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 Moulded vacuum switchgear
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai - 400 030,
Maharashtra, India, an Indian Company
INVENTORS
Kulkarni Shantanu Pradeep, Gosavi Gopal Madhukargiri and Shukla Raghunath Gajanan, all of Crompton Greaves Ltd, Switchgear Division, A-3, M I DC Ambad, Nashik - 422010 Maharasthra, India, all Indian nationals
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
This invention relates to a moulded vacuum switchgear.
BACKGROUND OF THE INVENTION
Moulded vacuum switchgears are protective electrical devices used in power distribution systems in power systems. A moulded vacuum switchgear comprises a housing having a vacuum circuit breaker mounted on a mobile carriage and located in the breaker chamber of the housing. A drive mechanism is connected to the mobile carriage to move the vacuum circuit breaker forward and backward. The circuit breaker comprises an upper row of three movable contacts and a lower row of three movable contacts projecting outwardly in the direction of a spout plate which is vertically disposed and mounted in the busbar chamber of the housing in spaced apart relationship with the vacuum circuit breaker. The spout plate comprises an upper row of 3 fixed contacts enclosed in spouts corresponding to the busbar side of the housing and a lower row of 3 fixed contacts enclosed in spouts corresponding to the feeder side of the housing. The movable contacts of the vacuum circuit breaker are adapted to be in contact with and out of contact with the respective fixed contacts. In the isolated state of the switchgear ie when the movable contacts are out of contact with the fixed contacts and the fixed contacts are open, the circuit breaker is in its retracted position and the fixed contacts are exposed. In case humans or other conductor bodies happen to touch the naked fixed contacts serious electric shocks will be experienced. This can not only cause accidents but may even lead to death or fire. Dust or such

other foreign particles will also start depositing on the naked fixed contacts thereby reducing their conductivity.
In order to prevent electric shocks and accidents and dust formation on the fixed contacts, the fixed contacts are closed with a shutter mechanism interposed between the circuit breaker and the spout plate. The shutter mechanism comprises a pair of bell crank levers each located at each side of the panel and pivoted at their corners. One ends of the bell crank levers are disposed in the proximity of a pair of actuator members projecting outwardly from the opposite sidewalls of the housing of the circuit breaker. The other ends of the bell crank levers rest against stoppers provided in the housing. A fibre reinforced plastic shutter is disposed over the fixed contacts and held in position with a pair of links fixed to the shutter at the ends thereof. The free ends of the links are fixed to the other ends of the bell crank levers. The shutter comprises a row of three openings positioned to lie between the upper row of fixed contacts and lower row of fixed contacts in the isolated state of the switchgear. The shutter is raised and lowered during forward and reverse movements of the vacuum circuit breaker with the mobile carriage. In the raised position of the shutter, the openings in the shutter align with and expose the upper row of fixed contacts and the bottom end of the shutter remains above the lower row of fixed contacts thereby exposing the lower row of fixed contacts also. The circuit breaker is moved forward to make contact amongst the movable contacts and fixed contacts thereby rendering the switchgear in the service state.
Fibre reinforced plastic shutter is very costly and its processing cost is very high. Travel of the shutter with respect to the upper row of fixed contacts is limited to the up and down travel of the

other ends of the bell crank levers about the pivots thereof. As the travel of the shutter is limited, the electrical clearance between the fixed contacts and the earth is restricted. Therefore, it is not possible to increase the rating of the switchgear as switchgears of higher rating will require larger electrical clearance between the fixed contacts and the earth. Fibre reinforced plastic shutters deform after a number of operations and start malfunctioning. As a result, the reliability and life of the shutter are reduced. In case the shutter is exposed to fire it will start burning releasing toxic materials hazardous to health. Due to the fibre reinforced plastic shutter being non-conducting, the residual charge or residual electric field being generated in the switchgear remain floating on the shutter. The floating residual charge will cause fatal electric shock and accidents in case the gap between the shutter and the earth is bridged by humans or conductor bodies. As a result of all this, the shutter is not safe.
OBJECTS OF THE INVENTION
An object of the invention is to provide a moulded vacuum switchgear which is economical, sturdy and strong and reliable and has increased life.
Another object of the invention is to provide a moulded vacuum switchgear which can have increased rating.
Another object of the invention is to provide a moulded vacuum switchgear which does not release toxic gases on getting burnt and does not carry residual charge and is safe.

