FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
AND
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2005
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
A low noise and low loss fan cover system
APPLICANT:
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR:
Bhatia Dinesh, Crompton Greaves Ltd, Analytics Centre, C G Global R&D Centre, Bhaskara Building, Kanjurmarg (E), Mumbai - 400042, an Indian National.
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:
This invention relates to the field of mechanical assemblies.
Particularly, this invention relates to the field of heat exchangers and motors.
Still particularly, this invention relates to the field of fan covers related to heat exchangers.
More particularly, this invention relates to a low noise and low loss fan cover system.
BACKGROUND OF THE INVENTION:
A motor typically includes a rotor, a stator and associated assemblies, which assemblies are heat generating assemblies. There is a need to dissipate the heat for long life of the motor and so that the motor works according to specified standards.
There is, hence, provided a heat exchanger mechanism adapted to receive hot air from the motor. A fan is driven to extract relatively cold air from the surrounding atmosphere into the heat exchanger. Guided through the conduits of the fan cover having intermittent baffles, the relatively cold air comes into contact with the hot air from the motor at the tubes, and effective cooling of the ambient air around the motor and in the motor housing is carried out. The previously relatively cold air, records an increase in temperature due to transfer of heat.

The relatively cold air enters the heat exchanger through an inlet guide which cooperates with a fan cover housing a fan and which acts as a guide for the incoming air towards the heat exchanger tubes.
Figure 1 illustrates a motor with associated heat exchanger and air exhaust assembly with silencer mechanism.
A motor (10) is placed in a motor housing (12). A common shaft drives a plurality of fans (14, 16, 18). Relatively smaller fans (14, 16) guide the air, which is relatively hotter, from the motor housing in the direction of the heat exchanger (20). Relatively larger fan (IS) sucks in ambient air which is relatively cooler. The fan (18) is placed in a fan cover (22). Ambient relatively cooler air is channeled through the fan cover and guided in a dispersed manner through the tubes which form the heat exchanger (24), thereby coming in communication with the relatively colder sucked in ambient air. Heat exchange takes place (as shown by circular arrows), here. The hot air around the motor, in the motor housing, is relatively cooler, now. Figure 1 also shows the external flow circuit assembly for an HT motor. Air enters at one end (19) and is then guided through the fan cover (22) and heat exchanger tubes (24) and exits (31, 33) through the silencer (30).
There is an external fan (relatively larger fan) at the inlet of the associated heat exchanger mechanism which sucks in ambient (relatively colder) air.
The external fan is placed in a fan cover. Ambient relatively cooler air is channeled through the fan cover and guided in a dispersed manner through the tubes which form the heat exchanger, thereby coming in communication with the relatively

colder sucked in ambient air. Heat exchange takes place (as shown by arrows), here. The hot air around the motor, in the motor housing, is relatively cooler, now.
The air flow, through, this inlet mechanism is not guided. It has been observed that the maximum source of noise in a motor is due to this induced air through the inlet means.
Hence, there is a need for an improved silencer mechanism which overcomes the issues of the prior art.
There is a need to obviate the limitations of the prior art.
OBJECTS OF INVENTION:
An object of the invention is to provide a fan cover system for reducing the noise level and temperature rise in the motors.
Another object of the invention is to provide a fan cover system with relatively low noise.
Another object of the invention is to provide a fan cover system with relatively low loss.
Yet another object of the invention is to provide reduction of overall noise level in a motor, with a fan cover, with air as a cooling medium.

Still another object of the invention is to provide an improved fan cover system with a choice of noise elimination characteristics.
Another object of the invention is to provide an improved fan cover system which efficiently directs the incoming air with less turbulence.
SUMMARY OF THE INVENTION:
According to this invention, there is provided a low noise and low loss fan cover system, said fan cover comprises an operative lower circular portion housing a fan, characterised in that, the fan centre is horizontally offset from the centre of said lower circular portion of said fan cover, said offset being in a direction pre-defined in accordance with fan rotation direction, thereby providing an expanding substantially circular channel defined between the perimeter of the fan and the perimeter of the fan cover.
According to this invention, there is also provided a low noise and low loss fan cover system, said fan cover comprises an operative lower circular portion housing a fan, characterised in that, the fan centre is horizontally offset from the centre of said lower circular portion of said fan cover, said offset being in a direction predefined in accordance with fan rotation direction, wherein, said horizontal offset being defined by said fan centre being placed to the operative right with respect to the centre of said lower circular portion of said fan cover, for a clockwise rotating fan, thereby providing an expanding substantially circular channel defined between the perimeter of the fan and the perimeter of the fan cover.

