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Publication numberUS3681731 A
Publication typeGrant
Publication dateAug 1, 1972
Filing dateApr 16, 1971
Priority dateApr 16, 1971
Publication numberUS 3681731 A, US 3681731A, US-A-3681731, US3681731 A, US3681731A
InventorsKozacka Frederick J
Original AssigneeChase Shawmut Co
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Cartridge fuse with outer casing and overload interrupting chamber formed by inner sub-casing
US 3681731 A
Abstract
A cartridge fuse includes a main casing and a sub-casing inside the main casing. The sub-casing houses the overload current interrupting means of the fuse and does not contain a pulverulent arc-quenching filler. The space bounded by the inner surface of the main casing and the outer surface of the sub-casing is filled with a pulverulent arc-quenching filler embedding the major fault current interrupting means of the fuse. The sub-casing is closed at least at one end by a pair of discs having juxtaposed rectangular cut-outs and defining a straight narrow slit. The sub-casing, the overload current interrupting means therein and the pair of ribbon fuse link sections extending from both sides of the sub-casing form a self-contained and self-sustaining sub-assembly which can readily be handled in the process of manufacturing the fuse. The aforementioned ribbon fuse link sections are pre-bent at sharp angles and form jointly with the sub-casing and the parts therein a clip-on unit, i.e. a unit that can simply be clipped on to the main casing without any metal-forming operation and without use of any tool.
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Description  (OCR text may contain errors)

United States Patent Kozacka [54] CARTRIDGE FUSE WITH OUTER [58] Field of Search ..337/l59, 162, 166, 185, 231, 337/237, 248, 251, 252, 253, 254, 292, 247,

[56] References Cited UNITED STATES PATENTS 3,491,322 1/1970 Kozocka ..337/166 x 3,483,501 12/1969 Kozocka ..337/l66 961,891 6/1910 016111 ..337/252 x 1,103,987 7/1914 Murray ..337/248 1,788,770 1/1931 La Mar ..337/254 x [151 3,681,731 1451 Aug. 1, 1972 Primary Examiner-Bernard A. Gilheany Assistant Examiner-Dewitt M. Morgan Attorney-Erwin Salzer ABSTRACT A cartridge fuse includes a main casing and a sub-casing inside the main casing. The sub-casing houses the overload current interrupting means of the fuse and does not contain a pulverulent arc-quenching filler. The space bounded by the inner surface of the main casing and the outer surface of the sub-casing is filled with a pulverulent arc-quenching filler embedding the major fault current interrupting means of the fuse. The sub-casing is closed at least at one end by a pair of discs having juxtaposed rectangular cut-outs and defining a straight narrow slit. The sub-casing, the overload current interrupting means therein and the pair of ribbon fuse link sections extending from both sides of the sub-casing form a self-contained and selfsustaining sub-assembly which can readily be handled in the process of manufacturing the fuse. The aforementioned ribbon fuse link sections are pre-bent at sharp angles and form jointly with the sub-casing and the parts therein a clip-on unit, i.e. a unit that can simply be clipped on to the main casing without any metal-forming operation and without use of any tool.

6 Claim. 5 Drawing Figures PATENTED M13 1 3.681. 731

FIG.I

l2 0 FREDERICK J. KOZACKA BY WWW ATTY.

BACKGROUND OF THE INVENTION There is a number of instances where it is necessary to immerse some of the fusible means of an electric cartridge fuse in a pulverulent arc-quenching filler, and to keep the pulverulent arc-quenching filler away from other fusible means of the cartridge fuse. A so-called dual element fuse includes a fusible overload interrupting device and separate means for interrupting major fault currents. It is desirable to immerse the ribbon fuse links for interrupting major fault currents in a pulverulent arc-quenching filler capable of absorbing large amounts of energy, such as quartz sand, and to keep the pulverulent arc-quenching filler, in particular quartz sand, away from the break or breaks formed for interrupting overload currents of inadmissible duration. In such instances a cartridge fuse may include a cylindrical main casing of electric insulating material and a cylindrical sub-casing having a smaller outer diameter than the inner diameter of the main casing, arranged inside of the main casing in spaced relation from the lateral wall thereof. The sub-casing is closed at its ends but has means for the passage of current-carrying conductors through it. The space bounded by the main casing is filled with a pulverulent arc-quenching filler, except that occupied by the sub-casing, i.e. the latter defines a void or empty space for the overload current interrupting means.

