Abstract: To provide a novel cartridge fuse which can prevent the melted fuse member ends from being shorted together after the fuse member has been blown out and to firmly hold terminal members connected by a fuse member within a housing, the cartridge fuse comprises a fuse housing formed with an insulating partition extending therewithin to some extent to form a pair of terminal compartments; a pair of opposing terminal members each formed with a stay portion extending beyond the insulating partition and a contact portion housed within the terminal compartment, a fuse member connected to the stay portions of the opposing terminal members; and elastic members for applying a tension to fuse member in the longitudinal direction thereof.

Abstract: Disclosed is a fuse material consisting of aluminum or a rollable aluminum alloy having a copper plating deposited thereon and optionally being provided with a tin plating deposited on the copper plating. A fuse made of the fuse material shows a small temperature rise and has an extended useful service life as compared to conventional fuses.

Abstract: A current limiting fuse for a transformer bushing including a glass tubing, an elongate ribbon spirally wound in the tubing, the ribbon including a number of tabs formed integral therewith to space the ribbon inwardly of the walls of the tubing, a terminal stud mounted on one end of the tubing and being electrically connected to the ribbon, a conductive rod connected to the other end of the ribbon and sealed in the other end of the tubing, a granular dielectric material completely filling the tubing, a self-sealing, self-bonding, rubber tape wrapped around the outside of the tubing and a glass reinforced tape wrapped around the outside of the rubber tape.

Abstract: A fuse terminal comprising a fusible conductor formed of a Cu alloy having a conductivity of 20--less than 60% (IACS), the fusible conductor being formed with a narrow fuse portion at an intermediate position, and a pair of connection terminals formed at both ends of the fusible conductor and arranged in opposed relation with each other by bending the fusible conductor at both end portions thereof in a gantry fashion. The terminal is characterized by a surface area of the fusible conductor which is 1/8-1/2 of that of the connection terminals.

Abstract: An electrical fuse having an element which includes a strip of conductive metal connectable to the fuse terminals, the strip of conductive material having a plurality of holes through its thickness dimension spaced along the center line of its width, successive ones of the holes through the strip each having a slot joining that hole with an opposite one of the edges from the edge joined by the adjacent hole and its associated slot, the spacing of the holes and their associated slots being such that the current flowing through the fuse element is forced to zig-zag through regions which constrict the current and successive regions which have broad area and volume so that undesired abnormally high temperature rises within the fusing element, which might arise with ordinary over-loads which are not destructive and would cause unnecessary opening of the fuse element, are prevented, while, at the same time, the sensitivity of the fuse element to destructive current surges is retained and, if necessary, fusing time

Abstract: Small plug-in electrical fuses, e.g., for automotive use are formed with a fusible link portion which is partially cut but with the walls of the cut in substantial electrical contact with each other and opposite ends of each link rigidly supported. Initial heating of the link due to current flow in excess of the fuse rating causes bending of the link to open the cut, reducing the available cross-section for current flow and therefore greatly shortening the time necessary to open the link and minimizing the total heat generated in the process.

Abstract: A fuse assembly having a casing, a fuse element made of an electrically conductive material having a low fusion point, and tab insertion sockets into which tab terminals are inserted and which are made of a highly resilient, electrically conductive material having a high fusion point, the fuse element and the tab insertion socket being combined with each other in the casing, the fuse element alone being replaced when blown at a relatively low level of heat generation.

Abstract: In a relay tongue unit intended to be included in an electric relay the unit comprises at least one tongue unit in the form of a resilient sheet consisting of an attaching member, which comprises a main portion (1), a fuse portion (2) and a transition portion (3), and a tongue portion (4). This has at its free end a contact (5) and a resistance portion.

Abstract: A plug-in fuse assembly comprises a housing made of insulating material and having relatively closely spaced vertical side walls bridges by vertical end walls and a metal plug-in fuse element having laterally spaced, generally parallel confronting terminals at the bottom thereof projecting downwardly from the bottom of said housing and upwardly extending current-carrying extensions of said terminals and a unique S-shaped fuse link extending between said current-carrying extensions. The S-shaped fuse link has about a 45.degree. angled upper and lower leg of at least about one-half the length of the central leg thereof and a width to thickness ratio of about 1/2 or less which maximizes its volume without the position contraints placed on the fuse link.

