US2550128A

US2550128A - Circuit breaker

Info

Publication number: US2550128A
Application number: US667759A
Authority: US
Inventors: William R Taliaferro
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1946-05-07
Filing date: 1946-05-07
Publication date: 1951-04-24
Anticipated expiration: 1968-04-24

Description

April 24, 1951 w. R. TALzAFx-:RRO 2,550,128

CIRCUIT BREAKER Patented Apr. 24, 1951 vzssonzs CIRCUIT BREAKER William R. Taliaferro, Pittsburgh, Pa., assign'or to Westinghouse Electr-'c Corporation, East Pittsburgh,- Pa.,

aY corporation of Pennsylvania Application May 7, 1946, serial No. 667,759

This invention relates to circuit breakers and, more particularly, to circuit breakers ofthe type that are tripped automatically in response to overload currents.

An object of the invention is to provide a circuitr breaker with an improved trip device having means for increasing the time .delay tripping in response to higher value overload currents; Y

Another object of the invention is to provide a circuit breaker with an improved trip device embodying a mechanicalY escapement time delay having means for limiting the rate of escapement in response` to higher value overload currents. Y

' Another object of the invention is to' provide a circuit breaker-With an improved time delay l trip device of the mechanical oscillator type emitself, however, bothk as tolstructure and operation, together' with additional objects and advantages" thereof, `will bef bestunderstood from the following detailed description of a preferred embodiment` thereof when read in conjunction With the accompanying drawings, in which:

Figure lis a vertical. sectional. view through the' center pole of a multipole circuitbreak'er elnbodying a trip device constructedV in accordance Withi the invention; y y

Fig. 2' isk an enlarged detail View showing the mechanical escapement timedelay device Fig. 3 is an enlarged front elevational` View showing the time delay trip'device Fig. 4 is a. vertical sectional` view takens'ubstantially on linev IVe-IV of Fig. 3; and looking in the direction of the arrows;

Fig. 5 a sectional View taken ony the line V--V of Fig.f3, and showing'th'e oscillator" de'- vice.Y

Referring togFig'. l f'the' drawings', thev circuit 'breaker is provided with an operating mechanism common to allV of the poles of the breaker; The operating mechanism is mounted in 'a ll'sh'aped frame l1 havin'g'sides which are rigidly connected by a: cro'Ss'- member' 191 The frame l1- is mounted: onv thefcentrall-portlon of f 20 Claims. (Cl.-200-108) a base ll of insulating material and is secured thereto by means of bolts 2| and 23. The outer ends of the frame are rigidly connected by a cross member 25'.

The bolt 23 extends through the base and the cross member I9 and serves to rigidly secure a connector 21 of conducting material to the cross member' I9 and to the frame. A shaft 29 eX- tending through an opening in thefconnectorv 21 and through openings in the sides of the frame l1 pivotally supports a pair of contact arms 3l having their free ends integral with a contact arm 30 for the center pole. The contact arms (not shown) for the outer polesV of the breaker are identical with the contact arm 30 for the center pole, butarenot provided with arms 3l. The lcontact arms are rigidly secured to a tie bar 61 which has an insulating cover 69 and extends across all of the poles and is securely clamped to the center pole contact arm 30' by means of a split clamp 10 and screw 1l.

y"The movable contact structures and the stationary structures for the several poles are alike; hence only the contacts for the center pole' are illustrated. The contact arm 30 pivotally carries a main movable contact member 41 and a movable ar'cin'g contact member 55 which cooperate respectively with a main stationary contact 39 and a stationaryarcing contact 31- The stationary contacts 39 and 31 are secured to a conductor 4IV which extends through an opening in the base Il and forms a terminal connector 45. Contact pressure for the main contacts is provided4 by a' spring 53 and a spring 63' provides contact pressureV for the arcingV contacts.

