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



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 breaker and particularly to air circuit breaker. The present invention more particularly relates to a switch contact arrangement mechanism in air circuit breaker.
B) BACKGROUND OF THE INVENTION
[0002] Circuit breakers are the mechanical switching devices capable of making, carrying, and breaking currents under normal circuit conditions and also making, carrying for a specified time, and breaking currents under specified abnormal conditions. A circuit breaker basically consists of a pair of separable contacts and an interrupting medium. The function of the contacts is to conduct the electrical current when the breaker is closed and withstand the arcs while interrupting. Generally, the electrical contacts have a stationary part and a moving part. By bringing the moving contact to touch the stationary contact, electric current flows and the breaker is closed. By driving the moving contact away from the stationary contact the electric arc develops and by quenching it the current stops flowing and the breaker is open.
[0003] An air circuit breaker is a switching device in which the force necessary to open or close the main contact assembly is provided by an arrangement of compression springs. Air circuit breakers are so named because they utilize air as the insulating medium to break the arc when the contacts open. Air circuit breakers are generally of three types. They are molded case circuit breaker, low voltage circuit breaker and medium voltage circuit breaker. Regardless of the type of circuit breaker, they use air as a medium to extinguish an arc. When the contacts separate to interrupt the current, an arc is produced that contains a great deal of heat.
[0004] The circuit breaker contacts must carry the load current without excessive heating, and must also withstand the heat of the arc produced when interrupting the circuit. When a current is interrupted, an arc is generated this arc must be contained, cooled, and extinguished in a controlled way, so that the gap between the contacts can again withstand the voltage in the circuit.


[0005] The contact arm in a multiple contact circuit breaker is made of a number of fingers mounted on a common pivot pin. Contact spring bias the contact fingers against the stationary contacts in the closed position to provide contact pressure and to accommodate for wear. The Movable contacts in the circuit breaker are in the form of fingers assembled in pole. The Fingers are assembled in pole cage using spacer and bearing pin. During short circuit conditions a high force produced try to push the contacts apart. As fingers are pivoted on bearing pin, pin bends in absence of proper support. This produces small gap in contacts and initiates arcing. Arching propagates due to ionization of nearby air which results in failure of breaker.
[0006] Hence there is a need to provide a contact support for the movable contacts in the air circuit breaker to prevent the bending of the pin upon which the fingers are pivoted during short circuit conditions.
[0007] The prior art patent No. EP1298692B1 discloses a Switch contact arrangement for a low voltage circuit breaker. The Switch contact device for low voltage power switch includes spacers between contact levers provided with support surfaces limiting movement of contact carrier and deformation of contact carrier bearing bolt. In this the spacer pieces are in the form of an individual part. The spacer pieces have through opening to match to the bearing bolt and for the purpose of limiting bending of bearing bolt, an outer supporting face opposite the contact carrier. This contact . arrangement requires assembly of individual pieces and fingers and also the position of the fingers with respect to pole is not governed by the pieces.
[0008] The prior art patent No. US7068131B2 discloses a switching contact arrangement for an electrical switch. It includes a plurality of contact levers pivoted on a contact support via bearing pin. The contact support is provided with at least three support elements for racially supporting bearing pin. At least one of the support elements can have metal element that is at least partially embedded in a plastic shaped element of the contact support. It requires Composite molding which involves high cost and specialized technology. Also in practice, support given is at more number of points through out the length of bearing pin.


[0009] The Movable contacts in breaker are in form of fingers assembled in a pole cage. The fingers are assembled in pole cage using spacer and bearing pin. During the short circuit period, the high forces produced try to push contacts apart. As the fingers are pivoted on the bearing pin, the bearing pin bends in the absence of a proper support. This produces small gap in contacts & initiates arcing. Arching propagates due to ionization of nearby air which results in failure of breaker.
[0010] Hence there is a need to provide a contact support for the movable contacts in the air circuit breaker to prevent the bending of the pin upon which the contact fingers are pivoted during high short circuit conditions. Hence there is a need to develop a simplest and easy to manufacture switch contact arrangement to maintain the position of the contact fingers during short circuit conditions.
C) OBJECTS OF THE INVENTION
[0011] The primary object of the present invention is to provide a method and device to transfer short circuit forces to pole cage while maintaining the position of finger contacts.
[0012] Another object of the present invention is to provide a switch contact arrangement to transfer short circuit forces to pole cage easily and efficiently.
[0013] Yet another object of the present invention is provide an integral spacer to maintain the position of the finger contacts in the pole cage of an air circuit breaker reliably.
[0014] Yet another object of the present invention is to provide an integral spacer to avoid the bending of the finger support pin during the application of very high forces.
[0015] Yet another object of the present invention is to provide an integral spacer to support the bearing pin and to transfer forces to pole cage easily and efficiently during the application of very high forces to the circuit breaker.


