US2520257A - Thermally operated secondary breaker - Google Patents

Description

Aug. 29, 1956 R. R. PITTMAN ETAL 2,520,257

THERMALLY OPERATED SECONDARY BREAKER Filed June 28, 1945 3 Sheets-Sheet l INVENTORS Aug. 29, 1950 R. R. PITTMAN EIAL 4 2,520,257

THERMALLY OPERATED SECONDARY BREAKER Filed June 28, 1945 s Sheets-Sheet 2 1950 R. R PITTMAN EI'AL 2,520,257

THERMALLY OPERATED SECONDARY BREAKER Filed June 28, 1945 3 Sheets-Sheet 5 Fig. 5

Mun:

TO LOAD Patented Aug. 29, 1950 THERMALLY OPERATED SECONDARY BREAKER Ralph R. Pittman, Park Hill, and Carroll H. Walsh, Pine Bluff, Ark.

Application June 28, 1945, Serial No. 602,056

Claims.

This invention relates generally to circuit breakers, and in particular to an outdoor type of low voltage breaker adapted for use in connection with the secondary windings of outdoor distribution transformers.

Among the objects of the present invention may be noted the provision of an outdoor type of secondary breaker construction adapted for mounting on the bushing terminal of an outdoor transformer, and suitable for manipulation with a linemans switch hook; a secondary breaker having an operating characteristic coordinated with the heating characteristic of an associated transformer; a breaker having a latch lever of semaphore type for visibly indicating when the breaker has automatically opened; a breaker having a snap-action movement when manually opened; a breaker having a trip-free mechanism; a breaker embodying a contact movable about a double pivoted mounting to provide high contact pressure and fast opening movement; a breaker having a. resilient stationary contact normally under high pressure to provide energy for opening movement. an integral portion of the stationary contact being formed to provide an arcing contact; and a breaker of simple design, rugged strength and inexpensive construction.

Heretofore secondary breakers have been combined with outdoor transformers, the most popular arrangement being one in which an indoor type of breaker is mounted inside of the transformer tank. This arrangement has the serious defect of inaccessibility, so that inability to close the breaker for any reason renders the transformer use ess until it is disassembled and the condition remedied. For example, a breaker inside of a transformer tank and submerged in hot oil cannot be reclosed until the whole mass has cooled, even if the load is reduced, if the necessary thermally-responsive element is embodied in the tripping mechanism. In the meantime, serious results due to the long attendant service interruption may occur. Attempts have also been made to mount housed indoor breakers on the outside of the tank of the transformer, resulting in an expensive construction unadapted to the service requirements. So far as we are aware, no satisfactory outdoor type of secondary breaker having the important advantages present in our invention and necessary to meet the service conditions, has been heretofore constructed.

With the above objects in view, our invention resides in the novel features of design and disposition of the various constituent elements, and in the novel apparatus provided by our combination of our breaker with an outdoor transformer, and the scope of the invention will be indicated in the appended claims.

An embodiment of the invention is illustrated in the accompanying drawing, in which: Fig. 1 is a side elevational view of the breaker, shown partly in section; Fig. 2 is a sectional View of the breaker, taken along the line 2-2 of Fig. 1; Fig. 3 is another sectional view of the breaker, taken along the line 33 of Fig. 1; Fig. 4 is another sectional view of the breaker, taken along the line 44 of Fig. 1; Fl". 5 illustrates the com bination breaker and transformer, showing the breaker in the open position; and Fig. 6 fragmentarily illustrates in plan the supporting and connecting structure.

Referring to the details of construction illustrated in Figs. 1 through 4, a block 26, of weatherresistant insulating material, such as porcelain, has mounted thereon the metal supporting member l3, by means of the bolts 21. The supporting member I3 embraces respective opposing sides of the block 25, and is formed to provide a pair of arms i4 and !5, extending in parallel relationship downwardly and outwardly beyond the block 26. The member [3 also extends upwardly above and across the top of the block 26 in vertical spaced relationship therewith. Preferably the supporting member I3 is formed as a U-shaped piece from a flat strip of copper, the respective arms of which are rigidly bolted to the block 26.

The bayonet-type terminal It] extends downwardly through the top of the supporting member E3, the flange l l resting on the bushing insulator l2, the latter serving to insulate the terminal I!) in its passage through the member [3. The bimetallic current-responsive element, shown more clearly in Fig. 3, extends horizontally outward beyond the block 25, from the terminal ill. The bimetallic element includes the bimetallic strip ll, one end of which is connected to and supported by the lower end of the terminal H] by the nut l8, and the other end of which is connected to and supported from the supporting member [3 by means of the bolt I9, the nut 20, and the metal spacing washer 2!. At its outer end, the latch detent 23 extends along the unfastened end of the strip H, being rigidly attached thereto by the rivets .22, and insulated therefrom by the insulating material 24, which is conveniently formed from a strip of mica. The bimetallic element is so arranged that the latch detent 23 moves upwardly when the strip bends in response to heating. If desired, the cover l6 may be provided over the bimetallic element.

