US2782286A - Ferrule type renewable cartridge fuse - Google Patents

Description

Feb. 19, 1957 DETCH ,782,286

FERRULE TYPE RENEWABLE CARTRIDGE FUSE Filed Feb. 17, 1953 2 Sheets-Sheet 2 FlGJg FIGJ4 FIGJ5 FIGJG ITF --63 XI: f T 54- IN V EN TOR.

"/(MSM ATTORNE Y United States Patent 2,782,286 FERRULE TYPE RENEWABLE CARTRIDGE FUSE A" Lewis Detch, Pittsburgh, Pa.

Application February 17, 1953, Serial No. 337,357

" 9 Claims. (Cl. 200-131 This invention relates to electric circuit breakers, particularly thermal current breakers and more especially fusible element breakers of the well knownferrule type renewable cartridge fuse form.

Those acquainted with well known ferrule type cartridge electric fuses are well aware that known forms are so constructed that the electrical connection between the interior fusible link and the metallic'end ferrules is such that considerable wasteful and deleterious heat is generated. They further known that this wasteful heat is so inefficiently dissipated that the horn fibre cartridge is slowly carbonized and often ultimately destroyed by this heat. They also know that upon thermal destruction of the fusible element, the hot metal, vapors and gases are so inefiiciently conducted to the outside of the fuse that the horn fibre cartridge is subjected for so long a time to these products that it is carbonized and often ultimately destroyed and, in addition, nearby inflammable materials are often subjected to a heat quite sufiicient to ignite them. Furthermore the several metal parts at the ends of the fuse are frequently soldered firmly together by the vaporized metal, upon cooling, so that it is often difiicult to disassemble the fuse after destruction of the fusible element therein.

It is also well known that the usual types of ferrule cartridge fuses are so constructed that a thoroughly efiicicnt electrical contact of low ohmic resistance between the several current carrying parts of a permanent, lasting and uniform nature is not obtained.

It is further known that the time lag of blowing or thermal destruction of the fusible link is decreased in known forms of ferrule type cartridge fuses by reason of the lack of proper and firm and lasting connections and lack of heat reservoirs or heat absorbers of sufficient thermal capacity at the several ends of the fuse, and as a consequence, a greater portion of the fusible link is destroyed upon blowing thereby increasing the deleterious effects caused by hot metal, vapors, and gases.

A principal object of this invention is to provide a' fuse of the type specified that, compared to present well known forms: develops less wasteful heat during the ordi-' nary passage of current therethrough; dissipates more efficiently any such wasteful heat that may be generated;

efficiently absorbs the heat of hot metal, vapors and gases formed when thermal destruction of the fusibleelement occurs, so-that adjacent inflammable materials are not so readily ignited and closely adjacent parts of the fuse arenot so readily soldered-together; and by-reason of the less generation of wasteful heat and the more efiicient dissipation of wasteful heat generated and the heat gen-i erated when thermal destruction of the fuse element occurs, the cartridge'shell of thefuse isless' subjected to carbonization and'destruction and so has a longer life.

A further object of the invention is to provide a fuse of the type specified comprising relatively few partsjeasily and inexpensively constructed and easilyand quicklyassembled, jso formed and related that, as compar'edto Y "ice well known forms, such lasting firm contact is readily obtained between metal current carrying members that relatively little wasteful ohmic resistance is introduced into a circuit of which the fuse forms a part.

A further object of the invention is to provide a fuse of the type specified which is so constructed that with a given fusible element it will give a longer time lag than the same given fusible element will when installed in well known forms.

A further object of the invention is to provide a fuse of the type specified which will be so constructed that, upon thermal destruction of the fusible element, less of the fusible element will be volatilized than in well known fuses of like rated capacity.

A further object of the invention is to provide a fuse of the type specified which will be so constructed that the ends thereof will be so closed that hot metal, vapors and gases generated upon thermal destruction of the fusible element will be forced to come in contact with a substantial body of heat absorbable metal before flowing into the outer air whereby superior cooling will be effectuated.

