Abstract
The present invention relates to a guided contact locking system for current limiting circuit breaker adapted to lock contacts in repelled open position to avoid re-striking of contacts. The system comprises plurality of contacts including stationary contact (12) operatively linked to moving contact (1) wherein the moving contact (1) being ergonomically designed, locking mechanism which includes modular driving section (3) receiving a holder means (2), plurality of pin means and plurality of actuation means. Plurality of pin means include fixed pin (4) and sliding pin (6) maintaining a predetermined mutual separation between themselves whereby the sliding pin (6) travels across the modular driving section (3) through a predetermined cut (10). The holder means (2) is operatively connected to the sliding pin (6) by means of plurality of link elements (8). The plurality of actuation means (5) operatively engages with the fixed and the sliding pins (4 and 6) so as to generate force on the sliding pin (6) directing towards or away from the fixed pin (4) for providing sufficient contact pressure and thereby torque so as to lock the moving contact (1) in repelled open position.
Specification
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention.- GUIDED LOCKING SYSTEM FOR CURRENT LIMITNG CIRCUIT BREAKER
2. Applicant (a) NAME: LARSEN & TOURBO LIMITED (b) NATIONALITY: An Indian Company (c) ADDRESS: L&T House, Ballard Estate, Mumbai 400 001 State of Maharashtra, India
3. PREAMBLE TO THE DESCRIPTION
State of Maharashtra, India
FIELD OF INVENTION
The present invention relates to an improved guided contact locking system for current limiting circuit breakers. More particularly, the invention relates to an improved guided contact locking system comprising improved contact locking mechanism to avoid fault re-striking in low voltage circuit breakers in short circuit condition by locking the moving contact in repelled open position.
BACKGROUND OF INVENTION
Generally, circuit breakers should have an arrangement to generate enough contact pressure so that in normal condition at rated current temperature rise of breaker should remain with in specified limits and at the same it should also work as per required by current limiting feature of the breaker.
At the time of short circuit, current flowing through stationary and movable contacts of breaker contact system is parallel but in opposite directions and this anti-parallel current through contacts creates a repulsive force on contacts .As stationary contact is firmly fixed so it cannot be moved by electromagnetic forces created by anti-parallel current in stationary and moving contacts. These electromagnetic forces also act upon moving contact and cause motion of moving contact. This moving contact moves on a locus which is product specific. Because of this movement of moving contact an arc gets generated between moving contact and fixed contact and in turn produces an arc voltage which acts opposite to the system voltage and limits the fault current and extinguishes the arc later on.
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Once repelled, it is desired that the moving contact should not come back towards the stationary contact in short circuit fault. One disadvantage is coming back of the moving contact would cause re-striking between the moving contact and the stationary contact which affect the electrical health of the other components / equipments connected to the power distribution system.
Thus there is a need to provide for an improved guided contact locking system for current limiting low voltage circuit breakers to avoid fault re-striking in circuit breakers in short circuit condition by locking the moving contact in repelled open position.
The present inventors have found that an improved guided contact locking system comprising a locking mechanism would provide enough contact pressure in ON condition which could keep the moving contact in repelled open position thereby avoiding re-striking of the moving and the stationary contacts.
OBJECTS OF INVENTION
One object of the present invention is to provide an improved guided contact locking system for current limiting circuit breakers.
Another object of the present invention is to provide a locking mechanism for locking the moving contact in repelled open position during short circuit.
Yet another object of the present invention is to provide enough contact pressure.
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SUMMARY OF INVENTION
According to one aspect of the present invention there is provided an improved guided contact locking system for current limiting circuit breakers adapted to lock contacts in repelled open position to avoid re-striking of contacts, said system comprising :
plurality of contacts including stationary contact operatively linked to moving contact wherein the moving contact being ergonomically designed and characterized in that the moving contact comprises moving contact button located in a predetermined manner;
locking mechanism including
modular driving section receiving a holder means , said holder means being mechanically coupled to the moving contact;
plurality of pin means assembled in the said driving section wherein said pin means comprises fixed pin and sliding pin whereby said sliding pin travels across the modular driving section through a predetermined cut provided in the driving section so as to allow the sliding pin to move to and fro; the fixed pin and the said holder means being pivoted to each other and the holder means being operatively connected to the sliding pin by means of plurality of link elements; and
plurality of actuation means operatively engaging the fixed and the sliding pin so as to generate force on the sliding pin directing towards or away from the fixed pin for providing sufficient contact pressure and thereby torque so as to lock the moving contact in repelled open position.
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DETAILED DESCRIPTION OF INVENTION
Guided locking system of the present invention is provided so that moving contact remains open and doesn’t come back or in other words it remains there locked open. By this locking it can be ensured that fault re-striking will not take place due to come back of moving contact toward stationary contact.
