US3562680A

US3562680A - Circuit breaker

Info

Publication number: US3562680A
Application number: US858768A
Authority: US
Inventors: Ryoji Ozaki; Kunio Igarashi; Kiyoshi Kandatsu
Original assignee: Fuji Electric Co Ltd
Current assignee: Fuji Electric Co Ltd
Priority date: 1969-09-17
Filing date: 1969-09-17
Publication date: 1971-02-09
Anticipated expiration: 1988-02-09
Also published as: GB1272649A

Abstract

THE CIRCUIT BREAKER ASSEMBLED IN A MOLDED CASING INCLUDES FOR EACH POLE THEREOF TWO CONTACTING MEMBERS HAVING CONTACTING POINTS AT THEIR TIPS, THE TWO CONTACTING MEMBERS BEING SO ARRANGED THAT AN ELECTROMAGNETIC REPULSIVE FORCE IS CREATED THEREBETWEEN WHEN A CURRENT PASSES THROUGH THE CONTACTING MEMBERS AND THE CONTACTING POINTS AT THE TIME THE CIRCUIT BREAKER IS CLOSED, AT LEAST ONE OF SAID CONTACTING MEMBERS BEING FURTHER PROVIDED WITH CURRENT LIMITING ENGAGEMENT PARTS, WHICH ARE RELEASED WHEN THE CURRENT PASSING THROUGH THE CIRCUIT BREAKER EXCEEDS A PREDETERMINED VALUE. UPON DISENGAGEMENT OF THE EMGAGEMENT PORTIONS, THE CONTACTING MEMBERS ARE ABRUPTLY SEPARATED BY THE ELECTROMAGNETIC REPULSIVE FORCE, AND THE CURRENT PASSING THROUGH THE BREAKER IS INTERRUPTED. THE ENGAGEMENT PARTS ARE REENGAGED WHEN THE CONTACTING MEMBERS ARE OPENED AT THEIR MAXIMUM OPENING POSITIONS BY MEANS OF, FOR INSTANCE, A CONVENTIONAL TRIPPING MECHANISM.

Description

Feb. 9, 1971 nRY'QJI OZAK, ET AL 3,562,680

CIRCUIT BREAKER 3 Sheets-Sheet 1 Filed Sept. 17, 1969 N m W s O P D E s O I.. C

N m W S O D' on mm UP NO O PF1, m Dn *lf` FIG.3

INVENTOR` OZA KI ET AL Feb. 9, 19.71

Filed sept. 17, 1969 RYOJI ozAKl ETAL CIRCUIT BREAKER 5 Sheets-Sheet 2 INVENTORJ` RYOM OZAKI ET AL Hrrwtfvevf Feb. 9, 1971 Filed Sept. l?, 1969 RYOJI OZAKI ETAL CIRCUIT BREAKER 5 Sheets-Sheet 5 INVENTORJ RYOJI OZAK! ET AL :United States Patent O 3,562,680 CIRCUIT BREAKER Ryoji Ozaki, Kunio Igarashi, and Kiyoshi Kandatsu, Kawasaki-shi, KanagaWa-ken, Japan, assignors to Fuji Denki Seizo Kabushiki Kaisha, Kamigawa-ken, Japan Filed Sept. 17, 1969, Ser. No. 858,768 Int. Cl. H01h 77/10 U.S. Cl. 335-16 8 Claims ABSTRACT OF THE DISCLOSURE The circuit breaker assembled in a molded casing includes for each pole thereof two contacting members having contacting points at their tips, the two contacting members being so arranged that an electromagnetic repulsive force is created therebetween when a current passes through the contacting members and the contacting points at the time the circuit breaker is closed, at least one of said contacting members being further provided with current limiting engagement parts, which are released when the current passing through the circuit breaker exceeds a predetermined value. Upon disengagement of the engagement portions, the contacting members are abruptly separated by the electromagnetic repulsive force, and the current passing through the breaker is interrupted. The engagement parts are reengaged when the contacting members are opened at their maximum opening positions by means of, for instance, a conventional tripping mechanism.

