FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
and
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, rule 13]
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
Mr. Khot Prashant Ramchandra, Mr. Wagh Sachin Devdas and Mr. Kakade Sandeep Kashinath
All 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 disclosure and the manner
in which it is to be performed.

TECHNICAL FIELD
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, the back pressure of exhaust tends to increase due to blocked exhaust flow.
The applicants of this disclosure have earlier filed a patent application number 2732/MUM/2008, titled "A Novel Muffler Structure and Method of Assembling the Muffler Structure For Internal Combustion Engine," filed on 31/12/2008, and this application is an addition disclosure on the said application.
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.
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.
Further objects and features of the disclosure will become apparent from the following detailed description when considered in conjunction with the drawings
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.
Figure 5 shows an exploded perspective view of a second embodiment of the present invention.
Figure 6 shows an exploded perspective view of the second embodiment of the present
invention.
Figure 7 shows an internal view of the second embodiment of the present invention.
Figure 8 shows a perspective view of whole muffler according to the second embodiment of the
present invention.
DETAILED DESCRIPTION OF INVENTION
Referring now to figures I to 8, 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 other end is spot welded to perforated tube (17). Sound absorbing material 20 like glass wool, and steel wool are placed in the absorption chamber (23) which surrounds 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) to 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 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) strikes the wall of chamber (21) and reflects back to perforated tube (17). When two acoustic waves with different amplitude move into opposite direction to each other then the amplitude of resultant wave is smaller than these two acoustic waves.

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 covers 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.
Referring now to another embodiment of the muffler structure, illustrated in FIG. 5 through 7, the muffler structure is a combination type of silencer. This embodiment of the muffler structure is specially designed for both low and high frequency noise attenuation. The muffler structure also referred to as "silencer," shown in figure-1 to 7, comprises a housing. The housing is made up of two halves 102 and 127. The two halves, also referred to as two external silencer bodies (102 and 127), seam welded together. The two external silencer bodies (102 and 127) are made of corrosion resistant material. These are designed to arrest maximum radiated noise from the silencer body.
The muffler structure further includes a plurality of baffle plates. The plurality of baffle plates, also referred to as partition plates (109 and 110) divide the shells (housing) into three major acoustic chambers namely, an acoustic expansion chambers (135), an acoustic absorption chamber (136) and an acoustic reflection chamber (134), best illustrated in FIG. 8. A plurality of perforated tubes is disposed in or passing through said housing and said baffle plates (109 and 110). One such perforated tube, namely the inlet sound wave tuning pipe (111) is supported by the partition plates (109 and 110). The inlet sound wave tuning pipe (111) opens into the acoustic reflection chamber (134). This acoustic reflection chamber (134) is connected to the acoustic expansion chamber (135) through interconnecting sound wave tuning pipe (112). A sound wave tuning pipe (112) is welded to both the partition plate (109 and 110) for its support. A sound wave tuning pipe (113) welded to partition plates (109 and 110), acts as passage for gases from the acoustic expansion chamber (135) to the acoustic absorption chamber (137). The sound wave tuning pipe (114) within the acoustic reflection chamber (134) is perforated and is enclosed by two channel shells (115 and 116) having absorption material. The two channel

shells (115 and 116) are welded together and all this channel assembly is welded to the sound wave tuning outlet pipe (119) for rigidly fixing it to the sound wave tuning outlet pipe (114). This channel shell assembly volume along with the absorption material internally acts as an acoustic absorption chamber (137). Fiber material like steel wool, glass wool and glass fiber are used as the high frequency noise absorption material.
A connecting flange (120), which is welded to the exhaust connecting pipes (121 and 123) with decoupling below (122), interconnects the entire silencer assembly with engine exhaust manifold through the exhaust catalytic converter. The silencer mounting hooks (106, 107 and 108) are used for mounting of said silencer assembly, which is welded to silencer bodies (102 and 127). This assembly is suspended to the hooks (131, 132 and 133), welded to vehicle by anti-rotation rubber suspensions (130). The silencer heat shields (103, 104, 105, 124 and 125) are further used to maintain the temperature of system within limits. These are bolted and welded to the silencer bodies and inlet sound wave tuning pipe (121) of the silencer, as shown in figures. During the utilization of the muffler structure of the present embodiment, the exhaust gas enters the muffler structure through the sound wave tuning inlet pipe (111) and flows directly into the acoustic expansion chamber (135), the acoustic absorption chamber (136) and the acoustic reflection chamber (137), respectively. The gas expands in the acoustic expansion chamber (135), where the temperature of exhaust gases drops and reduces the gas pressure causing an acoustic impedance mismatch. Also, in the acoustic absorption chamber (136) high frequency noise is absorbed. In acoustic refection chamber (137), the gas coming out strikes the wall of the silencer body and gets reflected back, causing destructive interference of waves 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 reduction of amplitude of the resultant wave. This helps mostly in the attenuation of the low frequency contents present therein.
Through the sound wave tuning connecting pipe (112), after the reflection, exhaust gas accumulates at the bottom of the acoustic reflection chamber and then enters the acoustic expansion chamber (135). In the acoustic expansion chamber (135) the gas again expands suddenly 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.

From the acoustic expansion chamber the gases flow into the sound wave tuning pipe (114) through the sound wave tuning interconnecting pipe (113). The gases then passes through the perforated sound wave tuning pipes (114) and escapes through the small perforations 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 sound wave tuning outlet pipe (119).
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. A muffler structure for an internal combustion engine, the muffler structure comprising:
at least two halves of housing joined together by joining means to form a complete
housing;
a plurality of baffle plates configured to be disposed which devices the housing in three compartments;
a plurality of perforated tubes disposed in or passing through said housing and said baffle plates;
at least one muffler mounting bracket attached to muffler housing by joining means; and an acoustic absorption chamber being defined at a portion of one perforated tube by enclosing said portion with a pair of channel shells.
10. The muffler structure as claimed in any of the preceding claims, wherein the pair of
channel shells includes absorption material.

11. The muffler structure as claimed in any of the preceding claims, wherein the pair of channel shells is welded to each other over a perforated portion of one the perforated tube.