The invention relates to an inflatable element (also referred to as airbag) for use interiorly in a fuel tank of a vehicle, vessel or aeroplane.

It is known that the fuel in a fuel tank of a vehicle, vessel, aeroplane or train (hereafter vehicle) affects the behaviour, the stability and the performance of the vehicle. The weight of the fuel increases the weight of the vehicle and thereby influences the acceleration and brake behaviour of the vehicle and in case of an aeroplane also the load factor. Besides the aforementioned effects resulting from the static weight of the fuel, the fuel within the fuel tank exerts dynamic forces or effects - during driving, sailing or flying (hereafter driving) - onto the vehicle by movement of the liquid fuel within the tank. The to and fro moving or sloshing liquid may exert additional momentum and/or moment onto the fuel tank wall, which may disadvantageously influence the stability, the drivability and the performance of the vehicle. For fast moving vehicles like (combat) airplanes and like vehicles adapted for speed contests like racing cars, the acceleration and brake behaviour and the stability are of utmost importance. The dynamic behaviour of the fuel in the fuel tank of a car or racing car results in variation of the tyre slip angle, tyre slip point and the weight load and as a result thereof in a general decrease of the tyre grip and a reduction of the road holding or - stability. As a result more slip in longitudinal of driving direction and/or lateral direction is necessary, leading to a lower maximum engine power and therefore to a decrease of the performance of the vehicle.

In order to prevent sloshing or swinging of the liquid within the fuel tank baffle plates or similar measures are mounted into the fuel tank of a racing car, or the entire fuel tank is partitioned. However this solution has several disadvantages like an increase of weight of the fuel tank due to the weight of the baffles or like a decrease of the capacity of the holder or like making it more difficult to rapidly refill the fuel tank during a race. A fuel tank provided with baffles shall therefore still pass on a portion of the momentum of the swaying liquid to the holder and the vehicle and transmit forces and energy onto the holder wall.

It is known that vapour is formed above the liquid surface depending upon the known physical liquid-vapour equilibrium and the resulting vapour pressure as a function of temperature. Particularly volatile liquids such as fuels, which have a high vapour pressure at ambient temperatures, will completely fill the free space of the holder with vapour of the fuel after the liquid is removed. The vapour is also present when the liquid only partially fills the holder. Therefore it is not possible to use all of the loaded liquid because a portion thereof is evaporated into vapour during emptying of the tank and therefore discharged into the air during refilling of the tank. Due to these vapour losses during a race a racing car must be refueled sooner or a larger and therefore heavier fuel tank must be used. Furthermore it is known that vapour/air mixtures of fuels may easily explode particularly when stoichiometrically mixed, making extensive security measures necessary. Also measures must be taken against undesired emissions of vapour from the holder into the environment like the surrounding air.

Object of the invention is to provide for an inflatable element for use interiorly in a fuel holder of a vehicle for reduction of sloshing or swinging of the liquid and also for reduction of the vapour space and vapour losses, and also to prevent condensation of water and to increase the refill speed.

This objective is achieved by an inflatable element being provided with means, by which inflating gas is supplied into or discharged from the inflatable element.

The above mentioned features allow for an easy adaptation of the inflatable element to the changed shape and size of the free space above the liquid, whereby the fuel tank may be refilled rapidly without inflow of air into or outflow out from the fuel tank being required. Furthermore is prevented that moisture condensates from the ambient air and accumulates into a part of the fuel tank.

Alternative advantageous embodiments are described in claims 2 - 9. With these measures the pressure within the inflating element may be easily, at low cost, be maintained or controlled and the reliability of the device may be increased.

The invention also relates to a fuel holder for a vehicle, vessel or aeroplane, provided with an inflatable element according to the invention.

