US2010657A - Liquid fuse - Google Patents

Description

2 Sheets-Sheet l #La 5 mi fm 5 i o W O neu O U F 7 #s 1 F/ w% /f w WM O R. H. EARLE LQUID FUSE Filed May 5, 1932 R. H. EARLE 2,L,657

LQUD FUSE Filed May 5, 1952 2 Sheets-Sheet 2 Patented Aug. 6, 1935 PATENT OFFICE LIQUID FUSE p Ralph H. Earle, Wauwatosa, Wis., assignor to Line Material Company,

South Milwaukee,

Wis., a corporation of Delaware Application May 5, 1.932, Serial No. 609,452

5 Claims.

This invention relates to liquid fuses.

Objects of this inventionare to provide a novel form of liquid fuse which will respond to overloads whether suddenly or gradually applied,

'-1 which will quickly separate the two portions of the fuse link when fusing occurs, and'which will quickly withdraw one of the portions of the fuse link below the surface of an arc extinguishing liquid.

Further objects are to provide a fuse of this general type which is so constructed that the fuse link, although capablev of being formed to respond to a small value of current, nevertheless is not subjected to undue or excessive mechanical lstrain, but which is so made that the fuse link and the method of anchoring the ends thereof provide mechanical strength to withstand the initial handling, while the device is being re- A fused, and also to withstand the steady pull of a yspring without danger of any of the parts failing from mechanical weakness.

Further objects are to provide a fuse in which the fuse link is of composite construction with the upper and lower parts soldered together but Vwhich is ofgreat tensile strength, even at the soldered joint due to an overlapping face to face contact of flat, ribbon like members, preferably with the ribbon member of one part received between or intermeshing with two ribbon 4members of the other part.

When fuses having soldered portions are under mechanical strain, it has been found that with the usual type of soldered joint that such ljoint is frequently twisted, bent or otherwise placed in such a position it is subjected to tensile strain as well as pure shear. Under these conditions tests have shown that the action of the fuse is not wholly satisfactory. There seems to be somewhat of a gradual mechanical failing of the joint hastened whenever the joint is hot.

Further objects of this invention are to provide a novel form of fuse in which the soldered joint is in pure shear and cannot turn or be so positioned that it is subjected to tensile stresses,

' which would interfere with the accurate functioning of the fuse. Instead, the joint is so made that although a considerable mechanical stress or pull may be imparted to the joint, that nevertheless the soldered joint is itself in pure shear and consequently a gradual failing or an alteration of the accuracy of the fuse is avoided.

Further objects are to provide novel forms of attaching means for both the upper and lower ends of the fuse link to not only give an adequate andfiirm mechanical attachment for the ends of the fuse link, but also to secure an unusually good electrical contact between the ends of the fuse and the adjacent conducting portions to which the fuse link is attached.

It has been found that with the usual types of fuses that accurate calibration is extremely difficult and that calibration is usually very uncertain, only a very rough approximation being secured.

This invention is designed to overcome the defects noted immediately above, and further objects of this invention are to provide a novel form of fuse in which accurate calibration may be obtained with the utmost facility, and in which the fuses, although made by quantity production,

are nevertheless substantially uniform, and in which fuse strips of different values, that is to say different fusing current values, may be most easily constructed in a simple and relatively precise manner.

In greater detail, further objects of this invention are to provide a novel form of fuse which is so made that the 12R, watts developed is substantially constant at the soldered joint, irrespective of the current value for which the fuse is designed, the variation in current value for different sizes or capacity fuses being obtained by varying the composition of the fuse strips or members, or by varying their crosssectional area, preferably by varying their thickness. This invention, therefore, provides a means whereby solder or other readily fusible material having av substantially definite fusing point may be used for all sizes or capacity of fuses, and in which the same dies may be employed, if desired, for stamping out the fuse strips or members of the same width, the variation in capacity of the fuse being obtained by varying the thickness. Thus, this invention materially reduces the cost of manufacture of fuses and at the same time reduces the equipment necessary for making fuses of different capacities. Either one or both of the two Ways of securing different value or different capacity fuses may be employed, or, if desired, solders of different fusing points may be employed, although it has been found that this last method is a great deal more unsatisfactory and less precise than to use solder of a definite melting point for all sizes of fuses and obtain the variation in rating or capacity of the fuse by either of the two methods detailed hereinabove.

