US3827010A

US3827010A - Composite sectionalized open-type drop-out-type fusible output with series enclosed current limiting fuse

Info

Publication number: US3827010A
Application number: US00232129A
Authority: US
Inventors: F Cameron; J Carothers; W Shaw
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1972-03-06
Filing date: 1972-03-06
Publication date: 1974-07-30
Anticipated expiration: 1991-07-30
Also published as: JPS4912351A; JPS5471635U; AU5245973A; CA975410A

Abstract

A sectionalized open-type drop-out fusible cutout is provided having a high-current interrupting section, a mechanicallyconnected low-current interrupting section in electrical series therewith, the low-current section including a tensioned fuse and attached fuse-link cable, which, when fused, releasing the cable, effecting the breaking of the associated toggle linkage, and drop-out indicating action of the open-type fusible device. A high-current section includes a current-limiting fuse section, which is operative only during the interruption of heavy fault currents, and not operable during the interruption of relatively low overload currents, which overload currents are interrupted solely by the low-current section. The low-current section is of the expulsion type, having a fuse-link cable extending out through the lower open end of the fuse tube thereof, and maintaining the toggle linkage in its underset condition. The fusing of the low-current interrupting section, effects fusing of the fuse link and releases the fuse-link cable, and consequent breaking of the toggle linkage to permit consequent drop-out action of the open-type fusible cutout device. The aforesaid composite sectionalized open-type fusible device may be associated, with a load-break extension device, which will permit manual load breaking of load currents without either of the series fuse sections operating. Preferably, associated with the load-break device is an auxiliary arc-chute structure, serving to interrupt the load current within the arc-chute structure upon manual operation of the cutout device.

Description

United States Patent [191 Cameron et al.

[111 3,827,010 July 30, 1974 [75] Inventors: Frank L. Cameron; John W.

Carothers, both of Irwin; Woodrow G. Shaw, Export, all of Pa.

[73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

22 Filed: Mar. 6, 1972 21 Appl. No.: 232,129

[52] US. Cl 337/168, 337/169, 337/171, 337/175 [51] Int. Cl. l-l0lh 71/20 [58] Field of Search 337/168-179 [56] References Cited UNITED STATES PATENTS 2,230,955 2/1941 Johnson 337/170 2,441,692 5/1948 Earle 337/237 X 2,483,577 10/1949 Fahnoe 337/161 3,235,688 2/1966 Fink ct a1 337/156 3,377,447 4/1968 Hermann ct a1. 337/273 X Primary Examiner. l. D. Miller Assistant ExaminerFred E. Bell Attorney, Agent, or FirmW. R. Crout 57 ABSTRACT A sectionalized open-type drop-out fusible cutout is provided having a high-current interrupting section, a mechanically-connected low-current interrupting section in electrical series therewith, the low-current section including a tensioned fuse and attached fuse-link cable, which, when fused, releasing the cable, effecting the breaking of the associated toggle linkage, and drop-out indicating action of the open-type fusible device.

A high-current section includes a current-limiting fuse section, which is operative only during the interruption of heavy fault currents, and not operable during the interruption of relatively low overload currents, which overload currents are interrupted solely by the low-current section. The low-current section is of the expulsion type, having a fuse-link cable extending out through the lower open end of the fuse tube thereof, and maintaining the toggle linkage in its underset condition. The fusing of the low-current interrupting section, effects fusing of the fuse link and releases the fuse-link cable, and consequent breaking of the toggle linkage to permit consequent drop-out action of the open-type fusible cutout device.

The aforesaid composite sectionalized open-type fusible device may be associated, with a load-break extension device, which will permit manual load breaking of load currents without either of the series fuse sections operating. Preferably, associated with the load-break device is an auxiliary arc-chute structure, serving to interrupt the load current within the arc-chute structure upon manual operation of the cutout device.

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COMPOSITE SECTIONALIZED OPEN-TYPE DROP-OUT-TYPE FUSIBLE OUTPUT WITH SERIES ENCLOSED CURRENT LIMITING FUSE CROSS-REFERENCE TO RELATED APPLICATIONS United States patent application, filed Aug. 26, 1970, Ser. No. 67,175, by Frank L. Cameron, and assigned to the assignee of the instant application, teaches the use of a composite sectionalized protective indicating-type fuse structure having a high-current interrupting section and a mechanically-connected low-current interrupting section in electrical series therewith. The lowcurrent interrupting section is replaceable, following a low-current interruption, which has no effect upon the high-current interrupting section, the latter remaining intact, and may be further used. During high-current interruption, both sections are simultaneously fused, and collectively contribute together to a quick interruption of the connected electrical circuit, again there being an external indicated condition of the blown condition of the fuse by an ejection of the fuse-link cable.

Also, United States patent application, filed Aug. 26, 1970, Ser. No. 67,183, by JamesN. Santilli, and likewise assigned to the assignee of the instant invention, shows a similar composite-type fuse structure, in which a high-current interrupting section and a low-current interrupting section are utilized in series, the lowcurrent interrupting section being capable of being utilized' with a standard-type fuse-link.

BACKGROUND OF THE INVENTION Todays distribution systems are changing in numerous ways. There are to be found higher-density load areas, with attendanthigher-fault-current short-current capacities than existed in the past. This is coupled with an increasing accent on safety, noise reduction, and convenience. In view of these new requirements, some formerly widely-used interruptingdevices and circuitprotective devices are no longer fully suitable by todays standards. A case in point is the distribution fuse cutout. These devices, while adequate for relatively rural areas, havebeeen, and are used in large quantities to protect distribution transformer circuits. The advantages of this type of device are its low cost, relative ease of refusing, and the wide standardization of fuse characteristics, which prevail. The device is less than desirable from the standpoint of limited interrupting rating a performance that is characterized by loud noise, and the expulsion of considerable are products, and its relatively unsafe performance in view of the materials expelled. Maintenance men are subjected to this hazard.

SUMMARY OF THE INVENTION In accordance with a preferred embodiment of the present invention, there is provided a dual composite sectionalized open-type drop-out-type fusible cutout device, comprising a high-current section mechanically I connected and in electrical series with a separable lowtion of relatively low currents (which have no effect upon the high-current unit), and results in a drop-out indicative action of the associated toggle-linkage device, which thereby gives an indicating readily discernible visible view of the operated and blown condition of the device by the dropout action.

The low-current interrupting section preferably includes an expulsion-type of fuse tube, which ejects the fuse link terminal and the associated attached fuse link cable, releasing the toggle linkage during fuse operation and thereby permits the assembly to drop to an external observable indicating position, and moreover permits ready drop-out action of the fusible device.

