US2281743A

US2281743A - Circuit breaker

Info

Publication number: US2281743A
Application number: US347637A
Authority: US
Inventors: Louis M Brown
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1940-07-26
Filing date: 1940-07-26
Publication date: 1942-05-05
Anticipated expiration: 1959-05-05

Description

May 5, 1942. L. M. BROWN CIRCUIT BREAKER Filed July 26, 1940 3 Sheets-Sheet 2 INVENTOR LOL/Z5 MBTOZUH.

Air N Y WITNESSES:

:2J HV1/6 L. M. BROWNl May 5, 194".

. CIRCUIT BREAKER Filed July 26, 1940y latentcd May/5, 1942 cmourr nimma ,Louis M. Brown, wennen, N. 1.1,nhignor to Westinghouse Electric Manufacturing pany, East Pittsburgh, Pa.,

P'ennsyl Uoma corporation o Application July 26, 1940, Serial No. 347,637

11 (Cl. 23h-11B) The invention relates to circuit interrupters of the enclosed type, and more particularly' to enclosed circuit breakers which are totally immersed in a body of oil within an enclosing housing or tank.v c

Circuit breakers for use in hazardous locations where gasoline, naptha, lacquersolvent vapors, and 'other explosive materials are present, and also where corrosive gases are encountered are usually mounted in an enclosing housing or tank and totally immersed in a body of oil within the housing for' complete protection against the above-mentioned conditions. The total immersion of the circuit breaker in oil has heretofore prevented the use of conventional thermally responsive overload trip devices for such breakers because directconta'ct of the heater element of the thermalA unit with the oil destroys the thermal characteristic of the trip device. Moreover, providing a liquid tight casing for the breaker or its trip device is not practical from either an 'economical or operational standpoint.

An object of vthe-present invention is the'provision of a circuit breaker totally immersed in a body of oil within an enclosing housing and embodying athermally responsive overload trip device, the thermal vcl'ntracteristic of which is unaffected by the oil.

Another object of the invention is the provision of an explosion resisting or corrosion resisting circuit breaker apparatus comprising a circuit breaker having a magnetically responsive and a thermally responsive overload vtrip rdevice totally immersed in a body of oil within an enclosing housing with means for preventing the thermally responsive unit and its heater from being. in contact withthe oil.

Another object of the invention is the provision of an improved explosion resisting or corrosion resisting circuit interrupter as previously described which is simple, accurate and reliable in operation, and inexpensive to manufacture. y 2

The novel features that are considered characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to structure and operation together with additional objects and advantages thereof will be best understood from the following detailed description of one embodiment therof when read in conjunction with the accompanying drawings, in which:

Figure 1 is a vertical sectional view of the circuit breaker housing with the circuit breaker mounted therein, I

' Fig. 2 is another vertical sectional view of the apparatus taken at right angles to the section of Fig. l,

Fig. 3 is a fragmentary sectional view on an enlarged scale showing a portion of the circuit 00. end of the tank II support spaced vertical supporting bars 39.

breaker and tank, a part of broken away to reduce the width of the figure, Fig. 4 is a perspective view on an enlarged scale of the trip device of the circuit breaker, and

- Fig. 5 is an enlarged fragmentary sectional view showing the thermally responsive trip means and a portion of the electromagnetic trip means of one poleof the circuit breaker.

Referring to the drawings, the reference numeral-v l designates an explosion resisting and corrosionresisting circuit breaker housing which comprises an oil tight metal tank II and a cast metal top or cover 4section I3 Ywhich serves to the tank II and close the open end thereof. the cover section I3 by a plurality of captive bolts I5 and cooperating nuts I1, the bolts I5 being carried by brackets i9 secured to the tank I I in spaced relation around the upper end thereof. The bolts I5 are adapted to extend through openings provided therefor in the lugs 2| which are formed integral with the cover section I3 along the bottom edge, and the nutsv I1 are threaded on the upper ends of the bolts I5 to tightly secure the tank to the cover section I3. A gasket 23 is secured to the abutting edge of the cover section I3 to provide a tight seal at the joint between the tank and the cover section.