According to this invention, there is also provided a low noise and low loss fan cover system, said fan cover comprises an operative lower circular portion housing a fan, characterised in that, the fan centre is horizontally offset from the centre of said lower circular portion of said fan cover, said offset being in a direction predefined in accordance with fan rotation direction, wherein, said horizontal offset being defined by said fan centre being placed to the operative left with respect to the centre of said lower circular portion of said fan cover, for an anti-clockwise rotating fan, thereby providing an expanding substantially circular channel defined between the perimeter of the fan and the perimeter of the fan cover
According to this invention, there is also provided a heat exchanger with a low noise and low loss fan cover system with said heat exchanger being placed beyond an exit member and in direct communication with said exit member, said fan cover comprises an operative lower circular portion housing a fan, characterised in that, the fan centre is horizontally offset from the centre of said lower circular portion of said fan cover, said offset being in a direction pre-defined in accordance with fan rotation direction, thereby providing an expanding substantially circular channel defined between the perimeter of the fan and the perimeter of the fan cover.
According to this invention, there is also provided a heat exchanger with a low noise and low loss fan cover system with said heat exchanger being placed beyond an exit member and in direct communication with said exit member, said fan cover comprises an operative lower circular portion housing a fan, characterised in that, the fan centre is horizontally offset from the centre of said lower circular portion of said fan cover, said offset being in a direction pre-defined in accordance with fan rotation direction, wherein, said horizontal offset being defined by said fan centre

being placed to the operative right with respect to the centre of said lower circular portion of said fan cover, for a clockwise rotating fan, thereby providing an expanding substantially circular channel defined between the perimeter of the fan and the perimeter of the fan cover.
According to this invention, there is also provided a heat exchanger with a low noise and low loss fan cover system with said heat exchanger being placed beyond an exit member and in direct communication with said exit member, said fan cover comprises an operative lower circular portion housing a fan, characterised in that, the fan centre is horizontally offset from the centre of said lower circular portion of said fan cover, said offset being in a direction pre-defined in accordance with fan rotation direction, wherein, said horizontal offset being defined by said fan centre being placed to the operative left with respect to the centre of said lower circular portion of said fan cover, for an anti-clockwise rotating fan, thereby providing an expanding substantially circular channel defined between the perimeter of the fan and the perimeter of the fan cover
Typically, said system includes a pluarlity of vanes, placed vertically above said lower circular portion of said fan cover which houses said fan.
Preferably, said system includes a pluarlity of vanes, placed vertically above said lower circular portion of said fan cover which houses said fan, said vanes being curvilinear vanes.
Preferably, said system includes a pluarlity of vanes, placed vertically above said lower circular portion of said fan cover which houses said fan, said vanes being

curvilinear vanes, the curve defining the curvilinear equation for each vane changing in accordance with its placement, characterised in that, the vane closer to one wall is slightly curved, while each further adjacent vane is relatively differently curved than the previous adjacent vane. The difference in curve is the angle of curvature.
Preferably, said system includes a pluarlity of vanes, placed vertically above said lower circular portion of said fan cover which houses said fan, said vanes being curvilinear vanes, with the curvature direction following the direction of the expanding substantially circular channel (between the perimeter of the fan and the perimeter of the fan cover) and increasing from one wall to another such that the air that is exited from the fan area is guided without vortex formation.
Preferably, said system includes a pluarlity of vanes, placed vertically above said lower circular portion of said fan cover which houses said fan, said vanes being rounded off at their operative top and bottom ends in order to prevent turbulence and reduce noise, thereof such that the shape and placement of vanes ensure impact-free entry for the flow of air, exiting from the fan area, into the passages made by adjacent vanes.
Typically, said system includes a tongue where the circumferential wall of said fan cover mates with the wall adjacent the vanes located above said lower circular portion housing a fan.

