US3447114A - Dropout fuse structure - Google Patents

Description

May 27, 1969 RE. FRINK ET AL DROPOUT FUSE STRUCTURE Filed Aug; 24, 1967 INVENTORS Russell E, Frink and Clayton T. Walker ATTORNEY United States Patent O 3,447,114 DROPOUT FUSE STRUCTURE Russell E. Frink and Clayton T. Walker, Pittsburgh, Pa.,

assignors to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Aug. 24, 1967, Ser. No. 663,020 Int. Cl. H01h 71/20 US. Cl. 337171 7 Claims ABSTRACT OF THE DISCLOSURE A pivotally mounted fuse holder having fusible means disposed therein is normally latched in a closed circuit condition with a pair of spaced, relatively stationary contacts. Upon fusion of the fusible means, a movable member in the fuse holder actuates a latching means to release the fuse holder and to move it to a dropout position in which an air gap is interposed between the stationary contacts.

BACKGROUND OF THE INVENTION Field of the invention The invention relates to circuit interrupters and more particularly to dropout fuse structures.

Description of the prior art SUMMARY OF THE INVENTION According to the invention, a releasable latching means for a dropout fuse structure comprises a generally L- shaped actuating lever pivotally supported adjacent to a line contact of the fuse structure and a latch member which is pivotally supported on the actuating lever and includes a roller thereon which engages a terminal on a pivotally mounted fuse holder in the closed position of the fuse holder. A first spring means biases the latch member and the roller thereon toward engagement with the terminal of the fuse holder and a second spring means comprising a pair of coil springs biases the actuating lever and a roller thereon to bear against and to actuate the fuse holder to drop out to an open position upon the fusion or operation of a fusible means in the fuse holder. Upon the fusion of the fusible means in the fuse holder, a movable part in the fuse holder engages and releases the latch member to permit the actuating lever to actuate the fuse holder to an open position. The relatively stationary contacts may be arranged to carry substantially all of the electrical current through the fuse structure independently of the parts which mechanically support the fuse holder and the latching means which is released to initiate a dropout movement of the fuse holder.

It is an object of this invention to provide a more compact releasable latching means for a dropout fuse structure.

Another object of this invention is to provide a dropout fuse structure which substantially minimizes the forces required for manually opening or closing the fuse structure or for automatically actuating the fuse holder into an open position upon the operation of a fusible means which forms part of the fuse structure.

Other objects of the invention will, in part, be obvious and will, in part, appear hereinafter.

3,447,] 14 Patented May 27, 1969 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view, partially in section and partly broken away, of a high voltage dropout power fuse structure which embodies the principles of the present invention and which is shown in the normally closed operating condition;

FIG. 2 is an enlarged top plan View of the lower hinge member which forms part of the fuse structure shown in FIG. 1;

FIG. 3 is a bottom view of the upper latchin and contact assembly which forms part of the fuse structure shown in FIG. 1; and

FIGS. 4 and 5 are diagrammatic views illustrating different stages in the operation of the fuse structure shown in FIG. 1 during a closing operation of the fuse structure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, and FIG. 1 in particular, the structure shown comprises a power fuse structure of the high voltage, dropout type. As illustrated in FIG. 1, the dropout fuse structure 10 includes a base (not shown) formed of sheet metal and a pair of outwardly extending or projecting insulator supports 272 and 282 which are spaced from one another along the associated base. The upper insulator support 272 fixedly supports in position a latching and contact assembly 250 which includes a relatively stationary line contact 252. The lower insulator 282 supports a hinge and contact assembly 260 which pivotally supports a fuse unit and which includes a relatively stationary hinge line contact 150. As illustrated in FIGS. 1 and 3, the fuse unit 100 serves to electrically bridge the relatively stationary spaced line contacts 252 and so that electric current will normally pass therebetween by way of the upper and lower terminals pads 313 and 172, respectively, to which an external electrical circuit may be connected.

The fuse unit 100 may be of the type which is described in greater detail in copending application Ser. No. 633,127, filed Aug. 24, 1967, now Patent 3,401,247 issued Sept. 10, 1968, by C. W. Upton, Jr., C. C. Patterson, and F. L. Cameron, copending application Ser. No. 663,029, filed Aug. 24, 1967, now Patent 3,401,245 issued Sept. 10, 1968, by F. L. Cameron, and copending application Ser. No. 663,021, filed Aug. 24, 1967, now Patent 3,401,244, issued Sept. 10, 1968, by C. C. Patterson which are all assigned to the same assignee as the present application. More specifically, the fuse unit 100 includes a generally tubular fuse holder 32 which is formed from a suitable weatherproof, electrically insulating material and a pair of spaced upper and lower end fittings or terminals 34 and 36, respectively, which are disposed adjacent to or at the opposite ends of the holder 32 and which are formed from an electrically conducting material. The upper and lower end fittings or terminals 34 and 36, respectively, may be securely fastened to the opposite ends of the associated holder or tube 32 by suitable means, such as a cement and a plurality of pins (not shown) which pass transversely through both the end fittings 34 and 36 and the associated holder 32.

