GB2240647A - Low pressure and temperature warning device for vehicle tyres - Google Patents

Abstract

A tyre safety device ensures that substantially equal pressure is present between the tyros of a double-tyre wheel and also warns when any one of the tyres become seriously underinflated or when an excessive temperature condition exists in the tyres. The device comprises a control block 1 adapted to be fitted on a double-tyre wheel, the block 1 including a through-conduit 6A -6C which is connected to the valves of the two tyros of the wheel to provide equal pressure conditions between the tyres. A pressure sensitive valve 11 - 14 closes the through-conduit 6A - 6C when there is an excessive air pressure fall. The valve 11 also operates an actuator 18 of a switch 24A, 25A, 26A in an electric warning circuit for the generation of a warning signal. The actuator 18 is pan of a telescopic arrangement enabling the switch contacts 24A, 25A, 26A to be housed internally for contamination protection. Additionally, a temperature responsive device 31 surrounding the actuator 18 reacts with a frusta-conical wall 18B of the actuator to move the actuator for closure of the warning circuit switch at an excessive air temperature condition in the through conduit. <IMAGE>

Description

"Improved Safety Device for Tyres" The present invention relates to a safety device for tyres, especially motor vehicle tyres, and in particular relates to a tyre safety device of the type serving to equalise air pressure between the tyres of a double-tyre wheel.

Safety devices of the above type for a double-tyre wheel are described in the present applicant's International application PCT/89/00731 filed 30 June 1989 (publication number ); these devices including an air-control block adapted for connection to the stems of the tyres of a double-tyre wheel, for example by means of flexible pipelines, the air-control block housing a conduit permitting air to flow between the tyres to maintain substantial equal pressure between the tyres and an air regulating device halting air flow between the tyres when the pressure in one tyre falls below a predetermined level, there additionally being provided an electric warning circuit including electrical contacts which are closed automatically at low pressure conditions for the provision of a warning signal, which, in particular, can be a radio signal.

It is an object of the present invention to provide improvements in the above tyre safety device, particularly with regard to the maintenance of reliable operation over a prolonged period of use.

According to the present invention a tyre safety device for use with a double-tyre type wheel comprise a body adapted for fitting on a double-tyre wheel; a conduit within the body defining an air passage; a pair of outlets at the ends of the conduit adapted for connection to respective air valves of the double tyres on a double-tyre wheel whereby air is permitted to flow between the tyres via said conduit; an air-inlet to the conduit including a one way valve, said air inlet enabling inflation of the tyres; valve means to shut said air passage automatically when the air pressure in either tyre falls below a predetermined value; an electrical air-pressure warning device responsive to air-pressure in the conduit including electric contact means, and an actuator movable in an axial direction to open and close said electric contact means; a housing for said electric contact means extending in said axial direction; a post extending into the housing with the arrangement such that movement is provided between the housing and the post; , said contact means including a set of contact elements at least one of which elements is located on the post; one of said housing and post being defined by the actuator; and means to shield said electric contact means from air in said conduit.

Preferably an air-bleed line extends from the housing. Preferably the housing is located in the actuator while the post is carried by a stationary member, and preferably a sealing ring is provided between the post and a housing wall to shield the electric contact means in the housing.

Preferably the actuator has a large diameter end defining said shield means.

Preferably further, a temperature responsive device is provided responsive to temperature in said conduit, said temperature responsive device causing axial movement of the actuator at increased temperature conditions to close the electric contact means. In a preferred embodiment, the actuator includes a frusto-conical wall while the temperature responsive device comprises temperaturesensitive actuating means reacting with said frusto-conical wall for operative movement of the actuator.

Preferably the actuator is located between oppositely biassed spring means.

The above safety device provides improved reliability over a prolonged period of use as the electric contact means of the air-pressure warning device are shielded from contaminants in the air passage of the body.

It should be understood that air within a vehicle tyre normally is far from "clean.

An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings wherein: Fig 1 shows a cross-sectional view of a safetydevice for the tyres of a double-tyre wheel, through the section A-A in Fig 2, and in accordance with the present invention; and Fig 2 shows the device of Fig 1 through section B-B of Fig 1.

