US3792404A

US3792404A - Circuit breaker having mechanical lock to prevent automatic operation

Info

Publication number: US3792404A
Application number: US00285046A
Authority: US
Inventors: L Ettlinger; D Barger
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1972-08-30
Filing date: 1972-08-30
Publication date: 1974-02-12
Anticipated expiration: 1991-02-12

Abstract

A mechanical lock for a circuit breaker. The locking mechanism includes a pivoted lever mounted on a fixed portion of the circuit breaker. The pivoted lever includes a hooked portion which may be pivoted into or out of engagement with the latch member of the circuit breaker. When engaging the latch member, the pivoted lever prevents automatic operation of the circuit breaker, while still allowing manual operation thereof. The pivoted lever has an operating member which is operable from the exterior of the tank enclosing the circuit breaker.

Description

[111 3,792,404 [451 Feb. 12, 1974 CIRCUIT BREAKER HAVING FOREIGN PATENTS OR APPLICATIONS 662,606 5/1963 Canada................................. 337/79 MECHANICAL LOCK TO PREVENT AUTOMATIC OPERATION [75] Inventors: Louis F. Ettlinger,Con0ver; Donald Primary Examiner-Bernard A. Gilheany Barger Newton both of NC Assistant ExaminerA. T. Grimley [73] Assigneez. General Ekctric Company, Attorney, Agent, or Firm-Francis X. Doyle; John J.

pittsfield, Mass Kelleher; Volker R. Ulbrich [22] Filed:

[57] ABSTRACT A mechanical lock for a circuit breaker. The locking mechanism includes a pivoted lever mounted on 21 Aug. 30, I972 [21]. Appl. No.: 285,046

fixed portion of the circuit breaker. The pivoted lever includes a hooked portion which may be pivoted into 4 n 7 m n 3m 2 O 4 7 8H w ,1 3M 3/ 9 .1 27 Who Mme 7 3 m mmh "c H r ""3 "m& L Tr C n. smk UIF HUN 555 or out of engagement with the latch member of the circuit breaker. When engaging the latch member, the pivoted lever prevents automatic operation of the cir- References Cited cuit breaker, while still allowing manual operation UNITED STATES PATENTS thereof. The pivoted lever has an operatingmernber 1 1/1954 12/1954 1 1/1949 10/1965 2,695,401 Broverman 340 222 which is Operable from the exterior of the tank 611C105;

ing the circuit breaker.

Treanor.......... 337/79 x 337/79 x Leonard................................

337/50 4 Claims, 1 Drawing Figure Favre...........

PATENTEI] FEB 1 21974 CIRCUIT BREAKER HAVING MECHANICAL LOCK TO PREVENT AUTOMATIC OPERATION BACKGROUND OF THE INVENTION This invention relates to circuit breakers and more particularly, to a mechanical lock for circuit breakers which prevents automatic operation of a circuit breaker used for protecting electrical apparatus such as transformers.

The type of circuit breaker forming the basis of this invention is conventionally placed inside the tank of the transformer. The circuit breaker is provided with means which will automatically trip the breaker open when a predetermined current flow occurs in the transformer. The automatic tripping means can be manually reset from outside the tank and the circuit breaker can also be manually opened and closed fromv outside the tank. Some forms of this type of circuit breaker are provided with an indicating means which is visible from outside the tank. The circuit breaker has automatic tripping means for placing the indicating means in an indicating condition before the trip point of the breaker is reached. This tripping means can likewise be manually reset from outside the tank. The indicating means is for the purpose of showing whether the transformer has been overloaded and whether it is about to be tripped off the line by the circuit breaker. After the indicating means is placed in an indicating condition the overload in the transformer may subside whereby the circuit breaker is not tripped open. The manually operable means which is provided on the outside of the tank for the indicating means can be operated to place the indicating means in a non-indicating condition even though the circuit breaker has not tripped open.

