FORM2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention. - CIRCUIT BREAKER MECHANISM PROVIDING AUTOMATIC DISCHARGE
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 a circuit breaker and more particularly to an improved circuit breaker mechanism providing automatic discharge.
BACKGROUND AND THE PRIOR ART
A circuit breaker is a switch that automatically interrupts the flow of electrical current when the rated current is exceeded due to an electrical overload or fault. Basically a circuit breaker comprises of a set of fixed and moving contacts. The fixed contacts are connected to the input supply and the moving contacts are connected to the mechanism via pole shaft. The contacts are separated by means of an operating mechanism. Each pole of the circuit breaker comprises one or more interrupters or arc extinguishing chambers. The interrupter encloses a set of fixed and moving contacts. The moving contacts can be drawn apart by means of the operating links of the operating mechanism. The operating mechanism of the circuit breaker gives the necessary energy for opening and closing of the contacts of the circuit breaker.
During the normal operating conditions, the circuit breaker can be opened or closed by a station operator for the purpose of switching and maintenance. During the abnormal or faulty conditions the release, sense the fault and close the trip circuit of the circuit breaker. Thereafter the circuit breaker opens. The circuit breaker has two working positions - ON (close) and OFF (open). These correspond to close circuit breaker contacts and open circuit breaker contacts respectively. The operation of automatic opening and closing the contacts is achieved by means of the operating mechanism of the circuit breaker. As the relay contacts close, the trip circuit is closed and the operating mechanism of the circuit breaker starts the opening operation.

The mechanism used is stored energy type wherein the energy stored in a spring is used for closing operation. This spring is called the "Main spring" or "Closing Spring". The spring in "charged condition" is held by a Closing latch. Upon release of this closing latch, the spring energy gets released and is used for turning ON the Circuit Breaker. Similarly, for turning OFF the Circuit breaker, a spring known as "Opening spring" or "Return spring" is used. This spring is charged when the circuit breaker is turned ON. The energy stored in this spring is used for opening operation.
A circuit breaker has been categories into two versions Fixed and Withdraw-able. Withdraw-able type of version consists of withdraw-able unit also known as cradle and the Breaker part. In draw-out version of the circuit breaker, there are four positions, namely connected, test, disconnected and maintenance position. To load the breaker in the cradle, rails needs to be pulled out in maintenance position, after loading the breaker, it is push inside to the disconnected position. Racking mechanism is used to rack in the breaker from disconnected to the test and test to the connected position and rack out the same vice versa.
US 6,184,483 discloses an extractable circuit breaker is equipped with an operating lever which can take at least three positions: an inoperative position, an opening control position in which operating lever operates in conjunction with, an opening latch of the circuit breaker, and a closing control position in which it operates in conjunction with a closing latch of the circuit breaker. When the circuit breaker is in the plugged-in position, the operating lever is inoperative. When the circuit breaker leaves its plugged-in position, the operating lever operates in conjunction with a countergear lever supported by the fixed frame accommodating the circuit breaker and performs opening of the poles of the circuit breaker.
The drawbacks of the prior art design is that when in maintenance position, say a breaker is in ON condition and spring is in charged condition can be pushed to

disconnected position. To rack in the breaker from disconnected position to the connected position, firstly OFF button is pressed for opening of the racking shutter for the insertion of the racking handle. Pressing of OFF button ensures the contact separation or opening before further racking, but does not ensure the discharging of the already charged mechanism spring. A charged spring if gets accidently discharged can create hazardous conditions.
For Rack out operation from Connected to Disconnected and then pull out to maintenance position is discussed below:
In prior art design, for racking out the breaker from connected position, racking shutter needs to be open. An interlock is provided between racking shutter and the breaker contact position. Breaker needs to be made OFF, i.e. OFF button required to be pressed for opening of the racking shutter for the insertion of the racking handle. This ensures the positive separation of contacts but mechanism spring remains in charged condition (if mechanism spring is charged). After withdrawing the breaker from connected to the disconnected position, breaker will be in OFF condition and mechanism spring is in charged condition. Operator pulls out the breaker from the disconnected position to the maintenance position for unloading the breaker for maintenance purpose. As the springs of breaker is in charged condition, it is hazardous considering the operator safety, because breaker can get ON accidently.
For Rack-in operation: Pushing in from maintenance position to Disconnected and then racking in to connected position is discussed below:
In maintenance position, say a breaker is in ON condition and spring is in charged condition can be pushed to disconnected position. To rack in the breaker from disconnected position to the connected position, firstly OFF button is pressed for opening of the racking shutter for the insertion of the racking handle. Pressing of OFF