Where the interrupting duty of a fuse is not severe a tubular sub-casing may be made of a tubular material capable of being squashed and thus closed. Dual element fuses having sub-casings of this description are disclosed in US. Pat. No. 3,483,501 to Frederick J. Kozacka, Dec. 9, 1969 for Electric Cartridge Fuse. In cases where the interrupting duty is relatively severe the sub-casing ought to be made of a relatively stiff material that does not lend itself to squashing. Nor can the squashing technique shown in the above patent be adopted in instances where the reduction of the internal volume of the sub-casing inherent in the sub-casinG squashing technique is not desirable, or not acceptable. In some instances it is possible to close one or both ends of a sub-casing by a circular cover disc having an aperture or slit therein for the passage of ribbon conductor means through the cover disc, the aperture or slit fitting the ribbon conductor means sufficiently close to preclude penetration of the pulverulent arcquenching filler from the space outside the sub-casing into the sub-casing. Closing of a sub-casing by an apertured disc or washer becomes difficult if and when it is desired to have pre-bends in the conductor or conductors extending through one or both end surfaces of a sub-casing.

This invention refers to an improvement of the structure shown in the above referred to US. Pat. No. 3,483,501. This improvement consists, in essence, in imparting such a configuration to the overload interrupting means and to the major fault current interrupting means that they jointly form a clip-on unit that can simply be clipped on to the main casing without resorting to any tool, or tools. The structure includes prebent fusible conductors, a non-squashed sub-casing and cover means which make it possible to conveniently close a sub-casing irrespective of the configuration of the portion of the conductor means or ribbon fuse link which is situated outside of the sub-casing.

SUMMARY OF THE INVENTION In fuses according to the present invention at least one end of a cylindrical sub-casing is closed by a pair of circular discs having substantially the same diameter as the sub-casing and having juxtaposed rectangular cutouts. Said pair of discs is arranged at right angles to the axis of the sub-casing and in abutting relation to the latter. The discs define between the cut-outs thereof a straight narrow slit for the passage of one of a pair of ribbon fuse link sections from the outside of the subcasing into the inside thereof. The aforementioned ribbon fuse link sections are pre-bent in such a fashion that they form jointly with the sub-casing a substantially C-shaped self-contained and self-supporting clipon assembly unit, i.e. a unit which can be clipped on, or fastened to, the main casing without metal-forming and without resorting to any tool, or tools.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is partly a side elevation of a fuse embodying this invention and partly a longitudinal section of such a fuse taken substantially along H of FIG. 2;

FIG. 2 is in substance a top plan view of the structure of FIG. 1 showing the end surface of the terminal cap as being partly broken away and the lateral surface of the terminal tap sectioned by a horizontal plane;

FIG. 3 is a side elevation of the top end of the structure of FIG. 1 as seen from right to left;

FIG. 4 is an exploded top-plan view of a detail of the structure of FIG. 1; and

FIG. 5 is a portion of FIG. 1 drawn on a larger scale than FIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENT Referring now to the drawings, numeral 1 has been applied to indicate a tubular main casing of electric insulating material, e.g. fiber or glass-cloth melamine. Casing l is closed on the ends thereof by terminal caps or ferrules 2, each provided with a knife blade contact 2a. The axially inner edges 3 or terminal caps 2 are crimped into casing l. Sub-casing 4 is arranged inside of main casing l in coaxial relation to the latter. The outer diameter of sub-casing 4 is substantially less than the inner diameter of main casing 1. Therefore a toroidal gap is formed between main casing l and subcasing 4. The upper portion of sub-casing 4 is provided with a liner 4' of insulating material forming an upper shoulder 4". A like shoulder is formed by liner 4' substantially midway between the ends of sub-casing 4. The sub-housing 4 houses two spring-biased parts 6'and 7 of which the former is substantially in the shape of a plunger and the latter substantially in the shape of a bell, or inverted pot. The upper end surface of part 7 forms an annular flange, and helical spring 8 rests with the upper end thereof against that flange. The lower end of helical spring 8 rests against a flange integral with plunger 6 inside of bell-shaped member 7. Member 7 is also provided with a radially outwardly projecting flange 7a abutting against the lower rim or circular edge of sub-housing 4. The bottom of member 7 is closed by a disc-shaped cover plate 13 of metal and the axially inner end of fusible element or ribbon fuse link 9" is soldered at 7' to cover plate 13 by a soft solder having a relatively high fusing point. Reference character 6' has been applied to indicate two solder joints formed by soft solder having a relatively low fusing point. One of these two solder joints conductively interconnects parts 6 and 7, and the other of these two solder joints conductively interconnects plunger 6 and the axially inner end of a fusible element or ribbon fuse link 9'. Fusible element sections 9 and 9" are perforated copper ribbons as clearly shown in FIG. 3 wherein reference character 14 has been applied to indicate perforations in fusible element or fuse link 9.

