US3493952A

US3493952A - Electric circuit breaker with contact condition indicator

Info

Publication number: US3493952A
Application number: US570486A
Authority: US
Inventors: William H Jette
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1966-08-05
Filing date: 1966-08-05
Publication date: 1970-02-03
Anticipated expiration: 1987-02-03
Also published as: JPS4535103B1; AT279716B; GB1187446A; CH483105A; BR6790976D0; CH470745A

Description

Feb. 3, 1970 w.;H.' JETTE ELECTRIC CIRCUIT BREAKER WITH CONTACT CONDITION INDICATOR Filed Aug. 5. 1966 INVNTORJ WILL/A Warm, BY W ATTORNEY United States Patent 3,493,952 ELECTRIC CIRCUIT BREAKER WITH CONTACT CONDITION INDICATOR William H. Jette, Pittsfield, Mass, assignor to General Electric Company, a corporation of New York Filed Aug. 5, 1966, Ser. No. 570,486 Int. Cl. G08b 21/00 US. Cl. 340242 10 Claims ABSTRACT OF THE DISCLOSURE Detection and indicating means are described for response to loss of normal contact bias in a biased closed electric circuit interrupter, as by loss of vacuum in a vacuum-type interrupter. A movable switch member positively coupled to the movable contact is connected by a lost-motion coupling to an actuating mechanism. Means are provided to move the switch member toward its circuit-opening position independently of the actuating mechanism upon loss of normal closing bias, and an indicator is actuated by such independent movement.

My invention relates to electric circuit breakers, and particularly to improved circuit breaker actuating mechanism including signal means operable in response to a defective contact condition. The invention is especially adapted for application to vacuum type circuit interrupting devices to indicate loss of vacuum in the contact envelope.

A typical vacuum type circuit interrupter comprises a highly evacuated envelope and a pair of relatively movable contacts located within the envelope. When the interrupter is in closed position the contacts are engaged and are thus capable of carrying current through the interrupter. Circuit interruption is effected by separating the contacts to draw an arc therebetween, soon after which the arc is extinguished and prevented from reigniting by the action of the vacuum. To assure that the arc will be extinguished and prevented from reigniting it is important that the pressure inside the envelope be maintained below a predetermined value.

=It is particularly important to prevent leakage into the evacuated envelope (and consequent loss of vacuum) where the interrupting device is to be located under oil or other ambient liquid. In such case a vacuum leak sufficient to admit liquid to the envelope will result not only in failure to interrupt an are but may also result in destructive internal pressures due to overheating of the admitted liquid. Pressure changes due to loss of vacuum or other defective contact condition may be reflected in reversely initiated actuation of the contact operating mechanism, and it is one object of my invention to utilize such reversely initiated actuation to monitor contact condition in an electric circuit breaker. It will be evident to those skilled in the art that while my invention is especially adapted to monitoring loss of vacuum in a vacuum type electric circuit interrupter it is applicable also to the monitoring of contact condition in other circuit breakers where reversely initiated contact actuaton results from some defective contact condition.

Accordingly it is a more general object of my invention to provide improved signalling means associated with a circuit breaker operating mechanism for monitoring a contact condition.

It is another object of my invention to provide simple and reliable mechanical means for monitoring contact condition in an electric circuit breaker while the circuit breaker is in closed circuit current conducting position.

It is a particular object of my invention to provide 3,493,952 Patented Feb. 3, 1970 improved signal means associated with the contact operating mechanism of a vacuum type electric circuit interrupter for indicating significant loss of vacuum in the interrupter envelope.

A specific object of my invention is to provide simple and reliable mechanical signal means responsive to reversely initiated contact movement for indicating loss of vacuum in a vacuum type electric circuit interrupter.

In carrying out my invention in one preferred embodiment, I employ a vacuum type circuit interrupting device having a movable electrode biased to one operative position by means responsive to differential pressure within and without the evacuated envelope. Actuating mechanism for the movable electrode includes a lost-motion connection and an indicating member movably latched in position on one actuating member of the mechanism. The indicating member is arranged to be released for movement to a fault indicating position only in response to such relative movement at the lost-motion connection as results from contact movement reversely initiated by loss of differential pressure bias on the moving electrode.

My invention will be more fully understood and its various objects and advantages further appreciated by referring now to the following detailed description taken in conjunction with the accompanying drawing where- 1n:

FIG. 1 is a diagrammatic representation of a circuit breaker embodying my invention showing the circuit breaker actuating mechanism in cross section with the fault indicating device in normal operating position, and

FIG. 2 is a fragmentary representation of the same embodiment of the invention shown at FIG. 1 but with the fault indicator shown in tripped position.

