US3506937A - Movable contact unit of circuit interrupter - Google Patents

Description

April 14, 1970 `TUTQMU` HANAFUSA 3,506937 MCVABLE CONTACT lUNITCF CIRCUIT INTERRUPTER e shets-sheet x Filed Nov. 27, 1968 INVENTOR TUTOMU HANAF USA ATTORNEYS pril`14,` 14970, TUTOMU HANAFUSA 3,506,937

`MOVBLE CONTCT UNIT OF' CIRCUIT INTERRUPTER Filed Nov. 2'?, 1968 6 Sheets-Sheet 2 N .ci

, INVENTOR 'TUToMu HANAFUSA BY I ATTORNEYS April 14, 1970 TUTOMU HANAFUSA 3,506,937

MOVABLE CONTACT UNIT OF CIRCUIT INTERRUPTER INV ENT OR TUTOMU HANAFUSA y BY ATTORNEYS April 14, 1970 Y TUTOMUIHANAFUSA 3,506,937

MOVABLE CONTACT UNIT OF CIRCUIT INTERRUPTER INVENTOR TUTOMU HANAF U SA l BY ATTORNEYS April 197.0 l TuTQMul HANAFUsA l 3,506,937 l MOVABLE CONTACT UNIT OF CIRCUIT INTERRUP'IERl Filed Nov. 27, 1968 e sham-sheet s INVENT OR TUTOMU HANAFUSA ATTORNEYS United States Patent O 3,506,937 MOVABLE CONTACT UNIT OF yCIRCUIT INTERRUPTER Tutomu Hanafusa, Osaka, Japan, assignor to Terasak Denki Sangyo Kabushiki Kaisha, Osaka, Japan Filed Nov. 27, 1968, Ser. No. 779,565 Claims priority, application Japan, Nov. 28, 1967, 42/ 99,407; Dec. 20, 1967, 42/ 81,220 Int. Cl. H01h 77/10 US. Cl. 335--16 2 Claims ABSTRACT OF THE DISCLOSURE One of two movable contact units includes two mova-ble contact arms normally bridging the opposite movable contact unit and having on the adjacent end portions a circular protrusion and a V-shaped groove maintained in double line contact relation by a tension spring spanned between the arms. Upon an electromagnetic repulsion generated between both contact units due to a flow of shortcircuiting current through them, both arms are rotated in the opposite directions about the center of the circular protrusion while the central portion of the spring abuts against a stopper positioned below that center to be bent into its expanded state. As the repulsion decays the spring returns back to its straight-forward shape to put the arms into predetermined positions from which they can easily be brought into their open positions through the operation of the associated tripping and switching mechanisms.

BACKGROUND OF THE INVENTION This invention relates to improvements in a movable contact unit of a circuit interrupter divided into a pair of movable contact arms bridging the opposite movable contact unit in the closed position of the interrupter and including a tension spring spanned between the movable contact arms to maintain them in electric contact with each other, the movable contact arms responding to an electromagnetic repulsion generated between both the contact units due to a iiow of very excessive current such as shortcircuit current through the interrupter to be rotated while they are maintained in electrically contacting relationship thereby to interrupt the cuttent.

In the conventional type of circuit interrupters referred to, the rotational movements of the movable contact arms stemming [from a flow of shortcircuiting current through the interrupter could be generally eifected at a high speed until the arms strongly struck against the associated stoppers leading to a fear that the arms -would sometimes damage. Also the associated switching mechanism has been required to provide a relatively high force in order to bring the rotatable contact arms into their normal open positions after the rotational movement has terminated.

