US2047442A

US2047442A - Muffler

Info

Publication number: US2047442A
Application number: US36352A
Authority: US
Inventors: Gail C Starkweather; Luclen L Haas
Original assignee: BUFFALO PRESSED STEEL Co
Current assignee: BUFFALO PRESSED STEEL Co
Priority date: 1935-08-15
Filing date: 1935-08-15
Publication date: 1936-07-14
Anticipated expiration: 1953-07-14

Description

July 14, 1936 G. c. sTARKwL-:ATHER ET Al. 2,047,442

July 14, 1936 G. c. STARKWEATHER ET A1. 2,047,442

MUFFLER Filed Aug. l5, 1955 j 2 Sheets-Sheet 2 Patented July 14, 1936 UNITED STATES PATENT VFFICE Haas, Buffalo, N. Y.,

assignors to Buffalo Pressed Steel Company, Buialo, N. Y.

Application August 15, 1935, Serial No. 36,352

16 Claims. (Cl. 181-48) 'Ihis invention relates to improvements in mufflers or silencers, such for example as are used in connection with the silencing of noises of the exhaust or intake of internal combustion engines.

The objects of this invention are to provide a muilier of this kind of improved and simplified construction and having greatly increased silencing properties; also to provide a muffler of this kind provided with an inner conduit through which gases and sound waves may pass directly from one end of the conduit to the other, and which is provided with a relatively slight restriction and with perforations or apertures arranged forwardly and rearwardly of the restrictions, so that a greater proportion of the sound waves will pass out of and again into the inner conduit through the perforations than would pass through perforations of a similar conduit without such restrictions; also to provide a muier of this kind in which the inner conduit is arranged within a shell and' in which means are provided for deflecting sound waves approximately tangentially of the inner shell into the space between the two shells.

A further object of the invention is to provide a muffler or silencer which will be effective in reducing the sounds accompanying the flow of gas through the same, and which will have a very low resistance to the ow of gas through the same, which will aid in the rapid dissipation of heat from the exhaust gases and which will be light in weight and strong structurally.

Another object of the invention is to provide an improved and simplified construction for forming an intermediate shell for a muffler.

Further objects of the invention are to improve the construction of muiiiers in other respects hereinafter specified.

The muier shown in the accompanying drawings is designed primarily for use in connection with the silencing of the exhaust of internal combustion engines, but it will be understood that the muiiier may be used for other purposes, such, for example, as the silencing ofthe intake to the engine.

In the accompanying drawings:

Fig. l is a longitudinal central sectional view of a mufiier embodying this invention.

Fig. 2 is a similar view of a muffler of modified construction. i

Fig. 3 is a similar view of a muier of still another construction.

Fig. 4 is a transverse sectional view, on line 4 4, Fig. 2.

Fig. 5 is a fragmentary longitudinal sectional view of a portion of an inner conduit of a muffler of modified construction.

In all of theconstructions shown, A represents the outer shell of the mufller and one end of each mufer is provided with a head B secured 5- to the outer shell A and having a tubular extenn sion or intake duct b, which may, for example, be formed integrally with the head B and with which an exhaust pipe D leading from an engine may be connected. Each muilier also has a disl0 charge head C and a duct c connected therewith to which a tail pipe may be secured. The outer shell and the heads of the muiiler may be of any suitable or desired construction and of themselves do not constitute a part of this invention.

In all of the muiilers shown, the inner conduit or shell is of the uninterrupted or through type and is provided with perforations throughout a large part of its length so that gases and sound waves may pass through the inner conduit from one end thereof to the other, and certain portions. of the gases and sound waves may pass into and out of the inner conduit through the perforations or apertures in the conduit. The conduit is preferably of a slightly smaller diameter'25 than the exhaust pipe-and the diameter of this conduit should not materially exceedthat of the tail or discharge pipe.

