US2670418A - Fuse and fuse holder - Google Patents

Description

Feb. 23, 1954 Filed Oct. 9, 1952 F. J. KOZACKA FUSE AND FUSE HOLDER 3 Sheets-Sheet l 1954 F. J. KOZACKA ,670,418

FUSE AND FUSE HOLDER Filed Oct. 9, 1952 5 Sheets-Sheet 2 Feb. 23, 1954 J. KQZACKA 2,670,418

FFFFFFFFFFFFFFF ER Fig. 3 is a side elevation of a fuse according to Figs. 1 and 2 inserted into a fuse holder embodying this invention;

Fig. 4. is a side elevation of the structure shown in Fig. 3;

Fig. 5 is a top plan view of the structure shown in Fig. 3;

Fig. 6 is a perspective illustration of a fuse and of the right hand portion of a fuse holder for extremely high currents, the identical left hand portion of the fuse holder being omitted;

Fig. '7 is a top plan view of another combination of fuses and of a fuse holder embodying this this invention;

Fig. 8 is a cross-section along 8-8 of Fig. '7, and

Fig. 9 is partly a side elevation and partly a longitudinal section of a fuse embodying the present invention.

Referring now to Figs, 1 and 2, the fuse shown therein comprises a pair of cylindrical terminal elements I preferably made of solid copper and arranged in spaced relation. Each of terminal elements l is provided With a coaxial cylindrical projection la. forming an integral part thereof. Projections la form connectors or connector studs for inserting the fuse into a fuse holder of the type shown in Figs. 3 to 9, inclusive. A plurality of slots lb are milled into each terminal element l at juxtaposed surfaces thereof. The depth of slots lb may be in the order of and the angular displacement thereof in the order of 20 degrees. Each slot or groove lb is adapted to receive a plurality of fuse links 2. Each of said plurality of fuse links 2 consists of a ribbon of silver or copper and each such ribbon is provided with a plurality of points of reduced cross-section. The points 2a of minimum cross-section of each link 2 limit the peak of the let-through current to a relatively low value, far below the peak of the available short-circuit current of 1 the circuit into which the fuse is inserted. The large mass of copper of the terminal elements l (see Fig. 1) normally absorbs and dissipates the heat generated at the points of links 2 of reduced cross-sectional area. Fusion of the links 2 at the points 2a of minimum cross-sectional area occurs upon occurrence of a current of shortcircuit current proportions. If it is desired to use the fuse for overload protection each of the links 2 may be provided with a tin rivet 2b. Tin rivets 2b fuse upon occurrence of relatively small protracted overloads and the metal of which links 2 are made diffuses into the melted tin, thus resulting in dispersal of links 2 and interruption of the circuit. The spaces between the fuse links 2 are filled with a pulverulent arc extinguishing substance 3, preferably pure quartz sand having a grain size in the order of 50-60 U. S. sieve number. Inasmuch as the let-through current and the are energy of the structure of Figs. 1 and 2 are small, the quantity of filler 3 required is small and the volume occupied by the entire structure is correspondingly small.

Terminals l are securely held apart the required relatively limited distance by a central spacer structure. This structure includes a pair of concentric tubes 4, 5 of a material which combines high heat and heat shock resistance, mechanical strength and good insulating properties. The tubular elements 4, 5 are preferably made of a glass-cloth laminate impregnated with a suitable synthetic resin. The radially inner tubular element 5 is provided with a pair of metal caps 5a secured to it by steel pins 5b and may contain a filler rod 50 of insulating. material.

Caps 5a enter cylindrical recesses lc in terminal elements I. Only the left hand cap 5a, the left hand steel pin 5b and the left hand terminal recess lc have been shown in Fig. l. A large amount of pressure is applied for inserting the structure 5, 5a, 5b into the terminal elements I, thus establishing the required high degree of dimensional stability. The links 2 and the granular arc-extinguishing filler 3 are enclosed in an insulating shell or casing E which is secured to terminals l by means of steel pins 'l. Ferrules B of sheet metal are arranged at both ends of the fuse structure. It will be apparent that the cross-sectional area'of connector studs la is considerably smaller than the cross-sectional area of casing 6.

