FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
Title of the invention.-CIRCUIT BREAKER WITH IMPROVED MECHANISM
2. Applicant
(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 which it is to be performed :

Field of the invention
The present invention relates to a spring component of innovative profile adapted for hassle free actuation of contacts in a circuit breaker. More particularly, the invention relates to a spring component adapted for hassle free swift controlled rotational movement of contacts and deciding accurate dead center positioning in a circuit breaker.
The invention also relates to a moulded case circuit breaker fork arrangement which provides precise circuit breaking/closing operation.
The spring finds its application in moulded case circuit breakers, any assemblies and/or subassemblies which incorporate use of spring rotationally in a small slot (where slot size cannot be increased due to space constrain).
Background and prior art
The basic functions of circuit breakers are to provide electrical power and distribution system protection. Whenever there are abnormalities on any part in the power and distribution system due to unhealthy electrical conditions like sudden high voltage, voltage or current surges and transients circuit breaker provides coordination in the components of the electrical system. For proper functioning of the contacts closure during circuit breaker
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operation hassle free smooth rotational movement is required
Moulded case circuit breaker (MCCB) is a tri-stable device having three stable states viz. TRIP, ON and RESET states. MCCB is normally actuated by stored energy in a extension spring. This energy is used to give fast movements to the upper contacts of the circuit breaker. There are usually two springs used in the breaker assembly both of which work in tandem to operate the mechanism. The stored energy is utilized during RESET-to-ON stage.
US4,885,444 discloses a switchgear operating mechanism is disclosed which includes two helical springs which are stretched to store energy to close and then open circuit breaker contacts. A mechanism is provided for stretching the springs in response to reciprocating movement of a hook stick. A single operating handle is provided with a spring biased detent arrangement such that the handle may be moved from a predetermined reset position to a closed position to close the circuit breaker contacts using energy from the charged springs. The handle is returned to the reset position by the spring biased detent arrangement and may be moved from that position to an open position to open the circuit breaker contacts using energy from the charged springs. The handle is preferably operable by a shot gun type hook stick. No teaching is found of hook profile having an advantage of smooth rotational motion along its axis.
US5,692,599 discloses a toggle spring for a circuit breaker operating mechanism which provides better performance and
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reliability is provided. The toggle spring includes a unique spring eye having a back hook portion extending around a spring shank so as to dramatically increase the force supportable by the spring eye. The toggle spring is provided having a body portion having a first end and a second end. A first spring eye extends from the first end of the body portion and a shank extends from the second end of the body portion. A second spring eye extends from the shank and includes the back hook portion which extends around the shank. But it is was not known that a profile could be provided at the hook portion which could give smooth rotational motion of the spring with in hook in a slot and thereby could provide a hassle free circuit breaker operation.
The disadvantages prevailing with the prior art as discussed hereinabove are as follows :
1. Due to insufficient slot size (diameter), the rotational movement of extension spring hook is restricted at the inclination stage. In order to free it, the slot diameter has to be increased or the spring wire diameter has to be decreased. Both of the changes are major design changes in a basic product which is very costly and laborious.
Thus there is need to provide for a spring with a profile so as to provide hassle free controlled rotational movement of contacts and deciding accurate dead center positioning in a circuit breaker.
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The present inventors have found that by way of a unique chamfer profile in the spring, the spring can be rotated about its axis in a slot with diameter less than about twice the diameter of the spring and even then hassle free movement of upper contacts of the breaker and direct positioning of the dead center can be achieved.
Objects of the invention
Accordingly, one object of the present invention is to overcome the problems/disadvantages of the prior art.
Another object of the present invention is to provide a spring with chamfer profile such that free rotational movement of the spring in a slot having less than about twice the spring's diameter.
Another object of the present invention is to provide actuation of breaker assembly in one shot without any operational discontinuity.
