US3158721A - Main and auxiliary contacts wherein main relatively stationary contact is pivotally mounted to move in opposite direction to switch arm - Google Patents

Description

Nov. 24, 1964 A P. DELANEY 3,158,721

MAIN AND AUXILIARY OONTACTS WHEREIN MAIN RELATIVELY STATIONARY CONTACT IS PIVOTALLY MOUNTED TO MOVE IN OPPOSITE DIRECTION TO SWITCH ARM Filed June 11, 1962 s Sheets-Sheet 1 /6 ,fiy' E 36\ 77 40 44 52 54 I I 1 r7 I LJIIJ; 45 752mm; W 33 14 vi? i 35 l l H 3/ l hi 7.?

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MAIN AND AUXILIARY CONTACTS WHEREIN MAIN RELATIVELY STATIONARY CONTACT IS PIVOTALLY MOUNTED TO MOVE IN OPPOSITE DIRECTION TO SWITCH ARM Filed June 11, 1962 5 Sheets-Sheet 2 Jim- 3 E /ML 00m Nov. 24, 1964 A. P. DELANEY 3,158,721

AND AUXILIARY CONTACTS WHEREIN MAIN RELATIVELY MOVE MAIN

STATIONARY CONTACT IS PIVOTALLY MOUNTED TO IN OPPOSITE DIRECTION TO SWITCH ARM Filed June 11, 1962 5 Sheets-Sheet 3 United States Patent MAIN AND AUXILIARY CONTACTS WHEREIN MAIN RELATIVELY STATIONARY CONTACT IS PIVOTALLY MOUNTED TO MOVE IN OPPOSITE DIRECTION TO SWITCH ARM Augustine P. Delaney, South Milwaukee, Wis, assignor to McGraw-Edison Company, Milwaukee, Wis, a corporation of Delaware Filed June 11, 1962, Ser. No. 261,604 2 Claims. (Cl. 200-146) This invention relates to circuit breakers and more particularly to the contact structure for high voltage circuit breakers.

High voltage circuit breakers of the type having contacts which part in air and means for blowing the arc magnetically or by a gas blast into interrupting structure, are generally provided with main current carrying contacts and auxiliary arcing contacts. The auxiliary arcing contacts are normally connected in shunt with the main current carrying contacts and are arranged to part after the main current carrying contacts have parted so that the are will be carried by the auxiliary contacts. In addition, such auxiliary contacts are arranged to engage upon closure of the circuit breaker prior to the engagement of the main current carrying contacts so that any pre-strike will also be carried by these auxiliary contacts. This insures that the main current carrying contacts are not damaged by repeated arcings.

In order to insure that no arc is struck between the main current carrying contacts, the auxiliary contacts should remain in engagement until after the main current carrying contacts have separated a predetermined distance. As a result, however, interruption of the arc is thereby delayed because arc interruption does not begin until after the auxiliary contacts have parted.

It is an object of the invention to provide high voltage circuit breaker contacts having stationary main current carrying and auxiliary arcing contacts co-operable with corresponding contacts carried on a switch arm wherein the main current carrying contacts part at a speed greater than that of the switch arm allowing more rapid opening of the arcing contacts.

A further object of the invention is to provide high voltage circuit breaker contact structure having stationary main current carrying and auxiliary contact co-operable with corresponding contacts carried on a switch arm wherein the stationary main current carrying contacts pivot in a direction opposite to that of the switch blade upon movement of the switch blade toward its open position to permit more rapid parting of the current carrying contacts.

Another object of the invention is to provide a stationary circuit breaker contact member having a main current carrying contact mounted on one side of its pivotal axis and an arcing contact on th other side thereof and biasing means urging rotation of the one side away from a cooperating switch arm and other side toward said arm so that the main current carrying contact will move in a direction opposite to the switch arm when the latter opens to provide rapid separation while the auxiliary contact momentarily remains in engagement therewith. Yet another object of the invention is to provide such a contact with means for permitting limited sliding as well as pivotal movement.

These and other objects and advantages of the instant invention will become more obvious from the detailed description thereof taken with the accompanying drawings in which:

FIG. 1 is a portion of a circuit breaker incorporating contact structure according to the instant invention;

FIG. 2 is a side elevational view, partly in section, of

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one embodiment of contact structure according to the instant invention;

FIG. 3 is atop plan view of the contact structure shown in FIG. 2;

FIG. 4 is a front view, with parts broken away, of the stationary portion of the contact structure illustrated in FIG. 2;

FIGS. 5 and 6 illustrate the operation of the contact structure shown in FIG. 2;

FIG. 7 is a side elevational view, partly in section, of an alternate embodiment of the instant invention; and

FIGS. 8 and 9 illustrate the operation of the embodiment shown in FIG. 7.

