US2821604A - Fuse constructions - Google Patents

Description

Jan. 28, 1958 J. M. WALLACE 2,321,604

' FUSE qonsmucnons S 4 Sheets-Sheet 1 Filed Nov. 29. 1952 WITNESSES: INVENTOR 9/ 1 LX James M. Wallace %1/ (F1; @(r 4 WW ATTORN Jan. 28 1958 u, M. WALLACE FUSE consmuc'nons Filed Nov. '29. 1952 INVENTOR James M. Wallace Material ATTORNEY strain-wire construction, which r 2,821,604 Ice Patented Jan. 28, 1958 FUSE CONSTRUCTIONS James M. Wallace, Montclair, N. J., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application November 29, 1952, Serial No. 323,185 2 Claims. (Cl. 200135) 'IIhis invention relates generally to circuit-interrupting devices, and more particularly, to fusible interrupting devices adapted to automatically interrupt a circuit upon the passage therethrough of currents of a predetermined magnitude.

-A primary object of my invention is to provide an improved fusible interrupting device which will be more economical to manufacture than those heretofore used in the industry, and, more important, which will be more effective and eflicient in operation.

A more specific object of my invention is to provide a novel fuse link which will have an improved strain-wire construction.

It is well known in the art to parallel the fuse, in a fusible interrupting device, with a strain wire, the latter havlng a relatively high tensile strength to hold in tenslon a retracting spring, fuse terminals upon the fusion thereof. The retracting spring, which is under tension, rapidly separates the fuse terminals and sobrings about a greater contact of the es- .tablished are within the interior of an enclosing tube, within which the fusible device is housed. Generally, the interior walls of the housing or fuse tube evolve an arcextinguishing gas upon contact with the arc drawn upon fusion of the device.

Since the tensile strength of the fuse itself is relatively low, it is common practice to relieve the fuse of such tensile stresses by the employment of the parallel-disposed strain element, the latter furnishing the high tensile strength required to maintain the retracting spring under tension.

Prior art constructions of this type have been rendered ineffective and subject to faulty operation by the strain elements breaking under normal conditions due to mechanical failure, or being improperly secured to the fuse terminals. Since fusible devices are a high quantity" production item, it is necessary to provide a construction adapted for rapid assembly, and which will make allowance forany errors which may occur during the assembly ,operation by the human factor. Accordingly, it is a further object of myinvention to provide an improved not only will be effective, maintain its tensile strength, avoid the possibility of being .misassembled, but will also be economical to manufacture.

out, depicted in the fused condition;

Fig. 2 is an enlarged, fragmentary, vertical sectional view through the open-link fuse employed in the construction illustrated in Fig. 1;

Fig. 3 is a view taken at right angles to Fig. 2; Fig. 4 is an enlarged view of the fuse proper of Fig. 3,

:to more clearly indicate the method of attachmentof myimproved strain clip; Fig. 5 is a plan view of the strain clip in blank form;

which serves to separate the Fig. 6 is a side elevational view of the strain-clip blank after preforming operations have taken place;

Fig. 7 is an end view of the strain clip of Fig. 6;

Fig. 8 is a plan view of the fuse proper;

Fig. 9 is an edge view of the fuse shown in Fig. 8;

Fig. 10 is a vertical, sectional View through a fuse holder having therein a fuse-refill unit incorporating features of my invention; 7

Fig. 11 is an enlarged sectional view of the fuse-refill unit employed in the fusible interrupting device of Fig. 10;

Fig. 11A is a plan view of the strain-clip blank employed in this form of my invention; and

Fig. 12 is a view similar to Fig. 11, but shown at right angles thereto.

Referring to the drawings, and more particularly to Fig. 1 thereof, the reference numeral 1 generally designates an open-link cut-out employing my invention, and

shown in the fused condition. The cut-out 1 includes asupport insulator 2, preferably composed of a suitable weather-proof material, such as porcelain or the like, which is supported in a substantially vertical position as shown,'by amounting plate 3. The mounting plate 3v is secured to any suitable support, such as a cross-bar associated with the top of a distribution pole, not shown.

