formed as knifeblade contacts of the fuse, by means of which the fuse is tightly matching insertable into suitable fork-shaped seats in order to be integrated into an electric circuit, which is upon that protected by means of said fuse.

[0053] In recently described embodiments, which substantially refer to Figs. 3 and 4, the electric fuse comprises a single melting member 4, which is centrally arranged within said passage 10 in the fuse casing 1 and which is mechanically and electrically connected with said electric conductive fuse covers 2, 3 and is moreover surrounded with said arc extinguishing material 5.

[0054] However, and embodiment of a heavy duty fuse is also possible, according to which (Fig. 5) the fuse comprises at least two melting members 4, 4’, 4”, which are spaced apart from each other and are arranged substantially in parallel with each other within said passage 10 in the fuse casing 1, and are moreover each per se mechanically and electrically connected with said electric conductive fuse covers 2, 3 and also surrounded with arc extinguishing material 5. In the shown embodiment, the fuse comprises three or four melting members 4, which are all arranged within said passage 10 in the fuse casing 1, and are properly spaced apart from each other, wherein each of them is also surrounded with said arc extinguishing material 5 and is, independently on the other melting members 4, 4’, 4”, mechanically and electrically connected with both belonging electric conductive covers 2, 3 on the fuse casing 1.

[0055] Regarding the fuse according to the invention, various embodiments are possible also in view of the shape of said throughout bores 41, 41’, 41 ” in the weakened areas 40, 40’, 40” of the melting member 4 according to the invention. In the first one of these embodiments, each one of said throughout bores 41, 41’, 41” in each weakened area 40, 40’, 40” of the melting member 4 is formed as a round bore with a characteristic dimension D, which corresponds to the diameter of circumferential circle of the bore 41, 41’, 41 ”. In the second embodiment, each one of said throughout bores 41, 41 ’, 41 ” in each weakened area 40, 40’, 40” of the melting member 4 is formed as an elliptic bore with a characteristic dimension D, which corresponds to the longer geometric axis of the ellipse, which forms the circumference of the bore 41, 41’, 41”. In the third embodiment, each one of said throughout bores 41, 41’, 41” in each weakened area 40, 40’, 40” of the melting member 4 is formed as a rectangular bore with a characteristic dimension D, which corresponds to the longer side of the rectangle, which forms the circumference of the bore 41, 41’, 41”. In the fourth embodiment, each one of said throughout bores 41, 41’, 41” in each weakened area 40, 40’, 40” of the melting member 4 is formed as a square bore with a characteristic dimension D, which corresponds to the side of the square, which forms the circumference of the bore 41, 1 ’, 41”.

[0056] Modification of the electric fuse, which by means of the previously expressed features thereof resolves the initially stated technical problem, in fact required also a brand new concept of a method for manufacturing of the melting member 4 as such. Manufacturing thereof by using known, commonly used and at a first glance logical approaches would namely lead to inaccuracy and variations of shape and / or dimensions of throughout bores 41, 41’, 41” and bridges 42’, 42” arranged between each two of them, which would have direct impact to the cross-section of the melting member 4 and the electric resistance thereof. Such method for manufacturing of a melting member 4 is namely performed by processing of an electric conductive metal plate 49 having a pre-determined thickness A and consisting of a material with a pre-determined melting temperature and electric resistance, which is cut to strips 49’ of a pre-determined length L and width T and is then furnished with a pre-determined number of weakened areas 40, 40’, 40”, which are in the longitudinal direction of said strip 49’ spaced apart from each other, such that each of said weakened areas 40, 40’, 40” consists of a perforated, transversally with regard to said longitudinal direction of the strip 49’ extending sequence of equally distanced throughout bores 41, 41’, 41 ” of a pre-determined shape and characteristic dimension D. Consequently, an electric conductive bridge 42, 42’ is established between each two neighboring bores 41, 41 ’, 41”, the thickness of which corresponds to the distance d between each two neighboring throughout bores 41, 41’, 41” of said pre-determined shape and characteristic dimension D. Formation of the required ridges 45, 45’, 45” and grooves 46, 46’, 46” upon that would no doubt lead to modification of shape and / or characteristic dimension D of throughout bores 41, 41 ’, 41” and / or of each bridge 42, 42’ established between each two of them.

