FORM2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention: IMPROVED MECHANISM TO OPERATE CONTACTS OF A CIRCUIT BREAKER
2. Applicant(s):

(a) NAME : LARSEN & TOUBRO LIMITED
(b) NATIONALITY: An Indian Company.
(c) ADDRESS: L & T House, Ballard Estate, Mumbai 400 001,
State of Maharashtra, India
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed:

TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to circuit breakers and more particularly to an improved mechanism to operate contacts of a circuit breaker.
BACKGROUND AND THE PRIOR ART
Circuit Breaker is a mechanical switching device capable of making, carrying and breaking currents. Under normal circuit conditions it will make the circuit closed, carry current for a specified time and breaks the circuit under specified abnormal circuit conditions.
Moulded Case Circuit Breakers (MCCB) are employed for current interruption. More particularly MCCBs are utilized to protect instruments from damage during adverse conditions prevailing during the operation of the circuit in which moulded case circuit breaker is employed. During adverse conditions like short circuit, the current rises to an alarmingly high level. This high current may cause damage to the parts in the electrical system. Hence during these conditions the circuit has to be opened to protect the parts after the breaker.
A circuit breaker can be manually opened and closed, as well as automatically opened to protect conductors or equipments from 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 the credibility of the breaker. A good mechanism should ensure quick and manually independent opening and closing of contact system.

Five operations are to be performed by the MCCB mechanism. They are ON, OFF, TRIP, TRIP FREE and 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.
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.
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 the state of the circuit breaker.
According to 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 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 after the resetting operation, it is possible for the operator to switch 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 taken from their respective ON or OFF positions to a position called dead center beyond which the mechanism becomes independent of the operator and completes the respective action by its own.
The drawbacks/disadvantages/limitations of the existing technologies are as follows:
1. For changing the modular or non-modular contact system, one has to redesign the link orientation to achieve same degree of rotation which contributes the velocity, contact pressure.
2. For optimizing the knob force & trip force, the link orientations has to be changed in conventional mechanisms.
3. For centering the rotor, one has to make some other arrangement in modular or non-modular contact system themselves. Normally, the rotor will be centered towards the contact system, not the mechanism. Due to this reason, it results in not achieving the desired degree of rotation, desired contact pressure and desired velocity.
Thus, there is a need to overcome the problems of the prior art. Therefore, the present inventors have developed a universal mechanism for circuit breakers which would be used for any type of modular or non-modular contact system having different drive
points.

OBJECTS OF THE INVENTION
A basic object of the present invention is to overcome the disadvantages/drawbacks of the known art.
Another object of the present invention is to provide an improved mechanism to operate contacts of a circuit breaker.
These and other advantages of the present invention will become readily apparent from the following detailed description read in conjunction with the accompanying
drawings.
SUMMARY OF THE INVENTION
There is provided an improved mechanism to operate contacts of a circuit breaker.
According to one embodiment of the present invention, there is provided improved mechanism to operate contacts of a circuit breaker, said mechanism comprising atleast one mounting plate, said mounting plate providing a profile to facilitate mounting; atleast one knob attached to a fork mounted on said profile, said fork blocked in trip position using a reset pin; atleast one trip lever hinged on said mounting plate using a trip lever pin; atleast one upper link connected to each side of said trip lever using an upper link pin; atleast one lower link connected to a connecting link using lower link-connecting link pin (24); atleast one cassette rotor shaft; atleast one spring pin connected between said fork and a spring pin; atleast one trip latch holding a trip lever; atleast one trip plate holding said trip latch.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
In the appended drawings:
Figure 1 illustrates an isometric view of mechanism with cassette.
Figure 2 illustrates an exploded view of the mechanism.
Figure 3 illustrates ON POSITION of the mechanism.
Figure 4 illustrates OFF POSITION of the mechanism.
Figure 5 illustrates TRIP POSITION of the mechanism.
Figure 6 illustrates TRIP FREE POSITION of the mechanism.
Figure 7 illustrates the component CONNECTING LINK which makes the mechanism universal.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The following drawings are illustrative of particular examples for enabling methods of the present invention, are descriptive of some of the methods, and are not intended to limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description.
Reference is first invited to Fig 1 where the isometric view of the mechanism along with the cassette is shown.

