US2235901A

US2235901A - Electric circuit breaker

Info

Publication number: US2235901A
Application number: US173585A
Authority: US
Inventors: Ronnberg Daniel
Original assignee: ASEA AB
Current assignee: ABB Norden Holding AB
Priority date: 1936-11-14
Filing date: 1937-11-09
Publication date: 1941-03-25
Anticipated expiration: 1958-03-25
Also published as: GB492486A; BE424598A; FR829062A; NL49564C

Description

Filed NOV. 9. 1937 6 Sheets-Sheet 1 March 25, 1941.

D. RCNNBERG 2,235,901

ELECTRIC CIRCUIT BREAKER Filed Nov. 9, 1937 6 Sheets-Sheet 2 a sheets-sheet s 1 C o 1L Q 0 N 5% 1% l w 4E m D. RONNBERG ELECTRIC CIRCUIT BREAKER Filed Nov. e. 1937 March 25, 1941.

March 25, 1941.

D. RONNBERG 2,235,901

ELECTRIC CIRCUIT BREAKER Filed Nov. 9,1937 6 Sheets-Sheet 4' Fig (9 6 Sheets-Sheet 5 fm e/zfar pe/rauma fW/orney.

@011 (P5 Fo'hnr D RUNNBERG ELECTRIC CIRCUIT BREAKER FllBd Nov 9. 1937 March 25, 1941.

Patented Mar. 25, 1941 ELECTRIC CIRCUIT BREAKER Daniel Riinnberg, Ludvika, Sweden, assignor to Allmanna Svenska Elektriska Aktiebolaget, Vasteras, Sweden, a corporation of Sweden Application November 9, 1937, Serial No. 173,585 In Sweden November 14, 1936 6 Claims. (Cl. 200-450) In electric circuit breakers, the arrangement pairs, one of which the main pair has been arof extinguishing pots surrounding the breaking ranged inside an extinguishing pot and intended gap, in which the arc is brought in intimate confor breaking the circuit, whereas the other contact with a flow of an extinguishing liquid or gas, tact pair the auxiliary pair intended for the closhas considerably increased the breaking ability ing of the circuit has been arranged outside the of the circuit breakers. In spite of the fact that extinguishing pot, but [in contradiction to the the provision of extinguishing pots of the above known circuit breakers, where the two contact mentioned kind has considerably increased the pairs have been independently actuated by the breaking ability, however, no corresponding inoperating mechanism] according to the present 10 crease of the ability of the circuit breaker to close invention, one of the contact pairs is directly 10 a current has been obtained, at least if the voltoperated by the operating mechanism and the age has been high. This is due to the fact that other contact pair is operated by one of the conwhen closing a circuit, at least when the voltage tacts in the first-mentioned contact pair. is high, an arc is lighted in the extinguishing pot, By the above arrangement of the contacts oi and this causes a sudden shock of pressure, which the two contact pairs a very convenient and suit- 15 if the current is high can be so powerful that the able form of circuit breaker is attained, especially extinguishing pot will burst. with respect to the insulation, so that without The pressure generated by an arc increases any difiiculties it can be adapted for high tenwith the amount of heat generated by the arc, sions. This is due to the fact that only one of and the amount of heat generated per unit of the contact pairs is directly connected with the 20 time is directly proportional to the product of operating mechanism. Further the auxiliary conthe arc voltage and the current. The are voltage tact pair intended for the closing of the circuit in turn is proportional to the length of the arc may also be so arranged that it serves for interand to the existing pressure. It is therefore clear ruption of the circuit in cooperation with the that the pressure arising in the first moment of C a P in the eXtinguiShing D closing of the circuit must be higher than the On the accompanying drawing several forms of pressure arising at interruption of the circuit, the invention are shown. Fig. 1 shows schematibecause when the arc is lighted at closing the cally one pole of a circuit breaker with one of circuit, the contacts are at a rather great disthe contacts of the main contact pair movable 3o tance from each other whereas at the interruptand connected with one of the contacts of the ing of the circuit, the arc is formed between the auxiliary contact pair which is arranged outside contacts when they are in immediate proximity of the extinguishing pot but inside a container of each other. If the breaking point is enclosed enclosing the extinguishing pot. in an extinguishing pot, the arc voltage and Fig. 2 shows the auxiliary contact pair arthus the pressure is further increased by the ranged below the extinguishing pot with one of 35 resistance against an equalization of the pres its contacts connected with the operating mechsure depending upon the fact that the arc is anism, and its other contacts connected with the enclosed in a comparatively confined space. movable contact of the main contact pair, the

