US3289786A

US3289786A - Muffler with return bend tuning passage

Info

Publication number: US3289786A
Application number: US428639A
Authority: US
Inventors: Walter H Powers
Original assignee: Walker Manufacturing Co
Current assignee: Walker Manufacturing Co
Priority date: 1965-05-17
Filing date: 1965-05-17
Publication date: 1966-12-06
Anticipated expiration: 1983-12-06

Description

Dec. 6, 1966 W. H. POWERS I. MUFFLER WITH RETURN BEND TUNING PASSAGE Original Filed April 2, 1956 Dec. 6, 1966 W. H. POWERS 3,289,786

MUTFLEN WITH RETURN BEND TUNING PASSAGE Original Filed April 2, 1956 B'Sheets--Sheet 2 Dec. 6, 1966 w. H. POWERS MUFFLER WITH RETURN BEND TUNING PASSAGE 8 Sheets-Sheet 5 Original Filed April 2y 1956 INVENTGR /7/ 70 we 75 ffa nm -QN Dec. 6, 1966 W. H. POWERS 3,289,786

\ MUFFLER WITH RETURN BEND TUNING PASSAGE Original Filed April 2, 1955 8 Sheets-Sheet 4 /rf l 1074 INVENTOR. M1/fer )9x/wens Dec. 6, 1966 w. H. POWERS 3,289,786

MUFFLER WITH RETURN BEND TUNING PASSAGE Original Filed April 2, 1956 8 Sheets-Sheet 5 Dec. 6, 1966 w. H. POWERS MUFFLER WITH RETURN BEND TUNING PASSAGE 8 Sheets-Sheet G Original Filed April 2, 1955 IN VEN TOR. H we 7s y ,ff

Dec. 6, 1966 w. H. Fowl-:Rs

MUFFLER WITH RETURN BEND TUNING PASSAGE Original Filed April 2L 1956 B Smets-Sheet '7 i NVENTOR. //d//er /7/ F0 wens* @me 70W/wsu@ Dec. 6, 1966 W. H. POWERS 3,289,786

MUFFLER WITH RETURN BEND TUNING PASSAGE Original Filed April 2, 1956 8 Sheets-Sheet 8 NN nl WN NN H N Nm United States Patent O 3,289,786 MUFFLER WITH RETURN BENI) TUNING PASSAGE Walter II. Powers, Jackson, Mich., assignor to Walker 3 Claims. (Cl. 181-54) This application is a `division of U.S. Serial No. 136,287 filed September 6, 1961 (now abandoned) which in turn is a division of U.S. Serial No. 575,404, filed April 2,1956 (now abandoned).

This invention relates to muier constructions and, in particular, to muiers of the type .adapted to silence the exhaust stream of automotive internal combustion engines.

It is .the object of this invention to provide a muflier construction that may be economically manufactured and yet which is rugged and dur-able in construction and which will efficiently silence the powerful modern day automotive engines, particularly those having automatic transmissions, without appreciable back pressure.

The invention accomplishes this and other objects by means of a construction in which theY gas passages within the ymuffler casing are arranged in a tri-How pattern and subjected to the .action of `a number of spit chambers both large and small which will remove the roughness and high frequency sounds. The gases and sounds lare'also exposed to the action of a number of resonator chambers which will act to :remove the lower frequency heavy power notes. The internal tri-flow construction is of such a nature that it can be preassembled; that is, prepared as a subassembly and then inserted into the mutller casing. The lover-all design is such as t-o meet the cost and performance requirements of automotive manufacturers, particularly those manufacturing V-S engines.

The invention is illustrated in modified forms in the accompanying drawings in which:

FIGURE 1 is a longitudinal section ot a preferred form of the invention as taken on line 1-1 of FIG. 3;

FIG. 2 is an end View taken from the left of FIG. 1;

FIG. 3 is a cross section taken along the line 3-3 of FIG. l, the louvers being omitted for simplification;

FIG. 4 is a side elevation of the gas conduits with parts broken away to show the structure of the louvers in the tube;

FIG. 5 is a cross section through the louvers shown in FIG. 4 and llaid out straight rather than on the curved contour of the tube;

FIG. 6 is a longitudinal cross section through -a slightly modified type of muiiier, the end view and sectional view being the same for this rnuiiier as FIGS. 2 and 3;

FIG. 6A is a section on line 6A-6A of FIG. 6;

FIG. 7 is a longitudinal section through the front end of a muiiler somewhat similar to the muffler shown in FIG. 6, lthe structure in FIG. 7 revealing a pancake inlet arrangement;

FIG. 8 is a section on line `8--8 of FIG. 7;

FIG. 9 is a view showing =a .modied arrangement for forming the trifiow passages in the muier, this constituting a pancake arrangement consisting of complemental stampings which when iitted together will define the spit chambers around the outermost passages and define the .inner passage itself;

FIG. 10 is a longitudinal cross section of a modified form of mutlier;

FIG. 11 is an end view taken from the inlet side of the muler of FIG. 10;

FIG. 12 is a cross section taken along the line 1212 of FIG. 10i;

nr' ICC FIG. 13 is a longitudinal section through another muffier embodying the invention;

FIG. 14 is an end elevation taken rom the inlet end of'the muie'r of FIG. 13;

FIG. l5 is an end elevation taken from the outlet side of the muiiier of FIG. 13;

FIGS. 16 and 17 are cross sections taken -along .the lines 16--16 and 17-17 respectively of FIG. 13;

FIG. 18 is a longitudinal section through another form of mutiier embodying the invention;

FIG. 19 is an end view from the inlet end of the muffler of FIG. 18;

FIGS. 20 and 21 are cross sections taken along the lines 2li-20 and 21-21 of FIG. 18;

FIG. 22 is a longitudinal section through another muffler embodying the invention;

FIG. 23 is an end elevation taken at .the inlet end of the muiiier;

FIG. 24 is an end elevation taken at the outlet side of the muflier; and

FIGS. 25 and 26 are cross sections taken along the lines 25-25 and 26-26 of FIG. 22.

Considering iirst the muiler 1 that is shown in FIGS. 145, there is a casing 3 of oval cross sectional form constructed in accordance with known practice so that inten nal bailes or partitions can be spot welded to it. It is provided with a head 5 at the inlet end and a head 7 at the outlet end, both heads being interlocked as shown at 9 with the ends of the casing 3. An inlet bushing 11 is expanded as shown lat 13 int-o -a tight contact with the outwardly turned flange or neck 15 on the head 5 so that the bushing 11 can be properly spot welded to the neck after the head and internal pa-rts have been assembled with the casing 3. The head 7 has an outwardly turned neck or flange 17 in which is fitted an outlet bushing 1-9 that is expanded diamet-rically into -contact with `the neck 17 as shown at 21 so that the bushing 19 can be spot welded to the ilange 17 after the head and internal parts have been assembled to the casing 3. Gas to be silenced Hows from the engine through a suitable exhaust line into the inlet bushing 11 and passes through the various gas silencing apparatus within the casing 3 and out through the bushing 19 to the tail pipe of the exhaust system.

