US3815070A

US3815070A - Circuit breaker with wide opening contacts

Info

Publication number: US3815070A
Application number: US00317754A
Authority: US
Inventors: Torre J De
Original assignee: Federal Pacific Electric Co
Current assignee: PROVIDENT INDUSTRIES Inc
Priority date: 1972-12-22
Filing date: 1972-12-22
Publication date: 1974-06-04
Anticipated expiration: 1991-06-04
Also published as: ES421743A1; JPS4989864A; AU6402473A; CA1009694A; AU475656B2; GB1458022A

Abstract

The circuit breakers involved are of the type having a contact arm pivoted between its ends and operable by a manually erected toggle for closing the contacts. A bell-crank, pivoted to one end of the contact arm, has a latch arm restrained by an over-current latch also carried by the contact arm. That type of circuit breaker is given increased interrupting capability by modification of its component parts, especially the handle and the linkage operated by the handle, to produce greatly increased contact separation.

Description

United States Patent DeTorre I June 4, 1974 CIRCUIT BREAKER WITH WIDE OPENING 3.134.871 5/1964 Norden 200/145 x 3.464.040 8/1969 Powell 1 r 335/l9l CONTACTS 3.599.136 8/l97l DeTorre.... 337/71 [75] Inventor: John DeTorre, Albemurle, NC. 3.6IO.856 10/1971 DeTorre 200/153 0 Assigneez Federal Pacific Electric p y, 162L189 ll/l97l, Lmk Z\()0/l53 G k, NJ. Newar Primary Examiner-A. T. Gnmley [22] Filed: Dec. 22, 1972 [2]] Appl. No.: 317,754 [57] ABSTRACT The circuit breakers involved are of the type having a 52 us. c1 337/59, 335/191, 337/13. Contact am pivoted between its ends and Operable y 7 7 a manually erected toggle for closing the contacts. A 1511 Im. c1. 110111 71/16 bell-Crank, pivoted to one end of the Contact arm, has [58] Field f Search 7 3 36 37 5 7 a latch arm restrained by an over-current latch also 337/71, 72, 75 5 53 G carried by the contact arm. That type of circuit breaker is given increased interrupting capability by [56] References Cited modification of its component parts,.especially the UNITED STATES PATENTS handle and the linkage operated by the handle, to produce greatly increased contact separation. 2.733.312 l/l956 Christensen 337/110 X 2.876.308 3/1959 4 Claims, 5 Drawing Figures Christensen 337/] H) X ing and the closed conditions of the circuit breaker,

and a manual toggle drives the movable contact closed as the toggle becomes erect and slightly over-set. De-

spite the continued efforts over the years to improve the circuit breaker, to impart increasedinterruption capacity without proportional increase in dimensions of the mechanism and the enclosure, increased interruption capacity remained a problem.v This type of circuit breaker is exemplified by U.S. Pat. No. 2,700,713 issued .Ian. 25, 1955 to T. M. Cole et a]. Earlier forms of that circuit breaker are shown in U.S. Pat. No. 2,647,186 issued July 28, 1953 to T. M. Cole, U.S. Pat. No. 2,459,427 issued Jan. 18, 1949 to H. A. Humpage and U.S. Pat. No. 2,209,310 issued July 30, 1940 to P. M. Christensen. In U.S. Pat. No. 2,700,713, the arc chute (where interruption of the arc takes place during opening of the contacts) is formed of parts that are intreme measures represented in U.S. Pat. No. 3,134,871

issued May 26, 1964 to A. R. Norden met with limited success, particularly with respect to dependable interruption at higher voltages and with increased available current.

Circuit breakers of this type as produced heretofore provide a contact-opening travel of approximately fivesixteenth of an inch. An object of the present invention resides in greatly increasing the contact-opening travel of such a circuit breaker without correspondingly enlarging the parts. In a practical form of circuit breaker made pursuant to the present invention, a contactopening travel of five-eighth of aninch has been realized without changing the size of the contact arm or the bell-crank, by improvements that will be pointed out in greater detail in discussing the illustrative embodiment of the present invention that is shown in the accompanying drawings and described in detail below. Through the present invention, are interruption has been achieved with a single-pole circuit breaker in circuits having an available short-circuit current of 10,000 amperes in a 277-volt alternating current distribution line.

