*

DESCRIPTION

This invention concerns a tyre and wheel monitoring system. 5 With the need of road safety always of paramount importance there is one sphere which is as important as any, if not more so than most, and that lies at the vehicle to road contact points ie. the tyres upon the road.

10 It is now universally accepted that tyre and wheel conditions are a prime consideration in regard to safety, yet in the modern road going vehicle virtually every other issued is "warning tagged". For example engine vitals, such as oil and water are monitored,

15 brake wear or malfunction, but usually nothing for the tyre and wheel, which along with the brakes and steering are possibly the most vital safety considerations there are, especially in this era of the mass produced performance car and greater access to extremely high

20 performance models.

An object of this invention is to provide a tyre and wheel monitoring system.

According to the invention there is provided a tyre and wheel monitoring system comprising means for

monitoring and/or reacting to tyre or wheel parameters to indicate an alarm state and/or to provide interim safety measures. In one preferred embodiment of the invention a tyre pressure sensor for generating a signal at least when tyre pressure is above or below safe limits and means actuated by said signal to give and audible or visible warning.

In a second preferred embodiment of the invention a tyre and wheel monitoring system comprises means for counteracting tyre deflation.

In a third preferred embodiment of the invention a tyre and wheel monitoring system includes means for indicating looseness of wheel fit on its hub.

In a fourth preferred embodiment of the invention a vehicle tyre includes means for indicating wear.

Further objects and features of the invention will now be further described, by way of example only, with reference to the accompanying drawings, in which:- Figure 1 shows a pressure sensor; Figure 2 shows schematically a comparator circuit in relation to the pressure sensing device at Sir- Figure 3 shows another compatible circuit; wherein the pressure sensing device is again utilised at Sl and relative to the circuit as transistors TRl (n.p.n.) as switches;

Figure 4 shows in section a tyre pressure monitoring device suitable for attachment to a tyre valve;

Figure 5 shows another tyre pressure monitoring devic ;

Figure 6 shows yet another tyre pressure monitoring device;

Figures 7 A and B show respectively in plan and section a yet a yet further tyre pressure monitoring device;

Figures 8 A and B show respectively in plan and section another tyre valve attachment;

Figure 9 shows a tyre pressure monitor for a double tyred wheel; Figures 10 A, B and C are respectively side, end and sectional views of the monitor of Figure 9;

Figures 11 A, B and C are perspective, side and plan views of an attachment frame for the monitor of Figures 9 and 10; Figures 12 A, B and C show respectively plan, side and end views of another attachment frame;

Figure 13 shows the frame fitted to a wheel dish;

Figure 14 shows a security type screw to impede illicit removal of a tyre pressure monitor from an attachment frame;

Figure 15 shows the use of the screw of Figure

14;

Figure 16 show monitor sensor/transmitter circuitry; Figure 17 the receiver/output circuitry;

Figure 18 shows circuitry for greater interrogation of the incoming signal giving a precise analysis of which wheel or tyre is affected and how;

Figure 19 shows schematically logic circuitry of a typical diagnostic system;

Figure 20 shows typical encoder/decoder circuitry;

Figures 21 A and B are plan and side views respectively of a tyre pressure sensor for attachment to a wheel;

Figure 22 shows an alternative sensor for attachment to a wheel;

Figure 23 shows a wheel with monitoring facilities. Figure 24 shows a variation on Figure 23;

Figure 25 illustrates a low battery warning circuit;

Figure 26 is a section through __ wheel with provision of a "constant" power supply together with a permanent data path;

Figures 27 A and B are respectively side and end.

views of a modified calliper and disc; * ^* -* Figure 28 shows a compatible brake pad;

Figure 29 shows a brush assembly;

Figures 30 A and B are respectively side and end 5 views of a brush/pad assembly;

Figure 31 shows a modified brake disc- Figure 32 shows a hub wheel interface unit; Figures 33 A, B and C are respectively section, plan and perspective views of a brake pad; 10 Figure 34 shows the pad of Figure 33 fitted to a modified calliper;

Figure 35 illustrates an alternative modified brake disc- Figure 36 shows a constant supply system; 15 Figure 37 shows another constanct supply system;