Referring to the drawings in greater detail, FIG. 1 shows a circuit breaker designated generally by the reference numeral 10 and including contact structure 12 and schematically illustrated arc interrupting structure 14. The contact structure 12 includes a stationary contact assembly 16 carried on the inner end of a stud 17 which is supported on the circuit breaker frame 18, and a movable contact assembly 20 carried at the upper end of a switch arm 22. The switch arm 22 is pivotally mounted at its lower end on the inner end of a second stud 23.

Each of the studs 17 and 23 carries a disconnect contact 24 and 25, respectively, at its outer end for engagement with coacting disconnect contacts, not shown, for connecting the circuit breaker 10 to the system being protected. This establishes a series circuit through the device from the stud 17 to the stud 23, through the stationary contact structure 16, the movable contact structure 29, and the switch arm 22. It will be understood by those skilled in the art that a switch operating mechanism (not shown) will be connected to the switch arm 22 by a link 26 so that the switch arm 22 may be pivoted clockwise from its closed position shown by full lines in FIG. 1 to an open position shown by dotted lines. It will also be understood by those skilled in the art that upon separation of the contact structure 12, an arc will be struck between the stationary contact assembly 16 and the movable contact assembly 20. Means (not shown) such as a magnetic coil or gas blast structure will be provided for blowing the are up into the interrupting structure 14.

Referring now to FIGS. 2, 3 and 4, the stationary contact assembly 16 is shown to include a conductive base 28 secured to the end of the stud 17 and a pair of arms 29 integral with and extending forwardly of the base 28. A contact member 31 is pivotally and slidably mounted between the arms 2 by means of a pin 33 extending therebetween. The contact member 31 consists of a pair of spaced pivot plates 34 each having an elongate slot 35 formed therein for embracing the pin 33. The plates 34 are joined at their upper ends by an arcing contact mass 36 and at their lower ends by a current carrying contact mass 37. It will be understood that the plates 34 and the contact masses 36 and 37 are formed of a highly conductive material, such as copper, and are afiixed by any well known means such as brazing to form a rigid integral structure and to provide good current interchange between the contact masses and the plates 34.

Upper and lower spring assemblies 40 and 42, respectively, extend between the base 28 and the contact masses 36 and 37 to urge the contact member 31 toward the movable contact assembly 20 and the upper spring as sembly 40 is shown in FIG. 2 to include a spring 44 whose left end resides in and bears against a recess 45 formed in the upper end of the base 28 and Whose right end bears against the head 47 of a spring guide 48. The spring guide 48 has a longitudinal recess formed therein for receiving the body of a pivot base 52. The pivot base 52 has a conical head 54 and a reverse conical recess 56 formed at the point of the head 54 to provide a bearing surface for the head of a pivot pin 59 embedded in the arcing contact mass 36. The spring guide 48, the pivot base 52 and the pivot pin 59 prevent the spring 44 from buckling as the contact member 31 moves on the pin 33.

The lower spring assembly 42 also includes a spring 60 whose left end is received in and bears against a recess 62 formed in the lower end of the base 28. In addition, a spring guide 64, a pivot base 65 and a pivot pin 66 are also provided in the lower spring assembly 42 and these elements perform the same functions as the corresponding members in the upper spring assembly 40.

The movable contact assembly 20 includes a main current carrying contact 70 for co-operatively engaging the stationary current carrying contact 37 when the switch arm 22 is in its closed position as shown in FIG. 1 and a movable arcing contact 71 for engaging the stationary arcing contact 36. It will be understood by those skilled in the art that the engaging portions of the stationary main current carrying contact 37 and the corresponding movable contact 76 will be provided with inserts 73 and 74, respectively, of a material such as a silver alloy for better conduction. Similar inserts 76 and 77 will be provided in the stationary and movable arcing contacts, respectively.

It can be seen from FIG. 2 that when the contact arm 22 is in its closed position, the pin 33 is intermediate the ends of the slot 35. As the switch arm 22 begins pivoting away from the stationary contact assembly 16, during a switch opening operation, the movable contact assembly 16 will begin moving toward the night as viewed in FIG. 2. This will allow the springs 42 and 44 to push the stationary contact member 36 in the same direction until the pin 33 is engaged by the left end of the slot 8t as shown in FIG. 5. As the switch arm 22 continues pivoting, further movement of the stationary contact member 31 toward the right is prevented.

