US2959654A

US2959654A - Latched type shunted contact for three stage contact construction

Info

Publication number: US2959654A
Application number: US781541A
Authority: US
Inventors: Arthur S Caswell; William A Carter
Original assignee: ITE Circuit Breaker Co
Current assignee: ITE Circuit Breaker Co
Priority date: 1958-12-19
Filing date: 1958-12-19
Publication date: 1960-11-08
Anticipated expiration: 1977-11-08

Description

NOV- 8, 1950 A. s. CASWELL ETAL 2,959,654

LATCHED TYPE SHUNTED CONTACT FOR THREE STAGE CONTACT CONSTRUCTION 5 Sheets-Sheet 1 Filed Dec. 19, 1958 Nov. 8,y 1960 A. s. cAswELL ETAT 2,959,654

LATCHED TYPE SHUNTED CONTACT FOR THREE STAGE CONTACT CONSTRUCTION 3 Sheets-Sheet. 2

Filed Dec. 19, 1958 Nov. 8, 1960 A. s. CASWELL ErAL 2,959,654

LATCEED TYPE SHUNTED CONTACT FOR THREE sTACE CONTACT CONSTRUCTION Filed Deo. 19, 1958 5 Sheets-Sheet 5 lHllWlllll /a United States Patent 2,959,654 Patented Nov. s, 1960 hice LATCHED TYPE SHUNTED CONTACT FOR THREE STAGE CONTACT CONSTRUCTION Arthur S. Caswell, Greensburg, and William A. Carter, Chester, Pa., assignors to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsyl- Vania Filed Dec. 19, 1958, Sel'. No. 781,541

7 Claims. (Cl. 200-146) The instant invention generally =relates to circuit breakers and more particularly to a circuit breaker in which the magnetic blowout means -is mechanically inserted in the circuit by a novel latched type shunt contact.

Air magnetic circuitbreakers are usually provided with an arc extinguishing means including a plurality of spaced arc plates stacked so as to form an arc chute, and associated with the chute is a blowout coil which is positioned so as to direct the arc formed by the parting of the circuit breaker contacts into the arc chute. In one prior art construction, the blowout coil was mechanically inserted into the circuit by the main arcing contacts. However, on the closing of the breaker the blowout coil was not protected from the high magnetic forces accompanying high peak inrush currents when closing on a fault current. In order to protect the blowout coil from these high magnetic forces on closing :of the circuit breaker, other prior art constructions have provided an arc transfer means in the form of a jump gap. This has resulted in poor interruption at low values of current since the arc is often unable to jump the gap thereby preventing the arcing current from flowing through the blowout coil.

In the circuit breaker of the instant invention the movable contact bridge has been provided with a contact assembly including a main contact, a shunt contact, and an arcing contact which cooperate with co-rresponding stationary contacts. The bridge contacts are so mounted that upon closing ofthe circuit breaker the shunt contacts are first to close, followed by the arcing contacts, and finally the main contacts whereas upon opening, the main contacts are first to open, followed by the shunt contacts, and finally the arcing contacts.

The shunt contacts are positioned in the circuit such that when they are closed the blowout coil is completely shorted. Thus, upon closing of the circuit breaker the initial formation of a continuous current path results in the shorting of the blowout coil thereby protecting this coil from peak inrush currents. The shunt contacts also provide additional protection for the main contacts on opening of the breaker. Y

The preceding operation is accomplished by mounting the shunt contact to the circuit breaker bridge in a manner such that it is always biased toward engagement with its stationary cooperating shunt contact. A shunt contact latch is also carried by the bridge and is biased toward latching position. When the bridge moves the contacts toward circuit closed position, the engagement of the movable shunt contact with its cooperating stationary shunt contact moves the shunt contact, against its bias, to a position wherein the shunt contact is beyond the engaged position of the latch and is maintained in this position with the force of the biasing means.