[0016] Yet another object of the present invention is to provide an integral spacer which is manufactured easily.
[0017] Yet another object of the present invention is to provide an integral spacer with a simple structure.
[0018] Yet another object of the present invention is to provide an integral spacer to eliminate the need for molding thin walls in a pole cage of an air circuit breaker.
[0019] Yet another object of the present invention is to provide an integral spacer to simplify the assembly of poles in the circuit breaker.
[0020] Yet another object of the present invention is to provide an integral spacer to increase area of contact to avoid the buckling of the walls of the spacer.
[0021] Yet another object of the present invention is to provide an integral spacer with sufficient wall thickness to acquire comprehensive strength to withstand the forces during short circuit.
[0022] 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
[0023] The abovementioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.
[0024] The various embodiments of the present invention provide a device and method to transfer short circuit forces in an air circuit breaker. The various embodiments provide an integral spacer to maintain the position of the finger contacts


in a pole cage while avoiding the bending of the bearing pin supporting the finger contacts during the application of very high forces in the circuit breaker.
[0025] According to one embodiment of the present invention, an integral spacer is provided in the pole cage of the air circuit breaker to assemble the finger contacts in the air circuit breaker. The integral spacer has a base formed integrally with molded walls at one surface. The walls are protruded from the base of the integral spacer to form the individual spacers. The integral spacer is fit exactly in a groove provided in the pole cage. The individual finger contacts are inserted in the opening provided between the spacers against the pole springs. Each spacer wall has a hole so that the holes on all the spacer walls are aligned to receive a bearing pin. The pole pin is made to pass through the pole cage, contact fingers and the spacers. The area of contact face of the spacer is increased to avoid the buckling of the spacer under the forces against the pole cage.
[0026] According to another embodiment of the present invention, the contact fingers are first inserted in a pole cage against the springs. The integral spacer is inserted in the contact fingers from the top so that the walls of the spacer are made to contact the surface of the pole cage. Then a bearing pin is inserted from the sides. The gap between the bearing pin and the integral spacer is reduced. The gap between the integral spacer and the wall of the pole cage is also reduced to a minimum gap.
[0027] When the circuit breaker is closed, the pole cage is positioned by a mechanism and the pole springs are compressed against the contact fingers. During the supply of the current at a normal level, the dimensions of the bearing pin are sufficient to withstand the entire applied force. During short circuit condition, very high forces try to repel the pole fingers from top terminal. As the position of the pole is fixed, the individual fingers transfer this force to the bearing pin. In absence of proper support, the bearing pin gets bent and a gap is produced between the finger contacts and the top terminal. Due to this gap, an arcing is generated to ionize nearby air and the arcing is propagated.
[0028] The integral spacer provides a support between the bearing pin and the walls of pole cage. During short circuit, the contact fingers experience force and try to bend
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the pin towards the pole cage. As the contact fingers are solely supported on the bearing pin which it self is supported in the pole cage at its ends, it tries to bend in middle portion. The spacer fills the gap between the bearing pin and the pole cage thereby transferring the forces to the pole cage. The thickness of the walls of the spacers is set to preset values so that the compressive strength of the spacers is sufficient to withstand the forces that occur during a short circuit period. Also the area of the spacer surface which rests on the pole cage is increased to avoid the buckling of the walls of the spacer. Thus the integral spacer of this invention avoids the bending of bearing pin and the failure of pole in short circuit condition.
[0029] 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
[0030] 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:
[0031] FIGURE. 1 illustrates a front perspective view of an air circuit breaker installed with an integral spacer according to one embodiment of the present invention, in which the integral spacer is mounted first to receive the finger contacts.
[0032] FIGURE. 2 illustrates a front perspective view of an air circuit breaker installed with an integral spacer according to one embodiment of the present invention, in which the integral spacer is mounted after installing the finger contacts.
[0033] FIGURE. 3 illustrates a side sectional view of an air circuit breaker shown in FIGURE. 1 and installed with an integral spacer according to one embodiment of the present invention.


(0034] FIGURE. 4 illustrates a side sectional view of an air circuit breaker shown in FIGURE.2 and installed with an integral spacer according to one embodiment of the present invention.
[0035] FIGURE. 5 illustrates an exploded perspective view of an air circuit breaker shown in FIGURE. 1 and installed with an integral spacer according to one embodiment of the present invention.
[0036] FIGURE. 6 illustrates a side sectional view of an air circuit breaker shown in FIGURE.2 and installed with an integral spacer according to one embodiment of the present invention.
[0037] 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
[0038] 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.
[0039] The various embodiments of the present invention provide a device and method to transfer short circuit forces in an air circuit breaker. The various embodiments provide an integral spacer to maintain the position of the finger contacts in a pole cage while avoiding the bending of the bearing pin supporting the finger contacts during the application of very high forces in the circuit breaker.


