US3447630A - Exhaust gas muffler with multiple outlet tubes - Google Patents

Description

3,447,630 EXHAUST GAS MUFFLER WITH MULTIPLE OUTLET TUBES Filed Sept. 27, 1957 June 3, 1969 c. DAVIDSON FIG-5 INVENTOI? GEORGE L. DAVIDSON June 3, 1969 G. vmso 3,447,630

EXHAUST GAS MUFFLER WITH MULTIPLE OUTLET TUBES Filed Sept. 27, 1967 Sheet 2 of s l/VVE/VT'OI? GEORGE L. DAVIDSON G. L. DAVIDSON EXHAUST GAS MUFFLER W'I TH MULTIPLE OUTLET TUBES Filed S pt. 27. 1967 June 3, 1969 v Sheet FIG-.13

M/VEWTOR GEORGE L. DAVIDSON United States Patent US. Cl. 181-60 30 Claims ABSTRACT OF THE DISCLOSURE The engine exhaust gas mufiler includes a plenum, an inlet pipe receptive of engine exhaust gases, and a peculiar arrangement of small exhaust tubes through which gases from the plenum are finally released; the exhaust tubes having certain critical dimensions and arrangements relative to each other and to an inclined mounting plate associated with the plenum. The exhaust tubes are of two kinds, which working together, apparently create in the plenum a pulsing vortex of exhaust gas presumably moving at a sudden accelerated rate through the small exhaust tubes to produce a negative pressure within the plenum chamber for promptly and noiselessly dispatching the exhaust gases and any other media fed to the mufller. Several dimensional limits as disclosed, as well as critical relationships of constituent parts, are of primary importance to the invention. 1

The present invention relates to an engine exhaust gas mufl'ler, such as may be employed in controlling the exhaust gases of internal combustion engines of various kinds.

An object of the invention is to provide an improved mufller which minimizes objectionable noise and backpressure, and the emission of live sparks, from the exhaust gases of an internal combustion engine.

Another object of the invention is to provide an improved mufller of the character stated, which in terms of the desirable objectives realized thereby, is highly superior in performance to muffiers as heretofore constructed.

A further object of the invention is to provide in a mutiler, means of a simple and inexpensive nature for obtaining superior performance and a high degree of e'fficiency in the attainment of the objectives above stated, without sacrificing durability and longevity of service.

Another object of the invention is to provide an acoustical plenum-type muffler having the desirable characteristics and advantages above stated, which employs no movable or adjustable parts capable of.producing noise and rattle in the presense of vibration and eventual deterioration resulting from the corrosive effects of the gases controlled, which may include water of condensation rendered corrosive by the exhaust gases.

A further object is to provide an improved muffler which is effective for use in controlling the exhaust gases of all types of internal combustion engines, including marine engines which exhaust coolant as Well as exhaust gases through the mufiier, and diesel engines which exhaust scavenger additives with the products of combustion.

The foregoing and other objects are attained by the means described herein and illustrated upon the accompanying drawings, in which:

FIG. 1 is a side elevational view of the improved muffier, which includes a plenum chamber, an inlet pipe, and a plurality of outlet tubes.

FIG. 2 is a fragmentary enlarged cross-section transversely through the plenum chamber, and in the direction of the outlet tubes.

FIG. 3 is a view similar to FIG. 2, showing a modification.

FIG. 4 is an enlarged cross-section taken on line 4-4 of FIG. 1.

FIGS. 5 and 6 are side elevational views, partly broken away, and showing two forms of outlet tubes utilized in the muffler construction.

FIG. 7 is a fragmental side elevation showing a modification of FIG. 1.

FIG. 8 is a view similar to FIG. modification of FIG. 7.

FIG. 9 is a fragmental side elevation similar to FIG. 8, showing the plenum chamber equipped with a lesser number of outlet tubes.

FIG. 10 is an enlarged cross-section taken on line 10-10 of FIG. 9.

FIG. 11 is a view similar to FIG. 10, showing the plenum chamber equipped with a greater number of outlet tubes.

