US2800558A

US2800558A - Electric circuit breaker

Info

Publication number: US2800558A
Application number: US583126A
Authority: US
Inventors: Scheuermeyer Emil
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1956-05-07
Filing date: 1956-05-07
Publication date: 1957-07-23
Anticipated expiration: 1974-07-23
Also published as: JPS341830B1

Description

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July 23, 1957 SCHEUERMEYER 2,800,558

ELECTRIC CIRCUIT BREAKER Filed May '7, 1956 2 Sheets Sheet 1 lnve n tor: Emil Scheuermeger,

July 23, 1957 SCHEUERMEYER I 2,800,558

ELECTRIC CIRCUIT BREAKER I 2 Sheets-Sheet 2 Filed May '7, 1-956 Inventor: Emil Scheuerrneger,

United States Patent O ELECTRIC CIRCUIT BREAKER Emil Scheuermeyer, Drexel Hill, Pa., assignor to General Electric Company, a corporation of l ew York Application May 7, 1956, Serial No. 583,126

14 Claims. (Cl. 200-146) This invention relates to an electric circuit breaker or switch and, more particularly, to improvements in circuit breakers or switches of the general type shown and claimed in U. S. Patent No. 2,399,485, issued to W. G. Harlow et al., and assigned to the assignee of the present application.

The circuit breaker of the aforementioned Harlow patent comprises a movable main contact and an arcing contact pivotally mounted on the main contact. A suitably controlled spring causes the arcing contact to open at high speed after a predetermined opening movement of the slower-moving main contact, and this high speed motion of the arcing contact desirably tends to minimize the duration of the arcing interval during an opening operation. During a closing operation, however, the arcing contact of the aforementioned Harlow patent moves at essentially the same speed as the main contact, and this has led to undesirably long arcing intervals as the contacts approach closed position, especially where relatively slow speed closing devices are to be relied upon.

Accordingly, one of the objects of my invention is to effect high speed closing movement of an arcing contact which is mounted on a relatively slow-moving main contact.

Another object is to effect such high speed closing movement of an arcing contact by means of a new and improved stored-energy mechanism which lends itself to being readily included in a circuit breaker of the general type shown in the aforementioned Harlow patent.

Another object is to design the stored-energy mechanism in such a manner as to preclude the possibility of objectionable contact-rebound following a closing operation.

In carrying out my invention in accordance with one form thereof, I provide first contact structure, a main contact blade pivotally-mounted for movement into and out of engagement with said first contact structure, and an arcing contact pivotally mounted on said blade for movement with respect to both said blade and said first contact structure. Closing movement of the arcing contact is controlled by a chargeable spring having a pivotally-mounted lever coupled thereto. The spring is charged during a portion of a breaker closing operation by utili z, ing closing movement of the blade contact to drive the lever in a spring-charging direction. At a subsequent intermediate point in the closing stroke, the lever is released to permit the spring to discharge and drive the lever in an opposite direction. Force-transmitting means actuated by this latter movement of the lever is provided for driving the arcing contact away from the blade and into engagement with the first contact structure at a speed appreciably higher than closing speed of the blade.

For a better understanding of my invention, reference may be had to the following description taken in connection with the accompanying drawing, wherein:

Fig. 1 is a side elevational view, partly in section, of an air circuit breaker or switch embodying my invention 2,800,558 Patented July 23, 1957 with the breaker being shown in the closed-circuit position.

Fig. 2 is a side elevational View of the circuit breaker of Fig. l with the breaker being shown during an initial portion of a circuit-opening operation. Certain of the parts shown in Fig. 1 have been omitted for simplificatron.

Fig. 3 is fragmentary view showing a portion of the circuit breaker when the breaker is in its fully open position.

Fig. 3a is view taken along the line 3a-3a of Fig. 3 with only a portion of the circuit breaker of Fig. 3 being shown.

Fig. 4 is side elevational view, partly in section, showing the circuit breaker during an intermediate portion of a circuit-closing operation.

Fig. 5 illustrates certain parts of the breaker during a portion of an opening operation.