The improved composite open-type sectionalized fusible device of the present invention may be utilized either with, or, optionally, without an auxiliary loadbreak extension device, as illustrated, and described, in part, in US. Pat. No. 3,235,688, issued Feb. 15, 1966,

to Austin J. Fink, Robert J. Lawrence, and Gene L. Miller, and assigned to the assignee of the instant application.

However, the improved composite open-type sectionalized fusible cutout device of the present invention may be utilized, to advantage, even in the absence of such a load-break extension device, and, in such an eventuality, utilized merely as a fusible protective device having the two series-related interrupting sections and having no manual load-break characteristics.

It is, accordingly, a general object of the present invention to provide an improved composite open-type sectionalized fusible cutout device having indicative drop-out characteristics.

Another object of the present invention is to provide an improved protective open-type fusible device having high and low-current interrupting sections separably and detachably mechanically and electrically connected together, so that replacement of the low-current section may easily take place without affecting the continued further use of the high-current interrupting section.

Another object of the present invention is the provision of an improved drop-out type fusible cutout device having interrupting capabilities far in excess of those attained heretofore.

Another object of the present invention is the provision of an improved open-type composite sectionalized fusible cutout device of the drop-out type, which may be adapted both with, and without, an auxiliary loadbreak extension device.

Still a further object of the present invention is the provision of an improved composite sectionalized drop-out fusible cutout device having a current-limiting fusible section associated therewith.

Another object of the present invention is the provision of an improved drop-out type fusible cutout device having a high-current current-limiting section, and a serially-related low-current expulsion-type fuse-tube section having a fuse-link therein, capable, when fused, of actuating an associated toggle-linkage device to permit thereby quick drop-out action to an observable indicating position.

Still a further object of the present invention is the provision of an improved fusible device of the type set forth in the immediately-preceding paragraph capable of being used with a standard-type fuse-link, such as k or T" links, for example, inserted into the lowcurrent section, with the advantage of ready replacement and known electrical characteristics.

Further objects and advantages will readily become apparent upon reading the following specification, taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of a composite opentype sectionalized fusible cutout device embodying the principles of the present invention, and incorporating, as an optional addition, a manually-operable loadbreak extension device, the cutout device being shown in the closed-circuit position;

FIG. 2 is a side elevational view of the composite fuse-holder assembly, only, with the auxiliary blade assembly, which is utilized in conjunction with the fusible device of FIG. 1, the fusible cutout device being illustrated in its unfused intact condition;

FIG. 3 is a sectional view taken substantially along the line IIIIII of FIG. 2;

FIG. 4 is a fragmentary vertical side elevational view taken substantially along the line IV-IV of FIG. 2;

FIG. 5 is a top plan view of the composite fuse-holder assembly of FIG. 2;

FIG. 6 is an enlarged side-elevational view, partially in section, of the high-current interrupting section, in this instance being of the current-limiting type, the high-current section being illustrated in its unfused intact condition;

FIG. 6A is an end view of the current-limiting fuse of FIG. 6;

FIG. 7 is a vertical sectional view taken through the low-current interrupting section, illustrated in this particular instance as of the expulsion-fuse type.

FIG. 8 is a top plan view of the auxiliary interrupter with a portion being sectionalized to show the auxiliary contents;

FIG. 9 is a top plan view of the stationary latch for the main contact;

FIG. 10 is a front elevational view of the top casting;

FIG. 11 is a diagrammatic view illustrating the component parts of the cutout device, including the loadbreak attachment, the device being indicated in the closed-circuit position;

FIG. 12 is a diagrammatic view, similar to that of FIG. 11, but illustrating the position of the parts during the initial portion of the opening operation, while the main contacts are open, and the auxiliary contacts are still latched closed;

FIG. 13 is a diagrammatic view illustrating the fusible cutout device without the optional load-break attachment, the device being illustrated in the closed circuit position;

FIGS. 14-18 are various views of the load-break mounting bracket;

FIGS. 19 and 20 are front and side elevational views of the spacer washer used in the absence of the loadbreak mounting bracket of FIGS. 14-18, when the load-break attachment is not desired;

FIG. 21 is an enlarged side elevational view of a standard-type fuse-link, with a portion of the fuse-tube casing broken away to illustrate the interiorly-disposed fusible link;

FIG. 22 illustrates the cutout device of FIG. 1 closed, with the load current being carried by the main contacts;

FIG. 23 illustrates the cutout device half open, with the quick-break blade and arc-chute contact now carrying the load current;

FIG. 24 illustrates a further step in the opening operation, when the quick-break blade is beginning to be released, showing the main contacts of the cutout having been open sufficiently to prevent the are from restriking between the openedmain contacts;

FIG. 25 illustrates the quick-break blade having been released upon further opening movement of the cutout device, and illustrating how the blade snaps the full length of the arc-chute elongating and de-ionizing the arc, with the coil spring at the bottom of the blade providing the opening energy thereof;

FIG. 26 illustrates the disposition of the load-break device during a closing operation, when the blade is half closed with the main cutout contacts still disengaged, showing that the circuit is closed upon the loadbreak contacts, and not at the main contacts;

FIG. 27 is a side elevational view of the composite sectionalized fuse-holder assembly, without the loadbreak attachment feature, the device being fragmentarily illustrated as in contact with the associated stationary maincontact assembly supported by the upper end of the porcelain insulating support;

FIG. 28 is a fragmentary side-elevational view taken along the line XXVIII-XXVIII of FIG. 27, illustrating the upper portion of the composite sectionalized fuse holder assembly of FIG. 8;

FIG. 29 is a top plan view of the upper end of the sectionalized composite fuse-holder assembly of FIG. 27, taken substantially along the line XXIXXXIX of FIG. 27;

FIG. 30 is an elevational view of the fuse-link flipper, and diagrammatically indicating the rotatable pivot therefor;

FIGS. 31-32 are detail views of the top contact bracket for the fuse-holder assembly,

FIGS. 33 and 34 are detail views of the auxiliarycontact biasing spring; and,

FIGS. 3537 are various views of the toggle-link hinge member, with FIG. 37 being a partial sectional view taken along the line XXXVIIXXXVII of FIG. 36.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Todays distribution systems are changing in numerous ways. There are to be found higher density load areas, with attendant higher fault current short-circuit capacities than existed in the past. This is coupled with an increasing accent on safety, noise reduction and convenience. In view of these new requirements, some formerly widely-used interrupting devices and circuitprotective devices are no longer fully suitable by todays standards. A case in point is the distribution fuse cutout. These devices, while adequate for relatively rural areas, have been and are used in large quantity to protect distribution transformer circuits. The advantage of this type of device is its low cost, relative ease of refusing, and the wide standardization of fuse characteristics which prevail. The device is less than desirable from the standpoint of limited interrupting rating, a performance that is characterized by loud noise and the expulsion of considerable are products, and its relatively unsafe performance in view of the materials expelled.

