A) TECHNICAL FIELD
[0001 ] The present invention generally relates to circuit breakers and particularly relates to the plug-in contacts of circuit breakers. The present invention more particularly relates to the plug-in contacts for providing the required contact pressure based on the current rating of the circuit breaker with less spring force.
B) BACK GROUND 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 circuit 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. By making the moving contact to touch the stationary contact, an electric current flows and the breaker is closed. By driving the moving contact away from the stationary contact, an electric arc develops. Further, by quenching the electric arc, the current flow stops and the breaker is opened.
[0003] In the existing technique, the plug-in contacts deliver the required contact pressure using a spring, which is greater than or equal to the required contact

pressure. Further in the existing technique, the higher contact pressure is achieved either by using a bigger spring or increasing the number of springs for the plug-in contacts. The springs used for delivering higher contact pressure causes the one or more components in the circuit breakers to experience higher stress, due to which the life of the contact deteriorates. The hugeness of the springs results in dimensional constraints and also limits the contact pressure.
[0004] The one or more components are joined together in the circuit breakers through a spring force or the bolted joints. The components are joined together for maintaining an electrical connectivity between the components. A tremendous force is applied to join the one or more components but the components carmot be merged as the contact area of the one or more components differs from each other. Further the lower contact area of the one or more components leads to higher resistance thereby a circuit consisting of more joints will have higher resistance as compared to the circuit consisting of fewer joints. An increase in resistance in the circuit in turn increases the temperature. Further as the number of joints increases in the circuit, the I^R losses increases, due to which the temperature of the product also increases.
[0005] Another technique discloses that a plurality of components is used in the circuit breaker to bring down the temperature thereby increasing the mass of the system. Further due to the plurality of components used in the circuit breaker, the maintenance cost also increases.

[0006] Thus there is a need for a plug in contact system to generate a required contact pressure in the circuit breakers with comparatively less spring force.
[0007] The above mentioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.
C) OBJECT OF THE PRESENT INVENTION
[0008] The primary object of the present invention is to provide a plug in contact system for the circuit breakers that provides a required contact pressure with less spring force.
[0009] Another object of the present invention is to provide a plug-in contact system with a predefined profile to dissipate heat generated in the circuit breaker
[0010] Yet another object of the present invention is to provide a plug in contact system with less number of electrical contact joints.
[0011] Yet another object of the present invention is to provide a plug-in contact system with a simple spring design.

[0012] Yet another object of the present invention is to provide a plug-in contact system adapted to generate the required contact pressure on the fixed contact assembly and the moving contact assembly.
[0013] Yet another object of the present invention is to provide a plug-in contact system to generate contact pressures at definite prescribed points.
[0014] Yet another object of the present invention is to provide a plug-in contact system to avoid stresses exerted on the components of the circuit breaker by reducing the spring force.
D) SUMMARY OF THE INVENTION
[0015] The various embodiments of the present invention provide a plug-in contact system for circuit breakers. The plug- in contact system includes a fixed contact assembly, a moving contact assembly, a connecting leaf assembly, a finger proof pin and a circular spring. The finger proof pin is adapted to interconnect the moving contact assembly with the connecting leaf assembly, The circular spring is used to interconnect the fixed contact assembly with the connecting leaf assembly. Further the circular spring is designed such that the spring force at one point produces contact pressures higher than the spring force applied.

[0016] According to one embodiment of the present invention, the plug-in contact system for circuit breakers includes a plug-in base on which the fixed contact assembly and the connecting leaf assembly are attached.
[0017] According to one embodiment of the present invention, the connecting leaf assembly includes at least one connecting leaf which contacts over the surface of the moving contact assembly and the fixed contact assembly.
[0018] According to one embodiment of the present invention, the plug-in contact system for circuit breakers includes the circular spring coupled to the connecting leaf assembly that is adapted to generate the required contact pressure on the fixed contact assembly and the moving contact assembly.
[0019] According to one embodiment of the present invention, the connecting leaf assembly includes a pre-defined profile for transferring the contact pressure produced higher than a spring force applied. The. predefined profile of the connecting leaf assembly is adapted to touch the fixed contact assembly on an inner side of the at least one connecting leaf.
[0020] According to one embodiment of the present invention, the predefined profile of the connecting leaf assembly is such that the contact pressures are generated at definite prescribed points. The predefined profile of the connecting leaf

assembly provides a spherical surface for higher heat dissipation thereby reducing temperature rise of contacts at higher currents.
[0021 ] According to one embodiment of the present invention, the finger proof pin is snap fitted with the fixed contact assembly to prevent contact with live parts. The finger proof pin is made up of an electrically insulating material.
[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.
E) BMEF DESCRIPTION OF THE DRAWINGS
[0023] 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:
[0024] FIG. 1 illustrates the exploded perspective view of one or more components in a plug-in contact system according to one embodiment of the present invention.

