US1152147A - Electric fuse. - Google Patents

Description

c. w. DAVIS.

ELECTRIC FUSE.

' APPLiCATION FILED APR.22. 1913. 1,152,147. Patented Aug. 31, 1915.

L 6 6 I, r

l 7 I 8 1o 8 i9 v 20 1 t 21 {6 9 T -i ri Q UNITED STATES PATENT OFFICE.

CHARLES. 'W'. DAITIS, OF EDGEWORTH, PENNSYLVANIA, ASSIGNOIR. TO STANDARD UNDERGROUND CABLE COMPANY, OF PITTSBURGH, PENNSYLVANIA, A COR,-

I PORATION E PENNSYLVANIA.

ELECTRIC F SE.

Specification of Letters Patent.

Application filed April 22, 1913. Serial No. 762,8 8 6.

To all whom it may concern .Be it known that I, CHARLES W. DAVIS,

. residing at Edgeworth, in the county of Allegheny and State of Pennsylvania, a citi- .zen of the United States, have invented or discovered a certain new and useful Imous; and has particularly to do with fuses used in connection with high voltage currents.

It is sometimes desirable that the fusible portion 'of the current carrying element be relatively short to the end that there will be a minimum amountof resistance to the current and hence a minimum loss of energy due to such resistance. On the other hand it is desirable that upon the blowing of the fuses the distance between the unconnected ends of the conducting element be relatively large so that arcing may be speedily stopped.

To embody these desirable features in fuses it has been suggested to impose a tension on the fuse strip, so that, when the short fusible element blows, the adjacent ends of the strip will rapidly separate and widen the arc gap. In fuses for high voltage and low amperage currents the fusible. element must, particularly when surrounded by an arc-dampening liquid, be very small in cross-section and hence of low tensile strength, so that, when heated, it is llable to rupture under its tensile strain before its rated current-carrying capacity has been reached. Y

With these considerations in view it is the object of my present invention to provide a fuse structure wherein the conduct 'ing element is free from tensile stress, but is of such a character, so far as its physical properties or shape is concerned, that its end connected to such fusible portion, will be bodily moved away from its normal position by the exploslve force generated by the blowing of the fusible portion, such conducting element being surrounded by a cis- I 'ing adapted to direct said explosive force along the general line of the ducting element.

In the accompanying drawing, which forms part of my specification, I have illustrated two embodiments of my invention.

unfused con- Patented Aug. 31, 1915.

Figure 1 of the drawing is a vertical sec-.

tional view of a junction box having two terminal-provided cables entering therein, and a fuse connecting them, the casing for such fuse being shown partly in longitudinal section and partly in elevation; Fig. 2 is an end elevation of the fuse structure, the plane of view being indicated by the line II.II, Fig. 1; and Fig. 3 is a longitudinal sectional view of a second form of fuse.

Like numerals are used to designate like parts.

While my invention is not limited to fuses immersed in an arc-dampening liquid such as oil or carbon tetra-chlorid, the forms shown herein are particularly well adapted for such use. Accordingly the fuse structure is shown in a junction box casing 1 filled with an arc-dampening liquid up to the level indicated by the line 2. Each entering cable 3 is provided with a suitable terminal structure 4, which has at its outer end a knife-blade contact clip 5, and extending from each side of the terminal there is a guide post 6. Y

The complete fuse structure, as shown in Figs. 1, and 2, comprises a suitable frame or handle 7 of insulating material, having a yoke or groove 8 ateach-end adapted to fit around the guide posts -6, and provided at its lower edge with knife blade, contacts 9 adapted to t into the contact clips 5. Extending laterally from and electrically connected to the knife blades 9, are arms 10, each provided at its outer ends with laterallyprojecting ribs 11 and with a binding post 12. An open ended fuse casing 13 extends over and is supported by theribs ll'and the fuse strip 14, 15 is connected at its opposite ends to the binding posts 12.

As stated above the conducting.eleinent consists of two portions, a low fusion portion and adjoining it a flexible high fusion portion, which is readily distortable by the explosive or blowing force of the low fusion portion. In the particular embodiments of my invention illustrated herein, the low fusion portion 14 is centrally disposed within pressure-resisting faces in the path of the fuse-explosion chamber. are preferably placed on and borne by the portion 15 near the ends of thefusible porexplosive force, and the central portion 14 being narrower than said end portions, and

consequently of less current-carrying capacity than the end portions. Itwill readily be seen that, when the portion Hfuses, the gas of fusion confined by the casing wall will exert its pressure upon the several faces of end portions 15 and cause their unconnected ends to rapidly move toward the end openings of the casing, thus diminishing the liability of ,a continuing arc.. In Fig. 3 the portions/15 consist of very flexible stranded conductors, which will likewise be forced toward the ends of the casing 13 upon the blowing of the fusible portions 11, such fusible portion consisting either of one or more strands of such conductors, or of a separate conducting element electrically 30 connected to the ends of the portions 15.

