Piezoelectric assembly

The assembly has a piezoelectric unit (111) that expands in one dimension due to the application of a voltage to two electrodes. The unit (111) is placed between an upper cap (12) and a piston unit. A lower cap (13) is placed in a fixed distance to the upper cap (12). The two caps are firmly attached to a rigid tube and a Belleville spring that is situated between the piston unit and the lower cap (13).