Typically, said system includes a tongue where the circumferential wall of said fan cover mates with the wall adjacent the vanes located above said lower circular portion housing a fan, said tongue being a protrusion upto a pre-defined depth.
Typically, said system includes a tongue where the circumferential wall of said fan cover mates with the wall adjacent the vanes located above said lower circular portion housing a fan, said tongue being defined by pre-defined curvilinear equations in accordance with desired noise and tonal elimination characteristics.
Typically, a first wall which includes the tongue and a second opposite wall is a straight wall.
Alternatively, a first wall which includes the tongue and a second opposite wall is a curved wall.
Typically, said fan cover system is an external fan cover system for motors.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
The invention will now be described in relation to the accompanying drawings, in which:
Figure 1 illustrates a motor with associated he^t exchanger and air exhaust assembly with silencer mechanism; and

Figures 2 illustrates a front view of the fan cover and its design according to the prior art.
Figure 3 illustrates a rear view of the fan cover and its design according to the proposed design; and
Figure 4 illustrates the fan cover design in its rear view.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
According to this invention, there is provided a low noise and low loss fan cover (200) system.
Figure I illustrates a motor with associated heat exchanger and air exhaust assembly with silencer mechanism.
A motor (10) is placed in a motor housing (12). A common shaft drives a plurality of fans (14, 16, 18). Relatively smaller fans (14, 16) guide the air, which is relatively hotter, from the motor housing in the direction of the heat exchanger (20). Relatively larger fan (18) sucks in ambient air which is relatively cooler. The fan (18) is placed in a fan cover (22). Ambient relatively cooler air is channeled through the fan cover and guided in a dispersed manner through the tubes which form the heat exchanger (24), thereby coming in communication with the relatively colder sucked in ambient air. Heat exchange takes place (as shown by circular arrows), here. The hot air around the motor, in the motor housing, is relatively cooler, now. Figure 1 also shows the external flow circuit assembly for an HT

motor. Air enters at one end (19) and is then guided through the fan cover (22) and heat exchanger tubes (24) and exits (31, 33) through the silencer (30).
Figures 2 illustrates a front view of the fan cover and its design according to the prior art. Reference numeral 55 refers to heat exchanger. The centre (51) of the fan (42) and the centre (53) of the lower circular portion of the fan cover are vertically aligned.
This design does not provide a proper path for air flow exiting from the fan in order to chanel its flow in the operative vertical direction, from where it is exited towards the heat exchanger. As a result, the system is a large loss, large noise producing system. The large flow path resistance, due to flow recirculation, results in high power consumption reducing the overall efficienty of the motor.
The fan cover (100) structure is a substantially tubular component (41) which generally comprises an inlet member (40) at the lower operative front side of the fan cover. This inlet member (40) is in front of a fan (42) which is placed inside the fan cover so that there is direct communication of incoming air from the inlet member (40) to the fan (42). The exit member (44) of the fan cover is at the operative top of the fan (42). The tubular component (41) blends into the exit member (44) for directing the air flow towards the heat exchanger (55). This heat exchanger (55) is placed beyond the exit member (44) and in direct communication with the exit member (44).
Figure 3 illustrates a fan cover and its design (in its side view) according to the invention, along with placement of the fan. The centre (51) of the fan (42) and the