On the opening of the circuit breaker, the latch engages and is held in engagement with the shunt contact until such time as the bridge reaches the end of the opening stroke. At this time, the latch strikes `a trip plate thereby releasing the shunt contact so that it is free to be acted upon by its bias. With the shunt contact unlatched upon closing of the'circuit breaker, the shunt contact is the first of the three movable contacts to engage its cooperating stationary contact.

The advantage of this construction over its conventional counterparts in the prior art is that the high peak inrush currents, encountered when closing Ia circuit breaker on a faulted circuit are diverted from the blowoutcoil by the shunt contact. In this manner, the extra high magnetic force, which varies as the square of the current, that the blowout coils must be built to withstand, is greatly reduced. In addition, a greater protection for the main contacts is provided.

Accordingly, a primary object of the instant invention is to provide a novel construction for a circuit breaker wherein the blowout coils thereof are mechanically inserted into the circuit.

Another object is to provide a circuit breaker having a latched type shunt contact for protecting the blowout coils upon closing of the circuit breaker.

Still another object is to provide a circuit breaker wherein the movable bridge thereof is provided with three contacts whose closing and opening sequences are different from one another.

A further object is to provide a shunt contact for the protection of a circuit breaker blowout coil and a latch means engageable with the shunt contact whereby the shunt contact is latched while the circuit breaker is being opened and remains unlatched while the circuit breaker is being closed.

These `as well as other objects of the instant invention shall become readily apparent after reading the following description of the accompanying drawings in which:

Figures 1-4 are side elevations of the contact structure illustrating the positions of the contacts at different positions of the contact bridge. In Figure l the circuit breaker is fully closed; in Figure 2 the circuit breaker is fully open with the shunt contact unlatched; in Figure 3 the shunt contacts and arcing contacts are engaged during the closing stroke and the main contacts are still open; and the shunt contacts are not latched, while in Figure 4 the shunt contacts and the arcing contacts are engaged during the opening stroke with the shunt contacts being latched and the main contacts being open.

Figures 5 and 6 are schematics of a circuit breaker constructed in accordance with the instant invention. In Figure 5 the circuit breaker is shown during the closing operation and in Figure 6 the circuit breaker is shown during the opening operation.

Now referring to the figures and more particularly to Figures 5 and 6, circuit breaker 20 comprises a stationary contact

structure including contacts

21, 23, 25 and a movable contact

structure including contacts

22, 24, 26. Cooperating

contacts

21, 22 are designated the main contacts, cooperating

contacts

23, 24 are designated the arcing contacts, and cooperating

contacts

25, 26 are designated the shunt contacts.

Movable contact structure

24, 26, 28 is mounted to one end of conducting bridge 27 while the other end of bridge 27 is pivoted at 28 to lower current stud 29. Stationary main contact 2l and shunt contact 25 are both mounted to upper current stud 30. The stationary arcing contact 23 is mounted to arcing contact member 34 which is insulated from upper current stud 3i) by insulating member 96 interposed between member 99 and upper current stud 30. An insulating sleeve 98 disposed in an aperture through member 99 surrounds the body of screw 97 which secures member 99 to upward extension 9S of upper stud 30. Insulating washer 97' is interposed between the head of screw 97 and member 99.

Current studs

29, 30 extend through inthereof to arcing contactmem'ber 34. The rear=runner` 36 of parallel' plate arc chute 37 is also electrically connected to arcing contactY member 34 while front runner 38 is electrically connected to lower current stud 29. As -is well known in the art, blowout coil 35 is positioned to force an electric current arc drawn bei tween arcing contacts 23,' 24, upon parting thereof, into arc chute 37 where the arcing gases are cooled and otherwise de-ionized to vbring about the extinctionv of the arc.

