FORM2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention. -
SINGLE TORSION SPRING FOR RELEASE MECHANISM IN
CIRCUIT BREAKER
2. Applicant(s)
(a) NAME : LARSEN & TOUBRO 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
The following specification particularly describes the invention and the manner in whichIt is to be performed :

Field of Invention
The present invention relates to a single torsion spring adapted for release mechanism of moulded case circuit breaker. More particularly, it relates to a single torsion spring adapted for release mechanism of moulded case circuit breaker and capable of generating two different opposition torques with different values on different links of the release mechanism.
Background Art
The circuit breaker consists of a main mechanism and the release mechanism. Main mechanism is basically active in ON and OFF (RESET) positions of the breaker, whereas the release mechanism is responsible for the working of the main mechanism in ON and OFF (RESET) positions and bringing the breaker to TRIPPED position by making the main mechanism inactive,
US645S059B1 teaches a return spring comprising fixed first end and moveable second end. So, in US6459059B1 only one arm of the spring is moving and applying force normal to the contact surface of the roller. There is no arrangement in US6459059B1 for moving the two arms of the spring simultaneously and generating two different torque values on two different links.
Thus, there is a need to provide for a single torsion spring in the release mechanism of moulded case circuit breakers for applying two different opposition torques with different values on two different links of the release mechanism.
Object of the Invention
It is thus the basic object of the present invention to provide a single torsion spring producing two different opposition torque values on two different components of release mechanism in MCCB.
Another object of the present invention is to cost effectively manufacture of torsion springs.
Further object of the present invention is directed to provide a compact arrangement in the release mechanism of MCCB.
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SUMMARY OF INVENTION
Thus according to the basic aspect of the present invention there is provided a single torsion spring for release mechanism of circuit breakers and adapted for generating two different opposition torques of different values, said spring comprising:
(i) plurality of extended arms having bends at definite distances from the horizontal axis of the coils of the said torsion spring;
(ii) the said bend in one of the said extended arms being such that it provides proper contact on the surface or extension of the surface of one of the latches of the release mechanism adapted for transmit of load on the surface of the latch and;
(iii) the bend in the other arm of the plurality of extended arms being so as to provide less torque on one of the latches of the release mechanism and is adapted to prevent locking of the release mechanism.
Further aspect of the present invention is to provide a release mechanism adapted for tripping the main mechanism of the moulded case circuit breaker, the said release mechanism comprises:
(i) bracket adapted for housing and holding the release mechanism;
(ii) plurality of latch means held inside the said bracket;
(iii) single torsion spring adapted for generating two different opposition torques of
different values being operatively connected to the said plurality of latch means
and;
(iv) means for holding and rotating the latch means.
DETAILED DESCRIPTION OF THE INVENTION
In the present invention the single torsion spring is operatively connected to the latch assembly link and the latch link in the release mechanism. The stationary link or the bracket is adapted for holding and housing all the components of the release mechanism. The said
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latch assembly link of the release mechanism is mounted on the roller, which is provided on the pin passing through the latch assembly link.
The single torsion spring of the present invention comprises two extended arm portions having bends at a particular distance from the horizontal axis of the coils of the spring. The bend in one of the said extended arms being such that it provides proper contact including either line or point or surface contact on the surface or extension of the surface of one of the latches of the release mechanism, The upper arm of the single torsion spring is extended such that the torque produced on the latch assembly link is greater than the torque on the latch link generated due to the action of the lower arm of the spring. Greater extension of the upper arm compared to the lower arm of the single torsion spring is adapted to prevent locking of the release mechanism and bringing the latch assembly link and the latch link to the stable position giving proper change over of the circuit breaker knob during operation. The bends are such as to provide line contact between the latch assembly link and the single torsion spring. The upper arm of the single torsion spring delivers force (F1) on the latch assembly link. The upper arm comprises bend ensuring line contact between the torsion spring and the latch assembly link. The said line contact is adapted to transmit uniform distributed load (UDL) on the surface of the latch assembly link. The bend of the other arm i.e. the lower arm is such that the perpendicular distance of the point of application of the force on the latch assembly link is less than the perpendicular distance of the bend from the horizontal axis of the coils of the spring. The lower arm bend of the single torsion spring ensures the distance d2 of the force F2 is greater than that of distance d3 of the force F3. This prevents locking of the release mechanism.
