US3020374A - Circuit breaker arcing contact construction - Google Patents

Description

Feb. 6, 1962 G. D. TOOTELIAN 3,020,374

CIRCUIT BREAKER moms CONTACT CONSTRUCTION Filed July 2, 1959 Kw f NV EN TOR.

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. 1 4504 50. morn/4M 3,020,374 CIRCUIT BREAKER ARUING CUNTACT CONSTRUCTION George I). Tootelian, Brooinall, Pa., assi'gnor to I-T-E Circuit Breaker tlornpany, Philadelphia, he, a corporation of Pennsylvania Filed July 2, 1959, Ser. No. 824,583 8 filaims. (Cl. 200-146) My invention relates to an arcing. contact construction wherein the arcing current sets up a magnetic flux to drive the arcing contact into engagement with respect to its cooperating contacts and counteracts the normal blow-cit forces tending to open the arcing contact.

In the circuit breakers of the type set forth in US. Patent No. 2,891,123, issued June16,-1959, entitled High Speed Circuit Breaker in the name of Chailiss I. Clausing and assigned to the assignee of the present invention, the movable contact is normally constructed of a main movable contact electrically connected in parallel with an arcing contact. The movable contact arm is normally controlled and constructed so that when the circuit breaker is operated to its engaged position, the main movable contact will first disengage with a current path remaining in parallel therewith which includes the arcing contact. Therefore, there is no arc drawn to the main movable contact. As the disengaging operation continues, the arcing contact finally moves away from its cooperating contact and an arc is then drawn to the arcing contact which is specifically constructed to withstand arcing duty.

During closing, the arcing contact will normally close the circuit first and is followed by the movable contact. Therefore, when the movable main contact closes, the circuit has already been completed and the main movable contact is subjected to very little closing duty.

States Patent 3,.GZ9,374 Patented Feb. 6, 1962 ice tobias the arcing contact in a direction to oppose blowoff force.

Accordingly, a primary object of my invention is to provide a novel structure for opposing the blow-off force applied to an arcing contact.

Another object of my invention is to do away with the necessity of powerful springs for biasing an arcing contact toward its engaged position. A further object of my invention is to utilize the biasing spring of an arcing contact as a solenoid winding for moving an arcing contact in a direction against the blow- During the opening operation, it is desirable to have the main movablecontact open to a substantial distance before the arcing contact opens. However, there is a substantial blow-off force exerted upon the arcing contact which normally is pivotallymounted on the movable contact structure carrying both the main movable con tact and the arcing contact. These blow-off forces can, in a circuit breaker carrying large load currents and which are subjected to large short circuit currents reach sizable magnitudes of force and exert a considerable opening force on the pivotally mounted arcing contact be fore the movable contact has reached a sufficiently open position. For this reason, the arcing contact is backedup with large springs which normally bias toward the contact engaged position. When, however, the blow-oil? force in a particular circuit is large enough, it is not feasible to provide biasing springs large enough to withstand the bloW-ofi force.

I have discovered that I can utilize the energy of the arcing current to help withstand the blow-oil force by causing this current to operate a solenoid carried by the movable contact and which includes a magnetic member connected to the pivotally mounted arcing contact. If desired, the normally used biasing spring may be connected to act as an electrical winding or an auxiliary'means may be provided. Thus; I can utilize a biasingspring which is of a relatively high conductivity material and insulatethe pivotaliy mounted arcing contact from the contact arm; The biasing; spring is then electrically connected between the arcing contact and the contact arm so that under arcing conditions, the current is carried at least in part by the spring.

-A magnetic core which is mechanically connected to the arcing contact is then acted upon by the current through this spring which acts as a solenoid winding cit force applied thereto during current conduction through the arcing contact.

A stillfurther object of this invention is to insulate an arcing contact from the contact arm carrying the arcing contact and electrically connecting the arcing contact to the contact arm by circuit means which will operate to exert a force upon the arcing contact in opposition to the blow-oil force applied thereto.