As shown in FIG. 1, the fuse unit 100 also includes a hook eye 274 which is pivotally mounted on a laterally projecting portion 34A of the upper terminal 34 and which may be utilized for effecting opening and closing movements of the fuse unit 100 by means of a conventional hook-stick. More specifically, the hook eye 274 includes an inwardly projecting actuating arm 274A which may be formed integrally therewith and which may be rotated to effect release of the latching assembly 250 to initiate an opening movement of the fuse unit 100, as will be explained in greater detail hereinafter. The upper terminal 34 of the fuse unit 100 also includes a projecting portion 263 which may be formed integrally therewith and which projects axially upwardly, as viewed in FIG. 1, to be engaged by the latching assembly 250 in the closed position of the fuse unit 100 to thereby maintain the fuse unit 100 in the closed position shown in FIG. 1.

In order to automatically release the latching assembly 250 and to initiate a dropout movement of the fuse unit 100 upon the operation of the fusible means which is disposed inside the fuse holder 32 of the fuse unit 100 following the interruption of the circuit which normally extends between the terminals 34 and 36, the fuse unit 100 includes an axially movable member or plunger, as indicated at 262 in FIG. 1, which is arranged to project through a central opening in the end cap 261 which is releasably secured to the upper end of the fuse holder 32 of the fuse unit 100 to thereby actuate the release of the latching assembly 250, as will be explained in detail hereinafter. As explained in detail in the copending applications previously mentioned, the axially movable member 262 only actuates the release of the latching assembly 250 following the interruption of the are which normally results inside the fuse holder 32 of the fuse unit 100 upon the operation of the fusible means which is disposed inside the fuse holder 32.

The lower fuse terminal 36 of the fuse unit 100 includes a pair of trunnions which extend laterally from the opposite sides of the terminal 36 and which may be formed integrally therewith. The trunnions 44 are adaped to be received by the hinge and contact assembly 260 which pivotally supports the fuse unit 100. In order to permit lifting movements of the fuse unit 100 out of or into the hinge assembly 260 for replacement of the fuse unit 100 or of the fusible means which forms part of the fuse unit 100 or for initial installation of the fuse unit 100, the lower terminal 36 of the fuse unit 100 includes a hinge lifting eye 38 which may be formed integrally with the lower terminal 36 and which may be employed in conjunction with a conventional hook-stick to effect a physical removal of the fuse unit 100 from or insertion of the fuse unit 100 into the hinge assembly 260. In order to facilitate current transfer between the lower terminal 36 of the fuse unit 100 and the relatively stationary contact means 150 which forms part of the hinge and contact assembly 260, the lower terminal 36 includes a generally arcuate portion 182 which may be formed integrally with the lower terminal 36 and which extends laterally in a direction which is generally transverse to the axis of the fuse unit 100, as viewed in FIG. 1.

In order to guide the rotational opening and closing movements of the fuse unit 100 and to assist in retaining the fuse unit 100 in assembled relationship with the latching and contact assembly 250 and the hinge and contact assembly 260, the lower terminal 36 includes a pair of generally cylindrical projecting portions 42 which may be formed integrally with the lower terminal 36 and which project laterally in opposite directions from the terminal 36 generally transversely with respect to the axis of the fuse unit 100 at a location which is axially displaced from the trunnions 44. For the same purpose,

the lower terminal 36 also includes a pair of sector-shaped portions 46 which may be formed integrally with the lower terminal 36 and which also project laterally in opposite directions from the lower terminal 36 generally transversely with respect to the axis of the fuse unit 100 at locations which are generally radially displaced from the associated trunnions 44. As will be explained hereinafter, the projecting portions 42 and the sector-shaped portions 46 cooperate with associated parts of the hinge assembly 260 to assist in maintaining the fuse unit 100 in assembled relation with the hinge assembly 260 in all positions of the fuse unit 100 except when the fuse unit 100 is in a completely dropped out position which is angularly displaced from the position of the fuse unit 4 100, as shown in FIG. 1, by an angle of substantially 180.

