U.S. patent application number 11/866882 was filed with the patent office on 2008-03-13 for exhaust muffler.
This patent application is currently assigned to Arctic Cat Inc.. Invention is credited to Robert J. Rauch, Ole E. Tweet.
Application Number | 20080060870 11/866882 |
Document ID | / |
Family ID | 36594292 |
Filed Date | 2008-03-13 |
United States Patent
Application |
20080060870 |
Kind Code |
A1 |
Rauch; Robert J. ; et
al. |
March 13, 2008 |
EXHAUST MUFFLER
Abstract
The present specification discloses a muffler for attenuating
exhaust noise from an internal combustion engine. The muffler
includes a main chamber, an intermediate pipe, a diffuser chamber,
a spark arrester, and an exhaust pipe. Exhaust gases from the
engine enter the main chamber after which they flow through the
intermediate pipe. The intermediate pipe extends back through the
main chamber to the diffuser chamber. The spark arrester is a
screen held within the exhaust muffler and removably coupled to the
exhaust pipe. Gases flow through the screen to separate hot
particles. The exhaust pipe extends within the main chamber,
completing a 180.degree. bend within the chamber before exiting the
main chamber and the muffler. An outer enclosure may surround the
muffler. A method of attenuating exhaust gas noise is also
disclosed.
Inventors: |
Rauch; Robert J.; (Thief
River Falls, MN) ; Tweet; Ole E.; (Thief River Falls,
MN) |
Correspondence
Address: |
BLACK LOWE & GRAHAM, PLLC
701 FIFTH AVENUE
SUITE 4800
SEATTLE
WA
98104
US
|
Assignee: |
Arctic Cat Inc.
Thief River Falls
MN
|
Family ID: |
36594292 |
Appl. No.: |
11/866882 |
Filed: |
October 3, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11019154 |
Dec 20, 2004 |
7287622 |
|
|
11866882 |
Oct 3, 2007 |
|
|
|
Current U.S.
Class: |
181/272 |
Current CPC
Class: |
F01N 13/0097 20140603;
F01N 1/02 20130101; F01N 2230/04 20130101; F01N 2230/06 20130101;
F01N 3/08 20130101; F01N 1/083 20130101 |
Class at
Publication: |
181/272 |
International
Class: |
F01N 1/08 20060101
F01N001/08 |
Claims
1. An apparatus for exhaust noise attenuation as exhaust exits an
internal combustion engine, the apparatus comprising: a. a muffler
having an exhaust entrance port, a first chamber, and an exhaust
exit port; and b. an outer enclosure spaced from and substantially
enclosing a majority of said muffler, said muffler exhaust exit
port dumping exhaust into said outer enclosure, said outer
enclosure further having an enclosure exit port.
2. The apparatus of claim 1, wherein said muffler includes at least
two walls, said outer enclosure being separated from at least two
of said at least two walls, said outer enclosure forming a chamber
between said at least two walls and said outer enclosure.
3. The apparatus of claim 2, wherein said enclosure exit port is
disposed through a wall of said enclosure removed from said exhaust
exit port.
4. The apparatus of claim 1, wherein said outer enclosure provides
a heat shield for said muffler.
5. The apparatus of claim 1, further comprising an outlet pipe
secured to said exhaust exit port.
6. The apparatus of claim 5, wherein said outlet pipe includes at
least one bend within said outer enclosure, exhaust gases being
channeled within said outlet pipe before being dumped within said
outer enclosure.
7. The apparatus of claim 1, further comprising a catalyst pack
within said muffler, exhaust gases passing through said catalyst
pack before exiting said muffler.
8. The apparatus of claim 7, wherein said catalyst pack is coupled
to said entrance port.
9. The apparatus of claim 7, wherein said catalyst pack is coupled
to said exit port.
10. The apparatus of claim 7, wherein said catalyst pack is coupled
between said entrance port and said exit port.