These and other objects of my invention will become apparent from the following description when taken in connection with the drawings in which:

FIGURE 1 shows a first embodiment of my novel movable contact arm structure wherein the biasing spring for biasing the arcing contact is used as a solenoid winding under arcing conditions.

FIGURE 2 shows a second embodiment of. my inventi'on. wherein the solenoid need not act as the main biasing spring for the pivotally mounted contact.

FIGURE 3 is similar to FIGURE 2 and shows the movable contact arm in partially and fully disengaging position.

FIGURE 4 shows a further embodiment of the invention Where the auxiliary spring is concentric with the biasing spring.

Referring now to FIGURE 1, a movable contact arm ll of conductive material is pivotally mounted on pivot 12. -A main contact 14 is pivoted to arm 10 at pivot The upper end of conto arm that pivot 2d. The pivotal connection between arm 16 and arcing contact '18 is an insulated connection and is formed of a main central pin 22 and an outer insulating cylinder 24. A relatively stationary contact for cooperating with main contact 14 and arcing contact 18 is partially shown as stationary contact member 26 and includes contact surfaces 28 and 31 for cooperating with the main movable contact 14 and arcing contact 18 respectively. I I

The arcing contact 18 has a rearwardly projecting portion 30 which is positioned under an insulated adjustable stop 32 which is formed by a threaded screw member carried by frame 10. The arcing contact 18 is then biased toward engagement with stop 32 by a spring 34 which is preferably a beryllium copper spring. The beryllium copper spring is electrically connected at its ends between arcing contact 18 and movable contact arm 10.

In accordance with the present invention, the relatively movable non-magnetic member 38 and a magnetic plunger 40 are positioned within spring 34 and are axially movable therein. Accordingly, when the movable con tact arm to is moved toward a disengaged position by operating means 42, the main movable contact 14 will disengage with respect to stationary contact 28 while the arcing contact 18 will remain engaged with cooperating contact '31 because of the biasing spring 34 which biases the arcing contact toward its engaged position. The current flow will now form a relatively U-shaped path going through the stationary arcing contact 31, arcing contact 18, spring 34 land to the main contact arm 10. This U-shaped current path will cause a blowoii action against arcing contact 18 tending to rotate it in clockwise direction about pivot 20 and thus open the circuit before suflicient clearance is achieved between the main movable contact 14 and its cooperating contact 28.

The only force counteracting this blow-off force in the past has been the biasing spring 34. When, however, the current magnitudes are sufficiently high, this spring force will be overcome prematurely.

In accordance with the present invention, when the main contact 14 disengages, the arcing current flows through spring 34 so that the spring acts as a solenoid winding. Accordingly, the plunger 40 of magnetic material will be drawn upwardly with a strong force into engagement with member 38 which, in turn, engages the rearwardly projecting portion 3a of the arcing contact to drive it in a counter-clockwise direction and against the blow-off force.

FIGURE 2 shows a second embodiment of my novel invention wherein numerals similar to those used in FIGURE 1 identify similar components. The embodiment of FIGURE 2 diifers from the embodiment of FIGURE 1 in having the auxiliary blow-off force means independent of the biasing spring 34 of FIGURE 1 so that the material used for the biasing spring may be selected to have the best spring properties. In FIGURE 2, biasing spring 34 is not shown in order to simplify the drawings, but is present and operates in the same manner as described in FIGURE 1 with the exception of the electrical action.

FIGURE 2 shows a projecting arm 44 which is directly connected to arcing contact 18 to be rotatable therewith. The end of arm 44 is terminated by a magnetic button 46. Magnetic button 46 is positioned adjacent an iron core 48 and separated therefrom by an air gap and core 48 is rigidly connected to contact arm 10. A spring member or coil 50 which is of a material having good electrical conducting characteristics has one end 52 mechanically and electrically connected to arcing contact 18 and its other end 54 mechanically and electrically connected to contact arm 10. The spring 50 surrounds magnetic core 40 and button 46.

