GB2347391A - Maintaining air pressure in a punctured tyre - Google Patents

Abstract

A tyre-pressure-maintenance device 1 comprises an inflatable bag 2 of tough, flexible and thin material located on each wheel 3 within a tyre 4, bags of all wheels being connected to each other by means of a common pipeline 5. As a puncture occurs through a piercing of the tyre 4 by a sharp object 6 a pressure sensor 7 notices the sharp drop in tyre pressure and a signal sender 8 actuates a control valve 9 on each of the inflatable bags 2 so that air is allowed to flow out from the unaffected tyres into the inflatable bag in the punctured tyre. The inflatable bag in the punctured tyre is expanded and is of greater cross-section than the tyre so that it forms itself around the sharp object 6 and seals-off air leak points in the tyre 4. The pressure sensor 7 in each tyre 4 informs each valve 9 when the air pressure in each tyre 4 has been equally balanced, at which point the control valves 9 close.The pressure signal sender 8 informs the driver control panel instrumentation of the puncture and its status.

Description

Device for Maintaining Air Pressure in a Punctured Tyre The present invention relates to a device for maintaining sufficient air pressure in a punctured tyre to allow continued travelling at normal speed without having to stop the vehicle thereby removing the need to carry a spare wheel within the vehicle. The device comprises a lightweight system of interconnected inflatable bags each fitted to one wheel inside the vehicle tyre cavity, and each having a control valve to direct the flow of air between the individual bags and tyres as directe by a pressure sensor and signal sender located within each tyre cavity. Air is drawn from the tyres which are not punctured to supply the inflatable bag within the punctured tyre until the pressure in each of the tyres is equally balanced.

The resulting advantages of the device are: -more storage space available within the vehicle due to the elimination of the spare wheel ; -reduced fuel consumption due to the difference in weight between the lightweight device and the previously used spare wheel ; -reduced exhaust emissions from the vehicle due to reduced fuel consumption; -increased convenience through not having to stop and change a wheel, particularly in uncomfortable surroundings and/or conditions; -increased personal security through not having to stop in isolated areas, particularly at night.

Systems for dealing with a puncture already exist in different forms.

The most common puncture handling system is the straightforward replacement concept whereby a spare wheel is used to substitute the original wheel holding the damaged tyre. This concept is coming under increasing scrutiny driven by environmental legislation pressure to reduce the weight of vehicles and subsequently lower fuel consumption and corresponding exhaust emissions. The elimination of the spare wheel would contribute to achieving these goals.

Additionally the spare wheel has a restricting effect on vehicle design flexibility and demands space which could be utilised for other purposes such as further storage capacity.

An existing alternative to the spare wheel is the injection of a rubber compound solution inside the tyre which hardens and thereby seals the puncture hole. This method has limitations regarding the size of hole which can be effectively sealed and puncture holes of over 5mm are not repairable with this concept.

Another concept is the run-flat tyre comprising a plastic ring fitted within the tyre cavity to the wheel rim which prevents the tyre from slipping off the wheel and allows the driver to continue travelling without having to fit a spare wheel. The drawbacks to this approach are that : a) with four solid plastic rings each of larger-than-wheel diameter the device is not particularly lightweight; b) one wheel is smaller than the others following a puncture; and c) the punctured tyre no longer provides pneumatic shock-absorption.

The reinforced-sidewall tyre is another approach which allows the driver to continue without replacing the damaged tyre. Again, as with the run-flat ring, the driving conditions are anormal with no pneumatic shock-absorption. Additionally the distance able to be travelled is limited and the concept removes the normal-condition performance of flexible sided tyres.

It is an object of the present invention to provide an inexpensive, lightweight device in the form of a series of bags of tough, thin, flexible material each fitted to an individual vehicle wheel within the tyre cavity which: -are fitted with the bag held in a folded, flat form ready to be deployed in the event of a puncture, -deploy individually through the supply of air from an interconnecting pipeline typically of plastic material, from the other tyres so that air is distributed equally to all tyres as determined by pressure sensors with a signal sender in each tyre cavity, -have a potential fully-inflated size larger than the tyre cavity, but which when inflated are restricted in size to the form of the tyre cavity, -prevent air from escaping from the tyre and thereby maintain sufficient tyre pressure within the tyre cavity to keep the tyre in a fully-functional, operational condition until a tyre replacement point is reached without having to carry out tyre replacement or to stop the vehicle, -eliminate the need to carry a spare wheel, and -can inform the driver of a puncture through control-instrument information.

