US2842639A

US2842639A - Fuse cutout construction

Info

Publication number: US2842639A
Application number: US540288A
Authority: US
Inventors: Ronald W Thiede; William H Nash
Original assignee: McGraw Edison Co
Current assignee: McGraw Edison Co
Priority date: 1955-10-13
Filing date: 1955-10-13
Publication date: 1958-07-08
Anticipated expiration: 1975-07-08

Description

July 8, 1958 R. W. THIEDE T AL FUSE cuTouT coNsTRUcTxoN Filed oct. 15, 1955 Zl/Z'ZZn'am H. Nas/z INVENToRs.

BY 2% l ttarny United States Patent FUSE CUTOUT CONSTRUCTION Ronald W. Thiede, Las Cruces, N. Mex., and William H. Nash, South Milwaukee, Wis., assignors to McGraw- Edison Company, a corperation of Delaware Application October 13, 1955, Serial No. 540,288

4 Claims. (Cl. 20G-114) The present invention relates to a fuse cutout construction, and particularly relates to a cutout characterized by its ability to safely close an electric circuit even though fault conditions may exist thereon.

When a fault condition develops on a distribution circuit, causing the fusible element of a fuse cutout to rupture, large mechanical forces may develop in the cutout. Conventional housed cutouts are constructed with suilicient strength to counteract any expulsive forces caused by rupture of the fuse link when all of the cooperating members are in secure mechanical engagement relative to one another. This is true even with the relatively confined space provided in conventional cutout housings.

However, when an attempt is made to reclose conventional cutouts after replacement of a ruptured fuse link, and when there exists a low impedance fault on the line, violet arcing between contacts often occurs with consequent profused evolution of hot gases. Inasmuch as the gases are relatively confined, it will act immediately to force an incompletely closed cutout door open with such violence as to injure or burn a lineman servicing the fuse. In many cases, there is even the possibility of the porcelain housing being blown apart by the evolution of relatively confined gases.

Recently, there has been developed a number of housed cutouts which incorporate an auxiliary electrical circuit including an auxiliary circuit-closing means for completing the electrical circuit through the fusible element after the various cooperating parts have been placed in secure mechanical relationship with one another.

The aforesaid cutouts have either included relatively expensive and complex means for closing the circuit after securement of the cooperating parts or have included devices that comprise parts that either are suspended below the cutout or are positioned in a manner that makes them diflicult to actuate or act to lessen the ashover insulation level between line terminals.

It is therefore an object of the present invention to provide an improved auxiliary switch means for electrically bridging an insulating gap in one of the line terminals after the cooperating members of the cutout have been mechanically secured relative to one another.

It is a particular object of the present invention to provide an improved auxiliary switch means which includes a manipulating trigger member extending exteriorly of the door of the conventional housed cutout, which trigger member acts to release a latch member internally of the cutout to permit the release of an open switch means normally urged towards circuit closed position and thereby close the circuit through the fuse link after the various contact members have been placed in secure mechanical engagement relative to one another.

An embodiment of the invention is shown in the accompanying drawing, in which:

Fig. 1 is a side elevational view, in section, of a housed cutout embodying the present invention with the various cooperating parts being in mechanical securement relative to one another, and being shown with the electrical circuit being in non-conductive arrangement;

Fig. 2 is a cross sectional view taken on lines 2 2 of Fig. l.

Referring to the drawing, it will be seen that the fuse cut out comprises an insulating housing 1 which may be of porcelain and which is supported on a metallic bracket 2, and includes a door 3. The door is also of insulating material, such as reinforced Bakelite, and is hingedly supported on the housing by means of pivot pins 4 extending laterally from each side thereof. The pins are arranged to be removably seated within the spaced apart hook-like portions of rigid brackets 5 fixed at the lower end of each side of the housing 1.

The door 3 is adapted to pivot into closed relation with the housing 1, as shown in Fig. 1, and to be removed from bracket 5. The construction of the hinge assembly is well known, and has been illustrated here in dotted portions for convenience in disclosing the novel features of the present structure.

