GB2247880A

GB2247880A - A fuel tank assembly

Info

Publication number: GB2247880A
Application number: GB9019916A
Authority: GB
Inventors: Ronald Pardy
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1990-09-12
Filing date: 1990-09-12
Publication date: 1992-03-18
Anticipated expiration: 2010-09-12
Also published as: GB2247880B; GB9019916D0

Abstract

A fuel tank assembly formed in a plastics material as a single blow-moulding comprises a fuel tank 1, a filler pipe 2 and a sensing tube 3. The sensing tube 3 determines the maximum level of fuel in fuel tank 1 its purpose being to preserve the ullage space during refuelling. The sensing tube 3 may be connected to the filler pipe and/or to the tank by an integrally moulded web (6 Fig. 3) of plastics. <IMAGE>

Description

FUEL TANK ASSEMBLIES The present invention relates to fuel tank assemblies made in plastics material.

It is a safety requirement that fuel tanks be designed so that a residual volume of vapour or air is trapped above the fuel in the tank after the tank has been completely filled. The space thus occupied by a trapped volume of vapour is called the ullage space.

Where the fuel filler pipe enters the tank below the top of the tank, the tank can only be filled above the level of the filler pipe if air/vapour can escape from the top of the tank. This can be achieved by providing an escape passage from the top of the tank, which passage is itself closed off by the rising fuel level at a point designed to provide a limit to the level to which fuel can rise in the tank. This passage is referred to as a sensing tube.

Theoretically, it would be possible to arrange the point at which the filler pipe enters the tank so that the upper edge of the filler pipe opening into the tank forms a limit to the level to which the tank can be filled with fuel. However in practice, other factors such as the packaging of other vehicle components and the provision of passenger/luggage space dictate the actual position of the filler pipe.

Generally the sensing tube is of comparatively narrow gauge in relation to the gauge of the filler pipe. One end of the tube is open close to the top of the filler pipe, and the other end opens in the fuel tank at a level which defines the ullage space.

Conventionally, the sensing tube comprises three parts namely a stub tube projecting into the fuel tank, a stub tube connected into the filler pipe and a flexible hose connecting the two.

Such an arrangement is labour intensive to assemble and requires a number of different parts. Clamps for attaching the flexible hose to the stub pipes can be overlooked or incorrectly fitted.

US Patent Specification 3 187 936 describes an integral fuel filler and vent tube made of a plastics material which is separately attached to a short neck provided on the upper part of a metal fuel tank and is not integrally moulded with the tank. There is a similar disclosure in the specification of GB Patent Specification 2 065 580.

The specification of US Patent 3 330 439 describes a fuel tank made of a plastics material having an integrally moulded filler neck and venting means. This specification indicates that "....various structural features of the fuel container are formed integrally with the wall portions.... (col 3,line 53). It also indicates that "...fuel tank structures.. may have a 'modification' to receive a separable combination vent and filler tube means integral as to each other per se though removable from the tank..." thereby implying that the vent and filler tube may be integral with the tank. (col 5,line 55).

All these proposals are concerned with the need to provide venting for the vapour in the ullage space during vehicle operation. Such venting is always required to prevent excessive pressures building up inside the tank, for example in hot weather when the fuel vapour pressure will be high. This is however a different requirement from that of the present invention, where the sensing tube is only 'active' during refuelling and is closed when the fuel filler cap is replaced. Fuel tank venting is in fact often closed off during refuelling, to prevent so-called trickle filling of the tank which can lead to filling of the ullage space.

Accordingly the present invention is for a fuel tank assembly made of a plastics material comprising a fuel tank, a filler pipe therefor and a sensing tube connecting the fuel tank with the filler pipe and all formed as a single blow-moulding.

By forming the filler pipe and the sensing tube integrally in one and the same blow-moulding operation, additional components and additional assembly and checking steps are avoided.

The end of the sensing tube which extends into the tank cavity is located so as to ensure that the ullage space is preserved and that the fuel tank cannot be overfilled.

For at least part of its length it is desirable that the sensing tube runs parallel to and in tandem with the filler pipe.

The sensing tube may be connected to the filler pipe adjacent the top end of the filler pipe. The sensing tube is preferably also connected to the filler pipe by a web of plastics material for the whole or part of the distance that the sensing tube and the filler pipe run in parallel. This web of plastics material will normally be continuous. Its width may be as small as one millimetre.

