US2921169A - Electric circuit breaker - Google Patents

Description

Jan. 12, 1960 E- B- JUDD ET AL ELECTRIC CIRCUIT BREAKER Filed Aug. 22, 1957 5 Sheets-Sheet 1 INVENTORS' EDWIN Bduoo, JOHN D. Youme ATTORNEY Jan. 12, 1960 E. B. JUDD ETAL 2,921,169

ELECTRIC CIRCUIT BREAKER Filed Aug. 22, 1957 3 Sheets-Sheet 2 INVENTORS EDWIN B. d UB0,

1: 1111/1/11 VII/l JOHN D. YOUNG Jan. 12, 1960 E. B. JUDD ET AL 2,921,169

ELECTRIC CIRCUIT BREAKER Filed Aug. 22, 1957 3 Sheets-Sheet 3 INVENTORS Enwm B. duoo, \JOHN D. Youme KM/ t C 7 United States Patent 2,921,169 ELECTRIC CIRCUIT BREAKER Edwin B. Judd, Gonic, N.H., and John D. Young, Schenectady, N.Y., assignors to General Electric Company, a corporation of New York Application August 22, 1957, Serial No. 679,607

4 Claims. (Cl. 200153) Our invention relates to electric circuit breakers and particularly to manually. operable circuit breakers adapted to' control relatively high values of current.

A type of operating mechanism which has been generally satisfactory for use in circuit breakers of low and medium ampere rating, such as 20-100 amperes at 250 volts, is shown in Patent No. 2,640,127, assigned to the same assignee as the present invention. This mechanism includes a toggle linkage supported on a releasable toggle carrier and applying contact-closing force through a straightening action of the toggle linkage. Difiiculties are encountered, however, when it is endeavored to adapt a mechanism of this type for use in circuit breakers of relatively high rating, such as 800 amperes at 600 volts, where it is necessary to operate large contacts at high speeds and to exert high contact pressures, all while maintaining a compact structure. It is found, for instance, that an optimum arrangement of pivots for the mechanism for the purpose of providing high contact force does not permit adequate opening movement of the contacts, and vice versa. In addition, the size and weight of the contacts makes high-speed automatic opening difficult to achieve.

It is anobject of our invention to provide a circuit breaker operating mechanism of the type having a toggle linkage supported on a releasable toggle carrier which is adapted to occupy a relatively small space and to exert maximum contact force while also providing a maximum amount of contact opening movement.

Another objectof our invention is to provide a circuit breaker for relatively high currents and voltages including a composite contact member comprising 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 accordance with our invention, we provide an electric circuit breaker having an operating mechanism including a collapsible toggle linkage adapted to hold a pair of contacts closed when in straightened condition. The toggle linkage is movable as a whole to a tripped position. An auxiliary lever is provided which is adapted to engage the toggle linkage to partially collapse it while it is moving toward tripped condition. This action provides an amount of contact opening greater than would otherwise be possible. It also provides an accelerated contact opening action, which, combined with specially designed movable contact assemblies, affords a selective contact opening action. The selective action causes the main or current-carrying contacts to open first, and the ,arcing or current interrupting contacts to open last.

In accordance with this latter aspect of 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 pivotally supported on a contact arm. The weight of each contact is so distributed with respect to its pivotal support that f ice iii a high-speed automatic opening operation, inertia causes the main contacts to open first, and the arcing contacts to open second, thereby providing a more effee= tive 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 of our invention will be more particularly pointed out in the appended claims.

In the drawings,

Figure 1 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 Figure 1, the near side of the mechanism supporting frame being removed forclarity, and the parts being shown in the on condi. tion;

Figure 3 is a view similar to Figure 2, the parts being;

shown in the tripped condition;

Figure 4 is an exploded view in perspectiveof'some; of the parts of the mechanism of Figures; 1 and 2;

Figure 5 is an elevation viewofja modified form- Off the invention of Figure 1; and.

Figure 6 is an exploded view. invperspective of some of the parts of the mechanisrnof Figure 5.

In the drawings, we haveshownour invention as em-. bodied in a three-poleelectric circuit breakercomprising; an insulating outer or main insulating casing having in base 10 and a cover 11.

Monnted on the base 10: at oneend; thereof are; threeload ter minals, 12 (only one shown) and, at the; opposite end of-the base 10 three line terminals 13 (only one shown). The line terminals 13; are each connected to line contact straps 14 carrying at the opposite end thereof a pair of side-by-side stationary main contacts 15 (only one shown.) and a stationary arcing contact 16, the three contacts being arranged in a triangular configuration.

