US2287875A - Circuit breaker - Google Patents

Description

June 30, 1942. o, GROBER 2,287,875

CIRCUIT BREAKER @Zh/7207 Graber yf @ln/ June 30, 1942. O. GROBER 287,875

CIRCUIT BREAKER Filed April 19, 1941 2 sheets-sheet 2 WITNESSES: INVENTOR Patented 30, 1942 I UNITED f s'rATlfzs;v 'PATENT ol-Fl'c 2,231,975 CIRCUIT BBEAKElL Othmar Graber, Berlin-Siemensstadt, Germany, assigner to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania l Application April 19, 1941, Serial No. 389,387

In Germany October 25, 1939 18 Claims. (Cl. 200-116) 'I'he invention relates to circuit breakers, and more particularly, to circuit breaker mechanisms of the manually and automatically operable tripfree type.

The prior art trip-free circuit breaker mechanism with which I am familiar utilizes linkages and lever systems connecting the actuating parts which are of relatively complicated forms and require very great precision in the manufacture thereof. Moreover, the mechanism requires a greater amount of space than is desired.

An object of the invention is the provision of an improved trip-free circuit breaker mechanism which is simple and compact and relatively inexpensive to manufacture.

YAnother object of the invention is the provision of an improved trip-free circuit breaker mechanism of small dimension and inexpensive construction which is accurate, safe in operation, and requires relatively light forces for the operation thereof.

In accordance with the invention, the movable switch actuating element and the element which releasably holds the actuating element in the closed position cooperate with each other through mechanical elements constructed as rollers.

The novel features that are consideredas characteristic of the invention are set forth in particular in the appended claims. 'I'he 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 when read in conjunction with the accompanying drawings, in which:

Figure 1 is a vertical sectional view of a circuit breaker constructed in accordance with the invention, the parts being shown in the circuitclosed position;

Fig. 2 is a vertical sectional view of the breaker similar to Fig. 1, showing the tripped-open position of the parts the instant the breaker has been tripped;

Fig. 3 is a vertical sectional View similar to Figs. 1 and 2, but showing the open position of the mechanism parts to which they are automatically reset following a tripping operation;

Fig. 4 is a transverse sectional View of the circuit breaker taken substantially along the line IV-IV of Fig. 1 and looking in the direction of the arrows; and

Fig. 5 is a plan view of the circuit breaker.

Referring to the drawings, the reference numeral 5 designates the circuit breaker housing lwhich comprises a sheet metal frame 'I having a front wall 9 and side walls which are secured in any suitable manner as by screws I3 to a base I5 o1' insulating material which forms the back wall of the housing. The housing 5 of the circuit breaker contains a resilient switch element |1 comprising a strip of resilient conducting material which carries a movable contact I9, a cooperating stationary contact 2|, a circuit closing member 23, a circuit opening member 25, a releasable element 2l for holding the switch element I1 in closed position, a movable latch element 29 for normally restraining the releasable element 21 in operative position, and a current responsive bimetallic trip e1ement3l which is operable in response to predetermined overload conditions to move the latch element 29 and release the circuit breaker mechanism.

The stationary contact 2| is carried by a terminal strip 33 which is secured to the insulating base l5 in any suitable manner. The resilient switch element Il is rigidly secured adjacent one end by rivets 3| to a bracket 35 which is, in turn, secured between the side walls of the frame 1. A conducting strip 31 secured to the resilient switch element l1 electrically connects the moving contact I9 to one end of the current responsive trip element 3|, the other end of the trip element 3| being electrically connected to a terminal strip 39 which forms the other terminal of the circuit breaker.

The current responsive trip element 3| comprises a bimetal strip which is U-shaped in plan as shown in Fig. 4. 'I'he legs of the U-shaped bimetal strip comprising the element 3| are secured to an angularly extending portion of the terminal strip 39, one leg being electrically insulated from the terminal strip 39 by an insulating plate 4l. This leg of the bimetal strip is electrically connected by the conducting strip 31 to the moving contact I9. The other leg of the bimetallic trip element 3l is directly electrically connected to the terminal strip 39. Thus the bimetal trip element 3| is connected in series with the contacts I9 and 2| of the circuit breaker so as to be traversed by the current flowing in the circuit controlled by the breaker.

