Fluid handling – Diverse fluid containing pressure systems – Fluid separating traps or vents
Reexamination Certificate
2002-09-26
2004-06-29
Michalsky, Gerald A. (Department: 3753)
Fluid handling
Diverse fluid containing pressure systems
Fluid separating traps or vents
C137S043000
Reexamination Certificate
active
06755206
ABSTRACT:
The present application is based on Japanese Patent Application No. 2001-300346, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a fuel cutoff valve mounted on an upper part of a fuel tank and enabled to switch communication and cutoff between the fuel tank and the outside by opening and closing a connection conduit, which connects the inside of the fuel tank to the outside.
2. Related Art
Hitherto, there has been known such a kind of a fuel cutoff valve disclosed in JP-A-2000-266208 (corresponding to U.S. Pat. No. 6,286,539).
FIG. 6
is a sectional view showing a conventional fuel cutoff valve. The fuel cutoff valve
110
is mounted on an upper part of a fuel tank FT and operative to switch communication and cutoff between the fuel tank FT and the outside by opening and closing a connection conduit
122
, which connects the inside of the fuel tank to the outside. The fuel cutoff valve
110
comprises a casing
120
, a float
130
, and a cover
140
. The cover
140
can be thermally welded to the upper part of the fuel tank FT and is made of a resin material having a higher fuel swelling property than the material of the casing
120
. An engagement projection
126
formed on the casing
120
is engaged with an engagement hole
142
formed in the cover
140
as means for attaching the cover
140
to the casing
120
. Moreover, a holding part
124
is formed in the casing
120
. A fitting part
144
of the cover
140
is held by this holding part
144
. In the valve of this configuration, when the fitting part
144
of the cover
140
is expanded owing to fuel swelling, the fitting part
144
is held by the holding part
124
. At that time, when the cover
140
swells, the holding part
124
enhances a supporting force by increasing mechanical bond strength between the holding part
124
and the fitting part
144
. Thus, such a holding part
124
provides stable opening/closing characteristics to the fuel cutoff valve
110
.
However, the conventional fuel cutoff valve
110
has problems in that the structure of a mold for injection-molding of the holding part
124
and the fitting part
144
becomes complex and needs high dimensional accuracy.
SUMMARY OF THE INVENTION
The invention solves the problems of the conventional valve. Accordingly, an object of the invention is to provide a fuel cutoff valve, which does not have shakiness owing to fuel swelling and can obtain a stable valve-closing characteristic.
To solve the problems, according to the invention, there is provided a fuel cutoff valve adapted to be mounted on an upper part of a fuel tank for switching communication and cutoff between an inside and an outside of the fuel tank by opening and closing a connection conduit, the fuel cut off valve comprising:
a casing forming a valve chamber communicating with the fuel tank;
a cover including a cover welding end that is made of a first resin material, which is thermally weldable to the upper part of the fuel tank, and that is configured to be thermally welded to the upper part of the fuel tank, and a cover supporting part for supporting an upper part of the casing;
a valve element accommodated in the valve chamber to open and close the connection conduit;
a sealing member disposed on an outer periphery of the casing;
a seal holding member that is made of a second resin material, which is thermally weldable to the cover supporting part, and that has a higher shape stability against fuel than the cover,
the seal holding member including a pressing face adapted to press the sealing member from an outside of the casing and a holding-member-side welding end configured to be thermally welded to the cover supporting part so as to press the sealing member, thereby sealing the inside of the fuel tank from the outside and supporting the casing.
The casing of the fuel cutoff valve according to the invention has a valve chamber communicating with the fuel tank. A valve element accommodated in this valve chamber rises and falls by increasing and decreasing a buoyant force according to the level of fuel contained in the fuel tank. Thus, the valves opens and closes the connection conduit to thereby prevent the fuel from flowing out of the fuel tank. Further, the cover is made of a resin material, which can be thermally welded to the upper part of the fuel tank, and thermally welded thereto, so that the fuel cutoff valve is mounted on the upper part of the fuel tank. Consequently, the fuel cutoff valve can easily be mounted on the upper part of the fuel tank without needing joining members.
The casing is made of a resin material that has a lower fuel swelling property than the cover. Thus, a seat face for opening and closing a fuel path can be formed with high accuracy. Further, the seal holding member thermally welded to the cover supporting part has a high degree of the shape stability against the fuel. Thus, even when exposed to the fuel, the seal holding member does not largely swell. Instead, the seal holding member reliably holds the sealing member by the pressing face so that high sealing ability is maintained. Incidentally, shape stability is defined as a combined property of the stiffness and the fuel swelling property of the member in a fuel atmosphere, indicating sealing and holding property to the casing.
Furthermore, the seal holding member is thermally welded to the cover supporting part. Thus, the sealing ability of the part provided therebetween is enhanced. Moreover, the supporting force for the casing can be increased. Therefore, the fuel cutoff valve does not cause troubles due to the shakiness. That is, the fuel cutoff valve can obtain stable opening/closing characteristics without causing reduction in impact resistance (i.e. mechanical strength against an impact) and variation in level of fuel when the fuel cutoff valve opens and closes.
The adding of a fibrous material thereinto, the use of a resin material that excels in fuel swelling resistance over the cover, and the embedding of an insert member can be taken as measures to increase the shape stability still more.
Further, the following resin materials are used for thermally welding the cover to the fuel tank, and for welding the seal holding member to the cover. That is, the casing is made of a material selected from a group consisting of polyacetal, polyamide, polyphenylene sulfide, and polybutylene terephthalate or of a blend of these materials of the group. The cover is made of polyethylene. The seal holding member is made of polyethylene, into which fibrous materials are added. Incidentally, the fibrous materials are glass fibers and asbestos fibers to be added thereto so as to improve the mechanical and dimensional stability against the fuel swelling without impairing the properties of the resin materials.
Further, as another preferred embodiment of the cover, the cover may be configured so as to have a cover inner layer, which is formed in such a manner as to face the connection conduit and to support the cover supporting part, and a cover outer layer that is formed by two-color molding and chemically bonded to this cover inner layer and has the cover welding end. In this case, the cover inner layer and the cover outer layer may be adapted so that the cover inner layer and the cover outer layer are made of different resin materials that are thermally welded to each other, that the cover inner layer is made of a resin material, which can be thermally welded to the seal holding member, and that the cover outer layer is made of a resin material, which can be thermally welded to the upper wall of the fuel tank. For example, the fuel cutoff valve may be adapted so that the casing is made of a material selected from the group consisting of polyacetal, polyamide, polyphenylene sulfide, and polybutylene terephthalate or of a blend of these materials of the group, that the cover outer layer is made of polyethylene, and that the cover inner layer is made of modified polyamide, which can be thermally welded to polyethylen
Aoki Tomohide
Kito Hiroaki
Nishi Hiroshi
Michalsky Gerald A.
Posz & Bethards, PLC
Toyoda Gosei Co,., Ltd.
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