US3041426A - Circuit interrupter - Google Patents

Description

June 26, 1962 c. H. BAKER 3,041,426

CIRCUIT INTERRUPTER Filed Dec. 1. 1960 2 Sheets-Sheet 1 Q3 5/ INVENTOR. 22/23 B C/2045515. Bake/7 Wm WM United States Patent M 3,041,426 CIRCUIT INTERRUPTER Charles H. Baker, Arlington Heights, 111., assignor to S & C Electric Company, Chicago, 111., a corporation of Delaware Filed Dec. 1, 1960, Ser. No. 72,934 Claims. (Cl. 200--114) This invention relates, generally, to circuit interrupters and it has particular relation to drop out fuse cutouts of the kind and character shown in U.S. Patent Nos. 2,745,921 and 2,816,979 issued, respectively, May 15, 1956, and December 17, 1957, and arranged to be manually manipulated by a loadbreak tool such as that shown in US. Patent No. 2,816,981, issued December 17, 1957.

In the expulsion type cutout, such as shown in U.S. Patent No. 2,745,921, issued May 15, 1956, as the magnitude of the current interrupted increases, the upward thrust on the fuse tube increases. One limitation in the maximum current which can be interrupted successfully by the cutout is the strength of the fittings which support the cutout. If the upward thrust becomes too great, the supporting fittings may be forced out of their original shape and make the device unsuitable for further use. This is particularly true when the fusible section, where the arc is drawn, is located at the upper end of the fuse tube and remote from the lower open end.

'One arrangement for reducing this upward thrust in a cutout of the expulsion type is described in U.S. Patent No. 2,816,979, issued December 17, 1957. This involveslocating the fusible section in spaced relation to the upper end of the fuse tube and nearer to the lower open end by employing a conductor, preferably in the form of a rod, which extends into the fuse tube from the top and thus serves as the upper terminal of the fuse link at a point intermediate the ends of the fuse tube rather than at the extreme upper end. By so positioning the fusible section nearer to the lower open end, the energy released for any given value of fault current was reduced with a corresponding reduction in the upward thrust applied to the fuse tu-be tending to distort the fittings. However, as the fault current to be interrupted exceeds a predetermined relatively high value, even the arc shortening means provided by the rod-like conductor may not limit the energy incident to circuit interruption to such an extent that the support fittings are not distorted.

Accordingly, among the objects of this invention are: To counteract in a new and improved manner the upward thrust on the fuse tube when it is required to interrupt relatively high fault current by applying a downward thrust the magnitude of which is a function of the magnitude of the fault current; to close the upper end of the fuse tube with a cap capable of resisting the upward thrust and holding the conductor or rod in place when the fuse blows; to provide an auxiliary exhaust passageway at the upper end of the fuse tube and to close it by a rupturable member arranged to vent the exhaust passageway when the fault current exceeds a predetermined value; to maintain the relative positions of the upper line contact and the pull ring on the upper fuse tube terminal while providing the auxiliary exhaust passageway; to position the exhaust passageway at an angle to the bore of the fuse tube and in communication therewith in order to develop a downward component of thrust on the fuse tube and to direct the discharge away from the upper line terminal and away from the operator undertaking to close the fuse on a fault; and to locate the exhaust passageway in a branch of the upper fuse tube terminal in such position that it does not interfere with the operation of a load-break tool employed to open the fuse.

3,041,426 Patented June 26, 1962 Other objects of this invention will, in part, be obvious and in part appear hereinafter.

In the drawings:

FIG. 1 is a perspective view of a drop out fuse cutout in which the present invention is embodied.

FIGS. 2A and 2B, taken together, with the former placed above the latter, show a longitudinal cross sec tional view of the fuse tube and fuse tube terminals forming a part of the fuse cutout illustrated in FIG. 1.

FIG. 3 is a view, similar to FIG. 2A, and showing a modified arrangement.

