US3021404A - Heat responsive wire controlled overload circuit breaker - Google Patents

Description

Feb. 13, 1962 M. B. wooD 3,021,404

HEAT RESPONSIVE wIRE coNIRoLLED ovERLoAD CIRCUIT BREARER Filed oct. 9, 1959 H91 Fig. 4

iff-I 1331959, in the'nanie of thepresent inventor;

.... m... V' E i CONTRQLLED l I Fna ou. 9.,19s9saeNuL-84s81 9J(laims;.- (CL 20G-21:10: The presentA invention? relatesu tor improvementsin elecpa-rticularly'a's describedl infaf prior application for United States Letters-Patentp Seriall No. 786,644; `filedlanuary `Il'n inventaris@ prior application` there-is ldisclosed an easily j manufactured ,co'rnpactf construction" contained within` anf'insulatlngl framev and,l providedwith a bimetallic thermoetatiolatch` employed: as av current responsive' breaker? trippin'gedeviccp It has longbeenk thedesir'e' of circuitbreakerv manufacturers to avoidfthe useo binneice' v i FIlG. 5 is a sectional' bottom planf viewfvof' thefbrealter 'Phe tiip-reefoverload breaker illustrated in the: draw-f ingsisj both? manually operated; t'o open' and closeI a cir;` cuit, to` be vprotected and automatically: operated inr response lt current.` overload to'fopen the circuit andato'- vprei/ent ranual closure off thccircuit until .the conditions causiriglther overload a're corrected.r The breaker is alsory designed:l te reset itsela automaticany',A so thaty it may f k1 be closed; manually' by, a' single# downward: movement of af circsiiit-v closingf button;v Thevv mechanism for/actuating, thenbreakeri isjtheisane ina mnyrespects a's-thatof the' prior application,4 above identitied, in thatl a-locked`re`- leasablemember,arjmovable .contact actuating:` member or support andra't wed'gingmember'connectedr to arman# ually:actuated-buttonfareprovided Toopenthe' contacts tallio latches or thermostaticcontrols ofsimilar nature I for many reasonsginotlthe leastofV which are their critical and delicate responsiveness to temperature. change, their changeability in use and their diculty inf'adjus'tment-'after assembly iria'circuit1 breaker. n Furthermore;`r bimetallic latches are generally known tof provide extremelyV weak forces when'heated or cooled,y so that every mechanical advantage mustibe taken in' the designofbreal e1-s ern-y phloyingytherriy tofree them `of-` anyf` possibility of 'simple f-rietional-load;- whichwould impede their effectiveness; The; breaker of the prior application has been found the movableacontact [support isjin` the, form of` a resilientl v strip whichA is biased ,towardf circ'uit-v openin g1. position and@ isf forced-z against its bia`s toward circuit closing position Referring'l more particularly' to the drawings, an insuL lat-fingV hollowl` frame willf be seen' at 10,' the nianual"v circuit closing' btto'hiat 12;l and the lockiedfreleasableA member l in the form of a cam lever'at 14.,rrr The contactl actuating ,stripyat' 16l isareverselfy ben't,a1'1dv the wedgingimember,

to beofv desirable construction'inv4 avoiding difficulties ofv this nature,-especially` for rlowcurrentv capacity circuit breakers and accordingly-the-present inventor has been encouragedto extendythev design-` of4 theT prior breaker-j to use-with even` more elemental, weaker forms/of thermostatic latch; not-employing bimetallic devices- It is; accordingly arr importantfeatureo the present f invention ltovjpirovidel a simple` inexpensive; circuit breakerl of thetrip-free"Y type` disclosed in-,the priorapplication; aboveidentiied which is eiectivewith overloads of low intensity and is not dependent-4 upon abimetallic latch such yas, yrequired i nthe prior breaker.- Irrthis respect, a more specific object of thek invention is to v provideanl improvedtrip-free low capacity circuit breaker,` utilizing as its current responsive device a convenient arrangement employing a short lengthl of electrical` resistance Wire.v

To the extent outlined Jabove,y the invention atVha-nd `residesjin ay trip-free overload circuit` breaker having an insulating frame,1xed and-,movable contacts intheframe; arsupport for the movable contact,y ak locked releasable member, a wedging member acting between the releasable` member and4 the movable contactsupportl and a, detent engaged with the vreleasable memberv to lockit-against separation from (the, movableY contact support,l yin which there is provided a heat responsive-wirestretchedv between 1 sponsivewirei-'of heatz resistant alloy,.suchjas stainless the detentg and theV frame for restraining thef'detentjin locking relation withfthe releasable member. 5

These and other features of the invention, as! hereinl after described,r and claimed; will readily bel understood froml the followingdetailed specification and drawings,

FIG1 is a sectional frontvi'ew of altrip-freeg. auto-r i matic'ally reset circuit breaker embodying thefeatures ofthe presentinyention, the contactsofV the breaker being shown in c losed relation; f `FIG. 2 isr a ,sectional plan lView of the breaker, ytaken along the line II-II of FIG. 1;.v l

