FORM2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention. - REAR DOOR INTERLOCK FOR MV
SWITCHGEAR PANEL
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
This invention relates generally to a switch board arrangement. More particularly the present invention relates to improved interlock assembly for switchgear panel to prevent direct access of live parts thereby preventing opening of rear cover. Present invention provides a rear door interlock for MV switchgear panel.
BACKGROUND AND THE PRIOR ART
In conventional switchboard there is no provision to prevent the direct access of live parts from rear. Anybody can open the rear cover easily in service condition of switchboard. To avoid this type of accident, present invention provides a safety interlock in switchboard.
US5027931 provides a brake/shift interlock assembly mounted on the steering column in operational cooperation with a column mounted shift control mechanism for an automatic transmission. The brake/shift interlock assembly includes a pivotal latch for selectively locking the detent bar of the shift control mechanism in the park position, a solenoid assembly with an actuator rod for magnetically holding the latch in the locking position, a return spring for normally biasing the actuator rod and latch in the locking position, a spring lever for selectively moving the latch to an unlock position and an electrical control circuit for energizing the solenoid when the ignition system is on and the foot brake switch is open.

US2007045946 provides a sheet feeding device includes a casing having an engagement portion, and a sheet stacker detachably housed in the casing. The stacker has a liftable stacking plate, a handle, a lock claw, and a transmission mechanism. The plate is provided for loading a plurality of sheets. The handle is pivotable between operational and nonoperational positions. The claw is pivotable between engaged and disengaged positions. In the engaged and disengaged positions, the claw is engaged with, and disengaged from, the engagement portion, respectively. The mechanism has a solenoid and an interlock member. The solenoid has a plunger movable between locking and unlocking positions according to an input driving signal. The member allows, only with the plunger in the unlocking position, the claw to be moved from the engaged position to the disengaged position in association with pivot movement of the handle from the nonoperational position to the operational position.
The cited prior art provides for a solenoid having a plunger, the solenoid moving the plunger between a locking position and an unlocking position according to an input driving signal. The present invention provides an interlock arrangement for switchgear panels which is configured with a solenoid and logic circuitry. The logic circuitry provides for actuation of solenoid based on preprogrammed logic.
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 a safety interlock arrangement for switchgear panel to prevent direct access of live parts from rear.
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 an interlocking arrangement.

According to one aspect of the present invention, there is provided an improved interlock assembly for switchgear panel to prevent direct access of live parts thereby preventing opening of rear cover, said assembly comprising a rear door provided on said switchgear panel; a plurality of bolts for fixing said rear door; a plurality of spring means integrated with said rear door; a rear cover interlock door; a padlock bracket attached to said rear cover interlock door; a solenoid coil actuated using a push button connected in series; a plurality of substantially potential free interlocking contacts connected to said solenoid coil; a programmable logic circuitry providing for actuation of said solenoid coil on fulfilling all logic conditions provided by these interlocking contacts; a lever means provided to move a locking rod integrated to said coil.
BRIEF 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.
Fig 1 illustrates the internal view and rear outer view in lock condition.
Fig 2 illustrates the internal view and rear outer view in un-lock condition.
Fig 3 illustrates the circuit diagram of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Accordingly in the present invention, an interlock arrangement is provided an improved interlock assembly for switchgear panel to prevent direct access of live parts thereby preventing opening of rear cover.
Operating process are given below -
1. Ensure that the vacuum circuit breaker is in 'Test' position.
2. Remove all bolts on rear cover and padlock of cable access interlock cover.

3. Press the push button of MIL [Magnetic Inter-lock -a solenoid coil which actuate when supply is ON] and simultaneously move the lever 'C to right side & open the rear door.
4. To activate the interlock press the push button after taking the rear door to its close position.
5. Tighten the bolts & put the padlock.
Cable Access Interlock (C.A.I):-
a) Cable: The word cable identifies a power cable of electric voltage insulation level of 3.6 kV and up to 50 kV.
b) Panel: A panel is housing for accommodating an electric circuit breaker with all the protection and/or measurement equipment for a feeder in a switchboard. An electric power input/output device is connected to the panel through a cable.
c) Cable Access Interlock: A cable access interlock is an interlocking arrangement in a panel of a switchboard between an electric power switching device called as circuit breaker OR panel earthing switch and the cover for accessing the power cable connecting the panel with the feeder.
Operation of Cable Access Interlock: -
A C.A.I is used in an electric circuitry of a panel for preventing the opening of rear cover of
the chamber (where a power cable is connected to the circuit breaker) when the feeder is
live.
Q1 : ELECTRIC CIRCUIT BREAKER WITH AUXILIARY CONTACTS
S 1: EARTH SWITCH WITH AUXILIARY CONTACT
R : R-PHASE POWER SUPPLY
Y : Y-PHASE POWER SUPPLY
B : B-PHASE POWER SUPPLY
F1: FUSE

