US3489978A - Fuse assembly - Google Patents

Description

Jan. 13, 1970 H.-W.-M|KL.JLECKY 3, 9,97

FUSE ASSEMBLY Filed Deg. 19, 1966 2 Sheets-Sheet 1 INVENTOR. yam/5y MMy/KZ/LECK) 3M WM V$7TORNEX Jan. 13, 1970 H. w. MIKULECKY FUSE AS SEMBLY 2 Sheets-Sheet 2 Filed Dec. 19, 1966 [/VVf/VTOR 77$4RV5) 2% dV/KULECKY a? TTOP/VE) United States Patent 3,489,978 FUSE ASSEMBLY Harvey W. Mikulecky, Racine, Wis., assignor to McGraw- Edison Company, Milwaukee, Wis., a corporation of Delaware Filed Dec. 19, 1966, Ser. No. 602,949 Int. Cl. H01h 73/24, 85/12 US. Cl. 337156 6 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a fuse assembly and, more particularly, to an assembly for mechanically and electrically supporting a plurality of fuses in a parallel relation.

It is an object of the invention to provide a new and improved current limiting fusible protective device.

Another object of the invention is to provide a current limiting fusible protective device having a plurality of fuse tubes connected in an electrically symmetrical and parallel arrangement.

Yet another object of the invention is to provide an assembly for supporting a plurality of fuse tubes in a symmetrical parallel relation which permits ease of fuse tube replacement.

Still a further object of the invention is to provide an assembly for supporting a plurality of fuse tubes in a symmetrical parallel relation which is hingedly operable by means of a hookstick for being moved into and out of a bridging relationship relative to a pair of spaced apart terminals.

These and other objects of the instant invention will become more apparent from the detailed description thereof taken with the accompanying drawings, in which:

FIG. 1 is a side elevational view of a fusible protective device according to the instant invention;

FIG. 2 is an exploded view of the protective device illustrated in FIG. 1;

FIG. 3 shows the current path through the fuse tube end support assembly; and

FIGS. 4 and 5 illustrate how the number of fuses in the protective device according to the instant invention may be varied.

In general terms, the invention comprises a plurality of fuse tubes, a pair of conductive end fitting means releasably engageable with the fuse tube end terminals, and spaced apart stationary contact means for engaging the end fitting means, wherein one of the end fitting means includes hinge means so that the fuse tube means may be pivoted between open and closed positions relative to the stationary contact means, and wherein each of the end fitting means is constructed and arranged to provide an electrically symmetrical current path between the stationary contact means and the terminal means.

Referring again to FIG. 1, a fusible protective device 10, according to the instant invention, may be mounted in any conventional manner, such as at the top of a pair of insulators 11 and 12 which may be mounted with their axes disposed in parallel spaced relation on a support "Ice member (not shown). In addition, terminal assemblies 15 and 16 are mounted atop each of the insulators 11 and 12, respectively, for being bridged by the protective device 10 when the latter is in its position shown by full lines in FIG. 1.

The terminal assemblies 15 and 16 are each shown to include a support member 18 afiixed to its respective insulator 15 or 16 and a flat, elongated, conductive terminal pad 19 which is afiixed adjacent one of its ends to its associated support member 18. The terminal pads 19 are disposed in general alignment and extend in opposite directions generally normal to the insulators 11 and 12, and each carries a conductor clamp 22 adjacent its free end for being placed in circuit with the system being protected by conductors (not shown). 7

In the embodiments of FIGS. 1-3, the protective device 10 is shown to include a pair of fuse tubes 24 and 25 which are joined at one end by a conductive metallic hinge end fitting 27 and a conductive metallic break end fitting 28. In general, each of the fuse tubes 24 and 25 includes a tubular insulating casing 29 for enclosing a fusible element (not shown) and which is closed at each end by conductive metallic terminals 30 and 31.

Integral lugs 33 and 34 extend from the center of each of the terminals 30 and 31, respectively, and each is receivable in one of a pair of apertures 35 formed in each of the end fittings 27' and 28. A pair of threaded holes extends radially from each of the apertures 35 for receiving set screws 38 which secure the fuse tubes 24 and 25 to the end fittings 27 and 28 and force the lugs 33 and 34 into high pressure electrical engagement with the sides of their respective apertures 35. In addition, the lugs 33 and 34 may have a central bore 39 for receiving a blownfuse indicator 40 which is coupled to the fusible element (not shown) for indicating when the latter has parted. For a more complete description of a fuse which may be employed with the instant invention, reference is made to US. Patent 3,243,552, which is assigned to the assignee of the instant invention.