In the drawings:

FIG. I is a lateral view of a presently preferred embodiment of the invention, showing a circuit breaker in its closed configuration, the cover of the two-part enclosure being removed and certain parts being shown in cross-section for clarity;

FIG. 2 is a fragmentary view of the circuit breaker of FIG. 1 with the mechanism shown in the position it would assume following over-current release with the operating handle held in the on" position;

FIG. 3 is a fragmentary view of the circuit breaker of FIG. 1 with contacts open and the handle in the off" position;

FIG. 4 is a fragmentary perspective view illustrating part of the operating linkage of the circuit breaker of FIGS. 1 to 3; and

FIG. 5 is a cross-sectional view along the broken section line 5-5 in FIG. 4.

Referring now to the drawings, the circuit breaker as shown includes an enclosure formed of two parts and 11 of molded insulation. Screw terminal 12 includes a part 12a that carries a stationary contact 14 which acts as a companion contact to movable contact 16. Movable contact 16 is united to elongated contact arm 18, ordinarily a copper alloy for high conductivity. Contact arm 18 is povited near its center on a helical coil spring 20 whoseaxial ends are received in bearing cavities in the opposite side walls of the insulating enclosure 10, ll.

Bimetal 22 and magnetic yoke 24 are united to contact arm 18 by an integral rivet 18a. Armature 26 is carried by yoke 24 on pivot 26a and is biased counter-clockwise (as viewed-in FIG. 1) by a leaf spring 28, shown in greater detail in U.S. Pat. No. 3,599,136. Armature 26 has a dependingportion 26b in which there is a cut-out, andbimetal '22 extends through that cutout. A transverse ledge at the bottom of the'cut-out is biased upward against a small piece of insulation 30 which is suitably retained in the assembled position shown. Spring 28 biases the ledge of armature 26 upward against insulator 30.

Extending from bimetal 22 is a flexible braid 32 as of fine strands of copper wire, extending to a terminal 34.

I In the closed condition of the circuit breaker, a circuit can be traced from terminal 12 through contacts 14 and 16, along contact arm 18, bimetal 22, and along braid 32 to terminal 34.

A so-called bell-crank 36 is carried on pivot 36!) in the end of contact arm 18 remote from contact 16 and has a latch arm which end 36a abutting against the end of armature 26 forms a latch for restraining the bellcrank when the circuit breaker is closed. Armature 26 and bimetal 22 and yoke 24 form an over-current release for the circuit breaker, in that sudden extreme values of overload current cause armature 26 to be attracted downward and out of the (clockwise) path of latch arm end 36a. For moderate overloads of prolonged duration, bimetal 22 flexes downward and draws armature 26 down and out of the path of latch arm end 36a. Accordingly, armature 26 and its

control elements

22 and 24 constitute an over-current release.

A manual operator 38 has a hand lever 40 and is operable about a stationary metal pivot pin 42 whose ends are received in bearings in the two sidewalls l0 and 11 of the insulating enclosure (FIG. 5). Coil spring 44 (also called the push-off" spring) is compressed between a projection 46integral with manual operator 38 and a projection of contact arm 18. It biases contact arm 18 counter-clockwise about pivot 20, the contactopening direction. When manual operator 38 has been shifted clockwise, partway toward the opposite extreme from that shown in FIG. 1, projection 46shifts to the left and then spring 44 exerts clockwise bias on manual operator 38. This bias tends to rotate the manual operator clockwise about pivot 42, as viewed in FIG.

