Document Mo7m2ZRyBoB8Y1vwk5a1m8xGk

FILE NAME:McGraw-Edison (ME) DATE: EZ DOC#: ME0 DOCUMENT DESCRIPTION: WD'ZZWZZZ ZEZ United States Patent (19) Gaia et al. 11 4,058,786 45) Nov. 15, 1977 (54). PROTECTOR FOR ELECTRICCIRCUITS 75 Inventors: Aldino J. Gaia; Angelo Urani, both of St. Louis, Mo. 73) Assignee: McGraw-Edison Company, Elgin, Ill. 21 Appl. No.: 632,621 22 Filed: Nov. 17, 1975 51) Int. Cl'............................................. H01H 85/04 52 U.S. Cl. ..................................... 337/293; 337/161 58 Field of Search ............... 337/293, 161, 162,274, 337/229 56) References Cited U.S. PATENT DOCUMENTS 3,253,104 5/1966 Fister ................................... 337/274 3,735,317 5/1973 Jacobs .................................. 337/161 Primary Examiner-Harold Broome Attorney, Agent, or Firm-Jon Carl Gealow; Thomas E. McDonald; Ronald J. LaPorte 57 ABSTRACT The dual element fuse of the present invention has at least one fusible element and at least one mass of heat softenable material; and that fusible element will re spond to a short circuit to fuse and thereby assure open ing of the circuit, whereas that mass of heat softenable material will respond to a long-continued relatively-low potentially-hurtful overcurrent to soften and thereby initiate opening of the circuit. That dual element fuse has a shunt element which shunts the mass of heat soft enable material and which will fuse after that mass of heat softenable material has initiated opening of the circuit. That shunt element has a current rating which is larger than the current rating of the mass of heat soften able material; and that shunt element has a current interrupting characteristic which has the same shape as that of the current-interrupting characteristic of the fusible element. 15 Claims, 10 Drawing Figures 9? Asses assary 24 222 Syyyyatt's SSSYY E. 46 g/ /2A6. t 3. 7968 (68.30 966 96%. 462 /221N 222, NZ '3 67%5 al N27 K35 2232 SSS t yyyyyyyyy A 444 (KE 4 % M26 U.S. Patent Nov. 15, 1977 Sheet 1 of 2 4,058,786 A/G. s. 2A beetle setse 7/ NYNY Y-Ns3S 70 2 22.7762246 463,2272 e2 2. ge (2322A a 1. 3e327 2T32 SY2NN--522 60 1. 4,058,786 2 PROTECTOR FOR ELECTRIC CIRCUITS FIELD OF THE INVENTION This invention relates to dual element fuses. More particularly, this invention relates to dual element fuses In the drawing and accompanying description, a pre ferred embodiment of the present invention is shown and described, but it is to be understood that the draw ing and accompanying description are for the purpose of illustration only and do not limit the invention and that the invention will be defined by the appended claims. which have shunt elements therein. BRIEF DESCRIPTION OF THE DRAWING DESCRIPTION OF THE PRIOR ART 10 Referring to the drawing in hereof, A true dual element fuse has at least one fusible ele FIG. 1 is a side elevational view of one preferred ment and at least one mass of heat softenable material. embodiment of dual element fuse that is made in accor Many prior dual element fuses, such as the dual element dance with the principles and teachings of the present fuse of Fister U.S. Pat. No. 3,122,619 which was invention, granted Feb. 25, 1964, have had shunt elements which 15 FIG. 2 is a sectional view, on a larger scale, through shunted the masses of heat softenable material. Those the dual element fuse of FIG. 1, and it is taken along the shunt elements opened the circuits after the masses of plane indicated by the line 2-2 in FIG. 1, heat softenable material softened in response to long FIG. 3 is a sectional view, on the scale of FIG. 2, and continued relatively-low potentially-hurtful overcur it is taken along the broken plane indicated by the bro rents, and those shunt elements coacted with the fusible 20 ken line 3-3 in FIG. 2, elements to open the circuits in response to short cir FIG. 4 is another sectional view, on the scale of FIG. cuits; but the shapes of the current-interrupting charac 2, and it is taken along the plane indicated by the line teristics of those shunt elements were not similar to 4-4 in FIG. 2, those of the current-interrupting characteristics of those FIG. 5 is yet another sectional view, on the scale of fusible elements. 25 FIG. 2, and it is taken along the plane indicated by the line 5-5 in FIG. 2, SUMMARY OF THE INVENTION FIG. 6 is a further sectional view, on the scale of The dual element fuse of the present invention has at FIG. 2, and it is taken along the plane indicated by the least one fusible element and at least one mass of heat line 6-6 in FIG. 2, softenable material; and that fusible element will re 30 FIG. 7 is a partially broken-away sectional view, on spond to a short circuit to open the circuit, whereas the the scale of FIG. 2, and it is taken along the plane indi mass of heat softenable material will respond to a long continued relatively-low potentially-hurtful overcur cated by the line 7-7 in FIG. 2, FIG. 8 is a sectional view, on a still larger scale, rent to open the circuit. That dual element fuse has a 35 through the dual element fuse of FIG. 1, and it is taken along the plane indicated by the line 8-8 in FIG. 2, shunt element which shunts the mass of heat softenable FIG. 9 is a perspective view of part of a subassembly material, and will thereby minimize arcing as that mass for the dual element fuse of FIG. 1, and of heat softenable material initiates opening of the cir FIG. 10 is a plan view, on an even larger scale, of a cuit. That shunt element has a current rating which is portion of the length of one of the fusible elements of larger than the current rating of the mass of heat soften the dual element fuse of FIG. 1. able material; and that shunt element has a current interrupting characteristic which has the same shape as DETAILED DESCRIPTION OF THE that of the current-interrupting characteristic of the PREFERRED EMBODIMENT fusible element. It is, therefore, an object ofthe present Referring to the drawing in detail, the numeral 20 invention to provide a dual element fuse which has a 45 generally denotes a blade-type terminal of one preferred least one fusible element and at least one mass of heat embodiment of dual element fuse which is made in softenable material, and which has a shunt element that accordance with the principles and teachings of the has a current-interrupting characteristic which has the present invention; and that terminal preferably is made same shape as that of the current-interrupting character of copper. A T-shaped opening 22 is formed in that istic of the fusible element. 50 terminal, as indicated particularly by FIG. 2; and open Where the dual element fuse of the present invention ings 24 and 26 are formed in that terminal adjacent the has a plurality of fusible elements and a plurality of inner end thereof, as indicated particularly by FIGS. 2 masses of heat softenable material, a connecting ring and 3. That terminal is rectangular in plan view and in electrically interconnects one end of each of those fus longitudinal section, but it has rounded edges in end ible elements. In doing so, that connecting ring keeps 55 VeW, any higher-than-normal-electrical-resistance connec The numeral 28 generally denotes a heat absorber tion between one of those fusible elements and an adja which has narrow, spaced-apart projections 30 and 31 cent heat absorber from generating so much heat that it extending from the left-hand end thereof, as indicated initiates premature softening of the mass of heat soften by FIGS. 1, 3 and 6; and that heat absorber preferably able material which is a part thereof. It is, therefore, an 60 is made of copper. Those projections overlie the right object of the present invention to provide a dual ele hand end of the terminal 20; and they have openings ment fuse which has a plurality of fusible elements, a therein which are aligned with the openings 24 and 26 plurality of masses of heat softenable material, and a in that terminal. The opening in the projection 30 is connecting ring which electrically interconnects one aligned with the opening 24 in the terminal 20, as shown end of each of those fusible elements. 