[0057] Of that reason, a method for manufacturing of the melting member 4, having previously disclosed features and being suitable for mounting into an electric fuse, has been developed in accordance within the scope of the present invention, wherein said method provides that - in the first step ( / ) a suitable band-shaped raw material is formed of an electric conductive metallic plate 49 having a pre-defined electric resistance, a pre-defined melting temperature and a pre-defined thickness A, wherein the width of said rawmaterial band is selected in such manner that it is equal or longer than the total length of the melting member 4 with claimed features and processed according to the subsequent steps in its straight i.e. flat state, wherein said thickness A of the metallic plate 49 is selected within the range

[0058] 0,04 mm A 0,5 mm,

[0059] - upon which, in the second step (w), said raw-material band, namely said metallic plate 49, is by means of cold deformation transformed to a semi-product, consisting of unprocessed flat terminal areas 48’, 48” as well as of an orthotropic, namely bent and corrugated central area 48, which consists of a sequence of substantially rectangular in their profile shaped ridges 45, 45’, 45” and grooves 46, 46’, 46” of a pre-determined width C and height B, which extend equidistantly and in parallel with each other and are mutually equal with regard to dimensions thereof, so that between each two neighboring ridges 45, 45’, 45” on said semiproduct a groove 46, 46’, 46” is formed, or vice versa, and that, depending on said thickness A of said plate 49 as well as on each selected shape and characteristic dimension D of said throughout bores 41, 41', 41" in said weakened areas 40, 40', 40" of the melting member 4, the height B of each one of said ridges 45, 45’, 45”, and also of each one of said grooves 46, 46’, 46”, fulfills the condition

[0060] 10xA B 40xA, and the width C of each one of said ridges 45, 45’, 45”, as well as of each one of said grooves 46, 46’, 46”, fulfills the condition

[0061] 1,0xD C 2,0xD;

[0062] - upon which, in the third step (z77), in the area of at least three of said ridges 45, 45’, 45”, or in the area of at least three of said grooves 46, 46’, 46”, said metallic plate 49 is exposed to perforating with the aim of providing said weakened areas 40, 40’, 40” by forming of an along each selected ridge 45, 45’, 45, or of an along each selected groove 46, 46’, 46” extending and centrally arranged sequence of equidistantly, namely at a distance d, which is selected within the range

[0063] 0,1 mm d 0,5 mm, apart from each other spaced through bores 41, 41’, 41” of a pre-determined shape and characteristic dimension D, so that between each two neighboring throughout bores 41, 41 ’, 41 ” an electric conductive bridge 42, 42', 42" is established, the thickness of which corresponds to thickness A of the metallic plate 49, and the width thereof corresponds to the distance d between each two neighboring throughout bores 41, 41’, 41 ” of a pre-determined shape and characteristic dimension D,

[0064] - upon which, in the fourth step ( / v), said semi-product, upon being cold formed in said second step (ii) and then perforated in said third step (Hi), is exposed to cutting in the transversal direction with regard to orientation of the metallic band as used in the first step (Z), due to establishing of separate strips 49’ with corrugated central area 48 and a pre-determined width T, which corresponds to the width of the produced melting member 4, which is then, if needed, followed by final cutting due to adjusting of the length of the final product, which is performed in the longitudinal direction, when taking into consideration the orientation of the belt used in the first step (Z), namely adjusting of the length thereof, which corresponds to the length (L) of a finalized melting member 4 suitable for being integrated into an electric fuse, which is determined by the distance between both electric conductive covers 2, 3 on the casing 1 of the electric fuse, into which said melting member 4 is mountable.