11. The apparatus of claim 1, wherein said muffler further
comprises: a. a chamber in fluid communication with said exhaust
entrance port, and b. an exhaust pipe in fluid communication with
said chamber and with said exhaust exit port, said exhaust pipe
extending within said chamber and having a bend therein within said
chamber.
12. The apparatus of claim 1, further comprising a spark arrester
secured to said exhaust exit port, said arrester being removably
secured to said outer enclosure.
13. The apparatus of claim 1, further comprising a tail pipe
secured to said exhaust exit port, said tail pipe extending within
said outer enclosure to channel exhaust gases from said muffler to
said outer enclosure.
14. The apparatus of claim 11, wherein said tail pipe extends
within said outer enclosure a majority of the length of said outer
enclosure.
Description
PRIORITY CLAIM
[0001] This application is a divisional of U.S. application Ser.
No. 11/019,154, filed Dec. 20, 2004, contents of which are
incorporated herein.
FIELD OF THE INVENTION
[0002] This invention relates generally to exhaust mufflers for
internal combustion engines and, more specifically, to a compact
exhaust muffler for small vehicles.
BACKGROUND OF THE INVENTION
[0003] Mufflers with spark arresters attenuate exhaust gas noise
and sparks from internal combustion engines. However, mufflers add
size, weight, and power-robbing backpressure to an engine. Small
vehicles, such as all terrain vehicles (ATVs), motorcycles, and
snowmobiles, need high power-to-weight ratios for optimum
performance. Small size and low weight help the driver maneuver the
vehicle through off-road obstacles. A high power-to-weight ratio
helps the vehicle climb and accelerate, and increases available
load-carrying capacity. While an effective muffler adds weight and
reduces horsepower, quiet operation without exhaust spark emissions
not only enables the vehicle to meet mandatory government
regulations, but increases the vehicle acceptance by both the user
and others wishing to enjoy the outdoor environment.
[0004] Typical commercially available mufflers reduce noise levels
to regulation standards. However, the noise level may still not be
acceptable to users and others in the vicinity. Manufacturers may
be reluctant use mufflers that decrease the noise level much below
government mandates since such reductions usually result in an
increase in muffler weight, size, and/or backpressure. Muffler
noise reductions may be increased with additional baffles and
chambers or by increasing size--the very changes that also increase
weight and backpressure. Such changes also increase the complexity
and cost of manufacture.
[0005] Backpressure occurs when exhaust gases do not have a direct,
easy-flow exit route. The engine must push the gases out through a
tortuous (although noise-canceling) path of chambers, baffles,
tubes, and turns. Thus, backpressure restricts power that would
have been available to propel the vehicle.
[0006] Therefore, a need exists for a muffler that decreases
backpressure without increasing noise, or conversely, that
decreases noise without increasing backpressure. Further advantages
would result with simplified manufacturing and lighter weights.
SUMMARY OF THE INVENTION
[0007] The present invention provides a muffler for a small vehicle
of a size that fits within the envelope of the current systems. The
muffler reduces noise, weight, and complexity. It also decreases
exhaust gas backpressure.
[0008] The present invention provides a muffler for attenuating
exhaust gas noise from an internal combustion engine. The muffler
includes a main chamber and an exhaust pipe. Exhaust gases are
channeled into the main chamber from the engine. The main chamber,
in the preferred embodiment, encloses at least a third of the
volume of the muffler. The exhaust pipe is in fluid communication
with the main chamber. The exhaust pipe extends through the main
chamber and receives exhaust gases from the main chamber
(preferably via a diffusion chamber).
[0009] In one aspect of the invention, an intermediate pipe is
provided. The intermediate pipe is in fluid communication with the
main chamber (preferably via a transition chamber) at its first end
and with the exhaust pipe at its second end. The intermediate pipe
extends through the main chamber.