A further object of the invention is to provide a fuse of the type specified which will be so constructed that the usual clamping of the bent over end of the fusible element will ensure a superior broader area initial electrical contact between the end of the fusible element and the usual.

ferrule, and so a lower ohmic resistance, and also a superior mechanical clamp of a more permanent nature, so designed that the fusible element will not be twisted when the usual ferrule is tightened, said mechanical clamp being of greater mechanical permanence, effectiveness and uniformity in application and operation and of greater ease of assembly than known types.

A further object of the invention is to provide a fuse of the type specified which will provide means by which it may be more readily manually disassembled without the use of tools.

Other objects and advantages will appear as the description of the particular physical embodiment selected to illustrate the invention progresses and the novel features will be particularly pointed out in the appended claims.

In describing the invention in detail and the particular physical embodiment selected to illustrate the invention, reference will be hadto the accompanying drawings and the several views thereon, in which, like characters of reference designate like parts throughout the several views, and in which:

Fig. l is a plan view of a ferrule type renewable cartridge fuse of my invention;

Fig. 2 is a longitudinal sectional view of the device as shown by Fig. 1;

Fig. 3 is a longitudinal sectional view of the device, as shown by Fig. 1, taken at an angle of 90 from the plane upon which the view, Fig. 2, is taken;

Fig. 4 is a face view of a plug or fusible element retaining member used in my invention;

Fig. 5 is a cross sectional view of the device as shown by Fig. 4;

Fig. 6 is a view of the device as shown by Fig. 4 as viewed from the end opposite to that from which Fig. 4

is viewed;

Fig. 7 is a fragmentary sectional view illustrating a modified form of fuse terminal construction embodying my invention;

Fig. 8 is across sectional view of the device, as shown by Fig. 7, on the plane indicated by the line VIlIVIII of Fig. 7 viewed in the direction of the arrows at the ends of the line;

Fig. is a fragmentary sectional view of a further modified form of fuse end construction embodying my invention;

Fig. 11 is a cross sectional View of the device as shown by Fig. 10 on the plane indicated by the line Xi-Xl, viewed in the direction of the arrows at the ends of the line;

Fig. 12 is a rear or inner end view of the plug or fusible element retaining member as shown in Fig. 10;

Fig. 13 is a fragmentary sectional view of a modified fuse end construction of my invention;

Fig. 14 is a face or outer end view of the fusible element retaining member as shown in the device as shown by Fig. 13;

Fig. 15 is a cross sectional view of the fusible element retaining member, as shown in Fig. 13, on the plane indicated by the line XV-XV viewed in the direction of the arrows at the ends of the line;

Fig. 16 is a rear or inner end view of the fusible element retaining member illustrated in Fig. 13;

Fig. 17 is a fragmentary sectional view illustrating a further modified fuse end construction of my invention;

Fig. 18 is an outer or face view of the fusible element retaining member illustrated in Fig. 17;

Fig. 19 is a cross sectional view corresponding to the cross sectional view Fig. 15 but of the fusible element retaining member shown in Fig. 17; and

Fig. 20 is a rear or inner end view of the fusible element: retaining member shown in Fig. 17.

Fig. 1 illustrates a common and well known form of ferrule ty e cartridge renewable fuse, in-so-far as outward appearance is concerned, with one exception, and that is the knurling 1.

The device as shown by Figs. 1 to 3 inclusive includes an elongated hollow cylinder formed of insulating material, preferably horn fibre and open at each end.

The cylinder 2 serves to enclose a fusible element 7 of any of the usual forms and made of any usual material, such as zinc or aluminum or an alloy thereof.

The fusible link 7 is connected to the external circuit by interior metallic members and exterior metallic ferrules, caps or outer closing members, one at each end, and designated 3. These metallic caps or end pieces are preferably made of brass and in the particular form shown in Fig. 2 are hollow cylinders with a side wall in which an internal screw thread 4- is formed and with a single end Wall 5 formed with a nub or protuberance 6 projecting inwardly from the inner face. Said end wall 5 closes the respective end of the collar 10 and cylinder 2.