Secured by a support 5 at the upper end of theinsulator 2 is an upper contact arm 6, preferably formed of a suitable resilient wire, such as a Phosphor bronze wire. The contact arm 6 is, therefore, inherently somewhat resilient, and serves to support, in a return bend 7 thereof, theeyelet 8 of an open-link fuse, generally designated by thereference numeral 10.

Clamped by aclamp 11 to asupport plate 12, at the lower end of theinsulator 2, is a lower or bottomcontact arm assembly 13. The contact arm assembly'13 is formed of wire, preferably resilient and preformed as shown. Again the wire is preferably Phosphor bronze, and the free end of thearm 13 has areturn bend 14, which securely holds thelower contact button 16 of the open-link fuse 10.

As well known by those skilled in the art, theopenlink fuse 10 is mounted in place by the usual hook stick, one prong of which is inserted within theupper loop 17 of thefuse link 10, so that thecontact button 16 may be guided into position withinthereturn bend 14. When this is done, the further upward movement of the hook stick causes thehelical spring 18, integrally formed with thearm 13, to be moved into tension at the same time that theloop 17 is raised upwardly into position within the return bend 7 of the upper contact arm 6.

Upon the occurrence of 'a short-circuit condition in the line connected to theterminals 19, '20, thefuse link 10 will fuse and thelower cable 21 will be released'to permit thelower contact arm 13, under the tension of thespring 18, to withdraw the fuse remnants out of thefuse tube 22, thereby extinguishing the arc and breaking the circuit. When this occurs, a maintenance man must remove theloops 17, 17a from the contact arms 6, l3 and replace thespent fuse link 10 with a new fuse link.

Figures 2-9 more clearly show the internal construction of the open-link fuse 10. Referring to these figures, with particular attention being directed to Figs. 2 and 3 thereof, it will be noted that thefuse tube 22 is of composite con struction, thetube 22 comprising an outer tube 22a formed of a weather-proof material, such as a suitable phenolic condensation product, and aninner tube 22b, which is preferably composed of a gas-evolving material, such as fiber. 1

Disposed at the upper end of thefuse tube 22 is acap 23, which is preferably soldered to theupper cable 24. Hence, thecap 23 closes the upper end of thefuse tube 22 to prevent rain or snow entering therein.

Secured, as by soldering, to the lower end of the "conductingcable 24, constituting afuse terminal 25, is astrain clip 26, the configuration of which is more clearly shown in Figs. 5-7 of the drawings.

Preferably thestrain clip 26 is stamped from sheet material into blank form, as indicated in Fig. 5. Preferably the strain clip is formed of a high-resistance material having the requisite mechanical strength, such as material being a copper-nickel alloy, for example.

Following the blanking operation producing the clip, as shown in Fig. 5, preforrning operations are manipulated to result in thestrain clip 26 assuming the configuration as shown in Figs. 6 and 7. V

It will be observed that thestrain clip 26 has an intermediately disposedstrain strap portion 27 and clampingportions 28 at the opposite ends thereof. Eachclamping portion 28 haslugs 29 which embrace thefuse terminals 25, 30, thelower fuse terminal 30 constituted by the upper end of the conductingflexible cable 21.

As mentioned, soldering operations are performed at each clampingend 28 following the clamping of thelugs 29 about thecables 21, 24. The flexible leads orcables 24, 21 may be formed of a plurality of tinned copper strands.

Soldered to theclamping portions 8, at opposite ends of thestrain clip 26, is afuse 31, more clearly shown in Figs. 8 and 9 of the drawings. Preferably thefuse 31 has abend 32 formed therein so that the entire strain will be taken by thestrain clip 26, and not by thefuse 31. As shown in Fig. 4, it will be noted that with the construction used, the lower sides of the clampingportions 28 of thestrain clip 26 formsuitable surfaces 33, to which theends 34 of thefuse 31 may be soldered.

With the construction shown, upon a fault condition occurring in the circuit, thefuse 31 and the strain-strap portion 27 of thestrain clip 26 will be fused substantially simultaneously, to thereby permit thehelical spring 18 of the cut-out 1 to withdraw thecable 21 and thelower fuse terminal 30 from the open lower end of thefuse tube 22. The are established between thefuse terminals 25, 30 will be brought into engagement with the gas-evolving material of theinner fuse tube 22b. The turbulent evolution of gas from theinner fuse tube 22b will pass through the drawn arc and eject thelower fuse terminal 30 out of the lower end of thefuse tube 22 to rapidly extinguish the lengthening arc.

