US2343371A - Suction muffler for airplanes, automobiles, and the like - Google Patents

Description

March 7, 1944. Q FlSHER 2,343,371

SUCTION MUFFLER FOR AIRPLANES, AUTOMOBILES, AND THE LIKE Filed Sept. 9, 1941 IN ENTOR W yaw l I ORNEY Patented Mar. 7, 1944 SUCTION MUFFLER FOR AIBPLANES, AUTOMOBILES, AND THE LIKE John A. Fisher, Steinhatchee, Fla. Application September 9, 1941, Serial No. 410,138

Claims.

My invention comprises certain new and useful improvements in mufllers for internal combustion engines, especially those of airplanes and automobiles, and its principal purpose is the elimination or minimizing of all detrimental back pressure in-the exhaust gases and the reduction of the sounds of the motor explosions to an unobiectionable minimum before and during the discharge or evacuation of the exhaust gases from the motor.

In the internal combustion engine art it has long been recognized that in the case of the types of muiilers now in use a great power loss is caused by the back pressure of the exhaust gases, including atmospheric and other restrictive presures, and also that means are desirable to reiuce the sound of the motor explosions.

These considerations are of very great importance in the case of airplanes as the reduction of atmospheric back pressure against the exhaust gases of the motor results in an increase of the available power and consequently in the speed of travel, and the reduction in the sound renders it more diflicult to detect at a distance the approach of an airplane in times of war or to determine by the sound of its motor the nationality of the-approaching plane.

At present it is the accepted practice in the case of airplanes to discharge the exhaust gases along with the explosive sounds directly into the compact air of the slip stream, where such noises blend and partially synchronize with the slashing or ping-like noises of the whirling propeller, which latter noises, without this blending and synchronization, would not be audible beyond a relatively short distance; and thus the approach of an airplane is audibly heralded long before the approaching airplane becomes visible to observers.

With these advantageous ends in view I have invented a new and improved muilier structure which provides an induced suction efiect whereby the exhaust gases emerge into a belt or zone of rarifled air, thus eliminating back pressure, and also subduing the noises of explosion inasmuch as noises cannot be produced or transmitted in a vacuum, and in a highly rarifled atmosphere or partial vacuum they are effectually dampened and their transmittal reduced to a minimum.

Again, due to the internal structure and contour of my improved muiiler, the noises are so baiiled and absorbed as to be materially reduced even at low speeds of travel of the airplane.

However, the greater the speed of travel of the airplane, the atmospheric air at the tall or discharge end of the muilier is rarifled and its pressure reduced to a greater degree, and thus the efliciency of my improved muiller both in reducing back pressures of any kind whatsoever and noise increases in a commensurate degree with the speed of travel.

In the accompanying drawing, wherein I have illustrated a practical embodiment of the principles of my invention,

a Fig. 1 is a top plan view of the suction muf- Fig. 2 is a side elevation of the same, partially in section;

' Fig. 3 is an end view lokoing from the right in Figs. 1 and 2;

Fig. 4' is a side view, partially in section, showing an application of the principles of my inven tion to the nacelle or cover of the motor mounted on the wing of an airplane;

Fig. 5 is a side elevation illustrating the principles of my invention applied to an airplane, the motor of which is mounted on the fuselage;

Fig. 6 is a broken front elevation of the strumture illustrated in Fig. 5;

Fig. 7 is a broken side elevation showing theprinciples of my invention applied to an automobile;

Fig. 8 is a view similar to Fig. 3 but illustrating a modification.

Referring first to Figs. 1 to 4, inclusive, l0 indicates the body of the muiiier which is of flattened form, having a materially greater internal width than vertical height. II indicates the mouth of the body III which is centrally located in the front wall of the body and is of annular form and of proper dimensions to be attachable directly tothe exhaust manifold. or the pipe leading from the latter. The contour of the front wall of the body is curvilinear to produce a neck and provide a horizontally expanding path of travel for the exhaust gases. The mouth I I may be provided with a perimetral flange Ila, as shown in the drawing for the ready attachment of the muiiier to the exhaust exit of the motor. The body may, for the sake of convenience and economy of construction be formed of two sections, upper and lower, which are joined along the lines indicated at IS in Fig. 1, in any convenient and well known manner.

The chamber formed interiorly of the body i0 is of such shape or relative dimensions as to direct the exhaust gases in the form of a wide but relatively shallow stream as they flow toward and into beige tail box I4 hereinafter more tully descri To facilitate such direction and formation of the stream of exhaust gases I provide in the top wall of the body It] a dent or depression located somewhat to the'rear but adjacent to the mouth of the body and of rearwardly diverging side walls which may advantageously more or less parallel the diverging inner surfaces of the front wall of the body. This provision materially aids in laterally spreading and widening the stream of gases entering through this mouth II.

The top and bottom walls of the body gradually converge, as shown in Fig. '2, to further shallow the stream of gases.