In order to increase the ability of a circuit contact connected with the operating mechanism breaker to close a circuit when the current is being provided with a piston which by the aid 4 large, it has previously been proposed to provide of a liquid column actuates the main contact the circuit breaker with two series connected pair so that it is closed before the auxiliary concontact pairs, one of which has been enclosed in tact pair is closed. an extinguishing pot and chiefly intended for the Fig. 3 shows a slight modification of the aropening of the circuit, whereas the other, which rangement of Fig. 2. 45 had for its purpose only to close the circuit, has Fig. 4 shows an extinguishing pot in which been arranged outside the extinguishing pot. Inone of the contacts of the auxiliary contact pair stead of the provision of an auxiliary contact is connected with a differential piston actuated pair outside it, it has also been proposed to proby the pressure generated by the arc, this, piston vide the extinguishing chamber with special memhaving the function to open the auxiliary contact 50 bers, by which the extinguishing pot has been pair. In this form also an insulating wall is opened when closing the circuit but closed when provided which has an opening traversed by one interrupting the circuit. of the contacts of the auxiliary contact pair so The present invention also refers to circuit that when opening the circuit breaker this conbreakers of the kind provided with two contact tact is washed by a flow of fluid.

Fig. 5 shows the same arrangement as Fig. 4 but with an additional difierential piston which causes a flow of fluid against the arc between the contacts of the main contact pair.

Fig. 6 shows the same arrangement as Fig. 4 but with an additional difierential piston which causes a flow of fluid through the wall traversed by one of the contacts of the auxiliary contact pair.

Fig. 7 shows a combination of the arrange ments shown in Figs. 5 and 6 and is thus provided with two additional differential pistons.

Fig. 8 shows in detail a vertical section of the arrangement shown schematically in Fig. 5, and

Fig. 9 is a detail section of the arrangement shown in Fig. '7.

Fig. 10 is a detail section of a modified form of the arrangement schematically illustrated in Fig. 5.

In Fig. l, I designates a. container filled with an insulating medium. This container contains the two contact pairs and the bottom of the container is provided with an opening for the corn tact 2 operated by the operating mechanism of the breaker. This contact extends in the closed position of the circuit breaker into the extinguishing pot 3, which consists of an upper cylinder 3 and a lower cylinder 5, which latter has a smaller diameter than the former. The extinguishing pot is closed at its lower extremity by a bottom 6 and at the top by a cover 7. In the double cylinder thus formed there is provided a differential piston 8, which at the top has a collar 9, which fits the cylinder 4 and at the bottom has a collar I II, which fits the cylinder 5. The bottom II of the differential piston is of insulating material and is provided with an opening I2 for the movable contact 2. The stationary contact I3 is attached to a rod I4, which on the other end. carries a contact I5. This rod extends through an opening I6 in the cover I. Immedi ately above the stationary contact I3 is a piston I? attached to the rod I4. The rod I4 is surrounded by a cylinder I8, which at the top has a cover IS] with an opening 20 for the rod I l. This cylinder has on the outer side a collar 2I, which can be pressed tightly against the cover 1. The

stationary contact I3 is normally held in its lower position by means of a helical spring 22, which at the lower end rests on the piston I1 and at the upper end against the cover I9 of the cylinder I8. This helical spring presses the cylinder I S upwards so that the collar 2I ispressed against the cover I. The cylinder I8 is provided with openings 23, the purpose of which is described below. The piston II has such a diameter that it tightly slides inside the cylinder I8. The extinguishing pot 3 is supported by the leading-in conductor as by means of a disc 25 and insulating rods or an insulating cylinder 26. In the case that it is a cylinder, this is provided with openings on the side. On the disc 25 a contact 21 is fastened, with which the contact I5 can be brought into engagement.

