Vacuum actuated tank vapor vent valve

Abstract

A tank vapor vent valve assembly mounted to the top of the tank wall has a piston actuated by a source of engine vacuum which maintains a fill vapor exit closed until the gas cap is removed to relieve the vacuum and allow the piston to open.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. In a vehicle having a source of engine vacuum, a fuel tank having a fuel vapor collection space and a fuel tank filler neck with a closure cap that is removed when said tank is filled, and a fuel vapor storage canister, a valve assembly for selectively admitting to said canister the fuel fill vapors displaced from said tank when it is filled, comprising: a valve housing secured to said fuel tank and opening into said vapor collection space across a valve seat of a size sufficient to pass said fuel fill vapors,   a canister line running between said valve housing and said canister,   a vacuum chamber located proximate to said valve seat,   a piston in said vacuum chamber movable between a closed position blocking said valve seat and an open position, said piston further having a resilient bias toward said open position,   a vacuum supply line running between said engine vacuum source and said vacuum chamber of a size sufficient to slowly evacuate said vacuum chamber to pull said piston to said closed position,   a vacuum relief line running between said vacuum chamber and said filler neck of a size sufficient to quickly refill said vacuum chamber, and,   a plug in said filler neck movable from a closed position blocking said vacuum .[.exhaust.]. .Iadd.relief .Iaddend.line when said closure cap is in place to an open position when said closure cap is removed,   whereby, when said cap is in place, said vacuum chamber remains evacuated and said piston remains closed, and when said cap is removed to fill said tank, said vacuum chamber refills at a more rapid rate than said vacuum supply line can evacuate it, and said piston opens to allow fuel fill vapors to exit said tank to said canister through said valve seat.   
     
     
       2. In a vehicle having a source of engine vacuum, a fuel tank having a fuel vapor collection space that collects both the normal fuel vapors generated in said tank and the fuel fill vapors displaced when said tank is filled, said fuel tank also having a fuel tank filler neck with a closure cap that is removed when said tank is filled, and a fuel vapor storage canister, a valve assembly that continually admits said normal fuel vapors to said canister, but admits said fuel fill vapors only during fuel fill, said valve assembly comprising, a valve housing secured to said fuel tank over said vapor collection space, said valve housing having a single outlet and a pair of inlets opening into said vapor collection space, including a larger inlet of a size sufficient to pass said fuel fill vapors and a smaller inlet of a size sufficient to pass only said normal fuel vapors,   a canister line running between said valve housing outlet and said canister,   a vacuum chamber in said housing located over said larger inlet,   a piston in said vacuum chamber movable between a closed position blocking said larger inlet and an open position, said piston further having a resilient bias toward said open position,   a vacuum supply line running between said engine vacuum source and said vacuum chamber of a size sufficient to slowly evacuate said vacuum chamber to pull said piston to said closed position,   a vacuum relief line running between said vacuum chamber and said filler neck of a size sufficient to quickly refill said vacuum chamber, and,   a plug in said filler neck movable from a closed position blocking said vacuum .[.exhaust.]. .Iadd.relief .Iaddend.line when said closure cap is in place to an open position when said closure cap is removed,   whereby, when said cap is in place, said vacuum chamber remains evacuated and said piston remains closed so that fuel vapors may pass only through said smaller inlet, and when said cap is removed to fill said tank, said vacuum chamber refills at a more rapid rate than said vacuum supply line can re-evacuate it, and said piston opens to allow fuel fill vapors to exit said tank to said canister through said larger inlet as well.   
     
     
       3. In a vehicle having a source of engine vacuum, a fuel tank having a fuel vapor collection space and a fuel tank filler neck with a closure cap that is removed, when said tank is filled, and a fuel vapor storage canister, a valve assembly for selectively admitting to said canister the fuel fill vapors displaced from said tank when it is filled, comprising, a valve housing secured to said fuel tank and opening into said vapor collection space across a valve seat of a size sufficient to pass said fuel fill vapors,   a canister line running between said valve housing and said canister,   a vacuum chamber located proximate to said valve seat,   a piston in said vacuum chamber movable between a closed position blocking said valve seat and an open position, said piston further having a resilient bias toward said open position,   a vacuum supply line running between said engine vacuum source and into said vacuum chamber across a restricting orifice of a size sufficient to slowly evacuate said vacuum chamber to pull said piston to said closed position,   a vacuum relief line running between said vacuum chamber and said filler neck of a size larger than said restricting orifice, and,   a plug in said filler neck movable from a closed position blocking said vacuum .[.exhaust.]. .Iadd.relief .Iaddend.line when said closure cap is in place to an open position when said closure cap is removed, and,   a sealed splash door located in said filler neck below said plug,   whereby, when said cap is in place, said vacuum chamber remains evacuated and said piston remains closed, and when said cap is removed to fill said tank, said sealed splash door maintains said filler neck sealed from atmosphere while said vacuum chamber refills at a more rapid rate than said vacuum supply line can evacuate it, and said piston opens to allow fuel fill vapors to exit said tank to said canister through said valve seat. .Iadd.   
     
     
       4.  In a vehicle having a source of engine vacuum, a fuel tank having a fuel vapor collection space that collects both the normal fuel vapors generated in said tank and the fuel fill vapors displaced when said tank is filled, said fuel tank also having a fuel tank filler neck with a closure cap that is removed when said tank is filled, and a fuel vapor storage canister, a valve assembly for selectively admitting to said canister the fuel fill vapors displaced from said tank when it is filled, comprising, a valve housing having an outlet and a pair of inlets opening into said vapor collection space, including a larger inlet of a size sufficient to pass said fuel fill vapors and a smaller inlet of a size sufficient to pass only said normal fuel vapors,   a canister line running between said valve housing outlet and said canister,   a vacuum chamber in said housing located over said larger inlet,   a piston in said vacuum chamber movable between a closed position blocking said larger inlet and an open position, said piston further having a resilient bias toward said open position,   a vacuum supply line running between said engine vacuum source and said vacuum chamber to evacuate said vacuum chamber to pull said piston to said closed position,   whereby, said vacuum chamber remains evacuated and said piston remains closed to allow only said normal fuel vapors to exit said tank to said canister through said smaller inlet when engine vacuum is applied, and said piston opens to allow fuel fill vapors to exit said tank to said canister through said larger inlet when engine vacuum is absent. .Iaddend.