US 3710891 A
A muffler having a fluid inlet tube defining a Venturi throat and a perforate fluid outlet tube provided with an abutment at its inner end aligned with and spaced from the throat. In one form of the muffler, the inlet tube terminates at the throat and, in another form, the throat is connected by a perforate tube of relatively small diameter with said abutment. A sound absorber surrounds the inlet and outlet tubes.
Description (OCR text may contain errors)
United States Patent 1 Flugger 1541 AUTOMOTIVE MUFFLER  Inventor: Ray T. Flugger, PJO. Box 2098,
Petaluma, Calif. 94952  Filed: Aug. 25, 1971  App1.No.: 174,829
Related U.S. Application Data  Continuation-impart of Ser. No. 123,346, March l l,
152] US. Cl ..l81/50, 181/57  Int. Cl ..F01n 1/10  Field of Search ..181/49,50,55,57,58,59
 References Cited UNITED STATES PATENTS 1,820,972 9/1931 Haas ..l8I/49 2,150,811 3/1939 Starkweather et a1. ..181/55 2,523,260 9/1950 Campbell ..181/50 2,583,366 1/1952 Engels ....181/58 UX 1 1 Jan. 16,1973
FOREIGN PATENTS OR APPLICATIONS 988,370 4/1951 France ..l8l/59 1,343,005 10/1963 France ..l8l/55 1,347,893 11/1963 France ..181/49 199,437 2/1958 Austria ..181/49 Primary ExaminerRichard B. Wilkinson Assistant Examiner-John F. Gonzales Attorney-Townsend and Townsend  ABSTRACT A muffler having a fluid inlet tube defining a Venturi throat and a perforate fluid outlet tube provided with an abutment at its inner end aligned with and spaced from the throat. In one form of the muffler, the inlet tube terminates at the throat and, in another form, the throat is connected by a perforate tube of relatively small diameter with said abutment. A sound absorber surrounds the inlet and outlet tubes.
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mwmr W51 ATTORN EYS AUTOMOTIVE MUFFLER This is a continuation-in-part application of application Ser. No. 123,346, filed Mar. 11, 1971 and entitled Improved Muffler.
This invention relates to mufflers for reducing the noise caused by discharge of gas such as, for example, from the exhaust of an internal combustion engine. More particularly, the invention relates to an automotive muffler having a Venturi throat.
Automotive mufflers are of two general classifications depending upon the mode by which sound energy is removed from the gas stream passing therethrough. Those devices which attenuate by reflecting sound back to the source are called non-dissipative (reactive). Devices which absorb sound energy as the gas passes through them are called dissipative devices. Reactive mufflers are predominantly used in the exhaust of automobiles and other reciprocating engines and compressors. Among the methods for providing the necessary reflection are the change in direction caused by bends in the pipe confining the gas stream. Other configurations involve a straight-through gas path with side branch resonators to produce attenuation. Other known mufflers utilize combinations of resonators, filters and flow-reversing bends to provide adequate noise control. The muffler of the present invention utilizes characteristics of both the reactive and dissipative classification to accomplish the end result desired.
The muffler of the present invention utilizes an inlet tube having a Venturi portion defining a Venturi throat by means of which the pressure of combustion gases can be increased progressively as the gases enter the muffler. This increase in pressure thereby reduces any tendency for back pressures to develop in the exhaust manifold itself, thus assuring proper exhausting of the combustion gases without affecting the operation of the exhaust valves. After the gases pass the throat of the Venturi portion, they are caused to move laterally, thus conveying the sound energy associated with the gases laterally also. The soun d energy continues laterally and passes through a sound absorbing medium, is reflected by the internal surface of the outer casing of the muffler, then is returned back toward and through the sound absorbing medium. In this way, the sound energy is dissipated and, at the same time, the gases themselves pass outwardly of the muffler through a perforated exhaust or outlet tube which is generally of a relatively large cross section with respect to the throat of the Venturi.
