US2959652A

US2959652A - Electric fuse

Info

Publication number: US2959652A
Application number: US796599A
Authority: US
Inventors: William A Gaskill; William H Russell
Original assignee: SOUTHERN STATES EQUIPMENT CORP
Current assignee: SOUTHERN STATES EQUIPMENT Corp
Priority date: 1959-03-02
Filing date: 1959-03-02
Publication date: 1960-11-08
Anticipated expiration: 1977-11-08

Description

Nov. 8, 1960 W, A. GASKILL ETAL ELECTRIC FUSE Filed March 2, 1959 INVENTOR. FIG. 3 W/LL/AM A GASK/LL W/LL/AM H RU SELL va/; W

ATTOR NEY United States Patent ELECTRIC FUSE William A. Gaskill, Hampton, and William H. Russell,

Forest Park, Ga., assignors to Southern States Equipment Corporation, a corporation of Georgia Filed Mar. 2, 1959, Ser. No. 796,599

3 Claims. (Cl. 200--127) This invention relates to electric fuses and more particularly to electric fuses which are especially adapted to interrupt a wide range of fault currents.

In electric fuses of the type in which an outer shell houses a fusible element it has been the practice to arrange a biasing means to react against the shell and against one end of the fusible element in such a way as to aid in ejecting the one end of the fusible element upon rupture of the fusible element during a circuit interrupting operation. Such fuse ejecting operations facilitate interruption and, in addition, serve as insurance against the retention of both ends of the fusible element within the housing structure immediately following a circuit interrupting operation. By ejecting one end of the fusible element after circuit interruption the possibility of having the circuit reestablished is minimized or eliminated. The structure using the biasing means above described sometimes fails to interrupt the circuit during low current conditions due to the fact that low currents generate very low pressures resulting in poor scavenging of the fuse housing structure.

A principal object of this invention is the provision of an improved fuse structure wherein means are provided for promptly and quickly ejecting one end of a fusible element from within its fuse tube and wherein means are provided for facilitating interruption during low fault conditions.

Still another object of the invention is the provision of an improved high voltage electric fuse wherein means are provided for facilitating interruption during low faults and which'means also operates promptly to eject one end of the fusible element from the fuse tube after the performance of a circuit interrupting operation.

The invention in one form as applied to an electric fuse comprises a fuse tube, a fusible element mounted within the fuse tube and having one end of the fusible element secured within the fuse tube, a closure element disposed adjacent one end of the fuse tube and arranged normally to constitute closure means therefor, and a releasable biasing element operably related with the free end of the fusible element and with the closure element, the releasable means being effective to hold the closure element in its tube closing position for a short time after circuit interruption and which is operable shortly thereafter to aid in ejecting the free end of the fusible element from within the fuse tube.

The invention will be better understood from the following detailed description taken in conjunction with the accompanying drawings in which Fig. 1 is a side view of a conventional power fuse to which the invention is applied; Fig. 2 is an enlarged view partially in section of the lower end of the fuse tube and its mounting structure shown in Fig. 1 but with certain elements removed for 2,959,652 Patented Nov. 8, 1960 ICC clarity; Fig. 3 is an enlarged cut-away view partially in section of the lower end of a fuse tube to which the invention has been applied and which shows the essential features thereof in their normal closed circuit positions before the beginning of an interrupting operation; and in which Fig. 4 is a view similar to Fig. 3 but which shows the parts in the positions which they occupy during the performance of a circuit interrupting operation.

With reference to Fig. l, the numeral 1 denotes a base structure such as a metallic channel member adapted to be mounted on suitable supporting structure. AffiXed to the upper end of channel support 1 is an insulator stack 2 while a similar insulator stack 3 is affixed in known fashion to the lower end of channel 1. Secured to the right-hand end of insulator stack 2 is a terminal element 4. Terminal element 4 is mounted to insulator stack 2 by means of a plurality of bolts 5 and a terminal pad 6 by which connection is made to the circuit controlled by the fuse is integrally formed with terminal structure 4. Pivotally mounted to the right-hand end of terminal element 4 is a sleet hood 7, the pivotal connection between hood 7 and terminal element 4 being by way of the pivot pin 8. As is well understood in the art, the sleet hood 7 is provided on the interior surface thereof with a latching surface not shown in the drawings. This latching surface formed within the sleet hood 7 engages the left-hand extremity of terminal structure 9 secured by a pressed fit and by means of pin 10 to the upper end of fuse tube 11. As is wellunderstood in the art, the terminal element 9 may be provided with a ring structure 12 through which the end of a hookstick may be inserted for operation and handling of the fuse. Furthermore, if desired, the upper end of the fuse tube 11 may be provided with a releasable closure element generally designated in Fig. l by the numeral 13. If desired, this releasable closure element 13 could be constructed in accordance with the disclosure of patent application Serial Number 663,479, filed June 4, 1957, by Olan Richardson which issued as Patent 2,903,538 and which is assigned to the assignee of this invention.

