US3747033A

US3747033A - Circuit breaker with improved trip means

Info

Publication number: US3747033A
Application number: US00220667A
Authority: US
Inventors: R Bennett
Original assignee: Westinghouse Electric Corp
Current assignee: ABB Inc USA
Priority date: 1972-01-25
Filing date: 1972-01-25
Publication date: 1973-07-17
Anticipated expiration: 1990-07-17
Also published as: CA959893A; JPS4897647U; JPS5344684Y2; AT320058B; DE2302039A1; CH544406A

Abstract

A circuit breaker is provided with improved compactly constructed trip means comprising a thermal trip operable with time delay in response to a sustained overload above a first predetermined value to effect automatic opening of the breaker and an electromagnetic trip operable instantaneously upon the occurrence of an overload above a second predetermined value to effect automatic opening of the breaker.

Description

United States Patent [191 Bennett July 17, 1973 CIRCUIT BREAKER WITII IMPROVED TRIP MEANS [75] Inventor: Ronald E. Bennett, Conover, NC.

[73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

[22] Filed: Jan. 25, 1972 [2]] Appl. No.: 220,667

[52] U.S. Cl. 335/35, 335/173 [51] Int. Cl. I'IOIh 75/12 [58] Field of Search 335/21, 22, 23, 43,

[56] References Cited UNITED STATES PATENTS 3,525,058 8/1970 Astleford, Jr. 335/173 3,451,016 6/1969 Ellenberger 335/23 Prir riqry Exanzjne r-l-larold Broome Attorney A. T. Stratton, William A. Elchik et al.

[ 5 7] ABSTRACT A circuit breaker is provided with improved compactly constructed trip means comprising a thermal trip operable with time delay in response to a sustained overload above a first predetermined value to effect automatic opening of the breaker and an electromagnetic trip operable instantaneously upon the occurrence of an overload above a second predetermined value to effect automatic opening of the breaker.

7 Claims, 4 Drawing Figures CIRCUIT BREAKER WITH IMPROVED TRIP MEANS BACKGROUND OF THE INVENTION 1. Field of the Invention Circuit breakers of the type comprising thermal and electromagnetic trip means.

2. Description of the Prior Art In the patent to Leonard et al., U.S. Pat. No.

I 2,686,242, there is disclosed a circuit breaker similar -to the circuit breaker herein disclosed except that the circuit breaker in the Leonard et al patent does not include an electromagnetic trip. In the patent to Astleford, Jr., U.S. Pat. No. 3,525,058, there is disclosed an improvement over the circuit breaker disclosed in the above-mentioned Leonard et al. patent in that an electromagnetic trip was added to one end of the cir- SUMMARY OF THE INVENTION An improved compactly constructed circuit breaker comprises an elongated movable contact arm that is pivotally connected intermediate the ends thereof to an operating link of 'a spring-type operating mechanism. The elongated movable contact arm is provided with a contact at one end thereof for cooperating with a stationary contact. The contact arm is latched at the other end thereof by means of an elongated primary latch that is pivotally supported intermediate the ends thereof. The spring-type operating mechanism is manually operable between open and closed positions to pivot the contact arm about the latched end between open and closed positions with a snap-action. Trip means is provided comprising a thermal trip and an electromagnetic trip. The thermal trip comprises a secondary; latch member that is latched by abimetalact-ivated latch and that is spring-biased toward a tripping position. Upon the occurrence of a sustained overload above a first predetermined value the bimetal flexes with a time delay to release the secondary latch whereupon the secondary latch moves to strike the primary latch ona first side of the pivot of the primary latch to pivot the primary latch to a position releasing the latched end of the contact arm whereupon the spring means biases the contact arm about the pivot of the operating link to a tripped-open position. The electromagnetic trip comprisesa flapper type armature that is pivotally supported for movement about the same axis as the primary latch. Upon the occurrence of a severe overload-above a second predetermined value, the armature. is attracted to move to strike the primary latch on the first side of the pivot of the primary latch to pivot the primary latch to a releasing position to effect a tripping operation of the circuit breaker.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side sectional view of a circuit breaker embodying principles of this invention with the breaker being shown in the manually closed position in full lines and with the manually open position of the breaker being indicated in broken lines;

FIG. 2 is a view similar to FIG. 1 with the breaker being shown in the tripped-open position following an electromagnetic tripping operation;

FIG. 3 is a partial sectional view taken generally along the lines III-III of FIG. 2; and

FIG. 4 is a perspective view of the armature structure seen in FIGS. 1-3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS vides contact pressure in the closed position of the contacts.

