Abstract:
A fuel tank vent apparatus for controlling discharge of fuel vapor from an interior region in a fuel tank includes a housing and a valve received in the housing that moves between an open position and a closed position. The valve assumes the open position when the fuel level in the fuel tank is relatively low and the valve assumes the closed position when the fuel level in the fuel tank is relatively high.

Description:
PRIORITY CLAIM 
       [0001]    This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application Ser. No. 61/695,549, filed Aug. 31, 2012, which is expressly incorporated by reference herein. 
     
    
     BACKGROUND 
       [0002]    The present disclosure relates to a fuel tank vent apparatus included in a vehicle fuel storage system, and particularly to a fuel tank vent apparatus for controlling venting of a fuel tank. More particularly, the present disclosure relates to a fuel tank vent apparatus including a housing and a buoyant float received in the housing that is lifted and lowered within the housing by the rising and falling of fuel in the fuel tank. 
       SUMMARY 
       [0003]    A fuel tank vent apparatus is adapted to be mounted to a fuel tank to allow fuel vapor to escape from the fuel tank when fuel level in the fuel tank is low and to block liquid fuel and fuel vapor from escaping from the fuel tank when the fuel level in the fuel tank in high. The fuel tank vent apparatus includes a housing extending into the fuel tank and a valve received in the housing that moves between an open position and a closed position. The valve assumes the open position when the fuel level in the fuel tank is low allowing fuel vapor to escape from the fuel tank through vent ports formed in the housing of the fuel tank vent apparatus. The valve assumes the closed position when the fuel level in the fuel tank is high blocking liquid fuel and fuel vapor from sloshing out of the fuel tank through the vent ports formed in the housing. 
         [0004]    In illustrative embodiments, the valve includes a buoyant float and an intermediary diaphragm arranged between the float and the vent ports formed in the housing. The buoyant float is lifted by the fuel level in the fuel tank. The intermediary diaphragm is lifted with the buoyant float and cooperates with the buoyant float to close the vent ports when the valve is in the closed position so that liquid fuel and fuel vapor are blocked from escaping through the housing. 
         [0005]    In illustrative embodiments, the intermediary diaphragm is formed to include an emission port and a float-pusher spring. The emission port is closed by the buoyant float when the buoyant float is lifted by high levels of liquid fuel in the fuel tank. The float-pusher spring of the intermediary diaphragm stores energy developed by the rising of the float and by increasing pressure inside the fuel tank. The float-pusher spring applies the stored energy to the buoyant float to push the buoyant float downwardly, away from the emission port, to open the emission port when liquid fuel levels in the fuel tank are lowered. The open emission port allows some fuel vapor to escape the internal space through the emission port and a central vent port formed in the housing so that the valve is able to fully re-open as the buoyant float and the intermediary diaphragm fall away from the vent ports releasing the built up pressure in the fuel tank. 
         [0006]    Additional features of the present disclosure will become apparent to those skilled in the art upon consideration of illustrative embodiments exemplifying the best mode of carrying out the disclosure as presently perceived. 
     
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
         [0007]    The detailed description particularly refers to the accompanying figures in which: 
           [0008]      FIG. 1  is a partially diagrammatic view of a fuel storage system including a fuel tank, a fuel vapor recovery canister located outside the fuel tank, and a fuel tank vent apparatus for venting pressurized fuel vapor from the fuel tank to the fuel vapor recovery canister when pressure in the fuel tank is greater than atmospheric pressure outside the fuel tank showing that the fuel tank vent apparatus includes a housing mounted in the top wall of the fuel tank, a multi-part valve arranged inside the housing, and a spring arranged inside the housing and showing that the valve includes a buoyant float adapted to be lifted by liquid fuel in the fuel tank, an intermediary diaphragm arranged between the buoyant float and a ceiling of the housing, and a diaphragm-support cage coupled between the buoyant float and the intermediary diaphragm; 
