FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
& THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
ARC QUENCHING MECHANISM FOR CIRCUIT BREAKERS;
LARSEN & TOUBRO LIMITED, A COMPANY INCORPORATED UNDER THE COMPANIES ACT, 1956, WHOSE ADDRESS IS L&T HOUSE, BALLARD ESTATE, ' MUMBAI - 400 001, MAHARASHTRA, INDIA
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 circuit breakers, and more particularly to arc quenching in circuit breakers.
BACKGROUND OF THE INVENTION
Circuit breakers protect electrical circuits from damage by isolating the circuit in the event of a short-circuit. During the process of isolation, an undesirable arc is formed b etween the opening contacts of the circuit breaker. An arc is a luminous discharge of electric current that is formed when a strong current jumps a gap such as that between the opening contacts of a circuit breaker. Arcs may vary in size and intensity depending upon the amount of short-circuit fault current, and minimizing the arc is important as the arc can damage the contacts. Arcs may further ionize gasses inside the circuit breaker casing which can damage the circuit breaker. Further, arcs can also severely damage the equipments surrounding the circuit breaker. Therefore, a circuit breaker must not only isolate electrical circuit but also control and quench the arc generated in the process of isolation.
Various arc control mechanisms such as stretching the arc; breaking the arc into smaller segments; cooling the arc; blowing-out the arc; vacuum interruption of the arc; and the like are known in the art.
However, there is still a need in the art for an improved arc quenching mechanism.

SUMMARY OF THE INVENTION
Accordingly, in one aspect, the present invention provides a circuit breaker comprising a housing, a pair of contacts, and an arc quenching screw, wherein the arc quenching screw is adapted in front of the housing, the arc quenching screw having wings, the wings enabling quenching of an arc.
In another aspect, the present invention provides an arc quenching screw for a circuit breaker, the said screw is a wing screw comprising of a screw head, a screw shaft, and a plurality of metallic wings arranged in a spaced-apart relationship on at-least a part of the screw shaft such that the arrangement of metallic wings draws a generated arc, and elongates the arc to quench the arc. BRIEF DESCRIPTION OF THE DRAWINGS
Reference will be made to embodiments of the invention, examples of which may be illustrated in the accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in the context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
Figure 1 shows an arc quenching screw adapted to a circuit breaker, in accordance with an embodiment of the invention.
Figure 2 shows a detailed isometric view of the arc quenching screw, in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION
Various embodiments of the present invention provide an arc quenching screw and a circuit breaker using the arc quenching screw. The arc quenching screw is a wing screw having a plurality of metallic wings arranged in a spaced-apart relationship on at-least a part of a shaft of the wing screw such that the arrangement of the metallic wings draws, elongates and subsequently quenches a generated arc.
Figure 1, shows an arc quenching screw 200 adapted to a circuit breaker 100, in accordance with an embodiment of the invention. Circuit breaker 100 comprises a housing 102, a moving contact (not shown), a terminal 104, a fuse contact 106, and an arc quenching screw 200. Fuse contact 106 has a fuse contact hole 108.
Arc quenching screw 200 is illustrated in detail in figure 2. In accordance with an embodiment of the invention, arc quenching screw 200 is a wing screw comprising a screw head 202, a screw shaft 204 having a cylindrical cross-section, and a plurality of metallic wings 206 arranged in a spaced apart relationship on at-least a part of screw shaft 204. As shown, metallic wings 206 are arranged substantially near screw head 202, and extend substantially along length of screw shaft 204. One skilled in the art will appreciate that shape and size of the arc quenching screw and the metallic wings may vary depending upon design considerations.
In an embodiment of the present invention, the arrangement of metallic wings 206 of arc quenching screw 200 elongates and subsequently quenches an arc generated when contacts are disengaged.
As shown in figure 1, arc quenching screw 200 is adapted in front of housing 102 at fuse contact 106. Arc quenching screw 200 engages with fuse contact 106 via a fuse contact hole 108.

When circuit breaker 100 is in ON condition, the moving contact of circuit breaker 100 engages with terminal 104 and fuse contact 106, and current flows through terminal 104 to the moving contact, and to fuse contact 106. The current eventually flows out of terminal 104.
When circuit breaker 100 is turned OFF, the moving contact disengages from terminal 104 and fuse contact 106, and an arc is generated due to quick disengagement of the contacts. The generated arc is thrust upwards, and arc quenching screw 200 draws the arc towards it. Metallic wings 206 on arc quenching screw 200 elongate the arc increasing surface area of the arc which reduces its intensity and eventually extinguishes the arc.
The present invention advantageously quenches the arc using an arc quenching screw and enhances the life of the current carrying components in circuit breakers. Advantageously, the arc quenching screw also provides arc quenching while fastening a fuse contact to a housing of circuit breakers. Also, the arc quenching screw utilizes less material compared to conventional arc chute assemblies, and hence is cost-effective.
For the purpose of brevity, a detailed description of the known constructions and functions has been omitted.
While the present invention has been described with respect to certain embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims:

WE CLAIM:
1. A circuit breaker comprising:
a housing;
a pair of contacts; and
an arc quenching screw, wherein the arc quenching screw is adapted in front of the
housing, the arc quenching screw having wings, the wings enabling quenching of an arc.
2. The circuit breaker as claimed in claim 1, wherein the pair of contacts has a moving contact and a fuse contact.
3. The circuit breaker as claimed in claim 1, wherein the screw comprises: a screw head;
a screw shaft; and
a plurality of metallic wings arranged in a spaced apart relationship on at-least a part of the screw shaft, the arrangement of metallic wings drawing and elongating a generated arc towards the screw.
4. The circuit breaker as claimed in claim 3, wherein the screw shaft has a cylindrical cross-section.
5. The circuit breaker as claimed in claim 3, wherein the metallic wings are arranged substantially near the screw head.
6. A screw for quenching an arc in a circuit breaker, the screw comprising: a screw head;
a screw shaft; and
a plurality of metallic wings arranged in a spaced apart relationship on at-least a part of
the screw shaft such that the arrangement of metallic wings draws the arc, and

elongates the arc to quench the arc; the arc being produced as a result of separation of contacts of the circuit breaker.