*In one type of the conventional circuit interrupters referred to, a movable contact unit of bridge type has comprised a pair of movable contact arms pivotably mounted on separate pivot pins and having their respective adjacent portions in the for-m of circular arcs maintained in rolling contact relationship. It has been required for the pair of movable contact arms to include their separate fulcra disposed at a predetermined interval within the associated closed enclosure having a limited dimension. Also the movable contact arms have been maintained in contact with each other on a single contact line which exhibits, in turn, a relatively high resistance to a ow of load current through the contacting portions of the arms. In order to prevent such a load current from increa-sing the temperature of the contacting arm portions beyond a ice certain limit, it has been necessary to decrease the rated current of the associated circuit interrupter to a small value as compared with the rated current as determined Iby the particular dimension and type of an electrically conductive material for the movable contact arms. Further it is presently demanded to provide enclosed circuit interrupters small in size and light in weight.

SUMMARY OF THE INVENTION Accordingly it is an object of the invention to provide, in a circuit interrupter of the type utilizing an electromagnetic repulsion generated between a pair of opposite movable contact units due to a ow of very excessive current through the interrupter, one of the contact units including a pair of movable contact arms normally bridging the other contact unit and responsive to the electromagnetic repulsion to ybe rotated in the opposite directions While they are maintained in electric contact relationship, an improved mechanism for decaying the rotational movements of the movable contact arms to halt them at such psoitions that the arms can easily be brought from their halted positions to their open positions through the succeeding operation of the associated tripping and switching devices Withut sacrificing the interr-upting capability of the circuit interrupter.

It is another object of the invention to provide a simple and light structure of the pair of movable contact arms as described in the preceding paragraph rotatable in the opposite directions about a common axis of rotation while they are maintained in electric contact relationship with a relatively large area.

With the above cited objects in View, the invention resides in a circuit interrupter utilizing an electromagnetic repulsion generated between a pair of iirst and second movable contact units disposed in substantially parallel relationship in the closed position of the interrupter upon the occurrence of a flow of very excessive current, and including a pair of movable contact arms forming the first contact unit and bridging the second contact unit in the closed position of the interrupter, tension spring means spanned between the movable contact arms, the movable contact arms being responsive to the electromagnetic repulsion to be rotated in the opposite directions about the respective centers of rotation while the arms are maintained in electric contact relationship until the arms are held in their predetermined positions through the movement of the central portion of the tension spring means across the centers of rotation, and stopper means disposed at a predetermined distance below the center of the partial circle in order that during their movement along with the movable contact arms, the tension spring means abut against the stopper means to expand into arcuated Ibent shape. As the electromagnetic repulsion decays, the tension spring means return back to its straightforward shape to put the arms in their positions as determined by the stopper means from which positions the arm can easily be brought into their open position through the succeeding operation of the associated tripping and switching devices.

Preferably, one of the movable contact arms may have a protruding end portion in the form of a partial circle always maintained in bendable engagement mith the adjacent end portion in the form of a V-shaped groove of the other movable contact arm by the action of the tension spring means, the one movable contact arm being pivotably carried at the center of the partial circle such that the movable contact arms respond to the electromagnetic repulsion to be rotated in the opposite directions about that center to interrupt the current while both the arms are maintained in rolling contact relationship.

3 BRIEF DESCRIPTION OF THE DRAWINGS The invention will become more readily apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

FIGURE 1 is an elevational sectional view of a three pole circuit interrupter constructed in accordance with the principles of the invention and put in its closed position;

FIGURE 2 is a plan view of the interrupter as viewed from its bottom with a common cover for arc extinguishing chambers removed, with a iirst movable contact unit contacted in accordance with the principles of the inventions for the central pole removed to illustrate a second movable contact unit and with the first and second contact units and arc extinguishing devices for another pole also omitted;

FIGURE 3 is a fragmental side elevational View, partly in section of the interrupter illustrated in its open or reset position into which it is brought through the operation of the associated operating handle;

FIGURE 4 is a view similar to FIGURE 3 but illustrating the interrupter in its tripped position into which it is brought by the associated trip device actuated upon a flow of ordinary overload current therethrough;

FIGURE 5 is a view similar to FIGURE 3 but illustrating 4the iirst and second movable contact units moved to their most separated positions in response to a flow of shortcircuiting current therethrough and independent of the operation of the associated tripping and switching devices; and

FIGURE 6 is a view similar to FIGURE 3 but illustrating the first movable contact unit after it has abutted against and halted by the associated stopping pins.