The arrangement acts in the following way. When closing the circuit breaker, the main contact 2 is moved upwards and is brought into engagement with the contact I3, which by a further movement of the contact 2 i moved upwards until the contact I5 auxiliary is caused to engage with the contact 27. When the contact I3 moves upwards, the fluid in the cylinder I8 is partly forced out through the openings 23 and thence through the space between the collar 2| and the cover '1 into the space 3I. When opening the the outer container I.

circuit breaker, the contact I3 is held back by the piston II. When the piston I'I tends to move downwards, a vacuum is created on the upper side of it, so that the cylinder I8 is raised a little, and the collar 2i is tightly pressed against the cover 7. The opening of the circuit will therefore take place between the contacts 2 and I3 and the extinguishing pot will then act in the common manner, so that the pressure developed in it acts on the piston 8 which moves downwards thereby forcing the extinguishing medium from the space 32 through the opening I2 into the space 35, and at the same time extinguishing medium is forced out from the annular shaped space 33, which is in free communication with v The openings in the cylinder 'l are so dimensioned that extinguishing medium'may stream out through them, but they are so restricted that at the breaking a suiiicient pressure can arise in the pot for moving the piston 8. The downward motion of the contact I3 is effected by the action of the spring 22. This downward motion is, however, so delayed that a vacuum is formed above the piston I'I due to the fact that, by the pressure in the pot, the collar 25 is pressed up against the cover I. The tightening between this collar 2I and the cover I is not complete, however, and the time for the motion of the piston II will therefore depend upon the leakage between the collar 2I and the cover 5,

I and by the choice of a suitable leakage the separation of the contacts I5 and 2'! can be so delayed that the interruption of the circuit will always be completed by the contacts 2 and I3.

The container I is closed by a cover 34!, which i is provided with large openings for the escape of the gases. Instead of attaching the contact I 3 on the rod I i, it is also possible to have it formed as a sleeve contact and attached to the cylinder 8. The movable contact 2 will in this case pass through the contact I3 up against the piston I! thus moving it and the rod I4 until the contact 55 engages with the contact 21.

In the form shown in Fig. 2, 37 designates a cylinder with a cover 36. The stationary contact is fastened to thi cover. The cylinder 3'1 is provided with an inwardly bent edge 59, on which an insulating cylinder 38 is fastened. This cylinder 38 has an intermediary wall 39, which is provided with an opening for a contact 42.

This contact is connected to a piston 43 movable in the cylinder 38, which piston also carries a contact i l, with which the contact 45 connected to the operating mechanism of the circuit can be caused to engage. The contact 45 carries a piston 45, which fits the cylinder 38. In the extinguish- 111g pot formed by the cylinders 31 and 38 there is a differential piston 48 with bottom 49. This piston is normally held in its upper position by means of a helical spring 59. The cylinder 37 is provided on its side with openings 5| and in the same manner the cylinder 38 is provided with openings The

contacts

52 and 44 with piston are normally pressed against the ring H by means of a helical spring 4?.