When thec'ontact' arm 30 is moved to open the contacts, the arcy drawn across the arch-ig contacts' 55-31 by rupture of the current is drawn into an arc' extinguisher indicated generally at 16V where it is cooled and extinguished.

The movable arcing contact member 55 is connected by a flexible shunt conductorv 11 to the main movable contact member 41, and another flexible shunt conductor 19 connects the contact' member 41 to the`A connector 21. A coni ductor 8| secured to the connector 21 by means of bolts 14, extends' downwardly therefrom rearwardly through the base to form the other terminal connector 83" which, together with the terminal connection 45, serves to connect the breakerin an electrical circuit.

The contactarme 3G are biased in a clockwise or opening direction by means-of a pair of springs 85" (only one being" shown). These springs' are' tensioned between the center pole contact arm 30 and a fixed pivot 81 supported in the main frame |1. In the closed position of the breaker, the center pole contact arm and consequently all of the contact arms are releasably restrained in the closed contact position by means of a toggle and linkage mechanism which is collapsible to cause opening of the contacts.

This collapsible linkage includes a yoke shaped lever B9 pivotally mounted on a fixed pivot 9| supported on the main frame |1. The lever 89 is operatively connected to the support arms 3| of the center pole contact arm 30 by a main operating toggle comprising

toggle links

93 and 95. The toggle link 93 has one end pivotedlon a pin supported on the lever 89, and the link 95 is pivoted on a pivot pin 99 in the arms 3|. The

links

93 and 95 are pivotally connected by a knee pivot pin 91. The toggle link 95 comprises a pair of links rigidly connected by means of an integral cross bar II5.

The free end of the lever 89 is pivotally connected by means of a link |03 to one arm of a lever |05 pivoted on the fixed pivot 81. The other end of the lever |05 is pivotally connected to a toggle link |01 of a tripping toggle comprising the link |01 and a toggle link |09. The link |09 is pivoted on a xed pivot |I3 supported on the frame I1 and comprises a pair of links joined near the pivot I |3 by an integral yoke |23. The link |01 comprises a pair of links connected by an integral yoke l I9 having a bent portion to which is secured an extension I2| of insulating material. The toggle links |01 and |09 are pivotally connected by a knee pivot pin III. The purpose of the extension |2| is to cooperate with a part connected to a manually operable handle IIII to manually trip the breaker.

The above-described linkage serves to releasably hold the movable contacts for all of the poles of the breaker in closed contact position. In the closed position, the main operating toggle 93-95 is over center above a line through the centers of the pins 99 and |0I, and a second toggle, one link of which comprises the overcenter links 93-95 and the other link of which comprises the lever 89, is over center above a line through the centers of the pins 99 and 9|. The overcenter movement of the main operating toggle 93--95 is limited by the projecting end of the link 93 engaging vthe cross bar I|5 of the link 95.

With the main operating toggle 93-95 and the toggle comprising the links 93-95 and the lever 89 in the overcenter position, the springs 85 bias the lever 89 in a clockwise direction. Clockwise movement of the lever 89, however, is normally prevented by the tripping toggle |01|09 which is over center to the left of a line through the center of the fixed pivot IIB and the point of connection of the link |01 with the lever |05. A spring |28 tensioned between the yoke |I9 and the fixed pivot II3 biases the tripping toggle to its overcenter position. The overcenter position of the tripping toggle I01| 09 is adjustably determined by the projection |25 of the yoke |23 engaging an adjusting screw |29.

The tripping toggle |01-l09 is adapted to be moved over center outwardly in a direction to cause its collapse to effect opening of the contacts by means of an overload trip device indicated generally at |33, or by a shunt trip device indicated generally at |38. The overload trip device |33 is operable in response to overload currents in the circuit of the breaker to actuate a trip rod |35 and cause collapse of the tripping toggle I01l09. The shunt trip device is adapted to be energized from any suitable source separate from the circuit of the breaker to actuate a tubular trip member |40 surrounding the trip rod |35 and cause the collapse of the tripping toggle |01-I 09 independently of the operation of the trip rod |35.

