US2072961A - Silencer - Google Patents

Description

Mara] 9, 1937.

C. E. NELSON 4 SILENCER Filed March 1, v1934 2 'sheets-sheet 1 INVENTOR C /Ve/saf? BY A l I. ATTORNEYS C. E. NELSON March 9, 1937.A

SILENCE-R Filed March l. 1934 2 Sheets-Sheet 2 Patented Mar. 9, 1937 UNITED STATES PATENT OFFICE C. F. Burgess Laboratories, Inc., Chicago, Ill

a corporation of Delaware Application March 1,` 1934, Serial No. 713,438

11 Claims.

This invention relates to an improved silencer especially applicable to the silencing of the exhausts of internal combustion engines in which occur sound, and also gaseous-pressure waves other than those due to sound.

The silencer of this invention is an improvement over the constructions shown in the Schnell Patent No. 1,811,762, issued June 23, 1931, and Jack Patent No. 1,921,468, issued August 8, 1933,

in that it provides a construction whereby the inventions of these patents may be used within a limited space. It often is necessary to limit the length of silencers because of space limitations within the frame members on the'under side of automobile bodies. My invention provides means whereby the length required for eective silencing may be obtained even though the available space is limited.

Various specic embodiments of the herein aimed invention are illustrated in the accompanying drawings in which:

Fig. 1 is a side elevation in partial section of one embodiment of my invention;

Fig. 2 is a transverse, sectional view on line 2-2 of Fig. 1;

Fig. 3 is a similar view on line 3 3 of Fig. 1;

Fig. 4 is a longitudinal, sectional view of another form of the invention;

Fig. 5 is a transverse, sectional view of the silencer shown in Fig. 4;

Fig. 6 is a longitudinal, sectional view of another form showing concentric inlet and outlet;

Fig. 'l' is a transverse, sectional view of another form of the invention;

Fig. 8 is a longitudinal, sectional view of another form of thepinvention showing the inlet and outlet -arranged at the same end of the silencer;

40 Fig. 9 is a transverse, sectional view of the form shown in Fig. 8;

Fig. 10 is a longitudinal, sectional View of another form of the invention showing a concentric inlet and a concentric outlet;

Fig. 1l is a transverse, sectional view on line II-I.I of Fig. 10; and

Fig. 12 is a similar view on line I 2-I2 of Fig.

Referring to Figs. 1 to 3, the silencer therein illustrated consistsof a substantially imperforate cylindrical shell I0 having end anges II and I2. These flanges are provided Withf an inlet I3 and .an outlet I4, respectively. The passage connecting inlet I3 and outlet I4 is made up of four parallel and connected juxtaposed ducts I5, I6, I'I and I8 and the remaining space within the casing is lled with sound and gas-pressure absorbing material I9 which forms the walls of the ducts. Some of these parallel ducts are con- 60 nected in series. Such absorber may be made of any suitable material such as mineral wool, pumice, aggregate formed from heat expanded clay and known under the trade-mark Haydite, exfoliated vermiculite and the like bound by a suitable adhesive, preferably an alkali silicate such as silicate of soda. Porous, molded, fired clay shapes also may be used. The preferred composition is a mixture of exfoliated vermiculite and silicate of soda. within the ranges of composition described in the above noted Jack patent, the more dense mixtures thereof being preferred.

Following is a specific mixture which has given excellent results:

Pound Exfoliated vermiculite 6-10 mesh 1 42 B. sodium silicate (lNarO: 3.25 SiOz ratio) 1.2 Limestone dust 0.3 Water 0.05

"This is packed to a density of -40 lbs. per cubic foot, lbs. being preferred. When dry this mix has a porosity of 25% to 35%, 28% being a good average.

