US3701069A

US3701069A - Electric cartridge fuse

Info

Publication number: US3701069A
Application number: US142877A
Authority: US
Inventors: Richard A Belcher
Original assignee: Chase Shawmut Co
Current assignee: GOLUD INC A DE CORP; Chase Shawmut Co; Gould Inc
Priority date: 1971-05-13
Filing date: 1971-05-13
Publication date: 1972-10-24
Anticipated expiration: 1989-10-24

Abstract

An electric cartridge fuse includes a tubular main casing and a tubular sub-casing inside of the main casing. The latter is closed at least one one side thereby by an additional cover means resting against an axially outer edge of the sub-casing and held in position by a radially outwardly projecting bulge formed in the fusible element of the fuse and engaging the cover means adjacent the center thereof. Further disclosed are other applications of the fusible element bulge concept for positioning partitions in electric cartridge fuses.

Description

United States Patent Belcher 154] ELECTRIC CARTRIDGE FUSE [72] Inventor: Richard A. Belcher, Hampton Falls,

Assignee: The Chase-Shawmut Newburyport, Mass.

Filed: May 13, 1971 Appl. No.2 142,877

[ Company,

' I References Cited UNITED sTATEs PATENTS 12/1966 Kozocka; ..337/166 11/1910 Leueenetal. ..337/231 51 Oct. 24, 1972 3,291,942 12/1966 Kozocka ..337/276 X 2,787,684 4/1957 Laing ..337/292 X 1,425,692 8/ 1922 Procter et al. ..337/23l X 3,483,501 12/1969 Kozocka ..337/166 1,103,987 7/1914 Murray ..337/248 Primary Examiner-Roy N. Envall, Jr. Attorney-Erwin Salzer [57] ABSTRACT An electric cartridge fuse includes a tubular main casing and a tubular sub-casing inside of the main casing. The latter is closed at least one one side thereby by an additional cover means resting against an axially outer edge .of the sub-casing and held in position by a radially outwardly projecting bulge formed in the fusible element vof the fuse and engaging the cover means adjacent the center thereof. Further disclosed are other applications of the fusible element bulge concept for positioning partitions in electric cartridge fuses.

9 Claims, 9 Drawing Figures PATENTED BI 24 7 3.701.069

sum 1 or 2 all I! i l/7. I

mvemoa: RICHARD A. BELCHER BY g ATTY.

PATENTEDHN24 Ian 3.701.069

II'IIII I 'IIIIIII III/IA J "II/III/IIII/III/I/ I INVENTOR: RICHARD A. BELCHER BY MAM M ATTY.

ELECTRIC CARTRIDGE FUSE BACKGROUND OF THE INVENTION The design of cartridge fuses often calls for the provision of a sub-casing arranged inside of the main or principal casing of the fuse housing portion of the fusible element means of the fuse and keeping the pulverulent arc-quenching filler embedding other portions of the fusible element means away from the particular portion thereof which is housed in the sub-housing.

One structure of the aforementioned character is disclosed and claimed in U.S. Pat. No. 3,294,937 to Frederick J. Kozacka, Dec. 27, 1966 for TIME LAG DUAL ELEMENT FUSE HAVING MEANS FOR PRECLUDING ARC INITIATION ADJACENT TER- MINALS. Another structure of the aforementioned character is disclosed and claimed in US. Pat. No. 3,483,501 to Frederick J. Kozacka, Dec. 9,1969 for ELECTRIC CARTRIDGE FUSE.

The structure shown in the first mentioned patent includes a sub-casing formed by a length of tubular insulating material which is closed on both sides by additional cover means. The structure shown in the last mentioned patent includes a sub-casing formed by a length of tubular insulating material which is squashed and flattened on one side and closed by a staple on the side where squashed and flattened. The first mentioned alternative is more desirable as it does not affect the mechanical integrity of the sub-casing, is not limited to casing materials capable of being squashed and flattened, and does not reduce the space availableinside of the sub-casing as in case that one side of the sub-casing is closed by squashing, flattening and stapeling of the flattened end of the sub-casing. The squashed, flattened and stapled variety of sub-casing is, however, much less expensive to manufacture than that shown in US. Pat. No. 3,294,937.

It is, therefore, the principal object of the invention to provide cartridge fuses including sub-casings which fuses have all the advantages of prior art fuses whose sub-casings are covered by additional cover means, but whose cost of manufacture is much less than those of prior art fuses whose sub-casings are covered by additional cover means.

