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 Exhaust Muffler Internal Structure For An 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, Ganesh Iyer,
Saurabh Shukla and Somnath Sea
All are 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 an exhaust silencer for an internal combustion engine and more particularly it relates to a novel silencer structure for pulsating noise reduction of an Internal Combustion Engine.
BACKGROUND OF INVENTION
Generally internal combustion engines are coupled with a silencer for expanding and compressing the exhaust gas emitted from engine so as to dissipate the energy of exhaust gas for attenuating the sound produced thereby. The problem of silencing the noise generated due to exhaust gas from an internal combustion is well known. Many types of silencer and sound attenuating devices have been developed to address this problem. Silencers are mainly classified into three fundamental types:
1) Reactive silencers: The reactive silencers are designed to reflect part of the
acoustic energy back to the source. This type of silencer uses the series of baffle
plate to radically change the path of exhaust gas. By interrupting or changing the
direction of gas flow sound waves passing thereby are reflected back towards the
noise source by baffle plates and silencer shell walls thus mechanically canceling
each other where they meet. This type of silencer does reduce noise to some
extent. However back pressure of exhaust tends to increase due to blocked exhaust
flow.
2) Dissipative or absorptive Silencers: While dissipative silencers dissipate the
energy of exhaust gas to sound absorbing material in the form of heat. These
silencers are advantageous as they provide lower back pressure, but are not very
effective in reducing the levels of noise. They help only in attenuating noise levels
at higher frequencies.
3) Combination of reactive and absorptive silencers: These are more
commonly preferred for automotive applications.

OBJECT OF INVENTION
The main object of the present invention is to provide a novel silencer structure for pulsating noise improvement of an Internal Combustion Engine
Yet another object of the present invention is to provide a novel silencer internal structure which reduces the overall noise level and improves the perceived sound quality.
Yet another object of the present invention is to provide a novel silencer structure which is having minimal back pressure.
Still another object of the present invention is to provide a novel silencer structure which is economical in construction, reliable in operation, rugged and able to withstand higher acceleration for sustained period and which has compact configuration compatible with under vehicle mounting.
STATEMENT OF INVENTION:
A novel exahust muffler internal structure comprises; at least two halves each having at least two shell or layers forming an inner and outer shell joined together to constitute muffler housing ; plurality of non perforated hollow cylindrical members having varying length; at least one perforated hollow cylindrical member; at least two non perforated baffle plates joined to said muffler housing for providing support to said non perforated hollow cylindrical members and constituting at least three compartment within said muffler housing; sound absorbing material disposed around said perforated hollow cylindrical member; split able cylindrical shell or cover for enclosing said sound absorbing material on said perforated hollow cylindrical member.
An exhaust muffler structure, in accordance with this invention, wherein said two shell or layers of said two halves are forming an inner layer and outer layer made

up of different materials and are joined together by seam welding to constitute muffler housing.
An exhaust muffler structure, in accordance with this invention, wherein length and depth or height of said outer layers of each said first and second halves are greater than width of the said inner layers of said first and second halves.
A exhaust muffler structure , in accordance with this invention, wherein at least two said non perforated baffle plates are disposed in said muffler housing for dividing said muffler housing into a reflection chamber, first expansion chamber and second expansion chambers.
An exhaust muffler structure, in accordance with this invention, wherein at least one said non perforated hollow cylindrical member constituting an exhaust inlet member.
An exhaust muffler structure, in accordance with this invention, wherein at least one said non perforated hollow cylindrical member is U shaped which opens into second expansion chamber and supported by said non perforated baffles plates.
An exhaust muffler structure, in accordance with this invention, wherein said second expansion chamber is connected to said reflection chamber through a non perforated hollow cylindrical member constituting an interconnecting member welded to each said non perforated baffle plates.
An exhaust muffler structure, in accordance with this invention, wherein at least one of said non perforated hollow cylindrical member constiture a passage for gases from said reflection chamber to said first expansion chamber.
An exhaust muffler structure , in accordance with this invention, wherein said at least one perforated hollow cylindrical member is provided to constitute an exhaust outlet and directly connects said first expansion chamber to exhaust orifice.

An exhaust muffler structure, in accordance with this invention, wherein portion of said exhaust outlet is perforated and is enclosed by two halves of said splitable cylindrical shell or cover having absorption material and disposed in said second expansion chamber.
An exhaust muffler structure , in accordance with this invention, wherein said two halves of said splitable cylindrical shell or cover are seam welded to each other and spot welded to said exhaust outlet for rigidly connecting to said exhaust outlet.
BRIEF DESCRIPTION OF INVENTION:
In accordance with the present invention a novel silencer structure comprises; at least two halves, each having two shell or layers forming an inner and outer shell joined together to constitute muffler housing; plurality of non perforated hollow cylindrical members 1,4,5,6 having varying length; one perforated hollow cylindrical member 8; two non perforated baffle plates 2,3 joined to the said inner shell for providing support to the said hollow cylindrical members and constituting of at least three compartment within said mufller housing 25; sound absorbing material 7 disposed around said perforated hollow cylindrical member 8; split able cover 9 for enclosing said sound absorbing material 7 on said hollow cylindrical member 8.
The said non perforated baffle plates 2, 3 are joined to said inner shell with the help of welding for supporting the said plurality of said hollow cylindrical members. The baffle plates 2, 3 is crimped and welded to the ends of the said hollow cylindrical members disposed in said muffler housing. The said baffle plates 2, 3 divides the said muffler housing into an absorption or reflection chamber 15, first expansion chamber 16 and second expansion chamber 17. The said split able cylindrical shell or cover 9 for enclosing the sound absorbing material 7 around said perforated hollow cylindrical member 8, The said split able cylindrical shell or cover 9 forms the absorption chamber 18.

