FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
Inverter assembly for a railway engine
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTORS
Sathe Mahesh Kashinath of Industrial Design Centre, C G Global R&D Centre, Crompton Greaves Ltd, Kanjurmarg (E), Mumbai - 400042, Maharashtra, India, and Meduri Maruthi Krishna of Electronic Design Centre, C G Global R&D Centre, Crompton Greaves Ltd, Kanjurmarg (E), Mumbai - 400042, Maharashtra, India, both Indian Nationals
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed

FIELD OF THE INVENTION
The present invention relates to an inverter assembly for a railway engine. More specifically, the present invention relates to an improved inverter assembly for railway engines having air curtain effect in an inductor portion for reducing dust entry.
BACKGROUND OF THE INVENTION
A typical inverter assembly for a railway engine comprises a housing which encloses one or more electronic/electrical/mechanical components and an air duct substantially surrounding the housing for cooling the components disposed therein. Example of electronic/electrical/mechanical components, includes, but is not limited to, inductor.
Both the inductor housing and the air duct have air outlets for expelling exhaust air therefrom. Conventionally, the air outlets are disposed quite near to roof of the engine and the gap between the outlets and engine roof is quite less. Further, the velocity of expelled air is in the range of 8-9m/s, due to which the expelled air strikes the roof of the engine and wipes out some accumulated dust of the engine roof. The wiped out dust enters into the inductor housing and get accumulated on the components disposed therein.
The dust keeps on accumulating in the housing for years and thus results in accumulation of lot of unnecessary waste material in the inductor housing. Conventionally, no system exists for reducing dust entry through air outlets into the inductor housing.

Hence, there is a need for an invention, which reduces dust entry from the air outlets, into an inductor housing of an inverter assembly without incurring additional costs and without effecting the functioning of the air duct surrounding the inductor housing.
DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION
Various embodiments of the present invention provide an inverter assembly for a railway engine which comprises a rectangular housing for holding one or more electronic/electrical/mechanica] components formed by a top perforated wall, a bottom perforated wall, and a pair of side walls, and a U-shaped air duct substantially surrounding the rectangular housing defined by a pair of vertical leg portions connected by a horizontal leg portion, each vertical leg portion disposed adjacent to a side wall, and the horizontal leg portion disposed adjacently below the bottom perforated wall. Each of the vertical leg portions comprise an air inlet disposed at respective lower portion and connected to an air blowing means, an air outlet disposed at respective upper portion, and at least one perforation at an upper portion of adjacently disposed side wall for diverting a portion of air flowing from the air inlet towards the air outlet, into the rectangular housing for creating an air curtain adjacently below the top perforated wall. Preferably, the air outlet is covered by a perforated member. Preferably, the air blowing means is a fan disposed below the air inlet. Preferably, the rectangular housing and components of the U-shaped duct are joined together using fixture-less welding technologies.

These and other aspects, features and advantages of the invention will be better understood with reference to the following detailed description, accompanying drawings and appended claims, in which,
Fig.l is a front perspective view of a portion of an inverter assembly for a railway engine in accordance with an embodiment of the present invention;
Fig.2 is side perspective view of a portion of the inverter assembly for a railway engine in accordance with another embodiment of the present invention; and
Fig,3 is a front cross-sectional view of a portion of the inverter assembly in accordance with an embodiment of the present invention.
Fig.l is a front perspective view of a portion of an inverter assembly 100 configured to be disposed inside a railway engine. The inverter assembly 100 comprises a rectangular housing 10 disposed for housing one or more electronic /electrical/mechanical components such as inductor. The housing 10 is formed by a top perforated wall 12, a bottom perforated wall 14, and a pair of side walls 16 and 18.
The inverter assembly 100 further comprises a U-shaped air duct 20 substantially surrounding the rectangular housing 10. The U-shaped air duct 20 is defined by a pair of vertical leg portions 22 and 24 connected by a horizontal leg portion 26. The vertical leg portion 22 is disposed adjacent to the side wall 16, the vertical leg portion 24 is disposed adjacent to the side wall 18, and the horizontal leg portion 26 is disposed adjacently below the bottom perforated wall 14.
The vertical leg portion 22 comprise an air inlet 28 disposed at respective lower portion and an air outlet 30 disposed at respective upper portion. Similarly, the

