US2958389A - Silencer or muffler - Google Patents

Description

NOV. I, 1960 F, E, DEREMER 2,958,389

SILENCER OR MUFFLER Filed April 8, 1957 2 Sheets-Sheet 1 INVENTUR FL DVD E. DBREMER TTY.

Nov. 1, 1960 F. E. DEREMER SILENCER 0R MUFFLER 2 Sheets-Sheet 2 JNVENTDR FL am EUMEMLR.

y x I v I I l I i l i v 4 l hilt I I l i i l Filed April 8, 1957 AIT TY.

United States Patent O SILENCER R MUFFLER Filed Apr. 8, 1957, Ser. No. 651,249 4 Claims. (Cl. 181-54) assignor to Oldberg Grand Haven, Mich., a cor- This invention relates to sound attenuating or sound damping devices and more especially to sound attenuating devices, mufers or silencers for use with the exhaust gas system or stream of internal combustion engines for damping, destroying or attenuating sound waves entrained in the exhaust gas stream.

Heretofore it has been conventional practice in the construction of mufflers for use with exhaust gas streams of internal combustion engines to provide the interior of the muiiler with gas passage tubes in communication with high-frequency resonating chambers for damping or attenuating high frequency sound waves and to include in the muffler, one or more resonators or resonating chambers of the so-called dead types `for damping or attenuating low frequency sound waves principally through sound absorption. Such low frequency resonator chambers are of the Helmholtz type which, in effect, provide sound traps in which the low frequency sound waves are substantially dissipated by absorption. The so-oalled dead chambers for attenuating low frequency sound Waves are not in the path of the exhaust gas stream and the exhaust gases do not circulate therethrough although they are disposed whereby low frequency waves enter the chamber and are dissipated therein.

While sound attenuating arrangements or mutliers of this character have been extensively used, several disadvantages are inherent in such arrangements. For example, the length of the attenuating system is relied upon to attenuate the low frequency Waves and the presence of one or more dead chambers necessarily limits or decreases the length of the sound attenuating system and hence the range of low frequency waves that may be successfully attenuated is reduced when the effective length of the attenuating system is shortened.

Another disadvantage of a dead sound trap chamber arrangement resides in substantial temperature differentials lengthwise of the muffler construction. The exhaust gases from an internal combustion engine are very hot, usually in excess of 1200 F., and this heat is readily transmitted from the exhaust gases to the walls of the gas passage tubes through which the gases flow and such metal walls become highly heated while the walls delining the dead chambers or Helmholtz type resonators remain relatively cool as the gases do not circulate therethrough. These extreme dilferentials in temperature in various regions or Zones of a sound attenuating muler result in the accumulation of moisture condensation in regions of reduced temperature in the muffler and, as the components of a mufer construction are usually fabricated of ferrous metals, oxidation and rusting ensues and in a comparatively short period of time the oxidation penetrates through and disintegrates the shell wall rendering the muler ineffective for sound attenuating purposes.

The present invention embraces the provision of a mufer construction or sound attenuating means usable with moving gas streams wherein the gases of the stream are circulated throughout substantially all of the interior regions of the muier construction and which embodies rice means for attenuating low frequency sound waves without the use of dead chambers substantially isolated from the gas stream.

The invention has for an object the provision of a sound attenuating device or muler construction wherein the sound attenuating system includes gas passage means and sound wave conveying means so arranged that sound Waves are effectively attenuated, nullied or destroyed by being reected or reverberated between the end heads of the muler shell construction or between the end heads and baffle arrangements whereby substantially uniform temperatures are maintained throughout the entire interior region of the mutlier.

Another object of the invention is the provision of gas passage means .arranged in a muler construction having end heads or closures and partitions or transverse Walls so arranged in respect of the gas passage means that sound waves of low frequencies are caused to reverberate or bounce from one end head to the other or to a baiile whereby the low frequency sound waves are attenuated by wave interference with a minimum of attenuation by absorption.

Another object of the invention resides in the provision of a muler construction embodying gas passage and sound conveying means of a substantial length, the interior components of the muier construction being arranged whereby an increased range of sound waves or frequencies may be attenuated without enlarging the muffler construction.

Still another object of the invention is the provision of `a multi-pass muiiler in which the gas passage and baffle or partition means are arranged whereby substantially ,all interior portions or regions of the mufller construction are directly subjected to heat from the exhaust gas stream at sufficient temperatures to prevent or minimize the formation of moisture condensation within the muffler construction.

