US2077338A - Circuit interrupter - Google Patents

Description

April 13, 1937. H. J. LING'AL ET AL CIRCUIT INTERRUPTER Filed Sept. 12, 1934 2 Sheets-Sheet 1 INYENT Harry-f llflga/ and WITNESSES A'TTORNE H. J.LINGAL ET AL CIRCUIT INTERRUPTER April 13, 1937.

2 Sheets- Sheet 2 Filed Sept. 12, 1934 WITNESSES: d7ff%z.

Patented Apr. 13, 1937 UNITED STATES PATENT OFFICE cIncUrr mmaamaa Application September 12, 1934, Serial No. 743,696 20 Claims. (01. 200-150) Our invention relates generally to circuit interrupters and has particular application to contact structures for high-capacity electric switches.

In recent years, it has become increasingly common practice in the electrical art to interconnect alternating current power distribution systems into large networks which may extend over large areas, and which may include a great number of separate sources of power. These systems ordinarily transmit alternating current power at high voltages, which fact in combination with the large amounts of available power, causes the problem of circuit interruption of fault currents to be one of'particular seriousness.

To insure system stability, even very large overloads must be interrupted within extremely short periods of time, often less than one cycle. This necessitates extremely rapid movement of the separating contact members in order that 9 an arc of considerable length may be drawn during the allowable period of circuit interruption. At the same time, the amount of power whichmay be transmitted over the circuit is often comparatively large, thereby necessitating the use of contact members having a very considerable cross-sectional area. In other words, while the contact members must be moved rapidly to prevent undesirable circuit disturbances, those members must be quite large physio cally, due to the considerable amounts of power normally carried therethrough. The problem is further aggravated, because of the fact that the increasingly high voltages in use on network systems necessitates a comparatively large amount of contact separation to prevent the are from restriking during the circuit interrupting operation.

'The principal object of our invention, therefore, is to provide an improved, high capacity circuit interrupter for use with high-voltage circuits, our improved device toinclude means for effecting a very rapid separation of the cooperating contact members within an extremely short period of time. This principal-object of our invention is accomplished through the provision of a contact structure which includes two pairs of separable contact members, oneof which is separable prior to-the other during the circuit interrupting operation, and means whereby the heated are products resulting from the separation of the first pair of separable contact memhers is caused to effect a more rapid separation of the second pair of separable contact members than could be effected by the actuating mechanism alone. In the preferred embodiment of this arrangement, one of the pairs of separable contact members opens within a pressure chamber which is filled with a gas evolving substance, and the pressure of the resulting gas is caused to actuate a movable piston which. effects the separation of the second pair of separable contact members.

A further object of our invention is to provide a simple contact structure wherein the energy of a short are may be utilized for eifecting the separation of a pair of contact members which are disposed within an arc extinguishing device.

These and other objects of our invention will be made more apparent by reference to the accompanying drawings wherein are shown two modifications oi the structure of our invention:

Figure 1 is a sectional view, partially in elevation, showing a circuit interrupter utilizing contact structures according to our invention;

Fig. 2 is a sectional view through one of the contact structures and one of the are extinguishing devices embodied in the circuit interrupter shown in Fig. 1;

Fig. 3 is an enlarged sectional view on the line IIIHI of Fig. 2;

Fig. 4 is a sectional view on the line IV--IV of Fig. 2;

Fig. 5 is a sectional view through a modified form of contact structure which may be used with the device shown in Figure l;

Fig. 6 is a sectional view on the line VL-VI of Fig. 5; and

Fig. 7 is a sectional line on the line VII- VH of Fig. 2.

The circuit interrupter illustrated in Fig. 1 is of the conventional, double-break, fluid immersed type. 'It includes a tank I having the cover 3 bolted thereto, a pairof insulating bushings 5 mounted on the cover through suitable flanges 1 and bolts 9, a pair ofstationary contact structures ll, one of which is affixed to the lower end of the conductor 13 disposed within each of the insulat- =-ing bushingsi. an arc extinguishing device l5 associated'. with each of the contact structures H,

albridging member ll adapted to electrically conblage II, and thence through the conductor 3 disposed within the right-hand bushing 5.

