Document EqyMvE1zaX2Q1N9VbBng9XMR0

FILE NAME: McGraw-Edison (ME) DATE: 1959 Feb 16 DOC#: ME016 DOCUMENT DESCRIPTION: Patent - Protectors for electric circuits [Approved 1966 May 24] May 24, 1966 A. J. FISTER 3,253,104 PROTECTORS FOR ELECTRIC CIRCUITS Original Filed Feb. 16, 1959 2 Sheets-Sheet 1 r/Q . l May 24, 1966 A. J . F IST E R 3,253,104 PROTECTORS FOR ELECTRIC CIRCUITS Original Filed Feb. 16, 1959 S Sheets-Sheet 3 F/q.JJ 12 2 '66 *52 r/Q .iz 8*----- y t . / 2 0 0 /9 F/Q.13 /84 *2 /3 f / q.1 4 183 /te ^ INVENTOR. '2 8 b Auorsius J F/sree. BY a y t J * i!T T -K U nited States Patent Office Patented Ma3y,22543, ,1190646 1 2 cuitmg chamber. As a result, the heat-absorbing member 3,253,104 can be intimately bonded to the short-circuiting chamber PROTECTORS FOR ELECTRIC CIRCUITS and to the connector, and can be given enough mass and Aloysius J. Flster, Overland, Mo., assignor to McGraw- enough surface area to absorb sizeable quantities of heat Edison Company, Elgin, 111., a corporation of Dela ware 5 and then to radiate appreciable portions of that heat, and Original application Feb. 16, 1959, Ser. No. 793,415, now yet not permit undue interchange of heat between the Patent No. 3,122,619, dated Feb. 25, 1964. Divided heat-generating conductor and the fuse links of the short- and this application May 16, 1963, Ser. No. 280,968 circuiting chamber. It is therefore an object of the present 5 Claims. (Cl. 200--120) invention to provide a heat-absorbing member which has 10 a large mass and a large surface area and which can be This is a division of my co-pending application Serial intimately bonded to the short-circuiting chamber and to No. 793,415 for Protectors for Electric Circuits which the connector without permitting undue interchange of was filed February 16, 1959, now Pat. No. 3,122,619. heat between the heat-generating conductor and the fuse This invention relates to improvements in protectors links of the short-circuiting chamber. for electric circuits. More particularly, this invention re 15 The heat-generating conductor of the fuse provided by lates to improvements in dual element fuses. the present invention supplies heat to heat-softenable ma It is therefore an object of the present invention to pro terial that normally holds the connector in mechanical vide an improved dual element fuse. and electrically-conducting engagement with the heat-gen It is desirable, in the protection of many electric cir erating conductor and with the heat-absorbing member. cuits, to equip those circuits with dual element fuses. 20 That heat-generating conductor must be kept from apply Such fuses have thermal cut-outs that can respond to ing binding forces to the connector which could keep that long-continued low overloads to open, and thereby protect connector from moving out of the said mechanical and the circuits, and they also have fuse links that can respond electrically-conducting engagement when the heat-soften to higher overloads to open, and thereby protect the cir able material softens; and yet the recurrent and appreci- cuits. Whether the dual element fuses open in their ther 25 able expansions and contractions of that heat-generating mal cut-outs or in their fuse links, those fuses limit the conductor during the operation of the fuse can tend to current passing through the electric circuits and thereby warp and distort that heat-generating conductor and there protect those circuits. A number of such dual element by tend to cause that heat-generating conductor to apply fuses have been proposed, and some of them have been such binding forces to the connector. The expansions sold widely. 30 and contractions of the heat-generating conductor can be The capacities of electric circuits have exhibited steady appreciable where the fuse is subjected to high overloads growths throughout the years, and hence it has become that are continued long enough to raise the heat-soften important to make some fuses with current-limiting char able material to its softening temperature or .to raise the acteristics that are even greater than those possessed by fuse links of the short-circuiting chamber to their blow- prior dual element fuses. It would be desirable to have a 35 ing temperature even though those high overloads are fuse that possesses the time-lag characteristics of a dual not continued long enough to soften the heat-softenable element fuse on light overloads but .that responds to high material or to blow the fuse links of the short-circuiting er overloads to open the circuit more rapidly than can chamber. Expansions and contractions of the housing prior dual element fuses. Such a fuse could open the elec of the fuse can also tend to cause the heat-generating con- tric circuit, and thereby limit the current in that circuit, 40 ductor to apply binding forces to the connector, and those before that current reaches the capacity of that circuit. expansions and contractions can easily be caused by vary The present invention provides such a fuse; and it does ing conditions of temperature and humidity. The present so by providing a short-circuiting chamber which is invention compensates for such expansion and contrac equipped with fast-blowing fuse links and which is con tions of the heat-generating conductor and of the housing nected in series with a thermal cut-out. A heat-generating 45 for the fuse and thereby keeps the heat-generating con conductor is disposed adjacent one end of the thermal ductor from applying binding forces to the connector by cut-out and the short-circuiting chamber is disposed adja mounting the heat-absorbing member and the short-cir cent the other end of that thermal cut-out; and both the cuiting chamber of the fuse so they can move relative heat-generating conductor and the fuse links of the short- to the housing of the fuse as the heat-generating conductor circuiting chamber will generate heat whenever current 50 or the fuse housing expands and contracts. That move flows through the fuse. It would not be desirable to have ment of the heat-absorbing member and of the short-cir unlimited interchange of heat between the heat-generating cuiting chamber permits the heat-generating conductor to conductor and the short-circuiting chamber, and such in remain substantially stress-free despite its expansion and terchange of heat is prevented by the present invention by contraction or that of the fuse housing; and that move- providing the heat-absorbing member of the thermal cut 55 ment minimizes the likelihood that the heat-generating out with a portion of reduced cross section. conductor will apply binding forces to the connector. It The heat-generating conductor and the short-circuiting is therefore an object of the present invention to provide chamber, and the connector and heat-absorbing member an electric fuse wherein the heat-absorbing member and of the thermal cut-out are all intimately bonded together; the short-circuiting chamber are mounted to move rela- and they essentially constitute one continuous and integral 60 tive to the fuse housing as the heat-generating conductor conductor. There is, as a result, minimum contact re or the fuse housing expands and contracts. sistance between the various current-carrying components The short-circuiting chamber of the fuse provided by the of the fuse provided by the present invention; and hence present invention has a casing that is shorter and is smaller local heating due to contact resistance is avoided. While in cross-section than the housing for the fuse; and that the present invention minimizes contact resistance be 65 short-circuiting chamber has end bells which close the tween the various current-carrying components of the ends of that casing. Those end bells coact with .that cas fuse by intimately bonding those components together, it ing to provide a tight chamber for the fuse links of the still limits the interchange of heat between the heat-gen fuse; and such a chamber confines any pressures that are erating conductor and the fuse links of the short-circuiting generated when the fuse links blow, and those pressures chamber by reducing the cross section of that end of the help quench any arcs that may form when the fuse links heat-absorbing member which is bonded to the shor.t-cir- blow. 'Further, those end bells and that casing hold arc 3 ,2 5 3 ,1 0 4 3 quenching filler in engagement with those fuse links while 4 Those paths are undesirable, and they can be obviated keeping that filler from impeding the movement of the by using anhydrous calcium sulphate as the inert ma heat-absorbing member and of the short-circuiting cham terial in the short-circuiting chamber. It is therefore ber as the heat-generating conductor or the fuse housing an object of the present invention to provide anhydrous expands and contracts. 