POSITIONING APPARATUS

摘要

An actuator (20) able to move along a track (22). The actuator has an elasti c coupling member (30) that surrounds the track (22). The coupling member (30) has a regularly grooved internal surface (32). Ther e are pairs of piezoelectric transducers (34) surroundin g the coupling member. These transducers (34) are polarized with each member o f a pair being polarized in a direction different from t he other member of the pair. There is an insulator (36) between neighbouring pa irs of transducers (34) and absorbers (38) at each end o f the actu? (20). Voltage can be applied to the transducers (34) whereby the appli cation of voltage expands and contracts the transducers (34), gen?ng waves in the coupling member (30) causing it to move along the track (22).