The contact structures II and the arc extinguishers 5 are normally submerged in a body of insulating fluid 2|] which is contained within the tank I. This fluid- 20 is preferably one which is capable of evolving considerable amounts of arc extinguishing gas when placed in proximity to an electric are, both to facilitate the are drawing operation of the contact structures and the extinguishing operation of the arc extinguishers. Oil is a satisfactory fluid.

The preferred embodiment of the stationary contact structures of our invention is illustrated in Fig. 2, and each of these includes a support member 2| adapted to be bolted to the end of the conductor l3 disposed within the cooperating bushing 5, a casing 22, which defines the outer walls of a pressure chamber, aiflxed to the support member 2| through the agency of a flange 23 and a threaded tubular member 25, and a pair of movable contact members 21 and 29, one of which (21) is positioned within the tubular member 25 and the other of which (29) is positionedwithin the pressure chamber 22. The lower end of the casting which defines the pressure chamber 22 terminates in a flange 3| which is adapted to serve as a support for the cooperating arc extinguishing device l5.

The upper contact member 21 is supported for slidable movement by means of a guide member 33 positioned within the tubular member 25 and is biased in the direction of the arc extinguishing device l5 by means of a spring 35. The upper end 31 of the contact member 21 is enlarged, and this enlarged portion is adapted toengage a suitable cooperating portion 39 formed within the guide member 33, the portions 31 and 39 being so related that they form a dashpot. which regulates the downward movement of the contact member 21 under the action of the biasing spring 35. A flexible shunt 4| serves to electrically connect the upper contact member 21 with the contact support 2|.

The pressure chamber, as is shown particularly in Figs. 2 and 4, comprises a pair of cast, hollow cylinders 22 and 42, one of which (42) is disposed within the other. The space 43 between the outer and the inner cylindrical members comprises the pressure chamber proper and it is within this space that the cooperating contact surfaces of the'upper contact member 21 and the lower contact member 29 are adapted to separate.

The space 44 within the inner cylindrical member comprises a piston chamber whichdirectly connects with the pressure chamber 43. An insulating plate 45,,suitable insulating bushings 41, and insulating washers 49 serve to electrically insulate the pressure chamber structure and the lower contact member 29 from the flange 23 and the upper contact member 21. A small vent opening 5| is formed within the flange 23 in order that the pressure chamber 43 may connect with the main body of liquid contained within the breaker enclosure.

The lower contact member 29 is provided with a circular support plate 53 rigidly aflixed thereto at. its mid-portion and is adapted to be slidably supported through the agency of a suitable guide opening 55 formed in the member 51 which encloses the top of the piston chamber 44 and a similar guide opening 59 in the bottom of the main closure 22 of the pressure chamber. A spring 6|, within the piston chamber 44, engages the support plate 53 and biases the second contact member 29 in the direction of the arc extinguishing device l5. A piston member 63 is normally positioned within the lower portion of the piston chamber, and when moving therein is free to slide for a short distance on the lower contact member 29. A vent opening 65 leads from the piston chamber 44 to the main body of liquid.

The lower end of each of the lower contact members 29 extends into one of the arc extinguishing devices..|5 which is shown particularly in Figs. 2 and 7. The particular form of this arc extinguishing device is not an important feature of our invention, but we prefer to use a structure similar to' that shown in Patent No.

l,911,072,"which was issued on an application of L. W. Dyer, et al., on May 23, 1933, and which is assigned to the assignee of this invention. This type of arc extinguishing device comprises essentially a plurality of superposed plates of insulating material having aligned slots therein, these slots being adapted to form a groove or passage 61 which is entirely lined with insulating material and within which the arc is drawn, and being provided with cut-out portions 69 along the sides thereof. The cut-out portions 69 form pockets for retaining the arc extinguishing fluid along the sides of the passage 61 wherein the arc is drawn. The various plates are held together by four through bolts which extend through insulating tubes 12. In addition to the insulating plates which define the walls of the arc passage, each of the arc extinguishers I5 is provided with a plurality of spaced, slotted plates 1| of magnetic material, which cause the arc to move transversely within the groove or are passage 61 during the arc extinguishing operation by virtue of the magnetic effect exerted thereon. This transverse movement brings the arc into contact with the arc extinguishing fluid retained in the pockets 69 disposed along the arc passage. The fluid retained therein is volatilized, and the resulting gas is caused to flow transversely through the arc in venting, thereby preventing the are from restriking after the first current zero in the current wave. Cut-out portions in some of the insulating plates define the vent openings 13 which are spaced longitudinally along the arc passage.

