FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION (See section 10 and rule 13)
1. TITLE OF THE INVENTION:
"Canopy for Noise Reduction in Power Generating Units"
2. APPLICANT:
a. NAME: MAHINDRA & MAHINDRA LIMITED
b. NATIONALITY: Indian Company registered under the provisions of
the Companies Act-1956.
c. ADDRESS: R&D Center, Automotive Sector, 89,
M.I.D.C, Satpur, NASHIK - 422 007 Maharashtra State, India
3. PREAMBLE TO THE DESCRIPTION:
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.

Canopy for Noise Reduction in Power Generating Units
Field of the invention
The present invention relates to a noise reduction shield for sound generating devices, and more particularly, to a sound absorption type shield for noise reduction in power generating units.
Background of the invention
Environmental noise caused by land vehicles and other modern machineries can often be an annoyance. To maintain the noise below acceptable levels, noise suppression techniques are often employed. Noise suppression has, therefore, become an important technology with a wide variety of industrial and residential applications. The noise suppression devices are often applied in heating ventilation and air conditioning (HVAC) systems, electricity generators, industrial machinery and complexes, transportation vehicles, and any machinery that may tend to produce unacceptably high levels of noise.
In recent years, the shortage of power coupled with unreliable and poor quality of the power supply has resulted in a proliferation of captive generator sets, run with either diesel or petrol, as an alternate source of power. This happens particularly in urban areas where the need is greater. Unfortunately, in most of these places there is an overlap of commercial, residential and industrial areas which together with poor planning for the installation of generator sets and absence of any acoustic treatment/enclosure, leads to excessive noise pollution. Lots of effort has been made to tackle this problem through prescribing noise standards and developing guidelines for providing acoustic enclosure/treatment for diesel run generator (DG) sets.

In the existing electricity generating sets, from the engine source to the receiver, the maximum noise reduction achieved in l m distance from the DG set (25kVA) at 1800 rpm (75% Load) is 57 dB (A). To achieve this reduction in noise level, a dual cabin canopy as shown in figures la and lb is used that comprises an outer cabin (1) followed by air gap (2) and then an inner cabin (3) which is again followed by an inner door secondary panel (4). This increases the weight of the product which ultimately increases the product cost. Also, in order for the person to inspect the engine or the generator unit present inside the canopy, the service person has to enter in by two doors. The first entry door is at the outer cabin (1) and the second entry door is at the inner cabin (3).
Accordingly, there exists a need to provide a canopy in power generating sets that overcomes drawbacks of the prior art.
Objects of the Present Invention
An object of the present invention is to reduce noise level from power generating units.
Yet another object of the present invention is to provide a canopy for reducing noise level which is cost effective and simple in construction.
Summary of the invention
Accordingly, the present invention provides a canopy for noise reduction in a power generating unit. The canopy comprises a housing, at least two doors, an inlet and an outlet. The housing encloses the power generating unit. The housing is made of a wail. The wail is made up of at least four layers that are stacked together by an adhesive.

The housing formed by the wall is a single cabin acting as a dual density absorber-barrier for noise reduction in the power generating unit. The housing includes the at least two doors configured thereon for accessing the power generating unit. The inlet is configured on the housing for air intake and the outlet is configured on the housing for exhaust.
Brief Description of the Drawings
The objectives and advantages of the present invention will become apparent from the following description read in accordance with the accompanying drawings wherein,
Figures la and lb show a top plan view and a one side cut sectional view of a double cabin canopy of a power generating unit of a prior art;
Figure 2 shows a top view of a canopy for noise reduction in a power generating unit, in accordance with the present invention;
Figure 3 shows a front view of the canopy of figure 2;
Figure 4 shows a sectional view of a four layered wall of a housing of the canopy of figure 2; and
Figure 5 shows a graph of transmission loss curve of the double cabin canopy of the prior art and the canopy of the present invention.
Detail Description of the Invention
The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and

