US3184568A

US3184568A - Circuit interrupter embodying 2, 4 dichloro benzoic acid or 3, 4 dichloro benzoic aci

Info

Publication number: US3184568A
Application number: US227335A
Authority: US
Inventors: Harold H Fahnoe
Original assignee: S&C Electric Co
Current assignee: S&C Electric Co
Priority date: 1962-10-01
Filing date: 1962-10-01
Publication date: 1965-05-18
Anticipated expiration: 1982-05-18

Description

H. H. FAHNOE 3,184,568

2 Shets-Sheet 1 D7//////////Hfll/Y//////Y///ZI/IZIAV/l/l/JA ASH,

INVENTOR. HAROLD H. FAHNOE MOVEMENT OF LOWER END OF ROD LIKE TERMINAL ditty.

May 18, 1965 CIRCUIT INTERRUPTER EMBODYING 2,4 DICHLORO BENZOIC v ACID OR 3,4 DIGHLORO BENZOIC ACID Filed 001:. l, 1962 v y 1965 H. H. FAHNOE 1 3,184,568

CIRCUIT INTERRUPTER EMBODYING 2 ICHL BENZOIC ACID on 3,4 are HLORO BE IS A Filed Oct. 1, 1962 2 SheetsSheet 2 ADHESIVE WRAPPER DICHLOR BENZOIC ACID OR A MIXTURE THEREOF.

BORIC ACID United States Patent CIRCUIT INTERRUPTER EMBODYTNG 2,4 Dl- CHLORO BENZUIC A811) @R 3,4 DEQHLQRG BENZUIQ ACID Harold H. Fahnoe, Evanston, 111., assignor to S. 81 C. Electric Company, Chicago, Tlh, a corporation of Delaware Filed Oct. 1, 1962, Ser. No. 227,325 11 Claims. (Cl. 260-420) This invention relates, generally, to circuit interrupters and it has particular relation to are extinguishing means in circuit interrupters for use on alternating current transmission circuits operating at voltages of the order of 34.5 kv. and above.

It is conventional to draw an arc in a bore formed in a stack of cakes of boric acid from which an arc extinguishing medium in a vapor or gaseous form is evolved that assists in extinguishing the arc. There is an optimum relation between the diameter of the bore and the current flow that can be interrupted efiiciently therein at a given voltage while leaving the surface of the bore after arc extinction capable of withstanding the open circuit and transient voltages that may be applied so that the arc will not restrike. The larger the diameter of the bore the greater will be the ability of the circuit interrupter to interrupt current flow and extinguish the arc incident thereto. However, when the device is required to interrupt a substantially smaller current flow in the same material and the same bore, the operation is much less efiicient.

Accordingly, among the objects of this invention are: To improve the operating characteristics of a circuit interrupter of the solid material type provided with a bore in which the arc is drawn and extinguished, particularly for the lower current ranges while utilizing its inherent elliciency for the interruption of current flows in the higher current ranges; to form a continuation of the high current interrupting bore in solid arc extinguishing material at the same diameter which continuation inherently is capable of assisting in the efficient interruption of relatively low current flow and is much less efiicient in assisting in the interruption of the relatively high current flow; to form the arc extinguishing materials into stacks of apertured cakes in endwise relation and to cement them in place inside a tubular insulating housing with the apertures in the cakes forming a bore through which a rod like terminal moves to draw the arc therein; and to pre vent the cement from having direct contact with the stack of cakes of arc extinguishing material that are adapted particularly for the eflicient interruption of relatively low current flows or the flow of relatively low fault currents.

' In the drawings:

FIGS. 1A, 1B and 1C placed one above the other in the order named show a circuit interrupter of the solid material fuse type in which this invention is embodied, the construction being a vertical longitudinal sectional view of such a fuse.

FIG. 2 is a vertical sectional view, at an enlarged scale, of a sub-assembly for the arc extinguishing material that is capable inherently of assisting in the extinction of relatively low current arcs.

FIG. 3 is a horizontal sectional view, at an enlarged scale, taken generally along the line 22 of FIG. 1B.

Referring now particularly to FIGS. 1A, 1B and of the drawings, it will be observed that the reference character 11} designates, generally, a circuit interrupter of the solid material type that is intended to be pivotally mounted at its lower end and to be latched at its upper end. The circuit interrupter 10 can be employed in a dropout fuse mounting constructed as shown in US. Patout No. 2,578,255, issued December 11, 1951, to S. l.

3,184,568 Patented May 18, 1965 Lindell. Also it can be employed in the dropout fuse construction shown in US. Patent No. 2,651,695, issued September 8, 1953, to C. H. Baker. It can be employed without the dropout features in a non-dropout solid material type of fuse construction such as shown in US. Patent No. 2,961,514, issued November 22, 1960, to S. I. Lindell. More specifically it can be employed in the dropout fuse construction shown in copending application Serial No. 232,845 filed October 24, 1962 in the name of Henry J. Barta and assigned to the assignee of this application.