           [0009]      FIG. 2  is a cross-sectional view of a portion of the fuel storage system of  FIG. 1  showing the valve closing vent ports formed in the ceiling of the housing when the buoyant float is lifted by liquid fuel in the fuel tank so that liquid fuel is blocked from splashing out through the vent port, showing that the intermediary diaphragm of the valve is formed to include an emission port that aligns with a central vent port, and showing that the buoyant float closes the emission port formed in the intermediary diaphragm when the valve is closed; 
           [0010]      FIG. 3  is a cut-away perspective view of the intermediary diaphragm of  FIGS. 1 and 2  showing that the intermediary diaphragm is a monolithic component formed to include an outer vent port closure sized to close outer vent ports arranged radially outward of the central vent port when the valve is closed, an anchor extending radially inward from the outer vent port closure and configured to couple the intermediary diaphragm to the diaphragm-support cage, and a float-pusher spring extending radially inward from the anchor and configured to provide means for storing energy by deforming as the buoyant float is lifted, as shown in  FIG. 3A , and for applying the stored energy to the buoyant float to push the buoyant float downwardly away from the emission port, as shown in  FIG. 3B , to thereby open the emission port allowing some fuel vapor to escape the internal space through the emission port and the central vent port when the buoyant float is not held in contact with the intermediary diaphragm by liquid fuel in the internal space after the level of liquid fuel is reduced during operation of a vehicle; 
           [0011]      FIG. 3A  is a detail cross-sectional view of a portion of the fuel vapor recover canister showing the float-pusher spring included in the intermediary diaphragm deformed to store energy and showing that the float-pusher spring applies the stored energy to the buoyant float to push the buoyant float downwardly, away from the emission port formed in the intermediary diaphragm to open the emission port and allow some fuel vapor to escape the internal space as shown in  FIG. 3B ; 
           [0012]      FIG. 3B  is a view similar to  FIG. 3A  showing the float-pusher spring of the intermediary diaphragm after pushing the buoyant float downwardly away from the emission port formed in the intermediary diaphragm to open the emission port and allow some fuel vapor to escape the internal space; 
           [0013]      FIGS. 4A-4D  are a series of partially-diagrammatic views of a fuel storage system including a fuel tank located near an exhaust system, a fuel vapor recovery canister located outside the fuel tank, and the fuel tank vent apparatus of  FIGS. 1-3  for venting pressurized fuel vapor from the fuel tank to the fuel vapor recovery canister when pressure in the fuel tank is greater than atmospheric pressure outside the fuel tank, the views showing that the fuel tank vent apparatus includes a housing mounted in the top wall of the fuel tank and a valve movable within an internal space formed by the housing from an open position that allows fuel vapor to escape the fuel tank when fuel level in the fuel tank is low, as shown in  FIG. 4A , to a closed position that blocks fuel vapor and fuel from escaping the fuel tank when fuel level in the fuel tank is high, as shown in  FIG. 4B , and showing that the valve in the closed position as fuel from the fuel tank is consumed, as shown in  FIG. 4C , prior to the valve being reopened by an intermediary diaphragm included in the valve that pushes downwardly on the buoyant float included in the valve from the housing in response to increased pressure building in the fuel tank as suggested in  FIG. 4D ; 
           [0014]      FIG. 4A  is a diagrammatic view of the fuel storage system showing the valve of the fuel tank vent apparatus in the open position allowing fuel vapor in the fuel tank to escape the fuel tank through the fuel tank vent apparatus prior to the fuel tank being filled, as shown in  FIG. 4B , and showing diagrammatically that the valve includes a spring, the buoyant float, a seal support, and the intermediary diaphragm; 
           [0015]      FIG. 4B  is a view similar to  FIG. 4A  showing the valve of the fuel tank vent apparatus lifted by the fuel in the fuel tank to the closed position blocking fuel vapor and fuel in the fuel tank from escaping the fuel tank through the fuel tank vent apparatus when the fuel level in the fuel tank is high; 
           [0016]      FIG. 4C  is a view similar to  FIGS. 4A and 4B  showing the valve of the fuel tank vent apparatus in the closed position blocking fuel vapor in the fuel tank from escaping the fuel tank through the fuel tank vent apparatus after the level of fuel in the fuel tank is lowered by fuel use prior to the valve being re-opened to allow fuel vapor in the fuel tank to escape during fuel use as shown in  FIG. 4D ; 
           [0017]      FIG. 4D  is a view similar to  FIGS. 4A-4C  showing the valve of the fuel tank vent apparatus in the open position after being re-opened to allow fuel vapor in the fuel tank to escape the fuel tank through the fuel tank vent apparatus as the level of fuel in the fuel tank is lowered by fuel use; 
