F O R M 2

THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)

1. Title of the invention:
TRIPPING SYSTEM USING A COLLAPSIBLE MECHANISM AND A METHOD THEREOF

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 which it is to be performed:

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to a system and method of tripping for circuit breaker and more particularly, to a tripping system comprising a collapsible mechanism to generate an impact force required to de-latch main mechanism of circuit breaker during abnormal condition and a method thereof.

BACKGROUND AND THE PRIOR ART

A circuit breaker is a mechanical switching device, capable of making, carrying and breaking currents under normal circuit conditions and also making, carrying for a specified time and breaking currents under specified abnormal circuit conditions such as those of overload, short circuit (Short circuit is an accidental or intentional connection, by a relatively low resistance or impedance, of two or more points in a circuit which are normally at different voltages)
The main function of any electrical switching apparatus is to carry the rated current. Therefore the current carrying capacity of any circuit breaker is so important that if the unit fails to carry the rated current it will cause damage to itself as well as to the electrical equipment to which it is protecting.
Circuit breakers have three positions corresponding to the status of the separable contacts. For example, these positions would include an ON position, in which the separable contacts are closed, an OFF position in which the contacts are open and Trip position in which the contacts are tripped open.
The circuit breakers are susceptible to undesirable/nuisance tripping under vibration of higher amplitude. The circuit breaker mechanism can be made more stable by increasing the trip force of the mechanism. When the trip force of the mechanism is increased, the amount of energy required to trip the mechanism is also very high. This calls for higher volume of bimetal and higher temperatures of the system. As per complying standard of the product, the temperature rise should be limited to a certain value. Thus the requirements are contradictory. This contradictory requirement of higher trip force of the mechanism and limiting the temperature of the current conducting path (terminals) within certain limit and using optimum volume of bimetal is achieved by using an extra two bar mechanism as disclosed in this invention.
These circuit breakers / switching devices are usually installed in an enclosure so as to have all the control and distribution network laid in form of metallic sheets and or cable wires inside and all operating means from outside so as to prevent access to high voltage and thus a potential hazard.
Under short circuit condition, circuit breaker tries to move the separable contacts to open position after sensing the fault condition through short circuit sensing mechanism (such as magnetic arrangement). The time taken from a fault condition initiation and the fault current being interrupted by circuit breaker determines the let through energy / arc energy passed by the circuit breaker to the downstream equipments. A circuit breaker is said to be more efficient when the let through energy is minimal.
It is required for any circuit breaker to carry current up to its rated value. However, sometimes the circuit breakers are found tripped even when the electric system is healthy. It was observed that the circuit breaker trips due to vibration generated by tripping of circuit breaker installed nearby.
Here are some Patents on Tripping mechanism:
US 2009/0128265 A1 provides a mechanism for a circuit breaker contact arm that allows current limiting by reducing the opening time. A secondary trip assembly is arranged to actuate due to magnetic forces generated during an undesirable electrical condition such as a short circuit. The secondary trip system releases a contact arm assembly allowing the contact arm to rotate to an open position that interrupts the flow of electrical power.

CN 201355599 provides utility model of a tripping mechanism for a circuit breaker, which comprises a traction rod, a fastener, a lever, a first spring, an energy storing part and a second spring. The traction at least comprises a rotary arm; one end of the lever supports against the rotary arm on the traction rod while the other end is provided with a stop hook; a rotary shaft is arranged at the center of the lever; the first spring acts on the lever to drive the lever to support against the rotary arm on the traction arm; the energy storing part can be rotatably arranged on a second rotary shaft; a locking arm and a triggering arm are arranged on the energy storing part; the end of the locking arm is hooked to the stop hook on the lever; the triggering arm is in contact with the fastener; and the second spring acts on the energy storing part to drive the end of the locking arm to abut against the stop hook. The tripping mechanism needs smaller tripping force and can guarantee the reliable action of the circuit breaker.
In case of control panel, when the control panel receives any undesired / unwanted / nuisance impact on external surface (i.e. Earth quake, vibration due to hitting etc) the vibrations generated due to these unwanted impacts gets transferred to the circuit breaker and in response to these vibrations circuit breaker trips. It was therefore necessary to device a circuit breaker which is immune to the vibrations generated due to unwanted impacts.
The above discussed nuisance tripping can be avoided by increasing the trip force of the mechanism. When the trip force of the mechanism is increased, the bimetal volume and temperature of current carrying parts and hence bimetal required is more. The complying standard puts limitation over the temperature rise of the current carrying parts. So meeting the requirement of higher trip force of the mechanism and complying the standard requirement of limiting the temperature rise is contradictory requirement.
When a circuit breaker is in ON condition and overload fault condition arises, higher amount of fault current flows through the circuit. This higher amount of current increases the temperature of the current carrying parts of the circuit breakers. The bimetal is connected to current carrying part of the circuit breakers and heated by this heat. The bimetal volume required to trip the circuit breaker mechanism is given by:

