FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
AND
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
A damper system to reduce the over travel of crank wheel rotation after circuit breaker closing operation.
APPLICANT(S)
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company.
INVENTOR (S)
Rao Sudhendra Nagesh and Tambe Sangram Dnyaneshwar; both of Crompton Greaves Ltd, S3-R&D Switchgear (S3) Division, Switchgear Complex, A-3, MIDC, Ambad, Nashik - 422010, Maharashtra, India; both Indian Nationals.
PREAMBLE TO THE DESCRIPTION:
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:

FIELD OF THE INVENTION:
This invention relates to the field of mechanical engineering.
Particularly, this invention relates to circuit breakers and shock absorbing mechanisms, thereof.
Specifically, this invention relates to a damper system to reduce the over travel of crank wheel rotation after circuit breaker closing operation.
BACKGROUND OF THE INVENTION:
The term 'switchgear', used in association with electric power systems, or grids, or power transmission systems and networks refers to the combination of electrical disconnects, fuses and/or circuit breakers used to isolate electrical equipment. Switchgear is used both to de-energize equipment to allow work to be done and to clear faults.
An effective form of switchgear is gas insulated switchgear (GIS). In a GIS, there are a plurality of electrical components where the conductors and contacts are insulated by pressurized sulfur hexafluoride gas (SF6).
Circuit breakers are one type of switchgear component. Circuit Breaker mechanisms are used in electrical equipment, as an adjunct mechanism, for preventing said electrical equipment from current / voltage aberrations such as overload, short circuit, or the like. A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to interrupt continuity upon detection of a fault condition to immediately discontinue electrical flow. The circuit breaker

must react to fault condition; in low-voltage circuit breakers this is usually done within the breaker enclosure. Circuit breakers for large currents or high voltages are usually arranged with pilot devices to sense a fault current and to operate the trip opening mechanism. The trip coil that releases the latch is usually energized by a separate battery, although some high-voltage circuit breakers are self-contained with current transformers, protection relays, and an internal control power source.
Once a fault is detected, contacts within the circuit breaker must open to interrupt the circuit; some mechanically-stored energy (using springs or compressed air or any resilient means) contained within the breaker is used to separate the contacts. Small circuit breakers may be manually operated; larger units have coils to trip the mechanism, and electric motors to restore energy to the springs.
The circuit breaker contacts must carry the load current without excessive heating, and must also withstand the heat of the arc produced when interrupting (opening) the circuit. Contacts are made of copper or copper alloys, silver alloys, and other highly conductive materials.
A trip coil is a type of solenoid in which the moving armature opens a circuit breaker or other protective device when the coil current exceeds a predetermined value. A closing coil is adapted to shut the circuit breaker completely.
In its working mode, if a power surge occurs in the electrical system, the breaker will trip. This means that a breaker that was in the "on" position will flip to the "off position and shut down the electrical power leading from that breaker. Essentially, a circuit breaker is a safety device. When a circuit breaker is tripped, it

may prevent a fire from starting on an overloaded circuit; it can also prevent the destruction of the device that is drawing the electricity.
Conventionally, damping elements or shock absorbers are known to be used along with a moveable contact of a circuit breaker. These shock absorbers of the prior art are double acting shock absorbers but can be mounted in one way only. The shock absorber functions along with trip spring action of the circuit breaker. The circuit breaker is open when trip spring is released, and the circuit breaker is closed when trip spring is tensioned. The shock absorber is adapted to play its shock absorbing role while opening and closing the circuit breaker. In this design of the prior art, the shock absorber can be mounted only on the rear side.
Crank wheels are used in Circuit Breakers to translate the energy stored in the closing spring for effecting actuation of a rod or mechanism associated with it.
An efficient design of a circuit breaker acknowledges the working parameters of overtravel and Closing Operation (CO) condition.
Overtravel is the excess travelling energy in the moving components which result in circuit breaker operation. An optimum amount of overtravel is necessary for providing the sufficient time as well as space for the latching system. Excess overtravel may lead to unnecessary stress in the components consisting of the latching system. Due to high impact load on crank wheel locking system, reliability of components is decreased and some failures observed. On the other side less overtravel may lead to CO condition which in itself is extremely detrimental for the mechanism as well as the pole components.

In order to avoid the additional stress during overtravel, there is a need for an improved damping or shock absorbing mechanism for the closing spring of a circuit breaker.
OBJECTS OF THE INVENTION:
An object of the invention is to provide a damping or shock absorbing mechanism which does not exert pressure on contacts or components of circuit breaker assembly.
Another object of the invention is to provide a damping or shock absorbing mechanism which is associated with the working of a closing spring of a circuit breaker.
Yet another object of the invention is to provide a damping or shock absorbing mechanism using which impact load on crank wheel reverse rotation locking system decreases.
Still another object of the invention is to provide a damping or shock absorbing mechanism because of which reliability of components of a circuit breaker assembly and associated closing spring increases.
An additional object of the invention is to provide a damping or shock absorbing mechanism which reduces the over travel of crank wheel rotation after circuit breaker closing operation.
SUMMARY OF THE INVENTION:
According to this invention, there is provided a damper system to reduce the over