When operated by their respective trip devices |33 or |38, the trip rod |35 or the trip member |40 strikes the projection |21 of the yoke |23 and rocks the toggle link |09 clockwise about the fixed pivot I|3. This movement of the link |09 causes collapse of the tripping toggle I01-I09 permitting clockwise movement of the lever 89 which permits the springs 85 to actuate the movable contact structure clockwise to open the contacts.

The main operating toggle 93--95 does not immediately collapse, but the force of the springs applied through the contact arms 30--3| and the main operating toggle causes collapse of the toggle comprising the links 93-95 and the lever 89 which results in a clockwise movement of the lever 89.Y This movement is transmitted through the link |03 and the lever |05 to complete the collapse of the tripping toggle |01|09.

The clockwise or opening movement of the contact arms 30--3I is arrested by projections (not shown) thereon striking the frame I1. At this time, the rebound of the inertia of the main operating toggle 93-95 and the parts of the linkage 89, |03 and |05 starts the main operating toggle 93--95 over center in a direction to kcause its collapse. By the time the knee pin 91 of the toggle has passed over center below the line 99-I 0| the weight of the parts acts to complete the collapse of the toggle 93-95 and causes the linkage 89, |03, |05 andthe tripping toggle to be automatically reset to their normal holding positions. The main toggle 93-95 remains in collapsed condition until the contacts are closed.

The contacts are closed manually by clockwise rotation of the handle I4|- This movement of the handle, through connections not shown, thrusts a link I5| downwardly, and, due to the engagement of the link with a projection |53 on a yoke shaped closing lever |45, rotates the closing lever in a clockwise direction. The closing lever |45 comprises a pair of spaced levers disposed on the outside of the frame I1 and are pivotally supported on the fixed pivot 9 Clockwise movement of the closing lever |45 engages a roller |55 pivotally carried on the inner end of the lever with the toggle link 93 now in its collapsed position and moves the toggle 93-95 to its overcenter position. Since at this time the tripping toggle |01-I 09 has been restored to its overcenter holding position, rotation of the lever 89 is prevented, and consequently the force applied by the roller |55 to straighten the operating toggle 93-95 rotates the contact arms 30 counterclockwise to close the contacts and tension the springs 85.

The handle I4I is restored to its normal position by means of a spring |59 tensioned between the closing lever |45 and the frame I1. Upon release of the handle following a closing operation, the spring |59 moves the closing lever |45 counterclockwise and, through the projection |53 and link I5 I, restores the handle |4| to its normal position.

The circuit breaker may be tripped manually by rotation of the handle I4| through a small angle in a counterclockwise direction from its neutral position. Rotation of the handle I4I in tripping 4direction engages a. projection` (noti shown). on the link |5|v with: theextension |21 on'- the Yoke H9 of thetripping.. toggle link |01 and rocks the link counterclockwise about its point of connectionvviththe lever |41 and rocks the link countersc'lo'ckwis'e about its point of connection withthe lever |05.. This moves the tripping.V toggle |01- |09 over center in tripping direction: andA effects opening of the contacts` inthe previously described manner.

As previously set forth, the trip rod |35 is operated to eiect. collapse of the tripping toggle |01 |09 by means of the current-responsive trip device |33. There is a trip device |33 providedA for each pole of the breaker, but'. since the trip devices are alike only the one associated; with thev center pole will be described.