An arc horn of suitable arc-resisting material is afiixed to the flange 3| of the pressure chamber closure 22 in order to aid in the transverse movement of the are by the arc extinguishing device.

The bridging'memb'er I1 is provided with a pair of upstanding rod members 19, each of which is adapted to engage the lower end of one of the contact members 29. It is thus apparent that each of the contact structures is provided witha pair of separable contact surfaces electrically connected in series. The actuating mechanism, during the circuit opening operation, moves the bridging member l1 and with it the upstanding contact portions 19 in the direction of the bottom of the breaker closure. The downward movement of each of the upper contact members 21 is retarded by means of the dashpot action resulting from the close engagement of the enlarged portions 31 of those members and the cooperating portions 39 of the guide members 33 therefor. As a result, the springs 6| biasing each of the lower movable contact members 29 away from the upper contact members 21 cause the lower pair of separable contact surfaces for each contact structure to remain in engagement unfit til the support members" for the biasing springs 8| engage or are engaged by the cooperating movable piston 93.

As a result, an arc is established between the cooperating contact surfaces of each of the upper pairs of separable contact members, which members separate within the upper portion of the pressure chambers 93. The heated are products resulting from this separation cause a pressure to be developed which acts on the lower end of the movable piston 99 for each contact structure and causes that piston to move upwardly within the guide cylinder 99 therefor. This upward movement takes place at a very high speed, particularly when the breaker is interrupting a large magnitude overload, and it produces two effects. First, the upper contact surface of the lower pair of separable contacts is caused to move away from the contact surface of the cooperating up: standing portion of the bridging member I! at a very high speed, thus eifecting a very rapid separation of each of the lower pairs of cooperating contact surfaces. At the same time, the upward movement of the lower contact members 29 causes a re-engagement of each of the upper pairs of separable contact surfaces, thereby extinguishing the arcs which were formed therebetween. By extinguishing the arcs which were established within the pressure chambers 93 the developing of excessive pressures within those chambers is prevented and the safety and reliability of the operation of the interrupter is considerably improved. As a further protection from the building up of excessive pressures within the pressure and piston chambers, the vent openings are adapted to be uncovered if the pistons 63 are moved to the extreme upward portion of their stroke.

When either 'of the lower contact members 29 has been moved upwardly as a result of the generationof pressure within the associated pressure chamber 49, it returns to the normal open circuit position rather slowly, due to the fact that the only outlet for the fluid within the piston and pressure chambers is the small vent opening 5| in the upper flange 23 and the normal leakage around the guide opening 59 for the contact. Immediately following the separation of one of the lower pairs of separable contact surfaces and the upward movement of the lower contact memher-29, the upper end of the are established therebetween will transfer to the arcing horn 15, thereby preventing undue burning of the lower con tact surface of the lower movable contact member 29. The automatic reclosing of each of the upper pairs of separable contact surfaces likewise limits the burning of those surfaces. If desired, each of those surfaces may be formed from a portion .9I of arc resistance material welded or otherwise rigidly afllxed thereto. One particularly suitable form of material for, this use comprises a mixture of silver and tungsten in the proportions of 40% of the former and 60% of the latter.

The rapid separation of each of the lower pairs of separable contact surfaces which are disposed within the arc extinguishing devices effects a rapid increase in the arc voltage of the resulting are. As a, result large amounts of gas areevolved from the arc extinguishing fluidwhich is contained within the circuit breaker enclosure and a rapid interruption of the controlled circuit is assured.

In order to maximize the speed of separation of the lower pair of separable contact members,

it is desirable that the inertia of the movable as rapid a separation of the cooperating contact surfaces as is necessary for extremely high-speed circuit interruption resulted mainly from the fact that the entire bridging structure had to be moved by the actuating mechanism during each circuit interrupting operation. Our device, however, makes possible a. very rapid arc drawing movement which is independent of the speed of movement of the heavy bridging members, and it is chiefly through this means that much of the improved operation of our device results.

