US2866032A - Combination fuse cutout and switch - Google Patents

Description

G. R. M CLOUD COMBINATION FUSE CUTOUT AND SWITCH Dec. 23, 1958 2 Sheets-Sheet 1 Filed Feb. 27, 1956 K 3 4 a M .4

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United States Patent COMBINATION FUSE CUTOUT AND SWITCH George R. McCloud, Cudahy, Wis., assignor to McGraw- Edison Company, a corporation of Delaware Application February 27, 1956, Serial No. 567,842

11 Claims. (Cl. 200-414) This invention relates to a combination fuse cutout and switch for controlling an electric circuit. The invention is particularly, but not exclusively, adaptable to an insulating bushing of the type used on electrical apparatus housed in an oil filled tank, such as a transformer, for connecting an exterior line wire to an interior apparatus terminal.

An object of this invention is to provide a fusible element in an insulating bushing and to incorporate a switch in the form of a fuse bridging member which may be easily connected in the circuit in the event of fuse rupture or if by-pasing the fuse becomes desirable for other reasons.

It is a further object of this invention to provide in a bushing mounted circuit protective device means for remotely actuating a fuse bridging member through the agency of an insulating stick without requiring withdrawal of the protective device from its bushing so that a lineman servicing the apparatus will be afforded a great degree of safety and convenience.

Another object is to provide a switch which is totally enclosed and locked in an insulating housing.

Still another object is the provision of a protective bushing adapted to receive a manually insertable conductive fuse assembly which may be securely locked in the bushing before the fuse is permitted to advance for completing an electric circuit therethrough by actuation of an exteriorly located manual tripping means. The merit of this object lies in reducing the danger incidental to closing an electric circuit under fault conditions.

Other more specific objects will appear from time to time in the course of the specification and claims.

The present invention is an improvement over related subject matter described and claimed in a co-pending application of the instant inventor, assigned to the same assignee, filed October 12, 1954, and having Serial Number 461,780, now Patent No. 2,783,328, dated February 26, 1957.

Referring to the drawings:

Fig. 1 represents a vertical sectional view of the invention comprising a unitary construction, but divided in two parts on the parting line AA for convenience in representing it to a larger scale;

Fig. 2 is a fragmentary sectional view taken on a line corresponding with 22 in Fig. 1, showing a switch latch element;

Fig. 3 is a horizontal sectionalview taken on a line corresponding with 33 in Fig. 1, looking in the direction of the arrows;

Fig. 4 is a fragmentary view, partially in section, taken on a line 44 of Fig. 3 and showing details of the means for locking the novel protective device in its insulating bushing;

Fig. 5 is a horizontal sectional view taken on a line corresponding with 5-5 in Fig. 1 looking in the direction of the arrows;

Fig. 6 is a horizontal sectional view taken on a line 2,866,032 Patented Dec. 23, 1958 corresponding with 66 in Fig 1 looking in the direction of the arrows;

Fig. 7 is a vertical sectional view similar to Fig. 1 but showing the fuse bridging member operated to active position, the unitary structure being divided into two parts on the parting line BB for convenient representation to a larger scale;

Fig. 8 is a fragmentary vertical sectional View taken on a line corresponding with 88 in Fig. 7, looking in the direction of the arrows;

Fig. 9 is a schematic representation of a fluid filled tank, housing electrical apparatus in the form of a transformer in conjunction with the combination fuse cutout and switch forming the subject of the instant application; and, N

Fig. 10 is a vertical sectional view of an alternative embodiment of the invention, with parts broken away.

Before proceeding with a detailed description of the invention it will be described in general terms in connection with a schematic representation of a transformer such as in Fig. 9 where the novel protective device, designated generally by the reference number 1, is shown mounted on the cover 2 of a metallic transformer tank 3. Interiorly of the tank is seen a transformer core and coil assembly 4, constituting the electrical apparatus being protected, immersed in a dielectric fluid to the level indicated by the dashed lines 5. The transformer secondary coil is connected at 6 to a lead wire extending into a relatively low-voltage porcelain bushing 7, only one of which is shown and which projects into tank 3 beeath the level of the dielectric fluid and outwardly through the cover 2 to which it is sealingly engaged. A secondary line wire, not shown, may be connected to the bushing at a terminal 8 provided for that purpose. Certain transformer lead wires are omitted from Fig. 9 for the sake of clarity.