During the occurrence of light overloads of a continuing nature, which may be harmful to the apparatus protected by thefuse link 10, thefuse 31, which normally carries most of the current, will fuse first, thereby forcing the total current to pass through the high-resistance strain clip 26 through the strain-strap portion 27 thereof.

The result will be a fusion of the strain-strap portion 27, which will thereby permit thespring 18 to withdraw thelower fuse terminal 30 out of thefuse tube 22, as before, with are extinction taking place in a similar manner.

It will be observed that thestrain clip 26 is easily blanked out in economical fashion, and may be readily formed. Moreover, theexpansive areas 33 of the clampingportions 28 provide a secure grip upon thecables 21,

'24 when thestrain clip 26 is clamped thereto. Also, the

aforesaidexpansive areas 33 provide considerable soldering area between the clampingportions 28 and thecables 21, 24. Further, the saidexpansive areas 33 provide good :seats for the ends of thefuse 31 to be soldered thereto, as indicated in Fig. 4 of the drawings. The result is a strong strain-wire fuse-link construction, in which hightensile strength is achieved in the strain element, with no chance of mechanical breakage under normal conditions.

In the modification of my invention illustrated in Figs. -12, it will be observed, with particular attention being directed to Fig. "10 thereof, that afuse holder 35 is provided, having anupper terminal ferrule 36 and alower terminal collar 37. Theterminal ferrule 36 is preferably threadedly secured to the upper end of thefuse tube 38,

4 as at 39. A set screw 40 secures theterminal collar 37 rigidly in place adjacent the lower end of thefuse tube 38.

The fuse-refill unit, generally designated by thereference character 41 in Figs. 11 and 12, is passed downwardly interiorly within thefuse tube 38, as shown in Fig. 10, with thehead 42 thereof clamped between the top of theterminal ferrule 36 and a terminal cap 43, the latter being threadedly secured to anupper extension 44 of theferrule 36. The lower end of the cable, or tail, 45 is secured by aset screw 46, having a knurled head, to theterminal collar 37.

As Well known by those skilled in the art, theterminal ferrule 36 and theterminal collar 37 electrically and mechanically engage suitable fuse clips, not shown, connect ing thereby thefuse holder 35 into the circuit to be protected.

Referring more particularly to Figs. 11 and 12, it will be observed that thehead 42 has a lower dependingrodshaped portion 47 constituting a fuse terminal which is embraced by the clampingportion 48 of astrain clip 49, the configuration of the blank form of which is more clearly shown in Fig. 11A of the drawings.

In a manner similar to that heretofore described in connection with Fig. 5, thestrain clip 49 is blanked out, as shown in Fig. 11A. Preferably, it is formed from a suit able high-resistance material such as a copper-nickel alloy. As mentioned, one clampingportion 48 thereof is crimped to therod portion 47 of thehead 42, and is soldered thereto following such crimping operation. Theother clamping portion 48 is crimped and soldered to the fuseterminal end 50 of theflexible conducting cable 45.

Situated between the lowerterminal end 52 of therod portion 47 of thehead 42 and theupper end 53 of thecable 45 is afuse 54 having a bend 55 (Fig. 11). Thefuse 54 is soldered into place upon the clampingportions 48 of thestrain clip 49.

Following such operations, an enclosingtube 56 is slipped over thecable 45 in the manner shown in Fig. 11. At least the inner surface of thetube 56 is of a material which will evolve an arc-extinguishing gas when contacted .by an electric arc.

The complete assembly of the fuse-refill unit 41 within afuse holder 35 is depicted in Fig. 10. During heavy overload conditions, or under short-circuit situations, thefuse 54 and the strain-strap portion 57 of thestrain clip 49 will be disintegrated, substantially simultaneously. The resulting are established between thefuse terminals 52, 50 will contact the inner wall of thefuse tube 56, thereby evolving a considerable quantity of gas. The pressure of such evolved gas will forcibly eject thelower fuse terminal 50 and thecable 45 out of the open lower end of thefuse tube 56, thecable 45 hanging downwardly from theterminal collar 37 indicating thereby a blown condition of the fuse.

