FORM 2
THE PATENTS ACT 1970
(39 of 1970)
and
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE OF THE INVENTION
Straight through combination type exhaust muffler with annular
dissipation chamber
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
Sanjoy Biswas Anirban chakraborty
All Indian national
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 performed.

Field of invention
The current invention is related to the exhaust system of vehicles more particularly to straight through combination type exhaust muffler with annular dissipation chamber. The current invention is related to sound attenuating system of exhaust gas of diesel engine of Commercial Vehicles preferably Medium and Heavy Commercial Vehicle.
Background of invention
Exhaust muffler is used to attenuate the noise of exhaust gas. coming out from engine to the desired decibel to decrease sound pollution for all type of vehicles. Desired Noise reduction is the primary requirement of all categories of exhaust muffler. Secondly, its shapes to be such, that will not affect the packaging or fitment of all other aggregates of vehicles. Thirdly, it design and configuration to be suitable to fit on vehicles easily and meets the required fording depth. Fourthly, it should be cost-effective muffler. Currently, the Exhaust muffler used on six liters range engines of Cummins is not meeting the required level of noise reduction in many BS-II1 vehicle models. The available exhaust mufflers also have limitations in fordability and fitment requirements.
Object of invention
The main object of the present invention is to obviate the above mentioned drawbacks.
Another object of the invention is to develop a high performing (noise attenuation level)
Exhaust Muffler for medium and heavy range of Commercial Vehicles.
Yet another object of this current invention is to introduce Annular type dissipation
chamber instead usage of conventional one, for reduction of Noise, in addition to reactive
chambers for this exhaust muffler.
Yet another object of present invention is to develop an improved exhaust muffler with
increased ford-ability which is one of the essential parameter of vehicles plying on hostile
terrain.

Summary of invention
An Exhaust system consists of an elbow fitted on engine, exhaust pipes up to the Exhaust Muffler, Exhaust muffler and tail pipe for all type of road vehicles. An Exhaust muffler selection depends on Engine size, application area of the vehicle and other aggregates placement on the vehicle.
The exhaust muffler is used to attenuate the exhaust noise. Its shape may be elliptical or round type. Based on requirements the muffler's inside construction varies. Different types of principles or combination of many are used to design a high performing exhaust muffler.
The current invention is basically an improved Exhaust muffler from existing. It is a combination type muffler with different internal configuration.
Shell arrangement of proposed muffler is sandwich type where between the two shells (outer and inner) a ceramic blanket is used to reduce inside noise and heat reduction of outer shell as existing. This is one of the steps for margin the cost of present muffler.
Total muffler volume is separated in three chambers using two baffles. First two chambers are resonate or reactive type. These two chambers connected trough two Assembly Intermediate Pipe, fitted with baffle. In first chamber assembly inlet pipe is inserted centrally, welded with front end cover of muffler. Two assembly intermediate pipes are inserted in second chamber and are equal distance offset from centre of muffler. Third chamber is annular dissipative type. Here, perforated outlet pipe pass across and welded with second baffle and rear end cover of current muffler. A concentric outer perforated pipe fitted between the baffle and rear end cover. A high quality (property wise) glass wool bag is used in space between outer perforated pipe, Inner shell of this chamber to achieve good sound absorption. This helps to increase the life of Glass wool

and increase noise reduction considerably higher amount. Further, all these chambers are arranged in such a way that the exhaust is straight through exhaust muffler.
As mentioned assembly inlet pipe is welded on front end cover centrally, consists of perforated tube and inlet pipe baffles. This baffle is perforated type. Assembly Intermediate pipes are almost similar in feature wise to assembly inlet pipe. Rather providing holes in baffles to interconnect the reactive chambers, two assembly intermediate pipes used for this. The Outer Diameter and length of this assembly intermediate pipe are different from assembly inlet pipe.
Axial and central entry and exit of exhaust gas arrangement is introduced in current exhaust Muffler. This arrangement indirectly helps to reduce exhaust backpressure and better scavenging of exhaust gas. further, this improves the fording depth of vehicle from existing muffler once fitted on vehicle.
The Existing Tail pipe can be fitted at any angle of rotation with outlet pipe, using the pipe clamp and fasteners in this muffler. This is because of axial exit of outlet pipe. This provides the flexibility to both Left Hand Drive and Right Hand Drive vehicle with out modifying the exhaust muffler.
Brief description of drawings
FIG. 1 Shows the Front view, top view and cross sectional View of Assy Muffler
FIG. 2 Shows sectional view of Assy Muffler
FIG. 3 Shows the Details of Assy Inlet Pipe and Assy Intermediate Pipe muffler
FIG. 4 Shows the Assy Muffler (ISO view).
FIG. 5 Shows the Assy muffler with tail pipe fitment arrangement (ISO view).