65 particularly by FIG. 3. An offset 32, which is essentially Other and further objects and advantages of the pre rectangular in plan view, is displaced below the plane of sent invention should become apparent from an exami the heat absorber 28 by an inclined portion 33, as shown nation of the drawing and accompanying description. by FIG. 3. That offset is in register with the longitudinal 4,058,786 3 4. center line of the heat absorber 28; and the right-hand ring, as indicated particularly by FIG. 9. At the time end of that offset extends to the right beyond the rest of those projections are punched and bent outwardly from the right-hand edge of that heat absorber. that planar wall, other portions of that planar wall are The numeral 34 generally denotes a heat absorber punched out to define a large, generally-rectangular which is identical to the heat absorber 28. However, the 5 opening 68, as shown by FIG. 9. heat absorber 34 is oriented so the offset 40 hereof is The numeral 70 denotes a circular disk of insulating disposed above, rather than below, the plane thereof, as material, such as vulcanized fiber, which has rectangu shown by FIG. 3. Projections 36 and 38 of the heat lar openings 72 and 74 therein, as shown by FIG. 7, to absorber 34 are disposed below, rather than above, the accommodate the ends of the fusible elements 50 and terminal 20, as indicated by FIG. 3. Openings in the 10 560. That disk has a rectangular opening 71 to accom projections 36 and 38 are aligned with the openings 26 modate the end of the shunt element 46, as shown by and 24 in the terminal 20; and the opening in the projec FIGS. 2, 3, 7 and 9; and it has two further rectangular tion 38 is aligned with the opening 24, as shown by FIG. openings, not shown, to accommodate the ends of the 3. fusible elements 52 and 54. The disk 70 is dimensioned A rivet 42 is disposed within the aligned openings of 15 to fit snugly within the cylindrical portion 66 of the the projections 31 and 36 and the opening 26 of the connecting ring 56, as shown by FIGS. 2 and 3. terminal 20; and a rivet 44 is disposed within the aligned The numeral 76 denotes a disk of insulating material, openings of the projections 30 and 38 and the opening such as asbestos, which has a rectangular opening 78 24 in that terminal. Those rivets fixedly secure the heat therein, as shown by FIG. 8, to accommodate the left absorbers 28 and 34 to the terminal 20; and high melting 20 hand end of the fusible element 560. That disk has three temperature solder, not shown, is applied to the joints further rectangular openings, not shown, which accom between those rivets and those projections. As a result, modate the left-hand ends of the fusible elements 50, 52 low resistance electrical connections are provided be and 54. In addition, the disk 76 has a rectangular open tween the terminal 20 and the heat absorbers 28 and 34. ing 79 to accommodate the left-hand end of the shunt The rivets 42 and 44 coact with the terminal 20 to tend 25 46, as shown by FIGS. 3 and 8. to hold the confronting faces of the offsets 32 and 40 of The numeral 80 denotes a ferrule-like closure which the heat absorbers 28 and 34 in confronting relation and preferably is made of copper and which has five coined spaced apart just a few thousandths of an inch. sockets 82 therein, as indicated by FIG. 2. Those coined The numeral 46 denotes a shunt element which pref. sockets are dimensioned to accommodate the right erably is made of copper and which has a number of 30 hand ends of the fusible elements 50, 52, 54 and 560 and longitudinally-extending slots therein and a number of of the shunt element 46. A blade-type terminal 84, notches in the edges thereof that coact to define a plu which preferably is of copper, is fixedly secured to the rality of longitudinally-spaced weak spots for that shunt planar wall of the ferrule-like closure 80 by high tem element. The left-hand end of that shunt element is perature solder 90. That blade-type terminal has a T disposed between the confronting faces of the offsets 32 35 shaped opening 86 therein, as indicated by FIG. 2. and 40, as indicated particularly by FIGS. 2 and 3. A High-temperature solder 88 is used to mechanically rivet 48 is disposed within aligned openings in those secure and electrically bond the right-hand ends of the offsets and in that shunt element to fixedly secure that shunt element to the heat absorbers 28 and 34. High melting temperature solder, not shown, is applied to the fusible element 50, 52, 54 and 560 and of the shunt ele ment 46 to the planar wall of the ferrule-like closure 80. The numeral 92 denotes a tubular casing of insulating joints between the shunt element 46 and the offsets 32 and 40 to provide low resistance electrical connections between that shunt element and the heat absorbers 28 material, such as vulcanized fiber, which telescopes within the cylindrical portion 66 of the connecting ring 56 and within the cylindrical portion of the ferrule-like and 34. closure 80. That tubular casing coacts with the connect The numerals 50, 52, 54 and 560 denote fusible ele- 45 ing ring 56, with the disks 70 and 76, and with the fer ments that preferably are made of copper; and each of rule-like closure 80 to enclose the major portions of the them has a number of longitudinally-extending slots lengths of the fusible element 50, 52, 54 and 560 and of therein and a number of notches in the edges thereof the shunt element 46. Arc-quenching filler material 93, that coact to define a plurality of longitudinally-spaced such as quartz sand, is disposed within the tubular cas weak spots for that fusible element. The left-hand ends 50 ing 92 in intimate engagement with the fusible elements of those fusible elements are coextensive with, but are 50, 52, 54 and 560 and with the shunt element 46. spaced away from, the portions of the heat absorbers 28 Four point-like areas 94 of the cylindrical portion 66 and 34 that are disposed at opposite sides of the offsets of the connecting ring 56 are staked into holding en 32 and 40 of those heat absorbers. Those fusible ele gagement with the left-hand end of the tubular casing ments are substantially coextensive with, but are spaced 55 92; and four point-like areas 96 of the cylindrical por away from, the shunt element 46. The longitudinally tion of the ferrule-like closure 80 are staked into holding extending slots and the notches in each fusible element engagement with the right-hand end of that tubular preferably are identical to the corresponding longitudi casing. As a result, the shunt element 46, the fusible nally-extending slots and to the notches in the shunt elements 50, 52 and 54 and 560, the connecting ring 56, element, so the weak spots of those fusible elements and the weak spots of that shunt element have the same locations and configurations. However, each of those the disk 70, the disk 76, the ferrule-like closure 80, the tubular casing 92, and the arc-extinguishing filler 93 constitute a sub-assembly which can be assembled and fusible elements is thicker than that shunt element. tested independently of the rest of the dual element fuse. The numeral 56 generally denotes a connecting ring The left-hand end of the shunt element 46 and the left which preferably is made of copper and which has a 65 hand ends of the fusible elements 50, 52, 54 and 560 pass planar wall and a cylindrical portion 66. Four flat, rect through the appropriate openings in the disks 76 and 70, angular projections 58, 60, 62 and 64 are punched and and also pass through the generally-rectangular opening bent outwardly from the planar wall of that connecting 68 in the planar wall of the connecting ring 56. The 4,058,786 5 6 left-hand ends of those fusible elements are bent into cally connect the fusible elements 52 and 54 to the heat intimate engagement with the left-hand ends and with absorber 30 and normally coact to electrically connect the wide faces of the projections 58, 60, 62 and 64 on the the fusible elements 50 and 560 to the heat absorber 28. connecting ring 56, as indicated by FIGS. 3 and 9. Helical extension springs 140, 142 and 144 are secured, The numeral 98 denotes a tubular casing of insulating 5 respectively, to S-shaped connector 138 and hook 126, material, such as vulcanized fiber. The inner diameter of to S-shaped connector 136 and hook 132, and to S the tubular casing 98 is large enough to permit the con shaped connector 134 and hook 130. A fourth helical necting ring 56 and the ferrule-like closure 80 to tele extension spring, not shown, is connected to the S scope within that tubular casing; but the inner diameter shaped connector, not shown, for the fusible element 54 of that tubular casing is small enough to assure contact O and to hook 128. between the inner surface of that tubular casing and The numeral 146 denotes a circular disk of insulating appreciable areas of the outer surface of the cylindrical material, such as Vulcanized fiber, which is dimensioned portion 66 of that connecting ring and appreciable areas to fit snugly within the tubular casing 98. That disk has of the cylindrical portion of that ferrule-like closure. a generally-rectangular opening 148 therein which is Semi-circular disks 100 and 102 of insulating material, 15 shown particularly by FIG. 7, and which is dimen such as asbestos, have notches therein to accommodate sioned to accommodate the right-hand ends of the off. the side edges of the terminal 20, as indicated by FIGS. sets 32 and 40, respectively, of the heat absorbers 28 and 2 and 5. The confronting edges of those semicircular 34, and also to accommodate the left-hand end of the disks are spaced