US2665347A - Electric circuit breaker - Google Patents

Description

1954 R. c. INGWERSEN ELECTRIC CIRCUIT BREAKER 2 Sheets-Sheet 1 Filed May '24, 1952 INVENTOR. a

Jan. 5, 1954 Filed May 24, 1952 R. c. INGWERSEN ,665,347 ELECTRIC CIRCUIT BREAKER 2 Sheets-Sheet 2 INVEN TOR. 773%.?! fj/ijh q f.

Patented Jan. 5, 1954 ELECTRIC CIRCUIT BREAKER Richard Castle Ingwersen, Jackson, Mich., as-

signor to Mechanical Products, Mich a corporation of Michigan Inc., Jackson,

Application May 24, 1952, Serial No. 289,742

This invention relates to electric circuit breakers of the kind which comprise a hollow casing in which a thermal element adapted to be responsive to the heat of the conducted current is mounted for movement with respect to a relatively fixed abutment contained Within the casing along with fixed and movable contacts corresponding to a circuit, the opening of which is effected automatically upon the occurrence of current of a predetermined value, due to the thermal element freeing itself from engagement with its abutment and releasing the movable contacts to move to open position.

In connection with circuit breakers of the above kind the split casing construction is required in order to permit the thermal element, contacts and associated parts to be assembled in operative position, but the problem arises how to mainta n the casing construction as simple and inexpensive as possible ing shall be able to withstand the forces set up within the casing due to arcing when the circuit is suddenly broken upon the occurrence of the current overload. These forces are quite pronounced, as is appreciated by those skilled in the art, and are attendant with the evolvement of gases and flame due to the arcing condition mentioned. Also, in connection with these circuit breakers having oppositely disposed fixed and movable contacts enclosed within a casing, arcing occurs upon the circuit being suddenly broken at the contacts and gives rise to a flow of flame and gases in a magnetic loop-like path, from which it is desirable that the conductors carrying the fixed contacts, in particular, should be protected in order to by erosion.

It is an object of the invention to provide a circuit breaker of the above kind with an improved casing construction which has a baffling eiTect upon the arc to shield the fixed contact carrying conductors against the direct effect of the arc and in which, additionally, the thermal element is also protected against the direct action of the arc.

These, and other objects and advantages of the invention, residing in the construction, arrangement and combination ofparts will be more clearly realized from a consideration of one practical form of the invention, by way of example, with reference to the accompanying drawings, in which:

avoid damage to the conductors yet provide that the cas- 2- Claims. (Cl. 200-416) W and securing screw occupy in the assembled condition of the parts,

Fig. 2 is a longitudinal section of a circuit breaker and casing assembly according to Fig. l but with the parts completely assembled and taken in a plane corresponding to the line a-a Fig. 1 is an elevational view looking upon the inside of one half of the casing of the circuit breaker according to the invention, with the separate metal parts, instead with the abutment in Fig. l, the contacts, thermal latch and plunger parts being shown in elevation,

Fig. 3 is a transverse section on the line b--b of Fig. 1, and

Figs. 4 and 5 are transverse sections on the lines cc and dd of Fig. 1, with the thermal latch and associated parts removed.

In the drawings, the casing construction is shown composed of two similar semi-cylindrical casing sections i and 2 of insulating material, which sections define a longitudinally extending split 3 in the casing and are 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 6, in which there are mounted a pair of diametrically spaced fixed contacts I, 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 8 comprises a thermal latch assembly presenting oppositely disposed substantially U-shape bimetallic parts it! united by integral bridge portions 1 l upon which portions the movable contacts l2 are mounted for engagement with their companion fixed contacts I.

The unit 8 is slidable relatively to the plunger 9, with the parts i 3 located upon opposite sides of the plunger and adapted to have releasable latching engagement with abutment ledges 13 (Fig. 1) secured upon the plunger. These ledges are preferably provided by separate metal L-shape parts secured upon the plunger 9, as by a rivet it. By providing the abutment ledges l3 upon of directly upon the plunger, undue wear upon the plunger is avoided, it being appreciated that the plunger itself is formed from insulating material.

ihe unit 8 is held stressed into engagement ledges 13 by the action of a pair of coil springs l5 connected between the bridge portions ii and laterally protruding ears 16 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 I with their abutment ledges I3. It is to plunger farther out of the corresponding casingi end when the latch parts Ill are disengaged from the ledges I3. automatically, due to the bi-metallic nature-of the parts I0 and their distortionunder themiiuence of the heat of the conducted current, and will occur when the current reaches a pre-determined value, corresponding to that "for which the bimetallic parts III have been calibrated and which may be, for example, 15, 20, or

amperes; V i L The plunger is provided'with a band'porti on 213, which extends outside the casing when the plunger end i9'is projected, v as stated, and, by being distinctively colored, for example, serves to give avisible indication that the circuit has been broken. I V

Mounted upon'tlie plunger there is a washer 2'I, which seals again'stthe insideof'the central opening 22 in the'ca'sing' end wall 23 when the circuit is broken andservesto seal that opening against the escape therethrough of the'attendant electrical arc' and the evolved flame and gases. An-additional seal is provided by a washer 2'4 retained between the casing end wall 23 and the end'cap'l;

, The sealing washer 2 4", by'ext'ending across and covering'ltheu'ppe' ends of the split 3, serves to seal thecasing interior against the'escape of the aforesaid evolveda rc gases and name;

Theend" cap tisdeforined at its inner end, as by spinning, to permanently embracethecasin'g' shoulder 25; as'indicated at26.