The rear wall of the cast metal c over section I3 is formed to provide a flat mounting base 2S which projects laterally beyond the sides of the housing, and the base is provided with a plurality of holes 21 for receiving bolts or cap screws to mount the housing on a suitable s upport. The top and side walls of the cover section I3 are provided with tapped holes' 29 for accommodating the incoming and outgoing electrical conductors which lead to the circuit breaker within the housing, it being understood that the electrical conductors are brought into the housing through conduits (not shown), the ends of which aresecured in the threaded openings 29.

A multipole circuit breaker indicated generally at 3| is disposed in a 'vertical position within the lower portion of the housing andfis supported from the cover section I3. The' circuit breaker is secured by mounting bolts 33 (Figs. 2 and 3). to a verticalmounting plate 35 which is in turn secured by brackets 31 to a pair of The supporting bars 39 are carried by the cover section fl, each bar being rigidly secured at its upper end to the cover section I3 by means of a pair of cap screws 4I. Y

The incoming electrical conductors 43 -and the outgoing electrical conductors 45 are held clamped in proper position adjacent the upper by a pair of transversely exthetonkbemg The tank I I is removably secured to tending clamping bars Il of insulating material which are secured at their ends bybolts 48 to a pairgof brackets 5| carried by the supporting bars 39. The

conductors

43 and 45 are also held clamped at a position in` back of the circuit breaker 3| by apair of insulating clamping plates 53 which are secured at their ends to brackets 55 carried by thesupportin'g bars 39. The conductors 43 are electrically connected to the three lower terminal studs 51 of the circuit breaker 3|, and the conductors. are electrically connected to three spaced terminalsy 59 carried by the mounting plate 35 below the center of the breaker.' The three terminals 59 are in t'i'-*ielectrically connected to the upper terminal 'studs 'BI of the circuit breaker by means of conducting straps 83.

The circuit breaker in the embodiment of the invention shown isv of the same general construc tion as the circuit breaker fully described' in Patent 2,047,739 of-Harry J. Lingai, issued July 14,

1936, and assigned to the assignee of the present invention.

Referring to Fig. 3, the circuit breaker, briefly, comprises a two part casing 65-'of molded insulating material having therein a stationary contact 61 and a cooperating movable contact 69 for each of the three poles. The movable contacts 69 are carried by switch arms 1| which are mechanically connected for simultaneous movement together about a common pivot 13 by means of an insulating tie bar 15. 'I'he switch arms are actuated by one overcenter spring mechanism at the center pole ot the breaker comprising a pair of toggle links 11 .and.19 connected to the center pole switch arm 1| and to a pivoted vreleasable carrier 8| which isl pivoted at 83 on a frame 85 secured to the base of the circuit breaker. A pivoted actuating member 81 is connected by overcenter springs 89 to the knee of the toggle for manually `actuating the circ'uit breaker.

The trip device 9| of the circuit breaker is mounted inthe upper end of the circuit breaker casing 65 and normally servesy to restrain the pivoted `carrier lever 8| in the latched position shown in Fig. 3. The trip device is operable inl response to an overload on any of the three circuits controlled by the circuit breaker to effect release of the carrier 8| and thus cause automatic opening of all of the contacts of the breaker. When the breaker is tripped, the actuating member 81 is automatically moved to a tripped indicating position intermediate its on" and oif positions. The circuit breaker mechanism is manually reset following tripping by movement of the actuating member 81 to its ofi' position to reset the carrier lever 8| to its latched position in which it is normallyA held by the trip device 9|.

The trip device 9| is a unitary structure entirely assembled upon its own insulating base 93 and is completely removable from the circuit v breaker casing 65, the screws 95 and bolts 6| being utilized to mount the trip device in the circuit breaker casing and also to make `the necessary electrical connections. The trip device includes a thermally responsive trip e1e' ment 91 and a magnetically responsive trip means for each of the three poles of the breaker.

The three conducting bars or strips 99, one of which is associated with each of the polesof the breaker have the quadruple function of providing terminals for the trip device, of providing energizing means for each of the electromagnetic trip means, of providing heater means for -the thermally responsive elements 91, and for providing a mounting means for the entire trip structure.

Each thermally responsive trip element 91 is composed of a strip of bimetallic material and is fastened by 'rivets to one of the conducting strips 99.