FIGg is a further, sectional plan view of the breaker, taken Lalong the line IIIe-III of FIG. l; A g

FIG., 4 is amsectional side View ofthe breaker, taken along the Hna Iv-iv of FiG. 1; and

button=-1=2`islsliding1y mounted` in akv collar formedin-a plater 20 'securedl` to the open-'upper end*y of th'e' hollow frame 10 and movable-alofngny a central pathy between and parallel' to` theV sidesfof the' Vframe 10:, beingi pressed bre'alcer and plledfpwardly tof open'thefcircuit; Upon the occurrence: of anjoverloadf inthe controlled circuit f thefcontaeto are opened and theparts ofsthefbreaker are y moved` torresetpositions;k withfthef button 12'beingm`ovd .upwardly tot-indicate ariv open' circuitl and to? facilitate required. or` the closure is-jattempted^too= soon' to' permit a` current qnickf closing: by a* sin'gle downwardl movement when Ifhowever, the' overloadfinfthe circuitpersists responsive element to cool, the releasable; memberwill be'unlocked! anclthe breaker Held?in`-opencircuitl position.

Instead1v of utilizinga bimctallio strip;y asf iri1the breaker of tle prior application, asiaetherr'nostatic trippingrfdevice the`r breaker, ofi t'ney present invention eiploys alheatre'i steel or eveni'less'4` expehsive material o readily- Vheat look thereleasabllever 1f4 against"separation` fromly the mtwablevcontactl actuating-strip" 162 when engaged bythe Vparallel; plates' (zsee` F'IGS 3 and"E `4)f fastened together y i'n space-'tl'rela-tiorA byAV threeri-vets i265..y 28' and 3'0. FPhe' passies tlirou'gh*y aL roll 63 disposed between the` plates.

tiener one" a kfeatA support', for die'. mvabe' confaot; indicated aff 4c.

p, i lPatented-r Feb.. 13,- 1.962;

the button is depressed the rivet rides along the cam surface 34 of the releasable lever 14 and the roll presses the movable contact support to press the movable contact 4t) against a fixed contact 42 on the right side of the frame, as shown in FIG. 1.

To insure reliable operation of the detent 24 in accordance with the temperature of the heat responsive wire 22 the wire is stretched under uniform tension between the detent 24 and a resilient clip 44 attached at one end to a terminal plate 46 inside the frame 10. The resilient clip has a free end secured to the lower end of the heat responsive wire, which extends in adjacent parallel relation with the left side of the frame as viewed inFIG. 1. The detent has a horizontal arm to which the upper end of the wire 22 is secured. Along a central portion of the detent it is provided with parallel flanges having nar row, edge opening recesses to t loosely about a fulcrum pin 48 engaged at its ends in openings in the liners 32 between the front and rear walls of the frame. Y

At its lower end the detent 24 has an opening through which passes a projecting angular shoulder 50 on the releasable lever 14, the force of the releasable lever acting directly along the length of the detent on the fulcrum pin 48. The angle formed by the shoulder 50 is selected to provide a smooth quick release of the locked lever 14 by a wedging action of the Ylower end of the detent away from the locked lever 14, the heat responsive wire restraining the detent from displacement while the locked lever is locked.

Current flowing through the heat responsive wire 22 heats it and causes it to expand. When heated suciently the expansion of the wire 22 permits release of the shoulder on the locker Alever 14 and the movable contact separates from the fixed contact 42. As soon as the contacts separate the lever is turned in a counterclockwise direction about a fulcrum pin S2, also engaged at its ends within openings in the liners 32 and held in position lengthwise by the front and rear walls of the frame 10. In turning about the pin 52 the cam surface 34 changes its angle and the force of the resilient movable contact support strip 16 presses the rivet 30 on the wedging member upwardly, shifting the wedging member bodily out from between the locked lever and the support 16. The button also moves upwardly to indicate an open circuit condition.

As soon as the releasable locked lever 14 is released and the wedging member shifted upwardly the released lever is reset. For this purpose the fulcrum pin 52 is surrounded at either side of the lever 14 by coils of a resetting spring 53 of hairpin shape engaging along its central portion the lever 14 and at its ends an internally projecting ilange portion 54 on the frame. At the same time that the lever 14 is reset, the detent 24 relocks the lever. To relock the releasable lever 14 the detent 24 has near its upper end a centrally perforated leaf spring 56 fastened to it with. the lower end of the spring slidingly engaged with the left inner side of the frame. The wire 22 passes through the perforation in the leaf spring 56 and urges the detent into locking relation with the releasable lever.

