Abstract:
An improved fuel level responsive peelaway action valve for vehicle fuel tanks, in which a float moves a valve closure element into sealing contact with a vapor venting outlet, and then pulls or “peels” the valve element off the vapor venting outlet when fuel level drops. The valve closure element comprises a thin, flexible sealing portion for engaging the vapor venting outlet with low sealing forces, and a stiffened marginal portion acted on by a rigid cage or frame which is connected to the float. As the float drops, the cage contacts the stiffened marginal portion and levers the valve element off the venting outlet.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
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     MICROFICHE APPENDIX 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     The present invention is in the field of fuel level responsive valves used in vehicle fuel tanks. 
     Fuel level responsive valves are well known in the art of controlling the venting of fuel vapor from vehicle fuel tanks. These valves typically have a float mechanism trapped within a valve body to move a valve closure element into and out of sealing engagement with a vent outlet in response to rising and falling fuel levels. Such valves are most often employed as rollover valves, responding to fuel slosh or vehicle tilt and rollover situations to protect a vapor-processing canister from liquid fuel, although they can also be used for fill control shutoff and primary onboard vapor control. 
     Some successful float-operated valves are shown in U.S. Pat. No. 4,753,262 issued to Bergsma, and U.S. Pat. No. 5,313,977 issued to Bergsma, et al., both co-owned with the present application. These valves employ a peelaway type opening action, in which a rigid plastic plate- or paddle-like valve element is initially “cracked” open over a limited segment of its sealing surface with the vent outlet by an actuator attached to the float, and subsequently “peeled” from the vent outlet, either circumferentially or in lever fashion. By initially cracking or peeling only a portion of the valve element from the vent outlet, the pressure differential acting across the valve element is reduced to prevent the float from becoming “hung up”, or lodged in the closed position, unable to overcome the force of the pressure differential acting across the surface area of the valve element to open the valve when fuel level drops. The net downward force comprising the weight of the float, less buoyancy forces is not sufficient to move the entire valve element off the vent outlet at once, because the accumulated force of the vapor pressure differential acting across the entire surface area of the valve element is substantially greater. 
     Heretofore rigid valve elements have been employed because they are more responsive to the initial “cracking” or “peeling” action of the float. It is therefore necessary to either machine the sealing surfaces of the rigid valve element and the vent outlet carefully to ensure an adequate vapor and liquid seal, or to apply an additional resilient, rubberlike seal member to either the valve element or the vent outlet to improve the seal between them. 
     Another prior approach has been the use of pliable, ribbonlike valve elements which are opened in a generally continuous peeling fashion. Examples of such valves are shown in the above-described patent to Bergsma, et al. and in U.S. Pat. No. 4,770,201 and published European Patent Application EP 0724098A1 to Zakai, et al. 
     While pliable, rubber-type valve elements provide improved sealing with the vent outlet, rubber-type seals have tended to provide a continuous peeling action which has been found not as desirable as the cracked-open lever action of rigid valve elements. Such seals have also been found prone to “bunching up” or deforming due to high volume vapor flow, large pressure differentials, and any horizontal sliding motion of the float relative to the vent outlet. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention solves the foregoing disadvantages of the prior art valve with a valve element having a pliable, resilient diaphragm-like seal member peripherally stiffened by a thickened rim to give the resilient seal a lever-type opening action. 
     In a preferred form, the float has a generally ring-shaped cage or frame which traps the resilient seal member. The trapped resilient seal is preferably stiffened, for example with a thickened edge to provide body or shape holding characteristics to a thin, pliable center section which engages the vent outlet. 
     The seal member is trapped inside the cage for limited vertical, and preferable also limited horizontal movement within the cage to assist with the opening action. 
     In the preferred form the cage is integrally formed with the float and has a flexible strip portion or “living hinge” portion which is folded and snap-locked in place after insertion of the seal member in the cage for retaining the seal member in the cage. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic representation of a vehicle fuel system of the type in which a valve according to the present invention is capable of being used; 
     FIG. 2 is a perspective view of the rollover vent valve of FIG. 1; 
     FIG. 3 is a cutaway or section view taken along section indicating lines  3 — 3  of FIG. 2, showing the valve fully open; 
     FIG. 4 is an enlarged view of a portion of FIG. 3 showing the initial peelaway stage when the seal between the valve element and the vent outlet is first broken; 
     FIG. 5 is a view showing the valve element further opened from the position of FIG. 4; and, 
     FIG. 6 is a perspective view of the top of the float with the cage opened for insertion of the valve member. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring first to FIG. 1, a valve indicated generally at  16  according to the present invention is shown schematically illustrated in a typical vehicle fuel system environment including a fuel tank  10 , a filler pipe  12 , and a vapor recovery apparatus such as a carbon canister  14  connected to valve  16  by a conduit or hose  17 . 
     Fuel level responsive vapor control valves such as  16  are typically mounted in the upper wall of fuel tank  10 , positioned to close vapor venting from the tank to canister  14  when fuel level  18  submerges valve  16 , for example during refueling, or during fuel slosh or vehicle rollover conditions. Valve  16  reopens when fuel level  18  drops, or when the slosh or rollover condition is alleviated. 
