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: SAFETY SHUTTER ASSEMBLY FOR DRAW OUT TYPE AIR
CIRCUIT BREAKER


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 present invention generally relates to circuit breakers and particularly to safety shutter device with padlock for draw out type circuit breakers.
B) BACKGROUND OF THE INVENTION
[0002] The circuit breakers protect electrical circuit from overload and short circuit damages. Air circuit breakers use air as a medium to extinguish arcs in circuit breaker used in industrial applications. Air circuit breakers are used for main power distribution in large industrial plants. The cradle assemblies connected to main power are used to enclose heavy and large circuit breakers. Mechanical racking mechanisms are provided in the cradle assembly which can be operated manually or by using motors. The circuit breakers are provided with complimentary draw-out construction for easy installation and separation from the cradle assembly without disturbing main power connections.
[0003] The circuit breakers can be tested and serviced by mechanically moving it away from the cradle terminals coupled to the main power circuit. The complete isolation of the main power has to be achieved to ensure safety of the personnel during maintenance. Extreme caution has to be adopted to ensure complete isolation during maintenance for preventing any inadvertent lapse in safety mechanism.
[0004] The currently available safety shutters has complex operating lever arrangements to engage and disengage circuit breakers. The actuating mechanism to
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open or close the safety shutter is mounted on another component in the cradle. Some shutter actuators are installed in the cradle interior. The installation of multiple shutters is complex and time consuming and requires precise alignment of openings to actuate the shutters. The external shutter locks are placed over the shutter actuators and secured with padlocks to prevent an inadvertent contact of the breaker terminals and main power source during maintenance. The cost of assembling and maintaining a complex operating lever and actuating mechanism is substantially high. Hence there is a need to provide a simple shutter operating and actuating mechanism at reduced cost.
[0005] The currently available safety mechanisms adopt complex mechanical arrangements to provide the required safety to the maintenance personnel. Thus there is a further need to provide a shutter assembly with a simple mechanism to open and close the safety shutters during the insertion and withdrawal of the circuit breakers.
[0006] The abovementioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.
C) OBJECT OF THE INVENTION
[0007] The primary object of the present invention is to provide a safety shutter assembly with a simple structure for a draw-out type air circuit breaker to open and close the safety shutters during the insertion and withdrawal of the circuit breakers.
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[0008] Another object of the present invention is to provide a safety shutter assembly with self actuating shutter doors for draw out type air circuit breakers.
[0009] Yet another object of the present invention is to provide a safety shutter assembly for individual pole phases in a circuit breaker.
[0010] 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
[0011] The various embodiments of the present invention provide a safety shutter assembly with a padlock for draw out type circuit breakers. According to one embodiment of the present invention, a shutter assembly has a base support mounted on two cross pieces which are connected in parallel between the two side plates of a cradle assembly in a circuit breaker. The base support has a protrusion at the top and a hole at the bottom. The protrusion is engaged with the top cross piece and a screw is passed through the bottom hole to fix the base support with the bottom cross piece.
[0012] The shutter assembly has an actuating mechanism comprising two movable shutter doors mounted on the base support so that the shutter doors are moved orthogonally to permit the entry of a breaker terminal in the circuit breaker, when the circuit breaker is inserted into the cradle. Several grooves are provided on the base support to receive the movable shutter doors. A padlock is provided between the shutter doors to restrict the orthogonal movement of the shutter doors. The padlock is
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provided with an interlocking mechanism which is locked with a locking doorway provided at one side edge of the shutter assembly. The padlock is provided to ensure the safety of the personnel at work.
[0013] A spring is provided on the base support and connected to movable shutter doors so that one end of the spring is connected to the movable door while the other end is fixed rigidly inside the grooves provided at the side edges of the base support. The live current carrying part of the main circuit is isolated through the safety shutter assembly to prevent the occurrence of shock or mishap to the operating personnel, when the circuit breaker is disengaged from the cradle assembly. The shutter doors are kept opened, when the breaker is engaged into the cradle assembly.
