US3277407A

US3277407A - Circuit interrupter

Info

Publication number: US3277407A
Application number: US437487A
Authority: US
Inventors: Kobayasi Yoshio
Original assignee: Terasaki Electric Co Ltd
Current assignee: Terasaki Electric Co Ltd
Priority date: 1964-03-16
Filing date: 1965-03-05
Publication date: 1966-10-04
Anticipated expiration: 1983-10-04
Also published as: FR1455834A; GB1095192A

Description

OCII. 4, 1966 YOSHlO KOBAYA5| 3,277,407

C IRCUI T INTERRUPTER Filed March 5, 1965 United States Patent C) 3,277,407 CIRCUIT INTERRUPTER Yoshio Kobayas, Nara, Japan, assignor to Terasaki Denki Sangyo Kabushiki-Kaisha, Abeno-ku, Osaka,

This invention relates to improvements in a circuit interrupter.

T-he primary object of the invention is to provide an improved circuit interrupter, in addition to being brought into its stable open state through the operation of the conventional thermally or electromagnetically operated tripping device, capable of opening the associated circuit without any delay upon the occurrence of a llow of heavy current such as a shortcircuiting current and a little later, being maintained in its stable open state through the operation of such tripping device.

With this object in view, the invention resides in a circuit interrupter comprising a pair of movable contact arms having disposed on the extremities thereof a pair of contacts respectively and disposed in substantially parallel relationship in the closed state in which the contacts engage each other, the pair of movable contact arms being arranged such that, upon the occurrence of la ow of heavy current such as shortcircuiting current, one of the movable contact arms is immediately moved away from the other contact arm `under the action of an electromagnetic repulsion generated between the parallel disposed contact arms due to the ow of heavy current therethrough thereby to be brought into its open position while at a little later, the other contact arm constrained in its closed position by a switching mechanism is moved to be separated far away from the one contact arm through collapsing of the switching mechanism due to the operation of a thermally or electromagvnetically tripping mechanism, and a spring member for providing a contact pressure for the contacts and returning the one contact arm to its original position as the electromagnetic repulsion decreases.

The invention will become more readily apparent from the following detailed description taken 4in conjunction with the accompanying drawings in which:

FIG. l shows, partly in section and partly in elevation, a circuit interrupter constructed in accordance with the teachings of the invention;

FIG. 2 is a fragmental elevational view of a pair of movable contact arms and their associated components in their ON and OFF positions; and

FIG. 3 is a view similar to FIG. 2 but illustrating the contact arms in their tripped position.

While the invention' will be shown and described in conjunction with a circuit interrupter of three pole type, it is to be understood that the same is equally applicable to circuit interrupters of single pole type and other multiple pole types. Also it is to be understood that the components common to all the poles will be described in terms of the central pole alone.

Referring now to the drawings and more particularly to FIG. 1, there is illustrated a three pole circuit interrupter constructed in laccordance with the teachings of the invention. The circuit interrupter illustrated comprises a base member 1 and a detachable cover plate 2. The Ibase member 1 and the cover plate 2 may be conveniently made of any suitable electrically insulating plastic by the molding technique and constitute a closed enclosure. Within the enclosure a pair of movable contact arms 3 and 4 are disposed so as to be substantially horizontally positioned in parallel relationship .in the closed position of the inter- 3,277,407 Patented Oct. 4, 1966 rupter. The contact arms 3 and 4 are made of any suitable electrically conductive material and have a pair of

contcts

3a and 4a attached at their free ends respectively.

The lower contact arm 4 is pivotally mounted on a rotatable shaft 7 by a U-shaped support Imember 8 for rotation about the shaft 7. Disposed on either common side of the lower contact arm 4 and U-shaped support member 8 is a helical spring 9 having one end hooked to a pin 10 extending through the contact arm and the other end secured to a pin 11 disposed on the U-shaped support member. The spring 9 serves -to provide to the lower contact on the lower Contact arm 4 a pressure under which the contact 4a engages the upper contact 3a. The lower contact arm 4 has the other end connected by way of a flexible conductor 12 to a conductor 13 connected to a source terminal 14.

The lupper contact arm 3 is rotatably secured to a contact holder 15 pivotally mounted on a holder shaft 16 common to all `the poles and also is connected to a connector 17 through a llexible conductor 18.

In order to prevent any effective shortcircuiting between the opposing portions of the upper and lower contact arms 3 and 4 in their closed positions or in parallel relationship, a thin insulation 5 is interposed therebetween.

In order to manually move the upper movable contact arm 3 from its closed position as illustrated at solid line in FIG. 2 to its open position as illustrated at dot-and-dash line in FIG. 2 and at solid line in FIG. 3 and vice versa, an operating mechanism generally designated by the reference numeral 20 is provided including an operating handle 21, an operating spring 22 and a tripping plate 23. The tripping plate 23 is then operatively connected to the contact holder 15 through a pair of toggle levers 24.