A metal member 48 is received snugly in recesses in manual operator 38 and is held in assembly to operator 38 by pivot pin 42, forming a fixed part of the manual operator. Hand lever 40 and member 48 are approximately opposite each other in relation to the axis of pivot 42. A connecting link 50 has a pair of

pins

52 and 54 in members 48and 36, respectively. When the circuit breaker is closed, (FIG. 1) pin 52 is located slightly above a straight line between pivot 42 and pivot 54 and, consequently,

member

38, 48 and connecting link 50 constitute a toggle which is slightly overset. In turn, pivot 54 is located slightly above a straight line between the centers of pivot 52 and pivot 36b. Any thrust along the line between

pivots

52 and 54 produces a clockwise bias on bell-crank 36 urging the latch arm end 360 against the end of armature 36., b

When the circuit breaker is open, as shown in FIG. 3, the hand lever 40 rests against a portion a of the enclosure, being biased into that position by coil spring 44. Correspondingly, contact arm 18 is biased counterclockwise about spring pivot so that contact arm 18 is pressed against a stop 10b of the enclosure. In this condition of the circuit breaker, coil-spring pivot 20 is substantially straight, end to end.

. When the circuit breaker is to be closed, manual operator 38 is moved counter-clockwise. Member 48 drives connecting link 50 so that bell-crank 36 swings until its latch arm end 36a is arrested by armature 26. Thereafter, bell-crank 36, armature 26 and contact arm 18 act as a latched triangular unit, in'the further closing operation of the circuit breaker, driving contact arm 18 clockwise about pivot 20. Movable contact 16 engages the companion contact 14 at a time when member 48 has still some distanceto move before assuming the position in FIG. 1. When contacts 14 and 16 engage, pivot 52-is well below a straight line between

pivots

42 and 54. Further counter-clockwise operation of hand lever 40 tends to erect.

parts

48 and 50 which act as an operating toggle for the circuit breaker mechanism. During this erection of the toggle, contact arm 18 is forced clockwise about its contact 16 as a fulcrum. During this motion spring pivot 20 becomes stressed so that the mid-portion of that spring which carries contact arm 18 shifts downward relative to the ends of the spring pivot seated in cavities in opposite walls 10 and 11 of the insulating enclosure. During this motion, considerable contact pressure develops. Spring pivot 20 accommodates over-travel of the operating linkage, after the contacts have come into engagement. As is well known, pivot 20 might be replaced by a rigid pin and then companion contact 14 could be made movable and spring-biased toward contact 16 as one of several other ways of providing for over-travel".

An arcrunner 56 of iron has one end adjacent to and touching contact 14. A series of iron arc-splitter plates 58 below are runner 56 are suitably held in mutually spaced relationship. Plates 58 are U-shaped, so that the contact 16 cam move between the legs of each U as contact arm 18 moves toward stop l0b.

In the event of an overload, such that armature 26 is drawn downward,either by magnetic attraction toward magnetic yoke 24 or as the result of downward deflection of bimetal 22 due to over-current flowing through the circuit breaker, bellcrank 36 is no longer restrained. Spring 20 immediately drives contact arm 18 upward about contact 16 as a fulcrum. As this occurs, bell-crank 36 moves clockwise through a substantial angle. This clockwise motion of bell-crank 36 continues as push-off spring 44 starts to drive contact arm 18 counterclockwise for driving contact 16 away from contact 14 and toward its fully open position.

An arc is drawn between contacts 14 and 16, and shifts along arc runner 56. The are expands toward the left-hand ends of the arc splitter plates. The are is cooled and hot gases are emitted through wire mesh which is disposed across vent opening 62. During the contact-opening operation, contact arm 18 is guided between suitable bosses in the housing, including boss 10c.

Referring now to FIGS. 4 and 5, certain details will be described that are of controlling importance to the full realization of the objects of the invention. Bell crank 36 that is formed of sheet-metal includes a pair of,

opposite side portions

360 and 36d that may be called parts or strips disposed and operable in parallel planes at opposite sides of contact arm 18. A bridge portion 36e extends opposite the end of contact arm 18 (but spaced therefrom) and interconnects and unifies

strips

36c and 36d of the bell-crank. These parts 36c,

36d and 36e are all formed of a'single piece of sheetmetal.

