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, 6th Floor, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR:
Bhatia Dinesh of Crompton Greaves Ltd, Analytics Centre, C G Global R&D Centre, Bhaskara building, Kanjurmarg (E), Mumbai - 400042, Maharashtra, India; 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 (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).
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 eliminating the need for baffles.
Another object of the invention is to provide an improved fan cover system which efficiently directs the incoming air with reduced turbulence.
SUMMARY OF THE INVENTION:
According to this invention, there is provided a low noise and low loss fan cover system, said system comprises a substantially tubular component consisting of an inlet member at the operative lower front side of the tubular component, said inlet member being placed in front of a fan placed inside said fan cover such that there is direct communication of incoming air from said inlet member to said fan, and an exit member at the operative top front side of the tubular component such that the tubular component blends into the exit member for directing the air flow towards a heat exchanger, characterised in that, said fan comprises an enveloping curvilinear fan shroud adapted to curve operatively away from said fan into said inlet member of said fan cover with said curvilinear portion of said fan shroud extending away from said fan to form a substantially straight portion, formng a cylinder, said straight portion extending into said inlet member and being overlapped by the circumferential wall of said inlet member upto a pre-defined length.
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 system comprising a substantially tubular component consisting of an inlet member at the

operative lower front side of the tubular component, said inlet member being placed in front of a fan placed inside said fan cover such that there is direct communication of incoming air from said inlet member to said fan, and an exit member at the operative top front side of the tubular component such that the tubular component blends into the exit member for directing the air flow towards a heat exchanger, characterised in that, said fan comprises an enveloping curvilinear fan shroud adapted to curve operatively away from said fan into said inlet member of said fan cover with said curvilinear portion of said fan shroud extending away from said fan to form a substantially straight portion, formng a cylinder, said straight portion extending into said inlet member and being overlapped by the circumferential wall of said inlet member upto a pre-defined length,
Typically, said system includes a clearance between said inner circumferential wall of said inlet member and said outer circumferential wall of said fan shroud.
Typically, said fan shroud is a rotating assembly.
Typically, said system includes an operative lower front portion, characterised in that, said front portion of said fan cover is a stepped operative front portion, said stepped portions including a stepped cut above said inlet member and below said inlet member in order to restricts the lateral passage for air flow.
Typically, said system includes a curvilinear connect between said tubular component and a heat exchanger placed at an operative top rear portion of the fan cover, said curvilinear connect being at the operative curved rear end of said fan cover.

Typically, said system includes a curvilinear connect between said tubular component and a heat exchanger placed at an operative top rear portion of the fan cover, said curvilinear connect portion providing a gradual turn from a fan back cover wall to the horizontally placed heat exchanger, thereby eliminating the need for baffles and extra components in the fan cover assembly.
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 heat exchanger and air exhaust assembly with silencer mechanism; and
Figure 2 illustrates a fan cover and its design according to the prior art.
Figures 3 and 4 illustrates the new and improved fan cover design in its side view.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
According to this invention, there is provided a low noise and low loss fan cover system.

Figure 1 illustrates a motor with associated heat exchanger and air exhaust assembly with silencer mechanism.
Figure 2 illustrates a fan cover and its design according to the prior art. 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 (46). This heat exchanger is placed beyond the exit member (44) and in direct communication with the exit member (44).
Figure 3 illustrates the fan cover design in its side view.
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 (46). This heat exchanger is placed beyond the exit member (44) and in direct communication with the exit member (44).

The air flow, after passing through the fan (42), goes into the heat exchanger (46) placed adjacent the exit member (44) of the cover.
The design of the fan cover system, according to the prior art, is a high pressure loss producing system with a large amount of noise. As a result, for a given mass flow rate, the power consumption of the system is very high. Also, the high flow separation results in a large noise producing system.
In accordance with an embodiment of this invention, there is provided a curvilinear (45) fan shroud (52) adapted to curve operatively away from the fan (42) into the inlet member (40) of the fan cover (100). The curvilinear portion (45) of the fan shroud (52) extends away from the fan to form a substantially straight portion (47) and forms a cylinder. This straight portion (47) extends into the inlet member (40) and is partially overlapped by the circumferential wall (49) of the inlet member (40). This overlap is of a pre-defined length. There is a clearance between the inner circumferential wall (49) of the inlet member and the outer circumferential wall (straight portion referenced by numeral 47) of the fan shroud (52). The fan shroud (52) may be a rotating assembly.
Due to this overlap and the curvilinear portion, the flow path from the inlet member (40) is appropriately channeled with the flow of air. The dipersion of air into the fan cover is not at right angles according to the prior art design, but is in a gradually expanding form according to the system of this invention. This avoids turbulence, provides room for gradual expansion, and reduces the leakage flow (flow not passing through the fan). Also, the flow of air enters the fan without any separation, which is an advantage over the earlier design.