Referring now to Fig. l, I have shown an air circuit breaker or switch 10 of a type which is adapted both to interrupt load currents and to disconnect its associated circuit in the general manner of an air break disconnecting switch. In many respects the circuit breaker 10 is similar to the breaker shown and claimed in the aforementioned Harlow patent.

The breaker 10 comprises a pair of spaced-apart stationary terminals, indicated at 11 and 12, and a main current-carrying contact member 13 which in its normal closed-circuit position shown in Fig. 1 is arranged to electrically interconnect the terminals. The main contact member 13 is formed as a contact blade which is pivotally mounted at its lower end on a stationary shaft 14. As can be best seen in Fig. 2, this shaft 14 is suitably supported on conductive terminal brackets 15, and suitable spring washers 16 are provided to urge the blade 13 into frictional engagement with the brackets so as to form a current-carrying hinge joint.

An operating link 18 is pivotally connected to the blade 13 and is driven by suitable means (not shown) to cause pivotal circuit-controlling movement of the blade to: ward and away from the upper terminal 11.

Electrically and mechanically connected to the upper terminal 11 is fixed contact structure including a stationary arcing contact 21 and main current-carrying finger contacts 22 arranged to be engaged by the blade 13. These contacts are preferably of the same general type as described in the aforementioned Harlow patent. Also fixedly mounted on the upper terminal 11 is an arc-chute 24 which may be of any suitable type but is preferably of the type shown in the aforementioned Harlow patent. This arc chute 24 acts in a well-known manner to extinguish the are which is drawn adjacent the stationary arcing contact 21 during a circuit-opening operation.

For ooacting with this stationary arcing contact 21 to establish an are, there is provided a movable arcing contact 26. This arcing contact 26 is suitably electrically connected to the contact blade 13 and is pivotally mounted on the contact blade by means of a laterally-extending pivot pin 28. A conventional torsion spring 30 encircles the pivot pin 28 and biases the arcing contact 26 clockwise toward open position. When the main contact blade 13 is held in its closed position of Fig. l (by means not shown), the arcing contact 26 is prevented from rotating in a clockwise opening direction about its pivot 28 by a stop 31 fixed to the blade 13 and coacting with a slot 32 formed in the lower end of the arcing contact 26.

When the contact blade 13 is driven in a clockwise opening direction by a force applied to the operating link 18, the main contacts at 13, 22 first part contact and move a predetermined distance toward fully open position before parting of the

arcing contacts

21 and 26. Since the arcing contact 26 is electrically connected to the main contact blade 13, the circuit between the terminals will be opened at the arcing contacts rather than at the main contacts. The position of the various parts just prior to parting of the arcing contacts is shown in Fig. 2, where the

main contacts

13 and 22 are shown separated and the

arcing contacts

21 and 26 are shown still in engagement.

To insure that the arcing contacts part at high speed so as to minimize the duration of the arcing interval, the movable arcing contact 26 is initially latched in closed position and movement of the blade 13 is utilized for charging the torsion spring 30. When the blade 13 reaches a predetermined open position, somewhat beyond that of Fig. 2, it releases the latch and permits the spring 30 to drive the arcing contact 26 at high speed toward open position. 7

The above-mentioned latch is preferably in the form of a

toggle

33, 34 that is arranged to be overset, as shown in Figs. 1 and 2, and resiliently held in this position by means of a suitable overcenter spring 35. The upper end of the toggle link 34 is provided with a pin 36 guided for limited vertical reciprocation in a slot 36a formed in the movable arcing contact 26. The pin 36 also carries a roller 37 laterally offset so as to be in alignment with a fixed catch 38 secured to the lower part of the arc chute along an edge thereof. The lower link 33 is connected to a guide link 39 that is pivotally connected at 40 to the arcing contact and is biased by the spring 41 in a counterclockwise direction so as normally to hold the

latching toggle

33, 34 as a unit in its upper latching position.

