US2689284A - Fuse cutout - Google Patents

Description

Sept. 14, 1954 Filed July 20, 1950 G. l.. HILL FUSE CUTOUT 3 Sheets-Sheet l ATToRNi-:YJ

G. L. HILL FUSE CUTOUT Sept. 14, 1954 INVENTOR GEORGE L ESL /E H/LL BY ATTORNEYS FUSE CUTOUT Filed July 20, 1950 3 Sheets-Sheet 3 INVENTOR CEGRGE ESL/E H/LL ATTORNEY Patented Sept. 14, 1954 UNITED STATES PATENT yOFFICE 7 Claims.

This invention relates to open type fuse cutouts such as are used in relatively high voltage circuits. In such cutouts the fuse member is mounted within an expulsion tube, usually of hard ber, which may or may not ibe surrounded by an outer reinforcing tube of laminated phenolic material. In such fuses the fuse element itself comprises a relatively rather short fusible link, mounted adjacent the sealed end of the tube, to which is attached a flexible conductor or fpigtail which is quite long, protruding from the opposite end of the tube. When a fault ocn curs and t'he link ruptures an arc forms within the tube between the open ends of the circuit and gas pressure generated by the arc expels the conductor and the fused metal from the tube with considerable force, thus forming a long gap which breaks the arcand prevents its reestablishment.

While fuses of this general type which have heretofore been marketed have been widely used they do fail upon occasion and such failure is accompanied by a considerable hazard. The pigtail and fused metal are very hot immediately after the arcing occurs; if blown completely out of the vtube they may fall to the ground and set fire to dry grass or rubbish beneath them. This may be prevented by a catch basket secured to the lower end of the expulsion tube, such basket being perforated to permit egress of the gases, as is shown in my prior Patent No. 2,094,013, issued April 5, 1938.

Beside the re hazard above mentioned cases have been known where,"on relatively light fault currents, the pigtail part of the fuse element is blown out of the expulsion tube but not completely detached; in such cases a loose end can swing up and around the supporting insulator and make contact with the supporting hardware or with the hardware on a lower crossarm. Under such circumstances there may be cases where a dangling conductor is excited indirectly through circuits which have not broken, forming a serious hazard to linemen climbing the pole on which the cutout is mounted. This also is, of course, prevented by the catch basket described .in the prior patent above referred to.

Other common hazards exist in other types of cutout. I-Iigh speed moving pictures, taken of such equipment under testI show that the arc gases emitted under heavy faults are of considerable magnitude and may be expelled to a distance of 8 or 10 feet from the open end of the expulsion tube. These gases are hot and ionized and may cause flash-over to metallic grounded 2. structures or an adjacent line of another phase. These motion pictures also show that the hot expelled gases mushroom back over the fuse tube and upon occasion may cause flash-over outside of the tube after the circuit has been interrupted within the tube.

In. order to reduce the hazards above mentioned this dropout type of fuse cutout has been devised. In this cutout the fuse tube is used as a switch arm, the switch being urged into'an open position by a spring, gravity, or both and held closed by a latch mechanism. The latch, in turn, is held in engagement by tension on the fuse element; when the fuse blows the latch is released and the fuse-switch-arm falls open, forming a second air gap in series with the rst and thus reducing the probability of the arc reestablishing itself when once broken, and preventing leakage currents which otherwise might char and destroy the expulsion tube. The primary purpose of this invention is to pro vide a cutout of the dropout type which will retain the advantages inherent therein while at the same time avoiding the above mentioned difficulties. Specifically, among Athe objects` of this invention are to provide means whereby a catch-basket and de-ionizing chamber can tbe used in connection with a cutout ofthe drop-out type, and to provide a release mechanism which `is simple, rugged, economical and at `the same time completely reliable in operation and to provide an open type drop down cutout wherein the expulsion tube drops down in longitudinal alignment with the vertical axis of the supporting in.. sulator and is latched in this position after the fuse blows, during circuit interruption. and to provide an air gap between the top ferrule of the fuse tube and the top line terminal of the cutout after circuit interruption.

