US1989497A - Circuit breaker - Google Patents

Description

Jan. 29, 1935. L. c. REED 1,989,497

CIRCUIT BREAKER Filed March 20, 1930 2 Sheets-Sheet 1 Jan. 29, 1935.

v5727 275 l Z 54 fr f4 da 5 ZN VEN To R y/hdr; C Feed TTQRNEY Patented` Jan. 29,' 1935 r v Y i I UNITED sTATEs PATENT OFFICE CIRCUIT BREAKER Lyman C. Reed, New Orleans, La., assigner, by mesne assignments, to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of New Jersey Application March 20, 1930, Serial No. 437,513 23 Claims. (Cl. 20D-89) This invention relates generally'to apparatus trical apparatus of the so-called panel-board for interrupting and protecting electrical cirtype; and to improve and simplify the construccuits or systems and, more particularly, to a certion of circuit-breakers generally.

tain new and useful improvement in such appa- And with the above and other objects in View, ratus of the type commonly known as circuitmy invention resides in the novel features of 5 breakers, form, construction, arrangement, and combina- Heretofore, so far as I am aware, circuittion of parts hereinafter described and pointed breakers employed for the purpose of protecting out in the claims. electrical systems against so-called overload and In the accompanylg drawings (2 Sheets)- short-circuit conditions have been actuated on Figure 1 is a side elevational view of a circuit- 10 release of a spring-operated mechanism which breaking apparatus embodying my invention, has a fixed time-interval of circuit-opening re- Shown in circuit-closing position, intermediate sponse to such overload or short-circuit condipositions of slome of the members being shown tion, such time-interval being dependent wholly by dot-dash lines, one of the side walls of the l5 upon the action of spring pressure operating on housing being omitted and the top Wall thereof 15 associated fixed weights. In such cases, the now being shown in section;

of short-circuit current very often attains a mag- Figure 2 is a planview of the apparatus, the nitude approximately equal to the capacity of top wall of the housing being removed; the system in which the short occurs, and fre- Figure 3 iS a Sectional VBW hrOugh the appaquently causes the destruction of the circuitratus taken approximately along the line 3 3, 20

breaker or some part of it before the current- Figure 1; now in the circuit is ruptured. The lost time Figure 4 is a view similar to Figure 1, the apoccasioned by such fixed time-interval of rupparatus, however, being shown in circuit-openture of the circuit is exceedingly important on ing DOSitOn aS When the Circuit-breaker is autooverloads of the magnitude of short-circuits, not matically actuated or tripped as on an overload 25' only because the heating of the separable conin the circuit; and

tacts of the breaker is unnecessarily prolonged, Figure 5v is a sectional view through the appabut because the short-circuit current has the opratus taken approximately along the line 5 5, portunity of growth to many times the magni- Figure 4.

tude it would have if interrupted in a time-inter- Referring now more in detail and by reference 30 val having a variable relation to the strength of characters to the drawings, which illustrate a the initial current ow caused by the shortpreferred embodimentof my inventionthe workcircuit. ing parts of the apparatus are for the most part My present invention has hence for its prinenclosed preferably by a housing A which incipal object the provision of an efficient circuitcludes a top wall l and separable side walls 2 35 breaking or interrupting apparatus for both of suitable contour and constructed preferably A. C. and D. C. systems adapted for the solution of any suitable insulation material. Fixed beof the various problems stated above and the tween the side Walls 2 to form one end wall of accomplishment in approximateiy the lowest the housing A, is an insulation block 3 having possible time of the results sought; and in addisubstantially an inverted L shape, the inturned 40 tion, the provision of means for protecting such horizontal leg 4 thereof being spaced from the electrical systems against simple overloads while top wall l and extending somewhat more than permitting momentary heavy or so-cailed starthalf the length thereof. Also fixed between the ing overloads current-flow to pass through, vside walls 2 at the other end of the housing, is a without tripping, the circuit-breaker; to prosubstantially L-shaped block 5 of insulation ma- 45 vide a circuit-breaker arranged for calibration terial, its bottom leg forming a portion of the in a manner to distinguish between simple overbottom wall of the housing, and its upstanding loads and short-circuit overloads; to provide leg 6 being spaced from the opposing side walls such protection in an automatic manner irre- 2 and terminating approximately halfway the spective of deliberative action taken for closing height thereof. 50