DETAILED DESCRIPTION OF THE INVENTION
According to the invention there is provided a moulded vacuum switchgear comprising a vacuum circuit breaker mounted on a mobile carriage and located in the breaker chamber of a housing, the vacuum circuit breaker comprising an upper row of three movable contacts and a lower row of three movable contacts, a spout plate vertically disposed and mounted in the busbar chamber of the housing in spaced apart relationship with the vacuum circuit breaker and having an upper row of 3 fixed contacts enclosed in spouts corresponding to the busbar side of the housing and aligned with the upper row of movable contacts and a lower row of 3 fixed contacts enclosed in spouts corresponding to the feeder side of the panel and aligned with the lower row of movable contacts and a shutter mechanism located in the housing between the circuit breaker and spout plate, the shutter mechanism comprising a metallic upper shutter and a lower shutter disposed in front of the fixed contacts for guided up and down movement in opposite direction relative to each other, the upper shutter and lower shutter being adapted to overlap each other and close the upper row of fixed contacts and lower row of fixed contacts, respectively in the isolated state of the switchgear and being adapted to move away from each other in opposite directions and expose the upper row of fixed contacts and lower row of fixed contacts respectively in the service state of the switchgear and drive means for operating the shutters.
The following is a detailed description of the invention with reference to the accompanying drawings, in which:

Fig 1 is a side view of a moulded vacuum switchgear according to an embodiment of the invention in the isolated state thereof;
Fig 2 is side view of the shutter mechanism of the switchgear of Fig 1;
Fig 3 is a side view of the shutter mechanism of Fig 1 in the service state thereof; and
Fig 4 is a front view of the spout plate of the switchgear of Fig 1.
The moulded vacuum switchgear 1 as illustrated in Figs 1 to 4 of the accompanying drawings comprises a circuit breaker 2 mounted on a mobile carriage 3 and located in the breaker chamber 4 of a housing 5. The vacuum circuit breaker comprises an upper row of three movable contacts 6 and a lower row of three movable contacts 7. Only one of the movable contacts of both the upper row of movable contacts and lower row of movable contacts is seen in Figs 1 and 3 as the remaining movable contacts are behind the ones that are seen in Figs 1 and 3. The drive mechanism for moving the circuit breaker along with the mobile carriage in the forward and reverse directions has not been illustrated and described in the specification as such is not necessary for understanding the invention. 8 is a spout plate vertically disposed and mounted in the busbar chamber 9 of the housing in spaced apart relationship with the vacuum circuit breaker. The spout plate comprises an upper row of 3 fixed contacts 10 enclosed in spouts II corresponding to the busbar side of the housing and aligned with the upper row of movable contacts and a lower row of 3 fixed contacts 12 enclosed in spouts 13 corresponding to the feeder side of the panel and aligned with the lower row of movable contacts. 14 is a shutter mechanism

disposed in the housing between the circuit breaker and spout plate. The shutter mechanism comprises a pair of bell crank levers 15 each located at each side of the housing and pivoted at the corners thereof (pivots marked 16). One ends of the bell crank levers are disposed in the proximity of a pair of actuator members 17 projecting outwardly from the opposite sides of the housing of the vacuum circuit breaker. The other ends of the bell crank levers rest against stoppers 18 provided in the housing. Only one bell crank lever and corresponding one ends and other end of the crank lever are seen in Figs 1 and 3 as the other crank lever is behind the one seen in Figs 1 and 3. An upper shutter 19 and a lower shutter 20 are slidably disposed over a pair of vertically held guide rods 21 each at each side of the housing and mounted to the housing. The shutter mechanism also comprises a pair of links 22 one ends of which are fixed to the upper shutter and the other ends of which are fixed to the other ends of the bell crank levers. The shutter mechanism also comprises a pair of pulleys 23 each mounted at each side of the panel at the top thereof in the proximity of the guide rods and having a wire rope 24 engaged over it. One ends of the wire ropes are fixed to the upper end of the upper shutter and the other ends of the wire ropes are fixed to the upper end of the lower shutter. The shutters are arranged such that they overlap each other and the upper shutter closes the upper row of the fixed contacts and the lower shutter closes the lower row of the fixed contacts in the isolated state of the switchgear and the shutters move away from each other exposing the respective fixed contacts in the service state of the switchgear. The shutters are of identical length and width and the upper shutter is slightly heavier than the lower shutter. Preferably the shutters are made of mild steel. 25 is a busbar chamber in the housing.