In one embodiment of the present invention the system comprises plurality of contacts which includes fixed contact operatively connected to moving contact wherein the moving contact comprises moving contact buttons provided superficially on the moving contact. The said moving contact is assembled to a holder means hereinafter referred to as contact holder which is received by the locking mechanism after a predetermined distance.
In another embodiment of the present invention the locking mechanism comprises plurality of pin means assembled in modular driving section having two limb portions separated parallely from each other by a predetermined gap so as to receive the contact holder. One pin out of this plurality of pins is fixed (hereinafter referred to as fixed pin) to the driving section passing through the limbs of the said section laterally. Another pin (hereinafter referred to as sliding pin) travels across the modular driving section through a predetermined cut provided in the driving section so as to allow the sliding pin to move to and fro. The contact holder is pivoted about the fixed pin and is operatively connected to the sliding pin by means of plurality of link elements.
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Yet in another embodiment of the present invention the link element comprises of ergonomical structures which are operatively hinged at one end with the contact holder and is pivoted at the other end with the sliding pin. The fixed and the sliding pins are engaged to each other by actuation means comprising springs (hereinafter referred to as extension springs) such that the extension spring elongates when in ON condition of breaker contact holder rotates in such a way that sliding pin is pushed away from fixed pin by links. This elongation of the extension spring generates pulling force Fi to the sliding pin gets transferred to contact holder by link elements. The force F1 passes through axis of hinge point on the contact holder and sliding pin. Force F1 creates a torque about axis of the fixed pin thereby rotating contact holder and moving contact in clockwise direction. The force F1 generates contact pressure between moving contact button and fixed contact.
During short circuit fault moving contact assembly with contact holder moves in such a way that force direction on contact holder because of the elongation of extension spring changes from one side to the other side of the rotation axis (Axis of fixed pin) of contact holder and this change causes torque in opposite direction and because of torque in opposite direction moving contact gets locked in this repelled open condition. In this invention the position of the contact can be maintained by a cut in driving part so that components don't slip off.
BRIEF DESCRIPTION OF ACCOMPANYING FIGURES
Figure 1 illustrates a front perspective view of locking mechanism with modular driving section (3).
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Figure 2 illustrates the side view of locking mechanism with driving section (3) hidden.
Figure 3 illustrates the side view of figure 1 with driving section (3) hidden and moving contact (1) is at the verge of toggling.
Figure 4 illustrates the side view of the locking mechanism with driving part (3) hidden and showing moving contact locked in toggled position.
DETAILED DESCRIPTION OF ACCOMPANYING FIGURES
Referring to figure 1 modular driving section (3) which can be used in single pole driveshaft or multi-pole driveshaft, is employing contact holder (2), links (8), fixed pin (4) and sliding pin (6). Moving contact (1), which can be single break per pole arrangement or multi-break per pole arrangement, is assembled on contact holder (2). Moving contact buttons (11) are fixed at both the ends of moving contact (1). Extension springs (5) ride on fixed pin (4) and sliding pin (6) . Sliding pin slides in a cut (10) . The cut (10) is designed in such a way that moving contact (1) position can be predefined in normal and repelled open condition of breaker. Contact holder (2) is pivoted on fixed pin (4) and links (8) are hinged at hinge point (9) on contact holder (2). The other end of links (8) is pivoted on sliding pin (6). The sliding pin (6) and the fixed pin (4) are mutually separated such the minimum distance between the axis of fixed pin (4) and sliding pin (6) is greater than the distance between the axis of two hooks of extension spring (5) in un-stretched condition and this leads to the elongation of extension springs (5) and because of this
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elongation, sliding pin (6) is always pulled toward fixed pin (4) by extension springs (5).
Referring to figure 2 extension spring (5) rides fixed pin (4) and sliding pin (6) . Extension spring (5) always pulls sliding pin (6) toward fixed pin (4) . The pulling force by extension spring (5) to sliding pin (6) gets transferred to contact holder (2) by links (8) and is shown as (F1) in figure 2. The force (Fi) passes through axis of hinge point (9) and sliding pin (6) . The force (Fx) creates a torque about axis of fixed pin (4) and tries to rotate contact holder (2) and moving contact (1) in clockwise direction. The force (F1) generates contact pressure between moving contact button (11) and fixed/stationary contact button (12).
Referring to figure 3, in short circuit fault condition an electro-magnetic force is created upon moving contact (1) and because of this electro-magnetic force moving contact (1) starts moving in anti-clockwise direction and so hinge point
(9) also starts moving in anti-clockwise direction and because of this movement sliding pin (6) is pushed away from fixed pin
(4) by links (8) . In motion of moving contact (1) in anticlockwise direction a moment comes when force (F2), created by elongation of spring (5) , passes through the axis of hinge point (9), sliding pin (6) and fixed pin (4) and at this moment torque because of the force (F2) about axis of pin (4) on moving contact (1) becomes zero and in this condition moving contact (1) is at the verge of toggling.