FIG. 12 is a transverse cross-section similar to FIG. 4, and showing the plenum chamber equipped with a single circular row of outlet tubes.

FIG. 13 is a side elevation, partly broken away, showing a muffler similar to that of FIG. 1 but modified espe cially for marine engine application.

FIG. 14 is a cross-sectional view on an enlarged scale, and taken on line 1414 of FIG. 13.

The acoustical muffler as illustrated by all the drawing views, may comprise an elongate hollow plenum chamber or body 20, preferably cylindrical of shape, and constructed preferably of a corrosion-resistant metal. The plenum chamber or body 20 may be provided with a front or inlet end closure plate or member 22, and a rear or outlet end closure plate or member 24, each of which may be peripherally attached to an open end of body 20 in any suitable manner, as by means of welding or crimping, to establish the volumetric capacity of the plenum chamber.

The front closure plate 22 may support an inlet pipe 26 through which exhaust gases from an engine may be introduced into the plenum chamber. The inlet pipe communicates with the plenum chamber through an opening in plate 22, as will be understood.

The rear closure plate 24 is located at the discharge end of the plenum chamber, and is provided with a plurality of openings in which may be fixedly supported a series of exhaust outlet tubes which project generally rearwardly from plate 24. The exhaust outlet tubes bear the identifying characters A and B, and the inside diameter of each thereof is considerably smaller than the inside diameter of inlet pipe 26. The tubes A and B are open at opposite ends thereof, said open ends being designated 28 and 30. The ends 28 may be referred to as the inner ends of the exhaust tubes, and the ends 30 may be considered the outer ends thereof, due to their inner and outer disposition with respect to the interior of the plenum chamber.

The principal difference between an exhaust tube A and an exhaust tube B, is that tube A is provided with a single side aperture 32 (FIG. 6), whereas a tube B (FIG. 5) is provided with a double side-aperture, or two sideapertures 34 and 36 whose centers are located substantially at opposite ends of a diameter of tube B, near the open end 28 thereof as will be explained later in greater detail. The side-apertures are in every instance disposed within the confines of the plenum chamber, and each exhaust tube is to be fixed upon plate 24 at a location between its side-aperture or apertures, and the outer end 30 of the tube. Fixation of the exhaust tubes to plate 24 may be effected in any suitable manner, and by means of welds, for example. The side-apertures are to be lightly chamfered exteriorly of the exhaust tubes.

The major axes of all the tubes A and B preferably 7, showing a slight are substantially parallel to one aonther. In some instances, the major axes of the tubes A and B are parallel to the major axis of the plenum chamber, as in FIGS. 1 and 13, whereas in other instances the major axis of the tubes A and B may be inclined to the major axis of the plenum chamber, as in FIGS. 7, 8 and 9. The tubes A and B may be of equal length.

Several critical considerations are to be observed in fabricating and assembling the constituent parts of the mufller in order to achieve the desired maximum reduction of noise level, back-pressure, and spark-arresting performance. It has been determined, for example, that inclination of the rear closure plate with respect to a plane normal to the plenum chamber axis, must approximate 12 (twelve) degrees, and may not depart from the twelve degree inclination more than 2 (two) degrees in either direction. Thus it will be understood that inclination of the rear closure plate with respect to a plane normal to the plenum chamber axis, must be between and 14 degrees. The rear closure plate is to be substantially flat, or planar, where exposed to the interior of the plenum chamber.

Another critical consideration resides in the selection of tubes such as A and B, and their relationship to the inner surfaces of rear closure plate 24 and the inner wall of the plenum chamber. Considering FIGS. 1, 3 and 4, and particularly FIG. 4, it will be noted that the rear closure plate or member 24 supports an outer circular row of tubes A and B, and an inner circular row of such tubes. The tubes A and B of the outer circular row, of which there are fifteen shown by Way of example (but not of necessity), are arranged so that in the main, tubes A are alternated with tube B in the circular row, but the number of tubes B (the double-apertured tubes), exceeds the number of signal-apertured tubes A in the same row. In the FIG. 4 example, the number of B-tubes exceeds by one, the number of A-tubes employed; however, it must be understood that the excess of B-tubes must be more than one with a maximum of two.

