US2047815A

US2047815A - Circuit breaker

Info

Publication number: US2047815A
Application number: US667855A
Authority: US
Inventors: Winfield A Atwood
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1933-04-25
Filing date: 1933-04-25
Publication date: 1936-07-14
Anticipated expiration: 1953-07-14
Also published as: GB454083A; FR772259A; FR48505E; US2053934A; FR47374E; US2047842A; GB483889A; US2053972A; GB420042A

Description

July 14, 1936. W ,1 ATWOQD` l 2,047,815

CIRCUITv BREAKER Filed April 25, 1933 E) His Attorney.

Patented July 4, 1936 UNITED STATES cmcm'r Bama Winfield A. Atwood, Lansdowne, Pa., assignonto General Electric Company. a corporation of New York Application Aprll'25, 1933, Serial No'. 667,855` v 9 Claims. (Cl. 200-116) My invention relates to circuit breakers, more particularly to circuit breakers of the type known as branch circuit circuit breakers which provide the protective features characteristic of a fuse as well as the additional advantages of a manually operated switch, and has for an object the provision of a simple, reliable and inexpensive circuit breaker of this character.

Heretofore, branch circuit breakers have been provided with a thermal release arranged to trip the circuit breaker upon the occurrence of an overload, and with a manually operable handle for opening and closing the circuit independently of the thermal release. However, much is yet to be desired in such circuit breakers hitherto proposed to replace fuses because of the fact that the arc has been extinguished by means'of magnetic blowouts and the like with resulting flame and arc gases. Inasmuch as branch circuit breakers, as applied to panelboards for the protection of lighting circuits, are called upon to interrupt currents of very considerable magnitude, it will be apparent that a considerable quantity of arc gases are generated and .that the flame of the arc is quite appreciable. Thesetwo features are very undesirable in circuit breakersfor household use. Furthermore. since the fuses which have hitherto been used accomplish this interruption of the circuit without spurts of llame, and without loud popping accompanying the interruption of an overload current of high magnitude, a satisfactory circuit breaker should also possess these advantages.

In carrying out my invention in one form thereof, I Iprovide a circuit breaker which is capable of interrupting overload currents of large magnitude without the emission of llame, or arc gases, and without noise, by enclosing the contacts in a sealed steel chamber of restricted volume. More specically, I provide a mechanism for both closing and opening the contacts with a snap action as well as one which opens the contacts with a snap action in response to overload current. The contacts move within the sealed metallic chamber so that when an arc is drawn between the separating contacts the pressure within the chamber increases quite rai'iidly.V

This pressure rmay be of the order of 1000 pounds per square inch. The resistance of the arc increases rapidly with pressure so that as the pressure is built up the resistance becomes so great that the arc can no longer exist, and it is extinguished.

For a more complete understanding of my invention, reference should now be had to the accompanying drawing wherein I have shown diagrammatically in Fig. 1 aside view, partly in section, ofA a circuit breaker embodying my invention; Figs. 2 and 3 show the different positions of the circuit breaker of Fig. 1, while Fig. 4 shows an end view of ithe circuit breaker of Fig. 1.

Referring to the drawing, I have shownv my invention in one form as applied to a branch circuit breaker suitable for lighting circuits. The breaker is mounted on a base I of molded insulation which forms a support for the operating mechanism as well as for the arc interrupter Il.

The arc interrupter or compression chamber Il is inserted within an enclosure l2 molded integrally with the base I0. 'Ihe particular form of arc interrupter or compression chamber II forms no part of the present invention, as it is fully described and broadly claimed in a copending application Serial No. 667,856 iiled April 25, 1933, Walle, entitled Circuit breaker and assigned to the'same assignee as the present invention. In the present application the compression chamber will be described by saying that it comprises a steel cylinder I4 within which a pair of insulating members or bushings l5 and I6 extend. The steel cylinder and the insulating members are so arranged as to provide a sealed chamber of relatively small volume. The contact, members I 'I and I8, formed of suitable arc-resisting material, are supported in spaced relation with the steel cylinder by the respective bushings .l5 and I6. When the contact I8 is moved to the open position relative to the stationaryV contact Il, the arc drawn between them causes a -rapid increase in the air pressure within the chamber.