In order to pivotally support the fuse unit and to transfer electric current to the lower terminal 36 of the fuse unit 100 from whatever electrical circuit is electrically connected to the fuse structure 10, the hinge and contact assembly 260 includes a generally U-shaped hinge member 110, as shown in FIG. 2, a relatively stationary line contact 150 and a terminal pad member 162 which are all removably secured to the lower insulator support 282 by suitable means, such as the bolts 153, as shown in FIG. 1. More specifically, the generally U-shaped hinge member 110 includes a pair of laterally spaced side wall portions 102 and 104 and a connecting rear or bight portion 152. Each of the side walls 102 and 104 of the hinge member 110 includes a front portion which projects diagonally upwardly, as viewed in FIG 1, to provide a surface, as indicated at 117, along which one of the trunnions 44 of the fuse unit 100 may slide or travel during the insertion of the fuse unit 100 into the hinge assembly 260 until the trunnions 44 at the opposite sides of the lower terminal 36 of the fuse unit 100 reach their final positions, as shown in FIG. 1, in which the trunnions 44 pass through the slots, as indicated at 116, in the side walls 102 and 104 of the hinge member 110. In order to assist in guiding the rotational movement of the fuse unit 100, each of the side walls 102 and 104 has mounted thereon a snub pin, as indicated at 112 and 114 respectively, with the pins 112 and 114 projecting laterally inwardly toward each other, as viewed in FIG. 2. In order to additionally guide the movement of the fuse unit 100 during its rotational movements and to assist in retaining the fuse unit 100 in assembled relationship with the hinge assembly 260 during certain operating conditions, the side walls 102 and 104 of the hinge member 110 include the forwardly projecting guide portions 106 and 108, respectively, which together with the lower portions of the side walls 102 and 104, respectively,define the slots 118, as indicated in FIG. 1 which cooperate with the projecting portions 42 provided on the lower terminal 36 of the fuse unit 100'. It is to be noted that during the removal or insertion of the fuse unit 100 into the hinge assembly 260 and the latching assembly 250 of the fuse structure 10, the projecting portions 42 on the lower terminal 36 of the fuse unit 100 will bear against and travel along the under surface of the guide portions 106 and 108 of the side walls 102 and 104, respectively, during at least a portion of the rotational travel of the fuse unit 100, while during other portions of the rotational travel of the fuse unit 100, the snub pins 112 and 114 will be disposed between the trunnions 44 and the associated sector-shaped portions 46 on the lower terminal 36 of the fuse unit 100 to guide the travel of the fuse unit 100 and to assist in retaining the fuse unit 100 in assembled relationship with the hinge assembly 260 and the latching assembly 250. A bumper 103 formed of a resilient material, such as rubber, may be mounted on a metal leaf spring member which extends downwardly from the hinge member 110 to limit the dropout movement of the fuse unit 100 to a position which is angularly displaced from that shown in FIG. 1 by substantially 180. It is also to be noted that when the fuse unit 100 is actuated to a completely dropped out position which is angularly displaced from the position shown in FIG. 1 by an angle of substantially 180, the fuse unit 100 can be lifted out of the hinge lower terminal 36 will be disengaged from the guide pormember 110 since the projecting portions 42 on the tions 106 of the hinge member 110 and the snub pins 112 and 114 on the hinge member 110 will be disengaged from the sector-shaped portions 46 on the lower terminal 36 of the fuse unit 100.

In order to transfer electric current between the relatively stationary line contact of the hinge assembly 260 and the contact portion 182 on the lower terminal 36 of the fuse unit 100, the relatively stationary contact 150 is disposed to engage the contact portion 182 on the lower terminal 36 of the fuse unit 100 in the closed position of the fuse unit 100, as shown in FIG. 1. More specifically, the generally U-shaped or J-shaped contact 150 is formed from a resilient or spring type electrically conducting material, such as beryllium-copper, zirconiumcopper, Phosphor bronze or the like. The left leg of the stationary contact 150, as viewed in FIG. 1, is secured between the bight portion 152 of the hinge member 110 and the terminal pad member 162, while the right leg of the stationary contact 150 includes two spaced contact portions, as indicated at 150A and 150B, which independently resiliently engage the contact portion 182 provided on the lower terminal 36 of the fuse unit 100.