centre (63) of lower circular portion of the fan cover are horizontally displaced with respect to one another.
Figure 4 illustrates the fan cover design in its rear view.
The new fan cover design in as shown in Figure 4 (rear view) of the accompanying drawings. The fan cover shape is such that the flow exiting from the fan is well guided providing a proper path for the flow to go in vertical direction. The lateral flow distribution is assured with the help of vanes provided at the exit of the fan. This low loss system also results in low noise.
In accordance with an embodiment of this invention, there is provided a fan (42) with its centre (61) horizontally offset (62) from the centre (63) of lower circular portion (64) of the fan cover (200). The offset (62) is in a direction pre-defined in accordance with fan (42) rotation direction. As the fan (42) rotates, it causes the flow along the direction of rotation of the fan (42).
For a clockwise rotating fan (42), this horizontal offset (62) is such that the centre of the fan (61) is on the operative right with respect to the centre (63) of the lower circular portion (64) of the fan (42). This ensures that there is an expanding substantially circular path (65) from the operative left of the lower circular portion (64) of the fan cover towards its operative right, thereby providing appropriate flow direction to the flow exiting from the fan (42), reducing losses and noise.
For an anti-clockwise rotating fan (42), this horizontal offset (62) is such that the centre of the fan (42) is on the operative left with respect to the centre (63) of the

lower circular portion (64) of the fan (42). This ensures that there is an expanding substantially circular path (65) from the operative right of the lower circular portion (64) of the fan cover towards its operative left, thereby providing appropriate flow direction to the flow exiting from the fan (42), reducing losses and noise.
Instead of having a uniform substantially circular channel between the perimeter of the fan and the perimeter of the fan cover, this expanding substantially circular channel ensures uniform pressure distribution across the circular channel and provides a proper path for the circumferential flow between the fan and the lower circular portion of the fan cover. Air speed increases as it flows along the direction of rotation of the fan, and provisioning of expanding space in the substantially circular direction in accordance with fan rotation direction provides room for the increased turbulant air, thereby reducing losses and noise.
In accordance with another embodiment of this invention, there are provided a pluarlity of vanes (67), placed vertically above the lower circular portion of fan cover which houses the fan (42). These vanes are curvilinear vanes. The curve defining the curvilinear equation for each vane changes in accordance with its placement. The vane closer to one wall may be straight or slightly curved, while each further adjacent vane may be relatively differently curved than the previous, with progressive change in angle of curvature. The curvature direction follows the direction of the expanding substantially circular channel (between the perimeter of the fan and the perimeter of the fan cover) (65) and increases from one wall to another such that the air that is exited from the fan area is guided without vortex formation.

The vanes (67) are rounded off at their operative top and bottom ends in order to prevent turbulence and reduce noise, thereof. This shape of vanes (67) and placement of vanes (67) ensure impact-free entry for the flow of air, exiting from the fan area, into the passages (68) made by adjacent vanes (67).
This provides proper flow distribution in a lateral direction which results in uniform flow distribution at the heat exchanger inlet (55) resulting in low noise and proper heat transfer due to uniform inlet flow to the heat exchanger (55).
In accordance with yet another embodiment of this invention, there is provided a tongue (69) where the circumferential wall of the fan cover mates with the wall adjacent the vanes (67). This tongue (69) is a protrusion into the flow upto a predefined depth. While air rotates along the circumferene of the fan (42) along the direction of fan rotation, the inward protruberence of the tongue (69) ensures that a component of air departs away from the expanding substantially circular channel into the passages (68) created between the vanes (67), and the residual portion returns into the channel. Air impacts at this tongue (69) and division of air occurs. This inward protruberence or tongue (69) divides the flow from the fan exit, directing part of it to go around in the expanding substantially circular path (65) around the fan (42) in direction of fan rotation and part of it in upward direction by a smooth gradual turn.
A small curvature of the circumferential wall of the fan results in a relatively larger indent. This relatively larger indent aims to reduce noise with introducing a small tonal component of noise.

