US2698429A - Load indicator - Google Patents

Description

Dec. 28, 1954 E. D. TREANOR LOAD INDICATOR Filed Jan. 20, 1954 United States Patenti "O :LOAD INDICATOR :Edward D. Treanor, Pttsfield, Mass., assignortoGeneral Electric Company, .a corporation ofNew ork Application-January 20, `1954, SerialNo. 405,141

'.7 Claims. :(Cl.340`222) This invention relates zto a load indicator, land 4.more particularly, fto :a load .indicator .for .electrical apparatuses.

A well known type of .switch vor .circuit 'breaker :cornprises ta pair Iof circuit breaker contacts :and a load :indicator or signal mechanism. .A :.bimetallic element, .movably tresponsive to the amount .of current drawn by an electrical apparatus to 'be protected from overloads or the .like '.by said :circuit breaker, :is operable rst to actuate -said signal mechanism from .a .non-indicating Icondition `to an .indicating .condition upon a predetermined ioverload level Iless than a :predetermined .overload Strip level of said .circuit breaker contacts, .and then to lactuate Vsaid :circuit breaker ycontacts from a closed :posi- `tion to .a 'tripped open position 'when the overload .trip level :of Asaid circuit breaker contacts -has .been reached.

LOne Iform `of such :type of switch or circuit Vbreaker is Y lshown :in Patent 2,487,534 issued :November 8, 1949 toll. A. Favre, and assigned'to `.the same :assignee .as lthe instant application.

When 4such type .of .switch or circuit breaker :is .used to sprotect .an .electrical ksystem :such las `a transformer, it may not always lbe .desirable `for .the :circuit breaker @to take the transformer oit the line .the moment the circuit breaker `contacts voverload 'trip level have 'ibeen reached. vFor instance, theoverload condition may be only transient and .not of :a 4serious .enough nature 'to damage :the transformer or materially decrease -tslifeexpectancy. However, `if 'the Vtransformer 'is `taken off fthe line, there :is an interruption in service lduring the :time :required :for :an operator to go :out to the .transformer station to .reset and `close 'the circuit breaker.

Accordingly, :in a `circuit :breaker radapted to fprotect an :electrical :circuit :from overloads or ithe like, said circuit breaker Z'having .a :movable bimetallic element positioned `electrically `in Vseries in said `electrical circuit, .said circuit breaker having a signal `mechanism .and .a pair of circuit lbreaker Icontacts positioned electrically in series :in vsaid circuit, said `bimetallic element operable :rst to :actuate said signa'l 'mechanism ,from `a .non-indieating condition .to `an indicating condition upon Athe occurrence of .an overload .in said .circuit less :than a predetermined overload trip .1 level of :said Ycircuit breaker -contacts,'andithen operable 'to actuatesaidscircuit breaker lcontactsfrom a closed Iposition Atoaltrlipped open :position when :the overload trio level `of 'said circuit breaker contactshave ibeen reached, .it is an 'obect of this finvention Ito provide means whereinwhen said :circuitbreaker contacts iare :actuated to :said etripped openposition said circuit 'willzremain Aelectrically closed :and .-a .shunt path will "be .provided :in vsaid 'circuit Varound fsa'id .fbimetallic `:element to .protect Vsai'cl bimetall'ic felement Ifrom yoverfcurrents in fsaid circuit whereby "said circuit :breaker iis rconverted into f'aload `indicator lat .a minimum IVcost.

It ,is Ja 'further :object of ithis :invention to :provide Van loverload indicator having van :actuating 'bimetallic element 'adapted to be disposed in an :electrical circuit,

and shunt means operative substantially instantaneously subsequent to .actuation fof said overload indicator by `said `bimetallic 4element Ewhereby said fbimetallic .element `is 'substantially protected `:from an .overcurrent -in :said circuit, said :shunt meansfproviding a shuntpath around said bimetallic element whereby said'overcurrent will substantially 'bypass fsaid bimetallic element.