Duct I5, which communicates directly with inlet i3, extends to the opposite end of the cylindrical shell I0. 'Ihere it connects with both ducts l'l and I8 by means of a transverse passage 20 which is formed by cutting away a portion of the intervening absorbing walls. The two parallel ducts Il and I8 extend to the opposite end of the shell I0 and are connected with duct I6 by a transverse passage 2l which is also formed by cutting away a portion of the intervening absorbing walls. Duct I 6 extends in the opposite direction and connects directly with outlet I 4. The gases entering the silencer through inlet I3 travel to the opposite end of the shell I0 in duct I5 to a point adjacent the outlet i4, reverse their direction in transverse passage 20, divide and enter ducts I1 and I8, travel to the end of the shell I0 to a point adjacent the inlet I3, reunite in transverse passage 2| and reverse their direction to travel in duct I6 to outlet I4.

As the gases pass through the parallel ducts their pressure decreases so that there is a pressure differential between duct I5 and ducts I'I and I8, between duct I5 and duct I6, and between ducts I 1 and I8 and duct I6. The greatest difference is between duct I5 and duct I6. The intercommunicating pores and' channels of the absorbing material permit some gas to flow or leak from a duct at a higher pressure to one at a lower pressure. I have discovered that the silencer has a greater silencing efliciency when the walls or partitions permit such leakage than a similar construction in which impervious partitions between adjacent ducts are used and which prevent such leakage. The leakage must not be too great or the silencing efliciency may again drop to a point where the construction does not silence suciently. For the best silencing the amount of leakage, which is determined by the physical characteristics of the absorber, that is, the number, size and other characteristics of the intercommunicating pores and channels, has to be determined by experiment for the conditions under consideration.

In the lsilencer illustrated in Figs. 1 to 3, the absorbing material preferably is a molded unit or block. The unit may be molded separately with the necessary ducts and channels and then inserted into the shell I0 and the end flanges Il and l2 fastened in place. I prefer, however, to mold the unit in the shell l0. The shell I0, without the end anges Il and I2 is filled vwith a plastic mass of aggregate and adhesive such as exfoliated vermiculite and silicate of soda solution. The proportions of these should be such that when the molded product is dried it will have. the desired strength and porosity. The proportions may be those set forth in the Jack patent previously referred to. 'Ihe ducts are then formed by a spearing operation, that is, sharp tipped rods are punched completely through the mixture. These punches may be so formed that they also simultaneously form the transverse passages 2G and 2l. The best results are obtained if the spearing of the different ducts is done simultaneously from opposite ends. This simultaneous operation prevents the plastic mixture from accumulating or bunching at one end because of the drag of the plastic mass. The spearing operation as described densies the material sufficiently and uniformly and forms a smooth-walled duct which is desirable for best results in silencers for the exhaust gases of internal combustion engines.

After the spearing operation is completed the end'flanges Il and l2 are inserted in the shell. The metallic shell expands more than the molded m'mture when subject to temperature changes. and, in order to prevent gas leakage adjacent the end anges, tubes 22 and 23 are inserted through inlet i3 and outlet ld for a limited distance into the molded ducts. This construction anchors the molded unit and prevents gas leakage at these points. The molded mass is dried and hardened before it is placed into service.

In the silencer of Figs. 1 to 3 ducts Il and i8 are in parallel and are formed so that a portion' of the shell lll forms a portion of the walls of these ducts. Among the shapes of ducts which are commercially practical in a circular casing and which have equal cross sectional area the arrangement described above provides the greatest uniform wall thickness and strength. This construction also provides a change in the crosssectional area in successive ducts, which increases the attenuation of the gaseous-pressure waves passing therethrough.

In another arrangement, Figs. 4 and 5, the transverse ducts connecting the parallel ducts are not molded into the absorbing material. A substantially imperforate casing 2li has end anges 25 and 26 which contain the inlet 21 and outlet 28, respectively. The molded absorbing material 29 contains three parallel juxtaposed ducts 3U, 3l and 32. The absorbing material does not extend to the end flanges 25 and 26 thereby leaving end spaces 33 and 3G. Plates 35 and 36 preferably are used to face the end of the absorbing material though these may be omitted. The inlet 21 is connected to duct 30 by a pipe 37. This pipe preferably projects a short distance into the duct. The outlet 28 is similarly connected duct 3l by pipe 3B.