5 calcium sulphate as the inert material in a short-circuit The casing for the short-circuiting chamber is made of ing chamber. a sturdy, air-impervious and dimensionally-stable dielec The heat-absorbing member of the fuse provided by the tric material. Such a casing is desirable because it makes present invention has the heat-generating conductor ad it possible to use an inexpensive dielectric material in jacent one end thereof and has the fuse links of the short- making the housing for the fuse. Further, such a casing 10 circuiting chamber adjacent the other end thereof, and is desirable because it can be given a tight fit with the that heat-absorbing member can become quite warm. A end bells, and it can then be depended upon to main terminal will be connected to the opposite end of the tain that tight fit. Such a casing is additionally desirable short-circuiting chamber, and that terminal will be kept because it prevents the expulsion of vaporized metal or of cool by the fuse clips of the fuse holder; and that terminal hot gases when the fuse links blow. 15 will cool the said opposite end of the short-circuiting To make the fuse links really fast-acting, those fuse chamber. The present invention disposes the arc-quench links should be made quite short. However, short fuse ing sand adjacent the said opposite end of the short-cir links mean that the end bells of the short-circuiting cham cuiting chamber, and thereby keeps the sand cool. This ber will be close together; and the closeness of those end is desirable because the cooler the sand, the smaller the bells creates the possibility of an arc traveling along the 20 cross-section that can be given the fuse links; and small exterior of the short-circuiting chamber when the fuse cross-section fuse links can be very fast-acting fuse links. links blow. Any such arc would be momentary, and The heat-absorbing member of the fuse provided by would be due to the fact that the voltage drop across the the present invention is not cylindrical because a cylindri short-circuiting chamber can rise, during the blowing of cal heat-absorbing member would have its periphery im the fuse links, to two or three times its normal value; 25 mediately adjacent the inner surface of the fuse housing but any such arc could not be tolerated at the exterior of the fuse housing.' However, by using the fuse housing and could have its heat-absorbing action materially af fected by the temperature of that fuse housing. The heat to completely enclose the short-circuiting chamber, the absorbing member of the fuse provided by the present in present invention makes it possible to tolerate momentary vention is flat; and the greatest portion of the surface of arcs that could form at the exterior of the short-circuiting 30 that heat-absorbing member is spaced from the inner chamber during the blowing of the fuse links within that surface of the fuse housing to provide an air space. That chamber; and it thereby makes it possible to use very air space acts as an insulator and thereby keeps the tem short, and thus very fast-acting, fuse links. perature of the fuse housing from materially affecting The housing of the fuse protects the exterior of the the heat-absorbing action of the heat-absorbing member short-circuiting chamber and keeps that exterior clean. 35 of the fuse. In doing so, that housing keeps dirt or contaminants from Electric fuses are usually made in standard sizes. Thus, providing paths, at the exterior of the short-circuiting fuses that are to be used to protect circuits utilizing cur chamber, which have low enough resistances to enable rents in the range of zero to thirty amperes will be of one arcs to form and to follow those paths during the blowing size, fuses that are used to protect circuits utilizing cur of the fuse links of that short-circuiting chamber. Such 40 rents in the range of thirty one to sixty amperes will be of paths could not only foster the striking of arcs, but they could also maintain those arcs; and hence the action of the fuse housing in keeping the exterior of the short-cir cuiting chamber clean is very important. a larger size, fuses that are used to protect circuits utiliz ing currents in the range of sixty one to one hundred amperes will be of a still larger size, and so on. Here tofore the current-limiting abilities, of the fuses that had The fuse housing includes an elongated tube of insul- 45 the same physical dimensions but had different ampere lating material; and that tube overlies and insulates the ratings, differed; and therefore to be sure that fuses, made heat-absorbing member and its bonded connections to the to have ampere ratings that differ from the standard and short-circuiting chamber and to the connector. In doing usual ampere ratings, would have the desired current- so, that tube provides important protection against arcing limiting abilities, it was necessary to make detailed tests which might otherwise occur if two of the fuses were 50 of the current-limiting abilities of those fuses. Such tests set in adjaent recesses of a fuseholder equipped with cut are expensive and time-consuming; and the present in away insulating, baffles. Such bailies are cut-away to pro vention minimizes the need of such tests. It does so by vide openings, adjacent the centers of the fuses, to fa providing current-limiting fuse links, for the short-circuit cilitate ready removal of the fuses from the fuseholder; ing chamber, that can be used with most of the differ and those openings could permit arcing between the heat 55 ently rated fuses having the same physical dimensions. absorbing members of the adjacent fuses if those fuses As a result, to make a fuse that has a desireed ampere were not provided with tubes of insulating material. rating, a desired size, and a known current-limiting ability, In a number of instances, sand is used as an arc-quench it is only necessary to make up a thermal cut-out having ing filler at one end of a short-circuiting chamber, and an the desired ampere rating and then intimately bond the inert material is provided at the other end of that short- 60 heat-absorbing member of that thermal cut-out to the circuiting chamber. The sand can respond to arcs, thal short-circuiting chamber for the desired size fuse. It is form during the blowing of the fuse links of that short- therefore an object of the present invention to provide circuiting chamber, to form fulgurites during the quench a short-circuiting chamber which can provide predeter ing of arcs. The inert material keeps those fulgurites mined current-limiting characteristics and to use that from extending all the way between the two end bells of 65 short-circuiting chamber with thermal cut-outs of diferent the short-circuiting chamber, and thereby keeps those ampere ratings to provide fuses with predetermined cur fulgurites from establishing after-blow, current-carrying rent-limiting characteristics but with different ampere paths between those end bells. Different inert materials ratings. have been used to keep the fulgurites from extending all When the connector of a dual element fuse is separated the way between the end bells of the short-circuiting 70 from the heat-generating conductor of that fuse to open chamber; and while most of those inert materials do keep the circuit, an arc can tend to form. It is impractical to the fulgurites from extending all the way between those surround the connector with arc-quenching filler because end bells, those inert materials seem to respond to the that filler would interfere with the requisite ready sepa blowing of the fuse links to permit after-blow, current ration of the connector from the heat-generating conduc carrying paths to form in the short-circuiting chamber. 