US2061301A - Circuit interrupter - Google Patents

Description

Nov. 17, 1936. p DUFFING 2,061,301

CIRCUIT INTERRUPTER Filed May 25, 1952 2 Sheets-Sheet 1 BY W lATToRN Y P. DUFFING 2,061,301

CIRCUIT INTERRUPTER Filed May 25; 1952 2 sheets-sheet 2 Nov. 17, 1936.

"l lll INVENToR Pal/Z 'Da/'fing ATTORN EY Patentedl Nov. 17, 1936 uNiTjao stares cargar arrasa CIRCUIT INTERRUPTER ration of Pennsylvania.

Application May 25, 1932, serial No. 613,455 In Germany May 27, 1931 as claims. (or. 20o-15o) My invention relates to circuit interruptera and particularly to circuit interrupters of the socalled expansion type, in which the arc is established in a pressure. chamber and then brought into contact with a vapor. \The theory of operation and -certain ofthe structural features of this type of circuit interrupter'are disclosed inthe applications of Kesselring, Serial No1 461,325, filed June 16, 1930, and Kesselring et al., Serial No.

'496,218, filed November 17, 1930, both of which are assigned totheassignee of this invention.

One object of my invention is toy provide an expansion type circuit interrupter in -which the expansion chamber is normally free of the` arc 1,5 extinguishing liquid, and whichyzhas means associated therewith for injecting fa predetermined quantity of this liquid into the' chamber during each operation of the interrupter. Another object of my invention is, to provide an expansion chamber for -an arc extinguishing device which shall have a piston associated there- D with for moving a predetermined amount of liquid into the'arc extinguishing chamberduring' each" Moperation of the breaker. A

Another object oimy invention is to provide means whereby the volume of the arc extinguishing chamber of a circuit breaker arc extinguish-- ing device may be decreased during the separation of the breaker contacts.

` Another object of my invention is to provide an improved type of expansion chamber vfor circuit breaker arc extinguishing devices which shall be economical to manufacture and shall be lmore eiective than previous structures of thistype.

'Another object of my invention is to provide an expansion chamber for an` arc extinguishing device which shall comprise a plurality of separable plates having centrally disposed openings through which the moving contact of the breaker 40 moves, these openings aligningM to form the expansion chamber.

A further object of my invention isV to provide a circuit breaker having separable contacts and an arc extinguishing device with a hollow insu- 45r lator for providing an enclosed passageway within which one of the separable contacts may be moved out of engagement with the arc extinguishing. device, thus making possible the complete enclosing of all the movable parts of the circuit 50` breaker.

' A still further object of my invention4 is to provide a circuit interrupter having separable contacts and an arc extinguishing device with a transparent insulator for providing an enclosedv 55 path through which one of the separable contacts moves, the transparent insulator making it possible to determine the position of the contacts visually.

The principal eld for immediate application of my invention is in connection with circuit interrupters for controlling power circuits, and I shall 1 hereinafter describe an embodiment of my invention as applied to such circuit breakers, without, however, in any way intending to restrict the scope of the inventon, except as indicated in the appended claims. U

In this embodiment of my invention, I provide a pair of separable contact members for opening the circuit, an arc extinguishing device associated therewith, an operating means for separatingthe contact members, and a supporting means for mounting the entire structure in an operative position. In addition, I provide a transparent insulator, having a passage therethrough, disposed adjacent to the arc extinguishing device, the passage aligningwith the arc extinguishing device in such manner that it provides a closed passageway wherein one of the separable contacts moves.'V