Where,
A - Deflection at tip
a - Specific Deflection
L - Active length
b - Width
s - Thickness
E - Young's Modulus
T - Bimetal Temperature
To- Ambient Temperature
F – Opposing force to Bimetal (Force provided by mechanism) post bimetal deflection
Fo- Initial Opposing force to Bimetal (Force provided by mechanism) before bimetal deflection
Thus it is seen from above expression that if the opposing force to bimetal is reduced. So the bimetal length and thickness required for same deflection can be reduced. Thus by reducing the force exerted by mechanism against bimetal, the costly bimetal volume can be optimized.

By using the present invention, a tripping system using a collapsible mechanism to generate an impact force required to de-latch main mechanism of circuit breaker during abnormal condition is achieved.

OBJECTS OF THE INVENTION

A basic object of the present invention is to overcome the disadvantages/drawbacks of the known art.

Another object of the present invention is to provide a tripping system using a collapsible mechanism to generate an impact force required to de-latch main mechanism of circuit breaker during abnormal condition.

Another object of the present invention is to provide a tripping method using a collapsible mechanism that generate an impact force required to de-latch main mechanism of circuit breaker during abnormal condition.

Yet another object of the present invention is to use energy stored in the compression spring.

These and other advantages of the present invention will become readily apparent from the following detailed description read in conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION

The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.

There is provided a system of an improved tripping system using stored energy principle for use in circuit breaker.

According to one embodiment of the present invention, there is provided tripping system using a collapsible mechanism to generate an impact force required to de-latch main mechanism of circuit breaker during abnormal condition, said tripping system comprising a housing for incorporating said tripping system; a cover engaged with said housing; a trip actuator placed on said housing configured to rotate about the axis; a compression spring having one end placed on said trip actuator, other end of said trip actuator engaged with a cover; a trip plate placed on said housing and configured to rotate about its axis; said trip plate providing overlap support to said trip actuator; a torsion spring used as a return spring for said trip plate to bring it back to original position.
Other embodiment of the present invention provides a tripping method using a collapsible mechanism that generate an impact force required to de-latch main mechanism of circuit breaker during abnormal condition comprising the steps wherein a bimetal bends and deflects a trip plate rotating it in de-latching direction, said rotation causing disengagement of a trip actuator with said trip plate, said disengagement causing rotation of a trip actuator, said rotation of said trip actuator providing impact force to the trip bracket of said main mechanism, a compression spring providing additional force to said trip bracket, said impact force causing rotation of said trip actuator thereby reducing overlap with main latch of said main mechanism, said reduction in overlap collapsing said main mechanism thus opening up the contact system.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

In the appended drawings:

Figure 1 illustrates the front view of dismantled components.
Figure 2 illustrates isometric view of dismantled components.
Figure 3 illustrates the front view with assembled components.
Figure 4 illustrates the front view of mechanism where the Tripping system is used.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The following drawings are illustrative of particular examples for enabling methods of the present invention, are descriptive of some of the methods, and are not intended to limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description.

Reference is first invited to Fig 1 where the tripping system in accordance with the present invention is shown.

Fig. 2 shows Trip actuator, Compression spring, Torsion spring, Trip plate, Housing & Cover etc.

Fig. 3 shows the operation of the invented system. It shows impact force offered to trip bracket of main mechanism, resetting force received from knobs and tripping force received from bimetal and moving magnet.

Fig. 4 shows Trip bracket and impact received from Trip actuator.

The invented system is thus a tripping system using a collapsible mechanism to generate an impact force required to de-latch main mechanism of circuit breaker during abnormal condition.