Summary of the invention
According to one aspect of the present invention there is provided a spring component comprising
a helical portion;
plurality of hook portions extending out from both ends of
said helical portion, said hook portions having
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predetermined curvature with the central axis of the helical portion; said hook portions comprising of free ends
wherein said free ends of the hook comprises chamfered profile
such that on engaging the spring with a slot having diameter same and/or lesser than and/or greater than the spring diameter said chamfered profile resting in the slot aids the spring to rotate about its central axis.
Another aspect of the present invention is to provide a fork arrangement for use in a moulded cases circuit breaker said arrangement comprising
a base portion;
plural arms operatively supported on said base portion,
said base portions comprising plural slots profiles so as
to engage with a spring component one end of which rests in
the slots of the base portion, the other end being in
operative connection with upper contacts of the circuit
breaker;
said spring component comprises
a helical portion;
plurality of hook portions extending out from both ends of
said helical portion, said hook portions having
predetermined curvature with the central axis of the
helical portion; said hook portions comprising of free ends
wherein said free ends of the hook comprises chamfered profile
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wherein said central axis of the spring being superimposed with the vertical axis of the fork
wherein the angle of rotation of the chamfer profile of the hook corresponds to the angular displacement of the central axis of the spring component.
Detailed description of the invention
In the present invention describes a spring component profiled in a manner such that it provides a hassle free, smooth rotational movement in all assemblies and sub assemblies which incorporate use of spring rotationally in a small slot where slot size cannot be increased due to space constrain.
The spring component comprises a helical portion having predefined number of threads which maintain a predetermined spring pitch between each of the threads. The helical portion on both ends extends out to form hook portions having predetermined curvature with the central axis of the helical portion. One end of the hook portions is free to get engaged in a slot provided in the assemblies or subassemblies where it will be used.
The hook portion at its free end comprises chamfered profile. The chamfered profile comprises plurality of side portions which converge at predetermined angle such that whenever said spring is engaged with the slot whose diameter is even lesser than about twice the diameter of
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the spring wire, the chamfered profile resting in the slot aids the spring to rotate about its central axis.
Another embodiment of the present invention describes a fork arrangement for use in moulded case circuit breaker. The fork comprises a base portion, plural arms operatively supported on said base portion. The base portion comprises plural slot profiles which includes plural longitudinal slots and plural rounded slots. The hook portion of the spring travels through the longitudinal slot so as to engage the free end of the hook into the rounded slot. The other end of the spring is in operative connection with upper contacts of the circuit breaker. Such fork arrangements finds its applications in circuit breakers, switchgears and the like. Such type of fork arrangement can also be used in any assembly/sub-assembly wherein spring hooked to a slotted profile gives rotational movement.
In a preferred embodiment of the present invention the spring is extension spring type.
Brief description of the accompanying figures
Figure 1 illustrates schematic views of the spring of the present invention.
Figure 2 illustrates a fork which is assembled in a circuit breaker.
Figure 3 illustrates the spring of the present invention when assembled with the fork.
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Figure 4 illustrates an isometric view of the spring along with the fork.
Figure 5A illustrates a schematic view of the spring engaged in the fork at 0° inclination.
Figure 5B illustrates a schematic view of the spring engaged in the fork at 5° inclination.
Figure 5C illustrates a schematic view of the spring engaged in the fork at 10° inclination.
Figure 5D illustrates a schematic view of the spring engaged in the fork at 15° inclination.
Detailed description of the accompanying figures
The invention will now be illustrated with reference to accompanying drawings, which are provided for ready and better understanding of the invention. The drawings represent only a specific working embodiment of the assembly according to the invention although variants of the assembly may be made within the scope and ambit of the present invention.