apart to accommodate an elongated pin shunt element 46. In addition, that disk has generally 104 of rectangular cross section which extends through 20 rectangular slots 150 and 152 therein which accommo the opening 22 in the terminal 20. The ends of that date the projections 60 and 62 on the connecting ring 56 elongated pin abut the left-hand end of the tubular cas and which also accommodate the ends of the fusible ing 98, as shown by FIG. 3. elements 52 and 54 which are bent around those projec The numeral 106 denotes a circular disk of insulating tions. Further, the disk 146 has two further generally material, such as vulcanized fiber, which is dimensioned 25 rectangular slots, not shown, therein which accommo to fit snugly within the tubular casing 98. That disk has date the projections 58 and 64 on the connecting ring 56 four rectangular openings 110, 112, 114 and 116therein, and also accommodate the ends of the fusible elements as shown by FIG. 6. The openings 110 and 116 of that 50 and 560 which are bent around those projections. disk are dimensioned to accommodate the projections The left-hand end of the shunt element 46 will be 36 and 38 of the heat absorber 34; and the openings 112 30 telescoped through the opening 148 in the disk 146, the and 114 of that disk are dimensioned to accommodate projection 60 plus the bent end of the fusible element 52 the projections 31 and 30 of the heat absorber 28. The will be telescoped through the opening 150 in that disk, openings 110, 112, 114 and 116 are, respectively, tele the projection 62 plus the bent end of the fusible ele scoped over the projections 36, 31, 30 and 38 prior to ment 54 will be telescoped through the opening 152 in the time those projections are riveted to the terminal 20. 35 that disk, and the projections 58 and 64 plus the bent The disk 106 also has four smaller rectangular openings ends of the fusible elements 50 and 560 will be tele 118, 120, 122 and 124 therein, as indicated by FIG. 6. scoped through the remaining two openings in that disk Hooks 126, 128, 130 and 132 are fixedly mounted within 146 prior to the time that shunt element is assembled the openings 120, 122, 124 and 118, respectively. As with the offsets 32 and 40, respectively, of the heat indicated particularly by FIGS. 2 and 3, those hooks absorbers 28 and 34. Also, prior to the time those offsets extend to the right from the disk 106. are assembled with that shunt element, the right-hand The numeral 134 denotes an S-shaped connector ends of those offsets will be forced apart sufficiently to which normally has a portion thereof telescoped over enable them to accommodate the left-hand end of that the left-hand end of the fusible element 52; and the shunt element therebetween. Thereafter, the openings numerals 138 and 136 denote further S-shaped connec 45 in those offsets will be aligned with the opening in the tors which normally have portions thereof telescoped left-hand end of the shunt element 46; and then the rivet over the lefthand ends of the fusible elements 50 and 48 will be passed through those aligned openings and 560. A fourth S-shaped connector, not shown, normally "headed' over to permanently secure the heat absorb has a portion thereof telescoped over the left-hand end ers 28 and 34 to the shunt element 56 - and hence to of the fusible element 54. Four masses of heat softenable 50 the subassembly of which that shunt element is a part. material, such as low melting point alloy, normally The numeral 154 denotes a pin which is disposed mechanically secure and electrically bond those S within the opening 86 in the terminal 84; and the ends of shaped connectors to those fusible elements and to the that pin abut the right-hand end of the tubular casing 98. heat absorbers 28 and 34. Portions of one of those That pin is essentially identical to the pin 104; and the masses of heat softenable material are denoted by the 55 engagements between the ends of those pins and the numeral 135 in FIG. 8; but the rest of that one mass of ends of the tubular casing 98 limit movement of the heat softenable material cannot be shown completely terminals 84 and 20 inwardly relative to that tubular because it takes the form of a film on a large percentage casing. The numerals 156 and 158 denote semi-circular of the surface of that S-shaped connector. Small por disks of insulating material, such as asbestos; and those tions of the four masses of heat softenable material are 60 semi-circular disks are identical to the semi-circular shown in FIG. 7; and the other three of those masses of disks 100 and 102. The semi-circular disks 100 and 102 heat softenable material are denoted by the numerals closely engage terminal 20, elongated pin 104, and the 137,139 and 141. It will be noted that the masses of heat inner surface of the tubular casing 98; and the semi-cir softenable material also electrically bond the bent ends cular disks 156 and 158 closely engage terminal 84, of the fusible elements 50, 52, 54 and 560, respectively, 65 elongated pin 154, and the inner surface of the tubular to the projections 58, 60, 62 and 64 on the connecting casing 98. ring 56. The four masses of heat softenable material and The numeral 160 denotes a ferrule-like closure of the four S-shaped connectors normally coact to electri metal which has the cylindrical portion thereof tele 4,058,786 7 8 scoped over the left-hand end of the tubular casing 98. weak spot which is defined by the right-hand end of the The planar wall of that ferrule-like closure has a gener slot 566 and by a generally-triangular notch which ex ally-rectangular slot 162 therein which accommodates tends inwardly from the adjacent edge of the fusible the terminal 20. Screws 164 extend radially inwardly element 560; and the numeral 596 denotes a dependent through openings in the cylindrical portion of that fer 5 weak spot which is defined by the left-hand end of the rule-like closure and are seated in the left-hand end of slot 568 and by a generally-triangular notch which ex the tubular casing 98. Arcextinguishing filler material tends inwardly from the adjacent edge of that fusible 166, such as calcium sulphate, fills the space within the element. The numerals 592 and 594 denote parts of a left-hand end of the tubular casing 98 which is defined two-part dependent weak spot which are defined by the by the disk 106 and by the semicircular disks 100 and 10 left-hand end of the slot 566 and by the right-hand end 102. The numeral 170 denotes a similar ferrule-like clo of the slot 568 and by generally-triangular notches sure for the right-hand end of the tubular casing 98. The which extend inwardly from the opposite edges of the planar wall of that ferrule-like closure has a generally fusible element 560. rectangular slot 172 which accommodates the terminal The function and operation of the fusible element 560 84. Screws 174 extend radially inwardly through open 15 can, and preferably will, be identical to the function and ings in the cylindrical portion of that ferrule-like closure operation of the similarly-numbered fusible element in and are seated in the right-hand end of the tubular cas the said Gaia application. Further, the fusible elements ing 98. Arc-extinguishing filler material 176, such as 50, 52, and 54 preferably will be identical to the fusible calcium sulphate, fills the space within the rightend of element 560. In addition, the slots and the inwardly the tubular casing 98 which is defined by the ferrule-like 20 extending notches of the shunt element 46 will be identi closure 80 and the semi-circular disks 156 and 158. Fur cal in configuration and location to those of the fusible ther arc-extinguishing filler material 178, such as cal element 560, so that the shape of the current-interrupt cium sulphate, fills the annular space between the outer ing characteristic of that shunt element will be substan periphery of the tubular casing 92 and the inner periph tially identical to the shape of the current-interrupting ery of the tubular casing 98. 