The-trip device |33 includes a U'-shap`e'd magnet core |61 and a U-shapedf frameVv comprising side platesv |63 rigidly connected by an integral cross member |65. The frame |63 isprovidedfwith inwardly formed feet |51, and' bolts |69" passing through openings in` the feet |61 and the core member |6| rigidly secure these parts to the base Il.. An armature |19 which cooperat'esswith the core member |6| is mounted in one end of a trip lever |13 pivotally mounted on a pivot pin |15 supported in the frame |63. The trip lever |13 comprises' a pair of levers rigidly connected at their right-hand ends` by an integral yoke I 11. The yoke |11 carriesa screw'l 8| which, upon operation of the trip lever |13, moves the trip rod |35 upwardly to effect trippingofthe breaker'in the manner previously set forth. The magnetcore |61- isf energized t'o attracty the armature |19 and operatethe trip lever |13 by overload currents flowing in the circuit of'tl-e breaker including the conductor 8| which, as' illustrated, passes between the legs of the U-sha'ped core I6 l. Normal rated current traversing the conductor 8| does not energizethe coremember |`6 Ii enough to overcome the tension of'a pair of biasing springs |9| (onlyone being shown) having one end attached to the yoke |11 and the other end attached to a movable adjusting member |93 threadedly engaged by an adjusting screw, the knurledl head |91 of which bears against the bottomvof' the cross member |65. Rotation of the screw moves the member |93 to adjust the tension of 'the'springsg thereby varying the minimum overloadtripping point of the breaker. The springs |9| normally bias the yoke |11 ofthe trip lever |13' against a stopy screw 284 whichdetermines the* open air gap of the magnet. *Y

A trip bar |81 isi rotatably mounted in arms |88 of a bracket |89 (.Fig; 3) secured to. ayushaped frame'- |51 of the shuntl trip device-|38?. The` frame'Y |51 which is of magnetic Inateralr is secured by means ofsc'rews |83'to flange-portions |95 integral with the mainframe |.1. TheVVA frame |51 is also secured to and spaced" from a front plate |99 by means of abar 20| and screws 2035, the front plate being securedV to an insulating bracket |43 suitably secured to the main frame l1. The trip-bar |81 extends across all of." the poles: of the breaker and is provided with a plurality 'of' arms |85 secured thereto" byV means` of screws 201; there beinganl arm: |8 5ioreach pole; only the one associated with the center" poler'is bifurcated and straddles the lower end ofthe trip rod |35 between flanges 205 secured to the trip rod, one above and. one below the arm |185; It can thus" be seen that operation. of the. trip bar. |181 by they trip device |33; for anyI-poleiof. the breaker also: operates. thecenterf pole. arm. |85

6 which. thrusts' the trip' rod upwardly vto" trip. the brealzer.4 Aspring 2.09 has one end hooked over a spring stud 2| carried by a lever 2I5 pivotally mounted onthe trip bar |81 and forming a part ofthe' timeK delay means, and the other end. of the spring is. anchoredy to` a spring stud 2|3 secured to thearm4 |85 for the' center pole of the breaker. "Ihespringv 289 thus biases the trip bar 81 and all of the arms 851 in a counterclockwise direction. to

1 theposition shown in Fig. 1, where a reduced portion of the stud 213 engages a shoulder 216 on the lever 2 l 5.

The lever 2| 5' is provided with an'arcuate rack 22.1 (Fig. 4) the teeth of which mesh with a pinion 229 rotatably mounted on a shaft 23 I supported in the two arms of the bracket 22|. The pinion 229 is rigidly connected by means of a sleeve 233 to an escapement wheel 235 also sup-e ported for rotation on the shaft 23|. The escapement wheel 235 is provided with teeth around a portion of itsperiphery and these teeth engage spaced` projections 231' onV an oscillator bar 239 whichis mountedy for oscillatory movementl on a shaft'24l supported in the spaced legs of the bracket 22|'. Two`

oscillator plates

243 and 245, disposed one on each side of the oscillator bar are pressed into frictional contact with. the sides of the oscillator bar near the ends thereof by means of Ysprings `M1 and 249, respectively. The

springs4

241 and 249 surround the shaft 24| and are compressed between collars 25| and 253, respectively, secured to the shaft 24|, and the corresponding'

oscillator plates

243 and 245.

