Exhaust muffler

[57] ABSTRACT

Disclosed herein is a muffler comprising an elongated housing including a generally cylindrical side wall and, at each end thereof, an inwardly concavely dished end wall, and a dished partition dividing the housing into an inlet chamber and an outlet chamber and extending convexly with respect to the inlet chamber, together with a beveled port which is located in the partition, which extends from the inlet chamber into the outlet chamber and which includes a tubular part having a length extending parallel to the length of the housing and being formed, at least in part, by the material of the partition with an inlet having a margin which merges with the partition and which has an arcuate form in a plane extending radially of the length of the tubular part, and an outlet tube including an inlet portion extending lengthwise within the housing through the partition and having an inlet in the outlet Chamber and including an outlet portion extending at least partially in the inlet chamber and outwardly through said side wall.

Claims, 3 Drawing Figures

<img file="US3776366A_D0001.tif" />

PATENTED DEC 41975

3,776,366

<img file="US3776366A_D0002.tif" />

7'

3,7'

EXHAUST MUFFLER

BACKGROUND OF THE INVENTION

The invention relates generally to exhaust mufflers for internal combustion engines and more particularly to exhaust mufflers which are particularly adapted for snowmobile usage.

One known prior muffler construction is shown in Outboard Marine Print No. 162,002 deposited with the United States Patent Office at the time of filing, on May 31, 1972, of the Smale United States patent application Ser. No. 258,260.

SUMMARY OF THE INVENTION

The invention provides a muffler which beneficially reduces noise level while having a substantially minor effect on engine power. In accordance with the invention, the muffler is sub-divided into various chambers by dished or partially spherical end walls and intermediate partitions. In addition, the partitions are provided with ports which provide communication between the chambers, which are preferably formed, at least in part, from the material of the partitions, which preferably include beveled inlet margins which merge with the dished or partially spherical partitions, and which preferably have a relatively short length axially of the muffler.

In further accordance with the invention, one or more discharge tubes are provided, which discharge tubes preferably extend lengthwise within the housing for a substantial distance and have a relatively small cross sectional area as compared to length within the housing. As a consequence, the considerable length of the discharge tubes apparently prevents significant ³³backflow of atmospheric air into the mufflers and thereby serves to prevent backfiring within the muffler.

In still further accordance with the invention, there is provided a muffler including ports which afford communication between chambers and which are of relatively short length, together with one or more tail pipes which have a substantial length within the muffler and which have a relatively small cross sectional area in relation to length within the muffler.

Still further, the invention provides a deflector plate which is preferably perforated and which is mounted in an inlet chamber in the path of incoming exhaust gases so as to diffuse such incoming exhaust gases throughout the inlet chamber and to thereby reduce structural deformation caused by heat concentration.

One of the principal objects of the invention is the provision of a muffler which has superior noise reducing capability, together with little apparent disadvantageous effect on horsepower output.

Another of the principal objects of the invention is the provision of a muffler construction in which backfiring within the muffler is substantially reduced or prevented.

Still another of the objects of the invention is the provision of a muffler in which means are provided for diffusing or deflecting the hot incoming exhaust gas so as to reduce heat concentration in the walls of the muffler.

Other objects and advantages of the invention will become known by reference to the following description, claims and accompanying drawings.

'6,366

DRAWINGS

FIG. 1 is a fragmentary top view of a muffler embodying various of the features of the invention.

FIG. 2 is a sectional view taken along line 2—2 of FIG. 1.

FIG. 3 is a sectional view, partially broken away, taken along line 3—3 of FIG. 2.

Before explaining the invention in detail, it is to be 10 understood that the invention is not limited in its application to the details of construction and arrangement of parts set forth in the following general description or illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being 15 practiced or carried out in various ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

₂₀ GENERAL DESCRIPTION

Shown in the drawings is a muffler 11 which embodies various of the features of the invention and which includes a housing or shell 13 defined by an arcuately extending outer or side wall 15. Preferably, the outer 25 or side wall 15 is cylindrical in form. At its ends, the side wall 15 is closed by respective end walls 17 and 19 which are dished. Although other arcuate shapes and arrangements could be used, the illustrated end walls 17 and 19 are each partially spherically shaped and are ³⁰ preferably concavely inwardly arranged. Connected to the outer surface of the end walls 17 and 19 are respective support brackets 21.