25 characteristic of each of the fusible elements 50, 52, 54 The fusible element 560 can, and preferably will, be and 560. However, the thickness of the shunt element 46 identical to the similarly-numbered fusible element of will be less than the thickness of any of the fusible ele Aldino J. Gaia application Ser. No. 511,059 for Protec ments 50, 52, 54 and 560; so that shunt element will have tor For Electric Circuit which was filed on Oct. 1, 1974. a current rating which is less than the current rating of That fusible element has slots 562, 564, 566 and 568 30 any of those fusible elements. In one fuse of the present therein; and the slots 564 and 568 are disposed at one invention, which is rated as a six hundred amperes, six side of the longitudinal axis of that fusible element, hundred volts or less dual element fuse, each of the while the slots 562 and 566 are disposed at the opposite fusible elements 50, 52, 54 and 560 has a thickness be side of that longitudinal axis. The numeral 570 denotes tween one hundred and seventy-five and one hundred a controlling weak spot which is defined by the right 35 and eighty ten-thousandths of an inch whereas the shunt hand end of the slot 562 and by a generally-triangular element 56 has a thickness between one hundred and notch which extends inwardly from the adjacent edge thirteen and one hundred and seventeen ten-thou of the fusible element 560. The numeral 572 denotes a sandths of an inch. controlling weak spot which is defined by the adjacent Although the current rating of the shunt element 46 is ends of the slots 562 and 564; and the numeral 574 de less than the current rating of each of the fusible ele notes a controlling weak spot which is defined by the ments 50, 52, 54 and 560, the current rating of that shunt left-hand end of the slot 564 and by a generally-triangu element is greater than the current rating of each of the lar notch which extends inwardly from the adjacent connections between the fusible elements and the heat edge of the fusible element 560. The numeral 576 de absorbers. Specifically, the softening temperature of the notes a dependent weak spot which is defined by the 45 heat-softenable material in the masses of heat softenable right-hand end of the slot 562 and by a generally-trian material is very much lower than the melting tempera gular notch which extends inwardly from the adjacent ture of the copper of the shunt element 56; and hence edge of the fusible element 560; and the numeral 582 the masses 135, 137, 139 and 141 of heat softenable denotes a dependent weak spot which is defined by the material will reach their softening temperature at cur left-hand end edge of the slot 564 and by a generally 50 rent values which are considerably below the current triangular notch which extends inwardly from the adja values at which that shunt element will fuse. cent edge of that fusible element. The numerals 578 and As long as the value of the current flowing through 580 denote parts of a two-part dependent weak spot the dual element fuse of the present invention does not which is defined by the left-hand end of the slot 562 and exceed the rating of that dual element fuse, that current by the right-hand end of the slot 564 and by generally 55 will flow through a number of electrical paths between triangular notches which extend inwardly from the the terminals 20 and 84. One of those electrical paths opposite edges of the fusible element 560. includes projection 31 of heat absorber 28, includes the The numeral 584 denotes a controlling weak spot portion of that heat absorber which is intermediate that which is defined by the right-hand end of the slot 566 projection and the S-shaped connector 134 which is and by a generally-triangular notch which extends in 60 bonded to that heat absorber and to the fusible element wardly from the adjacent edge of the fusible element 52 by the mass 139 of heat softenable material, includes 560. The numeral 586 denotes a controlling weak spot that S-shaped connector and that mass of heat soften which is defined by the adjacent ends of the slots 566 able material, includes that fusible element, and also and 568; and the numeral 588 denotes a controlling includes part of the planar wall of the ferrule-like clo weak spot which is defined by the left-hand end of the 65 sure 80. A second of those electrical paths includes slot 568 and by a generally-triangular notch which ex projection 30 of the heat absorber 28, includes the por tends inwardly from the adjacent edge of the fusible tion of that heat absorber which is intermediate that element 560. The numeral 590 denotes a dependent projection and the S-shaped connector, not shown, 9 4,058,786 10 which is bonded to that heat absorber and to the fusible elements 50, 52, 54 and 560 and the heat absorbers 28 element 54 by the mass 141 of heat softenable material, and 34 could generate relatively small amounts of heat includes that S-shaped connector and that mass of heat even if one or more of those connections were, some softenable material, includes that fusible element, and how, to have a higher-than-normal electrical resistance. also includes part of the planar wall of the ferrule-like 5 Specifically, if one of the four connections between closure 80. A third of those electrical paths includes four fusible elements and one or more heat absorbers of projection 36 of heat absorber 34, includes the portion a shunt-equipped prior dual element fuse were, some of that heat absorber which is intermediate that projec how, to have a higher-than-normal electrical resistance, tion and the S-shaped connector 138 which is bonded to the current through that connection and through the that heat absorber and to the fusible element 50 by the 10 adjacent fusible element would decrease-with a conse mass 137 of heat softenable material, includes that S quent increase in the currents flowing through the shunt shaped connector and that mass of heat softenable mate and through the other three connections plus the adja rial, includes that fusible element, and also includes part cent three fusible elements. Although the reduced cur of the planar wall of the ferrule-like closure 80. A fourth rent flowing through that one connection and its adja of those electrical paths includes projection 38 of heat 15 cent fusible element would tend to decrease the amount absorber 34, includes the portion of that heat absorber of heat which was generated by that connection, the which is intermediate that projection and the S-shaped higher-than-normal electrical resistance of that connec connector 136 which is bonded to that heat absorber tion would tend to increase the amount of heat gener and to the fusible element 560 by the mass 135 of heat ated by that connection. Because the current flowing softenable material, includes that S-shaped connector 20 through each connection and its adjacent fusible ele and that mass of heat softenable material, includes that ment is inversely proportional to the sum of the electri fusible element, and also includes part of the planar wall cal resistances of that connection and fusible element, of the ferrule-like closure 80. A fifth of those electrical an increase in the electrical resistance of that connection paths is a branched electrical path which includes pro would not produce a corresponding decrease in that jections 30 and 31 of heat absorber 28 plus projections 25 current. Further, because the electrical resistance of 36 and 38 of heat absorber 34, includes the portions of that connection is much less than the electrical resis those heat absorbers which are intermediate those pro tance of that fusible element, the decrease in current jection and the offsets 32 and 34, includes those offsets, through that connection would be so small that the includes the shunt element 56, and includes part of the amount of heat generated by the higher-than-normal planar wall of the ferrule-like closure 80. 30 electrical-resistance connection would be greater than The connecting ring 56 is electrically connected to the amount of heat generated by a normal connection. each of the fusible elements 50, 52,560 and 54 by direct The overall result is that any increase in the electrical engagement with its projections 58, 60, 64 and 62 and resistance of any one of the four connections between also by the masses 137, 139, 135 and 141 of heat soften four fusible elements and one or more heat absorbers of able material; and it is connected to each of the S 35 a shunt-equipped prior dual element fuse would cause shaped connectors 138, 134, 136 and the fourth connec that connection to generate appreciably more heat than tor, not shown. However, under all normal conditions, would a normal connection-and hence would apprecia little or no current will flow through the planar wall of bly reduce the number of seconds during which that the connecting ring 56. dual element fuse could carry an overcurrent of five Whenever current flows through any of the five elec 40 hundred percent. Contrariwise, if one of the connec trical paths between the terminals 20 and 84, each por tions between the fusible elements 50, 52, 54 and 560 and tion of each of those electrical paths will respond to the the heat absorbers 28 and 34 were to have a higher-than current flowing therethrough to generate heat. Because normal electrical resistance, the amount of heat that was the electrical resistance of each of the heat absorbers 28 generated by that connection would decrease. Specifi and 34 is very much less than the resistance of any of the 45 cally, the connecting ring 56 would permit the current fusible elements 50, 52, 54 and 560, only insignificant which flows through the fusible element attached to amounts of heat will be