Claims

CLAIMS1. Electric fuse with a melting member (4), wherein said fuse comprises a tubular casing (1), which consists of an electric insulating material and is furnished with a centrally arranged longitudinal passage (10), which is on each one of both front sides (11, 12) of said casing (1) tightly closed by means of an electrically conductive contact cover (2, 3), and an electrically conductive melting member (4) is available between said contact covers (2, 3), which extends along said passage (10) within the casing (1) and is in the area of each one of its terminal portions (44’, 44”) mechanically, in a non-detachable manner, and also electrically connected with each one of said contact covers (2, 3), wherein such melting member (4) consists of a material having a pre-determined electric resistance and melting temperature and is formed of a metallic strip (49’) of a pre-determined thickness (A) and width (T), which is, when extending in the longitudinal direction (100) of said passage (10) within the fuse casing (1), in a previously mentioned manner mountable between said covers (2, 3) and is furnished with at least three weakened areas (40, 40’, 40”), which are, when observed in the longitudinal direction of the melting member (4) of the fuse, arranged equidistantly with regard to each other, wherein each of said weakened areas (40, 40’, 40”) consists of a sequence of throughout bores (41, 41’, 41”), wherein each one of said sequences is oriented transversally with regard to said longitudinal direction of the melting member (4), and said bores are distanced apart from each other at uniform distance (d) and are equal to each other with regard to a shape and a characteristic dimension (D) thereof, and wherein an electric conductive bridge (42’, 42”) is arranged between each two neighboring bores (41, 41 ’, 41 ”) and has a predetermined cross-section, which is defined by its thickness, which corresponds to said thickness (A) of the strip (49’), and its width, which corresponds to the distance (d) between each two neighboring bores (41, 41 ’, 41 ”) within thesequence of each weakened area (40, 40’, 40”) on the melting member (4), by which, depending on the width (T) of said metallic strip (49’) of the melting member (4) and the number of said throughout bores (41, 41', 41") and the bridges (42’, 42”) available among them, the complete cross-section of each weakened area (40, 40’, 40”) is defined, on which the electric resistance of the melting member (4) as such is depending, and wherein said passage (10) within the fuse casing (1) is filled with a granulated electric insulating and arc extinguishing material (5), by which the melting member (4) is at least partially surrounded, characterized in that said melting member (4) is conceived as a strip (49’), which consists of an electrically conductive metallic material having pre-determined electric resistance and melting temperature, which is easily deformable, namely extensible and / or shrinkable in its longitudinal direction, and which comprises straight terminal portions (44’, 44”), which extend co-planar with each other in the longitudinal direction of said throughout passage (10) within the fuse casing (1), and between which there is a corrugated central portion (48), which is formed as a sequence of ridges (45, 45’, 45”) and grooves (46, 46’, 46”) of a pre-determined width (C) and height (B), which are in view of dimensions thereof equal to each other and extend equidistantly and transversely with regard to the longitudinal axis of the melting member (4) and in parallel with each other, so that a groove (46, 46’, 46”) is available between each two neighboring ridges (45, 45’, 45”), or vice versa, wherein all of the disposable weakened areas (40, 40’, 40”), which consist of mutually equal throughout bores (41 ’, 41 ’, 41”) having a characteristic dimension (D) of each of them smaller than said width (C) of ridges (45, 45’, 45”) or grooves (46, 46’, 46”) and being equidistantly arranged at the distance (d) apart from each other, are arranged in just some of disposable ridges (45, 45’, 45”), or in just some of disposable grooves (46, 46’, 46”), namely exclusively on the one side of the melting member (4), when observed relatively to the central longitudinal direction (100) of the passage (10) within the fuse casing (1).