The present invention is particularly concerned with a new type of device, which, in many instances, wil supplant the fuse cutouts and answer, or overcome theobjectionable features associated generally with fuse cutouts. In more detail, the present invention may be called a fused distribution limiter. The fused distribution limiter has a very high fault-current interrupting rating, is still low in cost, operates with a minimal noise and discharge, and yet retains time-current characteristics, which do not depart from application patterns set in the past. Especially desirable is the feature that the fused distribution limiter of the present invention can be used physically interchangeably with the commonlyused distribution cutouts. The present device of our invention will replace the same voltage of fuse cutout, and will fit into the same mounting, or fuse-support assembly as is used for the cutout. The device is further characterized by the feature that on many conditions of fault interruption, thework of refusing and replacement of the blown fuse-link is no more extensive than that which is performed with the standard fuse cutout. Only in the event of very high-fault currents does the improved and new current-limiting section of the device operate to give the characteristically higher interrupting rating and lower discharge associated with current-limiting fuses. Our fuse distribution limiter may, optionally, be used for either load-break, or non-loadbreak applications by the simple expedient of easilymounted bolt-on parts. The constructional details of the improved fuse distribution limiter of the present invention may be best understood by reference to FIGS. 1-7 of the drawings, which illustrates the improved composite sectionalized drop-out fusible device of the present invention, taken in conjunction with the readily attachable load-break extension device.

FIG. 1 illustrates the device in the closed-circuit position and is designated by the reference numeral 1. As shown, there is provided an upstanding insulating support 2, which has a centrally-disposed back-bracket 3, which may be bolted, or otherwise suitably secured to the cross-arm (not shown) of a transmission-line pole. Disposed at the upper end of the insulating support 2 is an upper main stationary contact assembly, generally designated by the reference numeral. 4. Also, associated with the lower end of the insulator support 2, and extending laterally therefrom, is a lower stationary main contact assembly 6.

Referring more particularly to the upper end of the interrupting device 1, it will'be observed that the upper stationary main contactassembly 4 includes a top casting 7 supporting the main stationary contact assembly, generally indicated at 4, and a secondary, or auxiliary contact assembly, generally indicated at 9. The top casting 7 is comprised of suitable conducting material, such as aluminum'bronze, for example; and is secured to the insulator support 2 by any suitable means, such as by a bolt 10 extending through an aperture in the casting and an aperture extending through the insulator support 2. A nut, not shown, secures the bolt 10 to the insulator 2 and is accessible through an aperture from the rear of the insulator support 2. The casting 7 includes a curved rearwardly-extending portion 7a to mate with the curvature of the insulator support 2, thus providing a snug fit.

A line-terminal clamp, generally indicated at 12, is associated with the conducting casting 7, and has a terminal bolt 10 extending through an aperture in the casting 7, as shown in FIG. 13. A clamp 17 is secured to casting 7 by means of nut 18.

The main stationary contact assembly 4 includes a leaf contact member 20 curved in a basically U-shaped configuration, and having a notch, or other opening, not shown, at one end for attachment by means of a bolt 21 to an apertured contact mount 22 integral with, and protruding from the top casting 7. The stationary contact 20 may be comprised of any suitable conducting material, such as phosphor bronze, for example.

A first contact latching device 24 is associated with the main stationary contact 4, and is comprised of a basically U-shaped wire 25 having

leg portions

25a, 25b (FIG. 9) connected by a bight portion 250. The bight portion 25c is recurved to fit around the shank of bolt 21 for anchoring the first latching device 24 to the contact mount 22, as shown in FIG. 1. The outer ends of

legs

25a, 25b are bent inwardly towards each other, and are received in the ends of a metal tube 26, which tube 26 serves as a contact-engaging member, as hereinafter described. v

The auxiliary contact assembly 9, shown in FIGS. 1 and 2, comprises a support member 27 having a flat base 28 for attachment to the casting 7 and an integral rib 29 (FIG. 8) on the base for supporting an auxiliary contact assembly and an arc-chute. The support member 27 includes a pair of outwardly-extending studs 30, 31 foraffixing the base member to the top casting 7 by means of a pair of bolts 32 (only one being shown) extending through

apertures

33, 33 in the top casting 7 and into the studs 30, 31.

A pair of auxiliary contact strips 34, 34 are mounted at opposite sides of the rib 29 by means of a rivet 35 extending through the rib 29, and the inner ends of the

contacts

34, 34 as shown in FIG. 8. The outer ends 340 of the contacts 34 are flared outwardly with respect to each other, to serve as a guide for the incoming auxiliary blade 36 to be hereinafter described. Each contact blade 34 includes an integral tabular indentation 34b immediately adjacent the outer end 34a, each indentation 34b extending inwardly toward the other substantially half the thickness of the rib 29, so that the indentations 34b normally touch, thus comprising a second latching device, or stop 37, for the auxiliary blade 36, as hereinafter described. The

contacts

34, 34 may be constructed from any desirable conducting material, such as phosphor bronze, for example.

The arc-chute 39 is comprised of a pair of opposing

arcing plates

41, 43 fixedly mounted to the rib 29 by any suitable means, such as bolts 45, and attached to each other at various points around their perimeters by suitable means, such as bolts 46. The arcing

plates

41, 43 have the outer edge flared, as in FIG. 8, to provide a converging entrance'portion 48 to the slot 49 between the

plates

41, 43. The inner sides of the

plates

41, 43 are spaced from each other, except at the top and rear, where they are joined, to provide access for the auxiliary blade 36. The

plates

41, 43 are recessed,

as at 51 and 52, to provide space for the contacts 34.

Indentations 54, 54 areprovided in the interface of each

plate

41, 43 to serve as a seat for compression springs 55, 55, each compressed between one of the indentations 54 and the indentation formed by the previously-described tabular stop 34b, 34b on the

contacts

34, 34. It is seen that the tabular portion 34b on each blade 34 serves a dual purpose in providing stop means for the auxiliary blade 36 and a spring seat for the biasing springs 55. One of the plates 43 includes an integral insulating hood 56 (FIG. 8) comprising a bottomless box extending over the main contact assembly 4, and having cutout front and rear portions 56a, 5612. Generally, the

arc plates

41, 43 are comprised of a material which is capable of evolving an arc-extinguishing gas when in the proximity to an electric arc. However, the present loadbreak fuse cutout is of the open, or non-enclosed type intended for outdoor usage, and when so applied, the

arc plates

41, 43 must be comprised of suitable material having acceptable arcquenching and weather-resistant abilities.