           [0018]      FIG. 5  is a diagrammatic view of the fuel tank vent apparatus of  FIGS. 1-4D  showing that the bias spring is arranged between a floor of the housing and the valve to provide some pre-loaded lift to the valve inside the housing, showing that the valve includes the buoyant float, the intermediary diaphragm, and the diaphragm-support cage interconnecting the buoyant float and the intermediary diaphragm, and suggesting that the float-pusher spring included in the intermediary diaphragm is adapted to push downwardly on the buoyant float; 
           [0019]      FIG. 6  is an exploded perspective view of an exemplary fuel tank vent apparatus in accordance with  FIGS. 1-5  showing that the housing includes a lower shell and an upper shell that cooperate to form the internal space in which the valve is located, and showing that the exemplary valve includes the buoyant float, the diaphragm-support cage, and the intermediary diaphragm; 
           [0020]      FIG. 7  is a perspective view of the fuel tank vent apparatus of  FIG. 6  cut away to show the assembled valve situated in the internal space of the housing and showing that the diaphragm-support cage includes a central cylindrical body and arms extending outwardly from the central cylindrical body into slots formed in the buoyant body of the buoyant float to couple the intermediary diaphragm to the buoyant float while allowing a predetermined amount of motion of the buoyant float relative to the intermediary diaphragm as shown in  FIGS. 11A and 11B ; 
           [0021]      FIG. 8  is a perspective view of the exemplary fuel tank vent apparatus with the valve in the open position corresponding to  FIG. 4A  showing that fuel vapor is entering the fuel tank vent apparatus through inlet ports formed in the ceiling and the side walls of the housing and is exiting the fuel tank vent apparatus through the vent ports formed in the ceiling of the housing; 
           [0022]      FIG. 8A  is a cross-sectional view of the fuel tank vent apparatus of  FIG. 8  taken along line  8 A- 8 A showing the valve in the open position spaced apart from the ceiling of the housing; 
           [0023]      FIG. 9  is a perspective view of a portion of the fuel tank vent apparatus in the closed position corresponding to  FIG. 4B  showing that fuel vapor is allowed to enter the fuel tank vent apparatus through the inlet ports of the housing but are blocked from exiting the fuel tank vent apparatus through the vent ports; 
           [0024]      FIG. 9A  is a is a cross-sectional view of the fuel tank vent apparatus of  FIG. 9  taken along line  9 A- 9 A showing the valve in the closed position with the outer vent port closure of the intermediary diaphragm in contact with the ceiling of the housing to close the vent ports of the housing and with the stem of the buoyant float in contact with the float-pusher spring to close the emission port formed in the stem pusher spring so that fuel vapor and fuel is blocked from escaping the fuel tank through the fuel tank vent apparatus; 
           [0025]      FIG. 9B  is a detail cross-sectional view of the stem of the buoyant float and the float-pusher spring of the intermediary diaphragm showing that the stem closes the emission port formed in the float-pusher spring and that the float-pusher spring is part-way deformed when the valve is in the closed position; 
           [0026]      FIG. 9C  is a diagrammatic force balance of the buoyant float corresponding to the buoyant float when the valve is in the closed position showing the buoyant float lifted up by the force of the bias spring and the force of buoyancy and pushed down by the force of gravity and by a small force applied by the float-pusher spring; 
           [0027]      FIG. 10  is a perspective view of a portion of the fuel tank vent apparatus when the valve is in the closed position after the fuel level in the fuel tank is lowered corresponding to  FIG. 4C  showing that fuel vapor is allowed to enter the fuel tank vent apparatus through the inlet ports of the housing but is blocked from exiting the fuel tank vent apparatus through the vent ports; 
           [0028]      FIG. 10A  is a is a cross-sectional view of the fuel tank vent apparatus of  FIG. 10  taken along line  10 A- 10 A showing the valve in the closed position while pressure is built up in the housing to deform the float-pusher spring and store additional energy in the float-pusher spring that is in turn applied to the buoyant float, pushing the buoyant float away from the vent ports formed in the ceiling of the housing to open the emission port; 