The central part of the apparatus within the muffler 1 is a subassembly 23 which can be 'manufactured as a unit and inserted in the muier, the various other parts being assembled later on from both ends of the Inuiiier and then the heads 5 and 7 attached by interlocking at 9 to the casing after which the bushings 11 and 19 are expanded at 13 and 21, respectively, into contact with the

necks

15 and 17 and spot welded in place. The subassembly 23 is supported by the parallel transverse partitions 25 and 27. These have flanges 25a and 27a. that -run parallel to ythe inside surface of the casing 3 and which are turned outwardly so that they can be spot welded to the casing ,3 by suitable spot welding apparatus including inner and outer electrodes that are radially aligned inside and outside of the casing, the outwardly turned flanges permitting such apparatus to be inserted inside the casing in yproper position. The partition 25 has three outwardly turned flanges or necks 29, 30, and 31 which are aligned, respectively, with the outwardly turned anges o-r necks 4on partition 27 that are designated by reference numbers 32, 33, .and 34 respectively. Spot welded in position to the necks 29 and 32 is an intermediate tube 35 having louvers 37 formed therein ralongvthe surface which are of the type shown in FIGS. 4 and 5 so tha-t they can direct gas circumferentially around t'ne outside of the t-ube 35. Mounted in `and spot welded to the necks 30- and 33 is lan outlet tube 39 and this projects some distance beyond the end of the partition 27 as shown at 41. Mounted in and spot welded to the necks 31 and 34 is the inlet tube 43 and this tube has a.

somewhat enlarged en-d projecting toward the inlet end from the partition 25 as will be seen at 45. The tubes 39 and 43 each have louvers 37 of the type already rnentioned. The inlet tube 43 has a pair of spit chambers 47 and 48 formed .around it and the intermediate pass tube 35 has spi-t chambers 49 and 51 formed a-round it.

The chambers 47 and 48 as well as the chambers 49 and 51 are formed by

pancake assemblies

53 and 55 respectively. The

pancake assemblies

53 and 55 are substantially identical so that the description of one will sufce. Each assembly consists of a pair of identical stampings or halves 52 which are provided with flanges 57 that lie in the plane of the original sheet metal from which the pancake halves were originally formed, the chamber portions being pressed or bowled out of the at pieces. The flanges 57 are joined together face to face as clearly seen in FIG. 3 and spot welded together so that the two halves form a shell around the tube. The ends 59 and 61 of the halves of the pancake are formed to snugly t the periphery or semi-periphery of the tube as is the center portion 62. These can be spot welded to the tubes if desired. Angularly spaced from the flanges 57, the halves of the

pancake assemblies

53 and 55 are formed with flats as shown at 65 and one edge of the pancake assembly is trimmed so that the ange 57 is removed beyond the diameter of the spit chambers as will be seen at 67 in FIG. 3. By removing the flange 57 at the point 67 and forming the flats 65 it is possible to tit the pancakes 53 closely to the contour of the casing 3 and to get a good deal of additional space adjacent the center outlet tube 39 as is evident from FIG. 3. The pancake assembly halves are so formed that they can be considered standard parts to be used in muler 1 or in various other mulers having different over-all dimensions and internal spacings. The ats 65 and the cut oif outer flanges increase the flexibility in this respect because they reduce the space taken up by the pancakes, enabling them to be used in mufllers Where quarters are more cramped than in muffler 1.

It will be seen that the partitions 25 and 27 with the

tubes

35, 39 and 43 spot welded in the respective necks and in turn carrying

pancake assemblies

53 and 55 can all be assembled as a subassembly into a spot welded integral unit. This unit 23 can then be inserted into the center portion of the casing 3 whereupon the partitions 25 and Z7 can be spot welded in place to the casing and, after this, the elements to the left and to the right of the subassembly 23 can be inserted into the muffler as a part of the nal assembly operation. When inserting assembly 23 I prefer to put the casing 3 in a fixture that will hold the casing in its proper shape and I also prefer to outwardly flare the ends of the casing so that the assembly 23 will in effect be funneled into it. These steps will eliminate diiculties caused by having the outwardly turned flanges on partitions 25 or 27 as the leading edge during insertion.

Adjacent to but spaced longitudinally toward the inlet end of the mufer is a transverse partition 71 and spaced between it and the header 5 is another transverse partition 73. The partitions 71 and 73 have inwardly and outwardly turned flanges or necks 75 and 77, respectively, through which extends a connecting inlet pipe 79, with louvers 37 therein, that slidably ts within the enlarged end 45 (flared at 83) of the tube 43 (which is a part of the subassembly 23) as will be seen at the point 81. The outermost end of the tube 79 is spot welded at 85 to the inner end of the inlet bushing 11. It will be seen that this arrangement provides a reinforcement for the head 5 since the bushing 11 is spot welded to the head and then to the tube 79 which in turn is spot welded to the partitions 73 and 71 by way of necks 77 and 75.

The chamber between the head 5 and the partition 73 constitutes a resonator chamber 87. The chamber 89 between the partition 71 and the partition 25 is a cross'over chamber. Connecting the cross-over chamber S9 with the resonator chamber 87 is a tuning tube 91 that is spot Welded in and to inwardly and outwardly turned flanges or necks 93 and 95, respectively, in the partitions 71 and 73.

At the outlet end of the casing 3 there is a transverse partition 97 that is spaced from the partition 27 to define therewith a cross-over chamber 99. Between the partition 97 and the head 7 is a partition 101 which like the partition 97, and the other partitions herein, has an outwardly extending ange running around it by means of which it is heated in position on the inside of the casing 3 and then spot welded to the casing by radial electrodes on the inside and outside of the casing. The space between partition 97 and partition 101 constitutes a resonator chamber 103 while the space between the partition 101 and the end header 7 constitutes another resonator chamber 105. The outlet bushing 19 iits in an outwardly turned flange or neck 107 in the partition 101 and is spot Welded to it, thus tying the head 7 to the partition 101 to reinforce the head 7. As shown at 109, fitting inside of the end of the bushing 19 and spot welded to it is a connecting tube 111 that is enlarged at its end as shown at 113 and flared so that it slip ts over the end 41 of the outlet passage tube 39, the tube 111 extending through the inwardly flanged neck 115 of the partition 97 and being spot welded to it. A tuning tube 117 is spot welded to inwardly and outwardly turned flanges 119 and 121 on partitions 97 and 101 and is preferably aligned with tube 43. Flanged opening 123 connects chambers 103 and 105 to form a compound resonator.

