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A vent valve for use in controlling discharge of fuel vapor from a fuel tank. The vent valve includes a housing for attachment to the fuel tank includes a wall defining a cavity therein. The float is contained in the cavity of the housing and is responsive to the level of liquid in the fuel tank. Th

A vent valve for use in controlling discharge of fuel vapor from a fuel tank. The vent valve includes a housing for attachment to the fuel tank includes a wall defining a cavity therein. The float is contained in the cavity of the housing and is responsive to the level of liquid in the fuel tank. The level in the fuel tank rises, the float rises within the housing. When the level of liquid in the fuel tank drops, the float moves downwardly in the housing. A passage is provided in the housing which communicates with an external portion of the tank. The vent valve includes at least one vent positioned proximate to and communicating with the passage for providing venting passage of vapor therethrough and to the passage. The vent valve includes a vent assembly having a flexible diaphragm which is displaceably positioned proximate to the passage to control the flow of vapor through the vent and through the passage. The diaphragm is attached to the float making it responsive to the rise and fall of liquid level in the tank. The diaphragm is generally concentrically peeled from a position overlying at least the vent or progressively opening and closing the vent.

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1. A vent valve for use in controlling discharge of fuel vapor from a fuel tank, comprising:a housing for attachment to a fuel tank;a wall of the housing defining a cavity,a float contained in the housing;the float being responsive to a level of liquid in the fuel tank;the housing having a passage t

1. A vent valve for use in controlling discharge of fuel vapor from a fuel tank, comprising:a housing for attachment to a fuel tank;a wall of the housing defining a cavity,a float contained in the housing;the float being responsive to a level of liquid in the fuel tank;the housing having a passage therein communicating with an external portion of the tank;at least one vent positioned proximate to and communicating with the passage;a flexible diaphragm attached to at least the float;the diaphragm being a generally circular diaphragm, generally concentric with the passage in the housing;a generally annular outer edge of the diaphragm being attached to the float;an annular portion of the flexible diaphragm, spaced generally radially inwardly of the outer edge of the diaphragm being displaceably positioned least proximate to the passage to control the flow of vapor through the vent and through the passage;movement of the float toward the passage causing a portion of the flexible diaphragm to contact a surface of the housing at least proximate to the passage and the vent to prevent the flow of fuel vapor through the passage and vent; andmovement of the float away from the passage causing the flexible diaphragm to move out of contract with the surface of the housing permitting passage of fuel vapor through the vent and passage. 2. A vent valve in claim 1, further comprising:an aperture extending through a portion of the diaphragm;the aperture communicating with the vents; anda protrusion carried on the float proximate to the aperture in the diaphragm for abutting and closing the aperture. 3. The vent valve in claim 2, further comprising:a flexible diaphragm having a first side, at least a portion of the first side displaceably abutting a surface of the housing;a second side of the diaphragm generally opposite the first side of the diaphragm, the second side generally facing at least a portion of the float;a bore extending through at least one of the diaphragm and float; andthe bore communicating with the cavity of the housing and with a gap between the second side of the flexible diaphragm and the float. 4. The vent valve in claim 1, further comprising: the diaphragm being formed as a convoluted structure having a generally annular extending portions extending toward the passage;the extending portion being spaced generally radially form the passage for abutting a corresponding surface of the housing proximate the passage; andthe extending portion providing an annular seal proximate to and spaced from the passage. 5. The vent valve in claim 1, further comprising:the at least one vent being formed in the portion of the housing proximate to the passage;the at least one vent formed in the housing communicating with the passage;the at least one vent formed in the housing communicating with the cavity of the housing when the diaphragm is displaced away from the vent;the diaphragm abutting the surface of the housing proximate to the passage and covering at least a portion of the vent when the float is moved toward the passage; andthe diaphragm being progressively displaced away from abutment with the inside surface of the housing in response to displacement of the float away from the passage. 6. The vent valve of claim 5, further comprising:theat least one vent being positioned at least generally radially extending from the perimeter of the passage. 7. The vent valve of claim 5, further comprising:the at least one vent generally tapering along at least one dimension spaced from the passage. 