Claims:We claim:

1. A method of controlling venting of fuel vapor in a small engine fuel tank for a portable appliance comprising:
disposing a filler tube through a wall of the tank and extending one end of the tube to a desired level of fuel fill in the tank, wherein the filler tube is configured to provide visual notice that the fuel in the tank has reached the desired level of fuel fill;
disposing a float operated vent valve in the tank, wherein the vent valve vents vapor and closes in response to a rising fuel level, and wherein a vapor outlet of the vent valve is connected to at least one of a storage canister and an engine air inlet; and,
disposing a check valve in the vapor outlet of said vent valve to block flow therethrough at vapor pressures less than a predetermined minimum level above atmosphere pressure.
2. The method as claimed in claim 1, wherein the method comprises permitting reverse flow through the check valve upon occurrence of sub-atmospheric pressure in the tank.
3. The method as claimed in claim 1, wherein said step of disposing a check valve includes forming a bleed passage bypassing the check valve for limited bleed flow when the check valve is closed.
4. A system for maintaining a vapor dome in a small engine fuel tank for a portable appliance and connected to a vapor storage device comprising:

(a) a filler tube with one end extending to a predetermined level in the tank and configured to provide visual notice that a fuel level in the tank has reached the predetermined level, wherein the filler tube is closable by a user operable closure on an end of the filler tube communicating exteriorly of the tank;

(b) a conduit defining a vapor vent path from the tank to the vapor storage device;

(c) a pressure responsive valve disposed in the vapor vent path and operable to substantially prevent vapor flow when vapor pressure in the tank remains below a predetermined threshold and to substantially permit vapor flow to the vapor storage device when the vapor pressure in the tank reaches the threshold, wherein upon removal of said closure and refueling through said tube, fuel reaching the predetermined level causes fuel to reach different levels in the filler tube and in the tank to provide visual notice of the fill level and preserve a vapor dome in the tank.
5. The system as claimed in claim 4, wherein the pressure responsive valve
comprises:

a valve member that is moveable to close against a valve vent seat to prevent vapor flow, and

a bleed passage bypassing the valve member for permitting limited bleed flow.
6. The system as claimed in claim 4, wherein the valve member has a spherical configuration.
7. The system as claimed in claim 4, wherein the pressure responsive valve comprises a pressure relief valve.
8. The system as claimed in claim 4, wherein the pressure relief valve comprises a reverse flow vacuum relief valve.
9. The system as claimed in claim 7, comprising a float operated valve operable to block the vent path when the fuel level in the tank reaches a fuel level.
10. A method of controlling fuel vapor emission in a small engine fuel system for a portable appliance comprising:
(a) disposing a filler tube on the tank with an operable closure on one end and locating the end opposite said one end at a predetermined fill level in the tank such that, upon reaching said predetermined fuel level, the fuel in the filler tube rises at a different level than the fuel in the tank, thereby forming a vapor dome in the tank, wherein the filler tube is configured to provide visual notice that the fuel in the tank has reached the predetermined fill level;

(b) forrning a vapor vent flow path from the interior of the tank to the exterior thereof; and
(c) disposing a normally closed pressure responsive valve in said vent path and opening the valve when the vapor pressure in the tank reaches a predetermined level.
11. The method as claimed in claim 9, wherein the step of forming a vapor vent flow path comprises disposing a float operated valve in the flow path fluidically in series with the pressure responsive valve.
12. The method as claimed in claim 9, wherein the step of disposing a pressure responsive valve comprises disposing a vacuum responsive reverse flow valve.
13. The method as claimed in claim 9, wherein the step of forming a vapor vent flow path comprises attaching a vent valve over an access opening in the tank.
14. The method as claimed in claim 9, comprising connecting said vent path to one of a storage device and an engine air inlet.
, Description:TITLE OF INVENTION
[0001] Controlling Vapor Emission In A Small Engine Fuel Tank System.

BACKGROUND OF THE INVENTION
[0002] The present invention relates to fuel tank systems for small engines of
the type employed for portable appliances such as portable power generating
sets, garden tractors, lawn mowers and other such devices where the fuel tank is
either mounted on the engine or closely adjacent thereto. Fuel tanks of this type
are typically refueled by removing the filler cap and pouring fuel from a container
having a pouring spout, or by pouring from a container and using a funnel.
[0003] Small engine fuel systems have recently been subjected to mandated
requirements for fuel vapor emission control and it has been required to prevent
vapor emission from the tank during operation and when the engine is not
operating.