the circuit-breaker against abnormal current- The circuit-breaker proper includes a fixed now; to substantially abate the growth of arc terminal member l secured to and upon the top at the separating contacts of the circuit-breaker; of the inner end of the insulation block 4 by a to provide an automatic circuit-breaker adapted suitable fastening element 8. 'I'he terminal 'I 5 especially, though not exclusively, for use in elechas a part depending over the end of the mem- 55 ber 4 to form a stationary'conducting pole ory contact 9a. Co-operating with the pole 9a, is a separably engaging conducting pole or contact 9 adapted for actuation into and out of engagement with the contact 9a for respectively closing and opening the circuit. -The contact or pole 9 is embracingly carried by, and secured with a suitable lfastening element 10 in the bight of, an inverted substantially U-shaped swingably actuable contact-carrier 11.

'I'he depending legs of the member 11 terminate in oppositely presented'axially aligned ears or pivot members 12 edgewise presented for disposition in and rockably engaging aligned grooves 13 formed in the forked ends 14 of a horizontally 'disposed conducting-terminal 15 suitably xed on the upper end of the member 6 with its other end projecting outwardly therebeyond, for purposes soon appearing. Transversely threaded through the lower end of the block 6 into a recess i8 formed for the purpose in the member 5, is an adjusting pin or screw l7 movable in the plane of swinging actuation of the holder l1 oppositely of the pivotal axis thereof. Pivotally secured at an end to the pin 17, is an elongated coiled spring or tensionally yieldable member 18 having its other end stretched past the pivotal axis of the holder 11 and attached intermediate its legs to a pin 19 disposed transversely therethrough, as best seen in Figure 3.

It may be here stated that the spring 18 is caused, on swingable actuation of the contactcarrier 11, to take a position alternately on opposite sides of the pivotal axis thereof. So arranged, the spring 18 and the swingable carrier 1l co-operatively constitute a toggle which, when knuckled in one direction, acts to engage the carried contact 9 with the fixed contact 9a in circuit-closing position. However, when the toggle is knuckled in the opposite direction, the spring 18 acts. with increasing force to separate and acceleratingly widely space the contacts 9 and 9a in circuit-opening'actuation. This wide spacing of the contacts 9, 9a, is accomplished with such a high resulting velocity and in such a short interval of time as to rupture the current-flow substantially and abate the occurring arc before the same can grow to appreciable magnitude.

By manipulating the screw 1'7, the pivoted end of the spring 18 may be shifted relatively to the pivotal axis of the member 11 to regulate the contact pressure between the poles 9 and 9a and' consequently the force or eiort required to be exerted on the member 1l for knuckling the toggle into circuit-opening position.

The automatic tripping mechanism includes an electromagnet B preferably comprising a pair of windings 20 mounted on van inverted substantially .U-shaped core 21 of suitable material, the yoke thereof being sunk into the lower face of the member 4 and therein secured by fastening elements 22, the depending legs of the core 21 termi` nating in preferably horizontally aligned magnetic-poles l23. Electro-magnetically associated with the windings 20, is a swingable so-called overload-armature 24 having an end pivotally supported in a suitable recess in the wall 3 on a pin25 iixed therein, for actuation of its other end toward and away from the poles 23. lSecured between a lug 26 depending from the armature 24 and an adjusting screw .27 threaded through the wall 3, is a calibrating spring or tensional member 28 adapted, by suitable regulation of the 'screw 27, to tensionally weight the armature 24 for yieldingly opposing tl"e response thereof toand at less than a predetermined or normal current flow through the windings 20.

At its s'wingable end, the armature 24,;carries an endwise presented lug 29 normally spaced from butv adapted, on upward actuation of said armature, to impinge, a pimficglaterally presented for such purpose from the swingable end of another or short-circuit-armature 30 also electromagnetically associated with the windings 20, 20, and pivotally supported on the pin 25 for swingable actuation alongside of the armature 24. The armature 30 is provided at its swingableend with an endwise presented lug 31 substantially touching for disengageably impinging an end of a strikerlink 32 depending from a pin 33 laterally spaced from the pivotal axis of the contact-holder ll and secured to and between the legs thereof.

The depending end ofthe link 32 and the cooperating swingable end of the armature 30 work in the recess 16 which is suitably open at an end for such purpose.