8. The vent valve of claim 1, further comprising:a flexible diaphragm having a first side, a portion of the first side displaceably abutting the surface of the housing;a second side of the diaphragm which generally opposite the first side of the diaphragm, the second side generally facing at least a portion of the float;a bore extending through at least one of the diaphragm and float;the bore communicating with the cavity of the housing and with a gap between the second side of the flexible diaphragm and the float;a protrusion extending from first side of the diaphragm for engagement in the passage; andengagement of the protrusion in the passage restricting flow of fuel vapor through the passage. 9. The vent valve of claim 8, further comprising:at least one vent defined in the portion of the housing proximate to the passage;the vents communicating with the passage;the vents communicating with the cavity of the housing when the diaphragm is at least partially displaced firm the vents; andwherein the protrusion engages the passage when the float is positioned towards the passage, engagement of the protrusion in the passage restricting flow of fuel vapor through the passage, the flexible diaphragm covering an end of the at least one vent when the float is positioned towards the passage, covering of the vents by the diaphragm preventing passage of vapor through the vent to the passage, displacement of the diaphragm from the vent permitting initial venting of fuel vapors through the vent to the passage. 10. The vent valve of claim 9, further comprising:a guide protrusion extending from the second side of the diaphragm;a guide recess defined in the float generally opposite the guide protrusion for receiving the guide protrusion therein; andengagement of the guide protrusion in the guide recess providing guidance and alignment of movement of the diaphragm relative to the passage and housing. 11. The vent valve of claim 1, further comprising:a generally tubular wall defining the passage;the at least one vent being defined in the wall providing communication between the cavity of the housing and the passage;the flexible diaphragm being positioned generally against an outside surface of the wall; andthe flexible diaphragm being displaceably positioned over the vent. 12. The vent valve in claim 11, further comprising:the flexible diaphragm being positioned and retained between the float and an outside surface of the wall;movement of the float on an increasing level of fuel in the tank causing the flexible diaphragm attached to the float and the outside surface of the wall to displaceably cover the vents; andmovement of the float on a decreasing level of fuel in the tank causing the flexible diaphragm to displaceably uncover the vent. 13. The vent valve of claim 11, further comprising:at least one channel provided between a portion of the housing and the float providing a tortuous path through which fuel vapor must travel, the tortuous path providing surfaces to facilitate condensation of liquid carried in the fuel vapor, draining of the condensate into the fuel tank. 14. A vent valve for use in controlling discharge of fuel vapor from a fuel tank, comprising:a housing for attachment to a fuel tank;a wall of the housing defining a cavity;a float contained in the housing;the float being responsive to a level of liquid in the fuel tank;the housing having a passage therein communicating with an external portion of the tank;at least one vent positioned proximate to and communicating with the passage;a flexible diaphragm attached to at least the float;the diaphragm being a generally circular diaphragm, generally concentric with the passage in the housing;a generally annular outer edge of the diaphragm being attached to the float;an annular portion of the flexible diaphragm, spaced generally radially inwardly of the outer edge of the diaphragm being displaceably positioned least proximate to the passage to control the flow of vapor through the vent and through the passage;movement of the float toward the passage causing a portion of the flexible diaphragm to contact a surface of the housing at least proximate to the passage and the vent to prevent the flow of fuel vapor through the passage and vent; a movement of the float away from the passage causing the flexible diaphragm to move out of contact with the surface of the housing permitting passage of fuel vapor through the vent and passage;a generally tubular wall defining the passage;the at least one vent being defined in the wall providing communication between the cavity of the housing and the passage;the flexible diaphragm being positioned generally against an outside surface of the wall;the flexible diaphragm being displaceably positioned over the vent;the flexible diaphragm being positioned and retained between the float and an outside surface of the wallmovement of the float on an increasing level of fuel in the tank causing the flexible diaphragm attached to the float and the outside surface of the wall to displaceably cover the vents;movement of the float on a decreasing level of fuel in the tank causing the flexible diaphragm to displaceably uncover the vent;a second flexible diaphragm retained between the float and the outside surface of the wall; andthe second diaphragm being spaced from the first diaphragm and the vent. 15. A vent valve for use in controlling discharge of fuel vapor from a fuel tack, comprising:a housing for attachment to a fuel tank;a wall of the housing defining a cavity;a float contained in the housing;the float being responsive to a level of liquid in the fuel tank;the housing having a passage therein