     In the illustrated embodiment, valve  16  is depicted as a “rollover” valve typically used in conjunction with one or more additional valves in the fuel tank to supplement refueling vapor control and pressure relief functions. It will be apparent to those skilled in the art, however, that valve  16  incorporating the present invention can be employed in almost any type of fuel level responsive valve, and is not limited to the rollover valve application now described. 
     Referring next to FIGS. 2 and 3, the inventive valve  16  is illustrated in detail, generally comprising the valve closure and reopening structure at the top of a float mechanism and its relationship to a vapor venting outlet in the upper end of the valve where fuel vapor is vented to the vapor recovery apparatus outside the fuel tank. In particular, valve  16  includes a valve body  20  having a generally hollow cylinder made from a fuel-resistant plastic material, although the exact composition of valve body  20  is not critical to the present invention. Valve body  20  includes an interior float chamber  22  designed to receive a fuel level responsive float  24  in a sliding arrangement. Float chamber  22  typically includes at least one, and usually several lower fuel entry ports (not shown) and one or more higher fuel vapor entry ports (not shown) such that liquid fuel freely enters chamber  22  when the fuel level in the tank reaches valve  16 , thereby forcing the float  24  upwardly toward vapor venting orifice or outlet  32  located in the upper end of the float chamber and having the lower end thereof forming a valve seat  36 . Outlet  32  communicates with a passage  35  on the portion  37  of the valve external to tank  10 , which portion  35  is adapted for connection to conduit or hose  17  connected to canister  14 . The fuel vapor entry ports in the upper end of the valve body, usually in the form of radial windows (not shown) in the sidewall around chamber  22 , admit fuel vapor to be vented through outlet  32  until the outlet is closed by a valve element on the float contacting valve seat  36 . 
     Float  24  carries a valve closure element indicated generally at  25  on its upper end, captured on the float at one end by flange ring  38  and posts  28 ,  29 ,  31  and hinged port  30 , illustrated in FIG. 6 as an integral part of float  24  projecting from its upper surface and which forms a cage indicated generally at  33 . The cage  33  thus comprises a flange or ring  38  supported by posts  28 ,  29 ,  31  and  30  which allow the valve element some limited up and down and side to side travel or lost motion relative to the float for a peelaway type reopening action described in further detail below. 
     Referring to FIG. 6 hinged post  30  is shown in the open position enabling the valve seal element  26  to be inserted in cage  33 , prior to snap locking the end of post  30  into cutout  39  formed in flange ring  38 . 
     Valve element  25  is shown in its valve closed position in FIG. 4, forced against vent seat  36  and outlet  32  and is shown in partially peeled open state. In this beginning to open position, valve element  25  is contacted at its rim by the undersurface of the flange or ring  38 . 
     Referring to FIGS. 3,  4  and  5 , in accordance with the present invention, valve element  25  comprises a soft, pliable, rubberlike seal element  26 . 
     Valve closure element  25  is preferably a disk-shaped element with a stiffened, preferably, thickened edge  27 , illustrated as an annular bead, surrounding a thin, pliable central webbing or diaphragm-like seal element portion  26 . For purposes of illustration, the central webbing seal element portion  26  is preferably on the order of 0.015 inches (0.38 mm) in thickness, although it will be apparent to those skilled in the art that different thicknesses with different pliability characteristics may be used depending on the valve application. As shown in FIG. 4, central seal element portion  26  makes a closely-conforming seal with valve seat  36  of vent outlet  32  which is generally superior to the seal formed by rigid plastic valve elements. The thin, pliable nature of central seal element portion  26  provides what is known as a “low sealing force” seal with the vent outlet, which is generally desirable in most applications. 
     The pliable, reinforced rubber seal  26  is trapped for limited vertical and horizontal movement inside cage  33  which results in improved sealing and reopening action. It will be understood that when the fuel level begins to drop float  24  begins to descend in float chamber  22 . Referring to FIG. 4, while the pliable rubber seal  26  remains closed on vent seat  36  of outlet  32  due to the pressure differential between the fuel tank and the canister, and the underside  34  of the flange  38  contacts the upper surface of bead rim  27  and has begun to “crack open” a portion of seal  26  from the vent port valve seat  36 . 
     This initial cracking or peeling action breaks the seal between rubber disk  26  and vent outlet  32  to begin reducing the pressure differential across rubber seal  26 . 
     Referring next to FIG. 5, float  24  has dropped further to bring the underside of actuator flange  38  lower to continue the peeling action and break any remaining contact between rubber seal  27  and vent outlet  32  by pulling it straight off the vent outlet. As shown in FIG. 5, the reinforced edge  27  on pliable rubber seal  26  serves to stiffen the overall rubber seal to pull it off the vent outlet in a manner similar to a rigid seal element for the final opening stages. 
     In FIG. 3, float  24  is shown as having descended far enough to pull valve element  25  completely free from the vent seat  36  of outlet  32 , such that valve element  25  now drops back down to rest on the upper surface of the float, with internal rubber seal  26  dropping down inside paddle frame cage  33  to its ramp-centered lower position on upper surface  40  of float  24  shoulder  26   h.    
     It will be apparent to those skilled in the art that various modifications may be made to the disclosed structure for different valve applications, without departing from the spirit and scope of my invention. For example, the size and shape of valve element  25  may vary depending on the vent outlet which it is intended to close. The invention is not to be limited by the foregoing exemplary illustrations, except as provided by the following claims.