US2581954A

US2581954A - Fused drop-out cutouts

Info

Publication number: US2581954A
Application number: US13704A
Authority: US
Inventors: David C Hubbard; William L Hollander
Original assignee: AB Chance Co
Current assignee: AB Chance Co
Priority date: 1948-03-08
Filing date: 1948-03-08
Publication date: 1952-01-08
Anticipated expiration: 1969-01-08

Description

1952 D. d. HUBBARD ET AL 2,581,954

FUSED DROP-OUT CUT-OUTS Filed March 8, 1948 3 SheetsSheet 1 Jan. 8, 1952 D. c. HUBBARD ET AL FUSED DROP-OUT CUT-OUTS 3 Sheets-Sheet 2 Filed March 8, 1948 jmzw/zyril'r 0 6a CZ/[arrzezr 1952 D. c. HUBBARD ET AL 2,581,954

FUSED DROP-OUT CUT-OUTS Filed March 8, 1948 3 Sheets-Sheet 5 Patented Jan. 8, 1952 FUSED DROP-OUT CUTOUTS David C. Hubbard and William L. Hollander,

Centralia, Mo., assignors to A. B. Chance Company, Oentralia, Mo., a corporation of Missouri Application March 8, 1948, Serial No. 13,704

22 Claims. 1

The present invention relates to fused drop-out cut-outs, and is particularly concerned with automatic fuse devices of the type adapted to be used upon transmission lines for interrupting the flow of current when the current exceeds a predetermined amount, the interruption being accompanied by the melting of the fuse and the expulsion of the parts of the fuse, accompanied by the automatic mechanical opening of the circuit, after the circuit is broken, to assure the permanent breaking of the circuit until it is manually closed, and to give an indication of the condition of the circuit.

One of the objects of the invention is the pro vision of an improved drop-out type fuse cut-out adapted to utilize the standard universal fuse links and provided with a fuse tube, which is closed at the top and open at the bottom and so constructed that the lower contact of the fuse tube is ejected from the bottom contact of the circuit, so that the fuse tube will hang with its opening downward before and after operation, thus protecting the fiber liner of the fuse tube from all adverse weather conditions.

Another object of the invention is the prochanical opening of the circuit will be delayed until the arc has been definitely extinguished within the fuse tube.

Another object is the provision of an improved device of the class described in which there is a wiping contact between the contacts on the fuse tube and those on the support so that the contacts may be kept in good condition and so that the wiping contact at the lower contact of the fuse tube may be used during the unlatching of the fuse tube to assist in delaying the mechanical opening of the circuit until the arc has been extinguished within the tube.

A further object of the invention is the provision of an improved drop-out fuse construction in which the jet action from the opening at the lower end of the fuse tube reacts with the upper trunnion to produce a torque that tends to swing the lower end of the fuse tube inward towards its contact to hold the lower contact in engaged position during the blast of the are so as to delay the mechanical opening until the arc has been extinguished.

Another object of the invention is the pro vision of an improved construction for devices of the class described in the form of the resilient spring supported contacts, and the provision of stops which protect the springs during jet action to prevent the straining of the springs and to cause the forces to react in such manner that the top trunnion of the fuse tube is also held in closed position during the violent jet action from the lower end of the fuse tube.

Another object of the invention is the provision of an improved ejector construction adapted to pull the fuse link from the fuse tube quickly at all times even though the rupturing currents are too light to generate sufficient gases within the fiber tube to eject the link rapidly, thus assuring the extinguishment of the arc in a minimum time.

- Another object of the invention is the provision of an improved fuse tube drop-out cut-out, the parts of which are protected from the weather at all times and which is also adapted to be operated in a conventional way as a disconnect by permitting the manual disengagement of the upper contacts by merely pulling outward on this end of the tube, leaving the tube supported by its lower contacts and indicating that it has been manually operated as a disconnect.

Another object of the invention is the provision of an improved fuse construction which is adapted to be re-fused and operated in accordance with conventional procedure so that the operators will already be familiar with the mode of handling the device.

Another object of the invention is the provision of an improved fuse drop-out cut-out which is trip-free even during the manual closing of the circuit so that when the fuse tube unit is being connected with its contacts, the operator cannot force the closing of the circuit during the existence of an overload, but while the operator is swinging the upper contact into closed position and holding it, the device may nevertheless open at the bottom contact automatically if a short circuit exists at that time.

Another object of the invention is the provision of an improved fuse tube unit which is provided with means for guiding and diverting the molten elements and the major force of the blast which takes place on fusing, away from the operator, so as to provide limited but effective protection for the operator and particularly for his face.

Another object is the provision of an improved 3 device of the class described having a mechanism that is unaffected by accumulations of ice and which is adequately protected from such accumulations as may occur.

Another object of the invention is the provision of a device of the class described which gives a visual indication in the open position whether the device has been operated automatically indicating the existence of a fault, or whether the device has been opened manually, indicating the purposeful de-energizing of the circuit for repairs or other reasons.

Another object is the provision of an improved contact structure which is self-aligning withrelation to the trunnions on the fuse tube unit, and the provision of stops and buffers to arrest the reaction that is due to the jet action and to prevent over-stressing the contact springs.

Another object is the provision of an improved fuse tube unit and support therefor, which is so constructed that the forcibleclosing of the contacts by slamming the fuse 'tubeinto position, tendsto force theejector arm against the bottom of the fuse tube-rather than to cause the arm to :placeadditionaltension on the, fuse link element, 3:.

thus eliminating the shocks that are imparted to the-fragile fuse link in the devices of the-prior art. Another object of the invention is the provision f an .improved ejector mechanism for the fuse leader in which the cable is so arranged that it doesnot slide over the end of the ejector lever as the lever moves, thus: reducing or substantially eliminating the friction which would be caused by such asliding action and which would resist the ejector lever operation.

Another object is the provision of improved contacts arrangements .by'means of which the contact fixtures on the fuse tube unit are-resilientlyurgedinto engagement with the fixed contact arms, and by means of which the contacts areselfealigning'with respect to. thetrunnions on the fuse tube unit, and by means of which the longitudinal pressure on the fuse tube which sometimes causes bending, after a long period of. time, is substantiallyeliminated.

Another object is the provision=of improved arrangements for holding the fuse tube unit against swinging and againstrreturn of :its lower end into engagement with thelower .contact arm,

after the fuse has blown, the lower endhas been released and the fuse tube unithas swung down ;atits lower end into a vertical position.

Otherobjects and advantages willbe. apparent from the following description and the accompanying-drawingsin which similar characters of reference indicate similar parts throughout the several views.