During forward movement of the vacuum circuit breaker along with the mobile carriage to establish contact amongst the movable contacts and the fixed contacts, the actuator members engage against the one ends of the bell crank levers in the proximity thereof and move the one ends of the bell crank levers in the forward direction. As a result, the other ends of the bell crank levers move upwardly about the pivots of the bell crank levers. The upper shutter moves up and the lower shutter moves down with the wire ropes thereby exposing the respective fixed contacts and allowing the movable contacts to make contact with the respective fixed contacts and the switchgear remains in the service state thereof. During reverse movement of the vacuum circuit breaker along with the mobile carriage, the actuator members disengage from the one ends of the bell crank levers and the one ends of the bell crank levers move back and the other ends of the bell crank levers move down about the pivots of the bell crank levers. The downward movements of the other ends of the bell crank levers are limited by the stoppers. As the other ends of the bell crank levers move down the upper shutter moves down and the lower shutter moves up until the other ends of the bell crank levers abut and stop against the stoppers. The shutters overlap each other marginally and completely close the fixed contacts and the switchgear remains in its isolated state. Because of the upper shutter being marginally heavier, the upper shutter moves down under gravity as the other ends of the bell crank levers move down.
According to the invention the shutters are made of conductor materials like metal, preferably mild steel. Shutters made of materials like mild steel are of low cost and their fabrication cost is also low. The shutters are strong and sturdy and do not deform even after repeated operations. As a result, the shutters have long life and are reliable. As the shutters are moving away relative

to each other, it is possible to have large travel distance between the shutters. Therefore, it is possible to have larger electrical clearance between the fixed contacts and the earth and to increase the rating of the switchgear. In case of fire, the shutters do not burn and release toxic gases. On the contrary the shutters are fire resistant to a great extent. The residual charges on the shutters do not give rise to electric shocks and accidents due to the conducting nature of the shutters. The shutters do not allow the residual charge to remain floating on the shutters but instead establish equipotential with the earth. Therefore, bridging of the gap between the shutters and earth by humans or other conductor bodies do not lead to electric shocks and accidents. As a result of all this, the shutters are safe.
It is understood that the drive means for moving the shutters up and down away from each other can be of a different construction and configuration. It is also understood that the shutters can be made of any other mechanically strong sturdy and lasting conductor material. Variations in the construction and configuration of the drive means which are obvious to the person skilled in the art, are to be construed within the scope of the invention.

We claim:
1. A moulded vacuum switchgear comprising a vacuum circuit breaker mounted on a mobile carriage and located in the breaker chamber of a housing, the vacuum circuit breaker comprising an upper row of three movable contacts and a lower row of three movable contacts, a spout plate vertically disposed and mounted in the busbar chamber of the housing in spaced apart relationship with the vacuum circuit breaker and having an upper row of 3 fixed contacts enclosed in spouts corresponding to the busbar side of the housing and aligned with the upper row of movable contacts and a lower row of 3 fixed contacts enclosed in spouts corresponding to the feeder side of the panel and aligned with the lower row of movable contacts and a shutter mechanism located in the housing between the circuit breaker and spout plate, the shutter mechanism comprising a metallic upper shutter and a lower shutter disposed in front of the fixed contacts for guided up and down movement in opposite direction relative to each other, the upper shutter and lower shutter being adapted to overlap each other and close the upper row of fixed contacts and lower row of fixed contacts, respectively in the isolated state of the switchgear and being adapted to move away from each other in opposite directions and expose the upper row of fixed contacts and lower row of fixed contacts respectively in the service state of the switchgear and drive means for operating the shutters.
2. The moulded vacuum switchgear as claimed in claim 1, wherein the drive means comprises a pair of bell crank levers each located at each side of the housing and pivoted at the corners thereof, one ends of the bell crank levers being disposed in the proximity of a pair of actuator members projecting outwardly from the opposite sides of the housing of the vacuum circuit breaker and the other ends of the bell crank levers resting against stoppers provided in the

housing, the shutters being slidably disposed over a pair of vertically held guide rods each at each side of the housing and mounted to the housing, a pair of links one ends of which are fixed to the upper shutter and the other ends of which are fixed to the other ends of the bell crank levers, a pair of pulleys each mounted at each side of the panel at the top thereof in the proximity of the respective guide rod and having a wire rope engaged over it, one ends of the wire ropes being fixed to the upper end of the upper shutter and the other ends of the wire ropes being fixed to the upper end of the lower shutter, the shutters being of identical length and width and the upper shutter being heavier than the lower shutter.
3. The moulded vacuum switchgear as claimed in claim 1 or 2, wherein the shutters are made of mild steel.