` tends to open the cutout is restrained, not by the tension on the fuse element itself, but by a hook or latch which is mounted off-center so that it tends to disengage under the stress of the spring. The flexible conductor of the fuse element, when the fuse is set, is passed around this hook and holds it in engagement, thus requiring a very small stress in comparison with the total pressure of the spring. Upon rupture of the fuse, however, this tension of the flexible conductor upon the 'hook is released and it immediately disengages. y

V `The above will be more readily understood by reference to the ensuing detailed description of 3, certain preferred embodiments of this invention, taken in connection with the accompanying drawings wherein: f

Fig. 1 is an elevation of the cutout closed position, the upper end of the expulsion tube being shown partly in section Fig. 2 is a similar elevation showing a slightly modified form of cutout in the position assumed when the fuse has blown;

Fig. 3 is a transverse sectional view of a portion of the cutout of Fig. l, the plane of section being indicated by the lines 3-3 in the first figure;

Fig. 4 is a fragmentary sectional view of the lower end of the cutout of Fig. 1, the plane of section being indicated by the appropriately numbered lines of Fig. 3;

Fig. 5 is a longitudinal sectional view of the lower end of a fuse and latch mechanism showing a modified mechanical structure; and

A Fig. 6 is a front elevation ofv the structure shown in'Fig. 5, the pla-ne of section of vthe last `narnedffigure being indicated by the lines 1 1. f The two variant forms of the invention shown fin Figs. 1 and 2 are so nearly the same that they will be described together, the minor differences being indicated in the course of the explanation. vBoth forms of the device comprise the usual insulator I, usually of porcelain. This insulator Ais provided with abracket 3, shown only in part, fwhereby the insulator is secured to a. crossarm y'or other structure upon which the cutout is to be mounted.

- vThe upper end of the insulator I carries yan upper contact bracket 5 which may be of purely Yconventional type. Secured to this contact -bracket, by a clamp 1, is an upper contact spring 9-. This may be of Phosphor bronze wire formed 'into a loop,-only one vside of which is shown in the drawings. The spring has considerable strength and is intended to press against the upper ierrule or contact of the fuse itself. -It is indented upwardly, as `shown at 9', to engage a fuse ferrule and is provided with a slanted end 9", forming a ramp against which the ferrule bears as the fuse A'ls closed to raisethe spring `and permit the end of the fuse to latch into the indentation.

"f The 4lower end of the Phosphor vbronze wires of `which `the contact is formed may be brought up varound the clamp and formed into arcing horns as best indicated at II inFig. 2, the horn being broken away -in Fig. 1 to show theconstruotion of Vthefuse itself. VAll of this structure is largely Yconventional rand is described here only for the 'sake of completeness Aas it is not directly the subject of the present invention.

Atthe other end of the insulator I is a lower bracket I3. To this is fastened a hook-shaped trunnion bearing member I5. This comprises a pair of hooks, only the nearer -of which appears `in the drawing,` these hooks being provided with projecting lips I5 which merge with oval recesses I1 f or receiving trunnions I9 on a'U shapedguide Imember A29. Both the bracket 5 and bracket I3 areprovided with terminals, 23 and 2-3', to which the line 25 to be protected by the fuse cutout is secured.

- `In the form of the device shown in Fig. 2 the 'trunnion bearing member |-5 is also provided with a spring latchf24, forengaging the U shaped guide member 2|i and preventing-'it from `swing- 'ing outward, when the fuse blows, unt-il purposely 'released bya maintenance man for the purpose of replacing the fuse. The U shaped guide vmember 26 itself may be formed of sheet metal. It comprises-a `substantially ver-tical plate 29, `the sides of which are bent back to form flanges 2 |I to add stiffness and support to the trunnion I9. Substantially parallel horizontal arms 21 and 29 project forwardly from the plate 26, the whole guide member 26 being generally U-shaped with the base of the U vertical. Both of the arms of the U are apertured so as to receive slideably the expulsion tube 3| of the fuse itself. The latter is surrounded by a compression spring 33 which bears against the upper arm 21 and a flange 35 `which surrounds and is secured to the expulsion tube by the set screw 34. When the fuse is loaded and in the unblown condition the spring 33 is compressed as shown in Fig. 1. When the fuse is blown the spring forces the entire fuse assembly downward until the flange 35 strikes against the lower bracket 29 as shown in Fig. 2. This action is normally prevented by a hook or latch 31 which swings from a pivot 39 on the arm 29. The latch engages a recess in a basket 4| screwed to the `lower end of the expulsion tube 3|. The basket will be described more in detail hereinafter.