communicating with an external portion of the tank;at least one vent positioned proximate to and communicating with the passage;a flexible diaphragm attached to at least the float;the diaphragm being a generally circular diaphragm, generally concentric with the passage in the housing;a generally annular outer edge of the diaphragm being attached to the float;an annular portion of the flexible diaphragm, spaced generally radially inwardly of the outer edge of the diaphragm being displaceably positioned least proximate to the passage to control the flow of vapor through the vent and through the passage;movement of the float toward the passage causing a portion of the flexible diaphragm to contact a surface of the housing at least proximate to the passage and the vent to prevent the flow of fuel vapor through the passage and vent; a movement of the float away from the passage causing the flexible diaphragm to move out of contact with the surface of the housing permitting passage of fuel vapor through the vent and passage;a generally tubular wall defining the passage;the at least one vent being defined in the wall providing communication between the cavity of the housing and the passage;the flexible diaphragm being positioned generally against an outside surface of the wall;the flexible diaphragm being displaceably positioned over the vent;the flexible diaphragm being positioned and retained between the float and an outside surface of the wallmovement of the float on an increasing level of fuel in the tank causing the flexible diaphragm attached to the float and the outside surface of the wall to displaceably cover the vents;movement of the float on a decreasing level of fuel in the tank causing the flexible diaphragm to displaceably uncover the vent; anda second diaphragm positioned between and attached to an outside surface of the float and a corresponding inside surface of the housing. 16. A vent valve for use in controlling discharge of fuel vapor from a fuel tank, comprising:a housing for attachment to a fuel tank;a wall of the housing defining a cavity;a float contained in the housing;the float being responsive to a level of liquid in the fuel tank;the housing having a passage therein communicating with an external portion of the tank;at least one vent positioned proximate to and communicating with the passage;a flexible diaphragm attached to at least the float;the diaphragm being a generally circular diaphragm, generally concentric with the passage in the housing;a generally annular outer edge of the diaphragm being attached to the float;an annular portion of the flexible diaphragm spaced generally radially inwardly of the outer edge of the diaphragm being displaceably positioned least proximate to the passage to control the flow of vapor through the vent and through the passage;movement of the float toward the passage causing a portion of the flexible diaphragm to contact a surface of the housing at least proximate to the passage and the vent to prevent the flow of fuel vapor through the passage and vent; a movement of the float away from the passage causing the flexible diaphragm to move out of contact with the surface of the housing permitting passage of fuel vapor through the vent and passage;a generally tubular wall defining the passage;the at least one vent being defined in the wail providing communcation between the cavity of the housing and the passage;the flexible diaphragm being positioned generally against an outside surface of the wall;the flexible diaphragm being displaceably positioned over the vent;the flexible diaphragm being positioned and retained between the float and an outside surface of the wallmovement of the float on an increasing level of fuel in the tank causing the flexible diaphragm attached to the float and the outside surface of the wall to displaceably cover the vents;movement of the float on a decreasing level of fuel in the tank causing the flexible diaphragm to displaceably uncover the vent;the flexible diaphragm being retained on an upper portion of the float and attaching to an outside surface of the wall defining the passage; and a rim attached to the float proximate to the diaphragm the rim being spaced from the outside surface of the wall with the diaphragm extending between the rim and the wall, the rim facilitating controlled movement and retention of the convoluted shape of the diaphragm as it travels relative to the at least one vent. 17. A vent valve for use in controlling passage of fuel vapor in a fuel tank, comprising:a housing for attachment to a fuel tank;a wall of the housing defining a cavity;a float contained in the housing;the float being responsive to a level of liquid in the fuel tank;the housing having a passage therein communicating with an internal portion of the tank for returning fuel vapor and liquid fuel to the tank;a portion of the housing having at least one vent therein, the vent being positioned proximate to and communicating with the passage;a flexible diaphragm attached to at least the float;the diaphragm being a generally circular diaphragm, generally concentric with the passage in the housing;a generally annular outer edge of the diaphragm being attached to the float;an annular portion of the flexible diaphragm, spaced generally radially inwardly of the outer edge of the diaphragm being displaceably positioned least proximate to the passage to control the flow of vapor through the vent and through the passage;movement of the float on a rising liquid level causing a portion of the flexible