[0010] In a further aspect of the invention, the exhaust pipe
includes a bend in a mid portion thereof as it extends within the
main chamber. Preferably, the bend substantially completes a
180.degree. turn within the main chamber. With such bend, the
exhaust pipe is longer than the main chamber.
[0011] In still a further aspect of the invention, a diffusion
chamber is situated adjacent the main chamber. Gases enter the
diffusion chamber after leaving the main chamber and before
entering the exhaust pipe. The diffusion chamber may be smaller
than the main chamber.
[0012] The preferred embodiment of the invention also includes a
spark arrester disposed within the diffusion chamber and connected
to the exhaust pipe. Gases pass through the spark arrester before
entering the exhaust pipe. In one aspect of the invention, the
spark arrester is removable from the outside of the muffler.
[0013] The present invention may also be defined as a muffler for
an internal combustion engine including a chamber, a first pipe
portion, a second pipe portion, and a muffler exit. Exhaust gases
are channeled into the chamber from the engine. The chamber
includes a chamber exit. The first pipe portion is in fluid
communication with the chamber exit. The first pipe portion extends
through at least half of the length of the chamber. The second pipe
portion is also in fluid communication with the first pipe portion.
The second pipe portion also extends through at least half of the
length of the chamber. The muffler exit is in fluid communication
in the second pipe portion. Exhaust gases are channeled from the
chamber through the first pipe portion to an opposite end of the
chamber and then through the second pipe portion and out of the
muffler.
[0014] The present invention further includes a method of
attenuating exhaust noise of an internal combustion engine. The
method includes channeling exhaust gases from the engine into the
main chamber. The gases are then channeled from the main chamber
into an exhaust pipe that extends through the main chamber. The
exhaust pipe is longer than the length of the main chamber, as the
pipe includes a bend within the main chamber. Finally, the gases
are channeled from the pipe to an exhaust exit.
[0015] In the preferred method of the invention, the gases are
channeled through an intermediate pipe between the main chamber and
the exhaust pipe. The gases are also channeled through a transition
aperture to a diffusion chamber between the intermediate pipe and
the exhaust pipe. Thus, the gases flow from the engine to the main
chamber out of the main chamber exit (e.g., through the transition
aperture and transition chamber), through the intermediate pipe
into the diffuser, through a spark arrester disposed between the
main chamber and the exhaust pipe in the diffuser, and through the
exhaust pipe including surrounding the bend within the exhaust pipe
to exit the external portion of the muffler.
[0016] In still a further aspect of the invention, an apparatus for
exhaust noise attenuation is provided. The apparatus includes a
muffler and an outer enclosure. The muffler has an exhaust entrance
port, a first chamber, and an exhaust exit port. The outer
enclosure is spaced from and at least substantially encloses a
majority of the muffler. The muffler exhaust port dumps exhaust
into the outer enclosure. The outer enclosure further includes an
enclosure exit port.
[0017] The further aspect of this embodiment of the invention, the
muffler includes at least two walls. The outer enclosure is
separated from the two walls. The outer enclosure forms a chamber
between the two walls and the outer enclosure. Preferably, the
enclosure exit port is disposed through a wall of the enclosure
removed from the exhaust exit pipe port.
[0018] The muffler with the spark arrester arrangement may also be
defined as including an exhaust entrance port, a diffuser chamber,
a diffuser chamber exit port, and a spark arrester. The diffuser
chamber is in fluid communication with the entrance port. The spark
arrester is at least partially disposed within the diffuser
chamber. It is coupled to the diffuser chamber exit port. The spark
arrester includes a screen through which exhaust gases pass to flow
through the diffuser chamber exit port. The screen is removably
coupled to the diffuser chamber such that it can be removed from
the muffler.
