Engine muffler

Details Engine muffler Engine muffler

2001-11-06

2004-09-14

Hsieh, Shih-Yung (Department: 2837)

Acoustics

Sound-modifying means

Muffler, fluid conducting type

C181S273000, C181S275000, C181S276000, C181S212000, C181S255000, C181S256000

Reexamination Certificate

active

06789644

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a muffler applied for smaller engines.
2. Prior Art
Mufflers applied for the smaller engines used in conventional brush cutters or chain saws are constructed such that, as shown in
FIG. 1
, an exhaust gas first expansion chamber
2
having an exhaust gas inlet
1
connecting to an exhaust gas outlet of the engine (not shown in the figure) and an exhaust gas second expansion chamber
4
having an exhaust gas outlet
3
, the first expansion chamber
2
and the second expansion chamber
4
being separated by a partition board, a part of the partition board being removed to install an exhaust gas purifier
5
made of stainless steel and coated with a catalyst to purify the gas passing through the purifier
5
. Said purifier is provided with innumerable numbers of honeycomb-like small holes.
Another conventional mufflers are constructed such that, as shown in
FIG. 2
, the exhaust gas first expansion chamber
2
having the exhaust gas inlet
1
connecting to the exhaust gas outlet of the engine and the exhaust gas second expansion chamber
4
having an exhaust gas outlet
3
, an exhaust gas receiver
6
located in the first expansion chamber
2
and one end of the exhaust gas receiver
6
is closed and the other end of which being opened, said exhaust gas receiver
6
being provided with a plurality of through holes
6
b
and the open end of which being placed facing to the exhaust gas inlet
1
in the first expansion chamber
2
and the first expansion chamber and the second expansion chamber
4
being separated with a partition board, one part of the partition board being removed and an exhaust gas purifier
5
made of stainless steel and coated with a catalyst to purify the exhaust gas passing through the honeycomb small holes is applied.
In conventional engine mufflers shown in
FIG. 1
, an exhaust gas of the engine is introduced into the first gas expansion chamber
2
through the gas inlet
1
, passing through the exhaust gas purifier
5
provided in the chamber and the exhaust gas is introduced into the second expansion chamber
4
and the gas is exhausted to the atmosphere through the exhaust gas outlet
3
. Accordingly, an outside wall
2
a
of the first expansion chamber
2
and an outside wall
4
a
of the second expansion chamber
4
are heated up to approximately 700~800° C. by the heat of the exhaust gas. When the muffler is installed to the engine it is required to provide a metallic cover plate
7
at a position with a predetermined distance from the outside wall
4
a
and further it is required to install a heat durable plastic cover plate
8
at a position with another predetermined distance from the metallic cover plate
7
. Accordingly, an exterior shape of the muffler becomes larger against a tendency to make the engine assembly smaller.
In the muffler illustrated in
FIG. 2
, one open end of the exhaust gas receiver
6
provided with a plurality of gas through holes
6
b
on a cylindrical surface
6
a
is placed facing to the exhaust gas inlet
1
to increase an efficiency to absorb the sound of the muffler. Incomplete combustion gasses are burnt and generation of unfavorable carbon monoxide or nitrogen oxides is controlled. Even such improvement has been added, since the outside wall
2
a
of the first expansion chamber
2
and an outside wall
4
a
of the second expansion chamber
4
are heated by the exhaust gas up to approximately 700~800° C., the metallic cover plate
7
must be added at a location with a predetermined distance from the outside wall
4
a
of the muffler and further the heat durable plastic cover
8
is required at a location with a predetermined distance from the metallic cover plate
7
. The engine assembly including the muffler becomes larger against the tendency to make the engine assembly smaller.
The present invention is to offer an improved engine muffler to keep the outside wall of the second expansion chamber not to become hotter.
SUMMARY OF THE INVENTION
The present invention is explained with reference to
FIG. 3. A
muffler provided with a first expansion chamber
12
of the exhaust gas provided with an exhaust gas inlet
11
connecting to an exhaust gas outlet aperture of the 2 cycle or the 4 cycle engine, a second expansion chamber
14
provided with a gas exhaust outlet
13
, the first expansion chamber
12
and the second expansion chamber
14
are separated with a partition board
20
, a part of which being cut out to place a first exhaust gas purifier
15
coated with a catalyst to purify the exhaust gas, the purifier
15
is provided with innumerable numbers of small holes. The wall that does not face to the engine of said second expansion chamber
14
is made as a double-wall construction having a wall
14
a
and a wall
14
b
with a predetermined distance between them. It is of course possible to have a double wall construction having a wall
12
a
and a wall
12
b
as shown in FIG.
4
A.
It goes without saying that a catalyst is not applied to the first exhaust gas purifier if there is no particular restriction in the gas purification concentration degree. This case is shown in FIG.
4
B.
The muffler is also explained with reference to
FIG. 5A
that the double walls
12
a
and
12
b
,
14
a
and
14
b
are packed with a heat insulating material to enhance the heat insulating efficiency.
It goes without saying that a catalyst is not applied to the first exhaust gas purifier if there is no particular restriction in the gas purification concentration degree. This case is shown in FIG.
5
B.
The engine muffler is also devised as illustrated with reference to
FIG. 6. A
cover plate
17
provided with one open aperture at a place surrounding the exhaust gas purifier
15
in the first expansion chamber
12
for the engine of 2 cycle or 4 cycle type illustrated in FIG.
3
and another cover plate
17
′ surrounding said gas purifier
15
in the second expansion chamber
14
provided with one open aperture at a place surrounding the exhaust gas purifier
15
in the second expansion room
14
are added. In such a manner, a gas introducing aperture is provided in the first expansion chamber
12
and a gas exhausting aperture is provided in the second expansion chamber
14
. Thus, the flow of gas is rectified to store the heat within the cover pate
17
and the cover plate
17
′ to prevent the heat from being transferred to the outside walls.
It goes without saying that a production process becomes easier if the partition board
20
and the cover plate
17
located in the first expansion chamber
12
are manufactured in an integral molding manner.
The engine muffler is also illustrated with reference to FIG.
7
. Said engine muffler is an improved ones shown in FIG.
3
and FIG.
6
. Apart of the double walls
14
a
and
14
b
in the second expansion chamber
14
is removed to provide an open aperture
14
c
through which the exhaust gas is partly released outside. The outside wall
14
′ is fastened to a cover plate
19
with a bolt and a nut. Further, a cover plate
17
′ for the exhaust gas purifier
15
in the second expansion chamber
14
is fastened to the partition board
20
with a bolt and a nut. If required, the cover plates
14
′ and
17
′ are unfastened to take out the exhaust gas purifier
15
for replacement or cleaning. This model change is done to assist the life of the exhaust gas purifier
15
.
A distance between the cover plate
17
in the first expansion chamber
12
and the exhaust gas purifier
15
is widened. Meanwhile, a distance between the cover plate
17
′ in the second expansion chamber
14
and both sides of the exhaust gas purifier
15
is made nil. By this construction it becomes easier to take out the exhaust gas purifier
15
from the second expansion chamber
14
. It is also easy to put back the exhaust gas purifier
15
to the place where it is located in the first expansion chamber
12
.
The muffler illustrated in
FIG. 4A
is reconstructed to have the cover plates

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