Embodiments of the invention are shown in the accompanying drawings, in which:-

Figure 1 is a side elevation, partly in section, ofV the liquid fuse.

Figure 2 is a View of the upper portion of the liquid fuse, the section for such view being at right angles to that of Figure l.

Figure 3 is a sectional .view on the line 3 3 of Figure 1.

Figure 4 is a sectional View on theline 4 4 of Figure 1. v

Figure 5 is an enlarged sectional view on the line 5 5 of Figure l.

Figure 6 is a further form of fuse link.

Figure 7 shows a further form of fuse link and a diiierent means of attaching such link to the bridge member. l f

Figure 8 shows a further form of fuse linkand a diiierent way of attaching it to the vbridge member.

Figure 9 sho-ws a further form of fuse link and a different manner of attaching it to the bridge member.

Figure 10 shows a further form of fuse link.

Figure v11 shows a form of fuse link and mannerV Figure 16 is a sectional viewon theline IS-li of Figure 8. i v Y Figure 17 is a sectional View on theline irl- IT of Figure 12. i Y. f Referring to the drawings, Vit will be :seen Eth'at the liquid fuse eomprisesa tubular or cylindrical container l, preierablyofglass or othergsuitable Yinsulating material, which is provided with a lower metal cap or contact member 2 and anV upper metal sleeve or contact member'S each secured to the glass tubular body portion I in a gas and liquid tight manner.

The upper contact membengor ksleeve 3, is externally threaded and receives' the ring nut 4. which Vtightly clampsa gasket disk, or closure' member 5, in place., The disk 5f is formed ofa yielding and somewhat eXpansible material such as lead, aluminum, tinfoil',l orV some other alloy which is'soft and expansible. Y

This gasket: disk 5, when clamped in place byV the ring nut e, forms agas seal, andffis adapted to be rupturedand the part closing ther opening throughthe member-3 bodily blown away' when the fuse blows. This provides an instantaneous relief for the pressure gases' and avoids placing excessivestrain upon the glass body portion.

The sleeve 3. isprovided withrdiametrically opposed slots V6 which; are open at their upper ends and which are .provided with rounded shoulders at their lower ends. Y K strong arch like member or bridgemember 'l has. its ends rounded and seated loosely within the slots t and resting,r upon the rounded'shoulders at.

the bottom of such slots.V k This arch like member 'l is in reality a stro-ng 'metal strip which is a support for the' composite fuse link.

VThe composite fuse link is preferably formedv .of an upper and a lower portion, the upper portion consisting of tworibbn like members 8 between Which'a Vsingle ribbon like` member S form` ing the lower portion is secured. The upper ribbon like members'of the fuselink pass throughv a central aperture Lf'ormed'in the support. 1', pass' vare'preferably formedvo ribbon, providing a suitable resistance to heat the soldered joint.

' the melting temperature.

1 havingy a substantiallyv definite melting point may k be employed, and that the heat developed at Y the soldered joint may be constant for all sizes of A transverse, relatively Y over the upper face of the support, and have their ends wrapped or positioned beneath the rounded ends of the member l. When pressure is applied to the fuse link, it is apparent that the supporting member 'l acts likea toggle and causes a 5 i between the members 8 and is soldered to such members. This forms an intermeshing or overlapping of the iat ribbon like fuse strips, which The material of which the ribbons or other shaped members forming the fuse link, either in 'lected for its particular characteristics. For eX- ample, different materials for dilerent amperage v linksare employed. A high resistance material j like a nickel chromium alloy is employed for low amperage "links,- and a very low lresistance material, such as copper, may be employed for high ampera'g'e links, adjusting the material and the thickness of the material sol as to give a very constant 12R development at the soldered joint. This 12R is that which is required to raise the solder to It is, therefore, apparent that a given solder fuses, the capaci-ty or rating of the fuse being varied preferably by varying the thickness of the fuse strips or members and their composition. This enables the manufacturer to use substantiall-ythe same dies or apparatus for forming the members of the fuse link, although fuse links of widely Vdifferent ratings may be selectively produced'asV desired by means of the characteristics of` `this invention which have been outlined immediately above. Y

