US2277132A - Silencer - Google Patents

Description

March 24, 1942. c. c. Moss SILENQER Filed Aug. '28, 1939 INVENTOR heser C'. Nass BY I f%9flc4.

. A oRNEYs.

Patented Mar. 24, 1942 SILENCER Chester C. Moss, Jackson, Mich., assigner to Walker Manufacturing Company of Wisconsin, a corporation of Wisconsin Application August 28, 1939, Serial No. 292,169

3 Claims.

The present invention relates to silencers, and particularly to silencers especially designed for, but not restricted in their application to, use as exhaust silencers for automobile engines.

The principal objects of the present invention are to provide a silencer of the above indicated type, and a method of making the same, characterized as embodying an improved arrangement for minimizing shell noises, increasng the overall strength of the shell and otherwise increasing the efficiency of the silencer; to provide such a construction having a laminated shell embodying an outer shell member and a cooperating inner shell member; to provide such an arrangement wherein the meeting edges of the inner shell are overlapped relative to each other; and to generally improve the shell construction of exhaust silencers.

With the above, as well as other objects in view, which appear in the following description and in the appended claims, a preferred but illustrative embodiment of the invention is shown in the accompanying drawing, throughout the several views of which corresponding reference characters are used to designate corresponding parts, and in which:

Figure l is a view in longitudinal section of an exhaust silencer embodying the invention;

Fig. 2 is a View in vertical transverse section taken along the line 2-2 of Fig. 1;

Fig. 3 is an enlarged fragmentary view, taken along the line 3 3 of Fig. 1;

It will be appreciated that exhaust silencers conventionally comprise a shell-like structure having an inlet adapted for connection to the exhaust pipe of the associated engine, and having an outlet adapted for connection to the usual tail pipe. The shell is conventionally interiorly provided with silencing structure, so constructed and arranged that as a consequence of the passage of the exhaust gases through the shell from the inlet to the outlet thereof, the objectionable sounds thereof are partially or entirely silenced.

By'virtue of the fact that the exhaust gases are delivered from the engine to the silencer as a succession of pressure impulses, it will be appreciated that the exhaust gases circulate through the shell at continuously and rapidly varying pressures. The circulation through the shell oi the exhaust gases under the just mentioned periodically varying pressure conditions is generally regarded as accounting in large part at least for producing objectionable sounds known as shell noises. In certain instances, the shell noise is regarded as being produced. directly by the rapid changing of pressure within the shell, which rapid changes cause expansion, and permit contraction, of the shell and in certain other instances, are regarded as being produced by thev impinging against the shell of gaseous particles. Various expedients have heretofore been proposed for the purpose of minimizing the shell noises, but such expedients have not proven entirely satisfactory. The arrangement described below has been found markedly effective in silencing shell noises and in otherwise improving the performance of exhaust silencers.

It will be understood from a complete understanding of the invention that the improvements in the shell construction herein provided are, in their broader aspects, applicable to a wide variety of silencer constructions. By way of illustration, but not of limitation, however, the improvements of the present invention are herein illustrated in connection with a silencer of the socalled three tube or retroverted type.

Referring to the drawing, the illustrated construction comprises generally a shell, designated as a whole as I6, the respectively opposite ends whereof are closed by heads I4 and I6, and which is interiorly provided with a silencing structure comprising the series of parallel passages I8, 20, and 22, and the partitions 24, 26, and 28. The inlet pipe 66, which is adapted for connection at its outer end to the usual engine exhaust pipe (not shown), extends through an opening provided therefor in the head I4, and is rigidly connected thereto as by welding at a plurality of points around the flange 32, which is formed in the head I4. The outlet 34, in turn, extends through a corresponding inwardly directed nipple 36 formed in the head I6, and is correspondingly rigidly secured thereto as by welding at a plurality of points therearound. The inner end of the inlet 36 is telescoped over the end of the passage 20, which passage, in turn, passes through and is secured as by welding at the points 38', 4D, and 42, to the partition members 24, 26, and 28. The inner end of the outlet 34 is secured to the rear end of the exhaust passage I8, which passage in turn is secured to the partitions 26 and 28 as by welding at the points 44 and 46. It will be understood that the remaining passage 22 also extends between, and has its ends welded to, the partitions 26 and 28.

The partitions 24 and 26 will be recognized as providing a transverse passage or cross-over 48, whereas the partition 28 and the header I6 will be recognized as providing a corresponding crossover 56. The partition 24 and the header I4 in turn afford a silencing chamber 52, which is in acoustic communication with the cross-over 48 through an opening 54 formed in the partition 24.

