Vehicle tyre deflation detector

摘要

A deflation detector for detecting when the tyre (10) becomes deflated and for indicating to the driver of the vehicle that the tyre is deflated comprises a plunger member (48) subject to the pressure in the tyre and a transmitter (72) controlled by said member to emit a signal when the pressure in the tyre falls below a predetermined amount. The transmitter is carried by the wheel rim (14) and includes an electric circuit incorporating a pair of contact terminals (66) one of which is connected to a source of power (74) for the transmitter. The plunger member is movable by the pressure in the tyre against a spring (58) bias to a first position in which it holds the contact terminals apart and a second position in which it permits the contact terminals to move into electrical contact thereby to permit power to be supplied to the transmitter. In a modification the plunger is connected to operate a rheostat that gives a signal which is dependent upon the pressure in the tyre.