In assembly, after unit 23 has been inserted and spot welded in place, the partitions 71 and 97 with tubes 91, 111, and 117 already spot welded to flanges 93, 115, and 119 are inserted and the outwardly turned partition flanges spot welded to the casing by spot welding apparatus inserted through the ends of the casing. Partition 73 with tube 79 spot welded to flange 77 (and bushing 11 spot welded to tube 79) and partition 101 with bushing 19 spot welded to flange 107 are then inserted, the outwardly turned flange slipping readily over tube 91 and the ared end of bushing 19 slipping over the end of tube 111. Then, from the inside of the casing, the outwardly turned partition flanges are spot welded to the casing, the tubes 91 and 117 are spot welded to outwardly turned flanges 95 and 121, and the end 109 of tube 111 is spot welded to bushing 19. It may be noted that end louvers 37 Will engage partition 71 to limit the slipping of tube 79 into tube 43 and that ange 75 will catch under flare 83 to control insertion of partition 71. It may also be noted that the tubes 79 and 43 may be connected together, if desired, in the same sort of joint as bushing 19 and tube 111, i.e., the tube 43 slipping inside and spot welded to tube 79 which in turn was spot welded to flange 75. After the partitions and members have been inserted and spot welded in place, as described, the end headers 5 and 7 may be interlocked at 9 and the bushings 11 and 19 expanded and spot Welded to

flanges

15 and 17.

In operation, gas enters the inlet bushing 11 and flows through the tube 79 into the tube 43. Some of the gas passes through the louvers 37 of tube 79 into the large spit chamber 121 between partitions 71 and 73. Other gas passes through louvers 37 of the tube 43 into the spit chambers 47 and 48, these various spit chambers acting to eliminate roughness and relatively high frequency sounds. Gas leaving the tube 43 enters the cross-over chamber 99 and passes upwardly to the intermediate owback tube 35. Heavy notes may pass through the imperforate tube 117 into the resonator chamber 105 and this action is compounded by means of the flanged tuning neck or opening 123 in partition 101 which connects the resonator chamber in a compound relationship with the resonator chamber 103. The gas that is flowing through the tube 35 is subjected by means of its louvers 37 to the high frequency spit chamber control of chambers 49 and 51 and flows into the cross-over chamber 89. Heavy notes still in the gas may pass through the imperforate connecting tuning neck 91 into the resonator or tuning chamber 87. The gas ilows toward the outlet through the tube 39 and from louvers 37 into the spit chamber of relatively large size 125 which lies between the partitions 25 and 27. The gas flows through tube 39 into the tube 111 and thence into the outlet bushing 19 from which it goes to the tail pipe and to the exhaust.

It may be noted that aligned apertures 124 in the headers and partitions are drain holes and may be formed at the bottom of all six internal partitions and preferably, for standardization, also at the tops thereof as shown. When all the internal partitions are provided with the drain openings 124, which are preferably about 1A diameter, water within the muffler will flow back and forth lengthwise of the mulller from the cool to the hot chambers as the muffler rocks back and forth slightly due to movement of the vehicle in which it is mounted. This water will be `vaporized by the hot exhaust gases and carried out by them without the need for any external drainage openings. The end chambers 87, 121, 103 and 105 tend to run cooler than the other central chambers and act as natural condensers but due to the lconnection of these chambers with the hotter central chambers by way of openings 124 the condensate will move to the central chambers and be evaporated, thus markedly reducing corrosion of the mulller. These features are of particular importance in dual mulller systems as the mulllers therein tend to be cooler and thus more likely to corrode.

Turning now to the form of mulller shown in FIG, 6, this mulller being designated by the reference number 141, it will be seen that there is found within the casing 143 of the mulller a subassembly which is identical to the subassernbly 23 and which will therefore be identified by the reference number 23', no further details of structure being mentioned since it is interchangeable with the unit 23 that has already been described. At the inlet end of the mufller 141 are a pair of transverse partitions 145 and 147. The partitions have inwardly and outwardly turned necks 149 and 151, respectively, vthrough which extends an imperforate tuning neck or tube 153 which is spot welded to both of the necks 149 and 151, being spot welded to neck 149 outside of the casing and to neck 151 inside the casing in accordance with assembly techniques discussed above. The partitions 147 and 145 also have flanged openings or necks 155 and 157 and through these extends a long inlet tube 159. The tube 159 is spot Welded to the neck 157 and projects beyond the partition 145 as shown at 161. It also projects a very substantial distance beyond the partition 147 toward the inlet of the mufller as shown at 163. The tube 159 may be of a lock seam construction and provided with spaced embossments 165 whereby it is readily turned into a tubular section from a ilat section and spot welded to the neck 157 on the embossments prior to being inserted in the casing. The tube 159 is provided with a set of louver openings similar to those previously described and shown in FIGS. 4 and 5, these being identified by reference number 167 and omitted from FIG. 6A for simplicity. The louvers 167 are located between the partitions 145 and 147 and open into the chamber dened by these partitions, this constituting a large spit chamber 169 and louvers 16'7a abut partition 145. Outwardly of the embossment 165 area, the tube 159 is provided with another set of similar louvers 171. Around the tube and around the set of louvers 171 is a pancake construction 173 of the same type as previously described pancakes 55 and consisting of complemental hal-Ves 175, as shown in FIG. 6A. The halves are flat sheet metal pieces bowled out and spot welded together around their flanges 176 to provide a spit chamber 177. The closely fitting ends 175a of the pancakes are spot welded to the tube 159. One ilange 176' is cut off llush with the periphery, as before, so that it fits snug against the casing. The halves are provided with flats 174 to decrease over-all size as indicated in connection with pancakes 55.

A flanged partition 181 at the inlet end has a flanged tuning neck or opening 183 that is larger than the tube 159 and the inlet bushing 185 which is spot Welded to the tube 159 at 187.

The partition 181 also has flanged openings 189 and 191. The space between the partitions 181 and 147 coustitutes a resonator chamber 193 and the space between the partition 181 and the inlet end header 195 constitutes another resonator chamber 195 which, being in series with the chamber 193, the two chambers act as a compound resonator construction. The header 195 is assem-l bled to the casing 143 after the parts already described have been inserted in accordance with principles outlined above and is interlocked as shown at 197 with the ends of the casing. The header 195 has an outwardly flanged neck 199 that is larger than the inlet bushing 185 so after assembly the bushing 185 is expanded as shown at 201 into tight engagement with the neck 199 and then it can be spot welded to the flange or neck 199. j

At the outlet end of muiller 141 there is a dished partition 203 which has a ilanged neck or opening 205 in which is spot welded imperforate tuning tube 207 prior to insertion in the casing. The space between the partition 203 and the partition 27 constitutes a cross-over chamber 209. Also spot welded to a neck 211 in the partition 203, prior to insertion in the casing, is the inlet bushing 213 and it will be seen that it slip lits over the projecting end 41' of the outlet passage tube 39. The outlet end header 215 can be placed over the bushing 213 and the periphery thereof interlocked at 197 with the end of the casing. The bushing 213 can then be expanded at 217 into tight contact with the neck 219 of the header 215 and spot welded to it. It will be seen that from this arrangement the inlet bushing 185 and the outlet bushing 213 both act to tie their

respective headers

195 and 215 to the internal parts of the mufller and thus serve to reinforce the heads against strain or blowout.

