Muffler

Sept. 17, 1935.

P. G. PEIK

MUFFLER

Filed Oct. 31, 1S32

2,014,666

Sheets-Sheet 1

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PAUL G- P£/K

Sept. 17, 1935.

P. G. PEIK

MUFFLER'

2,014,666

Filed Oct. 31, 1932 2 Sheets-Sheet 2

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PAUL G- P£/K

Ύ- ^ίθ-trvC . I *

Patented Sept. 17, 1935

2,014,666

UNITED STATES PATENT OFFICE

2,014,666

MUFFLER

Paul G. Peik, Chicago, Ill., assignor to The Halsey W. Taylor Company, Warren, Ohio, a corporation of Ohio

Application October 31, 1932, Serial No. 640,557

Claims. (CI. 137—160)

This invention relates to mufflers for silencing the exhaust noises of engines, particularly internal-combustion engines.

The main object of the invention is to pro5 vide a muffler having the highest muffling efficiency and lowest back pressure known in the art, and at the same time having a degree of compactness heretofore unattained in mufflers of comparable efficiency .

Another object of the invention is to provide a muffler of highest known efficiency at a cost materially lower than the cost of mufflers of comparable efficiency.

The following brief reference to the behavior 16 of sound waves and the nature of sound impulses in the exhaust stream of internal combustion engines will serve to show how the above objects are attained and to bring out the salient features of this invention.

Fundamentally all sound .deadening is due to resonance action. The highest efficiency of sound deadening,—that is, elimination of any sound wave in one cycle,—is attained only by providing a separate chamber tuned exactly to the length of that wave. This method is not feasible in a muffler, due to the multiplicity of sound waves in the exhaust stream, and the constant variation of their frequency due to the acceleration and deceleration of the engine. While each in30 dividual air space in sound absorbing material employed in mufflers of the so-called acoustic type, is far too small to have an efficient sound deadening action in one cycle, acoustic mufflers are nevertheless very efficient in deadening high frequencies of sound due to the multiplicity of air spaces and the high rate of oscillation of the high frequencies. Thus the so-called acoustic mufflers are extremely efficient in eliminating the high frequencies, but (for reasons which are 40 explained later) are so inefficient in their action on the low frequencies that such mufflers must be made in a considerable length to obtain the necessary elimination of the low sound frequencies, so long in fact that it is common practice to make 45 them in two units so that they can be mounted between the re-inforcing members of the modem automobile chassis.

The lower efficiency of acoustic mufflers in eliminating the low frequencies of sound is, of 50 course, due to the low rate of oscillation of the low range of sound frequencies. These are more efficiently eliminated by the relatively large chambers employed in resonance mufflers, but the action of these resonance chambers is so in55 efficient on the high frequencies that resonator mufflers require a long series of such chambers, resulting in a muffler of extreme length. Obviously the relative inefficiency of these resonance chambers on the high frequencies is due to the fact that the chambers are relatively few in number 5 and not a multiplicity of spaces or cells to multiply the effect of the oscillations, as is the case in acoustic material.

Before stating how the objects of this invention are accomplished it is necessary to refer briefly io to another characteristic of the sound impulses in the exhaust stream of internal-combustion engines; namely, in the entire acceleration range there is a relatively small number of low periods of frequency of sufficient amplitude or intensity, 15 as to be ineffectively absorbed by acoustic material. The rest of the frequencies in the low range are of a much weaker intensity so that they are sufficiently eliminated by acoustic material despite its characteristic inefficiency in deadening 20 sounds of low frequency.

Thus the objects of the invention are accomplished by (1) combining the acoustic and resonator principles providing the most efficient deadening of both the high and and low ranges of 25 sound frequencies (2) by employing a new and useful form of resonance chamber which (a) produces resonance so that the loud period or band of low frequency may be tuned out decisively by one chamber and (b) which can be employed in 30 a muffler having an overall length only a fraction of the length of any of the resonance chambers required to decisively tune out the loud period of low frequency.