As will b'e more fully explained hereinafter, as bridge 27 is moved clockwise about pivot 25 from the circuit breaker closed position (Figure l) by any one of many operating mechanisms known to the art, the main contacts 2l, 22 are first to part. Since lthey are parallel by

shunt contacts

25, 26, no arcing will occur at main contacts 2l, 22. Therefore,

shunt contacts

25, 26 part so that blowout coil 35 is energized even before arcing

contacts

23, 24 pant. Thus, thev arc, from its inception, is acted upon by the magnetic force accompanying current flow through blowout coil 35. Since the energization of blowout coil 35 is independent of arc current magnitude even an arc of low current value will be acted upon by some magnetic force urging the arc into arc chute 37.

Upon counter-clockwise movement of bridge 27 from the circuit breaker full open position (Figure 2),

shunt contacts

25, 25 will be rst to engage to complete a current path between the upper 3) and the lower 29 current studs which bypasses blowout coil 35. Thus, coil 35 is protected from high inrush currents encountered when closing circuit breaker on a faulted circuit. After

shunt vcontacts

25, 26 are closed, arcing

contacts

23, 24 will close followed by the closing of

main contacts

21, 22. The Structure for achieving the contact opening and closing sequence hereinbeforel outlined will now be described with particular reference to Figures 1 4.

Movable shunt contact 26 is mounted to movable contact element 4o near the lower end thereof while movable arcing contact 24 is mounted near the upper end of element 4t).l Contact element 40 is pivotally mounted near arcing contact 24 to pivot 41 which is secured to bridge 27 near the free end thereof.

Compression spring 42 seated between clip 43 and con`` tact element 40 biases element 4i) clockwise about pivot 4i. Clip comprises a U-shaped member whose free ends are bent over pins 44, 45 to secure clip 43 to bridgel 27. Spring 42'sur'rounds rod 46 which is pivoted at one end 47 to contact element 4t) near shunt contact 26. The other end 43 of rod 46 is threaded and extends through an opening in the web of clip 43 to be engaged by knob 49 which establishes the point in the closing stroke of bridge 27 at which

shunt contacts

25, 26 are initially engaged. n p

An L-shaped latch member 50 is pivotally mounted at pin 51 to bridge 27. Oneend of latch member 50 is secured to one end of tension spring'52 whose other end is secured -to trip lever 53 near the pin 54 about which lever 53 is pivoted. Pin 54 is mounted to triangular extension 55 of bridge 27.

Spring 52 biases latch member 50 clockwise about lpin 5l to a latching position wherein latch tip 56 is operatively positioned to engage latch surface 57 of contact element 40. The cooperation of latch tip 56 and latch surface 57 prevents contact element 40 from being moved clockwise under the Vinlluence of spring 42 to the limit established by knob 49. Lever 53 yis also biased by spring 52 to a ylatching position or a position at which lever 53 does not prevent latch member 50 from assuming its latching position. One end 58 of trip lever 53 is engageable with Atrip `plate 59 at the end of the -bridge opening stroke (Figure 2). The engagement of lever end 58 with plate 59 moves trip lever 53 clockwise about pivot 54 against the influence of spring 52. Thls causes the other end 60 of lever 53 to engage latch member 50 and move it counter-clockwise to an unlatching pos1t1on thereby permitting movable shunt contact 26, under the urging of spring 42, to move to limit established by knob 49.

Beginning with the circuit breaker 20 in the fully closed position of Figure 1, the initial movement of bridge 27 on the clockwise opening stroke causes main contacts 2l, 22 ,to separate. During this movement of bridge 27, spring 42 moves element 40 clockwise since latch surface 57 is spaced from latch tip 56 so that during this

period shunt contacts

25, 26 remain in engagement. Also, during this period, spring 61, which is interposed between abutment 62 and nut 63, urges rod l64 to the right with respect tov Figure'l. Abutments 62 and 67 extend upward from the support member 99 for arcing contact 23. Since rod kv64 is pivotally connected at 65 to arcing contact member 34,y this member will be rotated clockwise about pivot 66, mounted to member 99, so that arcing

contacts

23, 24 remain engaged. At this point, it should be understood that even lthough contact 23 Vhas been referred toas a stationary contact it is actually a semi-stationary contact. v

Continued clockwise movement'ofY bridge 27 causes latch tip 56 4to engage latch surface 57 thereby preventing further clockwise movement of element 40. Thus, movable shunt contact 26 now moves together with bridge 27 and disengages stationary shunt contact 25. However, during this interval member 34 continues clockwise movement about pivot 66 so that arcing

contacts

23, 24 remain in engagement.