[0019] Further aspects of the spark arrester included with the
muffler include accessibility from outside of the muffler. The
spark arrester forms a tube shape having two ends. One end of the
spark arrester engages the diffuser chamber exit port. The other
end has a cap thereon. The end with the cap is adjacent the
diffuser chamber sidewall. The cap engages the end of the diffuser
chamber and end of the muffler.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Preferred and alternative embodiments of the present
invention are described in detail below with reference to the
following drawings:
[0021] FIG. 1 is a cross-sectional view of two halves of a
prior-art muffler illustrating the various chambers;
[0022] FIG. 2 is a side elevational view of the prior-art muffler
shown in FIG. 1;
[0023] FIG. 3 is a perspective view of a muffler of the present
invention showing the outer shell in phantom;
[0024] FIG. 4 is a cross-sectional view of the muffler;
[0025] FIG. 5 is an isometric view of the spark arrester
element;
[0026] FIG. 6 is a side elevational view of the cage portion of the
spark arrester;
[0027] FIG. 7 is a schematic view of the muffler including the
outer enclosure;
[0028] FIG. 8 is a schematic view of a muffler with a complete
enclosure;
[0029] FIG. 9 illustrates the enclosure of FIG. 8 with the addition
of a removable spark arrester;
[0030] FIG. 10 illustrates the details of the spark arrester
illustrated in FIG. 9;
[0031] FIG. 11 is an isometric view of the spark arrester;
[0032] FIG. 12 is a side elevational view of an alternate spark
arrester with a tapered screen;
[0033] FIG. 13 is a schematic view of an enclosed muffler and
pipe;
[0034] FIG. 14A is a schematic view of an enclosed muffler having a
catalytic converter;
[0035] FIG. 14B is a schematic view a variation of the muffler of
FIG. 14A; and
[0036] FIG. 14C is a schematic view a further variation of the
muffler of FIG. 14A.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0037] An understanding of a typical prior-art muffler helps
develop an appreciation for the present invention. A standard
muffler 10 such as that used with ATVs is illustrated in FIGS. 1
and 2. Muffler 10 has a generally cylindrical shape with an inlet
pipe 12 and an outlet pipe 26 at opposing ends thereof. Various
chambers are situated between inlet pipe 12 and outlet pipe 26. In
the illustrated example, six chambers are included. Inlet pipe 12
extends through an outer shell 40 to direct exhaust gases from the
engine into first chamber 14. First chamber 14 is generally
cylindrical in shape and is bounded by an inner shell 42, which is
secured to outer shell 40, as well as the first end of outer shell
40 and a wall between first chamber 14 and second chamber 16. The
diameter of first chamber 14 is about twice its length. First
chamber 14 creates a small expansion chamber for hot gases from
inlet pipe 12. These gases are then directed through second chamber
inlet pipe 28 into second chamber 16.
[0038] Second chamber 16 is also cylindrical in shape, but has a
length approximately equal to its diameter. Furthermore, second
chamber 16 includes second chamber inlet pipe 28 and second chamber
outlet pipes 30 therein. These pipes extend nearly the entire
length of the chamber. Exhaust gases enter second chamber inlet
pipe 28, pass through the pipe and into second chamber 16 at the
far end thereof. The gases then circle back to the front end of the
chamber to enter into the three-second chamber outlet pipes 30.
These pipes are smaller in diameter than inlet pipe 28. However,
three pipes are included to channel the gases out of second chamber
16 and into third chamber 18.
[0039] Third chamber 18 is much smaller than second chamber 16.
Third chamber 18 is bounded on its downstream end by a diffuser
wall 32. Diffuser wall 32 includes diffusion openings to circulate
the air into fourth chamber 20.
[0040] Fourth chamber 20 is approximately the same size as third
chamber 18, but includes a separation wall 34 to separate any
sparks from the remaining exhaust gases. The debris (e.g., carbon
deposits) is collected beneath the separator wall 34 and may be
removed from muffler 10 with soot plug 46 as illustrated in FIG. 2.
Exhaust gases leave fourth chamber 20 through fifth chamber inlet
pipe 36.