The door 3 fixedly supports a fuse cartridge assembly, indicated generally by the reference numeral 10. When the door 3 is closed with respect to the housing 1, as illustrated in Fig. l, the upper terminal cap 11 of the cartridge 10 contacts and becomes electrically engaged with an upper stationary spring contact 12 aixed within the housing in electrical association with a pair of U- shaped yieldable contact clips 13 serving to guide the cap 11 into alignment with the spring-type contact 12. Members 12 and 13 are connected to an incoming electric line conductor 14 by means of a conventional screw-type connector 15.

The outgoing line conductor 19 is spaced from the conductor 14 and is connected in a conventional manner through the medium of a screw-type connector 20 to a lower contact clip, in the form of a U-shaped resilient member 21.

When the door 3 is swung to closed position, the lower stationary terminal clips or members 21 are adapted to electrically receive therebetween a conductive contact member 22, which in turn supports the cartridge assembly 10. The contact member 22 is rigidly ailxed to the door by means of screws 23 to prevent the cartridge assembly 10 from sliding with respect to the contact 22. To further secure the cartridge from sliding axially relative to the contact 22, a straight pin 24 is driven through the contact and engages the outer peripheral wall of the insulating fuse tube 27. The fuse tube 27, forming a part of the cartridge assembly 10, is conventionally manufactured of an insulating material such as Bakelite having an inner bore lined with an arc-extinguishing material such as horn fibre. The horn libre is characterized in that it has the ability to release copious quantities of non-ionized gases in the presence of an electrical arc.

Mounted at the far end of the fuse tube 27, there is a conducting terminal member 30, which may be a stamping or cast to shape, and includes an integral ferrule portion 31 circumjacent to the tube 27, and which is pinned in place by means of a straight thru pin 32. The member 3l) includes a conventional threaded stud 33 preferably staked thereto, and to which a leader portion of a fuse link 34 is electrically -connected by means of a knurled thumb screw 35. The leader of the fuse link 34 extends from the lower end of the fuse tube 27 and is pulled tightly over the conventional flip-out lever 36 pivotally mounted on the terminal member 30. The lever 36 is biased for clockwise movement with reference to Fig. l by means of a torsion spring 37, and normally urges the leader in a direction towards removal from the fuse tube 27 on overcurrent rupture of the fusible element (not shown).

Fig. l. The invention is directed particularly to an irnproved auxiliary switch means for completing the electrical circuit from the fuse link 34 through the terminal 30, and from there to the line conductor 19. This circuit is only to be completed 'after complete closure of the cutout door 3,`and after secure mechanical engagement of the terminal cap 11 on the cartridge assembly 1G with the upper terminal 12.

Auxiliary switch means of the general nature disclosed has been heretofore illustrated, and the present invention is directed to an improved auxiliary switch which includes a minimum Ynumber of parts and which improvement insures secure mechanical engagement of the parts in open circuit position, and which further provides trigger means which may be actuated in a convenient and safe manner for release of the parts towards closed circuit position by atlineman safely removed from the vicinity of the cutout.

The improved auxiliary switch means comprises auxiliary cooperable contacts 4i) and41. The auxiliary stationary contact 4t) is preferably fastened directly to or is an integral part of the fuse tube contact member 2.2 and provided with a slot 42. for engageably receiving the movable contact 41. The movable contact 41 is pivotally attached to the member 3i) by means of a thru pivot pin 45 and is biased for rotative movement in a clockwise direction with relation to Fig. l by means of a torsion springV 46. The movable contact 41 also includes Ia restraining stop member in the form of a laterally extending pin 47. The pin 47 is slidably engageable'with the stem portion 4S of a trigger member 4?. The stern portion 48 terminates in a recess provided in an upwardly extending portion 54B of the member 3Q. A compression coil spring 51 engages the stern 43 at one end thereof and acts to urge the trigger in an axial direction towards cngagement with the recess in the portion 50. The opposite end of the spring 51 abuts the inner surface of the door 3. The trigger 49 extends through an aperture in the door to provide a hook-like configuration exteriorly thereof. Both the hook-like configuration of the trigger 49 and an integral manipulating eyelet 55 on the door 3 are adapted to receive the hook portion of a switch stick (not shown) for manual operation of the door and of the trigger as will hereinafter be described.