Statement of Invention
Accordingly the present invention discloses a straight through combination type exhaust
muffler with annular dissipation chamber comprising of
a muffler body comprising two layers outer Shell (1) and inner shell (2);
at least one ceramic blanket (12) sandwiched inside said outer Shell (1) and inner shell
(2) to reduce the inside noise radiation;
at least one front end cover (3) and one rear end cover (4);
at least three chambers separated by front baffle (5) and rear baffle (6) into first chamber,
second chamber and third chamber wherein said first chamber further comprising of
assembly inlet pipe (7) made of inlet pipe (7a) and inlet pipe baffle (7b) inserted centrally
in first chamber to fasten it to front end cover (3); said second chamber is interconnected
to said first chamber through at least two number of perforated type assembly
intermediate pipe (8a) and intermediate pipe baffle (8b) fastened to said front baffle (5) at
equal offset distance from centre of muffler; said third chamber is annular dissipative
type having two perforated pipes, a out let pipe (10) and outer perforated pipe (9)
fastened concentrically between rear baffle (6) and rear end cover (4); and
at least one high density glass wool bag adapted to be provided in space between said
outer perforated pipe (9) and inner shell in this chamber for high frequency sound
absorption by retaining its properties
Detailed description of invention
The present muffler is designed focusing on considering better performance and easy manufacturability to meets of same engine volume ranges of vehicles such as Medium and Heavy Commercial Vehicle. It is made of below mentioned components -
1) Outer Shell
2) Inner Shell
3) Front End Cover
4) Rear End Cover

5) Front baffle
6) Rear Baffle
7) Assembly Inlet Pipe

a) Inlet Pipe.
b) Inlet Pipe baffle
8) Assy Intermediate pipe
a) Intermediate pipe
b) Intermediate pipe baffle 9) Outer perforated pipe

10) Out let pipe
11) Glass wool bag
12) Ceramic Blanket/C era-blanket
Here a ceramic blanket (12) is placed between the two shells (outer (1) and inner (2)) to reduce shell inside noise and heat reduction at outer shell (2) of muffler as existing. This is one part of approach to margin the cost of the muffler and reduction of lead time of product development.
There are three chambers in this muffler. This separation is done using two numbers of End covers (Ie- front End Cover (3) and Rear End Cover (4)) and baffles (i.e. - Front Baffle (5) and Rear baffle (6)). First two chambers of this muffler is reactive type which is suitable for low frequency noise reduction. These two reactive chambers are interconnected through two number of Assy Intermediate Pipe (8) fitted with Front Baffle (5). Assy inlet pipe (7) is inserted centrally in first chamber, and welded with Front end cover (3) of current muffler. It is made of Inlet pipe (7a) and Inlet pipe Baffle (7b). Both these components (i.e. - Inlet pipe and Inlet pipe Baffle) are perforated type and hole-diameter preferred for these are of same size. Hole size kept between 4-6 mm (diameter) rather usage of higher diameter hole as existing. Features of Entry side of Assy Inlet Pipe are kept same as Existing muffler so that existing exhaust pipe can use. Further,