SUMMARY OF THE INVENTION An electric fuse embodying this invention includes a tubular main casing and a pair of terminal elements arranged at the ends of said main casing and closing the same. Fusible element means inside the main casing conductively interconnect said pair of terminal elements. Said fusible element means include a major fault current interrupting portion in ribbon form and an overload current interrupting portion. A body of pulverulent arc-quenching filler is contained inside the main casing, and the major fault current interrupting portion of the fusible element means is embedded in the body of arc-quenching filler. A tubular sub-casing inside of the main casing houses the overload current interrupting portion of the fusible element means and separates the latter from the pulverulent arc-quenching filler. A perforated cover means is arranged at least at one of the end surfaces of the sub-casing, closing the sub-casing and allowing passage of the fusible element means. The closing means is maintained in position by fastener means. The latter include a radially outwardly projecting mound-like bulge formed in said fusible element means andforrning an abutment engaging said cover means. The bulge is bounded by a closed curve situated within the surface or plane defined by said fusible element means. This means that the formation of any gap or gaps between the mound-like bulge and the fault current interrupting portion of the fusible element is avoided, and/or that the mound-like bulge is unsevered at any point thereof from the fault current inten'upting portion of the fusible element.

The aforementionedfastener means are not limited to cartridge fuses including casings and sub-casings, but may be applied whereever it is desired to sub divide the casings of cartridge fuses by means of partitions into separate chambers.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a longitudinal section of a cartridge fuse embodying this invention taken substantially along I-I of FIG. 3;

FIG. 2 is an end view of the structure of FIG. 1;

FIG. 3 is a longitudinal section of the same fuse as shown in FIG. 1 taken along III-III of FIG. 1;

FIG. 4 is a longitudinal section of another cartridge fuse embodying this invention;

FIG. 5 is an isometric view of a detail of the structures of FIGS. l-4;

FIG. 6 is a longitudinal section on a larger scale than FIGS. 1-4 of the detail of the structures of FIGS. 1-4 shown in FIG. 5;

FIG. 7 is a longitudinal section of another fuse embodying this invention;

FIG. 8 is a longitudinal section of still another fuse embodying this invention; and

FIG. 9 is a longitudinal section of a fuse similar to that shown in FIGS. I-3 and embodying this invention.

DESCRIPTION OF PREFERRED EMBODIMENT Reference character 1 has been applied to indicate a tubular main casing of electric insulating material closed on the ends thereof by a pair of terminal elements or terminal caps 2 mounted on the outer surface of casing 1. Caps 2 are conductively connected by fusible element means. A tubular sub-casing 3 is arranged inside of main casing 1 in coaxial relation to the latter. The fusible element means are formed by a ribbon of silver or of copper having serially related points of reduced cross-sectional area formed by circular perforations. The portion of the fusible element means inside of sub-casing 3 is provided with an overlay 4 of a metal capable of severing upon fusion thereof by a metallurgical reaction the base metal silver or copper, respectively upon which the overlay 4 is deposited. The portions 5a of the fusible element means outside of sub-casing 3 are major fault current interrupting means and the portion 5b within sub-housing 3 supporting overlay 4 are a means for interrupting overload currents. The main casing 1 contains a body of pulverulent arc-quenching filler 6, e.g., quartz sand. Sub-casing 3 keeps the arc-quenching filler 6 away from the overload interrupting portion 5b of the fusible element means. The sub-casing 3 is closed on both its ends by disc-shaped cover means 7 of electric insulating material, e.g., vulcanized fiber. Each disc 7 engages and abuts against the circular edge of sub-casing 3 ima of the fusible element means immediately adjacent cover means 7 are provided with a radially outwardly projecting bulge 5c formed in the fusible element means and forming abutments engaging cover means 7 adjacent the centers thereof and maintaining cover means 7 in firm engagement with the circular edges of sub-casing 3. As is apparent from FIGS. 5 and 6 the bulge 5c is bounded by a closed, substantially eggshaped curve which is situated within the surface or plane defined by the fault current interrupting portion 5a of the fusible element means.

