US3747041A - Current limiting fuse with improved fuse elements - Google Patents

Current limiting fuse with improved fuse elements Download PDF

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US3747041A
US3747041A US00219712A US3747041DA US3747041A US 3747041 A US3747041 A US 3747041A US 00219712 A US00219712 A US 00219712A US 3747041D A US3747041D A US 3747041DA US 3747041 A US3747041 A US 3747041A
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Prior art keywords
fuse
fusible material
fuse element
diameter
helical
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US00219712A
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English (en)
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F Cameron
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Westinghouse Electric Corp
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Westinghouse Electric Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H69/00—Apparatus or processes for the manufacture of emergency protective devices
    • H01H69/02—Manufacture of fuses
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H85/00—Protective devices in which the current flows through a part of fusible material and this current is interrupted by displacement of the fusible material when this current becomes excessive
    • H01H85/02—Details
    • H01H85/04—Fuses, i.e. expendable parts of the protective device, e.g. cartridges
    • H01H85/05—Component parts thereof
    • H01H85/055—Fusible members
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/49002—Electrical device making
    • Y10T29/49107—Fuse making

Definitions

  • a cartridge type current limiting electrical fuse including at least one fuse element.
  • the element is made from a length of fusible material which is tapered substantially along its legth to a minimum central taper point or portion and then widened again, or which is varied in discrete steps along its length.
  • the fusible material is then wound into a helical or spring-like shape.
  • the effective diameter of the resulting spring-like solenoid 0r helically wound coil is made to vary in accordance with the variation in the diameter of the fuse material. The smaller the diameter of the fuse material at any point along its length, the smaller is the diameter of the corresponding solenoid or coil at that point or portion.
  • the finished or overall helical coil or fuse element solenoid will vary continuously to form corresponding maximum and minimum alternating solenoid diameters. If the cross-sectional area of the fuse material varies discretely such as in steps, as would be the case if sections of fusible material of varying diameters or size were joined end-to-end, the corresponding solenoid or helical coil formed will also vary discretely. The size of the diameter for any section of wire depends upon the spring constant or spring rate developed in the solenoid or coil of fusible material.
  • the spring rate is kept preferably substantially constant for any section of fusible wire regardless of the wires diameter by adjusting the diameter of the fuse to a predetermined value for the diameter of the wire. Consequently, a spring-like fuse element is ultimately formed having a generally constant spring-rate along substan tially its entire length. lf the spring shaped fuse element is then either expanded or contracted longitudinally within a reasonable limit generally corresponding to Hookes Law, the pitch of the helical spring element will remain constant along the length of the spring although naturally it will change for each increment the spring is expanded or contracted.
  • a current limiting fuse element may be formed with its cross section along its length varied to cause the fuse element to form multiple arcs at predetermined points along its length as the melting temperature of the fuse material is reached such as disclosed in US. Pat. No. 2,157,907 issued to K. H. Lohausen May 9, 1939. This construction is employed to produce a plurality of voltage droping arcs which tend to limit the amount of current flowing through the fuse element during overload conditions.
  • fuse elements of this type are required to be very long in addition to being tapered or stepped in size; however, it is impractical for reasons of overall size in such applications to employ a single length of straight fusible material in a cartridge type fuse.
  • One solution has been to wind the fusible material into a helical coil so that the effective axial length of the fuse element is made suitable for mounting in a particular size of cartridge type fuse while the effective overall length of the fuse element is sufficient for a particular voltage application.
  • fuse element supports or mandrels have proved to be expensive, time consuming and electrically poorer in certain applications.
  • This short circuit may be short lived or relatively permanent and may have the effect of changing the interrupting characteristics of the instantaneously melting fuse element or providing a permanent short circuit between what should be electrically insulated portions of an interrupted electrical circuit. Therefore, it is desirable to eliminate the need for mandrels for fuse elements of relatively long lengths which may be formed into the shape of a helical coil having a substantially constant minimum pitch between helical sections or portions.
