FORM 2
The Patents Act 1970
(39 of 1970) &
The Patent Rules 2003 COMPLETE SPECIFICATION
(See Section 10 and rule 13) TITLE OF THE INVENTION:
INTERLOCK MECHANISM FOR CHANGE-OVER
SWITCH
APPLICANT:
LARSEN & TOUBRO LIMITED
L&T House, Ballard Estate, P.O. Box No. 278,
Mumbai, 400 001, Maharashtra . INDIA.
PREAMBLE OF THE DESCRIPTION:
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

A) TECHNICAL FIELD
[0001] The embodiments of the present invention generally relate to electrical switching devices like switches, circuit breakers etc. The embodiments more particularly relates to mechanical interlocking and complete electrical isolation of multiple power sources in a change-over switch.
B) BACKGROUND OF THE INVENTION
[0002] Electrical power supply can be interrupted by power outages requiring the electrical supply system to provide an alternate power source. In the event of a power outage, it is desirable to replace the main power supply with secondary power supply such as generators or inverter. The main source is coupled to a first switching mechanism in the change-over switch. The auxiliary power source is coupled to a second switching mechanism in the change-over switch. The switching mechanisms corresponding to the alternate power sources are interlocked to avert the danger of connecting the two sources to the load simultaneously.
[0003] In change-over switches, interlocking assembly is provided to electrically isolate the switching mechanisms. An actuator activates a switching member in the interlock assembly to activate the corresponding switch. The activation of a switching member prevents the activation of the interlocked switching member thus ensuring a single power supply to the load.

[0004] The currently available interlocking assemblies adopt various arrangements to turn ON a single switching mechanism and lock the interconnected switch in the OFF state. In some arrangements, a linkage-type mechanism interposed between the switch members prevent both the members from being in same state simultaneously. Springs are used to move the switch members in the interlocking assembly from the ON state to the OFF state. However, charging a single spring and movement of the switch member by the discharging of the spring can limit the life of the assembly due the enormous stress on the spring. Further, depth of the switch is substantially increased to accommodate the vertically arranged switching mechanisms which might not be desirable. More over none of the currently available switching devices has two dead centers.
[0005] Hence there is a need to provide a compact interlocking assembly to ensure complete electrical isolation of switching mechanisms. Further there exists a need to substantially increase the durability of the components of the assembly.
C) OBJECT OF THE INVENTION
[0006] The primary object of the present invention is to develop an interlock system for change over switch with a single mechanism having two dead centers.
[0007] Another object of the present invention is to develop an interlocking assembly for a change-over switch with an actuator mechanism to activate the switching member of a single switch to ON state and retain the other switching mechanism in OFF state.

[0008] Yet another object of the present invention is to develop an interlocking assembly for a change-over switch to store two switching devices vertically in a compact manner by reducing the overall depth of the switch by using the horizontally displaced the switching mechanisms.
[0009] Yet another object of the present invention is to develop an interlocking mechanism for a change-over switch where closing and opening of contacts of a switch is manually independent.
[0010] Yet another object of the present invention is to develop an interlocking mechanism for a change-over switch with complete electrical isolation between both the switches.
[0011] Yet another object of the present invention is to develop a change over switch with gear meshing and demeshing mechanism to achieve the interlocking of the two switches.
These and other objects and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.
D) SUMMARY OF THE INVENTION
[0012] The above mentioned shortcomings, disadvantages and problems are address herein and which will be understood by reading and studying the following specification.

[0013] The various embodiments of the present invention provide a single system and method to interlock two switching mechanism in a change-over switch using a single mechanism having two dead centers.
[0014] According to one embodiment of the present invention, the change over switch has a first switch arranged over a second switch along a vertical direction. Each switch has switch housing. Each switch housing is made up of thermo plastic material to house guide terminals, a moving contact bridge and a switching mechanism, A bottom switch cover and a top switch cover are provided to cover the internal pars of the switch to prevent the exposure of the switch components to outside. Each switch cover is made up of thermo plastic material. Each switch has 8 terminals which form the fixed contact of the switch. The moving contacts of the switch are arranged in the moving contact bridge. A terminal shroud is provided at both sides of the top cover to cover a box clamp assembly.
[0015] Each switch has a slotted gear connected to rack gear engaged to a gear mechanism in the driver assembly. Each slotted gear has an arm provided with a slot to receive a bridge pin which is coupled to a moving contact bridge. Each slotted gear is provided with a pair of torsion springs to couple the slotted gear to the housing.
[0016] An operating handle is provided on the top side of the switch to actuate a drive mechanism to move a switch to ON position from OFF position and vice versa. The operating handle is mounted on the top a driver mechanism. The driver is a metallic component provided with a pair of gear mechanisms. The rotating operation of the handle is converted into a transtational movement of the rack, gear which drives the