In a circuit breaker adapted .to =protect'fan.:electrieal 4circuit =fromvovercurrents andfthelike said circuitf'breaker flraving a :movable bimetallic element positioned felec- Iftricallyiin series :in-'said ."circuit, `asaiirl circuit '.breaker Elrav-V nl LA 2,698,429 .Patented Dec. 28 1,954

.a :pair .of circuit breaker A,contacts rpos'itioned @electri- -cltlly in fseres iin .said circuit and :a .signal smechanism, .said bimetallic element .adapted :to -actuate .said signal .means :and :trip :open .said circuit breaker :.eontacts, :actu- .ation'offsaid signal means preceding tripping fopeniof said .circuit breaker contacts, any :invention comprises shunt Vmeans ffor 4automatically shunting fsaid .bimetallic 'element 'to protect isaid bimetallic ielement ifrom overcurrents iin said .circuit :and .for automatically :electrically closing .said :circuit upon Y.tripping fopen of :said Vcircuit breaker contacts l:whereby said .circuit breaker fis .convened finto :a load :indicator at a minimum =cost.

My Y.invention :further :comprises a :signal imeehanism having a movable bimetallic element positioned `relecice " trically :in an electrical circuit, said bimetallic lelement operable :to actuate :said signal mechanism :upon the voccurrence of .an overcurrent :in :said scircuit, and .fshunt means -for automatically :shunting said .bimetallic 1elementfollowing :actuation 4-o'i :said `:signal mechanism .z-by -said bimetallic element wherebysaid ,fbirnetallic element is `substantially protectedfrom said overcurrent The :features t,of my invention which I believe to be .novel are .set AIforth with particularity in -the appended claims. My yinvention itself, however, fboth as to 'its `organization vand -method -of operation, together -with further objects and vadvantages thereof, may :best tbe understood -by reference rto fthe following fdescription taken in connection `with :the :accompanying idrawing.

In the drawing, rFig. .l isa partly .broken .away'perspective view of an embodiment :of "my invention. `Fig. 42 :is :a 'diagrammatic electrical circuit illustration vof vmy (invention. fLike,referencenumeralswill -be used inF-igs. `1 and .2 :to designate identical par,

AReferring now to the drawing, and .more particularly, to Fig. l, shown .therein -is Ia yswitcher circuit :breaker ;in fitsltripped opened position. Slhe switch `or circuit breaker comprises za fpair of bimetallic elements 10, only `one yof ywhich isfshown in Fig. 1, a :pair'of stationary contacts -11,:and a `pairof movable=contacts 12. Each bimetallic -element .1 0 comprises a rpair :of Yelongated .bimetallic imernbers 213 .and 14 disposed Ygenerally parallel -with respect fto each other -and electrically disconnected from eachother .except `at their lrear ends. ,Art'said rear iends :the -pair .fof yelongated lb'imetallic I'members Y13 :and v:14 are velectrically interconnected by'a'nger .15.

The Vbimetallic :elements -10 .are :immovably vmounted .at their forward endsfin an insulating material `base '16, .and said rear --ends or lingers :15 :are floating'ly -mounted lwhereby said rear ends or fingers 15 arefree forupward .deflection upon .the `-ilow V.of an :electrical .current 'through gparts Ar13, .15, and 14. The :stationary contacts 11 :are -electricallyfconnectedfto the .bimetallicmembers `14. The left-hand -bimetallic element .'10 land -the leftfhand zeontacts -1-1 and :12 -are disposed'electrically in 'series in an f: .electrical circuit to be protected by the circuit breaker or switch. ,fFor instance, one Y.terminal of the electrical circuit -to b e protected :is connected to -.the :lett-handbi- ,metallic member ^15 ,at leftehand :tab 17 and another .terminal .-of ysaid electrical ieircuit -is :connected to `the left-hand movable contact 12 at left-hand tab .#18 selec- .trically in :Contact -with Athe :left-hand :movable contact 12. 'With the left-hand contacts 11.and,12 closedrelectrical current vwill Aflow ,from ttab 17 ,to 'bimeitallic f mem- 4ber 13 dinger 15 bimetallicsmember .14, vstationary ;con- .tact11,;movablefcontact.'12, 4and thence fto Stab l18. As -will :be Vmore -clear hereinafter, upon -the :occurrence :of an `overload for overcurrent of a predetermined :level fin said electrical circuit .the :end ,15 vof `.bimetall'ic :element .10 will .be deflected iupwardly :and .result "in :actuation fof :a signal means, to :be `desrsrtibed hereinafter, from .a ;non` indicating :condition ito -aniindicating condition. Also, vvif:said-.:overload orovercurrent :reaches a .slightly higher :predetermined level, the finger .'15 of bimetallic velement g1'0 will `vbe :deflected fupwardly still 'further ywhich lwill result in :triping :open .of Ythe circuit 'breaker contacts l1 and 1.2.