The line of action of the force (F3) on latch assembly link from latch link due to the latch link is in such a direction that it will try to lock the release mechanism if torque of the latch assembly link is less than the torque of the latch link. If the release mechanism gets locked in this position, the latch assembly link and the latch link would not come to stable position because of which main mechanism could not be latched into the latch assembly link and thus the breaker will always remain in tripped condition. The net maximum deflection of the upper arm and the lower arm of the single torsion spring corresponds to the rotation of both the latch assembly link and the latch link.
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The latch assembly link of the release mechanism is engaged to the main latch of the main mechanism and is adapted for active operation of the main mechanism. During operation of the main mechanism, the force to the latch link is transferred through the pin and the roller, which are assembled in the latch assembly link. The stopper provided in conjunction with the other limb of the latch link is adapted to prevent the rotation caused by the force transmitted from the lower limb of the latch assembly link. In absence of the stopper the latch rotates due to the force applied by it on the latch assembly link. Consequently, the latch assembly link rotates and hence the main latch of the main mechanism gets disengaged making the main mechanism inactive.
The single torsion spring is operatively connected to the latch assembly link and the latch link. The single torsion spring is adapted for bringing latch assembly link to a stable position thus engaging the main latch of the main mechanism into the latch assembly link and latch link of the release mechanism in a position where the stopper comes below it. At this position when force is applied by the latch assembly link on the stopper, the stopper prevents rotation of the latch assembly link.
The pin of the latch assembly link passing through the side walls of the said bracket is adapted for holding the latch assembly link and the single torsion spring such that both the components can rotate about the axis of the pin of latch assembly link. Similarly, another pin of the latch link passes: through the walls of the said bracket and is adapted to hold the latch link and rotate it about pin axis.
BRIEF DESCRIPTION :OF ACCOMPANYING FIGURES
Figure 1 illustrates different views of the single torsion spring of the present invention.
Figures 2(a) and 2(b) illustrate two different isometric views of the release mechanism comprising the single torsion spring.
Figures 3(a) and 3(b) illustrate the side views of the release mechanism with different deflected positions of the single torsion spring.
Figure 4 illustrates an isometric view of the main mechanism assembled with release mechanism.
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Figure 5 illustrates an isometric view of the release and main mechanism after tripping.
Figure 6 illustrates an isometric view of the stable position of the release and main mechanism.
DETAILED DESCRIPTION OF THE ACCOMPANYING FIGURES
In figure 1 different views of the single torsion spring of the present invention are illustrated. The single torsion spring (1) comprises two extended arm portions having bend (2) at a particular distance from the horizontal axis of the coils of the torsion spring (1). The upper arm (3) of the single torsion spring (1) is extended more than that of the lower arm (4).
In figures 2(a) and 2(b) two different isometric views of the release mechanism comprising the single torsion spring are illustrated. In the figure the pin (5) of the latch assembly link (7) passes through the side walls of the said bracket (6) and is adapted for holding and rotating the latch assembly link (7) and the single torsion spring (1). The pin (8) of the latch link (9) passes through the walls of the said bracket (6) and is adapted to hold the latch link (9) and rotate the latch link (9) about the axis of the pin (8).
In figures 3(a) and 3(b) the side views of the release mechanism with different deflected positions of the single torsion spring are illustrated. The upper arm (3) and the lower arm (4) of the single torsion spring (1) is deflected to a position with the latch link (9) resting on the stopper (10). In figure 3 (b) the single torsion spring (1) is in its maximum deflected condition. The stopper (10) is deflected to rotate latch link (9) and the latch assembly link (7).