The operation of the device is as follows:

It will be apparent that the improved cartridge-door assembly may be used either as a permanently installed component of a fuse cutout, or in the alternative, as a temporary safety device for testing an electric line subsequent to replacement of a blown fuse link assembly. In either case, the operation would be substantially identical. For purposes of illustration, it will be assumed that the cartridge assembly 1i? `and the door 3 are provided'as a permanent assembly component for the cutout housing 1. It is further to be 'assumed that the door 3 and assembly are mechanically secured in operating position, and with its respective cooperable contacts being in electrical engagement with the spaced apart terminals 3 and 4 within the housing 1.

On the occurrence of an overcurrent or other fault occurring on the line which would cause the fuse link 34 to be ruptured at its fusible element (not shown), the door Y3, with the cartridge assembly 10, is swung outwardly on, the pins 4 and is removed from the hook-like bracket 5. After removal of the assembly from the housing 1, the cap 11 is unscrewed and the ruptured portions of the fuse link 34 are removed from the fuse tube 27. The leader portion of the link 34 is also removed from the stud 33.

After a new fuse link has been installed in the cartridge assembly 10 and fastened around the lever 36 and the stud 33 in the conventional manner, the lineman rotates t movable contact 41.

vthe auxiliary movable contact 41 about its pivot 45 by finger pressure, 'and withdraws the trigger member 49 slightly to permit the stop member 47 of the movable contact Vto be inserted under the stern portion 48 of the trigger member 49. Thus, the movable contact 41 will be secured in place to insure an open circuit between the terminal member 30 and the contact 22.

The circuit through the cartridge assembly is now interrupted and the door 3 may be safely replaced on the bracket 5 'and swung into closed position as shown in Fig. l, with the terminal cap 11 being placed in secure mechanical and electrical engagement relative to the upper terminal members 12 and 13. Thus, the door may be fully mechanically closed without completing the electrical circuit through the cutout. Consequently, even though a fault should remain on the electric circuit, no arcing or dashing will occur, nor will any danger insue to the lineman closing the fuse box as the cartridge 10 is in non-conductive position during this closing operation.

After the lineman has removed himself from the immediate vicinity of the fuse cutout, he may engage the loop of the trigger member 49 with the hook portion of the switch stick (not shown) Vand pull the trigger member 49 axially outwardly relative to the door 3 for a distance which will permit release of the stop member 47 on the movable auxiliary Contact 41, the 'fusible element (notV shown) of the fuse link 34 may rupture due Vto the overcurrent condition. However, no serious consequences result because all arcing will be confined to `the interior of the fuse tube 27 which is specically designed for extinguishing any arcs created therein.

The improved auxiliary switch means provides a convenient arrangement for securely restraining the auxiliary movable cont-act 41 from movement to closed circuit posit-ion even under rough handling of the assembly during replacement operations, and which further provides a readily accessible trigger means for release of a movable contact from a safe distance without groping for internal cutout rele-ase mechanisms with a hook stick, which might be as much as 10 ft. long. The hook portion of a hook or switch stick may be readily engaged with the trigger rnember 49 with relative ease even though lthe lineman is rernotelystationed during the circuit testing operation.

As suggested above, it is not necessary 'to secure the benefit of this invention byrcquiringevery cutout and electrical system to be provided with the novel cartridgedoor assembly. Rather, the invention may be adapted for use as a test device and only one such device need be carried in a line crew truck of a size that will fit any conventional cutout of the particular rating in a system. Where there may be reasonable doubt as to whether or not a fault has been cleared, the present cartridge-door assembly may be temporarily installed and actuated to determine whether or not `the fusible element therein will rupture.

