FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
ECUMENICAL MECHANISM FOR CIRCUIT BREAKERS;
LARSEN & TOUBRO LIMITED, A COMPANY INCORPORATED UNDER THE COMPANIES ACT, 1956, WHOSE ADDRESS IS L&T HOUSE, BALLARD ESTATE, MUMBAI - 400 001, MAHARASHTRA, INDIA
THE FOLLOWING SPECIFICATION
PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

FIELD OF INVENTION
The present invention relates to molded case circuit breakers for operating contact system.
BACKGROUND OF INVENTION
A circuit breaker is a mechanical switching device capable of making, carrying and breaking currents. Under normal circuit conditions it makes the circuit closed, carries current for a specified time and breaks the circuit under specified abnormal circuit conditions. A circuit breaker can be manually or automatically opened and closed, to protect conductors or equipments from damage caused by excessive heating due to over current in abnormal conditions such as overload or short-circuit.
Moulded Case Circuit Breakers (MCCBs) are employed for current interruption. MCCBs are typically utilized to protect instruments from damage during adverse conditions prevailing during operation of the circuit in which the MCCB is employed. During adverse conditions like short circuit, the current rises to an alarmingly high level. This rise in current beyond a limit may cause damage to the parts in the electrical system. Hence during these conditions the circuit requires to be 'opened' to protect the parts of the electrical system.
The mechanism of the circuit breaker plays a vital role in determining the credibility of the breaker. A good mechanism must ensure quick and independent of manually opening and closing of contact system.
Basically there are five operations that an MCCB performs. These operations are (1) ON (2) OFF (3) TRIP (4) TRIP FREE and (5) RESET.
The first two operations are initiated by operator whereas the trip signal is given by the release which senses the abnormal conditions and gives TRIP command to the mechanism, so that the latter opens the circuit.

Generally, a user or an operator accesses the mechanism through a knob projecting outwards from the housing of the breaker. The knob is placed over the fork of the operating mechanism. In conventional type MCCBs, breaker features three positions in the top cover near the knob to show. These positions are ON, OFF and TRIP. 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 OFF and TRIP indicates the OFF and TRIP state of the circuit breaker.
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) should be marked as ON POSITION. The other extreme end in both cases is marked as the OFF POSITION. The knob will be somewhere near the center (based on the design of the mechanism) to indicate the TRIP POSITION.
As said above, TRIP command is given automatically to the contacts by the release if it senses an abnormal condition like overload and short circuit. If the trip signal is given, the breaker opens the circuit and the knob goes to the trip position to show the operator that a fault has occurred in the system. If the operator wants to switch ON the breaker after the breaker is tripped, he/she cannot do it without resetting the breaker. This is to make sure that the operator shouldn't switch ON the breaker before clearing the fault.
Resetting of the breaker is done by moving the knob (fork) towards the OFF position from the TRIP position. This movement loads the mechanism spring and now it is possible for the operator to ON the breaker. All these mechanisms are called semiautomatic mechanisms since for ON and OFF operation, the knob of the breaker has to be taken from their respective ON or OFF positions to a position called dead center beyond which he mechanism becomes independent of the operator and completes the respective action by its own automatically.
However, in such mechanisms, the latch bracket interrupts the rotation of the trip lever, and stops the reset operation. Further, it is difficult to retain the latch bracket in its original position during reset. Also it is difficult to achieve the trip-free and contact reset due to the constraint in the height of the fork.

A novel mechanism for typical circuit breakers is therefore required and the same is disclosed as follows.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a stopper to arrest the rotation of the latch bracket during tripped condition, so that the latch bracket may not interrupt the rotation of the trip lever, and stop the reset operation.
It is an object of the present invention to provide a spring action for retaining the latch bracket in its original position during reset.
It is an object of the present invention to provide trip-free and contact reset by providing an optimum height of the fork.
In accordance with this there is provided a mechanism for a circuit breaker. In one embodiment herein, the mechanism comprises a latch bracket having a first profile and a second profile. The first profile guides the latch bracket and helps in stopping its rotation during tripped condition. The second profile acts as a spring for retaining the original position of the latch bracket during reset. Further, there are provided bends in the fork for allowing the trip lever to rotate further for obtaining a trip free and contact resetting.
BRIEF DESCRIPTION OF THE DRAWINGS
Reference will be made to embodiments of the invention, examples of which may be illustrated in the accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in the context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
Fig. 1 shows exploded view of the mechanism according to the present invention.
Fig. 2 shows the ON POSITION according to the present invention.
Fig. 3 shows the OFF POSITION according to the present invention.
Fig. 4 shows the TRIP POSITION according to the present invention.