The novel primary or high voltage protective bushing 1 likewise extends through cover 2 and underneath the surface of the dielectric fluid where it terminates in a connection 11 supplying the primary winding of the transformer. At the lower end of protective bushing 1 and interiorly thereof, there is a fusible element 12 in heat exchange relationship with the dielectric fluid and adapted for response to temperature of the dielectric fluid and to heat developed by excessive current flowing through the transformer primary.

As indicated, the protective bushing 1 is provided with a fusible element 12 normally in the circuit to protect an electrical apparatus from excessive currents. It is, of course, advisable to select a fusible element which is properly coordinated with the thermal rating of the insulation in the apparatus being protected in order to avoid premature deterioration of the insulation. How ever, in practice, emergency conditions occasionally arise where it is more important to provide continuous electric service than it is to be concerned about reducing the life of the apparatus. Hence, where the fusible element ruptures from excessive current of a transient nature or due to a sustained overload, and it is for the moment inconvenient to replace the apparatus with that of a larger capacity, it may be advisable to by-pass the fusible element, especially where uninterrupted electric service is imperative. The instant invention enables rapid restoration of electric service under such emergency conditions by merely operating a trip handle 13 on the circuit protective device 1 through the agency of a linemans insulated stick.

The combination fuse and switch 1 may be seen in greater detail in Fig. 1 where it is shown enclosed in an insulating bushing 14 of the conventional petticoat type. Bushing 14 is engageable with apparatus tank cover 2 in sealing relation by means of a gasket or ce ment, not shown,, disposed in an annular channel near its mid-section. The bushing may be tightly secured to cover 2 by a conventional bushing clamp, not shown, or 11; may be supported in open space on a suitable bracket.

The novel circuit protecting device is made in convenient form for manually inserting and withdrawing it from bushing 14 which is provided with a concentric bore 17 substantially coextensive with its length. At its lower end, bushing 14 is counterbored' at 18 for receiving a load terminal comprising a plurality of resilient spring clips 19 which may be anchored in the counterbore by any suitable bonding means such as metallizing theinterior thereof and flowing in solder 20., A pigtail 21 is embedded in solder for the purpose of providing a connection to an'electrical apparatus. Resilient fingers 19 are substantially U-shaped in cross-section and adapted to exert their inherent force in a radially inward direction; It is to be noted that fingers 19 are provided with an offset portion 22 diverging radially outwardly to define a circumferential socket 23 for electrical engagement by the end portion 24 of an axially advance able andretractable'fuse short circuiting sleeve or bridging member 25.

Terminal fingers 19,,see Fig. 1, are always in contact with the conductive ferrule 26 of a protective fuse, designated generally by the reference numeral 27. Fuse 27 comprisesa hollow insulating tube 28 of horn fibre or other'well known material through which a fusible element 12 extends. One end of the fusible element 12 is connected to conductive ferrule 26,- which is in contact wtih the terminal fingers 19, and the other end terminates in a button head 29 which is held in tight compressive relation with fibre tube 28 by means of an internally threaded cap 30. An electric circuit through fuse 27 is maintained by a conductive rod 32 extending from the fuse to the upper portion of the protective bushing.

If it is desired to bypass the fuse 27 just described, bridging sleeve is adapted to be telescoped downward- 1y on rod 32 into direct contact with terminal fingers 19, thereby providing a preferential path for the current to flow. It will appear hereinafter that when sleeve 25 is inbridging position as indicated in Fig. 7, conductive rod 32 is not relied upon exclusively as a current path.