Further objects and advantages are within the scope of this invention such as relate to the arrangement, operation and function of the related elements of the structure, to various details of construction and to combinations of parts, elements per se, and to economies of manufacture and numerous other features as will be apparent from a consideration of the specification and drawing of a form of the invention, which may be preferred, in which:

Figure l is a longitudinal sectional View of a muler construction embodying a form of the invention, the section being taken substantially on the line 1-1 of Figure 3;

Figure 2 is an end view of the construction shown in Figure 1;

Figure 3 is a transverse sectional view taken substantially on the line 3-3 of Figure l;

Figure 4 is a transverse sectional view taken substantially on the line 4 4 of Figure l;

Figure 5 is an isometric view cf a baille means or intermediate shell forming an element of the muiiler constmction shown in Figure l;

Figure 6 is a longitudinal sectional View of a mufller construction embodying another form of the invention;

Figure 7 `is a transverse sectional view taken substantially on the line 7-7 of Figure 6;

Figure 8 is a longitudinal sectional View of a muler construction illustrating `another form of the invention, and

Figure 9 is a transverse sectional view taken substantially on the line 9 9` of Figure 8.

While the preferred arrangements of the invention as illustrated in the drawings are embodied in mutller constructions of the type or character especially adapted for attenuating or damping sound waves entrained in exhaust gas streams from an internal combustion engine, it is o to be understood that lthe principles of the invention may be utilized or embodied in other types of sound attenuator or silencer for attenuating sound waves of a moving gas stream.

The principles of the invention are embodied in a muier construction of `a type suitable for use with the exhaust gas system of an internal combustion engine, the construction being inclusive ofV a casing, housing or shell of tubular configuration having closed ends and provided with gas passage means `and sound attenuating components, passages or resonating chambers within the muffler shell or casing or attenuating or alleviating sound waves and wherein the exhaust gases iow in paths or are distributed or dispersed throughout the interior of the mufer lshell or casing wherein sot-called dead chambers are eliminated with a consequent improvement in the distribution of heat throughout the various regio-ns of the mufiier and an attendant improvement in sound attenuating or damping characteristics.

Referring to the drawings in detail, and rst with particular reference to the arrangement shown in Figures 1 through 5, the shell casing or housing construction of the muffler is preferably of the double Wall type comprising an inner wall or layer 10 and an outer wall or layer 12, said shell walls being formed of sheet metal and preferably each as an independent sheet. The shell Icomponents or walls 1t) and 12 are preferably spaced in the manner shown in Figure 3 and the meeting or edge regions of the metal layers or sheets are folded or bent upon themselves to form an interlock as at 15, aud the folded or bent portions of the metal sheets being crimped to form a fluid tight seam or juncture extending lengthwise of the mutiier construction.

While the arrangement of the invention may be ernbodied in a muier construction embodying a single walled casing or shell, it is found that a double walled arrangement of the character disclosed herein improves the reduction or elimination of so-called shell noise. As particularly shown in Figures 2, 3 and 4, the cross sectional configuration or shape of the muffler construetion or shell is generally oval or ellipsoidal, but it is to be understood that the shell or casing configuration may be circular or polygonal in cross section if desired.

While the shell or casing construction illustrated herein is formed of two sheets of metal, the shell may be fabricated of a single metal sheet rolled upon itself with overlapping end regio-ns of the sheet welded to provide a seam and a double or multiple wall construction.

In the illustrated embodiment of Figures l through 5 the outer metal layer, wall or sheet 12 is -formed with' peripherally spaced indentations, depressions or recesses 17 which provide inwardly extending ridges o-r lands extending longitudinally of the muier shell or casing and form longitudinally arranged chambers or confined zones 19.

YF[he shell or casing construction -is provided with end walls, heads or closures 22 and 24, each of the heads or closures being formed with a peripheral ilange arrangement 26 of generally U-shaped cross section torming a peripheral recess or groove which receives the mating or engaging end regions of the shell walls iti and 12 in the manner shown in Figure 1.

It should be noted that the end regions of the walls and 12 are brought into contiguous engagement and are embraced in the recess provided by the `Flange construction 26, the latter being crimped so as to form a fluid-tight juncture between the ends of the shell construction and the end heads or end walls 22 and 24. The chambers or confined zones 1.9, provided between adjacent ridges formed by the depressed portions or recesses 17 of the outer wall or layer, provide individual chambers extending lengthwise of the shell and substantially isolated one from another whereby there is little or nopcirculation of air between the shell walls peripherally of the shell construction.

The ylongitudinally extending chambers 19 are completely isolated from the interior region defined by the inner wall of the shell construction, the coniined zones or chambers 19 forming individual air spaces or air cushions which assist in reducing shell noise or vibration which may be set up or established by flow of exhaust gases through the muiiier shell.

