US2227507A - Circuit interrupter - Google Patents

Description

Jan. 7,1941. J. B. MaoNElLL cIncuIT INTERRUPTER Filed Nov. 1, 1938 2 Shgets-Sheet 1 INVENTOR t/b/.yfff/l ATTORNE wlTNEssEs: @97m 75" M Jan. 7, 1941. .1. B. MacNElLL CIRCUIT INTERRUPTER Filed Nov. 1, 1938 2 Sheets-Sheet 2 Patented Jam?, 1941 PATENT j OFFICE f '2.221.507 cmcmr maxaman .101m s. Mmmm. wnkimbmr, rs., mmf u ufaotnring UNi'rED vsTA'rlas Westinghouse Electric t Man pany, East Pittsburg ."ennsylvania .Oom- Pa., a corporation of Application November l, 1938, Serial No. 238,122

20 (Halma.v (Cl. 20o-146) u The arc produced by the interruption of the circuit is flrst established between the arcing contacts and then transferred to arc transfer horns. Froin the horns it is drawn into a chamber where it isbrokenupand deio In circuit in'terrupters constructed in accordance with the teachings of the prior art, of which I a'm aware, the engagementbetween the arcing contacts is of the butt type. That is to say. the the arcing contact surfaces, when the circuit is closed. engage ina single plane perpendicular to the direction of-current flow. Butt arcingcontacts operate satisfactorily in cases in which the current to be interrupted and .the potential at which the interruption takes place is of moderate g magnitude. 'Wherel relatively'highvinterrupting capacity, such as is now encounteredin many generating is involved, 1 have found the circuit interruptor ofthe-prior art to be totally inadequate.

n In a particular case an interrupting capacity of 900,000 kllovolt amperes at l5 kilovolts was required. Numerous-experiments were carried out in an endeavor to required interruptins capacity with the circuit interrupters of the 35 prmrart. ywnue incertain cases moderate success was achieved, the results were on the whole unsatisfactory. lThe principal ydinlcu'lty which was encountered in theattempted-use of the prior art circuit breakers was that the arcing contacts .o failed to' localize the arc inthe region of the horn towhichit wastobe transferred. Inmany cases the arc was ignited in regions in the circuit breaker apparatus Awhere it could not possibly be It is, accordingly', a general object of my invention to provide a circuit'interrupter having high interrupting capacity of the order of aty least' 900,000 kilovoitamperes at i5 kilovolts. Another object of my invention is to provide an 50 air circuit lnterrupter'for interrupting high cur--` rent at mtstsngm potentials in which the am provide an arcing contact arrangement for an air circuit interrupter such that the transfer of the arc into the extinction chamber and its extinction shall be expedited.

My invention arises from a detailed analysis of the operation of a circuit interrupter and of the demands made upon it by the circuit to be interrupted. It is based on the realintion, as an outgrowth of the investigation, of the principal causes for thefailure of the arc to be localized in the desired region; A primary condition imposed on a circuitLbreaker is that it shall prevent the flow of over-currents or short circuit currents for any appreciable length of time. The interrupting elements of a vcircuit breaker must. therefore, operate at a relatively high speed. For the current and voltage involved in the present situation,

ythe time required for the contacts to reach a full `open position should be not more than .l second or 6 cycles of the 60-cycle frequency most often encountered. 'Ihe time required for both pairs of cbntactsto part should be at most 3.5 periods of the 6 periods. Of the 3.5 periods the opening of the current carrying contacts vconsumes of the order of 3.3 periods and the opening of the arcing contacts .2 period or .0033 second. It is the last mentioned short interval o! time which is the source of the principal difficulty arising in the use of butt arcing contacts'.

During normal closed circuit operation both the arcing contacts and the current carrying contacts are closed and the current divides itself between them, a greater portion flowing through the current carrying, contacts since the resistance between the .arcing contacts is relatively high. When the circuit is being opened, therel is a rush of current to the arcing contacts at the instant at which the current carrying contacts are Just opened. However, at the same time a small potential difference remains between the latter contacts and a small spark is produced between them.

