GB2025862A

GB2025862A - Pneumatic Tire Monitoring Device

Info

Publication number: GB2025862A
Application number: GB7921536A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-06-21
Filing date: 1979-06-20
Publication date: 1980-01-30

Abstract

A tire monitoring device comprises a sound wave generating unit operable by means of a source of energy e.g. the inflation air within a pneumatic tire, and inflation pressure operated control means for coupling the sound-wave generating unit with the source of energy at a predetermined tyre inflation pressure sensed by the control means. In use, the device is rotatable with the vehicle mounted pneumatic tire wheel assembly. As illustrated in Fig. 6 the sound generating unit is a whistle 41, and flow of inflation air to the whistle is occasioned by spring 38 overcoming inflation pressure to move piston 39 to the right. In Fig. 4 the control means is a pressure switch 6 which when closed connects battery 9 to a buzzer 10. The unit may alternatively be a speaker or an ultra sonic generator. A circuit for receiving sounds produced by its unit may be provided in the vehicle. <IMAGE>

Description

SPECIFICATION Pneumatic Tire Monitoring Device This invention relates to a pneumatic tire monitoring device and more particularly to a device adapted to issue a warning if the pressure and/or temperature of a pneumatic tire deviates outside a predetermined limit.

It is well known that pneumatic tires, in particular those located on vehicles, are dangerous when they become underinflated.

Amongst the dangers which exist are the fact that the vehicle may be difficult or impossible to control thereby creating a danger to other road users as well as to the occupants of the vehicle concerned. In the case of transport vehicles having double wheel assemblies at the rear thereof, the side-walls of the pneumatic tires can rub together and thereby render both tires useless for further service. This type of occurrence gives rise to high costs being incurred by transport fleet owners since both tires have to be completely replaced.

Also, it is well known that a vehicle engine will consume additional fuel as a result of the increased resistance occasioned by the underinflation of pneumatic tires supporting such vehicle.

Many types of warning devices have been proposed. These range from complicated systems utilizing radio frequency transmission of information concerning tire pressure from a wheel to a relatively fixed part on the body, to purely mechanical devices which are operated as a result of the deflection of the load bearing portion of a tire on a wheel.

The purely mechanical type of devices which usually embody a member attached to the tire or bearing thereagainst have not proved successful generally, in view of the fact that the tire will be subjected to different degrees of deflection according to the load thereon. Other devices, and in particular one which utilizes a back emf to transmit an electro-magnetic signal from the tire, have proved to be successful but are generally costly both to manufacture and to install.

It is the object of this invention to provide a simple tire monitoring device which will overcome the disadvantages experienced in transmitting information from the moving wheels to a stationary part of the body of the vehicle.

In accordance with this invention there is provided a tire monitoring device comprising a sound-wave generating unit operable by means of a source of energy associated, in use, with a pneumatic tire assembly; pressure operated control means for selectively coupling the soundwave generating unit with the source of energy at a preselected pressure sensed by the control means, and communication means for connecting said pressure operated control means to a pneumatic tire assembly so as to be operable according to the internal pressure of such pneumatic tire, wherein the sound-wave generating device, control means, communication means, and source of energy are all, in use, rotatable in unison with a pneumatic tire assembly.

Further features of the invention provide for the sound wave generating unit to be adapted to produce sound waves of a predetermined frequency characteristic of such unit, for such frequency to be either in the audible or ultrasonic frequency ranges and, optionally where the sound waves are audible, and essentially where the sound waves are ultrasonic, for a receiver unit to be provided for mounting on a vehicle in a position suitable for reception of the characteristic frequency of the sound waves emissible from the generating unit.

Where a receiver unit is included in the arrangement it embodies suitable filter or tuning means to ensure that it is operated by the characteristic frequency alone. This is considered to be essential as a result of the wide variety of noises which can be present in a vehicle whilst travelling and the characteristic frequency can be chosen so as to be substantially impossible to occur from any other source on the vehicle. Such a receiver unit may be located near an appropriate tire and thus sound waves of low intensity may be utilised.