When an' overload current of relatively low value, up to, for instance, 400% of normal rated current, occurs in the circuit through any pole of the. breaker, the armature |19 (Fig. 1) for that pole is attracted and applies a force tending to rotate the arm |85 and the trip bar 81 in a clock- Wise'direction. This force is applied throughthe strong spring 289', but without stretching the spring, to thelever 2|5` urging this leverr in a clockwise direction (Fig. 4) about its pivot. The lever2al5, through theY rack 221 and pinion 229 rotates the escapement wheel 235 in a counterclockwise directionsetting the oscillator 239 in motion, the rotation. of' the escapementf wheel 235" and the speed ofV operation ofthe trip device beingjretarded; by' they alternate engagement of the projections 231 of'the osci1lator'239 with the teeth of the escapem'ent wheel 235. The retarding action of. theescapement device will continue until the last tooth of the esc'apement wheel', indicated at 255 (Figs. 2 and 4) escapes the' lefthand projection 231 of the oscillator bar 239 (as viewedin Fig; 2), whereupon the armature |19 (Fig. 11) acts to quickly movev the trip rodA |35 upwardly to trip the breaker in the previously described. manner.

A relatively light spring 259 (Fig. 3) having one end. anchored to' a spring stud 26|' onV the arm' |85/for the center pole and the other end anchored. on a. spring stud 263 on the bracket |151/ is provided'. to bias the.- tripA barv |81V and the; lever: 2;|f5- c'ounterclockwise toy their. normal unoperated positions (Fig. 1) and to restore Athe trip bar and the mechanical escapement device to normal position following a time delay tripping operation. During the resetting operation the spring 259, acting through the arm |85 and pin 2|3, rotates the lever 2|5 counterclock- Wise to the position in which it is shown in Fig. 4. Counterclockwise movement of the lever` 2|5 and the rack 221 rotates the pinion 229 and the escapement wheel 235 in a clockwise direction to the normal position. The oscillator 239 imposes but little restraining action on the wheel 235 during the resetting movement due to the relatively light forces involved.

On higher value overload currents below the instantaneous tripping point of the breaker, the armature |19 is attracted with a much greater force and. operates the escapement device at much higher rate of speed with a consequent reduction in the amount of time delay. In certain instances, it is desirable to provide a greater amount of time delay in the intermediate range of overload currents, for instance, between 400% and 1000% of rated current. 'Io this end, the

oscillator plates

243 and 245 are provided vand are pressed into frictional engagement with the oscillator bar 239 by the

springs

241 and 249, respectively. In response to overload currents in the low range of overload currents, that is, up to approximately 400% of rated current, the oscillator bar 239 and the

oscillator plates

243 and 245 oscillate as a mass since the force involved is insuicient to cause relative movement between the bar 239 and the

plates

243, 245. In the intermediate range of overload currents, however, the force applied by the escapement Wheel 235 to the oscillator bar 239 causes the latter to oscillate rapidly. At a critical force the

oscillator plates

243 and 245 start to slide relative to the oscillator bar 239 thus introducing frictional losses which impose additional restraint on the escapement wheel and reduce the rate of oscillation. Since the plates 243-245 oscillate through a greater angle than the oscillator bar 239, the average mass of the oscillator assemblage oscillates through a greater angle than the bar 239 further reducing the rate of oscillation. This reduced rate of oscillation delays tripping of the breaker, in response to overload currents in the intermediate range, for a longer time than if the

plates

243 and 245 were not free to move relative to the oscillator bar 239.

The movement of the plates 243 'and 2454 relative to the oscillator bar 239 is limited by pins 256 mounted in the oscillator bar 239'and extending to each side thereof through arcuate slots 251 in the

plates

243 and 245. At or near the maximum degree of oscillation, the pins 256 engage the ends of the slots 251 thus limiting the relative movement of the

plates

243 and 245 and the bar 239 and imposing additional restraint on the bar.

