Liquid purification or separation – Electrical insulating or electricity discharging
Reexamination Certificate
1999-02-04
2001-01-09
Lithgow, Thomas M. (Department: 1724)
Liquid purification or separation
Electrical insulating or electricity discharging
C210S446000
Reexamination Certificate
active
06171492
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is not related to any pending United States or foreign patent application, nor is it referenced in any microfiche appendix.
BACKGROUND OF THE INVENTION
Virtually all devices that consume liquid fuel include a fuel filter. The most common example of a liquid fuel filter is that used on automobile and truck engines. Fuel filters have always been important as a part of internal combustion engines since any dirt or contamination in fuel can very readily cause carburetor problems or in newer engines, fuel injector problems. Most manufacturers of internal combustion engines specify periodic replacement of fuel filters to make certain that they don't become clogged and impair engine performance and to be certain that filtration of the fuel is effective to remove solids and other contaminants.
When fuel filters were first marketed for internal combustion engines, they were typically in the form of a permanently mounted housing that could be disassembled and the filter element itself replaced. In recent years, substantially all manufacturers of internal combustion engines, and particularly manufacturers of cars and trucks, employ disposable filters in which the housings that contains the filter elements are integral and are not subject to being disassembled. That is, when it is necessary to replace a fuel filter, the entire filter housing is thrown away.
A problem which has long been known to the designers of fuel systems for automobile and truck engines is that fuel flowing through a filter can result in the accumulation of a static electricity charge. As fuel passes through a filter media the flowing fuel is stripped of electrons with the electrons collecting on the inside of the filter housing. If the fuel filter housing is metal this electrical charge is readily conducted away, but when the housing is made of a non-conductive material, such as plastic, the charge is not readily conducted away and thus a buildup of electrostatic charge can occur to the point where a static discharge can take place. When an electrostatic charge builds up in a filter that exceeds the dielectric strength of the material of which the filter body is formed a discharge can occur between the filter housing and an adjacent conductive part of the engine with which the filter is employed. A discharge through a plastic filter housing can cause a pinhole in the housing and leakage of fuel can occur. One way to reduce static electric discharges through fuel filter housings made of plastic is to increase the conductivity of the filter housings. The invention herein provides a way to reduce static discharge.
Others have attacked the problem of electrostatic discharge through plastic fuel filter housings by including conductive materials, such as fibers of stainless steel, in the plastic matrix of which the housing bodies are formed. This technique may be employed effectively in the improved filter for liquid fuels as will be described herein.
PRIOR ART
For more background information relating to fuel filters, particularly of the type that employ plastic housings, reference can be made to the following previously issued United States and foreign patents and to the listed publication referenced:
PATENT NO.
INVENTOR
TITLE
3,002,870
Belgarde et al.
Liquid Filters
4,500,595
Gerteisen et al.
Stainless Steel Fiber-
Thermosplastic Granules and
Molded Articles Therefrom
4,664,971
Soens
Plastic Article Containing
Electrically Conductive Fibers
4,675,143
Wakita et al.
Process for Producing a
Shaped Electroconductive
Thermoplastic Resin
Composition Article
4,788,104
Adriaensen et al.
Granular Composite Contain-
ing Crimped Fibers and
Plastic Articles Made
Therefrom
4,812,247
Fahner et al.
Plastics Moulding Containing
Reinforced Fillings
5,076,920
Danowski et al.
Electrostatically Dissipative
Fuel Filter
5,085,773
Danowski
Anti-Static Fuel Filter
5,164,084
Danowski et al.
Electrostatically Dissipative
Fuel Filter
5,164,879
Danowski et al.
Electrostatically Dissipative
Fuel Component
5,380,432
Brandt
Fuel Filter with Electrostatic
Charge Preventing Media
5,382,359
Brandt
Plastic Fuel Filter with
Conductive Coating for
Providing an Evaporative
Barrier and for Dissipating
Electrostatic Charges
5,798,048
Ries
Multilayer Plastic Fuel Filter
Having Antistatic Properties
2,150,936
Lode Soens
Plastics Articles Containing
(Great Britain)
Electrically Conductive Fibers
OTHER ART
AUTHOR
TITLE
DATE
PUBLICATION
Joseph T. Leonard
Effect of
Received
Journal of Colloid
&
Conductivity on
7/2/69
and Interface
Homer W. Carhart
Charge Generation
Accepted
Science, Vol. 32,
in Hydrocarbon
10/31/69
No. 3, March
Fuels Flowing
1970, pages
through Fiber Glass
383-394
Filters
SUMMARY OF THE INVENTION
The invention herein provides an improved filter for liquid fuel and particularly a fuel filter made of a moldable plastic, the filter being of the throw away type in which the filter element contained within the housing is not separately removable and replaceable. The fuel filter is in the form of an elongated tubular housing having a cylindrical wall and having an inlet end and an outlet end. An integral elongated tubular inlet connector portion is integrally formed with the housing inlet end. An integral elongated tubular outlet connector portion is, in the same way, integrally formed as a part of the housing outlet end. The housing cylindrical wall has an imaginary cylindrical axis and in a preferred arrangement of the filter the inlet and outlet connector portions have tubular axes that are coaxial with the housing cylindrical axis.
A filter element is positioned within the tubular housing. A typical filter element is formed of filter media that defines a central passageway that is closed at one end, the passageway having an opposite end that is in sealed communication with the housing tubular outlet connector portion. The filter media has an external circumferential surface that is in communication with the housing tubular inlet connector portion. Liquid fuel flowing into the housing through the inlet connector portion contacts the exterior circumferential surface of the filter element, passes through the filter element where any entrained solid components are intercepted and into the filter element central passageway where the fuel flows out through the housing tubular outlet connector portion.
The liquid fuel filter housing, including the opposed inlet and outlet ends, are formed in a double wall configuration having an inner wall portion and an outer wall portion with a space therebetween.
The fuel filter as described above is, by virtue of the double wall, a housing of reduced weight for preselected mechanical strength and employs a reduced quantity of plastic to achieve required structural rigidity.
Further, the double wall filter housing of this invention can, if desired, be manufactured utilizing plastic material that is inherently electrically conductive or that has electrically conductive material therein such as short length fibers of stainless steel or other conductive materials.
A better understanding of the invention will be obtained from the following description and claims, not taken in conjunction with the attached drawings.
REFERENCES:
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patent: 1146748 (1915-07-01), Bennett
patent: 1623074 (1927-04-01), Tartrais
patent: 1871103 (1932-08-01), White
patent: 2053114 (1936-09-01), Sinks
patent: 2065658 (1936-12-01), Compton
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patent: 2263221 (1941-11-01), Merrill
patent: 2524509 (1950-10-01), Barney
patent: 3002870 (1961-10-01), Belgarde et al.
patent: 3004670 (1961-10-01), Zonker
patent: 3070132 (1962-12-01), Sheridan
patent: 3160785 (1964-12-01), Munday
patent: 3166688 (1965-01-01), Rowand et al.
patent: 3186551 (1965-06-01), Dornauf
patent: 3231091 (1966-01-01), Kingsbury et al.
patent: 3233737 (1966-02-01), Hultgren
patent: 3295684 (1967-01-01), Webb
patent: 3334747 (1967-08-01), Niccum et al.
patent: 3361261 (1968-01-01),
Bryson Theodore M.
Hedgepeth Richard E.
Barnes & Thornburg
Lithgow Thomas M.
Purolator Products Company
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