The upper portion of bushing 14 is provided with a cylindrical member 33 constituting a line terminal which isin turn provided with a radially projecting ear 34 for attaching an incoming line wire by means of a set screw, neither thewire nor screw being shown; Cylindrical terminal 33 has a flanged portion 35', which bears upon the end of bushing 14, and an axial depending extension 36 which projects into a counterbore 37 in the bushing. The flanged portion 35 is soldered to a metallic shell-like ring 38 which is rolled into sealing relation with the bushingas shown. It is advisable to interpose a resilient gasket'such as 39 between shell 38 and the bushing to augment sealing. The structure described in this paragraph is affixed with respect to the bushing 14 and forms a permanent integral part thereof.

Elements for providing the normal and auxiliary current path through bushing 14 are carried on a cap member 40 engageable by means of a hot-stick through an arch-shaped hole 46 provided for that purpose. Cap member '40 may be made of red brass or any suitable highly conductive material. In Fig. 1, it will be ob served that cap 40 is diametrically larger than cylindrical terminal 33 so that the former may overhang the latter for preventing entry of moisture or other contaminants.

In order to lock cap 48 to cylinder 33, the cap is provided near its lower margin with a radially enlarged annular portion 41 which has two locking pins 42 pro jecting radially inwardly from it. A complementary diametrically enlarged portion 43 on cylindrical terminal 33-has a J-slot 44 cut in it for receiving locking pins 6t, 42. It is obvious that when cap 40 is deposited over cylinder 33, pins 42 will enter J-slots 44, whereupon the entire cap may be given a slight rotary movement for engaging the pins in a circumferentially disposed portion 45 of the J-slot.

Cylindrical terminal 33 is also provided with a resilient ring gasket 4-7 for sealing cap 40. It will be noted that locking pins 4-2 are of such radial length that they do not cut the peripheral surface of gasket 47 when the cap is placed upon terminal 33.

Cap 413 has a tubular extension 48 projecting integrally fro-m it into counterbore 37 of the bushing. Guide means in the form of a cruciform shaped member 49 is soldered or brazed to the bottom of tubular extension 4-3 and tapped at its center for receiving the threaded end of conductive rod 32 which is surrounded by bridging sleeve 25 both of which extend axially down into the bushing bore 17. Although not apparent in Fig. 1, it may be seen particularly in Fig. 6 that cruciform 49 does: not totally close the lower opening in tubular extension 48 for the reason that it includes a central circularportion of small diameter, as compared with the interior diameter of extension 48, and two radial winglike portions 50 by means of which it is soldered to extension 48.

It will be observed that there is an'electric circuit developed between line terminal 33 and tubular extension 48 throughthe agency of a plurality of wiping contact fingers 51 hearing on extension 58. Fingers 51 are inherently resilient and are anchored by means such as high temperature solder disposed in appropriate sockets in the depending portion 36 of line terminal 33.-

Tubular fuse bridging sleeve 25 extends coaxially within tubular extension 48, the former being provided with a pair of diametrically opposite longitudinal slots 52 beginning at 53 and terminating downwardly at 54. Slots 52 are of a size adapted to closely receive the transverse wing-like portions 50 of cruciform guide means 49. Consequently, sleeve 25 may telescope interiorly of extension 48 from its normal position as shown in Fig. l to its fuse bridging position illustrated in Pig. 7 without interference by the transversely disposed cruciform guide means.

Innormal operating position, tubular bridging sleeve 25 is biased downwardly by a compression spring 55 interposed between cruciform 49 and a constricted neck 56 in sleeve 25. A bearing washer 57 is provided for maintaining spring 55 square with respect to rod 32.

