A) TECHNICAL FIELD

[0001] The present invention generally relates to circuit breakers and particularly relates to current limiting circuit breakers such a Moulded Case Circuit Breaker (MCCB). The present invention more particularly relates to providing an operating mechanism for MCCB to increase opening velocity of contacts during fault in the MCCB.

B) BACKGROUND OF THE INVENTION

[0002] A circuit breaker can be manually opened and closed, as well as automatically opened to protect conductors or equipment fix)m damage caused by excessive heating due to over current in abnormal conditions such as overload or short-circuit. The mechanism of the circuit breaker plays a vital role in determining die credibility of the circuit breaker. A circuit breaker mechanism should ensure quick and manually independent opening and closing of contact system. Four operations are performed using die mechanism namely ON, OFF, TRIP and Trip Free mechanisms. The first two operations are initiated by operator whereas for the next two. A trip signal is given by the release which senses the abnormal conditions and gives TRIP command to the mechanism, so that the mechanism opens the circuit the operator has access to the mechanism through the knob which will be projected outwards from the housing of the breaker. The knob is placed over the fork of the operating mechanism. In conventional type MCCBs, breaker will feature three positions in the top cover near the knob to show ON, OFF and TRIP conditions in the circuit breaker. When the knob indicates ON it means the breaker is in ON condition i.e., the current path is closed. Similarly the position of the knob indicates other states of the circuit breaker.

[0003] According to the standards, the top position of the knob (if the breaker is placed vertically) or the longest distant position of the knob away from the operator (if the breaker is mounted horizontally) shotdd be marked as ON POSITION. The other extreme end in both cas is marked as the OFF POSITION. The knob will be somewhere near to tiie centre (based on the design of the medianism) to indicate the TRIP POSITION. A TRIP command is given automatically to the contacts by the releaw if it senses an abnormal condition like overload and short circuit. Following flie trip signal the circuit breaker opens the circuit and the knob goes to the trip position to show the operator that a iault has occurred in the circuit hreaker. Once the iH-eaker is tripped, switching ON the circuit breaker by the operator gets failed without resetting the breaker. This is to make sure that the c^omtor shouldn't switch ON the breaker before clearing the fault.

[0004] Resetting of the breaker is done by moving iJie knob (foric) towards tiie OFF position fixm the TRIP position. This movement loads the mechanism spring and now makes it possible for the operator to ON the breaker. All these mechanisms are called semi-automatic mechanisms since for ON and OFF operation, the knob of the breaker has to be takm frcn then- respective ON or OFF positions to a position called dead centre bond which the mechanism becomes independent of the operator and completes tibe respective action by its own automatically. However, the opening velocity of flie existing mechanism is low since a considerable amount of time is taken to trip the breaker. This makes the contacts to open comparatively slow Smog tmli condition which brings down the life of the breaker. Moreover, frow required to opo-ate the knob during ON and OFF operation is high.

[0005] Hence, there exists a need to provide an effidait operating mechanism for the MCCB to increase opening velocity of contats within the MCCB during the MCCB fault. Also there exists a need to reduce the force required to opCTate the knob during ON and OFF operation of the circuit breaker. Further there exists a need to increase the life of the circuit breier by reducing fauh clearing time.

[0006] The ifcove maition^ shortcomings, dis^aatages and problrans are ad^essed herein and which will be understood by reading and studying the following specification.
C) OBJECT OF THE INVENTION

[0007] These and other objects and advantages of tte present invention will become readily apparait from the following d^led description taken in conjunction with the accompanying drawings.

[0008] The primary object of the present invaiti(i is to provide an operating mechanism for MCCB to increase opening velocity of contacts within the MCCB during the MCCB fauh.

[0009] Another object of the present invraition is to provide an operating mechanism for MCCB to reduce the force required to operate the knob during ON and OFF operation of the MCCB.

[0010] Another object of the present invention is to |Wovide an operating mechanism for MCCB to increase the life of the circuit breaker by reducing fault clearing time or total trip time during circuit bradter fault.

[0011] Yet another object of the present invention is to provide an operating mechanism for MCCB including fewer compcnts in assembly of the mechanism and few operating Unks.

[0012] Yet anothor object of the present invention is to provide an operating mechanism for MCCB having higher mechanical advantage for knob force to main spring force provided in the mechanism.

D) SUMMARY OF THE INVENTION
[0013] The various embodiments of the jMresent inventifm iwovide an operating mechanism for MCCB to increase the op«iing velod of contacts within the MCCB during fault in the MCCB. According to cme embodiment of the present invention the operating mechanism includes a knob attached to a fork, which is mounted on the mounting plates with the help of fork rivets. The Fork-Trip lever pin is used to stop the fork in the trip position and to reset the mechanism back to the OFF position. The trip lever is hinged to the mounting plates with the help of trip lever rivets. The operating links are connected separately to each side of the trip lever with the help of Trip lever-Link rivets.