The circuit interrupter 1d includes a tubular housing 11 of insulating mateiral that is weatherproof and has substantial strength. For example, the tubular housing 11 can be formed of a phenolic condensation product or like material. At its upper end it is provided with an upper tubular terminal 12 which is telescoped inside of the upper end. At its lower end the tubular housing 11 has a lower terminal 13 in the form of a ferrule telescoped over the outer surface thereof.

The upper end 14 of the tubular terminal 12 is inwardly flanged to overlie a washer 15 having a central opening 16 through which a latch trip pin 17 can project for tripping the latch mechanism of the fuse mounting to release the circuit interrupter 1t and permit it to swing downwardly in conventional manner for providing an air gap in the circuit.

The latch trip pin 17 constitutes an upward extension from a rod like terminal 18 which is provided at its upper end with a rod end fitting 19 having a downwardly facing shoulder 20 against which the upper end of a coil compression spring 21 reacts. The lower end of the coil compression spring 21 bears against an inclined shoulder 22 that is located near the lower end 23 of the tubular terminal 12. It is secured by rivets 24 to the lower end of a contact sleeve 25. The contact sleeve 25 includes upwardly extending contact fingers 26 which are urged inwardly by a garter spring 27 into contact engagement with a contact section 23 of the rod like terminal 18. it will be understood that this construction provides a simple and efficient means for making a low resistance connection between the tubular terminal 12 and the rod like terminal 13. When the rod like terminal is released for upward movement under the influence of the coil compression spring 21, the circuit is completed from the contact fingers 26 to the smaller diameter portion of the rod like terminal 18 below the contact section 28 for the short time during which the rod like terminal 18 moves upwardly to effect circuit interruption.

The rod like terminal 18 is restrained from upward movement under the influence of the coil compression spring 21 by a fusible element that is indicated, generally, at 31. The fusible element 31 is connected to a terminal rod 32 which is stationarily mounted at the lower end of the tubular housing 18. The fusible element 31 preferably includes a fuse wire 33, that may be formed of silver, and a strain wire 34 that may be formed of nickel chromium alloy wire. The fuse and strain wires 33 and 3d are suitably secured in the respective end of the rod like terminal 13 and the terminal rod 32 by deformation of the latter onto the former. The terminal rod 32 extends through and is anchored to a transversely disposed bridge 35 by nuts Bid-36. The bridge 35 is mounted on an inner metallic sleeve 37 which extends upwardly through the lower end of the tubular housing 11 with its lower end 38 being secured by rivets 39 to the lower end of the lower terminal 13. The exhaust lower end of the tubular housing 11 is closed by a disc 4-0 of suitable insulating material which can be readily ruptured or blown out as the result of pressure generated in the inner metallic sleeve or exhaust tube 37 occasioned by the blowing of the fusible element 31.

The rod like terminal 18 extends downwardly from the contact section 28 through a cup shaped end washer 43 and through a bore 44 that is formed by the apertures in a stack of cakes of arc extinguishing material to be described.

The upper end of the bore 44 extends through a subassembly that is indicated, generally, at 45 and is shown in detail in FIG. 2. As here shown, the sub-assembly 45 includes an upper end cake 46 f boric acid. Below the upper end cake 46 of boric acid there is a stack of cakes 47 that are formed of 2,4-dichloro benzoic acid or 3,4-dichloro benzoic acid or a mixture of equal parts of these materials. The extinguishing ability of that portion of the bore 44 extending through the cakes 4'7 is exceptionally eflicient for assisting in interrupting relatively low current arcs but, due to the deposition of carbon over the surface of the bore 44 after arc extinction, they are not as efficient as boric acid for the interruption of high current arcs. At the lower end of the stack of cakes 47 there is a cake 48 of boric acid through which the bore 44 extends. The lower end cake 48 of boric acid and the upper end cake 46 provide terminal sections for the sub-assembly 45 with the cakes 47 of 2,4-dichloro benzoic acid or 3,4- dichloro benzoic acid or a mixture of equal parts thereof interposed therebetween with the bore 44 extending entirely therethrough for receipt of the rod like terminal 18. Overlying these cakes in stacked relation is an adhesive wrapper 49. It may be formed of suitable pressure sensitive insulating material which not only maintains the

cakes

46, 47 and 48 in the stacked relationship but also it prevents a self setting epoxy cement, to be described, from contacting the exterior surfaces of the cakes 47, a condition that is not conducive to the proper curing of the self setting epoxy cement.

