US2285602A - Circuit interrupter - Google Patents

Description

`lune 9, 1942. F, MCMAHON CIRCUIT INTERRUPTER 2 Sheets-Sheet 2 Filed Nov. '7, 1938 www@ 'wnttention will first be directed to certain prior Patented June 9, 1942 CIRCUIT INTERRUPTER George F. McMahon, Chicago, Schweitzer & Conrad, Inc., poration of Delaware Ill., assigner to Chicago, Ill., a cor- Application November 7, 1938, Serial No. 239,263

, 37 Claims. (Cl. 29o-120) My invention relates generally to circuit interrupting apparatus, and it has particular relation to the provision of means for extinguishing arcs in high tension electric power circuts.

Various attempts have been made in th'e past to provide circuit interrupters that are capable of efficiently and economically interrupting fault circuits in high tension electric power systems over a range extending from a few amperes to several thousands of amperes. The circuit interrupter intended for use in interrupting fault currents in the lower ranges, i. e., less than ve thousand amperes may not be capable of satisfactorily interrupting fault currents above this range. It is to the provision of means for interrupting fault currents over substantially the entire range of current values and at voltages likely to be encountered in commercial practice that mynvention is addressed.

patents which illustrate what has been done in this field. A review of these patents indicates that they do not provide a satisfactory and economical solution to the problem for which the present invention affords a satisfactory and complete answer.

Ringwald Patent Re. 19,097, shows a fuse in which the fusible element is embedded in a body of chlorinated naphthalene. On blowing of the fusible element chlorine is released from this material and assists in extinguishing the arc thus formed. This device is satisfactory for interrupting only relatively small fault currents and obviously would not be satisfactory for use over the entire range likely to be encountered in commercial practice. There is a suggestion that fluorine might be used instead ,of chlorine since it is a more active chemical, and there is an indication that further experimental work would be carried out along this line. However, in so far as I am aware, any such experimental work was never carried out by said patentee Ringwald. Attention is here directed to the fact that the chlorinated napthalene proposed by Ringwald is soluble in the halogen derivatives of hydrocarbons which are customarily employed as arc extinguishing liquids.

Strom et al. Patent No. 2,077,282, discloses an insulating and arc extinguishing material in the form of solid blocks of boric acid. This material may also be in powered form. According to this patent electrical conductors are arranged to be insulated by the boric acid. In theevent of a short circuit between the conductors water vapor is evolved from the boric acid which has excelrangement is such that small fault currentarcs are interrupted in the small bore, while large fault current arcs are interrupted in the large bore. In either case the arc extinguishing is effected by the evolution of water vapor from the walls of the bores. the water vapor tending to blanket the arc in a manner now well known.

In my Patent No. 1,966,901, I have disclosed a fuse device in which one of the terminals is drawn below the surface of an arc extinguishing liquid when the fuse blows. The arc extinguishing liquid is directed into the arc stream where it assists in extinguishing it. In this patent I have disclosed the use of an arc extinguishing liquid comprising trichloroethylene in mixture with tetrachloroethylene.

In my Patent No, 2,077,429, I have disclosed a fuse construction which is generally similar to that of my prior patent with the exception that a condenser is added for the purpose of cooling and condensing the products of the arc when the fuse blows. In this case a preservative in the form of aniline is mixed with the arc extinguishing liquid in order to prevent deterioration of its dielectric properties. v

Triplett Patent No. 2,091,424, shows a fuse construction in which a liquid arc extinguishing medium is provided for extinguishing relatively small fault current arcs. The higher ranges of fault current arcs are interrupted by the evolution of water vapor from the inner surface of a sleeve of boric acid or silicic acid, or from water vapor that is obtained by the destruction of vials containing the same. Difliculty is encountered in maintaining the dielectric properties of the liquid arc extinguishing medium when 'the boric acid or silicio acid is used. Moreover, the water vapor evolved on the operaton of the device using either of these acids or water itself will cause the arc extinguishing liquid to be contaminated, thereby reducing its dielectric properties and making it possible that an arc may be maintained through it or may be restruck because of its lowered insulating properties.

Accordingly, the principal object of my invention is to provide a circuit interrupter that is capable of interrupting in ay satisfactory and ecoacid formed by several nomical manner any fault current arc that can occur in .a commercial electric power system.

Another object of my invention is to provide for interrupting a small fault current arc or a large fault, current arcv in a single circuit interrupter in an improved manner.,

Another object of my invention is to provide an arc extinguishing 'material which will accomsolid arc extinguishing material that does not evolve water vapor when subjected to the heat of an arc and which is insoluble in commercial arc extinguishing liquids such as halogen derivatives of hydrocarbons. y

Still another object of my invention is to provide a solid arc extinguishing material thatis substantially unaffected by the heat generated by the current flow through the fusible element of a fuse during normal operation.

