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
An inlet silencer mechanism for heat exchangers
APPLICANTS :
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR (S):
Pangal Sarvesh of Crompton Greaves Ltd, Large & Traction Machines Division, D5, Industrial Area MPAKVN, Mandideep, 462046, Madhya Pradesh, 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 inlet silencer mechanisms for motors.
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 standard.
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.
This hot air, now, is then exited through the heat exchanger.

Typically, there are two internal fans in the motor for air circulation (for guiding out hot air from the motor). There relatively smaller fans guide the air, which is relatively hotter, from the motor housing in the direction of the heat exchanger 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.
Prior Art:
US6729859 discloses an Airflow Generating device air intake. A shroud having an air intake aperture consists of funnel shaped cowl and a conical airflow deflection body, enclosing a portion of motor housing adjacent to fan

assembly is disclosed. There is no active sound absorbing characteristic in this patent document.
US6069423 discloses a Motor cooling and sound absorbing system. A recess preferably in the shape of a truncated cone, is formed generally centrally in acoustic foam block which is surrounding the fan. However, it does not relate to an external fan of a motor and heat exchanger assembly.
Objects of Invention:
An object of the invention is to provide an improved noise control device (silencer mechanism) in a motor for reducing the noise level and temperature rise in the motors,
Another object of the invention is to provide an improved noise control device (silencer mechanism) in an induction motor.
Yet another object of the invention is to provide reduction of overall noise level in an induction motor with air as a cooling medium.
Still another object of the invention is to provide an improved noise control device in closed air circuit air cooled motor which noise control device (silencer mechanism) having low maintenance.
Another object of the invention is to provide an improved noise control device in closed air circuit air cooled motor which noise control device (silencer mechanism) having new aerodynamic baffle to control noise.

Summary of the Invention:
According to this invention, there is provided an inlet silencer mechanism for heat exchangers, said mechanism comprises:
a. cylindrical housing extending from an operative rear end to an
operative front end of said housing, wherein said operative rear end
and said operative front end are open ends adapted to allow exit and
entry of air respectively into said housing and said operative rear end
cooperating with an external fan;
b. cone shaped element with a back-plate, placed co-axial to said
cylindrical housing, and adapted to guide entry of air away from the
centre of said housing towards inner walls of said housing, with the
slope of said cone extending from said centre towards said inner walls
of said cylindrical housing to channel the flow of air towards said
walls, thereby creating a streamlined guided airflow; and
c. foam with noise absorbing characteristics lined on said inner walls in
order to dampen noise element of said guided air.
Typically, said operative rear end is defined by a rear annular ring.
Typically said rear annular ring is a flanged ring.
Typically, operative front end is defined by a front annular ring.
Typically, said housing includes stiffener members extending longitudinally through said housing in order to strengthen said housing.

Typically, said cone shaped element is a reduced diameter cone shaped element as compared to said cylindrical housing diameter.
Typically, said cylindrical housing includes transverse elongate support elements that run from said rear annular ring to said back-plate in order to hold said cone shaped element in place, spaced away from said walls.
Preferably, said radially placed transverse elongate support elements are rib
elements.
Typically, said cone shaped element is a foam coated cone shaped element.
Brief Description of the Accompanying Drawings:
The invention will now be described in relation to the accompanying drawings, in which:
Figure 1 illustrates a schematic motor and heat exchanger along with an inlet silencer mechanism;
Figure 2 illustrates an isometric view of the inlet silencer mechanism;
Figure 3 illustrates a side cross-sectional view of the inlet silencer mechanism of Figure 2;

Figure 4a illustrates a schematic front isometric view of the inlet silencer mechanism of Figure 2;
Figure 4a illustrates a schematic back isometric view of the inlet silencer mechanism of Figure 2; and
Figure 5 illustrates a sound-intensity-map of the motor - heat exchanger -fan mechanism.
Detailed Description of the Accompanying Drawings:
According to this invention, there is provided an inlet silencer mechanism for heat exchangers.
Figure 1 illustrates a schematic motor and heat exchanger along with an inlet silencer mechanism (100).
A motor (12) is associated with a heat exchanger (14) which is placed operatively above it. The relatively hotter air from the motor rises towards the heat exchanger, where it is cooled due to the heat exchanging mechanism, and relatively colder air from the heat exchanger settles downwards towards the motor placed operatively beneath it. This action of rising and rotation of the air is propelled by internal fans (16, 18).
The heat exchanger, mentioned and used herein, is an air-cooled heat exchanger.