BACKGROUND OF THE INVENTION This invention relates generally to electrical circuit breakers and more particular to a new and improved circuit breaker having a high interrupting capacity.

In general, various circuit breakers of the type wherein two contacts having contact points at their tips are so arranged as to become parallel when closing a circuit path, and when a large current such as a short-circuit current flows through the path, the two parallel contacts are opened apart directly by the electromagnetic repulsion force generated therebetween the interrupting time being shortened and the short-circuit current being limited thereby to increase the interrupting capacity are known.

However, since all of these known circuit breakers have an organisation whereby the contacts are caused directly by electromagnetic repulsion to open apart, when a large current flows instantaneously, the contacts which have opened apart once for an instant close again in some cases, thereby giving rise to fusion seizure for sticking of the contact points.

Furthermore, when an excessive current ows, the contact pressure is reduced by the electromagnetic repulsive force, whereby there is the risk of overheating of the contact parts and of fushion seizure of the contact points.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a circuit breaker which has an organisation similar to that of the above described conventional circuit breakers, that is, wherein the electromagnetic repulsive force between two parallel contacts is utilised to shorten the interrupting time and limit the short-circuit current thereby to increase the interruption capacity, but in which the above described difliculties accompanying known organisations have been eliminated.

According to the present invention, briefly summarized, there is provided a circuit breaker comprising a movable contacting member and a stationary contacting member both arranged so that au electromagnetic repulsive force ice is created therebetween by a current passing through the two members, a holder connected with at least one of the two members, said at least one of the contacting members and said holder including parts engageable at a position nearer to contacting points of the two contacting members than the acting point of the resultant electromagnetic repulsive force, means for stabilizing the engagement of the engaging parts, means for releasing the engagement thereof by displacing one of the contacting members having one of the engaging parts at the time the electromagnetic repulsive force exceeds a predetermined value, and means for restoring the engagement of the engaging parts after the opening of the two contacting points has been completed, whereby the contacting pressure between the contacting points of the contacting members is substantially increased when the electromagnetic repulsive force is less than a predetermined value, and at least one of the contacting members abruptly opens the contacts when the electromagnetic repulsive force exceeds the predetermined value.

The nature, principle, and utility of the invention will be more clearly apparent from the following detailed description with respect to examples of preferred embodiment of the invention when read in conjunction with the accompanying drawings, in which like parts are designated by like reference numerals.

BRIEF DESCRIPTION OF DRAWINGS FIG. l is a sectional profile Iview of a circuit breaker according to the present invention shown in the closed state;

FIG. 2 is a sectional prole view of the circuit breaker showing only the principle parts thereof which are manually brought into the open state;

FIG. 3 is a sectional profile view of the same circuit breaker showing only the principal parts thereof which are brought automatically into the open state;

FIG. 4 is a similar sectional profile view of the same circuit breaker which is brought into an initial automatic opening state by a current limiting mechanism;

FIG. 5 is also a sectional prole view of the same circuit breaker ywhich is brought into a maximum separating position by the automatic opening operation of the current limiting mechanism;

FIG. 6 is an enlarged prole view showing the principal parts of the current limiting mechanism;

FIG. 7 is an explanatory diagram for the operation of the current limiting mechanism; and

FIGS. 8, 9, and l() are enlarged views showing the principal parts only of other embodiments of the current limiting mechanism.

DETAILED DESCRIPTION Referring now to FIGS. l through 6, there is indicated a circuit breaker, each pole of which comprises a movable contact member 1 having a contacting point 2 at one end thereof and a stationary contact member 3 having a contacting point 4 likewise at one end thereof and performing a switching action in cooperation with the movable contact member 1. Each pole of the circuit breaker also comprises a holder 5 mounted on an insulating shaft `6 commonly provided for all poles of the circuit breaker, and the holder 5 is coupled to a trip lever 9 of the switching mechanism 101 through

toggle links

7, 8. The movable contact member 1 is provided with an inverted V shaped catching member t12 having a catching portion 10 and a cutout portion 11, the catching portion 10 engaging Iwith a slit 14 of a trigger rod 13 provided at an end of the holder 5.

