FORM 2
THE PATENTS ACT, 1970 COMPLETE SPECIFICATION
(See Section 10)
COUPLING ARRANGEMENT FOR THE CIRCUIT BREAKER
CONTACT SYSTEM
Numbered as dated
INVENTORS:
a) AMOL. L. SUTAR
APPLICANT:
M/s. LARSEN & TOUBRO LIMITED
L&T House, Ballard Estate, P.O. Box No 278,
Mumbai, 400 001, Maharashtra,
INDIA
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THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
NATURE OF THE INVENTION

COUPLING ARRANGEMENT FOR THE CIRCUIT BREAKER
CONTACT SYSTEM
A) Technical field
[0001] The embodiments herein generally relate to current limiting circuit breaker, and more specifically to a coupling arrangement of the fork type contact system.
B) Background
[0002] Circuit breaker is an automatically as well manually operated electrical switching device used for protection in switchgear against the very high over current. In low voltage power system, generally the current limiting principal is used in the circuit breaker to operate against the very high over current fault.
[0003] The circuit breaker with fork type contact system which can be termed as double break contact system is used mainly for application with system where operating voltage is more than 415 volts and is up to 1000 volts. The fork type contact system breaks the electric circuit in two separate arc extinguishing section in each pole of circuit breaker.
[0004] The following U.S. patents and publications, the complete disclosures of which, in their entireties, are herein incorporated by reference provide some
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conventional solutions to coupling arrangement for the circuit breaker. U.S. Patent No. 6,771,151 discloses device for arranging the actuating shaft of a low-voltage circuit-breaker and multipole low-voltage circuit breaker with a device for arranging the actuating shaft. The invention discloses a bearing assembly such that the switching shaft, which is already prepositioned in its installed position and is provided with the coupling levers, is mounted at the point where the switching forces act.
[0005] U.S. Patent No. 4,211,906 discloses a rotary actuating device for low-voltage circuit breakers with toggle lever. Invention provides fork-shaped lever with a sliding system which is guided radially relative to the fulcrum of the lever and which a head piece having an opening for accepting the end of the toggle lever and a spherical surface for cooperating with the slider.
[0006] U.S. Patent No. 4,211,906 discloses a low-voltage protective circuit breaker with a forked locking lever. Invention discloses a low voltage protective circuit breaker with an actuating lever that can be moved by an operating handle and is connected by means of a drive spring and two toggle levers to a control shaft on which movable contacts for the circuit breaker are mounted.
[0007] In case of circuit breaker with double contact system, a mechanical pressure is required for each pole that is equally distributed on the two limbs contact surfaces between moving and fixed contacts. The unequal mechanical pressure on two contact limbs would have adverse effect on the electrical conductivity which can deteriorate the electric contact joint further leading to
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overheating of the conducting path over the period of time.
[0008] While the conventional solutions are advantageous for their limited intended purposes, however it does not provide adequate solution for high rating circuit breakers where the contact cross section is larger.
[0009] Hence, there is a need to develop a coupling arrangement wherein moving contacts can rotate clockwise & counter clockwise which would distribute the equal mechanical pressure on both fixed contacts.
C) Object of the Invention
[0010] An object of the invention is to provide coupling arrangement for circuit breaker contact system.
[0011] Another object of the invention is to provide a coupling arrangement for circuit breaker in which the structure of the movable contacts and their connection to the switchgear allows to improve the distribution of mechanical stresses and to avoid adverse effect on the electrical conductivity which deteriorates the electric contact joint further leading to overheating of the conducting path.
[0012] Yet another object of the embodiment is to provide a coupling arrangement of the fork type contact system wherein for each pole mechanical
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pressure can be distributed equally on the two limbs contact surfaces between moving and fixed contacts.
D) Summary
[0013] The embodiments herein provide a system and method for the coupling arrangement for a circuit breaker. In one embodiment a pin is fixed to fork shaped copper contact by means of welded joint at one end and the other end is coupled with a hollow tube. The hollow tube comprises a through hole perpendicular to its plane to pivot it in the driveshaft of the circuit breaker by means of the small rod. Another end of the hollow tube is connected to set of the compression spring for generating mechanical pressure. The end portion of the pin is threaded which is attached to the hollow tube with the means of nut such that the pin with fork shaped copper contact is free to rotate in both clockwise and counterclockwise direction.
