DESC:FIELD OF THE INVENTION
The present invention relates to an improved arrangement for dual purpose ventilation in electrical switching devices in particular a circuit breaker, a disconnector or a contactor to be used preferably in low voltage electrical systems.
Electrical switching apparatus, such as circuit breakers, are employed in diverse capacities in power distribution systems, for example, to provide protection for electrical equipment from electrical fault conditions (e.g. without limitation, current overloads, short circuits, abnormal level voltage conditions). Therefore the short circuit capacity of any circuit breaker is totally governed by the performance of its contact system & arc quenching chamber. The performance of the arc quenching chamber is decided by two factors: deionization capability and absorption and reduction of thermal energy. Ventilation plays a crucial role in absorption, hence reduction of thermal energy developed in the arcing chamber during arcing. The venting component provides a path of exhausting out the extra energy to be released out from the breaker in such way that does not hamper the normal operation of the system in the downstream or upstream.
The venting component is designed in such a way that this arrangement serves dual purpose of ventilating as well as cooling of internal gaseous arc products, hot explosive gas, carbon and molten metal debris. This channelizes the gases to an external location substantially above the load strap of the breaker whereby electrical components are not damaged by the gases reducing the chances of occurrence of earth fault or any kind of external flashover.
BACKGROUND OF THE INVENTION
In a circuit breaker, during an event of abnormal condition, the two contacts separate when the protection release system senses an abnormal condition and reacts to overcome it. An electric arc struck in between the contacts. The arc is then moved towards the arc quenching mechanism which consists of arc chute where it splits into several series of small arcs and cools down, raising the arc voltage and thus quenching the arc. During this arcing period, dielectric strength of the air breaks down substantially to a lower value. Formation of relatively high pressure gases as well as ionization of air molecules within the arc chamber takes place. These gases are hot and contain high amount of metallic particles which are deleterious to electrical components. Moreover, they are volatile and ignitable in nature. Therefore, these gases are to be kept separated until ionization has dissipated and the temperature of these gases has moderated.
In conventional arc chambers two or three separate vents are used which generally occupies more space in the circuit breaker in addition to more assembly time. In the present invention, three layers of vents are stacked into a single assembly which replaces a single vent alone. Thus, the present vent doesn’t need any extra space and assembling it in the breaker is also simpler. This ease of assembly reduces extra component space resulted in higher productivity and lesser cost.
The prior art vent system consists of single or double or in some cases triple vents which when subjected to a short circuit releases the gas pressure and then extinguishes the arc but requires higher time. The long arcing time leads to severe stresses on the downstream equipments due to large amount of let through energy. This long arcing time also results in higher erosion of contact buttons which ultimately lowers the life of breaker. This is because of their inability to rapidly move the high pressure ionized gases and avoid severity during high fault conditions. These venting arrangements are inefficient in terms of lowering the total let through energy passed on to the downstream devices. The housing of these types of circuit breakers has to withstand high amount of pressure. Also these types of vents are inefficient in terms of assembly time results in lesser productivity. Moreover, these prior art vents require additional place to accommodate, resulted higher size of breaker.
These and other drawbacks have been taken care in present invention.
Some comparable patents developed in this similar field areUS5153545, US4581511.
To overcome the disadvantages faced earlier with the prior art vent, in the present invention, prior art vent is replaced by an arrangement of layer of vents which are stacked into a single vent within same area as it was in prior art. The highly volatile gases produced during arcing are needed to be exhausted from the breaker in such a way that the exhaust gases are channelized properly to the exterior in the shortest time possible. As the present invention does not need any additional extra space or add any extra component in the breaker, the assembly remains simple. This helps to design a compact circuit breaker of higher rating.
During arc interruption very high pressure gets generated inside the arcing chamber. The arc chute must withstand this high pressure so as to minimize the stresses induced on the circuit breaker housing and cover. In the presently described vent arrangement, the high pressure gases are channelized from interior high pressure zone to external lower pressure zone in a high speed in a short duration of time using “Venturi effect” / “Nozzle Effect”. This relaxes the breaker housing from stresses of high in built pressure. With the reduction in stresses, the safety margin for the housing & cover can be increased.

OBJECTS OF THE INVENTION
One object of the invention is to overcome the disadvantages/drawbacks of the prior art.
A basic object of the present invention is to provide an improved arrangement for dual purpose ventilation in electrical switching devices.
These and other advantages of the present invention will become readily apparent from the following detailed description taken 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.
In an aspect of the present invention, there is provided an arrangement for ventilation in electrical switching devices, the arrangement comprising:
a front layer with one or more vent;
a rear layer with one or more vent; and
a perforated sheet, said perforated sheet inserted between the front layer and rear layer, thereby providing a single venting component;
wherein the venting component placed in a slot provided on the housing ofthe electrical switching device, therefore providing proper ventilation for a gaseous arc product(s) generated in the electrical switching device.
Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

BRIEF 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.
Fig 1 : Venting Arrangement
Fig 2 : Venting arrangement Rear side view
Fig 3 : Venting arrangement Front view
Fig 4 : Assembly of the whole Venting component
Fig 5 : Assembly location of the Vent Arrangement
Fig 6 : Molded case circuit breaker Assembly
Fig 7 : Enlarged view of the motion of Gases through the venting arrangement
Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure.
Throughout the drawings, it should be noted that like reference numerals are used to depict the same or similar elements, features and structures.

