Vehicle air suspension system with ultrasound measuring arrangement

On the cover plate (8) of a roll bellows (4) is mounted an ultrasonic transmitter/receiver (14). A stop buffer (28) mounted on the piston (10) forms a two step reflector. The first step (16) acts as the target reflector and the second, the reference reflector (26) is formed by the base of a blind hole (20), forms. The instantaneous clear height of the bellows is then given by the equation:- starget - ttarget x sref/(tref - ttarget) where: s= clearance to transmitter/receiver t = propagation time of sound beam The figure shows a section through a roll bellows to the present invention. bellows 4 cover plate 8 piston 10 step 16 blind hole 20 reference reflector 26 stop buffer 28