In operation, inlet gas enters the bushing 185 from the exhaust line of the engine and passes along tube 159 into the tube 43. As the gas passes the spit chamber 177 (in resonator chamber 193) certain of the high frequency sounds and roughness are removed. When it passes the larger spit chamber 169 some of the lower frequency roughness and noise is removed by passage through the louvers 167. In the tube 43 the gas is subjected to the action of spit chambers 47' and 48. Gas leaving the tube 43 enters the cross-over chamber 209 and some of the lower noise may pass through the imperforate tuning neck 207 which is in alignment with the intermediate tube 43' and be subjected to the action of the resonator chamber 221 which lies between the partition 203 and the end header 215. Gas passing through the intermediate passage 35 is subjected to the action of the spit chambers 49' and 51 and then passes into the cross-over chamber 223 between the partition 25 and the partition 145. Gas in the cross-over chamber 223 is subjected t6 the action of the compound

resonator chamber construction

193 and 195, the gas or sound waves passing through the tube 153 into the chamber 193 and from thence it can pass through the openings 183, 191, or 189 into the chamber 195, it of course being obvious that anything entering these chambers must be reflected back to the cross-over chamber 223 through the tuning tube 153.

VIn order to leave the cross-over chamber 223 for the eX- haust line, the gases must pass through the outlet pipe 39' and in doing so they will be subjected to the action of the large spit chamber 125. Gas then enters the outlet bushing 213 and passes onto the tail pipe and thence to atmosphere.

FIGS. 7 and 8 show a modified form of inlet end construction for a muiller 141', similar to mulller 141 as shown in FIG. 6, in which tuning occurs olf thek inlet tube 159. In this arrangement there is an imperforate 7' transverse partition 251 and a transverse partition 253 having a flanged opening or slot 255, a necked large opening 258, and smaller openings 257 which communicate the chamber 259 :between the partitions with the chamber 261 between the inlet header 195' and the partition 253, The partition 253 is of the particular shape that is seen best in FIG. 8. The inlet tube section 159 has a long series of louvers 263 preferably similar to those shown in FIGS. 4 and 5, these being omitted from FIG. 8 for simplicity. Supported on and around the inlet tube 159 is a pancake construction 265 which consists of the stamped identical halves 267 and 268 formed from initially at sheet metal. The flanges are intermediate web 269 and 271, respectively, of the halves are spot welded together to form a unitary section and the end necks 273 and 274 are spot welded to the tube in the manner that has already been discussed above in connection with the pancakes used to provide the spit chambers. The halves .are formed to provide a long split chamber 275 around the openings 263. Communicating with the spit chamber 275 is a fairly long tuning passage 277 (constituting with chamber 275 a long reverse bend passage) which lears gases from the spit chamber into the resonator chamber 259 where the gases are subject-ed to the tuning action of chambers' 259 and 261. The construction will serve in some applications to replace tuning from the crossover chamber 223 in the muliier of FIG. 6. The llange 269 is cut off on one side as shown at 269' to provide a snug lit to the side of the casing. The pancake 265 is supported by spot welding of the necks 273 and 274 on the tube 159 and also by spot welding of anged slot 255 thereto at points of contact 279. Partitions 251 and 253, tube 159', and pancake 265 may be put together as a subassembly and inserted into the casing prior to interlocking of head 195. Obviously the structure shown in FIGS. 7 and 8 could be modilied to include an inlet bushing expanded onto neck 199 and spot welded to tu'be 159 just as in FIG. 6, if desired.

FIG. 9 shows a modified pancake construction 301 for the subassembly 23 or 23'. In this arrangement the outlet passage 39" as well as the spit chambers 47, 48 49, and 51" are all formed in the two

complemental pancake stampings

303 and 305 which are spot welded together in the contacting lianges and

webs

307 and 309. The spit chambers are necked down in the same manner as before to contact and be spot welded to tubes 35" and 43". The outlet passage 39" formerly provided by

tubes

39 or 39 is, in this case, formed right in the

halves

303 and 305. Louvers 37 for passage 39 lare formed in the

halves

303 and 305. It is obvious that pancake 301' can be combined with partitions 25 or 27 (or 25 and 27') to form a spot lwelded su-bassembly 23 having the advantages and functions already described.

FIGS. -12 show another muier 401 embodying the principles of this invention. This muiiier has an outer shell or casing 403 consisting of a spirally wrapped double ply inner shell 402 which is interlocked at 405 to the inlet and

outlet end headers

407 and 409 and around which is disposed a single layer 404 of sound deadening metal which is attached in place after the partitions have been spot welded to the double wrapped shell 402, the friction between the two layers ldissipating sound energy. Disposed within the casing 403 is a tri-ow subassembly 23a which corresponds to the unit 23 that has already been described, the principal difference being that pancake spit chamber are provided around only one of the three tubes. The subassembly 23a comprises inlet and outlet side partitions 411 and 413 having three sets of aligned openings all of which are provided with outwardly extending flanges 415, 417, and 419. Spot welded in the sets of flanges are the inlet tube 421, the intermediate tube 423, and the outlet tube 425. Each of the tubes is provided with louvers, the tubes 423 and 425 having louvers 427 which are more or less tubular shaped while the tube 421 has louvers 429 that are shaped like the en a louvers 37 of FIGS. 4 and 5. Mounted on the tube 421 around the louvers 429 is a double pancake assembly 431 identical to those already described in connection with the other modifications and which provides a pair of spit chambers 433 communicating with the inlet tube 421.

Between the subassembly 23a and the inlet header 407 is a transverse partition 435 having an outwardly turned flange whereby it may be spot welded to the casing after insertion of the subassembly 23a. The partition 435 has a central opening provided with an outwardly extending ange 437 and this is aligned with the flange 439 around the inlet in the header 407. An inlet bushing 441 extends through the outwardly extending flange 439 and is spot welded to it. The inlet bushing is necked down at 443 and ared at its inner end as shown at 445 so that it slidably receives the outer end of the inlet tube 421 which is spot welded at assembly to it, the ange 437 and the bushing 441 also being spot welded together at a pre-assembly operation (i.e. before the parts are inserted in casing 403). The partition 435 also has a tuning tube 447 spot welded to the liange 449 of an opening therein which is aligned with tube 423, this being done prior to insertion of the partition 435 in the muffler casing. The partition 435 divides the space between partition 411 and header 407 into a resonator chamber 451 and a cross-over chamber 453.