A large curvature of the circumferential wall of the fan results in a relatively smaller indent. This relatively smaller indent aims to reduce tonal component but increases broadband noise.
The choice of indentaiton is a designer's choice in accordance with desired tonal and noise elimination characteristics.
While one wall includes the tongue, the opposite wall may be a straight wall or a curved wall.
This fan cover shape can be used in any external fan system for HT motors.
While this detailed description has disclosed certain specific embodiments of the present invention for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention as defined in the following claims, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We Claim,
1. A low noise and low loss fan cover system, said fan cover comprising an operative lower circular portion housing a fan, characterised in that, the fan centre is horizontally offset from the centre of said lower circular portion of said fan cover, said offset being in a direction pre-defined in accordance with fan rotation direction, thereby providing an expanding substantially circular channel defined between the perimeter of the fan and the perimeter of the fan cover.
2. A low noise and low loss fan cover system, said fan cover comprising an operative lower circular portion housing a fan, characterised in that, the fan centre is horizontally offset from the centre of said lower circular portion of said fan cover, said offset being in a direction pre-defined in accordance with fan rotation direction, wherein, said horizontal offset being defined by said fan centre being placed to the operative right with respect to the centre of said lower circular portion of said fan cover, for a clockwise rotating fan, thereby providing an expanding substantially circular channel defined between the perimeter of the fan and the perimeter of the fan cover.
3. A low noise and low loss fan cover system, said fan cover comprising an operative lower circular portion housing a fan, characterised in that, the fan centre is horizontally offset from the centre of said lower circular portion of said fan cover, said offset being in a direction pre-defined in accordance with fan rotation direction, wherein, said horizontal offset being defined by said fan centre being placed to the operative left with respect to the centre of

said lower circular portion of said fan cover, for an anti-clockwise rotating fan, thereby providing an expanding substantially circular channel defined between the perimeter of the fan and the perimeter of the fan cover
4. A fan cover system as claimed in claim 1 wherein, said system includes a pluarlity of vanes, placed vertically above said lower circular portion of said fan cover which houses said fan.
5. A fan cover system as claimed in claim 1 wherein, said system includes a pluarlity of vanes, placed vertically above said lower circular portion of said fan cover which houses said fan, said vanes being curvilinear vanes.
6. A fan cover system as claimed in claim 1 wherein, said system includes a pluarlity of vanes, placed vertically above said lower circular portion of said fan cover which houses said fan, said vanes being curvilinear vanes, the curve defining the curvilinear equation for each vane changing in accordance with its placement, characterised in that, the vane closer to one wall is slightly curved, while each further adjacent vane is relatively differently curved than the previous adjacent vane.
7. A fan cover system as claimed in claim 1 wherein, said system includes a pluarlity of vanes, placed vertically above said lower circular portion of said fan cover which houses said fan, said vanes being curvilinear vanes, with the curvature direction following the direction of the expanding substantially circular channel (between the perimeter of the fan and the perimeter of the

fan cover) and increasing from one wall to another such that the air that is exited from the fan area is guided without vortex formation.
8. A fan cover system as claimed in claim 1 wherein, said system includes a pluarlity of vanes, placed vertically above said lower circular portion of said fan cover which houses said fan, said vanes being rounded off at their operative top and bottom ends in order to prevent turbulence and reduce noise, thereof such that the shape and placement of vanes ensure impact-free entry for the flow of air, exiting from the fan area, into the passages made by adjacent vanes.
9. A. fan covet system as claimed m claim 1 v/hetem, said system includes a tongue where the circumferential wall of said fan cover mates with the wall adjacent the vanes located above said lower circular portion housing a fan.
10. A fan cover system as claimed in claim 1 wherein, said system includes a tongue where the circumferential wall of said fan cover mates with the wall adjacent the vanes located above said lower circular portion housing a fan, said tongue being a protrusion in the inner side upto a pre-defined depth.
11. A fan cover system as claimed in claim 1 wherein, said system includes a tongue where the circumferential wall of said fan cover mates with the wall adjacent the vanes located above said lower circular portion housing a fan, said tongue being defined by pre-defined curvilinear equations in accordance with desired noise and tonal elimination characteristics.

12. A fan cover system as claimed in claim 1 wherein, a first wall which includes the tongue and a second opposite wall is a straight wall.
13. A fan cover system as claimed in claim 1 wherein, a first wall which includes the tongue and a second opposite wall is a curved wall.
14. A fan cover system system as claimed in claim 1 wherein, said fan cover system is an external fan cover system for motors.
15. A heat exchanger with a low noise and low loss fan cover system with said heat exchanger being placed beyond an exit member and in direct communication with said exit member, said fan cover comprising an operative lower circular portion housing a fan, characterised in that, the fan centre is horizontally offset from the centre of said lower circular portion of said fan cover, said offset being in a direction pre-defined in accordance with fan rotation direction, thereby providing an expanding substantially circular channel defined between the perimeter of the fan and the perimeter of the fan cover.
16. A heat exchanger with a low noise and low loss fan cover system with said
heat exchanger being placed beyond an exit member and in direct
communication with said exit member, said fan cover comprising an
operative lower circular portion housing a fan, characterised in that, the fan
centre is horizontally offset from the centre of said lower circular portion of
said fan cover, said offset being in a direction pre-defined in accordance
with fan rotation direction, wherein, said horizontal offset being defined by