[0041] Fifth chamber inlet pipe 36 directs gases into fifth chamber
22 in a manner similar to second chamber inlet pipe 28 with regard
to second chamber 16. Likewise, fifth chamber 22 also includes
fifth chamber outlet pipes 38 that channel the exhaust gases
through another wall and into sixth chamber 24. One inlet pipe 36
is utilized and three fifth-chamber outlet pipes 38 are
provided.
[0042] Sixth chamber 24 is used to collect the exhaust gases for
channeling them to outlet pipe 26.
[0043] Note that an inner shell 42 is secured to outer shell 40
with spacing between the two shells. An absorption layer 44 is
placed within the spacing for noise attenuation. Absorption layer
44 may include standard glass packing materials.
[0044] The prior-art muffler accomplishes the goals of reducing
noise levels to within legal limits and provides a spark arrester
feature with a soot cleaning plug 46. The muffler is also of a size
that allows it to fit within the space required on the back of a
small vehicle such as an all-terrain vehicle (ATV). However,
further reductions in noise levels may be preferable for users and
others in the vicinity of the user of the vehicle. Furthermore, the
muffler introduces excessive back pressure such that the horsepower
of the engine is adversely affected. Opening up the muffler to
decrease the back pressure may be accomplished, but not without
noise increases.
[0045] Furthermore, in situations where certain amount of back
pressure is desired for optimum engine performance, the prior-art
mufflers require that different designs be created and produced to
tune the muffler for each engine application. This is the case, for
example, with a family of ATVs of differing engines and engine
sizes. Back pressure requirements would differ in each case. Thus,
a different muffler must be designed and manufactured for each ATV.
This will increase the cost of manufacture of the mufflers since
each will necessarily be produced in lower quantities. This may not
be an issue in many instances since the back pressure introduced by
the muffler in order to create sufficient noise reduction is such
that it exceeds the back pressure needed for optimum engine
performance. In such instance, engine performance (horsepower)
suffers, as explained above.
[0046] The present invention provides a muffler that has low back
pressure with a device for changing the back pressure dependent
upon the engine requirements for optimum horsepower. The system is
also lighter weight and cheaper to manufacture than prior-art
mufflers. This muffler and its various components are illustrated
in FIGS. 3-6.
[0047] Referring first to FIG. 3, the internal construction of
muffler 100 is illustrated. Muffler 100 includes an outer shell 102
(shown in phantom in FIG. 3). Outer shell 102 includes a first end
wall 104 at the upstream end of muffler 100 and a second end wall
106 at the downstream end. First and second inner walls 108 and 110
lying in plains parallel to end walls 104 and 106 are also provided
within outer shell 102.
[0048] End walls 104 and 106 along with inner walls 108 and 110
divide muffler 100 into three chambers: a main chamber 112, a
transition chamber 114, and a diffusion chamber 116. Main chamber
112 is the largest of the chambers and preferably comprises
one-third to one-half or more of the total volume of muffler 100.
Transition chamber 114 is at one end of the muffler being bounded
by first end wall 104 and first inner wall 108. Diffusion chamber
116 is at the opposite end of muffler 100 being bounded by second
inner wall 110 and second end wall 106. Alternatively, any type of
diffuser may be employed, whether a diffusion chamber, a diffuser
wall, or other device. In the preferred embodiment a diffusion
chamber is used as illustrated and described herein.
[0049] As can be seen in FIGS. 3 and 4, numerous pipes are situated
within muffler 100. An inlet pipe 118 is extends through first end
wall 104 and first inner wall 108 to channel exhaust gases from the
pipe leading from the engine of the vehicle into main chamber 112.
At the opposite end of muffler 100 exhaust pipe 120 allows the
gases to escape muffler 100. Two intermediate pipes 122 extend
within muffler 100 and channel the gases between the transition
chamber and the diffusion chamber. Intermediate pipes 122 are in
fluid communication within transition chamber 114 and diffusion
chamber 116. These pipes extend through main chamber 112, but are
not open thereto.