[0014] According to an embodiment of the presoit inv«ition, the spring pin maintains the orientation and position of the operating links. The spring pin helps in the synchronous movement of the operating links. The springs are coimected betwerai the fork and spring pin throu vMdi the transihissiOn of energy occurs from knob to the drive shaft Pin. The operating links are different from the conventional mechanisms, which performs the operations meant for the MCCB. The operating links employ a slot through which the drive shaft Pin can slide through during ON and OFF cqierations of the MCCB. During trip operation and trip free operations, the drive diaft Pin is pulled along with the operating links, as a result, the trip operaticm will be faster.

[0015] According to one embodiment of the pres«ait invention, the trip latch holds the trip lever in its original position. And the trip plate holds the trip latch in the ON and OFF conditions of the MCCB. Dimng trip and trip free operations a trip signal is gven to the trip plate thus, tfie trip latch is released enabling the trip lever to rotate about its pivot point. The components trip latch pin, trip plate pin, trip latch & trip plate comjaises a trip system.

[0016] Accofding to one embodimait of the ff3 inveion, wlwsi the MCCB is in ON, the fork reaches a position far away from the trip system the opoting links holds the contacts in the closed circuit condition with the help of the drive shaft pin. When in OFF position of the MCCB the fork reaches a position very near to the trip systan, the operating links holds the contacts in the open circuit condition with the help of the drive diaft pin.

[0017] According to one embodiment of the jwesent invention, when the MCCB is in TRIP position, the fork will be in a poi^tion between the ON and OFF position. Further the trip position is constnuned by the rotation of trip lever. The fork-trip lever pin stops the trip lever frwn further rotation. Thus, the contacts of the MCCB will be in the opened condition.When in TRIP FREE position of the MCCB which is an unstable position for the foric, as the knob will be held in the knobs ON position by the cerator.

[0018] In one embodiment of the present invention, a reset operation is a manually dq)endent operation, where the forit and the knob are moved towards the direction of the trip system. The Fork-Trip lever Pin in turn presses the trip lever, opposite to the direction towards which the trip lever pin is rotated during trip OR trip free operations. Ehaing this time, the spring is charged and when the trip lever is latched by the trip latch, the mechanism attains the OFF position. This opaation is called RESET operation. Without resetting a breaker to its OFF position from TRIP OR TltlP FREE position, it is impossible to close the circuit in the MCCB.

[0019] According to an embodiment of the present invraition, the mechanism reduces the force required to operate the knob during ON and OFF operation of the MCCB. The mechanism helps in increasing the life of the circuit breaker by reducing fault clearing tune or totrf trip time during circuit breaker fault. The mechanism includes fewer components in assembly of the mechanism and few operating links.

E) BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The other objects, features and advantages will oamr to those skilled in the art from the following description of the prefmd embodiment and the accompanying drawings in which:

[0021] FIG. 1 illustrates an exploded view in an MCCB operating mechanism according to one embodiment of the present invention.

[0022] FIG. 2 illustrates side pCTspective view of MCCB operating mechanism in ON position according to one ranbodiment of the prent invention.

[0023] FIG. 3 illustrates side perspective view of MCCB operating mechanism in ON position without springs according to one embodiment of the present invention.

[0024] FIG. 4 illustrates side perspective view of MCCB operating mechanism in OFF position according to one embodiment of the preint invention.

[0025] FIG. 5 illustrates side perspective view of MCCB operating mechanism in TRIP position without springs according to one embodiment of the pres«it invention.

[0026] FIG. 6 illustrate side perspective view of MCCB opiating mechanism in TRIP FREE position without springs according to one anbodiment of the {M-esent invention.

[0027] Althou specific features of the present inventiwi are shown in some drawings and not in others. This is done for cwivenience only as each feature may be combined with any or all of the other features in accordance with tlw present invention.

F) DETAILED DESCRIPTION OF THE DRAWOfC
[0028] In the following detailed description, refefence is made to the accompanying drawings that form a part hereof, and in which the ecific embodimaits that may be practiced is shown by way of illustration. These embodiments are described in sufBcient detail to msSah those skilled in the art to practice the embodiments and it is to be uiideratood that the logical, mechanical and otho* changes may be made without detailing fixnn the scope of the embodiments. The following detailed description is therefore not to be taken in a limiting soise.

[0029] According to one embodiment of the i»%seiit invoition the opo'ating mechanism includes a knob attached to a fork, whidb is mounted on the mounting plates with the help of foik rivets. The Feration. Without resetting a breaker to its OFF position from TRIP OR TRIP FREE position, it is impossible to close the circuit in the MCCB.