On the outlet side of the subassembly 23a are three partitions455, 457, and 459, all provided with outwardly extending flanges so that they may :be spot welded to the casing after insertion therein. The partition 455 has an opening aligned with the outlet tube 425 and provided with an inwardly extending flange 461 to which is spot welded the -outlet tube 463. The outlet tube 463 is also spot welded in a neck 465 formed in the outlet header 409 and it slidably tits in a flanged opening 466 in partition 457 and extends through an enlarged opening 467 in the partition 459. The tube 463 is enlarged at its inner end and flared to slidably lit over the end of the tube 425 at assembly, the outwardly flared end engaging the ange 419 to control the location and insertion of the tube 463.

Aligned with the inlet tube 421 is a tuning tube 468 that is spot welded at a pre-assembly operation to the flange 469 in partition 455 and after assembly to the outwardly ange 470 of partition 457, the outer end of the tube 463 terminating in but being spaced from the flanged edges of an opening 471 in the partition 459. The partitions 455, 457, and 459 dene with the partition 413 and the outlet header 409, a series of chambers which in FIGURE l0 are from left to right as follows: a crossover chamber 472, a large spit chamber 473, a resonator chamber 474, and a resonator chamber 475 which is compounded with the resonator chamber 474 through the openings 467 and 471 in the partition 459 as well as by a flanged opening 476 in partition 459 (the anged openings in the partition 459 acting as tuning necks). Louvers 477, similar to louvers 37, in the tube 463 open into the spit chamber 473.

The opposite sides of the muli-ler casing 403 may, in the region of chambers 451 and 475, be provided with inwardly extending embossments or beads 478 to prevent iutter of the side walls and the inlet bushing 441 may have a pair of indentations 479 formed therein on opposite sides as stops for the pipes to be inserted therein.

In operation of the muiiier 401, gases enter the inlet bushing 441 and pass through the tube 421 where some of the higher frequency sounds are silenced in spit chambers 433. Some of the gas passes through the tube 468 where lower notes are silenced in the resonator chambers 474 and 475 but this gas must return through the tube 468 and with gas from the outlet of the tube 421, enter crossover chamber 472 and reverse its direction to pass through tube 423 wherein additional silencing is accomplished by communication through louvers 427 with the large spit chamber 400 between the partitions 411 and 413, some back pressure reducing cross bleeding occurring from tube 423 to outlet tube 425 through chamber 480. Gas leaving the tube 423 enters cross-over chamber 453 and communicates through rtuning tube 447 with a resonator chamber 451 where further low notes may be removed. From cross-over chamber 443 gas passes rearwardly through tube 425 and out of the muiiiler through the bushing 465 after additional silencing in spit chambers 480 and 473 takes place through communication with these chambers by way of louvers 427 and 477,

To permit condensed water to ow to the relatively

hot chambers

472, 453, and 480 the six partitions in the muffler 401 are provided with small (14 diameter) drain holes at their midplane at the top and bottom thereof as seen at 481 in FIG. l2, the inlet and

outlet headers

407 and 409, however, being imperforate. This arrangement provides for internal drainage of water that accumulates inside the casing 403 so that the hot gases passing through the muiller will evaporate the water and pick up the resulting vapor and carry it out yof the muiiier.

FIGS. 13-17 show another modied form of muffler 501 using a tri-iiow subassembly 23h similar to the assemblies already described. This muflier has a casing 503 t-o the opposite ends of which are interlocked, after insertion of all the inner parts, the inlet and

outlet headers

504 and 505, respectively. The subassembly 23h comprises the inlet side partition 506 and the outlet side partition 507 each of which have outwardly turned peripheral flanges whereby they may be spot welded in place in the casing 503 after insertion. The partitions 506 and 507 have sets of aligned holes provided with outwardly extending iianges as shown at 508 and 509 to which are spot welded the inlet tube 510 and the return ow tube 511, respectively. The tubes 510 and 511 have rows of louvers 512, 513 formed therein opening into the charnber 514 :between partitions 506 and 507. The partition 506 has a central opening provided with an outwardly turned iiange 515 to which is spot welded the end of an outlet tube 516. The outlet tube 516 has three sets of

louvers

517, 518, and 519 all of which are similar to louvers 37. The louvers 51S and 519 are encased by a pancake subassembly 520 of the type already described in detail which forms small volume spit chambers 521 and 522 around the outlet tube, the louvers 517 opening directly into the relatively large volume chamber 514. The pancake 520 projects through the double diameter neck 523 formed in partition 507 and which has a shape best seen in FIG. 17, the at sides of the pancake being paral- -lel to at sides of the opening.

On the inlet side of the subassembly 23h are two partitions 524 and 525 each of which has an outwardly turned ange so that it may be spot welded to the casing 503 after it has been inserted therein. The partition 525 has an inwardly extending flange 526 around an opening that is aligned withthe outlet tube 516 and to which is spot welded the inner end of a tuning tube 527 prior to insertion of the partitioin 525 in the casing. The outer end of the tube 527 is supported on and spot welded at assembly to the flange 528 in the partition 524. The partition 525 also has an inwardly turned flange 529 around an opening that is aligned with the inlet tube 510 and to this ange is spot welded, prior to assembly, an inlet tube 530. The tube 530 is necked down at 531 and flared at its inner end so that it can readily slide over the projecting end of the tube 510. The tube 530 is provided with two sets of louvers 532, similar to louvers 37, and these open into spit chambers 533 provided around the tube 530 by the pancake assembly 534 of the type already described. The outer end of the tube 530 extends through a tuning neck 535 of larger diameter than the tube and over its outer end is slipped the end ofthe inlet bushing 536 which is spot welded to the tube 530 on the outside of the header 504 as indicated -at 537, the bushing 536 having been spot welded to an inwardly flanged neck 538 on the head 504 at a pre-assembly operation. The partitions 524 and 525 act with the inlet header 504 and the 10 partition 506 to define the chambers 540 and 541 which act as a compound resonator chamber connected by tube 527 with the cross-over chamber 542. Another tuning neck 543 is formed in partition 524 to act with the neck 535 to intercommunicate the chambers 540 and 541.