It will be obvious that the

springs

241, 249 may be omitted and the increased time delay on overload currents in the intermediate range provided by permitting the pins 256 to drive the

plates

243, 245.

When an overload current of 1000% of rated current or over, or a short circuit occurs, the armature |19 actuates the trip bar with suiicient force to stretch the spring 209 and to operate the trip rod |35 to instantaneously trip the breaker.

The shunt trip device |38 comprises a solenoid having an energizing winding 260 and a movable core (not shown) which is secured to the tube |40. The winding 260 may be energized from any source by either a manually or automatically controlled switch (not shown). When the Winding 260 is energized, the movable core (not shown) is attracted upwardly moving the tube |40 therewith to engage and operate the tripping toggle |01| 09 and trip the breaker.

It will be understood by those skilled in the art that the operating characteristics of the trip device may be varied by changing the design of the electromagnet and also by vchanging the strength of the springs. The limits of the ranges of overload current values set forth above are to be considered merely by way of example, and these limits may be varied to suit particular requirements.

From the foregoing it will be apparent that the instant invention provides an improved time delay trip device having an improved time-current tripping curve on overload currents in the intermediate range without affecting the low overload time delay or the instantaneous trip'- ping.v

Having described the invention in accordance with the patent statutes, it is to be understood that various changes and modifications may be made in the structural details and combination of elements disclosed without departing from some of the essential features of the invention. It is, therefore, desired that the language of the appended claims'be given as reasonably broad interpretation as the prior art permits.

I claim as my invention:

l. In a circuit breaker comprising relatively movable contacts and operating means therefor, an electromagnetic trip device operable t0 cause automatic operation of said operating means comprising an energizing winding, an armature movable to cause tripping of the breaker, time delay means for retarding operation of said trip device in response to overload currents of predetermined value, and a member frictionally engaging said time delay device and movable relatively thereto in response to overload currents above said predetermined value to further retard operation of said trip device.

2. In a circuit breaker comprising relatively movable contacts and operating means therefor, a trip device comprising an eectromagnet having a movable armature operable to trip the breaker, a time delay device operatively related to said trip device for at times retarding operation of said armature, and a member biased into engagement with said time delay device and frictionally movable relative thereto when said trip device is operated in response to overload currents of predetermined value to increase the retarding action of said time delay device.

3. In a circuit breaker comprising relatively movable contacts and operating means therefor, a trip device comprising an electromagnet and an armature movable to trip the breaker, a time delay device comprising a mechanical escapement device for retarding tripping movement of said armature, and a mass frictionally engaging said mechanical escapement and operable in response to predetermined overload currents to increase the retarding action of said mechanical escapement.

4. In a circuit breaker comprising relatively movable contacts and operating means therefor, a trip device comprising an electromagnet and an armature movable to trip the breaker, a time delay -device ,comprising a mechanical escapement `device for -retarding tripping ,movement of said armature, ,and anlass `ifrictionally related to said `mechanical escapement and movable relative thereto in response to predetermined overload currents to increase the .retarding action oi said mechanical escapement, .said trip device being operable at times independently of Said time delay device to instantaneously trip `vthe breaker.

5,. In a circuit breaker comprising relatively movable contacts and operating mechanism therefor, a trip member operable t cause ,automatic operation of said .operating mechanism, tripr means operable in response to overload currents to operate said trip member, a time delay -device .comprising a mechanical-escapement mechanism .and an oscillator operable to yretard tripping operation of said trip member, and a member biased into frictional engagement with said .oscillator operable in responsefr to overload currents of predetermined value to reduce .the rate of oscillation of said oscillator.

6. In a circuit breaker comprising relatively movable contacts and Operating mechanism therefor, a trip member operable to cause automatic operation of said operating mechanism, an electromagnetic trip device operable in response to overload currents to operate said trip member, a time delay device including oscillating means operable to retard tripping operation ofsaid trip device, and a member engaging said oscillating means, for-at times automatically increasing the extent of the effective oscillation of said oscillating means to thereby increase the retarding action of said time relayfmeans.

