US3076882A

US3076882A - Electric circuit breaker

Info

Publication number: US3076882A
Application number: US847731A
Authority: US
Inventors: Edwin B Judd; John D Young
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1957-08-22
Filing date: 1959-10-21
Publication date: 1963-02-05
Anticipated expiration: 1980-02-05

Description

Feb. 5, 1963 E. B. JUDD ET AL 3,076,882

ELECTRIC CIRCUIT BREAKER Original Filed Aug. 22, 1957 5 Sheets-Sheet 1 i., WL

Feb. 5, 1963 E. B. JUDD ETAI.

ELECTRIC CIRCUIT BREAKER Original Filed Aug. 22, 1957 5 Sheets-Sheet 2 Il 1l 4 INVENToRs v 9G mm o. dY BD. N wuN.. Ed

Feb. 5, 1963 E. B. JUDD ET Al. 3,076,882

ELECTRIC CIRCUIT BREAKER Original Filed Aug. 22, 1957 5 Sheets-Sheet 3 INVENTORS EDWIN B. duoo, doHN D. YouNG BY @My-@v7 A TroRA/EY envases ELECTR'C ClRCUl'E BREKER Edwin E. .lu-:ld and .lohn D. Young, Schenectady, assignors to General Electric Company, a corporation i New Yori:

@riginal application Aug. 22, i957, Ser. No. 679,667, now Patent No. 2,92Ll69, dated `lan. l2, well. Divided and this application Oct. 2l, 1959, Ser. No. 847,73

l Ciaim. (Cl. 29d-146) .tions are usually provided on a single contact member which moves in such a way as to cause the arcing portions oi the contact assemblies to meet first during closing operation, followed by the current-carrying portions. Conversely, in opening, the current-carrying portions open first, followed by the arcing contacts, which thereby bear g the burden of the most severe arcing.

In circuit breakers using such composite contacts, diiliculty is encountered in ensuring the proper sequence of operation of the contacts, especially during short-circuit interruption, when the contacts move extremely fast. In addition, such contact assemblies have relatively high resistance, due to the tact that not all contact surfaces are utilized.

Circuit breakers of the type referred to herein are called upon to interrupt normal currents of the order of 100 to 80() amperes at 250, 490, or 60() volts.

Accordingly, it is an object of our invention to provide a circuit breaker for relatively high currents and voltages including a composite contact member which includes articulated main or current-carrying contacts and arcing or current-interrupting contacts, so arranged that the speed of opening helps to provide a. predetermined desired sequence of opening thereof.

in accord-ance with our invention, we further provide a contact assembly including at least one main or current-carrying contact, and one arcing or current-interrupting contact. Each contact is plvotaly supported on a Contact arm. The weight of each Contact is so distributed with respect to its pivotal support that in a highspeed automatic opening operation, inertia tends to cause the main contacts to open first, and the arcing contacts to open second, thereby providing a more effective and less-damaging interrupting action.

Additional aspects of our invention will be pointed out in the following detailed description and illustrated in the accompanying drawings, while the scope or our invention will be more particularly pointed out in the appended claim.

In the drawings:

FIGURE l is a side elevation view partly in section,

of an electric circuit breaker incorporating our invention;

FIGURE 2 is a side elevation View of the operating mechanism of the circuit breaker of FEGURE l, the near side of the mechanism supporting frame being removed for clarity, and the parts being shown in the On condition;

FIGURE 3 is a View similar to FIGURE 2, the parts being shown in the tripped condition;

FIGURE 4 is an exploded view in perspective of some of the parts of the mechanism of FIGURES ll and 2;

hill@ FGURE 5 is an elevation View of a modilied form of the invention ot FlGUiE l;

FIGURE 6 is an exploded view in perspective of some of the parts ot the mechanism of FlGURE 5; and

FGURE 7 is a plan View of the stationary Contact assemby of one pole of the circuit breaker of FIGURE l.

