FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
INTEGRAL DE-IONIZER FOR ARC CHUTES FOR A CIRCUIT BREAKER;
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 INVENTION
The present invention relates to arc extinguishers for a switching device and more particularly to an arc extinguisher for a circuit breaker.
BACKGROUND OF INVENTION
Generally, design of a switching apparatus (e.g. a circuit breaker) is made such that an arc chute is placed above the switching contacts. An arc chute generally contains several number of de-tonizing plates stacked with a certain space between them and placed so as to split the switching arc. Various barriers having vents are placed above the de-ionizing plates. Thus, with such an arrangement when an arc is produced, the arc gases are sufficiently cooled down and are released from vents in the barriers at the top of the switching apparatus.
Similar arrangements of arc chutes are discussed and taught in various prior art documents described below.
(1) US Patent US3555224 discloses 'Arc Chute for an Air Circuit Breaker'. It describes about an exhaust cooler for the arcing products leaving the arc chute of an electric circuit breaker. The cooler has four open sides. Through one of these sides the arcing products enter the cooler, and through the other three sides the arcing products exhaust after passing through the cooler. The cooler comprises a stack of corrugated metal sheets that allow the arcing products to pass between the sheets along the length of the corrugations and out one of said open exhaust sides of the cooler. The corrugated sheets are perforated to permit arcing products also to pass transversely of the length of the corrugations and out the remaining two open exhaust sides of the cooler.
Another Patent Document US5756951 discloses "'Arc Chute having three Barriers for the Passage of Arc Gases'. It talks about an arc chute for a circuit-breaker that has a chute member with arc splitters and an end member that seals off the chute member to the top. The end member has three barriers for arc gases, the first and the second barrier have webs with a more or less square cross-sectional shape which are arranged in double the pitch of the arc splitters. Situated above the second barrier is a cooling chamber, which is sealed off to the

outside by the third barrier that is provided with outlet orifices". The novelty of this prior art invention is in webs which acts as support.
Another patent document US5889249 is Tightly Joined Wire Mesh Deionizing Device for a Current Breaker. It discloses "a gas deionization device and an arc extinguishing chamber notably for a multipole low voltage circuit breaker with a molded case, A porous shield comprising one or more superposed metallic wire cloths. Each cloth is formed by a crisscrossing of straight wire yarns spaced apart from and parallel to one another with tight joined undulated wire yarns that extend appreciably perpendicular to the straight wire yarns, and pass alternately over and under at least one of the successive straight wire yarns. At least three superposed wire cloths have progressive mesh openings." The novelty of this prior art invention in its wire yarns designs.
Another Patent document EP1251533A1 - 'Integral Diffuser for an Electrical Switching Device'. This prior art invention discusses more about materials.
The patent document US6248971 - 'Circuit Breaker with Parallel Connected Pole Compartments1 discloses " A circuit breaker comprises a plurality of pole compartments juxtaposed inside an insulating case, in each of which compartments there are arranged an arc extinguishing chamber and at least one pair of separable contact parts comprising at least one movable contact part, at least two of said pole compartments being contiguous and separated from one another by a partition. The separating partition of the twinned poles comprises a communicating aperture of dimensions and location such that it is able to appreciably influence the distribution of the arcing energy between the two compartments when the latter are connected in parallel. A circuit breaker with a high breaking capacity is thus obtained from a standard multipole circuit breaker of lower breaking capacity." This prior art document talks about arc distribution.
US6670872 B2 / US0168433 A1 teach "LV Circuit Breaker with an Arc -extinguisher chamber & a switching gas damper". This talks about the other fitting structures for holding the mesh and not the structure of mesh.
US0170876 A1 discloses 'Circuit Breaker With Switching gas Cooling'. This talks about contacts and material for it.
Similarly US6784393 B2/ US0062341 A1 disclose "Arc Quenching Device for LV Switching Devices", US Patent US4581511 describes a 'Molded Case Circuit Breaker with an Improved Internal Venting System', and EP0437151 - 'Multipolar Circuit Breaker with a Gas Filter which is common to Different Poles', also describes the arrangement for protection of the switching device.

