US2689895A - Electric circuit breaker with spark sealed casing - Google Patents

Description

SePL 21, 1954 R. c. INGwERsEN 2,689,895

ELECTRIC CIRCUIT BREAKER WITH SPARK SEALED CASING Filed Jan. 19, 1953 3 Sheets-Sheet 2 I N V EN TOR. )FIL/:iard 6. J/(gh/arse/z 7. Mmm

SePt- 21, 1954 R. c. lNGwERsEN 2,689,895

ELECTRIC CIRCUIT BREAKER WITH SPARK SEALED CASING Filed Jan. 19, 1955 3 SheetsPSheet 3 Patented Sept. 21, 1954 ELECTRIC CIRCUIT BREAKERfWITH SPARK SEALED CAfSING Richard C. Ingwersen, Jackson, Mich., assignor toMfechanical Products, Inc., Jackson, Mich., ya

corporation of Michigan ApplicationJanuary. 1'9, 1953,. SeriaLNo. 331,769

(Cl. 200e-114) 6 Claims. 1.

T-his invention relates to electriecircuit breakers of the kindv which comprise a split .casing structure enclosingxed; and movable contacts, with-.the movable contacts being electrically connectedfwith a thermal latch device, which device is operative toA release the movablecontacts.to4 InoveV rapidly andgtutomatically toopen position` upon the occurrence of.'Gulf-:rentv overload or a short circuit. More` particularly, the invei'itionA relates to plug type thermalcircuit pro,tectorSfy foruse in a standard, Edison base iguseholder to,

provide overcurrentgand short circuit protection` for-branch and service circuitsand. comprising .av

casing composed of two semi-cylindricalca-sing.

sections of. insulating material ,held connected togetherin cylindricalplug form byiseparate endcaps .mounted over opposite end portions of the assembled casing-sections, These assembledcasr ing sections deline ahollow space within the casing, .in which space the xedand movable contacts are located, andx which. space is open -at oneend ofthecasing toa centra-l: .Opening.for-med)l inthe corresponding casing` end` wall and; end.. cap` for the passage oigan actuator plungenwhieh plunger is actuatable to re-set the thermal latch.

and close the movable cont-actsiagainst the.. xedr contacts;

In connection with these electric circuit break.- ers, it has beennecessary, in order toV satisfy Underwriters Laboratories requirements, tonde.-l votemuch attentionto the problem oreffectvely' sealing the casing against theegressrof: the elec.-

tric arc llame which occurs within the casina;

upon the controlled; circuit-being suddenly broken, at the xed and movable contacts. and, further, to .preventing thegases evolved, upon arcing occurring, from forming .an electrical. conductive path with respectto the outside of. the casing.

Itshould be pointed out here that the present invention is concerned withk acircuit breaker of. the above kind in. which the iixed and; movable contacts are located within a portion of the split casing. interior so that the electrical. arc: lecon.- centrated in such interior casing portion and comesinto contact with such. portion ot the. metal contactsv and their conductor strips as it; is not practically possible to. shieldk from the electrical arc. Further, when arcing Voccursthisfgiveszrise to internal pressure Ywhich .tends to'` burst openthesplit casing so thatythe arcevolved gases/tend to flow towards the casing splits and carryzwitgh. themparticles of the contacts andconductors resulting from volatilizing of themetal due to; the arc flame.. The portion` .of the .casing interiorin which this arcing and .attendant volatilizngaclll r tionoccurs is. encased by anv exteriorly appliedmetal end cap, which resists actualbursting apart of the casing sections, but whichmust be pro tectedagainst the possibility of setting upfwith g, thesaid particleladen gases anelectrically con-4. ductive path if the circuit breaker isto possess.

the-'necessary dielectric strength.

It isan `important.object of the` present invention, therefore, to providean electric circuit breaker of the above kind which has satisfactory dielectric strength between the interior contacts and `.the encircling end cap.

Itiswalso anobject of the inventionto provide an eleetriccircuit breaker ofA the above kind in whichfthe gasesevolved upon the occurrence ofv alcng are prevented from formingr an` electrin cally conductive path between the live contacts andthe encircling casing end cap.