At a point spaced from the supporting member 53, a stationary contact support 3! is mounted at the rear of the block 26, by means of the bolt 2?; and the nut 32, the head of the bolt 29 being positioned a substantial distance within the block 26 in the recess 28. The stationary contact support 3i extends both downwardly and upwardly along therear side; of the blocki'zt beyond the nut Swan-d is provided with a threadedopening at its upper end, through which a set screw 32 is extended to engage the rear surface of the block 25,-for the purpose of adjusting:theposition-oi the downwardly extending portion of the support 3i. The stationary contact 33, conveniently formed from a looped strip of resilientconducting material, such as Phosphor bronze, is mounted on the support 3| by means of the rivets t l extending outwardly and forwardly therefrombelowthe lower end of the block 26. For convenience --of connection, the stationary contact support 3! extends-below the stationary contacttt, and at its -lowerend 'is provided with the load terminal 53.

-Aiatch-lever -25, =1ormed as- -a semaphore, is

" 5 straddlesand is pivotally mounted on the latch lever for rotary movement about the pivot" 53,

the latter extending laterally from-eaclnside of "the-latch lever 25 at a -point slightly-above and inwardly-with respect to the pivot 58. The-rela- -.tionship-oi the pivot points t and i8 is suchthat -the: inwardly-extending portions-3E and 3? or the movable contact engage and resiliently deform -.-thestationary contact- 33 when: thelatch lever 25 is in=the normal. position'in engagement with the latch detent rii. The-resilient stationary contact :is-so= forme'd -'-that when deformed-a pressure acting, outwardly and upwardly is provided tending to concurrently rotate both the-latch lever 2 5 about the pivot point 68 and the movable -contact-about thepivot points 43. Normally the engagement of the: latch lever 25. with the detent 23 ef the loiinetallio element restrains rotative movement or the latch lever -25, and engagement .of the movable contact withthe-pivotal-mounting' of the latch lever restrainsrotative movementof the movable contact.

A-pair of aligning washers 'lll ail-dd"? maintain the:alignment-of=-the movable contact with respect to the: stationary contact, and the spring-4G is arranged to continuously urge the movable contact and latch lever to' jack-knif-e to the rela- -tive positions-shownby the broken lines of Fig. '1, ..or the solid lines in Fig. 5.

' Ihe lower most ends of-thearms-l t and i5 are joined and held in the desired spaced relationship =by means-of the spacing-sleeve, through which is --extended the bolt ll. The sleeve 49 also provides a stop-:to limit'movement of the-movable contact, for the purpose of preventing engage- -ment with the terminal 53. If desired, the flexible conductors 44 and '45 -may'be utilized to directly electrically connect the movable contact to the supporting member l3.

AS shown in Figs. 1 and 2,.an integral portion 35 of the stationary contact-33 extends outwardly beyond the face of the contact between the-legs.

The movable contact, in-'-' the breaker in the tripped-open position, which "might-1 651116 from an overload on the transformer w nding supplied through the load conductors 59 andlll. In this construction the bushing termi;nal*;5'i is insulated from the tank wall Ed by means of the bushing as, and the breaker is both supported irom and connected to the bushing terminal El by clamping the bayonet terminal it of the breaker bet een the eye bolt 58 and the terminal 5'5 (Fig. 6).

current path-through the: breaker when in --close'd -position is irom the terminal ill to -the bimetallic strip lithence to themechanism supportl, thence through the flexible conductors l l and 55 to the movablecontact, thence through thestationary contact to the other terminal 53. .W hen. a predeterminedcurrent passes through the breaker, the bimetallic e?ement moves upward at its outer end, releasing the latch lever =2-for rotativemovementabout itspivot ls. Under the bias of the resilient contact the movable contactznoves abou'rits pivot 43 concurrently with itsinovenient substantiallyendvvise bodily away from thestationary-eontact 38 about the pivot res, the breaker assumingthe tripped-open; position indicated by the-broken lines of-Fig; 1. Con --.cui=r-ent -ly the "spring d etlects the jack-knifing of-thelatch leverilii w .i-respect tothe movable contact, and the latchlever. semaphori-cally indioates tliat the breaker has automatically tripped to the open-position. While not-essential to oper- -ation; it is desir-able that the-bimetallic element be suchthat i-ts heating --character-istic parallels closely that or the associated transiormer.