As will be seen the hook or latch 31 is generally L-shaped, and the pivot 39 is laterally displaced from the foot or latch portion of the L. There is, accordingly, a lateral lever arm which tends to rotate the hook around its pivot and disengage it. This is prevented by the flexible copper conductor 43 of the fuse element itself which passes around and over the hook and is secured to a suitable binding post or connector 45 on the'lower arm 29 of the U shaped guide member V26.

The expulsion tube 3| is preferably formed of Bakelite tubing or other water resistant and mechanically strong material and is provided with a liner `41 which may be of horn fiber tubing. This, of course, is a conventional construction. Screwed to its upper end is a ferr-ule 49, which is of highconductivity metal such as brass or bronze and is provided with a reduced end or thimble r49. This thimble is externally threaded to receive a ferrule cap 5|. The ferrule and thimble are tu"- bular, and the fuse assembly is provided witha flange 53 which rests on the end -of the thimble and is held in place by the ferr-ule cap until such time as the cutout is loaded, when the stress on the conductor or pigtail 43, of course, holds itin place. The ferrule cap 5| forms the actual upper contact of the fuse against which the contact spring 9 presses and also serves as a closure or Aseal `for the upper end of 'the expulsion tube. A pullring 52, for manipulating the fuse, is lsecured to the upper end of the tube.

The lower ferrule 55 and catch basket Il is fshown in detail in Fig. 4 and is an improvement to that described in my prior Patent No. 2,094,013 uabove mentioned. It comprises a -threaded metal ferrule 55 screwed or otherwise secured to the expulsion tube 3|. Threaded onto the 'ferrule is Ythe catch or deionizing basket 4| proper, this being of brass, bronze, or the like, and being formed with an interior chamber 51. Apertures 59 are formed at the bottom of the catch basket `and there are preferably provided, betweenthe walls of chamber 51 andthe sides of the basket itself, means for condensing the hot Ygases resulting from the Vare formed upon blowing lof lthe fuse. Such means may comprise coiled-corrugated copper strip 6I-. Strips of copper netting may likewise be usedif desired.

An additional aperture 63, as shown Sin Fig. 4 is formed on one side of the 'catch basket. upper edge of this latter aperture forms -a lip which is engaged by- Athe hook 31; the aperture isl of sufiicient size to admit the `endl-of the pigtail finder the hook when the latter is engaged, thence passing around it and up to the binding post 45.

From what has been described the operation of the device under a fault should be apparent. When the fuse blows the gases generated by the are expel the pigtail from the tube into the chamber l of the basket, where it is held and kept from swinging and causing damage which has been described above. Gases, escaping from the basket through the vent holes 59, are cooled materially by passing through the condensing strips 8|, thus reducing the re and ilashover hazard. As this occurs the constraining action of the pigtail upon the hook 3l is released and it immediately swings out of the way, as indicated in Fig. 2, and the fuse is forced down by the powerful spring 33 out of contact with the upper contact of latch spring 9. If the form of the device shown in Fig. 1 is used the off-center weight of the entire mechanism swings it around the trunnions I9 and opens the auxiliary gap more widely, not only tending to prevent reestablishment of the arc but also visibly signalling the blowing of the fuse. Normally the upper contact is made to the live or supply side of the line, thus minimizing the danger encountered in replacing the ruse and closing the cutout. This is usually done by means of a fuse stick, consisting of a hook mounted upon a pole, which engages the pull-ring The fuse tube and the U-shaped member 28 can be lifted out-of the trunnion bearing member I5 with the fuse stick, the fuse replaced, the device reset and the whole assembly can then be'reengaged in the trunnion bearing member and the cutout closed.

In the case of the form shown in Fig. 2 the only difference in this operation is that instead of the fuse swinging outwardly upon blowing it is held in place by they latch 24 until released by a sharp outward tug on the pull-ring 52.