It will be seen that the structure of the body as illustrated in Figs. 1 and 2 is such that it has no interior angles or surfaces which might reflect the sound waves directly toward the rear of the body. The side walls of the body are preferably parallel or may even converge slightly toward the rear end of the body.

An important concept of my invention is that the chamber provided by the body be such so that the gases introduced thereinto by the succession of explosion puffs or blasts, incident to the operation of the motor, have suflicient volumetric space to spread and expand laterally and to obviate choking or back pressure. The gradual con vergence of the top and bottom walls of the flat body ll! serves to deflect, confine and absorb most of the firing noises and produce a thin or shallow but widely spread stream of gases which thus formed can carry but little sound.

The vertical bend or curve aids in the convenient positioning of the tail end of the mufller and also aids in the spreading of the exhaust stream as it travels rearwardly, thus restricting sound.

I The outlet of the body In is thus a widely extended but vertically restricted slotted opening.

The tail box I is of the full width of the body but interiorly of materially greater vertical height to augment suction effect. In its front wall it is provided with a horizontal slotted opening l6 extended for the width of the tail box and of equal horizontal length with the exit opening of the body which it matches. For convenience of attachment, the edges of the opening l6 may be provided with an outwardly extending spaced flange 16a which may fit over the end of the body It and be secured thereto as by welding or bolts.

The top, bottom and sides of the tail box I are closed, but the rear end of the tail box is open, except as hereinafter explained.

l1 represents a baflle which is mounted horizontally in the tail box l4 and held in place as by the end flanges l8 which fit against the interior surfaces of the tail box and are welded or otherwise secured thereto. The baflle I1 is provided with an arcuate surface facing the direction from which the stream of gases flows, and said baflle is preferably of cylindrical cross sectional shape.

The bafile I1 is placed adJacent but to the rear of the entrance opening l6 of the tail box and the baffle is of such diameter as to provide passages l9 above and below the baffle extending to the full width of the tail box and of sumcient vertical dimension to provide for the free passage of the stream of gases, which is divided into two diverging branches by the baflle. A horizontal rib Ha at the front of the baffle H is preferably provided to facilitate the division of the gas into two diverging streams.

The baflie is arcuate in its vertical crosssectional characteristic, having its concave surface faced toward the baflle l1.

The baflle 20 extends to the full width of the tail box I! and is secured at its ends thereto as by flanges 2|. The baflle 2D is stepped back from the baille l1 sufficiently to form between the two baflies the arcuate passage 22 of sufficient capaciltsy to receive the gases passing from the passages The baflle 20 spans the full height of the tail box I and is provided at its center with a horizontally elongated port 23 extending from side to side of the tail box, and through which the traveling gases pass rearwardly. The port 23 is of sufficient capacity to prevent restriction of the travel of the gases.

Next in the rear of the bafile 20 is the horizontal arcuate baflie 24 having its concavity toward the baflle 20 and spaced therefrom to provide the passage 25. Like the baflles I1 and 20, the baille 24 extends from side to side of the tail box I and is secured in position as by the end flanges 25a. The vertical extent of the bafiie 24 is such as to form between its horizontal edges and the top and bottom walls of the tail box the ports 26 for the escape rearwardly of the gases passing through the port 23 and passage 25. The top and bottom walls of the tail box preferably diverge somewhat adjacent its rear end, as indicated at 21 in Fig. 2, to provide ample capacity for the ports 26 to permit the free flow of the gases without restriction.

The ports 26 may be provided with screenin as shown at 21, to further reduce sound.

Again the rear baflle 24a may span the full height of the tail box, as illustrated in Fig. 8, and be provided with a plurality of perforations and ports, such as indicated at 24b, spaced over its area for the escape of the gases.

Insulation may be applied exteriorly' of the body 10 as indicated at 28, and also may be applied to the walls of the tail box as indicated at 29.

In Fig. 4 I indicate a convenient manner in which the mufller may be installed in the nacelle or covering 36 of a motor which is installed on the-wing 3| of an airplane. In this instance the rear end of the nacelle is sheared oil and the tail box mounted flush therewith. Thus the tail box is adjacent the upper surface of the wing where the drag or suction effect is very great.

In Figs. 5 and 6 I show the application of the principles of my invention to a motor mounted in the fuselage 82 of an airplane, the muffler being mounted in. the airfoil 33 built close to the wing 34. The exhaust of the motor is led to the body ID by means of the connecting pipe 35.

In Fig. '1 I show the miller applied to the back or rear end of an automombile where the suction effect is great and commensurate with speed, the pipe 36 leading from the exhaust manifold of the engine to the body I!) and the tail box I assembly which is mounted under the ferred embodiment of my invention but it should be obvious or understood that a very important part of my invention, namely, the tail box arrangement for suction effect upon the exhaust,

can be applied with some degree oi advantage to other or common types of muillers.

