US2318298A - Circuit breaker - Google Patents

Description

May 4 1943- H. D. DORFMAN ETAL 2,318,298

CIRCUIT BREAKER Filed June 24, 1941 2 Sheets-Sheet 1 May 4, 1943` H. D. DORFMAN ETAL. 2,318,298

CIRCUIT BREAKER Filed June 24, 1941 2 Sheets-Sheet 2 ventV vibration. or chatter Patented Mey 4, 1943 Freese Awestnignense meen-le a l'a., signers to Oom-- pany, East Pittsburgh Pa., a mondano Pennsylvania application June lr4, 1941, semi No. 399,456 v lzclaims.

invention relates te circuit breakers, and more particularly to circuit breakers of the type which are manually operable to open or to close One object of the invention is to provide a cir-- cuit breaker having improved means to cause .quick opening and closing of the contacts.

Another object of the invention is to provide a circuit breaker having improved means for causing the contacts to open a greater distance without increasing the size oi the operating mechanism.

Another object of the invention is to provide a circuit breaker with improved means to preof the contacts when they'are opened or closed.'

Another object of the invention is to provide a circuit breaker with improved means i'or applying contact pressure to the contacts when said contacts are closed:

Another object of the invention is the provision of a circuit breaker having improved circuit opening and closing characteristics, and which is simple in construction and inexpensive to manuiacture.

Another object of the invention is to provide 'a circuit breaker having a contact a'rm pivoted on af movable switch member and a toggle for.

operating the contact arm to cause a greater separation of the contacts than ir the contacts w'eremounted in the usual way on the switch member.

Another object of the invention is to provide a circuit breaker with means for increasing the contact pressure as the contacts start to open.

Another object of the invention is to provide a circuit breaker with novel vmeans whereby the pressure applied t the contacts increases as the contacts wear.

A further object of the invention' is to provide a circuit breaker with improved means to cause the contacts to open and close with a wiping'v tion, together with additional objects and ad-v vantages thereof, will be bestunderstood from the following detailed description of several em- .bodiments thereof when read in conjunction with the accompanying drawings, in which:

Figure iis a iront elevational view o! a three- 55 (ci. zoo-'61) pole circuit breaker embOdyina the principal ele*- ments of the invention. The .cover has been partly broken away to more clearly show some of the parts of the breaker. Fig. 2 is a vertical sectional view of the circuit breaker taken substantially on line lI-IIfoi.' Fig. 1 and looking in the direction of the arrows, the breaker. being shown in closed circuit position,

Fig. 3 is a vertical sectional view of the circuit breaker similar to Pig. 2, but showing the breaker in its tripped open position, Y l Pig. 4 is an enlarged detail view of a modi ilcation of the movable contact arm, said arm being shown in closed contact position by the full lines and in its iully open position by the dot and dash lines. Referring to F185.. 1 and 2 of the drawings. the circuit breaker includes a base Il of molded insulating material on which the several elements o! the breaker mechanism are mounted. A cover I2 also of molded insulating material is remov` ably secured to the base and cooperates therewith to form an enclosing housing for the parts oi thel circuit breaker.A Y 25' The circuit breaker is oi the multi-pole type, each pole comprising a pair oi' terminals I I and il, one mounted at each end of the base, a stak tionary contact Il, an arc extinguisher Il and a movable 'contact 2|.l A .common operating mechanism indicated generally at 22 is provided contacts 2|, and a three pole trip device. serves to effect automatic opening of the three movable contacts 2l in response to predetermined overload conditions in the circuit through any pole of the breaker. Each of the movable contacts 2| is mounted on a contact arm 2l pivotallyl supported intermediate its ends on a pivot pin 20 in the free endsoi* a pair of switch arms 21. The arms 21 aremounted on a rectangular tie bar 2l of insulating material and are joined by a rectangularsleeve Il surrounding the tie bar and secured thereto so that all of the arms 21 move as-a unit. A flexible shunt conductor Il connects the-contact arm 2l with an angular terminal 32 secured by a screw I3 to one end ot a conductor 35. The other end of the conductor I5 is connected by a nexible shunt conductor I1 to a point' near the iree end of s bimetal element Il, said bimetal element being rigidly secured on the inner end of a conductor Il. The terminal I5 is securedto the outer end or the conductor 4I. Each o! the stationary contacts l1 is mounted on the inner end for simultaneously actuating the three movable' I of a conductor 43 having its outer end connected to a corresponding terminal I3.