As shown particularly in Fig. 5, the conducting strips 99 are bent` so as to form two reflex bends |0| and |03. The straight part |05 of the strip 99 is utilizedv as a single turn conductor for energizing the magnetically responsive trip means, while the loop |0| is utilized as a heater for the thermally responsive trip element 91. The portion of the conducting strip 99 which is used in forming the loop 0| is tapered so as to give a conducting section of gradually increased electrical resistance, thereby forming a heater for the bimetal trip element 91. The straight portion |05 of the strip 99 is not of reduced section and does not heat appreciably while carrying the rated current of` the breaker. Each of the conducting strips 99 is fastened by rivets to a `:frame or bracket |01 which is, in turn, secured to the trip base 93.

The magnetically responsive trip means of each pole comprises a U-shaped core |09 (Fig.- 4) of magnetic material secured to the bracket |01, and a movable armature which is movably vmounted for movement toward and away from the core |09 by means of a guide pin I|3 secured to the armature ||I and slidably mounted in an opening provided therefor in a bracket |,|5 secured to the frame |01. The armature is biased yto unattracted position away from the core |091'by means of a spring ||1 interposed between the bracket I5 and a collar on the guide pinl I I3, as shown in Fig. 5. The straight portion |05 of the conducting strip 99 passes through the U ofthe stationary core |09 and thus forms a singleturn energizing winding for the electromagnetic trip means.

The. trip device includes a pivoted latch ||9 which is pivoted at |2| (Fig. 3) on -a bracket |23 carried on the lower side of the trip base 93, and this latch is biased to latching position in which it engages and restrains the releasable carrier 8| in latching position, as shown in Fig. 3. The latch ||9 has an upwardly extending portion which projects through an opening in the trip base 93 and which is adapted to be normally engaged and held by a latch projection |25 carried by a commonV trip bar |21 to thereby hold the latch ||9 in latching position. Q

The common trip bar |21 is of molded insulat- -ing material and is adapted to be actuated to eiect release of the latch H9, and thereby release of the carrier 8|, by any one of the individual trip devices. This trip bar |21 has two downwardly extending arms |29, one at each end, for engaging pivot pins `|3| which project through suitable openings in supporting brackets |33 mounted on the trip base 93 at each end. A second projection |35 of the trip bar extends downwardly therefrom and through the agency of a suitable recess engages a compression spring |31 (Fig. 3) which biases the tripbar |21 to latching position.

The heads of the armature guide pins 3 engage in notches provided therefor in the molded trip bar |21, thereby connecting the trip bar to each of the movable armatures for actuation thereby. Three adjusting screws |39I lthrough the corresponding pole.

each in a position to be engaged by the free end of one of the thermally responsive bimetal trip elements 91, thereby providing for actuation of the trip bar |21 by deflection of any one of the thermally responsive bimetal trip elements 91 when, the element is heated a predetermined amount by overload current. -A cover |4| of molded insulating material is secured to the upper end of the brackets |33 by fastening screws and this cover cooperates with the ,base 93 to form an enclosure for the trip device.

Each of the conductor strips 99 is connected at its upper-end to one of the upper terminals 6| of the circuit breaker, and is electrically connected at its lower end through the agency of a flexible shunt conductor |42 to the movable contact 69 of its corresponding pole. Thus each l electromagnetic trip means is energized by the vcurrent flowing through its correspondingpole and each thermally responsive trip element 91 is heated in response to the current The automatic operation of the circuit breaker is briefly as follows. When an overload current of more than a predetermined magnitude, for example, more than l times rated current, oc-

- curs in the circuit of any pole of the breaker, the

corresponding electromagnetic trip means is energized thereby a sufficient amount to pull its movable armature to attracted position and therebymove the trip bar |21 to effect release of the latch ||9 and the releasable carrier 8| of the circuit breaker. The release of the carrier 8| effects automatic opening of the circuit breaker,-

since the overcenter springs 89 immediately act to rotate the three switch arms 1| to open circuit position, and also effect collapse of the

toggle

11 and 19.