As shown in FIGS. 13 and 10, the bore 44 continues through a stack of cakes 50 of boric acid that are located below the sub-assembly 45. The lowermost cake 50 is provided with a conical throat 51 into which the arc is first drawn on blowing of the fusible element 31. Below the lowermost cake 50 is a fiber plug 52 that defines an arcing chamber 53 in which the principal portion of the fusible element 31 is positioned and in which the are initially is drawn.

The assembly of the sub-assembly 45 and the cakes 50 of boric acid in the tubular housing 11 is carried out generally in accordance with the teaching of U.S. Patent No. 2,961,514, issued November 22, 1960, to S. I. Lindell. The assembly as shown in FIGS. 1A, 1B and 1C is made without application of the lower terminal 13 and with the rod like terminal 18, coil compression spring 21, fusible element 31 and terminal rod 32 omitted. The arrangement is such, as shown here, that a slight space is provided between the several parts and the inner surface of the tubular housing 11. This space is filled with a self setting cement which is indicated at 54 in FIG. 3. Preferably, as indicated in the patent last mentioned, the cement 54 is an epoxy resin. After the cement 54 has suitably cured, the remaining assembly is made of the various parts to complete the circuit interrupter 10.

In operation, upon blowing of the fusible element 31 as the result of the flow therethrough of a relatively high fault current, the rod like terminal 18 is released and it is moved upwardly under the influence of the coil compression spring 21. The are is drawn between the upper end of the terminal rod 32 and the retreating lower end of the rod like terminal 18 first in the arcing chamber 53 and then it is extended into the lower end of the bore 44 in the cakes 50 of boric acid. Here the large current arc is efficiently extinguished as the result of the evolution of an arc extinguishing medium in vapor form from the surface of the bore 44. Within the interrupting capability of the circuit interrupter 10, the large current are will be extinguished before the lower end of the rod like terminal 18 is moved past the uppermost cake 50 of boric acid. However, the construction is such that the lower end of the rod like terminal 18 can be moved to a final position that is indicated by broken line 55, FIG. 13, which extends through the upper cake 46 of boric acid at the upper end of the sub-assembly 45.

In the event that the current flow through the fusible element 31, while sufficient to cause it to blow, is of a relatively small magnitude, the arc tends to persist while the lower end of the rod like terminal 18 is being drawn entirely through that portion of the bore 44 in the cakes 50 of boric acid and is extended into that portion of the bore 44 that extends through the cakes 47 that are formed of 2,4-dichloro benzoic acid or 3,4-dichloro benzoic acid or a mixture of these materials. Here the relatively low current are is extinguished in the bore 44 which has the same diameter throughout the

several cakes

46, 47, 48 and 58 of arc extinguishing material.

As pointed out above, the circuit interrupter 10 employing the sub-assembly 45 is capable of interrupting relatively low fault currents as well as fault currents of much higher magnitude. To demonstrate this wide range of current interrupting ability 2. test was made using cakes of boric acid, such as the cakes 59, in a number such as to provide a length of nineteen inches. While this construction was capable of interrupting relatively high fault current, it was not capable of clearing fault currents of a mag nitude below amperes. For comparison purposes a comparable construction was made in which the subassembly 45 comprised

cakes

46 and 47 of boric acid each having a length of one inch and located at the ends of cakes 47 of 2,4-dichloro benzoic acid having a length of five inches in combination with cakes 50 of boric acid having a length of twelve inches, the total length being nineteen inches. The circuit interrupter 10, using this arrangement of arc extinguishing materials, readily cleared fault currents down to the minimum melting current of ten amperes of the smallest fusible element 31 that was used. In addition this arrangement was capable of clearing all higher values of fault current of the order of those cleared by the construction using boric acid cakes alone. In order that a proper comparison of operating characteristics could be made the tests just referred to were conducted under identical conditions of available recovery voltage and available rate of rise of recovery voltage at the time of fuse clearing.

What is claimed as new is:

1. An electric circuit interrupter comprising, in com bination:

(a) means between which an arc is formed on interruption of the circuit, and

(b) means adapted to confine and extinguish said are disposed along the path thereof from which an arc extinguishing medium can be evolved due to the heat of said are for extinguishing it, the last named means being selected from the class consisting of 2,4-dichloro benzoic acid and 3,4-dichloro benzoic acid.

2. The invention, as set forth in claim 1, wherein the arc confining and extinguishing means comprises a mixture of 2,4-dichloro benzoic acid and 3,4-dichloro benzoic acid.

3. A sub-assembly for use in a circuit interrupter, in combination,

(a) a stack of cakes of arc extinguishing material selected from the class consisting of 2,4dichloro benzoic acid and 3,4-dichloro benzoic acid having a bore extending therethrough,

(b) a cake of boric acid at each end of said stack having an opening therethrough to provide continuations of said bore, and

(c) an adhesive wrapper impervious to epoxy resin surrounding said cakes and holding them in endwise assembled relation.