The response of the armature 30 to current flow in the windings 20 is opposed by the force of the spring 18, which is brought into action on lifting impingement of the lug 3l with the link 32. As has been described, this force of the spring 18 .may be varied, and in such respect the spring 18 may be arranged to yield or calibrated, as may be said, for circuit-opening actuation of the member l1 on response of the armature 30 to and at more than a predetermined or abnormal current flow through the windings 20, said abnormal current flow being selected in view of the maximum or short-circuit capacity of the system being protected. In magnitude between this maximum overload or short-circuited current-now and the said normal current-ow is a minimum over-load current-how, and for accordingly protecting the` system, the armature 24 responds to current flow greater than that predetermined by its calibration by advancing on the poles 23 with an increasing momentum substantially impartedas a sharp blow or kick to the armature 30y on impingement of the lug 29 'with the pin Y 29a, as shown by dot-dash lines in Figure 1. Such momentum.is additive to the pull of the windings 20 on the armatures 24 and 30 and more especially augmented by rea'son of the relatively small air gap then existing between the poles 23 and the armature 24. Together these several forces suce to open the circuit with extreme rapidity, the armature 24 being most effective for overcoming the inertia of the moving parts of the circuit-breaker'before coming to rest against the poles 23.

The armature, however, is capable of a more extensive. circuit-opening movement accommodating that required for swinging the contactmember 1l past and beyond the dead-center'of toggle of which it forms a partfthe speed of the last portion of such movement being progressively increased by reason of the increasing force with which the windings 20 act on the armature 30 as it approaches the polesv 23, additive to the increasing force'with which the .spring 18 acts on the swingable member 1l, the final circuitopening position being shown in Figure 4, and

being obtained after the armature 30 strikes the pole-pieces 23 by .the force Aof the spring 18 conjointly with `the momentum ofthe moving parts acquired during the initial circuit-opening actuation thereof.`

On bverloads, armature 24 coacts with armature 30 to open the circuit, but on short-circuits armature 30` acts substantially alone, thus providing independent and non-interfering protective agencies against overload and short-circuit conditions, for upon occurrence of a short-circuit, the flow of current is such that armatures 24 and 30 are attracted simultaneously by windings 20, 20, hence the lug 31 substantially touching the striker 32, the armature 30 acts at once to open the circuit. The rise of flux in the magnetic circuit of the-windings 20 is in phase with the rise of current therein, hence the magnetic circuit reaches its saturation point in less time under heavy short-circuit conditions than under light ones, and the armature 30 is actuated sooner under the first condition than under the second. The armature 30 is set to open the circuit at a point substantially below saturation of its magnetic circuit, and its actuation being directly responsive to the growth of current and the capacity of the protected system, the circuit-rupturing time-interval of all the automatic circuit-rupturing parts of the breaker is inversely proportional to the growth of short-circuit current flow. As a result, excessive growth of current in the protected system and consequent destructivearcing at the poles of the breaker is avoided.

The apparatus Y also includes a manually .manipulative actuating mechanism for closing the circuit-breaker, kwhich comprises means for rendering the tripping means trip-free or operable independently of the actuating means. For such purpose, one of the depending legs of the holder 11 is provided with a substantially rhomboidal aperture 34, its front wall 35 being inclined from the rear wall 35 so that the aperture 34 is wider at its top wall 36 than at its bottom wall 36. Provided at its forward end with a finger or detent 37 laterally presented ,in the aperture 34l for alternately impinging the several walls thereof, is a shiftable latch-lever 38 pivoted at its rear end, as at 38a, on a leg of a U-shaped swingably upstanding inverted substantially U-shaped lever 39, the depending legs thereof embracing the member 6 for impinging opposed stops 39a formed inthe terminal 15 and being pivotally supported on the laterally projecting ends of a pin 40 fixed through the member 6 adjacent its lower end. On actuating the lever 39, the finger .37 shifts correspondingly in the aperture 34. The latch 38 is also swingable on the lever 39 and urged thereto by a spring or tensional member 41 having its opposite ends suitably engaging the latch and the lever, respectively. On forward swinging of the levr39 from off or circuit-opening position to "on or circuit-closing position, corresponding to like positions of the member 11, their latch 38 advancingly engages its nger 37 with the walls 35, 36', at their corner and is frictionally held thereto by the opposition of the spring 18 while so advancing, until the/toggle constituted. by the spring 18 and member 11 is forwardly past its dead-center, from whence further continuing movement is caused by breaking the toggle in that direction, the member 11 being thereby actuated to circuit-closing position with increasing force, or, as may be said, the breaker is snapped closed.