In certain installations of muffler construction, it may be desirable to provide a non-metallic heat insulating medium or layer between the shell Walls in order to further reduce sound transmission as Well as to minimize radiation of heat from the muffler shell. As shown in Figure 3, a sheet orlayer 29 of heat resistant material such as asbestos or mineral fibers such as glass fibers may be disposed so as to extend throughout subtantially Vthe entire perimeter of the `muffler s-hell as shown in Figure 3 or may extend over a portion of the region between the shell walls if desired.

The end wall or head 22 formed of sheet metal is provided with a circular ilange 32 defining an opening adapted to accommodate a coupling sleeve or tubular tting 34 extending therethrough in the manner shown in Figure l. The portion of the fitting exterior of the mufer end head is formed with a slot 35 and a clamping v means (not shown) is applied to this region of the tting 34 to draw the tting into snug engagement with an exhaust tube or pipe from an engine or other tube adapted to conduct a moving gas stream into the muier.

In the arrangement illustrated in Figure l the iitting 34 serves or functions as a portion of an inlet gas passage means fo-r conveying exhaust gases into the interior of the muflier construction. Spaced from the end head 22 is a transversely extending partition, wall or header 38 and spaced from the header 38 is a second header, wall or partition 40 of substantially the same conguration as the partition 38.

Disposed within the muflier shell construction are additional transversely extending headers or partitions 42 and 44 disposed in spaced relation as illustrated in Figure 1. Telescoped with a region of the tubular inlet fitting 34 is an inlet tube 46 forming a gas passage means within the mufer shell, the partitions 38, 40` and 42 being formed with flanged openings to snugly receive and accommodate the gas passage tube 46 as shown in Figure l. The innermost end of the tube 46 is -in communication with a transversely arranged gas passage or charnber 48 defined or formed by the partitions or headers 42 and 44.

The headers or Walls 38, 40 and 42 are formed with anged openings to snugly receive and accommodate a second or intermediate gas passage tube 50 which forms a gas passage or gas conveying means through which the gases are retroverted toward the inlet end of the muffler. The headers or partitions 38, 40, 42 and 44 are formed with anged openings to receive a tube or conduit 54 which forms a gas passage outlet means in the muflier shell.

The end head 24 is formed with an opening to receive a tubular outlet itting 56 which is telescoped with an end region of the gas passage discharge tube or means 54 as shown in Figure l. An end region of the fitting 56 is provided with a slot 57 and a clamping means (not shown) is adapted to surround the slotted region of the fitting to clamp the same in engagement with a tail pipe passage'tubes 46 and 54.v Disposed betweenthe `headersV 38 and 40 and extending across the inner space defined by the inner shell wall and surrounding the portion of the gas passage tube 50 between the partitions 38 and 40 is an intermediate shell or baffle means 62 which is generally of tear-drop or pear shape in cross section as in Figures 3, 4 and 5. The baie or intermediate shell 62 is formed of a single sheet of metal, the end regions overlapping as at 64 and being secured together by spot welds 66 or other suitable joining means.

The curvilinear portion of the shell 62 is joined to the shells by means of spot welds 68 and the opposite region 69 of the shell is spot welded as at 70 to the shell walls. During the application of the spot welds 68 and 70 the material of the outer shell at the region of the weld is brought into contiguous or welding contact with the inner shell wall 10, the latter being in contact with the intermediate shell 62 so that the shell walls 10 and 12 at these regions are welded together and to the intermediate shell 62.

The transversely extending members or walls 38 and 40 are respectively formed with shoulders 71 and 72 of the same contour or shape as the cross sectional configuration of the baiiie member 62. The batiie member 62 is adapted to engage the shoulder portions 71 and 72 forming a tear-drop or pear-shaped sound resonating chamber 73 surrounding a perforated region 75 of the intermediate tube 50.

The member 62 provides an intermediate shell or baie which with the partitions or headers 38 and 40 define the chamber 73, the baffle means 62 preventing the direct transverse flow or passage of exhaust gases from the openings 77 formed in the region of the wall 46 between the partitions 38 and 40 and the openings 79 formed in the wall of the region of the tube 54 disposed between the headers or partitions 38 and 40. The bafe 62 thus forms high frequency resonating chambers 78 and 80.

The partition or header 38 and the end head or closure 22 at the inlet end of the mufer construction define a transversely arranged chamber or passage 81 for effecting the ow or transfer of exhaust gases from an end of the tube 50 into the tube 54 so that there is a continuous circulation of exhaust gases in the transverse passage 81. As the region of the tube 46 between the partition or header 38 and the end closure 22 is imperforate, the exhaust gases which move through the passage 81 must first flow in a right-hand direction through the tube 46 as viewed in Figure l thence in a retroverted or lefthand direction through the tube 50 before passing into the outlet tube 54.