Bridging sleeve 25 is normally restrained or latched upwardly in opposition to the force of compression spring 55, as in Fig. l, by means of a flattened central portionon cross-shaft 58 forming part of operating handle 13. Cross-shaft 58 has apair of sealing gaskets 59 which develop enough friction with the bore 60 of cap 40, in which the cross-shaft is journaled, so that handle 13 will tend to remain in any angular position in which it is placed. Handle 13 is prevented from withdrawal from cap 40 by means of snap-rings 61 disposed in spaced relation on shaft 58 immediately adjacent either side of cap 40. By reference to Fig. 2 it will be noted that cross-shaft 58 has a central flattened portion 62 equal in one dimension to a diametrical slotted hole 63 extending through the extreme upper end of tubular bridging sleeve 25. By means of handle 13, flattened portion 62 is rotatable from its horizontal position illustrated in Fig. 2 until it assumes a vertical position where it fits through an axial slot 64 in the end of tubular bridging sleeve 25. Upon unlatching sleeve 25 in this manner, the energy stored in compression spring 55 is released for driving tubular sleeve 25 downwardly from its position in Fig. 1 into contact relation with U- shaped spring terminal clips 19 located at the lower oil immersed end of insulating bushing 14.

From the description thus far it is evident that the {:urrent-path-through bushing 14 during normal operation commences at line terminal 33, continues through fingers 51, to tubular extension 48, to cruciform wings 50 and down to fuse assembly 27 through the medium of solid rod 32.

When by-passing fuse assembly 27, it will be observed in Fig. 7 that the lower contact end 24 of sleeve 25 makes firm contact with spring clips 19 but is in radialspaced relation with clamping cap on the upper end of the fuse assembly 27. Accordingly, sleeve 25 constitutes the principal current path from the pigtail lead wire 21. In order to assure the most directelectrical path between bridging sleeve 25 and tubular extension 48 at the upper end of bushing 14, another pair of auxiliary resilient fingers 66 are provided in a plane rotated 90 degrees from the plane in which fingers 51 are disposed. Auxiliary fingers 66 are anchored, by brazing or other means, flush with the outer periphery of tubular extension 48, see Fig. 8, and they have a portion extending through an axial slot 67 into direct electric contact relation on the outer periphery of internal tubular bridging member 25. Auxiliary fingers 66 reside in the same horizontal plane as stationary fingers 51 when the protective assembly is locked within bushing 14 but it is impossible to cause their inadvertent interengagement because they do not align in the same plane until locking pins 42 have entered J-slots 44 whereupon the auxiliary fingers can no longer be rotated through the 90 degrees necessary to cause their interengagement;

It is now evident, see Fig. '7, that when the protective device is in its fuse bridging position, current follows a principal path beginning at spring clips 19, directly through tubular bridging sleeve 25 to the upper portion of the bushing where it transfers from the sleeve to tubular'extension 48 by means of auxiliary fingers 66. Thereafter the current follows its normal path from tubular extension 48 to main fingers 51 and line terminal 34.

Use and operation of the invention is a comparatively simple matter. Assuming that normal operation is required, that is, where the fusible element 12 performs its protective function, a fuse assembly 27 will be attached to conductive rod 32 as shown in Fig. 1 when the protective assembly is withdrawn from bushing 14. Tubular bridging sleeve 25 may then be manually urged in the direction of cap for compressing spring 55. At this time handle 13 is in a horizontal position and its central flattened portion 62 is in a vertical position for permitting entry of slot 64 and circular hole 63 in the extreme upper end of bridging sleeve 25. Upon this event, handle 13 is rotated so that flattened portion 62 assumes a horizontal whereupon sleeve 25 is restrained compression spring 55. The entire assembly is then placed in insulating bushing 14 by means of an insulating stick, not shown, by engaging hole 46 in cap 40. Cap 40 is then given a slight rotation for the purpose of engaging locking pins 42 with J-slothooked portions 45. This closes the circuit throughfuse assembly 27, for normal operation.

If the fusible element 12 ruptures, or other emergency conditions arise whereupon it is desired to bridge the fuse assembly 27, sleeve 25 may be released to bridging position by merely tripping handle 13 without withdrawing the assembly from bushing 14. Rotation of handle 13 through 90 degrees permits flattened portion 62 of shaft 58 to be passed by slotted end 64 of the tubular bridging member 25. When so released tubular bridging member 25 is projected with a snap action into contact relation with clips 19 under the influence of compression spring 55. Under these conditions it is immaterial whether fusible element 12 is ruptured or intact, for the current will follow the path of least resistance from spring clips 19 directly through tubular bridging member 25 and to upper line terminal 33 as described hereinabove.