75 tor; and hence an arc at the connector could continue to 3.253.104 s 6 burn. Such an arc can be of appreciable duration where FIG, 15, and it is taken along the plane indicated by the the fuse opens a circuit which utilizes direct current. The line 16--16 in FIG. 15, and present invention obviates arcing at the connector when FIG. 17 is a longitudinal section through another form that connector moves to open the circuit; and it does so of fuse that is made in accordance with the principles by placing a readily fusible shunt wire in parallel with the 5 and teachings of the present invention. heat-generating conductor. That shunt wire will be un Referring to the drawing in detail, the numeral 20 de able to carry the rated current of the fuse, much less over notes tubular housing for one embodiment of fuse that load currents, and it will fuse and open the circuit after is made in accordance with the principles and teachings the connector moves. However, that shunt wire will take of the present invention. That housing can be made a fraction of a second to heat up to its fusing tempera 10 of a readily available, inexpensive, insulating material ture; and it will carry all of the current through the fuse such as fiber. That housing has a smooth and uninter as it does so, thereby preventing arcing when the connec rupted interior surface, and it has threaded openings 22 tor moves. The shunt wire will be embedded in filler, adjacent the ends thereof. and any arc that might form when the shunt wire fuses A terminal 24, that is rectangular in plan, has a width will quickly be quenched by the filler. It is therefore 15 that is less than the inner diameter of the .housing 20. an object of the present invention to provide a shunt wire That terminal has an opening 30 adjacent the right-hand for the heat-generating conductor of a dual element fuse and to embed that shunt wire in filler that will quench end thereof, and it has a second opening 28 spaced to the left of the opening 30. A bar-like pin 26 is pressed arcs that form when the shunt wire fuses. into and fixedly held, by the opening 28, and that pin Other and further objects and advantages of the present 20 extends transversely of that terminal. That pin has a invention should become apparent from an examination of the drawing and accompanying description. In the drawing and accompanying description, several preferred embodiments of the present invention are shown length equal to the outer diameter of the housing 20. As a result, the pin 26 limits the extent to which the right-hand end of the terminal 24 can be telescoped into the left-hand end of the housing 20. When the flat face and described but it is to be understood that the drawing 25 of the pin abuts the left-hand end of the housing 20, the and accompanying description are for the purpose of opening 30 in the terminal 24 is disposed within that illustration only and do not limit the invention and that the invention will be defined by the appended claims. housing. The numeral 32 denotes a cup-shaped closure for the In the drawing, FIG. 1 is a longitudinal section through left-hand end of the housing 20, and that closure has one embodiment of fuse that is made in accordance with 30 an inside diameter which is slightly larger than the outer the principles and teachings of the present invention, diameter of that housing. The closure 32 has a slot FIG. 2 is a broken, longitudinal section, on a greatly 34 in it, and that slot is just slightly larger than the cross enlarged scale, of the left-hand portion of the fuse shown section of the terminal 24. The closure 32 also has open in FIG. 1, ings 35 which can be set in register with the openings 22 FIG. 3 is a sectional view through the fuse shown 35 in the housing 20. The alined openings 22 and 35 re in FIG. 1, and it is taken along the plane indicated by ceive threaded fasteners 36, and the threaded shanks the line 3--3 in FIG. 1, of those fasteners extend through the openings 35 and seat FIG. 4 is another sectional view through the fuse shown in the openings 22 to rigidly secure the closure 32 to the in FIG. 1, and it is taken along the plane indicated by housing 20. Also, the fasteners 36 enable the closure 32 the line 4--4 in FIG. 1, 40 to hold the pin 26 and the terminal 24 rigidly fixed rela FIG. 5 is another sectional view through the fuse tive to the housing 20. shown in FIG. 1, and it is taken along the plane indicated by the line 5--5 in FIG. 1, FIG. 6 is a perspective view of the heat-absorbing The numeral 38 denotes a conductor which is made so it will generate appreciable amounts of heat whenever currents greater than the rated current of the fuse pass member of the fuse shown in FIG. 1, 45 through it. That conductor has an opening 40, adjacent FIG. 7 is an end view, on a large scale, of the short- the left-hand end thereof, which can be set in register with circuiting chamber of the fuse shown in FIG. 1 before the opening 30 in the terminal 24. The conductor 38 has the end bells are affixed to that short-circuiting chamber, two portions 42 and 44 of reduced cross section, and FIG. 8 is a perspective view of the heat-generating con those portions of that conductor will be the hottest por- ductor of the fuse shown in FIG. 1, 50 tions of that conductor. The conductor 38 also has a re FIG. 9 is a perspective view of one of the fuse links duced cross-section, right-hand end 46. As indicated in the short-circuiting chamber of the fuse shown in particularly by FIGS. 1 and 2, the conductor 38 is bent FIG. 1. FIG. 10 is a sectional view, on a considerably enlarged upwardly at a point to the right of the opening 40, and it is bent downwardly at a point adjacent the left-hand scale, through the short-circuiting chamber of FIG. 7, 55 end of the reduced cross-section portion 46. and it is taken along the plane indicated by the line The numeral 52 denotes a support which has the form 10--10 in FIG. 7, of a circular disc; and that support is made small enough, FIG. 11 is a longitudinal section through another em relative to the inner diameter of the housing 20, to en bodiment of fuse that is made in accordance with the able that support to move freely relative to that housing principles and teachings of the present invention, 60 in the axial direction. The support 52 is of insulating FIG. 12 is a sectional view through the fuse shown matrial, such as fiber, and it has two slots 54 and 56 in FIG. 11, and it is taken along the plane indicated by in it. The slot 54 accommodates the reduced cross-sec the line 12--12 in FIG. 11, tion, right-hand and 46 of the heat-generating conductor FIG. 13 is another sectional view through the fuse 65 3ti8o,n,anledftt-hheansdloetn5d6oafcacohmeamt-oadbastoersbitnhge mreedmucbeedr 6c2ro. ssT-sheact- shown in FIG. 11, and it is taken along the plane in reduced cross-section end of the heat-absorbing member dicated by the line 13--13 in FIG. 11, has an opening 64 in it, and that opening will be disposed FIG. 14 is a perspective view of the right-hand ter to the left of the support 52 whenever that heat-absorb minal of the fuse shown in FIG. 11, and it shows that ing member is assembled with that support. The heat- terminal after it has been provided with protuberances 70 absorbing member is flat and it is wide, but its edges are at the opposite sides thereof, spaced inwardly of the interior surface of the housing 20 FIG. 15 is a longitudinal section through another em to provide an insulating air space intermediate the heat bodiment of fuse that is made in accordance with the absorbing member and the housing. The right-hand end principles and teachings of the present invention, 63 of the heat-absorbing member 62 is also reduced in FIG. 16 is a sectional view through the fuse shown in 75 cross-section, but it is wider than the reduced cross-sec 3,253,104 7 8 tion, left-hand end of the heat-absorbing member. The shown by FIG. 5. A hook 60 is set in a slot in the sup width of the right-hand end 63 of the absorber 62 is ap port 58, and the right-hand end of that hook is riveted proximately one half of that of the absorber 62. over to maintain that hook in assembled relation with The numeral 50. denotes a sleeve-like rivet that is tele that support. That hook receives and holds the other scoped through the aligned openings 30 and 40 of the 5 end of the helical extension spring 72, and that spring terminal 24 and heat-generating conductor 38, respective biases the connector 70 for movement out of its normal ly; and it is also telescoped through a washer 48. That engagement with the heater 38 and with the heat-absorb rivet permanently secures the terminal 24 and the heat ing member 62. As a result, when the heat softenable generating conductor 38 together; and it coacts with the material 74 responds to heat to soften and release the support 52 to hold the heat-generating conductor 38 ad 10 connector 70, that connector will respond to the spring jacent the geometric axis of the housing 20. 