generated by either of those that connection to divide, and thereby flow through the heat absorbers. Because the electrical resistance of each other connections as well as through that connection; of the connections between those fusible elements and and the resulting decrease in the current flowing those heat absorbers is much less than the resistance of 50 through that higher-than-normal-electrical-resistance any of the fusible elements 50, 52, 54 and 560, only connection would reduce the amount of heat generated relatively small amounts of heat will be generated by by the connection to a value less than the amount of each of those connections. However, even the rela heat generated by a normal connection. The increased tively small amounts of heat which are generated by current through the other connections of the fuse of each of the connections between the fusible elements 55 FIG. 1 would increase the amount of heat generated by and the heat absorbers are significant; because almost all those other connections; but the increase in current in of the heat that is generated by each of those connec each of those other connections would be smaller than tions will serve to increase the temperature of the mass the decrease in current through the higher-than-normal of heat softenable material which is part of that connec electrical-resistance connection. Consequently, the tion, and thereby will tend to limit the current ratings of 60 amount of heat which could be generated by any of that connection and of the dual element fuse. those other connections would be considerably less The connections between the fusible elements and the than the amount of heat which could be generated by a heat absorbers of a prior dual element fuse were able to higher-than-normal-electrical-resistance connection in a generate relatively small amounts of heat only as long as prior dual element fuse which differed from the fuse of the electrical resistances of all of those connections 65 FIG. 1 solely in not having the connecting ring 56. were quite low. However, because the dual element Moreover, any increased amount of heat which would fuse of the present invention is equipped with the con be generated by any of those other connections of the necting ring 56, the connections between the fusible fuse of FIG. 1 would tend to be absorbed or dissipated 4,058,786 11 12 by the connecting ring 56; and hence that fuse is able, with a higher-than-normal degree of certainty, to carry an overcurrent of five hundred percent for at least ten seconds. As a result, it should be apparent that the con necting ring 56 minimizes the effect which a higher of heat softenable material to soften in less than two hours whenever the fuse of FIG. 1 is subjected to an overcurrent of one hundred and thirty-five percent. Also, those thicknesses are selected so those masses of heat softenable material will not soften in less than ten than-normal resistance of a connection between the seconds whenever the fuse of FIG. 1 is subjected to an left-hand end of any one of the fusible elements 50, 52, overcurrent of five hundred percent. However, the 54 and 560 and the adjacent heat absorber could have thicknesses of the fusible elements 50, 52, 56 and 560 are on the overall operation of the fuse of FIG. 1. selected so those fusible elements will promptly and The cylindrical portion 66 of the connecting ring 56 10 safely fuse on overcurrents greater than five hundred is immediately adjacent the inner surface of the casing percent and on short circuits. 98; and hence it can transfer appreciable amounts of As long as the current flowing through the dual ele heat to that casing. This is desirable; because it enables ment fuse of the present invention does not exceed the that connecting ring to act as a heat absorber, and rating of that fuse, the masses 135, 137, 139 and 141 of thereby helps reduce the rate at which the temperatures 15 heat softenable material will not soften and the fusible of the masses 135, 137, 139 and 141 of heat softenable elements 50, 52, 54 and 560 will not fuse; and hence the material will rise in response to overcurrents. shunt element 46 will remain intact. If an overcurrent in The upper portions of the S-shaped connectors of the the range of one hundred and thirty five percent to four fuse of FIG. 1 are made considerably thicker than the hundred percent develops and continues for a suffi upper portions of the S-shaped connectors of prior dual 20 ciently long time, the masses 135, 137, 139 and 141 of element fuses of the same ampere rating. That extra heat softenable material will soften and the helical ex thickness enables the upper portion, of whichever S shaped connector happens to be the last S-shaped con tension springs 140, 142, 144 and the fourth helical ex nector to respond to a long continued relatively-low, tension spring, not shown, will pull the S-shaped con nectors 138, 136 and 134 and the fourth S-shaped con potentially-hurtful overcurrent move away from its 25 nector, not shown, away from the left-hand ends of the adjacent fusible element, to withstand the heavy current which will pass through that upper portion. fusible elements 50, 560, 52 and 54, respectively. There The space or gap which is defined by the upper por upon, all of the current flowing through the fuse of tion of each of the S-shaped connectors of the fuse of FIG. 1 will pass through the shunt element 46; and, FIG. 1 is larger than the space or gap which is defined 30 immediately, that shunt element will fuse. That shunt by the upper portion of an S-shaped connector for a element will operate in the manner in which the fusible prior dual element fuse; because the combined thick element 560 of the said Gaia application will fuse to nesses of the re-entrant bent end of a fusible element and open the circuit; and the arcs which will form as that of the projection around which it is bent are much shunt element opens the circuit will quickly be greater than the thickness of a fusible element of a prior 35 quenched by the arc-quenching filler material 93 within dual element fuse of the same ampere rating. However, the casing 92. the manufacturing tolerance of the space or gap which In the event an overcurrent substantially greater than is defined by the upper portion of each of the S-shaped five hundred percent or a short circuit develops, the connectors of FIG. 1 can be much smaller than the shunt element 46 will promptly fuse; and the fusible manufacturing tolerance of the space or gap which is elements 50, 52, 54 and 560 will, either simultaneously defined by the upper portion of any S-shaped connector with or immediately after the fusing of that shunt ele for a prior dual element fuse; because the projections 58, ment, fuse to open the circuit. Because the shape of the 60, 62 and 64 of the connecting ring 56 precisely fix both current-interrupting characteristic of the shunt element the attitudes and positions of the re-entrant bent ends of is substantially identical to the shape of the current the fusible elements 50, 52, 54 and 560. The closer man 45 interrupting characteristic of each of the fusible ele ufacturing tolerance of the space or gap which is de ments, the clearing time of the fuse of FIG. 1 is substan fined by the upper portion of each of the S-shaped con tially as short as the clearing time of any one of those nectors of the fuse of FIG. 1 would permit the amount fusible elements. Further, because the shunt element of heat softenable material, between the re-entrant bent and the fusible elements are embedded within the large end of a fusible element and the confronting surfaces of 50 mass of arc-quenching filler material 93 within the cas the adjacent S-shaped connector, to be reduced-with a ing 92, the clearing actions of that shunt element and of corresponding reduction in the electrical resistance of those fusible elements are rapid and quiet. The fusible the connection of which that S-shaped connector is a elements 50, 52, 54 and 560 and the shunt element 46 part. will fuse in the same manner as, and as effectively as, the The connecting ring 56 and the ferrule-like closure 80 55 fusible element 560 of the said Gaia application fuses. connect the fusible elements 50, 52, 54 and 560 in paral In the event an overcurrent in the range of four hun lel relation with each other; and hence the currents dred to five hundred percent develops, the masses 135, flowing through, and the amounts of heat generated by, 137, 139 and 141 of heat softenable material may soften those fusible elements will be substantially equal. Be and release the S-shaped connectors before the fusible cause the shunt element 46 is thinner than any of the elements 50, 52, 54 and 560 fuse, or those fusible ele fusible elements 50, 52, 54 and 560, the current flowing ments could fuse before those masses of heat softenable through, and the amount of heat generated by, that material could soften. In the former instance, the shunt shunt element will be less than the current flowing element 46 would open the circuit after the S-shaped through, and the amount of heat generated by, any of connectors had been released; and in the latter instance, the fusible elements 50, 52, 54 and 560. 