This arrangement acts in the following Way. When closing the circuit breaker, the piston 46 enters the cylinder 38, and as it moves upwards the fluid in the space 52 is moved upwards and moves the piston &3 so that the contact 42 is caused to engage the contact 35, At first after the contact =32 engages the contact 35 the piston 43 reaches the openings 40. The fluid pressed by the piston 66 will therefore, after it has served for the displacement of the contact 42, flow out through the openings 40 and the contact 45 is on further upward motion caused to engage the contact 44. No pressure is thus developed in the extinguishing pot, and if an arc should ignite between the

contacts

44 and 45, the gases generated thereby will escape through the openings 40. At the opening of the circuit breaker in the common manner, a pressure will arise in the extinguishing pot and will move the piston 48 downwards, The fluid enclosed in the space 56 will then stream through the openings 5|, and as long as the contact 42 still occupies the opening in the intermediary wall 39, the fluid in the space 54 will flow out through the opening in the piston bottom 49 into the space 55, and at the further motion of the contact 45, the contact 42 is moved downwards by the helical spring 41, but when the piston 43 has reached the ring 4|, the contact 42 can no longer move downwards. The upper tip of it will therefore remain immediately before the opening in the intermediary wall 39, which is the most advantageous position of the contact in relation to the opening in the intermediary wall in order to get the most favourable extinguishing conditions. As soon as the opening in the intermediary wall 39 is made free, liquid and gas from the extinguishing pot will be blown out through this opening and through the openings 48.

The arrangement according to Fig. 3 differs from the arrangement shown in Fig. 2 chiefly in that the differential piston is arranged around the extinguishing pot instead of inside it. The differential piston is in this case formed by the cover 36, which is provided with an opening for the rod 65, and by the cylinder 31, which is provided with an inwardly directed collar 59, which tightly fits the cylinder 63. This cylinder and the cylinder 60 with its collar are carried by the rod 65.

The arrangement acts in the same manner as the arrangement shown in the preceding figure, so that the piston 46 forces the fluid in the space 52 upwards, which fluid then actuates the piston 43 until the contact 42 engages the stationary contact 35. With this motion, the contact 42 moves through the opening 62 in the insulating intermediary wall 6|. When the piston 43 has moved a sufiiciently long way, the space 52 is brought into communication with the space out side the cylinder 38 by the openings 40, so that the gases, which may be developed by an are between the

contacts

44 and 45 easily can escape. The pressure generated at the breaking is transmitted from the space 55 to the space 55, but also through the opening 62 to the

spaces

54 and 51. The pressure generated by the arc moves the piston 36, 31 against the action of the helical spring 50; so that the space 51 is decreased, and the fluid in this space will therefore be forced through the openings 58 into the space 54 and from there through the channels 62 into the space 55. As in the preceding figure, the motion of the contact 42 is limited by the ring 4|, so that also in this arrangement the tip of the contact 42 will stop in the position most suitable for the extinction. The arrangement may be such that the contact 42 in its end position rests in the opening in the bottom 64, but it is also possible to provide a form, where it moves so far that the opening in the intermediary wall 64 is free so that gas and liquid can escape through this opening.

In Fig. 4, 1| designates a cylinder of insulating material, which at the lower end is provided with a bottom 12 also of insulating material, This is provided with an opening 13 for the movable contact 14. The other contact of the contact pair in the extinguishing pot is designated by 15, and this contact is by means of the cylinder 16 connected with the piston 11, which is movable in the cylinder 18. The piston 11 is actuated by a helical spring 8| and the space between the

cylinders

16 and 18 communicates by means of a channel 89 with the space outside the extinguishing pot. The extinguishing pot is at the top closed by an intermediary wall 83 of insulating material, which wall has an opening 82 for one of the contacts 19 of the contact pair outside the extinguishing pot. The other contact in this pair of contacts is designated by 84, and the space in which the contact pair 19, 84 is contained communicates by means of large openings 85 with the space outside the extinguishing pot.

This arrangement acts in the following way.

When opening the circuit breaker the contact 14 H is drawn downwards, and then an arc is formed between the contacts 14 and 15. This generates in the extinguishing pot a pressure, which acts on the upper side of the piston 11, which moves downwards and pulls the contact 19 out of contact with the contact 84 and down through the opening 82. As soon as this opening has been liberated, a flow of extinguishing medium in contact with the arc is caused between the contacts 19 and 84. There will therefore in this form be two series connected arcs, one are between the contacts 14 and 15 and one arc between the contacts 19 and 84, which arcs are extinguished by the extinguishing medium flowing through the openings 13 and 82 respectively.

