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:
CHING CUM ARC QUENCHING SYSTEM FOR SWITCHING DEVICES
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 and particularly to electrical contacts separating systems in switching devices like change over switches, switches gear, etc. The present invention more particularly relates to arc quenching and current interrupting systems in the switching devices.
B) BACKGROUND OF THE INVENTION
[0002] In electrical switches, the flow of electrical current is maintained by providing a contact between the moving contacts and the stationary contacts. The moving contacts are mounted on a moving bridge. The moving bridge is moved away from the stationary contact when the switch is turned off and the flow of current is stopped by isolating the moving and stationary contacts. However, transient arcs, caused due to the inability of the contact in dropping the value of the current to zero instantaneously, can affect the components of the switch units adversely.
[0003] The electrical switches further comprise an arc quenching system to cut off the arc generated between the moving and stationary contacts of a system during the switching off condition. There are several systems used in the switching devices to quench the arc. The type of the system used in a switching device depends on the construction and utility of the switching device.
[0004] The low-voltage circuit breakers use air to quench the arc. High-voltage circuit beakers use metal plates or non-metallic arc chutes which divide and cool the arc. The high voltage circuit breakers often use a blast of high pressure air, a special dielectric
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gas (such as SF6 under pressure), or immersion in mineral oil to quench the arc when the high voltage circuit is broken. Further magnetic coils are also used to deflect the arc into arc chutes.
[0005] The currently available arc quenching systems shifts the moving contact bridge substantially away from the stationary contacts to increase the contact gap to ensure that the arc is quenched thoroughly. The moving bridge is substantially heavy to move the movable contacts away from the stationary contacts to ensure a safe contact gap. Further, the overall size of the currently available switching devices is large enough to accommodate large contact gap for arc quenching and the arc quenching method adopted.
[0006] Hence there is a need to provide an effective arc quenching mechanism and reduce the overall size of the switching device. Further, there exists a need for minimal movement of moving bridge and reduction in weight of the bridge. The arc quenching time needs to be substantially reduced to completely cut off the current flow.
C) OBJECT OF THE INVENTION
[0007] The primary object of the present invention is to develop a switching cum arc quenching system for switching devices to provide a single system for switching electrical systems and quenching the arc generated between the contacts in the switching device.
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[0008] Another object of the present invention is to develop a switching cum arc quenching system for switching devices to provide a physical barrier between the contacts to reduce the overall size of the electrical switch.
[0009] Yet another object of the present invention is to develop a switching cum arc quenching system for switching devices to provide a physical barrier between the contacts to reduce the contact gap for arc clearance.
[0010] Yet another object of the present invention is to develop a switching cum arc quenching system for switching devices to provide an effective arc quenching mechanism to reduce the arcing time.
[0011] Yet another object of the present invention is to develop a switching cum arc quenching system for switching devices in which the weight of the moving bridge is reduced to provide a low torque for operation.
[0012] Yet another object of the present invention is to develop a switching cum arc quenching system for switching devices to provide a single system for switching electrical systems and quenching the arc generated between the contacts in the switching device thereby eliminating the need for the arc chutes.
[0013] Yet another object of the invention is to develop a switching cum arc quenching system for switching devices in which a single system is provided for switching electrical systems and quenching the arc generated between the contacts thereby reducing the size of the switching device for a given rating.
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[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 a single system and method for switching and quenching arcs in an electrical switching device. According to one embodiment of the present invention, a physical barrier is provided between the moving contacts and the stationary contacts to cut off the power supply. The physical barrier is an insulation sheet. The insulation sheet is interposed between the moving contact and the stationary contacts to move the moving contact away from the stationary contacts to separate the moving contact from the stationary contacts to cut off power supply.
[0017] According to one embodiment, a switching device is provided with a physical barrier such as insulation sheet to separate the contacts. The switching device is provided with the Input and the Output conductors which are fixed. A moving conductor is provided to connect the input and the output conductors. The moving conductor has movement along one direction only. The insulation sheet is slidably moved between the stationary contacts and the moving contacts to move away the moving contact from the stationary contacts to cut off the power supply. The insulation sheet also quenches the arc rapidly. The contact gap between the fixed and
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the moving contacts is kept equivalent to the thickness of the insulation sheet thereby reducing the size of the switching device. The thickness of the insulation sheet is the minimum thickness that is required to maintain the isolation between the two current carrying conductors.