diaphragm to contact a sealing surface at least proximate to the vent to prevent the flow of fuel vapor through the vent; andmovement of the float on a lowering liquid level causing the flexible diaphragm to move out of contract with the surface permitting passage of fuel vapor through the vent. 18. The vent valve of claim 17, further comprising:a generally tubular wall defining the passage;the at least one vent being defined in the wall providing communication between the cavity of the housing and the passage;the flexible diaphragm being positioned generally against an outside surface of the wall; andthe flexible diaphragm being displaceably positioned over the vent. 19. A vent valve for use in controlling discharge of fuel vapor from a fuel tank, comprising:a housing for attachment to a fuel tank;a wall of the housing defining a cavity;a float contained in the housing;the float being responsive to a level of liquid in the fuel tank;the housing having a passage therein communicating with an external portion of the tank;a vent assembly having a primary sealing structure and a secondary sealing structure;the vent assembly having at least one vent therein, the vent being positioned proximate to and c ommunicating with the passage;the primary sealing structure providing at least partial sealing of the passage;the secondary sealing structure providing additional sealing of the passage to prevent flow of vapors therethrough;the secondary sealing structure being attached to at least the float;the secondary sealing structure being a generally circular diaphragm, generally concentric with the passage in the housing;a generally annular outer edge of the diaphragm being attached to the float;an annular portion of the flexible diaphragm, spaced generally radially inwardly of the outer edge of the diaphragm being displaceably positioned least proximate to the passage to control the flow of vapor through the vent and through the passage;movement of the float toward the passage causing a portion of the flexible diaphragm to contact a surface of the housing at least proximate to the passage and the vent to prevent the flow of fuel vapor through the passage and vent; andmovement of the float away from the passage causing the flexible diaphragm to move out of contract with the surface of the housing permitting passage of fuel vapor through the vent and passage. 20. A tank vent apparatus comprisinga valve housing formed to include an inlet port an outlet port, and an interior region arranged to receive fuel vapor admitted into the valve housing through the inlet port and to communicate fuel vapor to the outlet port for discharge from the valve housing,a partition located in the valve housing to divide the interior region into an upstream passageway arranged to receive liquid fuel and fuel vapor admitted into the interior region through the inlet port and a discharge chamber arranged to discharge fuel vapor from the interior region through the outlet port, the partition including an upright interior wall providing a valve seat located in the upstream passageway and formed to include at least one vent port configured to communicate fuel vapor from the upstream passageway into the discharge chamber, anda vent port valve formed to include a central aperture receiving the upright interior wall therein and mounted for movement in the upstream passageway relative to the upright interior wall in an axially upward direction to a closed position engaging the valve seat and closing the at least one vent port and in an axially downward direction to an opened position disengaging at least a portion of the valve seat and opening the vent port to allow fuel vapor to flow in a radial direction through the vent port from the upstream passageway into the discharge chamber to be discharged from the interior region through the outlet port. 21. The apparatus of claim 20, wherein the vent port valve includes a float positioned to lie in the upstream passageway and a seal coupled to the float to move therewith in the upstream passageway relative to the valve seat to close the at least one vent port upon movement of the vent port valve to the closed position and to open the at least one vent port upon movement of the vent port valve to the opened position. 22. A tank vent apparatus comprisinga valve housing formed to include an inlet port, an outlet port, and an interior region arranged to receive fuel vapor admitted into the valve housing through the inlet port and to communicate fuel vapor to the outlet port for discharge from the valve housing,a partition located in the valve housing to divide the interior region into an upstream passageway arranged to receive liquid fuel and fuel vapor admitted into the interior region through the inlet port and a discharge chamber arranged to discharge fuel vapor from the interior region through the outlet port, the partition including an upright interior wall providing a valve seat located in the upstream passageway and formed to include at least one vent port configured to communicate fuel vapor from the upstream passageway into the discharge chamber, anda vent port valve mounted for movement in the upstream passageway in an axially upward direction to a closed position engaging the valve seat and closing the at least one vent port and in an axially downward direction to an opened position disengaging at least a portion of the valve seat and opening the vent port to allow fuel vapor to flow in a radial direction through the vent port from the