Referring now to the drawing, I have shown my invention applied to a vacuum type electric circuit interrupting device 10 comprising an evcuated envelope 11 having at one end a deformable wall portion shown as a reentrantly positioned metallic bellows 12. A pair of relatively movable cooperating switch contacts are positioned within the envelope 11 and comprise a fixed contact member 13 and a slidably movable contact member 14 actuable into and out of engagement with the contact 13. The movable inner end of the bellows 12 is connected in sealing relation with the contact 14 as indicated at 15.

The actuating mechanism for the movable contact member 14 as illustrated in the drawing comprises a pair of axially aligned slidable rods 16 and 17 having a lost-motion coupling therebetween indicated generally as 18. The switch actuating member or rod 17 is arranged to be driven from circuit opening to circuit closing position by a motor-driven operating cam 19 and a latch 20 is provided to retain the actuating rod 17 in its circuit closing position. A solenoid 21 is shown for releasing the latch 20. The operatng cam 19 is driven by a motor 22 energized from a suitable source of control power through a normally open control switch 23 which for the purpose of illustration is shown as manually operable. The switch actuating rod 17 is strongly biased toward its circuit opening positon by means of an actuating compression spring 24 positioned between a shoulder 25 on the rod 17 and a suitable fixed support or frame portion 26.

By means of the lost-motion connection 18 the switch operating rod 17 is loosely connected to a movable switch member shown as an axially aligned slidable hollow rod or shaft 16. The movable switch rod 16 is slidably mounted in the frame portion 26 and is positively connected to the movable contact member 14 by means of a bell crank 27. The lost-motion connection 18' is illustrated as a cage-like head portion 30 on the upper end of the switch actuating rod 17 in cooperation with a shoulder or flange 31 at the lower end of the switch 3 rod 16. The shoulder 31 is positioned within the cage 30 for limited relative movement within the cage.

The movable switch member 16 and the positively connected movable contact member 14 are biased toward circuit closing position by reason of the differential pressure exerted upon the expansible bellows 12. This differential pressure arises by reason of the fact that the fixed end of the bellows which is sealed to the envelope 11 at a point 32 is open to the ambient fluid surrounding the vacuum interrupting device so that the bellows is pressed inwardly by the differential pressure within and without the envelope 11. Opposing the closing bias of the bellows 12 I have shown an oppositely acting compression spring 33 acting between the frame bracket 26 and the head 31 of the switch member 16. The spring 33 is normally overcome by the biasing force of the bellows 12 so that the net bias of the switch member 16 and movable contact 14 is in the contact-closing direction. As will become more evident hereinafter the opposing compression spring 33 acts only as a push-off spring to ensure that the moving contact 14 moves to open circuit position in the event that the differential pressure bias of the bellows 12 is diminished by some predetermined amount.

The vacuum interrupter actuating mechanism thus far described is in itself the invention of Howard A. Fohrhaltz and is shown and described in a co-pending patent application Ser. No. 570,485 filed by Howard A. Fohrhaltz on Aug. 5, 1966 and assigned to the same assignee as my present application.

Briefiy, the mode of operation of the foregoing switch actuating mechanism may be described as follows. Referring to FIG. 1, it will be observed that the circuit breaker is there shown in circuit closing position with the swtch actuating member 17 shown latched up against the bias of the actuating spring 24. When the latch 20 is released by energization by the trip solenoid 21 the actuating rod 17 moves vertically downward under action of the spring 24 and after a limited amount of lost motion in the connection 18, the cage engages the shoulder 31 of the movable switch rod 16. Thereafter the switch rod 16 and positively connected movable contact 14 are constrained to follow the spring actuated downward movement of the actuating member 17 thereby to separate the

contacts

13 and 14. In the open circuit position of the mechanism the shoulder 31 on the switch member 16 is held in engagement with the upper lip of the cage 30 by reason of the closing bias exerted on the switch member 16 by the expansible bellows 12. To return the actuating mechanism to circuit-closing position the motor 22 is energized by closing the control switch 23 thereby to rotate the cam 19 and drive the switch actutaing member 17 positively upward against the bias of the spring 24. In this upward movement the movable switch member 16 remains in contact with the upper lip of the cage 30 by reason of the closing bias on the switch member and is thus constrained to move upward to circuitclosing position at the same rate as the actuating member 17. When the

contacts

13 and 14 come into engagement further upward movement of the switch member 16 is prevented and thereafter the switch actuating member continues to move to its latched position by reason of the overtravel permitted in the lost-motion coupling 18. When the latch 20 is engaged the mechanism has returned to its position shown at FIG. 1.

