FORM 2
The Patents Act 1970
(39 of 1970)
&
The Patent Rules 2003
PROVISIONAL SPECIFICATION
(See Section 10 and rule 13)


TITLE OF THE INVENTION: INTEGRATED RATING ERROR PREVENTING DEVICE AND MAINTENANCE LATCH FOR 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 switching devices like circuit breakers and particularly to a maintenance latch for circuit breakers. The present invention more particularly relates to an integrated rating error preventing device and maintenance latch for circuit breakers like draw out type circuit breakers.
B) BACKGROUND OF THE INVEION
[0002] A circuit breaker is an automatically-operated electrical switch designed to protect an electrical circuit from a damage caused by an electrical overload condition or short circuit condition. The circuit breakers are made in varying sizes, from small devices that protect an individual household appliance up to large switch gear units designed to protect high voltage circuits feeding an entire city.
[0003] The Electrical switches, more particularly circuit breakers or contactors, are sometimes of the draw-out type. The draw out type switches or circuit breakers has a fixed frame containing the contacts indicating the connected or disconnected position, and also a possible intermediate test position of the apparatus.
[0004] The Industrial-rated draw-out type circuit breakers include a pair of connectors (usually male) for each pole on one side of the breaker housing for electrically connecting the draw-out type circuit breaker to a compartment or housing. The housing includes load and line straps for each pole so that the draw out type circuit
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breaker is connected to a power distribution circuit. This configuration allows the circuit breaker to be quickly and easily removed or replaced. The circuit breaker includes movable and fixed contacts for opening and closing the distribution circuit. The contacts should be kept open for safety reasons, when the draw out type circuit breaker is inserted or removed.
[0005] The circuit breaker is attached to a chassis or cradle which is connected to the main power supply through cables, links or any other means in a draw-out type circuit breaker. Normally the circuit breaker is placed on a moving part called as a guiding rail inside a cradle. Ordinarily the draw-out type circuit breaker can be held in any of the following four positions with respect to the cradle. It may be held in a maintenance position so that the circuit breaker is removable from or loadable into the cradle. The circuit breaker may be held in an isolated position in which the circuit breaker is totally disconnected from power and control supply but is firmly engaged to cradle. The circuit breaker may also be held in a test position at which the circuit breaker is inside the cradle and connected to the control supply which is used to supply power to the accessories of the breaker. The circuit breaker may also be held to a service position in which the circuit breaker is connected to the power supply and is fully operational.
[0006] The loading and the un-loading of the circuit breaker housing into the cradle is usually done manually or by using some handling equipments such as small cranes or hoists. However these modes of loading and unloading the circuit breakers are extremely inconvenient due to the constraints of weight and space. Since the breaker
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is heavy element the loading of the circuit breakers is labour intensive and consumes enough time. The guiding rails are in fully drawn-out position for loading the circuit breaker. A latching arrangement is required to avoid the sliding of the rail due to accidental application of force. The circuit breaker can be locked to the cradle using plurality of padlocks.
Moreover a circuit breaker can be taken out of the cradle as and when required such as during the maintenance period. The part which is connected to main power supply has various ratings even though the structural parts remain the same. It is essential that cradle receives the breaker with a compatible rating.
[0007] The circuit Breaker for low voltage application generally finds an application at operating current ranges of 400A to 6300A. Since a very wide range of current ratings is covered in a single product, it is divided into number of different frames depending on the rating. For example, 400A-2000A is covered with a frame 1 while 2000A-3200A is covered by the frame 2. The current with a range of 3200A-4000A is covered by the frame 3 while a current with a range of 5000 A-6300A is covered by the frame 4. In a plant, there will be pluralities of draw-out type circuit breakers. Each breaker has a typical load connected to it. Based on the frame size and load requirement, breakers of different ratings have to be accommodated. Hence any mismatch of the breaker rating and the frame will result in nuisance tripping or no protection condition. So it is important to provide an interlocking between the breaker rating and the frame size. The breakers with required characteristics or ratings are to be put in the cradle with corresponding configuration to prevent the unwanted tripping condition.