I claim:

1. An improved baflle structure for the exhaust gases of internal combustion engines, comprising walls deming a compartment having a long slotted opening in its front wall for the admission of the gases in the form of a wide shallow stream, baille means within the compartment to divide such stream into two diverging shallow sub-divisions flowing rearwardly, a second baiiie means in the rear of the first baiiie means to direct said sub-divisions toward each other, and an outlet for the escape of gases from the second balile means.

2. An improved baille structure for the exhaust gases of internal combustion engines, comprising walls defining a compartment having a longslotted opening in its irontwall for the admission of the gases in the form of a wide shallow stream, baille means within the compartment to divide such stream into two diverging shallow sub-divisions flowing rearwardly, a second baflie means in the rear of the first baille means to direct said sub-divisions toward each other, and a long slotted opening in the second baflle means for the escape of the gases past the latter.

3. An improved baille structure for the exhaust gases of internal combustion engines, comprising walls defining a compartment having a long slotted opening in its front wall for the admission of the gases in the form of a wide shallow stream. bafiie means within the compartment to divide such stream into two diverging shallow sub-divisions flowing rearwardly, a second bafile means in the rear of the first baiile means to direct said sub-divisions toward each other, a long slotted opening in the second baflle means for the escape of the gases past the latter, and a third baiile means to again divide the gases into two wide shallow streams as they emerge from the compartment.

4. An improved muiller structure for the waste gases of an internal combustion chamber comprising walls defining a pair of chambers, one of said chambers having an inlet opening at one end to be connected to the exhaust of the engine and a widely extended outlet opening at the opposite end for the escape of the gases and. the walls of the chamber relatively disposed to form the gases traveling from the inlet opening to the outlet opening in a thin widely extended stream, the second chamber having an inlet opening connected to the outlet opening of the first chamber and an outlet opening at the opposite end, and baille means in the second chamber interposed in the path of the stream of entering gases and dividing the same into two diverging thin streams which pass rearwardly toward the outlet opening of the second chamber.

5. An improved mufller structure for the waste gases of an internal combustion chamber comprising walls defining a pair of chambers, one of said chambers having an inlet opening at one end to be connected to the exhaust of the engine and a widely extended outlet opening at the opposite end for the escape of the gases and the walls or the chamber relatively disposed to form the gases traveling from the inlet openin to the outlet opening in a thin widely extended stream, the second chamber having an inlet opening connected to the outlet opening of the first chamber and an outlet opening at the opposite end, baflle means in the second chamber interposed in the path 01 the stream of entering gases and dividing the same into two diverging thin streams, and second bume means at the rear of the first baiile means intercepting said two streams and uniting them into one widely extending and thin stream as they pass toward the outlet of the second chamber.

6. An improved muiiler structure for the waste gases of an internal combustion chamber comprising walls defining a pair of chambers, one of said chambers having an inlet opening at one end to be connected to the exhaust of the engine and a widely extended outlet opening at the opposite end for the escape of the gases and the walls of the chamber relatively disposed to form the gases traveling from the inlet opening to the outlet opening in a thin widely extended stream, the second chamber having an inlet opening connected to the outlet opening of the first chamber and an outlet opening at the opposite end, baffle means in the second chamber interposed in the path of the stream of entering gases and dividing the same into two diverging thin streams which pass rearwardly toward the outlet opening of the second chamber, and means for again dividing the stream of gases as they escape from the second chamber.

7. An improved mufiier structure, for the waste gases of an internal combustion engine employed to drive an airplane or other vehicle, comprising walls defining a pair of chambers, one of said chambers serving to absorb the firing noises and having an inlet opening at one end to be connected to the exhaust of the engine and a widely extended slot-like outlet opening at the other end for the escape of the gases, and the walls of the chamber being relatively disposed to spread the gases traveling from the inlet opening to the outlet opening in a thin widely extended stream, the second chamber having an inlet opening corresponding in dimensions to the outlet opening of the first chamber and communicating therewith for the unobstructed emission of the stream of gases from the first chamber into the second chamber, and the second chamber having an out let opening into atmosphere in the area of low pressure resulting from the travel of the airplane to facilitate the suction withdrawal of the stream of gases from the first chamber.

8. The structure of claim 'I, wherein the crosssectional area of the second chamber adjacent its inlet opening is greater than the cross-sectional area of the first chamber adjacent its outlet opening.

9. An improved mumer structure for silencing the stream of exhaust gases of an internal combustion engine, comprising walls defining a chamber having a centrally disposed inlet in its front arranged to be connected to the exhaust of the engine, the side walls of the chamber diverging from said inlet opening and the top and bottom walls of the chamber converging from the front of the chamber toward the rear end of the chamber, and an extended slot-like outlet opening at the rear end of the chamber extending from one side wall to the other to spread the gases as they pass through the chamber into a thin widely extending stream.

10. The structure of claim 9 wherein the interior of the chamber adjacent its inlet opening is provided with a laterally extending baiile to facilitate the spreading of the gases toward the side walls of the chamber.

JOHN A. FISHER.

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