The modified contact structure shown particularly in Figs. 5 and 6 diflers in structural details from the arrangement shown in the other figures of the drawings. This modified structure is believed by applicants to be somewhat less expensive to manufacture and to be more readily applicable to existing breakers than the previously described embodiment. It includes a tubular outer casing 9| of metal which defines the outer walls of the pressure chamber proper 93 and which is similar, to the casing 22 of the previously described modification. This casing 93 is provided with a lower flange 95 for supporting the cooperating arc extinguishing structure l5 and an upper flange 91 which is adapted to engage a suitable collar or support member 99 affixed to the lower end of the conductor illl positioned with the cooperating insulating bush- A fixed contact member I03 is rigidly supported on the support member 99, and the lower end of this contact member defines the upper contact surface for the upper pair of, separable contact surfaces. Thewalls I95 of the piston chamber 101 are cast integral with the walls 9i of the pressure chamber 99 and are machined to accommodate the movable piston I99 which is positioned therein. The upper end of the piston chamber I0! is closed by a threaded closure member III which is provided with a suitable guide opening H9 fordetermining the path of movement of the upper movable contact member H5. A vent opening ill of small cross-sectional area connects the pressure chamber 93 with the body of liquid 20 contained within the main circuit breaker closure I and a somewhat larger vent H9 serves to connect the piston chamber with that body of liquid.

The upper movable contact member I15 is supported upon a circular plate l2l through the agency of a nut I22, and is electrically connected tosthe-lower movable contact member l23.by means of a flexible shunt I25. The plate member i 2| isbiased downwardly by a spring 121 to the upper end of the lower movable contact member I23. These rods I3 I also pass through openings I35 in the piston I09, which is slidably movable upon the upper portion of the lower movable contact I23, and are provided at their lower ends with enlarged portions I3I. The enlarged portions I31 cooperate with outwardly projecting fingers.I39 formed integral with the lower contact member I23 in order to define the amount of relative movement between the upper and lower plate members I2I and I33. v

The upper end of each of the guide rods I3I terminates in a piston portion I which moves within a dashpot I43 affixed to the top of the upper plate I2I. Suitable springs I45 are provided within these dashpots I43 for biasing the pistons I4I toward the upper end of the dashpot chambers. A spring I 48 of considerable strength biases the two plates I2I and I23 away from each other.

The operation of this modified form of our invention is essentially similar to the operation of the previously described embodiment. Upon the occurrence of certain predetermined conditions, the actuating mechanism begins to move the bridging member I'I downwardly toward the open circuit position. The lower plate member I33 and with it the lower movable contact I 23 are moved downwardly a short distance by the spring I48 until the outwardly projecting fingers I39 engage the enlarged portions I31 on the ends of the guide rods I3I. When this occurs; the two movable contact members H5 and. I23 move as a unit under the influence of the upper biasing spring I21 to cause separation of the upper pair of contact surfaces, the dashpot action of the pistons I 4I and the chambers I43 preventing the lower spring I21 from moving the upper movable contact member in the direction of the fixed contact I03.

An arc is thereupon established within the upper portion of the pressure chamber 93. This are decomposes the oil or other liquid contained within that chamber and almost immediately forms a considerable pressure therein. This pressure is communicated directly to the movable piston I09 and causes that member to move upwardly at a high speed. Very shortly after this upward movement is initiated, the upper end of the piston I09 engages the plate member I33 affixed to the lower movable contact member and moves that member upwardly, thereupon efiecting a very rapid separation of the lower pair of separable contact surfaces.

As a result, a long are is formed at high speed within the arc passage 61 of the arc extinguishing device I5. The magnetic action of the are moving plates II within that device moves the arc transversely therewithin and effects intimate contact between the arc and the liquid retained in the pockets 59. The are being drawn at high speed quickly develops sufllcient energy to assure the generation of an adequate volume of gas to effect ajvery rapid completion of the arc extinguishing operation.

Simultaneously, with the high speed separation of the lower pair of contact surfaces, the upwardly moving piston I09 eifects a reengaging of the upper pair of contact surfaces. In both of the structures shown, the reengaging of the upper pair of contact surfaces is assured. by virtue of the fact that the spring biasing the lower movable contact member downwardly (the spring 6| or the spring I48) is stronger than 3 77,838 in, the lower circular plate I33 which is aflixed the spring biasing the upper movable contact member downwardly (the spring 35 or the spring I21). This action is not so important in the embodiment previously described, but in this modified structure it is imperative that these springs be of dissimilar size. If the spring I48 were weaker than the upper spring I21, the upward movement of the piston I09 would not effect the reclosing of the upper pair of contact surfaces but would merely serve to compress the spring I 48 v The vent opening II9, which is provided ad jacent the upper end of the path of movement of the piston I 09, prevents excessive pressures from being built up within the piston and pressure chambers, and allows the fluid normally contained within the piston chamber to escape freely during the upward motion of the piston.