The portion of the resilient switch element |1 adjacent the moving contact I9 is reversely bent back upon itself and provided with a depression 43 which engages an auxiliary roller 45. The roller 45 carries a pivot pin 41, the ends of which are guided in slots 49 provided therefor in the side walls with the frame 1. The roller 45 is thus guided for movement in a path parallel to the path of movement of the movlng contact I9. The resilient strip which comprises the switching element I1 is of substantial 81 relative to the end of the Abimetal trip elewidth and the roller 45 being only of slightly less width than the distance between the side walls of the frame 1 is thus maintained parallelto the side walls of the frame in its guided movement therebetween and moves freely in its guided path without anyr substantial frictional restraint by the side walls of the frame 1.

The circuit-closing member 23 comprises a yoke-shaped carriage which is guided for vertical movement within the frame 1 by means of lugs 5| which extend laterally from the spaced sides of the carriage 23 and engage in vertical slots 53 provided in the side walls of the frame 1. The carriage 23 carries a roller 55 which is mounted on the carriage for movement approximately parallel to the path of movement of the roller 45, i. e., toward and away from the stationary contact 2|, by means of ,a pivot pin 51 carried by the roller, the ends of which engage in a pair of slots 59 provided in the sides of the carriage 23. A push button 60 is secured to the outer end of the carriage 23 and projects through an opening provided therefor in the front wall 9 of the circuit breaker frame 1. Inward or closing movement of the carriage 23 is limited by a stop 6| provided on the side wallof the frame 1 which is engaged by the push button 6|! inthe closed position of the circuit closing member 23. A spring 63 mounted on a stud 65 of the frame serves to bias the circuit closing member 23 to the open position shown in Fig. 3.

The resilient switching element I1 is so shaped and mounted that its resiliency causes it to be biased to the open position shown in Figs. 2 and 3 with a predetermined force, and the movable switch element is adapted to be moved ment 3| is adjusted by means of an adjusting screw 89 to provide rfor adjustment of the thermal tripcharacteristic of the circuit breaker. When the bimetal trip element 3| is heated a predetermined amount by overload current, its free end deflects upwardly causing the adjustable element 81 thereof to engage and movel the pivoted latch element 89 in a clockwise direction to eect release of the pivoted releasable member 21. The release of the releasable member 21 causes automatic opening of the circuit breaker by reason of the fact that the circuit closing roller 55 is no longer restrained in closed position so that the spring bias of the resilient switching element I1 causes the switching element to be moved to open circuit position. In moving to open circuit position, the resilient switch element I1 moves the three rollers 45, 55 and 13 to the left or to the tripped position shown in Fig. 2 in which the pivots 41 and 51 of the rollers 45 and 55 are disposed at the left-hand end of their respective guide slots.

The circuit breaker may also be manually -opened by depressing the circuit opening member 25, which is guided for vertical movement within the frame 1 by means of lugs 9| which project laterally `from the circuit-opening member and engage in suitable slots 92 provided against its bias to closed-circuit position by the roller 55 of the circuit-closing member 23 when the circuit-closing member is manually depressed to closed position as shown in Fig. 1, providing the roller 55 is held at the righthand end of its guide slot 59.

The releasable member 21 is yoke-*shaped and pivotally mounted on a pivot pin 61 supported' between the side walls of the frame 1. The releasable member has an arm 69 which carries a rotatable roller 1| for cooperating with the circuit-closing roller 55. The roller 1| is mounted on a pivot 13 carried by the arm 69 and normally forms a iixed counter-bearing for the circuit closing roller 55 as long as the releasable member 21 is restrained in operative position by the latch element 29. The other arm 15 of the yoke-shaped releasable member 21 is normally adapted to be engaged by the latch arm 11 of the latch element 29. The latch 29 is pivotally mounted on a pivot 19 supported between the side walls of the frame 1. The releasable member 21 is biased in a counter-clockwise direction to its normal or operative position by means of a spring 8| which serves to reset the releasable member 21 to its operative position following a tripping operation of the breaker. The pivoted latch element 29 is also biased in a counter-clockwise direction to its latching position by means of a spring 83 which serves to automatically reset the latch element to its latching position immediately following a tripping operation.