slotted gear rotatably. As a result the bridge pin in the slotted gear is moved translationally to move the moving contact bridge. The bridge pin moves in a translational manner in the slot of the slotted gear and the bridge hosing simultaneously.
[0017] The torsion spring is a helical spring having two arms. While one arm of the spring is immovably fixed to the switch housing while the other arm is connected to the extended arm of the slotted gear. As the angle between the two arms of the helical spring deviate, from its natural rest position/ free condition, it exerts a force which is proportional to the angle of deviation. The springs are charged during the movement of the switch to the rest positions (OFF/ON) from a dead center position and the stored in the energy is released during the movement of the switches from the dead center to the active position (ON/OFF), when the switches are moved from the OFF position to ON position. The torsion springs has maximum potential energy at the dead center position. The torsion spring is said to be in a pre-compressed state, when the maximum allowable angle of the spring is less than the free angle of that spring. The torsion spring remains in the ON or OFF positions due to the pre compression state of the springs.
[0018] When the output speed (i.e. speed or velocity of pin in this case) depends on (proportionate with) the speed at which the operator rotates the operating handle, the operation is known as manual dependent. When the output speed (i.e. speed or velocity of pin in this case) is not depends on (not proportionate with) the speed at which the operator rotates the operating handle, the operation is known as manual independent.

[0019] The first switch may be coupled to one power supply such as a main power supply and the second switch may be coupled to another power supply such as an auxiliary power supply or redundant power supply.
[0020] According to one embodiment of the invention, an interlock system is provided for change over switch including two switches connected to two power supplies. The system has an operating handle mounted on a driver assembly provided with first and second gear mechanisms. The first and the second gear mechanisms are engaged to the first rack and the second rack respectively. A first switch is connected to the first rack while the second switch is connected to the second rack. A first slotted gear provided in the first switch is engaged with the first rack whereas the second slotted in the second switch is connected to the second rack. [0021] A first bridge pin is provided in a slot provided at an arm of the first slotted gear and coupled to a first moving contact bridge so that the rotary motion of the first slotted gear is transformed into the translational motion of the first bridge pin to move the first moving contact bridge. A pair of torsion springs is connected movably to one end of the slotted gear and to the switch housing. The operating handle is rotated in clock wise direction to operate the driver to rotate the first slotted gear in anticlock wise direction through the first driver thereby moving the first bridge pin to move the first bridge to turn the first switch to ON position, when the first switch is turned to ON position and the second switch to OFF position.
[0022] Similarly a second rack is connected to the driver through a gear mechanism. A second switch connected to the driver through the second rack. The second rack is arranged vertically below the first rack. A second slotted gear provided in the second

switch is engaged to the second rack. A second bridge pin is provided in a slot provided at an arm of the second slotted gear and coupled to a second moving contact bridge the rotary motion of the second slotted gear is transformed into the translational motion of the second bridge pin to move the second moving contact bridge.
[0023] A pair of torsion springs are connected movably to one end of the slotted gear and to the switch housing. The operating handle is rotated in anti clock wise direction to operate the driver to rotate the second slotted gear in clock wise direction through the second driver thereby moving the second bridge pin to move the second bridge to turn the second switch to ON position, when the second switch is turned to ON position and the first switch to OFF position.
[0024] The first and second pair of torsion springs are charged continuously during the movement of the respective first and second switches from the ON/OFF position to the dead center position and releases the stored energy during the movement from the dead center position to OFF/ON positions. Both the first and the second pairs of torsion springs include two helical springs. The helical springs in both the first and the second pair of torsion springs have maximum potential energy at the dead center posit. The helical springs are said to be pre compressed in OFF or ON position of the first and second switches. The speed of the helical springs is manually dependent during the movement of the switch from the ON/OFF position to the dead center position. The speed of the helical springs is manually independent during the movement of the switch from the dead center position to ON/OFF position. Both the first and the second moving contact bridge support plurality of moving contact

terminals and reciprocatably moved due to the force exerted by the respective bride pins.
[0025] The two switches coupled to two power sources in a change-over switch are interlocked by gear meshing and de-meshing. The interlock assembly prevents the movement of switch member of second switch from moving to ON position when first switch is in ON position. Further, the interlock assembly prevents the movement of the switch member of the first switch from moving to ON position when the second switch is in ON position. Both the switches can be maintained in OFF position simultaneously. The two switches in the change-over switch are electrically isolated from each other completely.
E) BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which:
[0028] FIG. 1 illustrates a top perspective view of the changeover switch according to one embodiment of the present invention.
[0029] FIG. 2 illustrates an exploded view of the changeover switch according to one embodiment of the present invention.

[0030] FIG. 3A and 3B illustrate the interlocking assembly of two switching components.
[0031] FJG. 4A illustrates the top view of the interlocking assembly when both the switches are in OFF condition according to one embodiment of the present invention.
[0032] FIG. 4B illustrates the top view of the interlocking assembly when both the switches are in OFF condition according to one embodiment of the present invention.
[0033] FIG. 5A illustrates the top view of the interlocking assembly with Switch I in intermediate state between OFF condition and dead centre while being turned ON according to one embodiment of the invention.
[0034] FIG. 5B illustrates the bottom perspective view of the driver and racks for Switch I in intermediate state between OFF condition and dead centre position while being turned ON according to one embodiment of the invention.
[0035] FIG. 6A illustrates the top view of the interlocking assembly with Switch I in dead centre position while being turned ON according to one embodiment of the invention.
[0036] FIG. 6B illustrates the bottom perspective view of the driver and racks with Switch I in dead centre position while being turned ON according to one embodiment of the invention.

