FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE OF THE INVENTION
A Novel Muffler Structure And Method Of Assembling The Muffler Structure
For Internal Combustion Engine.


APPLICANTS
TATA MOTORS LIMITED, an Indian company
having its registered office at Bombay House,
24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India

INVENTORS
Sachin Wagh, Umesh Abhyankar and Saurabh Shukla
AH Indian Nationals of TATA MOTORS LIMITED
an Indian company having its registered
office at Bombay House, 24 Homi Mody Street,
Hutatma Chowk, Mumbai 400 001 Maharashtra, India
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner
in which it is to be performed.


FIELD OF INVENTION
The present invention relates to muffler for internal combustion engine and more particularly it relates to muffler structure and assembly thereof
BACKGROUND OF INVENTION
Internal combustion engine are generally coupled with silencer or Muffler for expanding and compressing the exhaust gas emitted from engine to dissipate the energy of exhaust gas for attenuating the sound produced thereby. The problem of silencing the noise generated to exhaust gas from internal combustion is well known. Many types of muffler and sound attenuating device have been developed to address this problem. One type of generally referred to absorption muffler directs the exhaust gas straight through perforated tube with a uniform configuration from end to end with sound absorbing material such as glass fiber between the tube and an outer housing . These mufflers are advantageous in that they provide low back pressure, but not very effective in reducing the level of noise. Another type of muffler is one characterized as a resonator. This type of muffler uses the series of baffle plate to radically change the path exhaust gas. By interrupting or changing the direction of gas flow. Sound frequencies passing there through are reflected back towards the noise source by baffle plates thus mechanically canceling each other where they meet. This type of muffler does reduce noise to some extent. However back pressure of exhaust tends to increase due to blocked exhaust flow.
OBJECT OF THE INVENTION
The main object of present invention is to provide a muffler structure for vehicles.

Another object of the present invention is to provide a method of assembling muffler structure for vehicles.
Another object of the present invention is to provide a muffler structure for vehicles which reduce the noise level and also has little or no back pressure.
Yet another object of the present invention is to provide a muffler structure for vehicles which is economical in construction, reliable in operation rugged and able to withstand automotive racing for sustained period and which has compact configuration compatible with under vehicle mounting.
BRIEF DESCRIPTION OF INVENTION
The muffler structure comprises; at least four clamp shell (10,11,12,13) seam welded together , three perforated tubes (16,17,19) with different length, perforated baffle plate (15) , non perforated baffle plate (18) and sound absorbing material (20) like steel wool glass wool and glass fiber. The said clamp shell is of two layers with different material. The said perforated tube (19) is supported at one end by perforated plate (15) and at other end by non perforated plate (18). The said perforated baffle (15) and non perforated baffle plate (18) having holes which have been crimped or welded to end of said tube (19). The perforated plate and non perforated plate are welded to shells (11,12). The shell formed after combining said four clamp shell is further divided in three chambers (21, 22, 23) by perforated plate (15) and non perforated plate (18) for reflection, expansion and absorption respectively.
The muffler of present invention allows rapid expansion of exhaust gas as it enter from inlet tube into expansion chamber through perforated tube (16, 17) , thereby allowing the exhaust gas to drop in temperature and change acoustical frequency

therein. From expansion chamber (22), the exhaust gas enter into chamber (21) where the amplitude of pressure variation is reduced by reflection and chamber (23) where the amplitude of pressure variation is reduced by absorption. The exhaust gas from chamber (21) again expend in chamber (22) through perforated tube (19). This device thus allows substantially uninterrupted flow of exhaust creating little back pressure while also allowing minimal noise emission.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 shows an exploded perspective showing of a first embodiment of the
invention
Figure 2 shows an exploded perspective view of baffles and perforated tubes
Figure 3 shows an internal structure of muffler
Figure 4 shows whole muffler with inlet pipe, outlet pipe along with mounting
brackets for muffler
DETAILED DESCRIPTION OF INVENTION
Referring now to figures I to 4. wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting the same,
The muffler shown in figure (1) comprises a housing made up of an first half shell of two layers (10 , 11) and second half shell of two layer (12 , 13) with different material which are joined to each other by seam welding. Both the length and depth (height) of each of the half shell 10, 11, 12, 13 are greater than width of the shell.
The perforated baffle plate (15) and non perforated baffle plate (18) divides the shells into three chamber expansion chamber (22) , reflection chamber (21) and absorption chamber (23), which are spot welded to shell (10) as shown in figure-03.

