US3110358A - Sound attenuating gas conduit - Google Patents

Description

Nov. 12, 1963 E. LUDLow ETAL 3,110,358I

SOUND ATTENUATING c-As coNDuIT Filed July 10, 1961 2 Sheets-Sheet l .IMPJT v/ S E. LUDLOW ETAL v SOUND ATTENUATING GAS CONDUIT Nov. 12, 1963 2 Sheets-Sheet 2 Filed July l0, 1961 INVENTORS. fom/N0 awww mw BYf/VJAM//v In w/N masia' i H TTOB NEPS.

United States Patent O 3,110,353 SUND AT'EENUATWG GAS CGNDUIT Edmund Ludlow and Beniamin H. lrwin, Columbus, lud., assignors to Arvin Industries, Inc., Columbus, Ind., a corporation of indiana- Filed .'luly lil, 1961, Ser. No. 122,891 Claims. (Cl. 181-59) This invention relates to a sound attenuating gas conduit, and more particularly to a conduit for conveying, and attenuating the noise level of, a gas stream.

It is the object of our invention'to provide a sound attenuating gas conduit which can Ibe simply and easily manufactured from inexpensive tubing, which will hav'e its weight ldistributed along its length, and which can be tuned to attenuate different and overlapping bands of sound wave frequencies.

It -is a specific object of our invention to provide a sound attenuating gas conduit which can be used in association `with an internal combustion engine for conveying, and attenua-ting the noise level of, the exhaust .gases emanating from said engine.

In accordance with one form of our invention, there is provided an clon-gated pipe forming a gas-flow passage and having a plurality of interlitting shells mounted within it. Each of said shells is provided with a closed end which is received in the open end of the next adjacent shell with portions of the walls of the intertitting ends of each pair of said shells being disposed in spaced relation to each other so that the interiitting ends of each pair of shells dene a resonator throat. Said throat is in open communication with the gas-dow passage and a resonator volume formed by the adjacent closed ends of said pair of shells and the side walls of the shell in said pair off shells in which the other'shell in said Vpair is received. In this manner, each pair of interlitting shells defines a resonator throat and volume disposed in the gas-flow passage for attenuatin'g the noise level of the gases 4in said passage.

Other objects and features of our invention will become apparent from the more ydetailed description which follows and'from the accompanying drawings, in which:

FIG. .l is a fragmentary longitudinal section of a sound attenuating gas conduit embodying our invention;v

FlG. 2 is a vertical section taken on the line 2 2 of FIGA;

FIG. 3 is an enlarged isometric view of the resonatorforming shell shown in FIG. l;

FIG. 4 is an isometric view o-f another embodiment of the resonator-forming shell shown in FIG. 3;

FlG. 5 is ya fragmentary longitudinal section of a sound attenuating lgas conduit employing another embodiment of our resonator-forming shell;

FlG. 6 is a fragmentary longitudinal section of a sound attenuating gas conduit employing another embodiment of our resonatornforming shell; and

FiG. 7 is afragrnentary longitudinal section of a sound attenuating gas yconduit employing another embodiment of our resonator-forming shell.

Our invention is adapted to convey a moving gas stream cfrom one point to another andto attenuate the noise level of said gas stream. Although it may be ernployed to convey, and attenuate the noise level of, many different ykinds of gas streams, it is primarily adapted for use with an internal combustion engine in an automotive vehicle .for conveying, and attenuating the noise level of, the exhaust gases discharged from said engine. The sound waves in such exhaust gases extend over a wide range of frequencies, i.e., from about 30 cycles per second to about 1,500 icycles per second. Our invention is adapted to attenuate the noise level of such a range of dd M5358 Patented Nov. 12 1953 ICC frequencies, and is particularly well adatped to attenuate the difficult to silence frequencies below 200 cycles per second. Our conduit may be used alone, lin which case it extends `directly yfrom the exhaust manifold of an engine to the desired Igas discharge point, or it may be used in combination with other sound attenuating systems or components, in which case it may constitute one or more short sound attenuating conduits employed with said systems.

