The invention relates to the field of tyre inflation, in particular the use of pyrotechnic means for tyre inflation.

BACKGROUND OF THE INVENTION

Vehicles can include an onboard tyre inflation system that can be used to keep vehicle tyres at a desired inflation level. It can be desirable to top up pressure periodically or to compensate for a puncture. A tyre inflation system usually includes a pneumatic air source, a control system, conduits, and valves at each vehicle wheel.

For example, the Bushranger™ onboard air kit comprises a 4.5 litre air tank, a 275c compressor, a high pressure hose, and an on board air hook up kit which is made up of 6.1 metres of airline, a 150psi pressure switch, a safety valve, wiring, gauges and mounting hardware.

A disadvantage with this type of system is that it is necessary to include a reservoir tank, usually fitted under the vehicle body, which is heavy and space- consuming. It is also necessary to connect each tyre separately to the pneumatic air source, which is complicated and requires valves, airlines, and rotary couplings to be installed at each wheel hub. This equipment adds cost, weight and complexity to a vehicle and will require periodic maintenance.

SUMMARY OF ASPECTS OF THE INVENTION

The present invention provides a system whereby tyre pressure can be increased locally at the wheel (e.g. within the tyre) which obviates the need for any external pneumatic source. The present invention thus provides an pyrotechnic device whose combustion discharge gasses are utilized for the purpose of tyre inflation. In a first aspect, the present invention provides a wheel comprising a pneumatic cavity, wherein the wheel comprises an pyrotechnic device, or a plurality of pyrotechnic devices, in pneumatic connection with the pneumatic cavity such that combustion discharge gasses produced by the pyrotechnic device(s) cause the pneumatic cavity to inflate.

The pneumatic cavity may be, for example, an inner tube, or a tyre with or without an inner tube.

The pyrotechnic device(s) may be mounted on to or into the wheel (for example on to the hub of the wheel), on to or into the tyre, on to or into the tyre valve, or on to or into the inner tube.

The wheel, may, for example, comprise between 1 and 10; 2 and 5; or about

3 pyrotechnic devices.

The term "pyrotechnic" is used in its conventional sense to mean a material capable of undergoing self-contained and self-sustained exothermic chemical reactions for the production of heat, light, gas, smoke and/or sound. In the context of the present invention, the pyrotechnic device produces gas. The pyrotechnic device may be, for example, an explosive device or a combustion device. Pyrotechnic devices suitable for use in the invention are known in the art. For example, similar devices are currently used in automotive safety systems such as for the inflation of air bags.

The pyrotechnic device may be mounted on to or into a wheel, tyre or inner tube (if present). It may be mounted such that, when detonated, its discharge gasses are directly channeled to the pneumatic volume of the tyre or inner tube. Alternatively, there may be a channeling system, such as piping or manifold to direct the combustion discharge gasses to the pneumatic cavity.

In one embodiment the wheel may comprise a "back-up" inner tube, which remains in a deflated state until recovery action is required due to failure of an existing tyre/inner tube, at which point the pyrotechnic device(s) is/are detonated and the back-up inner tube is inflated by the combustion discharge. The back-up inner tube may alternatively be a flexible membrane.

For safety, the pyrotechnic device may be prevented from detonating until mounted. For example, the device may be unable to detonate until the tyre or inner tube is inflated.

One way of achieving this is to include an arming device which prevents detonation of the pyrotechnic device until the arming device is pressurized to an arming pressure. Conveniently, the arming device may be pressurized by the pneumatic volume of the tyre.

The arming device may also return to unarmed when the tyre is deflated, for example, for removal.

The wheel may also comprise a sealant source, wherein detonation of the pyrotechnic device(s) causes release of the sealant. The sealant may be released into the pneumatic cavity. The sealant may act to repair a puncture or leak.

In a second aspect, the present invention provides a tyre comprising an pyrotechnic device, or a plurality of pyrotechnic devices, which may be used to produce a wheel according to the first aspect of the invention.