When an overload of less than the predetermined magnitude occurs in the circuit of any pole of the breaker, the bimetallic trip element 91 'of that pole is heated by the overload current and if the overload persists for a sufficient length of time to heat the bimetallic trip element a predetermined amount, the trip element deflects upwardly away from the circuit breaker mechanism to engage and move the trip bar |21, thereby effecting release of the circuit breaker mechanism and automatic opening of the circuit breaker in the manner previously described.

An operating means is provided for manually operating the circuit breaker 3| from outside of the housing 9. The operating means comprises an operating shaft |43 which projects through a side of the cover section |3-and is rotatably mounted on the cover section in a bearing |45 provided therefor. An operating handle |41 is rigidly secured to 4the portion of the operating shaft |43 which projects outside of the housing. The operating shaft |43 is provided with a crank arm |49 on the end of the Y shaft which projects inside of the housing 9, and this crank arm is mechanically connected by a link |5| to a transversely extending operating yoke |53 which is pivotally mounted at |55 on the vertical supporting bars 39. The operating yoke |53 straddles the circuit breaker 3| and is provided with a slot |56 which engages the breaker actuating member 81. The connecting link |5| is pivot-ally connected at |51 to the free end of the crank arm |49 and its other end is pivotally connected at |59 to one side of the yoke |53.

The operating shaft |43 has a close flt in the opening of its bearing' |45 and the length of the flowing engaged parts of the shaft, and bearing is sufficient to make the shaft opening flame proof or flame tight.

`A body of oil |6| is disposed within the tank to a level above the circuit breaker 3| so that the circuit breaker is completely immersed in the oil and the parts thereof are thereby protected from corrosion. The body of oil also prevents the arcs drawn between the contacts of the breaker upon interruption of the circuit from igniting any explosive gases or materials which may be present in the atmosphere surrounding the apparatus.

In order to prevent the oil within the housing from affecting the thermal characteristic of the thermally responsive means of the trip device, a diving bell |63 is provided which is mounted over the upper end of the circuit breaker 3|, as shown in Figs. l and 2. The diving bell |63 comprises,

carried by the vertical supporting bars 39. The f lower edge of the vessel |63 is disposed some distance below the trip device 9| of the. circuit breaker 3|, so that the vessel prevents the oil from rising up around the trip device, lby reason of the air which is trapped within the upper portion of the vessel |63, as indicated in Fig. 2. I t will thus be seen that the vessel |63 prevents the oil from coming in contact with the thermally responsive trip elements 91 and the heaters Ill'l of the trip device, thereby preventing the oil from affecting or destroying the thermal operating characteristic of the trip device. Since the trip device is disposed below the level of the oil, the parts thereof are not subjected to the corrosive action of the atmosphere surrounding the apparatus.

While the invention has been disclosed in accordance with the provisions of the patent statutes, it is to be understood that various changes in the structural details and form of elements may be made without departingfrom the essential features of the invention. It is desired, therefore, that the appended claims be given the broadest reasonable construction vthat is permissible in view of the prior art and the language of the claims.

I claim as my invention:

l. In combination, a circuit interrupter having relatively movable contacts and thermally4 responsive means hea-ted in response to thecurrent of the circuit and operable when heated a predetermined amount to cause opening of the contacts, an enclosing housing in which the cirsuit interrupter is mounted, said housing containing a body of insulating liquid in which the circuit interrupter with its thermally responsive means is totally immersed, and means for preventing the liquid from affecting the thermaloperating characteristics of said thermally responsive means.

2. In combination, a circuit breaker having relatively movable contacts and thermally responsive means heated in response to the current cf the circuit for causing automatic opening of the contacts when said means is heated a predetermined amount, an enclosing housing in which the circuit breaker is mounted, said housing containing a body of insulating liquid in which the circuit breaker with its thermally responsive means is completely submerged, and

means i'or preventing the liquid from coming in contact with said thermally responsive means.

3. In combination, a circuit breaker having K relatively movable contacts andk thermally responsive means heated in response to the current of the circuit which is operable when heated a predetermined amount to cause opening of saidcontacts, an enclosing housing in which the circuit breaker is mounted containing the body of insulating liquid in which the circuit breaker with its thermally responsive means is at least partially submerged, and a vessel closed at the top and sides and open at the bottom surrounding said thermally responsive means to prevent the liquid from coming in contact with the thermally responsive means.