The source of energy may be an electrical storage battery or the like carried in a housing which can optionally house the necessary switch in addition to the sound-wave generating unit.

However, it is preferable that the source of energy be gas under pressure (optionally liquified) and such gas may be contained in a separate container such, for example, carbon dioxide bottles of a size generally used for charging soda siphons and which are marketed under the Trade Mark "Sparklets". The most preferred source of energy is the air under pressure in a pneumatic tire itself.

The use of air emanating from a tire to generate sound-waves can be achieved using suitable whistle arrangements. It is considered that such a whistle should emit a high frequency sound wave which is of a suitable volume. One form of whistle which is considered to be emanently suitable is one which is sold under the trade mark "Shriek" as an Alarm and is powered by an aerosol type of container of liquified gas under pressure, Where required a suitable cover or protective sheath may be provided for ensuring that any necessarily open apertures, such as may be present in a whistle, remain open and thus properly functional.

Where the unit embodies a battery or any other source of electrical power to aid or promote its function a test circuit may be provided for testing the operation of the unit. An analagous arrangement may be provided where air or other gas under pressure is utilised to generate sound waves in which case a manually operable valve can be provided for anchoring tests.

Preferably, if the unit embodies any weighty parts these can be located in a housing adapted to be mounted co-axially with the wheel so as to avoid upsetting the balance of a wheel. However, where the parts are relatively light in weight this may be avoided and the unit may be capable of direct attachment to a valve assembly or, where tubeless tires are concerned, the unit may be adapted for installation into a hole in a wheel rim communicating with the interior of the tire.

From the above it will be apparent that the sound wave generating unit may be adapted to be directly audible by a driver of a vehicle when it is activated as will usually be the case with small or relatively light and quiet vehicles. However, optionally by choice, or in the case of heavy, noisy vehicles possibly of necessity, the receiver arrangement may be provided as outlined above.

In such an instance there may be provided, conveniently in the cab of the vehicle, a hooter, buzzer or the like optionally in addition to a warning light. Also, a counter of electromechanical type or electronic type may be embodied in a unit mounted on the vehicle in use.

The invention will now be further described by way of example reference being made to the accompanying drawings in which: Fig. 1 is an isometric view of a wheel supporting a tire monitoring device according to the invention, Fig. 2 is a similar view illustrating a somewhat modified form of device, Fig. 3 is an enlarged view of the central region of Fig. 2, Fig. 4 illustrates diagrammatically a device powered by means of a storage battery, Fig. 5 illustrates in sectional elevation a valve device for connecting a sound generating unit to the air under pressure in a tire, Fig. 6 illustrates an alternative form of device according to Fig. 5 together with a special tire valve stem, Fig. 7 illustrates an alternative axially movable operating member for the device of Fig. 6, Fig. 8 illustrates in broken-away view the installation of a device directly into a wheel rim for use with tubeless tires, Fig. 9 is a schematic sectional elevation of one wheel and illustrating a receiver unit, and, Fig. 10 is a block diagram of the receiver unit of Fig. 9.

As mentioned above the tire monitoring device according to this invention may, as required, embody a battery and optionally an electrically operated sound wave generating unit. In general a pressure operated switch would be included in such a circuit and the whole apparatus may be included in a housing 1 as shown-in Fig. 1 and which is mounted on a transverse metal support 2 therefor. The metal support is preferably in the form of a bent strip of metal which can be secured to a wheel 3 carrying a pneumatic tire 4 by means of the nuts 5 utilized to secure the wheel to its hub. This metal support 2 in any event preferably extends diametrically with respect to the wheel such that weight is substantially centered around the axis of rotation.

In the case where an electrically powered sound wave generating unit is employed a pressure switch 6 can simply be attached to a tire valve 7 so that a circuit is closed when the pressure within the pneumatic tire falls to below a predetermined minimum.