Still another object of my invention is to pro-P vide a solid arc extinguishing material which will evolve a medium that will chemically combine with the vaporized particles of a silver fusible element when the fuse blows to form a nonconducting substance. y

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

Accordingly, my invention is disclosed in the embodimentsl shown in the accompanying drawings and it comprises the features of construction, combination of elements and arrangement of parts which will be exemplified in the construction hereinafter set forth and the scope of the application of which will be indicated in the appended claims.

For a more complete understanding of the nature and scope of my invention reference may be had to the following detailed description' taken in connection with the accompanying drawings, in which:

Figures l-A and l-B taken together illustrate a longitudinal sectional view of a fuse type of circuit interruptor embodying my invention;

Figure 2 is a longitudinal sectional view of another embodiment of my invention in which the fuse housing is provided with a number of corrugations; and

Figure 3 is a detail sectional view of the upper end of a fuse type of circuit interrupter embodying-my invention with which a. condenser is provided.

Referring now particularly to Figures 1-A and 1--B, the 'reference character III designates generally a circuit interruptor constructed in accordance with my invention. The interrupter III is provided with a cylindrical housing II formed of insulating material; preferably glass, having at its upper and lower ends terminal ferrules I2 and I3, respectively.l The ferrule I2 is secured to the upper end of the housing II by a suitable alloy as indicatedy at I4, and the lower ferrule VI3 is likewise secured in place by alloy as indicated at I5. The upper ferrule I2 is provided with a vent Chrome cap IB which may be blown oil under severe overload operation in order to vent the interior of the housing II the ready escape of the products formed as a result of the arc which is drawn on operation of the device.

A support member per ferrule I2 as illustrated, and it is provided with a central opening that is closed by a metal button or terminal I8. It will be understood that the ferrule I2, metal support member I1 and the metal button or terminal It together form one terminal of the .circuit interrupter III.

Secured to the metal button or terminal I8 is a fusible element 2l that is preferably composed of pure silver or an alloy containing 9. large percentage of silver. A strain wire 22, preferably formed of high strength metal vsuch as niwire is also secured to the metal button or terminal I8 for relieving the fusible element 2I of tension strains that would otherwise be imposed thereon.

At their lower erxls the fusible and strain elements 2I and 22 are suitably secured in the upper end of a rod-like terminal 23. It will be understood that an arc is formed between the upper terminal comprising the ferrule I2, support 1 member I1 and the metal button or terminal I8 'liquid 30 gases which serve `arc extinguishing type and the rod-like terminal 23 when the fusible and strain elements 2I and 22 have melted. Ordinarily, this is accompanied by an expulsion of the `metal button and terminal I8 after the vent cap I6 has been blown off, with the result that the arc plays between the metal support member |21 and the upper end of the rod-like terminal 3.

At its lower endthe terminal 23 is threaded into a spring and cable fastener shown generally at 24. A coil tension spring 25 and a pair of flexible leads 26 are secured at their upper ends to the spring and cable fastener 24 as shown. At their lowerends Athe spring 25 and cables 26 are secured to a spring and cable fastener shown generally at 21, which is threaded into a suitable boss in the lower ferrule I3.

With .a view to extinguishing relatively small current arcs, i. e., arcs through which about 2000 or less amperes flow, the rod-like terminal23 is drawn below the surface of a liquid arc extinguishing material 30 which fills the lower end of the housing II to the level indicated at 3l. The interruption of arcs in this current range is eiected by evolving from the arc extinguishing to blanket the arc and deionize the arc space at the zero points of the alternating current cycles, and at the same time providing a blast action outwardly of the housing II.

The liquid 30 that may be employed may vary, depending upon the operating conditions and other factors. For example, the arc extinguishing liquids disclosed in my priorpatents referred to hereinbefore may be employed. I have found that an arc extinguishing liquid composed of six per cent. trichloroethylene and ninety-four per cent. tetrachloroethylene having a trace of aniline therein will serve this purpose admirably.

Diiiiculty has been experienced in interrupting some of the higher short circuit currents which may occur in some installations when reliance is placed solely upon a liquid arc extinguishing material. Accordingly, I` propose to extend the current range o f circuit interrupters of the liquid by modifying them in such manner that they are capable of interruptto thel atmosphere and permit l I1 ls threaded into the uping higher ranges of current while at the same time retaining the excellent arc extinguishing characteristics of a liquid arc extinguishing material for the low current ranges.