Each of the main and arcing contacts 15 and 16 of each pole cooperates with a corresponding movable main contact 17 and a movable arcing contact 18, respectively.

26, carried by the base 10.

The movable arcing contact member 18 of each poles 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 effect of this is that:-

the inertia of the contacts causes the main contacts tm open first and the arcing contact to open last, which is: the desired sequence. The movable contacts 17 and of each pole are connected by means of multi-strand fleflb ible braids 21 to one terminal 22 of the trip unit 23, and the load terminal 24 of the trip unit 23 is connected directly to the main load terminal 12 of the circuit breaker.

For the purpose of moving the movable contacts 17 and 18 into and out of engagement with the stationary or line contacts 15 and 16, both manually and automatically, we provide a main operating mechanism indicated generally at 25. The operating mechanism 25- includes a generally U-shaped supporting frame member- 26 and a plurality of parts pivotally supported between the opposite sides thereof. These parts include three-v contact arms 19, there being one contact arm for each pole of the circuit breaker.

The contact arms 19 are adapted to be rotated about,

their pivotal support by means of a toggle action linkage j including the toggle links 27 and 28 connected together:

.straightenedand collapsed positions by means ofan p 7 erating handle 32 in cooperation with a pair 'o'f 'tension typesprings 33 interconnected between the-handle 32 and the knee point 29 of the toggle linkage 27, 28.

When the handle member 32 is in the position shown in' Figure 1, the contacts are in closed position, and when the handle is moved counterclockwise from this position toward-.the left end of the breaker as viewed, the contacts aremoved to the open' circuit position.

The end 31 of the toggle carrier 31 is formed to act as a latching element and to engage an intermediate latch member 34 which is pivotally supported on a pin 35 carried by an extension 26 of the frame 26. The action of the tension springs 33 is such as to bias the togglef carrier 31 for rotation in a clockwise direction. The toggle carrier 31 is restrained from movement in such a direction, however, by its engagement with-the intermediate latch member 34. A biasing spring, 34, constantly urges the intermediate latch 34in a clockwise direction as viewed in the figures. By reason of the greaterforce exerted on it by the toggle carrier 31, however, the intermediate latch member 34 is biased in a counterclockwise direction whenever the breaker is latched. I i

For the purpose of normally restraining the intermediate latch member, and therefore the toggle carrier 31 and the operating mechanism as a whole, in the on position except in the case of predetermined overload conditions, we provide a trip unit generally indicated at 23. The 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 an application filed concurrently herewith by H. M.

Steven and R- W. Marshall, and assigned to the same assignee as the present invention.

The trip unit 23.includes a latch member '36 adapted normally to prevent the intermediate latch member 34 from rotating in a counterclockwise direction. The latch member 36 ,is pivotally supported on the trip unit 23 on a pivotpin 37,extending through aligned openings in a boss 38 molded integral with the housing of the trip unit 23. t

Thelatch member 36 carries a latch roller 39 supported on a pin 40 extending between opposed, spaced apart, portions of the latch member 36. The intermediate latch member 34 is provided with a cam surface 41 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 figures. 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 36 moves to the left, allowing the intermediate latch member 34 to rotate counterclockwise, releasing-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. During this movement, a portion 32' of the handle engages 'the carrier 31 and rotates it counterclockwise. When "the latch tip of the carrier 31 engages the surface 345 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 34, and the intermediate latch is returned to its normal position by the action of the spring 34, thereby relatching the breaker.

When the toggle carrier 31 is released from the intermediate latch 34, the carrier 31 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 19 are also moved upwardly or in a counterclockwise direction, toward open circuit position. Because of the necessary proportioning and dimensions and arrangement of the 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 30 definitely across the center line of action of the mainsprings 33.

The action of the parts, as so far described, therefore, is such as to move themovable contact arm 19 in an opening direction by movementof the toggle'linkage upwardly I as a whole, without any substantial breaking 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 43 supported on a pivot pin 44 between the sides of the mechanism frame 26. j

The 'toggle lever 43 is movable independently of the toggle carrier 31, and is biased by a biasing spring 45 in a counterclockwise direction against a portion 46 of the mechanism fram'e'26. The forward end' 43' of the toggle lever 43 is rounded and is adapted to coact with a projection or'detent 47 on the upper toggle link 27 in a manner to be described.