4. An electric circuit interrupter comprising, in combination:

(a) a tubular housing providing a bore in which an arc is drawn and extinguished,

(b) means for drawing the are into said bore at one end,

(c) a first solid arc extinguishing material comprising boric acid in said housing defining said bore at said one end and characterized by being effective for the interruption of relatively high current arcs and substantially less effective for the interruption of rela tively low current arcs, and

(d) a second solid arc extinguishing material selected from the class consisting of 2,4-dichloro benzoic acid and 3,4-dichloro benzoic acid in said housing and defining a continuation of said bore and characterized by being effective for the interruption of relatively low current arcs and substantially less effective for the interruption of relatively high current arcs.

5. The invention, as set forth in claim 4, wherein the means for drawing the are into the bore is a rod like terminal that is shifted as a part of a continuous movement through the bore in the first solid arc extinguishing material and then through the bore in the second are extinguishing material.

6. The invention, as set forth in claim 5, wherein:

(a) the first solid arc extinguishing material comprises a stack of apertured cakes in spaced relation to the inner surface of the tubular housing,

(5) the second solid are extinguishing material cornprises a stack of apertured cakes in spaced relation to said inner surface of said tubular housing, and

(c) an adhesive means fills the space between said cakes and said inner surface of said tubular housing and secures them together as an integral unit.

7. The invention, as set forth in claim 6, wherein:

(a) the adhesive means is an epoxy resin, and

(b) a layer of insulating material impervious to epoxy resin overlies the stack of cakes forming the second solid arc extinguishing material and prevents direct contact therebetween.

8. The invention, as set forth in claim 6, wherein an apertured cake of the first solid are extinguishing material provides a continuation of the bore at the end remote from the end where the are is drawn and within which the are drawing end of the rod like terminal is located at the end of its movement.

9. An electric circuit interrupter comprising, in combination:

(a) a tubular housing providing a bore of substantially uniform diameter in which an arc is drawn and extinguished,

(b) means for drawing the arc into said bore at one end,

(c) a first solid arc extinguishing material in said housing defining one section of said bore at said one end and characterized by being particularly effective for the interruption of relatively high current arcs, and

(ci) a second solid arc extinguishing material in said housing different from said first solid arc extinguishing material and defining another section of said bore remote from said one end and having the same diameter as that of said one section thereof adjacent thereto and characterized by being exceptionally etficient for the interruption of relatively low current arcs and substantially less efficient for the interruption of relatively high current arcs.

10. An electric circuit interrupter comprising, in combination:

(b) means for drawing the are into said bore including a stationary terminal at one end thereof and a rod like terminal that is shifted as a part of a continuous movement through said bore and substantially filling the same,

(0) a first solid arc extinguishing material in said housing defining said bore at said one end and characterized by being particularly effective for the interruption of relatively high current arcs, and

(d) a second solid arc extinguishing material in said housing different from said first solid arc extinguishing material and defining a continuation of said bore of the same diameter and characterized by being exceptionally efiicient for the interruption of relatively low current arcs and substantially less efiicient for the interruption of relatively high current arcs.

11. An electric circuit interrupter comprising, in combination:

(c) a first solid arc extinguishing material in said housing defining said bore at said one end and characterized by being particularly eifective for the interruption of relatively high current arcs,

(d) a second solid arc extinguishing material in said housing different from said first solid arc extinguishing material and defining a continuation of said bore of the same diameter and characterized by being exceptionally efficient for the interruption of relatively low current arcs and substantially less efiicient for the interruption of relatively high current arcs, and

(e) a solid arc extinguishing material in said housing defining a continuation of said bore in said second solid are extinguishing material and formed of said first solid arc extinguishing material and within which the are drawing end of said rod like terminal is located at the end of its movement.

References Cited by the Examiner UNITED STATES PATENTS 2,531,007 11/50 Strom et a1. 200--l4-9 2,577,899 12/51 Linton 200135 2,752,458 6/56 Baker et a1 200- 2,913,49 11/59 Dazzi 252-63.2 2,976,381 3/61 Lindell 200-420 BERNARD A. GlLHl-EANY, Primary Examiner.

Claims

1. AN ELECTRIC CIRCUIT INTERRUPTER COMPRISING IN COM BINATION: (A) MEANS BETWEEN WHICH AN ARC IS FORMED ON INTERRUPTION OF THE CIRCUIT, AND (B) MEANS ADAPTED TO CONFINE AND EXTINGUISH SAID ARC DISPOSED ALONG THE PATH THEREOF FROM WHICH AN ARC EXTINGUISHING MEDIUM CAN BE EVOLVED DUE TO THE HEAT OF SAID ARC FOR EXTINGUISHING IT, THE LAST NAMED MEANS BEING SELECTED FROM THE CLASS CONSISTING OF 2,4-DICHLORO BENZOIC ACID AND 3,4-DICHLORO BENZOIC ACID.