The movable contact is fixedly mounted on one end I of an elongated contact arm structure 25 that is latched, at the other end 27 thereof, in the operating position seen in FIG. 1 by means of an elongated primary latch member 29. The primary latch member 29 is mounted for pivotal movement, intermediate the ends thereof, on a fixed pivot 30. The contact arm structure 25 comprises an elongated arm portion 31 and a U-shaped member 33 that carries the contact 15 and that is mounted on the portion 31, by means of a pivot pin 35, for limited movement relative to the arm portion 31 to provide contact alignment in the closedcontact position. The movable contact 15 is fixedly mounted on the U-shaped member 33. The contact arm structure 25 is supported at 27 on a latch surface 37 of the primary latch 29, and the contact arm 25 pivots on the latch surface 37, during manual operation of the circuit breaker in a manner to be hereinafter described. A tension spring 39 is connected at one end thereof to an extension 41 of the contact arm structure 25, and at the other end thereof to a stationary spring support pin 43. The contact arm structure 25 is pivotally connected, intermediate the ends thereof, to an operating link 45 by means of a pivot pin 47. A pair of operating springs 49 (only one of which is seen in FIG. 1) are connected at one end to a pin 51 on the upper end of the operating link 45 and at the other end to an insulating operating handle 53. The operating link 45 comprises twin members connected by means of the pin 51. A roller 55 is mounted on the pin 47 between the twin members of the link 45 and a roller 57 is mounted on the pin 51 between the twin members of the link 45. The

rollers

55, 57 are positioned in a generally triangular shaped opening 59 in the insulating base 11, and they engage the surfaces defining the opening 59 to guide movement of the operating link 45in a manner to be hereinafter described.

The insulating handle 53, which is biased inward by means of the tension springs 49, rides on an arcuate surface 61 which guides the handle 53 for movement between the on" and on positions.

In the closed position of the circuit breaker (FIG. 1) the line of action of the operating springs 49 is below the center indicated at A about which the handle 53 moves so that the springs 49 bias the handle to the on position. The line of action of the springs 49 is also below the center indicated at B about which the roller 57 travels on the surface 59 so that the roller 57 is biased to the right in the opening 59 to maintain the operating link 45 in the closed position seen in FIG. 1. When the operating handle 53 is moved from the on position seen in full lines to the of position seen in broken lines, the line of action of the operating springs 49 moves to the left over the center line B-57. When this occurs, a component of the force of the springs 49 biases the roller 57 causing the roller, together with the link 45, to move from the closed position seen in full lines to the open position seen in broken lines to pivot the movable contact arm structure 25 about the latch surface 37 from the closed position seen in full lines to the open position seen in broken lines. This movement of the operating link 45 and movable contact arm structure 25 occurs with a snap-action.

The breaker is closed by reverse movement of the handle 53 from the off position to the on position. During this movement, the line of action of the operating springs 49 crosses over the center line B-57 where-' upon the springs 49 bias the roller 57 to move the operating link 45 and movable contact arm structure to the closed position. with a snap-action- Referring to FIG. 1, it will be seen that in the closed position of the circuit breaker, the circuit extends from a conductor 65 through a conductor 21, the stationary contact 13, the movable contact 15, the member 33, flexible conductors 67 that are connected at one end to the member 33 and at the other end to a conductor 69, the conductor 69, a bimetal 71 that is connected at one end to the conductor 69 and at the other end to a conductor 73, the conductor 73 to a flexible conductor 75 that is connected to the conductor 73. The bimetal 71 is fixedly secured at the upper side thereof to an adjusting arm A that is suitably pivotally secured to the housing 11 in the manner more specifically described in the above-mentioned U.S. Pat. No. 2,686,242. A latch member 77, which is fixedly secured at one end thereof to the free end of the bimetal 71, latches a secondary latch member 79 that is pivotally mounted on a stationary pivot 81 and that is biased in a clockwise (FIG. 1) direction by means of a tension spring 83.

