FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
As amended by the Patents (Amendment) Act, 2005
&
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 switch mechanism for obtaining the states of disconnection, earthing, and neutral in switchgear equipment.
APPLICANT
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company.
INVENTOR
Meghavath Shivakumar of Crompton Greaves Limited, Global R& D centre, Bhaskara building, Kanjurmarg (East), Mumbai-400042, Maharashtra, India, An Indian National.
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 assemblies and mechanical engineering.
Particularly, this invention relates to switchgear equipment.
More particularly, this invention relates to a switch mechanism for obtaining the states of disconnection, earthing, and neutral in switchgear equipment.
BACKGROUND OF THE INVENTION:
The term 'switchgear', used in association with the electric power system, or grid, 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. 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 something such as springs or compressed air) 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.
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.
In switchgear components and equipment, a disconnector or isolator switch is used to make sure that an electrical circuit can be completely de-energised for service or

maintenance. A Gas Insulated Switchgear (GIS) comprises a plurality of electrical components and includes gas as primary insulating medium typically at high voltages. In the GIS, an electric component is typically connected to a power supply via a disconnector switch and to the ground through an earthing switch. Both the disconnector and earthing switches are interrupters, each of which comprises a fixed contact and a movable contact linearly movable relative to the fixed contact. Under normal operating conditions, the disconnector switch of an electric component is closed and the earthing switch is opened. However, when the circuit breaker or the Busbars need to be isolated for testing/maintenance, the disconnector switches need to be opened and earthing switches closed. Thus, both the disconnector and earthing switches operate in conjunction in a GIS.
Prior art mechanisms include an arrangement wherein only a close or an open position can be achieved,
There are other prior art mechanism wherein, there is provided a first position of contacts such that disconnecting can be achieved, a second position of contacts such that earthing can be achieved, and a third position of contacts, intermittently positioned between the first position and the second position, in order to achieve a neutral condition.
This arrangement, operation, and actuation of contacts form a control mechanism. The prior art mechanism include relatively greater number of drives for providing mechanical interlocking.

There is a need for a switch mechanism which exercises precise control to obtain fast and distinct switching between the states of 1) disconnecting; 2) earthing; and 3) neutral.
Also, there is a need for a switch mechanism which reduces the number of drives required and provides mechanical interlocking without any external means and which maintains clearances between moving and stationary contacts.
OBJECTS OF THE INVENTION:
An object of the invention is to provide a mechanism which provides precise actuation of contacts to achieve the states of 1) disconnecting; 2) earthing; and 3) neutral.
Another object of the invention is to provide a mechanism which provides distinct actuation of contacts to achieve the states of 1) disconnecting; 2) earthing; and 3) neutral.
Yet another object of the invention is to provide a mechanism which provides relatively faster actuation of contacts to achieve the states of 1) disconnecting; 2) earthing; and 3) neutral.
Still another object of the invention is to provide a mechanism which reduces the number of drives required.

An additional object of the invention is to provide a mechanism which provides mechanical interlocking without any external means.
Yet an additional object of the invention is to provide a mechanism which maintains clearances between moving and stationary contacts.
SUMMARY OF THE INVENTION:
According to this invention, there is provided a switch mechanism for obtaining the states of disconnection and earthing in switchgear equipment comprises;
A. first axially located stationary contact adapted to be a disconnector contact;
B. first moving contact adapted to axially engage with said first axially located
stationary contact to obtain a close switch position and a disconnect mode of
said switch mechanism;
C. second axially located stationary contact adapted to be an earthing contact;
D. second moving contact adapted to axially engage with said second axially
located stationary contact to obtain a close switch position and an earthing
mode of said switch mechanism; and
E. drive mechanism adapted to drive the axial movement of each of said first
moving contact and said second moving contact, in order to obtain said
disconnect mode and said earthing mode with an intermittent neutral mode.
Typically, said drive mechanism comprises:
a. drive rod, externally driven, containing helical grooves, adapted to meshes with a worm wheel;

b. eccentric cam located on said worm wheel, said eccentric cam being offset
from the centre, in that, the centres of said eccentric cam and said worm
wheel are spaced apart with respect to each other; and
c. driving link positioned co-axial to said eccentric cam, said driving link being
an arm element such that it extends in opposite directions with respect to
said eccentric cam angular displacement axis.
Typically, said first moving contact is an operative horizontal cylinder with mating surfaces at either ends, such that the axial movement of said first moving contact is an operative horizontal movement such that as one of the mating surfaces engages with said first axially located stationary contact, disconnecting switch is closed and as the mating surface moves away from said first axially located stationary contact, disconnecting switch is open.
Typically, said second moving contact is an operative horizontal cylinder with mating surfaces at either ends, such that the axial movement of said second moving contact is an operative horizontal movement such that as one of the mating surfaces engages with the second axially located stationary contact, earthing switch is closed and as the mating surface moves away from the second axially located stationary contact, earthing switch is open.
Typically, said mechanism comprises a first connecting link provided from a first end of said driving link, said first connecting link being a tubular element adapted to mechanically couple said driving link to said first moving contact at its not mating surface.

