Apparatus and method for indicating condition of a rotating body

Abstract

Apparatus and method particularly adapted for detecting over and/or under inflated conditions in a wheel structure of the type comprised of a pneumatic tire mounted on a wheel rim. A generator unit is mounted to the wheel generally coaxial of the axis of wheel rotation and is constructed such that the generator rotor is operably journalled within the generator stator in a manner facilitating rotation of the rotor independently of the remainder of the generator unit and wheel itself. One side of the rotor is weighted so that as the wheel and generator unit are rotated, the rotor disposition remains generally stationary due to the influence of gravity forces on the weighted area. The relative rotation thus achieved between stator and rotor causes a voltage to be induced in the stator field winding which is utilized to energize a small radio transmitter mounted on the wheel with the generator unit. Pressure sensing means communicating with the tire controls energization of the transmitter in response to a predetermined tire pressure condition. The transmitted radio signal is then received by a receiving unit spaced remote from the wheel to cause energization of convenient indicating means located in the vehicle to show that the predetermined air pressure condition has been detected.