In order to produce a strong and rigid construction, the bushings I5 and 'le are inserted into the ends of the steel cylinder. The' ends 0i the cylinder are then swaged over the extensions 2| and 22 so that a very rigid construction of the arc -chamber is produced. The stationary contact member Il is provided with screw threads 24 which cooperate with' a threaded member25 forming a part of a conductor 26. The insulating bushing I6 permits the reciprocal longitudinal movement of the movable contact member I8. A leather sealing washer is provided around the movable contact member I8, the washer being provided with an inwardly projecting cylindrical extension 3l which performs an important function in the operation of the circuit breaker. Since a certain amount of metal vapor is produced when the circuit breaker interrupts current of large magnitude, it is necessary to prevent this metal vapor from collecting on the movable contact member I8 where it may harden and interfere with successive operations of the circuit breaker. The leather washer with its inwardly extending projection tends to prevent this collection of metallic vapor and cleans off any loosely adhering particles when the contact rod passes through the washer when the breaker is opening the circuit. The washer furthermore assists in maintaining a substantially air-tight connection around the movable Contact member I8.

As soon as the arc is drawn between the contacts I1 and I8, the pressure within the chamber of the arc interrupter increases rapidly. The potential drop across the arc is not entirely dependent on the rise in pressure inasmuch as the cross sectional area of an arc is approximately proportional to the current. It is believed that the arc drop is approximately proportional to the inverse square root of the current. This characteristic of the arc, in addition to the rise in pressure in the chamber, causes a quick interruption of the circuit. Furthermore, since the rise in pressure with a given volume depends upon the magnitude of the current interrupted, it will be seen that A the greater the overload current the more quickly will the pressure rise to a point where the arc resistance becomes so great that the arc can no longer exist. This pressure also exerts an expulsive action on the movable contact I8 'accelerating its movement to the open circuit position.

Continuing with the operation of my invention, the operating mechanism-is supportedl from the base I0 by means of a U-shaped support or frame 45. Extending at right angles from the upper ends of the upright legs of the frame are a pair of outwardly projecting extensions 46, which extensions are provided with notches 46m for engagement with'projections 41 molded integrally with the enclosure I2. The frame is secured, by screws 48 extending'through the base Il), in a position such that the vertical portion 49 of the frame abuts a closure member 50.' The frame, therefore, performs the functions of maintaining the closure 50 in place, supporting the operating mechanism and absorbing the blow incident to the expulsion of the movable contact I8 from the compression chamber.

The reciprocal longitudinal movement of the contact member I8 is obtained by means of a pair of over-center springs 52, which springs have their corresponding upper ends carried by prov 'ections 54 secured on opposite sides of the operating handle 55. 'I'he opposite ends of the springs are secured to a pin 51 extending through an aperture in the movable contact I8 near its end. The operating handle 55 is secured to an inverted U-shaped operating member 55a which in turn has its legs mounted on the portion of a pivot pin 62 extending outwardly beyond the legs of the frame 45. When the operating handle is moved from its left-hand position, shown in Fig. v1,'to

its right-hand position, shown in Fig. 3, the movable contact I8 is moved from its open circuit' position to closed circuit position with a snap action. The reciprocal longitudinal movement of the movable contact I8 is insured by a member 60 comprising two parallel legs connected together by a mid-cross portion 60a, which legs are mounted on the pivot pin 62 while their lower ends are pivotally secured to the pin 51. Since the lower end of the member 60 moves in a curved f path about the pivot 62, 'the opening inthe movable contact member I8 through which the pin 51 extends is elongated in a vertical direction; i. e., in the direction of the pivot pin 62 so that suilicient lost motion is obtained in a. vertical direction to provide for freedom of movement of the 5 pin 51.

vIn case oi.' overload, a bimetallic thermal element 65,` which is U-shaped, as shown in Fig. 4, and connected in circuit with the switch contacts so as to be heated Vby the current passing through 10 the breaker, is caused to flex away from a latch 10 to permit a quick opening of the circuit. It

` will be observed that the latch 10 is supported by va tripping member 1I which is mounted on the pivot pin 62. The member 1I has Ia notch 12 into which extends a rod 13 into abutting relation with the member 1I. A compression spring 15 encircles the rod 13 and has one end normally engaging a stop member 16 secured to the extension 46 of the frame 45 while the other end is 20 arranged to engage a member 18 secured to the rod 13. As shown in Fig. 3, the contacts are..` closed and the tripping spring 15 is restrained under compression. As soon as the thermal `element 65 releases the latching member 10, it will be observed that the force exerted bythe tripping spring 15 is applied to the member 1I at the notch 12. This force urges the tripping member 1I in a clockwise direction around itsv pivot 62. The