During light continuing overloads of a harmful nature, thefuse 54 will first fuse, thereby forcing the total current to pass through the strain-strap portion 57 of thestrain clip 49. Since thestrain clip 49 is formed of a relatively high-resistance material, it will soon fuse, thereby establishing an arc between thefuse terminals 50, 52. Gas evolution and are extinction occur as in the same manner described in connection with short-circuit conditions.

From the foregoing constructions, it will be apparent that I have provided an improved and highly effective fuse-link construction involving an improved strainwire construction. The strain clips 26, 49 are mechanically strong, easily and economically manufactured, and are highly resistant to mechanical failure under normal operating conditions. An application of my invention to fusible interrupting devices eliminates the uncertainty of faulty operation of the prior-art strain elements. Moreover, with the constructions which I disclose, .it will be apparent that there is considerable soldering and crimp ing area involved, so that there is no likelihood of soldering connections breaking or of cables pulling loose. In addition, it will be noted that the construction is compact, and easily assembled into a complete fuse-refill unit.

Although I have shown and described specific structures, it is to be clearly understood that the same were merely for the purpose of illustration, and that changes and modifications may be readily made, by those skilled in the art, without departing from the spirit and scope of the invention.

I claim as my invention:

1. A fusible interrupting device wherein a fuse link assembly electrically interconnects a pair of spaced fuse terminals and wherein overload protection is obtained by fusion of the fuse link assembly, characterized by the combination of a strain element composed of conducting sheet material through which current may pass, an elongated fuse secured adjacent the ends of the strain element in electrical parallel thereto, the conducting strain element having at least one widened clamping end portion embracingly clamping the inner end of one of the fuse terminals, said widened clamping end portion being an integral part of the strain element and formed of the same conducting sheet material as the strain element, and the current passing through the strain element after the fuse melts.

2. A fusible interrupting device wherein a fuse link assembly electrically interconnects a pair of spaced fuse terminals and wherein overload protection is obtained by fusion of the fuse link assembly, characterized by the combination of a strain element composed of conducting sheet material through which current may pass, an elongated fuse secured adjacent the ends of the strain element in electrical parallel thereto, the conducting strain element having at least one end crimped to one fuse terminal, said one end of the conducting strain element being an integral part of the strain element and formed of the same conducting sheet material as the strain element, and the current passing through the strain element after the fuse melts.

References Cited in the file of this patent UNITED STATES PATENTS 1,226,151 Weinberg May 15, 1917 1,663,333 Carmean Mar. 20, 1928 2,043,024 Williams June 2, 1936 2,050,277 Crabbs et al. Aug. 11, 1936 2,056,760 Austin Oct. 6, 1936 2,172,226 Smith Sept. 5, 1939 2,174,767 Triplett et a1. Oct. 3, 1939 2,208,440 Williams July 16, 1940 2,250,210 Smith July 22, 1941 2,324,044 Tripplett et al July 13, 1943 2,394,590 Boothe Feb. 12, 1946 2,493,601 Smith Jan. 3, 1950 2,563,566 Von Hoorn Aug. 7, 1951 2,640,128 Fahnoe et a1. May 26, 1953 FOREIGN PATENTS 185,889 Great Britain Sept. 21, 1922 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,821,604 January 28, 1958 James M. Wallace I It is hereby certified the requiring correction and that t below.

t error appears in the above numbered patent he said Letters Patent should read as corrected In the drawin gs, Sheet 4 should be canceled; l, 2 and 3,

in the heading toSheets line 3, for "4 Sheets" each occurrence, read --3 Sheets--. Signed and sealed this 29th day of April 1958.

SEAL) Atfiest:

KARL H. AXLINE ROBERT C. WATSON Attestlng Officer Comnissioner of Patents UNITED STATES PATENT OFFICE January 28, 1958 James M. Wallace I It is hereby certif' requiring correction and that the said L below,

In the drawi ngs, Sheet 4 should 1, 2 and 3,

be canceled;line 3, for "4 Sheets" each occurrence Signed and sealed this 29th day of April 1958.

in the heading to Sheets read --3 Sheets--.

(SEAL) Attest:

KARL H. AXLINE ROBERT C. WATS N Attesting Officer 0 Conmissioner of Patents

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