Secured to the lower end of the fuse tube 11 is terminal structure generally designated by the numeral 14. This terminal structure 14 is secured to the fuse tube 11 by a pressed fit and by a suitable fastening pin such as is designated by the numeral 14A in Fig. 3.

As is shown in Fig. l, the lower end of the fuse tube 11 and its associated terminal structure 1.4 is mounted on the terminal element 15 secured by a plurality of bolts 16 to the right-hand end of the insulator stack 3. Formed integrally with the terminal element 15 is a terminal pad 17 by which connection is made in known manner to the circuit controlled by the fuse tube. If desired, the fuse shown in Fig. 1 may be provided with a buffer device 13 which is mounted in known fashion on the terminal element 15 and which acts to arrest the downward swinging movement of the fuse holder 11 and parts associated therewith during a circuit interrupting operation.

As is best shown in Fig. 2, a conducting element 19 is connected by a pivot pin 20 to the terminal element 14. Furthermore, as is shown in Fig. 2, the conducting element 19 is provided with a pair of trunnions 21 which engage a pair of spaced jaws 15A constituting essential elements of the terminal element 15.

As is well understood in the art, the conducting element 19 is held in the position shown in Fig. 2 by means of the fuse link 22 which is secured by bolt 23 to the conducting element 19, the other end of fusible element 22 being in contact with terminal structure 9 as is well known. Thus so long as the fusible element 22 disposed within the fuse tube 11 is intact the conducting element 19 is held in the position indicated in Fig. 2.

The circuit between terminal element 15 and conducting element 1.9 is maintained by conducting brush 24 which is secured to terminal element 15 by the bolt 25 and which engages the surface 14A of conducting element 19.

When the fusible element 22 ruptures duringa circuit opening operation the conducting element 19 swings in a clockwise direction about the trunnions 21 and the lower end of the fuse tube 11 moves downwardly and somewhat to the right as swinging movement about pin 20 occurs. Shortly thereafter the latch at the upper end of the fuse tube between the terminal structure 9 and the sleet hood 7 is released and the entire assembly associated with the fuse tube 11 swings clockwise about the trunnions 21 to establish a circuit interrupting gap between terminals 6 and 17.

As is well known, the fuse tube 11 constitutes an outer shell of insulating material 11A and an inner fiber liner 11B. i i

In accordance with a feature of the invention the lower end of the fuse tube 11 may be counterbored as is indicated by the numeral 26. Secured within the counterbored portion 26 of the fuse tube is a disc-shaped closure means 27 which is freely slidable on the fusible element 22 due to the fact that the disc 27 is provided with a centrally disposed opening through which the fusible element 22 extends and which is larger than the fuse link. Disposed to engage the lower surface of the closure ele ment 27 is a compression spring 28 the lower end of which engages the flange 29 of a ferrule 30 which is secured to the fuse link 22 by indenture means designated at 31 or by other suitable known means.

Thus as is shown in Fig. 3, the closure element 27 is biased upwardly against the shoulder 26A by the helical spring 2% the lower end of which is held in position by the fiange 2% of the ferrule 30.

it will be understood that when the fuse link 22 is ruptured due to over-current conditions for example, the helical spring 23 promptly expands causing the ferrule 29 and the lower end of the fusible element 22 to be drawn downwardly to the positions of the parts as indicated in Fig. 4. During this initial portion of a circuit interrupting operation the closure element 27 is maintained securely in its tube closing position against the counterbored shoulder 26A. Thus if the interrupting current is of a low order of magnitude the tubewill remain closed and, for at least a short time, sufiicient pressure will be developed within the interior of the fuse tube 11 to aid substantially in interrupting such low fault currents. In this way interruption of low currents is materially facilitated according to a feature of the invention. A

After interruption, spring 28 acts as an ejecting means thereby quickly to withdraw the entire lower end of the fusible element 22 and to eject it from the lower end of the fuse tube 11. Of course the closure element 27 ordinarily is blown out of the lower end of the fuse tube by the pressure generated by the are being interrupted.

