Fluid handling – Processes – Cleaning – repairing – or assembling
Reexamination Certificate
2001-03-08
2002-05-07
Michalsky, Gerald A. (Department: 3753)
Fluid handling
Processes
Cleaning, repairing, or assembling
C137S043000, C137S202000, C137S587000
Reexamination Certificate
active
06382231
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel cutoff valve for mounting onto the upper wall of a fuel tank to open and close a fuel conduit that connects the fuel tank to the outside to facilitate removal of fuel vapors from the fuel tank.
2. Description of Related Art
Fuel cutoff valves of this kind are known in the art, being described in JPA 11-315765, which has the structure depicted in FIG.
11
. As will be apparent from the sectional view in
FIG. 11
, the fuel cutoff valve
100
is mounted on the upper tank wall FTa of a fuel tank FT, and comprises a casing
102
, a cover
110
, a float
120
, and a spring
130
. The casing
102
comprises a top wall
103
, a side wall
104
integrally formed with outside edge of top wall
103
, and a base plate
105
attached to the bottom end of side wall
104
so as to define an internal space constituting a valve chest
102
S. Within valve chest
102
S is housed a float
120
having a valve portion
120
a
in its upper portion. This valve portion
120
a
opens and closes a fuel conduit
103
d
connected to the outside of fuel tank FT. The float
120
is supported by a spring
130
arranged on the base plate
105
.
The cover
110
comprises a cover main body
112
for attachment to the casing
102
, a cover passage forming portion
114
, and a flange
115
, these elements being of unitary construction. The cover
110
is a separate element from the casing
102
and is assembled with the casing by fitting the two together. A leak-prevention rib
122
is interposed between casing
102
and cover
110
to create a labyrinth structure providing increased mating surface area for sealing.
When the fuel tank FT is being filled, fuel vapor present within fuel tank FT flows to the outside (canister) via a through-hole
105
a
formed in the base plate
105
of casing
102
, a through-hole (not shown) in side wall
104
, the valve chest
102
S, the fuel conduit
130
d,
and the passage
114
a
in cover
110
. When the fuel entering fuel tank FT reaches a predetermined level FL
1
, fuel flows into valve chest
102
S via through-hole
105
a,
providing a buoyant force that causes the float
120
to rise. The rise of float
120
causes the valve portion
120
a
formed in the top portion of float
120
to block fuel conduit
103
d,
preventing fuel from flowing out from the fuel tank FT.
With the fuel cutoff valve
100
described above, however, the cover
110
and casing
102
are assembled together via a leak-prevention rib
122
. Accordingly, if the gap therebetween is small, the cover
110
and casing
102
will be difficult to assemble. Conversely, if the gap is made larger in order to facilitate assembly, a poor seal will result. The conventional fuel cutoff valve
100
thus has the drawback that it is difficult to simultaneously provide a better seal while attempting to improve the ease of assembly.
SUMMARY OF THE INVENTION
An aspect of this invention is to provide a fuel cutoff valve featuring a simplified assembly operation as well as an excellent seal.
Specifically, the first embodiment of the present invention provides for a fuel cutoff valve for mounting on the upper tank wall of a fuel tank having a cover, casing and valve body. The upper portion of the casing constitutes an insert member having a plurality of sealing ribs projecting substantially vertically towards the cover, and a stopper formation extending at substantially right angles to the sealing ribs. The cover is unified with the upper portion of the casing by means of overmolding such that said sealing ribs and stopper formation are embedded in the cover. The cover is fabricated of a first resin material that is thermally weldable to the upper tank wall. The cover has an annular welding end for thermal welding onto the upper tank wall and a passageway for removing fuel vapor from the fuel tank. The casing is made of a second resin material different from the first resin material. The casing is further provided with a valve chest that connects the fuel tank interior to a fuel conduit connecting the fuel tank interior to the outside to facilitate fuel vapor removal. The valve body is housed within the valve chest and opens or closes off the fuel conduit depending on the fuel level in said fuel tank.
The valve body housed within this valve chest rises and falls with changes in buoyant force produced by changes in fuel level within the fuel tank. When the valve body rises due to buoyant force, it closes off the fuel conduit, preventing outflow of fuel from the tank. The cover is made of a resin material that is thermally weldable to the top of the tank, and is mounted onto the tank by means of thermal welding to the upper tank wall. In this way, the need for a fastening member on the top of the fuel tank is obviated, allowing for easy mounting of the fuel cutoff valve.
The casing is made of a different resin material than the cover, which is specifically a resin having better resistance to fuel swelling than the cover, to improve sealing in the seat portion, etc. The casing consists of a resin material that is not welded to the cover, but is unified with the cover by means of overmolding. Specifically, the casing constitutes an insert member having a plurality of sealing ribs projecting substantially vertically or upward towards the cover, and a stopper formation extending at substantially right angles to the sealing ribs, the cover being unified with the upper portion of the casing by overmolding such that the sealing ribs and stopper formation are embedded in the cover. As used herein, overmolding refers to a process wherein, after initially molding the cover or casing, the companion part is formed by injection molding in such a way as to partially enclose the first part; it includes various processes such as insert molding and two-color molding. Since the casing is used as an insert member and is integrally formed with the cover, the two resin materials, while not being welded together, fit together tightly so that fuel cannot leak out between them. The labyrinth structure created by the plurality of sealing ribs provides an extended passage for fuel vapors, affording reduced passage of fuel.
The cover experiences greater swelling by fuel in the fuel tank than does the casing, which has the effect of reducing the gaps at the locations of the sealing ribs and thereby increasing the connecting force thereof to the casing, affording even greater reductions in passage of fuel.
The stopper formation is at least one substantially horizontal step that extends at substantially a right angle to the sealing ribs and provides secure attachment between the cover and the casing in effect locking these elements together. The horizontal step includes but is not limited to a protruding member, a stopper hole that includes a recess or through-hole subsequently filled by overmolding, or a combination thereof. This obviates the need for structures that include engagement tabs or the like for attaching the cover and the casing together, so as to provide a simpler structure. Therefore the casing does not give rise to problems associated with chatter against the cover, namely, reduced mechanical strength to resist impact and change in the liquid level at which the fuel cutoff valve opens and closes, thereby providing stable opening and closing characteristics.
The sealing ribs are composed of a plurality of divided arcuate projecting portions in an annular configuration. These arcuate projecting portions are arranged such that the gaps separating them from their neighbors do not lie on straight lines passing through the centers of concentric circles. By means of this structure, resin flowing into the sealing ribs and stopper formation may proceed smoothly during overmolding of the cover onto the upper portion of the casing, thereby avoiding filling defects.
In another embodiment, the upper portion of the casing is further provided with an outer rib situated to the outside of the sealing ribs across a predetermined gap. The outer rib projects out suc
Nojiri Masanori
Sugizaki Tomohiro
Michalsky Gerald A.
Pillsbury & Winthrop LLP
Toyoda Gosei Co,., Ltd.
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