It may be observed that with the circuit breaker mecanism in the circuit-closing position shown in FIG. 1 the actuating mechanism illustrated provides for automatic separation at the

contacts

13 and 14 in the event that vacuum is lost (i.e., internal pressure increases) in the envelope 11 by a predetermined amount. This predetermined amount is determined by the point at which the differential pressure bias of the bellows 12, as it is diminished by loss of vacuum, is overcome by the opposing force of the push-off spring 33. At this point the moving contact 14 will move to open circuit position under the reverse bias force exerted by the spring 33. This movement is permitted by reason of lost motion provided in the coupling 18 and the fact that the upward overtravel movement of the switch actuating member 17 is so proportioned that only a portion of the lost motion is taken up in overtravel on contact closure. The member 16 is thus free to move downardly away from its circuitclosing position independently of circuit-opening movement of the switch actuating member 17 and within the limits of lost motion provided in the coupling 18. This automatic response to predetermined loss of vacuum in the vacuum interrupting device 10 renders it impossible thereafter to engage the

contacts

13 and 14. Thus protection against loss of vacuum is provided by preventing switch operation under such defective contact conditions. Such a protective means is described and claimed in a co-pending patent application Ser. No. 570,- 484 filed by O. P. McCarty and F. S. Urbanek on Aug. 5, 1966 and assigned to the same assignee as my present application.

By my present invention I provide means for indicating or otherwise signalling the fact that the movable contact member and connected switch member 16 have moved to open circuit position independently of the switch actuating member 17, as due to vacuum loss in the interrupting device 10. The signalling means illustrated comprises a cylindrical cap 40 movably mounted upon the upper end of the hollow switch rod 16 and biased for movement to an extended position relative to the rod 16 by means of a compression spring 41 interposed between the upper end of the rod 16 and the outer end of the cap 40. The indicating cap 40 is latched against its bias in a normal operating position shown at FIG. 1 by means of a pair of diametrically opposite movable ball detents-42 which are positioned in holes in the upper end of the hollow rod 16 and cooperable with normally aligned internal recesses, shown as holes 43, in the cap 40.

The detent balls 42 are normally retained in radially extended position engaging the cap 40 by means of a retainer plug 44 positioned in the upper end of the hollow switch member 16. The retainer plug 44 is enlarged at its upper end and this upper end fits into an end portion of the rod 16 having an enlarged internal diameter. Thus the retainer plug 44 can move into the hollow switch rod 16 only to the limited extent shown at FIG. 1 but is free to move axially outward (i.e., upward as shown in the drawing) with respect to the switch rod 16. If the retainer 44 is so moved axially outward with respect to the end of the hollow rod 16 the detent balls are free to move radially inward against the smaller diameter lower portion of the retainer 44 in the manner shown at FIG. 2. By such inward movement the detent balls release the indicating cap 40 for upward movement under the bias of its spring 41.

Normally the detent retainer plug 44 described above moves upwardly and downwardly as an integral part of the movable switch member 16 and thus retains the indicating cap 40 in fixed position in respect to the switch member 16. Means are provided, however, for moving the retaner plug 44 upward with respect to the switch rod 16 and thus releasing the indicating cap 40 in the event that the switch member 16 is moved downwardly independently of the switch actuating member 17. The actuator for the retainer plug 44 is an axial interference pin 45 engaging the retainer 44 at its lower end by means of a shoulder 46 and extending downwardly through the center of the hollow switch rod 16 into engagement with the switch actuating member 17. As illustrated at FIG. 1, the overtravel of the switch actuating rod 17 with respect to the switch rod 16 in the normal circuit-closing position of the mechanism takes up only a portion of the lost mo tion provided in the coupling 18. This amount of relative movement between the rods 16 and 17 is insufficient to move the actuating pin with respect to the rod 16, and in the normal operation of the actuating mechanism only this limited amount of lost motion is utilized. In normal operation, therefore, the actuating pin 45, the retainer plug 44, and the indicating cap 40 all remain relatively fixed in position with respect to the rod 16 and move integrally therewith.

In the event that the switch member 16 moves downwardly independently of the actuating member 17 with the actuating member 17 in its latching position the remainder of the lost motion provided by coupling 18 is taken up, as indicated at FIG. .2, and this extended relative movement of the rods 16 and 17 actuates the ball detent latch to release the indicating cap 40. Such release of the latch is due to the fact that, while the switch rod 16 is free to move downwardly independently of the latched actuating member 17, the pin 45 is not so free to move. When the rod 16 therefore moves downwardly independently, as by reversal of the bias on member 16 due to loss of vacuum in the interrupting device 10, the pin 45 is held against movement by the actuating member 17. As the rod 16 moves downwardly in this manner the retainer plug 44 is pushed partially out of the top end of the rod 16 and the ball detents are allowed to release the indicating cap 40 in the manner indicated at FIG. 2.

