US2357791A - Silencer - Google Patents

Description

Sept. 5,' 1944. w. H. POWERS S ILENCER 5 Sheets-Sheet 2 Filed March 24, 1941 Sept. v5, 1944. w` H. POWERS 2,357,791

sILENcER Filed March 24, 1941 5 Sheets-Sheet 3 SePt 5, 1944- w. H. POWERS 2,357,791

SILENCER Filed March 24, 1941 5 Sheets-Sheet 4 JJJJ 14 Egli. 14,7 274 2.9: 94,72 258, 235 2go gigi@- Sept. 5, 1944.

` W` H. POWERS SILENCER Filed March 24, 1941 5 Sheets-Sheet 5 NVENTOR Patented Sept. 1944 SILENCER walter n. rowers, Jackson, Mich., signor to Walker Manufacturing Company of Wisconsin,

Racine, Wis., a corporation of Wisconsin Application March 24, 1941, Serial N o. 384,791

12 Claims.

The present invention relates 4to silencers, and

in particular is directed to the provision of silencers for automotive service.

The principal objects of the present invention are to provide sllencers embodying a primary discharge path, resonator structure associated with the path, and improved means for placing the resonator structure in acoustic communica- 'tion with the primary path; to provide such structures characterised in that a dynamic or velocity head developed by the gas stream during its now through the primary path is utilized to drive part of the stream into the resonator structure; to.

provide such structures characterized in that a conduit forming part of the primary exhaust path opens directly into an otherwise closed resonator chamber, said conduit having an outlet in the side wall thereof through which gases mayl ow after being subjected to the action of the resonator chamber; to provide silencer strucune IAA- MA er rig. 15;

Fig. 14B is a fragmentary view taken along Fig. 9 is a view in section taken along the'linef'w 9--8 of Fig. 8;

Fig. 10 is a fragmentary view, illustrating the third gas passage of the structure of Figs. 8 and 9; Fig. l1 is a fragmentary view, taken along the line Ii-ii of Fig. 12, illustrating a modification of the structure of Figs. 8, 9, and 10;

Fig. 12 is a view taken along the line i2-I2 of Fig. l1;

Fig. 13 is a view in longitudinal central section of a. further modification of the invention; f Fig. 14 is a view in section taken along the line iI-Il of Fig.13:

Fig. 14A is an enlarged the line MBV-I 4B o! Fig. 14A; Fig. v15 is a fragmentary view, illustrating th third gas passage of the structure of Figs. 13 and tures embodying the aforesaid dynamic tuning features wherein the primary path of gas iiow is of the retroverted type; to .provide such structures wherein the primary path of gas flow is of the straight-through type; to provide such structures wherein the direct or dynamic tuning fea.- ture enables certain economies and simplifications in a manufacturing sense; and to generally improve the construction, arrangement and op eration of silencers.

With the above as well as other objects in view,Y

which appear in the following description and in the appended claims, preferred but illustrative embodiments of the invention are shown in the accompanying drawings, throughout the several views of Y which corresponding reference characters are used to designate corresponding parts and in which:

Figure 1 is a view in tion of a silencer embodying the invention;

Fig. 2 is a view in vertical transverse section taken along the line 2-2'of Fig. l;

Fig. 3 is a view in longitudinal central section of a modified embodiment of the invention;

Fig. 4 is a view in yvertical transverse section taken along the line 4 4 of Fig. 3;

Fig. 5 is a view in longitudinal section of a further embodiment of the invention;

Fig. 6 is a view taken along the line B-. oi Fig;

Fig. 'l is a fragmentary sectional view, illustrat. ing the third gas passage of the embodiment oi Figs. 5 and 6;

Fig. 8 is aview in longitudinal central section of a further modication of the invention;

longitudinal central sec- Fig. 18 is a view in longitudinal central section oi! a'further modification of the invention;

Fig. 17 is a view taken along the line I'i-Il of Fig. 1li;A

tion of a further modincation of the invention:

and v Fig. 19 is a view takenv along the line IS-IB of Fig. 18.

It will be appreciated from a complete understanding of the invention that the improvements hereof may be embodied in silencer structures of widely varying constructions, intended for widely differing purposes. By Iway of illustration of preferred embodiments, the present improvements are herein illustrated in connection with silencer-s specifically designed for automotive service.