For this purpose I have provided a tubular housing 32 of insulating material such as Bakelite which may be threaded into the support member I1 at its upper end as illustrated. Within the tubular housing 32 there is positioned a tubular member 33 of a solid arc extinguishing material. A ring 34 is provided at the upper end Aof the tubular member 32 for holding the tubular body of arc extinguishing material 33 in place. At the lower end a plug 35 is threaded into'the tubular member 32 for adjustably securing the body 33 of are extinguishing material in place. The body 33 of arc extinguishing material is provided with a longitudinal bore 36 through which the rod-like terminal 23 is freely movable and from which it may be quickly withdrawn by the coil tension spring 25 on blowing of the fusible and strain elements 2| and 22. The upper end of the body 33 of arc extinguishing material is flared outwardly as indicated at 31' in order to assist in the expulsion of the products of the arc that is formed on operation of the interrupter.

The character of the body 33 of aro extinguishing material is such that .relatively little if any arc extinguishing gases are evolved from the surface of the bore 36 in the small current operating range. In this range, as indicated, relance is placed for arc extinction upon the withdrawing of the rod-like terminal 23 below the level of the liquid 30 and the evolution of an arc extinguishing medium therefrom which provides a blast action through the bore 36 and tends to expel the ionized particles which would otherwise serve to permit the restriking or maintaining of the arc.

The characteristics required in the body 33 of arc extinguishing material are such that extreme care must be exercised in selecting it. It should be of such a nature that the heat generated by the fusible and strain elements l2| and 22 during normal operation will not cause any evolution of arc extinguishing vapors therefrom or other deterioration thereof. At the same time it must be capable of evolving large quantities of an arc extinguishing medium as the result of heat generated on flow of relatively large arc current so as to provide the desired blast and arc extinguishing action under these severe operating conditions. The arc extinguishing medium which is evolved under these conditions should be such that it will not materially increase the pressure inside the'housing Il to a point lwhere it might be destroyed before the vent cap IB `is blown off.

There are other important characteristics. The material forming the body 33 of arc extinguishng material should be relatively inert or insoluble in the arc extinguishing liquid 30. Further, it should remain intact throughout its useful life. When it is recalled that circuit interrupters of this class may remain connected in a circuit for many weeks or months, or possibly years, without being called upon to operate, it will be appreciated that the insulating properties of the liquid 30 should remain unchanged regardless of the time that the device has been in service.

. The arc extinguishing medium that is evolved from the body 33 of a'rc extinguishing material must be such that it will not contaminate the liquid 30 or combine therewith in such manner as to reduce its dielectric properties. Thus, either before or after operation of the device the body 33 of solid arc extinguishing material must havesuch characteristics that it will not in the slightest'impair or affect the insulating qualities of the arc extinguishing liquid 30. When it is recalled that the liquid 30 is intended to provide a major portion of the dielectric between the upper ferrule I2 .and the rod-like terminal 23 after the device has operated, the importance of maintaining the liquid 30 uncontaminated will be more readily appreciated.

After` conducting a long series of experiments and tests under actual operating conditions I have found that there are certain materials and combinations of materials that will satisfy the above enumerated requirements for the body 33 of arc extinguishing material. In particular, I have found that metallic compounds of iluorine in which the fluorine content is fty per cent. or above by weight provide the desired characteristics for the body 33 of arc extinguishing material. The following table sets forth three of these compounds and certain data with respect thereto: l

It will be observed that the materials set forth in this table comprise halogenated anhydrous materials, or inorganic halides, or metallic halides which are insoluble in halogenated hydrocarbons. Because of its high iiuorine content lithium fluoride is the preferred material. However, magnesium fluoride and aluminum fluoride may be employed.

' I have also found that a mixture of thirtyseven per centf lithium fluoride and sixty-three per cent. aluminum fluoride provides a suitable solid arc extinguishing material. In such a mixture the melting point is lower than the melting points of either of the ingredients. This permits the evolution of fluorine at lower temperatures.

When these various iluorine compounds are employed fiuorine in gaseous form is evolved from the surface of the bore 36 on flow of relatively great fault current through the arc. The fiuorine combines with the vaporized silver of the fusible element 2| to form silver fluoride which is highly resistantv to current ow.