  • a fusible element for cartridge type current limiting fuse is formed by winding variable cross-section fusible material into a helical coil.
  • the effective diameter or size of the overall fuse element varies along the axial length of the fuse element as a predetermined function of the diameter of the fusible material.
  • a long length of fusible material which is in the form of tapered circular cross-section wire having a plurality of narrow neck portions of narrow cross-sectional portions where the fuse element will blow or melt initially is wound into a solenoid-like or helical coil fuse element having residual springiness.
  • Those parts of the solenoidor coil corresponding to the smaller cross-sections of the wire are more tightly wound or in other words wound with a smaller diameter to form the .coil or solenoid.
  • Those parts of the larger diameter fusible wire near the ends of the coil or solenoid are wound with the largest effective diameter.
  • the ultimate aim in winding a fuse element of fusible wire or fusible material in this manner is to provide a helically coiled fuse element which may be expanded or compressed like an accordion but in such a manner that the pitch between adjacent sections of each contributing member of the spiral is always substantially the same.
  • the fuse element may burn awayor melt in a plurality of current limiting sections which may generally correspond to the number of previously mentioned thin necks or reduced cross-sectional portions along the length of the fuse element.
  • a point is reached at which the distance between the ends of the blown portion is so large that the interposed fulgurite acts as a sufficient dielectric to prevent further electrical conduction between burned away ends of the remainder of the fuse element. This may happen substantially instantaneously depending upon the overload current since an entire helical portion of a fuse element may burn away within a fraction of a second.
  • the expanding, heated fulgurite which has limited electrical conducting properties may overlap to make electrical contact with the next adjacent helical section or turn of the fuse element.
  • the distance between one end of the melted fusible material and the next adjacent helical section may be considerably smaller than the distance between the two remaining end sections or end pieces of the fusible wire or material.
  • a short circuit or electrically conducting path may then exist between the higher voltage end of the burned away fuse element and the next adjacent turn or helical portion which is electrically connected to the lower voltage end of the burned away fuse element.
  • this phenomena or operation may have the effect of modifying or distorting the interrupting characteristics of the fuse element or in another sense causing a permanent short circuit between supposedly interrupted ends of an electrical fuse if not prevented by the teachings of this invention.
  • Fuse elements similar to those previously described may be formed in accordance with the invention by using a length of fusible material comprising adjacent or serially connected sections of fusible wire which may be circular and which may have different diameters. Those wires having the smaller diameters or smaller cross-sectional areas are of course more likely to burn away or blow when an overload current condition exists in the cartridge fuse.
  • a fuse element embodying the teachings ofthe invention may also be formed by winding the fusible wire or material in such a manner thatthe radius or diameter of the resultant solenoid or coil or spring-like fuse element varies in discrete steps.
  • Those fuse elements formed from placing end-to-end sections of wire each having a different but substantially constant diameter may be pre-wound on a manufacturing mandrel in such a way that those sections of wire having relatively large circular cross-sectional areas will be wound in relatively larger diameter portions of the overall solenoid or coil and those sections of wire having relatively smaller diameters will be formed into those parts of the solenoid having relatively smaller solenoid diameters.
  • the reason for this is to provide a substantially constant spring pressure or spring constant along the entire length of the solenoid or helical fuse element.
  • a substantially uniform spring rate allows the wire to be expanded, for example, to a length suitable for mounting in a cartridge type fuse and concurrently having a constant pitch which provides adjacent sections or coils of the overall coil which are sufficiently spaced from other turns or sections so that a burned out or fused portion of the wire will not be electrically connected by a section of fulgurite to form an electrically conducting path or short circuit circuit between adjacent helical sections or turns of the overall fuse clement.
  • the teachings of this invention also include the use of unique manufacturing or forming mandrels and a process for manufacturing the previously mentioned solenoids or spring-like coils of fuse elements.