Thev operation` of my invention depends upon the combination of several known scientific facts: First, itv is well known that a current carrying arc is made up of a large number of electrons and ions, that is, the arc path is in an ionized state. Second, it is well known. that the extinguishing of an alternating currentarc may be most eiiectively accomplished at the time of current .z'ero, because it is only at the time of current zero that new electrons are not being forced into. the arc path by the current flow. Thus, since o new electrons are entering the arc path, and since the accelerating force on those electrons which are already there is comparatively small` (for usual high power factors.) it is necessary onlyto remove the free electrons existing at the time of current zero to deionize the arc path and extinguish the arc. Thirdfit has been shown that between an electron and a molecule, (or atom), or between an ion and molecule (orA atom), there exists la mutual attraction which is inversely proportional to the fourth .power of the distance'l between the'm. The attraction is thus eiective only when the distance between the molecule andelectron, or between vthe molecule and the'ion, is" very small. In the case of a gas which obeys the general law PV=RT, the distance between the individual molecules (or atoms) of the gas is so large that any possiblev combining of electrons and molecules (or atoms):

or ions and molecules (or atoms), as a result of this attraction is negligible. Fourth, it is well known that as a gas approaches the liquid state, that is, as a gas passes through the vapor condition, it no longer follows the PV=RT equation; it now being necessary to use Van der Waal's equation which is The constant A arises from taking into account the attraction between individual molecules, the magnitude of which can be determined from his equation. Or in other Words, when afluid is in the vapor state, it contains a much greater number of molecules (or atoms for a uni-valent iiuid) per unit volume than vdoes a fluid which is in the gaseous state'. Thus, if we are to effect the deionization of a quantity of ionized gas by causing the ions and electrons of that gas to combine with molecules (or atoms as the case may be), it is necessary that a very large number of molecules be present in the region surrounding the ionized portion at the time of current zero.

This combination of an electron with aneutral molecule (or atom) is most effective in preventing the reionization of the'arc path because the acceleration which may be given to the electronmolecule or to the electron-atom combination is very small as compared with the acceleration which may be given to a single electron-it being possible for the mass of the combination to be as much as 30,000 times that of the electron alone. It will thereby become apparent, at once, that a very effective delonizing action would result from the surrounding of an arc path with a iiuid in the vapor state-it being important to note that the delonizing action of a uid in the liquid state is not as effective as the delonizing action of a fluid in the vapor state because the intermolecular forces existing in a liquid practically preclude the possibility of sufficiently free motion of the individual molecules (or atoms) to be of any real value in removing the free electrons from the arc path. With a vapor, however, there is a suilicient number of molecules per unit volume to effectively remove from the arc path a larger part of the free electrons existing at the time of current zerothe electrons being attracted to and combining with the free molecules.

It is upon this theory that the so-called expansion breaker operates. It is obvious that the arc extinguishing liquid used in this type of.

breaker must be vaporizable rather than of a type which breaks down, irreversibly, into less complex components upon the application of heat. Als o, it is necessary that the fluid used in this type' of breaker be capable of existing in the vapor state at ordinary atmospheric pressures. One of the most satisfactory fluids found so far is pure water, or water having glycerine, alcohol, or some salt added thereto for the purpose of preventing freezing. l

The operation of a circuit breaker of this type is as follows: The arc is established within a substantially closed chamber having a means associated therewith for releasing the pressure of the gas formed by the arc at some predetermined point. As pointed out in the above-mentioned applications, the release pressure, when using watefas the arc extinguishing fluid, is usually less than 30 atmospheres. Thewater, or other liqwhich is vaporized by the arc passes almost gaseous state as a result of the high temperature. The pressure within the chamber builds up very rapidly--usually within an alternation or two-and then the pressure releasing means is operated. The pressure releasing means is so constructed that the iiuid is held in the vapor state for a period greater than one alternationthis being necessary to assure the presence of vapor adjacent the arc path during at least one current zero. The portion of ionized gas which `was, prior to current zero, the arc path is thus As the current passes through the zero point and 20 as the voltage increases further, the number of free electrons has been reduced to such a small value that it is no longer possible to reignite the arc by the ionization resulting from the collision of the electrons and the free molecules in the space between the two terminals.

The features of my invention which I believe lto be new are particularly pointed out in the appended claims, and for a fuller understanding of the invention reference may be had to the accompanying drawings, in which:

Figure 1 is a side elevational view showing a circuit breaker equipped with the arc extinguishy ing device of my invention,

Fig. 2 is a front elevational view of the circuit breaker shown in Figure 1,

Fig. 3 is a fragmentary sectional view, partially in elevation, through the arc extinguisher shown in Fig. l, a

Fig. 4 is a sectional view. similar to Fig. 3, showing a modified type of arc extinguisher, and

Fig. 5 is a sectional view through the arc extinguishing device shown in Fig. 3 on the line V-V.