It is to be noted that during a closing movement of the fuse unit 100 to the position shown in FIG. 1 the contact portions 150A, 150B of the right leg of the stationary contact 150 resiliently bear against the contact portion 182 provided on the lower terminal 36 of the fuse unit 100. It is also to be noted that the terminal pad 162 which is mounted on the lower insulator support 282 projects laterally, as indicated in FIG. 2, and includes a plurality of bolt holes to which an electrical conductor, as indicated at 172, from an electrical circuit may be secured to electrically connect the fuse structure in circuit relation with an external electrical circuit. The electrically conducting path between the terminal pad 162 and the lower terminal of the fuse unit 100 extends from the terminal pad 162 through the left leg of the stationary contact 150, through the right legs 150A and 150B of the stationary contact 150, through the contact portion 182 on the lower terminal 36 to the lower end of the fuse unit 100. It is important to note that the hinge member 110 is not required to carry any electrical current in the disclosed structure of the hinge assembly 2 60 and that the hinge member 110 may be constructed from a material having a greater mechanical strength, such as galvanized steel, to provide improved support for the fuse unit 100 and to avoid any thermal stressing of the parts which form the hinge member 110.

When a discharge filter as indicated in phantom of the type shown in detail in U.S. Patent No. 3,178,537 issued Apr. 13, 1965 to C. C. Patterson and assigned to the same assignee as the present application is provided in certain applications, such a discharge filter would normally be mounted at the lower end of the fuse unit 100 and extend axially downwardly therefrom. In such applications, a stop pin 158 may be provided which extends between the side walls 102 and 104 behind the right leg of the lower stationary contact 150 as shown in FIGS. 1 and 2 and is supported by the side walls 102 and 104. When the discharge filter 107 in such applications strikes the contact 150, the dropout movement of the fuse unit 100 and the associated discharge filter is stopped. The purpose of the pin 158 is to prevent deformation of the contact 150 by overbending during such an operation. The rotation of the fuse unit during such a dropout operation is of the order of 45 in a clockwise direction from the position shown in FIG. 1 about the axis of rotation of the fuse unit 100.

In general, the latching and contact assembly 250 is provided to releasably latch the fuse unit 100' in the closed circuit position shown in FIG. 1 and to provide the necessary means for transferring electrical current from an external circuit to which the fuse structure 10 may be electrically connected and the upper end of the fuse unit 100 at the upper terminal 34. In addition, the latching and contact assembly 250 is provided to automatically actuate the dropout movement of the fuse unit 100 from the closed circuit position shown in FIG. 1 to an open circuit dropout position which is angularly displaced from the position of the fuse unit 100 in FIG. 1 by an angle of substantially 180 upon the operation of the fusible means which forms part of the fuse unit 100 following the interruption of the are which sults within the fuse unit 100.

More specifically, the latching and contact assembly 250 includes a generally rectangular enclosing housing or hood 310 which is formed from an electrically conducting material and which is secured to the upper insulator support 272 by suitable means, such as the bolts 307. As shown in FIGS. 1 and 3, the enclosing housing 310 includes a pair of spaced side wall portions 314 and 316 which are interconnected by a rear Wall portion 315 and a top wall portion 312. In order to facilitate the entrance of the upper end of the fuse unit during opening and closing movements of the fuse unit 100, the enclosing housing 310 includes a front opening, as indicated at 319, in the path of movement of the upper end of the fuse unit 100. As best shown in FIG. 3, the side wall 316 of the enclosing housing 310 includes a substantially flat external surface which is adapted to function as a terminal pad, as indicated at 313, to which an electrical conductor, as indicated at 372, of an external electrical circuit may be connected by suitable means, such as bolts, which pass through a plurality of aligned openings in the electrical conductor 372 and in the terminal pad portion 313 of the enclosing housing 310. It is to be noted that the lower portions of the side walls 314 and 316, as indicated at 314A and 316A respectively, are outwardly flared to facilitate and guide the entrance of the upper end of the fuse unit 100 during a closing operation of the fuse structure 10'.