  • a mandrel which is correspondingly wider or broader at the ends than in the middle may be formed by joining two sections of mandrel together at the smaller inner area in any convenient fashion such as by threading one end of one mandrel and tapping a hole in the corresponding end of the other mandrel and screwing one mandrel into the other.
  • the tapered fuse wire can then be wound on the mandrel forming a coil having gradually smaller diameter as the wire advances toward the middle of the mandrel and then a larger diameter as the wire advances away from the middle towards the other end of the mandrel.
  • the mandrel can then be unscrewed and pulled out from the formed spiral or solenoid without distorting or in any way damaging the formed solenoid or coil.
  • the same method can be employed with a stepped mandrel.
  • FIG. 1 shows a prior art fuse element formed in the shape of a solenoid or helical coil and having a melted or blown portion;
  • FIG. 2 shows a longitudinal section of a prior art tapered fuse element or wire with a blown portion
  • FIG. 3 shows a prior art fuse element assembly with parallel fuse elements or wires wound on a supporting member or mandrel
  • FIG. 4 shows a prior art cartridge fuse structure with parallel fuse elements mounted in the associated housing without the benefit of a mandrel or supporting member
  • FIG. 5 shows a prior art fuse element including stepped or discrete sections of fuse wires joined end-toend and a corresponding solenoid or fuse element coil that may be formed from such a fuse element;
  • FIG. 6 shows a stepped fuse wire similar to that shown in FIG. 5 but formed into a substantially constant pitch helically coiled fuse element in accordance with the invention
  • FIG. 7 shows a section or length of tapered fuse wire and a corresponding prior art solenoid or coil type fuse element which may be formed from it;
  • FIG. 8 shows a second fuse element in accordance with the invention which may be formed from the ta-' pered fuse wire shown in FIG. 7 as a substantially constant pitch-solenoid or coil;
  • FIG. 9 shows a cartridge type fuse similar to the one shown in FIG. 4 but with a substantially constant pitch solenoid or coil fuse element formed from fusible material of discretely varying size;
  • FIG. 10 shows a cartridge fuse similar to the one shown in FIG. 4 with a substantially constant pitch solenoid or coil fuse element formed from fusible material of continually varying or tapered diameter or size in accordance with the invention
  • FIG. 11 shows a mandrel for forming a substantially constant pitch helically wound fuse element of discretely varying size in accordance with the invention
  • FIG. 12 shows a mandrel for forming a constant pitch helically continuously varying spiral fuse section in accordance with the invention.
  • FIG. 13 shows a helical describing vector system.
  • a prior art generally helically wound fuse element 10 is shown which is suitable for mounting in a current limiting cartridge type fuse.
  • the fuse element 10 comprises a length of fusible material 12 wound into the shape of a resilient or spring charged helical coil having a diameter D.
  • the size of the fusible material 12 may be of the tapered or stepped variety.
  • the fuse element shown is typical of many known helically wound fuse elements, during interruption it may have a relatively high voltage V1 applied at end or terminal 16 and a different voltage V2 applied at another end or terminal 14.
  • a current I is shown flowing through a portion of the length of fusible material 12.
  • Current I may be of sufficient magnitude to cause fusible material 12 to flow or melt at a predetermined weakened point or portion in the fusible 12 between points or fused end sections 20 and 24.
  • a high voltage are is nearly instantaneously established between point or arc anode 20 and are cathode 24 to limit the rate of magnitude of current I.
  • the fusible material 12 is normally surrounded by a pulverulent arc quenching material 27 and as the heat of the arc established between points or ends 20 and 24 melts or fires thearc-quenching material 27, a fulgurite or conglomerated mass of arc-quenching material 28 is formed. The.
  • arc may cause the fusible material 12 to burn backwards such that points or ends 20 and 24, although shown in one instant of time, effectively progress or move away from each other as the arc between them consumes the fusible material forming fuse wire 12.
  • the arc will cease or be interrupted when electrical point 20, which may be at high electrical potential V1, is sufficiently burned back or removed a distance L2 from electrical point 24, which may be maintained at a significantly lower electrical potential V2, to create an insulating gap filled with fused pulverulent material 28.