[0037] FIG.. 7A illustrates the top view of the interlocking assembly with Switch I in intermediate state between dead centre and ON condition while being turned ON according to one embodiment of the invention.
[0038] FIG.. 7B illustrates the bottom perspective view of the driver and racks with Switch I in an intermediate position between the dead centre position and OFF position while being turned ON according to one embodiment of the invention.
[0039] FIG.. 8A illustrates the top view of the interlocking assembly with Switch I in ON condition and Switch II in OFF condition according to one embodiment of the invention.
[0040] FIG. 8B illustrates the bottom perspective view of the driver and racks with Switch I in OFF position according to one embodiment of the invention.
[0041] FIG. 9A illustrates the top view of the interlocking assembly with Switch II in intermediate state between OFF condition and dead centre while being turned ON according to one embodiment of the invention.
[0042] FIG. 9B illustrates the bottom perspective view of the driver and racks with Switch II in intermediate state between OFF condition and dead centre position while being turned ON according to one embodiment of the invention.
[0043] FIG.. 10A illustrates the top view of the interlocking assembly with Switch II in dead centre position while being turned ON according to one embodiment of the invention.

[0044] FIG.. 10B illustrates the bottom perspective view of the driver and racks with Switch II in dead centre position while being turned ON according to one embodiment of the invention.
[0045] FIG.. 11A illustrates the top view of the interlocking assembly with Switch II in intermediate state between dead centre and ON condition while being turned ON according to one embodiment of the invention.
[0046] FIG. 11B illustrates the bottom perspective view of the driver and racks with Switch II in an intermediate position between the dead centre position and OFF position while being turned ON according to one embodiment of the invention.
[0047] FIG. 12A illustrates the top view of the interlocking assembly with Switch II in ON condition and Switch I in OFF condition according to one embodiment of the invention.
[0048] FIG. 12B illustrates the bottom perspective view of the driver and racks with Switch II in ON position and Switch I in OFF position according to one embodiment of the invention.
[0049] Although specific features of the present invention are shown in some drawings and not in others. This is done for convenience only as each feature may be combined with any or all of the other features in accordance with the present invention.

F) DETAILED DESCRIPTION OF THE INVENTION
[0050] In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which the specific embodiments that may be practiced is shown by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments and it is to be understood that the logical, mechanical and other changes may be made without departing from the scope of the embodiments. The following detailed description is therefore not to be taken in a limiting sense.
[0051] The various embodiments of the present invention provide a single system and method to interlock two switching mechanism in a change-over switch using a single mechanism having two dead centers.
[0052] According to one embodiment of the present invention, the change over switch has a first switch arranged over a second switch along a vertical direction. Each switch has switch housing. Each switch housing is made up of thermo plastic material to house guide terminals, a moving contact bridge and a switching mechanism. A bottom switch cover and a top switch cover are provided to cover the internal pars of the switch to prevent the exposure of the switch components to outside. Each switch cover is made up of thermo plastic material. Each switch has 8 terminals which form the fixed contact of the switch. The moving contacts of the switch are arranged in the moving contact bridge. A terminal shroud is provided at both sides of the top cover to cover a box clamp assembly.

[0053] Each switch has a slotted gear connected to rack gear engaged to a gear mechanism in the driver assembly. Each slotted gear has an arm provided with a slot to receive a bridge pin which is coupled to a moving contact bridge. Each slotted gear is provided with a pair of torsion springs to couple the slotted gear to the housing.
[0054] An operating handle is provided on the top side of the switch to actuate a drive mechanism to move a switch to ON position from OFF position and vice versa. The operating handle is mounted on the top a driver mechanism. The driver is a metallic component provided with a pair of gear mechanisms. The rotating operation of the handle is converted into a translational movement of the rack gear which drives the slotted gear rotatably. As a result the bridge pin in the slotted gear is moved translationally to move the moving contact bridge. The bridge pin moves in a translational manner in the slot of the slotted gear and the bridge hosing simultaneously.
[0055] A pair of torsion springs are connected to the slotted gear and to the switch housing. The torsion spring is a helical spring having two arms. While one arm of the spring is immovably fixed to the switch housing while the other arm is connected to the extended arm of the slotted gear. As the angle between the two arms of the helical spring deviate, from its natural rest position/ free condition, it exerts a force which is proportional to the angle of deviation. The springs are charged during the movement of the switch to the rest positions (OFF/ON) from a dead center position and the stored in the energy is released during the movement of the switches from the dead center to the active position (ON/OFF), when the switches are moved from the OFF position to ON position. The torsion springs has maximum potential energy at the

