U.S. Philips Corporation

Frans Josef Frankort

Nico Valentinus Franssen

A device for converting electric into acoustic vibrations and vice versa, provided with a diaphragm, comprising at least one layer of a piezoelectric polymer material, which is polarized in a transverse direction and which at either side is provided with electrodes, the diaphragm being undulated in at least one orthogonal section, whilst each flank of the undulation is polarized in the same direction over its entire width and in the operating condition the direction of the applied electric field relative to the direction of polarization in adjoining flanks are alternately parallel and anti-parallel. Two types of embodiments are possible. In the first embodiment the direction of polarization in each flank is opposed to that of at least one adjacent flank; in the second embodiment all flanks are polarized in the same direction, each flank being provided with a pair of electrodes which are oppositely disposed relative to each other, which pair is electrically isolated from a corresponding electrode pair of at least one adjacent flank, which last-mentioned pair in the operating condition has an opposite polarity relative to the first-mentioned electrode pair. The use of polyvinylidenefluoride as a piezoelectric material has been found to be very favorable.

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Bocholtz, Netherlands

Frans Josef Frankort