Referring first to the embodiments of Figs. l

and 2, the silencer comprises 'an outer shell It of elliptical form, having end heads 32 and 34'. The

head l2 is provided with a neck through which a silencing structure comprising the previously view taken along the Fig. 1s is a view m longitudinal central se'c-4 2' i. mentioned lonclmdmauyextendmgoonduits n and 42 and an additional conduit Il, which con-V witiiin ponent-msy be expected to-by-pass the moss` ,duits are supported within the silencer by means oi' partitions' 68,43, it, and 52.- Il is perfor-ate, one 'relatively large opening 54 therethrough being shown, and, with the head 32 The partition and the partition". forms a compound reso-- nator chamber-ll within thev shell, -wl'lichcom-` municates. with the balance oi `thefailencini;

- structure'only through the opening` at the end Il of the conduit-M, which end projects into the just-mentioned Aand v consti- The partitions 48 connecting portions o! the shell, denne a cross over I8, which provides a gas 'path between the conduits M and '42. The'partition vli'ianti en'd Y head Il, in turn, together with the connecting sito` so, together with the suonano; onsmbor n. another ooin.

over 6l, and it is possible, also, that some reverse ilow oi gases occurs through the louver openings 6I. It is possible, also. that certain parts of the.

gas stream. which pass out of the conduit 38 or M through the corresponding louver openings.

directly re-.entersuch conduit through such lou;v

ver openings.v

The pressure pension thereof within the relativelylarge cham..

portions of shell" l0, -deiine va crossover B l,

.which mm BBS Path'between the righthand endsoi'theconduitsldandlgx. v e.

, In addition, the partitions,"

acoustic communication with the` interiorsof .the

:indultos-ether jj with-the'connectlon portionsoffme shell. dennean additional silencing chamber I2. which is m1 conduits 3 8and Il throughthe louvre openings g 84 formed in the side wallsthereof.. 'I'he louvre openings 64 may, in the broader aspects oi the invention. be variously arranged, but preferablythese louvre openings taire-the tangential forniv 01' purposes ber I2.- Itl may be expected. also. that some de- ,struetive interference is caused by the' reJoinde'r. o vinthe conduit Il, of the two components, which i pressure oi further attenuates the entiregas stream. ,Y

" The partially silencedr zas of this velocity head,` is directed in'llfge Part at lcastpait the outlet 'il and thence 4through the tuning-neck il into the resonator i5. Each pres- -V sure peak entering Athe resonator 55,"01 course,

and arrangement described in, Gunn Patent Netv-A 1,949,074, which is f as the' present application.

In 'accordance with the invention. also.

' the conduit 42 `is provided. betweenthe partitions il 52,'.with' an intermediate shell B6. The

space4 between conduit 411 and EE is 'dividedinto two separate chambers GtA and l by partiticnszl; 14 and'; The chambersfi" and' 1l are isolated from-the balance oi" thefsilencerstructure; except for Athe isicousticmim-v municationfbetween these' chambers-and the in terior of theconduit 42', which is provided by' means cithelouvre openings 8l provided in the side walls oithe conduit 52, and .whichlouv'ie 45 openings preferably' have the romand-errang@ mont oithepreviously described louvre openings,- 1'- It'will be noticed 'that the conduit M extends from the crossover- 8d ,throughthe crossover '58 and terminates in the previouslyv described 'como poundy resonator chamber 5o..' In order m prof vide communication between the interioroi thev conduit. M and the crossover 58, the conduit 45 is provided'with a gas outlet within the crossovm'- More specically, this gas outlet takes o rt wm to" tesy matta-economi u myrte. regarded as having s,l forcingportion, lying tothe 1 right ci the outlet 1l, and-as ha'vingajtuning 1 neck portion 88; lying to the left ot the outlet 18.

The'velocityhead. which imparts drivingiorce by which'thestream is driven into the reslonator,l is built uli.wii..hin the lust-mentionedv forcing portion aridv the length -of this portionsA therefore, determines the degree of this drivin force.

'or range of frequencies; which such resonator chamber is en ective' `tc'silence.

Y in' the Apresenti;.'sun'rancemerit,. the compound t resonator El is proportioned toattenutorni o! a plurality ci eircumierentially and an; j

iallv distributed openings 18, which, in the embodiment now being described; preferably-have' a. large enough total areafso as to not substan tially restrict the flow ci ses from the conduit M' intothecross'over 38. Y. Considering notv the operationof the struc wreef Figs. 1 and 2, 'it will he' appreciated that the exhaust sasl stream discharged from theengine into the inlet ailofded by, the condmt 36.

ate those freouenciesjvhich, in automotive practice.y are'usually to as "note"; that is to Y* say. those soundshavins 'frequencies falling, for

example, in the range-trom 40`to 110 cycles per second and tliegharmonics' thereof.'