Thereupon, the finger 37 is disengaged from the wall 35, as shown by dot-dash lines in Figure 1, the spring 41 swinging the latch 38 upwardly until the finger 37 impinges the opposite corner of the aperture formed by the walls 35', 36, Figure 1, thereby rendering the member 1l trip free of the lever 38.

On circuit-opening actuation of the circuitbreaker proper, the member 11 moves independently of the latch 38 sumciently by reason of the clearance between the finger 37 and the corner of its walls 35, 36, to break the toggle in circuit-opening direction and thus snap the breaker open for interrupting the circuit. A stop 42, preferably comprising a protruding end of the pin 19, depressingly engages an edgewise presented camface 43 on the latch 38 for clamping or locking the finger 37 into impingement with the walls 35, 36', at their corner on completion of the circuit-opening movement of the member 11 accomplished by the action of the spring 18, thereby restoring the lever 38 to'actuating position. 'I'he final portion of such movement is imparted to the latch 38 for correspondingly returning the lever 39 to off position, Figure 4. Thus there is an intermediate circuit-opening position to which the member 11 may be tripped when the lever 39 is in its on position, such intermediate position being obtained when attempting to close the circuit-breaker against a continuing abnormal condition in the protected circuit. From its on position, however, the lever 39 may be manually or otherwise swung rearwardly, the finger 37 engaging the wall 36' for actuation of the member 11 in circuit-opening movement until the toggle is broken in that direction, when the spring 18 acts to complete the movement, as above described. For manual manipulation ofthe circuit-breaker, a handle 44 preferably of insulation material is endwise presented from the lever 39 for work- ;ing in a slot 44a in the top wall 1, the handle 44 having a pair of oppositely'presented laterally arcuate wings 45, 46, bearing suitable insignia, as off and on, respectively, for usual presentation thereof through the unoccupied portions of the slot 44a at corresponding positions of thehandle 44.

By reason of its compact arrangement, the apparatus is adapted especially, though not exclusively, for use in connection with panel-board types of electrical switching apparatus, for which purpose the wall 1 may conveniently constitute apart of the panel of the switch-board, each leg of the circuit being protected by the singlepole type of circuit-breaker shown. 47 designates the usual bus-bar of such a panel-board assembly. The terminal 15 is endwise presented from the housing of the apparatus and electrically connected to the bus 47 by a suitable fastening element 48. The current flows through the terminal 15 and thence through the forked ends 14 to the pivot-members 12 rockably standing in the grooves 13 for co-operation therewith in providing a flexible electrical connection having a yielding live contact between the pivot member 12 and the walls of the groove 13 under pressure caused by the spring 18, the current conducting efficiency thereof being such that said parts operate at a lower temperature than that of the poles 9 and 9a when the latter are engaged in circuit-closing position. The current ow is thus established directly through the member 11, the usual pig-tail being omitted and the spring 18 forming no part of the electrical circuit and hence being free from any distortional heating effect. From the pole 9a, the current flows through the terminal 7 and thence by leads 49, 50, in series through the pair of windings 20, 20, to a terminal 51 secured to the member 4 by a suitable fastening element 52 and having electrical connection with the protected system or circuit through a suitable lead 53. A tap 54 is provided intermediate the coils 20 for use when it is desired to connect the same in parallel. v

An unloading time-delay shunt 55 is preferably connected between the terminals 7 and 51, being in'parallel with or across the windings 20, 20. The shunt 55 is of some positive temperature coemcient substance and is adapted to function to substantially short-circuit the windings 20, 20, at the beginning of current ow, but to direct an increasing proportion of the shunted current through the windings 20 as the temperature of the shunt increases, so that the growth of current ow in th electromagnet 20 is delayed for a time inversely proportional to rate of growth of current how in the circuit, which arrangement constitutes a very successful time-delay device, whereby heavy overloads. as may occur when a motor is started or when type C lamps are thrown on the circuit, may be carried momentarily without tripping the breaker. However, on short-circuit conditions, the ow oi current through the windings 20 is suicient to substantially instantaneously actuate the armature for opening the circuit-breaker. Hence, there is pro- A vided substantially instantaneous protection against short-circuits, and time-delayed protection against overload conditions. As a variable resistance responsive to rate of growth of current ilow in the circuit, the device 55 provides a discharge resistance for absorbing the greater portion of the inductive discharge ofthe windings 20 occurring when the circuit-breaker is opened on heavy overloads and short-circuits. Hence, further, the growth of arc at time of rupture is substantially abated and pitt i the separable contact 9 and 9a substantially 'u i fn d.