Referring to the drawings, the arc extinguishing device I is mounted on two upright insulators 3 which, in turn, are ai'iixed to a base 5. Projecting upwardly from the base 5 are two arms 1 which support an enclosure 9 containing the mechanism for operating the separable contacts. A transparent insulator II having a passageway I2 therein extends upwardly from the arc extinguishing device I and engages the breaker operating mechanism enclosure 9. This transparent insulator Il provides an enclosed passageway wherein the movable contact member I3 moves after that member leaves the arc passage. Terminal contacts I4 and I5 are provided for connecting the interrupter in the external circuit. A

The operating mechanism 9 is not a feature of my inventian, and since these mechanisms are well known in the art, it will be necessary for a full understanding of my invention to merely mention that the moving contact I3 is moved,4 thereby, into and out of engagement with the other contact member which is disposed in the base of the arc extinguisher I. The breaker shown in Figs. 1 and 2 is in the open position and it will 'be noted that a portion of the moving contact I3 aceaeoi i'ixed to the base I5 and comprises, in general, v

a cylindrical chamber 23 closed at the bottom and having a piston 25 which moves therein. The piston 25 is also used as one of the separable contact members, the portion 21 engaging the end 29 of theother contact I3. A guide member 3l having a funnel shaped opening 33 therein is disposed in the upper portion of the cylindrical member 23, being affixed thereto by the spokelike supports 34; this member 3l assists in guiding the end 29 of the contact member i3 when that member is moving to the open or to the closed position. The top of the cylindrical member 23 is closed by the bottle shaped flange 35 having a cylindrical opening 31 therein. A

, plurality of circular plates of insulating material 39, each having a centrally disposed opening 4I and annular cut-out portions 43, are positioned above the cylindrical base 23. Each of the plates 39 has four other openings 45, therein, through which the guide pins 41, of insulating material, are placed; the upper end of the pins l1 being aixed to the casing I9. The openings 4I and 45 align upon the assembly of the individual plates, and combine to form, respectively, a centrally disposed passage through which the contact member I3 moves to establish the arc, and openings for assembling and guiding the individual -plates I39. In like manner, the cut-out portion 43 of each of the plates 39 aligns with the corresponding cut-out portion 43 of the adjoining plate to form an annular recess connecting with the through passage or chamber formed by the openings 4I. 'I'hese annular recesses and the through passage comprise the upper portion of the arc extinguishing chamber proper, and it is within this portion of the chamber that the arc extinguishing uid is rst gasiiied under pressure and then changed to the vapor state by releasing the pressure. 'I'he base member 49 of the assemblyof plates 39 has a sleeve portion 5I which slidably engages the opening 31 inthe top iiange 35. The base plate 49 is biased upwardly by the springs53 and provides a releasable means for holding the insulating plates 39 inv contact with each other.- The passageway i2, While it connects with the arc passage, is not used for aiding in arc extinction and. the arc is never drawn thereinto. Rather, the function f this passage is to make possible the complete enclosing of the moving parts of the breaker and to permit the circuit position of the breaker to be determined by visual inspection.

An opening 54 having a gland 55 and packing 51 therein is .disposed in the top portion of the insulating casing I9 and provides a means for engaging the sides of the contact member i3 and thereby effectively sealing the arc extinguishing chamber. The gland and packing also prevent the arc extinguishing fluid from being forced into the passageway I2. ,Other openings 59 are provided in the casing member I9 for preventing the building up of dangerous press'ures within the casing itself'during the operation of the interrupter. 1

The insulating means II is preferably constructed of glass andas previously mentioned,

has a central opening or passageway I2 therein.