In the drawings, we have shown our invention as embodied in a three-pole electric circuit breaker comprising an insulating outer or main insulating casing having a base lil and a cover tl.

Mounted on the base l@ at one end thereof are three load terminals l2 (only one shown) and, at the opposite end of the base l0 three line terminals i3 (only one shown). The line terminals i3 are each connected to line contact straps 1d carrying at the opposite end thereof a pair of side-by-side stationary main contacts i5 (only one shown) and a stationary arcing contact lo, the three contacts i5", i5, lo, ot' each pole being arranged in a triangular configuration, as shown in FIGURE 7.

Each of the main and arcing contacts and in of each pole cooperates with a corresponding movable main contact 17 and a rnova le arcing Contact i3, respectively. Each of the three movable contacts of each pole is independently movable and is pivotally supported on a common pivot pin i9' carried by the Contact arm 19, and each is biased away from the contact arm i9 by a separate one of the contact pressure springs i7 and lil'. The contact arm i9 is pivotally supported on axis Ztl in frame Zo, carried by the base it?.

The movable arciug contact member liti of each pole has most of its weight forward of the pivot pin 19. Each of the movable main contacts has most of its weight to the rear of the pivot pin 19. The eft'ect of this is that the inertia of the contacts tend to cause the main contacts to open iirst and the arcing Contact to open last, which is the desired sequence. The movable contacts i7 and 13 of each pole are connected by means of multi-strand flexible braids 2l to one terminal 22 of the trip unit 23, and the load terminal of the trip unit Z3 is connected directly to the main load erminal l2 of the circuit breaker.

For the purpose of moving the movable contacts l and l into and out of engagement with the stationary or line contacts l5 and lo, both manually and automatically, we provide a operating mechanism indicated generally at The operating mechanism 25 includes a generally U-shaped supporting frame member 2o and a plurality of parts pivotally supported between the opposite sides thereof. '.`hese parts include three Contact arms i9, there being one contact arm for each pole of the circuit breaker.

The contact arms i9 are adapted to be rotated about their pivotal support by means of a toggle action linkage includinrl the

toggle links

27 and 28 connected together at a toggle knee point 2% and supported at tr eir upper end on a pivot pin Tali carried by a toggle carrier 3l. The toggle links Z7 and Zd, in turn, are operated etti/een straightened and collapsed positions by of an operating handle 32 in cooperation with a pair of tension type springs 33 interconnected between the handle 32 and the knee point 29 oi the toggle link 27, When the handle member 32 is in the on shown in HG- URIE l, the contacts are in closed position, and when the handle is moved counterclockwise from this position toward the et end of the breaker as viewed, the contacts are moved to the open circuit position.

The end 3l of the toggle carrier 3l is formed to act as a latching element and to engage an intermediate latch member 3f" which is pivotaiiy supported on a pin 35 carried by an extension Zo of the frame 2e. The action of the tension springs 33 is such as to bias the totale carrier wie 3l for rotation in a clockwise direction. The toggle car- .sp-rases rier 3l is restrained from movement in such a direction, however, by its engagement with the intermediate latch member 34. A biasing spring, 3d', constantly urges the intermediate latch 34 in a clockwise direction as viewed in the figures. By reason of the greater-force exerted on it by the toggle carrier 3l, however, .the intermediate latch member 3d is biased in a counterclockwise direction whenever the breaker is latched.

'For the purpose of normally restraining the intermediate latch member, and therefore the toggle carrier 3l and the operating mechanism as a whole, in .the on position except in the case of predetermined overload conditions, we provide a trip v.unit `generally .indicated zat 23. rThe particular construction and operation of the trip unit is not critical to our :present invention and any suitable type may be used. The particular trip unit illustrated, however, is described more fully and claimed in application Serial No. 679,606, filed August 22, 1957, by H. M. Steven and Il. W. Marshall, and assigned to the same assignee as the present invention.