Furthermore, the movable contact member 1 is, at a rotating axis 15 provided thereon, rotatably connected to a link 16 which is also rotatably mounted around a 3 shaft 17 on the holder 5. Between the movable contact member l1 and the holder 5, there is provided a tension spring 18 which urges the link 116 to rotate counterclockwisely around the shaft 17 until the movement of the link 16 is stopped by its abutting against a stopper 19 provided on the holder so that the engagement between the catching portion and the trigger rod 13 is assured.

Since the movable contact member 1 andthe holder 5 are interlinked as described above, these two members move in cooperation in the normal switching operation of the circuit breaker.

When the circuit breaker is in the closed state as shown in FIG. 1, an electric circuit is closed between one terminal 20 and the other terminal 27 through a conductor 21, a flexible piece 22, the stationary contact member 3, the movable contact member =1, another exible piece 23, a conductor 24, a trip mechanism 36, and a conductor 26. As is apparent from FIG. 1, the circuit breaker is further provided with a casing 28, a cover 29, a contacting spring which urges the stationary contact member 3 to rotate around a shaft 31 in the clockwise direction imparting a higher contact pressure against the movable contact member 1, and a stopper pin 32 which limits the movement of the stationary contact member after it is rotated through a predetermined angle at the time the circuit breaker is brought into open state. Between a shaft 33 which is linking the

toggle links

7 and 8 and a handle 34 rotatable around a pivotal point 25, tension springs 35 are provided.

When it is desired to open the circuit breaker by manual operation, the handle 34 is thrown to the opening position maintaining a trip lever 9 at an engaging position with a catch 37 of a tripping device 36, 'which trips the circuit breaker when an over current flows through the breaker. At the time the handle 34 is thrown into the open position, the acting line of a tension of the springs 3S is shifted to the righthand side of a pivot pin 38, and the

toggle links

7 and 8, thus being folded back, in turn rotates the holder S around the axis 6, the rotation of the holder 5 opening the movable contact member 1 interlinked with the holder 5. FIG. 2 shows the thus opened state of the circuit breaker.

When the handle 34 is thrown into the closing position, the acting line of the tension of the springs 35 is shifted back to the left side of the pivot pin 38, and under the action of this tension spring 35, the

toggle links

7 and 8 are brought into the extended positions, whereby the contact members are closed as shown in FIG. 1 with a snap action.

When the tripping device 36 is operated through an over-current or a short circuit current, the catch 37 is rotated clockwise around the shaft 39, and the trip lever 9 engaging with the catch 37 is rotated counterclockwise around the shaft 40, whereby the pivot pin 38 is shifted to the lefthand side of the acting line of the tension springs 35. As a result, the

toggle links

7 and 8 are folded back, rotating the holder S around the shaft 6, and the movable contact member 1 interlinked with the holder 5 is brought into the opening state. Next, when the handle 34 is thrown into the closing position, the acting line of the tension spring 35 is shifted to the left side of the pivot pin 38, and under the action of the spring 35, the

toggle links

7 and 8 are brought to their straight states, whereby the contact members are closed as shown in FIG. 1 with a snap action. FIG. 3 shows the thus opened state of the circuit breaker.

When it is desired to close again the circuit breaker after it has been opened by the automatic tripping device 36, the handle 34 is moved from the above described tripped position rst to the opening position. In this way, a projection 42 of the catch 37 is pushed down by an end `41 of the tripping lever 9, rotating the catch 37 in the counterclockwise direction, and the catch 37 is again engaged ywith the tripping lever 9. Thus, the

circuit breaker is brought back from the state shown in FIG. 2 to that of FIG. 1.

As is apparent from the above description, while the circuit breaker is operated in manual closing and opening manner or in an automatic trip operation, the movable contact member 1 and the holder 5 are operated 1n an interlinked manner, hence being operated similarly as in a conventional circuit breaker.