65 that shunt element would fuse immediately before, or The thicknesses of the fusible elements 50, 52, 54 and simultaneously with, the fusible elements 50, 52, 54 and 560 are selected so those fusible elements will generate 560. In all instances, the only arcs which could develop enough heat to enable the masses 137, 139, 141 and 135 would develop in, and be rapidly and safely extin 13 4,058,786 14 guished by, the arc-quenching filler material 93 within The fact that the shape of the current-interrupting the casing 92. characteristic of the shunt element is substantially iden The shunt element 46 and each of the fusible elements tical to the shape of the current-interrupting character 50, 52, 54 and 560 are straight throughout the heat istic of each of the fusible elements is important. In the generating portions of the lengths thereof; and those first place, it provides a very short clearing time for the heat-generating portions incorporate therein all of the fuse of FIG. 1. Further, it facilitates more precise test slots and notches of that shunt element and of those ing of that fuse at various established test conditions. fusible elements. The heat-generating portions of the Additionally, it facilitates extrapolation of test data, shunt element and of the fusible elements are contacted obtained at various established test conditions, for all and surrounded by the arc-quenching filler material 93. 10 other possible conditions of loads and overcurrents The full-width left-hand ends of the shunt element and which could be met in the field. of the fusible elements extend through and beyond the The notches and slots of the shunt element 46 define left-hand end of the casing 92; but the full-width left more than one electrical path and, similarly, the notches hand end of the shunt element is directly connected to and slots of each of the fusible elements 50, 52, 54 and both heat absorbers whereas the full-width left-hand 15 560 define more than one electrical path. The peak end of each fusible element is connected to just one of current (I) and energy (I2t) of each electrical path in the heat absorbers by an S-shaped connector and the the shunt element 46 are, respectively, two hundred appropriate mass of heat softenable material. percent or less of the peak current (I) and energy (I2t) If desired, a large mass of heat softenable material of each electrical path in each of the fusible elements 50, could be substituted for the four S-shaped connectors 20 52, 54 and 560 when that shunt element and those fus and four masses of heat softenable material. That large ible elements are tested at the interrupting rating of the mass of heat softenable material would respond to long dual-element fuse of FIG. 1. Further, that dual-element continued, relatively low, potentially-hurtful overcur fuse has a lower peak current (I) and lower energy (I2) rents to melt and flow away from the bent ends of the than any prior shunt-equipped dual element fuse of the fusible elements 50, 52, 54 and 560. Thereafter, the shunt 25 same rating. All of this means that the fuse of FIG. 1 can element 46 would fuse to open the circuit, be made smaller in size, can be made with lighter The fuse of FIG. 1 is a dual element fuse which has an strength casings and ferrule-like closures, or can have a ampere rating of six hundred amperes and a voltage current-interrupting capability which is even greater rating up to six hundred volts. For fuses which had a than the presently-established standard current-inter smaller ampere rating, fewer fusible elements and fewer 30 rupting capability of two hundred thousand amperes, S-shaped connectors could be used. For some dual ele and yet maintain I2t and I values which are presently ment fuses, just one heat absorber could be used, felt to be adequate. The connecting ring 56 is very useful in the fuse of The fuse of FIG. 1 embeds the heat-generating por FIG, 1; but it would be useful in other dual element tion of the shunt element 46 within the same larger mass fuses as well. In fact, that connecting ring would be 35 of arc-quenching filler material 93 in which the heat useful in a dual element fuse that was not equipped with generating portions of the fusible elements 50, 52, 54 a shunt element. In those fuses, as well as in the fuse of and 560 are embedded. As a result, the present inven FIG. 1, the connecting ring would act to absorb heat tion eliminates all need of a special insulating sheath or from the connections between the fusible elements and separate casing for the shunt element, and also obviates the adjacent heat absorbers, and also would fix the posi 40 the need of locating that shunt element close to the tions and attitudes of those ends of the fusible elements inner surface of the fuse casing. In fact, the shunt ele which constitute parts of those connections. ment and the fusible elements of the fuse of FIG. 1, and Because the shunt element 46 is made so the shape of of any larger or smaller dual element fuse using such a the current-interrupting characteristic thereof is sub shunt element, could be arranged in any desired pattern stantially the same as the shape of the current-interrupt 45 or relative disposition to facilitate the most desirable ing characteristic of each of the fusible elements 50, 52, assembly procedures or to provide the most desirable 54 and 560, that shunt element can be dimensioned to circuit-opening action. carry proportionately more current than could any Prior shunt-equipped dual element fuses have utilized shunt of a prior dual element fuse. This is desirable, wire-like shunts. For example, in said A. J. Fister U.S. because it reduces the amount of current which must 50 Pat. No. 3,122,619 a wire-like shunt extended from one flow through the four connections between those fus knife blade terminal to the heat-absorbing member, in ible elements and the two heat absorbers, and it thereby A. J. Fister U.S. Pat. No. 3,253,103 which was granted reduces the amount of heat which will be generated by May 24, 1966 a wire-like shunt extended from one knife those connections. All of this means that the shunt ele blade terminal to the other knife blade terminal, and in ment 46 of the fuse of FIG. 1 not only enables that fuse 55 J. S. Withers U.S. Pat. No. 3,453,580 which was granted to have a desirable clearing action but it also enables July 1, 1969 a two-piece wire-like shunt that had two that fuse to carry a five hundred percent overcurrent reduced-diameter portions extended from one terminal for appreciably more than ten seconds. to the heat-absorbing element. Because the shunts of The re-entrant bent ends of the fusible elements 50, those patents were wire-like, the current-interrupting 52, 54 and 560 are desirable because they space the 60 characteristics of those shunts were distinctively differ punched ends of those fusible elements away from the ent from the current-interrupting characteristics of the gaps or spaces which are defined by the upper portions fusible elements of those patents. Further, to enable the of the S-shaped connectors, Those re-entrant bent ends clearing times of those wire-like shunts to be sufficiently also are desirable because they increase the area of short to avoid undue prolongations ofthe clearing times engagement between the fusible elements and the 65 of the fuses of those patents, the maximum current car masses of heat softenable material-with consequent rying capacity of each of those shunts was made quite reductions in the electrical resistances between those small relative to the maximum current carrying capac fusible elements and those S-shaped connectors. ity of the fuse, of which it was a part, when that shunt 4,058,786 15 16 and that fuse were tested at the current-interrupting elements are tested at the current-interrupting rating of rating of that fuse. By using the shunt provided by the said electric fuse, said first electrical path responding to present invention, it is possible to make the maximum a long-continued potentially-hurtful relatively-low current carrying capacity of that shunt higher than the overcurrent to electrically disconnect said fusible ele maximum current carrying capacity which was deemed ment from at least one of said terminals, said second to be desirable for the shunts in correspondingly-rated electrical path thereafter responding to said long-con fuses in said Fister and Withers patents, and yet not tinued potentially-hurtful relatively-low overcurrent to have the clearing time of that shunt prolong the clearing open the circuit