Other solid arc extinguishing materials may be employed that have the characteristics enumerated above. For example, arsenic trioxide (AszO) and molybdenum trioxide (MoO3) may be employed. Arsenic trioxide sublimes readily as the temperature increases and it has no deflnite melting point. Molybdenum trioxide melts kat about 791 C. and is somewhat slower to act than is arsenic trioxide. Y

I have found that none of the materials enumerated hereinbefore that are suitable for forming the body 33 of solid arc extinguishing material will contaminate the usual arc extinguishing liquid employed in apparatus of this kind. It will be recalled that the liquid 30 comprises one or more halogen derivatives of hydrocarbons as set forth in my prior patents previously referred to. Since these materials are anhydrous there is Anumber of corrugations 51.

tion of sumcient pressure no possibility that um liquid :c wm be contaminated by water or water vapor derived from them, and its dielectric properties correspondingly reduced. This is the device has operate tion of water or water vapor 88 is concerned. Consequently, it is possible to form the body 83 of arc g material of lithium fluoride or of the other\materials mentioned, or of combinations thereof and permit the circuit interrupter I6 to for long periods of time without in the slightest causing a deterioration in its interrupting ability. Therefore, it will be apparent that the present invention materially extends the range of current values which can be successfully interrupted by devices of this nature.

In the modified `construction shown in Figure 2 of the drawings a circuit interrupter designated is provided having certain charare not foundin the circuit interrupter I6 previously described. The circuit interrupter 48 that is preferably formed of glass. The housing 56 is provided adiaeentthe upper end with a These corrugations serve not only to increase the mechanical strength of the tubular housing 50,

true both before and after in so far as any evolufrom the material tribute interrupter 49 is subjected tion. In Conrad'Patent No. 2,091,431, the importance 'of the corrugations 5I is more fully disclosed. In the present construction a larger number of corrugaticns has been employed in order to satisfactorily meet certain operating conditions.

At its upper end the with a ferrule 52 while a ferrule 58 is provided at the lower end. The ferrule 52 is secured to the housing 56 by suitable alloy as indicated at 54, and likewise the ferrule 58 is secured in position by suitable alloy as indicated at 55. .A vent cap 56 serves to close the upper end of the ferrule 52 and may be readily blown oi'f on the generawithin the housing 56. is mounted on a suitable during or after, opera- A metallic spider 56 comprises a tubular housing 56.

housing 56 is provided flange at the upper end of the ferrule 52. It"

carries a. terminal stud 55 to which are attached a silver fusible element 6l and a strain element 62. It will be understood that the terminal stud v59, spider 58 and ferrule 52 comprise the upper terminal of the interrupter 48.

At their lower ends the fusible and strain elements 6i and 62 are secured to an auxiliary ter-l minal 68 which is threaded in the upper end of a rod-like terminal 64. The lower end of the rod-like terminal 64 is threaded in a suitable spring and cable anchor shown generally at 65. The upper end of a coil tension spring 66 and the upper end of a flexible cable 61 are secured as illustrated to the spring and cable fastener 65. At their lower ends the spring 66 and cable 61 are secured to a spring and cable fastener shown generally at 68, which is threaded in a suitable boss carried by the ferrule 53.

A filling of are extinguishing liquid 16 is provided in the housing 58, to the level indicated at 1|, for the purpose of extinguishing arcs. in the small current range, as previously described. The liquid 16 that is employed may be as hereinbefore specied. Y

With a view to extending the range of current interruption of the interrupter 49 while at the same time retaining the advantages of the low current operating range .afforded by the liquid 16, a tubular member 12 of insulating material such as Bakelite is secured at its upper end in a metallic ring 13 by suitable pins 14, the ring 18 being threaded in the ferrule 52 4as shown.

Within the tubular member 12 is abody 15 of solid arc extinguishing material that may be composed of lithium iluoride or any of the other soli'd arc extinguishing materials set forth hereinbefore, or mixtures thereof.

The body 15 of solid arc extinguishing material is held in place -in the tubular member 12 by a plug 16 at the lower end and by a suitable ring 11 at the upper end, both the plug 16 and the ring 11 being threaded in the tubular member 12. As shown, the ring 11 is flared outwardly to facilitate the expulsion of the products of the arc.

The body15 of solid arc extinguishing material is provided with a bore 18 through which a rod-like terminal 64 isY freely movable. The length of the body 15 of solid arc extinguishing material and the number of corrugations 5I may be varied for diierent voltage ratings.

In operation, when the fusible and strain elements 6I and 62 are blown because of an overload. an arc is formed between the terminal stud 58 and the auxiliary terminal 68. If the arc thus formed is a relatively small current arc then it may be readily extinguished on withdrawal of the auxiliary terminal 63 below the level of the liquid 16 by the spring 66. The arc extinguishing medium that is evolved from the liquid 10 in such case will serve to deionize the arc path as described. If the flow of current is suillciently-great through the arc sumcient pressure may be generated to blow off the vent cap 4 56. However, in the low current range sufficient strain elements 6| .and 62, the bore 18 is substantially filled thereby and sufllcient heat is generated to evolve a considerable amount of arc extinguishing medium from the surface of the bore 18 which serves to delonize the arc space and to extinguish the arc.