The arcing contacts should now yremain. closed until the spark is extinguished. i. e.. of the order of .2period. Ifthishappenathearcislocaliaed at the arcing contacts and is properly drawn into the extinction chamber. The difficulty with the prior art circuit breakers is that in their operation this desirable condition does not exist.

When the current carrying contacts are iust opened andeven while they are opening, the sudden rush of current tothe 'arcing contacts produces a mag'ne lc'force causing the arcing contacts to be blo open before they shouldbe opened in normal operation. The arcing contacts thus open before' the spark between the current carrying contacts has been completely extinguished and the result is that the arc instead of being ignited between the arcing contacts is actually ignited between the current carrying contacts. Since there is no provision in the circuit interrupter for extinguishing the arc in the region of the current carrying contacts, it continues to burn and eventually not only are the contacts destroyed but the apparatus in the circuit which is being interrupted is materially damaged.

It is seen from the foregoing analysis that the solution of the problem which arises here involves the prevention of the premature opening of the arcing contacts. It will be noted in solving this problem, the introduction of a substantial delay between the opening of the current carrying contacts and the opening of the arcing contacts is not practicable in view of the fact that the interrupter must be completely opened in a short time. It is the sequence of the operations which must be maintained and timed, and the proper sequence can only be attained if each operation occurs at precisely the instant that it should occur and not prematurely.

To obtain the desired timing of the operations, I provide cooperative arcing contacts which are with certainty prevented from opening prematurely. One of the arcing contacts is of the iinger type and clamps the other the more tightly as the current in the region of the engagement of the contacts increases. The arcing contacts can, therefore, only open when receiving the proper impulse from the releasing mechanism. The electromagnetic stresses in the region of the contacts are large at the instant that the arc is ignited since the power interrupted is high. Hence after the arc .has been ignited it may happen that under the enormous electric and magnetic nelds it is drawn to parts of the apparatus where its presence is undesired. To suppress this undesired condition, the arcing contacts are, in accordance with my invention, of a form such that the current flow at the point of nnal interruption is in a loop convex towards the adjacent arc horn. The tendency of the arc in such a loop is to increase in its radius of curvature and, therefore, the arc moves towards the arc horn and is quickly transferred thereto. In accordance with a further aspect of my invention, the arc uhorn adjacent to the arcing contacts is moreover disposed as closely as possible to the point at which the arc is formed. To attain this desideratum the are horn is slotted in a direction parallel to the planes of the engaging surfaces of the fixed and movable arcing contacts and the moving arcing contact penetrates into the slot without engaging its sides.

'I'he novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation together with additional objects and advantages thereof will best be understood from the following description of a specific embodiment when read in connection with the accompanying drawings, in which:

Figure 1 is a view in front elevation, partly in section, of a circuit interrupter constructed in accordance with my invention,

Fig. 2 is an enlarged view in side elevation of the contacts of the circuit interrupter shown in Fig. 1, and

Fig. 3 is a plan view of the contacts shown in Fig. 2.

The apparatus shown in the drawings comprises an arc extinguishing chamber 5 formed between composite metallic uprights 1 and 9 and covers Ilot insulating material secured to the uprights. Each upright 1 and 9 consists of a channel beam I3 with transverse plates l5 welded to the edges of the lower opening in the channel.

The transverse plates I5 have a total width less than that of the channel and longitudinal plates |1 extend from the inner edges of the transverse plates forming between them an elongated opening of smaller width thanthat of the channel. 'Ihe web of each channel is provided with openings near its four corners and with a central opening. Through the corner openings insulating bars l5 of phenolic condensation material pass and on them the plates 2| whereby an arc is broken up and deionized, are stacked. Cylindrical insulators 33 and 24 abut the central openings and a conducting bar 25 passes through the openings and the insulators.

The deionizing stack 2| is of the usual structure comprising vertical iron and copper plates with iish paper insulating sheets between them. One form of such a deionizing stack is shown in Slepian Patent No. 1,927,904, issued September 26, 1933, and it will not be described herein detail.