Perforated Baffle is used in Assy Inlet pipe rather the complete closed baffle as conventional.
For interconnection of first two chambers, two numbers of Assy Intermediate pipes (8a) and (8b) are used. It is inserted in second chamber and welded with Front Baffle (5) at equal distance offset from centre of muffler. The Assy Intermediate pipe is also made an Intermediate Pipe and an Intermediate Pipe Baffle (8b). Both this components are perforated type as Assy Inlet Pipe. The sheet thickness and diameter hole of perforation for both these components are same.
Third chamber of current muffler is annular dissipative one where two numbers of perforated pipes (i.e. - Outlet Pipe (10) and Outer Perforated Pipe (9)) are fitted concentrically. Diameter of Hole and material properties preferred in both these Outlet Pipe and Outer Perforated Pipe is same .The Outlet pipe pass across the third chamber and its features of exit end is same as existing muffler. This is done considering cost effective ness and flexibility in design so that Existing Tail pipe can be fitted easily with any angle of rotation and in both Left Hand Drive and Right Hand Drive Vehicles. A high density (i.e. - property wise very good) glass wool bag is used in space between Outer perforated Pipe, inner shell in this chamber. It is well known to all Glass wool bag is very effective in high frequency sound absorption but lose its property at higher temperature. This Annular arrangement is not only helps to increase the life of Glass wool but also effective in higher noise reduction compare to conventional dissipative chamber of vehicle mufflers.
All baffles and end cover are made of same material and having same thickness. The opening position is centrally in both the End covers (3) and (4) and Rear Baffle (6). In Front baffle (5), there are two opening of same size at equal distance offset from centre. In this muffler Exhaust gas entry and exit arrangements is same i.e. Axial and central. This arrangement is helpful for reduction of exhaust backpressure and better scavenging

of exhaust gas. All these arrangements described above paragraphs are signifies the straight through exhaust muffler & annular dissipation chamber Muffler concept.
Further, Axial and central entry and exit of exhaust gas arrangement in current muffler improves the fording depth of vehicle marginal amount from existing if all other fitment condition remain same on vehicle.
Referring to the drawings where the showings are for the purpose of illustrating a preferred embodiment of this invention only.
The muffler body is made of two layers of shell namely Outer Shell (1) and Inner shell (2) respectively. This shells are of equal thick (prefer 1-2 mm thick) and having good corrosive, heat resistant properties. Inside of these two shells a Ceramic blanket (12) of thickness l-3mm is sandwiched. Chemical composition of ceramic blanket or cerablanket (12) is very good to sustain very high temperatures. These arrangement is same as existing it is helps to reduce the inside noise radiation (i.e. - doubling effect for better noise reduction).
The total muffler volume is same as existing (i.e. - 7 to 9 times of Engine swept volume) and it is separated to three chambers using the Front baffle (5) and Rear Baffle (6) based on wavelength characteristic of exhaust gas. Both end of the muffler Front End Cover (3) and Rear End Cover (4) are fitted. Material properties and thickness of all baffles and End covers are same. Thickness of these is l-3mm. The opening in Front end Cover (3), Rear End Cover (4) and Rear Baffle (6) is centrally located, where as in Front baffle (5), there is two same diameter opening at equal offset distance from center. The two baffles are welded with Inner shell (2) of Muffler where as both end covers are welded with both the shell (i.e.-Outer Shell (1) and Inner shell (2)). All these baffles and cover are modified in opening areas from existing and used in this exhaust muffler.