Arcing

contacts

23, 24 remain engaged until nut 63 engages abutment 67 through which rod 64 extends. Continued movement of bridge 27 then causes the separation of arcing

contacts

25, 26.

When the bridge 27 finally reaches the end of the opening stroke (Figure 2), lever end 58 engages trip plate 59 causing latch member 50 to' be moved to an unlatching position. Spring 42 then urges latch surface 57 past latch tip 56 so that movable arcing contact 26 is moved to the left to an extended position.

Since movable shunt contact 26 is now extended, the counter-clockwise closing stroke movement of bridge 27 first causes shunt

contacts

25, 26 to be brought into engagement. Arcing contact 23 is now in its extended position so that arcing contacts 23, `24 are next to engage. Finally at the end of the closing stroke main contacts v21, 22 are brought into engagement.

During the portion of the closing stroke after engagement of

shunt contacts

25, 26 element 43 is forced counterclockwise against the -force of spring 42. This causes latch surface 57 to move past latch tip 56 so that tip 56 may once Yagain assume a latching position in preparation for thesubsequent opening stroke.

Thus, this invention provides a novel circuit breaker construction whereby the blowout coils are mechanically inserted into theY circuit yet protected from high peak inrush currents. This is achieved by providing a pair of latchable shunt contacts in addition to the conventional arcing and main contacts. The operation of the contacts are differently sequenced on the opening and closing strokes of the circuit breaker that is, on closing the order of contact engagement is shunt contacts rst to engage, followed by the engagement of the arcing contacts, and lastly the engagement of the main contacts. On-

opening the main contacts are first to part, followed by the parting of the shunt contacts, and lastly the arcing contacts part.

Although we have here described preferred `embodiment :of our novel invention, many variations and'modi-v cations willnow be apparent to those skilled Yin the specific disclosure herein, but only by the appending claims.

We claim:

1. A circuit breaker comprising a first, a second, and a third pair of cooperating contacts; a first means operable between a first and a second position; one contact of each of said pairs of cooperating contacts being mounted to said first means; each of said pairs of cooperating contacts being operated into engagement by operation of said first means to said first position and being operated out of engagement by operation of said first means to said second position; upon operation of said first means from said first to said second position said first pair of contacts is first to disengage, followed by the disengagement of said second pair of contacts, and finally followed by the disengagement of said third pair of contacts; upon operation of said first means from said second to said first position said second pair of contacts is first to engage, followed by the engagement of said third pair of contacts, and finally followed by the engagement of said first pair of contacts.

2. A circuit breaker comprising a first, a second, and a third pair of cooperating contacts; a first means operable between a first and a second position; one contact of each of said pairs of cooperating contacts being mounted to said first means; each of said pairs of cooperating contacts being operated into engagement by operation of said first means to said first position and being operated out of engagement by operation of said first means to said second position; upon operation of said first means from said first to said second position said first pair of contacts is first to disengage, followed by the disengagement of said second pair of contacts, and finally followed by the disengagement of said third pair of contacts; upon operation of said first means from said second to said first position said second pair of contacts is first to engage, followed by the engagement of said third pair of contacts, and finally followed by the engagement of said first pair of contacts; said circuit breaker including an arc extinguishing means comp-rising an arc chute and a blowout coil operatively positioned to urge an electric current arc, initiated by the disengagement of said third set of contacts, deeply into said arc`A chute; said arc chute including a first and a second arc runner and a stack of spaced plates positioned between said arc runners; said blowout coil being electrically connected between the other contact of said second pair of contacts and said first runner.