Ihe longitudinal plates I1 extending from the channels 3 rest on base blocks 21 to which they are secured. The openings in the channels I3 face-away from the deionizing stack 2| and cover plates 29 are provided for these openings and the coextensive opening between the plates l1. The channels |3 and the coextensive plates i1 thus form flues through which the gases generated on the interruption of a circuit are exhausted.

The fixed current carrying contact assembly 3| and lthe ilxed arcing contact assembly 33 are mounted in a box-shaped casting 35 which is supported below the left-hand upright 1 on parallel columns 31. The latter columns are preferably composed of a phenolic condensation material. The upper ends of the columns 31 engage lips 39 projecting from the casting 35 and the lower ends are secured to a suitable supporting frame 4I. The columns 31 are held laterally by blocks 43 and 45 bolted respectively to the casting 35 and the frame 4|.

A large double walled beam 41 in the form of a right angle, with the wall spacing equal to the distance between the columns 31, is supported by the columns 31 and by a pair of short columns 4I of similar material. The angle 41 is disposed with its sides 5| and sa horizontal and vertical respectively. 'I'he horizontal sides 5| are secured at the ends to the centers of the long columns l1 and the short column 49 passes through the apex of the angle and engages lips 54 projecting from the vertical sides 53. The vertical sides 53 of the angle are coextensive with the column 49. 'The columns 31 and 49 and the angle 41 are held laterally by blocks 55, 51 and 59 which are bolted to the parts to which they are secured.

The horizontal sides 5| of the angle 41 serve as bearing supports for the pins 6| and 53 which carry at their centers the movable contact arm 5l and the spring 51 whereby the arm is actuated. The pins 5| and 53 are rotatable in their bearings and the arm 55 and spring 51 may pivot about the axes of the pins. The width of the horizontal side 5| .of the angle 41 is such that the vertical side 53 is coextensive with the righthand upright 9 of the arc extinguishing assembly 5.

The uprights 1 and 9 rest on the casting 35 and on the vertical sides 53 of the angle I1. For

this purpose, a slab 89 is secured to the Aupper ends of the vertical sides 53. The slab 89 is fastened to the right-hand block 21 and thus supports the right-hand upright 9. The left-hand block 21 rests on an insulating washer 1| sup-y ported on a horizontal projection 13 extending from the casting 35. Below the projection 13 a second insulating washer 15 is provided and the projection is secured to the block 21 by a bolt 11 extending through the washers and the projection and insulated from the projection by a sleeve 19.

From the upper surface of the casting 35 and from the slab 89 extend studs 8| and 83 respectively, which are adjustable in height. Composite boards having internal insulating faces 85 are supported on the studs and secured to horizontal studs 81 projecting on both sides from the upright plates I1. A chamber extending from the deionizing stack 2| to the circuit interrupting contacts 3|, 33 and 89 and 9| is thus formed between the boards. The arc is moved through the chamber into the deionizing stack 2|.

The specific structure of the arc chamber does not concern the present invention. However, briefly, its walls are composed internally of brous insulating material 85, in which inserts 93 of a. refractory insulating material are disposed, and externally of iron (not shown). In Fig. 1 the interior surface 85 of a single wall is shown. The other wall is of similar structure but has been removed for the purpose of showing the interior of the chamber.

Within the arc chamber arc transfer horns 95 and 91 are provided. The horns are secured to the channels I3 and tothe plates I1 coextensive with the channels, the left-hand horn 95 being fastened to studs 99 which project outwardly from the faces of the left-hand plates l1. The tip of the left-hand horn is located immediately adjacent to thecontact terminals |03 of the ilxed arcing contact assembly 33.

The ilxed current carrying contact assembly 3| is of composite structure comprising a pair of contact terminals preferably composed of silver plated copper. The ends of the terminals |05 are slotted and in the slots (not shown) flexible shunts |01 composed of thin ribbons of copper are fastened, preferably by sweating. At the other ends, the shunts are bolted to a tail projection |09 integral with the casting 35. The fixed arcing contact assembly 33 is of similar composite structure comprising a pair of contact terminal elements |03 slotted at their ends. The

yslots receive the strandsof the shunts ||3 |03 and |05 may pivot in a direction perpendicular to their faces about the pins. Ihe blocks of each pair of terminals are urged into engagement with each other by springs I9 wound on pins 2| extending through the walls of the4 casting 35, through the terminal blocks transverse to their sides. The engagement between the pins |2| and the blocks of the terminals |03 and |95 ,is loose so that the blocks may slide along the pins. The pins |2| are' secured to the walls of the casting and the springs ||9 rest in recesses |23 in the walls engaging the walls on the one hand and the sides of the terminal blocks on the other. The fixed current carrying and arcing terminals |05 and |03 arethus of the slotted or finger type with the walls of the slots or fingers resiliently urged into engagement with each other.