In the foregoing we have disclosed how very rapid separation of the main contacts of a high capacity circuit interrupter may be efiectedthrough the utilization of an auxiliary pair of contact surfaces which are adapted to separate prior to the separation of the main arc-drawing surfaces. In addition, we have shown certain preferred structural arrangements, utilizing a piston'chamber and a pressure chamber wherein the initially separating contact surfaces are disposed for effecting this high speed contact separation, and we have shown how this improvedcontact structure may be applied to an arc extinguishing chamber of the side-vented type. It is, of course, within the province of our invention that a contact structure employing the above described principles may be applied to a circuit interrupting device utilizing an arc extinguisher of the so-called expulsion type, and it is our intention .that the language of the appended claims should be interpreted sumciently broadly to include such devices.

While in accordance with the patent statutes we have disclosed certain specific structures for accomplishing the objects of our invention, the

principles of effecting rapid contact separation which we have disclosed above are believed to be applicable to a large number of different structural arrangements, and we believe that improved operation of substantially all types of circuit interrupters would result from the application of those principles thereto. In view of this, it is our desire that the language of the accompanying claims shall be accorded the broadest reasonable interpretation and shall be limited by only what is expressly stated therein and by the prior art.

We claim as our invention:

1. In a circuit interrupter, contact means having two pairs of separable contact surfaces, actuating means for said interrupter, meanswhereby one of said pairs of contact surfaces is the circuit interrupter is in full open position.

2. In a circuit interrupter, contact means havmg two' pairs of separable contact surfaces which are electrically connected in series with each aovassa other, actuating means for said interrupter, means defining a pressure chamber within which one of said pairs of contact surfaces is positioned, means whereby the operation of said actuating means during the circuit opening operation causes said pair of separable contact surfaces positioned within said pressure chamber to separate prior to the separation of said other pair of separable contact surfaces, and means operable by the pressure generated within said pressure chamber by the heated are products resulting from the separation of said first pair of separable contact surfaces therein for efiecting a high speed separation of said other pair of contact surfaces and for effecting a reengagement of said first pair of contact surfaces in order to extinguish the are which is initially formed therebetween, and said first pair of contact surfaces remaining in engagement during the opening movement of the circuit interrupter,

3. In a circuit interrupter; contact means having two pairs of separable contact surfaces; actuating means for said interrupter; means'defining a pressure chamber within which one of said pairs of separable contact surfaces is normally positioned; means within said pressure chamber which evolves a gas when placed in proximity to an electric are; means whereby the operation of said actuating means, during the circuit interrupting operation, causes said pair of separable contact means positioned within said pressure chamber to separate prior to the separation of said other pair of separable contact surfaces, the separation of said first pair of contact means causing an arc to be established within said pressure chamber which are evolves gas from said gas evolving means; and means, including a movable piston and a cylinder which communicates with said pressure chamber, for separating said other pair of contact surfaces and for returning said first-mentioned pair of contact surfaces into engagement where they remain in order to extinguish the are which is initially established therebetween.

4. In a circuit interrupter; contact means having two pairs of separable contact surfaces which are electrically connected in series, means defining a pressure chamber within which one of said pairs of separable contact surfaces is normally positioned; means whereby the operation of said actuating means, during the circuit inter-,

rupting operation, causes said pair of separable contact means positioned within said pressure position.

5. In a circuit interrupter; contact nfeans'having two pairs of separable contact surfaces which are electricallyconnected in series; means defining a pressure chamber within which one of said pairs of contact surfaces is positioned; means disposed within said pressure chamber which is capable of evolving a gas when placed in proximity to an electric are; means whereby the operation of said actuating means, during the circuit sure of the gas evolved from said means disposed within said pressure chamber as a result of the separation of said first pair of contact surfaces,

said piston when moved separating said other pair of separable contact surfaces and reengaging said first pair of separable contact surfaces in order to extinguish the arc which is initially established therebetween, and said first pair of contact surfaces remaining in engagement when the circuit interrupter is in open position.

