US3105131A

US3105131A - Electric circuit breakers

Info

Publication number: US3105131A
Application number: US33827A
Authority: US
Inventors: Coleman Edward
Original assignee: JA Crabtree and Co Ltd
Current assignee: JA Crabtree and Co Ltd
Priority date: 1959-06-16
Filing date: 1960-06-03
Publication date: 1963-09-24
Anticipated expiration: 1980-09-24
Also published as: GB905639A; DE1141365B; CH384686A

Description

3 Sheets-Sheet?, 1

Filed June 5. 1960 sept. 24, 1963 E. @LEMAN 3,105,131

4ELECTRIC CIRCUIT BREAKERS Filed June 5, 1960 3 Sheets-Sheet 2 ttorney Sept 24 19.63 E. COLEMAN 3,105,131

ELECTRIC CIRCUIT BREAKERS Filed June I5., 1960 3 Sheets-Sheet 3 Z In vanto: l MEM Attorney 3,105,131 ELECTRIC CIRCUIT BREAKERS 'Ihis invention relates to so-called miniature or moulded case circuit breakers of the kind in which the contacts are disengaged on short circuit or overload conditions by thermally or magnetically tripped mechanism, and in which the casing comprises a pair of flat members between which the contacts and mechanism are housed, such mechanism being automatically re-set, that is prepared after a tripping operation, to be manually actuated to the on position by a handle or dolly.

In order to prevent overheating of the contacts of such circuit breakers it is desirable to provide a high pressure engagement between them while the force required for performing tripping should be relatively low. In known constructions the main `spring for imparting the contact force also imposes a pressure on the latch engagement of the trip mechanism. Hence any increase in the force of this spring for increasing the contact pressure, renders it necessary undesirably to increase the energy required for effecting release of such latch. Por the purpose of minimising this disadvantage lever means may be introduced between the contact arm and the latch so that the force required for releasing the latter may be reduced.

Such arrangements however involve a reduction in the operating lspeed of the trip mechanism due to the increased inertia caused by the introduction of the lever means between the latch and the contact arm.

The principal object of the present invention is to avoid the disadvantages referred to and to provide an improved circuit breaker .of simple and compact construction which can be economically produced while possessing eicient electrical characteristics.

According to this invention the latch or trip force is independent of the main spring. Thelatter may act on a contact arm connected to one end of a toggle, the other end of which is actuated by a handle for manually operating the circuit breaker to the on and off positions. On the occurrence of a short circuit or overload, the toggleis broken by a trip lever which is independent of the main springand contact arm.

This trip lever may have releasable latching engagement with a catch plate operated by the overload mechanism.

Y Thus the armature of an electromagnet may be adapted for l imparting an impact or impacts on the catch plate in order to release the latch and enable the spring-stressed trip lever to break the toggle. The tripping energy of the overload mechanism is requisite only for overcoming the latching force imposed by the spring acting on this lever and is independent of the force of the main spring which may be relatively high in order to ensure an effective contact pressure. The spring force acting on the trip lever may be relatively low however so that the small amount of energy available for overcoming the latching force is adequate for consistent and reliable operation.

The catch plate acts as an intermediate member betweenthe armature and the trip lever for the purpose of releasing the spring-loaded trip lever. Thus the latchingv force is constant and dependent only on the strength of the .trip spring and is independent of the contact pressure,

in order to achieve the advantages of an effective contact force while necessitating only a low trippingenergy.

According to a further feature of the inventiona pair of high reluctance paths are provided in the magnetic circuit of a circuit breaker in which the contacts are disengaged on short circuit or overload conditions by magnetically tripped mechanism incorporating a hydraulic time delay and comprising a hermetically sealed tube containing a spring and a plunger operating in a fluid such as silicone. One of the high reluctance paths provides a flux for operating an armature on overload conditions and the other for causing its operation on short circuits as hereinafter described.

The one-piece armature floatably located on the magnet frame is adapted to pivot freely against the action of an adjustable spring so as to impinge on a catch plate for releasing the latched engagement of the latter with the trip lever. The catch plate may be pivotally mounted midway of its length, one end being pressed by a spring into latched engagement at its other end with the pivotally mounted trip lever. The latter may be a three-armed construction, one arm being engageable with a toggle connected between an operating dolly and the contact arm, `a second arm having latchable engagement with the catch plate and a third arm pivotally mounted in the casing of the circuit breaker.