At the outlet side of the subassembly 23h is a partition 544 with an outwardly turned flange so that it may be spot welded to the casing after insertion therein. This has an opening aligned with the outlet tube provided with an outwardly extending ilange 545 in which are seated the embossments 546 formed on the outlet tube 516 and which embossments are spot welded to the ange 545 at assembly. The outer end of the outlet tube 516 is enlarged as seen at 547 and spot welded to the outlet neck 548 formed integrally in the outlet header 505. The partition 544 acts with the outlet header 505 to provide a spit chamber 549 that communicates with the outlet tube 516 through louvers 550, similar to louvers 37, in the outlet tube. It acts with the partition 507 to deiine a lcross-over chamber 551 connecting the inlet tube 510 and the intermediate tube 511.

In operation, exhaust gas enters the inlet bushing 536 and passes through the inlet tube 530 wherein certain high frequency noisesand roughness are removed by the spit chambers 533. In passing through the inlet tube 510 additional noise is removed yin the large spit chamber 514 by passage through louvers 512. The gas leaving tube 510 enters cross-over chamber 551 and reverses direction to pass through tube 511 back toward the inlet of the muier. During passage through tube 511 certain noise and roughness is removed in chamber 514 by communication therewith through louvers 513. Gas leaving the tube 511 enters the cross-over chamber 542 and reverses direction to enter the outlet tube 516. The gas in the cross-over chamber 542 and the outlet tube communicates with the compound resonator provided by chambers 540 and 541 through the tube 527, which is aligned with the outlet tube 516, so that heavy notes or low frequencies will be removed. Gas passing through the tube 516 passes by the louvers 517 which connects the gas with chamber 514. High frequencies and roughness still remaining in the gas are removed in spit chambers 521 and 522 and finally in spit chamber 549.

It will be noted that the gas in cross-over chamber 551 4can communicate through a tuning neck 523 with the chamber 514 so that this chamber acts to some extent as a tuning chamber to remove tones or notes `by virtue of this connection and as a spit chamber to remove roughness and noise by virtue of communication with the three tubes through

louvers

512, 513, and 517. It will also be seen that cross bleeding from tubes 510 and k511 land chamber 551 to louvers 517 in outlet tube 516 will lower back pressure.

Drain holes on opposite sides of each of the tive interior partitions are provided as shown at 552 and these will give internal or inter-chamber drainage via the hot gases as already explained. Additionally, a very small hole 553 (1/16-13" diameter, preferably 3/32 diameter) may be provided in the outlet header on the bottom side of the muflier to provide for external drainage, this hole being so small that it does not affect the acoustic characteristics of the chambers within the muier, especially the chamber 549, (Le. acoustically the muiiier shell is substantially imperforate) but at the same time being large enough to permit water to leak out of the muier when the muier is cold and there are no hot gases to evaporate the water.

Another modified form of muiiier 601 is shown in FIGS. 18-21 in which a tri-iiow type subassembly 23C is preassembled and inserted as a unit into the casing 603 prior to closing of the ends of the casing by interlocking the inlet and outlet headers 605 and 606 to the ends of the casing as shown at 607. The subassembly 23e` includes an inlet side partition 608 and an outlet side partition 609. The partition 608 has three openings formed ll l therein for the support of tubes, the flanges around these openings being designated by the reference numerals 610, 611, and 612, respectively. The partition 608 also has a series of relatively large and non-restrictive openings 613 formed therein. The partition 609 has three flanged openings to support tubes Which are aligned respectively with the anges 610, 611, and 612, these annular flanges being designated by the reference numerals 614, 615, and 616, respectively. Supported in and spot welded t-o the flanges 610 and 614 prior to insertion of the subassembly 23C is an inlet tube section 617; spot welded to flanges 612 and 616 is an intermediate tube 618; and spot welded to the flanges 611 and 615 is a combination tuning tube and outlet tube 619. The tubes 617 and 618 have louvers 620, similar to louvers 37, formed therein and these are covered by pancake units 621 similar to those already described but which provide single spit chambers 622 around the tubes. The tube 619 has relatively large and unrestricted openings 623 formed in the rear portion thereof, the front portion being imperforate.

On the inlet side of the subassembly 23C are the partitions 624 and 625 each of which have outwardly extending peripheral flanges so that it may be spot welded to the casing after insertion therein. The partition 625 has three openings formed therein delined by the flanges 626, 627, and 628. Spot welded to these flanges prior to insertion of the partition 625 into the casing 603 are the short tuning tube 629, the long tuning tube 630, and an expanded tube 631, all of these tubes projecting to some extent beyond the outlet side of the partition 625 and the tube 630 being adapted to slide within the flared enlarged end 632 of the tube 619 and the tube 631 being ared and adapted to slide over the end of the tube 617 when the partition 625 is inserted in place in the housing 603. The partition 624 has an outwardly extending flange 633 around an opening that slips over the tube 630 when the partition 624 is inserted in the casing after which the ange 633 is spot welded to the tube 630. Prior to such insertion the tube 629 is spot welded adjacent its outer end as shown at 634 to the tube 630. The partition 624 also has a necked opening 635 which slips over tube 631 when the partition is put into the casing 603.

Within the tube 631 is an inlet tube 636 which is illustrated as being of the same diameter as the tube 617 and aligned with it. It will be observed that the tube 636 has louvers 637 formed in it and these may be similar to louvers 37 already described. However, the outer diameter across the louvers 637 is no greater and preferably slightly less than the enlarged outer end section 638 of the tube 636 which slides within a portion 639 of tube 631 and is spot welded to such portion. The tube 631 is expanded at 640 opposite the louver 637 to provide a spit chamber 641 surrounding the tube 636 and coextensive with the louver 637. The inner end of the tube 631 is necked down at 642 to fit in the annular flange 628 and be spot welded thereto in a pre-assembly operation as previously indicated. The inner end 643 of the tube 636 has a slide tit in the portion 642 and it will be apparent that the tube 636 can be inserted at assembly through the outer end of tube 631 and spot welded to the portion 639. The portion 639 may be spot welded to the inner end of the inlet bushing 644, the outer portion of which is radially expanded on both sides of the flanged opening 645 in the inlet header 605 and spot welded thereto. It will be noted that the use of the expanded outer tube 631 in conjunction with the inner tube 636 provides an inexpensive method of forming a spit chamber of substantial length around the inner tube and one which takes up somewhat less space than the pancake assemblies illustrated hereinbefore. It is also capable of standardization so that it can be used in various mulfler At the outlet end of the muffler 601 are the

partitions

647 and 648 each with outwardly turned flanges so that they may be spot welded in place to the casing after insertion. The partition 647 has an inwardly extending 12 ange 649 defining an opening in alignment with the tube 619 and spot welded at a pre-assembly operation to the flange 649 is an outlet tube section 650 which is necked down and flared at its inner end to slip over the end of tube 619. Over the outer end of tube 650 is slipped the inner end of a bushing 650e which is spot Welded to the flanged outlet neck 651 on the outlet header 606. The tube 650 has a series of louvers 652, similar to louvers 37, formed therein and mounted on the tube and bushing is a pancake assembly 653 which provides a spit chamber 654 around the louvers. The pancake assembly 653 is similar to those already described and extends through and is supported by a flanged opening 655 in the partition 648, the shape of the opening 655 being best seen in FIG. 21. On the outlet side of the louvers 652 is mounted a restrictor member 656 in bushing 65001 which consists of a reversely bent tube section, the outer portion of which is spot welded to the tube 650 at a pre-assembly operation and the inner portion 657 of which reduces the eifective area of the outlet tube to serve with the tuning or resonator chambers to help silence pulses and beats.