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[0008] Various mismatch protection techniques are provided. The currently available breaker systems do not have a facility to prevent the inadvertent sudden movement of the guide rail during the loading of the heavy circuit breakers and prevent the mismatch between the frame and the rating of the circuit breaker. Also none of the circuit breakers have an integrated structure to prevent the sudden inadvertent movement of the circuit breaker and the mismatch between the frame size and the rating of the circuit breaker.
[0009] Hence there is a need to provide a latching arrangement to prevent the inadvertent movement of the circuit breaker during the circuit breaker loading period to avoid accident and to provide the safety to the operating personnel. Also there is a need to provide a rating error preventing device in the circuit breaker to avoid the mismatch between the frame size and the rating of the circuit breaker. There is yet another need for a system to provide an integrated rating error prevention function and the maintenance latch function.
C) OBJECT OF THE INVENTION
[0010] A primary object of the present invention is to provide a maintenance latch to prevent the inadvertent sliding of the guide rail and the movement of the circuit breaker during the loading of the circuit breaker to load the circuit breaker safely thereby providing safety to the operating personnel during the maintenance of the circuit breakers.
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[0011] Another object of the present invention is to provide a rating error preventing device to avoid the mismatch between the frame size and the rating of the circuit breaker to prevent the unwanted tripping condition.
[0012] Yet another object of the present invention is to develop an integrated system for providing rating error prevention function and loading the circuit breaker safely.
[0013] Yet another object of the present invention is to develop an integrated rating error preventing device and latching system provided with an actuator to push the guide rails inside the cradle for trial purposes, even when the circuit breaker is not loaded on the guide rail.
[0014] 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
[0015] The above mentioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.
[0016] The various embodiments of the present invention provide an integrated system with a rating error prevention function and a latching function to load the circuit breaker safely to provide a safe working condition during maintenance
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operation and to prevent the loading of the circuit breaker with improper rating into the housing.
[0017] According to one embodiment of the present invention, circuit breaker housing is mounted on a moving part called guiding rail provided in a cradle to store a circuit breaker. The guide rail provided with slots slides against a side plate in the cradle. A maintenance latch called m-latch is hinged to the guide rail and moved vertically. The m-latch is provided with preset number of holes and blockers. The blockers are flower shaped and collapsible. An actuator is mounted on the guide rail and connected to the m latch. The actuator is horizontally movable to move the m-latch. Normally the actuator is projected out of the guide rail, when the guide rail is not loaded with a circuit breaker. Two stoppers are provided on the side plate. The stoppers are projections formed protrudingly to prevent the movement of the m- latch. A bracket provided with preset number of holes and pins is mounted on the circuit breaker housing. The number and the configuration of the pins in the bracket depend on the rating of the circuit breaker.
[0018] When a breaker is not loaded on the guide rail, the movement of the m-latch on the side plate is prevented by the first stopper. When a breaker is loaded into the guide rail, the projections in the bracket are received into the slots in the guide rail to push the guide rail down and the m-latch is moved by the actuator so that the m -latch moves into the gap between the two stoppers to load the circuit breaker safely. When a breaker is loaded on the guide rail, the actuator is pushed inside to lower the m-latch to enable the free movement of the guide rails inside the cradle for trial purposes, even when the circuit breaker is not loaded on the guide rail. When a breaker with a
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proper rating is loaded into the guide rail, the pins in the bracket are received into the holes in the m-latch thereby pressing down the m-latch to enable the free movement of the m-latch into the gap between the two stoppers to load the circuit breaker safely. When the circuit breaker with an improper rating is loaded on the guide rail, the pins in the bracket press the blockers in the m-latch to tilt the m-latch so that the movement of the m-latch is stopped by the second stopper.
[0019] Thus the various embodiments of the present invention provide an integrated system to enable the safe loading of the circuit breaker and to prevent the loading of the circuit breaker with improper rating on the guide rail.
[0020] 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.
E) BRIEF DESCRIPTION OF THE DRAWINGS
[0021] 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:
[0022] FIGURE.l shows a front side perspective view of circuit breaker housing and the side plate of the cradle according to one embodiment of the invention, when the guide rail is not loaded with a circuit breaker.