Referring now particularly to FIG. 1 of the drawings, it will be observed that the reference character 9 designates a support bracket which constitutes one of a pair of brackets that is employed for mounting devices on a cross arm carried at the upper end of a pole that is employed for supporting an electrical transmission line. The support bracket 9 is arranged to carry an insulator mount ing as indicated, generally, at 10 which may be of the type shown in U.S. Patent No. 2,606,954, issued August 12, 1952. It will be understood, however, that other insulator mountings can be employed in practicing the present invention. The insulator mounting 10 includes a rearwardly extending support arm 11 which is, secured, as shown, to the lower forwardly extending portion of the support bracket 9 and an insulator 12. Upper and lower metallic terminal supports 13 and 14 are provided, as shown, at the upper and lower ends of the insulator 12. The metallic terminal supports 13 and 14 extend forwardly of the insulator 12 which, preferably, is formed of porcelain. These terminal supports carry, respectively, upper and lower line terminal members 15 and 16 and a fuse tube that is indicated, generally, at 17. In accordance with conventional practice the fuse tube 17 is removable and is arranged to drop out upon the occurrence of an overload suflicient to cause the fuse link therein to blow. At its lower end the fuse tube 17 is provided with a lower fuse terminal assembly, shown generally at 18, that is pivotally and slidably mounted on the lower line terminal member 16. At its upper end the :fuse tube 17 has an upper fuse terminal assembly, shown generally at 19, which cooperates with the upper line terminal member 15.

The lower line terminal member 16 comprises a hinge casting, shown generally 'at 22, that is formed of suitable good conducting metal, such as brass, and has an inverted' U-shape. It is secured by a bolt 23 to the terminal support 14 at the lower end of the insulator 12. A split bolt connector 24 extends rearwardly from the hinge casting 22 and serves to receive a line conductor. At the opposite end of the hinge casting 22, slots 25 are provided in the opposite sides 22 for slida-bly and pivotally receiving trunnions 26 that extend from opposite sides of a toggle member 27 through which a shaft 28 extends. The toggle member 27 is preferably formed of a brass casting and a more detailed description of its construction and operation is set forth in US. Patent No. 2,553,098, issued May 15, 1951. The toggle member 27 is pivotally secured by a hinge pin 29 to arms 30 that extend rearwardly from a lower brass ferrule 31 which forms a part of the lower fuse tube terminal assembly 18.

As shown more clearly in FIG. 2B of the drawings, a flipper 34 is rocka-bly mounted on the shaft 28. As described in US. Patent No. 2,553,098, issued May 15, 1951, the flipper 34, biased by a spring, is arranged to withdraw the flexible lead of a fuse link from the fuse tube 17 and also is arranged to keep the toggle linkage, of which the toggle member 27 forms a part, in the operative position until the fuse link blows. For this latter purpose the flipper 34 has a shoulder 35 which is arranged to engage a shoulder 36 on a detent 37 that extends rearwardly from the lower ferrule 31.

Within the fuse tube 17, as shown in FIGS. 2A and 213, there is provided a fuse link 38 of conventional construction which has a flexible lead 39 extending therefrom and out of the lower end of the fuse tube 17. It will be observed that the lower end of the flexible lead 39 extends over the flipper 34 and, as long as the fuse link 38 remains intact, it serves to hold the flipper 34 in the position where the shoulder 35 engages the shoul der 36. The extreme lower end of the flexible lead 39 extends around a stud 40 and is clamped securely thereto by a clamp nut 41.

The toggle member 27 has an eye portion 42 that is arranged to receive a prong of a switch stick. The purpose of this is to facilitate the handling of the fuse tube 17 for removing it from the mounting and replacing the same.

As illustrated in FIG. 2A the upper fuse terminal assembly 19 includes a ferrule 43, preferably formed of brass, which has an extension 44 at its upper end that provides a passageway 45 which constitutes an extension of the bore or passageway 46 in the fuse tube 17. The upper end of the extension 44, which is integral with the ferrule 43, is closed by a threaded cap 47 which may be formed integrally with a stud or rod-like conductor 48. Instead of forming the stud or rod-like conductor 48 integrally with the threaded cap 47, it may be formed separately as described in U.S. Patent No. 2,816,979, issued December 17, 1957. If desired, the stud or rodlike conductor 48 can be extended to position its lower end well below the lower end of the ferrule 43 for voltage stress distribution purposes. As set forth in this patent, the stud or rod-like conductor 48 is provided for receiving a threaded portion 49 of a fuse link terminal 50 located at the upper end of the fuse link 38 for the purpose of locating the fusible section 38 nearer to the lower open end of the fuse tube 17 with the result that the energy incident to blowing of the fuse link 38 is reduced and thus there is a corresponding reduction in the upward thrust applied to the fuse tube 17. It will be understood that the threaded cap 47 is a reusable cap and that it is adapted to hold closed the passageway 45 under all operating conditions within the capability of the fuse tube 17 for handling fault currents. An eye portion 51 is formed integrally with the ferrule 43 for receiving the prong of a switch stick or one of the terminals of a loadbreak tool.