The volume of each chamber can be varied by changing the position of baffle plate to cater the wide range of frequency.
The one end of perforated tube (17) is extended through non perforated baffle plate (18) up to expansion chamber (21) which is spot welded to said baffle plate (18) shown in figure -03 and other end of the said perforated tube (17) is welded to perforated tube (16) . The one end of said perforated tube (19) is extended through said baffle plate (18) and kept open to reflection chamber (21) and other end passing through expansion chamber (22) to absorption chamber (23) and connected to exhaust outlet (32 ). The said perforated tube (19) is welded to baffle plates (15 , 18). The perforated tube (16) is connected to exhaust inlet pipe (34 ) at one end and crtfear end is spot w&ded to perforated tube (1 ?). Sound absorbing material 20 like glass wool, steel wool are placed in the absorption chamber (23) which surround the one end of the perforated tube (19).
The flange (35) which is welded to exhaust inlet pipe (34) interconnect the entire muffler assembly with engine exhaust manifold through the catalytic cone . The brackets (30) and (31) are used for mounting of said muffler assembly which are welded to shells (10,13).
The exhaust gas enters the muffler through the exhaust inlet pipe (34). The exhaust gas is flowing along the perforated tube (17), Due to perforation in tube (17) exhaust gas is coming out of the tube( 17) and expands in the expansion chamber (22) where the amplitude of pressure variation of exhaust gas reduce and enter into absorption chamber (23) through perforated baffle plate (15) . Sound absorbing material (20) like glass wool is there at absorption chamber (23) absorb the exhaust gas and

exhaust gas flows over the porous of sound absorbing material (20) and reduce the amplitude of pressure variation of exhaust gas.
When engine runs at high speed the velocity of exhaust gas is also high. The exhaust gas does not have much time to come out of of perforated tube (17) and enter into the reflection chamber (21) where the amplitude of pressure variation of exhaust gas get reduce due to interference of acoustic wave. The acoustic wave from perforated tube (17) strike the wall of chamber (21) and reflect back to perforated tube (17). When two acoustic wave with different amplitude move into opposite direction to each other then the amplitude of resultant wave is smaller than these two acoustic wave.
After the reflection, exhaust gas accumulate at bottom of reflection chamber (21) and go out into expansion chamber (22) through the perforated tube (19) where it expand and go the absorption chamber (23).
The present invention reduces sound pressure level of the low frequency noise and high frequency noise and cover the wide range of frequency. Pre silencer , main silencer, post silencer are integrated into one muffler box which perform all desired function of pre silencer , main silencer, post silencer.
The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purpose of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.

WE CLAIM
1. A novel muffler structure for internal combustion engine comprising
at least two halves of housings joined together by joining means to form complete housing;
plurality of baffle plates configured to be disposed which divides said housing to at least three compartments;
plurality of perforated tubes disposed in or passing through said housing and said baffle plates;
sound absorbing material for sound absorption and reduction of all frequencies of noise level;
and at least one muffler mounting bracket attached to muffler housing by joining means.
2. The muffler structure as claimed in claim 1, wherein said at least two halves comprises at least two layers made up of two different materials.
3. The muffler structure as claimed in claim 1, wherein said baffle plates are at least one perforated baffle plate and at least one non perforated baffle plate.
4. The muffler structure as claimed in claim 1, wherein the said three compartments of muffler housing are reflection chamber, expansion chamber and absorption chamber.
5. The muffler structure as claimed in claim 1 and 2, wherein the position of the baffle plate can be varied to cater wide range of frequency.

6. The muffler structure as claimed in claim 1, wherein the said perforated tubes are
fixed to the said baffle plates at holes provided on the said baffle plates by joining
means.
7. The muffler structure as claimed in claim 1 and 2, wherein absorption chamber
comprises sound absorbing materials.
8. A method of assembling the muffler structure comprising the steps of;
a. joining together said two halves of housings by joining means to form complete
housing;
b. joining said perforated plate and non perforated plate to the housing by joining
means for dividing the said housing into at least three compartment to form at
least three chambers for reflection, expansion and absorption;
c. connecting one end of the said first perforated tube to the exhaust inlet pipe and
is extended through the said housing and other end is connected to one end of
the said second perforated tube;
d. extending other end of the said second perforated tube through said non
perforated baffle plate and kept open to the said expansion chamber;
e. extending one end of the said third perforated tube through said non perforated
baffle plate and kept open to said reflection chamber and passing other end of
said third perforated tube through said expansion chamber to said absorption
chamber and connecting to exhaust outlet;
9. The novel muffler structure for internal combustion engine as herein described substantially with reference to the accompanying drawings.

10. A method of assembling the muffler structure as herein described substantially with reference to accompanying drawings
Dated this 31st day of December 2008