  • the fulgurite material 28 which may have expanded outwardly and which may have sufficient electrical conductivity such that the distance represented by Ll between electrical points 20 and 32, which may also be maintained as voltages V1 and V2 respectively, is insufficient to prevent the continued arcing or flow of current I along path L1.
  • Ll the distance represented by Ll between electrical points 20 and 32
  • V1 and V2 voltages
  • the short circuiting of current I through path L1 may cause a drastic change in the current limiting characteristics of'fuse element 10.
  • the availability of the short circuit or conducting path Ll between the points and 32 will allow current I to flow between terminals 16 and 14 even though fuse element 10 ostensibly has blown or opened between the burned away points 20 and 24.
  • FIG. 2 a view of a prior art fuse element 10. including electrically conducting fusible material 12 similar to fusible material 12 shown in FIG.
  • a voltage or potential V1 exists at point or region 20 and the voltage or potential V2 exists at point or region 24'.
  • the electrically conducting properties of the fulgurite 28 may be sufficient in this geometric configuration to prevent further current flow between points 20' and 24. This is the way a fuse normally provides an insulating gap in the electrical curcuit in which it is connected.
  • the distance Ll can be made larger than the distance L2, which is the maximum distance over which an arc may be sustained between points 20 and 24 in the presence of a predetermined potential difference, an additional arc along line Ll between points 20 and 32 will'not be possible.
  • the minimum distance between point 20 and anadjacent point such as 32 in the next turn or helical portion is represented by the distance S; S being the measure of the pitch of the winding of the coil of fuse element 10.
  • FIG. 3 a prior art cartridge fuse structure 40 is shown having electrically conducting end sections or ferrules 44 and 46 with contacting members 50 and 48 respectively. Tie-down or braid tie points or end terminals 52 and 54 are shown mounted adjacent to ferrules or end caps 46 and 44 respectively. A mandrel or electrically insulating supporting member 56 is disposed between end portions or end caps 44 and 46. An electrically insulating cylindrical or tubular casing 43 surrounds the mandrel56 and an interposed arc quenching material 57. As illustrated there are five parallel fuse elements or fuse wires spaced from one and connected between the common points 52 and 54 of fuse section 40 as indicated by fusible conducting wires or elements 12a, 12b, 12c, 12d and 12e.
  • the minimum distance between any two wires S can be quite easily maintained at a value sufficient to prevent flashover between adjacent turns or helical sections 53 and 55 for example.
  • the fixed distance S is maintained by relatively rigidly winding the wires 12a, 12b and 12c and 12d and l2e on the supporting mandrel 56.
  • FIG. 4 a prior art fuse structure similar to the one shown in FIG. 3 isdepicted. End sections or ferrules 44 and 46' are shown'having a cylindrical electrically insulating main housing 43 disposed between and supporting them. A pulverulent arc quenching material 57 such as quartz or silica sand is enclosed by cylinder 43' and end sections 46' and 44'. Spring loaded electrically conducting plunger 48' is also provided. Helically wound or charged fuse elements of fusible material 60 and 62 are mounted within casing 43'. Helical coil or solenoid 60 is supported at ends 64 and 66 and solenoid or helically wound fuse element 62 is supported at ends 68 and 70.
  • End sections or ferrules 44 and 46' are shown'having a cylindrical electrically insulating main housing 43 disposed between and supporting them.
  • a pulverulent arc quenching material 57 such as quartz or silica sand is enclosed by cylinder 43' and end sections 46' and 44'.
  • the helically wound fuse elements 60 and 62 have been prefabricated on a mandrel, removed from the mandrel and stretched spring loaded or charged to be placed or assembled in fuse structure 56.
  • Pitch S varies along the entire axial length of both solenoids 60 and 62. This is because the overall diameter of the spring-like winding generally constant along its length and, because the mandrel upon which the winding was pre-fabricated has 'a uniform diameter. However in most circumstances the diameter of the fusible material from which the fuse elements are formed is varied either continu ously or discretely in steps in order to establish points or areas where arcs may begin upon the heating of the fuse elements'60 and 62 due to overcurrent.