Abstract: An asymmetrical fuse link employs a planar conductive member with the top and bottom surfaces manifested by having a series of alternating partial apertures with the alternating apertures in the top surface being of a first larger area followed by a second smaller area followed by a next larger area and so on. The bottom surface of the link also having a plurality of alternating partial apertures with the smaller diameter aperture of the bottom surface aligned with a larger diameter aperture in the top surface and so on. Thus the top and bottom surfaces each have partial apertures, with one of which is of a larger area and the next of a smaller area and arranged along a common axis and separated by a central aperture. Based on the above construction of the link, an arc generated during current interruption of the fuse is caused to zig zag along opposite edges of the planar member from a first to a second end.

Abstract: A fuse assembly has a fuse link extending suspended in a housing between a pair of terminal extensions, which the fuse link interconnects electrically. A fuse blowing current-reducing material like tin is carried on the fuse link and spaced from and on opposite sides of the hot spot of the fuse link where the fuse is expected to blow.

Abstract: A fuse comprising a casing, a fusible element disposed within the casing and a member made of ceramics mounted to the fusible element, the fusible portion of the fusible element being situated within a recess formed in the member.

Abstract: The fuse block assembly has a block which holds an element of substantially inverted U-shape. Co-operating projections and holes or recesses hold the element in position in the block. The ends of the legs of the element project out of the block to act as blade-type electrical terminals. The legs are joined to each other by a fusible portion which acts as the fuse. The plane of the terminals is transverse to the plane of the U. This configuration is stronger than a configuration in which the plane of the terminals lies in the plane of the U. It can be made by bending a flat strip into a U which is less wasteful of materials than cutting out the space between the legs.

Abstract: A fuse is disclosed for protecting thick film devices. The fuse comprises two blocks of material mounted to the substrate that carries the thick film device. The blocks are mounted in close proximity to one another, in axial alignment, but in a spaced apart relationship. An electrically conductive fusible link (e.g. solder) straddles the two blocks so as to complete an electric circuit.

Abstract: An electric fuse includes a tube of insulating material with first and second open ends. Metallic or electrically conducting end caps are placed on each of the first and second ends. A fuse element is mounted with the tube in electrical contact with the end caps. The fuse element includes an elongated body defined by a plurality of heavy portions and a plurality of weak spots. Each weak spot is located between adjacent heavy portions. The weak spots are linear fusible portions integrally connected to adjacent heavy portions and are transverse to an axis extending along the length of the element. Each heavy portion includes first and second ends. A first adjacent heavy portion is connected at a first end of a weak spot and a second adjacent heavy portion is connected to a second end of the weak spot, such that the first ends of adjacent heavy portions are transversely offset from each other.

Abstract: Cylindrical fuses in which, when overcurrent flows to an electric circuit, the part of the electric circuit formed by metal having a low melting point is fused to maintain safety of various electric machinery and equipment.The cylindrical fuse includes a cylindrical or bar like insulator formed of glass, porcelain, ceramics, plastics and the like and metals having a low melting point which are adhered to the cylindrical or bar like insulator by means of printing, coating, electroplating and the like, for example, lead or an alloy of lead and tin. A fuse terminal to be formed at both ends or one end of the cylindrical or bar like insulator and a fuse portion formed continuously between and connecting the fuse terminals are formed by the adhesion of the metals of low melting points.

Abstract: An electrical fuse comprises a fusible ribbon having one or more weak spots along its axial length which is highly resistant to mechanical fatigue caused by cyclic heating and cooling of the fusible ribbon. The weak spot comprises a series of apertures arranged in a curvilinear or angular configuration extending transversely to the axis of the fuse ribbon between the opposite sides thereof. Centers of adjacent apertures of the series are offset from each other with respect to the axis of the fusible ribbon by a distance at least equal to the shortest distance between the geometric center and the peripheral edge of any one of the adjacent apertures such that the cross-sectional area of the weak spot is distributed transversely across the fuse ribbon.

Abstract: An electrical fuse wherein one or more portions of the fuse element are provided with two adjacent parallel weak spots separated by dielectric material or air gap, and arranged such that the direction of current flow in one of the adjacent weak spots is opposite that in the other adjacent weak spot, such that a magnetic field is generated which produces a separating force between the two weak spots. Arcs formed during the fusing of the weak spots are forced apart by the generated magnetic field thus increasing the arcs path lengths which increases arc voltage thereby forcing arc current to zero.