' Theproportioningoi theconduit and related elements ofthe structureare preferably so proportioned that`the.driving.'iorcezhuilt up in theV v forcing portion thereo'fiis-fsuiiicient to drive a substantial part, if'nct all;oithe gas stream past posses to thought along solo conduit mvo the f `conduit Il.

A major component of this gas stream may.' by virtue of the velocity head there-1 the louver openings Si in the side; wall of the con-f duit de, he expected to pass directly' through the conduit '38 into' the crossover Si, from whence the gases ow toward the left through the conduit 45,' By virtue ci the louver openings 6d in those portions of the conduits 563 and 38, which lie of, and by' virtue of the restriction afforded by the side mitlet it, therebyffsubjecting substa'ntiallsz'if not all, oi the zas stream to the silencing effect of the` resonator B5. This forcing action has been foundinpractice to very ymaterially increase the `eilectiveness-oi'-resonatorstruc'- The above-mentioned rejcinder. o: the outflow l.

from the resonator and theon'comlng gas stream occurs in the regionpf theoutlet 18, and y the resultant ses stream then passes through the outlet 'id into the crossover 5B. From the crosspulsations in that component o! the gas stream which passecthrough the cham- "beriareattenuatedinpartinpassingthrough the'louver openings N, and-innert bythe ex stream.- whichl may, of description, be regarded as up of a'succession-oi pressure peaks alternating with valleys, develops a substantial velocity-head within the conduit M and, under the iniiuence length and cross-sectional'area' ofthe tuning neck portion It; on the otherhand;

inconiunction with the volume of the compound resonator chamber Si. 'determine the frequency` referred toasthe unpitchedsounds.

Y assvmi msainemnmnnusnysusnirusimm passesthroughtheeonduitl! to'thssilencer out- 'ilet Il. Portions of the gas stream passing throughtheconduit I! alsopassintoandoutof thesrnallehambersllandltwhicmaswillbe understood-'serve to silence what vmami iss cooperate with uis sneu to denne a transverse passage or crossover AIII into which the lefthand end f the Outlet conduit I directly l opens. The partition ill is additionally provided with one or moreopenings, such as I, therein which ailord communication between the crossover `IM and an expansion chamber ill.

' In 'the modiiled embodiment of the invention showninFigs.8and4,thesilencercomprisssan.

v' outerahell 8l. having end heads l2 and u, which enelosethe endsofthe shelland also accommo.v 'i

date theinlet nipple Il' and the outlet nipple Il'. As before. also,` the silencer is provided with a primary gas passage, comprising the conduits ss, ss and n. which are supported wiinm die v silencer bymeans ofthe partitions, Il, Il l and --llt .The partitions It and as. together with the shellilandtheheadthdeilneacompoundresmater-ist. The partitions Il and Ill, together 'ith the shell, denne a crossover lll. The Darftition i Yand thevhe'a'd u cooperate-with the Tho chamber Il8.inturn.isdeilnedbetweenthepar titions illand i". "lhe partition lll. head Il! and'shell l deilne a resonator'chamber ill. l

Withinv the chamber in, the imei eonsuiiiu' v is Provided with an intermediate shell l", which shellto denne a crossover ill. and thepa'rtitions i and III cooperate with the lheil to demie In 'intermediate-silencing chamber III.' In this in. stance. also. the outlet-conduit l! is providedwith is supported in spaced relation to the conduit il.

by partitions il! and Ill, so as to deiine a silenc. ing chamber i". The chamber ill is in acoustic communication with the interior of the conduit illthrough the louvre openings Il inthe walls '.'thereof,andisinacousticcommunicationwiththe interior of the chamber Ithrough- Il. in the will o! the intermediate shell. Ill( Asin the case oflisalandztheopenend oi the intermediate conduit illfextends into-,tbe

resonator chamber lll, and acoustic communica-,-

v tion is ailorded between the intermediate conduit an intermediate shell' ill; which, with thepartitions IM, ill, Hlan'd ill. defines a succession of high frequency or spit chambers, which communicate. respectively. with the interior of the conduit l2 through the louver openings Il. 11n the instance now being described, .the entering conduit es is impe-imei, utenti-.mediate een.

duit Il is provided with louver openings Il. prei'- e erablv ci the previously identinedy vtypewhich an'ord acoustic communication between the in. terior of the conduit It and the chamber lil.'

The intermediate and outlet conduits are provided, within the crossover III. with outlets eomings i and |20,- respectively, which. asin the previouscase. preferably have total areas 'large prising series of `cii'cumferentially arranged'openenough to afford a substantially unrestricted ilow of the gas stream.

