FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION:
"Manoeuvering Mechanism for Circuit Breakers"
2. APPLICANT:
(a) NAME: Larsen & Toubro Limited
(b) NATIONALITY: Indian Company registered under the
provisions of the Companies Act-1956.
(c) ADDRESS: LARSEN & TOUBRO LIMITED,
L&T House, Ballard Estate, P. 0. Box: 278, Mumbai 400 001, India
3. PREAMBLE TO THE DESCRIPTION:
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.

Manoeuvering Mechanism for Circuit Breakers
Field of the invention
The present invention relates to the molded case circuit breakers (MCCB), more particularly, it relates to operating of a contact system using manoeuvering mechanism.
Background of the invention
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.
Molded Case Circuit Breakers (MCCB)' is 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 molded 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 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 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 automatically.
Disadvantages of the prior art
> Achieving Trip free with optimal latch link rotation is a challenge, where the circuit breakers of the prior art normally use side plate navigation. In this method navigation pins to be riveted on upper link which is tedious in lower range of breakers.
> There is a need of a separate stopper to arrest the rotation of the latch bracket during trip condition in the circuit breakers of the prior art; otherwise the latch bracket will interrupt the rotation of the trip lever, stopping the reset operation.
> There is a need of a separate pin to be mount biasing spring to retain Trip Plate to lock latch bracket during reset.
Therefore, there is a need to a mechanism for circuit breaker, which overcomes all the drawbacks of the prior art technology.

Objects of the Invention
Object of the present invention it to provide a manoeuvering mechanism for circuit breakers, which requires less number of components and is ease of assembly.
Another object of the present invention it to provide a manoeuvering mechanism for circuit breakers, which can be assembled and tested separately without contact system.
Yet another object of the present invention it to provide a manoeuvering mechanism for circuit breakers, in which release can be integrated or disintegrated without disturbing the mechanism by giving access to electrical joint through trip plate.
Further object of the present invention it to provide a manoeuvering mechanism for circuit breakers, which has reliability in operation, as the dependency on the pins are reduced from existing mechanism.
Summary of the invention
According to the present invention there is provided a manoeuvering mechanism for operating contact system of a circuit breakers. The manoeuvering mechanism having includes a latch link 2, a upper link 3, a lower link 4, a latch bracket 5, a double arm trip plate 6, a fork 7, a knob 8, a latch link pin 9, a spring pin 10, a upper link pin 11, trip plate pins 12, latch bracket pins 13, a spacer 14, biasing spring! 5 and a drive pin 16. The latch link 2 is secured to a mounting plate 1 by a latch link pin 9. The upper link 3 is disposed on the latch link 2. The upper link pin 11 is provided for connecting the upper link 3 with the latch link 2. The lower link 4 with a spring and a spring pin 10 is connected to the upper link 3. The latch bracket 5 and a double arm trip plate 6 are secured to the mounting plate 1 through

respective latch bracket pins 13and trip plate pins 12. The fork 7 is secured to the spring. The biasing spring 15 is mounted on the trip plate pin 12 for retaining a double arm trip plate 6 to its original position and for lock the latch bracket when the mechanism is being reset after trip. Moreover, the mechanism is mounted on a contact system through mounting screws (not shown) and the lower link 4 connected to the drive shaft with the drive pin 16 , therefore when the mechanism is maneuvered the circuit breaker will be able to carry current and break current there through.
Brief description of the drawings
Figure I shows a perspective view of a circuit breaker;
Figure 2 show an exploded perspective view of a manoeuvering mechanism for a circuit breaker in accordance with the present invention;
Figure 3 show a perspective view of a manoeuvering mechanism for a circuit breaker in 'ON' position;
Figure 4 show a perspective view of a manoeuvering mechanism for a circuit breaker in 'OFF' position;
Figure 5 show a perspective view of a manoeuvering mechanism for a circuit breaker in 'TRIP' position;
Figure 6 show a perspective view of a manoeuvering mechanism for a circuit breaker in 'TRIP FREE' position;
Figure 7 show a perspective view of a lacth link of the manoeuvering mechanism in accordance with the present invention;

Figure 8 show a perspective view of a double arm trip plate of the manoeuvering mechanism in accordance with the present invention;
Figure 9 show a perspective view of a trip plate pin of the manoeuvering mechanism in accordance with the present invention;
Figure 10 show a top view the manoeuvering mechanism, and
Figure 11 show a perspective view of a trip free position with spacer navigator of the manoeuvering mechanism in accordance with the present invention.
Detail description of the invention
For a thorough understanding of the present invention, reference is to be made to the following detailed description, including the appended claims, in connection with the above-described drawings. Although the present invention is described in connection with exemplary embodiments, the present invention is not intended to be limited to the specific forms set forth herein. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but these are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present invention. Also, it is to be understood that. the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.
The present invention a manoeuvering mechanism for circuit breakers, which requires less number of components and is ease of assembly. Further, the manoeuvering mechanism can be assembled and tested separately without contact system. Furthermore, the manoeuvering mechanism release can be integrated or disintegrated without disturbing the mechanism by giving access to electrical joint