.Referring now valso to flig. i2, ."the.;hereinbefore men- -tion'ed'fsignal 'or `indicating :mechanism comprises la warning .light tcircuitghauing a *stationary l.warning :light :contact .20., ia :movable @warning flig'ht contact :21, and :a warning A:light 52.2 ,shown only :in Eig. .2. ilig. i12 the :Warning light contacts and 21 are shown in their disengaged position whereby the warning light 22 is off, and in Fig. 1 the warning light contacts 20 and 21 are illustrated in their engaged position wherein the warning light circuit is closed and the warning light 22 is on. Movable warning light contact 21 is a generally horizontally disposed rod-like member connected to a generally vertically disposed elongated member 23 as by welding or the like. Elongated member 23 is disposed substantially normal to the rod-like movable warning light contact 21. Disposed substantially parallel to the rod-like movable warning light contact 21 adjacent the lower end of elongated member 23 is a latching plate 24. Latching plate 24 is carried by a pivotally mounted and horizontally disposed member which is continuously biased clockwise by a not shown spring. The elongated member 23 is continuously urged downwardly and rearwardly by an inclined spring 26.

As will be seen from Fig. 2, when the warning light 22 is off the lower end of the elongated member 23 rests upon the upper surface of the latching plate 24 whereby the movable warning light Contact 21 is raised from elecn trical contact with the stationary warning light contact 20. The inclined spring 26 retains the elongated member 23 from sliding off the upper surface of latching plate 24 and falling below the latching plate 24. As will be clearly seen from Fig. 1, the free end 15 of bimetallic element 10 has a contact proection 27 thereon adapted to engage an integral projection 28 of the member 25. Accordingly, when an overcurrent of sufficient magnitude occurs and the bimetallic element 10 is deflected upwardly, the member 25 with its latching plate 24 will be pivoted counterclockwise whereby the latching plate 24 will be removed from the downward path of movement of the elongated member 23. Thereafter the inclined spring 26 l is free to pull the elongated member 23 downwardly below the latching plate 24 to place the movable warning light contact 21 in engagement with the stationary warning light contact 20, as illustrated in Fig. l.

As will be seen more clearly from Fig. 2, the pair of movable circuit breaker contacts 12 are carried by switch arms 30 pivotally mounted at their rear ends. When the contacts 11 and 12 are engaged with each other, a not shown latching mechanism, fully described in the heretofore mentioned Patent 2,487,534, has a latching tooth thereof in engagement with the upper surface of latching plate 24. However, a greater portion of said latching tooth is in engagement with the latching plate 24 than there is of the lower end of elongated member 23 in engagement with latching plate 24. Accordingly, as the latching plate t 24 is pivoted counterclockwise the lower end of elongated member 23 will be released first to close the warning light contacts 20 and 21. If the overload condition in the electrical circuit to be protected by the circuit breaker or switch persists and reaches a still higher level, the ends 15 of the bimetallic elements 10 will be deflected upwardly still further after which the latching plate 24 will be pivoted counterclockwise sufficiently to release the previously mentioned. latching tooth. Thereafter, the switch arms 30 are free to be snapped upwardly by a spring 31, see Fig. 1, whereby the movable circuit breaker contacts 12 are disengaged from the stationary circuit breaker contacts 11 to interrupt or open the electrical circuit to be protected.

Opening of the electrical circuit to be protected by the switch or circuit breaker is not always desirable. For instance, in Fig. 2 the circuit breaker or switch is illustrated as being adapted to protect an electrical apparatus, such as a transformer, from overcurrents of overloads in the secondary windings 32 of said transformer, the neutral point of winding 32 being grounded as is well known in the art. Many overcurrents or overloads in electrical apparatuses such as transformers are only of an instantaneous or transient nature and not severe enough to cause damage to said transformers or decrease their life expectancies. In such a situation it may be more economical to keep the transformer on the line during said instantaneous or transient overcurrent or overload rather than for the transformer to be taken off the line and thereby have a resulting discontinuity in electrical service until an operator can get out to the transformer station to reset and close the switch or circuit breaker and reestablish electrical service. Accordingly, in my invention l provide means whereby though the signal mechanism is actuated to its indicating condition and though the circuit breaker contacts are mechanically tripped open to their electrical circuit open position the electrical circuit to be protected is electrically closed. That is, the circuit breaker function of the switch or circuit breaker is eliminated whereby the circuit breaker functions only as a load indicator.