           [0029]      FIG. 10B  is a detail cross-sectional view of the stem of the buoyant float and the float-pusher spring of the intermediary diaphragm showing that the stem closes the emission port formed in the float-pusher spring and that the float-pusher spring is fully deformed storing energy from pressure built up in the fuel tank that is applied to the buoyant float to push the buoyant float away from the vent ports formed in the ceiling of the housing and out of contact with the float-pusher spring to open the emission port as shown in  FIGS. 11A and 11B ; 
           [0030]      FIG. 10C  is a diagrammatic force balance of the buoyant float corresponding to the buoyant float when the buoyant float is in the closed position and the float-pusher spring is fully deformed showing the buoyant float lifted up by the force of the bias spring and pushed down by the force of gravity and by a large force applied by the float-pusher spring; 
           [0031]      FIG. 11  is a perspective view of a portion of the fuel tank vent apparatus when the buoyant float moved away from the intermediary diaphragm and the valve is in the process of opening showing that fuel vapor is allowed to enter the fuel tank vent apparatus through the inlet ports of the housing and is beginning to escape through the vent ports; 
           [0032]      FIG. 11A  is a is a cross-sectional view of the fuel tank vent apparatus of  FIG. 11  taken along line  11 A- 11 A showing the buoyant float moved away from the intermediary diaphragm and the valve moving to the open position, and showing that arms of the seal support are contacted by the buoyant float as the buoyant float falls away from the ceiling of the housing to pull the intermediary diaphragm away from the vent ports formed in the ceiling of the housing to completely open the valve as shown in  FIGS. 12 and 12A ; 
           [0033]      FIG. 11B  is a detail cross-sectional view of the stem of the buoyant float and the float-pusher spring of the intermediary diaphragm showing that the stem is moved away from the emission port formed in the float-pusher spring; 
           [0034]      FIG. 11C  is a diagrammatic force balance of the buoyant float corresponding to the buoyant float when the valve is opening showing the buoyant float lifted up by the force of the bias spring and pushed down by the force of gravity; 
           [0035]      FIG. 12  is a perspective view of a portion of the fuel tank vent apparatus when the valve is open corresponding to  FIG. 4D  showing that fuel vapor is allowed to enter the fuel tank vent apparatus through the inlet ports of the housing and allowed to escape through the vent ports of the housing; 
           [0036]      FIG. 12A  is a is a cross-sectional view of the fuel tank vent apparatus of  FIG. 12  taken along line  12 A- 12 A showing the valve in the open position with the outer vent port closure of the intermediary diaphragm spaced apart from the ceiling of the housing to completely open all the vent ports of the housing so that fuel vapor is allowed to escape from the fuel tank through the fuel tank vent apparatus; 
           [0037]      FIG. 12B  is a detail cross-sectional view of the stem of the buoyant float and the float-pusher spring of the intermediary diaphragm showing that the stem is in contact with the float-pusher spring but that the float-pusher spring is not deformed and is not storing energy; and 
           [0038]      FIG. 12C  is a diagrammatic force balance of the buoyant float corresponding to the buoyant float when the valve is opening showing the buoyant float lifted up by the force of the bias spring and by the force of buoyancy applied when the buoyant float is supported by remaining fuel in the fuel tank and pushed down by the force of gravity. 
       
    
    
     DETAILED DESCRIPTION 
       [0039]    A fuel storage system  10  includes a fuel tank  12 , a fuel vapor recovery canister  16 , and a fuel tank vent apparatus  20  as shown, for example, in  FIG. 1 . Fuel vapor recovery canister  16  is located outside fuel tank  12 . Fuel tank vent apparatus  20  is configured to vent pressurized fuel vapor from fuel tank  12  to fuel vapor recovery canister  16  when pressure in fuel tank  12  is greater than atmospheric pressure outside fuel tank  12  and liquid fuel levels are low enough to avoid sloshing of fuel out of fuel tank  12  as suggested by arrows  20 V in  FIGS. 4A and 4D . 
         [0040]    Fuel tank vent apparatus  20  includes a housing  28 , a valve  30 , and a bias spring  58  as shown in  FIG. 6 . Housing  28  is adapted to be mounted in top wall  22  of fuel tank  12  as shown in  FIG. 1 . Valve  30  is movable within an internal space  32  formed by housing  28  from an open position, shown in  FIGS. 4A and 8A , to a closed position shown in  FIGS. 4B and 9A . Valve  30  is configured to assume the open position when the liquid fuel level in fuel tank  12  is low allowing fuel vapor to escape fuel tank  12  as shown in  FIGS. 4A and 9A . Valve  30  is configured to assume the closed position when the liquid fuel level in fuel tank  12  is high blocking liquid fuel and fuel vapor from escaping fuel tank  12 , as shown in  FIGS. 4B and 10A . 