travel of crank wheel rotation after circuit breaker closing operation, said system comprises:
a. cam adapted to be co-axially located with said crank wheel of said circuit
breaker assembly, said crank wheel adapted to be angularly displaced, along
with said crank wheel;
b. cam mounted shaft adapted to be placed on the external face of said cam and
adapted to be angularly displaceable along with said cam, said cam mounted
shaft further being adapted to engage with further assemblies of said damper
system, upon angular displacement, at pre-defined positions of angular
displacement; and
c. oil damper system adapted to be acutated by said cam mounted shaft in order
to provide damping to angular displacement of said cam and thereby to said
crank wheel.
Typically, said cam is an angularly displaceable cam adapted to be angularly displaced along with said crank wheel.
Typically, said cam is an angularly displaceable cam adapted to be angularly displaced along with said crank wheel once a closing spring is delatched.
Typically, said cam mounted shaft forms a secant on said cam profile and is adapted to be angularly displaced along with said cam angular displacement.
Typically, wherein said damper system comprising an oil bath, associated damping assemblies in said oil bath, and a piston extending operatively upward from said oil bath, said piston adapted to be driven by said cam mounted shaft in order to engage

and actuate said damper system in order to dampen the load effect caused due to spring expansion or decompression on the crank wheel.
Typically, wherein said damper system comprising an oil bath, associated damping assemblies in said oil bath, and a piston extending operatively upward from said oil bath, said piston adapted to be driven by said cam mounted shaft at pre-defined position of angular displacement of said crank wheel and said cam.
Typically, wherein said damper system comprising an oil bath, associated damping assemblies in said oil bath, and a piston extending operatively upward from said oil bath, said piston adapted to follow profile of cam by said shaft.
Typically, said damper system being a torque enabling damping system adapted to enable an opposing torque in a direction to oppose said angular displacement of said crank wheel.
Typically, said damper system comprises a piston, said piston profile being designed such that it is adapted to operate only after full closing operation of said circuit breaker assembly.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 illustrates a schematic view of a crank wheel and closing spring of a circuit breaker assembly, with the closing spring in compressed condition;
Figure 2 illustrates a schematic view of a crank wheel and closing spring of a circuit breaker assembly with the crank wheel at bottom dead centre position at the end of closing operation;

Figure 3 illustrates a schematic view of a crank wheel and closing spring of a circuit breaker assembly in lock position after crossing the bottom dead centre position of Figure 1; and
Figure 4 illustrates a graph of crank wheel rotation versus time required for the circuit breaker assembly of Figure 1.
The invention will now be described in relation to the accompanying drawings, in
which:
Figure 5 illustrates a schematic view of a crank wheel and closing spring and
damper system of a circuit breaker assembly, with the closing spring in
compressed condition;
Figure 6 illustrates a close-up schematic view of a crank wheel and damper system of a circuit breaker assembly of Figure 5;
Figure 7 illustrates a schematic view of a crank wheel and closing spring and damper system of a circuit breaker assembly after closing operation;
Figure 8 illustrates a close-up schematic view of a crank wheel and damper system of a circuit breaker assembly of Figure 7 after closing operation; and
Figure 9 illustrates a graph of crank wheel rotation versus time required for the circuit breaker assembly with damper system of Figure 5.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 illustrates a schematic view of a crank wheel and closing spring of a circuit breaker assembly, with the closing spring in compressed condition.

Figure 2 illustrates a schematic view of a crank wheel and closing spring of a circuit breaker assembly with the crank wheel at bottom dead centre position at the end of closing operation.
Figure 3 illustrates a schematic view of a crank wheel and closing spring of a circuit breaker assembly in lock position after crossing the bottom dead centre position of Figure 1.
Figure 4 illustrates a graph of crank wheel rotation versus time required for the circuit breaker assembly of Figure 1.
Figure 1 represents initial closing spring compressed condition. During closing operating a de-latching mechanism releases a compressed spring (12) which expands in linear direction. This is discharging action. Reference numeral 11 refers to charged closing spring.
This linear expansion causes angular displacement of an associated crank wheel (14). This angular displacement, typically, is anti-clockwise angular displacement. This angular displacement results in closing operation of the circuit breaker. Reference numeral 13 refers to closing spring at bottom dead centre position.
After full closing operation of the circuit breaker, due to high angular momentum, the crank wheel crosses a bottom dead center position, as shown in Figure 2 of the accompanying drawings.
Hereafter, closing spring gets compressed as shown in Figure 3 of the accompanying drawings. The crank wheel and spring gets locked in final position

due to locking system which is provided on same shaft in order to prevent the reverse rotation of crank wheel. Reference numeral 15 refers to final closing spring position after overtravel.
The graph of total rotation of crank wheel during closing operation is shown in Figure 4 of the accompanying drawings. X-Axis represents time (in seconds). Y-axis represents angular displacement (rotation) (in degrees).
According to this invention, there is provided a damper system to reduce the over travel of crank wheel rotation after circuit breaker closing operation.
Figure 5 illustrates a schematic view of a crank wheel and closing spring and damper system of a circuit breaker assembly, with the closing spring in compressed condition.
Figure 6 illustrates a close-up schematic view of a crank wheel and damper system of a circuit breaker assembly of Figure 5.
Figure 7 illustrates a schematic view of a crank wheel and closing spring and damper system of a circuit breaker assembly after closing operation.
Figure 8 illustrates a close-up schematic view of a crank wheel and damper system of a circuit breaker assembly of Figure 7 after closing operation.
Figure 9 illustrates a graph of crank wheel rotation versus time required for the circuit breaker assembly with damper system of Figure 5.