72 and move out of its normal mechanical and elec The numeral 66 denotes a wire that has a cross section trically-conducting engagement with the heater 38 and that is much smaller than the cross section of the heat with the absorber 62. generating conductor 38, and that wire will blow when The numeral 76 denotes an end bell of metal which ever it has to carry all of the rated current of the fuse. 15 has its right-hand face machined away to form a shallow, That wire is encased in asbestos or some other heat- cup-like recess. The numeral 78 denotes an end bell of insensitive insulating material. One end of the wire 66 metal which has its left-hand face machined away to is stripped of its insulation and is extended up through form a shallow, cup-like recess; and the end bell 78 is the sleeve-like rivit 50, and the other end of that wire is materially thicker and thus has more thermal capacity stripped of its insulation and is extended up through the 20 than the end bell 76. The end bells 76 and 78 are made opening 64 in the reduced cross-section, left-hand end so their diameters are smaller than the inner diameter of the heat-absorbing member 62. Bonding material 68, of the housing 20; and therefore those end bells can such as solder, holds the wire 66 in electrically-conduct move freely relative to the housing 20 in the axial direc ing relation with the terminal 24 and with the heat-absorb tion. The reduced cross-section portion 63 of the heat ing member 62. The wire 66 is made long enough so it 25 absorbing member 62 is permanently connected to the can be spaced from the heat-generating conductor, and left-hand face of the end bell 76, as by silver solder or thereby kept from being heated appreciably by that heat the like; and a terminal 82 is permanently connected to generating conductor. An inert filler 106, such as calcium the right-hand face of the end bell 78, as by silver solder sulfate, is disposed in the compartment defined by the or the like. The terminal 82 is rectangular in plan, and closure 32 and the support 52, and that filler will help 30 it is narrow enough to permit the left-hand end thereof keep the wire 66 from being appreciably heated by the to telescope within the right-hand end of the housing 20; heat-generating conductor 38. Also, that filler will help but it is as wide as the diameter of the end bell 78. quench any arc that may form when the wire 66 blows. The terminal 82 has protuberances 83 thereon, and those The numeral 70 denotes a connector that is made from protuberances are conveniently formed by a staking opera two U-shaped pieces of metal, from a square piece of 35 tion. metal, and from one end of a helical extension spring A closure 86 of cup-shaped configuration has an inner 72. One of the U-shaped pieces of metal is lighter in diameter which is slightly larger than the outer diameter weight than the other, and it is disposed so its open end of the housing 20, and that closure can be telescoped faces to the left, as that connector is viewed in FIG. 2. over the right-hand end of that housing. A slot 88 is The other U-shaped piece of metal is disposed so its open 40 provided in the closure 86, and that slot is sufficiently end faces to the right, and so its upper arm overlies the larger than the terminal 82 to enable that terminal to lower arm of the upper U-shaped piece of metal. The move longitudinally relative to that closure. The closure square piece of metal is disposed within the other U- 86 will be telescoped over the terminal 82 and over the shaped piece of metal; and it underlies the lower arm of right-hand end of the housing 20 before the protuberances tohfe thueppheerliUca-lshsappreindg p7ie2ceis odfismpoestaeld. beTthweeelenftt-hheansdqueanrde 45 w83illarperefovremntedunolnimthitaetdtemrmoivneaml,eanntdotfhotsheeprtoetrumbienraalnc8e2s piece of metal and the lower arm of the other U-shaped to the left. The closure 86 has openings 85 which can piece of metal. be set in register with the threaded openings 22 in the The two U-shaped pieces of metal, the square piece of housing 20 adjacent the right-hand end of that housing. mpoestiatli,ona,nadndthtehelenfta-hhaenadvyepnrdesosfurteheis sapprpinliged7t2o athree useptpeinr 50 Fthaesteonpeernsin8g4s w85ithanthdresaedaeteddshinantkhse ctahnrebaedepdasosepdentihnrgosug2h2 and lower faces of the upper and lower arms, respectively, to fixedly prevent separation of the closure 86 from the of the other U-shaped piece of metal. That pressure is housing 20. heavy enough to clamp the arms of that other U-shaped The numeral 90 denotes a right-circular cylinder which penietcseooffthmeetcaolntnigehcttolyr e7n0ouinghpetormhaonledntallyl faosusermcbolmedporne 55 iaslummaidnea coefraamhiicghis-aFluremnicnhatocwernamPiocr;cealnadin oCnoemsupcahnyhiNgho-. lation. When the connector 70 is completed, its upper 4462. That cylinder is resistant to abrasion, corrosion, U-shaped piece of metal will define a recess that can thermal shock and mechanical shock, and it has good telescope freely over the right-hand end 46 of the heat dielectric properties. The cylinder 90 has a number of mgeanteerraiatilngsuccohnadsucstooldr e3r8, .fillAs tmhaatssre7ce4s,soafnhdeaatl-ssoofetnegnaagbeles 60 cshyoliwndnribcyalFpIaGsSsa.g1e-s109,2ththerroeuagrhe itth; raenedpiansstahgeeesm9b2.odiHmoewnt the heat-absorbing member 62. That mass normally holds ever, more or fewer passages 92 can be formed in the the connector 70 in mechanical and electrically-conducting cylinder 90. The end faces, and the end portions of the engagement with the heat-generating conductor 38 and outer surface, of the cylinder 90 are provided with thin wcainthrtehsepohnedat-toabhsoerabtintog smoeftmenbearn6d2.relHeaoswe etvheart, cthoantnemcatossr 65 cfooramtinegds b9y3 oaf mmeettaalll;izianngd pthroocseessc.oatiInngsthaarte pprroecfeersas,blya for movement out of that engagement; and when that material such as Frenchtown Porcelain Company Nicote connector moves it will move as a unit. is painted on, or otherwise applied to, the end faces and A support 58 of insulating material has the form of the end portions of the outer surface of the cylinder 90, a notched circular disc; and the diameter of that disc is 70 and then that cylinder is fired at a high temperature. smaller than the inner diameter of the housing 20. As Soft solder is then applied to the metallized coatings a result, that support can move freely relative to the hous to "tin" them; and then the cylinder 90 is cleaned to free ing 20 in the axial direction. The notch 59 in the sup it of solder flux. port 58 is wide enough to slip over the reduced cross The numeral 94 denotes a fusible conductor or fuse section end 63 of the heat-absorbing member 62, as 75 link which has a number of transversely-directed narrow 3,283,104 . 9 openings 96 therein ana which has a circular opening 97 10 Three additional cup-shaped washers 98 will then have therein. That conductor will preferably be made of the slots 100 thereof telescoped over the upper ends of silver; and it is dimensioned so it can be disposed within the fuse links 94, and those upper ends will then be bent one of the cylindrical passages 92 without having any over to maintain those cup-shaped washers in assembled portion thereof touch the wall of that passage. The fuse 5 relation with those fuse links. Further solder 101 will shown in FIGS. 1-10 has three fusible conductors 94; be used to bond those cup-shaped washers 90 to the one for each passage 92. upper ends of the links 94, and also to secure those cup Cup-shaped washers 98 are provided to close the ends shaped washers to the tinned metal coatings 93 on the of the passages 92 in the cylinder 90; and the tapered ends of the cylinder 90. This further solder 101 coacts walls of those washers engage and are centered by the 10 with the solder 101 at the opposite end of the cylinder passage-defining portions of that cylinder, as shown par 90, and with the cup-shaped washers 98 at both ends of ticularly by FIG. 10. Each of the cup-shaped washers the cylinder 90, to hermetically seal the passages 92. 98 has a diametric slot 100 therein, and those slots are The cylinder 90, with its fuse links 94 and its fillers 102 made slightly larger than the cross sections of the fusible and 104, serves as the short-circuiting chamber of the conductors 94. The tapered walls of the cup-shaped 15 fuse shown in FIGS. 1-10. washers 98 will center the slots 100 relative to the pas At this time the end bell 78, to which the terminal 82 sages 92, and those slots will center the fuse links 94 has previously been permanently secured, is set so its relative to those passages 92. The overall result is that recessed end is uppermost. That end bell is then heated the fusible conductors 94 are positively centered with to the melting point of solder, the cylinder 90 is set so regard to the passages 92. Solder 101 engages the cup 20 the sand-filled end thereof is within the recessed end of shaped washers 98 and also engages the tinned coatings end bell 78, solder is applied to that recessed end and is 93 of metal and the fuse links 94. That solder her caused to melt and bond that cylinder and end bell to metically seals the ends of the passages 92 and elec gether, and then the end bell and solder are permitted to trically bonds the fuse links 94 and the cup-shaped washers cool. That solder will mechanically and electrically 98 and the tinnned metal coatings 93 together. The cup 25 bond the short-circuiting chamber to the end bell 78. shaped washers 98 not only center the links 94 but also The end bell 76, to which the absorber 62 has pre provide adequate contact area between those links and viously been permanently secured, is then set with its the end bells 76 and 78. recessed