In order to enable the invention to be readily understood reference will now be made to the accompanyingdrawings illustrating by way of example one construction of electromagnetically tripped circuit breaker, for carrying the invention into eect, in which drawings:

FIGURE 1 is a sectional elevation with the parts in the ofi position.

FIGURE 2 is a similar view URE l showing the parts in the on position.

FIGURE 3 is a section on the line III-III of FIG- URE 1.

FIGURES 4 and 5 are side elevations of the fiat moulded casing members. v

Referring to the drawings a casing comprising a pair of flat mouldings 1, 2, ribbed and recessed for receiving the parts and components between them, has a lever or dolly 3 for operating the switch mechanism. On overload the latter is tripped by an electromagnetic device incorporating a hydraulic time delay and comprising a hermetically sealed non-ferrous tube 4I, containing a spring 7 and a ferrous plunger 6 operating in a fluid such as silicone. The tube 4, formed with an integral closed end 4, has a short counterbore 4b at its' open end.'

After introduction of the spring 7 plunger 6, and fluid, a closure disc 8 is seated on the annular flange formed by the counterbore, the tube is peened over, and the opening is flooded with solder 10. The helical compression spring 7 acts on a shoulder 6a of the plunger so that the parts normally occupy the position shown in FIGURE 1.

The tube 4 is disposed within an insulating sleeve 11 which has a short length of reduced thickness to form an internal shoulder l1a on which is seated a short ferrous sleeve or magnetic shield 12 encircling the forward end of the tube 4. The insulating sleeve 11 is formed with an annularflange 11X on which is seated the rectangular member 13 of an L-shaped magnet frame or bracket. This member is apertured to enable it to be passed over the iron sleeve 12 `and. the other lateral member 13a of the frame, is provided near the bend of the L with a'v headed pin 14 on which is loosely pivoted one end of a strip-shaped armature 15, disposed substantially parallel to the arm 13a. Between this pin 14 and its end the arm 13a is formed with a hole 13X of such dimensions as to leave only :a narrow width of metal on each side of A the hole. The reduction in area -on each side of this hole produces high reluctance flux paths.

The rear end of the tube 4 is seated in a shallow cirof the upper part of FIG-i between the armature and the end 18a of the pole piece. A coil 16, disposed varound the insulating sleeve or former4 11,V has` one tailY end lcconnected by brazing or welding to a terminal 16a extending through an Yopening in the lower wall Vof the casing and the other tail 16d, similarly connectedV to one end of a short length Y13a is a short air gap 13b. VA gap 15b is also present of ilexible braid 16h, the other end of which is Welded v to a moving contact yarm 17. rShield 12atfords the use of a longer length of coil by which the ampere-turns may be increased without undesirable reduction in the cross- Asection of the wire. This construction reduces ythe watt Y a pin 14 and is retained by the head of the latter. The

other end of the armature is bent and is of reduced width to form Va Vshoulder 15aV against which bears a helicalV compressionadjusting yspring 19. The improvedV arrangement',iwhich'can be simply and economically produced,`

facilitates operation of the` larmature by virtue of its floating location on the rivet 14 which avoids the employment of a. bearing involving friction.

The narrow end of the armature 15 Yextends freely through a rectangular opening a formed in the bent end of a one-piece catch plate 20 to whichis secured, midway of itslength, a pin 21 the ends of which enter holes in the casing parts to permit pivoting of the plate. The pin, 21 is inserted between small semi-circular formations bent outwardly from the plate. v t

, The catch plate 20 adjacent the rectangular aperture 20a, is formed with an ear 20h for latching engagement with the end of oneagrmiZia Vof a three-armed trip'lever 24, pivotally mounted on a pin 25 projecting, through a hole in the end ofa' second arm 24h, into recesses in the casing parts, and the third arm 2401s formed as a Y pair ofjaws 24d, 24e.' The jaw VZ4@ isV adapted for irnpingement on the cen-tre pin 26 of a toggle, comprising the levers V27, 28, and connected betweenthe moving con- Y Vtact arm 17 andthe .actuating lever or dolly 3. The three#A Y armed lever 24 is made from a iiat pressing which si-m` plies'production and enables its different eifectivepoints fto be accurately located relatively to one another. A

nose 2.4f between the arms 24a, 24b of the lever 24 locates a compression spring 31,Y operative between the casing andthe lever forr urging it to turn in an anti-clockwise direction about jitspivot 25. Since this effectively operating lever, which ensures accurate tripping, has no bends, itfeanjbe' economically made from a fiat blank.-

V The moving contact arm- 17 is provided with the contact tip- 29 at its upper end, and rhas a transverse pin 32 extending through ahole at its'lower end. yThe endsl ofV f this pin enter shortY horizontal slots 33 yformed in internal bosses 34 on the casing parts. A'compression spring 35 l26 for collapsing'the toggle.

