US2053972A - Circuit breaker - Google Patents

Description

Sept. -8, '1936.

J. W. SEAMAN CIRCUIT BREAKER Filed May 4, 1955 z may; ES

. iiilunnlm i I, A

n II I Inventor: Joseph W. Seaman,

9 Hmttorneg Patented Sept 8, 1 93s SAES AFN? @FFHQ General Electric Company,

New York a corporation of Application May 4, 31935, Serial No. 19328 8 illaims.

My invention relates to circuit breakers, more particularly to circuit breakers provided with circuit interrupters of the compression chamber type and has for an object the provision of a simple, reliable and inexpensive circuit breaker of this character.

Heretofore circuit breakers having interrupting devices of the compression chamber type have been provided with thermal releasing means ar- 10 ranged to trip the circuit breaker upon the occurrence of an overload, and a manually operable handle for opening and closing the circuit independently oi the thermal releasing means. A circuit breaker of this type, which combines the protective features of a fuse and the advantages of a manually operable switch, is described and claimed in a copending application of Ludwig S. Walle, now Patent No. 2,07,842, issued July 14, 1936.

V The circuit breaker disclosed in the above Walle patent is arranged to interrupt overload currents without the emission of flame or are gases, and without noise, by enclosing the contacts in a sealed pressure-resistant chamber of at restricted volume. The contacts move within the sealed chamber so that when an arc is drawn between the separating contacts, a rapidly increasing gas pressure is generated within the chamber., This pressure may be of the order of 1000 pounds per square inch and since the resistance of the arc increases rapidly with pressure,

the resistance of the arc becomes so great as the pressure is built up that the arc can no longer exist and it is extinguished. While this circuit breaker provides satisfactory circuit interruption under various operating conditions, it has been found that when the circuit breaker is utilized to interrupt direct current circuits, there is some tendency for the arc to hang on between the contacts for an appreciable interval, which may of course be undesirable.

The interrupting qualities of a breaker of this type when applied to direct current circuits may be improved by increasing the efiective length of the gap between the contacts when the contacts are in their open circuit position, but the problem is complicated by the fact that breakers of this type, especially when applied to panelboard installations, are considerably limited so far as physical dimensions are concerned. For this reason it has been found'impracticable to provide the movable contact with a long enough stroke to obtain the length 01. gap between the contacts which is necessary for the best operation and accordingly, resort must be had to other ((Jl. wit-Md) methods of increasing the effective length of the gap between the contacts.

It has heretofore been proposed in connection with various types of circuit breakers to provide means for establishing a magnetic field adjacent 5 the point of separation of the contacts, the resulting reaction between the magnetic field and the arc stream causing the arc to be attenuated to such a degree as to effect extinguishment thereof, and I have found that the application of suit- 10 able magnetic blowout means to a circuit breaker having an interrupting device of the compression chamber type will render the circuit breaker capable of quickly interrupting a direct current circuit. 15

In order appreciably to aiiect the arc, the strength of the magnetic field must be of considerable magnitude and accordingly, resort has heretofore been had to electromagnetic means connected either in multiple circuit or in series 20 circuit relation with the contacts for producing a suitable blowout flux in connection with power switches or circuit breakers. Such electromagnetic blowout means, however, are unsuitable for application to circuit breakers of the type de- 25 scribed in the above-identified Walle application, due principally to the losses which occur in a winding connected in circuit with the contacts of the circuit breaker. Furthermore, the provision of an electromagnet winding capable of 30 withstanding the severe overload conditions to which circuit breakers of this type are subjected is prohibited by the physical dimensional limits of the circuit breaker. Therefore, much is yet to be desired in a circuit breaker of this type for 35 quickly interrupting a direct current circuit and accordingly, it is a further object of my invention to provide a circuit breaker having an interrupting device of the compression chamber type provided with means for producing a strong mag- 40 netic field adjacent the point of separation of the contacts.