In order to provide an electrically conducting path between the upper terminal 34 of the fuse unit 100 and the electrically conducting housing 310, the upper line contact 252 which is generally U-shaped in configuration is provided as part of the latching and contact assembly 250 and is secured to the upper insulator support 272 inside the housing 310 by suitable means, such as the bolts 305, as shown in FIGS. 1 and 3. The upper line contact 252 is preferably formed from a resilient, electrically conducting material, such as zirconium-copper, and includes a pair of laterally spaced contact arms 252A and 2528 which are structurally interconnected by a bight portion, as indicated at 252C in FIG. 3. The resilient contact arms 252A and 252B are diverging at the outer ends thereof, as best shown in FIG. 3, to facilitate the entrance of the upper terminal 34 of the fuse 100 and to engage the opposite sides of the upper terminal 34 with a minimum of frictional forces. The electrically conducting path between the upper terminal 34 of the fuse unit 100 and the external electrical circuit, such as indicated by the electrical conductor 372, extends through the electrically conducting housing 310 and then through two electrically parallel paths through the contact arms 252A and 252B to the upper terminal 34 of the fuse unit 100. It is to be noted that the electrically parallel current paths through the contact arms 252A and 252B of the line contact 252 increase the pressure of the contacts between the upper terminal 34 and the contact arms 252A and 252B during fault current conditions but the angles of contact between the contact arms 252A and 252B are approximately the friction angles so that any dropout movement of the fuse unit 100, as will be described hereinafter, is not impeded or retarded.

In order to actuate the dropout movement of the fuse unit 100 from the closed position shown in FIG. 1 in a clockwise direction, as viewed, in FIG. 1, to the open position upon the operation of the fusible means which forms part of the fuse unit 100 which actuates the movement of the axially movable member 262 beyond the upper end of the fuse unit 100 as viewed in FIG. 1, a generally L-shaped, bifurcated actuating lever 320 is disposed inside the housing 310 and is pivotally supported on a pivot pin 332 which extends between the side walls 314 and 316 of the housing with the ends of the pivot pin 332 extending through aligned openings in said side walls which act as support bearings and being normally reretained in assembled relation with the housing 310 by suitable means, such as lock washers or lock rings, at the outer ends thereof. As best shown in FIGS. 1 and 3, the actuating lever 320 includes a pair of laterally spaced side wall portions 322 and 324 which are interconnected by -a bight or connecting portion 326. The upper portions of the side walls 322 and 324 include substantially aligned elongated slots, as indicated at 333, for the side wall 324 in FIG. 1 through which the pivot pin 332 passes. It is to be noted that the upper portions of the side walls 322 and 324 are disposed generally at a right angle with respect to the lower portions of the side walls 322 and 324, as shown in FIG. 1 and that the axis of rotation of the actuating lever 320 extends generally transversely with respect to the axis of the fuse holder in the closed position as shown in FIG. 1. In order to bias the actuating lever 320 in a counterclockwise direction about its axis of rotation which is defined by the pivot pin 332, as viewed in FIG. 1, and to actuate the dropout movement of the fuse unit 100, as will be explained hereinafter, a pair of coil springs 334 and 335 are disposed on the pivot pin 332 between the respective side walls 322 and 324 respectively and the adjacent side walls 314 and 316, respectively, of the enclosing housing 310, as best shown in FIG. 3. The outer ends of the coil springs 334 and 335 are dis posed to bear against integral inside walls of the adjacent side walls 314 and 316, respectively, of the housing 310 as indicated at 317 for the coil spring 334 in FIGS. 4 and 5, while the inner ends of the coil springs 334 and 335 bear against a pivot pin 372 which extends between and beyond the side walls 322 and 324 of the actuating lever 320, as best shown in FIGS. 3 and 4. In order to facilitate the actuation of the dropout movement of the fuse unit 100 by the actuating lever 320 under the influence of the biasing springs 334 and 335, an actuating roller 352 is pivotally mounted or supported at the lower end of the actuating lever 320 on a pivot pin 353 which extends between the side walls 332 and 324 of the actuating lever 320 to bear against the upper terminal 34 of the fuse unit 100 when the fuse unit 100 is in the closed position shown in FIG. 1. It is to be noted that the force exerted on the actuating lever 320 by the springs 334 and 335 biases the actuating lever in a counterclockwise direction about the pivot pin 332, as viewed in FIG. 1, which in turn tends to actuate the upper end of the fuse unit 100 in a clockwise direction about the axis of rotation which is defined by the trunnions 44 at the lower end of the fuse unit 100 as viewed in FIG. 1.