It will be apparent from Figure 1 that all of the exhaust gases moving through the muffler construction are retroverted through at least a portion of the length of tube 50 before they are discharged through the outlet pipe or passage 54.

The partition or transversely extending wall 44 together with the end head or closure 24 at the discharge end of the muier construction dene a chamber 83 which is in communication with a region of the tube 54 by means of a large number of small openings or apertures 85 formed in that portion of the wall of tube 54 disposed between the partition 44 and the end closure 24. The chamber 83 forms a sound attenuating means or chamber. The exhaust gases continually circulate through chamber 83, owing into and out of the chamber 83 through the openings 85.

It should be noted that in the arrangement shown in Figure l there are no chambers or sound attenuating regions which are isolated against circulation or flow of exhaust gases so that the exhaust gases traverse all the internal regions and passages in the muiiier construction. One of the salient features of the invention is the elimination of resonator chambers which are substantially isolated from the moving exhaust gases as in prior muffler arrangements.

yIn muflier constructions embodying isolated sound attenuating chambers of the so-called Heimholtz resonator type, very high temperature differentials exist within such a muier construction whereby certain regions become intensely hot by reason of direct contact with the intensely hot exhaust gases while other regions of the muffler construction which are out of the path of flow of exhaust gases are of much lower temperatures.

The differential temperatures were of suiiicient magnitude in prior muiiier constructions as to foster the condensation of moisture in regions of lower temperature in the muffler.

The formation of moisture condensation persisted by reason of the lack of flow of exhaust gases throughout the entire interior regions of the mutiier. Hence within comparatively short periods of time, the collected moisture condensation resulted in oxidation of the ferrous metal Walls of the muliier causing disintegration of the shell walls.

In the arrangement of the present invention, the gases flowing through the gas passages and chambers within the muiiier traverse substantially all of the interior regions of the muffler whereby substantially uniform temperatures are maintained throughout the entire length of the muffler.

Thus the elimination of regions of reduced temperature wi-thin the muffler prevents the formation and accu- -mulation of moisture condensation as the heat of the exhaust gases and the fact that exhaust gases flow throughout the entire interior regions of the mufer volatilize and carry away the moisture thus preventing puddling of moisture or water within the muier.

Some of the gases moving in a right-hand direction through the tube 46 flow transversely through openings S6 formed in the wall of tube 46 between the partitions 40 and 42 into openings 88 formed in an adjacent wall portion of the gas passage tube 50 whereby some of the exhaust gases bypass the transverse passage y48. The passages or chambers defined by the partitions 38, 40, 42, 44 and the end closures 22 and 24 provide sound attenuating chambers or passages for damping or attenuating sound waves.

The paths of ow of exhaust gases through the muffler are 4as follows: The gases from an exhaust system enter the inlet tube 46 and some of the gases flow through the openings 77 in pipe 46 into the high frequency resonating chamber '78. Incoming exhaust gases in the inlet pipe 46 may iiow transversely through the openings 86 into the openings 88 formed in the wall of tube 50 while other gases from the inlet tube flow transversely through the connecting passage or chamber 48 and then ow in a reverse or retroverted direction through the intermediate tube 5G into the transverse passage 81 thence into the outlet pipe 54. Gases entering the discharge tube 54 may iiow through openings 79 into and circulate through the resonating chamber 8G.

The exhaust gases moving through the outlet tube 54 may iiow into and circulate through the passage or chamber 83 through the openings 85 formed in the wall of tube 54. Gases in the region between the partitions or headers 4@ and 42 may iiow into the regions between the partitions 38 and 40 at either side of the tear-drop shaped bafe or shell 62 through comparatively large openings 60 shown in Figure 3 formed in the partition or wall 40.

The chamber regions transversely of the gas passage means or tubes 46, 50 and 54 form high frequency sound attenuating chambers which are acoustically coupled with the gas passage means through the small openings in the tube walls for damping or attenuating high frequency sound waves.

An important feature of the muffler construction of the present invention involves the attenuation, destruction or nulliiication of low frequency sound waves by reverberation or reflection so that the low frequency waves are caused to interfere with one another and thus affect or eliminate the low frequency sounds. For example, low -frequeney sound waves entrained inthe exhaust gases moving in aV right-hand direction through the inlet .pipe or gaswpassage 46 impinge upon a flat portion 45 of the partition or wall 44 and are reverberated or reilected in a reverse direction toward succeeding incoming sound waves in the inlet tube 46.

