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A closure device, such as a fuel cap, for controlling evaporative emissions from a fuel tank. In one aspect, the invention comprises: a housing defining an internal chamber containing a hydrocarbon adsorbing media; a fuel vapor diffuser extending from a floor of the internal chamber and into the int

A closure device, such as a fuel cap, for controlling evaporative emissions from a fuel tank. In one aspect, the invention comprises: a housing defining an internal chamber containing a hydrocarbon adsorbing media; a fuel vapor diffuser extending from a floor of the internal chamber and into the internal chamber, the fuel vapor diffuser comprising: (1) an inlet passageway extending from a fuel vapor inlet port to a plenum in a top portion of the fuel vapor diffuser; and (2) a downcomer passageway extending from the plenum to at least one aperture located at a bottom portion of the fuel vapor diffuser, the at least one aperture forming a passageway between the downcomer passageway and the internal chamber; and at least one outlet passageway extending from the internal chamber to an atmospheric air outlet port.

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1. A closure device for controlling evaporative emissions from a fuel tank comprising: a housing having an axis and defining an internal chamber containing a hydrocarbon adsorbing media;a stem extending from a floor of the internal chamber along the axis, a first portion of the stem residing between

1. A closure device for controlling evaporative emissions from a fuel tank comprising: a housing having an axis and defining an internal chamber containing a hydrocarbon adsorbing media;a stem extending from a floor of the internal chamber along the axis, a first portion of the stem residing between the floor and a roof of the internal chamber, the first portion comprising a majority of an axial length of the stem;a sheath disposed over the first portion of the stem so as to form an annular gap between the sheath and the stem, the sheath having a closed top end that is spaced from a roof of the internal chamber;at least one aperture that forms a passageway between a bottom portion of the annular gap and the internal chamber;the stem comprising an inlet passageway extending from a fuel vapor inlet port to a top portion of the annular gap; andat least one outlet passageway extending from the internal chamber to an atmospheric air outlet port. 2. The closure device according to claim 1 wherein the inlet passageway comprises a control section for preventing liquid fuel from the fuel tank from passing through the inlet passageway and a coupling section in which a first end of a tether is anchored. 3. The closure device according to claim 1 further comprising: the stem terminating in a top surface located at a first axial height from the floor, the inlet passageway extending from the vapor inlet port and terminating in an opening in the top surface of the stem, a plenum located between the top surface of the stem and the closed top end of the sheath that fluidly couples the inlet passageway to the top portion of the annular gap; andthe at least one aperture having a top located at a second axial height from the floor; andwherein the first axial height is greater than the second axial height. 4. The closure device according to claim 3 further comprising: a diffuser plate positioned within the internal chamber that separates the internal chamber into an upper zone and a lower zone, the diffuser plate comprising at least one diffuser hole forming a passageway between the upper and lower zones, the diffuser plate located a third axial height from the floor, the first axial height being greater than the third axial height. 5. The closure device according to claim 1 further comprising: a diffuser plate positioned within the internal chamber that separates the internal chamber into an upper zone and a lower zone, the diffuser plate comprising at least one diffuser hole forming a passageway between the upper and lower zones;a particle filter disposed in the upper zone atop the diffuser plate;the at least one aperture forming a passageway between the bottom portion of the annular gap and the lower zone, the hydrocarbon adsorbing media disposed in the upper zone;the inlet passageway comprising a control section for preventing liquid fuel from the fuel tank from passing through the inlet passageway and a coupling section in which a first end of a tether is anchored; andthe fuel vapor inlet port being located on a bottom surface of the stem, the inlet passageway extending from the vapor inlet port and terminating in an opening on a top surface of the stem. 6. A closure device for controlling evaporative emissions from a fuel tank comprising: a housing defining an internal chamber containing a hydrocarbon adsorbing media;a stem extending from a floor of the internal chamber;a sheath disposed over the stem so as to form an annular gap between the sheath and the stem, the sheath having a closed top end;at least one aperture that forms a passageway between a bottom portion of the annular gap and the internal chamber;the stem comprising an inlet passageway extending from a fuel vapor inlet port to a top portion of the annular gap;at least one outlet passageway extending from the internal chamber to an atmospheric air outlet port; andwherein the inlet passageway comprises a first longitudinal section having a first transverse cross-sectional area, a third longitudinal section having a third transverse cross-sectional area, and a second section disposed between the first and third longitudinal sections and having a second transverse cross-sectional area that is less than the first and third transverse cross-sectional areas. 7. The closure device according to claim 6 further comprising a tether having a first end anchored within the first longitudinal section of the inlet passageway and a liquid entrapment filter disposed in the third longitudinal section. 