FORM 2
THE PATENT ACT, 1970,
(39 OF 1970)
&
THE PATENTS RULE, 2003
COMPLETE SPECIFICATION
(SEE SECTION 10; RULE 13)
"MUFFLER WITH MULTIPLE FLUTED TUBES FOR SOUND SUPPRESSION
IN AUTOMOBILES"
MAHINDRA & MAHINDRA LIMITED
AN INDIAN COMPANY,
R&D CENTER, AUTOMOTIVE SECTOR,
89,M.l.D.C.,SATPUR,
NASHIK-422 007,
MAHARASHTRA, INDIA.
THE FOLLOWING SPECIFICATION DESCRIBES THE NATURE OF THE INVENTION AND MANNER IN WHICH IT IS TO BE PERFORMED

FIELD OF INVENTION:-
The present invention relates to a method of suppressing the sound generated from the muffler and more particularly the present invention relates to a method of suppressing sound in the muffler with the integrated fluted hole tubes without compromising the transmission loss.
BACKGROUND OF THE PRESENT INVENTION:-
In automobiles, for achieving good transmission toss oat higher frequencies in the exhaust pipe/muffler the current practice is of using glass wool absorptive materials. This involves additional cost and thus makes the muffler expensive.
In the prior art United States Granted Patent US 4360076 A, the inlet pipe is a convergent tube and has series of holes on it. From the inlet of the muffler the pipe is in convergent shape. In the muffler disclosed in this patent there are no baffles which mean that muffler is having no compartments in it. In this muffler disclosed in this patent, the minimization of pressure pulsation is achieved by a variety of means including appropriately-located apertures in those portions of the waiis of said pipes within said main body, an aperture partition within said main body so located that exhaust gas passes through said partition, and appropriate tapering of said pipes.
In another prior art United States Granted Patent US 4580657 A, the construction of the muffler involves lot of complex shapes which are used for modifying the exhaust gas flow. The tube is formed of a cylindrical portion with generally circular inlets and outlets and a constricted portion between those ends and within the constriction, a plurality of bypasses there through. The constriction also includes a frontal portion having a generally concave surface which rises to an apex and thereafter forms a plurality of convex rear portions toward the outlet end.
In this United States Granted patent US 7503427 A, the muffler has 3 chambers. The muffler has a muffler body, an upstream pipe that opens in the

muffler body, and a downstream pipe that opens in the muffler body. An opening is formed in a side wall of the downstream pipe in the muffler body. The opening consists of many small holes arranged in an elongated area extending in an axial direction of the downstream pipe.
All the attempts which were to achieve transmission loss at higher frequencies has many disadvantages as the configurations of the mufflers used in these attempts are complicated in design which makes these muffler not economical.
The present invention provides such a muffler which meets or exceeds the prior art characteristics for sound suppression while providing substantial reduction in cost and overall dimensions of the package.
OBJECTS OF THE PRESENT INVENTION:-
An object of the present invention is to provide a muffler for the exhaust gas of an engine generating pulsating noise, which can efficiently muffle the noise of the exhaust gas.
Another object of the present invention is to provide a muffler which can achieve good transmission loss at higher frequencies.
Another object of the present invention is to provide a muffler having the above mentioned characters, while it is simple in construction.
STATEMENT OF INVENTION:-
Accordingly invention provides a muffler with multiple fluted tubes for sound suppression in automobiles comprising a closed longitudinal main body, having outer shell (7) with end plates at both side, of with geometrical shape cross section; a first chamber (7A) and a second chamber (7B) formed and separated in the said body by a baffle (4) having small series of holes through therein; an inlet pipe at one end at central axis of the body provided in the first chamber for the exhaust gas to enter into the said body; a first

divergent in shape pipe (2) attached to the said inlet pipe at the said first chamber; at least two number of fluted tubes, having one through hole in the upstream of pipe (3) and series of holes in the downstream, at parallel to and distant from the longitudinal axis of the said body provided passing through and supported in the said baffle; an outlet pipe (5) in the said second chamber provided at other end at central axis of said body; a second divergent Pipe (6) attached to the said outlet pipe at the outside of the said body.
BRIEF DESCRIPTION OF THE FIGURES:-
The objects and other advantages of the present invention will become apparent when the disclosure is read in conjunction with the following figures of accompanying drawings, wherein
Figure 1 shows a schematic line diagram of the muffler with integrated fluted tubes;
Figure 2 shows a CFD plot of the exhaust gas velocity plot for the muffler of the present invention;
Figure 3 shows a graph of NVH transmission loss for the muffler of the present invention;
DETAILED DESCRIPTION OF THE PRESENT INVENTION:-
The foregoing objects of the 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 embodiment.
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.