[0018] According to another embodiment of the present invention, a change over switch is provided with at least two contact systems so that each contact system opens alternatively. Each contact system has two fixed terminals and two moving contacts. An operating bar is provided to move the moving contact towards the fixed contacts and the leaf spring used to provide the contact pressure and also holding the moving contacts in position. The moving contacts connect the fixed contacts by use of a leaf spring to complete a current path. An insulating bridge is coupled to an actuator like solenoid actuator through a linear shaft. The solenoid actuator is activated to move the insulation bridge towards the contact system. The operating bar releases the leaf spring to enable the free movement of the moving contact. Simultaneously the insulation bridge is moved in between the moving contact and the fixed contacts and the current supply path is cut off.
[0019] Thus the various embodiments of the invention provide a system and method to provide a single system for switching and quenching arcs. The system is provided with a physical barrier such as insulation sheet to reduce the contact gap between the fixed and moving contacts thereby reducing the size of the switching device. Since the insulation sheet is used to quench the arcs, the need for an arc quenching mechanism is eliminated. Since the current supply is cut off by a solid physical barrier such as insulation sheet and there is reduction of distance for the insulation bridge/sheet to travel, the arching time is reduced.
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E) BRIEF DESCRIPTION OF THE DRAWINGS
[0020] 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:
[0021] FIGURE 1 illustrates a top perspective view of the stationary and moving contacts with insulation barrier in the inserted condition in a switch, according to one embodiment of the present invention.
[0022] FIGURE 2 illustrates a top perspective view of the stationary and moving contacts with insulation barrier in the non-inserted condition in a switch, according to one embodiment of the present invention.
[0023] FIGURE 3 illustrates a top perspective view of the stationary and moving contacts with the insulation barrier being inserted between the contacts in a switch, according to one embodiment of the present invention.
[0024] FIGURE 4 illustrates the side sectional view of the change over switch with contacts in closed condition according to one embodiment of the present invention.
[0025] FIGURE. 5 illustrates the top perspective view of a changeover switch with contacts in closed condition, according to one embodiment of the present invention.
[0026] FIGURE. 6 illustrates the side sectional view of the change over switch with contacts in open condition according to one embodiment of the present invention.
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[0027] FIGURE. 7 illustrates the top perspective view of a changeover switch with contacts in open condition, according to one embodiment of the present invention.
[0028] 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 Nvith arty ox ah of the other features m accordance with the present invention.
F) DETAILED DESCRIPTION OF THE INVENTION
[0029] 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.
[0030] The various embodiments of the present invention provide a single system and method for switching and quenching arcs in an electrical switching device. According to one embodiment of the present invention, a physical barrier is provided between the moving contacts and the stationary contacts to cut off the power supply. The physical barrier is an insulation sheet. The insulation sheet is interposed between the moving, contact and the stationary contacts to move the moving, contact away from the stationary contacts to separate the moving contact from the stationary contacts to cut
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off power supply. The moving contacts are moved away from the fixed contacts like a butt contact thereby providing the moving contacts with only one direction of motion. Hence the insulation sheet acting like bridge displaces the moving conductors in one direction only. As a result the need for carrying the isolation conductor by the moving contact is eliminated thereby reducing the weight of the moving contact bridge.
[0031] According to one embodiment, a sv/itchmg device is provided with a physical barrier such as insulation sheet to separate the contacts. The switching device is provided with the Input and the Output conductors which are fixed. A moving conductor is provided to connect the input and the output conductors. The moving conductor has movement along one direction only. The insulation sheet is slidably moved between the stationary contacts and the moving contacts to move away the moving contact from the stationary contacts to cut off the power supply. The insulation sheet also quenches the arc rapidly. The contact gap between the fixed and the moving contacts is kept equivalent to the thickness of the insulation sheet thereby reducing the size of the switching device. The thickness of the insulation sheet is the minimum thickness that is required to maintain the isolation between the two current carrying conductors.