It is preferred, as illustrated, to provide the tubes I8, 20, and 22, in the portions thereof falling between the partitions 26 and 28, with a series of louver openings 56 so as to afford acoustic communication between the interiors of such tubes and the silencing chamber 58, which lies between the partitions 26 and 28. In addition, in the illustrated construction, the tube I8 is provided with an additional shell member 60, which, with the associated partitions 6I, 62, 63, and 64, define a plurality of small spit chambers surrounding the tube I8. Access from the interior of the tube I8 to the interior of the individual spit chambers is afforded through the louver openings such as 56 provided along the body of the tube I8.

With the foregoing relation, it will be understood that the silencer provides a primary exhaust passage for gases entering through the inlet 30, which extends through the tube 28, the cross-over 50, the tube 22, the cross-over 48, and thence through the tube I8 to and through the outlet 34. By virtue of the louver openings 56, the gases traveling through the just-mentioned path are enabled to circulate between each of the tubes I8, 28, and 22 and the silencing chamber 58. In addition, portions of the gases are enabled to pass into and out of the silencing chamber 52 through th'e openings 54. Portions of the gases passing through the tube I8 are also enabled to circulate into and out of the small spit chambers provided between the tube I8' and the inner shell 60.

Referring now particularly to the construction of the shell itself, it will be noted that the shell I8 is constituted by an outer cylindrical member 10, the marginal edges whereof are rolled together in accordance with conventional practice, to form a lock seam 12; and by an inner shell member 14, disposed within the shell member 1D. The longitudinal marginal edge portions 'I6 and 'I8 of the inner shell are in overlapped relation to each other and are displaced from the seam 'I2 by an angle of approximately 180. The outer ends of the inner and outer shell members I4 and 'I0 are rolled with the marginal edge portions of the h'eads I4 and I6, so as to form the rolled seams 8U and 82, thus affording a rigid and secure connection between the heads and the shell members.

In respect to the assembly of the above structure it is preferred to roll or otherwise bring the outer shell 'I0 from flat to cylindrical form, and form the lock seam 'I2 therein, in accordance with conventional practice. Thereafter, it is preferred to slide the inner shell 'I4 into th'e outer shell and allow the inner shell, when properly positioned therein, to expand slightly under the iniluence of its own spring-like characteristics, so as to bring the outer surface of the inner shell into engagement with the corresponding inner surface of the outer shell. With the shell members thus preliminarily assembled, the silencing structure, comprising the partition members and the conduit portions I8, 20, and 22, may be slid into place, after which the heads I4 and I6 may be applied to the ends of the shell members and secured in place by means of the rolled seams 8|) and 82. To facilitate assembly, it is preferred to initially form the inner and outer shells of substantially the same length,

and it will be understood that when the rolled seams and 82 are formed, some axial sliding occurs between the extrem'e end portions of the inner and outer shells, and that, in the completed seam, such extreme ends such as 14a and 10a lie in slightly oifset relation to each other, as is clearly shown in Fig. 3.

The resultant construction has been found in practice, as previously mentioned, to markedly improve the characteristics of exhaust silencers. Certain of the advantages resulting from the above described method and arrangement are as follows.

In respect to the reduction in shell noises, it will be appreciated that the above laminated construction produces the damping action which is characteristic of a laminated diaphragm or other element. That is to say, the pressure impulses which are transmitted through the silencer, tend to cause vibratory movements of the inner and outer shell members, which vibratory movements produce the effect known as shell noise. By virtue of the fact that the inner and outer shells are in laminated relation to each other, however, or, stated otherwise, are in continuous engagement with each other, the vibratory movements of the inner and outer shell members result in minute components of slippage between the inner and outerl shells, which slippage components materially dampen the shell noise. The present laminated construction is, therefore, substantially free in service of objectionable shell noises.

A further and important advantage has to do with the increased strength' of the silencer as a whole. It will be recognized that the pressure impulses transmitted through th'e silencer subject the latter to substantial forces tending to rupture the shell. In conventional structures, the longitudinal lock seam is, of course, a relatively weak part of the structure, and these forces frequently rupture the lock seam. With the present construction, however, the resistance to rupture is very materially increased by the provision of the inner shell. It will be noticed that the overlap in the inner shell is spaced from the lock seam in the outer shell by approximately The pressure is applied to the lock seam accordingly not directly, but only through the inner shell. The substantial pressures existing within the inner shell act to form a substantial frictional connection between the overlapped edges of the inner shell, which frictional engagement enables the inner shell to itself withstand substantial expansive pressures. The inner shell, accordingly, not only functions to reinforce the outer shell, by itself sustaining a substantial part of the expansive pressure, but also protects the lock seam formed in the outer shell, and prevents the expansive pressures from being directly applied to the lock seam.