The electrical circuit for each of the poles is essentially the same and extends from the terminal I3 through the conductor 43, stationary contact I1, the movable contact 2|, the contact arm 25, the exible shunt conductor 39, the terminal 32, the conductor 35, the flexible shunt conductor 31, the bimetal element 39 and the conductor 4 I to the terminal I 5.

In order to prevent ilashovers between the poles of the breaker, barriers 42 (Figs. 1 and 2) are molded integral with the base II and extend the length of the breaker. When the cover I2 is in place, barriers 45 (Fig. 2) molded integral with said cover are in alignment with the barriers 42 and form separate compartments for the poles. The tie bar 29 is provided with annular projections 49 which t within recesses 50 in the barriers 42 to close the openings in the barriers through which the tie bar extends.

The operating mechanism for the breaker indicated generally at 22 (Fig. 2) is supported on a frame comprising a pair ofirame members 44 inserted in slots in the barriers 42 and suitably secured to the center part of the base I I. The operating mechanism includes a forked operating lever 41, toggle links 49 and 5|,- a pair of overcenter springs 53 and a. releasable cradle 55 controlled by the trip device 23. The springs 53 mounted on the outer end of operating lever 41.v

A manual operating handle 63 integral with the shield 59 projects through the opening 6I to permit manual operation of the breaker mechanism.

The toggle links 49 and 5I are pivotally connected by a knee pin 65. The link I is pivotally connected by a pivot pin 6T to the arms 21 which carry the contact arm for: the center pole and the link 49 is bifurcated at its outer end and pivotally engages a pin 89 on. the cradle 55 beingv retained in engagementl therewith by the overcenter springs 53 tensioned between the knee pin 55 and the outer:` portion. of the operating lever 41. The overcenter movementv of the toggle A 49--5I is limited by Stud 5E. on the link' 5| just below the knee pin 55 striking a projecin'onz'` on the cradle 55. This projection 58 also acts to positively start the toggle iny a directiony to cause collapse thereofv when the breaker is tripped automatically` in response to an, overload as will be described later.`

The arms 2T which pivotally carry the contact arms 25 for all three poles'r are mounted on the insulating tie bar 29 so thatl the contacts for all poles are operated simultaneously, and yet: each pole is insulated from the other poles- An axially disposed metal shaftv 1I extends through the tie` bar 29 and rotatably supports the tie bar in bracketsv 13 suitably' secured tn thebase II of the breaker.

' overcenter springs Vll are associated with the contact arms 25. These; springs surround contact arm. operating members 19 and are compressed between angular brackets ll secured to the pivoted ends of the switch arms 21' and shoulders 83 on the members 19. The springs 11 The cradle 55 is f hold the ends of the members 19 in engagement with recesses 85 in the inner ends of the contact arms 25. The brackets 8| serve to support and guide the members 19, the members 19 extending through enlarged guide openings in the brackets 8|. Each contactarm 25 and its cooperating toggle member 19 forms a snap action toggle which, in the closed circuit position, is overcenter in adirection which permits the spring 11 to apply pressure to the contacts.

As previously stated, the trip device 23 includes a bimetal 39 connected in series in the circuit for each pole of the breaker. The trip device also includes a trip bar 81 of molded insulating material pivotally supported in bearings in the side walls of the breaker base.

Each pole of the breaker is provided with a latch lever 93 pivotally supported on a U-shaped frame 95 by a pivot pin 91, the frame 95 being mounted on the base ll. A spring |05 compressed between a bar |91, supported between the legs of the frame, and the latch lever 93, biases said lever in a clockwise direction. Clockwise rotation of the latch lever'- 93 is normally prevented by engagement of its latch end with a latch |09* on the free end of the bimetal 39.