dead center position. The torsion spring is said to be in a pre-compressed state, when the maximum allowable angle of the spring is less than the free angle of that spring. The torsion spring remains in the ON or OFF positions due to the pre compression state of the springs.
[0056] When the output speed (i.e. speed or velocity of pin in this case) depends on (proportionate with) the speed at which the operator rotates the operating handle, the operation is known as manual dependent. When the output speed (i.e. speed or velocity of pin in this case) is not depends on (not proportionate with) the speed at which the operator rotates the operating handle, the operation is known as manual independent
[0057] The first switch may be coupled to one power supply such as a main power supply and the second switch may be coupled to another power supply such as an auxiliary power supply or redundant power supply.
[0058] FIG. 1 illustrates a top perspective view of the changeover switch according to one embodiment of the present invention. The changeover switch comprises of two switches with one connected to the main power supply and the other connected to the auxiliary power supply such as generators or inverters. With reference to FIG.. I, the top switch, herein referred to as switch I, is an assembly of various components which includes contact terminals and a bridge. Further the switch is housed in switch housing and covered at the top. The bottom switch, herein referred to as switch II I, is an assembly of various components which includes contact terminals and a bridge and housed in switch housing and covered at the bottom. An operating handle 16 is

used to actuate the switching mechanism of the switches in the change-over switch. Handle 16, which may be a plastic component, acts as an effort arm to actuate a switching mechanism to be turned ON or OFF.
[0059] FIG.. 2 illustrates an exploded view of the changeover switch according to one embodiment of the present invention. The change-over switch comprises of switch II, I is housed in switch II housing 3. Switch II housing 3 may be a thermoset plastic component coupled to switch II I which houses various components including guide terminals, bridge coupled to switch II 2 and the interlocked switching mechanism of switch I. 2. Further the bottom part of switch II, 1 is covered to prevent exposure of the internal parts of the switch using cover 5 which may be made of thermoset plastic, switch I, 2 is housed in switch I housing 4 which may made of thermoset plastic to house the guide terminals 7, bridge coupled to switch I 2, and the interlocked switching mechanism of switch II, 1. The top of switch I, 2 is covered with switch I cover 6 which may be made of thermoset plastic to prevent the exposure of internal parts of the switch.
[0060] The switches comprise of plurality of stationary contact terminals 7 made of conductive metals. A plurality of moving contacts which is equal to the number of the stationary contact terminals is provided. The moving contacts are supported by bridge 9. Bridge 9 may be an assembly of plastic component which reciprocates to the force exerted by the corresponding bridge pins in the switching mechanism. The moving contacts may be made of copper and can be coupled or decoupled to the stationary contacts to turn the switch to ON or OFF condition. The box clamp assembly is

covered by using terminal shroud housing 8 which may be made of plastic. The handle 16, which may be a plastic component, acts as an effort arm to actuate a switching mechanism to be turned ON or OFF. The actuator, herein referred to as driver 11, may be a metal part which is coupled to a operating handle 16 at the tip. Driver 11 may be guided to rotate in switch II housing 3 and switch I housing 4.
[0061] FIG. 3A illustrates the interlocking assembly of two switching components. The figure illustrates components of switching mechanism of switch I 2, which includes slotted gear 13b which is a cast component having gear teeth which can engage and disengage with a central gear. Slotted gear 13b has an extended arm with a slot. A metallic pin, bridge pin 14b translates in the slot provided in slotted gear 13b and the housing simultaneously. Bridge pin 14b translates motion from slotted gear 14b to bridge 9 of switch II 1. Bridge pin 14b exerts force on the bridge assembly of Switch II 1 which supports moving terminals to close or open the contact with the stationary terminals of the switch. Torsion springs 15c and 15d with two arms exert force on slotted gear 13b. One arm of spring 15c is coupled to an edge of the extended arm of slotted gear 13b and the other arm is immovably fixed. One arm of spring 15d is coupled edge of the extended arm of slotted gear 13b and the other arm is immovably fixed. Driver 11 rotates to actuate a linear motion of coupled rack 12a. Driver 11 can be operated by an external handle 16 to turn ON or OFF switch I, 2. Rack 12a transmits motion from the driver 11 to slotted gear 13b according to one embodiment of the invention.

[0062] FIG.. 3B illustrates the interlocking assembly of two switching components according to various embodiments of the present invention. The figure illustrates components of the switching mechanism of Switch II I, which includes a slotted gear 13a which is a cast component having gear teeth which can engage and disengage with a central gear. Slotted gear 13a has an extended arm with a slot. A metallic pin, bridge pin 14a translates in the slot provided in the slotted gear 13a and the housing simultaneously. Bridge pin 14a translates motion from slotted gear 14a to bridge 9 of Switch II 1. The bridge pin 14a exerts force on the bridge assembly of switch II 1 which supports moving terminals to close or open the contact with the stationary terminals of the switch. Torsion springs 15a and 15b with two arms exert force on slotted gear 13a. One arm of spring 15a is coupled to an edge of the extended arm of slotted gear 13a and the other arm is immovably fixed. One arm of spring 15b is coupled edge of the extended arm of slotted gear 13a and the other arm is immovably fixed. Driver 11 rotates to actuate a linear motion of the coupled rack 12b. Driver 11 can be operated by an external handle 16 to turn ON or OFF Switch II 1. Rack 12b transmits motion from driver 11 to slotted gear 13a according to one embodiment of the invention.
[0063] FIG.. 4A illustrates the top view of the interlocking assembly when both the switches are in OFF condition according to one embodiment of the present invention. Switch I, 2 is in OFF condition where extended arm of slotted gear 13b is inclined towards the centre and the bridge pin is in the extreme left position in the slot. In the figure, switch II, 1 is in OFF condition with extended arm of slotted gear 13a is