F2: FUSE F3 : FUSE F4: FUSE
S4 : AUXILIARY CONTACT
S5 : AUXILIARY CONTACT OF EARTH SWITCH .
S2 : PUSH BUTTON OF C.A.I
S3 : PUSH BUTTON OF C.A.I
Kl : SOLENOID COIL OF C.A.I
K2 : SOLENOID COIL OF C.A.I
Gl: CONTROL SUPPLY FOR C.A.1
G2: CONTROL SUPPLY FOR C.A.I
STEPS FOR THE OPERATION OF C.A.I:-
STEP1: Ensure that the earthing device i.e Earth Switch is ON, the corresponding changeover contact (S4 or S5) of the earth switch will go to NC.
STEP2: Push button (S2 or S3) is then pressed to actuate the solenoid coil of the C.A.I
STEP3: Move the Lever C of the C.A.I and the cover can be opened.
WORKING:-
Opening of the rear cover:-
A C.A.I has a solenoid coil which is connected in series with a push button and potential free interlocking contacts. A solenoid coil can only be actuated by the bush button if it fulfills all the logic conditions provided by these interlocking contacts. The shaft of the solenoid coil moves and the main rod providing strong mechanical interlocking (as shown in fig 1 & 2) with the rear cover is free to move. The Lever C is provided to move the main rod .As the main rod is moved it frees the bracket of the rear cover and it can be opened easily.

Closing of the rear cover:-
The solenoid coil is re-actuated by the push button which moves its shaft thereby allowing the movement of main interlocking rod. The Lever C is moved to latch the bracket of rear cover. Once the rear cover gets latched, it can be further bolted.
Door bypass operation Of Cable Access interlock: -
In case of emergency, there is facility to bypass the interlock. The process of bypassing the interlock is given below-
1. Remove the bolts marked red on head as shown in photograph.
2. Loose the other two bolts.
3. Shift up the top bolt & shift down the bottom bolt.
4. Then open the rear door.
List of Components:-
• Solenoid Coil
• Push button to actuate the Solenoid coil.
• Solenoid Coil Housing
• Lever "C"
• Locking rod (square bar)
• Spring. ADVANTAGES:

1) It prevents the direct access of live parts from rear side of panels.
2) It ensures that the breaker is in test/disconnected before open the rear door.
Or
Earth switch is ON during maintenance.

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 interlock assembly for switchgear panel to prevent direct access of live
parts thereby preventing opening of rear cover, said assembly comprising:
a rear door provided on said switchgear panel;
a plurality of bolts for fixing said rear door;
a plurality of spring means integrated with said rear door;
a rear cover interlock door;
a padlock bracket attached to said rear cover interlock door;
a solenoid coil actuated using a push button connected in series;
a plurality of substantially potential free interlocking contacts connected to said solenoid coil;
a programmable logic circuitry providing for actuation of said solenoid coil on fulfilling all logic conditions provided by these interlocking contacts;
a lever means provided to move a locking rod integrated to said coil.
2. Assembly as claimed in claim 1 wherein said solenoid coil is placed in a housing means.
3. Assembly as claimed in claim 1 wherein said rear door is a substantially hingable door.
4. Assembly as claimed in claim 1 wherein movement of said main rod frees said bracket thereby opening said cover.

5. Assembly as claimed in claim 1 wherein said solenoid coil configured for re-actuation by said push button that moves said shaft thereby allowing movement of main rod and said lever means moved to latch said bracket of rear cover thereby allowing it to be bolted.
6. Assembly as claimed in claim 1 wherein said rear door comprising a bypassing assembly to bypass said interlock assembly.
7. An improved interlock assembly for switchgear panel as herein described and illustrated with reference to accompanying drawings.