The intermediate portion of the composite fuse link. is reduced in cross-section by narrowing the ribbon like members, as, indicated generally at lll .in YFigure 2, so that the cross-sectional area remains approximately the same throughout the entire length of the fuse link. If desired, the in- Y termediate portion of thefuse link may be covered by a cork or other member ii.

The lower member Q of the fuse link continues vdownwardly and is supplemented by an additional. member 9' riveted or otherwise secured thereto to provide a double thickness, Vor two ribbon like members lfor-the lowest part ofthe lower portion of the composite. fuse link. These ribbonV like portions are separated and are positionedbeneath inturned channel shapedy arms of a lower fitting l2. Y The arms l 2 are preferably integralwith each other and are approximately of U.-shaped formation having a iiat bottom connecting yoke I3, see Figure l.. The channel portions of lthese arms are indicated more clearly in Figure 5. The upper ends of the arms I2 converge or approach each other, as shown most clearly in Figure 1.

An inverted V-shaped wedging member M, see

^ Figure' l; is positioned between'therportions 9 and 9 of the fuse strip and the arms i2 of the lower fitting,V so that whenthe lower iitting or con-V 75.Vv

r-is secured to a transverse plate I5.

suitable manner.

ducting portion is drawn downwardly, the fuse link is tightly wedged against the arms I 2, see Figure 5, thereby securing an excellent electrical contact.

It is to be noted at this point that the electrical connection between the upper and lower ends of the fuse link and the adjacent conducting portions is secured, in this form of the invention, without the use of screws or other fasteners of this type. This construction also affords a Wedging or binding contact between the fuse ends and the conducting portions, thereby securing good contact and reducing the heating at these points. y

As shown in Figure l, it is preferable to bend the ends of the members 9 and 9 over the bottom ends of the member I4 to facilitate positioning of the parts.

The conducting member or fitting just described Preferably the yoke I3 is locked lto the plate or bar I5 by upwardly and inwardly turned ears kI6 formed integrally with the bar I5, kas shown in Figures l and 4. The bar I5 is soldered or otherwise secured to a exible leader or stranded conductor I'I whose lower end is secured to the lower terminal or contact member 2.

A helical spring I8 loosely surrounds the leader I'I and is secured to the lower contact 2 in any The bar I5 extends between convolutions of this spring and thus provides a very secure attachment of the spring to the lower member I2.

It is preferable to provide some form of protection for mechanically protecting the diaphragm 5, see Figures l and 2.` This protecting means may take the form of a cap I9 provided with spring fingers 20 which snap beneath the bottom edge of the ring nut 4.

The tubular body portion is preferably completely filled with some arc extinguishing liquid, such as carbon tetrachloride. Obviously the tubular body portion may be lled to any desired height, although the complete filling is probably the simplest.

When the fuse blows, the diaphragm 5 is ruptured around its margins and blown, together` with the cap I9, from the fuse body. The arch shaped supporting member is released from the `pressure and consequently wedging of its ends and the adjacent portion of the iuse against the annular member 3 is instantly relieved, and this arch shaped member and the remaining upper portion ol the fuse is blown bodily from the tui bular body portion.

rounded members may have reduced portions 23v and 24 cut to half thickness and soldered together, particularly as shown in Figure l5. The 'upper member 23 may be secured to the bridge member 25 in any suitable manner. In the form shown in Figure 7 it is attached by means of a bolt 26 in one of the arms of the bridge member.