The fixed arcing terminal |03 is' composed of blocks of silver-plated copper, each ,of which is provided with inserts |25 and |21 of silvertungsten alloy. The alloy is arc resistant and, therefore, is not deteriorated by the arc generated at the terminal.

The movable contact assembly 95 is of composite structure consisting of a heavy steel support |29 to which a copper contact carrier |3| is secured. Near the upper end of the carrier `|3| the movable'arcing contact 89 projects; the mov.. able current carrying contact 9| is parallel to the contact 89 from a position below the latter. The movable contacts 89 and 9| are of the knife type adapted to be engaged and held firmly by the resiliently pivoted blocks making up the corresponding fixed terminals |03 and |05.

The movable current carrying contact 9| is composed of silver plated copper and is prefer-l ably attenuated at its end |33 so as to limit the space necessary for the contacts when in engagement. The movable arcing contact is similarly attenuated at its end |35 and in the attenuated region is provided with inserts |31 and |39 of the arc resistant silver tungsten alloy.

The fixed arcng contact terminal |03 projects into the arc space -5 and, as has been-explained, is adjacent to the tip |0| of the left-hand arc transfer horn 95. So as to expedite the movement of the are into the arc space, the horn 95 is slotted near its tip |0| and the movable contact 89, when the circuit breaker is in the closed position, penetrates into the slot ill.

The movable contact assembly is actuated by a rod |43 which may be moved in the usual manner by an electromagnetic system. The specific moving structure is not shown as it does not concern the present invention. In general, the rod |43 is pivotally connected tothe actuating system at its lower end |45. At its upper end |31 the' rod engages the common movable pivot pin |49 of a pair of sets of toggle arms |5| and |53. The former set |5| pivots about a fixed pin |55 secured to the vertical sides 53 of the angle 41 and the other, |53, about a pin |51 in the steel support |29 of the movable contact assembly 55. Below the latterv pivot pin |51 the circuit opening spring 61 is secured to pivot pin |59. The movable contacts 89 and 9| are disengaged from the xed contact terminals |03 and |05, respectively, by the action of the spring 51` when the mechanism whereby the rod |43 is moved into and held in the closed position is released. In open- -ing the movable contact assembly 65 strikes against a shock absorbing stud |6| and thus is not damaged.

I When the circuit interrupter is in the closed position, the current is primarily carried'by the current carrying contacts 9| and 3| since the resistance between the arcing contacts 89 and 33 is relatively high. The current carrying contacts and the arcing contacts are so positioned in their respective supportsthat when the circuit breaker opens the current carrying contacts 9| and |05 are first disengaged and then the movable arcing contact 89 is disengaged from the flxeu arcing fingers |03. An arc is, therefore, produced between the latterelements. When the current carrying contacts are opening, the current in each of the arcing fingers |03 is increasing. Since the current paths through the fingers are parallel and in the same direction, the effect of the resultant increasing magnetic fields is to cause theflngers to hold the fixed contact l! more tightly until the moment for release as determined by the moving mechanism arrives. 'Ihe establishment of an arc at the current carrying contacts and Il! by reason of the opening of the arcing contacts Il and |05 only a very short fixed interval after the opening of the currenti'carrying contacts is thus entirely precluded. I

