Depolarization protection for ceramic piezoelectric motor

Claim 2

In a piezoelectric motor of the type having at least one piezoelectrically excitable polarized ceramic bending strip carrying at least one pair of electrodes for receiving an alternating voltage from an electrical supply and mounted at its ends in mounting devices of which one is to reciprocate, the improvement therein comprising an input circuit including a rectifier, and a resistor connected in parallel with said rectifier, said parallel connected rectifier and resistor connected in series with the electrodes of said one bending strip with said rectifier poled opposite to the direction of polarization of said ceramic strip between said electrodes and said resistor having a value to limit the peak voltage applied across said ceramic strip during blocking operation of said rectifier to a predetermined fraction of the peak voltage received from the electrical supply.

Claim 3

The improvement set forth in claim 1, further defined wherein said bending strip comprises an elongate carrier strip, a pair of elongate ceramic elements secured to opposite sides of said carrier strip, a plurality of pairs of electrodes including said one pair of electrodes, said plurality of electrodes including four individual electrodes connected to and extending from the ends of said ceramic strips toward the opposite ends and a pair of elongate electrodes interposed and connected between said carrier strip and respective ones of said ceramic elements, each said elongate electrode being included in an electrode pair with the two of said four individual electrodes connected to the same ceramic element, said ceramic elements polarized in a first direction between its one pair of electrodes and in an opposite direction between its other electrode pair, said elongate electrodes electrically connected and adapted for connection to the electrical supply, and wherein said input circuit comprises a second rectifier and a second resistor connected in parallel therewith, and having a resistance value similar to that of the first-mentioned resistor, each of the rectifier-resistor combinations serially connected with two pair of said electrode pairs of separate ones of said ceramic elements and poled opposite to the direction of polarization of said ceramic elements between the respective pairs of electrodes, said rectifiers connected together and adapted for connection to the electrical supply.

Claim 4

The improvement set forth in claim 1, wherein said polarized ceramic bending strip includes a plurality of pairs of electrodes for receiving an exciting voltage and is permanently polarized so that the exciting voltage is alternately in the direction of polarization for one pair of electrodes and in an opposite direction for another pair of electrodes.

Claim 5

The improvement set forth in claim 1, wherein said bending strip comprises two mechanically interconnected ceramic strips each having at least one pair of electrodes.

Claim 6

The improvement set forth in claim 1, wherein said bending strip comprises two mechanically interconnected ceramic strips, two pairs of electrodes on one of said ceramic strips spaced in the longitudinal direction thereof, two other pairs of electrodes on the other ceramic strip spaced in the longitudinal direction thereof, and a second rectifier-resistor combination, each of said rectifier-resistor combinations connected in series with respective ones of said pairs of electrodes.

Claim 7

The improvement set forth in claim 1, comprising a plurality of pairs of electrodes, said electrodes carried on each side of said bending strip and spaced apart longitudinally of said bending strip and adapted for application of opposite polarities of voltages to produce S-shaped bendings.

Claim 8

The improvement set forth in claim 1, comprising a plurality of said bending strips having respective pairs of electrodes mechanically connected in parallel and electrically connected to said input circuit in the same manner as the first mentioned bending strip.