The insulating tube 2, preferably, and in the form shown in Fig. 2, has reduced portions at each end as 8. These reduced portions accommodate metallic collars 10, open at each of their ends, preferably made of brass and preferably force fitted into place on the ends of the tube 2 so as to be fixed relative thereto. These collars, in the form shown in 2, are provided with an external screw thread 12 matching and adapted to cooperate with the screw thread 4 of the caps 3. These collars 10 in the form shown in Fig. 2 are provided with radially inwardly extending portions 14, and these inwardly extending portions 14 preferably abut the ends of the tube 2.

At each end of the tube 2 a fusible element retaining member 16 is provided. This feasible element retaining member or substantially cylindrical, solid and massive plug is formed of metal, preferably brass, and as well shown in Figs. 4 to 6 inclusive, includes a body portion 18 which is slightly tapered and a radially outwardly extending flange portion 20. It is also provided with a through slot 22 and centrally located in the outer end face 24 there is formed a cup shaped or inwardly diminishing frusto conical depression 26. As best shown by reference to Fig. 6, the plug 16 may also be provided with vents as 28, 30, 32 and 34. Two of these, and. 34, extend from the tapered portion 18 to the outerperiphery ofthe enlarged portion 20. The outer two vents, 28 and 32, extend from the slot 22 to the outer periphery of the enlarged portion 20.

As will be seen by reference to Figs. 2 and 3, the fusible link 7 has its ends passing through the slots, as 22, and protruding to some extent beyond the outer face of the plug 16. These protruding ends are each bent down into the plane of the outer face of the plug 16 and then when the cap or ferrule 3 is tightened by being screwed down into place, the nub or protuberance 6 forces the bent-over end of the fusible element into the depression 26, and thus not only secures an inward electrical contact of superior broader area, but also a more permanent electrical contact than is usual in fuses of this type, because the end of the fusible element is forced into a cup shape into the frusto conical depression 26 of the plug 1.6. The end portion 7A in fact assumes a frusto conical shape tightly clamped in and tightly fitting in the said depression 26, as the diameter of protuberance 6 is slightly less than the lesser diameter of the depression 26. Said lesser diameter is roughly one third the greatest diameter of plug 16.

In the usual type of well known fuses, when the cap 3 is screwed in. place, and the turned over end of the fusible link is pressed against the fusible link retaining member, which is, in the well known form, merely a pierced washer resting on the end of the insulating cylinder or collar, the twisting movement of the cap is imparted to the link and to the washer, and both are frequently turned or twisted to such an extent that the fusible link is damaged by tearing and sometimes by actual destruction. By my construction, however, this is avoided. The plug 16 has a tapered body 18 and this taper just fits tightly between the inwardly extending portions 14 of the collar. This plug fits so tightly that the twisting movement of the cap will not cause it to turn. The twisting and perhaps injury or destruction of the fusible element 7 is thus entirely avoided.

The plug 16 is of metal and is of quite a substantial body. It has a thermal capacity probably greater than three or four of the usual washers commonly employed in well known types of ferrule fuses. Its length is approximately half of its greatest diameter. By reason of this substantial heat absorbing body of considerable thermal capacity, any heat which may be generated when the fuse is inserted in a circuit, is readily absorbed and transmitted to the collar 10 and the ferrule 3 and so to the outer atmosphere. Due to this ready absorption of heat by the plug 16, the interior surface of the tube 2 does not become so highly heated and so is not so readily carbonized and perhaps destroyed. The net result of the construction is that the cylinder 2 lasts a considerably longer time.