The inner circular row of tubes A and B in the FIG. 4 example, comprises eight tubes mainly alternated, though not strictly so, since the number of B-tubes exceeds by two the number of A-tubes employed. Here, as in the outer circular row of tubes, the double-apertured tubes B must exceed in number the number of singleapertured tubes A if the best mufiie performance is to be obtained.

It is imperative that the tubes of the outermost circular row be spaced from one another, and from the inner cylindrical surface of the plenum chamber 20, a distance not less than one-fourth inch, this being a prerequisite whether or not the structure includes an inner circular row of tubes, which may be omitted as in FIGS. 10, 11 and 12. Regardless of the number of tubes employed in the outer circular row, the tubes of the row require a spacing of not less than one-fourth inch from the closest point on the inner surface of the plenum chamber wall.

With reference again to FIGS. 3 and 4, attention is directed to the illustrated angular disposition of the side apertures 32, 34 and 36, with respect to radii of the plenum chamber passing through each exhaust tube axis. Considering tube A of FIG. 3, it is seen that the centerline of side aperture 32 has a required angularity of to 30, to a chord C which bisects tube A and meets radius R at right angles on the tube axis. The 20 to 30 angle mentioned is denoted L in FIG. 3, and indicates a clockwise rotation of tube aperture 32 from the line of chord C, so that the aperture center-line meets the inner cylindrical wall of plenum chamber 20 at an acute angle.

Tube B of FIG. 3 likewise is turned in clock-wise direction, to dispose the center-line of aperture 34 at an angle L to chord C, said angle L being of a value between 20 and 30. Chord C bisects tube B and meets radius R at right angles on the axis of tube B. The center-line of sideaperture 34 of tube B meets the inner cylindrical wall of chamber 20 at an acute angle which corresponds to the angle at which said wall is intersected by the side-aperture 32. Thus, the center-lines of side- apertures 32 and 34 of tubes A and B, project obliquely outwardly in a generally common direction within the plenum chamber. The side-aperture 36 of tube B, however, faces in an opposite direction, and is farther distant from the chamber wall than is aperture 34.

All of the exhaust tubes in the outer circular row of FIG. 4 are seen to bear the above-described orientation to the plenum chamber cylindrical wall, and to one another, as an important factor in the construction of the improved mufiler. The mufller may be constructed either with or without the inner circular row of exhaust tubes, and if the inner row is incorporated in the construction, the'sideaapertures of the inner row of tubes are to be angled according to the teaching recited in the next preceding paragraph. That is, each one of the tubes of the inner row will have its center located upon a radius of the plenum chamber, and will be rotated in clockwise direction to dispose a side-aperture center-line at an angle of 20 to 30 to a chord which bisects the tube and meets the chamber radius at right angles on the tube axis. Thus, corresponding side-apertures of the tubes A and B constituting the inner circular row of tubes, will have their center-lines projected in the same general direction as those of the outermost circular row of tubes.

The aforesaid angular disposition of the tube sideapertures, in combination with the unequal porting resulting from utilizing a greater number of B-type tubes than A-type tubes in the muffler construction, is believed to create a highly beneficial vortex pattern of gases within the plenum chamber as the gases pass therethrough. Also, for best performance, it has been determined that exhaust tubes A and B must project into the plenum chamber at least one inch, and the diameter of the side apertures 32, 34, 36, must closely approximate one-half the inside diameter of the exhaust tube. The inside diameter of tubes A and B must not exceed .750 inch; if larger tubes are used, a substantial loss of control of the exhaust gases will ensue. An exhaust tube inside diameter ranging between .750 and .350 inch, is considered preferable, and as above stated, the diameter of the side-aperture or apertures shall closely approximate one-half the inside diameter of the exhaust tube in all cases.

The length of each exhaust tube may approximate 7 or 8 inches, in mufilers designed for use with engines of the sizes ordinarily applied to passenger automobiles. A 20 percent increase or decrease in the length specified may be expected to produce no unfavorable results.