The use of highly-polymerized formaldehyde as an arc interrupter, is broadly disclosed and claimed in US. Pat. No. 3,059,081, issued Oct. 16, 1962 to Gordon C. Gainer and Albert P. Strom, and assigned to the same assignee as the present application.

The lower stationary contact assembly 6 comprises a suitably-configured hood plate 58 having a top wall portion 58a, side wall portions 58b, and a rear wall portion 580. The rear wall 58c is curved to mate withthe outer periphery of the insulator 2 and includes laterally-extending apertured ear portions 58d, (only one shown) for connection to a bracket 59 surrounding the insulator 2 and having studs 60 (only one shown) extending through the apertured ears 58d and secured thereto by nuts, 61, 61.

A flexible stationary contact plate 63 is securedto the inside of the rear wall by a suitable means, such as a rivet 64. The plate 63 may be comprised of any suitable conducting material, such as aluminum bronze, for example.

A line terminal clamp 66, similar to the previouslydescribed line terminal clamp 17, is attached to the hood plate 58.

The hood 58 has provided on its side walls 58b means providing a hinge pivot 67 for a composite fuse holder assembly to be hereinafter described. More specifically, trunnion guide slots 68 are provided in the side walls 58b of the hood 58, and have offset trunnion bearings, or seats 68a associated therewith.

The improved fusible device 1 of the present invention comprises two serially-related

fusible sections

70, 71, one section 70 being a high-current section and attached to a mechanically-connected low-current section 71, the two

sections

70, 71 preferably being removably threaded, or otherwise detachably secured together, as indicated more clearly in FIG. 1 of the drawings. With reference to FIG. 6 of the drawings, it will be observed that the high'current interrupting unit 70 generally comprises an enclosed cartridge device, or casing 72 at least partially filled with a granular material 73, such as white sand, for example, and enclosing a fuse link 74 of silver, for example, which extends from one end ferrule 76 to the other end ferrule 77.

As shown in FIG. 6, the right end ferrule assembly 77 include a threaded sleeve 78, which accommodates, in threaded engagement, a slip nut 80 having-a flange portion 80a, which abuts the upper end ferrule assembly 82 of the lower low-current unit 71, which is preferably of the expulsion-fuse type, and has a bore 84 therein for accommodation of a fuse and a fuse-link cable, the latter being designated by the reference numeral 86 in FIG. 1.

The low-current section 71, as more clearly illustrated in FIG. 7, comprises an insulating expulsion tube 87, having a plurality of boric-acid blocks 88 stacked therein between a pair of end plugs 89 and 90. The boric-acid blocks 88 evolve a condensible gas, including water vapor, during the heat of interruption, which occurs upon fusing of the fuse-link disposed within the bore 84 of the low-current section 71.

The expulsion section utilizes an interrupting medium of compressed boric acid, rather than the more commonly-used hard fibre, or Delrin. The use of boric acid in this section significantly reduces the discharge occurring when the device operates to clear low-magnitude fault currents. At high values of fault current, that is current magnitudes higher than from 400 to 1,200 amperes, the current-limiting section operates as well, so that the total discharge occurring continues at a reduced level.

Extending out the lower open end 84a of the expulsion fuse tube 87 is the fuse-link cable 86. This cable extension is a portion of the fuse-link, generally designated by the reference numeral 85, and enclosed within the fuse tube 87, having at the upper end thereof a fusible portion 85a, as well understood by those skilled in the art.

The lower end of the fuse-link cable extension 86 is secured by a wing bolt 91 to a toggle-link hinge mem ber 93, shown in detail in FIG. 2 of the drawings. Disposed adjacent the lower end of the fuse tube 87 is a bottom clamping casting 95, shown in more detail in FIGS. 2 and 3. The clamping casting 95 receives the fuse tube 87 therein, and is affixed thereto in any suitable manner, as by cement and being pinned at 95a. A pair of spaced integral leg portions 95b are provided on casting 95. The legs 95b are apertured at the outer ends to receive therethrough a shaft 96, which shaft 96 is also received in suitably-apertured integral leg members 97 on toggle link 93, thereby pivotally hinging the casting 95 to toggle member 93, which together constitute a unitary toggle assembly, designated by the reference numeral 99.

The toggle member 93 is provided with an eyelet 100 enabling the prong of a switch stick to be inserted therein, so that the fuse-holder assembly 102 may be bodily lifted out of the trunnion bearings 68a following fuse operation and dropout action for a refusing operation. Also, the toggle-link hinge member 93 is provided with trunnions, or stub shafts 103, which cooperate with the trunnion bearings 68a of the lower hood 58. The base of each stub shaft 103 is provided with a cam 104 having a narrow end 105. The cam provides maximum clearance for removal and replacement of the fuse-holder assembly 102, and, by cam action reduces the side play of the fuse-holder assembly 102 in the slots 68 as the cutout'nears the closed position assuring that the main contact and auxiliary blade will always be aligned for proper closing regardless of the angle of the closing force. A contact portion 107 on the toggle member 93 cooperates with the flexible contact 63 to engage therewith when the load-break fuse-cutout assembly 102 is in the closed position, as illustrated in FIG. 1 of the drawings.

A fuse-link flipper 108 is rotatably mounted on a shaft 109 extending between the legs 93a of the toggle hinge member 93. The flipper 108 includes a pair of off-set leg members 108a having apertures at their ends surrounding the shaft 109, and having a bight portion 108!) connecting the legs 108a. The bight portion l08b carries an integral latch portion 110 normally bearing against an integral catch 112 on the bottom of hinge casting 95. The latch 110 is normally held in engagement with the catch 112 by the tension of fuse cable 86 against the bight 108b, thus preventingdropout opera-' tion of the cutout 102, and reducing the strain on the fuse link 85, that would otherwise be exerted by the downward pressure of the'top contact 20 when latched. An integral spacer 114 on casting 95 abuts an integral stop-brace portion 116 to hold'casting 9 and toggle link 93 in under-toggle relationship. Thus, the top leaf contact member and the bottom flexible contact plate 63 collectively constitute a toggle-link biasing means 11 acting to break the underset toggle linkage 118.