After the are has been extinguished the rodlike terminal 64 accompanied by the auxiliary terminal 63 will have been withdrawn through the bore 18 to a. position below the level of the liquid 10. In such-case there is a considerable dielectric stress present between the rod-like terminal 64 and the upper ferrule 52 since `they are now separated by a dielectric and are maintained at a considerable difference of potential. This dielectric stress is distributed by the corrugations 5I to a large extent so as to reduce the concentration of electrostatic stress which might puncture the wall of the housing 56.

Another function of the corrugations 5I is to resist the mechanical stress that is applied to the housing 50 when the circuit interruption takes place. At the time because of therapid evolution of gases from the solid and liquid are extinguishing materials considerable pressure is generated within the housing 50. By providing 5I this mechanical stress and shock are efficiently resisted.

Referring now particularly to Figure 3 of the drawings, it will be observed that only the upper end portion of a modified form of circuit interwhich in turn carries a with a ferrule 96 ,material in the form of blocks 98 rupter is shown generally at 80. This circuit interrupter comprises a housing 8|, preferably of glass, having a ferrule 82 at its upperfend which is secured thereto by a suitable alloy as'indicated at 83. The ferrule 82 carries a spider 84 terminal stud 85, the stud 85, spider 84 and ferrule 82 constituting the upper terminal of the interrupter 80. Secured to the stud 85 are a silver fusible element 86 and a strain element 81. At their lower ends the fusible and strain elements 85 and 81 are secured to a rod-like terminal 88 the lower end of which is threaded in a suitable spring and cable fastener shown generally at 89.

As previously described, an arc extinguishing liquid 90 is provided in the housing 8| to the level indicated at 8|. This arc extinguishing liquid is of the nature previously set forth and is intended to effect eicient and rapid interruption of arcs 'in the small current range.

In the embodiments of the invention shown in Figures l-A and 2 a tubular member 32 and 12, respectively, is shown for holding the body of solid arc extinguishing material. This tubular member is formed, as described, of insulating material such as Bakelite, In some instances it has been noted that a flashover may be caused along the surface of this material between the upper terminal and the rod-like terminal after the device has operated. This is due to the fact thatthe surface of the tubular member 32 or 12 has been rendered conducting by carboniza tion or breakdown of the Bakelite sometimes happens at excessively high voltages.

With a view to obviating this difficulty, I have provided in the embodiment of the invention shown in Figure 3 a tubular housing 93 that is formed of glass. At its upper end the glass housing 93 is alloyed as indicated at 94 in a suitable ring 95 that is threaded in the ferrule 82. At its lower end the tubular housing 93 is provided that is alloyed thereto as inbody of solid arc extinguishing thereof is positioned inside of the glass housing 93. These blocks together form a body of solid arc ex tinguishing material having a longitudinal bore 95 through which the rod-like terminal 88 is readily movable.

With a view to condensing the products of the arc and particularly the gas evolved from the solid and liquid arc extinguishing materials, a condenser shown generally at .is provided at the upper end of the housing 8|. The condenser |0| comprises an extension |02 formed in tegrally with the ferrule 82. The extension |02 is closed at its upperend by a cap |03 to which is secured a vent cap |04. The cap |03 is provided with suitable apertures |05 through which the gases may be vented when the vent cap |04 is blown olf. The cap |03 is also provided with a stem |06 that carries a plurality of condenser plates or fins |01 on the surface of which the gases may be cooled and condensed. l

The operation of the circuit interrupter 80 dicated at 91. A

`is generally similar to that previously described.

The gases evolved from the liquid arc extinguish- Which' ing material or from the solid arc extinguishing material are cooled and condensed by the fins or plates |01. If suflicient pressure isgenerated within the extension |02 the vent cap |04 may be blown off, thereby venting the interior of the circuit interrupter to the atmosphere.

Since certain further changes may be made in the foregoing constructions and different embodiments of the invention may be made without departing from the scope thereof, it is intended that all matter shown in the accompanying drawings or set forth herein shall be interpreted as illustrative and not in a limiting sense. I claim as my invention:

l. A circuit interrupter comprising, in combination. a pair of arcing terminals relatively movable apart along a predetermined path, a liquid arc extinguishing material along onepart of said path adapted to evolve an arc extinguishing medium due to the heat of an arc when the current flow therethrough is relatively small, the insulating properties of said liquid arc extinguishing material being substantially reduced on contamination with water, and a solid anhydrous arc extinguishing material along another part of said path and adapted to evolve an arc extinguishing medium due to the heat of the arc only when the current flow therethrough is relatively great, the insulating properties of said liquid arc extinguishing material being substantially unimpaired by the presence of said solid arc extinguishing material and the arc extinguishing medium evolved therefrom.