The muffler of the present invention consists of divergent tubes, fluted tubes and baffle. The divergent tubes are used to reduce the back pressure. The fluted tubes are having smaller diameter for having good transmission loss and having perforations in a pattern similar to that of the flute (wood wind musical instrument). The baffle is used for attenuating high frequency noise as the perforations are having smaller diameter compared to those in tubes.
The muffler of the present invention comprises
♦ Inlet pipe - pipe no 1
♦ Divergent tubes - pipe no 2 ♦ Fluted tubes - pipe no 3
♦ Baffle with holes - pipe no 4
♦ Outer pipe-pipe no 5
♦ Outlet pipe - pipe no 6
♦ Outer shell - 7 (first chamber 7A & Second chamber 7B)
The divergent tubes are used to reduce the back pressure. The fluted tubes are having smaller diameter for having good transmission loss and having perforations in a pattern similar to that of the flute (wood wind musical instrument). The baffle is used for attenuating high frequency noise as the perforations are having smaller diameter compared to those in tubes.
Referring to the figure 1 of the present invention, the exhaust gas enters through the inlet pipe (1). It is divergent in shape (pipe 2) as it enters main body 7. The main body has two chambers represented by (7A) and (7B). The separation of main body is by the baffle (4) which has small series of holes through it. The baffle supports two fluted tubes (3) which pass through it. The fluted tubes have one through hole in the upstream of pipe (3) and series of holes in the downstream. In the chamber (7B) there is a pipe (5) which helps in taking the exhaust gases out from the chamber (7B) to outside through the outlet pipe (6). Pipe (6) is divergent in shape and pipe (5) has holes in it.

A muffler with multiple fluted tubes for sound suppression in automobiles comprising a closed longitudinal main body, having outer shell (7) with end plates at both side, of with geometrical shape cross section. A first chamber (7A) and second chamber (7B) formed and separated in the said body by a baffle (4) having small series of holes through therein. An inlet pipe at one end at central axis of the said body provided in the first chamber for the exhaust gas to enter into the said body. A first divergent in shape pipe (2) attached to the said inlet pipe at the said first chamber. At least two number of fluted tubes, having one through hole in the upstream of pipe (3) and series of holes in the downstream, at parallel to and distant from the longitudinal axis of the said body provided passing through and supported in the said baffle. An outlet pipe (5) in the said second chamber provided at other end at central axis of the said body. A second divergent Pipe (6) attached to the said outlet pipe at the outside of the said body.
The longitudinal body is having circular, or rectangular, or hexagonal, or elliptical cross section.
The said series holes at distant on down stream provided on the flute tube entire surface in straight line and diametrically opposite.
The length of the said flute is more in the first chamber than the second chamber.
Referring to figure 2 of the present invention, it shows an exhaust gas velocity plot of the muffler with fluted tubes wherein when the exhaust gas enters the main body through the inlet pipe (1), it reduces the pressure because of the divergent pipe (2). Some of the exhaust gas comes out through the small holes given in pipe (2) and enters the fluted tubes (3) through the through hole above pipe (2). The majority of the exhaust gases passes hits the baffle (4) with small holes. It bounces back and passes through the series of holes available on the downstream end of pipes (3). The gases hit the main body in chamber (7A) forming a y pattern. When the fluted tubes pass the baffle (4) the velocity is slightly increased and exhaust gases travel to the chamber (7B). In chamber

(7B) the exhaust gases coming out from the fluted tubes 3, passes through the pipe 5 and comes out to atmosphere through the outlet pipe 6. Here the backpressure is less because of the fluted tubes.
Referring to the figure 3 of the present invention, it represents the graph of the transmission loss for the muffler. The x axis is Frequency and Y axis is in dB values. Higher the values in the Y axis represent better the performance of the muffler. From the graph it is clear that the higher values are at 750 Hz and 1600 Hz and between 2000 to 2500 Hz.
It should be understood that the present invention is not to be limited by the exact details of the illustrated embodiment. However, it is to be taken as the preferred example of the invention and that various changes may be resorted to by a person skilled in the art without departing from the spirit of the invention. Also, the terminologies used herein are for the purpose of description and should not be regarded as limiting.

WE CLAIM:-
1. A muffler with multiple fluted tubes for sound suppression in automobiles comprising a closed longitudinal main body, having outer shell (7) with end plates at both side, of with geometrical shape cross section; a first chamber (7A) and a second chamber (7B) formed and separated in the said body by a baffle (4) having small series of holes through therein; an inlet pipe at one end at central axis of the said body provided in the first chamber for the exhaust gas to enter into the said body; a first divergent in shape pipe (2) attached to the said inlet pipe at the said first chamber; at least two number of fluted tubes, having one through hole in the upstream of pipe (3) and series of holes in the downstream, at parallel to and at distant from the longitudinal axis of the said body, provided passing through and supported in the said baffle; an outlet pipe (5) in the said second chamber provided at other end at central axis of the said body; a second divergent Pipe (6) attached to the said outlet pipe at the outside of the said body.
2. The muffler as claimed in claim 1 wherein the said longitudinal body having circular, or rectangular, or hexagonal, or elliptical cross section.
3. The muffler as claimed in claim 1 and 2 wherein the said series holes at distant on down stream provided on the flute tube entire surface in straight line diametrically opposite.
4. The muffler as claimed in claims 1 to 3 wherein the length of the said flute is more in the first chamber than the second chamber.