DESCRIPTION OF THE PREFERRED EMBODIMENT While the invention will be illustrated 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 in common to al1 the poles will be described in terms of the central pole alone.

Referring now to the drawings and more particularly to FIGURE 1, there is illustrated a three pole circuit interrupter constructed in accordance with the principles of the invention. The circuit interrupter illustrated comprises a closed enclosure including a main body member 1, a detachable top cover member 2, and a detachable bottom cover member 3. All the members 1, 2, and 3 may be conveniently made of any suitable, electrically insulating plastic by the molding technique. Within the enclosure a pair of movable contact units generally designated by the reference numerals 4 and 5 respectively are disposed so as to be substantially horizontally 1ocated in opposed parallel relationship in the closed position of the interrupter.

A irst or lower one of both units 4 includes a pair of rst or lower contact arms 4s and l having a pair of contacts 6s and l attached to the extremities or free ends respectively. The contact arms 4s and l may be conveniently made of any suitable electrically conductive material. Both contact arms 4s and l are of a bilaterally symmetric configuration excepting that one of them in this case arm 4s has a protrusion 7s of partially circular section at the other end while the other Contact arms 4l has a V-shaped groove 7s formed at the adjacent end. Both arms are bilaterally disposed in alignment with each other in the closed position of the interrupter. The protrusion 7s is then forced always to engage the groove 7l under a pressure by the action of two tension springs 8 (see also FIGURE 2) on both sides of the arms 4s and l spanned between a pair of anchoring pins 9s and l rigidly extending through the respective arms. Then the contact arm 4s is mounted at the center of the protrusion 7s on a pivot pin 10 rotatably carried by a pair of spaced contact holders 11 and 11' and therebetween. Thus the iirst Contact arm 4s is arranged to be rotatable about the axis of the pin 10 while the contact arm 4l is rotatable about the same axis with the circularly arcuated surface of the protrusion 7s maintained in rolling contact 'with the V-shaped groove 7l on two contact lines designated by the reference characters 7a and b. Therefore the protrusion 7s and the V-shaped groove 7l are always main-V tained in contact with each other at any positions or any rotated positions of the movable contact arms 4s and l to permit a current to ow from the contact 10s to the contact 10] through the two contact lines with exhibiting a low resistance to the current.

A flexible shunt lead 12 of any suitable conductive material is connected between the movable contact arms 4s and l as shown in FIGURE 1. The shunt lead 12 is formed thin insuiciently to permit any iiow of continuous load current therethrough and has only the Ifunction to prevent arcing from occurring on the contact lines 7a and b of the protrusion and V-shaped groove 7s and l when the protrusion 7s may be instantaneously separated away from the groove 7l for some reasons. The thin shunt lead 12 contributes greatly to allow the movable contact arms 4s and l to move as nimbly as possible without impeding rotational movements of both the contact arms into their bent state as will be described hereinafter.

The tension springs 8 spanned between the anchoring pins 9s and l serve to maintain the contact arms 4s and l or contacting each other under a predetermined contact pressure.

The second or upper contact unit 5 includes a pair of second or upper contact arms 5s and l of bilaterally symmetrical configuration spaced away from each other and having a pair of contacts 13s and I attached to their free ends or extremities respectively. The upper contact arms may be conveniently made of the same metallic material as the lower contact arms. In the closed position of the interrupter, those sides facing the first contact arms of the second contact arms 5s and l are substantially flush with each other and bridged by the first contact unit 4 by having the contacts 13s and l engaged by the respective contacts `6s and l. The upper contact arms 5s and l are pivotably mounted at the other ends on pivot pins 14s and l respectively.