Referring to the three sheets of drawings accompanying-this specification,

Fig. 1 isa side-elevational view in partial-secation, showing the complete fused drop-out cutout assembly, withtheparts in the position which ,they assume when it has been provided with a suitable fuse and mounted in position to protect fuserhas blown;

Fig.3.is a fragmentary elevational view in partial section,:showing the position of the parts at the lower contact :arm and the lower end of the fuse tube unit at-the time when this fuse tube unit is being supported in inverted positiondur- 4 ing its installation for attachment of its lower contact, now shown uppermost, to the lower supporting arm;

Fig. 4 is a view similar to Figure 3, showing the same parts, as the fuse tube unit is being swung from the position of Figure 3 to that of Figure 1;

Fig. 5 is a fragmentary sectional view taken on the plane of the line 5-5 of Figure 1, looking in the direction of the arrows;

Fig. 6 is a, fragmentary elevational view of the lower end of the assembly, difiering from Figure 1 in that the lower contact is shown in elevation with the contact arm and hood in section; and

Fig. 7 is a fragmentary elevational view of the lower contact arm and lower end of the fuse tube unit, with the parts in the position which they assume when the upper end of the fuse tube unit has been opened manually to use the device as a manual disconnect, the fuse tube unit being swung onthe lower trunnions during this action.

Referring to Figure 1, 10, indicates in its entirety the. fuse drop-out cut-out assembly, which preferably. includes a supporting structure I I and fuse tube unit 12 carried thereby. The supporting structure H may be embodied in the single insulator type shown inFigure l or it may be car,-

.arated by grooves l5, and the insulator preferably has a reduced cylindrical portion 16 adjacent at itsmiddle, and additional reduced sion 23 provided with an aperture for receiving another screw bolt 26, which passes through the attaching flange 25 of an offset bracket 26 securing it to the clamping band 19. The offset bracket 26 has its body 21 extendingat right anagles to the attaching flange 25 and has'another attaching flange 28 extending at an obtuse angle to the body 21.

Attaching flange 28 issecured to the supporting flange 29 of a cross-arm clamping member 30 by means of a screw bolt 35. The cross-arm clamping member 38 is adapted to engage 'oneside of a cross-arm, the other side being engaged by a clamping plate 32, and the two clampingmembers'ti and 32 are drawn together by longer-screw boltstt, tlipassing through suitable apertures in the cross-arm.

Thus the insulator is is adapted to be supported from a horizontal cross-arm in a tilted position, so that the fuse tube unit 12 will extend diagonally upward and away from the cross-arm in such manner that whenever the fuse tube unit hangs only from the upper contact arms, it hangs in a vertical position by gravity. By reason of this position of the insulator and fuse tube unit, the fuse tube unit is so supported that it may pivot upon either the upper trunnions or the lower trunnions by gravity to a position which it will retain by gravity.

lhe reduced cylindrical portions l1 and H3 at each end of the insulator is are bordered by one of the insulator skirts I4 on one side and a radially projecting rib on the other side, forming a groove for receiving the clamping bands 36 or 31 of the upper and lower contact supporting arms 38, 39. These contact supporting arms comprise elongated narrow straps of sheet metal each having a partially cylindrical portion 36 or 31, which embraces the insulator, and each having a pair of parallel laterally projecting portions 4|, 42, for supporting the spring contacts.

The projecting attaching flanges 42 of the band 31 are provided with a pair of apertures for receiving the

screw bolts

43 and 44, which pass through both flanges and through the supporting flange 45 of a lower contact fixture 46, having a hood or partial housing 41 for supporting the lower contact trunnions and for enclosing the ejector mechanism and contact mechanism and protecting it from rain, snow and other adverse weather conditions.

The lower fixture 46 may consist of a cast metal member provided with a relatively flat attaching flange 45, and with an aperture 48 for passing a connector bolt 49, which is apertured belowits elongated head 50 for receiving a conductor that is clamped in a groove 5| by a nut on the shank of the bolt which pulls the head against the conductor.

A similar connector 49 is carried by an upwardly projecting flange 52 carried by the upper contact fixture 53. The hood 41 has parallel .

side walls

54, 55, Figure 5, a curved top wall 56, a flat rear wall 51 and a flat depending wall 58, Figure l, leaving the bottom open between the side walls 54, '55, when the fixture is installed properly, as

in Figure l.

The

side walls

54, 55 are provided with laterally projecting cylindrical lugs 59, '60, having threaded apertures 6| for receiving a pair of cylindrical trunnions 62, 63 (Figure 5). The trunnions are threaded at their outer ends, and engaged in the threaded bore 6! where they are secured by means of spring washers 64 and lock nuts 65.

The inner ends 66, 6! of the trunnions are spaced from each other sufllciently to pass the relatively flat flange portions of an ejector arm 68, Figure l, which is pivotally mounted on the tube unit [2.

The hood 4'! supports a leaf spring 69, which extends along the inside of its top wall '56 and which is initially spaced from the top wall, being tensioned when bent upward as shown in Figure 1. This leaf spring 69 passes through an aperture in the rear wall 51, and is secured to a horizontal flange 10 by means of a screw bolt H. Spring 69 urges the contact portions of the fuse tube unit l2 resiliently against the trunnions 62, 63.

The fuse tube unit l2 comprises an insulating tube 12, preferably having an outer portion 13 which is adapted to resist exposure to weather, and an inner portion 14 which is adapted to resist burning by the heat generated in the melting of the fuse, these two portions being integrally cemented together to form a single tube.

At its lower end the fuse tube 12 supports the contact fixture 15, which has an upwardly open tubular member 16 for receiving the lower 'end of the fuse tube. The fuse tube is fixedly secured in the ferrule 16 of the lower fixture 15 by a pair of rivet pins 77 which pass through the ferrule, and are riveted therein at such a point that the rivets 11 also pass through grooves in the side of the fuse tube 12.

The fuse tube terminates at 18, inside the blast 6. chute 19, and is open at its-lowerendwhere it is constantly protected from the weather by hanging downward, either in the position of Figure 1 or after blowing of the fuse in the vertical position of Figure 2. The lower fixture 15 supports the integral blast chute 19, which has-a pair of parallel side walls 80, a top wall 8| flush with the end 18 of the tube and a diagonally extending rear wall 82 which extends over toward the center of the tube 12, and is adapted to deflect the gases downwardly and toward the right away from the face of the operator.

The side walls of the blast chute 19 each support an outwardly projecting cylindrical stud 83, which is adapted to provide the pivotal support and point of attachment of a fuse leader guard adapted to receive and hold the cable of the fuse when the fuse is blown. The fuse leader guard forms no part of the present invention, and may be substantially as shown in the prior patent of David C. Hubbard, No. 2,461,898, dated February 15, 1949.