However, in the conventional construction of the tripping mechanism, there is a time delay of several m1111- seconds in the opening-and-closing operations from the instant the tripping device is operated to the instant when the movable contact starts to operate, and within this delay time, the maximum value of the short circuiting current passes through the circuit breaker. Although the passage of the maximum current through the circuit breaker does not create any problem if the short circuit current is of minor value, it would be preferable to open the contacts before the maximum current passes through the circuit breaker so that the maximum current is thereby limited when the short circuit current is of a considerably large rvalue.

The current limiting effect cannot be expected when a circuit breaker having no current limiting mechanism is employed. When a type of conventional circuit breaker having a current limiting mechanism is employed, the above described current limiting eiect may be obtained. However, such a type of conventional circuit breaker still has drawbacks such as fusion seizure, sticking of the contact points, or over-heating or burning of the contact points. According to the present invention, a novel type of the current limiting mechanism is provided whereby the above described drawbacks of the conventional circuit breakers have been substantially eliminated.

The construction of the novel type of the current limiting mechanism will now be described. Since the movable contact member 1 and the stationary contact member 3 are in their closing condition disposed in parallel as shown in FIG. 1, an electromagnetic repulsion force is created by the current owing therethrough. Although the repulsion force created by the rated current for the circuit is moderate, the repulsion force created at the time a short circuit current of high value flows through the circuit breaker is of extraordinarily high magnitude because the repulsion force increases in proportion to the second power of the flowing current. The conventional construction of the current limiting mechanism has utilized this intensified electromagnetic repulsion force directly for opening the contacts, and hence had the above described drawbacks such as fusion seizure.

As is apparent from FIG. 6, in the current limiting mechanism according to the present invention, the movable contact member 1 is provided with a catching portion 10 of the catching member 12 engaging with a slit 14 on a triggering rod 13 provided at the tip of the holder 5 at a position nearer to the contacting points than is the holder point of the electromagnetic repulsion force. For this reason, when an electromagnetic repulsion force is exerted, the movable contact member 1 is subjected to a torque F1 acting in the counterclockwise direction around the engaging point 102 between the catching portion 10 and the slit 14 of the triggering rod 13. On the other hand, since the stationary contact member 3 is freely rotatably mounted around the shaft 31, which is positioned nearer to the contacting points than is the acting point of the electromagnetic force, the stationary contact member 3 is subjected to a torque F3 in the clockwise direction caused by the electromagnetic force around the shaft 31.

As described before, the stationary contact member 3 receives a contacting pressure in the closed state of the circuit breaker due to the contacting spring 30, and this pressure constitutes a clockwise torque F2 around the engaging point 102.

At a time when the electromagnetic repulsion force is Weak, and the torque F1 cannot overcome the torque F2 due to the contacting pressure, the movable contact member 1 is maintained in the closed position. However, when the electromagnetic repulsion force becomes large, and the counterclockwise torque lFl around the engaging point 102 overcomes the sum of the torques F2 and F3, the movable contact member 1 can be rotated in the counterclockwise direction around the engaging point 102.

When such a condition occurs, the link 16 interlinking the movable contact member '1 and the holder 5 is displaced around the shaft 17 at the upper end thereof against the tension of the spring 18 as shown by chain lines in FIG. 6. The movable contact member 1 is shifted to the contact side, as is most clearly apparent from FIG. 7, by a distance l, which in terms of the rotating angle 0 of the link 16 at this time, an angle a between the link 16 at the stationary condition and the vertical line, and the length l of the link 16 can be expressed as If this shifted distance Al is less than the length S of the catching portion of the catching member 12 engaging with the slit 14 on the triggering rod 13, the engagement of the movable contact member 1 at the engaging parts 102 is not released. Thus, while the movable contact member 1 is not moved or is not released from the engagement when it is moved slightly, the movable contact member 1 is subjected to a counterclockwise torque F1 due to the electromagnetic repulsion force, and the stationary contact member 3 is subjected to a clockwise torque.

