Note: Descriptions are shown in the official language in which they were submitted.
S
TITLE
"EXHAUST MUFFLER"
INVENTORS
Donald K. Stephenson and Donald R. Hanson
BACKGROUND OF THE INVENTION
The invention relates to exhaust mufflers
for internal combustion engines and more particularly
to exhaust mufflers particularly adapted for use on
snowmobiles.
In order to reduce the noise eminating from
vehicles powered by an internal combustion engine,
particularly snowmobiles, considerable effort has
been directed towards developing exhaust mufflers which
are capable of attenua~ing the noise generated by
the pulsating exhaust gases without substantially
reducing the engine power. Prior muffler constructions
are disclosed in the following United States Patents:
Smale 3,853,201 issued December 10, 1974
Betts et al 3,776,366 issued December 4, 1973
Jozepaitis 3,419,107 issued December 31, 1968
Bryant 2,960,179 issued November 15, 1960
Bryant 2,825,421 issued March 4, 1958
Bryant 2,520,756 issued August 29, 1950
Chipley 2,239,549 issued April 22, 1941
Powell 1,998,385 issued April 16, 1935
SUMMARY OF THE INVENTION
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~" The invention provides a muffler comprising an
elongated tubular housing having an outer wall and
including an internal partition dividing the housing
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into an inlet chamber and an outlet chamber, which
partition includes at least one port communicating
between the inlet and outlet chambers, an inlet in
the housing outer wall for admitting exhaust gases
into the inlet chamber, an elongated tubular header
pipe disposed inside and extending lengthwise of the
housing through the partition, which header pipe has
an outlet portion located in the inlet chamber and an
inlet portion located in and communicating with the
outlet chamber, and a plurality of discharge tubes
which are axially spaced on the header pipe, are
connected in communication with the header pipe outlet
portion,and extend outwardly through the housing outer
wall.
In accordance with one embodiment of the invention,
the discharge tubes have an internal cross-sectional area
smaller than the internal cross-sectional area of the header
pipe outlet portion.
In accordance with one embodiment of the invention,
at least three discharge tubes are employed.
~; In accordance with one embodiment of the invention,
the header pipe inlet portion includes a plurality of
small perfora~ions through which the exhaust gases enter
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the header pipe from the outlet cham~er.
In accordance with one embodiment of the invention,
the header pipe inlet portion includes an open outer end
through which the exhaust gases enter the header pipe
from the outlet chamber.
Other features, aspects and advantages of
the embodiments of the invention will become apparent
upon reviewing the following detailed description,
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the drawing, and the appended claims.
Fig. 1 is a side sectional view, partially broken
away, of a muffler embodying various of the ~eatures of the
invention.
Fig. 2 is a side sectional view, partially broken
away, of an alternate construction of a muffler embodying various
features of the invention.
Before explaining the invention in detaiL, it is to
be understood that the invention is not limited in its applica-
tion to the details of construction and the arrangements of
the components set forth in the following description or illus-
trated in the drawing. The invention is capable of other embodi-
ments and of being practiced and carried out in various ways.
Also, it is to be understood that the phraseology and terminology
employed herein is for the purposes of description and should not
be regarded as limiting.
DESCRIPTIO~ OF THE PREFERRED EMBODIMENTS
Illustrated in the drawing is a muffler 10 which
embodies various of the features of the invention and which
incl~des an elongated tubular shell or housing 12 having an outer
or sidewall 14. The outer wall 14 preferably is cylindrically
shaped and is closed at the opposite ends by respective dished
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end walls 16 and 18. While other arcuate shapes and arrangements
can be used, the end walls 16 and 18 preferably are partially
spherically shaped and are inwardly concave.
The housing 12 is divided into a first or inlet
chamber 20 and a second or outlet chamber 22 by a dished internal
partition 24 which preferably is located so that the length of
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the inlet chamber 20 is substantially longer than th~ outlet
chamber 22. While in ~he specific construction illus~rated the
partition is partially spherically shaped and is concave with
respect to the inlet chamber 20, it can be convexed with res-
pect to the inlet chamber 20 and can have an arcuate shape other
than spherical.