The lower fixture 1'5 is formed with an integral ring 84 located on its upper side, in Figure 1, for reception of the laterally projecting operating pin of a disconnect stick upon which the fuse unit I2 is hung when it is to be installed. Lower fixture 15 also has an integral substantially cylindrical body portion 85 below the ring 84, and provided with a cylindrical bore 86 for receiving an ejector spring 81.

' The ejector spring comprises a helical coil spring reacting at its right end on the end of the bore 88, and engaging at its left end the washer 88 of a suitable ejector strut 89. Ejector strut 89 comprises a stiff strut of metal, having a reduced end 90 which passes through an aperture in the metallic washer 88, and having at its other end 9| a V-groove or fork for engaging on both sides of the ejector lever 68 at its right edge. Thus the ejector spring 8! urges the ejector lever 68 toward the left, in Figure 1, by means of the strut B9.

The upper wall of the cylindrical formation 85 is extended toward the left to form a part of a roof 92, which curves upwardly under the top wall 56 of the hood to make sure that the hood overlaps and. drains on the lower fixture 15 at a point where the water will not run into the mechanism. 5

Referring to Figure 5, the laterally projecting portion 93 of the lower fixture 15 is provided with a rectangular slot 94 open toward the-left, and adapted to receive the pivot flange 95 of the ejector lever 68 which is pivoted on the rivet 96. The rivet 96, which forms the pivot for the ejector lever, also has a laterally projecting cylindrical portion 91, Figure 5, about which the cable leader 98 may be wrapped when the fuse is installed in the fuse unit l2.

Lower contact fixture 15 also has a laterally projecting cylindrical threaded stud 99 provided with a knurled thumb nut [00, which is adapted to clamp the end of the fuse leader 98 after it has been passed about the threaded stud 99.

The present fuse units H! are adapted to receive standard fuses, each of which has a circular button at the top adapted to be clamped aaginst an end surface on the upper fixture l9! by means of the internally threaded cap I02. The fusible portion of the fuse is located in the upper end of the tube '12, and is connected to the stranded copper wire leader cable wire 98, which extends downwardly out of the lower end of the tube 12 and out of the blast chute 19.

Fuse leader 98 passes around: the. end I83 of the ejector lever 58, and .is located in a groove 104 in the bottom or endof ejector lever 68. From the groove I34 the leader 98 passes about the stud '91., Figure 1, Figure 5, and its end is passed "about the stud 93 and clamped by the thuinb nut I03. When the fuse leader is-so installed, the ejector lever 58 is tensioned, that is, it is moved from the position of Figure 2 to that of Figure 1, compressing the spring 81 and causing thefuse ejector lever 68 to place a tension on the fuse leader 98.

The ejector lever 63 is pivotedin the slot 94 between the parallel portions I05 of the lower fixture :15, and ejector lever 68 has a relatively flat body flange I05 which is relatively thin but which is re-enforced by a thicker border flange 1-8-1.

The oval aperture I88 (Figure 2) inthe ejector lever flange IE6 is merely for convenience in machining adjacent surfaces, comprising the flat inner surface 189 and the cylindrical end surface I:I'il"cn a pair of laterally projecting uide flanges III. These guide flanges, which are on bothesides of the ejector lever 68, also have downwardly extending lips I'I2, with a diagonally extending face I13 forguiding the trunnions 62, 63 into proper position. The lateral thickness of the re-enforcing border flange I! is such that it :passes between the ends 66, 6-7 of the trunnions which are carried by the hood 41.

The laterally projecting body 93 of the lower fixture l haseach of its side webs 105 provided with, the laterally projecting curved contact members 'II4. These arcuate contact members have lower partially cylindrical surfaces II5 for engaging the trunnions-62, 63, against which they are urged by the spring 69 which bears on the top of the lateral extension 93 at the flange 92,

Figure 1.

The-side webs m5 of the lower contact fixture 15 are extended toward the left, in Figure 2, to form the curved camming surfaces H6, which engage the spring '69 in the installation of the fuse tube unit I2 and urge the fixed contacts H4 into proper engaging position with the trunnions 62. 63.

- The. ejector lever 68 is also'preferbly provided with :"a, pair of laterally projecting .hammer flanges III, which are beveled at I IS on the lower left corner to provide asharp edge at H9. The sharp edge H9 is so located that itis adapted to pass above the curved upper surface of each trunnion 62, 63, so that the trunnions will be struck by-the beveled surfaces H8, one of which is 'located on each side of the ejector lever. Thus the ejector lever has a cam II8, which is forced over-the fixed trunnions to lift the fuse tube unit untilthe overhang of contact I I4 rises abovethe trunnions. At the same time the impact urges contact I I4 off the trunnions.

Referring to the upper contact supporting arm '38, Figure 1, here the parallel attaching flanges 41 are made longer than the flanges 42 at the bottom arm 39, for the-reason that the upper arm fixture 53 is shorter and it is desired to support the. tube 12 substantially parallel to the insulator I13. Bolt 43 clamps the band 38 on insulator I3.

.Two additional screw'bolts I and I2I pass through both the flanges 4I adjacent their ends,

and also through 'an'attachlng flange I22 of the contact arm fixture 53 to secure this fixture to the upper arm 38. The fixture 53 pivots on the bolt I 2I by reason of the clearance provided by an enlarged aperture I23 in attaching flange I22 surrounding the bolt I28. This pivotal movement provides a predetermined amount of adjustment of the jaws of the upper fixture -53 to accord variations in length of the fuse tube unit I2, and still bring the upper trunnions I24 into good contact engagement with the upper fixed contacts.v

The upper contact fixture 53, on arm 38, has a rearwardly extending horizontal flange I25 provided with a threaded bore for receiving screw 00117126; which passes through the end of a leaf spring I21 and secures it to the flange I25. The other end of leaf spring I2? engages a rotatable sleeve I28 carried by a bolt I29, whichis secured inapertures in the'flanges 4 I-4 I. The rotatable sleeve I 28 is located between the flanges 4.I-4I, and serves as a roller for engaging leaf spring I2l with a minimum amount of friction. The leaf spring I21 initially extends downwardly at its left end, Figure 1, but is bent upwardly by engagement with the roller I28, which gives it an intial tension and urges the upper contact fixture 53 in a clockwise direction on its pivot bolt I2 I.