2. Fuse according to Claim 1, characterized in that the thickness (A) of the metallic plate (49) or the metallic strip (49’), of which the melting member (4) consists, is selected within the range0,04 mm <, A 0,5 mm, the width (d) of each bridge (42’, 42”) between each two neighboring bores (41, 41’, 41”) in each weakened area (40, 40’, 40”) is selected within the range0,1 mm d < 0,5 mm, said width (B) of each ridge (45, 45’, 45”) and also of each groove (46, 46’, 46”) is determined on the basis of the thickness (A) of the metallic strip (49’), of which the melting member (4) consists, in such a way that the following condition is fulfilled10xA B 40xA while said width (C) of each ridge (45, 45’, 45”) and also of each groove (46, 46’, 46”) is determined depending on characteristic dimension (D) of each one of said throughout bores (41, 41 ’, 41”) in the belonging weakened area (40, 40’, 40”) in such a way, that the following condition is fulfilled1,0 x D C 2,0xD.

3. Fuse according to Claim 1 or 2, characterized in that each one of both electric conductive covers (2, 3), with which the melting member (4) is electrically and mechanically connected, is furnished with a plane, smooth and continuous external front surface (20, 30).

4. Fuse according to Claim 1 or 2, characterized in that each one of the electric conductive covers (2, 3), with which the melting member (4) is electrically and mechanically connected, is in the area of its external front surface (20, 30) furnished with an electric conductive protrusion (21, 31), which is arranged rectangular with respect to said front surface and protrudes in a direction away from the fuse casing (1) and the melting member (4).

5. Fuse according to Claim 4, characterized in that said apart from each other protruding protrusions (21, 31) on said electric conductive covers (2, 3) are co-planar i.e. arranged within the same plane and are formed as knife-blade contacts of the fuse.

6. Fuse according to anyone of Claims 1 - 5, characterized in that it comprises a single melting member (4), which is centrally arranged within said passage (10) in the fuse casing (1) and which is mechanically and electrically connected with said electric conductive fuse covers (2, 3) and is surrounded with arc extinguishing material (5).

7. Fuse according to anyone of Claims 1 - 5, characterized in that it comprises at least two melting members (4, 4’, 4”), which are arranged in parallel with each other within said passage (10) in the fuse casing (1), and which are spaced apart from each other and are each per se mechanically and electrically connected with said electric conductive fuse covers (2, 3) and also surrounded with arc extinguishing material (5).

8. Fuse according to anyone of Claims 1 - 7, characterized in that each one of said throughout bores (41, 41’, 41”) in each weakened area (40, 40’, 40”) of the melting member (4) is formed as a round bore with a characteristic dimension(D), which corresponds to the diameter of circumferential circle of the bore (41, 41’, 41 ”).

9. Fuse according to anyone of Claims 1 - 7, characterized in that each one of said throughout bores (41, 41’, 41”) in each weakened area (40, 40’, 40”) of the melting member (4) is formed as an elliptic bore with a characteristic dimension (D), which corresponds to the longer geometric axis of the ellipse, which forms the circumference of the bore (41, 41 ’, 41”).

10. Fuse according to anyone of Claims 1 - 7, characterized in that each one of said throughout bores (41, 41’, 41 ”) in each weakened area (40, 40’, 40”) of the melting member (4) is formed as a rectangular bore with a characteristic dimension (D), which corresponds to the longer side of the rectangle, which forms the circumference of the bore (41, 41’, 41 ”).

11. Fuse according to anyone of Claims 1 - 7, characterized in that each one of said throughout bores (41, 41 ’, 41 ”) in each weakened area (40, 40’, 40”) of the melting member (4) is formed as a square bore with a characteristic dimension (D), which corresponds to the side of the square, which forms the circumference of the bore (41, 41’, 41 ”).

12. Melting member (4) of the electric fuse according to Claims 1 - 11, said melting member comprising all features from the characteristic portion of Claim 1 as well as from the Claims 2 - 5 and 8 - 11.