Itis a further object. of; the invention to provide 4anvelectric circuit breaker-'of the above `kind in which the casing split is effectively sealed against. the escape of the arc llame and gases.

The above and further objects and advantag-esiof thefinvention, residing in the construc-v f tion, arrangement.l and combination ofy parts will become clearfrom a. consideration .ofil the follow--y ingv description of one practicalform of the invention, by way of example, with reference to the accompanying drawings, and from the. appended claims.

inthe drawings:

Fig. 1; isf a. perspective View of an electric cir-V cuit breaker. in accordance with the invention,

with an end portion of the casing.y andI corre.- sponding'end cap broken away to reveal the side Splitsealing means..-

lig`- 2 isan. elevational view looking upon the;

inslepfl one half of the casing of the circuit breaker according to the invention, with the other cas-ing half removedbut showing' the thermal latchand actuator plunger. in position and, intdottedlines, the position which: the end caps and` sealing washers occupy in. thev assembled condition of the parts,

l Fig. 3 is a Alongitudinal. section of. a. circuit breaker and .casing assembly accordingto Fig. 2 but with. the parts completely assembled and taken ina plane corresponding to the line rtf-a in Fig. 2, the` contacts, thermal latch andl plunger partsfbeing shown in elevation,

Fig. 4` is atransverse section on the line b-b OfEig: 2.,.

Figs.. 5; andl 6 are. transverse sections on the lines-cf-c and tif-lt,,respectivelys ofyEig. 2, with the thermal latch and l associated parts removed,

, Fig. '7 is a detail view, illustrating the sealing washer with diametral side split sealing iinger portions,

Fig. 8 is a perspective cut-away View of this circuit breaker, with the contacts closed, and

Fig. 9 is a similar View to Fig. 8 but with the contacts open.

IIn the drawings, the casing construction is shown composed of two similar semi-cylindrical casing sections I and 2 of insulating material, which sections when the casing sections are assembled together denne diametrically opposite longitudinally extending splits 3 on the opposite sides o1 the cylindrical casing, the casing sections being held in assembled relationship by a pair of end caps, indicated generally at 4 and 5.

The casing sections combine to form an enclosed interior chamber indicated generally at 6, in which there are mounted a pair of diametrically spaced fixed contacts l, and in which chamber there is also mounted a thermal latch and movable contact unit, indicated generally at 8, and an actuator plunger 9.

The unit comprises a thermal latch assembly presenting oppositely disposed substantially U-shaped bimetallic latch parts II) united by integral bridge portions II, upon which portions the movable contacts I2 are mounted for engagement with their companion iixed contacts l. The fixed contacts 'I and movable contacts I2 are located within an end portion 3a of the chamber E disposed adjacent the casing end wall 23 having the central opening 22 through which the actuator plunger 9 extends. An opening ib in the end cap Il provides for the passage oi the plunger with all round clearance, as seen in Figs. 1 and 3.

The unit Il is slidable relatively to the plunger 9, with the latch parts Ii] being located upon opposite sides of the plunger and being adapted to have releasable latching engagement with abutment ledges I3 (Figs. 2, 8 and 9) secured `upon the plunger. These ledges are preferably provided by separate metal L.shaped parts secured upon the plunger 9, as by a rivet I4. By providing the abutment ledges I3 upon separate metal parts, instead of directly upon the plunger, undue wear upon the plunger is avoided, it being appreciated that the plunger itself is formed from insulating material.

The unit 8 is held stressed into engagement with the abutment ledges I3 by the action of a pair of coil springs I5 connected between the bridge portions II and laterally protruding ears I6 at the inner end of the plunger. These springs are stressed when the unit 8 is moved relatively to the plunger 9 to engage the bimetallic latch parts I0 with their abutment ledges I3 as seen in Figs. 2, 3 and 8. It is to be noted that the parts Ill are electrically conductive. `When the contacts II and I2 are closed, and the circuit breaker is in circuit, the current ilow takes piace between the contacts, in series along the limbs of the U -shaped latch parts I0.

