F0RM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention. - AN IMPROVED MECHANISM FOR CIRCUIT
BREAKER USING A UNIQUE EXTENSION SPRINGS ARRANGEMENT
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:

FIELD OF THE INVENTION
The present invention relates to an improved mechanism of a circuit breaker using a unique extension springs arrangement. More particularly, the invention relates to an improved mechanism comprising extension spring arrangement having unique design providing high spring force which result in high contact velocity in "ON", "OFF" and "TRIP" operations in circuit breakers.
BACKGROUND OF THE INVENTION
Conventionally the mechanisms used in Circuit Breakers use single extension spring per side of the mechanism as energy means. The velocity of the contact depends on the spring potential energy which again depends on the spring force.
US 5,369,384 relates to a breaker mechanism for power circuit breakers is the energy storage link between the handle and the contact systems. Known breaker mechanisms are generally too expensive to manufacture. When contact welding occurs, there is also the risk that, in spite of the tripping of the breaker mechanism, the contact system will not open. The new breaker mechanism reliably opens the contact system and consists of fewer and technologically simpler individual parts. It is inserted between two symmetrical breaker plates held in a die cast housing, and in which a connecting piece is mounted. Two toggle levers are connected at a distance from one another by means of a connecting shaft engaged in crossbar cam slots. A toggle lever spring is engaged between the connecting piece and the connecting shaft. A bracing lever which can be driven by the connecting piece is friction locked in the breaker plates, and the toggle levers in the bracing lever. A latch lever and a latch holding the latter in the locked position are friction locked by means of a latch spring in recesses of the breaker plates.

US 6,479,774 relates to a circuit breaker operating mechanism comprises a movable handle yoke, a mechanism spring extending in tension from the handle yoke to a pin, and a lower link extending from the pin to a crank operably connected to a contact arm bearing a movable contact. The crank is positionable in open and closed positions, being in an open position when the movable contact is separated from an associated fixed contact and being in a closed position when the movable contact is mated to said associated fixed contact. The circuit breaker further comprises an interface formed on said crank and a blocking prop having a first surface that engages said interface, the first surface preventing the crank from rotating towards the closed position.
US 6,590,172 discloses a circuit breaker is provided wherein the circuit breaker comprises a contact arm movable between a closed position, an open position and a blown open position wherein the contact arm is disposed in the circuit breaker. A bumper disposed to contact the contact arm when the contact arm is in the blown open position. In addition, a stop member disposed to be in contact with a linkage assembly so as to create a gap between the bumper and the contact arm when the contact arm is disposed in the open position.
The disadvantages of the above mentioned prior arts are that it relates to a circuit breaker mechanisms with single extension springs. These mechanisms use extension springs with hook or an external element is attached to the end of the springs. These above mentioned mechanisms do not give high spring force which would increase the potential energy and in turn increase the contact velocity.
Thus there is a need to provide an improved mechanism, which would give higher spring force resulting in high circuit breaker contact velocity. The inventors have found that high spring force resulting in high contact velocity for fast "ON", "OFF" and "TRIP" operations in circuit breakers can be achieved by way a unique design of extension springs used in the circuit breakers. Further the spring arrangement of the present invention would give higher spring force in less space.

OBJECTS OF THE INVENTION
The main object of the present invention is to overcome the disadvantages of the prior art.
Another object of the present invention is to provide an improved mechanism which result in high contact velocity of a circuit breaker.
Yet another object of the present invention is to provide a co-axial extension spring arrangement to give higher spring force.
Yet another object of the present invention is to provide a spring arrangement which would require less space.
Yet another object of the present invention is to provide an improved mechanism which would quicken and improve the ON-OFF operations.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided an improved mechanism for enhancing the performance of ON-OFF-TRIP operations in circuit breakers, said mechanism comprising:
(i) a knob means;
(ii) plurality of spring assembly means operatively associated with said knob means, said spring assembly means comprising
(a) plurality of co-axially located extension spring means, wherein said spring means comprises 1) an outer extension spring having desired pitch profile at its two ends and 2) inner extension spring being operatively disposed inside said outer spring such that two ends of said inner spring being operatively engaged with the pitch profile provided at the ends of said outer spring;

(b) plurality of hook means operatively engaged with the upper and lower ends of said inner spring means;
(c) plurality of pin means operatively engaged with said hook means and said spring means;
and (iii) a rotor means operatively connected to the said spring means adapted to perform said ON-OFF-TRIP operations.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Figure 1 illustrates Isometric view of the Circuit Breaker cassette
Figure 2 illustrates Isometric view of Mechanism in ON condition with mechanism cassette hidden
Figure 3 illustrates Isometric view of Mechanism in OFF condition
Figure 4 illustrates Isometric view of Mechanism in TRIP condition
Figure 5 illustrates Isometric view of Mechanism in ON condition with plate hidden
Figure 6 illustrates exploded view of co-axial extension springs
Figure 7 illustrates assembly of co-axial extension springs
Figure 8 illustrates assembly of co-axial extension springs
Figure 9 illustrates Force - Deflection characteristics for co-axial extension springs.

DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a Circuit Breaker which is a mechanical switching device, capable of making (i.e. switching ON), carrying and breaking (i.e. switching OFF) current under normal circuit conditions and more specifically breaking current (Tripping) during abnormal circuit conditions such as short-circuit. Quite often, the short circuit current is sensed automatically and the signal is given to the mechanism as a TRIP command which leads to opening of the contacts by means of mechanism. However, during normal ON-OFF and OFF-ON operation, input to mechanism is given through the rotation of knob by manual means. The rotation of knob leads to storing potential energy (spring charging) in the spring member while restricting the contact movement during the charging operation. At a specified instance the potential energy of spring is released in form of Kinetic energy through Mechanical Linkages leading rotation of the contacts at high velocity. Circuit breaker mechanisms use dead centre based Extension spring arrangements.
Present invention proposes the Co-axial extension springs arrangement which offers high spring force hence high contact velocity.
To propose the spring arrangement in the same space for the circuit breaker mechanism to provide high spring force for same deflection to result in high circuit breaker contact velocity.
Elements and Construction:
Knob (1) It is the spring actuating device facilitating the ON-OFF operation of the circuit breaker. Input to mechanism is given through the rotation of Knob by manual means.
Co-axial extension spring assembly (2): It consists of the two co-axial extension springs connected to the hooks.

Upper hook (2a): It is a sheet metal component to which spring is connected
Lower hook (2b) It is a sheet metal component to which spring is connected
Outer Extension spring (2c): It is an extension spring without hook
Inner Extension spring (2d): It is an extension spring with hook
Upper pin (2e): It is a part of the circuit breaker mechanism. One end of the spring is connected to this pin.
Lower pin (2f): It is a part of the circuit breaker mechanism. Another end of the spring is connected to this pin.
Rounded slot profiles (2g) in both upper and lower hook comprising rounded slot profiles accommodating pins.
Square slot profile (2h) in both upper and lower hook adapted to secure said hook of the inner extension spring means
Rotor (3): It is a part which houses moving contact assembly Mechanism: It consists of various linkages. It is a 4 bar mechanism.
Dead center- Dead center is an equilibrium condition of actuating mechanism. In this condition the mechanism spring is fully charged and beyond this point mechanism flips & operates independently due to energy discharged by mechanism spring.
As illustrated in the figure 2 circuit breaker in at ON position. Input to the mechanism is given through the rotation of Knob (1) by manual means. When knob (1) is rotated (clockwise) extension springs which are connected to upper pin 2e and lower pin 2f through upper hook (2a) and lower hook (2b) get extended up to dead center. When springs are extended potential energy is stored in the

springs. Stored potential energy gets converted into kinetic energy and contact is rotated from ON to OFF position.
Similarly when breaker is in OFF condition as shown in fig. 3 to make breaker ON knob (1) is rotated in opposite direction (anti clock wise). Again springs get extended up to dead center and potential energy is stored in the springs which get converted to kinetic energy and contact gets rotated from OFF to ON condition.
Figure 2, 7 and 8 further illustrates two co-axially located extension spring ,where the spring comprises an outer extension spring having desired pitch profile at its two ends and inner extension spring being operatively disposed inside said outer spring such that two ends of said inner spring being operatively engaged with the pitch profile provided at the ends of said outer spring.
Figure 9 further illustrates the force - deflection characteristics of the spring-2c and spring-2d. It also shows the force - deflection characteristics of co-axial spring's arrangement. As co-axial springs work parallel to each other for the same deflection of the two springs combined force is more than the individual springs force. As force is increased more potential energy is stored in the springs. As this potential energy gets converted into kinetic energy more potential energy increases circuit breaker contact velocity.
Hence higher spring force in the same space increases the potential energy which leads to increase the contact velocity.
. Advantages:
Co-axial extension spring arrangement gives more spring force in less space. Higher spring force results in more circuit breaker contact velocity.

We Claim
1. An improved mechanism for enhancing the performance of ON-OFF-
TRIP operations in circuit breakers, said mechanism comprising :
(i) a knob means;
(ii) plurality of spring assembly means operatively associated with said knob means, said spring assembly means comprising
(a) plurality of co-axially located extension spring means, wherein said spring means comprises 1) an outer extension spring having desired pitch profile at its two ends and 2) inner extension spring being operatively disposed inside said outer spring such that two ends of said inner spring being operatively engaged with the pitch profile provided at the ends of said outer spring;
(b) plurality of hook means operatively engaged with the upper and lower ends of said inner spring means;
(c) plurality of pin means operatively engaged with said hook means and said spring means;
and (iii) a rotor means operatively connected to the said spring means adapted to perform said ON-OFF-TRIP operations.
2. Mechanism as claimed in claim 1 wherein said knob means is adapted to facilitate/initiate said ON operations of said circuit breaker by rotating the knob in clockwise directions.
3. Mechanism as claimed in claim 1 wherein said knob means is adapted to facilitate/initiate said OFF operations of said circuit breaker by rotating the knob in anticlockwise directions.

4. Mechanism as claimed in claim 1 wherein said ON -OFF operations comprise of charging and discharging operations in each.
5. Mechanism as claimed in claim 1 wherein said inner extension springs comprising hooks at its two ends.
6. Mechanism as claimed in claim 1 wherein said hook means comprising rounded slot profiles accommodating said pin means.
7. Mechanism as claimed in claim 1 further comprising square slot profile adapted to secure said hook means of the inner extension spring means.
8. Mechanism as claimed in claim 1 wherein said charging operation continues till said spring reaches its dead center.
9. Mechanism as claimed in claim 1 wherein said discharging operation starts after the spring reaches said dead center.
10. Mechanism as claimed in any of the preceding claims wherein said spring means being adapted to store potential energy during charging operation.
11. Mechanism as claimed in any of the preceding claims wherein said spring means being adapted to release the potential energy in the form of kinetic energy to perform said ON-OFF-TRIP operations.
12. The mechanism as claimed in claim 1 wherein said rotor means comprises of moving contact assembly.
13. The mechanism as claimed in claim 1 wherein said contact assembly rotates at a high contact velocity during said discharging operation to perform ON-OFF operations.

14. Mechanism as substantially described hereinbefore with reference to accompanying drawings.