6 to the end of the tube as shown in FIGURE 1. With small overcurrents with which it is desired to eifectV tripping in a time-delayed manner the current passing through the coil 16 will cause the plunger to be pulled towards the plate 18. Thus ux passes through the plunger 6, the pole piece 18a and gap 15b, the armature l5, the magnet frame 13 and the sleeve l2. The armatureV 15 is attracted to the pole piece and the trip mechanism is actuated.

v On short cirouitconditions, in which tripping must be effected without time delay, the plunger 6 remains in the position'shown in FIGURE l, and a shortened flux .path fromy the reducedend of the plunger across to the arm,` in the 'region of the hole, the armature and the bracket, causes attraction of the armature to produce actuation of the trip mechanism. Thus even `though the ux in the air gap 13b` between the arm 131ab and the pole piece 18a and the air gapjllb between the latter and the armature may be undesirably neutralised byl an ex-l ternal field, the attraction of the'` armature is still ensured. This is due to the concentration of llux through the high reluctance paths in the arm 13a leaking into the armature and producing an effective pull between the bracket and l the armature. Y

VWhen the armature 15 is attracted'it impinges on the bent end of the catch plate 2d to cause the latterto be turned anti-clockwise about its'pivot pin 21 against the action of la short helical compression spring 22 seated in a recessed wall 23 of the casing. As a result the ear 2'0" is removed from its l'atched engagement with the trip lever`24 which can' -thereupon be turned anti-clockwise by its spring 3lV to cause the jaw 24e to strike the pin The main spring 3S is4 then able Ito force the contact arm 17 forwards so that the pin 32 moves tojthe closed ends of the slots 33, and the rarm pivots in a clockwisedirection around this pin as -a pivot,

spring having its centre loop coiled around the for- Wand pin 44 of the toggle, with one arm bearing on the centre pin 26 `and the other arm of the boss 3b of the dolly. During this movement the energy of the main spring 35 causes the rear pin 37 of the toggle to lbe pressed 'against the jaw 24d of the trip lever to cause it i' to turn clockwise in order to stress itsv spring 31 so that seated on the rear wall of the casing part 1 bears o-n thek armbetween the

pins

32 and 37 and acts Yas hereinafter described. The moving contact 29 cooperates with a rixed contact 30 whichris provided on the end ofV a bentY terminal strip 36, introduced through an opening in the upper end wall of the casing part. A1".

the "0n and/off positions. f* n The forward memberV 27].of the toggle may consist of y a pair of arms joined by a bridge27a and the rearward toggle memberf28 may similarly comprise a pair of arms joined yby la bridge 28a.r One of these arms may be ofyextended'length and formed with ahook shaped'end 23b f for abutting against the pin 44 in thel extended position of the. toggle.

'ln thegnormal position the spring 7 urges the Vplunger it will be restored to latching'engagement 'with the catch plater20 when the dollyV is operated 'to the on position. The catchrplate is restored in readiness Afor such 1re-engagement byvits spring V22.l v

When the partshave been 4moved to the fon position, and the contacts yare pressed'int-o engagement the main spring 35 is'ena-bled to turn the `contact arm about the rear pin of the toggle so that the locating pin 32 moves to theforwand end ofthe `slots 33t. j f Y i' ltl'willbe noted that the Vlatch force, that -is the force which'is effective for the latching engagement of the trip levei 2-4'with'the \catch1plate. 20, is dependent only on the spring 31, land is quite4 independent of -themain spring 35. V'Hence the strength of the latter may be substantial for ensuring :adequate contactpressure, While the strength ofthe spring 31 maybe relatively weak so that only a small tripping force is required forreleasing the latch engagement. The catch plate releases the :lever .which is loadedby the'spring 31, this lever being operated inldependently of themainispring and the toggle.