Typically, said mechanism comprises a first connecting link having angular displacement play.
Typically, said mechanism comprises a second connecting link provided from a second end of said driving link, said second connecting link being a tubular element adapted to mechanically couple said driving link to said second moving contact at its not mating surface.
Typically, said mechanism comprises a second connecting link having angular displacement play.
Typically, said connecting links are modular connecting links designed in a manner such that there is flexibility in increasing and decreasing the clearances between said stationary contacts and said moving contacts, thereby resulting in changing the time required for achieving disconnection and earthing, respectively.
Typically, said mechanism comprises a first stopper link adapted to anchor a first end of said driving link to a stationary housing which houses said switch mechanism such that one end of said first stopper link is stationary, and the other end of said first stopper assembly has partial angular displacement play, which prevents overriding of the first moving contact in its forward movement.
Typically, said mechanism comprises a second stopper link adapted to anchor a second end of said driving link to a stationary housing which houses said switch mechanism such that one end of said second stopper link is stationary, and the

other end of said second stopper assembly has partial angular displacement play, which prevents overriding of the second moving contact in its forward movement.
Typically, said drive mechanism is placed in a moving-contact housing.
Typically, entire switch mechanism is placed in a housing with space being provided so that the worm wheel can freely angular displace as the drive rod angular displaces.
According to this invention, there is also provided a method for obtaining the states of disconnection in switchgear equipment, said method comprises the steps of: I. angularly displacing a worm wheel carrying an eccentric cam on it, by 180
degrees; and II. moving a driving link connected to said eccentric cam towards a first axially located stationary contact causing a first moving contact to move from its non-engaged position to its engaged position with respect to said first axially located stationary contact, thereby achieving the disconnector close condition.
Typically, said method comprising further steps of simultaneously, causing a second moving contact to move from its engaged position to its non-engaged position, thereby achieving the earthing open condition.
According to this invention, there is also provided a method for obtaining the states of earthing in switchgear equipment, said method comprises the steps of:

i. angularly displacing a worm wheel carrying an eccentric cam on it, by 180
degrees; and ii. moving a driving link connected to said eccentric cam towards a second axially located stationary contact causing a second moving contact to move from its non-engaged position to its engaged position with respect to said second axially located stationary contact, thereby achieving the earthing close condition.
Typically, said method comprising further steps of simultaneously, causing a first moving contact to move from its engaged position to its non-engaged position, thereby achieving the disconnecting open condition.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
The invention will now be described in relation to the accompanying drawings, in which:
Figure 1 illustrates a schematic view of the switch mechanism in its disconnector open position;
Figure 2 illustrates a schematic view of the switch mechanism in its disconnector close position;
Figure 3 illustrates a schematic view of the switch mechanism in its earthing open position; and

Figure 4 illustrates a schematic view of the switch mechanism in its earthing close position.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
According to this invention, there is provided a switch mechanism for obtaining the states of disconnection and earthing in switchgear equipment.
Figure 1 illustrates a schematic view of the switch mechanism in its disconnector open position.
Figure 2 illustrates a schematic view of the switch mechanism in its disconnector close position.
Figure 3 illustrates a schematic view of the switch mechanism in its earthing open position.
Figure 4 illustrates a schematic view of the switch mechanism in its earthing close position.
In accordance with an embodiment of this invention, there is provided a first axially located stationary contact (12) adapted to be the disconnector contact.
In accordance with another embodiment of this invention, there is provided a first moving contact (14) adapted to axially engage with the first axially located

stationary contact (12). Axial engagement results in making contact of first moving contact with the first axially located stationary contact, thereby resulting in a close switch position and in a disconnect mode of the switch mechanism. The first moving contact is, typically, an operative horizontal cylinder with mating surfaces at either ends. The axial movement of the first moving contact is an operative horizontal movement such that as one of the mating surfaces engages with the first axially located stationary contact, disconnecting switch is closed. And as the mating surface moves away from the first axially located stationary contact, disconnecting switch is open.
In accordance with yet another embodiment of this invention, there is provided a second axially located stationary contact (16) adapted to be the earthing contact.
In accordance with still another embodiment of this invention, there is provided a second moving contact (18) adapted to axially engage with the second axially located stationary contact (16). Axial engagement results in making contact of second moving contact with the second axially located stationary contact, thereby resulting in a close switch position and in an earthing mode of the switch mechanism. The second moving contact is, typically, an operative horizontal cylinder with mating surfaces at either ends. The axial movement of the second moving contact is an operative horizontal movement such that as one of the mating surfaces engages with the second axially located stationary contact, earthing switch is closed. And as the mating surface moves away from the second axially located stationary contact, earthing switch is open.
In accordance with an additional embodiment of this invention, there is provided a drive mechanism to drive the axial movement of each of the first moving contact