In figure 4 an isometric view of the main mechanism assembled with release mechanism is illustrated. The release mechanism (11) is assembled with the main mechanism (12), The main mechanism (12) comprises main latch (13), which is latched to latch assembly link (7). The upper arm (3) of the torsion spring (1) provides line contact to the latch assembly link (7) generating a uniform distributed load on the surface of the latch assembly link (7).
In figure 5 an isometric view of the release and main mechanism after tripping is illustrated. The main mechanism (12) is assembled with the release mechanism (11) comprising latch
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assembly link (7) and the latch link (9) in unstable position. The main latch (13) of the main mechanism (12) is de-latched from the latch assembly link (7).
In figure 6 an isometric view of the stable position of the release and main mechanism is illustrated. The latch assembly link (7), latch link (9) and the upper arm (3) are in the stable position during tripped condition of breaker. The main latch (13) rests on the latch assembly link (7) and the latch link (9) rests on pin (5).
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We claim
1. A single torsion spring for release mechanism of circuit breakers and adapted for
. generating two different opposition torques of different values, said spring
comprising:
(i) plurality of extended arms having bends at definite distances from the horizontal axis of the coils of the said torsion spring;
(ii) the said bend in one of the said extended arms being such that it provides proper contact on the surface or extension of the surface of one of the latches of the release mechanism adapted for transmit of load on the surface of the latch and;
(iii) the bend in the other arm of the plurality of extended arms being so as to provide less torque on one of the latches of the release mechanism and is adapted to prevent locking of the release mechanism
2. A single torsion spring as claimed in claim 1, wherein the plurality of extended arms comprises upper arm and the lower arm with bends at a definite distance from the horizontal axis of the coils of the torsion spring.
3. A single torsion spring as claimed in claims 1 and 2, wherein the upper arm comprising bend adapted for proper contact providing line or point or surface contact with the surface of the latch means such that uniform distributed load is transmitted on the surface of the latch means.
4. A single torsion spring as claimed in claims 1 to 3, wherein the lower arm comprising bend adapted for preventing locking of the release mechanism.
5. A release mechanism adapted for tripping the main mechanism of the moulded case circuit breaker, the said release mechanism comprises:
(i) bracket adapted for housing and holding the release mechanism;

(ii) plurality of latch means held inside the said bracket;
(iii) single torsion spring adapted for generating two different opposition torques of
different values being operatively connected to the said plurality of latch
means and;
(iv) means for holding and rotating the latch means.
6. A release mechanism as claimed in claim 5, wherein the plurality of latch means comprises latch assembly link and latch link.
7. A release mechanism as claimed in claims 5 and 6, wherein the latch assembly link comprises pin and roller adapted for keeping the main mechanism active by transferring force to the said latch link.
8. A release mechanism as claimed in claims 5 to 7, wherein the single torsion spring comprising two extended arms operatively connected to the latch means of the release mechanism such that the spring delivers two different opposition torques on the latch assembly link, and latch link adapted for active operation of the main mechanism.
9. A single torsion spring and release mechanism of the circuit breaker comprising the same as substantially herein described and illustrated with reference to the accompanying figures.
Dated this 25th day of April, 2005

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ABSTRACT
Title: Single Torsion Spring For Release Mechanism In Circuit Breaker
A single torsion spring (1) for release mechanism (11) of circuit breakers and adapted for generating two different opposition torques of different values, said spring comprising plurality of extended arms (3, 4) having bends (2) at definite distances from the horizontal axis of the coils of the said torsion spring (1), the bend (2) in one of the said extended arms being such that it provides proper contact on the surface or extension of the surface of one of the latches of the release mechanism (11) adapted for transmit of load on the surface of the latch and the bend (2) in the other arm (4) of the plurality of extended arms (3, 4) being so as to provide less torque on one of the latches (7, 9) of the release mechanism (11) and is adapted to prevent locking of the release mechanism. Release mechanism (11) adapted for tripping the main mechanism (12) of the moulded case circuit breaker, the said release mechanism (11) comprises bracket (6) adapted for housing and holding the release mechanism, plurality of latch means (7, 9) held inside the said bracket (6), single torsion spring (1) being operatively connected to the said plurality of latch means and means for holding and rotating the latch means.