When a persistent relatively low overload current above a first predetermined value occurs in the circuit through the breaker, the bimetal 71 becomes heated and flexes, with a time delay, upward (FIG. 1) whereupon the latch 77 releases the secondary latch member 79. Upon release of the secondary latch member 79, the spring 83 snaps the secondary latch member 79 clockwise about the pivot 81 causing a projection 85 on the secondary latch member 79 to engage the one end 87 of the primary latch member 29 to pivot the primary latch member 29 in a counterclockwise direction about the fixed pivot 30, against the bias of a torsion spring 89. This movement moves the latch surface 37 to release the latched end 27 of the contact arm 25 whereupon the tension spring 39 moves the contact arm 25 about the pivot 47 to a tripped-open position with a snap-action.

The mechanism is reset and relatched following an automatic opening operation by moving the handle 53 to a position slightly past the off" position. During this movement with part of one end of the contact arm 25 engaging a surface 91 on the insulating housing 11, when the operating link 45 is moved to the position shown in broken lines in FIG. 1, the latching end 27 of the contact arm 25 is moved up over the latch surface 37 of the primary latch member 29, and as the handle 53 approaches the off position, a projection 93 thereon engages the secondary latch member 79 to rotate the secondary latch member 79 counterclockwise about the pivot 81 where the latch member 79 is again relatched by the latch 77. When the secondary latch member 79 is moved to the relatched position, the projection 85 moves away from the one end 87 of the primary latch member 29, and the torsion spring 89 re turns the primary latch member 29 to the latching position seen to relatch the contact arm 25 in the operating position. The movement of the primary latch member 29 to the latching position is stopped when the one end of the primary latch member 29 engages a projection 97 on the base 11. The reset circuit breaker (FIG. 2) may then be operated in the same manner as was hereinbefore described. The above-described operation is more fully described in the above-mentioned U.S. Pat. No. 2,686,242.

In addition to the bimetal or thermal trip 71, the trip means 19 comprises an electromagnetic trip that comprises an armature structure indicated generally at 101. The armature structure 101 (FIG. 4) comprises a support arm 103 having a support bearing 105 secured thereto. The support bearing 105 has an opening therein for receiving the fixed pivot pin 30 (FIG. 1) to pivotally support the armature structure 101 on the fixed pivot pin 30 for pivotal movement about the same axis as the primary latch 29. A laminated magnetic armature 107 is secured to the support arm 103 by means of a pair of rivets 109. An insulating fiber wrapper 113 is suitably secured to the armature 107. A striker arm 115 is secured to the armature 107 on the underside of the armature 107. As can beunderstood with reference to FIGS. 1-3, the striker member 115 of the armature structure 101 is disposed under the primary latch 29 to engage the primary latch 29 upon attraction of the armature structure, which engagement is on the same side of the pivot 30 of the primary latch 29 as the support surface 37 that the contact arm 25 is pivoted on. As is disclosed in FIG. 1, the armature structure 101 is positioned in an unattracted position spaced from the bimetal 71 and conductor 69 with the armature structure 101 being maintained in the unattracted position by means of the pull of gravity. It is to be understood that a biasing spring could be utilized to bias the armature structure 101 to the unattracted position for certain applications. Pivotal movement of the armature structure 101 to the unattracted position seen in FIG. 1 is limited by engagement of the armature structure 101 with a surface 116 of the insulating housing 11.

Upon the occurrence of a severe overload or short circuit above a second predetermined value higher that the above-mentioned first predetermined value, the magnetic forces generated by the current in the bimetal 71 and conductor 69 attract the armature structure 101 whereupon the armature structure 101 pivots in a counterclockwise direction on the fixed pivot 30 from the unattracted position seen in FIG. 1 to the tripped position seen in FIG. 2. During this movement, the striker arm 115 strikes the primary latch 29 to move the releasing position to release the contact arm 25. Upon release of the contact arm 25 the spring 39 moves the contact arm to the tripped-open position seen in FIG. 2 in the same manner as was hereinbefore described with regard to the thermal tripping operation. As can be seen in FIG. 2, the armature structure 101 is in the attracted position to show the position at the moment of tripping. It can be understood that when the circuit is open the armature structure 101 will be returned by gravity (or a biasing spring if a biasing spring is used) to the unattracted position seen in FIG. 1. As can be understood with reference to FIG. 2, re lease of the secondary latch 79 is not necessary for an electromagnetic tripping operation in that the primary latch 29 is engaged by the striker arm 115 to directly move the primary latch 29 to the releasing or tripped position. Following an electromagnetic tripping operation, the contact arm 25 is reset by movement of the handle 53 to the off position during which movement the operating link 45 is moved to the position shown in broken lines in FIG. 1, and with the one-end of the contact arm 25 engaging the projection 91, the'contact arm 25 is'moved to the position shown in broken lines in FIG. 1 whereupon the torsion spring 89 biases the primary latch 29 to the the latch position so that the latch surface 37 engages theclatch end 27 of the contact arm 25 to relatch the contact arm 25 in the operating position. Thereafter, the circuit breaker can be manually operated in the same manner as was hereinbefore described. It can be understood that although during the thermal tripping operation the secondary latch 79 was-first released to strike theprimary latch 29 to effect unlatching movement of the primary latch 29, during an instantaneous electromagnetic tripping operation the armature structure 113 directly strikes the primary latch 29 to move the primary latch 29 to the unlatching position. Although the electromagnetic tripped-open position is disclosed with the secondary latch 79 still in the latch position, it can be understood that the overload could heat the bimetal sufficiently to cause the bimetal 71 to flex to release the secondary latch; but it is to be noted that the electromagnetic tripping operation is instantaneous and the secondary latch, in these cases, would be released after the circuit breaker has been tripped.