[0050] An intermediate wall 124 is provided between intermediate
pipes 122 at the portion thereof that is not adjacent exhaust pipe
120. Intermediate wall 124 prevents early back flow through
transitional aperture 138 as explained below. Exhaust pipe 120
extends from diffusion chamber 116 through main chamber 112. A bend
126 allows exhaust pipe 120 to extend back through second inner
wall 110, through diffusion chamber 116 to exit through second end
wall 106 at an external portion 128. Exhaust pipe 120 is preferably
stamped in halves and fitted together. Stamping the halves allows
the straightforward manufacture of a pipe with a bend having a
larger cross section so as to not restrict air flow. Alternate
embodiments include a simple bent pipe to form pipe 120.
[0051] A spark arrester 130 is secured to the end of exhaust pipe
120 that is in fluid communication with diffusion chamber 116. An
arrester aperture 132 is formed in second end wall 106 to allow
spark arrester 130 to be removed and replaced within muffler
100.
[0052] An inner shell 134 is provided within main chamber 112,
spaced from outer shell 102. An absorption layer 136 is positioned
between inner and outer shells 134 and 102. Inner shell 134
includes perforations therein for effective noise attenuation with
absorption layer 136.
[0053] Note also that transitional aperture 138 is formed within
first inner wall 108 to allow the flow of gases from main chamber
112 to transition chamber 114. Transition aperture 138 is
preferably at least as large as the diameter of inlet pipe 118.
[0054] The basic flow of gases through muffler 100 will now be
described. Exhaust gases from the engine enter inlet pipe 118.
Inlet pipe 118 directs the gases past transition chamber 114 into
main chamber 112. The volume of main chamber 112 is large enough to
effectively create an expansion chamber for the gases. This is
where the main noise attenuation occurs. Thus, this is the place
where inner shell 134 and absorption layer 136 are positioned for
noise attenuation. The gases travel throughout main chamber 112,
aided by intermediate wall 124. The gases then must pass around the
outer walls of exhaust pipe 120 and intermediate pipes 122 before
they pass through transition aperture 138 to enter transition
chamber 114. Transition chamber 114 is relatively open and provides
for little restriction to the flow of exhaust gases to then enter
into intermediate pipes 122. Intermediate pipes 122 flow through
the body of main chamber 112 without being open thereto.
Intermediate pipes 122 channel the exhaust gases from transition
chamber 114 at one end of muffler 100 to diffusion chamber 116 at
the other end. The exhaust gases then flow through spark arrester
130 and into exhaust pipe 120. Exhaust pipe 120 then extends
through the middle of main chamber 112 bending therein to exit back
through diffusion chamber 116 and out second end wall 106. The
exhaust gases then exit external portion 128.
[0055] The flow system described creates very little back pressure
while creating superior noise attenuation. Noise attenuation is
accomplished by routing the pipes through the main chamber where
the gas first enters muffler 100 through inlet pipe 118. The long
pipes extending therethrough tend to attenuate the noise while not
appreciably increasing back pressure. The system is also easy to
manufacture from pipes and stamped metal channels. Furthermore, the
muffler system created is lightweight. The system is also tunable
for different engines by simply changing the spark arrester as
described below in connection with FIGS. 5 and 6.
[0056] FIGS. 5 and 6 illustrate the details of spark arrester 130.
Spark arrester 130 includes a screen 140 wrapped around a cage 142.
Cage 142 is fixed to an endplate 144 that engages with second end
wall 106 with fasteners 153 through holes 152. A band 146 helps
secure screen 140 to cage 142.
[0057] Cage 142 is constructed with struts 148 and end rings 150.
The size of struts 148 are widened or narrowed in order to tune the
back pressure of muffler 100 for optimum engine performance in a
specific engine application. This is the only piece that need be
changed in order to tune the muffler for a specific engine. Thus,
muffler 100 can be used for an entire family of ATVs by simple
changes to spark arrester 130. This helps decrease the
manufacturing costs as more units are produced that are the same.