Figure 38 shows an alternative constant supply system;

Figure 39 illustrates use for providing laser technology paths for data and supply; 20 Figure 40 shows a combined rotational supply and data transmission path system;

Figure 41 shows detail of the system of Figure 40;

Figure 42 illustrates use of the laser not only

25 to provide data transmission but also to provide a supply for the sensing module by extracting energy from

the laser with solar cell cladding;

Figure 43 shows detail of a fibre optic and solar cell cladding;

Figure 44 shows another alternative for the use of solar cells;

Figures 45 A and B are respectively plan and section views of a wheel fitment monitoring system; Figure 46 shows a circuitry for the system of Figure 45; Figures 47 A and B show respectively plan and section views of an alternative for monitoring wheel tightness;

Figure 48 shows circuitry of the system of Figure 47; Figure 49 shows an anti blow out wheel;

Figures 50 A and B are respectively front and sectional views of the anti blow out wheel;

Figure 51 shows detail of the anti blow out wheel; Figures 52 A and B show respectively fron and section views of another anti blow out wheel;

Figure 53 illustrates a further alternative anti blow out wheel;

Figure 54 shows in detail of a hydraulic piston for an anti blow out wheel;

Figure 55 shows another piston with suspension;

Figure 56 details another suspension design; Figure 57 shows an anti blow out wheel with tyre in place;

Figure 58 shows a yet further form of anti blow out wheel;

Figures 59 A and B are respectively front and end sectional views of another yet further anti blow out wheel;

Figure 60 shows detail of the wheel of Figure 59; Figures 61 and 62 shows further detail of the wheel of Figure 59;

Figure 63 shows a split wheel anti blow out embodiment;

Figure 64 shows an alternative split wheel embodiment;

Figures 65 A, B and C show respectively plan and sectional views of the split wheel of Figure 64;

Figure 66 shows sealing of split wheel to avoid air loss; Figure 67 shows a sealing method at the inter face of a split wheel;

Figure 68 illustrates an alternative sealing method;

Figure 69 illustrated another sealing method; Figure 70 shows a tyre modified to show wear;

Figure 71 ^• shows a tyre with an electrical wear

sensor; and

Figure 72 shows an alternative method of showing tyre wear.

Referring to the accompanying drawings, Figure 1 illustrates schematically a pressure sensing device capable of discriminating varying pressures either gas or liquid, comprising a basic bridge network, from which a potential difference is extracted at Sl and S2 when pressure is applied. The pressure is proportional to the applied pressure. The device is calibrated to required parameters by the varying of discrete components. In this example, for instance, motor car tyre pressures, typically 0-50 p.s.i.. Higher pressure sensing devices are available which would allow for deployment in the passenger service and heavy goods vehicle fields.

This ability to calibrate the sensor means that should a tyre start losing pressure, a warning system could commence operation. A variety of methods to give warning can be used, for instance in its basic format, the triggering of an audible alarm, illumination of l.e.d. 's, transmission of other signals (when used with compatible circuitry) or all three if necessary.

Figure 2 details a comparator for use in conjunction with the sensor.

Two variable resistors VR1 and VR2 set the

operational parameters whilst the buzzer PI and L.E.D. (visual warning) are in circuit with the bridge rectifier BRl which is coupled to the sensor at Sl and the potential divider. The comparator circuit is now in a position to fulfill its design function; the constant voltage from the sensor is operational at BRl, since BRl has a p.d. in relation to the reference voltage set at the potential divider VR1 - VR2 this e.m.f. operates the warning elements in the circuit. Also shown are two variable resistors VRl and VR2 which will set the operational parameters. BRl, the bridge rectifier is instrumental in the operation of LED DI and buzzer PI, when a potential difference in created. The circuit is energised with a battery. Figure 3 emphasises flexibility in the design, giving an alternative compatible circuit using transistors (n.p.n.). TR1 is constantly on in normal operation, TR2 is off. Low Pressure is Detected; TR1 switches off (hold energy too low) PI, D2 operate via Rl, DI.

At high pressure TR2 switched on allowing for operation of PI, D2. (TR1 is of course also on).