Abstract: A simple and inexpensive low current fuse consists solely of a rigid rod of electrically insulating material and, extending throughout the length of and carried by the rod, at least one longitudinally continuous layer of electrically conductive material. At each of its ends the thickness of the layer is increased to constitute an effective fuse terminal and, at a position intermediate its terminals, is of such a cross-sectional area that it will melt or otherwise change state to interrupt a circuit at a predetermined overload or short circuit condition. The rod may be of tubular form and, in this case, the longitudinally continuous electrically conductive layer may be on the inner surface of the tubular rod and may extend over each end face of the rod and on to the outer surface of the rod at each end to form terminals of appropriate cross-sectional area.

Abstract: A spiral wound fuse body comprises a core of insulating material formed by a limp, dead yarn made of twisted together initially sizing-coated strands of fine ceramic filaments, where the sizing was subsequently removed so that there is no sizing to leave a conductive residue under fuse blowing conditions. Such a fuse body is mass produced by spiral winding fuse wire upon a continuous length of said yarn unwinding from a spool upon which the yarn was wound when the sizing was removed. The resulting self-supporting body can be wound into rolls and subsequently unwound so that individual fuse bodies can be severed from the end of the unwinding roll of fuse body-forming material.

Abstract: A plug-in electrical fuse comprises a fusible wire (9) disposed within an insulating housing (1) and connected between the ends of two blade-like terminals (4) secured within and projecting from the housing. Fuses of this type are manufactured by forming a strip of terminal members from strip metal, each member comprising two spaced substantially-coplanar blade-like terminal portions interconnected at their leading ends (5) by an integral cross-bar portion, and each terminal member being integrally connected with each adjacent terminal member in the strip by an interconnecting bar of the metal strip. Fusible wire is secured to the terminal portions adjacent their rear ends to form a strip of terminal and wire assemblies, and this strip of assemblies is mounted in a strip of insulating housings with the fusible wires disposed within the housings and the leading ends of the terminal portions projecting therefrom.

Abstract: A fuse comprising a casing, a fusible element disposed within the casing and a member made of ceramics mounted to the fusible element, the fusible portion of the fusible element being situated within a recess formed in the member.

Abstract: A flat fuse including two plug blades arranged next to one another in the same plane, being spaced from one another. The plug blades are fabricated from stamped sheet metal parts, the plug zones of which extend, in each case, rearwardly in a one piece construction into current-conducting straps. Between the straps, there is arranged a fuse fusion wire which is fastened to the straps. The current-conducting straps and the fusion conductor are surrounded by and enclosed in a plastic casing. The fuse fusion wire includes a copper wire with a silver sheathing, and the current-conducting straps as well as the plug blades are fabricated from brass, in which arrangement at least the current-conducting straps, but preferably also the plug blades, are superficially tinned. The fusion conductor is welded, in each case, to a flat side of the current-conducting straps.

Abstract: A time delay fuse is disclosed which does not require stored energy devices or separated chamber construction, and is dependent on the mass of the low melting point material and metal connector blocks to absorb heat on short duration overloads. The time delay fuse includes one or more fusible links having a combination of relatively high melting point material and a relatively low melting point mass enabling short circuit protection at a multiple of rated current and sustained overload protection at values above rated current. The number of fuse links used in the fuse is directly related to the intended current rating for the total fuse but may be from one to at least 15 links.

Abstract: An electric low-voltage current-limiting fuse completely or substantially complying with the Underwriters Laboratories Inc. Standard Class R fuses. The current carrying part of the fuse comprises a fusible element having serially arranged perforations. This part may be of silver or of copper. The current carrying part of the fuses further comprises tabs of copper bent over the rims of the casing and conductively interconnecting the ends of the fusible element with the terminal caps of the fuse. The fusible element is provided with an M-effect metal to limit the temperature rise of the fusible element and of the casing. The tabs are considerably thicker than the fusible element. If the fusible element is of silver the thickness of the tabs of copper is larger than the thickness required to fully compensate for their higher resistivity.

Abstract: Electrical fuse comprises an insulating body having a pair of coplanar blades extending from one end thereof. The blades have portions which are supported in the body and a fuse metal link is contained in the insulating body and extends between the supported portions. The conductors which comprise the blades and the supported portions of the blades are produced by die casting and the fuse metal link is insert die cast in these conductors. The insulating body is molded onto the conductors.