A latch member III secured to projections ||3 molded integral with the trip bar 81 normally engages the latch end of. the cradle 55 and thereby restrains the cradle 55 in its operative position.

When any one of the bimetal elements 39 is heated a predetermined. amount in response to an overload current, it exes in a direction to unlatch its corresponding lever 93 whereupon the spring |05 rocks the lever 93 in a clockwise direction. During this movement the end of the lever l93 strikes a projection II5 on the trip bar and rocks said trip bar counterclockwise causing the latch member to release the cradle 55. This permits the overcenter.`r springs 53 to actuate the operating mechanism. and open the contacts as will be more fully described later.

'The trip device is also operated magnetically to instantaneously trip the breaker on the occurrence of a heavy overload. for instance, 1000% or more of rated 4current or on short circuits in. the circuit of any one ofthe poles.

.For this purpose each pole of the breaker is provided with an electromagnety indicated generally at 86 and which includes a U-shaped stationary core I1 through which extends the conductor 35, the conductor being suitably insulated from the magnet corev II1. The electromagnet is` also provided with a hinged armature |23 havinga projecting arm I 24 which is adapted to engage a projection |4| on the. trip bar 81 and rock said bar and the latch member III counterclockwise to trip the breaker when the electromagnet` is energized by heavy overload or short circuit current flowing through the conductor 35. 'I'he armature |23 is biased` to unattracted position by a spring |35.

A leaf spring |43 (Fig. 2) disposed in a recess in one of the barriers 42 is tensioned against a flat surface of the trip bar 81 to bias the trip bar to neutral position andk to prevent accidental tripping of the breaker due to jars or shocks.

The circuit breaker mechanismV is shown in Fig. 2 in the closed circuit position. When the tripy bar 91 is-rocked in4 unlatching direction in response to an overload. current in the circuit of any one of the poles., the latch III disentritgesv the cradle 55 and permits the springs 52 to rotate the cradle ina clockwise direction about its pivot 55. At the start of this rotation of the cradle 55, the projection 55 engages the stud 55 on the toggle link and starts the toggle 49-5l in-the direction to cause it to collapse. .Continued movement of the cradle 55 carries the center line of the toggle'link 45 to the rightof the line o f action of the springs 53 which then act to complete the collapse of the toggle. This -rocks the arms 21 and the tie bar 25 counterclockwise carrying the contact arms 25 therewithv to open circuit position.

In the clod circuit position (Fig. 2) the line of action of the spring 11 is above the pivot 25 of the contact Yarm 25 and biases the contact arm 25 in a clockwise direction about its pivot 25 to provide contact pressure. When the arms 21 are rocked counterclockwise, as above described, a tail |45 on the member 15 strikes a projection |41 molded integral with the base causing the member 19 to rock clockwise pivoting at its point of contact with the bracket 5| and rocking the contact arm 25 counterclockwise about its pivot 25 on the arms 21. 'Ihis movement of the contact arm 25 is limited by a projection on said arm striking a pin |49 in the arms 21. The breaker is shown in its tripped open position in Fig. 3.

The result of the pivoted contact arm construcvtion and'of the action of the overcenter spring 11 is to eilect a greater contact separation when the breaker is opened, and also a higher speed of operation of 'the contacts in both opening and` closing. decreases the possibility of restriking of the arc, and also eliminates re-arcing due to vibration of the contact arm since the action -oi the contact toggle opposes rebound of the moving contact.

It-may be stated here that the greater separation of the contacts resulting from the action of the toggle 15-25 makes possible the use of` circuit breakers of the type disclosed in circuits carrying substantially higher value currents than l has heretofore been possible with the required degree of safety. This-resultsl in considerableV economy of manufacture, since the same base and operating mechanism may be utilized for breakers having low capacity rating and high capacity rating by substituting the contact arm of the invention for the prior art contact arm where the movable contact is mounted directly on the switch arm. Y

Another important advantage of the present invention is that, due to the pivoted contact arm construction, a. greater pressure is applied to the contacts and a wiping action between the contacts is effected as the contacts start to open. As the switch arm 21 starts to move the contact arm pivot 25 away from the bese Ii, the spring 11 rocks the. contact arm 25 clockwise about its pivot maintaining the'tip of the'contact `2| in engagement-with the stationary contact |1. At the same time the clockwise rotation of the contact arm 25 moves the line of action of the spring anV additional distance above the pivot 25, thus increasing the pressure` applied by the spring 11 to the contact and causes the tip of .the contact 2| to wipe along the face .of thel stationary con-V tact |1 during the initial opening movement.