vertical leg portion 24 comprise an air inlet 32 disposed at respective lower portion and an air outlet 34 disposed at respective upper portion.
Each of the air inlets 28 and 32 is connected to an air blowing means (40, 42) which is preferably a fan disposed therebelow. For example, the air inlet 28 is connected to a fan 40 disposed therebelow and the air inlet 32 is connected to a fan 42 disposed therebelow. The fans 40 and 42 blow air for circulation in the U-shaped duct 20 and in the housing 10 for cooling the electronic/ electrical / mechanical components disposed therein. The air circulated in the duct 20 and housing 10 is expelled out by natural convection only through the air outlets 30 and 34, and the top perforated wall 12.
Preferably, the air outlets 30 and 34 are covered by perforated members 44 and 46 respectively. The perforated members 44 and 46 may be made of same material as of the duct 20 and are disposed adjacent to the top perforated wall 12, such that the top perforated wall 12, and the members 44 and 46 substantially lie in same plane.
The vertical leg portion 22 further comprises at least one perforation 45 at an upper portion of the side wall 16 and the vertical leg portion 24 comprises at least one perforation 47 at an upper portion of the side wall 18 for diverting a portion of air flowing inside the portions 22 and 24 into the housing 10 for creating an air curtain just below the top perforated wall 12.

Referring to Fig.2, when the air blowing means 40 and 42 are turned on, a portion of the air incoming at the air inlet 28 flows towards the air outlet 30 and another portion flows towards the horizontal leg portion 26. Similarly, a portion of the air incoming at the air inlet 32 flows towards the air outlet 34 and another portion flow towards the horizontal leg portion 26. The air incoming at the air inlets 28 and 32 is bent by 90 degrees to enter into the horizontal leg portion 26. However, bending of air by 90 degrees reduces its velocity, therefore, perforations 27 are provided in the horizontal leg portion 26 at spaced apart positions, for ensuring air velocity inside the horizontal leg portion 26 to not to fall to zero and be maintained at a particular value due to Venturi effect.
The horizontal air flow 48 inside the leg portion 26 is completely diverted into the rectangular housing 10 through the bottom perforated wall 14 for creating a vertical air flow 50 inside the housing 10 for cooling the electronic/electrical/mechanical components disposed therein.
A portion of the air flowing towards the outlets 30 and 34 is diverted (diversion represented by arrows 52 and 54) into the rectangular housing 10 through perforations 45 and 47 respectively for creating an air curtain in an upper portion 56 adjacently disposed below the top perforated wall 12. The air curtain in the upper portion 56 reduces dust entry in the housing 10 and decreases accumulation of dust onto various electronic components of the housing 10. The air curtain can also be referred to as an air barrier which debars the dust entry inside the housing 10.

Further, the diversion results in an air outflow of reduced speed from the outlets 30 and 34 as well as from perforated members 44 and 46 above the vertical leg portions 22 and 24. Thus, in an inverter assembly 100 disposed near to the roof of a railway engine, the velocity at which the expelled air from the leg portions 22 and 24 strikes the roof of the engine is considerably less as compared to prior art and therefore, amount of dust wiped out from the roof of the railway engine for entry into the housing 10 is also less. Thus, dust entry into the housing 10 and the U-shaped duct 20 is considerably reduced without incurring additional costs and equipment.
Referring to Fig.3, the rectangular housing 10, the vertical leg portions 22 and 24, the horizontal leg portion 26, and the fan assemblies 40 and 42 are joined together through fixture less welding technologies, which include employing riveted (fit & forget bolted) joints 58, 60, and 62 for holding joining members during welding. Various components of the inverter assembly 100 are first joined using bolts and then welded together. This increases the overall strength of the inverter assembly 100 and ease in manufacturing. The panel frames of the inverter assembly 100 are designed such as to eliminate the requirement of welding fixture during welding processes, thus reducing overall costs and time involved in the manufacturing of the inverter assembly panel frames.
Although the invention has been described with reference to a specific embodiment, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiment, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such modifications can

be made without departing from the scope of the invention as defined in the appended claims.

We claim:
1. An inverter assembly for a railway engine comprising:
a rectangular housing for holding one or more electronic components formed by a top perforated wall, a bottom perforated wall, and a pair of side walls; and
a U-shaped air duct substantially surrounding the rectangular housing defined by a pair of vertical leg portions connected by a horizontal leg portion, each vertical leg portion disposed adjacent to a side wall, and the horizontal leg portion disposed adjacently below the bottom perforated wall, each of the vertical leg portions comprising:
an air inlet disposed at respective lower portion and connected to an air blowing means;
an air outlet disposed at respective upper portion; and
at least one perforation at an upper portion of adjacently disposed side wall for diverting a portion of air flowing from the air inlet towards the air outlet, into the rectangular housing for creating an air curtain adjacently below the top perforated wall.
2. The inverter assembly as claimed in claim 1, wherein the air outlet is covered by a perforated member.
3. The inverter assembly as claimed in claim 1, wherein the air blowing means is a fan disposed below the air inlet.

4. The inverter assembly as claimed in claim 1, wherein the rectangular housing and components of the U-shaped duct are joined together using fixture-less welding technologies.