The silencer of present invention allows rapid expansion of exhaust gas, which enters from exhaust inlet pipe 1 into said second expansion chamber 17 through said U shaped cylindrical member 4, thereby allowing the exhaust gas to drop in temperature and change acoustical frequency therein. From said second expansion chamber 17, the exhaust gas enters into said absorption or reflection chamber 15 where the amplitude of pressure variation is reduced by reflection which causes destructive interference of sound waves. The exhaust gas from said reflection chamber 15 again expands in said first expansion chamber 16, once it passes through pipe 6, causing further expansion causing substantially uninterrupted flow of exhaust gases causing minimal back pressure while also allowing minimal noise emission. The high frequency contents in the exhaust noise is then finally taken care off when the gases enters perforated hollow cylindrical member 8 which is enclosed by said cylindrical shell 9, and finally is terminated at the exhaust opening.
BRIEF DESCRIPTION OF DRAWING
Figure 1 shows an exploded perspective view of baffles and perforated tubes
Figure 2 shows an exploded perspective showing of a first .embodiment of the
invention
Figure 3 shows an internal structure of silencer
Figure 4 shows whole silencer with inlet pipe, outlet pipe along with mounting
brackets for silencer
DETAILED DESCRIPTION OF INVENTION:
Referring now to the drawings 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.
In accordance with the present invention a novel silencer structure comprises; at least two halves each having at least two shell or layers forming an inner and outer shell joined together to constitute the muffler housing plurality of non perforated

hollow cylindrical members 1,4,5,6 having varying length; at least one perforated hollow cylindrical member 8; at least two non perforated baffle plates 2,3 joined to said inner shell for providing support to said hollow cylindrical members and constituting at least three compartment within said mufller housing; sound absorbing material 7 disposed around said perforated hollow cylindrical member 8; split able cylindrical shell or cover 9 for enclosing said sound absorbing material 7 on said hollow cylindrical member 8.
The first half comprising at least two layers 10, 11 and second half comprising at least two layers 12,13. The said two layers of said first half and second half forms an inner 11,12 and outer layer 10,13 joined together by seam welding to constitute mufiler housing. Said two layers of said two halves are made of different materials. The said non perforated baffle plates 2, 3 are joined to the said inner layer of said first and second halves of said muffler housing with the help of welding for supporting the said plurality of said hollow cylindrical members. The said baffle plates 2, 3 are crimped and welded to the ends of the said hollow cylindrical members disposed in said muffler housing.
At least two said non perforated baffle plates 2, 3 which are disposed in said muffler housing for dividing the said muffler housing into a reflection chamber 15, first expansion chamber 16 and second expansion chamber 17.
The said splitable cylindrical shell or cover 9 is provided for enclosing the sound absorbing material 7 around said perforated hollow cylindrical member 8. Said splitable cylindrical shell or cover 9 forms the absorption chamber 18.
The length and depth or height of said outer shell layers of each said first and second halves are greater than the width of the said inner shell layers of said first ansd second halves.

Said sound absorbing materials 7 is steel wool glass and glass fiber. The volume of both the expansion and reflection chambers can be varied by changing the position of baffle plate to cater to the required range of frequency.
Said first expansion chamber 16 is smaller and said second expansion chamber 17 is bigger in size.
The at least one non perforated hollow cylindrical member constituting an exhaust inlet member 1.
At least one said non perforated hollow cylindrical member 4 is U shaped which opens into second expansion chamber 17 and is supported by said non perforated baffles plates 2,3.
The said second expansion chamber 17 is connected, to said reflection chamber 15 through another non perforated hollow cylindrical member which constitutes an interconnecting member 5 which is welded to each said non perforated baffle plates 2,3 for its support.
At least one of said non perforated hollow cylindrical member 6 constitutes a passage for gases from reflection chamber 15 to said first expansion chamber 16. Said non perforated hollow cylindrical member 6 is welded to said non perforated baffle plate 3.
At least one perforated hollow cylindrical member 8 provided to constitute an exhaust outlet 8.
Said perforated hollow cylindrical member 8 is welded to the said non perforated baffle plate 2 and directly connects the said first expansion chamber 16 to the exhaust orifice.
The portion of said exhaust outlet 8 is perforated and is enclosed by two halves of said split-able cylindrical shell or cover 9 having absorption material and is