As best shown in FIGURE 2, the pivot pins 14s and l are rigidly secured to a pair of opposed holding frames 15s and l which are, in turn, mounted to the main enclosure body 1 through the respective screws 16s and l. Spanned between an anchoring pin 17s rigidly extending through the substantially middle portion of the Contact arm 5s and a stop pin 18s fixed on the holding frame 15s on both sides of the contact arm for the purpose of imparting to the contact 13s a pressure under which it is in engagement with the mating contact 6s. For the same purpose the contact arm 5l are operatively associated with the corresponding component 171, 18] and 191. The tension springs 8 operatively coupled to the lower contact arms 4s and l also aid to provide contact pressures for the contacts 6s and l. It is noted that the second contact unit 5 has only the contact function.

As shown in FIGURE 1, the upper contact arm 5s is electrically connected through a flexible lead 20s to a connecting element 21s Welded to one end of a stationary electric conductor 22s. The conductor 22s are embedded in an electrically insulating partition 1a for physically separating the contact units 4 and S from a switching mechanism as will be described hereinafter and is connected to a source terminal 23s disposed on one edge of the main enclosure body 1. Similarly the upper contact arm 5l is electrically connected through a flexible lead 20l, a connecting element 211 and another stationary electric conductor 221 to a load terminal 231 disposed in opposite relationship with the source terminal 23s and on the opposite side of the main body 1.

As shown in FIGURE 1, the circuit interrupter further includes a pair of opposed arc extinguishing chambers 24s and l of the conventional construction adjacent to the free end portions of the upper and lower contact arms. Therefore the bottom cover member 3 also serves as a common cover for the chambers.

In order to manually open and close the circuit interrupter, that is to say, to manually move the lower contact unit 4 away and toward the upper contact unit 5, there is a switching mechanism generally designated by the reference numeral 25. The switching mechanism 25 comprises a pivotable operating handle 26 having one end portion loosely projecting beyond the top cover member 2, and a switching lever 27 of inverted U-shape secured to the operating handle 26 at the other end. Then the lever 27 is pivotably mounted at the free or other end on a pivot pin 28 planted on support plates 29 suitably disposed on the main enclosure body 1. Thus the operating handle 26 and the switching lever 27 as a whole are adapted to be turnable about the axis of the pin 28. The mechanism further comprises a pair of toggle elements 30 and 31 articulated at a pin 32 to each other with the free end of the toggle element 31 pivotably mounted on a pivot pin 33 secured to one end of a contact lever 34. A pair of tension springs 35 on each side of the switching lever Z7 are anchored at one end to the switching lever 27 and at the other ends to the toggle pin 32. The contact lever 34 is pivotably mounted on the pivot pin 28 and has extending through the other end an interlocking switching shaft 36.

Fitted onto the interlocking switching shaft 36 are three pairs of spaced contact holders 11 and 11 at the upper ends in spaced parallel relationship one pair for each pole. The contact holder 11 or 11' for each pole is made preferably of any suitable reinforced synthetic plastic high in mechanical strength, and loosely extends through a vertical complemental opening 1c or c bored throughout a central post 1b formed integrally with the main enclosure body 1 (see FIGURE 2). The lower portions of the two contact holders 11 and 11 projecting beyond the opening 1c and c is enlarged in width and have centrally extending at the lower ends a retaining pin 37 provided at each end with a guide roller 38 serving as a stopper and adapted to roll along a guide groove 3a formed on each of the common side walls of the arc extinguishing chambers 24s and l for the purpose as will be apparent hereinafter. The first or lower movable contact unit or the two lower movable contact arms 4s and l is or are sandwiched between the lower wider portions of the two mating contact holders 11 and 11' and above the retaining pin 37 for rotational movement about the axis of the pivot pin 10. The mating contact holders are provided on lboth side of the lower end portion-with a pair of bilateral recesses 39s and l along which are guided the anchoring pins 9s and l on the respective lower contact arms 4s and l.

