US1740699A

US1740699A - Electric fuse

Info

Publication number: US1740699A
Application number: US252439A
Authority: US
Inventors: Murray Joseph Bradley; Jr Thomas E Murray; John F Murray
Original assignee: Individual
Current assignee: Individual
Priority date: 1928-02-07
Filing date: 1928-02-07
Publication date: 1929-12-24
Anticipated expiration: 1946-12-24

Description

Dec. 24, 1929. T. E. MURRAY v1,740,699

l ELECTRIC FUSE Filed Feb. 7, 1 928 wuemtoz 'o/w15 Ef MHRA r.

Patented Dec. 24, 1929 uNilri-:o STATES y PATENT" oFl-ICE- THOMAS E. MURRAY, OF BROOKLYN, YORK; JOSEPH BRADLEY MURRAY, THOMAS E. MURRAY, JR., AND JOHN F. MURRAY, EXECUTORS SAID THOMAS E. MURRAY,

- 'DECEASED ELECTRIC FUSE The invention aims to provide certain improvements in fuses designed particularly for high voltages but applicable also for ordinary Fig. 3 is a vertical section of amodiii-ca-Y tion.

Fig. 4 is a similar-section of another modi fication.

.Referring to the drawings the `fuse strip'or element 1 is provided at an intermediate point in its length with a portion 2 of reduced cross section to form a localized blowing oint. Near the blowing point, according to Figs. 1 and 2, are heads or plungers 3, one on each side, separated from each other Iby a slight space. Theseplungers are adapted tok move freely in a cylinder preferably composed of an inner insulating tube 4 of fibre and an outer tube 5 of stronger material such as iron or steel to withstand the force of the explosion. The heads 3 may be of ber, heattreated wood or other suitable material. When the fuse Ablows or burns out at the narrow part 2, the (gas vgenerated therein will separate the hea s 3 forcibly and ly forcing one or both of them so rapidly out of the open ends of the tube that any arc formed at the blowing point will be unable to follow the widely separated parts of the fuse strip. The strip'may be fastened in the plungers 3 in any suitable way. For greater security they may be bent as at 6, Fig. 2, be-

- fore being imbedded in the heads. The outer portions may be curved as at 7 to vyield more easily to the force of the explosion.

v The chief diiiicultyinvolved in the use of fuses on high voltage circuits isa tendency of the current to form and retain an arc between the burned ends of the fuse, with generation of large quantities of gas. The imbedding of the ends of the sections in the romptheads or plungers as shown diminishes the dangerous possibilities in this direction. The arc will not follow the fuse strip for any substantial distance into the heads. Particularly will it be stopped by .the crooked direction of the fuse strip in the head as shown in Fig. 2. Furthermore the location of the heads 3 in the cylinder 4 produces a piston or plunger effect and a Wide separation of the ends of the strip after a blow and thus further reduces the chance of'establishing or maintaining an arc.

In a previous patent of Thomas E. Murray,

Jr., No. 1,120,226, dated December 8, 1914,

a fuse is shown so arranged that the as generated upon a blow will force the en s of the two sections apart. A similar operation is o btained in thepresent case, with the addition of the heads 3 with a confined space between them which will cause the gas pressure to throw the heads violently apart, and with the additional protection provided by the imbedding of the ends of the broken strip in the heads, and particularly the crooked shape of the strip in such heads. y

The space for confining the gases may be .closely restricted, as in the Murray patent referred to above; or the clear space bet-Ween the heads 3 may be somewhat greater, as in the present drawings, equal to or slightly in excess of the length of the restricted portion of the fuse strip, giving more room' for the generation of gas.

The tube in Fig. 1 is carried on the to of a post 8 of insulating material. The use strip passes up from terminals 9 at the bottom of the post, to the top of the same and around and into the open ends of the tube 5. Thus, we have a repulsion effect between the two parts lO-and 11 of the fuse or conductor on opposite sides of the porcelain or other non-conducting post 8 as described in a atent of Thomas E. Murray,` Jr., No. 1,0 3,619 dated September 23, 1913, which itself tends to throw the ends of the fuse apart when the reduced portion thereof burns through. In addition, we have plenty of room for the heads or pistons when they are thrown apart. The apparatus is carried in a case with a bottom 12,side walls 13 and top 14 which may be of wood, for example, and plates 15 of wood are located on the inside in position to receive the blow of the expelled plungers 3 with metal reinforcing strips 16 on the outside. When a blow occurs the pistons and the ends of the fuse will be blown out against the parts 15 and to approximately the positions indicated in dotted lines; thus effecting a quick and Wide separation of the ends of the fuse. l/Vith such an arrangement on a 15,000 volt current of 25 cycles, using a 200 ampere fuse, I have opened the circuit in from three to iive cycles; the tube in this case being two and one-half inches in diameter and eighteen inches long. And with a ampere fuse I have opened the same circuit in half a cycle.