The partition 647 has an inwardly flanged opening 661 formed therein to which is spot welded a tuning tube 662. The tube 662 extends through the outwardly extending flange 663 of an opening in the partition 648. Partition 648 also has a tuning neck 664 formed therein.

In operati-on of the mutller 601, gas enters thev inlet bushing 644 and passes through tube 636 where roughness -and high frequency noises vare removed in the spit chamber 641. They are further removed during passage through tube sect-ion 617 in the spit chamber i622. On leaving the inlet tube 617 the igases enter the cross-over chamber `671 between

partitions

609 and 647. In this cham-ber they communi-cate through tuning tube 662 with a resonator chamber 673 between the outlet header 606 and the partition 648 and also through tuning neck 664 with a resonator chamber 674 between

partitions

647 and 648, the chambers 674 and `673 thus acting as a compound resonator. Gases in cross-over chamber 671 reverse direction and pass through tube 618 wherein they are subjected to the action of the spit chamber 622. On leaving tube 618 they enter a cross-over chamber 676 between the partitions 625 and 608. Gases y-in the cross-over chamber 676 are subjected to the action of a resonator chamber 677 between partitions 624 .and 625 thnough the tuning neck 629 which .is offset from the axis of the tube 618. The gases in crossover chamber 676 pass through the non-restrictive openings 613 into the chamber 678 between partitions 608 and 609 and from there through nonrest-rictive openings 623 yinto the t-ube 619 from which they can ow through tube 650 and restrict-or 657 to the outside of the muiler, being subjected to the action of spit chamber 654 on the way through the tube 650. Gases in the tube 623 are also subjected to the action of the resonator chamber `68() between the inlet header 605 and the partition l624 by means of the tube 630 and the front portion of the t-u'be 619. It will be observed that by providing openings 613 in the partition 608 to Iget flow into the -outlet tube through the volume of chamber 678, it is possible to make the tuning tube, pr-ovided by a section of tube 619 `added to the Itube 630, lof unusually long length. This enables low frequencies to be removed in a relatively short muffler.

FIGS. 22-26 show another form of muffler 701 having a casing 703 with the ends in-terlocked at 705 with the inlet header 706 and the youtlet header 707. Within the casing 703 ,is a .subassembly 23d correspon-ding in most respects to the subassemblies of this type previously described. Thi-s subassembly includes an inlet side partition 708 and an outlet side partition 709, Iboth 4having outwardly turned ilanges whereby they can be spot welded to the casing after inserti-on. The partitions '708 and 7 09 have .aligned openings defined by anges 710 in which is mounted an inlet tube section 711 which is spot welded yin the subassembly to the flanges 710. The tube 711 is provided with louvers 712 opening xinto the chamber 7.13 between the

partitions

708 and 709. The partition 708 has an intermediate openin-g defined by a flange 714 in whi-ch is supported and spot welded the end of an outlet tu-be 715. The outlet tube 715 has three .sets of louvers 716, similar to louvers 37, each of which opens in'to a zspit chamber 717 forme-d by the pancake assembly 7118 which is similar to the pancake assemblies already described. The thirdunit of the pancake assembly extends through the inwardly turned neck 719 of an opening in the partition 709, the shape of the neck 719 being best seen in FIG. 26. The outer end of the pancake assembly 718 extends linto a cross-over chamber 721 formed between the partition 709 and-an imperforate partition 722 which has an outwardly turned llia-nge whereby it can be spot welded t-o the shell after insertion. Partition '722 4has an Aannular ange 723 in which are seated the embossments 724 that are .formed -on the tube 715' and which are spot welded tothe flange at assembly. The tube 715 has a set of louvers 725, similar to louvers 37, opening into `the chamber 726 between the partition 722` and the outlet header 707, the chamber 726 thus being a spit chamber. The end of the tube 715 is spot welded to the inside of the drawn outlet nipple 727 on the outlet header 70-7.

On the inlet side of the subassenibly 23d are partitions 729 and 739 each having out'wardlyturned danig/es so that they can .be spot welded to the shell after insertion. The partition 739 has a central opening `defined by a arige 740 in which is spot welded -a tuning tube 741 'that is somewhat larger than the outlet passage 715 but generally aligned with it, though the laxes are offset from each other. The partition 739 also has an opening define-d by the flange 742 in which is spot Welded at pre-'assembly the inlet tube section 743, the end of the section 743 being necked Kdown and flared to fit over the end of the tube 711 and abut .the ange 710 as seen in FIG. 22. The tube 743 has two .sets of louvers 745 which open into the two split chambers 746 yfor-med 'by a pancake assembly 747 of the type already described. The tube 743 extends with substantial clearance through a tuning neck 749 in the partition 729 and its outer end is supported in and spot welded to the end of an inlet bushing 751 which is expanded and spot welded to the outwardly turned flange 743 of the inlet header 706. The partition 729 has an outwardly turned tiange 755 which at assembly tits over .the end of the tube 741 and is spot welded to it.

In operation of the muffler 701, igases enter the inlet bushing 751 and pass through the tube section 743 wherein high frequencies, noises, and roughness are removed in the spit chamber 746. Additional silencing is accomplished in chamber 713 las the gases tgo through tube section 711 and pass through louvers 712 into chamber. lGases leaving the tube 711 enter the crossover chamber 721 and can pass through the neck -719 or through an opening formed by an outwardly turned flanged 757 into the chamber 713. Aligned with the opening 757 is a somewhat larger opening provided by an outwardly turned neck 759 .in the partition 708 so that it will 'be seen that the lreturn passage .is provided by the volume of chamber 713 rather than by -a tube as in the previous embodiments. Gas leaving the chamber 713 through opening 759 enters a cross-over chamber 761 between

partitions

739 and 708 and can then enter the outlet tube 715 and be subjected therein to the action of the ispit chambers i717 and 726. Low notes in the chamber 761 are subjected to the action of .the tuning tube 741 which connects them to the compound :resonator formed by the chamber 763 between header 706 and partition 729 which in turn is connected through tuning

necks

765 and 749 to the chamber 7167 between partitions 729 and 739. It will be noted that cross bleeding to opening 759 is provided through louvers 712 and opening 719 thus enabling -opening 75.7 t-o be reduced in :size over lopening 759 and providing noise elimination wit-hout an increase in back pressure. The volume passage gas iiow between 757 and 759 in combination with the resonators 763 and 767 land the lange size '(high energy absorbing) tuning tube 741 will be especially effective in eliminating the otherwise exceptionally loud torque converter Ipower note.