Fig. 2 shows different components used in the present mechanism.
Fig. 3-6 shows ON, OFF, TRIP and TRIP FREE position of the mechanism.
Fig. 7 shows the connecting link of the mechanism.
The invented mechanism is thus an improved mechanism for operating contacts of a circuit breaker.
DETAILED DESCRIPTION OF THE INVENTION
Accordingly in the present invention there is provided an improved mechanism for circuit breakers, which is a universal mechanism for any modular or non-modular contact system which is having a uniform degree of rotation.
The present invention has a knob 1 attached to the fork 3, which is mounted on the profile given in the mounting plates 4. The reset pin 21 is used to stop the fork in the trip position and to reset the mechanism back to the OFF position as indicated in figure. 6. The trip lever 11 is hinged to the mounting plates 4 with the help of trip lever pin 10. The upper links 2 are connected separately to each side of the trip lever 11 with the help of upper link (UL) pin 22. The orientation and position of the upper links 2 and lower links 5 are maintained by the presence of upper link - lower link (UL-LL) pin 23. The lower links 5 are connected to the connecting link 8 by using lower link - connecting link (LL-CL) pin 24. The connecting link 8 is connected to the mounting plates 4 by using the coupling pin 24. The 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 the drive shaft Pin 9. The upper links 2 and the lower links 5 which performs the operations meant for an MCCB through connecting link 8. The

connecting link 8 which in turn rotates the contact system accordingly by making use of drive shaft pin 9. The rotor is centered with respect to the mechanism.
The trip latch 15 will be holding the trip lever 11 in its original position as shown in figures 3 and 4 and the trip plate 16 will be holding the trip latch 15 in the ON and OFF conditions. During trip and trip free operations the trip signal will be 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.
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 herein below:
ON position:
ON position will be as shown in figure.3. 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.
OFF/RESET position:
OFF/RESET position will be as shown in figure 4. 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.

TRIP position:
TRIP position will be as shown in figure 5. 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.
TRIP FREE position:
TRIP FREE position will be as shown in figure6. 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 knob1, all the other parts will be as described in trip position.
The present invention uses the same mechanism for various types of contact system having uniform degree of shaft rotation by means of changing the connecting link 8 alone. By using the connecting link 8, the mechanism can be used for any types of modular or non-modular contact system having different drive points.
The mechanism can be used for any type of breaker by changing the angles between the arms 8a and 8b (a) of the connecting link 8 as shown in figure 7.
The mechanism can be assembled separately and can be introduced into any type of breaker due to its modularity. After keeping it in its original position we can just insert the connecting pin(s) to integrate with the contact system.

ADVANTAGES:
1. Making a mechanism universal to use for any types of modular or non-modular contact system having different drive points.
2. The mechanism can be assembled separately and can be introduced into any type of breaker due to its modularity.
3. Reliability in operation.
Although the embodiments herein are described with various specific embodiments, it will be obvious for a person skilled in the art to practice the embodiments herein with modifications. However, ail such modifications are deemed to be within the scope of the claims.
It is also to be understood that the following claims are intended to cover all of the generic and specific features of the embodiments described herein and all the statements of the scope of the embodiments which as a matter of language might be said to fall there between.

WE CLAIM:
1. An improved mechanism to operate contacts of a circuit breaker, said mechanism comprising:
atieast one mounting plate, said mounting plate providing a profile to facilitate mounting;
atleast one knob means attached to a fork mounted on said profile, said fork blocked in trip position using a reset pin;
atieast one trip lever means hinged on said mounting plate using a trip lever pin;
atieast one upper link means connected to each side of said trip lever using an upper link pin:
atieast one lower link means connected to a connecting link using lower link-connecting link pin (24);
atieast one cassette rotor shaft;
atieast two springs connected between said fork and a spring pin:
atieast one trip latch holding a trip lever;
atieast one trip plate holding said trip latch.
2. Mechanism as claimed in claim 1 wherein said reset pin providing for resetting of said mechanism.
3. Mechanism as claimed in claim 1 wherein orientation and position of said upper link and said lower link maintained using an upper link-lower link pin (23).

4. Mechanism as claimed in claim 1 wherein said connecting link connected to said mounting plate using a coupling pin.
5. Mechanism as claimed in claim 1 further comprising a drive shaft pin connecting said connecting link to said cassette rotor shaft.
6. Mechanism as claimed in claim 1 wherein said main spring transmit energy from said knob to said drive shaft pin.
7. Mechanism as claimed in claim1 wherein said connecting link rotating said contacts using said drive shaft pin.
8. Mechanism as claimed in claim 1 wherein said connecting link having a pair of arms.
9. Mechanism as claimed in claim 8 wherein angle between said arms of connecting link is varied by rotating said arms.
10. An improved mechanism to operate contacts of a circuit breaker as herein described and illustrated with reference to the accompanying drawings.