[0014] In another embodiment, a pin is fixed to fork shaped copper contact by means of welded joint at one end and the other end is coupled with a hollow tube. A portion of the pin comprises the through slot in which another small pin is fixed perpendicular with its plane. The hollow tube comprises a through hole perpendicular to its plane to pivot it in the driveshaft of the circuit breaker by means of the small rod. At the end portion of hollow tube where first pin is attached, has an oblong through slot to guide the fixed small pin such that first pin with copper contact is free to rotate in both clockwise and
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counterclockwise direction. Another end of the hollow tube is connected to set of compression spring for generating mechanical pressure.
[0015] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.
Brief description of the drawings
[0016] The embodiments herein will be better understood from the following detailed description with reference to the drawings, in which:
[0017] FIG. 1 illustrates one of the coupling arrangements for the fork type contact system according to an embodiment herein;
[0018] FIG.2 is the side section view of the FIG .l;
[0019] FIG.3 is the exploded view of coupling arrangements shown in FIG. 1;
[0020] FIG.4 illustrates a coupling arrangement for the fork type contact system according to another embodiment of the invention;
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[0021] FIG.5 is the side section view of FIG. 4;
[0022] FIG.6 is the exploded view of coupling arrangements shown in FIG. 4;
[0023] FIG.7 is the section view of FIG. 4 at particular rotational position of the contact;
[0024] FIG.8 is the section view of FIG. 4 at another rotational position of the contact.
E) Detailed description
[0025] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0026] A preferred embodiment provides a system and method for the Coupling
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arrangement for a fork type circuit breaker. In the embodiment a pin is attached to fork shaped copper contact by means of welded joint at one end. The other end of the pin is coupled with a hollow tube. The hollow tube comprises a through hole perpendicular to its plane to pivot it in the driveshaft of the circuit breaker by means of the small rod. Another end of the hollow tube is connected to set of the compression spring for generating mechanical pressure. The end portion of the pin is threaded which is attached to the hollow tube with the mean of nut such that the pin with fork shaped copper contact is free to rotate in both clockwise and counterclockwise direction.
[0027] In another embodiment, a pin is attached to fork shaped copper contact by means of welded joint at one end. Other-end of the pin is coupled with a hollow tube. A portion of the pin comprises the through slot in which another small pin is fixed perpendicular with its plane. The hollow tube comprises a through hole perpendicular to its plane to pivot it in the driveshaft of the circuit breaker by means of the small rod. At the end portion of hollow tube where first pin is attached, has an oblong through slot to guide the fixed small pin such that first pin with copper contact is free to rotate in both clockwise and counterclockwise direction. Another end of the hollow tube is connected to set of the compression spring for generating mechanical pressure.
[0028] FIG. 1 schematically illustrates coupling arrangement for the fork type contact system 100 according to one embodiment. The fork shaped contact formed from the copper material 102 is connected to one end of pin 104. Other end of pin 104 is coupled with in hollow tube 106 so that it is free
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to rotate in clockwise and counterclockwise direction. Hollow tube 106 comprises a through hole 110 perpendicular to its plane to pivot it in the driveshaft of the circuit breaker.
[0029] FIG. 2 shows the detailed arrangement of one embodiment. FIG. 2 is side section view of the FIG. 1. Pin 104 is connected to fork shaped contact 102 formed from copper at one end by means of welding or brazing process, so that the assembly becomes homogeneous. The opposite end of pin 104 has threading where hollow tube 106 is connected by means of nut 108. The hollow tube 106 comprises a through round hole 110 by which the contact assembly is pivoted in the driveshaft of the circuit breaker.
[0030] FIG. 3 is the exploded view of the coupling arrangements for the fork type contact system shown in FIG. 1. The nut 108 is inserted from the open end of hollow tube 106 and is also connected with pin 104 through threading.
[0031] FIG. 4 schematically illustrates another embodiment of coupling arrangements for the fork type contact system 200. Fork shaped contact 202 formed from copper material is connected to the pin 204. Pin 202 is coupled with hollow tube 206 so that it is free to rotate in clockwise and counterclockwise direction. The special spring washer 210 is inserted between hollow tube 206 and the pin 204 to take care of the manufacturing variation. Hollow tube 206 comprises a through hole 212 perpendicular to its plane to pivot it in the driveshaft of the circuit breaker!