An external fan (20) which propels the movement of ambient air towards the heat exchanger in order to continuously supply the tubes of the heat exchanger (14) with relatively colder air is placed co-axial to the motor. As the motor works, a common shaft hoisting the rotor of the motor and the external fan rotates, thereby pressing them into action simultaneously.
A sound intensity map was drawn in order to figure out the pain points in relation to sound generation in such an assembly (motor - heat exchanger -fan mechanism). This is shown in Figure 5 of the accompanying drawings. It can be seen that the maximum noise occurs at the fan cover where the external fan is located. Hence, there is a need for a silencer mechanism at this point.
Figure 2 illustrates an isometric view of the inlet silencer mechanism (100).
In accordance with an embodiment of this invention, there is provided a cylindrical housing (22) extending from an operative rear end to an operative front end. The operative rear end and the operative front end are open ends to allow exit and entry of air respectively. The operative rear end cooperates with the external fan (20).
The operative rear end is defined by a rear annular ring (24). Typically, said rear annular ring is a flanged ring. The flange allows the inlet silencer mechanism (100) to be fitted to the motor housing.

The operative front end is defined by a front annular ring (26).
In accordance with another embodiment of this invention, there are provided stiffener members (28) extending longitudinally on the housing in order to strengthen the housing.
Figure 3 illustrates a side cross-sectional view of the inlet silencer
mechanism of Figure 2.
Figure 4a illustrates a schematic front isometric view of the inlet silencer
mechanism of Figure 2.
Figure 4a illustrates a schematic back isometric view of the inlet silencer
mechanism of Figure 2.
In accordance with yet another embodiment of this invention, there is provided a cone shaped element (32) with a back-plate (34) adapted to guide the entry of air away from the centre of the inlet silencer mechanism. The slope of the cone extending from the centre towards the inner walls of the cylindrical housing (22) channel the flow of air towards the walls (33). The walls are lined with foam (36) in order to dampen the noise. The foam (36) has good noise absorbing characteristics. The cone shaped element (32) with the back-plate (34) is placed co-axial to the cylindrical housing (22) and is of a reduced diameter as compared to the cylindrical housing (22). The cone shaped element (32) is held in place, spaced away from the walls (33) by means of radially placed transverse elongate support elements (38) that run from the rear annular ring (24) to the back-plate (34).These radially placed transverse elongate support elements are rib elements.

In Figure 3 of the accompanying drawings, the dark dotted lines (with arrowheads) depict the curvilinear path of air entering the inlet silencer mechanism (100). This flow of air in the given path reduces turbulence and provides a gradient flow of air. Moreover, the air flow's contact with foam on the inner walls of the cylindrical housing dampens the turbulence. There is a wide channel beyond the back-plate (34) in the cylindrical housing (22) in order to allow the dampened air flow to be passed into the heat exchanger through the external fan (20).
The purpose of introducing the inlet silencer is to dampen the noise generated by the external fan (20). Airborne noise is major source of noise generated in an induction machine which is cooled by air. By the introduction of this part into the external air circuit path, a noise damping of around 4 db was achieved, according to an exemplary embodiment. The overall noise level of the motor was brought down from 88db to 84db due to this component in the exemplary embodiment.
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. An inlet silencer mechanism for heat exchangers, said mechanism comprising:
a. cylindrical housing extending from an operative rear end to an
operative front end of said housing, wherein said operative rear end
and said operative front end are open ends adapted to allow exit and
entry of air respectively into said housing and said operative rear end
cooperating with an external fan;
b. cone shaped element with a back-plate, placed co-axial to said
cylindrical housing, and adapted to guide entry of air away from the
centre of said housing towards inner walls of said housing, with the
slope of said cone extending from said centre towards said inner walls
of said cylindrical housing to channel the flow of air towards said
walls, thereby creating a streamlined guided airflow; and
c. foam with noise absorbing characteristics lined on said inner walls in
order to dampen noise element of said guided air.
2. A mechanism as claimed in claim 1 wherein, said operative rear end is defined by a rear annular ring.
3. A mechanism as claimed in claim 1 wherein, said rear annular ring is a flanged ring.
4. A mechanism as claimed in claim 1 wherein, operative front end is defined by a front annular ring.

5. A mechanism as claimed in claim 1 wherein, said housing includes stiffener members extending longitudinally through said housing in order to strengthen said housing.
6. A mechanism as claimed in claim 1 wherein, said cone shaped element is a reduced diameter cone shaped element as compared to said cylindrical housing diameter.
7. A mechanism as claimed in claim 1 wherein, said cylindrical housing includes transverse elongate support elements that run from said rear annular ring to said back-plate in order to hold said cone shaped element in place, spaced away from said walls.
8. A mechanism as claimed in claim 7 wherein, said radially placed transverse elongate support elements are rib elements.
9. A mechanism as claimed in claim 1 wherein, said cone shaped element is a foam coated cone shaped element.