The resilient contact support strip 16, the resetting spring 53 and the relooking spring 56'are graded as to forces of resiliency. The force of the strip 16 is the greatest and is capable of overpowering the two springs, the force of the resetting spring 53 next in `resiliency and the relooking spring 56 is the weakest. If necessary, the clip 44 may yield suiciently to permit the releasable lever 14 to be relocked by the detent 24, the clip maintaining the wire 22 under tension at all times.

To determine the position of engagement of the detent 24 with the shoulder 50 on the releasable locked lever 14 and consequently to adjust the sensitivity of the breaker the resilient clip 44 at its free end, to which the wire 22 is secured is engaged with an adjustingA screw '58 threaded into the lower left corner of the frame. The

4 inner end of the screw 58 is engaged with the clip and the other end of the screw is exposed outside the frame to enable change in the relation of the detent and the releasable locker lever 14 without dismantling the breaker.

By mounting the detent 24 and the heat responsive wire 22 lengthwise along one side of the frame in adjacent parallel relation thereto and the reversely bent movable contact support in parallel relation to the detent and wire at the side of the frame opposite to the wire and detent and with the wedging member and releasable lever mounted to act between the detent and the support, a compact and effective construction is provided.

The circuit through the breaker runs from the terminal plate 46 which extends through the bottom of the frame 10, the clip 44, wire 22, the upper end of the detent 24, a flexible lead 66 connected between the detent 24 and a threaded block 62, the movable contact support 16, contacts 4t) and 42, and a terminal plate 64 clamped by screws 66 to the right side of the frame 10. The terminal plate 46 is clamped similarly to the bottom of the frame by screws 68 kpassing through the frame and into threaded engagement with the terminal plate 46.

The nature and scope of the invention having been set forth and an embodiment having been described it is inended to include withinv the contines of the invention all modifications and equivalents which fall within the scope of the appended claims. f

What I claim is:

l. A trip-free overload circuit breaker having a frame, a fixed contact in the frame, a movable contact, a resilient support to which the movable contact is secured and mounted for movement toward and from the xed contact, a lockable releasable cam member, a wedging member acting between the releasable cam member and the resilient support for engaging the movable contact with the fixed contact, and a detent engaged with the releasable member to lock said releasable cam member against movement under the influence of said resilient support when actuated by the wedging member, in combination with a heat responsive wire stretched between the detent and the frame for restraining the detent in locking relation with the releasable member when the heat responsive wire is cold and for freeing the detent from the releasable member when the wire is heated.

2. A trip-free overload circuit breaker, as in claim l, in which there is provided a spring fastened to the detent for urging the detent into locking relation with the releasablev member.

3. A trip-free overload circuit breaker, `as in claim 2, in which there is provided 'a resetting spring connected to the releasable member to return it to locked position after the contacts are separated.

4. A trip-free overload circuit breaker, as in claim 3, in which there is provided a button connected to the wedging member for actuating it to open and close the contacts manually.

5. A trip-free overload circuit breaker, as in claim l, in which there is provided a resilient clip in the frame with a free end secured to the heat responsive wire to maintain the wire under tension.

6. A trip-free overload circuit breaker, as in claim 5, in which an adjusting screw is threaded into the frame with one end engaged with the clip and the other end exposed outside the frame to enable change in the relation of the detent and the releasable member without dismantling the breaker.

7. A trip-free overload circuit breaker having a frame, a fixed contact in the frame, a movable contact, a locked vreleasable member, a wedging member to engage the movable contact with the iixed contact, and a detent engaged with the releasable cam member to lock said releasable cam member against separation `from the wedging member, in combination with a heat responsive wire stretched between the detent and the frame in adjacent parallel relation to one side of the frame for retaining the detentin locked relation with the releasable member when the heat responsive wire is cold and ,for releasing the detent from the releasable member when the wire is heated and a reversely bent resilient support, to one end of which the movable contact is secured in parallel relation to the wire and the other end of which support is tixed to the side of the frame opposite to thefheat responsive L wire. f

8. A trip-free overload circuit breaker cornprisir'ig: a

kixed contact; amovable contact; a resilient support for said movable contact; a pivotally mounted releasable cam member; adetent; a heat responsive wire connected to said detent, said detent being adaptedto restrain the movement of said pivotally mounted releasable cam mem ber only when coldy and to yield to ksaid pivotally mounted releasable cam member when conditioned oy a current overload; an operating member; and a wedging member carried by said operating member rfor acting be` tween said cam member and said resilient support so as to close said contacts in response to movement of the operating member.

9. Acircuit breaker according to claim 8 wherein said n detent has a shoulderrand said releasable cam member has a shoulder, said shoulders beingnormally'interengaged-forproviding said restraint of the releasable cam member, and wherein rotation ofthe detent in releasing the restraining engagement of the releasable cam member positions said shoulders inwedging relationV for smoothly moving ysaid `detent out of lrestrainingengagementfwith.

the releasable cam member. 1 f References 'Cited in the file of this patent t t t UNITED STATES PATENTS .i

2,943,172 Ingwers'en l lune 28,

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