The invention also relates to a system for maintaining a preset pressure within an inflatable element as described in claim 13. This configuration allows for maintaining the pressure within the inflatable element in a simple manner and at low cost, by using low cost elements like a drain valve. De pressure is maintained in case of a (small) leakage of the inflatable element so that the whole system keeps functioning and the inflatable element remains inflated. The invention also relates to a method for operating an inflatable element within a fuel holder of a vehicle. The method comprises the following steps:

- inflating the inflatable element by means of an inflating gas supply means, through the external inflating means, by supplying inflating gas, until the pressure within the fuel tank reaches the preset value.

- supply or discharge inflating gas respectively during discharge or supply of fuel from or to the fuel holder respectively.

The invention is further explained by means of a drawing of an embodiment of the inflatable element, whereby features and other advantages will come forward.

Fig.l shows a fuel tank provided with means for controlling the pressure within the inflatable element,

Fig.2 shows an advantageous embodiment of the control system of the inflatable element.

In Fig. l a fuel holder 2 is shown provided with an inflatable element 4 and a pressure control assembly adapted for controlling the pressure in the inflatable element 4 positioned within the holder 2. In this example the inflatable element 4 is provided with a (control) valve 31 controlled by a pressure sensor 32. When measuring low pressure the valve 31 will make a connection with the compressor 34 of the inflating gas supply, when measuring high pressure the valve 31 will make a connection with the inflating gas discharge 33. Instead of a compressor for supplying inflating gas to the inflatable element 4, a high pressure inflating gas reservoir 35 may be provided. In the example as shown in Fig. l a safety or drain valve 30 is mounted upon the inflating means 9 between the control valve 31 and the inflatable element 4. The pressure within the inflatable element 4 is preset at such a value that the fuel 3 within the fuel holder 2 obtains a small overpressure of -for example- 0,1 bar. As a result no vapour can be formed within the fuel holder 2, when during driving or racing -in case of a racing vehicle- although the fuel holder 2 is almost empty. This has the advantage that during refilling no fuel vapour is emitted to the surroundings so that explosive air- fuel compositions are not formed. Furthermore condensing of water within the fuel tank is prevented. Because fuel holder 2 is maintained upon a small overpressure, it is possible with this configuration to pump the fuel to the engine, without fuel pump by only using the overpressure in the fuel tank. Particularly for racing vehicles this is advantageous, because a weight reduction is realised, leading to a performance improvement of the racing car. Furthermore the fuel tank configuration has the advantage that the fuel 3 will not swing within the fuel holder notwithstanding no baffle plates or compartments are provided within the interior. Because in the use position the walls of the inflatable element are provided with wall tension, the liquid fuel cannot move and displace so that the stability and the driving characteristics of (racing) vehicles will not be affected unfavourably. In particular the high acceleration forces acting when braking, accelerating and cornering bends exert also high forces upon the liquid in the fuel holder, so that the uncontrolled swinging and moving liquid will exert additional forces upon the vehicle. These additional forces must be compensated by the tyres of the vehicle leading to a decrease in the maximum delivered engine power. Therefore a weight reduction may be realized because baffle plates are not necessary anymore. Or with an equal size of the fuel tank more fuel may be loaded, so that during the race less stops for refill will be necessary.

The pressure control system comprises in a preferred embodiment two (master - slave) control loops with a second pressure sensor 20, which measures the fuel pressure within the fuel tank 2. When there is a difference between the preset fuel pressure and its actual value, the set point must be adjusted of the first pressure control loop comprising the first pressure sensor 31 inside the inflating air. When the tank is empty the internal pressure within the inflatable element must be set somewhat higher due to the internal elasticity of the material of the inflatable element or airbag. In Fig.l a simple schematic control valve 31 is shown; other combinations or separate or combined valves - open/close or controlling - may be applied.