The fixed inserts |21 in the arclng contact terminal |03 are in the form of tips extending upwardly towards the tip Ill of the arc horn I5. The fixed arcing contact assembly I3 is moreover so disposed in the casting 35 that the direction of the current ow in it between the region of separation of the contacts and the point of connection of the line at the instant of interruption is first at a small angle to the horizontal and, as the point of interruption is approached, at an angle rapidly approaching the vertical. The insert |39 of the cooperative movable contact I0 is also in the form of a tip so positioned that it engages the inserts |21 when the contacts 80 and |03 are last in engagement during the opening operation. 'I'he contour of the'inserts |21 and Il! is such that at the point of final disengagement, the sides of the inserts |21 and i form an acute angle having its apex at the extreme upper region of the contacting surfaces, the apexbeing also the point of last engagement of the contacts. It happens, therefore, that in the region of separation of the arcing contacts the current flow is in a sharp loop convex towards the tip IUI of the adjacent arc transex' horn QI. For this reason when the arc is produced, it also is in a sharp loop convex towards'the tip Ill as shown in Fig. 2, and since the electromagnetic effect of current flowing in a loop is to increase the radius of curva.V ture of the loop, the arc produced decreases its curvature towards the tip |0| vand is quickly transferred to the horn I5.

By the transfer of the arc to the horn l5, an inductance loop is closed. The loop consists of vertical straps |63 extending betweenthe projection 13 of the rod 25 passing through the insulator 23, vertical straps |65 extending from 'the remaining end of the rod 2l, a pair of rods |61 extending from the lower ends of the straps |85 outside of the arc chamber 5, metallic strips |09 extending from the remaining ends of the latter rods |01 to the lugs 99 to which the arc transfer horn II adjacent to the' fixed arcing contact I3 is secured. When the arc is transferred to the horn, a circuit is completed through this loop which extends from the line connection to the i'ixed contacts 2| and 33 through the strapsi, the bar 2i, the straps |65, the rods |01, the strip I, the arc horn $5, the movable contact assembly tl to the other line connection. By the action of the inductive loop, the arc is now transferred to the other arc horn 91. Since the latter horn is connected to the right angle 41, the circuit through the inductive loop is not broken and the movement of the arc continues upward until it passes into the deionizing assembly and is extinguished.

Although I have shown and described certain specific embodiments of my invention, I am fully aware that many modifications thereof are possible. My invention, therefore, is not to be restrictof the casting l5 and the adjacentv end A edexcept insofar as is necessitated by the prior art and by the spirit of the appended claims.

I claim as my invention:

l. A high voltage air circuit breaker having an interrupting capacity of at least 60,000 amperes comprising fixed land movable contact means through which the current passes when the circuit is closed, a chamber containing arc extinguishing means, mean.; including an arc-transfer horn for drawing an arc into said chamber, and additional nxed and movable contact means disengaged after said first named contact means when the circuit is being opened, said additional contact means comprising a pair of cooperative elements one of which is in the form of a slot into which the other penetrates engaging the sides of the slot ilrmly when the circuit is closed, said cooperative elements having portions nearest said chamber and arc-extinguishing means which disengage last on opening of the circuit, and said horn extending to a point immediately adjacent to the region in which said additional contacts are last engaged when the circuit is being opened and between said region and said chamber.

2. Circuit interrupting apparatus comprising fixed and movable contact means between which an arc is ignited when the circuit is interrupted, a chamber containing arc extinguishing means, and means including an arc transfer horn for drawing said arc into said chamber, said horn being disposed adjacentto a portion of said fixed and movable contact means when they are in engagement and between said chamber and said portion, said portion comprising cooperative contact elements one of which is in the -form of a slot into which the other penetrates engaging the walls of the slot firmly when the circuit is closed,

said elements being so disposed on said contact means that they are disengaged last when a circuit is being opened, the walls of said slot near said horn being formed with tips extending toward said chamber, the cooperative element being provided with a tip at a point such that said last mentioned tip and the tips on said wall are disengaged last when said circuit is being opened and said contact means being so arranged that Just before the contacts part the current flow in the region of lastA engagement is in a loop convexed toward said chamber.