In the description of FIGS. 1, 3 and 4, reference was made to an assembly procedure wherein all of the exhaust tubes A and B were fixed after being rotated in a clockwise direction, by an amount ranging between 20 and 30 from a starting position at which the center-lines of the side-apertures coincided with a chord such as C or C. An alternative assembly, equally effective, is to rotate the exhaust tubes counter-clockwise, by the same amount. The effect of the alternative procedure is merely to reverse the direction of the vortex pattern of gases within the plenum chamber as the gases pass therethrough. Such alternative procedure is suggested by FIGS. 2, 10, 11, 12 and 14 of the drawings.

In FIGS. 2, 10, 11, 12 and 14, and with particular reference to the enlarged view of FIG. 2, it is apparent that tube A has been rotated counter-clockwise from a starting position at which the center-line 40 of side-aperture 32 coincided with chord C. The resultant angle L may range between 20 and 30. Similarly, it is apparent that tube B has been rotated counter-clockwise to form an angle L between the chord C and the center-line 42 of side-aperture 34, the angle L measuring not more than 30 nor less than 20. The tubes A and B are to be spaced from one another, and from the inside surface of the plenum chamber wall, 'a distance not less than one-fourth inch. The chords C and C pass, respectively, through the axes of tubes A and B, and meet the radii R and R at right angles. The lines 37 and 39 represent tangents which are parallel to chords C and C.

The above-described disposition of the tube side-apertures is tobe observed, whether the mufller construction embodies a single circular row of tubes as in FIGS. 2, 10, 11, 12 and 14, or a double circular row of tubes as in FIG. 4. It is important that all tubes of a given muffler be rotated in one direction only, either clockwise, or counterclockwise; and the number of B-tubes employed must exceed the number of A-tubes as previously explained.

The total number of exhaust tubes incorporated in a muffler depends upon the engine displacement, and the amount of exhaust gas back-pressure at which the engine is designed to operate. In general, the total cross-sectional area of all the exhaust tubes, measured interiorly of the tubes, will be somewhat less than the input area of the engines exhaust manifold. The number of exhaust tubes employed, therefore, will be dependent upon the engine characteristics.

The inside diameter of the plenum chamber has been found to bear a peculiar relationship to the length of the plenum chamber. The optimum for masking sound on all db scales of A, B, C, appears always to fall in the 2.5 :1 area. It is therefore desirable that the length of the plenum chamber be 2.5 times the diameter; however, if a deeper pitch of sound is desired, the ratio of 2.5:1 may be altered in a direction approaching unity, or 1:1. Altering the ratio in the opposite direction will produce a higher pitch of sound.

The mufiler construction of FIG. 8 differs from that of FIG. 1, in that the exhaust tubes of FIG. 8 are fixed to rear plate 24 at right angles to the plane of said plate,

Whereas in FIG. 1 the exhaust tubes project angularly from the plane of the rear plate. Otherwise stated, the exhaust tubes of FIG. 8 are inclined to the major axis of the plenum chamber, whereas in FIG. 1 the exhaust tubes have their major axes disposed in substantial parallelism with the major axis of the plenum chamber. In either case, however, the inclination of the end plate to a perpendicular line on the plenum chamber axis, is to be 12 degrees, plus or minus 2 degrees, as previously pointed out herein.

In the FIG. 7 modification, the inclined rear end plate 24 may be considered a baffle plate separate and apart from a true end closure plate 24' through which the exhaust tubes pass also. The exhaust tubes may be welded or otherwise fixed to closure plate 24, which in turn is welded or otherwise fixed to the plenum. end. If desired, the tubes may pass through individual tube-supporting openings in plate 24, without being welded thereto. However, plate 24 is to be appropriately supported within the plenum chamber at the aforesaid inclination of 12 degrees, plus or minus 2 degrees, with reference to a perpendicular line intersecting the major axis of the plenum chamber. The inner ends 28 of the exhaust tubes are to extend beyond plate or baflie 24 and into the plenum chamber a distance of at least one inch. Thus, the sideapertures of all the exhaust tubes will be located within the main chamber of the plenum.