inclined towards the centre and the bridge pin is in the extreme right position in the slot.
[0064] FIG. 4B illustrates a bottom perspective view of the gear rails on the driver and the position of the racks when both the switches are in OFF condition. The gear teeth of rack 12a which transmits linear motion to switching mechanism of switch 1, 2 is not engaged with gear rail 17a of driver 11. Slotted gear 13b coupled to rack 12a is in OFF state as shown in FIG. 4A.
[0065] Further, in FIG. 4B, the gear teeth of rack 12b which transmits linear motion to switching mechanism of switch II, I is not engaged with gear rail 17b of driver 11. Slotted gear 13a coupled to rack 12b is in OFF state as shown in FIG. 4A.
[0066] The switch I, 2 is turned ON from the OFF condition by rotating the external handle 16 in clockwise direction. External handle 16 is coupled to driver 11 which rotates in switch I housing 4. The rotation of driver 11 actuates the motion of rack 12a linearly. The linear motion of rack 12b is transmitted to the slotted gear 13b which rotates in anticlockwise direction. The head of slot which is along the length of the arm of slotted gear 13b moves to the right along with bridge pin 14b. Springs 15c and 15d get charged and increase in potential energy stored in the springs with reduction in distance between the arms of the springs.
[0067] FIG. 5A illustrates the top view of the interlocking assembly with switch I in intermediate state between OFF condition and dead centre while being turned ON according to one embodiment of the invention. Rack 12a actuated by driver 11 moves

to the right and transmits the motion to slotted gear 13b which rotates in anticlockwise direction. Bridge pin 14b moves to right in the slot of slotted gear 13b. The distance between spring arms of 15c and 15d decreases charging the springs.
[0068] FIG. 5B illustrates the bottom perspective view of the driver with switch I in intermediate state between OFF condition and dead centre position while being turned ON according to one embodiment of the invention. The gear teeth of rack 12a which transmits linear motion to switching mechanism of Switch I, 2 is partly engaged to the gear rail 17a of the driver 11. The position of slotted gear 13b coupled to rack 12a is in between OFF state and dead centre state as shown in FIG. 5A.
[0069] Further, in FIG. 5B, the gear teeth of rack 12b which transmits linear motion to switching mechanism of switch II, 1 is not engaged to gear rail 17b of driver 11. Slotted gear 13a coupled to rack 12b is in OFF state as shown in FIG. 5A.
[0070] FIG. 6A illustrates the top view of the interlocking assembly with switch I in dead centre position while being turned ON according to one embodiment of the invention. Switch I 2 is in dead centre position with springs 15c and 15d charged to the maximum. The angle between the arms of springs 15c and 15d reduces from OFF state to dead centre position by the anti-clock rotation of slotted gear 13b and the movement of the bridge pin 14b to the right. The velocity of bridge pin 14b which moves from the OFF state to the dead centre position is dependent on the manual speed of rotating handle 16. The angle between the arms of the torsion springs is reduced to a minimum and the potential energy stored in the springs is the maximum in the dead centre position of the springs.

[0071] FIG. 6B illustrates the bottom perspective view of the driver with switch I in dead centre position while being turned ON according to one embodiment of the invention. The gear teeth of rack 12a which transmits linear motion to switching mechanism of switch I, 2 is partly engaged to gear rail 17a of driver 11. Slotted gear 13b coupled to rack 12a is the dead centre position as shown in FIG. 6A.
[0072] Further, in FIG. 6B, the gear teeth of rack I2b which transmits linear motion to switching mechanism of switch II, 1 is not engaged to gear rail 17b of driver 11. Slotted gear 13a coupled to rack 12b is in OFF state as shown in FIG. 6A.
[0073] FIG. 7A illustrates the top view of the interlocking assembly with switch I in intermediate state between dead centre and ON condition while being turned ON according to one embodiment of the invention. Slotted gear 13b moves in the anti-clock wise direction due to the movement of springs 15c and I5d from the dead centre position to the free condition by releasing the stored potential energy. The angle between the arms of the springs 15c and 15d increases which moves the slotted gear 13b in the anti-clock wise direction. Bridge pin 14b moves to the right in the slot of extended arm of slotted gear 13b. The velocity of the bridge pin 14b is dependent on the releasing force of springs 15c and 15d and independent of manual speed of rotating handle 16. The bridge moves with bridge pin 14b after crossing the dead centre position.
[0074] FIG. 7B illustrates the bottom perspective view of the driver with switch I in an intermediate position between the dead centre position and OFF position while being turned ON according to one embodiment of the invention. The gear teeth of

