GB2390839A

GB2390839A - Fuel tank

Info

Publication number: GB2390839A
Application number: GB0216424A
Authority: GB
Inventors: Graham Smith
Original assignee: FPT Industries Ltd
Current assignee: FPT Industries Ltd
Priority date: 2002-07-16
Filing date: 2002-07-16
Publication date: 2004-01-21
Anticipated expiration: 2022-07-16
Also published as: GB2390839B; GB0216424D0

Abstract

A fuel tank comprises a thermoplastic laminated skin 10 with seams 18 that are thermally welded while on a foam former 14 which also acts to reduce slosh and vapour in the finished tank, and an outer fabric layer with a suitable polymer 16 filling the space between the fabric layer and the thermoplastic skin 10 to act as a self sealing agent. In another embodiment there may not be a former 14 and the seams may be welded using a sacrificial media as a separator.

Description

\DV.NCED I:UF, CELL CONSTRUCTION TECHNIQUE.

I'his invention relates to vehiclelaircraft fuel cells.

['here are many techniques for constructing fuel tanks or ceils used in vehicles and aircraft. The two or three main ones f r aircraft include "wet wing". flexible rubber cells and rigid fabricated or rotationally moulded tanks. In military aircraft it is sometimes desirable to make the fuel cells self sealing or "fire proof''. This can be achieved by lining the walls of the cell (usually a double walled rubber one) with a polymer which expands on contact with fuel. This expansion means a cell of this construction will seal itself after being penetrated by a foreign object.

One problem with fuel cells is the build up of vapour in the space above the fuel when the tank is not completely full and the subsequent release of this vapour when next refuelling. One means to overcome this is to fill the tank with foam blocks. Using the correct type of foam the entire tank can be filled with them with a loss in fuel volume of only 3 XO approx. These blocks also have the effect of damping the movement of t'ucl in the fuel cell to reduce the effect of 'slosh' and subsequent effects on aircraft stability. I'hese foam blocks are usually cut to match the shape of the inside of the cell, then "diced" to enable it to be passed through a suitable fitting in the cell and reassembled.

I'he shape of' the cell itself is usually created on a former (which is sometimes sacrificial). Another means of overcoming release of fuel vapour that has been tried. is to use an internal lining with a diaphragm. Some ot'these have been made from a thermoplastic lamination which usually consists of polyethylene and nylon.

However one thing that has not been tried before is to use such a lamination to construct the entire libel cell and not just line it. Such a construction could include built in bat'fles' bonded or thermal welded fittings and Velcro i'asteners for holding the cell in position in the aircraft structure.

The fuel cell construction could consist of flat or shaped (thermoformed) segments of cast extruded laminated sheet which could then be welded together by overlapping the edges of adjacent panels. The welding machine generally used has a jaw like assembly with the bottom jaw consisting of sponge. Welding takes place across these jaws unless a separator is used. This separator could be a sheet of paper. and this would prevent the overlapped edges welding to the underside of the cell. Another means of achieving separation lor welding would be to use a material that would form part of the final cell construction, such as the foam blocks.

Why not form the cell by using the foam as a former which would aid the welding process by acting as a separator? This would eliminate the need for a former and for cutting the foam into blocks to feed through a fitting in the tank. This would speed up construction considerably and reduce manufacturing, effort.

According to the present invention there is provided a self sealing t'uel cell comprising of a foam former which acts a a separator when thermowelding a thermoplastic laminated material together to form the double skin of said t'uel cell. This fuel cell could include built in baifes that not only help control the movement of fluid but support the cell walls to prevent sagging. At least one layer of the laminate should be capable of one or more of the t'ollowing requirements:

< I. Providing a barrier against permeation of fuel (liquid or gaseous).

ii. Providing a welding' medium for thermowelling or other wokling process. Such a fuel cell might use a woven or knitted t:abric incorporated into the construction of the cell panels when they are welded together or afterwards by adhesion to a suitable outer surface. This fabric could add wear and scuff resistance to the outer surt:ace of the cell.

Alternatively. an outer layer or layers ot'tabric reint'orcement may be attached to the tuel cell using local features similar to those already mentioned.

I'he double skin of the fuel cell can be filled with a polymer to make the tank self' sealing. A specific embodiment of the invention will now be described by way of example with reference to he accompanying drawing in which: Figure I shows in cross section a self sealing single skinned fuel cell construction with an outer permanent reinforcing layer.

A self sealing Duel cell comprises a thermoplastic laminate I (). which is formed to shape on a former made from vapour/slosh reducing foam 14, that also acts as a separator tor the welding machine to enable a seam 18? thy be made on one side of the ceil without at't'ecting the other side. self sealing is achieved by filling the space between the thermoplastic laminate 10, and the fabric reint'orcing 12, with a suitable polymer 16.

A self sealing? fuel cell comprises a thermoplastic laminate 10, an outer fabric reinforcing layer 12 a former 14, a polymer 16, thermal welded seams 18 and local attachments 20.

i CLAIMS

I. A fuel cell consisting of a thermoplastic laminated skin whose seams are thermal welded while on a loam former which also acts to reduce 'slosh' and/or vapour in the finished cell, and an outer fabric layer with a suitable polymer filling the space between said layer and said thermoplastic skin to act as a self sealing, agent.

9. A fuel cell as in claim I. but without the polymer to act as a self sealing agent.

3. A fuel cell as in claims I and 2 but with two thermoplastic laminated skins.

4. A fuel cell as in claim 3 where the polymer acting as a self sealing agent lills the space between the two thermoplastic skins.

5. A fuel cell as in claim 1 but without the polymer to act as a self sealing agent and without the outer fabric layer.

6. A fuel cell as in claim a, which does not use a former that also acts to reduce slosh' and/or vapour in the finished cell, and whose seams are welded by using a sacritcial media such as paper as a separator in the welding process.

7. A fuel cell as in claims 2, 4 and 6 where an outer reinforcing layer is provided by means of local attachments such as press studs or velcro patches allowing it to be dettachable.

Claims

Amendments to the claims have been filed as follows CLAIMS

. A Fuel cell consisting of a thermoplastic laminated skin whose seams are thermal welded while on a foam Conner which also acts to reduce 'slosh' and/or vapour in the finished ceil, and an outer fabric layer with a suitable polymer filing the space between said layer and said thermoplastic skin to act as a self sealing agent.
2. A Mel cell as in claim 1, but with two thermoplastic laminated skins.
3. A fuel cell as in claim 2, but with one thermoplastic laminated skin and ailc'.i,ei skid of a ilffeici; ma.ei-ia..
4. A fuel cell as in claims 2 and 3 where a polymer actin:, as a selfsealin agent fills the space between the two skins.