lower end 18a of the tripping member 1I engages s'o'' clockwise direction quickly operates the contact 315 I8. to its open circuit position as shown in Fig. 2. An indication that the circuit breaker has been tripped is obtained by providing a projection 19 onthe tripping member 1I, which projection is located justl below the extensions 1Ia and 1lbl forming a part of the operating handle 55. An opening is provided' in the extension 1 Ib. The relative movement of the tripping member 1I from the positions shown in Fig. 3 to the'position shown in Fig. 2 brings a suitably colored portion on the projection 19 into registering relation with the opening 80 so that an indication is given that the circuit breaker has been tripped by an overload to its open circuit position. t i v In'order to close the circuit breaker, after it has been opened by overload as just described, the handle 55 is rst moved in a counter-clockwise direction from the on position shown in Fig. 2. An extension formed integrally with the operating member 55a. strikes the tripping 5 member 1 I and thereby rotates the tripping member in a counter-clockwise direction until the latching member 10 is again returned to the latched position as shown in Figs. 1 and 3. Again referring to Fig. 2, it will be seen that as co' the handle 55 is moved from the on position to the oil position, the over-center springs 52 cross the pivot pin 62 so that the biasl applied to the handle is in the direction to move the handle toward the oil? position. The bias of the spring 52, c5 applied through the handle to the tripping member 1I, tends to rotate the tripping member 1I towardsits rst or latched position. The eiIort required in resetting the breaker is therefore only the difference between thebiasing forces exerted 70- on the tripping member 1I by the

springs

15 and 52. The switch closing operation is then completed by operating the handle 455 in a clockwise direction to the position shown in Fig. 3. A secy ond projection 81 formed on the operating inem- 75 ber 55a strikes the frame I5 at the point indicated by the reference numeral 90 and acts as a stop for the operating member 55a.

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 modiications may be made, and I, therefore, contemplate by the appended claims to cover any such modications 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:

1. A circuit breaker comprising a stationary contact and a movable contact operable between open and closed circuit positions, an operating mechanism comprising a U-shaped frame having a pivot extending through its upper portion, a U-shaped operating member mounted on said pivot, a pair of spaced parallel arms having adjacent ends mounted on said pivot and having their other ends pivotally connected to said movable contact, said movable contact being provided with a slot to provide lost motion between said movable contact and said arms, an overcenter spring having its respective ends connected to said operating member and said movable contact for ope-rating said movable contact between open and closed circuit positions with a snap action, a tripping member mounted on said pivot and nesting between said spaced arms and said U-shaped member, a tripping spring normally biasing said tripping member from one position to a second position, a. bimetallic thermal element for latching said tripping member .I into said one position against the bias of said spring whereby upon the occurrence of an overload said thermal element releases said tripping member to operate said movable contact to said open circuit position under the inuence of said tripping spring.

2. 'I'he combination with a circuit breaker provided with a stationary contact and a movable contact, of an operating mechanism for operating said movable contact between open and closed circuit positions with a snap action, comprising a U-shaped frame, a pivot extending through the adjacent arms of said frame, a U- shaped operating member mounted on said pivot `nd embracing said frame, said operating member being provided with a stop and an extension forminga reset member, a pair of over-center springs having their opposite ends connected to said operating member and said movable contact for operating said movable contact with a snap action, a pair of parallel spaced arms having adjacent ends mounted on said pivot and nesting within the arms of said frame and having their other ends pivotally connected to said movable contact member, a cross member connecting said arms together, a tripping member pivoted to said shaft and nesting between said arms, said tripping member being arranged to engage said cross member, a tripping spring for biasing said tripping member against said cross member so as normally to bias said contacts to said open circuit position, a thermal element for normally latching said tripping member out of engagement with said cross member so that said operating member is free to operate said circuit breaker independently of said tripping member, said reset member being operable by said operating member into engagement with said tripping member to rotate the same against its bias into its latched position.

3. A circuit breaker comprising relatively movable contacts, an operating mechanism therefor comprising a frame having a pivot pin extending through its upper portion, an operating member mounted on said pivot pin, an operating arm having one end mounted on said pivot pin and its other end pivotally connected to one of said contacts, said pivotal connection being provided with a slot, an over-center spring having its respective ends connected ,to said operating member and said one contact for operating said contact between open and closed circuit positions with a snap action, a tripping member mounted on said pivot pin, a tripping spring normally biasing said tripping member from one position to a second position, a bimetallic thermal element responsive to the current in said switch for latching said tripping member into said one position against the bias of said spring whereby upon the occurrence of a predetermined current'in said switch said thermal element releases said tripping member to operate said movable contact to said open circuit position under the influence of said tripping spring.