The plunger 9 is itself biased by a coil spring I8, which spring is compressed when'the latch parts Ill are engaged with their abutment ledges I3, but acts immediately to project the end I9 of the plunger farther out of the corresponding casing end when the latch parts I0 are disengaged from the ledges I3 as seen in Fig. 9.. Such disengagement takes place automatically, due to the bimetallic nature of the latch parts I0 and their distortion under the influence of the heat of the conducted current, and will oc- 4 cur when the current reaches a predetermined value, above that for which the bimetallic parts I0 have been calibrated, which calibration may be, for example, 15, 20, 25 or 30 amperes.

The plunger is provided with a band portion 20, which extends outside the casing when the plunger end I9 is projected, as stated, and by being distinctively colored, for example, serves to give a visible indication that the circuit, controlled by the circuit breaker, has been broken.

Fixedly mounted upon the plunger there is a washer 2|, which is formed and arranged to seal against the inside of the central opening 22 in the casing end wall 23 when the circuit is broken so as to seal that opening against the escape therethrough of the arc flame and evolved gases resulting from the circuit being suddenly broken at the contacts 'I and I2 due to the release of the latch parts I0 from their abutment ledges I3 and the action of the springs I5. An additional seal is provided by a washer 24 retained between the casing end wall 23 and the end cap 4. Yet a further seal is provided by a second sealing washer 25 having a disc portion mounted upon the washer 24 and formed with integral diametral finger portions 21 which are deformed to extend along and cover the portions of the longitudinal casing splits 3 which lie within the confines of the side flange 4a of the end cap 4. It is important to note that the flange 4a of the end cap 4 completely embraces that portion-of the casing which contains the chamber 6a in which the fixed and movable contacts are located and in which'arcing occurs. It is also important to note that the diametral linger portions 21 of the sealing washer 25 extend the entire extent of the inside of the end cap flange 4a and are deformed by this flange into firm and sealing engagement with respect to the portions of the longtiudinal casing splits 3 embraced by said cap flange. These finger portions 25 seal the casing slits against the possible egress of gases, resulting from arcing, and thereby prevent these gases, with metal particles carried thereby, from forming an electrically conductive path with the end cap 4.

The sealing washers 24 and 25 could be formed in one, if desired, and are conveniently formed from vulcanized fibre material. When formed in one the disc portion of the washer may be relatively rigid, the finger portions 21, however, being capable of deformation into their required sealing position over the said portions of the casing splits 3 when the end cap 4 is applied, as will be understood.

The end cap 4 is deformed inwardly at its inner end to permanently embrace the casing shoulder 25, as indicated at 26, this shoulder being located on the casing beyond the said chamber portion 6a.

The other end cap 5 is shown formed with a screw threaded skirt portion 21, screwed into position upon the corresponding screw threaded end portion 28 of the combined casing sections, and adapted for screwing into operative position with respect to a socket (not shown) containing the main electric supply terminals of the circuit to which the circuit breaker is required to be applied, and with which supply terminals electrical connection is maintained by a terminal end cap 29.

The casing sections I and 2, along their longitudinally opposed edge surfaces, are formed with complementary, elongated recesses 30, which define longitudinally extending channels 3l in which electrical conductor vstri-ps 32 and 433 I are :ac-v commodated, the conductor .33 being 'in -electrical conducting -relationship tothe terminal end cap 29, and the other conductor strip 3.2 'bei-ng in electrical conducting relationship with-respect to `the screwed cap portion 21.

These conductor strips are xed in position within the casing, and carry the fixed contacts 1. As appears clear in Figs. 2, f8 `and i9, the channels 3I are of tortuous form, and the conductor strips are correspondingly shaped. As ia result, such portion of the evolved. arc flame or flash as may :seek to escape along these conductor strips within their respective channels will Vbe lconstrained to follow a correspondingly'tortuous path so as thereby to bailie its flow to the outside of `the casing.