Abstract: A quick-acting fuse comprising a fuse base encased within an insulated fuse cartridge. The fuse base consists of a lower insulating plastic (phenolic) plate and an upper conductive metal (copper) plate coextensively bonded to the lower plate. The fuse base has an enlarged mid-section of generally hexagonal or polygonal configuration which necks down on both sides to a pair of projecting arms whose ends are soldered to end caps used to seal the fuse cartridge when the fuse base is placed therein. The mid-section of the fuse has a generally elliptical hole and the upper metallic plate is partially etched away around said hole so as to provide a pair of spaced-apart and opposed conductive terminals. A pair of opposed grooves is provided, one at each end of said conductive terminals, and a fusible element is stretched between said grooves across said generally elliptical hole. A solder pool is provided next to each groove for quantitative soldering the ends of the fusible element.

Abstract: A plug-in fuse assembly comprises a one-piece fuse element secured to a housing and having tubular terminal prong portions adapted for insertion into receptacle terminals. The terminal prong portions have retaining means cooperating with locking means formed in the housing for fixedly securing the terminal prong portions to the housing. A fuse link portion of the fuse element extends transversely between the terminal prong portions and is enclosed by the housing. The fuse element is made by punching from a flat sheet of fuse metal a flat blank comprising two laterally spaced and longitudinally extending prong members interconnected at their inner lateral edges by a link member having a non-rectilinear configuration, and then elongating the link member by flexing it from its non-rectilinear configuration to define the fuse link portion while shaping the prong members into tubular form to define the terminal prong portions.

Abstract: In a printed circuit board, a safety means is provided to prevent the circuit elements such as semiconductor devices, resistors, and the like from suffering damage due to overcurrent flow. The safety means thus improved has a narrow gap provided within a metal foil pattern on the surface of the printed circuit board and a low-melting point metal such as solder bridges this gap to connect the metal foil.

Abstract: A fuse element is a ribbon of aluminum or aluminum alloy having a terminal at each end of the ribbon. Each terminal is made of copper sheet material having a portion that is tin plated. The tin plated portion is folded over the end of the ribbon to contact both sides and is welded to the ribbon to form a connection capable of carrying short circuit currents and able to withstand repeated temperature changes. Preferably the weld consists of three side-by-side spot welds extending on either side of the ribbon to the respective tin plated terminal portion.

Abstract: This two-piece fuse comprises a generally rectangular plastic, dielectric housing, and a one-piece wire conductor. The conductor is folded into generally W-shaped configuration, and its inverted, V-shaped center section is inserted into a central recess in the bottom of the housing in such manner that its two, spaced, V-shaped legs are bent around the grooved, rounded ends of a pair of rigid web sections which project from the underside of the housing. Opposite ends of the folded wire are secured in a pair of spaced openings in the housing so that the two V-shaped legs of the wire are supported in a common plane by two web sections of the housing. The diameter of the wire is greater than the depth of the groove in each web section so that portions of the wire legs project out of the grooves for engagement with contacts when the leg sections of the wire are inserted into a cooperating female receptacle.

Abstract: A fusible element of a current-limiting fuse has a plurality of hole groups with at least two holes in each group. Separation between adjacent holes within the group is substantially less than separation between adjacent groups. Accordingly, while fault currents driven by voltages at two different levels are effectively extinguished, the back voltage developed by the fuse during interruption of a fault current driven by the lower voltage is prevented from exceeding a selected value.

Abstract: A fuse assembly for a miniature plug-in fuse is provided with a pair of parallel spaced-apart conductive legs, each having plug-in members at one end. A fuse link of generally constant cross sectional area, integrally formed with the conductive legs, extends therebetween to form a fuse assembly of substantially planar construction. The fuse link is provided with one or more transverse offsets, each forming a weak spot.

Abstract: A composite fusible element of silver and copper includes an inlay of silver and a base formed by a thicker strip of copper than the inlay of silver. The strip of copper is severed by a pair of juxtaposed incisions, so that the entire current is carried at this particular point only by the strip of silver. Moreover, the incisions penetrate into the strip of silver, producing in it a point of reduced cross-section. The strip of copper is preferably provided with a concave groove. The strip of silver is preferably convex and fits into the concave groove of the strip of copper. The composite fusible element may include several parallel strips of silver in a joint base of copper.