[0025] FIG. 2 illustrates the assembled and cut away sectional view of the plug-in contact system according to one embodiment of the present invention,
[0026] FIG.3 illustrates the sectional view of the plug-in contact system indicating the point of application of spring force and points of contacts of pressure generation according to one embodiment of the present invention.
[0027] FIGS.4A-4C illustrate a sectional view of the plug-in contact system indicating the working of the plug-in contact system, according to one embodiment of the present invention.
[0028] FIG.5 illustrates a top side perspective view indicating the mounting on the plug-in base with finger proof pin, according to one embodiment of the present invention.
[0029] Although the 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
[0030] In the following detailed description, a 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.
[0031] The various embodiments of the present invention provide a plug-in contact system for circuit breakers. The plug- in contact system includes a fixed contact assembly, a moving contact assembly, a connecting leaf assembly, a finger proof pin and a circular spring. The finger proof pin is adapted to interconnect the moving contact assembly with the connecting leaf assembly. The circular spring is used to interconnect the fixed contact assembly with the connecting leaf assembly. Further the circular spring is designed such that the spring force at one point produces contact pressures higher than the spring force applied.
[0032] FIG. 1 illustrates the exploded perspective view of the plug-in contact system, according to one embodiment of the present invention. The one or more components in the plug-in contact system includes a moving contact assembly 102, a finger proof pin 104, a connecting leaf assembly 106, a circular spring 108, and a fixed contact assembly 110. The finger proof pin 104 is adapted to interconnect the moving contact assembly 102 with the connecting leaf assembly 106. The circular spring 108 is used to interconnect the fixed contact assembly 110 with the connecting

leaf assembly 106. Further the circular spring 108 is designed such that the spring force at one point produces contact pressures higher than the spring force applied. The connecting leaf assembly 106 includes at least one connecting leaf which contacts over the surface of the moving contact assembly 102 and the fixed contact assembly 110.
[0033] The fixed contact assembly 110 is rigidly connected to the Plug-in base on which the connecting leaf assembly 106 is held together by the circular spring 108 at one end. The plug- in contact system is designed in such a way that the required contact pressure is achieved by applying a lesser spring force. Further, due to the lesser spring force applied, the unnecessary stress on the one or more components in the plug-in contact system are eliminated.
[0034] FIG. 2 illustrates the assembled and cut away sectional view of a plug-in contact system, according to one embodiment of the present invention. The one or more components in the plug-in contact system includes the moving contact assembly 102, the finger proof pin 104, the connecting leaf assembly 106, the circular spring 108, and the fixed contact assembly 110.
[0035] The connecting leaf assembly 106 includes at least one connecting leaf, which contacts over the surface of the moving contact assembly 102 and the fixed

contact assembly 110. The connecting leaf assembly 106 includes a pre-defined profile for transferring the contact pressure produced higher than a spring force applied. Further, the pre-defined profile of the connecting leaf assembly 106 is designed in such a way that it touches the fixed contact assembly 110 on an inner side of the at least one connecting leaf The circular spring 108 holds the connecting leaf components at one end and the other end of the connecting leaf assembly 106 produces the required contact pressure on the moving contact assembly 102 and the fixed contact assembly 110.
[0036] FIG.3 illustrates a sectional view of the plug-in contact system with the spring force applied point and contact pressure generated points, according to one embodiment of the present invention, while the FIGs.4A-4C illustrate a sectional view indicating the operation and the working of the plug-in contact system at various stages, according to one embodiment of the present invention. With respect to FIG.3 and FIGs.4A-4C, the fixed contact assembly 110 is electrically connected to the moving contact assembly 102 through the contact points. The contact points on the fixed contact assembly 110 provide a higher contact area. Further, when the moving contact assembly 102 is plugged, the moving contact pushes the connecting leaf assembly 106 against the spring force. The plug- in contact system further includes a plug-in base on which the fixed contact assembly 110 and the connecting leaf assembly 106 are attached.

[0037] The circular spring 108 is designed such that the spring force 302 at one point produces contact pressures higher than the spring force 302 applied. The circular spring 108 holds the connecting leaf assembly 106 at one end and the other end of the connecting leaf assembly 106 produces the required contact pressure on the fixed contact assembly 110 and the moving contact assembly 102. The connecting leaf assembly 106 includes a pre-defined profile for transferring the contact pressure produced higher than a spring force applied.
[0038] The predefined profile of the connecting leaf assembly 106 is designed in such a way that the contact pressures are generated at definite prescribed points. The contact pressure is generated on the fixed contact assembly 110 at the prescribed points 304 and the contact pressure is generated on the moving contact assembly 102 at the prescribed points 306. Further, the predefined profile of the connecting leaf assembly 106 provides a spherical surface for higher heat dissipation thereby reducing temperature rise of contacts at higher currents.
[0039] The connecting leaf assembly 106 includes four connecting leaf components that ensure the proper contact over the cylindrical surface of moving contact assembly 102 and fixed contact assembly 110. The spherical profile of the connecting leaf assembly 106 transfers the higher force and also enables higher heat dissipation. The predefined profile of the connecting leaf assembly 106 provides a

spherical surface for higher heat dissipation thereby reducing the temperature rise of contacts at higher currents.
[0040] Let us consider a simply supported beam with a force F2 at distance
x/3 from Fi and x from F3. Taking moment about Fi

[0041] From the above derivation, let us consider that the forces Fi, F2, F3 are the contact pressure 306 on the moving contact 102, the contact pressure 304 on the fixed contact 110 and the spring force 302 respectively. It is evident from the equation that the applied spring force F3 is lesser than the contact pressures Fi generated on the moving contact assembly 102 and the contact pressures F2 generated the fixed contact assembly 110.