One form of the muffler utilizes an inlet tube which terminates at the Venturi throat so that a space is formed between the throat and an abutment aligned with and spaced from the throat and secured to the inner end of the exhaust tube. Thus, the incoming gases, whose pressure is increased by the Venturi portion, can expand after passing through the throat and the abutment will prevent the gases from moving into the exhaust tube. Thus, the gases must move laterally and toward the sound absorbing medium, thereby directing the sound energy toward and into the medi- Another form of the muffler utilizes a perforate,
inner tube interconnecting the throat of the Venturi portion with the abutment on the inner end of the exhaust tube, the inner tube having a diameter of approximately the same size as the throat. The inner tube operates to cause a progressive decrease in the pressure of the gases while allowing the gases to move laterally and outwardly of the inner tube and toward the sound absorbing medium, thereby directing the sound energy toward and into the medium itself.
The sound absorbing medium may be of a material, such as fiberglass or the like, which presents a plurality of paths through which the sound energy must pass. Alternately, a portion of the combustion gases can be directed into the region immediately within the outer casing of the muffler to provide a buffer medium for absorbing the sound energy of the combustion gases as they move laterally after passing through the Venturi throat.
It is a principle object of this invention to provide a muffler of improved construction having components which are highly effic'ient in abstracting sound energy from gas flowing therethrough.
It is a further object of this invention to provide a muffler of relatively small size so that it will operate at a higher temperature where moisture condensation will be minimized.
It is a further object of this invention to provide a muffler that produces additional burning of the automotive exhaust gases in the exhaust flow with the attendent minimizing of air pollution.
It is still another object of this invention to reduce the noise level of vehicular equipment while increasing the efficiency of operation and longevity of such equipment.
It is still a further object to provide a muffler that minimizes back pressure upon the engine of the motor vehicle.
Other objects of this invention as well as features and advantages thereof will become more apparent from the following description and accompanying drawings, wherein:
FIG. 1 is a longitudinal cross-sectional view through one form of muffler embodying the invention;
FIG. 2 is a cross-section view taken along the line 2- 2 of FIG. 1;
FIG. 3 is a perspective view of the muffler of FIGS. 1 and 2 with a portion thereof cut away to reveal certain components thereof;
FIG. 4 is a view similar to FIG. 1 but showing a second form of the muffler;
FIG. 5 is a view similar to FIG. 4 but showing still I another form of the muffler; and
FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. 5
Referring now to the drawings wherein similar characters of reference represent corresponding parts in each of the several views, muffler 10 includes a generally cylindrical outer casing 12 necked down at opposite ends and having at one end an imperforate, cylindrical tube 14 coupled to an inlet tube 18 defining a Venturi portion with a throat. A perforate, cylindrical exhaust or outlet tube 16 is connected to and passes through the outer end of casing 12. Tube 16 is adapted for attachment to the tailpipe of an exhaust system of a motor vehicle. In fluid impervious engagement with a portion of exhaust tube 16 is an imperforate, cylindrical sleeve segment 20.
Exhaust tube 16 has a perforate, cylindrical inner portion 22 having holes 24 therethrough. Inner portion 22 extends substantially between the inlet and outlet opening of casing 12 although it is shown slightly spaced from the inlet opening in FIG. 1. Tube 22 has an inner diameter approximately one-half that of casing 12, although diameter ratios of about 1:15 to 1:4 are also satisfactory. Holes 24 communicate with a space 32 between the Venturi throat and an imperforate abutment 26 to provide a total cross-section .inwardly of the throat about 10 to 20 percent greater than the cross-section of the throat opening itself. It is also preferred that the capacity (total open area) of the perforations 24 of tube 22 opening out of chamber 36 in tube 22 be equal to or up to 20 percent greater than the inlet capacity (cross-section) of the inlet opening in inlet tube 18. I
Abutment 26 has a flange that is secured such as by welding to tube 22. Abutment 26 is slightly convex relative to the inwardly tapering tube 18, so as to enhance dispersion of the exhaust stream impinging thereon from tube 18. The interior of outer casing 12 is lined with a sound absorbing material, such as a layer 28 of fiber glass, maintained in a generally cylindrical configuration adjacent to casing 12 by wire mesh 30 or other similarly perforated supporting member. The foregoing elements of muffler l define entry space or chamber 32, intermediate chamber 34 and egress chamber 36, each of which comprises a sound attenuating zone.