The improved'oatch plate ensures thatthe tripping mechanismis proof against inadvertent operation due to vibration. The armature construction, provides a small gap with allow magnetic;V reluctance and the entry oiitsv narrowed end-.into the enlarged aperture Ztl? inthe catch plate, permitsa limited j freedomrof movement which f provides an impact or series of impacts, which result in a highly effective tripping action. For, even with a relatively small overload, a series of rapid vibrational impacts may be imparted to the catch plate 20 by the armature 15, to result in the release of the trip lever, while with a ygreater overload the initial impact may be adequate. The improvements also enable the succession of impacts to be readily effective as the production of the catch plate 20 in brass avoids the possibility of corrosion at the latching zone between the ear 20h and the lever 24.

The compression spring 19 acting on the armature l1'5 may be adjusted in order to vary the tripping force. rI'his adjustment may be effected by :a screw 38 disposed in a threaded opening in the lower end of the casing. After this factory adjustment has been performed, a rivet for connecting the casing parts may be introduced through aligning holes 39 in such parts, this rivet obstructing the tapped opening, so that subsequent unauthorized access to the screw 38 is prevented.

The conta-ct arm 17 is seated at its pivotally mounted end between the bosses 34 of the casing parts and, at its contact end, it is spaced from arcuate barriers 40` on such parts. 'l'lhus at lits contact-engaging end, the contact arm is free from engagement with the casing parts 1, 2, the arcuate barriers thereby contributing to the efficient electrical characteristics. These barriers also serve to confine the 'arc |and gases to the contact chamber 40a which may be fitted in known `manner with V-shaped plates A41 between which the contacts are engaged and disengaged.

The gases from such chamber pass to a part-cylindrical chamber 42 in which a swirling action 4is imparted to them before their emission', |at relatively low velocity, through rearwardly `directed vents 43. The impingement of hot particles and gases on the curved walls of the chamber 42 assists the cooling action thereon before their emission through the vents.

In the off position the contact arm 17 abuts against a transverse pin 42a seated 'at its end in countersunk holes in' bosses 43a on the internal walls of the casing parts and disposed on the side of the barriers 40 remote from the contact chamber 40a. These bosses being adapted to form an extended creepiage path between the fixed contact land the switch mechanism. The movement of the locating pin 32, of the contact arm 17 in the open-ended slots 33 produces a wiping action of the moving contact 29 on its fixed contact 30.

The dolly 3 has a cylindrical boss 3a which fits closely into a shaped mouth 1a of the casing, thereby tending to -prevent the emission of gases through such mouth. The boss is formed with axles 3b entering recesses in such parts and constituting pivot mountings for the dolly. The boss' has a rearward extension 30 to which the toggle is pivotally connecte-d by the pin 44. v

The components of the mechanism are individually Iassembled and trapped in position between the opposed casing members 1, 2, FIGURES 4 and 5, the improved arrangement enabling mechanical fixing means and processes involving phys-ical union such -as press operations,

brazing and soldering to be dispensed with, so as to facilitate assembly and rendering it economical in cost. The various holes and slots for receiving the pins and other parts are designated in FIGURES 4 iand 5 by the suffix xf to the numerals designating such parts. These holes are countersunk in order to facilitate registration and,V assembly. The two Vcasing members are secured together by rivets passing through holes 56X.

` The forms of the invention here described and illustrated are presented merely as examples of how'tlhe invention may be embodied and applied. Other forms, embodiments and applications of the invention, coming within the proper scope of the appended claims, will, of course, suggest themselves to those skilled inthe art. l I claim: Y l

"1. An electric circuit breaker comprising .la fixed and a movable contact, a main spring for providing contact pressure, magnetically tripped mechanism including a releasable latch, Iand trip means for disengaging said latch and said kcontacts upon short circuit and overload, said latch and said trip means being independent of said main spring, |a pair of molded fiat case members housing said contacts, said spring and said mechanism therebetween, a handle for manually actuating said mechanism to its on position and means for automatically resetting said mechanism after such disengagement -for such manual actuation.

2. An electric circuit breaker according to claim 1 wherein said latch includes a trip lever, said trip means includes a low pressure spring, and said circuit breaker includes a moving contact Iarm cooperating with said fixed contact and actuated by said main spring, a toggle connecting said arm with said handle, and an actuating means working independently of said arm upon overload to permit said trip lever to break said toggle and allow said main spring to release said arm from contact-engaging position.

3. An electric circuit breaker according to claim 2 wherein said actuating means includes an armature of said electro magnetic mechanism, a catch plate actuated by said armature, said trip lever having releasable latching engagement with said plate, said `armature acting independently :of said arm to permit said low-pressure spring to urge said trip lever to break said toggle and disengage said contacts upon overload.