The trip unit Z3 includes a latch member So'adapted normally to prevent the intermediate latch member 34- from rotating in a `counterclockwise direction. The'latch vmember .35 is `pivotally supported on the trip unit 123 on a pivot pin 37, extending through aligned openings lin :a boss 23d molded integral with Athe housing of the trip unt23.

The latch member 3.6 carries a latch roller 39 supported on a pin 4d extending between opposed, ,spaced apart, portions of the latch member 36. The vintermediate latch member '34 is provided with a cam surface 4I which, when the breaker is latched, as shown in FIGURE 1, bears against the roller 39 and biases the latch member 36 in a counterclockwise direction, that is, to the left as viewed in the gures. The latch member 36 is prevented from moving to the left by means which is releasable upon the occurrence of predetermined current conditions. When released by such current-responsive means, the latch 3o moves to the left, allowing the intermediate latch member 34 to rotate counterclockwise, vreleasing the carrier 31. Following such release, the intermediate latch 34 is moved clockwise by its bias spring 34 against a stop portion of the frame 26.

In order to reset the breaker following a tripping operation, the handle 32 is moved manually to the left as viewed to and slightly beyond the normal off position. yDuring this movement, a portion 32 of the handle engages the carrier 3l and rotates it counterclockwise. When the Vlatch tip of the carrier SI engages the surface 34S of the intermediate latch 34, further counterclockwise movement of the carrier causes the intermediate latch 34 to move to the left, as viewed, with a combined pivoting and sliding action, as permitted by the elongated pivot notch 34N. The ends of the bias spring 34 also are adapted to slide along the inner surface of the portion 34S to permit this sliding retracting action. The latch tip 31 of the carrier 31 finally clears the latch surface of the intermediate latch 3d, and the intermediate latch is returned to its normal position by the action of the spring 34', thereby relatching the breaker.

'hen the toggle carrier 31 is released from the inter'- mediate latch 34, the carrier Si is rotated in a clockwise direction by the action of the main operating springs to the position substantially as shown in FIGURE 3. As the pivot point 29 moves upwardly, the contact arms I9 are also moved upwardly or in a counterclockwise direc tion, toward open circuit position. Because of the necessary proportioning and dimensions and arrangement of lthe parts, it will be found that, for substantial angular opening movement and maximum contact pressure, it is not possible to allow the toggle carrier to rotate clockwise far enough to carry the pivot pin 3@ definitely across the centerline of action of the main springs 33.

The action of the parts, as so far described, therefore, is such as to move the movable contact arm I9 in an opening direction by movement of the toggle linkage uping the arm 19 further in i wardly as a whole, without any substantial Vbreaking or collapsing thereof.

The distance through which the movable contact is moved by this means, however, is not as great as is ordinarily desirable for circuit breakers of the rating of the subject device, i.e., 600 to 800 amperes at 600 volts.

In order to provide additional contact opening movement, and also to .accelerate the contact opening movement, we `provide a toggle lever t3 supported on a pivot pin 44 between the sides of the mechanism frame 26. The toggle lever 43 is movable'independentlyof the toggle carrier 31, and is biased by a biasing spring 4 5 in a counterclockwise direction against a portion 46 of the mechanism frame 26. The forward end 43 of the toggle lever t3 is .rounded and is'adapted to coact with a projection or vdetent 47 on the upper toggle link 2.7 in a manner to be described.

As long as the toggle carrier is in vits latched condition .as shown in FIGURE I2, the toggle lever 43 'is maintained in the position ,shown in FIGURE 2. Thus 'the toggle linkage is moved between collapsed and straightened conditions without altering the position of .the toggle lever 43.

When the toggle carrier 31 is released `from the intermediate latch member 34, land rotates clockwise, however, .the projection 47 engages the rounded end .-43 of the toggle lever '-43 and the two parts remain in engagement as further rotation vof the toggle carrierl occurs.