-The 'outlet conduit i! is continued directly through the. righthand portion oi' the compound resonator l into the lefthand portion thereof,

. and the saine is true oi the intermediate conduit M. Ihe outlet conduit l! is, however, provided" with an enclosing wall or plug |28, which prevents commimication through this conduit between the chamber i and the crossover Il.. The conduit l is additionally provided with an outlet comprlsing a series od openings III. which are positioned within the righthand portionofthe cornpound resonator chamber ill.

The operation of the embodiment of Figs. 3 and noted. however, that the tuning neck between the s correspondan there: riga 1 and mit beine i two parte of the resonator IM, aiiorde'd by the leithand yend portion ofthe conduit Il, alters the frequency or. rame odirequencies for or over which isfeflective Intliefurthermoiiinederubodinientoil'ig's.5,

Alofi'. of the outlet In. As inthe case 0f Pili 1,'

|52 and the chamber III through an outlet constituted by a series of circumierentially arranged l openings il! inthe wall od the conduit lil.l The openingsl in prefersbly have a total area auiiicient Ato provides substantially unrestricted ilow therethrough. 1

i ln the operation of the ,righthand end of the intermediate conduit lli.

A smaller component oi such gas stream passes through the louver openings ll into the chamber Ill and from thence, through the openings III, into the intermediate expansionchamber ill. It will be understood that this smaller component o!thegasstreamiisiiilencedinpiirtatleaiithy its passage through the openings M and i" and through the chamber l", and is further silenced by theexpansion thereof, which results when it i enters the enlarged expansion chamber i".

the intermediate conduit Ill, by way o! the crossover itl, ultimately passes through the outlet il! into theexpansionchamber. Asinthecaseo! however, I a substantial Apart, if not. all thereof. initially lsdriven into the resonator chamber lli, the outflow wherefrom reioins the oncoming stream in destructive out-of-phase relation, as described above. It will be noticed that the conduit il! may be regarded as having a forcini;` portion Ilia, lyk!! to the right of the outlet III, and a tuning neck portion illb, lyingto the the"veiocity head, which, as aforesaid, imparts dand'l,thesilencerccsnprisesaaheil Ml. having enclosing .end heads-it! and i, whichaccommodate the inlet 8|" andthe outlet 4l". and

further comprises a primarygas passage afforded by the longitudinally extending conduits i, i j

'A and III. The lust-mentioned conduits are suvported within the shell by means oi the intermediate partitlons ill, i" and I". The partition!" and the end head Il cooperate with the to denne a crossover it! into which the rishthand ends of the inlet and intermediate conduits Ill and 'III directly open. The partitions driving force by which the gas stream is driven -into the resonator, is. ci course. built up within.

the Just-mentioned forcing portion Ilia of the -conduit'ili and thelength o! this portion, therefore, determines the degree of this driving force. The length ci' the tuning neck portion I Ilb, on i the other hand, in conjunction with the volume of the resonator chamber ill, determines the frequency or range of frequencies which the chamber ill is eilective to silence. It will be recognieed, therefore, that this outlet il! may be 'variously positioned along the length of the conembodiment c: riga j 5, Sand '1, the gas stream entering the-.inlet The component of the' gas stream which enters f duit 922 to provide a desirable balance between the frequency for which the resonator IBI is de-v signed and the degree ci the driving force, which it is desired to impart to the gas stream.

Continuing with the operation, the gas vstream passes through the outlet |82. into the expansion chamber 58 and mingles with the previously described relatively small component of the gas stream. Further silencing results from this mixing by virtue ofthe different lengths of the paths travelled by the several components.

The gases entering the chamber 168, as afore= said, pass therefrom through the openings |66 into the crossover I64,vfrom whence theyow through the outlet conduit |64v to the silencer outlet Gil.

As in the previous instances, the outlet conduit ld is provided with a series of high frequency or spit chambers |90, which are defined by the intermediate she1l-i92 and the indicated partia tions. 'The spit-z-ichnbers communicate, as will be obvious."withltheputlet conduit through the louver openings therein.

Figs. 8, 9 and 10 disclose an embodiment oi' the invention, -which distinguishes from the embodiment of Figs. l and 2, in that, among other things, the resonator chamber is interposed in the gas circuit'between the .inlet and intermediate passes, rather than between the intermediateand outlet passes. Referring particularly to Figs. 8, 9 and 10, the silencer comprises generally a cylindrical shell 200, having enclosing end heads 202 and 2M, which accommodate, re-

spectively,`the inlet 3B and the outlet 4B. The

silencing structure Within the shell 200 com- A prises the inlet conduit 2id, intermediate conrespectively, connected directly to the inlet 36l and the outlet 40.