Through this method, reverberated waves reflected from or bouncing off of the surface 45 establish inter-V ference with succeeding incoming sound waves so that certain frequency waves are attenuated or nullified by the interference through the, Wave reverberation in the inlet pipe '46. The same wave attenuating action is prevalent in reference to low Afrequency sound waves moving from the chamber 48 through the intermediate gas passage tube or means 511 into the transverse passage or connecting chamber 81.

Thus sound waves moving through the tube 50 impinge upon the end wall or end closure 22 of the muffler and are reverberated in a right-hand direction through the passage 50 and establish interference with sound waves entering and moving through the tube 50 from the transverse connector or passage 48. In this manner, sound waves of certain low frequencies are attenuated within the passage Si) and repeated reverberation of sound waves takes place between the fiat surface 49 of the partition 44 and `the region of the closure 22 aligned with the tube U.

Through this arrangement, a substantial range of low wave frequencies is attenuated inthe gas passage tube 50 between the surface 49 and the end Wall 22. In reference tothe temperatures in various regions of the muffler construction, a substantial portion of `the intensely hot incoming exhaust gases move in a right-hand direction through the inlet tube 46 and the heat of these gases or a substantial amount of heat therefrom is transferred by direct contact to the transverse Wall or partition 44.

This factor assists in increasing the heat transferred to the regions of the mui'lier construction defining the chamber' 83 to augment or increase the temperature to supplement the heat transferred from the cooler exhaust gases which ow through the openings 85 in the wall of the outlet tube 54 and circulate through the chamber 83.

Through this method of iiowing exhaust gases through all interior regions of the mufiier eiecting transfer of heat to the partitions and transverse passages, only minor variations in temperature occur throughout the entire interior of the muiiler construction. Furthermore it is found that attenuation or damping or sound waves of low frequency is improved over an increased range through the reverberation and wave interference system without increasing the length of the paths of travel of the exhaust gases through a retroverted type or multiple pass muffler.

The arrangement shown in Figures 6 and 7 involves multiple gas passage and sound wave traversing means whereby the path of traverse of the exhaust gases and entrained sound waves is substantially increased without increasing the length of the muiiler construction and wherein exhaust gases are circulated throughout the entire interior regions of the muiiler so as to provide for substantially uniform temperatures throughout all i-nterior regions of the muifler.

The mufer construction shown in Figures 6 and 7 includes an inner shell 100 and an outer shell y162 which are of substantially the same construction and coniiguration as the corresponding walls 1t) and 12 of the arrangement shown in Figure l. The muiher construction is inclusive of end heads, walls or closures 184 and 106, each end closure being providedl with a peripheral flange construction 16S of generally U-shaped configuration in cross section which embraces the adjacent end regions of the inner and outer shell walls 190 and 102. The flans? @Fang-www1@ .is crimped, erk Pressed. into suus engagement with the shell walls to provide a gas tigh seal.

In this form of construction the inlet and outlet Vgas passage means Iare disposed generally centrallyV ofthe muffler and offset or laterally disposed with respect to a plane through other gas passage means `in the mumer construction. Y

The end head 104 is formed with an opening deiined by a iiange which receives and accommodates a tubularcoupling or iitting` 112 at the inletend of the muffler, the iitting 11,2 adapted to be connected with an exhaust duct for an internal combustion engine or the like.

rTelescopedrwithin the fitting 112 is a gas passage or gas inlet tube 114-which extends through transversely arranged partitions or walls 116 and 118, the partitions 116 and 118 being substantially of the same configuration as the partitions or walls 38 and 40 shown in Figure 1.

Disposed between the partitions 116 and 118 is a teardrop shaped baille orintermediate shell 62 of the same shape and construction las the member 62 shown in Figure 3. In the arrangement shown in Figure 6, the intermediate tear-drop shaped shell 62 surrounds a perforat-v ed region 120 of the inlet pipe 114.

The muffler arrangement shown in Figure 6 is inclusive of transversely arranged partitions, walls or headers 122, 124, 126 and 128. These partitions together with partitions 116 and 118 and the end closures 104 and 106 define transversely arranged gas passages or chambers 136, 134, 136, 13S, 140 and 142. The partitions 116 and 118 together with the tear-drop shaped intermediate shell 62- deh-ne high frequency resonating chambers 144 and 146.

A comparatively short tube 148 establishes gas pas. sage means between the chambers or transverse passages 134 and 13G, the incoming gases entering the mufller through the tube 114 traversing the passage 134, then iiow in a reverse direction through the tube 148 into the transverse passage 130. The walls of the tube 148 are formed with a plurality of small openings or apertures 150 which form acoustic couplings with the high frequency resonating chamber 144 for attenuating high frequency sound waves.