Upon occurrence of a major fault the portions 50 of fusible element means fuse and form series breaks, resulting in a sufficiently high are voltage to cause a current-limiting interruption of the fault currents. Upon occurrence of overloads of inadmissible duration overlay 4 melts and causes formation of a break inside of sub-housing 3. The length of this break increases by burnback resulting in an arc voltage which is sufficiently high at the end of a few half cycles to result in the cessation of current flow.

The same reference characters as in FIGS. 1 and 3 with a prime added have been applied in FIG. 4 to indicate like parts.

Main casing 1 closed by terminal caps 2' houses coaxial sub-casing 3'. A cup 8 of brass or like metal closes the left side of sub-housing 3, and a disc 7 of insulating material closes the right side of sub-housing 3'. Cup 8 houses plunger 9 biased from right to left by helical spring 10. Ribbon fuse link sections 5a connect terminal caps 2' conductively with cup 8 and plunger 9, respectively. Reference character 11 has been applied to indicate a solder joint conductively connecting the axially inner end of left ribbon link section 5a to cup 8. Reference character 12 has been applied to indicate solder joints conductively interconnecting cup 8 and plunger 9 (which are relatively movable contacts) and conductively connecting right fuse link section 5a and plunger 9. The right fuse link section 5a is provided with bulge 5c abutting against the center region of cover disc 7 and maintaining the latter in firm engagement with the right hand edge of sub-casing 3.

Bulges

5c and 5c, respectively, are formed by the displacement of metal out of the general plane of the

ribbon fuse links

5 and 5a respectively. The formation of

bulges

5c and 50 does not involve the removal of metal and does not affect the current rating of the fuse structures.

The fuse shown in FIG. 4 operates in the same way as that shown in FIGS. 1 and 2 when subjected to major fault currents. Upon occurrence of protracted overload currents solder joints 12 melt and plunger 9 is then free to move and moves under the action of spring from right to left. As a result, an arc gap is formed between plunger 9 and the axially inner end of right fuse link portion 5a. As shown in FIGS. 5 and 6 bulge 5c is not symmetrical, its slope adjacent cover disc 7 being steeper than its slope at the side remote from cover disc 7, where no abutment function is required.

Referring now to FIG. 7, the tubular casing 1" of electric insulating material, e.g., fiber, is closed on the ends thereof by terminal caps 2". The latter are conductively interconnected by ribbon fuse link 5". Casing 1" is subdivided by a partition 13 into a left chamber 14 and a right chamber 15. The diameter of partition 13 is substantially the same as the inner diameter of casing 1". Partition 13 has a slit for the passage of fusible element 5" and the latter is provided with two radial bulges each to one side of partition 13. The

bulges 5c" are of the same nature as the bulges 5c shown in FIGS. 5 and 6 and described in their context. Chamber 15 is filled with a pulverulent arc-quenching filler 16, and chamber 14 may be filled with pulverulent filler other than filler 16, or does not contain any filler.

The structure of FIG. 8 is substantially the same as that of FIG. 7, except that the former is provided with two partitions 13, each clamped between a pair of bulges or mounds 50" formed by ribbon fuse link 5". Partitions 13 form a center chamber 17 which does not contain any pulverulent arc-quenching filler, and a pair of axially outer chambers 18 containing the pulverulent arc-quenching filler 19. Reference character 4" has been applied to indicate a link-severing overlay of a low fusing point metal, e.g., tin, placed on ribbon link 5" of copper or silver.

The modification of the structure of FIGS. 1-3 shown in FIG. 9 includes casing l, sub-casing 3,

fusible element

5a,5b,5a, pulverulent arc-quenching filler 6, a pair of cover plates 7 for sub-casing 3, and a low fusing point link-severing overlay 4 on portion 5b of the fusible element or fuse link. The left cover plate 7 for subcasing 3 is arranged between two mounds or bulges 5c of

fuse link

5a,5b,5a and the right cover plate 7 of subcasing 3 is clamped by a mound or bulge 5c of the

fuse link

5a,5b,5a against the right rim or circular edge of sub-casing 3.

In terms of performance the structure of FIG. 9 does not differ from that of FIGS. 1-3, however, the structure of FIG. 9 may be assembled in a way different from the structure of FIGS. 1-3, which mode of assembly is particularly desirable in some instances.