To house the above circuitry many methods would be permissible the variance in design combating the varied lengths of the different tyre valves may dictate its ultimate shape.

In Figure 4, a generally cylindrical sensor housing 10 internally screw threaded at one end 12 for fitting onto a tyre valve. The housing 10 contains a pressure sensor 14 connected to a circuit board 16, which is itself connected to a battery power source 18, a l.e.d. 20 and a buzzer 22. The housing 10 includes air passages 24 permitting air flow from the tyre to the sensor and a pressure release member 26 to act on the tyre valve release pin as the housing is screwed onto the valve.

Figure 5 shows a variation of the sensor of Figure 4, in which the housing 30 is T-shaped. That allows easier fitting and removal thereof due to the available leverage. Figure 6 shows a variation on the "T" design to negate the need for removal of the device should air be required in the tyres. The housing 40 has upper valved air inlet 42 to a pressure chamber 44 which leads to the air passages 24". The sensor 14" is situated in a side of the chamber 44. The inlet 42 will normally be covered by a dust shield. When the pressure chamber 44 is pressurised via the air passages 24", valve 42 is closed. The sensor is also monitoring the pressure ie. the tyre pressure. Should air be needed, the dust shield is removed and the air hose applied as normal. Any excessive back pressure because of the stricture

11 created by the diameter of the air passages 24" would cause the main air inlet to close, until equalisation has occurred.

Figures 7 A and B show plan and sectional views of a housing designed with a view to lowering the centre of gravity of the pressure sensing unit by strategic deployment of the components then covering the exposed part of the valve to sit tight against the wheel. A cylindrical adapter 50 screws onto tyre valve 52 and has annular ribs 54 for locating in corresponding grooves 55 of.passageway 56 and sensor housing 58. The passageway 56 leads to air passages 60 giving access to a sensor 62 and to an inlet valve 64 for supplying air to the tyre through the housing. The sensor 62 and its associated circuitry 66, battery power supply 68, l.e.d. 70 and buzzer 72 are situated in an annular chamber 74 around the passageway 56. The refinement would also be necessary where limited space around the valve would proscribe the turning of any unit when attempting to screw it on.

The lowering of the sensors centre of gravity would tend to inhibit any "flopping" about, bending or dragging over of the valve where a long valve stem is to be connected to. Figures 8 A and B show in plan and section an alternative arrangement similar to that of Figure 7 but

SUBSTITUTE SHEET

using a circular housing 80, which is again a snug fit over the tyre valve by means of internal screw threading 82 in passageway 56'.

Figures 9 and 10 show a system for a double wheeled axle, so popular on commercial vehicles. Two distance pressure chambers 90 are allied together with a differentiating sensor 92 set between them.

The sensor 92 is capable of monitoring two different pressures, with this capability in mind (though 2 standard sensors would be equally capable of the job) the sensor is so positioned, that two pressures are acting upon it. This is achieved via two hoses 94 each of which are connected to each tyre valve 96. Each tyre pressure is now under constant scrutiny and any discrepancy in pressure will function as alarm system as outlined previously. Since the units are distinct and each will house independent audible and visual alarms, isolation of the offending wheel will be possible. Inflation of the tyres would be catered for without the removal of the sensing unit as outlined earlier through valves 98.

The hoses 94 are of such a construction to handle the pressures and allow for connection to the tyre valves without loss of pressure. The hoses 94 are, in fact, provided with valves 98 for that purpose. However, the application to the sensing unit will force

open the valve to permit the pressure to access the sensor, via the valve in the same way as the standard tyre valves themselves function. The circuitry may be modified to accommodate dual operation. Figures 10A, B and C show a typical circuitry arrangement in which the circuit board is indicated at 100, a l.e.d's at 102 and buzzers at 104.

Figures 11A, B and C show perspective, side and plan views of a frame onto which a sensing device can be located to secure the unit to prevent it being damaged as the wheel spins and centrifugal force is developed.

The frame comprises two plates 110 and 112 interconnected for telescopic movement relative to each other. Each plate has its free end formed as a return 114 for gripping a wheel dish part of an HGV. Two threaded rods 116 and nuts 118 are used to draw the two plates towards each other via pairs of upstanding lugs 120 on each plate to provide a tight grip on the wheel dish. The plate 110 has a rectangular housing 122 in which the sensing unit can be secured.