In order for the member 31 to rotate in the desired direction, it is necessary for the torque exerted by the upper spring 44 to be greater than that exerted by the lower spring 60. This can be accomplished either by providing a stronger spring at 44 or having it act through a larger moment arm. In the preferred embodiment of the invention, both of these methods are employed since spring 44 is a greater distance from the pin 33 than the spring 60 and it also exerts a greater force. Thus, as the switch arm 22 continues moving, the stationary contact member 20 will pivot clockwise, see FIG. 6, as the spring 44 holds the stationary arcing contact 36 in engagement with the movable arcing contact 71. However, such clockwise rotation disengages the stationary main current carrying contact 37 from the movable current carrying contact 76.

It will be appreciated that clockwise rotation of the stationary contact member 31 has the effect of moving the stationary main current carrying contact 37 toward the left as viewed in FIG. 6 and away from the movable main current carrying contact 70 which is moving in the opposite direction due to the pivotal movement of the switch arm 22. As a result, the relative movement of the main current carrying contacts 37 and 70 is substantially greater than that attributable to movement of the switch arm 7 alone. Thus, the predetermined gap separation between the main current carrying contacts, which is necessary before the arcing contacts 36 and 71 can disengage, is achieved with substantially less pivotal movement of the switch arm 22 than would be the case if the main current carrying contact 37 were stationary.

Clockwise rotation of the member 31 will continue as the switch blade 22 pivots until its lower left hand corner 32 engages the rear wall of the base 28. Upon this event the arcing contacts 36 and 71 will disengage and any arc struck therebetween will be extinguished in the are extinguishing assembly 15, in a manner well known in the art.

While the switch is in its open position, the contact member 31 will remain pivoted. As a result, movement of the switch blade 22 towards its closed position will cause the movable arcing contact 71 to engage the stationary arcing contact 36 prior to the engagement of the contacts 37 and '70, as shown in FIG. 6 so that any prestrike, which may occur if the device is closed under load, will be drawn through the arcing contacts. After the arcing contacts engage in this manner, the contact member 31 will then be rotated counterclockwise around pin 38 until the main current carrying contacts 37 and 70 engage as shown in FIG. 5. Further movement of the switch blade 22 will move the contact member 21) toward the left compressing the springs 42 and 44 until the contact assembly resumes its position shown in FIG. 2.

When the contact assembly is in its closed position current must be transferred from the arms 29, which are rigidly afiixed to the base 23, to the contact member 31 which is rotatably mounted relative thereto. For this purpose an annular groove 84 is formed in each of the arms 29 and encompassing the pin 33. Disposed in each of these annular grooves is a helically wound annular current interchange spring 85. As seen in FIG. 4 the distance between the bottom of the groove 84 and the opposed surface of the plate 34 is less than the normal outside helical diameter of the spring 85 so that each of the convolutions of the spring 84 are forced to lay over at an angle relative to their helical axis. As a result of the resiliency of the spring 85, each convolution bears in firm electrical engagement with the groove 84 and the plate 34 to provide a current path therebetween. Thus, a large number of parallel current paths are provided between the members 34 and 29 to form a low friction high current capacity joint. In this manner, current is transferred from the contact member 34 to the arms 29 without impairing the relative rotational movement therebetween. For a more detailed description of the current interchange structure just described, reference is made to copending application Serial No. 847,263, filed October 19, 1959, now Patent No. 3,056,- 101, and assigned to the assignee of the instant invention.

In the alternate embodiment of the invention illustrated in FIG. 7, the stationary contact structure is shown to include a base having a pair of forwardly extending arms 101 integral therewith. A stationary contact member 102 is pivotally mounted between the arms 1491 by means of a pin 103 and includes a pair of side plates 104 which are joined at their lower end by a stationary main current carrying mass 105 and at their upper end by a stationary arcing contact mass 106.

The contact member 102 is biased for rotation in a clockwise direction by means of a spring 107 connected at one end to a first pin 108 extending between the arms 101 and located to the rear of the pivot pin 103 and at its other end to a second pin 163 extending between the plates 104 and located below said pivot pin 103.