To-reelose-the breakerethe eyefi? be urged upwardly-withalinemansswitch hook until the latch lever-again engages the-bimetallic element, ass-hown in Fig. 1,-and then'pu-lled down to engage-and seat the contacts. lil'hile the movable contact and the latchleverare in folded position, the -=contacts can-not be engaged, I because the "movable contact is sufiicientlyretracted to prevent contact engagement. The contacts are "therefore not engaged as the latch lever is latched -to the bimetallic element, but onlywhen'the eye-:52 is pulled downafter'latchingthe latch lever. "In the eventthat an excesseurrentpasses -throug-h the-breaker 'atthe instant of --ccntact, the downward pullis in the direction to I urge the breaker to open position. Since'the spring ill-continuously urges the movable contaotto fol'dagainst the latch lever, the reaker is'tri-p free-for the reason that contacts cannot be engaged if these elements-are in folded-position,

' and cannot bemaintained in any-other position unless latched to the bimetallic element.

ibis-desired to-manuallyopenthe breaker, thisis accomplishedby urging theeye' fl upwardly until the contact-ends of the movable contact pass downwardly over-center ofthe iace of the stationary contact, at ---which time the spring All-opens the breaker with snap action. 'Thelatch lever doesnotrnove -when--the breaker is manually opened.

It -may be seen that-our --breaker 1 is ---of such with rotary movement ofsaid movable con" about the pivotal mounting of the latter to on simple and ruggedfconstruction'that the components may be readily formed of common ini organic materials, such as porcelain, copper and copper alloys, and for this reason is an effective outdoor type-of device for the purpose requiring no container, and functionally capable of accomplishing the objectives Stated above.

It is intended that the description and drawing of the preferred embodimentof the invention herein presented will be regarded as illus- 'trative rather than limiting.

We claim, as our invention:

1. A secondary breaker comprising relatively 'movable contacts including a resilient stationary -.lever, pivotally mounted atone end and releasably engaged with said current-responsive element the otherend, means pivotally mounting said movable contact on said latch lever adjacent said one end and relatively remote irom the other end, said latch lever being urged to rotary'move ment through its pivotal connection with said movable contact when said' inovable contact engaged With said resilient stationary contact and rotating about said one end concurren y circuit position in response to the occurrence of a predetermined current through said current- .responsive element. r 2. A secondary breaker comprising a of insulating material, a supporting member of conducting material fastened at the respective of said block, said supporting member extending upivar ly therefrom and across the top of said block in spaced relationship therewith and downwardly forwardly beyond the lower end of said block, a terminal extending downwardly through the top of said supportin member in insulated relationship therewith, a bimetallic element connected in series relationship between said terminal and said supporting member, a contact support fastened at the back of said block and extending downwardly therefrom, a resilient stationary contact carried b said contact support, a latch lever pivotaily mounted on the forwardly extending portions of said supporting member and normally extending upwardly to engagement with said bimetallic element, a movable contact pivotally mounted on said latch lever and normally engaging said stationary contact, said latch lever being normally urged for rotary movement by said stationary contact through said movable contact and released for rotary move-- ment in response to a predetermined movement of said bimetallic element.

3. A secondary breaker comprising a block of insulating material, a supporting member including a pair of outwardly and downwardly ex tended arms embracing and fastened to said block, a contact support fastened to said block in spaced insulated relationship with said supporting member, a bimetallic element carried by said supporting member, a resilient stationary contact mounted on said contact support, latch lever pivotally mounted between the extended arms of said supporting member and extending upwardly to normally latched engagement with said bimetallic element, a movable contact iii-- cluding a pair of legs straddling said latch lever and normally extendin to engagement with said stationary contact, said movable contact being pivotally mounted on said latch lever adjacent to and above the pivotal mounting of said latch lever, the arrangement being such that both said latch lever and said movable contact rotate about the pivotal mounting of said latch lever concurrently with the rotation oi said movable contact about its pivotal mounting on said latch lever under the bias of resilient contact when said latch lever is unlatched.

4. In a secondary breaker having a pivotally mounted latch lever normally releasably latched to a bimetallic element, a resilient stationary contact, a movable contact having legs straddling said latch lever pivotally mounted thereon and extending to engagement with said resilient contact, said resilient contact normally urging said movable contact toward rotary movement about both pivotal mountings in a direction away from said resilLent contact, the movement about the pivotal mounting of the latch lever being normally restrained by engagement with said bimetallic element and the movement about the pivotal mounting of said movable contact being normally restrained by engagement of a portion thereof with the pivotal mounting of said latch lever.