In the structure of FIGURE 2, when the movable contact arm is operated to move toward a disengaged position and after a disengagement of the main movable contact 14, a current flow is established through spring 50 as seen from the solid line position in FIGURE 3. This establishes a magnetic'field within the spring so that magnetic button 46 is attracted toward core 48 to exert a counter-clockwise force on arcing contact 18 about pivot 20 which, along with the biasing force of the normal biasing spring acting on arcing contact 18, will counteract the blow-01f force imparted to contact 18.

As seen in the solid line position of FIGURE 3, the arcing contact 18 will remain in engagement with contact 31 in which movable contact 14 has established a sufiicient clearance distance from main stationary contact 28. After this distance has been reached, the continued motion of contact arm 10 to its fully disengaged position shown in the dot-dash view of FIGURE 3 will move the arcing contact 18 away from contact 31 and against stop 32. which picks-up rearwardly projecting end 30 of arcing contact 18.

A further embodiment of the auxiliary spring solenoid means of FIGURES 2 and 3 is shown in FIGURE 4 where the auxiliary conducting spring 56 is concentrically positioned with respect to the main biasing spring 58 which is similar to biasing spring 34 of FIGURE 1.

In FIGURE 4, the main biasing spring 58 is seated upon an insulated base 60 carried by contact arm it] and conductive spring or coil 56 which is electrically connected to arcing contact 18 at end 62 and to movable contact arm 10 at end 64 is concentrically positioned with respect to main spring 58. As was the case of FIGURE 1, a magnetic plunger 66 which is axially movable within spring 56 serves as the solenoid plunger for the solenoid winding formed by spring 56.

Accordingly, when current is established through the arcing contact, this current flows from arcing contact 18 through spring 56 to contact arm 19 to establish a magnetic field which will drive plunger 66 upwardly. This will force plunger 68 into engagement with rearwardiy extending portion 30 of arcing contact 18 to thereby drive it in a counterclockwise direction and reinforce the biasing force of main biasing spring 58.

In the foregoing, I have described my invention only in connection with preferred embodiments thereof. Many variations and modifications of the principles of my invention within the scope of the description herein are obvious. Accordingly, I prefer to be bound not by the specific disclosure herein but only by the appending claims.

I claim:

1. A movable contact arm for a circuit breaker; said movable contact arm being movable between an engaged and disengaged position with respect to a cooperating contact; said movable contact arm carrying a main contact and an arcing contact; said arcing contact being pivotally connected to said contact arm; abutting means mounted to said movable arm for limiting the motion of said arcing contact with respect to said contact arm; said arcing contact being electrically insulated from said contact arm at the pivot point; a biasing means for normally biasing said arcing contact towards an engaged position with respect to said cooperating contact; an auxiliary means for imparting additional force to said arcing contact in the direction of the force imparted by said biasing means; said auxiliary means electrically connecting said arcing contact to said contact arm for generating a magnetic field; said auxiliary means including a magnetic means movable against and imparting a force to said arcing contact responsive to said magnetic field.

2. A movable contact arm for a circuit breaker; said movable contact arm being movable between an engaged and disengaged position with respect to a cooperating contact; said movable contact arm carrying a main contact and an arcing contact; said arcing contact being pivotally connected to said contact arm; abutting means mounted to said movable arm for limiting the motion of said arcing contact with respect to said contact arm; said arcing contact being electrically insulated from said contact arm at the pivot point; a biasing means for normally biasing said arcing contact toward an engaged position with respect to said cooperating contact; said biasing means including a. high conductivity spring electrically connecting said arcing contact to said contact arm; said spring having a magnetic member contained therein; said magnetic member being movable toward said arcing contact to impart a force to said arcing contact in the same direction as the biasing force of said spring responsive to current flow therethrough.