disposed in said second expansion chamber 17.
The said two halves of said split-able cylindrical shell or cover 9 are seam welded to each other and spot welded to the said exhaust outlet 8 for rigidly connecting said cover 9 to the said exhaust outlet 8. The cylindrical volume of said cylindrical shell or cover 9 with the absorption material internally acts as an absorption chamber 18.
The flange 19 which is welded to exhaust inlet pipe 23 interconnects the entire silencer assembly with engine exhaust manifold through the catalytic converter. . The brackets 23, 24 are used for mounting of said silencer assembly which is welded to said outer layer 10, 13 of said muffler housing. The silencer heat shield 22 is further seam welded to the said outer layer 10,13 of the silencer.
Exhaust inlet member 20 connected to said non perforated inlet cylindrical member and outlet member 21 is connected to said perforated hollow cylindrical member 8. Connecting flange 19 for connecting to exahust manifold. Exhaust brackets 23, 24 for mounting said muffler housing.
The exhaust gas enters the silencer through the said exhaust inlet pipe 1 and flows directly into the said second expansion chamber 17 through the U shaped cylindrical member 4. The gas expands in the expansion chamber where the temperature of exhaust gases drops and reduces the gas pressure causing an acoustic impedance mismatch.
From the said expansion chamber the gases flow into the said reflection chamber 15 through the said interconnecting pipe 5. The gas coming out from said interconnecting pipes 5 strikes the wall of the inner shell and gets reflected back and reduces amplitude of pressure variation of the exhaust gas. This happens when two acoustic waves with different amplitude and phase moves in opposite direction causing destructive interference in the waves which reduces amplitude of the

resultant wave. This helps mostly in the attenuation of the low frequency contents present therein.
After the reflection, exhaust gas accumulates at the bottom of the said reflection chamber 15 and then enters the first expansion chamber 16 through pipe 6. The gases again expand suddenly in said smaller expansion chamber 16 and further reduction of temperature of gases occurs, causing a change in acoustic impedance. A major chunk of low frequency noise is attenuated until this point. The exhaust gases then passes through the said perforated outlet exhaust pipe 8 and escapes through the small perforations on said outlet pipe 8 and come in contact with the absorption material. The absorption material attenuates most of the high frequency contents of the exhaust noise. The gases then escapes into the atmosphere through the orifice at the end of said outlet pipe 8.
The present invention integrates the pre silencer, main silencer, post silencer into a single silencer package which performs all desired function of pre silencer, main silencer, and 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 as they come within the scope of the invention as claimed or the equivalents thereof.

We claim
1. A novel exahust muffler internal structure comprises; at least two halves each having at least two shell or layers forming an inner and outer shell joined together to constitute muffler housing ; plurality of non perforated hollow cylindrical members having varying length; at least one perforated hollow cylindrical member; at least two non perforated baffle plates joined to said muffler housing for providing support to said non perforated hollow cylindrical members and constituting at least three compartment within said muffler housing; sound absorbing material disposed around said perforated hollow cylindrical member; split able cylindrical shell or cover for enclosing said sound absorbing material on said perforated hollow cylindrical member.
2. An exhaust muffler structure as claimed in claim 1, wherein said two shell or layers of said two halves are forming an inner layer and outer layer made up of different materials and are joined together by seam welding to constitute muffler housing.
3. An exhaust muffler structure as claimed in claim 1, wherein length and depth or height of said outer layers of each said first and second halves are greater than width of the said inner layers of said first and second halves.
4. A exhaust muffler structure as claimed in claim 1, wherein at least two said non perforated baffle plates are disposed in said muffler housing for dividing said muffler housing into a reflection chamber, first expansion chamber and second expansion chambers.
5. An exhaust muffler structure as claimed in claim 1, wherein at least one said non perforated hollow cylindrical member constituting an exhaust inlet member.

6. An exhaust muffler structure as claimed in claim 1, wherein at least one said non perforated hollow cylindrical member is U shaped which opens into second expansion chamber and supported by said non perforated baffles plates.
7. An exhaust muffler structure as claimed in claim 1, wherein said second expansion chamber is connected to said reflection chamber through a non perforated hollow cylindrical member constituting an interconnecting member welded to each said non perforated baffle plates.
8. An exhaust muffler structure as claimed in claim 1, wherein at least one of said non perforated hollow cylindrical member constiture a passage for gases from said reflection chamber to said first expansion chamber.
9. An exhaust muffler structure as claimed in claim 1, wherein said at least one perforated hollow cylindrical member is provided to constitute an exhaust outlet and directly connects said first expansion chamber to exhaust orifice.
10. An exhaust muffler structure as claimed in claim 1, wherein portion of said exhaust outlet is perforated and is enclosed by two halves of said splitable cylindrical shell or cover having absorption material and disposed in said second expansion chamber.
11. An exhaust muffler structure as claimed in claim 1, wherein said two halves of said splitable cylindrical shell or cover are seam welded to each other and spot welded to said exhaust outlet for rigidly connecting to said exhaust outlet.

12. A novel exhaust mufller internal structure as herein described with reference to accompanying drawings.