As seen in Figs. 1 and 2 interconnecting the disengageable contacts 11 and 12 are exible conductors 35. Accordingly, when the circuit breaker contacts 11 and 12 are mechanically tripped open the electrical apparatus to be protected is not taken off the line. However, since the electrical circuit of the electrical apparatus to be protected is not interrupted upon the occurrence of an overcurrent or overload in said electrical circuit, the overcurrent will continue to ow through the bimetallic elements 10. Repeated subjection of the bimetallic elements 10 to overcurrents rapidly decreases their life expectancy. Accordingly, in my invention I provide shunt means whereby after the switch or circuit breaker contacts have been mechanically tripped open the overcurrent will substantially bypass the bimetallic elements 10 thereby protecting them from rapid deterioration.

Said shunt means comprises two generally U- shaped members 36. As seen most clearly from Fig. l, the generally U-shaped members 36 are disposed so that their base portions extend in a generally vertical direction. A leg of the U-shaped members 36 is electrically connected to the bimetallic members 13 and the other leg of the U-shaped members 36 overlies the movable circuit breaker contacts 12.` When the movable circuit breaker contacts 12 are engaged with the stationary circuit breaker contacts 11, the upper leg portions of generally U-shaped members 36 are vertically superposed with respect to the tabs 18 and spaced therefrom. However, when the movable circuit breaker contacts 12 are tripped open, the tabs 18 will be raised upwardly along with the contacts 12 and be placed in electrical contact with the upper leg portions of the U-shaped members 36. Accordingly, a shunt circuit is provided around the bimetallic elements 10 after the circuit breaker contacts 12 have tripped open whereby the overcurrent in the electrical circuit to be protected can substantially bypass the bimetallic elements 10. If the exible conductors 35 interconnecting the contacts 11 and 12 were not present the U-shaped members 36 alone would keep the electrical circuit to be protected closed despite the fact that the circuit breaker contacts 12 have been disengaged from the contacts 11. However, from the instant after which the contacts 12 leave the contacts 11 until the instant during which the tabs 18 come in electrical contact with the upper leg portions of the U-shaped members 36 an instantaneous discontinuity in electrical service is introduced. Accordingly, in my invention I prefer to also utilize the flexible conductors 35 so that there is no discontinuity in service whatsoever while the circuit breaker contacts are being mechanically disengaged. Furthermore, without the fiexible shunt conductors 35 the instant the contacts 12 become disengaged from the contacts 11 electrical arcing would occur therebetween. Electrical arcing between the contacts 11 and 12 may tend to deteriorate them. However, if the contacts 11 and 12 are interconnected by the exible shunt conductors 35, no electrical arcing can occur between the contacts 11 and 12 thereby tending to preserve them. After contacts 12 are tripped open shunt elements 36 also shunt the contacts 11, 12 and the flexible conductors 35.

Thus, it will now be apparent that I have provided a load indicator at a minimum cost by uniquely eliminating the circuit interrupting function of a well known type of circuit breaker having a signal mechanism; the load indicator comprising a signal mechanism and a bimetallic element adapted to actuate said signal mechanism from a non-indicating condition to an indicating condition with shunt means automatically operable to substantially protect said bimetallic element from overcurrents or the like.

While there has been shown and described a particular embodiment of the invention, it will be obvious to those skilled in the art that changes and modifications can be made without departing from the invention, and that it is intended by the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A load indicator comprising a signal mechanism adapted to be actuated from a non-indicating condition to an indicating condition and a bimetallic element adapted to be electrically positioned in an electrical circuit, said bimetallic element movably responsive to overcurrents in said circuit to actuate said signal mechanism, shunt means automatically operable substantially instantaneously subsequent to actuation of said signal mechanism to said indicating condition for shunting said bimetallic element whereby said overcurrents will substantially bypass said bimetallic element.