rack 12a which transmits linear motion to switching mechanism of Switch I. 2 is partly engaged to the gear rail 17a of the driver 11. The slotted gear 13b is forced to move by the releasing force of torsion springs 15c and 15d. Slotted gear 13b coupled to rack 12a is in an intermediate position between the dead centre position and ON position as shown in FIG. 7A.
[0075] Further, in FIG. 7B, the gear teeth of rack 12b which transmits linear motion to switching mechanism of switch II, 1 is not engaged to gear rail 17b of driver 11. Slotted gear 13a coupled to rack 12b is in OFF state as shown in FIG. 7A.
[0076] The motion of the bridge is independent of the manual rotation of the handle 16. The movement of the bridge coupled the moving contacts is initiated and sustained by the bridge pin 14b when the pin is moved by the releasing force of charged torsion springs 15c and 15d from the dead centre position to ON position.
[0077] FIG. 8A illustrates the top view of the interlocking assembly with switch I in ON condition and switch II in OFF condition according to one embodiment of the invention. The release of torsion springs 15c and I5d further forces slotted gear 13b to rotate in the anti-clock wise direction and bridge pin 14b to move to the right-most position. In the right-most position of the bridge pin 14b the coupled bridge moves to close the contact between the moving contact terminals and stationary contacts to switch ON switch I 2.
[0078] FIG. 8B illustrates the bottom perspective view of the driver with switch I in OFF position according to one embodiment of the invention. The gear teeth of rack

12a which transmits linear motion to switching mechanism of switch I, 2 is engaged to the gear rail 17a of the driver 11. Slotted gear 13b coupled to rack 12a is in ON position as shown in FIG. 8A.
[0079] Further, in FIG. 8B, the gear teeth of rack 12b which transmits linear motion to switching mechanism of Switch II, I is not engaged with gear rail 17b of driver 11. Slotted gear 13a coupled to rack 12b is in OFF state as shown in FIG. 8A.
[0080] The switch I, 2 can be turned OFF from ON state by rotating handle 16 in anticlockwise direction. Driver 11 translates the rotational motion to rack 12a which moves linearly towards driver 11 or in the direction opposite to the direction of the rack when the switch is turned ON. The slotted gear 13b moves in the clockwise direction. The motion of bridge pin 14b towards left is lost in the slot provided in slotted gear 13b. The velocity of motion of the bridge pin 14b is dependent on the speed of rotation of handle 16. The angle between arms springs 15c and 15d is reduced to the minimum when slotted gear 13b moves to the dead centre position. The potential energy stored in each of the springs is maximum in the dead centre position. Springs 15c and 15d release the stored energy after crossing the dead centre position further moving slotted gear 13b in clock wise direction. Bridge pin 14b moves to left in the slot of the arm of slotted gear 13b. The velocity of bridge pin 14b is dependent on the releasing force of springs 15c and 15d and independent of manual speed of rotating handle 16. The bridge moves with bridge pin 14b after crossing the dead centre position.

[0081] The motion of the bridge is independent of the manual rotation of the handle 16. The movement of the bridge coupled the moving contacts is initiated by bridge pin 14b when the pin is moved by the releasing force of the charged torsion springs 15c and 15d from the dead centre position to the OFF position.
[0082] The switch II, 1 is turned ON from the OFF condition by rotating external handle 16 in clockwise direction. External handle 16 is coupled to driver 11 which rotates in switch I housing 4. The rotation of driver 11 actuates the motion of rack 12b linearly. The linear motion of rack 12b is transmitted to slotted gear 13a which rotates in the anticlockwise direction. The head of the slot which is along the length of the arm of slotted gear 13a moves to the right along with bridge pin 14a. Springs 15a and 15b gets charged which increases with the reduction in the distance between the arms of the springs.
[0083] FIG. 9 A illustrates the top view of the interlocking assembly with switch II in intermediate state between OFF condition and dead centre while being turned ON according to one embodiment of the invention. According to the embodiment, switching mechanisms of switch I, 2 and switch II, I are in OFF condition as illustrated by FIG. 4. External handle 16 is rotated in the anti-clock wise direction which is transmitted to the coupled driver 11. Rack 12b actuated by driver 11 moves right and transmits the motion to slotted gear 13a which rotates in the clock wise direction. Bridge pin 14a moves to the left in the slot of slotted gear 13a. The distance between spring arms of 15a and 15b decreases charging the springs.