Although this type of arrangement as taught in these prior art documents provides protection, the protection is only up to a lower level of breaking capacities say up to 35KAmps, to the enclosure in which the switching apparatus is being placed.
Thus, in such arc chutes, there are chances that during high current faults (above 35kAmps) , when the switching contacts get opened, the arc gases may reach the enclosure as well as the control circuit/secondary circuit/ auxiliary wiring at the top and may damage it.
An arc may be produced when the metallic contacts arranged to form a contact get disconnected from one another. The arc thus produced has a high burning voltage in the order of magnitude of driving voltage of the power supply system. Due to this the surface particles of the contacts gets burnt off and later gets ionized as a result of high temperature in the gas chamber. These gases possess a threat of electrical flashovers or other damage occurring in the vicinity of the switching device.
The locations in which the low voltage switchgear is used may differ widely. This in turn governs the temperature and the extent of ionization of gases which emerge from arc extinguisher devices. In order to take account of these different conditions, arc extinguisher devices require separate cooling devices to be installed. Therefore, every time it becomes necessary to study the operating load or change in method of operation for better cooling of the switching gases before installation of the switchgear device.
Thus a novel mechanism is required for cooling of the switching gas in order to enhance the performance of the switching device.
SUMMARY OF THE INVENTION
It is an object of the present invention to improve breaking capacity of an arc chute and allow faster cooling of the Switching gases to enhance the performance of the same.
Another object of the present invention is to enable an arc chute to maintain the breaking capacity and also to enhance the breaking capacity of the switching device.

In accordance with this there is provided an integral de-ionizer for de-ionizing arc chutes for a typical circuit breaker. The de-ionizer comprises a stack of gratings. The gratings may have offset cross-section and each grating may have same or different profile. A base cover is also provided on which the stack of gratings may be mounted. The base cover has a plurality of vents for removal of breaking gases. The offset cross-section of gratings formed in the stack may contain multiple layers including layers of perforated sheets, or mesh of different sizes, types and materials.
In one embodiment herein, the de-ionizer also comprises a stack of arc de-ionizing plates and an insulating wall. The insulating walls may be provided with notches corresponding to the de-ion plates for proper positioning of the plates and for holding the base cover perpendicular to the de-ionizing plates.
On an event of higher level of fault current, an arc is formed that travels to the arc extinguisher under the influence of a magnetic self blast field and the arc is split between the de-ionizing plates into a large number of smaller arcs. The arc gases release out of vents and enter into space, where they are further cooled down due to convection of the air present in the space.
Said de-ionizer can be retrofitted in one of the elementary compartments of an already installed circuit breaker.
In one embodiment herein the stack of gratings may be spot welded.
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.
Fig. 1 is the exploded view of an arc extinguisher having integral de-ionizer according to the present invention.
Fig. 2 represents a longitudinal cross-section of the circuit breaker.
Fig.3 is the exploded perspective view of the rear side of the breaker.

DESCRIPTION OF THE INVENTION
Disclosed herein is an integral de-ionizer for deionizing arc chutes for a typical circuit breaker. The de-ionizer comprises a stack of gratings having offset cross-section. Each grating has same or different profile. A base cover having vents is provided on which the stack of grating is mounted. The vents helps in removal of breaking gases away from the circuit breaker. The stack of gratings helps in acquitting the fumes into the external environment.
Fig. 1 is the exploded view of an arc extinguisher 3 for a switching device such as a circuit breaker. In one embodiment herein the arc extinguisher 3 comprises an integral de-ionizer comprising stack of arc de-ionizing plates 4, an arcing horn 12, a base cover 14, and a stack of gratings 10.
According to the present invention, the stack of gratings 10 is mounted on the base cover 14. Each grating 10 has offset cross-section. Also, each grating has same or different profile. The base cover 14 has a plurality of vents 5 for removal of breaking gases 6. The stack of gratings 10 helps in limiting the fumes into the external environment.
An insulating wall 11 having notches corresponding to the de-ionizing plates 4 is provided for proper positioning of the plates 4 and for holding the base cover 14 perpendicular to the de-ionizing plates 4.The base cover 14 is located perpendicularly to the insulating walls 11 and to the de-ionizing plates 4. The base cover 14 has a plurality of vents 5 for removal of breaking gases. The stack of gratings 10 helps in freeing the fumes into the external environment when breaking capacity of the switching device increases.
Fig. 2 represents a longitudinal cross-section of the circuit breaker. Here, when the breaker is turned ON, the moving contacts 2 touch the fixed contacts 1, and current flows through the main contacts. In this condition, if the breaker is tripped due to higher level of fault current, the main contacts get opened and an arc 9 is formed. The high temperature of the arc 9 produces gases 6 due to heating of material in its vicinity.
The arc 9 travels to the arc extinguisher 3 or the arc quenching device 3 under the influence of a magnetic self blast field. In the arc extinguisher 3, the arc 9