In the operation of muffler l0, exhaust gases entering tube 14 are increased in velocity and working pressure as they pass through the restricted opening created by inwardly tapering tube 18. By forming tube 18 so that its respective larger and smaller ends have a diameter ratio of about 2 to l, the velocity of the exhaust gas can be increased by a factor in excess of 3 without significantly increasing the exhaust back pressure entering tube 14. The Venturi aspect of tube 18 provides for expansion of the gases into chamber 32 wherein a decrease in the intensity of sound wave energy, in a reversed megaphone effect, is obtained. As the exhaust gases emerge form the throat of the Venturi portion, i.e., the inner end of tube 18, they impinge upon convex abutment 26, whereby they are reflected rearwardly and move outwardly of chamber 32 through perforations 24 in the portion of tube 22 rearwardly of abutment 26. The acceleration ofthe gases as they emerge from tube 18 also provides for an increase in temperature at that point, thereby enhancing the reburning of unburned fuel that has accumulated in the exhaust flow.
' Diffusion of the exhaust gases from the primary chamber 32 into lowpressure chamber 34 allows the redistributed exhaust gases to expand both into expansion chamber 34 and into layer 28 of the sound absorbing material. The gas in chamber 34 is then forced to flow longitudinally of chamber 34 into and out of layer 28 from whence it "passes through holes 24 located beyond partition 26 and into redistribution chamber 36. Finally, the gases are caused to pass out through tube 16 and into the tailpipe for other outlet.
Muffler can be fabricated with an outer casing having a diameter as small as 3 inches for automobiles or even smaller for other types of reciprocating or air engines, thereby enabling the device to be fitted into positions underneath many automobiles not presently capable of utilizing conventional mufflers. Those skilled in this art will appreciate that the components of muffler 10 can be fabricated in a conventional manner such as by welding with standard materials such as steel, aluminum, and the like and alloys thereof.
A second embodiment of the muffler of this invention is shown in FIG. 4 and is broadly denoted by the numeral 50. Muffler 50 includes an outer, generally cylindrical casing 52, a tubular, wire mesh inner casing 54 spaced inwardly from casing 52. A tubular layer of a sound absorbing material, such as fiber glass, is disposed in the space 56 between casings 52 and 54. Casing 52 has a fluid entrance end and a fluid exit end.
A conical tube 62 is in fluid communication with and extends inwardly from the entrance end of casing-52. Tube 62 defines a V enturi section having a throat 63. A perforate, cylindrical, inner tube 58 is connected to and extends inwardly from the throat of tube 62. Tube 58 has across section which is substantially the same as that of throat 63 and has a number of spaced holes 60 therethrough. The inner end of tube 64 is connected to an imperforate or plate 68 secured to and closing the inner end of a perforate, cylindrical exhaust tube 64 extending through the exit end of casing 52. Tube 64 has holes 66 therethrough and has a cross-section greater than that of inner tube 58 but less than that of inner casing 54. A cylindrical inlet tube is coupled at one end thereof to the inlet end of conical tube 62 and is adapted to be secured at its opposite end to a source of fluid under pressure, such as the exhaust manifold of an internal combustion engine. 7
In use, tube 70 is, for instance, coupled to the exhaust manifold of an internal combustion engine and combustion gases enter muffler 10 through tube 62. The pressure of the incoming gases is increased and, at throat 63, the pressure and velocity of the gases are at maximum valves due to the Venturi effect. As the gases enter tube 58, they expand through holes 60 and move laterally and outwardly of tube 58 into the space surrounded byinner casing 54. The sound energy associated with these gases is in the form of pressure waves. These waves'also pass through holes 60 and travel toward and through inner casing 54 and into space 56. Some of the sound energy is dissipated in the material in space 56 and some of such energy passes through to the inner surface of outer casing 52 from which it is reflected and returned to themat'erial in space where it is further absorbed. The gases pass through the region surrounding tube 58, around wall 68 and into tube 64 through holes 66. Then the gases pass outwardly of muffler 10 through the exit end of tube The pressure of the gases in tube 58 progressively decreases since the gases can exit from this tube through holes 60; thus, there will be a minimum buildup of back pressure upstream of conical tube 62. Tube 58 is also able to direct the sound energy associated with the gases laterally along with the gases through holes 60; thus, the sound energy can enter the fiber glass material and thereby be effectively trapped and dissipated by the many paths it must travel therethrough. By the time the gases exit from the muffler, the sound energy will, for the most part, have been adequately dissipated to avoid noise pollution due to the exhausting of the gases.