The pivoted latch element 29 is provided with a projection 85 which is adapted to be engaged by an adjustable element 81 carried by the free end of the current responsive bimetal trip element 3|. The position of the adjustable element therefor in the frame 1. The circuit opening member has a push button 93 secured to the outer end thereof which projects through an l opening provided for the push button in the front wall 9 of the circuit breaker frame 1. The circuit-opening member 25 is provided with a cam projection 95 which is adapted to engage a projection 91 of the latch element 29 when the circuit-opening member is depressed to cause movement of the pivoted latch element 29 in a clockwise direction to its released position. This movement of the pivoted latch 29 to released position by depressing the circuit-openingmember 25 causes opening of the circuit breaker in the same manner described above for the automatic operation by the bimetal trip element 3|. The circuit opening member 25 is biased outwardly to a normally inoperative position by means of a compression spring 99 disposed between a projection |0| of the frame 1 and the bent outer end of the circuit opening member 25.

The operation of the circuit breaker is briefly as follows: To close the circuit breaker the circuit-closing member 23 is moved inwardly to closed position by manually depressing the closing push button 60. 'I'he roller 1| of the releasable member 21 being restrained in its operative position by the latch element 29, forms a fixed counter bearing for the circuit closing roller 55.

Consequently, the roller 55 rolls on the roller.

1| and also on the auxiliary roller 45, causing the resilient switch element I1 to be moved to closed position as shown in Fig. l, and after the dead-center position is passed, the roller 55 is held rigidly in closed position between the roller 1| and the auxiliary roller 45 of the switch element I1 by reason of the counter resilient force or bias of the switch element I1. The circuitclosing roller 55 passes its dead-center position when the pivot 51 thereof passes below a line joining the pivot 13 of the roller 1| and the pivot 41 of the auxiliary roller 45. The axis of rotation 13 of the roller 1| is disposed below a line joining the pivot axis 61 of the releasable member 21 and the axis of rotation 51 of the assaut circuit closing roller 55 in the closed position of the breaker.

When the current responsive bimetal trip element 3| is heated a predetermined amount byl an overload current, the free end thereof deiiects upwardly and engages and rotates the pivoted latch element 29 to the released position eii'ecting disengagement of the latch arm 11 from the arm 15 of the releasable member 21 to release the releasable member. Upon release of the releasable member 21, the resilient switch element I1 is moved to open position by its bias, causing movement of the auxiliary roller 45 and the circuit-closing roller 55 to the left-hand ends of their respective guide slots, and also movement of the pivoted. releasable member 21 to its released position, as shown Vin Fig, 2. In this position of the parts, the axis of rotation 51 of the circuit-closing roller 55 is disposed above, i. e., on the side o1' the circuit-closing member 23 of the line joining the axis of rotation 13 of the roller 1| and the point of contact between the auxiliary roller 45 and the circuit-closing roller 55. Under the spring action of the resilient switch element I1 and the return springs 63, 8| and 83, all of the elements of the circuit reaker mechanism are reset to their initial open position as shown in Fig. 3. The circuit breaker, however, cannot be reclosed until the current responsive bimetal trip element V3| has cooled and returned to its normal position to permit return of the latch element 29 to latching position by its return spring 83. The releasable member 21 must be restrained in its normal operative position by the latch 29 in order to form a fixed counter-bearing for the circuit closing roller 55, otherwise the circuit breaker cannot be closed or held closed. Thus the circuit breaker mechanism is entirely trip free.

The circuit breaker may be manually opened by depressing the circuit opening member 25. When the circuit opening member 25 is manually depressed to open the circuit breaker, the cam projection 95 thereof engages and moves the pivoted latch 29 to released position eiiecting opening of the circuit breaker in the same manner as when the current responsive bimetal trip element 3| operates to release the latch.

The invention provides an automatic trip-free circuit-breaker mechanism of. exceptionally small dimensions, and the frictional resistance between the parts of the mechanism is much smaller than in the case of linkage mechanisms heretofore used. Due to the low frictional resistance of the parts, the amount of force required to both open and close the circuit breaker is materially decreased as compared to the prior art linkage constructions. The mechanism is particularly safe in operation because of the extremely small frictional resistance, and the danger of inadvertent jamming or catching of the mechanism parts is much less than in the prior art linkage constructions. Moreover, the invention provides a circuit breaker mechanism which is much simpler and less expensive to manufacture than the prior art circuit breakers which use linkage connections between the actuating parts. The prior linkage connections have relatively complicated forms and require very great precision in manufacture. g

While the invention has been disclosed in accordance with the provisions of the patent statutes, it is to be understood that various changes ,l in the structural details and arrangement of the parts may be made without departing from some of the essential features of the invention.

