Fluid handling – Diverse fluid containing pressure systems – Fluid separating traps or vents
Reexamination Certificate
2000-09-22
2001-10-16
Michalsky, Gerald A. (Department: 3753)
Fluid handling
Diverse fluid containing pressure systems
Fluid separating traps or vents
C137S587000
Reexamination Certificate
active
06302137
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates to a tank venting system, and particularly to a system for venting multiple fuel vapor chambers coupled to a fuel tank. More particularly, the present invention relates to a system for venting two chambers coupled to a fuel tank which are not in fuel vapor-transferring communication with one another when the fuel tank is full or nearly full.
It is well understood that significant quantities of fuel vapor can escape from a fuel tank through the filler neck to the atmosphere during the refueling of motor vehicles. Early attempts to control the vapor escape focused upon control devices fitted to a fuel-dispensing pump nozzle connected to a service station fuel pump. Later, control devices mounted directly on-board the vehicle were developed. See, for example, U.S. Pat. No. 4,816,045 to Szlaga et al., relating to a vapor-recovery system mounted on the fuel tank filler neck. Tank venting systems which mount to a fuel tank have also been developed as shown, for example, in U.S. Pat. No. 5,156,178 to Harris. The foregoing '045 and '178 patents are hereby incorporated by reference herein.
In addition to controlling vapor escape, well-designed tank venting systems also assist in controlling the amount of liquid fuel which can be pumped into the fuel tank during refueling for safety reasons, fuel systems are designed so that the fuel tank is never completely filled with liquid fuel. Rather, at least a predetermined portion of the space inside the fuel tank is left for liquid fuel and fuel vapor expansion. Although fuel pump nozzles typically include sensors for shutting off the flow of liquid fuel into the fuel tank when the fuel tank is nearly filled, fuel pump users may manually override the sensors by continuing to pump fuel after the sensors have automatically and temporarily shut the pump nozzle off. To assist in preventing tank overfill under such conditions, a tank venting system is usually provided with a “fill-limit” control system which assists in triggering the nozzle shut-off mechanism when the level of liquid fuel in the fuel tank has risen to a predetermined level. See, for example, the fill-limit control system disclosed in U.S. Pat. No. 4,816,045 to Szlaga et al., which disclosure is hereby incorporated by reference herein.
It has also long been recognized that fuel vapor is generated in the fuel tank during operation of the vehicle, for example, by evaporation or by sloshing of the liquid fuel against the walls of the tank. Excessive pressure can build up in the fuel tank as a result of the newly formed fuel vapor unless control devices are provided to vent the fuel vapor from the fuel tank during vehicle operation. Such valves have been referred to as “run-loss” valves or tank venting rollover valves because they handle fuel vapor loss during vehicle run and are capable of preventing liquid fuel carry-over during vehicle rollover.
Fuel tanks are being made now out of plastics materials and being shaped to nest in various irregular nooks and crannies formed on the underside of vehicles. Such fuel tanks may be formed to include, for example, two vapor chambers positioned to fit into such nooks and crannies and lie above what would otherwise be the top wall of the fuel tank. Heretofore, it has been necessary to make two hole cuts in the fuel tank having two vapor chambers, one hole cut for each of the vapor chambers, so that a vent valve can be provided for each of the two vapor chambers.
According to the present invention, a tank venting system includes a tank, first and second vapor domes mounted on top of the tank to lie in spaced-apart relation to one another so that each dome receives fuel vapor generated by liquid fuel extant in the tank, yet the domes are isolated from one another when the tank is full of fuel, and a vent apparatus coupled to the first vapor dome and adapted to vent pressurized fuel vapor in the first vapor dome to an external destination. The tank venting system further includes dome vent means located inside the fuel tank for transferring pressurized fuel vapor extant in the second vapor dome into the first vapor dome so that such transferred fuel vapor can be vented to an external destination by the vent apparatus coupled to the first vapor dome.
In preferred embodiments, the dome vent means includes a fuel vapor transfer conduit formed to include a conduit inlet, a conduit outlet, and a vent passageway extending between the conduit inlet and outlet. The dome vent means also includes conduit support means for supporting the transfer conduit in an interior region of the tank so that it is able to pivot about an axis to move the conduit inlet from a lowered position to a raised position within the tank as the fuel level rises in the tank during refueling while the conduit outlet remains in the first vapor dome.
The conduit support means includes a buoyant float coupled to the transfer conduit at the conduit inlet to cause the conduit inlet always to remain above the top surface of liquid fuel extant in the tank and to communicate with and receive pressurized fuel vapor extant in the second vapor dome when the tank is full. The conduit support means also includes an anchor mounted in an aperture formed in a top wall of the first vapor dome. The anchor includes a sleeve extending through the aperture and surrounding the vent apparatus and a support frame having one end rigidly coupled to the sleeve and another end pivotably coupled to the transfer conduit at the conduit outlet.
When the tank is full or nearly full, pressurized fuel vapor trapped in the isolated second vapor dome passes into the vent passageway formed in the fuel vapor transfer conduit through the conduit inlet that is raised above the top surface of liquid fuel in the tank by the buoyant float. Except for the conduit inlet and outlet, most of the fuel vapor transfer conduit is submerged in liquid fuel extant in the tank when the tank is full or nearly full. Pressurized fuel vapor admitted into the vent passageway through the conduit inlet is then conducted by the transfer conduit into the first vapor dome for discharge from the tank to an external destination (such as a vapor-recovery canister) by the vent apparatus coupled to the first vapor dome. Thus, no vent apparatus need be mounted on the second vapor dome to vent pressurized fuel vapor from the second vapor dome and only one hole cut need be made in the first vapor dome to receive the single first vapor dome vent apparatus (and the sleeve of the anchor that surrounds that vent apparatus) therein.
Additional features of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.
REFERENCES:
patent: 4816045 (1989-03-01), Szlaga et al.
patent: 5156178 (1992-10-01), Harris
patent: 5687778 (1997-11-01), Harris
patent: 5694968 (1997-12-01), Devall et al.
patent: 6089249 (2000-07-01), Thibaut et al.
Barnes & Thornburg
Michalsky Gerald A.
Stant Manufacturing Inc.
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