approaches are overcome by the present invention as described below in the preferred embodiments.
The present invention provides a canopy for noise reduction in power generating units. The canopy completely eliminates the need of two cabins to achieve noise reduction and also eases the access to the generator/engine set. The canopy is cost effective and simple in construction.
The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description.
Referring to figures 2-4, there is shown a canopy (100) for noise reduction in a power generating unit (200), in accordance with the present invention. In an embodiment, the power generating unit (200) is a diesel generator unit. The canopy comprises a housing (80), at least two doors (50, 60), an inlet (40) and an outlet (30). The above mentioned elements are assembled by any suitable means known in the art.
The housing (80) encloses the power generating unit (200). The housing (80) includes is made up of at least four layered wall (78). The four layers (70, 72, 74, and 76) of the wall (78) are held/stacked together by an adhesive. In an embodiment, the adhesive is a synthetic rubber adhesive such as dendrite. The four layers include a first layer (70), a second layer (72), a third layer (74) and a fourth layer (76). The first layer (70) is an outermost layer made of a high surface weight barrier material selected from a cold rolled close annealed (CRCA) steel panel. The second layer (72) is made of a high density absorber material particularly fire retardant PU foam having a density of 70kg per cubic meter. The third layer (74) is made of a low surface weight barrier material and specifically from Ethylyne Vinyl Acetate (EVA). The fourth layer (76) is an

innermost layer made of a low density absorber material and specifically from fire retardant PU foam having a density of 50 kg per cubic meter. The PU foam serves as a de-coupler material. However, it is understood that the four layers (70, 72, 74, and 76) of the wall (78) can be made from any suitable material of appropriate density in alternate embodiments of the present invention. Specifically, the housing (80) formed by the wall (78) is a single cabin acting as a dual density absorber-barrier and weighs very less as compared to the existing double cabin canopy designs. Thus dual density absorber-barrier wall (78) includes high surface weight steel panel and low surface weight EVA acting as the double wall barrier and the PU foam of different densities serving as the double wall absorber. This combination has improved the transmission loss in mass controlled region. In an embodiment, the wall (78) has a width of about 100 mm.
The housing (80) includes at least two doors (50, 60) configured thereon. Specifically, one door (50) is configured on a left hand side (not numbered) thereof and the other door (60) is configured on a right hand side (not numbered) thereof. Any one of the two doors (50, 60) are opened to provide access to the power generating unit (200) enclosed inside the housing (80). The housing (80) includes the inlet (40) configured on a first side (not numbered). The inlet (40) is configured for intake of air. The outlet (30) is configured on a second side (not numbered) of the housing (80) for air exhaust.
Referring to figure 5, there is shown a graph to indicate transmission loss curves (A and B) for the dual cabin canopy of the prior art and the canopy (100) of the present invention respectively. The graph shows a conventional concept of absorber - barrier with effective working range of material highlighted in the transmission loss curve (A). However, with the canopy (100) of the present invention, the transmission loss of the canopy (100) exceeds sum of the transmission loss of the individual walls in mass controlled region as the double

wall barrier utilizes an air space/ de-coupler material to isolate the barrier walls
from each other.
Advantages
1. The canopy (100) provides a better NVH performance achieved with very less material.
2. The canopy (100) saves over all material cost to minimum 20% as compared to the dual cabin canopy of the prior art.
3. The canopy (100) weight reduction is up to 40% and is compact in size as compared with the dual cabin canopy of the prior art.
4. The canopy (100) provides good heat dissipation therefrom.
5. The canopy (100) provides an easy access to the power generating unit (200) as only one door (50, 60) needs to be opened for entering into the housing (80).
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the spirit or scope of the present invention.

We claim:
1. A canopy (100) for noise reduction in a power generating unit
(200), the canopy (100) comprising:
• a housing (80) enclosing the power generating unit (200), the housing (80) made of a wall (78), the wall (78) being made up of at least four layers (70, 72, 74, and 76) held/stacked together by an adhesive;
• at least two doors (50, 60) configured on the housing (80) for accessing the power generating unit (200);
• an inlet (40) configured on the housing (80) for air intake; and
• an outlet (30) configured on the housing (80) for exhaust, wherein the housing (80) formed by the wall (78) is a single cabin acting dual density absorber-barrier for noise reduction in the power generating unit (200).

2. The canopy (100) of claim 1, wherein the four layers (70, 72, 74, and 76) of the wall (78) of the housing (80) are made up of a material selected from any of a high surface weight barrier material, a high density absorber material, a low surface weight barrier material, a low density absorber material and a combination thereof.
3. The canopy (100) of claim 1, wherein the power generating unit (200) is accessed by opening any one of the at least two doors (50, 60).