US1277045A

US1277045A - Electric-fuse link.

Info

Publication number: US1277045A
Application number: US22517818A
Authority: US
Inventors: Robert C Cole
Original assignee: PRATT JOHNS CO
Current assignee: JOHNS-PRATT Co; PRATT JOHNS CO
Priority date: 1918-03-28
Filing date: 1918-03-28
Publication date: 1918-08-27
Anticipated expiration: 1935-08-27

Description

INVENToR.

Patented Aug. 27, l1918.

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R. C. COLE. ELECTRIC FUSE LINKI APPLICATION FILED MAR. 28. 1918.

A TTORNE Y.

UNITED STATES PATENT OFFICE.

ROBERT C. COLE, OF HARTFORD, CONNECTICUT, ASSIGNOR T0 THE JOHNS-PRATT COM- PANY, OF HARTFORD, CONNECTICUT, A CORPORATION 0F CONNECTICUT.

ELECTRIC-FUSE LINK.

Patented Aug. 27, 191s.

Application filed March 28, 1918. Serial No. 225,178.

To all whom t 'may concern:

Be it known that I, ROBERT C. COLE, a citizen of the United States, residing at Hartford, in the county of Hartford and State of Connecticut, have invented a new and useful Improvement in Electric-Fuse Links, of which the following is a specification.

This invention relates to the construction of the fuse links of inclosed electric fuses.

The object of the invention is to provide a simple, cheaply formed and accurately calibrated link which will indefinitely carry a normal amount of current withoutl undue heating, and which will either in a filled or in an unfilled case under gradual-overload or severe short circuit conditions open the circuit in which it is placed with less explosive effect and more quietly than the links in common use.

This object is attained byarranging calibrating perforations in such manner that there will be in the link a plurality of attenuated sections or constricted current paths in multiple, and a plurality of these multiple attenuations or constrictions in series whereby when an abnormal current flows there will' be but small sections of metal to melt and these will be so distributed that there will be a number of arcs in multiple-series of relatively small size, consequently suflicient internal pressure is quickly built up to compress and extinguish the arcs before they become violently destructive and pressure enough is generated to burst the tube or blow off the end caps.

Links which embody this invention have distinct advantages in filled fuses, but they are particularly serviceable for use in unfilled renewable fuses, and consequently they are illustrated herein as used in the latter fuses.

Figure 1 of the accompanying drawings shows a central 4longitudinal section of an inclosed fuse of the ferrule' Contact type provided with a link constructed according to this invention. Fig. 2 shows the link removed from the case of this fuse. Fig.- 3 shows a link of substantially the same carrying capacity constructed for a higher voltage fuse. Fig. 4: shows a central longitudinal section of an inclosed fuse of the knife blade contact. type, provided with a linkV which embodies this invention. Fig. 5 shows the link removed from the knife blade fuse. Fig. 6 shows a link for a knife blade fuse of higher voltage.

The case 1 of these fuses is usually formed `of a piece of fiber tubing. On the ends of the tubular case shown in Fig. 1 metallic sleeves 2 are threaded, and screwing upon the outer ends of these sleeves are metallic caps 3. In the ends of the sleeves and resting on ,shoulders therein bent over these washers and clamped thereto by the caps are the endsvof the fusible link 5.- These links are usually formed of thin zinc strips. In the form first illustrated two triangular perforations 6 are made through the strip on each side of the middle. This results in forming on one side of the middle of the strip two attenuated sections 7 8, near the edges and an attenuated section 9 along the center of the strip, and forming on the other side of the middle two attenuated sections 10,11, near the edges and an attenuated section 12 along the center of the strip. This strip, which has the desired current carrying capacity and with the calibration perforations properly spaced apart according to the voltage, thus has three constricted current carrying paths 7 8, 9, in multiple, and in series therewith three constricted current carrying paths 10, 11, 12, which are in multiple with each other. Between these attenuated sections there is a sufficient mass of metal to are washers 4 and provide the required current carrying ca'- pacity and proper heat radiation for insuring the desired result. /The attenuated sections, however, are so small that when an abnormal current flows the metal melts quickly where the current paths are constricted, and as these portions melt three small arcs are formed in multiple at one side o the middle and threesmall arcs in multiple are formed at the other side of the middle. As the result of the small amount of metal that is necessary to be melted and the d1- viding of the currentl `in this manner the several arcs are relatively small and they are smothered by the internal pressure before they become sufficiently7 large to become eXplosively ,violent For a relatively low voltage fuse there need be but two sets of calibration perforations providing three'constricted multiplecurrent paths in series with three other constricted multiple-current paths. For fuses of higher voltage more calibration openings may be arranged, as shown in Fig. 3. In this form there are four series of three attenuated sections arranged in multiple.

The knife-blade type of fuse shown in Fig. 4 has an insulating tubular case 13 With end caps 14 screwed thereon. Extending through the end caps and through Washers In these links there may kbe as many of these sets of calibrations providing multiple attenuated sections arranged in series asthe voltage may require for the successful op eration of the fuse, and these calibration perforations may vary 1n size and outllne according to the conditions.

This construction provides a sufficient amount of-metal in the strips to insure the necessary radiation to keep the stripsl cool when in use under normal conditions,' and yet the sections' of metal necessary to be melted for opening the circuit are so small that they melt easily and Witlout generating an excess of pressure in the cases and as the current is broken up into a number of arcs When these small sections melt the arcs are not sufficiently powerful to become violently destructive and they are easily smothered -by a relatively lo'W pressure generated in the metal having sets of Calibrating perforations located to provide in series with each other a plurality of constricted current carrying Isections that are in multiple with each other.

2. A fuse link formed of a strip of fusible I metal having a plurality of Calibrating perforations arranged in pairs.

3. A fuse link formed of a strip of fusible metal having Calibrating perforations located to provide in series a-plurality of restricted current carrying paths that are in multiple.

4. A fuse link formed of a strip of fusible metall having Calibrating 'perforations located to provide a number in series of three constricted current carrying paths that are in multiple.

5. Av fuse link formed of a strip of fusible metal having a plurality of pairs of triangularly shaped Calibrating perforations.

6. A fuse link formed of a strip of fusible metal having Calibrating perforations located to form three constricted current carrying paths at a number of points along the length of the strip.

7 A fuse link formed of a strip of fusible metal having a pair of triangularly shaped Calibrating perforations located base to base each side of the middle of the length of the strip.

ROBERT C. COLE.