Further in accordance with the invention, the housing 13 is sub-divided into an inlet chamber 23 and an outlet chamber 25 by a first dished partition 27 which is located so that the inlet chamber 23 has a length slightly greater than about % the length of the housing 13. Although other arcuate shapes could be employed, in the illustrated construction, the partition 27 is par⁴θ tially spherically shaped and extends convexly with respect to the inlet chamber 23, although the partition 27 could extend convexly with respect to the outlet chamber 25.

Still further in accordance with the invention, the ⁴⁵ outlet chamber 25 is further sub-divided into an intermediate sub-chamber 29 and an outlet sub-chamber 31 by a second, dished partition 33 located generally centrally of the length of the outlet chamber 25. While other arcuate shapes could be employed, the illustrated partition 33 is partially spherically shaped and extends concavely with respect to the intermediate subchamber 29, although the partition 33 could extend concavely with respect to the outlet sub-chamber 31. _gg Still further in accordance with the invention, the first partition 27 is provided with at least one port 35 which is preferably formed, at least in part, from the material of the first partition 27 and which includes a tubular part or portion 37 extending for a relatively ₆θ short length from the inlet chamber 23 and into the outlet chamber 25 and including an inlet 39 having a margin which merges with the first partition 27 and has a curved cross section in a plane extending radially with respect to the length or axis of the tubular portion. The ₆₅ port 35 also includes an outlet 41 at the end of the tubular portion 37 spaced from the first partition 27 and located inwardly of the outlet chamber 25 in a plane generally perpendicular, to the length of the tubular

3.776.366 ³ portion. Although the tubular portion could extend at an angle to the length of the muffler housing 13, it is preferred to form the port 35 as illustrated with the tubular portion 37 extending parallel to the length of the muffler housing 13.

In the preferred form of the invention, the first partition 27 also includes a second port 43 located in angularly spaced relation to the first port 35 and of generally the same construction.

Further in accordance with the invention, the second partition 33 includes at least one port 45 communicating between the intermediate sub-chamber 29 and the outlet sub-chamber 31. In the preferred embodiment of the invention, a second port 47 is also employed, which ports 45 and 47 are located in angularly spaced relation to each other and to the ports 35 and 43 in the first partition 27.

Each of the ports 45 and 47 in the second partition 33 is preferably formed, at least in part, from the material of the second partition 33 and includes a tubular portion 49 having an inlet 51 with a margin which merges with the second partition 33 and has a curved cross section in a plane extending radially with respect to the length or axis of the tubular portion. The ports 47 and 45 also include an outlet 53 at the ends of the tubular portions 49 located inwardly of the outlet subchamber 31 and in a plane generally perpendicular to the length of the tubular portions 49. Although the tubular portions could extend at an angle to the length of the muffler housing 13, it is preferred to form the ports 45 and 47 as illustrated with the tubular portions 49 extending parallel to the length of the muffler housing 13.

In still further accordance with the invention, the muffler 11 includes an inlet tube or duct 55 which extends radially outwardly from the inlet chamber 23 through the side wall 15 and includes, at its outer end, an attachment flange 57.

In still further accordance with the invention, the muffler further includes at least one outlet or discharge tube or duct or tail pipe 59 which communicates with the outlet sub-chamber 31 and extends outwardly through the side wall 15. In the preferred embodiment, a second discharge tube 61 extends in generally parallel relation to the discharge tube 59.