Exhaust gases from an internal combustion engine ~not
shown) are admitted into ~he inlet chamber 20 through an inlet
tube or duct 26 which extends radially outwardly from the inlet
chamber 20 through the housing sidewall 14 and in~ludes suitable
attachment means ~not shown) for connection to the engine exhaust
system. The exhaust gases flow from the inlet chamber 20 into
the outlet chamber 22 through one or more ports 28 provided in
the partition 24. Each port 28 preferably is integrally formed
from the material of the partition 24 and includes a tubular
portion 30 extending for a relatively short length from the
inlet chamber 20 and into the outlet chamber 22 and has a rounded
or curved mouth or inlet 32.
Extending lengthwise inside the housing 12 and through
an opening 33 provided in the partition 24 is an elongated
tubular member or header pipe 34 including an inlet portion 36
and an outlet portion 38 having a rlosed outer end 40. The
header pipe 34 preferably is rigidLy affixed to the housing,
such as by brackets (not shown) attached, such as by welding,
to the inside of the outer wall 14. In order to accommodate any
differences between the thermal expansion of the header pipe 34
and the partition 24, the header pipe 34 preferably is slidably
moun~ed in the parti~ion opening 33. Preferably, the header pipe
34 extends within the housing 12 for a substantial length and
has a relatively small cross sectional area in comparison to the
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Length thereof.
The exhaust gases enter into the header pipe 34 from
the outlet chamber 22 and are discharged from the header pipe
34 to the atmosphere through a lurality of axially spaced
discharge tubes or tailpipes 42 which are connected in communi-
cation with the outlet portion 38 of the header pipe 34 and
extend outwardly through the housing outer wall 14. While five
tailpipes A2 are shown in the specific construction illustrated,
a fewer or greater number can be used if desired. However, as
the number of tailpipes are reduced from five, the noise emanat-
ing from the mu~fler in~reases even though the back pressure on
the engine remains constant. Preerably, at least three tail-
pipes 42 are provided,
To obtain a more e~ective reduction in the noise
emanating from the mu~fler 10, the tailpipes 42 have an internal
cross-sectional area smaller than the internal cross-sectional
area o~ the outlet portion 38 of the header pipe 34.
In the embodiment illustrated in Fig. ~, the inlet
portion 36 o~ the header pipe 34 is located in the outlet chamber
22 and includes a plurality of sm~ll apertures or perforatisns
44 through which the exhaust gases enter the header pipe 34 from
the outlet chamber 22. The per~orations 44 are sized to
attenuate middle and high requ~ncy noise without creating an
excessive resistance to the flow o~ the exhaust gases. As a
guide, as many as about 200 perforations having a diameter of
11/16 inch can be provided in the inlet portion 36 of the header
pipe 34. In this embodiment, the outer end 46 of the header
pipe inlet portion 36 preferably is closed but can include one
or more perforations 44. Although in the specific and preferred
constructions illustrated in Fig. 1 and 2, the outlet portion 38
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of the header pipe 34 and all of the tailpipes 42 are disposed
in the inlet chamber 20, all or part of the header pipe outlet
portion 38 and/or all or part of the tailpipes 42 can be dis-
posed in the outlet chamber 22.
In the embodiment illustrated in Fig. 2, the outer
end 50 of the inlet portion of the header pipe 34 is open. With
this arrangement, there may be a slight reduction in the degree
of attenuation of middle and high frequency noise. However,
this is at least partially offset by a lower restriction to the
flow of the exhaust gases and a xesultant lower back pressure
on the engine, which may be more desira~le for some applications.
The muffler provided by the invention beneficially
reduces the noise level without substantially reducing engine
power. As the exhaus~ gases pass through the muffler, there is
provided a snubbing action which progressively, but only par-
tially, smooths out the pulsating flow of the exhaust gases.
M~re specifically, some attenuation of noise occurs as the
exhaust gases expand into the inlet chamber 20 and the sound
waves reflect against the inside o the outer wall 14, the end
wall 16, and the partition 24. Some urther attenuation of noise
is effected in the outlet chamber 22 because of the reflection
and cancellation of sound waves occurring therein. As mentioned
above, the perforations 44 in the inlet portion 36 of the header
pipe 34 (when used) tend to attenuate middle and high frequency
noise. A final stage of reflection and cancellation of sound
waves occurs in the header pipe 34 as the exhaust gases flow
there~hrough and exit through the tailpipes 420 The relatively
small, rigidLy mounted header pipe 34 is believed to prevent, or
at least minimize, the introduction of shell noise into the
exiting exhaust gases, whereas many mufflers of conventional
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cons~ruction are prone to introduce a drumming or shell noise
into the exhaust gases irmnediately upstream of the tailpipe.
Various of the features of the invention are set
forth in the following claims.
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