In order to increase the conductor-moving effectiveness of the explosive force of the fuse, means may be provided within the casing and'surrounding the conductor strip for resisting such force. To such an end'two' abutments 16, preferably formed of a suitable insulating material, are borne by the strip 14, 15 of Fig. 1, such abutments being readily movable through the casing 13, and forming with the wall thereof a These abutments tion 14. In the embodiments of my invention illustrated in .Fig. 3 substantially the same end is obtained by securing an abutment 16 to the casing 13 at the center of and surrounding the fuse portion 14 In addition to directing the explosive force toward each end of the casing 13, the abutment 16 is also effective to dampen out or diminish the size of the are formed when the fuse blows. In each embodiment of my invention it will be observed that the conducting ele'ment is unstressed, or, in other words, free from tensile strain during the normal operation of the fuse.

While, as stated-above; the fuse structures shown herein are particularly well adapted for use in a junction box partly filled with an arc-dampening liquid, my invention may be advantageously employed in fuses wherein the fusible portion is not surrounded by such aliquid. For example, in the fuse particularly illustrated in Fig.

1, the fuse-explosion chamber formed by the central portion of the casing 13 and the abutment 16 may be filled with an inert material, such as slaked lime or magnesia; and, in case such inert material tends to become incandescent upon the blowing of the low fusion portion 11 of the conductor, the gas generated would rapidly separate said abutments and thus widen the gap between ing the force of the expelled liquid and for deflecting such liquid away from the casing opening and into the body of liquid withinthe box.

The means to this end, which I have illustrated herein, comprise deflecting bells 17, preferably formed of insulating material and secured to bars 18, which are yoked together by means of rods 19, the

entire structure being suitably supported in the junction box by means of brackets 20. Each bell is placed with its concave side toward the casing opening, and is provided with a central tapering projection 21, the point thereof being in line with the center of the casing opening so that the expelled liquid will be turned away from such opening.

The operation of the fuse will be readily understood from its foregoing description. During the normal operation of the fuse, when submerged in a liquid, such liquid circulates through the open-ended casing, thu keeping the strip cool; the abutment 16 being small enough to permit of such circulation. If desired, however, the casing 13 may be provided with small openings 22 in order to facilitate the circulation of the liquid. In case the portion 14 blows, the liquid, being relatively non-compressible, materially aids in the forcing of the free ends of the portion 15 away from each other. After the fuse blows the entire fuse structure may be readily removed by grasping the handle 7; and, structure to its operative position, the guide posts 6 are of a substantial advantage.

I claim as my invention: p

1. In an electric installation, the combination of a junction box, a pair of cables entering therein'each provided with a ter- .minal structure, each of said terminals being provided with a contact element and with guldes, and a removable fuse structure in returning the fuse 4 adapted to electrically unite said terminal contact elements, said structure having as parts thereof guideways adapted to engage said terminal guides.

2. In an electrical installation, the combination with a junction box, and electrical conductors therein, of a fuse strip electrically uniting two of said conductors, a casing surrounding said fuse-strip and provlded with an expulsion opening, said casing and its contained conductor being submerged in an arc-dampening liquid, and.

means interposed between said casing opening and a wall of said junction box for resisting the force of the fluid expelled from said casing-opening upon the blowing of said fuse strip. I

3. In an electrical installation, the combination with a junction box, and electrical conductorstherein, of a fuse strip electrically uniting two of said conductors, a casing surrounding said fusestrip and provided with an expulsion opening, said junction box being filled with an arc-dampening fluid above the level'of said fuse. casing, and V Y a single means interposed between said casing opening and a wall ofsaid junction box for resisting the force of the fluid expelled from said casing-opening and for deflecting said expelled fluid away from said casingopening upon the blowing of said fuse strip.

4. In; an electric fuse, the combination of a conducting strip comprising an unstressed low fusion portion and an adjoining flexible and readilydistortable high fusion portion, a casing surrounding said strip and provided with an expulsion opening, the flexible portion of said strip being movable toward said opening solely by the explosive force generated by the blowing of said low fusion portion, and means for preventing said flexible portion, when thus moved, from being expelled from the casing.

In testimony whereof I I have hereunto set my hand.

CHARLES w. DAVIS.

Witnesses:

PAUL N. CRITGHL W,

FRANCIS J. ToMAssoN.

Images