Referring now to Figs. 3-5, it will be apparent from these figures that the pair of coaxial cylindrical connectors or connector studs Id projecting from the fuse structure generally designated by the reference letter F, and more particularly from the cylindrical casing 6 of the fuse structure F, have been inserted into a fuse holder particularly designed to receive said cylindrical connectors or connector studs. The fuse holder comprises a pair of substantially L-shaped brackets 9 of solid copper arranged in spaced relation each with one shank 9a thereof in a pair of parallel planes and each with the other shank 9b thereof in a common plane. The shanks 9a are formed by substantially equilateral square blocks of copper substantially equal in length to the diameter of casing G. Shanks 9a form adivided bearing substantially equal in diameter to the diameter of the connectors or connector studs la and in cooperative engagement therewith.

I Reference numberal ll] has been applied to the cylindrical bearing surfaces which are in cooperative engagement with connector studs la. The clamping screws H are secured to the lower portions of the divided bearings and pass loosely through bores l2 provided in the upper portions or bearing caps thereof. Nuts l 3 enable to clamp firmly the bearing surfaces ll) in the upper and lower portions of the divided bearings against the cylindrical connector studs la, thus ensuring the amount of contact pressure required to minimize 1 -1 losses at the contacts. A small gap 2%) is always present between the upper portion or bearing cap and the lower portion of each contact bearing.

As nuts l3 are being tightened initially two opposite line contacts are established between the surface of each connector stud la and each bearing surface It]. Further tightening of nuts l3 increases the contact pressure prevailing at these two substantially linear contacts of each connector stud la but simultaneously each connector stud la is being deformed and engages the bearing surfaces l8 under pressure at progressively increasing areas. With further increase of contact pressure the deformation of the connector studs la progresses and the contact area changes accordingly from the above referred to initial pair of linear contacts to a surface type or butt contact, i. e. current is then transmitted along substantially the entire peripheral surface of studs la. Since the surface type or butt contacts involve a larger contact area and a higher contact pressure than the linear contacts formed during the initial stages of the tightening process of the contact bearing, it is readily apparent that the surface or butt contacts involve relatively less 1 -1 losses than the linear contact arrangement of which they are an out.- srowth.

It will also be read y apparent from Fi s. 3 9 hat the renewal of a new fuse for a blown fuse is a simple matter of loosening and tightening but a few screws. In prior art fuses and fuse. holder structures having a comparable current rating. 1. e. a currenpcarrying, capacity in the order of several thousand amperes. the bladecontacts of the fuse had to be secured directly to the bus bars. This involved loosening and tightening 01'. a much. larger number of screws. It takes therefore much more time and effort to renew prior art fuses than fus s according to this invention,

As shown in Figs. 3 to 5.. inclusive. the shanks a r brackets 9 are each provided with a. plurality of transverse bores or holes 14. These transverse bores or holes M are adapted for attachment f the fuse holder and the fuse F to a system of spaced bus bars shown at 15'.

It will be apparent froms Figs. 3 to 5-. inclusive. that the shanks 9a. of the two substantially L.- shapcd fuse holder brackets 9 which are arranged. n a pair of parallel planes are spa ed a distance slightly in excess of the length of the casing 6 of fuse .F. Ea h bracket 9 is arranged with the other shank 9b thereof a common plane at right angles to the above pair of parallel, planes. The shanks 9c are formed by substantially equilateral sq are blocks substantially equal in. length to the diameter of the casing G of fuse F. These. square blocks are each subdivided. into two parts to form. a divided contact bearing having a cylindrical bearing surfa e to su stantially equal in diameter to the. diameter of connector studs la.

The structure shown in Fig. 6 is substantially the same as that shown in F gs. 3 to 5 xcept that the former is provided with two pairs of para el shanks 9a, 9a of which only one is shown in the drawing. Each pair of shanks 9c. 8c is arranged in. a separate pair of par ll l planes and each pair of shanks 9a, 9a forms a pair of divided bearings for the connector studs la.