The upper contact fixture 53 may comprise a cast metal member, and it is preferably formed with a housing having a pair of parallel side walls I30 integrally joined to a curved top wall I3I, and a depending straight back wall I32, forming a hood which is open at the bottom for receiving the upper end of the fuse tube unit I2, and for protecting the contacts and upper mechanism from snow, rain and other weather conditions.

The upper contact fixture IUI, on the fuse tube unit I2, has a cylindrical body I33, with a cylindrical bore for receiving the fuse tube 12 which is again secured in place by a plurality of rivet pins I34 in. a manner similar to the pins 'I'I at the lower end. The cylindrical body I33 has a reducedcylindrical extension I35 which is threaded externally to receive the internal threads of the cap I82, which is closed at its upper end I36.

There is a bore I3I extending through the fixture HH and registering with the bore I38 in fuse tube '52 for receiving the fuse and its leader. At the upper right corner of the cylindrical portion I33, Figure 2, the cylindrical body I33 is provided with a pair of laterally projecting cylindrical trunnions I24, and these trunnions I24 form the upper contacts carried by fuse tube unit I2.

At its lower end the cylindrical body I33 of the upper contact fixture 'Ilil has a partially cylindrical extension I48, which carries a laterally projecting operating ring I4I. aperture I42 like the rin 84, of suflicient size to pass the head on the laterally projecting pin of a disconnect stick by means of which the fuse tube unit I2 may be manipulated.

Ring MI is used for operating the unit as a disconnect by merely pulling out and disconnecting the upper contact, while the unit l2 pivots on the lower trunnions. Ring MI is also used in the installation of the fuse tube unit to swing the unit upward from the position of Figure 3, through that of Figure 4 to that of Figure 1.

The parallel side walls I30 of the'upper contact fixture are spaced sufliciently to receive the trunnions I24, which extend laterally from one side wall IilI to the other side wall lei. Above the trunnions I24 the side walls IllI mayagain have inner walls I43, which are spaced sufficient- This ring has an 1y to pass the cap I02 but which terminate in lower shoulders I44 locatedabove the trunnions I24. In other words, the side walls of fixture 53 are thickened at I43.

The lateral shoulders I44 are formed with upwardly curved shoulders I45, above the trunnion I24 in Figure 1, for retaining the trunnion I24 in the fixture 53. Trunnion engaging shoulders I44 extend upwardly and toward the right, Figure 1, and curve upwardly at I46 to provide a camming surface for engaging the trunnions I24 to cam the fixture 53 upward until the trunnions I24 pass in the hood and behind the retaining shoulders I45.

The retaining shoulders I45 constitute the fixed contacts for engaging trunnions I24. The relatively thick parallel walls I43 of fixture 53 have outwardly flaring guide surfaces I41 at the right end (Figure 1) for engaging the cap I02 and guiding it in between the walls I43. The fixture 53 has its attaching flange I22 provided with threaded bores for receiving the screw bolts I48, Figure l, which secure the left end of the leaf spring I49 to the fixture 53.

This leaf spring extends upwardly and is formed with a hump I50 engaging the trunnions I24 and urging them against the fixed contacts I45, when the parts are in the position of Figure 1. The right end of leaf spring I 49 is bent downwardly, and has its end portion II engaging a laterally projecting flange I52 carried by each of the side walls I30. Such a leaf spring I49, is provided on each side of the fixture 53 adjacent each side wall I30 for engaging each trunnion.

The leaf spring I49 may also be utilized for holding the blown fuse unit I2 in the vertical position of Figure 2, and for preventing it from swinging back and forth in the wind, which might accidentally result in an accidental engagement of the lower contact with the lower fixture. For this purpose the trunnions I24 may each be provided with a flat surface at I53, Figure 2, which flatly engages the spring I49, in the depending position of Figure 2, to keep the fuse tube unit from swinging.

Another mode of preventing the swinging of the fuse tube unit is to provide a spring I54, Figure 2, which has a partially cylindrical portion I55 hooked over the bolt I20, and has its rear end I56 under the roller I28. From the bolt I this spring I54 extends diagonally downward at I51 under the depending wall I32, where it is bent upward to provide a resilient end portion I58 that engages the side of the cap, in the position of Figure l, and engages the top of the cap in Figure 2. Thus, when the fuse is blown and the unit 52 swings down from the position of Figure l to that of Figure 2, the spring I54 will thereafter tend to keep it from swinging on its upper pivots.

Operation The mode of manipulation and mode of operation of the mechanism is as follows: A fuse with its leader 98, arranged as shown in-Figure l, is first placed in the fuse tube unit I2, then ejector lever 58 being pressed up against the end of the bafile wall 82 tensions the spring, the leader passing through the groove I04 around the pin 91, and being secured by means of thumb nut I00.

A predetermined tension is thus placed upon the fuse leader 98, tending to withdraw this leader from the tube 12 as soon as the fuse melts. The explosive tendency of the melting fuse; supplemented by the leader ejector 58, tends to 10 break the circuit as quickly as possible and to extinguish the are inside the tube 12.

The fuse tube unit I2 having been re-fused, it is then hung upon a disconnect stick by means of the ring 84, in the position of Figure 3, and then the fuse tube unit may be lifted by means of the stick until the lip II2 passes over the trunnions 52, 53, as shown in Figure 3, and the unit is hung on the trunnions 53 by means of the cylindrical portions IIO of the laterally projecting flanges III.

It should be understood that the trunnions 62, 03 project laterally from each

parallel side wall

54, 55, but terminate with a space between their ends into which the ejector lever can be inserted. The laterally projecting flanges I I I on the ejector lever project far enough to extend over the inwardly projecting trunnions carried by the side walls 55, so that the ejector lever serves at this time as a support with which to hang the fuse tube unit I2 on the lower trunnions in the inverted position of Figure 3.

The operator then removes his disconnect stick from the ring 84 and places it in the ring I4I which is the lowermost, but not shown in Figure 3. The operator then uses the disconnect stick to pivot the fuse tube unit I2 counterclockwise from the position of Figure 3, through that of Figure 4, to the position of Figure 1.

As the fuse tube unit I2 passes from the depending position of Figure 3 to the position of Figure 4, it will be seen that the laterally projecting flange III engages the trunnions 62 and 53 by means of its flat surface I09, Figure 4. As the fuse tube unit moves upward counterclockwise from Figure 4, it will be seen that the tendency of gravity is to cause the fuse tube unit I2 to slide toward the left on the

trunnions

52, 63, due to the fact that the surface I09 will slope downward toward the left, and the

trunnions

52, 63 will move into engagement with the fixed contacts II4.