l'claim as my invention:

1. A circuit breaker comprising a stationary contact, a movable contact, an elongated contact arm carrying said movable contact at one end thereof, a primary latch supported for movement about a first axis and being in a latching position latching the other end of said contact arm, a secondary latch in a latched position, biasing means biasing said secondary latch toward a tripping position, a bimetal-actuated latch latching said secondary latch in said latched position, a spring operating mechanism pivotally connected 'tosaid contact arm intermediate the ends of said contact arm, said spring operating mechanism beingmanually operable to pivot said contact arm about said other end on said primary latch between open and closed positions with a snap action, upon the occurrence of lesser overloads above a first predetermined value said bimetalact'uated latch releasing said secondary latch whereupon said biasing means moves said secondary latch to effect movement of said primary latch to unlatch said contact arm whereupon said spring operating mechanism moves said contact arm to a tripped-open position, an armature structure, pivot support means supporting said armature structure for pivotal movement about said first axis, said armature structure being pivotally movable relative to said primary latch, upon the occurrence of overloads above a second predetermined value higher than said first predetermined value said armature structure pivotally moving to strike said primary latch to move said primary latch to unlatch said contact arm whereupon said spring operating mechanism moves said contact arm to a tripped-open position.

2. A circuit breaker according to claim I, and said spring operating mechanism being operable when said contact arm is in said tripped-open position to move said contact arm to relatch said contact arm to prepare said circuit breaker for manual operation.

3. A circuit breaker according to claim 1, upon the occurrence of lesseroverloads above said first predetermined value said bimetal-actuated latch releasing said secondary latch whereupon said biasing means moves said secondary latch to strike said primary latch on a first side of said first axis to thereby move said primary latch to unlatch said contact arm whereupon said spring operating mechanism moves said contact arm to a tripped-open position, and upon the occurrence of overloads above said second predetermined value said armature structure pivotally moving to strike said primary latch on said first side of said first axis to move said primary latch to unlatch said contact arm whereupon said spring operating mechanism moves said contact arm to said tripped-open position.

4. A circuit breaker comprising a stationary contact, a movable contact, an elongated contact arm carrying said movable contact at one end thereof, a primary latch supported on a fixed pivot and comprising a latch part on a first side of said fixed pivot engaging the other end of said contact arm to latch the other end of said contact arm, an operating mechanism comprising an operating link, means pivotally connecting said contact arm intermediate the ends thereof to said operating link, an operating member, an operating spring connected between said operating member and said operating link, said operating member being manually operable to an open position to operate through said operating spring and operating link to move said latched contact arm about said other end to a manually open position, said operating member being manually operable to a closed position to operate through said operating spring and operating link to move said latched contact arm about said other end to a manually closed position, trip means'comprising a thermal trip operating with a time delay upon the occurrence of a sustained overload above a first predetermined value to move said primary latch to an unlatching position to unlatch said other end of said contact arm, said trip means comprising an electromagnetic trip comprising a movable armature movable instantaneously upon the occurrence of an overload above a second predetermined value to engage said primary latch on said first side of said fixed pivot to move said primary latch to said unlatching position to unlatch said other end of said contact arm, and trip-spring means operating when said contact arm is unlatched to move said contact arm about the intermediate pivot thereof to a tripped-open position.

5. A circuit breaker according to claim 4, said primary latch being supported on said fixed pivot for pivotal movement about a first axis, and said movable armature being pivotally supported for movement about said first axis.