The interrupter also further comprises a thermally responsive device generally designated by the reference numeral 25 for the purpose of tripping the interrupter upon the occurrence of a flow of ordinary overload current. The thermally responsive device 25 includes a bimetal element 26 electrically connected to the connector 17 through a conductor 27 and an electric resistor 28 of U- shaped disposed Iadjacent the bimetal element 27. The resistor 28 has one end connected to the conductor 27 and the other end connected to another conductor 29 which, in turn, is connected to a load terminal 30. As shown in FIG. l, an adjusting screw 31 is secured integrally at the free end of the bimetal element 26. Upon the occurrence of a ilow of ordinary overload current, the resistor 28 and hence the bimetal element 26 will be heated whereby the element is bent leftwardly as viewed in FIG. l to actuate a tripping mechanism which will be subsequently described.

The tripping mechanism generally designated by the 'reference numeral 32 includes -a tripping piece 33. Upon the occurrence of a ow of ordinary overload current, the tripping piece 33 is forced by the adjusting screw 31 to rotate a tripping rod 34 integral with the tripping piece and a shaft 35 for the tripping rod whereby a tripping cam 36 disengages from `a tripping hook 37 mounted on the tripping rod 34 resulting in a tripping operation.

If an excessive current whose magnitude may be in the order of 8 to 10 times the ratin-g current flows through the interrupter then an electromagnet device including a stationary iron core 38 and a movable iron core 39 is energized to perform an instaneously tripping operation. More specifically, the lstationary iron core 3S is excited with a current flowing through the conductor 27 to attract the movable iron core 39 thereby to rotate the tripping rod 34 to disengage the tripping cam 36 from the tripping hook 37 resulting in a tripping operation.

With the arrangement thus far described, a How of overload current owing through the interrupter in its closed position causes energization of both the thermally responsive device 25 and the electromagnet device 38-39 thereby to trip the circuit interrupter. That is, the upper Imovable contact arm 3 is released from its constrained state to rotate in the clockwise direction until the same reaches its position as illustrated at dot-and-dash line in FIG. 2 and at a solid line in FIG. 3. This completes the tripping operation.

However, if a very high current such as a shortcircuiting current flows the circuit interrupter then such current will flow through the upper and lower contact arms 3 and 4 disposed in parallel, in the opposite directions, which generates an electromagnetic repulsion between both contact arms. This electromagnetic repulsion does not aect the upper contact arm 3 because the latter is constrained in its closed position by the switching or operating mechanism 20 but is effective for driving the lower contact arm 4 having a contact pressure applied thereto by the spring 9 and tending to rotate the arm 4 in the clockwise direction .about the shaft 7. Therefore, magnetic repulsion causes rotational movement of the lower contact arm 4 and accordingly the lower contact 4a against the contact pressure just described with the result that the lower contact arm 4 is separated away from the upper contact arm 3 and hence the upper contact 3a resulting in the interrupter being interrupted,

Thus the lower contact arm 4 has now been separated from the upper contact arm 3 thereby to interrupt the very high current. A little later, the electromagnetically tripping device 38-39 is operated to override the ability of the switchin-g mechanism 2-0 to constrain the upper contact arm 3 thereby to rotate the upper contact arm 3 in the clockwise direction as viewed in FIG. 2 to be further separated away from the lower contact arm 4 until the same is brought into its open position as illustrated at s-olid line in FIG. 3. Immediately before or after the upper contact arm 3 has been brought into its open position the electromagnetic repulsion as previously is damped to be lower than the force of the spring 9 tending to rotate the lower `contact arm 4 clockwise whereupon the arm 4 returns back to its original position as illustrated at solid line in FIG. 3.

If it is then desired to close the interrupter, a resetting operation leads to the interrupter being ready for closing state.

From the foregoing it will be appreciated that due to the provision of a pair of movable contact arms 3 and 4 disposed in substantially parallel relationship in their closed positions a flow of heavy current such as shortcircuiting current generates an electromagnetic repulsion between both contact arms thereby to separate one of the movable contact arms away from the other contact arm without any delay while the other contact arm remains stationary by the action of the switching mechanism with the result that the associate circuit is interrupted within a very short period of time. This causes the current limiting eiect and the interruption capacity of the interrupter to increase. A little later `after this interruption, the thermally responsive and/ or electromagnetic tripping mechanisms of the conventional type are or is operated to put the other contact arm in its open position. Then as the electromagnetic repulsion decreases the one contact `arm returns back to its original position by the action of the associated spring resulting in the readiness for the subsequent closing operation.