3. Circuit interrupting apparatus having an interrupting capacity of the order of 900,000 kilovolt amperes at 15 kilovolts and operating to completely open a circuit in an interval of time of the order of .10 second comprising nxed and movable contact means between which the current is transferred when the circuit is closed, a chamber containing arc extinguishing means, means including an arc-transfer horn for drawing an arc into said chamber, and additional fixed and movable contacts disengaged after said first named contact means when the circuit is being opened and through-which the current is shunted upon separation of said flrst-named contact means, said additional contacts comprising a pair of cooperative elements one of which is in the form of a slot into which the other penetrates engaging the sides of the slot firmly when the circuit is closed, the sides of said slots being provided with tips extending towards said chamber and the other cooperative element of the pair being provided with a tip, said tips being so arranged that they are in engagement last when said circuit is being opened and said additional contacts being so arranged that the current flow in the region of saidI tips when the circuit is being opened is in a loop escaso? S convexed toward said chamber, and said horn extending to a point immediately adjacent to the region in which said additional contacts are last engaged when the circuit is being opened and between said region and said chamber.

4. A- high voltage air circuit breaker having an interrupting capacity of at least 60,000 amperes comprising xed and movable contacts in engagement with each other over a substantial area when the circuit is closed, means for disengaging said' contacts, the disengagement of the contacts being a gradual operation starting in one region of said contacts in engagement and ending with the ignition of an arc an interval of time of the order of .05 second later in another region of said contacts, one of the contact means in said other region being in the form of a slot into which the other penetrates engagingthe walls of the slot firmly when the circuit is closed, a chamber including arc-extinguishing means, means including an arc transfer horn for transferring said arc into said chamber, said arc transfer horn being disposed immediately adjacent said other region of said contacts, and means for causing l said arc to be transferred from one said contacts in said other region to said horn and from said horn to said chamber.

5.i Circuit interrupting apparatus comprising fixed and movable contacts in engagement with each other over a substantial area when the circuit is closed, means for disengaging said contacts, the disengagement of the contacts being a gradual operation starting in one region of said contacts in engagement and ending with the ignition of an arc an interval of time of the order of .05 second in another region of said contacts, one of the contacts in said other' region being in the form of a slot in to which the other penetrates engaging the walls of the slot firmly when the circuit is closed, a chamber including arc-extinguishing means, means including an arc transfer horn for transferring said arc into said chamber, said arc transfer horn being disposed immediately adjacent said other region of said contacts and having a slot therein penetrated by said other contact in said other region when said contact means are in engagement, and means for causing said arc to be transferred from one said contact means in said other region to said horn and from said-horn to said chamber.

6..An air circuit breaker comprising current carrying contact means, a chamber including arc extinguishing means, an arc transfer horn for transferring an arc into said chamber, means for localizing the arc generated by the interruption of a circuit in the region of said horn including arc ing contact means, incorporating a slot-shaped contact element and a cooperative contact element which penetrates said slot-shaped element and engages the walls of the slot when the circuit is closed, said contact 'elements having portions disposed immediately adjacent said horn which disengage last during opening of the circuit, and means for opening said current carrying contact means and, an`interval of vtime of thelorder of .003 second after said current carrying contact means have opened, opening said varcing contact means, and means for lcausing the arc generated at said arcing contacts and transferred to said khorn to` be transferred from said horn. ito said chamber. I

7. Apparatus according 'to claim 6 characterized by the fact that the horn is disposed between the arcing contacts and the chamber and the coj operative contact elements are so shaped that the current now at the instant of interruption at said elanents is convexed towards said horn and said chamber.

8, Circuit interrupting apparatus having an interrupting capacity of the order of 900,000 kilovolt amperes at 15 kilovolts comprising a ilxed current-carrying contact of the finger type, a movable current-carrying contact of the knife type to engage said fixed contact, a chamber containing arc'extinguishing means, an arc transfer horn for moving an arc into said chamber, means for localizing the arc generated by the interruption of a circuit inthe region of said horn including a fixed arcing contact of the finger type disposed adjacent to said horn, a movable arcing contact of the knife type to engage said fixed arcing contact when said circuit is closed, said arcing contacts having portions nearest said horn which disengage last upon opening of the circuit, and means for opening said current carrying contacts and, aninterval of time of the order of .003 second after the opening of said current-carrying contact, opening said arcing contacts, and. means for transferring the arc ignited by the opening of said arcing contacts and transferred to said horn from said horn to said chamber.