The base member 53 of the insulating means Illmay be of metal, as shown, and is aiiixed to the top of the casing i9 by means of the screws 55 which engage suitable threaded openings there- The stationary contact assemblage 2i is designed for a triple purpose; it provides a means for contacting the movable contact member i3 and, at the same time, it provides a means for moving a predetermined quantity of the arc extinguishing fluid into the arc extinguishing chamber proper during each operation of the interrupter;A in addition, it reduces the volume of xthe chamber.- These desired results are made possible through the particular construction embodied therein. The bottom of the cylindrical member 23 is provided with an opening 61 to permit the passage of thefarc extinguishing liquid il therethrough. A flap valve 69 which opens inwardly into the cylindrical member 23 is provided for closing the opening 51. The piston 25 is biased upwardly by the springs 1i and has two openings 13 therein, each of which isI closed by a ap valve 15. The electrical circuit is maintained through the springs 1I which connect the piston 25 with the base i5.

The interruptor is shown in Fig. 3 in the closed position. Upon the occurrence of an overload or short -circuit condition, the operating mechanism 9 moves the contact member i3 upwardly. The piston 25 follows this movement until the portion 21 abuts against the bottom of the guide member 3i. The insulating discs 39 are normally out of `contact with the arc extinguishing liquid l1 which lls only the base I5 of the arc extinguishing chamber, and the piston 25 isolates that portion of the arc extinguishing liquid above the piston from the main body of liquid. Thus the upward movement of the piston forces a predetermined quantity of the arc lextinguishing liquid I1 up into the spaces existing between the insulating plates 39 and the contact member I3 (the upper portion of the ard extinguishing chamber) -the flap valves 15 beingviieid in the closed position. As the end 29 oi the contact member I3 continues its upward This separation of the vplates lreleases the gas pressure within the extinguishing/chamber very nearly to atmospheric and, in so doing, changes the fluid from the gaseous to the vapor state. The curprent passes through the zero point during this release of the gas pressure and deionization of the arc is effected as previously pointed out. o

The upward movement of the contact member I3, subsequent to the extinguishment of the arc, is carried beyond the arcu extinguishing chamber and into thepassageway I2 in the transparent insulating members Il. This separation of the contact member I3 and the arc extinguishing device I gives an increased margin of safety and -reduces the electrostatic stresses existing on open circuit; it also makes it possible to determine by inspection whether the breaker is open or closed. In addition, the provision of an enclosed passageway wherein the movable contact member moves is of particular advantage in outdoor breakers, because the gap existing between the arc extinguisher and the contact member is protected from rain, snow, and dangerous ice formations, all of Which are apt to interfere with the reliability of operation. In fact, so satisfactory has this breaker proven on outdoor installations that it has been found possible to eliminate the disconnecting switches usually provided with outdoor circuit breakers.

When the piston '25 moves upwardly, during the opening operation of the breaker, the flap valve 69 lifts and permits the in-iiow of the arc extinguishing liquid |1. During the closing operation of the breaker,.the end 29 of the contact member I3 moves downwardly through the arc extinguishing chamber, the opening 33 in the guide member 3|, and contacts with the portion 21 of the piston 25. Upon further downward movement of the` contact member I3, the valve 69 closes, if not already closed, and the valves 15 open, thereby permitting the passage of a predetermined quantity of liquid into the space above the piston. The entire structure is then returned to the position shown in Fig. 3. Both of the flap valves 15 and the valve B9 are biased to the closed position by suitable means (not shownf). The provision of the discs 39 forming the passage in which the arc is extinguished above the level of the liquid, with a piston for throwing the liquid into the passage before the arc is drawn, makes possible the use of a minimum amount of liquid, and gives better arc extinguishing action since the liquid is held by the discs in close, contact with the arc so as to be most effective. i