As in all other forms of the muflier disclosed, the modifications of FIGS. 7 and 8 require a greater number of B-type tubes than A-type tubes, and the side-apertures thereof must be angles in accordance with the teaching of either FIG. 2 or FIG. 3, as previously explained in detail herein.

The side-apertures of all tubes A and B are to be of a diameter closely approximating one-half the inside diameter of a tube, and the center-line of each side-aperture is to be distant from the inner end 28 of the tube by the amount of one-half inch. Projection of the inner ends 28 of the tubes A and B into the plenum chamber, may be one inch or slightly more, but not less than one inch.

As was previously pointed out herein, any of the mufiler forms herein disclosed is suitable for marine engine use, as well as for use with engines that do not exhaust water or coolant through the exhaust system thereof. FIGS. 13 and 14, however, illustrate a mufiler construction which is especially adapted for marine engine use. It employs the same system of A and B type exhaust tubes, constructed and arranged in accordance with the teaching hereinbefore disclosed, but with the B-type tubes in much greater predominance over the A-type tubes.

In accordance with FIGS. 13 and 14, there is provided an elongate duct or channel member 46 of rigid material, such as metal for example, having its legs 48 and 50 welded or otherwise fixed to the inside of the plenum, with the channel member inverted to provide a passageway 52. The channel member may extend from the approximate location of front closure plate 22, rearwardly to and through rear closure plate 24, with its open bottom. exposed beyond the plenum at 54 from rear plate 24 to the outer terminal end '56. The channel member may be straight as shown, and disposed in substantial parallelism with the major axis of the plenum chamber.

The upright legs 48 and 50 may be apertured at several locations within the confines of the plenum chamber, to provide a multiplicity of ports 58 into which coolant water from the engine jacket may enter, to be discharged at the open bottom '54 and the open end 56 of the channel member. When the marine engine is in operation, the coolant water and exhaust gases will enter the plenum chamber through inlet pipe 26, and the major portion of the water, if not all of it, will gravitate into the duct or passageway 52 for expulsion from the muffler at 54 and 56. The gaseous portion of the exhaust from the engine will enter the exhaust tubes A and B, possibly along with some of the water at times, for expulsion through the open rear ends 30 of the tubes.

The gaseous exhaust in passing through the plenum chamber and tubes A and B, will by the action of said tubes become a pulsing vortex of gas, apparently moving at a sudden accelerated rate through the several exhaust tubes. This accelerated rate of gas movement, so far as can be determined, apparently functions somewhat as a negative pressure generator within the plenum chamber and has shown unusual capability to assist in discharging the water portion of the engine exhaust, as well as the gaseous portion thereof. The same reaction appears to occur in the muffiing of diesel engine exhaust gas, wherein may be present in varying degrees, scavenger or blower air additives which must be discharged through the mufiier with dispatch in the interests of engine efi'iciency and fuel conservation. The same reaction appears to occur in the mufliing of gasoline-fueled engine exhaust gases, with great efliciency resulting along with quiet operation.

In cases of diesel as well as marine engine application, optimum results have been obtained when the plenum chamber capacity is equal to, or within plus or minus 5 percent of the engine displacement.

In conclusion, it is necessary to consider that no definitely reliable theoretical basis has evolved from the many tests and experiments that have been conducted in bringing the present invention to fruition. It is known, however, that certain of the arrangements and critical dimensions disclosed herein, and the limits within which such dimensions may be varied, must be observed if the device of the invention is to perform the high degree of effectiveness of which the device is capable.

It is to be understood, however, that various modifications and changes of a non-critical nature may be made in the device without departing from the spirit of the invention.

