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Патент USA US2404589

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July 23, 1946-
Filed Dec. 27', 1944
Patented July 23, 1946
Henry W. Monaghan, New Orleans, La., assignor
t0 Higgins Industries, Inc., New Orleans, La., a
corporation of Louisiana
Application December 27, 1944, Serial No. 569,961
4 Claims. (01. 181—,45)
This invention relates to unsubmerged exhaust
mufflers, particularly adapted for marine internal
combustion engine power plants.
In general, unsubmerged mufflers have the ad
vantage of being subject to less back pressure
than under-Water mu?lers, and in shallow draft
These concurrent noises have different
sound characteristics, producing interference, so
that the net effect is a dampening of the ob
jectionable noise of the exhaust.
Much ingenuity and mechanical skill has been
devoted to the problem of reducing the impact
of the expanding slugs against the shell wall
in reducing the velocity and expansive effect
torn off when the hull slides over shoals or upon
of the issuing jet against atmosphere. The sub
10 ject invention stems from a scienti?c study of
Unsubmerged mufflers in general use vary in
the causes which produce a noisy exhaust, and
noise dampening e?iciency with the R. P. M. of
by the novel construction and arrangement of
the engine. At high speeds they may be ac
parts is believed to have created a more e?icient
ceptably effective, but at low speeds, quite noisy.
muffler than those heretofore known.
vessels such as landing craft, it is quite essential
that the muffler be above water, to avoid its being
The cause of this may be explored by consid
ering the factors which produce noisy exhaust
discharge. When the exhaust valve of the engine
opens, slugs of hot combustion products under
pressure and in potential condition to expand
are discharged. In the exhaust pipe these slugs
follow one another at close intervals, alternat
ing with intervening regions of exhaust gas of
less concentrated heat and pressure. In the
absence of a muffler, when the pent slugs reach
atmosphere at the end of the exhaust pipe, they
suddenly expand, giving an impact blow to the
atmosphere, resulting in objectionable staccato
noise. At high engine speeds the slugs follow one
another at such close intervals as to have the
characteristics more or less of a continuous ?ow
One of the objects of the invention is to pro
vide a tandem muffler, the forward unit being
devoted principally to cushioning the internal
shock of the expanding slugs within the shell,
and in obliterating the independent slug charac
teristics of the exhaust, while the posterior unit
functions principally to reduce the velocity of the
effluent gases, although both units participate to
an extent in supplementing the functions of one
Another object of the invention is to connect
the anterior and posterior units of the muffler by
means of a nonmetallic ?exible coupling so that
vibrations set up in one unit shall not be com
municated to and accentuated by the other.
Other objects of the invention ‘will appear as
the following description of a preferred and prac
and the separateness of the noise impulses is not
so keenly detected by the car.
tical embodiment thereof proceeds.
If a simple mu?ler, for example, a hollow shell
In the drawing‘
of larger diameter than that of the exhaust pipe
l is a perspective view of a mu?‘ler em
and having a tail pipe, is connected to the end
principles of the invention;
of the exhaust pipe, the ?rst slug to enter has
Figure 2 is a perspective view of a longitudinal
room to expand within the shell; therefore, its
half of the muffler, showing the butterfly valves
velocity is checked. Before it has had time to
in place;
reach the tail pipe, another slug has entered the
3 is a diametrical section taken along
shell and partially expanded. The effect of the 40 theFigure
line 3-3 of Figure 2.
two slugs within the shell at the same time and
Referring now in detail to the several ?gures,
in different expansion phases is to mix the ex
the numerals l and 2 represent, respectively, the
haust products constituting the slugs, so as to
anterior and posterior muffler units which are
destroy their independent slug characteristics, so
preferably fabricated by Welding. Figure 2 shows
that the discharge from the tail pipe more nearly
that each unit includes a pipe section, 3 and 4,
approaches a continuous ?ow. However, when
respectively, which sections are in axial align
each slug expanded within the shell, it delivered
ment and connected by a ?exible, preferably non
an impact blow against the wall of the shell, the
metallic coupling 5.
vibrations of which are communicated to the
Under such circumstances there are produced
at one and the same time, the noise caused by
the expanded issuing jet at the tail pipe and those
noises resultant from the knocking of the slugs
expanding into the shell, against the wall of the
The pipe sections 3 and. 4 are surrounded by
the cylindrical shells 6 and 7, respectively, said
pipe sections passing through the respective
shells and extending beyond the ends 8 thereof.