[0040] According to one embodiment of the present invention, an integral spacer is provided in the pole cage of the air circuit breaker to assemble the finger contacts in the air circuit breaker. The integral spacer has a base formed integrally with molded walls at one surface. The walls are protruded from the base of the integral spacer to form the individual spacers. The integral spacer is fit exactly in a groove provided in the pole cage. The individual finger contacts are inserted in the opening provided between the spacers against the pole springs. Each spacer wall has a hole so that the holes on all the spacer walls are aligned to receive a bearing pin. The pole pin is made to pass through the pole cage, contact fingers and the spacers. The area of contact face of the spacer is increased to avoid the buckling of the spacer under the forces against the pole cage.
[0041] According to another embodiment of the present invention, the contact fingers are first inserted in a pole cage against the springs. The integral spacer is inserted in the contact fingers from the top so that the walls of the spacer are made to contact the surface of the pole cage. Then a bearing pin is inserted from the sides. The gap between the bearing pin and the integral spacer is reduced. The gap between the integral spacer and the wall of the pole cage is also reduced to a minimum gap.
[0042] When the circuit breaker is closed, the pole cage is positioned by a mechanism and the pole springs are compressed against the contact fingers. During the supply of the current at a normal level, the dimensions of the bearing pin are sufficient to withstand the entire applied force. During short circuit condition, very high forces try to repel the pole fingers from top terminal. As the position of the pole is fixed, the individual fingers transfer this force to the bearing pin. In absence of proper support, the bearing pin gets bent and a gap is produced between the finger contacts and the top terminal. Due to this gap, an arcing is generated to ionize nearby air and the arcing is propagated.
[0043] The integral spacer provides a support between the bearing pin and the walls of pole cage. During short circuit, the contact fingers experience force and try to bend the pin towards the pole cage. As the contact fingers are solely supported on the bearing pin which it self is supported in the pole cage at its ends, it tries to bend in middle portion. The spacer fills the gap between the bearing pin and the pole cage
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thereby transferring the forces to the pole cage. The thickness of the walls of the spacers is set to preset values so that the compressive strength of the spacers is sufficient to withstand the forces that occur during a short circuit period. Also the area of the spacer surface which rests on the poie cage is increased to avoid the buckling of the walls of the spacer. Thus the integral spacer of this invention avoids the bending of bearing pin and the failure of pole in short circuit condition.
[0044] FIGURE. 1 illustrates a front perspective view of an air circuit breaker installed with an integral spacer according to one embodiment of the present invention, in which the integral spacer is mounted first to receive the finger contacts. With respect to FIG.1, an integral spacer 3 is provided inside the pole cage 1 of the air circuit breaker to assemble the finger contacts 2 in the air circuit breaker. The integral spacer 3 has a base formed integrally with molded walls at one surface. The walls are protruded from the base of the integral spacer 3 to form the individual spacers. The integral spacer 3 is fit exactly in a groove provided in the pole cage 1. The individual finger contacts 2 are inserted in the opening provided between the spacers against the pole springs 5. Each spacer wall has a hole so that the holes on all the spacer walls are aligned to receive a bearing pin 4. The bearing pin 4 is made to pass through the pole cage 1, contact fingers 2 and the spacers. The area of contact face of the spacer 3 is increased to avoid the buckling of the spacer 3 under the forces against the pole cage.
[0045] FIGURE. 2 illustrates a front perspective view of an air circuit breaker installed with an integral spacer according to one embodiment of the present invention, in which the integral spacer is mounted after installing the finger contacts. With respect to FIG.2, the contact fingers 2 are first inserted in a pole cage 1 against the springs 5. The integral spacer 3 is inserted in the contact fingers 2 from the top so that the walls of the spacer 3 are made to contact the surface of the pole cage 1. Then a bearing pin 4 is inserted from the sides. The gap between the bearing pin 4 and the integral spacer 3 is reduced. The gap between the integral spacer 3 and the wall of the pole cage 1 is also reduced to a minimum gap.
[0046] FIGURE. 3 illustrates a side sectional view of an air circuit breaker shown in FIGURE. 1 and installed with an integral spacer according to one embodiment of the present invention. With respect to FIG.3, an integral spacer 3 is provided inside the