Abstract: The invention relates to a fuse having a fusible conductor (5) which is wound on a substantially straight carrier body (4). The wire (5) consists of a zinc alloy which contains 0.005% to 2% by weight of manganese.

Abstract: A laminated electric safety fuse which is built up laminated design consisting of various conductive materials which are embedded on an electrically insulating supporting member. The supporting member comprises one or more layers of electrically insulating material, a predominant part of which is a material having good thermal conductivity.In this design a narrowing effect is obtained which is up to 10 times larger than in known fuses, without sacrificing the current-carrying capacity of the non-narrowed parts of the fuse element.The various layers from which the safety fuse is built up can consist of materials with different electric conductivity, providing a new variable for obtaining an increased narrowing effect. The individual layers can be built up as films, e.g. by evaporative deposition.

Abstract: A fusible element for electric fuses based on M-effect, i.e. the severing of a high fusing point base metal by a low fusing point overlay metal by a process of metal interdiffusion. The M-effect, or Metcalf effect, as widely used in electric fuses, has a main limitation consisting in requiring too long periods of time for severing the base metal. The problem of severing the base metal by the overlay metal in shorter times is solved, according to this invention, by arranging the overlay metal on the front side and on the rear side of the base metal, in spaced relation to a point of reduced cross-section of the base metal.While the invention is applicable to all M-effect fuses, it is of particular importance in regard to Standard for Class L fuses of the Underwriters Laboratories Inc. which have fusible elements that are of copper, as distinguished from Class L fuses having fusible elements of silver, or Class L fuses having fusible elements in part of copper, and in part of silver.

Abstract: Fuses having different ratings, all of which comply with the Standard for Class L fuses of the Underwriters Laboratories Inc.The fusible elements of the fuses have identical points of reduced cross-section which fuse simultaneously on major fault currents, except one point of reduced cross-section which fuses ahead of the others.A relatively large temperature gradient prevails between the aforesaid points of reduced cross-section that fuse on short circuit current and the M-effect low fusing point overlay of the copper links that severs the current path through the latter by a diffusion process. The M-effect overlay metal may just reach its fusing point, while the immediately adjacent points of reduced cross-section may have a much higher temperature, e.g. 300.degree. to 400.degree. C. Thus the fusing M-effect metal will flow to the point of higher temperature and a rapid severing of the latter will take place.

Abstract: A fuse comprises a slender tube, a fuse element installed therein and terminals attached to both ends of the tube, wherein said fuse element being characterized by a plate substance having supporting sections extended respectively from each end of a fusing section, said supporting sections connected electrically to each terminal and said fusing section being bent at least at one part thereof.

Abstract: A fusible element for electric fuses combining considerable time lag with current-limiting action. Time lag is achieved by providing the fuse with a combination of a plurality of means for achieving this end, such as folding the perforated center portion of the fusible element twice in a direction longitudinally thereof to achieve mutual heating of the folded portion, providing the center portion with end portions or heat dams of reduced cross-section which limit the flow of heat from the center portion to the terminals of the fuse, and are folded in transverse direction, and providing the fusible element with means capable of severing the fusible element by a metallurgical reaction, widely known as M-effect. The M-effect means increase time lag because of their mass and because they derate the fusible element. They cause severing of the center portion of the fusible element and are heated, in addition to i.sup.2 .multidot.

Abstract: A fusible element for use in fuse construction wherein the fusible element is made of an elongated, heat-conductive metal or alloy having regions of reduced cross sectional area, including a middle reduced region and two reduced intermediate regions, each of said reduced regions being disposed between two unreduced regions of the fusible element. The dimensions (width and length) of the reduced regions are selected to optimize the performance of the fusible elements.Another embodiment of the invention contemplates a fusible element with a plurality of reduced regions having specified relative dimensions for improved performance characteristics.

Abstract: A fuse comprises a thin metal strip of constant thickness mounted on an insulating support and having relatively wide portions mutually spaced apart and interconnected by a relatively narrow portion constituting a fusible link which overlies a recess or aperture in the support so that the fusible link is spaced apart from the support surface. Preferably, the strip is folded about one end of the support with the fusible link remote from the fold, the relatively wide portions extending around the fold on each side of the support to constitute tab contacts for mating with a receptacle.