13. Method for manufacturing of a melting member (4) by processing of an electric conductive metal plate (49) having a pre-determined thickness (A) and consisting of a material with a pre-determined melting temperature and electricresistance, which is cut to strips (49’) of a pre-determined length (L) and width (T) and furnished with a pre-determined number of weakened areas (40, 40’, 40”), which are in the longitudinal direction of said strip (49’) spaced apart from each other, such that each of said weakened areas (40, 40’, 40”) consists of a perforated, transversally with regard to said longitudinal direction of the strip (49’) extending sequence of equally distanced throughout bores (41, 41 ’, 41 ”) of a pre-determined shape and characteristic dimension (D), so that an electric conductive bridge (42, 42’) is established between each two neighboring bores (41, 41 ’, 41 ”), the thickness of which corresponds to the distance (d) between each two neighboring throughout bores (41, 41’, 41”) of said pre-determined shape and characteristic dimension (D), characterized in that- in the first step ( / ) a suitable band-shaped raw material is formed of an electric conductive metallic plate (49) having a pre-defined electric resistance, a predefined melting temperature and a pre-defined thickness (A), wherein the width of said raw-material band is selected in such manner that it is equal or longer than the total length of the melting member (4) according to the preceding claims and processed according to the subsequent steps in its straight i.e. flat state, wherein said thickness (A) of the metallic plate (49) is selected within the range0,04 mm A 0,5 mm,- upon which, in the second step («*), said raw-material band, namely said metallic plate (49), is by means of cold deformation transformed to a semi-product, consisting of unprocessed flat terminal areas (48’, 48”) as well as of an orthotropic, namely bent and corrugated central area (48), which consists of a sequence of substantially rectangular in their profile shaped ridges (45, 45’, 45”) and grooves (46, 46’, 46”) of a pre-determined width (C) and height (B), which extend equidistantly and in parallel with each other and are mutually equal withregard to dimensions thereof, so that between each two neighboring ridges (45, 45’, 45”) on said semi-product a groove (46, 46’, 46”) is formed, or vice versa, and that, depending on said thickness (A) of said plate (49) as well as on each selected shape and characteristic dimension (D) of said throughout bores (41, 41', 41") in said weakened areas (40, 40', 40") of the melting member (4), the height (B) of each one of said ridges (45, 45’, 45”), and also of each one of said grooves (46, 46’, 46”), fulfills the condition10xA B 40xA, and the width (C) of each one of said ridges (45, 45’, 45”), as well as of each one of said grooves (46, 46’, 46”), fulfills the condition1,0xD C 2,0xD;- upon which, in the third step Hi), in the area of at least three of said ridges (45, 45’, 45”), or in the area of at least three of said grooves (46, 46’, 46”), said metallic plate (49) is exposed to perforating with the aim of providing said weakened areas (40, 40’, 40”) by forming of an along each selected ridge (45, 45’, 45), or of an along each selected groove (46, 46’, 46”) extending and centrally arranged sequence of equidistantly, namely at a distance (d), which is selected within the range0,1 mm < d 0,5 mm, apart from each other spaced through bores (41, 41’, 41”) of a pre-determined shape and characteristic dimension (D), so that between each two neighboring throughout bores (41, 41’, 41”) an electric conductive bridge (42, 42', 42") is established, the thickness of which corresponds to thickness (A) of the metallicplate (49), and the width thereof corresponds to the distance (d) between each two neighboring throughout bores (41, 41’, 41”) of a pre-determined shape and characteristic dimension (D),- upon which, in the fourth step (zv), said semi-product, upon being cold formed in said second step (it) and then perforated in said third step (Hi), is exposed to cutting in the transversal direction with regard to orientation of the metallic band as used in the first step (z‘), due to establishing of separate strips (49’) with corrugated central area (48) and a pre-determined width (T), which corresponds to the width of the produced melting member (4), which is then, if needed, followed by final cutting due to adjusting of the length of the final product, which is performed in the longitudinal direction, when taking into consideration the orientation of the belt used in the first step (z‘), namely adjusting of the length thereof, which corresponds to the length (L) of a finalized melting member (4) suitable for being integrated into an electric fuse, which is determined by the distance between both electric conductive covers (2, 3) on the casing (1) of the electric fuse, into which said melting member (4) is mountable.

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