button ensures the contact separation or opening before further racking, but does not ensure the discharging of the already charged mechanism spring.
Although readily available the prior art fails to provide automatic discharge of the spring. Also, the Conventional circuit breaker causes stress on the mechanism while withdrawing the circuit breaker. Consequently if a charged spring gets discharged accidently, it may lead to hazardous conditions considering the operator safety.
Thus there is a need to provide an automatic discharge of the charged spring of mechanism while pulling out the breaker from the disconnected position to maintenance position for the unloading of the breaker.
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 arrangement which is possible to mount at the site for converting the breaker into the breaker with automatic discharge of the spring feature while pulling out the breaker from disconnected position to the maintenance position before unloading of the breaker.
Another object of the present invention is to reduce the stresses occurring on the mechanism while withdrawing the breaker.
Yet another object of the present invention is to provide delay is between closing of the breaker due to spring discharge and tripping of the breaker by having two separate actuations while pulling out breaker from disconnected position to the maintenance position.

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 a system and method of a withdrawable circuit breaker having spring discharge arrangement adapted for automatic discharge of the charged spring.
According to one embodiment of the present invention, there is provided improved circuit breaker mechanism providing automatic discharge, said mechanism comprising a spring means for switching ON and OFF said circuit breaker; a cradle comprising a base plate and a pair of humps separated by a distance ensuring lower stress; a racking shutter having a racking handle for racking out said breaker from connected position; a pair of push buttons for ON and OFF operation for regulating a racking shutter; a plurality of jaws provided at each of the contact jaws locations; an interlock provided between said racking shutter and a breaker contact; a gap maintained between said first and second hump providing a time delay in closing and opening operation wherein said spring means adapted to automatically discharge during rack in and rack out operation.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig 1 illustrates breaker in Disconnected position (View 1). Fig 2 illustrates breaker in Disconnected position (View 2). Fig 3 illustrates cradle.

Fig 4 illustrates racking Shutter Open and Racking Cam upward.
Fig 5 illustrates breaker Mechanism (View 1).
Fig 6 illustrates breaker Mechanism (View 2).
Fig 7 illustrates cradle and breaker interface (Racking Shutter Closed and Racking Cam downward).
Fig 8 illustrates cradle and breaker interface (Racking Shutter Open and Racking Cam upward) (View 1).
Fig 9 illustrates cradle and breaker interface (Racking Shutter Open and Racking Cam upward) (View 2).
Fig 10 illustrates closing link interface with cradle.
Fig 11 illustrates actuation of closing link.
Fig 12 illustrates actuation of trip link.
Fig 13 illustrates breaker closing operation (View 1).
Fig 14 illustrates breaker closing operation (View 2).

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 circuit breaker in disconnected position is shown. Withdrawal unit comprise of cradle 1 and the breaker 2. Jaw 3 engages contacts of the circuit breaker.
Fig 2 shows another view of circuit breaker in disconnected position. It shows Base plate 12, cradle facia 13, racking shutter 14, and position indicator 15 of cradle 1. Also constructional features of Breaker like spring status indicator 21, Breaker facia 22, ON-OFF indicator 23 and ON-OFF push buttons are shown.
Fig 3 shows constructional features of cradle like secondary isolating contacts 11, cradle side plates 16, rail 17 and racking cam 18.
Fig 4 shows racking shutter 14 open and racking cam 18 upwards. Also the racking shield 4 comprising of tripping hump 41 and closing hump 42.
Fig 5 shows breaker mechanism 24 comprising mechanism side plate 241, tripping link 242, mechanism OFF push button 243 and mechanism ON push button 244.
Fig 6 shows another view of breaker mechanism 24 comprising mechanism side plate 241, tripping link 242, mechanism OFF push button 243 and mechanism ON push button 244.