A pair of links 110 are pivotally connected at one end to a pair of pins 111 extending laterally from the opposite sides of the stationary arcing contact 196. In addition, each of the links 110 have an elongate slot 113 formed in their other ends for engagement with pins 12 extending from the opposite sides of the base 100.

The movable arcing contact assembly 115 comprises a slidable conductive member 116 disposed in a recess 118 formed in the upper end of the movable contact arm 120. A cavity 121 formed in the rear of the contact member 116 receives a compression spring 123 which urges the contact finger toward the left as viewed in FIG. 7 and into engagement with the stationary arcing contact 106. A channel 124 is formed in each of the upper and lower surfaces of the contact member 116 for receiving current interchange springs 125 so that current interchange may be provided between the relatively movable contact member 16 and the upper and lower walls of the cavity 118.

For a more detailed description of the movable contact assembly 115, reference is made to copending application Serial No. 848,888, filed October 19, 1959, now Patent No. 3,087,038, and assigned to the assignee of the instant invention.

As seen in FIG. 7, when the contact assembly is in its closed posit-ion the pin 112 is located intermediate the ends of the slot 113. As the contact arm 120 begins pivoting toward the right, as viewed in FIG. 7, the spring 123 will overcome spring 107 to pivot the contact member 102 through a slight counterclockwise angle until the right end of the slot 113 engages the pin 112. Further, counterclockwise rotation ofthe stationary contact member 102 is prevented. At this point the stationary contact assembly is in the position shown in FIG. 8 and both the arcing contacts and the main current contacts are still in engagement.

As the switch blade 120 continues clockwise rotation, the contact member 102 will be held in its counterclockwise pivoted position as the spring 123 urges the member 116 toward the left. As a result, the arcing contacts 106 and 116 will remain in engagement as the switch arm 120 continues to pivot, but the main current carrying contacts 105 and 130 will begin to disengage. When such movement of member 116 toward the left brings a shoulder 120 formed on the contact member 116 into engagement with a lip 128 in the mouth of the cavity 118, further movement of the contact member 116 relative to the arm 120 is prevented. Upon this event, further movement of the switch blade 120 will permit clockwise rotation of the contact member 120 by the spring 107. As a result, the arcing contacts 106 and 116 will remain in engagement while the main current carrying contacts 105 and 130 will be moving in opposite directions. The contact member 102 will continue such clockwise rotation until the left end of the slot 13 engages the pin 112 whereupon the arcing contacts 106 and 116 will part.

It can be seen that in the embodiment of the invention depicted in FIG. 7, the main current carrying contacts 105 and 130 will be moving in opposite directions prior to disengagement of the arcing contacts 106 and 116. As a result, more rapid separation of the main current carrying contacts 105 and 130 is possible than would be the case if separation were due to movement of the contact 130 alone.

It will be understood that current interchange between the arms 101 and the contact member 102 may be achieved with current interchange spring 132 in a manner similar to that discussed relative to the embodiment of FIGS. 2-6.

While the invention has been shown and described with respect to one particular kind' of circuit breaker, it will be understood by those skilled in the art that it may be employed in other types of circuit breakers as well. In addition, while only two embodiments of the instant invention have been disclosed, it is not intended that the invention be limited thereby, but only by the terms of the appended claims.

I claim:

1. In a circuit interrupter, the combination of, a stationary contact assembly, a pivotally mounted switch arm, a movable contact assembly mounted on the free end of said switch arm, said movable contact assembly including a first main contact and a first auxiliary contact, said first auxiliary contact being mounted for movement on said switch arm in a direction toward said stationary contact assembly, a first biasing means urging said first auxiliary contact in said direction, stop means limiting the movement of said first auxiliary contact, said stationary contact assembly including a contact member mounted for limited rotational movement about an axis intermediate its ends, a second main contact being mounted adjacent one end of said contact member and a second auxiliary contact mounted adjacent the other end thereof, said first and second main contacts and said first and second auxiliary contacts being respectively engageable when said switch arm is in a closed position, a second biasing means urging said contact member to rotate in a direction which moves the other end of said contact member toward said switch arm, said first biasing means exerting a greater torque on said contact member than said second biasing means so that said other end of said contact member will initially rotate in a direction away from said switch arm after a switch opening operation begins, the engagement of said first auxiliary contact with said stop means ailowing said contact memher to rotate toward said switch arm so that said main current carrying contacts will move in opposite directions and said auxiliary arcing contacts will be held in engagement for a limited time when said switch arm begins pivoting toward an open position.