As shown in Figs. 1 and 2, the latching toggle is controlled by means of a tripping rod 42 secured to the blade 13 at its right hand end and carrying a laterally ofiset extension 43 at its other end. The tripping rod 42 clears the toggle but the offset extension 43 is arranged so as to be substantially in alignment with the knee or central pivot 45 of the toggle. The toggle is held in the overset position shown in Figs. 1 and 2 by the spring 35 and an extension formed on the lower toggle link 33 to engage the upper toggle link 34. Accordingly, when the knee of the toggle is moved suificiently overcenter by the action of the extension 43, as will soon be described, the spring 35 causes collapse of the toggle so that the roller 37 moves downward in the slot 36a sufficiently to clear the catch 38.

Thus it will be apparent that when the blade 13 is moved in a clockwise opening direction from the position of Fig. 1 to the position of Fig. 2, the toggle latch roller 37 will encounter the catch 38 and temporarily restrain the arcing contact 26 in engagement with the stationary arcing contact 21. The

overset toggle

34, 35 will maintain the movable arcing contact 26 in this closed position until the moving blade 13 has driven the extension 43 into engagement with the knee 45 of the latching toggle. Thereafter the action of the extension 43 causes the toggle to collapse and permits the overcenter spring 35 to drive the roller 37 downwardly out of latching relationship with the catch 38. This releases the arcing contact 26 and permits it to be snapped clockwise away from the fixed arcing contact 21 by the action of the torsion spring 38, which had been tensioned by prior opening movement of the contact blade 13. This snap action of the arcing contact quickly draws an arc across the lower end of the chute and permits the arc to be rapidly extinguished within the chute in a well-known manner. As the opening motion of contact blade 13 continues, the spring 41 of the toggle resets the toggle into its overset condition of Figs.

1 and 2. In the fully open position the contact blade 13 is essentially horizontally disposed and rests against a suitable stop 47 which is provided therefor.

If a relatively low speed mechanism is to be used for actuating the contact blade 13, then the arcing contact 26 should be actuated toward closed position, as well astoward open position, at a considerably higher speed than that of the blade. Otherwise, arcingfor an undesirably long interval will occur as the contacts approach closed position at the end of a closing stroke.

For producing such high speed closing of arcing contact 26, I have provided a stored-energy type of closing mechanism generally indicated at 50. As may be best seen in Figs. 3 and 3a, this mechanism 50 comprises a compression spring 51 which is supported at its lower end by means of an adjustable nut 53 carried at the threaded lower end of a mounting rod 54. The mounting rod 54 is pivotally suspended at its upper end by means of a pivot pin 55 supported on a stationary bracket 56. This bracket 56 projects from the lower terminal of the breaker and is located adjacent the contact blade 13. Operatively coupled to the spring 51 is a lever or bell crank 58, which is mounted for pivotal motion about a stationary axis provided by a pivot pin 60. The pivot pin 60 is suitably supported on stationary bracket structure 62 which also projects from the lower terminal adjacent the contact blade 13. As shown in Fig. 3a, the lower end of the lever 58 is formed as a clevis which embraces and is pivotally connected to an annular thrust member 63, against which the upper end of the compression spring 51 bears. This thrust member 63 is mounted for sliding movement along the mounting rod 54. Thus, it will be apparent that the compression spring 51, as seen in Fig. 3, normally urges the lever 58 in a clockwise direction about its pivot 60 and into engagement with a suitable stop 65.

For reasons which will soon appear, the upper arm of the lever 58 is of an articulated construction and includes a pawl 67 which is pivotally joined to the main body of the arm by a pivot pin 68. This pivot pin 68 is carried by a tongue-like projection 69 which is freely received in a suitable clevis formed at the lower end of the pawl 67. The lower clevis end of the pawl 67 has surfaces 71 which bear against corresponding abutting shoulders provided on the lever 58. An extension spring 72 normally maintains these surfaces 71 in engagement with said abutting shoulders so as to preclude counterclockwise rotation of the pawl about its pivot 69 from the position shown in Fig. 3.

This stored-energy closing mechanism 50 is normally in a discharged condition, as can be seen in Figs. 1 and 3. However, as will soon appear, when the blade 13 is moved counterclockwise from the position of Fig. 3 to close the breaker, closing movement of the blade 13 becomes effective to charge the mechanism 50. At a subsequent point in the closing stroke, when the mechanism 50 is charged, it is released and permitted to discharge at high speed. This discharging action is utilized to drive the arcing contact 26 about its pivot 28 and into closed position at a speed appreciably higher than the normal closing speed of the blade 13.