4. A circuit breaker comprising a stationary contact and a movable contact operable between open and closed circuit positions, a frame having a pivot extending through its upper portion, an operating member mounted on said pivot, an arm having one end mounted on said pivot and its opposite end pivotally connected to said movable contact, said movable contact being provided with a slot to provide lost motion between said movable contact and said arm, an over-center spring' having its respective ends connected to said operating member and to said movable contacts for operating said movable contact between open and closed circuit positions with a snap action, a thermal element connected in circuit with said contacts, a tripping member mounted on said pivot having one portion arranged to engage said arm and a second portion for latching said member in one position and arranged to bel freed by operation of said thermal element, and a tripping spring normally biasing said tripping member from said one position to a second position 'whereby upon the occurrence of .a predetermined overload said thermal element releases said tripping member to operate said arm and said movable contact to said open circuit position, a third portion of said tripping member indicating the overload tripping of said circuit breaker.

5. A circuit breaker comprising a switch operating arm movable between open and closed circuit positions, a frame, means pivotally mounting said operating arm on said frame, a manually operable handle member pivotally mounted on said frame, an over-center spring connected to said handle member and to said switch arm for operating said switch arm between said open and closed circuit positions with a snap action, a tripping member pivotally supported on said frame, a tripping spring normally biasing said tripping member from one position to a second position, and current responsive means for hold-4 ing said tripping member in said one position against the bias of said tripping spring whereby upon the occurrence of a predetermined current said current responsive means releases said tripping member, said tripping member being arranged to operate said switch arm to said open circuit position under the influence of said tripping spring.

6. A circuit breaker comprising a switch member movablebetween open and closed circuit positions, an operating mechanism therefor comprising a frame, an operating arm, means pivotally mounting one end of said operating arm on said frame, means connecting the other end of said operating arm to said switch member, an operating member pivotally mounted on said frame, an over-centerpspring having its respective ends connected to said operating member and said switch member for operating said switch member between said open and closed circuit positions with a snap action, a tripping member pivotallysupported on said frame, a tripping spring normally biasing said tripping member from one position to a second position, overload current responsive means for holding said tripping member in said one position against the bias of said tripping spring whereby upon the occurrence of a predetermined overload said overload means releases said tripping member, said tripping member being arranged to operate said switch member toA said open circuit position under the influence of said tripping spring, and means operated by said operating member for engaging and returning said tripping member to said one position.

7. A circuit breaker comprising relatively movable contacts, an operating mechanism there- -for comprising a frame, an operating member pivotally supported on saidI frame, an operating arm one end of which is connected to one of said contacts and the other end of which is pivotally supported on said frame, an over-center spring having its respective ends connected to said operating member and to a point on said operating arm remote from the end supported on i said frame for operating said contact between open and closed circuit positions with a snap action, a tripping member pivotally supported on said frame, a tripping spring normally biasing said tripping member for movement from one position to a second position, overload means responsive to the current through said contacts for latching said tripping member in one position against the bias of said tripping spring whereby upon the occurrence of a predetermined current through said contacts said overload means releases said tripping member for operation from said one position to said second position, said` tripping member being arranged to engage said operating arm to operate said one of said contacts to said open circuit position irrespective of the position ofmsaid overcentr spring, and means operative by said operating member after said overload tripping of said tripping member for returning said tripping member'to said one position against the bias of said tripping spring.

8. A circuit breaker comprising a switch member movable between open and closed circuit posi-l tions, an operating handle movable between on and on positions, an over-center spring connected between said operating handle and said switch member for operating said switch member with a snap action to said closed circuit position when said handle is moved from said oiI to said on position, a tripping member, a tripping spring normally biasing said tripping member from one position to a second position, said tripping member when moved from said one position to said second position causing the operation of said switch member to said open circuit position irrespective of the position of said operating handle, and a connection between said handle and said tripping member for positively returning said tripping member to said first position when said handle is moved from said on to said off position, said over-center spring during a substantial portion of said movement acting in opposition to said tripping spring to minimize the eiort required to return said tripping member to said iirst position.

9. A circuit breaker comprising a switch member movable between open and closed circuit positions, an operating mechanism therefor comprising an operating handle movable between on and off positions, an overcenter spring one end of which -is connected to said switch member and the other end of which is connected to said operating handle forl operating said movable switch member between open and closed circuit positions with a snap action in response to movement of said operating handle between on and oil? positions, a tripping member, a trippingspring normally biasing said tripping member from one position to a second position, overload current responsive means for restraining said tripping member in said one position against the bias o! said tripping spring whereby upon the occurrence of a predetermined overload said overload means releases said tripping member for operation from said one position to said second position, and means operable by said tripping member to operate said switch member to said open circuit position independently of said overcenter spring, means operable by the movement of said handle from said on position to said oiI position for returning said tripping member to 50 4said-ane position, said over-center spring acting WINFEID A. A'I'WOOD.