8. A closure device for controlling evaporative emissions from a fuel tank comprising: a housing defining an internal chamber containing a hydrocarbon adsorbing media;a stem extending from a floor of the internal chamber;a sheath disposed over the stem so as to form an annular gap between the sheath and the stem, the sheath having a closed top end;at least one aperture that forms a passageway between a bottom portion of the annular gap and the internal chamber;the stem comprising an inlet passageway extending from a fuel vapor inlet port to a top portion of the annular gap;at least one outlet passageway extending from the internal chamber to an atmospheric air outlet port;a diffuser plate positioned within the internal chamber that separates the internal chamber into an upper zone and a lower zone, the hydrocarbon adsorbing media disposed within the upper zone;a particle filter disposed in the upper zone atop the diffuser plate;the at least one aperture forming a passageway between the bottom portion of the annular gap and the lower zone; andthe at least one outlet passageway extending from the upper zone to the atmospheric air outlet port. 9. The closure device according to claim 8 wherein the diffuser plate is integral with the sheath and comprises a plurality of diffuser holes forming passageways between the lower zone and the upper zone. 10. A closure device for controlling evaporative emissions from a fuel tank comprising: a housing defining an internal chamber containing a hydrocarbon adsorbing media:a fuel vapor diffuser extending from a floor of the internal chamber and into the internal chamber, the fuel vapor diffuser comprising: (1) an inlet passageway extending from a fuel vapor inlet port to a plenum in a top portion of the fuel vapor diffuser; and (2) a downcomer passageway extending from the plenum to at least one aperture located at a bottom portion of the fuel vapor diffuser, the at least one aperture forming a passageway between the downcomer passageway and the internal chamber;at least one outlet passageway extending from the internal chamber to an atmospheric air outlet port; andwherein the inlet passageway comprises a liquid entrapment filter for preventing liquid fuel from the fuel tank from passing through the inlet passageway;wherein the fuel vapor diffuser comprises: a stem comprising the inlet passageway; andthe plenum formed between a top surface of the stem and a closed top end of a sheath, and the downcomer passageway formed between the sheath and the stem; andwherein the housing comprises an axis, a first portion of the stem residing between a floor of the internal chamber and a roof of the internal chamber, the first portion comprising a majority of an axial length of the stem; the top surface of the stem located at a first axial height from the floor, the inlet passageway extending from the vapor inlet port and terminating in an opening in the top surface of the stem; the at least one aperture having a top located at a second axial height from the floor; and wherein the first axial height is greater than the second axial height. 11. The closure device according to claim 10 further comprising a tether having a first end anchored within the inlet passageway, the first end of the tether being located at a height above a top surface of the floor of the internal chamber. 12. A closure device for controlling evaporative emissions from a fuel tank comprising: a housing defining an internal chamber containing a hydrocarbon adsorbing media;a fuel vapor diffuser extending from a floor of the internal chamber and into the internal chamber, the fuel vapor diffuser comprising: (1) an inlet passageway extending from a fuel vapor inlet port to a plenum in a top portion of the fuel vapor diffuser; and (2) a downcomer passageway extending from the plenum to at least one aperture located at a bottom portion of the fuel vapor diffuser, the at least one aperture forming a passageway between the downcomer passageway and the internal chamber;at least one outlet passageway extending from the internal chamber to an atmospheric air outlet port; anda diffuser plate positioned within the internal chamber that separates the internal chamber into an upper zone and a lower zone;a particle filter disposed in the upper zone atop the diffuser plate; andthe hydrocarbon adsorbing media disposed in the upper zone above the particle filter. 13. The closure device according to claim 12 wherein the at least one aperture forms a passageway between the downcomer passageway and the lower zone. 14. A closure device for controlling evaporative emissions from a fuel tank comprising: a housing having a longitudinal axis and defining an internal chamber;a first diffuser distributing fuel vapor from a fuel vapor inlet port into a lower zone of the internal chamber as a radial flow of the fuel vapor, the first diffuser comprising a first passageway transporting the fuel vapor in a first axial direction and a second passageway receiving the fuel vapor from the first passageway and transporting the fuel vapor in a second axial direction, the second axial direction being substantially opposite the first axial direction;a second diffuser disposed in the internal chamber that separates the internal chamber into the lower zone and an upper zone, the second diffuser distributing the fuel vapor from the lower zone into the upper zone as an axial flow of fuel vapor;at least one outlet passageway extending from the upper zone of the internal chamber to an atmospheric air outlet port, the at least one outlet passageway discharging the fuel vapor into an external atmosphere via the atmospheric air outlet port in a third axial direction, the third axial direction being substantially opposite the first axial direction; andwherein the housing comprises an axis, the first passageway extending from the fuel vapor inlet port to an opening, the opening located at a first axial height above a floor of the internal chamber, the second diffuser located a second axial height from the floor of the internal chamber, the first axial height being greater than the second axial height. 15. The closure device of claim 14 further comprising: a closure plate coupled to the housing to form a roof of the internal chamber, the closure plate comprising a hole forming a passageway for allowing the fuel vapor to exit the internal chamber;a cap portion coupled to the housing and overlying the hole in the closure plate;wherein the at least one outlet passageway is a tortuous pathway extending from the hole in the closure plate to the atmospheric air outlet port. 16. The closure device according to claim 14 wherein the fuel vapor is distributed from the lower zone into the upper zone via an annular gap formed between an edge of the second diffuser and an inner surface of the housing. 17. The closure device according to claim 14 wherein the fuel vapor is distributed from the lower zone into the upper zone via a plurality of diffuser holes in the second diffuser.