Fig 7 shows cradle and breaker interface where racking cam 18 is in downward position when racking shutter 14 is close.
Fig 8 shows cradle and breaker interface where Racking Cam 18 in upward position when Racking Shutter 14 is open.
Fig 9 shows cradle and breaker interface where Racking Cam 18 is upward when Racking Shutter 14 is Open.
Fig 10 shows closing link interface with cradle 1 where breaker mechanism 24 comprises tripping shaft 245, closing shaft 246, tripping shaft connector 252 etc.
Fig 11 shows actuation of closing link 250 riding over the closing hump 42. Closing link 250 connected to square closing shaft 251.
Fig 12 shows actuation of trip link 242 and tripping hump 41.
Fig 13 shows breaker closing operation. When breaker is in disconnected position; trip link 242 is disengaged from racking cam 18. For taking the breaker in maintenance position it is pulled out side and closing link 250 rides over the closing hump 42 and it rotates the square shaft 251. In turn it rotates link 252 which pulls down the vertical link 249. This vertical link 249 is engaged with the closing shaft rotator 247. Closing shaft rotator 247 is rigidly couple with the closing shaft 246. As closing shaft rotates breaker contacts closes and breaker indicates ON condition.
Fig 14 shows another view of breaker closing operation comprising of trip link 242, closing link 250, vertical closing link 249 etc.

The invented system is thus a withdrawable circuit breaker having spring discharge arrangement adapted for automatic discharge of the charged spring.
DETAILED DESCRIPTION OF THE INVENTION
Accordingly, the present invention provides for a withdrawable circuit breaker having spring discharge arrangement adapted for automatic discharge of the charged spring
A circuit breaker has been categorized into two versions Fixed and Withdraw-able. Withdraw-able type of version consists of withdraw-able unit also known as cradle 1 and the Breaker 2 part. In draw-out version of the circuit breaker, there are four positions, namely connected, test, disconnected and maintenance position. First three conditions are shown by position indicator 15.
In maintenance breaker 2 is pulled out from the cradle 1. To load the breaker 2 in the cradle 1, rails 17 needs to be pulled out in maintenance position, after loading the breaker 2, it is pushed inside to the disconnected position. Racking mechanism is used to rack in the breaker from disconnected to the test and test to the connected position and rack out the same vice versa.
In present design, in maintenance position, say a breaker 2 is in ON condition and spring is in charged condition can be pushed to disconnected position. To rack in the breaker from disconnected position to the connected position, firstly OFF button 26 is pressed for opening of the racking shutter for the insertion of the racking handle. Pressing of OFF 26 button ensures the contact separation or opening before further racking, but does not ensure the discharging of the already charged mechanism spring. A charged spring if gets accidently discharged can create hazardous conditions.

When breaker is in disconnected position, trip link 242 is disengaged from racking cam 18. For taking the breaker in maintenance position it is pulled out side and closing link 250 rides over the closing hump 42 and it rotates the square shaft 251. In turn it rotates link 252 which pulls down the vertical link 249. This vertical link 249 is engaged with the closing shaft rotator 247. Closing shaft rotator 247 is rigidly couple with the closing shaft 246. As closing shaft rotates breaker contacts closes and breaker indicates ON condition (Fig 13 and 14).
After closing of the breaker, tripping link rides over the tripping hump 41 of the racking shield 4.
Racking interlock cam 18 is linked with the racking shutter 14. If racking shutter 14 is open racking cam 18 will be in upward position (Fig 9), if shutter 14 is close racking cam 18 will be in downward position (Fig 7). Racking interlock cam 18 presses a link 242 of breaker mechanism 24. Link 242 is connected with a vertical trip link 248, this link is connected with the mechanism OFF push button 243 and button rotates the trip shaft 245 of the breaker mechanism 24 through tripping shaft connector 252. Breaker contacts are opened.
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, all 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 circuit breaker mechanism providing automatic discharge, said mechanism comprising;
a spring means for switching ON and/or OFF said circuit breaker;
a cradle comprising a base plate and at least pair of humps separated by a distance ensuring lower stress;
a racking shutter having a racking handle for racking out said breaker from connected position;
a pair of push buttons for ON and OFF operation for regulating a racking shutter;
plurality of jaws provided at each of the contact jaws locations;
an interlock provided between said racking shutter and a breaker contact;
a gap maintained between said first and second hump providing a time delay in closing and opening operation;
wherein said spring means adapted to automatically discharge during rack in and rack out operation.
2. Mechanism as claimed in claim 1 is a wholly and/or partially withdrawable type.
3. Mechanism as claimed in claim 1 wherein said one of said humps adapted to actuate a lever thereby closing said breaker.

4. Mechanism as claimed in claim 1 wherein one of said humps adapted to actuate an interlock Jink thereby tripping a breaker.
5. Mechanism as claimed in claim 1 wherein said gap between first hump and second hump providing a time delay in closing and opening operation.
6. An improved circuit breaker mechanism providing automatic discharge as herein described and illustrated with reference to accompanying drawings.