  • Fusible material 72 comprises, in this example, three fuse wires of generally circular cross-section abutted or joined end-toend in some convenient fashion such as brazing.
  • Wire 74, having a diameter d1 is abutted at point 80 to fuse wire 76 having diameter d2 and fuse wire 76 is abutted at point 82 to fusible material 78 having diameter d3.
  • the pitch of adjacent sections of spiral may vary depending upon the strength or crosssectional size of the fuse material making up each particular part of the winding.
  • the pitch S1 existing between points 90 and 92 of fusible material 74 may be greater than the pitch S2 existing between points 94 and 96 of the fusible material 76 which, in turn, may be different than the pitch S3 existing between points 101 and 102 of fusible material 78.
  • the solenoid or spring-like fuse element 73 has a common centerline or longitudinal axis 84.
  • the disclosed invention is illustrated in a fuse element 73'.
  • the length of fusible wire 72 as was shown in FIG. is once again wound into a helically shaped fuse element 73.
  • the pitch between adjacent sections of each fuse element is mantained at a substantially constant or predetermined distance which may be S4 as shown in this case.
  • the distance between adjacent corresponding points of fusible material or wire 74, as shown by S4, between points 90' and 92' is generally the same as the distance S4 which may exist between corresponding points or turns 94' and 96 of fusible material 76. This also applies for the distance S4 between points 100' and 102' of the fusible material 76.
  • a common centerline or longitudinal axis 84' exists for the helical fuse element.
  • An important difference between fuse elements 73 and 73' is that the overall diameter of the formed helix or fuse element 73 varies as a function of the thickness or diameter of the fusible material or wire that is being wound into the helix shape. Consequently, wire 74 having a diameter d1 is formed into a helical fuse element portion having a helical diameter D4. Likewise, fusible wire 76 having a diameter d2 is formed into a helical portion having a helical diameter D2 and finally fusible wire 78 having a diameter d3 is formed into a helical fuse element portion having a diameter D3.
  • the diameter of the helical section of stepped or discretely varying fuse material is made substantially proportional to the actual diameter of the wire forming the particular portion of the overall helical fuse element.
  • This fuse element construction provides a generally constant spring rate along the length of the solenoid or helical section 73'.
  • a fuse element can be formed with great accuracy so that the distance between adjacent corresponding turns or points such as 94' and 96 in the same longitudinal plane (provided that longitudinal plane contains centerline 84') will be the same for any degree of extension or flexing of the helical fuse element 73.
  • Fusible material 104 is circular and has a relatively larger diameter at its ends 108 and 110 and a relatively smaller diameter in the middle 106.
  • the variations between points 108 106 and 110 are continuous rather than discrete, as was shown in FIG. 5 for the fusible materials employed. Consequently, the helical section or spring-like section 105 of silver com position fusible material when stretched or extended will provide varying spaced, distances or gaps between adjacent corresponding sections or turns of the helical section 105. For example distance S5 between points 114 and 116 on the helix 105 is shorter than the distance S6 between points 118 and 120.
  • the fusible wire 104 in accordance with the invention may be wound into a helically shaped coil 105' having a varying overall diameter.
  • the diameter of the helix 105' in the vicinity of the relatively larger cross-sectional areas of wire 106 near ends 108 and 110 is shown as D6 which is larger than the overall diameter D7 of the helix or fuse element portion shown in the vicinity 104 of the relatively smaller crosssectional portion of the wire 106.
  • the effect of this construction is to maintain substantially uniform spacings S7 between adjacent corresponding turns or sections of the helical fuse elemlent 105' which are equal for any given extension of the helix or fuse element 105
  • the distance or spacing S7 between points 114' and 116 is generally equal to the distance S7 between the points 118' and 120' even though the cross-sectional area of the fusible material in wire 106 is larger in the vicinity of points 114' and 116' than the cross-sectional area of the material in the wire 106 in the vicinity of the ends 118 and 120.