The threaded cap 47 has a convex head 52 that engages the underside of a seat 53 formed integrally in the lower arm of a U-shaped top contact 54 as shown in FIG. 1. A top contact strip 55 is connected by rivets 56 to the upper arm of the top contact 54. At its rear end the contact strip 55 is positioned underneath a leg of an I-shaped terminal pad 58 which carries a split bolt connector 59 for receiving the other line conductor. A bolt 60 extends through the terminal support 13 together with the contact strip 55 to hold these elements securely in position.

With a view to providing a relatively stiff spring for resisting the upward thrust of the fuse tube 17, there is provided a recoil bar 63 that is clamped by the bolt 60 to the terminal support 13. The recoil bar 63 extends forwardly in cantilever fashion over the upper end of the fuse tube 17. Preferably the recoil bar 63 is formed of magnetic material such as cold rolled steel. Near the outer end of the recoil bar 63 there is a tapped opening for receiving a hollow threaded bushing 64 as described in more detail in US. Patent No. 2,745,923, issued May 15, 1956. The bushing 64 is screwed into the recoil bar 63 and a portion projects above it for receiving a lock nut 65. It is desirable to interconnect the rearwardly extending arms of the U shaped top contact 54. For this purpose a contact stud 66 is employed. -It is formed of good conducting material, such as brass, and its upper end 67 extends through the upper arm of the top contact 54 and is headed over Within a suitable opening in the forward'end of the contact strip 55. A coil compression spring 71 reacts downwardly against the seat 53 and is disposed coaxially with the contact stud 66 which islocated to be coaxial with the vertical axis of the fuse tube 17. The upper end of the coil compression spring 71 extends around the lower end of the hollow bushing 64 and bears against the underside of the outer end of the recoil bar 63. The coil compression spring 71 is held in prestressed condition by the contact stud 66 and can be readily further stressed as compared to the recoil bar 63 so that the initial upward movement of the fuse tube 17 acts first to compress further the spring 71 without causing any substantial upward movement of the outer end of the recoil bar 63. When only relatively small fault current is required to be interrupted, only the coil compression spring 73 will be stressed to any appreciable extent.

An L-shaped reinforcing bar 72 is mounted on the underside of the recoil bar 63 and below the terminal support 13. The horizontal arm 73 of the reinforcing bar 72 extends underneath the terminal support 13 and is secured thereto by the bolt 60. The downwardly extending arm. 74 of the reinforcing bar 72 extends parallel to the vertical axis of the fuse tube 17 and is positioned rearwardly thereof between it and the insulator 12. Under certain conditions it is desired that there be conjoint movement of the reinforcing bar 72 and the re coil bar 63. For this purpose a pin 75 is employed.

At the lower end of the downwardly extending arm 74 there is provided a combination guideand anchor that is shown, generally, at 79. The combination guide and anchor 79 includes forwardly extending arms 80 at the outer ends of which are rearwardly curved arms 81. The forwardly extending arms 80 serve to guide the upper fuse terminal assembly 19 or the fuse tube 17 into proper position generally regardless of the direction from which force is applied to the eye portion 51 that is formed in tegrally with the ferrule 43 to swing the fuse tube 17 to the closed position so that the threaded cap 47 will reg ister with the seat 53. Preferably the combination guide and anchor 79 is formed of good conducting material, such as brass, since it may be called upon to conduct current when the fuse tube 17 is moved out of the circuit closed position while it is carrying load current as de scribed in more detail in US. Patent No. 2,816,981, issued December 17, 1957, by the use of the loadbreak tool described in this patent.

When the fuse link 38 is assembled in the fuse tube 17 as described hereinbefore with the flexible lead 39 overlying the flipper 34 and clamped to the toggle member 27 by the clamp nut 4-1, the shoulder 35 is held in engagement with the shoulder 36 and a rigid construction is provided that can be handled as a unit. The prong of a live line tool or switch stick is inserted in the eye 42 and the fuse tube 17 is lifted to position the trunnions 26 in the slots 25. When so manipulated, the fuse tube 17 hangs downwardly and the trunnions 26 occupy positions at the bottoms of the slots 25. Then the prong of the live line tool or switch stick is inserted in the eye portion 51 and the fuse tube 17 is swung upwardly to the position shown in FIG. 1 which is the closed position.

When it is desired to move the fuse tube 17 to the open position while it is carrying load current, a loadbreak tool, constructed as described in US. Patent No. 2,816,- 981, issued December 17, 1957, can be used. One terminal of the loadbreak tool is caused to engage one or the other of the rearwardly curved arms 81 of the combination guide and anchor 79 while another terminal of the loadbreak tool engages the eye portion 51, Then the loadbreak tool is operated to separate the upper fuse terminal assembly 19 from the upper line terminal member 15 and to shunt the load current through the loadbreak tool. On subsequent manipulation of the loadbreak tool, this current flow is interrupted within the tool and without external arcing. Thereafter, the terminals of the loadbreak too are detached from the combination guide and r anchor 79 and from the eye portion 51 leaving the fuse tube 17 in the open pendant position.