The gases enter duct 30 through inlet pipe 31 and pass therethrough into end space or transverse duct 34. Here the gases reverse their direction and pass into duct 32 and thence therethrough and into the end space or transverse duct 33. Here they reverse their direction again and pass into duct 3l. After traversing the length of duct 3| the gases pass out of the silencer by means of outlet pipe 38. Since the absorber 29 is porous a small proportion of the gases pass through the porous walls from a duct at higher pressure to one at lower pressure. It may be desirable to place the ducts laterally closer'together which follow one another immediately in the path of the gas stream and between which there is less differential pressure thanv there is between ducts which are more remote from one another in the path of the gas stream. This is illustrated in Fig. 5 where duct 32 is closer to either duct 30 or 3l than the latter are to each other. The absorber o'f this construction preferably is formed by spearing while in the shell 2G as described in connection with Figs. 1 to 3 although the molded absorbing member may be molded and dried independently of the shell.

It is obvious that the ducts may be lined with a foraminous material such as a screen or perforated metal as described in the Schnell and Jack patents. Such a lining decreases the erosion of the absorber material and permits the use of absorbing materials which are otherwise destroyed by the destructive exhausts of internal combustion engines.

The constructions of Fig. 1 and Fig. 4 place the inlet and outlet off-center of the end flanges. Fig. 6 shows a construction incorporating the silencer of Fig. 1 with the inlet and outlet concentric of the end flanges. In this construction, I employ a substantially, imperforate casing 39 for the molded -absorber lll] containing the juxtaposed parallel ducts. End flanges il and 32 are disposed at the ends of the absorber, and the casing is extended beyond these anges. A second set of end flanges d3 and ld are arranged at the ends of the casing, thereby forming end volumes 45 and 56. These end flanges contain centrally loc-ated inlet d'1 and outlet Q8, respectively.

All of the ducts in the absorbing material may be formed so that the outer shell i9 forms a wall of the juxtaposed parallel ducts 55, 5l and 52 as shown in Fig. 7. In this construction the ducts are lined with perforated metal linings 53, 5d and 55, which are backed with porous absorber 56. This construction also allows gas leakage between the ducts.

In Figs. 8 and 9 a construction is shown in which the inlet and outlet are at the same end of the silencer. Absorbing material 5I is contained in a shell 58. A flange 59 closes one end of the shell. A ange 60 at the other end contains both inlet pipe 6| and outlet pipe 62. These pipes preferably extend a slight distance into juxtaposed parallel ducts 53 and 5&1.' The ducts are connected by curved transverse duct S5. Instead of the curved duct the end space construction of Fig. 4 may be used.

In Figs. 10, 11 and 12 another construction is shown in which the inlet 66 and outlet 67 are concentric with the outer casing 68. An end plate 69 is spaced from the inlet within the casing and forms a space IIJ into which the gases pass The absorbing material 'il is placed in the casing beyond this end plate 69. The absorbing material is molded to provide ducts 12, 13 and 16 therein. Ducts 12 are adjacent the casing 68. These ducts communicate with the space 1U through openings in end plate 69. Ducts 12 are connected with ducts 13 by means of transverse ducts 14 formed adjacent the end ange 15. The gases pass from ducts 12 into ducts 13, the direction being thereby reversed. Ducts 13 extend to the end plate 69 and are connected with central duct 16 by means of a transverse passage 11. Central duct 16 connects with outlet 61, tube 18 preferably extending into duct 16 for a short distance. The gases in ducts 13 pass into central duct 16 and leave the silencer by means of outlet 61 and tube 18.

It is obvious that variations of the described constructions may be made without departing from the principles of my invention. For exam' have the shells or ducts of the shapes shown inv the drawings.

I claim:

1. A silencer for the exhaust gases 'of an infV ternal combustion engine comprising a plurality of juxtaposed parallel ducts for said gases, at l least three of said ducts being arranged in series, sound and gas pressure absorbing material lexposed in the walls of said ducts and vforming the Ipartitions between adjacent ducts, said ab-r 5. The silencer of claim 3 in which a substantial portion'of the longitudinal wall of at least one of said parallel ducts is formed by said imperforate shell.

