US2921167A - Fuse - Google Patents

Description

Jan, 12, 1960 P. A. DAHLEN FUSE Filed June 4, 1958 FIG.3

INVENTOR.

PAUL A.DAHLCN United States Patent FUSE Paul A. Dahlen, Mansfield, Ohio, assignor to Stevens Manufacturing Company, Inc., a corporation of 01110 Application June 4, 1958, Serial No. 739,769

9 Claims. (Cl. 200117) The invention relates in general to an electrical fuse and more particularly to a fuse structure which is consistent and reliable in its operation.

Electrical fuses are placed in electrical circuits as a safety link to protect thecircuit upon occurrence of some dangerous condition either in the electrical device, or the electrical supply source, or both. Fuses are devices which have some form of a fusible material which will melt upon the occurrence of the dangerous condition such as an overload of current or excess heat to thus open the electrical circuit. Many fuses are constructed of a ribbon or wire of a low melting point alloy which is so proportioned in size and shape as to melt upon a given excess of current for a particular voltage rating. In modern manufacturing techniques many variables are encountered and it has many times been observed that fuses do not always function to interrupt the electrical circuit at exactly the same value of current or the same value of the other variable determining the operation. Many devices are capable of examination after failure to determine the cause of failure, but a fuse inherently is extremely difiicult to examine after failure to determine the cause of failure because by its very nature it destroys itself in operation. The fusible element used in any fuse is subject to many variables such as poor electrical connection to the terminal connections, various cross sectional area actually in use at any series connected point in the circuit, impurities in the fusible material, variations in stress on the fusible material, impurities at the terminal connections, etc. With these many variables many prior art fuses have been subject to considerable variation in operating pointwhen they were supposedly all calibrated by size and shape for a particular operating point.

Accordingly, an object of the invention is to provide a fuse structure which is capable of consistent and reliable operation.

Another object of the invention is to provide a fuse wherein the variables affecting the operation are maintained at a minimum.

Another object of the invention is to provide a fuse wherein any impurities in the fusible material and any stressing of the fusible material and any impurities on the terminal connections of the fusible material have negligible affect on the operational characteristics.

Another object of the invention is to provide a fuse wherein a plurality of areas of fusible material are all connected in parallel in the electrical circuit and connected in parallel in the mechanical arrangement.

Other objects and a fuller understanding of this invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawing, in which:

Figure 1 'is a side elevational view of a fuse embodying the invention;

Figure 2 is a front elevational view of the fuse; and

' Figure 3 is an isometric view of the fuse.

Figures 1 and 3 show different views of a fuse struc ture 11 which is mounted on a base 12, which base may be of insulating material. The fuse includes generally first and second operating portions 13 and 14 carried on the base 12 and, as shown in the drawing, these operating portions 13 and 14 are carried on blades 15 and 16, respectively. The blades 15 and 16 may for convenience and economy be made of one-piece construction; and also for economy, ease of assembly, and minimization of parts, they may be made identical. The blade 15 has a first or terminal end 19, and the operating portion 13 is at the second end thereof. The second blade 16 has a first or terminal end 20, and the second operating portion 14 is at the second end thereof. Each blade hasfirst and second right angle bends 21 and 22 in opposite directions to form a shoulder 23 therebetween. The base 12 has first and second slots 24 and 25 shaped to fit the cross sectional shape of the blades 15 and 16. Rivets 26 pass through the base 12 and the shoulders 23 to fasten the blades at the shoulders 23 to a first side 27 of the base 12. The blades 15 and 16 by passing through the slots extend on a second side 28 of the base 12. The terminal ends 19 and 20 may be of any suitable shape for providing electrical connection into the electrical circuit with which the fuse 11 is used, and in the drawing these terminals are shown as spade type terminals.

The blades 15 and 16 are of strip material, that is, they are elongated and are resilient current carrying conductors. The operating portions 13 and 14 may be, and preferably are, identical with the operating portion 13 having first and second legs 31 and 32, and the second operating portion 14 having first and second legs 33 and 34. Each of these operating portions 13 and 14 is generally in the form of a U-shape to support the legs on the respective blade.

The blades 15 and 16 normally extend generally parallel to each other on the second side 28 of the base 12 caused by their shape in being formed, their natural resilience, and the positioning during mounting on the base 12. This inherent position of the blade 15 is shown in dotted lines in Figure 1. During manufacture the two operating portions are held together against the resilient urging of the blades 15 and 16, and solder 35 or other fusible material is caused to interconnect the operating portions 13 and 14. Thus, the solder 35 appears in three discreet areas interconnecting the side surfaces of the four legs 31-34.