[0014] The safety shutter assembly is installed on the draw out type circuit breaker in a simple operation. The safety shutter assembly has a modular design. The modular safety shutter assembly is fixed on individual pole/phase. The total number of shutter assembly used will vary across the range. When a basic breaker is inserted into the cradle, the breaker terminal pushes the movable shutter doors orthogonally to provide an opening to permit the entry of the breaker terminal. The surface of the breaker terminal is made to contact the inner surfaces of the shutter doors. As the breaker terminal is further moved inside, the shutter doors are moved inside the grooves and the springs are compressed. In the final position, the movable shutter door rests on the surfaces of the breaker terminal. Thus the breaker terminal is passed through the opening between the shutter doors to contact the cradle terminal to complete an electrical circuit.
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[0015] When the breaker is disengaged from the cradle assembly, the breaker terminal is moved out of the shutter assembly. The spring pushes the movable doors forward to close the doors thereby ensuring the safety of the operating personnel.
[0016] Thus the various embodiments of the present inversion provide a safety shutter assembly for isolating main power supply in a draw out type circuit breaker. A shutter assembly is provided for each of the pole in breaker assembly with self-actuating shutter doors. The shutter doors may be actuated to open or close by the movement of the breaker terminals. The shutter doors are closed to ensure the safety of the operating personnel., when the breaker terminals are removed. The padlock with interlocking mechanism is provided to prevent the orthogonal movement of the doors thereby preventing the inadvertent movement of shutter floors during, maintenance to ensure further safety of the operating personnel.
E) BRIEF DESCRIPTION OF THE DRAWINGS
[0017] 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;
[0018] FIG. 1 illustrates a top perspective view of a cradle assembly mounted with a safety shutter assembly according to one embodiment of the present invention.
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[0019] FIG. 2 illustrates side perspective view cradle assembly mounted with a circuit breaker and a safety shutter assembly according to one embodiment of the present invention.
[0020] FIG. 3 illustrates a front perspective view of a safety shutter assembly according to one embodiment of the present invention.
[0021] FIG. 4 illustrates a top side view of breaker terminal and safety shutter doors in a safety shutter assembly according to one embodiment of the present invention, when the breaker terminals are at initial position.
[0022] FIG. 5 illustrates a top side view of breaker terminal and safety shutter doors in a safety shutter assembly according to one embodiment of the present invention, when the breaker terminals are completely inserted.
[0023] 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
[0024] 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
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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.
[0025] The various embodiments of the present invention provide a safety shutter assembly with padlock for draw out type circuit breakers. According to one embodiment of the present invention, a shutter assembly is provided between a breaker terminal and a cradle terminal coupled to main power source. A shutter assembly is provided for each pole in a breaker pole assembly. The shutter assembly has self-actuating shutter doors to isolate main power supply, when the breaker assembly is disengaged from the cradle assembly.
[0026] A draw out type circuit breaker has a breaker unit mounted on a cradle assembly. The breaker unit has current carrying pole assembly for interrupting the main circuit. A rack-in mechanism is provided on the cradle assembly to engage or disengage the breaker unit from the cradle assembly during maintenance or inspection operation. When the circuit breaker is disengaged from cradle assembly, live current carrying part of the main circuit must be isolated via the safety shutter to prevent a mishap to the operating personnel during maintenance. The safety shutter must be kept open, when the breaker is engaged into the cradle assembly.
[0027] The cradle assembly has a cradle support mounted between two cross pieces that are connected to the side plates in parallel. The cradle terminal with jaw units is mounted on the side plates. The circuit breaker has a pole assembly to interrupt the
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main circuit. A breaker terminal is connected to the poles. When the breaker is engaged to the cradle assembly, the jaw units are inserted into breaker terminal to complete the main circuit.
[0028] A safety shutter assembly is fixed on the two parallel cross pieces. The safety shutter assembly is installed on the draw out type circuit breaker using a simple operation. The safety shutter assembly is arranged in modular design and is fixed on individual pole/phase so that the total number of shutter assembly installed on a breaker will vary according to its range.
[0029] The shutter assembly has a base support mounted on two cross pieces which are connected in parallel between the two side plates of a cradle assembly in a circuit breaker. The base support has a protrusion at the top and a hole at the bottom. The protrusion is engaged with the top cross piece and a screw is passed through the bottom hole to fix the base support with the bottom cross piece.
[0030] The shutter assembly has an actuating mechanism comprising two movable shutter doors mounted on the base support so that the shutter doors are moved orthogonally to permit the entry of a breaker terminal in the circuit breaker, when the circuit breaker is inserted into the cradle. Several grooves are provided on the base support to receive the movable shutter doors. A padlock is provided between the shutter doors to restrict the orthogonal movement of the shutter doors. The padlock is provided with an interlocking mechanism which is locked using a locking doorway provided at one side edge of the shutter assembly. The padlock is provided to ensure the safety person in work.