6. A circuit breaker according to claim 4, a secondary latch, said thermal trip comprising a bimetal in an initial position to effect latching of said secondary latch, upon the occurrence of said overload above said first predetermined value said bimetal flexing to unlatch said secondary latch and said secondary latch moving to operate against said primary latch on said first side of said fixed pivot of said primary latch to move said primary latch to the unlatching position, said otal movement about said fixed pivot pin.

III i l

Claims

1. A circuit breaker comprising a stationary contact, a movable contact, an elongated contact arm carrying said movable contact at one end thereof, a primary latch supported for movement about a first axis and being in a latching position latching the other end of said contact arm, a secondary latch in a latched position, biasing means biasing said secondary latch toward a tripping position, a bimetal-actuated latch latching said secondary latch in said latched position, a spring operating mechanism pivotally connected to said contact arm intermediate the ends of said contact arm, said spring operating mechanism being manually operable to pivot said contact arm about said other end on said primary latch between open and closed positions with a snap action, upon the occurrence of lesser overloads above a first predetermined value said bimetal-actuated latch releasing said secondary latch whereupon said biasing means moves said secondary latch to effect movement of said primary latch to unlatch said contact arm whereupon said spring operating mechanism moves said contact arm to a tripped-open position, an armature structure, pivot support means supporting said armature structure for pivotal movement about said first axis, said armature structure being pivotally movable relative to said primary latch, upon the occurrence of overloads above a second predetermined value higher than said first predetermined value said armature structure pivotally moving to strike said primary latch to move said primary latch to unlatch said contact arm whereupon said spring operating mechanism moves said contact arm to a tripped-open position.

2. A circuit breaker according to claim 1, and said spring operating mechanism being operable when said contact arm is in said tripped-open position to move said contact arm to relatch said contact arm to prepare said circuit breaker for manual operation.

3. A circuit breaker according to claim 1, upon the occurrence of lesser overloads above said first predetermined value said bimetal-actuated latch releasing said secondary latch whereupon said biasing means moves said secondary latch to strike said primary latch on a first side of said first axis to thereby move said primary latch to unlatch said contact arm whereupon said spring operating mechanism moves said contact arm to a tripped-open position, and upon the occurrence of overloads above said second predetermined value said armature structure pivotally moving to strike said primary latch on said first side of said first axis to move said primary latch to unlatch said contact arm whereupon said spring operating mechanism moves said contact arm to said tripped-open position.

4. A circuit breaker comprising a stationary contact, a movable contact, an elongated contact arm carrying said movable contact at one end thereof, a primary latch supported on a fixed pivot and comprising a latch part on a first side of said fixed pivot engagIng the other end of said contact arm to latch the other end of said contact arm, an operating mechanism comprising an operating link, means pivotally connecting said contact arm intermediate the ends thereof to said operating link, an operating member, an operating spring connected between said operating member and said operating link, said operating member being manually operable to an open position to operate through said operating spring and operating link to move said latched contact arm about said other end to a manually open position, said operating member being manually operable to a closed position to operate through said operating spring and operating link to move said latched contact arm about said other end to a manually closed position, trip means comprising a thermal trip operating with a time delay upon the occurrence of a sustained overload above a first predetermined value to move said primary latch to an unlatching position to unlatch said other end of said contact arm, said trip means comprising an electromagnetic trip comprising a movable armature movable instantaneously upon the occurrence of an overload above a second predetermined value to engage said primary latch on said first side of said fixed pivot to move said primary latch to said unlatching position to unlatch said other end of said contact arm, and trip-spring means operating when said contact arm is unlatched to move said contact arm about the intermediate pivot thereof to a tripped-open position.

6. A circuit breaker according to claim 4, a secondary latch, said thermal trip comprising a bimetal in an initial position to effect latching of said secondary latch, upon the occurrence of said overload above said first predetermined value said bimetal flexing to unlatch said secondary latch and said secondary latch moving to operate against said primary latch on said first side of said fixed pivot of said primary latch to move said primary latch to the unlatching position, said armature being supported for pivotal movement, and upon the occurrence of an overload above said second predetermined value said armature being attracted to pivotally move to operate against said primary latch on said first side of said fixed pivot of said primary latch to move said primary latch to the unlatching position.

7. A circuit breaker according to claim 6, said primary latch being supported on a fixed pivot pin for pivotal movement about said fixed pivot pin, and said armature being supported on said fixed pivot pin for pivotal movement about said fixed pivot pin.