Not only does the large thermal capacity body 16 keep the insulating tube 2 cooler, but it also has a decided etfect upon the functioning of the fusible element 7. As it extends a much greater distance along the fusible element 7 than does the ordinary and well known washer form of fusible element retainer, it keeps the fusible element cooler than it would otherwise be so that when an excessive current tends to flow through the fusible element, the fusible element is at a lower temperature than in well known forms of fuses and consequently it requires a greater time to heat the fusible element up to the melting or destruction point. This is very advantageous as it increases the time lag of blowing or destruction of the fuse when an excessive current occurs, so that at times, if the excessive current is not too great, the fuse will withstand it, and there will arise no necessity to renew the link.-

In summation, the link 7 is in tight electrically conductive and heat transfer relation with the plug 16 and end piece 3, and the plug is in tight electrical and heat transfer relation with the collar 10 and thus with the end piece. The elements 3, 7, 10 and 16 thus related become electrically and thermally almost a single massof metal. Each element is itself a single or unitary piece of metal, and each is in-tight contact with two others. In any given split second, half of the heat of portion 7A will transfer to nub 6 and be disssipated by the exterior surfaces of piece 3, while the remainder will be quickly absorbed by the massive plug 16 and transfer through surface 18A and flange 20 to collar 10 and thus to the piece 3. At the first two points of transfer the portion 7A is deformed, brightened and clamped, and heat transfer is facilitated to the exterior piece 3 and to the massive plug 16.

When the link 7, enclosed in a fuse of my invention, does actually blow or become thermally destroyed, and the molten metal, hot vapors and heat gases are generated within the tube 2, they are obliged to flow along the outer surface of the tapered portion of the plug 16, that is, along the tapered surface 18A, and also through the slot 22 where they are incontact with a very extensive coo-ling surface, so that before the hot material generated by the destruction of the fusible element is in position to pass out from the fuse down through and along the cooperating threads 4 and 12 of the collar 10 and the cap or outer closing member 3, they have been so quite thoroughly cooled that upon issuing they are not of suflicient temperature to readily ignite closely adjacent inflammable material and are so cool by the time they reach the cooperating thread between the collar and the cap or outer closing member that they have no great tendency to solder the threads together.-

After the hot metal, and vapors and gases pass the contact between the plug 16 and the inwardly projecting members 14 of the collar, I provide a somewhat freer path by reason of the venting of channels and 34 which extend radially across the inner face 20A of the flange portion 20. I deem it preferable to provide supplementary venting channels 28 and 32 between the slots 22 and the outer periphery of the enlarged or flange portion of the plug.

The hot metal, vapor and gases are not only cooled by the plug 16, but those materials of destruction which pass up through the slot 22 also expand into the space between the plug 16 and the inner face of the end wall of the cap or outer closing member 2 and are thereby quite well cooled before issuing through the cooperating thread between the cap 3 and the collar 10.

The fusible element retaining member or plug 16 has' a portion of its periphery, that is, the enlarged or flange portion 20 which abuts the sleeve 10, scored as by knurling. This scoring or knurling serves two purposes, one, it effectually breaks up the direct flow of gases therepast which have flowed through the slot 22 whereby hot metal may be deposited on the knurling and, two, it provides a means whereby the plug may be removed from its position in the fuse especially when it has been jammed down tightly into the space provided by the inwardly extending portions of the collar 10.

As my fuse is so constructed that soldering of the parts together is avoided, there is really no necessity for the use of tools to open the fuse aftera blow. I may provide slots ,as 36 to facilitate the use of a screw driver inremoving the outer closing member or cap 3, but I prefer to 'knurla small portion, as 1, of the cap, so that a manual grip may be obtained on the caps sufficient to enable one to remove the cap without the use of tools, thereby greatly facilitating and hastening the renewal of the fusible link after the fuse has blown.

In Fig. 7 I have shown a fragment of the terminal portion of the fuse in which the outer closing member or cap 3 is of the type previously described and the collar 38 is formed with depressed portions as 40 and 42 to cooperate with projections as 44 and 46 on the plug 48. These cooperating depressions and projections serve to prevent relative rotation between the plug and the collar.