9. Circuit interrupting apparatus comprising a fixed current-carrying contact of the finger type, aimovable current-carrying contact of the knife type to engage said fixed contact, a chamber containing arc extinguishing means, an arc transfer horn for moving an arc into said chamber, means for localizing the arc generated by the interruption of a circuit/in the region of said horn including a xed arcing contact of the linger type disposed adjacent to said horn, a movable arcing contact of the knife type to engage said fixed arcing contact when said circuit is closed, said movable arcing contact penetrating said horn and said horn being slotted to receive said arcing contact, and means for opening said current-carrying contacts and, an interval of time of the order of .003

, second after the opening of said current-carrying contacts, opening said arcing contacts, and means for transferring the arc ignited by the opening of said arcing contacts and transferred to said horn from said horn to said chamber. y

10. Circuit interrupting apparatus comprising a xed current-carrying contact, a movable currentl carrying contact tov engage said fixed con- 4tact, a chamber containing arc extinguishing circuit is closed, said movable arcing contactY penetrating said horn and said horn being slotted to receive4 said arcing contact, and means for open-ingsaid currentl carrying contacts and immediately thereafter opening said arcing contacts,

1l. Circuit interrupting apparatus comprising-af xed current-carrying contact of the ingerptyp'e's" a` movable current-carrying contact ofthe-knife type to engage said fixed contact, a chamber corr--A taining arc extinguishing means, an arc transfer?. horn for moving anarc into said chamber, means for localizing the arc generated by the interrupfk tion of a'circuit in the'region of, said horn includ-- ing a ilxed arcing contact of the finger type dis-I posed adjacent to said horn, a movable arcingl contact of the knife type to engage said fixed arcing contact when said circuit is closed, said arcing contacts having portions nearest said horn which disengage last upon opening of 'the circuit, and means for opening said current-carrying contacts and, an interval of time of the order of .003 second after the opening of said current-carrying contact, opening said arcing contacts, and'means for transferring the arc ignited by the opening of said arcing contacts and transferred to said horn from said horn to said chamber.

12. Circuit interrupting apparatus comprising fixed and movable contact means in engagement with each other over a substantial area when the circuit is closed, means for disengagini said contactmeans, the disengagement of the contact means being a gradual operation starting in one region of said contact means in engagement and ending with the ignition of an arc in another region of said contacts, one of the contact means in said other region being in the form of a slot into which the other penetrates engaging the walls of the slot firmly when the circuit is closed, a chamber including arc-extinguishing means, means including an arc transer horn for transferring said arc into said chamber, said arc transfer horn being disposed immediately adjacent said other region of said contacts and having a slot therein penetrated by said other contact in said other region when said contact means are in engagement, and means for causing said arc to be transferred from one said contact means in said other region to said horn and from said horn to said chamber.

13. In a circuit interrupter, fixed contact means comprising a pair of pivoted finger contacts, a pair of flexible shunt conductors connected to" said finger contacts, said finger contacts being biased towards each other by the parallel current ow through said finger contacts when the interrupteris closed, a cooperating movable knife contact firmly engaged on opposite sides byv said finger contacts when theinterrupter is closed, means forming a chamber containing arc-extinguishing means, said contacts having portions disposed nearest said chamber which disengage last when the circuit is opened, and means including an arc transfer horn for drawing an arc into said chamber and extinguishing means, said horn being disposed immediately adjacent the portions of said contacts which disengage last and between said chamber and said portions of the contacts.

14. In a circuit interrupter, fixed contact means comprising a pair of finger contacts, a cooperating movable knife contact firmly engaged on. op.- posite sides by the finger contacts when the interrupter is closed, Ameans forming a chamber containing arc-extinguishing means, said finger contacts and knife contact having portions nearest said chamber which are disengaged last on opening of the circuit, and means including an arc horn for drawing the arc into said chamber and extinguishing means, said arc horn being disposed immediately adjacent the portions of said contactswhich are last disengaged and between said arc-extinguishing means and said portions of said contacts.

