Tire deflation detector

Claim 2

A tire condition indicating device comprising a detector for detecting the condition of a tire on a wheel of a vehicle rotatable about a wheel axis, a signal emitter emitting a signal when the detector detects the said condition, a counter connected to the emitter whereby the emitter can transmit a signal equivalent to the number of rotations that each wheel makes during a particular journey and power supply means providing power to the signal emitter to emit the signal as aforesaid, wherein the power supply means comprises an electric power generator comprising first and second parts that are relatively rotatable about a generator axis, the first part being connected to the wheel to be rotated thereby.

Claim 3

A device as claimed in claim 1 wherein the counter counts the number of relative revolutions of the first and second parts of the electric generator.

Claim 4

A tire condition indicating device comprising a detector for detecting the condition of a tire on a wheel of a vehicle rotatable about a wheel axis, a signal emitter emitting a signal when the detector detects the said condition, power supply means providing power to the signal emitter to emit the signal as aforesaid, said power supply means comprising an electric power generator having an axis which is coincident with the wheel axis, the generator comprising: a first part rotatable with the wheel, and a second part that is relatively rotatable to the first part about the generator axis, the second part being rotatably carried by the wheel and being attached to an offset weight which tends to hold the second part stationary when the wheel rotates: wherein the offset weight comprises a cross plate and a mass member, the cross plate being attached to the second part, the cross plate being rotatable about its centre, through which the generator axis passes, and the mass member being carried by the cross plate eccentrically of the generator axis.

Claim 5

A tire condition indicating device comprising a detector for detecting the condition of a tire on a wheel of a vehicle rotatable about a wheel axis, a signal emitter emitting a signal when the detector detects the said condition, power supply means providing power to the signal emitter to emit the signal as aforesaid, said power supply means comprising an electric power generator having an axis which is coincident with the wheel axis, the generator comprising: a first part rotatable with the wheel, and a second part that is relatively rotatable to the first part about the generator axis, the second part being rotatably carried by the wheel and being attached to an offset weight which tends to hold the second part stationary when the wheel rotates: wherein the offset weight comprises a cross plate and a mass member, the cross plate being attached to the second part, the cross plate being rotatable about its centre, through which the generator axis passes, and the mass member being carried by the cross plate eccentrically of the generator axis.

Claim 6

The device as claimed in claim 3 wherein the first part is rotatable with the wheel and wherein the wheel axis and generator axis are coincident.

Claim 7

A double wheel arrangement comprising a pair of wheels respectively carrying a pair of tires and a tire indicating device as claimed in claim 3 comprising a pair of detectors coupled respectively to the tires.

Claim 8

A device as claimed in claim 3 wherein the mass member comprises a substantially hemi-cylindrical part, the ends of which are connected to the ends of the cross member.

Claim 9

A device as claimed in claim 6 incorporating a housing with a generally cylindrical inner part centred on the generator axis and having an opening therein within which the core is received and a rotary support carrying the second part, there being an annular space between the housing and the inner part within which space the hemi-cylindrical part is about the generator axis.

Claim 10

A device as claimed in claim 3 wherein the second part comprises a permanent magnet located within an electro-magnetic core which comprises the first part there being windings on the core connected to the signal emitter to provide it with electric power.

Claim 11

A device as claimed in claim 8 wherein the permanent magnet is arranged with its north/south axis parallel to the generator axis.

Claim 12

A device as claimed in claim 3 wherein the the signal emitter comprises a radio frequency transmitter carried by a printed circuit board.

Claim 13

A device as claimed in claim 10 wherein the transmitter has an antenna formed from the printed circuit board.

Claim 14

A vehicle comprising a plurality of wheels each carrying a tire and tire condition indicating devices as claimed in claim 3.

Claim 15

A vehicle as claimed in claim 12 further comprising a driver's cabin and, within the driver's cabin, a receiver for receiving signals from the transmitter.

Claim 16

A vehicle as claimed in claim 13 wherein the receiver incorporates indicating means identifying each tire whereby the driver will receive signals indicating the condition of each tire.

Claim 17

A device as claimed in claim 3 wherein the detector is a tire pressure detector.

Claim 18

A device as claimed in claim 15 for use with a tubeless tire having a valve projecting from the wheel, and wherein the entire pressure detecting incorporates a pressure transducer connected to the valve by a conduit.

Claim 19

A device as claimed in claim 16 further comprising a union connected in the conduit and incorporating a valve control member inlet through which the tire can be inflated via the conduit.

Claim 20

A device as claimed in claim 15 for use with a tire incorporating a tube that has a valve projecting through the wheel wherein the tire pressure detector comprises a pressure transducer and a conduit connecting the transducer to the valve.

Claim 21

A device as claimed in claim 18 further comprising a union connected in the conduit and incorporating a valve control member inlet through which the tire can be inflated via the conduit.

Claim 22

A device as claimed in claim 18 wherein the the signal emitter comprises a radio frequency transmitter carried by a printed circuit board and wherein the transducer is mounted on the printed circuit board.