Muffler structure

Details Muffler structure Muffler structure

2000-10-19

2002-05-28

Dang, Khanh (Department: 2837)

Acoustics

Sound-modifying means

Muffler, fluid conducting type

C181S265000, C181S272000, C181S282000

Reexamination Certificate

active

06394225

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a muffler structure in which a sound absorbing material is arranged on the inside surface of an outer tube, and is retained with an inner tube made of a metal that is punched with a plurality of holes.
2. Description of Prior Art
Mufflers for motorcycles are of such a design that a sound absorbing material is installed between outer and inner tubes, and furthermore the interior of the inner tube is divided into a plurality of expansion chambers to deadening an exhaust sound. The muffler will be explained in detail by referring to the following drawing.
FIG. 6
is a schematic view of a conventional muffler structure. A sound absorbing material
102
(glass wool) is installed on the inside surface of an outer tube
101
of a muffler
100
, and then is retained by an inner tube
103
made of a metal that is punched with a plurality of holes. Exhaust gas from the engine (not shown) is discharged out of the muffler
100
through the inner tube
103
as indicated by an arrow.
The inner tube
103
is formed of a punching metal as stated above, so that the glass wool
102
will appear out of punched holes
104
. . . made in the punching metal, thereby absorbing the exhaust sound.
In the inner tube
103
, hot exhaust gases flow, and therefore the butt portion is jointed at both ends
105
and
106
in order that the inner tube
103
will not be opened at these ends
105
and
106
with exhaust heat. Since no clearance is formed at both ends
105
and
106
, the glass wool
102
will never be scattered with the exhaust pressure.
To joint the butt portion
107
, a welding operation is needed, resulting in an increase in time and manpower for manufacturing the inner tube
103
. It is, therefore, hard to improve muffler productivity and to lower costs.
FIG. 7
is a developed view showing a punching metal for a conventional inner tube. The punching metal
110
has closed punched holes
104
. . . at both ends
105
and
106
, so that the butt portion
107
may be welded properly at both ends
105
and
106
when forming the inner tube
104
(shown in FIG.
6
).
Since the punched holes
104
. . . at both ends
105
and
105
of the metal that is punched with a plurality of holes
110
are needed to be closed, commercial punching metal is not usable for the inner tube
103
because the punched holes
104
. . . at both ends
105
and
106
of the commercial punching metal are left open.
Therefore, there is a necessity to manufacture special metal that is punched with a plurality of holes for the inner tube
103
, which will be a factor responsible for an increase in the cost of the muffler.
SUMMARY AND OBJECTS OF THE INVENTION
It is, therefore, an object of the invention to provide a muffler structure capable of lowering the cost of the muffler.
In view of the above-described problems, this invention provides in a first aspect a muffler structure in which a sound absorbing material is laid on the inside surface of an outer tube; the sound absorbing material is retained by an inner tube made of a metal that is punched with a plurality of holes. The inner tube is separated into a plurality of expansion chambers. Exhaust gas from an engine is directed into one of the expansion chambers by an inlet pipe. The exhaust gas is discharged out after passing through the other expansion chambers one after another through a connecting pipe. In the muffler structure, the inner tube is made of an approximately flat punching metal by rolling until its opposite edges are butted to each other, and is fitted in the outer tube, with the butt portions not jointed, so that the butt portions will come behind one of the connecting pipes when viewed from the inlet pipe side.
The inner tube, therefore, is inserted into the outer tube in such a manner that the butt portion of the inner tube will come behind one of the connecting pipes when the butt portion of the inner tube is viewed from the inlet pipe side. Therefore the radiant heat of the inlet pipe can be shielded by the connecting pipe, thereby enabling to prevent the direct transfer of the radiant heat of the inlet pipe to the butt portion of the inner tube. Therefore, no large clearance will occur at the butt portion that is not joined.
Furthermore, because it is unnecessary to joint the butt portion of the punching metal, a metal that is punched with a plurality of holes having open punched holes at both end portions is usable. Therefore, a commercial punching metal may be used after cutting to a predetermined shape, whereby a metal that is punched with a plurality of holes for the inner tube is obtainable at a low cost.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.


REFERENCES:
patent: 4851298 (1989-07-01), Fukuda
patent: 5718045 (1998-02-01), Tsukahara et al.
patent: 5969299 (1999-10-01), Yamaguchi et al.
patent: 6138791 (2000-10-01), Zanzie

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