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:
ARC SPLITTER PLATE FOR AN ARC CHUTE ASSEMBLY AND A METHOD OF MAKING THE SAME.

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 an arc chute assembly for circuit breakers and more particularly, to an arc splitter plate for an arc chute assembly to limit the duration and intensity of the current in circuit breakers and a method of making the same.

BACKGROUND AND THE PRIOR ART

Electrical switching devices are employed in the electrical circuit to carry the rated current, close/open the electrical circuit at normal or abnormal currents. During the opening of switching devices while current is flowing through it results in discharge of electrical current in form of arc. The proper isolation is achieved by extinguishing the electrical arc by cooling, stretching, elongating and splitting the arc into small arcs. For performing the above operation inside electrical switching devices an arc chute assembly is employed.
An arc chute assembly consists of arc splitter plates which are stacked together by insulating material called arc chute linings preferably with an air gap between the plates. The arc elongates between the splitter plates forms small arcs in the gap between them. Also there is arc chute assembly comprising a plurality of arc plates having an ablative material sandwiched between two electrically connected ferromagnetic metal plates as shown in Fig. 2 and Fig. 3.
US Patent No. 4,375,021 discloses an arc plate of U-shaped configuration, wherein the curve of the U-shape plate faces the contacts and the arms of the U insulated from one another by a thin insulating sheet. However, U-shape limits the number of plates in an arc chute assembly that can be physically accommodated in the arc chute.
The above mentioned splitter plate provides a considerable challenge in manufacturing for mass production and achieving desired quality. Therefore, the present invention discloses a novel assembly which is much easier to manufacture. The present invention provides a completely different bending area. Also the arc plate of present invention has a completely different configuration.
The filling of insulation material with ablative property between the folded splitter plates is done by placing a thin sheet of ablative based insulating material on one side of the plate before folding, and molding the material in between them.

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 an arc chute assembly limiting the duration and intensity of the current in circuit breakers.

Another object of the present invention is to provide a method of making an arc chute assembly.

Yet another object of the present invention is to provide a simple method of manufacturing arc splitter plate in mass scale.

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

There is provided an arc chute assembly limiting the duration and intensity of the current in circuit breakers.

According to one embodiment of the present invention, there is provided an arc splitter plate of an arc chute assembly for limiting the duration and intensity of the current in circuit breakers, said arc splitter plate comprising: a single metal piece folded to provide a pair of arms joined by a curved portion; a slot cut out in the said metal piece; a thin layer of electrical insulation means interposed between said pair of arms. The electrical insulation means possess the ablation property wherein during arcing the ablative material vaporizes in a controlled manner along with erosion of splitter plate and release the gases of high dielectric capacity than air. This high dielectric medium enables proper clearing of high short circuit currents.

Other embodiment of the present invention provides a method for making an arc splitter plate of an arc chute assembly for limiting the duration and intensity of the current in circuit breakers, comprising the steps of: folding a single metal piece to provide a pair of arms joined by a curved portion; cutting out a slot from the said metal piece; placing a thin layer of ablative based electrical insulation means between said pair of arms.

Additionally the present invention provides arc plates for an arc chute assembly which can be used for electrical switching devices such as circuit breaker, molded case circuit breaker, motor protection circuit breaker, contactor, etc.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

In the appended drawings:
Figure 1 illustrates an arc chute assembly of prior art.
Figure 2 illustrates an arc plate according to prior art.
Figure 3 illustrates a cross-sectional view of an arc plate according to the prior art.
Figure 4 illustrates arc quenching using arc plates of prior art.
Figure 5 illustrates the metal plate.
Figure 6 illustrates an arc plate without insulating material according to invention.
Figure 7 illustrates an arc plate with insulating gassing material on half surface of any one side of the plate.
Figure 8 illustrates an arc plate with insulating gassing material on the full surface of any one side of the plate.
Figure 9 illustrates a complete arc plate made by folding the plate.
Figure 10 illustrates the cross section of arc plate.
Figure 11 illustrates the arc chute assembly comprised arc plate mentioned in present invention.

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 arc chute assembly based on the prior art description is shown.

Fig. 2 provides arc plate design according to the prior art in which a number of plates are stacked together in parallel configuration with ablative based insulating material placed between them.

Fig. 3 shows the insulation layer present in accordance with the prior art description. The arc plate (10) comprises of two metal plates (2A, 2B) electrically connected and an insulating material layer (4). The ablative based insulating material layer (4) is sandwiched between the two metal plates (2A, 2B).

Fig. 4 shows the arc quenching process in accordance with prior art description.

Fig. 5 shows the single metal piece that is folded to form an arc splitter plate.

Fig. 6 shows the slot carved out from the single metal piece.

Fig. 7 shows an arc plate with ablative based insulating gassing material on half surface of any one side of the plate.

Fig. 8 shows an arc plate with ablative based insulating gassing material on the full surface of any one side of the plate.

Fig. 9 shows an arc splitter plate formed by folding the single metal piece. It has substantially a U shaped structure.

Fig. 10 shows the side view of the arc splitter plate clearly showing the placement of the ablative based insulating material between the arms of the splitter plate.

Fig. 11 shows an arc chute assembly having the arc plates placed in parallel configuration in accordance with the present invention.

The invented system is thus an arc splitter plate of an arc chute assembly limiting the duration and intensity of the current in circuit breakers.