It is to be noted that the fixed contacts .1 vare carried upon Aend portions 3d of rthe conductor strips which are bent inwardly in opposite 4directions into substantially arcuate form, as shown in Figs. 4, 8 vand 9 to dispose their xed contacts 'I in diametrically spaced relationship and AVas remotely as possible from the casing split 13. It is also to be noted with respect vto Figs. 4 land. '5, in particular, that the casing interior is formed with inwardly projected wall portions 35 which present wall surfaces 36 in proximity to the curvedly bent portions 31 of the conductor strip portions 34. These casing wall portions S35 and their wall surfaces 36 are of particular importance and serve the purpose of protecting the portions 31 of `the conductor strips from the direct eect of the arc which occurs when the circuit is suddenly interrupted at the contacts 1 and I2. In this connection, and as will be appreciated by those skilled in the art, this varc will tend to follow a substantially circular or magnetic loop-like path in which the conductor strip portions (t1 are located. However, .the wall surfaces Sii are Yalso located in said path, immediately ahead of their respective conductor strip portions 31 and, accordingly, said wall surfaces serve as baffles to prevent the arc name or flash from striking against the otherwise exposed conductor strip portions and causing erosion thereof. That this is so has been proven in practice, by observing the occurrence of fscorching upon these wall surfaces upon arcing occurring.

Protection from the direct eiTect of the arcing is provided with vrespect to the bimetallic latch portions It by tting the bridge portions II with surface plates 38 having side portions 39 which overlie the upper ends of the latch portions It, as seen in Figs. 4, 8 and 9, in particular, and thus conceal the latch portions from the direct effect of such arcing, which, as concerns these latch portions, must rst hit against the surface plates 38.

In operation, with the parts as shown in Figs. 2 and 3, the circuit is closed at the contacts 1 and I2 and current can be conducted from the conductors 32 and 33, through the closed contacts and the series connected U-shaped latch parts It.

As the latch parts Ili become heated by the1 conducted current they will distort laterally outwards from their position of contact with their abutment ledges i3 and, in the event the overload current value is reached, will distort to such extent that the latch parts disengage these ledges. When this happens the unit 8 will immediately move downwardly (as seen in Figs. 2 and 3) by the action of the coil springs I5 and cause the circuit to be broken suddenly at the contacts 6 1 and I2. This movement `olf 'the unit i8 will vbe arrestedwhen the parts I.I come into-contact Withfiixed abutment surfaces 40 'formed within the split-:casing interior. be dissipated within the casing by the ,combined action of the seals v2I, 124, `25 `and '21, the baie walls 36, the surface plates 38 :and tortuous :channels 3|, preventing bursting of the casing I., '.2 andthe possibility of .any .exterior harmfuleifect. Withzthe opening of the contacts the plunger .S will immediately .snap 4outwards 'by the yaction of its spring. I8 and cause the indicator band 20 to be visibly .positioned outside the l:casing wall 23.

To.re-set the :circuit breaker it is merely necessary to push the plunger Sfinwards .to re-position the abutment ledges I3 with :respect tothe latch parts Ili, it being appreciated that the unit II! is held positioned for thisto take .place due to the engagement of parts Il with .the abutment surfaces 40. Release of the plunger then :allows the movable contacts I2 to re-engage their fixed contacts 1 with the latch parts f-also 11e-,positioned for operation to break the circuitfupon the reoccurrence of an overload.

-The disc portions of the sealing washers24 and 25., or the single .disc portion if the separate washer: 24 is dispensedwith, are formed with central openings 2.9 through which the plunger e9 is able to have a sliding t. These washers, however, extend completely over the :diametral splits formed in the casing end wall 2.2i and thus seal these splits upon the outside of said end wall.

The washer 2|, on the plunger t is shownin Fig. 4 as being of substantially.rectangularshape and as providing surface portionswhich will cornpletely cover the inner end lof the Aopening 22 provided for the passage of the plunger 9. and presented to the interior of said casing lchamber portion Ea. When the plunger is inthe set position, with the contacts closed, this washer 2l will be spaced inwardly from the said opening 22. However, it is found in practice that ,the action ofthe springs Yi5 upondisengagement of the thermal latch parts IB is so rapid that the washer 2 I lreaches the opening 22 to seal the same at the time'when arcing occurs due to breaking of the controlled circuit yat the `contacts 1 and I2.

