Abstract:
A float operated fuel vapor vent valve for use in a vehicle fuel tank. The float has a membrane valve caged for lost motion movement on the top of the float. Upon refueling, the float rises and seals the membrane on a vent port valve seat. A projection extending downwardly from the top of the cage contacts the membrane to peel away a localized area of the membrane valve from the valve seat to ensure re-opening upon the float descending as fuel is withdrawn from the tank.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to vapor vent valves of the type employed in fuel tanks filled with volatile fuel for operating an internal combustion engine and for which it is desired to control the emission of fuel vapors during periods in which the engine is not operating. 
     Heretofore, fuel tank vapor vent valves have had problems with valve failure in arrangements where the rising level of the liquid fuel in the tank closes the valve outlet which is connected to the vent port through the wall of the tank. In particular, in such arrangements, upon withdrawal of fuel, problems have been encountered with the valve sticking and failing to reopen. A relatively large valve area is required to provide the desired vapor flow at low vapor pressures. Where a relatively low valve closing force is available from the float it has been necessary to use a relatively flexible and soft valve member which can be effectively seated on a valve surface with the available relatively low closing force. 
     A known float operated valve has employed a relatively thin flexible membrane valve member to effectuate closing with a relatively low closing force acting thereon. However, problems have been experienced with such valves upon the tank being completely filled with liquid fuel with the valve sticking closed or “corking”. Subsequently, when fuel is withdrawn and the float descends to a level intended to reopen the valve, the increased vapor pressure acts to continue to hold the membrane valve member closed on the valve seat. 
     Thus, it has long been desired to provide a way or means of ensuring a positive reopening of flow operated fuel vent valve having a relatively thin flexible valve member which seals readily upon the vent port seat with the available low closing forces from the float and which will positively reopen without sticking upon fuel withdrawal the float descending to the level wherein vapor venting is required. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention solves the above described problem by providing a float actuated fuel vapor vent valve having a flexible elastomeric membrane type valve member caged for limited lost motion movement on the float assembly, with the upper portion of the cage having a downwardly extending projection for effecting localized peeling of the valve member from the valve seat upon lowering of the float assembly due to withdrawal of the liquid fuel from the tank. A preferred form of the float assembly has the cage formed with an inclined upper portion to effect peeling away of one side of the membrane from the valve seat thereby minimizing the force required to continue reopening of the valve on further lowering of the float assembly to ensure complete re-opening. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-section of the valve assembly employed in the present invention; and, 
     FIG. 2 is an enlarged view of the float assembly employed in the valve of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, the valve assembly of the present invention is indicated generally at  10  and includes a body or housing indicated generally at  12  which includes an upper portion  14  intended to be disposed externally of the fuel tank and which includes a hose fitting  16  having formed therein a vapor outlet passage  18 . The upper portion  14  of the housing includes an outwardly extending annular flange portion  20 . The valve body  12  further includes a downwardly extending portion  22  which is intended to extend into the interior of the fuel tank through the access opening (not shown) provided the tank; and, the portion  22  has formed therein a float cavity  24  which has slidably received therein a float assembly indicated generally at  26 . 
     The outward extending flange  20  formed on the upper portion  14  has an annular attachment flange  28  disposed thereover preferably by plastic overmolding and which includes a support or retainer ring  30  which engages flange  28  and the portion  22 . An elastomeric seal material  32  is formed over the outer periphery thereof and which forms a substantially vapor impervious seal between the flange  20  and the overmold  28 . It will be understood that overmold  28  is adapted for weldment to a plastic tank of similar material. 
     A valve seat member  34  is disposed in body  12  and includes an annular valve seat  36  formed on the lower end of a valving passage  38  extending vertically through member  34 . The upper end of the passage  38  has seated thereon a preferably spherical gravity responsive check valve  40  which is positioned thereon by an annular retaining wall  42  preferably formed as part of the valve seat member  34 . 
     The lower portion of the body  22  has received thereover a guard or cover  44  which, in the presence practice of the invention, preferably has a cup shaped configuration, or alternatively a U-shaped configuration, and which may be secured over the lower portion of the body  22  with any suitable expedient such as by snap locking engagement or by weldment. 
     The upper end of the vapor passage  38  has at least one, and preferably a plurality, of cross grooves  46  formed thereon to permit a minimum bleed flow of fuel vapor when the check valve  40  is registered against the end of the passage  38 . In the event of excessive vapor pressure in the tank, the downward force of the weight of the check valve  40  is overcome by the pressure acting over the area of the seated valve; and, this pressure causes the valve  40  to move upwardly increasing the flow area to relieve the pressure. 
     Referring to FIG. 2, the float assembly  26  is shown in greater detail and includes a body having a generally annular or tubular configuration denoted by reference numeral  48  with a core  50  disposed therein and which preferably has a curved surface  52  formed on the upper end thereof. The core  50  may be secured within the body  48  by any suitable expedient as for example by snap locking or by weldment. 
     The body  48  has a cage  54  formed on the upper end thereof in which is received a resilient flexible valve member denoted by reference numeral  56  preferably having a relatively thin membrane configuration and preferably with an annular bead rim  58  disposed about the outer periphery thereof and preferably formed integrally therewith. A rigid plate or disk  60  is disposed under the valve member  58  and is seated on the curved surface  52  for pivotal movement thereon and extends outwardly to contact the bead  58  to provide a registration or seating surface therefor. 
     The cage  54  has the upper end  62  thereof inclined at an angle to the axis of the float body  48 ; and, the upper end  62  of the cage includes a downwardly extending projection  64  which is preferably located adjacent the inner periphery of the bead  58 . The projection  64  is operative to provide localized contact and deflection of the membrane  56  upon downward movement of the float assembly  26  as will be herein after described in greater detail. It will be understood that the cage  54  is of sufficient height from the core  52  to permit limited relative motion or lost motion therein of the valve member  56  and the disc  60 . 
     Referring to FIG. 1, the float assembly is biased upward by a spring  66  having its lower end registered against the inside of the cup  44  with the upper end of the spring  66  registered in an annular grooves  68  formed in the lower end of the core  50 . 
     In operation, as the fuel level in the tank rises, the float is moved upwardly to the position shown in dashed outline in FIG. 1 whereupon the valve member or membrane  56  contacts the valve seat  36 , and is sealed thereagainst by the disc  60  pressing against the peripheral bead  58  of the membrane as the curved surface  52  of the float core contacts the under surface of the disc  50 . 
     Upon withdrawal of fuel from the tank and the lowering of the fuel level, the float assembly  26  is lowered causing the projection  64  to contact locally a portion of the valve member or membrane  56  to effect localized peeling of that portion of the valve member  56  from the valve seat  36  thereby preventing the valve member or membrane  56  from sticking against the valve seat  36 . Further downward movement of the float assembly  26  causes the underside of the top  62  of the cage to contact the bead rim  58  of the valve member and effect a further peel away of one side thereof. Upon further lowering of the float assembly  26  the upper or higher portion of cage  62  contacts the side of membrane valve member rim  58  opposite projection  64  and effects complete opening of the valve member from the seat  36 . 
     The present invention thus provides, a unique and novel construction for a float operated fuel vapor vent valve having a relatively thin resilient valve member mounted within a cage on the float for limited lost motion on the float for sealing on a stationary vapor vent valve seat as the float rises. Upon withdrawal of fuel and lowering of the float, a downwardly extending projection on the float cage contacts a localized area of the valve membrane and causes the localized area to be peeled away from the valve seat thereby preventing the valve from remaining in a completely closed condition. Upon further lowering of the float, the cage peels this member  56  completely away from the valve seat. 
     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.