We claim:

l. -In a housed fuse cutout having spaced apart line terminals,*a door assembly for said housed cutout including a fuse cartridge assembly arranged to mechanically bridge said terminals', pivot means pivotally supporting one end of said 'cartridge assembly for rotativemovement into and out of bridging engagement with said terminals, and a fuse link contained within said cartridge assem'bly and normally electrically connecting said line terminals'; auxilia-ryswitch means interposed between said fuse link and one of said terminals and-comprising a pair of auxiliary contactsexternallyof said cartridge assembly,

The torsion spring 46 will nowV one of said contacts being movable and pivotally mounted and biased for movement towards electrical engagement with `the other, latch means normally restraining said movement, biasing means normally urging said latch means towards restraining position, a trigger member operably engageable with said latch means and having a manipulating portion remotely positioned relative to said contacts, said `trigger member adapted for manual release of said latch means against the restraining action of said biasing means, said release being eected after said fuse cartridge assembly has been pivotally rocked into mechanically secure bridging relationship with said line terminals.

2. In a fuse cutout having spaced apart line terminals, -a fuse cartridge assembly arranged to mechanically bridge said terminals, and a fuse link contained within said cartridge assembly and normally electrically connecting said line terminals; auxiliary switch means interposed between said fuse link iand one of said terminals and comprising a pair of auxiliary contacts externally of said cartridge assembly, `one of said contacts being movable and pivotally mounted and 'biased for movement towards electrical engagement with the other, latch means normally restraining said movement and including a stop on said movable auxiliary contact, lan axially slidable member releasably engageable with said stop and biased for movement in a direction towards restraining engagement with said stop, and manually operable trigger means remotely positioned relative to said auxiliary contacts and operatively associated with said slidable member for effecting its axial movement towards release of said stop on said movable auxiliary contact after said fuse cartridge assembly has been mechanically secured in 'bridging relationship with said line terminals.

3. -In a housed fuse cutout having spaced apart line terminals, a fuse cartridge assembly arranged to mechanically bridge said terminals, an insulating door for said cutout supporting said assembly interiorly thereof, and `a lfuse link contained within said cartridge assembly and normally electrically connecting said line terminals; auxiliary switch means interposed between said fuse link and one of said terminals and comprising a pair of auxiliary contacts externally of said cartridge assembly, one of said contacts being movable and pivotally mounted and biased for movement towards electrical engagement with the other, latch means normally restraining said movement Iand including a stop on said movable auxiliary contact, an axially slidable member releasably engageable with said stop and biased for movement in a direction towards restraining engagement with said stop, and manually operable trigger means exteriorly of said door and operatively associated with said slidable member for effecting its axial movement towards release of said stop on said movable auxiliary contact after said fuse cartridge assembly has been mechanically secured in bridging relationship with said line terminals.

4. -In a housed fuse cutout having spaced apart line terminals, a fuse cartridge assembly arranged lto mechanically bridge said terminals, an insulating door for said cutout supporting said assembly interiorly thereof, and a fuse link contained within said cartridge assembly and normally electrically connecting said line terminals; auxiliary switch means interposed between said fuse link and one of said terminals and comprising a pair of auxiliary contacts externally of said cartridge assem'bly, one of said contacts being movable and pivotally mounted and lbiased for movement towards electrical engagement with the other, latch means normally restraining said movement and including a stop on said movable auxiliary contact, an axially slidable member releasably engageable with said stop and biased for movement in a direction towards restraining engagement with said stop, said slidable member terminating exteriorly of said door in a manually operable hook-like portion for axially withdrawing said slidable member against said biased movement for effecting release of said stop -on said movable auxiliary contact after said fuse cartridge assembly has been mechanically secured in `bridging relationship with said line terminals.k

References Cited in the file of this patent UNITED STATES PATENTS 1,288,951 Matthews et al. Dec. 24, 1918 `1,556,829 Wyman Oct. 13, 1925 2,150,249 Sanford Mar. 14, 1939 2,357,853 Smith Sept. 12, 1944 2,438,746 Garrison Mar. 30, 1948 2,452,872 Schultz Nov. 2, 1948 2,617,908 Lincks Nov. 111, `1952 2,734,966 Schneider Feb. 14, 1956 2,741,726 Branick Apr. 10, 1956