For a tripping operation, there is provided a trip mechanisrn generally designated by the reference numeral 40. The trip mechanism 40 may be of the conventional construction and in the embodiment illustrated comprises a trip lever 41 pivotably mounted at one end on a pivot point pin 42 bridging the two parallel support plates 29 as previously described and provided on the central portion with a toggle pin 43 on which, the free end of the toggle element 30 is pivotably mounted. The trip lever 41 is normally engaged at the other end by a trip hook 44 pivotably mounted on a hook -pin 44e supported by the support plates 29. The trip hook 44 has one end portion 44a shaped into a grooved edge normally engaging the trip lever 41 and the other end 44b serving to receive a trip piece 45 secured on an interlocking trip shaft 46. The trip shaft 46 is pivotably supported by the support plates 29 and vfurther includes a trip piece similar to the piece 45 just described for each of the remaining poles except pole to normally engage the trip hook 44.

Further the circuit interrupter comprises a thermally responsive mechanism 50 and an electromagnetically responsive mechanism 56 each of which may be of the conventional construction. 'Ihey do not form a part of the invention and need not be described in detail.

The circuit interrupter thus far described is operated as follows: In FIGURE 1 wherein the interrupter is illustrated in its closed position, the operating handle 26 can be manually turned to the OFF side to cause the toggle elements 30 and 31 to collapse thereby to rotate the contact lever 34 about the axis of the pin 28 in the clockwise direction as viewed in FIGURE l. This rotational movement of the contact lever 34 is accompanied by the downward movement of the contact holders 11 and 11 to permit the lower contact arms 4s and l to be separated from the upper contact arms 5s and l and while the upper arms are maintained in a horizontal straight line as in their closed position until the lower contact arm are brought into their positions as illustrated in FIGURE 3. That is the lower contact arms 4s and l are translated to their open position. It will be appreciated that the guide rollers 38 on the holding pin 37 slide downwardly along the associated guide grooves 3a on the opposite insulating side walls of the are extinguish chambers 24s and l to ensure that the lower contacts are smoothly and rapidly separated away from the upper contacts.

If it is desired to close the open interrupter, the operating handle 26 can be manually turned to the ON side to cause the process reversed from that as above described to proceed until the lower contacts 6s and l are put and maintained in engagement with the upper contacts 13s and l respectively.

With an ordinary overload current flowing through the circuit interrupter in its closed position, the thermally responsive and/or electromagnetically responsive mechanisms 50 and 56 or mechanism will be operated in the well-known manner to cause both the trip piece 45 and the interlocking trip shaft 46 to be rotated in the counterclockwise directions as viewed in FIGURE 1 whereby the trip piece 45 disengages from the trip hook 44 resulting in the rotational movement of the trip hook 44 in the counterclockwise direction. This causes the trip lever 41 to disengage from the trip hook 44 whereupon the toggle elements 30 and 31 collapse. Thereafter the process as above described in terms of -the manual operation, is repeated until the interrupter is brought into its tripped position as illustrated in FIGURE 4.

If an excessive current whose magnitude is equal to from five to ten times the rating current for the interrupter in its closed position ilows through the latter, the movable iron core 60 is immediately attracted to the stationary iron core 57 to rotate the instantaneously tripping lever 59 until the trip responsive pin 61 on the trip piece 45 is raised. This raising of the piece 45 causes the process as above described in conjunction with the deection of the bimetallic element 51 to be repeated until the interrupter is similarly brought into its tripped position.

If a very excessive current such as a shortcircuiting current flows through the interrupter in its closed position, the current flows in the opposite directions through second contact arms 5s and 5l and the rst contact arms 4s, 4l to develop an electromagnetic repulsion which serves to rotate immediately the iirst or lower contact arms 4s and l in the opposite directions about the axis of the pivot pin 1-0. It is to be noted that during these rotational movements, the V-shaped groove 7l on the arm 4l continuously contacts the periphery of the partially circular protrusion 7s on the arm 4s on a pair of contact lines 7a and b and under a pressure exerted by the tension springs 8 whereby the contact arms 4s and l are maintained in good electric contact. This results in a decrease in electric resistance to a flow of Current through the contacting portions of both the first contact arms. The arms 4s and l may eventually abut against stopper faces 3b and b disposed on the internal surface of the bottom cover member 3.