The upper end of sub-housing 4 is closed by a pair of circular discs 5a,5b of electric insulating material of which the lower disc 5b rests against shoulder 4" and the upper disc 5a rests upon lower disc 5b. As seen in FIG. 4 the juxtaposed sides of discs 5a,5b are provided with rectangular cut-outs. When discs 5a,5b are superimposed in registry these rectangular cut-outs define a narrow slit allowing the passage of fuse link section 9' from the space within sub-casing 4 to the space outside sub-casing 4 and within main casing 1.

The ends of fuse link sections 9',9" immediately adjacent sub-casing 4 extend along the axis of main casing 1. Each fusible element section 9',9" has a first bend inside of main casing 1 and a second bend coextensive with one of the rims of main casing 1. The axially outer ends of fusible element means 9',9" are sandwiched between the outer surface of easing l and the radially inner surfaces of caps 2. Each of caps 2 has a circular aperture 2c in the lateral surface thereof arranged opposite to, or in registry with, one of the ends of fusible element means 9',9". A solder joint 11 is arranged inside each of the circular apertures 2c in caps 2, each solder joint 11 conductively connecting the axially outer end of one of fuse links 9',9" to one of terminal caps 2. The radially outer surface of each solder joint 11 is covered with a heat resistant protective layer 12 to avoid exposure thereof to the effects of ambient atmospheres. Protective layer 12 may be formed by silicone grease.

Sub-casing 4 is surrounded by a body of pulverulent arc-quenching filler l embedding fusible element section 9,9" filling main casing 1. Discs 5a,5b preclude arc-quenching filler from penetrating into sub-casing 4 where its presence is not desired. Discs 5a,5b may be held in position by friction. Upon filling main casing 1 with filler 10 the latter tends to maintain discs 5a,5b in proper position.

0n occurrence of protracted overloads solder joints 6 soften and plunger 6 moves under the action of spring 8 away from the axially inner end of fusible element 9. Thus an arc is kindled which is confined to a chamber formed by sub-casing 4. This chamber does nOt contain any pulverulent arc-quenching filler whose properties are not compatible with the interrupting requirements for low current arcs. Thus parts 4,4, 5a, 5b,6,7,8 and 13 form an effective overload interrupting device.

The ribbon fuse link sections 9, 9" are a means for interrupting major fault currents, such as short-circuit currents.

ribbon fuse link section 9,9" must be sufiiciently stiff I to retain without support any shape imparted to them, and more particularly the shape shown in FIG. 1. It is apparent from FIG. 1 that each fuse link section 9,9" includes an inner end and an outer end both parallel to the axis of main casing 1. The intermediate portions of fuse link sections 9,9" are diverging radially outwardly and the aforementioned sub-assembly forms a clip-on unit that can readily be affixed to casing 1, thus greatly reducing the cost of, and the amount of time involved in, production of the fuse.

When assembling the fuse shown in FIG. 1 the aforementioned clip-on unit is first inserted into the main casing 1. It has substantially the same configuration prior to its insertion into main casing 1 as thereafter, i.e. each fuse link section 9,9" is pre-bent at two points prior to insertion of the subassembly or clip-on unit into main casing 1. Each fuse link section 9,9" has a first bend co-extensive with one point of the axis of sub-casing 4 and a second bend situated at a point having a radial spacing from said axis substantially equal to the radius of main casing l. The aforementioned second bend of each fuse link section 9',9" is clamped between one rim of casing l and one end surface 2b of one of the terminal caps of ferrules 2. The axial spacing of said first bend of fuse link sections 9',9" is substantially less than the length of easing 1. The axial spacing of the second bend of ribbon fuse link sections 9',9" are sufficiently equal to the length of casing l. Fuse link sections 9,9" are sufiiciently stiff to retain the shape thereof without any support other than the support provided by parts 6 and 7 and sub-casing 4. On the other hand, the fuse link sections 9,9" are relatively resilient to make it possible to be bent from right to left (as seen in FIG. 1) and then snap into place, i.e. the position shown in FIG. 1. Upon having inserted the snap-on unit 9',6,7,8,5a,5b,4,4',13 and 9" into main casing 1 one terminal cap 2 is mounted in place and thereupon the pulverulent arc-quenching filler 10 is filled into casing 1. Then the other terminal cap 2 is mounted on main casing 1 and the two solder joints 1] are formed.