The inner conduits in most muiilers of this type have heretofore been made of uniform diameter 3U throughout or of tapering form and generally muffiers of this kind have been provided with resonance chambers arranged between the outer shell and the conduit for reducing the noises of the exhaust gases. In accordance with this invention, the silencing effect of muiiiers is greatly reduced by providing the inner conduit at intervals with restrictions or contractions, which effect a reduction in the cross sectional area of the inner conduit at one or more places length- 40 wise of the conduit. These restrictions while very slightly increasing the back pressure of the muliier, have the property of causing a much greater percentage of the gases and sound waves to iiow outwardly through the perforations in the inner conduit, and then back again through other perforations into this conduit and this action in turn greatly increases the silencing effeet of the muiiier with a practically negligible amount in increase in back pressure. Possibly the increased silencing effect is due to the fact that sound waves passing out of the inner conduit through perforations in the same and then back again into the inner conduit will, because of the increased distance through which they have traveled, upon returning into the conduit be out of phase with sound waves that have passed straight through the restriction in the conduit. The silencing effect may be further increased by providing the inner conduit with suitable means, such as louvres for causing the gases, and possibly sound waves, which pass out through the perforations in the inner conduit, to be deected in an approximately tangential direction. These louvres may be arranged to cause a whirling or rotary movement of gases in the space or spaces surrounding the inner conduit. This causes sound waves to travel around the inner conduit in a somewhat helical path, and consequently, the distance through which such sound waves must travel is further increased, thus ythrowing the sound waves returning into the conduit further out of phase with those sound waves which have passed straight through the conduit.

One or more restrictions or contractions of the inner conduit may effectively be used in connection with various types of resonating or sound absorbing chambers arranged in the space be tween the inner conduit and the outer shell ci the muliler, and one or more intermediate shells together with baiiles may be employed in connection with these restrictions in the inner conduit. It has been found, however, that when an inner conduit is provided with restrictions or contractions of this type and arranged with referu ence to the perorations in the inner conduit as herein described, the number of resonance or sound deadening chambers in themuiiier may be greatly reduced without sacriiicing silencing efiect and the cost and weight of the muiiier is, consequently, proportionately reduced.

In order to illustrate this invention, certain simplified forms of inuiilers embodying the invention are illustrated in the drawings, but it will be understood that this invention is usable in connection with muriers of many other types.

In Fig. l, l@ represents the inner conduit of the muiiler which is provided with a relatively large number of small periorations ll distributed throughout the greater part of the length oi the inner conduit. The inner conduit in this construction is connected at its ends with the heads b and c, and the conduit receives gases and sound waves at one end thereof,for exampleirom the inlet duct c and discharges the gasthroug'h discharge duct b. rThe perforations or apertures lll in the inner conduit are preferably associated with louvers or deflectors, which may, for example, be formed integrally with the conduit it, and which are so arranged that gases which pass outwardly through these perforations or apertures into the space between the conduit and outer shell, will be deflected tangentially oi the conduit. The louvers m'ay all face in the same direction tangentially or may be arranged to oppose each other, or alternate groups of louvers lengthwise of the conduit may face in opposite directions to produce diierent bodies of gases lengthwise of the muilier which move in opposite directions. Fig. 4 shows an arrangement whereby the louvers on one half of the conduit face in a direction opposite to the louvers on the other half.

The inner conduit lll shown in Fig. l, is provided at intervals with unperforated portions, and suitable restrictions, such for example, as baies or restricting members i 5, may be secured within the inner conduit, three such restricting members being illustrated in Fig. l. Each restricting member as shown has a substantially cylindrical portion I 6 iitting within the inner diameter of the conduit l and secured thereto, for example, by welding. The sm'allest inner diameter of the restricting member is large enough to provide for an ample ow of gases and sound waves through the restricting member, but at the same time to retard the flow sufficiently to cause a considerable portion of the gas and sound waves to pass outwardly through the apertures or perforations ll arranged ahead of the restrictions l5. For example, the muiilers in which the inner conduit is of 1.75 inches internal diameter, the smallest internal diameter of the restricting members may be from ll/r to lll/2 inches, this diameter varying in accordance with the amount of silencing eect that must be produced. i

It is also a desirable feature of this invention that the passage of gases through the apertures or perorations il be facilitated as much as possible and for this purpose, it is preferred that the combined areas of the openings in the inner conduit in advance or ahead of a restriction be not less than the cross sectional area of the restricting member measured at its smallest internal diameter. Similarly the apertures rearwardly of a restriction, through which gases and sound waves may re-enter the conduit, should have a combined area of at least that of the smallest internal diameter of the restriction.