Simultaneously with the rotational movements of the first or lower contact arms 4s and l the second or upper contact arms 5s and l are rotated in the opposite directions about the axis of the respective pins 14s and l. Thus the contacts 6s and 13s are rapidly separated in the opposite directions away from each other as do the contacts 6l and 131 lo interrupt the shortcircuiting current with a maximum possible separation between each of the contact 6s or l and the associated contact 13s or l.

The rotational movements of the first contact arms 4s and l in the opposite directions are accompanied by the displacement of the anchoring pins 9s and l thereon leading to the reversion of the direction of action of the tension springs 8 to maintain the first contact unit 4 in its inverted V-shaped position. On the other hand, the second contact unit 5 is maintained in its V-shaped position as illustrated in FIGURE 5 as long as the electromagnetic repulsion is higher in magnitude than the force exerted by each tension spring 19s or l. As the repulsion decays, the second contact arms 5s and l are returned back to their positions Where they are nearly aligned with each other as in their open position. It will be understood that while the second contact arms 5s and l are rotating the tension springs 19s and l 4may readily be reversed in direction of action thereby to maintain the second arms in their open positions.

A little later after the interruption operation as above described has been completed, the trip device 40 is operated to release the switching mechanism 25 from its constrained state to depress the interlocking shaft 45 as well as the contact holders 11 and 11. In the process just described, the first or lower movable contact arms 4s and l abut the stopper faces 3b and b to further depress the contact holders 11 and 11'. Alternatively these arms if not contacting the faces 3b and b abut against the latter to depress the contact holders. Thereby the arms are forced upwardly or toward the respective second contact arms to reverse the direction of action of the tension springs 8 until the first contact arms are brought into their open positions where they are aligned on a straight line.

'Ihen a resetting operation may be performed in order that the interrupter is ready for the succeeding closing operation as do the conventional interrupters.

As previously described, the lower movable contact unit 4 is divided into two arms only one of which is pivotably mounted on the pivot pin and includes the protrusion 7s in the form of a partial circle having its center on the axis of the pin 10. Then the other contact arm has formed on the corresponding end portion the V-shaped groove 7l which, in turn, contacts the protrusion on a pair of contact lines 7a and b under a pressure exerted by the associated tension springs 8. This arrangement is required only to include a single pivot axis positioned at the middle point between the remote ends of the arms. Thus it will be appreciated that as compared with the conventional circuit interrupter in which a separate pivot axis is necessarily provided for each of the movable contact arms, there is advantageous in that apart from the contact arm 4s including the protrusion 7s, the contact arm 4l can increase in length to increase its moment of rotation. Also as both the contact arms 4s and l contact each other on the pair of parallel contact lines 7a and b, the contacting portions of the arms are halved in electric resistance leading to an increase in rated current of the interrupter.

Also the Stoppers 38 have been mounted on the retaining pin 37 secured to the contact holders 11 and 11' for the purpose of halting the central portions of the tension springs 8 at a predetermined distance from the axis of the pivot pin 10 after the springs have been reversed in the direction of action during the rotational movements of the first contact units 4 and 5 due to the occurrence ofan electromagnetic repulsion may be sometimes of such a magnitude that the first mova-ble contact arms 4s and l will be caused to halt short of the stopper faces 3b and b on the bottom cover member 3 without abutting against the stopper faces. However a flow of shortcircuiting current through the interrupter will generally produce an electromagnetic repulsion having a magnitude sufficient ot rotate the first contact arms 4s and l until they abut against the stopper faces 3b and b. Under these circumstances, the tension springs 8 are caused to halt by the stopper 38 by having the central portions thereof abutting against the latter (see FIG- URE 5) after which the arms 4s and l continue to be rotated until they abut against and halt by the stopper faces 377 and b. This rotational movement of the contact arms 4s and l are accompanied by revolutions of the anchoring pins 9s and l on the arms 4s and l about the axis of the pivot pin 10. Therefore the tension springs 8 having both ends anchored to the pins 9s and l expand to be arcuated concavely toward the stoppers 38 thereby to decay the rotational movements of both the arms.