Thus, a specific spark arrester cage 142 may be different from one
engine to the next, but the balance of muffler 100 is the same from
one to another.
[0058] End ring 150 at the inner end of cage 142 is sized to fit
over the outer diameter of the entrance to exhaust pipe 120. The
openings in screen 140 are such as to provide proper spark arrester
function. The ability to remove spark arrester 130 also allows
debris and soot material to be expelled from diffusing chamber 116
as may be required. Suitable fasteners 153 through holes 152 may be
used to secure endplate 144 to second end wall 106, which may
include fastener receptacles therein.
[0059] Turning now to FIG. 7, an additional aspect of the present
invention will be described. FIG. 7 illustrates a muffler 154 that
includes an outer enclosure 156 surrounding a majority thereof.
Muffler 154 may be a standard muffler such as that illustrated in
FIGS. 1 and 2 or may be a muffler as described in connection with
FIGS. 3 and 4.
[0060] Muffler 154 includes an inlet pipe 158, a main body, and an
outlet pipe 160. Mounting brackets 162 are preferably secured to
the top and side thereof for securement to a vehicle such as an
ATV.
[0061] Enclosure 156 includes enclosure walls 164 that create an
outer chamber 166. Outer chamber 166 encloses a majority of muffler
154 and creates a place where exhaust gases are dumped from outlet
pipe 160 before exiting into the environment. Outer chamber 166 is
of a size sufficiently large such that expansion of gases is easily
accomplished and additional back pressure is minimal. An enclosure
exit 168 is provided. enclosure exit 168 may be situated anywhere
on enclosure walls 164. Preferably, it is not in the direct line of
exhaust exit from outlet pipe 160. Thus, exhaust gases enter
muffler 154 then exit through outlet pipe 160 to enter outer
chamber 166 where the gases are further cooled and quieted before
exiting enclosure exit 168. This arrangement provides additional
noise attenuation as well as a cooler interface between the user
and the hot exhaust gases. Enclosure 156 also reduces heat at the
user and machine parts interface to the extent that it preferably
completely replaces any remote heat shields that are customarily
attached to the outer wall of muffler 156 or to other parts of the
machine to deflect heat from the muffler. External heat shields are
often used to protect parts of the machine or vehicle that may
overheat or even melt, such as the carburetor and plastic parts.
The heat shielding effect of enclosure 156 reduces or eliminates
the need for such additional shields. Noise reduction is
accomplished through a reduction in exiting exhaust gas noise as
well as attenuation of muffler shell noise.
[0062] Enclosure walls 164 may completely encompass muffler 154, as
illustrated in FIG. 8, or may partially encompass the muffler as
illustrated in FIG. 7. In the case of complete enclosure, struts
170 between muffler 154 and enclosure walls 164 preferably hold the
spaced relationship between the two members with mounting brackets
162 secured on enclosure walls 164. Other arrangements are also
possible that accomplish the purposes of having an outer chamber
into which the exhaust gases are dumped before exiting the muffler
system.
[0063] Turning now to FIG. 9, an embodiment of a completely
enclosed muffler is illustrated. However, in this embodiment, a
spark arrester is held within the enclosure body. A separate spark
arrester may or may not be included within the main muffler 154.
Enclosure 156a includes an opening into which fasteners 153 secure
spark arrester assembly 172. Spark arrester assembly 172 is similar
to spark arrester 130 except that assembly 172 also includes an
exit pipe 174 secured directly to the outer end thereof. Spark
arrester assembly 172 includes an endplate 144a with an aperture
there through to which exit pipe 174 is secured, preferably by a
weld.