6. In a circuit interrupter; an enclosure, a body of liquid within said enclosure, contact means having two pairs of separable contact surfaces, said contact means being normally submerged in said body of liquid; actuating means for said interrupter; means whereby one of said pairs of contact surfaces separates prior to the other of said pairs of contact surfaces during the circuit interrupting operation; and means actuated by the gas evolved from said liquid, as a result of the separation of said first pair of contact surfaces, for separating the other of said pairs of contact surfaces at high speed independently of said actuating means and for returning said firstmentioned pair of contact surfaces into engagement with each other where they remain so as to extinguish the are which is initially formed therebetween.

7. In a'circuit interrupter; contact means including two pairs of serially connected, cooper- .ating contacts; a single operating member movable to both open and close the circuit through said pairs of contacts; said operating member when moved causing one of said pairs of contacts to be opened prior to the other during each circuit opening operation of said interrupter and to be closed prior to the said other pair of contacts during each circuit closing operation.

8. In a circuit interrupter; contact means, including two pairs of separable contacts; means for electrically connecting said pairs of contacts in series with each other; a single operating rod movable for both opening and closing the circuit through said pairs of separable contacts; means whereby one of said pairs of contacts is caused to separate prior to the other of said pairs of contacts during each circuit opening operation; means whereby the heated are products resulting from the separation of said first pair of contacts are caused to effect a high speed separation of the other of said pairs of contact surfaces; and means for causing said first mentioned pair of contacts to be closed prior to said last mentioned pair of contacts during each circuit closing oper-' ation of said interrupter.

9. In a circuit interrupter; contact means including two pairs of separable contacts which are electrically connected in series; means actuated by movement of one of said contacts for both opening and closing the circuit through said pairs of separable contacts; means whereby one of said pairs of contacts is caused to separate prior to the other of said pairs of contacts during each circuit opening operation; means defining the walls, of a pressure chamber within which said first mentioned pair of contacts is positioned and is adapted to separate; means disposed within said pressure chamber which evolves a gas'when exposed to an electric are; means whereby the gas which is evolved within said pressure chamber, as a result of the separation of said first mentioned pair of contacts therein, causes high speed separation of the other of said'pairs of contacts; and means for causing said first mentioned pair of contacts to be closed prior to said last mentioned-pair of contacts during each circuit closing operation of said interrupter.

10. In a circuit interrupter; contact means including two pairs of separable contacts which are electrically connected in series; a common actuating member for both opening and closing the circuit through said pairs of separable contacts; means whereby one of said pairs of contacts is caused to separate prior to the other of said pairs of contacts during each circuit opening operation; means defining the walls of a pressure chamber within which said first mentioned pair of contacts is positioned and is adapted to separate; means disposed within said pressure chamber which evolves a gas when exposed to an electric arc; a cylinder; a piston movable therein; means whereby the pressure of the gas evolved from said means disposed within said pressure chamber as a result of the separation of said first mentioned pair of contacts is .impressed upon said piston, said piston being movable under the influence of this pressure to effect the separation of said other pair of contacts, independently of said operating mechanism; and means for caussition, in order to complete the electrical circuit therebetween; said intermediate contact means being movable during the initial stages of each circuit opening operation of said interrupter to establish an arc between itself and said first contact means, and to subsequently establish a second arc between itself and said movable contact means; means whereby the are products resulting from the initially established arc are caused to effect high speed separation of said movable contact means and said intermediate contact means, in order to increase the speed at which said second arc is drawn; and means whereby said intermediate contact means is caused to engage said first contact means prior to the engagement of said movable contact means with said intermediate contact means during each circuit closing operation of said circuit interrupter.

12. In a circuit breaker, contact means including at least two pairs of serially connected cooperating contacts, a common actuating member for both opening and closing the circuit through said pairs of contacts, means responsive during the opening movement of one of said pairs of contacts for delaying the separation of the other of said pairs of contacts, and means responsive to the separation of the first-named pair of contacts for accelerating the separation of the second-named pair of contacts, said last-named means causing the reengagement of said flrstnamed pair of contacts for extinguishing the arc therebetween, and said first-named pair of contacts remaining in engagement when the circuit breaker is in open position.