As a result, the contacting pressure between the two contacting points is increased, and separation of the contacts or decrease of the contacting pressure due to the increase in the current does not occur. When the current drops before the engagement is broken, the movable contact member 1 is shifted back to its original stable state under the effect of the spring 18, and the engagement at the point 102 is also brought back to the initial condition. Accordingly, over-heating or fusion seizure of the contact points which has frequently occurred in the conventional circuit breakers is prevented.

When the electromagnetic repulsion force is further elevated, and the displacement Al of the movable contact member 1 becomes larger than the length S of the catch porion 10, the engagement between the catch portion and the triggering rod 13 is broken. As a result, the movable contact member 1 is rotated around the shaft 17 and also around the shaft 15 in cooperation with the link 16, whereby the separation of the contact points due to the electromagnetic repulsion force is realized. 'Ihis separation of the contact points is rapid because the separation is carried out through the swinging motion of the movable contact member which has least inertia of rotation. It will also be apparent that the separation speed of this contact is faster than in the conventional construction wherein the separation is directly carried out by the electromagnetic repulsive force because no decelerating effect due to the contact pressure is created in the former case.

In this way, only the movable contact member 1 is separated before the separation of the switching mechanism 101 occurs as shown in FIG. 4, and the short circuit current is limited prior to the maximum value thereof is attained.

Until the condition as shown in FIG. 4 of the movable contact member 1 is attained, the tripping operation due to the tripping device 36 of the switching mechanism 101 is also started although it has a delay in comparison with the separating movement of the movable contact member 1. Accordingly, the separation of the contacting points further progresses without stopping in the state of FIG. 4 until the contacting points are in their maximum separaltion position `as shown in FIG. '5 so that `the interruption of the short circuit current is assured.

After the state shown in FIG. 5 is attained, the movable contact member 1 is sustained by a stopper shaft 43, and only the holder 5 continues its upward movement. As a result, the triggering rod 13 is again raised to the location of the catching portion 10, and, under the action of the tension spring 18, these are engaged together as they were in the initial state. Thus, the opening operation of the circuit breaker is completed, and all of the components of the circuit breaker are in the same positions as those when the breaker is automatically tripped only by the tripping device 36, which case is shown in FIG. 3, and the closing operation thereafter can also be performed in the same manner.

As described above in detail, in the circuit breaker according to the present invention, the movable contact member 1 does not move out until a predetermined value of the electromagnetic repulsive force is attained, and the contacting pressure of the contacting points is thereby increased. When the electromagnetic repulsive force exceeds the predetermined amount, the engagement between the triggering rod 13 and the catching portion 10, both constituting the engaging parts 102 described above, is broken, and the movable contact member 1 is thus freed from the engagement to open the contacting points abruptly.

The circuit breaker according to the present invention thus permits ordinary manual switching operation and automatic switching operation similarly as in the case of an ordinary circuit breaker whenever the overload current or a short circuit current passing therethrough is less than a predetermined value. More specifically, the circuit breaker is operated manually or automatically by the tripping of the tripping device 36 but without operating the current limiting mechanism 100. However, when the overload current or the short circuit current exceeds the above described preset value, the current limiting mechanism operates and the above described fusion seizure or burning of the contacting points is thereby prevented.

Although the present invention has been described with respect to a preferred embodiment thereof, it will be apparent to those skilled in the art that various modifications or alternations may be made therein Without departing from the spirit and scope of the present invention.

For instance, while in the above described embodiment of the invention, the engaging parts 102 comprise the catching member 12 having a catching portion 10 and a cutout portion 11 and provided on the part of the movable contact member 1 and the triggering rod 13 having a slit 14 and provided on the holder 5 side, this may be modified as shown in FIG. 8 so that the engaging parts 102 comprise a catching portion 44 and a cutout portion 45 both provided on the holder 5 side and a triggering rod 47 having a slit 46 and provided on the side of the movable contact member 1.

Moreover, while the triggering rod 13 shown in FIGS. 1 through 6 and also the tirggering rod 47 shown in FIG. 8 both having

slits

14 and 46, respectively, have a semicircular cross section as apparent from these figures, these may be modified so that they have a cross section of rectangular, of polygonal such as hexagonal, or of circular configuration.