What is claimed is:

1. An exhaust mufiler for internal combustion engines, comprising:

(a) a substantially cylindrical plenum chamber including an outer wall, an inlet end and an outlet end wherein the outlet end is inclined 10 to 14 from a plane normal to the longitudinal axis of the chamber;

(b) a plurality of elongate cylindrical exhaust tubes projecting through said outlet end, said tubes each having an inner open end and an outer open end, with an inner end of each exhaust tube extending at least one inch into the plenum chamber;

(c) certain of said exhaust tubes having a single transverse side-aperture through that portion of the tube wall disposed inside the plenum chamber;

(d) other of said exhaust tubes having a pair of transverse diametrically aligned side-apertures through that portion of the tube wall disposed in the plenum chamber, and

(e) wherein the number of exhaust tubes having a pair of side-apertures exceeds the number of exhaust tubes having a single side-aperture.

2. An exhaust mufiler as described in claim 1, wherein the axes of the side-apertures in the exhaust tube walls pass through the major axis of each respective tube, with the axes of said apertures of all of the tubes being inclined to 30 either counterclockwise or clockwise relative to a reference line passing through the center of each tube and standing perpendicularly upon a plenum radius passing through the center of each respective tube.

3. An exhaust mufiler as described in claim 2, wherein the side-aperture of each exhaust tube having a single aperture faces toward a point on the wall of the plenum, which point is located between adjacent exhaust tubes.

4. An exhaust muffler as described in claim 3, wherein the diameter of the respective side-apertures through the Walls of the exhaust tubes are one-half the inside diameter of said tubes.

5. An exhaust mufiier as described in claim 4, wherein the center-line of said side-apertures in the walls of the exhaust tubes are one-half inch from the inner open ends thereof.

6. An exhaust muffler as described in claim 1, wherein the ratio of the length to internal diameter of the plenum chamber is 2 /2 to 1.

7. An exhaust muffier as described in claim 1, wherein the combined area of the exhaust tubes is less than the inlet area to the plenum chamber.

8. An exhaustrnufiier as described in claim 1, wherein there are two less exhaust tubes having a single aperture than exhaust tubes having a pair of apertures.

9. An exhaust muffler as described in claim 1 wherein the outer wall of an exhaust tube is at least A inch from the inner surface of the outer wall of the plenum chamber.

10. An exhaust muffler as described by claim 1, wherein the exhaust tubes are substantially parallel to one another, and are arranged upon the plenum chamber outlet end in circular row formation, characterized by substantial alternation of the exhaust tubes having a Single side-aperture, with those exhaust tubes having a pair of side-apertures.

11. An exhaust muffler as described by claim 10, wherein the side-apertures of all the exhaust tubes are of a diameter approximating one-half the inside diameter of the tubes in which the apertures are formed, and wherein the axes of the side-apertures in the exhaust tube walls pass through the major axis of each respective tube, with the axes of said apertures of all the tubes being inclined 20 to 30 either clockwise or counter-clockwise relative to a reference line passing through the axis of each tube and standing perpendicularly upon a plenum chamber radius which passes through the center-line of each respective tube.

12. An exhaust mufller as described by claim 11, wherein the axes of all the side-apertures are spaced one-half inch from the inner ends of their respective exhaust tubes, and the diameter of any such side-aperture does not exceed .750 inch.

13. An exhaust muffler as described by claim 12, wherein the spacing between adjacent exhaust tubes, and the spacing of each exhaust tube from the plenum chamber wall, is no less than one-fourth inch.

14. An exhaust mufiler as described by claim 13, wherein the open inner ends of the exhaust tubes project into the plenum chamber at least one inch.

15. An exhaust mufiler as described by claim 11, wherein the inner ends of the exhaust tubes project into the plenum chamber at least one inch.

16. An exhaust muffier as described by claim 14, where in the ratio of length to internal diameter of the plenum chamber approximates 2 /2 :1.

17. An exhaust mufller as described by claim 1, wherein the side-apertures of the exhaust tubes are chamfered at the exterior surface of said tubes.

18. An exhaust mufller as described by claim 2, wherein the combination includes: an inverted elongate channel member having spaced substantially parallel legs edgewise abutting the inner surface of the plenum wall to form therewith an elongate passageway, said channel member at one end extending exteriorly of the plenum through the outlet end of the latter to convey exhaust from the chamber of the plenum, said channel member being apertured interiorly of the plenum chamber to provide for fluid communication between the plenum chamber and the channel member passageway.