It will be noted in Fig. 1 that no sound absorbing or deiiecting devices are provided in the space betweenthe conduit and the outer shell A. A muffler or" this kind, nevertheless, produces very eiectlve silencing and this may be due to the fact that sound waves passing out through the apertures ahead of the nrst restricting member l5 may pass through the space between the conduit and outer Shell either to the apertures immediately in rear of the rst restricting member l5, or to those apertures in rear of the second or the third restricting members. Because of the tangential deflection of gases and sound Waves by the louvers and because of the movement of the gases in the space between the outer shell and the central conduit, sound waves entering the diierent sets of apertures will be out of phase to diierent degrees with respect to those sound waves which have passed straight through the inner conduit, and consequently, a very eiective silencing will result, it being understood, of course, that if two equal sound waves are brought together which are completely out of phase with one another, so that the crest of one wave coincides with the trough of the other wave, the sound will be eliminated.

In Fig. 2, a muler lis shown in which the inner perforate conduit 2li having apertures 2l is connected with the end heads of the muier substantially in the same manner as the mufer shown in Fig. 1. In this construction, however, only two restrictions 22 are provided within the inner conduit, which are of a construction similar to that shown in Fig. l. In this construction, the space between the inner conduit and the outer shell is shown as divided by means of a transverse batie 24 into two spaces. It will be noted too that the baiile 2&3 is located in a plane intermediate between the two restricting members 22. For certain engines, a muiler having a transverse barile in the outer shell has been found desirable, since this'produces between the bailie 24 and the head B of the muffler a chamber in which the sound waves and gas are controlled, so that they will pass back into the inner conduit through the apertures or perforations spaced between'the first restricting member 22 and the baille 24. If desired, a number of baiiles similar to the baille 24 may be provided at intervals lengthwise of the muiiier, in similar spaced relation to the restrictions in the inner conduit, and the baille may be perforated or unperforated as desired.

The muilier shown in Fig. 2 is also provided at the opposite end thereof with a short intermediate shell 25 extending about the two groups of apertures in the inner shell or conduit. This intermediate shell forms with the inner shell small resonating chambers 29 and 30 communieating. with the interior of the conduit through the apertures. These resonating chambers have been found particularly desirable in connection with the suppressing of high frequency sound waves. While only two of these high frequency resonating chambers 29 and 3U are provided, it will be obvious that the number of these chambers may be increased or decreased, depending upon the extent to which such chambers are found necessary for silencing a particular en- The intermediate shell 25 also forms with the outer shell A an imperforate resonator space 3l, into which sound waves forced out ofthe inner conduit by means of the second restriction shown in Fig. 2 may enter. Some ofO these sound waves when travelling to the end of the space and being deflected back bythe head C, are then out of phase with other sound waves passing through the inner conduit. 'lhis portion of the muler operates in conjunction with longer and lower frequency sound waves, so thati by means ofthe arrangement of the intermediate shell, as shown, two types of sound waves are eliminated. It will, of course, be understood that.the intermediate shell 25 may be used'in a muilier of this type l without the baille 24, and the bame 24 may also be used without the intermediate shell 25 but preferably, if, another transverse baille is used between the conduit and outer shell, an additional restriction is provided in the conduit. Such construction, for example, is shown in Fig. 3, in which two transverse baiiies 34 are employed and three restrictingv members 35. It will be noted in Fig. 3 that each restriction is spaced between two groups of apertures, one group being located in advance of the restricting member and the other rearwardly thereof in the direction of flow of the gases through the inner conduit. When baflles are employed between the inner conduit and an outer shell, such bailles are preferably arranged so that at least two groups of apertures and a restricting member are located in advance or ln rear of the baille, so that a bypass around the inner conduit is provided.