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[0023] FIGURE.2 shows a front side perspective view of circuit breaker housing and the side plate of the cradle according to one embodiment of the invention, when the guide rail is loaded with a circuit breaker with a proper rating.
[0024] FIGURE. 3 shows a front side perspective view of circuit breaker housing and the side plate of the cradle according to one embodiment of the invention, when the guide rail is loaded with a circuit breaker with an improper rating.
[0025] 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
[0026] 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.
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[0027] The various embodiments of the present invention provide an integrated system with a rating error prevention function and a latching function to load the circuit breaker safely to provide a safe working condition during maintenance operation and to prevent the loading of the circuit breaker with improper rating into the housing.
[0028] According to one embodiment of the present invention, circuit breaker housing is mounted on a moving part called guide rail provided in a cradle to store a circuit breaker. The guide rail is provided with slots and slides against a side plate in the cradle. The guide rail is fully withdrawn out during the loading of the circuit breaker housing on the guide rail. A maintenance latch called m-latch is hinged to the guide rail to latch the guide rail to prevent the movement of the guide rail during the loading of the circuit breaker housing. The m-latch is vertically movable and may be slidably moved on the side plate in the cradle. The m-latch is provided with preset number of holes and blockers. The blockers are flower shaped and are collapsible. The m-latch is provided with a spring to enable the auto return movement of the m-latch.
[0029] An actuator is mounted on the guide rail and connected to the m latch. The actuator is horizontally movable to move the m-latch slidably on the side plate. Normally the actuator is projected out of the guide rail, when the guide rail is not loaded with a circuit breaker. The actuator is pushed inside to lower the m-latch to enable the free movement of the guide rail inside the cradle for the trial purposes, even when the circuit breaker housing is not loaded on the guide rail.
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[0030] Two stoppers are provided on the side plate. The stoppers are projections formed protrudingly to prevent the movement of the m- latch. A bracket provided with preset number of holes and pins is mounted on the circuit breaker housing. The number and the configuration of the pins in the bracket depend on the rating of the circuit breaker.
[0031] When a breaker is not loaded on the guide rail, the movement of the m-latch on the side plate is prevented by the first stopper. When a breaker is loaded into the guide rail, the projections in the bracket are received into the slots in the guide rail to push the guide rail down and the m-latch is moved by the actuator so that the m -latch moves into the gap between the two stoppers to load the circuit breaker safely. When a breaker is loaded on the guide rail, the actuator is pushed inside to lower the m-latch to enable the free movement of the m-latch over the side plate. When a breaker with a proper rating is loaded into the guide rail, the pins in the bracket are received into the holes in the m-latch thereby pressing down the m-latch to enable the free movement of the m-latch into the gap between the two stoppers to load the circuit breaker safely. When the circuit breaker with an improper rating is loaded on the guide rail, the pins in the bracket press the blockers in the m-latch to tilt the m-latch so that the movement of the m-latch is stopped by the second stopper.
[0032] Thus the various embodiments of the present invention provide an integrated system to enable the safe loading of the circuit breaker and to prevent the loading of the circuit breaker with improper rating on the guide rail.
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[0033] FIG. 1 illustrates a front side perspective view of circuit breaker housing and the side plate of a cradle according to one embodiment, when the guide rail is not loaded with a circuit breaker. The circuit breaker housing 1001 comprising of plurality of circuit breakers may be placed in the chassis called "cradle". The guide rail 1003 is attached to the side plate 1002 of the cradle to mount the circuit breaker housing 1001 to the cradle. The guide rail 1003 may be attached parallel to the base of the cradle so that the guide rail is projected perpendicularly out of the side plate in the drawn-out position. The guide rail 1003 has slots to receive the projections 1013 provided on the circuit breaker housing.
[0034] A maintenance latch (m-latch) 1004 is hinged to the guide rail 1003. The m-latch 1004 is latched to secure the position of the circuit breaker housing 1001 during a maintenance operation. The circuit breaker housing 1001 may be removed or loaded into the cradle during the maintenance operation. The m-latch 1004 has preset number of holes and blockers 1019. The blockers 1019 are flower shaped collapsible components.