7. In ,a circuit breaker comprising ,relatively movable contacts and operating mechanism therefor, a trip member operable kto cause automatic operation ofasaid operating mechanism, an electromagnetic trip device operable in response to overload currents to operate said trip member, a time delay device including oscillating means operable to retard tripping operation of said trip device, and a member cooperative with said oscillating means for at times automatically increasing the ext-ent of the effective oscillation of said oscillating means to thereby increase the retarding action of said time delay means'and said trip member being operable at .times independently of ,said time delay means .to vinstantaneously trip thek breaker.. Y

8. In a circuit breaker` comprising relatively movable contacts and .operating mechanism therefor, a trip device Operable to cause automatic operation of said operating mechanism, a time `delay device operable'to retard operation of said trip device, ycomprising an oscillator'having a predeterminedrate of oscillation in response to overload currents of predetermined value and a higher rate of oscillation in response to overload currents above said predetermined value, and a member engaging said oscillator for movement therewith in response to overload currents of said predetermined value and movable relative to said oscillator in response to overload currents above said predetermined value to automatically reduce the rate of oscillation of said oscillator to thereby increase the retarding action of said time delay device.

9. In a circuit breaker comprising relatively movable contacts and operating mechanism therefor, an electromagnetic trip device operable to cause automatic operation of said operating mechanism, time delay means` comprising an oscillator operable to retard tripping operation of said trip device, and means disposed in fric- 10 tional relation tcsaid oscillator and ,movable relative to said Oscillator in response to overload currents of .predetermined value to retard operation of said oscillator to thereby increase the retarding action of said time 4delay means.

11.0. In a circuit breaker comprising relatively movable contacts and operating mechanism therefor, an electromagnetictrip device operable to causegautomatic operation of said operating mechanism, time delay means comprising an oscillator operable to retard tripping operation'of said trip device, and a member disposed in frictional relation vto .said oscillator and movable relative to said oscillator in response to overload currents of predetermined value tov retard operation of said oscillator to thereby increase the retarding action of said time delay means,

1,1. In a circuit breaker comprising relatively movable contacts and operating mechanism therefor, .an electromagnetic trip device operable to cause automatic operation of said operating mechanism, time delay means comprising an oscillator operable to retard tripping operation of said trip device, and a plurality of members disposed in frictional relation to said oscillator and movable relative to said oscillator in response to overload currents 0f predetermined value to retardoperation of said oscillator to thereby increase the retarding action of said time delay mea-ris.V V y l `12. In a circuit breaker `comprising relatively movable contacts and operating rmechanism therefor, `an electromagnetic trip device operable to cause rautomatic `.operation of said operating mechanism, time delay means comprising an oscillator operable to retard tripping operation of saidv trip device .and means disposed in frictional relationeto said oscillator and movable relative to Vsaid oscillator in response to overload currents of predetermined value to retard operation of said oscillator to thereby increase the retarding action of said time delay means, and spring means providing frictional pressure between said meansand said oscillator.

V13. In a ,circuit breaker comprising relatively movable,A contacts vand operating mechanism therefor, :an electromagnetic trip device operable to causeautomatic operation of said operating mechanism, time delay means comprising an oscillator operable to retard tripping operation of said trip device, anda member disposed in f-rictional relation to said` oscillator andmovable relative to said oscillator in response to overload currents of predetermined value vto retard-operation of said Aoscillatorfto thereby increase the `retarding, action of "said, time ldela-y means, and spring means providingxfrictional pressure between-said member andsaidoscillator.

14. In a circuit breaker comprising relatively movable contacts and operating mechanism therefor, an electromagnetic trip device operablev to cause automatic operation of said operating mechanism, time delay means comprising an oscillator operable to retard tripping operation of said trip device, and a plurality of members disposed in frictional relation to said oscillator and movable relative to said oscillator in response to overload currents of predetermined value to retard operation of said oscillator to thereby increase the retarding action of said time delay means, and a plurality of springs providing frictional pressure between said members and said oscillator.