[0032] According to another embodiment of the present invention, a change over switch is provided with at least two contact systems so that each contact system opens alternatively. Each contact system has two fixed terminals and a moving contact. An operating bar is provided to move the moving contact towards the fixed contacts and held in a position by the use of a leaf spring. The moving contacts connect the fixed contacts by use of a leaf spring to complete a current path. An insulating bridge is coupled to an actuator like solenoid actuator through a linear shaft. The solenoid
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actuator is activated to move the insulation bridge towards the contact system. The operating bar releases the leaf spring to enable the free movement of the moving contact. Simultaneously the insulation bridge is moved in between the moving contact and the fixed contacts and the current supply path is cut off.
[0033] Thus the various embodiments of the invention provide a system and method to provide a single system for switching and quenching arcs. The system is provided with a physical barrier such as insulation sheet to reduce the contact gap between the fixed and moving contacts thereby reducing the size of the switching device. Since the insulation sheet is used to quench the arcs, the need for an arc quenching mechanism is eliminated. Since the current supply is cut off by a solid physical barrier such as insulation sheet and there is reduction of distance for the insulation bridge/sheet to travel, the arching time is reduced.
[0034] FIGURE. 1 illustrates a top perspective view of the stationary and moving contacts with insulation barrier in the inserted condition in a switch, according to one embodiment of the present invention. With respect to FIG.l, the switch has input conductor 1 and output conductor 2 which are fixed. A moving conductor which may be moved in one direction only is used to connect the input and output conductors to form a closed current path. An insulation sheet is slidably moved between the moving conductor 3 and the input and output conductors 1,2 to cut off the power supply. In the switched ON condition, the current path is formed between the input and output conductors 1,2 through the moving conductor 3. In the switched OFF condition, the insulation sheet 4 is placed between the moving conductor 3 and the input/output conductor 1,2 to cut off the current path.
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[0035] FIGURE 2 illustrates a top perspective view of the stationary and moving contacts with insulation barrier in the non-inserted condition in a switch, according to one embodiment of the present invention. The switch has fixed input contact 1 and an output contact 2. The moving contact 3 is resiliency in contact with the fixed input contact 1 and output contact 2 to form a closed circuit. The insulation barrier 4 such as insulation sheet is placed adjacent to the fixed contacts when the circuit is closed.
[0036] FIGURE 3 illustrates a top perspective view of the stationary and moving contacts with the insulation barrier being inserted between the contacts in a switch, according to one embodiment of the present invention. With respect to FIG.3, the insulation sheet 4 is inserted between the input/output contacts 1, 2 and moving contact 3 to cut off the current path and to quench the arc generated between the input/output contacts 1,2 and moving contact 3. The moving contact 3 begins to move away from the fixed input contact 1 and fixed output contact 2.
[0037] FIGURE 4 illustrates the side sectional view of the change over switch with contacts in closed condition according to one embodiment of the present invention. With respect to FIG.4, the change over switch is provided with two contact systems. One contact system is kept in open condition while the other contact system is kept in closed condition. Each contact system has fixed input and output contacts 103, 104 and moving contacts 109, 110. The electrical circuit is formed between the input contacts and the output contacts through the moving contacts in closed position. The first operating bar 107 is coupled to the moving contact 109 to move the moving contact 109 towards or away from the fixed contacts 103,104. The leaf spring 105 co-acts between the first operating bar 107 and the moving contact 109 to resiliency bias the movement of the moving contact 109. The second operating bar, 108 is coupled to
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the moving contact 110 to move the moving contact 110 towards or away from the fixed contacts 103,104. The leaf spring 106 co-acts between the second operating bar
108 and moving contact 110 to resiliently bias the movement of the moving contact 110. In the closed contact position, the flow of current is established from fixed contact 103 to moving contact 109 and 110, and to fixed contact 104. The actuator activates the insulation bridge 111 through the linear shaft 112. The moving contact
109 and the operating bar 107 are arranged in the top housing 101 while the moving contact 110 and the operating bar 108 are arranged in the bottom housing 102.
[0038] FIGURE. 5 illustrates the top perspective view of a changeover switch with contacts in closed condition, according to one embodiment of the present invention. With respect to FIG. 5, a changeover switch is provided with two contact systems A and B which open and close alternatively. The working of the first contact system A when the second contact system B is closed is mentioned above. The actuator 113 is activated to insert the insulation sheet in the contact gap between the fixed and moving contacts.