When the fuse tube unit reaches the position of Figure 1 then the fixed contacts II4 engage the trunnions 62, 63, with a slight overhang of the fixed contacts II4 behind or to the left of the trunnions 62, 63, whereby the lower contacts II4 are retained in engagement with the trunnions 62, 53.

When the upper end of the fuse tube unit I2 approaches the upper contact fixture 53, the cap I02 will be guided between the side walls of the upper hood by the flaring guide surfaces I41, and the trunnions I24 will pass under the curved surface I46 and along under the shoulder I44 until the trunnions I24 engage and compress spring I49 and snap behind the curved retaining shoulder or fixed contact I45. Then the fuse unit has been installed, as shown in Figure 1.

Operation as a disconnect To operate the assembly as a disconnect, with the parts in the position of Figure l, the lineman may hook the end of a disconnect stick in the upper ring I4I. By pulling on the disconnect stick the curved upper surface of the trunnions I24 will cam the retaining shoulder or fixture contact I45 upward, this motion being permitted by its pivotal mounting on the bolt I2 I, and being resisted by the spring I21. I

The shape of the parts is such that the fuse tube'unit I2 can be pulled out of engagement with its upper contacts and can be lowered into the position of Figure 3, pivoting on the lower trunnions. 62, 63. The location of the parts in 11 this position, hanging from its lower trunnions, indicates to the user that the line has been purposefully opened, using the device as a disconnect.

The disconnect can be closed in the same manner as it was closed in the installation of the fuse tube unit, by swinging the fuse tube unit upward counterclockwise with the disconnect stick engaging the ring I l! until the contacts I24, I55 engage each other.

Operation as a fused drop-out cut-out When a surge of current melts the fuse carried by the upper end of the fuse leader 9B, the

gases and melted parts are expelled out of the lower end of the tube 12 and are directed by the blast chute 'I'Qaway from the face of the operator. At the same time the release of the tension on the fuse leader 9B permits the ejector lever 68 to be moved by its spring in a clockwise direction, in Figure '1, to withdraw the fuse leader 98 from the tube 12 and assure the mechanical disconnection of the leader from the cap I82 by pulling the leader out of the tube :72.

In this action it is advantageous to have the leader wound about the extension 91 of the ejector lever pivot, because this involves no sliding across that point of support of the leader and thus minimizes the friction in pulling out the leader.

' When the ejector lever '68 moves clockwise, on theblowing of a fuse, hammer flange I IT has its sharp end moved toward the trunnions 62, 63 until the sharp end of this hammer lever engages between the trunnion and the, fixed contact I I4,

on each side of the lower fixture 15.

This tends to raise the contacts H4 and the entire fuse tube unit 12' sufiiciently for the overhang of the contacts H 4 to clear the trunnions 62, 63;arid simultaneously urges the contacts H4 outwardly toward the right away from the trun nions 62, 63. The fuse tube unit tends to swing by gravity also from the position of Figure 1 to that of Figure 2, and thus as soon as the overhang of the contacts IN on tru'nnio'ns 62, '63 is released the fuse tube unit 12 tends to swing to the right,"at its lower end, in a counterclockwise direction from the position of Figurefl, to that of Figure 2. When the fuse tube unit is in this position itfi's an indication that the "circuit has not been opened by using the device as 'a disconnect, but it has been opened by the blowing of a fuse.

It will thus be observed that 'wehave invented a fused drop-out cut-out in which the jet action'of the expelled gases will tend to push the fuse tube unit into engagement with its upper and its lower contacts, retarding any tendencies of the device to 'opentoo quickly. The device will not open, until the power arcs are extinguished, because it "is only after the arc is extin'guished that thej-et. action ceases from pressing the fuse tube unit b'ackwardly into engagement with its contacts.

The present assembly hasjthe contacts so arranged that they are self-aligning to compensate for discrepancies in the length of the fuse tube units or in the spacing between the contact supporting arms, which are due to the variations in manufacture. The advantages of our improved device may be summarized as follows:

1 It is adapted to use standard universal fuse links of any manufacturer and to be handled according to conventional practice.

' 2. The 'lowercontact of the fuse tube is ejected 12 from the bottom contact arm upon rupture of the fuse link so that the fuse tube will hang with its opening extending. downward after operation, thus protecting the interior of the fuse tube from all adverse weather. conditions.

3. The construction of the mechanism is such that the mechanical opening of the lower contacts is delayed until the arc has been definitely extinguished.

4. The jet action from the lower end of the tube, tends to keep the upper end of the fuse tube in its proper position and to hold the lower end in position until after the blast, thus delaying mechanical opening until the arc, has been extinguished.

5. The resilient spring contacts with their wide flaring ends are adapted to register with the trunnions of the fuse tube units, even though the dimensions may vary due to manufacturing tolerances and the contacts may give sufiiciently to become self-aligning as they. engage the trunnions.

GJAny. undue strain on the spring contacts is prevented by the provision of stop surfaces which take the thrust that iscaused by jet action during rupture of a fuse.

7. The present fuse unit may be operated as a disconnect switch, but when so operated its automatic mechanism is still trip-free, so that a'. fault on the line will open the lower contacts even while the operator is closing. and holding the upper contacts.

8. The device gives a visual indication at all times whether it is actively in the circuit or whether the circuit has been broken purposefully at the top or automatically by rupture'of a fuse at the bottom.

While we have illustrated a preferred embodiment of our invention, many modifications may be made without departing from the spirit of the invention, and we do not wish to be limited to the precise details of construction set forth, but desire to avail ourselves of all changes within the scope of the appended claims.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent of the United States, is:

' 1. In a drop-out fuse cut-out, the combination of; an insulating support, with-an upper contact arm, a fuse tube unit and means for pivotally supporting said fuse tube unit from said upper contact arm, a lower contact arm carried by said support, a trunnion carried by said lower contact arm, a fixed contact carried by said fuse tube unit for engagement with said trunnion, a spring-biased fuse ejector lever carried by said fuse tube unit, and cam means carried by the ejector lever and adapted to engage the trunnion and lift the fuse tube unit to effect a release of the fixed contact from the trunnion when the fuse is melted releasing theejector lever.

2. In a drop-out fuse cut-out, the combination of an insulating support, with an upper contact arm, a fuse tube unit and means for pivotally supporting said fuse tube unit from said upper contact arm, a lower contact arm, carried by said support, a trunnion carried by said lower contact arm, a fixed contact carried by said fuse tube unit for engagement with said trunnion, a spring-biased fuse ejector lever carried'by said fuse tube unit, and cam means carried by the ejector lever and adapted to engage the trunnion and lift the fuse tube unit to effect a release of the hired contact from the trunnion when the 75 fuse is'mel'ted' releasing the ejector lever, said 13 fixed contact comprising an arcuate member engaging above the trunnion and overhanging behind the trunnion to latch the fuse tube unit to the trunnion.