From the arrangement of the mechanism of the cutout itself it should be evident that a large number of modifications are possible without departing from the spirit of this invention. One such modication is shown in Figs. 5 and 6. The modification referred to concerns particularly the U-shaped guide member 99, ferrule ||9 and deionizmg chamber 4|', ferrule and de-ionizing chamber; the insulator, upper contacts, and trunnion bearing member l5 employed therewith may be identical to that already described or may themselves be modiiied. The U-shaped guide member 99 itself, however, is formed of sheet material which is bent into the shape shown. Like the one previously described it is generally U- shaped, comprising a pair of substantially parallel horizontal arms 95 and |0| apertured to receive the fuse, 'the arms, however, projecting inwardly in this case. Of these arms the lower, designated by the reference character 95, is provided with anges 91 on each edge. These flanges are bent up from the sides of the arm and are lobed at the end to carry trunnion pin I9.

Distantly from the trunnion I9 the lower horizontal arm 95 is bent upward at right angles to form a backplate 99, above which it is bent inwardly again to form the arm |0|. being the upper of the two parallel arms of the U-shaped guide member 99.

The backplate carries a conventional binding post |03 for securing the ends of the pigtail 43. Below the binding post there is formed slot |05 shaped like the letter `H laid on its'side. Two short tabs |01 extending horizontally toward each other and separated by the cross bar of the H,

.form 'the pivots on which the hook or latch Y 31. is swung. Ihe hook is double, being punchedor otherwise formed from two identical pieces of sheet metal, separated by a smallstrut |09, the ends of which are rivetted to secure the two sides of the hook in place. To assemble this device the two sides are pressedtogether and inserted between the tabs |01, and then allowed to spring back into place.

In this form of the device the fuse itself is also slightly modified. The expulsion tube 3|' is provided with a tubular metallic extension I which projects upwardly through the aperture in the lower arm and is threaded to the lower end of the expulsion tube. A ilange 35', between which and the upper arm I0| the spring 33' is compressed, is held in place on the upper end of the extension |0| by a split -spring-ring ||3 fitting in a groove in the extension in well known manner. Below the lower arm 95 the extension is provided with asection l5 of somewhat larger diameter, on the end of which is formed a threaded coupling Ill. The catch basket 4I is screwed to` this coupling. This basket diiTers in shape, but not in function, from the catch basket 4| previously described.

An orice I I9 is formed in the portion |5 above the coupling, and a lip |2| extends outwardly above this orice for engagement by the hook 3l'. In setting the fuse the pigtail 43 is brought out through this orice and over the rivetted strut |09 tothe binding post |03, where it is secured.

It should be quite apparent that the advantages of the -constructions herein described are not limited to the specic type of release'shown but that the combination of a hook latch which carries the major portion of the stress applied by a spring which tends to open the cutout but is held in engagement by the fuse link assembly can be used in many other forms. I therefore do not desire to be limited to the exact structures herein described but rather to obtain the full protection warranted by the scope of the following claims.

I claim: 1.' In a fuse cutout of the dropout type employing a fuse comprising an expulsion tube enclosing a fuse link provided with a flexible conductor extending therefrom; a guide member for holding said fuse comprising upper and lower substantially parallel arms apertured to receive slideably said expulsion tube, a compression spring between said arm and proportioned to surround said expulsion tube, bearing against said upper arm and said tube to force the latter downward, and latching means for retaining said tube in said guide member and said spring in compression and means for securing the flexible conductor of said fuse link to said guide member around said latching means to hold the same in engagement until said fuse ruptures,

2. In a dropout fuse cutout of the type wherein tension on a fuse link is employed to restrain a spring tending to open said cutout; a fuseassembly including an expulsion tube, a fuse member having a fusible link and a flexible conductor secured thereto within said tube and a contact ferrule to which one end of said fuse member is secured, one end of said conductor projecting from said expulsion tube at the end opposite said ferrule, a resilient contact for said ferrule, a pair of substantially parallel arms apertured for mounting said assembly slidably with respect to saidspring contact, a spring mounted between said arms and bearing against one of said arms' @maar and said assembly to move said fuse and ferrule out of engagement with said contact, and latchlng means for retaining said ferrule in engagement against the action'of said `spring while said fuse member is unruptured.