3. A circuit breaker comprising a first, ia second, and a third pair of cooperating contacts; a first means operable between a first and a second position; one contact of each of said pairs of cooperating contacts being mounted to said first means; each of said pairs of cooperating contacts being operated into engagement by operation of said first means to said first position and being operated out of engagement by operation of said first means to said second position; upon operation of said first means from said first to said second position said first pair of contacts is first to disengage, followed by the disengagement of said second pair of contacts, and finally followed by the disengagement of said third pair of contacts; upon operation of said first means from said second to said first position said second pair of contacts is first to engage, followed by the engagement of said third pair of contacts, and finally followed by the engagement of said first pair of contacts; said circuit breaker including an arc extinguishing means comprising an arc chute and a blowout coil operatively positioned to urge an electric current arc, initiated by the disengagement of said third set of contacts, deeply into said arc chute; said arc chute including a first and a second arc runner and a stack of spaced plates positioned between said arc runners; said blowout coil being electrically connected between the other contact of said second pair of contacts and said first runner; the other contact of lsaid third pair of contacts being electrically connected to said first runner.

4. A circuit breaker comprising a first, a second, and a third pair of cooperating contacts; a first means operable between a first and a second position; one contact of each of said pairs of cooperating contacts being mounted to said first means; each of said pairs of cooperating contacts being operated into engagement by operation of said first means to said first position and being operated out of engagement by operation of said first means to said second position; upon operation of said first means from said first to said second position said first pair of contacts is first to disengage, followed by the disengagement of said second pair of contacts, and finally followed by the disengagement of said third pair of contacts; upon operation of said first means from said second to said first position said second pair of contacts is first to engage, followed by the engagement of said third pair of contacts, and finally followed by thel engagement of said first pair of contacts; said circuit breaker including an arc extinguishing means comprising an arc chute and a blowout coil operatively positioned to urge an electric current arc, initiated by the disengagement of said third set of contacts, deeply into said arc chute; said arc chute including a first and a second arc runner and a stack of spaced plates positioned between said arc runners; said blowout coil being electrically connected between the other contact of said second pair of contacts and said first runner; the other contact of said third pair of contacts being electrically connected to said first runner; a first biasing means urging said one contact of said second pair of contacts in a first direction toward engagement with its cooperating contact; a latch means carried by said first means and engageable with said one contact of said second pair of contacts after said first set of contacts are disengaged upon operation of said first means from said first to said second position; said latch means when engaged with said one contact of said second pair of contacts restraining this contact from movement in said first direction.

5. A circuit breaker comprising a first, a second, and a third pair of cooperating contacts; a first means operable between a first and a second position; one contact of each of said pairs of cooperating contacts being mounted to said first means; each of said pairs of cooperating contacts being operated into engagement by operation of said first means to said first position and being operated out of engagement by operation of said first means to said second position; upon operation of said first means from said first to said second position said first pair of contacts is first to disengage, followed by the disengagement of said second pair of contacts, and finally followed by the disengagement of said third pair of contacts; upon operation of said first means from said second to said first position said second pair of contacts is first to engage, followed by the engagement of said third pair of contacts, and finally followed by the engagement of said first pair of contacts; said circuit breaker including an are extinguishing means comprising an arc chute and a blowout coil operatively positioned to urge an electric current arc, initiated by the disengagement of said third set of contacts, deeply into said are chute; said arc chute including a first and a second arc runner and a stack of spaced plates positioned between said arc runners; said blowout coil being electrically connected between the other contact of said second pair of contacts and said first runner; the other contact of said third pair of contacts being electrically connected to said first runner; a first biasing means urging said one contact of said second pair of contacts in a first direction toward engagement With its cooperating contact; a latch means carried by said first means and engageable with said one contact of said second pair of contacts after said first set of contacts are disengaged upon operation of said first means fronrsaid first Ato said second position;"said latchfmeans when Vengagedk with said' one contact of said second pair of contacts restraining thiscontkact 'from movement in said first direction; said latch'meansengageable with said one contact of said second pair of contacts prior to the disengagement of said third pair of contacts as said first means is operated from said first tosaid second position.