The arrangement shown in Fig. 5 differs from that of Fig. 4 in that the extinguishing pot is provided with a differential piston 9|, which in the bottom has an opening 92 for the contact 14. This differential piston is normally held in its upper position by a helical spring 94, which at the lower end rests against the inwardly bent part 86 of the cylinder 1|. This inwardly bent part carries also an insulating cylinder 81, which thus forms an extension of the extinguishing pot and is closed at the lower end by a bottom 12 of insulating material. In this bottom there is a hole 99 for the contact 14 and back valves 89. In the cylinder 1| are openings 93 in order to allow the extinguishing medium below the flange of the differential piston to escape from the extinguishing pot.

In the form shown in F g. 6, the cylinder 81 instead of forming an extension downwards forms an extension. upwards of the cylinder 1| and the differential piston is in this form arranged in the upper part of the extinguishing not so that b it a blow-out of the extinguishing medium through the opening 82 is effected. In the form of the circuit breaker shown in this figure the same extinguishing action is obtained between the contacts 14 and 15 as in the arrangement according to Fig. 4, but at the contacts 19 and 84 a considerably increased extinguishing action is obtained by means of the powerful stream of extinguishing medium forced out through the opening 82 by means of the piston 9|.

The arrangement according to Fig. 7 differs from the preceding one only in that the extinguishing pot is provided with two differential pistons 9|, of which the lower one causes an extinction of the arc between the contacts 14 and 15 and the upper an extinction of the are between the contacts 19 and 84.

In Fig. 8 an arrangement principally the same as in Fig. 5 is shown in detail. In this figure, IOI designates the stationary contact in the extinguishing chamber and I02 the movable contact. The stationary contact is, however, to a certain extent movable and is connected with a difierential piston described below. The extinguishing pot itself is formed by an insulating cylinder I03, which is fastened to a metal cylinder I04, which in turn is fastened to an annular part I05 of metal, and this part is upwardly continued by an insulating cylinder I03, fastened to a cover I61 carrying the extinguishing pot.

In the extinguishing pot there is a differential piston I90 consisting of an insulating cylinder I09 with bottom H0, which is also of insulating material and is provided with a flange III. The intermediary part I05 consists of a ring I I2 and a ring H3, which by means of arms H4 carries a nave II 5. In this nave a metal cylinder II 6 is inserted, and in this cylinder another cylinder II! with a tightening ring H8 moves. The cylinder II! also fits in a tightening ring H9 of the nave II 5.

The cylinder II'I carries the stationary contact IIII, which in a known manner is formed as a sleeve contact, and further the cylinder IIT carries a pipe I20, which at the upper end is closed by one of the contacts I2I in the auxiliary contact pair outside the extinguishing pot.

In the cylinder I06 there is an intermediary wall I22 with an opening I23, through which the auxiliary contact I2I can pass on its way to its counter-contact I24. The space in the cylinder m6, which contains this contact is connected by large openings I25 with the space outside the cylinder I06, so that the contact pair IZI, I24 can be regarded as arranged outside the extinguishing pot.

Between the nave H5 and the cylinder H6 there is a space I26, which is in communication with the space outside the extinguishing pot through channels I 21 in the arms H4. These channels are provided with ball valves I28, which allow liquid to enter the space I26, but prevent liquid escaping from this space. In one or a plurality of the channels in the arms H4, the ball valves are replaced by plugs which seep holes of suitable size.

The ball valves I28 consist of a cylinder I29, which at the outer end is provided with an inwardly directed rand I30. Immediately to this rand the cylinder is provided with two or several holes I3I, and in the cylinder there is a ball I32, and the motion of this ball is outwardly limited by the said rand, and its motion inwardly is limited by a pin I33.

The space below the differential piston I is on the drawings designated by I34 and the space above it by I35, and further the space above the intermediary wall I22 is designated by I35.