In actual practice,A a circuit-breaker embodying my present invention has been subjected to some ve to sixhuhdred dead shorts with sustained potential across its terminals, the circuit-breaker o in every instance and the electrical connections thereof functioning according to their several intended purposes for the entire period. The manner in which the toggle constituted by the spring 18 and member 11 operates to separate the poles 9 and 9a with such high velocity as to substantiallyabate the growth of arc therebetween; the manner in which the springs 18 and '28 may be calibrated, the former for dead-shorts and the latter for overloads; the freedom of such springs from current-dow, which would otherwise aiect their calibration; the small air-gap 'and consequent strong pull of the armature 24 under overload conditions for initiating circuitopening actuation of the breaker; the fact that the handle 43"has only' two operative positions, namely, oil and on", whether the'breaker is opened manually or automatically; the fact that der pressure ot the spring 18; the fact that the rupturing time-interval varies inversely as the current flow; the tact that the breaker is actuated by power supplied by the excess of the shortcircuit or overload current; the absence of springs or weights for initial actuation of the breaker;

the manner in which heavy overloads may be momentarily carried, and the inductive discharge of the windings 20 provided for, by the variable shunt 55; all resulting in complete and adequate protection both to the system being protected and the breaker itself, are among the advantages provided by the co-operant instrumentalities of my invention.

The use of the aparatus having been set forth as the description proceeded and its several advantages pointed out, it is to be understood that changes and modifications in the form, construction, arrangement, and combination of the various parts of the breaker may be made and substituted for those herein shown and described without departing from the nature and principle of my invention.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. An electric circuit interrupting apparatus comprising, in combination, a first contact-member, a toggle including a swingable second-contact member for movement into and out of engagement with the first contact-member for respectively closing and opening the circuit, and current flow responsive means including a pair of swingable armatures for co-operably knuckling the toggle for shifting the second contact-member out of engagement with the rst contact-member to open the circuit.

2. An electric circuit interrupting apparatus comprising, in combination, a frame, a iirstcontact-member, a toggle including a pivoted carrier, a second contact-member carried by the carrier, a spring attached at one end to the frame and at its'other end to the carrier adapted to act on opposite sides of the axis of the carrier for swingably actuating the same for carrying the second contact-member into and out of yielding engagement with vthe iirst contact-member for respectively closing and opening the circuit, a link pivotally depending from the carrier, and current ow responsive means comprising .a swingable armature adapted for engagement with the link for knuckling the toggle for shifting the second contact-member out of engagement with the rst contact-member to open the circuit.

3. An electric circuit interrupting apparatus comprising, in combination, a rst contact-member, a second contact-member, toggle means for' swingably actuating the second contact-member into and out of engagement with the iirst contactmember for respectively closing and opening the circuit, said toggle means including a fixed support, a pivoted carrier for the second contactmember, and a spring attached at one end to the support and at its other end to the carrier adapted to act on' opposite sides of the axis of the carrier, and means for knuckling the toggle to circuit, an armature actuable in opposition to the circuit closing force of the tensional member for r opening the circuit, and a second armature actu' able for assisting the first armature in overcoming the circuit-closing force of the tensional member.

5. An electric circuit interrupting apparatus comprising, in combination, a. iirst contact-member,.a swingable secondcontact-member, means including a tensional member adapted to act for yieldingly engaging the second contact-member with the iirst contact-member for closing `the circuitand to act with opposite eii'ect l for opening the circuit, an armature actuable in opposition to the circuit closing force of the tensional member for opening the circuit, a second armature actuable for assisting the iirst amature in overcoming the circuit-closing force of the tensional member, and means for regulating the actuation o1' said second amature.

6. An electric circuit interrupting 'apparatus comprising, incombination, a rst contact-member, a second contact-member, toggle means 'for actuating the second contact-member into and out of engagement with the rst contact-member u for respectively closing and opening the circuit,

tripping means for the toggle including a pair of co-operating armatures, one armature being calibrated for actuation on short circuit overloads, and the other armature being calibrated to assist the actuation of the nrst armature on simple overloads, and means for independently calibrating the respective armatures.