end uppermost. That end bell is then heated The numeral 102 denotes quantities of anhydrous cal to the melting point of solder, the short-circuiting charri- cium sulfate that are disposed within the passages 92 of 30 her with its attached end bell 78 and terminal 82 will cylinder 90 and that embed the left-hand ends and the then be inverted and set in the recess of the end bell 76. left-handmost openings 96 of the fusible conductors 94. Solder will then be applied to the recess in the end bell The numeral 104 denotes quantities of quartz sand that 76, and that solder will melt and intimately bond that are disposed within the passages 92 of cylinder 90 and end bell to the short-circuiting chamber; and then that that embed the circular openings 97 and the remaining 35 end bell and the solder will be permitted to cool. openings 96 of the fusible conductors 94. The interfaces The support 52 will then have its slot 54 telescoped between the quantities of anhydrous calcium sulfate and over the reduced cross-section, left-hand end of the quartz sand will be intermediate the circular openings 97 absorber 62; and the heater 38, which has previously and the left-handmost openings 96 of the fusible conduc been riveted to the terminal 24, will have its reduced tors 94. The quartz sand can respond to blowing of the 40 cross-section portion 46 telescoped through the slot 54 fuse links 94 to form fulgurites during extinction of arcs in that support 52. The axis of the terminal 24 will that form when those fuse links blow. The anhydrous then be alined with the axis of the absorber 62, and calcium sulfate keeps the fulgurites from spanning the thereafter the connector 70 will be set so the lower loop full lengths of the passages 92 of the cylinder 90, and thereof rests upon the absorber 62 and so the upper loop it also prevents the establishment of after-blow resistance 45 thereof telescopes over the reduced cross-section end 46 paths through the passages 92 of cylinder 90. of the heater 38. Heat-softenable material 74 will then In assembling the fuse links 94 with the cylinder 90, be applied to the connector 70, to the heater 38, and to each of the fuse links 94 has one of its ends bent, and the absorber 62; and that heat-softenable material will then has its other end inserted through a slot 100 in mechanically and electrically bond the connector 70 to one of the cup-shaped washers 98. The fuse links 94 50 that heater and absorber. are then moved through the slots 100 until the bent ends The notch 59 is the support 58 will then be telescoped thereof prevent further movement. At such time, solder down over the reduced cross-section portion 63 of the 101 is used to bond those fuse links to the cup-shaped absorber 62; and that support will thus be intermediate washers 98. Thereafter, the other ends of the fuse links the end bell 76 and the full-width portion of the heat 94 are telescoped through the passages 92 until the 55 absorbing member 62. The right-hand end of the helical tapered walls of the cup-shaped washers 98 intimately extension spring 72 will then be secured to the upper engage and are held and centered by the passage-defining end of the hook 60. That spring will be under tension portions of the cylinder 90; and at that time further solder and will bias the connector 70 for movement out of its 101 is used to seal those cup-shaped washers to the tinned mechanical and electrically-conducting engagement with metal coatings 93. 60 the heater 38 and absorber 62. Preferably the bent ends of the fuse links 94 will be The opposite ends of the wire 66 will be stripped of adjacent the right-hand end of cylinder 90, and the other their insulation and will then be telescoped upwardly ends of those fuse links will be adjacent the left-hand end through the rivet 50 and through the opening 64 in the of that cylinder, as that cylinder is viewed in FIG. 1. absorber 62. Solder 68 will be applied to those ends Where that is the case, the cylinder 90 can be rotated 65 of that wire to bond those ends to the terminal 24 and to ninety degrees in the clockwise direction from the posi the absorber 62. At this time, all of the electrically- tion shown in FIG. 1, and quartz sand 104 can be intro conducting components of the fuse will be electrically duced in the passages 92. That sand will embed the bonded together to constitute one, continuous, integrated circular opening 97 and the three narrow openings 96 conductor. intermediate that circular opening and the lower end of 70 The wire 66 will be in parallel with, and will thus shunt, each of the fuse links 94. Once this has been done, the heater 38. The overall resistance of the wire 66 will anhydrous calcium sulfate will be introduced into, and be materially greater than that of the heater 38; and, will be used to fill, the upper ends of the passages 92. therefore, as long as the connector 70 is in its normal, That anhydrous calcium sulfate will embed the uppermost electrically-conducting engagement with the heater 38 opening 96 in each of the fuse links 94. 75 and absorber 62, the shunt wire 66 will carry very little 3,253,104 11 12 current. However, when the connector 70 is moved out supplied to, and held by, the absorber 62 be great enough of its normal, electrically-conducting engagement with the to soften the heat-softenable material 74. However, once heater 38 and absorber 62, the wire 66 will have to that material does soften, it will release the connector 70; carry all of the current; and that current will cause that and the spring 72 will thereupon move that connector out wire to blow. 5 of its electrically-conducting engagement with the heater The fusible conductors 94 are in parallel with each 38 and absorber 62. At such time, the circuit through other, and each of those fusible conductors will carry its the heater 38 will be interrupted, but the circuit through proportionate share of the total current passing through the shunt wire 66 will be intact. The circuit through the the fuse. The openings 96 and 97 provide weak spots shunt wire 66 will prevent or minimize arcing in the com in those fusible conductors, and those weak spots will 10 partment defined by the supports 52 and 58; and this is generate the greatest temperatures generated by those very desirable. The shunt wire 66 will be unable to carry fusible conductors. The amount of heat generated by the rated current of the fuse, much less any overloads those fusible conductors will be great enough to blow that cause the heat-softenable material 74 to soften; and those fusible conductors on heavy overloads and on short hence that wire will blow. However, any arcs that form circuits. Because the quartz sand 104 within the pas 15 when that wire blows will be quickly extinguished by the sages 92 is kept relatively cool by the end bell 78 and filler 106 which embeds that wire. the terminal 82, the fuse links 94 can be made of smaller- If the overloads to which the fuse is subject are ex than-normal cross section, and the openings 96 and 97 tremely heavy overloads or are short circuits, the fuse can be made larger than normal. The overall result is links 94 will blow in one or more of their openings 96. that the fuse links 94 are very fast-acting and can pro 20 Any arcs that form will be extinguished by the fillers 102 vide important and desirable current-limiting character and 104. The fuse links 94 will open very promptly, and istics. The overall integrated conductor, including the termi nals 24 and 82, the heater 38 and the shunt wire 66, the thus they will limit the current that has to be carried by the circuit whenever a heavy overload or a short circuit occurs. connector 70, the absorber 62, the short circuiting cham 25 Where heavy overloads of short duration are recur ber 90, and the end bells 76 and 78 is then telescoped rently applied to the fuse, the heater 38 will expand and into the housing 20. That telescoping will be done by contract appreciably; and that heater can tend to force passing the terminal 82 all the way through the housing the connector 70 to move axially of the housing 20. Such 20; and that telescoping will be limited by the engagement movement will not cause binding of that connector be of the pin 26 with the left-hand end of the housing 20. 30 cause that movement will be compensated for by the Once the overall integrated conductor has been telescoped axial movement of the absorber 62 and of the short cir within the housing 20, the compartment defined by the cuiting chamber with its end bells. That axial movement support 52 and the left-hand end of the housing 20 will thus compensates for expansions and contractions of the be filled with a filler such as calcium sulfate 106. There heater 38; and it also compensates for changes in the over upon, the closure 32 will have its slot 34 alined with, and 35 all length of the housing 20 due to expansion or contrac telescoped over, the terminal 24; and then that closure tion of that housing. will be moved into holding engagement with the pin 26. The fuse of FIGS. 1-10 thus provides the desirable The fasteners 36 can then be passed through the openings time lag of a dual element fuse on low overloads, and 35 in the closure 32 and seated in the threaded openings provides current-limiting operation on heavy overloads 22 adjacent the left-hand end of the housing 20 to per 40 and on short circuits. Thus, the fuse of FIGS. 1-10 pro manently secure the overall integrated conductor and the closure 32 to the housing 20. Thereafter, the closure 86 vides exceptionally desirable circuit protection. FIGS. 11--14 show a fuse which is very similar to the will have its opening 88 alined with, and telescoped over, fuse of FIGS. 1-10. The principal difference between the terminal 82; and that closure will be moved until its the fuse of FIGS. 11-14 and the fuse of FIGS. 1-10 is openings 85 are in register with the threaded openings 22 45 the substitution of stamped end bells for the machined adjacent the right-hand end of the housing 20. At this end bells of the fuse of FIGS. 1-10. time, the fasteners 84 will have their threaded shanks The fuse of FIGS. 11-14 has a tubular housing 120 of passed through the openings 85 and seated in those open a readily available, inexpensive insulating material such ings 22. Those fasteners'will permanently secure the clo as fiber. That housing has an unobstructed interior sur sure 86 to the housing 20; but the terminal 82, the end 50 face, and it has threaded openings 122 adjacent the op bell 78, the cylinder 90, the end bell 76, the support 58, posite ends thereof. A terminal 124 has an opening, not the absorber 62, the connector 70 and the support 52 will shown, adjacent the right-hand end thereof, and it also be free to move axially of the housing 22. Thereafter, has a second opening, not shown, to the left of the first the terminal 82 will be staked to form the protuberances opening. That second opening receives and fixedly holds 83 at each side thereof; and those protuberances are 55 a transversely-directed, bar-like pin 126; and that pin spaced a short distance to the right of the closure 86, and bears against the left-hand end of the housing 120. they project outwardly beyond the sides of the slot 88 of The numeral 132 denotes a cup-shaped closure that can closure 86. Those protuberances will keep a heavy pres telescope over the left-hand end of the housing 120; and sure or a severe blow from driving the terminal 82, the that closure has a slot 134 which telescopes over the ter end bell 78, the cylinder 90, the end bell 76 and the ab 60 minal 124. That closure can abut the pin 126 and fixedly sorber 62 to the left to cause binding between the con hold that pin and the terminal 124 rigid relative to the nector 70 and the heater 38. housing 120. The closure 132 has openings that can be Under normal conditions of operation, the fuse of FIGS. set in register with the threaded openings 122 adjacent H 0 will carry its rated current and will occasionally the left-hand end of the housing 120; and fasteners 136 carry transient overloads. The reduced cross-section por 65 have threaded shanks which pass through the openings tions 42 and 44 of the heater 38 will respond to the pas in the cup-shaped closure 132 and seat in the threaded sage of the rated current through the fuse to generate heat, openings 122. Those fasteners fixedly secure the ter and the weak spots in the fuse links 94, formed by the minal 124, the pin 126 and the closure 132 to the hous openings 96 and 97, will also respond to the passage of ing 120. that current to generate heat. The heat absorber 62 will 70 The numeral 138 denotes a heater that has an opening, respond to the heating of the heater 38 and of the fuse not shown, in the left-hand end thereof which can be set links 94 to become heated, but that absorber will not be in register with the first opening in the terminal 124. That come hot enough to permit the heat-sofenable material heater has two reduced cross-section portions 142 and 74 to soften. Only where an objectionable overload is 144, and it also has a reduced cross-section, right-hand continued for an objectionable length of time will the heat 75 end 146. A washer 148 has the opening therein alined 3,253,104 13 . 14 with the opening in the heater 138 and with the first open current-limiting characteristics of the fuse of FIGS. 11 ing in the terminal 124; and a sleeve-like rivet 150 tele 14 will not be as great as those of the fuse of FIGS. scopes through those openings and is riveted over to fix 1-10. However, the fuse of FIGS. 11-14 will have im edly secure the heater 138 in permanent engagement with portant and desirable current-limiting characteristics; the terminal 124. 5 and it will provide important and valuable circuit protec The numeral 152 denotes a support of insulating ma tion, as by permitting the connector 170 to move on low terial, and that support has the form of a circular disc. overloads and by permitting the links in the short-circuit The outer diameter of the support 152 is less than the ing chamber to blow on heavy overloads and short inner diameter of the housing 120, and therefore the sup circuit. port 152 can be moved relative to that housing in the 10 Referring to FIGS. 15 and 16, the numeral 220 de axial direction. That support has a slot 154 therein that notes a tubular housing of a readily available, inexpensive accommodates the reduced cross-section, right-hand end insulating material such as fiber. That housing has an 146 of the heater 138, and it has a slot 156 that accom unobstructed interior surface, and it has threaded open modates the reduced cross section, left-hand end of a ings 222 adjacent the opposite ends thereof. A terminal heat-absorbing member 162. That left-hand end of the 15 224, similar to the terminals 24 and 124, has an opening, absorber 162 has an opening, not shown, through it; and not shown, adjacent the right-hand end thereof; and it that opening accommodates one end of a shunt wire 166 which is encased in asbestos or some other heat-insensitive has a second opening, not shown, to the left of the first opening. That second opening receives and holds a bar insulating material. The other end of that shunt wire ex like, transversely-extending pin 226. That pin is longer tends upwardly through the sleeve-like rivet 150; and 20 than the inner diameter of the housing 220, and the flat solder 168 bonds the ends of the wire 166 to the terminal face of that pin abuts the left-hand end of that housing. T24 and to the absorber 162. Filler material 206 will A cup-shaped closure 232 has a slot 234 which accommo embed the wire 166 and will quench any arcs that may dates the terminal 224; and it also has openings which can tend to form when that wire blows. can be alined with the threaded openings 222 adjacent the A connector 170, which is identical to the connector 70 25 left-hand end of the housing 220. Fasteners 236 have of the fuse of FIGS. 1--10, is bonded to the heater 138 threaded shanks that extend through the openings in the and to the absorber 162 by heat-softenable material 174. closure 232 and seat in the threaded openings 222 of the That connector is normally bonded in mechanical and housing 220. electrically-conducting engagement with the heater 138 The numeral 238 denotes a heater which has reduced and the absorber 162; but it can move out of that en 30 cross-section portions 242 and 244 and which has a re gagement when that heat-softenable material softens. duced cross-section, right-hand end 246. That heater is The right-hand end of the absorber 162 has a reduced substantially identical to the heaters 38 and 138 of the cross-section portion 163, and that reduced cross-section fuses of FIGS. 1-10 and 11-14, respectively. An open portion has a width approximately one half of the width ing, not shown, in the left-hand end of the heater 238 is of the absorber 162. The reduced cross-section portion 35 alined with the first opening in the right-hand end of the 163 accommodates a notch 159 in a circular support 158 of terminal 224; and a washer 246 has its opening alined insulating material. That support receives and holds a with those openings. A sleeve-like rivet 250 extends hook 160; and that hook receives and holds the right- through the alined openings in the heater 238, the termi hand end of a helical extension spring 172. That spring nal 224, and the washer 246; and that rivet permanently biases the connecter 170 for movement out of its electri 40 secures the heater 238 to the terminal 224. cally-conducting engagement with the heater 138 and A support 252 of insulating material has the