2. A circuit interrupter comprising, in combination, a pair of arcing terminals relatively movable apart along a, predetermined path, a liquid arc extinguishing material along one part of said path adapted to evolve an arc extinguishing medium due to'the heat of an arc when thev current flow therethrough is relatively small, the insulating properties of said liquid arc extinguishing material being substantially reduced on contamination with water, and a solid anhydrous inorganic arc extinguishing material along another part of said path and adapted to evolve an arc extinguishing medium due to the heat of the arc only when the current ow therethrough is relatively great, the insulating properties of said liquid arc extinguishing material being substantially unimpaired by the presence of said solid arc extinguishing material and the arc extinguishing medium evolved therefrom.

3. In a circuit interrupter having arcing terminals, a liquid arc extinguishing material along one part of the path of an arc drawn between said terminals adapted to evolve an arc extinguishing medium due to the heat of the arc, and a solid halogenated arc extinguishing material along another part of said arc path adapted to evolve an are extinguishing medium due to the heat of the arc, said solid arc extinguishing material being substantially insoluble in said liquid arc extinguishing material whereby the dielectric properties thereof remain substantially unimpaired.

4. In a circuit interrupter having arcing terminals, a liquid arc extinguishing material along one part of the path of an arc drawn between said terminals adapted to evolve an arc extinguishing medium due to the heat of the arc when the currentilow therethrough is relatively small, and a solid halogenated are extinguishing material along anothenpart of said arc path adapted to evolve an arc extinguishing medium due to the heat of the arc when the current ilow therethrough is relatively great, said solid arc extinguishing material being substantially insoluble in said liquid arc extinguishing material whereby the dielectric properties thereof remain y substantially unimpaired.

`one or more halogen derivatives of a hydrocarflow'therethrough is relatively small, and a solid halogenated anhydrous arc extinguishing material disposed along another part of said arc path and adaptedto evolve an arc extinguishing medium due to the heat of the arc when the current flow therethrough isrelatively great, said solid arc extinguishing material being substantially insoluble in said liquid arc extinguishing material whereby the dielectric properties thereof remain substantially unimpaired.

6.' In -a circuit interrupter having arcing terminals, a liquid arc extinguishing material along one part of the path of an arc drawn between said terminals adapted to evolve an arc extinguishing medium due to the heat of the arc, and a solid are extinguishing material comprising one or more metallic halides along another part of said arc path adapted to evolve an arc extinguishing medium due to the heat of the arc.

7. In a circuit interrupter having arcing terminals, an arc extinguishing liquid comprising k\one or more non-metallic halides and disposed along one part of the path of thearc drawn between said terminals and adapted to evolve an arc extinguishing medium due to the heat of the arc, and a solid arc extinguishing material.

comprising one or more metallic halides disposed along another part oi said arc path and adapted to evolve an arc extinguishing medium due to the heat of the arc. Y

8. In electrical apparatus, an inorganic arc extinguishing material containing at least iifty per cent. by weight of fluorine. l

9. In a circuit interrupter having arcing terminals, a solid inorganic arc extinguishing material containing at least fty per cent. by Weight of fluorine along the path of the arc drawn beminals, and a solid arc extinguishing .minals, and arc extinguishing material comprising one or more metallic halides along said lpath, said arc ex hing material evolving one or more halogens in gaseous form on blowing of said silver fusible element to form one or more silver halides.

lll. A circuit interrupter comprising, in oombination, a pair of arcing terminals relatively ,movable apart` along a predetermined path, a

silver fusible element interconnecting said termaterial comprising one or more metallic halides along said path, said arc extinguishing material evolving one or more halogens in gaseous form on blowing of said silver fusible element tok form one or more silver halides, v

14. A circuit interrupter comprising, in combination, a pair of arcing terminals relatively movable apart along a predetermined path, a silver fusible element interconnecting said terminals, and inorganic arc extinguishing mate'- rial containing asubstantial amount of fluorlne along said path, said arc extinguishing material evolving fiuorine in the form of a gas due to the heat of the arc formed on blowing of said silver fusible element to form silver fluoride.

l5. A4 circuit interrupter comprising, in combination, a pair of arcing terminals relatively movable apart -along a predetermined path, a

.silver fusible element interconnecting said terminals, and a solid inorganic arc extinguishing material containing at least fifty per cent. by

I weight of fluorne along said path, said arc extween said terminals and evolving fluorine in the form of gas due to extinguishing the same.

10. In a circuit interrupter having arcing terminals, a liquid arc extinguishing material along one part of the path of an arc drawn between said terminals adapted to evolve an arc extinguishing medium due to the heat of the arc when the current flow therethrough is relatively small, and a solid'inorganic arc extinguishing material containing at least fifty per cent. by weight of fluorine along another part of said arc path adapted to evolve fiuorine in the form of gas due to the heat of the arc when the current flow therethrough is relatively great.