DETAILED DESCRIPTION OF THE INVENTION

Accordingly the present invention proposes the novel way of manufacturing the arc splitter plate. The filling of ablative based insulation material between the bended splitter plates can be done by placing the thin sheets of ablative based insulating material, applying the coating of ablative based insulation material on one side of the plate before bending, inserting the ablative based insulating material in between said plates.

Figure 1 illustrates an arc chute assembly (100) of prior art comprising of a plurality of arc plates (10) arranged in a stack of closely spaced, generally parallel configured in between two plates (20) known as lining made of electrically insulating material. The arc chute assembly (100) is generally adapted in close proximity to the contacts (not shown) of a circuit breaker (not shown) to attract & quench an arc that may be generated at the contacts in response to an overload or short-circuit condition.
Figure 2 & 3 of prior art illustrates detailed configuration of an arc plate (10). The arc plate (10) comprises of two metal plates (2A, 2B) electrically connected and an ablative based insulating material layer (4). The ablative based insulating material layer (4) is sandwiched between the two metal plates (2A, 2B).
The insulating material layer (4) is an ablative material namely, Polyoxymethylene (POM), Polytetrafluoroethylene (PTFE), Polyamide (Nylon) & Melamine Formaldehyde (MF). The high resistance material (6) is also placed in sandwiching process.
The present invention describes the arc plate that can be easily manufactured and can be used in mass production. A single metal plate (30) is used as shown in Figure 5 to manufacture the arc plate (50) as shown in Figure 9. The single metal piece is folded to provide a pair of arms. The slot (40) is made in the metal plate by means of cutting or using any other manufacturing processes. The metal plate (30) can be of ferromagnetic material or any other refractory materials for arc movement. The metal plate (30) is coated with nickel, zinc or copper for improved arc movement.
The ablative based insulation material (7) is placed on any side to cover the half surface as shown in Figure 7 or to cover the full surface by means of pasting the strips of the material, painting, spraying or coating with insulation material. The slot (40) can also be made after placing the ablative based insulation material on metal plate. There after the ablative based insulation material (7) placed plates is folded by means of bending or pressing or any other manufacturing processes to get the desired arc plate (50) as shown in Figure 9.
The cross sectional view of the arc plate is shown in Figure 5 which clearly illustrates the bending of metal plate (30) and ablative based insulation material (7) filled in it. The ablative based insulation material (7) can be filled by molding or placing the strip after bending the plate (30).
The arc chute assembly (101) made up of arc plate (30) is shown in Figure 5 which will be used in switching devices to quench the electric arc. The arc chute assembly made up of arc plate according to the present invention is shown in Figure 11 which will be used in switching devices to quench the electric arc.
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. An arc splitter plate for an arc chute assembly to limit the duration and intensity of the current in circuit breakers, said arc splitter plate comprising:
a single metal piece folded to provide a pair of arms joined by a curved portion;
a slot cut out in the said metal piece;
a thin layer of electrical insulation means interposed between said pair of arms, wherein said insulation means being substantially ablative comprising ablative material that vaporizes during arcing and release the gases of higher dielectric capacity than air.

2. Arc splitter plate as claimed in claim 1 wherein said metal piece is substantially U-shaped.
3. Arc splitter plate as claimed in claim 1 wherein said metal piece is a ferromagnetic material or refractory material for easier arc movement.
4. Arc splitter plate as claimed in claim 1 wherein said metal piece is selectively coated with nickel, zinc or copper for an improved arc movement.
5. Arc splitter plate as claimed in claim 1 wherein said electrical insulation means is substantially an ablative material selected from a group comprising Polyoxymethylene (POM), Polytetrafluoroethylene (PTFE), Polyamide (Nylon) & Melamine Formaldehyde (MF).
6. Arc splitter plate as claimed in claim 1 wherein said electrical insulation means is a high resistance material.
7. A method of making an arc splitter plate for an arc chute assembly to limit the duration and intensity of the current in circuit breakers, comprising the steps of:
folding a single metal piece to provide a pair of arms joined by a curved portion;
cutting out a slot from the said metal piece;
placing a thin layer of electrical insulation means between said pair of arms, said insulation means substantially an ablative material that vaporizes during arcing and release the gases of higher dielectric capacity than air.
8. Method as claimed in claim 7 wherein said insulation means is provided on one side of said metal plate.
9. Method as claimed in claim 7 wherein said insulation means is provided on metal plate by pasting the said insulation means or painting/spraying/coating using said insulation means.
10. Method as claimed in claim 7 wherein said insulation means is selected substantially depending on the desired rating of the circuit breaker.
11. Method as claimed in claim 7 wherein said folding is substantially a U shaped configuration.
12. Method as claimed in claim 7 wherein the desired folded shape of arc plate can be achieved substantially by cutting/ punching/ bending/ extruding or any other manufacture process.
13. Method as claimed in claim 7 wherein said insulation means is exposed to arcing to facilitate positive ablation.
14. An arc splitter plate for an arc chute assembly to limit the duration and intensity of the current in circuit breakers as herein substantially described and illustrated with reference to the accompanying drawings.
15. A method of making an arc splitter plate for an arc chute assembly to limit the duration and intensity of the current in circuit breakers as herein substantially described and illustrated with reference to the accompanying drawings.