When assembling the structure of FIG. 9 first the bulge 5c situated to the left of left cover plate 7 is formed, thereafter the fuse link is threaded through the slit in the aforementioned cover plate intended for the passage of the fuse link, thereafter the bulge 50 to the right of the aforementioned cover plate 7 is formed, thereafter the fuse link is threaded through sub-casing 3 until the left edge or rim thereof abuts against left cover plate 7, thereafter the fuse link is threaded through the slit in right cover plate 7 intended for the passage thereof until it is engaged by the right rim or edge of sub-casing 3, and finally the right bulge or mound 5c is formed in the

fuse link

5a,5b,5a.

The formation of mounds or bulges 5c,5c and 5c" is effected by means of a small tool or press, appropriate for the purpose in hand.

I claim as my invention:

1. An electric cartridge fuse including a. a tubular main casing;

b. a pair of terminal elements arranged at the ends of said main casing and closing said main casing;

c. fusible element means inside said main casing conductively interconnecting said pair of terminal elements; said fusible element means including a major fault current interrupting portion in ribbon form and an overload current interrupting portion;

d. a body of pulverulent arc-quenching filler inside said main casing embedding said major fault current interrupting portion of said fusible element means;

e. a tubular sub-casing inside said main casing housing said overload current interrupting portion of said fusible element means and separating said overload current interrupting portion of said fusible element means from said arc quenching filler;

f. perforated cover means at least at one of the end surfaces of said sub-casing closing said sub-casing and allowing passage of said fault current interrupting portion of said fusible element means; and

g. fastener means abutting against said cover means for maintaining said cover means in position, said fastener means including a radially outwardly projecting mound-like bulge formed in said fault current interrupting portion of said fusible element means by transversely displaced metal thereof, said transversely displaced metal forming said mound-like bulge being unsevered at any point or points thereof from the fault current interrupting portion of said fusible element, thus avoiding gap formation between said mound-like bulge and said fault current interrupting portion of said fusible element, and said mound-like bulge being bounded by a closed curve situated within the plane defined by said fault current interrupting portion of said fusible element means.

2. An electric cartridge fuse as specified in claim 1 wherein a. said sub-casing houses a pair of separable, springbiased, normally solder-means-restrained contacts, one of said pair of contacts closing one of the end surfaces of said sub-casing; and wherein b. said perforated cover means closes the other of the end surfaces of said sub-casing and abuts on one side thereof against the edge formed by the end of said-sub-housing remote from said one of said pair of contacts and abuts on the other side thereof against an external moundlike bulge of said fault current interrupting portion in ribbon form of said fusible element means.

3. An electric cartridge fuse as specified in claim 1 wherein said perforated cover means is formed by a circular disc of electric insulating material having a straight radially extending slot for the passage of said fault current interrupting portion of said fusible element means, and wherein said outwardly projecting mound-like bulge engages said disc at a point immediately adjacent to the center of said slot.

4. An electric cartridge fuse as specified in claim 3 wherein the slope of said mound-like bulge is steeper at the side of said bulge adjacent said disc than at the side of said mound-like bulge remote from said disc.

5. In an electric cartridge fuse the combination of a. a tubular casing of electric insulating material;

b. a fusible element in ribbon form arranged inside said casing;

c. a plate of insulating material arranged at right angles to said casing and having a slit therein for the passage of said fusible element, said fusible element projecting from one side of said plate through said slit to the other side of said plate; and

d. means for positioning said plate relative to said in "i fnilfiil lbiflltifiilfieil ufniifii oililiity transversely displaced fusible element metal unsevered at any point or points thereof from said fusible element and thus avoiding gap formation between said mound-shaped abutment and said fusible element, and said mound-shaped abutment being bounded by a closed curve situated within the plane defined by said fusible element.

6. An electric fuse as specified in claim 5 wherein said plate separates spaces containing different media.

7. An electric cartridge fuse as specified in claim 5 wherein a. said tubular casing is provided with terminal caps on the ends thereof; wherein b. said terminal caps are conductively interconnected by said fusible element; wherein c. said plate has the same diameter as the inner wherein a. said tubular casing is arranged inside of another tubular casing of electric insulating material, said another casing having a larger inner diameter than the outer diameter of said casing; wherein b. said another casing is provided with terminal caps on the ends thereof and said terminal caps are conductively interconnected by said fusible element; and wherein c. said plate is positioned relative to said fusible element by abutting engagement on one side thereof by one of the rims formed by one of the ends of said casing and is further positioned relative to said fusible element by engagement on the other side thereof by said substantially mound-shaped abutment.