When the circuit breaker is installed in the transformer, its trip point is adjusted so that the circuit breaker will trip open at some predetermined load in the transformer. In some installations, the transformer is repeatedly overloaded. These overloads trip the breaker open and result in interruptions in electrical service for the electrical power customer. When this happens the existing transformer is usually replaced by another transformer which has a higher load capacity. However, during the interim the utility company is faced with the problem of how to provide the customer with continuous electrical service. Several forms of this type of circuit breaker are provided with means for raising the trip point of the circuit breaker. In some cases the trip point can be raised as much as percent above its initial setting. Raising the trip point this much may avoid repeated interruptions in electrical service. However, in some situations even raising the trip point by this much does not remedy this situation. The magnitude of overloads may be more than 15 percent in which event the circuit breaker continues to trip open each time overloads occur.

The repeated interruptions in electrical service are an inconvenience and may be costly to the electrical customer. These repeated interruptions are also costly to the utility. Each time the circuit breaker trips open the utility must send a lineman out to the transformer site to reclose the breaker. In some cases, the transformer site may be several miles away from the service station and several trips may need to be made in a single day. The overloaded transformer cannot be pennanently taken off the line because this leaves the electrical power customer without any power at all. Ordinarily, it will take several days before a higher rated transformer can be obtained and substituted for the overloaded transformer. 5 It is an object of this invention to provide an improvement in the above discussed type of circuit breaker which will overcome the above discussed disadvantages.

A further object of this invention is to provide an improved circuit breaker having a mechanical lock to prevent automatic operation of such circuitbreakers on overload current.

Yet another object of this invention is to provide an improved circuit breaker for electrical apparatus with a mechanical lock which will prevent automatic operation of such circuit breaker, but which will allow the circuit breaker to be manually opened and closed.

SUMMARY OF THE INVENTION In one form of our invention uncomplicated and low cost means which is manually operable from outside the tank is provided for locking the latch member of the circuit breaker so that the circuit breaker will not automatically trip open when the transformer is being subjected to repeated overloads. This means that there will be no discontinuity in electrical service until a higher rated transformer can be substituted for the overloaded one. The means for preventing the circuit breaker from being automatically tripped open does not interfere with manual opening and closing of the circuit breaker. Additionally, in those situations where indicating means is provided with-the circuit breaker the means for preventing the circuit breaker from automatically tripping open does not interfere with automatic operation of the indicating means to an indicating condition and the ability to manually place the indicating means in a non-indicating condition.

The features of our invention which we believe to be novel are set forth with particularity in the appended claims. Our invention itself, however, both as to its organization and method of operation; together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING I The single FIGURE is a broken away perspective DESCRIPTION OF PREFERRED EMBODIMENT The invention is illustrated with respect to a wellknown form of circuit breaker for protecting transformers. The illustrated circuit breaker is described in detail in construction and operation in Broverman U.S. Pat. No. 2,695,401 issued Nov. 23, 1954 and assigned to the same assignee as the instant patent application. Therefore, only those parts of the circuit breaker will be described herein which are necessary for a clear understanding of the invention.

The circuit breaker is shown as being positioned inside a transformer tank 10. A bimetallic element 12 of the citcuit breaker is connected in one of the secondary line leads 14 of the transformer 16. When a predetermined amount of current flows through the bimetallic element 12 and the separable circuit breaker contacts l8 and 20 the bimetallic element 12 will be deflected in an upward direction as indicated by arrow 120. This will result in rearward or counterclockwise rotation of a pivoted bar 22 and a latching plate 24 mounted thereon as indicated by arrow 24a. In its closed position, C, which is illustrated, the circuit breaker trip means has a latch member 26 which is engaged with the latching plate 24. When the latching plate 24 is moved sufficiently in a rearward or counterclockwise direction the latch member 26 is released therefrom which releases a circuit breaker trip element or carrier member 28 for forward movement. The trip element 28 of the tripping means is mounted on a fixed pivot 30. When the member 28 pivots in a forward direction this buckles a pair of

extended levers

32 and 34 in a rearward direction. When this occurs, a spring 36 which is connected to the knee pin 38 is able to move a switch arm 40, for the contact 20, to open position.

