FORM 2
THE PATENTS ACT, 1970 COMPLETE SPECIFICATION
(See Section 10)
TORSION SPRING FOR FRICTIONLESS CONTACT LOCKING OF
SWITCHING DEVICE
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

TORSION SPRING FOR FRICTIONLESS CONTACT LOCKING OF
SWITCHING DEVICE
A) Technical field
[0001] The embodiments herein generally relate to switching device, and more specifically to the torsion spring used for locking arrangement of the contact system for current limiting circuit breaker.
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] Circuit breaker is used as protection device in switchgear as against the very high over current. The circuit breaker comprises a spring loaded contact system made of copper material to carry and break the current under abnormal conditions like very high over current. Under abnormal conditions circuit breaker is supposed to operate and break the electrical circuit rapidly so that the electrical system will have less stress and minimum damage of the circuit breaker contacts.
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[0004] Circuit breaker operates on current limiting principal that is when very high over current flows through circuit breaker contact system, magnetic repulsion occurs and contact gets separated. With the means of arc chute, arc gets quenched and current breaks. Since the contact system is spring loaded, during said separation the contacts may bounce back and restore the current which leads to its damage. A contact locking is required to avoid this. Contact separation action should be fast enough so that arc quenching will be quick. To achieve faster contact separation there should be friction less contact separation action. Moving contact should be spring loaded without any supporting component.
[0005] U.S. Patent No. 4,140,986 discloses a circuit breaker switch. Invention provides an improved circuit breaker for periodic current which, when the current intensity exceeds a predetermined magnitude, permits a circuit breaking operation only in a predetermined synchronism with the phase of the current.
[0006] U.S. Patent No. 4,368,444 discloses a low-voltage protective circuit breaker with locking lever. Invention provides a circuit breaker including a locking lever pivotably mounted in the housing of the circuit breaker and engaging the handle to be moved thereby and provided with means to engage the carrier when the handle is moved toward the "off position if the carrier is locked on its "on" position by welding of the fixed and movable contacts together.
[0007] German Patent number DEI 02 39 641 B3discloses a contact system for
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a low voltage switch, in particular a power switch, with electro-dynamically effected contact opening and with a pressure spring that is compression spring which provides contact force and tilt jump, which is arranged between a bearing position in the housing and a point of action on the contact arm.
[0008] While the conventional solutions are advantageous for their intended purposes, torsion spring has not been utilized for fnctionless and faster locking mean.
[0009] Hence, there is a need to develop a system and method with torsion spring which can provide faster contact separation action and fnctionless locking arrangement to current limiting circuit breaker.
C) Object of the invention
[0010] An object of the invention is to provide fnctionless locking arrangement for current limiting circuit breaker.
[0011] Another object of the invention is to provide fast contact separation action for current limiting circuit breaker during abnormal conditions like very high over current.
[0012] Yet another object of the invention is to provide torsion spring which can provide additional force to magnetic repulsion force for locking the
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contacts during contact separation action.
D) Summary
[0013] The embodiments herein provide a system and method for frictionless locking arrangement for current limiting circuit breaker. A torsion spring is assembled between the slot of moving contact and driveshaft. In abnormal condition like very high over current, torsion spring generates addition force to lock the contact in separated position. The present embodiment can be utilized for the contact system of double break type like fork type contact arrangement as well as for single break type with one or multi-fingers.
[0014] 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.
E) Brief description of the drawings
[0015] The embodiments herein will be better understood from the following
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detailed description with reference to the drawings, in which:
[0016] FIG. 1 illustrates contact system arrangement in driveshaft by means of the springs and pin according to an embodiment herein;
[0017] FIG. 2 is side view of the FIG. 1 which illustrates position of the assembled contact and spring when circuit breaker is closed;
[0018] FIG. 3 illustrates position of assembled contact and spring after the magnetic repulsion of the contact where the contacts are in locked position;
[0019] FIG.4 illustrates shape of torsion spring.
F) Detailed description of the Invention:
[0020] 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
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limiting the scope of the embodiments herein.
