Marine propulsion – Means for accomodating or moving engine fluids – Means for handling exhaust gas
Reexamination Certificate
2001-06-22
2003-04-22
Sotelo, Jesus D. (Department: 3617)
Marine propulsion
Means for accomodating or moving engine fluids
Means for handling exhaust gas
C114S055500, C181S264000
Reexamination Certificate
active
06551155
ABSTRACT:
FIELD OF INVENTION
The present invention relates to a personal watercraft, and more specifically, to the exhaust system of a personal watercraft.
BACKGROUND OF THE INVENTION
Personal watercraft are typically constructed by attaching a deck shell to a hull shell to form an engine compartment therebetween. The propulsion systems for these personal watercraft normally include an inboard-mounted, internal combustion engine and a jet propulsion unit in the form of an impeller assembly positioned in a tunnel open to the underside and the stem of the hull. Because of the compact size of personal watercraft, limited space is available within the hull.
The compactness of personal watercraft presents a number of unique design problems. One such design problem is the layout of the exhaust system for discharging exhaust gases generated by the engine. This problem is rendered particularly acute because, as is typical with marine propulsion systems, the engine exhaust gases are typically discharged to the atmosphere either at, below or close to the water level depending on the speed of the watercraft. For example, at slow speeds the exhaust outlet may be below the waterline. At high speeds, the exhaust outlet will be located at a higher position and may be above the waterline. Because of this location of the exhaust outlet, care must be taken to ensure that water cannot enter the engine through the exhaust system. This problem is compounded because there is a possibility that the watercraft could capsize. Therefore, when capsized and subsequently righted, an adequate exhaust system design must ensure that any water that has entered the exhaust system will be prevented from finding its way into the engine. Additionally, even where the personal watercraft does not capsize, the exhaust system must be designed to inhibit coolant water that is directed into the mufflers via a water jacket from entering the engine. To prevent such occurrences, exhaust systems typically include exhaust pipe configurations designed to impede water flow toward the engine. This is typically accomplished by the combination of water traps, upwardly sloped exhaust pipes, and the use of mufflers, which also act as water traps in addition to providing sound attenuation of the exhaust gases. One such exhaust system design is disclosed in U.S. Pat. No. 5,699,749, the entirety of which is hereby incorporated into the present application by reference. The '749 patent utilizes two mufflers positioned on opposite sides of the watercraft, and which are connected by a U-shaped transfer pipe. An exhaust pipe extending from the second expansion chamber discharges the exhaust gases on the same side thereof and contiguous with the water level. With this design configuration, when the discharge end becomes submerged, water may enter the second muffler and becomes trapped therein. However, when the watercraft is capsized, in order to prevent the water in the second muffler from moving along the U-shaped transfer pipe to the first muffler, the watercraft must be uprighted by rotation about its longitudinal axis in only one direction. Rotation in the wrong direction will allow water to flow from the second muffler into the first muffler via the transfer pipe and thus increase the possibility of water entering the engine.
For example, viewing
FIG. 4
of the '749 patent, rotation of the watercraft in a counterclockwise direction will prevent such flow because the inertia of the water tends to force against the muffler wall away from the inlet of the transfer pipe
49
. However, rotation of the watercraft in a clockwise direction will cause water to flow by its own inertia from one muffler
52
along the U-shaped transfer pipe
49
to the other muffler
39
. Once the water is in muffler
39
, it is possible that the water can then flow towards and into the exhaust manifold of the engine if the watercraft is tilted at a forward pitch. If water is allowed to flow into the engine, it will flow into the piston chamber, which is designed for the combustion of a compressible charge. Because liquid water is incompressible, such water entering the combustion chamber creates water lock (also referred to as hydrolock) and renders the engine inoperable until the water is drained therefrom. In a worst case scenario, the engine may be permanently damaged, thereby requiring a replacement engine.
To impede water flow therethrough, mufflers may include internal chambers defined by partitioning walls, the internal chambers being interconnected to each other. The sequential expansion of the exhaust gases as it passes through each internal chamber also attenuates engine sound. However, the manufacture of mufflers with multiple internal chambers which must be interconnected is difficult.
Another design problem associated with vehicles powered by engines is the transmission of engine vibration to the exhaust system. Engine vibration is particularly severe when starting the engine. When the engine vibration is transmitted to the exhaust system, fatigue cracking of the exhaust system components and welded seams may occur rapidly, which can render the exhaust system in need of major repairs or replacement. To reduce the engine vibration to the exhaust system, flexible coupling devices are used between exhaust pipes. One such coupling device is disclosed in U.S. Pat. No. 5,967,565. The '565 patent discloses an exhaust pipe connected to an engine with a cover member installed about the exterior of the exhaust pipe. A guiding member extends from an end of the cover member to form two pockets on either side of the guiding member. A first pocket is formed between the guiding member and the rim of an inner retainer, and a second pocket is formed between the guiding member and an outer retainer. The first and second pockets contain elastic buffering members that absorb stress from the engine vibration. To protect the cover member from heat, a bellows is disposed between the inner retainer and the cover member. The bellows prevents leakage of exhaust gas and absorbs elastic and bending displacement experience by the coupler. However, the coupler disclosed in '565 is a complex arrangement that is difficult to manufacture and install.
SUMMARY OF THE INVENTION
It is the object of the present invention, therefore, to provide an exhaust system for a personal watercraft with an improved design for preventing the flow of water therein towards and into the engine.
It is also the object of the present invention to provide for an improved muffler that makes full use of the muffler space.
It is also the object of the present invention to provide an improved coupling device for coupling exhaust system components.
It is also the object of the present invention to provide an improved water trap device.
The present invention meets the above described need by providing a personal watercraft with an improved exhaust sytem, the watercraft including a hull having a longitudinal axis, an internal combustion engine mounted in the hull, the engine being constructed and arranged to generate power for use in propelling the watercraft and exhaust gas as a by-product of generating power. The exhaust system includes a first muffler and a second muffler, the first muffler being disposed in the hull on one of a port side and starboard side of the longitudinal axis and the second muffler being disposed on the other side of the longitudinal axis. An engine exhaust communication member fluidly communicates the engine with the first muffler. An intermediate exhaust communication member fluidly communicates the first muffler with the second muffler. An outlet exhaust communication member fluidly communicates the second muffler to the atmosphere at an exhaust point on the same side as the first muffler, where the exhaust communication members and the first and second mufflers cooperate to establish an exhaust path from the engine to the atmosphere through which the exhaust gas generated by the engine can flow. The outlet exhaust communication member has a portion between the second mu
Bourret Robert
Lachance Robert
Lecours Gaetan
Ménard Éric
Oler Jeff
Bombardier Inc.
Pillsbury & Winthrop LLP
Sotelo Jesus D.
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