9. An electric cartridge fuse as specified in claim 8 wherein a. said casing is closed on each of both ends thereof by one of a pair of plates of insulating material each having substantially the same diameter as the diameter of said casing; wherein b. one of said pair of plates is positioned relative to said fusible element by a pair of substantially mound-shaped abutments formed by transversely displaced fusible element metal each being bounded by a closed curve situated within the surface defined by said fusible element; and wherein c. the other of said pair of plates is in abutting engagement on one side thereof with one of the rims formed by one of the ends of said casing, and is engaged on the other side thereof by a substantially mound-shaped abutment formed by transversely displaced fusible element metal and being bounded by a closed curve situated within the surface defined by said fusible element.

Claims

1. An electric cartridge fuse including a. a tubular main casing; b. a pair of terminal elements arranged at the ends of said main casing and closing said main casing; c. fusible element means inside said main casing conductively interconnecting said pair of terminal elements; said fusible element means including a major fault current interrupting portion in ribbon form and an overload current interrupting portion; d. a body of pulverulent arc-quenching filler inside said main casing embedding said major fault current interrupting portion of said fusible element means; e. a tubular sub-casing inside said main casing housing said overload current interrupting portion of said fusible element means and separating said overload current interrupting portion of said fusible element means from said arc-quenching filler; f. perforated cover means at least at one of the end surfaces of said sub-casing closing said sub-casing and allowing passage of said fault current interrupting portion of said fusible element means; and g. fastener means abutting against said cover means for maintaining said cover means in position, said fastener means including a radially outwardly projecting mound-like bulge formed in said fault current interrupting portion of said fusible element means by transversely displaced metal thereof, said transversely displaced metal forming said mound-like bulge being unsevered at any point or points thereof from the fault current interrupting portIon of said fusible element, thus avoiding gap formation between said mound-like bulge and said fault current interrupting portion of said fusible element, and said mound-like bulge being bounded by a closed curve situated within the plane defined by said fault current interrupting portion of said fusible element means.

2. An electric cartridge fuse as specified in claim 1 wherein a. said sub-casing houses a pair of separable, spring-biased, normally solder-means-restrained contacts, one of said pair of contacts closing one of the end surfaces of said sub-casing; and wherein b. said perforated cover means closes the other of the end surfaces of said sub-casing and abuts on one side thereof against the edge formed by the end of said sub-housing remote from said one of said pair of contacts and abuts on the other side thereof against an external mound-like bulge of said fault current interrupting portion in ribbon form of said fusible element means.

5. In an electric cartridge fuse the combination of a. a tubular casing of electric insulating material; b. a fusible element in ribbon form arranged inside said casing; c. a plate of insulating material arranged at right angles to said casing and having a slit therein for the passage of said fusible element, said fusible element projecting from one side of said plate through said slit to the other side of said plate; and d. means for positioning said plate relative to said fusible element, said positioning means including a substantially mound-shaped abutment formed by transversely displaced fusible element metal unsevered at any point or points thereof from said fusible element and thus avoiding gap formation between said mound-shaped abutment and said fusible element, and said mound-shaped abutment being bounded by a closed curve situated within the plane defined by said fusible element.

7. An electric cartridge fuse as specified in claim 5 wherein a. said tubular casing is provided with terminal caps on the ends thereof; wherein b. said terminal caps are conductively interconnected by said fusible element; wherein c. said plate has the same diameter as the inner diameter of said casing and subdivides said casing into a pair of compartments; and wherein d. said means for positioning said plate relative to said fusible element include a pair of substantially mound-shaped abutments formed by transversely displaced fusible element metal and arranged to opposite sides of said plate, each of said mound-shaped abutments being bounded by a closed curve situated within the surface defined by said fusible element.

8. An electric cartridge fuse as specified in claim 5 wherein a. said tubular casing is arranged inside of another tubular casing of electric insulating material, said another casing having a larger inner diameter than the outer diameter of said casing; wherein b. said another casing is provided with terminal caps on the ends thereof and said terminal caps are conductively interconnected by said fusible element; and wherein c. said plate is positioned relative to said fusible element by abutting engagement on one side thereof by one of the rims formed by one of the ends of said casing and is further positioned relative to Said fusible element by engagement on the other side thereof by said substantially mound-shaped abutment.