[0021] A preferred embodiment provides a system and method for frictionless contact locking for current limiting circuit breaker. Torsion spring is used for faster contact separation and frictionless locking. Moving contact of circuit breaker is pivoted in the driveshaft by means of rod. Torsion spring is assembled between slot of moving contact and driveshaft that generates the pressure to ensure the good electrical connection between the contact systems. One arm of the torsion spring is rested in the driveshaft slot and other arm exerts force on the moving contact slot During very high over current, contacts separate against the spring force due to magnetic repulsion. During this action torsion spring arm bends up to certain angle along changing the force direction. When force direction crosses the contact axis, spring force adds to the magnetic repulsion force. In this condition torsion spring generates the force to lock the contact in separated position.
[0022] FIG. 1 schematically illustrates the driveshaft assembly of the circuit breaker. Contact system 102 formed from copper material is pivoted to the holes in the driveshaft 106 by means of metal pin 108. Contact system 102 is always under mechanical pressure due to torsion spring 104.
[0023] FIG. 2 illustrates side view of the FIG. 1. FIG. 2 illustrates position of the assembled contact and spring when circuit breaker is closed. The contact system 102 is pivoted to the driveshaft 106 by mean of metal pin 108 which always remains under mechanical pressure by means of torsion spring 104. One
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arm of spring 104 is attached to driveshaft 106 and other exerts force on the moving contact 102. Direction of torsion force produced by spring is designated by 'F in FIG. 2.
[0024] FIG. 3 illustrates position of assembled contact and spring after the magnetic repulsion of the contact where contacts are in locked position. When very high current flows through the circuit breaker contacts gets separated due to the magnetic repulsion between the moving contact and fixed contact. One arm of torsion spring 104 bends up to a certain angle. When torsion spring force ‘F' crosses dead centre by changing position, contact system 102 gets locked in separated position as shown in FIG. 3.
[0025] FIG. 4 illustrates the shape of the torsion spring 104 used in embodiments. Closed loop of the torsion spring 104 is engaged in slot of the moving contact 102. Free arms of torsion spring 104 are coupled with driveshaft 106 as shown in FIG. 2 and FIG. 3. The spring parameters are designed as per the contact system design requirement.
[0026] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by 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
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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 contact locking system for current limiting circuit breaker for faster
contact separation action and frictionless locking comprising:
a torsion spring that provides additional force to lock contacts in separated position, wherein torsion spring is assembled between the slot of the moving contact and driveshaft that generates the pressure to ensure the good electrical connection between the contact systems; and contact system of circuit breaker pivoted in the driveshaft by means of rod, wherein circuit breaker contacts gets separated due to magnetic repulsion between said moving contact and fixed contact when very high current flows through.
2. The system of claim 1, wherein one arm of said torsion spring is coupled
in driveshaft slot and other arm exerts force on the moving contact slot
to provide frictionless mechanism.
3. The system of claim 1, wherein closed loop of said torsion spring is engaged in slot of said moving contact.
4. The system of claim 1, wherein one arm of torsion spring engaged with moving contact bends up to certain angle when very high current flows through the circuit breaker resulting in change of spring force, wherein
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said spring force adds to said magnetic repulsion force to lock the contact in separated position.
5. A method for providing frictionless contact locking system coupled with torsion spring for current limiting circuit breaker, providing additional spring force along with magnetic repulsion force to lock the contact in separated position to ensure faster contact separation and frictionless locking.
6. A method of claim of claim 6, wherein one arm of torsion spring engaged with moving contact bends up to certain angle when very high current flows through the circuit breaker resulting in change of spring force, wherein said spring force adds to the magnetic repulsion force to lock the contact in separated position.
Dated this the 28™ 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 system and method for frictionless contact locking for current limiting circuit breaker. In the preferred embodiment torsion spring is used for faster contact separation and frictionless locking. Moving contact of circuit breaker is pivoted in the driveshaft by means of rod and torsion spring is assembled between the slot of the moving contact and driveshaft that generates the pressure to ensure the good electrical connection between the contact systems. One arm of the torsion spring is rested in the driveshaft slot and other arm exerts force on the moving contact slot. During very high over current, contacts separate against the spring force due to magnetic repulsion. Torsion spring arm bends up to certain angle along changing the force direction adding additional spring force to magnetic repulsion force.
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