In carrying out my invention in one form, I provide a circuit breaker provided with an interrupting device of the compression chamber 45 type and with magnetic means for establishing a strong magnetic field adjacent the point of separation of the contacts. More specifically, the interrupting device comprises a. sealed com pression chamber for enclosing a pair of rela- 0 tively movable contacts, the chamber having a volume such that high gas pressures are generated therein by the are formed between the contacts, and the magnetic means comprises a small permanent magnet mounted adjacent the 55 r with certain parts broken away more clearly to compression chamber of sufficient strength to tional per cent up to about 10% cobalt, the remainder of the composition being iron. As set forth in the Ruder patent, such an alloy may have a coercive force of about 460 gilberts per centimeter. Means are also provided for manually operating the contacts between open and closed circuit position, together with current-responsive means for operating the contacts to open circuit position upon the occurrence of overload conditions.

Although I prefer to use a permanent magnet formed from the above-described alloy, I have found that a magnet formed from the alloy described in Patent No. 1,947,274 issued February 13, 1934 to William E. Ruder, will provide a satisfactory blowout flux. This alloy consists of about 6% to 15% aluminum, about 20% to 30% nickel, the remainder of the composition being iron, and has a coercive force varying from about 330 to 350 gilberts per centimeter.

For a more complete understanding of my invention, reference may now be had to the drawing in which Fig. 1 is an elevational, sectional view of a circuit breaker embodying my inven-' tion; Fig. 2 is a plan view of the circuit breaker illustrate the parts below; Fig. 3 'is a sectional view taken along the line 33 of Fig. 1; and Fig. 4 is a view in exploded perspective of the permanent magnet and the supporting means therefor.

Referring now to the drawing, for purposes of illustration I have shown my invention as applied to a circuit breaker of the type described and claimed in a copending application of Winfield A. Atwood, now Patent No. 2,047,815, issued July 14, 1936. 'The circuit breaker shown comprises a base ll] of molded insulation for supporting an operating mechanism and an arc interrupting device" of the compression chamber type which interrupt-device is mounted in an enclosure Ii formed integrally with the base Ill. The interrupting device is preferably of the type described and claimed in the above-mentioned Walle patent andfor the purposes of the present invention, may be described as comprising a cylinder l2 formed of non-magnetic pressure-- resistant material such, for example, as .brass at the opposite ends of which are supported a pair of insulating bushings I3 and M. The insulating bushing l3 forms a closure for one end of the cylinder l2 and rigidly supports a fixed con-' tact member .I 5 which extends through the bushing i3 and is electrically connected to a conductor l6. Slidably journaled in the bushing 14 for reciprocal movement into abutting engagement with the fixed contact i5 is a movablecontact ll, the other end of which is electrically connected to a flexible conductor l8. Suitable sealing means (not, shown) are provided which cooperate with the movable contact I1 and the bushing l4 gas tightly to seal the compression chamber.

As fully explained in the above-mentioned Walle patent, when the movable contact H is operated to its open circuit position, an arc will be drawn between the contacts l5 and i1 and a pressure will be built up within the cylinder l2 so as quickly to extinguish the arc. However, as before mentioned, there is a tendency for the arc to hang on between the contacts when the circuit breaker is applied to direct current installations and in accordance with my invention, I provide a permanent magnet I9 made of a material having a high coercive force, such as previously referred to herein, for establishing a magnetic field adjacent the point of separation of the contacts in order to assist in quickly interrupting the circuit between the contacts l5 and I1. In order that the magnetic field established by the magnet IE! will exert a maximum displacing force on the arc, the magnet is disposed to establish a field substantially at right angles to the path of movement of the contacts. As shown, the permanent magnet I9 issubstantially U-shaped and is arranged with the legs of the U disposed in a pair of apertures 20 formed in a wall of the enclosure II, with the yoke of the U -shaped magnet resting on the portion 2| of the enclosure wall intermediate the apertures 20, the pole faces of the magnet I9 being preferably-curved, as shown, to correspond to the curvature of the cylinder'lZ.