Finally the protective silicone grease layers are placed into the apertures 20 of caps 2.

I claim as my invention:

1. A sub-assembly for making time-lag fuses includa. a cylindrical overload interrupting device casing;

b. a fusible overload interrupting device including a spring-biased switching means and a soft solder element normally maintaining said switching means in the closed position thereof arranged inside said casing;

. means for closing the end surfaces of said casing;

. a pair of ribbon fuse link sections for interrupting major fault currents connected in series with said overload interrupting device each projecting away from one of the end surfaces of said casing, said ribbon fuse link means being sufficiently stiff to retain without support the shape imparted to them, each of said ribbon fuse link sections being prebent and having an inner straight end substantially parallel to the axis of said casing, an outer straight end substantially parallel to said axis of said casing and an intermediate straight portion inclined to said axis of said casing, said pair of fuse link sections being sufficiently resilient to snap back to the position thereof upon having undergone limited transverse bending, and said pair of fuse link sections and said casing jointly forming a substantially C-shaped self-contained and self-supporting clipon unit adapted to be clipped in position inside of a fuse casing.

2. A sub-assembly as specified in claim 1 wherein at least one end of said casing is closed by a pair of circular discs of insulating material having substantially the same diameter as said casing and superimposed in registry, each of said pair of discs having a substantially rectangular cut-out and the cut-out of said pair of discs defining a straight narrow slit for the passage of one of said pair of ribbon fuse link sections.

3. A sub-assembly for making time-lag fuses includmg I a. a cylindrical overload interrupting device casing;

b. a fusible overload interrupting device inside said casing, said overload interrupting device including a switch means spring-biased to the open position thereof and a solder joint normally maintaining said switch means in the closed position thereof;

c. means for closing the end surfaces of said casing;

d. a pair of ribbon fuse link sections for interrupting major fault currents connected in series with said overload interrupting device each projecting away from said overload interrupting device in a direction substantially longitudinally of said casing, said ribbon fuse link sections being sufficiently stiff to retain without support a shape imparted to them, each of said ribbon fuse link sections being pre-bent and including a substantially straight inner end conductively connected to said overload interrupting device, a substantially straight radially outer end substantially parallel to said axis of said casing and an intermediate substantially straight portion inclined to said axis of said casing, said pair of fuse link sections being sufficiently resilient to snap back to the initial position thereof upon having undergone some transverse bending out of said position, and said pair of fuse link sections and said casing jointly forming a self-contained and self-supporting clip-on unit adapted to be clipped in position inside a fuse casing.

4. A sub-assembly as specified in claim 3 wherein said housing is closed on one of the cylindrical ends thereof by a metallic cover plate to which Said radially inner end of one of said pair of fuse link sections is soldered, and wherein said housing is closed on the other of the cylindrical ends thereof by a pair of circular discs having substantially the same diameter as said casing and having juxtaposed rectangular cut-outs forming therebetween a narrow slit for the passage of one of said pair of ribbon fuse link sections from the outside of said casing to the inside thereof.

5. An electric cartridge fuse including a. a cylindrical main casing of electric insulating material;

b. a pair of terminal caps mounted upon the ends of said main casing and closing the ends thereof;

c. a cylindrical sub-casing having a smaller outer diameter than the inner diameter of said main casing arranged inside said main casing in spaced relation from the lateral wall thereof;

d. a fusible overload interrupting device inside said sub-casing, said overload interrupting device including a pair of relatively movable springbiased parts normally restrained in position by solder joint means;