While the discharge tube or tubes could pass directly through that portion of the side wall 15 which defines the outlet sub-chamber 31, it is preferred to at least partially locate the outlet tubes 59 and 61 lengthwise within the housing 13 in inward and outward radial relation to each other. More specifically, it is preferred that the discharge tubes 59 and 61 extend within the housing for a substantial length and have a relatively small cross sectional area as compared to the length thereof. In this regard, it is preferred to construct the tubes 59 and 61 with a ratio between the cross sectional area (in square inches) and the length within the housing 13 (in inches) within the range of 0.25 to 0.073, which ratio is expressed as a decimal by dividing the length into the area. Still more specifically, in the illustrated construction, the discharge tubes 59 and 61 are located in co-planar relation to each other in a plane slightly offset from, and parallel to, a plane extending diametrically of the tubular, housing 13 and with the discharge tube 61 being located radially inwardly with respect to the discharge tube 59.

Still further, each of the outlet tubes 59 and 61 is formed with an elongated inlet portion 63 which ex⁴ tends lengthwise of the muffler housing 13 through both the first and second partitions 27 and 33, respectively, and which includes an inlet 65 in the outlet subchamber 31. Each of the outlet tubes 59 and 61 also in5 eludes an outlet portion 67 which communicates with the inlet portion 63 and which extends, at least in part, through the inlet chamber 23 and outwardly through the side wall 15 defining the inlet chamber 23. As shown in FIG. 3, both the outlet or discharge tubes 59 10 and 61 have an identical length except that the radially outward tube 59 has a larger outlet portion 67 so that the outlet portions 67 of both of the discharge tubes 59 and 61 terminate at about the same place. As a consequence, the inlet portion 63 of the radially inner dis¹⁵ charge tube 61 extends within the outlet sub-chamber 31 for a greater distance than does the inlet portion 63 of the radially outer discharge tube 59.

In order to facilitate assembly, the first and second partitions 27 and 33 respectively can be provided with ²⁰ radially spaced and relatively short ports or tubes 69 which receive the discharge tubes 59 and 61 and which are preferably slip fitted over the discharge tubes 59 and 61.

₂₅ In further accordance with the invention, a deflector or plate 71 is mounted in the inlet chamber 23 in the path of incoming exhaust gas flow from the inlet tube 55. In the preferred invention, the deflector 71 comprises a plate which extends in a plane extending dia₃₀ metrically of the muffler housing 13, which is fixedly connected to and supported by the radially inner discharge tube 61, and which includes a series of perforations 73. Accordingly, the deflector plate 71 is arranged so as to disperse or deflect the incoming exhaust ₃5 gases throughout the inlet chamber 23 so as thereby to prevent structural deformation caused by heat concentration in a particular area.

The disclosed muffler 11 beneficially reduces noise level without substantially reducing the engine power 40 and, in addition, substantially reduces or eliminates muffler backfiring. More specifically, the curved, dished, or partially spherical condition of the end walls 17 and 19 and the partitions 27 and 33 is believed to prevent or reduce drumming or shell noise produced by 45 the muffler in response to excitation by the exhaust gases within the various chambers. The length of the discharge tubes.or tail pipes 59 and 61 from the outlet portion 67 to the outlet sub-chamber 31 is also believed to beneficially substantially reduce or eliminate back50 firing within the muffler by preventing significant backflow of atmospheric air into the muffler for combination with the hot, unburned gases therein so as to cause explosion. The formation of the ports 35, 43, 45, and 47 with beveled or curved inlet margins is believed to give a preferential flow to the exhaust gases and to be particularly advantageous with respect to the operating characteristics of the muffler 11. Still further, the relative shortness in length of the tubular portions 37 and 49 of the ports 35, 43,45, and 47 affords minimal back pressure loss prior to the discharge tubes 59 and 61 so as to permit maximum allowable back pressure loss to occur in the discharge tubes 59 and 61. The shortness of the tubular portions 37 and 49 is also believed to reduce the resonant frequency of the muffler. In addition to reducing backfiring, the discharge tubes 59 and 61 also beneficially function to reduce the amplitude of low frequency noise.

3,776,

Various of the features of the invention are set forth in the following claims.