and the second moving contact. A drive rod (22), externally driven, contains helical grooves, which meshes with a worm wheel (24). An eccentric cam (26) is located on the worm wheel (24). This eccentric cam is offset from the centre, in that, the centres of the eccentric cam and the worm wheel are spaced apart with respect to each other. Space is provided so that the worm wheel can freely angular displace as the drive rod angular displaces. A driving link (32) is positioned coaxial to the eccentric cam. The driving link (32) is an arm element such that it extends in opposite directions with respect to the eccentric cam (26) angular displacement axis.
A first connecting link (34) is provided from a first end of the driving link (32). The first connecting link (34) is a tubular element which mechanically couples the driving link (32) to the first moving contact (14) at its not mating surface. The first connecting link (34) has angular displacement play.
A second connecting link (36) extends is provided from a second end of the driving link (34). The second connecting link (36) is a tubular element which mechanically couples the driving link (32) to the second moving contact (16) at its not mating surface. The second connecting link (36) has angular displacement play.
As the worm wheel (24) angularly displaces, it carries the eccentric cam (26) on it, and the eccentric cam (26) angularly displaces, too. In the first 180 degrees of angular displacement of the worm wheel (24) and its connected eccentric cam (26), the driving link (34) on the cam (26) moves towards the first axially located stationary contact (12) and hence, the first connecting link (34), extending from the

end of the driving link (34), causes the first moving contact (14) to move from its non engaged position (of Figure 1 of the accompanying drawings) to its engaged position with respect to the first axially located stationary contact (12), thereby achieving the disconnector close condition as shown in Figure 2 of the accompanying drawings.
As the worm wheel (24) angularly displaces further, it carries the eccentric cam (26) further on it, and the eccentric cam (26) angularly displaces further, too. In the second 180 degrees of angularly displacement of the worm wheel (24) and its connected eccentric cam (26), the driving link (34) on the cam (26) moves towards the second axially located stationary contact (16) and hence, the second connecting link (36), extending from the end of the driving link (34), causes the second moving contact (18) to move from its non engaged position (of Figure 3 of the accompanying drawings) to its engaged position with respect to the second axially located stationary contact (16), thereby achieving the earthing close condition as shown in Figure 4 of the accompanying drawings.
Simultaneously, during the first 180 degree angular displacement, the driving link (34) movement away from the second axially located stationary contact (16) causes the second moving contact (18) to move from its engaged position to its non-engaged position, thereby achieving the earthing open condition as shown in Figure 3 of the accompanying drawings.
Also, simultaneously, during the second 180 degree angular displacement, the driving link (34) movement away from the first axially located stationary contact (12) causes the first moving contact (14) to move from its engaged position to its

non-engaged position, thereby achieving the earthing open condition as shown in Figure 1 of the accompanying drawings.
The connecting links are designed in a manner such that there is flexibility in increasing and decreasing the clearances between the fixed contacts and the moving contacts. This results in changing the time required for achieving disconnection and earthing, respectively.
In accordance with an additional embodiment of this invention, there is provided a first stopper link (42) adapted to anchor a first end of the driving link (34) to a stationary housing which houses the switch mechanism. Thus, one end of the first stopper link is stationary, and the other end of the first stopper assembly has partial angular displacement play, which prevents overriding of the first moving contact in its forward movement.
In accordance with yet an additional embodiment of this invention, there is provided a second stopper link (44) adapted to anchor a second end of the driving link (34) to a stationary housing which houses the switch mechanism. Thus, one end of the second stopper link is stationary, and the other end of the second stopper assembly has partial angular displacement play, which prevents overriding of the second moving contact in its forward movement.
The drive mechanism is placed in a moving contact housing (52). The entire switch mechanism is placed in another housing (54).