3. In a drop-out fuse cut-out, the combination of an insulating support, with an upper contact arm, a fuse tube unit and means for pivotally supporting said fuse tube unit from said upper contact arm, a lower contact arm carried by said support, a trunnion carried by said lower contact arm, a fixed contact carried by said fuse tube unit for engagement with said trunnion, a spring-biased fuse ejector lever carried by said fuse tube unit, and cam means carried by the ejector lever and adapted to engage the trunnion and to effect a release of the fixed contact from the trunnion when the fuse is melted releasing the ejector lever, said fixed contact comprising an arcuate member engaging above the trunnion and overhanging behind the trunnion to latch the fuse tube unit to the trunnion and said cam means lifting said fuse tube unit until the overhang passes forwardly over the trunnion to release the fuse tube unit to swing by gravity to the open position.

4. In a drop-out fuse cut-out, the combination of an insulating support, with an upper contact arm, a fuse tube unit and means for pivotally supporting said fuse tube unit from said upper contact arm, a lower contact arm carried by said support, a trunnion carried by said lower contact arm, a fixed contact carried by said fuse tube unit for engagement with said trunnion, a spring-biased fuse ejector lever carried by said fuse tube unit and a supporting flange carried by the ejector lever, and facing upward when the fuse tube unit is installed for temporarily supporting the fuse tube unit on said trunnion, when the fuse tube unit hangs downwardly from the lower contact arm during instal lation or when used as a disconnect by separating the fuse tube unit from the upper contact arm.

5. In a drop-out fuse cut-out, the combination of an insulating support, with an upper contact arm, a fuse tube unit and means for pivotally supporting said fuse tube unit from said upper contact arm, a lower contact arm carried by said support, a trunnion carried by said lower contact arm, a fixed contact carried by said fuse tube unit for engagement with said trunnion, a spring-biased fuse ejector lever carried by said fuse tube unit and a supporting flange carried by the ejector lever, and facing upward when the fuse tube unit is installed for temporarily supporting the fuse tube unit on said trunnion, when the fuse tube unit hangs downwardly from the lower contact arm, said flange having a partially cylindrical formation for engaging the top of the trunnion with the fuse tube unit depending.

6. In a drop-out fuse cut-out, the combination of an insulating support, with an upper contact arm, a fuse tube unit and means for pivotally supporting said fuse tube unit from said upper contact arm, a lower contact arm carried by said support, a trunnion carried by said lower contact arm, a fixed contact carried by said fuse tube unit for engagement with said trunnion, a springbiased fuse ejector lever carried by said fuse tube unit and a supporting flange carried by the ejector lever, and facing upward when the fuse tube unit is installed for temporarily supporting the fuse tube unit on said trunnion, when the fuse tube unit hangs downwardly from the lower contact arm, saidflange having a partially cylindrical formation for engaging the top of the trunnion with the fuse tube unit depending, and said flange having an upwardly extending guide portion for supporting the fuse tube unit on said trunnion as the fuse tube unit is swung upward, and for guiding the trunnion into engagement with said fixed contact.

. 7 In a drop-out fuse cut-out, a lower arm supporting structure comprising an insulating support and a transversely extending arm carried by said support, a lower contact member comprising a metal member formed with a hood having substantially parallel side Walls and enclosed on its upper side between said side walls, said hood having a pair of aligned inwardly projecting cylindrical trunnions carried by said side walls for engagement with a fixed contact on the lower end of a fuse tube unit.

8. In a drop-out fuse cut-out, a lower arm supporting structure comprising an insulating support and a transversely extending arm carried by said support, a lower contact member comprising a metal member formed with a hood having substantially parallel side walls and enclosed on its upper side between said side walls, said hood having a pair of aligned inwardly projecting cylindrical trunnions carried by said side Walls for engagement with a fixed contact on the lower end of'a fuse tube unit, said side walls being provided with threaded bores, and said trunnions each having a threaded shank for reception in one of said bores, and locking means on said shank outside of said hood for securing said trunnions.

9. In a drop-out fuse cut-out, a lower arm supporting structure comprising an insulating support and a transversely extending arm carried by said support, a lower contact member comprising a metal member formed with a hood having substantially parallel side walls and enclosed on its upper side between said side walls, said hood having a pair of aligned inwardly projecting cylindrical trunnions carried by said side walls for engagement with a fixed contact on the 1 lower end of a fuse tube unit, said hood also sup porting a leaf spring extending from its top rear side across a curved portion of its top to permit bowing of the leaf spring toward said curved portion, and for engaging a fuse tube unit contact fixture and urging a fixed contact into engagement with said trunnions.

10. In a fuse drop-out cut-out, the combination of an insulating support, with a pair of contact supporting arms carried by said support, a hooded upper contact structure carried by the upper of said arms, a fuse tube unit having means at its upper end for pivotal and latching engagement with said upper contact structure, a lower contact structure carried by the lower of said contact arms, a fuse ejector lever pivotally mounted on said fuse tube unit, a fixed contact mounted on the lower end of said fuse tube unit and adapted to have latching engagement with the lower contact structure on said arm, and means actuated by said fuse ejector lever for releasing said latching engagement whereby the blowing of the fuse effects a release of the lower end of the fuse tube unit from said support to pivot to vertical position on its upper end, said lower contact also having a pivotal engagement whereby the upper contacts may be disconnected, the fuse tube unit pivoting on its lower contacts to serve as a manual disconnect, said lower contact on said fuse tube unit comprising an arcuate contact member bearing against a trunnion carried by the lower arm, and having an overhang behind said trunnion to latch said contact. to said trunnion.

11. In a fuse drop-out cutout. the combination of aninsulating support, with-a. pair of. contact supporting armscarried by, saidsupport, a hooded. upper contact structure carried bythe upper. of. said arms, a fuse tube. unit having. meansat its upper end for ivotal and. latching engagement with. said upper contact. structure, av lower con.- tact structure. carried by the lower ofesaid cong tact. arms, a fuse ejector lever pivotally'mounted on said-fusetube unit, a fixed/contact mounted onthe. lower end ofv said fuse tube unit. and adapted to have latching engagement with the lower contact. structure'on said arm, and means actuated by said fuse ejector lever. for releasing said latching engagement wherebythe blowingoi' theiuse effects a release of the lower end of the fusev tube unitirom saidsupport to .pivottovertiiii:

cal position on its upper end, said lower contact also having a pivotal engagement whereby. the upper contacts may. be disconnected, the fuse. tubeunit pivoting on itslowercontactsto serve as a manual disconnect, said lower contact on said fuse tube unit comprising an arcuate contact member bearing against. a trunnion carried by the lower arm, and having an overhang behind said trunnion to latch said contact to saidtrunnion, said fuse ejector lever being spring-biased,

upper end of the. fuse-tube uniton said :support,

latching means for pivotally securing the lower end of the fuse tube unit to said support,.sai.d fuse tube unit. beingclosed at its. upper end=and open at. its lower end, and having blast. deflecting means at its. lower end so directedthat the jet action urges boththe upper and the lower. latching means toward the latched position, whereby the ejection of gases tends to keepthefuse-tube unit latched inmechanicalcontact until the arc is broken.