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[0031] A spring is provided on the base support and connected to movable shutter doors so that one end of the spring is connected to the movable door while the other end is fixed rigidly inside the grooves provided at the side edges of the base support. The live current carrying part of the main circuit is isolated through the safety shutter assembly to prevent the occurrence of shock or mishap to the operating personnel, when the circuit breaker is disengaged from the cradle assembly. The shutter doors are kept opened, when the breaker is engaged into the cradle assembly.
[0032] When a basic breaker is inserted into the cradle, the breaker terminal pushes the movable shutter doors orthogonally to provide an opening to permit the entry of the breaker terminal. The surface of the breaker terminal is made to contact the inner surfaces of the shutter doors. As the breaker terminal is further moved inside, the shutter doors are moved inside the grooves and the springs are compressed. In the final position, the movable shutter door rests on the surfaces of the breaker terminal. Thus the breaker terminal is passed through the opening between the shutter doors to contact the cradle terminal to complete an electrical circuit.
[0033] When the breaker is disengaged from the cradle assembly, the breaker terminal is moved out of the shutter assembly. The spring pushes the movable doors forward to close the doors thereby ensuring the safety of the operating personnel.
[0034] FIG. 1 illustrates a top perspective view of a cradle assembly mounted with a safety shutter assembly according to one embodiment of the present invention. With respect to FIG. 1, cradle assembly 1 has base plate 2 to support circuit breaker and side plates 3 provided with grooves. A set of parallel guide rails 7 slide inside the
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grooves in side plates 3. The guide rails are used to move breakers inside the cradle assembly. A racking in mechanism 6 is provided on base plate 2 to move the guide rails 7 inside the cradle. The side plates 3 are supported by top cross piece 4 and bottom cross piece 5. Both the bottom cross piece 5 and the top cross piece 4 are arranged in parallel. A cradle support is mounted on the cross pieces 4, 5. Safety shutter assembly 9 is mounted between top and bottom cross pieces 4 and 5 to provide safety to maintenance personnel during work.
[0035] FIG. 2 illustrates a side perspective view of a cradle assembly mounted with a circuit breaker and a safety shutter assembly according to one embodiment of the present invention. The cradle assembly has a pair of side plates 3 mounted on base plate 2. Breaker assembly 20 is mounted on guide rails 7 which slide inside the grooves provided in the side plates 3. Guide rails 7 are moved by a rack in mechanism 6 mounted on the base plate 2. Two cross pieces 4, 5 are connected between the side plates 3 in parallel. Cradle support 8 is provided between top cross piece 4 and bottom cross piece 5. The cradle terminals with jaw units are arranged on the cradle support 8. Breaker terminals 21 are connected to the pole assembly of basic breaker assembly 20. Breaker terminal 21 is inserted into jaw units of the cradle terminals to connect basic breaker assembly 20 to main circuit. Basic breaker assembly 20 may be racked out from the cradle terminal to disconnect live current carrying part for maintenance. Basic breaker assembly 20 may be rigidly held in the maintenance position by racking in mechanism 6. Safety shutter assembly 9 is provided to isolate live current terminal in main circuit, when breaker 20 is disengaged.


[0036] FIG. 3 is a perspective view of shutter assembly according to one embodiment of the present invention. The shutter assembly 9 is fixed on each pole. Shutter assembly 9 has supporting structure 10 provided with protrusion 14 at the top and hole 15 at the bottom. The protrusion 14 is inserted in a cut provided in top cross piece 4. A screw is inserted into the hole 15 to fix the supporting structure 10 with bottom cross piece 5. The shutter assembly 9 has a pair of safety shutter doors II, 12 mounted on the support structure 10. A set of parallel groves 18 are provided on the supporting structure 10 to receive the movable shutter doors 11 and 12. Shutter doors 11 and 12 are provided with self actuating mechanism to engage and disengage the breaker terminal from the cradle terminals. Pluralities of protruding grooves 17 are provided orthogonal to shutter doors 11 and 12. Plurality of springs 16 are provided so that one end of each spring 16 is coupled to groove 17 while the other end of spring is coupled to a shutter doorll, 12. Padlock 13 is provided between shutter doors 11, 12 to restrict inadvertent orthogonal movement of shutter doors 11, 12. Padlock 13 with interlock mechanism is provided to lock the shutter assembly with a locking doorway 19 during maintenance to ensure the safety of the operating personnel.