The Assembly Inlet Pipe (7) is welded with Front End Cover (3) and inserted to the muffler chamber axially. It consists of an Inlet pipe (7a) and Inlet pipe baffle (7b).The Inlet pipe (7a) is perforated type and having different dia in front and rear end. There are no changes in dia and other features of front end of Inlet pipe (7a) from existing muffler. Outer Diameter of rear end (perforated portion) of the Inlet pipe (7a) is 74-78 mm. There are 10 rows of perforation holes at 30 pitch at alternate rows and having hole diameter of 6-8 mm on rear end of Inlet pipe (7a). All holes are made in alternative to avoid shocking of series holes. 10-15 nos of holes are exists in each row of perforation. The Inlet pipe baffle (7b) is perforated type. One hole is located at centre and rest 36 holes are at 3 different PCD of this baffle. Baffle Outer Diameter of the Inlet pipe baffle (7b) is < Inner Diameter of inlet pipe (7a). Diameter of these holes is same as the inlet Pipe (7a). The sheet thick ness of both inlet pipe (7a) and inlet pipe baffle (7b) is 1-3 mm. The porosity ratio (ie- total area perforations/ cross sectional area of inlet pipe (7a)) of Assy Inlet pipe (7) is kept in between 1.3 to 1.6. Rather using the big diameter holes of less numbers in Assy inlet pipe for perforation as existing series muffler, here small diameter holes of higher numbers are incorporated. This is one of the unique features of this muffler. These help to improve the performance of reactive chamber indirectly the Exhaust muffler.
Assembly Intermediate pipe (8) is also made of an Intermediate Pipe (8a) and an Intermediate pipe baffle (8b). There are 11 rows of perforation holes at 30 mm pitch at alternate rows. The diameter of these holes is 3-7 mm and to avoid shocking of holes, these are made in alternative rows. In each row of perforation, there are 10-15 nos of holes are available. The Intermediate pipe baffle (8b) is also perforated type. There are 19 nos of holes available one it and among that one hole is located at centre and rest 18 holes are at 2 different PCD of this baffle. Baffle Outer Diameter of the Intermediate pipe baffle (8b) is < Inner Diameter of Intermediate Pipe (8a). Diameter of all holes is same in Assy Intermediate pipe (8). The sheet thickness of both Intermediate Pipe (8a) and Intermediate Pipe baffle (8a) are 1-3 mm. The Interconnecting porosity ratio between two chambers is kept in between 0.9 to 1.1. Here, Assy intermediate pipes are used to interconnect the first two chambers, Instead of directly usage of Perforated Front baffle as

existing. In this case also comparatively very smaller diameter holes are used in Assy Intermediate pipe (8) from existing Perforated Front baffle. This armament is also help to reduce noise comparatively higher amount from existing (NT series mufflers) as flow through perforated pipe is more effective than flow through baffles.
Further, one more thing to be noted perforated baffle is used in both Assy Inlet Pipe (7) and Assy Intermediate pipe (8) in this exhaust muffler. This is an unique feature of this muffler. This arrangement is for precaution to control the backpressure.
Third chamber of this Muffler is Annular Dissipative type. Here, two perforated pipes namely Out let pipe (10) and Outer perforated pipe (9) are fitted concentrically with Rear baffle (6) and Rear end Cover (4). The out let pipe (10) has different diameter in front and rear end. There are no changes in outer diameter and other features of rear end/Exit side of Out Let Pipe (10) from existing. It is done so that existing Tail pipe can fit. Outer Diameter of perforated portion (inlet side/front end) of Outlet pipe (10) is same as perforated portion of Inlet pipe (7a). There are 23 rows of perforation holes at 30 pitch at alternate rows and having hole diameter of 4-6 mm on perforated portion Out Let Pipe (10). Each row consists of 18 nos of holes. Outlet pipe (10) passes across the third chamber and welded with Rear baffle (6) and Rear end Cover (4) of current muffler. Similarly, a concentric Outer Perforated Pipe (9) fitted between the Rear baffle (6) and Rear end Cover (4).Here, perforation are made in 22 rows of holes at alternative rows at 30 pitch and diameter of holes of 4-6 mm. A Glass wool bag (11) is placed in space between outer perforated Pipe (9), inner shell of this chamber. The density of is 115-135 kg/m3. The function of this chamber is high frequency sound absorption. This annua] type arrangement is not familiar in Exhaust muffler of vehicles. This arrangement is more effective for reduction of noise than conventional single straight through dissipative chamber. Further, the life of glass wool is considerably increase higher amount as the exhaust gas is not directly coming contact with it. This is one of uniqueness of this muffler.