Figures 12A,B and C show in plan*-, end and side views another type of frame 123 for a sensing unit and Figure 13 shows the frame fitted to an HGV wheel dish. One side of expandable/retractable hooked arms 125 situated at the rear of the sensing module are of a ratchet type design. When wishing to fit the frame to a

wheel dish, hooked end A is engaged to one ridge of the most convenient or applicable wheel dish hole and hooked end B is then pushed back to engage the ridge of the next hole. It will be remembered that B is the rachet end, therefore, the unit will be locked into position. For security reasons, the rachet is of such a design that only further tensioning of security screws 127 will ease the rachet and allow for further expansion at point B, to release the whole unit. Total removal then simply consists of undoing the hoses. The screws 127 pass through a sensing unit 129 and abut ratchet arm 126. The screws 127 are shown in more detail in Figure 14 and are provided with a special head 130. A complementary driver 132 is then required to turn the screws. A screw locking plate 134 is also provided.

The driver 132 could come as part of any package and of course could easily be coded in terms of number and length etc. For example, the head of the screw could be made such that it would swivel unless the code was complete. The fact also that the ratchet disengagement can only be achieved by tensioning of the screws further enhances security.

Figure 15 shows the whole arrangement of frame, sensor and security screws. It is desirable to use any signal produced by a sensing unit to produce an in-vehicle signal, preferably

through a diagnostic interface.

In Figure 16 there is shown a transmitter circuit; to which a sensor is coupled at S^ and S ₂ , in this case acting as a resistance. For clarity sake the event breakdown is set out below;

SENSOR - SIGNAL CODED XITTED RECEIVED - DECODED

At the decoding point a varying voltage is produced as in Figure 1 and 2.

Figure 17 illustrates a suitable receiver circuit.

Figure 18 shows a receiver/decoder for an diagnostic system. The receiver/decoder is interfaced with the relevant circuitry 178 so far discussed and additional circuitry to be described below. The system includes l.e.d. 's 180 to provide instant visual warning of a signal pressure discrepancy and an audible alarm PI to ensure a signal is not easily overlooked. A liquid crystal display 182 is also included.

Figure 19 shows a logic system for a diagnostic system. In principle the onboard diagnostic would remain the intelligence gathering heart of a system to which would be connected the various forms of monitoring of the wheel to road contact points, already described and to be described later. Figure 20 shows an input encoder/decoder and output relationship to detail the concept behind a logic

circuit.

Figure 21 shows a typical transmitter component for attaching to the vehicle's wheel. The component has a casing 218 with a weatherproof lid 220. Pressure inlet 210 is screwed pressure tight into the wheel rim. Pressure is monitored via sensor 212 coupled to suitable circuitry 214 powered by batteries 216.

Figure 22 shows a transmitter with a flexible hose connection 224 to overcome possible fixture difficulties at the wheel base.

Figure 23 shows a cross section of a wheel rim in relation to the transmitter of Figure 21 fitted and a second pressure sensor 230. The purpose of the second sensor 230 is to monitor the wheel structure itself. This is achieved by a pressure level being maintained in sealed capillary tube 232. The pressure may be exerted by either gas or liquid. Should a structural defect occur i.e. a crack in a wheel spoke for example, then the ensuing pressure loss will be detected. A liquid may be used as the pressure medium, probably brightly coloured, then immediate diagnosis and identification of a point of pressure loss would be possible.

Figure 24 shows a variation of Figure 23 but with a differential sensor 240. This sensor is capable of differentiating simultaneously between two pressures, so the requirement for a second sensor would be dispensed

with. The sensor 240 has capillary tubing 242 above it and is open to tyre pressure below. It is possibly worth a mention in passing that this idea is aimed more at the very high performance vehicles where alloys of a very light nature are used (power/weight ratios etc) but tremendous stresses and strains occur due to the very nature of the increased power necessary to produce the improved performances.