Referring to figure 4 elongation of extension spring (5) causes a force (F3) which passes through the axis of sliding pin (6) and hinge point (9) . The force (F3) gets transferred from sliding pin (6) to contact holder (2) by links (8) and
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this force (F3) creates a torque about axis of fixed pin (4) in anti-clockwise direction and opposes the comeback (rotation of moving contact (1) in clockwise direction) of moving contact (1) and keep moving contact (1) locked in this toggled condition.
The invention has been described in a preferred form only and many variations may be made in the invention which will still be comprised within its spirit. The invention is not limited to the details cited above. Other springs can be used linking the fixed and sliding pin to achieve the to and fro movement and still the invention can be performed. The structure and its improvement thus conceived is susceptible of numerous modifications and variations, all the details may furthermore be replaced with elements having technical equivalence. In practice the materials and dimensions may be any according to the requirements which will still be comprised within its true spirit.
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WE CLAIM
1. Guided contact locking system for current limiting circuit breaker adapted to lock contacts in repelled open position to avoid re-striking of contacts, said system comprising :
plurality of contacts including stationary contact operatively linked to moving contact wherein the moving contact being ergonomically designed and characterized in that the moving contact comprises moving contact button located in a predetermined manner;
locking mechanism including
modular driving section receiving a holder means , said holder means being mechanically coupled to the moving contact;
plurality of pin means assembled in the said driving section wherein said pin means comprises fixed pin and sliding pin maintaining a predetermined mutual separation between themselves
whereby said sliding pin travels across the modular driving section through a predetermined cut provided in the driving section so as to allow the sliding pin to move to and fro; the fixed pin and the said holder means being pivoted to each other and the holder means being
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operatively connected to the sliding pin by means of plurality of link elements; and
plurality of actuation means operatively engaging the fixed and the sliding pin so as to generate force on the sliding pin directing towards or away from the fixed pin for providing sufficient contact pressure and thereby torque so as to lock the moving contact in repelled open position.
2. System as claimed in claim 1, wherein the actuation means comprises extension springs.
3. System as claimed in claim 1, wherein the fixed pin and sliding pin being axially mutually separated such that the minimum distance between the axes of the pins is greater than the distance between the axes of two hooks of extension spring in un-stretched condition leading to elongation of the springs.
4. System as claimed in claims 1 to 3, wherein the extension spring is adapted to generate pulling force to the sliding pins so as to push the sliding pins away from the fixed pin.
5. System as claimed in claim 1, wherein the link element comprises of ergonomical structures operatively hinged at one end with the holder means and pivoted at the other end with the sliding pin so as to provide anti-clockwise and/or clockwise movement of the moving contact.
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6. System as claimed in any of preceding claims, wherein the link element being co-operatively connected to the extension spring and the holder means in a manner to co-axially align the force generated by the extension spring with axes of hinge point, sliding pin and fixed pin thereby providing zero torque adapted to toggle the moving contact to locked position.
7. System as claimed in any of preceding claims, wherein the link element is adapted to transmit the force of the extension spring passing through the axis of the sliding pin and hinge point thereby generating torque about the axis of fixed pin in anti-clockwise direction opposing rotation of moving contact in clockwise direction thereby keeping the moving contact locked in this toggled condition.
8. Guided contact locking system for current limiting circuit breaker substantially as herein described and illustrated with reference to the accompanying figures.
Dated this 3rd day of June 2006
Abhishek Sen
Of S. Majumdar & Co.
(Applicant's Agent)
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ABSTRACT
Title : GUIDED LOCKING SYSTEM FOR CURRENT LIMITING CIRCUIT BREAKER
The present invention relates to a guided contact locking system for current limiting circuit breaker adapted to lock contacts in repelled open position to avoid re-striking of contacts. The system comprises plurality of contacts including stationary contact (12) operatively linked to moving contact (1) wherein the moving contact
(1) being ergonomically designed, locking mechanism which includes modular driving section (3) receiving a holder means (2), plurality of pin means and plurality of actuation means. Plurality of pin means include fixed pin
(4) and sliding pin (6) maintaining a predetermined mutual separation between themselves whereby the sliding pin (6) travels across the modular driving section (3) through a predetermined cut (10). The holder means (2) is operatively connected to the sliding pin (6) by means of plurality of link elements (8) . The plurality of actuation means (5) operatively engages with the fixed and the sliding pins (4 and 6) so as to generate force on the sliding pin (6) directing towards or away from the fixed pin (4) for providing sufficient contact pressure and thereby torque so as to lock the moving contact (1) in repelled open position.
Figure 1.