After the interruption of the shortcircuiting current as previously described, the electromagnetic repulsion exerting upon the rst contact arms 4s and l decays to return the anchoring pins 9s and l back to their halting positions determined by the Stoppers 38 by means of the restoring force of the springs 8. This permits the first movable contact arms 4s and l to disengage from the stopper faces 3b and b to assume their positions as shown in FIGURE 6. It will be readily understood that a force required to move the contact arms 4s and I from their positions as illustrated in FIGURE 6 to their open positions as illustrated in FIGURE 3 is much smaller than that required to move them from their positions as illustrated in FIG- URE 5 where the Stoppers 38 are assumed to be omitted to their open positions.

It is recalled that a little later after the first movable contact arms 4s and l have responded to the generation of an electromagnetic repulsion resulting from a flow of shortcircuiting current through the interrupter to interrupt that current, the trip device 40 is operated to actuate the switching mechanism 25. Then the switching mechanism 25 causes the contact holders 11 and 11 to be depressed along with the first movable contact arms 4s and l put in their positions as illustrated in FIGURE 6. Thus the arms 4s and l abut on the free end portions against the stopper faces 3b and b while the contacting portions of the arms are additionally depressed whereby the arms are forced to be rotated upwardly. This permits the tension springs 8 to go upwardly across the pivot pin 10` thereby to return the lirst movable contact arms 4s and l back to their original, straight aligned positions. That is, only the operation of the switching mechanism 25 permits the first rotated contact arms 4s and l to be moved into their original state in which they are aligned on a line with each other.

Therefore it is not required to provide any resetting mechanism for returning the first moved contact arms back to their positions where they are put on a line, such as a link mechanism by which the guide roller 38 connected to the first movable contact arms 4s and l through a link responds to the descent of the contact holders 11 and 11 resulting from the particular tripping operation to slide along a guide groove 3a provided in the cover member for the arc extinguishing chambers (see FIG- URE 1) and abut against the bottom thereof after which a force acts on the first contact arms 4s and l to be returned back to their original aligned state. Thus the first movable contact unit becomes simple inconstruction.

As previously described, if an electromagnetic repulsion has a suiciently high magnitude, the first contact arms 4s and l can continue to be rotated about the axis of their common pivot pin 10 even after the tension springs 8 have abutted on the central portion against the Stoppers 38 to halt. The arms eventually abut against the stopper faces 3b and b whereupon a maximum separation is formed between each contact 6s or l on the .lirst arm 4s or l and the associate contact 13s orl on the second arm 5s or l. This separation is large and does not adverse- 1y affect the interruption performance of the interrupter.

Also an electromagnetic repulsion having a high magnitude causes the first movable contact arms 4s and l to be rotated at high speed until they strike against the stopper faces 3b and b'. Under these circumstances, after the central portions of the tension springs 8 has been caused to halt by the stoppers'38 the springs are forcedly expanded to become arcuate against the opposing force thereof. This results in buffer means for alleviating any harmful inpulsive force with which the first movable contact arms 4s and l strongly strike against the stopper faces 3b and b to be bent.