Figure 25 illustrates an audible and visual low battery warning circuit for integration with sensing devices described herein. A voltage is applied via DI to the op-amp ICI. This voltage is compared at this stage to a second voltage which is derived via VRl. The circuit is now normal in relation to the set parameters. Presume a low battery voltage; a potential difference is developed across the inputs of ICI. This difference is amplified and then used to activate the warning elements in the circuit.

A constant source of power is desirable for serving devices of the invention rather than using conventional batteries that have to be changed from time to time. Solar powered battery power may be a possibility but an alternative is illustrated in Figures 26, 27A and 27B which are respectively section, side and end views.

Shown here are the disc 260, wheel 261, brake-

calliper 262, brush 264, hub 266 and tyre 268 of a typical wheel arrangement. The dotted lines represent the electrical supply path and data transmission path from and to tyre pressure sensor 265 through interface 267.

The brake disc 260 is arranged to provide a path for supply to the sensing module and transmission of wheel data to an onboard diagnostic facility, as well as its normal braking function. To provide this path the brake callipers/brake pads 262 themselves are fitted with brushes 264 that contact the disc 260.

It should be noted that among other advantage this use of the callipers will provide a static reference point in relation to the turning motion of the wheel. The modifying of the callipers and brake pads while contending with this obstacle, enables the paths to be used at all times, while also maintaining as intended facet of the design that it should not impair or alter the function or efficiency of the braking system.

This should be clear from the drawings. In case it is not, it is worth the mention that there are points on the brake disc which most pads do not utilise. Also the pad can be elongated to accommodate the insertion of the brushes. This means that on any vehicle the cross

sectional area of braking pad need not be reduced. Also the design intrinsically allows for the brushes to be "sprung" so that on application of the brakes the brushes will not impede their function but merely depress into their housing whilst still maintaining contact with the disc.

Figure 28 shows one example of a modified brake pad allowing for insertion of a brush comprising a slotted back plate 280 and pad 282'. Figure 29 shows in detail a brush 290 fitted to a brake pad 292. Insulation 294 is provided between housing 296 and the pad 292, to ensure isolation and therefore, discretion of data and supply. The housing 296 is retained by resilient clips 295. Figures 30 A and B are side and end views showing brake callipers 300 with brushes 290 fitted to brake pads 292. Transmission wires 302 are connected to the brushes. The brushes 290 are spring loaded.

Turning to Figure 31, brake disc 304 has insulated brush contact paths 305 on opposite sides of the disc. The disc 304 is shown on its wheel hub 306 in turn on axle 308. Transmission paths 310 are shown linking the paths 305 with interface 312. The transmission paths include plug in connections 314 where the disc abuts the hub.

Referring to Figure 26 where the sensor and

interface are shown as separated, they can be combined into a single unit possibly of two part plug-in construction as shown in Figure 32. The mating of the two parts utilises available space between the area of the wheel immediately under the tyre and hub.

Figures 33 and 34 show a modified brake pad 330 to allow easier maintenance by allowing for easy removal of the pads from the callipers. The pad 330 includes a spring connector 332 that locates on a plug 334 of a calliper.

Figure 35 shows a laminated disc so that the brushes merely run on the face of the disc itself. The disc has insulation 350 separating front and back faces of the disc 352. Figure 36 shows how a wheel bearing 360 may be used for constant supply and data transmission. The bearing 360 has an outer fixed ring 362 and an inner rotating ring 364 separated by balls 366. Plugged into the bearing 360 is a similar two ring system having an inner ring 368 with connection 370 to a sensing unit and an outer fixed ring 371 having spring loaded contacts 372 for making connections with the inner ring and data and supply paths 374, 376 respectively.

Figure 37 shows an alternative for bearing this time using trailing arms 378 to pick up the data and supply.

Figures 38 A, B and C shows bearing adapted as the medium of transmission.

In Figure 38 A two dedicated ball bearings 380 carry the data and supply, insulated (382) to maintain the integrity of the circuits. Figure 38 B uses trailing arms 384 and Figure 38 C uses the ball bearings 386 alone.

It is envisaged that laser technology may be utilised for constant power supply and transmission of intelligence.