4. In Icombination, a circuit breaker having relatively mov-able contacts and a trip unit including a thermally responsive trip element and a heating element therefor heated by -the current of the circuit, said thermal trip element being operable when heated a predetermined amount to cause automatic opening of said contacts; an enclosing housing in which the circuit breaker is mounted, said housing containing a body of insulating liquid in which the circuit breaker is at least partly submerged, and a vessel closed at the top and sides and open at the bottom surrounding said trip unit to prevent the liquid 'from coming in contact with said thermally responsive trip element and said heater element.

5. In combination, a multipole circuit breaker having a plurality of pairs of relatively movable contacts, actuating mechanism for said contacts, and a trip device mounted adjacent the upper end of the breaker having a plurality of thermally responsive trip means one for each of at least two of the poles of the breaker, each trip means being heated in response to the current owing through its corresponding pole and each being operable when heated a predetermined amount to cause automatic opening of the contacts of the breaker, an enclosing housing in which the circuit breaker is mounted, said housing containing a body of insulating liquid in which the circuit breaker with its trip device is at least partly submergedfand a vessel closed at its top and sides and .Open at its bottom sur- A rounding the upper end of said breaker and the trip device to prevent the liquid 'from coming in contact with said thermally responsive itrip means.

6. In combination, a circuit breaker having relatively movable contacts, operating means therefor, and a trip device operable in response to predetermined current conditions to cause automatic opening of said contacts, an enclosing housing in which the circuit breaker is mounted, said housing containing a body of insulating liquid in which the circuit breaker with its trip device is at least partly submerged, and a vessel closed at the top and sides and open at the bottom surrounding said trip device, the bottom edge of said vessel extending into said liquid below the surface of the Yliqui '7. In combination, a circuit breaker having relatively movable contacts, operating means therefor, and a trip device adjacent the upper end of the breaker operable in responsie to predetermined overload conditions to cause automatic opening of the contacts, said trip device including electromagnetictrip means energized by the current of the circuit operable to cause the current exceeds a predetermined magnitude, and thermally responsive trip means heated in response to the current 4of the circuit and operinstantaneous 'tripping of the breaker Whenever 75 able to cause tripping of the breaker when said thermally responsive means is heated a predetermined amount by overload current, an enclosing housing in which the circuit breaker is mounted, said housing containing a body of insulating liquid in which said breaker and its trip device are at least partly submerged, and a liquid tight hood open at the bottom disposed over the trip device for preventing the liquid from rising in contact with the heating portionsof the trip device.

8. In combination, a housing comprising a top section and a tank removably secured to said top section, a circuit breaker mounted in said housing and supported from said topl section of the housing, said circuit breaker having a trip device adjacent the upper end thereof including a thermally responsive trip means heated in response to the current of the circuit and operable when heated a predetermined amount to cause opening of the breaker, said tank containing a body of insulating liquid in which the circuit breaker with its trip device is completely immersed, and a liquid tight open bottomed vessel supported from said top section and surrounding the upper end of the breaker where the' trip device is located for preventing the liquid from coming in contact with the trip device and its thermally responsive trip means.

9. In combination, a circuit breaker havingy relatively movable contacts, and thermally responsive means heated in response to the current of the circuit which is operable when heated a predetermined amount to cause opening of said contacts, an enclosing housing in which the circuit breaker is mounted containing 'a body of insulating liquid in which the circuit breaker is at least partially submerged, and a, vessel completely closed at its top and sides and open at the bottom surrounding said thermally responsive means, the open 'bottom of said vessel extending into said liquid below the surface thereof.

10. In combination, a circuit interrupting device having means operable in response to predeterminedabnormal conditions of the circuit to cause said device to interrupt the circuit, an`

ing a thermally responsive means heated'in response to the current oflthe circuit and operable when heated a predetermined amount to .cause said interrupter to interrupt the circuit,

an enclosing housing in which said circuit interrupter is mounted, said housing containing a body of insulating liquid in which said circuit interrupterV and its thermally responsive means is submerged, and' a vessel closed at its top and sides and open at the bottom surrounding said thermally responsive means to prevent Vsaid liquid from coming in contact with said thermally responslve means.

LOUIS M. BROWN.