[0004] Heretofore small engine fuel systems have often employed a tank
having an open vent in the filler cap for providing make-up air in the tank as fuel
was withdrawn but which permitted escape of fuel vapor to the atmosphere.
[0005] In order to meet the requirement that a fuel tank for a small engine not
emit fuel vapor, the filler cap must be sealed to prevent fuel vapor emission. If
the filler cap is sealed then other provisions must be made for admitting make up
air to the tank during engine operation. Furthermore, provisions must be made
for overpressure relief. Thus, it has been desired to find a way or means of
sealing a small engine fuel tank, yet provide for make-up air and over pressure
relief and to do so in a cost-effective manner without requiring redesign or
retooling of the tanks.

[0006]

EP 0790144 teaches a refueling valve for a motor vehicle includes an integrated
control valve therein having a vent tube that has a first valve seat on one end thereof
and a second valve seat on the other end thereof that cooperate respectively with a
float valve and with a diaphragm controlled pressure responsive cut-off valve that is
operative in accordance with a sensed pressure condition in a fuel filler pipe to
control fuel venting to a charcoal canister and to prevent the escape of fuel vapors
from a filler neck. The diaphragm is communicated with a pressure sensing port in
the filler neck below a trap door therein that opens during refueling and is closed
once the fuel nozzle is removed. The pressure sensing port is located upstream of a
venturi that produces negative pressure at the pressure sensing port and on the
diaphragm. A spring biases the cut-off valve normally closed. The diaphragm
member is responsive to a reduced pressure condition in the filler neck to open the
cut-off valve to allow vapors to be vented •from the fuel tank to the charcoal canister
during refueling

US 5,66,989 discloses a fuel vapor control system comprising a fuel tank, a vapor
vent valve arranged to vent excess fuel vapor from the tank to a vent outlet and to
close the vent outlet when the fuel level reaches a predetermined level in the tank, a
filler neck joined to the side wall of the tank at a level below the upper wall of the
tank, and a normally closed valve disposed to block vapor flow in said vent outlet
and operable to open at a predetermined positive vapor pressure in the tank. As is
described in column 8, lines 40-48, of document D2, upon refueling the liquid fuel
reaches the inner end of the filler neck and then rises up the filler neck to provide an
indication to either the operator or an automatic shutoff of the fuel dispensing nozzle
to shut off the input of fuel into the filler neck, while creating an expansion volume in
the upper portion of the fuel tank.

BRIEF SUMMARY OF THE INVENTION
The present invention provides a fuel vapor emission control valve in the tank which
controls the flow of fuel vapor through a passage extending exteriorly of the tank and
also includes a rollover or upset valve preventing liquid fuel from escaping the tank. The vapor vent valve includes a head valve which
retains the vapor in the tank until a predetermined positive pressure is reached;
and, the vent valve also includes a reverse flow check valve permitting make-up
air to enter the tank as fuel is withdrawn or upon a sub-atmospheric pressure
occurring in the tank such as, for example, by cooling of the tank. The fuel vapor
vent passage may be connected externally to either a vapor storage device or the
air inlet of the engine. The invention includes fitting an existing fuel tank with a
filler tube extending to a predetermined level or depth in the tank to cause the fuel
to rise rapidly in the filler tube upon reaching the lower end of the tube during
refueling to signal the operator that tank has reached the desired fill level. This
arrangement prevents overfilling and preserves a vapor dome in the tank above
the liquid level of the fuel to ensure proper functioning of the vapor vent valve.

BRIEF DESCRIPTION OF THE DRAWINGS
[0008J FIG. 1 is a pictorial schematic showing a small engine fuel tank in
cross-section with the filler tube and vapor vent valve of the present invention
installed thereon; and, the connections to either a vapor storage device or
alternatively the engine air inlet are shown in dashed line;
[0009J FIG. 2 is an enlarged detail of the vapor vent valve of FIG. 1;
[0010J FIG. 3 is an enlarged view of a portion of FIG. 2 with the vapor vent
valve closed;
[0011] FIG. 4 is a view similar to FIG. 3 showing the vapor vent valve opened;
and,
[0012J FIG. 5 is a view similar to FIG. 3 with the reverse flow valve shown
open in response to a vacuum in the tank.