7. An electric circuit interrupting apparatus comprising, in combination, a first contact-member, a second contact-member, means for actuating the second contact-member into and out of engagement with the first contact-member forrespectively closing and opening the circuit, and means for actuating the flrst means to open the circuit, said last means including a pair of armatures respectively actuable at maximum and lesser values of current iiow, the latter armature being adapted to impinge the other armature at less than maximum current flow for circuit opening actuation therewith.

8. In an electric circuit-interrupting apparatus, in combination, a iirst contact-member, a pivotally swingable recessed carrier, a second contact-member mounted on the carrier, and operating mechanism including an element operatively engaging the wall of the carrier-recess for swingably actuating the carrier for positively carrying the second contact-member substantially into circuit-closing engagement with the first contact-member, and means for moving the element away from operative connection between said operating mechanism and said carrier recess when the contact-members are in engaging relation.

9. In an electric circuit-interrupting apparatus, in combination, a iirst contact-member, a pivotally swingable recessed carrier, a secoL contact-member mounted on the carrier, means including an element operatively engaging the wall of the carrier-recess for swingably actuatthe carrier for positively carrying the second contact-member substantially into circuit-closengagement with the first contact-member, the element being biased to carrier trip free position when the contact-members are in engaging relation, and means for restoring the element inte actuating engagement with the carrier when the latter is in circuit-opening position.

1G. In an electric circuit-interrupting apparasus incombination, a rst contact-member, a pivotally swingable recessed carrier, a. second contact-member mounted on the carrier, and means for swingably actuating the carrier for carrying the second contact-member into and out of engagement with the rst contact-member, said means including an element operatively engaging the wall of the carrier-recess, and a shiftable handle having pivoted connection with said element.

11. In an electric circuit-interrupting apparatus, in combination, l a pivotally swingable recessed carrier, a second contact-member 'mounted on the carrier, and means for swingably actuating the carrier for carrying the second contact-member into and out of engagement with the rst contact-member, said meansincluding a lever operatively engaging the wallof the carrier-recess, and a shiftable handle having pivoted connection with the lever, the lever being biased in carrier trip tree position when the contact-members are -in circuitclosing engagement'.

12. In an electric circuit-interrupting apparatus, in combination, a a pivotally swingable spring-pulled carrier, a second contact-member mounted on the carrier, and means for swingably snapping the carrier for carrying the second contact-member into and `out of yielding engagement with the first contact-member, said means including a lever operatively engaging the carrier, and a shiftable handle having pivoted connection with the lever, the lever being biased in carrier trip free position when the contact-members arein circuitclosing engagement.

13. An electric circuit interrupting apparatus comprising, ber, a second contact-member, an apertured swingable carrier for the second contact-member, means including a swingable latch engageable with a corner of said aperture for circuit closing actuation of the second contact-member and engageable with a diagonally opposite corner of said aperture and trip free of the second contact member when the latter is in engagement with the iirst contact-member, and means for restoring the latch into actuating engagement with the second contact-member when in circuit-opening position.

J4. In an electric circuit-interrupting apparatus, in combination, circuit-closing means including a contact-carrier shiftable into and out of circuit-closing position, said carrier having a recess, carrier-shifting mechanism including a handle shiftable from off to on position, a lever operatively engageable with the wall of the carrier recess and operated by and movable with respect to said handle for shifting the carrier to circuit-closing position, means for biasing the lever in carrier trip free position when the carrier is in circuit closing position, and means for restoring the lever to engagement with the wall of the carrier recess subsequent to initial circuit rupturing movement of the carrier for restoring the handle to'oif position.

' 15. A trip-free circuit breaker comprising stationary contact-structure, an arm carrying movable contact structure for engagement therewith, a xed pivotal support for saidarm, an overcenter spring for holding said contact structures in engagement, an overload responsive device for overpowering said spring to effect separation of said contact structures against the holding force thereof, a manually operable lever, a member resiliently mounted thereon and connected with a lost motion to said pivoted arm, to allow circuit-closing movement of said movable contact structure initiated by said lever to be completed by over-center Amovement o f said spring and to permit automatic circuit-opening movement of said movable contact structure to be effected despite restraint of said lever.