The fragmentary view, Fig. 10, shows a terminal construction in which the collar 50, is formed with an internal thread 52 and the portion corresponding to the outer cap 3 of Figs. 1 to 6 inclusive is replaced by a disc member 54 which is provided with an external thread 56.

The plug 58 of Figs. 10, 11 and 12 is formed with a slot 60 which opens in the side periphery of the plug as at 62.

The fragmentary showing, Fig. 13, illustrates a terminal construction of the fuse in which the fusible link retaining member 64 is formed with a depending polygonal projection 66 to fit into a corresponding polygonal opening formed in the inwardly extending portion 68 of the collar 70. This construction effectually prevents rotation of the fusible link retaining member relative to the collar 70.

Fig. 17 illustrates a terminal construction of a fuse in which the fusible link retaining member 72 is made identically on both sides thereof, that is, there is a circular depression 74 on one side thereof and a corresponding circular depression 76 on the other side thereof, so that the fusible link retaining member 72 may be used either side outwardly.

It is to be understood that the various modifications may beused interchangeably in fuses, for instance, I do not mean to exclude the use of a collar, as 50, with a portion projecting above the inwardly extending portion with a cap such as 3.

Although I have particularly described a particular preferred form of my invention and various modifications thereof, nevertheless, I desire to have it understood that the forms selected are merely illustrative, but do not exhaust the possible physical embodiments of the idea of means underlying my invention.

What -I claim as new and desire to secure by Letters Patent is:

1. In a cartridge fuse having an elongated hollow cylinder open at both ends formed of electrical insulating material, a fusible link within the cylinder, a metallic collar on each end formed with external screw threads, and an outer closing member on each end formed with screw threads mating and cooperating with the screw threads of the collar, the invention comprising -a fusible link retaining member resting on each collar and closing the end of the cylinder, said fusible link retaining member formed with a slot for passing the end of the fusible link in the cylinder therethrough with the end of the fusible link protruding, said fusible link retaining member also formed on its outer face with a central depression, said outer closing member formed with a nub positioned to cooperate with the central circular depression in the face of the fusible link retaining member whereby the protruding end of the fusible link may be bent down and be held firmly by the nub in the circular depression, said fusible link retaining member further "being formed with a venting slot connecting said first mentioned slot with the periphery of said retaining member. I

2. In an electrical fuse of the type comprising an insulating cylindrical shell open at each end, conductive collars mounted at each end of said shell, said collars being open at each of their ends, end pieces threadedly engaging said collars and closing the outer ends thereof, slotted fuse link retaining members held between said collars and said end pieces and a fusible link extending through the slots of both of said retaining members and having its end portions bent over and clamped between said retaining members and said end pieces, the improvement comprising said retaining members each having an outer end face formed with a cup shaped central depression and said end pieces each being formed with an inward extending circular protuberance which upon tightening of said end piece forces the bent over end portion of said link into tightly clamped cup shape, said collars further having at their outer ends radially inwardly extending portions, said retaining members further having at their outer ends outwardly extending flanges abutting said inwardly extending portions of said collars, said flanges further having inner faces formed with vent slots extending thereacross.

3. In an electrical fuse of the type comprising an insulating cylindrical shell open at each end, conductive collars mounted at each end of said shell, said collars being open at each of their ends, end pieces threadedly engaging said collars and closing the outer ends thereof, slotted fuse link retaining members held between said collars and said end pieces and a fusible link extending through the slots of both of said retaining members and having its end portions bent over and clamped between said retaining members and said end pieces, the improvement comprising said retaining members each having an outer end face formed with a cup shaped central depression and said end pieces each being formed with an inward extending circular protuberance which upon tightening of said end piece forces the bent over end portion of said link into tightly clamped cup shape, said collars further having at their outer ends radially inwardly extending portions, said retaining members further having at their outer ends outwardly extending flanges abutting said inwardly extending portions of said collars, said flanges further having inner faces formed with vent slots extending from said link slots to the periphery of said flanges.