11. In a circuit interrupter having arcing terminals, an arc extinguishing liquid comprising one or more halogen derivatives of a hydrocarbon and disposed along one the arc drawn between r said terminals and adapted to evolve an arc extinguishing medium due to the heat of the arc when the current flow therethrough is relatively small, and a solid inorganic arc extinguishing material containing at least fifty per cent. by weight of iiuorine disposed along another part of said arc path and adapted to evolve fluorine in the form of gas due to the heat of the arc when the current flow therethrough is relatively great.

l2. A circuit interrupter comprising, in combination, a pair of arcing terminals relatively movable apart along a predetermined path,'a silver fusible element interconnecting said terthe heat oi the arc for part of the path oi!v tinguishing material evolving fluorine in the form of a gas due to the heat of the arc formed on blowing of said silver fusible element to form -silver iiuoride.

16. A circuit interrupter comprising, in combination, a pair of arcing terminals relatively movable apart along a predetermined path, a silver fusible element interconnecting said terminals,'and a solid arc extinguishing material comprising lithium iiuoride along said path, said arc extinguishing material evolving fluorine in the form of a gas due to the heat of the arc formed on blowing'of said silver fusible element to form silver uoride.

17, In electrical-apparatus, an arc lextinguishing material comprising lithium uoride.

18. In a circuit interrupter having arcing terminals, a solid arc extinguishing material comprising lithium uoride disposed along the path ofthe arc drawn between said terminals and evolving fluorine due to the heat of the arc for extinguishing the same.

19. In a'circuit interrupter having arcing terminals, a liquid arc extinguishing material along one part of the path of an arc drawn between said terminals adapted' to evolve an arc extinguishing medium due to the heat of the arc, and a solid arc extinguishing material comprising lithium iiuoride along another part of'said arc path adapted to evolve fluorine due to the heat of the are for extinguishing the same.

20. In a circuit interrupter having arcing terminals, an arc extinguishing liquid comprising one or more halogen derivatives of a hydrocarbon and disposed along one part of the path of the arc drawn between said terminals and adapted to evolve an arc extinguishing medium due to the heat of the arc, and a solid arc extinguishing material comprising lithium fluoride along another part of said arc path adapted to evolve fluorine due to the heat of the arc for extinguishing the same.

21. In electrical apparatus, an arc extinguishing material comprising magnesium fluoride.

22. In a circuit interrupter having arcing terminals, a solid arc extinguishing material comprising magnesium fluoride disposed along the path of the arc drawn between said terminals and,

evolving iiuorine due to the heat of the arc for extinguishing the same.

23. In acircuit interrupter having arcing terminals, a liquid arc extinguishing material along one part or". the path of an arc drawn between said terminals adapted to evolve an arc extinguishing medium due to thev heat of the arc, and a solid are extinguishing material comprising magnesium iluoride along another part of said arc path adapted to evolve iuorine due to the heat of the arc for extinguishing the same.

24. In a circuit interrupter having arcing terminals, an are extinguishing liquid comprising one or more halogen derivatives of a hydrocarbon and disposed along one part of the path of the arc drawn between said terminals and adapted to evolve an arc extinguishing medium due to the heat of the arc when the current flow therethrough is relatively small, and a solid arc extinguishing material comprising magnesium iluoride along another part of said arc path adapted to evolve iluorine due to the heat of the arc when the current flow therethrough is relatively great for extinguishing the same. l

25. In electrical apparatus, an arc extinguishing material comprising aluminum fluoride.

26. In a circuit interrupter having arcing terminals, a solid arc extinguishing material comprising aluminum iiuoride disposed along the path of the arc drawn between Said terminals and evolving iiuorine due to the heat of the arc for extinguishing the same.

27, In a circuit interrupter having arcing terminals, a liquid arc extinguishing material along one part of the path of an arc drawn between said terminals adapted to evolve an arc extinguishing medium due to the heat of the arc, and a solid arc extinguishing material comprising aluminum uoride along another part of said arc path adapted to evolve iluorine due to the heat of the arc for extinguishing the same.

28. In electrical apparatus, an arc extinguishing material comprising a mixture of 'metallic halides the melting point of which is substantially less than that of any of the halides forming the mixture.

29. In electrical apparatus, an arc extinguishing material comprising a mixture of lithium iluoride and aluminum fluoride.

30. In electrical apparatus, an arc extinguishing material comprising a mixture of thirty-seven per cent. of lithium fluoride and sixty-three per cent. of aluminum iiuoride.