[0039] FIGURE. 6 illustrates the side sectional view of the change over switch with contacts in open condition according to one embodiment of the present invention. With respect to FIG.6, The actuator 113 activates the linear shaft 112 to move the insulation bridge 111 towards the first system A. The activation of the linear shaft 112 moves the first operating bar 107 and the second operating bar 108 simultaneously. The leaf springs 105 and 106 are released by the movement of the operating bars 107 and 108 respectively. The moving contacts 109 and 110 move away from the fixed contacts due to the release of the resilience based springs 105 and 106 to create a contact gap. The insulation bridge 111 is simultaneously inserted between the contact
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gap to cut off the current path by isolating the contacts and quenching the arc. The moving contact 109 and the operating bar 107 are arranged in the top housing 101 while the moving contact 110 and the operating bar 108 are arranged in the bottom housing 102.
[0040] FIGURE. 7 illustrates the top perspective view of a changeover switch with contacts in open condition, according to another embodiment of the present invention. With respect to FIG. 7, a changeover switch is provided with two contact systems A and B which open and close alternatively. The actuator 113 can be activated to insert the insulation sheet in the contact gap between the fixed and moving contacts to isolate the contacts and to quench the arc generated between the contacts.
G) ADVANTAGES OF THE INVENTION
[0041] Thus the various embodiments of the invention provide a system and method to insert the insulation barrier in the contact gap and completely quench the arcs by isolating the contacts in an electrical switch. A quenching mechanism is provided to quench the arcs efficiently by isolating the contacts by inserting the insulation barrier to cut off the path for arcing completely. An insulation bridge is inserted in the contact gaps of multiple contact systems which are closed alternatively. The system is provided with a physical barrier such as insulation sheet to reduce the contact gap between the fixed and moving contacts thereby reducing the size of the switching device. Since the insulation sheet is used to quench the arcs, the need for an arc quenching mechanism is eliminated. As the current supply is cut off by a solid physical barrier such as insulation sheet and there is reduction of distance for the insulation bridge/sheet to travel, the arching time is reduced.
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[0042] 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.
[0043] 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: November 28, 2008. RAKESH PRABHU
Place: Bangalore. Patent Attorney
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CLAIMS
What is claimed is:
1. A switching cum arc quenching system for switch devices including fixed
and moving contacts comprising:
a physical barrier inserted between the fixed and moving contacts to isolate the contacts to cut off the power supply.
2. The system according to claim 1, wherein the physical barrier is an insulation sheet.
3. The system according to claim 1, wherein the insulation sheet is inserted between the fixed and the moving contacts to physically isolate the contacts to cut off the power supply and to quench the arc generated between the contacts.
4. A switch with improved arc quenching mechanism comprising:
An input conductor;
An output conductor;
A moving conductor; and
A physical barrier;
Wherein the physical barrier is inserted between the moving conductor and the
input and output conductors to cut off the current path.
5. The switch according to claim 4, wherein the physical barrier is an insulation sheet.
6. The switch according to claim 4, wherein the insulation sheet is inserted between the moving conductor and the input and output conductors to physically isolate the contacts to cut off the power supply and to quench the arc generated between the contacts.
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7. A change over switch with improved arc quench mechanism comprising:
two contact systems wherein each contact system including an input conductor, an output conductor, two moving contacts, an insulation bridge and an actuator whereby the actuator upon activation inserts the insulation bridge between the moving contacts and the input and output conductors to cut off the power supply and to quench the arc.
8. The change over switch according to claim 7, further comprises a linear shaft coupled to the insulation bridge and to the actuator so that the actuator moves the linear shaft upon activation to insert the insulation bridge between the moving contacts and the input and output conductors to cut off the current supply path and to quench the arc generated in the gap between the contacts.
9. The change over switch according to claim 7 further comprises operating bars connected to the moving contacts respectively to move the moving contacts towards or away from the fixed contacts.
10. The changeover switch according to claim 7, further comprises leaf springs connected to the operating bars to hold the moving contacts in contact with input and the output conductors resiliency.
Dated this 28th of November, 2008
Rakesh Prabhu,
Patent Agent, ALMT Legal,
No.2, Lavelle Road, Bangalore-560 001, INDIA
To,
The Controller of Patents,
The Patent office, Mumbai
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