It was pointed out hereinbefore that the use of the stud or rod-like conductor 48 serves to position the fuse link 38 at a location relatively closer to the open lower end of the fuse tube 17 than if it were placed at the extreme upper end. Because of this positioning of the fuse link, the energy released on blowing of the fuse link 38 is reduced and there is a corresponding reduction in the upward thrust applied to the fuse tube 17. However, as the fuse cutouts of this type are called upon to interrupt higher and higher fault currents, it has been found that, even when the rod-like conductor 48 is employed, still the upward thrust on the fuse tube 17 may be such that on interruption of exceedingly high fault currents the upper and lower fuse terminal members 15 and 16 are deformed along with deformation of the upper terminal member 15.

In accordance with this invention provision is made for counteracting this upward thrust by providing a downward thrust which is a function of the magnitude of the fault current. For this purpose a branch 82 is formed integrally with the upper fuse terminal assembly 19 and it has an exhaust passageway 93 extending therethrough at an angle to the passageway 45 and bore or passageway 46 in the fuse tube 17. In the arrangement shown, the angle of inclination is 45. The outer end of the branch 82 is threaded for receiving a threaded expendable cap 84 which is provided with an annular slot 85 thereby forming a weakened central section 86 that is arranged to be blown out when it is subjected to predetermined pressure.

In operation, when the fuse link 38 blows under relatively low fault current conditions, only the coil compression spring 71 is stressed sufficiently to permit the fuse tube 17 to move upwardly, n the interruption of a still higher fault current, the thrust on the fuse tube may be such as to further stress the recoil bar 63 and move it upwardly. Under these assumed conditions the fuse tube 17 is vented only at its lower end. However, should the device be subjected to an extremely heavy fault current that otherwise would cause the fuse tube 17 to move upwardly through an extent likely to damage the lower and upper fuse terminal assemblies 18 and 19 and the upper terminal member 15, the pressure under these circumstances within the upper fuse terminal assembly 19 is sufficient to rupture the expendable cap 84 and blow out the central section 86. The fuse tube 17 is vented at the upper end at an angle to the vertical axis with the result that there is a downward component of force developed which acts in a direction opposite to the upward thrust applied to the fuse tube 17. The fuse tube 17 is not moved upwardly as far as it otherwise might be. Within the capabilities of the device to interrupt fault current the upward movement of the fuse tube 17 is reduced together with the likelihood of damage to the terminal fittings.

It will be observed that the branch 82 providing the exhaust passageway 83 is directed outwardly and upwardly away from the upper terminal member This directs the products of the arc blast away from the upper terminal member 15 and also away from the operator located on the ground should he close the fuse tube 17 on a fault of a magnitude suflicient to rupture the expendable cap 84.

In some instances it may be desirable to locate the fuse link 38 at the extreme upper end of the fuse tube 17. Such an arrangement is illustrated in FIG. 3 where a removable button head 90 is threaded onto the threaded portion 49 of the fuse link terminal 50, Here the threaded cap 47 serves only to clamp the button head 90 in place on the upper end of the extension 44 of the upper fuse terminal assembly 19 and to hold closed the passageway 45 under all fault currents within the capabilities of the device to interrupt,

What is claimed as new is:

1. In a device for interrupting a high voltage electric 6 power circuit on flow therein of relatively small or relatively great fault current, in combination, a fuse tube open at one end, a terminal closing the other end of said fuse tube and capable of maintaining it closed on in terruption of fault current within the range of capability of the device, said terminal including a rod-like conductor extending therefrom along the axis of said fuse tube toward said open end and adapted to receive at its inner end one terminal of a replaceable fuse link the other terminal of which extends out of said open end of said fuse tube, means providing an exhaust passageway transverse to and communicating at its inner end with the opening through said fuse tube at said other end and intermediate the ends of said rod-like conductor, and rupturable means closing off the outer end of said exhaust passageway and capable of withstanding the pressure generated within said fuse tube on blowing of the fuse link to interrupt the flow of relatively small fault current and adapted to rupture and vent said fuse tube at said other end on blowing of the fuse link to interrupt the flow of relatively great fault current.