         [0041]    Valve  30  includes a buoyant float  56  and an intermediary diaphragm  60  as shown illustratively in  FIGS. 5-7 . Buoyant float  56  is buoyant and causes valve  30  to be raised (closed) and lowered (opened) depending on the fuel level in fuel tank  12 . Intermediary diaphragm  60  is arranged between buoyant float  56  and vent ports  48 C,  48 O formed in housing  28 . Intermediary diaphragm  60  cooperates with buoyant float  56  to block fuel vapor from escaping housing  28  through vent ports  48 C,  48 O when valve  30  is closed. 
         [0042]    Intermediary diaphragm  60  is illustratively formed to include an emission port  71  and a float-pusher spring  70  as shown in  FIG. 3 . Emission port  71  is closed by buoyant float  56  when buoyant float  56  is lifted by high levels liquid fuel in fuel tank  12  as shown in  FIG. 2 . Float-pusher spring  70  of intermediary diaphragm  60  is configured to store energy, as suggested by arrows  70 S in  FIG. 3A , and to apply the stored energy to buoyant float  56  to push buoyant float  56  downwardly away from the emission port, as suggested by arrows  70 R and  56 D in  FIG. 3B , to open emission port  71 . Float-pusher spring  70  thereby opens emission port  71  to allow some fuel vapor to escape housing  28  through emission port  71  and a central vent port  48 C formed in the housing  28  so that valve  30  is able to re-open, releasing pressure in fuel tank  12 . 
         [0043]    Housing  28  of fuel tank vent apparatus  20  includes an upper shell  36  and a lower shell  38  that cooperate to form internal space  32  as shown illustratively in  FIGS. 5 and 6 . Upper shell  36  includes a ceiling  39  (sometimes called a top wall), a flange  41  extending up from ceiling  39  to engage top wall  22  of the fuel tank  12 , and a cylindrical outer side wall  40  extending down from the ceiling  39 . Lower shell  38  includes a floor  42  and a cylindrical inner side wall  44  extending up from floor  42 . Housing  28  also includes an O-ring  45  that extends around flange  41  to provide vapor-sealed mounting of flange  41  to top wall  22  of fuel tank  12 . 
         [0044]    Upper shell  36  and lower shell  38  are formed to include inlet ports  46  providing fluid communication between an interior  49  of fuel tank  12  and internal space  32  of housing  28  as shown, for example, in  FIG. 8A . Inlet ports  46  allow fuel and fuel vapor to enter housing  28  as suggested by arrows  40 E in  FIG. 8 . Upper shell  36  is also formed to include a central vent port  48 C and outer vent ports  48 O located inside a perimeter of flange  41  and extending through the ceiling  39 . Outer vent ports  48 O are spaced outward a radial direction from central vent port  48 C and are arranged around central vent port  48 C. Vent ports  48 C,  48 O provide communication from internal space  32  of housing  28  to an upper receiving chamber  47  defined by flange  41 . Upper receiving chamber  47  is in fluid communication with fuel vapor recovery canister  16  as shown in  FIG. 2 . 
         [0045]    Valve  30  includes buoyant float  56 , intermediary diaphragm  60 , and a diaphragm-support cage  62  as shown, for example, in  FIGS. 5-7 . Buoyant float  56  is configured to be lifted by a buoyant force F B  provided by liquid fuel in the fuel tank  12 . Bias spring  58  contacts buoyant float  56  and housing  28  to provide a spring force F S1  that pushes buoyant float  56  upwardly so that only a minor buoyant force F B  is needed to overcome weight F W  of buoyant float  56  during lifting of buoyant float  56  as suggested in the force diagram of  FIG. 9C . Intermediary diaphragm  60  is arranged between buoyant float  56  and ceiling  39  of housing  28  so that intermediary diaphragm  60  is lifted with buoyant float  56  as the fuel level in fuel tank  12  rises. Diaphragm-support cage  62  is coupled to intermediary diaphragm  60  and is coupled to buoyant float  56 . Diaphragm-support cage  62  and buoyant float  56  cooperate to provide a diaphragm carrier  55  that lifts intermediary diaphragm  60  when liquid fuel levels in fuel tank  12  rise. Diaphragm-support cage  62  allows buoyant float  56  to move downwardly away from intermediary diaphragm  60  when liquid fuel levels in fuel tank  12  fall providing a predetermined amount of lost motion between the buoyant float  56  and intermediary diaphragm  60  during re-opening of valve  30 . 