A modified form of the arc extinguishing device of my invention is shown in Fig. 4. The metallic base 11 of the cylindrical casing is aiiixed to the upper portion 19, which is of insulating material, by means of the bolts 8| and their associated nuts 82 which press together suitable faced surfaces 83 and 95. A plate member 91 is disposed between th'e faced surfaces 83 and 85 and provides a supporting means for the arc extinguishing structure proper. This structure includes a flat plate of insulating material 89 which is rigidly aliixed to the base plate 81 and has openings 9| therein. A cylindrical member of insulating material 93 is affixed to the insulating plate 89 and has openings 95 therein to permit the passage of the arc extinguishing fluid 91, which partially fills the casing. A piston 99, which is biased upwardly by a spring and has a contact member |03 fixed thereto, is positioned inside the cylindrical member 93. Disposed above the cylindrical member 93 are a plurality of separable plates and 01. These plates are substantially circular in outline and have central openings '|09 and respectively, therein. They are retained in position Yby a top plate assemblage ||3 of insulating material `which is slidably fastened to the base plate 81 by means of a plurality of equally spaced metallic rods ||5, each having Aan insulating casing ||1 disposed about YY.the rod. The rods ||1 extend ,v through suitable openings in the base plate El and have heads H9 on the ends thereof which engage springs |2i. These springs |2| provide a suitable means for biasing the separable plates |09 and |01 toward each other with a predetermined forc-e. An opening E23 is provided in the cylindrical member 93 which is of substantially the same size as the end |3| of the cylindrical contact member |03, and, when the interrupter is in the open position, the end |,3| of the contact member |03 ts into the opening |23. Two openings |25 are provided in the top portion 19 of the casing to prevent the building up of dangerous gas pressures. The moving contact member |21 enters the arc extinguisher through an opening |29.

The operation of this modified form of arc extinguisher is substantially the same as the operation of the extinguisher shown in Fig. 3. The contacts are shown in the closed position in Fig. 4. When the moving contact |21 is moved upwardly by the operating mechanism, the engaging contact |03 and piston 99 which is aflixed thereto also moves upwardly. The upward movement of the piston 99 decreases the volume of the arc extinguishing chamber and at the same time keeps that chamber filled with the arc extinguishing liquid. The upward movement of the contact |03 stops when the portion |3| engages the opening |23 in the insulating member 93. The engaging contacts then separate and the arc is established therebetween. A predetermined amount of the arc extinguishing liquid has been trapped within the spaces |33- since the lower end ofthe arc extinguishing chamber has been closed against the main body of liquid by the piston |03-and this liquid is gasied by the action of the arc. As in the case of the previously described arc extinguisher, this gasifying occurs very rapidly and as a result considerable pressure is built up within the spaces |33 in the arc extinguisher chamberthe bottom of the arc extinguishing chamber being closed by the end |3| of the contact |03. When this gas pressure has reached a predetermined magnitudedepending upon predetermined calibration of the springs l2 |the top member ||3 is moved upwardly and the plates |05 and |01 separate thereby releasing the pressure within the arc extinguishing chamber. This release of pressure causes the gas to pass into the vapor state and the vapor, lmme diately upon the occurrence of a current zero, effects a deionization of the arc path.

This modification of my invention is particularly adapted for interrupting medium'current arcs; it being possible to reduce the amount of arc extinguishing liquid, within the chamber to a minimum. Actually, the volume of the chamber is reduced but the effect is a reduction of the quantity of liquid which must be gasiiied by the arc. This reduction in volume of the arc extinguishing iiuid is particularly desirable when interrupting the lower current arcs, because it assures the complete gasification of all of the liquid, and also assures a rapid production of sufcient gas pressure to operate the vapor producing means.

Threaded holes 35 are provided in casing 19 in order to mount an insulating means similar to the insulator 4|| used in the arc extinguisher shown in Fig. 3.

It will thus be seen that I have disclosed an improved arc extinguishing struct-ure, of the expansion type, which is capable of functioning to extinguish an arc with maximum efficiency. In accomplishing this, I have disclosed an arc extinguishing device which has means associated therewith for introducing a predetermined quantity of arc extinguishing fluid into the arc extinguisliing chamber during' each operation of the interrupter, and for reducing the volume of aocgneoi the chamber, to the point of maximum effectiveness, during each operation of the breaker.