Fig. 5 shows the TRIP-FREE POSITION according to the present invention. Fig. 6 shows in detail the latch bracket according to the present invention. Fig. 7 shows in detail the fork according to the present invention. Fig. 8 shows the present mechanism according to the present invention.
DESCRIPTION OF THE INVENTION
Disclosed herein is a universal mechanism for MCCBs that comprises a latch bracket having a first profile and a second profile. The first profile guides the latch bracket and helps in stopping its rotation during tripped condition. The second profile acts as a spring for retaining the original position of the latch bracket during reset. Further, there are provided bends in the fork for allowing the trip lever to rotate further for obtaining a trip free and contact resetting.
Fig. 1 is the exploded views of the mechanism according to the present invention. Fig 1 shows a knob 1 attached to a fork 3, which is mounted on the mounting plates 4. A reset pin 21 is used to stop the fork in the TRIP position and to reset the mechanism back to the OFF position. This is also shown in Fig. 4. A trip lever 11 is hinged to the mounting plates 4 with the help of a trip lever pin 10. Upper links 2 are connected separately to each side of the trip lever 11 with the help of a UL pin 22.
The orientation and position of the upper links 2 and lower links 5 are maintained by the using UL_LL pin 23. The lower links 5 are connected to a connecting link 8 by using LL_CL pin 20. The connecting link 8 is connected to the mounting plates 4 by using a coupling pin 25.
A drive shaft pin 9 is used to connect the connecting link 8 and cassette rotor shaft. The main springs are connected between the fork 3 and spring pin 7 through which the transmission of energy occurs from knob 1 to a drive shaft Pin 9. The upper links 2 and the iower links 5 which performs the operations meant for an MCCB through connecting link 8. The connecting link 8 in turn rotates the cassette accordingly by using the drive shaft pin 9.
Fig. 2 shows the ON POSITION and Fig. 3 shows the OFF position POSITION according to the present invention. A trip latch 15 is provided for holding

the trip lever 11 in its original position as shown in Fig. 2 and Fig. 3. The trip plate 16 hold s the trip latch 15 in the ON & OFF conditions. During TRIP & TRIP-FREE operations the trip signal is given to the trip plate 16 and as a result, the trip latch 15 is released enabling the trip lever to rotate about its pivot point.
Fig. 4 shows the TRIP POSITION and Fig. 5 shows the TRIP-FREE POSITION according to the present invention. The components trip latch pin 13, trip plate pin 14, trip latch 15 and trip plate 16 comprises of the trip system. All the operations are explained below.
(1) ON position : The ON position is shown in Fig.2. In this position, the fork will be in the position far away from the trip system. The upper links 2, lower links 5 and connecting link 8 will be holding the contacts in the closed circuit condition with the help of the drive shaft pin 9.
(2) OFF/RESET position : The OFF/RESET position is as shown in Fig.3. In this position, the fork will be in the position very near to the trip system. The upper links 2, lower links 5 and connecting link 8 will be holding the contacts in the open circuit condition with the help of the drive shaft pin 9.
(3) TRIP position : The TRIP position is shown in Fig. 4. In this position, the fork 3 will be in the position anywhere between the ON & OFF positions and the position is constrained by the rotation of trip lever 11. The Reset pin 21 stops the trip lever 11 from further rotation. And the contacts will be in the opened condition.
(4) TRIP FREE position : The TRIP FREE position is shown in Fig. 5. This is an unstable position for the fork 3, as the knob will be held in the knob's ON position by the operator. In this position, except the fork 3 and knob 1, all the other parts will be in the positions as described in the trip position.
Fig. 6 and Fig. 7 show in detail the latch bracket and the fork according to the present invention.

Fig. 8 shows the present mechanism according to the present invention. It can be seen from the figure that the present invention helps in reducing the number of components and increase the rotation of the trip lever.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

We Claim
1. A mechanism for circuit breaker comprising:
a latch bracket having a first profile and a second profile,
the first profile guiding the latch bracket and stopping its rotation during tripped condition, and
the second profile eliminating acts as a spring for retaining the original position of the latch bracket during reset;
a fork provided with bends for allowing the trip lever to rotate further for obtaining a trip free and contact resetting.
2. The mechanism as in claim 1, wherein the first profile comprises a reset pin for stopping trip lever of the circuit breaker from further rotation and for resetting the mechanism back to the OFF position
3. The mechanism as in claim 1, wherein the mechanism includes a knob attached to the fork, which is mounted on mounting plates.
4. The mechanism as in claim 3, wherein a trip lever is hinged to the mounting plates with the help of a trip lever pin.