In ordinary circuit breakers when the contacts wear, the result is a decrease in the pressure applied to the contacts due to the lengthening of the contact springs. Another important feature' cation of increased contact pressure as the contacts wear. Referring to Fig. 2, it is obvious that as the faces of the contacts l1 and 2| wear, the contact arm 25 is permitted to rock farther in a clockwise direction about its pivot 25 which moves the line of action of the spring 11 farther above the pivot 25 permitting the spring to apply increased pressure on the contacts.

Following each automatic opening of the breaker due to an operation of the trip device, it is necessary to reset the mechanism to an operative condition before the circuit breaker can be reclosed. To reset the mechanism the lever 41 is rotated from the position in which it appears in Fig. 3 to its extreme counterclockwise or open position. Movement of the lever 41 is transmitted to the cradle 55 by means of a hook projection I 5| which engages a portion |52 ofthe cradle 55 and rocks the cradle counterclockwise therewith.` As the cradle 55 is rotated, the latching end thereof passes the latch member and engages a projection |55 on the trip bar 51 rocking said trip bar clockwise slightly past normal position. At

this rotation of the trip bar the projection ,l I5

thereon rocks the. latch lever 93 counterclockwise compressing the spring |55 and 4reengaging the lever 53 with the latch |55. 'I'he latch member now has assumed its normal latching position in the path of the cradle 55.

' After the cradle 55 has been rentened, the con-y tacts may be closed manually by movin'g the handle 53 clockwise to its closed circuit position.

-During this movement of the handle, the line of sition, the arm 25 strikes a projection |51 on the` base at a point to the left of thepivot 25 (Fig. 2), causing clockwise rotation of the arm 25 about its pivot 25 and moving the line of action of the spring 1'| overcenter above the pivot 25. The effect of this action is to cause a very quick snap action to close the contacts and to provide a more stable contact pressure which prevents bouncing or chattering of the contacts upon closure.

In order to open the contacts manually, the operating lever 41 is moved counterclock-wise about its pivot. This movement carries the line of action of the springs 53 to the left of the pivot axis 59 of the toggle link 45 and the-force exerted by the vsprings 53 now biases the toggle -5I away from its overcenter position.l Before the lever-.541 reaches its extreme counterclockwise orl j")pen position, this force becomes sui'liciently great to cause the toggle to collapse.

Since thetoggle link 5| is pivotally connected to the switch, 'arms-21 for the center pole, the arms 21 for vv,all 'of the poles are rotated in a counterclockwise direction, causing simultaneous opening of the contacts for all of the poles of the breaker. The contacts are closed manually in the previously described manner.

The circuit breaker is entirely trip free. that is. it operates automatically in response to an overload to open the contacts regardless of the position of the operating lever 41.

The arc extinguishers i9, there being one provided for each pele of the breaker, are of the .spaced plate type, and comprise, generally.. a

of the instant invention is the automatic appli'- 75.

stack of slotted'plates of magnetic material positioned adjacent the paths of movement of theV contacts 2|. s The presence of these plates causes the arc resulting from the rupture of the circuit to be drawn in the direction toward the ends of the slots which results in the breaking up of the arc into a plurality of short arcs and causes said arcs to be cooled and extinguished.

Fig. 4 illustrates a modified form of the contact arm 25. In this gure, the parts are shown in closed circuit position by the full lines and in open position by the dot and dash lines. The contact arm is provided with a hook projection |59 which, in the closed contact position, projects into an opening |6| in a plate |63 secured to the base of the breaker. When the breaker is opened either automatically or manually and the arms 21 rock counterclockwise, the projection |59- engages the upper edge of the opening |6| causing the contact arm 25 to rock counterclockwise about its pivot 26. When this occurs, a spring |65 compressed between the bracket 8| and a shoulder on va rod |61 pivotally connected to the contact arm25 by a pivot pin |69, is moved below the center line 26`|69 and acts to complete the counterclockwise movement of the contact arm 25 about the pivot 26. The projection |59 moves free of the opening |6| permitting the arms 21 to carry the contact arm 25 to fully open position as indicated by dot and dash lines (Fig. 4).