Release of the indicating cap 40 may be utilized at any desired manner to indicate loss of vacuum in the device or to actuate appropriate signalling or control devices. In the drawing at FIG. 1, I have illustrated schematically a control switch 50 actuated through a bell crank lever 51 upon release of the indicating cap 40. The switch 50 includes a normally open contact 52 connected in series circuit relation with a suitable alarm device, such as a bell 53, so that when the switch 52 is closed upon release of the indicating cap the alarm device 53 is also actuated. The switch 50 is provided also with a normally closed contact 54 connected in series circuit relation with the closing motor 22. When the indicating cap is released the contact 54 will be opened thereby to disable the motor 22 and prevent any subsequent closing movement of the actuating rod 17.

While I have described a preferred embodiment of my invention by way of illustration, many modifications will occur to those skilled in the art, and I therefore wish to have it understood that I intend herein to cover all such modifications as well 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. In an electric circuit breaker, a pair of relatively movable cooperating switch contacts biased to a circuitclosing position, a movable switch member positlvely connected to at least one of said contacts and having circuit-opening and circuit-closing positions, actuating means loosely coupled to said switch member to provide lost motion therebetween, means responsive to a predetermined defective condition of said contacts to move said switch member toward its circuit-opening position independently of said actuating means, and signal means responsive to said independent movement of said switch member.

2. A circuit breaker according to claim 1 wherein said signal means comprises a signal member movably mounted on said switch member, and means responsive to said independent movement to move said signal member relative to said switch member.

3. A circuit breaker according to claim 2 wherein said signal member is biased to a fault indicating position and normally latched against its bias in a normal operating position and wherein said means responsive to independent movement of said switch member includes latch releasing means.

4. A circuit breaker according to claim 1 wherein said signal means comprises a signal member movably mounted on said switch member and biased to a fault indicating position, latch mean-s for holding said signal member against its bias in a normal operating position, means responsive to circuit-opening movement of said switch member to release said latch means, and means responsive to simultaneous circuit-opening movement of said switch actuating member for disabling said latch releasing means.

5. In an electric circuit interrupter of the vacuum interrupting type, an evacuated envelope, a pair of relatively movable cooperating switch contacts mounted in said envelope, means responsive to differential pressure within and without said envelope for biasing said contacts to circuit-closing position, a movable switch member positively connected to move said contacts between open and closed circuit position, said switch member having corresponding open and closed circuit positions, a switch actuating member loosely connected to said movable switch member to provide lost motion therebetween, said movable switch member being movable away from its circuit-closing position independently of said switch actuating member, means operable upon significant decrease in said differential pressure effect independent circuit opening movement of said movable switch member, and signal means responsive to said independent circuitopening movement.

6. A circuit breaker according to claim 5 wherein said signal means comprises a signal member movably mounted on said movable switch member and biased to a fault indicating position, latch means for holding said signal member against its bias in a normal operating position relative to said movable switch member, and latch-releasing means responsive to said independent circuit opening movement of said movable switch member.

7. A circuit breaker according to claim 6 in which said latch releasing means comprises a member movable relative to said movable switch member and positioned to be operatively engaged by said actuating member upon said independent circuit opening movement of said movable switch member.

8. In an electric circuit breaker, fixed and movable cooperating switch contacts biased to circuit closing position, an axially movable switch rod positively connected to said movable contact and having circuit opening and circuit closing positions, an axially movable actuating rod loosely coupled to said switch rod to provide limited lost motion therebetween, said actuating rod being movable in circuit closing operation to a normal overtravel position relative to said switch rod intermediate the limits of said lost motion thereby to permit independent circuit-opening movement of said switch rod, an indicating member movably mounted on said switch rod and biased to a fault-indicating position, latch means retaining said indicating member against its bias in normal operating position, and an interference member operable to release said latch means in response to abnormal relative movement of said rods.

9. An electric circuit breaker according to claim 8 wherein said movable switch rod is hollow and in axial alignment with said actuating rod, adjacent ends of said rods are connected through a lost-motion coupling, said indicating member and latch means are mounted on the remote of said end of said switch rod, and said interference member extends from said latch means through said hollow switch rod to operatively engage said actuating rod upon abnormal relative movement of said rods.

10. A circuit breaker according to claim 9 wherein said contacts are mounted in an evacuated envelope having a deformable wall portion sealed to said movable contact, differential pressure on said wall portion biasing said contacts to circuit closing position, and a push-off spring is provided to oppose but not normally overcome such differential pressure bias, said push-off spring being effective upon predetermined loss of vacuum in said envelope to move said movable contact to circuit-opening position independently of said actuating member.

(References on following page) 4 7 8 References Cited JOHN W. CALDWELL, Primary Examiner UNITED STATES PATENTS D. MYER, Assistant Examiner 1,176,202 3/1916 Cheney 317-54 3,403,297 9/1968 Crouch 340236 XR 3,404,247 10/1968 Glassanos 200 s3 XR 5