I claim as my invention:

1. A circuit breaker comprising a switching element movable to open and to closed-circuit position to open and to close the circuit, said switching element being biased, to open-circuit position, a movable operating member having a rotatable roller for moving the switching element to closedcircuit position, said roller being mounted for movement relative to said operating member in a direction to permit opening of said switching element, and releasable means engaged by said roller normally forming a fixed counter bearing for said roller.

2. A circuit breaker comprising relatively movable contacts biased to open position, actuating means therefor comprising a rotatable roller movable to close said contacts, an operating member for moving said roller to close said contacts, releasable means engaged by said roller having a normal position in which it forms a fixed counter bearing for said roller to cause said roller to cose said contacts when said roller is moved by said operating member to close said contacts, said means when released permitting said contacts to automatically open irrespective of the position of said operating member.

3. A circuit breaker comprising relatively movable contacts biased to open-circuit position, actuating means therefor comprising a rotatable roller movable to close said contacts, an operating member for moving said roller to cause closing of said contacts, releasable means engaged by said roller having a normal position in which it forms a iixed counter bearing for said roller to cause said roller to move in a predetermined path to close said contacts upon closing movement of said operating member and to cause said roller to restrain said contacts in closed position, said means when released permitting opening of said contacts irrespective of the position of said operating l member.

4. A circuit breaker comprising a switch member movable to open and to closed-circuit position to open and to close the circuit, said switch member being biased to open-circuit position, a movable operating member having a roller rotatably mounted thereon operable to move said switch member to closed position, said roller also being mounted for movement relative to said operating member to permit opening of said switch member, and a releasable member having a roller rotatably mounted thereon engaging the roller of said operating member, said releasable member having a normal position in which the roller thereof serves as a fixed counter bearing for the roller of said operating member to maintain said switch member in closed circuit position, said releasable member when released permitting movement of said switch member to open circuit position irrespective of the position of said operating member.

5. A circuit breaker comprising a switch member movable to open and to closed-.circuit position for opening and closing the circuit, said switch member being biased to open-circuit position, a movable operating member having a roller for moving said switch member to closed circuit position upon movement of said operating member to closed position, said roller-being movable relative to said operating member to permit movement of said switch member to open position, a releasable member having a roller which engages said iirstmentioned roller, said releasable member having a normal position in which the roller thereof serves as a xed counter bearing for the roller of said operating member to maintain the roller of said operating member and said switch member in closed position, means releasably restraining said releasable member in its normal position, and trip means operable to release said releasable means.

6. A circuit breaker comprising relatively movable contacts biased to open-circuit position, actuating means therefor'comprising a movable operating member having a roller rotatably carried thereby, said operating member being movable to closed position to cause said roller to close said contacts, said roller also being movable relative to said operating member in a direction to permit opening of said contacts, releasable means engaged by said roller having a normal position in which it supports said roller, said releasable means when released permitting opening of said contacts irrespective of the position of ysaid operating member, and a trip element operable to release said releasable means.

7. A circuit breaker comprising a switching element movable to open and to closed-circuit position, said switching element being biased to open-circuit position, a rst rotatable roller movable with said switching element, a movable operating member having a second roller for engaging said ilrst roller, said operating member being movable to closed position to cause saidv second roller to move said switching element to closed position, said second roller being mounted for movement relative to said operating member in a direction to permit movement of said switching element to open-circuit position, a releasable member having a third roller engaging said second roller, said releasable member having a normal position in which the roller thereof supports the roller of said operating member, means releasably restraining said releasable member in its normal position, and a trip element operable to effect release of said releasable means and said releasable member to permit opening of the breaker.