The arrangement acts in the following way. When closing the circuit breaker, the movable contact I02 is moved up against the stationary contact IIII and then moves the cylinder III with pipe I20 and contact I2I upwards, so that the latter is caused to engage the contact I2 4. The closing of the circuit will therefore take place between the two latter contacts, and if then an arc is ignited, the gases generated by it will escape through the openings I 25. During the upward motion of the cylinder II'I, liquid is sucked into the space I 26 through the ball valves I28.

When opening the circuit breaker, the interruption of the circuit takes place between the contacts IOI and I02. The pressure then generated in the extinguishing pot acts on the differential piston I08, so that it moves: downwards. (Normally the piston I08 is held in its upper position by means of the helical spring I31.)

The pressure in the pot also acts on the upper side of the bottom in the cylinder III. In fact, the cylinder II'I serves as a differential piston and tends to move downwards partly due to the pressure acting on it and partly due to the action of the helical spring I38. This downward motion is, however, damped by the liquid in the space I 26, which liquid can escape only through the above mentioned seep holes in some of the arms H4, and by regulating these seep holes the damping of the motion of the cylinder I I I can be regulated.

When the cylinder II'I moves downwards, the contact I2I is also moved downwards, and when it has passed through the opening I23, here also an extinguishing action is added to the extinguishing action provided in the opening of the bottom H0.

The damping of the motion of the contact IIII is connected with the advantage that with small currents the distance between the contact WI and the bottom H0 a longer time is maintained at a large value than if the current is large. The larger the current is the higher will be the pressure in the pot and the faster will the cylinder I I1 move downwards. In this way a smaller arc length is attained when the current is large, so that the energy developed by the arc during the interruption will be comparatively independent of the magnitude of the current traversing the circuit breaker when interruption takes place.

The fact that the space covered by the larger surface of the differential piston is opened and brought into communication with the space outside the extinguishing pot when the auxiliary contact moves downwards is followed by the great advantage that the piston in a shorter time can move back into the original position, because the gas generated in the extinguishing pot can easily escape through the opening for the auxiliary contact as the pressure on both sides of the difierential piston will then be equal. The helical spring I31 can move the piston back to the original position without any great resistance.

The arrangement according to Fig. 8 is in some cases followed by the disadvantage that if an arc is ignited between the contacts I2I and I24 before the contact I2I has reached the opening I23, the pressure generated in the space I36 can be transmitted through the hole I23 and thus cause a motion of the piston H18.

Fig. 9 shows in detail a form which principally is the same as the form shown in Fig. 7. In this form the above disadvantage is eliminated since as in Fig. 7 a difierential piston is arranged in the upper part of the extinguishing pot. This piston will cause a stream of extinguishing medium through the hole I23 when the contact I2I is drawn away from this hole.

In Fig. 9, IIII designates the stationary contact and I82 the movable one. The extinguishing pot is formed by a cylinder I04, which at the lower end carries a cylinder I03. The cylinder IM is in turn carried by an intermediary part I consisting of a ring H2 and a ring H3. The ring II3 carries by means of arms H4 a nave 7 H5. On the ring II 3 a cylinder I39 is fastened,

which is continued upwardly by a cylinder I40, which is provided with an intermediary wall I22 with an opening I23 for the contact I2I. The cylinder I40 is at the upper end closed by the cover I01, but the space I36 between the intermediary wall I22 and the cover I01 communicates by large openings I25 with a space outside the extinguishing pot. In the cylinders I04, I03 there is a differential piston I08, which consists of a cylinder I09 with bottom I I and flange III. In the cylinders I39 and I40 there is another difierential piston I4I, through which the contact I2I passes. The differential piston 508 is normally held in its upper position by means of the helical spring I31, and the differential piston MI is normally held in its lower position by means of the helical spring I43. On the nave H a cylinder H6 is fastened. In this cylinder another cylinder H1 is movable. This carries at the lower end the stationary contact IEII and is at the upper end provided with a tightening ring H8, which slides in the cylinder H6. The nave H5 has at the lower end an inwardly bent part, which fits the cylinder H1, and further the cylinder H1 is provided with a rim II9, which tightening ring H8 slides in the cylinder H6. The cylinder H8 may have an inner diameter decreasing downwards, which diameter at the lowermost part of the cylinder H8 is the same as the outer diameter of the ring IE9. The contact IN is joined by means of the pipe I20 to the contact I2I. The cylinder H1 with contact IIII is normally held in its lower position by means of the helical spring I38. The arms H4 are all, or only some of them, provided with channels I21, by which the space inside the nave H5 is in communication with the space outside the extinguishing pot, and further the cylinder H6 is provided with openings I5I, which connect the space between the cylinder H6 and the cylinder II1 with the space inside the nave I I5.