6. The silencer of claim 3 in which the lateral arrangement of the series connected ducts is such that those ducts which follow one another remotely in the path of the gas stream are further apart than those which follow one another immediately in the path of the gas stream.

l'1. A silencer for the exhaust gases of an interna] combustion engine comprising an imperforate shell having an inlet and outlet at op posite ends thereof, four juxtaposed parallel longitudinal ducts and two transverse ducts for said gases within said shell connecting said inlet with said outlet, two of said longitudinal ducts being spaced from each other and from said shell, the

. other two of said longitudinal ducts being spaced from each other and from said rst two longitudinal ducts and so formed that said shellV forms a tudinal ducts being connected to saidinlet and sorbing material containing intercommunicating pores and channels, said pores and channels occupying approximately 25 to 35 percent of the volumeof said absorbing material, said gases beingjfree to pass through said absorbing material directly from one to any other of said ducts; the passage of said gasesthrough said absorbing material being limited entirely by the porosity characteristics of said material.

2. The silencer of claim 1 in-which the sound and gas-pressure absorbing material comprises a molded mass of exfoliated vermiculite and binder.

3. A silencer for the exhaust gases of an internal combustion engine comprising a substantially imperforate shell having an inlet and outlet, a plurality of juxtaposed parallel ducts for said gases within said shell, Vat least three of said ducts being connected in series and connecting said inlet and saidoutlet, sound and gas pressure absorbing material exposed in the walls of said ducts and forming the partitions between adjacent ducts, saidabsorbing material containing intercommunicating pores and channels, said pores and channels occupying approximately 25 to 35 percent of the volume of said absorbing material, said gases being free to pass through said absorbing material directly from one to any other of said ducts, the passage of said gases through said absorbing material being limited entirely by the porosity characteristics of said material.

4. The silencer of claim 3 in which the inlet and outlet are at opposite ends of the imperforate shell and in which there are at least four longitudinal ducts and four transverse ducts at the ends thereof connecting said longitudinal ducts in such manner that the gases reverse their direction of flow twice, in passing from the inlet to the outlet and, at their first reversal, are divided into two streams, and, at their second reversal, are reunited into a single stream.

' the other being connected to said outlet, the two transverse ducts connecting the first two longitudinal ducts with said second longitudinal ducts Awhereby the exhaust gases reverse their direction of ow twice in passing from the inlet to the outlet, the gases in their rst reversal being divided into two streams and reuniting intoa single stream for the second reversal of ow; `the space within said shell and surrounding said ducts containing sound andgaspressure absorb'- ing material whose f intercommunicating,poresl l and channels open into saidfducts whereby some of the exhaust gases pass through said absorbing material from a duct at higher pressure into an adjacent duct at lower pressure.

8. A silencer for the exhaust gas of an internal combustion engine comprising a substantially imperforate. shell having an inlet and an outlet, a mass of sound and gas pressure absorbing material within said shell, said absorbing material having a plurality of juxtaposed parallel ducts for said gas molded therein and connecting said inlet with said outlet, at least three of said ducts being connected in series, said absorbing material containing intercommunicating pores and channels, said pores and channels occupying approximately 25 to 35 percent of the volume of said absorbing material, said gases being free to pass through said absorbing material directly from one to any other of said ducts, the passage of said gasesthrough said absorbing material being limited entirely by the porosity characteristics of said material.

9. The silencer of claim 8 in which the imperforate shell has flanges extending inwardly from the inlet and outlet thereof and into the ducts connecting with said inlet and outlet.

10. The silencer of claim 8 in which the crosssectional area of at least one of the series connected ducts is different from that of the others.

l1. The silencer of claim 8 in which the said mass has transverse ducts molded therein adjacent the ends of said imperforate shell, said transverse ducts forming the connections between the series connected longitudinal ducts.

CHARLES EMORY NELSON.

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