is split between the de-ionizing plates 4 into a large number of smaller arcs. The arc gases 6 also travel through the de-ionizing plates 4.
Above the de-ionizing plates 4, the stack of gratings 10 is placed such that it is trapped between the base cover 14 and a top cover 13. In one embodiment herein, the stack of gratings 10 may be spot welded. These gratings 10 have good thermal conductivity and high melting point.
In one embodiment herein the stack of metallic grating 10 has multiple layers. In the preferred embodiment of the present invention, the stack of metallic grating 10 consists of four layers wherein the first one is a perforated sheet having multiple holes of diameter 0.9mm and pitch of 1.7mm. The second one is a 22mesh (per square inch) made from using 32 wire gauge of stainless steel material. The third one is a perforated sheet having a hole of diameter 2mm and pitch of 8mm. The last and forth one is a 12mesh (per square inch) made from using 24 wire gauge of stainless steel material. This stack 10 is held together by spot brazing. The stack cools the ionized gases as well as reduces the pressure inside the arcing chamber to a larger extent.
After the arc gases 6 are released out of the vents 5, enter into space, they are cooled down due to convection of the air present in the space. The large space available also reduces the pressure of gases 6.
The short circuit current breaking capacity of the circuit breaker is improved by the help of the de-ionizer may be 100kA at 690V. Further, the arcing time of the de-ionizer may be 9.3miliseconds for 100kA at 415V.
The de-ionizer is capable of being retrofitted in any of the elementary compartments of an already installed circuit breaker.
Fig.3 is the exploded perspective view of the rear side of the circuit breaker. As illustrated in the figure, the arc quenching device 3 can be inserted in one of the elementary compartments of the circuit breaker. This construction enables the said device 3 to be replaced with a reduced number of handling operations. Hence the extinguisher 3 can be retrofitted in one of the elementary compartments of an already installed circuit breaker.

The present invention provides an integral de-ionizer for improving features of an arc chute or arc extinguishing device of a circuit breaker. Features and advantages of the novel de-ionizer are summarized below.
1) It provides a cost effective solution for panel builder
2) An effective arc resistant arrangement can be achieved by using this arc chute.
3) It is safe to use
4) It uses arc shield for higher breaking capacity version
5) It provides an improvement in the breaking capacity
6) It can be retrofitted and at a low cost.
7) It is easy to manufacture.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

We Claim
1. An integral de-ionizer for deionizing arc chutes for a typical circuit breaker, the
de-ionizer comprising:
a stack of gratings 10 having offset cross-section and each grating 10 having same or different profile;
a base cover 14 having a plurality of vents 5 for removal of breaking gases, and on said base cover 14 the stack of gratings 10 is mounted.
2. The de-ionizer of claim 1 further comprising,
a stack of arc de-ionizing plates 4;
an insulating wall 11 having notches corresponding to the de-ion plates for proper positioning of the plates 4 and for holding the base cover 14 perpendicular to the de-ionizing plates 4.
3. The de-ionizer of claim 1, wherein stack of gratings 10 is spot welded.
4. The de-ionizer of claim 1, wherein short circuit current breaking capacity of the circuit breaker is improved to 100kA at 690V.
5. The de-ionizer of claim 1, wherein arcing time obtained is 9.3mtliseconds for 100kA at 415V.
6. The de-ionizer of claim 1, wherein the de-ionizer can be retrofitted in one of the elementary compartments of an already installed circuit breaker.
7. The de-ionizer of claim 1, wherein on an event of higher level of fault current, an arc 9 is formed that travels to the de-ionizer under the influence of a magnetic self blast field and the arc 9 is split between the de-ionizing plates 4 into a large number of smaller arcs.

8. The de-ionizer of claim 1, wherein offset cross-section of gratings 10 formed in the stack contains multiple layers including layers of perforated sheets, or mesh of different sizes, types and materials.