Considerable difficulty has heretofore been experienced in the manufacture of silencers in respect not only to leakage between the several silencing or resonating chambers, but also in respect to leakage between the interior of the silencer and the outside atmosphere. In the usual manufacture of silencers employing a longitudinal lock seam, it has been conventional to space the ends of the lock seam a slight distance inwardly from the ends of the silencer, so as to allow for the formation of the joint between the shell and the heads, which joint is herein illustrated as being a rolled seam. This practice necessarily introduces a possibility of leakage between each end of the lock seam and the corresponding rolled or other seam at the end of the shell. This difliculty is entirely overcome with the present arrangement, since, as clearly appears, the inner shellextends entirely to the end of the shell structure. The pressures acting against the inner shell serve to hold it in tight frictional engagement; with the outer shell, and also serve as mentioned above to produce a substantial frictional engagement between the overlapped edges 16 and 18. Because of the latter frictional engagement, little, if any, leakage of gases occurs between such overlapped edges, and any such.

leakage, in order to escape from the outer shell, would have to travel in the space between the inner and outer shells from the position of the overlap to the position of the lock seam 12.

In respect to leakage which normally occurs between the silencing chambers positioned within the silencer, it will be appreciated that the rolling of the outer shell member tends to introduce some irregularities or unevenness in the form thereof, which irregularities afford leakage spaces around the cylindrical partitions such as 24, 26 and 28. In the present construction, the inner shell, upon being introduced into the outer shell, expands against the latter, and tends in large part to smooth out the just mentioned unevenness or irregularities, thus affording a sub-I stantially true cylindrical surface to receive the partitions and thereby minimize internal leakage.

The above described laminated construction is further advantageous in that, as will be appreciated, it lends itself to the provision of a silencer having the non-corrosive inner surface, without at the same time requiring that the entire shell structure be formed of relatively expensive noncorrosive material. That is to say, the outer shell may be formed of relatively inexpensive metal, and the inner shell may be formed of non-corrosive metal, thus affording all the advantages of the non-corrosive structure, without introducing the expense incident to the use of noncorrosive metal throughout.

The overlapped relation of the edges of the inner shell is advantageous, not only in respect to the features discussed above, but also in respect to the control of condensation, and the prevention of any condensate from entering the space between the inner and outer shells. It is usual to mount the cylinder on the associated vehicle in substantially the rotative position shown in Fig. 2, in which the lock seam 12 is at one side of theA silencer. In the present instance, the overlapped edges 16 and 18 are also positioned at the side of the silencer, with the inner edge 18 extending downwardly and inwardly over the compansion edge 16. With this relation, any condensate which accumulates along the inner surface of the shells, and flows downwardly along the side walls, is enabled to ilow across the junction between the edges 16 and 18 without entering the space between such edges.

It is believed evident from the foregoing detailed description that the present method and arrangement provides an extremely simple and effective silencer construction, and that various modifications in the form and arrangement of the parts may be made within the spirit and scope of the invention.

What is claimed is:

l. In a silencer for exhaust gases, the combination of a shell structure, acoustic silencing structure within said shell and cooperating with the shell to define at least one chamber, a portion at leastl of the wall whereof is constituted by said shell, said silencer having means for introducing gases into said chamber, said shell comprising an outer shell-like member and an inner shelllike member received in the outer member, the adjacent surfaces of the members being in continuous engagement with each other, each said member having a longitudinal joint therein, and said joints being in angularly displaced relation to each other.

2. In a silencer for exhaust gases, the combination of a shell structure, acoustic silencing structure within said shell and cooperating with the shell to define at least one chamber, a portion atleast of the wall whereof is constituted by said shell, said silencer having means for introducing gases into said chamber, said shell comprising an outer shell member, and an inner shell member positioned within said outer member, said inner member having a longitudinal seam therein, the adjacent edges of which are freely overlapped on each other throughout at least a major portion of the length of said inner shell, and said outer shell having a longitudinal seam therein in angularly displaced relation to the rst mentioned seam.

3. In a silencer for exhaust gases, the combination of a shell structure, acoustic silencing structure within said shell and cooperating with the shell to define at least one chamber, a portion ai, least of the wall whereof is constituted by said shell, said silencer having means for introducing gases into said chamber, said shell comprising an outer shell member, and an inner shell member positioned within said outer member, said inner member having a longitudinal seam therein, said outer shell having a longitudinal seam therein in angularly displaced relation to the first mentioned seam, and a head for enclosing each end of the shell, each head being rigidlly secured to each shell member, the adjacent edges of said inner shell being freely overlapped on each other except in the regions where said inner shell is secured to said heads.

CHESTER C. MOSS.

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