A further embodiment of the muffler of this invention is broadly denoted by the numeral 80 (FIGS. 5 and 6) and includes an outer, cylindrical imperforate casing 82 having front and rear walls 83 and 85, respectively, each of these walls having an opening therethrough. An inner, perforate casing 84 is disposed within and spaced from outer casing 82. A conical inlet tube 86 having a throat 87 is coupled at its apex end to one end of a cylindrical, perforate inner tube 88 of relatively small cross section. The opposite end of inner tube 88 is coupled to an abutment wall or plate 90 secured to one end of a cylindrical, perforate tube 92 whose cross-section is greater than that of tube 88. Tube 92 extends through the opening of rear wall 85 and a cylindrical tube 98 is secured to and extends outwardly from the outer end of conical tube 86 in fluid communication with the opening of front wall 83.
Tube 86 has an annular row of holes 102 therein near the entrance end of tube 86. Holes 102 communicate with the space 104 formed between casings 82 and 84, tube 84 having holes 106 therethrough, tube 88 having holes 108, and tube 92 having holes 110.
in use, muffler 80 is coupled to the exhaust manifold of an internal combustion engine. A major portion of the combustion gases entering tube 86 from tube 98 will flow toward and into tube 88 while a minor portion of the gases will enter space 104 through holes 102 and serve as a cushioning material for gases entering this space from tube 88. The Venturi effect of tube 86 causes an increase in pressure of the gases at throat 86 at which the pressure is a maximum. The pressure progressively decreases in tube 88 and passes laterally outwardly thereof through holes 108. The sound energy also passes laterally with the gases through holes 108 and the energy in the form of pressure waves passes through holes 106 in inner casing 84 and into space 104 at which the energy is dissipated by the pressurized gases within space 104. The sound energy is reflected off the inner surface of outer casing 82 and back into cushioning engagement with the gases in the space 104. Thus, the energy is effectively dissipated in this way.
The gases flow from tube 88, around abutment plate 90, and then into tube 92 through openings 110. The gases then exit from tube 92 through the rear end thereof.
The embodiments of FIGS. 4 and 5 allow the respective exhaust tubes 64 and 92 to be uniform in cross section throughout their entire lengths and permit a Venturi ratio between the entrance and exit ends of respective conical tubes 58 and 88 to be as much as a 3 to 1. Moreover, inner 58 and 88 are of the same cross section as respective Venturi throats 63 and 87 to permit the build-up of greater pressures yet allow such pressures to progressively decrease as respective abutment walls 68 and 90 are approached.
1. A muffler comprising: an outer, imperforate casing having a fluid entrance end and a fluid exit end; an inner, perforate casing within and spaced from the outer casing, the spaced between said casings adapted to receive a sound absorbing medium therein; a fluid inlet tube coupled at the entrance end of the casings, said inlet tube having a Venturi section provided with a throat; an abutment within the inner casing in alignment with said throat; and a perforate exhaust tube extending from the abutment through the exit end of said outer casing.
2. A muffler as set forth in claim 1, wherein said Venturi section terminates at said throat to present an open space between the throat and the abutment and extending outwardly to said inner casing.