This action maintains the intermediate part of the upper toggle link 27 at a vpredetermined distance 'from the pivot pin .44, and .causes the toggle linkage to assume a slightly broken or collapsed condition Vas illustrated jin FIGURE 3. This shortens the distance between Ithe opposite ends r`of the toggle linkage .and resultsin accelerating the :movement of Vthe contact arm wand in mova contact opening direction then would 4otherwise be possi-ble. This is especially true, and also especially important, when the handle ,32 is manually retained in the on or closed circuit position.

4In FIGURES 5 and 6 we have illustrated another embodiment of our invention, in which the toggle linkage 27', 28 is adapted to lbe maintained in a slightly broken or collapsed condition when tripping occurs. In this form, the projection 47 on the upperlink 27' is omitted. Instead, the toggle lever 49 is provided and the toggle carrier Sti is provided with a rounded abutment or cam follower surface 51 adapted to engage the underside of the toggle lever 49 and to rotate the toggle lever in a clockwise direction as tripping occur-s. The end 49 of the toggle lever engages the link 217' and forces the toggle linkage to a collapsed condition in a manner similar to that described in connection with FIGURES .Z and 3.

-In the form of FIGURE 5 the end 419 of the toggle lever 49 is arranged to initially engage the upper toggle link 27 at a predetermined point, and the action of the abutment 51 exerted on the toggle lever 49 causes the point of engagement of the toggle lever 49 to tmove upwardly along the toggle link 27 toward the upper pivot point 3h. In this manner, the leverage action of the toggle lever d@ on the toggle link 27 is greatest at the initial point of movement and decreases as the tripping action progresses. This affords an important prying action which assists in breaking any welds which might occur between the stationary and movable contacts, while at the same time affording a maximum rate of acceleration and a maximum opening distance of the movable contact. While the toggle lever 49 has been VYshown as of a different configuration from the toggle lever e3, it will be apparent that these toggle ylevers ,are substantially interchangeable.

While we have shown only particular embodiments of our invention, it will be apparent that many modications thereof mayreadily be made by those skilled in the art and we, therefore, intend by the rappended claim to cover all such modifications asfall within the true spirit and scope of our invention.

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

An el-ectric circuit breaker comprising;

(a) a support,

(b) at least one elongated contact arm pivotally supported adjacent one end thereof on said support, (c) means for operating said contact arm between open and closed circuit positions, said operating means comprising an overcenter operating spring adapted to move said contact arm between said open and closed positions with a snap action,

(d) an elongated arcing contact carrier pivotally supported on said contact 4arm adjacent the movable end of said contact arm and carrying an arcing contact at the end thereof remote from the pivotally supported end of said contact arm,

(e) a pair of main contact carriers pivotally supported on said contact arm co-axially with said arcing contact carrier and each having a main contact supported thereon adjacent the end thereof remote from said pivotally supported end of said contact arm, a compression spring between the outer end of each of said main contact carriers and said Contact arm and between the outer end of said arcing contact carrier and said contact arm respectively,

(g) flexible electrical conductor means connecting each of said contact carriers electrically in common,

(lz) said arcing Contact carrier having the greater part of its mass on the side of its pivotal support remote from the pivotaliy supported end of said contact arm,

(i) each of said main contact carriers having the greater part of its mass on the side of its pivotal support adjacent said pivotally supported end of said contact arm,

(j) whereby rapid yacceleration of said contact arm -from said closed position toward said open position causes the effect of inertia to act on said contact carriers in such a way as to cause said main contact carriers to be rotated about their pivotal support in a direction to open said main contacts and to cause said arcing contact carrier to rotate about its pivotal support in a direction to close said arcing contact.

References Cited in the tile of this patent UNITED STATES PATENTS 2,186,251 Lindstrom `ian. 9, 1940 2,437,863 Scott Mar. 16, 1948 2,664,479 Pokorny Dec. 29, 1953 2,761.040 Ulrich Aug. 28, 1956