15. In a circuit interrupter, fixed contact meansl comprising a pair of nger contacts, a cooperating movable knife contact posite sides by the finger contacts when the interrupter is closed, means forming a chamberl containing arc-extinguishing means, said contacts having tips nearestsaid chamber andarcfirmly engaged on opextinguishing means which are disengaged isst on opening of the circuit, and said contacts and theirtipsbeingarrangedsothatthecurrentiiow when the circuit is being opened is in a loop convexed toward said chamber, and means including an arc horn for drawing the arc into said chamber and extinguishing means, said arc horn being disposed immediately adjacent the tips of Asaid contacts and between said arc-extinguishing means and said tipsof the contacts.

16. In a circuit interrupter, fixed and movable main contact means, additional contact means through which the current is shunted upon sep ration of said main contact means, said additional contact means being disengaged after said main contact means when the circuit is opened and comprising a pair of finger contacts and a cooperating movable knife contact firmly engaged on opposite sides by said finger contacts, means forming a chamber containing arc-extinguishing means, said finger contacts and said knife contact having tips nearest said chamber and arcextinguishing means which are disengaged last upon opening of the circuit, said contacts being arranged so that the current now in the region of the tips when the circuit is being opened is in a loop convexed toward the chamber and srcextinguishing means, and means including an arc transfer horn for transferring the arc into said chamber and arc-extinguishing means, said are horn being disposed immediately adjacent the tips of said contacts and between said src-extinguishing means and said tips.

17. In a circuity interrupter, stationary contact means comprising a pair of main nnger contacts, a pair of arcing finger contacts, and s cooperating movable knife contact firmly engaged on opposite sides by the finger contacts, said knife contact being adapted to separate from said main nnger contacts before separating from said arcing finger contacts, means forming a chamber containing arc-extinguishing means, said arcing nnger f contacts and the cooperating portion of said knife contact having tips nearest said chamber and arcextinguishing means which disengage last upon opening of the circuit and arranged so that the current now in the region of the tips when the circuit is being opened is in s. loop convexed toward the chamber and the arc-extinguishing means, and means including an arc transfer horn for transferring the arc into said chamber and arc-extinguishing means, said horn being disposed immediately adjacent the tips of said contacts and between said arc-extinguishing means and said tips.

18. In a circuit interruptor, fixed contact means comprising a pair of nnger contacts, s cooperating movable knife contact firmly engaged on opposite sides by the finger contacts when the inter-4 rupter is closed, means forming a chamber containing arc-extinguishing means, said finger ccntacts and knife contact having portions nearest said chamber which are disengaged isst on opening of the circuit, and means including an src horn for drawing the arc into said chamber and ex means, said are horn being disposed immediately adiacent -the portions of said contactswhichsr'elsstdisengsgedsndbetweensaid src-extinguishing means ma nid pertain or und contacts, and said are horn having a slot adjacent said portion of said contacts which is penetrated by the end of the knife contact when the interfrupter is closed.

19. A circuit breaker comprising opposed substantially parallel nnger contacts, s cooperating movable knife contact ilrmiy engaged on opposite sldesbysaidnngercontactswhenthebreakeris closed, a chamber containing arc extinguishing means, and means including an arc horn for drawing the arc into said chamber, said horn being disposed adjacent to said iixed and movable contacts when theyy are in engagement and between said chamber and said contacts, said contacts having portions nearest said horn which are disengaged last when the circuit is being opened.

20. An air circuit breaker comprising stationary and movable main current carrying contacts. auxiliary contacts through which the current is shunted upon separation oi said main contacts,

il said auxiliary contacts being disengaged alter said main contacts when the circuit is opened and comprising a pair ot iinger contacts and a cooperating movablerknife contact nrmly engaged on opposite sides by said ilnger contacts and rigidly secnred for movement with the movable main contact, a chamber containing arc extinguishing means adjacent said auxiliary contacts, said iinger contacts and said knife contact having tips nearest said chamber and arc extinguishing means which are disengased last upon opening o! the circuit, and means including an arc horn for transferring the arc into said chamber, said horn being disposed immediately adjacent the tips of said auxiliary contacts and between said arc extinguishing means and said tips.

JOHN B. MACNEILL.

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