[0084] FIG. 9B illustrates the bottom perspective view of the driver with switch II in intermediate state between OFF condition and dead centre position while being turned ON according to one embodiment of the invention. The gear teeth of rack 12b which transmits linear motion to switching mechanism of switch II, I is partly engaged to gear rail 17b of driver 11. The position of slotted gear 13a coupled to rack 12b is in between OFF state and dead centre state as shown in FIG. 9A.
[0085] Further, in FIG. 9B, the gear teeth of rack 12a which transmits linear motion to switching mechanism of switch I, 2 is not engaged to gear rail 17a of driver 11. Slotted gear 13b coupled to rack 12a is in OFF state as shown in FIG. 9A.
[0086] FIG. 10A illustrates the top view of the interlocking assembly with switch II in dead centre position while being turned ON according to one embodiment of the invention.Switch 11, 1 is in dead centre position with springs 15a and 15b charged to the maximum. The angle between the arms of the springs reduces from the OFF state to dead centre position by the clock wise rotation of slotted gear 13a and the movement of bridge pin 14a to the left. The velocity of bridge pin 14a which moves from the OFF state to the dead centre position is dependent on the manual speed of rotating handle 16. The angle between the arms of the torsion springs is reduced to a minimum and the potential energy stored in the springs is the maximum in the dead centre position of the springs.
[0087] FIG. I0B illustrates the bottom perspective view of the driver with Switch I in dead centre position while being turned ON according to one embodiment of the invention. The gear teeth of rack 12b which transmits linear motion to switching

mechanism of switch II, 1 is partly engaged to gear rail 17b of driver 11. Slotted gear 13a coupled to rack 12b is in the dead centre position as shown in FIG. 10A.
[0088] Further, in FIG. 10B, the gear teeth of rack 12a which transmits linear motion to switching mechanism of switch I, 2 is not engaged with the gear rail 17a of driver 11. Slotted gear 13b coupled to rack 12a is in OFF state as shown in FIG. 10A.
[0089] FIG. 11A illustrates the top view of the interlocking assembly with switch II in intermediate state between dead centre and ON condition while being turned ON according to one embodiment of the invention. Slotted gear 13a moves in the clock wise direction due to the movement of springs 15a and 15b from the dead centre position to the free condition by releasing the stored potential energy. The angle between the amis of springs 15a and 15b increases which moves slotted gear 13a in the clock wise direction. Bridge pin 14a moves to the left in the slot of extended arm of slotted gear 13a. The velocity of bridge pin 14a is dependent on the releasing force of the springs 15a and 15b and independent of manual speed of rotating handle 16. The bridge moves with bridge pin 14a after crossing the dead centre position.
[0090] FIG. 1 IB illustrates the bottom perspective view of the driver with switch I in an intermediate position between the dead centre position and OFF position while being turned ON according to one embodiment of the invention. The gear teeth of rack 12b which transmits linear motion to switching mechanism of switch II, 1 is partly engaged to gear rail 17b of the driver 11. Slotted gear I3a is forced to move by the releasing force of torsion springs 15a and 15b. Slotted gear 13a coupled to rack

12b is in an intermediate position between the dead centre position and ON position as shown in FIG. 11A.
[0091] Further, in FIG. 1 IB, the gear teeth of rack 12a which transmits linear motion to switching mechanism of switch I, 2 is not engaged with gear rail 17a of driver 11. Slotted gear 13b coupled to rack 12a is in OFF state as shown in FIG. 11A.
[0092] The motion of the bridge is independent of the manual rotation of handle 16. The movement of the bridge coupled the moving contacts is initiated by bridge pin 14a when the pin is moved by the releasing force of charged torsion springs 15a and 15b from the dead centre position to the ON position.
[0093] FIG. 12 illustrates the top view of the interlocking assembly with Switch II in ON condition and Switch I in OFF condition according to one embodiment of the invention. The release of torsion springs 15a and 15b further forces slotted gear 13a to rotate in the clock wise direction and bridge pin 14a to move to the left-most position. In the left-most position of bridge pin 14a, the coupled bridge moves to close the contact between the moving contact terminals and stationary contacts to switch ON Switch II 1.
[0094] FIG. 12B illustrates the bottom perspective view of the driver with Switch I in OFF position according to one embodiment of the invention. The gear teeth of rack I2a which transmits linear motion to switching mechanism of switch II, 1 is engaged to gear rail 17b of driver 11. Slotted gear 13a coupled to rack 12b is ON position as shown in FIG. 12A.

[0095] Further, in FIG. 12B, the gear teeth of rack 12a which transmits linear motion to switching mechanism of Sswitch II, I is not engaged with gear rail 17a of driver 11. Slotted gear 13b coupled to rack 12a is in OFF state as shown in FIG. 12A.
[0096] The switch II, I can be turned OFF from ON state by rotating handle 16 in clock wise direction. Driver 11 translated the rotational motion to the rack 12b which moves linearly towards driver 11 or in the direction opposite to the direction of rack 12b when the switch is turned ON. Slotted gear 13a moves in the anti-clock wise direction. The motion of bridge pin 14a towards left is lost in the slot provided in slotted gear 13a. The velocity of motion of bridge pin 14a is dependent on the speed of rotation of handle 16. The angle between arms springs 15a and 15b is reduced to the minimum when slotted gear 13a moves to the dead centre position. The potential energy stored in each of the springs is maximum in the dead centre position. Springs 15a and 15b release the stored energy after crossing the dead centre position further moving slotted gear 13a in anti-clock wise direction. Bridge pin 14a moves to left in the slot of the arm of slotted gear 13a. The velocity of bridge pin 14a is dependent on the releasing force of springs 15a and 15b and independent of manual speed of rotating handle 16. The bridge moves with bridge pin 14a after crossing the dead centre position.
[0097] The motion of the bridge is independent of the manual rotation of handle 16. The movement of the bridge coupled the moving contacts is initiated by bridge pin 14a when the pin is moved by the releasing force of charged torsion springs 15a and 15b from the dead centre position to the OFF position.

