GB2269375A

GB2269375A - A vent valve for a vehicle fuel tank

Info

Publication number: GB2269375A
Application number: GB9216893A
Authority: GB
Inventors: Ronald Peter Pardy
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1992-08-08
Filing date: 1992-08-08
Publication date: 1994-02-09
Also published as: GB9216893D0

Abstract

A vent valve for a vehicle fuel tank is provided with a fuel-impervious cup 11 sealed around a conventional float valve which is mounted in the upper wall 2 in the vehicle fuel tank. The cup 11 has an inlet weir port 14 and a drain port 13 which is sealed by a non-return valve 12. Fuel may only enter the cup through the inlet port 14 when the fuel within the tank reaches the level of the inlet port. By positioning the port 14 close to the upper wall 2 of the fuel tank more of the potential volume of the fuel tank may be used for fuel storage. Alternative forms of one-way, non-return valves, eg a float valve (20, Figure 3), may be used to seal the drain port 13. The cup 11 may be formed integrally with the upper wall 2 or as part of the grommet 6 which is sealed into the wall 2 to provide a coupling to a vent pipe 7. The float valve is mounted within a cage 10. <IMAGE>

Description

Title: Vent Valve for a Vehicle Fuel Tank Field of the Invention The present invention relates to a vent valve for'a vehicle fuel tank. A vent valve is conventionally located in the upper wall of the fuel tank and operates to seal a vent pipe to prevent fuel entering the vent pipe especially when the tank is being filled with fuel. During normal usage of the vehicle the changes in ambient temperature and barometric pressure causes the vapour in the tank to expand or-contract and this is vented through the vent pipe to maintain the pressure within the tank substantially at atmospheric pressure.

Background to the Invention Float valves are made by a number of manufacturers to differing designs. However, the valves all work on the principle of a float rising with the fuel level and eventually sealing the vent pipe orifice as the fuel approaches the top of the tank in the vicinity of the vent pipe orifice. This may occur particularly during the fuelling operation but it also occurs when the vehicle is on a slope or when fuel slosh takes place when the tank is relatively full.

A fundamental disadvantage of using these valves, as currently designed, is that they reduce the useable volume of the tank from its total potential volume. A typical reduction in useable volume is 3 litres in a potential 42 litre tank.

Manufacturers try to design the valves so that they protrude into the tank as little as possible to utilise more of the potential volume. However the size reduction has to allow for the valve to release from the orifice and not be held up by pressure in the tank. Therefore the float must be sufficiently weighted to release from the orifice when it is not held shut by the level of fuel, and to be of sufficient volume and buoyancy to seal the orifice to prevent fuel loss into the vent pipe.

Summary of the Invention According to the present invention there is provided a vent valve for a vehicle fuel tank comprising a float having a seal thereon adapted for sealing an orifice set in an upper wall of the fuel tank and communicating with a vent pipe, said float being located within a cup having a containing wall formed from fuel impervious material and adapted to be sealed at its upper rim to the upper wall of the tank, said cup having a one-way valve set in a drain port in the wall below the float so that fuel can only drain from the cup into the tank, and wherein said cup has an inlet weir port in the wall of the cup close to the upper wall of the tank.

Preferably, a non-return float valve or duck-bill valve is provided as the one-way valve. The cup may be a separate item or may be formed integrally with the tank or the grommet coupling for the vent pipe which is set in the upper wall of the tank.

Descrintion of the Drawings The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawing in which: Figure 1 shows a float valve and vehicle fuel tank in cross section; Figure 2 shows an enlarged cross section view of the float valve; and Figure 3 shows an alternative form of one-way valve for use in the invention.

Specific Description Figure 1 shows a vehicle fuel tank having an upper wall 2 joined to a lower wall 3 by a seamed side wall 4. A float valve assembly 5 is set in the upper wall 2 to operate a valve held in a grommet 6 which is coupled to a vent pipe 7.

A typical level of the fuel within the tank is shown by the level 8. However when the vehicle is cornering or parked on a slope the level may be inclined as shown by the level 9.