Also, I have disclosed a new form of circuit interrupter which combines the featuresV of a disconnecting switch and a power circuit breaker in a single device wherein the moving parts are completely enclosed; in addition to this improvement, I have disclosed a means for visually determining the position of the separable' contacts of a circuit interrupter having an arc extinguishing structure associated therewith. l

While in accordance with the patent statutes,

I have given the foregoing details of a practical embodiment of my invention, it is to be understood that many of these are merely illustrative and that variations of their precise form will be desirable in some applications. I desire, therefore, that the language of the accompanying claims be accorded the broadest reasonable construction and that my invention be limited only by what is explicitly stated in the claims and by the prior art. I claim as my invention:

1. In a circuit interrupter, a pair of relatively movable conducting members for opening the circuit, an arc extinguishing device comprising a chamber having an opening therein, one of said moving contact members moving through said opening out of said arc extinguishing device during the circuit opening operation, a hollow insulating means, at least partially of transparent material, for providing an enclosed passage, external to said chamber and within which said contact member moves during the final stages of the circuit opening operation, one end of said moving contact remaining within said hollow insulating means when said interrupter is inthe fully open position in order to permit visual determination of `the position of said interrupter and means for sealing said arc extinguishing chamber from saidenclosed passage at least during each arc extinguishing operation.

2. In a circuit interrupter separable contact means, one of which comprises a piston, for opening and closing the circula-land an arc extinguishing device cooperating`\tl1erewith, said arc extinguishing' device including a body of liquid, a chamber open to said body of liquid when said contact members are in one position, andmeans coacting vithaid piston during the operation of said .interrupter to entrap a predetermined quantity of said liquid within said arc chamber and to closev said chamber to said bodyof liquid.

3. In a circuit interrupter,- two relatively movable contact members for opening and closing' the circuit, and an arc extinguishing devicecooperating therewith, said arc extinguishing device including a body of liquid, an arc extinguishing chamber at least a portion of which is not iilled with said liquid when said interruptor is in the closed position, one of said contact mem- Vbers being movable from said liquid into said uniilled portion of said arc extinguishing chamber, and piston means, operable during the opening of said interrupterffor moving some of said liquid into said unlled portion oi said arc extinguishing mber.

`- H4. In'a circuit interrupter, separable contact means, one of which comprises a piston, foropening andclosing the circuit, and an arc ex- Y ftjinguishing device including a casing, formed at lea'st-jparti'ally of insulating material andhaving 'a passage-extending therethrough, a body of l liquid 'contained-within said casing, said pas sage being normally only partially iilled with said liquid, and a means which coacts with said piston during the operation of said'interrupter to cause a predetermined quantity of said liquid to be moved into the normally unfilled portions of said passage and to close said passage to said body of liquid.

5. In a circuit interrupter, two relatively movable contactmembers for opening and closing the circuit, and an arc extinguishing device cooperating therewith, said arc extinguishing device including a casing, at least partly of insulating material, having an arc passage therein, a body of liquid contained in said casing, one portion of said passage being above the level of said liquid, said passage being open to said body of liquid when said interruptor is in the .closed position, and piston means for moving some of said liquid into said passage during the opening of said interrupter, one of said contact members moving through said passage during the opening of the interrupter to establish an arc therein, said casing having means, operable at a predetermined pressure, for releasing a portion of the gas formed within said passage during the extinguishing oi an arc.

6. In a circuit interrupter, relatively movable contact members for opening and closing the circuit, and an arc extinguishing device cooperating therewith, said arc extinguishing device including a casing,"a body of liquid contained therein, a'means, normally free of said liquidfor dehcircuit, and anl arc extinguishing device including a4 casing, a body offliquid contained therein,

a plurality of separable plates positioned abovev said body of liquid and having openings therein,

said openings aligning to form a substantiallyclosed chamber wherein the arc incident to the interruption of the circuit is established, and means for moving some of said liquid into said passageway.

8. In a circuit interrupter, relatively movable contact members for opening and closing the circuit, land an arc extinguishing device including a casing, a body of liquid contained therein, a plurality of separable platesipositioned above said body of liquid .and having openings therein, said openings aligning to form a substantially closed chamber wherein the arc incident to the interruption of the circuit is established, and a piston, movable in response to the movement of at least one of said separable contact members for moving some of said liquid into said chamber. during each operation of said interrupter.