         [0046]    Buoyant float  56  is illustratively a monolithic component formed from a buoyant body  64  and a stem  66  as shown illustratively in  FIGS. 6 and 7 . Buoyant body  64  is coupled to and surrounds stem  66 . Stem  66  extends up from buoyant body  64  and cooperates with intermediary diaphragm  60  to close vent ports  48 C,  48 O to block venting of fuel tank  12  when valve  30  is in the closed position as shown in  FIG. 9A . 
         [0047]    Intermediary diaphragm  60  is illustratively a monolithic elastic component formed from an anchor  68 , an outer vent port closure  69 , and a float-pusher spring  70  as shown, for example, in  FIGS. 5 and 6 . In the illustrative embodiment, intermediary diaphragm  60  is made from an elastic fluorosilicone material but in other embodiments may be made from another suitable elastic material. Anchor  68  is coupled to diaphragm-support cage  62  when intermediary diaphragm  60  is formed by over molding material onto diaphragm-support cage  62  as suggested in  FIG. 7 . Outer vent port closure  71  extends outwardly in the radial direction from anchor  68 . Float-pusher spring extends inwardly in the radial direction from anchor  68 . 
         [0048]    Anchor  68  illustratively includes an annular interior body  681 , an upper leg  682 , and a lower leg  683  that cooperate to define a radially-outwardly opening channel  684  as shown in  FIG. 3 . Interior body  681  extends downwardly from float pusher spring  70 . Upper leg  682  extends outward in the radial direction from the interior body  681 . Lower leg  683  extends outward in the radial direction from the interior body  681 . Radially-outwardly opening channel  684  receives a top wall  76  of the diaphragm-support cage that surrounds an opening  77  formed in top wall  76  of diaphragm-support cage  62 . 
         [0049]    Outer vent port closure  69  extends from upper leg  682  of anchor  68  as shown in  FIG. 3 . Outer vent port closure  69  includes a frustoconical wall  691  that extends outwardly in the radial direction and upwardly in the axial direction from the anchor  68  and a reinforcement ring  692  that extends downwardly from the wall  691  around the outer circumference of the wall  691 . Outer vent port closure  69  contacts an underside  39 U of ceiling  39  to close outer vent ports  48 O when valve  30  is in the closed position. 
         [0050]    Float-pusher spring  70  extends from upper leg  681  of anchor  68  as shown in  FIG. 3 . Float pusher spring  70  is configured bow upwardly along axis  20 A and to push downward in the axial direction along axis  20 A on the stem  66  of buoyant float  56  when the valve  30  is in the closed position as shown in  FIGS. 9-10 . Float-pusher spring  70  surrounds and defines emission port  71  that is closed by the stem  66  of the buoyant float  56  when valve  30  is in the closed position. 
         [0051]    Float-pusher spring  70  is formed to include a flange  92  and an annular tang  94  coupled to the flange  92  as shown in  FIG. 3 . Flange  92  extends inward in the radial direction from anchor  68  as shown in  FIGS. 9A and 9B . Tang  94  extends inward in the radial direction and downward in the axial direction from flange  92  as shown in  FIG. 3 . Tang  94  extends around and defines emission port  71 . 
         [0052]    Diaphragm-support cage  62  is coupled to the buoyant float  56  for slidable movement relative to buoyant float  56  as shown, for example, in  FIG. 7 . Diaphragm-support cage  62  is a monolithic component formed to include a cylindrical body  72  and a pair of arms  74 ,  75  coupled to cylindrical body  72  as shown in  FIG. 6 . Cylindrical body  72  includes a top wall  76  formed to include a round opening  77  and a side wall  78  extending down from the top wall  76 . 
         [0053]    Anchor  68  of intermediary diaphragm  60  is coupled to top wall  76  of diaphragm-support cage  62  by over molding anchor  68  on to top wall  76  around opening  77  as shown in  FIG. 7 . As a function of the coupling of the top wall  76  and anchor  68 , intermediary diaphragm  70  and seal support cage  68  move together. Side wall  78  is located between buoyant body  64  and stem  66  of buoyant float  56  as shown in  FIGS. 7 and 8A . Pair of arms  74 ,  75  extend radially outwardly from side wall  78  and are received in slots  84 ,  85  formed in buoyant body  64  of buoyant float  56  as shown in  FIG. 7 . 