[0034] FIG. 1 illustrates an exploded view in an MCCB (q>crating mechanism according to one embodiment of the iwesent invention. With respect to FIG. 1, the operating mechfflism includes a knob 1 ai^ached to a foric 3, which is mounted on the mounting plates 4 with the help of at rivets 5. The Foric-Trip lever pin 2 is used to stop the fork in the teip position and to reset the mechanism back to the OFF position (as shown in FIG. 4). The trip lever 11 is hinged to the mounting plates 4 with the help of trip lever rivets 10. The operating links 8 are connected separately to eadi side of the trip lever 11 with the help of Trip lever-Link rivets 12. The orioitation and position of the operating links 8 are maintained by the presence of spting pin 7. The spring pin 7 helps in the synchronous movement of the opentting links 8. The springs 6 are connected between the foric 3 and spring jrin 7 through which the transmission of energy occurs from knob 1 to the drive shaft Pin 9. The operating links 8 are different from the conventional mechanisms, which performs the operations meant for the MCCB. The operating links 8 employ a slot through which the drive shaft Pin 9 can slide thsoug^ during ON and OFF operations of the MCCB. During trip operation and trip free opo-ations, the drive shaft Pin 9 is pulled along with the operating links 8, as a result, the trip operation will be faster.

[0035] The trip latch 15 holds the trip lever 11 in its (niginal position as. And the trip plate 16 holds the trip latch 15 in the ON ai OFF conditions of the MCCB. During trip and trip free operations a trip agnal is given to the trip plate 16 thus, the trip latch 15 is released enabling tfw trip lever 11 to rotate about its pivot point. The components trip latch pin 13, trip plate pin 14, trip latch 15 & trip plate 16 comprises a trip system.

[0036] FIG. 2 illustrates side perspective view of MCCB operating mechanism in ON position according to one embodiment of the present invention. With respect to FIG. 2, in ON position of the MCCB the fb 1 in the direction away from trip latch 15 (as^diown in FIG. 1), there is mi useful action except the spring elongaticm, until the spring crosses the ON dad centre. Simultaneously, when the springs 6 CTOSS the ON dead coatre, the q>»ating links 8 are pulled through the qwing pin 7 towards the ON position (as slK>wn in fig.2), and the circuit will be closed by the MCCB. The fork comes to ite stable ON position.

[0037] FIG. 3 illustrates side perspective view of MCCB)erating mechanism in ON position without springs accordmg to one onbodiment of the ja-esent invention. In ON position of the MCCB the fork 3 reach a position far away from the trip system, the operating links 8 holds the contacts in the closed circuit condition with the help of tfie drive shaft pin 9. Wh«i an operator moves the foric 3 indirectly through the knob 1 in the direction away from trip latch 15 (as shown in FIG. 1). The trip latch 15 holds flie trip lever 11 in its original position (as shown in figs.2 and 3).

[0038] FIG. 4 illustrates side perspective view of MCCB operating mechanism in OFF position according to one embodimait of the present invention. With respect to FIG. 4, when in OFF position of the MCCB the fork reaches a position very near to the trip system, the operating links 8 holds tiie contacts in the open circuit condition with the help of the drive shaft pin 9. When an operator moves the fork 3 indirectly throu the kacA 1 in the direction towards trip latch 15, there is no usefiil action exc the spring elongation, until the spring crosses the OFF dead centre. Simidteneously, when the springs 6 cross the OFF dead centre, the operating links 8 sat pulled through the spring pin 7 towards the OFF position, and the circuit will be opened by the circuit breaker. The fork comes to its stable OFF position.

[0039] FIG. 5 illustrates side perspective view of MCCB opiating mechamsm in TRIP position without springs according to one onfaodiment of the present invention. With respect to FIG. 5, in TRIP position of the MCCB the fork 3 will be in the position betweoi the ON and OFF positions. Further the trip position is constrained by the rotation of trip lever 11. The foric-trip lever jrin 2 stops the trip lever 11 from fiirther rotation. Thus, the contacts of the MCCB will be in the opened condition.

[0040] The trip opwation is a spontaneous action. When a trip signal is received by the circuit breaker, the trip plate 16 gets disturbed and the trip latch 15 releases the trip lever 11, Further, the trip levar 11 rotates about the axis of trip lever rivet 10 and the operating links 8 are pulled towards the foric 3 (as shown in fig.5). Thereby the circuit of the MCCB gets opened protecting the MCCB and associated devices which are connected down the line. The fork knob 1 comes to a position in between the ON and OFF positions indicating tripping of the circuit breaker.