Each of the end fittings 27 and 28 has an enlarged central portion 42 provided with a transverse groove 43 for being respectively engaged by the hinge end stationary contact 45 and a break end stationary contact 46. Each of the stationary contacts 45 and 46 consists of a generally fiat, U-shaped conductive member 48 and a substantially identical spring back-up member 49, the lower ends of which are bent at substantially a right angle for being affixed to their respective terminal pads 19 by screws 50. In addition, the upper ends of the stationary contacts 45 and 46 are angularly shaped at 52 for engaging the grooves 43 in the end fittings 27 and 28.

The fuses 24 and 25 are alternately arranged so that one of the blown fuse indicators 40 faces each end of the assembly 10 whereby one will be visible regardless of whether the assembly is in its closed position shown by full lines in FIG. 1 or its open position shown by broken lines. An eye 53 is integrally formed on each of the end fittings 27 and 28 so that the assembly 10 may be conveniently manipulated by means of a hookstick.

The terminal assembly 15 includes a generally U- shaped hinge member 54 which pivotally supports the hinge end of assembly 10 and terminal 16 includes a generally U-shaped guide member 55 which guides the break end of the assembly 10 into and out of its closed position. In addition, each of members 54 and 55 protects its associated stationary contact members 45 and 46 and each is suitably secured to its associated support member 18 by bolts 21. The hinge end fitting 27 has a pair of integral trunnions 58' extending laterally from the opposite sides of one end for engaging a pair of shaped slots 59 formed in the upper ends of the legs of U-shaped member 54. Each of the slots 59 includes a generally oval portion 60 which extends at a generally 45 degree angle relative to the fuse tube 24, and in which the trunnions 58 normally reside, and a generally arcuate slot portion 62 which is open at one end and which intersects the portion 60 to allow insertion and removal of the assembly 10 when it is in its open position.

It can be seen from FIG. 1 that when the assembly 10 is in its closed position, the trunnions 58 are not supported by the slot portions 60. The assembly is rather supported by the stationary contacts 45 and 46 so as to insure relatively firm contact pressure with the end fittings 27 and 28.

The upper ends of the legs of guide member 55 are flared outwardly at 63 to guide the break end fitting 28 into its closed position. In addition, a pin 65 extends between the legs of member 55 and adjacent the stationary contact 46 to prevent overstressing of said contact when the assembly 10 is moved into its closed position. A second pin 67 also extends between the legs of member 55 and adjacent contacts 46 for pre-stressing said contacts to provide the desired contact pressure and latching engagement with a minimum of movement during a closing operation.

When it is desired to pivot the assembly 10 to its open position, the eye 53 in the break end fitting 28 is engaged by a hookstick and the assembly 10 is pivoted from its position shown by full lines in FIG. 1 to its position shown by phantom lines. The shape and angular orientation of the oval slot portion 60 will generally retain the trunnions 58 in its lower end. A stop pin 66 extending between the legs of the hinge member 54 limits the rotation of the assembly 10 to substantially its position shown by phantom lines so that it will not be rotated into the terminal pad 19 and the conductor clamp 22. If it is desired to remove the assembly 10 for the replacement of fuses or otherwise, the eye 53; on the hinge end fitting 27 may be engaged by a hookstick whereby the assembly 10 may be lifted out of the slot portion 62.

A cross pin 68 extends between the lower ends of the legs of hinge member 54 in order to prevent the trunnions 58 from riding out of the slot 59 as the assembly 10 is being pivoted to its closed position.

FIG. 3 illustrates the path of the current I from the stationary contact 46 to the terminals 30 and 31 and through the break end fitting 28. Here it can be seen that, because the apertures 35 are symmetrically arranged relative to the contact groove 43, the current path through the end fitting 28 and to each of the fuse terminals 30 and 31 is identical and of equal length. In a similar manner, the current path at the opposite end of the fuses 24 and 25 through the hinge end fitting 27 is also symmetrical and of equal length. As a result, the resistance path of the current carried through the end fittings and to the fuses 24 and 25 will be substantially equal so each of the fuses will carry substantially the same current. In the event of a fault current, therefore, the are energy in each of the fuse tubes will also be substantially identical.