9. lIn a `circuit interrupter, relatively movable contact members for opening and closing the circuit,J and an arc extinguishing device including a casing, a body of liquid contained therein, a plurality of separable plates ofy insulating material positioned above said bodyl of liquid and having openings therein, means biasing said plates toward each other, said openings aligning to form a substantiallyzclosed chamber wherein thearc incident to the interruption ofthe circuit is established, and means 'for injecting some of said liquid into said chamber proximate said arc duringthe opening operation of said interrupter,

10. In a' circuit interrupter, relatively movable contact members for opening and closing the circuit, and an arc extinguishing device including a casing, a body of liquid contained therein, a plurality of separable plates having centrally disposed openings therein, said openings aligning to form a substantially closed chamber wherein the arc incident to the interruption of the .circuit is established, one end of said chamber being open to said body of liquid when said interrupter is in the closed position, and means for closing saidchamber to said body of liquid during the opening of said interrupter.

12. In a circuit interrupter; relatively movable contact members for opening and closing the circuit; a body of arc extinguishing fluid; and an arc extinguishing device including a substantially closed pressure chamber wherein an arc is established by said relatively movable contact members, piston means movable within said chamber to cause a predetermined quantity of said arc extinguishing liquid to be entrapped therein during each operation of said interrupter, the walls of vat least a portion of said chamber being dened by a plurality of separable plates of insulating material movable in response to pressure within said chamber to establish vent openings therebetween, and means biasing said plates toward each other.

13. In a circuit interrupter, means i'or dening a pair of connecting chambers, movable means having a portion for drawing an arc within one of said chambers, a body of arc extinguishing liquid within said one of said chambers for extinguishing the arc established therein by said arc drawing means, said movable means having a portion movable into said other chamber following the drawing and the extinguishing of the arc in said one of said chambers, said other of said chambers having walls at least partially of transparent insulating material, said movable means being visible through the transparent walls of said other chamber to permit visual determination of the condition of said interrupter, and means for sealing said chamber wherein the arc is extinguished from said other chamber at least during each arc extinguishing operation.

14. In a circuit interrupter; means, at least partially of insulating material, for defining a, tubular arc passage; means of conducting material for closing one end of said arc passage and for providing a terminal for said interrupter; a body of arc extinguishing liquid contained within said arc passage; arc drawing means for said interrupter,`including a contact movable through said arc passage; piston means movable to bring a quantity of arc extinguishing iiuid into more intimate contact with said arc, said piston means being actuated in response to movement of said movable contact; and means at least partially of transparent insulating material for defining a passageway which connects with said arc passage through a single opening, which opening is closed by said movable contact when said interrupter is in the closed circuit position and during each arc extinguishing operation; said arc drawing contact being moved into said passageway subsequent to the extinguishment of said arc in said arc passage and being visible through the transparent portion of said insulating means to 'permit visual determination of the circuit condition of said interrupter.

l5. In a circuit interrupter, two relatively movable contact members, one of which comprises a mpvable piston member and the other of which is movable away from the piston member, a guide means for said piston member, a. body of liquid, and means for defining the walls of an arc passage, at least. a portion of which is positioned above the normal level of said body of liquid, said piston member being movable during the circuit opening operation to cause a quantity of said liquid to be moved into said portion of said arc passage which is positioned above the normal level of said body of liquid.

16. In a circuit interrupter, two movable contact members, one of which comprises a movable piston means away from which the other contact is movable, a, body of arc extinguishing liquid, and an arc extinguishing device, including means for dening the walls of a substantially closed pressure chamber, wherein an arc is established by contact members during the circuit opening operation, and guide means for said piston means, said piston means being movable during each circuit opening operation, to cause a'predetermined quantity of said arc extinguishing liquid to be entrapped within said chamber.