The other end cap Sis shown rorme with a' screw: threaded rskirt portion" 21, screwed into,

position u'ponithe corresponding screw threaded end portion 2 8 of the combined" casing" sections; and adaptedfor screwing into "operative position with respect to a socket (not shown) containing the main" electric supply terminals of the circuit 50 to which the circuit breaker is required to be applied, and f with which supply terminals electrical connectionis maintained by a terminal end cap 29;

Thecasing sections I and 2, alongtheir longitudihally'opposed edge surfaces, are formed with complementary, elongated recesses 30', which define" longitudinally extending channels 3I" in which electrical conductor strips 32 and 33 are accommodated, the conductor 33 being in elec;

trical conducting relationship to the terminal end cap 29, and the'other conductor strip 32 being in electrical" conducting relationship'with' respect w the screwed cap portion 21.

These conductor strips are fixed in position within-the" casing, and' carry the fixed contacts I; As app ears'clear in Fig: l, in particular, the channels 3i are of tortuous form, and the conductor strips are correspondingly shaped; As a result, such'portion of the evolved arc gases and name as may seek to escape along these conductor strips within their respective channels will be constrained to follow a correspondingly tortuouspathandthereby baffle their flow to the outside of the casing.

Such disengagement takes place" It is to be noted that the fixed contacts I are carried upon end portions 34 of the conductor strips which are bent inwardly in opposite directions into substantially arcuate form, as shown in Fig. 3, to dispose their fixed contacts i in diametrically spaced relationship and as remotely as possible from the casing split 3. It is also to be noted'withrespect to Figs; 3 and-4j-in particular, that the casing inteiior-is formed with inwardly projected wall portions 35 which present wall surfaces 36 in proximity to the curvedly bent portions}? of the conductor strip portions 34. Thesecasingwall portions 35 and their wall surfaces 36 are of particular importance and serve the purpose ,of protecting the portions 31 of the cated. However, the wall surfaces-36 are-also located in said path, immediately ahead'o'f their respective conductor strip portions 31- and, accordingly, said wall surfaces serveas baflles to' prevent the arc name and gases 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 scorching? upon these Wall surfaces upon arcing" occurring. On the other hand, erosion occurred when the baffis were not present. i

Protection from the direct efi'ect of the arcing is provided with respect tothe bimetallic latch portions It by fitting thebri dgeportions I I with surface plates 38 av n side persons 39 which overlie the pper ends ofthe latch portions ID, as seen in Fig. 3-, in particular, and thus conceal the latch portions'frorn lthe direct effect of such arcing, which, as" concerns these latch portions, must nr's'thit'a ainstfthesurface plates 3 8L In operation, withthe parts as shown in Figs, 1 and 2', the" circuit is closed atQth contacts i and IZand'curi'ent can befcon'diicted from the conductors- 32 and: 3 3', through the closed COIl-r tacts and the series connected U shape latch parts It. I

A's the'latch" parts It! become heated by the conducted current they will" distort laterally outwards from their position of contact with their abutment ledges It and, in' theev'ent the overload current value is'r'ea'ched, will distort to such extent that the latch pai'tsdis'engag e these'ledge s; When this happens the unit" a will immediately move downwardly (as seen in Figs. 1 and 2) by the action of the coil springs I5 and cause the circuit to be broken suddenly at the contacts I and' I2. The resulting a'rc will be dissipated withinth'e casing by the combined action of the seals 25 and 24} the bafiiewallsf 36, the surface plates 38 and tortuous channels 3], preventing contacts? with the latch parts also re-positioned 5 for operation to break the circuit upon the reoccurren e of an overload.

Having thus described my invention what I claim as novel and wish to secure by Letters Patent is as follows:

1. In an electric circuit breaker having current overload protection, casing structure defining a cylindrical interior space, a pair of fixed contacts disposed in said space in diametrically spaced relationship, conductor strips carrying said fixed contacts, said conductor strips including end portions enclosed in said casing and opposite end portions extending transversely into said space from diametrically opposite locations on said casing and exposed in said space, said opposite and exposed conductor end portions extending in oppositely directed bent relationship to their said casing locations and terminating in spaced relationship within said space on a diameter substantially perpendicular to said casing locations with said bent conductor portions substantially following the cylindrical contour of said space, said fixed contacts being carried at said terminating conductor ends, movable contact means mounted within said casing space,

said movable contact means including spaced contacts positioned to engage with said fixed contacts and incorporating electrically conductive thermal latch means operable to hold said movable contact means closed with respect to said fixed contacts but automatically operable to free said movable contacts to move to open position upon the occurrence of current overload, said movable contact means bridging the space between said fixed contacts, and said fixed and movable contacts being so disposed, when closed, as to give rise to a substantially circular magnetic arcing path when the circuit is interrupted at said contacts, and are baiile means within said casing space, said are bafiie means being located between the said transversely bent exposed conductor portions adjacent the said casing locations and the terminating ends of the conductors carrying said fixed contacts so that said baflie means lie within the said arcing path.

2. An electric circuit breaker as claimed in claim 1, said baiile means being constituted by Wall portions on said casing projecting into and extending longitudinally of said space, said wall portions presenting wall surfaces located between the fixed contact on one said conductor and the portion of th other conductor where this conductor portion enters into the said space from a said location, said Wall surfaces having a longitudinal extent greater than the longitudinal extent of the space occupied by said exposed conductor portions and the closed fixed and movable contacts.

RICHARD CASTLE INGWERSEN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,378,648 Maseng June 19, 1945 2,459,629 Dorfman et al. Jan. 18, 1949 2,506,796 Krieger May 9, 1950

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