Furthermore, in the above described embodiment, a link 16 has been provided between the shaft 15 on the movable contact member 1 and another shaft 17 on the holder 5 for the purpose of shifting the movable contact member 1 of the current limiting mechanism 100 to the contact point side by the electromagnetic repulsion force. However, this may also be replaced by another construction, as shown in FIG. 9, wherein an elongated hole 48 is obliquely provided on the movable contact member 1 and a shaft 49 provided on the holder 5 is inserted in the hole 48.

Alternatively, as shown in FIG. l0, a shaft 50 may be provided on the movable contact member 1, and the shaft 50 may be inserted in a hole 51 obliquely provided on the holder 5.

In the above described embodiment, the current limiting mechanism has been provided only on the movable contact member side. However, this mechanism may be provided also on the stationary contact side, or two of the current limiting mechanisms may be provided respectively on the movable and stationary contact points may be doubled because of the provision of the two current limiting mechanisms, the current limiting effect in the circuit breaker is further improved.

We claim:

1. A circuit breaker comprising a movable contacting member and a stationary contacting member both arranged so that an electromagnetic repulsive force is created therebetween by a current passing through the two members, a holder `connected with at least one of said two members, said at least one of the contacting members and said holder including parts engageable at a position nearer to contacting points of said two contacting members than the acting point of the resultant electromagnetic repul* sive force, means for stabilizing the engagement of said engaging parts, means for releasing said engagement by displacing one of said contacting members having one of said engaging parts at the time the electromagnetic repulsive force exceeds a predetermined value, and means for restoring the engagement of said engaging parts after the opening of the two contacting portions has been completed, whereby the contacting pressure between the contacting points of the contacting members is substantially increased when said electromagnetic repulsive force is less than a predetermined value, and at least one of said contacting members abruptly opens the contacts when said electromagnetic repulsive force exceeds the predetermined value.

2. A circuit breaker as dened in claim 1 wherein said holder is connected with at least one of said contacting members through a link both ends of which are pivotally mounted on said holder and on said at least one of the contacting members, respectively.

3. A circuit breaker as defined in claim 1 wherein said engageable parts comprise an inverted V shaped catching member provided on said at least one of the contacting members and a triggering rod having an engaging slit provided on said holder.

4. A circuit breaker as del-ined in claim 1 wherein said holder is connected with at least one of said contacting members through a link both ends of which are pivotally mounted on said holder and on said at least one of the contacting members, respectively, and said means for stabilizing the engaging parts is a tension spring which, in cooperation with said link, pulls said at least one of the contacting members to one side so that the engagement of the engaging parts is thereby assured.

5. A circuit breaker as defined in claim 1 wherein said means for releasing said engagement between said at least one of the contacting members and said holder comprises a link both ends of which are pivotally mounted on said holder and on said at least one of the contacting members, respectively, whereby when the electromagnetic repulsive force exceeds a predetermined value, said at least one of the contacting member having one of said engaging parts is displaced toward one direction and the engaging parts are thereby released.

6. A circuit breaker as defined in claim 1 wherein said engagement between said at least one of the contacting members and the holder is not broken While the circuit breaker is tripped manually or automatically by a separate tripping mechanism.

7. A circuit breaker as dened in claim 1 wherein said engaging portions comprise a cutout portion provided on said holder and a triggering rod having a slit provided on said at least one of the contacting members.

8. A circuit breaker as dened in claim 1 wherein said holder and said at least one of the contacting members are connected together by means of an elongated slot and a pin combination instead of the link, and said elongated slot is somewhat inclined against the longitudinal axes of the holder and said at least one of the contacting members.

References Cited UNITED STATES PATENTS 3,127,488 3/1964 Bodenschatz 335-16 3,238,339 3/1966 Fehling 335--16 3,492,609 1/1970 Murai 335-16 3,500,266 3/1970 Torre 335-16 3,505,622 4/1970 Strobel 335--16 FOREIGN PATENTS 2,624,246 6/1968 Austria 335-16 HAROLD BROOME, Primary Examiner