Fig. 4 illustrates louvers 38, such as may be used on any of the muillers shown in Figs. 1 to 3. These louvers are preferably formed integrally with the inner conduit 31 and each louver projects over its aperture in such a manner that the gases and sound waves discharged through the apertures will be deflected substantially tangentially with reference to the conduit.

In place of restricting members formed separately and secured within the inner conduit, other means may, of course, be employed to provide the necessary restriction within this conduit andby way of example an alternative construction for producing a restriction within the conduit is illustrated in Fig. 5, in which the inner conduit 40 is provided with an annular portion 4I which extends inwardly and forms a restriction in the conduit. The restriction 4l may be pressed or rolled inwardly in any suitable or desired manner.

It has also been found very desirable'to construct the muillers in such a manner that the inner conduit is of a diameter which is preferably no greater than, or at least not materially greater than the diameter of the exhaust pipe D.

'I'he restrictions in the inner conduit togetherV with the arrangement for causing a relatively large portion of the gases and sound waves to take a longer path around the^inner conduit vbefore returning to the same, have been found weight and of lower cost than muillers hereto fore used and having silencing effect equal or superior to those heretofore produced. The use of restrictions in the inner conduit as herein described, since it eliminates or reduces the need for some or all of the intermediate shells heretofore used, also more readily dissipates the heat of the gases discharged into the muiller, since a large proportion of the gases passing through the muiller contact with the outer shellfwhich in turn is cooled directly by the surrounding atmosphere. 'I'his construction also lends itself particularly well for use in connection with many kinds of mulllers heretofore devised, since it may be easily applied to such muillers to materially increase the silencing effects of the same. It will, consequently, be understood that the particular constructions illustrated and described'are merely illustrative of a few applications of this invention to mulilers. l

'I'he restrictions in the inner conduit of the mufller have also been found to eliminate or materially reduce the swishing or hissing noises frequently made by perforate conduits in mumers as heretofore constructed. This may possibly be due to the fact that the restrictions tend to cause the gases to pass mainly through the axial portion of the conduit and to reduce the iiow of gases close to the wall of the conduit across the perforations in the conduit, or to the fact that a greater flow of gases through the perforations divided lengthwise into a plurality of parts.

As shown, this shell ismade in two halves which may be secured together lengthwise of the muler and also secured to another muffler shell. In. this construction, the intermediate shell of the muiller is formed in two half shells 26 and 21, both of these half shells being provided with laterally extending iianges 4| which may readily be secured together by welding or other means. By forming a muiiler shell in thismanner, the use of bafiies connecting the shell with an adjacent shell may be dispensed with since each half shell may be provided with webs. or portions 42 which terminate in substantially semi-cylindrical portions 43 adapted to be secured to an adjacent shell or securely held in place by other connections, such as the longitudinal anges 4|. The webs or portions 42 may be of any desired depth, so that the space between the cylindrical portion of the two half shells and the adjacent shell to which they are connected may be varied as may be necessary to obtain the desired silencing eil'ects. In the form illustrated, the webs 42 extend inwardly to engage with a shell arranged within the longitudinally divided shell, but obviously they could be formed to extend outwardly to engage with a. shell arranged about the divided shell. The cylindrical portions 43 are preferably welded or secured to unperforated portions of the adjacent shell. If desired, however, one or more of the webs 42 may be omitted, so that chambers of diderent lengths may be formed or a chamber that is open at one end, so that. for example, the chamber 29 could communicate with the chamber 3l.

, We claim as our invention:

1. A muiiler having an inlet end arranged to connect with an exhaust pipe of an internal combustion engine and having a discharge passage at the other end thereof, of a conduit in said muftler forming a passage from the inlet to the other end of said muiiler, said conduit having an external diameter no greater than the external diameter of said exhaust pipe and apertured throughout the greater part of the length thereof, a shell surrounding said conduit, and a' plurality of restrictions arranged at intervals lengthwise of said conduit to reduce noise made by gases flowing across the perforations in said conduit, the inner diameter of said restrictionsbeing at least two-thirds of the inner diameter of adjacent.