The legs on each operating portion are substantially parallel to each other and extend generally perpendicularly to the plane of the respective blade. Since the blades 15 and 16 are mounted so that they are nominally parallel, this means that all four legs are generally parallel. This further means that the urging means caused by the stressing of the blades 15 and 16 urges apart the operating portions in a direction substantially parallel to the planes of the legs 31-34. This establishes substantially only a shear stress in the solder or other fusible material 35. Previous fuse structures have been made which subject the fusible material to primarily a tension stress and using only a single mass of fusible material under stress, this means that if any portion of the fusible material is of smaller cross sectional area or contains impurities, this causes it to be the weakest link in the chain and will cause the fuse to fail, that is, operate, at a lower temperature or current rating than desired.

The present invention by utilizing a plurality, in this case three, of areas of solder which are mechanically stressed primarily in shear, this likelihood of false operation or malfunctioning is practically eliminated. These three areas mechanically stressed in shear also establish that there are three paralleled electrical paths between.

the first and second operating portions 13 and 14 which carry current; and hence, all three areas of fusible material must be melted before the fuse will operate.

The fuse 11 may be used in several different applications and one suitable application is. one in which the temperature of the ambientatmosphere is being controlled. Electrical current is necessarily passed through the fuse 11 with the fuse controlling this electrical current. The blades 15 and 16 may be made from beryllium copper, for example, which is a good conductor of electricity as well as having good elastic properties to maintain the resilient stress. In such case it is a relatively simple matter to proportion the current carrying parts of the fuse 11 so that the heating effect caused by the passage of current through the fuse is small relative to the heating effect of the entire fuse caused by the ambient atmosphere. In such case, upon the surrounding air becoming overheated, the fuse 11 will be actuated, that is, to melt the solder 35, so that the blades 15 and 16 spring apart and hence interrupt the electrical circuit to relieve the cause of the overheating of the ambient atmosphere. By making the two blades 15 and 16 of unitary construction and identical, this permits the fuse to be cheaply and quickly manufactured and assembled and minimizes the inventory of .parts necessary for con struction as well as providing for ready interleaving of the legs 31 and 32 with the legs 33 and 34. The fact that the solder 35 is in three separate areas means that should any impurities exist either in the solder-itself or on the side surfaces of the legs 31-34, such impurities or other causes of improper electrical connection between the fusible material and the operating portions 13 and 14 will have negligible affect on the operational characteristic of the fuse 11 because of the plurality of paralleled paths both electrical and mechanical.

Although this invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

What is claimed is:

1. A fuse structure, comprising, a base, first and second operating portions each having a pair of legs, means mounting said first and second operating portions on said base in mutually insulated relationship with said legs extending in spaced side-by-side relationship, means providing electrical connection to each said operating portion, said operating portions being positioned to interleave said legs, a mass of fusible material interengaging said four legs in the three areas between the side surfaces of said legs, and means urging apart said operating portions in a direction "substantially parallel to said side surfaces, whereby upon overheating said mass melts to permit said operating portions to spring apart to open the electrical connection therebetween.

2. A fuse structure, comprising, a base, first and sec ond substantially identical blades, each blade being elongated with first and second ends, means mounting each said first end to said base, first and second operating portions each formed by a pair of legs, means mounting said first and second operating portions to said first and second blades, respectively, in mutually insulated relationship, means providing electrical connection to each operating portion, the two pairs of legs extending Substantially parallel, said second ends of said blades being positioned to interleave said legs, a mass of fusible material interengaging said four legs in the three areas between the side surfaces of said legs, and means urging apart said operating portions in a direction substantially parallel to the planes of the legs, whereby upon overheatingsaid mass melts to permit said operating portions tospring.

apart to open the electrical connection,therebetween.

3. A fuse structure, comprising, an insulated base, first and second substantially identical blades, each blade being elongated with first and second ends, means mounting each said first end to said base, means providing electrical connection to said blades, a pair of legs on each said second end forming an operating portion with the pair of legs of each portion extending generally transversely to the plane of the respective blade, the two pairs of legs extending substantially parallel, said second ends of said blades being positioned to inter-leave said legs, a mass of fusible material interengaging said four legs in the three areas between the side surfaces of said legs, and means urging apart said operating portions in a direction substantially parallel to the planes of said legs to load said fusible material substantially only in shear, whereby upon overheating said mass melts to permit said second ends of said blades to spring apart to open the electrical connection therebetween.

4. A fuse structure, comprising, an insulated base, a blade of resilient material and elongated with first and second ends, means mounting said first end to said base, first and second U-shaped portions each formed by a pair of legs, means mounting said first U-shaped portion on said blade second end with a pair of legs extending generally transversely to the plane of said blade, means mounting said second U-shaped portion on said base with the two pairs of legs extending toward each other and extending substantially parallel, means providing electrical connection to each said U-shaped portion, said second end of said blade being deflected toward said second U-shaped portion to resiliently stress said blade and to interleave said legs, and solder interengaging said four legs in the three areas between the side surfaces of said legs, the stressing of said blade loading said solder in shear, whereby upon overheating said solder melts to permit said second end of said blade to resiliently spring away from said second U-shaped portion to open the electrical connection therebetween.