Referring to the drawings, a safety-device 1 for the tyres of a double-tyre wheel is generally in accordance with the device shown in Figs 10 to 12 of International application PCT/GB89/00731 (publication No ). Thus a single block element 2 is fluidly connected to the stems (not shown) of a double-tyre by means of suitably arranged flexible conduits 3, 4 (Fig 1), a suitable connecting piece (not shown) being provided at the outer end of each conduit 3, 4 which piece is fitted onto the relevant tyre stem such that the valve on the stem is opened. The block element 2 is securely fixed to the double wheel at a suitable location such that the conduits 3, 4 can pass to their respective valve stems. In particular, the specific means described in PCT/GB89/00731 for locating the block element on the wheel can again be used.An appropriate one of the conduits 3, 4 can pass through a wheel vent aperture to its respective valve stem.

The element 2 includes an upper layer 2A of plastics material in which is embedded the circuit (not shown) of a fault warning arrangement, and a metallic lower layer 2B which houses a conduit 6 defining an air passage between the conduits 3, 4. The air passage 6 is defined by a portion 6A of a through-boring 7 extending between end walls of the element 2, and branch portions 6B, 6C leading to said portion 6A. The layer 2B has recesses 8, 9 to receive end-pieces 10 of the conduits 3, 4 for example in snap-fitting manner, so that the conduits 3, 4 are in fluid communication with the internal conduit 6 respectively.A piston valve 11 in bore 7 is urged by spring 12 to bring a sealing ring 13 against an annular shoulder 14 (as shown dashed in Fig 1) for closure of the conduit 6, and a screw 15 located at one end of the bore 7 and which is suitably calibrated controls the operating pressure setting of the valve 11 via the spring 12. An air inlet 15 including a one-way valve feeds into the conduit 6. Energisation of the warning-signal circuit in layer 2A for the reduced tyre pressure condition or an excessive temperature condition is achieved by a control device 17 operating in conjunction with the piston valve 11.

The control device 17 comprises a generally frustoconical actuator spindle 18 having one end of cylindrical form to be received in a socket llA of the piston 11 whereby the piston 11 and spindle 18 are relatively axially movable, while the other end of the spindle 18 is movably supported by a stationary member 19 at the other end of the bore 7, for this purpose the member 19 having an axial post 20 located in a housing 21 in the spindle 18. The member 19 is of a cup-form to receive a battery 22 of the warning circuit and additionally carries electrical conduits 23, 24, 25 to enable power supply to the warning circuit from the battery 22, the member 19 being of insulating material, eg plastics, as is the spindle 18. The warning circuit includes openable electric contact means 26 in the housing 21 defined by a contact element 26A carried by the movable spindle 18 and elements 24A, 25A of the electrical conduits 24, 25. Access to the battery 22 is via a threaded cap 27 of insulating material. The spindle 18 or the post 20 carries sealing rings 28 to shield the contact means 26 from air in the conduit 6 while an air bleed conduit 29 in the post 20 enables escape of air from the housing 21 and provided a beneficial clamping effect with respect to axial movements between the post 20 and the spindle 18. A spring 30 oppositely biassed to the spring 12 urges the spindle 18 so as to open the contact means 26.

The spindle 18 includes a large diameter end portion 18A with a relatively large cone angle assisting deflection of air between the passage portions 6A, 6B and also mitigating against flow of air towards the housing 21, while the frusto-conical central portion 18B of the spindle 18 of much smaller cone angle, is surrounded by a temperature responsive device 31 which can abut against an annular series of buffers 32 alldwing air flow between air passage portions 6A, 6C. The device 31 shown comprises a central body 33 of resilient material and a peripheral clamping strip 34 of temperature expandable metal.

The normal operation of the above safety device 1 is exactly similar to that of the double-tyre safety devices described in PCT/GB89/00731 ( ), that is air is permitted to flow between the tyres of a double tyre wheel via the air passage 6, with valve 11 opened by the tyre operating pressure, to maintain pressure equality between the tyres, initial inflation of the tyres being achieved through the single air inlet 16. Where there is a serious loss of air in a tyre ie pressure falls below a predetermined level, the piston valve 11 moves to bring the seal ring 13 against shoulder 14 to close the air passage 6 and thereby preclude air flow between the tyres.