Ther interior of the shell is divided. by means of the partitions 21E, 218 and 22D, into a crossover 222, an intermediate orA expansion chamber 22d, a second crossover 226, and a resonator chamber 228, into which the righthand end 23B o the inlet conduit idextends to provide a tuning neck, as previously described.

Within the crossover` 226, the inlet conduit 230 is provided with anoutlet comprising a series of circumferentially distributed openings 232 for the previously described purpose, and the total area of which, as before, is preferably such as to provide a substantially unrestricted gas iiow. As in the previous instances, itis preferred to place the interiors of the inlet and interme diate conduits 2i@ and 282 in acoustic commu-t nication with the expansion chamber in by-pass relation to the crossover 2.26. For this purpose, the conduit 2li) and its associated intermediate shell 23:3 are provided with louvre openings ci,

'.gas circuit extends from the inlet 36, through the inlet conduit 2 i il. the openings 232, the crossn over 226, the intermediate conduit 2&2, the crossover 222, and thence through the outlet conduit assurer past the outlet 232 into the resonator chamber 228, thus enabling this chamber to exert a substantial silencing eect.

In a further modified embodiment of Figs. 11

and 12, the arrangement duplicates that described with reference to Figs. 8, A9 and 10,` with the exception that the previously described partition 220 is eliminated and a crossover 226' between the inlet conduit 210' and the intermediate conduit 212' is afforded by a member 250, the marginal iiange 252 whereof is adapted to be secured to the partition 2|8. The member 250 thus acts as a closure or conduit connecting the openings 232' in the conduit 210 with the end 'of the conduit 2i2. The member 250 is provided with an opening, which accommodates the end or tuning neck portion 230 of the conduit invention shown in Figs. 1,3, 14, and 15, the arrangement is somewhat similar to that described with reference to Figs. 5, 6, and 7, in that the intermediate pass o f the gas circuit is constituted by an enlarged expansion chamber. In Figs. i3, 14, and 15, the shell 260 is provided with enclosing end heads 262 and 264, which accommodate the inlet 36 and the outlet 40. The interior of the shell 260 is provided with an inlet conduit 210 and an exhaust conduit `212. Partitions 214 and 216 act to support the justmentioned conduits in place, and also serve to divide the interior of the shell into a crossover 218, an expansion chamber 280, and a resonator chamber 282. The chambers 218 and 280 com municate through the partition 214, and for this purpose, this partition is apertured, as indicated at 23d. The resonator chamber 282 is isolated from the balance4 of the silencing structure except for the acoustic connection provided by the open ended tuning neck portion 286 of the conduit 210, which projects into this chamber. The conduit 210 is provided, adjacent the partition 216, with an outlet comprising a series of relatively large openings 290, preferably having a total area suiiicient to enable a substantially unrestricted gas flow and is additionally-provided with aser-ies of louvre openings 292, which are distributed throughout the balance of the length of that portion of 'the conduitrwhich lies within the chamber 286. As in the previous instances, the outlet conduit 212 is provided with a series of-spit chambers 296. defined by the asociated intermediate shell 296 and the partitions 298.

The embodiment now being described also illustrates an improved connection between the louvre tube 212 and the partitions 214 and 29B associated therewith, which is claimed in applicants copending application Serial No. 509,263, iiled November 6, 1943. As most clearly appears in the enlarged views of Figs. 14A and 14B the louvres 213 in the tube 212 are of the tangentialform shown and describedin the above identiied Gunn Patent No. 1,949,974. These louvres are arranged in axially spaced and circiunferentially In the further modied embodiment of the` offset ring-like rows, the individual louvres in alternate rows being aligned with each other axially of the tube.

The partition 214, and similar comments aD- ply to the partitions 298, is provided with a neck 218 of conical form, the portion of largest diameter thereof being adjacent the junction between the neck and the bdy` of the partition. The diameter of this largest portion is preferably substantially equal to the diameter of the imaginary surface including the crests of the louvres 218. With this relation a relatively snug slip fit is provided between each portion of largest diameter and the tube 212 which enables the partition in question to be fitted over the louvre tube without deforming the individual louvres. This ntting operation, however, causes the individual louvres to deform each neck portion of minimum diameter from its` initial circular shape into a polysonal shape. the number of sides of which is equal to the number of louvres in two successive rings of such louvres. The dinerence between the minimum and maximum diameters is such that this deforming or ironing effect brings the surface of the neck in the region of the small endthereof into contact with or immediately adjacent the body of the tube than would otherwise be the case, and materially facilitates the completion of the connection between each neck and the tube.

It will be noticed that the length of each neck l is preferably approximately equal to the spacing,

axially of the louver tube, between two aligned rings of louvers. The nnal positioning of the partition 1s preferably such that the neck portion of largest diameter rests upon the louvers in one of such rings, thus bringing the portion of smallest diameter into registry with the other such ring.

The connection between each partition and the' louver tube is preferably made by eecting a series of welds between the tube and the neck portion. Preferably, also, such welds are. made adjacent the small end of each neck, and one such weld is made in the space between successive louvers in the corresponding louver ring.

Manufacturing variations may be expected to cause some variation in the exact point at which each such weld is made. In a general sense it has been found that the connection is satisfactory if the welds are made anywhere between the Ato minimize any leakage space between the surface of each tube and the' neck. Any such leakage spaces which are not eliminated by the welding operations are found to have only a negligible effect, if any, upon the perfomance of the si lencer. y

As will be understood, the described arrangement is particularly advantageous because it enables a given louver tube construction to be utilized in building up a silencer having differing numbers and differing sizes of chambers 294.

. 5 298, can be secured to the' louver tube at any of a plurality of points along l,the body thereof.

In operation, it will be understood that the gas stream passes through the inlet 38 into the inlet conduit 210, within whlchitmay be regarded as being divided into two components. The first and relatively small component passes through the louver openings 292 into the intermediate expansion chamber 28D. The second and larger component passes the openings 292, and ultimately passes through the outlet 280 into the expansion chamber 280. Under the inuence of the velocity head built up within the conduit 210, a substantial part of the second component passes into the resonator chamber 282, which functions sounds not silenced by the previously encountered silencing structure.

In the embodiment of Figs. 16 and 17, the shell 889 is provided with enclosing end heads 802 and 884, which are formed to define the inlet 88 and the outlet- 40, respectively. The inlet and outlet are directly connected, respectively, to the in let conduit Sill and an outlet conduit 812. It

vwill be noticed that the conduits lili and 812 are directly secured together throughout the intermediate portions thereof, and that these conduits extend through the shell in angled relation, thereby enabling both the inlet and the outlet to be centrally positioned relative tothe heads 802 and 'the inlet and outlet conduits and additionally divides the shell into an expansion chamber 8i! and a resonator chamber 3i8. the conduit 810 extends directly into the resonator chamber 3|8 and thus constitutes a tuning neck, as in the previous modification.

The chamber 318 constitutes the intermediate l pass of the silencer and this chamber is placed in communication with the inlet conduit 810 by means of an outlet, comprising the openings 822 in the conduit 810. In the instance now being described, the lefthand end 323 of the conduit 812v is closed by flattening the same, and this conduit is coupled to the chamber 818 by an outlet comprising the openings 824. As before, the openings 322 and 324 are preferably proportioned to permit a substantially unrestricted flow of gas therethrough. In addition, in order to increase the silencing effect of the expansion chamber Iii, the conduits 810 and SI2 are provided, throughout their length, with relatively small louver openings 828.

The modification shown in Figs. 18 and 19 is similar to the arrangement of Figs. 16 and 17, with the exception that additional partitions 880 and 882 are provided which, with the adjacent end heads, define, respectively, an expansion chamber884 at the inlet end of the structure and an expansion chamber 888 at the outlet end thereof. vIn this embodiment, also, the conduits 8|!! and 312 are supported in spaced relation to each other by the several partitions.

'I'he operation of the embodiments of Figs. 16 through 19 will, in general, be understood from the previous description of Figs. 13, i4 and 15.

This is because the individual partitions, such as Gases entering the inlet conduit divide into two As in the previous in- The end 820 of components, one smaller component passing through the small louver openings 32B, and the y It will be appreciated that from theA forego-l ing-description each oi the several embodiments of the present invention may be. generically characterized inr that the primary circuit, which accommodates vthe iiow of the gas stream through the silencer, isy arranged to provide Vstructure within which all or part of the gas stream may develop a predetermined. velocity head, under the driving force ofwhich a substantial portion of such'gas stream is caused to enter a resonator chamber or equivalent structure, whereby the silencing eiect of such resonator chamber, for a given size of chamber, is very materially increased. is regardedas.- being of generic character, has been found in practice, particularly in lcombination with additional silencing structure constructed in accordance with the above-describedy embodiments, to produce silencers whichareex= ceedingly eiilcient in ,operatiom Moreover, from a manufacturing standpoint, the present arrangements, wherein in each casea particular section of conduit defines not only a driving or forcing portion but also denes a tuning neck The just-mentioned feature, which portion, have beenfound to aiord substantial g economies and simplications.