19. An exhaust muffler as described by claim 18, wherein the apertures of the channel member are formed in the legs thereof, and the exteriorly extended end of the channel member passageway is open for unrestricted discharge of exhaust leaving the plenum chamber.

20. An exhaust mufiler for internal combustion engines, comprising in combination:

(a) an elongate plenum including an outer wall, an

apertured inlet end wall, and a multiple-apertured outlet end well, said walls defining a plenum chamber for exhaust media;

(b) said outlet end wall being substantially planar, and inclined 10 to 14 from a plane normal to the longitudinal axis of the plenum chamber;

(c) a plurality of elongate cylindrical open-end exhaust tubes projecting each though an aperture of the outlet end wall, with one end of each tube exposed exteriorly of the plenum chamber, and the remaining end of each tube disposed within said chamber;

(d) and means including said exhaust tubes, for creating within the plenum chamber a pulsing vortex of exhaust media introduced through the aperture of the plenum inlet wall and leaving the plenum chamber through said exhaust tubes.

'21. An exhaust muffler as described by claim 20, Wherein the means last mentioned includes tnansverse sideapertures formed in the exhaust tubes near those ends of the tubes which are disposed within the plenum chamber; some of said side apertures being directed toward the inner surface of the plenum outer wall at an angle of between 20 and 30 to a perpendicular line which intersects a second line projected outwardly from the center of the plenum chamber and through the major axis of a tube, said angles having their apieces projected toward the included angle located at the next adjacent tube.

22. An exhaust muffler as described by claim 21, wherein the exhaust tubes are arranged in a circular row upon the outlet end wall of the plenum, and wherein more than half of said tubes are provided each with a second side-aperture diametrically aligned with the firstmentioned aperture, most of the tubes which have but one aperture being alternated with tubes having two apertures, in forming the circular row of tubes.

23. An exhaust mufller as described by claim 22, wherein the exhaust tubes are of equal inside diameters, and the side-apertures thereof are of a diameter equal to one-half the inside diameter of a tube; said side-apertures being located with their centers spaced one-half inch from the interior end of a tube, and said interior end being projected into the plenum chamber at least one inch.

24. An exhaust mufiler as described by claim 23, wherein the exhaust tubes of the circular row of tubes are spaced from one another, and from the inner surface of the plenum outer wall, a distance of at least one-fourth inch; and wherein the side-apertures of the exhaust tubes are chamfered at the exterior surface of said tubes.

25. An exhaust mufiler as described by claim 24, wherein the ratio of length to internal diameter of the plenum chamber approximates 2 /2 :1.

26. An exhaust muffler as described by claim 24, wherein the total inside transverse area of all the exhaust tubes is less than the area of the plenum inlet wall aperture.

27. An exhaust muflier as described by claim 24, wherein the combination includes: an inverted elongate channel member having spaced substantially parallel legs edgewise abutting the inner surface of the plenum outer wall to form therewith an elongate passageway, said channel member having one end extended exteriorly of the plenum through the outlet end wall thereof, to convey exhaust media from the chamber of the plenum, said channel member being apertured within the plenum chamber to provide for fluid lcommunication between the plenum chamber and said passageway.

28. The exhaust mufiler as described by claim 27, wherein the apertures of the channel member are formed in the legs thereof.

29. The exhaust mufiier as described by claim 28, wherein the exteriorly extended end of the channel member passageway is open for unrestricted discharge of exhaust media leaving the plenum chamber.

30. The exhaust mufiler as described by claim 29, wherein the combined transverse area of the channel member and all the exhaust tubes, is less than the area of the plenum inlet wall aperture.

References Cited UNITED STATES PATENTS 1,903,803 4/1933 Barker. 2,996,139 8/1961 Patterson 18l-60 XR FOREIGN PATENTS 258 1913 Great Britain. 577,420 5/ 1958 Italy.

ROBERT S. WARD, JR., Primary Examiner.

US. Cl. X.R. 181-72

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