8. A circuit breaker comprising relatively movable contacts biased to open-circuit position, actuating means therefor comprising a movable operating member having a roller rotatably carried thereby, said operating member being mova roller engaging the roller of said operating member, said releasable member normally being held in a normal position in which the roller thereof cooperates with the roller of said operating member to force said contacts closed upon movement of said operating member to closed position, said releasable member when released permitting opening of said contacts irrespective to the position of said operating member, a latch for restraining said releasable member in said normal position, and an electro-responsive trip element operable in response to predetermined abnormal conditions to move said latch to eiect release of said releasable member.

-10. A circuit breaker having a movable switching element, an operating member movable to close said switching element and a member releasable to cause said switching element to be automatically actuated to open position irrespective of the position of said operating member, characterized by the fact that the said operating member and said releasable member Icoact with automatically actuated to open position irreable to closed position to cause said roller to close said contacts, said roller also being movable tacts irrespective of the position of said operating member, a latch for releasably restraining said releasable member in'said normal position, and an electro-responsive trip element operable in response to predetermined abnormal conditions in the circuit to move said latch to eiect release of said releasable member. u

9. A circuit breaker comprising relatively movable contacts biased to open-circuit position, operating means comprising a movable operating member and a roller for closing said contacts upon movement of said operating member to closed position, said rollerbeing movable relative to .said operating member to permit opening of said contacts, a releasable member having spective of the position of said operating member, characterizedby the fact that said operating member, said switching element and said releasable member engage and cooperate with each other through mechanical elements comprising rotatable rollers.

12. A circuit breaker comprising a stationary contact, a cooperating movable contactl carried by a movable switch member, said switch member being biased to open position, an operating member movable to open and to closed position in a'direction approximately perpendicular to the direction of motion of the moving contact, a rotatable roller carried by said operating member having a shaft supported for movement in guide slots of said operating member which extend approximately in the direction of movement of said movable contact, said roller being moved to close said contacts upon movement of said operating member to closed position, a releasable member having a roller rotatably mounted thereon engaging said first-mentioned roller, said releasable member normally being held in a normal position in which the roller thereof serves as a iixed counter bearing for the roller of said operating member, a movable latch for normally restraining said releasable member in said normal position, and a trip element operable to move said latch to release said releasable member.

13. A circuit breaker comprising a stationaryv contact, a cooperating movable contact biased to open-circuit position, a rotatable auxiliary roller movable with said movable contact, an

operating member movable to open and closed.

positions in a direction approximately perpendicular to the direction ofl motion of said-movable contact, a rotatable roller carried by said operating member having a shaft supported for movement in guide slots of said operating member `which extend substantially in the direction of movement of said movable contact, the roller of said operating member engaging the auxiliary roller and being movable to close said contacts upon movement of said operating member to closed position, a pivoted releasable member having a roller rotatably mounted thereon engaging the roller of said operating member, said releasable member normally being held in a normal position in which the roller thereof forms a fixed counter bearing for the roller of said operating member, a movable latch for normally restraining said releasable member in said normal position, and a trip element operable to move said latch to effect release of said releasable member and opening of said contacts.

14. A circuit breaker comprising a stationary contact, a cooperating movable `contact biased to open-circuit position, a rotatable auxiliary roller movable with said movable contact, an operating member movable to open and closed positions in a direction approximately perpendicular to the direction of motion of said movable contact, a rotatable roller carried by said operating member having a shaft supported for movement in guide slots of said operating member which extend substantially in the direction of movement of said movable contact, the roller of said operating member engaging the auxiliary roller and being movable to close said contacts upon movement of said operating member to closed position, a pivoted releasable member having a roller rotatably mounted thereon engaging the roller of said operating member, said releasable member normally being held in a normal position in which the roller thereof forms a fixed counter bearing for the roller of said operating member, a movable latch for normally restraining said releasable member in said normal position, a trip element operable to move said latch to effect release of said releasable member and opening of said contacts, the operating member when moved to closed position moving the roller carried thereby past a line joining the axes of rotation of said auxiliary roller and the roller of said releasable member and against a xed stop where it is held by the bias of said movable contact to maintain said contacts closed, the roller of said operating member when said releasable member is released being moved in said guide slots in a direction away from said stationary contact by the opening movement of said movable contact and moving said releasable member to released position, and spring means for automatically resetting said operating member to open position and said releasable member to said normal position and said latch to latching position following a tripping operation of the breaker.