15. A circuit breaker comprising relatively movable contacts and operating means therefor,

attains a trip device operable to cause automatic operation of said operating mechanism, time delay means comprising a mechanical escapement having an oscillator operable to retard tripping operation of said trip device, a member disposed in frictional relation with said oscillator, said oscillator and said member oscillating as a unit in response to overload currents of predetermined value to retard tripping operation of said trip device at a predetermined rate, and said oscillator and said member oscillating relative to each other in response to overload currents above said predetermined value to reduce the rate of oscillation of said oscillator.

l 16. A circuit breaker comprising relatively movable contacts and operating means therefor, a trip device operable to cause automatic operation of said operating mechanism, time delay means comprising a mechanical escapement having an oscillator operable to retard tripping operation of said trip device, a member disposed in friotional relation with said oscillator, spring means providing frictional engagement between said oscillator and said member, said oscillator and said member oscillating as a unit in response to overload currents of predetermined value to retard tripping operation of said trip device at a predetermined rate, and said oscillator and said member oscillating relative to each other in response to overload currents above said predetermined value to reduce the rate of oscillation of said oscillator.

17. A circuit breaker comprising relatively movable contacts and operating means therefor, a trip device operable to cause automatic operation of said operating mechanism, time delay means comprising a mechanical escapement having an oscillator operable to retard tripping operation of said trip device, a member disposed in frictional relation with said oscillator, said oscillator and said member oscillating as a unit in response to overload currents of predetermined value to retard tripping operation of said trip device at a predetermined rate, and said oscillator and said member oscillating relative to each other in response to overload currents above said predetermined value to reduce the rate of oscillation of said oscillator, and means for limiting relative movement between said oscillator and said member.

18. A circuit breaker comprising relatively movable contacts and operating means therefor, a trip device operable to cause automatic operation of said operating mechanism, time delay means comprising a mechanical escapement having an oscillator operable to retard tripping operation of said trip device, a member disposed in frictional relation with said oscillator, spring means for pro- Number Name Date 1,301,991 Aichele Apr. 29, 1919 50 2,340,973 May et al Feb. 8, 1944 2,352,048 Wallace June 20, 1944 2,417,728 Baylis May 18, 1947 FOREIGN PATENTS 55 Number Country Date 289,728 Germany Jan. 19, 1916 522,303 Great Britain June 14, 1940 viding frictional engagement between said oscillator and said member, said oscillator and said member oscillating as a unit in response to overload currents of predetermined value to retard tripping operation of said trip device at a predetermined rate, said oscillator and said member oscillating relative to each other in response to overload currents above said predetermined value to reduce the rate of oscillation of said oscillator, and means for limiting relative movement between said oscillator and said member. y

19. In a circuit breaker comprising relatively movable contacts and operating mechanism therefor, a trip device operable to cause automatic operation of said operating mechanism, time delay means comprising a mechanical escapement mechanism including an oscillator operable to retard tripping operation of said trip device, a member disposed in frictional relation with said oscillator andmovable with said oscillator in response to overload currents to retard tripping operation of said trip device, said member at times being movable relative to said oscillator to increase the amount of time delay for a given value of overload current.

20. In a circuit breaker comprising relatively movable contacts and operating mechanism therefor, a trip device operable to cause automatic operation of said operating mechanism, time delay means comprising a mechanical escapement mechanism including an dscillator operable to retard tripping operation of said trip device, a member disposed in frictional relation with said oscillator and movable with said oscillator in response to overload currents to retard tripping operation of said trip device, said member at times being movable relative to said oscillator to increase the amount of time delay for a given value of overload current, and means for limiting the movement o! said member relative to said oscillator.

W R, TALIAFERRO.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS