US3045423A - Muffled exhaust release for an outboard motor - Google Patents

Description

July 24, 1962 R. P. HULSEBUS 3,045,423

MUFFLED EXHAUST RELEASE FOR AN OUTBOARD MOTOR Filed Sept. 23, 1958 INVENTOR. Z/cmwep P. HULSEBUJ nited rates atent 3,945,423 Patented July 24, 1962 fiice I 3,045,423 MUFFLED EXHAUST RELEASE FOR AN OUTBOARD MOTOR Richard P. Hulsebus, Waukegan, Ill., assignor to Outboard Marine Corporation, Waukegan, [1]., a corporation of Delaware Filed Sept. 23, 1958, Ser. No. 762,744 6 Claims. (CI. 60-32) This invention relates to a mufiied exhaust release for an outboard motor.

It is an object of the invention to provide an alternate passage for the exhaust gases when the motor is operating at low speeds and the normal exhaust passage is blocked by the water through which the motor is traveling, without releasing the motor noises as such relief passages have done in the past. With that object in mind my outboard motor is provided with an exhaust tube extending downwardly from the exhaust manifold of the engine to a first expansion chamber in the lower unit, tubular passages from the first expansion chamber to a second expansion chamber, and a passage from the second expansion chamber to the outside air which includes a flexible tube to isolate the vibration of the expansion chamber from the motor housing. The first expansion chamber has the usual outlet below the water line, from which the water is drained at moderate to high speed by reduction of pressure due to the movement of the motor through the water. The entire system is designed for a minimum of back pressure on the exhaust port of the engine and a maximum of mufiling action at low speeds.

The drawing is a side elevational view of an outboard motor, with portions of the motor housing and lower unit broken away to show the exhaust system which comprises my invention.

The drawing shows an outboard motor having a motor housing 10 which not only covers the engine, but is continuous over the lower unit 11 to the water line 12, thus providing a sound barrier between the engine and the occupants of the boat. The cylinders of the engine are provided with exhaust ports 13 which open into an exhaust manifold 14. At the lower side of the exhaust manifold an exhaust tube 15 is secured to the manifold, extending downwardly into the lower unit 11. The lower unit 1 1 is provided with a bafiie -16 between the ends of the exhaust tube 15, and a resilient gasket 17 is provided between bafiie 16 and exhaust tube 15. -A shoulder 18 on the exhaust tube compresses gasket 17' against baffle 16, to seal the first, or lower expansion chamber 19 from the second, or upper, expansion chamber 20, and at the same time to prevent the transmission of vibrations from the exhaust tube to the lower unit 11.

Short tubes 21 extend from the lower, or first, expansion chamber to the upper, or second, expansion chamber. From the second expansion chamber a short tube 22 extends outwardly toward the motor cover 10, which is provided with a tapered opening 23 aligned with tube 22 and extending to the outside air. A corrugated flexible hose 24 is slipped over the tube 22, and is provided with a tapered end portion 25 which engages the tapered opening 23 in motor housing 10. -A spring 26 is seated on the end of tube 22 at one end and the other end seats on the tapered end of tube 24. Thus tube 24 is engaged firmly in tapered seat 23 regardless of the vibration of lower unit 11 with respect to motor cover 10.

The lower portion of first expansion chamber 19 is provided with an exhaust outlet 30 well below the water line and a passage 31 connecting the chamber 19- with the outlet 30, said passage 31 being inclined rearwardly with respect to the norm-a1 direction of travel so that when the motor attains a moderate speed through the water, the water in passage 31 will be drawn out of outlet 30, creating an area of lowered pressure which permits the exhaust to be discharged through outlet 30 in the conventional manner. The noise of the exhaust is thus dissipated in the water when the motor is moving at sufiicient speed. At lower speeds the water will not be drawn out of passage 31, and will block it, but the exhaust passes upwardly through tubes 21 in baffle 16 to the second expansion chamber 20 and thence through tubes 22 and 24 to the outside air. The length of the tubes 21 may be chosen to conflict with the wave length of the sound waves, greatly impeding the transmission of sound through baffle 16, and tube 15 may likewise be of a length to impede propagation of the sound waves. In general, an open tube having a length which is not a multiple of one-half of the wave length of the sound passing through it will prevent the formation of standing waves and will interfere with propagation of the sound waves. This length is determined by the sounds which are produced by the motor at low speeds, when the exhaust is discharged into the air through tube 24. The successive expansion chambers 19 and 20 will attenuate the sound because of their large volumes in comparison with that of the exhaust tube.