Preferably a test button 8 is embodied in the unit to enable the device to be tested as when required.

A suitable simple circuit for such a device is illustrated in Fig. 4 and shows the test switch 8 in parallel with the pressure operated switch 6 which in use is attached to the valve 7. In this case the battery 9 is arranged to power a sound generating unit composed.of a buzzer 10 arranged in series with a suitable oscillator 11 for driving it.

It will be understood that when either the test button switch or the pressure operated switch is closed, with the latter being adapted to occur when the pressure in a tire decreases to below a predetermined value, the buzzer will be operated and this may be directly audible or picked up by a receiver as outlined above and will be more fully described hereinafter.

As an alternative to the above type of mounting for the unit where it embodies weighty components such as a battery a housing 12 having a series of parallel legs 1 3 arranged in a circular path around the housing may be adapted such that the legs closely surround a protruding end 14 of a side shaft of a motor vehicle where this is present.

In such a case a simple circular clamp 15 can be utilized to secure the unit in position on the end of the side shaft and the unit could embody a speaker or buzzer as above described or alternatively a whistle. Where a whistle is embodied in the unit of this type a tube 1 6 is provided for connecting it to a tire valve outlet so that the valve arrangement within the unit can be communicated with the interior of the pneumatic tire.

It is in fact preferred that the source of energy be the air under pressure in the pneumatic tire itself since this is available in situ. It is considered that it would not be of any disadvantage to consume small amounts of such air under pressure in the event that a pneumatic tire going under pressure since the tire will already be a cause of concern and should result in a cessation of driving of the vehicle.

Various forms of valve arrangement are possible in order to enable the air under pressure within a tire to be utilized and to pass through a whistle or other sound generating unit usually of a mechanical type. One such valve unit is illustrated in Fig. 5 in which case the valve unit is adapted for direct connection to a tire valve 1 7.

This valve unit has a centrally located stop arrangement 1 8 adapted to depress the usual axially movable valve member 19 so as to open the valve when the unit is secured to the tire valve. To this end co-operating screw threads 20 are provided and a sealing ring, preferably in the form of an O-ring 21 is provided to ensure that no leakage occurs.

The valve casing 22 has a bore 23 in which is located an axially movable piston member 24 spring biased towards the tire valve 1 7 which is coaxial therewith. The spring 25 effecting the biasing will be chosen to provide the required pressure at which air from the tire is released by way of an outlet 26 to be discharged to a whistle or the like (not shown in Fig. 5).

The piston has three spaced O-ring seals 27 sealingly engaging the cylindrical wall of the valve housing and a passage 28 passes through the piston from the end thereof nearer the tire valve 7 to a position in between the two O-ring seals furthest from the tire valve 1 7.

From the above it will be understood that the pressure from the interior of a pneumatic tire, in use, bears upon the piston 24 so that it is urged away from the tire valve 1 7 against the action of the spring 25. The design of the valve assembly is such that the outlet 26 communicates with a position between the two O-ring seals nearer the tire valve 17 when the correct pressure is present in the tire.

However, when the pressure in the pneumatic tire decreases to below a certain predetermined minimum the piston will be urged towards the tire valve 1 7 by the spring 25. At a preselected pressure the passage 28 passing through the piston member will communicate between the tire valve 1 7 and the outlet 26 from the valve assembly. Air will then pass out of the outlet 26 and into a whistle or like arrangement which will be described below.

There may be provided a spring loaded bistable member 29 co-operating between the valve housing and the piston so as to ensure a sudden and positive change between a position in which the outlet 26 is closed and one in which it is communicated by way of the passage 28 through the piston with the tire valve 1 7.