Inflatable tubes inside tyres were previously used in the history of tyre development as a means of providing support shape to the tyre without allowing air to escape through non-airtight areas between the tyre and the wheel rim.

Gradually these inner tubes which were made of rubber became redundant through the introduction of improved-fit tubeless tyres.

The difference between the present invention and previous inner tubes is that the present invention: a) does not necessarily have to be inflated for normal operating conditions; b) is capable of being inflated while the vehicle is moving; c) is not made of rubber, rather of a tough, thin, flexible material such as certain forms of polyethelene ; and d) does not have a tight fit against the inner walls of the tyre, rather it is designed to have excess surface area due to it's oversize which creates tension absorbing folds.

The key principle of the present invention lies in the over-sizing of the inflatable bag allied to the toughness of the bag material. When a sharp object pierces the tyre outer wall, any tightly fitting inner tube which is already inflated within the tyre cavity, or any inner tube which is subsequently inflated as a result of the piercing, is also likely to be pierced as the surface of the inflated tube meets the sharp object.

However, when an inflated device is significantly larger than the tyre cavity, and of an appropriate, tough but thin material such as Tyvek polyethelene, the inflating device does not get pierced but rather wraps itself to the form of the sharp object and seals any air gaps around it.

At the moment of puncture, a pressure sensor detects the sudden drop in tyre pressure and the inflatable bag, which is located on the wheel rim inside the tyre cavity, is deployed. Air is supplied to the bag in the punctured tyre from the unaffected tyes through a lightweight flexible pipeline interconnected to each inflatable bag. A valve located on each inflatable bag controls the flow of air between the individual bags and tyres as directe by a pressure sensor and signal sender located within each wheel cavity.

Air is drawn from the tyres which are not punctured to supply the inflatable bag within the punctured tyre until the pressure in each of the tyres is equally balanced.

The driver is informed of the puncture by a signal display on the instrument panel and knows that the damaged tyre has to be checked and repaired or replaced at the next opportunity.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows a schematic of the air supply circuit and bag locations.

Figure 2 shows a section through the tyre cavity with the inflatable tube held in position ready for deployment.

Figure 3 shows a section through the tyre cavity with the inflatable tube in the process of deploying.

Figure 4 shows a section through the tyre cavity with the inflatable tube deployed.

According to the invention a tyre-pressure-maintenance device 1 comprises a series of inflatable bags 2 of tough, flexible and thin material located on each wheel 3 within a tyre 4 and connected to each other by means of a common pipeline 5. As a puncture occurs through a piercing of the tyre 4 by a sharp object 6 a pressure sensor 7 notices the sharp drop in tyre pressure and a signal sender 8 informs a control valve 9 on each of the inflatable bags 2. The control valves 9 on each bag open in such a way that air is allowed to flow out from the unaffected tyres into the inflatable bag in the punctured tyre. The inflatable bag in the punctured tyre is deployed so that it expands and forms itself around the sharp object 6 and seals-off air leak points in the tyre 4. The pressure sensor 7 in each of the tyres 4 informs each of the control valves 9 when the air pressure in each tyre 4 has been equally balanced, at which point the control valves 9 close. The pressure signal sender 8 informs the driver control-panel instrumentation of the puncture and it's status.

Claims (3)

1. CLAIMS 1. An inexpensive, lightweight device in the form of a series of bags of tough, thin, flexible material each fitted to an individual vehicle wheel within the tyre cavity, -which are fitted with the bag held in a folded form ready to be deployed in the event of a puncture which: -deploy individually through the supply of air from an interconnecting pipeline typically of plastic material, from the other tyres so that air is distributed equally to all tyres as determined by pressure sensors with a signal sender in each tyre cavity, -have a potential fully-inflated size larger than the tyre cavity, but which when inflated are restricted in size to the form of the tyre cavity, -prevent air from escaping from the tyre and thereby maintain sufficient tyre pressure within the tyre cavity to keep the tyre in a fully-functional, operational condition until a tyre replacement point is reached without having to carry out tyre replacement or to stop the vehicle, -eliminate the need to carry a spare wheel, and -can inform the driver of a puncture through control-instrument information.
2. 2. A device as claimed in Claim 1 which is modified in dimension and the number of bags to suit the application to motorbike tyres.
3. 3. A device as claimed in Claim 1 which is modified in dimension and the number of bags to suit the application to bicycle tyres.