.It will be appreciated that .the entire fuse assembly against the action of position with reference to slot 64,

$3 27 may be omitted and the other elements retained intact if it is desired to use the invention solely for the purpose of switching an electric circuit. This alteration reserves the advantage. of permitting closing of a circuit within an insulating housing with maximum safety.

Fig. 10 illustrates an alternative form of the invention modified to enable closing a fused circuit within an insulating bushing. The fragmentary view shown is broken away from a structure, which may be similar to that in Figs. 1 and 7, on a line slightly below parting lines A-A and BB respectively. Where components are the same as those described in connection with previous figures, like reference numerals are applied.

In Fig. 10 it will be noted that bridging sleeve 25' and rod 32' are shortened in comparison with an embodiment discussed earlier. Sleeve 25 directly carries a fuse assembly 27 whose conductive ferrule 26 is spaced lower from terminal clips 19 when automatic closing spring 55 is compressed as in Fig. 1. Fuse assembly upper cap 30' may be soldered in the end of sleeve 25' and fibre fuse tube 28 screwed into the cap in order to cause electrical connection between the cap 30' and the button head 29 of fusible element 12.

It will be apparent that the electric circuit through bushing 14 will be open by virtue of the space between fuse ferrule 26 and clips 19 when the combination assembly is initially locked into the bushing. Hence, there is no danger of serious arcing if a fault exists on the circuit being closed. Closing may be affected by rotation of tripping handle 13 so that the energy stored in compression spring 55 may be released suddenly for driving the fuse assembly 27 into circuit with the clips 19'.

Although the novel combination fuse and switch has been described with respect to a primary transformer bushing, those skilled in the art will readily perceive how to modify the teaching of this invention to other forms of protective devices. A preferred embodiment of the invention has been set forth for illustrative purposes but it is not to be construed as limiting the invention for it may be variously embodied and is to be interpreted as claimed.

What I claim is:

1. An electric circuit protective device comprising a tubular insulating bushing having a first terminal at one end and a second terminal at the other end, an elongated conductive member insertable in said bushing and having a fixed portion in contact with said first terminal and amovable conductive portion initially spaced with respect to said. second terminal, locking means engaging said fixed portion with said first terminal when said movable portion and second terminal are still in spaced relation, spring means biasing said movable portion toward said second terminal, latch means releasably engaged with said conductive member for restraining said movable force of said spring means, tripping means exteriorly of said bushing and coacting with said latch means to release said movable portion for advancing into contact relation with said second terminal under the influence of said spring.

2. An electric circuit protective device comprising, an insulating bushing having a bore coextensive with its length, a first terminal fixed to one end of said bushing and having a bore aligned with said bushing bore, a second terminal remote from said first terminal, a conductive assembly insertable in said bushing to electrically connect said terminals, said conductive assembly including cap means extending into electrical engagement with said first terminal, a fusible element serially connected between said cap means and second terminal when said conductive assembly is inserted, movable fuse bridging means in slidable electric contact with said first terminal but initially spaced from said second, terminal, spring means biasing said bridgportion in opposition to the 4 ins means. toward said. second, terminal, latch means. releasablyengageable with said bridging means and holding said bridging means in spaced relation to; said second terminahlocking means engaging said cap means with said, first terminal when said movable bridging means. and second terminal are still in spaced relation, tripping means operatively connected with said latch meansand extending therefrom to, the exterior of said cap, means, whereupon manipulation of said tripping means may release said latch means, for projecting said bridging means under, the influence of said spring into electrical contact with said second terminal, and in parallel circuit, with said, fusible; element.