upstream passageway into the discharge chamber to be discharged from the interior region through the outlet port wherein the vent port valve includes a float positioned to lie in the upstream passageway and a seal coupled to the float to move therewith in the upstream passageway relative to the valve seat to close the at least one vent port upon movement of the vent port valve to the closed position and to open the at least one vent port upon movement of the vent port valve to the opened position, the upright interior wall is cylinder-shaped and formed to include the discharge chamber therein, and the seal includes a base coupled to the float, a lip coupled to the upright interior wall, and a pliable annular membrane arranged to interconnect the base and the lip and configured to surround the upright interior wall and to roil back and forth relative to the valve seat and the at least one vent port formed therein as the float is raised and lowered in a rising and falling pool of liquid fuel extant in the upstream passageway to close the at least one vent port upon movement of the vent port valve to the closed position and to open the at least one vent port upon movement of the vent port valve to the opened position. 23. The apparatus of claim 22, further comprising an interior sleeve located in the interior region of the valve housing to surround the upright interior wall and to divide the upstream passageway into an intake chamber arranged to receive liquid fuel and fuel vapor admitted into the interior region through the inlet port and a float chamber containing the float and the seal therein, and wherein the interior sleeve is formed to include at least one lower fuel port configured to provide means for conducting liquid fuel from the intake chamber into a lower region of the float chamber whenever liquid fuel is admitted into the interior region of the valve housing through the inlet port to provide the rising and falling pool of liquid fuel for raising and lowering the float in the float chamber, and the interior sleeve is also formed to include at least one upper vapor port configured to provide means for conducting pressurized fuel vapor from the intake chamber into an upper region of the float chamber whenever pressurized fuel vapor is admitted into the interior region of the valve housing through the inlet port so that such pressurized fuel vapor passes through the at least one vent port into the discharge chamber whenever the vent port valve is moved in the float chamber to assume the opened position. 24. The vent apparatus of claim 22, wherein the valve housing includes a top wall adapted to be mounted to a top wall of a fuel tank, a bottom wall positioned to lie below and in spaced-apart relation to the top wall, and an outer side wall arranged to extend from the top wall to the bottom wall to define the interior region therebetween, the outer side wall is formed to include the inlet port and the bottom wall is formed to include the outlet port. 25. The apparatus of claim 22, wherein the valve housing includes a top wall adapted to be mounted to a top wall of a fuel tank, a bottom wall positioned to lie below and in spaced-apart relation to the top wall, and an outer side wall arranged to extend from the top wall to the bottom wall to define the interior region therebetween, the bottom wall is formed to include the outlet port, the upright interior wall is coupled to the bottom wall and arranged to extend upwardly toward the top wall, the float is ring-shaped and arranged to surround a lower portion of the upright interior wall and lie adjacent to the bottom wall, and the pliable annul membran e is arranged to surround an upper portion of the upright interior wall that is located between the lower portion of the upright interior wall and the top wall of the valve housing and is formed to include the at least one vent port. 26. A tank vent apparatus comprisinga valve housing formed to include an inlet port, an outlet port, and an interior region arranged to receive fuel vapor admitted into the valve housing through the inlet port and to communicate fuel vapor to the outlet port for discharge from the valve housing,a partition located in the valve housing to divide the interior region into an upstream passageway arranged to receive liquid fuel and fuel vapor admitted into the interior region through the inlet port and a discharge chamber arranged to discharge fuel vapor from the interior region through the outlet port, the partition including an upright interior wall providing a valve seat located in the upstream passageway and formed to include at least one vent port configured to communicate fuel vapor from the upstream passageway into the discharge chamber, anda vent port valve mounted for movement in the upstream passageway in an axially upward direction to a closed position engaging the valve seat and closing the at least one vent port and in an axially downward direction to an opened position disengaging at least a portion of the valve seat and opening the vent port to allow fuel vapor to flow in a radial direction through the vent port from the upstream passageway into the discharge chamber to be discharged from the interior region through the outlet port, wherein the vent port valve includes a float positioned to lie in the upstream passageway and a seal coupled to the float to move therewith in the upstream passageway relative to the valve seat to close the at least one vent port upon movement of the vent port valve to the closed position