Said pipe sections lie parallel to the axes of the
shells, but offset from said axes so as to de?ne
with said shells surrounding chambers which are
narrow beneath said pipe sections and capacious
above said pipe sections.
tion 4 is formed with the respective ?elds of perfo~
rations 28, 29, 30 and 3|, communicating with the
shell ‘B. Each baiiie is designed to apprehend and
mediate partitions Ill and H, perforated in that
baffle into the shell ‘I. The bleeding off of part
part which lies above the pipe section 3. Said
pipe section is provided with four ?elds of perfo
rations i2, i3, i4 and I5, extending circumferen
of the gas from the pipe section 4 reduces the
volume, and consequently the velocity of the por
tion remaining in said pipe section, and since the
ba?ies are spaced apart longitudinally, the reduc
tion in velocity of the gases in the front portion
of the pipe section 4 is progressive.
The gases discharged into the shell ‘I suffer
turbulence and thorough mixing in the same
Referring now to the anterior unit i, the shell
check the velocity of a portion of the gas travel
5 is divided into four compartments I9, 20, 2| and.
ing through the pipe section 4, and to cause it to
22 by a middle imperforate partition 9 and inter
pass through the perforations in front of said
tially thereabout and communicating respectively
with the compartments de?ned by said partitions.
Passage of exhaust gases through the pipe sec
tion 3 is controlled by a pair of butter?y valves
56 and ii, mounted on shafts journaled substan
tially in the planes of the intermediate partitions 15
it and I I. Said valves work together in the same
phase, closing and opening together. Said valves
are connected by conventional linkage designated"
manner as described in relation to the shell 6,
its velocity being further reduced by expansion
into‘ the capacious chamber of the shell 1. Any
residual slug or impulse characteristics of the ex
haust are nulli?ed by the mixing action in the
a rod, (not shown) , leading to a point from which 20 shell 1, and the gases are then returned to the
it can be conveniently manipulated.
rear portion of the pipe section 4 where their
When the butter?y valves are open, the pipe
mixture with the jet about to issue from the
section 3 affords an unrestricted through passage
muffler further homogenizes the exhaust gas in
for the exhaust gas. When the butter?y valves
said pipe section, which ?nally issues in the form
are closed, the exhaust gases are by-passed
of a steady ?ow at low velocity and without ob
through the shell 6. They ?rst pass through the
jectionable noise.
?eld of perforations i2 into the shell compart
In operation, if the engine is running at high
ment l9, then through the perforations in the
speed so that the exhaust impulses follow in such
partition it into the shell compartment as, then
rapid succession as to approach a steady flow,
through the ?eld of perforations l3 into the pipe
the butter?y valves are opened so that the ex
section 3, then back through the ?eld of perfora
haust gases travel direct through the pipe section
tions Ill into the shell compartment 2i, then
3, without being subjected to preliminary treat
through the perforations in partition ii into the
ment in anterior unit I. They are, however, sub
shell compartment 22, then back into the pipe sec
jected to the treatment afforded by posterior
tion 3 through the ?eld of perforations 15. The
unit 2. When the engine is running at slower
part of the exhaust gases that pass through those
speeds so that there is an appreciable interval
as a whole by the numeral l8, and operated by
perforations which communicate with the narrow
between Uthe exhaust impulses, the butter?y
side of the shell chamber are subjected to con
valves are closed and the exhaust gases by
trolled expansion, since they expand between the
passed through the shell 6, being subjected to
divergent walls of the pipe section and shell in 40 the noise dampening functions of both units.