4. An electric circuit breaker according to claim l wherein said electro magnetically operated trip mechanism comprises a hermetically sealed tube filled with liquid therein, a plunger and a spring pressing said plunger disposed in said tube, a coil disposed around said plunger, a magnetic shield encircling said tube at one end thereof and ran insulating former for said coil, said former hav-ing a length of reduced thickness and an internal shoulder for receiving said shield.

5. An electric circuit breaker according to claim 4 having an L-shaped frame, an aperture disposed in a first member of said frame to receive said shield therethrough, an armature iioatably mounted on the second member thereof, and wherein said shield comprises a sleeve encircling said tube for a portion of its length at one end thereof.

6. An electric circuit breaker according to claim 3 wherein said trip lever is provided with three arms, a first arm is engagea-ble with said toggle, a second farm has latchable engagement with said catch plate and a third arm is pivotally mounted on' said case.

7. An electric circuit breaker according to claim 3 wherein said catch plate is provided with an aperture at one end thereof, said armature extends through said `aperture and said mechanism causes said armature to vibrate within said aperture and impart a series of impactscn said catch plate. n

8. A molded case electric circuit breaker having magnetically tripped mechanism including an hydraulic time delay, said delay comprising a magnet frame, an armature pivot-ally mounted on said frame, a bermetically sealed tube `filled with liquid, a plunger and a spring acting on said plunger disposed in said tube, the magnetic Kcircuit ot said mechanism providing 'a pair of high reluctance paths, ya first path providing a flux for operating said armature on overload an'd a second path providing a fluxwfor operating said armature on short circuit.

' 9. An electric circuit breaker according to claim 5 wherein the opposite end of said armature to its floatable mounting is resiliently supported by a small spring and having adjustment means for regulating the operative action of said small spring against said armature.

10. An electric circuit breaker according to claim 7 having an L-shaped frame provided with a first and second member thereof, and in which a headed pin is carried by said second member, said armature is freely shield.

a screw lfor adjusting the compression of said spring threade-dly seatable in said bore, a rivet for securing said members together passing through said bore to prevent adapted to retain form-Setting material within said bore when applied against said screw to prevent vibrational turning thereof.

12. vA molded case electric circuit breaker comprising Y access to said screw after adjustment thereof, said rivet spring for actuating said arm, a manually operable lever',`

a toggle connecting said arm to saidV lever, a trip lever, a

weak spring engaging said trip lever and means acting` independently of said arm -to permit said weak spring to urge said trip lever to break said toggle and allow said strong spring to disengage said contacts on short Vcircuit or overload.

13. A molded case electric Vcircuit breaker comprising electric magnetically tripped mechanism, a fixed contact, a spring-actuated moving contact arm cooperative with said fixed contact, a primary spring actuating said arm, a handle, a toggle connecting said arm withy said handle, an Voverload device provided with an armature, a catch plate actuated by saidl armature, a trip lever having releas-y .able latching engagement with said plate, a secondary spring and means acting on said secondary spring independently yof'said arm upon overload for urging said lever to break said toggle and'enable saidprimary spring to Y n disengage said'arrn from said fixed contact.

14. VA molded case electric circuit breaker comprising electromagnetically operated trip mechanism having lan armature, a iixed contact, a spring-actuated contact arm cooperating with said iixed contact,` a primary spring for `actuating said arm, a handle, .a `toggle connecting said arm withy said handle, a catch plate actuated by said armature,

trip lever, a secondary spring for urging said lever to break said toggle and enable said primary spring to disengage said arm when said armature imparts a series of impacts on said pla-te on overload.

15,. A molded case circuitbreaker having electromagnetically operated trip mechanism, comprising a hermetically sealed tube lilled with liquid, a spring-pressed plunger disposed in said tube, a rst and `second sleeve disposed about said.tube,la coil encircling said tube for a portion of its length at oneV end thereof, saidirst sleeve having a length of reduced thickness and an internal-shoulder Y acting asl an insulating former for said coil, and said second sleeve seated Ion said shoulder `acting as a rnagnetn:v