As shofwn in FIG. 1, our invention comprises an elongated pipe 1tl forming a gas-flow passa-gc. Said pipe may be in the form of a runitary continuous length of pipe or a series of interconnected pipe sections. Mounted within said pipe is a plurality of elongated, axially aligned, resonator-forming shells 12 conveniently 'formed from lengths of metal-tubing. Each of the shells 12 comprises a body 14 open at one of its ends and integral and continuous `with a neck 16 at its opposite end. The end of the neck 16- remote from the body 14 is closed as at 18.

As shown in FIGS. l and 2, the neck 16 of each of the shells 12 has a slightly smaller cross-section than the body 14 to permit each pair of said shells to be intert one `within the other, as will be more fully explained hereafter.

The body 14 is provided with one or more deformations adjacent the open end thereof. Such deformations in the embodiment shown in FIG. 3 ycomprise axially extending inwardly projecting beads 20, formed in the shell side walls and spaced about its circumference, with the inner faces of said beads defining the locus of a circle having -a diameter approximating the outer diameter of the neck 16.

ln assemblying our shells 12, the neck 16 of one of said shells is slid, desirably as a press lit, into the open end of the Ibody 14- of the next adjacent shell. rThe beads 2li hold the portions of the side Wa-lls of the intertitting ends of said shells disposed between said beads in spaced relation to each other so that said wall portions define la resonator throat indicated at 22 in FIG. 2. The closed ends 18 of teach pair of interlitting shells form the end walls of a resonator volume indicated at 2Liin FIG. 1, with the side walls of said volume being formed by the side walls of the shell in which the next adjacent shell neck 16 is inserted.

As will lbe apparent, the size of each of the volumes 249 yand lthe length of each of the throats will be determined by the length to which one shell is inserted within the other. As will be understood from known principles of acoustics, the length and cross-sectional area of the throats 22 and the size of the volumes 24 determine the' sound wave frequencies which 4the resonators formed by said volumes and throats will attenuate. l-f the throats have relatively long lengths and/ or relatively large crosssections, the :resonators will attenuate relatively low sound wave frequencies. Conversely, resonators having shorter throats and/or smaller cross-sections will attenuate the higher sound wave frequencies. formed by the intertitting shells 12 may be tuned to attenuate `different and overlapping bands of sound Wave frequencies by controlling the length to which said shells are inserted one within the other, and/ or controlling the cross-sectional extent of the beads Ztl'.

The press tit provided by the beads 2l) will retain the shells in the ldesired position of intertitting adjustment during :assembly prior to mounting said shells in the pipe 1l). With the several shells disposed in such ian intertitting engagement said shells may be rigidly secured to the inner Wall lof the pipe 10 such las Iby welding or the like to dispose the resonators formed by said shells in direct acoustic and thermal coupling with the gases in said pipe to attenuate the noise level of the sound waves in said gases.

Thus, the resonators Another embodiment of our shell construction is i-llustrated in FIG. 4, and comprises a shell 25 having a body 26 open `at one of its ends and having its opposite end integral and continuous with a smaller diameter neck 27. The end of the neck 27 opposite the body 26 is closed as at 3), .and said neck is provided with outwardly projecting beads 3l `forme-d in its side walls. rlhe outer faces of the beads 3l define the locus of a circle having a diameter approximating the inner diameter of the body 26. In this manner, `a plurality yof the shells 25 may be inserted one within the other in a press t to define a series of resonators. The beads El hold portions of the side walls of the neck 27 of one shell 25 and body 26 of the next adjacent shell in which said neck is inserted in spaced relation to form a resonator throat in open communication with the gas stream and a resonator volume formed by the adjacent end `vvalls 30 of the intertting pair of shells and the side walls of the shell in which said neck is inserted. With the shells 25 disposed in the -desired interiitting relationship, they may be mounted in the gas-How passage of a gascarrying pipe in the same manner as the shells 12.