  • FIG. 9 a fuse structure 56' generally similar to the fuse structure 56 in FIG. 4 is shown.
  • end caps 44" and 46" and a spring loaded conducting plunger 48 There are end caps 44" and 46" and a spring loaded conducting plunger 48".
  • a pulverulent arc quenching material, such as silica sand 57" is enclosed within an electrically insulating cylinder or housing 43" and around the helical fuse elements 73T" and 73B".
  • Fuse element 73T" is stretched and connected between electrical contact points or terminals 64 and 66 which are connected to electrical end caps or ferrules 46" and 44" respectively.
  • helical fuse element 738" is connected at the ends 68 and 70 to the end ferrules or caps 46" and 44" respectively.
  • the helical fuse elements 73'1" and 73B" are of the discrete or stepped variety with respect to size as depicted in FIG. 6.
  • the helical electrical fuse element of 7ST" for example is divided in five easily identifiable discrete regions or portions each one having a different solenoid diameter associated therewith. Regions 124 and 132 have the relatively largest diameters; regions 126v and 130 have smaller diameters and region 128 has the smallest diameter. It is important to note that thepitch or spacing between adjacent corresponding points or turns of each of the fuse elements 73T" and 73B" is substantially uniform-or equal along the axial length of each of said fuse elements.
  • FIG. 10 a similar current limiting fuse structure 56" is-shown having a plurality of helical fuse elements 105T" and 1058" with continuously varying solenoid diameters.
  • Helical fuse element 105T is suspended orconnected between end points or.terminals 64"0 and 66" and helical fuse element 1058" connected between end points 68" and 70'.
  • the pitch of each of the helical fuse elemets T" and 10513" is thesame across the entire length of said helical fuse elements.
  • the amplitude or the diameter of the overall portions of helical section vary in proportion to the diameter of the fusible wire forming the helical portion at any point.
  • a manufacturing mandrel is shown for prefabricating or forming a variable diameter fuse element helix.
  • a stepped mandrel has left section 150L and a right section 150R which may be joined by the screwing or turning of a threaded member 156 into a taped hole 154 of section 150R. The discrete steps are shown at points 152.
  • Mandrel 160 may have left section 160L with a threaded protrusion 166 and a right section 160R with a tapped hole 164. Section 160L is screwed into the hole 164 in section 160R. A continuous taper results which decreases towards the middle is shown along the surface 162.
  • a centerline or longitudinal axis 170 is established between end points 111 and 172.
  • a rotatable or revolving vector V is mounted at one of its ends 173 to the imaginary centerline or axis 170 and is capable of rotating about centerline 170 with an angular velocity (O).
  • the other end 174 of vector V traces the path of the helical coil.
  • Vector V is capable of being moved with the velocity (v) from point 171 to 172 or vice versa. As it moves longitudinally the vector V rotates angularly about centerline 170 with an angular velocity Q.
  • the length of vector V is L(d), where d is the diameter of the fuse wire.
  • L(d) is variable such that the distance between hinge .point or pivot point 173 and end point 174 of vector V may vary as vector V is moved longitudinally and rotatably along line 170.
  • a generally circular type helix is contemplated in practicing the disclosed invention; however, helical coils of oblong cross-sections or elliptical cross sections may be provided where desired.
  • the discrete type variable diameter wire may have many discrete sections and the corresponding helical section will reflect the. corresponding size of the wire along the length of the fuse material.
  • the tapered type fuse helical section may have alternating large tapers and small tapers providing multiple are over points for the fuse material and correspondingly the helix form may have alternating large and small diameters along its length.
  • any type of fusible material may be used which is suitable for fusing or melting under overload conditions such as silver or silver alloys.
  • the cross section of the wire itself may vary along its entire lengthand need not necessarily be circular and it is also to be understood that the mandrels as shown in FIGS. 11 and 12 are only aids in forming the helical sections disclosed and need not necessarily be the means for fabricating the helcal sections.