This permits each of the fuses 24 and 25 to be employed up to its maximum rating, or in other words, each of the fuses may have one-half of the continuous current rating required of a single fuse at the same location in the system.

FIGS. 4 and illustrate how the end fittings may be modified to receive additional fuse tubes. For example, the end fitting 28a is generally in the form of an equilateral triangle. Here the apertures 35a are arranged equidistantly from the stationary contact engaging portion 43a. In this manner, the end fitting 28a can provide symmetrical current paths to three fuse tubes. In an analogous manner, FIG. 5 illustrates an end fitting 28b which is square-shaped and has apertures 35b displaced equidistantly from the stationary contact engaging portion 43b so as to provide symmetrical current paths between four fuse tubes.

While only a few embodiments of the instant invention have been illustrated and desired, it is not intended to be limited thereto but only by the scope of the appended claims.

I claim:

1. A protective device comprising:

first and second support means;

a plurality of fuse tubes each having terminal means at its opposite ends;

a pair of conductive end fitting means releasably engageable with said terminal means for joining said fuse tubes in electrical parallelism;

stationary contact means on each of said support means for engaging said end fitting means;

one of said end fittings including hinge means whereby said fuse tube means may be pivoted between open and closed positions relative to said stationary contact means;

each of said end fitting means being constructed and arranged to provide a current path of substantially equal impedance and of substantial electrical symmetry between said stationary contact means and said terminal means;

each of said end fittings including a plurality of first portions for engaging said terminal means and a second portion for engaging said stationary contact means, each of said first portions being symmetrically arranged relative to said second portion; and

each of said terminal means including lug means and each of said first portions comprising aperture means for receiving said lug means, and means releasably securing said lug means in said apertures and in high pressure electrical engagement therewith.

2. The protective device set forth in claim 1 wherein each of said stationary contact means resiliently engages its respective end fitting means with a line of action extending substantially parallel to said fuse tubes and toward the other of said stationary contacts to support said fuse tubes independently of said support means and provide high contact pressure between said stationary contact means and said end fittings.

3. The protective device set forth in claim 2 wherein said hinge means includes trunnion means formed on one of said end fittings and a stationary support member having open-ended slot means formed therein receiving said trunnion means, and each of said end fitting means having hookstick receiving means.

4. A protective device comprising:

first and second support means;

a plurality of fuse tubes each having terminal means at its opposite ends;

a pair of conductive end fitting means releasably engageable with said terminal means for joining said fuse tubes in electrical parallelism;

stationary contact means on each of said support means for engaging said end fitting means;

one of said end fittings including hinge means whereby said fuse tube means may be pivoted between open and closed positions relative to said stationary contact means;

each of said end fitting means being constructed and arranged to provide a current path of substantial electrical symmetry between said stationary contact means and said terminal means;

each of said end fittings including a first pair of first portions for engaging said terminal means of a pair of said fuse tubes and a second portion for engaging its respective stationary contact means, each of said first portions being symmetrically arranged relative to said second portions; and

each of said terminal means includes lug means, and each of said first portions comprises aperture means receiving said lug means, and means releasably securing said lug means in said apertures and in high pressure electrical engagement therewith.

5. An electrical system proctective device comprising:

a support means;

6 a plurality of fuse tubes each having terminal means said apertures to engage each lug means, thereby creatat opposite ends; ing a releasably engagea'ble end fitting. a pair of conductive end fitting means releasably engageable with said terminal means for connecting References ted saidffufie tubesl inl electrilcal parallelism and in sub- 5 UNITED STATES PATENTS s an 1a y equa e ec nca sy-rnme ry; a pair of stationary spring biased contact means atfi tached to said support means for engaging each of 60 1 said end fitting means, whereby a line of pressure 6/1959 Gaskl extends between said spring biased contact means 10 2301573 8/1959 Gesenschap' substantially parallel to and through the longitudinal 3,114,022 12/1963 Harder at axes of said fuse tubes. 6. An electrical system protective device as defined in BERNARD GILHEANY Pnmary Exammer claim 5 wherein each of said terminal means includes lug R, L, COHRS, A i t t E i means and said end fitting means includes apertures for 15 receiving said lug means, and at least one threaded de- US. Cl. X.R. vice extends through said end fitting means into each of 337-161

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