Connecting link 50 is also formed of a single piece of sheet-metal including a side portion oppositeparts or strips 50a and 50b in spaced-apart parallel planes. Strips 50a and 50b are integral with an interconnecting bridge portion 500. By like token, part 48 is formed of a single piece of sheet-metal including a pair of strips 48a and 48b united by an integral interconnecting bridge portion 48c.

Parts48a and 48b are separated from each other by a distance that is large enough to receive strips 50a and 50b between them. Interconnection 480 is at the side of parts 48a and 48b remote from member 50 in the open condition of the circuit breaker mechanism as shown in FIG. 3. Consequently, a large portion of connecting link 50 is received between or straddled by strips 48a and 48b when the circuit breaker is open and the handle is-in the ofF position (FIG. 3). By like token, parts 360 forming the operating arm and 36d of the bellcrank fit between strips 50a and 50b in the condition of the circuit breaker represented in FIG. 2, that is, when the circuit breaker has tripped open in response to an overload while the handle is held in the on position. In this same position, there is no possibility of interference between parts 48a and 48b with the

parts

36c and 36d of the bellcrank since the latter are much closer to each other than strips 48a and 48b. Finally, again in the position'of FIG. 2, it is noted that interconnection 36c of the bell-crank is disposed at a place where it is free of interference with any other part of the circuit breaker mechanism in all conditions of operation. FIGS. 1, 2 and 3. Notably, while bell-crank 36 has two strips and provides a stable forceresisting structure on contact arm 18 for erecting the toggle, nevertheless the latch arm end 36a of the bell-crank is free to'move alongside the contact arm (FIG. 2) when this becomes necessary as in FIG 3. By virtue of these relationships between the operating links of the circuit breaker, it becomes possible to locate stop 10b so far from contact 14 that roughly double the previous contact-separation is obtained with the described mechanism as compared with the prior art commercially standard mechanism represented for example in US. Pat. No. 2,700,713. The described linkage is symmetrical abouta central vertical plane in FIG. 5, so that no torsion forces develop in transmitting the contact-closing effort from handle 40 to contact arm 18. No lateral thrust develops in this operation. Moreover, the parts nest in one another, for achieving greatest collapse of the linkage, which become necessary in the condition of FIG. 3.

Manual operator 38 is shaped specially to accommodate operation of handle 40 through an unusually long are. This motion is needed for operating contact arm 18 through an increased angle, the contact-opening travel of contact arm 18 being greatly increased to achieve increased interruption ratings. The large angle of operation of handle 40 is realized, handle strength is preserved, and operating space for the linkage is made available (see especially FIG. 5) for accommodating the wide contact separation critically needed for'high interruption ratings. Hand lever 40 extends from the large-radius portion 38b adjacent to a small-radius portion 38a of the manual operator. The small-radius portion 38a is adjacent the operating linkage when the breaker is open and the hand lever is at the off stop. A large label OFF is provided on portion 38b and is exposed when the breaker is open and the parts are in the position of FIG. 3. Housing portions 100 and c cooperate with manual operator portions 38a and 38b, respectively, to confine hot gases that develop as a result of arcing. Beads 380 on the operator 38 are received in grooves in the housing, for confining the hot gases. Accordingly, the proportions of the manual operator 38 and hand lever 40 as shown in the drawing represent a strong handle and the casing cooperates with the manual operator to confine arc-generated hot gases, and yet the linkage is capable of assuming either of the positions in FIG. 2 or FIG. 3 with the contact arm in its unusually wide-open position as shown. All the desired practical properties of the prior-art type of circuit breaker are preserved in the illustrative novel breaker, and yet its interruption rating is greatly increased.