in which said electric fuse is connected, time of the fuse of FIG. 1 when that shunt and that fuse both said fusible electrical paths in said fusible element are tested at the current interrupting rating of that fuse. 10 and in said shunt element responding to a short circuit By having an increased maximum current carrying to help open said circuit. capacity, the shunt of the present invention makes it 2. An electric fuse as claimed in claim 1 wherein said possible to reduce the current-interrupting duty of each first electrical path includes heat softenable material of the fusible elements of the fuse of FIG. 1. that normally electrically connects said fusible element The maximum current carrying capacity of the shunt 15 to one of said terminals but that can respond to heat to element 46 should be less than forty percent of the maxi permit said fusible element to become disconnected mum current carrying capacity of the overall shunt from said one of said terminals, wherein said fusible equipped dual-element fuse of FIG. 1, so that shunt element is disposed within a chamber, wherein said element will fuse whenever the S-shaped connectors of shunt element also is disposed within said chamber, that dual-element fuse are released. However, the maxi 20 wherein arc-extinguishing filler is disposed within said mum current carrying capacity of the shunt element 46 chamber in engagement with said fusible element and should be equal to or greater than fifteen percent of the also in engagement with said shunt element, wherein maximum current carrying capacity of the overall said heat-softenable material is disposed within a second shunt-equipped dual-element fuse of FIG. 1, and it chamber which is adjacent the first said chamber, and should be one hundred and twenty percent or less of the 25 wherein one end of said fusible element and one end of maximum current carrying capacity of each of the fus said shunt element extend through the same end of said ible elements 50, 52, 54 and 560. first said chamber and into said second chamber. The shunt element 46 and the fusible elements 50, 52, 3. An electric fuse as claimed in claim 1 wherein said 54 and 560 could be made from copper, high-conduc fusible element is disposed within a chamber, wherein tivity copper alloys, silver or high conductivity silver 30 said shunt element also is disposed within said chamber, alloys. That shunt element could be made from the same wherein said fusible element and said shunt element are metal or alloy from which those fusible elements are substantially straight, and wherein one end of said fus made. ible element and one end of said shunt element extend The fusible elements 50, 52, 54 and 560 can be made through the same end of said chamber and into an adja flat throughout the effective portions of the lengths 35 cent chamber. thereof, as shown by the drawing, or they could be 4. An electric fuse as claimed in claim 1 wherein said folded or bent or bowed as shown in said A. J. Fister first electrical path includes means that can respond to U.S. Pat. No. 3,253,103 or in said J. S. Withers patent or a long-continued potentially-hurtful relatively-low in said Gaia application. Moreover, if desired, some of overcurrent to electrically disconnect said fusible ele the fusible elements 50, 52, 54 and 560 could be made 40 ment from at least one of said terminals, wherein said flat throughout the effective portions of the lengths means primarily determines said current rating of said thereof, as shown by the drawing, and the rest of those first electrical path, and wherein said shunt element is fusible elements could be folded or bent or bowed as connected in shunting relation with at least a part of said shown in said A. J. Fister U.S. Pat. No. 3,253,103 or in means to make said current rating of said second electri said J. S. Withers patent or in said Gaia application. 45 cal path appreciably different from said current rating Whereas the drawing and accompanying description of said first electrical path. have shown and described a preferred form of the pre 5. An electric fuse as claimed in claim 1 wherein said sent invention it should be apparent to those skilled in shunt element has a plurality of longitudinally-spaced the art that various changes may be made in the form of weak spots therein, and wherein the current rating of the invention without affecting the scope thereof. 50 said shunt element is smaller than said predetermined What I claim is: current rating. 1. An electric fuse that comprises terminals, a first electrical path between said terminals which has a pre determined current rating and a predetermined current 6. An electric fuse as claimed in claim 1 wherein said first electrical path includes heat-softenable material that normally electrically connects said fusible element interrupting characteristic and which includes a fusible 55 to one of said terminals but that can respond to heat to element, and a second electrical path between said ter permit said fusible element to become disconnected minals which is connected in shunting relation with at from said one of said terminals, and wherein the current least part of said first electrical path and which includes rating of said shunt element is larger than said predeter a shunt element, said fusible element having at least one mined current rating but is smaller than the current fusible electrical path therein which has a predeter rating of said fusible element. mined peak current (I) and energy (I2t), said shunt 7. An electric fuse as claimed in claim 1 wherein said element having at least one fusible electrical path first electrical path includes heat-softenable material therein which has a given peak current (I) and energy that can respond to said long-continued potentially (I2t), said peak current (I) and energy (I2t) of said fus hurtful relatively-low overcurrent to soften and thereby ible electrical path in said shunt element being, respec 65 permit said first electrical path to become open, and tively, two hundred percent or less of said peak current wherein said shunt element will subsequently respond (I) and energy (I2t) of said fusible electrical path in said to the opening of said first electrical path to fuse and fusible element when said shunt element and said fusible thereby open said second electrical path. 4,058,786 17 18 8. An electric fuse as claimed in claim 1 wherein said fusible element when said shunt element and said fusible first electrical path includes a heat-absorbing member elements are tested at the current-interrupting rating of and also includes heat softenable material which can said electric fuse, said first electrical path responding to respond to said long-continued potentially-hurtful rela a long-continued potentially-hurtful relatively-low tively-low overcurrent to soften and thereby permit overcurrent to electrically disconnect said fusible ele said first electrical path to become open, and wherein ment from at least one of said terminals, said second said second electrical path also includes said heat electrical path thereafter responding to said long-con absorbing member. tinued potentially-hurtful relatively-low overcurrent to 9. An electrical fuse as claimed in claim 1 wherein open the circuit in which said electric fuse is connected, said fusible element is made from a material in the group 10 both said fusible electrical paths in said fusible element consisting of copper, high conductivity copper alloys, and in said shunt element responding to a short circuit silver and high conductivity silver alloys, and wherein to help open said circuit, said fusible element being said shunt element also is made from a material in the disposed within a chamber, said shunt element also group consisting of copper, high conductivity copper being disposed within said chamber, said first electrical alloys, silver and high conductivity silver alloys. 