Although only several specific embodiments ofl the invention have been described in detail, it

willvben appreciated that various further modifications in the form, number and arrangement of parts may be made without departing. from the spirit and scope of the invention. I

- What is claimed is:

1. A silencer structure comprising an outer shell having an inlet and an outlet and silen' ing means within the shell, said structure in= cluding conduit means within the shell through which gases ilow .in passing from the inlet to the outlet and within a portion of which said gases develop a velocity head, said structure further including means deilning a resonator chamber within the shell into which said conduit means opens and which chamber is closed except for its connection with said conduit means. said velocity head serving to drive at least part of said. gases into said chamber, a portion of the` wall of said conduit means having at least one opening therein deiining a substantially non-restrictive gas outlet in the side thereof external to said chamberbut between said chamber and said rst mentioned portion, said side outlet communicating with said ilrst mentioned outlet,

and said wall portion serving-to direct said, part of the gases into said chamber.

2. A silencer structure comprising an outer shell having an inlet and an outlet and silencing means within the shell, said structure including conduit means within the shell through which gases' flow in passing fromthe inlet to the outlet and having successive forcing and `tuning neck portions, said structure further including means deiining a resonator chamber Within the shell into which said tuning neck portion opens and which chamber is closed except for its connection with said tuning neck portion, a portion-- of the wall of said conduit means having at least one opening therein defining a substantially non-restrictive gas outlet in the side thereof positioned between said portions, said side outlet communicating with 'said first mentionedoutlet,

said gases dev eloping a'velocity head in said forcing portion which drives at least a part of said` gases through said tuning neck portion into said chamber, and said wall portion serving to direct said part of said gases into said chamber.

3. A silencerl structure comprising an outer shell having an inlet and an outletand silencing means within the shell, said structure including conduit means within the shell through which gases ow in passing from the inlet to the outlet and having successive" forcing and tuning neck portions, said structure further including means dening a resonator chamber within the shell intowhich said tuningneck portion opens and which chamber is closed except for its connection with said tuning neck portion, a portion of the wall of said conduit means having at least' one opening therein de ilning a substantially non-restrictive outlet in the side thereof positioned between said portions, said tuning neck being arranged to project into t Y said chamber and being open at said projecting end, said side outlet communicating with said first mentioned outlet, said gases developing a velocity head in said forcing portion which drives at least a part of said gases through said tun' ing neck portion into said chamber, and said wall portion serving to direct said part of said gases into said chamber.

4. A silencer structure comprising an outer shell having'an inlet and an outlet and silencing means within the shell, said structure including conduit means within the shell through which gases flow in passing from the inlet to they outlet and having successive forcing and tuning necky portions, said structure further including means denlng a resonator chamber within the shell into which said tuning neck portion opens and which chamber is closed except for its con-v nection with said turning neck portion, a por-A tion of the wall of said conduit means having at least one opening therein defining a substantially non-restrictive outlet in the side wall thereof positioned between said portions and externally of said chamber, said side outlet communicating with said first mentioned outlet, said gases'developing a velocity head in said forcing.

portion which drives at least a part of said gases through said tuning neck portion into said chamber, and said wall portion serving to direct said part of said gases-into said chamber. Y

5. In a silencer structure comprising an outer shell having an inlet and an outlet and silencing means within the shell, said structure including conduit means within the vshell through which gases flow in passing from the inlet to the outles and .having successive forcing and tuning neck portions, said structure further 'including meansdening a resonator chamber within the shell into which said tuning neck portionv opens and winch chamber is closed except for its connection with said` tuning neck portion, a portion of, the wall of said conduit means having at least one opening therein defining a substantially nonrestrictive outlet in the side wall thereof positioned between said portions, said `side outlet communicating with said iirst mentioned outlet.

said gases developing a velocity head in said forcing portion which drives at least a part of said gases through said tuning neck portion into said chamber and said wall portion serving to direct said part of said gases into said chamber, and said conduit further havingv a series of restrictive openings in the side wall thereof positioned in the forcing portion thereof.