         [0054]    Valve  30  is moved to the open position as suggested by arrow  30 D in  FIG. 12A  when the fuel level in fuel tank  12  is lowered during vehicle operation as suggested in  FIG. 4A . When valve  30  is in the open position, fuel vapor that enters housing  28  of fuel tank vent apparatus  20  is free to vent out of housing  28  as suggested by arrows  20 V in  FIGS. 4A ,  8 , and  8 A. Valve  30  in the open position is spaced apart from ceiling  39  of housing  28  so that vent ports  48 C,  48 O are opened allowing fuel vapor to escape housing  28  toward fuel vapor recovery canister  16  and atmosphere  17  as shown in  FIGS. 1 and 8A . 
         [0055]    Valve  30  is moved to the closed position as suggested by arrow  30 U when the fuel level in fuel tank  12  is raised during refueling from a pump  90  as suggested in  FIG. 4B . Rising fuel level in fuel tank  12  causes the buoyant force F B  to be applied to the buoyant float  56  raising valve  30  to the closed position as suggested in  FIGS. 9A and 9C . When valve  30  is moved to the closed position, fuel vapor that enters housing  28  of tank vent apparatus  20  is blocked from venting out of housing  28  as suggested in  FIGS. 4B ,  9 , and  9 A. Valve  30  in the closed position contacts ceiling  39  of housing  28  so that vent ports  48 C,  48 O are closed blocking fuel vapor from escaping housing  28  toward fuel vapor recovery canister  16  as shown in  FIG. 9A . 
         [0056]    In the closed position, intermediary diaphragm  60  and buoyant float  56  cooperate to close vent ports  48 C,  48 O off from internal space  32  of housing  28  as shown in  FIG. 4A . Specifically, outer vent port closure  69  of intermediary diaphragm  60  contacts ceiling  39  of housing  28  to close outer vent ports  48 O of housing  28  and stem  66  of buoyant float  56  contacts float-pusher spring  70  to close emission port  71  formed in float-pusher spring  70  and aligned with central vent port  48 C so that fuel vapor and fuel is blocked from escaping fuel tank  12  through fuel tank vent apparatus  20 . Contact of stem  66  with float-pusher spring  70  causes float-pusher spring  70  to be part-way deformed and to apply a second spring force F S2  that resists further upward movement of buoyant float  56  as shown in  FIGS. 9B and 9C . 
         [0057]    To move valve  30  back to the open position, a two-stage re-opening process is initiated by intermediary diaphragm  60  as suggested in  FIGS. 11-12B . The first stage of re-opening is performed by the intermediary diaphragm  60  that pushes buoyant float  56  away from intermediary diaphragm  60  and ceiling  39  of housing  28  as suggested in  FIGS. 3B and 11A . The second stage of re-opening is performed by buoyant float  56  that pulls the intermediary diaphragm  60  away from ceiling  39  of housing  28  as suggested in  FIG. 12A . 
         [0058]    During the first stage of reopening, pressure may build in housing  28  as a result of atmospheric conditions and/or heat applied to the fuel in fuel tank  12  from an exhaust system  15  as suggested in  FIG. 4C . The built up pressure causes float-pusher spring  70  to be fully deformed, as suggested by arrows  70 S in  FIG. 3A , storing energy that is in turn applied to the stem  66  of buoyant float  56  as suggested in  FIG. 10B . The energy stored in float-pusher spring  70  is applied to stem  66  until the weight of the buoyant float F W  and the second spring force F S2  exceeds the first spring force F S1  from bias spring  58  and the force of buoyancy F B  which causes buoyant float  56  to be pushed downwardly as suggested by arrows  70 R and  56 D in  FIG. 3B  and as shown in  FIGS. 11A and 11B . 
         [0059]    During the second stage of reopening, buoyant float  56  is moved downwardly away from intermediary diaphragm  60  and ceiling  39  of the housing  28  as suggested in  FIG. 11A . Top edges  84 T,  85 T of slots  84 ,  85  of buoyant float  56  then contact arms  74 ,  75  of diaphragm-support cage  62  as shown in  FIG. 11A . As buoyant float  56  continues to move downwardly away from the ceiling  39  of housing  28 , diaphragm-support cage  62  and intermediary diaphragm  60  are pulled away from ceiling  39  of housing  28  so that valve  30  returns to the open position in which the central vent port  48 C and the outer vent ports  48 O are open as shown in  FIG. 12A .