Abstract: An electrical fuse is taught having a ribbon-like fuse element therein. The fuse element has a generally uniform width along its length, but the depth of the fuse element is tapered in some regions. Holes or openings of various shapes are disposed along the length of the fuse through the depth thereof. The holes may be circular, triangular, or rectangular in shape and may be through a central portion of the fuse element or may comprise notches at the edges of the fuse element or both. The depth of the fuse element may increase with longitudinal distance from a relatively thin central portion of the fuse element to relatively thick end portion thereof, or vice versa. During low current clearing, the relatively thin portion will melt first and then burns back along the tapered portions until the fault current is extinguished.

Abstract: A fuse-element for electric fuses is shaped as a metal strip with one or more zones of diminished cross-section.The temperature rise conditions of the fuse-element and of its zones of diminished cross-section can be established and evaluated in combination and--based on these data--a fuse-element can be designed the temperature distribution characteristics of which include different local peak values and the spots where such peak values develop can be set in a manner that the whole fuse-element consists of two parts as far as the temperature distribution is concerned, i.e. a first part where this distribution is in accordance with a steady state distribution (the highest current value still failing to cause any melting), and a second part where the temperature rise distribution determines the character of the melting process, this being the so-called transient distribution characteristic.

Abstract: A time-lag fuse of the type including a fusible element proper, and heat dams formed by strips of sheet metal folded in a direction transversely to the direction of the fusible element proper impeding the axially outer heat flow from said fusible element proper. The fusible element proper has several straight edges extending parallel to the axis of the casing of the fuse. Points of the heat dams engage the inner surface of the casing of the fuse and thus ensure correct positioning of the fusible element proper, i.e. in such a way that its edges extend always parallel to, and are equidistantly spaced from, the axis of the casing. The heat dams engage the inner surface of the casing at discrete points only, to minimize the area of engagement between said heat dams and the inner surface of the casing and to thus minimize direct heat flow from one to the other.

Abstract: A wide-range current limiting fuse assembly particularly adapted to protect capacitors. The device comprises a current limiting portion having a corrugated fusible ribbon for high fault current protection, and a low current portion having a fusible link surrounded end to end by a conductive metal sleeve connected to one terminal of the fusible link. The current limiting portion may, alternatively, be provided with a circularly cross sectioned fusible wire connected in series with the fusible ribbon.

Abstract: A high voltage combination fuse has a current limiting section which has a free standing, helical coil of fusible wire material. The support for the free standing coil comes only from the pulverulent arc quenching material which fills the fuse casing and surrounds the coil. The coil has a foot portion and a head portion of increased cross-section to avoid arcing in the immediate vicinity of the end caps. The foot and head portions are preferably formed by doubling back a length of wire at the respective end and wrapping the tip of the doubled back length around the wire.

Abstract: The fuse for the protection of electric circuits comprises a casing filled with quartz sand, terminal contacts and a fuse link made of aluminium or an aluminium alloy. The ratio of the mass of the quartz sand to the mass of the aluminium material of the fuse link is at least 40:1. The fuse link is made of strip metal conductors, the widest current-conducting section of each strip having a width-to-thickness ratio within the range of 2:1 to 100:1.

Abstract: A flat safety fuse having a carrier plate fabricated from a synthetic material on which is mounted a sheet metal member with at least one fusible arc. The fusible arc has an inner diameter equal to the distance between parallel inner edges of its supporting bases which are each attached to associated contact surfaces separated from each other by a slot. The sheet metal member is received in a recess provided in a surface of the carrier plate. Preferably, the sheet metal member is secured in the recess by pressure arcs and clamping portions provided on the sheet metal member and by raised clamping portions provided on the carrier plate. Preferably, the sheet metal member has a W-shaped configuration to provide two fusible arcs.

Abstract: A novel fuse arrangement for electrical and electronic circuits is provided having shorter arcing time and arc-extinguishing time as compared to the prior art fuses. The fuse arrangement described herein comprises a pair of electrodes having contact terminals for connection to the circuit and a support member preferably disposed triangularly relative to the electrodes. In one embodiment, a fusible wire elment is stretched between the electrodes and has its mid portion supported by the support member. The support member is made from a material of large heat capacity and high thermal conductivity to provide a heat dissipating surface for the heat generated in the fusible wire element.