Due this invention, the number of drives required for achieving the states of 1) disconnecting; 2) earthing; and 3) neutral is reduced. The invention provides mechanical interlocking without any external means and to maintain the clearances between the moving and stationary contacts. This motion, as explained above, is relatively more reliable and does not cause any over travel or over-drive of the moving contact.
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 switch mechanism for obtaining the states of disconnection and earthing in switchgear equipment comprising;
A. first axially located stationary contact adapted to be a disconnector contact;
B. first moving contact adapted to axially engage with said first axially located
stationary contact to obtain a close switch position and a disconnect mode of
said switch mechanism;
C. second axially located stationary contact adapted to be an earthing contact;
D. second moving contact adapted to axially engage with said second axially
located stationary contact to obtain a close switch position and an earthing
mode of said switch mechanism; and
E. drive mechanism adapted to drive the axial movement of each of said first
moving contact and said second moving contact, in order to obtain said
disconnect mode and said earthing mode with an intermittent neutral mode.
2. A switch mechanism as claimed in claim 1 wherein, said drive mechanism comprising:
a. drive rod, externally driven, containing helical grooves, adapted to meshes
with a worm wheel;
b. eccentric cam located on said worm wheel, said eccentric cam being offset
from the centre, in that, the centres of said eccentric cam and said worm
wheel are spaced apart with respect to each other; and
c. driving link positioned co-axial to said eccentric cam, said driving link being
an arm element such that it extends in opposite directions with respect to
said eccentric cam angular displacement axis.

3. A switch mechanism as claimed in claim 1 wherein, said first moving contact is an operative horizontal cylinder with mating surfaces at either ends, such that the axial movement of said first moving contact is an operative horizontal movement such that as one of the mating surfaces engages with said first axially located stationary contact, disconnecting switch is closed and as the mating surface moves away from said first axially located stationary contact, disconnecting switch is open.
4. A switch mechanism as claimed in claim 1 wherein, said second moving contact is an operative horizontal cylinder with mating surfaces at either ends, such that the axial movement of said second moving contact is an operative horizontal movement such that as one of the mating surfaces engages with the second axially located stationary contact, earthing switch is closed and as the mating surface moves away from the second axially located stationary contact, earthing switch is open.
5. A switch mechanism as claimed in claim 1 wherein, said mechanism comprising a first connecting link provided from a first end of said driving link, said first connecting link being a tubular element adapted to mechanically couple said driving link to said first moving contact at its not mating surface.
6. A switch mechanism as claimed in claim 1 wherein, said mechanism comprising a first connecting link having angular displacement play.

7. A switch mechanism as claimed in claim 1 wherein, said mechanism comprising a second connecting link provided from a second end of said driving link, said second connecting link being a tubular element adapted to mechanically couple said driving link to said second moving contact at its not mating surface.
8. A switch mechanism as claimed in claim 1 wherein, said mechanism comprising a second connecting link having angular displacement play.
9. A switch mechanism as claimed in claim 1 wherein, said connecting links are modular connecting links designed in a manner such that there is flexibility in increasing and decreasing the clearances between said stationary contacts and said moving contacts, thereby resulting in changing the time required for achieving disconnection and earthing, respectively.
10. A switch mechanism as claimed in claim 1 wherein, said mechanism comprising a first stopper link adapted to anchor a first end of said driving link to a stationary housing which houses said switch mechanism such that one end of said first stopper link is stationary, and the other end of said first stopper assembly has partial angular displacement play, which prevents overriding of the first moving contact in its forward movement.
11. A switch mechanism as claimed in claim 1 wherein, said mechanism comprising a second stopper link adapted to anchor a second end of said driving link to a stationary housing which houses said switch mechanism such that one end of said second stopper link is stationary, and the other end of said

second stopper assembly has partial angular displacement play, which prevents overriding of the second moving contact in its forward movement.
12. A switch mechanism as claimed in claim 1 wherein, said drive mechanism is placed in a moving-contact housing.
13. A switch mechanism as claimed in claim 1 wherein, entire switch mechanism is placed in a housing with space being provided so that the worm wheel can freely angular displace as the drive rod angular displaces.
14. A method for obtaining the states of disconnection in switchgear equipment, said method comprising the steps of:
I. angularly displacing a worm wheel carrying an eccentric cam on it, by 180
degrees; and II. moving a driving link connected to said eccentric cam towards a first axially located stationary contact causing a first moving contact to move from its non-engaged position to its engaged position with respect to said first axially located stationary contact, thereby achieving the disconnector close condition.
15. A method as claimed in claim 14 wherein, said method comprising further
steps of simultaneously, causing a second moving contact to move from its
engaged position to its non-engaged position, thereby achieving the earthing
open condition.

16. A method for obtaining the states of earthing in switchgear equipment, said
method comprising the steps of:
i. angularly displacing a worm wheel carrying an eccentric cam on it, by 180
degrees; and ii. moving a driving link connected to said eccentric cam towards a second axially located stationary contact causing a second moving contact to move from its non-engaged position to its engaged position with respect to said second axially located stationary contact, thereby achieving the earthing close condition.
17. A method as claimed in claim 16 wherein, said method comprising further
steps of simultaneously, causing a first moving contact to move from its
engaged position to its non-engaged position, thereby achieving the
disconnecting open condition.