The foregoing represents an exemplary embodiment of the invention, but variations will be introduced by those skilled in the art, so that the invention should be construed broadly in accordance with its full spirit and scope.

l claim:

1. A circuit breaker of the type having an elongated contact arm pivoted between its first and second ends and operable in a central plane perpendicular to the pivoted axis thereof, a movable contact carried by said first end of said contact arm and a companion contact engageable by said movable contact in the closed condition of the circuit breaker, a bell-crank having a latch arm and an operating arm, and means forming a first pivot between said arms of said bell-crank and carrying the bell-crank on said second end of said contact arm, overcurrent release means carried by said contact arm and including a latch engageable by the latch arm of said bell-crank for arresting said bell-crank against pivoting relative to said contact arm, said bell-crank and said contact arm and said overcurrent latch forming a latched unit in the closing and closed condition of the having a stationary second pivot and movable between an ON" position and an OFF position for closing and opening the contacts, said push-off spring also biasing the manual operator toward its OFF" position when the contact arm is in its open position, a connecting link, a third pivot connecting said connecting link to said manual operator, a fourth pivot connecting said connecting link to the operating arm of said bell-crank, all of said pivots having parallel axes perpendicular to said central plane, said manual operator and said connecting link forming a toggle for driving said latched unit in the contact-closing direction and for holding the contacts closed subject to control by said latch, characterized in that said operating arm of said bell-crank includes side portions disposed at opposite sides of said contact arm and a bridge portion interconnecting and unifying said side portions, both of said side portions bearing said fourth pivot, and said side portions acting on said contact arm via said first pivot means symmetrically with respect to saidcentral plane, further characterized in that said latch arm of the bell-crank is free of transverse structure that could impede movement thereof alongside the contact arm, for accommodating relatively wide separation of said movable contact from said companion contact 2. A circuit breaker as claimed in claim 1, wherein said. connecting link comprises side portions straddling the side portions of the bell-crank and a bridge portion interconnecting and unifying the side portions of the connecting link and wherein the side portions of said connecting link are free of transverse structure that could impede collapsing movement of said connecting link and said bell-crank as said latch arm moves into position alongside the contact arm when said manual operator is in its ON" position, thereby allowing travel of the contact arm to its full open position.

3. A circuit breaker as claimed in claim 1, wherein said manual operator comprises side portions straddling the side portions of the connecting link, both of said side portions of the connecting link bearing said third pivot, said side portions of said manual operator bearing on said third pivot symmetrically with respect to the central plane for applying a balance operating force to said connecting link, and wherein the side portions of said manual operator are free of transverse structure that could impede collapsing movement of said manual operator and said connecting link when the movable contact moves to its fully open position, following release of said bell-crank by the over-current release means, thereby allowing return of said manual operator to its OFF" position.

4. A circuit breaker of the type having an elongated contact arm pivoted between its first and second ends and operable in a central plane perpendicular to the pivotal axis thereof, a movable contact carried by said first end of said arm and a companion contact engageable by said movable contact in the closed condition of the circuit breaker, a bell-crank having a latch arm and an operating arm, a first pivot between said arms of said bell-crank and carrying the bell-crank on said second end of said contact arm, over-current release means carried by said contact arm and including a latch engageable by said latch arm of said bell-crank for arresting said bell-crank against pivoting relative to said contact arm, said bell-crank and said contact arm and said over-current latch forming a latched unit in the closing and closed condition of the contacts, a push-off spring biasing said contact arm away from said companion contact, a manual operator having a stationary second pivot and movable between an ON position and an OFF position for closing and opening the contacts, a connecting link, a third pivot connecting said connecting link to said manual operator, a fourth pivot connecting said connecting link to said operating arm of said bell-crank, all of said pivots having parallel axes, said manual operator and said connecting link forming a toggle for driving said latched unit in the contact-closing direction and for holding the contacts closed subject to control by said latch, characterized in that said manual operator and said connecting link and ing force to the bell-crank.