3. A movable contact arm for a circuit breaker; said movable contact arm being movable between an engaged and disengaged position with respect to a cooperating contact; said movable contact arm carrying a main contact and an arcing contact; said arcing contact being pivotally connected to said contact arm; abutting means mounted to said movable arm for limiting the motion of said arcing contact with respect to said contact arm; said arcing contact being electrically insulated from said contact arm at the pivot point; a biasing means for normally biasing said arcing contact towards an engaged position with respect to said cooperating contact; an auxiliary means including a solenoid Winding connecting said arcing contact to said contact arm, and a magnetic member within said solenoid; said magnetic member being movable toward said arcing contact to impart a force to said arcing contact in the same direction as the biasing force of said biasing means responsive to current flow through said arcing contact.

4. A movable contact arm for a circuitbreaker; said movable contact arm being movable between an engaged and disengaged position with respect to a cooperating contact; said movable contact arm carrying a main contact and an arcing contact; said arcing contact being pivotally connected to said contact arm; abutting means mounted to said movable arm for limiting the motion of said arcing contact with respect to said contact arm; said arcing contact being electrically insulated from said contact arm at the pivot point; a biasing means for normally biasing said arcing contact towards an engaged position with respect to said cooperating contact; an auxiliar y means including a solenoid winding connecting said arcing contact to said contact arm, and a magnetic member within said solenoid; said magnetic member being movable toward said arcing contact to impart a force to said arcing contact in the same direction as the biasing force of said biasing means responsive to current flow through said arcing contact; said biasing means being a spring. 1

5. A movable contact arm for a circuit breaker; said movable contact arm being movable between an engaged and disengaged position with respect to a cooperating contact; said movable contact arm carrying a main contact and an arcing contact; said arcing contact being pivotaily mounted with respect to said contact arm; said arcing contact being electrically insulated from said contact arm at the pivot point; 'a biasing means for normally biasing said arcing contact towards an engaged position with respect to said cooperating contact; said biasing means including a high conductivity spring electrically connecting said arcing contact to said contact arm; said spring having a magnetic member contained therein; said magnetic member being movable toward said arcing contact to impart a force to said arcing contact in the same direction as the biasing force of said spring responsive to current flow therethrough.

6. A movable contact arm for a circuit breaker; said movable contact arm being movable between an engaged and disengaged position with respect to a cooperating contact; said movable contact arm carrying a main contact and an arcing contact; said arcing contact being pivotally mounted with respect to said contact arm;

said arcing contact being electrically insulated from said contact arm at the pivot point; a biasing means for normally biasing said arcing contact towards an engaged position with respect to said cooperating contact; an auxiliary means including a solenoid winding connecting said arcing contact to said contact arm, and a magnetic member within said solenoid; said magnetic memher being movable toward said arcing contact to impart a force to said arcing contact in the same direction as the biasing force of said biasing means responsive to current flow through said arcing contact; said biasing means being a spring.

7. A contact for a circuit breaker; said contact being pivotally mounted on a movable contact arm; a biasing spring for biasing said contact in a first direction; and auxiliary means for imparting additionaliorce to said contact to move said contact in said first direction; said auxiliary means electrically connecting said contact to said contact arm and being operable responsive to current flow through said movable contact; said auxiliary operating means including a solenoid means winding conducting the current through said contact and a plunger movable toward engagement with said contact when said solenoid winding is energized.

8. A contact for a circuit breaker; said contact being pivotally mounted on a movable contact arm; a biasing spring for biasing said contact in a first direction; and auxiliary means for imparting additional force to said contact to move said contact in said first direction; said auxiliary means electrically connecting said contact to 7 References Cited in the file of this patent UNITED STATES PATENTS 1,762,604 Ainsworth June 10, 1930 1,804,628 MacNeill May 12, 1931 1,827,430 Greenwood Oct. 13, 1931 2,186,251 Lindstrom Jan. 9, 1940 2,761,040 Ulrich Aug. 28, 1956

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