For rapid refilling of the fuel holder 2 during a speed race a fuel tank 2 may be provided with a wide filling pipe 21 so that a filling speed of 12 l/s may be reached making a pit stop of only 6 - 8 seconds possible. The filling pipe 21 is in a preferred embodiment provided with an open/close valve 22, so that the fuel tank 2 is maintained on pressure and no leakage from the filling opening 21 may occur. The fuel tank 2 may be manufactured from metal or plastic; in case of a fuel tank for a racing vehicle or aeroplane, the fuel tank may be manufactured from flexible rubber, which does not bursts open caused by an accident or collision. By means of a drain pipe 23 the fuel is displaced or pumped to the vehicle engine or, when necessary, to a fuel pump.

In Fig.2 an alternative simple embodiment is shown of the system for maintaining the preset pressure within an inflatable element 4 according to the invention. The inflatable gas is supplied, from an inflating gas supply means, through the external inflating means 9, extending between the inflating gas supply means and the inflatable element 4, so that the inflatable element 4 will have and occupy a larger volume. When the inflating element 4 occupies the entire free internal space of the fuel tank, the inflatable element can not increase its volume so that as a result the inflowing inflating gas will increase the internal pressure of the inflatable element 4. When the internal pressure exceeds a preset safety pressure or discharge pressure, the safety valve or drain valve 30 will open until the internal pressure again lowers below the preset value. In this embodiment the inflating gas is supplied to the inflating element 4, from an inflating gas supply means, like an air pump or an air compressor 34, through external inflating means 9, like a conduit or channel. The inflating gas may also be supplied from inflating gas reservoir 35; this inflating gas reservoir 35 may also be applied in combination with an air pump 34. Optionally also safety valves or check valves are used, for example between the delivery port of the air pump 34 and the drain valve 30 in order to prevent emptying of the inflatable element 4 when the air pump fails or the inflating gas reservoir is empty. In use inflating gas continuously flows to the inflatable element 4 and, when there is no leakage in the configuration, subsequently is drained to the surroundings by means of the drain valve 30.

In Fig.3 an advantageous embodiment is shown of the inflatable element 4 according to the invention. The inflatable element 4 is an elongated flat bag with inflatable cavities 40, which cavities are interconnected through connecting channels 41 or connecting restrictions or points. The cavities 40 may be inflated with inflatable air, because the cavities are interconnected and form a continuous flow channel. The inflatable element 4 in this embodiment corresponds to a so-called 'Plastic Ice Cube Bag'; a bag provided with spaces or cavities for the formation of ice cubes. The inflatable element 4 of Fig.3 is preferable configured out of two foil sheets, an upper sheet 42 and a lower sheet 43, whereby the two sheets are mutually interconnected in a pattern, thus forming spaces or cavities 40. The inflatable element 4 of Fig.3 is zigzag folded positioned from the top to the bottom within the fuel tank 2, but any other method of folding inside the fuel tank 2 is also possible. The cavities 40 may mutually be connected by means of channels, but the cavities 40 may also be directly interconnectedly arranged within the inflatable element. The inflatable element 4 is preferable provided with a simple system for maintaining the preset pressure within an inflatable element 4, as shown in Fig.2. When fuel 3 flows via the drain pipe 23 to the engine, the pressure within the fuel tank 2 will decrease, so that inflating gas, through air pump 34 and via inflating means 9, flows to the first set of cavities 40 within the inflatable element 4. Drain valve 30 maintains the pressure within the inflating means 9 onto its preset desired value. Through connection channels 41, provided between the cavities 40, the inflating air penetrates further into the inflating element 4, so that the inflating element 4 is inflated further and being provided with a larger volume, in order to compensate for the fuel 3, flown out of the fuel tank 2.

The inflatable element may be positioned loose in the holder or may be (fixedly) attached with the holder; preferably the element is connected to the holder in such a way that only small forces are exerted upon the wall of the holder.

When in the description is mentioned "inflating" or "inflatable element" it includes all volume increasing systems having the same effect upon the solution of increasing the volume of an airbag without applying a high internal pressure.

The inflatable element may be manufactured from any suitable material like a plastic or fabric.

CLAIMS