Liquid purification or separation – With repair or assembling means
Reexamination Certificate
1999-06-25
2001-06-19
Lithgow, Thomas M. (Department: 1724)
Liquid purification or separation
With repair or assembling means
C210S315000, C210S338000, C210S342000, C210S416400, C210S444000, C210S450000
Reexamination Certificate
active
06248236
ABSTRACT:
TECHNICAL FIELD
This invention relates to fluid filters. Specifically this invention relates to a fuel filter assembly for a vehicle that provides enhanced filtration of the fuel prior to delivery to an engine.
BACKGROUND ART
Vehicle fuel systems typically have a fuel tank for holding a supply of liquid fuel for delivery to an engine. The fuel system also includes a lift pump for pumping fuel from the tank to the engine. Some engines, particularly those that have fuel injection, also have an injection pump which raises fuel pressure beyond that produced by the lift pump so that the fuel may be injected at high pressure into the combustion chambers.
Fuel filters are included in fuel systems to remove contaminants such as dirt and water from the fuel before it reaches the engine. Fuel filters are positioned in the fuel system either on the vacuum side or the pressure side of the lift pump. Each position for the fuel filter in relation to the lift pump has advantages and drawbacks.
If the fuel filter is positioned on the vacuum side of the lift pump, it has the advantage of removing contaminants before the fuel reaches the lift pump. This protects the lift pump from contaminants and prolongs its life. The drawback associated with this position of the fuel filter is that the amount of pressure available to push fuel through the filter is limited to atmospheric pressure. As a result, severe contamination may block flow and starve other fuel system components causing damage. Loss of flow may also occur in cold temperatures when wax or ice crystals form in petroleum fuels and block flow through the filter. Fuel heaters are needed in these situations to minimize the risk of problems.
A further problem associated with placing the fuel filter on the vacuum side of a lift pump is that lift pumps sometimes fail and generate contaminants. If these contaminants are carried downstream in the fuel they may cause damage to the high pressure/fuel metering pump or the fuel injectors.
An alternative fuel system configuration is to place the filter assembly on the pressure side of the lift pump. In this position more pressure is available to push fuel through the filter which reduces the risk of fuel starvation. Also, the heat energy imparted to the fuel by the lift pump tends to make fuels flow easier. In this position the high pressure pump and fuel injectors are protected from damaging debris from failure of the lift pump.
The drawbacks of positioning the fuel filter on the pressure side of the lift pump is that the lift pump is exposed to the contaminants which may shorten its life. Further, the pumping action tends to entrain the contaminants in the fuel which makes it more difficult to filter them out when they eventually reach the fuel filter assembly.
Thus, there exists a need for a fuel filter assembly that provides better filtration while reducing the drawbacks associated with positioning the filter on only the upstream or downstream sides of the lift pump.
DISCLOSURE OF INVENTION
It is an object of the present invention to provide a fuel filter assembly that provides enhanced filtration.
It is a further object of the present invention to provides a fuel filter assembly for a fuel system that provides fluid filtration to protect both the fuel lift pump, as well as the fuel injectors, fuel injection high pressure pump, and other precision fuel metering components.
It is a further object of the present invention to provide a fuel filter assembly for a vehicle fuel system that has a filter medium that is easy to replenish.
It is a further object of the present invention to provide a fuel filter for a vehicle fuel system that provides enhanced filtration while occupying little space.
It is a further object of the present invention to provide a fuel filter assembly for a vehicle fuel system that reduces the risk of fuel starvation of downstream components.
It is a further object of the present invention to provide a fuel filter assembly for a vehicle fuel system that is economical to manufacture and service.
It is a further object of the present invention to provide a fuel filter assembly for a vehicle fuel system that reduces waste when the filter is discarded.
It is a further object of the present invention to provide a vehicle fuel system that reduces the risk of contamination reaching an engine.
Further objects of the present invention will be made apparent in the following Best Modes for Carrying Out Invention and the appended claims.
The foregoing objects are accomplished by a double pass fuel filter assembly for filtering fuel being delivered from a fuel tank to an engine. The filter assembly has a head portion that is mounted on the vehicle. The head portion has a first inlet port communicating with the tank, and a first outlet port connected to the suction port of a lift pump. The head portion further has a second inlet port in communication with the pressure port of the lift pump and a second outlet port which is in fluid communication with the engine.
The fuel filter assembly includes an element portion that is removable from the head portion. The element has a bowl shaped enclosure. The enclosure encloses a cartridge having a continuous circular loop of a first filter media and a concentric continuous loop of a second filter media. The first media loop provides preliminary filtration for fluid flowing from the first inlet port to the first outlet port. The first media loop removes large impurities and slugs of water. A relief valve extends between the first media loop and will open if the first loop becomes substantially clogged. This minimizes the risk of starving downstream fuel system components.
The second media loop removes finer contaminants that have passed through or which have been generated by the lift pump, as fuel passes through the assembly from the second inlet port to the second outlet port. In a first embodiment of the invention, the second media loop is mounted on the replaceable cartridge. The first media loop is fixably mounted to the head portion and is accepted into the cartridge upon engagement of the element portion and the head portion.
In the first embodiment, the element portion further includes first and second sump areas for collecting contaminants separated from the fuel by the first and second media loops. A drain valve provides for periodically draining the contaminants from the sump areas.
An alternative embodiment has first and second media loops that are both mounted on the replaceable cartridge. This enables replenishment of both media loops when the cartridge is changed.
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Lithgow Thomas M.
Parker-Hannifin Corporation
Renner , Otto, Boisselle & Sklar, LLP
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