Figure 8 shows a further form of fuse link in which a pair of upper wires or other shaped members 21 receive between them a lower wire or other shaped member 28 which is soldered to the upper wires at their overlapping portions, particularly as shown in Figure 16. Obviously other shapes may be employed ii desired. The upper` ends oi the members 2 are secured by bolts or screws 29 to the arms of the bridge member 30.

Figure 9 shows a form of fuse link in which a pair of spaced ribbon like or other shaped upper members 3| are secured to the underside of the bridge member 32 by bolts or screws 33. A U- shaped lower member 34 has its arms soldered flatly 'to the members 3I and is preferably provided with a, reinforcing metal piece 35 in its horizontal loop to which the tension spring may be attached, and to prevent folding or drawing of the arms of the member 34 towards each other.

Figure l0 shows a further form in which the upper strip 36 oi ribbon or other shaped member is not joined directly to the lower member 3l but indirectly by means of symmetrically placed, overlapping intermediate portions 38, to which both upper and lower members are soldered. The upper end of the member 35 may be attached to the bridge piece 39 in any suitable way, as by means of the bolt 4).

Figure 1l shows a further form of construction in which ribbon like upper members 4I receive between them a lower ribbon like member 42 which is soldered thereto, as previously described.

This construction is similar to that shown in Figure 6 except that the upper ends of each of the members 4I are separately attached to the bridge piece 43 by means of screws or bolts 44, or other fastening means.

Figure l2 shows a further Yform of the invention in which the upper member of the fuse link consists of a tubular member 45 which receives within its lower end a round or wire like lower member 4S, such members being soldered together, as previously described. Preferably the upper portion of the tubular member 45 is riattened and split to provide tongues which may be oppositely folded, as v indicated at 4'I. These tongues are `secured to the bridge member 48 in any suitable manner, as by means of the bolts 49.

In the form shown in Figure 13 a different type of bridge member is employed. This bridge member, scribed bridge members, secures the same toggle effect as the other` members. -Howeven it consists of two hingedly joined arms 50 which may be joined by means of a pintle pin or other member 5I, as shown in Figures 13 and 14. The fuse link may-be of any desired type.

In the form shown, two wire or ribbon meinbers 52 constitute the upper portion of the fuse link and receive between them a lower member 53. The upper members 52 are looped over the pintle pin 5I, as shown most clearly in Figure 14, and are secured to the arms 5U by means of the screws or bolts 54.

It is to be noted that in this form of construction the upper contact member 3 of the body portion of the fuse is provided with slots which terminate in abrupt shoulders 55, as shown in Figure 13. This construction provides a sharp corner within the slot and the ends of the members 58 .are bevelled at a sharper angle than that between the shoulders 55 and the vertical portions 56 of the slots, and consequently such sharply pointed or bevelled ends of the members 50 have a line bearing. with the corner portions formed by the faces 55 and 56 of the slots. (Figacting like the other previously der ure 13 is a Vfragmentaryline section of the member 3.) l

1n au forms of `the invention it will be seen thatrthe toggle effect is obtained for the upper supporting or bridgermembe'r, and that a very The fuse can be readily re-iused and used over` and over again. In each form of the invention the rattachment of the fuse link'is of Very simple Aconstruction and is easy tof operate.

Further it is'to be particularly noted that the soldered joint in all forms of the invention is in pure shear and is not subjected to tensile stresses, which would cause an inaccuracy in the functioning of the fuse, as has been developed in great detail hereinabove.

The fuse link itself isrernarkably sturdy, although it may be small capacities. This permits the free han- V'dling of the fuse link in re-fusing'without danger of damage thereto.

It is to be distinctly understood that although a cork i l has been shown only in the form illus- Ytrated in Figures 1 and 2 of the drawings, that nevertheless it may be used with any other form of the invention. Further, it is to be noted that the cork could be replaced by some -other material or some other type of member which would o'ier a greater area'cf contact, either with the outrushing gases or with the pressure gases below its bottom face, so that it would assist in the action of clearing the fuse, as will be hereinafter described, although it has been found from actual practicev that the cork is well suited to this purpose'.Y The invention, however, is not limited to the use of arcork alone, but other material or other members could replace the cork.