A gas passage means or tube 152 extends through openings provided in the transverse partitions whereby to establish communication between the chambers or trans-. verse passages and 142 disposed adjacent the respective end closures 104 and 106 of the muffler construction. The portion of the tube 152 disposed between the transversely extending partitions 116 and 118 is formed with a plurality of small orifices or apertures 154 which form acoustic couplings between the interior of the tube 152 and the high frequency resonating chamber 146 for attenuating high frequency sound waves.

A substantial length of the wall of tube 152 disposed between the transversely extending partitions 124 and 126 is formed with a plurality of small circular openings or apertures 156 which form acoustic couplings with the chamber 138 deiined by the partitions 124 and 126. rthus exhaust gases flow through the openings 156 and circulate through the resonating chamber 13S.

The partition 126 is formed with a plurality of comparatively large openings 162, shown in Figure 7, establishing means facilitating the circulation of exhaust gases from chamber 138 into and through the chamber 1411.

Extending through openings provided in the partitions or transversely extending walls 124, 126 and 128 is a gas passage tube 164 to conduct or transfer exhaust gases from the end chamber or transverse passage 142 into the transversely extending passage 136 so as to facilitate discharge of exhaust gases through anoutlet passage or tube 166. The extremity of the outlet tube 166 adjacent the 11.41QlQSturelLis.telescopedwith an outlet iitting-IGS gi of the same construction as the inlet fitting or coupling member 112.

The general path of travel of gases through the mufer is as follows: The gases entering the inlet tube 114 ow through transverse passage 134 into the tube 148 and through the tube 148 into transverse passage 130. The gases in the passage 130 liow substantially the length of the muiiier through the tube 152 into the transverse passage 142 thence in a reverse direction through the passage or tube 164 into the transverse passage or chamber 136 and from this passage or chamber are discharged from the mnier through the outlet passage or tube 166.

iIt will thus be apparent from the foregoing that the gases traverse a system of passages of substantial length so that sound waves of a substantially wide range of frequencies are attenuated in the mutiler construction.

It will also be apparent that the openings or apertures 120, 150, 154, 156 and the larger openings 162 in the partition 126 facilitate the circulation of exhaust gases throughout the various chambers and passages in the mutlier construction whereby a substantially uniform temperature may be maintained throughout all of the interior regions of the muffler. In this arrangement there are no so-called dead chambers as far as the circulation of exhaust gases is concerned as the gases are enabled to circulate throughout all regions of the muftier.

The arrangement of Figures 6 and 7 provides for the reliection of reverberation of sound waves of lower frequencies between pairs of walls, partitions and end heads whereby sound wave interference is established to attenuate or eliminate sound waves of lower frequencies.

Thus `sound waves entrained in the gas stream moving through the tube 148 are reverberated or reflected between the end head 104 and a portion 170 on the partition 122 whereby sound waves of certain frequencies are attenuated by wave reverberation and interference.

The low frequency sound waves moving through the gas passage or tube 152 are reverberated or reflected be tween the end heads 104 and 106 of the muffler and are attenuated or destroyed by wave interference. Certain sound waves entrained in the gas stream moving through the gas passage tube 164 are attenuated and eliminated by wave interference through reflection or reverberation of the waves between the end head 106 and the wall portion 170 of the partition `or transverse header 122.

From the foregoing it will be seen that the exhaust gases and entrained sound waves move through several passage means of various lengths whereby effective sound attenuation is attained over a wide range of sound frequencies, Iand that the exhaust gases are enabled to circulate throughout all interior regions of the muler so as to foster the establishment of substantially uniform temperatures throughout all regions of the muler.

By offsetting the inlet pipe 114 relative to a plane through the axes of the gas passage tubes 148 and 152, the inlet tube 114 may be disposed adjacent a region of the muffler shell so as to enable the positioning of the mutiier close to the floor of a vehicle in which the muffler may be installed without interference with cross frame members adjacent the vehicle door. The outlet tube 166 may also be positioned in alignment with the inlet tube 114.

Another form ylof the invention is illustrated in Figures 8 and 9. In this form the outer shell construction is inclusive of an inner wall or layer 180 and an outer layer 182 of the same character as illustrated in the other forms of muffler construction disclosed herein. The end regions of the inner and outer layers or shells 180 and 182 are engaged by peripheral flange portions 183 formed on the end heads 184 and 186 as shown in Figure 8.

vA tubular tting 188 extends through an opening in the end head 184 delined by a flange 190 and is in telescoping relation with an end region of a gas inlet passage .1U means or tube 192 which extends substantially full length of the muier construction. Disposed transversely of the muier construction and spaced lengthwise thereof are interior walls or partitions 194, 196 and 198.