Claims

1. A circuit breaker of the type having an elongated contact arm pivoted between its first and second ends and operable in a central plane perpendicular to the pivoted axis thereof, a movable contact carried by said first end of said contact arm and a companion contact engageable by said movable contact in the closed condition of the circuit breaker, a bell-crank having a latch arm and an operating arm, and means forming a first pivot between said arms of said bell-crank and carrying the bell-crank on said second end of said contact arm, overcurrent release means carried by said contact arm and including a latch engageable by the latch arm of said bell-crank for arresting said bell-crank against pivoting relative to said contact arm, said bell-crank and said contact arm and said overcurrent latch forming a latched unit in the closing and closed condition of the contacts, a pushoff spring biasing said contact arm away from said companion contact, a manual operator having a stationary second pivot and movable between an ''''ON'''' position and an ''''OFF'''' position for closing and opening the contacts, said push-off spring also biasing the manual operator toward its ''''OFF'''' position when the contact arm is in its open position, a connecting link, a third pivot connecting said connecting link to said manual operator, a fourth pivot connecting said connecting link to the operating arm of said bell-crank, all of said pivots having parallel axes perpendicular to said central plane, said manual operator and said connecting link forming a toggle for driving said latched unit in the contact-closing direction and for holding the contacts closed subject to control by said latch, characterized in that said operating arm of said bell-crank includes side portions disposed at opposite sides of said contact arm and a bridge portion interconnecting and unifying said side portions, both of said side portions bearing said fourth pivot, and said side portions acting on said contact arm via said first pivot means symmetrically with respect to said central plane, further characterized in that said latch arm of the bell-crank is free of transveRse structure that could impede movement thereof alongside the contact arm, for accommodating relatively wide separation of said movable contact from said companion contact.

2. A circuit breaker as claimed in claim 1, wherein said connecting link comprises side portions straddling the side portions of the bell-crank and a bridge portion interconnecting and unifying the side portions of the connecting link and wherein the side portions of said connecting link are free of transverse structure that could impede collapsing movement of said connecting link and said bell-crank as said latch arm moves into position alongside the contact arm when said manual operator is in its ''''ON'''' position, thereby allowing travel of the contact arm to its full open position.

3. A circuit breaker as claimed in claim 1, wherein said manual operator comprises side portions straddling the side portions of the connecting link, both of said side portions of the connecting link bearing said third pivot, said side portions of said manual operator bearing on said third pivot symmetrically with respect to the central plane for applying a balance operating force to said connecting link, and wherein the side portions of said manual operator are free of transverse structure that could impede collapsing movement of said manual operator and said connecting link when the movable contact moves to its fully open position, following release of said bell-crank by the over-current release means, thereby allowing return of said manual operator to its ''''OFF'''' position.

4. A circuit breaker of the type having an elongated contact arm pivoted between its first and second ends and operable in a central plane perpendicular to the pivotal axis thereof, a movable contact carried by said first end of said arm and a companion contact engageable by said movable contact in the closed condition of the circuit breaker, a bell-crank having a latch arm and an operating arm, a first pivot between said arms of said bell-crank and carrying the bell-crank on said second end of said contact arm, over-current release means carried by said contact arm and including a latch engageable by said latch arm of said bell-crank for arresting said bell-crank against pivoting relative to said contact arm, said bell-crank and said contact arm and said over-current latch forming a latched unit in the closing and closed condition of the contacts, a push-off spring biasing said contact arm away from said companion contact, a manual operator having a stationary second pivot and movable between an ''''ON'''' position and an ''''OFF'''' position for closing and opening the contacts, a connecting link, a third pivot connecting said connecting link to said manual operator, a fourth pivot connecting said connecting link to said operating arm of said bell-crank, all of said pivots having parallel axes, said manual operator and said connecting link forming a toggle for driving said latched unit in the contact-closing direction and for holding the contacts closed subject to control by said latch, characterized in that said manual operator and said connecting link and said bell-crank individually comprise side portions operable in respective planes parallel to the central plane and symmetrical thereto, the side portions of said bell-crankbeind disposed at opposite sides of said contact bell-brank being at said first pivot, the side portions of said connecting link straddling said operating arm of said bell-crank, and the side portions of said manual operator straddling said connecting link at said third pivot, so as to enable the manual operator in moving toward its ''''ON'''' position to apply a symmetrical driving force to the bell-crank.