For charging the mechanism 50 during the closing stroke, the blade 13 is provided with a downwardly projecting lug or abutment 75, which is secured to the blade. When the blade 13 is rotated in a counterclockwise closing direction from the solid line position of Fig. 3, this ing 75, after a predetermined portion of the closing stroke, moves into engagement with rear edge of the pawl 67. The position of the parts at this instant is illustrated by dot-dash lines in Fig. 3.

' After this engagement occurs, continued closing movement of the blade 13 causes the lug 75 to rotate the lever 58 in a counterclockwise direction about its pivot 60, .thereby progressively compressing the spring 51. During this interval, the pawl 67 simply acts as a rigid extension of the upper arm of the lever 58 due to the abutting relationship between the surfaces at 71. Coincident with this spring-charging operation, the forward or driving surface of the lug 75 slides upwardly along the rear edge of the pawl 67, this relative movement resulting from the fact that the pivot for the blade 13 is laterally offset from the pivot for the lever 58. Eventually, this relative movement will progress to a point at jectional rebound movement.

which the driving surface of lug 75 moves out of engagement with the pawl 67, at which time the pawl 67 and its lever 58 will be released for reverse movement under the influence of the then-charged spring 51. The position of the parts just prior to such release is illustrated in solid lines in Fig. 4.

When release does occur, the spring 51 quickly discharges to drive the lever 58 clockwise at high speed about its pivot 60. As a result of such clockwise movement, the pawl 67 is driven into engagement with a forcetransmitting pin 77 secured to the lower end of the arcing contact 26. Thereafter, the discharging spring 51, acting through the pawl, or driving member 67 and the pin, or driven member, 77, drives the arcing contact 26 counterclockwise about its pivot 28 and into closed position with respect to the stationary arcing contact 21. The position of the parts after the spring 51 has discharged in this manner is illustrated by the dot-dash lines of Fig. 4.

From the solid line position of Fig. 4 it can be seen that at the instant the pawl 67 is released, the forcetransmitting pin 77 is spaced an appreciable distance from the pawl. This space, which might be termed an impacting distance, allows the pawl, when driven by discharge of the spring 51, to impart to the pin 77 a sharp hammer-blow which materially contributes to driving the arcing contact 26 into its closed position at high speed.

Closing movement of the arcing contact 26 is opposed by the contact opening spring 30, but the closing spring 51 is of such a size that it has ample power to overcome this opposition. The opposing force of the opening spring 30 does however tend to produce rebound of the arcing contact 26, and if such rebound were permitted, arcing could be undesirably reinitiated between the arcing contacts. To preclude such rebound, the pawl, or driving member 67 is provided with a cam surface 80 which rides underneath the pin, or driven member 77 shortly after the arcing contacts engage and, in such position, restrains the movable arcing contact 26 from significant reverse or rebound movement. The dotted lines of Fig. 4 show the cam surface 80 disposed in such a reboundpreventing position.

As closing movement of the main blade 13 continues in a counterclockwise direction from the dotted line position of Fig. 4, the force-transmitting pin 77 simply slides along the cam surface 80. As a result, the cam surface '80 continues to restrain the arcing contact 26 from ob- The cam surface 80 and later the slot 32 assure that the arcing contacts remain in engagement until the slow-moving main contact blade 3 finally engages its coacting stationary contact 22. Thereafter, the parts ultimately move into the normal closed-circuit position of Fig. l.

An'advantageous feature of my above-described circuit breaker is that the supplementary closing mechanism 50 does not interfere with the opening movement of the arcing contact 26. The pawl 67 is actually in the path of the arcing contact 26 during its opening movement, but since the pawl is free to collapse in a clockwise direction about its pivot 68, the arcing contact simply brushes it aside in a clockwise direction without significant interference therefrom. When the contact blade 13 has sufiiciently opened, the return spring 72 is free to reset the pawl 67 to its position shown in Fig. 3. The manner in which the pawl 67 is brushed aside to allow for opening operation is shown in Fig. where the pawl has been pivoted clockwise about its fulcrum 68.