The end head 184 and the partition 194 define a transversely arranged gas passage or chamber 200, and the end head 186 with the partition 198 define a transversely arranged gas passage or chamber 202. The extremity of the gas inlet passage means or tube 192 terminates in the transverse passage 202. The intermediate wall or partition 196 forms an intermediate or central supporting means for the gas passage tubes disposed in the muf tier.

Extending through openings in the partitions 194, 196 and 198 is a second gas passage tube 204 which establishes communication between the transversely arranged gas passages or ow connectors 200 and 202.

The walls 194, 196 and 198 are also provided with openings through which extends a gas passage means or tube 206 which forms a gas outlet or discharge means. The end o-f the outlet tube 206 adjacent the end head 186 is telescoped with an outlet tube or fitting or extension 208 which projects into or through an opening formed in the end head 186 and defined by a flange 210 as shown in Figure 8.

Surrounding the inlet gas passage means or tube 192 is a cylindrical sleeve or member 212 which extends between the partitions `or walls 194 and 198 providing a chamber region surrounding the inlet tube 192 and having its ends closed by means of portions of the walls 194 and 198.

Spaced lengthwise of the inlet tube 192 in the region between the wall of the tube and the sleeve or member 212 are partitions or walls 214, 216 and 218 which, with the walls 194 and 198, define high frequency resonating chambers 220, 222, 224 and 226. The region of the wall of the inlet tube 192 between the partitions 194 and 198 is formed with a plurality of small openings or apertures 228 which form acoustic couplingss with the high frequency resonating chambers 220, 222, 224 and 226 which function to attenuate high frequency sound waves entrained in the gas stream. The openings or apertures 228 also facilitate the circulation of exhaust gases through the high frequency resonating chambers.

The wall of the gas outlet or discharge tube 206 in the region between the partitions 194 and 198 is formed with a large number of comparatively small openings or apertures 230 which establish acoustic couplings with the chambers 232 and 234 dened by the transversely extending walls 194, 196 and 198. The chambers 232 and 234 form sound attenuating chambers for intermediate frequency sound waves moving through the gas *outlet tube 206.

The centrally disposed partition or wall 196 is provided with openings 236 shown in Figure 9 to facilitate or foster the circulation of exhaust gases through the chambers 232 and 234.

In the arrangement shown in Figures 8 and 9, the exhaust gases ow into the inlet tube 192 in a right-hand direction as viewed in Figure 8, thence transversely through the passage 202 and into the intermediate tube 204. The gases flow in a reverse direction through the tube or gas passage means 204 into the transverse passage or chamber 200. The gases ow transversely through the passage 200 `and into the exhaust discharge outlet tube 206, the gases moving through the outlet tube 206 in the same direction as the gases flowing through the inlet tube 192.

In this arrangement the gases are retroverted through the muliier so that a comparatively long path of traverse is provided through the medium of the tubes 192, 204 and 206 thus permitting the attenuation of a large range of sound frequencies. Furthermore the exhaust gases may flow through the high frequency resonators or resonating chambers 220, 222, 224, and 226 through the provision of the large number ofV openings 228 in the inlet:

pipe 192.

` rlhe exhaust gases moving in the outlet tube 206 may ow through the large number of orilices 230 into theV chambers 232 and 234, there being communication betweentthe latter mentioned chambers through the provision `of the openings 236 formed in the centrally disposed partition or wall 1%. It will thus `be apparent that the exhaust gases are permitted to i'low through all regions in the interior of the muiller, a condition which fosters the establishment of uniform temperature conditions throughout the entire interior of the muiller.

Some of the low frequency sound waves entrained lin the gas stream impinge upon theend head 186 and 'are reverberated or ireilected in a reverse directionfthrough theA tube 192 so` as to establish wave interference with' incoming sound waves and thereby attenuate or destroyV throughout all interior regions of the muiller and are not trapped or isolated in any portion of the mufller con struction,

In all forms of the invention the flow of exhaust gases through the mufler passages and chambers is such as to establish substantially uniform temperatures throughout all regions of the mufller to thereby prevent the formation of. moisture condensation or accumulation as there are no isolated regions of reduced temperature in the muffler constructions. This factor substantially eliminates oxidation or rusting of the components and shell walls thus prolonging the useful life of the muiller construction as compared with muillers heretofore utilized embodying dead chambers.

It is also found that the arrangement of the present invention improves the attenuation of an increased range of sound wave frequencies through wave interference as compared with the sound attenuating efficiency of muiilers embodying the so-called dead chambers wherein attenuationl is attained through absorption.

It is apparen-t that, within the scope of the invention, modifications and diilerent arrangements may be made other than is herein disclosed, and the present'disclosure isV illustrative merely, the invention comprehending all variations thereof.