This arrangement acts in the following way. When closing the circuit breaker, the contacts IOI and I02 are brought into engagement with each other, and when the contact I02 moves upwards the contact I2I also is moved upwards through the hole I23, so that it is brought into engagement with the contact I24. The spring I38 is then pressed together.

When opening the circuit breaker, the contact I02 is pulled downwards and in the first moment the contacts WI and I02 are separated. By means of the pressure generated by the are formed between these contacts, the differential piston I08 is moved downwards and at the same time the difierential piston MI is moved upwards. The pressure generated by the are between the contacts IOI and I02 acts at the upper side of the cylinder H1 and tends to move this cylinder with the contact IOI and the contact I2I downwards. This motion is, however, damped by the liquid enclosed in the space below the rim H9 between this rim and the lower inwardly bent part of the nave I I5. This liquid must in escaping to the space outside the extinguishing pot pass the rim IIS into the space I20 and from there through the openings I5I and the channels I21. Due to the fact that the cylinder H6 inwardly has a downwardly decreasing diameter, the play between the rim I I 9 and the inner wall of the cylinder H6 will decrease when the cylinder II1 moves downwards, so that a successively increasing damping of the motion of the cylinder H1 is obtained. When the contact I 2I is moved so far downwards that the opening I23 has been liberated, the differential piston I4I forces extinguishing medium from the space I44 through the opening I23. A part of this extinguishing medium will traverse the bore I42 in the contact I2I and from there out through the openings on the side of the pipe I20.

When closing the circuit breaker, the contacts IOI and I02 at first are brought into engagement with each other, and firstly after this contact is completed, the contact I2I commences the motion upwards. When an arc is then ignited between the contacts I2I and I24, the gases generated by this are will escape through the openings I25.

The arrangement according to Fig. differs from that of Fig. 9 in that the differential piston MI is replaced by an intermediary wall I45, which is provided with openings I46, the said openings being closed by back valves I41. A pressure generated in the space I44 therefore can not be transmitted to the space I35 and cause a motion of the piston I08. On the contrary, the pressure generated by the are between the contacts IOI and I02 can if it is sufficiently high allow a flow of liquid from the space I35 out through the openings I46 into the space I44 and from there through the opening I23. The gases which are generated by the arc between the contacts I2I and I24 can escape partly through the openings I25 and partly through the bore I48 and the openings I49 on the side of the pipe I24 out into the channels I50. In other respects the form shown in Fig. 10 is nearly the same as that shown in Fig. 9.

I claim as my invention:

1. In an electric circuit breaker an arc-extinguishing pot, a main contact pair enclosed in the said pot, an auxiliary contact pair arranged outside the pot and series connected with the main contact pair, a dash pot mechanism retarding the opening of the auxiliary contact pair, an operating mechanism acting on the main contact pair, a spring acting on the auxiliary contact pair in the opening direction, and a difierential piston actuated by the pressure generated by the arc in the arc extinguishing pot, said piston being connected with one of the contacts in the auxiliary contact pair and acting in the opening direction.

