The present invention relates to fuel vapor vent valves employed in fuel tanks filled with highly volatile fluids such as gasoline or mixtures of gasoline and alcohol and particularly relates to valves employed in motor vehicle fuel tanks.
Currently passenger cars and light truck vehicles employ fuel vapor storage devices connected to the vehicle fuel tank through a float operated valve which controls the flow of vapor in the dome above the liquid fuel level to a storage device. Currently, such valves are required to prevent the escape of liquid fuel in the event of overfilling the tank or angular displacement of the vehicle including rollover conditions.
With the advent of molded plastic fuel tanks, it has been found difficult to provide an economical design for the vent valve and the attachment of the valve to the tank. Heretofore, such vent valves had been installed through an access opening in the tank which requires sealing in a manner sufficient to prevent escape of vapor and permeation of the vapor through the material of the vent valve and the tank wall.
It has been found that the material required to withstand continuous exposure to the liquid fuel and vapor has the propensity to be permeable to the fuel vapor. This problem has been addressed by molding the tank wall of layers of different materials with a vapor impervious barrier layer embedded in the material of the tank wall.
If an access opening is formed in the top of the tank for installation of a vapor vent valve, the vapor barrier continuity is broken and the potential for localized vapor permeation has resulted.
Accordingly, it has been proposed to install the vapor vent valve on the interior of the fuel tank without forming an access opening in the upper wall of the tank.
The aforesaid proposal of mounting a vapor vent valve on the interior of the tank has been complicated by the use of high density polyethylene (HDPE) material for molding of the fuel tank. For economical installation of the vent valve on the inside of the fuel tank, the use of HDPE material for the valve has been required in order to permit securing the valve to the wall of the tank by weldment. However, HDPE material has been found not satisfactory for the structural components of the float operated valve and this has resulted in difficulties in designing and manufacturing a valve for interior installation in the tank.
The present invention provides a unique and novel technique for installing a float operated fuel vapor vent valve inside a fuel tank and securing the valve to the tank wall by weldment. The present invention provides for a cup-shaped or U-shaped attachment member with the valve received therein and recessed below the rim of the attachment member which is secured to the inner surface of the tank wall by weldment. The attachment member secures and retains the valve in the desired position and orientation in the tank. The arrangement of the present invention thus permits the body structure of the valve to be formed of a desired material different from the material of the attachment member which is required to be the same as the tank wall material in order to facilitate attachment by weldment.