2. In a fuse construction, in combination, a pair of line terminals in insulated spaced relation, a fuse tube having a fuse terminal at one end and open at the other end, said fuse terminal being normally connected to one of said line terminals, a conductor extending through said fuse tube; said conductor including in series a rodlike section connected to said fuse terminal, a fusible section, and a flexible section connected to the other line terminal; a metallic cap threaded on said fuse terminal to hold said rod-like section in circuit therewith and close said one end of said fuse tube, the connection of said fuse terminal to said one 'line terminal being through said metallic cap, said fuse terminal having an exhaust passageway communicating at its inner end with the opening through said fuse tube and having the outer end opening in a direction away from said metallic cap and said one line terminal, and rupturable means closing off said exhaust passageway whereby said fuse tube is vented at said one end thereof when a predetermined pressure is generated therein on blowing of said fusible section.

3. A device for interrupting a high voltage electric power circuit on flow therein of relatively small or relatively great fault current comprising, in combination, insulator means, upper and lower line terminals etxending laterally from said insulator means, a fuse tube open at its lower .end, upper and lower fuse terminals on said fuse tube engaging said upper and lower line terminals respectively, said upper fuse terminal closing the upper end of said fuse tube and capable of maintaining it closed on interruption of fault current within the range of capability of the device, conductor means including a fusible section interconnecting said fuse terminals and adapted on flow of fault current to generate substantial pressure acting against said upper fuse terminal to move said fuse tube upwardly with a force that increases with the magnitude of the fault current, branch means on said upper fuse terminal providing an exhaust passageway inclined upwardly to and communicating at its inner end with the opening through said fuse tube at its upper end and directed away from said upper line terminal, and rupturable means closing off said exhaust passageway and capable of withstanding the pressure generated within said fuse tube on blowing of said fusible section to interrupt the flow of relatively small fault current and adapted to rupture and vent said fuse tube at its upper end on blowing of said fusible section to interrupt the flow of relatively great fault current and cause the application of a force component to said fuse tube acting in a direction opposite to said force that moves said fuse tube upwardly.

4. A device for interrupting a high voltage electric power circuit on flow therein of relatively small or relatively great fault current comprising, in combination, insulator means, upper and lower line terminals extending laterally from said insulator means, a fuse tube open at its lower end, upper and lower line terminals respectively, said upper fuse terminal including a reusable cap closing the upper end of said fuse tube and capable of maintaining it closed on interruption of fault current Within the range of capability of the device, conductor means including a fusible section interconnecting said fuse terminals and adapted on flow of fault current to generate substantial pressure acting against said upper fuse terminal to move said fuse tube upwardly with a force that increases with the magnitude of the fault current, said upper fuse terminal having an exhaust passageway inclined upwardly to and communicating at its inner end with the opening through said fuse tube and directed away from said upper line terminal, and an expendable cap threaded on said upper fuse terminal and closing off said exhaust passageway, said expendable cap having a frangible portion capable of withstanding the pressure generated within said fuse tube on blowing of said fusible section to interrupt the flow of relatively small fault current and adapted to rupture and vent said fuse tube at its upper end on blowing of said fusible section to interrupt the flow of relatively great fault current and cause the application of a force component to said fuse tube acting in a direction opposite to said force that moves said fuse tube upwardly.

5. A device for interrupting a high voltage electric power circuit on flow therein of relatively small or relatively great fault current comprising, in combination, insulator means, upper and lower line terminals extending laterally from said insulator means, a fuse tube open at its lower end, upper and lower fuse terminals on said fuse tube engaging said upper and lower line terminals respectively, said upper fuse terminal including a reusable cap closing the upper end of said fuse tube and capable of maintaining it closed on interruption of fault current within the range of capability of the device, conducting means extending through said fuse tube; said conductor means including in series a rod-like section connected to said upper fuse terminal and held in position by said reusable cap, a fusible section, and a flexible section connected to said lower fuse terminal; said fusible section being adapted on flow of fault current to generate substantial pressure acting against said upper fuse terminal to move said fuse tube upwardly with a force that increases the magnitude of the fault current, means providing an exhaust passageway inclined upwardly to and communicating at its inner end with the opening through said fuse tube and directed away from said upper line terminal and said reusable cap, and an expendable cap threaded on said upper fuse terminal and closing off said exhaust passageway, said expendable cap having a fran- References Cited in the fileof this patent UNITED STATES PATENTS 2,109,090 Pittman et al Feb. 22, 1938 2,721,242 Curtis et al. Oct. 18, 1955 2,798,133 Curtis July 2 1957 2,816,979 Lindell Dec. 17, 1957 2,846,544 Wood Aug. 5, 1958

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