Figure 39 details a laser tube designed for this aspect with one side at a static reference point; in this instance say a purpose built brake calliper, the tube is shown elongated for the sake of explanation, though it in all probability it would be a fairly compact length being immaterial and in no way capable of diminishing the efficient functioning of the tube due to the efficiency of laser/fibre optics. (Also where space is at a premium the receiver can be located within the diagnostic and wired to the laser tube via the fibre optics) .

Figure 39 shows calliper attachment 390 with a laser 392 at one end and a receiver 394 positioned in outer tube 395. Between the laser and receiver is a fibre optic link 396 providing the path for relaying of the wheel intelligence being emitted from the sensing

module. Information from the sensing module concerning the wheel can be relayed in digital format to the receiver. The data may be forwarded on to a diagnostic facility via a decoder in the manner hitherto outlined. Electrical energy supply 398 for the operation of the sensing module is in inner tube 399

Figure 40 show the system of Figure 39 in detail. Ring 400 provides a path via brushes 402 through laser 392 along fibre optic 396 to the receiver 394 and onto a diagnostic system. Ring 403 provides the electrical path through brushes 404 to supply 398. With regard to wheel removal and replacement a similar format would be deployed as hitherto outlined in regard to a plug on, plug off facility, much in the same way for the brake disc and calliper development mentioned earlier. There are of course other options such as a purpose built hub itself. Plug-in connections 406 of the rings include seals 408 as shown in detail in Figure 41.

Figure 42 illustrates the possibility of using solar cell technology to supply the power required by the module allowing a laser beam to transverse via the fibre optic through a bank of solar cells, provision being made to allow it to access and thereby "act" upon the solar cells. The power of the laser or laser combination (possible use of dedicated fibres) would be gauged to fulfill the function of transferral of data

and or solar activation. Thus the laser tube would include optical fibre 420 and solar cells 422.

Figure 43 shows the solar cell system of Figure 42 installed in laser tube 430. Figure 44 details an alternative to the charging process of the solar cells by integrating them into the rotational extension arm of the laser tube 430. An additional laser 440 "fires" down a dedicated fibre optic link to play directly upon solar cells 442 ringed within rotational arm 444. These cells are of course turning and thus being charged as they do so, this energy being then utilised by the circuitry.

Figure 45 shows a system for signalling that a wheel has become loose due to wheel nuts 449 or studs becoming loose. The wheel hub 450 has spring (451) loaded piston 456 that are normally depressed by a wheel to contact switches 458. The switches form part of an alarm circuit shown in Figure 46 and opening of a switch 458 in signal path 459 due to release of a piston 456 if the wheel becomes loose will provide an audible and/or visual alarm signal. Supply path is shown at 457.

An alternative system shown in Figure 47 relies on using an hydraulic fluid 460 as an interface between piston 456 and sensor 460. The circuitry for the system of Figure 47 is shown in Figure 48. Line 480 is the power supply line and line 482 is the signal

transmission line. The normal sensor outputs will be of determined value and deviations from those values will activate an alarm signal.

The invention also proposes an anti-blow out wheel. Relatively instant deflation or blow-out of a tyre results in;

A) in the case of the front wheel(s); savage sudden biassing of the steering mechanism due to the loss of height corresponding to the deflation height of the tyre and hence loss of control, either temporarily or permanently of the vehicle and

B) in the case of the back wheels; loss of the back end" which usually takes the form of the rear end sliding from side to side, again resulting in attendant difficulties with controlling the vehicle. The principle according to the invention is to maintain the virtual height corresponding to the height of the tyre when it is inflated.

Accordingly it is proposed that a wheel hub have relatively expandable parts to maintain substantially a tyres inflated size upon deflation thereof.

Figure 49 details four hydraulicly driven pads

490 expandable into the vacant area between the wheel

492 and tyre tread 494. In more detail as shown in Figures 50 A and B the wheel 492 contains a hydraulic fluid reservoir 500 with

passages 502 therefrom the piston 504 of the pads 490. The hydraulic fluid reservoir 500 has a main piston 506 for pressurising same to force the pads outwards when the wheel is fitted to its wheel hub. Thus, i) attach the wheel and the pistons drive out in to the tyre; ii) remove the wheel and due to design criteria utilising springs or other hydraulic pipes etc. drive themselves back.