[0064] The details of construction of spark arrester assembly 172
are illustrated in FIGS. 10 and 11. Spark arrester assembly 172 is
constructed with a cage 142a having an inner cap 176. Cap 176 may
alternatively be at least partially replaced with screen material
similar to screen 140a that surrounds cage 142a. Clamps 146a secure
screen 140a to cage 142a. Fasteners are secured through holes 152a
and mounting plate 144a.
[0065] Exhaust gases within enclosure 156a go through screen 140a,
through endplate 144a and exit pipe 174.
[0066] An alternate embodiment of a spark arrester assembly is also
illustrated in FIG. 12. In this embodiment, the cage is eliminated.
A screen tube is provided having an inner, closed end compressed
together by rolling the screen material. Other fixation means to
close the end may alternatively be employed. The outer end includes
a clamp 146b that secures screen 140b to exit pipe 174b. Exit pipe
174b is welded to mounting plate 144b, but extends through such
that the outer end of screen 140b can be clamped thereto.
[0067] FIG. 13 illustrates an alternate embodiment similar to FIG.
9 with an elongated tail pipe 160c within outer enclosure 156c.
Tail pipe 160c extends from one end of muffler 154c some distance
within outer enclosure 156c, preferably to the other end of outer
enclosure 156c. A bend is preferably formed in pipe 160c such that
a long length of pipe fits within outer enclosure 156c. Spark
arrester assembly 172c is situated out of direct alignment with the
exhaust gas exit from pipe 160c. Thus in this embodiment it is on
the opposite side of outer enclosure 156c. This long-pipe
arrangement within enclosure 156c further quiets the exhaust noise
of the entire muffler assembly with little additional backpressure.
The additional silencing achieved with enclosure 156c may allow
more design flexibility for muffler 154c. Thus, a simpler, less
expensive design may be employed. Muffler 154c in one embodiment
includes an internal elongated pipe, while another embodiment omits
such pipe.
[0068] FIGS. 14A-C illustrate a muffler design variation including
a catalytic converter 178. Thus, in FIG. 14A catalyst 178d is
positioned within muffler 154d between inlet pipe 158d and exhaust
pipe 120d. As exhaust gases run through catalyst 178d, not only are
pollutants (such as carbon monoxide and nitrous oxides) reduced,
but noise is also diminished. In this embodiment, exhaust pipe 120d
forms a 180 degree bend within muffler main 154d. Exhaust pipe 120d
joins with outlet pipe 160d, which runs within enclosure 156d
outside of muffler 154d. Outlet pipe 160d preferably forms a 180
degree bend within enclosure 156d before dumping exhaust gases into
enclosure 156d for exit through spark arrester assembly 172d.
[0069] In a variation of the arrangement described above (FIG.
14B), a catalyst 178e is secured directly to an inlet pipe 158e.
Exhaust gases run through catalyst 178e as they enter muffler 154e.
The gases run through muffler 154e, after which they exit through
outlet pipe 160e and spark arrester assembly 172e. In the preferred
embodiment, outlet pipe 160e includes a 180 degree bend and an
elongated pipe similar to that discussed above in connection with
FIG. 13.
[0070] In a further variation (FIG. 14C), a catalyst 178f is
secured to outlet pipe 160f. In this embodiment, exhaust gases pass
through catalyst 178f as they exit muffler 154f. Again in this
preferred embodiment, outlet pipe 160f includes a 180 degree bend
and an elongated pipe.
[0071] The placement of catalyst 178 in any of the embodiments
discussed herein may be made depending on the particular engine and
its tuning requirements. In each embodiment herein catalyst 178
acts as an additional silencer in addition to its pollution control
capabilities.
[0072] While the preferred embodiments of the invention have been
illustrated and described, as noted above, many changes can be made
without departing from the spirit and scope of the invention. For
example, alternate shapes and pipes may be used. Different numbers
and arrangements of pipes may also be employed. Accordingly, the
scope of the invention is not limited by the disclosure of the
preferred embodiment. Instead, the invention should be determined
by reference to the claims that follow.
* * * * *