1.3. In a drop-out fuse cut-out, the. combination ofan. insulating support, with afuse tubeunit, and latching means for pivotally mounting the upper end of the fuse. tube unit on said'support, latching means for pivotally securing the lower end of the insertubeiunit to said support, said fuse tube unit beingclosed. at itsupper end and open at its lower end, and having blast deflecting means at its lower end so directed that the .jet action urges both the upper and the lower latching means toward the latched position, whereby the ejection of gases tends to .keep the fuse tube unit latched in mechanical contact until the arc is broken, and means carriedby the .fuse tube unit for effecting a release of thelowerend oi'the fuse tube'unit from said'suppor-t to effect a mechanical disconnectionaf-ter the arc hasibeen broken and the blastof gases has substantially. been completed.

14. In a drop-out fuse cut-out, the combination of an insulating support having an upper and a lower laterally projectingcontact arm extending substantially in the same direction at: an angle to the vertical, said upper contactarm being-propartially cylindrical shoulder, and a fuse unit comprising. an insulting tube and upper andlower contact fixtures carried thereby and joined by a fuse. in said tube,;said upper fixture having. a pair of laterally projecting. aligned cylindrical trllll-r nions receivable betweensaid thinside walls and engaging the shoulder of said thick side walls for pivotal movement on said trunnionsin a we. determined plane, the; lower contact fixture, also. having means for pivotalengagement with the lower contact arm so that the fuse tubeunitmay be pivoted on the lower contact arm into andgout of engagement with the upepr contact arm asa disconnect.

15. In a drop-out fuse cut-out, the combination of an insulating supporthav-ing an upper, and a lower laterally projecting contact armcx ifinding substantially in the same; direction atanangle to the vertical, said-upper contactarm being pro-.- vided with a bottom open and frontopen hood, said hood being provided with relatively thickparallel side walls formed at their lower edges with a, partially cylindrical shoulder engaging and holding trunnions,. and havingdepending; relatively thinner parallel side walls engaging and; guiding the end ofsaid trunnions, spring means carried by said hood adjacent eachthin side wall and. located to urge said trunnions against said partially cylindrical shoulder, and a fuse unit comprising an insulating tube and upper and lower contact fixtures-carriedtherebyand joined-- by a fuse in said tube, said upper fixture having a pair of laterally projecting aligned cylindrical trunnions receivable between said thin side walls and engaging the shoulder of saidthick side walls for pivotal movement on saidtrunnions-in aprodetermined plane, the lower contact fixture also having means for pivotal engagement with the lower contact arm so thatthe fuse tube unit may be pivotedon the lower contact arm into and'out of engagement with the upper contact arm as a disconnect, grooved supporting shoulderscarlied by the lower contact fixture for resting upon comple'nentary supporting members on. the lower contact arm, and means responsive to the the blowing of said fuse for lifting saidlower contact fixture off said supporting members, the-fuse tube unit pivoting by gravity on its upper-trunnionsto avertical position.

.16. In a drop-out fuse cut-out, the-combination of an insulating support having anuppenand a lower laterally projecting contact arm-extending substantially in. the same direction at an angle to the vertical, said-upper contact armybein provided with a bottom open; and front open hood, said hood being provided with relatively thick parallel side walls formed at their-lower, edges with a partially cylindrical shoulder engaging and holding trunnions, and having depending relatively thinnerparallel side walls engaging'and guiding the ends of said trunnions, spring means carried by said hood; ajacent each thinsidewall and located to urge said trunnions against said partially cylindrical shoulder, and a fuse unit comprising an insulating tube-and upper-and lowor contact fixtures. carriedthcreby and joinedby a. fuse in said tube, said upper fixture having a pair of laterally projecting aligned cylindrical trunnions receivable between said thin side walls and engaging the shoulder of said thick side walls for pivotal movement on said trunnions in a predetermined plane, the lower contact fixture also having means for pivotal engagement with the lower contact arm so that the fuse tube unit may be pivoted on the lower contact arm into and out of engagement with the upper contact arm as a disconnect, grooved supporting shoulders carried by the lower contact fixture for resting upon complementary supporting members on the lower contact arm, and means responsive to the blowing of said fuse for lifting said lower contact fixture off said supporting members, the fuse tube unit pivoting by gravity on its upper trunnions to a vertical position, said fuse tube being open at its lower end and being provided with a blast chute which is open forwardly and downwardly to direct the gases away from an operator.

17. In a drop-out fuse cut-out, the combination of an insulating support having an upper and a lower laterally projecting contact arm extending substantially in the same direction at an angle to the vertical, said upper contact arm being provided with a bottom open and front open hood, said hood being provided with relatively thick parallel side walls formed at their lower edges wih a partially cylindrical shoulder engaging and holding trunnions, and having depending relatively thinner parallel side walls en gaging and guiding the ends of said trunnions, spring means carried by said hood adjacent each thin side wall and located to urge said trunnions against said partially cylindrical shoulder, and a fuse unit comprising an insulating tube and upper and lower contact fixtures carried thereby and joined by a fuse in said tube, said upper fixture having a pair of laterally projecting aligned cylindrical trunnions receivable between said thin side walls and engaging the shoulder of said thick side walls for pivotal movement on said trunnions in a predetermined plane, the lower contact fixture also having means for pivotal engagement with the lower contact arm so that the fuse tube unit may be pivoted on the lower contact arm into and out of engagement with the upper contact arm as a disconnect, grooved supporting shoulders carried by the lower contact fixture for resting upon complementary supporting members on the lower contact arm, and means responsive to the blowing of said fuse for lifting said lower contact fixture off said supporting members, the fuse tube unit pivoting by gravity on its upper trunnions to a vertical position, said fuse tube being open at its lower end and having its upper trunnions located outwardly of the axis of the fuse tube so that the jet action of the gases expelled from the lower end of the tube tends to pivot the fuse tube unit toward engagement with the lower contact arm to delay interruption of the circuit at said contact arm until after expulsion of the gases.