In order to releasably maintain the fuse unit 100 in the closed position shown in FIG. 1 against the force exerted on the upper end of the fuse unit 100 by the actuating lever 320 under the influence of the biasing springs 334 and 325, the latching lever or member 330 is pivotally mounted on the actuating lever 320 by the pivot pin 372 which extends laterally between and beyond the side wall portions 322 and 324 of the actuating lever 320 generally where the upper portions of the side walls 322 and 324 meet the respective lower portions at substantially right angles with respect to one another. The latching member 330 includes a pair of spaced side wall portions 331 and 337 which are interconnected by a bight portion 335, as best shown in FIGS. 1 and 3. The latch member 330 pivotally supports a latch roller 362 which is pivotally supported on a pivot pin 363 which extends between the side walls 331 and 337 of the latch member 330 with the latch roller 362 being disposed in front of the axially extending portion 263 of the upper terminal 34 of the fuse unit 100 to prevent rotation of the fuse unit 100 under the influence of the force exerted on the upper terminal 34 of the fuse unit "100 by the actuating lever 320 under the influence of the biasing springs 334 and 335. The latch member 330 is disposed in the line of movement of the axially movable member 262 of the fuse unit 100 in the closed position of the fuse unit 100 and is biased in a clockwise direction about the pivot pin 372 toward the upper end of the fuse unit 100, as viewed in FIG. 1, by a coil spring 374 which is disposed on the pivot pin 372. One end of the coil spring 374 bears against the top of one of the side wall 331 of the latch member 330, while the other end of the coil spring bears against a projecting portion 329 on the actuating lever 320 as shown in FIG. 1 which projects toward the other side wall 322 of the latch member 330. It is to be noted that the outer end of the bight portion 335 of the latch member 330, as indicated at 339, projects diagonally upwardly to facilitate the entrance of the upper end of the fuse unit and the hook eye 274 and its actuating portion 274A, as shown in FIG. 1.

Referring to FIG. 4, the position of the operating parts of the latching contact assembly 250 is illustrated prior to the counterclockwise movement of the fuse unit 100 into the closed position, as shown in FIG. 1. It is to be noted that the top wall portion 312 of the enclosing housing 310 includes a stop member 318 on the inner surface which may be formed integrally with the top wall portion 312, as indicated at 3'18, to limit the counterclockwise movement or rotation of the actuating lever 320 under the influence of the coil springs 334 and 335. It is also to be noted that the projecting portion 329 which may be formed integrally with the side wall 324 of the actuating lever 320 acts as a stop member to limit the clockwise rotation of the latch member 330 about the pivot pin 372 with respect to the actuating lever 320, as shown in FIG. 4.

A closing operation of the fuse structure 10 will now be described. It will be assumed initially that the hinge lifting eye 38 at the lower end of the fuse unit 100 is employed to place or insert the trunnions 44 on the fuse unit 100 in the slots 116 in the side walls 102 and 104 of the hinge member 110. A hook-stick may then be inserted in the hook-eye 274 to rotate the fuse unit 100 in a counterclockwise direction about the lower hinge assembly 260 to the position shown in FIG. 4 which illustrates the position of the parts of the latching assembly 250 prior to the movement of the upper end of the fuse unit 100 into the closed position shown in FIG. 1. As shown in FIG. 4, the upper end of the fuse unit 100 and, more specifically, the upper terminal 34 will first bear against the roller 352 at the lower end of the actuating lever 320 and rotate the actuating lever 320 in a clockwise direction about the pivot pin 332 against the force exerted on the actuating lever by the associated bias springs 334 and 335. When the axially projecting portion 263 on the upper terminal 34 engages the latch member 330, the latch member 330 will be also actuated by the movement of the fuse unit 100 in a counterclockwise direction about the pivot pin 372 against the force exerted on the latch member 330 by the bias spring 374 until the latch member 330 reaches the position shown in FIG. 5. As the fuse unit 100 is actuated further in a counterclockwise direction, the axially projecting portion 263 on the upper terminal 34 of the fuse unit 100 will bear against the lower surfaces of the side walls 322 and 324 of the actuating lever 320, as indicated at 324A for the side wall 324 in FIG. 4, which act as cam surfaces to further rotate the actuating lever 320 both in a counterclockwise direction as viewed in FIG. 5 and also to push the actuating lever 320 in a generally upward direction as permitted by the size of the elongated slots provided in the sidewalls 322 and 324, as indicated at 333 for the side walls 324. It is to be noted that the elongated slots provided in the side walls 322 and 324 permit limited variations in the spacing between the lower hinge assembly 260 and the upper latching assembly 250 in a particular application. It is also to be noted that any upward pushing of the actuating lever 320 by the counterclockwise movement of the fuse unit 100 will be against the downward bias exerted on the actuating lever 320 by the coil springs 334 and 335. As the fuse unit 100 is rotated further in a counterclockwise direction to the position shown in FIG. 1, the axially projecting portion 263 will be rotated past the latch roller 362 on the latch member 330 which will then drop down in front of the axially projecting portion 263, as shown in FIG. 1, to releasably retain the fuse unit 100 in the closed position shown in FIG. 1. It is to be noted that the force exerted on the latch roller 362 on the latch member 330 by the axially projecting portion 263 on the upper terminal 34 of the fuse unit 100 is substantially in line with the axis of rotation of the latch roller 362 to minimize or eliminate any tendency for the latch member 330 to move with respect to the fuse unit 100 because of the force exerted on the fuse unit 100 by the actuating lever 320 under the influence of the biasing springs 334 and 335.