In this case, the sensing tube can be formed by pinching part of the wall of the blow-moulding to form the web, and to define the sensing tube alongside the filler pipe.

The filler pipe extends from the tank cavity to a filler neck which is n provided at its outer end with means such as a thread, flange or cam to engage with a filler cap.

The sensing tube may enter the fuel tank from a side surface or from an upper surface of the fuel tank.

The fuel tank assembly is formed from a plastics material by blow-moulding.

The plastics material may be for example polyvinylidene chloride, high density polyethylene or nylon.

The present invention is illustrated, by way of example, in the accompanying drawings in which: Figure 1 is a plan view of a fuel tank assembly according to the present invention; Figure 2 is a side view of figure 1; Figure 3 is an exaggerated cross sectional view on AA of Figure 2; Figure 4 is a side view of another fuel tank according to the present invention; and Figure 5 is a plan view of figure 4.

Referring to figure 1 of the drawing, a fuel tank 1 is integrally moulded with a filler pipe 2 and a sensing tube 3 to form a unitary body.

The sensing tube 3 enters the cavity of the fuel tank 1 at an opening 4 and enters the filler pipe 2 at an opening 5.

From figure 3 it is apparent that the filler pipe 2 is connected to the sensing tube 3 by a web 6 of plastics material.

The manner in which the fuel tank assembly functions may be appreciated from the following description. When, during refuelling, petrol reaches level L1, the vapour in the space above the petrol will not be able to escape via the filler pipe. However the vapour can still escape via the sensing tube 3. When the petrol reaches level L2 the vapour can no longer escape through the sensing tube and the pressure in the space above the petrol in the tank will prevent that space being filled any further. When this happens, further fuel poured into the filler pipe 2 from a fuel filler pump nozzle will only fill the filler pipe itself, and the fuel level in the pipe will rise rapidly, causing a back pressure to be experienced by the filler nozzle which will cause the cut-off mechanism in the filler nozzle to operate.

Even if a vent tube is provided as shown at 7 in Figure 2, the rate at which vapour escapes is slow in relation to the rate at which the tank fills with petrol.

Referring to figures 4 and 5, these show a one piece moulded filler tank assembly comprising a fuel tank 11, a filler pipe 12 and a sensing tube 13. The filler pipe 12 is located flush with a side 16 of the fuel tank 11. The sensing tube 13 extends between a point 14 where it enters the fuel tank 11 and a point 15 where it enters the filler pipe 12.

The sensing tube 13 is moulded alongside the filler pipe 12 for part of its length and is moulded to the side of the fuel tank 11 for the remainder of its length.

Level L3 in the fuel tank 11 represents the upper fuel level to which this tank can be filled. At this fuel level, air or vapour trapped in the space 18 cannot escape through the tube 13, and the space is maintained as an ullage space.

Other parts may be integrally moulded with the fuel tank as well as the sensing tube, for example as the vapour vent 7. The fuel tank assembly will also include components for supplying fuel to the engine, but such components are not illustrated in the drawings.

It will of course be apparent that the fuel tank, being a moulded object made from a plastics material, may be formed into a more complex shape than that illustrated in the drawings.

Claims

WHAT WE CLAIM IS

1. A fuel tank assembly made of a plastics material comprising a fuel tank, a filler pipe therefor and a sensing tube which has one end which enters the fuel tank at a position which is above the entry of the filler pipe to the tank, to determine the maximum level to which the tank can be filled, and a second end at a higher level, wherein the fuel tank, the filler pipe and the sensing tube are all formed as a single blow-moulding.

2. A fuel tank assembly as claimed in claim 1 or 2 wherein the second end of the sensing tube is connected to the filler pipe.

3. A fuel tank assembly as claimed in Claim 1 or Claim 2, wherein said one end of the sensing tube extends vertically within the tank.

4. A fuel tank assembly as claimed in Claim 2, wherein the second end of the sensing tube enters the filler pipe adjacent the top end of the filler pipe.

5. A fuel tank assembly as claimed in any of the preceding claims wherein for at least part of its length the sensing tube runs parallel to the filler pipe.

6. A fuel tank assembly as claimed in any preceding claim, wherein the sensing tube is connected to the filler pipe and/or to the tank by an integrally moulded web of plastics material.

7. A fuel tank assembly as claimed in any one of the preceding claims wherein the fuel tank assembly is made from high density polyethylene.

8. A fuel tank assembly substantially as hereinbefore described with reference to the accompanying drawings.