In a third aspect, the present invention provides an inner tube comprising an pyrotechnic device, or a plurality of pyrotechnic devices, which may be used to produce a wheel according to the first aspect of the invention.

In a fourth aspect, the present invention provides an pyrotechnic device, adapted for mounting on to or into a wheel, tyre or inner tube, and for pneumatic connection to a pneumatic cavity, which may be used to produce a wheel according to the first aspect of the invention. In a fifth aspect, the present invention provides a vehicle which comprises wheel according to the first aspect of the invention.

The vehicle may also comprise a tyre monitoring system which can be extended to provide control of the ignition of the pyrotechnic device(s). Tyre condition monitoring systems are known in the art. For example, tyre pressure monitoring (TPMS) devices are known which measure the pressure and optionally also the temperature of the air or other gas in the tyre. Alternative TPMS devices can infer tyre condition from other effects including changes to tyre rolling radius. TPMS devices often communicate with other control or display systems within the vehicle often but not exclusively via telemetry to avoid electrical connections between the rotating wheel and the vehicle.

In connection with the present invention, where the wheel comprises a plurality of pyrotechnic devices, the tyre monitoring system may cause the simultaneous, sequential or separate ignition of the pyrotechnic devices, depending on the amount and speed of inflation required.

The vehicle tyre monitoring system may monitor and optionally report on the condition of the pyrotechnic device(s). For example, if there is a plurality of pyrotechnic devices for each wheel, the monitoring system may provide information on how many devices have been detonated for each wheel.

In a sixth aspect, the present invention provides a kit which comprises an pyrotechnic device, or a plurality of pyrotechnic devices, according to the fourth aspect of the invention; and optionally any one or more of the following:

(i) means for mounting the pyrotechnic device(s) on to or into a tyre, inner tube or wheel;

(ii) a connector to channel the combustion discharge gasses to the pneumatic volume of the tyre or inner tube to cause inflation thereof;

(iii) an arming device which prevents detonation of the pyrotechnic device until the arming device is pressurized to an arming pressure; and/or

(iv) a control connection to electrically or pneumatically connect the pyrotechnic device(s) to an in-vehicle tyre monitoring system. The kit may be used for the modification of a tyre, inner tube, wheel or vehicle, to produce a tyre, inner tube, wheel or vehicle in accordance with the present invention.

In a sixth aspect, the present invention provides a method for making a tyre whose pressure can be increased locally within a wheel of a vehicle, which comprises the step of mounting an pyrotechnic device, or a plurality of pyrotechnic devices according to the fourth aspect of the invention, into or on to the tyre or its inner tube.

In a seventh aspect, the present invention provides a method for inflating a tyre or inner tube, by detonating one or more pyrotechnic device(s) in pneumatic connection with the tyre/inner tube, such that the discharge gasses of the pyrotechnic device(s) are channeled to the pneumatic cavity of the tyre/inner tube.

The pyrotechnic devices of the present invention may be used as part of an onboard tyre monitoring and inflation system that can be used to keep vehicle tyres at a desired inflation level.

The pyrotechnic devices of the present invention may also be used in a recovery action procedure following tyre failure, which may, for example, be due to puncture, other damage to the tyre and/or inner tube (e.g. caused by shooting) or blow-out. This may be particularly useful for applications in aircraft landing wheels, military vehicles and Formula I racing cars.

In such applications, a monitoring system may predict a blow-out and may be prevented by corrective inflation using the system of the present invention.

DETAILED DESCRIPTION

Figure 1 shows a pneumatic tyre 1 is mounted to a corresponding wheel 2 with or without an optional inner tube 3. It is desirable to know from time to time, or in the event of a leak, puncture or climatic change if the tyre 1 is correctly inflated. For this reason the wheel 2 and corresponding tyre 1 may be fitted with a Tyre Pressure Monitoring System TPMS 4.

In order to provide additional inflation if and when it is required, an pyrotechnic device 5 or plurality of pyrotechnic devices (shown) are arranged so as to inflate the tyre 1 with their combustion gasses when they are discharged. The device(s) may be mounted within or on the tyre 1 , within or on the wheel (shown) 2 or within or on an optional inner tube 3. The discharge gasses may be pneumatically channeled either directly (shown) or via piping or manifold to the pneumatic volume of the tyre 6 or optional inner tube 3 for the purpose of tyre inflation.