In order to assist in limiting the counterclockwise rotation of the fuse unit 100 into engagement with the upper line contact 252 and to additionally bias the initial movement of the fuse unit 100 when released, a stop spring member 308 is disposed inside the housing 310 and secured to the upper insulator support 272 by suitable means, such as the bolts 307. The spring member 308 is generally U-shaped in configuration and is disposed to augment the biasing action of the coil springs 334 and 335 in initiating the dropout movement of the fuse unit 100. The stop member 306 which is angle-shaped in configuration is disposed in back of the spring member 308 and is secured to the upper insulator support 272 by suitable means, such as the bolts 305, to limit the clockwise movement of the actuating lever 320 and to prevent over travel of the fuse unit 100 which might otherwise produce a permanent set in the upper line contact 252 as the line contact 252 deflects under the influence of the force exerted on it during a closing movement of the fuse unit 100.

The automatic operation of the fuse structure upon the fusion or blowing of the fusible means which normally forms part of the fuse unit 100 will now be described. Upon the operation of the fusible means which forms part of the fuse unit 100 which, as disclosed in detail in the copending applications previously mentioned, the axially movable member 262 will be actuated in an upward direction, as viewed in FIG. 1, following an interruption of the are which normally results inside the fuse holder 32 to thereby bear against the bottom of the latch member 330 and to actuate the latch member 330 in a counterclockwise direction about the pivot pin 372 to thereby release the axially projecting portion 263 at the upper end of the fuse unit 100. The actuating lever 320 will then be released to apply an actuating force to the upper end of the fuse unit 100 under the influence of the biasing springs 334 and 335 and the spring member 308 to thereby actuate the upper end of the fuse unit 100 in a clockwise direction about the lower hinge assembly 260. The clockwise movement of the fuse unit 100 after it is actuated in a clockwise direction by the latching assembly 250 will continue under the force of gravity until the fuse unit 100 reaches an open position which may be displaced from the position of the fuse unit as shown in FIG. 1 by an angle of substantially 180. The jet forces which result during the operation of the fuse unit 100 will normally tend to move the fuse unit 100 in an upward direction, as viewed in FIG. 1. The projecting portions 42 on the lower terminal 36 of the fuse unit 100 will then bear against the guide portions 106 and 108 of the hinge member 110 to prevent the fuse unit 100 from accidentally falling out of assembled relationship with the hinge assembly 260 and the latching assembly 250 at the upper end of the fuse unit 100. As the fuse unit 100 moves in a clockwise direction during its dropout movement from the position shown in FIG. 1, the projecting portions 42 on the lower terminal 36 of the fuse unit 100 will guide the movement of the fuse unit 100 during the initial portion of its rotational travel, While the sector-shaped portions 46 on the lower terminal 36 of the fuse unit 100 will guide an additional portion of the rotational travel of the fuse unit to its dropout position while insuring that the fuse unit 100 remains in assembled relationship with the hinge assembly 260.

In order to manually release the latching assembly 250, when the fuse unit 100 is in the closed position shown in FIG. 1, a conventional hook-stick may be inserted in the hook eye 274 to rotate the hook eye 274 in a clockwise direction, as viewed in FIG. 1. The actuating portion 274A of the hook eye 274 will then similarly actuate the latch member 330 in a counterclockwise direction to release the axially projecting portion 263 at the upper end of the fuse unit 100 which will then be actuated by the actuating lever 320 under the influence of the coil springs 334 and 335 and the spring member 308 to a dropout position as just described.

It is to be understood that in certain applications the snub pins 112 and 114 may be omitted and a cross pin 158 may be added as shown in FIG. 1 to limit the rotation of the fuse unit 100 to a position which is approximately 45 above a horizontal line through the trunnions 44 of the fuse unit 100.