In accordance with an embodiment of this invention, there is provided a cam (22) adapted to be co-axially located with the crank wheel (14) of the circuit breaker assembly. The crank wheel is adapted to be angularly displaced, typically, in an anti-clockwise direction once the closing spring is delatched. The tension in the compressed closing spring before delatching actuates this angular displacement. Simultaneously, the cam on the crank wheel is also angularly displaced in the same direction.
In accordance with another embodiment of this invention, there is provided a shaft (24) adapted to be placed on the external face of said cam. The shaft may form a secant on the cam profile and is angularly displaced along with the cam angular displacement. The cam mounted shaft is adapted to engage with further assemblies of this system, upon angular displacement, at pre-defined positions of angular displacement.
In accordance with yet another embodiment of this invention, there is provided an oil damper system comprising an oil bath (26), associated damping assemblies in the oil bath, and a piston (28) extending operatively upward from the oil bath. The piston (28) is adapted to follow profile of cam (22) by shaft (24). The shaft (24) drives the piston in to the oil bath in order to engage and actuate damping assemblies in order to dampen the load effect caused due to spring expansion or decompression on the crank wheel. The angular momentum of the crank wheel can, thus, be dampened and eventually arrested before it reaches the stages of overtravel. The damper system provides an opposing torque, typically, in a clockwise direction to oppose the anticlockwise angular displacement of the crank wheel.

The piston profile is designed, in accordance with this invention, such that it is adapted to operate only after full closing operation of circuit breaker assembly.
Comparing the graphs of Figure 4 of the accompanying drawings (prior art) and Figure 9 of the accompanying drawings (of the invention), it can be observed that there is reduction is angular displacement of crank wheel by about 40 degrees, thereby reducing overtravel, causing load disbursement, and reducing chances of mechanical failure of circuit breaker assembly.
The technical advancement of this invention lies in provisioning a damper system designed to counteract angular momentum of crank wheel effected by a compressed spring of a circuit breaker assembly. This damper system is configured to be operational only when full closing operation of circuit breaker assembly, thereby providing inventive step in relation to profile and design of the damper system.
While this detailed description has disclosed certain specific embodiments of the present invention for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention as defined in the following claims, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim,
1. A damper system to reduce the over travel of crank wheel rotation after circuit breaker closing operation, said system comprising:
a. cam adapted to be co-axially located with said crank wheel of said circuit
breaker assembly, said crank wheel adapted to be angularly displaced,
along with said crank wheel;
b. cam mounted shaft adapted to be placed on the external face of said cam
and adapted to be angularly displaceable along with said cam, said cam
mounted shaft further being adapted to engage with further assemblies of
said damper system, upon angular displacement,, at pre-defined positions
of angular displacement; and
c. oil damper system adapted to be acutated by said cam mounted shaft in
order to provide damping to angular displacement of said cam and
thereby to said crank wheel.
2. The damper system as claimed in claim 1, wherein said cam is an angularly displaceable cam adapted to be angularly displaced along with said crank wheel.
3. The damper system as claimed in claim 1, wherein said cam is an angularly displaceable cam adapted to be angularly displaced along with said crank wheel once a closing spring is delatched.

4. The damper system as claimed in claim 1, wherein said cam mounted shaft forms a secant on said cam profile and is adapted to be angularly displaced along with said cam angular displacement.
5. The damper system as claimed in claim 1, wherein said damper system comprising an oil bath, associated damping assemblies in said oil bath, and a piston extending operatively upward from said oil bath, said piston adapted to be driven by said cam mounted shaft in order to engage and actuate said damper system in order to dampen the load effect caused due to spring expansion or decompression on the crank wheel.
6. The damper system as claimed in claim 1, wherein said damper system comprising an oil bath, associated damping assemblies in said oil bath, and a piston extending operatively upward from said oil bath, said piston adapted to be driven by said cam mounted shaft at pre-defined position of angular displacement of said crank wheel and said cam.
7. The damper system as claimed in claim 1, wherein said damper system comprising an oil bath, associated damping assemblies in said oil bath, and a piston extending operatively upward from said oil bath, said piston adapted to follow profile of cam by said shaft.
8. The damper system as claimed in claim 1, wherein said damper system being a torque enabling damping system adapted to enable an opposing torque in a direction to oppose said angular displacement of said crank wheel.

9. The damper system as claimed in claim 1, wherein said damper system comprising a piston, said piston profile being designed such that it is adapted to operate only after full closing operation of said circuit breaker assembly.