Each of the ive partitions is provided with drain holes 769 at the top and bottom thereof adjacent the casing 703 :so that water can slosh from the end-s of the casing Yto the middle as the muffer .is rocked back and forth by movement of the automobile. The water Within the cooler chambers 763, 767, and 726 can thus 'ow to the chambers 761, 713, 4and 721, which are hotter due to the circulation of :gases therethrough, and be vapor-ized to pass `out of the muffler through tube 715. Direct liquid drainage to atmosphere can also be accommodated by a small hole 771 at the bottom of the outlet header which is of such a small size as not to permit lgas leakage, cau-se spitting or hissing, or adversely affect the acoustic characteristics lo'f the fnruier. The hole 771 is intended only to let the water leak outwhen the muffler is cold, eig., when the auto is stopped or just starting and should preferably be no larger than 1/8" diameter. It could be put in the 4casing wall '703 on the bottom side of the muiiler.

It will now be recognized that the invention provides many important improvements in the muffler eld. Costs of manufacture are reduced by the arrangements of structure which permit subassemblies to be made up outside of the casing and then inserted as units into the casing. The various pancake designs reduce cost over presently used methods and the combination of tubes 631 and 636 (FIG. 18) is an important innovation from the standpoint of cost reduction and standardization of parts. A very important feature which should be of great interest to the motoring public, as it will double or triple the life of a muffler, is the provision for inter-chamber drainage whereby the cold water collecting chambers are connected through drain holes in the partitions to the hot gas circulating chambers with the result that the water is vaporized as it sloshes back and forth during motion of the car and does not have an opportunity to eat out the muffler shell or the interior parts. This action can be enhanced by use of a layer of asbestos sheet in the shell constru-ction, such as disclosed in U.S. Patent No. 2,761,525 and assigned to the assignee hereof, as the asbestos wrapping will cause the mufer to run at a higher temperature thereby facilitating vaporization. Also very important is the way the various parts are tied together and to the end headers of the mufers to provide great strength that will resist blow-outs and backres. For example, three different methods of rigidly supporting the end headers by spot welding at a considerable distance lengthwise of the muffler away from the plane of the vibration (plane through interlocked joint, eg. 9) are shown, these methods giving a very high resisting moment to bending at the head neck radius and eliminating fatigue failures due to repeated bending. Among other illustrations, FIG. 1 shows the expanded bushing method; FIG. l0 outlet header shows the drawn head method; and FIG. 13 inlet header shows the inner ange header and bushing method. A further feature adding strength to the muffler is the use of several spot welded transverse partitions, some of which may be contoured, which not only form acoustic chambers but brace the oval casings against drumming. The embossments 478 also help to prevent drumming. n

From the operational standpoint, it will be noted that back pressure is at a minimum due to the relatively large gas tubes and cross-over chambers along with arrangements permitting cross-bleeding, especially cross-bleeding to the outlet tube. The constructions are such as to provide complete sound elimination for any given application. Several spit or filter chambers of different volumes are provided to eliminate noise and roughness over a frequency range from low to high and the harsh bark of modern high compression engines. The resonator chamber and tuning tube arrangements eliminate power notes, second harmonic beat frequencies, road load harmonics, run down noises, etc. Various features provide for high energy absorption; eg., the large tuning tubes or the restrictor of FIG. 18 and effective sound cancellation will be obtained in the non-turbulent tri-ow chambers over Wide speed ranges.

It will be recognized that modications may be made in the specic structures shown herein by way of illustration Without departing from the spirit and scope of the invention.

What is claimed is:

1. In an exhaust gas muffler, a casing having a closed end, a rst transverse apertured partition spaced from the closed end and dening therewith a first chamber, a second imperforate partition spaced from the first and delining therewith a second chamber, a tube extending through said partitions and closed end and opening outside of the casing and having louvers-in the portions thereof within each of said two chambers, and means defining a reverse bend passage surrounding said louvers and receiving all gas therefrom, said passage opening into the second of said chambers and constituting the only inlet and outlet for it and for the first chamber.

2. The invention set forth in claim 1 wherein said reversed end passage is provided by a pair of mating cavities in complemental pancake stampings spot welded together around a flanged periphery and embracing and spot welded at opposite ends of the tube, said stampings fitting within and supported by a'flan'ged slot in the rst partition.

3. In an exhaust gas muffler, a casing, a perforated gas passage tube in the casing, a combined spit chamber shell and tuning tube member mounted on said tube and surrounding perforations in said tube, said member comprising complementary halves having flanges secured together along a midplane of the tube, said halves dening an annular spit chamber space around the tube extending substantially the full length of the member and a tuning passage extending substantially normally to said tube and then turned to extend parallel to said tube and running subst'antially the full length of the member, said member including mating flanges on said halves secured together to separate the spit chamber space and the tuning passage.

References Cited by the Examiner UNITED STATES PATENTS 2,070,543 2/1937 Cary et al. 181-54 2,235,705 3/1941 Haas 181-54 2,580,564 1/1952 Ludlow 181-59 X 2,934,161 4/1960 Powers 181-53 RICHARD B. WILKINSON, Primary Examiner.

LOUIS I. CAPOZI, Examiner.

R. S. WARD, Assistant Examiner.

Claims

1. IN AN EXHAUST GAS MUFFLER, CASING HAVING A CLOSED END, A FIRST TRANSVERSE APERTURED PARTITION SPACED FROM THE CLOSED END AND DEFINING THEREWITH A FIRST CHAMBER, A SECOND IMPERFORATED PARTITION SPACED FROM THE FIRST AND DEFINING THEREWTIH A SECOND CHAMBER, A TUBE EXTENDING THROUGH SAID PARTITIONS AND CLOSED END AND OPENING OUTSIDE OF THE CASING AND HAVING LOUVERS IN THE PORTIONS THEREOF WITHIN EACH OF SAID TWO CHAMBERS, AND MEANS DEFINING A REVERSE BEND PASSAGE SURROUNDING SAID LOUVERS AND RECEIVING ALL GAS THEREFROM, SAID PASSAGE OPENING INTO THE SECOND OF SAID CHAMBERS AND CONSTITUTING THE ONLY INLET AND OUTLET FOR IT AND FOR THE FIRST CHAMBER.