2. A load indicator comprising an indicating mechanism adapted to be actuated from a non-indicating position to an indicating position and a bimetallic element positioned electrically in series in an electrical circuit, said bimetallic element movably responsive to a predetermined electrical load level in said circuit to actuate said indicating mechanism to said indicating position, a shunt automatically operable substantially instantaneously subsequent to actuation of said indicating mechanism to said indicating condition shunting said bimetallic element to protect said bimetallic element from substantial overcurrents in said circuit.

3. A load indicator comprising an electric light circuit having an electric light bulb therein and a pair of engageable and disengageable contacts therein adapted respectively to close and open said electric light circuit to respectively put said electric light bulb on and off, said load indicator having a bimetallic element adapted to be positioned electrically in series in another electric circuit, said bimetallic element movably responsive to a predetermined load in said another circuit to cause engagement of said contacts, and shunt means operable subsequent to engagement of said contacts to provide a shunt path in said another circuit around said bimetallic element.

4. In a switch adapted to protect an electrical circuit from a substantial overcurrent, said switch having a movable bimetallic element positioned electrically in series in said circuit movably responsive to a substantial overcurrent in said circuit, said switch having a signal mechanism and a pair of closed contacts positioned electrically in series in said circuit, said bimetallic element adapted to first actuate said signal mechanism, and then to open said contacts in response to a substantial overcurrent in said circuit, means automatically electrically shunting said bimetallic element to protect said bimetallic element from a substantial overcurrent in said circuit and for automatically electrically closing said circuit substantially instantaneously subsequent to opening of said contacts whereby said switch operates only as an overcurrent indicator.

5. In a circuit breaker adapted to protect an electrical circuit, said circuit breaker having a movable bimetallic element adapted to be positioned electrically in series in said circuit and movably responsive to overcurrents in said circuit, said circuit breaker having an indicating mechanism operable in response to movement of said bimetallic element, said circuit breaker having a pair of closed circuit breaker contacts positioned electrically in series in said circuit disengageable in response to movement of said bimetallic element, said bimetallic element adapted to actuate said indicating mechanism prior to disengagement of said contacts, shunt means automatically operable subsequent to disengagement of said contacts whereby substantial overcurrents in said circuit will substantially bypass said bimetallic element and said contacts substantially instantaneously subsequent to disengagement of said contacts for retaining said electrical circuit closed whereby said circuit breaker will operate only as an overcurrent indicator.

6. A load indicator having a movable bimetallic element disposed electrically in series in an electrical circuit movably responsive to overcurrents in said circuit, said load indicator having a signal mechanism actuatable in response to initial movement of said bimetallic element, said load indicator having a pair of closed contacts disposed electrically in series in said circuit adapted to be mechanically opened upon further movement of said bimetallic element, flexible conductor means electrically interconnecting said contacts whereby said circuit is electrically closed even though said contacts are mechanically opened, and shunt means operable subsequent to opening of said contacts whereby overcurrents in said circuit can substantially bypass said bimetallic element substantially instantaneously subsequent to mechanical opening of said contacts.

7. A load indicator for an electrical apparatus, said load indicator having a movable bimetallic element disposed electrically in an electrical circuit portion of said electrical apparatus and movably responsive to an overcurrent in said circuit portion, said load indicator having an indicating mechanism actuatable in response to movement of said bimetallic element upon passage of an overcurrent therethrough, said load indicator having a pair of closed contacts disposed electrically in said circuit portion, said contacts disengageable from each other in response to movement of said bimetallic element upon passage of an overcurrent therethrough, said bimetallic element and contacts disposed electrically in series in said circuit portion, said indicating mechanism actuatable prior to disengagement of said contacts, a ilexible conductor interconnecting said contacts for prohibiting electrical arcing therebetween during disengagement thereof, and a shunt shunting said bimetallic element, contacts and flexible conductor substantially instantaneously subsequent to disengagement of said contacts whereby an overcurrent in said circuit portion will substantially bypass said bimetallic element, flexible conductor, and contacts, said flexible conductor and shunt maintaining said circuit portion closed despite disengagement of said contacts.

No references cited.

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