INTERCHANGEABILITY The novel fuse-holder assembly. 102 of the present application is capable of use, optionally, with and without the load-break structure 122. The ferrule stud 124 at the upper end of the current-limiting fuse 70 has a notch 124a provided therein, which is in alignment with the slot 78a provided in the lower ferrule sleeve 78, as illustrated in FIG. 1. If the device is to be used in conjunction with the load-break attachment 122, as illustrated in FIG. 1, a hardware item, or load-break bracket 126, as illustrated in FIGS. 14-18, is slipped over the ferrule stud 124, so that the projection 126a (FIG; 15) fits within the recess 124a provided in the ferrule stud 124. The spring support bolt 128 is then forced through the apertures 126b provided in the downwardly-extending tabs 126a, as illustrated more clearly in FIG. 16 of the drawings. A torsion spring 130 surrounds the spring-support bolt 128 in a manner more clearly illustrated in FIG. 4 of the drawings. The rotatable auxiliary contact blade 36 has an aperture 36a provided through the lower portion thereof, which is pivotally mounted upon the torsion-spring support bolt 128, the latter having a threaded end portion 128a, which accommodates a castellated nut 132, which is fixedly secured upon the spring bolt 128 by a cotter pin 134. The rotatable auxiliary contact blade 36, in addition, has an offsetting boss portion 36b, which engages one end of the torsion spring 130, and is biased against the stop 126d, shown more clearly in FIG. 14 of the drawings. Thus, the rotatable auxiliary load-break contact blade 36 is pivotally mounted upon the springsupport bolt 128 to the bracket 126, and is capable of being latched, so that it may move in the direction indicated by the arrow 135 in FIG. 2, but not in the direction of the arrow 136 indicated in FIG. 2, since it is prevented from so doing by the stop portion 126d, a part of the load-break bracket 126.

However, if the load-break disconnecting device 122 is not desired to be used in conjunction with the fuseholder assembly 102, then merely asquare apertured spacer washer 137 is used in place of the load-break bracket 126, as illustrated in FIGS. 19 and 20 of the drawings. I

Whether the load-break blade assembly 122 is used or not, the next item to be assembled upon the ferrule stud 124 of the current-limiting fuse 70 is the contactand-pry-out assembly bracket 138, as illustrated more clearly in FIGS. 31 and 32. This will permit the latch 24 to be pried out by a downward pull exerted by a hook-stick upon the eyelet 139, as described hereinafter.

The contact bracket 138 includes a movable main contact portion 142. In addition, it provides two spaced apertured ear portions 138a supporting a pin 143, about which encircles a torsion spring 144 biasing an unlatching mechanism assembly 145 in a clockwise direction, as viewed in FIGS. 2 and 27. The latch release lever 146 has an unlatching nose portion 147 which engages the latch 26 to effect opening motion of the fuseholder 102.

'Thus, in any event, the contact-and-pry-out bracket device 138 is used with the fuse-holder assembly 102, regardless of whether the load-break bracket 126 and load-break blade 36 is used. As a final item upon the stud portion 124 is placed a washer 140, and, finally the locking nut 141. Thus, depending upon whether the load-break bracket 126 is used the device 1 may be used with, or without the load-break attachment 122. FIGS. 2 and 27 illustrate the two forms of the invention.

A torsion flipper spring encircles shaft 109, thus constantly urging the flipper 108 in a counterclockwise direction around pivot shaft 109. The flipper 108 also aids the fuse action in clearing faults by flipping the fuse cable 86 out of the fuse tube 87 during a fuse operation.

As shown, the manually-operable unlatching mechanism assembly, generally indicated at 145, is carried by the ferrule stud 124 for unlatching the latch 24 to effect load-break operation of the fuse cutout 1. The unlatching assembly comprises the rotatable unlatching arm 146 apertures at 146a to receive the pivot shaft 143. The shaft 143 extends through a pair of spaced upstanding ears 138a, thus pivotally relating to the unlatching device 145 with the upper end of the currentlimiting fuse 70. The free end 147 of the unlatching arm'146 extends around the ferrule 149 on top of contact portion 142 to normally rest beneath the latch tube 26 of latch 24, as seen in FIG. 1, when the switch 1 is in the closed position. Integrallyformed with the unlatching arm 146 is an operating ring, or eyelet 139 to render the unlatching device 145 suitable for operation by the usual hookstick device. A hook-eye spring 144 (FIG. 5) encircles the shaft 143 and has its end 144a bearing against the arm 146 to bias the unlatching device clockwise about pivot 143 in the normally latched position, as shown in FIGS. 1 and 5. It is seen that the unlatching mechanism 145 and the latch 24, or first latch device, comprise a positive latching assembly, which prevents accidental opening due to vibration or shock. The lineman must forceably pull down on eyelet 139 by his hookstick effecting thereby rotation of the rotating arm 146 to release the latch 24.

As shown in FIG. 1, the load-break fuse cutout is in its normal closed position with the main contact 142 latched into engagement with the main line contact 20 by the first latching device 24. At the same time the auxiliary blade 36 is received between the contact strips 34 inwardly of the stop means, or second latching device 37. At the lower end of the fuse-holder 102, the casting 95 and toggle hinge 93 are held in under-toggle relationship by the fuse-link cable 86 bearing upwardly against flipper 108.

The load-break fuse cutout 1 may optionally operate either as a fuse cutout, or as a loadbreak switch as has been described heretofore. In the operation of the loadbreak fuse cutout l as a fuse cutout, an overload or fault current passing through the device will fuse the fusible section 85 (FIG. 21) whereupon the cable extension 86 will become slack, and will enable the flipper 108 to urge the cable 86 downwardly out of the tube 87 as the flipper 108 rotates counterclockwise under the urging of spring 120. Operation of the flipper 108 releases the latch 110 on flipper 108 from engagement with catch 112 on casting 95, thereby permitting the fuse-holder assembly 102 to drop downwardly and outwardly about the hinge pivot 68a to the fully open disconnected position (not shown). The downward movement of the fuse-holder 102 lowers contact 142 away from the first latching device 24, thus effecting release of the main contact 142 with respect to the main stationarycontact 20. At the same time the auxiliary blade 36 is carried downwardly between

contacts

34, 34 and out of engagement therewith during the initial downward movement of the fuse-holder 102, so that the fuse-holder 102 is thereafter allowed to'freely move outwardly around pivot 67, as previously de scribed.