Instead of using two movable heads or plungers 3, a single such plunger may be used, as in Fig. 3, lconlining the gas by a iixed abutment 17 at the opposite side of the reduced section 2 of the fuse strip. The abutment 17 is iixed in the upper end of a tube 18 of non-conducting material, the latter being strengthened by a metal cap 19. The lower end of the strip 1 is bent laterally as at 20 to facilitate the easy expulsion of the plunger with the portion of the strip to which it is attached.

rlllhe plunger does not need to tit tightly in the tube. In Fig. 3,1 have illustrated a somewhat greater' clearance than in Fig. 2. rIhe closeness of iit required for practical success depends on the capacity and voltage o1t` the fuse and also on the length oit the plunger. If the plunger is long, the fit need not be so good as when the plunger is comparatively short. It must be such that the plunger is expelled from the tube, carrying with it the attached part of the fuse strip. This aim is facilitated by permitting the plunger to move easily through the tube, and also by the vertical arrangement of Fig. 3 with the plunger below thecontracted portion of the strip and with the lower end of the tube open and the strip bentaround out of the vertical line.

With this design, I have obtained satisfactory tests under short circuit conditions at 6600 volts and with fuse capacities up to 100 amperes. I have also operated this same gen eral type at 11,000 volts and have opened short circuit loads the equivalent. of 150,000 kw. These fuses may, therefore, be used as substitutes for circuit breakers of the complicated types now generally thought necessary on lines carrying heavy loads.

The vertical arrangement of Fig. 3 gives this advantage, that the single movable lunger is expelled in a downward direction. ut a doubleended tube, like that of Fig. 1, for example, may also be used efficiently in a vertical position expelling one plunger downward and the other upward. Such an arrangement is shown in. Fig. 4. In addition this figure shows a modification in the shape of the plungers 3. One or both of these plungers is formed on its inner face with a recess 20. The plungers are brought face to face. Thus the recesses 20 provide a more limited space than is allowed in the previous constructions where such spaces are of the full cross section of the plungers. The same method of restricting the space may be applied to the other constructions illustrated.

By expelling the plungers, with the ends of the burned fuse, to an unlimited distance the circuit cannot be reestablished, as might be the case, particularly -on high tension lines, where the ends of the burned fuse remain within a distance from each other which is limited by the ends of the casing. 'Ihe blowing of the fuse fills the space with a vapor ot' the metal which is highly expansible and conductive and will, therefore, immediately reestablish tlie circuit if the tension therein be great enough to itorm an arc of this gas. rIhis is particularly true'where the separated pistons remain in a casing from which the gas cannot escape or can escape only slowly.

The space between the plungers or abutments is regulated according to the character of the fuse metal and the volume of gas which will be generated. rIlhe plungers will limit the fuse metal gasified to that portion located betweentheir adjacent faces, with allowance for the gasification of a portion extending slightly into the plungers. There must be enough gas generated to move the plungers promptly and swiftly out of the casing or to a distance Well beyond that 'through which the calculated volume of gas will carry 10c the current by an arc. Any excess or' gas beyond that needed is objectionable because of its highly conductive character. The movement of the plunger or plungers should be substantially free so as to oppose no resistance to the explosive elfect of the gas and to permit operation with a minimum quantity of gas.

The space in which the fuse element is exposed is made so slight in proportion to the current carried that the consumption of all the fuse metal in this space is assured. And further consumption beyond the determined amountiis prevented by the pistons as above explained, so that the amount of metal to be consumed is regulated by the length of such space. v

The ends of the case are a considerable distance beyond the plunger. This guides the plungers and gives a prolonged pressure driv- 12o ing the plungers with an accelerating velocity. It also confines the highly conductive gas, or metal vapor, for a substantial distancebeyond the blowing point, so as to prevent its spreading to conductorsl at the opp osite end of the tube and making a short circuit.

various other modifications than those described may be made by persons skilled in the art without departure from the invention as dened in the following claims.