[0035] Two stoppers 1014, 1015 are provided in the side plate 1002 of the cradle to block the movement of the m-latch 1004 on the side plate 1002. The stoppers 1014, 1015 are projections formed on the side plate 1002 by lancing out the material from the side plate 1002. When the circuit breaker is not loaded on the guide rail 1003, the stoppers 1014, 1015 prevent the movement of the m-latch 1004 thereby preventing the sliding of the guide rail 1003.
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[0036] A bracket 1016 is mounted on the circuit breaker housing 1001 and provided with preset number of holes 1018 and pins 1017. The number and the configuration of the pins 1017 in the bracket 1016 depend on the rating of the circuit breaker stored inside the housing 1001. The pins 1017 in the bracket 1016 are received into the holes provided in the m-Iatch 1004 to push the m-latch 1004 down to enable the movement of the m-latch 1004 into the gap provided between the two stoppers 1014, 1015 so that the guide rail 1003 is pushed inside the cradle easily.
[0037] The actuator called "M-latch-actuator" 1005 is provided protrudingly on the guide rail 1003 and connected to the m-latch 1004. The actuator 1004 is used to push guide rails 1003 inside cradle during trial operations, even when the circuit breaker is not loaded. Normally the M-latch actuator 1005 is projected out of the unloaded guide rail 1003. The actuator 1005 is pushed inside during the pushing of the guide rail 1003 into the cradle to lower the m-latch 1004 to clear the obstruction of the stoppers 1014,1015 provided on the side plate 1002. The M-latch actuator 1005 comprises of the guides M-latch actuator guide "A" 1008 and M-latch actuator guide "B" 1009. A M-latch actuator return spring 1010 is provided to return the M-latch actuator 1005 to the projected position automatically when the guide rail 1003 is with drawn out for loading the circuit breaker.
[0038] FIG. 2 illustrates a front side perspective view of circuit breaker housing and the side plate of a cradle according to one embodiment, when the guide rail is loaded with a circuit breaker having a proper rating. The circuit breaker housing 1001 comprising of plurality of circuit breakers may be placed in the chassis called
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"cradle". The guide rail 1003 is attached to the side plate 1002 of the cradle to mount the circuit breaker housing 1001 to the cradle. The guide rail 1003 may be attached parallel to the base of the cradle so that the guide rail 1003 is projected perpendicularly out of the side plate 1002 in the drawn-out position. The guide rail 1003 has slots to receive the projections 1013 provided on the circuit breaker housing 1001.
[0039] A maintenance latch (m-latch) 1004 is hinged to the guide rail 1003. The m-latch 1004 is latched to secure the position of the circuit breaker housing 1001 during a maintenance operation .The circuit breaker housing 1001 may be removed or loaded into the cradle during the maintenance operation. The m-latch 1004 has preset number of holes and blockers 1019. The blockers 1019 afe flower shaped collapsible components.
[0040] Two stoppers 1014, 1015 are provided in the side plate 1002 of the cradle to block the movement of the m-latch 1004 on the side plate 1002. The stoppers 1014, 1015 are projections formed on the side plate 1002 by lancing out the material from the side plate 1002.
[0041] A bracket 1016 is mounted on the circuit breaker housing lOOland provided with preset number of holes 1018 and pins 1017. The number and the configuration of the pins 1017 in the bracket 1016 depend on the rating of the circuit breaker stored inside the housing 1001. When a circuit breaker with a proper rating is loaded on the guide rail 1003, the pins 1017 in the bracket 1016 are received into the holes provided
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in the m-latch 1004 to push the m-latch 1004 down to enable the movement of the m-latch 1004 into the gap provided between the two stoppers 1014, 1015 so that the guide rail 1003 is pushed inside the cradle easily.