What I claim is:

1. A circuit interrupter consisting essentially of a pair of movable .contact arms having opposed contacts at their respective extremities and disposed in substantially sideby-side parallel relationship in the closed state in which the contacts engage each other, so that the current flow in one arm is in the opposite direction to the current ow in the other arm, switching means coupled to one of said arms for driving said one arm from its closed position to its open position and vice versa, release means coupled to said one arm for -moving said one arm lfor causing automatic separation of said one movable contact arm from the other, thermally responsive and electromagnetic trip means responsive to a ow of overload current through the circuit interrupter and engageable with said release means to a-ctuate said release means, a support member having the other movable contact arm pivotably mounted thereon and rotatable about a pivot on said support member independent of the operation of said switching means, said releasable means and said thermally responsive and electromagnetic trip means, a spring member extending between said other movable contact arm and said support member and biasing said other movable contact arm toward its closed position whereby when a short circuiting current flows through said pair of movable contact arms in the opposite direction causing temporary separation of said other movable contact -arm from said one movable contact arm due to electromagnetic repulsion, a time is provided during which said electromagnetic trip means can respond tothe current, said one movable contact arm controlled by said switching means is moved to its open position through the operation of said switching means resulting from said response of said electromagnetic trip means whereupon the interruption operation is made permanent and the other movable contact arm is automatically returned to its original position as the electromagnetic repulsion decreases 2. A'circuit interrupter as claimed in claim 1 in which said spring member acts along a line between said other movable contact and said pin, and is suiciently strong to prevent pivoting of the said other contact arm far enough so that the spring is moved past its dead center position.

References Cited by the Examiner UNITED STATES PATENTS 2,932,706 4/ 1960 Bodenschatz 200-107 3,005,073 10/ 1961 Reiss et al. 200-94 3,127,488 3/ 1964 Bodenschatz 200-106 BERNARD A. GILHEANY, Primary Examiner. I. J, BAKER, Assistant Examiner,

Claims

1. A CIRCUIT INTERRUPTER CONSISTING ESSENTIALLY OF A PAIR OF MOVABLE CONTACT ARMS HAVING OPPOSED CONTACTS AT THEIR RESPECTIVE EXTREMITIES AND DISPOSED IN SUBSTANTIALLY SIDEBY-SIDE PARALLEL RELATIONSHIP IN THE CLOSED STATE IN WHICH THE CONTACTS ENGAGE EACH OTHER, SO THAT THE CURRENT FLOW IN ONE ARM IS IN THE OPPOSITE DIRECTION TO THE CURRENT FLOW IN THE OTHER ARM, SWITCHING MEANS COUPLED TO ONE OF SAID ARMS FOR DRIVING SAID ONE ARM FROM ITS CLOSED POSITION TO ITS OPEN POSITION AND VICE VERSA, RELEASE MEANS COUPLED TO SAID ONE ARM FOR MOVING SAID ONE ARM FOR CAUSING AUTOMATIC SEPARATION OF SAID ONE MOVABLE CONTACT ARM FROM THE OTHER, THERMALLY RESPONSIVE AND ELECTROMAGNETIC TRIP MEANS RESPONSIVE TO A FLOW OF OVERLOAD CURRENT THROUGH THE CIRCUIT INTERRUPTER AND ENGAGEABLE WITH SAID RELEASE MEANS TO ACTUATE SAID RELEASE MEANS, A SUPPORT MEMBER HAVING THE OTHER MOVABLE CONTACT ARM PIVOTABLY MOUNTED THEREON AND ROTATABLE ABOUT A PIVOT ON SAID SUPPORT MEMBER INDEPENDENT OF THE OPERATION OF SAID SWITCHING MEANS, SAID RELEASABLE MEANS AND SAID THERMALLY RESPONSIVE AND ELECTROMAGNETIC TRIP MEANS, A SPRING MEMBER EXTENDING BETWEEN SAID OTHER MOVABLE CONTACT ARM AND SAID SUPPORT MEMBER AND BIASING SAID OTHER MOVABLE CONTACT ARM TOWARD ITS CLOSED POSITION WHEREBY WHEN A SHORT CIRCUITING CURRENT FLOWS THROUGH SAID PAIR OF MOVABLE CONTACT ARM; IN THE OPPOSITE DIRECTION CAUSING TEMPORARY SEPARATION OF SAID OTHER MOVABLE CONTACT ARM FROM SAID ONE MOVABLE CONTACT ARM DUE TO ELECTROMAGNETIC REPULSION, A TIME IS PROVIDED DURING WHICH SAID ELECTROMAGNETIC TRIP MEANS CAN RESPOND TO THE CURRENT, SAID ONE MOVABLE CONTACT ARM CONTROLLED BY SAID SWITCHING MEANS IS MOVED TO ITS OPEN POSITION THROUGH THE OPERATION OF SAID SWITCHING MEANS RESULTING FROM SAID RESPONSE OF SAID ELECTROMAGNETIC TRIP MEANS WHEREUPON THE INTERRUPTION OPERATION IS MADE PERMANENT AND THE OTHER MOVABLE CONTACT ARM IS AUTOMATICALLY RETURNED TO ITS ORIGINAL POSITION AS THE ELECTROMAGNETIC REPULSION DECREASES.