As shown in Figure 51, the pads 490 themselves have an arcuate face 510 on which is a pre-determined thickness of a shock absorbent material say neoprene rubber. It is intended that this face should extend to within a scientifically determined point inside the tyre behind the tread. It is hoped at this particular point that the inherent quality of the pneumatic tyre is at all times retained (it would be determined at the behest of research that the face may possibly even touch the rear of the tread) . What this all means is that should the tyre encounter any object which would cause a puncture , especially of an instantaneous type, that crucial loss of air and hence tyre so detrimental to control of the vehicle would no be felt .so anything approaching its fullest extent, since the vehicle is now supported on the hydraulic pads cocooned within the tyre

itself, remembering that the pads would of course be "locked out".

Instead of a single drive piston, a dual drive piston and reservoir system may well have advantages in relation to flexibility of design to suit differing needs (see Figure 52). Each piston 520 has its own reservoir 522 and actuates pad 524 via its own piston 525.

In the above proposals the pads 490 or 524 do not form a complete circle about the respective wheels but leave gaps between their ends. That may be undesirable and an alternative is shown in Figure 53; in which one opposing pair of pads 530 is longer and overlies the other pair of pads 532. Obviously with one set of pads retained behind the other, the hydraulics would require the correct modus operandi ie. the longer pads opening out first on wheel fitment and on wheel removal operating behind the shorter set. This may be achieved by using suitable valves. The pads are shown in both the retrieved and extended positions. The dotted line represents the boundary presented by the wheel rim.

Figure 54 shows a variation on Figure 51 which includes a suspension chamber 540, its main facet being to provide a cushioned ride in parallels with the vehicle's own suspension ie. when the wheels encounter

obstacles in the normal course of motoring the tyre obviously flexes to some extent. In these instances it is of course possible that if the tyre on flexing met with resistance ie. the hydraulic pads; occupants could experience a bumpier ride than usual. The suspension is to compensate for this eventuality but at the same time inherent to its design is the facility for it to harden if a "blow out" is encountered. This is achieved by gas or liquid filling or part filling the chamber unit to a predetermined level and tuning the suspension unit accordingly.

Under normal motoring conditions the suspension modulates in relation to the wheel. In the event of a blow out the suspension unit encounters the full rigors of the vehicles weight etc. At this point the piston is driven into the chamber. With the parameters set correctly, a valve 542, depicted here as a finger or reed valve is tuned to the designated requirements ie. being sprung or manufactured so as resist complete closing given normal operational circumstances but under the rigors of the blow out the pressure it endures is such to close and prevent further gas or liquid relief into the side chamber, thus the spring unit is now damped and the suspension hardened accordingly. If the suspension chamber contains a liquid it will virtually lock out presenting very little give at all. Whatever ^'

the procedure adopted in terms of gas or liquid the principle will remain;

A) under normal motoring the suspension is "soft" and will modulate easily in sympathy with the tyre. B) under the inertia of a blow out the suspension would react to its severity and the corresponding increase in pressure would dampen the modulation accordingly.

It is worth the mention that centrifugal force would aid the suspension unit (especially in relation to the fluid) in tending to keep the internal force of the fluid to the fore of the chamber behind the piston, making for increased sensitivity of operation on encountering a blow out. A simpler variations shown in Figure 55 in that the suspension chamber 540'merely uses a spring 550. In this variation and the other of Figures 51 and 54, the pad 490 is connected to its piston 504 by a ball and socket joint 552 which it is felt may aid the floating ability of the pads so far discussed. The movement of the pads 490 would be limited to a practical level in order any that hard impact encountered could not drive it onto the tyre wall.

Figure 56 presents another variation on the suspension chamber system for use with gas or liquids working on a similar format to that shown in Figure 54.

Figure 57 highlights the wheel, piston, suspension, pad and tyre relationship.

Figure 58 illustrates continuing development of the concept of the anti blow out wheel, to maintain a solid ring within the tyre 586. This format of pads 580 supported by pistons 582 from wheel 584, may present on impact, after a blow out, a smoother ride.