e. a pair of ribbon fuse link sections for interrupting major fault currents each having an axially outer end conductively connected to one of said pair of terminal caps and an axially inner end conductively connected to one of said pair of relatively movable parts, each of said pair of ribbon fuse link sections being pre-bent at two distinct points including a first bend coextensive with one point of the axis of said sub-casing and a second bend situated at a point having a radial spacing from said axis substantially equal to the radius of said main casing, the axial spacing of said first bend of said pair of fuse link sections being less than the length of said main casing and the axial spacing of said second bend of said pair of fuse link sections being substantially equal to the length of 'said main casing, said pair of ribbon fuse link sections being sufficiently stiff to retain the shape thereof without any support other than the support provided by said pair of relatively movable spring-biased parts and said sub-casing, said pair of ribbon fuse link sections being sufficiently resilient to snap back to their initial positions following a limited transverse bending thereof, and said pair of relatively movable spring-biased biased parts, said sub-casing and said pair of ribbon fuse link section jointly forming a substantially C-shaped self-contained and selfsupporting clip-on sub-assembly unit;

f. a body of pulverulent arc-quenching filler inside said main casing surrounding said sub-casing and embedding said pair of fuse link sections; and

f. means for precluding said arc-quenching filler from entering into said sub-casing, said means including a pair of circular discs haVing substantially the same diameter as said sub-casing and having juxtaposed substantially retangulat cut-outs, said pair of discs being arranged at right angles to the axis of said sub-casing in abutting relation to said sub-casing and defining between said cut-outs thereof a straight narrow slit for the passage of one of said pair of ribbon fuse link sections from the outside of said sub-casing into the inside thereof.

6. An electric cartridge fuse as specified in claim 1 wherein a. said sub-casing includes an internal liner having a shorter length than said sub-casing and forming a first shoulder adjacent one end of said sub-casing and forming a second shoulder substantially midway between the ends of said sub-casing; wherein b. said pair of circular discs abuts against said first shoulder; and wherein 0. one of said pair of relatively movable spring-biased parts is formed by a hollow cylinder abutting with one of the end surfaces thereof against said second shoulder.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US961891 *Feb 21, 1910Jun 21, 1910Agostine J OrelliRechargeable electric fuse.
US1103987 *Mar 10, 1913Jul 21, 1914Thomas E MurrayElectric fuse.
US1788770 *Mar 23, 1928Jan 13, 1931Great Western Fuse CompanyRenewable fuse
US3483501 *Jun 17, 1968Dec 9, 1969Chase Shawmut CoElectric cartridge fuse
US3491322 *Sep 30, 1968Jan 20, 1970Chase Shawmut CoElectric multifunction fuse
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US5187463 *Feb 11, 1992Feb 16, 1993Gould, Inc.Compact time delay fuse
US5254967 *Dec 22, 1992Oct 19, 1993Nor-Am Electrical LimitedDual element fuse
US5355110 *Sep 15, 1993Oct 11, 1994Nor-Am Electrical LimitedDual element fuse
US7808362Aug 13, 2007Oct 5, 2010Littlefuse, Inc.Moderately hazardous environment fuse
US8674803Oct 26, 2009Mar 18, 2014Littelfuse, Inc.Moderately hazardous environment fuse
EP0555580A1 *Aug 5, 1992Aug 18, 1993Gould Inc.Time delay fuse
EP0590662A1 *Sep 30, 1993Apr 6, 1994Nor-Am Electrical LimitedDual element fuse
Classifications
U.S. Classification337/166, 337/248, 337/292
International ClassificationH01H85/055, H01H85/36, H01H85/045, H01H85/00
Cooperative ClassificationH01H85/36, H01H85/055, H01H85/0456
European ClassificationH01H85/055
Legal Events
DateCodeEventDescription
Jun 15, 1983ASAssignment
Owner name: GOLUD INC 10 GOULD CENTER ROLLING MEADOWS IL 60008
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:I-T-E IMPERIAL CORPORATION;REEL/FRAME:004167/0716
Effective date: 19821227
Owner name: GOULD INC
Free format text: MERGER;ASSIGNOR:I-T-E IMPERIAL CORPORATION;REEL/FRAME:004167/0705
Effective date: 19830607
Owner name: I-T-E IMPERIAL CORPORATION A DE CORP
Free format text: MERGER;ASSIGNORS:AIRMATIC - BECKETT HARCUM INC - THE CHASE SHAWMUT COMPANY COMPONETROL INC - DATAMETRICS INC - EFCO DIE CASTING CORPORATION - GENRE REALTY INC - IMPERIAL EASTMAN CORPORATION - INDUSTRIAL DESIGN INC - RUNDEL COMP;ONENTS INC - TERAC CONTROLS INC;REEL/FRAME:004167/0712
Effective date: 19761130