Multi-louvered Roughness Silencer

Abstract

A muffler has a plurality of perforated tubes telescoped over a perforated gas flow tube to provide a series of expansion chambers connected in parallel with the gas flow path.

Description

BRIEF SUMMARY OF THE INVENTION

It is the purpose of this invention to provide a low backpressure muffler containing silencing structure that provides an acoustic effect similar to a mass of glass fibers or the like, that is, it attenuates high frequencies and roughness and medium frequencies while allowing the power sound of the lower frequencies to remain audible.

The invention accomplishes this by means of expansion chambers arranged in parallel with the gas flow tube that are provided with perforated walls to permit gas flow from the tube to the various chambers.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross section through a muffler embodying the invention; and

FIG. 2 is a cross section along the line 2--2 of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

The muffler 1 has a housing 3 which has the ends swaged or otherwise reduced in diameter to provide an inlet bushing 5 and an outlet bushing 7. The bushings 5 and 7 are aligned and preferably offset from the axis of the housing 3, the latter being preferably circular as seen in FIG. 2. A straight-through gas flow tube 9 is supported in the bushings 5 and 7 and conducts gas from the exhaust pipe 11 straight through the chamber 10 defined by housing 3 to the tailpipe 13, the pipes 11 and 13 being telescoped over opposite ends of the tube 9.

Surrounding the flow tube 9 and tangential to each other and to the casing 3 along the line 15 are secondary tubes in the form of inner and outer tubular shells 17 and 19. The shells are preferably spot welded or arc-tacked to the housing 3 along the line of tangency. The halves of the tube 9 and the shells 17 and 19 which face away from their line of tangency with the shell are provided along most of the lengths with perforations that are preferably louvers 21 which arranged to direct the gas in a circular pattern as indicated in FIG 2. The flow tube 9 and the surrounding shells divide the interior 10 of the casing 3 into sub-chambers 23, 25 and 27. The shells 17 and 19 are preferably spaced slightly from the opposite ends of the housing 3 to provide end chambers 29 and 31 which communicate with the previously mentioned chambers.

In operation, gas flowing through the muffler 1 can pass from the exhaust pipe 11 to tailpipe 13 with a minimum of horsepower loss because of the low backpressure created by the straight-through flow path of tube 9. Pressure pulses in the gas as it passes through the tube can expand radially or sideways and pass, in series, into the chambers 23, 25 and 27 after passing through louvers 21. The gas can also expand longitudinally into the end chambers 29 and 31. Since the louver patches are radially aligned and extend over substantially less than all the circumferences of the tube 9 and shells 17 and 19, the non-louver subtended portions of chambers 23, 25 and 27 are partially "dead" (no flow through) and act in a special way to absorb acoustic energy.

The muffler 1 is principally effective on high frequencies and roughness and on medium frequencies so that the audible sound passed by the muffler is in the lower frequency range giving the deep power sound favored by sports car drivers. However, by placing the muffler 1 in an exhaust system so that the maximum pressure point or anti-node of a troublesome frequency falls centrally within the perforated region of the tube 9, attenuation of such lower frequency can be achieved to a substantial degree.

Modifications may be made without departing from the spirit and scope of the invention.

Claims

I claim:

1. A muffler comprising an imperforate outer housing having an inlet at one end and an outlet at the other end, a perforated straight-through gas flow tube in the housing connecting the inlet and outlet and defining a straight-through gas flow path for the muffler, said shell defining a chamber around said tube, and a plurality of radially separated perforated secondary tubes surrounding said flow tube and subdividing said chamber into radially separated sub-chambers, said sub-chambers being in radial communication by means of the perforations in the tubes with gas flowing through the flow tube, said secondary tubes being spaced from at least one end of the chamber to define an end chamber, and sub-chambers communicating with said end chamber.

2. A muffler comprising an imperforate outer housing having an inlet at one end and an outlet at the other end, a perforated straight-through gas flow tube in the housing connecting the inlet and outlet and defining a straight-through gas flow path for the muffler, said shell defining a chamber around said tube, and a plurality of radially separated perforated secondary tubes surrounding said flow tube and subdividing said chamber into radially separated sub-chambers, said sub-chambers being in radial communication by means of the perforations in the tubes with gas flowing through the flow tube, said inlet and outlet and said flow tube being offset from the center line of the housing and the smaller of said secondary tubes being substantially concentric with the flow tube.

3. A muffler as set forth in claim 2 wherein said secondary tubes are substantially tangent to each other and to the housing.

4. A muffler as set forth in claim 3 wherein the perforate areas in the tubes are substantially aligned radially and extend angularly over substantially less than the entire circumferences of the tubes whereby portions of the sub-chambers are dead.

5. A muffler comprising an imperforate outer housing having an inlet at one end and an outlet at the outer end, a perforated straight-through gas flow tube in the housing connecting the inlet and outlet and defining a straight-through gas flow path for the muffler, said shell defining a chamber around said tube, and a plurality of radially separated perforated secondary tubes surrounding said flow tube and subdividing said chamber into radially separated sub-chambers, said sub-chambers being in radial communication by means of the perforations in the tubes with gas flowing through the flow tube, each of said tubes having a perforate area that extends over substantially less than the entire circumference of the tube.