When the switch arms 21 are rocked to close the contacts, as above described, the toggle formed by the rod |61 and the contact arm 25 remains in the position indicated by dot and dash lines (Fig. 4) until the contact arm strikes the top of the plate |63 which thereupon causes clock-- wise rotation of the contact arm. 25 about its pivot 26. At this movement, the projection |59 reenters the opening |6| and the line of action of the spring |65 moves above the center line 26-| 69 causing the contacts to close with a snap action. In the closed position, thev spring |65 applies pressure to the contacts |1-2|.

The operation and advantages of this modiilcation of the contact arm construction are the same as described in connection with the original embodiment. The construction of this modification provides greater contact separation, higher speed operation of the contacts, wiping action of the contacts, increased contact pressure during the initial opening movement and also -when the contacts wear down, and prevents vibration or oscillation of the moving contacts, the same as in the original embodiment.

The, remaining structure of the circuit breaker and its operation is the same as shown and described. in connection with' the original embodiment.

Certain features of the circuit breaker and trip device construction illustrated and described in this application are disclosed and claimed in our copending application for Circuit breaker, Serial No. 399,457, led June 24, 1941, and assigned to the assignee of the present invention.

Having described several embodiments of the invention in accordance with the patent statutes, it is to bel understood that various changes and mcdications may be made in the structural details disclosed withoutv departing -from some of the essential features of the invention. It is, therefore, desired that the invention. be intelpreted as broadly as the prior art permits, and that it be limited only by what is expressly stated in the following claims.

We claim as our invention:

1. In a. circuit breaker, the combination" of relatively movableeontacts'including a stationary contact and a movable contact, a switch arm movable to open and close the contacts, actuating means for moving said switcharm, a contact arm pivotally mounted on the switch arm, said movable contact being mounted on said contact arm, means cooperating with said contact arm to form a toggle disposed for movement with the switchv arm, and means engageable by said toggle when the switch arm is moved to open the contacts to cause said toggle to move the contact arm about its pivot in an opening direction.

2. A circuit breaker comprising a stationary contact, a movable contact, a switch arm movable to open and close the contacts, actuating means for moving the switch arm, a contact arm pivotally mounted on the switch arm, a toggle link cooperating with the contact arm to form a toggle disposed for movement with the switch arm, and a xed member engageable bythe toggle when the switch arm isi moved to open and to closed positions to cause the toggle to move the contact arm about its pivot to open and close the contacts with a snap action.

3. In a circuit breaker, the combination of relatively movable contacts including a stationary contact and a movable contact, a pvoted switch arm movable to open and close the contacts, a contact arm pivotally mounted on said switch arm, the movable contact being secured on said contact arm, actuating means for movingr the switch arm, a spring actuated member cooperating with the contact arm to form a toggle mounted for movement with the switch arm, means engageable by said toggle when the switch arm is moved tov open position toy cause said toggle to move the contact arm about its pivot in an opening direction, and engageable by the toggle when the switch arm is moved to .close the contacts to cause said toggle to move the contact arm about its pivot in a. closingV direction with a snap action.

4. A circuit breaker comprising relatively movable contacts, a movable switch amr, av contact arm pivotally mounted on said switch arm, said contact arm having one of said contacts mounted thereon, operating mechanism for moving the switch arm to open and closed positions,y means cooperating with thev contact arm to form` a toggle for moving the. contactarm; about its pivot, said vtoggle being movable the switch army and means engageable by the: toggle for causing said toggle to move the. contact ann. about its pivot to open and', closed; positions whenv the switch arm is moved to open and closed positions.

