Liquid purification or separation – Electrical insulating or electricity discharging
Reexamination Certificate
1999-07-14
2001-06-12
Barry, Chester T. (Department: 1724)
Liquid purification or separation
Electrical insulating or electricity discharging
Reexamination Certificate
active
06245231
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based upon and claims the benefit of priority of Japanese Patent Applications No. H.10-232471 filed on Aug. 19, 1998 and Japanese Patent Applications No. H.11-128637, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel filter apparatus having a means for releasing static electricity to outside, that is, the fuel filter apparatus with an anti-electrostatic function.
2. Description of Related Art
A fuel system for vehicles is provided with a fuel filter apparatus for filtering the fuel to be supplied from a fuel pump to fuel injectors. The fuel filter apparatus has generally a filter housing made of design in which a filter element is contained. When the fuel passes through the filter element, static electricity is likely to be generated and taken on the resin filter housing. Therefore, if the static electricity discharges from the filter housing to adjacent metal components, the filter housing may be cracked due to a discharge impact of the static electricity.
To cope with this problem, it has been proposed to prevent the electrostatic discharge in a manner that an earth wire is connected to the outside of the filter housing made of conductive resin to release the static electricity.
However, conductive design is more expensive, compared with non-conductive design. Further, if the earth wire comes off the filter housing due to some reasons or its connection to the filter housing is forgotten, the static electricity is likely to be discharged from the filter housing because the entire filter housing is made of conductive resin. Therefore, a problem that the filter housing may be cracked still exists.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above mentioned problem, and an object of the present invention is to provide a filter apparatus in which the electrostatic discharge can be effectively prevented.
To achieve the above object, the filter apparatus is composed of a filter housing made of non-conductive material, a filter element made of conductive material contained in the filter housing, and a conductive plug with a sealing element. The filter housing has a bore and the conductive plug is inserted into the bore of the filter housing so that the clearance between the conductive plug and the filter housing is hermetically sealed by the sealing element. The conductive plug is connected in circuit to the filter element in a manner that a part of the plug is exposed out of the filter housing and an earth wire attached to the exposed portion of the plug to be connected in circuit to the plug.
According to the above construction, the static electricity generated in the filter apparatus is released via a conductive path extending from the filter element through the plug to the earth wire so that the electrostatic discharge may be prevented. Even if the earth wire comes off the plug or the earth wire's connection to the plug is forgotten, the electrostatic discharge from the filter housing is unlikely to take place owing to the non-conductive material of the filter housing. Further, as the earth wire is connected in circuit to the filter element via the conductive plug, a troublesome work of drawing the earth wire into the inside of the filter housing for connecting the same to the filter element can be eliminated. As a result, the connection work of the earth wire becomes simpler.
It is preferable to employ the conductive plug made of material having 10
7
to 10
11
&OHgr;·cm resistivity. Such a value of resistivity serves to assure not only an adequate conductivity for releasing the static electricity but also an adequate resistance for preventing the electrostatic discharge from the conductive plug, even if the earth wire comes off or its connection is forgotten.
To connect the plug in circuit to the filter element, it is preferable to employ an elastic member installed between the plug and the filter element for pressing against the plug and the filter element or to employ the plug having a sharp inserting portion at its leading end to be pierced into the filter element.
A pressure regulator for adjusting fuel pressure may be also used as the conductive plug, too, if the outer body of the pressure regulator is made of conductive material. A fuel inlet pipe of the pressure regulator is inserted into the filter housing and connected in circuit to the filter element through the elastic member such as a conductive coil spring.
In general, the filter housing is detachably assembled with a supporting member. When it is necessary to replace the filter element, the filter housing is detached from the supporting member. It is preferable to have a conductive connector for the earth wire placed between the filter housing and the supporting member in a manner that the conductive plug is easily connected in circuit with the connector for the earth wire, when the filter housing is assembled with the supporting member.
Preferably, the connector is made of an elastic material and presses against the plug by its own elastic force. This construction makes the connection and the disconnection in circuit between the plug and the earth wire very easy, when the filter housing is attached to and detached from the supporting member, respectively. Further, if the connector is always fixed on the supporting member, the connecting or disconnecting work of the earth wire is not necessary, whenever the filter element is replaced.
REFERENCES:
patent: 2534907 (1950-12-01), Ham
patent: 3478494 (1969-11-01), Lustenader
patent: 4187179 (1980-02-01), Harms
patent: 5164084 (1992-11-01), Danowski et al.
patent: 5185086 (1993-02-01), Kaali et al.
patent: 5352347 (1994-10-01), Reichert
patent: 5380432 (1995-01-01), Brandt
patent: 6099726 (2000-08-01), Gembolis
patent: B1 6168713 (2001-01-01), Sekine
patent: 61-8102 (1986-01-01), None
patent: 1-27856 (1989-08-01), None
patent: WO96/23569 (1996-08-01), None
CRC Handbook of Chemistry & Physics, 59th ed., p. E-84.
Maki Naoki
Mukaidani Akiyoshi
Nakai Hideyuki
Okabe Kenji
Umetsu Kunihiro
Barry Chester T.
Denso Corporation
Pillsbury & Winthrop LLP
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