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[0032] FIG.5 shows the detailed arrangement of second embodiment. The pin 204 is connected to fork shaped contact 202 formed from copper at one end by means of welding or brazing process. The opposite end of pin 204 has a hole perpendicular to its axis where a small pin 208 is fixed. The hollow tube 206 is further connected to the pin 204. Hollow tube 206 comprises a through slot 212 perpendicular to its axis in which pin 208 is guided to have rotation of the contact 202 in clockwise as well as counterclockwise direction. Hollow tube 206 comprises on through round hole by which the contact assembly is pivoted in the driveshaft of the circuit breaker.
[0033] FIG. 6 is the exploded view of second embodiment of coupling arrangements for the fork type contact system shown in FIG. 4. The special spring washer 210 is trapped between hollow tube 206 and the pin 204 to take care of the manufacturing variations.
[0034] FIG. 7 is the section view of the FIG. 4 where fork shaped contact 202 rotates in clockwise direction and the while small pin 208 moves in the slot of hollow tube 206.
[0035] FIG. 8 is the section view of the FIG. 4 where fork shaped contact 202 rotates in counter-clockwise direction and the while the small pin 208 moves in the slot of hollow tube 206.
[0036] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by
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applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the appended claims.
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CLAIMS
What is claimed is:
1. A coupling system for fork shaped circuit breaker contact system wherein the moving part of contact system is adapted for both clockwise & counter clockwise rotational movement which distributes the equal mechanical pressure on both fixed contacts. The coupling system comprises of a pin that is fixed to the fork shaped contact at one end and other end of the pin is coupled with a hollow tube.
2. The system of claim 1, wherein said pin is connected to the fork shaped contact at one end by means of welding or brazing process to design homogeneous assembly.
3. The system of claim 1, wherein said pin is coupled with hollow tube at opposite end by means of a nut or small pin which is fixed perpendicular with its plane.
4. The system of claim 3, wherein said nut is inserted from the open end of said hollow tube and connects threaded portion of other pin that is connected to said fork shaped contact.
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5. The system of claim 1, wherein said pin is adapted to rotate in clockwise and counterclockwise direction which distributes the equal mechanical pressure on both fixed contacts
6. The system of claim 1, wherein said hollow tube comprises a through hole perpendicular to its plane to pivot it in the driveshaft of the circuit breaker.
7. The system of claim 1, wherein said hollow tube is connected to set of
the compression spring at one end for generating mechanical pressure.
8. A method of distributing equal mechanical pressure on the two limbs contact surfaces between moving and fixed contacts in a circuit breaker with double contact system, wherein the moving part of contact system is adapted for both clockwise & counter clockwise rotational movement.
9. A method of claim 8, wherein a coupling system is provided for fork shaped circuit breaker contact system, wherein said coupling system comprises of a pin that is fixed to the fork shaped contact at one end and a hollow tube, which is couple to opposite end of the pin.
10. The system of claim 9, wherein said pin is connected to the fork shaped contact at one end by means of welding or brazing process.
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11. The system of claim 9, wherein said pin is coupled with hollow tube at the opposite end by means of a nut or small pin which is fixed perpendicular with its plane.
12. The system of claim 9, wherein said pin is adapted to rotate in clockwise and counterclockwise direction which distributes the equal mechanical pressure on both fixed contacts
13. The system of claim 9, wherein said hollow tube comprises a through hole perpendicular to its plane to pivot it in the driveshaft of the circuit breaker.
14. The system of claim 9, wherein said hollow tube is connected to set of the compression spring at one end for generating mechanical pressure.
Dated this the 28TH day of March, 2007

Rakesh Prabhu,
Patent Agent, ALMT Legal,
No.2, Lavelle Road, Bangalore-560 001, INDIA
To,
The Controller of Patents,
The Patent office,
At Mumbai
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Abstract
A coupling arrangement for fork type circuit breaker contact system wherein the moving part of contact system is adapted for both clockwise & counter clockwise rotational movement to distribute the equal mechanical pressure on both fixed contacts. The coupling system comprises of a pin that is fixed to the fork shaped contact at one end by means of welding or brazing process. Other end of the pin is coupled with a hollow tube by means of a nut or small pin which is fixed perpendicular with its plane. The other end of hollow tube is connected to set of the compression spring for generating mechanical pressure. Hollow tube comprises a through hole perpendicular to its plane to pivot it in the driveshaft of the circuit breaker.
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