13. In a circuit breaker, a plurality of pairs of contacts arranged in series, a common actuating adapted to contain an insulating fluid, means responsive during the initial opening movement of said actuating means for delaying the separation of the other of said pairs of contacts, and means responsive to the pressure of the insulating fluid within said chamber created by the are upon the separation of the first-named pair of contacts for accelerating the separation of the second-named pair of contacts and for causing said first-named pair of contacts to be reengaged until the breaker is opened again to extinguish the arc therebetween.

14. In a circuit breaker, a plurality of pairs of contacts arranged in series, a common actuating means for said pairs of contacts, a pressure chamber surrounding one of said pairs of contacts adapted to contain an insulating fluid, means responsive during the initial opening movement of said actuating means for delaying the separation of the other of said pairs of contacts, means responsive to the pressure of the insulating fluid within said chamber created by the are upon the separation of the first-named pair of contacts for accelerating the separation of the second-named pair of contacts and for causing the reengagement of said first-named pair of contacts to extinguish the arc therebetween, and means for maintaining the engagement of said first-named pair of contacts following the subsidence of pressure within said chamber.

15. In a circuit breaker, contact means comprising a pair of relatively movable contacts and a movable conducting member interposed between said contacts, actuating means for opening said contacts, said conducting member being biased toward one of said contacts for movement therewith during the initial opening movement of said actuating means for establishing an initial arc between said conducting member and the other of said contacts prior to the establishing of an are between said conducting member and said first-named contact, and means responsive to the pressure created by the initial arc for reversing the initial movement of said conducting member to accelerate lengthening of the subsequently established arc.

16. In a circuit breaker, contact means comprising a pair of relatively movable contacts and a movable conducting member interposed between said contacts, actuating means for opening said contacts, said conducting member being biased toward one of said contacts for movement therewith'during the initial opening movement of said actuating means for establishing an initial are between said conducting member and the other of said contacts prior to the establishing of an are between said conducting member and said first-named contact, and means responsive to the pressure created by the initial arc for reversing the initial movement of said conducting member to accelerate lengthening of the subsequently established arc and to cause the reengagement of said other contact and said conducting member to thereby extinguish said initial arc, and follow-upmeans for maintaining said other contact and said conducting member in engagement after 75 the subsidence of pressure created by said initial are.

17. In a circuit interrupter, an actuating member thereior movable to open and close the circuit, a pair of circuit interrupting contacts, one of which is connected to and directly moved by said actuating member, a pair of pressure forming contacts connected in series with said pair of circuit interrupting contacts, means operable when said actuating member is initially moved in circuit opening direction to hold said pair 01 circuit interrupting contacts in engagement until aiter said 'pair of pressure iorming contacts have separated. i5 18. In a circuit interrupter, an actuating'member therefor movable to open and close the circuit, a pair oi circuit interrupting contacts, one of which is connected to and directly moved by said actuating member, a pair of pressure forming 2 contacts connected in series with said pair of circuit interrupting contacts, means operable when said actuating member is initially moved in circuit opening direction to hold said pair oi circuit interrupting contacts in engagement until after said pair of pressure forming contacts have separated, and means for returning said pair 0! pressure forming contacts to be in engagement when the circuit interrupter is in open circuit position.

30 19. In a circuit interrupter, an actuating memher therefor movable to open and close the circuit, a pair of circuit interrupting contacts, one of which is connected to and directly moved by said actuating member, a pair of pressure forming contacts connected in series with said pair of circuit interrupting contacts, means operable when said actuating member is initially moved in circuit opening direction to separate said pair of pressure forming contacts and apply the pressure formed by the arc drawn therebetween to accelerate the separation of said pair of circuitinterrupting contacts.

v 20. In a circuit interrupter, an actuating member therefor movable to open and close the circuit, a pair of circuit interrupting contacts, one of which is connected to and directly moved by said actuating member, a pair of pressure forming contacts connected in series with said pair of circuit interrupting contacts, means operable when said actuating member is initially moved in circuit opening direction to separate said pair of pressure forming contacts and apply the pressure formed by the are drawn therebetween to accelerate the separation of said pair of circuit interrupting contacts, and said means reclosing said pair of pressure forming contacts while said pair of circuit interrupting contacts maintain the circuit interrupter in full open position.

HARRY J. LINGAL. WINTHROP M. LEEDS.

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