and to open the at least one vent port upon movement of the vent port valve to the opened position, the upright interior wall is cylinder-shaped to define the discharge chamber therein, and the float is ring-shaped and formed to include a central aperture receiving the upright interior wall therein to allow movement of the float relative to the upright interior wall. 27. The apparatus of claim 26, wherein the upright interior wall is formed to include the outlet port at a lower end thereof conduct fuel vapor from the at least one vent port to the outlet port through the discharge chamber defined by the upright interior wall. 28. The apparatus of claim 26, wherein the valve housing includes a top wall adapted to be mounted to a top wall of a fuel tank, a bottom wall positioned to lie below and in spaced-apart relation to the top wall, and an outer side wall arranged to extend from the top wall to the bottom wall to define the interior region therebetween, the outer side wall is formed to include the inlet port, and the bottom wall is formed to include the outlet port and to place the outlet port in communication with the discharge chamber defined by the upright interior wall to cause fuel vapor passing from the upstream passageway into the discharge chamber through the at least one vent port when the vent port valve is moved to assume the opened position to be discharged from the interior region of the valve housing through the outlet port formed in the bottom wall. 29. A tank vent apparatus comprisinga valve housing formed to include an inlet port, an outlet port, and an interior region arranged to receive fuel vapor admitted into the valve housing through the inlet port and to communicate fuel vapor to the outlet port for discharge from the valve housing,a partition located in the valve housing to divide the interior region into an upstream passageway arranged to receive liquid fuel and fuel vapor admitted into the interior region through the inlet port and a discharge chamber arranged to discharge fuel vapor from the interior region through the outlet port, the partition i ncluding an upright interior wall providing a valve seat located in the upstream passageway and formed to include at least one vent port configured to communicate fuel vapor from the upstream passageway into the discharge chambera vent port valve mounted for movement in the upstream passageway in an axially upward direction to a closed position engaging the valve seat and closing the at least one vent port and in an axially downward direction to an opened position disengaging at least a portion of the valve seat and opening the vent port to allow fuel vapor to flow in a radial direction through the vent port from the upstream passageway into the discharge chamber to be discharged from the interior region through the outlet port, wherein the vent port valve includes a float positioned to lie in the upstream passageway and a seal coupled to the float to move therewith in the upstream passageway relative to the valve seat to close the at least one vent port upon movement of the vent port valve to the closed position and to open the at least one vent port upon movement of the vent port valve to the opened position, andan interior sleeve located in the interior region of the valve housing to surround the upright interior wall and to divide the upstream passageway into an intake chamber arranged to receive liquid fuel and fuel vapor admitted into the interior region through the inlet port and a float chamber containing the float and the seal therein, wherein the interior sleeve is formed to include at least one lower fuel port configured to provide means for conducting liquid fuel from the intake chamber into a lower region of the float chamber whenever liquid fuel is admitted into the interior region of the valve housing through the inlet port to provide the rising and falling pool of liquid fuel for raising and lowering the float in the float chamber, and wherein the interior sleeve is also formed to include at least one upper vapor port configured to provide means for conducting pressurized fuel vapor from the intake chamber into an upper region of the float chamber whenever pressurized fuel vapor is admitted into the interior region of the valve housing through the inlet port so that such pressurized fuel vapor passes through the at least one vent port into the discharge chamber whenever the vent port valve is moved in the float chamber to assume the opened position. 30. The apparatus of claim 29, wherein the valve housing includes a top wall arranged to intersect the central vertical axis of the valve housing and adapted to be mounted to a top wall of a fuel tank, a bottom wall arranged to intersect the central vertical axis of the valve housing and positioned to lie below and in spaced-apart relation to the top wall, and an outer side wall arranged to extend from the top wall to the bottom wall to define the interior region therebetween, the outer side wall is formed to include the inlet port, and the bottom wall is formed to include the outlet ports. 