17. In a circuit interrupter, two relatively movable contact members, one oi' which comprises a movable piston means, a body ofrarc extinguishing liquid, and an arc extinguishing device, in-

cluding means for defining the walls of a substantially closed pressure chamber wherein an arc is established by said contact members during the circuit opening operation, at least a portion of said wall dening means comprising a pluralityof separable plates movable in response to pressure within said chamber to establish vent openings therebetween, means biasing said plates toward each other, and guide means for said piston means, said piston means being movable during each circuit opening operation to cause a predetermined quantity of said arc extinguishing liquid to be entrapped within said chamber.

18. In a circuit interrupter, two relatively movable contact members, and an arc extinguishing device cooperating therewith, said arc extinguishing device including a body of liquid, a. plurality of separable members for defining the walls of an arc passage which is open to said body of liquid ywhen said contact members are in one position and means operable during the circuit interrupting operation to close said arc passage to said body of liquid.

19. In a circuit interrupter, two relatively movable contact members, and an arc extinguishing device cooperating therewith, said arc extinguishing device comprising a body of liquid, a plurality of contiguous laminations for denning the walls of an arc passage which is open to said body of liquid when said contact members are in one position, and piston means operable during the circuit interrupting operation to close said arc passage to said `body of liquid.

2G. In a circuit interrupter, two relatively movable contact members, and an arc extinguishing device cooperating therewith, said arc extinguishposition; said arc extinguishing means including.

ing device comprising a body of liquid, a pressure chamber, the walls of which are defined by a stack of separable, superposed plate members, at least a portion of said chamber being positioned above the normal level of said body of liquid and said contact members being adapted to establish the arc incident to the opening of said interrupter within said pressure chamber, and means operable during the circuit opening operation to cause some of said liquid to be moved into that portion of said chamber which is positioned above the normal level of said body of liquid.

21. In a circuit interrupter, two relatively movable contact membersand an arc extinguishing device cooperating therewith, said arc extinguishing device comprising a body of liquid, a pressure chamber, the walls of which are defined by a stack of s'uperposed plate members, said contact members being adapted to establish the arc incident to the openingA of said interrupter within said pressure chamber, and piston means operable during the circuit opening operation to cause a predetermined quantity of said liquid to be entrapped within said chamber.

22. In a completely enclosed circuit interrupter; a pair of separable contacts; actuating means for said contacts; means for extinguishing the arc formed incident to the opening operation of said interrupter; and means for permitting a visual determination of the position of said contacts at least when said interrupter is in the open circuit a pressure chamber wherein` said contacts are adapted to separate, means disposed within said pressure chamber for generating an arc extinguishing gas when said arc is drawn therein, and means for permitting the escape ofA said gas from said pressure chamber when the pressure thereof reaches a predetermined value; said means for permitting a visual determination of the position ofsaid contacts including a second chamber which connects with said""pressure chamber to form a unitary closure, at least a portion of the walls of said second chamber being formed of transparent material, and means which seals said second chamber from said first chamber, at least during each arc extinguishing operation, in order to prevent said arc extinguishing gas or other arc products from entering said second chamber during the operation of said interrupter.

23. In a completely enclosed circuit interrupter; a stationary contact; a movable contact which comprises a rod member of conducting material for cooperating therewith; actuating means for moving said movable Contact into and out of engagement with said stationary contact; means for extinguishing the arc formed incident to the opening operation of said interrupter; and means for permitting a visual determination of the position of said movable contact at least when said interrupter is in the open circuit position; said arc extinguishing means including a pressure chamber wherein said stationary contact is disposed and within which the arc incident to the separation of said contacts is drawn, means disposed within said pressure chamber for generating an arc extinguishing gas when said arc is drawn therein, and means -for permitting the escape oiv lsaid gas from said chamber when the pressure thereof reaches a predetermined value; said means for permitting a Visual determination of the position ofsaid contacts including a second chamber which connects with said rst chamber to form a unitary closure, at least a portion of the walls of said second chamber being formed of transparent material, and means including a' gland adapted to cooperate with said movable contact rod so as to seal said second chamber from said pressure chamber, at least during each arc extinguishing operation, in order to prevent said arc extinguishing gas or other arc products from entering said second chamber.

PAUL DUFFING.

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