16. A molded case electric circuit breaker having elec- Vtro Vmagnetically operated trip mechanism comprising a hermetically sealed tube illed Vwith liquid, a magneticv shielding sleeve encircling a portion of `said tube, a plate for seating oneend of said tube therein, a portion of said plate forming a laterally bent pole piece, an L-shaped frame, a first member ofsaid frame being apertured to rpass over said sleeve,,the'fsecond'memberof said vframe extending to a pointlprox'imate saidpole piece, and an' armature floatably `supported on'said secon-d, member. I 177. A molded case electric circuit breaker comprising electromagnetically operated trip means including a liquid lilled tube, aspring-pressed plunger slidable in'said tube, a coilfdisposed around said plunger, a iioatably mountedV armature disposed laterally of said tube, afcatch plateY actuated'by said armature, a trip' lever having releasable latching engagement withxsaid catch plate, fixed and moving contacts, a mains'pring provided pressure engagement betweensaid contacts, means for disengaging said in saidrcase, and a catch plate provided withan aperture Y contacts, and an independentrspring `for urging said lever havingv latching engagement with said catch plate and a third arm being pivotally mounted on said case, and a trip spring for actuating said leverlto break said toggle when said plate 'is actuated to release such engagement, said trip spring being independent of said main spring.

19. A moldedfcase electric circuit breaker comprising magnetically tripped mechanism, a hydraulic time delay,

a hermetically sealed tube iilled with liquid, a spring and a plunger disposed in said tube, a pole piece forming a plate,'a short sleeve,A one end of said ytube being seated in said plate and theV other end in said sleeve, an L-shaped frame, a longitudinal arm Yor said frame provided with an aperture therein for encompassing said sleeve, a lateral arm of said frame extending to a point proximate said pole piece, an armature iioatably mounted on said lateral arm, the circuit through said mechanism providing a pair of high reluctance paths, one of said paths operating said armature on overload and the other of said paths operating said armature on short circuit.

n 20. A -circuit breaker according to claim- 19 wherein said armature is a flat metal strip loosely pivoted to said lateral arm and said lateral arm is provided with an opening therein'to provide two narrow ycross sectional areas producing linx paths of highreluctance either side thereof.

l2l. A molded case electric circuit breaker comprising an electromagnetically operated trip mechanism including a magnet frame, an adjusting spring, an armature oatably mounted onsaid frame and operable against the action of said spring, a main spring, a moving contact arm actuated by said main spring, a handle, a toggle connecting saidarm to said handle, a trip lever, a catch plate provided with an opening therein pivotally mounted between its ends, a third spring operative adjacent one end of said plate for pressing the other end thereof into latching engagement with said lever, said armature extending f freely into said opening forimparting vibrational impacts on said plate, and a fourth spring lfor urging said lever to impinge on said 'toggle'when such engagement is released. 1

- 22. AV molded case electric circuit breaker comprisingL aiixed contact, a moving contact, a trip lever, a plate for Vlatched engagement with said lever, magnetically operated trip'mechanism for releasing such engagement, means for j sleeve encircling said tubel for a portion `of its length,"a

wire Vcoiled around said plunger, said sleeve aiording increased length and number oampere turns of saidcoil wlthout reduction `of the cross-section of saidrwire to y effect `minimum watt loss .at normal current. v

. k24. VA molded case circuit :breaker comprising Ya iixed and a Vmoving contact, magnetically tripped mechanism ',providedwith aroatably 4mounted armaturer` for disengagtngsaid contacts, resilient `means Yfor supporting the free end-of'saidxarmature `adjustment means to vary the Vcompression tot said resilient means, access means to said adjustmentmeans after .assemblyof Y'said Vcircuit breaker at one end thereof, the lfree end of said armatureextending l .tljiroughV said Vaperture for engagement'withl said resilient means.

25. A circuit breaker according to claim 18 wherein a fiat blank Yforms said three-armed lever.

References Cited in the ie of this patent UNITED STATES PATENTS Beechlyn May 30, 1911 Cheney Dec. 31, 1918 Wilckens Mar. 9, 1937

Claims

1. AN ELECTRIC CIRCUIT BREAKER COMPRISING A FIXED AND A MOVABLE CONTACT, A MAIN SPRING FOR PROVIDING CONTACT PRESSURE, MAGNETICALLY TRIPPED MECHANISM INCLUDING A RELEASABLE LATCH, AND TRIP MEANS FOR DISENGAGING SAID LATCH AND SAID CONTACTS UPON SHORT CIRCUIT AND OVERLOAD, SAID LATCH AND SAID TRIP MEANS BEING INDEPENDENT OF SAID MAIN SPRING, A PAIR OF MOLDED FLAT CASE MEMBERS HOUSING SAID CONTACTS, SAID SPRING AND SAID MECHANISM THEREBETWEEN,