4. In an electrical fuse of the type comprising an insulating cylindrical shell open at each end, conductive collars mounted at each end of said shell, said collars being open at each of their ends, end pieces threadedly engaging said collars and closing the outer ends thereof, slotted fuse link retaining members held between said collars and said end pieces and a fusible link extending through the slots of both of said retaining members and having its end portions bent over and clamped between said retaining members and said end pieces, the improvement comprising said retaining members each having an outer end face formed with a cup shaped central depression and said end pieces each being formed with an in- Ward extending circular protuberance which upon tightening of said end piece forces the bent over end portion of said link into tightly clamped cup shape, said retaining members further having flanges abutting portions of said collars, said flanges having knurled peripheries for the cooling of gases escaping therepast.

5. In a cartridge fuse having an elongated hollow cylin der open at both ends formed of. electrical insulating mate rial, a fusible link Within the cylinder, a metallic collar on each end formed with screw threads, and an outer closing member. on each end formed with screw threads mating and cooperating with the screw threads of the collar, the invention comprising a fusible link retaining member resting on each collar and closing the end of the cylinder, said fusible link retaining member formed with a slot for passing the end of the fusible link in the cylinder therethrough with the end of the fusible link protruding, said fusible link'retain'ing member also formed on its outer face with a central depression, said outer closing member formed with a nub positioned to cooperate with the central circular depression in the face of the fusible link retaining member whereby the protruding end of'the fusible link may be bent down and be held firmly by the nub in the circular depression, said fusible link retaining member further being formed with a venting slot connecting said first mentioned slot with the periphery of said retaining member.

6. In a cartridge fuse having an elongated hollow cylinder of insulating material open at both ends, a fusible link within the cylinder, retaining means slotted to receive an end portion of said fuse link and a conductive and heat absorbing end piece clamping a bent over end portion of said fuse link against said retaining means, the improvement comprising a conductive and heat absorbing metallic collar fixedly mounted at an end of said cylinder and having screw threads, said retaining means being a substantially solid and massive body of conductive and heat absorbing material, said body being substantially cylindrical and having a length approximately half its largest diameter, said body further having an outer end face formed with a central depression, said end portion of said fusible link extending across said depression, said end piece further being formed with threads engaging the threads of said collar, said end piece further having a central circular protuberance extending inwardly therefrom, said protuberance upon tightening of the threads of said collar and of said end piece deforming said end portion of said fusible link into said depression and tightly clamping the same therein in electrically conductive and heat transferring relation, said retaining means further fitting in and tightly contacting said collar in electrically conductive and heat transferring relation.

7. A cartridge fuse according to claim 6, said protuberance further being an integral portion of said end piece.

8. A cartridge fuse according to claim 6, said depression being inwardly diminishing fmsto-conical and its smaller diameter being substantially one third the largest diameter of said retaining means.

9. A cartridge fuse according to claim 6, said retaining means further having a tapered side surface and said side surface being a portion thereof which tightly fits in and contacts said collar.

References Cited in the file of this patent UNITED STATES PATENTS 994,413 Mallory June 6, 1911 1,102,981 Daum July 7, 1914 1,443,887 Sands et al. Jan. 30, 1923 1,473,615 Folds Nov. 13, 1923 1,478,109 Ellison Dec. 18, 1923 1,502,883 Sandin July 29, 1924 1,700,080 Sandin Jan. 22, 1929 1,857,096 Glowacki May 3, 1932 1,881,369 Carney M Oct. 4, 1932 1,953,011 Cote Mar. 27, 1934 1,968,763 Hanson et al July 31, 1934 2,071,843 Korn Feb. 23, 1937 2,168,153 Brown Aug. 1, 1939 2,449,827 Von Hoorn Sept. 21, 1948 2,522,473 Vischer Sept. 12, 1950

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