US2031451A - Exhaust silencer for internal combustion engines - Google Patents

Description

H. C. AUSTIN Feb. 18, 1936.

EXHAUST SILENCER FOR INTERNAL COMBUSTION ENGINES Filed March 17, 1933 INVENTOR Harry 6. flush/7 44.42

ATTORNE Patented Feb. 18, 1936 EXHAUST SILENCER FOR INTERNAL COMBUSTION ENGINES Harry 0. Austin, Kansas City, Mo., assignor to Chester L. Austin, Kansas City, Mo.

Application March 17, 1933, Serial No. 661,314

2 Claims. (Cl. 137160) My invention relates to exhaust silencers for internal combustion engines and more particularly to a device adapted to eliminate the concussion from the exhaust of large Diesel engines.

The exhaust of large internal combustion engines of the Diesel type creates considerable noise. The use of Diesel engines to furnish power for industrial plants has necessitated the building of large muffler pits. The principle of all mufflers hitherto developed has been to slow down the exhaust gases to velocities below that of sound. The volume of the gases is generally from six to eight times that of the piston displacement which in the case of large Diesel engines is considerable. The building of concrete mufiie pits involved considerable expense, inasmuch as the volume of the pit must be usually about twenty times the total piston displacement. Frequently, in the starting of engines, ignition does not take place immediately, with the result that the pit becomes filled with unburnt gases and air. This mixture is usually an explosive mixture with the result that, when ignition does take place and explosion follows, it frequently is of considerable violence resulting in injury to limb and property.

In two-cycle Diesel engines, it is essential for efliciency that the back pressure be not increased. Types of mufflers which depend upon baflling and giving the exhaust gases a circuitous path through bailies and apertures tend to increase the back pressure. A frequent source of difiiculty is the clogging of the apertures by carbon depositions and resinous material which render the mufiier inoperative after a period of use. These devices, too, are of considerable size and unless extremely strongly built, it is found that the bafiles will vibrate and make considerable noise.

One object of my invention is to provide a strongly constructed, simple silencer for the exhaust of internal combustion engines.

Another object of my invention is to provide a silence-r which will not increase the back pressure materially.

Another object of my invention is to build a muffler which is light and small in size so that it may be installed directly in the exhaust pipe from the engine at any convenient part thereof.

Still another object of my invention is to provide a construction in which the danger of damage due to explosions of unburnt fuel is eliminated.

In the accompanying drawing which forms part of the instant specification and is to be read in conjunction therewith and in which like reference numerals are used to indicate like parts in the various views;

Figure 1 is an elevation, of my device installed in the exhaust pipe of a large Diesel engine.

Figure 2 is a sectional view of my silencer with the outer casing in section.

Figure 3 is a sectional View of my muffler with the outer and inner casings in section.

Figure 4 is a plan view taken on the line 44 of Figure 3.

In general, my invention contemplates providing a plurality of paths for the exhaust gases. Each path is of different length so that interference between the sound waves will be caused. The paths are adapted to give the exhaust gases a whirling motion and are substantially unobstructed to obviate the danger of clogging or of explosions. Likewise, unobstructed paths, I have found, will prevent the building up of back pressure. A pair of muffler sections are mounted in series separated by an adjustable tuning chamber. Frequently the principle of resonance amplifies the sound which remains after the gases pass through a muflier section. By adjusting the tuning chamber to the point of greatest dissonance, the sound is effectively muted with the result that the exhaust will be inaudible at the exit of the exhaust pipe.