31. In a circuit interrupter having arcing terminals, an arc extinguishing liquid comprising one or more halogen derivatives of a hydrocarbon and disposed along one part of the path of the arc drawn between said terminals and adapted to evolve an arc extinguishing medium due to the heat of the arc when the current iiow therethrough is relatively small, and a solid arc extinguishing material comprising aluminum fluoride along another part of said arc path adapted to evolve fluorine due to the heat of the arc when the current ilow therethrough is relatively great for extinguishing the same.

32'. A circuit interrupter comprising, in combination, a tubular insulating housing having a plurality of corrugations intermediate its` ends for increasing the mechanical strength thereof and distributing dielectric stress, stationary and movable arcing terminals within said housing, a quantity of arc extinguishing liquid in,l said housing, means for drawing said movable arcing terminal into said arc extinguishing liquid and away from said stationary terminal for extinguishing an arc drawn therebetween, and a tubular body of a solid arc extinguishing material comprising a metallic halide surrounding said movable terminal and adapted to have an arc extinguishing medium in gaseous form evolved from its inner surface due to the heat of an arc drawn between said terminals for extinguishing the same.

33. A circuit interrupter comprising, in combination, a tubular housing formed of insulating material, stationary and movable arcing terminals within said housing, tinguishing liquid in said housing, 4means for drawing said movablearcing terminal into said arc extinguishing liquid and away from said stationary terminal for extinguishing a relatively small current arc drawn therebetween, a tubular body of a solid anhydrous are extinguishing material insoluble in said liquid surrounding said movable terminal and adapted to have an arc extinguishing medium evolved from its inner surface due to the heat of a relatively great current are drawn between said terminals for extinguishing the same, and means for cooling and condensing the products of the arc drawn between said terminals and thearc extinguishing mediums evolved from said liquid and solid arc extinguishing materials. i

34. A circuit interrupter comprising, in combination, a tubular housing formed of insulating material, stationary and movable arcingterminals within said housing, a quantity of arc extinguishing liquid in said housing, means for drawing said movable arcing terminal into said arc extinguishing liquid and away from said stationary terminal for extinguishing a relatively small current arc drawn therebetween, a tubular body of a solid are extinguishing material comprising a metallic halide surrounding said movable terminal and adapted to have an arc extinguishing medium in gaseous form evolved from its inner surface due to the heat of a relatively great current arc drawn between said terminals for extinguishing the same, and means for cooling and condensing the products of the arc drawn between said terminals and the arc extinguishing mediums evolved from said liquid and solid arc l extinguishing materials.

85. A circuit interrupter comprising, in combination, a tubular housing formed of insulating material, stationary and movable arcing terminals within said housing, a quantity of arc extinguishing liquid in said housing, means for drawing said movable arcing terminal into said arc extinguishing liquid and away from said stationary terminal for extinguishing a relatively small current arc drawn therebetween, a tubular body of a solid arc extinguishing material comprising lithium nuoride surrounding said movable terminal and adapted to have iluorine in gaseous form evolved from its inner surface due' to the heat of a relatively great current arc drawn between said terminals for extinguishing the same, and means for cooling and condensing the products of the arc drawn between said terminals and the arc extinguishing mediums evolved from said liquid and solid arc extinguishing materials.

a quantity of arc exbination, a tubular housing formed of insulating material, stationary and movable arcing terminals within said housing, a quantity of arc extinguishing liquid in said housing, means for drawing said movable arcing terminal into said arc extinguishing liquid and away nom said stationary terminal, a tubular body of solid arc extinguishing material insoluble in said liquid surrounding said movable terminal and adapted to have an arc extinguishing medium evolved from its inner surface due to the heat of the arc drawn between said terminals, and a'sleeve of insulating material surrounding said body of solid arc extinguishing material for holding the same in operative position, said sleeve of insulating material being characterized by having its outer surface substantially free from the formation thereon of a conducting path resulting from an arc being formed therealong.

37. A circuit interrupter comprising, in comaasaeoa v i 36. A circuit interrupter comprising, in combination, a tubular housing formed of insulating material, stationary and movable arcing terminals within said housing, a quantity of arc extinguishing liquid in said housing, means for drawing said movable arcing terminal inw said arc extinguishingliquid and away from said stationary terminal, a tubular body of Vsolid arc extinguishing material surrounding said movable terminal and adapted to have an arc extinguishing medium evolved from its inner surface due to the heatl of the arc drawn between said terminals, and a sleeve oi insulating material surrounding said body of solid arc extinguishing material for holding the same in operative position,

.said sleeve of insulating material formed of car- Y bon free material whereby the outer surface thereof is substantially free from the likelihood of a conducting path being formed thereon during current interruption.

GEORGE F. MCMAHON.

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