6. A silencer structure comprising an outer shell .'having an inlet and an outlet and silencing means within the shell, said structure including a retroverted gas circuit constituted at least in part by a pair oi axially overlapping conduits through which gases flow in passing from said inlet to said outlet, one of said conduits having a portion in which said gases develop a velocity head, said structure further including means deflning a resonator chamber within the shell into which said one of said conduits opens and which chamber is closed except for its connection with said. one conduit, said velocity head serving to drive at least part of said gases into said chamber, a portion of the wall of said one conduit having atleast one opening therein defining a substantially non-restrictive outlet in the side thereof externally of said chamber, but between said chamber and said first mentioned portion,

said side outlet communicating with said first mentioned outlet, and said wall portion serving to direct said part of the gases into said chamber. 7. A silencer structure comprising an outer shell having an inlet and an outlet and silencing means within the shell. said structure including a retroverted gas circuit constituted at least in part by a pair of axially overlapping conduits, one of said conduits having successive forcing and tuning neck portions, said structure further including means defining a resonator chamber within the shell into which said tuning neck portion opens and which chamber is closed except for its connection with said tuning neck portion, a portion of the wall of said one conduit having at least one opening therein denning a substantially non-restrictive outlet in the side thereof between. said portions and externally of -said chamber. said side outlet communicating with said first mentioned outlet, said gases developing a velocity head in said forcing portion which drives at least a part of said gases through said timing neck portion into said chamber, and said wall portion serving to direct said part of said gases into said chamber.

8. A silencer structure comprising an outer shell having an inlet and an outlet and silencing means within the shell, said structure including a .retroverted gas circuit having at least two conduits through which gases flow in passing from the inlet to the outlet and a crossover between said conduits, said structure further including means defining a resonator chamber within the shell adjacent said crossover, one of said conduits being extended directly through said crossover and terminating within said resonator chamber, said resonator chamber being closed except for its said connection with said one conduit, and

said conduit having a substantially non-restrictive outlet in the side thereof within said crossover, said outlet being defined by a relatively few large openings in the wall oi said conduit.

9. A silencer structure comprising an outer shell having an inlet and an outlet and silencing means within the shell, said structure including a retroverted gas circuit having axially overlaping from the inlet to the outlet and an enlarged expansion chamber included in the gas path between two of said conduits, one of said two conduits having successive forcing and tuning neck portions, said structure further including means defining a resonator chamber within the shell into which said tuning neck portion opens, said resonator chamber being closed except for its connection with said one conduit, and a portion of the wall of said one of said two conduits having at least one opening therein defining a substantially non-restrictive outlet in the side thereof within said `expansion chamber and between said portions, said side outlet communicating Vwith said first mentioned outlet, said gases' desaid wall portion serving to direct said part of l said gases into said chamber.

10. A silencer structure comprising an outer shell having an inlet and an outlet and silencing means Within the shell, said structure including a retroverted gas circuit having at least two axially overlapping conduits through which gases flow in passing from the inlet to the outlet and means defining a crossover forming a gas path between said two conduits, said structure further including means defining a resonator chamber within the shell into which one of said conduits directly opens and which is closed except for its connection with said one conduit, and said one of said conduits extending through said crossover into said chamber and having a substantially non-restrictive outlet in the side thereof within said crossover, said outlet being defined by a'relatively few large openings in the wall of said conduit.

11. A silencer structure comprising an outer shell having an inlet andan outlet and silencing means 'within the-shell, said structure including a retroverted gas circuit through which gases flow in passing from the inlet to the outlet comprising an inlet conduit, an outlet conduit and an enlarged expansion chamber constituting an intermediate pass of said circuit, said structure further including means defining a resonator chamber within the shell into which one of said conduits directly opens and which resonator chamber is closed except for its connection with said one conduit, said one conduit having a substantially non-restrictive outlet in the side thereof positioned within said expansion chamber and said one conduit further having a series of relatively restricted openings which open into said expansion chamber. i

l2. In a silencer provided with an inlet and an outlet, a conduit forming part of a retroverted gas circuit through which gases flow in passing from the inlet to the outlet, means defining a crossover forming a gas path between said conduit and another part of said circuit, means dening a resonator chamber, said conduit being arranged to extend through said crossover to said resonator chamber and having an outlet which directly opens into said resonator chamber, and said conduit having a substantially nonrestrictive outlet in the side wall thereof positioned within said crossover, said outlet being defined by a relatively few large openings in the wall oi said conduit.

WALTER H. POWERS.

Intent No. 2,551,791;

auf the` above numbered patent requirl'ng'c'orrection as'follows: Page 6, sec;

CERTIFICATE c oRmzctr'IoNz. Y

392mb 5' 19h1 WALTER .H. mams. 11S vir hereby certified that error appears in.' the printed speeffcaion end column, line 148,.'ela1m 14, for the-word "turningfread tuning-M' page Piment No. 2.557.791#

Vv#of the. above numbered patet

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