The thickness of the blade 36 is slightly smaller than the spacing between the

contacts

34, 34 to allow the blade 36 to easily drop out of the auxiliary contact assembly 9 during the above-described cutout operation, and also to minimize the contact between the blade 36 and

contacts

34, 34 when the cutout l is closed, whereby the major share of the current is carried through the main stationary contact assembly 4 and main movable contact 142. I

In the operation of the load-break fuse cutout 1 as a load-break switch, the operating member 146, supported by the ferrule 149, is moved downwardly and outwardly, the downward movement pivoting the unlatching arm 147 upwardly about pivot 143 to engage the latch tube 26 and thereby release the first latching device 24 from engagement with contact 142, and the outward motion effecting rotation of fuse-holder 102 about the pivot 67 effecting disengagement between contact 142 and contact 20. During the initial outward movement of contact 142 away from contact 20, the auxiliary blade 36 is prevented from disengaging from

contacts

34, 34 by stop means or the second latching device 37 on contacts 34 engaging blade 36. As the contact 142 moves further outwardly, the blade 36 rotates about pivot bolt 128 (FIG. 4) on the load-break bracket 126, remaining for a time in engagement with contact stop or latching means 34, 34 and carrying the full line current at this time to prevent arcing between the main contacts 142 and as they separate. The relative movement between fuse-holder 102 and blade 36 will act to stress spring 130 (FIG. 4). As the ferrule 149 moves further outwardly, blade 36 slides downwardly over stop or latching means 34, 34 and, when the

main contacts

20, 142 have separated a sufficient distance to prevent flashover, is completely withdrawn from between the

contacts

34, 34 in the downward direction,

whereupon spring 130 quickly moves the blade 36 out-.

wardly from the

contacts

34, 34 in the opening direction and between the arc-plate means 41, 43 with a snap action out through the slot in the

plates

41, 43 until the movable blade 36 is again substantially parallel with the fuse-holder assembly 102 and in engagement with the stop means 126d on arm 126. The movement of the rotatable blade 36 through the arc shute 39 will extinguish the are formed when the blade 36 disengages from stationary

auxiliary contacts

34, 34. As is generally known, the arc is extinguished by attenuation and confinement between the

plates

41, 43, and the gas blast produced by the gasevolving material, as hereinbefore described.

To close the load-break fuse cutout 1, the operating device 146 is moved inwardly by the maintenance man, rotating the fuse-holder 102 about bearing 67, effecting engagement of the

auxiliary contact blade

34, 34 before the main movable contact 142 engages main stationary contact 20. The stop means 126d on arm bracket 126 bears against rotatable blade 36 during the closing operation effecting engagement with the

contacts

34, 34 before the main contacts 142 engage, and forcing the blade 36 inwardly between

guide members

34a, 34a and beyond stop means 34b to its normally closed position, as shown in FIG. 1. Upon the occurrence of relatively low-current faults, the standard fuse link 85 is fused and separates to clear the circuit and to allow the toggle arrangement 99 to unlatch, dropping the fuse device 102 to the dropout lower position. The expulsion section utilizes an interrupting medium of compressed boric acid, rather than the more commonly-used hard fiber or Delrin. The

use of boric acid in this section 71 significantly reduces the discharge occurring when the fusible device 1 operates to clear low-magnitude fault currents. At high values of fault current, that is current magnitudes higher than 400 to 1,200 amperes, for example, the currentlimiting section operates as well, so that the total discharge occurring continues at a reduced level.

Thus, from the foregoing remarks, it is apparent that during relatively low-fault current interruption, only the lower unit 71 operates, the upper unit 70 remaining intact, and merely replacement of a standard-type fuselink is required to convert the device again into operating condition, and to again close the circuit through the connected line. In the case of a relatively high fault current, both the high current and the low-

current interrupting sections

70, 71 fuse simultaneously, and there is a reduced display since part of the interrupting effort is accommodated in the enclosed high-current interrupting unit 70, such as the current-limiting section.

LOAD-BREAK OPERATION In electrical parallel with the top

main contacts

20 and 142 is another set of auxiliary contacts 34, and a quick-break stainless steel blade 36 located between two pieces of insulating

plate

41, 43, composed, of Delrin, for example. The lineman inserts his hookstick in the fuse holder hook-eye 139, and pulls down in the usual manner. First the

main contacts

20 and 142 separate; however, current is still carried through the quickbreak blade 36 until the

main contacts

20, 142 are far enough apart to prevent arcing. Second, the blade 36, by means of a strong spring action, then snaps away from its contact 34, drawing an are within the arc chute 39. A deionizing gas is generated from the Deli-in" plastic when subjected to this are heat. The gas, combined with the snap action of the blade 36, quickly extinguishes the are thus completing a simple and safe load-break operation.

An important factor of this load-break operation in part lies in the arc chute 39, made of Delrin plastic, for example. This is a tough, temperature and moisture resistant material, which is highly suitable for this purpose. The material cannot be ignited under load-break conditions, due to the fast extinguishing action of the arc-chute. The quick-break blade 36 is preferably made of stainless steel, for example. Pitting and erosion of the blade 36 after many operations, does not impair the load-breaking ability of the cutout. An important advantage is that a conventional standard hookstick is the only tool needed to open the cutout 1 under full load." Also, of important for the safety of linemen is the fact that the are is completely confined within the Delrin arc-chute 39 with no chance of external arcing, as with fuse-link-break type of devices, nor is safety dependent upon replacement of a gas capsule. In addition, under such load-break operations, no fuse-link need be replaced. Tests have clearly shown that the arc-chute 39 will interrupt 200 amperes over 200 times with the Delrin arc-chute 39 not tracking nor forming conducting carbonized paths during the entire life of the cutout.

FIG. 22 illustrates the cutout 1 closed with the load current being carried by the main contacts. FIG. 23 illustrates the cutout half open with the quick-break blade 36 in the arc-chute now carrying the load current. FIG. 24 illustrates the quick -break blade 36 just before the releasing action. It will be noted that the blade 36 cannot be released until the cutout is opened sufficiently to prevent the are from restriking between the

main contacts

20, 142..

FIG. 25 illustrates the blade 36 released and further opening of the cutout releases the blade 36, and it snaps the length of the arc chute elongating and deionizing the arc with the coil spring 130 at the bottom of the blade 36 providing the opening energy. FIG. 26 illustrates the blade half closed during a closing operation. This figure illustrates that the cutouts

main contacts

20, 142 engage after the quick-break blade 36 closes, thus preventing burning and pitting due to prestriking during a closing operation.

The present device 1 is capable of use either with or without the load-break feature 122, as previously described. The foregoing description has described the load-break attachment 122; however, it is to be clearly understood that the device is capable of use without the load-break attachment 122, as illustrated in FIGS. 27, 28 and 29 of the drawings. With respect to these figures, showing the use of the fusible device 1 without the load-break attachment 122, it is to be noted that many parts are similar in construction to the device, as described hereinbefore.

By the use of the hook-stick, the latch releasing lever 146 may be rotated about its pivot 143 to effect release of the latch 26 and permit opening motion of the fuseholder assembly 102.