l5. A circuit breaker comprising a stationary contact, a cooperating movable contact biased to open circuit position, an auxiliary roller movable with said movable contact, an operating member movable to open and to closed position in a direction approximately perpendicular to the direction of movement of said movable contact, a rotatable roller carried by said operating member having a shaft movable in guide slots of said operating member which extend approximately in the direction of movement of said movable Contact, the roller of said operating member engaging said auxiliary roller and being moved to close said contacts upon movement of said operating member to closed position, a. pivoted releasable member having an arm carrying a rotatable roller engaging the roller of said operating member and having a latch arm, said releasable member normally being held in a normal position in which the roller thereof serves as a xed counter bearing for the roller of said operating member, a movable latch for normally engaging the latch arm of said releasable member to restrain said releasable member in said normal position, and a trip element operable to move said latch to enect release of said releasable member and opening of said contacts, the axis of rotation of the roller of said releasable member being disposed on the side opposite the operating member of a line joining the pivot axis of said releasable member and the axis of rotation of the roller of said operating member when said breaker is in closed position.

16. A circuit breaker comprising a stationary contact, a cooperating movable contact biased to open circuit position, an auxiliary roller movable with said movable contact, an operating member movable to open and to closed position in a direction approximately perpendicular to the direction of movement of said movable contact, a rotatable roller carried by said operating member having a shaft movable in guide slots of said operating member which extend approximately in the direction of movement of said movable contact, the roller of said operating member engaging said auxiliary roller and being moved to close said contacts upon movement of said operating member to closed position, a pivoted releasable member having an arm carrying a rotatable roller engaging the roller of said operating member and having a latch arm, saidreleasable member normally being held in a normal position in which the roller thereof serves as a xed counter bearing for the roller of said operating member, a movable latch for normally engaging the latch arm of said releasable member to restrain said releasable member in said normal position, and a trip element operable to move said latch to eifect release of said releasable member and opening of said contacts, the axis of rotation of the roller of said releasable member being disposed on the side opposite the operating member of a line joining the pivot axis of said releasable member and the axis of rotation of the roller of said operating member when said breaker is in closed position, theroller of said operating member being moved in said guide slots in a direction away from said stationary contact by the opening movement of said movable contact and moving said releasable member to released position when said releasable member is released, and the axis of rotation of the roller of said operating member being disposed on the side of the operating member of the line joining the axis of rotation of the roller of the releasable member and the axis of rotation of the auxiliary roller when the releasable member is in the released position.

17. A circuit breaker comprising a stationary contact, a cooperating movable contact biased to open-circuit position, an auxiliary roller movable with said movable contact, an operating member movable to open and to closed position in a direction approximately perpendicular to the direction of movement of said movable contact, a rotatable roller carried by said operating member having a shaft supported for movement in guide slots of said operating member which extend in a direction approximately perpendicular to the direction of movement of said operating member and a'pproximatley parallel to the direction of movement of said movable contact, the roller of said operating member engaging said auxiliary roller and being moved to close said contacts -upon movement of said operating member to closed position, a releasable member carrying a rotatable roller engaging the roller of said operating member, said releasable member normally being held in a normal position in which the roller thereof forms a fixed counter bearing for the roller of said operating member, releasable means for holding said releasable member in said normal position, and a housing for the circuit breaker having guide slots for movably supporting the auxiliary roller and the f operating member.

18. A circuit breaker comprising relatively movable contacts biased to open-circuit position, operating means comprising a movable operating member having a roller rotatably carried thereby for closing said contacts upon movement of said operating member to closed position, said roller also being movable relatively to said operating member to permit openingof said contacts, a

' releasable member having a roller rotatably mounted thereon engaging the roller of said operating member, said releasable member normally being held in a normal position in which the roller thereof serves as a xed counter bearing for the roller of said operating member whereby the roller of said operating member forces said contacts closed upon movement of said operating member to closed position, said releasable member when released permitting opening of said contacts irrespective of the position of said operating member, a latch for restraining said releasable member in said normal position, and an electro-responsive trip element operable in response to predetermined abnormal conditions to move said latch to eiect release of said releasable member, and spring means -for automatically returning said operating member to open position and said releasable member to its normal position yfollowing a tripping operation of the breaker.

OTHMAR GROBER.

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