Additionally, the spindle 18 is moved by the piston valve 11, against the action of spring 30, to cause closure of the contact means 26. Consequently, the warning circuit is energised for the generation of a warning signal: this warning signal can be a radio signal and for this end radio transmitter circuitry described in PCT/GB89/00731 can be utilised. Appropriate light warning indicators can be provided to enable ready identity of the wheel where the fault is present.On a separate basis, where air temperature in the air passage 6 rises above a predetermined level, due for example to excess pressure conditions in the tyres or to a mechanical fault at the wheel, the clamping strip 34 of the temperature responsive device 31 in air passage position 6A expands to cause an increased clamping action on the body 33 with the result that the device 31 abutting against buffers 32 provides an axial component of force on the spindle 18 via the frustoconical portion 18B to move the spindle 18 to close the contact means 26 for the generation of a warning signal.

Modifications are of course possible in the device.

In particular the temperature responsive device could take some other form than that shown: for example the body 33 could be of expandable material eg wax surrounded by a rigid casing. Again, instead of the application of a radial force (providing an axial force component by means of the frusto-conical portion 18B), the device 31 could be arranged to provide purely an axial moving force, with the actuator spindle 18 arranged appropriately. In an alternative arrangement the housing for the electrical contact means 26 could be on the member 19 while the cooperating post 20 is carried by the moving spindle 18.

As will be noted generation of warning signals for both unacceptable pressure and temperature conditions is achieved through the single contact means 26 and this leads to a simplification. Even more significantly, the contact means 26 are effectively shielded from tyre air in the passage 6 so that build up of contaminant on the contact elements 24A, 25A, 26A which could render the warning circuit ineffective after a relatively short period of use is precluded.

Claims (12)

Claims

1. A tyre safety device for use with a double-tyre type wheel comprising a body adapted for fitting on a double-tyre wheel; a conduit within the body defining an air passage; a pair of outlets at the ends of the conduit adapted for connection to respective air valves of the double tyres on a double-tyre wheel whereby air is permitted to flow between the tyres via said conduit; an air-inlet to the conduit including a one-way valve, said air inlet enabling inflation of the tyres; valve means to shut said air passage automatically when the air pressure in either tyre falls below a predetermined value; an electrical airpressure warning device responsive to air-pressure in the conduit including electric contact means, and an actuator movable in an axial direction to open and close said electric contact means; a housing for said electric contact means extending in said axial direction; a post extending into the housing with the arrangement such that movement is provided between the housing and the post; said contact means including a set of contact elements at least one of which elements is located on the post; one of said housing and post being defined by the actuator; and means to shield said electric contact means from air in said conduit.

2. A tyre safety device as claimed in claim 1, wherein a temperature responsive device is provided responsive to temperature in said conduit, said temperature responsive device causing axial movement of the actuator at increased temperature conditions to close the electric contact means.

3. A tyre safety device as claimed in claim 2, wherein the actuator includes a frusto-conical wall while the temperature responsive device comprises temperaturesensitive actuating means reacting with said frusto-conical wall for operative movement of the actuator.

4. A tyre safety device as claimed in claim 3, wherein the temperature sensitive actuating means comprises an open band of temperature responsive material extending around the frusto-conical wall of the actuator.

5. A tyre safety device as claimed in claim 4, wherein an annular formation of resilient material eg rubber is located between the open-band and the frusto-conical wall.

6. A tyre safety device as claimed in any one of claims 3 to 5, wherein abutment means are provided to preclude axial movement of the temperature sensitive actuating means.

7. A tyre safety device as claimed in any one of the preceding claims, wherein an air-bleed line extends from the housing.

8. A tyre safety device as claimed in any one of the preceding claims, wherein the housing is located in the actuator while the post is carried by a stationary member.

9. A tyre safety device as claimed in any one of the preceding claims, wherein a sealing ring is provided between the post and a housing wall to shield the electric contact means in the housing.

10. A tyre safety device as claimed in any one of the preceding claims, wherein the actuator has a large diameter end defining said shield means.

11. A tyre safety device as claimed in any one of the preceding claims, wherein the actuator is located between oppositely biassed spring means.

12. A tyre safety device substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.