In a secondary breaker having a pivotally mounted latch lever, a resilient stationary contact having an outwardly-curved face, a movable con act extending on each side of said latch lever pivotally mounted thereon, said movable contact extending inwardly to engagement with sai s atlonary contact so that said movable contact is urged for movement in one direction away from said stationary contact bout both pivotal mountings, and means normally restraining said movement of said movable contact, the pivotal mounting of said movable contact being so related to said resilient contact that said movable contact passes over-center along and disengages said resilient contact when said movable contact is rotated in the direction opposite to said one direction, and resilient means urging the movement of said movable contact in said opposite direction to provide snap-action opening when said movable contact passes over-center of the face of said sationary contact.

6. In a circuit breaker having a pivotally mounted latch lever normally releasably latched to a current-responsive element, a stationary contact. a movable contact pivotally mounted on said latch lever and normally extending to engagement with said stationary contact, one of said contacts being resilient and effective for rotating said movable contact in one direction away from said sta ionary contact when said latch lev r is unlatched for providing a trippedopen position. and means operat've in response to manual rotation of said movable contact from the engaged position in the oth r direction for providing a manually-O en position.

'7. In a circuit breaker having a pivo ally mounted latch lever normally releasablv latched to a current-responsive element, a stationary contact, a movable contact pivotally mounted on said latch lever and normally extending to engagement with said stationary contact, one of said contacts being resilient and effective for rotating both said latch lever and said movable contact in one direction when said latch lever is unlatched for providing a tripped-open position visibly indicated by the altered position of said latch lever, and means operative in response to manual rotation of said movable conztact; in the other direction without. movementloi said-latch lever for providing. a;;manua1ly:-,open :nosition.

;8.,-A secondary breaker comprising relatively :movable contacts including ;;a I deformable sta- 'tionary contact of resilient. conducting material, .;,acontact movable to engage-and deforma-said @stationary contact, said. stationaryv. c.0ntact when ,deformed providing theronly force urgingthe movable contact from closed to open-circuitupowsition, ;;and ;.latch. means including .a bimetallic sstrip =under tension-for normally restraining-the movement of; said movable contact to. the open position, said latchumeans releasing saidnmova- Jule-contact for actuation to the .open position-in :response to a predeterminedhending movement 10f said bimetallic strip.

,9. :A secondary breaker comprising -relatively :movable contacts includingaa deformable estationarycontact of; resilient conducting material, -:a contact movableto engageand-.deformisaid r stationary contact, said stationaryv'oontact. vwhen deformed acting to ;,urge said movable contact :Ifrorn closed :'to the onen position, --;adiustable .means for manual-1v regulating the-deformation;

cot maid; sta-ticnarv cont st, and latch meansdncluding a bimetallic strip under tension. fore-inormallv restrain ng the movement ,of. movable contact to the open; position, said lately-means releas ng said: movable contactfor BJCEEEEl-tiOILtO rand-:- a;-'-.movab1e ;contact cpresaedwegainstl timestationaryieontact :and; extending outwardlyrthere- 1 from. latch meansincludingo cbimetallieelement cnormally holding tsaid -movable1 contact I :16!!- gaged; pOSitiQIL; said 'latchmeanszincludingalfilfer apivotally-nmountedatone end thereo f,;the,,-other end of said lever releasably enga in i said obi- ..wmetallic element, said vmovablevcontact' being pivotally mounted on said lever:intermediategeits respective endsand: guided for: movement therewith to disengage said stationary oontactoingresponse to a predetermined :movement-Eofisaidbi- --metalllc element,=sald ;movable;-contact concurrently :pivoting about its; pivotal mountingsand :swingin away Iroinsaid stationarylcontact.

CARROLL H. IFWJAISH.

' 1 REFERENCES CITED Tnextollowing referencesnare of :rrecordeaingthe "file of this patent:

UNITED iSTATES"PATENTS Number =Name .Date

1,473,960 7 Johnson 7.--- "Nome-"13, 91923 2,053,916 Merk1e -;Sept.z 8.21936 a 2,145,375 Schultz 1 Joann-73 1, 1939 2,160,562 Pittman et a1. May 30,- 1939 2,250,165 =-Mitschrich JulyZZylSl 2,349,609 Brown .7 May;23,.l94 2,359,605 Bellou ..,.,.v.. &.OCt-f3, -1944 FOREIGN PATENTS Nun her Country Date 599,119 vGermany c.llune i25, 1934

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