pole cage 1 of the air circuit breaker to assemble the finger contacts 2 in the air circuit breaker. The integral spacer 3 has a base formed integrally with molded walls at one surface. The walls are protruded from the base of the integral spacer 3 to form the individual spacers. The integral spacer 3 is fit exactly in a groove provided in the pole cage 1. The individual finger contacts 2 are inserted in the opening provided between the spacers against the pole springs 5. Each spacer wall has a hole so that the holes on all the spacer walls are aligned to receive a bearing pin 4. The bearing pin 4 is made to pass through the pole cage 1, contact fingers 2 and the spacers. The area of contact face of the spacer 3 is increased to avoid the buckling of the spacer 3 under the forces against the pole cage.
[0047] FIGURE. 4 illustrates a side sectional view of an air circuit breaker shown in FIGURE.2 and installed with an integral spacer according to one embodiment of the present invention. With respect to FIG.4, the contact fingers 2 are first inserted in a pole cage 1 against the springs 5. The integral spacer 3 is inserted in the contact fingers 2 from the top so that the walls of the spacer 3 are made to contact the surface of the pole cage 1. Then a bearing pin 4 is inserted from the sides. The gap between the bearing pin 4 and the integral spacer 3 is reduced. The gap between the integral spacer 3 and the wall of the pole cage 1 is also reduced to a minimum gap.
[0048] FIGURE. 5 illustrates an exploded perspective view of an air circuit breaker shown in FIGURE. 1 and installed with an integral spacer according to one embodiment of the present invention. With respect to FIG.5, an integral spacer 3 is provided inside the pole cage 1 of the air circuit breaker to assemble the finger contacts 2 in the air circuit breaker. The integral spacer 3 has a base formed integrally with molded walls at one surface. The walls are protruded from the base of the integral spacer 3 to form the individual spacers. The integral spacer 3 is fit exactly in a groove provided in the pole cage 1. The individual finger contacts 2 are inserted in the opening provided between the spacers against the pole springs 5. Each spacer wall has a hole so that the holes on all the spacer walls are aligned to receive a bearing pin 4. The bearing pin 4 is made to pass through the pole cage 1, contact fingers 2 and the spacers. The area of contact face of the spacer 3 is increased to avoid the buckling of the spacer 3 under the forces against the pole cage.


[0049] FIGURE. 6 illustrates a side sectional view of an air circuit breaker shown in FIGURE.2 and installed with an integral spacer according to one embodiment of the present invention. With respect to FIG.6, the contact fingers 2 are first inserted in a pole cage 1 against the springs 5. The integral spacer 3 is inserted in the contact fingers 2 from the top so that the walls of the spacer 3 are made to contact the surface of the pole cage 1. Then a bearing pin 4 is inserted from the sides. The gap between the bearing pin 4 and the integral spacer 3 is reduced. The gap between the integral spacer 3 and the wall of the pole cage 1 is also reduced to a minimum gap.
[0050] Thus the various embodiments of the present invention provide an integral spacer to transfer short circuit forces to the pole cage while maintaining position of fingers constantly and avoiding the bending of finger supporting pin. Thus the integral spacer has a simple structure and may be manufactured easily. The integral spacer apart from separating the contact fingers, supports bearing pin and transfer short circuit forces to pole cage to avoid the bending of fingers and pin and to maintain the position of fingers steady in case of very high forces also. The spacer also eliminates the need for molding thin walls in pole cage which is limitation of manufacturing in many cases. The integral spacer also simplifies assembly of pole to great extent. Moreover the spacer wall has sufficient thickness to avoid the buckling of the walls of the spacer.
G) ADVANTAGES OF THE INVENTION
[0051] The various embodiments of the present invention provide an integral spacer to transfer short circuit forces to the pole cage while maintaining position of fingers constantly and avoiding the bending of finger supporting pin. Thus the integral spacer has a simple structure and may be manufactured easily. The integral spacer apart from separating the contact fingers, supports bearing pin and transfer short circuit forces to pole cage to avoid the bending of fingers and pin and to maintain the position of fingers steady in case of very high forces also. The spacer also eliminates the need for molding thin walls in pole cage which is limitation of manufacturing in many cases. The integral spacer also simplifies assembly of pole to great extent. Moreover the spacer wall has sufficient thickness to avoid the buckling of the walls of the spacer.


Thus the integral spacer of this invention avoids the bending of bearing pin and the failure of pole in short circuit condition. The area at the contact face of the integral spacer is increased to avoid buckling of walls of spacer.
[0052] The integral spacer has a single component structure which may be manufactured easily. The integral spacer transfers short circuit forces to pole cage to avoid the bending of bearing pin. The spacing between the fingers is reduced. The position of the contact fingers with respect a pole cage is fixed. The area at contact face of integral spacer is increased to avoid buckling of spacer walls while transferring forces. The gap between the bearing pin and the integral spacer as well as the gap between the integral spacer and pole cage is kept minimum during assembly. The poles are assembled easily into the pole cage as the integral spacer is simply inserted in pole cage. The insertion of spacer in pole cage in wrong way is also avoided.
[0053] 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.
[0054] 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.
The detailed scope of the monopoly claimed for the invention shall be ascertained and provided at the time of filing of the Complete Specification.