3. A drop-out type expulsion fuse cutout comprising Ia supporting insulator, -upper and lower contacts on said insulator and a bearing on said lower contact, a fuse assembly comprising an insulating expulsion tube, an upper contact ferrule, means for securing a fuse element within Vsaid tube to said ferrule and a `lower Ierrule apertured laterally to permita exible-conductor attached to said fuse element to project outwardly therethrough; a metallic guide member on they tube pivotally mountable in said bearing and including a pair of spaced guide members having holes therein for slidably engaging said fuse `assembly and retaining it in alinement :between said contacts when said cutout is in closed position, a latch on said guide member engageable with said fuse assembly to retain it in longitudinal position to engage said upper contact, and means on said guide member for securing the uprojecting end of said flexible conductor over said latch to retain it in engagement so long as said fuse element is intact.

4. A drop-out type expulsion fuse cutout comprising a supporting insulator, upper and lower contacts mounted on said insulator; a fuse assembly comprising an insulating expulsion tube, an upper contact ferrule mounted on said tube, means within said ferrule for securing thereto a fuse element comprising a `fusible llink and an extended flexible conductor for connection with said lower contact, 'a lower fer-rule with a lateral aperture for passage of the conductor and an apertured bottom; a catch-basket attached to the apertured bottom ierrule for retaining portions of said fuse element expelled from said tube upon rupture of said fusible link while permitting downward escape of gases resulting from such rupture, a trunnion hinged to said lower contact and engaging said fuse assembly above said catchbasket and out of the path of gasesdischarged through .the apertures therein, latching means for holding said fuse assembly against rotation about its hinge and maintaining said upper :ferrule against said upper contact, and means for securing'the end of saidilexible'conductor to hold said latching means in engagement las long as said fuse element is intact.

5. In combination, a dropout `fuse cutout corn- I prising upper and lower yterminal members mounted on an insulator, a bearing for a trunnion on the lower terminal Vmemberfan expulsion fuse tube between the terminal members, a U- shaped metallic member on the-lower end of the tube, said tube passing through apertures in the extended parts of the VU -shaped metallic member, a trunnion pin on the U-shaped metallic member for insertion in the trunnion bearing, a fuse link `within the Yexpulsion tube, a compression spring for tensioning the fuse link, a latch for holding the tube in position and sustaining a large percentage of the force exerted by said spring, a terminal for the flexible conductor of said link land a catching and cooling chamber `on the open end of the expulsion tube for catching the expelled parts and cooling the gases during circuit interruption.

6. An expulsion cutout comprising upper and lower terminal members mounted on an insulator, an expulsion fusev tube between the terminal members, a U-shaped metallic member on the lower end of the tube, said tube passing through the `extended parts of the `U-shapefl metallic member, a collar on the tube within the U-shaped metallic member, a compression spring between the collar and the upper part of the U-shaped metallic member, a latch member mounted on `the lower terminal member engaging :the U- circuit interruption.

'7. In combination an open type drop-out fuse cutout comprising a supporting insulator, an upper terminal and a lower terminal mounted thereon, a trunnion bearing on the lower terminal anexpulsion fuse tube for insertion in the terminals, a metallic `member mounted on the lower end of the expulsion tube, a trunnion on the Ametallic member for insertion in the trunnion bearing and Ia latch mounted on the metallic member for restraining the expulsion tube in the closed position, a fuse link in the expulsion tube, said fuse link having its exible conductor hold the latch member in thenormal closed position, and a catching a-nd cie-ionizing chamber on the open end ofthe expulsion tube, said chamber consisting of an inner chamber for the reception of the expelled `parts of the fuse link and `an outer'chamber containing a cooling means and apertured for the escape of gases.

4References Cited in theflle of this patent UNITED STATES PATENTS Number Name Date 2,094,013 Hill Sept. 28, 1937 2,151,159 Schultz Mar. 21, 1939 2,203,928 Schultz June 11, 1940 2,231,510 Schultz Feb. 11, 1941 2,291,646 Ramsey Aug. 4, 1942 2,334,134 Steinmayer et al. Nov. 9, 1943 2,365,113 `Schultz Dec. 12, 1944 2,394,599 Boothe Feb. 12, 1946 2,458,742 Schultz Jan. 11, 1949 2,466,486 Schultz Apr. 5,1949 2,493,601 Smith, Jr Jan. `3, 1950

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