In order fixedly to secure the permanent magnet IS in the position shown, I provide a bracket 22 having a portion 23 arranged to engage the yoke of the permanent magnet and a portion 24 which extends along the upper wall of the enclosure II and is secured thereto by a portion of the operating mechanismin a manner to be more fully described. An insulating member 25 is protending at right angles from the upper ends of.

the upright legs of the frame are a pair of outwardly extending projections 21 which are provided with ears 28 for engagement with projections 29 molded integrally with the enclosure Ii.

The frame 26 is secured to the base In in a position such that the vertical portion of the frame abuts a closure member 30 for the enclosure II.

Reciprocal longitudinal movement of the contact I1 is obtained by means of a pair of overcenter springs 3|, the upper ends of which are carried by a pair of projections 32 secured on opposite sides of a U-shaped operating member 33 pivotally mounted on a pin 34 carried by the frame 26. The opposite ends of the'springs 3| are secured to a pin 35 extending through an aperture in the movable contact 11 near its end. Carried by the U-shaped operating member 33 is an insulated handle 36 arranged to extend through a suitable aperture 31 in the circuit. breaker cover 38, and it will be seen that when the handle'36 is moved from the position shown in the drawing to operate the u-shaped member 33 in a counter clockwise direction about its pivot 34, the movable contact IT is operated from its open circuit position to its closed circuit position with a snap action. Similarly, when the handle 36 is returned to the position shown in the drawing, the movable contact l! is moved to its open circuit position with a snap action.

In order to insure reciprocal longitudinal movement of the contact ll, a member as is provided which comprises two parallel legs connected together by a cross portion 30, which legs are mounted on the pivot pin 3% with their lower ends 39a pivotally secured to the pin 35. Since the lower ends 3911 of the member 39 move in a curved path about the pivot 341, the opening in the movable contact member it through which the pin 35 extends is elongated in a vertical direction, i. e. in the direction of the pivot pin 36 so that sufficient lost motion is obtained in a vertical direction to provide for free movement of the pin 35.

As shown, the operating mechanism includes means for operating the movable contact to its open circuit position in response to overload current conditions, which means comprise a bimetallic element ll connected in circuit with the circuit breaker contacts so as to be heated by the current passing through the breaker. Upon the occurrence of an overload, the bimetallic element M is heated suihciently to flex away from a latch '32 which is supported by a tripping member 63 mounted on the pivot pin 36. As more fully described inthe above-referred to Atwood patent, the tripping member $3 is provided with a portion arranged to engage the cross member 30 extending between the legs 39 and with a notched portion which is engaged by a rod, one end of which is indicated by the reference numeral Ji l. A compression spring encircles the rod M and has one end normally engaging a stop member 16 cooperating with the extending portions 2l l of the frame 26, the other end of the compression spring 45 being arranged to engage an enlarged portion (not shown) on the rod 516. When the latch d2 is engaged by the bimetallic element M as shown in the drawing, the spring 45 is restrained under compression and when the latch 32' is released, the rod M will be moved to the right as viewed in Figs. 1 and 2, to operate the tripping member 63 in a counterclockwise direction about its pivot 36 to engage the cross portion ill] on the member. 39, which member, it will be remembered, is connected to the movable contact ll, and thereby oper= ate the contact to its open circuit position.

As shown in Figs. 1 and 2, the portion 2a of the supporting bracket 22 is clamped between the stop member 46 and a wall of the enclosure it so as to secure the permanent magnet 59 in the position shown. While various shapes of permanent magnets may be employed and various arrangements for mounting the permanent magnet can be resorted to, the arrangementshown' is considered highly preferable. With the permanent magnet arranged externally of the compression chamber, as shown, a single line of circuit breaker bases, compression chambers and operating mechanisms may be manufactured for both alternating current and direct current application.

In order to adapt the circuit, breaker for direct current application, it is necessary only to insert the magnet I9 into the apertures 20 with the portion 23 of the bracket 22 engaging the yoke of the magnet, and then to clamp the bracket to the enclosure I I by mounting the operating mechanism and the frame 26 on the base l8. For alternating current operation, the magnet l9 and the supporting bracket 22 are simply omitted, and it will be seen that the apertures 20 detract neither from the appearance of the circuit breaker nor from its operating characteristics.