What I claim is: 'l 1. A fuse comprising anopen-ended case, a plunger within said case at a substantial distance from its end, an abutment, a fuse element engaged by said plunger and having a blowing point between the abutment and the plunger so that the gas generated by the blowing of ,the fuse isconiined, the case being unobstructed vfrom the plunger` tothe end of the case so that the plunger withits engaged portion of the fuse element ismoved promptly and swiftly away from the blowing point and is permitted to mgve freely through `the case and out of the/open end thereof when the fuse blows. v 2. A fuse comprising a case open at opposite ends, plungers within said case, av fuse element engaged by said plungers and having a blowing point between them sc thatthe gas generated by the blowing of the fuse is confined between said plungers, the case being unobstructed from 'the plungers to the ends of the case so that the plungers with their engaged portions -of the fuse element, are moved promptly and. swiftly away from the blowing point and through the case and out of the open ends thereof when the fuse blows.A

3.- A fuse comprising a case, a fuse element having a blowing point, a plunger in which the portion of the fuse element near the'blowing point is encased and an abutment 'separated from the face of said plunger by a distance less than the diameter of the plunger permit the plunger to move freely through f t e and out of the case on the blowing'o fuse.k v

' .4. A fuse comprising an open-ended case,

. to .move freely throughthe lcase and out of a plunger within saidcase, an abutment, a

fuse element engaged by said plunger andv having a blowing p oint between the abutment andthe plunger vso that the-gas generated by thev blowing of the fuse is confined and the plunger, with its engaged portion of the fuse element, is moved promptly and swiftly away from the blowing point and is permitted the open end thereof when the fuse blowsand areceptacle for the blown plunger outside of said case. l

5. A fuse for opening wan electric circuit, comprising a fuse element having a blowing point, means whereby the blowing of the fuse will displace the ends of the fuse element adv j accnt tothe blowing point to such a distance that .the circuit cannot beA re-established by --the passage of the current through the gas generatedy and'means for confining suchgas tity of gas.

`v for a substantial distance beyond the blowing point of thefuse.

6. A fuse for opening an electric circuit, comprising a fuse element having a blowing point, a plunger engaging the fuse element near the blowing point, means for displacing said plunger with'its portion of the fuse element upon the blowing of the fuse to such a distance that the circuit cannot be re-established by the passage of the current through the gas generated, andmeans for confining such gas for a substantial distance beyond the blowing pointof the fuse.

-7. A fuse comprising a case, a plunger within the case, .an abutment,a fuse element engaged by said plunger and having a blowing Vpoint between the abutment and the plunger, the portion of the fuse element between the abutment and the plunger being restricted so that the gasification thereof will be just suilicient to move-the plunger prompt- `ly and swiftly away from the blowing point to such a distance that the circuit cannot be re-established by the passage of the current throughv the gas generated, the movement of the plunger being substantially free so as to require the generation of a' minimum quan- 8. A fuse comprising a case, a plunger withinsaidcase, an abutment, a fuse element engaged by said plunger and having a blowing point between the abutmentand the plunger, the movement of the plunger being substantially free and the explosive effect of the gas generated by the blowing of the fuse being substantially unresisted so that when.

the fuse blows'the plunger with its .engaged portion of the fuse element is moved promptly and swiftly away from they blowing point o such a distance that the circuit cannot be liet-established by the passage of ,the current t`` rough the gas generated.

9. The fuse of claim 1, the pistonand the abutment being face',l to face with a recess in one of them-in which the blowing point of 'the fuse element lies. A 10. A fuse forautomatically opening an electric circuit carrying a h igh tension c urrent andmeans for automatically displacing the burned ends of the fuse element on the blowing of the. latter to such a distance as to prevent the rea-establishment of such current,

through a considerable distance during Asuch displacement. g

11. A fuse comprising `a fuse element, a l

plunger in which the fuse element is partly encased'andan abutment separated from the and means for guiding the displaced ends the amount of metal to be eonsumedis regulated by the length of said space.

12. A fuse comprising an open-ended case, a plunger within said ease, an abutment, a fuse element engaged by said plunger and having a blowing point between the abutment and the plunger, the plunger being held in position by the fuse element alone so that.

the gas generated by the blowing of the fuse is confined and, when the fuse blows, the plunger with its engaged portion of the fuse element is moved promptly and swiftly away from the blowing point and out. of the open end of Jche ease. v

In witness whereof, I have hereunto signed my name.

THOMAS E. MURRAY.