portions of said conduit. y

2. A muler having an inlet end arranged to connect with an exhaust pipe of an internal combustion engine and having a discharge passage at the other end thereof, of a conduit in said muiiler forming a passage from the inlet to the other end of said muiiier, said conduit having an external diameter no greater than the external diameter of said exhaust pipe and apertured throughout the greater part of the length thereof, a shell surrounding said conduit, and a restriction in said conduit arranged with apertures before and behind said restriction, said restriction forcing a portion of the gas and sound waves entering said mufiler to pass out of perforations arranged ahead of said restriction and to pass about said conduit in the space between said conduit and said shell, and then to return to said conduit through perforations located behind said restriction, the opening in said restriction being Aat least two-thirds of. that of adjacent portions of said conduit.

3. A muiiler having a conduit open at both ends to receive gases in one end thereof, and discharge gases from the opposite end thereof and extending continuously from end to end of said muf- `iler, a shell surrounding said conduit to form a closed chamber about said conduit, said conduit having a restriction intermediate of the ends thereof, and perforations in said conduit both before and behind said restriction to permit sound waves and gases to pass out of perforations before reaching said restriction and to pass in said chamber through perforations in said conduit behind said restriction, the opening in said restriction being at least two-thirds of that of adjacent portions of said conduit.

4. A muilier having an outer shell and a conduit confined within said shell and forming a..

continuous passage from end to end thereof for the greater portion of the gases entering said conduit and having perforations through which a lesser portion of the gases and sound waves may pass to and from the space between said shell and said conduit, and a restriction in said conduit and so arranged relatively to said perforations that certain of said perforations are lo- 5 cated forwardly, and others rearwardly of said restriction, with reference to the ow of gases through said conduit, the opening in said restriction being at least two-thirds of that of adjacent portions of said conduit.

5. A muiiier having an outer shell and a conduit confined within said shell and forming a continuous passage from end to end thereof for the greater portion of the gases entering said conduit and having perforations through which a lesser portion of the gases and sound waves may pass to and from the space between said shell and said conduit, means associated with said perforations' to cause gases discharged through said perforations to move about the axis of said conduit in the space between said shell and conduit, and a restriction in said conduit and so arranged relatively to said perforations that certain of said perforations are located forwardly, and others rearwardly of said restriction, with reference to the ow of gases through said conduit.

6. A muiiier including an outer shell, an inner conduit arranged within said shell and forming a.w continuous passage for gases through said muilier and having perforations throughout the greater part of the length thereof, a plurality of l restrictions in said conduit spaced from each other and each arranged between perforations located rearwardly and forwardly of said restriction with reference to the direction of flow of gases though said conduit, the inner diameter of said restrictions being at least two-thirds of the inner damter of adjacent portions of said conduit.

7. A muilier including an outer shell, an inner conduit arranged within said shell and forming a continuous passage for gases through said muiiier and having perforations throughout the greater part of the length thereof, a. plurality of restrictions in said conduit spaced from each other and each arranged between perforations located rearwardly and forwardly of said restriction with reference to the direction of iiow of gases through said conduit, the internal diameter of said restriction being at least two-thirds of the diameter of adjacent parts of said conduit, and means associated with said perforations to direct gases and sound waves discharged through said perforations substantially tangentially of said conduit.

8. A muffler including an outer shell, an inner conduit arrangediwithin said shell and forming 'a continuous passage for gases through said tween said shell and conduit from perforations 4" forwardly of a restriction to perforations located rearwardly of said restriction.

` 9. A muiller including an cuter shell, f an inner conduit arranged within said shell and forming a continuous passage for gases through said muiiler and having perforations throughout the greater part of the length thereof, a plurality of restrictions in said conduit spaced from each other and each arranged between perforations located rearwardly and forwardly of said restriction with reference to the direction of flow of gases through said conduit, and a baille connecting said conduit and shell and spaced about said conduit at a portion thereof intermediate of adjacent restrictions, and restricting the passage of gases and sound waves through the space between said shell and conduit from perforations forwardly1 of a restriction to perforations located rearwardly of said restriction, the combined areas of the perforations through which gases may flow out of or into said conduit about a restriction being at least equal to the cross sectional area oi the smallest passage through said restriction.