the region designated as 23 in Figure 3. The part
Anterior unit i can be called into play more or
of the exhaust gases entering the shell through
less by adjusting the butterfly valves to inter
the perforations which communicate with its
mediate positions. The greater the proportion
broad side undergoes relatively uncontrolled ex
of the exhaust gases that are passed directly
pansion into the capacious part of the shell cham 45 through the pipe section 3, the less will be the
ber. Thus, turbulence is set up in the shell cham
back pressure upon the engine.
ber, effecting a thorough mixing of the exhaust
What I claim as my invention is:
gases, augmented by the mixing which follows the
l. Muffler for the exhaust of internal combus—
successive . direction charges in the serpentine
tion engines comprising serially connected units,
path of travel of the exhaust gases through the 50 each unit comprising a closed ended shell and a
shell. This mixing has the eifect of substantially
pipe section passing longitudinally through said
obliterating the independent successive slug char
shell and extending beyond the ends thereof,
acteristics of the exhaust gases, so that the ex
means connecting the adjacent ends of said pipe
haust leaves the pipe section 3 substantially inv
section, transverse partitions in one of said shells
the form of a continuous ?ow.
dividing it into a plurality of compartments,
The chamber of the shell 6 always retains some
alternate partitions beginning with the most
exhaust gas under sub-atmospheric pressure, so
anterior being perforate, the intermediate parti
that when the successive slugs of exhaust gas
tion being imperforate, the pipe section which
under pressure from the engine blow through the
passes through said shell having fields of per
?eld of perforations l2 into the shell, their im
forations communicating with the respective
pact force is dampened by the gas under pressure
compartments, a pair of spaced butter?y valves
already in the shell, so that the shock with which
in said pipe section located substantially in the
they impinge upon the wall of the shell is damp
planes of said perforate portions, means for
ened to the extent that little or no noise vibra
moving said valves together to obstruct said pipe
tions are communicated through the shell wall
sections to compel a serpentine flow of exhaust
to the atmosphere.
gases through said pipe section and shell, longi
Passing now to a description of the posterior
tudinally spaced and circumferentially displaced
unit 2, the pipe section 4 has no cut-off valves,
baf?es in the anterior portions of the other pipe
therefore, it at all times presents a through pas-.
section, ?elds of perforations in said last named
sage for the exhaust gases discharging from the 70 section immediately forward of the respective
pipe section 3 of the anterior unit. However, the
ba?les, and a ?eld of perforations in the posterior
front half of the pipe section 4 is provided at suc
portion of said last named pipe section, all of
cessive longitudinal intervals with the inwardly
said ?elds of perforations in said last named pipe
directed baffles 24, 25, 26 and 21 circumferentially
section communicating with the shell which sur
displaced. Forwardly of said baf?es the pipe sec 75
rounds it, whereby part of the exhaust gases
of the intercommunicating perforations open
?owing through said last named pipe section are
into a narrow part of the shell chambers, while
de?ected by said ba?les into said shell through
other of said perforations open into a capacious
the forward ?elds of perforations and returned
part of said chambers.
to said last named pipe section through the ?eld 5
4. Muf?er as claimed in claim 1, the axes of
of perforations in its posterior portion.
said shells being offset from and above the axes
2. Mu?ler as claimed in claim 1, the connecting
of the pipe sections which they surround, whereby
means between said pipe section being a ?exible
the lower of the intercommunicating perforations
non-metallic coupling.
open into a narrow part of the shell chambers
3. Mu?ler as claimed in claim 1, the axes of 10 while the upper of said perforations open into
said shells being o?set from the axes of the pipe
a capacious part of said chambers.
sections which they surround, whereby certain
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