2. In an electric circuit breaker an arc-extinguishing pot, a main contact pair enclosed in the said pot, an auxiliary contact pair arranged outside the pot and series connected with the main contact pair, a dash pot mechanism retarding the opening of the auxiliary contact pair, an operating mechanism acting on the main contact pair, a spring acting on the auxiliary contact pair in the opening direction, a difierential piston actuated by the pressure generated by the arc in the arc extinguishing pot, said piston being connected with one of the contacts in the auxiliary contact pair and acting in the opening direction, and an insulating wall of the arc extinguishing pot provided with an opening traversed by the contact of the auxiliary contact pair connected with the differential piston.

3. In an electric circuit breaker an arc-extinguishing pot, a main contact pair enclosed in the said pot, an auxiliary contact pair arranged outside the pot and series connected with the main contact pair, a dash pot mechanism retarding the opening of the auxiliary contact pair, an operating mechanism acting on the main contact pair, a spring acting on the auxiliary contact pair in the opening direction, a differential piston actuated by the pressure generated by the arc in the arc extinguishing pot, said piston being connected with one of the contacts in the auxiliary contact pair and acting in the opening direction, an insulating wall of the arc extinguishing pot provided with an Opening traversed by the contact of the auxiliary contact pair connected with the differential piston, and a further difierential piston arranged inside the extinguishing pot causin a flow of fluid in contact with the are between the main contacts.

4. In an electric circuit breaker an arc-extinguishing pot, a main contact pair enclosed in the said pot, an auxiliary contact pair arranged outside the pot and series connected with the main contact pair, means for closing the main contact pair and afterwards the auxiliary contact pair, a differential piston actuated by the pressure generated by the arc in the arc extinguishing pot, said piston being connected with one of the contacts in the auxiliary contact pair and with the stationary contact of the main contact pair, an insulating wall of the arc extinguishing pot provided with an opening traversed by the contact of the auxiliary contact pair, actuated by the differential piston, a retarding device for the motion of the differential piston, a further diiferential piston arranged inside the extinguishing pot causing a flow of fluid in contact with the are between the main contacts, and a differential piston arranged inside the extinguishing pot, causing a flow of gases and liquid through the opening in the insulating wall of the pot, traversed by one of the contacts of the auxiliary contact pair.

5. In an electric circuit breaker with are extinguishing pots, a main contact pair enclosed in each extinguishing pot, an auxiliary contact pair arranged outside the extinguishing pot and series connected with the main contact pair, means for closing the main contact pair and afterwards the auxiliary contact pair, a diiferential piston actuated by the pressure generated by the arc in the arc extinguishing pot, said piston being connected with one of the contacts in the auxiliary contact pair and the stationary contact of the contact pair inside the arc extinguishing pot, an insulating wall of the arc extinguishing pot provided with an opening traversed by the contact of the auxiliary contact pair connected with the diiTerential piston, a retarding device for the motion of the difierential piston; a further differential piston arranged inside the extinguishing pot causing a flow of fluid in contact with the are between the main contacts, and an insulating Wall arranged inside the said insulating wall of the pot, provided with valves allowing a flow of gases and liquid only from the extinguishing pot to the space outside it.

6. In an electric circuit breaker with arc extinguishing pots, a main contact pair enclosed in each extinguishing pot, an auxiliary contact pair arranged outside the extinguishing pot and series connected with the main contact pair, means for closing the main contact pair and afterwards the auxiliary contact pair, a differential piston actuated by the pressure generated by the arc in the arc extinguishing pot, said piston being connected with one of the contacts in the auxiliary contact pair and the stationary contact of the main contact pair, an insulating wall of the arc extinguishing pot provided with an opening traversed by the contact of the auxiliary contact pair actuated by the differential piston, a retarding device for the motion of the difierential piston, a further clifierential piston arranged inside the extinguishing pot causing a flow of fluid in contact with the arc between the main contacts, and a difierential piston arranged inside the extinguishing pot, causing a flow of gases and liquid through the opening in the insulating wall of the pot, traversed by one of the contacts of the auxiliary contact pair.

DANIEL RoNNBERG.