DETAILED DESCRIPTION OF THE PRESENT INVENTION
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.
The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.
By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.
Accordingly, present invention provides an arrangement for ventilation in electrical switching devices.
Construction of the assembly mechanism of the present invention is explained with reference to the accompanying figures.
List of components:
1. Rear side / layer of vent
2. Front layer of vent
3. Mesh vent / perforated sheet
4. Housing of Molded case circuit breaker
5. Molded case circuit breaker assembly

The present invention relates to an improved ventilation of an electrical Switching device. The vent arrangement (shown in Fig 1) needs to just place into the slots of housing (component 4) for fitment as shown in Fig 5. The ease of assembly enhances the productivity.
The presently invented improved vent arrangement is shown in Fig. 2 and Fig. 3 The vent arrangement consists of single venting component with three layers of venting slots: rear side / layer (component 1), front layer (component 2) and a mesh vent (component 3) which can be of brass or mild steel depending on the requirement.
Slots in the front and rear side / layer are created in such a way that they do not fall in the direct ray of path of one another. This inhibits the direct exit of the gases to the exterior. The slot size restricts metallic globule particles to come out of the breaker. The third layer which is a mesh vent (component 3) is placed in between the two layers helps in further filtering of particles. The way mesh vent is assembled into the venting arrangement is shown in Fig 4.
The cross sectional area of the slots in the front layer (component 2) is lower than that in the rear side / layer (component 1) but higher than those in the mesh vent (component 3). This variable cross sectional area plays a satisfactory role in establishing Venturi effect. As the gas flows through the constricted mesh vent, the gas velocity increases to satisfy the principle of continuity and the gas pressure lowers down to satisfy the principle of conservation of mechanical energy.
The route of gas flow also increases as it passes through one layer after another. The lengthened route of gas flow promotes lowering down of the heated gas to an acceptable temperature.
Novel features of the device of the present invention and advantages,
I. The cooling of arc by the layers of vent helps the arc to get quenched faster.
II. The three layers of filtering of the highly metallic content molten gases reduce the probability of occurrence of external flashover on the load terminal side.
III. Replacement of two or three vents by a single vent makes proper utilization of space.
IV. Channelizing of the high pressure gases to the exterior based on Venturi Effect / Nozzle effect.
V. Use of brass mesh as the middle vent helps in cooling of the ionized gases.
VI. Use of mild steel mesh as the middle vent helps in pulling as well as cooling of the ionized gases.
VII. Either Brass or Mild steel can be used individually or in combination based on the available space to get better performance as desired.
VIII. Ease of assembly increases production time. ,CLAIMS:1. An arrangement for ventilation in electrical switching devices, the arrangement comprising:
a front layer with one or more vent;
a rear layer with one or more vent; and
a perforated sheet, said perforated sheet inserted between the front layer and rear layer, thereby providing a single venting component;
wherein the venting component is placed in a slot provided on the housing ofthe electrical switching device, therefore providing proper ventilation for a gaseous arc product(s) generated in the electrical switching device.
2. The arrangement as claimed in claim 1, wherein cross sectional area of the ventson the front layer is smaller than cross sectional area ofthe vents on the rear layer

3. The arrangement as claimed in claim 1, wherein cross sectional area of vent(s) on theperforated sheet is smaller than cross sectional area of vent(s) on the front layer and the rear layer.

4. The arrangement as claimed in claim 1, wherein said vents on the front layer, the rear layer and theperforated sheetbeing configured to facilitate a venturi effect for removing the gaseous arc product(s) from the device.

5. The arrangement as claimed in claim 1, wherein the vents on the front layer and the rear layer being configured in a manner to restrict a metallic globule particle(s) generated in the device during arcing form coming out from the device, therefore providing ventilation to gaseous arc product(s).

6. The arrangement as claimed in claim 1, wherein theperforated sheet is selected form a group comprising a brass mesh, a mild steel mesh and the like.

7. The arrangement as claimed in claim 1, wherein the perforated sheet facilitates cooling of the ionized gases generated during arcing in the device.

8. The arrangement as claimed in claim 1, wherein theventing component providing a short path for channelizing the gaseous arc product(s), therefore facilitating faster quenching of the gaseous arc product(s) form the device.

9. The arrangement as claimed in claim 1, wherein vent (s) on the front layer and the rear layer are provided in diverse ray of path, therefore inhibiting the direct exit of the gaseous arc product(s) from the device.