31. A tank vent apparats comprisinga valve housing formed to include an inlet port, an outlet port, and an interior region arranged to receive fuel vapor admitted into the valve housing through the inlet port and to communicate fuel vapor to the out let port for discharge from the valve housing,a partition located in the valve housing to divide the interior region into an upstream passageway arranged to receive liquid fuel and fuel vapor admitted into the interior region through the inlet port and a discharge chamber arranged to discharge fuel vapor from the interior region through the outlet port, the partition including an upright interior wall providing a valve seat located in the upstream passageway and formed to include at least one vent port configured to communicate fuel vapor from the upstream passageway into the discharge chamber, anda vent port valve mounted for movement in the upstream passageway in an axially upward direction to a closed position engaging the valve se at and closing the at least one vent port and in an axially downward direction to an opened position disengaging at least a portion of the valve seat and opening the vent port to allow fuel vapor to flow in a radial direction through the vent port from the upstream passageway into the discharge chamber to be discharged from the interior region through the outlet port, wherein the valve housing has a central vertical axis, the upright interior wall is cylinder-shaped and has a central vertical axis that is coextensive with the central vertical axis of the valve housing, and the upright interior wall is formed to include the discharge chamber therein. 32. The apparatus of claim 31, wherein the valve housing includes a top wall arranged to intersect the central vertical axis of the valve housing and adapted to be mounted to a top wall of a fuel tank, a bottom wall positioned to lie below and in spaced-apart relation to the top wall, an outer side wall arranged to extend from the top wall to the bottom wall to define the interior region therebetween, and the bottom wall is formed to include the outlet port at a lower end of the upright interior wall to cause fuel vapor in the discharge chamber to flow out of the interior region of the valve housing through the outlet port. 33. A tank vent apparatus comprisinga valve housing including a top wall adapted to be mounted to a top wall of a fuel tank, a bottom wall positioned to lie in spaced-apart relation to the top wall, and an outer side wall arranged to cooperate with the top and bottom walls to define an interior region, the outer side wall being formed to include an inlet port to communicate liquid fuel and fuel vapor into the interior region, the bottom wall being formed to include an outlet port to discharge fuel vapor from the interior region to a destination outside of the valve housing, the valve housing further including a partition arranged in the interior region to extend from the bottom wall to the top wall and formed to include a vent port configured to communicate fuel vapor admitted into the interior region through the inlet port to the outlet port, andflow-control means located in the interior region of the valve housing for closing the vent port formed in the partition to block flow of liquid fuel admitted into the interior region through the inlet port from the interior region through the outlet port and opening the vent port formed in the partition to allow flow of pressurized fuel vapor admitted into the interior region to flow from the interior region through the outlet port until liquid fuel extant in the interior region rises above the bottom wall to a level in excess of a predetermined level. 34. A tank vent apparatus comprisinga valve housing including a top wall adapted to be mounted to a top wall of a fuel tank, a bottom wall positioned to lie in spaced-apart relation to the top wall, and an outer side wall arranged to cooperate with the top and bottom walls to define an interior region, the outer side wall being formed to include an inlet port to communicate liquid fuel and fuel vapor into the interior region, the bottom wall being formed to include an outlet port to discharge fuel vapor from the interior region to a destination outside of the valve housing, andflow-control means located in the interior region of the valve housing for blocking flow of liquid fuel admitted into the interior region through the inlet port from the interior region through the outlet port and allowing flow of pressurized fuel vapor admitted into the interior region to flow from the interior region through the outlet port until liquid fuel extant in the interior region rises above the bottom wall to a level in excess of a predetermined level, wherein the flow control means includes a cylinder-shaped interior wall coupled to the bottom wall at the outlet port and formed to define a discharge chamber to conduct fuel vapor to the outlet port and at least one vent port configured t o admit pressurized fuel vapor into the discharge chamber, an annular float formed to include a central aperture receiving the cylinder-shaped interior wall therein and positioned to lie in the interior region of the valve housing for movement along the cylinder shaped shaped interior wall and between the top and bottom walls of the valve housing, and a seal including a base coupled to the float, a lip coupled to the cylinder-shaped interior wall at a location between the at least one vent port and the bottom wall, and a pliable annular membrane arranged to interconnect the base and the lip and configured to surround a portion of the cylinder shaped shaped interior wall and to roll back and forth relative to the portion of the cylinder-shaped interior wall and the at least one vent port formed therein as the float is raised and lowered in a rising and falling pool of liquid fuel extant in the interior region outside of the discharge chamber to close the at least one vent port.