[0042] FIG.5 illustrates a top side perspective view indicating the mounting of the plug-in contact system on the plug-in base with finger proof pin 104, according to one embodiment of the present invention. The plug-in contact system is assembled on the plug-in base on which the fixed contact assembly 110 and the connecting leaf assembly 106 are attached. Further, the finger proof pin 104 is snap fitted with the fixed contact assembly 110 to prevent contact with live parts. The finger proof pin 104 is snap fitted to the fixed contact assembly 110 so that the head of the finger proof pin 104 covers the top face of the connecting leaf assembly 106. Further the head of the finger proof pin 104 allows the access only to the mating surface, which can be accessed only by the moving contact assembly 102. The finger proof pin 104 also restricts the upward movement of the connecting leaf assembly 106 and guides the moving contact assembly 102 to get connected with the coimecting leaf assembly 106. The finger proof pin is made up of an electrically insulating material.
[0043] Further since the moving contact 102 is assembled on the circuit breaker, the current carrying parts such as the connecting leaf assembly 106 and the fixed contact assembly 102 comes under the head of the finger proof pin 104. The projection above the head of the finger proof pin 104 and the side wall around the plug-in contact provides a clearance through which the operator cannot access to the live parts.
G) ADVANTAGES OF THE INVENTION

[0044] The present invention provides provide a plug-in contact system for circuit brealcers.
[0045] The embodiments disclosed provide a mechanical advantage by generating contact pressure at both the contact points using a very less spring force.
[0046] The present invention provides the circular spring that is used to produce the contact pressure which is very simple to design and manufacture. Further the predefined profile of the connecting leaf assembly provides a spherical surface for higher heat dissipation thereby reducing temperature rise of contacts at higher currents.
[0047] According to one embodiment of the present invention, the initial plug-in force required is reduced to half because of the chamfered inner edge of the moving contact. Further the line contact in the present invention ensures that the proper contact pressure is achieved.
[0048] The plug-in contact system, according to the embodiment of the present invention, exerts a lower spring force as compared to the essential contact pressure. Thus the plug in contact of the present invention efficiently reduces the temperature rise of the Plug-in contacts thereby increasing the life and performance of the breaker.

[0049] The present invention provides the finger proof pin that is used to avoid accidental contact with the live parts of the circuit breaker.
[0050] 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.
[0051 ] It is also to be understood that the following claims are intended to cover all of the generic and specific features of the present invention described herein and all the statements of the scope of the invention which as a matter of language might be said to fall there between.

CLAIMS
What is claimed is:
1. A plug-in contact system for circuit breakers, the plug-in contact system
comprising:
a fixed contact assembly;
a moving contact assembly;
a connecting leaf assembly;
a finger proof pin adapted to intercormect the moving contact assembly with
the connecting leaf assembly; and
a circular spring to interconnect the fixed contact assembly with the
connecting leaf assembly;
Wherein the circular spring holds the connecting leaf assembly to produce a
high contact pressure on both the moving contact assembly and the fixed
contact assembly
2. The system according to claim 1, further comprising a plug-in base on which the fixed contact assembly and the connecting leaf assembly are attached.
3. The system according to claim 1, wherein the connecting leaf assembly includes at least one connecting leaf which contacts over the surface of the moving contact assembly and the fixed contact assembly.

4. The system according to claim 1, wherein the circular spring coupled to the connecting leaf assembly is adapted to generate the required contact pressure on the fixed contact assembly and the moving contact assembly.
5. The system according to claim I, wherein the connecting leaf assembly includes a pre-defined profile for transferring the contact pressure produced higher than a spring force applied.
6. The system according to claim 5, wherein the predefined profile of connecting leaf assembly is adapted to touch the fixed contact assembly on an inner side of the at least one connecting leaf.

7. The system according to claim 5, wherein the predefined profile of the connecting leaf assembly is such that the contact pressures are generated at definite prescribed points.
8. The system according to claim 5, wherein the predefined profile of the connecting leaf assembly has a spherical surface for higher heat dissipation thereby reducing temperature rise of contacts at higher currents.
9. The system according to claim 1, wherein the finger proof pin is snap fitted with the fixed contact assembly to prevent contact with live parts.

10. The system according to claim 1, wherein the finger proof pin is made up of an electrically insulating material.