18. In a drop-out fuse cut-out, the combination of an insulating support having an upper and a lower laterally projecting contact arm extend ing substantially in the same direction at an angle to the vertical, said upper contact arm being provided with a bottom open and front open hood, said hood being provided with relatively thick parallel side walls formed at their lower edges with a partially cylindrical shoulder engaging and holding trunnions, and having depending relatively thinner parallel side walls en- 18. I l. gaging and guiding the ends of said trunnions, spring means carried by said hood adjacent each thin side walland located to'urge said trunnions against said partially cylindrical shoulder, and a fuse unit'comprising an insulating tube and upper and lower contact fixtures carried thereby and joined by afuse in said tube, said upper fixture having a pair of laterally projecting aligned cylindrical trunnions receivable between said thin side walls and engaging the shoulder of said thick side walls for pivotal movement on said trunnionsin a predetermined plane, the lower contact fix: ture also having means for pivotal engagement with the lower contact arm so that the fuse, tube unit may be pivoted on the lower contact arm into and out of engagement with the upper C011". tact arm as a disconnect, grooved supporting shoulders carried by the lower contact fixturefor resting upon complementary supporting members on' the lower contact arm, and means responsive to the blowing of said fuse for lifting said lower contact fixture off said supporting members, the fuse tube unit pivoting by gravity on its upper. trunnions to a vertical position," said upper hood being pivotally mounted on said upper contact arm and spring urged toward the lower contact arm to provide a limited upward movement of the hood and fuse tube unit.

19. In a fused drop-out cut-out, the combination of an insulating support with a pair of laterally projecting contact arms carried thereby and extending at an angle to'the vertical, a fuse tube unit comprising an insulating tube and a contact fixture carried by each endo-f said tube and connected by a fuse in the tube, the upper of said contact fixtures being pivotally mounted on the upper contact arm, the lower ofsaid contact fixtures being provided with a rearwardly projecting part having a pair of partially cylindrical laterally projecting supporting shoulders, a hood carried by said lower contact arm and having parallel side walls provided with a pair of aligned inwardly projecting cylindrical trunnions, said shoulders resting on said trunnions and said fuse tube unit being releasable by lifting the fuse tube unit until its partially cylindrical shoulders clear the trunnions for pivotal movement forwardly of the fuse tube unit on the upper contact arm.

20. In a fused drop-out cut-out, the combination of an insulating support with a pair of laterally projecting contact arms carried thereby and extending at an angle to the vertical, a fuse tube unit comprising an insulating tube and a contact fixture carried by each end of said tube and connected by a fuse in the tube, the upper of said contact fixtures being pivotally mounted on the upper contact arm, the lower of said contact fixtures being provided with a rearwardly projecting part having a pair of partially cylindrical laterally projecting supporting shoulders, a hood carried by said lower contact arm and having parallel side walls provided with a pair of aligned inwardly projecting cylindrical trunnions, said shoulders resting on said trunnions and said fuse tube unit being releasable by lifting the fuse tube unit until its partially cylindrical shoulders clear the trunnions for pivotal movement forwardly of the fuse tube unit on the upper contact arm, said fuse tube unit being provided with a spring pressed pivoted member for tensioning the fuse and said member having an anvil located to engage between the shoulders and the trunnions upon blowing of the fuse to lift the lower contact fixture off said trunnions.

21. In a fused drop-out cut-out, the combina- 19 tlon of an insulating support with a pair of laterally projecting contact arms carried thereby and extending at an angle to the vertical. a fuse tube unit. comprising an insulating tube and a contact" fixture carried by each end of said tube and connected by a fuse in. the tube, the upper of said contact fixtures being pivotally mounted on the upper contact arm, the lower of said contact fixtures being. provided with a rearwardly projecting part having a pair of partially cylindrical laterally projecting supporting shoulders, a hood carried by said lower contact arm and having parallel side walls provided with a pair of aligned inwardly projecting cylindrical trunnions,

said shoulders resting on said trunnions and said fuse tube unit. being releasable by lifting th fuse tube unit until its partially cylindrical shoulders clear the. trunnions for pivotal. movement forwardly of the fuse tube. unit on the upper contact arm, said fuse tube unit being provided with a spring pressed pivoted member for tensioning the fuse and said member having an anvil located to engage between the shoulders and the trunnions upon blowing of the fuse to lift the lower contact fixture ofisaidtrunnions, said anvil having a 'rearwardly extending knife portion directed to the point between the said shoulders and trunnions;

22. In a fused drop-out-cut-out, the combination Of an insulating support with a pair of laterally projectingcontact arms carried thereby and extending at an angle to the vertical, a fuse tube unitcomprising an insulating tube and a contact fixture carried by each. end of said tube and connected bya fuse in. the tube, the upper of said contact fixtures being pivotally mounted on the upper contact arm, the lower of said contact fixtures being provided with, a. rearwardly projecting; part having a pair of; rtiallycylindrical laterur- Li? 20 ally projecting. supporting shoulders, a. hood earriedby said lower contac arm andhavinet P IeI. sidewalls provided. with. a pair of. aligned inwardly projecting cylindrical. trunnions, said shoulders resting. on. said trunnions and said. fuse tube unit being releasable by lifting the fuse tube. unit. until its partiall cylindrical shoulder clear the. trunnions for pivotal movement, forwardly of the fuse tube unit on the upper contact arm, said fuse tube, unit. being. provided. with a. spring pressed pivoted. member for tensioning. the fuse and said member having. an anvil located to en.-

gagebetween. the shoulders and. the trunnijons.

upon blowing of. the. fuse to lift the lower contact fixture off, said. trunni.ons,. said anvil having. a rearwardly extending knife portion directed to the point between the sa d shoulders and rum nions, the said pivoted member having means for attachment of an extension carried by the 111158. located substantially at the axis. of. pivot of said member.

DAVID C. HUBBARD. WILLIAM L. HOLLANDER.

REFERENCES CITED The following references are of record" in the. file of this patent:

UNITED STATES PATENTS Number Name Date 1,925,624 Boll Sept. 5, 1933. 2,028,421 Steinmayer Jan. 21, 1936 2,212,633. Bodendieck l l Aug. 27, 1940 2,290,382. Ramsey Ju1y2l, 1.942 2,,3l'7,641. Ramsey May 2 194.4. 2,354,907 Bennett et a1. a. Aug. 1.1.9.44. 2,561,898. Hubbard. in Feb. 15,1949