3. An electric: circuit protective device comprising, a bushing having a bore therethrough, a first terminal aflixed at one end of said bushing and having a bore aligned with said bushingzbore, a second terminal within. said, bushing spaced from said first terminal, a conductivev assembly insertable, in said bushing to connect said terminals, said assembly including cap means having a tubular extension within said first terminal, a fusible element connected between said extension and, second terminal under normal conditions, a fuse bridging sleeve normally in spaced relation with said second terminal and having a portion within said tubular extension, spring means biasing said sleeve toward said second terminal, latch means engageable with said tubular sleeve for restraining the latter in opposition to said spring means, tripping means exterior of said bushing and having a portion interior thereof cooperating with said latch means to release said bridging sleeve in response; to actuation of the tripping means for projection by said spring means into contact with said second terminal and in parallel with said fusible element.

4. An electric circuit protective device comprising, a bushing having a bore therethrough, a first terminal atfixed at one end of said bushing and having a bore aligned with said bushing bore, a second terminal carried by said, bushing in spaced relation to said first terminal, a conductive assembly insertable in said bush ing to connect said terminals, said assembly including cap means having a tubular extension within said first terminal, a fusible element connected between said extension and second terminal under normal conditions, contact finger means interposed between said tubular extension and said first terminal for effecting an electrical connection between them when said assembly is inserted in said bushing, bridging sleeve means adapted to telescope interiorly of said tubular extension and normally extend in spaced relation with said second terminal, spring means biasing said bridging sleeve means toward said second terminal, latch means engageable with said bridging sleeve means for restraining the latter in opposition to said spring means, and tripping handle means exterior of said bushing and having a portion interior thereof cooperating with said latch means to release saidbridging sleeve means in responseto actuation of said tripping handle means for projection by said spring means into contact with said second terminal and in parallel with said fusible element.

5. An electric circuit protective device comprising, a bushing having a bore therethrough, a first terminal affixediat one end of said bushing and having a bore aligned with said bushing bore, a second terminal axially spaced from said first terminal, a conductive assembly insertable in said bushing for connecting said terminals, said assembly including cap means having a portion embracing said first terminal and a tubular extension interior thereof, contact finger means carried by said first terminal and adapted to connect said tubular extension to said first terminal when said assembly is inserted in said bushing, a fusible element connected between said tubular extension and second terminal under normal conditions, a

' bridging sleeve telescoped within said tubular extension and having a longitudinal guide slot intermediate its ends and, a. slotted hole atone end, guide: means, transverse. of

said tubular. extension and protruding through said guide slot, spring means, biasing said bridging, sleeve toward said second terminal, a latching member normally ex-- tending through said slotted hole, a tripping handleadapted to change, theplane of said latch member for passing out of said slottedhole, whereby said bridging sleeve may be projected under the influence of said spring into contact relation withsaid second terminal and in parallel withsaid fusible element without removing the conductive assembly from the bushing.

6. An electric circuit protective device comprising, a.

bushing having anaxial bore, first and second terminals in, spaced relation at opposed ends of said bushing, a conductive assembly insertable in said bushing for connecting said terminals, said assembly including cap means having a portion overhanging said first terminal and a tubular extension portion interior thereof, contact finger means interposed between said first terminal and tubular extension for effecting electrical engagement between them when said assembly is inserted in said bushing, a fuse in series circuit with said second terminal, guide means transversely mounted on said tubular extension,

conductive rod means between said fuse and guide means and also having a slotted latching hole at its end, a spring.

surrounding said rod and interposed between said guide means and bridging sleeve biasing the latter toward said second terminal, a cross shaft having a flattened portion extending through said slotted hole for latching said bridging sleeve in opposition to said spring and also having a tripping handle exterior of said cap means,

whereby rotation of said flattened portion into the plane of said slotted hole by means of said tripping handle will unlatch said bridging sleeve for projection under the influence of said spring into circuit with said second terminal in parallel with said fuse without removing the conductive assembly from the bushing.