10. A muiiier having a straight substantially uninterrupted perforate conduit for gas and sound waves, a shell surrounding said conduit and forming a closed space about said conduit into and out of which gases and sound waves can pass only through the perforations in said conduit, said conduit having a small restriction therein intermediate of its ends to produce a slight resistance to the iiow of gases through said conduit, which causes a portion of said gases to bypass around said restriction through the space between said conduit and shell and which permits a larger portion of gases and sound waves to pass through said restriction.

11. A muilier having a straight substantially uninterrupted perforate conduit for' gas and sound waves, a shell surrounding said conduit, and forming a closed space about said conduit into and out of which gases and sound waves can pass only through the perforations in said conduit, said conduit having a restriction therein intermediate of its ends to produce a resistance to the ow oi gases through said conduit, which causes a portion of said gases to bypass around said restriction through the space between said conduit and shell, and which permits a larger portion of gases and sound waves to pass through said restriction, and means associated with said perforations for directing gases and sound waves discharged therethrough in a direction substantially tangentially of said conduit.

12. A muffler having a substantially uninterrupted perforate conduit for gas and sound waves, an outer shell surrounding said conduit and forniing a closed space about said conduit into which gases and sound waves can pass only through the perforations in said conduit, said conduit having a restriction therein spaced intermediate of its ends and between perforations, to cause gases and sound waves to pass through periorations ahead of said restriction into the space between said conduit and said outer shell and then back into said conduit through perforations located rearwardly of said restriction, and an intermediate shell spaced between a periorate portion of said conduit and said outer shell and forming with said conduit sound absorbing chambers ior high frequency sound waves and spaced from said restriction, said intermediate shell forming with said outer shell a resonance chamber for low frequency sound waves, which is closed at one end and communicates with said conduit at its other and.

13. A muiiler having a substantially uninterrupted perforate conduit for gas and sound waves, an outer shell surrounding said conduit and forming a closed space about said conduit into which gases and sound waves can pass only through the perforations in said conduit, said conduit having a plurality of restrictions therein spaced apart, each restriction in said .conduit being spaced between two groups of perforations, one group being located in advance of said restriction and the other group being located rearwardly of said restriction, and a baille connecting the said conduit and said outer shell and spaced between the two groups of perforations of one restriction and the two groups of perforations of another restriction.-

14. A muler having a substantially uninterrupted perforate conduit for gas and sound waves, an outer shell surrounding said conduit and forming a closed space about said conduit into which gases and sound waves can pass only through the perforations in said conduit, said conduit having a plurality of restrictions therein spaced apart, each restriction in said conduit being spaced between two groups of perforations, one group being located in advance of said restriction and the othergroup being located rearwardly of said restriction, and a baffle connecting the said conduit and said outer shell and spaced between the two groups of perforations of one restriction and the two groups of perforations of another restriction, and an intermediate shell surrounding apertorate portion of said conduit separate from the groups of perforations associated with said restrictions.

15. A muiiler having an outer shell, inlet and discharge heads secured to said shell and provided with gas receiving and discharge openings, a perforate conduit connecting said openings and providing a substantiallyv straight uninterrupted passage ior gases from said receiving opening to said discharge opening and provided at intervals between perforations with restrictions serving to cause a portion of the gases in the conduit to pass outwardly through perforations into the space between said conduit and said outer shell and back through other periorations into said conduit',

16. A muiiler having an outer shell, inlet and discharge heads secured to said shell and provided with gas receiving and discharge openings, a perforate conduit connecting said openings and providing a substantially straight uninterrupted passage for gases from said receiving opening to said discharge opening and provided at intervals between perforations with restrictions serving to cause a portion of the gases in the conduit to pass outwardly through perforations into the space between said conduit and said outer shell and back through other perforations into said conduit, and means in the space between said conduit and said outer shell for determining the length of travel of sound waves in said space between said conduit and outer shell to cause said sound waves when reentering the conduit to be out of phase with sound waves passing straight through said conduit.

GAILI C. STARKWEATHER. LUCIEN L. HAAS.