The structure of Figs. d and 8 is adapted to accommodate av pair of high current-carrying capacity fuses F and F" instead of merely one such fuse. The four parallel shanks 9a are designed to form each a contact bearing. Each pair of four contact bearings formed by shanks 9a accommodates one pair of Connector studs la.

The right hand shank 9b and the left hand shank 9b each support one pair of shanks 9a, e. each shank 9b is common to a. pair of shanks 9a. Shanks 9b are provided with a plurality of transverse bores l4 adapted to attach the fuse holder to a system of spaced bus bars (not shown).

Fig. 9 shows a high current-carrying and high interrupting capacity fuse similar to that shown in Figs. 1 and 2. The fuse comprises a casing 6 and a pair of coaxial cylindrical connector studs la projecting from opposite ends of easing 6. The connector studs la are hollow, at least in part, to increase the ratio of surface to crosssectional area, thus tending to increase the rate at which watt-losses within the fuse are being dissipated. As clearly shown in Fig. 9 that portion of connector studs Ia which is situated at the ends thereof remote from casing 6 is hollow. The portions of the studs la immediately adjacent casing 6 are solid. It is apparent that hollow connector studs will not only be better heat exchangers or heat dissipaters than solid studs, but will tend to be more readily deformed by the clamping pressure and hence tend to establish a better contact with any of the fuse holders shown,

i. e. either that shown in Figs. as. that shown in Fig. 6, or that shown in Figs. 7 and. &

It will be. understood that by illustrating several preferred forms of fuse structures and fuse holder structures, I do not intend to limit my invention thereto. It will further be understood that while the arrangements described. and illustrated herein are. the preferred embodiments of my invention, the same may take forms other than specifically shown and described herein. It will; be apparent for those skilled in the art that various changes and modifications may be made without departing hum the spirit of the inven tion or from the scope of the appended claims,

It is claimed and desired to secure by Letters Patent:

1. A structure including a cartridge type hizh current carrying capacity fuse comprising a casing having a relatively large cross-sectional area and a pair of coaxial cylindrical connector studs having a relatively small cross-sectional area pro- J'ecting from opposite ends. of said casing, and a fuse holder adapted to support said fuse and to receive said pair of connector studs of said fuse, said fuse holder comprising a pair of supports spaced 2. distance substantially equal to the length of said casing of said fuse, each of said pair of supports forming a. divided bearing having a cylindrical bearing surface engaging one of said pair of connector studs of said fuse and having clamping means for exerting clamping pressurein a direction transversely of said casing and said pair of connector studs for firmly clamping said 7 bearing surface against said one of said pair of connector studs of said fuse.

2. A structure according to claim 1 wherein each of said pair of cylindrical connector studs is hollow at the portion thereof remote from said casing of said fuse.

3. A structure including a cartridge type high current-carrying capacity fuse comprising a cylindrical casing having a. relatively large crossscctional area and a pair of cylindrical connectorstuds having a relatively small cross-sectional area arranged coaxially with respect to said casing and projecting from opposite ends thereof, and a fuse holder comprising a pair of fuse supports consisting of a pair of substantially- L-shaped brackets spaced a distance slightly in excess of the length of said casing, said pair of brackets forming a pair of divided bearings having substantially cylindrical bearing surfaces, said bearing surfaces having an internal diameter substantially equal to the diameter of said pair of connector studs, and each of said pair of connector studs being conductively engaged under pres sure by one of said bearing surfaces.