It will be obvious to those skilled in the art that the current-limiting fusible section 70, illustrated in FIG. 6 of the drawings, could bereplaced by other currentlimiting devices, such as those described in US. Pat. No. 3,569,891 Cameron, issued Mar. 9, 1971. Merely, by way of illustration only, has the particular type of current-limiting fuse section 70, illustrated in FIG. 6, been described in connection with the present invention. Alternates and different types of currentlimiting fuses could be substituted for that illustrated in FIG. 6. In addition, although boric acid blocks were described in conjunction with the expulsion-type fusible device, illustrated in FIG. 7, other types of expulsion fuses could be utilized with the condition, however, that the fuse-link cable 86 therein would necessarily have to be severed to enable breaking of the toggle linkage 118.

From the foregoing description, it will be apparent that there has been provided an improved composite sectionalized dropout-type of fusible device 1, in which the noise and display has been minimized by utilizing two interrupting

sections

70, 71 in series, one being a high-current interrupting section operable only during high-current interruption, whereas the other lowcurrent interrupting section 71 is operable both during low and high-current interruption Thus, the two

sections

70, 71 cooperate together to reduce the interrupting effort required by each.

To effect a fusing operation during low-current interruption, it is merely necessary to unscrew the connecting slip ring 80 and to replace the standard-type fuselink 85, illustrated more in detai in FIG. 21 of the drawings. Upon replacement of a standard fuse-link cable 86, the low-current section 71 may again be mechanically attached to the high-current section by screwing the connecting slip ring 80 about the threaded lower ferrule portion 78 of the upper high-current interrupting unit 70. The fuse-link cable 86 is then attached to the capstan device 150, and the fuse structure 102 is then capable of being reinserted back into the circuit.

From the foregoing description, it will be apparent that there has been provided an improved fusible device, particularly adapted for dropout operation, in which two

fusible sections

70, 71 are arranged in electrical series and adapted to be selectively fused. In other words, during low-current interruption, only the lower expulsion-type fusible device 71 functions, and the upper high-current unit remains intact. During high-current fault interruption, however, both

sections

70, 71 fuse simultaneously, thereby relieving each of them by their combined action, and the interrupting capability is increased with a concomitant lowering of noise and display. For load-break operation, merely by the expedient of attaching additional hardware parts, the load-break-extension device 122 may be readily accommodated. On the other hand, should such a loadbreak function not be required, the device 1 is fully capable of being operated independently thereof, and as a composite two-sectioned fusible device, as illustrated in FIG. 27 of the drawings. Also, from the foregoing description, it will be apparent that there has been provided a new circuitinterrupting device designed for use with a standard fuse-support assembly, the device being characterized by a higher and improved interrupting ability, achieved at the same time with a reduced noise and display level. Moreover, the device is capable of being used with standard-type fuse-links, which may be changed, depending upon thedesires of the maintenance man. Obviously, the fuse-links are of standard characteristics, and their level of current protection may be readily ascertained.

Although there has been illustrated 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 readily be made therein by those skilled in the art, without departure from the spirit and scope of the invention.

What is claimed is:

1. A composite open-type drop-out fuse cutout comprising, in combination, means defining a pair of spaced line-contact assemblies, a pivotally-mounted composite fuse-holder assembly including a toggle linkage and a fuse-tube assembly pivotally supported adjacent one end thereof to one of said line-contact assemblies, said composite fuse-holder assembly carrying a main movable contact adjacent the other end thereof to make main contacting engagement with the other line-contact assembly, means including a fuse-link extending through said fuse-tube assembly for maintaining said toggle linkage in an underset condition, means biasing said toggle linkage to a collapsed condition, said fuse-tube assembly including an enclosed currentlimiting fuse-section disposed adjacent said other end of the composite fuse-holder assembly, said lowcurrent interrupting section accommodating said fuselink, whereby on low-current interruption the lowcurrent section only need be replaced in a re-fusing operation, and during heavy fault-current interruption both the low-current section and the enclosed currentlimiting fuse-section fusing, and the enclosure of the current-limiting fuse-section preventing external emis sion of arc products.

2. The combination according to claim 1, wherein said composite open-type drop-out fuse cutout is adaptable for load-break operation, and delayed-acting load-break means having separable contacts and including a latching device is situated adjacent the free end of the rotatable fuse-holder assembly, the separable contacts of said load-break means being electrically in parallel with the circuit including said movable main contact and said one line-contact assembly.

3. The combination according to claim 2, wherein said load-break means includes a latching device, whereupon manual separation of said main movable contact from said other line-contact assembly will nevertheless cause continued latched contacting engagement of said delayed-acting load-break means for a predetermined time.

4. The combination according to claim 2, wherein said load-break means is responsive to the collapse of said toggle linkage during fault-current interruption to effect release of said latching device, whereby during fault-current interruption the fuse-holder assembly may freely rotate about said one line-contact assembly to an open indicating observable position.

5. The combination according to claim 1, wherein the low-current interrupting section is an expulsiontype interrupting section and includes a standard-type fuse-link.

6. The combination according to claim 1, wherein a readily detachable means interconnects mechanically the enclosed current-limiting fuse section and the lowcurrent interrupting section.

7. The combination according to claim 1, wherein a flipper exerts tension force upon the fuse-link cable, and biasing means is associated with said flipper to create said force tension.

8. The combination according to claim 2, wherein the load-break means includes an arc-chute structure including a pair of closely-spaced insulating plates.

9. The combination according to claim 8, wherein said closely-spaced insulating plates evolve an arcextinguishing gas.

10. The combination according to claim 1, wherein the free end of the fuse-holder assembly is capable of readily adapting attaching parts to adapt it to a loadbreak device.

11. The combination according to claim 1, wherein tube having a plurality of apertured gas-evolving blocks stacked therein.

12. The combination according to claim 11, wherein said apertured blocks are of boric acid.

13. The combination according to claim 1, wherein only a single fuse element is employed in the enclosed current-limiting fuse section.

14. A composite fuse-holder assembly including an enclosed current-limiting section and a serially-related low-current interrupting section, toggle means clamped to one end of said composite fuse-holder assembly, said toggle-means comprising a toggle-leg member fixedly clamped toone end of the fuse-holder assembly, a toggle-link hinge-member pivotally connected to said toggle-link member so as to form a toggle-linkage therewith, a fuse-link having a fuse-link cable disposed interiorly of said fuse-holder assembly and having one end of the fuse-link cable extending out of one end of the composite fuse-holder assembly and removably attached to said toggle-link hinge-member, whereby said toggle-means is maintained in an underset condition, said toggle-link hinge-member having a pair of laterally-extending trunnion-bearings so as to make said composite fuse-holder assembly adaptable for insertion into a conventional-type open-style fuse mounting, said fuse-holder assembly including an enclosed currentlimiting fuse-section disposed adjacent the other end of said composite fuse-holder assembly, the device functioning during low-current interruption to cause only fusing of the low-current section and no fusing of the current-limiting fuse-section, and said device further functioning on heavy fault-current interruption for both fuse sections to fuse with the enclosed housing of the current-limiting fuse section preventing the emission of hot arc gas products externally of the device.