More particularly referring now to the drawing, an exhaust pipe I leads the exhaust gases from the exhaust manifold of the internal combustion engine. Secured to the exhaust pipe I in any suitable manner, such as by a bolted flange 2, is a first section 3 of my muffler. This section comprises an outer casing 4 provided with a bolting flange 5. Within the casing 4 and in spaced relation thereto I provide a second casing 8. Between casings 4 and 8, I position a pair of helical baffles 6 and l which are welded to the inner surface of casing 4 and the outer surface of easing 8. It is to be understood, of course, that, while I have shown a pair of helical baffles, a single helical baflle or a plurality of helical bailies of any suitable number may be employed. The object in using more than a single helical bafile is to provide a spiral path of lesser pitch than would be required for a single helical baffle. The reduction of the pitch renders the component of back pressure created by the resistance of the baflies smaller than would be the case if a single baffle were used. Casings 4 and 8 are mounted in concentric relation. While I prefer to use cylindrical casings, it is to be understood that casings of any suitable cross sectional shape may be employed. I position a tube 9 with its axis coincident with the axes of casings 4 and 8. Between tube 9 and casing 8 I provide a second pair of helical baflles Ill and I I. These baflles are welded to the exterior of tube 9 and to the interior of casing 8 and form an unobstructed path for the exhaust gases. It is to be noted. that the gases passing through the passage l2 which is formed by casings 4 and 8 will have a. much longer path of travel than the gases passing through the passage I4. A certain portion of the exhaust gases may pass directly through the tube 9 and, this being a straight path, will be the shortest path. Casing 4 has a skirted projection l5 extending beyond the baflle section. I provide a cylindrical member l6 adapted to telescope with skirt l5, as can be readily seen by reference to Figures 2 and 3. Member [6 is provided with a flange l1 and a flange I8. Flange I8 is adapted to be bolted to flange 5 of muilier section 3' which is identical to the mufller section described above. The reference numerals applied to mufiler section 3' will be the same as those applied above, with primes to distinguish that they refer to the second muffler section. Around the exterior of casing 4 I weld a flange l9. Flange I9 is supported by triangular bracing members 20, welded thereto as can be readily seen by reference to Figure 1. Flange I1 is likewise provided with bracing members 2|. Secured to flange I9 are bolts 22 which are provided with adjusting nuts 23 and 24 as can be readily seen by reference to Figures 2 and 3. It will be readily appreciated that, by the respective loosening of nuts 24 and the tightening of nuts 23 that the casing IE will be moved to a greater depth of telescoping with skirt portion l5. This will result in a decrease of the size of the chamber 25, which as pointed out above, is the tuning chamber. By adjusting the chamber volume by the adjustment just described, a position of greatest dissonance may be reached, resulting in effective silencing. Very frequently a single muffler section and a tuning section are all that is required for silencing to an extent sufiiciently great to render the exhaust innocuous as far as the nuisance eifect of the exhaust noise is concerned. In zones where extreme silence is required, as for example in the vicinity of a thickly populated district, a second mui'lier section 3 may be installed outwardly of the first mufiler section. If desired, a plurality of muliier sections as needed may be required, though I have found that in no event is it necessary for practical purposes to use more than two muffler sections. In event that only one muffler section is employed, casing I5 may be the terminal portion of the exhaust pipe. In event the two muffler sections are employed as shown in Figure 1,'a

length of eduction casing 26 may be bolted to the second muiller section.

In practice, I have installed a muffler made according to my invention on a commercial unit in which the exhaust of a Diesel engine having five cylinders 16 inches in diameter and employing a stroke of 20 inches was to be silenced. The engine exhaust pipe was 24 inches in diameter. The external diameter of my muiiier was no greater than the diameter of the exhaust pipe, that is 24 inches. The entire length of my muflier was only 6 feet. The exhaust was eifectively silenced so that it was substantially inaudible within a radius of 10 feet. No vibration was perceptible. The

engine on which my mufiler was installed, had been employing a. commercial type of muiiler. It measured 23 feet in length and 42 inches in diameter. The exhaust was not effectively silenced and the vibration occasioned by the muffler baffles made considerable noise in and of itself.

It will be obvious that I have accomplished the objects of my invention. Due to the fact there are no small openings for the dispersion of the exhaust gases, the danger of clogging, due to carbon deposition is obviated. Due to the fact that the passage for the exhaust gases is substantially unobstructed, not only is loss of efficiency dueto back pressure prevented but the danger of explosion damage is obviated. It will be clear from the above description that in event unburnt gases do ignite, they will blow harmlessly out of the muffler pipe without doing damage. My muffler is of rigid construction and light in weight. There are no loose parts to vibrate and it may be conveniently installed at any desirable point. I have found that it is advisable in practice to install it near the terminal end of the exhaust stack.

It will be observed that, by creating three paths for the exhaust gases, of different length, that the exhaust gases will arrive at the outlet of the muffler section at diiferent times causing an interference of the sound waves tending to reduce their intensity. Likewise, the imparting of a whirling motion to the gases will not only tend to cut down their forward velocity but will cause turbulence which will result in the destruction of the sound waves. It is to be noted that the spiral path in passage I2 is opposite in direction of rotation from the spiral path [4. If desired, the spiral paths l2 and I4 may be given the same direction.

It will be understood that certain features and sub-combinations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and is within the scope of my claims. It is further obvious that various changes may be made in details within the scope of my claims without departing from the spirit of my invention. It is, therefore, to be understood that my invention is not to be limited to the specific details shown and described.

Having thus described my invention, what I claim is:

1. An exhaust silencer comprising in combination a helical bafiie structure providing a plurality of paths of different length, an enlarged chamber communicating directly with said baffle structure, means to vary the volume of said chamber to a predetermined point and a second baffle structure directly communicating with said chamber.

2. An exhaust silencer comprising in combination three imperforate casings having different cross sectional areas and disposed concentrically in spaced relation to each other and forming three passageways, said passageways having direct communication with the exhaust to be silenced whereby three paths are provided for the eduction of the exhaust gases, means constraining the exhaust gases to flow through the outer two passageways in respective helical paths of different length, the central casing being unobstructed and providing a direct path of flow for a portion of said gases.

- HARRY C. AUSTIN.

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