form of absorber 162. a circular disc; and that support has a diameter smaller The reduced cross-section, right-hand end 163 of the than the inner diameter of the housing 220. The support absorber 162 is permanently secured, as by silver solder 252 has a slot 254 that accommodates the reduced cross or the like, to a cup-shaped end bell 176. That end bell 45 section, right-hand end 246 of the heater 238, and it also is preferably formed by a stamping operation; and while has a slot 256 to accommodate the reduced cross-section, that end bell is not as tick as the end bell 76 of the fuse left-hand end of a heat-absorbing member 262. That left- of FIGS. 1-10, that end bell has appreciable thermal hand end of the absorber 262 has an opening through it; mass. Bonded to the right-hand face of the end bell 176 and one end of a shunt wire 266 extends through that by solder is a short-circuiting chamber including the cylin 50 opening. The other end of that shunt wire extends der 190, three fuse links 194, and six cup-shaped washers through the sleeve-like rivet 250; and the ends of that 198 which have diametric slots 200 to accommodate the? shunt wire are bonded to the absorber 262 and to the fuse links 194. The right-hand end of that short-circuiting terminal 224. That wire is encased in asbestos or some chamber is bonded, by solder, to a cup-shaped end bell other heat-insensitive insulating material. Filler mate 178; and that end bell is preferably formed by a stamping 55 rial 306 will embed the wire 266 and will quench any arcs operation. That end bell is permanently secured, as by that may tend to form when that wire blows. silver solder or the like, to the left-hand end of a terminal The numeral 258 denotes a support which is smaller 182; and that terminal is longer than the terminal 82 than the housing 220 and which can move freely within the of the fuse of FIGS. 1-10. That terminal has protuber housing 220 in the axial direction; and that support has a ances 183 at the sides thereof comparable to the pro 60 notch 259. That notch telescopes over the reduced cross tuberances 83 on terminal 82 of the fuse of FIGS. 1-10. section, right-hand end 263 of the absorber 262. That The right-hand end of the housing 120 is covered by a support carries a hook 260, and that hook receives and cup-shaped closure 186; and that closure has a slot 188 holds the right-hand end of a helical extension spring 272. which loosely accommodates the terminal 182. Fasten That spring biases a connector 270 out of its normal, ers 184 extend through openings in the closure 186 and 65 mechanical and electrically-conducting engagement with seat in threaded openings 122 adjacent the right-hand end the heater 238 and the absorber 262. The connector 270 of the housing 120; but while the fasteners 184 fixedly hold the closure 186 in assembled relation with the hous is identical with the connectors 70 and 170 of the fuses of FIGS. 1-10 and 11-14, respectively. Heat-softenable ing 120, they do not preclude axial movement of the material 274 normally holds the connector 270 in that terminal 182, of the short-circuiting chamber and its end bells 176 and 178, of the absorber 162, of the conductor 70 mechanical and electrically-conducting engagement, but 170, of the connector 170, and of the supports 152 and it will respond to heat to soften and release that con 158. nector. When that heat-softenable material softens, the Because of the substitution of the stamped end bells spring 272 will move the connector 270 to the right and 176 and 178 for the machined end bells 76 and 78, the 75 open the circuit of the fuse. 3,253,104 IS The numeral 276 denotes an end bell which is perma nently secured, as by silver solder or the like, to the re duced cross-section end 263 of the absorber 262. That end bell is a solid, cylindrical, metal disc, but it has a number of radially-extending openings at the periphery thereof. The numeral 278 denotes a similar end bell, and those end bells are dimensioned to telescope within a sleeve 290 of glass melamine. That sleeve will be dimen sionally stable, and it can be made so it has a very close fit with the peripheries of the end bells 276 and 278. The sleeve 290 has openings adjacent the ends thereof, and those openings will accommodate steel pins 291. Those pins will have press fits with the radial openings at the peripheries of the end bells 276 and 278, and those pins will permanently secure the sleeve 290 to the end bells 276 and 278. The inner diameter of the sleeve 290 is larger than the width of the absorber 262 but is smaller than the width of the terminal 282. Intermediate the end bells 276 and 278 are a number of fusible conductors 294; and each of those fusible con ductors has four narrow openings 296 therein plus one circular opening 297 therein. As indicated particularly by FIG. 15, the circular opening 297 is adjacent the lefthand end of the fusible conductor 294 but is spaced from that left-hand end by an intermediate narrow opening 296. The ends of the fusible conductors 294 are permanently secured to the confronting faces of the end bells 276 and 278, as by solder. Where desired, slots or notches can be formed in the confronting faces of the end bells 276 and 278, and those slots or notches will accommodate the ends of the fuse links 294. Anhydrous calcium sulfate 302 embeds the left-hand ends of the fusible conductors 294, and quartz sand 304 embeds the middles and also the right-hand ends of the fusible conductors 294. This arrangement of fillers is exactly the same as the arrange ment of fillers in the fuse of FIGS. 1-10. A terminal 282 is permanently secured, as by silver solder or the like, to the right-hand face of the end bell 278. That terminal has protuberances 283 at the oppo site sides thereof. That terminal has the left-hand end thereof loosely lodged within a slot 288 in a cup-shaped closure 286 for the right-hand end of the housing 220. That closure has openings which accommodate fasteners 284; and the threaded shanks of those fasteners extend through those openings and seat in threaded openings 222 adjacent the right-hand end of the closure 220. In fabricating the short-circuiting chamber which in cludes the sleeve 290, the end bells 276 and 278, the fusible conductors 294, and the filler materials 302 and 304, the end bells 276 and 278 are first equipped with the absorber 262 and. the terminal 282, respectively; and thereafter the fusible conductors 294 are soldered to the end bells 276 and 278. At such time, the end bell 276 is telescoped part way into the tube 290, and then anhy drous calcium sulfate 302 is poured into the sleeve 290. The end bell 278 is then telescoped within the right-hand end of the tube 290, and thereupon the threaded plug 310 can be removed from the threaded opening in the end bell 278. Quartz said 304 is then introduced through that opening; and once the compartment defined by the end bells 276 and 278 and the sleeve 290 is filled, the threaded plug 310 can be replaced. The fuse of FIGS. 15 and 16 differs from the fuses of FIGS. 1-10 and 11-14 in the construction of the shortcircuiting chamber; but the operation of the fuse of FIGS. 15 and 16 is the same as the operations of those other fuses. The short-circuiting chamber shown in FIGS 15 and 16 is cheaper and easier to make than are the shortcircuiting chambers of the fuses of FIGS. 1-10 and 11-14. Referring to FIG. 17, the numeral 320 denotes a hous ing of a dimensionally stable dielectric material, and one such material is glass melamine. Disposed within, and located adjacent the left-hand end of, the housing 320 is an end bell 376 \yhich differs from the end bell 76 of 16 FIGS. 1-10 because it had radially-directed openings 377 at the periphery thereof and because it has a terminal, rather than a heat-absorbing member, permanently se cured to it. An end bell 378, which is identical to the 5 end bell 376, is disposed within and adjacent the other end of the housing 320; and that end bell has radiallydirected peripheral openings 377, and has a terminal 382 permanently secured to it, as by silver solder or the like. Steel pins 379 extend through openings in the housing 10 320 and seat in the radially-directed peripheral openings 377 in the end bells 376 and 378 to permanently secure those end bells to that housing. The confronting faces of the end bells 376 and 378 are machined to form cup-like recesses, and those cup-like 15 recesses accommodate the ends of a cylinder 390 which is identical to the cylinder 90 of the fuse of FIGS. 1-10. That cylinder has metal coatings at the opposite ends thereof, has cup-shaped washers, and has fusible con ductors 394 extending through the cylindrical passages 20 392 therein. The only differences between the short-cir cuiting chamber of FIGS. 10 and 17 are that each of the