16. A trip-free circuit breaker comprising stationary contact structure, a pivoted arm actuating movable contact structure for engagement a first contact-member,

in combination, a rst contact-memfirst contact-member,

6 therewith, an over-center spring for holding said contact structures in engagement, a lever rocked manually -in opposite directions to eect overcenter movements of said spring for circuitopening and circuit-closing movementsv of saidl movable contact structure, a lost-motion con-4 nection between said lever and said pivoted arm to eiect trip-free circuit openingof said contact structures, and overload responsive means for voverpowering said spring to eilectcircuitopening movement of said movable contact structure.

1'7. A trip-free circuit breaker comprising a stationary contact, a movable contact, an overcenter spring adapted to snap said movable contact toward and away from engagement with said stationary contact when moved across center, means manually operable to move said spring across center, load-responsive means controlling means eiective to overcome said spring to move said movable contact from circuit-closed position, and a lost-motion connection between'said A manual means and saidmovable contact for rendering operation of said movable contact by said controlling means independent of said manual means.

18. A trip-free circuit breaker comprising a pivoted arm, a movable contact operated by said pivoted arm, a spring connected to saidpivoted arm. the line of action of said spring passing from one side to the other of the pivoted axis of said arm to give a snap action, and to bias said arm to apply contact pressure when in closed circuit position, actuating means adapted to move'said pivoted arm to circuit-closing position, means responsive to circuit conditions for controlling meanscapable of overcoming said spring lto move said arm to circuit-opening position, and a lost motion connection between said actuating means and said pivotedarm for rendering operation of said movablev contact by said controlling means independent of said pivoted arm.

19.- A trip free circuit breaker comprising a stationary contact, an arm movable about a fixed pivot, a movable contact. carried thereby, a spring adapted -to snap said movable vContact into engagement with said stationaryvcontact and to maintain said contacts in engagement, means manually operable to cause said spring to snap said contacts into engagement, and inverse time delay current-responsive means controlling means tovoverpower said spring and drive said movable arm toward open circuit position and lost-motion means interconnecting said movable arm and said manually operable means for rendering said movable arm incapable'of lrestraining the contacts in closed circuit position.

2 0. A trip free panel board circuit breaker comprising a Iixed contact, a movable contact, a spring, for moving'said movable contact with a snap action and for-holding said contacts in engagement; load-responsive means controllingy means eiective to overcome said spring and to drive said movable contact toward open-circuit position,v an enclosure for said contacts,- said spring, and said load-responsive means,'and a lever for manually controlling said contacts pivoted within said enclosure and extending through a slot therein, and a lost-motion connection between said lever and said movable contact whereby restraint .of said lever in closed circuit position is incapable of restraining said contacts in closed circuit position.

2l. A trip-free circuit breaker comprising cooperating stationary and movable. contact structures, a pivotally mounted arm controlling said movable contact structure to effect engagement and disengagement of said contact structures, an overcenter spring connected to bias said arm to circuit-opening or circuit-closing position, a

manually operable lever movable to eiect over-...v7.1-Y

center movements of said spring for -circuitopening and circuit-closing movements of said movable contact structure, the relationship of parts being such that circuit-opening movement of said movable contactstructure may be initiated independent of said manually operable lever, and electro-responsively controlled means for overpowering said spring to eiect circuit opening movement of said movable contact structure.

22. A trip-free circuit breaker comprising cooperating stationary and movable contact structures, a pivotally mounted 'arm controlling said movable contact structure to effect engagement and disengagement of said contact structures, an overcenter spring connected to bias said arm to circuit-opening or circuit-closing position, a manually operable lever movable to effect overcenter movements of said spring for circuitopening and circuit-closing movements vof said movable contact structure, the relationship of parts being such that circuit-opening movement of said movable contact structure may be eiected independent of said manually operable lever, and electro-responsively controlled means acting directly on said contact arm to overpower said spring and effect circuit opening movement of said movable contact structure.

23. A trip-free circuit breaker comprising cooperating stationary and movable butt contacts,

a pivotally mounted arm controlling said movable contact to eiect engagement and disengagement of said contacts, an overcenter spring connected to bias said arm to circuit opening or circuit-closing position whereby the contact pressure is dependent upon the deflection of said spring from its neutral position, a manual control lever operable to eiect overcenter movements of said spring Afor circuit-opening and circuitclosing movements of said movable contact structure, said movable contact being operable to circuit-opening position irrespective of the retention of s aid lever in circuit-closed position, and electroresponsively controlled means acting directly upon said contact arm to overpower said spring and effect circuit-opening movement of said movable contact structure. y

LYMAN C. REED.

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