A resilient gasket 32 is provided between lower unit 11 and motor cover 1'2 to further isolate the sound waves and vibration in lower unit 11 from motor cover 12 while maintaining the motor cover in its proper relative position. Gasket 32 is restrained from axial movement by shoulders 33 on lower unit 11.

The space between the motor cover 10 and the lower unit 11 is a dead air space 40 which isolates the exhaust system, since it completely surrounds the lower unit and is closed at the bottom, as shown by water line 12, and divided in the middle by gasket 32. Bellows tube 24 prevents transmission of vibrations across space 40.

The upper portion of the motor housing or cover 10 is secured to the engine supports in the manner shown in Irgens Patent 2,740,368, so that the cover is completely isolated by resilient members from the engine and other moving parts which produce vibration. Unlike the device of the Irgens patent, the lower resilient mem bers are a part of the exhaust silencing system, as outlined above. If desired, additional resilient members may be interposed between the motor cover and the transom bracket and associated vertical pivot, as shown in Irgens.

The transom bracket 41 and its associated parts are secured to motor cover 10, whether or not resilient members are interposed. Since the motor cover is isolated from vibration, the vibrations are not transmitted to the boat, which is thus prevented from acting as a sounding board to amplify the sound as has been the case in the past.

Other arrangements of the first and second expansion chambers are possible within the scope of my invention. It is also possible to arrange space 40 so that it is not fully closed, or omit it, without imparing the improvement in mufliing attained by the exhaust system itself.

Anexpansion chamberwithin the meaning of the present application is defined as a chamber having at least two dimensions which are materially greater than the largest dimension of the exhaust pipe in any direction transverse to the flow of exhaust gas therein.

I claim:

1. In an outboard propulsion device, the combination of,

a lower unit designed to operate partially submerged in water,

an engine mounted above said unit,

3 an exhaust gas conduit leading from said engine into said lower unit,

means in said lower unit defining a first expansion chamber connected with said conduit, having a materially larger cross section than said conduit in the direction of How of exhaust gases through said conduit, and having an outlet which is under water when the propulsion device is in use and from which exhaust gas is aspirated when said unit is in motion,

means in said lower unit defining a second expansion chamber,

means affording direct communication between said first expansion chamber and said second expansion chamber and having a materially smaller cross section than said second expansion chamber in the direction of flow of said exhaust gases therethrough, said second chamber having communication with said conduit solely through said first expansion chamber and said last mentioned means, and

permanently open means for discharging exhaust gases from the second exhaust chamber at a point above the normal water level after the exhaust gas has passed successively through said conduit, said first chamber, and said second chamber.

2. An outboard propulsion device according to claim 1 in which in which the means providing communication from the first mentioned chamber to the second expansion chamber comprises at least one tube of substantial length and difiering materially from any multiple of one half of the wave length of sound waves produced in exhaust gases at low engine speed.

4. An outboard propulsion device according to claim 1 in which said second expansion chamber is located above the first expansion chamber and is separated therefrom by a transverse partition,

said exhaust gas conduit comprises a tube of substantial length differing materially from any multiple of one half the Wave length of sound waves produced at low engine speed in the exhaust gases traversing the tube,

said tube being fixed to the engine and extending through said partition and having elastic packing extending about the tube between it and the partition,

the means aifording communication between the first expansion chamber and the second expansion chamber comprising a short tubular port in said partition.

5. An outboard propulsion device according to claim 1 further including an engine cover having a portion extending downwardly about said lower unit toward the level of the water in which said unit is operable in use,

means providing elastic spacing between the lower unit and the engine cover, and

said permanently open means for discharging exhaust gas from said second chamber being partially enclosed by said engine cover portion whereby the exhaust gas from said second chamber passes through said cover portion.

6. An outboard propulsion device according to claim 1 and further including a flexible hose having one end connected with the said lower unit about the said permanently open means and having its other end connected with said downwardly extending engine cover portion, the said portion having an open port above water level through which said hose opens in communication with the atmosphere.

References Cited in the file of this patent UNITED STATES PATENTS

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