6. A circuit breaker comprising a first, a second, and a third pair of cooperating contacts; a first means operable between a firstand a second position; one contac of each of said pairs of cooperating contacts being mounted to saidfirst means; each of saiddpairs' of col-l operating contacts being operated into Iengagement by operation of said first means to said first position and being operated out of engagement by operation of said first means to said secondposition; upon operation of said firstmeans fromsaid first to said second'position said first pair of contactsis first to disengage; followed1 by the disengagementof said' secondpair of contacts, and finally followed bythe disengagement ofnsaid third pair of contacts; upon operation of `said first means' from said second toV said first position said second pair of' contacts is firstto' engageLfollowed by the engagement of said` third pair ofk contacts, and finally followed by the engagement of said first pair of contacts; said'circuit breaker including an arc extinguishing means conrprising an arc chute and a blowout coil operatively positioned to urge an electric currentarc, initiated by the disengagement of said third set off/contacts; deeply into said arc chute; said arc chute includinga first and a second arc runner and a stack of spaced plates positioned between said arc runners; said blowout vcoil being electrically connected between theothe'r` Contact, of said second pair of contacts and said first runner; the other Contact of said third pair of contacts being electrically connected to said first runner; a first biasing means urgi ing said one contact of said second pair of contacts in a first direction toward engagement with its cooperating contact; a latch means carried by'said first means and engageable with said one contact of said secondpair of contacts after said first set'of contacts are disengaged uponoperation of said first means `from said first to said second position; said latch means when engaged with said one contact of said'second pair of contacts restrain-l ing this contact from movementk in said first direction; said latch means engageable with said one contact of said ysecond pair of contacts prior to the disengagement of said third pair of contacts as said first means lis op? erated from said first to said second position; trip means actuated when said first means is in Ysaid second position; said trip means when actuated operating said latch means to release said one contact of said second set of contacts thereby enabling this contact to be moved in said first direction through the action of said first biasing means.

7. A circuit lbreaker comprisinga first,l a second, and a third pair of cooperating contacts; a first means oper; able between a first and a second position; one contact of each of said pairs of 4cooperatingicontactsbeing mounted to said first means; each of said pairs of cooperatingy contacts being operated into engagement by loperation of said first means to -said first position and being operated out of engagement by operation of said first means to said second position; upon operation of saidl first means from said first to said second position said first pair of contacts is first to disengage, followed by the disengagement of said second pair of contacts,` and finally followed by the disengagement of said third pair of contacts; upon operation of said first means from said second to Asaid first position said second pair of contacts is first to engage, followed by the engagement of said third pair of contacts, and finally followed by the engagement of said first pair of contacts; said circuit breaker including an arcpextinguishing means comprising an arc chute and a blowout coil operatively positioned to urgean electric current arc, initiated by the disengagement of said third set of contacts, deeply into said arc chute; said arc chute including a first and a second arc rnnner and a stack of spaced plates positioned between said arc runners; said blowoutcoil being electrically connected between the other contact of said' second pair of contacts and said first runner; the other contact of said third pair of contacts beingelectrically connected to said first runner; a first biasing means urgingsaid one contact of said second pair of contacts in a first direction toward engagement with its cooperating contact; a latch means carried by said first means and engageable with said one contact ofsaid second pair of contacts after said first set of contacts are disengaged upon operation of said first means from said first to said rsecond position; said latch means when e11- gaged with said one contact of said second pair of contacts restraining this contact from movement in said first direction; said latch means engageable with said one contact of said second pair of contacts prior to the disengagement of saidthird pair of contactsras said first means is operated from said first to said second position; trip means actuated when said first means is in said second position; said trip means when actuated operating said latch means to release said one `contact of said second set of contacts thereby enabling this contact to'be moved in said first direction through the actionrof said first biasing means; a second biasing means urging the other contact of said third set of contacts ina second direction toward engagement with its cooperating contact.

References VCited in the file of this patent UNITED STATES PATENTS