15. The combination of claim 14, wherein the lowcurrent interrupting section is an expulsion-type fuse device having the upper end closed and causing the ejection of fuse products out of the lower open end of the expulsion-type fuse.

16. The combination according to claim 14, wherein the enclosed current-limiting section and the lowcurrent interrupting section are mechanically separable.

17. The combination of claim 14, wherein the lowcurrent interrupting section accommodates a standardtype fuse-link available in variant ratings and interchangeable within the low-current interrupting section.

18. The combination according to claim 14, wherein the fuse-holder assembly has an auxiliary contact-blade rotatably mounted adjacent the upper free end of the fuse-holder assembly.

19. The combination according to claim 18, wherein the auxiliary contact-blade is biased in the direction of opening drop-out motion of the composite-type fuseholder assembly.

20. The combination according to claim 14, wherein an optional load-break device including a rotatable auxiliary contact-blade may be attached adjacent the free end of the composite-type fuse-holder assembly at the option of the user.

21. The combination according to claim 16, wherein the detachable connection includes a rotatable sleeve having a threaded connection to one of the fuse sections.

. said blocks are of boric acid.

26. An open-type drop-out type fusible cutout including means insulatingly supporting in spaced relation a pair of main-line contacts, a hinge-support asso ciated with one of said main-line contacts, a rotatable fuse-holder assembly adapted for pivotable mounting about said one hinge-support and including in series relationship an enclosed current-limiting fuse-section and a serially-related low-current interrupting section of the expulsion-fuse type, said rotatable fuse-holder assembly having a movable main contact adjacent its outer free end, and load-break means carried partially by the outer free end of the rotatable fuse-holder assembly and also by said other line-terminal assembly, said load-break means including a quick-break auxiliary contact-blade, and an arc-chute with the arc-chute enclosing a cooperable auxiliary contact.

Claims

1. A composite open-type drop-out fuse cutout comprising, in combination, means defining a pair of spaced line-contact assemblies, a pivotally-mounted composite fuse-holder assembly including a toggle linkage and a fuse-tube assembly pivotally supported adjacent one end thereof to one of said line-contact assemblies, said composite fuse-holder assembly carrying a main movable contact adjacent the other end thereof to make main contacting engagement with the other line-contact assembly, means including a fuse-link extending through said fuse-tube assembly for maintaining said toggle linkage in an underset condition, means biasing said toggle linkage to a collapsed condition, said fuse-tube assembly including an enclosed current-limiting fusesection disposed adjacent said other end of the composite fuseholder assembly, said low-current interrupting section accommodating said fuse-link, whereby on low-current interruption the low-current section only need be replaced in a re-fusing operation, and during heavy fault-current interruption both the low-current section and the enclosed current-limiting fusesection fusing, and the enclosure of the current-limiting fusesection preventing external emission of arc products.

5. The combination according to claim 1, wherein the low-current interrupting section is an expulsion-type interrupting section and includes a standard-type fuse-link.

6. The combination according to claim 1, wherein a readily detachable means interconnects mechanically the enclosed current-limiting fuse section and the low-current interrupting section.

9. The combination according to claim 8, wherein said closely-spaced insulating plates evolve an arc-extinguishing gas.

10. The combination according to claim 1, wherein the free end of the fuse-holder assembly is capable of readily adapting attaching parts to adapt it to a load-break device.

11. The combination according to claim 1, wherein the low-current section includes an expulsion-type fuse tube having a plurality of apertured gas-evolving blocks stacked therein.

14. A composite fuse-holder assembly including an enclosed current-limiting section and a serially-related low-current interrupting section, toggle means clamped to one end of said composite fuse-holder assembly, said toggle-means comprising a toggle-leg member fixedly clamped to one end of the fuse-holder assembly, a toggle-link hinge-member pivotally connected to said toggle-link member so as to form a toggle-linkage therewith, a fuse-link having a fuse-link cable disposed interiorly of said fuse-holder assembly and having one end of the fuse-link cable extending out of one end of the composite fuse-holder assembly and removably attached to said toggle-link hinge-member, whereby said toggle-means is maintained in an underset condition, said toggle-link hinge-member having a pair of laterally-extending trunnion-bearings so as to make said composite fuse-holder assembly adaptable for insertion into a conventional-type open-style fuse mounting, said fuse-holder assembly including an enclosed current-limiting fuse-section disposed adjacent the other end of said composite fuse-holder assembly, the device functioning during low-current interruption to cause only fusing of the low-current section and no fusing of the current-limiting fuse-section, and said device further functioning on heavy fault-current interruption for both fuse sections to fuse with the enclosed housing of the current-limiting fuse section preventing the emission of hot arc gas products externally of the device.

15. The combination of claim 14, wherein the low-current interrupting section is an expulsion-type fuse device having the upper end closed and causing the ejection of fuse products out of the lower open end of the expulsion-type fuse.

16. The combination according to claim 14, wherein the enclosed current-limiting section and the low-current interrupting section are mechanically separable.

17. The combination of claim 14, wherein the low-current interrupting section accommodates a standard-type fuse-link available in variant ratings and interchangeable within the low-current interrupting section.

19. The combination according to claim 18, wherein the auxiliary contact-blade is biased in the direction of opening drop-out motion of the composite-type fuse-holder assembly.

22. The combination according to claim 14, wherein a spring-biased fuse-link flipper maintains tension upon the fuse-link cable.

23. The combination according to claim 22, wherein the toggle link member has a shoulder portion and the fuse-link flipper latches under said shoulder to somewhat relieve the tension-pressure upon said fuse-link cable.

24. The combination according to claim 14, wherein the low-current section includes a plurality of apertured gas-evolving blocks.

25. The combination according to claim 24, wherein said blocks are of boric acid.

26. An open-type drop-out type fusible cutout including means insulatingly supporting in spaced relation a pair of main-line contacts, a hinge-support associated with one of said main-line contacts, a rotatable fuse-holder assembly adapted for pivotable mounting about said one hinge-support and including in series relationship an enclosed current-limiting fuse-section and a serially-related low-current interrupting section of the expulsion-fuse type, said rotatable fuse-holder assembly having a movable main contact adjacent its outer free end, and load-break means carried partially by the outer free end of the rotatable fuse-holder assembly and also by said other line-terminal assembly, said load-break means including a quick-break auxiliary contact-blade, and an arc-chute with the arc-chute enclosing a cooperable auxiliary contact.