It will be seen that in the inclined state fuel may contact the float valve and, unless precautions are taken, it may enter the vent pipe 7.

The detailed operation of the invention and the components of the float valve assembly will be described now in more detail with reference to Figure 2 which shows the grommet 6 and the coupling to the vent pipe 7 set in the upper wall 2 of the fuel tank. The float valve assembly 5 consists of a conventional float (not shown) mounted within a cage 10 as known from conventional float valve designs. The float is arranged to seal an orifice to prevent fuel entering the vent pipe 7. According to this invention a fuel-impervious cup 11 surrounds the cage 10 and a one-way, non-return valve 12 is mounted on a drain port 13 below the float valve. An inlet port 14 is provided close to or as a depression in the upper rim 15 of the wall of the cup 11.

The operation of the invention will be described now with particular reference to Figure 2. In conventional operation, fuel may be filled to a level 16 when'the float valve closes. However because of the present invention the tank may be further filled closer to the upper wall 2.

Until the fuel reaches a level 17 no fuel will have entered the cup 11. As the fuel rises above the level 17 it enters the cup 11 through the weir inlet port 14. It will be appreciated that the size of the inlet port 14 will determine the rate of rise of the fuel within the cup. As the fuel rises within the cup 11 the float (not shown) within the cage 10 will operate in a normal manner to seal the orifice and so prevent fuel from entering the vent pipe 7. As the level of the fuel within the tank drops there will be a corresponding drop in the level of fuel within the cup 11 as it drains through the one-way duck-bill valve 12.

It will be appreciated that the level to which the fuel in the tank may be filled is dependent on the positioning of the inlet port 14 in the wall of the cup 11. That is to say if the inlet port is formed as a weir in the upper rim of the cup 11 and the upper rim is closely coupled to the upper wall 2 of tank 1, then the tank may be almost totally filled before the float valve closes the vent pipe orifice.

An alternative method of operation of the present invention occurs when the vehicle is parked on a slope or when cornering which causes fuel slosh in the tank. Without the cup 11 a conventional float valve would be operated if the fuel inclined to a level 18. It may be seen that even with the excess filling of the tank to the level 17, the cup 11 prevents the fuel from operating the float valve. Therefore by use of the present invention the useable volume of the tank is increased by a volume proportional to the height H.

It will also be appreciated that because the cup 11 isolates the float valve from splashing within the tank during normal vehicle use the vent pipe will not be intermittently sealed unless there is a danger of fuel entering the vent pipe 7.

An alternative form of one-way valve is shown in Figure 3.

Figure 3 shows a non-return ball valve consisting of a ball 20 which is adapted to seat onto a valve seating 21 when the buoyancy of the ball 20 causes it to float on the fuel. The ball 20 is contained within a cage 22. Other forms of oneway valve may be used to seal the drain port 13 according to the invention.

It will be appreciated that the cup 11 may be formed integral with the upper wall 2 of the tank 1.

Alternatively, the cup 11 may be formed together with the grommet 6 which is sealed to the upper wall 2 of the tank.

Claims

1. A float valve for a vehicle fuel tank, the valve comprising a float having a seal thereon adapted for sealing an orifice set in an upper wall of the fuel tank and communicating with a vent pipe, said float being located within a cup having a containing wall formed from fuel impervious material and adapted to be sealed at its upper rim to the upper wall of the tank, said cup having a one-way valve set in a drain port in the wall below the float so that fuel can only drain from the cup into the tank, and wherein said cup has an inlet weir port in the wall of the cup close to the upper wall of the tank.

2. A float valve as claimed in claim 1 in which the inlet weir port is at the upper rim of the cup.

3. A float valve as claimed in any preceding claim in which the one-way valve consists of a non-return float valve.

4. A float valve as claimed in claim 1 or claim 2 in which the one-way valve is a duck-bill type valve.

5. A float valve as claimed in any preceding claim in which the cup is integral with the upper wall of the tank.

6. A float valve as claimed in any of claims 1 to 4 in which the cup is integral with a housing forming a coupling grommet for the vent pipe, which grommet is adapted to be sealed into the upper wall of the tank.