In addition, all the arrangement i.e. entry and exits are centrally and straight through in this muffler. Due to the axial exit of exhaust gas the ford-ability is increases marginally from the Existing muffler. Further, it is stated earlier that existing tail pipe can be fitted with this muffler without any modification with any angle of rotation using required pipe clamp & fasteners. Because of axial entry and exit arrangement, there is a flexibility to use this muffler as it is in both LHD and RHD vehicles.
Here, the paragraph no 4, 5, 6 and 7 covers the main objective of this muffler. The paragraph no 2, 3 and 8 focus on 2n object of the invention. Third objective is highlighted in paragraph no7. Lastly, in the paragraph no 8, attention is given on fourth and last object of this current invention.
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 straight through combination type exhaust muffler with annular dissipation chamber comprising of
a muffler body comprising two layers outer Shell (1) and inner shell (2);
at least one ceramic blanket (12) sandwiched inside said outer Shell (1) and inner shell (2) to reduce the inside noise radiation;
at least one front end cover (3) and one rear end cover (4);
at least three chambers separated by front baffle (5) and rear baffle (6) into first chamber, second chamber and third chamber wherein said first chamber further comprising of assembly inlet pipe (7) made of inlet pipe (7a) and inlet pipe baffle (7b) inserted centrally in first chamber to fasten it to front end cover (3); said second chamber is interconnected to said first chamber through at least two number of perforated type assembly intermediate pipe (8a) and intermediate pipe baffle (8b) fastened to said front baffle (5) at equal offset distance from centre of muffler; said third chamber is annular dissipative type having two perforated pipes, a out let pipe (10) and outer perforated pipe (9) fastened concentrically between rear baffle (6) and rear end cover (4); and
at least one high density glass wool bag adapted to be provided in space between said outer perforated pipe (9) and inner shell in this chamber for high frequency sound absorption by retaining its properties.
2. the muffler as claimed in claim 1 wherein said first chamber further comprising of assembly inlet pipe (7) made of inlet pipe (7a) and inlet pipe baffle (7b) inserted centrally in first chamber are perforated type having 10 rows of perforation holes at 10-15 numbers of holes per row of perforation at 30 pitch in alternate rows to avoid shocking of series holes and having hole diameter of 6-8 mm on rear end of inlet pipe (7 a) and perforated inlet pipe baffle (7b) having one hole located at centre and rest 36 holes are at 3 different PCD of this baffle.

3. The muffler as claimed in claim 1 wherein said intermediate pipe (8a) and an intermediate pipe baffle (8b) have 11 rows of perforation holes at 10-15 numbers of holes per row at 30 mm pitch at alternate rows to avoid shocking of holes and perforated intermediate pipe baffle (8b) having one hole located at centre and rest 18 holes are at 2 different PCD of this baffle to reduce noise as flow through perforated pipe.
4. The muffler as claimed in claim 1 wherein said third chamber is annular dissipative type having said outlet pipe (10) having 23 rows of perforation holes at 18 numbers of holes of per row at 30 pitch at alternate rows and said concentric outer perforated pipe (9) having 22 rows of holes at alternative rows at 30 pitch and diameter of holes of 4-6 mm.
5. the muffler as claimed in claim 1 wherein said two layers outer shell (1) and inner shell (2) are of equal thickness and have good corrosive, heat resistant properties.
6. The muffler as claimed in claim 1 wherein said first two chambers of said muffler are reactive type which are suitable for low frequency noise reduction.
7. The muffler as claimed in claim 1 wherein outer diameter and other features of said assembly inlet pipe (7) are kept similar to that of existing muffler to accommodate existing exhaust pipe.
8. The muffler as claimed in claim 1 wherein outer diameter and other features of rear end/exit side of said outlet pipe (10) are kept similar to that of existing muffler to accommodate existing tail pipe and considering cost effective ness and flexibility in design so that existing tail pipe can be fitted easily with any angle of rotation and in both left hand drive and right hand drive vehicles.

9. The muffler as claimed in claim 7 and 8 wherein said entry and exits are centrally and straight through in said muffler to increase the ford-ability marginally over the existing muffler.
10. The straight through combination type exhaust muffler with annular dissipation chamber substantially as herein described with reference to accompanying drawings.