15 path including means that can respond to a long-con 10. An electric fuse as claimed in claim 1 wherein said tinued potentially-hurtful relatively-low overcurrent to shunt element is made from a high conductivity mate electrically disconnect said fusible element from at least rial, and wherein said fusible element also is made from one of said terminals, said means being disposed within a high conductivity material. an adjacent chamber, one end of said fusible element 11. An electric fuse that comprises terminals, a first 20 and one end of said shunt element extending through electrical path between said terminals which has a pre the same end of the first said chamber and into said determined current rating and a predetermined current adjacent chamber, arc-extinguishing filler being dis interrupting characteristic and which includes a fusible posed within the first said chamber, and said one end of element, a second electrical path between said terminals said fusible element being connected in series relation which is connected in shunting relation with at least 25 with said means within said adjacent chamber but said part of said first electrical path and which includes a one end of said shunt element being connected in shunt shunt element, said fusible element having at least one ing relation with a portion of said means and in series fusible electrical path therein which has a predeter relation with a further portion of said means. mined peak current (I) and energy (I2t), said shunt 13. An electric fuse that comprises terminals, a first element having at least one fusible electrical path 30 electrical path between said terminals which has a pre therein which has a given peak current (I) and energy determined current rating and a predetermined current (It), said peak current (I) and energy (I2t) of said fus interrupting characteristic and which includes a fusible ible electrical path in said shunt element being, respec element, a second electrical path between said terminals tively, two hundred percent or less of said peak current which is connected in shunting relation with at least (I) and energy (I2t) of said fusible electrical path in said 35 part of said first electrical path and which includes a fusible element when said shunt element and said fusible shunt element, said fusible element having at least one elements are tested at the current-interrupting rating of fusible electrical path therein which has a predeter said electric fuse, said first electrical path responding to mined peak current (I) and energy (I2t), said shunt a long-continued potentially-hurtful relatively-low element having at least one fusible electrical path overcurrent to electrically disconnect said fusible ele therein which has a given peak current (I) and energy ment from at least one of said terminals, said second (I2t), said peak current (I) and energy (I2t) of said fus electrical path thereafter responding to said long-con ible electrical path in said shunt element being, respec tinued potentially-hurtful relatively-low overcurrent to tively, two hundred percent or less of said peak current open the circuit in which said electric fuse is connected, (I) and energy (I2t) of said fusible electrical path in said both said fusible electrical paths in said fusible element 45 fusible element when said shunt element and said fusible and in said shunt element responding to a short circuit elements are tested at the current-interrupting rating of to help open said circuit said fusible element being dis said electric fuse, said first electrical path responding to posed within a chamber, said shunt element also being a long-continued potentially-hurtful relatively-low disposed within said chamber, and arc-extinguishing overcurrent to electrically disconnect said fusible ele filler being disposed within said chamber in engagement 50 ment from at least one of said terminals, said second with said fusible element and also in engagement with electrical path thereafter responding to said long-con said shunt element. tinued potentially-hurtful relatively-low overcurrent to 12. An electric fuse that comprises terminals, a first open the circuit in which said electric fuse is connected, electrical path between said terminals which has a pre both said fusible electrical paths in said fusible element determined current rating and a predetermined current 55 and in said shunt element responding to a short circuit interrupting characteristic and which includes a fusible to help open said circuit, said fusible element having a element, a second electrical path between said terminals plurality of weak spots therein ofa given configuration, which is connected in shunting relation with at least said shunt element having a corresponding plurality of part of said first electrical path and which includes a weak spots therein of substantially the same configura shunt element, said fusible element having at least one tion, and the thickness of said shunt element being less fusible electrical path therein which has a predeter than the thickness of said fusible element. mined peak current (I) and energy (I2t), said shunt 14. An electric fuse that comprises terminals, a fusible element having at least one fusible electrical path element which has a predetermined current-interrupt therein which has a given peak current (I) and energy ing characteristic, means connecting said fusible ele (12t), said peak current (I) and energy (I2t) of said fus 65 ment between said terminals and coacting with said ible electrical path in said shunt element being, respec fusible element to help form a first electrical path which tively, two hundred percent or less of said peak current interconnects said terminals, said means and said fusible (I) and energy (I2t) of said fusible electrical path in said element coacting to provide a predetermined current 4,058,786 19 20 rating and a predetermined current-interrupting charac relatively-low overcurrent to open the circuit, both said teristic for said electrical path, said predetermined cur first and said second electrical paths responding to a rent-interrupting characteristic for said first electrical short circuit to cause said fusible element and said shunt path being determined primarily by said current-inter element to fuse and thereby open the circuit. rupting characteristic of said fusible element at all levels 15. An electric fuse that comprises terminals, a first of current at which said fusible element initiates open electrical path between said terminals which has a pre ing of said first electrical path, a shunt element having a determined current rating and a predetermined current current-interrupting characteristic which has substan tially the same shape as said predetermined current interrupting characteristic and which includes a fusible interrupting characteristic of said fusible element, 10 element, and a second electrical path between said ter minals which is connected in shunting relation with at means, which differs at least in part from the first said means, connecting said shunt element between said least part of said first electrical path, said second electri cal path having a current rating which is appreciably terminals and coacting with said shunt element to form a second electrical path which interconnects said termi different from said current rating of said first electrical nals, the second said means and said shunt element co 15 path but having a current-interrupting characteristic acting to provide a current rating for said second elec which has substantially the same shape as said predeter trical path which is appreciably different from said mined current-interrupting characteristic at all levels of predetermined current rating while also coacting to current at which said fusible element initiates opening provide a current-interrupting characteristic which has of said first electrical path, said first electrical path substantially the same shape as said predetermined cur 20 responding to a long-continued potentially-hurtful rela rent-interrupting characteristic for said first electrical tively-low overcurrent to electrically disconnect said path at all levels of current at which said fusible element fusible element from at least one of said terminals, said initiates opening of said first electrical path, said first second electrical path thereafter responding to said electrical path responding to a long-continued poten long-continued potentially-hurtful relatively-low over tially-hurtful relatively-low overcurrent to electrically 25 current to open the circuit in which said electric fuse is disconnect said fusible element from at least one of said terminals, said second electrical path thereafter re sponding to said long-continued potentially-hurtful connected, both said first and said second electrical paths responding to a short circuit to open said circuit. 30 35 45 50 55 60 65 UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. : 4,058,786 DATED November 15, 1977 INVENTOR(S) : Aldino J. Gaia & Angelo Urani It is Certified that error appears in the above-identified patent and that said Letters Patent are hereby Corrected as shown below: Column 19, line 2, before "electrical" add -first eigned and Sealed this SEAL Attest: Fifteenth Day of August 1978 RUTH C. MASON Attesting Officer DONALD W. BANNER Commissioner of Patents and Trademarks UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. : 4,058,786 DATED : November 15, 1977 INVENTOR(S) Aldino J. Gaia & Angelo Urani It is Certified that error appears in the above-identified patent and that said Letters Patent are hereby Corrected as shown below: Column 19, line 2, before "electrical" add -first -- --- - - -- eigned and sealed this SEAL Attest: Fifteenth Day of August 1978 RUTH C. MASON Attesting Officer DONALD W. BANNER Commissioner of Patents and Trademarks