said fan centre being placed to the operative right with respect to the centre of said lower circular portion of said fan cover, for a clockwise rotating fan, thereby providing an expanding substantially circular channel defined between the perimeter of the fan and the perimeter of the fan cover.
17. A heat exchanger with a low noise and low loss fan cover system with said heat exchanger being placed beyond an exit member and in direct communication with said exit member, said fan cover comprising an operative lower circular portion housing a fan, characterised in that, the fan centre is horizontally offset from the centre of said lower circular portion of said fan cover, said offset being in a direction pre-defined in accordance with fan rotation direction, wherein, said horizontal offset being defined by said fan centre being placed to the operative left with respect to the centre of said lower circular portion of said fan cover, for an anti-clockwise rotating fan, thereby providing an expanding substantially circular channel defined between the perimeter of the fan and the perimeter of the fan cover
18. A heat exchanger as claimed in claim 1 wherein, said system includes a pluarlity of vanes, placed vertically above said lower circular portion of said fan cover which houses said fan.
19. A heat exchanger as claimed in claim 1 wherein, said system includes a pluarlity of vanes, placed vertically above said lower circular portion of said fan cover which houses said fan, said vanes being curvilinear vanes.

20. A heat exchanger as claimed in claim 1 wherein, said system includes a pluarlity of vanes, placed vertically above said lower circular portion of said fan cover which houses said fan, said vanes being curvilinear vanes, the curve defining the curvilinear equation for each vane changing in accordance with its placement, characterised in that, the vane closer to one wall is slightly curved, while each further adjacent vane is relatively differently curved than the previous adjacent vane.
21. A heat exchanger as claimed in claim 1 wherein, said system includes a pluarlity of vanes, placed vertically above said lower circular portion of said fan cover which houses said fan, said vanes being curvilinear vanes, with the curvature direction following the direction of the expanding substantially circular channel (between the perimeter of the fan and the perimeter of the fan cover) and increasing from one wall to another such that the air that is exited from the fan area is guided without vortex formation.
22. A heat exchanger as claimed in claim 1 wherein, said system includes a pluarlity of vanes, placed vertically above said lower circular portion of said fan cover which houses said fan, said vanes being rounded off at their operative top and bottom ends in order to prevent turbulence and reduce noise, thereof such that the shape and placement of vanes ensure impact-free entry for the flow of air, exiting from the fan area, into the passages made by adjacent vanes.
23. A heat exchanger as claimed in claim 1 wherein, said system includes a
tongue where the circumferential wall of said fan cover mates with the wall
adjacent the vanes located above said lower circular portion housing a fan.

24. A heat exchanger as claimed in claim 1 wherein, said system includes a tongue where the circumferential wall of said fan cover mates with the wall adjacent the vanes located above said lower circular portion housing a fan, said tongue being a protrusion in the inner side upto a pre-defined depth.
25. A heat exchanger as claimed in claim 1 wherein, said system includes a tongue where the circumferential wall of said fan cover mates with the wall adjacent the vanes located above said lower circular portion housing a fan, said tongue being defined by pre-defined curvilinear equations in accordance with desired noise and tonal elimination characteristics.
26. A heat exchanger as claimed in claim 1 wherein, a first wall which includes the tongue and a second opposite wall is a straight wall.

27. A heat exchanger as claimed in claim 1 wherein, a first wall which includes the tongue and a second opposite wall is a curved wall.
28. A heat exchanger as claimed in claim 1 wherein, said fan cover system is an external fan cover system for motors.