2. In a circuit interrupter, the combination of a stationary contact assembly, a pivotally mounted switch arm, a first main contact intermediate the ends of said switch arm, a first auxiliary contact including a cavity formed in the end of said switch arm and opening toward said stationary contact and a contact element slidably mounted in said cavity, first spring means urging said contact element toward said stationary contact assembly, stop means limiting the movement of said contact element, said stationary contact assembly including a base and a contact member pivotally mounted on said base about an axis intermediate its ends, a second main contact mounted adjacent the lower end of said contact member and engageable with said first main contact when said switch arm is in a closed position, a second auxiliary contact mounted adjacent the upper end of said contact member and engageable with said contact element, second biasing spring means urging the upper end of said contact member to rotate toward said switch arm, means including a pin afiixed to one of said base and contact member at one side of said axis and a slot formed in the other of said base and contact member for limiting the rotational movement of said contact member around said axis, said first biasing means exerting a greater torque on said contact member than said second biasing means so that the lower end of said contact member will rotate toward said switch arm after a switch opening operation begins and until said pin engages one end of said slot, the engagement of said contact element with said stop means allowing the upper end of said contact member to rotate toward said switch arm so that said main current carrying contacts will move in opposite directions and said auxiliary contacts will be held in engagement for a limited time, said auxiliary contacts moving out of engagement when said pin means engages the opposite end of said slot.

References Cited in the file of this patent UNITED STATES PATENTS 2,214,471 Ludwig et al Sept. 10, 1940 2,324,891 Thumin July 20, 1943 3,064,107 Date Nov. 13, 1962

Claims (1)

1. IN A CIRCUIT INTERRUPTER, THE COMBINATION OF, A STATIONARY CONTACT ASSEMBLY, A PIVOTALLY MOUNTED SWITCH ARM, A MOVABLE CONTACT ASSEMBLY MOUNTED ON THE FREE END OF SAID SWITCH ARM, SAID MOVABLE CONTACT ASSEMBLY INCLUDING A FIRST MAIN CONTACT AND A FIRST AUXILIARY CONTACT, SAID FIRST AUXILIARY CONTACT BEING MOUNTED FOR MOVEMENT ON SAID SWITCH ARM IN A DIRECTION TOWARD SAID STATIONARY CONTACT ASSEMBLY, A FIRST BIASING MEANS URGING SAID FIRST AUXILIARY CONTACT IN SAID DIRECTION, STOP MEANS LIMITING THE MOVEMENT OF SAID FIRST AUXILIARY CONTACT, SAID STATIONARY CONTACT ASSEMBLY INCLUDING A CONTACT MEMBER MOUNTED FOR LIMITED ROTATIONAL MOVEMENT ABOUT AN AXIS INTERMEDIATE ITS ENDS, A SECOND MAIN CONTACT BEING MOUNTED ADJACENT ONE END OF SAID CONTACT MEMBER AND A SECOND AUXILIARY CONTACT MOUNTED ADJACENT THE OTHER END THEREOF, SAID FIRST AND SECOND MAIN CONTACTS AND SAID FIRST AND SECOND AUXILIARY CONTACTS BEING RESPECTIVELY ENGAGEABLE WHEN SAID SWITCH ARM IS IN A CLOSED POSITION, A SECOND BIASING MEANS URGING SAID CONTACT MEMBER TO ROTATE IN A DIRECTION WHICH MOVES THE OTHER END OF SAID CONTACT MEMBER TOWARD SAID SWITCH ARM, SAID FIRST BIASING MEANS EXERTING A GREATER TORQUE ON SAID CONTACT MEMBER THAN SAID SECOND BIASING MEANS SO THAT SAID OTHER END OF SAID CONTACT MEMBER WILL INITIALLY ROTATE IN A DIRECTION AWAY FROM SAID SWITCH ARM AFTER A SWITCH OPENING OPERATION BEGINS, THE ENGAGEMENT OF SAID FIRST AUXILIARY CONTACT WITH SAID STOP MEANS A LOWING SAID CONTACT MEMBER TO ROTATE TOWARD SAID SWITCH ARM SO THAT SAID MAIN CURRENT CARRYING CONTACTS WILL MOVE IN OPPOSITE DIRECTIONS AND SAID AUXILIARY ARCING CONTACTS WILL BE HELD IN ENGAGEMENT FOR A LIMITED TIME WHEN SAID SWITCH ARM BEGINS PIVOTING TOWARD AN OPEN POSITION.

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