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US 4,359,136 AGranted
Muffler construction
AssigneeNelson Industries, Inc.
InventorLarry J. Eriksson
Life of this patent
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AssigneeNelson Industries, Inc.
InventorLarry J. Eriksson
Estimating the term…
A muffler construction comprising an outer body, and a pair of end walls extend transversely across the body to define an internal chamber. An inlet conduit is located in one of the end walls, while an outlet conduit is in the other end wall. In one embodiment, the inlet conduit is disposed axially of the body to excite symmetric higher order modes and the outlet is offset radially from the axis of the body and is located on a nodal circle of the transverse pressure distribution. In a second embodiment, the inlet is offset from the axis of the body causing excitation of asymmetric higher order modes and the outlet is located on a nodal line of the transverse pressure distribution. The construction of the invention maximizes attenuation of high order modes in mufflers.
A device for attenuating sound energy, comprising an outer body, a pair of transverse walls extending across said body and defining an internal chamber, said chamber being free of internal obstructions, an inlet conduit disposed in one of said walls for introducing gas into said chamber, an outlet conduit disposed in the other of said walls for discharging gas from said chamber, one of said conduits being offset from the axis of said body on a first radius and the other of said conduits being positioned along a diameter disposed at an angle of 90.degree. to said first radius, said outlet conduit beng located at a pressure nodal position of the first symmetric higher order mode of the chamber.
A device for attenuating sound energy, comprising an outer body, a pair of transverse walls extending across said body and defining an internal chamber, said chamber being free of internal obstructions, an inlet conduit disposed in one of said walls for introducing gas into said chamber, an outlet conduit disposed in the other of said walls for discharging gas from said chamber, said inlet conduit being disposed on the axis of said body and said outlet conduit being offset from said axis and disposed along a radius and located on a pressure nodal circle of the first symmetric higher order mode of the chamber.
A device for attenuating sound energy, comprising an outer body, a pair of transverse walls extending across said body and defining an internal chamber, said chamber being free of internal obstructions, one of said walls having an inlet for introducing gas into said chamber and the other of said walls having an outlet for discharging gas from said chamber, said inlet being offset from the axis of said body and disposed along a first radius, said outlet being offset from said axis and being disposed along a second radius displaced approximately 90.degree. from said first radius.
Dependencies are inferred from the claim text.
Term ended 9 Jun 2000 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
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Traditional muffler designs have paid little attention to the importance of the inlet and outlet locations relative to obtaining maximum attenuation from a given muffler volume. In the past, two standard approaches have typically been used. In the first, the inlet and outlet have been axially aligned as in a straight-through expansion chamber, a plug section or a resonator. The second approach has been to offset both the inlet and outlet along a diameter of the muffler body, as used in a so-called "pass-type" muffler. However, the positioning of the inlet and outlet has been primarily for convenience of construction and adaptation to engines, as opposed to obtaining maximum sound attenuation.
The invention is directed to an improved muffler construction which positions the inlet and outlet at precise locations to obtain maximum sound attenuation. In accordance with the invention, the muffler includes an outer body and a pair of spaced end walls or baffles extend across the body and define the internal unobstructed chamber. An inlet conduit is mounted in one of the end walls, while an outlet conduit is mounted in the other end wall.
In one embodiment of the invention, the inlet conduit is disposed axially of the muffler body, thereby causing excitation of symmetric higher order modes, and the outlet conduit is offset from the axis of the body and is located on a pressure nodal circle of the mode to be attenuated.
The drawings illustrate the best mode presently contemplated of carrying out the invention.
In the drawings:
FIG. 1 is a side elevation with parts broken away of a muffler constructed in accordance with the invention;
FIGS. 1 and 2 show a muffler constructed in accordance with the invention. The muffler comprises a generally cylindrical outer body 1 or shell, the ends of which are closed off by baffles or end walls 2 and 3. The space defined by the body 1 and baffles 2 and 3 constricts an internal chamber 4, which is free of obstructions, such as baffles, flanges, and the like. The exhaust gas is introduced into the chamber 4 through an inlet pipe 5, which is mounted within an opening in the baffle 2, and is connected to the engine exhaust. The gas is discharged from the chamber 4 through a pipe 6 which is mounted within an opening in the baffle 3.
In accordance with the invention, the inlet pipe 5 and outlet pipe 6 are positioned at precise locations with respect to each other to obtain maximum sound attenuation. As best shown in FIG. 2, the inlet pipe 5 is mounted axially of the body, while the outlet pipe 6 is offset radially from the axis of the body and is located on a pressure nodal circle of the symmetric higher order mode to be attenuated.
The basic propagating mode in a cylindrical muffler body is a plane wave mode in which there is essentially uniform pressure across the entire cross section of the body. Above certain frequencies, there are a number of different possible modes or pressure distributions and each mode has its own cut-off frequency which is determined by the diameter of the body and the sound velocity. With an axial inlet pipe, as shown in FIGS. 1 and 2, the higher order modes will be symmetric. On the other hand, if the inlet pipe is not mounted coaxially of the body, the higher order modes will be a symmetric.