GB2260109A

GB2260109A - A fuel tank support arrangement

Info

Publication number: GB2260109A
Application number: GB9121172A
Authority: GB
Inventors: Anthony Alan Fitzgerald
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1991-10-05
Filing date: 1991-10-05
Publication date: 1993-04-07
Also published as: GB9121172D0

Abstract

In order to prevent the bottom of a fuel tank 14a from bowing outwards when the internal pressure in the tank rises, the strap 22a which passes underneath the tank has a cross-sectional shape, such as a top-hat cross-section, which is stiff in bending. Part of the cross section of the strap is housed in a recess 36 in the bottom of the tank. The top-hat section resists outward bowing of the tank floor. <IMAGE>

Description

A FUEL TANK SUPPORT ARRANGEMENT This invention relates to a fuel tank support arrangement for supporting a fuel tank beneath a motor vehicle.

It is conventional to support a tank beneath a motor vehicle by passing a metal strap beneath the tank and securing the ends of the strap to two parts of the chassis.

There is often a requirement in vehicle design that the clearance between the road and the bottom of the tank be maintained above a certain limit. In order to achieve the best package, vehicle designers tend to work close to the lower limit for this clearance. However if the tank floor bows outwardly during operation, the tank bottom may approach closer than desired to the road surface.

Unwanted deflection of the bottom of the tank can arise as a result of the static and dynamic weight of the fuel in the tank. Also, it is well known that a superatmospheric pressure is generated inside motor vehicle fuel tanks during vehicle operation. Vent arrangements are provided to prevent this pressure rising to unacceptably high levels.

However the internal tank pressure can still rise to levels at which the walls of the tank distend and bow outwardly.

This is a particular problem with plastic tanks, because the inherent stiffness of the material is less than that of steel tanks.

According to the present invention, there is provided a fuel tank support arrangement comprising a fuel tank and at least one strap extending beneath the tank and being secured to a support structure to support the tank, wherein the lower part of the strap, which extends beneath the tank, has a cross-sectional shape, over a substantial part of its length, which is stiff in bending.

The lower wall of the tank preferably has an elongate recess for receiving the cross-sectional shape of the lower part of the strap.

The cross-sectional shape preferably merges into a flat strap cross section at the ends of the lower part of the strap, so that the strap does not intrude into the internal space of the tank at the edges of the tank. In a particularly preferred embodiment, the depth of the crosssectional shape is greatest at the centre of the lower part of the tank and gradually decrease towards the edges.

A suitable cross-sectional shape is that conventionally known as a top-hat section.

The recess in the lower wall of the tank will extend. into the internal space of the tank, but will preferably stop before the edge of the tank so that when the fuel level in the tank is low, the fuel can still flow all around the tank. Where the tank is a moulded plastics tank, the recess or recesses can be incorporated as part of the moulding process.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a fuel tank supported beneath the chassis of the motor vehicle, in accordance with the prior art; Figure 2 is a side view of a tank supporting strap in accordance with the invention; Figure 3 is a cross section through the strap on the line III-III and through a tank supported by the strap; and Figure 4 is a perspective view of a tank in accordance with the invention which has been cut open in a horizontal plane.

Figure 1 shows part of a motor vehicle chassis made up of a number of longitudinal beams 10 and transverse beams 12.

The chassis is typically that part of a van chassis which supports a load platform, for example on a Ford Transit (Registered Trade Mark) vehicle. Beneath the chassis is a fuel tank 14 which has a filler neck 16 and fuel feed and return lines 18 and 20. The tank is slung beneath the chassis on two straps 22, 24. The straps have end fittings 26 which engage in keyhole apertures 28 in the transverse beams 12. These straps which are in the form of flat strips of metal extend beneath the tank, from one side to the other, and have tensioning nuts 30 so that they can be tightened to hold the tank firmly.

Figure 2 shows a strap 22a in accordance with the invention which has end fittings 26 as in the prior art. The strap has a top-hat cross section, as can be seen in Figure 3, but the depth of the section varies along the length of the lower part of the strap, from a flat strap at the end 32 to a maximum height at the centre 34 of the strap.

It is well known that a top-hat cross section beam has considerable beam or bending stiffness, and such beams are often employed in engineering constructions.

The strap shown in Figure 2 will be used with a fuel tank, part of which is shown in Figure 4. The tank, which is a blow moulded construction, has a recess moulded into its lower face which results in the appearance of a rib 36 inside the tank.

Figure 3 shows a cross section through the strap with the tank 14a in place on it. The tank rests on lower flanges 42, 44 of the strap and/or on the top surface 46 of the section.

In use, when a high internal pressure is generated in the tank, the base 48 of the tank will tend to bow outwardly.

This tendency will be greatest in the middle of the tank where the floor has least support from its walls. However this tendency to bow outwardly will be resisted by the beam strength of the top-hat section 34.

It is important that fuel in the tank is always able to reach a fuel pickup point which itself is usually located near the centre of the lowest part of the tank. When the fuel level is below the top of the rib 36, then the fuel must still be able to flow around the rib, and this is ensured by making the outer parts of the strap 32 flat, so that the interior of the tank can have flat edge portions at 50, and fuel can always flow around the rib 36.

The support arrangement according to the invention therefore provides a simple but effective way of stiffening the bottom of the tank, without hindering the flow of fuel in the tank at low fuel levels.

Claims

Claims

1. A fuel tank support arrangement comprising a fuel tank and at least one strap extending beneath the tank and being secured to a support structure to support the tank, wherein the lower part of the strap, which extends beneath the tank, has a cross-sectional shape, over a substantial part of its length, which is stiff in bending.

2. A fuel tank support arrangement as claimed in Claim 1, wherein the lower wall of the tank has an elongate recess for receiving the cross-sectional shape of the lower part of the strap.

3. A fuel tank support arrangement as claimed in Claim 1 or Claim 2, wherein the cross-sectional shape merges into a substantially flat strap cross section at the ends of the lower part of the strap.

4. A fuel tank support arrangement as claimed in any preceding claim, wherein the depth of the cross-sectional shape is greatest at the centre of the lower part of the tank and gradually decrease towards the edges.

5. A fuel tank support arrangement as claimed in any preceding claim, wherein the cross-sectional shape is that conventionally known as a top-hat section.

6. A fuel tank support arrangement as claimed in any preceding claim, wherein the recess in the lower wall of the tank extends into the internal space of the tank, but stops before the edge of the tank.

7. A fuel tank support arrangement as claimed in any preceding claim, wherein the tank is a moulded plastics tank and the recess or recesses can be incorporated as part of the moulding process.

8. A fuel tank support strap with two ends for attachment to a vehicle chassis and a lower part which, in use, will extend beneath the tank, wherein the lower part has a crosssectional shape which is stiff in bending over a substantial part of its length.

10. A fuel tank support strap as claimed in Claim 9, wherein the cross-sectional shape is a top-hat crosssectional shape.

11. A blow-moulded plastics fuel tank, the outer bottom surface of which has a recess or recesses for receiving a supporting strap with a cross-sectional shape which is stiff in bending, the recesses being incorporated as part of the moulding process.

12. A fuel tank as claimed in Claim 11, wherein the recess or recesses from a ridge in the interior of the tank, which ridges stop short of the edges of the floor of the tank.

13. A fuel tank support arrangement substantially as herein described with reference to the accompanying drawings.

14. A support strap for a fuel tank substantially as herein described with reference to the accompanying drawings.

15. A motor vehicle fuel tank substantially as herein described with reference to the accompanying drawings.