The objects of this invention and the man- 35 ner in which these objects are accomplished will become apparent as the following description progresses and is considered in conjunction with the accompanying drawings wherein:

Figure 1 is a longitudinal sectional view through 40 the muffler according to the invention, the section being taken on line I—I of Figure 2;

Figure 2 is a cross sectional view of the muffler taken on line 2—2 of Figure 1;

Figures 3 and 4 are cross-sectional views of the 45 muffler taken on line 3—3 and line 4—4 respectively of Figure 1;

Figure 5 is a longitudinal sectional view through the muffler taken on line 5—5 of Figure 1;

Figure 6 is a cross sectional view on line 6—6 50 of Figure 5;

Figures 7 through 12 show a modified form of the muffler, provided with three separating fins, to increase the number of resonator chambers employed. Thus, Figure 7 is a longitudinal sec- 55

2,014,666 tional view through the modified muffler taken on line 1—1 of Figure 8 and Figure 8 is a cross sectional view on line 8—8 of Figure 7. Figures 9, 10 and 11 are cross sectional views taken on 5 line 9—9, 10—10 and 11—II respectively of Figure 7. Figure 12 is a perspective view of the inner portion of the muffler with the fins attached thereto to show the difference in length of the fins.

Referring more particularly to the structure disclosed in Figures 1 through 7 of the drawings the muffler I comprises outer and inner sheet metal concentrically arranged cylinders 2 and 3. These cylinders are connected at opposite ends 15 in any suitable manner, as by welding, to the front and rear end walls 4 and 5 respectively, thus forming an annular resonating space 6 between the two cylinders. These end walls are formed with inlet and outlet extensions 7 and 8 20 communicating with the inlet and outlet openings 9 and 10 respectively. A third shell or container 11 of octagonal or other multi-sided form is firmly enclosed within the inner cylinder 3, and this shell encloses a round sleeve or pipe 12 25 in axial alinement with the respective inlet and outlet openings 9 and 10, and extending from inlet opening 13 in inner end wall 14 of shell 11 to and through outlet opening 15 in the outer end wall 16 thereof. The outer end of pipe 12 30 terminates well within the outlet extension 8, while the inner end is flush with the wall of inlet opening 13. Both members II and 12 are made of perforated sheet metal, and the interior of the former member surrounding the pipe 12 is packed 35 with any sound absorbing, fire proof material 17 such as expanded micaceous material, slag wool, steel wool, etc.

The end walls 14 and 16 of shell 11 are spaced a small distance from the end walls 4 and 5 com40 mon to both cylinders 2 and 3, thus forming chambers 18 and 19 at the front and rear ends of the muffler respectively. The space inside of pipe 12 communicates with chamber 18 and constitutes an unobstructed main passage for the 45 exhaust gas. This passage communicates through perforations in pipe 12 with the expansion chamber or space 20 within octagonal shaped shell 11, which chamber is packed with sound absorbing and dissipating material and extends be50 tween the end walls 14 and 16 as previously stated. Expansion chamber 20 in turn communicates through perforations in the wall of shell 11 with the spaces or passages 21 between cylinder 3 and shell 11, which spaces are continues ous from end to end of chamber 20 and are constantly subjected to the full suction action of exhaust gases, blowing through and expelled from discharge end of pipe 12. These expelled gases draw the exhaust gases from spaces 21 with a 60 smooth venturi-like action due to the extension of pipe 12 into outlet extension 8. It will be noted that the passages 21 are in communication with chamber 18 as well as with chamber 19 and that in consequence an extremely free 65 flow of gas is obtained through the muffler, thus insuring the desirably low back pressure.