Iclairn:

1. A sound attenuating means for use with a gas stream including, in combination, a tubular shell of oval cross-section, closure walls secured to the ends of the shell, said closure walls being respectively provided with gas passage tubes forming gas inlet and outlet means, a third gas passage tube in said casing in `transverse overlapping relation with said inlet and outlet tubes, intermediate walls in said shell, one of said tubes being disposed with its axis offset from a plane passing through the axes of the other tubes, an intermediate tubular shell of pearshaped cross-section surrounding a region of the offset tube and extending between and secured to transversely opposed portions of the tubular shell, the wall region of the `tube surrounded by the intermediate shell being formed with a plurality of small openings providing acoustic couplings between 'the same andthe interior of another tubeone of the walls of one oftsaidtransversepassage means-being imperforate and arranged wherebysound waves; entrained in the gas stream.l and movingl lengthwise of the gas passage. tubes are irnpinged upon* the imperforate wall and reverberated through the tubes and attenuated by wave interference.

2; A sound. attenuating means for use with a gas,

stream including, in combination, a tubular shell, closure walls secured to the ends of the shell, said closure being respectively provided with gas passage tubes forming `gas v inlet `and outlet means, a third gas passage tube in said shell in transverse overlappingrelation with said inlet and outlet tubes, intermediate walls in said shell, one of said tubes being disposed with its axis oilset from a plane passing through the axes of the other tubes, a tubular baille means of pear-shaped cross-section surrounding a region of thevotlset tube and extending between and secured to opposed portions of the tubular shell and ydeiining with the adjacent intermediate walls a plurality ofr high frequency resonating chambers, the wall regions of the tubes adjacent the baille means being formed with a plurality of small apertures providing acoustic couplings between the tubes and the resonating chambers, certain of said intermediate walls and at least one of said end closure walls forming two longitudinally spaced trans-l verse gas passage means providing for transverse ilow of gases from an end of one tube -to an end of another tube, the walls of said transverse passage means, the intermediate lwalls and the openings in the tubes being arranged whereby the gases circulate through all regions interiorly of the shell to establish more uniform temperatures throughout all regions of the shell.

3. AV sound attenuating means for use with a gasstream including, -in combination, a double walled tubular casing of yoval cross-section, closure walls secured to the ends of the casing, said closure walls being respectively provided with gas passage tubes forming gas inlet and outlet means, a third gas passage -tube in said casing in transverse overlapping relation with said inlet and outlet tubes, partition walls in said casing, one of said tubes being disposed with its axis offset from a plane passing through the axes of the other tubes, tubular baille means having convergently arranged walls isolating a region of the offset tube and extending between and secured to diametrically opposed portions of the tubular casing, the wall region of the isolated portion of the tube being formed with a plurality of small openings providing acoustic couplings between the tube and the region dened by the tubular baille means, said partition walls and at least one of said end closure walls forming two longitudinally spaced transverse gas passage means providing for transverse flow of gases from an end of one tube to an end of another tube, one of the walls of said transverse passage means being imperforate and arranged whereby low frequency sound waves entrained in the gas stream and moving lengthwise of the gas passage tubes are limpinged upon the imperforate wall and reverberated` through .the tubes and attenuated by wave interference.

4. A sound attenuating means for use with a gas stream including, in combination, a tubular shell `casing of oval cross-section, closure walls secured to the ends of the casing, said-closure walls being respectively provided with gas passage tubes forming gas inlet and outlet means, a third gas passage tube in said shell in transverse overlapping relation with said inlet and outlet tubes, intermediate walls in said shell, one of said tubes being disposed with its axis oilset from a plane passing through the Aaxes of the other tubes, an intermediate tubular shell of pearshaped cross-section surrounding the offset tube at its region of transverse overlap with another of said tubes and extending between and secured to diametrically opposed portions ot the tubular shell casing, the wall of the tube surrounded by the intermediate shell being` formed with a plurality of smallY apertures forming acoustic couplings between the said tube and the interior of the intermediate shell, transverse gas passage means formed by at least one of the closure walls and intermediate.,

walls providing for transverse flow of gases from an end v ofonetubetoan end ofanother tube, the walls ofsaid.`

casing to establish substantially uniform temperatures throughout the interior of said tubular shell casing.

References Cited in the file of this patent UNITED STATES PATENTS 1,931,736 Noblitt et al Oct. 24, 1933 2,022,899 Oldberg Dec. 3, 1935 2,111,537 Noblitt et al Mar. 15, 1938 2,193,791 Hollerith et al. Mar. 9, 1940 2,652,128 Cary Sept. 15, 1953

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