  • the mandrels sections may be joined in any convenient manner.
  • the helix shape may be joined inany convenient manner.
  • the helix shape may vary continuously and is not limited to a tapered or stepped helix shape.
  • the voltages V1 and V2 may be of any value and V2 may be higher thanVl.
  • a helical fuse element may be provided without the use of a supporting mandrel which would therewise be mounted within a cartridge type fuse.
  • a substantially uniform or constant minimum pitch or distance or spacing between adjacent corresponding portions of a fuse element is provided so that as the fuse element blows or is melted a short circuit or electrically conducting path is not provided between adjacent fuse elements due to proximity and the formation of fulgurite material which may temporarily act as a conducting medium.
  • the heat dissipated during the fusing or melting process may be more easily absorbed by the arc quenching anheat absorbing pulverulent material such as silica or quartz sand.
  • the diameters of the respective sections of a length of fusible material may vary, when forming the helical fuse element, the fuse element may be compressed or stretched to any reasonable length, not exceeding Hookes Law, while maintaining relatively constant distance between each adjacent section of the fuse element for the compressing or stretching of the helical section. This aids in the convenient assembly and manufacture of the overall fuse structure.
  • the fuse elements may be prefabricated on mandrels which are separable after pre-fabrication in such a manner that the mandrels can be removed with out destroying the shape of the formed helical fuse section.
  • Another advantage lies in the fact that since the tension between adjacent sections of fuse material is retained at a constant spring rate or tension rate the likelihood of a tearing, breaking or failure of the fuse element for reasons other than the flow of overcurrent may be minimized.
  • Another advantage lies in the fact that if the fuse element is pre-stressed or charged at a certain pitch diameter when the fuse element blows there is less tendency for random longitudinal oscillation to occur among adjacent isolated parts of the blown helical element during the interrupting interval which might cause unusual and unpredicatable interrupting characteristics.
  • Another advantage lies in the fact that the use of a helical fuse element as disclosed provides an easy way to mount long lengths of fusible wire within a cartridge type fuse configuration.
  • a current limiting fuse structure comprising a fuse element including fusible material having the characteristic shape of a winding, said fusible material having a generally variable cross-sectional area, said winding having a generally central longitudinal axis, the shape of said winding relative to said axis being generally defined by the locus of points formed by the end ofa movable vector, said vector being generally terminated at said end by said fusible material and at the other end by said longitudinal axis, said vector being oriented perpendicular to said longitudinal axis, said locus of points being described by moving said vector longitudinally along said axis at a fixed rate and concurrently rotating said vector at a fixed angular rate about said longitudinal axis, the length of said vector at any time being related to said cross sectional area of said fusible material at any point along said longitudinal axis, said winding having two ends, said fuse structure having two terminals, said terminals being connected to said ends of said fuse element, the longitudinal components of distance between adjacent sections of the winding as measured in a plane including
  • a current limiting fuse structure comprising a fuse element including fusible material having the characteristic shape of a helical coil, said fusible material having a generally variable cross-sectional area, said helical coil having a central longitudinal axis, a variable radius and two ends, said radius of said helical coil at any point being related to said cross-sectional area of said fusible material at that point, the longitudinal components of distance between correspoonding portions of said helical coil as measured in a plane including said longitudinal axis being substantially equal, said distance being dependent on the axial length of said helical coil within a predetermined range of axial lengths, said coil being supported substantially only at said two ends.
  • a current limiting fue structure comprising a fuse element, electrically conducting end pieces, a dielectric container disposed to enclose said fuse element, said container being disposed between said end pieces, said fuse element comprising resilient fusible material having the characteristic shape of a helical coil, said fusible material having a generally variable crosssectional area, said helical coil having a variable radius, and a longitudinal central axis, said fusible material having two ends connected to said electrically conducting end pieces, said radius of said helical coil being related to said cross-sectional area of said fuse material such that the longitudinal separations between adjacent portions of said helical coil, as measured in a plane containing said longitudinal axis, are substantially equal,
  • corss-sectional area of said fusible material is generally circular, said circular fuse material having a radius wherein said latter-mentioned radius varies substantially linearly along the length of said fuse material, said radius of said helical coil correspoindingly varying substantially linearly.