7. An electric circuit protective device comprising, a bushing having an axial bore, first and second terminals in spaced relation at opposed ends of said bushing, a conductive assembly insertable within said bushing between said terminals, cap means having a tubular extension portion interior of said first terminal, a main contact finger connected to said first terminal and adapted to receive said tubular extension thereagainst, an auxiliary contact finger extending through the wall of said tubular extension, a bridging sleeve telescoped within said tubular extension and contacted by said auxiliary contact finger, spring means biasing said bridging sleeve toward said second terminal, latch means normally restraining said sleeve in opposition to said spring means, tripping handle means for rotating said latch to release said bridging sleeve for projection into contact rela tion with said second terminal under the influence of said spring without removing said conductive assembly from said bushing.

8. An electric circuit protective device comprising, a bushing having an axial bore, first and second terminals at opposed ends of said bushing, a conductive assembly insertable in said bushing for electrically connecting said terminals, said conductive assembly including a cap having an annular depending portion embracing said first terminal and an extension disposed within said first terminal, locking means interengaging said cap and first terminal, tripping handle means carried by said cap, a latch means actuable by said handle means, bridging means telescoped within said extension and releasably engagedv with said latch means, said bridging means being initially spaced from said second terminal after said locking means engages said cap and first terminal, spring means biasing said bridging means toward said second terminal, whereupon actuation of said tripping handle means unlatches said bridging means for projection into contact relation with said second terminal under the influence of said spring means.

9. An electric circuit protective device comprising, an insulating bushing having a bore therethrough, first and second terminals spaced from each other axially of said bore, an elongate conductive assembly insertable in said bushing to electrically connect said terminals, said conductive assembly including cap means having an integral extension within said first terminal and a movable conductive portion adapted to slide with respect to said conductive assembly, a fuse attached to said movable portion and in spaced relation with said second terminal when inserted in said bushing, locking means engaging said cap means with said first terminal when said fuse and secnd terminal are still in spaced relation, spring means biasing said movable portion toward said second terminal, latching means restraining said movable portion from said second terminal in opposition to said spring means, and tripping means manually operable exteriorly of said bushing to actuate said latch means for releasing said movable portion for projection of said fuse into connection with said second terminal under the influence of said spring means.

10. An electric circuit protective device comprising, an insulating bushing having a bore therethrough, first and second terminals spaced from each other axially of said bore, an elongate conductive assembly insertable in said bushing for electrically connecting said terminals, said conductive assembly including cap means having an integral tubular extension within said first terminal, contact finger means releasably electrically connecting said extension and first terminal, sleeve means having an end telescoped within said extension and another end projecting toward said second terminal, auxiliary contact finger means releasably electrically connecting said extension and sleeve means, spring means biasing said sleeve means toward said second terminal, latch means including manual trip means exterior of said bushing restraining said sleeve means in opposition to said spring means, a fuse in series circuit with said sleeve means and spaced from said second terminal when said assembly is inserted in said bushing, locking means engaging said cap means with said first terminal when said fuse and second terminal are still in spaced relation, whereby said fuse may be projected into contact with said second terminal under the influence of said spring means by actuating said trip means to release said sleeve means after said conductive assembly is inserted in said bushing.

11. An electric circuit protective device comprising a tubular insulating bushing having a first terminal fixed at one end and a second terminal fixed at its other end, an elongate conductive member insertable in said bushing and having a fixed portion in contact with said first terminal and an independently movable conductive portion initially spaced from said second terminal, a fuse assembly attached to said fixed portion and extending into contact with said second terminal for normally completing a circuit between terminals, spring means biasing said movable portion toward said second terminal and toward a position wherein it bridges said fuse assembly, latching means releasably engaging said movable portion in the vicinity of said first terminal for opposing said spring bias, locking means engaging said fixed portion with said first terminal when said movable portion and second terminal are still in spaced relation, and manually operable tripping means exteriorly of said bushing and coacting with said latch means to release said movable portion for bridging said fuse assembly under the influence of said spring means.

References Cited in the file of this patent UNITED STATES PATENTS 2,662,947 Kyle Dec. 15, 1953 2,663,825 Amundson Dec. 22, 1953 2,683,201 Miller et a1. July 6, 1954

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