Another embodiment of our shell construction is illustrated in FIG. in which a plurality of interitting shells 35 yare secured to the inner wall of a pipe 36 dening a gas-flow passage. Each of the shells 35 has a body 37 open at one of its ends and having its opposite end integral and continuous with a smaller .diameter neck 38 having its end opposite said body 37 closed las at 39. The neck 36 has an outer diameter approximating the inner diameter of the lbody 37 so that the shells may be press lit in interiiting relationship to ydefine a series of resonators. One or more outwardly projecting beads 40 are formed in the side walls of the body 37' of each shell so that with the next adjacent shell neck 38 disposed in the open end of said body, Isaid beads and the underlying portions of the side walls of said neck define one or more resonator throats 4l in open communication with the interior of the pipe 36 and a resonator volume 42 fonmed by the adjacent end walls 39 of the interiitting pair of shells land the side walls of the shell in which the next adjacent shell is inserted.

FIG. 6 illustrates still another embodiment of our shell construction in Which a plurality of intertJtin-g shells 44 are secured to the inner wall of a pipe 45 dening a gasilow passage. Each of the shells 44 has a body 46 open at one of its ends and having its opposite end integral and continuous with a smaller diameter neck 48 having its end opposite said body 46 closed as lat 50. The -neck 48 has an outer diameter approximating the inner diameter of the body 46 so that 4the shells may be press t in interiitting relationship to deiine a series of resonators. One or more inwardly projecting beads 51 are formed in the side walls of the neck 48 ot each shell so th-at with said neck inserted in the body 46 of the next adjacent shell, said beads 5l and the overlying portions of the side walls of said body will definel one or more resonator throats 52 in open communication with the interior of the pipe 45 and a resonator volume 54 formed by the adjacent end Walls Si) of the interitting pair of shells and the side Walls of the shell in which the next adjacent shell is inserted.

Although `all of the beads formed in the shells shown in FIGS. 1 6 have been illustrated as rectilinear, axially extending beads, such beads may have any desired configuration. It is only essential that said bead-s be formed in the shells in positions such that they form open ended throats-open to both the gas-how passage and the resonator volumes.

A sound attenuating conduit employing still another embodiment of our shell construction is illustrated in FIG. 7. As shown, a plurality of interiitting shells 55 are secured to the inner wall of a pipe 56 defining a gas-flow passage. Each oct said shells comprises a body 58 open at one of its ends and having its opposite end integral and continuous with a smaller diameter neck 60 having its end opposite said body closed as at 62. 'Ihe neck 60 has a smallerouter diameter than the inner diameter of the body 58 and is received in the body 58 of the next adjacent shell to dispose the side walls 'of the intertting shell ends in spaced relation to define a resonator throat 63. Said throat is in open communication with .the interior of the pipe 56 and a resonator volume 64 yfor-med by the adjacent end Walls 62 of the interitting pair of shells and the side walls of the shell in which the next adjacent shell is inserted.

The -throats of the 4resonators formed by the shells shown in FEGS. l-6 are tuned by adjusting the cross-sectional extent Aof the beads :and the length to which each pair of shells are interfit. In the embodiment yshown in FG. 7, such tuning is controlled by the length to which ieach pair of shells are intert Iand by -the relative diameters of the shell necks and bodies. As the diameters of the necks 66 become progressively smaller th-an the diameters of the Abodies 58, the side Walls of said necks and bodies are spaced farther apart when the shells are interiit, and the resonators attenuate progressively lower sound w-ave frequencies.

While we have described the modifications of our resonator-forming shells as having a circular cross-section and being adapted to be secured directly to the inner Wall of an elongated pipe, it is to be understood that such shells may have any desired cross-sectional configuration and may be mounted within a gas-carrying pipe in any convenient manner.