The end of the spring 36 which is opposite from the pin 38 is connected to a generally U-shaped and pivoted member 42. The end of the switch arm 40 which is opposite from the contact 20 is pivoted at a fixed pivot 44.

The automatic tripping means of the circuit breaker is manually reset from outside the transformer tank by moving a handle 46 in a counterclockwise direction as indicated by arrow 46a to R or reset position. When the handle 46 is pivoted counterclockwise a crank member 48 and a link 50 cause the U-shaped member 42 to rock in a rearward direction. As the member 42 rocks rearwardly, it engages the upper end of the trip element 28 and moves the element 28 in a rearward direction. This causes cocking of the latching means for the trip element 28 and an engagement of the latch member 26 with the latch plate 24.

The

separable contacts

18 and 20 can then be reclosed by moving the handle 46 in a clockwise direction to C or closed position. This results in forward rocking of the member 42. When the member 42 is rocked forwardly the spring 36 straightens the

links

32 and 34 until they butt up against the fixed pivot 30 of the trip element 28. In this straightened position of the

links

32 and 34 the contact 20 is engaged with the contact 18. The

links

32 and 34 will not buckle in a rearward direction inasmuch as the spring 36 is urging the

links

32 and 34 against the pivot 30.

The

circuit breaker contacts

18 and 20 cannot be closed as long as the circuit breaker tripping means is in a trip open position. The

contacts

18 and 20 can be closed only after the trip element 28 has been moved to a reset position and the latch member 26 has been latched with respect to the latch plate 24. However, once the tripping means has been reset the circuit breaker can be freely manually opened and closed. The circuit breaker is manually opened'by moving the bandle 46 counterclockwise to which results in rearward motion of the U-shaped member 42. After the spring 36 is carried by the member 42 to the rear of the lengthwise axis of the

extended links

32 and 34 the

links

32 and 34 will be buckled in a rearward direction which permits the spring to snap the switch member 40 open. The contacts 18 and can be manually reclosed as previously described by moving member 42 forwardly so as to cause the

links

32 and 34 to butt up against the fixed pivot 30 in their lengthwise extended position.

The illustrated form of circuit breaker may be provided with indicating means (not shown) as well as means actuated by handle 50 for raising the trip point of the breaker. However, inasmuch as the invention is also useful in circuit breakers which do not have indicating means and means for raising the trip point, the means for preventing the circuit breaker from tripping open on repeated overloads will be described now.

It will be obvious that the circuit breaker cannot be prevented from automatically tripping open when an overload occurs by moving the handle 46 to its extreme clockwise position and holding it in this position. This is because the member 42 cannot prevent the trip element 28 from pivoting forwardly once its latch 26 is released so as to buckle the

links

32 and 34 to enable the spring 36 to snap open the switch member 40. This is a desirable feature in a circuit breaker. Otherwise a lineman could absentmindedly close a tripped open circuit breaker without first resetting it. This would leave the transformer without any automatic overload protection.

In this invention, uncomplicated and low cost means are provided for locking the latch member 26 in its reset position which will prevent the circuit breaker from being tripped open but still permit manual opening and closing of the circuit breaker. The means for accomplishing this comprises a locking lever 52 which has a latch member 26 locking element or hook 54 formed thereon. Locking lever 52 is pivotedly mounted on astationary and flat frame member 56. The position of the lever 52 is manually controlled from outside the transformer tank by a handle 58 whichis connected to the element 52 by a stiff cable 60. When the handle 58 is rotated clockwise from dotted position 58a the member 52 is pivoted so as to place the latch member 26 locking element 54 into opening 26a in latch member 26 when in its latched position. When the hook 54 is in opening 26a of latch member 26, it is prohibited from moving forwardly to buckle the

links

32 and 34 even though the overload is serious enough to cause rotation of latch plate 24 to the unlatched position. The latch member 26 can be unlocked from its locked position by rotating the handle 58 in a counter clockwise direction to position 58a which will remove the hook 54 from opening 26a in latch member 26. If the latch 26 of the trip member 28 is unlatched from the plate 24 at this time, the circuit breaker will trip open as heretofore described. Since the circuit breaker is free to be manually opened and closed by the handle 46 when the latch member 26 is in its latched condition, positioning of the hook 54 in opening 26a of latch member 26 does not interfere with manual operation of the breaker.