Figure 6 illustrates a similar type of device where however the tire valve has a stem 30 having a branch 31 secured thereto so that two screw threaded attachments are provided on the tire valve stem. The one 32 is provided with the conventionai tire valve therein whilst the other, which may be provided with no tire valve at all, has secured thereto a valve arrangement conveniently made of plastics material. The valve arrangement 33 has a socket 34 which is secured onto the branch 31 of the valve stem and passages 35 communicate between the socket 34 and two spaced positions 36 in a bore 37 extending with its axis transverse to the branch 31.

A spring 38 is arranged to bias a first piston member 39 located within the bore 37 in a direction away from one end 40 of the body of the valve. This end of the bore 37 communicates with a whistle member 41 which is conveniently made substantially similar to that of the commonly available aerosel operated alarm units mentioned above and sold under the Trade Name "Shriek".

The spring 28 may be adjusted in its exact axial position by means of a stop member 42 which cooperates with a screw threaded end region of the bore 37 so as to be axially adjustable in position.

Any suitable locking means may be provided to ensure that this stop member 42 remains in the preset position.

The said first piston member 39 has a pair of spaced O-ring seals 43 which sealingly engage the walls of the bore 37. The spring and outlets 36 from the passages 35 are arranged such that the piston 39 bridges the one outlet 36 nearer the end having the whistle with the other outlet 36 communicating with the bore on the end of the first piston 39 opposite the whistle. Thus the pressure from the interior of a tire will act on the end of the first piston member 39 opposite the spring and the two forces are adapted to balance each other to maintain the first piston member in a position in which the O-ring seals 43 are located on opposite sides of the said co-operating outlet 36.

However, when the pressure of the air within the pneumatic tire decreases the spring will urge the the said first piston member past the co- operating outlet 36 and allow air under pressure to escape through the bore 37 and out through the whistle 41.

In order to ensure that the whistle is not activated when a tire is being inflated a second piston member 44 can be provided in the bore and this piston member may have an operating rod 45 extending out of the end of the bore opposite the whistle. This piston member and operating rod are arranged such that the second outlet as well as the first outlet 36 can be closed by manual maintenance of the second piston in a depressed position during inflation of a tire. After inflation the second piston is adapted to be urged such that its operating rod is extended from the end of the body of the valve assembly.

Figure 7 illustrates a slight modification to the first piston member described above and wherein three axially spaced O-ring seals 46 are provided along the length of the piston 47. The piston has a passage 48 therethrough communicating between the end co-operating with the spring 37 and a space between the two O-ring seals most remote from that spring.

It will be understood that by correct selection of a spring the passage 48 will initially communicate between the tire pressure and the whistle when a predetermined low pressure is sensed. However, when the pressure decreases further the outlet will again be closed as a result of location of the appropriate outlet 36 between the two O-ring seals 46 nearer the spring. This alternative is designed to achieve conservation of any air under pressure if the tire pressure has not been attended to upon initial activation of the warning.

The branch tire valve stem arrangement described above could easily be replaced in cases where a tubeless tire is utilized by a rubber bung arrangement 49 as illustrated in Fig. 8 installed simply through a hole 50 in a wheel rim 51 in the manner of a tire valve for a tubeless tire. In this case the rubber bung 49 would simply carry, optionally releasably, the valve and whistle arrangement 52.

As mentioned above, the sound wave generating unit could be adapted to emit ultrasonic waves and also may be such that audible sound waves emitted thereby cannot be heard satisfactorily or easily by a driver of a vehicle.

In such instances, an arrangement as illustrated in Fig. 9 and 10 may be employed. In this particular case a receiver unit embodying a microphone 53 could be utilized, the microphone being adapted to pick up the sound waves generated by the generating unit.

These sound waves are preferably characteristic and of a substantially predetermined frequency to enable them to be distinguished from other noises which may be created as a result of moving parts of a vehicle.

The microphone is thus connected to a filter or tuning unit 54 which, usually, will be a highpass filter as a result of the expected use of high characteristic frequencies for a device according to the invention. The output from the high pass filter or tuning unit may be passed to a level detector 55 adapted to activate an electronic switch 56 upon the sensing of a predetermined level of the characteristic frequency. Any suitable amplifier units may be embodied in the circuit and the employment of such amplifier units will be quite apparent to those skilled in the art.