The apparatus embodying the teachings of this invention has several advantages. For example, the arrangement of the electrical contacts substantially eliminates the electrical current carrying characteristics required in the mechanical operating parts as disclosed which might otherwise result in less mechanical strength or terminal stressing of such parts. In addition, the arrangement of the movable contacts which correspond to the upper and lower terminals 34 and 36, respectively, on the fuse unit 100 when the associated relatively stationary contacts 252 and 150, respectively, substantially minimizes the forces which are required for either manual or automatic opening and closing movements of the fuse unit 100 as described. In addition, the latching contact assembly 250 is more compact in construction than known means provided for the same purpose. It is to be noted that the actuating lever 320 is at least partially disposed between the opposing con-tact arms of the upper line contact 252. Finally the forces required for the operation of the fuse structure 10 are minimized by the use of the latch roller 362 on the latch member 330 and by the use of the roller 352 on the actuating lever 320 as disclosed. A final advantage of the disclosed fuse structure is that the means provided in the lower hinge assembly 260 insure that the fuse unit in the structure disclosed will remain in assembled relation with the lower hinge assembly 260 during opening and closing movements of the fuse unit 100 both during normal and abnormal operating conditions.

In some applications, it is desirable that the fuse structure be of the nondropout type, but that the fuse unit can be manually actuated to a disconnect position by the use of a hook-stick. The disclosed fuse structure 10 can be readily modified for nondropout operation. In a such modified structure the hinge assembly 260 would be the same as shown in FIGS. 1 and 2. The upper contact and latching assembly would be modified to include only the upper sctationary contact 252, the stop member 306 and a simple spring latching member which would be provided to hold the upper end of the fuse unit 100 in a latched position.

Since numerous changes may be made in the abovedescribed apparatus and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all the matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illu trative and not in a limiting sense.

We claim as our invention:

1. A dropout fuse structure comprising an elongated fuse holder having fusible means therein connected between spaced terminals on the holder; a line contact; means for pivotally mounting the holder for movement of one terminal thereof into and out of engagement with said line contact between corresponding closed and open positions of the holder; means for releasably maintaining said one terminal in engagement with the line contact, comprising a generally L-shaped actuating lever pivotally mounted adjacent the line contact for rotation about an axis which is generally transverse to the axis of the holder in the closed position, a first roller pivotally mounted on said lever adjacent one end thereof to bear against the holder in the closed position, a latch member pivotally mounted on the actuating lever for limited rotation about an axis which is generally parallel to the axis of rotation of the actuating lever, a second roller pivotally mounted on the latch member to engage the holder in the closed position, first spring means for biasing the actuating lever to apply a force to the holder to cause the holder to move toward the open position, second spring means for biasing the latch member toward the holder whereby the second roller engages the holder and maintains the holder in the closed position, and an axially movable member disposed in the holder adjacent said one terminal to project axially from one end of the holder upon fusion of the fusion means to engage and release said latch member to thereby permit the actuating lever under the influence of the first spring means to move the holder to the open position.

2. The combination as claimed in claim 1 wherein the line contact includes two spaced contact arms disposed generally transversely to the axis of the holder in the closed position to engage said one terminal at portions of the terminal spaced around its periphery.

3. The combination as claimed in claim 2 wherein the first roller on the actuating lever is disposed between the contact arms of the line contact in the closed position of the holder.

4. The combination as claimed in claim 1 wherein said one terminal of the holder includes a latch engaging portion which projects axially away from one end of the holder adjacent to said line contact to engage the second roller on the latch member in the closed position of the holder.

5. The combination as claimed in claim 1 wherein an enclosing hood is provided around the line contact, the actuating lever is pivotally supported on a pivot pin disposed inside the hood and the first spring means comprises a pair of coil springs disposed inside the hood on the pivot pin on opposite sides of the actuating lever between the actuating lever and the hood.

6. The combination as claimed in claim 1 wherein the actuating lever includes a pair of spaced side wall portions and the latch member is pivotally supported on a pin which extends laterally between and is supported by the side wall portions of the actuating lever.

7. The combination as claimed in claim 1 wherein the actuating lever includes integral portions which meet generally at a right angle with respect to each other and the latch member is pivotally supported adjacent to one end thereof on the actuating lever adjacent to where the different portions of the actuating lever meet.

References Cited UNITED STATES PATENTS 2,328,818 9/1943 Lindell et al 337-176 2,750,469 6/1956 Baker 337l78 X 3,002,070 9/1961 Bronikowski et al. 337--177 3,138,681 6/1964 Fink et al. 337--17l X BERNARD A. GILHEANY, Primary Examiner.

H. B. GILSON, Assistant Examiner.

US. Cl. X .R. 337- 177

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