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US00219712A 1972-01-21 1972-01-21 Current limiting fuse with improved fuse elements Expired - Lifetime US3747041A (en)

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JP (1) JPS5422929Y2 (enrdf_load_stackoverflow)
CA (1) CA937268A (enrdf_load_stackoverflow)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3825871A (en) * 1973-11-20 1974-07-23 Westinghouse Electric Corp Electric fuse with trip device
US4085396A (en) * 1976-09-27 1978-04-18 Bell Telephone Laboratories, Incorporated Electric fuse
US4099156A (en) * 1977-03-23 1978-07-04 Gould Inc. Electric fuse capable of interrupting small currents
US4700259A (en) * 1984-11-16 1987-10-13 University Of Sydney Electrical circuit breaking device
US20030227367A1 (en) * 2002-06-07 2003-12-11 Abb Research Ltd, Zurich, Switzerland Impact signaling system for a high-voltage protective device
US20120200974A1 (en) * 2011-02-04 2012-08-09 Murata Manufacturing Co., Ltd. Electronic control device including interrupt wire
US9425009B2 (en) 2011-02-04 2016-08-23 Denso Corporation Electronic control device including interrupt wire

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS555656B2 (enrdf_load_stackoverflow) * 1974-02-18 1980-02-08
JPS58140948A (ja) * 1982-02-15 1983-08-20 三菱電機株式会社 ヒユ−ズ

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2157907A (en) * 1934-12-11 1939-05-09 Gen Electric Fuse
US2157906A (en) * 1935-06-24 1939-05-09 Gen Electric Electric fuse
US2337938A (en) * 1941-09-11 1943-12-28 Gen Electric Electric fuse

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US350979A (en) * 1886-10-19 Machine for making spiral wire springs

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2157907A (en) * 1934-12-11 1939-05-09 Gen Electric Fuse
US2157906A (en) * 1935-06-24 1939-05-09 Gen Electric Electric fuse
US2337938A (en) * 1941-09-11 1943-12-28 Gen Electric Electric fuse

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3825871A (en) * 1973-11-20 1974-07-23 Westinghouse Electric Corp Electric fuse with trip device
US4085396A (en) * 1976-09-27 1978-04-18 Bell Telephone Laboratories, Incorporated Electric fuse
US4099156A (en) * 1977-03-23 1978-07-04 Gould Inc. Electric fuse capable of interrupting small currents
US4700259A (en) * 1984-11-16 1987-10-13 University Of Sydney Electrical circuit breaking device
US20030227367A1 (en) * 2002-06-07 2003-12-11 Abb Research Ltd, Zurich, Switzerland Impact signaling system for a high-voltage protective device
US6831546B2 (en) * 2002-06-07 2004-12-14 Abb Research Ltd Impact signaling system for a high-voltage protective device
US20120200974A1 (en) * 2011-02-04 2012-08-09 Murata Manufacturing Co., Ltd. Electronic control device including interrupt wire
US8971006B2 (en) * 2011-02-04 2015-03-03 Denso Corporation Electronic control device including interrupt wire
US9166397B2 (en) 2011-02-04 2015-10-20 Denso Corporation Electronic control device including interrupt wire
US9425009B2 (en) 2011-02-04 2016-08-23 Denso Corporation Electronic control device including interrupt wire

Also Published As

Publication number Publication date
JPS4891434U (enrdf_load_stackoverflow) 1973-11-02
US3848445A (en) 1974-11-19
CA937268A (en) 1973-11-20
JPS5422929Y2 (enrdf_load_stackoverflow) 1979-08-08

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