DETAILED DESCRIPTION OF THE INVENTION
[0013J Referring to FIGS. 1 and 2, the small engine fuel tank assembly of the
present invention is indicated generally at 10 and includes an existing tank wall
structure 12 with a new filler tube 14 having a vapor tight removable closure 16
received on the exterior end of the tube with the lower end of the tube 14
extending into the tank to a desired depth or level indicated by the reference

character d.
[0014] A separate access opening 18 is formed in the upper portion of the tank
wall and through which is inserted a combination rollover and vapor vent valve
indicated generally at 20 which has a lower housing portion 22 extending into the
tank and an upper housing portion 24 with an outwardly extending flange 26
thereabout attached to the tank wall and sealed thereabout by any suitable
expedient as, for example, weldment.
[0015] The lower valve housing 22 has a float 28 disposed therein with a
flexible valve member 30 disposed on the upper end of the float which closes in
the event that fuel rises above the level d due to sloshing, overfilling or the tank
becoming severely tipped or inverted, under which conditions valve member 30
seats upon a valve seat 32 formed in the upper housing 24.
[0016] The valve seat 32 is formed on the lower end of a vent passage 34
which communicates with an enlarged diameter upper portion 36 which
communicates with vent passage 38 which extends outwardly through attachment
fitting 40 which may be formed as part of the upper housing 24.
[0017] The enlarged diameter portion 36 of the vent passage has slidably
received therein a valve member 42 which has a passage 44 therethrough and
which has the lower surface 46 thereof configured to seat upon surface 48 formed
in the upper body at the upper end of passage 34. When the valve member 42 is
in the lower position shown in FIG. 3 and FIG. 5, flow through passage 34 must
transit through passage 44, not the enlarged diameter passage 36.
[0018] Valve member 42 has formed therein a valving chamber 50 with a
valve seat 52 formed in an inverted position therein on the lower end of the flow
passage 54 which communicates with vent passage 38. Chamber 50 has
received therein a check valve member 56 which may be in the form of a
relatively light weight ball which may be formed of plastic and which seats on
valve set 52 and closes passage 54 when a positive pressure exists in the fuel
tank.
[0019] With reference to FIGS. 3, 4 and 5, it will be seen that the enlarged
diameter 36, in which valve member 42 slides, has slots or passages 60 formed
therein to permit passage of vapors for communication with passage 38 when the
valve member 42 is in the upward position and not seated on the seating surface
48.
[0020] In operation, with the filler cap 16 removed and the tank refueled
through filler tube 14, when the level of the fuel reaches the height d, with
continued filling a fuel level increases rapidly in the tube 14 giving visual notice to
the operator that the tank has reached the desired fill level. After refueling when
the filler cap is replaced, the tank is sealed except for vent passage 38 so long as
the tank is in the upright position or is not substantially tilted so as to cause float
valve 30 to close on valve seat 32.
[0021] If the vapor pressure in the tank is substantially atmospheric or only
slightly above, the valve member 42 is seated on seating surface 48 and only a
small amount of vapor can enter the valving chamber 50 and the flow
therethrough passage 44 causes ball valve 56 to seat against the seating surface
52 as shown in FIG. 3 preventing escape of vapor. As the vapor pressure
increases, valve member 42 is moved upwardly to the position as shown in FIG. 4
permitting passage of vapor through passages 60 into the passage 38; and, as
shown in FIG. 1, to either a storage device 70 or to the engine air inlet 72.
[0022] In the event that the tank is suddenly cooled and the vapor pressure in
the tank drops below atmospheric, creating a vacuum in the tank, ball valve
member 56 drops from its upper seat 52 allowing make-up air to enter the tank. It
will be understood that this condition can also occur as fuel is withdrawn from the
tank.
[0023] The present invention thus provides a simple, relatively low cost and
easy to install technique for modifying an existing small engine fuel tank for
control of fuel vapor emissions to meet current requirements. The invention
combines a filler tube extending in the tank to maintain a vapor dome with a vapor
vent control/rollover valve to prevent fuel vapor from escaping to the atmosphere
upon connection to either a storage device or the engine air inlet.
[0024] Although the invention has hereinabove been described with respect to
the illustrated embodiments, it will be understood that the invention is capable of
modification and variation and is limited only by the following claims.