From figure 1 it is realizable that the spring component (11) comprises helical portion (12), hook portions (13) extending out from both end of helical portion (12) . The free ends (14) comprises on one end of the helical spring is engaged with a slot and on the other side is engaged with the upper contact of the circuit breaker (not shown
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here) . The free end comprises a chamfered surface (15) comprising two sides (16) In figure 1 the spring axis is (IB). In figure 2 the fork assembly (21) comprises longitudinal slots (2B) and rounded slots (2A) and comprises two arms (22) supported on base portion (23). In figure 2 axis (2E) is perpendicular axis with respect to axis (2D) and vertical axis with respect to the fork assembly.
In figure 3 the hook portion (13) of the spring component (11) is engaged with the rounded slot (2A) via the slot (2B) .
In figures 5A to 5D, the axis (IB) of the spring component (11) and vertical axis (2E) of the fork (21) have ZERO DEGREE inclination i.e. both the axis are mating (as shown in figure 5A) . Now, as the spring (11) takes a rotational movement, the angle between the axis (IB) and (2E) increases from 0° to 5° (as shown in figure 5B) . Further movement of spring component (11) increases the angle between axes (IB) and (2E) to 10° (as shown in figure 5C) . Further movement of spring component (11) increases the angle between axes (IB) and (2E) to 15° (as shown in figure 5D). Even with a smaller diameter of slot (2A) compared to the diameter of the spring wire, the hindrance between the rotational spring component (11) and slot (2A) is nullified by unique profile obtained by chamfer surface (15) at spring hook (13) ends.
The invention has been shown and described in a preferred form only and many variations may be made in the invention, which will still be comprised within its spirit. It is
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understood, therefore, that the invention is not limited to the details cited above. The ratio of diameters of the spring and the slot, angular displacement of the spring as herein described do not limit the scope of the present invention. The same can be replaced by its technical equivalence and yet the invention can be performed. The structure 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. A spring component comprising
a helical portion;
plurality of hook portions extending out from both ends of said helical portion, said hook portions having predetermined curvature with the central axis of the helical portion; said hook portions comprising of free ends
wherein said free ends of the hook comprises chamfered profile
such that on engaging the spring with a slot having diameter same and/or lesser than and/or greater than the spring diameter said chamfered profile resting in the slot aids the spring to rotate about its central axis.
2. A spring component as claimed in claim 1, wherein said chamfered profile comprises plurality of side portions which converge at predetermined angle in a manner to provide smooth rotational movement of the spring component.
3. A spring component as claimed in claims 1 and 2 is an extension spring.
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4. A fork arrangement for use in moulded case circuit breaker said arrangement comprising
a base portion;
plural arms operatively supported on said base
portion, said base portions comprising plural slots
profiles so as to engage with a spring component one
end of which rests in the slots of the base portion,
the other end being in operative connection with upper
contacts of the circuit breaker;
said spring component comprises
a helical portion;
plurality of hook portions extending out from both
ends of said helical portion, said hook portions
having predetermined curvature with the central axis
of the helical portion; said hook portions comprising
of free ends
wherein said free ends of the hook comprises chamfered profile
wherein said central axis of the spring being superimposed with the vertical axis of the fork
wherein the angle of rotation of the chamfer profile of the hook corresponds to the angular displacement of the central axis of the spring component.
5. A spring component as claimed in claim 1 to 3 adapted for use in circuit breakers, moulded case circuit breakers and the like and other assemblies and subassemblies using rotational type springs.
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6. A spring component and fork arrangement as substantially herein described and illustrated with reference to accompanying figures.
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ABSTRACT
TITLE : CIRCUIT BREAKER WITH IMPROVED MECHANISM
The present invention relates to a spring component comprising a helical portion (12), plurality of hook portions (13) extending out from both ends of said helical portion (13) . The hook portions (13) have predetermined curvature with the central axis of the helical portion (12) and comprises of free ends (14). The free ends (14) comprises chamfered profile (15) such that on engaging the spring with a slot having diameter same and/or lesser than and/or greater than the spring diameter said chamfered profile resting in the slot aids the spring to rotate about its central axis. The invention also relates to a fork arrangement for use in moulded case circuit breaker said arrangement comprising the spring component.
Figure 1