In accordance with an embodiment of this invention, there is provided a stepped operative front portion (62) of the fan cover. The stepped portions (64, 66) include a stepped cut above the inlet member and below the inlet member. This restricts the lateral passage for the flow which exits from the fan. There is no room for air flow to be unguided and create noise or turbulence. The incoming air flow from the inlet member is directed towards the fan directly, and in a gradual manner, without allowing for extra passage in the tubular component.
The removal of the additional region due to this embodiment reduces the noise and losses.
In accordance with an embodiment of this invention, there is provided a curvilinear connect (72) between the tubular component (41) and the heat exchanger placed at an operative top rear portion of the fan cover. This curvilinear connect is the operative curved rear end of the fan cover. This curvilinear connect portion provides a gradual turn from the fan back cover wall to the horizontally placed heat exchanger. This eliminated the need for baffles and extra components in the fan cover assembly.
The incorporation of this curvilinear connect reduces noise and flow losses. Elimination of baffles helps in uniform flow distribution at the heat exchanger inlet and as a result at the exit which reduces the noise from the system.
The shape of the fan cover is designed, in accordance with this invention, in such a way that it produces lower noise and a lower pressure loss through the system. As a result, for the same mass flow rate, the fan would consume lesser power. The

flow path is altered to produce lesser presure loss and the direct the flow to the heat exhanger with reduced flow separation.
The new design changes are shown in Figure 4 of the accompanying drawings (side view of the new fan cover).
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 system comprising a substantially tubular component consisting of an inlet member at the operative lower front side of the tubular component, said inlet member being placed in front of a fan placed inside said fan cover such that there is direct communication of incoming air from said inlet member to said fan, and an exit member at the operative top front side of the tubular component such that the tubular component blends into the exit member for directing the air flow towards a heat exchanger, characterised in that, said fan comprises an enveloping curvilinear fan shroud adapted to curve operatively away from said fan into said inlet member of said fan cover with said curvilinear portion of said fan shroud extending away from said fan to form a substantially straight portion, formng a cylinder, said straight portion extending into said inlet member and being overlapped by the circumferential wall of said inlet member upto a pre-defined length.
2. A fan cover system as claimed in claim 1 wherein, said system includes a clearance between said inner circumferential wall of said inlet member and said outer circumferential wall of said fan shroud.
3. A fan cover system as claimed in claim 1 wherein, said fan shroud is a rotating assembly.
4. A fan cover system as claimed in claim 1 wherein, said system includes an operative lower front portion, characterised in that, said front portion of said

fan cover is a stepped operative front portion, said stepped portions including a stepped cut above said inlet member and below said inlet member in order to restricts the lateral passage for air flow.
5. A fan cover system as claimed in claim 1 wherein, said system includes a curvilinear connect between said tubular component and a heat exchanger placed at an operative top rear portion of the fan cover, said curvilinear connect being at the operative curved rear end of said fan cover.
6. A fan cover system as claimed in claim 1 wherein, said system includes a curvilinear connect between said tubular component and a heat exchanger placed at an operative top rear portion of the fan cover, said curvilinear connect portion providing a gradual turn from a fan back cover wall to the horizontally placed heat exchanger, thereby eliminating the need for baffles and extra components in the fan cover assembly.
7. A fan cover system as claimed in claim 1 wherein, said fan cover system is an external fan cover system for motors.
8. 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 system comprising a substantially tubular component consisting of an inlet member at the operative lower front side of the tubular component, said inlet member being placed in front of a fan placed inside said fan cover such that there is direct communication of incoming air from said inlet member to said fan,

and an exit member at the operative top front side of the tubular component such that the tubular component blends into the exit member for directing the air flow towards a heat exchanger, characterised in that, said fan comprises an enveloping curvilinear fan shroud adapted to curve operatively away from said fan into said inlet member of said fan cover with said curvilinear portion of said fan shroud extending away from said fan to form a substantially straight portion, formng a cylinder, said straight portion extending into said inlet member and being overlapped by the circumferential wall of said inlet member upto a pre-defined length.
9. A heat exchanger with a low noise and low loss fan cover system as claimed in claim 1 wherein, said system includes a clearance between said inner circumferential wall of said inlet member and said outer circumferential wall of said fan shroud.
10. A heat exchanger with a low noise and low loss fan cover system system as claimed in claim 1 wherein, said fan shroud is a rotating assembly.
11. A heat exchanger with a low noise and low loss fan cover system system as claimed in claim 1 wherein, said system includes an operative lower front portion, characterised in that, said front portion of said fan cover is a stepped operative front portion, said stepped portions including a stepped cut above said inlet member and below said inlet member in order to restricts the lateral passage for air flow.

12. A heat exchanger with a low noise and low loss fan cover system system as claimed in claim 1 wherein, said system includes a curvilinear connect between said tubular component and a heat exchanger placed at an operative top rear portion of the fan cover, said curvilinear connect being at the operative curved rear end of said fan cover.
13. A heat exchanger with a low noise and low loss fan cover system system as claimed in claim 1 wherein, said system includes a curvilinear connect between said tubular component and a heat exchanger placed at an operative top rear portion of the fan cover, said curvilinear connect portion providing a gradual turn from a fan back cover wall to the horizontally placed heat exchanger, thereby eliminating the need for baffles and extra components in the fan cover assembly.
14. A heat exchanger with a low noise and low loss fan cover system system as claimed in claim 1 wherein, said fan cover system is an external fan cover system for motors.