It is to be noted that the cork actually furnishes an additional area of'contact with the outwardly rushing gases when the fuse blows and so assists in quickly removing the fuse, as it is bound thereto, This action takes place not only from the pressure developed on the underside of the cork by the outwardlyrushing jgases, but also'by the rictional contact of these outwardly rushing gases with the-side of the cork. Obviously another member could replace` Vthe cork and come within the spirit of this invention.

ln addition to these functions, the cork per- Vforms an additional function. It mechanically binds the partsl of the fuseV strips together and assists in preventing breaking of the fuse, particularly during handling or re-fusing.- It prevents kinkingV of the fuse or breaking Vor the fuse at the soldered joint, as it provides a mechanical reinforcing agency for this portion of the fuse strip, particularly as it extends completely over the soldered joint and over the ends of the soldered joint. v ,Y Y Y Y It will be seen that a novel form of fuse has been provided by this invention in which the 12R watts developed at the soldered joint is substan- Atially constant, irrespective of the rating or ca pacity oir-the fuse, and that the calibration of fuses of diierent ratings or the production by quantity production methods of fuses of any. de-

built for small overloads or inv sired rating may be easily followedlwith a resulting substantially constant accuracy.

Although 'this invention has been Vdescribed considerable detail, it is to be understood that such description vis intended vas illustrative rather than limiting,rv as the invention may be variously embodied and is to be interpreted as claimed.

Iclaim:V Y f l. A liquid fuse comprising a tubular'body portion,v an upper annular contact, an upwardly bowed member spanning said annular contact and having its ends supported from saidr annular contact, a Vfuse .link having an Lipper portion" formed of two strips independently secured'to said upwardly bowed member, said fuse link eX- tending'downwardly from the central portion of' said upwardly bowed member, a lower contact electrically connected to said fuse, and a sprin 1 for placing tension on said fuse link. v Y

2. A fusecoinprising an annular contact,a

fuse link, a toggle member supporting said fuselink and forcing an end of said fuse link into' engagementwith an inner wall of said contact,

a second contact electrically connected totheA kother end of said fuselink, and a spring for placing tension on said fuse link.

3. Affuse comprising a Contact, a conducting fitting, a spring tending to pull said fitting in a direction away from said contact, a fuse link between said contact and fitting, and wedging means at each end of saidl fuse link for forcingv said fuse link into binding engagement withv said contact and said fitting, the wedging action ben ing produced by the pull of said spring, said fuse link being in direct contact with bothVv said contact and said fitting and said wedging means increasingthe contact pressure directly between said use link and said contact and said fitting.

4. A liquid fuse comprising a tubular body portionadapted to hold an arc extinguishing liquid, an annular upper contact anda lower contact carried by said body portion, said annular contact having opposed notches, an upwardly` bowed member having its ends positioned within said notches, a fuse link extending through the central portion of said member and having a pair of upper ends passing through said meniber, a lower contact', a spring having its lower end secured. to said Vlower contact, 9. tting sel cured to the upper end of said spring, said fuse link having a lower portion engaging said fitting, and a wedge for forcing said lower portion against said tting.

5. A liquid fuse comprising a tubular bodyportion adapted to hold an arc extinguishing liquid, a, lower and an upper contact carried by the body portion, said upper contact having opposed shouldered portions, an arch shaped mem- .K

berhaving projecting arms seated on said op- Y posed shoulders Vand supported byV said shoul` ders, a fuse link suspended from an intermediate portion of the arch shaped member and having one end positioned between one of the arms lof,

said arch shaped member and one of said shoulders, and-a spring operatively coupled to the lower endYof-the fr-use link and to the lower contact, said arch shaped member having a toggle action forcing the upper end of the fuse link into direct binding engagement with said upper' contact..

RALPH H. EARLE.

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