G) ADVANTAGES OF THE INVENTION
[0098] Thus the various embodiments of the present invention provide a single system for interlocking two switching mechanisms in a change-over switch. According to an embodiment, the switching mechanisms of both switches are interlocked to turn ON a single switch and turn OFF the interlocked switch simultaneously. According to an embodiment, the interlock assembly provides complete electrical isolation between the switches. According to another embodiment the movement of the bridges of both switches are manually independent. According to another embodiment both switches are interlocked by gear meshing and de-meshing to increase efficiency and contact ratio with gear teeth of the racks. According to another embodiment, torsion springs are used to move the switching member to increase reliability of the interlock assembly. Further, two torsion springs are used to move the switching member to reduce stress and increase net spring force. According to another embodiment the depth of change-over switch is reduced by linearly actuating the laterally displaced interlocked switching mechanisms. [0099] Although the invention is described with various specific embodiments, it will be obvious for a person skilled in the art to practice the invention with modifications. However, all such modifications are deemed to be within the scope of the claims.
[0100] It is also to be understood that the following claims are intended to cover all of the generic and specific features of the present invention described herein and all the statements of the scope of the invention which as a matter of language might be said to fall there between.

CLAIMS
What is claimed is:
1. An interlock system for change over switch including two switches connected to two power supplies, the system comprising:
An operating handle;
A driver connected to the operating handle;
A first rack connected to the driver;
A first switch connected to the driver through the first rack;
A first slotted gear provided in the first switch to engage with the first
rack;
A first bridge pin coupled to the first slotted gear;
A first moving contact bridge provided in the first switch and connected to
the first bridge pin;
A second rack connected to the driver;
A second switch connected to the driver through the second rack;
A second slotted gear provided in the second switch to engage with the
second rack;
A second bridge pin coupled to the second slotted gear;
A second moving contact bridge provided in the second switch and
connected to the second rack;

Wherein the operating handle is rotated in clock wise direction to operate the driver to rotate the first slotted gear in anticlock wise direction through the first driver thereby moving the first bridge pin to move the first bridge to turn the first switch to ON position, when the first switch is turned to ON position and the second switch to OFF position.
2. The system according to claim 1, wherein the operating handle is rotated in anti clock wise direction to operate the driver to rotate the second slotted gear in clock wise direction through the second driver thereby moving the second bridge pin to move the second bridge to turn the second switch to ON position, when the second switch is turned to ON position and the first switch to OFF position.
3. The system according to claim 1, wherein the driver is provided with a first gear mechanism and a second gear mechanism.
4. The system according to claim 1, wherein the first rack is engaged to the driver through the first gear mechanism.
5. The system according to claim 1, wherein the second rack is engaged to the driver through the second gear mechanism.
6. The system according to claim 1, the second rack is arranged vertically below the first rack.

7. The system according to claim I, the first slotted gear and the second slotted gear are arranged in a horizontal direction.
8. The system according to claim 1, wherein the first slotted gear has an arm provided with a first slot.
9. The system according to claim 1, wherein the first bridge pin is arranged in the first slot of the first slotted gear so that the rotary motion of the first slotted gear is transformed into the translational motion of the first bridge pin to move the first moving contact bridge.
10. The system according to claim 1, wherein the second slotted gear has an arm provided with a second slot.
11. The system according to claim 1, wherein the second bridge pin is arranged in the second slot of the second slotted gear so that the rotary motion of the second slotted gear is transformed into the translational motion of the second bridge pin to move the second moving contact bridge.
12. The system according to claim 1, further comprising a first pair of torsion springs connected to the first slotted gear and to a first switch housing.

13. The system according to claim 1, further comprising a second pair of
torsion springs connected to the second slotted gear and to a second switch
housing.
14. The system according to claim 1, wherein the first and second pair of torsion springs are charged continuously during the movement of the respective first and second switches from the ON/OFF position to the dead center position and releases the stored energy during the movement from the dead center position to OFF/ON positions.
15. The system according to claim 1, wherein both the first and the second pairs of torsion springs include two helical springs.
16. The system according to claim 1, wherein the helical springs in both the first and the second pair of torsion springs have maximum potential energy at the dead center position.
17. The system according to claim I, wherein the helical springs are said to be pre compressed in OFF or ON position of the first and second switches.
18. The system according to claim 1, wherein the speed of the helical springs are manually dependent during the movement of the switch from the ON/OFF position to the dead center position.

19. The system according to claim 1, wherein the speed of the helical springs are manually independent during the movement of the switch from the dead center position to ON/OFF position.
20. The system according to claim I, wherein both the first and the second moving contact bridge support plurality of moving contact terminals and reciprocatably moved due to the force exerted by the respective bride pins.

Patent Agent, ALMT Legal,
No.2, Lavelle Road, BangaIore-560 001, INDIA
To,
The Controller of Patents,
The Patent office,
Mumbai