The output from the switch is adapted to be fed to an electromechnical counter 57 and also to an audible device 58 both of which can be located within a housing 59 located within the cab of a vehicle in use.

It will be understood that the sound waves emitted by a unit 60 associated with a wheel 61 in use can easily be picked up by a microphone 53 which can be suitably mounted on a rear axle 62 for example of a vehicle. Such a microphone may be located centrally between a plurality of wheel units or alternatively there may be one such microphone provided for each wheel unit.

In use the microphone, as will be quite ciear, picks up a sound wave generated by the sound wave generating unit and will cause through the action of the level detector the switch to be closed and the counter and speaker to be activated.

It will be understood that numerous other arrangements are possible within the scope of this invention which is not limited to the embodiments specifically described above.

Claims

1. A tire monitoring device comprising a sound-wave generating unit operable by means of a source of energy associated, in use, with a pneumatic tire assembly; pressure operated control means for selectively coupling the soundwave generating unit with the source of energy at a preselected pressure sensed by the control means, and communication means for connecting said pressure operated control means to a pneumatic tire assembly so as to be operable according to the internal pressure of such pneumatic tire, wherein the sound-wave generating device, control means, communicating means, and source of energy are all, in use, rotatable in unison with a pneumatic tire assembly.

2. A tire monitoring device as claimed in claim 1 in which the sound wave generating unit is adapted to produce, upon energisation thereof, sound waves of a predetermined characteristic frequency.

3. A tire monitoring device as claimed in either of claims 1 or 2 in which the sound wave generating unit is adapted to produce, upon energisation thereof audible sound waves of sufficient volume to be directly audible by a driver of a vehicle in use.

4. A tire monitoring device as claimed in claim 2 in which the device includes a receiver unit adapted for mounting to a vehicle near a wheel assembly and being arranged to be operable by said characteristic frequency to activate a warning device visible or audible by a driver of a vehicle to which such device is fitted.

5. A tire monitoring device as claimed in claim 4 in which said warning device includes recording means for recording occurrences of activation of the warning device.

6. A tire monitoring device as claimed in either of claims 4 or 5 in which the sound wave generating unit is adapted to produce ultrasonic sound waves.

7. A tire monitoring device as claimed in any one of claims 4 to 6 in which the receiver includes a filter or tuning device for selective operation by said characteristic frequency.

8. A tire monitoring device as claimed in any one of the preceding claims in which the source of energy is a battery or the like carried in a housing having means for securing it to a vehicle wheel in use.

9. A tire monitoring device as claimed in claim 8 in which the sound wave generating unit is an electrically operated unit and the pressure operated control means is a pressure operated switch.

10. A tire monitoring device as claimed in any one of claims 1 to 7 in which the source of energy is an optionally liquified gas under pressure contained within the containing means rotatable in unison with a wheel in use.

11. A tire monitoring device as claimed in claim 10 in which the gas under pressure is the air whereby a pneumatic tire on a wheel is inflated.

12. A tire monitoring device as claimed in claim 11 in which control means is a spring biased valve assembly.

13. A tire monitoring device as claimed in either of claims 11 or 12 in which the control means are mountable on a tire valve stem or branch thereof.

14. A tire monitoring device as claimed in any one of claims 10 to 1 2 in which the sound wave generating unit is a whistle or the like.

1 5. A tire monitoring device as claimed in any one of the preceding claims in which the device includes a housing mountable substantially coaxially with a wheel of a vehicle in use.

1 6. A tire monitoring device as claimed in claim 1 and embodying a valve unit substantially as described with reference to any one of Figs. 5, 6 or 8.

1 7. A tire monitoring device substantially as herein described or exemplified with reference to any one or more of the accompanying drawings.