Another factor which contributes to the ability of the arcing contact 26 to open without interference from the closing mechanism 50 is that the force-transmitting pin 77 is moved out of force-transmitting relationship with respect to the cam surface 80 during final closing movement of the contact blade 13. This can be seen in Fig. 1. .As a result of this disengagement, the cam surface 80 cannot restrain the arcing contact 26 from opening movement during a subsequent opening operation.

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention in its broader aspects and I, therefore, intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric circuit breaker comprising first contact structure, a main contact blade movable into and out of engagement with said first contact structure, an arcing contact pivotally mounted on said blade and movable with respect to both said blade and said first contact structure, a chargeable spring supported independently of said blade for controlling closing movement of said arcing contact, means controlled by closing movement of said blade for charging said spring during a portion of a closing stroke, means operable at a subsequent point in said closing stroke for releasing said spring to permit discharge thereof,and means actuated by discharge of said spring for driving said arcing contact away from said blade and into engagement with said first contact at an elfective speed appreciably higher than the closing speed of said blade.

2. An electric circuit breaker comprising first contact structure, a main contact blade movable into'and out of engagement with said first contact structure, an arcing contact pivotally mounted on said blade and movable with respect to both said blade and said first contact structure, a chargeable spring for controlling closing movement of said arcing contact, means controlled by closing movement of said blade for applying a springcharging force to one end of said spring during a portion of a blade-closing stroke, and means operable at a subsequent point in said closing stroke for releasing said spring at said one end thereof to permit said spring to discharge, and force-transmitting means actuated by discharge of said spring for driving said arcing contact about its pivot on the blade and into engagement with said first contact structure at an effective speed appreciably higher than the closing speed of said blade.

3. An electric circuit breaker comprising first contact structure, a pivotally-mounted main contact blade coacting with said first contact structure and movable with respect thereto, an arcing contact pivotally mounted on said blade and movable with respect to both said blade and said first contact structure, a chargeable spring for controlling closing movement of said arcing contact, a lever operatively coupled to said spring and mounted for pivotal motion, means controlled by closing movement of said contact blade for moving said lever in a direction to charge said spring during a portion of a closing stroke, and means for releasing said spring at a subsequent intermediate point in said closing stroke to permit said spring to discharge and move said lever in a direction opposite to the spring-charging direction, and force transmitting means actuated by movement of said lever in said opposite direction for driving said arcing contact away from said blade and into engagement with said first contact structure.

4. The circuit breaker of claim 3 in which lost motion is provided between said lever and said arcing contact for enabling said spring to impart a hammer blow to the arcing contact after release of said lever.

5. An electric circuit breaker comprising first contact structure, a pivotally-mounted main contact blade movable into and out of engagement with said first contact structure, an arcing contact pivotally mounted on said blade and movable with respect to both said blade and said first contact structure, a chargeable spring for controlling closing movement of said arcing contact, a lever operatively coupled to said spring and mounted for pivotal motion, an abutment movable with said contact blade and tion to said lever during a portion of a blade-closing stroke,

said driving surface being movable out of restraining relationship with said lever at a subsequent point in said closing stroke to permit said spring to discharge and move said lever in a direction opposite to that of said springcharging motion, and force-transmittingmeans actuated by movement of said lever in said opposite direction for driving said arcing contact away from said blade and into engagement with said first contact.

6. The circuit breaker of claim in which the pivot axis for said contact blade is laterally spaced from the pivot axis for said lever so as to enable the driving surface of said abutment to move out of restraining relationship with said. lever at said subsequent point in the closing stroke. T

7. An electric circuit breaker comprising first contact structure, a main contact blade movable into and out of engagement with said first contact structure, an arcing contact pivotally mounted on said blade and movable with respect to both said blade and first contact structure, a chargeable spring for controlling closing movement of said arcing contact, means controlled by closing move- 'ment of said blade for charging said spring during a portion of a closing stroke, means operable at a subsequent point in said closing stroke for releasing said spring to permit discharge thereof, and means actuated by discharge of said spring for driving said arcing contact away from said blade and into engagement with said first contact at an eifective speed appreciably higher than the closing speed of said blade, said last-mentioned means comprising a lever having a portion which is encountered by said arcing contact during a subsequent opening operation, and means for allowing said portion of the lever to move relative to the remainder of the lever When encountered by said arcing contact during an opening operation whereby to prevent said lever from interfering with said opening operation.