through trip plate. Moreover, the manoeuvering mechanism has reliability in operation, as the dependency on the pins are reduced from existing mechanism.
Referring now to figures 1 to 11, various views of a manoeuvering mechanism and its elements in accordance with the present invention is illustrated. The maneuvering mechanism includes a latch link 2, a upper link 3, a lower link 4, a latch bracket 5, a double arm trip plate 6, a fork 7, a knob 8, a latch link pin 9, a spring pin 10, a upper link pin 11, trip plate pins 12, latch bracket pins 13, a spacer 14, biasing spring] 5 and a drive pin 16. Further, the latch link 2 is secured to one side of the mounting plate 1 by the latch link pin 9. On the latch link 2, the upper link 3 is connected through the upper link pin 11. The spring (not shown) is inserted to the spring pin 10. The lower link 4 is connected to the spring pin 10. This set is connected to the upper link 3. The latch bracket 5 and double arm trip plate 6 are secured to the mounting plate 1 through respective latch bracket pins 13 and the trip plate pin 12 the pins which are fixed to the other mounting plate 1. Now these aligned and secured properly, a fork 7 in mounted. The other end of the spring is fixed to the fork 7. The biasing springl5 is mounted on trip plate pin 12 to retain the double arm trip plate 6 to its original position or to lock the latch bracket when the mechanism is being reset after trip.
Since the mechanism is modular, it is mounted on the contact system through mounting screws (not shown) and the lower link 4 is connected to the drive shaft with the drive pin 16. So that when the mechanism is maneuvered the circuit breaker will be able to carry current and break current there through.
The latch link 2 is designed in such a way, when the mechanism is maneuvered to make current the upper link 3 & the lower link 4 should be in definite position. To ensure this definite position of upper link 3, a bend in the latch link 4 is given. When mechanism is tripped the latch bracket 5 should not interrupt with latch link 2 during reset. This is taken care by providing a simple profile at the rear end of

latch link 2. At OFF condition, the lower link movement is limited by providing a profile in 2.
The double arm trip plate 6 is designed with two arms to lock the latch bracket 5. The gap between two arms is intentionally given to access the hardware and to mount the biasing spring 15 on the trip plate pin 12. A portion the trip plate pin 12 is a spacer between mounting plate 1 and the double arm trip plate 6 and the remaining portion the pin is used to mount the biasing spring 15 which fulfills a dual purpose.
Further, the lower link 4 navigates with help of spacer 14 in order to achieve Trip free avoiding additional components called navigation pins on upper links. A new idea called spacer navigator is implemented (shown in fig.11). The profile (a) is given in the latch link (Fig 7) to retain latch bracket in specified position, in order to avoid interruption of latch bracket and latch link during RESET. The gap between the two arms of the Trip Plate is provided in order to access the hardware to integrate/disintegrate release and also to accommodate biasing spring. The biasing spring is mounted on the trip plate pin, which eliminates another component.
ON position:
ON position will be as shown in fig.3. In this position, the fork 7 will be in the position far away from the trip system, the upper links 2; the lower links 5 will be holding the contacts in the closed circuit condition with the help of the through pin 16.
OFF/RESET position:

OFF/RESET position will be as shown in fig.4. In this position, the fork will be in the position very near to the trip system the upper links 3, lower links 5 will be holding the contacts in the open circuit condition with the help of the through pin 16.
TRIP position:
TRIP position will be as shown in fig.5. In this position, the fork 7 will be in the position anywhere between the ON & OFF positions and the position is constrained by the rotation of Latch link 2. The wings in the latch link 2 will hinder further rotation of fork 7. And the contacts will be in the opened condition.
TRIP FREE position:
TRIP FREE position will be as shown in fig.6. This is an unstable position for the fork 7, as the knob 8 will be held in the ON position by the operator. In this position, except the fork 7 & knob 8, all the other parts will be as described in trip position,
Advantages of the invention
The present invention reduces the number of components and to provide ease of assembly.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed. and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, and to thereby enable others skilled in the art to best utilize the present invention and various

embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but such omissions and substitutions are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present invention.

We Claim:
1. A manoeuvering mechanism for operating contact system of a circuit
breakers, the manoeuvering mechanism comprising:
a latch link 2 secured to a mounting plate J by a latch link pin 9;
an upper link 3 disposed on the latch link 2;
an upper link pin 11 for connecting the upper link 3 with the latch link 2;
a lower link 4 with a spring and a spring pin 10 connected to the upper link
3;
a latch bracket 5 and a double arm trip plate 6 secured to the mounting plate ] through respective latch bracket pins 13and trip plate pins 12;
a fork 7 secured to the spring; and
a biasing spring 15 mounted on the trip plate pin 12 for retaining a double arm trip plate 6 to its original position and for lock the latch bracket when the mechanism is being reset after trip,
wherein the mechanism mounted on a contact system through mounting screws (not shown) and the lower link 4 connected to the drive shaft with the drive pin 16 , therefore when the mechanism is maneuvered the circuit breaker will be able to carry current and break current there through.
2. The manoeuvering mechanism as claimed in claim 1, wherein the double
arm trip plate 6 having two arms to lock the latch bracket 5, wherein gap between
two arms enables access to the hardware and to mount the biasing spring 15 on the
trip plate pin 12.

3. The manoeuvering mechanism as claimed in claim 1, wherein a portion the trip plate pin 12 is a spacer between mounting plate 1 and the double arm trip plate 6 and the remaining portion the pin is used to mount the biasing spring 15 which fulfills a dual purpose.