3. A muffler as set forth in claim 1, wherein is included a perforate, inner tube extending from said throat to the abutment said inner tube having a cross section less than that of said exhaust tube.
4. A muffler as set forth in claim 1, wherein is provided a layer of a sound absorbing material in said space between the casings.
5. A muffler as set forth in claim 1, wherein said inlet tube is in fluid communication with the space between the casings to allow at least a portion of the fluid entering the inlet tube to enter said space.
6. A muffler comprising: an outer casing having a fluid entrance end and a fluid exit end; an inner casing within and spaced from the outer casing; a tubular space; a layer of sound absorbing material in the space between said casings; a fluid inlet tube extending inwardly from and in fluid communication with the entrance end of the outer casing, said inlet tube adapted to be coupled with a source of fluid under pressure and having a Venturi section provided with a throat; and a perforate exhaust tube extending through the exit end of the outer casing, the inner end of the exhaust tube having an imperforate abutment thereon in alignment with and spaced from said throat, the space adjacent to the throat and spanning the distance between the latter and the abutment being of a cross section greater than said throat.
7. A muffler as set forth in claim 6, wherein said sound absorbing material is fiberglass.
8. A muffler as set forth in claim 6, wherein said exhaust tube has a cross section greater than that of said throat.
9. A muffler comprising: an outer casing having a fluid entrance end and a fluid exit end; an inner casing within and spaced from the outer casing and presenting therewith a sound absorbing space; a fluid inlet tube extending inwardly from and in fluid communication with the entrance end of the outer casing, said inlet tube having a Venturi section provided with a throat; a perforate exhaust tube extending through the exit end of the outer casing and into the inner casing, the exhaust tube having an imperforate abutment thereon at the inner end thereof, for closing; and a perforate, inner tube in fluid communication with the inlet tube at said throat and spanning the distance between the throat and said abutment, said inner tube having a cross section less than the cross section of the exhaust tube.
10. A muffler as set forth in claim 9, wherein said inlet tube is conical, said exhaust and inner tubes being cylindrical, said space having a layer of fiberglass material therein.
11. A muffler as set forth in claim 9 wherein said inlet tube has a number of holes therethrough adjacent to and inwardly of the entrance end of the outer casing, said holes being in fluid communication with said space to allow combustion gases to enter said space.
12. A muffler as set forth in claim 9, wherein said inner casing comprises a tubular length of wire mesh.
13. A muffler for silencing sound in a flowing gas stream, comprising: a tubular casing having ends defining substantially aligned inlet and outlet openings; a layer of sound I absorbing material concentrically disposed along the inner surface of said casing; a generally cylindrical perforated tube extending substantially from said inlet opening to said outlet opening and being spaced inwardly from said layer; means communicating with and extending inwardly from said inlet opening and having an open throat downstream of said inlet opening'for forming a fluid path which progressively decreases in cross-section as the throat is approached; means blocking direct gas flow from said inlet'opening to the outlet opening of said casing, whereby when gas is directed through said inlet opening, into said forming means, and against said blocking means, it will be accelerated, expanded and reversed in its direction of flow to pass outwardly of said tube through the perforations thereof, into and out of said layer and back into the tube through the perforations thereof located between said blocking means and said outlet opening, and finally out of the-casing through said outlet opening.
14. A muffler invaccordance with claim 13, wherein the ratio of the inner diameter of said perforated tube to said outer casing is about 1:15 to 1:4.
15. A muffler in accordance with claim 13, wherein the ratio of the inner diameter of the inlet and outlet dimensions of said forming meansis about 2 to l.
16. A muffler in accordance with claim 15, wherein said forming means is a tapered tube.
17. A muffler in accordance with claim 13, wherein the ratio of the length of the casing to its width is about 6 to l.
18. A muffler in accordance with claim 13, wherein the cross-section of said tube between said forming means and said blocking means is 10 to 20 percent greater than the cross-section of the throat of said forming means.