Low permeation cam lock for plastic fuel tank vapor vent valve

[0002] The present invention relates to mounting of fuel vapor vent valves in plastic fuel tanks and particularly plastic fuel tanks for motor vehicles.

[0003] Presently in passenger cars and light trucks, the fuel tank has a vapor vent valve disposed in the fuel tank and positioned to have the valve inlet located in the vapor dome above the liquid fuel level and the valve outlet connected to a storage device such as a charcoal filled canister for storing fuel vapor when the engine is not running. Such valves are typically installed in the fuel tank through an access opening in the upper wall of the tank which requires adequate sealing of the valve about the opening.

[0004] Heretofore, it has been found satisfactory to provide portions of the valve exterior to the fuel tank formed of material compatible with the material of the fuel tank to enable sealing of the valve over the access opening by weldment. However, this technique has the disadvantages of relatively high cost in mass production and rendering the valve non-removable from the tank.

[0005] Furthermore, plastic fuel tanks are formed of material which is suitable for exposure to liquid fuel and vapor but which has a prohibitively high permeability to the vapor. Accordingly the tanks are formed with a non-permeable barrier layer embedded in the wall of the tank to minimize the escape of fuel vapor. However, where an access opening is formed in the upper wall of the tank for installation of the vapor vent valve, the barrier layer is broken and an area subject to vapor permeation is created.

[0006] It has thus been desired to provide a way or means of mechanically installing, sealing and retaining a fuel vapor vent valve through an access opening in the upper wall of a fuel tank in a manner which provides a simple one-piece assembly, is relatively low in cost and provides positive sealing of the vapor barrier layer in the tank wall.

[0007] The present invention provides a technique for positively retaining and sealing a fuel vapor vent valve through an access opening in the upper wall of a plastic fuel tank having an embedded vapor barrier in a manner which seals the vapor barrier layer and also eliminates the need for separate fasteners at installation. The vapor vent valve may be supplied as a subassembly complete with a seal ring and a discontinuous locking ring provided thereon. Portions of the locking ring engage torque transmitting surfaces on the valve to prevent relative rotation therebetween; however, limited axial movement of the ring with respect to valve is permitted to facilitate installation on the tank. At installation the subassembly is inserted through the access opening with the locking ring registered against the exterior side of the access opening. The subassembly is then rotated and the edge of the locking ring engages and feeds through a slit formed in the edge of the access opening; and, upon continued rotation, the locking ring feeds axially completely through the slit until fully positioned within and engaged with the interior surface of the tank wall with portions of the locking ring engaging the exterior of the valve to prevent rotation of the valve once installed.

[0008] The valve, seal ring and locking ring may thus form a self-contained subassembly ready for installation and locking in the fuel tank without the need for separate fasteners or tools upon installation on the tank.

[0009] FIG. 1 is a perspective view of the valve subassembly of the present invention viewed from below the exterior mounting flange of the valve;

[0010] FIG. 2 is an exploded view of the subassembly of the present invention and the access opening in the upper wall of a fuel tank;

[0011] FIG. 3 is a cross-section of a portion of the valve and tank wall showing the valve partially inserted into the access opening;

[0012] FIG. 4 is a view similar to FIG. 3 showing the valve subassembly in the fully installed position;

[0013] FIG. 5 is an enlarged view of a portion of the tank wall in the region of the access opening; and,

[0014] FIG. 6 is a plan view of the blocking ring.

[0015] Referring to FIGS. 1 and 2, a preferred form of the invention having a subassembly including the valve is indicated generally at 10; and, the fuel tank wall indicated generally at 12. The valve has a body with an annular external mounting flange 14 having a hose fitting 16 preferably extending from the axial face thereof with a reduced diameter of annular portion 18 formed on the undersurface of the flange 14 with an annular seal ring 20 received thereover. A further reduced diameter or lower portion 22 extends downwardly from the portion 18 and has at least one, and preferably a plurality, of torque transmitting surfaces which may take the form of axially extending recesses or grooves 24 formed therein in circumferentially spaced arrangement.

[0016] Referring to FIGS. 1, 2 and 6, a locking ring 26 preferably formed of spring material preferably has a radial slit 28 formed therethrough rendering the ring discontinuous with one edge thereof inclined to the plane of the ring form an axial lead portion denoted by reference numeral 30. However, it will be understood that alternatively a continuous spiral ring could also be employed, if desired. The inner periphery of the ring 26 has at least one, and preferably a plurality, of torque transmitting surfaces corresponding to those on the valve and which may take the form of radially inwardly extending tabs or lugs 32 formed thereon, which lugs are each engaged in one of the grooves 24 upon assembly of the ring over the reduced diameter portion 22 of the valve as shown in FIG. 1.

[0017] Referring to FIGS. 2 and 5, a portion of the wall of the tank 12 is shown with a vapor barrier layer 34 is shown broken by formation of an annular groove 36 in the outer surface of the tank wall, in the manner of a counterbore, about a smaller diameter access bore 38 formed through the wall of the tank. In the presently preferred practice the counterbore or annular groove is formed preferably by machining to provide dimensionally accurate surfaces for installation and sealing of the valve. In the presently preferred practice of the invention bore 38 and annular groove 36 are formed in the top wall of the tank; however, it will be understood they may be formed in any convenient area of the tank wall appropriate for proper function of the vent valve.

[0018] Referring to FIG. 5, a radially extending slit 40 which is inclined to the axis of the opening, is formed in the shoulder 42; and, the width of the slit is sufficiently greater than the thickness of the locking ring 26 to permit ease of passage therethrough.

[0019] Referring to FIG. 3, the subassembly 10 is shown partially installed with the reduced diameter 22 of the valve inserted through the access opening 38 and with the axial lead 30 of the locking ring 26 entered into the slit 40 by an initial rotation of the subassembly 10. It will be understood that the recesses or grooves 24 are of sufficient axial length on the reduced diameter 22 of the valve body to enable the necessary axial movement of the lugs 32 engaged therein without disengagement of the lugs 32 from the grooves 24.

[0020] Referring to FIG. 4, the valve is shown completely installed wherein the subassembly 10 has been rotated further from the position of FIG. 3 sufficiently to feed the locking ring 26 entirely through the slit 40 and to position the locking ring inside the tank and engaging the undersurface of the tank wall 12. In the installed position in FIG. 4, it will be seen that the annular sealing ring 20 engages the wall 36 of the access opening and the diameter 18 of the valve to seal therebetween.

[0021] Referring to FIG. 5, the annular seal 20 is shown in dashed outline as sealing against the diameter 36 of the access opening and the shoulder 42 and thus seals the edges of the vapor barrier layer 34 in the tank wall.

[0022] The present invention thus provides a vapor vent valve which may, if desired, have a seal ring and locking ring disposed therewith forming a subassembly to facilitate installation. Upon insertion of the lower portion of the valve into an access opening in a fuel tank, the valve is positively retained and sealed therein by rotation of the valve to feed the locking ring through a slit formed in the access open of the tank wall. Thereafter the locking ring engages the inner surface of the tank wall and the valve to retain the valve in the installed position. The valve of the present invention is thus capable of simple mechanical installation, locking and being sealed into a fuel tank access opening without the need for separate fasteners or tools.

[0023] Although the invention has hereinabove been described with respect to the illustrated embodiments, it will be understood that the invention is capable of modification and variation and is limited only by the following claims.