The pyrotechnic device or devices 5 may be ignited by a tyre pressure monitoring system (TPMS) 4 mounted within or onto the tyre 1 , or within an inner tube 3 and/or within or onto a corresponding wheel 2. In this arrangement the tyre 1 can manage its own inflation autonomously from the vehicle preferably without need for electrical or pneumatic connection to the vehicle. The TPMS device 4 and or other controller may be electrically or pneumatically connected, via a control connection 7 to the pyrotechnic device or devices 5 for the purpose of detonating the pyrotechnic device or devices 5 either sequentially or simultaneously as required for tyre inflation. An additional function of the control connection 7 may be to monitor and optionally report the condition of the pyrotechnic device or devices 5.

It is likely but not necessarily the case that the pyrotechnic device or devices

5 will need replacing during tyre 1 maintenance and or tyre 1 replacement. It is also likely that replacement of the pyrotechnic device or devices 5 may be undertaken by operatives not trained in the handling of pyrotechnic devices. For this reason an optional arming device 8 can be included which renders the pyrotechnic device or devices 5 harmless unless and until the optional arming device 8 is pressurized by the pneumatic volume of the tyre 6, to an arming pressure (for example, a pressure which confirms the tyre is properly sealed to the wheel). In this way, the pyrotechnic device or devices 5 are confirmed to be safely contained within the pneumatic volume of the tyre 6 before the system is armed, such that any subsequent explosion is safely contained.

Figure 2 shows a conventional tyre valve assembly 10 which has been modified by extending its rubber stem 11 inside the tyre in order to attach a blast capsule 12. The blast module 12 is filled with pyrotechnic 13 and sealed. It has an ignition module 14 similar to a gun shell and a 1 ^st burst valve 15 which ruptures when the pyrotechnic is ignited to allow the discharge of combustion gasses.

Rigidly attached to the blast capsule, is a pressure trigger housing 16.

Within the housing is a firing plate 17 which is pressed into the housing to create a sealed volume 18. An assist spring 19 may be used to apply an additional force to the firing plate. A flow port 10 allows pressurised gasses within an inflated tyre to enter the pressure trigger housing 16 and act against the firing plate 17.

The firing plate 17 is a bi-stable disc with 2 positions, at rest and cocked. When there is no pressure in the tyre, the firing plate 17 is in its rest position touching an ignition module 14. As the tyre is inflated, the pressure in the tyre and also acting on the firing plate 17 increases.

When the pressure reaches a cocking pressure the force acting on the firing plate 17 causes it to flip into its cocked position, compressing the assist spring 19 (illustrated). Typically inflation would continue until the correct tyre pressure is obtained. In this way, the device is armed only when it is safely inside a seated tyre.

In service the tyre pressure may reduce due to leakage or a puncture. When the pressure falls to a firing pressure which is below the cocking pressure the firing plate 17 assisted by the spring 19 flips back to its rest position where it re-contacts the ignition module 14 with sufficient impact to cause ignition. In turn this causes the pyrotechnic 13 to detonate, and combustion gasses to discharge from the blast capsule 12 through the 1 ^st burst valve 15 and into the tyre pneumatic volume, thus raising the tyre pressure. An optional Sealant capsule 21 can be attached to the blast capsule 12 in such a way that the explosion ruptures a 2 ^nd burst valve 22 in the sealant capsule, releasing sealant 23 into the pneumatic volume of the tyre to seal the puncture or leak.

During routine tyre replacement, the device is activated as soon as the tyre is sufficiently deflated such that it is safe when the tyre is removed.

The device can alternatively be mounted on or in the wheel rim, or on the inside of the tyre or an inner tube.

Various modifications and variations of the described methods and system of the invention will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention which are obvious to those skilled in engineering or related fields are intended to be within the scope of the following claims.