In the case of high voltage fuses the fusible element .22 is quite long and may tend to clog up the lower end of the fuse tube and thereby to interfere with efiicient ejection of the lower end of the fusible element 22. In this connection, and according to a feature of this invention, the biasing element 28 aids considerably in ejecting the lower end of the fusible element by exerting a downward pull thereon thereby effectively to prevent wadding of the fusible element within thelower portion of the fuse tube 11.

Should the fuse be called upon to interrupt high current arcs, ejection of the lower end of the fusible element 22 is facilitated. When 'a high current are is .formed within the fuse tube :a large pressure is quick- 1y generated and bears against the upper surface of the closure element 27. Such pressure may cause the closure element 27 to move downward quickly but in such event this downward movement tends to compress the helix 28 thereby aiding in ejecting the lower end of the fusible element 22.

While we have shown and described a particular embodiment of the invention we do not wish to be limited thereto and intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. A high voltage electric fuse comprising a fuse tube of insulating material having fault responsive gas emitting material along at least a part of its inner surface, a fusible element disposed within said tube, said fusible element having one end thereof secured within said tube and having the other end thereof extending toward an end of said tube, said fusible element being flexible and being of such size as to occupy a substantial part of the space within said tube and having a tendency to clog in said tube during low current faults, closure means normally closing the said end of said tube, and yieldable biasing means normally reacting between said fusible element and said closure means and. normally effective to maintain said closure means in its tube closing position, said biasing means being interrelated with said fusible element and closure means so as to aid in ejecting said other end of said fusible element from said tube in coordination with the performance of a circuit interrupting operation by said fusible element and being effective to react against said fusible element during low current faults so as to maintain said tube in sealed condition for a brief period following rupture of said fusible element to allow an effective are quenching pressure to build up in said tube.

2. An electric fuse comprising a fuse tube of gas emitting insulating material, said tube being counterbored at one end, a fusible element disposed within said tube, said fusible element having one end thereof secured within said tube and having the other end thereof extending toward said one end'of said tube, said fusible element also being flexible and having a tendency to clog in said tube particularly during low current faults, closure means disposed within the counterbored end of said fuse tube and normally closing'the said end of said tube, and biasing means normally reacting between said fusible element and said closure means and normally effective. to maintain said closure means in its tube closing position, said biasing means being positioned relative to said fusible element and to said closure means so as to aid in ejecting said other end of said fusible element from said tube in coordination with the performance of a circuit interrupting operation by said fusible element and being effective to react against said fusible element during low current faults so as to maintain said tube in sealed condition for a brief period following rupture of said fusible element to allow an effective arc quenching pressure to build up in said tube.

3. Anelectric fuse comprising a fuse tube of insulating material, said tube being counterbored at one end, a fusible element disposed within said tube, said fusible element having one end thereof secured within said tube and having the other end thereof extending toward said one end of said tube, said fusible elementbeing flexible and of such size as to occupy a substantial part of the space within said tube, closure means disposed within-the counterbored end of said fuse tube and normally closing the said end of said tube, said closure means being disc shaped and having an opening therethrough through which the said other end of said fusible element extends in slidable relation, and low inertia releasable means arranged normally to engage said closure means and effectjiye normally to hold said closure means inits tube closing position, said releasable means being operable References Cited in the file of this patent upon rupture of said fusible e1ement to release said UNITED STATES PATENTS I closure means from 1ts normal tube closing position only after a brief time delay period following rupture of said 2043O24 Wflhams June 1936 fusible element upon the occurrence of a low fault cur- 5 2450102 f 1939 rent condition and being effective promptly to release 22081440 Wlulams Juy 1940 said closure means from its tube closing position upon 2281795 Plttman et a 1942 the occurrence of a high fault current condition and said gg' r zz g releasable means being effective to aid in ejecting said other end of said fusible element following interruption. 10