5. A circuit breaker comprising a stationary contact and aV movable contact, a switcharm movable to cause openingv and closing of the contacts, operating mechanism for moving the switch arm to open and closed positions, a contact arm pivotally mounted. on the switch arm. and having said movable contact mounted thereon, means cooperating with said contact arm to form a toggle movable with the. switch arm for rotating the contact arm, means engageable by said toggle when the switch. arm. is moved to open position for moving the contact arm about its pivot in a direction away from the stationary contact, and other means engageable by the toggle when the switch arm. approaches closed position for moving the contact ann about its pvot in a direction towards the stationary concontact, a pivotally mounted switch arm, a contact member pivotally supported on said switch arm and adapted to cooperate with the stationary contact, actuating means for rotating the switch arm about its pivot to open and close the contacts, a toggle member cooperating with the contact member to form a toggle, and means engageable by said toggle when the switch arm is rotated to open the contacts to move said toggle overcenter in a direction to cause movement of the contact member about its pivot in an opening direction. i

'1. In a circuit breaker, the combination oi' a stationary contact and a movable contact, a switch arm movable to open position and to closed position, actuating means for moving the switch arm to open and close the contacts, said contacts forming the sole means for interrupting the circuit, a contact arm pivotally mounted on the switch arm, a spring actuated toggle link cooperatingwith the contact arm to form a toggle, said toggle being disposed for movement with the switch arm, and means comprising an insulating member engageable by the toggle when the switch arm is moved to closed position to cause the tog- 81e to move overcenter in 'a direction to close the contacts with a snap action, said toggle acting to apply pressure to the contacts when they arev closed.

8. In a circuit breaker, the combination of a stationary contact and a movable conta-ct. a switch arm movable to open and closed positions, a contact arm pivotally supported on theswitch arm, actuating means for moving the switch armto open and close the contacts,` a spring actuated member cooperating with the contact arm to form a toggle movable with-the switch arm, and means iirst part of the opening movement of the switch arm for moving the toggle overcenter in a direc tion to cause movement of the contact arm about its pivot in an opening direction with a snap action, said means beingengageable by the toggle when the switch arm approaches closed position for moving the toggleovercenter in a direction to cause the contacts to close with a snap action.

9. In a 'circuit breaker, the combination of relativelymovable contacts, a switch armmovable to open and closed positions, a contact arm pivotally mounted on the switch arm, actuating means including a toggle for moving the switch arm to open and close the contacts, an overcenter engageable by the toggle during the spring operatively associated with the contact arm for actuating said contact arm about its pivot and a fixed member engageable by said contact arm upon movement of the switch arm to open and closed positions to initiate movement of the contact arm about its pivot in opening and closing directions respectively.

10. In a circuit breaker, `the combination of relatively movable contacts, a pivoted switch member movable to open and closed positions, a contact arm pivotally supported on the switch member, actuating means for moving the switch member to open and close the contacts, and means cooperating with the contact arm to form a toggle, said toggle being engageable with a ilxed member upon movement oi! the switch member to open and closed positions t0 actuate the contact arm about its pivot in opening and closing directions.- l

11. In a lcircuit breaker, the combination of relatively movable contacts, aswitch member movable to open and close the contacts, a contact arm pivotally supported on the switch member, actuating means for the switch member, and a spring biased toggle link movable with the switch member and cooperating with the contact arm to form a toggle, said toggle during the first part of the opening movement of the switch member being eifective to apply increased pressure to said contacts, and ixed means engageable by said toggle at a predetermined point in the opening movement oi' the switch member to initiate actuation oi.' said contact arm about its pivot in opening direction.

l2. A circuit breaker comprising a stationary contact, a pivoted switch member movable to open and to closed circuit position, a contact arm pivotally mounted on the free end of said switch member for cooperating with said stationary contact, means comprising a compression spring associated with. said contact arm and said switch member for actuating said contact arm about its pivot, a guide link for supporting said spring pivotally engaged at one end 4with one end of said contact arm, a guide mounted on said switch member adjacent the pivoted endv thereof for slidably supporting the other end of'said guide link, said spring being disposed between said guide and a shoulder on said link.

Hmm?, D. DORFMAN. GERALD J. FREESE.

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