[0042] The actuator called "M-latch-actuator" 1005 is provided protrudingly on the guide rail 1003 and connected to the m-latch 1004. The actuator is used to push guide rails inside cradle during trial operations, even when the circuit breaker is not loaded. Normally the M-latch actuator 1005 is projected out of the unloaded guide rail 1003. The actuator 1005 is pushed inside during the pushing of the guide rail to lower the m-latch to clear the obstruction of the stoppers provided on the side plate. The M-latch actuator 1005 comprises of the guides M-latch actuator guide "A" 1008 and M-latch actuator guide "B" 1009. A M-latch actuator return spring 1010 is provided to return the M-latch actuator 1005 to the projected position automatically when the guide rail 1003 is with drawn out for loading the circuit breaker.
[0043] FIG. 3 illustrates a front side perspective view of circuit breaker housing and the side plate of a cradle according to one embodiment, when the guide rail is loaded with a circuit breaker having an improper rating. The circuit breaker housing 1001 comprising of plurality of circuit breakers may be placed in the chassis called "cradle". The guide rail 1003 is attached to the side plate 1002 of the cradle to mount the circuit breaker housing 1001 to the cradle. The guide rail 1003 may be attached parallel to the base of the cradle so that the guide rail is projected perpendicularly out of the side plate in the drawn-out position. The guide rail 1003 has slots to receive the projections 1013 provided on the circuit breaker housing 1001.
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[0044] A maintenance latch (m-latch) 1004 is hinged to the guiding rail 1003. The M-latch" 1004 is latched to secure the position of the circuit breaker housing 1001 during a maintenance operation. The circuit breaker housing 1001 may be removed or loaded into the cradle during the maintenance operation. The m-latch 1004 has preset number of holes and blockers 1019. The blockers 1019 are flower shaped collapsible components.
[0045] Two stoppers 1014, 1015 are provided in the side plate 1002 of the cradle to block the movement of the m-latch 1004 on the side plate 1002. The stoppers 1014 are projections formed on the side plats 1002 by 1ancing out the material from tne side plate 1002.
[0046] A bracket 1016 is mounted on the circuit breaker housing 1001 and provided with preset number of holes 1018 and pins 1017. The member and the configuration of the pins 1017 in the bracket 1016 depend on the rating of the circuit breaker stored inside the housing 1001. When a circuit breaker with an improper rating is loaded on the guide rail 1003, the pins 1017 in the bracket 1016 push the blockers 1019 to tilt the m-latch 1004 so that the movement of the m-latch 1004 is stopped by the stopper 1015 thereby preventing the movement of the guide rail 1003 and the loading of the circuit breaker.
[0047] The actuator called "M-latch-actuator" 1005 is provided protrudingly on the guide rail 1003 and connected to the m-latch 1004. The actuator 1005 is used to push guide rails 1003 inside cradle during trial operations, even when the circuit breaker is
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not loaded. Normally the M-latch actuator 1005 is projected out of the unloaded guide rail 1003. The actuator 1005 is pushed inside during the pushing of the guide rail 1003 to lower the m-latch 1004 to clear the obstruction of the stoppers 1014, 1015 provided on the side plate 1002. The M-latch actuator 1005 comprises of the guides M-latch actuator guide "A" 1008 and M-latch actuator guide "B" 1009. A M-latch actuator return spring 1010 is provided to return the M-latch actuator 1005 to the projected position automatically when the guide rail 1003 is with drawn out for loading the circuit breaker.
G) ADVANTAGES OF THE INVENTION
[0048] Thus the various embodiments of the present invention provides an integrated maintenance latch and rating error preventing device to lod the circuit breaker safely. The system prevents the inadvertent movement of the guide rail during the maintenance operation thereby providing a safe working condition for the maintenance personnel. The system also prevents the loading of the circuit breakers with improper rating to prevent the unwanted tripping or no protection condition.
[0049] 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.
[0050] 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
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statements of the scope of the invention which as a matter of language might be said to fall there between.
The detailed scope of the monopoly claimed for the invention shall be ascertained and provided at the time of filing of the Complete Specification
Dated this 28th of October, 2008

Rakesh Prabhu,
Patent Agent,
No.2, Lavelle Road, Bangalore-560 001, INDIA

To,
The Controller of Patents,
The Patent office,
Mumbai

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