Referring now to Figures 59A and B a further development involves adjacent pads 580 having their ends coupled to a common piston 582 by means of linkages 590 shown in more detail in Figures 60, 61 and 62. Each pad is coupled to two pistons at opposite ends by two pairs of links 600 on opposite sides of thereof. Each link is pivotally connected at one end 604 to the piston and to an opposite end of a roller 606 movable laterally in slots 608 of the pads. A guide member 610 on the piston is positioned to urge the links apart and hence the pad outwards when the piston itself moves outwards as the wheel is fitted to its hub (see Figure 50 for example). It may be possible to conceal the links etc. beneath a purpose built pad to maximise space with the attendant advantages of minimising distance travelled by the piston and links.

For radial tyres, particularly for high performance vehicles space between the tyre and the wheel may be restricted. Figures 63, 64 and 65 show

29a embodiments aimed at dealing with this problem. In Figure 63 the wheel 630 is split into two halves 630A and 630B, that are fastened together by studs and nuts 632, 634 respectively. The pads 580' are built proud of the wheel extending into the air space encompassed by the tyre (not shown). This of course means that the

30 travel of any piston is thus accordingly reduced. The hydraulic system will again operate via pistons 582 , this time dependant on the two wheel halves being joined together or being split apart. The overall concept allows for any changing of tyres and also the retention of the pneumatic qualities while reducing the amount of travel to be done by the hydraulic pistons in order to locate the pads most advantageously within the tyre void. It is envisaged that given modern methods of tyre replacement the split wheel with due attention paid to the machinery involved will not impede tyre removal. For on the removal from the vehicle the wheel will simply split in two and be withdrawn from the confines of the tyre. In Figures 64 and 65 the wheel 640 is in three parts. Two semi-circular parts 642 A and B are inserted into the tyre. These two parts carry the piston/pad arrangements 580 ^/ /582 and hydraulic reservoirs 644.

The third part 650 shown in Figure 65 fits into the central space created by the first two parts 642 A and B and it bolted in position. The part 650 when fitted acts on pistons 652 of hydraulic reservoirs 644 to expand the pads 580 . In both these designs sealing of the split wheel parts may be achieved in one of the ways shown in Figures 66 to 69. Abutting parts of the split wheel ^' are provided with rebates 660 and 662 to

31 receive in one case a seal module 664 having a spring- loaded blade extension 666, that may urge outwards hydraulically, pneumatically or mechanically say be coupling to the piston/pad expansion system, by utilising internal tyre pressure or by a lever system, and in the other case a slotted receiver 668 for the blade, the receiver being of or containing a suitable sealing material or being adapted to receive a sealing material. In Figure 67 the sealing material is a rubber elastomeric insert 670, in Figure 68 the sealing material is actually a rubber ring 680 on the blade and in Figure 69, the sealing material is a resilient sleeve 690 that is squeezed between the blade and the receiver 668.

Finally, Figures 70 shows a tyre 700 having means of indicating that a tyre is; i) near to illegality and ii) illegal The first indication is achieved by a first colour banding 702, say yellow, and the second by a second banding 704, say red, further into the tyre tread.

Included in the design is an idea for helping to also make the tyre a safer proposition for those who desire it stored below the tread is a suitable, pliable ^'

32 compound 706, which on a puncture being encountered, is forced to the hole and being of a type that toughens on contact with air helps seal the hole as an interim measure. it is foreseen that if the suitable material were employed, the sudden loss of air which can prove so devastating to a fast moving road vehicle could be pre¬ empted and minimise its effects.

Figure 71 shows a system for providing on-board tyre wear indication. A wire 710 is embedded into the tyre compound. When a predetermined level of wear is encountered the wire is broken to open a circuit that generates a warning signal. Should the wire be broken for any other reason other than that outlined it is meant to be replaceable. A further feature of a tyre and wheel monitoring system may be provided to indicate tyre wear. As shown in Figure 72 dye may be introduced at locations of possible tyre wear. One possibility is a dye reservoir

720 immediately below the tread and another possibility is a capillary tube 722 from below the tread to alongside the tyre side wall to a reservoir 724. Tyre wear will eventually expose a source of dye to indicate a point of unacceptable tyre wear.