fusible conductors 394 has a mass 395 of alloying ma terial pressed into the circular opening 397 thereof and that insulating discs 399 are intermediate the filler ma 25 terials 302 and 304. The masses 395 are made of an alloying material such as tin, which will respond to heat to alloy with the metal of the fusible conductors 394 and thereby causes blowing of those conductors. This alloy ing action will occur whenever objectionable overloads 30 continue for objectionable periods of time. The fuse of FIG. 17 will protect against heavy over loads and short circuits by blowing at the openings 396 of the links 394; and that fuse will protect against lesser overloads by the alloying action between the masses 395 35 and the metal of the fusible conductors 394. Thus the fuse of FIG. 17 provides full circuit protection. Whereas the drawing and accompanying description have shown and described several preferred embodiments of the present invention, it should be apparent to those 40 skilled in the art that various changes may be made in the form of the invention without affecting the scope thereof. What I claim is: 1. In an electric fuse, a body of insulating material, a 45 passage through said body of insulating material, metal lized deposits on the ends of said body of insulating ma terial adjacent the opposite ends of said passage, a cup shaped washer that has the dished portion thereof dis posed within one end of said passage, a second cup 50 shaped washer that has the dished portion thereof dis posed within the other end of said passage, openings in said washers that receive the ends of a fusible conductor, . said dished portions of said cup-shaped washers centering said cup-shaped washers relative to said passage and said 55 openings in said cup-shaped washers centering said fusible conductor relative to said cup-shaped washers, whereby said fusible conductor is centered relative to said pas sage, filler within said passage that embeds said fusible conductor, end bells, and solder that directly engages 60 said end bells and said metallized deposits and said wash ers and said fusible conductor and that bonds said end bells to said metallized deposits on the ends of said body of insulating material and to said cup-shaped washers and to said fusible conductor. 65 2. In an electric fuse, a body of insulating material, a passage through said body of insulating material, metal lized deposits on the ends of said body of insulating ma terial adjacent the opposite ends of said passage, a washer disposed at one end of said passage, a second 70 washer disposed at the other end of said passage, openings in said washers that receive the ends of a fusible con ductor, said washers being centered relative to said pas sage and said openings in said washers centering said fusible conductor relative to said washers, whereby said 75 fusible conductor is centered relative to said passage, 3,253,104 17 18 end bells, and solder that directly engages said end bells 5. An electric fuse that comprises a housing, a fusible and said metallized deposits and said washers and said conductor disposed within said housing, said fusible con fusible conductors and that bonds said end bells to said ductor having a plurality of portions of reduced cross metallized deposits on the ends of said body of insulating section intermediate the ends thereof, an alloying metal material and to said washers and to said fusible con 5 of low alloying temperature mounted on said fusible ductor. conductor adjacent one of said portions of reduced cross 3. In an electric fuse, a body of insulating material, a section, a closure adjacent one end of said (housing, a passage through said body of insulating material, metal second closure adjacent the other end of said housing, lized deposits on the ends of said body of insulating ma sand in said housing that embeds and directly engages terial adjacent the opposite ends of said passage, a wash 10 said one portion of reduced cross section and said alloy er disposed at one end of said passage, a second washer ing metal, said sand surrounding said one portion of re disposed at the other end of said passage, openings in said ducer cross section and said alloying metal to a depth washers that receive the ends of a fusible conductor, end sufficient to enable said sand to form a fulgurite as said bells, and solder that directly engages said end bells and fusible conductor blows to open the circuit, said fusible said metallized deposits and said washer and said fusible 15 conductor responding to a heavy electrical overload to conductor and that bonds said end bells to said metal blow and permit an arc to form' within said housing, said lized deposits on the ends of said body of insulating ma sand surrounding said one portion of reduced cross sec terial and to said washers and to said fusible conductor tion and said alloying metal responding to said arc to fuse to hermetically seal the ends of said passage. and thereby absorb heat from said arc to help extinguish 4, An electric fuse that comprises a housing, a fusible 20 said arc, said sand surrounding said one portion of re conductor disposed within said housing, a closure adja duced cross section and said alloying metal forming a cent one end of said bousing, a second closure adjacent fulgurite adjacent said portion of reduced cross section the other end of said housing, sand in said housing that and said alloying metal to absorb heat from said arc, embeds and directly engages a substantial portion of the and anhydrous calcium sulfate that embeds and directly length of said fusible conductor adjacent one end of said 25 engages another of said portions of reduced cross sec fusible conductor, said sand surrounding said substantial tion, said anhydrous calcium sulfate surrounding said portion of said length of said fusible conductor to a depth other portion of reduced cross section for a length and sufficient to enable said sand to form a fulgurite as said to a depth sufficient to space said sand far enough away fusible conductor blows to open the circuit, said fusible from said other portion of reduced cross section to keep conductor responding to a heavy electrical overload to 30 said sand from forming a fulgurite coextensive with said blow and permit an arc to form within said housing, said other portion of reduced cross section, said anhydrous sand adjacent said substantial portion of said length of calcium sulfate being free of chemically-bound or me said electrical conductor responding to said arc to fuse chanically-held water so it will prevent the formation of 'and thereby absorb heat from said arc to help extinguish an after-blow resistance path through said fuse, said anhy said arc, said and adjacent said substantial portion of said 35 drous calcium sulfate preventing the formation of a clo- length of said fusible conductor forming a fulgurite adja sure-to-closure fulgurite as said fusible conductor blows, cent said substantial portion of said length of said fusible said anhydrous calcium sulfate preventing the formation conductor as said sand fuses to absorb heat from said arc, of an after-blow resistance path by helping quench the arc, and anhydrous calcium sulfate that embeds and directly which tends to form as the fusible conductor blows, with engages a further portion of said length of said fusible 40 out evolving water vapor. conductor adjacent the other end of said fusible conduc tor, said anhydrous calcium sulfate surrounding said fur References Cited by the Examiner ther portion of said length of said fusible conductor for a length and to a depth sufficient to space said sand far enough away from said`further portion of said length of 45 said fusible conductor to keep said sand from forming a fulgurite coextensive with said further portion of said length of said fusible conductor, said anhydrous calcium sulfate being free of chemically-bound or mechanicallyheld water so it will prevent the formation of an after 50 blow resistance path through said 'fuse, said anhydrous 797,324 867,543 1,140,9,53 2,358,676 2,647,970 2,934,622 3,023,289 UNITED STATES PATENTS 8/1905 10/1907 5/1915 9/1944 8/1953 4/1960 2/1962 Sachs______________ 200__132 W eston____________ 200__120 Cole ______________ 200--120 W ood______________ 200__131 Edsalle et a l . _______ 200--120 M assar_________ 200--117 X M cAlister__________ 200--131 calcium sulfate preventing the formation of a closureto-closure fulgurite as said fusible conductor blows, said anhydrous calcium sulfate preventing the formation of an 55 after-blow resistance path by helping quench the arc, which tends to form as the fusible conductor blows, 20,483 706,206 732,428 FOREIGN PATENTS 9/1902 3/1954 6/1955 Great Britain. Great Britain. Great Britain. Without evolving water vapor. BERNARD A. GILHEANY, Primary Examiner.