While I have shown a particular embodiment of my invention, it will be understood, of course, that I do not wish to be limited thereto since many modifications may be made and I, therefore, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

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

l. A circuit breaker for interrupting currents of short-circuit magnitude comprising a pair of relatively movable contacts, means for operating one of said contacts through a relatively short range of movement between open and closed circuit positions to provide a relatively short interrupting gap between said contacts, walls of pressure-resistant material enclosing said contacts to form a sealed compression chamber, said chamber having a volume such that high gas pressures are generated therein by the arc formed between said contacts, the diameter of said chamber being such as to permit substantial lateral movement of said arc, and means including a permanent magnet supported externally of said chamber for producing a magnetic field adjacent to said gap substantially at right angles to the path of movement of said one contact, whereby said are is moved laterally from said gap and thereby elongated, the elongation of said are and the high gas pressures within said chamber cooperating quickly to extinguish said arc.

2. A circuit breaker for interrupting currents of short-circuit magnitude comprising a pair of relatively movable contacts, means for operating one of said contacts between open and closed circuit positions, walls of pressure-resistant material enclosing said contacts to form a sealed compression chamber having a volume of such magni tude that high gas pressures are created by the arc when said one contact is moved from said closed to said open circuit position and means including a permanent magnet supported on an external wall of said compression chamber for producing a magnetic field substantially at right angles to the path of movement of said one contact adjacent the point of separation of said contacts.

3. A circuit breaker forinterrupting currents of short-circuit magnitude comprising a pair of rela-- tively movable contacts, means for operating one of said contacts between open and closed circuit positions, walls of pressure-resistant material enclosing said contacts to form a sealed compression chamber having a volmne of such magnitude that high gas pressures are created by the arc when said one contact is moved from said closed to said open circuit position, a U-shaped permanent magnet disposed externally of said chamber with the pole faces of said magnet adjacent one field adjacent the point of separation of said contacts.

4. A circuit breaker comprising a pair of contacts one of which is movable between open and closed circuit positions, walls of pressure-resistant material enclosing said contacts to form a sealed compression chamber having a volume of such magnitude that high gas pressures are created by the arc whensaid one contact is moved from said closed to said open circuit position, means for operating said one contact between said open and said closed circuitpositions, means ineluding a permanent magnet for establishing a magnetic fieid adjacent the point of separation of said contacts and means including a bracket for supporting said permanent magnet on a wall of 5 said compression chamber, said bracket being secured by a portion of said operating means.

5. Acircuit breaker comprising a base having a portion forming an enclosure, said enclosure having a pair of apertures in a wall thereof, a compression chamber within said enclosure, a pair of relatively movable contacts within said compression chamber, said chamber having a volume such that high gas pressures are generated therein by the are formed between said contacts, means for operating one of said contacts between open and closed circuit positions, a portion of said op erating means being disposed adjacent said apertured wall of said enclosure, a U-shaped permanent magnet arranged with the legs thereof disposed in said apertures in said enclosure wall, and means clamped between said operating means and said enclosure wall for securing said permanent magnet in said apertures. 6. A circuit breaker comprising a pair of contacts one of which is movable between open and closed circuit positions, walls of pressure-resistant material enclosing said contacts to form a compression chamber, and-means including a permanent magnet for producing a magnetic field adjacent the point of separation of said contacts, said permanent magnet comprising an alloy consisting substantially of 6% to 15% aluminum, 12% to nickel an appreciable quantity up to about tacts one of which is movable between open and closed circuit positions, walls of pressure-resistant material enclosing said contacts to forma compression chamber, and means including a permanent magnet for producing a magnetic field adjacent the point of separation of said contacts, said permanent magnet comprising an alloy consisting substantially of about 6% to 15% aluminum, about 20% to 30% nickel, with the remainder substantially iron.

JOSEPH W. SEAMAN.

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