4. A structure including a cartridge type high current-carrying capacity fuse comprising a cylindrical casing having a relatively large crosssectional area and a pair of cylindrical connector studs having a relatively small cross-sectional area arranged coaxially with respect to said casing and projecting from opposite ends thereof, and a fuse holder comprising a pair of substantially L-shaped brackets, each of said pair of brackets being arranged with one shank thereof in a pair of parallel planes spaced a distance slightly in excess of the length of said casing of said fuse, and each of said pair of brackets being arranged with another shank thereof in a common plane, each shank of said pair of brackets arranged in said pair of parallel planes forming a divided bearing including a bearing cap and cap screws and having a cylindrical bearing surface cooperating with one of said pair' of con'n'ect'or' studs, and each shank of said pair of brackets arranged in said common plane being provided with means for attachment to a system of spaced bus bars.

5. A'structure including a cartridge type high current-carrying capacity fuse comprising a cylindrical casing having a relatively large crosssectional area and a pair of cylindrical connector studs having a relatively small cross-sectional area arranged coaxially with respect to said casing and projecting from opposite ends thereof and a fuse holder comprising a pair of substantially L-shaped brackets, each of said pair of brackets being arranged with one shank thereof in a pair of parallel planes spaced a distance slightly in excess of the length of said casing of said fuse, and each of said pair of brackets being arranged with another shank thereof in a common plane, each shank of said pairof brackets arranged in said pair of parallel planes being formed by a substantially equilateral substantially square block substantially equal in length to the diameter of said casing of said fuse, said blockforming a divided bearing substantially equal in diameter to the diameter of one of said pair of connector studs of said fuse and in cooperative engagement with said one of said pair of connector studs, each shank of said pair of brackets arranged in said common plane being provided with, a plurality of transverse bores adapted'for attachment thereof to a system of spaced bus bars.

6. A structure including a cartridge type high current-carrying capacity fuse comprising a casing having a relatively large cross-sectional area and a pair of coaxial cylindrical connector studs having a relatively small cross-sectional area projecting from opposite ends of said casing, said pair of connector studs being hollow at least in part to increase the ratio of surface to crosssectional area thereof, and a fuse holder adapted to receive said pair of connector studs, said fuse holder comprising two spaced fuse supports each forming a divided bearing having a cylindrical bearing surface in cooperative engagement with one of said pair of connector studs and each having clamping screws for firmly clamping said bearing surface against one of said pair of connector studs in a direction transversely of said pair of connector studs.

7. A structure including a cartridge type high current-carrying capacity fuse comprising a cylindrical 'c'asinghaving a relatively large crosssectional area and a pair of cylindrical connector studs having a relatively small cross-sectional area arranged coaxially with respect to said casing and projecting from opposite ends thereof, said pair of connector studs being hollow at least in part to increase the ratio of surface to crosssectional area thereof, and a fuse holder oomprising a pair of substantially L-shaped brackets, each of said pair of brackets being arranged with one shank thereof in a pair of parallel planes spaced a distance slightly in excess of the length of said spaced casing of said fuse, each of said pair of brackets being arrangecl'with another shank thereof in a common plane, each shank of said pair of brackets arranged in said pair of parallel planes being formed by a substantially equilateral square block substantially equal in length to the diameter of said casing of said fuse, said block forming a divided bearing substantially equal in diameter to the diameter of one of said pair of connector studs and in cooperative engagement with said one of said pair of connector studs, each shank of said pair of brackets arranged in said common plane being provided with a plurality of transverse bores adapted for attachment thereof to a system of spaced bus bars.

8. A structure including a cartridge type high current-carrying capacity fuse comprising a casing having a relatively large cross-sectional area and a pair of coaxial cylindrical connector studs having a relatively small cross-sectional area projecting from opposite ends of said casing, and a pair of solid metal blocks each defining a sleeve for receiving one of said pair of connector studs, each of said pair of metal blocks being divided by a slit extending radially with respect to said pair of connector studs and each said pair of metal blocks being provided with a pair of clamping screws arranged symmetrically with respect to the common axis of said pair of connector studs and at right angles with respect to said slit in each of said pair of metal blocks to press each of said pair of metal blocks against one of said pair of connector studs.

FREDERICK J. KOZACKA.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 746,050 Downes Dec. 8, 1903 1,197,957 Sachs Sept. 12, 1916

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