Thus, this invention provides a very inexpensive and uncomplicated means for avoiding repeated interrruptions in electrical service and repeated trips out to the transformer site in order to reset and close the circuit breaker even though the transformer is operated under overload conditions until such time as a higher rated transformer can be obtained to replace the overloaded transformer. The invention'requires only a slight modification in or addition to conventional circuit breakers. The invention comprises such a minor part of the whole circuit breaker that it can be readily provided in existing circuit breakers so that the invention will be available for use when the occasion arises.

The means for raising the trip point of the circuit breaker will now be described. It comprises a lever 62 which is pivoted by pivot 64 to the latch plate 24. The lever 62 is connected by cable 66 to handle 50. When the handle 50 is rotated in a counterclockwise direction as indicated by arrow 50a, lever 62 moves latch plate 24 inwardly toward latch member 26 so as to require the bimetallic element 12 to rotate the bar 22 a greater distance in a rearward direction to unlatch the latch member 26.

In the commercial form of the instant invention the trip point of the circuit breaker can be increased by about 15 percent by operating the handle 50. However, the magnitude of overload may surpass 15 percent in which event this means for increasing the tripping point of the circuit breaker will not avoid repeated interruptions in the electrical service. When this is the situation in this invention, the mechanical locking means is actuated by handle 58 to enable permanently locking the circuit breaker against automatically tripping open until such time as the overloaded transformer can be replaced with a higher rated one. Thus, this invention can be used in existing circuit breakers by making a very minor change by providing handle 58 and lever 52 with hook 54.

Of course, it will be understood that the circuit breaker shown may be provided with external trip indicating means, such as the external light bulb disclosed in US. Pat. No. 2,695,401. Such indicating means is reset by moving handle 46 to position L, as is well understood. However, since such indicating means are well known in the circuit breaker art, and form no part of this invention, they are not shown in the drawing.

While there has been shown and described a particular embodiment of the invention, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the true spirit and scope of the invention, especially as it is defined in the appended claims.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

l. A circuit breaker having a pair of separable contacts for controlling an'electrical circuit, manually resettable means including a latch member for automatically tripping said contacts open in response to a 'predetermined current flow through said contacts,

means for manually opening and closing said contacts, and manually operable locking means for rendering said automatic tripping means ineffective to trip said contacts open while said other means are left in operable condition, said locking means including a pivoted lever which is manually operable to lock said latch member of said circuit breaker in its latched position.

2. A circuit breaker as set forth in claim 1 in which said pivoted lever has a hook portion engaging and locking said latch member.

3. A circuit breaker for protecting an electrical apparatus which is positioned in a tank, said circuit breaker being positioned in said tank and having manually resettable automatic tripping means including a latch member for opening said breaker and means which are manually operable from outside said tank for opening and closing said breaker, and locking means which are manually operable from outside said tank for preventing automatic operation of said tripping means without preventing operability of said other means, said locking means including a lever pivoted on said circuit breaker manually operable by a handle positioned outside said tank, said lever being operable to a locking position engaging said latch member to hold said latch member in its latched position.

4. A circuit breaker as set forth in claim 3, in which said pivoted lever has a hook portion which is movable into an opening in said latch member to lock said latch member.

Claims

1. A circuit breaker having a pair of separable contacts for controlling an electrical circuit, manually resettable means including a latch member for automatically tripping said contacts open in response to a predetermined current flow through said contacts, means for manually opening and closing said contacts, and manually operable locking means for rendering said automatic tripping means ineffective to trip said contacts open while said other means are left in operable condition, said locking means including a pivoted lever which is manually operable to lock said latch member of said circuit breaker in its latched position.