[0041] FIG. 6 illustrates side perspective view of MCCB operating mechanism in TRIP FREE position without brings according to one embodiment of the present invention. With respect to FIG. 6 in TRIP FREE position of the MCCB which is an unstable position for the fork 3, as the knob will be held in the knobs ON position by the operator.

[0042] The trip free operation is a spontaneous action. When a trip signal is received by the circuit breaker, the trip plate 16 gets distrabed and the trip latch 15 (as shown in FIG. 1) releases the trip lever 11. Further, the trip lever 11 rotates about the axis of trip lever rivet 10, and flw operating links 8 are pulled towards the fork 3 (as shown in fig.5), Therdjy tfie circuit of the MCCB gets opened protecting the MCCB and associated devices which are connected down the line. During the trip free operatiwi the foric knob 1 is by the oparator. Further, when the op&t&tot releases the fork knob 1, tlw fork knob 1 goes back to a position in between the ON and OFF positioaa iicating tripping of the circuit breaker.

[0043] Unlike conventional mechanisms that are provided with four bar mechanian during ON and OFF conditions and 5 bar mechanism during the other two operating conditions, the system present invent tion has 4 bar mechanism in all the four opoations.

G) ADVANTAGES OF THE INVENTION
[0044] The various onbodiments of the invention provide an operating mechanism for MCCB to increase opening velocity of contacts within the MCCB during fault in the MCCB. The mechanian reduces the force required to opo-ate the knob during ON and OFF opoation of the MCCB. The mechanism helps in increasing the life of the circuit breaker by reducing fault clearing time or total trip time during circuit breaker fault.

The mechanism includes fewer components in assembly of the mectoiism smd few operating links. This makes the assembly easy and rediK^ the time involved in construction.

[0045] Although the invention is described wiA various specific embodiments, it will be obvious for a person skilled in the art to practice the invention with modifications. However, all such modifications are deemed to be within the scope of the claims.

[0046] It is also to be understood that the following claims are intended to cover all of the generic and specific features of the jOTsrait invention described herein and all the statonents of the scope of the invartion which as a matter of language might be said to fall there between.

CLAIMS
What is claimed is:

1. An operating mechanism for Moulded Case Circuit Breaker, the mechanism
comprising:
A plurality of mounting plates;
a fork mounted on the mounting plates;
a knob attached to the fork;
a trip lever attached to the plurality of mounting plates;
at least two operating links connected separately to each side of the trip lever;
a spring pin to interconnect the at least two operating links; and
a drive shaft pin;
wherein the at least two operating links provide a slot through which the drive shaft pin slide through during the ON and OFF operations and the drive shaft along with the at least two operating links is pulled to provide a faster trip and trip free operation.

2. The mechanism according to claim 1, wherein the operating links are provided with slots to work as a slider.

3. The mechanism according to claim 1, wherein 4 bar mechanism is provided in all the four operations.

4. The mechanism according to claim 1, wherein further comprising a fork-trip lever pin to provide at least one to lock the fork in the trip position and to reset the mechanism to the OFF position.

5. The mechanism according to claim 1, wherein the folk is mounted on the mounting plates using one or more fork rivets.

6. The mechanism according to claim 1, wherein the trip lever is hinged to the mounting plates using one or more trip lever rivets.
15

7. The mechanism according to claim 1, wherein the at least two operating links are connected separately to each side of the trip lever with the help of trip lever-link rivets.

8. The mechanism according to claim 1, wherein the spring pin maintains the orientation and the position of the at least two operating links.

9. The mechanism according to claim 1, further comprising one or more springs connected between the fork and the spring pin.

10. The mechanism according to claim 1, wherein the one or more springs provides for transmission of energy from the knob to the drive shaft pin.

11. The mechanism according to claim 1, further comprising a trip latch to hold the trip lever in the first position.

12. The mechanism according to claim 1, wherein a trip plate holds the trip latch in the ON and OFF conditions of the MCCB.

13. The mechanism according to claim 1, wherein the trip latch releases the trip lever during trip and trip free operations of the MCCB thereby enabling the trip lever to rotate about its pivot joint.

14. The mechanism according to claim 1, wherein at least one of the trip latch, trip lever, trip plate, and the trip pin forms a trip system.

15. The mechanism according to claim 1, wherein the fork is pushed away from the trip system and the at least two operating links holds the contacts in a closed circuit condition using the drive shaft pin when the MCCB is in ON position.

16. The mechanism according to claim 1, wherein the fork leaches a position close to the trip system and the at least two operating links holds the contacts in a closed circuit condition using the drive shaft pin when the MCCB is in OFF position.

17. The mechanism according to claim 1, wherein the fork attains a position between the ON position and the OFF position when the MCCB is in a TRIP position.

18. The mechanism according to claim 1, wherein the fork-trip lever prevents the trip lever from rotation from the trip position thereby leaving the MCCB in opened condition.