5. A fuse structure, comprising, an insulated base, first and second substantially identical blades, each blade being elongated with first andsecond, ends, means mounting each said first end to said base, means providing electrical connection to said blades, a pair of legs on each said second end forming a U-shaped portion, with the pair of legs of each portion extending generally transversely to the plane of the respective blade, the' two' pairs of legs extending toward each other and extending substantially parallel, said second ends of said blades being positioned to interleave said legs, solder interengaging said four legs in the three areas between the side surfaces of said legs, and means urging apart said U- shaped portions in a direction substantially parallel to the planes of said legs to load said solder in shear, whereby upon overheating said solder melts to permit said second ends ofsaid blades to spring apart to open the electrical connection therebetween.

6. A fuse structure, comprising, an insulated base, first and second substantially identical blades, each blade being of resilient material and elongated with first and second ends, means mounting each said first end to said base to establish said second ends spaced apart, terminals on said first ends of said blades for electrical connection, a

U-shaped portion formed on each said second end withthe pair of legs of each portion extending generally perpendicular to the plane of the respective blade, t-he two pairs of legs extending toward each other and extending substantially parallel, said second ends of said blades being deflected toward each other to resiliently stress said blades and to interleave said legs, and solder interengaging said four legs in the three areas between the side surfaces of said legs, whereby upon overheating said solder melts to, permit said second ends of said blades to resiliently spring apart to open the electrical connection therebetween.

7. A fuse structure for use in an electrical circuit, cornprising, an insulated base, first and second substantially identical blades, said blades being of resilient material, each blade being elongated and having first and second ends, means mounting each said first end to said base, terminals on said first ends of said blades for electrical connection of said fuse structure in said circuit, the mounting of said first ends of said blades establishing said second end-s spaced apart, a Uz-shaped portion formed on each said second end with the pair of legs of each portion extending generally perpendicular to the plane of the respective blade, the two pairs of legs extending toward each other and extending substantially parallel, said second ends of said blades being deflected toward each other to resiliently stress said blades and to interleave said legs, and solder interengaging said four legs in the three areas between the side surfaces of said legs, whereby upon overheating said solder melts to permit said second ends of said blades to resiliently spring apart to open said electrical circuit.

8. A fuse link for use in an electrical circuit, comprising, an insulated base, first and second substantially identical blades, said blades being of elongated resilient material, each blade having first and second ends, each said first end being a mounting end, said insulating base having first and second parallel and spaced slots shaped to receive said blades, first and second sides on said base, said blades passing through said slots and having a portion lying against said base, fastening means passing through said insulating base and each said portion to fasten each said blade to said base, terminals on said first ends of said blades for electrical connection of said fuse link in said circuit, the mounting of said first ends of said blades establishing said second ends spaced apart, a U- shaped portion unitarily formed on each said second end with the pair of legs of each portion extending substantially perpendicular to the plane of the respective blade, the two pairs of legs extending toward each other and extending substantially parallel, said second ends of said blades being deflected toward each other to resiliently stress said blades and to interleave said legs, and solder inter-engaging said four legs in the three areas between the side surfaces of said legs, the stressing of said blades loading said solder in shear, whereby upon overheating said solder melts to permit said second ends of said blades to resiliently spring apart to open said electrical circuit.

9. A fuse link for use in an electrical circuit, comprising, an insulated base, first and second unitary identical blades, said blades being of substantially flat resilient strip material, each blade having first and second ends, each said first end being a mounting end and including first and second right angle opposite bends to form a shoulder therebetween, said insulating base having first and second parallel and spaced slots shaped to receive said blades, first and second sides on said base, said shoulder of each said blade engaging said first side of said base, rivets passing through said insulating base and each said shoulder to fasten each said blade to said base, terminals on the protruding first ends of said blades for electrical connection of said fuse link in said circuit, the mounting of said first ends of said blades establishing said second ends resiliently extending substantially parallel to each other, a U-shaped portion unitarily formed on each said second end with the pair of legs of each portion extending substantially perpendicular to the plane of the respective blade, the two pairs of legs extending toward each other and extending substantially parallel, said second ends of said blades being deflected toward each other to resiliently stress said blades and to interleave said legs, and solder inter-engaging said four legs in the three areas between the side surfaces of said legs, the stressing of said blades loading said solder substantially only in shear, whereby upon overheating of the ambient atmosphere around said fuse link said solder melts to permit said second ends of said blades to resiliently spring apart to open said electrical circuit.

References Cited in the file of this patent UNITED STATES PATENTS 2,284,291 May May 26, 1942 2,457,941 Szabo Jan. 4, 1949 2,599,441 Ekman June 3, 1952 2,791,660 Sims et al. May 7, 1957 FOREIGN PATENTS 609,745 Great Britain Oct. 6, 1948 747,185 Great Britain Mar. 28, 1956

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