Piezoelectric drive excited by longitudinal and flexural waves

A piezoelectric drive which comprises a driven element provided with a friction layer and at least one monolithic plate-shaped piezoelectric transducer including large and smaller surfaces as the driving element, whose length is not equal to its width, as well as with first and second electrode groups on its large surfaces and with at least one friction element on its smaller surface being in elastic friction contact with the friction layer of the driven element, and further with an electric generator which is electrically connectable with the first and second eletrode groups, with the first and electrode group representing representing two areas of identical configuration on the two large opposite surfaces of the plate-shape piezoelectric transducer, which are metallized, and the first electrode group being a longitudinal wave generator and the second electrode group being a flexual wave generator for acoustic waves,

• wherein each of the first and second electrode groups forms at least one independent transducer of acoustic standing waves not coupled to each other which propagate along the long side of the piezoelectric transducer, a unidirectionally polarized piezoelectric ceramic oriented perpendicular to the first electrode group and arranged between the first and second electrode groups is located in sites of oscillation velocity nodes of the standing acoustic longitudinal wave propating in the transducer, and a piezoelectric ceramic which is oriented perpendicular to the electrodes and arranged between the electrodes and is uniderectionally polarized or heterodirectionally symmetrically polarized with respect to the longitudinal axis of the transducer, which is disposed in sites of oscillation velocity maxima of the standing acoustic flexual wave propagating in the transducer.