8. An electric circuit breaker comprising first contact structure, a main contact blade movable into and out of engagement with said first contact structure, an arcing contact pivotally mounted on said blade and movable with respect to both said blade and said first contact structure, a chargeable spring for controlling closing movement of said arcing contact, means controlled by closing movement of said blade for charging said spring during a portion of a closing stroke, means operable at a subsequent point in said closing stroke for releasing said spring to permit discharge thereof, and means actuated by discharge of said spring for driving said arcing contact away from said blade and into engagement with said first contact at an effective speed appreciably higher than the closing speed of said blade, said driving means comprising a driving member and a driven member, the driving member being provided with a cam surface which moves into rebound-preventing engagement with the driven member shortly after the movable contact engages said first contact structure.

9. In an electric circuit breaker of the type comprising first contact structure, a pivotally-mounted main contact blade movable into and out of engagement with said first control structure, an arcing contact pivotally mounted on said blade and movable with respect to both said blade and said first contact structure, and means including a first spring for moving said arcing contact away from said first contact structure and toward said blade after a predetermined opening movement of said blade; the combination of a second spring for controlling closing movement of said arcing contact, means controlled by closing movement of said blade for charging said second spring during a portion of a bladefclosing stroke, and means operable at a subsequent intermediate point in said closing stroke for releasing said second spring to permit discharge thereof, and means actuated by discharge of said second spring and opposed by said first spring for driving said arcing contact toward said first contact structure and away from said blade against the bias of said first spring.

10. The circuit breaker of claim 9 in which said means for driving the arcing contact toward said first contact structure comprises a lever having a portion which is encountered by said arcing contact during a subsequent opening operation, and means for allowing said portion of the lever to move relative to the remainder of the lever when encountered by said arcing contact during an opening operation whereby to prevent said lever from i11terfering with said opening operation.

11. The circuit breaker of claim 9 in which said means for driving the arcing contact toward said first contact structure comprises a driven member and a driving member, the driving member being provided with a cam surface which moves into rebound-preventing engagement with the driven member shortly after the movable arcing contact engages said first contact structure.

12. The circuit breaker of claim 11 in which final closing movement of said blade moves said arcing contact out of restrained relationship with respect to said cam surface whereby to permit initial opening movement of the contact to take place free from restraint by said cam surface.

13. The circuit breaker of claim 9 in which said means for driving the arcing contact toward said first contact structure comprises a driving member and a driven member which are moved out of force transmitting relationship with respect to each other by final closing movement of said blade.

14. In an electric circuit breaker of the type comprising first contact structure, a pivotally mounted main contact blade movable into and out of engagement with said first contact structure, an arcing contact pivotally mounted on said blade and movable with respect to both said blade and said first contact structure, and means including a first spring for moving said arcing contact away from said first contact structure and toward said blade after a predetermined opening movement of said blade; the combination of a second spring for controlling closing movement of said arcing contact, a lever operatively coupled ot said spring and mounted for pivotal motion, means controlled by closing movement of said blade contact for moving said lever in a direction to charge said spring during a portion of a blade-closing stroke, and means for releasing said lever at a subsequent intermediate point in said closing stroke to permit said spring to discharge and move said lever in an opposite direction, and force-transmitting means actuated by movement of said lever in said opposite direction and opposed by said first spring for driving said arcing contact toward said first contact structure and away from said blade against the bias of said first spring.

References Cited in the file of this patent UNITED STATES PATENTS 1,935,428 Atwood Nov. 14, 1933 2,399,485 Harlow et al. Apr. 30, 1946 2,697,153 Owens et al Dec. 14, 1954