DETAILED DESCRIPTION OF THE INVENTION

Accordingly the present invention provides a tripping system which consists of a collapsible mechanism which generates an impact force required enough to de-latch the mechanism of circuit breaker. The amount of impact force generated depends upon the load value of compression spring used to dissipate the energy stored within.
The present invention related to method of arrangement of components which amplifies forces, applied by thermal & magnetic protection system, into sufficient amount of forces using kinetic energy conversion principle. Least the energy required by thermal system (bimetal), maximum is the cost benefit by using simple, thin bimetal without emphasizing usage of special bimetal and this also helps to get rid of complex bimetal design to generate high trip force.
Arrangement of components, disclosed herein, is shown in Figure 1 onwards. Please refer Figure 1 for dismantled view of components. As shown in Figure 1, it consists of Trip actuator, Compression spring, Torsion spring, Trip plate, Housing & Cover. Trip actuator 1 is placed on the housing 2 such that it can rotate about the axis. One end of the compression spring 3 is placed on the Trip actuator 1 and the other end is engaged with the cover 4. Trip plate 5 is placed on the housing 2 in such a way that it can rotate about its axis. This trip plate 5 also provides overlap support to the trip actuator 1. Torsion spring 6 is used as a return spring for the trip plate 5 to bring it back to the original position. This total arrangement of six components can be called as “Tripping unit”
As shown in Figure 3, Trip actuator is reset by operating knob of main mechanism. Trip actuator is then held by Trip plate in reset condition. During abnormal condition (overload or short circuit) the bimetal bends and deflects the trip plate, rotating it in de-latching direction. This rotation causes disengagement of Trip actuator with Trip plate. Due to this the Trip actuator rotates and offers impact force to the Trip bracket of main mechanism.
Please refer Figure 4. As soon as the Trip bracket received force from Trip actuator, it rotates while reducing overlap with main latch of main mechanism, thereby collapsing the main mechanism and opening up the contact system.
In circuit breaker, to get better contact pressure and to avoid final position problem, mechanism springs of higher load values are used. In ON condition of circuit breaker, the resolved component of mechanism spring force is transferred / passed on to Trip bracket. This makes it difficult to de-latch the circuit breaker with less force. Thus it requires higher force at Trip bracket to open up the contact system (Trip / de-latch the breaker). To achieve higher force at Trip bracket, bimetal which could give higher load/force is used. Bimetal with higher thickness and wider width is used for this purpose which makes it costlier. This also leads to complex bimetal design to generate high trip force.
To achieve maximum impact force at the Trip bracket with the simple & thin bimetal is very difficult without the concept of present invention. The present invention converts the available force exerted by bimetal into higher trip force adequate to rotate the trip bracket and trip the circuit breaker. The energy stored in compression spring is utilized to rotate the trip bracket. Once tripped the tripping system is reset by operating knob while resetting. No additional / special operation is required to reset the tripping system.
Although the embodiments herein are described with various specific embodiments, it will be obvious for a person skilled in the art to practice the embodiments herein with modifications. However, all such modifications are deemed to be within the scope of the claims.
It is also to be understood that the following claims are intended to cover all of the generic and specific features of the embodiments described herein and all the statements of the scope of the embodiments which as a matter of language might be said to fall there between.

WE CLAIM

1. A tripping system using a collapsible mechanism to generate an impact force required to de-latch main mechanism of circuit breaker during abnormal condition, said tripping system comprising:
a housing;
a cover engaged with said housing;
a trip actuator means pivotally engaged on the said housing being configured to rotate about its pivotal axis;
a compression spring having one end placed on said trip actuator, other end of said trip actuator engaged with the cover;
a trip plate placed on said housing and configured to rotate about its axis; said trip plate providing overlap support to said trip actuator; and
a return spring for said trip plate to bring it back to original position.
2. Tripping system as claimed in claim 1 wherein said trip actuator is adapted to be reset by operating knob of said main mechanism.
3. Tripping system as claimed in claim 1 further comprising a bimetal adapted to bend and deflect said trip plate further rotating it in de-latching direction during abnormal condition.
4. Tripping system as claimed in claim 1 wherein said return spring is a torsion spring.
5. A tripping method using a collapsible mechanism that generate an impact force required to de-latch main mechanism of circuit breaker during abnormal condition comprising the steps wherein:
a bimetal bends and deflects a trip plate rotating it in de-latching direction, said rotation causing disengagement of a trip actuator with said trip plate, said disengagement causing rotation of a trip actuator, said rotation of said trip actuator providing impact force to the trip bracket of said main mechanism, a compression spring providing additional force to said trip bracket, said impact force causing rotation of said trip actuator thereby reducing overlap with main latch of said main mechanism, said reduction in overlap collapsing said main mechanism thus opening up the contact system.
6. Method as claimed in claim 5 wherein said compression spring provide said force due to energy stored therein.
7. A tripping system using a collapsible mechanism to generate an impact force required to de-latch main mechanism of circuit breaker during abnormal condition as herein described and illustrated with reference to the accompanying drawings.
8. A tripping method using a collapsible mechanism that generate an impact force required to de-latch main mechanism of circuit breaker during abnormal condition as herein described and illustrated with reference to the accompanying drawings.