Internal-combustion engines – Accessories – Covers – trays – vibrators – corrosion inhibitors – air filters
Reexamination Certificate
2000-01-19
2001-04-10
Kwon, John (Department: 3747)
Internal-combustion engines
Accessories
Covers, trays, vibrators, corrosion inhibitors, air filters
C123S1980DC
Reexamination Certificate
active
06213083
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to the field of internal combustion engines and, more particularly, to internal combustion engines that utilize fuel shutoff systems upon engine shutdown.
BACKGROUND OF THE INVENTION
Internal combustion engines are used in a variety of applications, such as lawn mowers, generators, pumps, snow blowers, and the like. Such engines often have carburetors wherein fuel received from a fuel source is mixed with air and supplied to a combustion chamber for ignition. The fuel mixture is drawn from the carburetor into the combustion chamber due to a low pressure created in the combustion chamber by the rotation of the engine. The products of combustion are then expelled from the combustion chamber into the exhaust manifold during the exhaust stroke of the engine.
An operator of an engine may shut the engine down by grounding the electrical ignition system, thereby causing the spark plug to cease firing. After shutdown, the engine does not immediately stop rotating. During the continued rotation or coasting of the engine after ignition shutdown, unburned fuel and air are drawn from the carburetor into the combustion chamber, and expelled into the exhaust system.
The continued draw of unburned fuel into the combustion chamber and exhaust manifold after engine shutdown causes problems. Fuel is wasted, and unburned fuel is released into the environment, thereby increasing exhaust emissions. Additionally, the muffler or muffler with catalytic converter often get very hot, and the unburned fuel may ignite when it contacts these components, thereby causing backfiring or afterburning. Backfiring and afterburning can shorten the useful life of the catalytic converter and of the muffler itself. Likewise, the presence of unburned fuel in the combustion chamber may cause dieseling.
To alleviate these problems, fuel shutoff mechanisms have been devised to control the flow of fuel after ignition shutdown. For instance, U.S. Pat. No. 5,301,644 to Olmr discloses a fuel shutoff mechanism which includes a solenoid valve. However, the '644 system, as well as other apparatus which use solenoids, typically require a battery to function. The addition of a battery to engines adds to the weight and cost of the engine. Additionally, solenoids, or other electric actuating devices, are expensive and are expensive to replace. In the small utility engine industry, for example, the additional cost, weight, and complexity are very undesirable.
Other fuel shutoff devices, such as the one disclosed in U.S. Pat. No. 5,092,295 to Kobayashi, use the throttle of the engine to act as a fuel blocker upon engine shutdown. This is done by adding structure which overrides the governor of the engine and closes the throttle valve upon shutdown. The problem with these devices, however, is that they are complex, and must be added onto and may disturb the delicate balance of the engine governor.
Yet other devices, such as U. S. Pat. No. 4,510,739 to Dluhosch, use a fuel shutoff valve which stops the flow of fuel into the fuel bowl. The disadvantage of these devices is that a substantial amount of fuel remains in the fuel bowl after the engine ignition is shut down, and can still be drawn into the combustion chamber and exhaust system after shutdown.
SUMMARY OF THE INVENTION
The invention is a fuel shutoff system that solves the problems of the prior art. More particularly, the invention includes a fuel shutoff system that is usable on engines without a battery, and is reliable, simple and less expensive than electrically operated solenoids. Additionally, the fuel shutoff operates without interfering with the engine governor, and effectively blocks the fuel flow downstream of the fuel bowl on engine shutdown.
One aspect of the invention is a fuel shutoff system for an internal combustion engine, wherein the engine has a carburetor with a fuel bowl, an intake valve, and a fuel conduit between the fuel bowl and the intake valve. The invention includes a blocking member for selectively blocking the fuel conduit downstream of the fuel bowl to substantially prevent passage of fuel to the intake valve, and a manually-operable control for actuating the blocking member. In each embodiment, the engine includes a throttle and a fuel metering device, and the blocking member is distinct from the throttle and the fuel metering device calibration.
In one embodiment of the invention, the engine includes a carburetor having a fuel nozzle, and the fuel shutoff system includes a mechanically operated blocking member for selectively blocking fuel from flowing from the fuel bowl into the fuel nozzle. In one form, the blocking member is selectively positioned adjacent the fuel nozzle in a first position wherein the blocking member blocks the fuel from flowing into the fuel nozzle, and in a second position wherein the blocking member allows the fuel to flow into the fuel nozzle. By blocking the fuel flow downstream of the fuel bowl, restarting the engine is simplified. The fuel bowl does not have to be refilled before starting.
In another embodiment of the invention, the engine has a passageway through which a gas (the fuel/air mixture) may pass to an intake valve of the engine, and the engine has a throttle valve disposed in the passageway. The blocking member is disposed in the passageway and can be selectively positioned in a first open position, and in a second closed position upon engine shutdown to substantially block the flow of gas or fuel/air mixture to the intake valve and to the combustion chamber.
Another aspect of the invention is an ignition grounding device for grounding the ignition system of the engine wherein the fuel shutoff system and the grounding device are both actuated by the same mechanical operation.
An important feature and advantage of the invention is that the invention reduces the amount of unburned fuel which is wasted and released into the environment since all fuel flow is shut off upon engine shutdown.
Another feature and advantage of the invention is that the fuel shutoff, particularly at the fuel nozzle, enables the engine to be transported with fuel and oil without the fuel passing through the engine into the crankcase, thereby avoiding oil dilution and hydraulic lock.
Another feature and advantage of the invention is that the fuel shutoff, particularly at the fuel nozzle, enables the engine to be transported with fuel without the fuel flowing into the carburetor during transport, thereby avoiding the potential for engine flooding.
REFERENCES:
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patent: 5092295 (1992-03-01), Kobayashi
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Briggs & Stratton Corporation
Kwon John
Michael & Best & Friedrich LLP
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