It is to be understood that the stopper 38 may be equally associated with a pair of movable contact arms rotatable in the opposite directions about the respective axis of rotation rather than about a common axis of rotation upon the occurrence of a very shortcircuiting current. Such movable contact arms are disclosed for example, in U.S. Patent No. 3,317,866, entitled Automatic Circuit Interrupter Having Magnetic Blowofr" Means, issued on May 2, 1967 to T. Hanafusa and U.S. Patent No. 3,343,- 108, entitled High Speed Circuit Interrupter Using Magnetic Blowol and Means for Decreasing the Inertial Effects During Interruption, issued on Sept. 19, 1967 to W. Murai, both patents being assigned to the present assignee. A pair of movable contact arms 23 and 23 shown in FIG. 4 of U.S. -Patent No. 3,317,866 may be Ioperatively associated with a stopper such as stopper 38 as described herein disposed on those sides of the respective trunnions 28 and 28 oposite to the associated stationary contact arms 22 and such positions that during. the rotational movements of the movable contact arms due to the particular electromagnetic repulsion between pins 28 and 28' about which the respective arms 23 and 23 are 'rotatable and at such a position that during the rotational movements of the arms due to the particular electromagnetic repulsion the sing spring is passed over the pins 28 and 28' and engaged on the central portion by the stopper to be expanded into an arcuated shape. Alternatively, it will be apparent that a pair of movable contact arms 42 and 42a disclosed in U.S. Patent No. 3,343,108 may be similarly associated with a stopper similar to the stopper 38 of the present invention with a slight modification apparent to those skilled in the art.

While the invention has been illustrated and described in conjunction with a few preferred embodiments thereof it is to be understood that numerous changes inthe details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention.

What is claimed is:

1. In a circuit interrupter of the type utilizing an electromagnetic repulsion generated between a pair of rst and second movable contact units disposed in substantially parallel relationship in the closed position of the interrupter upon the occurrence of a very excessive current thereby to interrupt the current, the combination of a pair of movable contact arms forming the lirst contact unit and bridging the second contact unit in the closed position of the interrupter, and tension spring means spanned between said first and second movable contact arms, said movable contact arms being responsive to the electromagnetic repulsion to be rotated in the opposite directions about the respective centers of rotation while the arms are maintained in electric contact relationship until the arms are held in their predetermined positions through the movement of the central portion of said tension spring means across said centers of rotation; stopper means disposed at such a position that during the rotational movements of said movable contact arm said tension spring means are moved across said centers of rotation and engaged on the central portion by said stopper means to be expanded into an arcuated shape, after which as the electromagnetic repulsion decays said pair of movable contact arms are permitted to occupy their positions deter-l mined by said stopper means under the restoring force of said tension spring means.

2. In a circuit interrupter of the type utilizing an electromagnetic repulsion generated betwen a pair of rst and second contact units disposed in substantially parallel relationship in the closed position of the interrupter upon the occurrence of a very excessive current thereby to interrupt the current, the combination of a pair of movable contact arms forming the rst contact unit and bridging the second contact unit in the closed position of the interrupter, tension means spanned between said first and second movable contact arms to provide a contact pressure between the first and second contact units, said iirst movable contact arms having a protruding end portion in the form of a partial circle always maintained in bendable engagement with the adja-cent end portion in the form of a V-shaped groove of said second movable contact arm by the action of said tension spring means, said rst movable contact arm being pivotably carried at said center of said partial circle such that said first and second movable contact arms are responsive to the electromagnetic repulsion to be rotated in the opposite directions about said center to interrupt the current while the arms are maintained in rolling contact relationship, and stopper means disposed at such a position that during the rotational movements of said movable contact arms said tension spring means are moved across said center of the partial circle and engaged on the central portion by said stopper means to be expanded into an arcuated shape, after which as the electromagnetic repulsion decays said pair of movable contact arms are permitted to occupy their positions determined by said stopper means under the restoring force of said tension spring means.

References Cited UNITED STATES PATENTS 3,317,866 5/1967 Hanafusa 335-16 3,343,108 9/1967 Murai 335-16 BERNARD A. GILHEANY, Primary Examiner R. N. ENVALL JR., Assistant Examiner

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