Having thus ldescribed my invention, what l claim :as novel and wish to secure by .Letters Patent is as follows:

l. In an electric circuit breaker having a hollow casing formed by separate casing sections held assembled together by exteriorly applied end cap means, and including fixed and movable electrical contacts enclosed within a portion of said casing interior and circuit breaker mechanism operative to suddenly open the controlled circuit at said contacts upon the occurrence of current overload, whereby arcing occurs within the said casing portion at said contacts, the provision of means for sealing the end cap means with respect to the arc flame and evolved gases, said casing portion including an end wall with a diametral split and longitudinal splits on opposite sides of the casing portion and said end cap means including an end cap with a side flange completely embracing said casing portion and with an end wall covering said casing end wall, said sealing means including a portion covering said longttudinal casing splits, said sealing means being held enclosed upon the said casing portion by said end cap.

2. An electric circuit breaker as claimed in claim 1, said sealing means comprising an end The resulting '.arc ,will

portion mounted upon the outside surface of said casing end wall and covering the diametral split in said end wall and nger portions extending from the outer periphery of said disc portions at diametrically opposite portions thereof, said finger portions closing the portions of the longitudinal casing splits included within said end cap ilange.

3. An electric circuit vbreaker as claimed in claim 1, said sealing means comprising an end portion mounted upon the outside surface of said casing end Wall and covering the diametral split in said end Wall and iinger portions extending from the outer periphery of said disc portions at diametrically opposite portions thereof, said iinger portions closing the portions of the longitudinal casing splits included within said end cap iiange, said nger portions being deformed into sealing engagement over said longitudinal casing splits by the application of said end cap to the said casing,

4. In an electric circuit breaker having a hol low casing formed by separate casing sections held assembled together by exteriorly applied end cap means and including xed and movable electrical contacts enclosed within a portion of said casing interior and circuit breaker mechanism connected with the movable contacts to cause these contacts to move automatically and rapidly to open position upon the occurrence of current overload with the occurrence of arcing within said casing portion, said circuit breaker means including a re-set actuator plunger extending through an opening in one of the casing end walls and projectable through said opening upon the occurrence of current overload, said casing end wall having a diametral split and said casing having opposed longitudinal splits extending along opposite sides of the casing, the provision of means for baffling the flow of the arc iiame within said casing portion and for sealing the end cap means with respect to the arc flame and evolved gases, said means comprising baffle wall portions in said casing interior portion in adjacent relationship to conductor strips carrying said contacts and in position to shield said conductor strips from the direct action of the arcing flame, sealing means covering said casing splits on the outside of the casing, and sealing means on the plunger for sealing the said end wall opening on the inside of the casing when the said plunger is projected through the opening upon the occurrence of current overload.

5. In an electric circuit breaker comprising a hollow cylindrical casing formed by separate casing sections forming the casing with a diametral split across one end wall thereof and longitudinal splits extending along opposite sides of the casing, and including fixed and movable contacts enclosed Within a chamber portion of said casing which includes said casing splits, and circuit breaker mechanism connected to suddenly open the controlled circuit at said contacts upon the occurrence of current overload, whereby arcing occurs Within said chamber portion at the contacts, said casing having an end cap retaining portion defined on its exterior surface and including an end cap firmly embracing the end portion of the casing which includes said chamber portion, said end cap having an end wall covering the said casing end wall and a side ange which completely embraces the portion of said casing containing said chamber portion and is held secured upon the outside of the casing by the engagement of the flange with said dened end cap retaining casing portion, the provision of means sealing said casing splits with respect to the interior of said chamber portion, said sealing means being conned upon the exterior of said casing by said end cap and including an end portion sealing said diametral casing split and side portions sealing said longitudinal casing splits.

6. In an electric circuit breaker including a split casing with xed and movable contacts mounted within the casing and thermal means connected with the movable contacts so as to break the circuit at said contacts upon the occurrence of current overload or a short circuit, said casing having an exteriorly applied metal end cap holding the split casing together, the provision of insulating means over the casing splits and between the casing and said end cap, said insulating means preventing the end cap from forming an electrically conductive path with gases evolved within the casing upon arcing occurring when the current is suddenly interrupted at said contacts.

Name Date Wood 1 Feb. 12, 1952 Number

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