[0037] FIG. 4 illustrates a top view of breaker terminal 21 and safety shutter assembly according to one embodiment of the present invention. The shutter assembly 9 has a pair of safety shutter doors 11, 12 mounted on the support structure 10. A set of parallel grooves are provided on the supporting structure 10 to receive the movable shutter doors 11 and 12. Shutter doors II and 12 are provided with self actuating mechanism to engage and disengage breaker terminal from cradle terminals.
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Pluralities of protruding grooves are provided orthogonal to shutter doors 11 and 12. Pluralities of springs 16 are provided so that one end of each spring 16 is coupled to protruding groove rigidly while the other end of spring 16 is coupled to a shutter doorl I, 12. When the breaker terminal 21 is inserted between the shutter doors 11. 12, the shutter doors are moved orthogonally into the grooves. When the breaker terminal 21 is further inserted, the surface of breaker terminal 22 contacts surface 23 of movable shutter door 12.
[0038] FIG. 5 illustrates a top view of breaker terminal completely inserted in safety shutter assembly according to one embodiment of the present invention. Surface 23 of movable shutter doors mounted on a base support 10 in the shutter assembly are moved away from breaker terminal 21, when the breaker terminal 21 is completely inserted. Springs coupled to the shutter doors are compressed, when the breaker terminals 21 are completely inserted.
G) ADVANTAGES OF THE INVENTION
[0039] Thus the various embodiments of the present invention provide a safety shutter assembly for draw out type air circuit breakers. The shutter doors are provided on the safety shutter assembly to isolate the main power supply when a circuit breaker is moved to the maintenance position. The shutter doors are moved orthogonally to provide an opening for the passage of the breaker terminals, when the breaker terminals are inserted to contact the cradle terminals to complete the main circuit. The shutters doors are closed to cut off the main circuit to provide safety to the operating
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personnel, when the breaker terminals are removed. A padlock mechanism is provided to lock the shutter doors in closed position to ensure safety of operating personnel, when the circuit breaker is withdrawn for maintenance.
[0040] 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.
[0041] 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.
Date: 04th February, 2009. RAKESH PRABHU
Place: Bangalore. Patent Agent
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CLAIMS
What is claimed is:
1. A safety shutter assembly for circuit breaker mounted on a cradle assembly
including a top cross piece and a bottom cross piece, the assembly comprising:
base support mounted on the cross pieces;
pair of movable shutter doors mounted on the base support;
plurality of grooves arranged on the base support to receive the movable shutter
doors;
plurality of springs connected to the shutter doors and to the base support: and
padlock mounted on the base support;
wherein the movable shutter doors are moved orthogonally and slidably moved
into the grooves, when the breaker terminals of the circuit breaker are moved
between the shutter doors.
2. The assembly according to claim 1, wherein the shutter doors are moved
orthogonally to permit the passage of the breaker terminals to contact the cradle
terminals to complete the main circuit, when the breaker terminals are inserted
between the shutter doors.
3. The assembly according to claim 1, wherein the shutter doors are closed to prevent the entry of the breaker terminals to isolate the main circuit, when the breaker terminals are removed.
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4. The assembly according to claim 1, wherein the shutter doors are moved into the grooves, when the doors are moved orthogonally during the insertion of the breaker terminal.
5. The assembly according to claim I. wherein the padlock is provided to lock the shutter assembly and to prevent the orthogonal movement of the shutter doors during the maintenance work to provide safety to the maintenance personnel.
6. The assembly according to claim I, wherein the springs are compressed, when the doors are opened fully.
7. The assembly according to claim 1, wherein the compressed springs are released to close the shutter doors to ensure the safety of the maintenance personnel, when the breaker terminals are removed from the shutter doors.
8. The assembly according to claim 1, wherein the base support comprises protrusion at the top and a hole at the bottom so that the protrusion is inserted into a cut provided on the top cross provided on the cradle assembly.
9. The assembly according to claim I, wherein the base support is attached to the bottom cross piece provided in the cradle assembly by using a fastener.
RAKESH PRABHU
Patent Agent
Date: 04th February, 2009. Place: Bangalore.
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