As'longas the toggle carrier is in its latched conditlon as shown in Figure 2, the toggle lever 43 is maintained in theposition' shown in Figure 2. Thus the toggle linkage is moved between collapsed andstraightened'conditions without alteringithe position of the toggle lever 43. 'When thetoggle carrier 31 is released from the intermediate latch member 34, and rotates clockwise, however, the projection 47 engages the rounded end 43 0f the toggle lever 43 and the two partsrema-in 1n engage ment as further rotation of the toggle carrier 31 occurs.

This action maintains the intermediate part of the upper toggle link 27 at a' predetermined distance from the pivot pin'44, and causes the toggle linkage to assume a slightly broken or collapsed condition as illustrated in Q Figure 3." This shortens, the distance betweenrthe opposite ends of the toggle linkage andresults in accelerating the movement of the contact arm 19 and inmoving the arm 19 further'in' a contact opening direction than would otherwise be possible. This is especially true, and also especially important, when the handle 32 is manuallyretained in the on or closed circuit position.

In'Figures' Sand 6 we have illustrated another embodiment of our invention, in which the toggle linkage 27,

'28 is adapted to be maintained in a slightly broken In this or collapsed condition when tripping occurs. form, the projection 47 on the upper link 27 is omitted.

Insteadjthe toggle lever 49 is provided and the toggle carrier 50 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 clockwisedirection as tripping occurs. The end 49, of the toggle lever, engages the link 27 and forces the toggle linkage to a collapsed condition in a manner similar to that described in connection with Figures 2 and 3.

In the form of Figure 5 the end 49 of the toggle abutment 51 exerted on the toggle lever 49 causes the point of engagement of the toggle lever 49 to move upwardly along the toggle link 27 toward the upper pivot point 30'. In this manner, the leverage action of the toggle lever 49 on the toggle link 27 is greatest at the initial point of movement and decreases as the tripping action progresses. This aifords an important prying action which assists in breaking any welds which might occur between the stationary and movable contacts, while at the same time afiording a maximum rate of acceleration and a maximum opening distance of the movable contact. While the toggle lever 49 has been shown as of a difierent configuration from the toggle lever 43, it will be apparent that these toggle levers are substantially interchangeable.

While we have shown only two embodiments of our invention, it will be apparent that many modifications thereof may readily be made by those skilled in the art and we, therefore, intend by the appended claims to cover all such modifications as fall 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:

' 1. An electric circuit breaker comprising a support, a contact arm supported on said support, a toggle carrier pivotally mounted on said support, a toggle linkage conmeeting said contact arm and said toggle carrier, said toggle carrier being movable between latched and tripped positions to move said contact arm between closed and opened positions respectively, a lever supported on said support for engaging and holding said toggle linkage in partially collapsed position when said toggle carrier is in said tripped position, and means for guiding the movement of said lever in accordance with the movement of said toggle linkage during movement of said toggle car- I rier to said tripped position.

2. An electric circuit breaker comprising a support, a contact arm pivotally mounted on said support, a toggle carrier pivotally mounted on said support, a toggle linkage connecting said contact arm and said toggle carrier,

said toggle carrier being movable between latched and tripped positions to move said contact arm between closed and opened positions respectively, a projection on said toggle linkage, a lever supported on said support adapted to engage and hold said toggle linkage in a partially collapsed position when said toggle carrier is in said tripped position, said lever being adapted to be engaged by said linkage projection and to be guided thereby during movement of said toggle carrier from said latched to said tripped position.

3. An electric circuit breaker comprising a support, a contact arm pivotally mounted on said support, a toggle carrier pivotally mounted on said support, the toggle linkage connecting said contact arm and said toggle carrier, said toggle carrier being movable between latched and tripped positions to move said contact arm between closed and opened positionsrespectively, a lever supported on said support and adapted to engage and hold said toggle linkage in a partially collapsed position when said toggle carrier is in said tripped position, said toggle carrier having a cam follower projection adapted to engage said lever to guide the movement of said lever when said toggle carrier moves from said latched to said tripped positiom 4. An electric circuit breaker as set forth in claim 1, said circuit breaker including means carried by said toggle carrier for engaging said lever and applying a force thereto at a point closely adjacent the pivot of said lever, the point of application of said force being closely adjacent the pivot of said lever initially and being more remote from the pivot of said lever as said toggle carrier moves to said tripped position.

References Cited in the file of this patent UNITED STATES PATENTS 2,208,387 Pierce July 16, 1940 2,550,623 Teruzzi Apr. 24, 1951 2,581,181 Favre Jan. 1, 1952 2,727,113 Mohr et a1. Dec. 13, 1955

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