Due to the functional factors of the venturi, this structure provides an unusually high degree of muffling efficiency. It is thus possible to obtain 70 any desired difference in the rate of flow between the main gas stream 12 and auxiliary gas streams 21. This staggering of the gas streams greatly facilitates the efficient expansion of high gas impulse peaks of main passage 12 into the low areas 75 of passages 21, and vice versa. It is likewise possible to increase the gas flow capacity of this structure to an unusual degree, without the necessity of correspondingly increasing the diameter of the muffler or the volume of acoustic material, and at the same time avoid over “riffling” 5 or turbulence in the gas streams with the resultant loss of muffling efficiency. These two factors are responsible for the unusually high degree of acoustic sound absorbtion within an extremely small diameter. 10

Up to this point I have described only the socalled acoustic action of the muffler, which action as previously explained is more effective on high sound frequencies than on the low, whereas the low frequencies are more readily muffled or 15 silenced by a resonating action. Good muffling of both high and low frequencies has heretofore only been obtained by employing relatively long mufflers which are difficult to mount, costly to manufacture, and due to their length stand in the £0 way of the easy and economical solution of other chassis problems, such as reinforcing cross members and proper mounting of other accessories, etc. In order to obtain the desired resonator effect in combination with the acoustic action £5 just described without the necessity of greatly increasing the length of the muffler of the present invention, the space between shells 2 and 3 is subdivided by fins 22, whereby an elongated reversed or U-shaped resonator chamber 23 of sub- S3 stantial length is formed. Chamber 23, which may be adapted to silence the loudest period of the loud periods of low sound frequencies, is approximately twice the length of the outer cylinder 2' and consequently is double the length of 35 the muffler as a whole, one-half of the length of chamber 23 being formed by the upper half circular space between cylinders 2 and 3, and the .other half by the corresponding lower half circular space. The fins 22 are shorter than the 40 muffler to afford free communication between the two halves of chamber 23. A series of openings 24, in the inner end portion of cylinder 3 extending from end wall 14 of shell 11 to end wall 4 of the muffler provide direct communication between 45 chamber 18 and one end only of resonance chamber 23. It should be noted that these openings are located only in one-half of the periphery of cylinder 3. This series of reversing sections in the resonance chamber makes it possible to 50 decisively tune out the low frequency in a muffler of simple construction and extremely short length. The present structure makes it possible to materially amplify the tuning out of the one extremely loud period of low freauency present 55 in the acceleration range of most motors.

In practice it has in many instances merely been necessary to make the total length of the resonator chamber 23 (and consequently its tuning) such as to decisively tune out this loudest GO period of low frequency without the necessity of any accurate tuning of other loud resonance periods in the low range to obtain a degree of muffling efficiency equal to that of so-called acoustic mufflers and resonator mufflers two times as long as 65 the muffler in question.

For internal-combustion engines having an unusually complex combination of distinct loud periods of low frequencies the number of resonator chambers of the muffler is preferably increased. 70 This can be effected by increasing the number of fins 22 subdividing the space between shells 2 and 3. A muffler provided with a larger number of resonance chambers is shown in Figures 7 to 12 of the drawings. The structure disclosed in 75

2,014,886 these figures closely resembles the muffler shown in Figures 1 through 6 with the exception that the space between shells 2 and 3 is subdivided by a fin 25 which is shorter than the length of the muffler and by the two fins 26 extending over the entire length of the muffler. This arrangement provides resonance chambers similar to long reverse bend chamber 23 and the other shorter resonance chambers referred to above, and an additional resonance chamber 21 extending between fins 26. Chamber 21 communicates through holes 28 in the wall of cylinder 3 with chamber 18, the latter being of slightly greater depth than chamber 18, previously described to permit proper location of the holes or openings 24 and 28 with respect to their resonance chambers.

From the foregoing it will be seen that by employing any number of resonance chambers or any number of reversing sections per chamber or both, mufflers according to this invention can be built which combine the highest degree of muffling efficiency known in the art yet having an overall length which may be any desired fraction of the length of resonance chainbers required for effective elimination of the loud periods in the low range of frequencies. Furthermore these results are obtained without any loss of the low back pressure so essential to the most efficient engine performance.