We claim as our invention:

l. In a sound attenuating gas conduit, an elongated pipe forming a gas-How passage having unrestricted flow at its ends, and a plurality of axially disposed interitting shells carried within said passage, each of said shells having a closed end received in an open end of the next adjacent shell, iirst portions of the side walls of interitting ends of each pair of shells being interit against each other and second portions of the side walls of said interiitting ends disposed in spaced relation to deiine a resonator throat in open communication with said gas-flow passage and a resonator volume formed by the adjacent closed ends of said pair of shells and the side walls ofthe shell in said pair of shells in which the other shell in said pair is received, whereby said resonator throat and volume will attenuate the noise level of the gases in said gas-How passage.

2. In a sound attenuating gas conduit, an elongated pipe forming a gas-How passage having unrestricted flow at its ends, and a plurality of axially extending interiitting shells carried Within said passage, each of said shells having a closed end received in the open end of the next adjacent shell and abutting the inner face of the side walls thereof, one or more elongated projections on the side walls of at least one of the shells in each pair of interitting shells operatively associated with the side walls of the other shell in said pair of shells to dispose portions of the side Walls of the interitting ends of each pair of shells in spaced relation to denne a resonator throat in open communication with said gas-iiow passage and a resonator volume formed by the adjacent closed ends of said pair of shells and the side Walls of the shell in said pair of shells in which the other shell in said pair is received, whereby said resonator throat and volume will attenuate the noise level of the gases in said gas-How passage, the length to which one shell in said pair of shells is received in the other shell in said pair of shells being adjustable to adjust the spacing between their closed ends and the length of the interfit of their ends to control the size and length of said resonator volume and throat.

3. In a sound attenuating gas conduit, an elongated pipe forming a gas-flow passage having unrestricted flow at its ends, and a plurality of interfitting elongated shells carried within said passage, each of said shells having one of its ends closed and its opposite end open, the closed end of said shell having a smaller cross-section than the open shell end whereby each shell is receivable in the open end the next adjacent shell, rst portions of the side walls of the intertting ends of each pair of shells presst together and second portions of the side Walls of said interfitting ends being disposed in spaced relation to dene a resonator throat in open communication with said gas-flow passage and a resonator volume formed by the adjacent closed ends of said pair of shells and the side walls of the shell in said pair of shells in which the other shell in said pair is received, whereby said resonator throat and volume will attenuate the noise level of the gases in said gas-How passage.

4. The invention as set forth in claim 3 with the addition that each of said shells has one or more inwardly extending projections formed in its side walls adjacent its open end and engageable with the side walls of the next adjacent shell received in said open end to form said rst portions and to dispose said second portions of said pair of shells between said first portions in spaced throatforming relation.

6 5. The invention as set forth in clairn 3 with the addition that each of said shells has one or more outwardly extending projections formed in its side Walls adjacent its closed end and engageable with the side walls of the next adjacent shell in which said closed end is received to form said rst portions and to dispose said second portions of said pair of shells between said rst portions in spaced throat-forming relation.

References Cited in the le of this patent UNITED STATES PATENTS 2,099,858 MacKenzie et al Nov. 23, 1937 2,109,995 Hawle Mar. 1, 1938 2,176,615 Starkweather et al. Oct. 17, 1939 FOREIGN PATENTS 484,771 Great Britain May 10, 1938 980,535 France Dec. 27, 1950

Claims (1)

1. IN A SOUND ATTENUATING GAS CONDUIT, AN ELONGATED PIPE FORMING A GAS-FLOW PASSAGE HAVING UNRESTRICTED FLOW AT ITS ENDS, AND A PLURALITY OF AXIALLY DISPOSED INTERFITTING SHELLS CARRIED WITHIN SAID PASSAGE, EACH OF SAID SHELLS HAVING A CLOSED END RECEIVED IN AN OPEN END OF THE NEXT ADJACENT SHELL, FIRST PORTIONS OF THE SIDE WALLS OF INTERFITTING ENDS OF EACH PAIR OF SHELLS BEING INTERFIT AGAINST EACH OTHER AND SECOND PORTIONS OF THE SIDE WALLS OF SAID INTERFITTING ENDS DISPOSED IN SPACED RELATION TO DEFINE A RES-

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